Abstract: An actuator assembly (1) comprises a body (2) in which works an actuating piston (7), a first piston (5) and at least one second piston (6), a chamber (26) containing a substantially incompressible fluid by which each of the first and second pistons (5, 6) acts on the actuating piston (7). The movement of the first piston (5) from a retracted position to an extended position acts via the fluid to cause the actuating piston (7) to move from a retracted position to an operational position, and subsequent movement of a second piston (6) from a retracted position to an extended position acts via the fluid to cause an actuation movement of the actuating piston (7).

Abstract: The invention relates to controlling the supply of fluid to a series of valves (1), in particular to the supply of air to a series of cuffs applying pressure to a wound. It is desirable to operate the series of valves by a single, small actuator (5) that does not require much power. A linear actuator is described comprising a solenoid operated plunger (15) having an external helical screw thread which co-operates with a drive ring (23). The drive ring (23) co-operates with cam means (8) which operate spring-loaded ball valves (30). A drive transmission (7) between the drive ring (23) and the cam means (8) allows movement of the cam means for one direction of movement of the linear actuator but not the other. A projection (25) on the cam means operate a first valve (1) until a second actuation closes the first valve and opens a second valve.