Patent ID: 7908963
Filing Date: 2011-03-22
Classification: B21J,B25B

Abstract:
1. A method of operating a hydraulic pressing unit comprising: providing a pressing unit having a hydraulic pump, a moving part, a stationary part and a return valve; filling a hydraulic chamber in said pressing unit with hydraulic medium from a supply chamber, said hydraulic chamber being capable of being in fluid communication with said return valve along a flow path; displacing the moving part into a pressing position by the buildup of a hydraulic pressure within said hydraulic chamber; automatically moving said moving part from the pressing position into an end position under the action of a restoring spring; wherein when said return valve is in an open position in which hydraulic medium is allowed to flow through said return valve, said return valve moves to a closed position in which the flow of hydraulic medium is prevented through said return valve after the hydraulic pressure acting on the return valve drops below a certain pressure as a result of the hydraulic medium flowing away from said return valve; and wherein means are provided in the flow path between said return valve and said moving part for causing the hydraulic medium to flow away from said return valve.