Means and method for reducing radius expansion in the bending of elongated materials

Claim 2

In an apparatus for hot bending elongated materials having an annular heating means for locally heating a limited portion of the material, an arm freely pivotable about an axis in the plane of the heating means, a clamp carried by said arm for engaging a leading portion of the material, and means for continuously advancing the material through said heating means and guiding the trailing, unbent portion of the material, the improvement wherein said advancing and guiding means is operative to maintain the longitudinal axis of the unbent portion of the elongated material at an acute angle with respect to a perpendicular to the plane of the heating means during the bending of the pipe by the pivotable arm, said angle being selected to compensate for the spring back material when the material is unclamped so that the material has the desired bending radius when the material is unclamped.

Claim 3

The apparatus of claim 1 further comprising means for detecting change in the radius of curvature of the material and moving the heating means a suitable distance to compensate therefor.

Claim 4

The apparatus of claim 2 further comprising means for detecting change in the radius of curvature of the material and for turning the unbent portion of the material a suitable angle to maintain the bending radius constant.

Claim 7

In a hot bending method for bending elongated material in which the material to be worked passes through a heating device such as a high frequency inductor capable of effecting high temperature heating on a limited area, with the leading end or a suitable middle part of said material being clamped to an arm pivotable about an axis within the plane of the heating device, the arm having a length that matches the bending radius of the material, and then continuously and straightforwardly advancing the material while heating the material locally by the heating device to a plastic deformation inducing temperature and thereafter immediately followed by cooling with the application of a bending moment to the material to cause continuous plastic deformation in the heated area of the material, the improvement wherein change of the bending radius of the material through spring back of the material after unclamping is reduced by maintaining the material in a position while bending, such that the longitudinal axis of the unbent portion of the material at the point of intersection of the material and a first line connecting the center of the bend with the heating means is turned a suitable angle with respect to a second line at right angles to said first line to compensate for spring back of the material when the material is unclamped, so that the material has a bending radius approximately equal to the length of the arm when the material is unclamped.

Claim 8

In a hot bending method for bending elongated material in which the material to be worked passes through a heating device such as a high frequency inductor capable of effecting high temperature heating on a limited area, with the leading end or a suitable middle part of said material being clamped to an arm pivotable about an axis within the plane of the heating device, the arm having a length that matches the bending radius of the material, and then continuously and straightforwardly advancing the material while heating the material locally by the heating device to a plastic deformation inducing temperature and thereafter immediately followed by cooling with the application of a bending moment to the material to cause continuous plastic deformation in the heated area of the material, the improvement wherein change of the bending radius of the material through spring back of the material after unclamping is reduced by maintaining the material in a position while bending, such that the longitudinal axis of the unbent portion of the material at the point of intersection of the material and a first line connecting the center of the bend with the heating means is turned a suitable angle with respect to a second line at right angles to said first line to compensate for spring back of the material when the material is unclamped, so that the material has a bending radius approximately equal to the length of the arm when the material is unclamped.

Claim 9

The method of claim 5, wherein the heating means is disposed on a straight line in the direction of advancement of the unbent material and at a position in the path of the advance of the material, a suitable distance from a line perpendicular to said straight line and passing through the center of the bend to compensate for the springback of the material when the material is unclamped.

Claim 10

The method of claim 5 wherein the heating means is moved responsive to change in the curvature of the bent portion of the material to maintain the bending radius constant.

Claim 11

The method of claim 5 wherein the unbent portion of the material is turned through a suitable angle responsive to change in the radius of curvature of the bent portion of the material to maintain the bending radius constant.