METHOD OF BENDING COIL PIPES Russian patent published in 1994 - IPC

FIELD: metal working. SUBSTANCE: method comprises steps of bending a rectilinear blank by a predetermined radius due to allying to zones of a portion to be bent different-direction twisting moments in such a way, that an axis of bending is parallel to an axis of a pipe in a mean zone of thickness of its one wall; applying an axial effort after each applying of twisting moment and changing a twisting sign for opposite one; displacing the bending zone after a predetermined number of bending cycles to a next portion of an initial blank and going on twisting cycles. Upon successive displacements of the bending zone without rotation around a lengthwise axis of the pipe loop-type coils are being produced; with rotation around the axis of the pipe spiral coils are being produced. In order to provide more intensive bending of elbow parts upon production of the loop-type coils it is possible to perform an additional bending of the blank in a plane, containing its axis, together with the twisting cycles. EFFECT: enhanced quality of coils. 3 cl, 3 dwg