Abstract:
An encapsulated fastener includes a nut adapted to receive a bolt. The nut is encapsulated by an encapsulation including an extension, which includes a tube adapted for receiving a portion of the bolt and a flange adapted for engaging a face of the nut. The encapsulation extension is placed on the nut in an overmolding tool, wherein an encapsulation base is injection molded over a portion of the encapsulation extension. The encapsulation base encapsulates the nut, except for its bore, which is sealed off during the overmolding process by a spring-mounted mandrel. Alternative embodiments of the invention include tubes with different configurations for contacting the bolt whereby the tube or cylinder is reinforced. A method and tooling for manufacturing the encapsulated fastener are also provided.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to fasteners, and in particular to an encapsulated fastener and a method and tooling for manufacturing same.  
         [0003]     2. Description of the Related Art  
         [0004]     Mechanical fasteners are available in a wide variety of designs, which accommodate various objects being joined. The specific fastener design features are generally determined by such criteria as the functional requirements of the applications, the static and dynamic loads imposed thereon, the materials being fastened and the operating environment.  
         [0005]     Threaded fasteners include bolts, nuts, screws, threaded rods and the like. An advantage of such fasteners is that they can be tightened and loosened with readily available hand and power tools. Consequently, threaded fasteners are used extensively in construction, manufacturing and other industries.  
         [0006]     Although steel is a logical material choice for many fasteners based on high strength and low cost, many steel alloys are susceptible to rust, corrosion and galvanic action. Such effects can be countered in some applications by making the fasteners of stainless steel and other alloys that are resistant to rust and corrosion. However, such materials tend to be relatively expensive or ineffective in applications requiring the cost-effectiveness and material strength of steel. Another solution is to zinc-coat (i.e. galvanize), paint or otherwise provide surface protection for the fasteners. However, such solutions can be ineffective in highly corrosive liquid environments, such as salt water, wastewater, process chemicals, acid compounds and base compounds. Examples of highly corrosive dry materials include fertilizers, calcium chloride and other caustic powders and granular materials. In addition to corrosion resistance, impact and abrasion resistance are important design objectives for fasteners installed in severe service applications.  
         [0007]     Fasteners that can withstand such severe service conditions are used extensively in the construction of tanks and other vessels for processing, storing and transporting highly corrosive liquids and solid bulk materials. Various applications for such fasteners are found in a number of industries, including petrochemical, manufacturing, agriculture, transportation, construction, defense, etc.  
         [0008]     For example, large tanks and storage vessels are commonly constructed on site using prefabricated steel panels, which can be coated or lined with suitable corrosion-resistant materials. Bolting the panels together on site tends to be a relatively efficient and cost-effective construction method. Moreover, bolts and nuts have the advantage of installing with basic hand and power tools.  
         [0009]     The prior art includes bolts and nuts encapsulated in injection-molded plastics, which can provide the necessary chemical resistance and other physical characteristics for these applications. For example, snap-on and spin-on plastic covers have previously been utilized for protecting the exposed portions of nut-and-bolt fasteners. The prior art also includes deep metal nuts with blind-end threaded receivers with sufficient lengths to enclose the bolts. Such nuts can be coated with anti-corrosive materials. However, such specialized fasteners tend to be more expensive than standard-size nuts. Moreover, manufacturing techniques generally require gripping the extended nuts by their interior internal threads in order for the entire exterior surface to be effectively coated. Another prior art nut encapsulation technique involves encapsulating standard size nuts in plastic materials with extensions adapted for receiving the bolt shafts protruding from the nuts. Problems with such encapsulation configurations include misalignment between bolt and extension internal threads and unsupported extensions when the extension bores are oversized to avoid contact with the bolt shafts received therein.  
         [0010]     Heretofore there have not been available an encapsulated fastener and a method and tooling for manufacturing same with the advantages and features of the present invention.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0011]     In the practice of an aspect of the present invention, an encapsulated fastener is provided, which includes a two-part encapsulation comprising a base encapsulating a nut and an extension encapsulating a portion of a bolt extending from the base. A manufacturing method embodying the present invention includes the steps of injection molding the encapsulation extension, placing it on a nut and overmolding the base over the nut and a portion of the extension with tooling embodying another aspect of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of a fastener including an encapsulated nut embodying an aspect of the present invention.  
         [0013]      FIG. 2  is a perspective view of a nut and an encapsulation extension.  
         [0014]      FIG. 3  is a perspective view of the nut placed on the encapsulation extension.  
         [0015]      FIG. 4  is a distal end view of the encapsulation extension.  
         [0016]      FIG. 5  is a cross-sectional view of a tool for injection molding the encapsulation extension.  
         [0017]      FIG. 6A  is a cross-sectional view of an overmolding tool for encapsulating nuts according to the present invention, shown in an open position with the nut and the encapsulation extension in place.  
         [0018]      FIG. 6B  is another cross-sectional view of the overmolding tool, shown in a closed position with the nut fully encapsulated.  
         [0019]      FIG. 7  is another cross-sectional view of the overmolding tool, shown in an open position with the encapsulated nut being ejected.  
         [0020]      FIG. 8  is a perspective view of an encapsulated nut embodying another aspect of the present invention.  
         [0021]      FIG. 9  is a distal end view thereof.  
         [0022]      FIG. 10  is a cross-sectional view of an application of the encapsulated nut.  
         [0023]      FIG. 11  is a cross-sectional view of another application of the encapsulated nut.  
         [0024]      FIG. 12  is a cross-sectional view of another application of the encapsulated nut.  
         [0025]      FIG. 13  is a cross-sectional view of the encapsulated nut taken generally along line  13  in  FIG. 8 .  
         [0026]      FIG. 14  is a cross-sectional view of an encapsulated nut embodying another aspect of the present invention.  
         [0027]      FIG. 15  is a cross-sectional view of an encapsulated nut embodying another aspect of the present invention.  
         [0028]      FIG. 16  is a cross-sectional view of an encapsulated nut embodying another aspect of the present invention.  
         [0029]      FIG. 17  is a distal end view of the encapsulation extension, shown in a mold with corner locator/ejector pins.  
         [0030]      FIG. 18  is a perspective view of a nut and encapsulation extension embodying another aspect of the present invention.  
         [0031]      FIG. 19  is a distal end elevational view thereof.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0000]     I. Introduction and Environment  
         [0032]     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.  
         [0033]     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, up, down, front, back, right and left refer to the invention as oriented in the view being referred to. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning. The invention can be fabricated in various sizes and configurations from a wide variety of suitable materials, which are chosen for their characteristics according to the intended use and the operation of the invention. For example, engineered plastics, such as glass-filled nylon, can be chosen for such characteristics as chemical resistance, rigidity and toughness. Without limitation on the range of suitable materials for manufacturing the encapsulated fasteners and practicing the manufacturing method, a wide range of plastics and other formable materials can be utilized to satisfy the applicable performance, manufacturing and cost parameters.  
         [0000]     II. Encapsulated Nut  2   
         [0034]     Referring to  FIG. 1  in more detail, the reference numeral  2  generally designates a fastener comprising an encapsulated nut  4  adapted for threadably receiving a bolt  6 . The encapsulated nut  4  includes a nut  8  within an encapsulation  10  generally comprising an encapsulation base  12  and an encapsulation extension or hat  14 . The nut  8  includes a nut bore  25  and is shown with a four-sided configuration, although hex nuts and other shapes could be employed with the present invention. As shown in  FIGS. 2-4 , the nut  8  is adapted for placement on the encapsulation extension  14 . The encapsulation extension or hat  14  includes a flange  18 , which can have a concave proximal face  20  with comers  22 , which are turned to form the concave configuration and accommodate the nut  8 , which has a corresponding convex face  24  adapted for mating with the concave proximal face  20  of the flange  18  whereby the nut  8  can be supported on the extension  14  in a predetermined, aligned configuration, as shown in  FIG. 3 . The extension also includes a distal cylinder  26  with a proximal end  28 , which intersects the flange  18  at an annular junction  32 , which can be radiused or filleted as shown for greater strength. The extension cylinder  26  includes a closed, distal end  34  whereat an inner, cylinder bore  36  terminates, thus providing the cylinder  26  with a closed-end configuration for encapsulating a portion of the bolt  6 . The cylinder  26  also includes multiple (e.g., two are shown), annular rings  38 , which are located distally from the junction  32 . The encapsulation extension  14  can be fabricated by any suitable process, such as injection molding, casting, etc. using any suitable materials, such as engineered plastics, thermoplastics, glass-filled nylon, etc.  
         [0035]      FIG. 5  shows a tool  94  for injection molding the encapsulation extension  14 . The tool  94  can comprise any suitable mold, such as an injection mold as shown with upper and lower mold halves  96 ,  98  and a mold cavity  100 .  FIGS. 6A, 6B  and  7  show an overmolding tool  40  adapted for overmolding the encapsulation base  12  over the nut  8 , the flange  18  and a portion of the cylinder  26  at a secure, fused interface adjacent to the cylinder proximate end  28 . The overmolding tool  40  is shown in an open position in  FIG. 6A  and includes a first or lower mold half  42  with a first or lower cavity  43  adapted to receive the encapsulation extension  14  and a second or upper mold half  44  with a second or upper cavity  45 , which includes a spring-mounted mandrel  46  reciprocably received in a mandrel receiver  47 . The mandrel  46  includes a conical end  48  and a shoulder  49  adapted for engaging the nut  8  in a secure, sealing connection with the internal threads  50  of the nut bore  25  with the mandrel  46  located within the nut  8 , as shown in  FIG. 6B  (tool  40  closed). In this configuration the mandrel  46  substantially seals the nut bore  25  and the extension cylinder bore  36  whereby plastic is excluded during the encapsulation base  12  overmolding step.  
         [0036]     The spring-compressed close fit of the nut convex face  24  and the flange proximal face  20  further seal the encapsulation extension  14  against the injected overmolding plastic. The mandrel  46  is biased downwardly by a compression spring  52 , which is adapted for accommodating variations in thicknesses of nuts  8  and tends to press the nut convex face  24  tightly and sealingly against the flange proximal face  20 .  
         [0037]     A subgate  54  is formed in the overmolding tool  40  for receiving the molten material for molding the encapsulation base  12 , which preferably fuses with the portion of the encapsulation extension  14  exposed within the lower mold cavity  43 . The distal-most ring  38  provides a stop for the encapsulation base  12  material.  FIG. 7  shows the upper mold half  44  raised and an ejector pin  56  protruding upwardly into the lower mold cavity  43  for engaging the cylinder distal end  34  and ejecting the completed encapsulated nut  4 .  
         [0038]      FIGS. 1, 8  and  9  show the completed encapsulated nut  4 . The two-step process of molding the encapsulation extension  14  and overmolding the encapsulation base  12  on the nut  8  and a portion of the encapsulation extension  14  results in a relatively strong, impact-resistant assembly. The encapsulation base  12  includes an opening  13 , which is aligned with and has approximately the same diameter as the nut bore  25 . The opening  13  is formed by the mandrel  46 . The encapsulation parts  12 ,  14  preferably fuse in the overmolding process and thereby attain strength characteristics similar to a monolithically molded encapsulation.  
         [0039]     Applications of fasteners embodying aspects of the present invention are shown in  FIGS. 10-12 .  FIG. 10  shows first and second plates  58 ,  60  with a gasket  62  therebetween and a square-headed bolt received in an encapsulated nut  4 .  FIG. 11  shows a hex bolt  66  with a washer  68 .  FIG. 12  shows a carriage bolt  70  with a finned neck  72 . In all of these applications, and various others not shown, the encapsulation  10  of the present invention effectively protects the nut  8  and the bolts  6 ,  66 ,  70  from the contents of a vessel or other structure enclosed by the plates  58 ,  60 . As shown in  FIGS. 10-12 , the fasteners embodying the present invention can be installed in various orientations. The overmolding of the encapsulation base  12  provides a strong and secure interface with the nut  8  whereby sufficient force can be applied with a wrench or similar tool in order to tightly torque the fasteners  2 .  
         [0040]      FIGS. 13-16  show alternative configurations for the extension cylinder, which can be adapted for structural reinforcement through contact with the bolt  6 .  FIG. 13  shows multiple (e.g., three are shown) splines  74  within the bore  36  of the extension cylinder  26 . The shaft of the bolt  6  (dashed lines) is in contact with the splines  74 , whereby the extension cylinder  26  is reinforced by the bolt  6  and is thus more impact-resistant.  FIG. 14  shows a modified, octagonal extension tube  76 , which contacts the bolt  6  along each of its eight sidewalls.  FIG. 15  shows a similar, hexagonal extension tube  78 .  FIG. 16  shows an oversized cylindrical tube  80  with a bore  82  having an inside diameter greater than the outside diameter of the bolt  6 , whereby an annular clearance space  84  is formed therebetween. This configuration avoids any interference between the bolt  6  and the extension cylinder  80 , which may be preferred in some applications. Other constructions within the scope of the present invention can include interference-fitting cylinders with smaller inside diameters, internal threading within the cylinder  26  aligned with the nut internal threads  50 , and other variations providing interference and interference-free clearance. The cylinder bore  36  can receive various sealant, adhesive and epoxy compounds for enhancing the strength, impact-resisting and sealing characteristics of the installed fasteners.  
         [0041]      FIG. 17  shows two pairs of locator/ejector pins  86 , which can be located at opposite comers of the nut  8  and under the encapsulation base  12  (dashed lines) whereby the nut  8  is positioned prior to the overmolding step during which the pins  86  are retracted (e.g., into the lower mold half  42 ) and after which they extend to eject the completed encapsulated nut  4 .  FIGS. 18 and 19  show locating spurs  88  formed on the edges of the flange  18  for engaging the sides of the nut  8 . The locating spurs  88  can be molded in optional subcavities  102  in the injection molding tool  94  ( FIG. 5 ). Alignment ribs  90  are provided on the encapsulation extension cylinder  26 , e.g. at 90° radial spacing, for maintaining the encapsulation extension  14  in proper alignment within the lower mold half  42 . The alignment ribs  90  can be formed in the injection molding tool  94  ( FIG. 5 ) and received in optional alignment rib receivers  92  ( FIGS. 6A, 6B  and  7 ) for properly aligning the encapsulation extension  14  within the lower mold half  42 .  
         [0042]     It is to be understood that the invention described here in can be embodied in various forms, and is not to be limited to the examples discussed above. Other components and configurations can be utilized in the practice of the present invention.