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: In operation of a support for a patient's body, used in medical or veterinary treatment, which applies alternating-pressure to the body in order to reduce or minimize the risk of pressure sores caused by prolonged pressure on the skin, inflatable cells of the support are inflated and deflated cyclically in a predetermined sequence. To provide improved effect in relieving or preventing pressure sores, the cells are deflated in the sequence in such a manner that the interior pressure falls from 10 mmHg (135 Pa) to 0 mmHg in a time period of not more than 15 s. Preferably the interior pressure falls to below 0 mmHg (ambient atmospheric pressure). A vacuum pump or pumps may be employed to achieve this result.

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).

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).

Abstract: An electromagnetic linear compressor has a linearly reciprocating piston (10) biased in one direction by a helical coil spring system. A rotational bearing (40) supports one end of the spring system (20a, 20b). To avoid uneven wear due to forces applied by the spring system, the spring system comprises two helical coil springs (20a, 20b) acting in series to bias the piston (10), and the rotation bearing (40) transmits thrust between the two springs while permitting relative rotation of the two springs about their common axis. The compressor also has a turbine (30) for exerting a unidirectional rotational force to rotate the piston (10) about its axis gradually during operation of the compressor.

Abstract: A cushion for the seat of a chair is provided, having at least two groups of cyclically inflatable tubes (4, 6, 8, 10), each group comprising at least one tube. Control means (18) inflates and deflates each group sequentially. The cushion also has a buffer chamber (12, 14) maintained by the control means (18) in communication with the inflated group or groups of cyclically inflatable tubes. The buffer chamber comprises at least one inflatable buffer tube which provides a part of the sitting surface of the chair.

Abstract: An air supply and control apparatus for an inflatable mattress 2 has several air compressors 1 which are operated in turn, during normal operation, to inflate the mattress 2. In the case of the pressure in the mattress 2 falling below an upper preset value the air supply is provided by having more than one air compressor 1 operate simultaneously. The apparatus has electronic circuitry for effecting this alteration of the mode of operation when pressure sensing means 4 detects a fall in mattress pressure. In the case of a more severe drop in mattress pressure a valve 16 in an air outlet of the mattress 2 is closed under control of the electronic circuitry. The apparatus is particularly suitable for use with a mattress 2 having a plurality of separately inflatable regions, air being supplied to the regions from the air compressors 1 via a distributor 3.