Bend arm apparatus for tube bending machine with cammed clamp die arrangement

A bend arm assembly pivotable about a given axis of a bending machine and including a clamp die mechanism with a clamp die for coaction with a rotary bend die for clamping a workpiece for bending, the bend arm assembly including the clamp die mechanism then pivoting through the desired bend angle, as a unit, about the axis of the bend die. The bend arm assembly includes a back plate, with first and second guide slots, with the clamp die assembly mounted on the end of a clamp die block, which has laterally protruding guide bolts extending into the guide slots. A cam plate is secured to the clamp die block in depending relation, and is provided with a cam slot. A hydraulic cylinder driven cam actuator arm assembly includes interconnected parallel arms, which pivot about an axis, which is pivotally coupled to the structure about which the bend die pivots, with a cam follower rod extending through the cam slot. The guide slots and the cam slot are configured for moving the clamp die assembly in a first direction at a slight angle to a line parallel to the pivot axis, and in a second direction generally perpendicular to the pivot axis, the distance of movement in the second direction being generally equal to the radius of the workpiece, with the cam slot configured for enabling linear and predictable application of clamping force on the workpiece being bent.