Elastic, pressure-sensitive orifice is used to automatically regulate the rate of gas flow into bearings under varying loads. Formed of a molded elastomer, theses orifices increase the stability of gas bearings

Batsch, F.

Laub, J. L.

English

NASA Technical Reports Server

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June 1964
	
Brief 63-10123 
NASA TECH BRIEF 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint industry 
with the technical content of an innovation derived from the NASA space program. 
Elastic Orifice Automatically Regulates Gas Bearings 
	
The problem: Recent trends in machine-tool and
	
Gas-lubricated bearings, on the other hand, have 
	
instrumentation technology have placed increasing
	
low frictional resistance at high operating speeds, 
	
emphasis on the development of externally pressurized
	
but their use has been limited because of their 
	
liquid bearings to obtain performance characteristics 	 relatively high power consumption (gas pressure 
	
that are difficult to achieve with rolling-contact
	
x orifice area x gas velocity) and low stiffness, espe-
	
bearings. Liquid bearings are inherently capable of
	
cially at higher bearing loads. A further limitation 
	
providing smoother operation than rolling-contact
	
is that these bearings have high efficiencies and opti- 
	
bearings, and eliminate the need for special lubricants 	 mum characteristics only at the loadings for which 
	
that must remain effective in extreme environments 	 they were designed, since at high loads not enough gas flows for lubrication and at low loadings flows 
	
(e.g., under high temperatures or vacuum). They have 	 are excessive. Thus, a method for automatic control 
	
many limitations, however, among which is a high 	 of gas flow was sought in order to permit bearings 
frictional resistance at high speeds.	 to be operated over wide ranges of loadings and speed. 
(continued overleal) 
	
This document was prepared under the sponsorship of the National	 this document, or that the use of any information, apparatus, method. 
	
Aeronautics and Space Administration. Neither the United States Govern- 	 or process disclosed in this document may not infringe privately-owned 
	
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 	 rights; or B. Assumes any liabilities with respect to the use of, or for 
	
any warranty or representation, express or implied, with respect to the 	 damages resulting from the use of, any information, apparatus, method, 
	
accuracy, completeness, or usefulness of the information contained in 	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19630000013 2020-03-11T16:45:09+00:00Z
The solution: Use of an elastic, pressure-sensitive 
orifice to regulate the rate of gas flow into the 
bearing under varying loads. Orifices of this kind, in 
comparative tests with fixed orifices, appear to be 
more stable and provide greater bearing stiffnesse 
(especially at higher loads), lower power consumption, 
and greater load-carrying capacity per unit of power 
consumption. 
How it's done: An orifice is formed in a circular 
disc of an elastomer (e.g., silicone rubber), by molding 
uncured elastomer around a metal pin and withdraw-
ing the pin after the elastomer has set. A cross-
sectional view of a typical spherical gas-lubricated 
bearing is shown above. In operation, the supply 
pressure is usually held constant. The pressure 
just downstream of any orifice is lower; it is at a 
minimum when the bearing is not loaded and at a 
maximum when it is loaded. Thus, the pressure dif-
ferential across a fixed orifice and the gas flow 
through it are very great under light loads and 
altogether too small under heavy loads. However, 
when the fixed orifice is replaced with an elastic 
one, an increased bearing load decreases the pressure 
differential across the orifice, allows the elastomer 
to relax, and thus leads to an increase in the 
effective diameter of the orifice. As a result, the gas 
flow tends to remain constant even though the load 
on the bearing varies widely; the overall result 
is a significant saving in gas and power consumption, 
especially at lighter bearing loads. 
The elastic orifice has been found to provide a 
definite improvement in stiffness. Although the maxi-
mum load-carrying capacity for a given bearing may 
be lower with an elastic orifice than with a fixed 
orifice, it can be shown that elastic-orifice bearings 
designed specifically for high loadings present definite 
advantages. Elastic orifices, furthermore, are partic-
ularly efficient when gas can be supplied at high 
pressures.
The results of preliminary tests indicate that an 
elastic orifice increases the stability characteristics 
of a given gas bearing, especially at low gas-flow 
rates. 
Elastic orifices tend to be free of clogging by dust 
particles, particularly when load variations are suffi-
ciently large, and are simpler to construct and main-
tain than other types of automatic fluid-control 
devices. 
Notes: 
1. Use of a bearing with an elastic orifice is recom-
mended in situations where improved load bearing 
stability is required, where major load variations 
occur or the exact load cannot be anticipated, and 
where gas and power consumption must be held at 
a minimum value. 
2. Alternative designs of the elastic orifice may 
be advantageous in some applications; for example, 
the elastic orifice may be placed between metal 
discs, or provisions may be made for inter-
changeable units. 
3. Instead of using the elastic properties of plastic 
materials, a flexible orifice may be constructed of 
metal by incorporating springs or diaphragms in a 
valve-type design. This would be preferable in 
high-temperature applications or in a radiation 
environment. 
4. For further information about this innovation, 
inquiries may be directed to: 
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B63-10123 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: John L. Laub and Frank Batsch 
(JPL- 135) 
Brief 63-10123


Elastic orifice automatically regulates gas bearings

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