Abstract:
A combination nut and washer is retained in a preassembled position by an annular pilot that extends toward the central hole in the washer to permit the washer to be rotated 360° with respect to the nut. The lower end of the pilot has a groove. A split ring is mounted in the groove to retain the washer in its preassembled position with respect to the nut.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    It is desirable to have threaded locking fasteners such as a nut and one or two lock washers retained in a preassembled condition to prevent the washers from being mounted in a reverse position when the nut is used as a fastener. The prior art discloses the use of a cylindrical pilot or sleeve carried on the nut. The washer is mounted on the sleeve. The lower end of the sleeve is flared outwardly to a diameter greater than the central hole in the washer to retain the washer on the nut.  
           [0002]    Examples of such prior art may be found in U.S. Pat. Nos. 3,238,581 issued Mar. 8, 1966 to Frank L. Sawyer for “Toggle Latch Construction”, see FIG. 4; 3,680,619 issued Aug. 1, 1972 to Harold R. Sparks for “Lock Washer”, see FIG. 8; 4,140,870 issued Feb. 20, 1979 to Jack C. Volkers et al. for “Cable Ground System”, see FIG. 5; 4,362,449 issued Dec. 7, 1982 to Emil J. Hlinsky for “Fastener Assemblies”, see FIG. 4; 5,190,423 issued Mar. 2, 1993 to Paul E. Ewing for “Locking Fastener”, see FIG. 5; 5,203,656 issued Apr. 20, 1993 to Alistair N. McKinlay for “Self-Centering, Self-Tightening Fastener”, see FIG. 5; 5,314,279 issued May 24, 1994 to Paul E. Ewing for “Locking Fastener”, see FIG. 5.  
           [0003]    U.S. Pat. No. 2,679,880 issued Jun. 1, 1954 to  0 . J. Poupitch for “Coupled Nut and Lock Washer” shows a similar instruction but in which the lower end of the cylindrical pilot has an annular flange for retaining the washer.  
           [0004]    The preferred embodiment of the invention comprises a wedge type locking nut and washer assembly comprising a nut and two washers connected together by a split ring retainer. The nut has a cylindrical pilot that extends along the turning axis of the nut beneath the camming face of the nut head. The length of the pilot is sufficient to mount a hex flanged nut and an inverted cup-type washer. The split ring retains the two washers on the pilot in a preassembled position with respect to the nut. For illustrative purposes, the hex flange nut has a cammed surface that faces and engages the cammed surface on the nut. The bottom surface of the hex flanged nut has an annular array of mini cams that is engageable with an annular array of similarly-shaped mini cams on the cup-shaped washer. The center portion of the cup-shaped washer has a concave configuration enclosing the retainer to permit the lower side of the cup-washer to engage the workpiece without interference with the pilot.  
           [0005]    Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description.  
         DESCRIPTION OF THE DRAWINGS  
         [0006]    The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:  
           [0007]    [0007]FIG. 1 is a sectional view taken through a fastener assembly illustrating the invention. The fastener assembly is shown securing two workpieces together.  
           [0008]    [0008]FIG. 2 is a view of a split ring used for holding the nut and washers together as a unit;  
           [0009]    [0009]FIG. 3 is a view of a resilient ring that can be used as a substitute for the ring of FIG. 2;  
           [0010]    [0010]FIG. 4 is a plan view of the preferred nut;  
           [0011]    [0011]FIG. 5 is a side view of the preferred nut, showing the pilot;  
           [0012]    [0012]FIG. 6 is a view of the nut as seen from the bottom of FIG. 5;  
           [0013]    [0013]FIG. 7 is a plan view of the preferred hex flange washer;  
           [0014]    [0014]FIG. 8 is a side view of the preferred hex flange washer;  
           [0015]    [0015]FIG. 9 is a bottom view of the hex flange washer;  
           [0016]    [0016]FIG. 10 is a side view of the cup washer; and  
           [0017]    [0017]FIG. 11 is a top view of the cup washer showing the mini cams. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Referring to the drawings, FIG. 1 shows a nut assembly constructed in accordance with the invention. The nut assembly is mounted on a steel button headed bolt  10  having a threaded shank  12  extending through two workpieces  14  and  16 . The nut assembly could be used as a wheel nut such as illustrated in my U.S. Pat. No. 6,039,524, issued Mar. 21, 2000 for “Self-Locking Safety Wheel Nut with Locking Wrench”.  
         [0019]    A steel nut  18  is mounted on the threaded shank. A flanged washer  20  and a cup-shaped washer  22  are mounted between the head of the nut and workpiece  14 . Washers  20  and  22  are held on the nut by a split retaining ring  24 . Retaining ring  24  prevents the washers from being mounted in a reverse direction on the nut.  
         [0020]    Bolt  10  has a button-shaped head  26  with a rounded exposed surface  28 . Shank  12  extends axially from head  26 . The rounded surface contour on the head resists being gripped by a wrench or pliers.  
         [0021]    The preferred nut assembly may be mounted on other threaded shanks, not having a button-head, which extend through an opening in a workpiece on which the nut is to be mounted.  
         [0022]    Referring to FIGS. 1 and 4- 6 , nut  18  has an internal threaded surface  30  meshed with a continuous thread surface on shank  12  by applying a wrench to flat multi-sided external surfaces  32  on the head of nut  18 . Preferably, the nut has a hexagonally-shaped head.  
         [0023]    The nut has a generally cylindrical sleeve or pilot  34 , which extends down from the bottom face of the nut. The pilot has a sufficient length to mount washers  20  and  22  while permitting each of the washers to be rotated in a 360° direction with respect to the head as well as providing some axial movement.  
         [0024]    The central opening of the pilot is also internally threaded to form a continuous thread with that of the nut head. The lower end of the pilot has an annular retainer groove  36  for receiving split ring  24  when the two washers have been assembled with the nut.  
         [0025]    The lower face  38  of the nut has a camming surface comprising a plurality of circumferentially spaced ramps  40  and a corresponding number of connecting shoulders  42 , for form an undulating cam surface.  
         [0026]    Nut  18  is hot formed from  1045  steel. Prior to heat treating, retainer groove  36  is formed on the lower outside of the pilot, and then heat-treated to HRC  38 - 40 .  
         [0027]    Flange washer  20  has a hexagonal head  44  with a configuration identical to the hexagonal head of the nut so the nut and washer  20  can be turned as a unit by the same wrench, not shown. Washer  20  has a top camming surface  35  comprising six ramps  46  connected by short shoulders  48 . The ramps and shoulders on camming surface  35  interlock with cams  40  and  42  on the bottom side of the nut. Each camming surface has a continuous uninterrupted undulating contour. There are no obstructions or ledges preventing relative rotation between the nut and the camming surface of the flange washer while the camming surfaces are engaged.  
         [0028]    The flanged washer has an annular flange  50 , which is larger in diameter than the hexagonal head  44 . The lower surface of the flange has a camming surface  52  which comprises 18 equally spaced mini-cams each comprising a ramp  54  and a shoulder  56 .  
         [0029]    The flange washer is also made  4140  steel material, hot formed and heat-treated to HRC- 37 - 39 .  
         [0030]    The flanged washer has a central opening  58  with a diameter slightly larger than the outside diameter of the pilot. Washer  20  is formed with an internal annular concave groove  60 . As best shown in FIG. 1, retaining ring  24  is mounted retainer groove  36  closely adjacent and within groove  60 .  
         [0031]    The cup type washer  20  is formed from a  10 - 10  steel material, case hardened to HRC- 45 - 60  to a depth of about 0.005 inches.  
         [0032]    Referring to FIGS. 10 and 11, cup-shaped washer  22  has a dish-shaped configuration with a central hole  64  for loosely sliding on the pilot. The distance between the top surface  66  and the bottom flat surface  68  of washer  22  is sufficient to enclose the retaining ring. Washer  22  has a flange  70  with a diameter corresponding to the diameter of flange  50 . The upper surface  72  of the flange has 18 mini-cams that are identical to the mini-cam profile on the bottom of the flanged washer and mate with camming surface  52  of the flanged washer.  
         [0033]    The convex side of the dish-shaped area of the washer fits into the concave groove  60  on the underside of the flanged nut, and leaves sufficient room for the split ring to be inserted into pilot groove  30  during final assembly.  
         [0034]    The two mating camming surfaces engage one another such that when the nut is rotated during the nut tightening operation, the bottom flat surface on the washer  68  becomes frictionally anchored to the top surface of workpiece  14 . Further, rotation of the nut in the tightening direction causes the shoulders on the two mating pairs of the camming surfaces to push the shoulders on the mating camming surfaces until the nut is fully tightened.  
         [0035]    When the nut is rotated in a loosening or a counter-clockwise direction as viewed in FIG. 4, either by vibration or deliberately, the ramps on the nut slide up the ramps on the flanged washer, while the ramps on the lower camming surface of the flanged washer slide up on the ramps surface on the camming surface  72  flange of the washer  22 . This camming action is illustrated in this type of wedge-locking fastener assembly, for example in U.S. Pat. No. 5,626,449, issued May 6, 1997 for “Wedge-locking Fastener Assembly with a Cammed Surface” in columns  4  and  5 , which are incorporated herein by reference, to describe the camming action of the two camming surfaces.  
         [0036]    When the nut is being assembled, washers  20  and  22  are assembled on pilot  34  and retaining ring  24  is snapped into retaining groove  36  to retain the washers in their relative position on the pilot.  
         [0037]    Alternatively, a resilient o-ring  74 , shown in FIG. 3, may be substituted for the split ring. The o-ring can be snapped into groove  36 . Referring to FIG. 1, when using either retaining ring, the outer portion of the ring extends beyond groove  36  and overlaps the inner diameter of the opening of both washers to hold both washers on the pilot.  
         [0038]    One advantage of this invention with respect to pilots that are flared outwardly is that the requirement for the flaring process limits the hardness heat treating level to a maximum of about HRC- 28 , thus sacrificing integrity and strength of the nut component.  
         [0039]    This new nut design allows the nut component to be heat-treated to a high end of SAE Grade  8  (Class  10  Metric), that is, of up to as high as HRC  38 - 40 . The result is a nut component with far greater hardness, strength and integrity, which will withstand the common abuses of installation, removal and severe in-service conditions. The superior hardness of this nut component also results in much stronger threads, useful for higher loads and tensile strengths.  
         [0040]    Another important feature is that the higher hardness level permits a lower profile nut which will fit in applications that taller nut assemblies currently cannot fit, and still exceed current industry standards regarding proof loads and tensile strength.  
         [0041]    This nut is useful not only when combined with a bolt, but also when used as a wheel nut. I believe that the double spring action feature due to the concave cavity of the hex flange washer and the geometrical shape of the inverted area of the cup-shaped washer causes a form of a rebound action resulting in the spring action of the two components working under load.  
         [0042]    Unlike current designs using an externally attached bottom component, a cup-type washer internally mounted on the pilot of the nut eliminates the possibility of the bottom washer moving “out-of-line” or slipping in relation to the top workpiece.