Dispositif de contrôle de la décompression du fluide de travail dans les machines hydrauliques telles que presses et machines équipées dudit dispositif

摘要

1,190,703. Hydraulic press. G. S. FORICHON. 31 Jan., 1968 [17 Feb., 1967], No. 5036/68. Heading B5F. A bleed device, for decompressing the working fluid in an hydraulic machine at the end of the working stroke of its ram, comprises an hydraulically damped relief valve seated in a chamber connected directly to the ram actuating chamber of the machine, the valve being biased to the closed position by a spring. The valve is initially lifted from its seat to vent the pressure fluid to reservoir either by manometric action when the pressure in the ram actuating chamber has reached a desired level, or by control rod action when the ram has reached the end point of its stroke, and is of such a shape that, once lifted, the fluid flowing past the seat quickly entrains the valve further away from the seat. This movement causes a cam carried by the valve to actuate switch gear which reverses the action of the pump thus initiating the return stroke, the relief valve being closed by the spring to terminate the bleed when the pressure in the ram actuating chamber has been lowered sufficiently. In the press shown in the figure, the relief valve 1, which is biased against seat S by spring 10 and the inbalance of pressure acting upon its various surfaces, carries cap 11 connected to rod 12, itself provided at one end with an adjustable nut adapted to be engaged by table 6 carried by the working piston 5. A spring biased pilot valve 23 connects the space above the valve seats to the space below it. For manometric operation, see Fig. 3 (not shown), the nut 13 is adjusted to stay clear of table 6 at all times and the spring 24 of valve 23 is adjusted so that valve 23 opens at the pressure developed in chamber 4 at the end of the stroke of the piston. When, at the end of the stroke, the pilot valve opens, pressure fluid flows through tube 36 to act upon shoulder 13 of the relief valve thus causing that valve to lift from its seat. The valve is immediately entrained downward and cap 11 actuates switch gear 29 thus retracting the piston, the relief valves subsequently closing upon the relief of pressure in chamber 4. For control rod operation, spring 24 is adjusted to keep valve 23 shut at all times, and nut 13 is adjusted so that it is engaged by table 6 at the end of the stroke of the piston. Upon engagement of the table with the nut the valve 1 is pulled slightly open and is subsequently entrained and further opened as before thus operating the switch gear to return the piston.