Importance

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Abstract

This invention is concerned with an apparatus for bending a hollow double-structured pipe for use in an exhaust pipe of an internal combustion engine, for example, and aims at providing such hollow double-structured pipe which is capable of effecting favorable bending work, even in the case of using an inner pipe of a thin wall thickness. The hollow double-structured pipe bending apparatus according to the present invention is of such construction that, in a hollow double-structured pipe bending apparatus, wherein an inner core metal 5 is inserted into an inner pipe 11 of the hollow double-structured pipe 10, while a tubular core metal 6 is interposed in a space gap between the inner pipe 11 and the outer pipe 12, and these core metals 5, 6 are positioned in the vicinity of the starting position for the bending work, followed by subjecting the hollow double-structured pipe 10 to the bending work by means of a bending dies 1, the apparatus being characterized in that one end part of the abovementioned tubular core metal 6 is made to protrude forwardly, in the bending direction, of the abovementioned starting position for bending, and, at the same time, a chamfered part 61, 62 is formed on the protruded part, in a substantially same shape as the final bent shape of the abovementioned inner pipe 11 and outer pipe 12.

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First Claim