Rotary draw tube bender

A tube bending process for bending tubular workpieces having a uniform outer diameter, said tube bending process comprising the steps of:

• providing at least one die set including a counter die and a plurality of bending dies with different and progressively increasing bend radii, two of said bending dies having an incremental difference in bend radius, said bending dies having a circumferential concave groove and said counter-die having a linear concave groove, said grooves being sized and shaped to substantially flushly engage the workpiece;
• providing a tube bending machine having a rotatable spindle, a rotatable radial arm, first and second hydraulic cylinders and a bend angle setting device, said radial arm having a radial track that slidably receives a counter-die assembly, said counter-die assembly having a base, quick release and ratchet assembly, said base slidably engaging said track and rotatably holding said quick release, said counter die assembly having ratchet teeth, said ratchet teeth having a unit length a fraction of said incremental difference in bend radius, said ratchet assembly incrementally radially aligning said counter-die assembly, said first hydraulic cylinder selectively rotating said spindle about an axis of rotation from a home position through an angular range of rotation in a first direction;
• said second hydraulic cylinder selectively rotating said radial arm and counter-die assembly about said axis of rotation from said home position through said angular range of rotation in an opposite direction, said bend angle setting device being adapted to selectively limit said angular range of rotation of said spindle and radial arm;
• a. selecting a bending die having a desired bend radius and a corresponding counter die to make a first bend;
• b. installing said selected bending die on said spindle, and installing said selected counter-die on said quick release of said counter-die assembly;
• c. aligning said selected counter-die a desired distance from said selected bending die by slidably and incrementally moving said base and counter-die assembly along said radial track, said ratchet assembly allowing incremental radial movement to set a proper die gap between said bending die and said counter-die;
• d. swinging said selected counter-die to an open position;
• e. inserting the workpiece between said selected die and counter-die;
• f. swinging said counter die to a closed position to grip the workpiece;
• g. locating said bend angle setting device to a desired bend angle;
• h. actuating said drive mechanism to simultaneously extend said first and second hydraulic cylinders to rotate said selected bending die in one direction and said selected counter-die in an opposite direction to bend the workpiece to said desired bend angle;
• i. swinging said counter die to said open position and removing said workpiece;
• j. actuating said drive mechanism to retract said first and second hydraulic cylinders to rotate said selected bending die and counter-die to said home position;
• k. selecting a new bending die with a different bend radius from said die set to make a second bend;
• l. removing said previously selected bending die from said spindle, and installing said newly selected bending die to said spindle;
• m. aligning said previously selected counter-die a desired distance from said newly selected bending die by slidably and incrementally moving said counter-die assembly an incremental amount along said radial track to set a proper die gap between said newly selected bending die and said previously selected counter-die;
• and,
• n. repeating steps e through j to make said second bend in the same workpiece.

A rotary draw tube bender for bending tubular workpieces such as a tube or pipe, each workpiece having a uniform outer diameter, said rotary draw tube bender comprising:

• at least one die set including a counter die and a plurality of bending dies with different and progressively increasing bend radii, two of said bending dies having an incremental difference in bend radius, said bending dies having a circumferential concave groove and said counter-die having a linear concave groove, said grooves being sized and shaped to substantially flushly engage the workpiece;
• a spindle rotatable about an axis of rotation and adapted to securely receive a selected bending die, said spindle and selected bending die rotating in unison;
• an arm extending radially from and rotatable about said axis of rotation, said arm rotating independently of said spindle and having a radial axis that intersects said axis of rotation, said arm having an alignment mechanism with a radial track that slidably receives a counter-die assembly adapted to receive a selected counter-die, said counter-die assembly having ratchet teeth, said track and teeth being substantially parallel to said radial axis, each of said teeth having a unit length that is an integer fraction of said incremental difference in bend radius of said bending dies, said alignment mechanism including a ratchet assembly to incrementally radially align said counter-die with said bending die to accurately set a die gap between them;
• a drive mechanism including first and second hydraulic cylinders positioned about a line of symmetry that intersects said axis of rotation, said drive mechanism having a home position, said first hydraulic cylinder having a drive side, a return side and a first drive rod connected to said spindle, said first drive rod being movable between retracted and extended positions to rotate said spindle, and said second hydraulic cylinder having a drive side, a return side and a second drive rod connected to said arm, said second drive rod being movable between retracted and extended positions to rotate said arm in an opposite direction relative to said rotation of said spindle;
• a bend angle setting device having a limit switch and a dial with a triggering device, said dial and triggering device being selectively rotatable relative to said limit switch to position said triggering device at a desired bend angle position relative to said limit switch, said limit switch triggering when said triggering device is angularly aligned with said limit switch;
• a control unit including a drive cycle control and a return cycle control, each of said controls being selectively movable to an engaged position;
• and,
• wherein engaging said drive cycle control simultaneously extends said drive rods at equal rates to rotate said bending die in a first direction and said counter-die in an opposite direction until said limit switch is triggered when a desired angular bend is formed in the workpiece, and wherein moving said return cycle control to said engaged position simultaneously retracts said drive rods and rotates said bending die and counter-die to return said drive mechanism to its said home position.