| 摘要 |
PROBLEM TO BE SOLVED: To provide a press brake for improving the accuracy in upper and lower positioning of a die by reducing the effects by the difference of bending length, change of oil temperature and deformation of a frame. SOLUTION: When bending work is executed to a plate by cooperation with a punch P and a die D, because a cutoff valve 17 is provided on one side of a lower table 7 or an upper table 9 and a critically positioning pin 21 for deciding a critical position on other side, the flow of hydraulic oil is interrupted by pushing a valve member with the critical positioning pin 21 through the pin 19 of the cutoff valve 17 when the table reaches the critical position. At this time, a cylinder which is integrally provided to the valve member is operated with the pressurized hydraulic oil and the hydraulic oil is interrupted by surely moving the valve member 45. When the supply of the hydraulic oil to hydraulic cylinders 5L, 5R is interrupted with the cutoff valve 17, the hydraulic oil which is fed from a pump is directly returned into a tank by the action of a relief valve.
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