Vorrichtung zum Abdichten von Bohrmotorwellen

1,229,340. Seals. SPETSIALNOE KONSTRUKTORSKOE BJURO PO ELEKTROBURENIJU. 9 July, 1969 [9 July, 1968], No. 34520/69. Heading F2B. A seal for separating a high-pressure space 1 from a low-pressure space 5 formed between relatively rotatable members 15, 17 in, for example, well drilling equipment comprises an intermediate pressure chamber 4 which is separated from the spaces by seals 2, 6 and collects leakage from the high-pressure space, a pump 10 driven by relative rotation of the members for returning the leakage to the high-pressure space, an annular piston 7 for urging the seal 2 into sealing contact, and a non-return valve 13 in the pump inlet which is rendered ineffective and held in the open position, as by a prod 18, upon movement of the piston away from the seal 2. The prod 18 on the underside of the piston 7 prevents the intermediate chamber pressure from falling beneath a predetermined value. During normal operation, the plunger 11 of the pump is reciprocated by a swash plate 23 and oil is drawn from the chamber 4 through the non-return valve 13 and discharged to the high-pressure space 1 through a non-return valve 14. The reduction in pressure allows the piston to descend so that the prod 18 on the underside of the piston maintains the non-return valve 13 in an open position. This prevents any further pumping action until the piston is raised once again by the pressure of leakage in the chamber 4.