| 摘要 |
PROBLEM TO BE SOLVED: To simplify a whole device even in case of quickly changing a set overload pressure. SOLUTION: A hydraulic pressure chamber 3 for overload absorption is arranged in a slide 2 of a machine press 1, when a pressure in the hydraulic chamber 3 exceeds a set overload pressure, an overload prevention valve 10 to relieve the overload pressure is arranged. An valve closing spring 37 and a pneumatic cylinder 38 to press a relief member 30 of the overload prevention valve 10 to a relief valve seat 28 are arranged. The pressing force of the valve closing spring 37 is set to the pressing force to prevent the overload of rotation transmission system T of a main gear, etc., of the machine press 1. A supply/ discharge means 41 to supply/discharge a compressed air of a prescribed pressure for an pneumatic pressure actuation chamber 40 of the pneumatic cylinder 38 is arranged, a pressure reducing valve 43, a supply/discharge selector valve 44 and a variable throttle valve 46 are in order from an up-strem side arranged to a pneumatic pressure supply passage 42 of the supply/discharge means 41.
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