Patent Publication Number: US-6908395-B2

Title: Lock nut member

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional application of U.S. Ser. No. 10/410,078, now U.S. Pat. No. 6,808,348, filed Apr. 9, 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to lock nuts having a plurality of resilient locking segments which deflect in a manner similar to that of a beam, and, more particularly, to a construction of the locking segments wherein the internal threads at the junction of adjacent beams are angled radially inward, thereby forming a V-shaped internal slot. The present invention also is directed to a new method of manufacturing the lock nut. 
   The present invention is an improvement in the design of a locking beam nut described and disclosed in U.S. Pat. No. 5,088,868. The locking beam nut of the &#39;868 patent discloses a design having a plurality of circumferentially-spaced resilient locking beams that were specifically configured to prevent any accumulated debris from preventing a desired deflection of the beams. The beams project from a substantially rigid body and have a circular opening extending completely through the body and the locking beams. The beams all taper inwardly, such that the circular opening they define have a uniformly decreasing diameter. Continuous threads of substantially uniform depth are defined in the aligned openings, for receiving an externally threaded member, wherein the locking beams resiliently deflect outwardly to lock the member in place. The confronting sidewalls of adjacent beams are configured to diverge outwardly from each other, such that any debris located between them could not inhibit inward deflection of the beams upon removal of the externally threaded member. 
   Although the design described in the &#39;868 patent was an improvement upon prevailing locking beam nut designs, all previous designs for slotted beam nuts possess beams that are curved which, through natural stiffening of a curved design of a beam, have a tendency to concentrate loads and cause stress risers at the attachment points of the beams to the body of the nut. Consequently, low reuse cycles and rapid deterioration of the prevailing torque is undesirable. Another problem with previous beam nut designs is that typically the nut, which is utilized with a bolt having a holdout spring, compresses the spring when rotated in the internal threads of the beam nut. Periodically, the flexible holdout spring can become wedged and locked in two axial slots located on the inside diameter of the beam nut. Additional problems of prior designs are that the locking torque was insufficient and manufacturing and fabrication operations were extremely high due to the slotting, tapping and subsequent retapping operations necessary to remove burrs. Consequently, an improved beam nut design is necessary to address these and other problems associated with prior beam nut configurations. 
   SUMMARY OF THE INVENTION 
   The present invention provides a beam nut construction and arrangement which addresses the problems associated with prior beam nut configurations. The invention is embodied in a locking beam nut having a plurality of circumferentially spaced resilient locking beams that are specifically configured to improve the performance and quality of the nut, and at the same time reduce manufacturing fabrication costs. The nut has unique features that provide substantially higher reuse cycles without rapid deterioration of the prevailing torque. The design allows for high reuse by lowering and reducing stress concentrations of a deflecting beam. The beam nut design of the present invention utilizes flat beams on the exterior portion of each beam, and a unique inside surface to substantially distribute the bending load through the length much more evenly, thus reducing stress concentrations. This is accomplished by incorporating an inside surface configuration wherein the internal threads at the junction of adjacent slotted beams are angled radially inwardly. This is in stark contrast to previous designs where the threads were 90° to the slotted beams. The angled radially inwardly inside beam configuration provides for a substantially “V-shaped” internal slot length that travels the full length of the beam, and, in certain applications can continue through the entire length of the nut. The V-shaped internal slot has the capability to improve cycle life or reusability performance due to the fact that the cantilevered beam now approaches the characteristics of a true rectangular beam. 
   The internal V-shaped slot also eliminates the probability of the holdout spring on the bolt from becoming wedged into the slot by supplying an angled slope wide enough to act as a detent and not capture the holdout spring. A secondary locking system is added to provide additional prevailing torque and is accomplished during installation and removal of the beam nut wherein the holdout spring ratchets into each beam V-shaped slot whereby the additional friction contributes to increased prevailing torque. 
   A significant manufacturing improvement is realized with the internal V-shaped slot by streamlining and removing a series of costly operations in producing the beam nut previously required. The invention is produced by utilizing a heading procedure to form V-shaped slots from the exterior surface of a nut blank facing inward toward an external flat beam surface. Next a tap drilling operation commences wherein the tap drill removes the core and the apex of the external V form thereby forming the individual beams. The internal V-shaped slots are then formed by a broaching procedure and the nut is then threaded to complete the manufacturing process. This is in stark contrast to prior systems which required the tapping of the internal threads, then a slotting operation to form individual beams, which resulted in burrs forming in the internal threads of the nut. A subsequent retapping operation was necessary to remove the burrs. The method for manufacturing the present invention eliminates the beam slotting operation, double tapping and the deburring operations. 
   Other features and advantages of the present invention will be appreciated from the following description of an exemplary embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the locking beam nut of the present invention; 
       FIG. 2  is a perspective view of a typical bolt for receipt of the nut of  FIG. 1 ; 
       FIG. 3  is a perspective view of the heading operation of the nut of  FIG. 1 ; 
       FIG. 4A  is a perspective view of the nut blank of  FIG. 3  after a drilling operation; 
       FIG. 4B  is an opposite end perspective view of the nut of  FIG. 4A ; 
       FIG. 4C  is an end view of the nut of  FIG. 4A ; 
       FIG. 5A  is a perspective view of the nut of  FIG. 4A  after a broaching operation; 
       FIG. 5B  is an opposite end perspective view of the nut of  FIG. 5A ; and 
       FIG. 5C  is an end view of the nut of FIG.  5 A. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is an improvement in the construction and operation of known locking beam nuts or lock nuts and, in particular, of the lock nut shown and described in U.S. Pat. No. 5,088,868. Lock nuts of this kind are generally of a one-piece construction. As shown in  FIG. 1 , each lock nut  20  has a non-deflectable or rigid body portion  21  and a plurality of locking segments or beams  22 . Each beam is formed integrally with the body portion  21  and extends axially therefrom. The body portion  21  has an internal axial opening extending completely through it. The opening is threaded so as to receive the, external threads of a bolt or like part or fastener. The body portion  21  may also have a plurality of flat wrenching surfaces (not shown) along its external surface. Lock nut  20  also includes a flange  23  adjacent the body portion  21  opposite from beams  22 . Flange  23  may have a plurality of positioners  23   a  which are used for alignment purposes in a cassette or the like. 
   The lock nut  20  is depicted to include six locking beams  22 . It should be understood, however, that the invention is not limited to any specific number of locking beams. Each locking beam  22  has an inner surface  24  and an opposite outer surface  25 , which is preferably flat. A top surface  26 , which is typically flat, extends between the inner and outer surfaces  24  and  25  and defines a free end of the beam. The plurality of locking beams  22  are arranged circumferentially at one end of the body portion  21  such that the inner surfaces  24  define a circular opening that is threaded. The threads  24   a  in the aligned openings of the body portion and the beams extend along the entire axial length of the aligned openings, and have a substantially uniform depth around their entire circumference. 
   Each locking beam  22  also has a first sidewall  27  and a second sidewall  28 . Each of these sidewalls extends between the body portion  21  and the beam&#39;s inner, outer and top surfaces  24 ,  25  and  26 , respectively. Preferably, both of the sidewalls are smooth or flat. The sidewalls  27  and  28  of each beam can be configured to be substantially perpendicular to the beam&#39;s outer surface  25 . The confronting sidewalls of adjacent beams therefore diverge from each other, with increasing radial distance, forming an angle A. The sidewalls  27  and  28  of each beam can also be configured to form a slightly acute angle with the outer surface  25 . Similarly, the sidewalls  27  and  28  of each beam can be configured to form a slightly obtuse angle with the outer surface  25 . Each of these three configurations performs a specific function of cleaning debris, as discussed in detail in U.S. Pat. No. 5,088,868. 
     FIG. 1  depicts the lock nut  20  as it appears in a free state, prior to the insertion of an externally threaded member or bolt  30 , as shown in FIG.  2 . It can be seen that the innermost portions of the beam sidewalls  27  and  28  are closely situated to adjacent beam sidewalls. As the bolt  30  is threaded onto the lock nut and secured therein, the beams deflect outwardly. Upon removal of the bolt, each of the beams returns to its free state by flexing inwardly. 
   The internal threaded surface  24  includes first and second angled radially-inwardly surfaces  32  and  34  positioned on the edges of the inner surface adjacent the side surfaces  27  and  28 . The angled surfaces  32  and  34  are positioned on opposite sides of the slots between individual beams. Angled surfaces  32  and  34  define a substantially V-shaped internal slot which runs the full length of the beam and can optionally continue through the full length of the nut  20 . Consequently, the internal threads at the junction of the slotted beams are angled radially inwardly. This V-shaped internal slot improves the cycle life or reusability performance of the nut because the cantilevered beam now approaches the characteristics of a true rectangular beam. A substantially rectangular beam distributes the bending load throughout the length of the beam more evenly, thus reducing stress concentrations. 
   The V-shaped internal slot also prevents the holdout spring  36  ( FIG. 2 ) of bolt  30  from becoming wedged into the slots between individual beams. The V-shaped internal slot acts as a detent so as not to capture the spring. In addition, a secondary locking system is added to provide additional prevailing torque, which is accomplished during installation and removal of the holdout spring as it ratchets into the V-shaped slots between the beams. The additional friction generated contributes to increased prevailing torque. 
   The nut is easily fabricated wherein, as shown in  FIG. 3 , a heading procedure forms a plurality of V-shaped channels  42  extending from an exterior surface  44  of a nut blank  40  inwardly toward the axis of the nut blank. There are six V-shaped channels  42  shown, however more or less are contemplated by the invention. The depth of the external V-shaped channel  42  is greater than a subsequent tap drill diameter TD as shown in FIG.  4 C. In other words, the diameter D extending between opposite V-shaped channels  42  is smaller than tap drill diameter TD. As shown in  FIGS. 4A-C , a tap drilling operation removes the core of the nut blank and the apex  46  of the external V-shaped channel  42 , thereby creating the individual beams  22 . The flange  23  can also be trimmed to produce the positioners  23   a . The tap drilling operation can also provide a counter bore  48  in the nut as necessary as shown FIG.  4 B. 
   As shown in  FIGS. 5A-C , the internal surface  24  is then broached to produce angled surfaces  32  and  34 , thus forming a V-shaped configuration for the slots between adjacent beams  22 . As seen best in  FIG. 5C , the depth of the broached surface is about the same as or slightly greater than a major diameter MD of threads  24   a . In other words, broached diameter BD is about the same or slightly greater than major diameter MD. Finally, the inside surface  24  is tapped to provide the threads  24   a  and the beams are crimped to create a smaller diameter at the free end of the beams than at the opposite end of the beams adjacent the body portion  21 . 
   Although the invention has been described in detail with respect to one embodiment thereof, one of ordinary skill in the art will appreciate that various modifications can be made without departing from the scope of the invention as hereinafter claimed.