Drive enables two concentric output shafts to be controlled independently or rotated as a unit. Possible uses are pointing and tracking devices, rotary camera shutters with variable light control, gimbal systems with yaw and pitch movement, spectrometer mirror scanning devices, etc

Gerdts, J. C., Jr.

Zeiger, R. J.

English

NASA Technical Reports Server

-St 
put 
ive 
DeceMber 1973
	
B73-10497 
NASA TECH BRIEF 
Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Mechanical Planetary Compensating Drive System
A planetary gear drive has been devised which 
enables two concentric output shafts to be controlled 
independently or rotated as a unit. Some other devices 
which ostensibly perform the same function have in-
teractions which lead to large cumulative errors in 
types of mechanical systems because of the rotation 
of one shaft while the other is stationary. Moreover, 
other devices with noninteracting outputs cannot pro-
vide continuous rotation of both outputs unless the 
motor drives mounted on them are equipped with 
electrical slip rings. 
The diagram is a longitudinal sectional view of the 
concentric output differential gearing arrangement of 
the device. The second output shaft is mounted on 
ball bearings held within the body of the first output 
shaft. Moreover, the rotational output of the second 
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned tights.
https://ntrs.nasa.gov/search.jsp?R=19730000497 2020-03-17T07:33:57+00:00Z
shaft can be converted to provide a limited transla-
tional movement by a sleeve which is threaded onto 
the second shaft, as indicated in the diagram, and 
keyed to the first output shaft. 
The first output shaft is directly connected to a 
worm wheel driven by a worm (the first input) which 
is journaled to the cage. The second output shaft is 
connected to the bevel gear indicated in the diagram; 
in turn, this bevel gear is driven by a bevel-gear idler 
which is powered by a third bevel gear that is at-
tached to the sun gear of the planetary gear cluster, 
as indicated in the diagram. The planetary gear clus-
ter (four) is attached to the carriage sprocket serving 
as a sprocket chain second input drive. Thus, rotation 
of the second input drive causes the planetary gears 
to rotate within the circle defined by an outer ring 
gear (attached to the first output shaft) and the sun 
gear; since the sun gear drives the third bevel gear, 
the second output shaft is rotated without effect on the 
first output shaft. However, because of the planetary 
cluster and outer ring gear, rotation of the first input 
shaft is translated into equal angular motion of both 
output shafts. 
The bevel gearing arrangement in the diagram 
drives the second output shaft opposite to the rota-
tion of the second input drive; if the bevel gearing is 
omitted and the sun gear is connected directly to the
second output shaft, the rotations will be in the same 
direction. 
Possible uses are pointing and tracking devices, 
rotary camera shutters with variable light control, 
gimbal systems with yaw and pitch movement, spec-
trometer mirror scanning devices, etc. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94085 
Reference: TSP 73-10497 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial de-
velopment should be addressed to: 
NASA Patent Counsel 
Mail Code 200-1A 
Ames Research Center 
Moffett Field, California 94085 
Source: Robert J
.
 Zeiger and
John C. Gerdts, Jr. 
Ames Research Center
(ARC-10462) 
B73-10497	 Category 06
	 0


Mechanical planetary compensating drive system

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