Device uses differential gears to drive either one of two nut-screw assemblies. In event that one assembly jams, second assembly is driven at twice its normal rate with no loss in overall performance

Benjamin, R. W.

English

NASA Technical Reports Server

August 1973	 B73-10070 
NASA TECH BRIEF 
Lyndon B. Johnson Space Center 
NASA Tech Briefs announce now 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. 
Redundant Screwjack 
Ball Nut 
	
and Screw (Left-Hand)	 Differential 
	
(or Any Nut/Screw)	 Gears 
End 
Fitting Input 
J,-._. Gears 
EN
	
EN 
End
Fitting 
frZIJ4	 f'f1''A	 Ball Nut 
and Screw (Right-Hand) 
External Driving	 (or Any Nut/Screw) 
Spline (Rotates) .	 1	 '	 '	 Internally Driven Rotary Input	 Spline (Rotates and (Mechanical, Electrical, 	 Reciprocates) 
Hydraulic) 
The problem: 
Screwjacks used as actuators on aircraft flap systems, 
and in other critical applications, may be subject to 
failures. These failures occur in the existing double-nut 
and telescoping-type screwjacks when any of the nut-
screw assemblies jams. 
The solution: 
A redundant screwjack uses differential gears to drive 
either one of the nut-screw assemblies, in the event that 
the other jams. 
How it's done: 
The redundant screwjack (see figure) utilizes input 
gears to drive a rotary external spline which, in turn, 
meshes with and drives an internal spline. The internal 
spline is designed to rotate and reciprocate with the 
external one. The internal spline also supports the spider 
input to the differential gears. These gears rotate the 
right- and left-hand bail nuts which move the left- and 
right-hand screws, extending or retracting them. The 
screws do not rotate but are firmly attached to the 
structure.
If either nut-screw combination jams, the differential 
gears will drive the other combination at twice its 
normal rate with no loss in overall performance. 
Note: 
No further documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Lyndon B. Johnson Space Center 
Code JM7 
Houston, Texas 77058 
Reference: B73-10070 
Patent status: 
NASA has decided not to apply for a patent. 
Source: R. W. Benjamin of
Rockwell International Corp.

under contract to
Johnson Space Center
(MSC-19200) 
Category 07 
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=19730000070 2020-03-17T06:44:15+00:00Z


Redundant screwjack

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