Abstract: The piston of a master cylinder in the power train of a motor vehicle is made, at least in part, of a thermosetting plastic material and cooperates with one or more annular seals to ensure that a source of hydraulic fluid is communicatively connected with the chamber in the housing of the master cylinder when the piston is moved by one or more springs or otherwise in a sense to increase the volume of the chamber. When a pedal or another actuator causes the piston to expel pressurized fluid from the master cylinder into a slave cylinder, the seal or seals cooperates or cooperate with the housing and/or with the piston of the master cylinder to seal the source from the chamber of the master cylinder. The slave cylinder can actuate the friction clutch between the prime mover and the transmission in the power train of the motor vehicle.

Abstract: A liquid reservoir, particularly for use in an hydraulic system. The reservoir includes a container and a cover cap, and it is intended for containing an hydraulic pressure medium. A pressure equalization component is provided within the container for compensating for pressure differences between the interior of the container and the surrounding atmosphere, and a level compensation component is provided for compensating for changes in the volume of the pressure medium. The pressure equalization component is functionally separate from the level compensation component.

Abstract: A power train for use in motor vehicles has a friction clutch including a housing which rotates with the output shaft of the engine and a clutch disc which transmits torque to the input shaft of a change-speed transmission in the engaged condition of the clutch. The clutch can be engaged and/or disengaged by one or more slave cylinders which is or are rotatably mounted on and is or are being held against axial movement relative to the clutch housing. At least one release bearing can be installed between the piston(s) of the slave cylinder(s) and the diaphragm spring of the friction clutch, and a second bearing is or can be installed between the slave cylinder housing(s) and the clutch housing.

Abstract: An hydraulic system that includes a master cylinder, a slave cylinder, a fluid conduit extending between the cylinders, and a pressure relief valve within the conduit between the cylinders. The pressure relief valve includes at least one port that is closed by an elastic member that overlies the port and that opens when fluid pressure acting through the port exceeds a predetermined level to cause the elastic member to open the port.