Abstract: A seal arrangement provides a seal between a bore and a rod movable in the bore with a gap formed between the bore and the rod. The seal arrangement includes a floating elastomeric sealing ring which is accommodated in a circumferential groove around the rod. The sealing ring sealingly engages the wall of the bore. An annular resilient biasing device is also accommodated in the groove. The biasing device acts between one wall of the groove and the sealing ring to urge the sealing ring against an opposing wall of the groove. In addition, the biasing device is configured to allow passage of fluid past the biasing device between a region of the groove disposed radially inwardly of the sealing ring and the gap between the rod and the bore on the side of the sealing ring opposite the opposing wall. The biasing device has, at least at some circumferential positions therearound, a cross-sectional profile that reduces in radial width towards one wall of the groove.

Abstract: A seal arrangement is disclosed that provides a seal between a bore and a rod movable in the bore with a gap formed between the bore and the rod. The seal arrangement includes a floating elastomeric sealing ring which is accommodated in a circumferential groove around the rod. The sealing ring sealingly engages the wall of the bore. An annular resilient biasing device is also accommodated in the groove. The biasing device acts between one wall of the groove and the sealing ring to urge the sealing ring against an opposing wall of the groove. In addition, the biasing device is configured to allow passage of fluid past the biasing device between a region of the groove disposed radially inwardly of the sealing ring and the gap between the rod and the bore on the side of the sealing ring opposite the opposing wall. The biasing device has, at least at some circumferential positions therearound, a cross-sectional profile that reduces in radial width towards one wall of the groove.

Abstract: A pressure fluid-actuated oscillator, especially suitable for use in lung ventilation equipment for emergency use, comprises a double-piloted 5-port valve and biased timer valves controlling the supply to its pilots to provide for repeated changeover of the 5-port valve at intervals determined by the respective timing periods of the timer valves. One of the timer valves has an adjustable timing period whereas the other has a nominally fixed timing period but is made sensitive to the duration of the immediately preceding timing period determined by the adjustable timer valve so as automatically to change its timing period in the same sense as adjustment of the adjustable timer valve.In lung ventilation equipment using such an oscillator, therefore, a single control may serve for directly setting the critical inhalation phase duration and to cause a complementary alteration of the exhalation phase duration that maintains the ratio of duration of the respective phases within desirably close limits.

Abstract: Lung ventilation equipment comprising a gas pulse source delivering pulses of breathable gas to a patient valve for introduction into the respiratory system of a patient for resuscitation or anaesthetic purposes is characterized by a restrictor in the pulse delivery line from the pulse source to the patient valve, the restrictor being constructed to operate in a sonic-flow "choked" condition during passage of a gas pulse therethrough so that system pressures and resistances downstream of the restrictor cannot affect operation of the pulse source. Downstream of such a restrictor, therefore, conduits may be of small bore while the patient valve may be of the low-pressure type that normally requires a large-bore supply conduit.

Abstract: A gas valve mechanism especially suitable for use as the patient valve in conjunction with a lung ventilator or resuscitation device by developing high actuating forces from low pressure gas supplies comprises a valve element movable in a body having a gas pulse inlet, a gas pulse outlet and an exhaust outlet. The valve element has a large effective area exposed to the gas pulse inlet and is moved by gas pressure at that inlet, against spring-loading, to open a restricted flow path to the gas pulse outlet, the flow path restriction developing a pressure differential acting to oppose the spring loading and hold the valve element positively in the flow path open position.