Starting and stopping device for an internal combustion engine

Information

  • Patent Grant
  • 6325036
  • Patent Number
    6,325,036
  • Date Filed
    Wednesday, August 23, 2000
    24 years ago
  • Date Issued
    Tuesday, December 4, 2001
    22 years ago
Abstract
A starting and stopping device for an internal combustion engine includes an energy storing device including at least one elastic member. The elastic member is loaded in response to rotation of a main shaft, and the main shaft rotates in an unloading direction in response to unloading of the elastic member. A locking mechanism selectively prevents the elastic member from unloading from a loaded state by preventing the shaft from rotating in the unloading direction. A clutch mechanism is operatively disposed between the main shaft and the locking mechanism to permit rotation of the shaft in the unloading direction when a preselected torsional threshold between the shaft and the locking mechanism is reached.
Description




FIELD OF THE INVENTION




The invention relates to starting and stopping devices for internal combustion engines.




BACKGROUND




It is known to provide an engine starting device that utilizes stored energy in a spring to rotate the crankshaft and to start the engine. In these engine starting devices, a mechanism must be provided to wind the spring. For example, U.S. Pat. No. 1,936,554, which is assigned to Briggs and Stratton Corporation (the assignee of the present invention) discloses an electric motor that is positioned adjacent the spring and which may be operated to wind the spring. It is also known to provide a manual crank mechanism interconnected with the spring and operable to wind the spring. Further, it is known to provide a winding mechanism interconnected with the crankshaft that is operable to wind the spring during normal engine running conditions.




SUMMARY




The present invention provides an internal combustion engine having a rotatable engine member, a shaft rotatable in a loading direction in response to rotation of said rotatable engine member, and an energy storing mechanism including at least one elastic member that is selectively coupled to the shaft and loaded by rotation of the shaft in the loading direction. Preferably, the engine further includes a locking mechanism selectively maintaining the elastic member in a loaded state, and a clutch mechanism permitting rotation of the shaft in an unloading direction when a preselected torsional threshold between the shaft and the locking mechanism is reached.




Preferably, the locking mechanism includes a ratchet member, and the clutch mechanism couples the ratchet member to the shaft by friction. The locking mechanism may further include a pawl and a pawl carrier. The pawl selectively prevents rotation of the ratchet member in the unloading direction, and the pawl carrier selectively moves the pawl into and out of engagement with the ratchet member. The engagement between the pawl and the ratchet member creates a line of force that self-energizes the pawl into engagement with the ratchet member when the pawl engages the ratchet member. The pawl carrier is positioned such that the line of force urges the pawl carrier to disengage the pawl from the ratchet member when the pawl engages the ratchet member. A shaft is selectively positioned in a slot in the pawl carrier to substantially prevent undesired disengagement of the pawl from the ratchet member. The pawl carrier is permitted to disengage the pawl from the ratchet member when the shaft is removed from the slot in the pawl carrier.




The engine may further include a gear having a central recessed portion that houses the clutch mechanism. The clutch mechanism may include a clutch plate, clutch washer, and spring washer. A clutch cover is preferably positioned over the recessed portion of the gear to pre-load the clutch mechanism. A brake disk is preferably positioned within the recessed portion of the gear, and the clutch mechanism is preferably sandwiched between the brake disk and the clutch cover to create friction between the brake disk and the gear and between the brake disk and the clutch plate. The ratchet member preferably includes depending ears that engage the clutch plate and couple the ratchet member and clutch plate for rotation together.




A pawl control member may be used to disengage the pawl from the ratchet member during loading of the elastic member. The pawl control member is preferably a friction device that moves the pawl in response to rotation of a rotatable element. The preferred embodiment of the pawl control member is a length of spring wire wrapped around the clutch cover and having a finger extending into a slot in the pawl. The clutch cover rotates with the gear, causing the spring wire to rotate and move the finger within the slot in the pawl. When the finger reaches the end of the slot, the spring wire moves the pawl out of engagement with the ratchet member. When the gear rotates in the unloading direction, the spring wire rotates with the gear due to friction between the spring wire and the clutch cover, permitting the pawl to engage the ratchet member.











BRIEF DESCRIPTION OF THE DRAWINGS




Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.





FIG. 1

is a perspective view of a lawnmower incorporating an internal combustion engine and an engine starting device embodying the present invention.





FIG. 2

is a perspective view of the engine starting device.





FIG. 3

, which includes

FIGS. 3A

,


3


B, and


3


C, is an exploded view of the engine starting device.





FIG. 4

is an exploded view of a portion of the engine starting device including the clutch assembly.





FIG. 5

is a plan view of the engine starting device illustrating the pawl in an engaged position.





FIG. 6

is a plan view of the engine starting device illustrating the pawl in a disengaged position.





FIG. 7

is a bottom perspective view of a portion of the locking mechanism.





FIG. 8

is a top perspective view of a portion of the engine starting device including the pawl control member.





FIG. 9

is a bottom perspective view of a portion of the engine starting device including the pawl control member.





FIG. 10

is a top plan view of the engine starting device with a locking cam engaging the pawl.











DETAILED DESCRIPTION




Before describing the preferred embodiment, it should be noted that not all of the structural and operational details of the preferred embodiment of this invention may be described in detail. Should additional details of that type be required, reliance is placed on the description and drawings in U.S. application Ser. No. 09/183,425, filed Oct. 30, 1998, now U.S. Pat. No. 6,230,678, the entire contents of which are incorporated herein by reference.





FIG. 1

illustrates a lawnmower


10


incorporating an internal combustion engine


12


and a device


14


for automatically starting the engine


12


.

FIG. 2

illustrates the starting device


14


mounted on the engine


12


. Portions of the starting device


14


have been cut away in

FIG. 2

to illustrate some of the internal components thereof, which components are discussed in detail below. The lawnmower


10


has a deck


16


and a handle assembly


18


extending outwardly and upwardly from the deck


16


. The internal combustion engine


12


is mounted on the deck


16


. The engine


12


is of the vertical shaft type and includes many components which are of conventional construction. Most of these engine components, however, are substantially enclosed by an engine housing and, thus, not shown in FIG.


1


. In addition to the engine starting device


14


, the lawnmower


10


is equipped with a recoil starter (not shown) that is mounted above a flywheel


26


(FIG.


2


). A shroud


28


is mounted over the recoil starter and a pull cord


30


operatively connected to the recoil starter extends outwardly through the shroud


28


.




Although the engine starting device


14


embodying the invention is particularly adapted for use with a lawnmower


10


, the engine starting device


14


may also be incorporated with various other manually operable outdoor power equipment and machinery, including, but not limited to, hand held lawn and garden machinery, snow blowers, pumps, pressure washers, and generators. Accordingly, the present invention is not limited to the lawnmower


10


or the engine


12


depicted in the drawings and described herein. For one having ordinary skill in the art, it will become apparent from the drawings and the description how the engine starting device


14


may be adapted for use with various types of machinery and/or various types of engines.




A first manual actuator in the form of an elongated deadman handle or bail handle


36


is interconnected with the handle assembly


18


. The bail handle


36


is biased toward the shutdown position shown in FIG.


1


. As is known in the prior art, release of the bail handle


36


will initiate shutdown of the engine


12


by disabling ignition to the engine and/or the activation of a brake.




A second manual actuator in the form of a push button


40


is mounted to the handle assembly


18


at a location preferably adjacent one of the pivot pins for the bail handle


36


. The push button


40


is operatively interconnected with the bail handle


36


. The engine starting device


14


is actuated by depressing the push button


40


and, while the push button


40


is depressed, pivoting the bail handle


36


downward to the starting position. Preferably, the button


40


must be depressed to enable the handle


36


to be pivoted. Thus, the engine starting device


14


may be operated only upon the operator employing two separate motions, i.e., depressing (and holding) the push button


40


, and pivoting the bail handle


36


downward.




In alternative embodiments, the bail handle


36


and push button


40


may be replaced by other manual actuators, such as one or more push button devices, lever mechanisms, or other suitable manual actuators. Also, the push button


40


may operate in a different manner than described above. For example, actuation of the push button


40


may actuate or enable a part of the lawnmower startup assembly other than the bail handle


36


to be actuated by the bail handle


36


.




As seen in

FIG. 3C

, the starting device


14


includes a mounting bracket


44


having a spring housing


48


mounted thereunder. The lower end of the spring housing


48


is closed by an end cap


52


, and a lower bearing


56


is fit in the end cap


52


. The spring housing


48


houses an elastic member or power spring


60


having an outer end that is coupled to the spring housing


48


with a spring retainer


64


, and an inner end that includes a small loop


68


.




Referring to

FIG. 3B

, the starting device


14


also includes a main shaft


72


that has an arbor portion


76


and first, second, and third reduced diameter portions,


80


,


84


,


88


respectively. The second reduced diameter portion


84


is knurled or splined. The main shaft


72


is supported for rotation at its bottom end by the lower bearing


56


. The arbor portion


76


of the main shaft


72


includes an eyelet


92


that releasably receives the loop


68


at the inner end of the power spring


60


. The main shaft


72


is rotated in a loading direction


96


to wind and load the power spring


60


. As the power spring


60


unloads, it causes rotation of the main shaft


72


in an unloading direction


100


opposite the loading direction


96


.




A middle bearing


104


(

FIG. 3C

) is fit into the mounting bracket


44


and further supports the main shaft


72


for rotation. The middle bearing


104


sits on top of the arbor portion


76


of the main shaft


72


, where a shoulder is formed by reducing the diameter of the main shaft


72


to the first reduced diameter portion


80


. The shoulder holds the middle bearing


104


above the power spring


60


. Alternatively, a snap ring or other structure may be provided on the main shaft


72


to hold the middle bearing


104


away from the top of the power spring


60


.




With reference to

FIGS. 3A

,


3


B, and


3


C, the first reduced portion


80


of the main shaft


72


extends through the middle bearing


104


, the mounting bracket


44


, a lower arm


108


, a washer


114


, and into a main gear


118


. The second and third reduced portions


84


,


88


extend through a brake disk


122


; a clutch assembly including a clutch plate


126


, a clutch washer


130


, and a spring washer


134


(e.g., a Belleville washer); a clutch cover


138


; a ratchet member or wheel


142


; a debris cover


146


; a pinion gear


150


; a starter spline or helix shaft


154


; a washer


158


; a push nut


162


; and an upper bearing


166


. The upper bearing


166


is housed in an upper arm or housing


170


, and further supports the main shaft


72


for rotation. The debris cover


146


helps deflect debris away from the ratchet member


142


and main gear


118


. The upper housing


170


is riveted or otherwise fixed to the debris cover


146


and the lower arm


108


. The lower arm


108


(along with the upper housing


170


and the debris cover


146


) is pivotable about the main shaft


72


with respect to the mounting bracket


44


.





FIG. 4

better illustrates the main gear


118


and clutch assembly. The main gear


118


includes a central recessed portion


174


having a hole extending therethrough. The recessed portion


174


has a pair of diametrically-opposed cutouts


178


. The brake disk


122


includes a central collar portion


182


that is press-fit onto the knurled second reduced diameter portion


84


of the main shaft


72


, and therefore may be said to be fixed for rotation with the main shaft


72


. The clutch plate


126


includes a non-circular opening


186


. The clutch washer


130


includes a pair of ears


190


that are inserted into the cutouts


178


in the main gear


118


to prevent relative rotation between the main gear


118


and the clutch washer


130


. The clutch cover


138


is riveted or otherwise permanently affixed to the main gear


118


, capturing the clutch assembly and brake disk


122


in the recessed portion


174


. The spring washer


134


pre-loads the clutch assembly, and drives the brake disk


122


against the bottom of the recessed portion


174


to cause a frictional interface therebetween. The main gear


118


is thereby frictionally coupled for rotation with the brake disk


122


and main shaft


72


.




A frictional interface between the brake disk


122


and the clutch plate


126


is also created by the preloaded spring washer


134


. The main shaft


72


and brake disk


122


are thereby frictionally coupled for rotation with the clutch plate


126


. The frictional interface between the clutch plate


126


and the brake disk


122


permits torque to be transferred between the clutch plate


126


and the brake disk


122


up to a torsional threshold at which point the clutch plate


126


will slip with respect to the brake disk


122


. The ratchet member


142


includes a pair of depending ears


194


that extend through the holes in the clutch cover


138


, spring washer


134


, and clutch washer


190


, and into the non-circular hole


186


of the clutch plate


126


. Interference between the non-circular hole


186


and the ratchet member ears


194


causes the ratchet member


142


to be rotationally coupled to the clutch plate


126


. This construction therefore couples the main shaft


72


to the ratchet member


142


through the frictional interface between the brake disk


122


and the clutch plate


126


.




Referring again to

FIGS. 3A

,


3


B, and


3


C, the mounting bracket


44


includes a raised portion


198


having a hole. The raised portion


198


extends through an aperture


201


in the lower arm


108


, and supports a washer


205


and a pawl carrier or pawl lever


209


. A cap screw


213


(

FIG. 3A

) or other suitable fastener extends through a hole


215


the pawl carrier


209


and through the washer


205


and is threaded or otherwise secured in the hole in the raised portion


198


to secure the pawl carrier


209


to the raised portion


198


. The pawl carrier


209


is free to rotate about the cap screw


213


with respect to the lower arm


108


and mounting bracket


44


, and the cap screw


213


provides an axis of rotation for the pawl carrier


209


. The pawl carrier


209


includes an open-ended slot


217


and carries a pawl


221


(FIG.


3


A). A pawl post


225


extends through the pawl


221


and is mushroomed like a rivet or otherwise secured in a hole


229


in the pawl carrier


209


. The pawl post


225


thus provides an axis of rotation for the pawl


221


that is spaced from the axis of rotation of the pawl carrier


209


and that permits the pawl to pivot with respect to the pawl carrier. A torsional spring


233


includes a first end secured to the pawl carrier


209


and a second end secured to the pawl


221


to bias the pawl


221


toward the ratchet member


142


.




As seen in

FIGS. 3A and 3B

, a bearing


237


(

FIG. 3B

) is inserted into a depression in the lower arm


108


, and supports a pinion shaft


241


for rotation. The pinion shaft


241


includes a toothed portion


245


that meshes with the main gear


118


. The portion of the pinion shaft


241


above the toothed portion


245


is selectively received in the slot


217


in the pawl carrier


209


. The pinion shaft


241


also includes a shoulder or knurl which supports an input member or roller


249


(FIG.


3


A). The top of the pinion shaft


241


is supported for rotation in a bearing


253


that is inserted into the upper housing


170


. The roller


249


and pinion shaft


241


are fixed (e.g., by a press fit over the knurl or with a key) for rotation together. A return spring


257


(

FIG. 3B

) extends between the mounting bracket


44


and the lower arm


108


, and biases the lower arm


108


to a rest position (

FIG. 5

) in which the pinion shaft


241


is received within the pawl carrier slot


217


. In the rest position, the raised portion


198


abuts the edge of the opening


201


in the lower arm


108


and resists further rotation of the lower arm


108


in that direction. Preferably, the lower arm


108


is interconnected with the bail handle


36


by way of a cable. The lower arm


108


is rotatable to a full-disengaged position (

FIG. 6

) in response to actuation of the bail handle


36


and push button


40


.




Shutdown of the engine will now be discussed. During normal operation, when the bail handle


36


is released, the return spring


257


biases the lower arm


108


to the rest position (FIG.


5


), wherein the roller


249


abuts the flywheel


26


(FIG.


2


), the pinion shaft


241


enters the pawl carrier slot


217


, and the pawl


221


engages the ratchet member


142


. The roller


249


is thus rotated by the flywheel


26


, which causes the main gear


118


to rotate, which in turn causes the main shaft


72


to rotate and the power spring


60


to be loaded. As the power spring


60


loads, the flywheel


26


is slowed down by the resistance and the engine


12


is stopped. In this regard, the starting device


14


may also be used by itself as a brake or a device to slow the flywheel, and could be used in conjunction with a separate brake. By the time the flywheel


26


has stopped rotating, the power spring


60


is loaded and held in the loaded state by the pawl


221


, ready to start the engine


12


the next time it is used.




Alternatively, the power spring


60


may be loaded during engine


12


operation, in which case the starting device


14


would not act as a brake. A mechanism (not shown) may be included to facilitate moving the roller


249


into engagement with the flywheel


26


until the power spring


60


is loaded, and then move the roller


249


out of engagement with the flywheel


26


. Alternatively, a loading clutch (not shown) may be used to permit loading of the power spring


60


during engine operation without the need for a mechanism that disengages the roller


249


from the flywheel


26


. The loading clutch would permit the power spring


60


to be loaded to a point where the resistance of the power spring


60


to further loading overcomes the torsional threshold of the loading clutch, permitting the roller


249


to continue rolling in response to rotation of the flywheel


26


without overloading the power spring


60


.




Regardless of when the power spring


60


is loaded, the pawl


221


permits the ratchet member


142


to rotate in the loading direction


96


, but substantially prevents it from rotating in the unloading direction


100


. As the ratchet member


142


rotates in the loading direction


96


, the pawl


221


rides up the ramp of a first ratchet tooth


261


and falls into the space between the first tooth


261


and a second tooth


265


. The torsional spring


233


ensures that the pawl


221


will snap into the space as soon as the pawl


221


clears the first tooth


261


. This process continues as the ratchet member


142


rotates with the main shaft


72


and the power spring


60


is loaded. The pawl


221


substantially prevents the ratchet member


142


from rotating in the unloading direction


100


under the influence of the power spring


60


. In this regard, the ratchet member


142


, the pawl


221


, and pawl carrier


209


are collectively referred to herein as a locking mechanism for the power spring


60


.




With reference to

FIGS. 8 and 9

, an optional pawl control member may be used with the starting device


14


to reduce the noise created by the pawl


221


clacking against the ratchet member


142


during loading of the power spring


60


. Broadly speaking, the pawl control member may be a frictional member moving in response to rotation of a rotating element. However, the pawl control member is a parasitic load on the system, and therefore should be calibrated to create just enough friction between it and the rotating element to move the pawl


221


out of engagement with the ratchet member


142


(e.g., enough friction to overcome the biasing force of the torsional spring


233


). Any additional friction between the pawl control member and the rotating element may further reduce the efficiency of the starting device


14


and should be avoided.




The illustrated pawl control member is a length of spring wire


268


and the illustrated rotating element is the clutch cover


138


. The spring wire


268


is wrapped tightly enough around the clutch cover


138


to rotate with the clutch cover


138


, and includes a free end bent or shaped as a finger


272


. The pawl


221


is provided with a slot


276


into which the finger


272


extends. As the clutch cover


138


rotates in the loading direction


96


, the finger


272


moves along the slot


276


in the pawl


221


. When the finger


272


reaches the end of the slot


276


, it pushes the pawl


221


away from the ratchet member


142


. The spring wire


268


holds the pawl


221


in the disengaged position and slips with respect to the clutch cover


138


as the clutch cover


138


continues to rotate in the loading direction


96


(i.e., as the power spring


60


is loaded).




After the flywheel


26


has come to a stop (or if the power spring


60


is loaded during engine operation, when the roller


249


is disengaged from the flywheel


26


or the loading clutch slips), the power spring


60


changes the direction of rotation of the main shaft


72


and the above-described elements that rotate with the main shaft


72


or in response to rotation of the main shaft


72


. During this transition, the main shaft


72


and other elements initially rotate relatively slowly in the unloading direction


100


as they gather momentum. This causes the spring wire


268


to rotate slowly in the unloading direction


100


. Only a small amount of rotation in the unloading direction


100


is necessary to move the finger


272


backward in the slot


276


and permit the torsional spring


233


to move the pawl


221


into engagement with the ratchet member


142


.




Whether the pawl control member is incorporated in the device


14


or not, once the power spring


60


is loaded, the ratchet member


142


is biased by the power spring


60


to rotate in the unloading direction


100


. A line of force


280


(

FIG. 5

) is thereby created due to the interface between the pawl


221


and the ratchet member


142


. The line of force


280


extends between the respective axes of rotation of the pawl carrier


209


and the pawl


221


(i.e., the cap screw


213


and pivot post


225


are positioned on opposite sides of the line of force


280


). The line of force


280


thus creates a moment force about the pawl axis of rotation that causes the pawl


221


to pivot toward the engaged position shown in FIG.


5


. The pawl


221


is thus selfenergized or urged to remain in the engaged position when it is in the engaged position and the power spring


60


is loaded.




As seen in

FIGS. 3A and 10

, a key shaft


284


, key link


290


, and lock link


294


are also provided and are interconnected with a lock cam


298


. As seen in

FIGS. 3B

,


5


,


6


, and


10


, a ground bracket


308


supporting a stop switch


312


is also provided. When the bail handle


36


is released, the lower arm


108


pivots to the rest position and a contact tab


314


of the lower arm


108


contacts the stop switch


312


, thereby grounding the ignition system to prevent the engine


12


from running. The ground bracket


308


is positioned adjacent the mounting bracket


44


. A dowel pin


316


(

FIG. 3C

) is inserted into a hole


320


in the mounting bracket


44


and extends through an aperture


324


(

FIG. 3B

) in the ground bracket


308


and an aperture


328


in the lower arm


108


. The lock cam


298


is mounted for rotation on the dowel pin


316


, and includes a stub shaft


332


that is pivotably received in a hole


336


in the lock link


294


. The key shaft


284


extends through the key link


290


and through a hole


340


in the ground bracket


308


. The key link


290


is pivotably interconnected with the lock link


294


by way of a depending post


344


. The post


344


extends through the lock link


294


and into a curved slot


348


in the ground bracket


308


such that rotation of the key shaft


284


causes the post


344


to follow the curved slot


348


and results in movement of the lock link


294


, including some linear actuation of the lock link


294


.




In

FIG. 5

, the lock cam


298


is rotated out of abutment with the pawl


221


, permitting the lower arm


108


to be moved out of the rest position. Movement of the lock link


294


causes the lock cam


298


to pivot on the dowel pin


316


into and out of a locked position (FIG.


10


). When in the locked position, the lock cam


298


abuts the pawl


221


, holding the pawl


221


in engagement with the ratchet member


142


and preventing movement of the lower arm


108


out of the rest position and movement of the pawl carrier


209


away from the ratchet member


142


. A removable key


352


(

FIG. 2

) may be used to rotate the key shaft


284


and move the lock cam


298


into the locked position. In this regard, the removal of the key


352


substantially prevents startup of the engine


12


.




Engine startup will now be discussed. Referring again to

FIG. 5

, the line of force


280


also creates a moment force about the pawl carrier axis of rotation urging the pawl carrier


209


to rotate out of the engaged position when the pawl


221


is in the engaged position. The pawl carrier design substantially reduces the force required to disengage the pawl


221


from the ratchet member


142


, and is therefore preferred over actuation of the pawl


221


directly by the pinion shaft. The pinion shaft


241


resists rotation of the pawl carrier


209


when the pinion shaft


241


is positioned in the slot


217


. However, when the lower arm


108


is pivoted to move the pinion shaft


241


out of the pawl carrier slot


217


, the pawl carrier


209


is urged away from the ratchet member


142


due to the moment force. Additionally, the pinion shaft


241


contacts the pawl carrier


209


and pawl


221


and further causes it to pivot toward the fully-disengaged position shown in FIG.


6


. When in the fully-disengaged position, rotation of the pawl carrier


209


is stopped by the end of the pawl carrier


209


abutting the lock cam


298


. The lock cam


298


is positioned to stop the pawl carrier's rotation so that the pinion shaft


241


will again enter the pawl carrier slot


217


upon rotation of the lower arm


108


toward the rest position.




As seen in

FIG. 7

, the pawl


221


may be provided (e.g., by stamping) with a depending projection


358


that engages a portion of the pawl carrier


209


to prevent the pawl


221


from pivoting over the pawl carrier slot


217


. When in the engaged position (shown in phantom), the pawl


221


is held slightly away from the slot


217


or is substantially perfectly aligned with the slot


217


(the substantially perfectly aligned walls indicated with reference numeral


362


in FIG.


7


). In this regard, the pinion shaft


241


does not have to move the pawl


221


with respect to the pawl carrier


209


as the pinion shaft


241


is moved out of the slot


217


, thereby decoupling the torsional spring


233


substantially entirely from movement of the pawl carrier


209


(i.e., the torsional spring has substantially no effect on movement of the pawl carrier


209


).




With the lock cam


298


rotated to the unlocked position shown in

FIGS. 5 and 6

, the bail handle


36


may be actuated (in combination with actuation of the push button


40


), causing the lower arm


108


to pivot to the position shown in

FIG. 6

, which causes the pawl


221


to move out of engagement with the ratchet member


142


, which then permits the power spring


60


to unload. As the power spring


60


unloads, the main shaft


72


is rotated in the unloading direction


100


. The bottom end of the helix shaft


154


engages the ears


194


of the ratchet member


142


, causing the helix shaft


154


to be rotated with the main shaft


72


. The speed of rotation of the helix shaft


154


causes the pinion gear


150


to climb up the helix shaft


154


. When at the top of the helix shaft


154


, the pinion gear teeth engage the teeth of a flywheel gear


366


(FIG.


2


), causing the flywheel


26


to rotate and start the engine


12


. As the engine ramps up in speed and the power spring


60


unloads, the flywheel


26


soon rotates faster than the main shaft


72


and helix shaft


154


(i.e., the flywheel overruns the pinion gear


154


) and causes the pinion gear


154


to rotate back down the helix shaft


154


.




As the power spring


60


approaches or achieves a fully unloaded state, the loop


68


at the inner end of the power spring


60


is extracted from the eyelet


92


of the arbor portion


76


of the main shaft


72


, decoupling the main shaft


72


from the power spring


60


. Such decoupling reduces wear and fatigue on the power spring


60


, increases the life of the power spring


60


, and substantially prevents snapping off the inner end of the power spring


60


.




Should the operator release the bail handle


36


as the power spring


60


is unloading, the return spring


257


will cause the lower arm


108


to move the pawl


221


into engagement with the ratchet member


142


. The dynamic force transferred to the pawl


221


under these circumstances may be very high due to the angular momentum of the rotating main shaft and other elements. To reduce damage to the pawl


221


, the torsional threshold of the clutch mechanism is set to permit relative rotation between the main shaft


72


and the ratchet member


142


under these circumstances. More specifically, the clutch plate


126


will slip on the brake disk


122


when the torsional threshold is reached. In such an occurrence, the power spring


60


may substantially entirely unload without being reloaded, and may require that the engine


12


be manually started with the recoil starter on the next startup.



Claims
  • 1. An internal combustion engine comprising:a rotatable engine member; a shaft rotatable in a loading direction in response to rotation of said rotatable engine member, said shaft rotatable in an unloading direction opposite said loading direction to start said engine; an energy storing mechanism including at least one elastic member, said elastic member being loaded in response to rotation of said shaft in said loading direction and causing said shaft to rotate in said unloading direction in response to unloading of said elastic member; a locking mechanism selectively preventing rotation of said shaft in said unloading direction to maintain said elastic member in a loaded state; and a clutch mechanism operatively disposed between said locking mechanism and said shaft to permit rotation of said shaft in said unloading direction when a preselected torsional threshold between said shaft and said locking mechanism is reached.
  • 2. The engine of claim 1, wherein said locking mechanism includes a ratchet member and a pawl selectively engageable with said ratchet member, said clutch mechanism coupling said ratchet member to said shaft for rotation therewith while the torsional force between said ratchet member and shaft is below said torsional threshold.
  • 3. The engine of claim 1, further comprising:a gear having a central recessed portion and a gear hole in said recessed portion; and a clutch cover affixed to said gear and at least partially covering said recessed portion and capturing said clutch mechanism within said recessed portion, said clutch cover having a hole in alignment with said gear hole, said shaft extending through said holes in said gear and said clutch cover.
  • 4. The engine of claim 3, further comprising:a brake disk attached to said shaft and disposed in said recessed portion of said gear; wherein said clutch mechanism includes a clutch plate, clutch washer, and spring washer captured between said clutch cover and said brake disk, said spring washer being compressed by said clutch cover to cause a frictional coupling between said brake disk and said gear and to cause a frictional coupling between said clutch plate and said brake disk; and wherein said locking mechanism includes a ratchet member having a hole through which said shaft extends and a pawl selectively engageable with said ratchet member, said ratchet member including a portion extending into said recessed portion and engaging said clutch plate to fix said ratchet member for rotation with said clutch plate.
  • 5. The engine of claim 1, wherein said torsional threshold is set to allow relative movement between said locking mechanism and said shaft in the event of an attempt to stop rotation of said shaft in said unloading direction during unloading of said elastic member.
  • 6. The engine of claim 1, wherein said torsional threshold is set to reduce damage to said locking mechanism.
  • 7. An internal combustion engine comprising:a rotatable engine member; an energy storing mechanism including at least one elastic member, said elastic member being loaded in response to rotation of said rotatable engine member; a ratchet member operatively disposed between said elastic member and said rotatable engine member, said ratchet member rotating in a loading direction in response to rotation of said rotatable engine member and said elastic member being loaded in response to rotation of said rotatable engine member; a pawl movable into engagement with said ratchet member to selectively prevent rotation of said ratchet member in an unloading direction opposite said loading direction and to thereby selectively prevent unloading of said elastic member, said engagement between said ratchet member and said pawl establishing a line of force, said pawl positioned with respect to said line of force such that said pawl is urged toward staying in engagement with said ratchet member when in engagement with said ratchet member; and a pawl carrier carrying said pawl and movable to remove said pawl from engagement with said ratchet member, said pawl carrier being positioned with respect to said line of force such that said pawl carrier is urged to disengage said pawl from said ratchet member when said pawl is in engagement with said ratchet member.
  • 8. The engine of claim 7, wherein said pawl is pivotable about a first axis of rotation and said pawl carrier is pivotable about a second axis of rotation, said first and second axes of rotation being positioned on opposite sides of said line of force.
  • 9. The engine of claim 7, wherein said pawl is pivotable about an axis of rotation, said engine further comprising a biasing member biasing said pawl toward engagement with said ratchet member.
  • 10. The engine of claim 7, wherein said pawl carrier includes a slot, said engine further comprising a shaft received in said slot to prevent said pawl carrier from moving said pawl out of engagement with said ratchet member, one of said pawl carrier and shaft being movable to remove said shaft from said slot and permit said pawl carrier to move said pawl from engagement with said ratchet member.
  • 11. The engine of claim 10, wherein said shaft is a pinion shaft, said engine further comprising an input element supported by said pinion shaft and selectively engageable with said rotating engine member to cause rotation of said ratchet member in said loading direction and loading of said elastic member.
  • 12. The engine of claim 10, further comprising an arm supporting said shaft and movable to cause said shaft to move out of said slot in said pawl carrier.
  • 13. The engine of claim 12, wherein said arm is biased to move said shaft into said slot.
  • 14. The engine of claim 7, further comprising a pawl control member moving one of said pawl and said pawl carrier to position said pawl out of engagement with said ratchet member in response to said ratchet member rotating in said loading direction.
  • 15. The engine of claim 14, further comprising a rotating element located near said ratchet member and rotatable in response to rotation of said rotatable engine member, wherein said pawl control member includes a length of spring wire at least partially wrapped around said rotating element, said spring wire engaging said pawl such that when said rotating element rotates in said loading direction, said spring wire moves said pawl out of engagement with said ratchet member, and wherein said spring wire permits said pawl to engage said ratchet member in response to said rotating element rotating in said unloading direction.
  • 16. The engine of claim 15, wherein said pawl includes a slot, and wherein said spring wire includes a finger extending into said slot.
  • 17. An internal combustion engine comprising:a rotatable engine member; an energy storing mechanism including at least one elastic member, said elastic member being loaded in response to rotation of said rotatable engine member; a ratchet member operatively disposed between said elastic member and said rotatable engine member, said ratchet member rotating in a loading direction in response to rotation of said rotatable engine member, said ratchet member rotating in an unloading direction opposite said loading direction in response to unloading of said elastic member; a pawl selectively movable into engagement with said ratchet member to selectively prevent said ratchet member from rotating in said unloading direction; and a pawl control member moving said pawl out of engagement with said ratchet member while said ratchet member rotates in said loading direction and moving said pawl toward engagement with said pawl in response to said ratchet member rotating in said unloading direction.
  • 18. The internal combustion engine of claim 17, wherein said pawl includes a slot, and wherein said pawl control member includes a length of spring wire including a finger received in said slot.
  • 19. The engine of claim 17, further comprising a rotating element located near said ratchet member and rotatable in response to rotation of said rotatable engine member, wherein said pawl control member includes a length of spring wire at least partially wrapped around said rotating element, said spring wire engaging said pawl such that when said rotating element rotates in said loading direction, said spring wire moves said pawl out of engagement with said ratchet member, and wherein said spring wire permits said pawl to engage said ratchet member in response to said rotating element rotating in said unloading direction.
Parent Case Info

This application is a continuation-in-part of U.S. application Ser. No. 09/183,425, filed Oct. 30, 1998, now U.S. Pat. No. 6,230,678, the entire contents of which are incorporated herein by reference.

US Referenced Citations (4)
Number Name Date Kind
950848 Gardner Mar 1910
3301243 Lyvers Jan 1967
3763842 Dooley et al. Oct 1973
4363298 Kuhn Dec 1982
Continuation in Parts (1)
Number Date Country
Parent 09/183425 Oct 1998 US
Child 09/644624 US