Abstract:
The present invention relates to a fastener assembly, comprising a nut provided with a plurality of threads, a torque transmitter shaped to transmit torque to the nut, and an annular surface that is undulating in shape, a washer provided with a clamp surface and a bearing surface that is undulating in shape and axially opposed to the annular surface on the nut, and a spring member located between the annular surface on the nut and the bearing surface on the washer.

Description:
This is a continuation-in-part of application Ser. No. 10/712,611, filed Nov. 13, 2004 now abandoned, which is a continuation-in-part of application Ser. No. 09/933,312, filed on Aug. 20, 2001, now U.S. Pat. No. 6,749,386, the disclosures of application Ser. No. 10/712,611 and U.S. Pat. No. 6,749,386 are hereby incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to fastener assemblies, and particularly to locking fastener assemblies provided with an undulating surface. 
   BACKGROUND OF THE INVENTION 
   Fasteners are known in the art and are used for threading onto a threaded member. The present invention is an improved locking fastener that is provided with an undulating surface. 
   SUMMARY OF THE INVENTION 
   The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary. Briefly stated, a fastener assembly, comprising a nut provided with a plurality of threads, a torque transmitter shaped to transmit torque to the nut, and an annular surface that is undulating in shape, a washer provided with a clamp surface and a bearing surface that is undulating in shape and axially opposed to the annular surface on the nut, and a spring member located between the annular surface on the nut and the bearing surface on the washer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an end view of a vehicle axle and wheel hub having a fastener assembly of an alternative embodiment threaded onto a stud; 
       FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 ; 
       FIG. 3  is an exploded perspective view a locking fastener assembly of an alternative embodiment; 
       FIG. 4  is a side elevational view of a locking fastener assembly of an alternative embodiment; 
       FIG. 5  is a side elevational view of a nut of an alternative embodiment; 
       FIG. 6  is a top view of the clamping surface on the washer of an alternative embodiment 
       FIG. 7  is a side elevational view of a spring member, partially in section; 
       FIG. 8A  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; 
       FIG. 8B  is a close-up view of an annular surface on a nut, a bearing surface on a bearing surface on a washer, and a spring member; 
       FIG. 9A  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; 
       FIG. 9B  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; 
       FIG. 9C  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; 
       FIG. 9D  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; and 
       FIG. 9E  is a close-up view of an annular surface on a nut, a bearing surface on a washer, and a spring member; and 
       FIG. 10  is a graphical illustration depicting pounds of force generated per degree of rotation of the nut and pounds of torque exerted on the nut per degree of rotation of the nut. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIGS. 1 and 2 , yet another embodiment of the locking fastener assembly is depicted at  250 . As shown, therein, the locking fastener assembly  250  is securing a wheel to a hub of a vehicle. The locking fastener assembly  250  includes three components, a nut  52 , a washer  54 , and spring member  256 . The washer  54  is preferably fabricated from chromium molybderium alloy steel. 
   Turning now to  FIGS. 3 ,  4  and  7 , the spring member  256  of the present embodiment is depicted. The spring member is preferably fabricated from  1095  tempered spring steel that is provided with a Rockwell hardness of C 48-51; otherwise known as blue tempered spring steel. As shown in  FIG. 7 , the spring member  256  is generally annular in shape and defines a bore  257  that is dimensioned to receive the collar  85  of the nut  52 . In this embodiment, the collar  85  on the nut  52  is adapted to extend axially into the bore  257  and within the generally cylindrical washer  82  whereupon a skirt  68  is formed by flaring the collar  85  outwardly under an undercut shoulder  83  within the washer  54 . 
   Also shown in  FIG. 7 , the spring member  256  is provided with a nut contact surface  295  and a washer contact surface  296 . The nut and washer contact surfaces  295 ,  296  are generally annular in shape and extend from the bore  257  to an intermediate surface  293  of the spring member  256 . As shown therein, the intermediate surface  293  extends radially around the bore  257  and is located between the nut contact surface  290  and the washer contact surface  291 . The intermediate surface  293  is provided with a thickness  294 , which preferably measures approximately 0.81 mm. 
   According to one aspect of the present embodiment, the spring member  256  is configured to increase the ratio of generated clamp load to exerted torque: 1 Generated clamp load Exerted torque on the nut 
   According to another aspect of the present embodiment, the spring member  256  is configured to reduce the exerted torque on the nut  52  when it is rotated relative to the washer  54 . According to another aspect, the spring member  256  is configured to reduce the friction between the nut  52  and the washer  54  by a factor of 10. By way of example, and not limitation, the clamp load generated at 500 ft lbs of torque, without the spring member  256 , is approximately 5,000 lbs, however, with the spring member  256  the clamp load is approximately 50,000 lbs. 
   According to one aspect of the present embodiment, the spring member  156  increases tension in the stud  26  as the nut is torqued. According to another aspect of the present embodiment, the spring member  156  increases the normal force that the threads  64  of the nut  52  exert on the threads of the stud  26  and the normal force that the threads of the stud  26  exert on the threads  64  on the nut  52 . According to yet another aspect of the present embodiment, the spring member  156  increases the friction between the threads of the stud  26  and the threads  64  of the nut  52 . According to another aspect of the present embodiment, the spring member  256  is configured to prevent the nut  52  from backing off the stud  26 . 
   When the nut  52  is threaded onto the stud  26 , the washer  54  and spring member  256  are pushed freely in front of it. As rotation of the nut  52 , with respect to the stud  26 , continues, eventually, the peaks  74  on the nut  52  begin to exert a load on the nut contact surface  295  of the spring member  256 . In this state, as shown in  FIGS. 8A and 8B , the spring member  256  is seated upon the bearing surface  284  of the washer  54 , whereby contact occurs between the washer contact surface  296  of the spring member  256  and the peaks  118  of the bearing surface  284 . Additionally, as shown therein, the nut  52  is seated on the spring member  256 , whereby contact occurs between the nut contact surface  295  of the spring member  256  and the peaks  74  of the bearing surface  72  of the nut  52 . Furthermore, the nut and washer contact surfaces  295 ,  296  are substantially flat and substantially perpendicular with respect to the axis  251  of the assembly  250 . 
   As rotation of the nut  52  continues, the peaks  74  on the nut  52  slide over the nut contact surface  295  of the spring member  256 . Eventually, however, as further rotation of the nut  52  continues, the load exerted by the peaks  74  deflects the spring member  256 .  FIGS. 9A-E  depicts the shape of the spring member  256  as the nut  52  is progressively rotated in the direction of arrow A. As shown therein, when the peaks  74  on the nut  52  are located between adjacent peaks  118 , such as peaks  118   a  and  118   b,  on the washer  54 , the spring member  256  is deflected and provided with peaks  297 , inclined faces  298 , and valleys  299 . The peaks  297  of the spring member  256  are seated on the peaks  118  of the washer  54  and the peaks  74  of the nut  52  are seated on the valleys  299  of the spring member  256 . The inclined faces  298  of the spring member  256  are preferably angled radially and circumferentially. Also shown in  FIGS. 9A-E , when the peaks  74  on the nut  52  are positioned axially above the peaks  118  of the washer  54 , the spring member  256  resiliently returns to a relatively flattened shape and is preferably provided with substantially flat nut and washer contact surfaces  295 ,  296 . 
   According to one aspect of the present embodiment, the extent of deflection is measured by the deflection angle  300  of the faces  298  on the spring member  256 . As shown in  FIG. 9C , the deflection angle  300  is measured with respect to a line A, which extends in a direction that is perpendicular to the axis  251  of the locking fastener assembly  250 . As shown in  FIGS. 9C-9E , the deflection angle  300  decreases as the peaks  74  on the nut  52  move away from the midpoints M.sub. 2  of the valleys  122  and towards the peaks  118  on the washer  54 . 
   According to another aspect of the present embodiment, the extent of the deflection of the spring member  256  is measured by the vertical height H of the peaks  297  on the spring member  256  above the valleys  299  of the spring member  256 . The vertical height H increases to a maximum when the midpoints M.sub. 1  of the peaks  74  on the nut  52  are positioned substantially above the midpoints M.sub. 2  of the valleys  122  on the washer  54 , as shown in  FIG. 9C . The maximum vertical height is dimensioned to be greater than the clearance between the threads  264  in the nut  52  and those on the stud  26 . In the preferred embodiment, the maximum vertical height measures approximately 0.15 mm. The vertical height H decreases to a minimum, when the peaks  74  on the nut  52  are positioned axially above of the peaks  118  on the washer  54 , as shown in  FIGS. 9A and 9E . 
   According to one aspect of the present embodiment, there is an increase in the normal force exerted on the threads of the stud  26  by the threads  64  on the nut  52 , when there is a decrease in the deflection angle  300  of the faces  298  on the spring member  256 . According to another aspect of the present embodiment, when the vertical height H transitions from the maximum to the minimum, there is an increase in the normal force exerted on the threads of the stud  26  by the threads  64  on the nut  52 . As a result, there is an increase in the tension in the stud  26  and an increase in friction between the threads on the stud  26  and threads  64  on the nut  52 . As friction increases between the threads on the stud  26  and the threads  64  on the nut, the amount of torque required to rotate the nut  52  increases. Thus, once the nut  52  is secured onto the stud  26 , the fastener assembly  250  can be relied upon to resist rotational forces tending to cause the nut  52  to back off the stud  26 . 
     FIG. 10  depicts a graphical illustration showing a torque tension analysis of the fastener assembly  250 . In  FIG. 10 , line L 1  represents the correlation between the amount of clamp load exerted on the substrate or tension exerted on the stud  26  per degree of rotation of the nut  52 . Line L 2  represents the pounds of torque exerted on the nut  52  per degree of rotation of the nut  52 . As shown by line L 1 , when the nut  52  is secured onto the stud  26 , tension in the stud  26  can only be reduced by first increasing tension in the stud  26 . Only by applying sufficiently large loosening torque to the nut  52  can the locking assembly  250  be removed. 
   Although this invention has been described in the preferred context of a vehicle wheel hub mounting arrangement and a vehicle wheel mounting arrangement, it should be understood that it might be otherwise employed and that modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.