GB800633A - Improvements in tube bending - Google Patents

Abstract

800,633. Bending tubes. GREEN & SON, Ltd., E. April 6, 1956 [April 7, 1955], No. 10269/55. Classes 83 (2) and 83 (4). A method of bending a, tube comprises first, bending the tube in a direction opposite that of the final bend, then bending the thus bent tube back in a direction opposite the first bend and then applying pressure to the inside of the thus partly-formed bend to move the tube between two spaced members to cause the limbs of the tube to move towards one another to form the final bend. A tube 1 first heated locally over the area to form the inside of the first bend is bent, by a 'bending former 3 moved between pivoted guide blocks 2, to form a bend of an inclusive angle of about 140 degrees and thickened at 6 on the inside. The thus bent tube first heated locally over the area B to form the inside of the second bend is bent back in the opposite direction to form a bend of an inclusive angle of about 120 degrees in this opposite direction. The inner wall of the bend is thus thickened while the outer wall remains in its already thickened condition. The former 8 used to effect this bending is shaped so as to ovalize the bend so that the longer axis of the oval is perpendicular to the plane of the bend. The legs of the part formed bend are then closed parallel to one another by a suitably shaped member 12 which pushes the tube between pivoted guide blocks 13 and shaped rollers 15, the ovality of the tube at the bend providing a clearance 17 between the bend and the member 12 to allow the inside wall to thicken without restricting the throat of the bend. A final sizing operation by squeezing the previously heated bend between a pair of shaped dies may be effected. The heating of the first two steps may be electric induction or flame heating. According to the Provisional Specification the first bend is formed to an inclusive angle of about 60 degrees and the final bending may be effected after local heating.