Patent Publication Number: US-2022228620-A1

Title: Range Taking Shear Bolts and Drive Tools

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/579,405, filed Sep. 23, 2019, which claims the benefit of U.S. Provisional Application No. 62/735,394, filed Sep. 24, 2018, each of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Electric power cables of all sizes are joined using connectors made from electrically-conductive material, usually metal. The predominant metals used are copper and aluminum. There are different types of connectors—some designed to be crimped, and some using bolts/screws to secure the conductors (cables/wires). 
     SUMMARY 
     Various embodiments of the present invention provide range taking shear bolts and bolt installation (drive) tools, which are configured for use with a variety of range taking connectors and conductor cables (or other articles being connected). 
     In some embodiments, the invention provides a range taking shear bolt, comprising: a hollow cylindrical body comprising a wall having an outer surface and an inner surface; a distal end constructed and arranged to abut a cable conductor; and a proximal end constructed and arranged to accept a drive tool, the outer surface having a substantially continuous screw thread thereon, and the inner surface having a plurality of spline teeth thereon, running longitudinally along a length thereof, wherein the wall is configured to shear within a predetermined shear zone when an applied torque reaches or exceeds a predetermined torque value. 
     In some embodiments, the predetermined torque value is a function of a thickness of the wall between the screw thread and the spline teeth. 
     In some embodiments, the bolt is formed from a metal or alloy. 
     In some embodiments, the inner surface of the cylindrical body further comprises a hexagonal impression proximate the distal end. 
     In some embodiments, the spline teeth run longitudinally from the proximal end to the distal end or, where present, the hexagonal impression. 
     In some embodiments, the spline teeth on the inner surface of the cylindrical body are symmetrical. 
     In some embodiments, the spline teeth on the inner surface of the cylindrical body are asymmetrical. 
     In some embodiments, the invention provides a range taking shear bolt kit, comprising: a range taking shear bolt; and a drive tool for installing the shear bolt in a range taking connector, the range taking shear bolt comprising: a hollow cylindrical body comprising a wall having an outer surface and an inner surface; a distal end constructed and arranged to abut a cable conductor; and a proximal end constructed and arranged to accept the drive tool, the outer surface having a substantially continuous screw thread thereon, and the inner surface having a plurality of spline teeth thereon, running longitudinally along a length thereof, wherein the wall configured to shear is within a predetermined shear zone when an applied torque reaches or exceeds a predetermined torque value; and the drive tool comprising: an inner portion configured to fit at least partially inside the cylindrical body of the shear bolt; and an outer portion configured to control a depth of tool insertion, the inner portion comprising a spline drive portion having a plurality of spline teeth running longitudinally on an outer surface thereof, the spline teeth on the outer surface of the spline drive portion constructed and arranged to mate with the spline teeth on the inner surface of the cylindrical body of the shear bolt. 
     In some embodiments, the invention provides a drive tool for a range taking shear bolt, comprising: an inner portion comprising a proximal head portion, a stem portion, a spline drive portion, and a distal end portion; and an outer portion comprising a tubular body, the distal end portion, the spline drive portion, and at least a portion of the stem portion configured to fit inside a hollow cylindrical body of the range taking shear bolt, the spline drive portion having a plurality of spline teeth running longitudinally on an outer surface thereof, the spline teeth on the outer surface of the spline drive portion constructed and arranged to mate with spline teeth on an inner surface of the cylindrical body of the shear bolt, and the tubular body configured to fit over the cylindrical body of the shear bolt, forming an external sleeve to control a depth of tool insertion. 
     In some embodiments, the head portion comprises a hexagonal head. 
     In some embodiments, the distal end portion has no spline teeth thereon. 
     In some embodiments, the inner portion and the outer portion are two separate pieces. 
     In some embodiments, a proximal end of the outer portion comprises an inwardly-facing flange configured to abut a lower surface of the head portion of the inner portion. 
     In some embodiments, the inner portion and the outer portion are formed as one piece. 
     Additional features and advantages of the present invention are described further below. This summary section is meant merely to illustrate certain features of the invention, and is not meant to limit the scope of the invention in any way. The failure to discuss a specific feature or embodiment of the invention, or the inclusion of one or more features in this summary section, should not be construed to limit the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of certain embodiments, will be better understood when read in conjunction with the appended drawings, in which there are shown certain preferred embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG. 1  is a side view of a range taking shear bolt according to some embodiments of the invention; 
         FIG. 2  is a sectional view, taken along line A—A of  FIG. 1 ; 
         FIG. 3A  is a top view of a range taking shear bolt of the present invention, showing spline teeth according to some embodiments; 
         FIG. 3B  is a top view of a range taking shear bolt of the present invention, showing spline teeth according to other embodiments; 
         FIG. 4  is an end view of a connector with range taking shear bolts of the present invention partially installed therein; 
         FIG. 5  is a sectional view, taken along line B—B of  FIG. 4 ; 
         FIG. 6  shows the end view of  FIG. 4  with a cable conductor and a bolt installation tool included; 
         FIG. 7  is a sectional view, taken along line C—C of  FIG. 6 ; 
         FIG. 8  shows the end view of  FIG. 6  with the bolts tightened against the conductor; 
         FIG. 9  is a sectional view, taken along line D—D of  FIG. 8 ; 
         FIG. 10  is a side view of a bolt installation tool according to some embodiments of the invention; 
         FIG. 11A  is a sectional view, taken along line E—E of  FIG. 10 ; 
         FIG. 11B  is an alternative sectional view, taken along line E—E of  FIG. 10 ; 
         FIG. 12  shows the end view of  FIG. 8  with the bolt heads sheared off and the bolt installation tool removed; 
         FIG. 13  is a sectional view, taken along line F—F of  FIG. 12 ; and 
         FIG. 14  shows detail L of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     In the case of bolted connections between a connector and an electrical cable, it is desirable to control the torque applied to the bolt, so that there is sufficient torque applied to create a secure connection (both electrically and mechanically), but not so much as to damage the conductor. 
     To accomplish torque control without using a torque wrench, a shear point or shear zone can be created, at or about where the driven portion of the bolt shears off (separates) from the clamping portion of the bolt at or approximate a predetermined torque value. The driven portion can then be discarded. 
     Separately, it is desirable to provide connectors that are “range taking”—meaning that a range of conductor sizes can be accommodated using the same connector. 
     Various embodiments of the present invention combine the features identified above, providing a range taking connector with the reliability of shear bolts. 
     For example, embodiments of the present invention provide range taking shear bolts that: break at a specific torque range; sufficiently clamp the conductors for both thermal cycling and mechanical pullout; break consistently (shear off) at or just below the outer surface of the connector; and/or are removable after shearing in the event that removal becomes necessary or desirable. Most products on the market have drawbacks related to one or more of these features. 
     With reference to  FIGS. 1 and 2 , an illustrative range taking shear bolt  100  is shown. Range taking shear bolt  100  is substantially cylindrical, comprising a hollow cylindrical body having a proximal end  101 , a distal end  102 , an outer surface  103 , and an inner surface  105 . As described in further detail below, proximal end  101  is constructed and arranged to accept a bolt installation tool  400 , also referred to herein as a drive tool (e.g., as shown in  FIG. 6 ), and distal end  102  is constructed and arranged to abut a conductor  300  (e.g., as shown in  FIG. 9 ). Proximal end  101  is preferably substantially or entirely open. Distal end  102  is preferably substantially or entirely closed. Outer surface  103  of range taking shear bolt  100  preferably has a screw thread  104  thereon. Screw thread  104  may comprise, for example, a substantially continuous external thread that allows range taking shear bolt  100  to be screwed into a connector  200 . It should be understood that such thread  104  need not extend along the entire length of the bolt  100 . 
     Inner surface  105  of range taking shear bolt  100  has a plurality of spline teeth  106  (e.g., female spline teeth) thereon, which can function like gear teeth. Spline teeth  106  may comprise, for example, a plurality of raised ridges running longitudinally along the length of inner surface  105  (e.g., from a shoulder  108  near distal end  102  all the way to an open proximal end  101 ). In certain embodiments, spline teeth  106  may have a substantially triangular cross-section. In some embodiments, as shown, for example, in  FIG. 3A , spline teeth  106  may be symmetrical. In other embodiments, as shown, for example, in  FIG. 3B , spline teeth  106  may be asymmetrical, similar to a saw tooth, such that a line extending from the drive face  109  would go through (or in close proximity to) the center of the cylindrical body of bolt  100 . In further embodiments, spline teeth  106  may have other shapes and/or arrangements that can complement and/or guide drive tool  400 . For example, the spline teeth need not run the entire length of the inner surface  105 . 
     The wall of cylindrical shear bolt  100  is configured to shear/break cleanly at or above a predetermined torque value (with an acceptable tolerance range). The predetermined torque value may be a function of the wall thickness between external thread  104  and internal teeth  106 . The thickness may be determined, for example, based on the physical properties/metallurgy of bolt  100  (e.g., type of metal, hardness, elongation, etc.). Bolt  100  may be made from any material. In some embodiments, bolt  100  may be formed from a metal (e.g., copper, zinc, etc.) or alloy, such as, but not limited to, brass. In other embodiments, non-metal materials may be used. 
     In some embodiments, inner surface  105  may also include a hexagonal broach  107  proximate a closed distal end  102  (solid bottom portion) of bolt  100 , bordering the distal end of longitudinal spline teeth  106  at shoulder  108 . Hexagonal broach  107  comprises a hexagonal impression at the bottom of inner surface  105  of range taking shear bolt  100 , which can facilitate removal of the clamping portion of bolt  100  once the driven portion (bolt head) has sheared off (see  FIGS. 12-14 ). Around the hollow hexagonal impression  107 , closed distal end  102  is solid. In alternative embodiments, other broaches or impressions may be used to facilitate removal. 
       FIGS. 4 and 5  show range taking shear bolts  100  partially installed in/positioned to be screwed further into a range taking connector  200 . The body of connector  200  may be substantially tubular, configured to accept cable, and may be made of any suitable material—for example, a machined metal, typically copper. A plurality of bolt installation sites  220  may be provided along the length of connector  200 , which may be staggered, for example, by 90 degrees.  FIGS. 4 and 5  show three set screws/bolts  100  (as used herein, the terms screw and bolt are interchangeable), two ( 100 A and  100 C) aligned as shown in the sectional view of  FIG. 5  (one of which,  100 A, is shown in  FIG. 4 ), and a third ( 100 B) offset by 90 degrees as shown in  FIG. 4 . Each bolt installation site  220  is configured to accept a range taking shear bolt  100  substantially perpendicular to the axis of the cable, and may comprise a threaded opening  222 . In some embodiments, the outer diameter of connector body  200  may comprise a recessed portion/depression  224  at each bolt installation site  220 . In other embodiments, the outer diameter of connector body  200  may comprise a substantially even surface. 
       FIGS. 6 and 7  show range taking shear bolts  100 A-C partially installed in connector  200  (as in  FIGS. 4 and 5 ), with a cable conductor  300  and a bolt installation tool  400  also illustrated. As shown, for example, in  FIG. 6 , the body of connector  200  has an inner diameter larger than that of cable conductor  300 , and thus can accommodate a range of conductor sizes. In certain embodiments, cable conductor  300  comprises a copper cable. 
     As shown, for example, in  FIG. 7 , in some embodiments, drive tool  400  comprises an inner drive portion  420  and an outer spacer portion  440 . Inner portion  420  is configured to be positioned inside the hollow cylindrical body of bolt  100  and/or inside spacer portion  440 , and comprises an inner drive tool with spline teeth to screw bolt  100  into connector  200 . Outer portion  440  is configured to be positioned outside the hollow cylindrical body of bolt  100  and comprises an outer spacer tube to control shear zone  500  on bolt  100 , as described further below. Outer portion  440  has an inner diameter that is approximately equal to or larger than an outer diameter of bolt  100 , so that outer portion  440  of tool  400  can fit over and slide along the outer surface  103  of bolt  100 . Inner portion  420  preferably has a distal end portion  428  (see also  FIG. 11A ) constructed and arranged to abut shoulder  108  on inner surface  105  of bolt  100 , so that inner portion  420  of drive tool  400  does not engage the hexagonal impression  107  in bolt  100 . 
       FIGS. 8 and 9  show range taking shear bolts  100 A-C (as in the views of  FIGS. 6 and 7 ) installed in connector  200  and tightened against conductor  300 . In some embodiments, outer tube  440  controls the depth of drive tool  400  to ensure that bolt  100  shears within a predetermined shear zone  500  at or about the outside surface of connector  200 , or the bottom of depression  224  (socket) if present. Shear zone  500  occurs between the distal end of spline drive  426  (see also  FIGS. 11A and 11B ) and connector  200  shear surface—i.e., the outer diameter of connector body  200 , or the bottom of depression  224  (socket) if present. 
       FIGS. 10, 11A, and 11B  show a bolt installation tool  400  in detail. In  FIGS. 11A and 11B , a simulated outer diameter of connector body  200  is depicted. Range taking shear bolt  100  is configured to shear off at or near this surface—specifically, within bolt shear zone  500 —regardless of its engagement depth into connector  200 . In some embodiments, a head portion  422  of the drive tool  400 , positioned at a proximal end of inner portion  420 , can be hexagonal (a hex head), for example, to tighten drive tool  400  using a conventional socket wrench. A middle portion  424  of inner portion  420  can comprise an elongated stem, which has a diameter less than that of head  422 , and less than the inner diameter of bolt  100 . A spline drive portion  426  of inner portion  420  comprises longitudinal spline teeth (e.g., male spline teeth) complementary to spline teeth  106  on inner surface  105  of bolt  100 . Spline teeth on spline drive portion  426  of drive tool  400  are constructed and arranged to engage with spline teeth  106  on inner surface  105  of bolt  100  to drive bolt  100  into connector  200  when drive tool  400  is rotated along its longitudinal axis. A distal end portion  428  of inner portion  420  of drive tool  400  can provide a short pilot diameter that has no spline teeth. 
     Thus, drive tool  400  can slide onto bolt  100  (as shown, e.g., in  FIGS. 6-9 ) with inner drive tool portion  420  configured to slide along the inner surface  105  of bolt  100  and stop when distal end portion  428  abuts the shoulder  108  of bolt  100 , and outer tube  440  configured to slide along the outer surface  103  of bolt  100  and stop when bottom edge  444  reaches the outer diameter of the connector body  200  (or the bottom of depression  224  at bolt site  220 , if present). Drive tool  400  can be turned (e.g., via head  422 ), and screw thread  104  on outer surface  103  of bolt  100  can engage with threaded opening  222  on connector  200 , to tighten bolt  100  against cable conductor  300  (as shown, e.g., in  FIGS. 8, 9 ) until a predetermined torque value is reached and bolt  100  shears at shear zone  500  (as shown, e.g., in  FIGS. 12-14 ). 
     In some embodiments, drive tool  400  may be provided in two pieces ( 420  and  440 ), as shown, for example, in  FIGS. 7, 9, and 11A . Using a two piece drive tool, outer spacer tube  440  may, for example, be held in place against connector  200  while inner tool  420  is turned to screw bolt  100  into threaded opening  222 , until the underside of head portion  422  abuts an upper shoulder  442  on tube  440  formed by a circumferential flange extending inward from the wall of tube  440 . In other embodiments, drive tool  400  may comprise a single piece, as shown, for example, in  FIG. 11B  (inner and outer portions  420  and  440  either formed as one or fused together/fixed to one another by welding, adhesive, or other connective means), and the entire drive tool  400  may be turned to screw bolt  100  into connector  200  until a lower face  444  of the outer spacer tube portion abuts the outer diameter of connector body  200  (or the bottom of depression  224  at bolt site  220 , if present). 
       FIGS. 12 and 13  show range taking shear bolts  100  (as in the views of  FIGS. 8 and 9 ) fully installed in connector  200 , with the bolt head (driven portion) sheared off. As shown, for example, in  FIGS. 13 and 14 , bolt  100  preferably shears at a point flush, within one revolution of thread  104 , with the outer diameter of connector body  200  (or the bottom of depression  224  at bolt site  220 , if present). Shear zone  500  is preferably approximately equal to one thread height of bolt  100 , although in other embodiments different widths may be used. In the present embodiments, shear zone  500  will occur at the outer surface of connector  200 , or the bottom of depression  224  if present, regardless of engagement depth. 
     While there have been shown and described fundamental novel features of the invention as applied to the preferred and exemplary embodiments thereof, it will be understood that omissions and substitutions and changes in the form and details of the disclosed invention may be made by those skilled in the art without departing from the spirit of the invention. Moreover, numerous modifications and changes may readily occur to those skilled in the art. Hence, it is not desired to limit the invention to the exact construction and operation shown and described and, accordingly, all suitable modification equivalents may be resorted to falling within the scope of the invention as claimed. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.