GB595147A - Improvements in and relating to hydraulic piston type control valves - Google Patents

Abstract

595,147. Valves; hydraulic presses. TOWLER, J. M., and TOWLER, F. H. Feb. 5, 1945, No. 2805. [Classes 69 (ii) and 135] An hydraulic control valve of the piston type is movable against loading means by manuallyoperable means to supply pressure liquid to a press or other hydraulic cylinder and when the pressure in the cylinder attains a predetermined value or the press ram reaches a certain position the manually operable means is automatically disconnected from the valve plunger which returns to its original position under the action of the loading means. Figs. 1 and 2 show the invention applied to the piston valve described in Specification 557,340. The hand lever h is secured to a transverse shaft 12 passing into the casing g. A short lever 13 with a pin 14 engaging a groove 15 in the valve plunger b is pivotally supported at 17 on the inner end of the shaft 12 and is normally pressed towards the valve plunger by a spring plunger 18. The pin 14 is disengaged from the groove 15 to allow the loading spring 16 to return the valve to the position shown in Fig. 1 by fluid pressure acting below a plunger 21 which actuates a round-ended lever 19 rigid with the lever 13. Passages 25, 26 permit the pressure liquid to escape when the plunger 21 has completed its stroke, the magnitude of which is governed by a distance piece 24. The lever h carries a spring- urged detent 27 engaging notches in a quadrant 28. Where the release of the valve plunger is dependent upon the attainment of a predetermined pressure in the press cylinder, the latter pressure acts on a master control valve such as that described in Specification 566,240 and the master control valve controls the application of pressure to the plunger 21. Where the release of the valve plunger depends upon the position of the press ram, the supply and exhaust of pressure fluid beneath the plunger 21 is controlled by a small leveractuated valve supplied from the press supply pipe and operated by a tappet on the press ram. To prevent the valve plunger from sticking when released, it is given an initial push by a further plunger to which pressure liquid is admitted in parallel with the supply to the plunger 21. The latter, however, is more lightly loaded and consequently operates first. The invention is equally applicable to valves controlling single acting devices. Specification 573,440 is referred to in the Provisional Specification.