Patent ID: 7600761

Claim:
A cylinder-and-piston unit comprising a cylinder, a piston and a sealing collar, the cylinder comprising a bore, and one of the piston and the cylinder having a wall surface along the bore, the wall surface comprising a first sidewall extending parallel to a longitudinal axis of the bore, a second sidewall contiguous with the first sidewall and extending generally perpendicularly to the first sidewall, a third sidewall contiguous with the second sidewall and extending generally parallel to the first sidewall, a fourth sidewall continuous with the third sidewall and extending generally parallel to the second sidewall, and a fifth sidewall contiguous with the fourth sidewall and extending generally parallel to the first sidewall along the bore, the second, third and fourth sidewalls being parts of one unitary body and bordering a groove that is recessed in the wall surface, the sealing collar being positioned in the groove and comprising an outside sealing lip and an inside sealing lip, the outside and inside sealing lips each having a free end, the sealing collar further including a circumferential extension that extends generally parallel to the sealing lips, is arranged radially between the outside sealing lip and the inside sealing lip and has a free end that projects axially beyond the free ends of the outside and inside sealing lips, the free end of the circumferential extension being provided with radial apertures allowing pressure fluid to pass through in a radial direction, the circumferential extension engaging the second sidewall of the groove and maintaining the free ends of the outside and inside sealing lips out of contact with the second sidewall, wherein the sealing collar includes a rear surface opposite the free ends of the outside and inside sealing lips, wherein the sealing collar has a maximum outside diameter at the free end of the outside sealing lip and a minimum outside diameter at the rear surface.