Patent GB-540719-A (GB)
Title: Improvements in or relating to hydraulic driving mechanism
IPC: B23G1/18
Filed: 1940-03-20
Abstract: 540,719. Hydraulic-machines. OLAH, G. March 20, 1940, No. 12184/41. Divided out of 540,684. [Class 69 (ii)] A hydraulically controlled driving-mechanism for a machine tool unit 24 comprises a hydraulic motor the cylinder 26 of which moves with the unit 24 on the base 25, and in order to prevent leakage around the piston 27 or in the control elements of the motor a circumferential groove or " screen " 30 is formed in the piston and this has connection with a conduit 32 which is connected to a "screen" valve 34 which tends to keep the pressure differential between the supply or metering circuit 33 and the "screen" circuit 32 practically nil. The liquid is supplied from a reservoir 3 by a pump 2 at a constant pressure determined by a relief valve 6 and at a constant viscosity, and the liquid normally passes through a metering throttle 36, valve 1, and conduit 33 through the piston to a chamber 29 to move the unit 24 from right to left. As shown the throttle 36 is byepassed by a throttle 361 and a quick feed valve 37 which is maintained in the position shown by a spring but can be moved to cut out the throttle 361 by a cam or the like. In the closed position of valve 37 leakage is prevented by connections from the circuit 32 with screen grooves 57 on both sides of the valve outlet 56. The pressures in the circuits 32, 33 are maintained substantially equal by means of a valve 34 comprising a chamber 40 fitted with a diaphragm 39 adapted to control the flow of liquid through an orifice 42 to exhaust. The conduit 33 is connected to the upper side of the chamber 40 and the lower side is connected at 43 to the circuit 32 and is connected by a throttle 44 to the supply conduit 2. In a modified form of valve, Fig. 2a, the diaphragm 39 is replaced by a plunger 121 in a chamber 123 connected to the circuit 33, and the rim of the plunger is arranged in a chamber 124 connected to the screen circuit 43, and controls orifices 42, 125 connected to the low pressure and supply conduits 3, 4 respectively. The screen circuit is also connected to a feed stabilizator valve 35 which tends to keep constant the pressure differential in the metering throttle 36 independently of the load on unit 24. The valve 35 comprises a piston with heads arranged in chambers 47, 48 the pressures in which determine the position of the piston and therefore the extent of throttling of a passage 461 connected to the conduit 31 leading from the chamber 28. The chamber 48 is connected by conduit 38 to the supply conduit 4, and the chamber 47 to the " screen " conduit 32, and the passage 461 leads to the reservoir 3 via conduit 5, or via conduit 51 to a conduit 38, according to the setting of the valve 1 which determines the direction of motion of the unit 24. The metering resistance 36 may be constructed to give a pre-determined constant or an adjustable value of throttling resistance, and may be in the form of a plug formed with a helical groove in its outer surface, or of an adjustable plug which is arranged to fit adjustably in a tube integral with a wider chamber which exerts no throttling effect. Or a plug 62, Fig. 5, Provisional Specification, formed with a tapered helical groove 68 closely fits a passage connecting two wider passages, and by adjusting the longitudinal position of the plug 62 the resistance of the liquid in passing from one passage to another can be varied. In a modified form the locus of the apices of the helical grooves may lie in a curved line 69.