A double-blank detecting apparatus for a press machine that is provided with a die cushion apparatus and is configured to form blanks one by one automatically and repeatedly. The double-blank detecting apparatus includes: a position signal acquiring unit configured to acquire a slide position signal indicating a position of a slide of the press machine; a load signal acquiring unit configured to acquire a die cushion load signal indicating a die cushion load generated on a cushion pad of the die cushion apparatus; and a double-blank detector configured to detect a state in which a plurality of blanks are stacked as a double blank based on the slide position signal acquired by the position signal acquiring unit and the die cushion load signal acquired by the load signal acquiring unit.

A double-blank detecting apparatus for a press machine that is provided with a die cushion apparatus and is configured to form blanks one by one automatically and repeatedly. The double-blank detecting apparatus includes: a position signal acquiring unit configured to acquire a slide position signal indicating a position of a slide of the press machine; a load signal acquiring unit configured to acquire a die cushion load signal indicating a die cushion load generated on a cushion pad of the die cushion apparatus; and a double-blank detector configured to detect a state in which a plurality of blanks are stacked as a double blank based on the slide position signal acquired by the position signal acquiring unit and the die cushion load signal acquired by the load signal acquiring unit.

A metal stamping tool includes a hybrid magnetorheological-nitrogen spring including a housing having an interior wall defining an interior volume. A fixed divider separates the interior volume into a nitrogen gas chamber and a magnetorheological fluid chamber. A piston extends into both the nitrogen gas chamber and the magnetorheological fluid chamber. The piston defines a magnetorheological fluid gap within the magnetorheological fluid chamber. An electric coil positioned adjacent the fluid gap to apply a magnetic field to magnetorheological fluid within the fluid gap when the electric coil is energized.

A metal stamping tool includes a hybrid magnetorheological-nitrogen spring including a housing having an interior wall defining an interior volume. A fixed divider separates the interior volume into a nitrogen gas chamber and a magnetorheological fluid chamber. A piston extends into both the nitrogen gas chamber and the magnetorheological fluid chamber. The piston defines a magnetorheological fluid gap within the magnetorheological fluid chamber. An electric coil positioned adjacent the fluid gap to apply a magnetic field to magnetorheological fluid within the fluid gap when the electric coil is energized.

A cushion pin pressure equalizing device that can absorb a variation in height of a plurality of cushion pins and control a die cushion load highly accurately, a die cushion device, and a cushion pin pressure equalizing method are provided. An initial pressure in ascending-side pressurizing chambers of a pressure equalizing hydraulic cylinder group for absorbing a variation in height of cushion pins is controlled so as to be an appropriate pressure. The variation in height of the plurality of cushion pins can be absorbed within a shortest stroke of a slide after the slide comes into collision with a cushion pad so as to equalize die cushion loads that are applied individually to the cushion pins and a target die cushion load can be generated within the shortest stroke of the slide, whereby a response to application of the die cushion load can be stabilized without excessive delay.

A cushion pin pressure equalizing device that can absorb a variation in height of a plurality of cushion pins and control a die cushion load highly accurately, a die cushion device, and a cushion pin pressure equalizing method are provided. An initial pressure in ascending-side pressurizing chambers of a pressure equalizing hydraulic cylinder group for absorbing a variation in height of cushion pins is controlled so as to be an appropriate pressure. The variation in height of the plurality of cushion pins can be absorbed within a shortest stroke of a slide after the slide comes into collision with a cushion pad so as to equalize die cushion loads that are applied individually to the cushion pins and a target die cushion load can be generated within the shortest stroke of the slide, whereby a response to application of the die cushion load can be stabilized without excessive delay.

According to the die cushion apparatus of a press machine and the die cushion controlling method of the present invention, in holding the cushion pad on standby at a desired standby position, it is possible to hold the cushion pad on standby in parallel with the lower faces of the dies mounted to the slide, and if the lower faces of the dies are inclined, it is possible to hold the cushion pad on standby in the state of being inclined. Through this configuration, it is possible to easily allow the material to come into contact with the lower faces of the dies from the beginning of the die cushion force control (beginning of the collision), and also possible to smoothen the die cushion action in the plane, thereby enhancing the formability.

According to the die cushion apparatus of a press machine and the die cushion controlling method of the present invention, in holding the cushion pad on standby at a desired standby position, it is possible to hold the cushion pad on standby in parallel with the lower faces of the dies mounted to the slide, and if the lower faces of the dies are inclined, it is possible to hold the cushion pad on standby in the state of being inclined. Through this configuration, it is possible to easily allow the material to come into contact with the lower faces of the dies from the beginning of the die cushion force control (beginning of the collision), and also possible to smoothen the die cushion action in the plane, thereby enhancing the formability.

A cushion pin device for a press having a cushion pad in which a blank holder is seated on the top thereof outside a lower mold, and locks a blank holder to an upper mold while pressurizing an edge of a molded panel, includes: a cushion support disposed below the cushion pad, a cushion cylinder connected with a lower part of the cushion pad to move up or down the cushion pad from the cushion support, a linear scale mounted between the cushion pad and the cushion support to measure the position of the cushion pad, a main pressure control unit that keeps internal pressure of each cushion cylinder similarly, and a sub pressure control unit that is interconnected with the main pressure control unit so as to control the locking position of the cushion pad when each cushion cylinder operates.

A cushion pin device for a press having a cushion pad in which a blank holder is seated on the top thereof outside a lower mold, and locks a blank holder to an upper mold while pressurizing an edge of a molded panel, includes: a cushion support disposed below the cushion pad, a cushion cylinder connected with a lower part of the cushion pad to move up or down the cushion pad from the cushion support, a linear scale mounted between the cushion pad and the cushion support to measure the position of the cushion pad, a main pressure control unit that keeps internal pressure of each cushion cylinder similarly, and a sub pressure control unit that is interconnected with the main pressure control unit so as to control the locking position of the cushion pad when each cushion cylinder operates.