Reinforced fluorocarbon cupseal, which provides an integral lip-type seal, replaces the metal piston rings in piston-cylinder configurations used in the compression of low density gases. The fluorocarbon seal may be used as cryogenic compressor piston seals

Morath, W. D.

Morgan, N. E.

English

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December 1967	 Brief 67-10591 
NASA TECH BRIEF	 4 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Fluorocarbon Seal Replaces Metal Piston Ring in Low Density Gas Environment 
OPPOSED PISTON FOR TWO-STAGE COMPRESSOR
(USED WITH OSCILLATING DRIVE MECHANISM) 
The problem: 
The compression of low density gases requires a 
closely conforming piston-cylinder configuration. 
Metal piston rings allowed excessive leakage through 
the ring gaps as well as leakage loss at bottom dead 
center (BDC) when the piston ring moved from one 
side of its groove to the other. 
The solution: 
A reinforced fluorocarbon cupseal for the piston 
which eliminates the requirement for rings and pro-
vides an integral lip-type seal. 
How it's done: 
A thread is machined on the ends of the under-
sized stainless steel piston and oversized fluorocarbon 
caps are screwed onto the piston and bonded in place 
with epoxy. The cupseal is then machined to the con-
figuration shown. A lip on the leading edge of the 
piston forms a seal with the cylinder. A stainless steel 
serrated disk spring preloads the lip to improve seal-
ing during the low pressure portion of the compres-
sion cycle.
Notes: 
The reinforced fluorocarbon seal performed better 
than piston rings for the following reasons: The 
thin sealing lip was sufficiently flexible to conform 
to the cylinder bore during changing conditions; no 
ring gap leakage losses; no leakage loss at BDC 
when a piston ring must move from one side of its 
groove to the other; no leakage loss from a ring 
sticking down in its groove; no high friction loss 
as is encountered when a ring is sufficiently spring 
loaded with an expander ring to prevent it from 
sticking in its groove. 
The dimensional accommodation through the 
large temperature range in the course of compres-
sion was excellent since the rings were an integral 
part of the piston and could not shrink into, ex-
pand out of, or stick to a ring groove. 
The fluorocarbon seal may be used as cryogenic 
compressor piston seals (especially compressors for 
H2 or He).
(continued overleaf) 
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=19670000590 2020-03-11T21:31:04+00:00Z
Inquiries concerning this innovation may be di-
	 Patent status: 
rected to:	 No patent action is contemplated.by
 NASA. 
Technology Utilization Officer	 Source: W. D. Morath 
Lewis Research Center 	 and N. E. Morgan 
21000 Brookpark Road	 of Vickers, Inc. 
Cleveland, Ohio 44135
	 under contract to 
Reference: B67-10591
	
	 Lewis Research Center

(LEW- 10277) 
Brief 67-10591
	 Category 05


Fluorocarbon seal replaces metal piston ring in low density gas environment

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