Simplified, energy-saving hydraulic under-clamp for sheet metal pressing

摘要

Fixtures (4) hold the double-acting cylinder (2) by its housing (3) to the ram head (1). The piston (6) has an upper rod (5) emerging at the top and a lower rod (8) emerging downward and connected by flange (10) to the sheet holder (9). In operation, a valve (16) supplies hydraulic fluid at controlled pressure below the piston (6), lifting it and at the same time opening a channel for fluid displaced above the piston to return to the tank (17). The same valve provides interconnections for zero force on the return stroke. A support and ejection cylinder (22) fastened below the table (22) works with the lower piston rod (8). Its piston may be forced upward in one setting of its control valve (21); in the second position, force-free descent is permitted. When it rises, the formed workpiece is ejected. In an alternative arrangement, the double-acting cylinder is mounted in the work table and below the sheet metal jaws. The support and ejection cylinder, formerly in line with the double-acting cylinder, is now displaced to one side, but has essentially the same function. Two or more similar double acting cylinders may act on a cross member together with a separate ejection cylinder. A number of further short lifting cylinders and pressure rods may be mounted in the cross-member. Further details of these basic arrangements are provided.