Abstract:
A dual washer pull plug for masking a mechanical part. The dual washer pull plug includes a first centering component and a second centering component. A first masking flange is located at a first end of the first centering component and the first centering component is configured to center the first masking flange relative to an aperture of a mechanical part on a first side of the mechanical part. A second masking flange is located at a first end of the second centering component and the second centering component is configured to center the second masking flange relative to the aperture of the mechanical part on a second side of the mechanical part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/758,678, filed Apr. 12, 2010, the entire contents of which are hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of masking devices, and more particularly to a double washer pull plug (DWP) for masking openings and threads during coating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]      FIG. 1   a  illustrates a side perspective view of an exemplary embodiment of an optimized DWP. 
           [0004]      FIG. 1   b  illustrates a sectional view of an exemplary embodiment of an optimized DWP. 
           [0005]      FIG. 2  illustrates a side perspective view of a second exemplary embodiment of an optimized DWP used for hanging parts. 
           [0006]      FIG. 3   a  illustrates a sectional view of a DWP known in the prior art positioned inside a weld nut. 
           [0007]      FIG. 3   b  illustrates a sectional view of an exemplary embodiment of an optimized DWP positioned inside a weld nut. 
           [0008]      FIG. 4  illustrates a sectional view of an exemplary embodiment of an optimized DWP being positioned inside a weld nut. 
           [0009]      FIG. 5  illustrates a side perspective view of a third exemplary embodiment of an optimized DWP. 
       
    
    
     GLOSSARY 
       [0010]    As used herein, the term “coating” refers to a substance applied to a surface to form a layer. Examples of coating may include, but are not limited to powder coating, wet spray, e-coat, dipping, plating and treating. 
         [0011]    As used herein, the term “coating error” refers to the distribution of coating particles on the threads of a weld nut, press nut or similar product or inside a non-threaded opening during the coating process. 
         [0012]    As used herein, the term “coating particles” refers to the fragments which make up a layer of coating. 
         [0013]    As used herein, the term “flexible” means capable of being bent, without breaking, allowing for temporary change in the shape of an object. An object or component (e.g., a flange) may be more or less flexible to facilitate movement, positioning and insertion in various embodiments. 
         [0014]    As used herein, the term “centering component” or “thread engaging protuberance” refers to any portion of an optimized DWP that grips or engages against the entrance thread on both sides of a threaded opening (e.g., of a weld nut, press nut or similar product) or against the walls of an opening to facilitate positioning of an optimized DWP. The diameter of the centering component(s) of an optimized DWP corresponds to the diameter of the weld nut, press nut, similar product being used, or opening which is being masked. 
         [0015]    As used herein, the term “flange” or “masking flange” refers to a protuberance, rim, ring or collar which covers a threaded or non-threaded opening. 
         [0016]    As used herein, the term “threaded opening” refers to an aperture within a component which contains threads. 
         [0017]    As used herein, the term “non-threaded opening” refers to an aperture within a component which does not contain threads. 
         [0018]    As used herein, the term “entrance thread” refers to the outermost threads of a threaded component (e.g., a weld nut, press nut or similar product). 
         [0019]    As used herein, the term “major diameter” refers to the diameter of a flange. 
       BACKGROUND 
       [0020]    Many types of manufactured parts must be coated with various substances in order to achieve the necessary or preferred characteristics before they may be used. These parts, however, often include surface portions (e.g., internal surface portions) that should not be coated. Most parts often include one or more openings which during the coating process allow coating materials to come in contact with internal surface portions of the part. Depending on the specific application for the part, contact between the coating and the internal surface portions of the part can be undesirable and/or can severely damage the part. An estimated 9.8 million dollars are spent each year on rework to ensure quality. 
         [0021]    Often the openings are threaded in order to engage with a threaded fastener or other part. The threads must engage the fastener or other part perfectly and the addition of coating particles disrupts the engagement of the threaded components. The protruding threads also interfere with the ability to mask the opening to prevent buildup of coating material. 
         [0022]    Many products, such as pull plugs and double washer pull plugs, are known in the art for masking surface portions of a part that is to be coated in order to prevent the coating material from contacting such surface portions during the coating process. 
         [0023]    Pull plugs, such as those taught by U.S. application Ser. No. 10/252,197 are designed to be seated in the part opening and to conform to the shape of the opening so that the plug segment engages the wall or threads of the part opening. The flange of the plug masks the edge of the part opening preventing coating material or other contaminants from coming in contact with the part opening and any threads and from moving through the opening. 
         [0024]    These pull plugs, however, are not desirable because they mask only the thread covered by the flange of the pull plugs allowing only one surface of the part to be coated at a time. To effectively protect the threads proximate to the undersurface of the part, the pull plug needs to be removed and reinserted in the opposite direction so that the flange now masks those threads. 
         [0025]    Double washer pull plugs known in the art, such as the one shown in  FIG. 3   a , are designed to mask both sides of a threaded component (e.g., a weld nut) preventing coating particles and contaminants from damaging the threads and/or reaching the internal surface portions of the part. The design of the prior art, however, made it difficult to perfectly center the double washer pull plug inside the threaded component leaving one side partially exposed to the coating material. In addition, the difficulty in ensuring that the double washer pull plug is centered results in a variance in the range of masking quality within a single part. 
         [0026]    It is desirable to have a plug which effectively masks both sides of a threaded or non-threaded component preventing coating error. 
       SUMMARY OF THE INVENTION 
       [0027]    The present invention is an optimized DWP apparatus comprised of a cylindrical plug body having a first end and a second end, a first centering component, a second centering component, a first masking flange, and a second masking flange. Each of the masking flanges has a major diameter, a flexibility coefficient, and an angle ⊖ 1 . The flexibility coefficient of the first masking flange is directly proportional to the amount of force necessary to pull said first masking flange through a predetermined opening that is to be masked. The cylindrical plug body, centering components and masking flanges are comprised of a material capable of withstanding temperatures of up to 600 degrees F. The two centering components center the DWP inside a threaded or non-threaded opening effectively masking the opening and/or threads during the coating process minimizing coating error. 
       DETAILED DESCRIPTION 
       [0028]    For the purpose of promoting an understanding of the present invention, references are made in the text to exemplary embodiments of an optimized DWP, only some of which are described herein. It should be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent materials, shapes and sizing may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention. 
         [0029]    It should be understood that the drawings are not necessarily to scale; instead, emphasis has been placed upon illustrating the principles of the invention. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements. 
         [0030]    Moreover, the terms “substantially” or “approximately” as used herein may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. 
         [0031]      FIG. 1   a  illustrates a side perspective view of an exemplary embodiment of optimized DWP  100  comprised of plug body  10  having first end  12  and first gripping ridge  12   a,  second end  14  having second gripping ridge  14   a,  first centering component  15 , and second centering component  20 . In the embodiment shown, first centering component  15  includes first flange  25  and second centering component  20  includes second flange  35 . In the embodiment shown, first flange  25  is more flexible than second flange  35  and bends when pressure is applied. For example, first flange  25  will bend when optimized DWP  100  is pulled through an aperture of a nut or other component having surfaces to be protected during the coating process. 
         [0032]    In the embodiment shown, plug body  10 , first end  12  and second end  14  are cylindrical with first gripping ridge  12   a  and second gripping ridge  14   a  having a slightly larger diameter than plug body  10 . In the embodiment shown, first gripping ridge  12   a  and second gripping ridge  14   a  have flattened side edges and a flattened end and are visually identical. In various embodiments, first gripping ridge  12   a  and second gripping ridge  14   a  may have rounded side edges, a rounded end, have varying dimensions (e.g., height, diameter), and/or may be visually distinct. 
         [0033]    In the embodiment shown, first and second centering components  15 ,  20  are substantially flat to correspond to the interior walls of an opening or the threads of a weld nut, press nut, or similar component. 
         [0034]    In the embodiment shown, first centering component  15  and second centering component  20  have equal diameters and are larger in diameter than plug body  10 ; and first flange  25  and second flange  35  have a larger diameter than first and second centering components  15 ,  20 . In the embodiment shown, first centering component  15  is thinner than second centering component  20 . 
         [0035]    In other embodiments, the diameters, shapes, thicknesses and flexibility of first and second centering components, and the distance between first and second centering components may vary depending on the size and shape of the threaded component that is to be masked. Depending on the application, the first and second centering components may both include thinner, more flexible flanges and/or have identical dimensions. 
         [0036]    In the embodiment shown, first and second centering components  15 ,  20  are not centered vertically on plug body  10  and the distance between first end  12  and first centering component  15  is greater than the distance between second centering component  20  and second end  14 . In other embodiments, the distances between the centering components and the ends of the plug body may vary, i.e., the distance between second centering component and second end may be greater than the distance between first centering component and first end or the distances may be equal. 
         [0037]    In the embodiment shown, the portion of plug body  10  located between first and second centering components  15 ,  20  is concave, but in other embodiments may be straight depending on the masking application. In various embodiments, the distance between first and second centering components  15 ,  20  may also vary depending on the masking application. For example, the distance between first and second centering components  15 ,  20  may vary with the height of the opening or threaded component. 
         [0038]    In the embodiment shown, optimized DWP  100  is manufactured from silicone and is flexible which allows the optimized DWP  100  to be inserted into a weld nut, press nut or other component and to conform to the threads of the threaded component. Optimized DWP  100  is reusable, and does not migrate, melt or harden allowing it to be used to mask openings in processes, such as powder coating, liquid coating, e-coating, anodizing and plating. In other embodiments, optimized DWP  100  is manufactured from another flexible material, such as EPDM rubber, cork, nylon, synthetic polymers, elastomers, equivalents and combinations Thereof. 
         [0039]    In the embodiment shown, angle ⊖ 1 , which represents the angle between cylindrical plug body  10  and first flange, is 107 degrees and angle ⊖ 2 , which represents the angle between cylindrical plug body  10  and second flange, is 128 degrees. In still other embodiments, angles ⊖ 1 , ⊖ 2  ma y  range from 10 to 170 degrees. 
         [0040]      FIG. 1   b  illustrates a sectional view of an exemplary embodiment of optimized DWP  100 . 
         [0041]      FIG. 2  illustrates a side perspective view of a second exemplary embodiment of optimized DWP  100  used for hanging parts for coating lines. In the embodiment shown, first end  12  is rounded and has aperture  50  for inserting a hook used to hang optimized DWP  100 . 
         [0042]    In the embodiment shown, first centering component  15  includes first flange  25  and second centering component  20  includes second flange  35 . In other embodiments, both first and second centering components  15 ,  20  have a flexible flange or have flanges that are of varying thickness and flexibilities. In various embodiments, first flange may be more flexible than second flange or first and second flange may be equally flexible. 
         [0043]    In the embodiment shown, the portion of plug body  10  located between first and second centering components  15 ,  20  is straight, but in other embodiments may be concave, convex or of another shape depending on the masking application. 
         [0044]    To hang a part for coating, first end  12  is inserted through a threaded or non-threaded opening in the part and optimized DWP  100  is pushed/pulled through until first flange  25  rests on the opposite side of the opening. When hung, the part rests on second flange  35  of second centering component  20 . In the embodiment shown, the thickness of second flange  35  makes it more rigid than first flange  25  and therefore more capable of supporting the weight of a part. 
         [0045]    In various embodiments, DWP  100  may further include a conductive material (e.g., carbon particles mixed in with silicone) for use with an electrostatic coating hanging system. Adding a conductive material to DWP  100  permits the charge to flow between the electrostatic system and the part, allowing the electrostatic coating system to function properly by attracting the oppositely charged coating particles to the part. 
         [0046]    The distance between the first and second centering components  15 ,  20  may vary depending of the weight of the part which is hung using DWP  100 . For example, for heavier parts, the distance between first and second centering components  15 ,  20  may be decreased to prevent the part from unseating itself. 
         [0047]    In the embodiment shown, first end  12  is rounded and second end  14  is flat with gripping ridge  14   a.  This helps the user to identify which end has aperture  50  and is nearest to first centering component  15  and first flange  25 . In other embodiments, first and second centering components  15 ,  20  each have an aperture for hanging. 
         [0048]      FIG. 3   a  illustrates a sectional view of DWP  200  positioned inside weld nut  250 . DWP  200  is one example of a double washer pull plug known in the prior art and is comprised of plug body  210  having first end  212  and second end  214 , first flange  225 , second centering component  220 , and second flange  235 . 
         [0049]    To insert DWP  200  into weld nut  250 , first end  212  is pushed through the opening in the bottom of weld nut  250  so that first flange  225  emerges from threaded region  260  and rests above the entry thread of weld nut  250 . In the embodiment shown, DWP  200  does not have a first centering component which engages the threads of threaded region  260  ensuring that DWP  200  remains centered. In the embodiment shown, DWP  200  is not centered in weld nut  250  and therefore does not effectively mask threaded region  260 . 
         [0050]      FIG. 3   b  illustrates a sectional view of an exemplary embodiment of optimized DWP  100  positioned inside weld nut  250  so that first centering component  15  engages the entry threads of weld nut  250  and second centering component  20  engages the exit threads of weld nut  250 . The inclusion of both first and second centering components  15 ,  20  ensures that optimized DWP  100  is centered inside weld nut  250  effectively masking threaded region  260 . 
         [0051]    The distance between first flange  25  and second flange  35  corresponds to the length of the opening or threaded region of the weld nut, press nut or similar component and the diameter of first and second centering components  15 ,  20  corresponds to the diameter of the opening or threaded region of the weld nut, press nut or similar component. 
         [0052]      FIG. 4  illustrates a sectional view of an exemplary embodiment of optimized DWP  100  being positioned inside the threaded opening of weld nut  250 . First end  12  of optimized DWP  100  is inserted into opening  255  of weld nut  250  and pushed through threaded region  260 . First flange  25  and first centering component  15  flex downward allowing DWP  100  it to be pushed through threaded region  260 . When first end  12  emerges from threaded region  260 , optimized DWP  100  can then be pulled through threaded region  260  and centered so that first flange  25  rests on the opposite side of threaded region  260 . First flange  25  will straighten when it exits threaded region  260 . 
         [0053]    To remove optimized DWP  100  from a threaded or non-threaded opening once the coating process is complete, second end  14  is pulled and first flange  25  flexes outward allowing it to pass through the opening (e.g., threaded region  260 ). 
         [0054]    In the embodiment shown, only first flange  25  is flexible; however, in other embodiments where both flanges are flexible or semi-flexible, it may be possible for either first flange  25  or second flange  35  to pass through a threaded or non-threaded opening allowing either end to be pushed/pulled to insert/remove optimized DWP  100 . 
         [0055]      FIG. 5  illustrates a side perspective view of a third exemplary embodiment of optimized DWP  100 . In the embodiment shown, DWP  100  has visually distinct ends which provide a visual clue as to the centering component(s) having the flexible flange (e.g., first flange  25 ) so the user knows which end should be used to remove optimized DWP  100  from the opening. First gripping ridge  12   a  has flattened side edges and a rounded end. Second gripping ridge  14   a  has rounded side edges and a flattened end. In the embodiment shown, first gripping ridge  12   a  has a height that is greater than that of second gripping ridge  14   a.    
         [0056]    In various embodiments, first gripping ridge  12   a  and second gripping ridge  14   a  may have rounded or straight side edges, a straight or rounded end, have varying dimensions (e.g., height, diameter), and/or may be visually identical.