Abstract:
A plate and fin type heat exchanger is disclosed which can be made in any convenient size with minimum tooling required. The heat exchanger is made from a plurality of stacked plate pairs having raised peripheral edge portions to define flow channels inside the plate pairs. The plates of the plate pairs are formed with offset, diverging end flanges that space the plate pairs apart. A U-shaped channel envelops the plate end flanges to form part of a manifold at each end of the plate pairs. End caps or plates close the open ends of the U-shaped channels to complete the manifolds, and inlet and outlet openings are formed in the manifolds as desired to complete the heat exchanger.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part application of U.S. patent application Ser. No. 09/685,818, filed Oct. 10, 2000, which was itself a continuation-in-part application of U.S. patent application Ser. No. 09/411,295 filed Oct. 4, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to heat exchangers, and in particular, to plate and fin type heat exchangers such as the type used with internal combustion engines for cooling engine coolant.  
           [0003]    In the past, engine coolant heat exchangers, such as radiators, have been made by providing a plurality of parallel, spaced-apart flat tubes with cooling fins located therebetween to form a core. Opposed ends of the tubes pass through openings formed in manifolds or headers located on each side of the core at the respective ends of the tubes. A difficulty with this type of construction is that the tube to header joints are difficult to fabricate and prone to leakage.  
           [0004]    A method of overcoming these difficulties is shown in U.S. Pat. No. 3,265,126 issued to D. M. Donaldson. In this patent, headers are provided with a continuous longitudinal opening, and the tubes are formed with specially shaped ends to fit into this continuous opening, thus simplifying the assembly and reducing the leakage problem. A difficulty with the Donaldson structure, however, is that the shape of the various components is quite complex resulting in high tooling costs.  
           [0005]    The present invention is a heat exchanger of universal application where relatively simple and inexpensive tooling is required to make heat exchangers of different types and even with differing sizes and configurations.  
         SUMMARY OF THE INVENTION  
         [0006]    According to one aspect of the invention, there is provided a heat exchanger comprising a plurality of stacked plate pairs formed of mating plates having central planar portions and raised peripheral edge portions. The edge portions are joined together in mating plates to define a flow channel between the plates. The plates have offset end flanges, the respective flanges at each end of each plate pair diverging. The flanges have lateral edge portions extending from root areas located at the joined peripheral edge portions. The end flanges also have transverse distal edge portions joined together in back-to-back stacked plate pairs to space the plate pairs apart and form transverse flow passages between the plate pairs. Opposed U-shaped channels enclose the respective end flanges of the plate pairs. The channels have rear walls spaced from the plate end flanges and side walls joined to the flange lateral edge portions covering the root areas. The U-shaped channels have open ends. End plates close the U-shaped channel open ends to form manifolds. Also, the manifolds define inlet and outlet openings therein for the flow of fluid through the plate pairs.  
           [0007]    According to another aspect of the invention, there is provided a method of making a heat exchanger comprising the steps of providing an elongate strip of plate material having a planar central portion and raised peripheral edge portions. The plate material is cut into predetermined lengths. The plate lengths are formed with offset end flanges extending in a direction away from the peripheral edge portions. The plate lengths are arranged into plate pairs with the offset end flanges diverging and the plate peripheral edge portions in contact. The plate pairs are stacked so that the end flanges engage to space the plate pairs apart. U-shaped channels are provided to enclose the plate offset end flanges, the channels having open ends. The channel open ends are closed to form manifolds, and inlet and outlet openings are formed in the manifolds. The plates and manifolds are joined together to form a sealed heat exchanger. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0009]    [0009]FIG. 1 is a top, left perspective view of a preferred embodiment of a heat exchanger made in accordance with the present invention;  
         [0010]    [0010]FIG. 2 is a bottom left perspective view of the lower corner of the heat exchanger shown in FIG. 1 as viewed in the direction of arrow  2 ;  
         [0011]    [0011]FIG. 3 is an enlarged perspective view taken in the direction of arrow  3  of FIG. 1 showing a portion of the heat exchanger of FIG. 1 being assembled;  
         [0012]    [0012]FIG. 4 is a plan view taken along lines  4 - 4  of FIG. 3;  
         [0013]    [0013]FIG. 5 is an enlarged scrap view of the area of FIG. 4 indicated by circle  5 ;  
         [0014]    [0014]FIG. 6 is a plan view similar to FIG. 4 showing the addition of a baffle in one of the manifolds;  
         [0015]    [0015]FIG. 7 is a plan view similar to FIGS. 4 and 6 but showing another preferred embodiment of the present invention;  
         [0016]    [0016]FIG. 8 is a vertical sectional view taken along lines  8 - 8  of FIG. 6 showing various types of baffles that could be used in the manifolds of the present invention;  
         [0017]    [0017]FIG. 9 is a plan view similar to FIG. 4 but showing another preferred embodiment of the invention;  
         [0018]    [0018]FIG. 10 is a plan view similar to FIGS. 4 and 9, but showing a modification to the embodiment of FIG. 9;  
         [0019]    [0019]FIG. 11 is a plan view similar to FIG. 4, but showing a modification to the flange extensions;  
         [0020]    [0020]FIG. 12 is a vertical sectional view taken along lines  12 - 12  of FIG. 11;  
         [0021]    [0021]FIG. 13 is a vertical sectional view similar to FIG. 12 but showing a modified form of flange extension;  
         [0022]    [0022]FIG. 14 is a bottom left perspective view of similar to FIG. 2 but showing a modification for locking the plate pairs together;  
         [0023]    [0023]FIG. 15 is a top, left perspective view of another preferred embodiment of a heat exchanger made in accordance with the present invention;  
         [0024]    [0024]FIG. 16 is an enlarged vertical sectional view taken along lines  16 - 16  of FIG. 15 showing the lower left corner of the heat exchanger of FIG. 15;  
         [0025]    [0025]FIG. 17 is a bottom left perspective view similar to FIG. 2 but showing another preferred embodiment of an end bracket;  
         [0026]    [0026]FIG. 18 is an enlarged view similar to FIG. 8 showing various types of baffles and turbulizing enhancements that could be used in the heat exchangers of the present invention;  
         [0027]    [0027]FIG. 19 is a view similar to FIG. 9 showing a plate formed with dimples;  
         [0028]    [0028]FIG. 20 is a view similar to FIG. 9 showing a plate formed with ribs;  
         [0029]    [0029]FIG. 21 is a perspective view of the turbulizer of FIG. 18; and  
         [0030]    [0030]FIG. 22 is a perspective view similar to FIG. 3 illustrating a strengthening element. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    Referring firstly to FIG. 1, a preferred embodiment of a heat exchanger according to the present invention is generally indicated by reference numeral  10 . Heat exchanger  10  is in the form of a radiator for cooling the coolant of an internal combustion engine, such as is typically found in an automotive vehicle. Heat exchanger  10  includes a filler cap  12  mounted in a suitable fitting  14  having an overflow or pressure relief outlet  16 . Heat exchanger  10  has a core  18  formed of a plurality of spaced-apart plate pairs  20  with cooling fins  22  located therebetween. Cooling fins  22  are the usual type of corrugated cooling fins having transverse undulations or louvres  24  formed therein to increase heat transfer (see FIGS. 3 and 8). Any type of cooling fin could be used in the present invention, or even no cooling fin at all, if desired.  
         [0032]    Heat exchanger  10  has a pair of manifolds  26 ,  28  located at the respective ends of plate pairs  20 . Inlet and outlet nipples or fittings  30 ,  32  are mounted in one of the manifolds  26 ,  28  for the flow of coolant into and out of heat exchanger  10 , as will be described further below. An optional temperature sensor  34  can also be mounted in one of the manifolds  26 ,  28  to sense the temperature of the coolant inside heat exchanger  10 .  
         [0033]    A top end plate  36  closes the upper ends of manifolds  26 ,  28  and provides a location for mounting the filler cap fitting  14  and also a bracket  38  for mounting heat exchanger  10  in a desired located. A bottom end plate  40  is also provided to close the lower ends of manifolds  26 ,  28  and provide a location for the attachment of another mounting bracket  42  for mounting heat exchanger  10  in a desired location. If desired, filler cap  12  could be mounted in or attached to the walls of either manifold  26  or  28  instead of end plate  36 .  
         [0034]    Referring next to FIGS. 3 and 8, plate pairs  20  are formed of top and bottom mating plates  44 ,  46 . Each plate  44 ,  46  has a central planar portion  48  and raised peripheral edge portions  50 ,  52 , so that when the plates  44 ,  46  are put together face-to-face, the peripheral edge portions  50 ,  52  are joined together and the planar central portions  48  are spaced apart to define a flow channel  54  (see FIG. 8) between the plates.  
         [0035]    As seen best in FIGS. 3 and 8, plates  44 ,  46  have offset end flanges  56 ,  58 . The respective end flanges  56 ,  58  at each end of each plate pair  20  diverge from a root area  60  where the raised peripheral edge portions  50 ,  52  are still joined together, to transverse distal edge portions or flange extensions  62 . The offset end flanges  58  also have lateral edge portions  64  that extend from root areas  60  to transverse distal edge portions  62 . It will be noted that transverse distal edge portions or flange extensions  62  are joined together in back-to-back stacked plate pairs  20 . This spaces the plate pairs  20  apart to provide transverse flow passages  66  between the plate pairs where cooling fins  22  are located.  
         [0036]    Manifolds  26 ,  28  are formed of opposed, U-shaped channels having rear walls spaced from the plate offset end flanges  56 ,  58 , and side walls  70 ,  72  joined to the flange lateral edge portions  64 . The channel side walls  70 ,  72  actually cover the root areas  60  where the peripheral flanges  50 , 52  are still joined together, and since the lateral edge portions  64  of offset end flanges  56 ,  58  are joined to the inside walls of channel side walls  70 ,  72 , a fluid tight seal is provided, so that fluid inside manifolds  26 ,  28  can only flow through the flow channels  54  inside plate pairs  20 .  
         [0037]    The U-shaped channels or manifolds  26 ,  28  are formed from folded or formed aluminum sheet or an aluminum extrusion cut to a desired length and thus have open ends  74 . Top end plate  36  closes the open ends  74  at the top of manifolds  26 , 28  and bottom end plate  40  closes the bottom open ends  74  of manifolds  26 , 28 . As seen best in FIGS. 2 and 8, bottom end plate  40  also has offset end flanges  76  that fit snugly inside the U-shaped channels or manifolds  26  and  28  and engage the flange extension  62  formed on the adjacent bottom plate  46 . Bottom end plate  40  is actually an inverted U-shaped member having side skirts  78  with distal extensions  80  that wrap around manifolds  26 ,  28  to help hold heat exchanger  10  together during assembly. If desired, top end plate  36  could be the same configuration as bottom end plate  40 .  
         [0038]    It will be appreciated that U-shaped manifolds  26 ,  28  could have other cross-sectional configurations, such as trapezoidal, or hemispheroidal. For the purposes of this disclosure, the term “U-shaped” is intended to include any cross-sectional configuration that is capable of enclosing offset end flanges  56 ,  58 .  
         [0039]    Referring next to FIGS.  3  to  5 , it will be seen that raised peripheral edge portions  50 ,  52  are formed with fingers  82  spaced from the flange lateral edge portions  64  to define slots  84  to accommodate the U-shaped channel side walls  70 ,  72 . As seen best in FIG. 5, slots  84  are slightly tapered inwardly to urge the U-shaped channel side walls  70 , 72  into tight engagement with lateral edge portions  64 . This provides a snug fit, so that manifolds  26 ,  28  actually clip on and are retained in position during the assembly of heat exchanger  10 . If desired, fingers  82  could be twisted 90 degrees during assembly to help lock the manifold walls  70 , 72  against lateral edge portions  64 . Slots  84  are slightly deeper or longer than the length of side walls  70 ,  72  that extend into the slots for purpose which will be described further below.  
         [0040]    [0040]FIG. 6 shows the use of a baffle  86  attached to one of the flange extensions  62  and extending between the U-shaped channel rear wall  68  and side walls  70 ,  72  to divide manifold  26  into separate compartments above and below baffle  86 . Baffle  86  would be used in a location, for example, such as is shown by chain dotted lines  88  in FIG. 1 to divide manifold  26  into a lower compartment  90  communicating with inlet fitting or opening  30 , and an upper compartment  92  communicating with outlet fitting or opening  32 . In this way, fluid entering inlet  30  would pass through the plate pairs  20  located below baffle  86 , enter manifold  28  and flow upwardly to pass back through the plate pairs located above baffle  86  to exit through outlet  32 . Baffle  86  could be located at any plate pair between inlet  30  and outlet  32  to balance the cooling inside heat exchanger  10 .  
         [0041]    [0041]FIG. 8 shows various types of baffles that could be used in heat exchanger  10 . This is for illustration only, because normally there would only be one baffle used in heat exchanger  10 . However, if it were desired to divide heat exchanger  10  into multiple discrete heat exchangers or zones, each having its own inlet and outlet, then any number of baffles could be used to divide up heat exchanger  10  into separate heat exchangers. Also, the baffles could be used selectively in both the manifolds  26 ,  28  to cause the coolant to flow in a serpentine path through the heat exchanger, if desired.  
         [0042]    In FIG. 8, baffles  86 ,  93 ,  94  and  95  are shown having bifurcated inner ends to engage the mating flange extensions  62 . These bifurcated ends  96  also help hold flange extensions  62  together during assembly of heat exchanger  10 . Baffles  86 ,  94  and  97  also have resilient wall portions  98  to act as springs to ensure a good seal against the U-shaped channel rear wall  68 , and to accommodate any movement of the heat exchanger components while they are being joined together, such as by brazing.  
         [0043]    It is also possible to fasten baffles to the rear wall  68  of the U-shaped channel  26  by mechanical fasteners, as illustrated in FIG. 18, wherein an illustrative baffle  200  is shown as affixed to the manifold  26  by a rivet  202 .  
         [0044]    [0044]FIG. 7 shows another preferred embodiment wherein the plate raised peripheral edge portions  50 ,  52  are formed with transverse notches  100  instead of slots  84  as in the embodiment of FIG. 6. Notches  100  are located inwardly of but adjacent to the lateral edge portions  64  and root areas  60  where offset end flange  58  start to diverge. Channel side walls  70 ,  72  are formed with inwardly disposed peripheral flanges  102  that are located in notches  100 . Notches  100  are deeper than flanges  102 , and side walls  70 ,  72  are somewhat resilient, so peripheral flanges  102  snap into notches  100  allowing the U-shaped channels to clip on to the core assembly and lock the assembly together.  
         [0045]    Plates  44 ,  46  in FIG. 7 are also formed with longitudinal, inwardly disposed matching ribs  104  which strengthen the plate pairs and keep the planar central portions  48  from sagging during the brazing process to complete heat exchanger  10 . If desired, longitudinal ribs  104  could also be employed in the embodiment shown in FIGS.  2  to  6 . Multiple ribs  104  could be provided as well. Also, instead of ribs  104 , central portions  48  could be formed with dimples  204  that extend inwardly in mating engagement in the plate pairs as illustrated in FIGS. 18 and 19, thereby to define flow restrictions in the flow channels  54 , to increase turbulence. Another possibility is to provide a flow enhancing turbulizer  208  in the flow channels  54 , between the plates of the plate pairs  20 , as illustrated in FIGS. 18 and 21. The turbulizer  208  illustrated in FIGS. 18 and 21 is of the expanded metal variety, although other turbulizers may be utilized. Instead of turbulizers it is also possible to form the plates with raised ribs or ridges  206  to project into the flow channels, as illustrated in FIGS. 18 and 20, thereby to provide for increased turbulence. The ribs  206  illustrated in FIG. 20 are arranged at an angle, preferably in a herringbone pattern, with one of the mating plates  44 ,  46  turned end for end, so that the ribs  206  engage in a crossing fashion, although other arrangements are possible. The ribs  206  can also be of shortened height, so that they do not engage in mating plates, if desired.  
         [0046]    Referring next to FIG. 9, another preferred embodiment of the invention is shown where peripheral edge portions  50 , 52  are formed with necked-in portions  106  instead of slots  84  as in the embodiment of FIG. 6. Necked-in portions  106  extend inwardly beyond lateral edge portions  64  and root areas  60  where offset end flanges  58  start to diverge, so that channel side walls  70 , 72  provide a sealed enclosure communicating with the flow passages between the plates of the plate pairs  20 .  
         [0047]    [0047]FIG. 10 is similar to FIG. 9, but shows side walls  70 ,  72  having outwardly disposed peripheral flanges  108 . Flanges  108  provide a surface upon which a fixture can press to urge manifolds inwardly to hold the components of heat exchanger  10  together during the assembly and brazing process.  
         [0048]    In the embodiments shown in FIGS. 9 and 10, manifolds  26 ,  28  are still considered to “clip on” for the purposes of the present invention, since the manifold side walls  70 ,  72  would be somewhat resilient and would frictionally engage lateral edge portions  64  to hold the manifolds in place, at least during the initial assembly of the components of the heat exchangers of the invention.  
         [0049]    [0049]FIGS. 11 and 12 show a further modification which is applicable to any of the embodiments described above. In the FIGS. 11 and 12 embodiment, the transverse distal edge portions or flange extensions  62  are formed with cutouts or notches  110 . Flange extensions  62  can be made with different widths to adjust the flow through manifolds  26 ,  28  and notches  110  can be used to further refine or fine tune the flow patterns inside the manifolds. As seen best in FIG. 12, flange extensions  62  are curved to ensure a good seal therebetween, in case the notches  110  do not line up perfectly in the assembly of heat exchanger  10 .  
         [0050]    [0050]FIG. 13 is a view similar to FIG. 12, but it shows a further modification of flange extensions  62  in that they extend inwardly instead of outwardly as in the previous embodiments. Again, this configuration could be used in any of the embodiments described above. The inwardly directed flanges  62  give the maximum unobstructed flow through manifolds  26 ,  28 .  
         [0051]    [0051]FIG. 14 is a view similar to FIG. 2, but it shows a modification to end plate  40  where distal extensions  80  have been eliminated. Instead of distal extensions  80  to help hold the heat exchanger components together during the assembly process, manifold rear walls  68  are formed with tabs  112  that are bent over to engage offset end flanges  76  of end plate  40 . Tabs  112  help hold the stack of plate pairs  20  together while the heat exchanger is being set up for brazing. If desired, however, both tabs  112  and the distal extensions  80  of the FIG. 2 embodiment could be used together in the same heat exchanger.  
         [0052]    Referring next to FIGS. 15 and 16, another preferred embodiment of a heat exchanger  112  is shown, which has top and bottom manifolds  28  and  26  instead of side mounted manifolds as in FIG. 1. In heat exchanger  112 , the U-shaped channels or manifolds  26 , 28  are formed with parallel, U-shaped, inwardly disposed ribs  114 , 116  adjacent to their ends to accommodate and act as locating guides for the offset end flanges  76  of end plates  40 . It will be noted that rib  116  is shorter than rib  114  to accommodate the adjacent plate flange extension  62 . The ribs engage and locate the end plates to ensure that good brazing joints are achieved between end plate offset end flanges  76  and manifolds  26 , 28 .  
         [0053]    [0053]FIGS. 15 and 16 also show some additional optional guide and braze enhancing means for the plate flange extensions  62 . One option is to use parallel, inwardly disposed, closely spaced-apart, short ribs  118  to sandwich therebetween the peripheral edges of flange extensions  62 . Another option is to use inwardly disposed bosses  120  that appear as dimples from the outside of manifolds  26 , 28 . The bosses could be U-shaped as indicated by U-shaped dimples  122  in FIG. 15 (not shown in FIG. 16). These U-shaped bosses or dimples  122  would be particularly useful where a baffle is employed in manifolds  26 , 28 .  
         [0054]    [0054]FIG. 16 also shows a couple of other modifications to the preferred embodiments, such as an extended distal flange extension  124  on one of the plates of a plate pair  20 . Extended flange extension  124  extends fully between the U-shaped channel or manifold rear and side walls to form a baffle inside manifolds  26 , 28 . A further modification is illustrated in FIG. 22, wherein the extended distal flange extension  124  on one of the plates of a plate pair  20  is provided with an aperture  216  so as to permit fluid flow. In this latter modification, the extended distal flange extension  124  is a strengthening element for the manifold  26 . As another embodiment, illustrated in FIG. 18, the extended distal flange extension  124  can have a resilient end portion  212  to act as a spring to ensure a good seal against the U-shaped channel rear wall  68 .  
         [0055]    [0055]FIG. 16 also shows that lateral or side flanges  126  could be provided on the plate offset end flanges  56 , 58  to help ensure good brazing joints between end flanges  56 , 58  and the adjacent walls of the manifolds  26 , 28 . Also shown are transverse, distal, offset flanges  128  that could be added to flange extensions  62  to keep flange extensions  62  straight during the brazing process and help provide good bonds therebetween.  
         [0056]    Referring next to FIG. 17, a modification to the end plates is shown where end plate  130  side skirts  78  extend integrally around offset end flange  76  to form a pan type end portion that engages the bottom walls of the manifolds  26 , 28 .  
         [0057]    In a typical application, the components of heat exchanger  10  are made of brazing clad aluminum (except for the peripheral components such as fittings  30 , 32 , filler cap and fitting  12 ,  14  and mounting brackets  38 ,  42 ). The brazing clad aluminum for core plates  44 ,  46  typically have a metal thickness between 0.3 and 1 mm (0.012 and 0.040 inches). End plates  36  and  40  have a thickness between 0.6 and 3 mm (0.024 and 0.120 inches), and baffles  86 ,  93 ,  94 ,  95  and  97  have a thickness between 0.25 and 3 mm (0.010 and 0.120 inches). However, it will be appreciated that materials other than aluminum can be used for the heat exchangers of the present invention, even plastic for some of the components, if desired.  
         [0058]    The preferred method of making heat exchanger  10  is to roll form an elongate strip of plate material having planar central portion  48  and raised peripheral edge portions  50 ,  52 . Preferably, the plates are formed of brazing clad aluminum. The plate material is then cut into predetermined lengths to determine the desired width of heat exchanger  10 . The ends of the plates are then formed, such as by stamping, to create offset end flanges  58  and either slots  84 , notches  100  or necked-in portions  106 . The plates are then arranged into plate pairs with the offset end flanges  58  diverging or extending in a direction away from peripheral edge portions  50 ,  52 . The peripheral edge portions  50 ,  52  are thus engaged or in contact. The plate pairs are then stacked together in any desired number. Cooling fins  22  are located between the plate pairs during the stacking process. U-shaped channels  26 ,  28  are then cut to length to match the height of the stacked plate pairs. Any desired baffles are attached to the plate pairs at selected locations, and the U-shaped channels are then pressed, slid or clipped onto the ends of the stacked plate pairs enclosing the offset end flanges  58 . Top and bottom end plates  36 ,  40  are then located to close the open ends of the U-shaped channels. Any other fittings or attachments, such as inlet and outlet fittings  30 ,  32 , filler cap fitting  14  or brackets  38 ,  42  can be located on the assembly, and the entire assembly is then placed into a brazing furnace to braze the components together and complete the heat exchanger.  
         [0059]    Having described preferred embodiments of the invention, it will be appreciated that various modifications may be made to the structures described above. Other types of cooling fins could be used, or no fins at all. The heat exchangers could be made of other materials than brazing clad aluminum such as plastic. Also, the manifolds could have other shapes, if desired.  
         [0060]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.