GB1172954A - Improvements in and relating to Power Presses - Google Patents

Abstract

1,172,954. Protecting presses. E. W. BLISS CO. June 11, 1968 [June 15, 1967], No. 27647/68, Heading F1P. A part of a press subjected to the press load cycle, e.g. a reciprocating slide 10, is provided with an overload protection system comprising a liquid filled chamber 34 arranged to be vented if the pressure therein exceeds a predetermined value, the value being different for different portions of the load cycle. The chamber 34 is defined between a cylinder 12 arranged to carry a die and a piston 26 disposed in the cylinder 12, the piston and cylinder being reciprocated as a unit by a crank-shaft 25 and connecting rod 16. The relief of pressure in the chamber 34 causes the slide to collapse and is also arranged to stop the press. A pump 52 supplies the chamber 34 through a check valve 55 and a line 53. Connected in the line 53 are a number of pressure switches 70-74 forming part of an electrical circuit, Fig. 2 (not shown), controlling the operation of solenoid valves 62, 63 in a vent line 57, 61 containing a relief valve 58. If a solenoid valve opens this allows the relief valve to open. The pressure switches 72-74 are set to operate at different pressures and are associated with cams 75, 76, 77 on a cam-shaft 78 rotatable in unison with the crank-shaft 25. The cams co-operate with the switches to render them effective in controlling the solenoid valves 62, 63 only during a predetermined portion of the press cycle. Pressure switch 71 operates in response to a full overload condition occurring at any point in the press cycle.