A hot press apparatus includes a first die part 2 and a second die part 3, and a control unit 9. At least one of the first and second die parts 2 and 3 includes a recess 3a in the surface facing the other die part in the direction of pressing. A movable die part 4 is provided in the recess 3a. The control unit 9 controls the movable die part 4 such that the bottom-dead-center holding period, for which the first and second die parts 2 and 3 are at the bottom-dead center, includes an abutment period for which the movable die part 4 abuts the metal sheet B and a non-abutment period for which the movable die part does not abut the metal sheet B.

A hot press apparatus includes a first die part 2 and a second die part 3, and a control unit 9. At least one of the first and second die parts 2 and 3 includes a recess 3a in the surface facing the other die part in the direction of pressing. A movable die part 4 is provided in the recess 3a. The control unit 9 controls the movable die part 4 such that the bottom-dead-center holding period, for which the first and second die parts 2 and 3 are at the bottom-dead center, includes an abutment period for which the movable die part 4 abuts the metal sheet B and a non-abutment period for which the movable die part does not abut the metal sheet B.

A balanced panel punch drive system. The system includes a main hydraulic drive including an outer casing forming an internal housing and a main piston slidably disposed within the internal housing. A main fluid chamber, a first output chamber and a second output chamber are formed within the internal housing. A pump is fluidly connected to the main fluid chamber by an input line. A first die hydraulic cylinder and a second die hydraulic cylinder each have an outer casing forming an internal housing and a die piston slidably disposed within the internal housing. An opening is formed through an end of the outer casing sized to receive a distal end of the die piston therethrough. A first output line fluidly connects the first output chamber to the first die hydraulic cylinder and a second output line fluidly connects the second output chamber to the second die hydraulic cylinder.

A balanced panel punch drive system. The system includes a main hydraulic drive including an outer casing forming an internal housing and a main piston slidably disposed within the internal housing. A main fluid chamber, a first output chamber and a second output chamber are formed within the internal housing. A pump is fluidly connected to the main fluid chamber by an input line. A first die hydraulic cylinder and a second die hydraulic cylinder each have an outer casing forming an internal housing and a die piston slidably disposed within the internal housing. An opening is formed through an end of the outer casing sized to receive a distal end of the die piston therethrough. A first output line fluidly connects the first output chamber to the first die hydraulic cylinder and a second output line fluidly connects the second output chamber to the second die hydraulic cylinder.

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.

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).

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).