Patent Publication Number: US-2011062163-A1

Title: Multi-layer coolant reservoir

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present patent application claims priority from U.S. provisional patent application No. 61/242,883 “MULTI-LAYER COOLANT RESERVOIR” filed Sep. 16, 2009 and all of the contents U.S. provisional patent application No. 61/242,883 are incorporated herein by reference and to the fullest extent of the law. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to internal combustion engine cooling systems and, more particularly, to engine coolant reservoirs or surge bottles for such cooling systems. 
     BACKGROUND OF THE INVENTION 
     Most internal combustion engines require a cooling system to remove the heat generated during fuel combustion from the engine components. Typically such systems circulate a liquid heat conducting coolant around a closed fluid loop to conductively remove heat from a heat source such as an internal combustion engine and release the heat into a heat sink such as an air cooled radiator. 
     Such closed loop cooling systems typically include a coolant reservoir or surge bottle to provide additional on-demand coolant fluid capacity to compensate for small coolant losses as well as to provide surge capacity to allow for the volumetric thermal expansion of the coolant. 
     Although coolant reservoirs may be directly vented to the atmosphere, it is more common to operate coolant systems at a positive pressure. A higher operating pressure raises the temperature at which the coolant may boil, thereby allowing for higher engine operating temperatures without the danger of boiling or vaporizing the coolant fluid. Coolant reservoirs may also include means for extracting or venting gases from the coolant. 
     Additionally, coolants may be formulated to include chemical components intended to extend coolant life or to reduce corrosion as well as the formation of deposits in the cooling system. These chemical components may not be chemically compatible with or may adversely react with some materials used in some coolant reservoirs. 
     Coolant reservoirs, as OEM components, are now very much commodity items, which means that component price is a critical factor to the award of business. There remains a need in the art for a coolant reservoir that permits the use of a wider variety of materials and results in a reduction in material usage, weight and cost in keeping with commodity business trends. 
     SUMMARY OF THE INVENTION 
     In aspects of the invention a multi-layer pressurizable coolant reservoir for providing surge and overflow capacity to an engine cooling system, includes an inner shell member shaped and configured to define at least one liquid storage chamber for storing coolant therein. An outer shell member is layered onto at least a portion of the outer surface of the inner shell member. The outer shell member is particularly adapted to provide structural stability and to resist pressure deformation of what may be a less robust inner layer. The outer shell may be formed of a higher strength material relative to the inner layer. The outer shell is isolated from the coolant by the inner layer. The material of the inner shell is selected for compatibility with the coolant and for lower cost or material savings. 
     In another aspect of the invention, the material of the inner shell is selected to be compatible with the temperature and for chemical compatibility with the stored coolant. The outer shell material is selected for strength and low cost to provide structural stability to the reservoir. The resulting coolant reservoir formed of the inner and outer shells is lower in weight or uses less material than a single layer reservoir. 
     In another aspect of the invention, the inner shell member includes molded plastic material and the outer shell member comprises a material different than the inner shell material. 
     In another aspect of the invention, the material of the outer shell includes metal. 
     In another aspect of the invention, the inner shell member includes a molded plastic upper shell portion and a molded plastic lower shell portion. The upper and lower shell portions are compatibly sized and configured to be weldable along mateable edge portions to form the inner shell member. 
     In another aspect of the invention, the outer shell member includes an upper shell portion and a lower shell portion. The outer shell upper and lower shell portions are shaped and configured to substantially match the shape of and overlay onto the respective ones of the inner shell portions. 
     In another aspect of the invention, the upper portions of the shells are molded as a unit using a two shot injection molding process and the lower portions of the shells are molded as a unit using a two shot injection molding process. 
     In another aspect of the invention, a substantially rigid skeletal shell member is provided and secured onto portions of the outer surface of the outer shell member. The skeletal shell member is operative to provide further structural stability to the inner and outer shell members. 
     In another aspect of the invention, the material of the outer shell member comprises nylon or glass fibers to strengthen the outer shell member. 
     In another aspect of the invention, the inner layer material is selected from the group including: polypropylene and polyethylene. 
     In another aspect of the invention, the outer shell material is selected from the set consisting of: nylon, glass fiber filled polypropylene and metal. 
     In another aspect of the invention, the outer shell member forms ribs extending within the liquid storage chamber. The ribs are encapsulated by rib encapsulating members of the inner shell member. The encapsulating members are configured to cover and protect the ribs of the outer shell member. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying Figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
       Features of the present invention, which are believed to be novel, are set forth in the drawings and more particularly in the appended claims. The invention, together with the further objects and advantages thereof, may be best understood with reference to the following description, taken in conjunction with the accompanying drawings. The drawings show a form of the invention that is presently preferred; however, the invention is not limited to the precise arrangement shown in the drawings. 
         FIG. 1  is a cut away perspective view of a multi-layer coolant reservoir, consistent with the present invention; and 
         FIG. 2  is a partial side sectional view of a multi-layer coolant reservoir, consistent with the present invention. 
     
    
    
     Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
     DETAILED DESCRIPTION 
     Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of apparatus components related to an improved coolant reservoir. Accordingly, the apparatus components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. 
     In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
       FIG. 1  is a cut away perspective view of a multi-layer coolant reservoir, consistent with the present invention.  FIG. 2  is a partial side sectional view of a multi-layer coolant reservoir, consistent with the present invention. 
     The multi-layer coolant reservoir  100  is configured to provide coolant storage, coolant surge or overflow capacity to an engine cooling system. The coolant reservoir includes an inner shell member  102  that is shaped and configured to define a closed liquid storage chamber  104  adapted for storing overflow or surplus engine coolant fluid therein. The liquid storage chamber  104  may be separated into sub chambers by one or more strengthening ribs or baffles  120 . Ribs  120  generally extend through the liquid storage chamber  104  and may secure to opposing walls of the coolant reservoir  100 . At least some of the ribs typically include fluid passages  122  or holes through the ribs that permit fluid to flow between the sub chambers defined by the ribs. In some variants of the invention, the coolant reservoir  100  may be pressurized and the ribs  120  provide additional structural support to the coolant reservoir to resist deformation due to the pressurization. 
     The coolant reservoir  100  may include a fitting  128  configured to receive a pressure relief device such as a pressure cap (not shown). The coolant reservoir  100  may include one or more overflow connections  130  and one or more outlet connections  132 . 
     In coolant reservoirs, including prior art coolant reservoirs, the ribs are positioned and sized to provide structural support to the coolant reservoir to resist stresses induced by pressurization of the coolant as well as mechanical stresses and loads expected during use. The ribs  120  also act to break up the interior of the coolant reservoir into sub chambers that act to reduce “sloshing” or movement of the coolant and resulting foaming within the coolant reservoir. 
     Referring again to  FIGS. 1 and 2 , surrounding and positioned supportively against the outside surface  106  of the inner shell member is an outer shell member  118 . The outer shell member  118  is layered over at least a portion of the outer surface of inner shell member  102 , and preferably is layered over a major portion if not the entirety of the outer surface of the inner shell member  102 . 
     As the inner shell member is in contact with the coolant, the material of the inner shell member is selected to be compatible with the chemistry of the coolant and suitable for the expected coolant temperature. Advantageously, a wider variety of materials are available and may be utilized for the inner shell than would be the case in a conventional single layer coolant reservoir. In the multi-layer coolant reservoir  100  the inner shell member  102  can rely upon outer shell members such as outer shell member  118  to provide required structural stability and support. The inner shell member may therefore utilize materials that in and of themselves do not provide sufficient structural stability to meet design requirements on their own. Advantageously, the material of the inner shell member  102  may be chosen to utilize less structurally robust but chemically and thermally suitable materials that are lower in cost than would otherwise be possible with prior art coolant reservoirs. 
     Advantageously, the inner shell member  102  and the outer shell member  118  may utilize different materials, each having properties selected to meet different requirements. For example, the inner shell member may utilize lower strength materials, such as (for example) a polypropylene or even a polyethylene or other low cost materials. 
     The outer shell member  118  utilizes higher strength materials which are structurally stable and able to resist the maximum expected pressurization of the coolant reservoir and other expected mechanical and thermal stresses. Some examples of more structurally stable outer shell member  118  materials include nylon, glass fiber filled polypropylene, or varieties of formed metal substrates. 
     As shown particularly in  FIG. 2 , in some variants of the invention, the ribs  120  may be formed as part of the outer shell member  118 , even though the outer shell member  118  is covered in its interior by the inner shell member  102 . This is advantageous as the outer shell  118  in many variations will be formed of more structurally stable and rigid materials than the inner shell  102 . In these variations the outer shell member material forming the ribs may be encapsulated or covered by rib encapsulating members  124  formed with the inner shell member  102  and overlaying the ribs formed by the outer shell member. In this way the outer shell member may form ribs in the interior of the reservoir that are covered and protected by the inner shell member. 
     In some variants of the invention, the upper shell portion  108  of the inner shell  102  and upper shell portion  112  of the outer shell  118  may be formed or molded as a unitary member by a two shot plastic injection molding process. Similarly, the lower shell portion  110  of the inner shell  102  and the lower shell portion  114  of the outer shell  118  may be formed as a unitary member by a similar two shot plastic injection molding process. 
     In another variant of the invention, the inner shell member  102  and structurally stable outer shell member  118  may be further strengthened by the addition of an overlaying outer skeletal shell  126 . The skeletal shell  126 , for example, may comprise a formed metal shell including steel or aluminum or other substantially rigid and structurally stable material. The skeletal shell may be adhesively or thermally welded onto the outer shell member and further operate to resist deformation of the inner and outer shell members due to stress loading, such as due to pressurization of the coolant in the coolant reservoir. 
     In the current art, coolant reservoir bottles are typically designed with a minimum wall thickness of 3.5 mm to 4 mm to meet the design and validation testing requirements of the application. Advantageously, use of a multi-layer coolant reservoir according to the present inventive disclosure permits the use of a wider range of structurally stable materials which are expected to result in the option to have reduced overall coolant reservoir wall thickness as well as a reduction in weight and materials usage. It is anticipated that a multi-layer coolant reservoir with an overall wall thickness of 3 mm can result in about a 9% reduction in material relative to prior art coolant reservoirs. It is further expected that in a multi-layer coolant reservoir according to the present inventive disclosure the amount of internal ribbing  120  may be reduced, or the spacing between the ribs increased due to the additional structural strength provided by multi-layer design. It is anticipated that removing or re-spacing ribs  120  in the liquid storage chamber  104  of the coolant reservoir  100  can result in an overall weight reduction of about 19%. 
     Multi-layer coolant reservoirs are particularly useful as pressurized coolant reservoirs in heavy truck and off-road/construction equipment applications. In these applications coolant reservoirs may utilize upwards of 3.8 Kg of material in order to provide the necessary structural strength and to meet durability requirements. Material and cost savings in such applications are expected to be quite considerable. 
     In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.