Method for actuating a tappet in a lifting or clamping device, especially for folding sheet metals in car manufacture

A device for processing a sheet, the device comprising:

• a base;
• a stationary folding tool mounted on said base;
• a folding bed movably mounted along said base in a first direction, said folding bed and said stationary folding tool being receivable of the sheets to be processed;
• a first wedge movably mounted between said folding bed and said base, said first wedge being movable in a second direction angularly spaced from said first direction;
• a second wedge movably mounted between said folding bed and said base, said second wedge being movable in said second direction, said first and second wedges having wedge surfaces sloped in opposite directions and interacting with said folding bed to move said folding bed in said first direction when said first and second wedges are moved in said second direction;
• a threaded drive connected to said first wedge with a first thread, said threaded drive being connected to said second wedge with a second thread, said first thread being in an opposite direction from said first thread, rotation of said threaded drive moving said first and second wedges toward and away from each other;
• a motor connected to said thread drive for rotating said threaded drive to move said first and second wedges which then move said folding bed in said first direction toward said stationary folding tool and process the sheet arranged between said folding bed and said stationary folding tool.