Patent GB-915911-A (GB)
Title: High temperature variable displacement pump
IPC: F04B49/10
Filed: 1959-05-05
Abstract: 915,911. Reciprocating pumps. NORTH AMERICAN AVIATION Inc. May 5, 1959, No. 15337/59. Class 102(1). [Also in Group XXIX]. In a radial cylinder pump the pistons 14 engage a reaction ring 29 which rests on a transverse member 25 and is engaged by a seal 26 so that the reaction ring together with the housing members 3, 4, 5 form two pressure chambers 23, 24 whereby the eccentricity of the reaction ring 29 may be varied by differential pressures fed to the chambers 23, 24. The chamber 23 is maintained at a constant pressure less than the pump outlet pressure by means of a valve 57, which together with springs 28 tend to move the reaction ring 29 towards its position of maximum eccentricity. Variable pressure under control of a governor valve 100 is supplied to the chamber 24 and tends to move the reaction ring 29 towards its concentric position. The cylinder block 12 is mounted on a pintle 8 having an inlet passage 19 and an outlet passage 20 which communicates with a chamber 46 and through a priority valve 45 with an outlet 7, the priority valve 45 comprising a differential piston valve 49 which prevents discharge from the pump below a preset pressure. The interior of the pump housing communicates through a valve 35 with a return outlet 17. The constant pressure valve 57 comprises a member 60 loaded by a spring 69 and having axial passages 61, 62 separated by a wall 63 the passages 61, 62 communicating with an annular chamber 72 via, passages 64, 65 respectively the annular chamber 72 communicating with the chamber 46. The chamber 68 communicates with the chamber 23, and the chamber 67 with the interior of the pump casing and the outlet 17. Initial operation of the pump discharges air through the passages 65, 62 and when pressure is built up in the chamber 68 the valve 57 moves down closing off the passage 65. The pump case pressure is controlled in relation to the inlet pressure by means of a valve 55 which comprises a seating 77 and a disc 75 which is opened by excess pressure in the chamber 67 to connect the chamber via a passage 78 to the inlet 6. The governor valve 100 is temperature compensated so that as the rate of deflection of the spring 108 increases with increasing temperature the displacement of the valve remains a linear function of the applied pressure. The valve comprises a steel piston 101 slidable in the steel cylinder 118 and having a valve portion 121 controlling ports 115, 116 the ports 115 communicating by passages 117 with a chamber 114 connected to the chamber 24. The piston 101 is rigidly connected to an aluminium piston 103 slidable in an aluminium cylinder 104 the outer surfaces of the pistons 101, 103 being subjected to the pressure prevailing in the chamber 46 via passages 112 and 107 the passage 112 including a filter 109. As the temperature of the liquid rises so there is differential expansion of the pistons 101, 103 whereby the increased area of the piston 103 compensates for the increase of deflection of the spring 108 with increased temperature. Movement of the valve 101 connects the passages 115 either to the pressure prevailing in the chamber 46 or to the chamber 99 connected to the interior of the pump casing. The passages 116 do not directly communicate with the chamber 114 and are slightly wider in the vertical extent than the passages 115 with which they commtmicate via a groove 122. When the passages 115 are closed by the valve portion 121 the passages 116 are still open to a very small extent and this two part closing prevents hunting of the valve pistons. The pistons 14 and the pintle 8 are provided with lubricating and like passages as described in Specification 856,693. The pump is stated to operate at a speed of 8,000 revolutions per minute or higher while producing a large volume flow rate at 4,0001bs per square inch discharge pressure and inlet temperatures of about 400F.