Abstract: Constant-velocity joints in tripod construction have an external joint component (1) in which are formed three circumferentially spaced axial guide tracks (2) with bearing surfaces opposite each other in the circumferential direction. An interior joint component (3) has three circumferentially spaced radial trunnions (4) which engage in the guide tracks (2). A roller unit (8) is on each of the trunnions (4) and is radially supported in the guide tracks (2). The roller units (8) are essentially held at constant angles in the guide tracks. The roller units (8) are, relative to the trunnions (4) and radially movable with angular mobility. The roller unit (8) are each mounted, free to rotate, on a roller carrier (6). The trunnions (4) have connected to their ends, spherical heads (5) which engage a radial internal recess of the roller carrier (6). A needle bearing (7) with a cage (9) is located between each roller carrier (6) and roller unit (8).

Abstract: A hydraulic cylinder has a piston in it with a rod projecting out of the cylinder and connectable with a tool which is operable by movement of the piston rod. A high pressure space is defined in the cylinder at one side of the piston and a low pressure space is defined at the other side of the piston. A partition defines the other end of the low pressure space. A diaphragm on the other side of the partition defines an equalizing space between the diaphragm and the partition. A low pressure line is in communication with the low pressure space and with the equalizing space. A change over valve in the lines to both the high pressure space and the low pressure space enables connection of high pressure from a pump either to one space or to the other space in the cylinder while always permitting communication from the low pressure line to the equalizing space, the connection to the equalizing space is in the low pressure line between the change over valve and a non-return valve at the pump.