Method of making a tube for a heat exchanger

Abstract: A tube (12) and method of making the same for a heat exchanger (10) includes a base (20), a top (22) spaced from and opposing the base (20), a first side (24) interposed between the base (20) and the top (22) along one side thereof, and a second side (26) interposed between the base (20) and the top (22) along another side thereof. The tube (12) includes an end form (32) formed solely on either one of the first side (24) and the second side (26) to create a stop for inserting said tube (12) into a manifold (14,16) of the heat exchanger (10).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for making a tube for a heat exchanger. 2. Description of the Related Art It is known to provide a tube for a heat exchanger such as a condenser in an air conditioning system of a motor vehicle, see for example US-A-5 052 479 or JP-A-58-221 393. The tube typically carries a first fluid medium in contact with its interior while a second fluid medium contacts its exterior. Typically, the first fluid medium is a liquid and the second fluid medium is air. Where a temperature difference exists between the first and second fluid mediums, heat will be transferred between the two via heat conductive walls of the tube. It is also known to provide manifolds for the ends of the tubes, see for example US-A-5 052 479 or JP-A-58-221 393. The manifolds have a plurality of slots spaced axially therealong to receive one end of the tubes. However, one disadvantage is that there is no consistency or predefined limit for inserting the end of the tube into the manifold. One known method of making such a tube includes a secondary operation for forming an end of the tube with a shoulder that creates a stop for insertion of the tube into the manifold. The secondary operation may be a separate operation from the tube mill, or it may be an operation as part of the tube mill at the downstream for the tube making flow after the tube has been cut-off. Although the above tubes have worked well, they suffer from the disadvantage that the tooling for the end forming, in general, is relatively expensive or costly. Another disadvantage of the above tubes is that a secondary operation is needed to form the end of the tubes. Therefore, there is a need in the art to provide a method of making a tube for a heat exchanges that overcomes these disadvantages. SUMMARY OF THE INVENTION The present invention provides a method of making a tube for a heat exchanger comprising the steps of : forming a tube strip having a base and a top opposing the base and a first side interposed between the top and the base and a second side interposed between the top and the base; and using a cut off and end forming tool to cut the tube strip and form an end-form on only one of the first and second sides of the tube in a single operation, the end form creating a stop for inserting the tube into a manifold of the heat exchanger. The advantage of the present invention is that a method is provided of making the tube with an end form that eliminates secondary operation for the end form. Yet another advantage of the present invention is that the tube is cut-off and end formed in a single station to save tube-manufacturing cost. Still another advantage of the present invention is that the tube eliminates tooling for a secondary operation, making the tube with an end form relatively inexpensive to manufacture. Other advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a tube illustrated in operational relationship with a heat exchanger of a motor vehicle. FIG. 2 is a partial side elevational view of a manifold for the heat exchanger of FIG. 1. FIG. 3 is a partial perspective view of an end view of the tube of FIG. 1. FIG. 4 is an elevational view of a cut-off and end forming tool for cutting off and forming the end of the tube in FIG. 3. FIG. 5 is an elevational view of the cut-off and end forming tool of FIG. 4 illustrating a first stage of operation. FIG. 6 is a view similar to FIG. 5 illustrating a second stage of operation. FIG. 7 is a view similar to FIG. 5 illustrating a third stage of operation. FIG. 8 is a fragmentary plan view of the tube and manifold of the heat exchanger of FIG. 1. DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Referring to the drawings and in particular FIG. 1, one embodiment of a heat exchanger 10, such as a condenser for an air conditioning system (not shown), is shown for a motor vehicle (not shown). The heat exchanger 10 includes a plurality of generally parallel tubes 10, according to the present invention, extending between oppositely disposed headers or manifolds 14,16. The heat exchanger 10 includes a fluid inlet (not shown) for conducting cooling fluid into the heat exchanger 10 formed in the manifold 14 and an outlet (not shown) for directing cooling fluid out the heat exchanger 10 formed in the manifold 16. The heat exchanger 10 also includes a plurality of convoluted or serpentine fins 18 attached to an exterior of each of the tubes 12. The fins 18 are disposed between each of the tubes 12. The fins 18 conduct heat away from the tubes 12 while providing additional surface area for convective heat transfer by air flowing over the heat exchanger 10. It should be appreciated that, except for the tube 12, the heat exchanger 10 is conventional and known in the art. It should also be appreciated that the tube 12 could be used for heat exchangers in other applications besides motor vehicles. Referring to FIGS. 2, 4, and 8, folded tube 12 extends longitudinally and is substantially flat. The folded tube 12 includes a base 20 being generally planar and extending laterally. The tube 12 also includes a top 22 spaced from the base 20 a predetermined distance and opposing each other. The top 22 is generally planar and extends laterally. The tube 12 includes a first side 24 interposed between the base 20 and the top 22 along one side thereof. The first side 24 is generally arcuate in shape. The tube 12 also includes a second side 26 interposed between the base 20 and the top 22 along the other side and opposing the first side 24. The tube 12 may include at least one, preferably a plurality of internal webs 28 extending from either one of or both the base 20 and top 22 to form a plurality of ports or flow paths 30 in the interior of the tube 12. The tube 12 is made of a metal material such as aluminum. The tube 12 has a generally rectangular cross-sectional shape. It should be appreciated that the tube 12 may have any suitable cross-sectional shape. Referring to FIG. 3 and 8, the first side 24 is generally arcuate in shape. The second side 26 is generally arcuate in shape and has an end form, generally indicated at 32, formed on the end thereof. The end form 32 has a recess 34 extending inwardly and a shoulder 36 at the end of the recess 34 that acts as a stop. Either one or both of the manifolds 14 and 16 extend axially and have a generally circular cross-sectional shape. The manifolds 14 and 16 have a side 38 extending axially to form an interior chamber 40. The side 38 has a plurality of slots 42 extending therethrough and spaced axially to receive one end of the tubes 12. The slots 42 are generally rectangular in shape and have a width less than a width of the tubes 12. The recess 34 of the end form 32 allows the end of the tubes 12 to be inserted through the slots 42 and into the interior chamber 40 until the shoulder 36 abuts or contacts the side 38. It should be appreciated that the tubes 12 are secured to the side 38 by suitable means such as brazing. It should also be appreciated that the end form 32 may be formed on the first side 24 or the second side 26, but is formed on only one of the sides 24 and 26 of the tube 12. Referring to FIGS. 4 through 7, a method, according to the present invention, of the making the tube 12 is shown. The method includes the steps of providing or forming the tube 12 with the base 20, top 22, first side 24, and second side 26. The tube 12 may be formed by extrusion in a relatively long strip in a tube mill (not shown). Once the tube 12 is formed, it advances to a single station (not shown) to be cut-off and end formed by a cut-off and end forming tool, generally indicated at 50, as illustrated in FIG. 4. The cut-off and end forming tool 50 includes a cut-off blade 52 and an offset block 54 affixed to the cut-off blade 52. The cut-off blade 52 has a leading edge 56 to cut the tube 12 using a single stroke. The offset block 54 has a generally arcuate edge 58 spaced axially from the leading edge 56 of the cut-off blade 52 to strike the side 26 and form the recess 34 and shoulder 36 of the end form 32. It should be appreciated that the cut-off and end forming tool 50 is connected to a reciprocating actuator (not shown), which is conventional and known in the art. The method includes the step of orientating the tube 12 so that it rests on the first side 24 and the second side 24 faces the cut-off and end forming tool 50. The method includes the step of moving the cut-off and end forming tool 50 toward the second side 24 to contact the tube 12 as illustrated in FIG. 5. The method includes the step of cutting the tube 12 with the leading edge 56 of the cut-off blade 52 using a single stroke to cut-off and form an end 60 of the tube 12 as illustrated in FIG. 6. At the bottom of the single stroke, that is, when the cut-off blade 52 is finished cutting the tube 12 completely, but the cut-off blade 52 is still moving downward, the method includes the step of contacting the second side 24 with the off-set block 54 and forming the end form 32 as illustrated in FIG. 6. The cut-off and end forming tool 50 is retracted and the recess 34 and shoulder 36 of the end form 32 has been formed and a scrap 62 of the tube 12 has been formed which falls away as illustrated in FIG. 7. The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.

Claims: A method of making a tube for a heat exchanger comprising the steps of: forming a tube strip having a base and a top opposing the base and a first side interposed between the top and the base and a second side interposed between the top and the base; and using a cut off and end forming tool to cut the tube strip to form an end thereon and an end-form on only one of the first and second sides of said end in a single operation, the end form creating a stop for inserting the tube into a manifold of the heat exchanger on one side of the tube only. A method as claimed in claim 1, in which the tube strip is produced by extrusion. A method as set forth in claim 1 or claim 2 including the step of orientating either the first side or the second side toward the cut-off and end forming tool. A method as set forth in claim 3 including the step of providing the cut-off and end forming tool with a cut-off blade having a leading edge and an off-set block having an end forming edge spaced axially from the leading edge. A method as set forth in claim 4 including the step of cutting the tube with the cut-off blade to form the end on the tube. A method as set forth in claim 5 including the step of moving the cut-off blade downwardly and contacting the tube with the off-set block. A method as set forth in claim 6 including the step of forming a recess in the tube with the off-set block and a shoulder at the end of the recess to form the end form. A method as set forth in claim 7 wherein the recess has an axial length equal to an axial depth of the off-set block. A method as set forth in any preceding claim, wherein said end form comprises a recess and a shoulder at one end of said recess. A method as set forth in any preceding claim, wherein said tube strip has a width greater than a width of a slot of the manifold. A method as set forth in claim 10, wherein a width between said end form and the other one of said first side and said second side is less than a width of the slot. A method as set forth in any preceding claim, wherein said tube strip is generally rectangular in shape. A method as set forth in any preceding claim, wherein said first side and said second side is generally arcuate in shape. A method as set forth in any preceding claim, wherein said end form extends axially a predetermined distance. A method as set forth in any preceding claim, wherein said end form has a recess extending radially inward. A method as set forth in any preceding claim, wherein said tube strip is made of an aluminum material.

Inventors: RHODES EUGENE E, WHITLOW GREG A, YU WEN FEI, RHODES, EUGENE E., WHITLOW, GREG A., YU, WEN FEI
Applicants: VISTEON GLOBAL TECH INC, VISTEON GLOBAL TECHNOLOGIES, INC.
Application year: 2001
Main classification: F28D1
IPC codes: F28D1, F28F9, F28F1