| 摘要 |
A pipe-bending machine mandrel having an integral rigid member or a rigid member consisted of a plurality of parts which are safely connected together in one body that depends on a radius of a curved line at which a portion of a pipe has to be bent is provided to be manufactured. As a pipe-bending machine mandrel comprising a rigid member(5) which can be inserted into a pipe(T) to be bent and can be tilted with the pipe to be bent in a bending process which is performed by a bending die to obtain a curved line having a prefixed mean radius Rm as measured between the rotation center(O) of the bending die and the longitudinal axis(1) of the pipe to be bent, the mean radius Rm and longitudinal axis being formed on a central plane(alpha) perpendicular to a symmetry plane of the pipe to be bent passing through the longitudinal axis, the pipe to be bent having an internal dimension Di as measured transversally to the longitudinal axis, the pipe-bending machine mandrel is characterized in that the rigid member has a side profile proximal to the rotation centre of the bending die comprising at least a concave intermediate portion as generated in a radius Rci section(50) of circumference, and a side profile distal to the rotation center of the bending die comprising at least two convex, divided, end portions as generated in respective radius Rce sections(51,52) of the circumference, wherein Rci=Rm-(Di/2)+t, and Rce=Rm+(Di/2)-t, and t is a period varying according to the accuracy of dimensional characteristics of the pipe to be bent and of the curved line to be obtained.
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