In the construction of a reinforcing bar concrete structure, in general, a deformed bar is mainly used as a reinforcing bar, wherein joints protrude in the horizontal direction and two line ribs are formed symmetrical over the whole length so as to enhance a coupling stress intensity with a concrete. Since the reinforcing bar is manufactured with a limited length for the sake of easier transportations or work conveniences, the reinforcing bars are coupled and used. There are a variety of deformed bar coupled ways.
The most widely used connection method is an overlapped joint method wherein the ends of two reinforcing bars are overlapped and tied using a tying wire. In this method, since the joint parts are supported by only an attaching force of the reinforcing bar, the safety may be degraded. In the gas pressure welding method wherein the ends of two steels are heated using an oxygen-acetylene gas flame and are coupled by pressing using a pressure welding machine, a thermal deformation may occur at the joint parts, thus causing a secondary stress, for which the joint parts may become weaker than a steel basic material. In a screw coupling method wherein both ends of each of two reinforcing bars are upset or a rib and a joint are processed into a circular shape through a casting, and a male screw is processed in a cutting and form-rolling method and is coupled using a female screw type coupler, an external force may be applied to the reinforcing bars, so a predetermined deformation may occur, which is different at the steel basic material. For this reason, it may become weaker than the basic material.
According to the regulation on the manufacturing of the reinforcing bars, the reinforcing bars are regulated to be manufactured while maintaining a material property which is similar with a concrete in terms of a thermal expansion ratio so as to prevent the steel concrete structure from being easily broken when heat is applied thereto. According the Korean regulation on the coupling of the reinforcing bars, the aforementioned overlapping coupling method is not allowed for the coupling of the reinforcing bars wherein the names of the steels are over D29 (the diameter is 29 mm), the reinforcing bars are being coupled by the gas pressure welding method or the mechanical method. This method, however, may need a secondary processing to supply heat or an external force to the reinforcing bar, so the natural material properties of the reinforcing bars could be lost. The reason why this method is inevitably allowed is that a variety of the reinforcing bar couplers are being developed, which are able to couple without changing the natural reinforcing bar properties.
In addition, recently according to the needs of the full couple method, as shown in FIG. 1, screw joint reinforcing bars 1 and 1a are developed, wherein a screw ridge type screw joint 11 is formed on the outer surface of a reinforcing bar. The screw joint reinforcing bars are coupled through a sleeve 4z having a female screw part 41 to which the screw joints 11 of the reinforcing bars 1 and 1a are engaged.
However, the pitches of the screw joints 11 of the reinforcing bars 1 and 1a are long, and the screws are formed inaccurate, for which the screw valley of the female screw 41 of the sleeve 4z is formed larger than the screw joint 11 of the reinforcing bars 1 and 1a for the sake of smooth engagements. In this state, if the two reinforcing bars 1 and 1a are coupled using the sleeve 4z, the space between the sleeve 4z and the reinforcing bars 1 and 1a may increase, which may cause an easier disengagement together with a slipping, thus causing a problem.
In order to resolve this problem, a lock nut 5z may be engaged to both ends of the sleeve 4z, and a grout material is filled in the inside of the sleeve 4z so as to remove any space. In this case, a work for preparing and charging a grout material may be complicated, and since the strength of the grout material is less than 10% of the reinforcing bar, a safe coupling may not be secured. Since the pitches of the reinforcing bars 1 and 1a are long, the slope angle of the screw ridge may be large, which may result in a lot of necessary force for the engagement of the lock nut 5z, and the lock nut 5z may be easily loosened by external vibrations, thus causing a safety problem.
Since two lock nuts 5z are provided in the form of separate components, not integrated with the sleeve 4z, the management of the components is hard, and since the lock nut 5z is relatively small-sized, a risk for the accident due to the falling of the lock nut may increase during a coupling work, for which a demand for a reinforcing bar coupler increases, which can be used for a temporal coupling due to a construction site which needs more cost saving through an enhanced safety and construction capability and a faster work speed.
In order to resolve the aforementioned problems, the Korean utility model registration number 0409526 describes a technology wherein as illustrated in FIG. 2, a semicircular sleeve 2 is provided, which is able to be loaded while covering screw joints 11, and both inclined sides of the semicircular sleeve 2 can be pressed in such a way to tighten a lock nut 5 at the left and right sides of the semicircular sleeve 2, thus coupling the spiral reinforcing bar 1a .
Since the aforementioned conventional technology requires a number of components, the construction performance may be degraded, thus causing a problem.