GB773560A - Variable delivery pump control apparatus - Google Patents

Abstract

773,560. Reciprocating pumps for liquids. NEW YORK AIR BRAKE CO. Jan. 6, 1955 (Feb. 24, 1954], No. 391/55. Class 102(1) To control a variable delivery pump, a space 43 in which a predetermined pressure is to be maintained is connected to the pump, e.g. the plungers 24, the delivery of which is variable between zero and a maximum by a mechanism including, e.g. spill valves 61, opposed by a spring 73 urging it towards maximum delivery with a force varying progressively between the limits, the mechanism being urged towards zero delivery by pressure developed in a motor such as a plunger 85 on the valve rod 64 and operating in a chamber 80 continuously in communication with the delivery space 43, the motor having a leakage characteristic which varies with the position of the plunger 85 in the chamber 80 in inverse relationship to the reaction force of the spring, being greatest at maximum delivery and least at zero, the communication between the motor chamber and the delivery space being restricted as at 94 but sufficient to neutralize maximum leakage from the chamber. The delivery pressure of a swash plate pump comprising a swash plate 56 and the plungers 24 working in cylinders 25 to deliver high pressure fluid past valves 41 through chambers 43 and passages 44 to an outlet 13, is controlled by the spill valves 61 on a spider 62 secured to the spring pressed piston rod 64. The rod slides in a cylindrical bush 86 having an enlarged central bore providing a motor chamber 80 communicating with the high pressure side of the pump through a passage 93 and choke 94. The diameter of the rod 64 is enlarged at 85 to form a differential piston urged by the pressure in the motor chamber to move the rod 64 and spider 62 to the right against the action of a multiple spring unit 73-77. Tapered portions 87, 88 on the piston rod 64 and enlargement 85 shorten the leak paths of the fluid to a low pressure chamber 31 housing the spider 62 and valves 61 and to the pump inlet ports 28 respectively and move out of their bores as the piston rod 64 &c. move to the right to'reduce the leakage and build up pressure in the chamber 80, as the spring resistance increases.