Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove pattern produces a pumping action toward the fluid when the shaft rotates which prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear

Ludwig, L. P.

English

NASA Technical Reports Server

t/.y*-.
REPLY TO
ATTN OF: GP
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
5
 1973
TO: RSI/Scientific & Technical Information Division
Attention: Miss Winnie M. Morgan
PROM: GP/Office of Assistant General Counsel for
patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, 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. :
Government or
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NASA Patent Case No.
t cr e>M
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Yes / 7 No / ^ /
Pursuant to Section 305(a) of the National Aeronautics and
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the Specification, following the words "... with respect to
an invention of ...H
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Enclosure
Copy of patent cited above
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United States Patent
Ludwig
[in 3,767,212
[45] Oct. 23, 1973
[54] SPIRAL GROOVE SEAL
[75] Inventor: Lawrence P. Ludwig, Fairview Park,
Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Dec. 21, 1970
[21] Appl. No.: 99,901
Related U.S. Application Data
[63] Continuation of Ser. No. 723,465, April 23, 1968,
abandoned.
[52] U.S. C.l : 277/25, 277/27, 277/96
[51] Int. Cl F16j 15/34
[58] Field of Search 277/3, 27, 96, 74,
277/88, 134, 133, 25
[56] References Cited
UNITED STATES PATENTS
2,354,478 7/1944 Reinhardt et al 277/88 X
3,109,658 11/1963 Barrett et al -... 277/96 X
3,499,653 3/1970 Gardner 277/96 X
3,527,465 9/1970 Guinard 277/96 X
FOREIGN PATENTS OR APPLICATIONS
1,009,940 11/1965 Great Britain 277/74
230,697 3/1925 Great Britain 277/88
OTHER PUBLICATIONS
Mechanical Engineering- "Dynamic Seal Technol-
ogy" pages 28-33 (see page 30 Fig. 2 left). March
1968
Primary Examiner—Samuel B. Rothberg
Attorney—N. T. Musial, G. E. Shook and John R.
Manning
[57] ABSTRACT
Mating flat surfaces inhibit leakage of a fluid around a
stationary shaft. A spiral groove pattern produces a
pumping action toward the fluid when the shaft ro-
tates which prevents leakage while a generated hy-
draulic lifting force separates the mating surfaces to
minimize wear.
5 Claims, 3 Drawing Figures
. Patented Oct. 23, 1973 3,767,212
FIG. I
34
FIG. 3
INVENTOR
LAWRENCE P. LUDWIG
BY
ATTORNEYS
(NASA-Case-LEW-10326-3) SPIEAL G E O C V E N74-10474
SEAL Patent ( N A S A ) 4 p CSCI 13E
Unclas
V 00/15 20126
 x
^ T ~ ; r ~ 3 7 7 ' 6 7 7 2 T 2 ~
1 2
SPIRAL GROOVE SEAL FIG. 2 is an elevation view of the rotatable seat taken
RELATED INVENTION al°ng the Ifae 2~2 '" FIG' 1: a"dKK  i tu II  v U  i IUIN
 F,G 3 ^ a partia, g ,^,,,,,] vjew showing the relative
This application is a continuation of copending appli- positions of certain parts of the seal when the shaft is
cation Ser. No. 723,465 which was filed Apr. 23, 1968, 5 rotating,
and now abandoned. DESCRIPTION
OWNERSHIP
 In the embodiment shown in FIG. 1 a shaft 10 ex-
The invention described herein was made by an em- tends into a container 12 of liquid 14. The shaft 10 is
ployee of the United States Government and may be 10 rotatable about its normal axis Y-Y' and may be used
manufactured and used by or for the Government for to transmit torque from motor to a pump. The liquid 14
governmental purposes without the payment of any may be an alkali metal, such as sodium, at a high tern-
royalties thereon or therefor. perature. Loss of the liquid 14 from the container 12
is prevented by a seal 16 constructed in accordance
BACKGROUND 15
 wjth the present invention.
This invention is concerned with sealing a rotating Tne seal 16 incorporates a rotatable seat 18 in the
shaft with a minimum amount of wear. The invention form of a shoulder on the shaft 10. The seal 16 further
is particularly directed to a low leakage shaft seal which includes a nosepiece 20 in the form of a ring member
can be used with many types of liquids, such as water, through which the shaft 10 extends. The nosepiece 20
sodium and oil 20 's mounted on a sleeve 22 which is secured to one end
Helic'al groove viscoseals and face contact seals have of a bellows 24' The °PP°site end of the bellows 24 is
been used with rotating shafts. Leakage has been en- attached to a flange 25 on a tubular housing 26 that is
countered with both types of seals. When a shaft having secured to the container 12. The bellows 24 prevents
a viscoseal stops rotating the seal ceases to function. . the rotation of the sleeve 22 while biasing the nose-
Leakage results from a lack of positive pumping action 25 Piece 20 towards the seat 18' The bellows 24 Provides
in a radial contact face seal. a mechanical spring force and functions as a secondary
Other problems encountered in sealing rotating seal to accomodate axial motion of the sleeve 22.
shafts in modern devices are the result of high liquid The "osepiece 20 has a radially extending surface 28
temperatures, limited weight requirements, and ex- ,0 and the seat 18 has a mating surface 30 which extends
tremely low leakage rate allowances. Many such de- 3° '"wardly from its periphery. The surfaces 28 and 30 are
. .. . ,
 f .. ..... , . maintained in sealing engagement by the biasing actionvices require a high degree of reliability over long pen-
 f , . „ .
6
*
6
 . . . . ..j , „ j j .• of the bellows spring force and by hydraulic pressureods of unattended operation. *: . e . * ' . _._r . _,
when the shaft 10 is stationary as shown in FIG. 1. The
SUMMARY dam formed by the sealing engagement of the surfaces
_, . , ,. , , , , . 35 28 and 30 prevents leakage of the liquid 14, and theseThe aforementioned problems have been solved by , v - ,. . ., „ n, , .
... . ... . , surfaces are preferably optically flat for best results.
using- a rotating seal seat ,n conjunction with a spiral
 A " *g 32 arc'chemicaU etched into
groove pattern arranged such that movement of the ^ ^
 18/TheB es 32 have a iral ^figuration
seal seat causes the grooves to produce a pumping ac-
 as shown .„ F,G 2 and afe arated „ ,ands 34 that
tion against the sealed fluid pressure Fluid is pumped 40
 are ,anar with the seali surface 30. „ • of ex.
back as fast as it leaks out. The spiral groove geometry
 amp,e spira, grooves 32 havjng a depth of Q 00,5 jnch
pattern provides a hydrodynamic lifting force which
 an an ave wjdth of QQ5 inch se ated by 0 021
produces a positive separation of radial sealing surfaces
 inch wide ,ands 34 wefe used jn the sea,s hsted jn Tab)e
when the shaft rotates. Engagement of these surfaces j
prevents leakage when the shaft is stationary, and sepa- 45 'Rotation of the shaft 10 in the direction of the arrow
ration of these surfaces when the shaft is rotating re-
 shown in FIG 2 produces a pumping action by the spi-
duces wear.
 raj grooves 32. This pumping is accompanied by a hy-
OBJECTS ' draulic lifting force at the lands 34 which moves the
surfaces 28 and 30 out of engagement thereby forming
It is, therefor, an object of the present invention to 50
 g gap shown jn F,G 3 This hydrauhc lifting force
provide a low leakage seal having a long operating life. maintains the gap between the surfaces 28 and 30 while
Another object of the invention is to provide positive
 tne pumping prevents leakage of the liquid 14. A liq-
contact sealing at static conditions when there is no ro-
 uid-gas interface 36 shown in FIG. 3 is formed between
tation or movement.
 tne seat |g and tne nosepiece 20.
A further object of the invention is to provide a seal 55 \t may be desirable to have the liquid located outside
having positive separation of the sealing surfaces in the the bellows 24. In this embodiment the position of the
operating mode.
 darn and the spiral grooves is reversed from that shown
These and other objects and advantages of the inven- jn FIG. 1. More particularly, the dam formed by the en-
tion will be apparent from the specification that follows gagement of the surfaces 28 and 30 is located inward
and from the drawing wherein like numerals are used from the spiral grooves 32. The prevention of leakage
throughout to identify like parts. is further aided by centrifugal force. In both the em-
_.„
 A „„,.,.-,c bodiments the spiral grooves are on the high pressureLIKAWIINLlo . , - , . « . .
side of the dam for best results.
FIG. 1 is an axial quarter section of a seal constructed It may also be desirable to form the spiral grooves in
in accordance with the present invention showing the the axially movable nosepiece instead of in the rotat-
relative position of the various parts when the shaft is able seat. In such an embodiment the grooves would
stationary; have a configuration that would pump toward the liq-
3,767,212
uid in the container. It is further contemplated that
grooves may be used simultaneously on both the seat
and the nosepiece.
Seals constructed in accordance with the invention
were used to seal a rotating shaft that extended into a
container of liquid sodium. The enclosure was pressur-
ized slightly above the ambient pressure with argon to
insure an inert environment around the containment
vessel. Flatness of the seal seat and-hosepiece was held
with one light band.
TABLE I
Run
Nosepiece material
Seal seat material
Location of spiral
groove
Sodium temperature °F
Sodium temperature °C
Sliding velocity ft/sec
Sliding velocity m/sec
Operating time, hr.
Surface condition after
run
I
Copper
Titanium Carbide
Nosepiece
375°
. 190°.
30
9.1
4.0
2
Copper
Molybdenum
Seal Seat
425 . 500
L.._2JJ__ 260.
48 64
15 20
7.0 2.0
Good
15
20
Excellent
Table 1 lists the leakage results and operating condi-
tions for several seals constructed in accordance with
the invention. The first seal had a copper nosepiece
with spiral grooves and a seal seat of titanium carbide.
This seal operated in liquid sodium for four hours at 20
pounds per square inch gage (14 N/cm2 gage) with
leakage less than the estimated detection limit of 0.02
cubic inch per hour (0.30 cm3/hr). Inspection of the
sealing services revealed several local wear areas on the
copper nosepiece, but the major portion of the surface
showed no evidence of rubbing contact.
Another seal used in Run 2 had a plain copper nose-
piece and a molybdenum spiral-groove seal seat. This
combination was operated for nine hours at various
speeds and at a sodium pressure of 20 pounds per
square inch gage (14 N/cm2 gage) with negligible leak-
age. Visual observation of the seal below 64 feet per
second (20 m/sec.) indicated leakage of intermittent
minute drops of liquid sodium which oxidized into
small pepper-size flakes. This visual observation re-
quired the opening of the enclosure, and some oxygen
was present around the seal area during inspection.
Above 64 feet per second (20 m/sec.) these drops
could not be observed. Sealing surfaces were in excel-
lent condition after nine hours of operation which indi-
cated that rubbing contact had occurred over most of
the surface. This rubbing contact probably occurred at
start up. Before start up, this seal showed no leakage
which indicated good contact and flatness at the sealing
surfaces. At shut down, the seal showed a slight leakage
of 0.02 cubic inches per hour (0.3 cnvVhr.) at zero ro-
tation which indicated some change in the surface flat-
ness had occurred.'
Spiral grooves were also incorporated into carbide
seal seats which were mated to carbide nosepieces in
another test. The leakage results were similar to those
shown in Table 1, and sliding surfaces were in excellent
condition after several hours of operation at 500°F
5 ( 260°G ) in liquid sodium.
While several embodiments of the invention have
been disclosed and described it will be appreciated that
various structural modifications may be made without
departing from the spirit of the invention or the scope
10 of the subjoined claims.
What is claimed is:
1. Apparatus for forming a seal about a rotatable
shaft extending into a container of liquid sodium com-
prising
a pair of juxtaposed members extending about said
shaft adjacent said liquid, one of said members
comprising a seat mounted on said shaft for rota-
tion therewith, said seat being of a material se-
lected from the group consisting of titanium car-
bide and molybdenum, a copper tubular member
mounted for reciprocable movement along said
shaft,
mating surfaces on said members, one edge of each
of said surfaces being in contact with said liquid so-
dium and the opposite edge being exposed to ambi-
ent pressure,
biasing means for moving said tubular member to-
ward said seat thereby moving said surfaces into
sealing engagement when said shaft is stationary,
and
spiral grooves on at least one of said mating surfaces
immediately adjacent said liquid, said spiral
grooves being separated by lands substantially co-
planar with said mating surface whereby rotation of
the said shaft pumps a portion of said adjacent con-
tained liquid sodium between said lands to gener-
ate a hydraulic lifting force thereby separating said
members in opposition to said biasing means while
inhibiting leakage.
2. Apparatus for forming a fluid seal about a rotat-
able shaft as claimed in claim 1 wherein the mating sur-
faces are substantially parallel and normal to the axis
of rotation of said shaft.
3. Apparatus for forming a fluid seal about a rotat-
able shaft as claimed in claim 1 wherein the grooves are
formed on the shoulder on said shaft adjacent said con-
tained liquid. .
4. Apparatus for forming a fluid seal about a rotat-
able shaft as claimed in claim 1 wherein the grooves are
formed on the ring adjacent said contained liquid.
5. Apparatus for forming a fluid seal about a rotat-
able shaft as claimed in claim 1- wherein the biasing
means comprises a bellows operably connected to said
55 rin«'
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30
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40
45
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60
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Spiral groove seal

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