Apparatus and method for bending insulated piping

A bending die for pipe coated with a compressible material comprising:

• structure forming an inverted cradle having a transversely concave longitudinally convex bearing surface for opposing forces applied to said pipe beyond the ends of said cradle;
• a plurality of bars extending transversely along said surface of said die in pipe confronting relation for opposing bending forces through said compressible material said bars being sufficiently spaced apart longitudinally for encouraging flow of said compressible material between said bars as bending forces cause deformation of said compressible material.

A bending die for pipe coated with a compressible material comprising:

• structure defining an inner surface in pipe confronting relation to the pipe during bending;
• and
• a plurality of bars extending longitudinally along said inner surface of said structure and in pipe confronting relation, said plurality of bars defining a transversely concave longitudinally convex bearing surface for opposing forces applied to said pipe beyond the ends of said cradle for opposing bending forces through said compressible material, said bars being sufficiently spaced apart laterally for encourging flow of said compressible material between said bars as bending forces cause deformation of said compressible material.

In a pipe bending machine having a stiffback and pin-up shoe for applying bending stresses to a pipe, the combination comprising:

• a bending die having a transversely concave longitudinally convex down facing surface and mounted in a die holder for opposing bending forces applied to a pipe by said stiffback and pin-up shoe;
• a plurality of bars extending transversely along said surface of said die and sufficiently spaced apart longitudinally to transmit bending forces between the pipe and said die through a compressible coating on said pipe so that the coating is deformed only adjacent said bars and is permitted to flow between said bars to prevent failure of the coating.

In a pipe bending machine having a stiffback and pin-up shoe for applying bending stresses to a pipe, the combination comprising:

• a structure defining an inner surface in pipe confronting relation to the pipe during bending and mounted to said pipe bending machine;
• a plurality of bars extending longitudinally along said inner surface of said structure and spaced apart laterally, said bars defining a transversely concave longitudinally convex down facing surface for opposing bending forces applied to said pipe by said stiffback and pin-up shoe to transmit bending forces between the pipe and said structure through a compressible coating on said pipe, said bars being sufficiently spaced so that the coating is deformed only adjacent said bars and is permitted to flow between said bars to prevent failure of the coating.

A method of bending pipe coated with a compressible material against a bending die, the bending die having a plurality of bars arranged along the inner surface of said die in pipe confronting relation, comprising the steps of:

• supporting the pipe against said bending die;
• precompressing the compressible material with said plurality of bars to oppose bending forces therethrough, said bars being sufficiently spaced apart for flow of said compressible material between said bars to resist damage to the compressible material by relieving the stresses in the compressible material;
• bending said pipe about said bending die, said bars defining a curved surface longitudinally to produce the desired radius of curvature in the pipe.