Two elastic springs connecting a hub and two spur gears absorb bidirectional step torque differentials and provide antibacklash characteristics between input and output shafts. This device is used in precise control systems

Baker, R.

Veilette, L.

Williams, S.

English

NASA Technical Reports Server

Get 
Pin and Slot 
Engaging Tooth 
of Gear B
Top Tc 
..
of Pin 
C 
Engaging Tooth 
of Gear A	 Lot
Bottom Tooth 
of Pinion
Input Shaft 
May 1965	 Brief 65-1014 
NASA TECH BRIEF H 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Bidirectional Step Torque Filter Eliminates Backlash 
Gear A
	
Load 
The problem: To maintain a constant output 
torque, free of backlash components, from a pulsating 
input torque. 
The solution: Two elastic elements (springs) con-
necting a hub and two spur gears absorb torque dif-
ferentials and provide the desired antibacklash charac-
teristics between input and output shafts. The system 
performs equally well in either direction of rotation. 
How it's done: The hub is securely attached to the 
output shaft and the two spur gears turn freely on the 
shaft. Spring I connects gear A to gear B and spring 2 
connects gear B to the hub. The input shaft pinion 
engages both spur gears. Spring I forces the engaging
tooth of gear A against the bottom tooth of the pinion 
and the engaging tooth of gear B against the top tooth 
of the pinion. This arrangement prevents backlash be-
tween the input and output shafts and spring I also 
serves as a torque filter between the two spur gears. 
When the input Shaft is rotated clockwise, its pulsating 
torque is transferred directly to gear A, which then 
drives gear B through spring I. The torque pulsations 
are filtered by the spring since the pinion does not di-
rectly drive gear B in this direction of rotation and 
gear B is free to rotate slightly with respect to the pin-
ion. The hub and output shaft are then driven counter-
clockwise with a smooth, constant torque by a pin in 
the hub that engages a slot in gear B. When the input 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000147 2020-03-11T17:22:26+00:00Z
shaft is rotated counterclockwise, it drives gear B di-
rectly. In this condition, gear B drives the hub and 
output shaft clockwise through spring 2, which filters 
out the pulsations in the input torque. 
Notes: 
1. This system is capable of filtering small angular 
displacements to less than 1 arc minute (essentially 
zero). 
2. This device should be of interest to manufacturers 
of precise control systems. 
3. Possible configurations and filter materials are 
limited only by the application desired.
4. Inquiries concerning this invention may be di-
rected to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland, 20771 
Reference: B65-10148 
Patent status: NASA encourages the immediate 
use of this invention. It is owned by NASA and in-
quiries about obtaining royalty-free rights for its com-
mercial use may be made to NASA, Code AGP, 
Washington, D.C., 20546. 
Source: Leo Veilette, Seth Williams,
and Ralph Baker
(GSFC-335) 
Brief 65-10 148
	
Category No. 05


Bidirectional torque filter eliminates backlash

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server