Pipe bend die unit, and pipe bending apparatus having the unit

A pipe bending apparatus comprising:

• a bend die having a pipe-receiving groove of half-circular cross section on an outer peripheral surface of the bend die to receive a pipe to be bent about a bending center, the bend die being rotatable about a rotary axis;
• a clamp die for clamping a pipe to be bent that is positioned in the pipe-receiving groove of the bend die;
• and
• a pressure die for pressing the pipe toward the bend die, wherein the bend die comprises:
• a clamp member rotatable about a rotary axis and having a circularly recessed portion forming a first groove part of half-circular cross section on an outer peripheral surface of the clamp member with a fitting recess formed on the first groove part and extending in a peripheral direction by a first predetermined length on a planar surface perpendicular to the rotary axis, the rotary axis passing through the bending center of the pipe, the rotary axis passing through the fitting recess;
• a counter pressure member having a second groove part of half-circular cross section formed on an outer peripheral surface of the counter pressure member, and a fitting protrusion extending in a peripheral direction by a second predetermined length from a tip end portion of the second groove part, the fitting protrusion being positioned in the fitting recess so that the first and second groove parts combine to form the pipe-receiving groove of half-circular cross section, the counter pressure member and the clamp member being hingedly connected to one another so as to be rotatable relative to each other about the rotary axis, to configure a pipe bend die unit;
• the fitting recess extending in a peripheral direction on a planar surface perpendicular to the rotary axis, the fitting recess being located at a bottom center of the circularly recessed portion of the clamp member, the first groove part of half-circular cross section being continuous with the circularly recessed portion including a part of the fitting recess;
• and
• the counter pressure member including a curved surface portion formed on opposite sides of the planar surface, the curved surface portion being configured to contact the circularly recessed portion, the curved surface portion possessing an arc center on an axis offset from the rotary axis and perpendicular to the planar surface in a direction spaced from the rotary axis, the second groove part on the outer peripheral surface of the fitting protrusion possessing the half-circular cross section, with a bottom center of the second groove part being provided on the planar surface perpendicular to the rotary axis adjacent the curved surface portion.

A pipe bend die unit comprising a bend die with a pipe-receiving groove of half-circular cross section formed on an outer peripheral surface of the bend die to receive a pipe to be bent during a bending operation that produces a bent portion in the pipe, the bend die being rotatable about a rotary axis, and the bend die comprising:

• a clamp member that includes a first groove part of half-circular cross section on an outer peripheral surface of the clamp member with a fitting recess formed on the first groove part and extending in a peripheral direction by a first predetermined length on a planar surface perpendicular to the rotary axis;
• the clamp member also possessing a circularly recessed portion that is continuous with the first groove part that faces the bent portion of the pipe during the bending operation and around which the pipe is bent during the bending operation, the circularly recessed portion being integral with the clamp member to rotate together with the clamp member about the rotary axis, the rotary axis passing through the fitting recess;
• a counter pressure member having a second groove part of half-circular cross section formed on an outer peripheral surface of the counter pressure member, and a fitting protrusion extending in a peripheral direction by a second predetermined length from a tip end portion of the second groove part, the fitting protrusion being positioned in the fitting recess so that the first and second groove parts combine to form the pipe-receiving groove of half-circular cross section, the counter pressure member and the clamp member being hingedly connected to one another so as to be rotatable relative to each other about the rotary axis;
• the fitting protrusion possessing an outer circumferential surface that is a concave curved surface, the concave curved outer circumferential surface of the fitting protrusion being a part of the pipe-receiving groove of half-circular cross section;
• and
• the counter pressure member including a first convex curved surface portion that is convexly curved in a direction upwardly away from the fitting protrusion when the fitting protrusion is positioned horizontally, the counter pressure member also including a second convex curved surface portion that is convexly curved in a direction downwardly away from the fitting protrusion when the fitting protrusion is positioned horizontally, the first and second convex curved surface portions each being of limited circumferential extent so that each of the first and second convex curved surface portions extends around only a portion of a circumference of the fitting protrusion, each of the first and second convex curved surface portions engaging respective concave surface portions of the circularly recessed portion of the clamp member and sliding along the circularly recessed portion of the clamp member during relative rotation of the clamp member and the counter pressure member.