Brake master cylinder seal

A ring seal for sealing a movable master cylinder piston in a bore of a master cylinder housing, the ring seal dividing the bore into first and second chambers, the ring seal being fitted within a generally rectangular groove of the piston, the groove having front and rear walls joined by a floor, the ring seal preventing fluid communication from the first chamber to the second chamber up to and including high pressure differentials and allowing fluid communication from the second chamber to the first chamber under very low pressure differentials, the seal comprising:

• a thick radially outer annular lip for sealing engagement with the master cylinder bore having a front end and a rear end, the front end extending toward the first chamber, the radially outer annular lip having a series of transverse slots along its front end to allow fluid communication between inner and outer sides of the radially outer annular lip when the radially outer annular lip is contacting the front wall of the groove;
• a mid-body portion integrally joined to the radially outer annular lip rear end extending generally parallel with the piston groove rear wall having a series of flow paths along its side adjacent the rear groove wall;
• and
• a thin radially inner annular lip with front and rear ends, the rear end being integrally joined with the mid-body portion and the radially inner annular lip having a series of flow paths aligned with the flow paths of the mid-body portion terminating at a position forward of the mid-body portion along the radially inner annular lip's inner surface which is adjacent to the groove floor, and the radially inner annular lip having a length shorter than that of the radially outer annular lip with the front end spaced away from the front groove wall, the radially inner annular lip front end having a diameter smaller than the radially inner annular lip rear end with an interference fit with the groove floor, the radially inner annular lip having a center of bending with the mid-body forward of a center of bending of the radially outer annular lip with the mid-body and the radially inner annular lip being far more responsive to pressure differentials between the first and second pressure chamber than the radially outer annular lip.