Patent ID: 7168536

Claim:
Tandem master cylinder (TMC) comprising a housing, a first piston that is linearly slidable in the housing and able to displace pressure medium out of a first chamber, a second piston that is linearly slidable in the housing and able to displace pressure medium out of a second chamber, wherein the first piston on a frontal end in the actuating direction is acted upon by the pressure of the first chamber and on an opposite frontal end is acted upon by the pressure of the second chamber, further comprising a first primary seal having a lip sealing the first chamber in relation to the reservoir pressure that prevails in a first reservoir chamber after a flow connection between the first chamber and the first reservoir chamber along a peripheral surface of the first piston has been closed, a second primary seal sealing the second chamber in relation to the reservoir pressure that prevails in a second reservoir chamber after a flow connection between the second chamber and the second reservoir chamber along a peripheral surface of the second piston has been closed, a first secondary seal sealing the second chamber along the peripheral surface of the first piston in relation to the reservoir pressure that prevails in the first reservoir chamber, a second secondary seal sealing the second chamber along the peripheral surface of the second piston in relation to the pressure in the ambience of the TMC, wherein the first primary seal is inserted into a first annular groove directly provided in the housing and, thus, is supported directly on the housing upon pressurization, wherein the width of the groove is larger than the width of the first primary seal, enabling pressure fluid to propagate to the lip of the first primary seal and prevent the first primary seal from adhering dryly to the housing, and wherein the flow connections between the chambers and the reservoir chambers are achieved exclusively by way of flow passages in the pistons and the housing.