Gearing system for eliminating backlash and filtering input torque fluctuations from high inertia loa

Baker, R. L.

Veillette, L. J.

Williams, S. R.

English

NASA Technical Reports Server

REPLY TO 
AT'TNOF: Gp 
NATIONAL AERONAU~ICS AND SPACE ADMINISTRATION 
WRSHINGTON. D C. 20546 
,r 
March 27, 1971 
TO : USI/Scient i f ic  & Technical Information Divis ion 
A t t e n t i o n :  M i s s  Winnie M, Morgan 
FROM : GP/Office of A s s i s t a n t  General 
Counsel f o r  Pa te r l t  Matters 
SUBJECT: Announcement of NASA-Owned 
U . S .  Patents  i n  STAR 
I n  accordance wi th  t h e  procedures contained i n  t h e  Code GP 
t o  Code US1 memorandum on t h i s  subject, dated June 8, 1970, 
t h e  a t t ached  NASA-owned U.S. patent i s  being forwarded for 
a b s t r a c t i n g  and announcement i n  NASA STAR. 
The following information is provided: 
U.S. Pa ten t  N o .  : 3,359,819 
Corporate Source : Goddard Space Flight Center 
Supplementary 
Corporate Source c 
NASA Pa ten t  Case N o , :  XGS-04227 
Gayle Parker  
Enclosure 
Copy of Pa ten t  N 0 
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[NASA CR OR TMX OR AD NUMBER) s 
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https://ntrs.nasa.gov/search.jsp?R=19710012269 2020-03-17T02:48:46+00:00Z
Dec. 26, 1967 1. J. VEILLETTE ETA: 3,3593 19 
BIDIRECTIONAL STEP TORQUE FILTER WITH ZERO 
BACKLASH CHARACTERISTIC 
Filed April 25, 1966 
F 1 G . 2 .  
BY 
INVENTORS 
Leo 3. Veillette 
Seth R. Williams&;s 
19 United States Patent Office Patented Dee, 26, 1967 
_ _ _ _ ~  
1 2 
20 which is fixed to the shaft as at 22. The hub and spur 
BmmECTIoNAL 3,359,819 FILTER gears 14 and 16 are interconnected through coil springs 24, and 26. Spring 24 connects gear 14 to gear 16 by con- ZERO BACKLASH CHARACTERISTIC 
L~~ J. veillette, ~ d ~ ~ ,  Seth R, willlarns, Seabrook, VentiOnd means and is accommodated in slots 28 and 38 
and Ralph L. Baker, Baltimore, Md., assignors to &e 5 formed in the respective gears. Slots 32 and 34 formed 
United States of America as represented by the Ad- in the gear 16 and the hub 20 carry the second springs 
miniitrator of the National Aeronautics and Space 26 which connect the hub to the latter gear. Note that 
Administration two complementary springs 26 are shown, and in the 
Fied Apr. 25,1966, Ser. No. 545,805 illustrated embodiment a second spring 24 (not shown) 
5 Claims. (CL 74-409) is similarly situated 180 degrees from the spring 24 seen 
in FIGURE 1. This complementary placement aids in 
The invention described herein was made by em- reducing bearing friction but it is to be understood that 
ployees of the United States Government and may be such spring pairs are not essential to an operable de- 
manufactured and used by O r  for the C h ~ ~ n m e n t  for vice, and that one spring for each connection would be 
governmental PurPoses without the Payment of any royal- 15 effective to accomplish the purposes of this sytsem. 
ties thereon or therefor. A pin 36 projects axially from the hub 20 and rides in 
The Present invention relates generally to a gearing the circumferential slot 38 in the gear 16. When the teeth 
system; and more particularly to a gearing system capable of spur gears 14 and 16 are meshed with the teeth of 
of eliminating backlash and filtering input torque flUCtUa- pinion gear 12 spring 24 is in tension and acts to bias 
tions from a high inertia load. 20 the spur gears in opposite directions of rotation. The 
In the application of a power source, such as a stepping second coil spring 26 is also placed in tension and assum- 
motor to drive a relatively large inertia load, it i S  de- ing no load at the output shaft the axial pin 36 will nor- 
sirable to eliminate input torque fluctuations and Corn- mally engage one end of the slot 38 as shown. 
ponents of backlash within the gear train to obtain a FIGURE 2 shows on an enlarged scale the mesh of 
smoothed torque at the output of the system. In the space 25 gears 14 and 16 with the pinion gear 12 carried by the 
sciences the elimination of such disturbances is important input shaft 10. Spring 24 which is pretensioned before 
in obtaining maximum efficiency from the performance the gears are meshed forces the engaging tooth 46 of gear 
of the spacecraft. For example, solar Panels and Para- 16 against the top tooth 40 of the pinion. At the same 
bolic arrays adapted to collect the sun's energy and con- time the engaging tooth 44 of spur gear 14 is forced 
vert it to eIectrica1 energy must be constantly aligned 30 against the bottom tooth 42 of the pinion. The driven 
with the sun to achieve maximum efficiency. The system gears are thus effectively biased in opposite directions 
which provides this alignment must be free from un- about the output shaft 18, giving the device an antiback- 
necessary angular fluctuations and overshoot and must lash characteristic. 
be effective in both directions of rotation. In operation when the input shaft 10 is rotated in a 
It is therefore an object of this invention to provide a 35 clockwise direction torque is transferred directly to gear 
gearing system capable of filtering torque fluctuations and 14 which then drives gear 16 through spring elements 24. 
eliminating backlash in both directions of rotation Of Any torque pulsations are filtered by the springs 24 since 
the input. the pinion does not directly drive gear 16 in this direction 
Another object is to provide a gearing system capable of rotation; a id  gear 16 is free to rotate slightly with re- 
of filtering torque fluctuations and eliminating backlash 40 spect to the pinion. %e hub 20 and output shaft 1s are 
while at the same time functioning as a gear reduction then driven counterclockwise with a smoothed torque 
system over an appreciable range of gear ratios. by the engagement of pin 36 in the end of slot 38. When 
A further object of the invention is the provision of a the input shaft is rotated counterclockwise it drives gear 
gearing system having torque filter and antibacklash char- 16 directly. Gear 16 then drives the hub through springs 
acteristics derived from single input and output means 45 26 which filter out pulsations in the input torque. Note 
without the necessity of intermediate idler means. that in this direction of rotation the pin 36 is free to move 
Still another object is to provide a device as above a limited distance in the circumferental slot 38 and there- 
described which is failsafe in the transmission of driving fore gear 16 when driven clockwise will not drive the 
torque. flange 20 directly but only through springs 26. 
Briefly stated, in accordance with one embodiment, the 50 The device thus comprises a bidirectional step torque 
invention comprises a gearing system inchding an input filter and anti-backlash driving system capable of filter- 
shaft and an output shaft, driving means fixed to the ing small angular displacements, less than one arc-minute 
input shaft, and a pair of driven gears mounted freely for (theoretically zero), In this application the elastic ele- 
rotation on the output shaft and interconnected through ments serve as enrgy storage devices. This permits con- 
elastomeric elements to a flange fixed on the output shaft 55 servation of power in step motor assemblies which drive 
in such a manner that variations in input torque are high inertia loads. Additionally, the system can provide 
absorbed to provide a smoothed torque on the output gear reduction for any reasonable gear ratio, simply by 
shaft. selection of the desired size pinion and spur gears. NO 
The exact nature of this invention as well as other ob- intermediate idler elements are necessary. Further, the 
jects and advantages thereof will be readily apparent from 6o pin and slot connection between the gear 16 and hub 20 
consideration of the following specification relating to the makes the system failsafe with respect to the elastic ele- 
annexed drawings in which : ments for should either or both of the elastic elements 
FIGURE 1 shows an isometric view, partly in section, fail gear 16 would still drive the hub through pin 36. 
of a preferred embodiment of the invention; and The system is also adjustable in that by rotating the 
FIGURE 2 is an enlarged view of the engagement of 65 gear 14 with respect to gear 16 before placing both gears 
the spur gears on the output shaft with the teeth of the in mesh with the driving pinion the biasing tension of 
pinion gear on the input shaft. springs 24 may be preselected according to the angular 
Referring now to FIGURE 1, there is shown an input displacement of the two gears. Of course, the number 
shaft 10 which carries at one end the pinion or driving and size of the springs used will depend upon the magni- 
gear 12 which is normally in mesh with two spur gears "O tude of the anticipated torque fluctuations. Also, elements 
14 and 16 both mounted to turn freely on the output shaft other than coil springs could be employed as long as the 
18. Also mounted on the output shaft is the hub or flange necessary elastomeric qualities are present. 
3,359,819 
3 4 
It should be understood, of course, that the foregoing fixedly mounted on said output shaft, and a second elas- 
disclosure relates to only a preferred embodiment of the tic means having one end connected to said second driven 
invention and that numerous modifications or alternations gear and the other end connected to said flange. 
may be made therein without departing from the spirit 4. A gearing system as defined in claim 3 wherein said 
and scope of the invention as set forth in the appended 6 flange carries an axially extending pin, and said second 
claims. driven gear has formed therein a circumferential slot to 
What is claimed is: accept said pin. 
1. A gearing system for providing a smooth torque 5. A gearing system as defined in claim 4 wherein 
on an output shaft in response to a variable torque on an said pin normally contacts one end of said slot and is 
input shaft comprising: 10 free for limited movement within said slot in one direc- 
a driving gear, tion of rotation of said driven gears. 
an output shaft, 
first and second driven gears meshed with said driving References Cited 
UNITED STATES PATENTS gear and mounted for free rotation on said output 
shaft, 15 
means for biasing said first and second driven gears in 2,310,232 211943 Hale __-________----_ 74-440  
opposite directions of rotation on said output shaft, 2,343,110 2/1944 Hale __- ____--_  -__ 74-440 
and means for rotating said output shaft in response to 2,680,386 611954 Selsted --_-_-__---.--_ 74-574 
rotation of one of said driven gears. 3,143,899 8/1964 York __-__________ 74-409 X 
2. A gearing system as set forth in claim 1 wherein the 20 1,449,903 3/1923 Leow _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  74-440 
means for biasing said f is t  and second driven gears com- 1,608,050 11/1926 Bailey _-_______---___ 74 440 
prises elesatic means having one end conected to said 1,648,715 11/1927 Bean _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  74-440 
first driven gear and the other end connected to said sec- 2,663,198 12/1953 Cairnes -_________-__ 74-409 
ond driven gear such that said elastic means is placed in 2,966,806 1/1961 Luning ______-_-_-__ 74 409 
tension when the driven gears are in mesh with said dnv- 26 
ing gear. 
3. A gearing system as defined in claim 2 wherein said 
means for rotating said output shaft includes a flange 
DONLEY J. STOCKING, Primary Examiner. 
LEONARD H. GERm, Assisirrni 


Bidirectional step torque filter with zero backlash characteristic Patent

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