Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove produces a pumping action toward the fluid when the shaft rotates. This prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear. Provision is made for placing these spiral grooves in communication with the fluid to accelerate the generation of the hydraulic lifting force

Ludwig, L. P.

Strom, T. N.

English

NASA Technical Reports Server

9-6-
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
REPLY TO
ATTN OF: GF
TOt
FROM?
' JAN 2 1 1974
RSI/Scientific & Technical Information Diviaioi
Attentions Miss Winnie M. Morgan
GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT » Announcement of NASA-Owned U.S. Patents in STAR
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U.S. Patent No. : J, / U /
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Source (if applicable)
NASA patent Case No.
s
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NOTE - If this patent covers an invention made by a corpor
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employee of a NASA Contractor, the following is applicable
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Yes J_ / No / t/\/
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Space Act, the name of the Administrator of NASA appears o;
the first page of the patent; however, the name of the acti
jnyentor (author) appears at the heading of column No. 1 ot
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an invention of ..."
Elizabeth A. Carter
Enclosure
Copy of patent cited above
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https://ntrs.nasa.gov/search.jsp?R=19740007012 2020-03-17T14:35:28+00:00Z
United States Patent
Ludwig et al.
[in 3,782,737
[45] Jan. 1, 1974
[54] SPIRAL GROOVE SEAL
[75] Inventors: Lawrence P. Ludwig, Fairview Park;
Thomas N. Strom, North Olmsted,
both of 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: Jan. 24, 1972
[21] Appl. No.: 220,251
Related U.S. Application Data
[60] Division of Ser. No. 54,540, July 13, 1970, Pat. No.
3,675,935, which is a continuation-in-part of Ser. No.
723,465, April 23, 1968, abandoned.
152) U.S. Cl 277/27, 277/91
[51 ] Int. Cl F16j 15/34
[58] Field of Search 277/3, 27, 96, 74,
277/88, 134, 133, 25,91
[56] References Cited
UNITED STATES PATENTS
3,109.658 11/1963 Barrett et al 277/96 X
3,499,653 3/1970
3,527,465 9/1970
2,354,478 7/1944
3,675,935 7/1972
Gardner ............................ 277/96 X
Guinard ............................ 277/96 X
Reinhardt et al ................. 277/88 X
Ludwig et al ......................... 277/25
FOREIGN PATENTS OR APPLICATIONS
1,009,940 11/1965 Great Britain ........................ 277/74
Primary Examiner—Samuel B. Rothberg
Attorney—N. T. Musial et al.
[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. Provision is made for placing these
spiral grooves in communication with the fluid to ac-
celerate the generation of the hydraulic lifting force.
7 Claims, 4 Drawing Figures
PATENTED JAN 1 1974 3.782,737
SHEET 1 Of 2
FIG. I
FIG. 2
FATENTEDJAN 1 1974 3,782,737
SHEET
----^==-—^8--i 46 =—^£^=--£
FIG . 3
52
FIG. 4
3,782,737
1 2
SPIRAL GROOVE SEAL FIG. 2 is an axial quarter section showing an alter-
DCI ATE™ ADDI ir-ATir>M nate embodiment of the seal;KhLAThD APFL1CA I ION pjQ
 3 js a partiaj ^ ^ ,^,3, view showing still another
This application is a division of copending applica- embodiment of the invention; and
tion Ser. No. 54,540, filed July 13, 1970, and now U.S. 5 FIG. 4 is an elevation view of the rotating seat taken
Pat. No. 3,675,935 which, in turn, is a continuation-in- along the line 4 — 4 in FIG. 3.
part of application Ser. No. 723,465, filed Apr. 23, r>cc/-Dn>Tir»M
1968 and now abandoned. DESCRIPTION
STATEMENT OF GOVERNMENT OWNERSHIP ,0
The invention described herein was made by employ- rotatable about its normal axis Y-Y' and may be used
ees of the United States Government and may be man- to transmit torque from motor to a pump. The liquid 14
ufactured and used by or for the Government for gov- may be an alkali metal, such as sodium, at a high tem-
ernmental purposes without the payment of any royal- perature. Loss of the liquid 14 from the container 12
ties thereon or therefor. IS is prevented by a seal 16 constructed in accordance
BACKGROUND OP THE ,NVENT,ON .
 rolM,We „_ „ in „.
This invention is concerned with sealing a rotating form of a shoulder on the shaft 10. The seal 16 further
shaft with a minimum amount of wear. The invention includes a nosepiece 20 in the form of a ring member
is particularly directed to a low leakage shaft seal which 20 through which the shaft 10 extends. The nosepiece 20
can be used with many types of liquids, such as water, is mounted on a sleeve 22 which is secured to one end .
sodium, and oil. of a bellows 24. The opposite end of the bellows 24 is
Helical groove viscoseals and face contact seals have attached to a flange 25 on a tubular housing 26 that is
been used with rotating shafts. Leakage has been en- secured to the container 12. The liquid 14 is outside the
countered with both types of seals. When a shaft having 25 bellows 24 and a gas, such as air, is inside the bellows
a viscoseal stops rotating the seal ceases to function. around the shaft 10. The bellows 24 prevents the rota-
Leakage results from a lack of positive pumping action tion of the sleeve 22 while biasing the nosepiece 20
in a radial contact face seal. towards the seat 18. The bellows 24 provides a me-
Other problems encountered in sealing rotating chanical spring force and functions as a secondary seal
shafts in modem devices are the result of high liquid 30 to accommodate axial motion of the sleeve 22.
temperatures, limited weight requirements, and ex- The nosepiece 20 has a radially extending surface 28
tremely low leakage rate allowances. Many such de- and the seat 18 has a mating surface 30. The surfaces
vices require a high degree of reliability over long peri- 28 and 30 are maintained in sealing engagement by the
ods of unattended operation. biasing action of the bellows spring force and by hy-
SIIMMARY OF THF INVFNTION ^ drauHc Pressure when the shaft 10 is stationary. TheSUMMARY OF THE INVENTION
 dam formed by ^ sealing engagernent of the surfaces
The aforementioned problems have been solved by 28 and 30 prevents leakage of the liquid 14, and these
using a rotating seal seat having a spiral groove pattern surfaces are preferably optically flat for best results.
arranged such that movement of the seal seat causes A plurality' of grooves 32 are chemically etched into
the grooves to produce a pumping action against the 40 the seat 18 outward from the dam formed by the en-
sealed fluid pressure. Fluid is pumped back as fast as it gagement of the surfaces 28 and 30. The grooves 32
leaks out. The spiral groove geometry pattern provides have a spiral configuration similar to the grooves shown
a hydrodynamic lifting force which produces a positive in FIG. 4 and are separated by lands 34 that are copla-
separation of radial sealing surfaces when the shaft ro- nar with the sealing surface 30.
tales. Engagement of these surfaces prevents leakage Rotation of the shaft 10 produces a pumping action
when the shaft is stationary, and separation of these by the spiral grooves 32. This pumping is accompanied
surfaces when the shaft is rotating reduces wear. by a hydraulic lifting force at the lands 34 which' moves
nHiFrrs OF THF INVFNTION the surfaces 28 and 30 out of engagement therebyOBJECTS OF THE INVENTION forming a gap shown in FIG. 1. This hydraulic lifting
It is, therefore, an object of the present invention to force maintains the gap between the surfaces 28 and 30
provide a low leakage seal having a long operating life. while the pumping prvents leakage of the liquid 14. A
Another object of the invention is to provide positive liquid-gas interface 36 shown in FIG. 1 is formed be-
contact sealing at static conditions when there is no ro- tween the seat 18 and the nosepiece 20. The prevention
tation or movement. of leakage is further aided by centrifugal force.
A further object of the invention is to provide a seal It may also be desirable to form the spiral grooves in
having positve separation of the sealing surfaces in the the axially movable nosepiece instead of in the rotat-
operating mode. able seat. In such an embodiment the grooves would
These and other objects and advantages of the inven- have a configuration that would pump toward the liq-
tion will be apparent from the specification that follows ,. uid in the container. It is further contemplated that
and from the drawing wherein like numerals are used grooves may be used simultaneously on both the seat
throughout to identify like parts. and the nosepiece.
•M -run no A U/IM/-C Passages may be provided in the nosepiece or seat to
IN I Ht UKAWiNUi
 meter leakage now into the spirai grooves and extend
FIG. 1 is an axial quarter section of a seal constructed
 6J lubrication over a greater area of the lands. A liquid-
in accordance with the present invention showing the gas interface is formed in the grooves and a similar in-
relative position of the various parts when the shaft is terface is formed on the land. This serves to increase
rotating; the load carrying capacity of the seal.
3,782,737
In the embodiment shown in FIG. 2 these principles
have been utilized to provide a liquid lubricated seal for
minimizing gas leakage in a turbine or the like. The seal
is balanced so that the spring forces and pressure forces
function in the manner previously described. The nose-
piece is prevented from contacting the seal seat during
rotation by a thin film of liquid on the lands separating
the grooves. The thickness of the liquid film is con-
trolled by the pumping action of the grooves and by the
force balance on the nosepiece.
Referring now to FIG. 2 a sealing ring 40 such as a
metal "O" ring is interposed between the sleeve 22 and
the outer wall of a circular protrusion 42 on the flange
25. The ring 40 prevents leakage of the liquid 14. A
spring 44 biases the sleeve 22 toward the rotatable seat
18. It will be appreciated that the sealing ring 40 and
the spring 44 perform the same function as the bellows
24 shown in FIG. 1.
In the embodiment shown in FIG. 2 liquid is intro-
duced to the spiral grooves 32 through passages 46
which extend through the nosepiece 20. Each passage
46 places a mating groove 32 in communication with
the liquid 14 that is under pressure. When the shaft 10
is stationary the seal operates in the manner previously
described in connection with the embodiment shown in
FIG. 1. When the shaft 10 is rotated each groove 32
tends to pump liquid from its matin passage 46 at a
faster rate than it is supplied. In this manner the
grooves 32 are only partially filled and a liquid-
interface 48 is formed in each groove 32.
Relative motion at the sealing interface introduces a
drag flow which tends to force the liquid toward the
leading edge of each land 34. Some of this liquid es-
capes over the land 34 and provides a liquid film sepa-
ration between the seal seat 18 and the nosepiece 20.
Also a second liquid-gas interface 50 is formed over the
land 34.
The continuous flow of lubricating liquid from the
passage 46 through the sealing interface 50 serves to
cool the seal. Fluid shear in the film over the land 34
results in a discontinuous type of heat input to any one
fluid particle. Therefore, while a particular fluid parti-
cle is passing over a land area it is performing part of
the total lubricating function and experiences heat
input due to fluid shear.
In the next sequence of events the fluid particle
leaves the thin film region over the land 34 and enters
the next spiral groove 32. Here it can mix with the
cooler liquid and undergo a reduction in temperature
before passing over the next land. The number of times
a liquid particle passes over a land area before being
expelled from the sealing interface is a function of seal
design. It is contemplated this embodiment of the in-
vention can be used in clutches or clutch plates.
The embodiment shown in FIGS. 3 and 4 utilizes spi-
ral grooves 52 formed in the seat 18. The grooves 52
are separated by lands 54 as in the previous embodi-
ments. Liquid 14 is introduced to the spiral grooves 52
through passages 46 which extend through the nose-
piece 20 in the manner previously described in connec-
tion with the embodiment shown in FIG. 2.
A circular feed groove 56 formed in the bottom of
the grooves 52 passes through the lands 54. This circu-
lar feed groove 56 is in alignment with the passages 46.
The feed groove 56 insures equal pressure in the
grooves 52. A circular feed groove having a depth of
about 0.010 inch has been satisfactory.
10
1 5
20
25
30
45
An important feature of the invention is the provision
of a circular dam 58 about the rotating seat 18. When
the shaft 10 is stationary the seal operates in the same
manner as the previously described embodiments. The
pressure balance made up of the force of the spring 44
together with the pressure force exerted by the liquid
14 is such that the seal is closed when the shaft 10 is
stationary.
When the shaft 10 rotates a liquid-gas interface 60 is
formed within the inner portion of the spiral pattern.
The-pressure at the feed groove is approximately the
same as the pressure at the adjacent land. The spiral
configuration increases the pressure from that of the
liquid 14 to a maximum at the junction of the spiral and
the outer dam 58.
The pumping effort of the spiral pattern produces an
opening force to balance the seal closing force. The
height of the sealing gap is a function of the closing
force and the pressure generation capacity of the spiral
patterns. The film thickness is greater for a spiral-feed
groove seal shown in FIGS. 3 and 4 than that of the spi-
ral groove seal as shown in FIG. 1. With the spiral
groove seal, the lift or film thickness is due to hydrody-
namic forces over the land areas. With the spiral-feed
groove seal shown in FIGS. 3 and 4 the lift is caused by
hydrodynamic forces generated within the groove and
across the dam 58.
What is claimed is:
1. Apparatus for forming a seal about a rotatable
shaft extending into a container of liquid comprising
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 and the other of said members com-
prising a 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
and the opposite edge being exposed to ambient
pressure,
means for biasing said tubular member toward said
seat for moving said surfaces into sealing engage-
ment when said shaft is stationary,
spiral grooves in said seat at its mating surface, said
spiral groove being separated by lands substantially
coplanar with said mating surface whereby rotation
of said shaft pumps a portion of said adjacent con-
tained liquid between said lands to generate a hy-
draulic lifting force thereby separating said mem-
bers in opposition to said basing means while inhib-
iting leakage, and
passage means in one of said members for placing
said spiral grooves in communication with said
contained liquid to accelerate the generation of
said hydraulic lifting force.
2. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 1 wherein the contained liquid
is located outwardly of said grooves so that the pump-
ing of said liquid is aided by centrifugal force.
3. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 1 wherein the passage means
comprises - . . . _.
a plurality of passages extending through said tubular
member for directing liquid into said spiral
--.-grooves. .
.. 4.. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 3 including a feed groove in
3,782,737
communication with each of said passages, said feed
groove being cut in the bottom of said spiral grooves
and extending through said lands.
5. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 1 including a dam surrounding
the grooves to increase the hydrodynamic lifting force
when the shaft is rotated.
6. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 5 wherein the passage means
comprises a plurality of passages extending through
said tubular member for placing the grooves in commu-
nication with the liquid in the container.
7. Apparatus for forming a seal about a rotatable
shaft as claimed in claim 6 including a feed groove
aligned with said passages, said feed groove being cut
in the bottom of said spiral grooves and extending
through said lands.
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Spiral groove seal

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