Palladium valve, permeable to hydrogen gas, is used to fill a bellows mechanism from a source of hydrogen to power an actuator. A similar valve provides retraction. The valves have no moving parts and are heat operated. One limitation on the use of this actuator is discussed

Ambruso, A.

English

NASA Technical Reports Server

September 1970
	
Brief 70-10516 
NASA TECH BRIEF 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Concept for a Gas Operated Actuator 
A palladium valve, permeable to hydrogen gas, can 
be used to fill a bellows mechanism from a source of 
hydrogen to power an actuator. A similar valve can 
be used to provide retraction. The valves would have 
no moving parts, and would be heat operated. An 
actuator operated in this manner could have numerous 
industrial applications. 
Actuator 
	
Conductors	 ( Conductors 
+	 -	 I	 Ir+	 - 
Palladium 
Tube
Inlet	 I 
Port Outlet	 \ 
	
Chamber	 Port	 Palladium 
Tube 
Shutoff Valve 
Storage Tank 
H Under Pressure 
of 2000 psi 
As shown in the schematic diagram, the conceptual 
actuator consists of a sealed bellows which is provided 
with inlet and outlet ports. A supply of hydrogen 
under pressure (typically 2000 psi) is contained in 
the storage tank. The tank is connected by tubing and 
a shutoff valve to a chamber completely enclosing a
sealed-off palladium tube connected to an inlet port. 
Electrical connections join a portion of the tube to 
an electrical source. 
A second closed-off palladium tube is connected 
to an outlet port. Electrical connections link a portion 
of the tube with source which may be different from 
the first source. The tubes constitute palladium valves, 
used initially to extend the bellows by inflating it with 
hydrogen under pressure, and subsequently allowing 
the bellows to return to the initial unextended state 
(or any intermediate state) by exhaust of the hydrogen 
gas. 
A section of the palladium-silver or other palladium 
alloy tubing can be brought to a temperature suffi-
ciently high, about 450°F, to effect a substantial in-
crease (approximately 100 times the permeation at 
50°F) in hydrogen permeation by conductors inducing 
electrical current between two spaced points on the 
tubing. Thus if the chamber is initially filled with 
hydrogen under pressure, and the tube is at a low 
temperature, about 50°F, hydrogen will not pass rap-
idly from the chamber into the interior of the bel-
lows. When the heated tube becomes much more 
permeable, the pressurized gas will transfer through 
the heated palladium membrane made up of the wall 
of the tube and will enter the interior of the bellOws. 
After sufficient hydrogen has passed, the bellows will 
be extended (indicated by the broken line in the fig-
ure), moving the load. 
When the currentis turned off, the palladium mem-
brane will no longer be as permeable to hydrogen and 
the bellows will remain "latched" in the extended 
position under the pressure of the contained hydrogen. 
To return the load to the initial position (or any inter-
mediate point), the outlet palladium tube is heated by 
(continued overleuf) 
Extended Bellows	 Load 
r	 / 
( 
.,
)
Sealed 
Bellows 
This 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
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=19700000498 2020-03-17T00:33:47+00:00Z
applying an electrical current through the conductors. 
The extent of retraction of the bellows under the force 
exerted by the load (or by a built-in spring force of 
the bellows itself) will depend upon the length of time 
that current is applied. It is obvious that although the 
actuator provides a linear movement, suitable motion 
transformation could provide a rotary movement; 
also by switching power between the tubes, a form of 
alternating movement is obtainable. 
Passage of hydrogen through the membrane is due 
to the formation of palladium hydride on the surface 
of either tube in contact with the hydrogen; the ele-
vated temperature causes decomposition of the hy-
dride to reform hydrogen on the other surface. Since 
this hydride forming reaction is reversible to some 
extent through the walls of either tube, it may be pref-
erable to contact the transferred hydrogen with a 
hydrogen reactive gas such as oxygen to form water. 
Notes: 
1. One limitation on the use of the actuator is that 
although palladium is permeable to hydrogen at 
any temperature above absolute zero, the rate of 
diffusion through the palladium membrane is ex-
tremely small until the critical temperature is 
reached. Thus the actuator would only be suitable 
for relatively short term use (on the order of hours) 
because the diffusion rate would be so low at tem-
peratures below critical, the actuator would remain 
latched. Such limits can only be established after 
construction of an actuator according to the con-
cept.
2. No further documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B70-10516 
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: A. Ambruso of

Beckman Instruments Inc.

under subcontract to

Caltech/J PL

NASA Pasadena Office

(N PO- 11340)
. 
. 
Brief 70-10516
	 Category 07


Concept for a gas operated actuator

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