Device and method for forming bent pipe of non-annular cross-section

Abstract

A device for converting a straight pipe having an annular cross-section defined between an inner diameter and an outer diameter into a bent pipe having a non-annular cross-section, and method for making the same are disclosed. The device includes a round, bar-shaped guide member having a first end portion and a second end portion which is spaced therefrom in the axial direction and for being mounted slidably with the straight pipe. A floating member is formed into a prismoid and connected to the second end of the round, bar-shaped guide member in a ball-and-socket joint. The prismoid includes a first end in the form of a small polygon whose maximum radial length is less than the inner diameter of the straight pipe, and a second end in the form of a large polygon similar to the small polygon in shape and spaced from the first end in the axial direction. The prismoid has trapezoid sides disposed between the first end and the second end in such a manner that a corner angle between two adjacent trapezoid sides decreases gradually away from the first end. A feeding device slides the straight pipe on the round, bar-shaped guide member toward the floating member so that the straight pipe is brought into engagement with the floating member, thereby establishing the non-annular cross-section of the straight pipe. Lastly, a bending device bends the resulting pipe by applying a force thereto.