Abstract:
A manifold assembly for a heat exchanger is manufactured and assembled by separately molding a tank portion and a header portion, and assembling the tank and header portions together by positioning them relative to each other and injecting a sealing substance in a cavity that is formed when the portions are so positioned. Ribs are incorporated in the tank and header portions to increase the interface area between the molded portions and the sealing substance, to achieve a mechanically sound, leak proof assembly without using gaskets or fasteners.

Description:
TECHNICAL FIELD OF INVENTION 
       [0001]    This invention relates to heat exchanger manifolds in general, and specifically to a method for manufacturing and assembling a plastic manifold assembly without requiring gaskets or fasteners. 
       BACKGROUND OF INVENTION 
       [0002]    A manifold for heat exchangers may be constructed by combining a molded tank portion with a molded header portion. The header portion of the manifold typically interfaces with a heat exchanger core comprising a plurality of finned tubes that transport a liquid coolant to a similar manifold at the opposite end of the core. Heat is conducted from the coolant through the walls of the tubes to the fins, where the heat is convected to the surrounding air. To achieve the necessary seal between the tank portion and the header portion to prevent coolant leakage it is often necessary to provide a gasket, either preformed or form-in-place. If a preformed gasket is used, care must be taken to maintain the proper position of the gasket throughout the assembly process. Form-in-place gaskets present challenges in manufacturing in terms of ensuring the material is dispensed in the proper location without dripping onto improper locations. Dispense nozzles may need to be purged periodically if the material is not dispensed in a timely manner, resulting in wasted material and associated disposal costs. Mechanical attachment of the tank portion to the header portion may require clinched fasteners around the periphery of the assembly, and may introduce failure modes associated with the clinched assembly process. It would be desirable to manufacture and assemble sealed manifold assemblies for heat exchangers without requiring additional gaskets and without requiring clinched fasteners. 
       SUMMARY OF THE INVENTION 
       [0003]    The subject invention provides a method for manufacturing and assembling a heat exchanger manifold assembly that provides a sealed assembly without requiring additional gaskets and without requiring clinched fasteners. 
         [0004]    In accordance with this invention, a tank portion and a header portion are each molded using known injection molding processes. Each of the tank portion and the header portion incorporates a peripheral flange, and each flange defines a pocket peripherally surrounding the open face of each portion. Within each pocket is a rib that extends from the floor of the pocket. Several options are available for the disposition of these ribs, which are discussed in further detail below. The ribs are oriented such that they are substantially parallel to the pull axis of the molding tools used to form the tank portion and the header portion. This allows the ribs to be formed without requiring extra slides in the molding tools. 
         [0005]    The ribs are located and sized so that when the tank portion and header portion are abutted together into their assembled positions, clearance remains between the ribs, as well as from each rib to the confines of the pockets. As a result, when the tank portion and header portion are brought together in their assembled positions the pockets in both flanges define a single connected volume. To complete the assembly of the manifold assembly, the tank portion and header portion are abutted into their assembled positions. Then a secondary injection step is performed to fill the volume defined by the pockets with a sealing substance in liquid form. Potentially this sealing substance is a thermoplastic resin in a molten state or a thermoset material injected in liquid form. As the sealing substance solidifies, it adheres to the surfaces of the pocket walls, pocket floor, and ribs, resulting in a strong, leak proof assembly. By including ribs in the pockets, the available surface area for interfacing with the sealing substance is increased, thus improving the strength of the completed assembly. In addition, the inclusion of ribs in the pockets decreases the probability of having a coolant leak path to the exterior of the manifold, thereby contributing to sealing the assembly. Several rib configurations are possible, as further described below. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]    This invention will be further described with reference to the accompanying drawings in which: 
           [0007]      FIG. 1  is an isometric view showing the tank portion separate from the header portion according to an exemplary embodiment of the method of this invention. 
           [0008]      FIG. 2  is a sectional view of a heat exchanger manifold assembly constructed according to an exemplary embodiment of the method of this invention. 
           [0009]      FIG. 3  is a partial sectional view of the manifold assembly according to an exemplary embodiment of the method of this invention after injection of the sealing substance. 
           [0010]      FIG. 4  is a partial sectional view showing the tank portion and header portion according to an exemplary embodiment of the method of this invention before assembly. 
           [0011]      FIG. 5  is a perspective view showing continuous ribs in the tank portion and header portion according to an exemplary embodiment of the method of this invention before assembly. 
           [0012]      FIG. 6  is a perspective view showing an embodiment comprising holes through the ribs. 
           [0013]      FIG. 7  is a perspective view showing an embodiment comprising a bevel feature to assist in alignment during assembly. 
           [0014]      FIG. 8  is a perspective view showing an embodiment comprising ribs with square crenellations. 
           [0015]      FIG. 9  is a perspective view showing an embodiment comprising ribs with rounded crenellations. 
           [0016]      FIG. 10  is a perspective view showing an embodiment comprising ribs with projections. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0017]    In accordance with exemplary embodiments of this invention, referring to  FIGS. 1 through 10 , a method for manufacturing and assembling a manifold assembly  10  includes providing a tank portion  100  and a header portion  200 .  FIG. 1  is an isometric view of the tank portion  100  and the header portion  200  positioned separate from each other. As shown in this figure, each of the tank portion  100  and the header portion  200  are generally box shaped. The tank portion  100  has a tank open face  104 , and a tank closed face  102  opposite the tank open face  104 . A tank flange  108  surrounds the periphery of the tank open face  104 . The tank flange  108  includes a tank rib  116 . Similarly, the header portion  200  has a header open face  204 , and a header closed face  202  opposite the header open face  204 . A header flange  208  surrounds the periphery of the header open face  204 . The header flange  208  includes a header rib  216 . 
         [0018]    Referring to  FIG. 2 , a sectional view is presented that shows the salient features of the tank portion  100  and the header portion  200  as they relate to an exemplary embodiment of the manufacturing and assembly method. Both the tank portion  100  and the header portion  200  are generally box shaped and are formed by injection molding. The axis along which the mold tools close and withdraw is indicated as axis A. Inclusion of both the tank portion  100  and header portion  200  with a common axis A in  FIG. 2  is not meant to indicate that both portions  100  and  200  are necessarily molded in the same tool or at the same time; this portrayal is intended to assist in defining the nomenclature assigned to the elements of the invention. It is also recognized that in order to mold other features in either the tank portion  100  or the header portion  200  beyond what is depicted, secondary slide mechanisms as are known in the art may be required in the mold tools. 
         [0019]      FIG. 3  presents an enlarged sectional view of the interface between the tank portion  100  and the header portion  200 . In  FIG. 3 , the tank portion  100  is shown to have a tank flange  108  surrounding the tank open face  104  and extending in a direction toward the tank closed face  102 . The tank flange  108  includes a tank pocket and an integrally molded tank rib  116  extending in an axial direction from the floor of the tank pocket. Similarly, the header portion  200  has a header flange  208  surrounding the header open face  204  and extending in a direction toward the header closed face  202 . The header flange  208  includes a header pocket and an integrally molded header rib  216  extending in an axial direction from the floor of the header pocket. The tank rib  116  and the header rib  216  are disposed so as to be mutually non-interfering when the tank portion  100  and header portion  200  are assembled together. The tank rib  116  and header rib  216  are also disposed to be spaced from the walls of the tank pocket and header pocket when the tank portion  100  and header portion  200  are assembled together. Thus, the tank rib  116 , header rib  216 , tank pocket, and header pocket cooperate to define a volume that is continuous in cross section when the tank portion  100  and header portion  200  are assembled together. Additionally, as previously shown in  FIG. 1 , the flanges, ribs, and pockets surround the open faces of the tank and header portions. As a result, in the assembled position there is a peripherally continuous common pocket volume. All regions of this common pocket volume are in fluid communication with all other regions of the common pocket volume around the entire periphery of the manifold assembly  10 . As shown in  FIG. 3 , the sealing substance  300  is injected into the continuous volume defined by the tank rib  116 , header rib  216 , tank pocket, and header pocket. As the sealing substance adheres to the surfaces of the pocket walls and the ribs, it acts to hold the assembly together. The presence of the tank rib  116  and header rib  216  contribute to the surface area available for adherence of the sealing substance  300 , thus adding to the strength of the assembly. Additionally, the sealing substance prevents coolant from leaking from the assembled heat exchanger manifold. The ribs also result in a longer leak path along the interface between the sealing substance  300  and the tank and header portions  100  and  200 , thus decreasing the probability of a coolant leak from the assembled manifold. 
         [0020]      FIG. 3  also indicates that the molded tank portion  100  may be molded to incorporate a tank barrier layer  122 . Similarly, the molded header portion  200  may incorporate a header barrier layer  222 . Ultimately the manifold assembly may be part of a heat exchanger containing a liquid coolant. By incorporating barrier layers  122  and  222  of a different material than is used for the remainder of the tank portion  100  and the header portion  200 , it may be possible to lower costs by not requiring hydrolysis resistant additives in the regions of the tank portion  100  and header portion  200  that are not in direct contact with the coolant. 
         [0021]      FIG. 4  is a partial sectional view, and  FIG. 5  is a perspective view, showing the tank portion  100  and header portion  200  before assembly, to allow the geometries of each portion to be seen more clearly. As shown in  FIG. 4 , the tank flange  108  defines a tank pocket  114 . An integrally molded tank rib  116  emerges from the floor of the tank pocket  114  and extends axially in the direction of the tank open face  104 . 
         [0022]    The header flange  208  defines a header pocket  214 . An integrally molded header rib  216  emerges from the floor of the header pocket  214  and extends axially in the direction of the header open face  204 . The tank pocket  114 , tank rib  116 , header pocket  214 , and header rib  216  are sized and located such that when the tank portion  100  and the header portion  200  are brought together, clearance is maintained between the tank rib  116  and the header rib  216  as well as between each rib and the surfaces defining each pocket. 
         [0023]    To complete the assembly process of the heat exchanger manifold assembly  10 , the tank portion  100  and header portion  200  are positioned as indicated in  FIG. 2 . Then, a secondary injection molding process is used to inject a sealing substance  300  in liquid form to fill the common pocket volume. Potentially the sealing substance is the same polymer resin that is used to mold the tank portion  100  and the header portion  200  or a thermoset material injected in liquid form. As the sealing substance solidifies, it adheres to the surfaces of the common pocket volume that are formed by the sides and floor of the tank pocket  114 , the tank rib  116 , the sides and floor of the header pocket  214 , and the header rib  216 , thus forming a substantially monolithic structure to hold the tank portion to the header portion in a leak-free manner. Injection of the sealing substance can be accomplished by Die Slide Injection molding or by other molding method as are known in the art. 
         [0024]      FIG. 6  depicts an embodiment in which the tank rib  116  and the header rib  216  contain holes  126 ,  226 . These holes may be formed during the molding process by using slides in the die, or alternatively may be formed by a machining operation performed on the tank portion  100  or header portion  200  after molding. In the embodiment of  FIG. 6 , the injected sealing material can flow through the holes. When the sealing material solidifies, the geometry of the solidified material defined by the holes  126 ,  226  provides additional mechanical interlocking against separation of the assembled manifold in the axial direction.  FIG. 6  shows the holes as being round, but holes of other shapes including but not limited to elongate, square, and rectangular are suitable. 
         [0025]      FIG. 7  is a partial section perspective view of an embodiment in which the tank rib  116  and the header rib  216  are as previously described, but the outer walls of the flange include complementary bevels  124  and  224 . The bevels serve to urge the tank portion  100  and header portion  200  into radial alignment when the portions are brought together in the assembly process. 
         [0026]      FIG. 8  and  FIG. 9  depict alternate embodiments that feature crenellated tank rib  116   a,    116   b  and header rib  216   a,    216   b.  In these embodiments, the ribs are mutually non-interfering by virtue of each crenellation fitting between crenellations in the opposing portion. This configuration allows the ribs to be generally collinear, allowing the method of this invention to be applied while reducing the required widths of the tank pocket  114  and the header pocket  214 , thereby allowing a smaller overall packaging envelope without reducing the coolant capacity of the heat exchanger manifold. In  FIG. 8  the crenellated ribs  116   a  and  216   a  are depicted as rectangular in profile and in  FIG. 9  the crenellated ribs  116   b  and  216   b  are depicted as having a curved profile, but the profiles of the crenellations could also be triangular, trapezoidal, or other shapes. Choice of the profile of the crenellations involves a tradeoff between the complexity of forming the profile in the mold tool, balanced against the requirement that the crenellation have sufficient strength at the root where it emerges from the pocket floor to withstand handling and to withstand the force imparted by the sealing substance as it is injected. 
         [0027]      FIG. 10  depicts a modification that can be made to the design of either or both of the ribs. In this embodiment, a projection is molded into the tank rib  116   c  and/or the header rib  216   c  to allow the solidified injected sealing substance to form an interlocking structure with the ribs. A tank rib projection  118  on a tank rib  116  can be molded with a mold tool that contains a detail that projects through the floor of the tank pocket  114 , resulting in a tank flange opening  120  through the floor of the tank flange  108   c.  Similarly, a header rib projection  218  on a header rib  216  can be molded with a mold tool that contains a detail that projects through the floor of the header pocket  214 , resulting in an header flange opening  220  through the floor of the header flange  208   c.  In this way, such a projection  118 ,  218  can be molded with the mold tool closing and releasing along its pull axis A without adding secondary slide mechanisms. In addition, the tank flange opening  120  and/or the header flange opening  220  through the floor of the corresponding flange provides a path to the common pocket volume that facilitates venting when the sealing substance is injected, as well as providing visual access to the common pocket volume to allow the presence of the sealing substance to be verified. 
         [0028]    While this invention has been described in terms of the embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.