Patent GB-630970-A (GB)
Title: Improvements in or relating to fluid pressure control units
IPC: F15B13/04
Filed: 1946-09-10
Abstract: 630,970. Valves. RUSTON - BUCYRUS, Ltd. Sept. 10, 1946, No. 27144. Convention date, Jan. 23. [Class 135] A fluid-pressure control unit for doubleacting cylinders comprises a valve seat 33 with five ports, namely two ports to the ends of the cylinder, a pump intake port, a pump output port, and a sump port, and a valve member 35 with four control positions, namely a " raise " position in which fluid is supplied to one end of the cylinder and returned from the other end of the cylinder both to the pump intake and sump ports, a " hold position " in which both ends of the cylinder are isolated and the pump output is directed exclusively to the sump, a " lower " position in which fluid is supplied to the opposite end of the cylinder and is returned from the first end of the cylinder direct to the pump intake and a " float " position in which both ends of the cylinder are freely connected with one another, with the pump output, and with the sump. The unit shown comprises a main housing 11, surmounted by a valve housing 12 and carrying on opposite sides oil tanks 13, 14 whence a gear pump 18, Fig. 7, draws its supply. The sides of the tanks slope outwardly and backwardly to clear the bush arms of an angling bulldozer. The valve housing 12 is connected by pipes 31, 32 to the ends of the operating cylinder and has a bore 33 for a piston valve 35 having annular bands separated by annular recesses 37, 38, 39, 40, 41. The recesses 37, 38 and 40 are connected by radial holes 43, 44, 45 respectively with a bore 42 closed by a plug 46. The bore 33 communicates with passages 25, 27, 28, 30 in the housing 11. The passages 25, 28 communicate with the pump inlet 19 whilst the passage 30 communicates with the pump delivery 20. The passage 27 opens into a passage 22a in turn connected with a transverse passage 22 the ends of which are shrouded by baffles 23 to prevent frothing. The housing 11 also has equaliser passages 21, 24 for air and oil respectively. The passages 25, 28 contain check valves 26, 29. The valve 26 has a byepass 54. Oil leaking into the ends of the bore 33 is returned to the tanks through bleeders 34. The valve 35 is operated by a rod 47, Fig. 9, through a chain- 48 and an offset link 49. A passage 50 branching from the passage 30 leads to a relief valve 51 the outlet of which is connected by an external pipe to the passage 22. The valve housing ends of all the passages 25, 27, 28, 30 as well as the passages connected to the pipes 31, 32 are bifurcated, the two branches leading to opposed radial passages bored from one side of the housing and closed by a plug 36. The bearing chambers of the pump are drained by passages 55, 56 connected to the oil equaliser passage 24. Fig. 1 shows the valve in position to supply oil to the " raise " end of the operating cylinder through the pipe 32, oil being returned through pipe 31 direct to the pump intake 19 through ports 44, 45 and the bore 42, and also to the tanks via the recess 39 and passages 27, 22a, 22. Fig. 3 shows the valve in position to supply the " lower " end of the operating cylinder through the pipe 31, oil being returned through pipe 32 to the pump intake only, any excess or deficiency of oil in the closed system being accommodated by the check valve 26 or the orifice 54. In the " hold position " (not shown) the pipes 31, 32 are sealed-off by the recesses 39, 41 and oil circulates back to the tanks only through the bore 42 and the passages 27, 22, 22a. In the "float " position (not shown) both ends of the operating cylinder are connected to one another, to the pump delivery and to the tanks. Specifications 519,151 and 576,624 are referred to.