CA1201609A

CA1201609A - Differential gear reducer

Info

Publication number: CA1201609A
Application number: CA000408398A
Authority: CA
Inventors: Leo G. Nickoladze
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-30
Filing date: 1982-07-29
Publication date: 1986-03-11
Also published as: JPS5865349A; IT8222630A0; IT1153119B; GB2102532A; GB2102532B; DE3228412A1; DE3228412C2; FR2510696A1; IT8222630A1; KR840000752A

Abstract

Abstract of the Disclosure:

Set out herein is a gearing mechanism wherein one gear of a smaller diameter engages in partial mesh another gear either in the form of a rack or a gear of a larger diameter. The pitch of the smaller diameter gear is made different than the pitch of the rack or the larger diameter gear thus achieving a pitch differential. To accommodate this in-equality in pitch the teeth of the smaller gears are radiused and the larger gear or rack may include rollers which engage these rounded teeth to accommodate the dif-ference in pitch by relative movement. In alternative implementations the smaller gear, rather than including teeth, may include a plurality of permanent magnets, once more distributed at a pitch different than a plurality of permanent magnets embedded in the larger gear or rack. The coercive force between the magnets can thus be used to transmit power at a gear ratio equal to the pitch differ-ential.

Description

:~Z~1~ t39 DIFFEREMTIAL GEAR REDUCER

The present invention relates to gearing devicesl and more particularly to gearing devices for providing large gearing ratios in a single stage.

Use of gearing to change the angular rate by a desired ratio has been known in the past. In most instances the typical gear configuration dictates teeth geometries which do not lend themselves convenient for large gear changes or ratios.
Thus, for example, a gear ratio of approximately sixty to one has most frequently been accomplished by way of a plurality of gear stages of some intermediate range which when multiplied provides the desired ratio. Since each gear stage entails both a loss inefficiency and manufacturing and maintenance costs, the unnecessary multiplication of gears has been the subject of extensive research. In the recent past gearing devices relying on the odd numbered teeth have been utilized for providing large gear ratios in a single stage. The disadvantage of these gearing devices is that the ratio increment that can be achieved depends on the integer increments which are tied to the number of teeth available in the gear. Thus, while qu:ite acceptable for uses where a particular gearing ratio is incorporated in the design of the gear stage khe foregoing odd toothed gear arrangements do not lend themselves to convenient modi-fication should different gear ratios be desired. In orderto achieve -the economies now dicta~ed by the marketplace it is thus necessary to find techniques through which large gear-ing changes can be achieved without the necessary commitment in tooling and in inexpensive form.
Accordingly, it is the general purpose and object of the present invention to provide a gearing device which by pitch inequalities can accommodate any desired gearing ratio.
Other objects of the invention are to provide a gear reducer having two unequal diameter gears arranged with differ-ent pitches to achieve the desired gear differential.
Yet additiona] objects of the invention are to provide a gear reducer which achieves the gear ratio by the expedient use of varying pitch selections.
Briefly, these and other objects are accomplished within khe present invention by providing apparatus for changing the rate of relative adirance between a driving element and a driven element, comprising a gear-like circular member having a peripheral edge provided with a plurality of driving sub-; elements spaced arGund that peripheral edge at a predetermined intervals, that circular member being mounted rotatably on that driving element for movelnent thereon; and further comprising a circular driven mem~er provided with a plurality of driven subelements spaced along tha-t member at equal preselected spaced increments, those driven subelements being operatively connec-ted to said driving subelements whereby the driven subelements are moved by successive engagement with the driving subelements dependent on -the movement of the circular member, charac-terized :~20~ 0~

in that the preselected spaced increments of the subelements of the driven memb.er are different from the predetermined in-tervals of the subelements of the driving element for moving the driven element at a distance and in a direction determined by the difference in spacing between the driven and the driving subelements said driving and driven elements rotating in oppo-site directions if the pitch of the driven elements is greater than the pitch of the driver elements.
Figure 1 is a .:Erontal view of a rack and pinion arrangement illustrating the inventive principle herein;

:~2~16(1~

Figure 2 is a front view, in partial cutout, of a planetary gear arrangement incorporating the principle of Figure l;

Figure 3 is a side view, in section, taken along line 3-3 of Figure 2;

Figure 4 is a front view of yet another planetary arrange-ment in combination with gears;

Figure 5 is a side view, in section, taken along line 5-5 of Figure 4;

Figure 6 is a further implementation of a planetary ar-rangement in frontal view;

Figure 7 is a front view of a magnetically coupled gear arrangement according to the invention herein;

Figure ~ is a detail view of a magnetic tooth arrangement useful with the structure of Figure 7;

Figure 9 is yet another implementation of a magnetically engaged gear arrangement;

Figure 10 is a sectional view taken alo~g line 10-10 of Figure 7;

Figure 11 i5 a front view o a planetary magnetically coupled gear arrangement in accordance with the invention;
and Figure 12 is a sectional view ta~en along the line 12-12 of Figure 11.

As shown in Figure 1 the inventive principal entailed herein is best illustrated by way of a rack-and-pinion assembly, generally designated by the numeral 10, comprising a pinion gear 11 mounted on a bearing 12, which in turn is supported on the shaft 13 extending orthogonally from a sliding engagement within grooves 15. Grooves 15 are formed on the s interior of a transversely aligned channel section 16 which is positioned in a parallel arrangement relative to a rack assembly 20. The groove 15 allows the shaft 13 to move along the groove but restricts vertical motion. The rack assembly is mounted for longitudinal movement. The rack assembly 20 is provided with a plurality of orthoyonally directed posts 21 spaced at equal increments along the longitudinal axis thereof and deployed for engagement with the periphery of the gear 11. Each post 21 supports on the exterior thereof a roller bearing 22 or a similar friction reducing exterior shield and it is by virtue of this ex-terior shield that most of the contact friction is alle-viated. The gear 11, around the periphery thereof, is provided with a plurality of cutouts 31 each separated by a corresponding tooth 32. The cutouts 31 are conformed to receive the rollers 22 with the projecting teeth 32 ex-tending therebetween and aligned to pass into the gaps between the roller bearings. To further assure good rolling contact each recess between teeth 32 is generally conformed in a circular arc joining the two straight surfaces defining the teeth. It is contemplated that the foregoin~ teeth 32, or the recesses or arcs therebetween, be spaced at a pre-determined circular pitch shown herein by way of the pitch arc P. The ~ nsion of the pitch arc P relative the center-to-center distance between posts 21, the center-to-center distance being shown herein as distance T, sets thegear ratio achieved by this device.

More specifically if the pitch dimension P plus the pitch dimension over the gear ratio desired is equal to the center-to-center distance T no reduction of motion will result. Shaft 13 will move to the right or left without transmitting any motion to rack assembly 20. Now if we make ~Z~6~g center-to-center distance between posts 22 equal to T + 1OO. P being equal to T, motion of shaft 13 to the right one inch will cause rack 20 to move to the left one hun-dredth of an inch thus providing 100:1 ratio of relative motion. Conversely, if center-to-center distance between post 22 i5 made T _ lTo, motion of shaft 13 to the right will cause rack 20 to move to the right one hundredth of an inch. The movement is caused by the caming of the rollers 22 along the walls of the grooves or cutouts 31. Thus, the difference between the advance of the shaft 13 within the groove 15 relative to the advance of the rack assembly 20 will be equal to the inverse of the differential between circular pitch P and the center-to-center distance T.

The foregoing principal may be utilized to advantage in a planetary gear arrangement shown in Figures 2 and 3. More specifically, as shown in these figures an input shaft 51 is secured at one end to a driven plate 52 which is substan-tially triangular in plan form, the input shaft joining the plate at the center thereof. Plate 52 is provided with three circular bores proximate each apex, shown herein as bores 53, each bore 53 receiving one end of a post 54. The other ends of post 54 are received, in a similar manner, in yet another plurality of bores 55 again proximate the apecies of a triangular plate 56. Plates 52 and 56 are substantially equal in plan form, plate 56 including a center shaft extending outwardly from the center thereof shown herein as center shaft 57. Thus, the input shaft 51 on one side of the structure formed by plates 52 and 56 and the corresponding posts 54 supports the assembly in ro-tation, each post 54 in turn supporting a corresponding gear60. It is this gear 60, that is similar to the gear 11 in Figure 1, that includes a plurality of circumferential cutouts separated by teeth. ~ore specifically, each gear 60 around the periphery thereof includes a plurality of cir-cular edged recesses 61 or cutouts formed between adjacentteeth 62. In the foregoing manner an integral assembly is 12()16~

formed carrying the gears 60 along with the shaft 51. In this form gears 60 are free to rotate about their respective posts thus duplicating the motions of gear 11 around shaft 12 in Figure 1. ~ccording to the same principal this planetary gear assembly is rotated within a right gear structure comprising two circular plates 71 and 72 spaced to support a plurality of rollers 75 therebetween. ~ollers 75 are distributed along the periphery of plates 71 and 72 in an alignment for engagement with the teeth of the gears 60.
Thus, once more, by appropriate selection of the pitch differential between the tooth spacing on gears 60 and the peripheral spacing of rollers 75, a large gear ratio can be achieved. Once more, the gear ratio achieved depends on the pitch differential rather than on the teeth numbers. In this form the plates 71 and 72 may provide an output pick-off shown herein as pick-off 76 through which the gear reduction occurs.

These same principles may be implemented into a differential assembly as shown in Figures 4 and 5. More specifically, as shown in these figures, a differential, generally designated by the numeral 100, includes an input shaft 101 extending into the interior of a ring gear cage 102 of substantially cylindrical section. Within the ring gear cage 102, shaft 101 is splined with a sun gear 103 cut with conventional gear teeth and in mesh with a plurality of planetary gears 104~ Planetary gears 104, in turn, are mounted on cor-responding shafts 105 which are supported for rotation in a planetary gear carrier comprising two circular end plates 106 and 107. Each of the shafts 105, splined to gear 104, is also keyed or splined with two gears 108 and 109 formed according to the invention herein. Gears 108 and 10g, in turn, engage a plurality of peripheral rollers 110 mounted proximate the peripheral walls of the differential cage 102.
Once more, each of the gears 108 and 109 includes peripheral cutouts 115 of a pitch different than the pitch of the peripheral rollers 110O Thus, once more, the pitch dif-12~)1609 --7--ferential can be used to advantage according to the prin-ciple set forth'above.

The structure shown in Figure'4 and 5 may be alternatively implemented according to the'illustration in Figure 6. For purpose of this clarity the's'ame numera~ls will be utilized as those shown in Figures'-4 and 5, Figure 6 illustrating additional features used to advantage More specifically, in Figure 6 the sun gear 103 is splined in common with an interior roller cage 125 of circular plan form, roller cage 125 including around the periphery thereof a plurality of rollers 130. The radial dimension of the placement of rollers 130 is such that contact is made therebetween and the gears 108 and 109. Furthermore, the peripheral spacing of rollers 130 may be selected to be e~ual with the circular pitch of gears 108 and 109 and a reversal will therefore occur. Thus, the rotation of the differential cage 102, in this instance, will be opposite and at a ratio proportional to the pitch differential to that of the shaft 101.

In all of the foregoing embodiments, the ratio geometry of the circular cutout and the roller surface provides for single point contact which insures high efficiencies. In each instance point contact provides the necessary gear ratio thus realizing equal efficiencies to that of a con-ventional gear train. Unlike a conventional gear train these efficiencies are realized in a single stage rather than the normally large number of stages to obtain the high ratio.

This same principle of pitch differenti~l gearing set out hereinabove may be rendered further efficient by the use of magnetic coupling. More specifically, as ahown in Figures 7 and 8, a planetary gear carrier 201 is driven in rotation by a shaft 202 on the interior of a ring gear assembly 203.
Supported for rotation within the planetary gear carrier 2al and equal radial separation from the center of the shaft 202 ~Zf~ q3 are a plurality of gears 205 each formed as a cylindrical section having extended around the periphery thereof a plurality of radial dipoles 206 magnetized north and south according to the direction set out in Figure 8. The ring gears assembly 203, in a manner similar thereto, includes an inwardly directed peripheral toothed ring 211 each tooth 212 thereof being, once more, magnetized as a magnetic dipole.
It is contemplated to align the magnetic polarity of the ring gear teeth 212 and the planetary gear teeth 206 for repulsion thus ensuring a contactless gearing arrangementO
The repulsion moves the gear 203 an amount corresponding to the pitch difference. Once more, the circular pitch of the ring gear teeth 212 and the teeth around the periphery of gears 205 may be unequal to provide the aforementioned differential gearing. In this form the necessary gear ratio is obtained in an arrangement which by virtue of the mag-netic repulsion will allow for some shaft absorption that will min;m; ze gear contact.

This same magnetic effect may be utilized to advantage according to the illustration in Figure 9. In this il-lustration the planetary gear 205 rather than including the peripherally extending magnetic dipoles includes semi-circular magnetic inserts 2~6 around the periphery thereof.
The ring ~ear 211 may be similarly provided with semi-circular magnetic inserts 232 the magnetic alignment of theinserts 226 and 232 are being North-South for mutual at-traction. Again, the peripheral spacing of the magnetic inserts 226 and the spacing of inserts 232 may be such as to obtain differential gearing. This last implementation provides effective gearing with the desired feature of no mechanical contact which is of particular utility for driving delicate devices like tape drives or similar ar-rangements.

In order to develop a higher torque a magnetic arrangement may be utilized as shown in Figure 10 where a fixed track ~ , ~ZV:16Q~

233 is provided. Circular spacing between magnets 226 and 233 is equal and circular spacing of magnets 232 is dif-ferent from spacing of magnets 226. Yet another config-uration is shown in Figures ll and 12 which is similar to Figure 6 except that gears are substituted with magnets.
Like reference numerals are applied to like parts with the numerals primed for like magnetic numbers.

In each of the foregoing embodiments the circular pitch of a gear is used to obtain large gearing ratios. In the case where solid contact is made, two unequally radiused surfaces assure a point contact which is further improved by the features of a roller. Thus, the same efficiency as those obtainable in a chain drive or a gear train are obtainable herein with the added advantage that only one stage achieves the same gear ratio which normally is only achievable through a plurality of gears. Since this contact point rolls around the periphery of the roller the assembly carrying the roller will be advanced by the surface of the cutout without the requisite opposite restraint. Thus, as each tooth is advanced into the intersp~ce between the rollers only one side of the tooth will maintain contact. The other side of the tooth or the cutout between the teeth will be free of any contact~ For this gear arrangement to advance over the rollers a necessary opposite translation will therefore occur in the roller assembly achieving the desired gearing. This opposite translation will occur even if the roller structure is perfectly flat, a feature not obtainable before. In the magnetically coupled gear arrangement the repulsion or attraction forces of magnets provides the driving force to cause the poles to line up to drive the gears while maintaining a meshing engagement.

Obviously, many modifications and changes may be made to the foregoing description without departing from the spirit of the invention. It is therefore intended that the scope of the invention be determined solely on the claims appended hereto.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for changing the rate of relative advance between a driving element and a driven element, comprising a gear-like circular member having a peripheral edge provided with a plurality of driving subelements spaced around that peripheral edge at predetermined intervals, that circular mem-ber being mounted rotatably on that driving element for move-ment thereon; and further comprising a circular driven member provided with a plurality of driven subelements spaced along that member at equal preselected spaced increments, those driven subelements being operatively connected to said driving subelements whereby the driven subelements are moved by suc-cessive engagement with the driving subelements dependent on the movement of the circular member, characterized in that the preselected spaced increments of the subelements of the driven member are different from the predetermined intervals of the subelements of the driving element for moving the driven ele-ment at a distance and in a direction determined by the dif-ference in spacing between the driven and the driving subele-ments said driving and driven elements rotating in opposite directions if the pitch of the driven elements is greater than the pitch of the driver elements.

2. Apparatus according to claim 1 characterized in that the driving members comprise a planetary gear assembly including a plurality of gears rotating on posts located within a circu-lar array of teeth comprising the driven member, the recesses of the driving members engaging the driven members and an in-put shaft centrally located with respect to said posts and said driven members.

3. Apparatus according to claim 2, wherein the driven subelements are carried on posts coupled to the driven member and rotate relative to said posts.

4. Apparatus according to claim 3, wherein the input shaft is secured at one end to an input plate driven in ro-tation by the input shaft.

5. Apparatus according to claim 4, wherein the input shaft is secured to the center of the input plate.

6. Apparatus according to claim 4, wherein the input plate further carries a plurality of posts each carrying a gear rotating on the post and comprising said plurality of driving subelements, said driving subelement gears rotating relative to said input shaft to create said differential.

7. Apparatus as claimed in claim 1, the driving element further comprising an input shaft, a pair of input plates con-nected together by posts and connected to the input shaft, said gear like circular drive member being supported on said posts for engagement with said driven member.

8. Apparatus as claimed in claim 1, the driving element comprising an input shaft, a gear splined to said shaft, a pair of plates connected by posts splined to gears meshing with said input shaft gear, said connecting posts carrying gears whose edges comprising the driving subelements, and a gear cage sup-porting the driven elements.