Leakproof soft metal seal for use in very high vacuum systems operating at cryogenic temperature

Kitts, W. T.

Platt, P. K.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: GP 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
October 15, 1970 
TO : USI/Scientific & Technical Information Division 
Attention: Miss Winnie M e  Morgan 
FROM ; GP/Office of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U.S, Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attached NASA-owned U,S. patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U,S, Patent No, : 3,301,578 
Corporate Source : Goddard Space Fliqht Center 
Supplementary 
Corporate Source 
NASA Patent Case No,: XGS-02441 
Enclosure: 
Copy of Patent 
Y 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19700032313 2020-03-17T02:12:22+00:00Z
Jan. 31, 1967 P. K. PLATT ETAL 3,30 1,578 
CRYOGENIC CONNECTOR FOR VACUUM USE 
Filed Nov. 17, 1964 
1 
3,301,59 atent Office Patented Jan. 31, 1967 
1 
3,301,578 
CRYOGENIC CONNECTOR FOR VACUUM USE 
Philemon K. Platt, Annapolis, Md., and W2liam T. Kitts, 
Houston, Tex., assignors to the United States of Ameri- 
ca as represented by the Administrator of the National 
Aeronautics and Space Administration 
Filed Nov. 17,1954 Ser. No. 411,944 
1 Claim. (Ci. 285-331) 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon. 
This invention relates to a seal for use in a very high 
vacuum environment and more particularly to a metal-to- 
metal leak-tight seal for use in a very high vacuum system 
which also operates at cryogenic or very low temperatures. 
There has been a marked increase in the demand for 
very high vacuum chambers, 10-6 to 10-9 torr (am. 
Hg abs.), such as in the area of space vacuum simula- 
tion and for the surface study of materials. Seals are 
required for .use h such chambers, for example to join 
various components together by fianges for pumping pur- 
poses. Various schemes have been used heretofore to 
form very high vacuum seals. These include the use of 
elastomer gaskets, metallic gaskets, glass-to-metal and 
glass-to-ceramic joints. Glass-to-metal and glass-to-cera- 
mic seals have found their major use in electrical feed- 
through and sight glasses. Elastomer seals, while widely 
used with flange designs, have a major drawback in their 
outgassing rate. 
Flanges using a soft deformable metal gasket such as 
copper, aluminum, gold and nickel are presently being 
used in a variety of combinations. However, these prior 
art metallic seal combinations are not suitable for use in 
very high vacuum chambers, as they are susceptible to 
damage, are costly to construct, require extremely ac- 
curate alignment and leak upon almost imperceptible 
scratches on the surface of the gasket. Soldering or 
welding has also been used in attempts to form an efficient 
seal; however, such a process introduces contamination 
into the vacuum chamber, is not easily constructed and 
is not readily adapted for disassembly. 
The various attempts to form a seal between two metal 
components, such as flanges in a piping mechanism, by 
the use of a soft metallic gasket have included what is 
known in the art as the stepped, knife edge and coined 
gasket seals. These, as well as modifications thereof are 
summarized in a handbook written by H. A. Steinherz 
entitled, "Handbook of High Vacuum Engineering," start- 
ing at page 149; however, a suitable metallic gasket seal 
which will be capable of providing a relatively leak proof 
(less than 1x10-5 std. atmos. cc./sec.) junction when 
aperation in a very high or ultra high vacuum environ- 
ment has not been fully realized. The use of elastomer 
and metallic seals for ultra high vacuum system is dis- 
cussed in U.S. Patent No. 3,144,035. 
Further, a metal-to-metal seal which is to be used in 
a space simulation chamber must be capable of withstand- 
ing thenmal-shocking within the temperature range from 
0" absolute to over 300" Fahrenheit. Thus, it is necessary 
that the seal be relatively leak proof not only at vacuum 
conditions (10-8 torr) but also at cryogenic temperatures 
(-320" F. and below). 
Therefore, it is an object of this invention to provide 
an improved sealing device for use at cryogenic tempera- 
tures in a very high vacuum environment. 
It is a further object to provide an improved seal which 
uses at least two sets of serrations positioned so as to 
form two sealing surfaces for each serration, the seal be- 
ing leak-tight although operating in a very high vacuum 
! 
I 
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10 
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30 
86 
40 
45 
60 
66 
80 
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m v b n t  and though W i g  subject to extreme thermal 
hock. 
The above objects are achieved by the use of a circular 
#oft metal gasket which is damped between two circular 
:onnecting members or portions of a flange. Each mem- 
xx includes a series of ridges and grooves which are posi- 
ioned to mate so as to deform the metaL gasket between 
hem. By this arrangement, each ridge on one member 
uhen mated with a corresponding groove on the other 
nember effectively foms  two sealing surfaces at each 
ddgewgroove combination. 
The above objects as well as the advantages and fea- 
tures of the present invention will, of course, become 
kippamnt and immediately suggest themselves to those 
skilled in the art to which the invention is directed from 
the reading of the following detailed description in connec- 
tion with the accompanying drawings in which: 
FIGURE 1 is a perspective view of the cryogenic con- 
aector of this invention; and 
FIGURE 2 is a partial side view of the sealing device 
of this invention. 
Referring now and in more detail to FIGURE 1, a cryo- 
genic connector for connecting to portions of a cryogenic 
fluid system is illustrated. Thus, flange members 10 and 
20 are to be connected so that, when joined, a suitable 
cryogenic liquid such as liquid nitrogen, may b pumped 
through openings 12 and 14. It is noted that each mem- 
ber 10 and 20 contains a series of circular ridges 16 and 
grooves 18, which are positioned so as to mate when 
members IO and 20 are joined. This joining or mating of 
the respective ridges and grooves will be shown more 
clearly in relation to FIGURE 2 infra. As may be seen 
in FIGURE I, each ridge possesses a sharp edge since the 
angle for forming the respective grooves is 60". Bt is 
noted that each flange member le and 20 contains a plu- 
rality of bores 22 and 24. The bores 22 on the lower 
member 20 are formed so as to coincide with carrespond- 
ing bores 24 on the *upper member 10. 
FIGURE 2 shows a partial side view of the flange and 
sealiqg gasket arrangement which provides the leak-tight 
seal. Member 10 is positioned with respect to member 
20 so that a ridge 16 on member 10 will fit into a groove 
18 on member 20. It is evident that a ridge on member 
20 also will mate with a groove on member 1Q. A seal- 
ing member gasket 30, which also is circular in the pre- 
ferred embodiment, and which is made of a yieldable ma- 
terial such as copper, is positioned so as to receive the 
ridges of both members 10 and 20. Other soft metals 
such as gold, al'uminum and silver may be used. Also 
shown in FIGURE 2 is a plurality of bolts 26 which are 
to be fit into bores 22 and 24. The bolts 26, which prefer- 
ably are stainless steel, together with corresponding bores 
22 and 24, form a conventional boIt arrangement by 
which uniform pressure may be applied to the flange in 
drawing members 10 and 20 tagether. 
Flange member 20 contains an annular recess 31 de- 
fined by a protruding continuous lip portion 32 formed 
on ,periphery of the flange member. Lip portion 32 acts 
as a guide for the insertion of flange member 10 into the 
recess 32 of flange member 20, and, in addition, upon 
the two flange members being drawn together by the tight- 
ening of bolts 26, it results in there being a snug At be- 
tween the two flange members and them being proper 
maw& of the respective ridges and grooves. 
It is also to 4e noted from FIGURE 2 that opening 
12 of flange member 10, includes a first cylindrical section 
33 and a second cylindrical section 34 and that opening 
14 of h g e  member 20 includes a first cylindrical section 
lo 35 and a second cylindrical section 66. Cylhdrical sec- 
tions 33 and 36 are chosen to have substantially the sam0 
3,501,178 t 
6 
10 
15 
20 
25 
30 
35 
40 
4s 
appended claim. $, 
What is claimed is: z A metal-to-metal cryogenic va~uum seal coupling for 
use in sealing vacuum chahbers at pressures below 10-6 
millimeter of mercury absolute and temperatures below 
-320 degrees Fahrenheit, comprising: 
a first ciroular flange member of stainless steel having 
an opening therethrough to permit the passage of 
fluid, said opening including a first cylindrical 8ec- 
tion and a second cylindrical section, said first cylin- 
drical section having a diameter greater than said 
second cylindrical section to form a shoulder at the 
junction of the two sections, said shoulder serving 
to limit the insertion of a pipe into said first section 
of said opening of said first flange.anember and to 
permit the inner surface of the pipe to mate with the 
inner surface of said second section such that there 
would be a substantially turbulant free flow of fluid 7o 716,079 1/1942 G ~ ~ ~ ~ .  
from the pipe through said first Bange; 
said 5mt flange memW having thereon six concentric 
- 
CARL w. TOMLIN, primwy Examfner, 
3 
diameter and to be greater in diameter than cylindrical 
sections 34 and 35. These latter two cylindrical sections 
are chosen to be of substantially the same diameter. With 
the cylindrical sections being dimensioned, as just de- 
scribed, shoulders 37 and 38 are formed at the junction 
of cylindrical sections 33, 34 and 35, 36, respectively. 
These shoulders determine the depth of insertion of a 
pipe into section 33 and/or section 36, as the case may 
be, and, in addition provide for a condition of substantially 
turbulent free fluid flow between the pipes and the flanges 
since they permit the inner surfaces of sections 34 and 
35 to make a substantially continuous connection with 
the inner surface of the pipes. 
In operation, a ,uniform sealing pressure is applied by 
tightening the series of bolts 26 within bores 22 and 24. 
(In FIGURB 2, the sealing member 30 is not shown as 
completely deformed.) As anifom pressure is applied 
the various ridges 16 deform sealing member 30 to form 
an effective leak-tight seal. It is noted that when seal- 
ing member 30 is so deformed each combination of a 
ridge on one member, and a groove on the other member 
effectively forms two sealing surfaces between the mem- 
bers 10 and 20. Thus, when a ridge 16 on member 20 
is forced into groove 18 in member 10, the sealing mem- 
ber 30 is so deformed that each sloping portion of ridge 
16 is sealed from each sloping portion of groove 18. As 
previously stated, the angle of slope approximates 60" 
in a specific embodiment. 
Typically in a preferred embodiment of this invention, 
member 10 consists of a stainless steel flange which in- 
cludes six concentric ridges and five concentric grooves. 
(Member 20 is also stainless steel and contains five con- 
centric ridges and six concentric grooves. Also the sharp 
edges of the ridges are broken at approximately a .005 
inch radius. Thus, effectively ten sealing surfaces may 
'be formed between members 10 and 20 and this insures 
the necessary low leak rate (less than 1 x 10-6 std. atmos. 
cc./sec.) at 10-8 torr at  -320" F. Conventional stepped 
and knife-edge seals are not capable of such performance 
at such conditions. 
'$'%e advantages of this seal are numerous since it is 
inexpensive and provides for efficient and easy installation 
and removal. Also soldering is eliminated altho- the 
seal still provides a strong junction capable of withstand- 
ing thermal shocks at vacuum premres. 
It is to be understood that the foregoing disclosure 
relates to a preferred embodiment of the invention, and 
numerous modications can be made, such as the use of 
the disclosed seal for the vacuum chamber door seal or 
for the vacuum line coupling or the like, without depart- 
ing from spirit or scope of the invention as defined in the 
4 
ridges and five concentric grooves starting closely 
adjacent the walls forming said second cylindrical 
Bection of said opening of said first flange member 
and continuing radially outwardly, said grooves al- 
ternating with said ridges and forming angles of 60' 
therewith, said ridges being conical in cross section; 
a second circular flange member of stainless steel hav- 
ing an opening therethrough to permit the passage 
of fluid, said opening including a first cylindrical 
section and a second cylindrical section, said second 
cylindrical section having a diameter greater than 
said first cylindrical section to form a shoulder at 
the junction of the two sections, said shoulder serv- 
ing to limit the insertion of a pipe into said second 
section of said opening of said second flange mem- 
ber and to permit the inner surface of the pipe to 
mate with the inner surface of said first section such 
that there would be a substantially turbulant free 
flow of fluid from said second flange through said 
pipe attached thereto; 
said second circular flange member having thereon five 
concentric ridges and six concentric grooves start- 
ing closely adjacent the walls forming said first cylin- 
drical section of said open& of said second flange 
member and continuing radially outwardly, said 
growes altematiug with said ridges and forming 
angles of 60" therewith, said ridges beins conical in 
cross section; 
said ridges and grooves of the first and second flange 
members being lpositioned such that the ridges of said 
first flange member will mate with the grooves on 
said second flange member and the ridges on said 
second flange member will a t e  with the grooves on 
said first flange member; 
said second flange member having an annular recess 
peripherally continuous lip por- 
, whdpby said first flange mem- 
id redess, and, upon being in- 
its outer surface both guided 
and held rigidly in position by said protruding lip 
portion to insure proper matihg of said grooves and 
ridges of the first and second flange mwnben and 
"and at the. same h e  provide a mating between the 
inner surfaces of said openings such that Buid flow 
between said first and second &mge nembera is mb- 
stantially turbulant free. 
References Cited by the Examlner 
UNITED STATES PATENTS 
1,715,854 6/1929 McKenzie _-________ 285-331 
3,211,478 10/1965 Batzer _ _ _ _ _ _ _ _ _ _ _  285-363 
FOREIO N PATENTS 
1,847,218 3/1932 Laarb -_------ _ _ _ _  285-363 X 
1,906,826 511933 Smith __--- _ _ _ _ _ _ _  2853354 


Cryogenic connector for vacuum use Patent

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