Punch press

A punch press comprising:

• a frame;
• a tool holder arranged on the frame, for removably supporting at a process position a tool set comprising a punch and a die;
• a ram supported on the frame, for striking the punch so as to punch a workpiece placed between the punch and the die;
• means arranged in the frame, for storing a plurality of tool sets to be exchanged for the tool set supported on the tool holder, said storing means being adapted to position a predetermined tool set selected from among the stored tool sets at a tool exchange position wherein a tool set to be exchanged is removed from the tool set storage means;
• and
• an automatic tool exchange device supported on the frame, for exchanging the tool set supported on the tool holder for a tool set stored in the tool set storage means,
• the automatic tool exchange device further comprising;
• (a) a pivotal shaft pivotally supported on the frame with a longitudinal axis thereof disposed vertically with respect to said frame;
• (b) a first arm supported on the pivotal shaft, for removing a tool set positioned at the tool exchange position on the storage means, and for setting the removed tool set to the process position on the tool holder;
• (c) a second arm supported on the pivotal shaft, for removing a tool set arranged at the process position on the tool holder, and for returning the tool set to the tool exchange position on the storage means,
• the second arm being supported on the pivotal shaft so as to be substantially perpendicular to the first arm in a plane disposed horizontally with respect to said frame, wherein said pivotal shaft is adapted to be pivoted and positioned at an angular position in which the first arm is located to face the tool exchange position on the tool set storage means and the second arm is located to face the process position on the tool holder;
• (d) means supported on the frame for pivoting the pivotal shaft, said pivotal shaft pivoting means capable of positioning the pivotal shaft at three different angular positions,
• wherein at the first angular position, the first arm is located to face the tool exchange position on the tool set storage means and the second arm is located to face the process position on the tool holder, at the second angular position, the first arm is located to face the process position with the second arm located to face a position other than the process position and the tool exchange position, and at the third angular position, the second arm is located to face the tool exchange position with the first arm located to face a position other than the process position and the tool exchange position;
• said pivotal shaft pivoting means further comprising;
• (i) a second cylinder supported on the frame,
• (ii) a first cylinder supported on the second cylinder with a longitudinal axis thereof parallel to a longitudinal axis of the second cylinder,
• said first and second cylinders each having respective pistons, the first cylinder being mechanically coupled to the second cylinder in a manner such that when the respective pistons of the first and the second cylinders are projected or retracted, the first cylinder is moved along the longitudinal direction thereof, and when both pistons of the cylinder are retracted to their stroke ends, the first cylinder is positioned at a first position with respect to the longitudinal axes of the first and second cylinders, when the piston of the second cylinder is retracted to the stroke end and the piston of the first cylinder is projected to the stroke end, the first cylinder is positioned at a second position with respect to the longitudinal axes of the first and second cylinders, and when the piston of the second cylinder is projected to the stroke end and the piston of the first cylinder is retracted to the stroke end, the first cylinder is positioned at a third position with respect to the longitudinal axes of the first and second cylinders, and
• (iii) means connecting the first and second cylinders with the pivotal shaft for pivoting the pivotal shaft in accordance with the movement of the first cylinder, wherein the first, the second, and the third angular positions of the pivotal shaft correspond to the first, the second, and the third positions of the first cylinder, respectively.