FIELD OF INVENTION The invention relates to building construction. More particularly, the invention relates to a mechanical coupling device for use in connecting reinforced bars.

BACKGROUND OF THE INVENTION The conventional art, apparatus and method for coupling reinforcing bars used in construction, such coupling method involves the use of a tubular steel coupling body or sleeve having a frictional inner surface configured to receive end segments of two reinforcing bars. Typically, the bars are secured within the coupling body using a number of engagers such as, bolts or screw which mount into the bars thereby wedging the bars against the frictional inner surface.

The coupled reinforcing bars are both wedged firmly against an inner surface of the tubular body in addition to provide resistance to a laterally applied loading force, or tensile force. A common problem encountered with prior art coupling device is that continuous exertion of tensile force on the reinforcing bars results in abrasion of the engager sharp ends on the reinforcing bars, substantially forming a groove between the reinforcing bars and engagers. The groove reduces the interaction and contact between the coupling device engagers and reinforcing bars, therefore the coupling of the reinforcing bars is unable to achieve and causes bar slippage.

The conventional conical sharp edge end profile of the bolts or screws that hold the reinforcing bars within the coupler, is described by wedging action for the bar penetration. A deep penetration of pointed bolt ends could destroy the rod rigidness. In particular, following by a maximum loading force on the bars, it is common to observe bar breakage at a region of bars having reduced cross-sectional surface area in addition to maximum load transfer from bar to coupling device. Due to the degree of penetration of the engagers into the reinforcing bars, the ability of prior art coupling devices to transfer load from bar to coupler body is reduced as a result of the reduced cross-sectional area of the bars at various wedged points along the bars within the couple body. Commonly, at least one bar breaks in region within the coupler device therefore providing a weak joint between reinforcing bars, which is the major drawback of the prior arts. However, the engagers need not to be deeply piercing the reinforcing bars to provide the optimum interaction and contact between the coupling device and reinforcing bars.

Another setback is that conventional coupling device comprises elongated tubular steel coupling body, reinforcing bars and plurality of engagers stretched out in array arrangement. The formation reduces the distance between the bolts and increases the coupling body length in such to grip the coupling body and the reinforcing bars. Lengthened coupling body and increased multiple engager usages do not improve the competence of the coupling device whereby only escalates the negative effects such as slippages and breakages. Accordingly, the invention strives to provide a coupling device which will not represent a weak point within the reinforced structure providing instead a bar coupled region having an equal or higher loading force tolerance to that found at an uncoupled region along the length of the bars. PRIOR ART

US7093402B2 discloses a coupling device for coupling reinforcing bars used in structural concrete comprising an elongate tubular body for receiving bar end portions, a plurality of engagers being adjustably positioned through the elongate tubular body, the coupling device being characterized in that the plurality of engagers are configured with a plurality of different end portions being configured for a different engaging of the reinforcing bars. SUMMARY OF INVENTION

The invention provides a device for joining a pair of reinforcing bars, comprises an elongate hollowed tubular sleeve for receiving the end portions of two reinforcing bars and having a plurality of holes, each extending from its outer surface to its inner surface, a plurality of engaging means dimensioned to pass through each hole to penetrate the reinforcing bars and to be retained therein, characterised in that the engaging means comprises a first tapered section and a second tapered section with a greater degree of taper than the first section such that the second taper section can penetrate the reinforcing bars.

Preferably, at least one portion of the inner surface of the sleeve or entirely can have a frictional or gripping texture.

Preferably, the plurality of holes are positioned in one array arrangement.

Alternatively, the plurality of holes can be positioned in multiple arrays arrangement.

Preferably, the plurality of holes are threaded holes. Preferably, the plurality of engaging means are threaded bolts and further the bolts can be shear bolts.

Preferably, the inner surface of the sleeve has threaded sides and a non-threaded recess sandwiched therebetween. One skilled in the art will readily appreciate that the invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments described herein are not intended as limitations on the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

Fig. 1 illustrates a first embodiment of a bolt coupler.

Fig. 2 is a cross section view of the bolt coupler taken at Y - Y of fig. 1.

Fig. 3 is another cross section view of the bolt coupler taken at X - X of fig.

1.

Fig. 4 illustrates a second embodiment of the bolt coupler.

Fig. 5 illustrates a shear bolt for use in the bolt coupler which embodies therein the principle features of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in greater detail, by way of example, with reference to the drawings. Referring to Figs. 1 to 3, a first embodiment of the mechanical bolt coupler is illustrated. The coupler comprises an elongate metal tube 1 for receiving the end portions of two reinforcing bars 8, 9. The tube 1 can be in any shape such as circle, oval, triangle, square, trapezium, diamond, rhombus, parallelogram, rectangle, pentagon, hexagon, heptagon, octagon and etc in cross section. The tube 1 has a plurality of longitudinally spaced holes 6, each extending from the outer surface 2 to the inner surface 3 of the tube 1. The holes 6 are threaded for receiving a plurality of engagers 7 such as bolt, pin, rivet or screw. Preferably, the engagers are shear type bolts. The tube 1 can also have at least two rows of longitudinally spaced holes 6 and being alternatively displaced as shown in Fig. 4. Not only this arrangement allows the tube 1 to be shorten, it can also effectively improve the gripping of the engagers 7 towards the reinforcing bars 8, 9 by increasing the distance between two neighbour engagers 7 of the same row. Furthermore, at least one part of the inner surface 3 or entirely are made to be rougher, preferably by having threaded surface 4 for preventing the reinforcing bars 8, 9 from sliding.

Referring to Fig. 5, a side view of the shear type bolt 7 as illustrated therein comprises a thread body 10 having a shear head 11 on one end and the opposing end 12, 13 is made to be pointed. The pointed end portion 12, 13 comprises a first tapered section 13 and a second tapered section 12 with a greater degree of taper than the first section 13. In operation, such bolts 7 are dimensioned to pass through each hole 6 to penetrate the reinforcing bars 8, 9 by its second tapered section 12 until it reaches the first tapered section 13, and then the first tapered section 13 will push the reinforcing bars 8, 9 towards the threaded surface 4. The shear head 11 will break off from its body 10 when the bolt 7 is tightly secured within the coupler.

In one preferred embodiment, the sides of the inner surface 3 are threaded and a non- threaded recess 5 is form between the two threaded sides. This arrangement allows bolts within the recess region to slightly bend the end portion of the reinforcing bars 8, 9 towards a direction opposite to the bolt engagement. The second tapered section 12 of the bolts 7 within this recess region will bend according to the bending movement of the reinforcing bars 8, 9 and the bending of the reinforcing bars 8, 9 will induce a bending tension force that pushes the reinforcing bars 8, 9 towards the threaded section 4 and being interlocked by the bended second tapered section 12 of the bolts 7.

The present disclosure includes as contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the scope of the invention.