Importance

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Abstract

A method for controlling a drive for a hydraulic press employed for at least one of forming and cutting sheets of metal. The method involves a press comprising: a press ram and at least one piston-cylinder unit operatively connected to the press ram and including a drive piston having an upper side and a lower side, the drive piston further comprising an upper cylinder chamber communicating with the upper side, and a lower cylinder chamber communicating with the lower side. The method comprises the step of pressurizing the drive piston with hydraulic medium on at least one of its upper side and its lower side for driving the press ram. The step of pressurizing comprises the steps of: supplying a system pressure network including pressure lines operatively connecting the upper cylinder chamber and the lower cylinder chamber with hydraulic medium at a predetermined maximum operating pressure from a hydraulic accumulator unit thereby equalizing pressures between the upper side and the lower side; and producing a downward movement of the press ram by extracting hydraulic medium from the lower cylinder chamber with a first hydraulic motor having an adjustable swivel angle and thereafter feeding the hydraulic medium to the upper cylinder chamber to pressurize the upper cylinder chamber thereby effecting a controlled volumetric flow of hydraulic medium through the pressure network.

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First Claim