JPH09189095A - Thread knot steel bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equip a high thread engagement strength and prevent a convex marking for distinguishing the sort of steel bar from being crushed when correction of a twist is conducted. SOLUTION: The peripheral surface of the body 10 of a steel bar has a pair of first plane parts opposing to each other in the radial direction and a pair of second plane parts 12 positioned between the first plane parts 11 and confronting each other in the radial direction. Threads 20 are formed only on the first plane parts 11, which are provided with a convex marking 30 in a position between the threads 20. The first plane parts 11 are arranged approx. along a virtual circle X, and the center in circumferential direction of the first plane parts 11 assumes a cut surface 15 recessed from the virtual circle X. The marking 30 is formed on this cut surface 15 and the mark 30 can be accommodated inside the virtual circle X.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw bar reinforcement used for reinforcing concrete in a building.

[0002]

2. Description of the Related Art As a reinforcing bar (steel bar) for reinforcing concrete, a reinforcing bar having a screw bush is well known. Since this screw bar reinforcing bar can be connected to the coupler nut via the pair of lock nuts, the connecting work can be simplified. It is obligatory to indicate the type (type classified by the yield point etc.) of this screw bar rebar. As one of the display methods, paint is applied to the end surface of the screw bar rebar. However, with this method, the type cannot be identified when the screw bar rebar is cut.

As a more preferable display method, Japanese Patent Laid-Open No. 6-
As disclosed in Japanese Patent No. 47402, there is a method of forming convex marks on the peripheral surface of a screw bar reinforcement at a predetermined pitch. The publication discusses where to form this mark.

Before introducing this discussion, the screw bar rebar will be briefly described. As is well known, a screw bar rebar has a rebar body and a thread formed on the rebar body. The peripheral surface of the reinforcing bar main body has a pair of first surface portions facing each other in the radial direction and a pair of second surface portions positioned between the first surface portions. These first and second surface portions extend along the longitudinal direction of the reinforcing bar body.

The threads are formed only on the first surface portion, not on the second surface portion. The main reason is the manufacturing process. Explaining the manufacturing process, first, a round bar-shaped element bar is hot-rolled into a cocoon cross-section with a pair of rolling rolls, and then hot-rolled with another pair of rolling rolls to obtain a width of the cross-sectional shape. The screw thread is formed while crushing the wider one. Therefore, the thread is not formed on the second surface portion that comes into contact with the former rolling roll, and the thread is formed only at the first surface portion that comes into contact with the latter rolling roll.

Returning to the discussion of where to mark on the peripheral surface, in the above-mentioned publication, as a conventional technique, the central portion in the circumferential direction of the screw thread on the first surface portion is cut off, and a convex mark is formed on this missing portion. The application is disclosed (see FIGS. 5 and 6 of the same publication). However, the publication teaches that if a part of the screw thread is omitted in this way, the screwing strength is lowered when the screw thread is partly screwed into the coupler nut or the lock nut.

[0007] Therefore, the publication proposes that a convex mark is formed on the substantially flat second surface portion where the screw thread is not formed (see FIGS. 1 to 4 of the publication). By doing so, it is possible to avoid a decrease in screwing strength. In the device for manufacturing the proposed screw bar rebar, when the element bar is rolled into a cocoon shape by a pair of rolling rolls at the stage before the thread formation described above, the mark is formed by the hole formed in this rolling roll. doing.

[0008]

However, when the 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 reinforcing bar is twisted. Therefore, it is necessary to suppress or straighten the twist by using a pair of straightening rolls after the forming. Since this twist correction is performed by applying a pair of straightening rolls to the pair of second surface portions, if there is a convex mark on the second surface portion as described above, this mark will be crushed by the straightening rolls. is there.

[0009]

According to a first aspect of the present invention, a peripheral surface of a reinforcing bar main body is located between a pair of first surface portions that face each other in the radial direction and between the first surface portions, and faces each other in the radial direction. A pair of second surface portions, the first and second surface portions extending along the longitudinal direction of the reinforcing bar main body, and the screw threads formed only on the pair of first surface portions. On the first surface part, located between the threads,
It is characterized in that a convex mark is formed to identify the type of screw bar rebar. According to a second aspect of the invention, in the screw bar reinforcement of the first aspect, the first
The surface portions are arranged substantially along an imaginary circle, and the central portion in the circumferential direction of the first surface portion is a cut surface recessed from the imaginary circle, and the mark is formed on the cut surface. Is within the virtual circle.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a screw bar rebar which constitutes an embodiment of the present invention will be described with reference to FIGS. The screw bar rebar 1 includes a rebar body 10 and a thread 20. The peripheral surface of the rebar main body 10 includes a pair of first surface portions 11 that face each other in the radial direction and a pair of second surface portions 12 that are located between the first surface portions 11 and face each other in the radial direction. Have These first and second surface portions 11 and 12 extend along the longitudinal direction of the screw bar reinforcement 1 in parallel with the axis thereof. A pair of first surface portions 11
In each of these, the screw threads 20 are formed at equal intervals in the longitudinal direction of the screw bar rebar 1. All the threads 20 of these pair of first surface parts 11 are located along a continuous spiral and therefore the threaded bar rebar 1 has a threading function. No threads are formed on the second surface portion 12, and the second surface portion 12 is substantially flat.

The pair of first surface portions 11 are shown in FIG.
As shown in FIG. 3, they are arranged on a virtual circle X. Between the screw threads 20, the central portion in the circumferential direction of each first surface portion 11 forms a flat cut surface 15 recessed from the virtual circle X. A convex mark 30 for identifying the type of screw bar rebar is formed in the center of one of the cut surfaces 15 of the pair of first surface portions 11 facing each other. The protrusion height of this mark 30 is determined so as to fit inside the virtual circle X. As shown in FIG. 3B, the cut surface 15 may be concave instead of flat.

The marks 30 are arranged at a predetermined pitch (every predetermined number of cut surfaces 15) along the longitudinal direction of the screw bar reinforcement 1.
Formed. As determined by the JIS standard, the number of marks 30 that appear at each predetermined pitch indicates the type of screw bar rebar 1 (type divided by the yield point). The absence of the mark 30 indicates the screw bar rebar having the lowest yield point. As shown in FIGS. 1 and 2, when one mark 30 is provided, it represents a screw bar rebar having a yield point one step higher than that. Further, as shown by an imaginary line in FIG. 1, as the marks 30 are formed on the adjacent cut surfaces 15 and the number of the marks 30 increases, it means that the bar is a screw bar with a higher yield point.

The screw bush rebars 1 having the above-mentioned structure are connected to each other by screwing their ends into the coupler nut from the opposite side and tightening the lock nuts screwed into these ends in advance. At this time, the screw thread 20 of the screw bar rebar 1
Has no missing portion for forming the mark 30 and is left in a complete shape, so that the screwing strength with the coupler nut and the lock nut can be maintained at a high level.

The fact that the mark 30 fits inside the virtual circle X as described above brings the following advantages. That is, the first
Even if the difference between the diameter of the imaginary circle X where the surface portion 11 is located and the inner diameter of the thread of the coupler nut or the lock nut is a slight clearance, the mark 30 does not hinder the screwing. As a result, the screw bar rebar 1 can be screwed onto the coupler nut or the lock nut without rattling, and the screwing strength can be improved also from this point. In addition,
Even if the mark 30 projects outward from the imaginary circle X, if the amount of this protrusion is equal to or less than the clearance between the imaginary circle X of the screw bar rebar 1 and the coupler nut or lock nut, the screwing action is hindered. There is no. In particular, when this clearance is relatively large, the mark 30 can actually project from the virtual circle X.

Although the screw bar rebar 1 is twisted at the end of the manufacturing process, the mark 30 is not crushed. The advantages will be described below while explaining the manufacturing apparatus shown in FIGS.

FIG. 4 shows the final part of the manufacturing apparatus for screw bar reinforcement. The pair of first rolling rolls 50, the pair of second rolling rolls 60, and the straightening roll 70 are arranged side by side on 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, a second
The surface portion 12 is formed. Next, the second rolling roll 60
Then, hot rolling is performed from the longitudinal direction of the cross-sectional shape, and the first surface portion 11, the screw thread 20, the cut surface 15, and the mark 3 are formed.
0 is formed.

As shown in FIG. 5, the second rolling roll 6 is used.
An annular molding recess 61 is formed on the peripheral surface of 0.
Grooves 62 corresponding to the threads 20 are formed in the molding recess 61 at a predetermined pitch. A flat surface 63 corresponding to the cut surface 15 is formed between the central portions of the groove 62 in the longitudinal direction. On the upper (one) second rolling roll 60, holes 64 corresponding to the convex marks 30 are formed at selected one or a plurality of locations on the large number of flat surfaces 63.

The screw bar rebar 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 flat rollers having a cylindrical surface, and by pressing the pair of second surface portions 12, the twist of the screw bar rebar 1 can be straightened. At the time of this correction, since the mark 30 is formed on the first surface portion 11 and does not hit the correction roll 70, it is possible to prevent the mark 30 from being crushed.

[0020]

As described above, according to the first aspect of the present invention, since there is no missing portion for forming the mark on the screw thread, the screw bar reinforcement 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 screw thread is formed, it is necessary to prevent the mark from being crushed at the time of the straightening of the screw bar reinforcement at the final stage. You can According to the invention of claim 2, the first
Since the mark fits inside the virtual circle where the surface part is located,
Even if the difference between the diameter of the rebar body and the diameter of the coupler nut is reduced, the mark does not hinder the screwing.Therefore, the screw bar rebar can be screwed onto the coupler nut without rattling. The combined strength can be further improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a screw bar rebar that constitutes an embodiment of the present invention.

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

3A is a sectional view taken along line III-III in FIG. 2, and FIG. 3B is a sectional view showing another embodiment.

FIG. 4 is a schematic plan view showing a manufacturing apparatus for screw bar reinforcement.

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

[Explanation of symbols]

 1 Screw Bushing Rebar 10 Rebar Main Body 11 First Surface Part 12 Second Surface Part 15 Cut Surface 20 Screw Thread 30 Mark X Virtual Circle

Claims (2)

[Claims] 1. A peripheral surface of a reinforcing bar main body has a pair of first surface portions facing each other in a radial direction and a pair of second surface portions located between the first surface portions and facing each other in a radial direction. ,
In the screw bar reinforcing bar in which these first and second surface portions extend along the longitudinal direction of the reinforcing bar main body, and threads are formed only on the pair of first surface portions, the first surface portion has a space between the screw threads. A screw stick rebar characterized by being formed with a convex mark for identifying the type of screw stick rebar. 2. The first surface portion is arranged substantially along an imaginary circle, and the central portion in the circumferential direction of the first surface portion is a cut surface recessed from the imaginary circle. The screw bar rebar according to claim 1, wherein the mark is formed and the mark fits inside the virtual circle.