JP2000104380A - Ribbed deformed reinforcing bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ribbed deformed reinforcing bar which has a high screwing strength and prevents a projected mark for discriminating kinds of reinforcing bars from being broken when correcting a torsion. SOLUTION: The peripheral face of a reinforcing bar body 10 is provided with a pair of first face parts 11 mutually facing in the radial direction and a pair of second face parts 12 positioned between the first face parts to face each other in the radial direction. The first and second face parts 11, 12 extend along the longitudinal direction of the reinforcing bar body 10. A screw thread 20 is formed only on the pair of first face parts 11. Recessed cut faces 15 are formed at specified positions of the screw thread and a projected mark 30 to discriminate the kinds of the ribbed deformed reinforcing bars is formed on the cut face 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread reinforcing bar used for reinforcing concrete of a building or the like.

[0002]

2. Description of the Related Art As a steel bar for reinforcing concrete, a thread reinforcing bar having a thread thread is well known. Since the thread reinforcing bar can be connected to the coupler nut via a pair of lock nuts, the connecting operation can be simplified. It is mandatory to display the type of the thread reinforcing bar, for example, the type classified by a yield point or the like. As one of the display methods, painting is performed on the end face of the screw reinforcing bar. However, in this method, when the thread reinforcing bar is cut, the type cannot be identified.

A more preferable display method is disclosed in
No. 47402 proposes forming a convex mark at a predetermined pitch on the side surface of the screw reinforcing bar, and further discusses where to form the mark. Before introducing this discussion, a brief description of the screw rebar will be given. As is well known, a thread reinforcing bar has a reinforcing bar main body and a thread formed on the reinforcing bar main body. The peripheral surface of the reinforcing bar main body includes a pair of first surface portions facing in a radial direction, and a first surface portion.
A pair of second surface portions located between the surface portions.
These first and second surface portions extend along the longitudinal direction of the reinforcing bar.

The thread is formed only on the first surface portion and not on the second surface portion. The main reason is the manufacturing process. The manufacturing process will be described. First, a round bar-shaped bar is hot-rolled by a pair of rolling rolls into a cocoon cross-sectional shape, thereby forming a thread while crushing a wider cross-sectional shape. For this reason, the thread is not formed on the second surface portion abutting on the preceding rolling roll, and the thread is formed only on the first surface portion abutting on the subsequent rolling roll.

Returning to the discussion of where to make the mark on the peripheral surface, the above-mentioned publication discloses that, as a conventional technique, the entire central portion of the thread on the first surface in the circumferential direction is cut off, and a convex mark is formed at the missing portion. (See FIGS. 5 and 6 of the publication). However, the publication teaches that if the thread is partially completely removed as described above, when the partially missing thread is screwed into the coupler nut or the lock nut, the screwing strength is reduced. .

[0006] Therefore, this publication proposes to provide a convex mark on a substantially flat second surface portion where no thread is formed (see FIGS. 1 to 4 of the publication). With this configuration, the screwing strength does not decrease. In the device to be manufactured with the proposed screw bar rebar, at the stage before the above-mentioned thread formation, when rolling the bar with a pair of rolling rolls into a cocoon shape,
The mark is formed by a hole formed in the rolling roll.

[0007]

However, when a convex mark is formed on the second surface portion as proposed in the above publication, the following inconvenience occurs. Generally, when the rolling for forming the thread is performed, the formed rebar is twisted. Therefore, it is necessary to control and correct the twist using a pair of straightening rolls after the forming. Since this straightening is performed by applying a pair of straightening rolls to a pair of second surface portions, if there is a convex mark on the second surface portion as described above, the marks will be crushed by the straightening rolls. is there.

An object of the present invention is to solve the above problems.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, the peripheral surfaces of the reinforcing bar main body are positioned between a pair of first surface portions radially opposed to each other, and between the first surface portions. And a pair of second surface portions radially opposed to each other, and the first and second surface portions extend along the longitudinal direction of the reinforcing bar main body, and a thread is formed only in the pair of first surface portions. In the obtained screw reinforcing bar, a convex mark for identifying the type of the screw reinforcing bar is formed on a cut surface provided by recessing a predetermined portion of the screw thread. According to a second aspect of the present invention, in the thread reinforcing bar according to the first aspect, the height of the mark with respect to the first surface portion is equal to or less than the height of the thread. According to a third aspect of the present invention, in the thread reinforcing bar according to the first aspect, the cut surface is formed to have a size that does not affect the screwing strength.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the thread reinforcing bar of the embodiment shown in FIGS. The screw reinforcing bar 1 includes a reinforcing bar main body 10 and a screw thread 20. The peripheral surface of the reinforcing bar main body 10 includes a pair of first surface portions 11 radially facing each other and a pair of second surface portions 12 located between the first surface portions 11 and radially facing each other. Have. These first and second surface portions 11 and 12 extend along the longitudinal direction of the screw reinforcing bar 1 in parallel with the axis thereof. A pair of first surface portions 11
Are formed at equal intervals in the longitudinal direction of the thread reinforcing bar 1. All the threads 20 of the pair of first surface portions 11 are located along a continuous spiral, and therefore, the thread reinforcing bar has a thread function. No thread is formed on the second surface portion 12, and the second surface portion 12 is substantially flat.

As shown in FIG. 1, for one of a fixed number of threads 20 arranged on the first surface portion 11 on one side of the reinforcing bar main body 10, a cut surface 15 recessed at the center in the circumferential direction is formed. . As shown in FIG. 3, the cut surface 15 formed on the screw thread 20 is on a circumference concentric with the reinforcing bar main body 20. A convex mark 30 for identifying the type of the screw reinforcing bar is formed at the center of the cut surface 15. The height of the mark 30 with respect to the first surface portion 11 is set to be equal to or less than the height of the thread 20.

The marks 30 are provided at predetermined pitches (every predetermined number of cut surfaces 15) along the longitudinal direction of the thread reinforcing bar 1.
Formed. As determined by the JIS standard, the type of the screw rebar 1, for example, the type classified by the yield point, is displayed by the number of the marks 30 that appear at every predetermined pitch. When there is no mark 30, it represents a screw bar having the lowest yield point. As shown in FIG. 1 and FIG.
When the number is one, it represents a thread reinforcing bar with a yield point one step higher than that. Each time the number of marks 30 increases, it indicates that the thread reinforcing bar has a higher yield point.

[0013] The screw bar rebars having the above-described configuration are connected to each other by screwing their ends to the coupler nut from the opposite side via screw threads 20 and tightening them with lock nuts previously screwed to these ends. You. At this time, a part of the thread 20 of the thread reinforcing bar 1 forms a cut surface 15 for forming the mark 30, and the cut surface 15 is the first surface.
The height with respect to the surface portion 11 is 25 to 5 of the height of the thread 20.
0%, and the central angle of the rebar body 10 with respect to the axis is 40%.
Since it is up to 60 °, there is no problem in screwing, and the screwing strength with the coupler nut or lock nut can be maintained at a high level.

As described above, the height of the mark 30 is equal to or less than the height of the thread 20 with respect to the first surface portion 11, so that a clearance is generated between the inside diameter of the thread of the coupler nut or the lock nut and the mark 30, The mark 30 does not hinder the screwing. As a result, the screw rebar 1 can be screwed with the coupler nut or the lock nut without play,
From this point, the screwing strength can be improved. Note that even if the height of the mark 30 is equal to or greater than the height of the screw thread, as long as the difference is equal to or less than the clearance between the screw thread and the coupler nut or the lock nut, there is no problem with the screwing operation. In particular, when the clearance is large, the height of the mark 30 can be made higher than the height of the screw thread.

Although the thread reinforcing bar 1 is twisted and corrected at the end of the manufacturing process, there is no inconvenience that the mark 30 is crushed. Hereinafter, the advantages will be described while describing the manufacturing apparatus of FIGS. 4 and 5. FIG.
The final part of the manufacturing process of the thread reinforcing bar as a steel bar is shown. A pair of first rolls 50, a pair of second rolls 60, and a straightening roll 70 are arranged in a straight line in this order. The first rolling roll 50 has a vertical rotation axis, the second rolling roll 60 has a horizontal rotation axis, and the straightening roll 70 has a vertical rotation axis.

In the first rolling roll 50, the bar 100 having a circular cross section, which has been thinly hot rolled in the previous step, is hot rolled into a cocoon cross section. As a result, the second sides are
A surface portion 12 is formed. Next, the second rolling roll 60
Then, hot rolling is performed from the longitudinal direction of the sectional shape, and the first surface portion 11, the thread 20, the cut surface 15, and the mark 3
0 is formed.

As shown in FIG. 5, the second rolling roll 6
An annular molding recess 61 is formed on the peripheral surface of the zero.
Grooves 62 corresponding to the screw threads 20 are formed at a predetermined pitch in the molding recess 61. A protruding surface 63 corresponding to the cut surface 15 is formed between the longitudinal central portions of the groove 62. In the upper (one) second rolling roll 60, holes 64 corresponding to the convex marks 30 are formed at one or more selected locations among the many protruding surfaces 63.

The thread reinforcing bar 1 formed by the second rolling roll 60 is twisted due to the inclination of the groove 62 of the second rolling roll 60. The pair of straightening rolls 70 are formed of flat rollers having a cylindrical surface, and can press the pair of second surface portions 12 to correct the twist of the thread reinforcing bar 1. In this correction, the mark 30 is formed on the first surface portion 11 and does not hit the correction roll 70, so that the mark 30 can be prevented from being crushed.

[0019]

As described above, according to the first aspect of the present invention, since there is no missing portion for forming a mark on the screw thread, the screw reinforcing bar can have a high screwing strength. Further, since the mark is formed not on the second surface portion but on the first surface portion where the thread is formed, it is possible to prevent the mark from being crushed at the time of correcting the twist in the final step of the screw reinforcing bar. Can be. According to the invention of claim 2, since the height of the mark on which the first surface portion is located is equal to or less than the height of the screw thread, the mark is formed even when the difference between the diameter of the reinforcing bar main body and the diameter of the coupler nut or the like is reduced. Does not hinder the screwing, and therefore
The screw rebar can be screwed to the coupler nut or the like without play, and the screwing strength can be further improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a thread reinforcing bar according to an embodiment of the present invention.

FIG. 2 is a side view of the screw reinforcing bar.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a plan view schematically showing an apparatus for manufacturing a screw reinforcing bar.

FIG. 5 is a front view showing a main part of a second rolling roll for forming a screw thread in the manufacturing apparatus.

[Explanation of symbols]

 1: screw reinforcing bar 10: reinforcing bar body 11: first surface portion 12: second surface portion 15: cut surface 20: screw thread 30: mark

[Selection diagram] Fig. 1

Claims (3)

[Claims] 1. A pair of first surface portions (11) having circumferential surfaces of a reinforcing bar main body (10) radially facing each other, and a pair of first surface portions located between the first surface portions and radially facing each other. A threaded reinforcing bar having two surface portions (12), wherein the first and second surface portions extend along a longitudinal direction of the reinforcing bar main body, and a thread (20) is formed only in a pair of first surface portions. In the above method, a concave cut surface (15) is formed at a predetermined portion of the screw thread, and a convex mark (30) for identifying the type of the screw reinforcing bar is formed on the cut surface. And screw thread rebar. 2. The thread reinforcing bar according to claim 1, wherein a height of the mark with respect to the first surface portion is equal to or less than a height of the screw thread. 3. The cut surface is located at the center in the circumferential direction of the first surface portion. The height of the cut surface with respect to the first surface portion is 50% to 25% of the height of the thread, and the reinforcing bar is provided. The central angle of the cut surface with respect to the axis of the main body is 40 to 60 °
The thread reinforcing bar according to claim 1, wherein: