Patent Document

This application claims priority from U.S. Provisional Application No. 60/263,860, titled “Reinforcing Bar Connection and Method,” filed Jan. 23, 2001. 
    
    
     TECHNICAL FIELD 
     This invention relates generally as indicated to a reinforcing bar connection, and more particularly to a high strength reinforcing bar splice which provides not only high tensile and compressive strengths, but also has the dynamic and fatigue characteristics to qualify as a Type 2 coupler approved for all United States earthquake zones. The invention also relates to a method of making the connection. 
     BACKGROUND OF THE INVENTION 
     In steel reinforced concrete construction, there are generally three types of splices or connections; namely lap splices; mechanical splices; and welding. Probably the most common is the lap splice where two bar ends are lapped side-by-side and wire tied together. The bar ends are of course axially offset which creates design problems, and eccentric loading whether compressive or tensile from bar-to-bar. Welding is suitable for some bar steels but not for others and the heat may actually weaken some bars. Done correctly, it requires great skill and is expensive. Mechanical splices normally require a bar end preparation or treatment such as threading, upsetting or both. They also may require careful torquing. Such mechanical splices don&#39;t necessarily have high compressive and tensile strength, nor can they necessarily qualify as a Type 2 mechanical connection where a minimum of five couplers must pass the cyclic testing procedure to qualify as a Type 2 splice in all United States earthquake zones. 
     Accordingly, it would be desirable to have a high strength coupler which will qualify as a Type 2 coupler and yet which is easy to assemble and join in the field and which does not require bar end preparation or torquing in the assembly process. It would also be desirable to have a coupler which could be assembled initially simply by sticking a bar end in an end of a coupler sleeve or by placing a coupler sleeve on a bar end. 
     SUMMARY OF THE INVENTION 
     A reinforcing bar connection for concrete construction utilizes a contractible jaw or assembly which is closed around aligned bar ends to form the joint and tightly grip the bars. The jaw assembly is closed from each axial end to constrict around and bridge the ends of end-to-end reinforcing bars. The jaws of the assembly have teeth which bite into the ends of the bar. The assembly is constricted by forcing self-locking taper sleeves or collars over each end which hold the jaw constricted locking the bars together. The teeth are designed to bite into the ribs or projecting deformations on the surface of the bar which forms the overall diameter, but not bite into the core or nominal diameter of the bar. In this manner, the splice does not affect the fatigue or ultimate strength properties of the bar while providing a low slip connection. The jaw segments may be held assembled by a frangible plastic frame. The configuration of the jaws limits the contraction and precludes undue penetration of the bar by the teeth. The connection or splice has high tensile and compressive strength and will pass the dynamic cycling and/or fatigue requirements to qualify as a Type 2 coupler. No bar end preparation or torque application is required to make the coupling. In the method, the closing and locking occur concurrently with a simplified tool to enable the splice to be formed easily and quickly. 
     To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a completed or assembled splice in accordance with the invention; 
     FIG. 2 is a similar view with the locking collars and one jaw of the assembled splice removed; 
     FIG. 3 is a perspective view of one of the jaws; 
     FIG. 4 is a bottom elevation of the jaw of FIG. 3; 
     FIG. 5 is an axial end elevation of the jaw as seen from the right hand end of FIG. 4; 
     FIG. 6 is a plan view elevation of the jaw as seen from the left hand side of FIG. 5; 
     FIG. 7 is an enlarged axial section of a preferred jaw tooth profile; 
     FIG. 8 is an axial end elevation with the bar in section of the jaw assembly contracted and gripping the bar ends; 
     FIG. 9 is a perspective of a plastic spacer for assembling the jaw elements with one jaw removed for clarity of illustration; 
     FIG. 10 is a similar perspective view of the splice assembly with the jaws open and locking collars assembled but not in locking positions; and 
     FIG. 11 is a perspective view of an installation tool for closing the jaw assembly from each axial end while placing locking collars on both axial ends. 
    
    
     DETAILED DESCRIPTION 
     Referring initially to FIGS. 1 and 2, there is illustrated a reinforcing bar connection in accordance with the present invention shown generally at  20  joining end-to-end axially aligned deformed reinforcing bars  21  and  22 . The reinforcing bars are shown broken away so that only the ends gripped by the splice or connection are illustrated. It will be appreciated that the bars may extend to a substantial length and may either be vertical, horizontal, or even diagonal in the steel reinforced concrete construction taking place. The connection and bars are designed to be embedded in poured concrete. The connection comprises a jaw assembly shown generally at  24 , which includes three circumferentially interfitting three jaw elements shown at  25 ,  26  and  27 . It will be appreciated that alternatively two jaw elements or more than three jaw elements may form the assembly  24 . 
     As seen more clearly in FIG. 2, the exterior of the jaw elements forms oppositely tapering shallow angle surfaces seen at  29  and  30 , on which are axially driven matching taper lock collars  32  and  33 , respectively. When the lock collars  32  and  33  are driven toward each other, the jaw assembly  24  contacts driving the interior teeth shown at  35  on each jaw element into the deformed, or projecting portions, of the bar such as the longitudinal projecting ribs  36  and the circumferential ribs  37 . The projecting rib formation on the exterior of the bars may vary widely, but most deformed bars have either a pattern like that shown or one similar to such pattern. The teeth  35  are designed to bite into such radial projections on the bar, but not into the core  38 , which forms the nominal diameter of the bar. It should be again noted that in FIG. 2, the jaw element  26  has been removed as well as the lock collars  32  and  33  to illustrate the interior teeth  35 . 
     Referring now to FIGS. 3 through 7, there is illustrated a single jaw  26 . Each of the three jaws forming the jaw assembly  24  are identical in form. Each jaw is a one-piece construction and is preferably formed of forged steel heat treated and stress relieved. 
     As seen more clearly in FIG. 5, since three jaw elements form the jaw assembly, each jaw element extends on an arc of approximately 120°. As seen more clearly in FIGS. 3 and 5, the 120° extends from one axial, or longitudinal, edge  40  to the other seen at  41  Such edges or seams between the jaw elements are axially parallel and uninterrupted except for the circumferential recesses  42  in the longitudinal edge  40  and the interfitting projection  43  on the longitudinal edge  41 . Each projection  43  is designed to fit into the notch  42  of the circumferentially adjacent jaw element. The interfitting projections and notches ensure that the jaw elements do not become axially misaligned as the connection is formed. The interfitting circumferential projections and notches also ensure that the jaw assembly remains an assembly as the splice is formed. The interfit of the circumferential projections with the notches of adjacent jaw elements is seen more clearly in FIG.  1 . The interfitting projections and notches may extend approximately 20° into or beyond the longitudinal seams. 
     As seen more clearly in FIGS. 4 and 6, each jaw element tapers from its thinnest wall section at the opposite ends  45  and  46  to its thickest wall section shown in the middle at  47 . The taper surfaces formed by the exterior of the jaw elements are low angle, self-locking tapers of but a few degrees and, of course, the tapers match the interior taper of the taper collars  32  and  33  which are driven axially on the end of the splice. The taper is preferably a low angle taper on the order from about one to about five degrees. 
     The taper exterior of the opposite ends of the jaw elements as well as the jaw assembly not only enables the matching lock collars to be driven on the splice, contracting the jaw elements with great force but locking them in contracted position. The configuration of the connection also enhances the dynamic and fatigue characteristics of the splice. This not only enhances the fatigue characteristics of the splice, but also enables the splice to qualify as a Type 2 coupler which may be used anywhere in a structure in any of the four earthquake zones of the U.S. 
     Referring now to FIG. 7, it will be seen that the interior of each jaw element is provided with a series of relatively sharp teeth  35 , which in the illustrated embodiment are shown as annular. However, it will be appreciated that a thread form of tooth may be employed. Each tooth  35  includes a sloping flank  50  on the side of the tooth toward the end of the jaw element. However, toward the middle of the jaw element, the tooth has an almost right angular flank  51  which meets flank  50  at the relatively sharp crown  52 . The flank  50  may be approximately 60° with respect to the axis of the jaw element while the flank  51  that is almost 90°. It will be appreciated that the teeth  35  may alternatively have other suitable configurations. 
     As seen in comparing the left and right hand side of FIG. 6, the teeth on the opposite end are again arranged with the angled flank on the exterior while the sharper almost perpendicular flank faces the mid-point  47  of the jaw element. 
     As indicated, the inward projection of the teeth is designed to bite into the projecting deformations on the bar, but not into the core  38 . As the teeth  35  press into the deformation, they provide additional cold working of the bar, resulting in better performance of the connection. By not pressing the teeth  35  into the core  38  of the bar, fatigue cracks and/or stress concentrations may thereby be avoided. 
     The three jaw elements are shown in FIG. 8 closed with the teeth  35  of the jaw elements biting into the bar deformation projections  36  and  37 , but not into the bar core  38 . When closed, the three longitudinal seams between the jaw elements seen at  54 ,  55  and  56  will be substantially closed preventing further contraction of the jaw assembly keeping the teeth from biting into the core. The total contraction of the splice is controlled both by the circumferential dimensions and the axial extent to which the lock collars are driven on each end of the splice. 
     It will be appreciated that a transition splice may be formed with the present invention simply by reducing the interior diameter of one end of the splice so that the teeth on that end will bite into the projecting deformations on a smaller bar. The exterior configuration of the jaw elements may also change or remain the same with different size or identical locking collars driven on each end. 
     It will be appreciated that alternatively other means may be utilized for contracting internally-toothed jaw elements to clamp ends of reinforcing bars, for example by use of a radially-contracting collar or band. 
     Referring now to FIGS. 9 and 10, there is illustrated a splice assembly  59  where the jaw elements are held open and spaced from each other by a plastic spacer shown generally at  60 . The plastic spacer comprises three generally axial or longitudinal elements seen at  61 ,  62  and  63 , each of which includes a center lateral projection  64  and an opposite notch  65 . The projection  64  snugly fits into the notch  42  of the jaw element while the notch  65  receives the projection  43  of the adjacent jaw element in a snug fit. 
     The three axially extending or longitudinal elements are held in place with respect to each other by the center three-legged triangular connection shown generally at  68 , which also acts as a bar end stop. In this manner, the three jaw elements are held assembled and circumferentially spaced. Each locking collar may be positioned on the end of the assembled jaw elements as seen at  32  and  33  and held in place by a shrink wrap, for example, as seen at  70  and  71 , in FIG. 10, respectively. In this manner, the jaw elements are held circumferentially spaced as seen by the gaps  72 . The assembly seen in FIG. 10 may readily be slipped over the end of a reinforcing bar and the end of the bar will be positioned in the middle of the splice by contact of the bar end with the triangular leg center connection  68 . When the opposite bar end is inserted into the open and assembled splice, the jaw assembly may then be closed by driving the two lock collars  32  and  33  axially toward each other. The force of driving on the lock collars will disintegrate not only the shrink wrap  70  and  71 , but also the support  60  which is made preferably of a frangible or friable plastic material. This then permits the jaw assembly to close to the extent required to bite into the radial bar projections to form a proper high fatigue strength coupling joining the two bar ends. 
     Referring now to FIG. 11, there is illustrated a tool shown generally at  78  for completing the splice or connection of the present invention. Although the tool is shown connecting the bars  21  and  22  vertically oriented, it will be appreciated that the bars and splice may be horizontally or even diagonally oriented. The tool is preferably made of high strength aluminum members to reduce its weight and includes generally parallel levers  79  and  80  connected by center link  81  pivoted to the approximate mid-point of such levers as indicated at  82  and  83 . Connecting the outer or right hand end of the levers  79  and  80  is an adjustable link shown generally at  85  in the form of a piston-cylinder assembly actuator  86 . The adjustable link may also be a turnbuckle or air motor, for example. The rod  87  of the assembly is provided with a clevis  88  pivoted at  89  to the outer end of lever  79 . The cylinder of the assembly  91  is provided with a mounting bracket or clevis  92  pivoted at  93  to the outer end of lever  80 . 
     The opposite end of the lever  79  is provided with a C-shape termination pivoted at  96  to a C-shape tubular member  97  having an open side  98 . A wedge driving collar shown generally at  100  is mounted on the lower end of the open tube  97 . The collar is formed of hinged semi-circular halves  101  and  102 . When closed and locked, the wedge collar has an interior taper matching that of the taper collars  32  or  33 . 
     The lower arm  80  similarly is provided with a C-termination  105  pivoted at  106  to open tube  107  supporting wedge collar  108  formed of pivotally connected semicircular halves  109  and  110 . 
     In order to make a splice, the coupler or splice assembly  59  seen more clearly in FIG. 10 is aligned with a first bar  21 , for example. The coupler assembly is then slid onto the bar end. A second bar  22  is then positioned in line with a coupler and the second bar is slid into position such that the coupler is centered between both bars. The bar ends will contact the triangular spider connection in the center of the bar splice assembly to ensure that the bar ends are properly seated with respect to the coupler assembly. The tool with the wedge collars  100  or  108  open is then positioned over the bars. The wedge collars are closed and the actuator, or piston cylinder assembly  86 , is extended to drive the wedge collars toward each other, driving the taper lock collars  32  and  33  on the jaw assembly to the position seen in FIG. 1, forming the splice  20 . The wedge collars  100  and  108  are then opened and the tool removed. The taper lock collars  32  and  33  remain in place. When the taper lock collars are driven on the ends of the splice or connection, the jaw elements contract and the teeth on the interior bite into the projecting deformations on the bar ends, but do not bite into the core diameter of the bar. 
     It will be seen that the present invention provides a high strength coupler or splice which will qualify as a Type 2 coupler and yet which is easy to assemble and join in the field and which does not require bar end preparation or torquing in the assembly process. 
     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. It will be appreciated that suitable features in one of the embodiments may be incorporated in another of the embodiments, if desired. The present invention includes all such equivalent alterations and modifications, and is limited only be the scope of the claims.

Technology Category: 4