Abstract:
A brazed in place heat exchanger core window is provided comprising a pair of coolant redirection boxes with coolant redirection tubes disposed therebetween. The coolant redirection boxes include a header and a pan, which are press fit to each other via overlapping legs. The headers include guides and slots to facilitate a press fit mating between the core tubes and each header, whereas the pans include ferrules to facilitate a press fit mating between the coolant redirection tubes and each pan. The core window is press fit to the heat exchanger core prior to brazing, and the entire core assembly, including the core window, may be brazed in a single operation.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a heat exchanger core window, which is brazed in place with other heat exchanger core components, and a method for making such a core window in an efficient manner. A heat exchanger including a core window made according to the present invention may be particularly advantageous for use with vehicles employing a front-end power take off.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many industrial vehicles, such as municipal trucks, use mechanical power take off (“PTO”) devices for powering snow plows, refuse packers, cranes and utility equipment. A PTO apparatus typically uses a spinning shaft that is connected to the vehicle&#39;s powertrain in order to transfer mechanical power to a hydraulic pump, which in turn is used to control the auxiliary equipment. Front end (or front engine) power take-off (“FEPTO”) uses a shaft extending from the front of a vehicle&#39;s engine to power the hydraulic pump, whereas rear end (or rear engine) power take-off (“REPTO”) uses on a shaft emanating from the rear of the engine.  
         [0003]     FEPTO is the lowest cost option for most PTO applications. Because of its location at the front of the engine, however, FEPTO shafts must be routed through or around a heat exchanger, such as a radiator, which also is generally located at the front of the engine. The heat exchanger may be raised so that the PTO shaft coming out of the engine runs under, rather than through, it. Alternatively, a modified hole, i.e., a “window,” may be created in the radiator cooling system through which a FEPTO shaft may pass.  
         [0004]     The latter design, though commercially expensive, allows a larger sized cooling system to be installed with a FEPTO. Although the window reduces the overall efficiency of the heat exchanger, in some applications the additional size can create a higher performing cooling system than a system that is packaged above the FEPTO.  
         [0005]     Prior to the present invention, creating a window for FEPTO in a heat exchanger&#39;s core was a time consuming task. First, it was necessary to weld, by hand, a separate box or boxes that redirected coolant into tubes that defined the window. This assembly was then fed into a brazing oven where the remainder of the core was attached. Because of variations in the hand welding process, the typical brazing operation did not result in a adequate seal of the window box(es) with the rest of the core. Consequently, heat exchangers manufactured to include windows for FEPTO shafts previously experienced a much higher failure rate than ordinary heat exchangers. Moreover, because each component of the window was custom made, the creation of a heat exchanger within a core window involved substantially higher costs when compared with windowless cores.  
       SUMMARY OF THE INVENTION  
       [0006]     A brazed in place heat exchanger core window, suitable for use with a motor vehicle, is provided. The core window is defined by a pair of coolant redirection boxes that that are connected by coolant redirection tubes. Each of the redirection boxes includes a header and a pan. These components are press fit to each other and to a conventional heat exchanger core. The components of the coolant boxes are desirably fabricated of the same or similar types of metal as the remainder of the core assembly in order to permit the core window to be brazed in the appropriate location along with the remainder of the heat exchanger components.  
         [0007]     In a preferred embodiment, each header of each coolant redirection box includes vertical legs that tightly overlap similar, but oppositely directed, vertical legs on each pan, and each pan further includes at least one opening that allows coolant to flow into and out of each box via redirection tubes. The boxes are press fit to each other and to the heat exchanger core, and the entire heat exchanger, including the assembled core window, is brazed in place in a single process.  
         [0008]     This arrangement has the particular advantage that no welding of redirection boxes is required. In addition, the press fit design of the header, pan and redirection tubes, ensure that a conventional brazing process will result in an adequate seal at all junction points.  
         [0009]     In a further embodiment, the headers include slots and guides in order to facilitate the quick and proper alignment of the core tubing to the coolant redirection boxes. By maintaining appropriate spacing between the slots and guides, the header, and therefore the entire coolant redirection box, may be quickly assembled to the remainder of the core.  
         [0010]     In yet a further embodiment, the pan includes ferrules at each opening. The ferrules insure that the pan, when assembled to the redirection tubes, results in a tight press fit. The ferrules on the pan may overlap the redirection tubes, or, in the alternative, the ferrules may fit within the redirection tubes.  
         [0011]     Further objects, features and advantages of the invention, will become apparent from the detailed description of the preferred embodiments that follows, when considered in conjunction with the attached figures of drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Exemplary embodiments of the invention are given below with reference to the drawing, in which:  
         [0013]      FIG. 1  is an illustration of a heat exchanger that includes a core window;  
         [0014]      FIG. 2  is a perspective view of a core window assembly according to an embodiment of the present invention;  
         [0015]      FIG. 3  is a top view of a header used in a core window a core window assembly according to an embodiment of the present invention;  
         [0016]      FIG. 4  is a section of the header of  FIG. 3  taken along the line  4 - 4 ;  
         [0017]      FIG. 5  is a side view of a header used in a core window a core window assembly according to an embodiment of the present invention;  
         [0018]      FIG. 6  is a top view of a pan used in a core window a core window assembly according to an embodiment of the present invention;  
         [0019]      FIG. 7  is a section of the pan of  FIG. 6  taken along the line  7 - 7 ; and  
         [0020]      FIG. 8  is a side view of a pan used in a core window assembly according to an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]      FIG. 1  shows a heat exchanger that is useful in a motor vehicle for cooling engine components. The heat exchanger  1  includes a heat exchanger core  2 , which is comprised of core tubes  3  through which coolant passes, and a pair of coolant boxes  4 , which direct the passage of coolant through the core tubes. Heat exchanger  1  further includes a window  5 , which permits a FEPTO shaft to pass through the core. As discussed above, prior to the present invention, the creation of window  5  was a difficult and time consuming process. The window  5  previously was manually welded and then attached to the core in separate steps. Because of this process, the window could not be efficiently brazed in place along with the remainder of the heat exchanger core. The present invention addresses this problem as is discussed in detail below in conjunction with preferred embodiments.  
         [0022]      FIG. 2  shows a perspective view of a preferred embodiment of the present invention. A core window is defined by a first coolant redirection box  6 , a first coolant redirection tube  9 , a second coolant redirection tube  10 , and a second coolant redirection box  11 . The first coolant box  6  is comprised of a first header  7  and a first pan  8 , and the second coolant box is likewise comprised of a second header  12  and a second pan  13 . The components, as described in more detail below, are press fit with each other as illustrated in  FIG. 2 .  
         [0023]      FIG. 3  shows a top view of a preferred embodiment of a header  7  made according to the present invention. Header  7  includes raised guide surfaces  14  and slots  15  into which the heat exchanger core tubes  3  ( FIG. 1 ) may be placed. The header further includes legs  16 ,  17  that extend perpendicularly from a plane defined by the top surface of the header. Legs  16  and  17  thus extend in the same direction as coolant redirection tubes  9 ,  10  and heat exchanger core tubes  3 .  
         [0024]     Because the heat exchanger core  1  is generally placed in an upright position with respect to the vehicle into which it is placed, coolant redirection tubes  9 ,  10  and heat exchanger core tubes  3  are typically disposed in a “vertical” direction, whereas the tops of coolant boxes  4  and redirection boxes  6  and  12  are typically disposed in a “horizontal” direction. Legs  15  and  16  of header  7  thus may be expressed as also extending in a “vertical” direction. It will be understood by persons of skill in the art, however, that the terms “vertical” and “horizontal” are used to facilitate an explanation of the various embodiments disclosed, and should not be understood as requiring a particular orientation of any component unless expressly so required by an attached claim.  
         [0025]      FIG. 4  shows a section through line  4 - 4  of header  7 . This section illustrates end leg  16 , which extends in a vertical direction, guide surfaces  14  and slots  15 . The raised guide surface  14  facilitates the entry of core tubes  3  into a redirection box.  
         [0026]      FIG. 5  is a side elevation of a preferred embodiment of a header  7  made according to the present invention. In this view, legs  16 ,  17  of header  7  are shown in a vertical orientation. Likewise, guide surfaces  14  extend in a vertical direction. Slots  15  are visible in  FIG. 5  and indicated by vertical reference lines. In addition,  FIG. 5  illustrates a portion of leg  16 , which is designated by reference numeral  18 . This leg portion  18  mates, in a press fit arrangement, with a corresponding leg portion of a pan.  
         [0027]      FIG. 6  illustrates a top view of a preferred embodiment of a pan  8  made according to the present invention. Pan  8  includes a pair of openings  19 ,  20 , which are maintained in fluid communication with redirection tubes  9 ,  10  after the core window is assembled. Similar to legs  16 ,  17  of header  7 , pan  8  also includes legs  21 ,  22 .  FIG. 7  illustrates a section of pan  8  along the line  7 - 7 . The vertical orientation of leg  22  is visible in  FIG. 7 .  FIG. 7  further illustrates a ferrule  23  on pan  8 , which is defined as the opening formed by protruding elements  24  and  25 .  
         [0028]     Protruding element  24 , as illustrated in  FIG. 7 , is formed as an extension to leg  22 . Likewise, protruding element  25  is formed as a bend in pan floor  26 . Persons of skill in the art will appreciate variations in the formation of ferrule  23 , however. For example, ferrule  23  may be formed by separate components, rather than by bending leg  22  and floor  26 . The embodiment as illustrated in  FIG. 7 , however, is advantageous in that fewer components are required for creation of ferrule  23 .  
         [0029]      FIG. 8  is a side elevation of a preferred embodiment of pan  8  made according to the present invention. This figure shows the location of ferrule  23  for opening  19  and a corresponding ferrule  27  for opening  20 . In addition, pan floor  26  and legs  21 ,  22  are illustrated. Legs  21  and  22 , similar to legs  16  and  17  of header  7 , are oriented in a vertical direction to pan floor  26 . The size of the opening of ferrules  23  and  27  is determined and controlled in order to insure a snug press fit when the pan is assembled to coolant redirection tubes  9 ,  10 .  
         [0030]     In a preferred embodiment, as illustrated in  FIGS. 3 through 8 , legs  16  and  17  of header  7  overlap legs  21  and  22  of pan  8 . The width and depth of header  7  is selected such that these dimensions are marginally greater than the width and depth of pan  8 . The margin is determined and controlled in order to insure a snug press fit when the header is assembled to the pan. Persons of skill in the art will appreciate, however, that the press fit arrangement could be reversed, i.e., the width and depth of pan  8  can be selected and controlled to be marginally greater than the width and depth of header  7 .  
         [0031]     The assembly of a single header  7  with a single pan  8  creates one of the pair of coolant redirection boxes, e.g., box  6 , that comprise a window to be placed in the heat exchanger core assembly  2 . A second assembly of a header  12  and pan  13  creates a second coolant redirection box, e.g., box  11 . In a highly preferred embodiment, the second box is thus identical to the first box. The window is defined by the interconnection of the first coolant redirection box  6  to the second coolant redirection box  11  via coolant tubes  9  and  10 . In this arrangement, the second coolant box  11  is oriented in an opposite direction, i.e., flipped, from the orientation of the first coolant box  6 .  
         [0032]     In order to manufacture a brazed in place heat exchanger core assembly according to a preferred embodiment of the invention, the core window is first assembled by press fitting two headers with two pans to form the needed pair of coolant redirection boxes. In this embodiment, the coolant redirection tubes are thereafter assembled to the coolant redirection boxes via the ferrules located on the pan. The core window is then press fit into the core by inserting the coolant tubes into slots on the redirection box headers. The core window thus may be set in place within the heat exchanger core prior to a brazing operation. As is known in the art, flux may be applied to the joints and the entire assembly may be placed into a brazing oven for brazing.  
         [0033]     The foregoing described process of brazing the core window in place is particularly advantageous for assembling heat exchanger cores made of materials that may be difficult to join, e.g., aluminum. In the present invention, the core window components may be selected from any material for which a known brazing or other joining operation exists. In addition, the press fit design of the invention reduces or entirely eliminates the need for separate welding of the coolant redirection boxes, which in turn ensures that the core window will remain tightly sealed with the core when assembled.  
         [0034]     While this invention has been described with an emphasis upon particular embodiments, it should be understood that the foregoing description has been limited to the presently contemplated best modes for practicing the invention. For example, the number of coolant redirection tubes described in the foregoing embodiments may be increased or reduced. In other words, a single coolant redirection tube could be employed to interconnect the pair of coolant redirection box. Likewise, three or more coolant tubes could be employed. In this variation, fewer or additional ferrules in the pan would be required to accommodate the lower or higher number of coolant redirection tubes.  
         [0035]     It will be apparent that further modifications may be made to the invention, and that some or all of the advantages of the invention may be obtained. Also, the invention is not intended to require each of the above-described features and aspects or combinations thereof. In many instances, certain features and aspects are not essential for practicing other features and aspects. The invention should only be limited by the appended claims and equivalents thereof, since the claims are intended to cover other variations and modifications even though not within their literal scope.