Abstract:
A louvered fin for a heat exchanger is disclosed, wherein the louvers include a rib formed thereon to maximize a strength and rigidity thereof and to minimize an amount of material required for production thereof.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to heat exchangers and more particularly to louvered fins for heat exchangers, wherein a rib is formed on the louvers to maximize a strength and rigidity thereof.  
       BACKGROUND OF THE INVENTION  
       [0002]     An air-cooled fin-type heat exchanger is very well known. Heat exchangers are used for changing the temperature of various working fluids, such as an engine coolant, an engine lubricating oil, an air conditioning refrigerant, and an automatic transmission fluid, for example. The heat exchanger typically includes a plurality of spaced apart fluid conduits or tubes connected between an inlet tank and an outlet tank, and a plurality of heat exchanging fins disposed between adjacent conduits. Air is directed across the fins of the heat exchanger by a cooling fan or a motion of a vehicle, for example. As the air flows across the fins, heat in a fluid flowing through the tubes is conducted through the walls of the tubes, into the fins, and transferred into the air.  
         [0003]     One of the primary goals in heat exchanger design is to achieve a high fin column strength. It is known that a greater composite thickness of a fin produces a greater strength of the fin. However, increasing the composite thickness of the fin results in a larger amount of material being used to manufacture the fins. The larger amount of material results in additional weight, which is undesirable. Various types of fin designs have been disclosed in the prior art with the object of increasing the composite thickness to increase the strength of the fin. It would be desirable to produce a louvered fin for a heat exchanger, wherein a strength associated therewith is maximized, and a material usage is minimized.  
       SUMMARY OF THE INVENTION  
       [0004]     Harmonious with the present invention, a louvered fin for a heat exchanger, wherein a strength associated therewith is maximized, and a material usage is minimized, has surprisingly been discovered.  
         [0005]     In one embodiment, a heat exchanger fin comprises a base wall having a first end, a second end, and a middle portion; a turnaround louver disposed in the middle portion of the base wall, the turnaround louver having a first edge and a second edge; a plurality of spaced apart entrance louvers disposed between the first end of the base wall and the turnaround louver, the spaced entrance louvers having a first edge and a second edge; a plurality of spaced apart exit louvers disposed between the turnaround louver and the second end of the base wall, the exit louvers having a first edge and a second edge; and at least one rib formed on at least one of the turnaround louver, the entrance louvers, and the exit louvers.  
         [0006]     In another embodiment, a heat exchanger fin comprises a base wall having a first end, a second end, and a middle portion; at least one turnaround louver disposed in the middle portion of the base wall, the turnaround louver having a laterally extending first edge, a laterally extending second edge and at least one rib formed between the first edge and the second edge; a plurality of spaced apart entrance louvers disposed between the first end of the base wall and the turnaround louver, the entrance louvers having a laterally extending first edge, a laterally extending second edge, and at least one rib formed between the first edge and the second edge; and a plurality of spaced apart exit louvers disposed between the turnaround louver and the second end of the base wall, the exit louvers having a laterally extending first edge, a laterally extending second edge, and at least one rib formed between the first edge and the second edge.  
         [0007]     A method of producing a heat exchanger fin, the method comprises the steps of providing a substantially planar sheet of material; forming a plurality of longitudinally extending ribs in the sheet of material; forming a plurality of laterally extending corrugations in the sheet of material; and forming a plurality of rows of longitudinally extending louvers in the sheet of material, is disclosed. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of an embodiment of the invention when considered in the light of the accompanying drawings in which:  
         [0009]      FIG. 1  is a perspective view of a heat exchanger fin in accordance with an embodiment of the invention;  
         [0010]      FIG. 2  is a top sectional view of a plurality of louvers of the heat exchanger fin illustrated in  FIG. 1  taken along line  2 - 2 ;  
         [0011]      FIG. 3  is a perspective view of a heat exchanger fin in accordance with another embodiment of the invention;  
         [0012]      FIG. 4  is a top sectional view of a plurality of louvers of the heat exchanger fin illustrated in  FIG. 3  taken along a line  4 - 4 ;  
         [0013]      FIG. 5  is a perspective view of a heat exchanger fin in accordance with another embodiment of the invention;  
         [0014]      FIG. 6  is a perspective view of a heat exchanger fin in accordance with another embodiment of the invention;  
         [0015]      FIG. 7  is an elevational view of an apparatus used for producing a heat exchanger fin in accordance with an embodiment of the invention; and  
         [0016]      FIG. 8  is an elevational view of an apparatus used for producing a heat exchanger fin in accordance with another embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed an illustrated, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.  
         [0018]      FIG. 1  shows a heat exchanger fin  10  having an outer surface  11 , an inner surface  13 , a first end  15  and a second end  17 . The heat exchanger fin  10  includes a plurality of base walls  12 . It is understood that more or fewer base walls  12  can be used without departing from the spirit or scope of the invention. The base walls  12  have an upper portion  14 , a lower portion  16 , a first end  18 , a second end  20 , and a middle portion  22 . The middle portion  22  is disposed intermediate the first end  16  and the second end  18 .  
         [0019]     The base walls  12  include a leading edge louver  23 , a plurality of entrance louvers  24 , a turnaround louver  26 , a plurality of exit louvers  28 , and a trailing edge louver  29 . The leading edge louver  23  and entrance louvers  24  are connected to the upper portion  14  of the base wall  12  at a first end  30  and to the lower portion  16  of the base wall  12  at a second end  32 . As more clearly shown in  FIG. 2 , the leading edge louver  23  and each of the entrance louvers  24  includes a first surface  33 , a second surface  35 , a first edge  34 , a spaced apart second edge  36 , and a rib  38 . The rib  38  is formed between the first edge  34  and the second edge  36  and extends laterally outwardly from the second surface  35 . A single rib  38  is shown formed on the leading edge louver  23  and each entrance louver  24 . However, it is understood that more or fewer ribs  38  can be formed on the leading edge louver  23  and the entrance louvers  24  as desired without departing from the scope of the invention. In the embodiment shown, the ribs  38  extend from the first end  30  to the second end  32  of the leading edge louver  23  and entrance louvers  24 . A gap  39  is formed between adjacent entrance louvers  23 ,  24  and between the turnaround louver  26  and the entrance louver  24  adjacent the turnaround louver  26 .  
         [0020]     The turnaround louver  26  is connected to the upper portion  14  of the base wall  12  at a first end  40  and to the lower portion  16  of the base wall  12  at a second end  42 . As illustrated in  FIG. 2 , the turnaround louver  26  includes a first surface  43 , a second surface  45 , a first edge  44 , a spaced apart second edge  46 , and a rib  48 . The rib  48  is formed between the first edge  44  and the second edge  46  and extends laterally outwardly from the second surface  45 . A single rib  48  is shown formed on the turnaround louver  26 . However, it is understood that more or fewer ribs  48  can be formed on the turnaround louver  26  as desired. The rib  48  extends from the first end  40  to the second end  42  of the turnaround louver  26 .  
         [0021]     The exit louvers  28  and the trailing edge louver  29  are connected to the upper portion  14  of the base wall  12  at a first end  50  and to the lower portion  16  of the base wall  12  at a second end  52 . As shown in  FIG. 2 , each of the exit louvers  28  and the trailing edge louver  29  includes a first surface  53 , a second surface  55 , a first edge  54 , a spaced apart second edge  56 , and a rib  58 . The rib  58  is formed between the first edge  54  and the second edge  56  and extends laterally outwardly from the second surface  55 . A single rib  58  is shown formed on each exit louver  28  and the trailing edge louver  29 . However, it is understood that more or fewer ribs  58  can be formed on the exit louvers  28  and the trailing edge louver  29  as desired. The ribs  58  extend from the first end  50  to the second end  52  of the exit louvers  28  and the trailing edge louver  29 . A gap  59  is formed between adjacent louvers  28 ,  29  and between the turnaround louver  26  and the exit louver  28  adjacent the turnaround louver  26 .  
         [0022]     As is known in the art, air is caused to flow through the gaps  39  between adjacent entrance louvers  24 . Heat removed from a fluid (not shown) flowing in flow tubes (not shown) is transferred through the heat exchanger fin  10  and the entrance louvers  24  to the air. The air is then caused to change direction at the turnaround louver  26 . The air flows through the gaps  59  between adjacent exit louvers  28  where additional heat is transferred from the exit louvers  28  to the air.  
         [0023]     A composite thickness of the louvers  24 ,  26 ,  28  is increased as a result of the formation of the ribs  38 ,  48 ,  58  on the louvers  24 ,  26 ,  28 . The increase in the composite thickness of the louvers  24 ,  26 ,  28  results in an increased strength of the fin  10 . For the embodiment shown in  FIGS. 1 and 2 , an increase in strength of about 18% has been measured.  
         [0024]     An increased strength of the fin  10  allows for the use of a thinner gauged flat stock of material to make the fin  10 . Accordingly, a fin  10  having a strength substantially the same as fin structures of the prior art can be made with less material. Thus, overall weight of the fin  10  is minimized. It has been shown that a fin  10  including louvers  24 ,  26 ,  28  having ribs  38 ,  48 ,  58  formed thereon can be made with up to 20% less material than fin structures of the prior art.  
         [0025]     The heat exchanger fin  10  shown in  FIGS. 3 and 4  includes ribs  381 ,  48 ′,  58 ′. Similar structure to that described above for  FIGS. 1 and 2  repeated herein with respect to  FIGS. 3 and 4  includes the same reference numeral and a prime (′) symbol. The ribs  38 ′,  48 ′,  58 ′ are formed to extend laterally outwardly from respective first surfaces  33 ,  43 ,  53 . The remaining structure is the same as discussed above for  FIGS. 1 and 2 . Air flow through the louvers  24 ′,  26 ′,  28 ′ is the same as described above for  FIGS. 1 and 2 .  
         [0026]      FIG. 5  shows a strong heat exchanger fin in accordance with another embodiment of the invention. Similar structure to that described above for  FIGS. 1 and 2  repeated herein with respect to  FIG. 5  includes the same reference numeral and a double prime (″) symbol. In this embodiment, the ribs  38 ″,  48 ″,  58 ″ extend from the first end  15  of the fin  10 ″ to the second end  17  of the fin  10 ″. The ribs  38 ″,  48 ″,  58 ″ may be formed to extend laterally outwardly from the inner surface  13  of the fin  10 ″ as shown in  FIG. 5 . The ribs  38 ′″,  48 ′″,  58 ′″ may also be formed to extend laterally outwardly from the outer surface  11  of the fin  10 ″ as shown in  FIG. 6 . Similar structure to that described above for  FIGS. 1 and 2  repeated herein with respect to  FIG. 6  includes the same reference numeral and a triple prime (′″) symbol. The remaining structure and air flow through the louvers  24 ″,  26 ″,  28 ″,  24 ′″,  26 ′″,  28 ′″ is the same as described above for  FIGS. 1 and 2 .  
         [0027]     A method of forming the heat exchanger fin  10  described in  FIGS. 1-2  will now be described. A substantially planar sheet of material  110  is provided, such as aluminum, for example. As shown in  FIG. 7 , the sheet of material  110  is fed into a retention roll  111  for height and straightness adjustments and then into a set of rib forming rolls  112 . A first one of the rib forming rolls  112  includes of a plurality of spaced annular protuberances (not shown). A second one of the rib forming rolls  112  includes a plurality of spaced apart annular channels or indentations. The protuberances and indentations of the rib forming rolls  112  cooperate to form a plurality of continuous ribs  38 ,  48 ,  58  in the sheet of material  110 . Optionally, the sheet of material  110  can then be fed into a second retention roll  111 , as illustrated in  FIG. 8 . Thereafter, the sheet  110  is fed into a set of corrugation fin forming rolls  114 . Cutters (not shown) disposed on the corrugation fin forming rolls  114  cut the sheet  110  to form a plurality of rows. Each of the rows includes a leading edge louver  23 , a plurality of entrance louvers  24 , a turnaround louver  26 , a plurality of exit louvers  28 , and a trailing edge louver  29 . The corrugation fin forming rolls  114  simultaneously alternately bend the sheet  110  to form corrugations and give the sheet  110  a wave-like shape. The corrugation fin forming rolls  114  also cooperate to flatten the sheet  110  between adjacent rows of louvers  23 ,  24 ,  26 ,  28 ,  29 . Thus, the ribs  38 ,  48 ,  58  formed on the top portion  14  and the bottom portion  16  of the sheet  110  are removed. The sheet  110  is fed into a density station  116  where further adjustments to the sheet  110  can be accomplished as desired. The sheet  110  is fed into a cutoff station  118  where the sheet  110  is cut to a desired length.  
         [0028]     To form the fin  10 ″ described in  FIG. 5  above, a flattening of the sheet  110  between adjacent rows of louvers  23 ″,  24 ″,  26 ″,  28 ″,  29 ″ is eliminated from the process described. The ribs  38 ″,  48 ″,  58 ″ produced by this method extend continuously from the first end  15  of the fin  10  to the second end  17  of the fin  10 , rather than terminating at the first ends  30 ,  40 ,  50  and the second ends  32 ,  42 ,  52  of the louvers  24 ″,  26 ″,  28 ″.  
         [0029]     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.