WO2008081228A1

WO2008081228A1 - Spiral gear drive train

Info

Publication number: WO2008081228A1
Application number: PCT/IB2007/000614
Authority: WO
Inventors: Charles St. Louis
Original assignee: Modelo Metalico, S.A.
Priority date: 2007-01-03
Filing date: 2007-01-03
Publication date: 2008-07-10

Abstract

This invention is a spiral driven gear train with large gear ratio reduction in a single stage. The gear train comprises a scroll gear (11) with spiral tooth or teeth driving a toothed driven gear (12). The spiral gear can be made to have rolling contact, multi-speeds, single and double enveloping. The driven gear can incorporate rolling contact, and be made to hydro-plane. The axis of the gears can be offset with each other. The drive train can be configured to drive at odd angles between driver and driven axis. The axes of the gear train can be adjusted while under power. Also the spiral drive train can be near parallel or made to run with the axis of the driver and driven parallel. Many of the above features can be used in combination in one drive train.

Description

ib

Spiral Gear Drive Train

ZO FIELD OF THE INVElNTiOiS

This Invention relates generally to gears and gear trains for the design of mechanical power transmissions, and more specifically to gear reducers with a large gear ratio in a single stage.

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40 background of invention Discussion of the Prior Art

There are several types of gear reducers which exist that can provide large gear reductions in a single stage. Some examples of these are a nutating gear inside an internal gear of slightly larger diameter, harmonic drives, or simply very small input spur gears driving very large output spur gears. While each of these and other types of gear trains have unique merits, they all have unique disadvantages such as high cost, low power capability or an unpractically large size. Because of these disadvantages none of these types of gear trains are widely used.

One of the most commonly used arrangements for large gear reduction in a single stage is a worm & gear (worm gear drive). The worm gear drive provides the most reasonable trade-off between complexity, size, gear reduction, cost and load carrying ability for risost applications but still falls short of an ideal gear train. Some of the shortcomings of the worm gear drive are the complex shapes of the worm and the toothed gear which make them more difficult and costly to fabricate. The worm also suffers from limited power capabilities due to the fact that the shape of the worm and the toothed gear restrict the tooth to the tooth contact area as well as restricting the number of teeth that can be engaged at any time.

Also, the worm gear drive is not tolerant of debris and foreign particles and can easily be jammed. Another shortcoming of the worm gear drive is that it does not tolerate misalignment between the worm gear and the toothed gear very well. A still further shortcoming of the worm gear drive is that the input and output shafts cannot be coplanar and must be arranged at 90 degrees and in offset planes making it difficult to employ for some applications.

The use of a spiral to cause uniform motion or intermittent motion has been used in indexing devices and intermittent motion mechanisms for many years. The use of the Archimedes spiral shaped scroll, in order to cause a uniform motion, has been around for centuries. The novelty of the invention is to apply the use of a spiral and driven toothed gear for the purpose of power transmission. The use of a spiral driving gear is not obvious in that conventional gear designers might discourage employing a spiral gear as a driving gear since there is much more sliding contact,i.e friction, when compared to a worm gear. In-depth analysis by the inventor has revealed numerous unique and advantageous characteristics of the spiral gear drive which mitigate the concerns of additional friction. In light of the many advantages identified and disclosed herein, the spiral gear drive will become an important and preferred means of gear reduction and power transmission for many applications.

The worm & gear transmissions have many characteristics that are useful and also some mechanical limitations. The design changes that have to be implemented to overcome those limitations add to the cost of manufacture. Described below are two of the known problems with a worm and gear drive trains. This invention does not have these two problems. SB

Disclosure of Invention Technical Problem

100

Some of the shortcomings of the worm gear drive are the complex shapes of the worm and the toothed gear which make them more difficult and costly to fabricate. The worm also suffers from limited power capabilities due to the fact that the shape of the worm and the toothed gear restrict the tooth to the tooth contact area as well as restricting the number of teeth that can be engaged io5 at any time for a given size gear train. The worm gear drive is not tolerant of debris and foreign particles and can easily cause jamming. Another shortcoming of the worm gear drive is that it does not tolerate misalignment between the worm gear and the toothed gear very well. A still further shortcoming of the worm gear drive is that the input and output shafts cannot be coplanar and must be arranged at 90 degrees and in offset planes making it difficult to employ for some no applications.

The worm & gear transmissions have many characteristics that are useful and also some mechanical limitations. The design changes that have to be implemented to overcome those limitations add to the cost of manufacture. Described below are two of the known design problems with a worm and gear drive trains. This invention does not have these two problems. us l)Double Enveloping worm & gear drives with twenty three teeth and less will have a worm thread whose root will be detrimentally undercut. 2)For gear ratios of over fifty to one the helix angle of the worm is decreased and the mechanical efficiency also decreases. Even though gear reducers with a gear ratio of fifty to one or higher are sometimes utilized in a single stage worm & gear drive train, these very high gear ratios will cause more friction and heating. The spiral i2o drive gear train Invention described herein overcomes these and some other problems common to traditional single step gear reducers.

Technical Solution

125 These and other objects of the present invention are obtained by providing; 1). A scroll gear made with either a flat, or concave or bowl shaped profile where the spirals lay. 2). A multi- speed scroll gear with single start and or multiple start spirals on its face. 3). A multi-speed scroll gear with either a flat or concave or bowl shaped profile where the spirals lay. 4). A modification to gear teeth that will induce hydraulic planing. 5). Rolling members located either in the form of

130 a spiral on scroll gear or in place of gear teeth on the diameter of the driven gear.

Advantageous Effects

Accordingly ;

135 It is the object of the present invention to provide a single step gear reducer with an large meshing surface.

It is an object of the present invention to provide a spiral drive train with single enveloping. It is an object of the present invention to provide a spiral drive train with double enveloping. It is another object of the present invention to provide a single step gear reducer with an off set 140 axis.

It is another object of the present invention to provide a single step gear reducer with the driving spiral gear engaging the driven gear at multiple angles.

It is another object of the present invention to provide a single step gear reducer with variable and adjustable drive axis angles under power.

145 It is another object of the present invention to provide a single step gear reducer with a spiral Gear Driving Multiple Output Gears.

It is another object of the present invention to provide a single step gear reducer with a spiral gear drive with near parallel axis.

It is another object of the present invention to provide a single step gear reducer with a parallel i5o axis spiral gear drive.

It is another object of the present invention to provide a single step gear reducer with rolling member teeth.

It is another object of the present invention to provide a single step gear reducer with fixed multiple speeds and a high gear reduction in a single stage using only two gear elements. 155 It is another object of the present invention to provide a scroll gear driving a spur gear with single step gear reduction that can be shifted without disengaging so as to obtain multiple fixed speeds.

It is another object of this invention to provide a multi-speed scroll drive train, with single step reduction, having either single or double enveloping. i6o It is another object of this invention to provide a spiral gear train that has mating surfaces mat will hydraulically plane.

It is another object of this invention to provide a spiral gear train that has rolling contact between driver and driven gears.

165 Description of Drawings

* The invention and its mode of operation will be more fully understood from the following detailed description when taken with the appended drawings in which:

Figure 1. 3D view of the Scroll Gear Drive Train i7o Figure 2. 3D view of Scroll Gear

Figure 3. 3D two speed scroll.

Figure 4. Layout of spirals and fixed speed positions.

Figure 5. Shifting driven gear in multi-speed scroll.

Figure 6. Multi-speed scroll gear with other Configurations 175 for order and quantity of spiral teeth starts.

Figure 7. Section of spiral gear showing concave profile.

Figure 8. A 3D bowl scroll drive train.

Figure 9. Section View of Bowl Spiral.

Figure 10. Vertical section view of bowl scroll drive train. i8o Figure 11. Profile of Bowl Scroll Vs. Concave Scroll Gears

Figure 12. 3D view of Bowl Scroll Driven Tooth Configuration

Figure 13. Single Enveloping Concave Multi-Speed Gear Train

Figure 14. Double Enveloping Bowl Multi-Speed Gear Train

Figure 15. Modification of a driven tooth that would induce Hydro-planing 185 Figure 16. Rolling contact bowl spiral

Figure 17. Centered Axis View of Scroll Gear Drive

Figure 18.0ffset Axis View of Scroll Gear Drive

Figure 19. Scroll Gear Engaging at Multiple Angles

Figure 20. Flexible Drive Angle Scroll Gear i9o Figure 21. A single Scroll Gear blank with Two Scrolls

Figure 22. Scroll Gear with Integral Spur gears Figure 23. Scroll Gear Driving Multiple Output Gears

Figure 24. Scroll Gear Drive Near Parallel Axis

Figure 25. Parallel Axis driven gear 195 Figure 26. Parallel Axis Scroll Gear Drive train

Figure 27. Internal Scroll Gear Drive train

Figure 28. Rolling Contact Driven Scroll Gear Train

Figure 29. Rolling contact scroll gear

Figure 30. Pressurized Oil for rolling contact scroll. 200 Figure 31. Pin hole modification.

Figure 32. Turn Hob hobbing machine layout

Figure 33. Turn Hob hobbing cutter.

* Note that all reference numbers in the text and in the drawings, begin with the figure number plus the reference number of the item. Example; Fig.8, item (4), will be item (84).

205

Best Mode of Operation

As a solution to these and other problems, the improvements that will be described herein relate to the spiral scroll gear drive train. The word scroll will be used in this document to denote a

2io spiral gear with more than one spiral on it's face. The spiral gear in its simplest embodiment consists of two parts as shown in Fig.l. It will be obvious to those skilled in the art of gear trains and power transmissions that bearings, housings, supports and seals will also be employed as required to create a complete operating gear reducer drive train. In Fig.l the gear train employs a spiral gear (11) and a spur gear (12). The driven spur gears in this document have been, in many

2i5 cases, illustrated with a hole placed in the center of its axis where an output shaft would normally be located. Output shafts have been omitted in some drawings so that more details of the scroll can be observed. The spiral gear will always be the driver or input, and the tooth or spur gear shall always be the driven or output. One revolution of a single start spiral driver gear will advance the driven spur gear by one tooth. One revolution of a multi-start spiral scroll gear

220 will advance the driven gear by a whole number multiple in direct relation to the number of coincident starts of spiral teeth on the face of the driving scroll gear.

Description of Invention

225

Description of the Flat Spiral Gear

The driving spiral gear shown in Fig.2 in its simplest embodiment is formed by wrapping a flat strip (21) into a spiral shape as shown in the drawings. The spiral is attached to a supporting 230 plate (22) that in turn is attached coaxially to a drive shaft (23). The shape of the spiral is a

"Spiral of Archimedes" as shown in Figure 2. It is desired that the output velocity of the gear tram will be constant with a constant input velocity. Aside from the flat strip having a rectangular cross section, the spiral can also be formed from strips with other cross sections such as triangular, semi circular, Bostock & Bramley, or most 235 likely involutes. Also the spiral driver could have a slot that would move pins as in many previously designed cams and motion mechanisms. The spiral gear could also have rolling elements used in place of the spiral gear teeth so as to reduce friction.

240 Description of the Driven Toothed Gear

The toothed driven gear item (12) fig.l can have almost any desired tooth profile. The common

245 involute tooth profile, or almost any tooth shape can be accommodated by the spiral drive as has been done in other spiral driven mechanisms. For precision and high load applications, the toothed gear will have a tooth shape that will closely mesh with the spiral gear. One way this shape is easily created is by hobbing the toothed gear with a spiral hob. The toothed driven gear could also have rolling elements used in place of the regular gear teeth so as to reduce friction as

250 will be illustrated later in this document. The spiral drive train & gear reducer is remarkably simple yet the advantages of this invention are both significant and numerous in its use and in its manufacture.

Description of a Flat Multi-Speed scroll Gear

255

Fig.3 is a 3D rendering of a two-speed scroll gear with an involute shape. Fig.4, diagram A & B, is a 2D view of a two speed flat spiral gear. The line of sight is perpendicular with the face of the spirals. This multi-speed scroll is shown with the minimum number of winds of the spiral teeth for clarity. The spirals have two levels or areas where the driven gear should mesh when

260 running at the two different fixed speeds. In practice, more winds could be made at each stage to optimize contact with the driven gear.

The scroll gear displayed in Fig.4, diagram A, shows spiral tooth (41) which begins at point (43). For this example the spiral tooth is made with a pitch of one for this first level of the scroll. At point (44) the pitch of spiral (41) begins to increase at a uniform pitch of two. Spiral (41)

265 completes one turn from point (44) to point (45) at a pitch of two. On a radial point between points (44) and (45), another spiral tooth (42) with the same profile as spiral tooth (41) begins at (46). Spiral tooth (42) runs parallel with and winds out at the same pitch of two as the spiral (41) in that region. The spiral tooth (42) fills in the gap that would be left from spiral (41) after the second turn at the new pitch. Inserting spiral (42) provides maximum contact between driver and

270 driven teeth. The gap created after the first orbit of the spiral (41) at the pitch of two will leave a clearance space. The driven gear passes through this space while shifting from one fixed speed to another fixed speed. To illustrate this better Fig.4, diagram B, shows two darker circles. Each circle (47 & 48), diagram B, would be the best distance from the axis of the scroll gear for the driven gear to mesh at either one of the two fixed speeds. The tangent of the driven gear would

275 mesh with the spiral tooth at circle (47) for the low speed , and at circle (48) for the higher speed . The driven spur gear would mesh with the spiral tooth within the band of space represented by arrow (49) between the circles (47 & 48) only when traversing from one speed to another. The multi-speed scroll allows for many speeds on one spiral disk. This may be used to increase or to decrease the gear reduction by a factor dependent upon the number of coincident starts and

280 different pitches made on the face of the scroll gear.

To effect the changing of gear ratios, the driven gear would have to be shifted back and forth in relation to the axis of the scroll gear. Diagram A in Fig.5 is a view perpendicular to the faces of the scroll gear (51). Shown is driven gear (52) meshing with a two speed scroll gear (51) in the high speed range where the spiral teeth have the greatest pitch. The arrow indicates that the

285 driven gear is on the outer level and a fixed speed of the scroll. Diagram B, Fig.5, the driven gear (52) is in the lower speed range and the arrow indicates that the spur gear is meshing with the inner fixed speed of the scroll. At all times the scroll and driven gear are meshing and do not need to disengage while changing speeds. This is because at least one spiral tooth will wind in or out from start to finish of the gear face. This is shown in Fig.6, diagram A, where the thick spiral

290 line (61) winds out from center of the scroll, out to the scroll gear circumference. Different Embodiments for a Multi-Speed Scroll

The multi-speed scroll in it's simplest layout is formed from a single strip making a couple of 95 spiral turns outward from a point nearest to center. As the pitch increases, another strip or spiral is added as described previously. Fig.6, diagram A & B, has lines drawn in the form of spirals that illustrate the axis of the spiral teeth for a multi-speed scroll. In diagram A, is shown a three speed scroll. The thick line (61) is the parent spiral that goes from beginning to end of the scroll gear, and the thin lines (62) represents added spiral teeth.

300 Other embodiments could be multi-speed scrolls starting out from their center with a multi start lead spiral gear tooth, as shown in Fig.6 diagram B. The four start spiral lines, see lines (63), represents spiral gear teeth. The four start coarse spirals, change into a single start spiral gear (64) in one step. Note that spiral gear tooth (64) winds in> and out from start to finish so it would be the parent spiral tooth in this case. The multi-speed scroll spiral could change from a single 305 start scroll, in one step, to a double start, triple start or any whole number start scroll, as required. The multi-speed scroll could also be made any number of different fixed speeds. The multi-speed scroll could also be made in combination with the concave & bowl scroll type of profile as will be described below.

310

Different Profiles & Configurations for Spiral Gears

There are three different types of profiles for the face of spiral gears that will be useful to make

3i5 up the spiral gear drive train. One is the flat spiral gear discussed above. The second is a concave pitch single enveloping spiral gear, and the third is a bowl spiral with double enveloping. As discussed already, the scroll gear can be configured to allow for more than one fixed speed driven off its face where the spirals lay. The driven teeth of the spiral gear train can be made to induce hydro-planing. The spiral gear drive train can have rolling contact. The concave spiral,

320 bowl spiral, multi-speed spiral gear drive train with single or double enveloping, hydro-planing, and rolling contact can best be presented by describing the different components and concepts that make up this drive train in their simplest form one by one. Once that has been done, the entire concept made up of these various components will be clearer and easily understood.

Below we shall describe each concept one by one and then discuss some combination's.

325 Starting with;

1. A description of the concave spiral driver & driven gear that provides single enveloping

2. A description of the bowl spiral driver & driven gear that provides double enveloping,

3. A comparison of the concave spiral gear & the bowl shaped spiral gear,

4. A description of the bowl spiral driven gear teeth,

330 5. A description of a multi-speed spiral drive train that is; single enveloped & double enveloped. 6. A description of induced hydro-planing

The Single Enveloping Concave Spiral Driver Gear

335 The concave spiral gear has a depression on the face where the spiral lays that coincides with the teeth of the driven gear. The depth of the depression would be specified by an engineer to suit any particular application. As can be seen in the half section view of Fig.7 the depression is located approximately between the axis of the scroll gear and the outermost diameter of the spiral. This allows for more contact with the meshing driven gear.

340 The Double Enveloping Bowl Spiral Driver Gear

The bowl spiral gear train shown in Fig.8, in its simplest embodiment is formed by wrapping

345 strip (81) into a spiral concave shape as shown in the drawings. The spiral is attached to a supporting plate (82) that has a concave depression similar to a common bowl. Plate (82) in turn is attached coaxially to a shaft (83). The driven spur gear (84), in this figure, meshes with the bottom quadrant of the bowl spiral driver. The teeth of the spur gear (84) rotate free and don't make contact with the teeth of the upper quadrant of the spiral gear. In addition to the gear teeth

350 having involute cross sections as shown, the spiral can also be formed from strips with other cross sections or with rolling contact element as will be shown latter. The reason for the bowl shaped driving spiral gear is to provide double enveloping contact between both gears.

In Fig. 9 shown is a half section view of the bowl spiral. The bowl spiral gear has a concave circular pitch diameter that coincides with the pitch diameter of the driven spur gear, see Fig.10.

355 The spiral teeth have a pitch from one tooth to the next that is constant. Fig.10 is a mid section view of the bowl spiral drive train cut vertically along it's axis. The hatching of the driven spur gear has been omitted for clarity. The spiral bowls gear tooth starts from its smallest diameter continually winding out from the axis and away from its beginning in the shape of a curved conical coil.

360 In Fig.10 the center of the arc (101), which represents the pitch diameter of the spur gear, is at point (102). Note that center point (102) is offset from the axis (103) of the spiral gear blank of a distance (104). That distance (104) is less than would be possible using a flat or concave spiral gear. Thus the bowl gear spiral axis and the driven gear axis is closer to coaxial than is possible with many other one-step gear reducers. Also note that the bowl spiral gear blank near it's axis

365 must not have teeth and must be left open at region (105) to provide clearance for the driven gear teeth as it rotates through that area.

The Bowl Spiral Gear Compared to Concave Spiral Gear, "What is the Difference"?

The difference in geometry between the teeth of the bowl spiral gear and the concave spiral

37o gear is the following. Fig.l 1, is a profile of the mid section of the bowl and concave spiral gears along their axis. The teeth that would normally lie on the concave arc have been omitted and the section lines have been omitted for clarity. In diagram A, Fig.l 1, the bowl spiral gear teeth would normally lie on an arc (111). If arc (111) is bisected with the two arc's (112), and line

(113) is drawn through where the arc's (112) intersect, then line (113) will cross the axis (114) of

375 the gear blank (115) . In Fig.l 1, diagram B, the concave scroll gear teeth would normally lie on an arc (116). If arc (116) is bisected with the two arc's (117), and line (118) is drawn through where the arc's (117) intersect, then line (118) will be parallel to and never intersect with the axis

(119) of the gear blank (11-10) . The concave scroll gear provides what is called a single enveloped gear train. The enveloping occurs around a sector of the circumference of the driven

380 gear. The bowl scroll gear, on the other hand, provides a double enveloped gear train. The bowl driver envelopes the driven gear on its circumference and radially along the axis of the driven gear teeth.

Concave & Bowl spiral Driven Gear Teeth

385

The axis of and ideal tooth profile of the concave spiral driven gear would be curved but could be drawn on one plane. The driven gear teeth in the bowl gear drive train should be radiused and curved along the axis of the gear teeth profile so they will coincide and mesh well with the teeth of the bowl spiral gear , see Fig.12. The radiused and curved shape of the driven teeth assures 390 that the full effect of double enveloping will be taken advantage of. The axis of a tooth profile of the bowl spiral driven gear would be curved and skewed and could not be drawn on one plane. These tooth forms can be generated with a hob that has the same profile as the bowl spiral gear. As with all spiral gears it is possible to use narrow straight tooth spur gears for some light load applications.

395

Single Enveloped Multi-Speed Concaved Scroll Drive Train

In Fig.13, the different profiles of spiral gear pitch diameters shown are as if the gear train was

400 sectioned along its axis vertically. The diagrams show how a driven gear (132) would move in relation to a two-speed concave scroll driver (131). The arc of concave scroll gear (131) and the driven gear (132) are shown without teeth. The sectors of the scroll gear, adjacent to where the driven gear would normally run at a fixed speed, are signified with a short arc (137) offset from the arc of concave scroll gear (131). As is shown in Fig.13, The driven gear (132) must have a

405 smaller radius than the arc of concaved portion of driver scroll gear (131) where the spiral teeth lay. The two reasons being, A) so gear (132) can be swung from one area of the driving scroll (131) sectors to another thus changing speeds, B) so the teeth on the driven gear will not make contact with different pitches of spiral teeth on the driver gear at the same time. Fig.13, Diagrams A, B, and C, illustrate three positions of the driven spur gear (132) as it meshes

4io with the spiral teeth. In all four diagrams, the axis of the driving scroll is at line (133), and the center point of the driven gear is at (134). Center (134) is shown in its various respective locations in each diagram. Fig.13, diagram A indicates a fixed speed. Diagram B shows the driven gear (132) in the transition part of the scroll where the driven gear would be traversing along the arc of (131) to the next fixed speed. In diagram B, the driven gear would be engaging

4i5 only intermediate spiral tooth or teeth as may be the case. The areas (136), indicated by the curved leaders, shows clearance spaces that are needed between scroll driver and driven spur gear during the changing of speeds, hence the need for the smaller diameter. The clearance space needed depends on the pitch and gear size required, i.e., the larger the teeth for the same size scroll driver the smaller the gear blank would have to be. Diagram C shows the driven gear (132)

420 meshing with the spiral teeth of a different pitch to that of position A, thereby causing the output speed to change. In diagram D, it can be seen that very little movement is required to shift the driven gear from one speed to another. To visualized this, note that center point (134) which is the axis of the driven gear (132), is swung along arc (135). Arc (135) has its center at (138) which is the center for the arc of the concave scroll (131). This movement causes contact with

425 different sectors of the bowl scroll (131). Arc (135) indicates the total movement required to change speeds for this example.

Double Enveloped Multi-Speed Bowl Scroll Drive Train

430 With a multi-speed bowl scroll gear drive train, the driven gear must be smaller in diameter by comparison than with a single fixed speed bowl spiral gear. In Fig.14, the different profiles of the gear pitches shown are as if the gear train was sectioned along its axis vertically. The diagrams show how a driven gear (142) would move in relation to a two-speed bowl scroll driver (141). The arc of concave scroll gear (141) and the driven gear (142) are shown without teeth. The

435 sectors of the scroll gear, adjacent to where the driven gear would normally run at a fixed speed, are signified with a short arc (147) offset from the arc of concave scroll gear (141). As is shown in Fig.14, The driven gear (142) must have a smaller radius than the arc of concaved portion of driver scroll gear (141) where the spiral teeth lay. The two reasons being, A.) the gear (142) can be pivoted from one area of the driving scroll (141) sectors to another, thus changing speeds. B.)

440 The teeth on the driven gear will not make contact with different pitches of spiral teeth on the driver gear at the same time. Fig.14 ,Diagrams A, B, and C, indicate three positions of the driven spur gear (142) as it meshes with the spiral teeth, hi all four diagrams the axis of the driving scroll is at line (143), and the center point of the driven gear is at (144) as shown in various locations in each diagram. Fig.14, diagram A indicates a fixed speed. Diagram B shows the

445 driven gear (142) in the transition part of the scroll where the gear would be traversing along the arc of (141) to the next fixed speed. In diagram B the driven gear would be engaging only intermediate spiral tooth or teeth as may be the case. The areas (146), indicated by the curved leaders, shows clearance spaces that are needed between scroll driver and driven spur gear during the changing of speeds. The clearance space needed depends on the pitch and gear size

450 required, i.e., the larger the teeth for the same size scroll driver the smaller the gear blank would have to be. Diagram C shows the driven gear (142) meshing with an area where the spiral teeth which are of a different pitch to that of position A, thereby causing the output speed to change. In diagram D, it can be seen that very little movement is required to shift the driven gear from one speed to another. To visualize this, note that point (144) which is the axis of driven gear

455 (142) is swung along arc (145). Arc (145) has its center at (148) which is the center for the arc of tiie concave scroll (141). This movement causes contact with different sectors of the bowl scroll (141). Arc (145) indicates the total movement required to change speeds for this example, hi all the examples above I have shown the concaved and the curved part of bowl drivers with arcs that are circular. In use, that would be the most practical embodiment of the gear train. The concave

460 and bowl scroll driver, specifically for multi speed applications could be configured with other profiles that could include; prolate, oblate, paraboloid, hyperboloid, irregular curves with straight portions, and mixes of the above combined with regular circular sectors. This could be done and still maintain a constant input output speed. The inventor realizes that by inducing slight irregularity's in the curvature of the scroll, that the output would be less than constant But a gear

465 train such as that should still fall under the scope and spirit of these drive trains in general.

Description of Hydro-Planing Driven Gear Teeth for Spiral Gear Drive Trains

The driven spur gear teeth for use in spiral gear transmissions can be made to induce hydro-

470 planing. What I mean by the word hydro-planing is that, when the spiral gear face spins adjacent to the spur gear face at high speeds, the spur gear will lift off and skim along on a film of oil. This will reduce friction and generation of heat.

In Fig.15 a straight tooth of a spur gear is shown for illustration purposes. Some of the details are exaggerated to illustrate the principals. As shown in Fig.15, the teeth can have a slight

475 chamfer on both ends of the face of the teeth where contact would be made with a spiral driver. This modification should be done to all four corners of the tooth face if load and output of the gear are to be reversed. The chamfer could be made on just one corner, for economy sake, if load and direction of rotation were always the same. The chamfer need not extend to the top or bottom of the gear tooth face. Area (151-A) would act like a scoop, trapping the oil that is

480 spuming with the driving spiral gear. The oil would be forced and squeezed into the contact area between driver & driven teeth. The gear tooth could include more than one chamfer on a tooth's edge and the chamfer could be made in the form of a fillet.

Another way of accomplishing hydro-planing would be to form a scoop with a chamfer Fig 15, (151-B), and direct the captured oil to a depression somewhere along the face of the spur gear

485 tooth as shown in fig. 15. The chamfer (151-B), would capture the high velocity incoming fresh oil from the spiral gear. The oil pressure that is created flows through veins (152) that in turn brings oil into a very shallow depression in the mid section of the gear teeth face (153). This depression could have small exit veins similar to (154) to promote the flow of oil. Vein (154) could exit at the root of the tooth instead of at the top as shown. This oil film would in effect

490 become an oil bearing that provides lubrication and assures that mating surfaces do not make contact. Note that surfaces (155) are coplanar. Care must be taken in design so that ample contact area is provided for use with a given load . Obviously this design is intended to work with oil baths or pressurized lubricating systems.

95 Description of Bowl spiral with Rolling Contact

In fig.16 a section view of bowl spiral (162) is attached to shaft (161), which spins on axis (160), and has spiral grooves (163) which are machined to coincide with rolling spherical bushings (164). Bushings (164) are sectioned for clarity and are free to spin on pins (165) which are fixed 500 to hub (166) which spin on axis (167). Thus a rolling contact double enveloped reducer is provided. This has been built along with a few other simpler configurations and has been found to perform very satisfactorily for author.

Industrial Applicability

505

Advantages in use of flat Spiral Gear Train;

1. The spiral gear drive provides a wide contact area between the gears. This reduces the localized stresses which by comparison is a great limiting factor for worm gear drives. 5io 2. The spiral gear drive can provide great gear reduction in a single stage.

3. The spiral gear drive train shown in Fig.17 can have its axis perpendicular and centered to driven gear face. Fig.17 is a top view when the two axis lie on a horizontal plane. This is the most common configuration and can be used in this fashion with or without a bearing on the outboard end. sis 4. The spiral gear drive can have its axis perpendicular and offset to one side of the face of the driven gear, Fig. 18 permitting the driver shaft to pass alongside the driven gear.

5. Multiple spiral gears can be used to drive a single driven gear. Complex gear trains can be easily built with great flexibility using scroll gears and corresponding driven gears.

6. The spiral gear drive can be mounted on a motors shaft and be allowed to mesh directly with 520 a gear running on its own axis. This, in many cases, will eliminate the need for a separate gearbox in simple machinery. Also, the spiral gear drive permits greater alignment tolerances as compared to a regular worm drive. If the axis of the flat spiral were on the horizontal plane, it can be adjusted up and down a significant distance with zero loss of performance. Therefore the alignment of the flat spiral drive gears will be more flexible as compared to worm gear drives 525 and other types of gear trains. .

7. The spiral scroll gear has an advantage in that the disk to which the spiral teeth are fixed will do a better job of radiating heat than a worm in a worm & gear drive train. The worm of a worm & gear drive has the teeth placed diametrically opposed and close to the area of contact at any given moment. This fact minimizes the time that a worm is out of contact with the driven gear

530 and thus limiting its ability to dissipate heat.

8. The spiral gear drive can engage the driven toothed gear at different angles as shown in Fig.19 and still achieve advantages stated in the above..

9. The angle between the axis of the spiral gear and the driven toothed gear can change while the gear train is under power with a specially hobbed driven gear. The driven toothed gear has a

535 convex radiused tooth profile on its O.D. allowing the scroll gear to swing around the radius and still mesh, see Fig 20. The contact area is reduced at any given angle as compared to a fixed angle design, but that disadvantage is offset by the ability to change angles.. The driven gears can be hobbed with a scroll gear hob, but it can also be made to run satisfactorily for many applications by simply using a relatively narrow standard spur gear of me correct size..

540 10. For certain applications, individual spirals could be projected from both sides of a central disc as shown in Fig.21. The spiral could posses the same or reverse spiral direction and with different pitches if desired. The driver plate could drive two separate gears at the same time or be manipulated to alternate back and forth so as to drive one gear or the other at any one time.

11. The spiral gear can also have gear teeth cut on its outer perimeter and an internal gear cut on the inside diameter of the spiral gear hub as shown in Fig.22. This permits many more gear interface options in a limited space.

12. Several driven gears can easily be arranged in an array to be driven by a single spiral gear as shown in Fig.23.

13. One size and design of flat spiral gear teeth will mesh with all gears of the same tooth size and design. There is no need to redesign the flat spiral gear for each case.

14. In certain applications where space or rigidity or both are a concern, the disc that carries the spiral gear can be fabricated with bearing races for ball bearings formed directly on the front face, the back face or the perimeter face of the spiral gear, or any combination of the these faces.

15. The tooth form can be of conventional shapes and sizes of standard gears or of shapes that might not normally be found on standard gears. For example, the tooth form could be rectangular, triangular, round, or other shapes. This flexibility will allow for special designs that would increase the allowable load per tooth, or to enhance lubrication properties and/or to work in reduced spaces.

16. As with a worm & gear, the spiral gear will inhibit freewheeling of the driven gear. Many positioning applications will be accommodated without the need for a separate brake.

17. The spiral Gear Drive can also be configured so that the toothed gear has teeth on the side face of the gear disk and the input and output shafts are nearly parallel as shown in Fig.24.

18. The spiral gear drive can be arranged to allow the input and output shafts to be parallel. The advantage of parallel shafts is not possible with worm gear drives. Fig.25 shows one embodiment of the spiral gear drive that allows the shafts to be parallel. This view has a portion cut away so that the position of pins over the cam can more easily be observed. In Fig.25, drive pins (253) are used for the teeth of the driven gear assembly. The pins are normally retracted. As the pins (253) and driven plate (254) rotate, the pins are forced outward by the cam lobe (252) on the grounded cam plate (251). The spiral gear engages the raised pins to drive the driven gear assembly. The none-driving pins retract to prevent interfering with the spiral gear, hi this embodiment of the invention, the pins could include rolling elements on the drive pins as shown in Fig,28. Instead of pins, balls could be nested in another bearing that would be fitted to the driven plate so as to provide rolling contact. This same system could be used to drive a rack. Fig.26 also shows the partial cut away view of the assembly in Fig.25, with the scroll gear placed appropriately.

19. The spiral gear could drive an internal toothed driven gear (See Fig.27).

20. The geometry of the spiral gear drive is tolerant of debris and is also self cleaning. The leading edge of the spiral gear will tend to push debris out of the teeth of the toothed gear as it enters the space between the teeth. This can be further improved by raking the leading edges of the scroll to help lift particles away from the toothed gear.

21. The spiral gear could drive a toothed chain over a sprocket, and likewise an appropriately toothed belt over a pulley.

22. Because the spiral gear has a relatively wide and flat arc which in turn can provide extra space, it is feasible to configure the driven gear with rolling contact teeth as shown in Fig.28. In Fig.28 the conventional teeth of the toothed gear are replaced by pins (281) that are used as axles for rolling members (282) forming rolling element teeth. These rolling element teeth can be cylindrical, barrel shaped, tapered or spherical. This rolling contact will reduce friction and increase efficiency. Fig.29 shows a rolling contact spiral gear with the pins in the form of a spiral on the face of the spiral gear. The rolling elements could be mounted on the spiral driver and the driven gear could have solid gear teeth. The driving pins (291) are located in the form of a spiral on the driving plate (292). In the same figure and diagram B, is a 3D view of the part of pin (291) that would stick out of the driving plate (292) of Diagram A. Fig.30, diagram A, shown is a section view of a spiral gear with one rolling element . The driven gear, (not shown,) would have solid teeth that would engage the pin and bushing assembly. In Fig.30 shown is a section 5 view along the axis of a rolling element spiral driver with only one driving pin attached. This view will be used to show how the lube system works that provides oil pressure between bushing and driving pin. Note in Fig.30, diagram A, that the spinning spiral gear (301), has veins (302), that feed oil from a hole (303), that is located in the shaft (304). The veins act as a centrifugal oil pump. The bushing (305) would be mounted on the pins (306). The veins (302) conducts the oil oo flow from the center of the driving shaft (304) through driving plate (307), (See cutaway View B), through the pins (306) and release the oil in the clearance space between the driving pins (306) and the bushings (305) . Thus the bushing rotates on a film of oil that would be between the bearing surfaces. Another possible configuration for a rolling contact driver would be to use needle bearings instead of bushings .Fig.31, diagram A, shows a partial sectioned view of a05 support gear blank or spiral plate for a rolling contact scroll gear system. The pin (311) could have a high stress area in the region (312), where the pins exit their nesting hole (313). That would be a concern especially in large load applications. This effect can be diminished if the hole, at its top, were made with a very slight taper (314) (See Fig,31, diagram B). This would allow the pins to flex a little, thereby maintaining the stresses over a larger area io on the pin and reduce the possibility of shear.

23. In addition to a spiral gear formed from a single strip, the scroll gear could be formed using multiple start strips. Two or more strips could be wrapped together to form the scroll. This may be used to increase the contact ratio between the scroll gear and the toothed gear and/or to decrease the gear reduction by a factor dependent upon the number of coincident starts. The usei5 of a combination of single and multiple start spirals on the same scroll gear can be used to provide multiple fixed speeds which is described herein.

Advantages in use of the Multi-Speed Scroll Gear 20 l.The multi-speed scroll gear drive provides multiple fixed speeds and gear changing without disengaging the mating gear teeth. 2.Since the multi-speed scroll gear consists of two mating gears providing different speeds, the number of gears i.e. parts required for a given application, is reduced..

3. Several driven gears with varying numbers of teeth can easily be arranged in an array to be25 driven by a single multi-speed scroll gear. This allows for many different out-put speeds from a single multi-speed driving scroll. 4. The multi-speed and the regular flat spiral scroll gear has an advantage in that the disk or drum to which me spiral teeth are fixed can also double as a surface for braking or clutching. If additional or quicker stopping power were needed, or a fail safe self locking feature were30 desired, this surface could be incorporated, saving the addition of another element.

Advantages in use of the Concave Spiral gear 35 l.The concave scroll gear drive provides single enveloping leaving a large contact area between the gears. This reduces the localized stresses which by comparison is a great limiting factor for worm gear drives.

2. The concave spiral gear teeth do not have to be undercut to mesh with gears that have 2340 teeth and less.

3. The hollow shape formed by the teeth of a concave spiral tend to retain the lubricant where needed and helps prevent the lubricant from being flung off by centrifugal force. Advantages in Use of the Bowl Spiral Gear

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1. The bowl scroll gear drive provides double enveloping leaving a large contact area between the gears. This reduces the localized stresses which by comparison is a great limiting factor for worm gear drives.

2. The bowl spiral gear drive provides large gear reduction in a single stage. so 3. The bowl spiral gear teeth do not have to be undercut to mesh with gears that have 23 teeth and less.

4. The bowl spiral gear has its axis perpendicular and centered to the driven gear circumference.

The distance between the axis of both gears as shown in (Figure 10) distance 104, is relatively small which makes them closer to coaxial. Therefore the space required to accommodate the gear

655 train is thus reduced as compared to a regular spiral drive gear train. This provides new options for gear reduction layouts not obtainable by worm drives.

5. The hollow shape form of the bowl spiral tends to retain the lubricant where needed and prevents the lubricant from being flung off by centrifugal force.

660 Manufacturing Advantages of Spiral Gears

The spiral gears can in most cases, be molded using a two-piece mold with powder metal, plastic, or the die cast process. They can also be formed by injection molding, sand casting, stamping, forging, cut on a hobbing machine, cut on a conventional milling machine as well as

665 other manufacturing techniques. A single gear box or frame size can accommodate numerous combinations of scroll gears and/or toothed gear sizes. This is not the case for worm gear drives. The worm drive type gear box has a very narrow range of gears that can be adjusted and made to work in the same frame. This advantage for the scroll gear drive will lead to reduced inventories of parts and also provide convenient, economical, and flexible gear ratio changes without the

670 replacement of an entire gear drive. Because of the greater tooth contact ratio, especially when compared to a worm gear drive, many applications would allow plastic and zinc die cast scroll gears to be adequately used instead of more costly steel worms. The multi-speed scroll and spiral disc can be relatively flat and small and made from very little material. The driven gear that is single and double enveloped can also be cast or molded with a simple two-piece mold. That is

675 not possible with a driven gear of an enveloped worm drive because of the concave tooth form that is made to envelope the worm. One size and design of flat multi-speed scroll gear teeth will mesh with all gears of the same tooth size and design even if the number of teeth on the driven gear varies.

680 Turn Hobbing

For those not skilled in the art of making hour glass double enveloping worms for worm & worm gear applications, some doubt might be raised over the practicality or possibility of producing a bowl or a concave spiral gear with the necessary tooth forms and layout. That is

685 because the tooth profiles rotate on an arc. What the inventor has done so as to be able to produce these gears with the geometry as shown in the drawings herein is a method I call turn hobbing which is very similar to the way double enveloped worms are produced.

What that means is that using a hobbing cutter, Fig.33, item (330), rotating on its axis and perpendicular to the axis of the scroll to be cut, a spiral gear can be generated. To be able to form

690 the spiral teeth of the spiral gear, both the hob and the scroll must rotate in synchronization. One arrangement for hobbing a spiral gear is shown in Fig.32. The gears are shown without teeth. This is a nobbing arrangement using a spiral gear (325) as part of the gear train. In Fig.32 the spiral gear to be cut is (321) and this is fixed to shaft (327) which feeds up and down as indicated by the arrows. The turn hob is (322), and is driven by shaft (323) which in turn is connected to 695 driven gear (324) which has the same number of teeth as the turn hob. The spiral gear (325) has the same number and pitch of teeth as the spiral to be cut (321). The gear (325) connected to shaft (326) which is driven from the motor (320), the gears (328) synchronize the vertical shafts

(326) & (327) and they turn in the same direction because of idler gear (329). In this case shaft

(327) would feed the spiral gear up into the hob to cut the spiral teeth, and down to remove the 700 finished gear. This arrangement could cut spirals of any sort and more specifically would be adequate for spiral gears. The turn hob acts as a rotating turning tool. As the hob takes a cut, it rotates and each cutting edge, which looks like a gear tooth in this case, will be cutting in succession a groove that will become the spiral tooth. The cutting teeth are not making intermittent contact like a milling cutter, but will cut smoothly from start to finish of the spiral

705 groove as it rotates. The cutting face (331) (See Fig.33) must be coplanar to the axis of the scroll gear to be cut. This process can be done satisfactorily in a hobbing machine as previously described. To fabricate the hob the profile of the teeth wanted is formed on the circumference of a hardened tool steel disk. The cutting edges (332) (See Fig.33) has to be backed off to provide the appropriate clearance or relief angles (333) for cutting. Before turn hobbing, the spiral gear

7io blank for bowl and concave applications can be radiused so that the hob is only removing the unwanted material, thereby forming the spiral gear teeth. In many applications it is possible to hob the spiral directly from a solid .It must be mentioned that the figures and diagrams in the above are for illustration purposes, and were not meant to be used for engineering for any specific application.

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Claims

745Claims

What I claim is:

A gear train and reducer that comprises of:

750 L A gear train in which a flat spiral shaped input gear is used to drive a toothed output gear for the purpose of mechanical power transmission.

2. A gear train in which a concaved spiral shaped input gear is used to drive a toothed output gear.

755

3. A gear train in which a bowl shaped spiral input gear is used to drive a toothed output gear.

4. A gear train in which a multi-speed scroll gear with single start and /or multiple start spirals on its face is used to drive a toothed output gear at different fixed velocities.

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5. A multi-speed scroll gear with either concave (single enveloping) or bowl shaped profile (double enveloping).

6. A modification to gear teeth that will induce hydraulic planing.

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7. A spiral drive train with rolling members located either hi the form of a spiral on scroll gear or in place of gear teeth on the diameter of the driven gear.

8. A spiral gear drive train with its axis at angles other than 90 degrees.

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9. A spiral gear drive train with variable and adjustable axis.

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