Method and apparatus for pressure expansion of tubing in coil assemblage

Abstract

A tube pressure expansion device for expanding in unison tubes on a workpiece coil having plural fins. A coil holder holds the workpiece coil. A pressure expansion manifold has plural cavities each configured to receive a free end of a tube on the workpiece coil. An interior wall surface in each cavity has a tapered wall surface. A hollow tapered bullet is provided in each cavity and is configured for entering a tube opening at each free end for effecting an expansion of each free end to urge the material of each free end into a clamped and sealed relation with the interior wall surface in each cavity. A pressurized fluid is supplied to an interior of the hollow tapered bullet to effect a pressurization of the interior of the tubes to effect an expansion of the tubes into an interference fit with the fins on the workpiece coil.

What is claimed is: 
     
         1 . A tube pressure expansion device for expanding plural hollow tubes on a workpiece coil having plural fins, each hollow tube having an open free end to an interior thereof, comprising:
 a pressure expansion manifold having plural cavities each configured to receive a free end of a respective tube on the workpiece coil, an interior wall surface in each cavity including a tube seating wall surface;   a hollow bullet provided in each said cavity and being configured for entering the tube opening at each free end for effecting an expansion of each free end to urge the material of each free end into a clamped and sealed relation with said tube seating wall surface in each said cavity;   plural passageways in said pressure expansion manifold each configured to supply a pressurized fluid to an interior of each said hollow bullet to effect a pressurization of the interior of each of the tubes to effect an expansion of the tubes into an interference fit with the fins on the workpiece coil.   
     
     
         2 . The tube pressure expansion device according to  claim 1 , wherein said plural passageways are configured to supply the pressurized fluid in unison to said interior of said hollow bullet. 
     
     
         3 . The tube pressure expansion device according to  claim 1 , wherein each said tube seating wall surface in each said cavity is tapered and each hollow bullet has a tapered outer surface. 
     
     
         4 . The tube pressure expansion device according to  claim 1 , wherein each said hollow bullet includes a piston and a hollow piston rod interconnecting said hollow bullet to said piston, and each said cavity includes a chamber and an elongate bore interconnecting said chamber to said tube seating wall surface region in said cavity, said piston being reciprocally supported in said chamber, said piston rod being reciprocally supported in said bore and said hollow bullet being reciprocally supported in said tube seating wall surface region of said cavity. 
     
     
         5 . The tube pressure expansion device according to  claim 4 , wherein said plural passageways in said pressure expansion manifold each configured to supply a pressurized fluid to each said hollow piston rod and thence to said interior of each said hollow bullet to effect a pressurization of the interior of each of the tubes to effect an expansion of the tubes into an interference fit with the fins on the workpiece coil. 
     
     
         6 . The tube pressure expansion device according to  claim 5 , wherein a plurality of further passageways are provided in said pressure expanding manifold configured to supply a further pressurized fluid to said chamber selectively drive said plural interconnected pistons, said hollow piston rods and said hollow bullets toward and away from said free ends. 
     
     
         7 . The tube pressure expansion device according to  claim 6 , wherein said further passageways includes a valve and a control means for controlling said valve to effect a supply of said further pressurized fluid to each of said chambers and a first side of each of said pistons to drive each of said pistons toward said workpiece coil to thereby cause said hollow bullet to be driven into the open free ends of each of the tubes to expand the material of each free end into a clamped and sealed relation with said tube seating wall surface in each said cavity. 
     
     
         8 . A tube pressure expansion device for expanding in unison a first outer diameter of each of a plurality of separate U-shaped tubes on a workpiece coil consisting of a plurality of stamped fins having a plurality of spaced apart holes therethrough, each hole being of a second inner diameter greater than the first diameter surrounded by an upstanding collar, said stamped fins being stacked on top of one another and separated from one another, legs of the U-shaped tubes being loosely laced through selected ones of the holes and collars so that free ends of the tube legs extend outwardly from one side of the coil and bight sections between respective pairs of the tube legs extend outwardly from a side of the coil remote from the aforesaid one side, comprising:
 a coil holder configured to hold the workpiece coil in a stationary position, said coil holder having a bottom wall configured to physically restrain all of the bight sections and plural wall sections configured to physically restrain the workpiece coil, support means for supporting one of said plural wall sections for movement between opened and closed positions to facilitate an insertion and removal of said workpiece coil into and from said coil holder;   a pressure expansion manifold supported for movement between first and second positions in response to said one of said plural wall sections being in said closed position so that said workpiece coil and said bight sections are physically restrained in said coil holder, said pressure expansion manifold having plural cavities therein each configured to receive therein a respective free end of a tube leg, an interior wall surface in each said cavity having a tapered wall surface, said first position of said pressure expansion manifold being spaced from said free ends, said second position corresponding with said free ends being received in said cavities;   plural hollow reciprocating rams on said pressure expansion manifold each having thereon a hollow tapered bullet located in each said cavity, each said tapered bullet being configured for entering a tube opening at each free end for effecting an expansion of the first outer diameter at each said free end to urge the material of each free end into a clamped and sealed relation with said interior wall surface in each said cavity;   a first supply of a first pressurized fluid;   a plurality of first passageways in said pressure expanding manifold configured to supply said first pressurized fluid to each said cavity to selectively drive said plural hollow reciprocating rams and said hollow tapered bullets therewith toward and away from said free ends;   a second supply of a second pressurized fluid; and   a plurality of second passageways configured to selectively supply the second pressurized fluid to an interior of each said hollow reciprocating rams and thence to an interior of said hollow tapered bullets in response to said pressure expansion manifold being located in said second position and each free end is in a clamped and sealed relation with said interior wall surface in each said cavity to thereby effect a pressurization of the interior of each of the U-shaped tubes and an expansion of the first outer diameter of the tubes into an interference fit with each hole and collar on said stamped fins on said workpiece coil.   
     
     
         9 . The tube pressure expansion device according to  claim 8 , wherein each hollow reciprocating ram includes a piston and a piston rod having a hollow tapered bullet oriented at a distil end of said piston rod remote from said piston, said pressure expansion manifold including plural chambers each having an elongate bore opening into said chamber at one end and said cavity at an opposite end, said piston being reciprocally supported in said chamber, said piston rod being reciprocally supported in said bore and said tapered bullet being reciprocally supported in said cavity. 
     
     
         10 . The tube pressure expansion device according to  claim 9 , wherein said plural first passageways connect said first supply to said chamber on opposite sides of said pistons in each of said chambers. 
     
     
         11 . The tube pressure expansion device according to  claim 10 , wherein said first supply includes a first valve and control means for controlling said first valve to effect a supply of said first pressurized fluid to each of said chambers and a first side of each of said pistons to drive each of said pistons toward said workpiece coil to thereby cause each said tapered bullet to be driven into the open free ends of each of the tubes to expand the first outer diameter at each free end to urge the material of each free end into a clamped and sealed relation with said interior wall surface in each said cavity. 
     
     
         12 . The tube pressure expansion device according to  claim 11 , wherein said second supply includes a second valve controlled by said control means to effect a supply of said second pressurized fluid to said an interior of each of said hollow piston rods and thence to an interior of each of said tapered bullets and an interior of each of the U-shaped tubes to thereby effect a pressurization of the interior of each of the U-shaped tubes for a finite period of time to cause an expansion of the first outer diameter of the tubes into an interference fit with each hole and collar on said stamped fins on said workpiece coil. 
     
     
         13 . The tube pressure expansion device according to  claim 12 , wherein said control means is configured to control at a conclusion of said finite period of time said second valve discharge of some or all of the supply of said second pressurized fluid followed by said first valve switching to direct said first pressurized fluid to said second side of each of said pistons to drive each of said pistons away from said workpiece coil to thereby cause said tapered bullet to be partially withdrawn from the open free ends of each of said tubes to at least partially relieve the internal mechanical clamping pressure inside said U-shaped tubes. 
     
     
         14 . The tube pressure expansion device according to  claim 1 , wherein each said tube seating wall surface in each said cavity is tapered and each hollow bullet has a tapered outer surface, an end of said taper remote from said chamber  24  terminating in a cylindrical shaped opening sized to cold work the material of the free ends of the tubes as said manifold is removed from engagement with the workpiece coil. 
     
     
         15 . A method for tube pressure expansion of plural hollow tubes on a workpiece coil having plural fins, each hollow tube having an open free end to an interior thereof, comprising:
 moving a pressure expansion manifold having plural cavities each configured to receive a free end of a respective tube on the workpiece coil toward a workpiece coil so that the free end of each tube is received in a respective cavity in the manifold, an interior wall surface in each cavity including a tube seating wall surface;   moving a hollow bullet provided in each said cavity relative to said manifold into each tube opening at each free end for effecting an cold working expansion of each free end to urge the material of each free end into a clamped and sealed relation with said tube seating wall surface in each said cavity;   supplying plural passageways in said pressure expansion manifold with a pressurized fluid and to an interior of each said hollow bullet to effect a pressurization of the interior of each of the tubes to effect an expansion of the tubes into an interference fit with the fins on the workpiece coil.   
     
     
         16 . The method according to  claim 15 , wherein said moving said pressure expansion manifold includes a movement of said manifold away from the workpiece coil after a completion of a tube expansion to draw the free ends of the tubes through a cylindrical opening into each cavity to return the free ends to a cylindrical shape.