The film stiffness of a face seal is improved without increasing the sealing and dam area by using an apparatus which includes a primary seal ring in the form of a nose piece. A spring forces a sealing surface on the seal ring into sealing contact with a seat to form a face seal. A circumferential clearance seal is formed in series with this face seal by a lip on the piece. The width of the surface of the lip is substantially the same as the width of the sealing surface on the face seal and the clearance between the surface on the lip and the shaft is substantially the same as the spacing between the face sealing surfaces on the face seal when the shaft is rotating. The circumferential clearance seal restricts the flow of fluid from a main cavity to an intermediate cavity with a resulting pressure drop. The hydrostatic opening face is strongly dependent on the face seal clearance, and the desired axial stiffness is achieved

Etsion, I.

Lipshitz, A.

English

NASA Technical Reports Server

United States Patent [I91 11 4,291,887 
Etsion et al. 1451 Sep. 29, 1981 
1541 
[76] Inventors: Robert A. Frosch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Izhak Etsion, Haifa, 
Israel; Abraham Lipshitz, University 
Heights, Ohio 
MODIFIED FACE SEAL FOR POSITIVE 
FILM STIFFNESS 
[21] Appl. No.: 92,145 
[22] Filed: Nov. 7, 1979 
[51] Int. Cl.3 ......................... F16J 15/34; F16J 15/40 
277/93 R 
[58] Field of Search ....................... 277/40, 41, 65, 59, 
277/84, 85, 93 R, 93 SD, 81 R, 27 
i-561 References Cited 
[52] U.S. C1. ........................................ 277/27; 277/40; 
U.S. PATENT DOCUMENTS 
2,444,714 7/1948 Voytech ... ........ 277/40 
3,462,159 8/1969 Baumann et al. ..................... 277/27 
3,536,333 10/1970 Gits et al. ......................... 277/40 X 
3,749,412 7/1973 Lingley ............................. 277/81 R 
4,026,564 5/1977 Metcalfe ............................. 277/96.1 
FOREIGN PATENT DOCUMENTS 
2144172 3/1973 Fed. Rep. of Germany .... 277/93 R 
462187 3/1937 United Kingdom ............. 277/81 R 
891419 3/1962 United Kingdom .................. 277/27 
Primary Examiner-Robert S .  Ward, Jr. 
Attorney, Agent, or Firm-N. T. Musial; J. R. Manning; 
Gene E. Shook 
1571 ABSTRACT 
The object of the invention is to improve the film stiff- 
ness of a face seal without increasing the sealing and 
dam area. 
The improved sealing apparatus (16) has a primary seal 
ring (20) in the form of a nose piece. A spring (24) forces 
a sealing surface (28) on the seal ring into sealing 
contact with a seat (18) to form a face seal. A circumfer- 
ential clearance seal is formed in series with this face 
seal by a lip (34) on the nose piece. The width of the 
surface (36) of the lip is substantially the same as the 
width of the sealing surface (28) on the face seal. Also 
the clearance between the surface (36) on the lip and the 
shaft (10) is substantially the same as the spacing be- 
tween the face sealing surfaces (28 and 30) on the face 
seal when the shaft is rotating. 
The circumferential clearance seal restricts the flow of 
fluid from a main cavity (14) to an intermediate cavity 
(32) with a resulting pressure drop. The hydrostatic 
opening face is strongly dependent on the face seal 
clearance, and the desired axial stiffness is achieved. 
4 Claims, 1 Drawing Figure 
16 
28 1 2" 
https://ntrs.nasa.gov/search.jsp?R=19820004569 2020-03-21T15:36:53+00:00Z
U.S. Patent Sep. 29, 1981 4,291,887 
Y' 
4,29 1,887 
1 2 
showing the relative position of the various parts when 
the shaft is rotating. 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
Referring now to the drawing, a shaft 10 extends into Origin of the Invention a container 12 of liquid in a main cavity 14. The shaft 10 
The invention described herein was made in the per- is rotated about its normal axis Y-y’ and may be used to 
formance of work under a NASA contract and is sub- transmit torque from a motor to a pump. The liquid in 
ject to the provisions of Section 305 of the National 10 the cavity 14 is at a pressure that is higher than the 
Aeronautics and Space Act of 1958, Public Law 85-568 pressure outside the container 12. Loss of liquid 14 from 
(72 Statute 435; 42 U.S.C. 2457). the container 12 is prevented by a seal 16 constructed in 
accordance with the present invention. 
Technical Field The seal 16 incorporates a rotatable seat 18 in the 
The present invention relates generally to face type 15 form of a shoulder on the shaft 10. The seal 16 further 
seals, and more particularly to improving film stiffness includes a primary seal ring 20 in the form of a nose 
without increasing the sealing and dam area. The pri- piece through which the shaft 10 extends. The nose 
mary objective of face type seals is to reduce the leak- piece is flexibly mounted on the container 12. 
age and friction losses to a minimum. However, these A secondary seal 22, such as a piston ring or elasto- 
two requirements contradict each other. 20 meric “0’ ring, is interposed between the ring 20 and 
It is extremely important to maintain a small clear- the container 12. The seal 22 prevents leakage of the 
ance as close as possible to the design value or a seal liquid in the main cavity 14 between the primary seal 
failure may occur. Hence, an axial film stiffness is vital ring 20 and the container 12. 
to the proper seal operation. One way of introducing A spring 24 biases the ring 20 toward the rotatable 
axial stiffness to a face seal is by angular misalignment, 25 seat 18. Rotation of the ring 20 is prevented by conven- 
but this also increases leakage and may initiate dynamic tional antirotation means. 
instability. Thus, parallel face operation is another de- The ring 20 has a circular insert 26 of a wear resistant 
sired condition in a seal. Unfortunately, face seals of the material, such as carbon, with a radially extending sur- 
type used in the prior art have no axial film stiffness face 28. The seat 18 has a mating surface 30. The sur- 
when they operate with the parallel faces unless such 30 faces 28 and 30 are maintained in sealing engagement by 
stiffness is introduced by means such as grooves or steps the biasing action of the spring 24 and by fluid pressure 
which require large face areas that increase friction. when the shaft 10 is stationary. The dam formed by the 
sealing engagement of the surfaces 28 and 30 prevents 
Background Art leakage of the liquid 14 from an intermediate cavity 32 
contact between the seal faces such as 35 between the ring 20 and the seat 18 adjacent to the shaft 
shown in U.S. Pat. No. 2,250,348 eliminates leakage but lo* The engagement Of the surfaces 28 and 30 form a 
produces high friction losses. A seal of the type shown face seal, and these surfaces are Preferably optically flat. 
in u.s. pat. No. 4,026,564 which relied on large clear- In accordance with the present invention a lip formed by a tubular insert 34 in the ring Ut extends circumferen- 
40 tially around the shaft 10. The lip has a surface 36 ance to reduce the friction produces an increase in the 
spaced from the shaft 10 to form a circumferential clear- leakage. Non-contacting face seals of the type shown in 
ance seal. Thus, the seal 16 comprises a face seal having 
between the mating faces is just sufficient to avoid any it. 
a secondary seal. diate cavity 32 is lower than that in the main cavity 14. 
procedures have been suggested to produce The hydrostatic opening force becomes strongly depen- 
axial stiffness in radial face seal. These include various dent on the face seal clearance between the surfaces 28 
in pat* No. 398049424* A major disadvantage Of 50 circumferential clearance seal acts in the same manner 
such methods is the need for large face to accom- as an external restriction in a hydrostatic thrust bearing. 
modate the various steps Or grooves. Large areas in- The effect of the film stiffness is similar to an orifice 
crease frictional losses. compensated seal, but the added friction torque can be 
reduced substantially. DISCLoSURE OF THE INVENTIoN It is important that the width of the surface 36 on the 
Seal Performance in terms of leakage and friction insert 34 measured axially along the shaft 10 is substan- 
losses is optimized with an improved Sealing apparatus tially the Same as the width of the surface 28 on the 
comprising a circumferential clearance Seal combined in insert 26 measured radially outward from the shaft 10. 
series with a face seal. With such an arrangement, the Also, the spacing of the circumferential clearance seal 
hydrostatic opening force is dependent on the face seal 60 between the surface 36 and the shaft 10 is substantially 
clearance and axial stiffness is achieved. the same as the clearance between the surfaces 28 and 
BRIEF DESCRIPTION OF THE DRAWING. 30 of the face seal when the shaft 10 is rotating for optimum performance. 
The advantages and novel features of the invention While the preferred embodiment of the invention is 
will be more fully apparent from the following detailed 65 disclosed and described it will be appreciated that vari- 
description when read in connection with the accompa- ous modifications may be made to the disclosed seal 
nying drawing which is an axial quarter section of a seal structure without departing from the spirit of the inven- 
constructed in accordance with the present invention tion or the scope of the subjoined claims. 
MODIFIED FACE SEAL FOR POSITIVE FILM 
STIFFNESS 
DESCRIPTION 5 
A 
Pat* No* 3y751’045 to this 
by a non-contacting face seal in which the a circumferential clearance seal combined in series with 
rubbing contact at the expense Of Some leakage through 45 By this arrangement the fluid pressure in the interme- 
stepped and grooved configurations Of the type shown and 30, and the desired axial stiffness is achieved. The 
55 
3 
4,29 1,8 87 
4 
We claim: 
1. In apparatus for sealing a rotatable shaft extending 
ber mounted on said shaft for rotation therewith and an 
annular seal ring member extending around said shaft in 
spaced relationship thereto for reciprocating movement 
toward and away from said seat along the axis of rota- 
tion of said shaft with means for biasing said ring mem- 
ber into engagement with said seat wherein said ring 10 
member has a substantially circular face directed 
toward said seat and a substantially cylindrical face 
spaced from said shaft, the improvement comprising 
from a flow of said fluid between said shaft and said 
cylindrical face to said seat, and 
ber in said cylindrical face and having a curved 
surface extending therefrom toward said shaft to 
form a circumferential clearance seal in series with 
said face seal to restrict said flow of said fluid to 
said seat thereby controlling said hydrostatic open- 
ing force, the radial width of said planar surface on 
said circular member being substantially equal to 
the axial width of said curved surface on said tubu- 
lar member to provide a predetermined axial stiff- 
ness of said face seal so that the spacing between 
said planar surface and said seat when said shaft is 
rotating is substantially the same as the spacing 
between said curved surface and said shaft. 
2. In apparatus as claimed in claim 1 wherein the 
3. In apparatus as claimed in claim 1 wherein the 
4. apparatus as claimed in claim 3 wherein the 
into a container of fluid of the type having a seat mem- a member mounted On said ring mem- 
a circular member.rigidly mounted on said ring mem- 15 
ber in said circular face and having a planar surface 
extending therefrom toward said seat for sealing 
engagement therewith by action of said biassing 
ing a face seal, said planar surface being moved out 
of engagement with said seat by a hydrostatic 
opening force when said shaft is rotating resulting 
biasing comprises a 'prink5 
when said shaft is stationary thereby form- 20 circular member is of a wear-resistant material. 
wear-resistant circular member is carbon. * * * * *  
25 
30 
35 
40 
45 
50 
55 
60 
65 


Modified face seal for positive film stiffness

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