Patent GB-944167-A (GB)
Title: Improvements in or relating to hydraulic circuits
IPC: F15B13/04
Filed: 1960-03-03
Abstract: 944,167. Valves. H. TEVES, E. A. TEVES, and M. TAUNSEND, [trading as ALFRED TEVES MASCHINENUND ARMATUREN FABRIK KOMM. GES.]. March 3, 1960 [March 3, 1959], No. 7582/60. Heading F2V. [Also in Division F1] An hydraulic system comprises a multipleway piston valve 2, Fig. 2, and flow-throttling means 3 co-operating with a pilot piston valve 5 which is disposed in a line connecting the multiple-way valve and a motor 1 to a pressure source 9 or a tank 10. The throttling means is hydraulically connected to opposed faces 12, 13 of the pilot piston valve 5 and mechanically connected to the spool of the multiple-way valve 2. When the multiple-way valve 2 is in its neutral position, the throttling means is positioned so as not to restrict the flow of fluid therethrough so that the pressure acting on the opposed faces 12, 13 is equal and the piston is urged to a position by a spring 6 wherein the flow from the valve 2 is unrestricted and passes to the tank 10. When the spool of the valve is manually moved in one direction or the other from its neutral position, the throttling means 3 is also moved to close a main passage and gradually open a restricted passage to apply a pressure differential across the piston 5 which moves to control the flow to the tank in such a way that the piston of the motor 1 moves at a constant speed. The throttling means and pilot piston valve may be in the supply line from the pressure source, which may be a pump or accumulator, to the multiple-way valve, or the throttling means may be in the return line and the pilot piston valve control a by-pass line from the pump to the tank. Excess pressure is relieved by a valve 11. The multiple-way valve 2, throttling means 3 and pilot piston valve 5 may be incorporated in a housing 18, Fig. 5, having a bore 24 connected by a line 34 to the pump 9, and lines 32, 33 to the motor 1. The spool 25 of the multiple-way valve is movable in the bore by a linkage 35 to selectively connect the pump to one side or the other of the motor and is formed with a sleeve 49 slidable on a stationary member 20, the sleeve having orifices 46, 47, 48, which co-operate with bores 54 in the member 20 to form the throttling means 3. The piston 5 is hollow, slidable in the spool 25, and urged against a circlip 40 by a spring 6. The piston has bores 41 communicating with bores 43 on the spool 25 and a groove 31 in the bore 24. In the neutral position shown, the fluid from the pump passes through the line 34 to the groove 31, through the bores 41, 43 to the interior of the piston 5 and member 20, through bores 54 and orifices 46, which do not restrict the flow, into a chamber 19 and through ports 45 to the return line 8 leading to the tank 10. The pressure in the chamber 19 is communicated by a chamber 22, line 23, chamber 21 and ports 39 to the face 13 of the piston 5, and, since the pressure on the face 13 is equal to that on the face 12, the spring 6 maintains the piston against the circlip and the piston does not control the flow of fluid. Movement of the spool 25 by the linkage 35 in one direction or the other, connects the pump to one side of the motor, the discharge from the other side passing through the groove 31 and bores 41, 43 to the interior of the piston 5 and member 20 and through the bores 54 and the orifices 47 or 48, depending on the direction of movement of the spool. The orifices 47, 48 are formed in a spiral on the sleeve 49 and restrict the flow of fluid to the chamber 19 and line 8 by an amount depending on the degree of movement of the spool 25. The consequent reduction in pressure in chamber 19 is communicated to the face 13 of the piston 5 and the resulting pressure differential across the piston moves the latter against the spring 6 so as to control the flow of fluid from the motor and maintain the movement of the piston constant.