JPH0886047A - Reinforcing connection device - Google Patents

Abstract

PURPOSE: To make it possible to connect a pair of threaded reinforcements by clamping with a small torque. CONSTITUTION: A connection device is provided with a pair of end joints 11 and 12 and one central joint 13. The end joints 11 and 12 have first female threaded parts 11a and 12a and second female threaded parts 11b and 12b which are communicated with each other straightly. The first threaded parts form the same pitch P1 with threaded reinforcements 1 and 2. The second threaded parts are shaped up as a fine screw at a small pitch P2 . The second female threaded parts 11b and 12b are identical to each other in their length but opposite to each other in their directions. The central joint 13 has a pair of male threaded parts 13a and 13b. The male threaded parts are identical to each other in their length but opposite to each other in their directions and form an identical pitch with the female threaded parts 11b and 12b. The central joint 13 is turned so that the male threaded parts 13a and 13b may be threaded with the second female threaded parts, thereby fastening the central joint 13 in a state that the end faces of the male threaded parts are arranged to be placed into contact with the end faces of threaded reinforcements 1 and 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing bar connecting device used for a splicing method of a reinforced concrete structure in the fields of construction, civil engineering and the like.

[0002]

2. Description of the Related Art In a piecing joint method for a reinforced concrete structure using a screw reinforcing bar, first, a reinforced concrete structure is formed by driving concrete with one end of a tubular joint screwed into one end of the screw reinforcing bar. To manufacture. In this structure, the other end of the joint is open on the outer surface of the concrete. When a new reinforced concrete structure is to be spliced into this existing reinforced concrete structure, the ends of the screw reinforcing bars are screwed into the joint and connected, and then concrete is poured.

In the above-mentioned piecing method, it is necessary to increase the connecting strength between the screw reinforcing bar and the joint. As a method therefor,
There are a method using a lock nut and a method using a grout material. To explain the former method in detail, the lock nut is screwed in advance at a sufficient distance from the end of the screw reinforcing bar, and the end of this screw reinforcing bar is screwed into the joint of the existing reinforced concrete structure. , Tighten the lock nut toward the end face of the fitting. An example of the latter method is disclosed in JP-A-5-171740. That is, after screwing the screw rebar into the joint, a grout material is filled between the two to increase the connection strength. More specifically, the injection tube is attached to the joint in advance. The injection pipe extends in the axial direction along the outer peripheral surface of the joint, has one end penetrating the central portion of the joint and opening to the inner peripheral surface, and the other end opening at the other end of the joint. There is. The grout material is injected from the opening of the injection pipe, enters the inside of the joint from the center part of the joint through the injection pipe, and due to the injection pressure, it fills the slight gap between the inner peripheral surface of the joint and the outer peripheral surface of the screw rebar. To be done.

[0004]

In the former method, the lock nut must be tightened with a large torque in order to increase the connecting strength between the reinforcing bar and the joint, which requires a large tightening device at the splicing site. I didn't like it. In the latter method, the joint structure was complicated because an injection pipe was required.

[0005]

In order to solve the above-mentioned problems, the reinforcing bar connecting device according to the invention of claims 1 to 4 comprises a pair of end joints and one central joint. The invention of claim 1 includes the inventions of claims 2 to 4. That is, each of the pair of end joints has a female threaded portion and a fine threaded portion arranged in a straight line, the female threaded portion is screwed to the end portion of the threaded reinforcing bar with the same pitch as the threaded reinforcing bar. The fine threaded portion has a pitch much smaller than that of the first female threaded portion, and the fine threaded portions of the pair of end joints have the same length and pitch and opposite screw directions. is there. The central joint has a tool hooking portion on at least a part of its outer periphery and has a pair of fine threaded portions arranged in a straight line, and these fine threaded portions have equal lengths and opposite screw directions. With
It has the same pitch as the fine threaded portions of the pair of end joints, and is respectively screwed into the fine threaded portions of these end joints.
In the invention of claim 2, each of the pair of end joints has a tubular shape and has a first female screw portion and a second female screw portion which are continuous in a straight line, and the first female screw portion is the screw. The second female thread portion is a fine thread having a pitch much smaller than that of the first female thread portion, and is screwed to the end portion of the screw rebar at the same pitch as the rebar. The second female screw portion of the end joint has the same length and pitch, and the screw directions are opposite to each other. The central joint has a tool hanging portion in the central portion, and has a pair of male screw portions extending in a straight line on both sides of the tool hanging portion,
These male screw portions have equal lengths and opposite screw directions, and form fine threads having the same pitch as the second female screw portions of the pair of end joints. Are combined. In the invention of claim 3, each of the pair of end joints has a tubular shape, and is provided with a first female screw portion and a second female screw portion arranged in a straight line, and between the first and second female screw portions. A partition wall formed on the first female screw portion, and the first female screw portion is screwed to the end portion of the screw reinforcing rod at the same pitch as the screw reinforcing rod, and the second female screw portion is the first female screw portion. Fine threads with a much smaller pitch are formed, and the second female threaded portions of the pair of end joints have the same length and pitch, but opposite screw directions. The central joint has a tool hanging portion on the outer circumference of the central portion, and has a pair of male screw portions extending in a straight line with each other on both sides of the tool hanging portion, and these male screw portions have equal lengths and screw directions. On the contrary,
A fine screw having the same pitch as the second female screw portion of the pair of end joints is formed, and is screwed into the second female screw portion of the pair of end joints, respectively. In the invention of claim 4, each of the pair of end joints has a tubular portion formed with an internal thread portion, and an external thread portion that extends in the opposite direction from the end of the tubular portion in the same straight line as the internal thread portion. However, the female screw portion is to be screwed to the end portion of the screw rebar with the same pitch as the screw rebar, and the male screw portion is a fine screw having a pitch much smaller than the female screw portion, and The lengths and pitches of the male screw portions of the pair of end joints are equal to each other, and the screw directions are opposite to each other. The central joint has a tubular shape, and at least a part of its outer periphery is a tool hanging portion, and
It has a pair of female screw portions that are continuous in a straight line, and the pair of female screw portions have equal lengths and opposite screw directions, and have the same pitch as the male screw portions of the pair of end joints. It is screwed to the part.

[0006]

According to the invention of claim 1, the central joint is turned while the female thread portions of the pair of end joints are screwed with the opposite end portions of the pair of threaded reinforcing bars, and the pair of fine threaded portions of the central joint are rotated. Is screwed onto the fine threaded portions of the pair of end joints. At this time, since the screw directions of the pair of fine threaded portions of the central joint are opposite to each other, the pair of end joints approach each other. Then, by tightening this central joint, the pair of screw reinforcing bars are connected via the pair of end joints and the central joint. The fine threaded part of the central joint and the fine threaded part of the end joint have a much smaller pitch than the threaded bar, so turn the tool hooked on the tool hook of the central joint with a smaller torque than before. Also, a strong tightening force can be obtained. As a result, a strong connecting strength of the screw reinforcing bar is obtained without using a large-sized tightening device, and workability is improved. According to the invention of claim 2,
The pair of male screw portions of the central joint are screwed into the second female screw portions of the pair of end joints. Then, the central joint is tightened in a state where the end faces of the male screw portions are in contact with the end faces of the screw reinforcing bars screwed to the first female screw portions of the pair of end joints. At this time, the end face of the screw reinforcing bar and the end face of the male screw portion receive a pushing force from each other. Therefore, not only the connecting strength between the male screw portion of the central joint and the second female screw portion of the end joint can be increased, but also the connecting strength between the screw reinforcing bar and the first female screw portion of the end joint can be increased. In addition, it goes without saying that the action of claim 1 can be obtained. In the invention of claim 3, the central joint is tightened with the end faces of the pair of male screw portions of the central joint hitting the partition walls. As a result, an action substantially equivalent to that of claim 1 is obtained. In the invention of claim 4, the central joint is tightened with the end faces of the male screw portions of the pair of end joints contacting each other. As a result, an action substantially equivalent to that of claim 1 is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 10 indicates screw rebars 1 and 2.
1 shows a rebar connecting device 10 for connecting the. The reinforcing bar connecting device 10 includes a pair of end joints 11 and 12 and one central joint 13. The end joints 11 and 12 each have a tubular shape, and have a hexagonal cross-sectional shape over the entire length, and the outer peripheries thereof are tool hanging portions 11x and 12x. Note that the tool hanging portion may be provided only in the central portion, and both side portions thereof may be cylindrical portions.

The one end joint 11 (the left end joint in the drawing) has a first female screw portion 11a and a second female screw portion 11b (fine screw portion). These female screw parts 11a, 11
b extends along the central axis of the end joint 11 and is continuous in a straight line. The first female threaded portion 11a opens at one end face (left end face in the figure) of the end joint 11 and
1b is open to the other end surface (right end surface in the figure) of the end joint 11.

The first female threaded portion 11 of the one end joint 11 described above.
a has the same pitch P ₁ of the above-mentioned screw rebars 1 and 2, and its screw direction is a right-hand thread like the screw rebars 1 and 2. The second female screw portion 11b is the first female screw portion 11a.
It has a much smaller pitch P ₂ and is as fine as a normal machine screw. For example, the pitch P ₁ of the first female screw portion 11a is ten and a few mm, and the pitch P ₂ of the second female screw portion 11b is about 1 to ₂ mm.

The other end joint 12 also has the same size and structure as the end joint 11, and has a tool hooking portion 12x, a first female screw portion 12a having a pitch P _{1 and} a second female screw portion having a pitch P ₂ . 12b (fine screw portion). However, the second female threaded portion 11b of the end joint 11 is a right-handed thread, whereas the second female threaded portion 12b of the end joint 12 is a left-handed thread.

The central joint 13 has a tool hanging portion 13x having a hexagonal cross section in the central portion, and a pair of male screw portions 13 extending in a straight line on both sides of the tool hanging portion 13x.
It has a and 13b (fine screw part). These male screw portions 13a and 13b have the same length, and the end joint 1
The same pitch P as the first and the second female threaded portions 11b and 12b
_{It has 2} fine screws. Also, these male screw parts 13
a and 13b have opposite screw directions, and one male screw portion 1
3a is a right-hand thread, and the other male thread part 13b is a left-hand thread.

Next, a method of joining the beams to the wall by using the reinforcing bar connecting device 10 will be described. As shown in FIG. 1 (A), the first female threaded portion 11a of the end joint 11 is screwed onto one end of each of a plurality of threaded reinforcing bars 1 (only one is shown in the figure). In this screwed state, the lock nut 3 screwed in advance to one end of the screw rebar 1 is tightened by applying torque to the end joint 11 to connect the screw rebar 1 and the end joint 11 to each other. . In addition, as described above, the lock nut 3
When applying a torque with a tool and tightening the tool, another tool is applied to the tool hooking portion 11x of the end joint 11 to prevent its rotation.

Next, with the opening (one end (right end) side) of the end joint 11 closed with a cap (not shown) and applied to the mold, the screw rebar 1 is housed in the mold and placed in the mold. By pouring concrete 5, the wall W as a reinforced concrete structure shown in FIG. 1 (A) is constructed.
After curing the concrete 5, the form is removed and the cap is removed from the opening of the end joint 11. As a result, the opening of the end joint 11, that is, the opening of the second female screw portion 11b appears on the surface of the concrete 5.

On the other hand, as shown in FIG. 1 (A), the first female screw portion 12a of the end joint 12 and the lock nut 4 are preliminarily provided at the end portion of the screw rebar 2 for the beam (reinforced concrete structure).
Are screwed together, and in this screwed state, the end nut 12 and the reinforcing bar 2 are connected by tightening the lock nut 4 by applying torque as in the case of the lock nut 3.

The screw reinforcing bar 2 is connected to the screw reinforcing bar 1 via a central joint 13 and end joints 11 and 12. When the connecting work is described in detail, as shown in FIG. 1 (A), the central joint 13 is arranged between the end joints 11 and 12, and
With the pair of male threads 13a and 13b of the central joint 13 and the end joint 12 and the threaded reinforcing bar 2 arranged in a straight line with respect to the end joint 11 and the threaded reinforcing bar 1, a pair of male threaded portions 13a of the central joint 13, The end of 13b is applied to the open ends of the second female screw portions 11b, 12b of the end joints 11, 12. In this state,
As shown in FIG. 1 (B), the tool hook 1 of the central joint 13
When a tool is hung on 3x and turned in the direction of the arrow, the pair of male screw portions 13a and 13b of the central joint 13 are screws in the opposite directions, so that the second female screw portion 11b of the end joints 11 and 12 are
It is screwed to 12b.

When the central joint 13 is further continued to rotate, FIG.
As shown in (C), the end faces of the pair of male screw portions 13a, 13b are preliminarily formed with the first female screw portions 11a, 11a of the end joints 11, 12, respectively.
The end faces of the screw rebars 1 and 2 screwed to the screw 12a are respectively contacted. After that, when the central joint 13 is further tightened, the end faces of the male screw portions 13a and 13b and the screw rebars 1 and 2 are
The end faces of each hit with strong force. As a result, there is a looseness between the threads of the male threaded portions 13a and 13b and the threads of the second female threaded portions 11b and 12b of the end joints 11 and 12, respectively, but the mutual contact on the abutting surface is prevented. Due to the repulsive force, the screw threads of these screw-engaged relationships come into contact with each other with a strong force, and thus a strong connection is obtained between the central joint 13 and the end joints 11, 12. Similarly, due to the repulsive force at the contact surface, the threads of the screw rebars 1 and 2 and the threads of the first female threaded portions 11a and 12a of the end joints 11 and 12 come into contact with each other with a strong force, so that a strong connection between the two is achieved. can get. When tightening the central joint 13 with a tool as described above,
Another tool is hooked on the tool hook 12x of the end joint 12 or the screw rebar 12 to prevent its rotation.

What is important here is that the second threaded portions 11b and 12b of the end joints 11 and 12 and the male threaded portion 1 of the central joint 13 are provided.
3a, the pitch P ₁ of 13b pitch P ₂ screw rebar 1,2
It is much smaller than that. Therefore, a large tightening force can be obtained by simply turning the tool hung on the central joint 13 with a relatively small torque manually or by using a small tightening device, and the connecting strength between the screw reinforcing bars 1 and 2 can be increased. Can be increased. Therefore, unlike the conventional case, a large-sized tightening device that generates a large torque is unnecessary.

Next, the beam is constructed by placing concrete in a state in which the screw rebar 2 is surrounded by a form for the beam,
Complete the splice.

In the above embodiment, the lock nuts 3 and 4 are tightened to the end joints 11 and 12 in an auxiliary manner, and a large torque is not required. Further, in order to make the connection of the screw reinforcing bars even stronger, even when a large torque is applied to the lock nuts 3 and 4, the tightening work of the lock nuts 3 and 4 can be performed even at the splicing site, It does not hinder workability improvement at the splicing site. These lock nuts 3 and 4 may be omitted.

The second embodiment shown in FIG. 2 is the first embodiment shown in FIG.
Since it is very similar to the embodiment, the same reference numerals are given and detailed description thereof is omitted. Only the different points will be described below. In the second embodiment, as shown in FIG.
The female screw portion 11a and the second female screw portion 11b are not communicated with each other and are separated by the partition wall 11c. In addition, on the peripheral wall surrounding the inner end portion of the first female screw portion 11a of the end joint 11,
An injection port 11d for the grout material is formed so as to penetrate therethrough. Similarly, the end joint 12 is also formed with a partition wall 12c and an injection port 12d for the grout material.

In the second embodiment, the grout material is injected from the injection port 11d while the end portion of the screw rebar 1 is screwed into the first female threaded portion 11a of the end joint 11, and the outer periphery of the screw rebar 1 is injected. By filling between the surface and the inner peripheral surface of the first female screw portion 11a, the connection strength between the screw reinforcing bar 1 and the end joint 11 is increased. Similarly, the grout material is injected from the injection port 12d in a state where the end portion of the screw rebar 2 is screwed into the first female screw portion 12a of the end joint 12 to enhance the connection strength between the screw rebar 2 and the end joint 12. To be

As shown in FIG. 2B, the point that the central joint 13 is turned to screw the male screw portions 13a and 13b into the second female screw portions 11b and 12b of the end joints 11 and 12 is the same as the first embodiment. It is the same. As this screwing progresses, as shown in FIG. 2C, the end faces of the male screw portions 13a and 13b of the central joint 13 hit the partition walls 11c and 12c of the end joints 11 and 12,
Further, by turning the central joint 13, tightening is performed. The male screw portions 13a and 13b and the partition walls 11c and 12c
Since the and are brought into contact with each other with a strong force, the connection strength between the central joint 13 and the end joints 11 and 12 is increased, and thus the connection strength between the screw reinforcing bars 1 and 2 is increased.

Although the grout material is used in the second embodiment, the structure required for injecting the grout material is the end joint 11,
Since only the injection ports 11d and 12d are formed in the end 12, the structure of the end joints 11 and 12 is not complicated. A lock nut may be used to increase the connecting strength between the reinforcing bar and the end joint. In this case, the lock nut can be tightened at a place different from the splicing site.

FIG. 3 shows a reinforcing bar connecting device 2 according to the third embodiment.
0 is shown. The rebar connecting device 20 also includes a pair of end joints 21 and 22 and a central joint 23. The one end joint 21 includes a tubular portion 21 '. This tube 2
1'has a hexagonal cross section, and the outer periphery thereof is the tool hanging portion 21.
It is x. A female screw portion 21a extending along the central axis of the tubular portion 21 'is formed on the tubular portion 21'. One end of the female screw portion 21a is closed. Tube part 21 '
From the end face of, the male screw portion 21b (fine screw portion) extends in the direction opposite to the female screw portion 21a in line with the female screw portion 21a. An inlet 21d for grout material is formed on the peripheral wall surrounding the inner end of the female screw portion 21a. The pitch P ₂ of the female screw portion 21a is equal to that of the screw rebars 1 and 2, and the pitch P ₂ of the male screw portion 21b is much smaller and finer. The other end joint 22 also has the same dimensions and the same configuration as the end joint 21, and the tubular portion 2
2 ', tool hook 22x, female thread 22 with pitch P ₁
a, a male screw portion 22b having a pitch P ₂ , and an injection port 22d for the grout material. However, the screw direction of the male screw portion 22b is opposite to that of the male screw portion 21b of the end joint 21.

The central joint 23 has a tubular shape, has a hexagonal cross section over the entire length, and has an outer periphery serving as a tool hanging portion 23x. Note that the tool hanging portion may be provided only in the central portion, and both side portions thereof may be cylindrical portions. Central joint 2
3 has a pair of female screw parts (fine screw parts) 23a and 23b. The female screw portions 23a and 23b are continuous with each other along the central axis of the central joint 23 in a straight line. The lengths of these female screw portions 23a and 23b are equal,
The boundary is located at the center of the central joint 23. The female screw portions 23a and 23b are the male screw portions 2 of the end joints 21 and 22.
It has a pitch P ₂ equal to 1b and 22b, and the screw directions are opposite to each other.

In the third embodiment, similarly to the second embodiment, the connecting strength between the reinforcing bars 1 and 2 and the end joints 21 and 22 is increased by the grout material, but it goes without saying that a lock nut may be used. . The central joint 23 and the end joint 2 are shown in FIG.
2, the rebar 2 is arranged so as to be in line with the rebar 1 and the end joint 11 in the wall W, and the central joint 23 is turned as shown by an arrow in FIG. Two
3a, 23b to the male screw portions 21b, 2 of the end joints 21, 22
Screw to 2b. When the center joint 23 is further rotated, the above-mentioned screwing progresses, and the male screw portions 21b and 22 of the end joints 21 and 22 are advanced.
The end faces of b hit each other. When the central joint 23 is further tightened, the connection strength between the central joint 23 and the pair of end joints 21 and 22 can be increased.

The reinforcing bar connecting device of the present invention can be used not only in the splicing method but also in other methods which require the connection of a pair of screw reinforcing bars.

[0028]

As described above, according to the inventions of claims 1 to 4, when connecting a pair of screw rebars, by using three joints having fine screws, a large tightening force can be achieved with a small torque. Therefore, it is not necessary to use a large-sized tightening device and workability is good. In addition, the structure of the joint is simple and can be manufactured at low cost. In the invention of claim 2, the central joint is tightened with the end faces of the pair of male screw portions of the center joint abutting the end faces of the screw rebars screwed to the first female screw portions of the pair of end joints. Therefore, not only can the connection strength between the male screw portion of the central joint and the second female screw portion of the end joint be increased, but also the connection strength between the screw rebar and the first female screw portion of the end joint can be increased. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing, in the order of (A) to (C), a jointing method using a reinforcing bar connecting device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing, in the order of (A) to (C), a splicing method using the reinforcing bar connecting device of the second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing, in the order of (A) to (C), a jointing method using the reinforcing bar connecting device of the second embodiment of the present invention.

[Explanation of symbols]

 10, 20 ... Reinforcing bar connection joint 11, 12, 21, 22 ... End joint 13, 23 ... Central joint 11a, 12a ... 1st internal thread part (internal thread part) 11b, 12b ... 2nd internal thread part (fine thread part) 11c, 12c ... Partition walls 13a, 13b ... Male screw part (fine screw part) 21 ', 22' ... Cylindrical part 21a, 22a ... Female screw part 21b, 22b ... Male screw part (fine screw part) 23a, 23b ... Female screw part (fine screw part)

Claims (4)

[Claims] 1. An apparatus for connecting a pair of threaded reinforcing bars, comprising a pair of end joints and a center joint, each of the pair of end joints having a female thread portion and a fine thread arranged in a straight line. And the internal threaded portion is screwed to the end of the threaded reinforcing bar at the same pitch as the threaded reinforcing bar, and the fine threaded section has a pitch much smaller than that of the first internal threaded section. Moreover, the fine threaded portions of the pair of end joints have equal lengths and pitches and opposite screw directions, and the central joint has a tool hooking portion on at least a part of its outer periphery and is aligned on a straight line. Has a pair of fine threaded portions, and these fine threaded portions have equal lengths and opposite screw directions, and have the same pitch as the fine threaded portions of the pair of end joints. Fine thread part of end joint Iron rod connecting apparatus characterized by being engaged respectively threadedly. 2. An apparatus for connecting a pair of threaded reinforcing bars, comprising a pair of end joints and a central joint, each of the pair of end joints having a tubular shape and a straight line. Has a first female screw portion and a second female screw portion that are continuous with each other, and the first female screw portion is screwed to the end portion of the screw rebar at the same pitch as the screw rebar, and the second female screw portion is The second female screw portions of the pair of end joints have the same length and pitch, and the screw directions are opposite to each other, and the central joint is It has a tool hanging part in the central part, and has a pair of male screw parts extending in a straight line with each other on both sides of the tool hanging part, and these male screw parts have mutually equal lengths and opposite screw directions, and Second female thread of a pair of end joints And which forms a fine thread of the same pitch, the iron rod connecting apparatus according to claim each be screwed into the second female threaded portion of these end fittings. 3. An apparatus for connecting a pair of screw reinforcing bars, comprising a pair of end joints and a central joint, each of the pair of end joints having a tubular shape and aligned in a straight line. It has a 1st internal threaded part and a 2nd internal threaded part which were arranged, and a partition formed between these 1st and 2nd internal threaded parts, and the 1st internal threaded part makes the same pitch as the said threaded rebar, and a threaded rebar The second female threaded portion is a fine thread having a pitch much smaller than that of the first female threaded portion, and the second female threaded portions of the pair of end joints are mutually connected to each other. The length and the pitch are equal and the screw directions are opposite, the central joint has a tool hanging portion on the outer periphery of the central portion, and a pair of male screw portions extending in a straight line with each other on both sides of the tool hanging portion, These male threads are equal in length to each other. The screw directions are opposite to each other, and fine threads having the same pitch as the second female screw portions of the pair of end joints are formed, and the fine screw threads are respectively screwed to the second female screw portions of the pair of end joints. Rebar connecting device. 4. An apparatus for connecting a pair of threaded reinforcing bars, comprising a pair of end joints and a central joint, each of the pair of end joints having a tubular portion formed with a female screw portion, It has a male screw portion that extends in the opposite direction from the end of the cylindrical portion in the same straight line as the female screw portion, and the female screw portion is screwed to the end portion of the screw reinforcing bar at the same pitch as the screw reinforcing bar. Yes, the male thread portion is a fine thread having a pitch much smaller than that of the female thread portion, and the male thread portions of the pair of end joints have the same length and pitch and opposite screw directions, and the central joint is Has a cylindrical shape, at least a part of the outer periphery of which is a tool-engaging portion, and further has a pair of female threaded portions that are continuous in a straight line. Is the opposite direction In, without the male screw portion and the pitch of the pair of end fittings, reinforcing bar coupling device, characterized in that screwed into these male screw portion.