Compact-vibration damping systems, consisting of rubber-coated metal bellows with a sliding O-ring connector, are used in vacuum lines. The device presents a metallic surface to the vacuum system and combines flexibility with the necessary stiffness. It protects against physical damage, reduces fatigue failure, and provides easy mating of nonparallel lines

Hegland, D. E.

Smith, R. J.

English

NASA Technical Reports Server

0-Ring Seal
Silicone 
Rubber 
Coated 
Bellows 
MaN 1966
	 Brief 66-10187 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Rubber-Coated Bellows Improves Vibration Damping in Vacuum Lines 
The problem: 
To design a compact vibration damping system for 
use in vacuum lines. Rubber hose and metal bellows 
are frequently employed for vibration damping. While 
the rubber hose is generally adequate for small sys-
tems (where vacuum connections are under one and 
one-half inches in diameter), they become cumber-
some and stiff due to wall thickness or reinforcement 
in larger diameter applications. The metal bellows 
becomes stiff when evacuated (thereby losing some of 
its damping properties) and it is subject to fatigue 
failure after continued cycling. 
The solution: 
A rubber-coated bellows with a sliding 0-ring 
connector, presents a metallic surface to the vacuum
system and combines flexibility with the necessary 
stiffness. 
How it's done: 
The vibration damping assembly consists of a sili-
cone rubber-coated bellows and a sliding 0-ring seal. 
The rubber coating on the bellows is a room-tempera-
ture vulcanizing silicone rubber adhesive which en-
sures that the rubber is not forced out of the con-
volutions of the bellows. Since the adhesive rubber 
compound cures by absorbing moisture from the air, 
it is necessary to make several thin applications and 
allow up to 48 hours of curing time per application. 
The rubber is applied with the bellows extended to 
ensure complete filling of the convolutions. 
(continued ocricit) 
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The sliding 0-ring seal is attached to the rubber-
coated bellows and provides good axial damping 
because of its high compliance and small area of 
contact for vibration transmission. 
Notes: 
I. The sliding 0-ring need not be permanently at-
tached to the rubber-coated bellows. Any good 
vacuum connector can be used to mate the two: 
however, the sliding 0-ring seal gives optimum 
performance. 
2. The device has several advantages: protection 
against physical damage, less likelihood of fatigue 
failure, no plastic deformation, and easy mating of 
nonparallel lines.
3. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio, 44135 
Reference: B66-10187 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. J. Smith and D. E. Hegland
of Lewis Research Center
(Lewis-273)
O 
Brief 66-10187
	
Category 02


Rubber-coated bellows improves vibration damping in vacuum lines

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