Method for manufacturing a bent heat exchanger

Abstract

An improved bending apparatus for bending a radiused corner at a window in a brazed heat exchanger core where no tubes and fins are located. A cylindrical mandrel and sliding pressure die are designed to completely surround the manifold in the areas of the window and provide a continuous, rolling contact area or profile support around the manifold as the bending moment is applied.

1 . A method of manufacturing a tube-to-manifold heat exchanger comprising the steps of:
 providing a tube-to-manifold heat exchanger core having a upper manifold, a lower manifold spaced apart from and substantially parallel to said upper manifold, and a plurality of substantially parallel and vertical flat tubes running between said upper and lower manifolds, wherein said plurality of tubes are spaced so as to define at least one open window bordered by sections of unencumbered upper and lower manifold defining an intended bend area of said core,   providing a rotatable, semi-cylindrical mandrel defining the desired radius of the bend and having a semi-cylindrical trough sized to substantially support the entire inner profile of the manifold over the desired bend,   providing a slidable pressure die opposed to the mandrel having a straight trough sized to substantially support the entire outer profile of the manifold over the desired bend,   applying a bending force to bend the manifold around the semi-cylindrical mandrel while concurrently rotating the mandrel and sliding the pressure die along the length of the manifold so as to maintain a rolling contact between the mandrel and pressure die to continually support substantially the entire profile of the manifold as it is being bent.   
     
     
         2 . The method according to  claim 2 , further comprising the step of applying the bending force by clamping the manifolds in the lead of the bend area between a pair of clamping elements and swinging the clamping elements about the pivot of the mandrel as the mandrel rotates. 
     
     
         3 . The method according to  claim 2 , further comprising the step of providing one of clamping elements to be integral to the semi cylindrical mandrel and rotating the mandrel and swinging the one clamping element concurrently. 
     
     
         4 . The method according to  claim 1 , further comprising the step of providing an additional length to the sliding pressure die to support the manifold trailing the bend.