Pin controlled retainer for epicyclic transmission

An epicyclic speed reducing transmission having cylindrical rollers for transmitting torque between first and second confronting surface regions includes a retainer for radially and axially positioning the rollers relative to the first and second confronting surface regions. The retainer includes first and second rings which contain lobes thereon having holes therein which accommodate a series of roller pins. Each of the roller pins has an enlarged roller body portion which rotatably supports the rollers.

CROSS-REFERENCES TO RELATED APPLICATIONS 
The present application is related to U.S. application Ser. Nos. 313,442 
and 362,195, one of the present inventors being one of the co-inventors of 
each of these related applications. The disclosure of each of these 
related applications is hereby incorporated by reference. 
BACKGROUND OF THE INVENTION 
The present invention relates to a retainer for maintaining cylindircal 
rollers in proper spaced relationship between an epitrochoidal-like shaped 
and a hypotrochoidal-like shaped conjugate set of races in an epicyclic 
speed reducing transmission of the kind described in the above-mentioned 
362,195 application. 
Good positional control of rollers held between epitrochoidal-like shaped 
and hypotrochoidal-like shaped races in an epicyclic speed reducing 
transmission is essential to obtain optimum performance. Accordingly, it 
is essential that the axial and radial positioning of the rollers be 
accurately controlled by a retainer as the epicyclic speed reducing 
transmission is operated. In addition, the structure of the retainer 
should not limit the design of the races so that the races can be designed 
to achieve optimum performance of the transmission. 
It is also desirable that the retainer used for maintaining proper 
positional control of the cylindrical rollers be constructed to allow 
confronting lobes on the epitrochoidal-like shaped and the 
hypotrochoidal-like shaped races to nearly touch at the point of closest 
approach. Such a lobe design of the races allows the cylindrical rollers 
to transfer maximum possible torque between the races. In addition, the 
retainer perferably should not contract any substantial part of the 
driving and driven surfaces of the races. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a retainer 
for maintaining cylindrical rollers in proper spaced relationship in an 
epicyclic speed reducing transmission which contains a set of conjugate 
epitrochoidal-like shaped and hypotrochoidal-like shaped races so that 
each of the cylindrical rollers is equally spaced from one another. 
A further object is to provide a retainer which achieves accurate 
positional control of the rollers and provides excellent axial positioning 
of the rollers. 
Another object is to provide a retainer which comprises a simple and 
economical design which can be easily formed. 
A still further object of the present invention is to provide a retainer 
which allows confronting lobes of the conjugate set of races to nearly 
touch at the point of nearest approach so that maximum possible torque is 
transferred between the races by the cylindrical rollers. 
These and other objects are achieved by a retainer which includes first and 
second circular rings, with each ring having a series of evenly spaces 
lobes extending therefrom which each have an aperture or hole therein. The 
rings are placed on opposite side surfaces of trochoidal-like shaped 
confronting surface regions such that the holes in the lobes of one of the 
rings are axially aligned with the holes in the lobes of the other ring. A 
plurality of rollers for transmitting torque between the confronting 
surface regions are rotatably retained between the confronting surface 
regions by a plurality of roller pins which extend through apertures in 
the rollers, and the roller pins are engaged in the holes of the lobes of 
the first and second rings and fixedly secured to these lobes. 
Accordingly, the roller pins structurally interconnect the first and 
second rings in a secure and strong manner while at the same time 
providing a simple and economic means for rotatably mounting and 
controlling the position of the rollers which are used for transmitting 
torque.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
1. Description of Epicyclic Speed Reducing Transmission 
FIG. 1 is a sectional view of an epicyclic speed reducing transmission 
disclosed in copending application Ser. No. 362,195. The epicyclic speed 
reducing transmission shown in FIG. 1 utilizes first and second conjugate 
sets of races 72, 53 and 92, 56 for achieving first and second speed 
reductions, respectively, and each set of conjugate races has a plurality 
of cylindrical rollers 80 disposed therein for transmitting torque between 
respective first and second confronting surface regions 72, 53 and 92, 56 
of each set of conjugate races. The shape of the first and second 
confronting surface regions 72, 53 of the first set of conjugate races 
utilized by the transmission of FIG. 1 is shown in FIG. 2, and a further 
description thereof is found in the copending application Ser. No. 
362,195, cited above. Methods of making these races are described in 
copending application Ser. Nos. 313,442 and 362,195. 
In FIG. 1, first gear means 70 is fixed to a stationary housing 20, and the 
first gear means 70 functions as a stator in operation. The first surface 
region 72 of the first gear means 70 is formed with a trochoidal-like 
curvature, and the first surface region confronts a second surface region 
53 which is also formed with a trochoidallike shaped curvature. The second 
surface region 53 is formed on a first gear element 52 of second gear 
means 50. The first and second confronting surface regions 72, 53 together 
comprise the first conjugate set of races. 
The second gear means 50 is a journalled on concentric cams 30 formed on an 
input shaft 10 by means of a ring of bearings 32. The input shaft 10 is 
received in the housing 20 and is journalled for rotation therein by means 
of roller bearings 11 which separate the input shaft 10 from an extension 
of an output shaft 60. The eccentric cams 30 and the input shaft 10 are 
further supported against the housing 20 by further bearing elements 31 
and against an output gear element 90 by bearing elements 33. 
As the input shaft 10 is rotated, the second gear means 50 is made to 
undergo orbital motion by the eccentric cams 30, and a pair of 
counterweights 40 are provided on the input shaft 10 opposite the most 
highly eccentric portion of the cams 30 for balancing the transmission as 
the input shaft 10 is rotated. The orbiting speed of the second gear means 
50 is proportional to the rotational speed of the input shaft 10. In 
addition, due to the presence of the bearings 32, the second gear means 50 
is capable of rotating about its axis independently of the orbital motion 
imparted thereto by the input shaft 10 and the eccentric cams 30. As is 
evident from the race positions shown in FIG. 2, a top dead center radial 
position of the cams 30 in FIG. 2 is aligned with arrow 136. As the cams 
30 rotate one full rotation, the top dead center position of the cams also 
rotates one full rotation, as does the point of closest approach 134 
between the races 53. 72. 
The cylindrical rollers 80 are maintained in spaced relationship between 
the first and second confronting surface regions 72, 53 of the first set 
of conjugate races, and the cylindrical rollers 80 transmit torque between 
the stator race 72 and its conjugate race 53. The second gear means 50 is 
a generally disc-shaped element which is bifurcated at its radial outer 
periphery to form the first gear element 52 and a second gear element 54, 
and, as indicated, the race 53 is formed on the first gear element 52. The 
second gear element 54 also has an outer surface 56 formed with 
trochoidal-like shaped curvature which confronts a further trochoidal-like 
shaped surface 92 formed on the output gear element 90. The surfaces 56, 
92 form the second set of conjugate races, and further cylindrical rollers 
80 are maintained in spaced relationship by an additional retainer 96 
between the surfaces 56, 92 so that the additional rollers 80 transmit 
torque between the surfaces 56, 92. The output gear element 90 is 
connected to the output shaft 60, and the bearing elements 29 support the 
output gear 90 against the housing 20. 
As the input shaft 10 is rotated, the eccentric cams 30 cause the second 
gear means 50 to orbit, and the second gear means 50 is caused to rotate 
at a first speed reduction due to the roller engagement between the first 
and second confronting surface regions 72, 53. The output gear element 90 
and its associated output shaft 60 are also caused to rotate at a second 
speed reduction due to the roller engagement between the second set of 
conjugate races 92, 56. 
The first and second sets of conjugate races 72, 53 and 92,56 are conjugate 
trochoidal-like shaped, with one of the surface regions of each of the 
sets being epitrochoidal-like shaped while the other surface region of 
each of the sets is hypotrochoidal-like shaped. Either of the surface 
regions of each set of conjugate races can comprise the epitrochoidal-like 
shaped race with the other surface region of that set comprising the 
hypotrochoidal-like shaped race. 
It should be noted that the first and second surface regions 72, 53, as 
well as the surface regions of the second set of the conjugate races, are 
not shaped so as to form true trochoidal curves and, specifically, true 
epitrochoidal and hypotrochoidal curves, since these surfaces are formed 
so that the center axis of each of the cylindrical rollers 80 travels a 
true trochoidal curved path as the rollers 80 transmit torque between the 
first and second surface regions 72, 53. Since the cylindrical rollers 80 
have a finite diameter, the first and second surface regions 72, 53 are 
necessarily spaced from the center axis of each of the cylindrical rollers 
and, accordingly, have a shape which necessarily deviates slightly from 
the true trochoidal path. However, the shapes of the surface regions 72, 
53 approach that of a true trochoidal curve and, specifically, a true 
hypotrochoidal and epitrochoidal curve, respectively, as the radius of the 
cylindrical rollers 80 approaches zero. 
Referring to FIG. 2, the hypotrochoidal-like shaped surface region is shown 
as being formed on the first surface region 72 and this surface region has 
two more lobes 126 and two more recesses 128, respectively, than does the 
epitrochoidal-like shaped surface region 53. The number of rollers 80 
disposed between the first and second surface regions 72, 53 corresponds 
to the number of lobes of the hypotrochoidal-like surface region, less 
one. The positioning of the respective lobes 126 and recesses 128 of each 
of the surface regions 72, 53 and the cylindrical rollers 80 range from a 
first position 130 where one of the rollers 80 is entrained within 
opposing first 128' and second 128" recesses 128 to a second position 132 
where another one of the roller 80 is entrained between first 126' and 
second 126" confronting lobes 126, with the first and second positions 
130, 132 being at diametrically opposite sides of the first gear means 80 
and the first gear element 52. 
In some embodiments, only half the number of rollers 80 are utilized than 
the number shown in FIG. 2. Accordingly, when only half as many rollers 80 
are utilized, one roller will be located at either the position 130 or 132 
while no such roller will be located at the other of these positions, 
though the surface regions are spaced apart so that one such roller could 
be located at this other position. 
According to the transmission of FIG. 1, as the inner gear member 52 orbits 
due to the rotational input from the input shaft 10 and the eccentric cams 
30, assuming that the outer first gear means 70 is stationary, the inner 
gear element 52 will be caused to rotate about its axis at a speed 
determined by the relative number of lobes on the first and second surface 
regions 72, 53 as the rollers circulate or rollingly engage both these 
surface regions. Specific formulae for determining the output speed ratio 
are set forth in the above-mentioned, copending application Ser. No. 
362,195. 
The second set of conjugate races 92, 56 are shaped like the first set of 
conjugate races 72, 53 except that the number of lobes and recesses on the 
second set of races differs from the number of lobes and recesses on the 
first set of races so that a second, different speed reduction is attained 
by the roller engagement of the second gear element 54 and the output gear 
element 90. 
2. Description of Retainer for Epicyclic Speed Reducing Transmission 
As indicated above, good positional control of the rollers 80 is essential 
in the epicyclic speed reducing transmission to achieve desired optimum 
performance, and it is essential that the radial and the axial positions 
of the rollers be accurately controlled in operation. 
FIG. 3 illustrates an exploded, perspective view of one embodiment of the 
retainer 96 for housing the cylindrical rollers 80 and for controlling the 
radial and axial positions thereof. The retainer 96 includes first and 
second circular rings 100, 102, with each ring having a series of evenly 
spaced-apart lobes 104 having apertures or holes 106 therein. The rings 
are shaped and arranged such that all of the holes 106 of the first ring 
100 are opposite and axially aligned with corresponding ones of the holes 
106 of the second ring 102 so that roller pins 108 can be retained between 
respective sets of the lobes 104 on the first and second rings, 
respectively. The pins can be secured to the lobes by deforming the ends 
of the pins after they have been inserted into the holes or by threading 
the ends of the pins so that they can accommodate nuts 150 and lock 
washers 152. The former method has the advantage of being relatively 
inexpensive, whereas the latter method has the advantage of providing a 
means for easily disassembling the retainer. In either case, the plurality 
of pins provide structural strength to the retainer since they fixedly 
interconnect the first and second rings 100, 102. The pins 108 extend 
through holes 110 in each of the rollers 80 used to transmit torque 
between the first and second confronting surface regions, with the rollers 
80 being rotatably supported by an enlarged pin body portion 112. 
In the embodiment of FIG. 3, the lobes 104 of the first ring 100 extend 
radially outward from this ring whereas the lobes 104 of the second ring 
102 extend radially inward from this ring. Accordingly, the outside 
diameter of the second ring 102 is larger than the outside diameter of the 
first ring 100 since the location of the lobes 106 on each of these rings 
are required to be axially aligned. 
Preferably, the retainer 96 is arranged in the transmission of FIG. 1 so 
that the larger diameter ring 102 confronts an inner side surface of the 
hypotrochoidal-like shaped surface region 72 (left side surface of race 72 
in FIG. 1A) while the smaller diameter ring 100 confronts an outer side 
surface of the epitrochoidal-like shaped surface region 53 (right side 
surface of race 53 in FIG. 1A), and the plurality of rollers 80 are 
rotatably supported between the rings 100, 102 and between the races 53, 
72 via the support provided by the pins 108 secured within the ring holes 
106. 
Referring to the transmission of FIG. 1, and in particular to the space 
between the side surface of a support plate 114 of the first gear means 70 
and a side surface of the first gear member 52 of the first gear means 50, 
it is evident that there is relatively little free space between the 
elements 52, 114 radially outwardly from the hypotrochoidal-like surface 
region 72 whereas there is a greater amount of free space between the 
elements 52, 114 radially inward from the epitrochoidal-like surface 
region 53. Accordingly, it is advantageous to place the smaller diameter 
ring 100 adjacent to a side surface of the epitrochoidal-like shaped race 
53 so as to confront the side surface of the support plate 114 as shown in 
FIG. 1A. Likewise, referring to the opposite side surface of the first and 
second confronting surface region 72, 53 (the left side surfaces as viewed 
in FIG. 1), it is readily observerable that there is more free space 
between the first and second gear elements 52, 54 at a position which is 
located radially outward from the hypotrochoidal-like shaped race 72 than 
exists at a position which is radially inward from the epitrochoidal-like 
shaped race 53. Therefore, it is advantageous to place the larger diameter 
ring 102 adjacent to the side surface of the hypotrochoidal-like shaped 
surface region 72 so as to confront the second gear element 54, as shown 
in FIG. 1A. Though the ring arrangement shown in FIG. 1 and 1A is 
preferable, it should readily be evident that, with minor modifications of 
the configuration of the elements 114, 70 and 52, it would easily be 
possible to position a pair of the smaller diameter rings 100 adjacent 
opposite sides of the epitrochoidal-like shaped surface region 53, as 
shown in FIG. 4; or alternatively, to position a pair of the larger 
diameter rings 102 adjacent opposite sides of the hypotrochoidal-like 
shaped surface region 72, as shown in FIG. 5, rather than utilizing both a 
smaller and a larger diameter ring 100, 102, respectively. 
The embodiment of FIG. 3 is advantageous when the axial width of the hypo- 
and epitrochoidal-like shaped surface regions are the same, as shown in in 
FIG. 1, since the structural strength provided by the rings and the pins 
secured to the lobes thereof minimize axial movement of the confronting 
surface regions. However, in some transmissions, it is advantageous to 
form the confronting surface regions so as to have differing widths in 
which case the "C" or "U" cross-sectional shapes illustrated in FIGS. 4 
and 5 are preferable so as to accurately position the rollers relative to 
one or the other of the confronting surface regions. 
Each of the lobes 104 of the rings 100, 102 are shaped so as to not extend 
radially beyond an outer circumferential surface of the cylindrical roller 
80 being retained by the corresponding pins 108 secured within the holes 
106 of each of these lobes to positively prevent any of the lobes from 
contacting driving and driven surface areas of the first and second 
confronting surface regions 72, 53. Specifically, when the confronting 
surface region 72, 53 have identical widths, axial play in the 
transmission could cause one of the races to be axially displaced to a 
small extent relative to the other race in which case one of the driving 
or driven surface areas thereof would be opposed to either the smaller 
diameter ring lobes or the larger diameter ring lobes. In such a 
situation, if the lobes 104 extended radially outward from an outer 
cylindrical surface of the roller 80 being retained thereby, contact 
between the lobe 104 and either the driving or driven surface areas of the 
surface region 72, 53 would occur which would impair the operation of the 
transmission. Also, the lobes 104 ar required to be shaped so as not to 
extend radially beyond the outer circumferential surface of the 
corresponding cylindrical roller 80 being retained thereby when the "C" or 
"U" cross-sectional shaped retainer illustrated in FIGS. 4 and 5 is 
disposed so as to be in close contact with opposite side surfaces of the 
surface region having the width smaller than the other surface region 
since the lobes would always be opposed to the driving or driven surface 
of this other surface region. 
As is readily evident, the retainers constructed in accordance with the 
embodiments of the present invention achieve accurate control of the 
rollers so that the rollers are maintained appropriately spaced apart. 
Also, since the side surfaces of the first and second rings confront and 
contact side surfaces of the first and second surface regions, and 
opposite end surfaces of the rollers are in close contact with the first 
and second rings, axial movement of the rollers is prevented or kept to a 
bare minimum. Since the various components of the retainer of the present 
invention comprise relatively simple geometric shapes, the retainer of the 
present invention is also relatively inexpensive to manufacture.