Stroke control for press

A cutting press comprising:

• a. two platens one of which is supported by a plurality of columns for movement towards and away from the other to effect cutting and return strokes of the press,
• b. drive means connected to the columns for effecting such movement of the movable platen, and
• c. stroke control means for limiting the movement of the movable platen towards the other platen, said stroke control means comprising a limit switch actuation of which is effective to reverse the operation of the drive means, whereby the cutting stroke is terminated and a return stroke is initiated,
• d. said stroke control means comprising a control circuit having,
• e. signalling means by which a signal is generated the magnitude of which at any time during a cutting stroke is dependent upon the sum of the distance moved by two portions of the movable platen, which portions are symmetrically located with respect to the columns.
• f. comparator means by which the magnitude of the signal is compared with a preselected value,
• g. switch actuating means by which, when the magnitude of said signal equals the preselected value, the limit switch is actuated, and
• h. said stroke control means comprises a further limit switch actuation of which is effective to terminate the return stroke of the press, together with further comparator means by which the magnitude of the signal generated by the signalling means is compared with a further preselected value, and further switch actuating means by which said further limit switch is actuated, when the magnitude of said signal equals the preselected value.