APPARATUS FOR DOUBLE-SIDE BENDING OF TUBULAR BLANKS Russian patent published in 2002 - IPC

FIELD: plastic metal working, namely apparatuses for restricted bending and axial compression of tubular blanks, possibly manufacture of sharply bent angles in building, machine engineering and other industry branches. SUBSTANCE: profile of guide is made according to curve of modified involute whose evolute is circle with radius equal to mean radius of bending tubular blank. Current radius of involute is calculated according to special formula. Profile of working surface of mandrel may be formed due to crossing portion of tore formed by rotation of circle with diameter equal to inner diameter of tubular blank around axis spaced from circle center by distance equal to mean bending radius. Said portion of tore is placed between two planes passing through axis of tore and mutually inclined by angle equal to half of bending angle of blank with cylinder surface whose base represents circle formed due to tore crossing with one of above mentioned planes. It allows to eliminate rupture on outer mostly tensioned fibers at forming sharply bent angles with cylindrical portion and at subsequent straightening and calibrating operations. EFFECT: enhanced quality of bent tubular blanks. 2 cl, 3 dwg, 1 tbl