Self-sealing gear pump with sealing pressure divider
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A self-sealing gear pump has seals formed between the end faces of the gear wheels and adjacent faces of a casing of the pump by thrust plates interposed between the end faces of gear wheels and the casing. The thrust plates have cavities formed behind them and are pressed against the end faces by the pumped fluid under pressure being admitted to the cavities. Each cavity is connected to both the high pressure side of the pump and the low pressure side of the pump by ports or nozzles, the flow section of the nozzle leading to the high pressure side being larger than that of the nozzle leading to the low pressure side. The surface area of each thrust plate exposed to its cavity is greater than its surface area exposed to the high pressure side of the pump and each cavity and the fluid connections to it are constructed as a hydraulic potentiometer which causes the pressure in the cavity and hence the sealing pressure of the plate against the gear wheels to be adjustable.