Tubular coupler for concrete reinforcing bars

#In the art of joining the adjacent end portions of two generally aligned concrete reinforcing bars or "rebars", it is known to use a tubular steel coupling body or sleeve which receives the end portions of the bars. The coupling sleeve is crimped or swaged with substantial force against the reinforcing bars with the aid of a hydraulically actuated press and die set, for example, as disclosed in U.S. Pat. Nos. 3,551,999 and 4,241,490. It is also known to form tapered or non-tapered threads on the end portions of each reinforcing bar, and to join the end portions together with a coupling sleeve having internal tapered or non-tapered threads, for example, as disclosed in U.S. Pat. Nos. 197,509 and 3,415,552.

#In order to avoid the need for a hydraulically actuated press, a hydraulic pump and power source and a crimping die set, or to avoid the threading operation and protection of the threaded end portions of the reinforcing bars, it is also known to use a tubular coupler sleeve with longitudinally spaced and radially extending screws. According to one coupler as disclosed in U.S. Pat. Nos. 4,666,326 and 5,046,878, each of the screws has a hex shaped outer end portion and a threaded inner portion integrally connected by a reduced neck portion. The screws are tightened through the coupling sleeve into the reinforcing bars until the torque is sufficient to shear the hexagonal head portions from the threaded inner portions at the neck portions generally flush with the outer surface of the sleeve. This tubular coupling sleeve is also provided with a pair of elongated racks or hardened strips with inwardly and outwardly projecting teeth, and the ends of the strips are welded to the coupling sleeve. It has also been proposed to inject an epoxy material into these coupling sleeves after the screws are tightened for further increasing the gripping strength of the coupler sleeve with the opposing end portions of the connected reinforcing bars.

#The forming of threads on the end portions of the reinforcing bars and the protection of the threads during handling and shipping of the bars add significantly to the cost of the reinforcing bars. In addition, the forming of internal threads within the tubular coupling sleeve adds to the cost of the coupling sleeve. In regard to the above described coupler with inner strips having teeth, the use of longitudinally spaced special screws significantly increases the cost of the coupling sleeve, and the cost of the sleeve is further increased by the cost of forming the internal hardened strips with teeth on opposite sides and the cost for welding the strips within the coupling sleeve. Also, during installation, the strips of teeth sometimes bind upon the reinforcing bars as they are being inserted. This difficulty creates additional field labor. Further, once the heads of the special screws have been sheared off there is no provision to loosen the screws to reposition the coupler if it has been misinstalled. Another problem with special screws is that they are sometimes unreliable because the heads do not shear off at the prescribed torque.

#FIG. 1 is an elevational view of a coupler constructed in accordance with the invention and shown assembled for positively connecting the adjacent end portions of two concrete reinforcing bars;

#FIG. 2 is an axial section of the coupler and the end portion of the reinforcing bars shown in FIG. 1 and with a row of set screws shown in elevation;

#FIG. 3 is an enlarged cross-section of the coupler and a reinforcing bar before the set screws are tightened;

#FIG. 1 illustrates a coupler 10 constructed in accordance with the invention and which includes an elongated tubular body 12 constructed from ductile seamless steel tubing, preferably Grade 1018, but steel grades 1012 through 1020 are also appropriate with selected mechanical properties. The coupler 10 forms a high strength rigid connection between the adjacent end portions 14 (FIG. 2) of a pair of concrete reinforcing bars 15. Each of the bars 15 has longitudinally spaced and circumferentially extending ribs 17 and also a pair of longitudinally extending and diametrically opposite ribs 18 which generally intersect the ends of the circumferential ribs 17.

#As shown in FIG. 3, the tubular body 12 has a generally diamond-shaped cross-sectional configuration and includes a longitudinally extending V-shaped wedge portion 22 formed by generally flat wall portions 24 with corresponding inner flat surfaces 26. The surfaces 26 form a V-shaped trough and define an included angle A between 50 degrees and 70 degrees and preferably about 60 degrees.

#The tubular body 12 also includes a pair of longitudinally extending and generally flat walls 32 which are integrally connected by a generally flat wall 34 (FIG. 2) in which is formed a row or series of axially or longitudinally spaced threaded holes 37. The walls 32 and 34 also form a generally V-shaped cross-sectional configuration and oppose the V-shaped wedge portion 22 of the coupler body 12. As shown in FIG. 3, the tubular body 12 defines an internal diamond-shaped chamber 40 which is sufficiently large to receive freely the opposing end portions of the reinforcing bars 15.