Patent Application
20060090340
The present invention relates to production of an enveloping worm pinion face gears in the field of face, spiral or hypoid gears manufacturing. The enveloping worm pinion face gears are used to reduce or to increase speed or increase or reduce torque in helicopter or automobile gearboxes, turbine gearboxes, ship's transmission, and industrial applications. Certain applications may be outside of these fields, like power windows, doors or seats, power steering systems, chainless bicycle or motorcycle transmissions, and much more.
A right angle gear transmission is well known for the transformation of motion and power between shafts where the axes of the pinion and the gear may be crossed or intersected. Recently two new types of enveloping pinion gear transmissions from my U.S. Pat. No. 6,148,683 and enveloping/globoid pinion face transmission from my patent application Ser. No. 10/435,143 made right angle gear transmission more attractive for use in many applications, even in applications where it was traditional to use parallel shaft gears. These gears are able to transfer mechanical power between crossed or intersected shafts more efficiently. Their pinion is a worm, which is known as an enveloping worm in the USA but in Europe it is known as a globoid worm. Enveloping shape can be concave or convex profile. It is a very broad definition. Machining of known enveloping worm thread includes generation of said enveloping worm thread surface by a cutter which rolls on a cutting plane around a tooling axis with simultaneous rotation of an enveloping worm blank around an axis of said enveloping worm. In my patent application Ser. No. 10/435,143 I name the enveloping worm with convex profile as an enveloping worm with inverted enveloping shape. This shape could be spherical or elliptical shape, but not limited to the specific cross section profile.
The use of pinion shape as dish-shaped or doorknob-shaped bodies in a mesh with a pin's gear teeth is also illustrated in the patents of Stokes et al, “Motion Transmitting Device,” U.S. Pat. No. 705,624 (1902); and Mohr et al, “Angular Drive Intermittent Motion Mechanism,” U.S. Pat. No. 5,197,354 (1993) and Rourke et al, “Pineapile Gear and Method Of Manufacturing the Same,” U.S. Pat. No. 5,497,671 (1996).
New technology lowers production cost of spiral bevel and hypoid ring gears, but to make hypoid or spiral bevel pinions, more machining time is still required. Production generating tool for machining mating pair of gear by face milling tool and face hobbing tool with cutting edges designed according with imaginary generating gears. Different methods of generation of standard spiral and hypoid gears are represented in U.S. Pat. No. 5,116,173 by Goldrich, U.S. Pat. No. 5,088,343 by Krenzer, which show the formation of mating teeth and mostly their cross sectional modifications.
Face gear of enveloping face gear is a very new invention and no information exists on how to make it in production, especially in mass production. The pinion can be referred to as “globoid” pinion that is more suitable for an enveloping worm with inverted enveloping shape.
Face gear teeth of enveloping face transmission have surfaces, which are defined by mating with enveloping worm thread allowing for good contact pattern. Theoretical standard spiral bevel has zero magnitude of relative linear velocity along instant axis between the gear's pair. Its production is achieved by kinematical motion of the machines. Wildhaber U.S. Pat. No. 1,622,255 teaches that spiral gear is formed by the cutting tool without generating any motion between the tool and a blank gear. The pinion is generated by second tool that represents the ring gear, which has relative motion to axis of pinion rotation. Production generating tool for machining mating pair of gear by face milling tool and face hobbing tool has cutting edges designed according with imaginary generating gears. Different methods of generation of standard spiral and hypoid gears are represented in U.S. Pat. No. 5,116,173 by Goldrich, U.S. Pat. No. 5,088,343 by Krenzer, which show the formation of mating teeth and mostly their cross sectional modifications. Longitudinal profile of the mating teeth represents the nature of the specific types of the gears, like spiral bevel gears, and reflects major characteristics of the gears.
Known enveloping worms have long threads with one or more than one of thread revolutions. This creates problems for manufacturing. In the Cone patent (U.S. Pat. No. 1,885,686), generation of an enveloping worm is made by relative rotation of a hob and worm blank in predetermined time relation on axes perpendicular to each other. Cutting tool is thin to avoid undesirable cuts of enveloping threads. During hobbing the distance between axes of the hob and the wheel blank changes and after completion of feeding the hob widens the gaps by additional angular displacement to generate sides of thread surfaces. It is a low speed production technology. In the Trbojevich patent (U.S. Pat. No. 1,987,877), generation of an enveloping worm is made by reciprocating a tool with helical cutting teeth in a helical path, placing the axis of the enveloping worm blank to be cut tangentially or transversely to the cutter path. This is also a low speed production technology. The more productive method for generation of an enveloping pinion is by Trbojevic (U.S. Pat. No. 1,812,384), where selected cutter is the face mill type placed in tangential relation to the work. By nature of enveloping worm with symmetrical thread profile along axis of the enveloping worm rotation when face mill tool passes through the midplane of the worm it removes material both on approach and recess due to the “helical interference”. Mating gear for above manufacturing pinion is not face gear. In patents by Wildhaber (U.S. Pat. No. 1,902,683 and U.S. Pat. No. 2,935,888 and U.S. Pat. No. 3,079,808), thin worm hob with variable orientation and feeding is able to generate surface sides of threads. Worm gear has composite tooth surfaces in order to be able to conjugate with an enveloping pinion. When Wildhaber worm is engaged with worm gear in standard enveloping worm and worm gear transmission, it produces reliable contact pattern only in one direction of rotation by concave side of threads. Convex side of threads is useless.
New unique enveloping worm face gears have asymmetrical thread profile along axis of the pinion rotation. They are very short and similar to spiral bevel or hypod gear profile. That is why manufacturing enveloping worm pinion by face mill type cutter does not have “helical interference”.
The standard generation motion for bevel and hypoid gears compromises of operatively engaging a rotating tool with a work piece in predetermined turning about a theoretical axis of rotation. Face enveloping pinion gears have a very similar design, but a very different performance. In new unique face enveloping gears enveloping worm pinion has an enveloping profile along axis of the enveloping worm pinion rotation. The pinion with enveloping shape envelopes the body of mating face gear and the pinion with inverted enveloping shape is enveloped by mating face gear. The longitudinal profiles of the mating enveloping pinion thread and face gear tooth are very different from spiral bevel or globoid gear profiles.
In spiral bevel or hypoid gear contact pattern moves across gear tooth flank from the top to the root of the tooth. Manufacturing of spiral bevel and hypoid gear requires very accurate generation of mating teeth cross section profiles. In general, relative motion of cutting tool during spiral bevel gears generation has two goals. First, is to establish conjugate action by profiles of meshing surfaces. Second, is to produce reduction motion in predetermined ratio. Face enveloping gears have contact pattern that moves along face gear tooth. This does not require any special cross section profile of the mating surfaces and it is less sensitive to cutting tool errors. This makes the possibility for face enveloping gears to be manufactured more similar to spiral bevel or hypoid gears, where technology already exists. By using generation motion for spiral bevel gears compromised of operatively engaging rotating cutter with a work piece to generate face gear, rotating cutter should have additional turning around imaginary enveloping wheel axis of rotation or theoretical generating gear for enveloping pinion. The imaginary enveloping wheel axis of rotation can be defined as axis of rotation of imaginary flat enveloping worm wheel or tooth shaper that can be used to generate enveloping pinion or in other words it is the theoretical generating gear for the enveloping pinion.
The turning can be defining by placing cutter on the inner circle of said face gear in tangential relation relative to the meshing of said enveloping worm thread and turning said rotating cutter relative to imaginary enveloping wheel axis of rotation until generating tooth is on the outer circle of the face gear.
Right angle gears have very wide use in many applications. Right angle gears for the same size of the pinion and the same ratio have almost 30 percent more torque capacity than traditional parallel shaft gearings. This is primarily due to high contact ratio. In existing enveloping worm and worm gear transmission it was not possible to use plunge feeding because gears became just index drives and were not efficient gears for transmission power. In face enveloping pinion gears, pinions have less than one revolution of threads or even less than 180 degree of threads revolution. This makes enveloping worm pinion more similar to straight worm and allows the use of very productive technology. In new unique enveloping pinion face gears the profile of the enveloping pinion generates the profile of mating face gear. It can be zero offset or offset face gears, similar to spiral bevel and hypoid gears. Open area of spaces between face gear teeth allow plunge feeding by shaping, hobbing or rolling. Enveloping worm thread has contact pattern of motion along the face gear tooth: from the left to the right or from the right to the left depending on the direction of rotation. A face gear along projection of globoid pinion axis of rotation on the face gear has a concave or sector of circuit shape. It allows the use of rotating tool that rotates around specific axis of rotation, where material removing elements on said rotating tool follow said circuit shape of said face gear.
To generate enveloping pinion, cutting tool should have additional turning relative to axis of rotation of imaginary enveloping wheel and relative turning to said enveloping pinion around axis of said enveloping pinion should be faster in ratio between meshed face enveloping gears. Additional turning relative to imaginary enveloping wheel axis of rotation can be defining by placing cutter on the inner circle of said face gear in tangential relation relative to meshing of said enveloping worm thread and turning of said rotating cutter relative to axis of rotation of imaginary enveloping wheel until generating tooth is on outer circle of the face gear.
Simplified manufacturing of face enveloping gears by rotating cutter having generating elements rotating about respective cutter-head axis consisting in positioning the cutter in tangential relation relative to the meshing of said enveloping worm thread having smallest pitch diameter with said face gear teeth and turning of said rotating cutter relative to axis of imaginary enveloping wheel until generating tooth is on outer circle of the face gear.
Simplified manufacturing of enveloping pinion machined by rotating cutter having generating elements rotating about respective cutter-head axis consisting in positioning the cutter in tangential relation relative to meshing of said enveloping worm thread having smallest pitch diameter with said face gear teeth and then turning of said rotating cutter relative to axis of theoretical generating gear for enveloping pinion and turning relative to the enveloping pinion around the axis of rotation of enveloping pinion until generating of a thread with the biggest pitch diameter. Relative turning to the enveloping pinion is faster in ratio between meshed face enveloping gears.
Above described manufacturing could be used for independent manufacturing of concave or convex surfaces of the enveloping pinion threads and face gear teeth or for simultaneous manufacturing of concave and convex thread surfaces or face gear teeth surfaces. Rotating tool can have cutting blades for machining or an abrasive surface for finishing. Using rotating tool like face milling or face hobbing allows for the use of very productive technology that was developed for standard spiral bevel and hypoid gears. The cost of production of enveloping face gears can be reduced.
Face mill type cutter or cup or dish shaped tool is a rotating tool having concave surface on one side and convex surface on another side. For generation of enveloping face gears, rotation tool has complementary cutters, one for enveloping pinion and another for face gear.
In another method of generating of face gear tooth shaper or helical rotating tool rotating around an axis of rotation of a theoretical generating gear for enveloping pinion with a predetermined relative motion to a work gear.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the complete description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the comprehensive description and the accompanying drawings, wherein:
The following discussion relating to
For manufacturing using motions for standard bevel gears to define theoretical generating gear for enveloping pinion it is necessary first to design an enveloping worm with the same ratio. This enveloping worm should have the same geometry on the side with smallest pitch diameter as a spiral bevel pinion: the same number of threads and cross sectional shape and size and the same helical or lead angle. Mating for this enveloping worm is an enveloping wheel, which can be referred to as a theoretical generating gear for enveloping pinion and its axis of rotation can be used for generating mating face gears. Axis 14 is a face enveloping gear rotating axis and axis 15 is axis of face type milling tool rotation. Axis 15 is located on line 16 that is perpendicular to line 17 that is located in tangential relation relative to meshing of said enveloping worm 13 thread located by smallest pitch diameter of the enveloping worm with teeth (not shown) of face gear. In
Machining of face enveloping gears can be done by conventional face milling, face hobbing or grinding tools that are used for standard spiral bevel or hypoid gear manufacturing. Tool 18 can have cutting blades or it can be a tool with abrasive surfaces.
The position of cutting tool 18 for preliminary cutting of face gear is shown in
After placing tool on the inner circle of the face gear, rotating cutter 18 turns relative to axis 11 of rotation of theoretical generating gear for enveloping pinion until generation of tooth on the outer circle of face gear 1. Final position of rotating cutter 18 is on the outer circle of face gear 1 shown in
For machining of enveloping pinion, rotating cutter 18 is positioned in tangential relation relative to meshing of said enveloping worm thread 13 by smallest pitch diameter section with teeth of face gear 1. This occurs by turning rotating cutter 18 relative to axis 11 of rotation of theoretical generating gear for enveloping pinion 12 and relative to enveloping pinion 10 around axis 9 of rotation of enveloping pinion 10 until generating thread with the biggest pitch diameter. For generation of face enveloping gears by using existing technology for standard spiral bevel or hypoid we are modifying existing geometry by adding enveloping shape for a worm pinion and modifying the shape of a face gear to complement the shape of an enveloping worm. By doing this we will change the longitudinal profiles of the mating gears that are responsible for the law of relative motion of meshed pair of gears without affecting their conjugate action. This can be illustrated by using the same setting for generation of mating enveloping pinion and face gear.
According with the invention, to manufacture face gear using rotating cutter 18 having generating elements rotating about respective cutter-head axis 15 by generation motion for spiral bevel gears comprising of operatively engaging a rotating tool with a work piece, said rotating cutter has additional turning relative to axis 11 of rotation of theoretical generating gear for enveloping pinion 12. This additional turning can be defining by placing cutter 18 on the inner circle of face gear 1 in tangential relation relative to meshing of said enveloping worm thread 13 and turning said rotating cutter 18 relative to axis 11 of rotation of theoretical generating gear for enveloping pinion 12 until generating tooth on outer circle of the face gear.
To manufacture enveloping pinion 10 using rotating cutter 18 having generating elements rotating about respective cutter-head axis 15 by generation motion for spiral bevel gears comprising of operatively engaging a rotating cutter 18 with a work piece, said rotating cutter 18 has turning relative to axis 9 of rotation of enveloping pinion (this is the motion used for manufacturing standard spiral bevel gears) and has additional turning relative to axis 11 of rotation of theoretical generating gear for enveloping pinion 12, where turning around the axis 9 of enveloping pinion is faster in ratio between meshed face enveloping gears. For pattern correction of mesh between convex surface of face gear and concave surface of the enveloping pinion thread, the turning around the axis 9 of enveloping pinion could be slower than ratio between meshed face enveloping gear. For example, for assemble of face gear with 30 teeth with an enveloping pinion having 11 threads each thread could be manufactured having a 30:11 ratio. Positioning of cutter 18 is in tangential relation relative to the meshing enveloping worm thread 13 of enveloping pinion 10 can be done by exactly positioning tangent to the tangential line 17 or with slight variations. Through variations we can make simultaneous modifications of enveloping pinion and mating face gear. By changing the radius of cutter 18 we can change helical angle of mating gears. The purpose for modifications is to increase torque capacity or increase efficiency of motion or to manufacture mating gear by compromising between the torque capacity and the efficiency for optimal performance of face enveloping gears. Cutter 18 is a standard cutter that comprises of inner generating elements or outer generating elements. It also can have both inner and outer generating elements. For face milling they are blades and for grinding the generating elements are abrasive particles. Using indexing motion of a work piece we can complete generation of an enveloping pinion threads and face gear teeth. If the motion of a rotating cutter is synchronized with motion of a work piece we will have continuous or face hobbing generation.
During feeding when rotating tool 29 (or 30) moves towards direction of work gear 19, the axis of rotation of rotating tool 29 is parallel (not shown) to imaginary axis 27 of rotation of theoretical generating gear for enveloping pinion 20 or it crosses axis 27 of rotation of theoretical generating gear for enveloping pinion 20. In final position of feeding the position of axis of rotation of rotating tool 29 is united to imaginary axis of rotation 27 position.
Above described method of manufacturing enveloping pinion face gears makes face gear less expensive in production than any current technology. It makes machining time for face gear equal to machining time of spiral bevel or hypoid ring gears. But more simple shape of enveloping pinion is required to reduce machining time for pinion production. In machining mating pair of gears it saves mashing time and tool expenses. Machines for manufacturing these enveloping pinion face gears are less expensive than widely used machines for manufacturing spiral bevel or hypoid gears. This method can be used for manufacturing enveloping face gears with offset between axis of pinion rotation or without offset, where the axis of pinion rotation intersects the axis of mating face gear. Design of the enveloping offset gears can be done with the same dimensions as spiral bevel or hypoid gears. By designing with the same outer and inner ring diameters and the same pinion diameter, enveloping zero offset or offset face gears can replace existing spiral bevel and hypoid gears in current applications. More efficient motion of enveloping (globoid or inverted enveloping worm) pinion face gears and ultra high torque capacity and lower production cost makes these new gears very competitive against known spiral bevel, hypoid or face gears.
In the invention being thus described, it is obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
