Abstract: A reciprocating vacuum pump has a disc shaped piston (22, 122) having a peripheral elastomeric seal (52, 152) with oppositely directed, radially outwardly extending skirt portions (54,56); the piston is driven axially by a rod (34, 134) reciprocal in a lubricated bearing (42, 142) and a lubrication flowpath (50,48; 150,148) is defined between the bearing (42, 142) and the side of the piston (22, 122) opposite thereto.

Abstract: A hydraulic braking system for agricultural tractor-trailer combinations, taking hydraulic power from a pump on the tractor. The system includes a pressure control valve movable by the main hydraulic service supply to connect the main supply with a chamber in communication with a restricted bore and an outlet for the by-passed braking fluid. A pilot valve responsive to braking pressure, or manually operable, admits fluid to the trailer brakes and operates a check-valve closing a connection between the chamber and a return line for fluid not required for braking. The check valve enables a clean switching action and eliminates any tendency to meter at some intermediate pressure. Both constant flow and constant pressure systems are described. The return line may be connected to a low pressure sink or to the flow at the services outlet port preferably via another check valve.

Abstract: A hydraulic ram system for tilting a vehicle cab which is resiliently mounted on the vehicle frame includes a ram cylinder of which that end in which the ram piston is located when the cab is in the lowered position is of increased bore diameter to render the piston passive in this position, a restriction being provided in the lower ram line across which a pressure drop is created when fluid is pumped through the line, while in the upper ram line a valve is provided responsive to the pressure differential across the restriction and thereby operable to interconnect the upper and lower ram lines.

Abstract: A hydraulic ram system for tilting a vehicle cab which is resiliently mounted on the vehicle frame includes a ram cylinder of which that end in which the ram piston is located when the cab is in the lowered position is of increased bore diameter to render the piston passive in this position, an auxiliary valve being provided in the upper ram line held by a spring-loaded detent in a closed condition and adapted to open when during a lifting operation the piston moves out of the increased bore zone.

Abstract: A hydraulic ram system for tilting the cab of a large commercial vehicle to provide access to the engine and other mechanism, where the end of the ram cylinder in which the ram piston is located when the cab is in the lowered position is of increased bore diameter and provides enough clearance around the piston to render the ram passive in this position, and the length of the increased diameter portion of the cylinder bore is sufficient to accommodate the maximum movement of the cab on its suspension.