Patent ID: 8312805

Claim:
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; and an 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; and 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; 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; and wherein said intra-seal interface comprises a cylindrical portion substantially coaxial with said first seal section cylindrical external surface portion.