| 摘要 |
<p>A pneumatic oscillator of the type having an operating piston (20) reciprocable in a cylinder (21) to control a poppet valve arrangement so as to control a gas flow path, and biassed to the flow path-closing condition with feedback of output supplementary to the bias in opposition to source pressure, is characterised by a piston seal comprising an O-ring (22) having both radial and axial clearance in a retaining groove in the piston (20) to provide low friction, and by a resilient buffer (33) to arrest the piston (20) at its stroke-end in the flow path-opening position and to cause piston (20) rebound to an extent to position the O-ring (22) against the lateral groove wall that is downstream to the prevailing pressure differential, thereby to ensure effective sealing at the switching point. The buffer (33) also suppresses noise of operation of the oscillator. The oscillator is particularly useful for generating breathable gas pulses for resuscitation and/or lung ventilation purposes.</p> |
