Recyclable actuator does depend on valves for its operation. Palladium cathode tube in electrochemical cell is used to generate hydrogen by electrolysis. Hydrogen pressure generated inside tube causes expansion of bellows, which raises load. Bellows can be retracted by reversing electrical connections to cell electrodes

Simmonds, P. G.

English

NASA Technical Reports Server

March 1973	 B73-10133 
C NASA TECH BRIEF 
NASA Pasadena Office
	 C 
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. 
Gas-Operated Actuator—A Concept 
The problem: 
To provide a recyclable actuator which does not 
depend on valves for its operation. 
The solution:
tube, and the hydrogen pressure will increase as long 
as current is allowed to flow until a maximum pres-
sure of about 4 MN/M2
 (600 psig) is obtained; how-
ever, in normal use, only enough hydrogen pressure 
Use a palladium tube cathode to generate hydrogen 
by electrolysis; the hydrogen pressure generated in-
side the tube structure causes expansion of a bellows. 
The bellows can be retracted when the palladium 
tube is made the anode.
	 -... 
How it's done:
Load
Bellows 
The general arrangement of the essential compon-
ents of the gas-operated actuator is shown in the 
diagram. The electrochemical cell consists of a body 
of electrolyte in contact with a tubular palladium 
electrode and platinum electrode. The tubular elec-
trode may also be made of palladium alloys or other 
metals which are permeable to hydrogen; alterna-
tively, the tube can be made of porous ceramic 
coated with a film of palladium or palladium alloy. 
The electrolyte is a mixture containing 90% of po-
tassium or sodium hydroxide, 10% lithium hydroxide, 
and 15% of water, which is the source of hydrogen. 
The electrolyte must be maintained fluid at an ele-
vated temperature to promote electrolysis and to 
maintain the palladium membrane at a suitable tem-
perature for diffusion of hydrogen (about 2500 C). 
Hydrogen gas is generated at the palladium elec-
trode when a source of power, such as a battery, is 
connected through a reversing switch to the electrodes 
and the polarity is such that the palladium electrode 
is the cathode. The hydrogen gas passes through the 
warm palladium walls into the interior recess of the 
Cis document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
:[ J.J4Palladium 
Tube 
is generated to expand the bellows and raise the load. 
The bellows is retracted by reversing the electrical 
connections to the electrodes; when the palladium 
tube is the anode, hydrogen in the tube—bellows 
system will pass through the permeable wall and be 
reoxidized to water. Thus, if the electrolytic cell and 
the bellows system is properly sealed and leak-free, a 
perfect balance can be maintained and none of the 
(continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000133 2020-03-17T07:08:42+00:00Z
water originally present in the electrolyte will be lost. 
If the bellows system has a small leak, a small decom- 
position current can be made to flow continuously 
through the cell to replace hydrogen lost by leakage. 
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,702,532). Inquiries concerning nonex-
elusive or exclusive license for its commercial devel-
opment should be addressed to:
NASA Patent Counsel 
Mail Code l 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: r eter C. Simmonds of
Caltech/JPL
under contract to
NASA Pasadena Office
(NPO-11369)
. 
. 
B73-10133	 Category 03


Gas-operated actuator: A concept

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