Abstract: A percussive device and method having, inside a machine housing (3), a reciprocally moveable percussive piston (2), the movement of which is controlled by a control valve (5), which is arranged to alternatively connect a chamber to a pressure source and to low pressure in dependence on a signal corresponding to the axial position of the percussive piston, and a valve (16) arranged to allow adjustment of the axial position of the percussive piston at which the signal is transmitted, by opening and blocking of a connection between one or more control channels (10, 11, 12, 13) and the control valve.

Abstract: A uniflow engine has a plurality of cylinders disposed symmetrically around a common crankshaft connected to pistons reciprocating in the cylinders. In response to the availability of a working fluid vapor at a predetermined condition, such as a high pressure or temperature, incoming vapor is supplied to those cylinders in which the respective pistons are in their working strokes to thereby initiate rotation of the crankshaft in a predetermined direction regardless of the position in which the crankshaft had stopped last. Once rotation is initiated and a predetermined mode change speed attained in a "start-up mode" by engine operation from start, vapor inlet valves are controlled to change engine operation over to a "running mode". In the "start-up mode" incoming vapor is admitted over a substantial portion of the piston working stroke, whereas in the "running mode" vapor inflow is terminated relatively early in the working stroke so that a vapor change does work in expandiing against the piston.

Abstract: A pilot assembly for switching the fluid supply valve of a hydraulic pump is actuated by the pressurized hydraulic fluid which operates the hydraulic pump. The hydraulic pump includes a main cylinder, a main piston within the main cylinder, and a main valve for supplying pressurized hydraulic fluid to the rear end of the main cylinder for driving the piston forwardly. The pilot assembly includes a pilot cylinder and a pilot spool within the cylinder. A first hydraulic conduit connects one end of the pilot cylinder to the front end of the main cylinder, and a second hydraulic conduit connects the other end of the pilot cylinder to the main cylinder at a position spaced rearwardly from the front end of the main cylinder. When the main piston passes forwardly of the second hydraulic conduit, the pressurized hydraulic fluid in the main cylinder moves the pilot spool, and pressurized hydraulic fluid is allowed to flow to the main valve to switch the main valve.

Abstract: The invention provides a hydraulically-driven reciprocatory tool comprising piston with a shoulder reciprocable in a cylinder, and a shuttle valve for controlling supply of fluid to a first face of the piston, the fluid producing a force on the first face which is alternately greater than and less than a constant bias force applied to a second face of the piston, wherein the position of the shuttle valve is determined by the pressure of fluid in a fluid connection between the shuttle valve and first and second ports in the wall of the cylinder, the fluid connection including a first non-return valve for preventing flow of fluid from one of the ports to the shuttle valve and a second non-return valve for preventing flow of fluid from the shuttle valve to the other of the ports. Preferably, each non-return valve has associated with it a variable throttle in the fluid connection and further means are provided for controllable flow of fluid along a branch of the fluid connection.