GB1329401A - Hydraulic ram machine - Google Patents

Abstract

1329401 Press brakes PACIFIC PRESS & SHEAR CORP 24 Feb 1972 [22 March 1971] 8668/72 Heading B3E In a bending press, the ram 1 is driven by two hydraulic piston and cylinder motors 3, 5 normally in series hydraulic circuit with a pump 21, and means is provided to reduce the ram speed towards the end of its stroke, to prevent whipping of the workpiece. In the apparatus described, the initial travel of the ram in its working stroke is at fast speed, valves 70, 74, 98, 90 and 94 being set by their respective solenoids and pilot valves to make operative the hydraulic circuit shown in heavy lines. At about the point in the working stroke where the work is engaged, a cam adjustably mounted on the ram operates a micro-switch on the frame to open valve 70 and close valve 98 so that fluid from motor 5 passes to reservoir 25, to decrease ram speed to normal (Fig. 3, not shown). At a further point in the working stroke, another cam operates a micro-switch to open valve 74, so that part of the pump output is returned to reservoir through a restriction 79, reducing the ram speed still further (Fig. 5, not shown). Closure of a further micro-switch ends the working stroke by closing valves 70, 74, and 90, and opening valves 98 and 94 to effect the return stroke, ended by closure of valve 98. A relief valve assembly 81 includes a check valve 86 adjustable for maximum pump output pressure, and a further check valve 184 is adjustable to limit the pressure for any item of work without disturbing the setting of valve 86. The valves can be calibrated by a pressure gauge 145, a push button closing valves 74, 98, 90, 148. An hydraulic power take-off is available on line 147 by operation of valve 148.