Abstract:
The preferred embodiment of a double ended stud fastening system includes a first segment for engaging a plastic component, a second threaded segment for engaging a nut and a lateral projection disposed between the segments. In another aspect of the present invention, the first segment is threaded and the lateral projection is a flange.

Description:
CROSS REFERENCED TO RELATED APPLICATIONS 
     This is a continuation-in-part of copending U.S. Provisional Application Serial No. 60/114,275, filed on Dec. 30, 1998, which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to fasteners and more specifically to a double ended stud fastening system. 
     It is common to arc weld an enlarged circular end of a threaded metal stud onto a sheet metal body panel of an automotive vehicle. Various parts are then inserted upon the single threaded stud and an internally threaded nut is rotationally inserted onto the stud. However, the nut installation is a time consuming process which often leads to undesirably varying fastening forces. 
     It is also known to use a pneumatic tool to swage and compress an unthreaded metal nut or sleeve over the arc welded stud in a torque-free manner. This torque-free construction employs a two-part stud, separated by a reduced diameter neck. The tool pulls off the threaded end after the nut is secured to the remaining threaded part of the stud. The nut can be unscrewed and reused. This stud is almost exclusively used without the need for holes in the sheet metal body panel. However, it is often undesirable to arc weld a stud directly to the sheet metal body panel. For example, the welding station is fairly expensive and takes up considerable space in the assembly plant. Furthermore, it is impractical to arc weld such a conventional stud to a plastic component instead of to the body panel. Thus, there is a need to secure a stud fastener directly to a plastic component while using a torque-free nut and a two segment threaded stud, in order to secure a plastic component to a body panel. 
     It is also known to press insert, insert mold or ultrasonically insert a knurled fastener into a plastic panel. See, for example, U.K. Patent Application GB 2 274 697 A entitled “Part Mounting Device and Method” which was published on Aug. 3, 1994. However, the bolt shown in FIG. 7B of the U.K. application is of a conventionally threaded variety using a standard threaded nut. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the preferred embodiment of a double ended stud fastening system includes a first segment for engaging a plastic component, a second threaded segment for engaging a nut and a lateral projection disposed between the segments. In another aspect of the present invention, the first segment is threaded and the lateral projection is a flange. A further aspect of the present invention provides a third segment, joined to the second segment by a reduced diameter neck, which is removable from the second segment after the nut is compressibly secured to the second segment of the stud. A method of fastening a panel to a member using a fastener is also provided. 
     The present invention is advantageous over traditional devices, in that the present invention fastener is secured to the plastic component off of the quickly moving assembly line and then the plastic component and fastener assembly are quickly attached to the body panel with a compression sleeve or nut. Engagement of the nut onto the threaded stud does not require any torque upon the nut or stud, thereby maintaining the desired mounting of the stud to the plastic component. Furthermore, a low cost nut can be used since it does not employ internal threads prior to insertion upon the stud. Moreover, the nut can be unscrewed and reused. The component-to-panel fastening also advantageously occurs on a single side of the body panel and is very quickly installed, compared to pre-threaded nuts, since the traditional nut run-down time is not required. Thus, the no torque fastening system of the present invention is ideally suited for direct mounting to plastic components. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially exploded and fragmented side elevational view showing a first preferred embodiment of a fastening system of the present invention; 
     FIG. 2 is an assembled and partially fragmented side elevational view showing the first preferred embodiment of the present invention fastening system; 
     FIG. 3 is a perspective view showing the preferred embodiment stud of the present invention fastening system; 
     FIG. 4 is a side elevational view showing the preferred embodiment stud of the present invention fastening system; 
     FIG. 5 is an enlarged side elevational view, taken within circle  5  of FIG. 4, showing the preferred embodiment stud of the present invention fastening system; 
     FIG. 6 is a cross sectional view showing the first preferred embodiment nut of the present invention fastening system; 
     FIG. 7 is side elevational view showing a second preferred embodiment nut of the present invention fastening system; 
     FIG. 8 is a side elevational view showing the preferred embodiment fastening tool of the present invention fastening system; 
     FIGS. 9-14 are a series of partially fragmented, side elevational views showing the assembly sequence of the second preferred embodiment of the present invention fastening system; 
     FIG. 15 is an exploded side elevational view, partially in section, showing a third preferred embodiment of the present invention fastening system; and 
     FIG. 16 is a side elevational view, partially in section, showing a fourth preferred embodiment of the present invention fastening system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, the first preferred embodiment of the fastening system  21  of the present invention employs a stud fastener  23  and a nut  25 . The nut  25  is also known as a sleeve. Stud  23  and nut  25  serve to fasten a plastic component or member  27  to a panel  29 . Plastic component  27  can be an automotive vehicle part, such as: an exterior mirror housing; heating/ventilation/air conditioning blower, heater, insulator, duct or shield; wire harness locator; hose locator; exterior trim panel; interior garnish molding; bumper fascia; tail light; and side window mounting. Panel  29  is preferably a stamped sheet metal body panel. 
     Stud  23  includes a first threaded segment  41 , a circular flange  43 , a second threaded segment  45 , a neck  47  and a third threaded segment  49 . This can best be viewed in FIGS. 3-5. First threaded segment  41  has a T6 by 1.6 mm thread, second threaded segment  45  has a M6 by 1.5 mm thread, and third threaded segment  49  has a M5 by 0.8 mm thread. The threads define external engagement patterns on the stud. Furthermore, neck  47  has a reduced diameter as compared to the threaded segments. Neck  47  is also provided with a forty degree (total) angular taper x and a circumferential radius at the apex of the taper to define the reduced diameter section. Stud  23  is preferably machined from 1010 steel. 
     FIGS. 1 and 6 show the first preferred embodiment nut  25 . This nut  25  has a circular-cylindrical section  51  and an enlarged diameter portion  53 . Nut  25  has a smooth and unthreaded internal aperture  55  prior to installation onto stud  23 . 
     FIG. 7 illustrates a second preferred embodiment nut  61 . Nut  61  has an externally chamfered end  63 , a circular-cylindrical section  65 , a hexagonal wrench receiving formation  67  and an enlarged diameter portion  69 . Nut  61  also has a smooth and unthreaded internal aperture  71  prior to installation onto stud  23 . Nuts  25  and  61  are preferably formed from 1010 steel. 
     A pneumatically actuated fastening/setting tool  31  is shown in FIGS. 8 and 10. Tool  81  employs a piston cylinder  83  and trigger  85  to operate parts inside a nose  87 . Tool  81  uses a standard air pressure between 85 and 100 psi to generate about 3000-5000 N of clamping force at the joint. Nose  87  of tool  81  further has a nose piece  89 , jaw case  91  and jaw  93 . 
     The sequence of fastening stud  23  to plastic component  27  and then, in turn, to panel  29  can be observed with reference to FIGS. 9-14. First, component  27  is injection molded from a plastic material such as Nylon. An unthreaded bore  101  is simultaneously formed inside a projecting boss  103 . Second, first threaded segment  41  is rotated while being pushed into bore  101 , as shown in FIG.  9 . The threads of stud  23  cause the internal surface of boss  103  to become threaded. Alternately, a threaded or knurled end of a stud can be insert molded into the boss; however, the stud cannot be easily disassembled from the component, unlike with the preferred embodiments. 
     Third, the assembly consisting of component  27  and stud  23  is placed adjacent to an outside surface of panel  29 . Flange  43  of stud  23  abuts and contacts against panel  29 . Fourth, second and third threaded segments  45  and  49  are inserted through a slightly larger circular hole in panel  29 . Fifth, nut  61  (or nut  25 ) is linearly slid past third threaded segment  49  and onto second threaded segment  45 . This can be seen by comparing FIGS. 10 and 11. 
     Sixth, referring to FIGS. 11 and 12, tool  81  is linearly inserted onto stud  23  and nut  61 . This step may be concurrent with the prior step. Third threaded segment  49 , acting as a mandrel, is received inside of jaw  93  while nose piece  89  and a distal end of jaw case  91  surround cylindrical section  65  of nut  61 . Seventh, jaw  93  firmly grips third threaded segment  49  while jaw case  91  linearly pushes nut  61  into desired abutting contact against the inside surface of panel  29 , creating a preload instead of torque. Eighth, jaw case  91  is caused to swage and compress cylindrical section  65  of nut  61  in an inward lateral manner thereby forming threads on aperture  71  of nut  61 . This advantageously causes identically matching threads and eliminates the traditional problem of cross-threading of misaligned pre-threaded nuts and bolts. Moreover, the tool does not significantly apply any rotational or torquing force upon stud  23  or nut  61  during fastening; this preserves the secure relationship of stud  23  to component  27  and achieves high and repeatable quality of fastening forces to panel  29 . 
     Finally, a comparison of FIGS. 12-14 demonstrates breaking of neck  47  wherein jaw  93 , still retaining third threaded segment  49 , is linearly moved away from second threaded segment  45 . Third threaded segment  49  is then discarded. Nut  61  can thereafter be unscrewed from stud  23  by use of a wrench. Nut  61  can be reusable approximately five times. 
     A third preferred embodiment of the fastening system is shown in FIG.  15 . In this embodiment, a stud  123 , like that with the first preferred embodiment, has a pair of threaded segments  145  and  149  joined by a reduced diameter neck  147 . A large diameter circular flange  143  is integrally attached to segment  145 . However, a distinguishing feature from the prior embodiments is that a knurled segment  141  is integrally attached to flange  143  in a longitudinally extending and coaxial manner. Knurled segment  141  includes a pair of nominal diameter circular sections with a generally parallel knurl pattern on the external radial surfaces of the sections. These knurled sections are separated by a reduced diameter section. Another reduced diameter and smooth section is located between flange  143  and knurled segment  141 . 
     An ultrasonic horn tool or high temperature conducting tool  181  is positioned adjacent a distal end of stud  123 . During the ultrasonic or conductive heating operation, tool  181  serves to heat stud  123  while applying a longitudinally pushing force against the distal end of stud  123 . Stud  123  is concurrently heated and inserted into a bore  201  in a fastening area  203  of a plastic component  127 . Bore  201  preferably has a frusto conically tapered lead-in angle of about 8 degrees total. After tool  181  is removed or deenergized, the melted plastic is allowed to cool and rigidly engage knurled segment  141  in a permanently fastened manner. The nut swaging and neck breaking steps are subsequently performed as discussed with the prior embodiments. 
     FIG. 16 illustrates a fourth preferred embodiment stud  223  having threaded segments  245  and  249  separated by a breakable neck  247 . A knurled segment  241  longitudinally projects from a circular flange  243  as with the third preferred embodiment. However, with the present exemplary embodiment, an opposing or crossed knurl pattern is employed at knurled segment  241 . Knurled segment  241  is ultrasonically or conductive heat inserted into a bore  301  of a projecting boss  303  depending from a plastic component  227 . The plastic adjacent bore  301  is melted during the ultrasonic or heat insertion process and then allowed to reharden. Hence, the plastic material of boss  303  permanently secures stud  223  to plastic component  227 . It is significant that the nut swaging operation does not tend to separate either embodiment of the knurled segments from the plastic component during the sheet metal panel fastening procedure due to employment of the circular flanges, as well as the non-rotational engagement of the nut with the corresponding threaded segments. 
     While various embodiments of the fastening system have been disclosed, it should be appreciated that other aspects can be employed within the scope of the present invention. For example, three or more studs may be necessary to retain a component onto a panel. Furthermore, the fastening system can be used to secure a motor housing, tube or other component to a panel of a household appliance, power tool or industrial machine. It is also envisioned that a traditionally pre-threaded nut and torquing action can be used with the present invention stud, although many of the advantages disclosed herein will not be achieved. Various materials and dimensions have been disclosed in an exemplary fashion, however, other materials and dimensions many of course be employed. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.