A gas spring comprising: a cup-shaped body; a movable piston which is inserted in an axially slidable manner in the cup-shaped body and is coupled to the cup-shaped body in a fluid-tight manner, so as to delimit a variable-volume closed chamber adapted to contain a pressurised gas; and a safety plug provided with a shank which extends in pass-through manner in the bottom wall of the cup-shaped body, and protrudes cantilevered within the cup-shaped body so that its distal end can be reached/struck by the movable piston in the case of overtravel; the distal end of the shank having a substantially tubular structure that directly communicates with the closed chamber.

A plurality of hydraulic cylinders capable of adjusting height direction positions of a plurality of die-cushion pins that are inserted into a plurality of die-cushion pin holes formed in a bolster, respectively, are arranged in a lattice state on a cushion pad, and the hydraulic cylinder faced with a die-cushion pin located below a projection surface of a blank holder in the plurality of hydraulic cylinders is selected. Then, by independently adjusting a height direction position of a piston rod of each of the selected hydraulic cylinders, respectively, the shim adjustment of substantially each of the die-cushion pins is realized.

A plurality of hydraulic cylinders capable of adjusting height direction positions of a plurality of die-cushion pins that are inserted into a plurality of die-cushion pin holes formed in a bolster, respectively, are arranged in a lattice state on a cushion pad, and the hydraulic cylinder faced with a die-cushion pin located below a projection surface of a blank holder in the plurality of hydraulic cylinders is selected. Then, by independently adjusting a height direction position of a piston rod of each of the selected hydraulic cylinders, respectively, the shim adjustment of substantially each of the die-cushion pins is realized.

There is provided a die cushion device that includes a cushion pad, a hydraulic cylinder configured to lift the cushion pad, and a hydraulic closed circuit connected to a die cushion pressure creation chamber of the hydraulic cylinder. The hydraulic closed circuit includes a pilot drive type logic valve that is operable as a main relief valve at the time of the die cushion operation, and a pilot relief valve configured to create pilot pressure for controlling the logic valve. Hydraulic oil is filled in the hydraulic closed circuit, in a pressurized manner, and the hydraulic oil in the hydraulic closed circuit is pressurized by only die cushion force applied from the cushion pad through the hydraulic cylinder, in one cycle period of the cushion pad.

There is provided a die cushion device that includes a cushion pad, a hydraulic cylinder configured to lift the cushion pad, and a hydraulic closed circuit connected to a die cushion pressure creation chamber of the hydraulic cylinder. The hydraulic closed circuit includes a pilot drive type logic valve that is operable as a main relief valve at the time of the die cushion operation, and a pilot relief valve configured to create pilot pressure for controlling the logic valve. Hydraulic oil is filled in the hydraulic closed circuit, in a pressurized manner, and the hydraulic oil in the hydraulic closed circuit is pressurized by only die cushion force applied from the cushion pad through the hydraulic cylinder, in one cycle period of the cushion pad.

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.

Provided is a cushion pin which applies sufficient supporting force to a blank holder of a press molding apparatus even if the number of cushion pins and an arrangement region are restricted. A cushion pin (1A) has a cylindrical main body section including a plurality of cylindrical members (2) and annular members (3). The cylindrical members (2) are arranged in series in an axial direction, and the annular members (3) are disposed between the adjacent cylindrical members (2). A rod member (4) and a coil spring (5) are disposed in each the spring chambers of the main body section. The rod member (4) includes a rod-shaped part (4b) and a flange part (4a). The rod-shaped part (4b) has a diameter allowing the rod-shaped part (4b) to slidably penetrate through an opening (3a) of the annular member (3). The coil spring (5) biases the flange part (4a).

Provided is a cushion pin which applies sufficient supporting force to a blank holder of a press molding apparatus even if the number of cushion pins and an arrangement region are restricted. A cushion pin (1A) has a cylindrical main body section including a plurality of cylindrical members (2) and annular members (3). The cylindrical members (2) are arranged in series in an axial direction, and the annular members (3) are disposed between the adjacent cylindrical members (2). A rod member (4) and a coil spring (5) are disposed in each the spring chambers of the main body section. The rod member (4) includes a rod-shaped part (4b) and a flange part (4a). The rod-shaped part (4b) has a diameter allowing the rod-shaped part (4b) to slidably penetrate through an opening (3a) of the annular member (3). The coil spring (5) biases the flange part (4a).

The die cushion device includes a first hydraulic cylinder for supporting a cushion pad, and a first hydraulic circuit for driving the first hydraulic cylinder. The first hydraulic circuit is a hydraulic closed circuit including a logic valve connected between a die cushion pressure generation line and a system pressure line, and a hydraulic pump driven by a first servomotor for applying a pilot pressure to the logic valve. The first controller controls the first servomotor (pilot pressure) based on a first pressure command corresponding to the die cushion force and the pressure detected by the first pressure detector to control the pressure in a lower chamber of the first hydraulic cylinder so that the pressure is equal to a pressure corresponding to the first pressure command.

The die cushion device according to the present invention includes a first hydraulic cylinder and a second hydraulic cylinder that are independently and simultaneously controlled. When a cushion pad is pre-pressurized, pressure control is performed on the first hydraulic cylinder via a first hydraulic circuit so that a pressure in a lower chamber of the first hydraulic cylinder is pre-pressurized to a preset pressure, and position control is simultaneously performed on the second hydraulic cylinder via a second hydraulic circuit so that the cushion pad is held in the die cushion standby position. A force with which the first hydraulic cylinder moves the cushion pad upward is balanced with a force with which the second hydraulic cylinder moves the cushion pad downward (a force for holding the die cushion standby position).