A high pressure piston for use within a liner sleeve of a reciprocating pump comprises a dual-durometer elastomeric seal having first and second coaxial seal sections and, in certain embodiments, a circumferential bearing ring. Interactions of the seal components, including seal elastomers, result i
A high pressure piston for use within a liner sleeve of a reciprocating pump comprises a dual-durometer elastomeric seal having first and second coaxial seal sections and, in certain embodiments, a circumferential bearing ring. Interactions of the seal components, including seal elastomers, result in stress redistribution within the seal which maintains sealing preload, with corresponding improved extrusion resistance and seal durability. When a bearing ring is present, a pump's pressure stroke causes at least a portion of the bearing ring to elastically expand radially to narrow or close the extrusion gap, thus tending to block elastomer extrusion by establishing sliding contact between the bearing ring's external surface and the liner. On the pump's return stroke the slightly wider extrusion gap allows cooling water directed generally toward the proximal flange of the piston hub to better cleanse, as well as cool, the liner wall.
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1. A piston hub and seal assembly having a longitudinal axis, said piston hub and seal assembly comprising: a piston hub substantially symmetrical about said longitudinal axis, said piston hub having at least one circumferential seal retention area; andan elastomeric seal cast-in-place in at least o
1. A piston hub and seal assembly having a longitudinal axis, said piston hub and seal assembly comprising: a piston hub substantially symmetrical about said longitudinal axis, said piston hub having at least one circumferential seal retention area; andan elastomeric seal cast-in-place in at least one said circumferential seal retention area, each said elastomeric seal being substantially symmetrical about said longitudinal axis and comprising: a first seal section having a cylindrical external surface portion adjacent to a frusto-conical external surface portion, said first seal section comprising a first polyurethane; anda second seal section, at least a portion of said second seal section lying radially between one said circumferential seal retention area and at least a portion of said first seal section, said second seal section contacting said first seal section along a substantially non-planar intra-seal interface, and said second seal section comprising a second polyurethane having a lower modulus than said first polyurethane;wherein said first seal section frusto-conical external surface portion is angled outwardly about 3 degrees to about 7 degrees with respect to said adjacent first seal section cylindrical external surface portion; andwherein said intra-seal interface comprises a cylindrical portion substantially coaxial with said first seal section cylindrical external surface portion. 2. The piston hub and seal assembly of claim 1, wherein said second seal section second polyurethane is not bonded to said at least one circumferential seal retention area. 3. The piston hub and seal assembly of claim 1, wherein said second seal section second polyurethane is bonded to at least one said circumferential seal retention area. 4. The piston hub and seal assembly of claim 1, wherein said first seal section first polyurethane is bonded to said second seal section second polyurethane along said intra-seal interface. 5. The piston hub and seal assembly of claim 1, wherein said first seal section first polyurethane is not bonded to said second seal section second polyurethane along said intra-seal interface. 6. The piston hub and seal assembly of claim 1, wherein said first seal section comprises polyurethane of about 95 durometer Shore A hardness to about 60 durometer Shore D hardness. 7. The piston hub and seal assembly of claim 6, wherein said second seal section comprises polyurethane of about 75 to about 85 durometer Shore A hardness. 8. A piston within a cylinder, said piston comprising the piston hub and seal assembly of claim 7. 9. The piston hub and seal assembly of claim 1, wherein at least one void extends radially between a portion of said second seal section and said circumferential seal retention area. 10. The piston hub and seal assembly of claim 1, wherein no void extends radially between said second seal section and said circumferential seal retention area. 11. A piston within a cylinder, said piston comprising the piston hub and seal assembly of claim 1. 12. A piston hub and seal assembly having a longitudinal axis, said piston hub and seal assembly comprising: a piston hub substantially symmetrical about said longitudinal axis, said piston hub having at least one circumferential seal retention area; andan elastomeric seal cast-in-place in at least one said circumferential seal retention area, each said elastomeric seal being substantially symmetrical about said longitudinal axis and comprising: a first seal section having a cylindrical external surface portion adjacent to a frusto-conical external surface portion, said first seal section comprising a first polyurethane;a second seal section, at least a portion of said second seal section lying radially between one said circumferential seal retention area and at least a portion of said first seal section, said second seal section contacting said first seal section along a substantially non-planar intra-seal interface, and said second seal section comprising a second polyurethane having a lower modulus than said first polyurethane; anda circumferential bearing ring partially embedded coaxially in said first seal section, said circumferential bearing ring having a cylindrical external surface portion;wherein said first seal section frusto-conical external surface portion is angled outwardly about 3 degrees to about 7 degrees with respect to said adjacent first seal section cylindrical external surface portion; andwherein said intra-seal interface comprises a frusto-conical portion substantially coaxial with said first seal section cylindrical external surface portion. 13. The piston hub and seal assembly of claim 12, wherein said first seal section first polyurethane is not bonded with said second seal section second polyurethane. 14. The piston hub and seal assembly of claim 12, wherein said first seal section first polyurethane is bonded with said second seal section second polyurethane along said intra-seal interface. 15. The piston hub and seal assembly of claim 12, wherein said first seal section comprises polyurethane of about 95 durometer Shore A hardness to about 60 durometer Shore D hardness. 16. The piston hub and seal assembly of claim 15, wherein said second seal section comprises polyurethane of about 75 to about 85 durometer Shore A hardness. 17. A piston within a cylinder, said piston comprising the piston hub and seal assembly of claim 16. 18. A piston within a cylinder, said piston comprising the piston hub and seal assembly of claim 12. 19. The piston hub and seal assembly of claim 12, wherein said circumferential bearing ring comprises bronze. 20. A piston hub and seal assembly having a longitudinal axis, said piston hub and seal assembly comprising: a piston hub substantially symmetrical about said longitudinal axis, said piston hub having at least one circumferential seal retention area; andan elastomeric seal cast-in-place in at least one said circumferential seal retention area, each said seal being substantially symmetrical about said longitudinal axis and comprising: a first seal section having a cylindrical external surface portion adjacent to a frusto-conical external surface portion, said first seal section comprising a first polyurethane; anda second seal section, at least a portion of said second seal section lying radially between one said circumferential seal retention area and said first seal section, said second seal section contacting said first seal section along an intra-seal interface and comprising a second polyurethane having a lower modulus than said first polyurethane;wherein said intra-seal interface comprises a substantially non-planar portion coaxial with said piston hub. 21. A piston hub and seal assembly having a longitudinal axis, the piston hub and seal assembly comprising: a piston hub having at least one circumferential seal retention area that is substantially symmetrical about the longitudinal axis; andan elastic seal positioned at least partially adjacent the at least one circumferential seal retention area of the piston hub and being substantially symmetrical about the longitudinal axis, the elastomeric seal comprising: a first seal section having a cylindrical external surface portion and a frusto-conical external surface portion, the first seal section having a first hardness; anda second seal section, at least a portion of the second seal section positioned between the at least one circumferential seal retention area of the piston hub and the first seal section,wherein the second seal section contacts the first seal section at an interface, and the second seal section having a second hardness that is less hard than the first hardness;wherein the frusto-conical external surface portion of the first seal section is angled outwardly with respect to the cylindrical external surface portion of the first seal section; andwherein at least a portion of the interface where the first seal section contacts the second seal section includes a cylindrical portion substantially coaxial with at least a portion of the external surface portion of the first seal section. 22. The piston hub and seal assembly according to claim 21, wherein at least a portion of the elastic seal is an elastomeric seal. 23. The piston hub and seal assembly according to claim 21, wherein at least a portion of the elastic seal is a polymer seal. 24. The piston hub and seal assembly according to claim 21, wherein at least a portion of the elastic seal is a polyurethane seal. 25. The piston hub and seal assembly according to claim 24, wherein the elastic seal is at least partially cured in place. 26. The piston hub and seal assembly according to claim 21, wherein at least a portion of the interface where the first seal section contacts the second seal section includes a curved portion that is coaxial with the piston hub about the longitudinal axis. 27. The piston hub and seal assembly according to claim 21, further comprising: a circumferential bearing ring having a cylindrical external surface portion that is positioned adjacent a portion of an external portion of the first seal section. 28. The piston hub and seal assembly according to claim 21, wherein the frusto-conical external surface portion of the first seal section is at least partially angled outwardly at an angle that is equal to or less than about 7 degrees with respect to the cylindrical external surface portion of the first seal section. 29. A piston hub and seal assembly having a longitudinal axis, the piston hub and seal assembly comprising: a piston hub having at least one circumferential seal retention area that is substantially symmetrical about the longitudinal axis;an elastomeric seal positioned at least partially adjacent the at least one circumferential seal retention area of the piston hub and being substantially symmetrical about the longitudinal axis, the elastomeric seal comprising: a first seal section having a cylindrical external surface portion and a frusto-conical external surface portion, wherein the first seal section includes a first polyurethane; anda second seal section, at least a portion of the second seal section positioned between the at least one circumferential seal retention area of the piston hub and the first seal section, wherein the second seal section contacts the first seal section at an interface, and the second seal section includes a second polyurethane having a lower modulus than the first polyurethane;a circumferential bearing ring having a cylindrical external surface portion that is positioned adjacent a portion of an external portion of the first seal section of the elastomeric seal;wherein the frusto-conical external surface portion of the first seal section of the elastomeric seal is angled outwardly with respect to the cylindrical external surface portion of the first seal section; andwherein at least a portion of the interface where the second seal section contacts the first seal section includes a portion that is coaxial with the piston hub about the longitudinal axis. 30. The piston hub and seal assembly according to claim 29, wherein at least a portion of the elastomeric seal is at least partially cured in place. 31. A piston hub and seal assembly having a longitudinal axis, the piston hub and seal assembly comprising: a piston hub having at least one circumferential seal retention area that is substantially symmetrical about the longitudinal axis; andan elastomeric seal positioned at least partially adjacent the at least one circumferential seal retention area of the piston hub and being substantially symmetrical about the longitudinal axis, the elastomeric seal comprising: a first seal section having a cylindrical external surface portion and a frusto-conical external surface portion, wherein the first seal section includes a first polyurethane; anda second seal section, at least a portion of the second seal section positioned between the at least one circumferential seal retention area of the piston hub and the first seal section, wherein the second seal section contacts the first seal section at an interface, and the second seal section includes a second polyurethane having a lower modulus than the first polyurethane; andwherein at least a portion of the interface where the second seal section contacts the first seal section includes a portion coaxial with the piston hub about the longitudinal axis. 32. The piston hub and seal assembly according to claim 31, wherein at least a portion of the elastomeric seal is at least partially cast-in-place. 33. The piston hub and seal assembly according to claim 31, wherein at least a portion of the elastomeric seal is at least partially cured in place. 34. The piston hub and seal assembly according to claim 31, wherein at least a portion of the interface where the second seal section contacts the first seal section includes a substantially non-planar portion coaxial with the piston hub. 35. The piston hub and seal assembly according to claim 31, wherein at least a portion of the interface where the second seal section contacts the first seal section includes a curved portion substantially coaxial with the cylindrical external surface portion of the first seal section.
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