Abstract: An electromagnetic reciprocating compressor has a body (1, 2), a piston (10) reciprocating in the body, and an electromagnetic drive (22, 23, 24) for the piston. The piston has a piston head (11) which slides in a cylinder (12) in the body to effect compression of fluid in the cylinder during operation of the compressor and, axially spaced from the piston head, a piston guide member (13) slidingly movable on a guide surface (14) provided by the body. The compressor has a compression spring arrangement (20) comprising at least one helical compression spring (20a, b) acting to drive the piston axially. The spring (20a, b) is mounted around the piston and is at least partly located within the cylinder during at least part of the piston stroke but is outside the working volume of fluid undergoing compression.

Abstract: A connector for use in connecting an air-inflatable mattress to a control unit, where the connector has three modes of operation: Off; On; and CPR (Cardio-Pulmonary Resuscitation) when the male body part and the female body part are mutually engaged. These modes arise from different alignments of the air passages of the first component and second component of the male body part at surfaces which abut one another. Fluid supply lines to be connected are attached to the unions. The female body part is attached to a wall of the control unit, and the male body part is on the ends of the supply lines running to the air-inflatable mattress.

Abstract: An electromagnetic reciprocating compressor has a body (1, 2), a piston (10) reciprocating in a cylinder (12) in the body and a piston guide (14) in the form of an insert which is radially located relative to the axis of the cylinder (12) by fitting against a registration surface (25a), the registration surface is on a body part (1) which also provides the internal cylinder surface (12a) of the cylinder. To improve the alignment of the insert (14), the registration surface (25a) and the internal cylinder surface (12a) are formed to their respective final diameters in the same machining operation by reference to a common axis. The piston guide (14) is axially located related to the cylinder (12) by being resiliently clamped between the stator (23) and an end portion (27a) of the body (1, 2) opposed to the stator (23) with a resilient member (27) interposed between the body end portion (27a) and the piston guide (14).