GB798748A - Improvements in stamps or hammers - Google Patents

Abstract

798,748. Power hammers. MASSEY, Ltd., B. & S., PICKWORTH, P. C. N., and BAINBRIDGE, F. March 19, 1956 [March 19, 1955], No. 8081/55. Class 83 (4). A drop stamp or hammer has its tup 10a raised by hydraulic fluid supplied continuously beneath a piston 12a and this fluid is also admitted above the piston to effect the downstroke. A pump 15a, preferably of constant delivery, driven by an electric motor draws liquid from a tank 14a and delivers it through pipe 18a to the space below piston 12a which space communicates with an air cushion accumulator 16a. For raising the tup an exhaust valve 22a is opened whereby the liquid above the piston is returned to the tank through pipe 23a. Near the end of the upstroke the exhaust valve is closed and an inlet valve 21a is opened to admit pressure liquid from pipe 20a and thereby cushion the end of the stroke. Inlet valve 21a may then be closed to retain the tup at its top position or it may remain open whereby the differential pressure on the piston assists gravity in performing a further blow or blows. The inlet valve is closed and exhaust valve opened at the end of the downstroke or earlier if lighter blows are required. Variation of the blows may alternatively be effected by shortening the stroke- or by throttling the liquid supply through the inlet valve 21a. A by-pass or unloading device for the pump is operated in response to the accumulator pressure. The inlet and exhaust valves 21a, 22a may be operated manually or automatically by the tup movement or changes in fluid pressure. For performing slow downstrokes during setting, pressure liquid is supplied above the piston through a pipe 28a controlled by a small hand valve 29a. A second hand valve 30a permits exhaust for slow raising of the tup. In another embodiment the extension rod 26 above the piston is omitted.