Seal assembly
A seal for acceptance in an annular gland in a piston comprises an annular primary sealing element, an annular secondary sealing element disposed radially inwardly of the primary sealing element, and a pair of axially spaced back up rings disposed in axially spaced relation on opposite sides of the primary sealing element and having radially inner portions, respectively, engaged with the primary sealing element so as to lock the backup rings in the gland of the piston.
Latest SKF USA Inc. Patents:
The piston of a hydraulic actuator is generally provided with a seal assembly to prevent leakage of hydraulic fluid past the piston. Such seal assemblies often comprise a relatively hard primary or dynamic sealing ring that is backed up by a relatively softer secondary or static sealing ring. Moreover, such seal assemblies are often provided with back up rings made of relatively hard material, for example, polyamide.
However, a problem exists in that known back up rings are often displaced incident to assembly of the piston into the cylinder bore. The back up rings may be forced out of the piston gland upon assembly with a cylinder or may fall out of the piston gland before the piston is telescoped into the cylinder. Moreover, known back up rings are susceptible of improper installation in the piston gland.
The aforesaid problems are solved, in accordance with a preferred constructed embodiment of the present invention, by providing a mechanical interlock between either the primary or secondary piston sealing ring and the back up rings. Stated in another manner, a locking arrangement between the back up rings and seal elements in the form of a mechanical interface between the back up rings and one or more sealing elements of the piston ring assembly precludes inadvertent disassembly as well as improper installation of the back up rings. The locking feature can be arranged to provide similar benefits in bi-directional and uni-directional rod seal assemblies.
As seen in
In accordance with a preferred embodiment of the instant invention, and as seen in
The secondary sealing element 34 is of T-shaped cross section defined by a stem portion 40 and axially oppositely extending flange portions 42 and 44. The primary sealing element 32 has an axial length that is greater than the axial length of the stem portion 40 of the secondary sealing element 34 thereby to define a pair of locking shoulders 46 and 48 which cooperate with shoulders 50 and 52 on the back up rings 36 and 38, respectively, to lock the back up rings 36 and 38 in the gland 24 of the piston 20. For example, the back up rings 36 and 38 may have annular cylindrical shoulders 50 and 52 engagable with complementary cylindrical shoulders 46 and 48 on the primary sealing element 32. Reverse assembly of the back up rings 36 and 38 is precluded by the relatively larger axial thickness of the radially inner portion thereof which will not pass the primary sealing element 32 if incorrect assembly is attempted. Moreover, the square corners 54 and 56 on the back up rings 36 and 38 would interfere with arcuate sections 58 and 59 on the static secondary seal 34 if incorrect assembly is attempted.
In accordance with another embodiment of the instant invention, and as seen in
The secondary sealing element 64 is of T-shaped cross section defined by a stem portion 70 and axially oppositely extending flange portions 72 and 74. The primary sealing element 62 has an axial length on the radially outer surface thereof that is greater then the axial length of the radially inner surface thereof thereby to define a pair of angular locking surfaces 76 and 78 which cooperate with complimentary angular surfaces 80 and 82 on the back up rings 66 and 68, respectively, to lock the back up rings 66 and 68 in gland 24 of the piston 20.
In accordance with another embodiment of the instant invention, and as seen in
In accordance with the embodiment of the instant invention seen in
In the embodiment of the instant invention seen in
The embodiment of the instant invention seen in
As seen in
As seen in
As seen in
In accordance with a three piece embodiment of the instant invention, and as seen in
In accordance with another three piece embodiment of the instant invention, and as see in
Claims
1. A circular piston seal for acceptance in an annular gland in a piston comprising:
- an annular primary sealing element of a first durometer;
- a secondary sealing element of a second durometer relatively lower than said first durometer disposed radially inwardly of said primary sealing element and juxtaposed against a radially inner wall of the gland in the piston; and
- a pair of axially spaced back up rings disposed on opposite sides of said primary sealing element respectively, said back up rings having radially inner portions, respectively, spaced axially from one another a distance less than a maximum axial dimension of said primary sealing element whereby said backup rings are positively locked in the gland of said piston by said primary sealing element.
2. The piston seal of claim 1 wherein said back up rings have convex accurate surfaces intersecting a radially inner face, thereof, respectively, for engagement with complimentary axially spaced concave surfaces, respectively, on said secondary sealing element.
3. The piston seal of claim 1 wherein said back up rings have annular cylindrical shoulders engagable with complimentary cylindrical shoulders on said primary sealing element, respectively.
4. The piston seal of claim 1, wherein said secondary sealing element includes a radially extending stem portion and an axially extending base portion.
5. The piston seal of claim 4, wherein said secondary sealing element exhibits a cross section which is substantially T-shaped.
6. The piston seal of claim 4, wherein said primary sealing element exhibits an axial length which is greater than an axial length of said radially extending stem portion of said secondary sealing element.
7. The piston seal of claim 4, wherein said radially extending stem portion of said secondary seal includes a reduced axial length portion configured to cooperatively mate with a protrusion on each of said backup rings.
8. The piston seal of claim 7, wherein said reduced axial length portion is located adjacent said axially extending base portion.
9. The piston seal of claim 1, wherein the primary sealing element includes a reduced axial length portion configured to cooperatively mate with a protrusion on each of said backup rings.
10. The piston seal of claim 1, wherein each of the backup rings exhibit an asymmetric cross section about an axis axially extending therethrough.
11. A seal assembly configured for acceptance in an annular gland comprising:
- a first annular seal member configured to be in contact with a radially inner wall of the annular gland;
- a second seal member disposed radially outwardly of the first annular seal member, wherein the first annular seal member is formed of a material of a first durometer and the second seal member is formed of a material comprising a second durometer greater than the first durometer; and
- at least one back up ring at least partially disposed radially inwardly of the second seal member and sized and configured to be radially spaced from the radially inner wall of the annular gland by an axially extending flange portion of the first annular seal member, the at least one back up ring having an axially extending protrusion, wherein the axially extending protrusion of the at least one back up ring cooperatively mates with a recess in the first annular seal member located proximate to the flange portion to radially lock the at least one back up ring substantially within the gland.
12. A seal assembly configured for acceptance in an annular gland comprising:
- an annular seal member including an axially extending base portion configured to be in contact with a radially inner wall of the annular gland and a radially extending stem portion, the radially extending stem portion including a first portion exhibiting a first axial length and a second portion exhibiting a second axial length smaller than the first axial length, the second portion being located radially inwardly from the first portion, and the axial length of the first portion being smaller that an axial length of the axially extending base portion;
- two backup rings, each backup ring of the two backup rings including an axially extending portion configured to cooperatively mate with the second portion of the stem portion of the annular seal member to radially lock each back up ring substantially within the gland, wherein each backup ring exhibits an asymmetric cross section about an axis axially extending therethrough.
13. The seal assembly of claim 12, wherein the second portion of the stem portion of the annular seal member includes a first concave surface and a second axially spaced concave surface.
14. The seal assembly of claim 13, wherein the axially extending portion of each of the two backup rings includes a convex surface sized and configured to cooperatively mate with the first and second concave surfaces of the stem portion of the annular seal member.
15. The seal assembly of claim 14, wherein the annular seal member exhibits a cross section which is substantially T-shaped.
1347351 | July 1920 | Murray et al. |
2349170 | May 1944 | Jackman |
2765204 | October 1956 | Josephson |
3188099 | June 1965 | Johnson et al. |
3215441 | November 1965 | Horvereid |
3394941 | July 1968 | Traub |
3469853 | September 1969 | Gullick |
3525530 | August 1970 | Bauer et al. |
3540745 | November 1970 | Flock |
3582094 | June 1971 | Whittaker |
3630532 | December 1971 | Traub et al. |
3771801 | November 1973 | Burke |
4268045 | May 19, 1981 | Traub |
4346647 | August 31, 1982 | Weaver |
4468041 | August 28, 1984 | Yoshimura et al. |
4576386 | March 18, 1986 | Benson et al. |
5467689 | November 21, 1995 | Carlin et al. |
5524905 | June 11, 1996 | Thoman et al. |
5879010 | March 9, 1999 | Nilkanth et al. |
6648337 | November 18, 2003 | Baehl et al. |
Type: Grant
Filed: Apr 10, 2003
Date of Patent: Aug 30, 2011
Assignee: SKF USA Inc. (Kulpsville, PA)
Inventor: Richard D. Zitting (New Harmony, UT)
Primary Examiner: Michael Safavi
Attorney: TraskBritt
Application Number: 10/411,620
International Classification: F16J 9/12 (20060101); F16J 9/20 (20060101);