Ramped clutch plate prevents damage to gear traing and provides ample linear motion for actuation of microswitch. Operation of device is not affected by number of revolutions which pinion shaft must make to produce required translations. Since ramps in spur gear are conical, device will actuate identically at each mechanical stop

Crissey, M. E.

English

NASA Technical Reports Server

a 
April 1975	 B75-10058 
•	 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. 
Motor-Driven Rack-Positioning Device 
The problem: 
To switch off power to an electric motor reliably 
when a rack that is geared to the motor is driven 
against a stop.
Drive 
Motor	 h.	 Gear 
Switch 
Rack  / 
Pin [1,,Spring 
Bushing 
	
Pinion /	 —	 Floating 
	
Ramp Jaws	 Gear 
The solution: 
Employ a ramped clutch plate to prevent damage 
to the gear train and to provide ample linear motion 
for actuation of a microswitch. 
How it's done: 
As shown in the diagram, a ramped interface is 
incorporated between a disc pinned to the pinion 
shaft and spring-loaded spur gear bushed to the same 
shaft. When a hard stop is reached, the motor con-
tinues to drive; this causes pins in the disc to move
up the ramps in the spur gear so that the pinned disc 
and the gear are separated. The motion along the 
shaft is more than adequate to cause positive action 
of the microswitch, which may otherwise be insensi-
tive because of temperature effects, spring character-
istics, etc. The torque at which ramp action begins 
can be set by adjusting the spring load against the 
face of the floating spur gear. 
Operation of the device is not affected by the 
number of revolutions which the pinion shaft must 
make to produce the required translations. Since the 
ramps in the spur gear are conical, the device will 
actuate identically at each mechanical stop. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B 75-10058 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Merrill E. Crissey of
Martin Marietta Corporation 
under contract to

Ames Research Center
(ARC-10864) 
Category 06 
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 rights.
https://ntrs.nasa.gov/search.jsp?R=19750000058 2020-03-19T20:05:35+00:00Z


Motor-driven rack-positioning device

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