Improvements in or relating to Gear Pumps and Motors

1,164,290. Rotary positive-displacement pumps and motors. INDUSTRIEWERKE KARLMARX-STADT VEB. Nov.24, 1966, No.52739/66. Heading F1F. A reversible rotary positive-displacement pump, or motor, of the externally-meshing geartype includes a pair of gears 2, 3, Fig. 1 attached to rotatable shafts 4, 5 mounted in axiallymovable bearing-bushes 6--9 that are pressed against the ends of the gears by pressure communicated to chambers 20, 21 containing seals 40, 41 from the high-pressure side of the gears through a channel 14, or 15, Fig.3, a bore 31, or 32, in one of a pair of fixed bushes 29, 30 that form a housing for a valve member 33, and a channel 19 having branches extending to said chambers. Leakage fluid escapes to the lowpressure side of the gears through bores 27, 28 in the shafts, non-return valves 24, 25, channels (22, 23, Fig. 2, not shown), a duct (16) containing the bushes 29, 30, and the channel 14, or 15. The valve member 33 closes either the bore 31 or the bore 32 according to the pressure difference between inlet and outlet chambers 12, 13 for the working fluid, which chambers are separated from each other by the intermeshing gear teeth.