Electrically or hydraulically powered, hermetically sealed angular or rotary actuator deflects mechanical members over a range of plus or minus 180 degrees. The actuator design provides incremental flexures which keep the local deflection rate within elastic limits

Wuenscher, H. F.

English

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August 1968	 Brief 68-10300 
NASA TECH BRIEF
 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Conceptual Hermetically Sealed Elbow Actuator 
-	 -
	 Bellows (Undetected)
	
The general purpose of this concept is to provide
	 environments is presently restricted to the endurance 
	
for an electrically or hydraulically powered, hermeti-
	 of the dynamic seals. The motion of flexural enclos-
	
cally sealed angular or rotary actuator that will de-
	 ures such as bellows and flexible hoses has to be 
	
Elect mechanical members over a range of =i=1800. 	 restricted to the elastic capability of the material they 
	
Existing rotary actuators must use dynamic seals at
	 are made from. Metal enclosures such as stainless steel 
	
torque input or output shafts,, because the relative
	 bellows are restricted to small deflections per convolu-
	
motion is too large for hermetic sealing by means of
	 tion and therefore can only move with small angular 
	
bellows-type flexural members. Dynamic seals are
	 changes of an actuator. 
	
subject to wear and leakage. The use of such actuators
	 This actuator design would overcome the disad-
	
under severe environmental conditions, as in the vac-
	 vantage of conventional devices by providing incre-
	
uum of space, or the salt water environment in the
	 mental flexures which keep the local deflection rate 
	
ocean, or in other severe chemical and temperature
	 within elastic limits. The mechanical linkage would 
(continued overleal) 
	
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.
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enable complete enclosure of the actuator by a hermet-
ically sealed bellows. ,The mechanical arrangement of 
the actuator, would produce the total angular deflec-
tion by incremental deflections over a permissible 
radius within the flexing capability of the bellows. 
The device achieves this incremental deflection by the 
use ofa number of angular multipliers I and 2, which 
are guided by blind actuator rods 3 and 4. The linear 
drive motor moves the linkage between arms 5 and 6. 
This motion rotates multiplier I over an angle a, 
which is compatible with the elastic capability of 
the bellows. The blind actuator rod 3 causes angular 
rotation of multiplier 2 over an additional angle fi, 
which is within the permissible deflection range of the 
bellows and adds to the deflection a. Blind actuator 
rod 4 rotates the drive member over the angle y, which 
is then deflected with respect to member 7 by the sum 
of the incremental deflection a, 3, and y to a total 
deflection c. Total deflections of more than 1800 
in the plane of the members or continuous rotation in 
a spiral mode can be achieved by adding angle multi-
pliers to the joint, which are all actuated by the
linear motor actuator. The deflection rate between 
angular multipliers can be changed by changing the 
proportions of the blind actuators and their linkage. 
In this way, the curvature can be kept within tolerable 
flexure limits of the bellows. The curvature can also 
be incrementally changed from one to the other angu-
lar multiplier in order to achieve a desired geometry 
of the total bend or a desired displacement of the drive' 
member during the operation of the actuator. 
Note: 
• rhis device is in the conceptual stage only; neither a 
a model nor a prototype has been built as of the date 
of this Tech Brief. 
Patent status: 
Inquiries' about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: H. F. Wuenscher 
(M FS- 14710) 
Brief 68-10300	 Category 05


Conceptual hermetically sealed elbow actuator

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