Patent ID: 6164113
Filing Date: 2000-12-26
Classification: B21D

Abstract:
A pipe bending apparatus comprising:a bending mechanism including a bending die, a stiffback, and at least one outboard bending cylinder, the bending die being rigidly mounted to a frame of the apparatus, the stiffback being movable with respect to the frame, and the outboard bending cylinder having a rod end and a blind end and being operably connected between the stiffback and the frame for moving the stiffback toward the bending die when pressurized hydraulic fluid is supplied to the blind end; anda hydraulic fluid supply system including a hydraulic pump and at least one pressure-sensitive regenerative valve assembly, the supply system being operably connected to the outboard bending cylinder such that when pressurized hydraulic fluid is being supplied to the blind end of the outboard bending cylinder and a fluid pressure in the blind end is less than a predetermined pressure, the hydraulic fluid exiting the rod end of the outboard bending cylinder is routed into the blind end without first passing through the hydraulic pump, and when pressurized hydraulic fluid is being supplied to the blind end of the outboard bending cylinder and the fluid pressure in the blind end is at least the predetermined pressure, the hydraulic fluid exiting the rod end of the outboard bending cylinder is routed back to the hydraulic pump.