Abstract:
An electromagnetic solenoid is provided with a bobbin having a generally cylindrical body and a pair of radially outwardly extending end flanges each disposed at opposite ends of the generally cylindrical body. The pair of end flanges each have an inner face facing one another and an outer face facing away from one another. The inner and outer faces of the pair of end flanges have a plurality of grooves formed in a surface thereof. The grooves provide for enhanced retention of an over-mold that seals a coil within the bobbin assembly.

Description:
FIELD 
     The present disclosure relates to electromagnetic solenoids, and more particularly, to a wire wrapped bobbin with an overmolded exterior for use in a solenoid. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Electromagnetic solenoid valves are commonly used in the automotive industry and many other industries for opening and closing valves and actuating various components. Road salt, water, dirt, and debris may enter a solenoid valve despite many efforts to properly seal the valve. Currently, solenoid valves utilize a wire wrapped around the bobbin to define a coil thereon which is then overmolded with an elastomeric material in order to attempt to prevent leakage. However, after numerous cycles where the solenoid is heated up and cooled down, leakage issues can develop between the over-mold and the bobbin so that debris can get into the coil and short-circuit the solenoid. Under thermal cycling, the over-mold expands earlier than the inner core and a gap of a few microns occurs. Repeated cycles create a ratcheting effect causing the gap to increase, thus circumventing the seals and creating multiple leak paths. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to the principles of present disclosure, a bobbin for use with an electro-magnetic solenoid is provided including a spool-type bobbin having a generally cylindrical body and a pair of radially outwardly extending end flanges each disposed at opposite ends of the generally cylindrical body. The pair of end flanges each have an interface facing one another and said pair of end flanges each have an outer face facing away from one another. The inner and outer faces of the pair of end flanges have a plurality of grooves formed in a surface thereof. When the bobbin is overmolded, the over-mold is received in the grooves in the inner and outer faces of the end flanges of the bobbin in order to mechanically lock the over-mold to the bobbin in order to prevent any leakage from forming therebetween as the solenoid is subjected to thermal cycling. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a cross-sectional view of a solenoid, according to the principles of present disclosure; 
         FIG. 2  is a perspective view of a bobbin, according to the principles of the present disclosure; 
         FIG. 3  is a perspective view of an alternative bobbin, according to the principles of present disclosure; 
         FIG. 4  is a partially cut-away perspective view of an overmolded bobbin and coil assembly, according to the principles of the present disclosure; 
         FIG. 5  is a schematic diagram of a molding device for molding the bobbin of  FIG. 2 ; and 
         FIG. 6  is a schematic diagram of a molding device for molding the bobbin of  FIG. 3 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With reference to  FIG. 1 , a solenoid  10  is shown including a bobbin  12  having a coil  14  wrapped around the bobbin  12  and an over-mold  16  overmolded over the bobbin  12  and coil  14 . A plunger  18  is received in the center of the bobbin  12 , wherein supplying a current to the coil  14  creates an electro-magnetic field that causes the plunger  18  to move axially for opening or closing a valve, or otherwise actuating another device. The bobbin  12  includes a cylindrical body  20  and a pair of end flanges  22 ,  24  which each include an inner face  22   a ,  24   a  and an outer face  22   b ,  24   b . As best shown in  FIG. 2 , the inner and outer faces  22   a ,  22   b ,  24   a ,  24   b  of the pair of end flanges  22 ,  24 , respectively, are provided with a plurality of grooves  30  formed in a surface thereof. The over-mold  16  is received within the grooves  30  that mechanically lock with the over-mold  16  to prevent separation of the over-mold  16  from the end flanges  22 ,  24  due to thermal expansion when the solenoid  10  is thermally cycled. 
     The grooves  30  can be formed in the flanges  22 ,  24  of the bobbin  12  during the molding of the bobbin  12 . As would be understood by one having ordinary skill in the art, the bobbin  12  can be made of plastic and can be molded in a mold cavity having several exterior cavity forming portions  40   a - 40   f , as shown in  FIG. 5 , are moved to an engaged position to define a mold cavity in the shape of the bobbin  12 , as illustrated in  FIG. 2 . When the mold components  40   a - 40   f  are removed from the molded part, each component  40   a - 40   f  has to be pulled in one direction A-F. Therefore, the grooves  30  formed on the flanges  22 ,  24  must align with the pull direction of the corresponding mold components  40   a - 40   f . With the bobbin as illustrated in  FIG. 2 , the flanges  22 ,  24  can be provided with grooves  30  that extend in one direction on one face, and in a perpendicular direction on its opposite face. With this configuration, the different direction grooves  30  on opposite faces work together to mechanically lock the over-mold  16  to prevent separation of the over-mold  10  from the flange  22 ,  24  during thermal cycling. 
     As an alternative embodiment as shown in  FIG. 3 , the end flanges  122 ,  124  are divided into four quadrants with the mold components  140   a - 140   d , as shown in  FIG. 6 , each corresponding to a quadrant of the flanges  122 ,  124  wherein the mold components  140   a - 140   d  can be pulled in a direction A-D aligned with the grooves  30 . Accordingly, each quadrant of the flanges  122 ,  124  are provided with grooves  130  that are generally perpendicular to the grooves in an adjacent quadrant of that face. These perpendicular grooves on adjacent quadrants provide a locking function to prevent separation of the over-mold  16  due to thermal expansion. 
       FIG. 4  shows a partially cut-away perspective view of an over-mold  16  on the bobbin  112  and coil  14  according to the principles of the present disclosure. 
     It is noted that the bobbin includes annular dovetail grooves  32  on opposite sides of the bobbin  12 ,  112 . In the solenoid assembly as shown in  FIG. 1 , a pair of O-rings are disposed between the dovetail grooves  32  and the housing. The dovetail grooves  32  dictate that the mold components  40   a - 40   f ,  140   a - 140   d  be pulled in a radial direction relative to an axial center of the bobbin  12 ,  112 . The orientation of the grooves  30 ,  130  allow for the pulling of the mold components  40   a - f ;  40   a - d  in the one direction as necessary. Accordingly, the bobbin  12 ,  112 , according to the principles of present disclosure, result in an over-mold bobbin  12  and coil assembly that has an appearance that is the same as prior overmolded bobbin and coil assemblies as well as performing the same function thereof. However, the improved retention strength of the grooves  30 ,  130  provides an overmolded bobbin and coil assembly that does not experience separation and leakage due to thermal cycling. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.