Seal assembly

Abstract

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.

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.