GB958059A - Improvements in or relating to reciprocating piston pumps - Google Patents

Abstract

958,059. Reciprocating pumps. SCHWEIZERISCHE LOKOMOTIV-UND MASCHINENFABRIK. Oct. 16, 1961 [Oct. 19, 1960], No. 37070/61. Heading F1A. In a reciprocating piston pump a control valve 20 has ports 23, 24, Fig. 1, which are associated with at least some of the cylinder chambers and communicate with the suction space 17, the position of the ports being adjustable relative to cylinder admission ducts 18, 19 to vary the flow cross-sectional area. At low operating pressure, the control piston 30 and control slide 20 are in the piston shown in Fig. 1 with ducts 18, 19 in register with ports 23, 24. At a predetermined fluid pressure in chamber 39, piston 30 moves control slide 20 against spring 27 thus restricting both the admission of liquid to the duct 18 and the delivery of the five large diameter plungers 8, whilst delivery from the five small plungers 9 is unchanged. Further rise of pressure causes the edge 32 of piston 30 to close duct 36 so that piston 30 is moved suddenly to its upper abutment causing slide 20 to close ports 18 completely and plungers 8 to cease delivery. Pressure in space 40 is relieved through ducts 37, 37a and 37b. The control slide 20 may be constructed to operate the large plungers when it is in its uppermost position and all plungers may be the same diameter. In a modification, a smaller piston may be mounted within piston 30 to move the control slide further upwardly to restrict admission to some or all of the small diameter cylinders. Either piston 30 or the smaller piston may be carried through cover 45 to provide for manual actuation of the control slide. In a further modification, a plurality of springs which operate simultaneously or one after the other, may replace spring 27. In a further embodiment the control slide is replaced by an annular control valve 50, Fig. 4, which is rotated by a piston 61, Fig. 5, connected by conduit 64 to pressure chamber 56. Control valve 50 has ports 71 . . . 82 of differing size communicating with spring loaded inlet sleeves 51 so that not all sleeves 51 are cut out at the same time. When the smaller control ports are closed, pressure acting on rod 85 raises piston 84 to bring opening 89 in communication with duct 87 so that any liquid still present in the cylinders is discharged through ducts 87-90 past a rubber non-return valve 91. In a modification the control valve 50 may be manually operated by handle 67. In a further modification the control slide may vary the supply to only some of the pump cylinders.