Abstract:
An interlocking nut and washer system exhibits a very high degree of inherent mechanical stability. The preferred embodiment includes an inner washer, an adjustment nut, an intermediate washer, and an outer nut completing an interlock assembly. Although the inner washer is technically optional, use thereof does reduce wear on the inner nut. While the invention maybe applied in different ways, the system is particularly suited to the controlled adjustment of tapered roller wheel bearings. In this case the system is provided on the spindle ends of an axle, which mounts a wheel assembly that includes tapered roller bearings.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to mechanical interlocks for threaded axles, and the like and, more particularly, to a high-integrity nut and washer system finding utility in applying and maintaining a desired preload compression condition against roller bearings. 
   BACKGROUND OF THE INVENTION 
   The need to safely install wheels on tractor/trailer combination vehicles has long been recognized, and numerous solutions have been made available. In 1962, a major producer of highway trailers introduced a new industry axle having a wheel retention system consisting of a single nut held in place by a cotter pin. Wheel installation using this single nut design was merely to tighten the wheel assembly in place and then back off the single nut to a position of loose clearance before placing the cotter pin in position to prevent rotational movement. 
   A potential weakness with all single nut designs is the inability to consistently eliminate all degrees of freedom between the threads of the spindle and those of the nut. Several tapered roller bearing manufacturers advised that a controlled amount of preload within the tapered roller bearings wheel assembly was not only acceptable, but it would be recommended if an accurate means could be achieved for that purpose. However, no known double nut configuration was capable of providing any measure of controlled preload on tapered roller bearings. In achieving the final jammed condition between the two nuts involved, it was always the case that the outer nut had to be tightened against the inner nut and during that process, additional pressure was brought to bear against the bearings. 
   The amount of additional preload pressure is related to the amount of clearance between the threads of the inner nut and the threads of the spindle. The tolerances of manufactured threads on axle nuts were so variable that inconsistent preload pressures would occur as a result of the inward movement of the inner nut through the space or lash between mating threads as the outer nut was tightened into the jammed condition. For this reason, the recommended practices by all manufacturers for installation of double nuts on tractor/trailer applications call for a back off of the inner nut prior to installing and tightening the outer nut. 
   My U.S. Pat. No. 5,795,037 describes a novel axle nut system adapted for use on the spindle ends of an axle which mounts a wheel assembly that includes tapered roller bearings. The system includes an adjustment nut, a washer and a retainer member. The adjustment nut is threaded into position having torque applied to it in a controlled manner to achieve specific preload bearing pressure against the outer bearings. Thereafter, the washer is placed into contact with the nut and is rotationally fixed with respect to the axle. Next, the threaded retainer member is rotated into contact with the washer. 
   With the threaded retainer member placed on the axle to prevent any outward movement of either the wheel assembly components or the adjustment nut and washer, the adjustment nut is rotated in the opposite direction by which it was installed until it jams forcibly against the washer and thus, the threaded retainer member. With this rotational movement of the adjustment nut, the original bearing pressure or preload exerted outward against the adjustment nut is transferred and bears against the washer and retainer member. 
   Since this patent issued, a number of different lock members have been tried in the interest of achieving the best tradeoff between reliability and convenience of installation. These various methods included bend-over tabbed washers, and the use of a setscrew to associate the retainer nut with the intermediate washer that engages the keyway of the axle spindle. Both of these systems were used over the course of the last several years, but both were also criticized by those who perform the installation procedure. 
   The use of the bend-over tabbed washer was somewhat compromised because it was necessary for the washer to be thin enough to facilitate bending yet strong enough to prevent shearing of the tab within the keyway at the time the inner adjustment nut was jammed outward against the outer nut or lock member. The finally selected thickness provides dependable resistance against shearing, but it was too thick to facilitate ease of bending of the locking tab over the outer nut. Also, the use of the bend-over tab was difficult because space constrictions within the hub cavity complicated assembly and disassembly operations. 
   SUMMARY OF THE INVENTION 
   This invention improves on the existing art by providing an interlocking nut and washer system exhibiting a very high degree of inherent mechanical stability. The preferred embodiment includes an inner washer, an adjustment nut, an intermediate washer, and an outer nut completing an interlock assembly. The configuration is based on the recognition that the retainer nut will positively engage with the intermediate washer using the backup force caused when the inner adjustment nut is rotated in the opposite direction. As a result, a physical locking interaction occurs between the outer nut and the intermediate washer in a manner not previously provided by any jam nut fastening system. Although the inner washer is technically optional, use thereof does reduce wear on the inner nut. 
   While the invention maybe applied in different ways, the system is particularly suited to the controlled adjustment of tapered roller wheel bearings. In this case the system is provided on the spindle ends of an axle, which mounts a wheel assembly that includes tapered roller bearings. After positioning the tabbed inner washer to engage within the spindle keyway while abutting against the outer tapered roller bearing, the adjustment nut is threaded into position having torque applied to it in a controlled manner to achieve the intended installation adjustment. 
   Either a slight dimensional clearance between the inner washer and the adjustment nut can be provided, or a specific preload bearing force against the outer tapered roller bearing can be applied. Thereafter, the intermediate washer that has interlock capability with the outer nut is positioned on the axle and is rotationally fixed with respect to spindle keyway engagement. 
   In the preferred embodiment, the locking mechanism involves a plurality of radially oriented grooves on the face of the intermediate washer and a projection on the face of the outer retainer nut. It will be appreciated that other interlocks may be used, such as dimples and divots, and that the projection may be provided on the washer with the corresponding receptacle on the nut. Recesses on the washer are preferred, however, as they can be placed on both side of washer while maintaining otherwise smooth faces. Projections are likewise preferably provided on both sides of the outer nut so that it, too, can be placed on the threads in either direction. 
   In use, the projection on the face of the threaded retainer nut is moved into interlocking contact within a slot on the contact face of the intermediate washer. This is accomplished by tightening the retainer nut against the contact face of the intermediate washer, causing the projection on the contact face of the retainer member to penetrate into the space of a slot. Using this procedure, the installer should sense the interference of the projection within the slot. With an additional amount of torque on the retainer member, the projection will be caused to separate from the initial slot and to rotate onward to engage the second slot of the intermediate washer. 
   If penetration of the retainer projection does not prevent further rotation of the retainer, it will disengage from the second slot and will progress to the third slot. At this point, it will become locked in place due to being positively engaged with the immovable intermediate washer. With the amount of penetration of the retainer projection into the third slot resulting from a designed maximum inward thread movement, the retainer projection will be prevented from disengaging from that slot even if significant torque is applied to the retainer. This constitutes an automatic position sensing arrangement that prevents the retainer nut from being tightened excessively. At this point, the inner adjustment nut is caused to rotate “in the second direction,” firmly jamming the inner adjustment nut, the intermediate washer, and the outer retainer into a locked condition. Having secured the three locking components forcefully together, it is not possible for the outer retainer to be moved because the projection within the slot of the intermediate washer prevents any rotation without shearing the projection. 
   This invention was conceived in recognition of the problems associated with tractor/trailer combination vehicles and appropriate designs have been formulated for the basic axle spindles commonly used. Applications of the principles of this invention described for the preferred embodiment makes it possible to standardize the wheel retention system on tractor/trailer combination vehicles providing control adjustment of tapered roller bearing preload or endplay at the three axle positions on the vehicle; the steer axle or the tractor, the drive axles of the tractor, and the axles of the trailer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which: 
       FIG. 1  is a plan view of an axle beam without any accouterments showing the two spindles in final form following the machining operations; 
       FIG. 2  is a section view of the axle spindle in  FIG. 1  having assembled thereon the components comprising the wheel and axle assembly, which includes an inner washer, an inner means, an intermediate interlocking washer, and an outer interlocking means, showing the respective relationship of all members in their final assembled positions; 
       FIG. 3  is an exploded perspective view of the components of the preferred embodiment of the axle nut system of the present invention that includes an inner washer, an inner member, an intermediate interlocking washer and an interlocking retainer member; 
       FIG. 4  is a plan view of the stationary inner washer that is positioned on the axle spindle between the inner means and the inner race of the outer tapered roller bearing; 
       FIG. 5  is the side view of the stationary inner washer shown in  FIG. 4 ; 
       FIG. 6  is a plan view of the inner means that is depicted as a nut with threads to engage the spindle threads; 
       FIG. 7  is a side view of the nut shown in  FIG. 7 ; 
       FIG. 8  is a plan view of the intermediate interlocking washer having a plurality of slots equally spaced on both faces to accept the projections provided on the face surfaces of the interlocking retainer member; 
       FIG. 9  is a side view of the intermediate interlocking washer shown in  FIG. 8 ; 
       FIG. 10  is a plan view of the interlocking retainer member that shows a plurality of projections on both face surfaces designed to engage within the slots on the intermediate interlocking washer shown in  FIG. 8 ; 
       FIG. 11  is a side view of the internal interlocking retainer member shown in  FIG. 10 ; 
       FIG. 12  is an enlarged section view taken of one of the slots shown in the plan view  FIG. 8  of the intermediate interlocking washer; 
       FIG. 13  is an enlarged section view taken of one of the projections shown in the plan view  FIG. 10  of the interlock retainer nut; 
       FIG. 14  is an enlarged scale side section view of a typical projection on either face of the interlocking retainer member shown in  FIG. 10  showing its relativity to a typical slot shown on either face of the intermediate interlocking washer shown in  FIG. 8  before contact is made as the result of inward movement of the interlocking retainer member on the mating threads of the spindle shown in  FIG. 3 ; 
       FIG. 15  is an enlarged scale side section view of same members shown in  FIG. 14  after tightening rotation of the interlocking retainer member has caused it to progress from its original position relative to the first slot to its relative position with respect to the second slot; and 
       FIG. 16  is an enlarged scale side section view of the same members shown in  FIGS. 14 and 15  after tightening rotation of the interlocking retainer member has caused it to move further inward from its position relative to the second slot to its realigned position with respect to the third slot. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference is now made to the Drawings, wherein  FIG. 1  depicts a prior-art axle beam  1  having conventional threads  2 , a washer keyway  3 , an outer bearing journal  4 , an inner bearing journal  5  and an oil seal surface journal  6 . Referring to  FIG. 2 , an oil seal  17  is shown in its respective position mounted between wheel or hub  18  and the axle spindle  1 . Inner tapered roller bearing  15  is positioned between the wheel or hub  18  and the bearing journal  5 . An outer tapered roller bearing  16  is also positioned in its working arrangement between the wheel or hub  18  and the outer bearing journal  4  of the axle spindle  1 . 
   The invention will now be described in conjunction with the prior-art components introduced with respect to  FIGS. 1 and 2 .  FIG. 3  is an exploded, perspective view showing the components of the preferred embodiment, which include an inner, hardened washer  7 , an adjustment nut  9 , an intermediate interlocking washer  10 , and an interlocking retainer nut  13 , all mountable on the axle spindle  1 . The inner hardened washer is also shown in  FIGS. 4 and 5 , and the adjustment nut  9  is shown in  FIGS. 6 and 7 . 
   The spindle keyway  3  serves to engage an inner projection  12  of the intermediate interlock washer  10  that is shown in detail in  FIGS. 8 and 9 . Slots  11  on the face surfaces of the intermediate interlock washer  10  depicted in  FIGS. 8 ,  9 , and  12  serve to engage a projection or projections on the faces of the threaded interlock retainer nut  13  shown in detail in  FIGS. 10 ,  11 , and  13 . 
   The assembly process provides for placement of the inner washer  7  around the threaded diameter  2  of the axle spindle  1  with the tab  8  engaged with the keyway  3 . This is followed by placement of the adjustment nut  7  in position to be tightened with a specific amount of torque applied by a calibrated torque wrench (not shown). The amount of installation torque applied by the torque wrench complies with the recommendations that correlate with the relative amount of preload force against the inner and outer tapered roller bearings  15  and  16  advocated by bearing manufacturers for reliable and safe operation. Having established the desired preload bearing force by controlled tightening of the adjustment nut  9 , the intermediate interlock washer  10  is placed around the spindle diameter  2  to engage its tab  12  within the spindle keyway  3 . 
   The result of tightening interlock retainer nut  13  is illustrated in  FIGS. 14 ,  15 , and  16 . Of interest is to recognize the relationship of the interlock retainer nut projection  14  with respect to encountering a series of three slots  11  as the result of this tightening operation. As interlock retainer nut  13  is tightened and moves inward toward the outer face of the intermediate interlock washer  10 , the interlock retainer nut projection  14  moves inward with respect to the first slot  11 , defined as “a” as shown in FIG.  14 . 
   After positioning with respect to slot  11   a  of the intermediate interlock washer  10  is sensed, the interlock retainer nut  13  may become positioned with respect to the intermediate interlock washer  10  by continuing to rotate it to a position with respect to the subsequent slot  11   b . Although the interlock retainer nut projection  14  is positioned within the cavity of slot  11   b  as shown in  FIG. 15 , its location against the sloped surface of slot  11   b  has not penetrated deeply enough to cause restraint further rotational movement. 
   Moving onward with slightly increased torque, retainer nut  14  and its interlock retainer nut projection will be further rotated and will come to rest after it reaches slot  11   c  as shown in FIG.  16 . At this stage of the assembly process, interlock retainer nut  13  cannot be rotated further because the additional depth of engagement of the interlock retainer nut projection  14  within interlock washer slot  11   c  will not allow disengagement as the projection  14  as it is no longer in contact with the sloped or angled surface of the slot. 
   With the interlock retainer nut projection  14  being in a captured position within the slot  11   c , and because the intermediate interlock washer key tab  12  is engaged within the spindle keyway  3 , the intermediate interlock washer  10  and the adjoined and connected internal retainer nut  13  are relatively secure. The assembly becomes absolutely secure with the follow-up step by which the inner adjustment nut  9  is rotated in the opposite direction by which it was originally installed and is caused to bear outward against the intermediate interlock washer  10 . With the ensuing jammed condition caused by an appropriate amount of torque applied to the adjustment nut  9 , further movement of the assembled wheel end fastener system is not possible until the outward force imposed by adjustment nut  9  is relieved with a reversed manual torque application to transfer the applied force imposed by the adjustment nut  9  axially inward. 
   Disassembly of the interlock retainer nut  12  and the intermediate interlock washer  10  cannot be accomplished until the outward jamming force applied to the interlock retainer nut  13  is relieved. The adjustment nut  9  must be rotated away from the intermediate interlock washer  10  before it becomes possible to disengage the interlock retainer nut projection  14  from within the intermediate interlock slot  11 . This must be accomplished before the wheel end interlocking retainer system can be disassembled. 
   The unique provision of a securely jammed connection of the intermediate interlock washer  10  to the interlock retainer nut  13  was designed to achieve correlated action between the axial penetration of the interlock retaining nut  13  and its interlock retainer nut projection  14  with the amount of rotational travel of the interlock retainer nut projection  14  between adjoining intermediate interlock washer slots  11 . Nevertheless, the profile configuration of the interlock retainer nut projection  14  remains compatible with the shape of the intermediate interlock washer slot  11  as shown in  FIGS. 12 and 13 . 
   Referring once again to  FIGS. 14 ,  15 , and  16 , the interlock retailer nut projection  14  progressively engages three appropriately spaced intermediate interlock washer slots  11  before becoming restricted from further rotational movement. Only by appropriately dimensioning the intermediate interlock washer slots  11 , will the retainer nut interlock projection  14  be allowed to progress past two initial slots before penetrating sufficiently into the third slot where disengagement becomes possible. After the vertical face of the retainer nut interlock projection  14  engages the vertical face of the intermediate interlock washer slot  11  as shown in  FIG. 16 , further rotational movement of the retainer nut interlock projection becomes securely restrained because the intermediate interlock washer key tab  12  shown in  FIG. 8  is engaged within spindle keyway  3  shown in FIG.  1 . 
   The correlated relationship between the axial movement of the retainer nut interlock projection  14  with respect to the amount of selected spacing of the intermediate interlock washer slots  11  is complex. For any given combination of thread pitch and spindle diameter, the ultimate design solution must also account for the dimensional considerations of the most appropriate profiles of both the retainer nut interlock projection  14  and the intermediate interlock washer slot  11 . The number of variables involved accordingly prevents assignment of absolute dimensional values. 
   Although the invention is primarily concerned with the application of a definitively controlled preload force on the tapered roller bearings, other purposes can be served. A number of vehicle operators prefer to install wheels on their tractor/trailer combination vehicles providing some actual clearance between the adjustment and the outer face of the outer bearing before securing the wheel assembly on the axle. This procedure is easily accomplished by backing off the adjustment nut for a measured rotation from the position where resistance to installation torque is first sensed before installing the intermediate interlock washer and retainer nut Recommended procedures and standard operating practices for this purpose are well defined in the instructions provided from a number of sources in the trucking industry. 
   Having described the principles of this invention as being directed for application to tractor/trailer combination vehicles, it is anticipated any automotive vehicle will benefit by having wheels mounted and the wheel bearings similarly adjusted using the means described. Other applications may include various forms of rotating machinery. 
   While the preferred embodiment of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.