Concept utilizes porous metal or nonmetal matrix containing liquid metal in porous structure and confines liquid metal to contact area between rotor and brush by capillary forces. System may also be used to lubricate bearing systems

Ferguson, H.

English

NASA Technical Reports Server

NASA TECH BRIEF 
Lewis Research Center H .
June 1973	 B73-10164 
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. 
Liquid Metal Porous Matrix Sliding Electrical Contact: A Concept 
The problem: 
Two types of slip rings are conventionally used to 
provide an electrical connection between the stationary 
and rotating parts of electrical machinery. One type 
uses a solid, electrically conductive brush and mechanical 
slip ring assembly to make the electrical contact 
between the rotating parts. The other type makes use of 
a liquid metal in the intervening space between the 
rotor and brush to provide the electrical path between
the two members. Both have operating limitations. 
Solid mechanical slip rings are subject to wear, 
high friction forces, electrical noise, debris formation, 
tendency to vacuum weld when static, and difficulty in 
retaining surface coatings in extended use. Present liquid 
metal slip rings are si'bject to debris formation, difficulty 
in retaining the liquid metal in the desired location and 
shape, and exposure of a relatively large liquid metal 
surface area promoting vaporization and contamination. 
Detail A
Porous Metal Sliding Contact 
KI
(continued overleaf) 
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	 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 
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	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000164 2020-03-17T07:06:53+00:00Z
The solution: 
This concept utilizes a porous metal or nonmetal 
matrix containing liquid metal in the porous structure 
and which confines the liquid metal to the contact area 
between rotor and brush by capillary forces. 
How it's done: 
The figure shows a conceptual assembly employing a 
porous metal brush filled with liquid gallium in contact 
with a solid metal rotor. The pore size and direction of 
the porous matrix grade and the brush-rotor separation 
are selected to provide for the proper direction of 
liquid metal flow into the contact space between rotor 
and brush under the influence of capillary forces. The 
edges of the brush at the contact site and the brush-
rotor separation are designed to retain the liquid metal 
at the moving contact site only and reduce its exposure 
to the operating environment. 
Alternate configurations and designs include the use 
of porous metal rotors with porous metal brushes, or 
porous metal rotors and solid metal brushes. The system 
may also be used to lubricate bearing systems.
Notes: 
1. This application has advantages over conventional 
mechanical slip rings in reduced friction, reduced 
wear, reduced electrical resistance, and ease of 
fabrication due to fewer complex mechanical parts. 
Advantages over conventional liquid metal slip rings 
include reduced exposure of the liquid metal to 
contaminants, reduced debris accumulation, location 
and exposure of liquid metal surfaces only in the 
vicinity of the contact site, and more intimate con-
tact of liquid metal with solid components. 
2. No additional documentation is available. Specific 
questions,however, may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10164 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Harold Ferguson
Lewis Research Center
(LEW-1173 5)
. 
S 
B73-10164	 Category 01,04


Liquid metal porous matrix sliding electrical contact: A concept

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