| 摘要 |
<p>To eliminate the need of a case drain, a reversible, high pressure gear pump comprises an insert transversely displaceable to and fro in a bore of a housing by fluid under pressure derived from the pump cavity, to seal against the tips of the gear teeth on the high pressure side and thereby place the (for the time being) low pressure, inlet port to the pump cavity in communication with a zone of the pump cavity which extends around a major portion of the periphery of the gears. A side wall member of the pump cavity is pressure balanced into sealing engagement with its adjacent side faces of the gears and the adjacent side face of the insert. This member is plastic faced with a material having the ability to creep into the wear space formed by the gears rubbing against it. In one embodiment, the side wall member urges the opposite side faces of the gears and of the insert, into sealing engagement with a ported side wall of the pump cavity formed as part of the casing. Alternatively, a further one of the side wall members may be pressure balanced into sealing engagement with said opposite side faces.</p> |
