Tools for Bending, Inc.

Gary E Demartelaere

Ronald R Stange

Larry D Campbell

There is provided a device and manner for bulge forming and bending a tube or hollow extrusion, such as a pipe or conduit. The one portion of the length of the tube is bulge-formed to define a radially expanded, contoured section of the tube, while another portion of the tube length is bent to define an angle or curve in the tube. The device employs a radially expandable mandrel which serves both as the expandable member for bulge-forming the tube, as well as a bending mandrel to stabilize the tube against wrinkling or collapse during bending.

Method and apparatus for bulge forming and bending tubes

Tube bending apparatus in which a tube is clamped between a U-shaped bend die and a cooperating pressure die, the pressure die being advanced in a linear direction as the bend die is rotated, a tube groove in each of the dies embracing diametrically opposite sides of the tube. The tube groove on the bend die is of generally U-shaped configuration having a semi-circular bend section and opposite sides extending in tangential directions to define tangential grooves along opposite sides of the bend die, the cross-sectional radii of curvature of the tube groove along the bend section and tangential sections are closely controlled to impart some temporary distortion to the tube which will resist wrinkling or collapse. Similarly, the tube groove on the pressure die has cross-sectional radii of curvature corresponding to those of the bend section of the bend die in order to cooperate with the bend die. In carrying out the method of the present invention, the tube to be bent is clamped between the pressure die and bend die so that it is forced to assume the configuration of the tube grooves on the pressure die and the bend section of the bend die as the bend die is rotated and the pressure die is advanced while maintaining a constant pressure on the tube. Preferably, the pressure die is advanced at variable pressure rates as the tube is bent around the bend section of the bend die so that the pressure die will impart a force tending to minimize the reduction of the outer wall of the tube as the inner wall of the tube is compressed.

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Conifer, CO, United States of America

Gary E Demartelaere