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Abstract

A platen press and method for operating a platen press that includes a fixed upper bolster (10) and a lower movable bolster (12) between which is positioned a plurality of platens (14). Fluid operated jack cylinders (17) are used to move the movable bolster to a closed position whereas separate main or clamping cylinders (16) apply a clamping force to the platens when the press is closed. A first source of pressurized fluid (104, 104') supplies pressurized fluid at first pressure to the jack cylinders during a press closing step. A second source of pressurized fluid (134) at a second pressure, lower than the first pressure prefills (via prefill valves (146)) the main cylinders during the closing step. When the press is closed, the communication of the second source of pressurized fluid to the main cylinders is terminated and the first source of pressurized fluid is communicated to the main cylinders in order to generate the clamping force. The first source of pressurized fluid is a high pressure low volume source such a positive displacement pumps (104, 104') used in connection with an accumulator (172). The second pressurized source is a high volume, low pressure source such as a centrifugal pumps (134), an accumulator (200) fed by a fluid pump (204) or a flow intensifier operated by fluid pump.

First Claim