JP7097550B2 - Fixing nuts for threaded reinforcing bars and their manufacturing methods - Google Patents

Description

The present invention relates to a fixing nut for a screw reinforcing bar used for fixing a screw reinforcing bar to concrete, and a method for manufacturing the same.

In a reinforced concrete structure, a fixing tool called a fixing nut or a fixing hardware may be used for the purpose of fixing a deformed reinforcing bar such as a screw reinforcing bar to concrete. Such a fixing tool is generally attached to the end of a deformed reinforcing bar such as a screw reinforcing bar, and then an organic or inorganic grout (material) is injected into the clearance between the deformed reinforcing bar and fixed. Used by.

Various fixing tools for fixing deformed reinforcing bars such as screw reinforcing bars to concrete have been proposed and used. For example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-213841), a tubular portion having both open ends and a female screw on the inner circumference to penetrate a threaded reinforcing bar in a screwed state, and a tubular portion in the radial direction from the tubular portion. A cylinder as a fixing hardware that is provided with an annular flange portion that protrudes outward and is fixed to the screw reinforcing bar by a grout that is filled in the clearance between the cylinder portion and the screw reinforcing bar to fix the screw reinforcing bar to concrete. An injection port for injecting grout is formed in the center of the portion, and an annular groove connected to the injection port is formed in the inner circumference of the center of the tubular portion. A fixing hardware having a groove connected to the openings at both ends via a clearance between a tubular portion and a threaded reinforcing bar has been proposed.

Japanese Patent Application Laid-Open No. 2003-213841

By the way, the fixing tool used for fixing a deformed reinforcing bar such as a screw reinforcing bar to concrete is manufactured according to various conventionally known manufacturing methods according to its size, shape, etc., but a sand mold is particularly used. By adopting the casting method, it is possible to enjoy advantages such as being able to keep the manufacturing cost low. When manufacturing a nut (fixing nut for screw reinforcing bars, hereinafter also simply referred to as a nut) used by screwing it to the end of a screw reinforcing bar according to a casting method using a sand mold, generally, a fixing nut for screw reinforcing bars is used. A pair of upper and lower dies for forming the outer shape and a core for forming the screw hole (and the female screw on the inner peripheral surface thereof) are used.

However, when the fixing nut for screw reinforcing bars is manufactured by the casting method, the manufacturing cost may be deteriorated due to the following factors. First, the core used to form the screw hole of the nut is a shell core that can accurately form a female thread on the inner peripheral surface of the screw hole (a core manufactured according to the shell mold molding method). Is advantageously used, but such shell cores are also generally molded using a pair of molding dies (upper and lower dies), and correspond to the mold matching surface of the molding dies on the core surface. Although minute burrs may occur at the site. Since such burrs may affect the shape accuracy of the female thread in the nut, which is a casting, a process such as inspection is required before casting the nut, and as a result, the manufacturing cost of the nut is increased. May make it worse. In addition, when a fixing nut for screw reinforcing bars is cast using a core and a pair of upper and lower dies, burrs are inevitably formed on the portion of the obtained nut surface corresponding to the matching surface between the upper and lower dies. Occurs. Removal of burrs from where even a small amount of such burrs may remain near both ends in the threaded axial direction in the threaded hole into which the threaded rebar is threaded, which may prevent the nut from being screwed into the threaded rebar. Must be carried out with the utmost care, resulting in increased manufacturing costs. Further, the fixing nut for threaded reinforcing bars requires an injection hole for injecting a grout (material) in the clearance between the nut and the threaded reinforcing bar. However, in the case of manufacturing a nut by casting, after casting. It is common to carry out a separate step to form the injection hole, and the presence of such a separate step has exacerbated the nut manufacturing cost.

Under such circumstances, the present invention has been completed, and the problem to be solved is that labor such as deburring during manufacturing according to the casting method is reduced, and as a result, it is low. It is an object of the present invention to provide a fixing nut for a screw reinforcing bar that can be manufactured at a manufacturing cost. Another object of the present invention is to provide a method capable of advantageously manufacturing such a fixing nut for a screw reinforcing bar.

Then, in order to solve such a problem, the present invention has a screw hole which is open at both ends in the screw axis direction and has a female thread formed on the inner peripheral surface, and has a screw hole formed from one end in the screw axis direction to the other. The two concave grooves extending to the ends of the screw hole and opening outward at both ends thereof are formed so as to face each other and cross the female screw formed on the inner peripheral surface of the screw hole. The gist of this is a fixing nut for screw reinforcing bars, which is characterized by the above.

Further, in the present invention, according to the method for manufacturing a fixing nut for a screw reinforcing bar having the above-described configuration, 1) a molded cavity that gives the outer shape of the fixing nut for the screw reinforcing bar in a molded state is formed. A pair of upper and lower dies are prepared with the plane including the axis center line of the screw shaft as the molding surface in the fixing nut for screw reinforcing bars, while 2) fixing for screw reinforcing bars in the molded state. A molded cavity that provides a male thread shape corresponding to the female thread in the nut and two ridges corresponding to the two concave grooves is formed, and the portion of the molded cavity that provides the two ridges is formed. After a core having the male screw shape and the two ridges on the outer peripheral surface is molded and prepared using a pair of molding dies in which the mold matching surfaces are located, 3) on the outer peripheral surface of the core. The core is placed in the molding cavity formed by the upper mold and the lower mold so that each of the two ridges formed in the mold is parallel to the molding surface of the upper mold and the lower mold. It is also a gist of a method for manufacturing a fixing nut for a screw reinforcing bar, which is characterized in that casting is carried out using an arranged upper mold, a lower mold and a core so arranged.

As described above, the fixing nut for the screw reinforcing bar according to the present invention is applied from the place where the two concave grooves are formed so as to cross the female screw formed on the inner peripheral surface of the screw hole so as to face each other. Due to the presence of the two concave grooves, when the nut is manufactured by the casting method, burrs generated due to the matching of the upper and lower molds for forming the outer shape of the nut are screwed to the threaded reinforcing bar. In addition, it is possible to reduce the influence on the case, and it is also possible to effectively suppress the formation (generation) of female threads having poor accuracy due to minute burrs on the surface of the core. In addition, the two concave grooves formed on the inner peripheral surface of the screw hole are open at both ends, and after screwing the fixing nut for the threaded rebar according to the present invention to the threaded rebar, grout (from the opening). Since the material can be injected, the step of providing a grout (material) injection hole in the nut after casting becomes unnecessary. As described above, in the case of the fixing nut for screw reinforcing bars according to the present invention, when the nut is manufactured by casting, the step of removing burrs on the nut surface, which is required for the nut having a conventional structure, is remarkably simplified. Alternatively, it becomes unnecessary, and as a result, the manufacturing cost can be kept low. In addition, the two concave grooves that serve as injection holes for grout (material) when screwed with the screw reinforcing bar are open at both ends in the direction of the screw axis, making it easy to inject grout (material). At the same time, the degree of grout (material) injection can be easily confirmed.

Further, according to the method for manufacturing a fixing nut for screw reinforcing bars according to the present invention, it is possible to manufacture a fixing nut for screw reinforcing bars at low cost.

It is a front view which shows an example of the fixing nut for a screw reinforcing bar according to this invention. It is a left side view which shows an example of the fixing nut for a screw reinforcing bar according to this invention. It is explanatory drawing which shows the cross section in the AA plane in FIG. It is a partially enlarged explanatory view of the part B in FIG. It is explanatory drawing which shows an example of the upper die and the lower die used when casting the fixing nut for a screw reinforcing bar according to this invention, (a) is the front view which shows the state which was molded, (b). Is an explanatory view showing a cross section on the CC plane in (a). It is explanatory drawing which shows an example of the core used when casting the fixing nut for a screw reinforcing bar according to this invention, (a) is a front view, (b) is a right side view. It is explanatory drawing which shows the molding mold for molding the core shown in FIG. 6, (a) is the front view which shows the state which the mold was matched, and (b) is the DD plane in (a). It is explanatory drawing which shows the cross section in. It is a partial cross-sectional explanatory view showing a state in which the upper mold and the lower mold shown in FIG. 5 and the core shown in FIG. 6 are matched.

Hereinafter, the present invention will be described in detail with reference to the drawings as appropriate.

1 to 4 show a fixing nut for screw reinforcing bars (hereinafter, also simply referred to as a nut) 10 according to an embodiment of the present invention. Specifically, FIG. 1 is a front view of the nut 10, FIG. 2 is a left side view, and FIG. 3 is an explanatory view showing a cross section that appears when the nut 10 is cut on the AA plane in FIG. Further, FIG. 4 is an explanatory diagram showing the portion B in FIG. 1 in a partially enlarged manner. The rear view is the same as the front view, and the right side view, the plan view, and the bottom view are the same as the left side view, so the illustration is omitted.

As is clear from FIGS. 1 to 4, the fixing nut 10 for screw reinforcing bars according to the present invention has a cylindrical shape as a whole, and the central axis of the cylinder is a screw axis and the direction of the central axis (FIG. Screw holes 12 are formed at both ends of the vertical direction of the paper surface in 1 and the left-right direction of the paper surface in FIG. 3; hereinafter referred to as the screw axis direction). The radial outer corners at both ends of the cylinder are chamfered.

On the inner peripheral surface of the screw hole 12, a spiral female screw 14 for screwing to a screw reinforcing bar (not shown) is formed. The female screw 14 corresponds to the shape of a male screw formed on the outer peripheral surface of the threaded rebar so that it can be easily screwed to the target threaded rebar and the screwed state can be ensured well. It is formed by the thread height and pitch.

Then, in the fixing nut 10 for screw reinforcing bars according to the present invention, from one end to the other in the screwing axis direction so as to cross the female screw 14 formed on the inner peripheral surface of the screw hole 12. A major technical feature lies in the fact that the two concave grooves 16a and 16b extending toward each other and opening outward at both ends thereof are formed so as to face each other with respect to the screw axis. be.

That is, by forming such two concave grooves 16a and 16b, for example, when the fixing nut 10 for a screw reinforcing bar is manufactured according to a casting method, an upper mold and a lower mold for forming the outer shape of the nut are formed. The effect of burrs generated due to alignment when the nut 10 is screwed to the thread rebar can be reduced, and female threads with poor accuracy due to minute burrs on the core surface can be reduced. It is also possible to effectively prevent the formation of. Further, since the two concave grooves 16a and 16b are open at both ends in the screwing axis direction, after the nut 10 is screwed to the threaded rebar, grout (material) is formed from the opening formed between the nut 10 and the threaded rebar. ) Can be injected, so that the nut 10 does not require a step of providing an injection hole for grout (material) after casting. Therefore, when the fixing nut 10 for screw reinforcing bars according to the present invention is manufactured by a casting method, the step of removing burrs generated on the core and the surface of the nut, which is required for the nut having a conventional structure, is remarkably simple. However, it becomes unnecessary, and the step of forming the injection hole of the grout (material) becomes unnecessary, so that the manufacturing cost can be kept low. At the same time, the two concave grooves 16a and 16b, which serve as injection holes for the grout (material) in a state of being screwed with the screw reinforcing bar, are open at both ends in the screwing axis direction, and the grout (material) The fixing nut 10 for screw reinforcing bars of the present invention has an advantage that the injection of grout (material) can be easily confirmed and the degree of injection of grout (material) can be easily confirmed.

Here, as shown in FIG. 4, the bottom surfaces of the two concave grooves 16a and 16b that cross the female screw 14 are recessed from the bottom surface of the valley portion that constitutes the female screw 14. In other words, each bottom surface of the two concave grooves 16a and 16b is formed so as to protrude outward in the radial direction of the nut 10 than the bottom surface of the valley portion constituting the female screw 14. Is preferable. By adopting such a configuration, it is possible to enjoy the above-mentioned effect of the present invention more advantageously. In FIG. 4 (and FIG. 1), the dotted line indicates the bottom surface of the valley portion constituting the female screw 14, and the amount of dent on the bottom surface of the concave groove (16a, 16b) with respect to the bottom surface of the valley portion constituting the female screw 14. If (d) in FIG. 4 is too small, the effect of the present invention may not be enjoyed, while if it is too large, problems such as a decrease in the strength of the nut 10 may occur. Therefore, the amount of dent (d) depends on the size of the nut 10 and the like, but is generally about 0.5 to 3 mm. The amount of each of the two concave grooves 16a and 16b may be different as well as the same.

Further, it is preferable that the corner portions on the bottom surfaces of the two concave grooves 16a and 16b have an R shape (see FIG. 4). Since the corners of the bottom surface are R-shaped, it is possible to advantageously prevent fracture due to stress concentration when the nut 10 is used in a reinforced concrete structure.

The fixing nut 10 for screw reinforcing bars according to the present invention is made of various metal materials like the conventional fixing tool used for fixing deformed reinforcing bars such as screw reinforcing bars to concrete.

By the way, the fixing nut 10 for screw reinforcing bars described above can be manufactured by, for example, a casting method according to the following procedure.

First, as the outer mold, a molding cavity that gives the outer shape of the fixing nut 10 for the screw reinforcing bar is formed in the molded state, and the plane including the axis center line of the screw shaft in the nut 10 is used as the mold matching surface. A pair of upper and lower molds are prepared.

5 shows such an upper mold and a lower mold, and FIG. 5A is a front view of the upper mold 20 and the lower mold 22 in a molded state, and is shown in FIG. 5 (a). b) is an explanatory view showing a cross section on the CC plane in the same (a). As is clear from FIGS. 5 (a) and 5 (b), the upper mold 20 and the lower mold 22 have a molding portion 24 that gives the outer shape of the fixing nut 10 for the screw reinforcing bar in a molded state, and a middle mold described later. The cavity 28 composed of the grip portions 26a and 26b for gripping the child is configured to be formed inside. Further, the upper mold 20 gives the outer shape of the portion of the upper half of the nut 10 (the upper half in the vertical direction of the paper surface in FIGS. 1 to 3), and the lower mold 22 gives the outer shape of the lower half of the nut 10 (FIG. 3). 1 to 3 are configured so that the outer shape of the part (lower half in the vertical direction of the paper surface) is given, so that the matching surface of the upper mold 20 and the lower mold 22 is a nut that is a cast product. Consistent with the plane containing the axis centerline of the screw axis at 10.

As the material (mold material) constituting the upper mold 22 and the lower mold 24, any conventionally known mold material can be used, but from the viewpoint of manufacturing cost and the like, the mold can be used. Sand (casting sand) is used advantageously. Further, although not shown in FIGS. 5A and 5B, the upper mold 22 is formed with a sprue and a runner for pouring the molten metal.

On the other hand, a core for forming the female screw 14 and the two concave grooves 16a and 16b in the fixing nut 10 for the screw reinforcing bar is prepared. 6A and 6B are explanatory views showing such a core, FIG. 6A is a front view of the core 30, and FIG. 6B is a right side view of the core 30.

As can be understood from FIG. 6, the core 30 is gripped in the cavities 28 of the upper die 20 and the lower die 22 described above at both ends in the direction corresponding to the screwing axis direction of the screw reinforcing bar fixing nut 10. It has support portions 32a and 32b for being screwed, and on the outer peripheral surface of the portion between the support portions 32a and 32b, a male screw portion 34 corresponding to the female screw 14 in the screw hole 12 of the nut 10 and a screw are screwed. Two ridges 36a and 36b corresponding to the two concave grooves 16a and 16b in the joint hole 12 are formed. The dotted lines in FIGS. 6 (a) and 6 (b) indicate the portions corresponding to the mold matching surfaces (mold matching lines) of the molding mold when the core 30 is molded using the molding mold described later. ..

Further, FIG. 7 shows a molding die used when molding the core 30. FIG. 7 (a) is a front view showing a molded state of a core forming mold 42 composed of a pair of upper molds 38 and a lower mold 40, and FIG. 7 (b) is a D of the same (a). -It is explanatory drawing which shows the cross section on the D plane.

As can be understood from FIG. 7, in the core molding die 42, in a state where the upper die 38 and the lower die 40 are molded, 1) the support portions 32a and 32b in the core 30 are provided inside the die. A molding cavity is formed consisting of parts 44a and 44b, 2) a part 46 that gives a male screw portion 34 in the core 30, and 3) parts 48a and 48b that give two protrusions 36a and 36b in the core 30. It is configured to be. Further, the upper mold 38 provides the upper half of the core 30 (the upper half in the vertical direction of the paper surface in FIGS. 6A and 6B), while the lower mold 40 provides the upper half of the core 30. Each is configured so that the lower half (lower half in the vertical direction of the paper surface in FIGS. 6A and 6B) is provided. Therefore, the mating surface of the upper die 38 and the lower die 40 coincides with the plane including the axis center line of the core 30 (in other words, the axis center line of the screw shaft in the cast nut 10). Will be.

When molding the core using the core molding mold 42 (upper mold 38, lower mold 40) described above, it is possible to mold according to the shell mold molding method in order to form the male screw portion 34 with high accuracy. preferable.

The pair of upper molds 20 and lower molds 22 prepared as described above and the core 30 are subjected to mold matching as shown in FIG. FIG. 8 shows a cross section of the upper mold 20, the lower mold 22, and the core 30 in the molded state when cut at the surface corresponding to the CC surface in FIG. 5 (however, the male screw in the core 30). It is explanatory drawing which shows (excluding part and ridge). At the time of such molding, the two protrusions 36a and 36b formed on the core 30 are parallel to the molding surfaces of the upper mold 20 and the lower mold 22, and more specifically, the core. The parts (the parts indicated by the dotted lines in FIG. 8) corresponding to the mold matching surface (mold matching line) of the core forming mold on the two protrusions 36a and 36b of 30 are the molds of the upper mold 20 and the lower mold 22. It is carried out so as to coincide with the mating surface.

Then, according to a conventionally known casting method, the molten metal is poured into the molds molded as described above to be solidified, and then the molds are disassembled. The fixing nut 10 is manufactured.

In the screw reinforcing bar fixing nut 10 thus obtained, two concave grooves 16a and 16b are formed so as to cross the female screw 14 formed on the inner peripheral surface of the screw hole 12 so as to face each other. Due to the presence of the two concave grooves 16a and 16b, burrs caused by the matching of the upper mold 20 and the lower mold 22 are formed in the two concave grooves 16a and 16b (more specifically, the two concave grooves 16a and 16b). It will occur at both ends of the recessed grooves 16a and 16b in the screwing direction), and the adverse effect of such burrs on the shape of the female screw 14 and, by extension, the effect on screwing to the threaded reinforcing bar will be small. .. Further, by arranging the core 30 with respect to the upper mold 20 and the lower mold 22 according to a predetermined positional relationship and performing casting, it is possible to form a female screw having poor accuracy due to a minute burr on the surface of the core 30. , Can be effectively suppressed. Further, the two concave grooves 16a and 16b formed on the inner peripheral surface of the screw hole 12 are open at both ends, and after the nut 10 is screwed to the screw reinforcing bar, the grout (material) is formed from the opening. Since it is possible to inject the grout (material) into the nut after casting, there is no need for a step of providing an injection hole for the grout (material). As described above, when the fixing nut 10 for screw reinforcing bars according to the present invention is manufactured by casting, the step of removing burrs on the nut surface, which is required for nuts having a conventional structure, is remarkably simplified. Or, since it becomes unnecessary, the manufacturing cost can be kept low as a result. In addition, the two concave grooves that serve as injection holes for grout (material) when screwed with the screw reinforcing bar are open at both ends in the direction of the screw axis, making it easy to inject grout (material). At the same time, it is possible to easily confirm the degree of injection of grout (material).

Although one of the typical embodiments of the present invention has been described in detail above, the present invention is by no means limited to the above-mentioned specific embodiments, and those skilled in the art are skilled in the art as long as they do not deviate from the gist of the present invention. It should be understood that various changes, corrections, improvements, etc. can be made based on the knowledge of.

10 Reinforcing bar fixing nut 12 Screw hole 14 Female thread 16a, 16b Concave groove 20 Upper type 22 Lower type 30 Core 34 Male thread part 36a, 36b Convex

Claims (1)

i) It has a screw hole that opens at both ends in the screw axis direction and has a female thread formed on the inner peripheral surface, ii) extends from one end to the other end in the screw axis direction, and at both ends. A method for manufacturing a fixing nut for a screw reinforcing bar, in which two concave grooves that open outward are formed so as to face each other and cross a female screw formed on the inner peripheral surface of the screw hole. ,
A pair of upper molds in which a molding cavity that gives the outer shape of the threaded reinforcing bar fixing nut is formed in the molded state, and the plane including the axis center line of the screwed shaft in the threaded reinforcing bar fixing nut is used as the matching surface. And the lower mold is prepared, while
In the molded state, a forming cavity is formed to provide a male thread shape corresponding to the female thread in the threaded reinforcing bar fixing nut and two ridges corresponding to the two concave grooves, and the forming is performed. A core having the male thread shape and the two ridges on the outer peripheral surface is molded and prepared using a pair of molding dies in which the mold matching surface is located at the portion of the cavity where the two ridges are to be provided. After that
The core is formed by the upper mold and the lower mold so that each of the two ridges formed on the outer peripheral surface of the core is parallel to the molding surface of the upper mold and the lower mold. A method for manufacturing a fixing nut for a threaded reinforcing bar, which is arranged in a formed forming cavity and casting is performed using an upper die, a lower die and a core so arranged.

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