Note: Descriptions are shown in the official language in which they were submitted.
A-36715/AJT
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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
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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
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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;
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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
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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
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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-
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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
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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
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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
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the scope of the invention be determined solely on the
claims appended hereto.
