Fluid flow control valve

摘要

1,029,470. Fluid pressure servomotorcontrol systems. NEW YORK AIR BRAKE CO. Dec. 8, 1964 [April 16, 1964], No.49864/64. Heading G3P. [Also in Divisions F1 and F2] A double acting piston motor 12, e.g.for raising and lowering the bucket and blade 13 of loaders and bulldozers, is controlled via a valving device 11 from a three position sliding plunger valve 14 whereby, with value 14 in the "raise" position, pressure fluid from pump 15 flows from port 17, conduit 26, port 22, passage 32, annular chamber 32a and radial passage 49, of valve plunger 36, to axial bore 47 thereof to unseat check valve 52 and pass via radial passages 51 and passage 33 encircling by-pass valve 61, to port 24 and passage 28 to the head end of motor 12 whilst, simultaneously, the rod end of motor 12 is vented to tank 16 by conduit 29, port 25, passage 31 encircling check valve 59, port 23, conduit 27 and port 18. The motor may be hydraulically locked in the "raised" position with valve 14 in neutral position, interrupting the supply and vent paths. The blade 13 is lowered by pressure fluid from pump 15 flowing, via port 18 and conduit 27, to the rod end of the motor 12 and which fluid pressure also acts in chamber 31a to displace plunger 36 against the action of spring 44 and the dashpot action of fluid in chamber 41 which is connected to passage 32 via restricted orifice 42 and to passage 33 via passage 75, chamber 69 and restricted orifice 74 in by-pass valve 61, whereby throttling notches 46 open communication between annular chambers 32a and 33a for the return flow from the piston end of motor 12a. Cavitation within the piston end of motor 12a is prevented by a balance between closing down of the throttle notches 46 as pressure in passage 31 decreases and opening of by-pass valve 61 and check valve 59 as pressure on annular surface 71 of valve 61 increases to open this valve against spring 68 and reduced pressure within chamber 69 arising from restriction 74. In digging operations, the blade 13 encounters resistance and with highest pressure in the passage 31 valve 36 assumes a position with maximum opening of throttles 46 and maximum pressure available on the piston. In an alternative embodiment,(Fig. 2 not shown) chamber 69 is not connected to chamber 41 but is connected directly to a separate "vent" section of valve 14 which is used to operate the valve 61 only when quick dropping of the blade is required; this has the advantage that the only path between ports 22 and 24 is closed in the event of failure of-valve 14 in the "raise" position. Chamber 41 effects a dashpot action upon valve 36 to minimise valve chatter.