Helically wound finned tubes for heat exchangers and improved method for securing fins at the ends of the tubes

Abstract

A finned tube for heat transfer from one medium to a second medium, and the method of manufacture, is disclosed. A helical fin of the finned tube has an area of compressed fins positioned proximate an insertion section which has a metal tube exposed with the helical fin removed therefrom. The compressed fins are a portion of the helical fin which has been compressed so that the helical fin in the area of the compressed fins is more closely spaced than the remaining portion of the helical fin. A base portion of the helical fin in the area of the compressed fins is layered and compressed on itself and is compressed against the metal tube. The layers of the base portion are compressed together and to the metal tube of the finned tube, which causes the layers of the base portion to bind together and bind to the metal tube to prevent movement of the helical fin in the area of the compressed fins in a direction parallel to the longitudinal axis of the finned tube.

1 . A method of compressing a number of helical fins near the end of a finned tube to expose a metal tube of the finned tube, the method comprising:
 positioning the finned tube in a fixture;   advancing a compression mechanism a predetermined distance into engagement with an end of the finned tube, the compression mechanism having a first end with an opening extending from the first end toward a second end, the opening dimensioned to receive the metal tube of the finned tube therein;   the advancement of the compression mechanism causing the first end of the compression mechanism to engage fin portions of the helical fin, causing the fin portions to compress upon themselves as the advancement of the stripping mechanism continues;   the advancement of the compression mechanism causing a base portion of the helical fin to move and become layered, the layers of the base portion being compressed together and to the metal tube, causing the layers of the base portion to bind together and bind to the metal tube as the advancement of the stripping mechanism continues;   retracting the compression mechanism to expose the metal tube of the finned tube from which the helical fin has been removed; and   removing the finned tube from the fixture.   
     
     
         2 . The method of  claim 1  wherein the compressed fin portions are maintained in position by the overlapping of the base portions of the fins, thereby preventing the helical fin from moving back over the exposed metal tube. 
     
     
         3 . The method of  claim 2  comprising applying fasteners to ends of the compressed fin portions to further secure the compressed fin portions in position. 
     
     
         4 . The method of  claim 4  wherein the fasteners are staples which are spaced apart on the compressed fin portions. 
     
     
         5 . The method of  claim 1  comprising clamping the finned tube in the fixture prior to advancing a compression mechanism the predetermined distance into engagement with the end of the finned tube. 
     
     
         6 . The method of  claim 5  wherein a clamp for clamping the finned tube in the fixture has a compliant material which forms around the helical fin when the clamp is brought into engagement with the finned tube, the compliant material molding around the helical fin to allow the clamp to maintain the finned tube in position relative to the fixture without damaging the helical fin. 
     
     
         7 . The method of  claim 6  wherein the compliant material engages a large area of the helical fin, whereby the forces applied by the compliant material on the helical fin are dissipated over a large area, allowing the forces applied to the helical fin at any particular location to be relatively small, allowing the clamp to maintain the finned tube in position without damaging the helical fin. 
     
     
         8 . The method of  claim 1  wherein the opening of the compression mechanism is dimensioned to allow for the layering of the base portion as the compression mechanism is advanced. 
     
     
         9 . A method of compressing a section of fins at an end of a finned tube to expose a tube portion of the finned tube, the method comprising:
 positioning the finned tube in a fixture;   clamping the finned tube in position relative to the fixture;   applying a force to the end of the finned tube to compress the portion of the helical fin, causing fin portions of the helical fin to compress upon themselves as the force is applied;   the applied force causing a base portion of the helical fin to move and become layered, the layers of the base portion being compressed together and to the tube portion, causing the layers of the base portion to bind together and bind to the tube portion as the force is applied;   whereby upon the removal of the force, the compressed portion of the helical fin is maintained in position by the binding of the layers together and to the metal tube, thereby preventing the helical fin from moving back over the exposed tube portion.   
     
     
         10 . The method of  claim 9  comprising applying fasteners to ends of the fin portions of the compressed helical fin to further secure the compressed helical fin in position. 
     
     
         11 . The method of  claim 10  wherein the fasteners are staples which are spaced apart on the fin portions. 
     
     
         12 . The method of  claim 9  wherein a clamp for clamping the finned tube in position relative to the fixture has a compliant material which forms around a non-compressed section of the helical fin when the clamp is brought into engagement with the finned tube, the compliant material molding around the non-compressed section of the helical fin to allow the clamp to maintain the finned tube in position relative to the fixture without damaging the helical fin. 
     
     
         13 . The method of  claim 12  wherein the compliant material engages a large area of the non-compressed section of the helical fin, whereby the forces applied by the foam on the non-compressed section of the helical fin are dissipated over a large area, allowing the forces applied to the non-compressed section of the helical fin at any particular location to be relatively small, allowing the clamp to maintain the finned tube in position without damaging the helical fin. 
     
     
         14 . A finned tube for heat transfer from one medium to a second medium, the finned tube comprising:
 a metal tube with a helical fin around the metal tube;   the helical fin having a base portion which conforms to an outside diameter of the metal tube;   the helical fin having a fin portion extending from the base portion;   an end of the finned tube having insertion sections in which the metal tube is exposed, with no helical fin projecting therearound;   the helical fin having an area of compressed fins positioned proximate to the insertion section, the compressed fins being a portion of the helical fin which has been compressed so that the helical fin in the area of the compressed fins is more closely spaced than the remaining portion of the helical fin;   the base portion in the area of the compressed fins being layered and compressed on itself and being compressed against the metal tube;   whereby the layers of the base portion being compressed together and to the metal tube causes the layers of the base portion to bind together and bind to the metal tube to prevent movement of the helical fin in the area of the compressed fins in a direction parallel to the longitudinal axis of the finned tube.   
     
     
         15 . The finned tube as recited in  claim 14  wherein the compressed fins of the helical fin are maintained in position on the metal tube by frictional engagement between the base portion of the helical fin and the metal tube. 
     
     
         16 . The finned tube as recited in  claim 14  wherein the compressed fins of the helical fin are maintained in position on the metal tube by frictional engagement between the layers of the base portion of the helical fin. 
     
     
         17 . The finned tube as recited in  claim 14  wherein the fin portion extends from the base portion in a direction which is essentially perpendicular to the base portion. 
     
     
         18 . The finned tube as recited in  claim 14  wherein fasteners may be inserted into the helical fin of the compressed fins to secure the compressed fins to each other and to further secure the compressed fins in position relative the metal tube. 
     
     
         19 . The finned tube as recited in  claim 18  wherein the fasteners are staples.