Abstract: A compressed-gas-operated reciprocating-piston device, e.g. a concrete breaker, rock drill or chipping hammer, has a cylinder component of composite construction, comprising a rigid inner metal tube in which the piston reciprocates and a moulded outer sleeve of rubber or plastics material, e.g. polyurethane, which surrounds the tube over the majority of its length and is bonded thereto. The sleeve has three integral moulded longitudinal ribs in which are moulded longitudinal passages for transmission of compressed air to the cylinder interior. An outer tubular muffler of rubber or plastics material surrounds the composite cylinder component and defines a sound-reducing path for exhaust gas from the cylinder to thge atmosphere. The exhaust gas is discharged into spaces defined between adjacent ribs of the sleeve within the muffler, these spaces forming part of an expansion chamber in the muffler.

Abstract: A method of draining oil from a transmission housing, of an oil-injected screw compressor comprising a compressor housing containing rotor means and a transmission housing. A shaft of the compressor extends into the transmission housing from the compressor housing and the transmission housing is underslung relative to the compression housing. The first portion of the compressor intake stroke, or rotation, is prevented from being filled with intake gas such that a depression is created. Said depression is applied via a bore to a sump portion of the transmission housing, so that the absolute pressure differential between the sump and the suction portion of the rotor means draws oil out of the sump and into the rotor spaces. A compressor employing this method of draining oil is also described.

Abstract: A reciprocating hydraulic motor, for example for a rotary percussive drilling head, includes a piston and cylinder having a piston face exposed to the pressure in a compression chamber which is connected through ports controlled by the piston to a supply pressure at one end portion of its stroke, and to exhaust at an opposite end portion of the stroke, while between these end portions of the stroke is a compression/expansion travel during which the compression chamber is closed and the liquid in it alternately expands over a higher range of pressure and is compressed over a lower range of pressure.For returning the piston, in the direction in which liquid is compressed, one of two opposed faces of the piston is exposed to the pressure in a biasing chamber which communicates permanently with a constant pressure supply while the other communicates with the compression chamber.