Marine drive system with improved drive belt

Abstract
An outdrive system for water craft includes in an embodiment use of plastic or other relatively flexible material, e.g., compared to metal, as a housing material, and techniques which enable and/or at least facilitate use of such housing material. Several of those techniques employ a flexible member, such as a belt, to couple power between the input and output of an outdrive, and heat conducting back bending surfaces to urge the belt legs toward each other and to remove heat from the outdrive, an anti-shear stuffer or fence to reduce energy losses such as heat, and lubricant requirements, and/or an eccentric mechanical tensioning device for the belt. The invention also relates to use in a vehicle drive, especially for water craft, of housing materials a substantial part of which are not subject to corrosion, galvanic action and the like. Other features include a rotational shock absorber system, an output shaft support, an improved sprocket tooth profile, a water by-pass silencer, an L C (analogous to an electrical inductor and capacitor filter) exhaust silencer, a split eccentric tensioner, an active tensioner, a transmission and a transmission shift mechanism, tensioning protocol and a cooling method. Also, in an embodiment the housing may be made partly or entirely of thermally conductive material, such as, aluminum, which facilitates and enhances heat removal by conduction to the water in which the outdrive is immersed.
Description




TECHNICAL FIELD




The present invention relates generally to drive systems for vehicles, especially water craft. More particularly, the invention relates to outdrives for water craft.




In an exemplary embodiment of the invention, features include, among others, use of plastic or other relatively flexible material, e.g., compared to metal, especially as a substantial part of the housing material, and techniques which enable and/or at least facilitate use of such housing material. One of those techniques employs a flexible member, such as a belt, to couple power between the input and output of an outdrive and/or others include heat conducting back bending surfaces to urge the belt legs toward each other and to remove heat from the outdrive, a stuffer or fence to reduce energy losses, such as heat, and lubricant requirements, and/or an eccentric mechanical tensioning device for the belt. The invention also relates to use in a vehicle drive, especially for water craft, of at least some housing materials that are not subject to corrosion, galvanic action and the like. Other features include rotational shock absorber, output shaft support, oil, anti-shear fence, sprocket tooth profile, water by-pass silencer, L C exhaust silencer, split eccentric tensioner, active tensioner, transmission design, transmission shift mechanism, tensioning protocol and exhaust thermal barrier. A still further feature includes use of a thermally conductive outdrive housing, such as aluminum, to facilitate and to enhance conducting heat to the water in which the outdrive is immersed.




BACKGROUND




In an exemplary drive system for a vehicle, there usually is a power supply, an output mechanism, a power coupling system, and a housing and/or structural apparatus. The power supply typically is an engine or a motor, although other means also may be employed. The output mechanism converts power received from the power supply to motive force for the purpose of moving and directing the vehicle. In a boat, the output mechanism typically is a propeller. The power coupling mechanism couples, transmits or transfers power from the power supply to the output mechanism. Often the power coupling system includes one or more of a drive shaft, an output shaft, other coupling gears and shafts, a clutch, a transmission, etc. The housing and/or structural support apparatus typically holds one or more of the other components of the drive system in relation to each other in order to accomplish the appropriate interaction to effect the desired driving function. Additionally, the housing and/or structural support mechanism may provide, to the extent needed and/or desired, appropriate enclosure functions.




The present invention preferably relates to drive systems for boats. As it is used herein, the term “boat” is intended to mean virtually any type of water craft, vehicle, apparatus, device, etc., that is intended to be operated on, in and/or under water. The features of the present invention are particularly useful with surface craft, i.e., boats that float and/or are operated at the water surface, and especially drive systems therefor that are rated at from about 100 horsepower up to about 1000 horsepower and beyond 1000 horsepower, and especially in the range of from about 100 hp to about 250 hp. However, it will be appreciated that features of the invention may be used with other boat drive systems and at other power levels, e.g., those that are rated at less than 100 horsepower or more than several hundred horsepower, or even more than 1,000 horsepower, depending on the sizes of the several components of the outdrive.




Moreover, although the features of the present invention are particularly useful in and relate to boat drive systems, it will be appreciated, and it is intended, that features of the invention may be used in drive systems for vehicles other than boats and/or in other applications, too. For compactness, though, the following description is directed to application of the features of the invention in drive systems for boats; application of features of the invention in other drive systems will be evident to those having ordinary skill in the art in view of the disclosure hereof.




Conventional boat drive systems often are categorized by labels inboard, outboard, and inboard/outboard. In an exemplary inboard drive system the power supply, which will be referred to hereinafter for convenience as an engine although it may be a motor or some other source of power, and the majority of the power coupling system are located within the boat, which provides at least some housing and structural support functions. The propeller and at least part of the propeller shaft, of course, are located outside the boat in the water, as also is the case for outboard and inboard/outboard drive systems. One example of an inboard drive system is an in line system in which the engine, clutch, transmission and propeller shaft generally are in line facing from the front to the back of the boat, the propeller being at or near the back. Another example of an inboard drive system is referred to as a V-drive. In an outboard drive system typically the engine and the power coupling system are located outside or mostly outside the boat. Furthermore, in an inboard/outboard drive system an exemplary configuration employs an engine located in the boat and a power coupling system that has a substantial portion located outside the boat. The foregoing is exemplary; it will be appreciated that various hybrid combinations of the foregoing categories of boat drive systems, as well as other types of boat drive systems also exist and/or may exist in the future.




The present invention includes features that may be useful in the various categories or types of boat drive systems mentioned above and in others that may not be specifically identified. However, according to the preferred embodiment and best mode, as is described in greater detail below, the present invention has particular utility when employed in and/or with the outdrive portion of the power coupling system of an inboard/outboard boat drive system and of outboard boat drive systems. Features of the invention also are especially useful in V-drive systems.




The term outdrive typically means that portion of a vehicle drive system, usually excluding the engine, which is located outside the hull of a boat. The outdrive usually is part of or is the entire power coupling system of a boat drive system and also may include the output mechanism, typically the propeller. As they are used herein, the terms outdrive and power coupling system may be used synonymously, and such terms also may be used to designate non-overlapping parts or functions, i.e., not synonymously; the context will make the usage clear. For example, the engine drive shaft itself may be considered part of the power coupling mechanism, as is the universal joint, but only the latter usually would be considered part of the outdrive.




In a conventional outdrive type of power coupling system, power is coupled between the engine and the output mechanism, which for convenience is referred to below as the propeller. Typically during use, the engine drive shaft or at least the power input shaft for the outdrive and the propeller shaft are oriented generally in parallel horizontal directions and are vertically spaced apart. The conventional outdrive includes a rigid coupling shaft and associated gears to couple the rotary output from the drive shaft to the propeller shaft. Accurate positioning of the various parts of such a conventional outdrive is necessary in order to assure proper alignment and meshing of respective gears and shafts, as is well known. Relatively rigid metal castings typically are used as housings for such outdrives to provide the necessary stiffness to obtain the necessary accurate positioning functions mentioned.




The gears, coupling shaft, and metal castings employed as housings and/or other parts for such conventional outdrives are relatively expensive to manufacture and are relatively heavy. It would be desirable to reduce the expense of manufacturing an outdrive.




The gears and coupling shafts of such conventional outdrives are usually located in an oil filled chamber. The oil provides usual lubricating function. Heat developed by the rotating gears and shafts heats the oil, which is cooled by thermal conduction through the metal housing of the outdrive to the water in which the outdrive, and indeed the boat, are immersed.




An outdrive usually is mounted on a pivot housing and/or gimbal ring to allow for steering, trimming (e.g., thrust angle), and tilt (e.g., for storage).




One example of an outdrive which uses a flexible power coupling member in the form of a belt is disclosed in Dunlap U.S. Pat. No. 3,951,096. Such outdrive has a metal housing with two separate hollow down legs to enclose the two respective legs of the belt. Such hollow down legs extend between the upper housing portion where a drive sprocket is located and the lower housing portion (sometimes referred to as the torpedo) where a driven sprocket is located. The driven sprocket is coupled to the propeller. The present invention includes a number of improvements that may be employed with such a belt driven outdrive.




Outdrives have included kickup features so that the outdrive kicks up or tilts out of the way when it strikes an object, such as a log, rock, lake bottom, etc. to avoid damages to the outdrive and/or other parts of the drive system or boat. Usually hydraulic cylinders having high pressure hydraulic fluid therein hold the outdrive, especially the propeller, at a particular trim angle to obtain a particular thrust angle for desired boat operation. If the outdrive strikes an object, hydraulic fluid in such cylinders is forced through small orifices to allow the outdrive to kickup out of the way of such object. The speed with which the fluid flows is a function of orifice size and fluid pressure, which in turn is a function of the force applied to the outdrive by the object struck.




U.S. Pat. No. 5,178,566, which is incorporated entirely by this reference, discloses an outdrive using a non-metal housing and a belt to couple power between the input and output. It has been found that energy losses may occur due to vortices generated within the oil between the belt legs and/or other unnecessary oil pumping actions. It would be desirable to reduce such losses. It also was found that belt tensioning sometimes was difficult; it would be desirable to improve belt tensioning techniques. It also was found that improved heat removal techniques would be advantageous.




Several other improvements to outdrives, such as the outdrive described in the '566 patent and other outdrives, also would be advantageous and are disclosed herein.




SUMMARY




Briefly, according to the present invention, a power coupling apparatus, such as an outdrive or the like, employs a housing structure that is generally less rigid than a conventional metal casting (although, if desired, in principle it could be made equally rigid), such housing being formed in part, for example, of plastic or plastic-like material, together with a number of features which cooperate to enable and/or to facilitate the use of such housing material in an outdrive. The housing structure and the various features according to the present invention are described in detail below and are particularly pointed out and distinctly claimed independently and in combination in various ones of the claims (if appended or subsequently drawn).




Another aspect of the invention is to employ techniques that enable use of plastic, polymer, resin or other materials that have similar properties as the material from which the housing and/or possibly other parts of an outdrive may be made.




According to one feature of the present invention, the housing, or at least a substantial portion of the housing, for an outdrive is a relatively lightweight material, and is non-corroding, such as a plastic material or plastic-like material. Compared to primarily metal housings for outdrives, a number of advantages inure to the use of plastic material, including, for example, lightness of weight, convenience and low cost of manufacturing using molding techniques, insensitivity to problems due to corrosion, galvanic action, receptivity of paint (such as anti-fouling paint without associated galvanic corrosion problems, bottom paint, etc.), as well as others.




However, compared to metal material, plastic material usually is more flexible and more susceptible to creep. Metal is stiffer and less susceptible to creep. Also, plastic material usually is less thermally conductive than metal, which therefore makes it unlikely that adequate heat removal by conduction through the outdrive housing into the water would be possible. Such flexibility may result in lack of adequate stability and/or accurate maintaining of relative placement and/or location of conventional outdrive parts, such as the gears, shafts, and/or other parts that affect coupling of power in a conventional outdrive.




According to another aspect or feature of the invention, the down leg or housing portion for an outdrive is made of thermally conductive material, such as aluminum or some other material; such material facilitates and expedites (e.g., makes more efficient) the dissipation of heat, which is generated or develops in the outdrive, to the water in which the outdrive is immersed.




According to a feature of the invention, an improved flexible power coupling is used to couple power in the outdrive to obtain an effective transfer of power, for example, between the drive shaft and the propeller shaft. Also, an improved housing including some thermally conductive material, such as metal, especially aluminum, is used as a part of the housing to provide heat dissipation and strength to maintain belt tension.




According to a feature of the invention, the flexible power coupling may be a belt, a chain, or an equivalent flexible member, which is not so sensitive to precision alignment as that required for conventional power coupling apparatus that employ gears and shafts. The flexible member will be referred to below as a belt for convenience. However, it will be appreciated that other flexible members, such as chains or equivalent devices, may be used in place of the belt according to the principles of the invention.




Another aspect is to back bend an endless loop flexible drive member during use, especially by using generally non-moving surfaces. Another aspect is to remove heat from a drive system using such a flexible drive member.




Another feature of the invention includes a technique for streamlining or reducing the profile of an outdrive that uses such a flexible coupling. Therefore, the outdrive will have an external appearance that is generally aesthetically pleasing in that it will be the same or similar to that of a conventional cast aluminum outdrive, for example. Also, the reduced profile improves the hydrodynamic characteristics, especially by reducing drag, compared to a large profile single leg housing that would be needed to contain the two belt legs, for example.




Accordingly, a technique is employed to bend or to urge the belt legs back toward each other in at least part of the down leg of the outdrive housing, i.e., that zone between the upper housing portion and the lower housing portion (torpedo). To effect such back bending back benders are provided in the housing, and the belt slides across the back benders which urge the belt legs toward each other. A lubricant, such as an oil material, may be used to reduce friction at the sliding interface between the back benders and the belt. It has been found preferable that the belt floats on a layer of oil, e.g., as in a journal bearing, rather than having direct surface-to-surface engagement with the back benders or like surfaces. Such back bending reduces the space required for the belt between the upper and lower housing portions and, thus, reduces the cross-sectional size dimensions or profile of the outdrive presented transverse to the travel direction through the water. Drag tends to be minimized while efficiency tends to be maximized.




To avoid vortices in the oil between belt legs during operation a fence or stuffer is between the belt legs, thus also reducing space where oil can exist in the drive and the volume of oil required for operation.




To remove heat from the outdrive is another feature of the invention, particularly since the preferred housing material usually would be less thermally conductive than prior metal housings. To remove heat whether the housing is plastic or metal, a portion of the housing at, near and/or including the back benders is thermally conductive and is at least partly immersed in water in which the boat is operating to conduct heat out of to the water. The oil constantly is scrubbed against the back benders which avoids boundary layers and enhances the thermal transfer from the oil to the back benders.




It also will be appreciated that a preferred embodiment of the invention is described in detail below. However, the scope of the invention is intended to be limited only by the scope of the claims and the equivalents thereof.




As it is used herein the term “plastic” means the conventional definitions of plastic, such as polymer material, synthetic material and so forth. Plastic includes both thermoset type plastic and thermoplastic. Plastic includes a material that preferably can be molded or laid up. It includes a material that will not encounter the types of corrosion and similar problems that may occur to a metal material. Usually a plastic material will be less stiff or rigid than metal, i.e., plastic typically is more flexible than metal. Plastic also usually has a greater tendency to creep than does a metal. Further, plastic often does not have as efficient a thermal conduction capability as does metal.




Various examples of plastic material may be used in accordance with the present invention.




Another aspect of the invention relates to a drive system including a power input shaft, a power output shaft, an endless loop flexible mechanism for coupling power between the shafts, the flexible mechanism having plural legs extending between the shafts, and a bending device for bending the endless loop flexible mechanism so that at least one of the legs is bent toward the other and a fence or stuffer in part of the volume between the two belt legs to reduce energy losses and/or oil requirements.




Another aspect relates to a technique for removing heat from an outdrive or the like which has in part a relatively non-thermally conductive housing and in part a thermally conductive housing.




Another aspect relates to a system for pretensioning a flexible drive member, such as a belt, chain or the like, including an eccentric mechanical support.




Another aspect relates to a mechanism for actively applying tension to a flexible member, such as a belt, chain or the like.




Another aspect relates to an improved muffler for an engine using an LC filter type effect.




It will be appreciated that the various features of the invention may be employed alone and/or in combination with other features in plastic outdrive systems and in other drive systems for boats and/or other vehicles.




The foregoing and other objects, features, advantages and embodiments of the invention will become apparent as the following description proceeds.




The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed. It is intended that the invention only be limited by the scope of the claims and the equivalents thereof.











BRIEF DESCRIPTION OF THE DRAWINGS




In the annexed drawings:





FIGS. 1A and 1B

are schematic illustrations of a boat and an inboard/outboard drive system therefor, including an outdrive according to an embodiment of the invention;





FIG. 2

is a front elevation view partly in section of the belt drive system with the back benders;





FIG. 3

is a schematic section view looking in side elevation showing the coupling of the outdrive to the transom of a boat;





FIG. 4

is a plan view of the outer transom housing;





FIG. 5

is a plan view of the inner transom housing;





FIG. 6

is a plan view of the gimbal ring and outdrive positioned in the outer transom housing;





FIG. 7

is a front elevation view of the gimbal ring in section;





FIG. 7A

is an enlarged side elevation-fragmentary view of the gimbal ring and upper rudder pin;





FIG. 7B

is a fragmentary bottom view of the gimbal ring and upper rudder pin of

FIG. 7A

;





FIG. 8

is a side elevation view of the gimbal ring in section;





FIG. 9

is a side elevation view, partly in section, of an upper sprocket assembly;





FIGS. 10 and 11

are, respectively, side elevation view, partly in section, and end view of a dynamic tensioning upper sprocket assembly;





FIGS. 12A and 12B

are, respectively, schematic illustrations depicting operation of the dynamic tensioning mechanism of the sprocket assembly of

FIGS. 10 and 11

;





FIG. 13

is a side elevation view, partly in section, of the lower sprocket assembly;





FIGS. 14

,


15


, and


16


are, respectively, side, front and back views of the outdrive housing;





FIGS. 14A and 16A

are, respectively, fragmentary side and back views of the bottom area of the outdrive housing showing a winged skeg arrangement of an alternate embodiment of the invention;





FIGS. 17 and 18

are, respectively, end and section views of the trim, tilt and kickup actuator assembly;





FIG. 19

is a side elevation view, partly in section, of a cone clutch assembly used with the upper sprocket assembly;





FIG. 20

is a schematic illustration of a locking mechanism to prevent inadvertent kickup of the outdrive power leg when operating to provide reverse thrust;





FIG. 21

is a schematic side elevation view, partly in section of another embodiment of outdrive with a hybrid housing;





FIG. 22

is an aft elevation view of the forward metal housing part of the hybrid housing;





FIG. 23

is an aft elevation view of the aft metal housing part;





FIG. 24

is a front elevation view of the aft metal housing part;





FIG. 25

is a front elevation view of the forward metal housing part;





FIG. 26

is a schematic plan view of a rotational shock absorber for the propeller shaft;





FIG. 27

is a side elevation view partly in section of the shock absorber of

FIG. 26

;





FIG. 28

is a graph of operation of the shock absorber;





FIG. 29

is a schematic view of an output shaft support for the propeller shaft;





FIG. 30

is a schematic partial isometric view of an anti-shear stuffer/fence;





FIG. 31

is a schematic partial view of a tooth profile of the belt;





FIGS. 32-34

are schematic views of a water bypass silencer;





FIG. 35

is a schematic view of a two stage LC muffler;





FIGS. 36 and 37

are schematic views of two embodiments of an eccentric tensioner, one is a dual piece and one is a single piece;





FIGS. 38 and 39

are schematic views of an active tensioner;





FIG. 40

is a broken away plan elevation view of the transmission looking aft;





FIG. 41

is a side elevation section view relative to the plan elevation view of

FIG. 40

of the transmission coupled to the outdrive; in FIG.


41


and subsequent drawings showing such side elevation views of the transmission in operative modes of forward, neutral or reverse, the views are not through straight vertical sections of

FIG. 40

, but rather are through sections sufficient to show the functional interrelation and operation of several parts which are angularly disposed about the transmission axis;





FIGS. 42-47

are schematic section views of a transmission and shift, respectively, in forward, reverse and neutral states, conditions or modes;





FIGS. 48-50

are schematic illustrations of the shift mechanism for the transmission; and





FIG. 51

is a schematic view of an exhaust thermal barrier.











DETAILED DESCRIPTION OF THE INVENTION




Introduction




Referring in detail to the drawings, wherein like reference numerals designate like parts in the several figures, and initially to

FIGS. 1A

,


1


B and


2


, a power coupling system


1


in accordance an embodiment of the present invention is illustrated coupled in a drive system


2


of a boat


3


(or other water craft). An exemplary waterline is represented at


4


near the bow


5


of the hull


6


of the boat


3


. The illustration of the boat is schematic and does not necessarily represent any specific boat or operational positioning or condition thereof, e.g., at rest, at slow or high speed, etc., relative to the water or otherwise. When the boat is at rest or is not at plane, the stern will be lower in the water than is illustrated, as is conventional.




The drive system


2


is of the inboard/outboard type, including a power supply


10


, an output mechanism


11


, the power coupling system


1


, and a housing


12


. The housing


12


provides functions of structural support, spacing and enclosing for the power coupling system


1


and the output mechanism


11


. As was mentioned above, the power coupling system


1


of the invention may be employed with other types of drive systems


2


for boats or other vehicles.




As is described in further detail below, the invention employs a number of novel features. Several of these include back bending of a drive belt


37


, a stuffer


500


(

FIG. 22 and 24

) to reduce energy losses, e.g., due to unnecessary pumping, cooling using a part of the housing that is thermally conductive substantially directly to the water in which the boat is immersed, and techniques for pretensioning the drive belt


37


. These and other features are described below. Furthermore, a number of features in combination can be employed in accordance with the invention to provide an efficient and cost effective power coupling system for a boat drive


30


or the like. Several exemplary advantages of using primarily plastic material in the power coupling system of a boat drive


30


include the elimination or reduction of corrosion problems, galvanic corrosion interaction caused by anti-fouling paints, due to stray electric currents, and/or other sources, and/or the like, facility and low cost of manufacturing, lightness of weight, and so on, to name but a few. The housing


12


may be a hybrid, e.g., plastic and metal, the metal portion designated


12




a


(in FIG.


21


).




Initially, reference is made to and an abbreviated description is presented here of the embodiments and features illustrated in

FIGS. 1-20

, which correspond to the disclosure in U.S. Pat. No. 5,178,566 which is incorporated by reference. Reference is made to the '566 patent for additional verbal description of such features which are only surveyed herein for brevity purposes. For convenience the same reference numerals are used in

FIGS. 1-20

herein and in the '566 patent. Additional improvements and features are subsequently described herein, particularly with respect to

FIGS. 22 through 51

.




Since a belt drive


31


is used in the power coupling system, the housing therefor can be made of plastic, which is less stiff than metal. Back bending the belt


37


, which is described in detail below, enables the power leg of the power coupling system, i.e., that portion which is in the water, for example, to have a relatively narrow profile or cross-sectional area transverse to the direction of travel through the water; and this characteristic improves hydrodynamics of the power leg, thus reducing drag in the water.




In the exemplary embodiment of the invention, then, the power supply


10


is an engine


13


. The engine has a drive shaft


14


which is rotated by the engine to provide power that ultimately causes rotation of the propeller


15


, which is mounted on a propeller shaft


16


.




If desired, although not necessarily preferred, a conventional transmission


17


may be included in the power coupling system


1


for the conventional purposes provided by a transmission. For example, the transmission may include reverse, neutral and forward gears to determine the direction of rotation of the propeller


15


and/or whether it rotates at all, as the drive shaft


14


is rotated. The transmission


17


also may include additional gears or other mechanism to change the ratio of the rotational speed of the propeller


15


with respect to the rotational speed of the drive shaft


14


. The transmission is shown in dotted outline in

FIG. 1A

because it is possible that such transmission may be omitted in the case that it is desired to have direct coupling of the engine


13


to the outdrive portion of the power coupling system


1


.




A clutch


18


also may be included in the power coupling system


1


of the drive system


2


. The clutch


18


may be a conventional clutch that serves conventional clutch functions. Exemplary clutches may be an automotive clutch, a dog clutch, or some other clutch of conventional or special design, as may be desired. The clutch


18


may be operated selectively to couple or to decouple the engine drive shaft


14


relative to the other parts of the power coupling system


1


. Coupling would be effected, for example, when it is desired to turn the propeller


15


in order to move the boat


3


. Decoupling would occur, for example, when the engine


13


is started, when it is desired to allow the engine


13


to run without turning the propeller


15


, when gears in the transmission


17


are shifted, etc.




The power coupling system


1


may be considered as including the drive shaft


14


, propeller shaft


16


, transmission


17


and clutch


18


, as those parts cooperate in the transmission of power from the engine to the propeller


15


. The power coupling system


1


also includes other portions, as will be described further below.




A number of controls


21


(and, if desired, displays) of conventional electrical, mechanical, hydraulic and/or pneumatic type (or other type), may be included to operate and/or to control various functions of the drive system


2


. For example, the controls


21


may be operated by the boat operator to start the engine


13


and/or to determine the engine speed. The controls


21


also may be coupled to the transmission


17


and to the clutch


18


to adjust gears and/or clutching functions in conventional fashion. Further, the controls


21


may be coupled to a power steering actuator which operates a tiller arm


22


to steer the boat. Still further, the controls


21


may be coupled to the power coupling system


1


to control trim and tilt functions, as are described in further detail below as well as locking to avoid tilting when driving in reverse. The controls


21


may include mechanical, electrical, hydraulic, and/or pneumatic controls and/or linkages, and so on, which are available to effect the desired control functions of the drive system


2


. The controls


21


, engine


13


, transmission


17


and clutch


18


may be mounted in the boat


3


in a conventional fashion and are operative, for example, in conventional fashion, to supply power in the form of rotational energy via the various other portions of an outdrive


30


of the power coupling system


1


to rotate the propeller


15


.




The Outdrive


30






A significant component of the outdrive


30


is the housing


12


, and according to an embodiment that housing is made of plastic material or of a material that has the characteristics of plastic material. Since plastic ordinarily is less stiff than metal, such as an aluminum housing, and tends to creep more than metal would, a belt drive assembly


31


is used to couple power from the upper housing portion


32


through the down leg


33


portion of the housing to the lower housing portion or torpedo


34


.




The belt drive assembly


31


includes a pair of upper and lower sprockets


35


,


36


and a flexible belt


37


, for example of rubber or polymer material, which is rotated about and between the sprockets


35


,


36


. The belt


37


runs in a chamber


38


in the housing


12


. A belt drive


31


, especially the belt


37


itself, is more forgiving as to positional alignment or tolerances than is a gear and shaft drive typically used in conventional outdrives. To avoid the need for two down legs, as is shown in the above U.S. Pat. No. 3,951,096, while minimizing the cross-sectional area of the down leg


33


required to house the legs


40


,


41


(

FIG. 2

) of the belt


37


and presented transversely of the direction of travel through the water, the belt legs


40


,


41


are bent toward each other. Such bending is effected by back benders


42


,


43


, which in the preferred embodiment are of metal material that have smooth surfaces


44


,


45


over, on, across, etc., which the belt


37


slides.




It will be appreciated that a belt


37


is but one form of flexible coupling member that may be employed in the invention, as was mentioned above. Preferably that flexible coupling member is in the form of a continuous loop or endless loop and is able to transmit rotary motion, torque, and, thus, power from the power input portion to the power output portion of the outdrive


30


. An exemplary belt


37


is sold by Gates Rubber Company under the model or brand Polychain, GT or GTX.




Heat may be developed in the outdrive


30


, for example by the belt


37


as it is bent and flexed by the back benders


42


,


43


and the sprockets


35


,


36


and as it slides on the back benders


42


,


43


. Heat also may be developed at other parts of the outdrive


30


, for example, at the respective sprockets


35


,


36


due to friction losses or the like. The back benders


42


,


43


may be metal plates to conduct heat to cooling liquid, e.g., water, flowing in contact with surfaces


47


,


48


in chambers


49


,


50


(FIG.


2


). Alternatively, the back benders


42


,


43


may be an integral part of the housing


12


a wall


46




a


,


47




a


as shown in

FIGS. 22

ans


24


, for example. The surfaces


46




a


,


47




a


are exposed to the external ambient, e.g., the water, (i.e., outside relative to inside the belt chamber


38


) to remove heat from the back benders


42


,


43


and, thus, from the outdrive


30


.




As is shown in

FIG. 2

, fluid


51


, for example, oil


712


, in the belt chamber


38


, which provides a lubricating function for the belt


37


and, if desired, for the sprockets


35


,


36


, transfers heat from the outdrive


30


to the back benders


42


,


43


, for example at the surfaces


44


,


45


. Whether the fluid


51


provides boundary lubrication or fluid film lubrication, e.g., depending on thickness of the lubricant between the belt


37


and back bender


42


,


43


surfaces


44


,


45


, it has been found that there is adequate heat transfer to the back benders


42


,


43


. The belt


37


tends to scrub the oil


712


against the back benders


42


,


43


to avoid boundary layers and to achieve good thermal transfer.




Preferably the back benders


42


,


43


are made of a relatively efficient thermally conductive material, such as metal, especially aluminum. Cooling flow


48


(

FIG. 1B

) of water in the outdrive


30


also may provide cooling for the outdrive


30


. The source of the cooling water flow


48


may be from the water in which the boat is immersed. For example, an opening in the housing


12


may provide an inlet for such water. The water flow


48


usually would have adequate cooling capacity after having removed some heat from the back benders


42


,


43


, so the flow paths (chambers)


49


,


50


, may be joined at


52


(

FIG. 1B

) and directed to couple the water flow to the engine


13


for cooling the engine in conventional fashion.




An exemplary trim, tilt and kickup mechanism provided the outdrive


30


is shown at


53


. Further details are described in the '566 patent. Other conventional trim, tilt and kickup mechanisms alternatively may be used.




The outdrive


30


is included in the power coupling system


1


and, for convenience, also may be considered to include the output mechanism


11


, namely, the propeller


15


. The outdrive


30


is mounted at the stern


70


of the boat


3


attached, for example, to a conventional pivot housing assembly and/or gimbal ring. The engine drive shaft


14


, or at least an extension portion


14




a


thereof on the output side of the clutch


18


(if such clutch, the transmission, or some other part(s) were used between the engine and the outdrive


30


), passes through an appropriate opening


71


in the stern transom


72


of the boat to couple rotary power to the outdrive


30


, as is described in greater detail below. Moreover, steering functions for the outdrive


30


are effected via the tiller arm


22


, which also is coupled to the outdrive


30


via an appropriate opening


73


in the transom


72


. Other connections such as for hydraulic lines, pneumatic lines, mechanical connections, and electrical connections, etc., also may be provided to the outdrive


30


via appropriate openings through the rear transom


72


of the boat or may be otherwise provided to the outdrive


30


, as may be desired.




The outdrive mounting structure


80


for mounting and supporting the outdrive


30


from the boat


3


is illustrated in FIGS.


1


and


3


-


8


, is described in detail in the '566 patent, and is summarily described below.




Referring to

FIG. 3

, a main gasket extends about the outer transom housing


84


facing the boat and prevents water leakage into the boat. The drive shaft


14


a passes through a gimbal bearing


91


, which is enclosed in a gimbal bearing housing


92


that is part of the outer transom housing; and the drive shaft


14


,


14




a


is covered by a water tight flexible boot


93


, for example, of rubber, at the connection thereof to the power input


94


for the outdrive


30


. The gimbal bearing housing


92


and boot


93


prevent water leakage at the drive shaft


14


a. The tiller opening


73


also is made water tight to prevent water leakage into the boat.




Continuing to refer to

FIG. 3

, mechanical power is supplied the outdrive


30


via the outdrive power input


160


, which includes a conventional universal joint


161


, the gimbal bearing assembly


91


, engine drive shaft


14


,


14


a as an input shaft, and a rotatable shaft


162


at the output side of the universal joint. The universal joint


161


is a conventional device having respective input and output connectors


163


,


164


, which are respectively coupled to the drive shaft extension portion


14


a and rotatable shaft


162


and are coupled to each other via the universal joint housing


165


. As is conventional, the universal joint


161


couples rotary motion between the input and output connectors


163


,


164


thereof while also permitting relative movement of those connectors in one or more planes and/or along one or more axes. The center of pivot of the universal joint


161


is located at the intersection of the rudder axis R and the tilt axis T. This arrangement permits freedom of rotation for the outdrive


30


about the rudder axis R and/or tilt axis T without interfering with the coupling of rotary power or torque through the universal joint


161


.




A power input chamber


170


of the housing


12


circumscribes the connector


164


of the universal joint


161


and part of the shaft


162


. The flexible boot


93


circumscribes the universal joint


161


and associated parts and is fastened between the outdrive housing


12


at the power input chamber


170


and the gimbal bearing housing


92


primarily to prevent water and dirt from entering the area


172


where the universal joint and associated parts are located. The flexible boot prevents water from entering such area


172


and from there gaining access into the boat. The flexible boot


93


permits the outdrive


30


to tilt about tilt axis T and to rotate about rudder axis R while still maintaining the function of enclosing the area


172


.




Outdrive


30


Power Leg


180






The outdrive


30


includes a so-called power leg portion


180


intended to transfer or to couple power received via the outdrive power input


160


to the propeller


15


. In the illustrated embodiment of the invention, the propeller


15


is a constant pitch propeller. Therefore, rotation of the propeller in one direction will tend to drive the boat forward and rotation of the propeller


15


in the opposite direction will tend to drive the boat in reverse direction. Reversing of the propeller


15


rotation direction can be achieved by appropriate adjustment of the transmission


17


. Alternatively, other means may be provided to change or to reverse the pitch, rotational direction and/or direction of thrust of the propeller


15


.




Upper Sprocket Assembly


35






One example of the upper sprocket assembly


35


, which is seen in

FIGS. 1

,


2


,


3


and


9


, includes a sprocket


181


having a plurality of teeth or grooves


182


intended to cooperate with the teeth


183


(shown in

FIG. 9

) in the belt


37


to move the belt


37


, such motion being referred to as rotation of the belt


37


, as the upper sprocket assembly


35


is turned. In this regard, the rotatable shaft


162


from the universal joint


161


is coupled to the upper sprocket assembly


35


to turn the same and, thus, the belt


37


. Various parts and operation of the upper sprocket assembly


35


and a dynamic tensioning mechanism therefor, e.g., as is illustrated in

FIGS. 10-12

, are described in further detail in the '566 patent.




The upper sprocket assembly


35


is mounted in the mechanical eccentric


901


described further below.




The various portions of the upper sprocket assembly


35


may be made of plastic material or of metal. For example, one or more of such parts may be made of various plastic materials so as to be relatively strong, relatively light in weight and not subject to corrosion. Preferably such parts can be made using relatively inexpensive methods, such as molding or extruding. The seal


191


may be of rubber, plastic or other material that provides an adequate sealing function for the described purpose.




Lower Sprocket Assembly


36






Referring to

FIGS. 1 and 13

, which are summarily described below and are described in further detail in the '566 patent, the lower sprocket assembly


36


, too, preferably is generally of a cartridge design mounted in the housing


12


by pairs of horizontal and vertical bosses


240


,


241


that form rails with respect to the upper sprocket assembly


35


. The lower sprocket assembly


36


includes a sprocket


242


that has a plurality of teeth


243


which mesh with the teeth


183


of the belt


37


. The diameter of the lower sprocket


242


is generally larger than the diameter of the upper sprocket


181


and the sprocket assemblies


35


,


36


have a correspondingly different number of teeth. Therefore, a rotational speed reduction is effected between the rotatable shaft


162


and the propeller


15


due to the ratio of the diameters and number of teeth on the respective sprockets


181


,


242


. Using different ratios, different speed reduction effects can be obtained without using additional gears, transmissions, or the like. Of course, if desired, a 1:1 ratio of diameters and teeth also may be used. Further, if a non-toothed belt


37


were used, the sprockets


35


,


36


preferably would not have teeth. Preferably the space between teeth on the upper and lower sprockets


181


,


242


is about the same and the ratio of the number of teeth on the larger to the smaller is from about 2:1 to about 1:1; and more preferably from about 1.7:1 to about 1.5:1. In an example, the lower sprocket


242


may have on the order of


39


teeth and the upper sprocket


181


may have on the order of


22


teeth. Using the sprockets to effect a reduction in speed between the rotatable shaft


162


and the propeller


15


provides a desired speed reduction of the type accomplished in the past by conventional gears in prior art outdrives.




The sprocket


242


is supported for rotary motion by a pair of bearings


244


,


245


, which are secured in position in the manner illustrated by respective cartridge housing portions


246


,


247


and generally in the manner described above with respect to the upper sprocket assembly


35


. The lower sprocket


36


preferably is fixed and does not move for adjustment. At the rear end of the sprocket


242


are a pair of seals


250


which circumscribe part of a stepped-down diameter output shaft portion


251


of the sprocket


242


to prevent water from reaching the bearing


244


and/or other interior portions of the sprocket assembly


36


and the belt chamber


38


. The seals also help to prevent lubricant or other fluid material intended to be in the belt chamber


38


from leaking out. The propeller


15


may be mounted directly onto the output shaft portion


251


of the sprocket


242


, for example, by using a threaded fastening connection, a conventional screw fastener, or adhesive material placed at the interfacial area


253


of connection between the propeller


15


and the shaft


251


. Other means also may be employed to secure the propeller


15


onto the shaft


251


.




It will be appreciated, then, that as the engine produces a rotary output, which is coupled by the drive shaft portion


14




a


to the universal joint


161


, the upper sprocket


181


is rotated to cause the belt


37


to be rotated. As the belt


37


is rotated, the lower sprocket


242


is rotated, which then turns the propeller


15


.




Variable pitch and reversible pitch propeller


15


, external features of the outdrive


30


, trim, tilt and kick up features of the outdrive


30


, cone clutch sprocket assembly, and tilt lock mechanism (to avoid tilting when operating in reverse) are shown in

FIGS. 14-20

and are described in greater detail in the '566 patent.




Back Benders


42


,


43






It is desirable that an outdrive


30


have a relatively small cross-sectional area transverse to the direction of travel through the water. See

FIGS. 2

,


15


and


16


. A potential disadvantage in using a belt


37


or other flexible member which has two legs


40


,


41


is that space is required to house each of the belt legs


40


,


41


. In the past such space requirement would have required a relatively broad cross-section or two down legs


33


as in the above Dunlap patent.




However, it has been discovered in accordance with the present invention that the belt


37


can be bent backwards to compress the legs


40


,


41


thereof toward each other in a way that tends to minimize the cross-sectional area profile of the outdrive


30


transversely to the direction of travel through the water.




The surfaces of the back benders


42


,


43


may be bent or curved in the manner illustrated so as to form a segment of an arc of a circle. Such circle preferably if extended would be tangent or approximately tangent with the travel direction of the belt


37


about the lower sprocket


242


. The back benders


42


,


43


may be of other shape.




A lubricating medium


51


, such as oil, transmission fluid, gear oil, or the like, is in the belt chamber


38


. The belt chamber


38


is coupled to a sump


320


, which extends from the bottom of the lower sprocket


242


part way up along the sides thereof, between the belt


37


and the housing


12


, as is illustrated in FIG.


2


. It has been found that an adequate amount of lubricant is available when the sump


320


is filled to a level that is less than about one-half the diameter of the lower sprocket


242


. Preferably the fluid


51


is relatively light weight, such as 5 weight or 10 weight. Preferably the fluid provides the lubricating functions and thermal conduction functions described herein. Moreover, it is desirable that the fluid be functional to reduce both static friction and dynamic friction occurring in the outdrive


30


.




Transmission




The transmission


930


, which may be used for the transmission


17


of

FIG. 1A

, may be made at least in part out of powdered metal parts, relatively inexpensive parts. The reason is that, it usually spends from 95% to 98% of its life in forward or neutral. In forward or neutral, none of the gears are in motion. They are placid. So most of the time the gears are not used for anything. The only time they are used for anything is when going backwards. One ordinarily does not go at full power in reverse.




Turning to

FIGS. 21-23

, another embodiment of outdrive


30


′ uses an hybrid housing


12




a


. The hybrid housing


12




a


has a metal portion


701


and a plastic or polymer portion


702


. The metal


1


portion


701


is selected of a material that is a relatively good conductor of heat compared to the material of which the polymer portion


702


is formed. Using a metal housing portion


701


, including at least a part of which is exposed to the water in which the outdrive


30


′ is immersed, the removal of heat developed in the outdrive


30


′ during operation can be facilitated, expedited and enhanced. Such heat may be transmitted directly through the metal housing portions


701


into the water in which the outdrive


30


′ is immersed. The proportion of the outdrive


30


′ of which the metal housing portions


701


is constituted may vary, depending on the amount of heat required or desired to be transferred through the metal housing portion


701


and dissipated into the water, temperature considerations, and so forth.




The metal housing portions


701


may be, for example, aluminum, which has good strength, relatively light weight, and other desirable properties, such as resistence to corrosion, especially when appropriately coated or painted, and so forth. Other metal materials also or alternatively may be used. Furthermore, materials that are other than metal or may include metal and something else may be used provided such material provides the desired heat conduction properties and, of course, strength characteristics.




In the embodiment of outdrive


30


′ illustrated in

FIGS. 21-23

, the metal housing portion


701


is formed in two parts


701




a


and


701




b


, which may be bolted together or otherwise sealed together along a parting line


703


. A chamber


38


is located in the metal housing part


701


and the belt


37


moves in that chamber as was described above to transfer power from the engine drive shaft


14




a


via the universal joint


161


to the propeller shaft


16


and propeller


15


.




The polymer housing portion


702


may be made out of various polymer, plastic, resin, or other materials. Preferably such materials are sufficiently strong to maintain shape, but usually such materials as used in conjunction with the hybrid housing


12




a


do not require the strength necessary to support tension of the belt


37


and stiffness for the down leg


33


′ of the outdrive


30


′ to maintain the shape thereof as power is transmitted to the propeller


15


and the boat to which the outdrive


30


′ is attached is propelled. In the illustrated embodiment of

FIG. 21

, for example, the polymer housing part


702


includes a cover


702




a


for the aft part of the outdrive


30


′, leading cover portions


702




b


at the forward end, and various other trim portions, etc.




The hybrid housing


12




a


has a hydrodynamic body that has a profile, shape, etc. similar to conventional outdrives


30


′, such profile being established by the combination of the metal housing part


701


and the plastic housing part


702


. The hybrid housing


12




a


is a structural component of the outdrive


30


′; it carries the load of the tension on the belt


37


as well as the weight of the outdrive


30


′ itself. For example, the tension on the belt


37


may be in the neighborhood of 800 to 1,000 pounds and the overall force on the housing


12




a


may be approximately 1,600 pounds when not immersed. The recommended amount of tension that the belt manufacturer suggests is about 2,800 pounds for the belt


37


mentioned elsewhere herein. Thermal expansion of the housing


12




a


and thermal contraction of the belt


37


(mentioned above) further increases the load. Adjustments may be made to accommodate such expansion and contraction characteristics while still avoiding excess belt tension beyond that recommended by the belt manufacturer. If the housing


12




a


of the down leg


33


′ were primarily or exclusively plastic material, it is possible that some additional skeletal components inside the housing


12




a


may be required to increase structural load strength. However, the housing


12




a


using a metal housing part


701


ordinarily adequately supports the forces mentioned above without additional skeletal support components, although these may be added if desired.




In an embodiment of the invention illustrated in

FIG. 21

, the outdrive housing


12




a


uses about 60% polymer housing part


702


and about 40% metal housing part


701


. These are exemplary numbers only and may vary widely depending on thermal transfer requirements for a the outdrive


30


′. For example, the polymer housing part


702


may be from 20% to 80% and the metal housing part


701


may be from about 80% to about 20% from the housing


12




a.






The back benders


42




a


,


43




a


of the hybrid housing


12




a


are integral with the metal part


701


. Thus, the surfaces of the back benders


42




a


,


43




a


in engagement with respective legs of the belt


37


actually are surfaces of the metal housing part


701


. Those surfaces are at the areas where the lead lines associated with the respective back bender reference numerals


42




a


,


43




a


point.




The belt


37


is moved in the chamber


38


by the upper sprocket


710


, which in turn is rotated directly or indirectly by the engine. The belt


37


turns the lower sprocket


711


. The lower sprocket


711


is coupled to the propeller shaft


16


to turn the propeller


15


. Oil


712


is in a sump area


320


, for example, similar to the oil


712


and sump arrangement described above with respect to FIG.


2


. The purpose of the oil


712


is to lubricate the belt


37


as it rides against the back benders


42




a


,


43




a


and also to lubricate the bearings


245


in the down leg


33


′, for example, those associated with the respective sprockets


710


,


711


. The oil


712


lubricates the back of the belt


37


and the combination of the back benders


42




a


,


43




a


, the oil


712


and the belt


37


is similar to or like a journal bearing. Test data has shown vary little wear between the belt


37


and the back benders


42




a


,


43




a.






In addition to providing a lubricating function, the oil


712


transfers heat to the back benders


42




a


,


43




a


. The heat is transferred by conduction through the metal housing part


701


to the exterior surfaces


46




a


,


47




a


for dissipation and transfer into the water in which the down leg


33


′ is immersed. Thus, the metal housing part


701


serves as a heat exchanger for the oil


712


. The oil


712


forms a film between the back benders


42




a


,


43




a


and the belt


37


and the heat from the oil


712


which is engaged with the back bender


42




a


,


43




a


wall surfaces is conducted directly into the metal housing part


701


for dissipation out through the surfaces


46




a


,


47




a


into the external water, thus providing a good heat transfer capability.




On the back side of this belt


37


are some transverse ribs. Those transverse ribs end up being bearing pads. There is oil


712


trapped in between pads, so the belt


37


transports oil


712


like a pump. The oil


712


is trapped in between the pads and is scrubbed at very high velocity over the cool surface of the back benders


42




a


,


43




a


. There is no boundary layer because the boundary layer is mechanically scrubbed away and as a result there is good heat transfer.




It will be appreciated that the metal housing parts


701


is a very efficient heat exchanger, having the back benders


42




a


,


43




a


having the oil


712


contact with the back benders


42




a


,


43




a


and also having the external surfaces


46




a


,


47




a


in direct contact with the water going by the boat so that heat is easily dissipated by conduction through the housing to the outside water to which the boat is immersed. Usually when the outdrive


30


′ is running and the boat is moving through the water, about 40% of the housing


12




a


is submerged so that there is a relatively large amount of the surface area


46




a


,


47




a


that is in such direct contact with the outside water.




It will be appreciated that the back benders


42




a


,


43




a


and the surfaces


46




a


,


47




a


preferably are of good heat conducting material, such as the mentioned metal, especially aluminum or some other metal material. The upper portion of the metal housing part


701


, such as that portion which is ordinarily not submerged, may be made of a material other than metal, such as plastic, for example, as such upper portion ordinarily does not have a primary heat transfer function as the lower portion.




Stuffer


500






A fence or a stuffer


500


is in the chamber


38


between the two legs


40


,


41


of the belt


37


. The stuffer


500


may be of metal, plastic or some other material. Primarily the stuffer


500


is located at the lower portion


701




c


of the metal housing part


701


, as is seen most clearly in

FIGS. 22 and 24

. It may be bolted to one or both metal housing parts


701




a


,


701




b


; it may be in one piece or split, e.g., along a common split line or plane with the housing parts


701


a,


701


b.




At such lower portion


701




c


of the metal housing part


701


, oil


712


tends to be pumped and moved by the belt legs


40


,


41


. The stuffer


500


serves as a fence or as an anti-shear device to prevent shearing effect (vortices) between oil


712


drawn up by one belt leg


40


,


41


relative to oil


712


drawn down by the other belt leg


41


,


40


. Further, the stuffer


500


takes up space in the chamber


38


where the oil


712


is providing its lubricating and heat removal functions in association with the belt


37


and back benders


42




a


,


43




a


, and, therefore, stuffer


500


displaces some of the oil


712


and, accordingly, reduces the volume of oil


712


required to provide the indicated functions.




It was found in the past that vortices were created in the oil


712


located between the belt legs


40


,


41


, particularly due to the mentioned shearing effect at the lower portion of the metal housing part


701


and/or due to unnecessary pumping of the oil


712


. Such vortices tended to waste energy and to create heat, which resulted in an energy loss for the outdrive


30


′. The stuffer


500


eliminates those losses by taking up a portion of the space between the belt legs


40


,


41


and by at least in part isolating those legs


40


,


41


from each other so the opposite direction pumping action occurring as the two legs


40


,


41


move in opposite directions do not confront each other and create vortices.




During operation of the outdrive


30


′ shown in

FIGS. 21-25

, oil


712


will come down along one of the back benders


42




a


,


43




a


, being drawn by the teeth of one of the belt legs


40


,


41


. The oil


712


also will come down between the belt leg


40


,


41


and the stuffer


500


and will be introduced into the area of the sump


320


and be introduced in the area between the lower sprocket


711


and the belt


37


. The oil


712


that gets between the lower sprocket


711


and the belt


37


will be squeezed out of the way so that the belt


37


can fit onto the sprocket


711


as it goes around. This is a pumping action that preferably is starved by reducing the amount of oil


712


in the sump


320


and also by making it difficult for oil


712


to get to the sump


320


, the stuffer


500


providing that function. The stuffer


500


also helps to reduce the amount of oil


712


that is in the area between the two belt legs


40


,


41


in the lower half of the metal housing part


710


and also which reaches the upper half of the metal housing part


711


in the chamber


38


above the portion of the back benders


42




a


,


43




a


and stuffer


500


are located. By reducing the amount of pumping required and the amount oil


712


, losses are reduced, too.




In an embodiment of the invention, there is a clearance of about 0.030″ between the stuffer


500


and the closest confronting surfaces (the flats of respective belt teeth


183


, for example). This is only one example and other clearances also may be provided. Test data has shown that oil


712


in the outdrive


30


′ of

FIGS. 21-25

tended to heat relatively rapidly without the stuffer


500


in place. However, using the stuffer


500


to reduce the amount of oil


712


in the chamber


38


and, thus, reducing the work being done on that oil


712


, the temperature rise in the oil


712


was reduced.




Tests were conducted of an outdrive


30


′ in accordance with the invention using a belt


37


that has a 4″ width and rated to run approximately at a rating of about 250 horsepower. The outdrive


30


′ was run satisfactorily for about five or six hours while being driven by an engine rated at 250 horsepower.




It will be appreciated that in the embodiment of outdrive


30


′ illustrated in

FIGS. 21-25

, at least a portion of the hybrid housing


12




a


of the outdrive down leg


40


,


41


is metal, such as aluminum, or other thermally conducted material that is relatively strong and sufficiently stiff to support the belt


37


. The amount of surface area presented by the metal housing portion


701


is sufficient to dissipate the heat that is a product of the losses in the outdrive


30


′. It will be appreciated that other means will be used to dissipate heat from the outdrive


30


′, such as using the cooling functions behind the back benders


42




a


,


43




a


, as is described with respect to the flow chambers


49


,


50


and flow passages


332


,


333


in the embodiment illustrated in FIG.


2


and described above. As another alternative, the housing part


701


may be made of a material other than metal, provided the material has sufficient strength and stiffness characteristics for the intended mechanical functions and suitable means are provided to dissipate heat. One example is the use of a thermally conductive polymer. However, most modern thermally conductive polymers have metal plates in them, and those plates may corrode, which may make such materials unuseful in the invention. It is anticipated that in the future there may be a polymer that will have sufficient thermal conductivity without corrosion, which may be used for the metal housing part


701


. Another embodiment may utilize a plastic or polymer housing for the metal housing part


701


. Such housing having metal or other thermally conductive pads or plates on the outside surfaces analogous to the surfaces


46




a


,


47




a


to conduct heat to the exterior water. Bolts, rivets or some other means may be used to connect the back benders


42




a


,


43




a


to such plates thereby to conduct heat from the back benders


42




a


,


43




a


to the plates for such dissipation.




Still other embodiments of housing for dissipating heat energy may include a plastic housing substituted for the metal housing part


701


, for example, and having passages through the housing wall to allow oil


712


to engage a metal plate outside the wall; the oil


712


transfers heat to the plate, and the plate transfers the heat to the water in which the outdrive


30


′ is immersed. Alternatively, the plate may replace the plastic part itself. Still further alternatively, a part of the plate may extend through the mentioned passages or be coupled to thermally conductive bolts, rivets or the like to transfer heat from within the chamber


38


to the exterior water.




Additional cooling may be provided by the water


48


flowing directly through the housing


12




a


. For example, as is described above, a water intake is provided for water


48


to flow into the housing


12




a


(see

FIG. 1B

) such inflow of water


48


may be directed through a flow passage


720


(

FIG. 25

) for delivery via a fluid conductor port


721


to the water pump (not shown) associated with the engine


13


(FIG.


1


A). The water


48


may be used to cool the engine. The water


48


may also provide a cooling function for at least part of the outdrive


30


′ through which the water


48


flows. The water


48


, after having provided the engine cooling function, may be discharged through the exhaust flow path of the engine.




It is desirable to pretension the belt


37


so the belt


37


does not become slack and start skipping teeth as the belt


37


enters the sprocket


710


,


711


or so the belt


37


does not try to climb over teeth. The manufacturer of the belt


37


mentioned herein ordinarily recommends a specific pretensioning of the belt. However, it has been found that the outdrive


30


′ having the configuration, geometry, and/or conditions, e.g., using back benders and oil as illustrated in

FIGS. 21-25

runs better with about 50% of that recommended pretension. Further, it has been found as the metal housing part


701


, especially such a part made of aluminum, heats up, the belt tension tends to increase because the housing


701


expands and grows in length; therefore, the center to center distance between the sprockets


710


,


711


increases. Furthermore, although many materials expand (get longer) as they heat, the exemplary belt


37


mentioned herein includes Kevlar cord material, which tends to shorten or to shrink in length as it heats. Kevlar material has a negative coefficient of thermal expansion. Accordingly, not only does the housing


701


swell (expand with the heat), but as the expanded housing increases the center to center distance between the sprocket


710


,


711


, the belt


37


is shrinking. Therefore, it has been found better to pretension the belt


37


at a lower level for the exemplary belt


37


thereby to accommodate such housing expansion and belt contraction.




Back Benders


42




a


,


43




a:






Back benders


42




a


,


43




a


are considered fundamental to the employment of belt technology. Not only do they cause the drive


30


′ to have a hydrodynamically clean profile, but they act significantly as a heat exchanger to cool the drive


30


′.




Cooling Method:




The Patent specifically teaches the use of oil


712


not only as a lubricant to reduce the friction in the drive


30


′, but as a heat transfer medium in conjunction with the action of the back benders


42




a


,


43




a


. Oil


712


, which is trapped between the back benders


42




a


,


43




a


and the belt


37


is scrubbed against the surface of the back benders


43




a


,


43




a


and is forced to give up its heat by virtue of this action. We have found that cooled back benders


42




a


,


43




a


are virtually transparent to heat, causing temperature differences between the coolant surface and the oil temperature of only a few degrees. Coupled with a reasonable velocity of water at the coolant surface, this heat exchange configuration is extremely effective. The prototype drive


30


′, currently running at about 205 hp, has an oil temperature of approximately 30-degrees F above the water temperature. This means that at twice that power, say 410 hp, the temperature rise would be on the order of 60-degrees F. For water temperatures of 90-degrees F (Amazon River water), an extremely high and unlikely temperature, the belt


37


would be reaching oil temperatures of 150-degrees F, well within the operating limitations of this belt


37


.




Active Tensioning:




The Patent specification teaches the need for an active tensioning device when a belt


37


is used with a composite or plastic housing


12




a


. Belts


37


used for transmitting high horsepower will require operating tensions of very large proportion. Tensions on the order of 3,000 and 4,000 pounds are not unusual. If these tensions are applied passively to the drive


30


′, the housing


12




a


will have to resist this tension, not only during operation, but permanently around the clock. Such large forces sustained continuously by a plastic member, during storage, possibly at elevated temperatures, will cause distortion and creep of the material. Since these belts


37


are very stiff, a small change in center distance will cause a substantial change in pretension, degrading ultimate performance.




Rotational Shock Absorber (

FIG. 26

)




When clutching the drive transmission, either into forward or reverse gears; and, especially, when going directly reverse to forward, a large rotational energy spike must be accormmodated. This is true particularly when using clutches with little or no slip as in dog clutches or cone clutches. This energy spike will cause very large stresses to occur that could ultimately break the drive


30


′. In the past, energy absorbing rotational couplings have been used at the input and output ends of the drive


30


′. This coupling employed room between the flywheel and the drive


30


′ in the bellhousing area and in the hub of the propeller


15


. Calculations have shown, that for these absorbers to be effective, an active rotation within the absorber of about ±20-degrees is necessary. Since shaft drives are much stiffer than this, energy absorbers are necessary. So too, belt drives


31


prove to be too stiff, absorbing only about one fourth of the rotation necessary for good shock attenuation.




The rotational shock absorber mechanism of

FIGS. 26-28

accommodates the above difficulty. Essentially, a closed four (4)-vane pump


750


is housed in the output sprocket


711


. This is the ideal location for the absorber because the reduction ratio of the drive


30


′ enhances its effectiveness. This location for the absorber also precludes the necessity for a compliant hub in the propeller


15


, making that element less costly to manufacture. Additionally, this location for the absorber frees up space behind the flywheel to accommodate a transmission mechanism.




The four (4)-vane pump


750


shown in the accompanying drawings is sealed and filled with a heavy oil


712


. Oil is pumped from one side of the vanes


751


to the other through a variable restriction


752


on the end plates. This restriction can be tailored to allow various characteristics; however, generally, it is designed to give increasing resistance to rotary motion with increasing rotational displacement. At the extremes, ±20-degrees, the chambered oil


712


has been displaced and the rotor


753


and stator


754


are bottomed and locked in rotational engagement. When torque is removed, as in shifting the drive transmission through neutral, a torsional spring


755


restores the rotor


753


to a central position arming the absorber for the next cycle. Since this device is rotationally symmetrical, shifting shocks will be attenuated for either forward or reverse cycles.





FIG. 28

shows a graphical representation of the operational characteristics of the rotational shock absorber.




Output Shaft Support


760


(

FIG. 21

)




When the propeller


15


strikes a foreign object, it has been found by calculation, that peak stresses on the output shaft


251


of a typical gear-driven outdrive


30


′ occur somewhat inboard of the aft bearing.




Also, with the large loads applied by belts


37


, it has been found desirable to keep the shaft support bearing close to the output sprocket


710


,


711


. With this configuration, peak stresses from a propeller strike occur at approximately the same place, as the geared shaft with an outboard bearing.




In order to make the shaft


16


less vulnerable to bending from a propeller strike, a deflection limiter


760


was constructed. This device bolts at


761


to the main housing


12




a


and continues aft to just before the propeller flange


16


. The output shaft


251


passes through this truncated conical member


760


and has a clearance


762


large enough to allow normal running deflection, but small enough so that shaft


16


deflection will be limited to lower than shaft material yield strengths. A drain hole


763


is provided at the forward bottom to prevent water entrapment when the drive


30


′ is out of the water.




A second function of this device


760


is that of a structural washer to capture the after plastic housing


702


at


764


(see FIG.


21


).




A third function is that the device


760


is manufactured from an aluminum material and not protected such that it acts as a sacrificial anode surrounding the cathodic stainless steel shaft


16


. In this manner, the main housing


12




a


, and especially the metal housing part


701


structure is protected from the major source of galvanic corrosion, the shaft


16


, and potentially, the propeller


15


, if it is also stainless steel.




Anti-Shear Fence/Stuffer


500


(

FIG. 30

)




It was found through calculation and observation that two mechanisms contribute to the energy loss resulting in rapid oil temperature rise.




First, the belt


37


being urged together by the back benders


42




a


,


43




a


, has a down-going side and an up-going side in close proximity. Oil


712


that is in the middle of the belt


37


sees a shear from these belt legs


40


,


41


. The result is a suspended vortex which has no circulation; and, therefore, is not cooled by the back bender


42




a


,


43




a


. The shear losses in this trapped vortex cause the temperature to rise rapidly.




Secondly, oil


712


trapped in the down-going leg


40


,


41


of the belt


37


is forcibly displaced by the sprocket


711


teeth and is pumped laterally out of the interstices. This loss mechanism also seems to be affected by the amount of oil


712


in the drive


30


′. That is, more oil


712


yields more losses.




It is desirable to have sufficient oil


712


in the drive


30


′, say one or two pints, so that frequent oil change is not necessary. The above results demanded that oil


712


be kept to a minimum, say one-half pint. The fence or stuffer device


500


was designed that could hold oil inventory out of direct engagement with the drive


30


′, and eliminate the shear loss at the same time minimizing the tooth-pumping losses. The fence also may be a two (2)-piece hollow thin-walled vessel, open at the top and capable of holding oil


712


.




The fence


500


fills the space between the belts


37


from approximately halfway down the down leg


33


to the bottom sprocket


711


. A controlled leak


501


at the bottom near the up-going belt leg


40


,


41


allows the oil inventory to circulate. The open top


502


accepts replenishment oil


712


. This design accomplishes all the objectives set above. The shear vortices are eliminated, the oil content


712


trapped in the teeth is minimized, and an extra amount of oil


712


is inventoried not in direct involvement with the belt


37


.




Sprocket Tooth Profile (

FIG. 31

)




A Sprocket Tooth profile is illustrated in FIG.


31


. The profile has been proven, having been used in test drives. Excellent belt wear and performance have resulted. The resulting profile can be described as a series of arcs with prescribed centers and tangencies. The accompanying drawing shows this design. This profile is exemplary and may be modified, especially to accommodate varying numbers of teeth.




Power Steering Eliminator




Present practice uses power steering on all outdrives


30


′ coupled with engines over 150 hp. The reason for this is that at the higher horsepowers; and, typically, at higher speeds, say 50 mph, the propeller


15


is ventilated by separation of the water at the down-leg strut. The separation entrains air and this aeration causes a difference in the propeller effectiveness above the rotational center as opposed to below the rotation center. The effective density of the water is larger below center than above. Accordingly, the propeller


15


will produce a side thrust acting as a paddlewheel, causing the drive


30


′ to be displaced laterally. This lateral displacement forces the boat into a turn not intended by the pilot of the vessel. Forces are great enough to make manual correction uncomfortable and; hence, power steering is widely used.




A significant change in the above characteristics can be achieved directly as a result of the use of back benders


42




a


,


43




a


, for example. As can be appreciated, the lateral profile of the drive


30


′ disclosed herein just beneath the ventilation plate is significant to the above phenomenon. With current outdrives


30


′, this thickness, when compared to the hydronamic chord at this location yields thickness-to-chord ratios of between 13 percent and 15 percent. The use of gears, shafts and vertical bearings demand sufficient thickness to accommodate them. As a consequence, the downleg is thicker just before the ventilation plate than an equivalent belt drive


31


with back benders


42




a


,


43




a


. In fact, back bender


42




a


,


43




a


geometry dictates that this location


780


(FIG.


22


), just below the ventilation plate


781


, is the minimum thickness, yielding the optimum condition to combat the side thrusts inherent in present outdrives


30


′. A prototype drive


30


′ has a thickness-to-chord ratio of less than 10 percent. This geometry is sufficient to eliminate all side thrust due to the separation phenomenon and preclude or reduces the necessity for power steering—a significant cost savings.




Water By-pass Silencer


790


(

FIGS. 32-34

)




Common practice for outdrives


30


′ is to provide a passage, near the junction of the y-pipe as the exhaust passes through the transom housing to eliminate most of the water entrained in the exhaust. This is desirable since the entrained water increases the backpressure through the outdrive


30


′ and causes net power losses. Also, this By-pass allows some portion of the exhaust gas to escape, further reducing the backpressure and enhancing the power available.




A negative side effect of this feature is that the exhaust noise also escapes here and is reflected by the transom. This reflection acts as a concentrator causing a large increase in noise when the boat is going away from the recipient. The noise inside the boat is also affected by this feature.




A water-bypass silencer device


790


shown in

FIGS. 32-34

can by-pass water without the accompanying noise problem. In fact, this device has means of tailoring the fraction of water removal so that an ideal amount of water still remains entrained without causing exhaust backpressure. The device


790


consists of a tubular extender


791


which carries the exhaust vertically downward close to the surface of the water while the boat is on plane and underway. Here, the exhaust admixes with the turbulent water surface and any noise generated dissipates substantially before any reflection from the hard transom surface can occur.




Some portion of the tubular member


791


protrudes into the main exhaust channel causing a portion of the water to by-pass this exit. Since the location of this device


790


is substantially a low area in the main exhaust passage, and since the water-laden exhaust gases have just made a sharp turn after traversing vertically downward through the “y” pipe, a substantial portion of the water will accumulate at the bottom of this exhaust passage. Given that the device


790


extends vertically upward, somewhat into this passageway, a portion of the water by-passes this exit and become re-entrained further downstream. Small holes


792


in this protrusion adjust the amount of water that escapes here. Water that is carried through the drive


30


′ greatly enhances the muffling effects within the powerleg, but also contributes to the drive's


30


′ cooling load. Exhaust water at about 160-degrees F is generally 50-degrees hotter than the drive


30


′; so when less water is passed through, the drive


30


′ runs cooler.




Various shapes and geometries have been tested. Present designs have demonstrated considerable effectiveness. Tests have shown a cockpit attenuation of


2


d


b


down and a goingaway attenuation of a huge


10


d


b


down! Passby testing at 50 feet shows attenuation on the order of


6


d


b


! Additionally, the noise spectrum is modified to yield a much more pleasant to the ear noise, making the


2


d


b


cockpit attenuation more significant than the meter reading would indicate. One such design is shown in the accompanying drawings. The down leg


791


is attached to a flange


793


having holes


794


. Bolts


795


through the holes


794


can attach the device


790


to the drive


30


′ at the “y” pipe as described.




L C Exhaust Silencer (

FIG. 35

)




The design of a muffler system for an internal combustion engine for marine use must accommodate two conflicting requirements. First, the noise resulting from exhaust pressure pulsations produced by the engine must be strongly attenuated to accommodate the limits set in accordance with use or legislation. Second, the exhaust manifold pressure rise resulting from exhaust gases flowing through the muffler system must be small enough so that engine output is not adversely affected appreciably. Small diameter piping gives good noise control, but restricts engine power. Conversely, open piping yields good engine power, but provides little noise control. However, very satisfactory results can be obtained in both areas by following the approach described here, which uses inertial effects to limit the transfer of acoustic power.




Referring to

FIG. 35

, to first order, the exhaust header and piping system


800


for a marine engine constitutes a volume


801


, usually amounting to a few hundred cubic inches in modern sport boat applications, into which interrupted hot exhaust gas flows


803


are introduced by the engine at repetition rates generally in the 20 to 200 Hz range. Flows of hot exhaust into the header can amount to several cubic feet per second. Although usually cooled by injected water, the outlet flows


805


through the remainder of the exhaust system


800


still can amount to a few cubic feet per second.




To prevent objectionable header pressures from developing as a result of these large flows through a muffler


800


, the minimum passage cross sections inside the muffler


800


must be at least a few square inches. The upstream pressures developed by gases entering a passage from a chamber within a muffler


800


are dynamic in nature and principally result from the acceleration of the gas. Very little of that pressure rise can be recovered when the gas leaves the passage and decelerates, however, so it is important to limit the number of serial accelerating restrictions within a muffler


800


to limit the total header pressure rise resulting from the exhaust flow.




Considering the header and exhaust pipe volume, and the volume of gas


803


which enters that exhaust system volume during the blowdown through an engine exhaust valve, it is clear that the resulting header pressure rise will be less than the engine cylinder pressure was immediately before blowdown by approximately the ratio of the cylinder volume divided by the header and piping volume. Therefore, the first feature one should incorporate in the design of a muffler system


800


is to make the header plus piping volume large as compared to the engine individual cylinder volumes. If the ratio of the header plus piping volume to the engine cylinder volume is too small; i.e., less than about 25:1, it may be advantageous from the standpoint of overall muffler size to add part of the muffler volume to the piping and header system.




The header, exhaust piping, and muffler input piping can, in a simplified view, be considered as a single chamber having both a steady-flow throughput


804


and a fluctuating pressure. The invention restricts the variable effects of the fluctuating pressure on the output stream


805


while interfering with the steady flow


804


as little as possible. These dual goals can be accomplished by causing the exhaust to exit the foregoing chamber through one or more long tubes having small cross-sectional areas. The gas in the tubes constitutes a mass which is proportional to the cross-sectional area of the tubes times the tube lengths. For the fluctuating flow component, the driving force is proportional to the cross-sectional area of the tubes times the magnitude of the pressure fluctuation. For frequencies corresponding to gaseous wavelengths long compared to the tubes, the kinetic energies imparted to the gas columns in the tubes are inversely proportional to the mass, and thus to the lengths, of those columns (tube lengths).




From the foregoing, it is seen that the variable kinetic energies in the gas columns, which are the sources of downstream acoustical energies, can be limited through the use of long tubes having small flow cross-sections. The effect of tube length on the steady component of the exhaust gas flow


804


is minimal, however, consisting only of surface drag. The major component of steady-flow pressure drop is the pressure required to accelerate the gas to the velocity it attains within the tubes, and even that component can be minimized by bell-mouthing the inlet ends of the tubes for good streamlining.




For some purposes, the above single-stage muffler


800


consisting of a chamber combining the volumes of the engine exhaust header, piping, and perhaps an inlet volume


801


in the muffler


800


itself, together with a section of long exit tubes (up to approximately one-quarter gas wavelength of the highest frequency of interest) may provide sufficient noise reduction. The tube cross-sectional areas should be sized to provide internal velocities of 150 to 200 feet per second at maximum exhaust throughput for maximum muffling effect without degrading engine performance appreciably.




Such a muffler


800


will also perform fairly well if the physical lengths of the tubes are reduced to essentially zero. In that case, the effective lengths of the gas columns are reduced, but do not become zero, however, because of the continuity of flow at each end of the resulting apertures. Such a device is known in the literature as a Helmholtz resonator, and in common with the single-stage muffler


800


described above, could be driven to resonate at a frequency determined by the physical dimensions of the components used in its fabrication. For use as mufflers


800


, however, both devices are operated at frequencies far above their acoustical resonant frequencies. Such acoustical devices have electrical analogues which behave similarly. The electrical analogues of these devices are single-stage R-L-C low-pass filters.




Single-stage mufflers


800


are most economical when noise amplitude reductions by factors of about 50 or less are needed. For multi-stage mufflers


800


, in which the output from each internal velocity stage enters the chamber of a following stage, it is important to correctly choose the reduction factor for the beginning single-stage device in order to yield the most cost-effective and smallest muffler


800


. If one begins with a single-stage muffler


800


with a noise reduction factor of 50, for example, and redivides that volume to optimize the noise reduction at constant overall pressure drop, one finds the optimum with three stages and an overall noise amplitude reduction ratio of 171. If one begins with a single-stage amplitude reduction factor of only 25, however, the optimum reduction factor is for two stages and is only 39.




The introduction of water into the exhaust headers is common in many types of boats as a safety measure. Its purpose is to cool the exhaust system


800


, thereby removing a potential source of fire. However, that practice results in the production of wet steam in the exhaust


805


, which greatly reduces the pressure fluctuations within the muffler chambers though rapid condensation and evaporation in response to pressure fluctuations. That process tends to hold chamber pressures very close to the saturation pressure of steam at the exhaust temperature and markedly improves the noise reduction behavior of mufflers. Because of this improvement, single-stage mufflers


800


can be used for most purposes when wet steam is present in the exhaust. One should make provisions in such cases for liquid water to exit the muffler chambers


800


through small diameter, long tubes, however. Pressure rises due to high mass flows through the velocity stages could otherwise result if the cooling water were to pass through those stages in the muffler designs described here.




The drawing of

FIG. 35

shows a typical two (2)-stage L C Muffler


800


incorporated in the present outdrive


30


′. In principle, each time the exhaust energy is changed from pressure to velocity, the pulsations are attenuated. Some frequencies are blocked almost entirely depending on the specific geometry of the device. The important dimensions are the volume of the separate chambers


801


,


802


, etc. and the length and cross-sectional area of the velocity tubes


803


,


804


,


805


, etc.




Eccentric Tensioner (

FIGS. 22-24

,


36


and


37


)




Belts


37


that transmit power require large tensile preloads. In operation, there is a tension leg of the belt


37


and a slack leg. Generally, it is desirable to hold the slack side tension at some positive value to prevent belt


37


“cogging,” a destructive episode wherein the slack side teeth crawl up the sprocket teeth and eventually slip or jump to the next tooth, causing the whole belt


37


to “slip” one tooth in serial fashion.




The preload tension must be large enough to provide the slack side positive tension while the belt


37


is transmitting maximum design torque. At rest, the preload tension is shared equally by both legs


40


,


41


of the belt


37


. When torque is applied, one leg tension increases and the other decreases a like amount. As can be seen by this explanation, the maximum torque that can be supplied is governed by the belt preload


901


, if slack side tensions are to remain finite and positive. As a result, the preload tensions are large on the order of 2,000 or 3,000 pounds.




The present drive


30


′ of

FIGS. 21-25

, for example, utilizes an aluminum crutch


900


to carry the belt loads, and a simple and effective preload device


901


. This device


901


is cost effective, has enough adjustment to allow the belt


37


to slacken enough to assemble the drive


30


′, and can easily adjust the belt preload tension. It consists of an input sprocket


710


bearing carrier


901


, cylindrical in nature, which has an outside diameter


902


eccentric with the inside diameter


903


. The bearings


904


are mounted at the inside diameter


903


and the outside diameter


902


rides in the aluminum crutch. As the cylinder is rotated, the bearing rotational center


905


will be caused to move in a direction to tighten or loosen the belt


37


. Total movement of the prototype eccentric


901


is 0.150 inches; however, only 0.050 approximately, is required to produce the tension in the belt


37


. The remainder of the motion will produce clearance to allow assembly.




In order to keep the rotational center of the sprocket


710


,


711


reasonably in line with the engine driveline, the eccentric


901


geometry is placed such that under anticipated tension, the centers coincide. The only misalignment would come from minor variation due to manufacturing tolerances, especially belt


37


lengths. These small misalignments are accommodated by the universal joint which is between the engine and the drive


30


′.




Experience has shown that a digital rotation of the eccentric


901


of about 4 degrees is sufficient to allow necessary adjustment. Various techniques could be used to effect this adjustment. In the present prototype, a series of holes


906


(FIG.


23


), radially spaced and differentially placed by 4 degrees allows for a pin to engage each 4 degrees of rotation. Visual alignment is used prior to engaging the pin. In production, a toothed circumference is visualized with features every 4 degrees and a zero position witness for visual location.




The eccentric


901


may be a single piece as in

FIG. 36

with both forward and aft bearings


904




f


,


904




a


being accommodated. If, however, the bearing carrier is split as in

FIG. 37

into forward and aft parts


901




f


,


901




a


, these parts can be molded of plastic and adjusted separately. Care must be given to adjust the pair synchronously. Belt Tensioning




It is desirable, and in many instances necessary, to apply tension to the belt


37


. The invention employs a pretensioning mechanism. The tension should be appropriate to assure that the belt


37


remains securely mounted on the upper and lower sprocket assemblies


710


,


711


and that it does not slip during operation of the outdrive


30


to transfer the appropriate amount of power. Also, the belt


37


needs to be pretensioned to offset the torque developed by the engine on the power leg


180


. Specifically, as torque is applied, one side of the belt


37


would tend to become slack. The tension helps to prevent this from occurring. The appropriate amount of tension may be from several hundred to several thousand pounds of tension, depending on the torque developed by or in the outdrive


30


′.




Referring to

FIG. 22

, the mechanical eccentric


901


provides the belt tensioning and holds the upper sprocket


710


in place. The eccentric


901


is a piece that is a cylinder. The outside diameter


902


is a cylinder with a center of its own. The inside diameter


903


has a different center that is off by, in this case, 150 thousandths, but any distance will do depending on what ratios and forces are needed and the distance the belt


37


is to be drawn up. There is a piece running on the inside of the housing


12




a


, in a certain diameter circle which has an eccentric


901


outside diameter


902


, but the inside diameter


903


where the bearings


904




a-f


are runs on a different circle. Then as the piece is rotated, that center will move, thereby drawing the inside circle away from or toward another location to tension the belt


37


or to lengthen the belt


37


out of tension. The bearings


904




a-f


and the upper sprocket


710


are on the inside diameter


903


of the eccentric


901


, and the outside diameter


902


runs in a hole (crutch) that is in the housing


701


itself. To tension the belt


37


, the eccentric


901


is rotated and draws up the belt


37


by virtue that it brings the bearings


904




a-f


in the sprocket


711


away from the lower sprocket


711


as it is rotating. It is a simple device that avoids gearing and other components that were used in the past for belt tensioning.




The eccentric


901


also contains or is coupled to the universal joint. The eccentric


901


is rotated from the outside. There is a cap (

FIG. 23

) that goes on it and the cap may be originally rotated with a torque wrench. Then, one can rotate a number degrees beyond that in order to control the amount of the stretch or displacement that is put into the belt


37


. The initial torque is put on to initially tension the belt


37


to make sure it is up snug and straight. That is done as described with a torque wrench. The rest of the adjustment is a forced displacement of so many thousandths of an inch, due to the relationship between the rotation and the displacement in view the eccentric


901


. As the eccentric


901


is rotated, the center line of the shaft “X” of the sprocket


710


,


711


is going to move up slightly thereby increasing belt tension.




Note the center line of the inside diameter


903


of the eccentric


901


and the center line of the outside diameter


902


of the eccentric


901


. The eccentric


901


rotates about its outside diameter


902


as it is rotated in the housing


12




a


. The center line of the sprocket


710


,


711


nevertheless is connected to the center line of the drive shaft


14


from the engine.




The eccentric


901


is a bearing carrier. It carries the upper sprocket


710


so this is a complete upper assembly.




The eccentric


901


has a hole in the center for the drive belt


37


to pass through. As it is torqued, there is a lot of friction that occurs between the eccentric


901


and the housing


12




a


, enough that when it is at full tension, it tends not to move. That is convenient but is not necessary. It would be acceptable if it could move, for it can be locked as is described below. The cap (

FIG. 23

) on the back of the eccentric


901


has a set of holes, for example, five holes, through which a screw may be passed and the screw will line up with one of several for example, 8 or 10, threaded holes in the housing. Those threaded holes will line up with one of the holes


910


(

FIG. 23

) in the cap every two degrees as the cap is rotated, which is the equivalent of a prescribed amount of belt tensioning, for example 0.002 inch tensioning of the belt


37


per hole so the belt


37


can be tensioned fairly accurately. Then a small screw through a hole tightens it up. That adjustment gives enough friction to keep the belt


37


from losing its tension during storage and shipment. Once the outdrive


30


′ is on the boat, the eccentric


901


is held in place by using clamps that are underneath the studs that are used to hold the whole outdrive


30


′ against the gimbal housing, and four of those six studs hold the clamps to give additional clamping of the eccentric


901


in place relative to the housing


12




a


. Therefore, the final clamping may be done when the outdrive


30


′ is actually secured to the boat.




In a two piece design of the eccentric


901


there would be two caps, one on each side. The cap would be an integral part with eccentric portion


901


, so there would be two eccentrics


901


.




A two piece design rather than a one piece design is more cost effective to build.




Active Tensioner (

FIGS. 38-39

)




Because the tensions on the belt


37


are so large, and especially when considering a plastic housing subject to creep from sustained tension, it is desirable to have a means whereby tension is an active function of torque. Such a device


920


, is schematically depicted in

FIGS. 38-39

.




As can be seen, a separate set of back benders


921


are placed just below the upper or input sprocket


710


. These back benders


921


are arranged for free lateral translation. When input torque is present, the tension or tight side of the Belt


37


will pull the tensioner back benders


921


to the left (FIG.


39


), as the belt


37


tries to assume a line tangent to the lower back benders


921


and the upper sprocket


710


. The more torque that is supplied, the more the tight side straightens causing slack to be taken up on the opposite leg.




Tests have shown that for the ratios such as those mentioned above, the upper sprocket


710


may be too small to account for the entire tensioning required. It is desirable for reasons described above to use a preload tension of approximately one-half the design tension in order that this mechanism


920


, belt


37


and associated apparatus of the outdrive


30


′ will track required tension all the way through design values.




Transmission Design (

FIGS. 40-50

)




In the transmission


930


there are two sun gears


931




a


,


931




b


, which are, respectively, relatively forward and aft. Forward and aft are, for convenience, typically more forward or relatively more aft in the transmission relative to use of the transmission in a water craft. There also are six planet gears


932




a-f


, three relatively forward and three relatively aft. There also are two dog clutches or dog clutch members


933




a


,


933




b


(one relatively forward and the other aft) which have teeth or dogs


934




a


,


934




b


or the like for inter-meshing type engagement, as is conventional for dog clutches, the operation of which is described below. The advantage of the dog clutch arrangement is that there is positive meshing of gear teeth without slippage and this connection is used in particular in the forward drive state of the transmission. The shift mechanism assures that the gears strongly pop into engagement or out of engagement, as is described further below. The planet gears


932




a-f


are arranged in respective pairs; the forward planet gears


932




a-c


cooperate with aft planet gears


932




d-f


. The forward planet gears


932




a-c


are spaced about the axis of the sun gear


931




a


at approximately 120° spacing. The aft planet gears


932




d-f


also are spaced about a sun gear, namely


931




b


, also at approximately 120° spacing, but as is seen in

FIG. 40

, angularly shifted about such axis relative to the forward planet gears


932




a-c


. Respective pairs of forward and aft planet gears are in meshed engagement so under appropriate conditions, namely, for reverse drive, described below the forward planet gears turn the aft planet gears. Therefore, when planet gear


932




a


is turned by a dog clutch member and sun gear in one direction, it turns the paired planet gear


932




d


in the opposite direction; so, too, with the respective pairs of planet gears


932




b-c


with planet gears


932




e-f


paired therewith.




In

FIG. 40

, which is a view looking aft, the dog clutch members


933




a


,


933




b


are hidden behind the forward sun gear


931




a


and are not seen.

FIG. 41

shows the transmission coupled to the outdrive


30


′ shifted for reverse operation or driving of the water craft.




It will be appreciated that relative to the view looking aft in

FIG. 40

, the side views of

FIGS. 41-44

cut through a section line of

FIG. 40

that is not completely vertical, but rather is somewhat angular to show the functional relationship and arrangement of parts of the transmission


930


.




The forward and aft sun gears


931




a


,


931




b


are held in place, so they do not drop out of position, by the respective three planet gears


932


surrounding them. The dog clutch members also can provide a retention/centering effect for the sun gears


931




a


,


931




b.






In the forward shifted condition of the transmission


930


shown in

FIG. 42

, the dog clutch member


933




a


is directly meshed with and turned by the drive shaft


14


at a splined connection


935


, is directly connected to the dog clutch member


933




b


at the direct connection


934


of interengaged teeth


934




a


,


934




b


(seen separated in FIG.


41


), and turns the dog clutch member


933




b


. The dog clutch member


933




b


is meshed at a splined connection


936


with the transmission output shaft


14




a


and causes it to turn, thus causing a forward rotation of the propeller


15


via the outdrive


30


′. The sun gears


931




a


,


931




b


and the planet gears


932




a-f


do not directly couple power in the forward direction and preferably they just idle` and either do not rotate or possibly may rotate depending on weak fluid coupling with the drive shaft


14


and/or the transmission output shaft


14




a.






In the reverse shifted condition of the transmission


930


shown in

FIG. 43

, the dog clutch member


933




a


is meshed by teeth or dogs


940




a


,


940




b


(shown separated in

FIG. 42

) at


940


with sun gear


931




a


. The sun gear


931




a


is meshed at


942


with respective planet gears


932




a-c


and turn such planet gears


932




a-c


, which respectively mesh with and turn respective paired planet gears


932




d-f


. The planet gears


932




d-f


mesh with sun gear


932




b


, which is meshed by teeth or dogs


943




a


,


943




b


(shown separated in

FIG. 42

) at


943


with and turn the dog clutch member


933




b


. The dog clutch member


933




b


meshes with the transmission output shaft


14




a


at a splined connection


936


and rotates it in a direction opposite the rotational direction of the drive shaft


14


, thus causing a reverse rotation of the propeller


15


via the outdrive


30


′.




In the neutral shifted condition of the transmission


930


shown in

FIG. 44

, the dog clutch member


933




a


is meshed with the drive shaft


14


, but the dog clutch member


933




a


is not meshed with any other gears, dog clutch type or planet type; therefore, the rotation of the drive shaft


14


is not coupled through to the transmission output shaft


14




a


. Similarly, dog clutch member


933




b


is meshed with the transmission output shaft


14




a


but is not meshed with any other gears or clutches. Therefore, in neutral the transmission does not couple power between the drive shaft


14


and the transmission output shaft


14




a.






The Transmission


930


has been designed as a cost-effective means to provide forward running, neutral and reverse running. Reverse gear is at a 1:1 ratio. The drawings of

FIGS. 40-44

show the intended design. It is a compact planetary arrangement with unique features to provide these functions:




Two (2) clutches are provided to allow no gears turning in either neutral or forward.




The above feature allows powdered metal construction throughout.




Reverse is accomplished by a novel arrangement of the planet gears


932


, clutches and sun gears.




Fewer bearings


904


are required since the sun gears float on the planet gears at the centers of the shafts.




Summarizing operation of the transmission


930


with respect to the schematic illustrations of

FIGS. 40-44

,

FIGS. 41 and 43

depict reverse operation to drive the water craft in reverse. The drive shaft


14


turns the forward dog clutch through a spline connection to rotate with the drive shaft as one unitary part. Through a dog clutch dog or teeth connection to the forward sun gear, the forward dog clutch drives the forward sun gear with the drive shaft as a unitary part. The forward sun gear then rotates the forward planet gear. The forward planet gear rotates the aft planet gear. The aft planet gear rotates the aft sun gear. The aft sun gear is engaged by a dog or teeth connection with the aft dog clutch and turns it. The aft dog clutch is in splined connection to the transmission output shaft


14


a and turns it in a direction opposite to the direction of rotation of the drive shaft


14


.




In the neutral state, the two dog clutches are relatively close together so they are out of engagement with each/either respective sun gear, yet the dog clutches are sufficiently far apart as not to be engaged with each other.




In forward operation the forward and aft dog clutches are moved closer together. Therefore, the dogs or teeth thereof engage or mesh with each other. Both dog clutches still are splined to respective shafts


14


,


14




a


. Therefore, there is the direct forward drive without any gears spinning needlessly, which reduces losses that would be encountered if one or more gears were rotating. Note, in the illustrated embodiment, if a sun gear is not rotated, then the planet gears associated therewith also will not rotate; when they rotate, the respective sun gears and the associate planet gears always rotate in concert with each other, but in opposite directions.




Since forward operation is with a direct connection via the dog clutch members


933




a


,


933




b


, power coupling is very efficient with minimal loss since there are no extra gears required to be turned. Usually a water craft is operated in reverse at relatively slow speed for short periods of time. Therefore, the sun and planet gears do not have to transmit substantial loads and can be relatively inexpensive parts, for example, being made using powdered metal technology.




Transmission Shift Mechanism


950


(

FIGS. 45-50

)




The shift mechanism


950


of the transmission


930


shifts the dog clutches


933




a


,


933




b


among forward, neutral and reverse modes for operation as described above. When shifting dog clutches


933




a


,


933




b


, care must be taken by the operator to move the shifting lever


951


so the shift mechanism


950


operates swiftly to achieve full engagement of the dog clutches


933




a


,


933




b


with each other or with respective sun gears


931




a


,


931




b


or to neutral. In the past, if an operator is not decisive, the dog clutches


933




a


,


933




b


would partially engage and cause the clutch members to skip issuing a grinding noise. This type of operation can be destructive and is to be avoided. This is a common occurrence, and has given a generally bad connotation to dog-clutch design. The present invention is meant to avoid this problem.




Briefly, the lever


951


imparts rotational motion to wind up a torsional spring


952


within a hollow shaft


953


. When the force in the spring


952


is sufficiently great and a mechanical direct engagement of the lever


951


or an associated mechanism with the shaft


953


overcomes the retention force of a detent mechanism


954


, the spring


952


is operable to cause a snap or pop action to quickly urge (slam) the shaft


953


to the desired “shifted” position which drives shifting forks


955


via balls


956


and slots


957


on the shaft


953


into the desired position. The shifting forks


955


drive the dog clutch members


933




a


,


933




b


toward or away from each other to the new “shifted” position.




The detent mechanism


954


holds the shift mechanism


950


in a given mode until motion of lever


951


causes contact with tabs on lever


986


to force its movement to overcome the detent mechanism


954


releasing built up spring energy to slam the shift mechanism


950


and clutch members


933




a


,


933




b


to the desired condition or operational mode.

FIGS. 45-50

shown the shift mechanism in the respective forward, reverse and neutral modes corresponding to the transmission


930


modes shown in respective

FIGS. 42-44

to throw or to move the movable dog clutch members


933




a


,


933




b


relative to each other.

FIGS. 45

,


48


show forward;

FIGS. 46

,


49


show reverse; and

FIGS. 47

,


50


show neutral.




The shifting mechanism


950


includes a housing


961


in which various portions are mounted. For example, the shaft


953


is mounted in respective receptacles or bearings


962


and one or more seals, such as the o-ring seal


963


, may be provided to keep the area within the housing clean and/or appropriately lubricated. The shifting forks


955


are mounted on part of shifting fork carriers


964


which may be cylindrical rings about the shaft


953


. The grooves


957


are on the inside surface of the carriers


964


and face corresponding aligned grooves


965


in the exterior surface of the shaft


953


. Preferably there are two carriers


964


one of which has left-handed threads and the other of which has right-handed threads; and the grooves


965


on the shaft


953


correspond. Therefore, as the shaft


953


is rotated, the balls


956


in respective grooves follow the rotation of the shaft and cause the carriers


964


to move toward or away from each other, thus moving the shifting forks


960


and the dog clutch members


933




a


,


933




b


respectively toward or away from each other. Although the carriers


964


move axially, preferably they are constrained by the housing


961


or otherwise as not to rotate.




In one or both of the shifting fork carriers


964


is the detent mechanism


954


. The detent mechanism may be a ball


970


urged by a spring


971


toward an outside surface


972


of the shaft


953


. Three respective recesses


973


in the shaft


953


are aligned with the path of the ball


970


as the ball follows a somewhat helical travel path relative to the shaft


953


as the shaft is rotated and the carrier


964


is moved axially relative to the shaft


953


. The three recesses correspond to rotational/angular orientation of the shaft


953


and, thus, axial orientation of the carriers


964


for the respective forward, neutral and reverse modes of operation of the transmission


930


.




The spring


952


may be welded or otherwise fixed to the shaft


953


, e.g., as at the connection


974


, which is located at one end of the shaft and spring. The spring


952


also is coupled as at


975


to the shift lever


951


so upon rotating the shift lever the spring is wound relative to the shaft


953


. For this purpose, a cover or clamp


976


may be fastened to the spring


952


, fixedly connected to the shift lever


951


, and relatively rotationally movable relative to the shaft


953


about the axis thereof. The shift lever


951


and the cover


976


are retained on the shaft


953


by a key


977


, which includes a partial concave surface


980


about at least part of the shaft and a protrusion


981


which holds in a recess or other lock point


982


of the shaft.




In

FIGS. 48-50

a spring-loaded motion limiter


983


is shown. The motion limiter includes a spring loaded pawl


984


, bias spring


985


, and detent surfaces


986


with which the pawl may engage to prevent motion of the shift lever


951


beyond desired extent. Thus, the pawl avoids overshoot when the shift is shifted.




In operation of the shift mechanism


950


, as the operator manually rotates the input lever


951


, the torsion spring


952


is wound up to store energy in the torsion spring


952


. When enough energy is stored to cause swift shifting action, the input lever


951


mechanically abuts the shifting lever to cause it to start a rotation of the hollow shaft


953


, which releases the detent mechanism


954


. The hollow shaft then rotates quickly and hard under the influence of the torsion spring


952


; that rotation is stopped by the pawl


984


. Rotation of the hollow shaft


953


moves the shifting forks


960


by the interaction of the right and left-handed ball threads


956


,


957


,


965


to rapidly move the dog clutch members


933




a


,


933




b


to a desired relative location for forward, neutral or reverse transmission and drive operation.




Exhaust Thermal Barrier (

FIG. 51

)




The current drive


30


′ has been designed to be both a source to ventilate the propeller hub


15


and a muffler


800


to attenuate the exhaust sound. Hot water laden exhaust products are directed through the aluminum housing


701


to connect the various passages that form the muffling chambers described above. As the exhaust impinges on the aluminum housing


701


and is accelerated though the transit passages, heat is transferred to the cooler aluminum. This is undesirable since this heat must be removed by the drive's heat exchangers, in this case, the back benders


42




a


,


43




a


,


921


and the system oil


712


.




Since the belt


37


is manufactured from polymers, its life is adversely affected by elevated temperature. It is, therefore, desirable to keep the incident heat load as small as possible.




A plastic heat barrier


970


which is an extension of the cooling water passage cover is shown in FIG.


51


. This barrier


970


causes the exhaust to impinge directly on the plastic surface of the barrier


970


, while heat transfer is discouraged by the poor conductivity of the plastic and the air gap that inevitably exists between the barrier


970


and the aluminum housing


701


.




Aluminum Housing


701






The aluminum housing


701


serves multiple design functions. It is the surface that forms the back benders


42




a


,


43




a


,


921


and, subsequently, also performs the heat exchange function, carrying heat directly to the water from the oil


712


trapped between the back benders


42




a


,


43




a


,


921


and the belt


37


. Also, as has been mentioned, the large preload forces are supported by the aluminum. There is, however, one function that has not been revealed, and is considered proprietary.




Since the belt


37


has a Kevlar


7


construction, and since Kevlar has a negative coefficient of thermal expansion, temperatures in the drive


30


′ above room temperature, or above the temperature that the preload was set, cause more preload to be added to the belt


37


.




Large preloads are necessary at high powers because it keeps the teeth engaged and because it promotes smooth engagement and disengagement of the teeth, minimizing the scrubbing action that promotes wear. However, at light loads, a high preload, while necessary for high powers, will actually promote premature wearing on the belt teeth


183


. It is, therefore, very desirable to employ some active preload device. The aluminum housing


701


does just that. Since the preload added by the differential expansion is a function of the bulk temperature of the drive


30


′ and since the temperature tracks roughly the power being expended, the aluminum housing


701


acts as an active tensioner, yielding a preload that increases with increasing power.




Belts


37


may be statically tensioned below recommended values and yield a better wear profile. No start-up cogging problems have been observed, probably because the nature of a propeller load is one of hydrodynamic slip when too much torque is applied.



Claims
  • 1. An outdrive for a water vessel comprising an hybrid housing including a plastic portion and a heat conducting portion, at least part of the heat conducting portion constituting an exposed external surface of the housing, a chamber area in the heat conducting portion, a belt at least partly in the chamber for coupling power from an input drive to a propulsion device, the belt being at least partly in thermal transfer relation with said heat conducting portion, wherein at least part of said heat conducting portion is operatively configured to be exposed to water external of the outdrive when the outdrive is immersed.
  • 2. The outdrive of claim 1, further comprising a fluid in said chamber providing thermal transfer between said belt and said heat conducting portion and providing lubrication between said belt and said heat conducting portion.
  • 3. The outdrive of claim 1, further comprising a preload device for adjusting tension in the belt, the preload device including a wheel which engages the belt, and a carrier operatively coupled to the wheel, an outer surface of the carrier being eccentric with an inner surface of the carrier, rotation of the carrier causing the wheel to move, thereby adjusting tension in the belt.
  • 4. The outdrive of claim 1, wherein the propulsion device includes a propeller shaft which protrudes from the housing, and further comprising a deflection limiter attached to the housing which limits deflection of the propeller shaft.
  • 5. The outdrive of claim 1, wherein the housing includes a region between the input drive and the propulsion device which has a thickness-to-chord ratio of less than 10 percent.
  • 6. The outdrive of claim 1, further comprising a preload device for adjusting tension in the belt, the preload device including a wheel which engages the belt, and a carrier operatively coupled to the wheel, an outer surface of the carrier being eccentric with an inner surface of the carrier, rotation of the carrier causing a center of the wheel to move, thereby adjusting tension in the belt.
  • 7. The outdrive of claim 1, further comprising an active tensioner which actively adjusts the tension of the belt.
  • 8. The outdrive of claim 1, further comprising a transmission which includes:a direct drive connection for connecting a power source to an output device to drive the output device in a primary direction, the output device being operatively coupled to the input drive; gearing for indirectly connecting the power source to drive the output device in a secondary direction; and a shifting mechanism for selectively decoupling the direct drive connection and connecting the gearing between the power source and the output device.
  • 9. The outdrive of claim 2, further comprising a stuffer in the chamber area, between legs of the belt.
  • 10. The outdrive of claim 2, wherein the heat conducting portion is made of metal.
  • 11. The outdrive of claim 2, wherein the heat conducting portion is made of aluminum.
  • 12. The outdrive of claim 2, wherein the heat conducting portion is between 30% and 50% of the hybrid housing.
  • 13. The outdrive of claim 2, wherein the belt is made of a material which has a negative coefficient of thermal expansion.
  • 14. The outdrive of claim 13, wherein the material which has a negative coefficient of thermal expansion includes a Kevlar cord material.
  • 15. The outdrive of claim 1, wherein the chamber area has oil therein.
  • 16. A transmission for a water vessel drive system capable of selectively coupling power in plural operational modes, comprisingdog clutch members, sun gears, and planet gears, a shifting mechanism to move the dog clutch members to direct engagement with each other for one operational mode, to engagement with respective San gears for interaction with respective planet gears for another operational mode, and out of engagement with each other and with sun gears and planet gears for a third mode.
  • 17. A transmission for a water vessel drive comprising:a direct drive connection for connecting a power source to an output device to drive the output device in a primary direction; gearing for indirectly connecting the power source to drive the output device in a secondary direction; and a shifting mechanism for opening the direct drive connection and connecting the gearing between the power souce and the output device; wherein the direct drive connection includes a pair of dog clutch members each coupled to a respective shaft, and the gearing includes a pair of sun gears coupled to one another by planet gears; and wherein the shafts rotate in a first relative way when the dog clutch members are directly engaged, the shafts rotate in a second relative way when the dog clutch members are engaged with respective of the sun gears, and in a neutral mode the shafts are not connected and one of the shafts is not driven directly or indirectly by the other of the shafts to rotate relative to the other of the shafts when the dog clutch members are neither directly engaged nor coupled to the respective sun gears.
  • 18. The transmission of claim 17, wherein the primary direction is a forward direction and the secondary direction is a reverse direction.
  • 19. The transmission of claim 17, wherein the planet gears and the sun gears are made of powdered metal.
  • 20. The transmission of claim 17, wherein each of the dog clutch members is slidably meshed to its respective shaft by a splined connection.
  • 21. The transmission of claim 17, wherein the planet gears and the sun gears rotate only when the dog clutch members engage the sun gears.
  • 22. The transmission of claim 17, wherein the shifting mechanism is coupled to the dog clutch members for moving the dog clutch members.
  • 23. The transmission of claim 22, wherein the shift mechanism includes a shifting lever coupled to a spring and a detent mechanism, and shifting forks coupled to the spring and the detent mechanism, the shifting forks coupled to the dog clutch members for moving the dog clutch members along the respective shafts.
  • 24. The transmission of claim 22, wherein the shift mechanism includes a shifting lever rotatably coupled to a hollow shaft and coupled to a torsional spring within the hollow shaft, and shifting fork carriers coupled to respective of the dog clutch members to move the dog clutch members along the respective shafts, the carriers also coupled to the hollow shaft such that rotation of the shaft causes the carriers to move toward or away from each other.
  • 25. The transmission of claim 24, wherein the shift mechanism further includes a detent mechanism between the carriers and the shaft.
  • 26. A water vessel belted outdrive spacer for use in an ontdrive having a chamber in which at least part of a transmitting belt is located, the spacer having a configuration for positioning between legs of the belt which is at least partially immersed in fluid, the spacer displacing some of the fluid and reducing flow in the fluid.
  • 27. The outdrive of claim 26, wherein the spacer is made of plastic.
  • 28. An outdrive for a water vessel comprising a housing having a chamber, a belt which moves within the chamber for transferring power from an input shaft to an output shaft, a fluid at least partially filling the chamber, and a spacer between legs of the belt which reduces the formation of vortices in the fluid.
  • 29. The outdrive of claim 28, wherein the spacer is made of plastic.
  • 30. The outdrive of claim 28, wherein the spacer is made of metal.
  • 31. The outdrive of claim 28, wherein the spacer has a portion of an external surface with a shape substantially conforming to a portion of the belt.
  • 32. The outdrive of claim 31, wherein the portion of the external surface of the spacer are approximately 0.030″ inches from the belt.
  • 33. The outdrive of claim 28, further comprising a transmission which includes:a direct drive connection for connecting a power source to an output device to drive the output device in a primary direction, the output device being operatively coupled to the input shaft; gearing for indirectly connecting the power source to drive the output device in a secondary direction; and a shifting mechanism for opening the direct drive connection and connecting the gearing between the power source and the output device.
  • 34. The outdrive of claim 28, further comprising an active tensioner which actively adjusts the tension of the belt.
  • 35. The outdrive of claim 28, further comprising a preload device for adjusting tension in the belt, the preload device including a wheel which engages the belt, and a carrier operatively coupled to the wheel, an outer surface of the carrier being eccentric with an inner surface of the carrier, rotation of the carrier causing a center of the wheel to move, thereby adjusting tension in the belt.
  • 36. The outdrive of claim 28, wherein the housing includes a region between the input shaft and the output shaft which has a thickness-to-chord ratio of less than 10 percent.
  • 37. A rotational shock absorber for a propopulsion system of a water vessel, comprising:a stator; a rotor coaxial with and within the stator, the rotor and stator defining chambers therebetween, the rotor having circumferenially-spaced vanes, each of the vanes dividing respective of the chambers into portions; restrictions connecting the portions of respective of the chambers to allow fluid flow between portions of each of the chambers; and means for coupling the stator and the rotor in the propulsion system of the water vessel.
  • 38. The shock absorber of claim 37, further comprising chamber-chamber seals which prevent fluid flow between the chambers.
  • 39. The shock absorber of claim 37, further comprising seals between the vanes and the stator for preventing flow between the portions along the respective vane.
  • 40. The shock absorber of claim 37, further comprising a heavy oil in the portions.
  • 41. The shock absorber of claim 37, wherein the rotational shock absorber is rotationally symmetric.
  • 42. The shock absorber of claim 37, wherein the restrictions give increasing resistance to rotary motion with increasing rotational displacement.
  • 43. The shock absorber of claim 37, further comprising a biasing device which biases the rotor to a central position.
  • 44. The shock absorber of claim 43, wherein the biasing device is a torsional spring.
  • 45. The shock absorber of claim 37, wherein the restrictions are passages in an end plate coupled to the rotor and the stator.
  • 46. The shock absorber of claim 37, as part of an outdrive for a water vessel.
  • 47. A deflection limiter for a water vessel outdrive comprising a member with a shaft hole through which a shaft may protrude, and means for attaching the deflection limiter to the outdrive, wherein the means for attaching includes a collar attached to the member, the collar having holes therethrough.
  • 48. The deflection limiter of claim 47, wherein the member is conical and the shaft hole is centrally located in the conical member.
  • 49. The deflection limiter of claim 47, wherein the member has a drain hole therein.
  • 50. The deflection limiter of claim 47, wherein the deflection limiter is made of aluminum.
  • 51. An outdrive for a water vessel comprising a propeller shaft protruding from a housing, and a deflection limiter attached to the housing which limits deflection of the propeller shaft, wherein there is a clearance gap between the shaft and the deflection limiter during normal running, and wherein the deflection limiter is made of a metal and the propeller shaft is made of a different metal, the deflection limiter functioning as a sacrificial anode.
  • 52. The outdrive of claim 51, wherein the deflection limiter is made of aluminum and the propeller shaft is made of stainless steel.
  • 53. An outdrive for a water vessel comprising a propeller shaft protruding from a housing, and a deflection limiter attached to the housing which limits deflection of the propeller shaft, wherein there is a clearance gap between shaft and the deflection limiter during normal running, and wherein the housing is a hybrid housing including a plastic portion, and the deflection limiter attaches to and is structurally supported by hybrid housing.
  • 54. An outdrive for a water vessel comprising a belt which moves within the chamber for transferring power from an input shaft to an output shaft, and a preload device for adjusting tension in the belt, the preload device including a wheel which engages the belt, and a carrier operatively coupled to the wheel, an outer surface of the carrier being eccentric with an inner surface of the carrier, rotation of the carrier causing a center of the wheel to move, thereby adjusting tension in the belt.
  • 55. The outdrive of claim 54, wherein the carrier is mounted within the wheel.
  • 56. The outdrive of claim 54, wherein the wheel is a sprocket.
  • 57. The outdrive of claim 54, wherein the preload device further includes an adjustment mechanism.
  • 58. The outdrive of claim 54, wherein the inner surface is oriented such that the belt is in tension when the wheel is rotationally aligned with an engine driveline operatively coupled to the input shaft.
  • 59. The outdrive of claim 54, further comprising a mechanism for adjusting the preload device and locking the preload device.
  • 60. The outdrive of claim 54, wherein the carrier has a toothed circumference for locking the preload device into place.
  • 61. The outdrive of claim 54, further comprising an overdrive housing having a series of holes therein and a pin for selectively engaging the holes, thereby locking the preload device in a desired position.
  • 62. The outdrive of claim 54, further comprising a housing having a series of holes therein, and a lQcking device insertable through the holes to engage the carrier and thereby lock the carrier in place, preventing it from being rotated.
  • 63. The outdrive of claim 62, wherein the locking device is a pin.
  • 64. The outdrive of claim 62, wherein the holes are threaded and the locking device is a threaded fastener.
  • 65. The outdrive of claim 54, wherein the preload device is a two-piece preload device, further including another carrier operatively coupled to the wheel.
  • 66. An outdrive for a water vessel comprising a belt which moves within a chamber for transferring power from an input shaft to an output shaft, and an active tensioner which actively adjusts the tension of the belt, wherein the active tensioner includes a device having a set of back benders slidably in contact with both legs of the belt, the device operatively configured to laterally translate relative to the belt.
  • 67. The outdrive of claim 66, wherein the device freely moves substantially perpendicular to the travel of the belt.
  • 68. The outdrive of claim 66, wherein the back benders are slidably in contact with outward-facing surfaces of the legs.
  • 69. The outdrive of claim 66, wherein surfaces of the back benders in contact with the legs are mirror images of one another.
  • 70. The outdrive of claim 66, wherein the chamber area has oil therein.
  • 71. A muffler for an internal combustion engine for marine use, the muffler comprising:a chamber; and tube means for providing noise reduction, said tube means being attached to the chamber; wherein tie tube means includes exit tubes having a length of up to approximately one-quarter an exhaust gas wavelength corresponding to a highest frequency of exhaust noise to be muffled.
  • 72. A muffler for an internal combustion engl for marine use, the muffler comprising:a chamber; and tube means for providing noise reduction, said tube means being attached to the chamber; wherein the tube means includes exit tubes having a length of up to approximately one-quarter an exhaust gas wavelength corresponding to approximately 200 Hz.
  • 73. A muffler for an internal combustion engine for marine use, the muffler comprising:a chamber; and tube maeans for providing noise reduction, said tube means being attached to the chamber; wherein the tube means are tube means sized to provide internal velocities of 150 to 200 feet per second at maximnum exhaust throughput.
  • 74. A mnuffler for an internal combustion engine for marine use, the muffler comprising:a chamber; and tube meansfor providing noise reduction, said tube means being attched to the chamber; wherein the tube means include aperture means for allowing the muffler to function as a Helmholtz resonator.
CROSS REFERENCE TO RELATED PATENTS, PATENT APPLICATIONS, AND/OR PROVISIONAL APPLICATIONS

This application claims priority under 35 U.S.C. 119(e) from Provisional U.S. patent applications Ser. No. 60,070,030, filed Dec. 8, 1997; Ser. No. 60/085,194, filed May 12, 1998; and Ser. No. 60/085,314, filed May 13, 1998. Reference is made to U.S. Pat. No. 5,178,566.

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Provisional Applications (3)
Number Date Country
60/085314 May 1998 US
60/085194 May 1998 US
60/070030 Dec 1997 US