Patent ID: 7370569
Filing Date: 2008-05-13
Classification: B30B,F03C,F15B

Abstract:
1. A hydraulic drive mechanism for a blanking or forming machine comprising a working cylinder having several pressure chambers, the piston of which acts directly or indirectly on a workpiece to be processed, wherein at least one pressure chamber of the working cylinder for retracting and extending the piston is adapted to be subjected to a tank pressure or a supply pressure via a continuously adjustable valve, and comprising a valve assembly arranged upstream of the continuously adjustable valve, whereby an inlet port (E) of the continuously adjustable valve may be subjected to a higher or lower supply pressure, wherein the valve assembly comprises a switching valve adapted to be switched over between a basic position and a switching position in dependence on the load pressure at the working cylinder, and wherein, in the basic position, the switching valve connects an inlet port of the continuously adjustable valve with the low-pressure source (ND), and, in the switching position, the switching valve blocks the connection to the low-pressure source and connects the inlet port with the high-pressure source (HD).