Patent ID: 6029487
Filing Date: 2000-02-29
Classification: B21C,B21D

Abstract:
A system for forming tubular metal products from tubular workpieces including:a base;a split die having first and second complementary portions, which, when closed together, define a cavity with a shape corresponding to the shape of a tubular metal product desired to be formed;an enclosing frame including a central portion arranged generally parallel to the axis of a workpiece and two lateral portions generally transverse thereto;a clamping device mounted on said central portion of said enclosing frame operative to hold together said first and second portions of said split die with at least a predetermined force;two setting mechanisms, each said mechanism being mounted on a preselected one of said two lateral portions of said enclosing frame symmetrically about said die and coaxially with the workpiece, each including a hydraulic setting cylinder and a setting punch, and, further, each operative to apply a setting force via said setting punch to an end of a tubular workpiece mounted in said die;a hydraulic fluid for filling and transferring a pressure to the interior of the workpiece;at least one hydraulic pressure amplifier operative to apply a pressure, by means of said hydraulic fluid, to the interior of the tubular workpiece via a central axial cavity in at least one of said setting mechanisms;control apparatus operative to determine and control said setting force and said pressure, varying them in a predetermined manner, while the desired tubular product is being formed, maintaining a predetermined functional relationship between said setting force and said pressure; anda hydraulic power unit operative to activate said hydraulic setting cylinders and said at least one hydraulic pressure amplifier;wherein the inward-facing surface of each of said setting punches is operative, when said setting force is applied thereby, to sealingly engage an end of the tubular workpiece mounted in said die so as to prevent loss of pressure of said pressurized hydraulic fluid via the ends of the workpiece,and wherein said control apparatus is operative, while the desired tubular product is being formed, to periodically reduce and increase said pressure and said setting force, thereby to increase the plasticity of the workpiece material, while maintaining said functional relationship between said pressure and said setting force.