GB1194623A - Hydraulic Ram Apparatus - Google Patents

Abstract

1,194,623. Hydraulic presses. NORTON TOOL CO. Ltd. 14 April, 1969 [22 April, 1968], No. 18826/68. Heading B5F. [Also in Division F1] An hydraulic press ram 10 is moved rapidly towards a workpiece by oil expelled from a cylinder 53 connected by a line 18, 19 to the ram, the oil being expelled by a differential area piston 50 driven by oil supplied to a line 35 from a pump 25; when the pressure in the line 18 rises due to the ram engaging the workpiece a pressure operated changeover valve 41 opens to allow the pump supply in line 35 to flow directly to the ram through lines 44, 38, 18. The ram is controlled by a valve 29 connected to the pump through a line 27. Rotation of a lever 32 either directs the pump output to the line 33, 35, or to a line 21 connected to the ram return chamber 20, the line unpressurized being connected to exhaust. When a foot pedal 74 is depressed, links 72, 73 move the lever 32 to the position shown wherein oil flows through the line 35 to a working chamber 47 in the differential area piston 50. The area relationships of the piston 50 are such that a small volume supply from the pump 25 causes a large volume to be expelled from the cylinder space 54 to the ram. During the stroke oil is drawn into the space 55 behind the piston 50 through non- return valves 56 and this oil prevents retraction of the piston 50 when the line 18 is subsequently pressurized directly by the pump 25. The return stroke is started either by releasing the pedal 74 so that a spring 75 returns the control valve lever 32, or by arranging for the automatic collapse of the toggle links 72, 73 by a device 63 operable in response to the occurrence of a predetermined maximum ram pressure. During the return stroke oil in excess of the cylinder space 54 and also oil in the space 55 is exhausted through non-return valves 57, 61. A repeat stroke may be started automatically by arranging for a ring 14 on the ram to lift a rod 80 and thus operate the valve 29 through linkage 77, 76. In a second embodiment, Fig. 2 (not shown), the cylinder 53 is of a different construction and is protected from the full ram pressure by a valve in the line 18.