GB1549546A - Meshing-screw type rotary hydraulic machine - Google Patents

Abstract

The machine can work as a pump or a motor. In the first case, the fluid flows from the low-pressure side to the high-pressure side. In the second case it is the other way round. The pressure difference between high pressure and low pressure attempts to push the conveyor worm (1) towards the low-pressure side (65). In order to compensate for this axial thrust, the conveyor worm (1) is provided with a compensation piston (2). In addition there are frictional forces which act in an axial direction. In a motor these forces act in the same direction as the pressure force due to the pressure difference; in a pump they act in the opposite direction. In the case of the pump, the piston area should be chosen to be smaller, and in the case of the motor to be greater than would be required for pressure equalisation. So as not to have to provide the conveyor worm (1) with different pistons (for pump or motor mode), the free end of the piston is given a smaller area (6, d2) than would be required for pressure equalisation, said smaller area being acted upon by the pressure (65) which prevails at the other end of the conveyor worm (1). The piston (2) further has a second area (d1) which is acted upon by an intermediate pressure between the high pressure (67) and the low pressure (65). The sum of the smaller area (6, d2) and the second area (d1) is greater than the area which would be required for pressure equalisation. The intermediate pressure arises in a chamber (9) which is bounded by piston (2) and its bearing (3) and which communicates with the high pressure and low pressure side (67, 65) via leak points (64, 66). The throttle effect of these leak points changes as the piston (2) moves. <IMAGE>