GB765279A - Improvements in or relating to swashplate liquid pumps - Google Patents

Abstract

765,279. Reciprocating pumps. BOSCH GES., R. March 2, 1955 [March 3, 1954], No. 6145/55. Class 102(1) In a multi-cylinder liquid pump having a rotatable cylinder block 8, 9 with several cylinder bores 12 containing pistons 14, a driving shaft 6 fixed to said block and a disc 27 surrounding the shaft and inclined thereto, the inclination of the disc determining the length of stroke of the pistons, one side 8 of the cylinder block is attached to one end of the shaft and the opposite side 9 is rotatably mounted on a fixed bearing stud 4 coaxial with the shaft, a chamber 22 being provided in the block adjacent the inner end of the bearing stud and adapted to be subjected to the full feed pressure of the pump whereby the thrust on the block produced by liquid pressure in the cylinder bores and tending to displace it in one direction is at least approximately compensated for by the thrust produced by the feed pressure existing in said 'chamber and tending to displace it in the opposite direction, namely away from the bearing stud. The cylinder bores have annular grooves 18 and 19, the groove 18 of each cylinder being connected by a passage 20 with the inner end of another cylinder bore which is off-set by 90 degrees round the cylinder pitch circle, while the groove 19 is connected by a passage 21 to the chamber 22. The pistons have longitudinal grooves 15 so dimensioned that they connect the groove 18 alternately with the interior of the housing 1 and with the groove 19 during movement of the piston 14, thereby controlling the inlet and outlet of liquid relative to the cylinder bore. The inclination of the disc 27 is adjusted by rotating it about an axis which lies in the plane 42 containing the outer ends of the pistons. A lever 39 attached to the disc is urged by a spring 40 to incline the disc as obliquely as possible. The pump obtains liquid from a reservoir 48, throttle valve 47 and inlet pipe 46, and delivers it to a pipe 50 leading to a hydraulic engine 51, from which it is exhausted back into the reservoir. When the pump output is to be reduced, the valve 47 is closed slightly. An increased partial vacuum is thereby produced in the cylinder bores which are taking in liquid so that the total pressure exerted on the swashplate 25 by the pistons at the bottom, is greater than that exerted by those at the top and the swashplate moves to a less inclined position until the tension in the spring 40 offsets this out of balance force, the change in inclination of the swashplate reducing the stroke of the pistons.and hence the pump output.