WO2004102036A2

WO2004102036A2 - Enveloping worm transmission and machining of enveloping worm transmission

Info

Publication number: WO2004102036A2
Application number: PCT/US2004/013446
Authority: WO
Inventors: Yakov Fleytman
Original assignee: Yakov Fleytman
Priority date: 2003-05-09
Filing date: 2004-04-30
Publication date: 2004-11-25
Also published as: WO2004102036A3

Abstract

An enveloping worm transmission is suitable for the transformation of motion and power between an enveloping worm (29, 33 or 35) and a worm gear (30), (34 or 36) wherein the axis of the worm gear and the enveloping worm may be crossed, parallel or intersected. An enveloping worm transmission is provided with a unique enveloping worm (56 or 57) and worm gear (55 or 58) with modified enveloping worm thread surfaces. The enveloping worm transmission of the present invention is much smaller than any existing gear transmission and is easy manufactured by using machines for traditional gear cutting.

Description

TITLE: ENVELOPING WORM TRANSMISSION AND ACHIINING OF

ENVELOPING WORM TRANSMISSION

FIELD OF THE INVENTION

An enveloping worm transmission is suitable for^ the transformation of motion and power between an enveloping worm and a worm gear wherein the axis of the worm gear and the worm may be crossed, parallel or intersected. The enveloping worm transmission includes one or multi-thread enveloping worm engaged with a worm gear. The worm gear has teeth generated by enveloping worm threads. The enveloping worm transmission allows for low or high speeds, high load applications such as helicopter or automobile gearboxes, front and rear drive axles of vehicles, power take - off units, and turbine gearboxes. Certain applications may be outside of these fields, like power windows, doors or seats, power steering systems, chainless bicycle drive mechanism, and many industrial applications.

BACKGROUND

Worm/worm gear transmissions, in particular double enveloping speed reducers or Cone drive worm/worm gears, are well known in the mechanical power transmission field. In Europe the name of the double enveloping speed is globoid gear transmission. The worm gear is driven by the rotation of the worm with which it meshes. The rotational speed of the associated shaft of the worm gear is a function of the number of teeth on the worm gear and the number of threads on the worm. The worm may be single or multiple threaded. In all standard double enveloping worm/worm gear transmissions, the enveloping worm gear has a surface that is generated by the profile of an enveloping thread of the worm. The term "generated" describes how the profile of a worm gear tooth may be defined. It could utilize mathematical calculations defining the profile from equations of the surface of the enveloping worm thread; hobbing of a gear blank by a tool, having the profile of the worm thread; or via computer modeling, where the profile of a 3D solid worm gear is cut by the profile of a 3D solid worm thread. Conventional enveloping worm/worm gear transmissions are using worm thread with at least one revolution of the thread or 360 degrees of revolution. Drive face of the thread has a concave and a convex surface and coast face of the thread also has concave and convex surfaces. According to the Popov (U.S. Pat. No. 4,047,449), in order to increase the amount of tooth contact by increasing the number of teeth in actual contact, the enveloping worm has more than one revolution of the thread. The McCartin patent (U.S. Pat. No. 3,597,990) discloses a transmission with enveloping worm meshed with threaded followers. Thus, the McCartin gear with threaded followers is not able to have an envelope profile. Profiles of standard enveloping worm gear teeth usually have a profile generated by hobbing. However, the McCartin thread followers could not be made by hobbing or by generation of the worm thread profile. McCartin drive is used for indexing motion and does not have a self-lock feature. McCartin patent can use one thread with more than two revolutions for accurate indexing.

In my patent (U.S. Pat. No. 6,093,126), there is a split enveloping worm. However, the splitting halve is able to transmit motion only in one direction. To reverse the direction of motion it uses the other half. This means that only one surface of the worm thread is able to transmit motion. Each side of a thread has a concave surface and a convex surface. Only the concave surface is able to transmit torque and the convex surface doesn't have any mesh with a gear's tooth. This problem is present in all existing transmissions with an enveloping worm (Faydor Litvin 1994, Gear Geometry and Applied Theory. PTR Prentice Hall, Englewood Cliffs, N.J. pages 599- 612). In my patents U.S. Pat. No. 5992259 and U.S. Pat. No. 6148683 the enveloping worm and the worm gear can be one half or less of a split worm, which can have only one supporting shaft. Using only half or less than a half of the split worm gear or enveloping worm allows for easier assembly of the enveloping worm with the worm gear. The enveloping worm according with my patent mentioned above is also able to transmit motion by concave side of the thread with very good surface contact and by convex part of the thread despite very poor contact between surfaces of worm thread and gear tooth. The convex part of the enveloping worm thread has good contact with half of the gear width and the contact by the edge of the thread with another half of the gear.

Contact by the edge of the enveloping worm thread prevents the use of the enveloping worm in different types of gear transmissions, like a hybrid gear drive U.S. Patent No. 6128969 or any well known face gear transmissions: hypoid or spiral bevel. These limitations are the reason to modify the worm thread to eliminate useless parts of the thread and the gear teeth and to make new types of the gear transmissions with an enveloping worm more efficient.

New technology lowers production cost of spiral bevel and hypoid gears, but to make face gear and especially enveloping pinion, more machining time is still required. 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 completed 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 of the cutter path. This is also a low speed production technology. 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 surfaces 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.

Stritzel U.S. Pat. No. 4,926,712 used plunging for machining hourglass (enveloping) gear, not enveloping worm. In his method, the rotating hob is fed in a radial direction towards the axis of the rotating blank. An enveloping gear has a very different profile compared to an enveloping worm or a face gear in enveloping face gear transmission. Even though it has an enveloping shape, the teeth are straight or helical. Enveloping worm threads are not similar to helical. These threads form an envelope and also have a twisted cross section along a thread. Face gear teeth of enveloping face transmission have very complicated surfaces, which are defined by mating with enveloping worm thread.

In U.S. Pat. No. 5,829,305 by A Cralg et al. uses rolling technology for enveloping pinion with plurality of teeth being substantially uniform in profile and substantially parallel to each other. They have an overall profile substantially non-uniform with reference to a longitudinal axis of a drive shaft. That is why they have a pitch between a first pair of said teeth that is different than a second pitch between a second pair of said teeth. In motion these gears do not have dynamic conjugacy action and is able to transfer a very limited amount of torque where for one direction of rotation they can transfer very small torque.

In another U.S. Pat. No. 6,247,376 by Zhou et al. an enveloping worm tooth thickness, radial tooth position and axial tooth position are varied in order to achieve equal worm gear index angles. Roll die has a profile of spur gear. Produced worm and worm gears also do not have dynamic conjugacy action and are able to transfer very limited torque.

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.

It was not useful to use plunging feeding by rotating tool to manufacture an enveloping worm for power transmission. New unique enveloping worm face gears have very short threads of enveloping worm that allowed very good contact pattern with mating face gear. That is why machining of this special enveloping pinion by using plunging feed became practical. Rotating tool for plunging of face gear for enveloping face transmission did not exist before.

SUMMARY OF THE INVENTION

Enveloping worm transmission with teeth surface generated by profile of a thread where an enveloping worm having at least one screw thread that is engaged by at least one tooth of said worm gear has limitations to transferring torque mostly by concave surface of the worm thread. It is also very important to use an enveloping pinion with different types of the worm gears, like face gears. It is convenient to generate enveloping worm thread profile by the base profile of the involutes rack (cutter) rolls around the base circle where the pinion tooth section is always on the same angle to the gear circle. It does not roll around it, it just transfers around it. The position of an enveloping worm thread in mesh with a worm gear placed on the axis of the base circle is the original position. It is better to keep the original enveloping worm's thread surface unattached but to change the orientation of convex surface of the thread to be able to have good mesh with a worm gear tooth. Also, it is better to change orientation of concave surface of the thread to improve mesh between worm gear tooth and concave surface of the enveloping worm thread. The efficiency of the new enveloping worm transmission is even greater than that of well-known hypoid gearsets which are used in low ratio right angle drives. Thus, the present invention can replace hypoid or bevel gearing in many applications by reason of high efficiency for low ratio. In addition, by transmitting torque this new enveloping worm transmission is able to back drive from the worm gear to the enveloping worm. For the same size of the pinion, this invention has almost twice the torque capacity of traditional hypoid gearing.

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 worm gear transmissions 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 that was developed for standard worm gears. The more expensive cost of production of enveloping worms can thus be reduced. In new unique enveloping worm face gears profile of the enveloping pinion generates profile of mating face gear. Generated plunge feeding by hobbing or rolling, enveloping pinion teeth profile does not affect performance of the gears. Enveloping worm face gears have relative rotational motion with large area of contact. Enveloping worm thread has contact pattern of motion along the tooth: from the left to the right or from the right to the left depending on the direction of rotation. This also makes using plunge (radial) feeding for production of face gear very productive. In spiral bevel or hypoid gears pinion threads have contact pattern of motion across the tooth: from the top to the bottom. This makes plunge rolling for accurate tooth forming impossible. 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.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: FIGS. 1 , 2 and 3 show an enveloping worm transmission utilizing a modified enveloping worm with less than one revolution of threads;

FIG. 4 is a side view of a worm gear having taped shape; FIG. 5 is a sectional view of an enveloping worm transmission with an enveloping worm threads and worm gear teeth having asymmetric profile; FIG. 6 is a view of a 360 degree thread of an enveloping worm engaged with a worm gear;

FIG. 7 is a view of a 360 degree thread of an enveloping worm marked every 90 degrees of revolution;

FIG. 8 is a view of a 180 surface of a thread of an enveloping worm marked every 90 degrees of revolution;

FIG. 9 is a view of a worm gear tooth with three different surfaces; FIG. 10 is combinations of worm thread surface displacements for part A of the thread;

FIG. 11 is combinations of worm thread surface displacements for part B of the thread;

FIG. 12 is combinations of worm thread surface displacements for parts A and B of the thread;

FIG.13 shows an enveloping worm gear transmission according to the principles of the present invention, where an enveloping threads of an enveloping worm are modified;

FIG. 14 is a sectional view of worm gears for the different design combinations with 360 degree of an enveloping worm;

FIG. 15 is a sectional view of worm gears for the different design combinations with an enveloping worm with less than one revolution of threads; FIG. 16 is an isometric view of the enveloping worm transmission with a thread having less than 90 degrees of revolution and with higher ratio than enveloping worm transmission in FIG. 10;

FIG. 17 is a view of a 360 degree thread of an enveloping worm and a face gear; FIG. 18 is a plan view of a design with enveloping worm placed in the middle of the face of worm gear with enveloping worm having less than 180 degrees of revolution of threads;

FIG. 19 is an isometric view of a design with enveloping worm placed in the middle of the face of worm gear with enveloping worm having less than 180 degree of revolution of threads;

FIG. 20 is a plan view of a design with an enveloping worm placed on the face of worm gear with offset and with enveloping worm having 90 degrees of revolution of a thread;

FIG. 21 is an isometric view of a design with an enveloping worm placed on the face of worm gear with offset and with enveloping worm having 90 degrees of revolution of threads; FIG. 22 is a plan view of a design with 180 degree of thread revolution of an enveloping worm placed on the face of a worm gear;

FIG. 23 is an isometric view of a design with 180 degree of thread revolution of an enveloping worm placed on the face of a worm gear;

FIG. 24 is a plan view of a design with an enveloping worm placed on the face of worm gear with enveloping worm having 90 degrees of revolution of threads, where the enveloping worm is designed for highest ratio enveloping worm transmission shown in FIG. 16 ;

FIG. 25 is an isometric view of a design with an enveloping worm placed on the face of worm gear with enveloping worm having 90 degree of revolution of threads, where the enveloping worm is designed for highest ratio enveloping worm transmission shown in FIG. 16;

FIG. 26 is a plan view of a design with an enveloping worm and worm gear with parallel shafts according to the principles of the present invention;

FIG. 27 is an isometric view of a design with an enveloping worm and worm gear with parallel shafts according to the principles of the present invention;

FIG. 28 is a plan view of a design with an enveloping worm gear transmission with less than 90 degrees between worm axes and face worm gear axes according to the principles of the present invention;

FIG. 29 is an isometric view of a design with an enveloping worm gear transmission with less than 90 degrees between worm axes and face worm gear axes according to the principles of the present invention;

FIG. 30 is a sectional view of an enveloping worm in mesh with a worm gear where the worm gear is inside of the enveloping worm;

FIG. 31 is a view of the enveloping worm with an inverted envelope in mesh with a worm gear where an enveloping worm is inside of the worm gear;

FIG. 32 is a sectional view of worm gears for different design combinations of a worm inside of the worm gear;

FIG. 33 is a view of a 360 degree thread of an enveloping worm and a worm gear having profile of helical gear; FIG. 34 is a plan view of a design with an enveloping worm gear having profile of helical gear and an enveloping worm having less than one revolution of threads;

FIG. 35 is an isometric view of a design with an enveloping worm gear having profile of helical gear and an enveloping worm having less than one revolution of threads;

FIG. 36 shows a machine setting for machining modified thread of an enveloping worm;

FIG. 37 is an isometric view of an enveloping face gears with enveloping worm having threads with less than one revolution and with crossing shafts' axes of rotation with 90 degrees angle;

FIG. 38 is an isometric view of an enveloping face gears with enveloping worm having threads with less than one revolution and with parallel shaft's axes of rotation;

FIG. 39 is an isometric view of enveloping pinion having threads with less than one revolution;

FIG. 40 is an isometric view of enveloping worm blank in mesh with rotating hob having helical form;

FIG. 41 is a front view of enveloping worm blank in mesh with rotating hob having helical form;

FIG. 42 is an isometric view of enveloping worm blank in mesh with rotating hob having helical form, where enveloping blank is shortened for use as an enveloping worm pinion;

FIG. 43 is a front view of enveloping worm blank in mesh with rotating hob having helical form, where enveloping blank is shortened for use as an enveloping worm pinion. Position of rotating tool is for preliminary feeding;

FIG. 44 is an isometric view of a taped disc hob in mesh with an enveloping blank for machining one enveloping worm pinion;

FIG. 45 is a front view of a taped disc hob in mesh with an enveloping blank for machining one enveloping worm pinion;

FIG. 46 is a side view of a taped disc hob in mesh with an enveloping blank for machining one enveloping worm pinion; FIG. 47 is an isometric view of a helical die in mesh with machining enveloping worm having threads with less than one revolution;

FIG. 48 is a front view of a helical die in mesh with machining enveloping worm having threads with less than one revolution;

FIG. 49 is an isometric view of two helical dies in mesh with machining enveloping worm blank. The enveloping worms could be split in half after machining; FIG. 50 is a front view of two helical dies in mesh with machining enveloping worm blank. The enveloping worms could be split in half after machining;

FIG. 51 is an isometric view of a screw (strait worm) hob in mesh with machining enveloping worm blank;

FIG. 52 is an isometric view of two screw (strait worms) dies in mesh with machining enveloping worm blank. FIG. 53 is a front view of a ball helical die (or hob) in mesh with machining enveloping worm blank, where axes of rotation of worm blank and the helical die (or hob) are parallel;

FIG. 54 is a front view of a ball helical die (or hob) in mesh with machining enveloping worm blank, where axes of rotation of worm blank and the helical die (or hob) are perpendicular;

FIG. 55 is a front view of a die (or hob) having concave shape along its axis of rotation in mesh with machining enveloping worm blank;

FIG. 56 is a front view of a die (or hob) having convex shape along its axis of rotation in mesh with machining enveloping worm blank; FIG. 57 is an isometric view of a rotating tool having thread with less than one revolution in mesh with a face gear blank;

FIG. 58 shows a machine setting for machining modified thread of an enveloping worm by using a rotating tool with plunge feeding;

FIG. 59 is an isometric view of a rotating tool replaced from original position into new position which is defined by combinations of transferring and turning said rotating tool relative to said base coordinate system and said enveloping worm blank axis of rotation;

FIG. 60 is another isometric view of a rotating tool replaced from original position into new position which is defined by combinations of transferring and turning said rotating tool relative to said base coordinate system and said enveloping worm blank axis of rotation;

FIG. 61 is an isometric view of a rotating tool used for generation of enveloping pinion;

FIG. 62 is an isometric view of another rotating tool used for generation of enveloping pinion;

FIG. 63 is a view of a rotating tool having tape shape used for generation of enveloping pinion, where the middle part could have different lengths;

FIG. 64 is an isometric view of a rotating tool used mostly for cold rolling, abrasive generation or finishing of enveloping pinion. FIG. 65 is an isometric view of enveloping worm in mesh with two rotating cutters for machining concave and convex surfaces of the enveloping worm threads. FIG. 66 is an isometric view of enveloping worm in mesh with rotating cutter for machining concave surface of the enveloping worm threads.

FIG. 67 is an isometric view of enveloping worm in mesh with rotating cutter for machining convex surface of the enveloping worm threads.

FIG. 68 is an isometric view of a helical hob for machining an enveloping worm thread.

FIG. 69 is an isometric view of a helical hob in mesh with manufacturing enveloping worm having threads with less than one revolution. Enveloping worm has a split line in the middle.

FIG. 70 is another isometric view of a helical hob in mesh with manufacturing enveloping worm having threads with less than one revolution. Enveloping worm has a split line in the middle.

FIG. 71 is isometric view of a helical hob in mesh with machining enveloping worm having threads with less than one revolution.

FIG. 72 is an isometric view of a helical hob in mesh with two machining enveloping worms having threads with less than one revolution. The enveloping worms could be split in half after machining.

FIG. 73 is an isometric view of a helical hob in mesh with two machining enveloping worms having threads with less than one revolution.

FIG. 74 is another observation of the isometric view from FIG. 12. FIG. 75 is an isometric view of a helical hob in mesh with three machining enveloping worms having threads with less than one revolution. The enveloping worms could be split in half after machining.

FIG. 76 is another isometric view of a helical hob in mesh with three machining enveloping worms having threads with less than one revolution. The enveloping worms could be split in half after machining.

FIG. 77 is an isometric view of a helical hob in mesh with four machining enveloping worms having threads with less than one revolution. The enveloping worms could be split in half after machining.

FIG. 78- FIG. 81 are cross sections of a helical cutter with different profile of cutting edges.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following discussion relating to FIGS. 1-81 provides a detailed description of the unique enveloping worm gear transmissions which can be utilized with the present invention. More torque capacity is the main advantage for using the enveloping worm transmission. For various torque capacities, the enveloping worm transmission could have different enveloping angles. The worm thread mostly has a rolling action contact relationship with the teeth of the worm gear which provides an increased efficiency. With standard worm designs, having more than one thread and a large enveloping angle, the inability to assemble the worm and worm gear was considered a major obstacle. With the enveloping worm and worm gear of the present invention, the enveloping worm and worm gear are easily assembled by properly orienting the worm thread and worm teeth. According to the present invention, the greater enveloping angle for one revolution of a worm thread permits the use of worm gear teeth without undercut portions.

Referring now to the drawings, one embodiment of an enveloping worm transmission of the present invention is illustrated in FIG.1. It consists of enveloping worm 1 which engages with worm gear 2. Enveloping worm 1 has two supporting shafts, 3 and 4. Enveloping worm transmission in FIG 2 has only one supporting worm 1 , shaft 3. FIG 3 illustrates self-locking enveloping worm transmission, where tooth 5 of the worm gear is generated by the surfaces of thread 6. FIG. 4 illustrates taped shape of the worm gear with one supporting shaft 7 for non - locking enveloping transmission. This shape could be useful for mass production of enveloping worm transmission by forging, casting or injection molding. FIG. 5 is a sectional view of the mesh between the enveloping worm and the worm gear, where worm thread 8 and worm gear tooth 9 have asymmetric profile. It could be useful for self-locking transmissions.

FIG. 6 is a 360 degree (one revolution) view of thread 10 that is generated by using a base circle 11. The coordinate system X, Y, Z is located in the center of the base circle 11. Thread 10 is located symmetric to plane ZY. We have the original position of the thread, where the thread is usually used in double enveloping worm worm/gear transmissions and we have the original position of surfaces on one side of the thread and on another side (drive and coast surfaces ) of the enveloping worm. Original position of the enveloping worm thread is the position of the thread where it was generated by rolling a cutter around base circle 11 with simultaneous rotation of enveloping worm blank. Original position of an enveloping worm thread surface is the position on the thread where the surface was generated by rolling a cutter around base circle 11 with simultaneous rotation of enveloping worm blank. Worm gear 2 shows the ends of thread 10. FIG. 7 is a location of generated thread 10 with drive and coast surfaces after rolling straight cutting edge around base circle 11. The enveloping worm surfaces on thread 10 are in the original position. FIG. 7 is a view of thread 10 in location used for further modifications of the thread's surfaces. The location of the enveloping worm thread 10 could be in any angular location around the axis of rotation of the enveloping worm. In other words, it could be in any location of the enveloping worm thread where it is engaged by at least one tooth of the worm gear for the cycle of rotation around the enveloping worm axis of rotation. For example, the location of the thread 10 in FIG. 7 is rotated 180 degrees around worm axis of rotation W from that in FIG. 6. The thread is split into two halves with parts AB and CD using XY plane. Each halve of thread 10 was further split into parts A, B, C and D using plane locating on the axes W of thread 10 (worm) rotation, parallel to plane ZX. Parts A and C have smaller lead angle than parts B and D. This thread has a convex surface on parts A and B (marks A and B are placed on the convex surfaces) and a concave surface on the parts C and D (marks C and D are placed on the concave surfaces). Each convex surface on one side of the thread becomes the concave surface and each concave surface of another side of the thread becomes the convex surface. FIG. 8 is a view of the convex surface 12 extracted from parts A and B of the thread 10. Part B has a bigger lead angle than part A. Surface 12 has edge 13 and edge 14 between parts A and B. FIG. 9 is a view of a worm gear tooth with three different surfaces, 15, 16 and 17 (Faydor Litvin 1994, Gear Geometry and Applied Theory. PTR Prentice Hall, Englewood Cliffs, N.J. page 610). It is well known that a 360 degree of revolution enveloping worm thread generates very complicated worm gear tooth profile, where a proper worm gear tooth surface is part 16, FIG. 9. Surfaces 15 and 17 are generated by the edge of thread. For 180 degree revolution of a worm thread, the thread generates gear tooth profile with only two parts 15 and 16. In enveloping worm transmission without thread modification with 180 degree of the thread, the concave part of the thread 12 generates one gear tooth profile by moving along the tooth profile, but the convex part of the thread generates two independent gear tooth surfaces: one by edge 13 and another by edge 14 for the same side of the gear profile. In reality it finally generates the surface which is closer to a worm gear axis of rotation. If we will use unmodified 180 degree worm thread we will make only non reversible transmission where we have mesh of concave part of a thread that is able to transmit torque. When we will have mesh by convex part of a thread we will have very poor contact between gear tooth surface and worm thread edge. Many production companies have techniques for modifying a worm thread profile to avoid generation of the gear profile by the edge of a thread. They change the position of the cutter but they don't change a cutting plane. They machine modified concave and convex surfaces of the enveloping worm thread from the same position of a cutter. For example one book (Faydor Litvin 1994, Gear Geometry and Applied Theory. PTR Prentice Hall,

Englewood Cliffs, N.J. page 611) illustrates that modifications solve the problem but the shape of contact lines is less favorable. Another example where worm gear has a predetermined surface is well known as Wildhaber enveloping transmission US 1903318, US 2935886. In his enveloping transmission a hob and enveloping worm thread surfaces are generated by spur planes in orthogonal rotating axis and worm gear tooth surfaces is spur plane milled by plane milling cutters. The Wildhaber's idea of modification has serious undercutting and pointing problems on the enveloping worm; that is why it is only used for high gear ratios, more than 1 :40. Our goal is to able to generate enveloping worm thread surface by the profile of the cutter, rolls around the base circle 11 and then be able to generate tooth gear profile by surface of the enveloping thread, not the edge of the thread. The surface of worm gear teeth should be generated by the surface of the thread or threads of the enveloping worm using both sides of the thread: convex and concave. To able to generate the enveloping worm thread we generate the enveloping thread surfaces separately; for concave enveloping worm surface from one position of the cutting plane and for the convex enveloping worm surface from another position of the cutting plane. A computer model simulation can be utilized to generate the surface of the worm gear tooth. The worm gear can also be formed using known techniques such as hobbing by using profile of the enveloping worm pinion as a master gear. When worm gear teeth are generated by the surface of the enveloping worm threads having different lengths (shortened), the profiles of the worm teeth are different. These principles of the worm thread modification could be applied to any degree of revolution of the worm thread: less than 90, 90, less than 180, 180, less than 360, 360 and more than one revolution of the thread. Longer worm thread has better contact ratio, but for low kinematics ratios (for example, less than 1 :8) it is more difficult to manufacture enveloping worm transmission and even to assemble an enveloping worm with a worm gear. From manufacturing position it is more convenient to have asymmetric worm thread. For self-locking enveloping worm transmission it is better to have offset of the worm thread placed on the top of the worm gear in order to illuminate part of the thread with smaller lead angle. To design the worm gear surface we should use common sense: if it is a concave surface of the asymmetric worm thread with more than 180 degrees of revolution generating a gear tooth surface we need to use parts with bigger lead angle. For a convex surface of the asymmetric worm thread with more than 180 degrees of revolution generating a gear tooth profile, we need to use parts with smaller lead angle.

The following are examples of modifications of thread surfaces of an enveloping worm 1. The enveloping worm with 180 degrees or less of a thread revolution with concave surface on one side of the thread and convex surface on an opposite side (these are parts A and B on the thread) has only the convex surface of the worm thread modified by repositioning from its original location. The repositioning could be done using various approaches. FIG. 10, FIG .11 and FIG. 12 show possible combinations of such reposition for part A, for part B and for parts A and B. The magnitude and direction of the reposition could be defined for each design configuration (ratio, center distance, number of an enveloping threads, number of worm gear teeth) and initial angular position of a thread relative to it axis of rotation. For non-locking enveloping transmission it will defined for concave surface parts A and B but for convex surface just part A. For self-locking transmission it will be defined for concave and convex part B and even for extending thread with more than one revolution, but without part A. For repositioning of the enveloping worm surface we can use more than one combination from FIG. 10, FIG. 11 or FIG. 13. Let's describe in more details modification of the convex geometry of the enveloping worm with surface 12 showing on FIG.8. Axes X and Y define a cutting plane and axis W of rotation of enveloping blank rotation is placed on the cutting plane X and Y. Axis Z is normal to cutting plane X and Y. Said thread with concave profile is modified by repositioning its surface from original position. It will be done by turning around axis Y in the negative direction (approximately 1 degree) and then transferring along axis Y in the negative direction (approximately 1 mm). It is (- A52) in FIG. 10, (-B52) in FIG 11 and (-AB52) in FIG 12. For the concave surface of the thread from FIG. 7 this will be done by turning around axis Y in the positive direction and then moving along axis Y in the positive direction. It is (A52) in FIG. 10, (B52) in FIG 11 and (AB52) in FIG 12. For enveloping worms that have different direction of thread rotation (counterclockwise versa clockwise) the directions of turning and transferring should be opposite. The reposition of the enveloping worm surface could be done by additional transfer and turning. It will be done by turning around axis Y in the negative direction, then transferring along axis Z in the negative direction and then transferring along axis X in negative direction. The reposition of worm thread surfaces from their original (not modified) position could be done using any of above transferring and/or turning or different combinations of moving and turning. For some of the modifications, the result could be change of the thickness along the worm thread. For same modifications worm thread has gradually changing thickness which is wide in the smaller lead angle part of the enveloping worm. It is not necessary to turn worm thread surface exactly around above specified axes. It could be different axis, positioned parallel and close to above X, Y, Z and W axes. It is not necessary to transfer worm thread surface exactly along above specified axes. It could be different axis, positioned parallel and close to above X, Y, Z and W axes. Main idea of the present invention is that modification of the enveloping worm thread is done without any deformation or alteration of original geometry of the original enveloping thread. The topology of enveloping thread surfaces is not changed. Changes are present only in the position of repositioned surfaces of enveloping worm thread from original position that were defined by generating original surfaces of the enveloping thread. The result is a new enveloping worm transmission shown in FIG. 13 where enveloping worm 18 is in mesh with worm gear 19 and where enveloping threads of an enveloping worm were modified by changing positions of surfaces according to the principles of the present invention.

We have combinations of 360 degrees thread worm with of worm gear and combinations of less than one revolution of the enveloping thread with the worm gear. Possible cross sections of worm gears for 360 degrees or more per revolution of enveloping worm thread are shown in FIG. 14A, FIG. 14B, and FIG. 14C, FIG. 14D with positions 20, 21 , 22 and 23 respectfully.

Possible cross sections of worm gears for 180 degrees or less of revolution of enveloping worm thread are shown in FIG. 15A, FIG. 15B, and FIG. 15C, FIG. 15D, FIG. 15E with positions 24, 25, 26, 27, 28 respectfully. FIG. 16 is an isometric view of the enveloping worm transmission which has enveloping worm 29 and worm gear 30 with a modified thread of less than 90 degrees of revolution, with higher ratio than enveloping worm transmission in FIG. 10.

We have new enveloping worm transmission comprising: a worm gear and an enveloping worm, said enveloping worm having at least one screw thread that is engaged by at least one tooth of said worm gear wherein said worm gear is a face gear and said enveloping worm is placed into face arrangement with said worm gear. In this enveloping worm face transmission the enveloping worm could have any design, however, it is preferred that the enveloping worm be relocated to face arrangement with said worm gear from its original position (where it is usually generated for well known enveloping or double enveloping worm /worm gear transmission). What it is meant by generated is that design of worm thread and topology of surfaces may be generated by rolling cutter around base circle 11 with simultaneous rotation of worm's blank. In reality the profile of enveloping worm thread could be produce from mathematical equations, computer simulation, machined by the special program. The same enveloping worm thread from FIG. 10 was used in different designs of face gears on the FIG. 18 - FIG. 21 , FIG. 26, FIG. 27, FIG. 28 and FIG. 29. FIG. 17 is a view of a 360 degree thread of an enveloping worm 31 and face gear 32.

FIG. 18 is a plan view of a design with enveloping worm 31 placed in the middle of the face of worm gear 32 with enveloping worm threads having less than 180 degrees of revolution.

FIG. 19 is an isometric view of a design with enveloping worm 33 placed in the middle of the face of worm gear 34 with enveloping worm 33 threads having less than 180 degrees of revolution.

FIG. 20 is a plan view of a design with an enveloping worm 35 placed on the face of worm gear 36 with offset and with enveloping worm threads having 90 degrees of revolution.

FIG. 21 is an isometric view of a design with an enveloping worm 35 placed on the face of worm gear 36 with offset and with enveloping worm threads having 90 degree of revolution. FIG. 22 is a plan view of a design with 180 degree of thread revolution of an enveloping worm 37 placed on the face of worm gear 38.

FIG. 23 is an isometric view of a design with 180 degrees of thread revolution of an enveloping worm 37 placed on the face of worm gear 38.

FIG. 24 is a plan view of a design with an enveloping worm 39 placed on the face of worm gear 40 with enveloping worm 39 having 90 degrees of revolution of threads, where the enveloping worm 39 was designed for highest ratio then enveloping worm transmission shown in FIG. 16.

FIG. 25 is an isometric view of a design with an enveloping worm 39 placed on the face of worm gear 40 with enveloping worm 39 threads having 90 degrees of revolution, where the enveloping worm 39 was designed for highest ratio then enveloping worm transmission shown in FIG. 16.

FIG. 26 is a plan view of a design with an enveloping worm 41 and worm gear 42 with parallel shafts according to the principles of the present invention.

FIG. 27 is an isometric view of a design with an enveloping worm 41 and worm gear 42 with parallel shafts according to the principles of the present invention.

FIG. 28 is a plan view of a design with an enveloping worm gear transmission with less than 90 degrees between enveloping worm 43 axes and face worm gear 44 axes according to the principles of the present invention;

FIG. 29 is an isometric view of a design with an enveloping worm gear transmission with less than 90 degrees between enveloping worm 43 axes and face worm gear 44 axes according to the principles of the present invention; In FIG. 18, FIG. 19 and FIG. 28, FIG. 29 said enveloping worm axis and said face gear axis are intersected.

The same principals of enveloping worm surfaces modifications, as described above were used for new face transmissions. The thread were repositioned but the topology of the surfaces was not change. When we used 180 or less than 180 degrees of revolution of enveloping worm thread no modifications of concave surface of enveloping thread are needed in order to have good mesh between enveloping worm thread and face gear. For more than 90 degrees of convex surface of enveloping thread or more than 180 degrees of revolution of concave surface of enveloping worm thread it is necessary to reposition concave or convex surfaces of the enveloping worm thread. In FIG. 28, FIG. 28 said enveloping worm axis and said face gear axis have less than 90 degree angles.

This is a non obvious usage of well known enveloping worm. By repositioning the enveloping worm thread from its original position, were it was generated by rolling of cutting edge around base circle 11 into arrangement with face gear, mesh with face gear teeth becomes possible. To use this enveloping thread in different designs of new enveloping face transmission the surfaces of the thread can be repositioned into new positions with the same topology of surfaces. Surface repositioning of enveloping worm for different designs of enveloping face worm transmissions could be made by the same principals as described above for conventional enveloping worm transmission. In FIG. 20, FIG. 21 said enveloping worm axis and said face gear axis are crossed, but not intersected.

FIG. 24 and FIG. 25 are views of a design with an enveloping worm placed on the face of worm gear 40 with enveloping worm 39 threads having 90 degrees of revolution, where the enveloping worm 39 was designed for highest ratio 4: 11 of enveloping worm transmission shown in FIG. 18, FIG. 19. Face gear 40 was generated by using lowest ratio 5: 13. This design has good mesh but is different from FIG. 18, Fig. 19 gear teeth profile. The principle of design of enveloping face worm gear transmission when we use an enveloping worm generated with a different ratio than is used to generate face worm gear could be applied to different modifications of enveloping face worm gear transmissions.

FIG.26, FIG. 27 shows an enveloping worm transmission with parallel shafts according to the principles of present invention. Enveloping worm 41 is in mesh with worm gear 42, which has a spherical shape. The topology of enveloping worm surfaces the same like shows for the worm 18 in the FIG. 13. The thread of enveloping worm 35 in FIG. 20 and FIG. 21 has an inverted envelope, but it is the same thread of enveloping worm 18 from FIG. 13 after reposition of a surface of said thread from original position.

FIG. 28 and FIG. 29 shows an enveloping worm gear transmission with less than 90 degrees between axis of the worm 43 and axis of face worm gear 44 , generated by the worm 43 , having the same thread surfaces like enveloping worm 18 in FIG. 13 according to the principles of the present invention. Result of described worm modification could apply to many different applications. FIG. 30 shows a sectional view of the enveloping worm 45 in mesh with worm gear 46 where the worm gear 46 is smaller than enveloping worm 45. Enveloping worm 45 has more than one revolution of the thread or could be with more than one thread. FIG. 31 shows a view of the enveloping worm 47 with an inverted envelope in mesh with worm gear 48 where an enveloping worm 47 is inside of worm gear48. The enveloping worm 47 has a spherical shape.

FIG. 32 shows a sectional view of worm gear 49 and 50 for different design combinations of the enveloping worm 47 inside of worm gear 48. The above principles of surface repositioning of enveloping worm of conventional enveloping transmission applied to the design is shown in FIG. 33 - FIG. 35 In FIG. 33 we have enveloping worm 51 thread with 360 degrees of revolution placed on top of worm gear 52. The enveloping worm 53 threads have less than 180 degrees of revolution and worm gear 54 has a profile of helical gear. These FIG. 34 and FIG. 35 are also examples of predetermined gear profile used to generate the enveloping worm 53. The enveloping thread of said worm 53 has gradually changing thickness which is wide in the smaller lead angle part of said enveloping worm. In enveloping worm transmission the use of shortened threads with only concave surface on one side of the thread and convex surface on another side of the thread is preferred. The enveloping worm threads with only concave surface on one side and convex surface on another side have less than one revolution.

The preferable shape of the teeth and threads for the worm gear and the worm are shown in the drawings, but could be different. Even so, a worker of ordinary skill in the art would recognize that other shapes would come within the scope of this invention. For back drive, when the worm gear is a driven member and the enveloping worm is a driving member, this enveloping worm transmission also has high efficiency compared to a hypoid gearset. It was confirmed by testing of a steel enveloping worm transmission constructed according to the present invention. Up to now, those skilled in the art were of the opinion that an enveloping worm transmission requires unique machining technology that presents an insurmountable barrier to commercial applications. But now, by using more simplified worm thread with less than 180 degree of revolution it is possible to use existing technology for already producing gears, like for hypoid and spiral bevel gears. FIG. 36 shows an example of machine setting for machining modified enveloping worm. X, Y, Z is base coordinate system, placed in the middle of the base circle 11 for cutting tool 55.

W is axis of rotation of worm's blank 56 is placed on the cutting plane which is defined by axes X and Y. Vector Z1 normal to cutting plane X and Y is made from intersection of axis Y with axis W. Position 57 is the direction of turning to reposition cutter 55. To machine modified convex thread of the enveloping worm we need to turn cutter 55 around Y axis and then transfer along Y axis. New cutting plane for machining convex surface is defined by XC and Y axes and new position of vector Z1 is defined by Z2.

This set-up can be used to machine just one surface of enveloping worm thread, concave or convex. To machine the opposite surface (concave or convex) there will be a different set-up.

Machining the thread of enveloping worm by using Gleason or Oerlicon machines requires defining trajectory of motion for a cutting tool in order to generate concave and convex surfaces of the enveloping worm thread. Modified surfaces of enveloping worm thread could be designed and then manufactured using derived equations of the repositioned surfaces or by computer modeling or special setup of a machine according with the principles of present invention

The enveloping worm thread could also be generated by predetermined cutter profile, identical to a worm gear 54 profile. It could be helical teeth worm gear profile (US 1903318, US 2935886) from FIG. 34, FIG. 35 or any predetermined worm gear tooth profile. In this case we need to place a cutter in the position by repositioning it from original position according with the principal of the invention. The enveloping worm thread generation by predetermined cutter profile could be done in general by mathematical equations, computer simulations or real machining. Worm gear generation (by hobbing) could be used by a cutting tool with one thread or more than one of modified threads. If we use computer simulation to generate data we can use the same principles of reposition of predetermined enveloping worm surface into new position. Then we can generate a computer model of the worm gear by using already defined enveloping worm thread surfaces. Taped shape of the enveloping worm and specially designed taped shape of the worm gear allows us to use very productive technology, like forging, or casting.

The basic inventive system of the present invention can be reconfigured into many , different mechanical transmissions. For example, it can be used in a front axle drive and differential drive rear axle of a car, power windows, escalator drive, and more. The enveloping worm transmissions described above can be utilized in a power takeoff unit of a four-wheel drive transaxle. FIG. 37 is an isometric view of face gear 55 of an enveloping worm face gear transmission in mesh with enveloping worm 56 as a pinion. The enveloping worm face transmission is a new type of right angle gears (U.S. patent application No. 10 /435,143). Said enveloping worm 56 has at least one thread that is engaged by at least one tooth of said face gear 55 wherein said enveloping worm 56 is placed into face arrangement with said face gear 55. In this enveloping worm face transmission the enveloping worm 56 could have any design, however, it is preferred that the enveloping worm is utilized for standard enveloping or double enveloping worm /worm gear transmission. The difference is that we are using threads with less than one revolution or 180 or less degree of revolution and even 90 or less degree of revolution. Degree of thread revolution means an angle of thread rotation around its axis of rotation.

FIG.38 is an isometric view of enveloping worm 57 where threads have less than 180 degrees of revolution in mesh with face gear 58 where axis of enveloping worm and axis of a gear are parallel. FIG. 39 is an isometric view of enveloping worm 57 which is a pinion for different design configurations in face enveloping worm transmissions.

Machining of enveloping pinion with less than one revolution of threads can be done by conventional hobbing, rolling (preferably cold) or grinding process with plunging feeding.

FIG. 40 is an isometric view of enveloping worm blank 58 in mesh with rotating hob 59 having helical form. Helical form hob could be with involute or straight side helical teeth. Design of cutting edges of the helical hob 59 is similar to design of a known helical shaper cutter or a helical broaching tool. The helical shaper cutter can also be used instead of helical hob 59. The cutting edges placed on the plane perpendicularly cross the hob to its axis of rotation. The teeth may be with symmetrical profile, but for some modifications they could be asymmetrical. Thickness of hob 59 is approximately equal to the diameter of root generating enveloping pinion from worm blank 58. The hob 59 is positioned by the middle of its height on cutting plane X and Y. Axis of enveloping worm blank 58 positioned on the cutting plane is defined by axes X and Y. Hob 59 is symmetrical to cutting plane defined by axes X and Y hob for cutting two halves of the enveloping worm pinion 58. FIG. 41 is a front view of enveloping worm blank 58 in mesh with rotating helical hob 59. Helical hob 59 could have a helical gear form. Enveloping worm blank 58 is being machined with plunging of rotating tool, hob 59. Hob 59 rotates about its axis of rotation simultaneously with enveloping worm blank 58 and has feeding direction towards the axis of the rotating enveloping blank 58. Hob 59 rotates in ratio time faster than enveloping blank 58. By removing the chips of enveloping worm blank only half of the hob is involved, which is located on one side of cutting plane XY.

Another half could be used by turning over hob 59 180 degrees. Hob 59 should have cutting edges on opposite side of the cutting teeth. After plunging the machined enveloping worm blank 58 it will be split into two halves. This makes two enveloping pinions at the same time. It is more technological to machine enveloping worm blank, then heat treat it, finished it and then split it into two halves.

FIG.42 is an isometric view of enveloping worm blank 60 in mesh with rotating hob 59. This blank has asymmetrical profile. Machining with plunging could be done the same way as was described for FIGS. 40 and 41. For enveloping worm face gears with bigger enveloping angle when they have lower ratios than 2.5:1 and less than 24 face gear teeth, plunging could shrink enveloping worm pinion's active thread length and reduce contact ratio. In this case machining of enveloping pinion could be done with preliminary feeding in angular direction, with an angle less than 90 degrees between axis 62 of rotation of said enveloping worm blank 61 and direction of feeding for preliminary cutting. Arrow 63 is the direction of preliminary feeding. The position of cutting tool 59 for preliminary cutting is shown in FIG. 43. Cutting tool edges are positioning asymmetric to cutting plane X Y, on one side. After preliminary cutting, rotating tool makes additional turning into desirable position for plunging. Preliminary cutting avoids undesirable cuts of enveloping thread's ends. The feeding during preliminary cutting has a very small displacement where direction and amount could be defined on a computer model or practically on the real part by feeding hob into real enveloping pinion profile until it will touch the threads. Rotation into desired position will proceed until cutting tool 59 is positioned for plunging toward the axis of rotation 62 of enveloping blank 61. FIG. 44, FIG. 45 and FIG. 46 shows a set-up for machining of enveloping worm blank 61 by taped disc hob 64. Machining by plunging could be the same as was described for FIGS. 40 and 41. If it is necessary, preliminary machining could be done with the following turning of hob 64 and then final plunging. Same principal of plunging rotating tool into enveloping worm blank could be done by using an abrasive hob or a rolling die. It could be machined using conventional roll (cold roll) machining techniques. This can be done by one helical die 65 according with FIG. 47 and FIG. 48 or more preferably by opposite pressure from two rotating dies 66 and 67 in FIG. 49 and FIG. 50.

Arrows show directions of dies and enveloping blank rotations. Die 66 is located in upper support 68 and die 67 is located in lower support 69. The enveloping worm could be split into two halves after rolling. Cutting tool for machining with plunge feeding can have a screw or straight worm form. It could be a hobbing or rolling tool. Examples of using these rotating tools are shown in FIG. 51 and FIG. 52. It can be worm hob 70 or screw dies 71 and 72. For hobbing or rolling machining, the cutting teeth of the tool are positioned tangentially in a helical path of enveloping worm. For different modifications of enveloping worm pinion with less than one revolution of threads, when machining with plunge feeding the shape of rotating tool may be different. Fig. 53, FIG. 54, FIG. 55 and FIG. 56 show a variety of rotating tools having a different shape profile along its axis of rotation. Ball shape of rotating tool 73 with rotating shaft can make machining with plunging of enveloping blank 74 with a different angle between axis of tool rotation and axis of enveloping worm blank rotation. FIG 53 shows that rotating shaft of enveloping worm blank 73 is parallel to rotation shaft of rotating tool 74. FIG 54 shows that rotating shaft of rotating tool 75 is perpendicular to rotation shaft 76 of worm blank 77. New technology allows the making of rotating tool from abrasive material, such as tool 78. This tool can be used for rough cutting and for finishing by plunging feeding. Concave shape of rotating tool 78 in mesh with enveloping worm blank 79 in FIG. 55 can be parabolic or hyperboloid. Convex shape of rotating tool 80 in mesh with enveloping worm blank 81 in FIG. 56 can be parabolic or hyperboloid.

Machining of face worm gear can be done by using rotating tool having shape of mating enveloping pinion with 180 degree or less of thread revolution or by traditional face milling cutter. Rotating tool can have 90 degree or less of thread revolution. Rotating tool can have even one thread in order to be able to manufacture face gear. Machining can be done by conventional hobbing, rolling (preferably cold) or grinding process with plunging feeding. Direction for plunging is the shortest distance from initial position of rotating tool to machining face gear blank. The initial position can be defined by reverse engineering: moving mating pinion from mesh position in direction parallel to axis of face gear rotation or in direction perpendicular to the bottom of the surface located between face gear teeth, until there is no possible interference while mating pinion is spinning. FIG. 57 can be used for illustration of relation between rotating tool 82 with one cutting thread and face gear blank 83. Rotating tool 82 can have shape of enveloping pinion 56 or 57 or it can be a hob, a roll die or an abrasive tool.

FIG. 58 shows an example of machine setting for machining modified enveloping worm.

X, Y, Z is a base coordinate system, placed in the middle of the base circle 11 for rotating cutting tool 86. It could be hob, rotary die for cold or hot roiling or abrasive tool, having helical design with involute or straight sides of teeth shape. W is axis of rotation of worm's blank 84, where axis W is placed on the cutting plane defined by axes X and Y. Vector Z1 is normal to cutting plane YX, which is made from intersection of axis Y with axis W. Position 85 is the direction of turning to reposition cutter 86.

To machine modified thread of the enveloping worm we can change the setup of the hob. It can be done by: Changing the cutting plane by;

Turning around the line between axis of rotation of tool 86 and axis of rotation of blank 84, which is axis Z.

Turning around axis W of blank 84. Offset displacement along axis X or Y or Z or combinations of offsets; Combinations of above initial set ups of rotating cutting tool 86.

For example we need to turn cutter 86 around the Y axis and then transfer along the Y axis. New cutting plane for machining enveloping worm thread surfaces is defined by XC and Y axes and new position of vector Z1 is defined by Z2. FIG. 59 and FIG. 60 show a 3D isometric view of such set-up. Rotating cutting tool can be cylindrical shape like shown in FIG. 61 , hob 86 or taped shape shown in FIG. 62, hob 87. Cutting edges of rotating hob 86 or hob 87 are offset on one side from cutting plane XY. Cutting tool 88 shown in FIG. 63 has taped profile with middle cylindrical part 89. This tool 88 can be used twice; by one side 90 that offsets from the cutting plane XY until it wears off cutting edges and then by another side 91. By turning 180 degrees over it can be used again. Half of the cutting tool 90 can be used for preliminary cutting and another half 91 for finishing. Cutting edges on one side 90 should be opposite to the cutting edges on side 91. Width of the middle part 89 can vary. For generation of longer enveloping threads the width of the middle part 89 could be shorter, down to sharper edge. In case of sharper edge, hob becomes helical shaper cutter. Initial position for machining of non-modified enveloping pinion is when the cutting edge of a hob is placed in the cutting plane X Y. Rotating tool 86, 87 or 88 is a hob, but it can be abrasive helical cutter or a roll die as tool 92 shown in FIG 64. Modified enveloping worm pinion has an extended working length of enveloping surface of the thread. It has improved contact pattern. Modified profile of the threads has equal strengths in forward and reverse directions. For machining the thread of enveloping worm by using Gleason or Oerlicon machines the cutting tool is a ring (face mill) with cutting edges located on a circle around a tooling axis of rotation. This is the same tool that is used for production of spiral bevel or hypoid gears. Enveloping worm 84 is in mesh with rotating cutter 85 having cutting edges A for machining convex surface and cutter 86 with cutting edges B for machining concave surface of the enveloping worm threads shown in FIG. 65. Tooling axis of rotation for cutter 85 is 87 and tooling axis of rotation for cutter 86 is 88. Method of producing an enveloping worm requires defining trajectory of motion for a cutting tool in order to generate concave and convex surfaces of the enveloping worm thread. To generate convex surface of an enveloping worm thread, cutter 85 rolls around a base circle 11 on a cutting plane XY with simultaneous rotation of an enveloping worm blank around axis W. Cutting edge A of said cutter furthermore rotates around a tooling axis. Said tooling axis 87 may be laying on cutting plane or be offset to cutting plane or intersect the cutting plane. The same applies to generation of concave surface of the enveloping worm thread. It includes generation of an enveloping worm thread surface as cutter 86 rolls around base circle 11 on a cutting plane with simultaneous rotation of an enveloping worm blank around axis W, where a cutting edge B of said cutter furthermore rotates around a tooling axis. Said tooling axis (12)88 may be laying on cutting plane or be offset to cutting plane or intersect the cutting plane. For more flexible cutting said tooling axis 87 or 88 has additional motion, in direction normal to cutting plane or has addition motion by changing an angle between said tooling axis of rotation and cutting plane. For precise cutting the radius of rotation of cutting edge A (distance from edge A to tooling axis 87) is equal to or bigger than the maximum radius of convex curvature of said worm thread and the radius of rotation of said cutting edge B (distance from edge B to tooling axis 88) is equal to or smaller than the maximum radius of concave curvature of said worm thread. Cutter 86 in FIG. 67 could be traditional face milling tool. When machining concave and convex thread surfaces of enveloping pinion 84 with one size of cutting tool, original thread profile is changed. For example, thickness of the thread will be wide at the minimum root diameter of the pinion and narrow at the bigger root diameter of the pinion.

Machining of modified convex thread of the enveloping worm can be done by placing said cutter in a new position defined by reposition of cutting plane from original position to said position. It will be done by turning cutting tool 5 (85 or 86) around Y axis and then transferring along Y axis. New cutting plane for machining convex surface is defined by XC and Y axes and new position of vector Z1 is defined by Z2. Modified surfaces of enveloping worm thread could be designed and then manufactured using derived equations of the repositioned surfaces or by computer modeling or special setup of a machine according with the principles of present invention, where said reposition of cutter 85 (or 86) from original position into said new position is defined by turning cutter 85 (or 86) relative to said base coordinate system and said enveloping worm axis of rotation. Another way of modifying profile of enveloping worm thread surfaces is by repositioning cutter 85 (or 86) from original position into said new position that is defined by transferring cutter 85 (or 86) relative to said base coordinate system and enveloping worm axis of rotation. It can also be done by combinations of transferring and turning said cutter relative to said base coordinate system and said enveloping worm axis of rotation. Placement of cutter 85 in said new position is for machining convex surface of enveloping worm thread 2 and placement of cutter 86 in said new position is for machining said concave surface of enveloping worm thread 84. Above describe method where we are using a tool with rotating cutting edges could as well be applied to manufacturing gears 2, 5, 30, 34, 36, 38, 55 and 58. Other ways to generate enveloping worm pinion is to use traditional tangential hobbing, with a tool similar to hob 88 or even by broaching with a helical broaching tool. To generate enveloping pinion by a hob for tangential hobbing or by a helical broach an enveloping worm blank and the hob for tangential hobbing or helical broach need to have relative rotation. Speed of the enveloping worm blank pinion around its axis of rotation is faster than the speed of the hob for tangential hobbing or the helical broach. It could be done without rotation of the hob for tangential hobbing or helical broach, but enveloping worm blank must rotate around its own axis of rotation and simultaneously around axis of the hob for tangential hobbing or the helical broach. Determination of relative speed of enveloping worm blank and the hob for tangential hobbing or helical broach speed can be the same as used for tangential hobbing.

FIG. 68 is an isometric view of cutter 89 for machining a blank of enveloping worm. Cutter 89 is a hob having shape of helical gear. Shape for hob can be the shape of a hob that is widely used for tangential cutting of worm gears, not enveloping worm (pinion).

Cutter's 89 linear feed motion could be calculated according with helical angle of the hob, lead angle of enveloping worm thread and desired cutting speed. Rotation speed of cutter 89 is slower than the rotational speed of the blank of enveloping worm. FIG. 69 is an isometric view of a helical profile cutter 89 in mesh with a blank for machining an enveloping worm having threads with less than one revolution. Enveloping worm is a solid piece that could be split after machining it into halves 90 and 91 of different enveloping worm pinions. Different view of FIG. 9 is shown in FIG. 70. FIG. 71 is an isometric view of a helical profile hob 89 in mesh with enveloping worm blank 90 having threads with less than one revolution. FIG. 72 is an isometric view of a helical profile cutter 89 in mesh with two enveloping worm blanks with synchronized rotation having threads with less than one revolution. The enveloping worm could be split in halves 92, 93, 94 and 95 after machining. FIG. 73 is an isometric view of a helical profile cutter 89 in mesh with two enveloping worm blanks 94 and 95 for machining enveloping worms having threads with less than one revolution. FIG. 74 is another observation of the isometric view from FIG. 72.

FIG. 75 is an isometric view of a helical profile cutter 89 in mesh with three enveloping worms with synchronized rotation for machining enveloping worms having threads with less than one revolution. The enveloping worm could be split in halves 92, 93, 94, 95, 96 and 97 after machining. FIG. 76 is another observation of the isometric view from FIG. 75.

FIG. 77 is an isometric view of a helical profile cutter 89 in mesh with four enveloping worm blanks for machining enveloping worms having threads with less than one revolution. The enveloping worm could be split in halves 92, 93, 94, 95, 96, 97, 98 and 99 after machining. FIG. 78 is a cross section of cutter 89 with straight cutting edges. FIG. 79 is a cross section of cutter 89 with involute cutting edges. FIG. 80 is a cross section of cutter 89 with crown convex cutting edges and FIG. 81 is a cross section of cutter 89 with crown concave cutting edges. For specific design, profile of cutting edges can be different, even more complicated. For generating enveloping worm that will be a pinion, it could be a cutter with straight cutting edges. For generating an enveloping worm that will be used us a hob to generate matting gear, profile of cutting edges could be crown profile with concave cutting edge. For machining of enveloping worm thread surface, axis of rotation of helical cutter 89 is placed in the center of base circle 11 and cutter's 13 cutting edges will be located around a base circle 11. To produce enveloping worm, enveloping worm blank 84 rotates around axis W of enveloping worm blank 84 and enveloping worm blank 84 has relative motion around tooling axis Z to helical cutter 89. Helical cutter 89 (or 13) furthermore has linear motion along its axis Z of rotation, which is linear motion normal to cutting plane X Y. This linear motion is tangential feeding. Helical cutter's 89 and enveloping worm's blank 84 relative motion around tooling axis Z can be done by helical cutter 89 rotating around tooling axis Z with simultaneous rotation of enveloping worm blank 84 around axis Z or by only rotating enveloping blank 84 around axis Z. Speed of relative motion is a function between number of helical cutter 89 teeth and number of generated threads on the enveloping worm blank 84. Linear feeding can be increment motion or step motion. Generation of enveloping worm from one blank can produce up to two enveloping worms with 180 or less degree of thread revolution and generation of enveloping worm from two blanks can produce up to four enveloping worms with 180 or less degree of thread revolution. Generation of enveloping worm from three blanks can produce up to six enveloping worms with 180 or less degree of thread revolution and generation of enveloping worm from four blanks can produce up to eight enveloping worms with 180 or less degree of thread revolution.

Above described method of machining enveloping worm face gears makes face gear less expensive in production than any current technology. More efficient motion of enveloping worm face gears and ultra high torque capacity and lower production cost makes these new gears very competitive against known helical, face, spiral bevel and hypoid gears.

GENERAL ADVANTAGES OF ENVELOPING WORM TRANSMISSION The invention has high torque capacity due to surface to surface contact mesh that reduces contact stresses and increases the torque capacity of the enveloping worm transmission. The above described gear transmission is transmitting more power with a smaller size. It is a compact alternative for helical, hypoid and spiral bevel gears in almost any application, especially in power expended applications, like helicopters, ships, boats and cars.

For the same pinion size, this invention can provide up to twice the torque capacity of hypoid gearing.

Contact pattern of motion along the tooth line: from the left to the right or from the right to the left depending on the direction of rotation. In hypoid gears contact pattern of motion across the tooth: from the root to the tip or from the tip to the root depending on the direction of rotation. Enveloping gear has better lubrication condition (suction vs. squeezing out) that may reduce the cost in assembly and increase driving efficiency. The efficiency of the new worm/worm gear transmission is equal to or even greater than efficiency in well-known spiral bevel gearing, which are used in right angle drives or helical gearing, which are used in parallel shaft drives. In automotive power train applications like front and rear drive axles, power take-off units, transmissions, traction systems and mechanical amplifiers it saves space up to 30 % and significantly reduces weight. It will work in power windows and power seats, steering drives.

In the traditional engineering practice enveloping (double enveloping) gears have been used with the ratio 1 :5 and higher. Hypoid and spiral bevel gears are always been used in the lower ratio applications. Enveloping worm transmission has higher percentage rolling/sliding motion and excellent dynamic lubrication. It has extending life even without lubrication. Enveloping worm transmission can be used in lower and high ratio applications. Manufacturing errors in machining of any gears are function of cutting tool geometry and kinematical error of a machine. For enveloping worm transmission only kinematical error of a production machine may be significant. For this reason gears in this invention can be produced more accurately, especially in mass production.

Asymmetric profile of the enveloping pinion with less than 180 degree of thread revolution allows backlash adjustment by linear tuning of the pinion along the axis of its rotation. This is very important to gears with parallel shaft axes. Helical gears can not be adjusted in this manner. Most of the time each thread of the enveloping worm is in mesh longer than any other known gear's pinions. It reduces impact of engagement and disengagement, increases the contact ratio and makes quieter motion. One directional motion of contact pattern along gear tooth produces friction forces in one direction that also helps to reduce noise. The lower noise of the enveloping worm transmission compared with hypoid and bevel gear transmissions make using the enveloping worm transmission of the present invention more beneficial, particularly in helicopter or in motor vehicle power train applications. Using existing gear cutting machines can make enveloping worm transmission cheaper than hypoid or spiral bevel gears. Sharpening of cutting tool, to generate enveloping worm pinion by hobbing where cutting edges are placed on the planes that are perpendicular to an axis of rotating hob, is less expensive than sharpening of cutting edges of traditional hob for helical gears generation. This makes production of enveloping worm transmission with parallel shafts cheaper than standard helical gears with parallel shafts. For some configuration forging technology or power metallurgy could be applied as well. There are very broad opportunities for the enveloping worm transmission made from plastic.

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.

Claims

CLAIMSWhat is claimed is:

1. An enveloping worm transmission comprising: a worm gear (2) and an enveloping worm (1), said enveloping worm (1) having at least one screw thread (10) that is engaged by at least one tooth of said worm gear (2) where said enveloping thread (10) of said enveloping worm (1) modified by reposition of a surface (12) of said thread (10) from original position.

2. The enveloping worm transmission as recited in claim 1 , wherein said enveloping worm (1) has 180 degrees or less than 180 degrees of a thread revolution with concave surface on one side where concave surface of said enveloping worm thread is modified by reposition from original position.

3. The enveloping worm transmission as recited in claim 1 , wherein said enveloping worm (1) has 180 degrees or less than 180 degrees of a thread revolution with convex surface on one side where convex surface of said enveloping worm thread (10) is modified by reposition from original position.

4. The enveloping worm transmission as recited in claim 1 , wherein said enveloping worm (1) has 180 degrees or less than 180 degrees of a thread revolution with concave surface on one side and convex surface on another side where concave side of said enveloping worm thread (10) is modified by reposition from original position and convex surface of said enveloping worm thread (10) is modified by reposition from original position.

5. An enveloping worm transmission comprising: a worm gear (34) and an enveloping worm (33), with said enveloping worm (33) having at least one thread that is engaged by at least one tooth of said worm gear (34) wherein said worm gear (34) is a face gear and said enveloping worm (33) is in a face arrangement with said worm gear (34).

6. The enveloping worm transmission as recited in claim 5, wherein said thread has 180 degrees or less than 180 degrees of revolution.

7. The enveloping worm transmission as recited in claim 5, wherein said enveloping worm axis and said face gear axis are intersected.

8. The enveloping worm transmission as recited in claim 5, wherein said enveloping worm axis and said face gear axis are crossed.

9. The enveloping worm transmission as recited in claim 5, wherein said enveloping worm axis and said face gear axis are parallel.

10. Machining of enveloping worm transmission having an enveloping pinion (55) in a mesh engagement with a face gear (56) where said enveloping pinion (55) is being machined with plunging of rotating tool (59) into an enveloping worm blank (58).

11. Machining of enveloping worm transmission as recited in claim 10, where said enveloping pinion (55) has 180 degrees or less of thread revolution.

12. Machining of enveloping worm transmission as recited in claim 10, where said rotating tool (59) has a helical form.

13. Machining of enveloping worm transmission according with claim 10, where said rotating tool has a screw form (70^.

14. Machining of enveloping worm transmission according with claim 10, where machining is hobbing and said rotating tool is a hob (59).

15. Machining of enveloping worm transmission according with claim 10, where machining is rolling and said rotating tool is a roll die (66).

16. Machining of enveloping worm transmission according with claim 10, where said rotating tool is an abrasive hob (78).

17. Machining of enveloping worm transmission having an enveloping pinion in a mesh engagement with a face gear (83) where said face gear (83) is being machined with plunging of rotating tool (82) having form of said enveloping pinion with 180 degrees or less of thread revolution.

18. Machining of enveloping worm transmission according with claim 17, where machining is hobbing and said rotating tool is a hob.

19. Machining of enveloping worm transmission according with claim 17, where machining is rolling and said rotating tool is a roll die.

20. Machining for face gears according with claim 17, where machining is abrasive hobbing and said rotating tool is an abrasive hob.

21. Machining of enveloping worm transmission including generation of an enveloping worm thread surface by a tool (86) rotating around a base circle

(11) on a cutting plane with simultaneous rotation of an enveloping worm blank (84) around an axis of said enveloping worm, including placement of said rotating tool (86) in a new position defined by reposition of cutting plane from original position to said position.

22. Machining of enveloping worm transmission as recited in claim 21 , where said reposition of said rotating tool (86) from original position into said new position is defined by turning said rotating tool (86) relative to said base coordinate system and said enveloping worm blank's (84) axis of rotation.

23. Machining of enveloping worm transmission as recited in claim 21 , where said reposition of said rotating tool (86) from original position into said new position is defined by transferring said rotating tool (86) relative to said base coordinate system and enveloping worm blank's (84) axis of rotation.

24. Machining of enveloping worm transmission as recited in claim 21 , where said reposition of said rotating tool (86) from original position into said new position is defined by combinations of transferring and turning said rotating tool (86) relative to said base coordinate system and said enveloping worm blank's (84) axis of rotation.

25. Machining of enveloping worm transmission as recited in claim 21 , wherein placement of said rotating tool (86) in said new position is for machining said convex surface of said enveloping worm blank's (84) thread.

26. Machining of enveloping worm transmission as recited in claim 21 , where said tool (86) is a rotating tool with its own axis of rotation.

27. Machining of enveloping worm transmission as recited in claim 26, wherein said rotating tool is a hob (87).

28. Machining of enveloping worm transmission as recited in claim 26, wherein said rotating tool is an abrasive helical cutter.

29. Machining of enveloping worm transmission as recited in claim 26, wherein said rotating tool is a roll die (92).

30. Machining of enveloping worm transmission as recited in claim 26, wherein said rotating tool is a face mill (86).

31. Machining of enveloping worm transmission including generation of an enveloping worm thread surface by a cutter (85) rolling around a base circle on a cutting plane with simultaneous rotation of an enveloping worm blank (84) around an axis of said enveloping worm, where a cutting edge of said cutter furthermore rotates around a tooling axis (88).

32. Machining of enveloping worm transmission as recited in claim 31 where said tooling axis (88) has additional motion, in direction normal to cutting plane;

33. Machining of enveloping worm transmission as recited in claim 31 where said tooling axis (88) has addition motion by changing an angle between said tooling axis (88) of rotation and cutting plane.

34. Machining of enveloping worm transmission as recited in claim 31 where radius of rotation of said cutting edge (86) is equal to or bigger than the maximum radius of convex curvature of said worm (84) thread.

35. Machining of enveloping worm transmission as recited in claim 31 were radius of rotation of said cutting edge (85) is equal to or smaller than the maximum radius of concave curvature of said worm (84) thread.

36. Machining of enveloping worm transmission as recited in claim 31 including placement of said cutter (86) in a new position defined by reposition of cutting plane from original position to said position.

37. Machining of enveloping worm transmission as recited in claim 36, where said reposition of said cutter from original position into said new position is defined by turning said cutter (86) relative to said base coordinate system and said enveloping worm (84) axis of rotation.

38. Machining of enveloping worm transmission as recited in claim 36, where said reposition of said cutter (86) from original position into said new position is defined by transferring said cutter (86) relative to said base coordinate system and enveloping worm (84) axis of rotation.

39. Machining of enveloping worm transmission as recited in claim 36, where said reposition of said cutter (86) from original position into said new position is defined by combinations of transferring and turning said cutter (86) relative to said base coordinate system and said enveloping worm (84) axis of rotation.

40. Machining of enveloping worm transmission as recited in claim 36, wherein placement of said cutter (86) in said new position is for machining said convex surface of said enveloping worm (84) thread.

41. Machining of enveloping worm transmission as recited in claim 36, wherein placement of said cutter (86) in said new position is for machining said concave surface of said enveloping worm (84) thread.

42. Machining of enveloping worm transmission as recited in claim 31 , wherein said rotating tool is a face mill (86).

43. Machining of enveloping worm transmission including generation of an enveloping worm thread surface using helical cutter (89) that is placed by tooling axis in center of a base circle, where an enveloping worm blank (90) rotates around an axis of said enveloping worm blank and said cutter (89) and said enveloping worm blank (90) have relative motion around a tooling axis to said cutter and said cutter (89) furthermore has linear motion along said tooling axis.

44. Machining of enveloping worm transmission as recited in claim 43 where it has additional worm blank (93) with synchronized rotation and said cutter generates surfaces from two worm blanks (92) and (93) simultaneously.

45. Machining of enveloping worm transmission as recited in claim 43 where it has two additional worm blanks (93) and (96) with synchronized rotation and said cutter generates surfaces from three worm blanks (92), (93) and (96) simultaneously.

46. Machining of enveloping worm transmission as recited in claim 43 where it has three additional worm blanks (93), (96) and (98) with synchronized rotation and said cutter generates surfaces from four worm blanks (92), (93), (96) and (98) simultaneously.

47. Machining of enveloping worm transmission as recited in claim 43 where said helical cutter (89) has straight cutting edges profile.

48. Machining of enveloping worm transmission as recited in claim 43 where said helical cutter (89) has crown cutting edges profile.

49. Machining of enveloping worm transmission as recited in claim 43 where said helical cutter (89) has involute cutting edges profile.