GB512010A - Prefill valves for hydraulic presses - Google Patents

Abstract

512,010. Hydraulic presses. CANNON, E. July 12, 1938, No. 20683. [Class 69 (ii)] A prefill valve for hydraulic presses comprises a reciprocating valve element adapted to open or close communication between the ram chamber and a source of supply of liquid at substantially atmospheric pressure, a valveclosing chamber connected to a source of supply of liquid at relatively high pressure, and a passage for passing liquid from the valve-closing chamber to the ram chamber to establish working pressure therein, the said passage being of such restricted area that, as liquid passes therethrough toward the ram chamber, sufficient back pressure is created in the valve-closing chamber to move the said valve element to its closed position. In an arrangement, Fig. 1, having a central tube 29 for introducing pressure liquid into a quick advance chamber in the ram, the prefill valve 16 is normally held open by a spring 24; to close the valve, liquid is introduced into the valve-closing chamber 23, communication between the latter and the work chamber 18 being through passages 35 of restricted area in the bore of the valve 16 surrounding the tube 29. In a modification, Fig. 3 (not shown), means separate from the prefill valve structure are employed for effecting rapid advance of the ram In a further modification, Fig. 5, the valve 16 is closed by the admission of liquid to chamber 47 and opened by admission to chamber 48; a balance chamber 46 communicates through bore 49 in the valve with the working chamber 18 and the restricted passages 54 connect the valveclosing chamber 47 with the bore 49. Specifications 509,248 and 509,925 are referred to.