JP2024011127A - Counter bore t-nut - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the manufacturing of a CBT nut which is used by being driven into a plate material or the like of a furniture member.

SOLUTION: A cylindrical body 11 and a plate-shaped flange 12 are formed by repeatedly applying press working to a plate-shaped body, and deep-drawing the plate-shaped body. Also, by notching a bottom portion from the bottomed cylindrical body 11 into a cap shape, and arranging a thin-thickness caulking-scheduled part 1121 at a tip 112, an original form of a CBT nut 1 can be obtained. After that, screw threads are press-worked at internal/external peripheral faces of the cylindrical body 11 by using inside/outside molds. When removing the molds, there appear the screw threads having slightly-mild inclinations due to spring-back, however, by combining tapping bolts 2, and spreading the mild inclination screw threads by the screw threads 21, fastening can be performed while performing partial screw-cutting. Therefore, when forming an inner screw of a nut, tap working can be dispensed with, production efficiency can be improved by shortening a cycle time, a cutting fluid at the screw-cutting becomes unnecessary, the treatment of chips also becomes unnecessary, and cost reduction can be achieved.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a counterbore T-nut for public use in furniture and the like.

An example of the counterbore T-nut is disclosed in Patent Document 1 by the inventor of the present invention. According to the prior art, a flange is provided at one end of a cylindrical body to form a T-shape in side view, and a thread is carved on the inner peripheral surface of the body to form a nut. has been done. Then, the main body is fitted into a hole drilled in a base material (component) such as wood, and is folded back and caulked so that the thin section at the tip of the cylinder that is to be caulked is expanded. This prevents the T-nut from falling off and enables fastening with bolts.

Patent No. 2940898

In the above-mentioned conventional technology, a plate-shaped body is deep-drawn by repeated press working with a progressive die equipped with a plunger to form the cylindrical main body and flange portion in the counterbore CB shape or step barrel shape. Then, after cutting and bending to form a tab in the same progressive die process, each tab T-nut is separated from the plate-shaped body, deburred, and barrel-polished. An internal thread is formed by tapping on the circumferential surface. Therefore, cutting oil is used in the two processes of deep drawing press working and tapping, and it is necessary to manage and treat the cutting oil and its cleaning fluid, and it is also necessary to treat chips. In addition, deburring and barrel polishing are also required for tapping. Therefore, there are problems in that the cycle time becomes longer and the cost increases.

An object of the present invention is to provide a counterbore T-nut that can improve productivity and reduce costs by omitting tapping.

The counterbore T-nut of the present invention is provided with a flange at one end of a cylindrical body, the cylindrical body is formed by deep drawing of a plate-like body forming the flange, and the cylindrical body is formed by deep drawing of a plate-like body forming the flange. The other end is a counterbore T-nut formed in a thin-walled portion to be caulked, and the main body is formed into a gentler curve at the top of the crest and the bottom of the valley than the thread on the outer peripheral surface of the bolt to be screwed. It is characterized by comprising an inner circumferential surface having a thread, and an outer circumferential surface having an outer thread of the thread formed substantially parallel to the thread on the inner circumferential surface by a predetermined thickness.

According to the above configuration, a flange is provided at one end of the cylindrical body, the cylindrical body is formed by deep drawing of a plate-like body forming the flange, and the other end of the cylindrical body A counterbore T-nut formed in a thin section to be caulked does not have a sharp threaded hole where the peaks and valleys correspond exactly to the bolt, and even though the pitch is the same, the distance between the valleys and peaks is narrow, that is, the valleys are shallow. The screw thread should have a gentle curve with low crests. Further, the cylindrical main body not only has the threads formed on the inner circumferential surface thereof, but also has substantially parallel threads formed on the outer circumferential surface at a distance of a predetermined thickness from the inner circumferential surface.

Such a counterbore T-nut includes, for example, an inner mold formed with an external thread corresponding to the thread on the outer circumferential surface of a bolt to be screwed into the counterbore T-nut, and an inner mold that is placed over the inner mold. Using an outer mold with an internal thread formed at a predetermined distance (thickness) from the thread of the mold, that is, almost parallel when viewed in cross section, and with the outer mold mutually divided, a cylindrical material is produced. By covering the inner mold and combining the outer molds with each other, an internal thread can be formed by pressing these inner and outer molds.

Then, by removing the outer mold and pulling out the inner mold, even if the internal thread does not correspond exactly to the thread of the bolt due to springback, it is possible to tighten the counter by screwing it in while pushing it out with a tapping bolt. A bore T-nut can be realized. In this way, tapping can be eliminated when forming the internal thread of the nut. This not only shortens cycle time and improves production efficiency, but also eliminates the need for cutting oil during thread cutting and the need to dispose of chips, thereby reducing costs.

In addition, since it is a counterbore T-nut, the counterbore T-nut is fitted into a hole drilled in the base material (component) and caulked to prevent it from falling out, making it possible to fasten with a tapping bolt. can do.

Further, the counterbore T-nut of the present invention is characterized in that the flange is cut and raised to form a pawl that pierces the base material and prevents rotation of the cylindrical main body around the axis.

According to the above configuration, after forming threads on the inside and outside of the cylindrical main body by press working, it is also possible to create a rotation stopper on the flange portion by cutting and raising the flange part by press working. Since this pawl prevents the T-nut from rotating (corresponding rotation) with respect to the screwing of the tapping bolt, even if the counterbore T-nut is created by pressing the inner and outer molds, It can fully demonstrate its function as a nut.

Furthermore, the counterbore T-nut of the present invention is a step barrel counterbore T-nut having an enlarged diameter portion on the flange side at a stepped portion.

According to the above configuration, even if the screw hole is formed slightly larger because it is difficult to drive a counterbore T-nut in the case of a thick board, especially wood, the enlarged portion can prevent rattling. Further, the enlarged portion makes the bending radius of one end of the main body looser, and thread cutting can be performed from the entrance near the stepped portion, which is preferable.

Preferably, the method for manufacturing a nut of the present invention is a method for manufacturing a nut in which the threaded portion of the nut is molded using an inner and outer mold, the method comprising molding the threaded portion of the nut with an outer mold that corresponds to the threaded portion on the outer peripheral surface of a bolt to be screwed into the nut. An inner mold in which a thread is formed, and an inner thread that can be separated from each other and is spaced a predetermined distance (thickness) from the thread of the inner mold when combined with each other and placed on the inner mold. The method is characterized in that an internal thread is formed in a cylindrical material by pressing the inner and outer molds using the formed outer mold.

According to the above configuration, when manufacturing a nut, an inner mold is formed with an outer thread corresponding to the thread on the outer peripheral surface of a bolt to be screwed into the nut, and a A cylindrical material is made using an outer mold with an inner thread formed at a predetermined distance (thickness) from the thread of the thread, that is, almost parallel when viewed in cross section, and with the outer mold separated from each other. By covering the inner mold and combining the outer molds with each other, an internal thread is formed by pressing these inner and outer molds.

Therefore, tapping can be eliminated when forming the internal thread of the nut. This makes it possible to shorten cycle time and improve production efficiency, and also eliminates the need for cutting oil during thread cutting and the need to dispose of chips, thereby reducing costs.

As described above, the counterbore T-nut of the present invention is a counterbore T-nut in which a flange is provided at one end of a cylindrical body, but the pitch is not a sharp threaded hole whose peaks and valleys correspond precisely to the bolt. Even if it is the same, the gap between the valley and the peak is narrow, that is, the valley is shallow and the peak is low and has a gentle curve.

Therefore, since such a counterbore T-nut can be produced by press working using inner and outer molds, tapping can be eliminated in forming the internal thread of the counterbore T-nut. This not only shortens cycle time and improves production efficiency, but also eliminates the need for cutting oil during thread cutting and the need to dispose of chips, resulting in a low-cost counterbore T-nut. be able to.

FIG. 2 is a perspective view of a counterbore T-nut and a tapping bolt that realize a screw fastening structure according to an embodiment of the present invention. FIG. 2 is an axial cross-sectional view of the counterbore T-nut of FIG. 1; FIG. 2 is a sectional view of a furniture member using the fastening structure of FIG. 1. FIG. FIG. 7 is an axial cross-sectional view of a counterbore T-nut according to another embodiment of the present invention.

FIG. 1 is a perspective view of a counterbore T-nut 1 and a tapping bolt 2 that realize a screw fastening structure according to an embodiment of the present invention, and FIG. 2 is an axial cross-sectional view of the counterbore T-nut 1. FIG. 3 is a sectional view of a furniture member 3 using the above-mentioned fastening structure. The screw fastening structure of this embodiment is used, for example, to mutually fasten the metal fittings 32 to the plate material 31 of the furniture member 3 serving as a base material (component). For example, the plate material 31 is a seat plate of a chair, on which a cushioning material 33 such as urethane and a surface material such as leather (not shown) are laminated as appropriate, while the metal fittings 32 are attached to the tops of the legs. This is a metal fitting with a screw hole 321 drilled therein. Then, the counterbore T nut 1 is inserted into the threaded hole 311 drilled slightly larger in the plate material 31, and the tapping bolt 2 loosely inserted into the threaded hole 321 drilled slightly larger in the metal fitting 32 is inserted into the counterbore T nut 1. By screwing onto the nut 1, the metal fitting 32 is fastened to the plate material 31.

The counterbore T-nut 1 has a flange 12 at one end 111 of a cylindrical main body 11, so that the counterbore T-nut 1 has a T-shape in a side view or in an axial cross section in FIGS. 2 and 3. The counterbore T-nut 1 of this embodiment further has claws 13 formed on the periphery of the flange 12 by cutting and raising. When the main body 11 is inserted into the screw hole 311, the pawl 13 pierces the plate material 31, thereby preventing the cylindrical main body 11 from rotating around the axis when the tapping bolt 2 is screwed in, which will be described later. .

Then, as shown in FIG. 3, after the counterbore T-nut 1 is inserted (driven) to such an extent that the back surface 121 of the flange 12 is substantially flush with the back surface 312 of the plate material 31, the counterbore T-nut The other end (tip) 112 of the cylindrical main body 11 of No. 1 is folded back so as to be expanded and caulked as shown by reference numeral 117, thereby preventing the counterbore T-nut 1 from falling off. , enables fastening with a tapping bolt 2 to be described later, and also guides the tapping bolt 2.

The flange 12 may be round or square, but in this embodiment, it is formed into a roughly octagonal shape, and a pair of claws 13 are raised from both sides of the two mutually opposing sides. Then, the remaining sides of the octagon are sandwiched from both sides by a pair of U-shaped holders, and the main body 11 and claws 13 are shipped with the parts protruding from between the holders. Loaded into the driving machine. If the plate material 31 is a resin molded product, a driving machine is provided near the molding machine in order to drive the counterbore T-nut 1 while it is still soft immediately after molding.

In the screw fastening structure configured as described above, it should be noted that in the counterbore T-nut 1 of this embodiment, as shown in FIGS. 1 to 3, the cylindrical main body 11 has an inner circumference The surface 113 does not have a sharp threaded hole whose peaks and valleys correspond exactly to the tapping bolts 2, but a gently curved thread 115 where the pitch is the same but the distance between the valleys and peaks is narrow, that is, the valleys are shallow and the peaks are low. It is to be formed. A substantially parallel thread 116 is also formed on the outer peripheral surface 114, spaced apart from the thread 115 of the inner peripheral surface 113 by a predetermined distance (thickness) D.

As an example of the manufacturing process of such a counterbore T-nut 1, first, a plate-shaped body is deep-drawn by repeated press working with a progressive die equipped with a plunger, and the cylindrical main body 11 and the plate-shaped body are It is formed on the flange 12. In this state after deep drawing, the bottom portion of the drawing remains, that is, the main body 11 has a cylindrical shape with a bottom, so the bottom portion is cut out into a cap shape. After that, the end portion (tip) 112 is formed from the step portion 1122 into a thin caulking portion 1121 using a punch for the folding 117, and then the flange 12 portion is shaped into the approximately octagonal shape. They are individually cut out to form counterbore T-nuts.

After that, what should be noted is that an inner mold made of a commercially available tap tool is fitted inside the cylindrical main body 11, and combined with a pair of outer molds, the inner and outer parts of the main body 11 as shown in FIG. The threads 115 and 116 are pressed. Therefore, the pair of outer molds can be separated from each other, and when they are combined with each other and placed on the inner mold, a predetermined distance (thickness) D (shown in Figure 2) from the thread of the inner mold. Threads are formed that are spaced apart, ie, substantially parallel when viewed in cross section. Note that the outer mold may be divided into three or more parts.

After the threads 115, 116 are pressed, the outer molds are separated from each other and the inner mold is also quickly pulled out. The pawl 13 is formed by pressing the screw threads 115 and 116 and then cutting and raising the screw threads 115 and 116 by pressing.

With this configuration, tapping can be eliminated when forming the thread 115 of the internal thread of the counterbore T-nut 1. This eliminates the need for deburring and barrel polishing before tapping, shortens cycle time and improves production efficiency, and eliminates the need to manage and treat cutting oil and its cleaning fluid during thread cutting. Furthermore, there is no need to dispose of chips, which can also reduce costs. Note that the thread 116 of the external thread formed as a result does not participate in the function as a nut, but bites into the threaded hole 311 of the plate material 31.

In the counterbore T-nut 1 of this embodiment, due to the springback and the like, the threads 115 and 116 are closer to the tops and valleys of the threads than the threads 21 on the outer peripheral surface of the tapping bolt 2 to be screwed into the T-nut 1. The bottom of the curve is formed into a gentle curve (the pitch is the same, and the distance between the valleys and peaks is narrow). In other words, the thread is not a sharp screw hole whose peaks and valleys correspond exactly to the threads 21 of the tapping bolt 2, but the pitch is the same but the gap between the valleys is narrow, that is, the thread is low, the valley is shallow, and the screw has a gentle curve. It is considered a mountain.

Correspondingly, in the screw fastening structure of this embodiment, the counterbore T-nut 1 is used in combination with a tapping bolt 2. The tapping bolt 2 is formed with high hardness by hardening, etc., and when the tapping bolt 2 is screwed into the counterbore T-nut 1, the thread 21 pushes the thread 115 on the inner peripheral surface 113 of the main body 11. By threading a portion while expanding, the thickness of the portion of the main body 11 into which the tapping bolt 2 is screwed may become slightly thinner as a result, as shown by reference numeral d in FIG.

Therefore, the pressure during press working of the threads 115, 116 by the inner mold and the outer mold can be reduced, and the cylindrical material (11) is less deformed, improving the yield. ). Further, since the threads 115 and 116 become loose, the tightening strength of the screws can be ensured by replacing the ordinary bolts with the tapping bolts 2 that can be easily carved by oneself.

In addition, if the material (11) has already been pressed by deep drawing and formed into a cylindrical shape, the tops of the threads and the bottoms of the valleys will be A gentle slope is preferable because it puts less stress on the material (11).

Furthermore, in the counterbore T-nut 1 of this embodiment, the threads 115 and 116 are formed inside and outside the cylindrical main body 11 by press working, and then the flange 12 is cut and raised by press working to prevent rotation. Claw 13 is being created. Therefore, this pawl 13 prevents the counterbore T-nut 1 from rotating (rotating along with it) when the tapping bolt 2 is screwed in, so that the T-nut is manufactured by pressing the inner and outer molds. However, the nut can still fully function as a nut.

Furthermore, by using the screw fastening structure as described above in the furniture member 3 as shown in FIG. 3, an inexpensive fastening structure can be realized, and an inexpensive furniture member can be realized.

Here, in Japanese Patent Application Laid-open No. 2006-297455, a press-fit nut is manufactured by combining inner and outer molds and press working, but what is formed by pressing is a groove formed by a protrusion extending inside the outer mold. , which bites into the base material to which the nut is attached. The inner thread of the nut itself is created by cutting as usual. Paragraph 0041 also states that when using self-tapping screws, it is not necessary to process internal threads, but if the depth of the trough (thread) becomes deep or the pitch becomes narrow, , it is necessary to increase the torque for tightening the tapping screw.

Furthermore, the present invention, as shown in the counterbore T-nut 1a in FIG. It can also be applied to the step barrel counterbore T-nut of Japanese Patent No. 3310934 in which the length is shortened. Here, in the case of a thick plate, especially wood, it is difficult to drive a counterbore T-nut, so the screw hole 311 is formed slightly larger. This causes wobbling, so by forming the proximal end (111) with the enlarged portion 15 and making it thicker, as in this step barrel counterbore T-nut, it becomes easier to drive and the wobbling can be prevented. Further, for example, if the plate thickness of the flange 12 is 1.2 mm, the base end (111) will not be bent at right angles with a radius of 1.2 mm, but the radius will be slightly larger, and therefore the base end (111) will not be bent at right angles with a radius of 1.2 mm. 111), there is a part where the thread cannot be cut. In this respect as well, the stepped barrel counterbore T-nut is preferable because the bending from the stepped portion 14 to the main body 11 is relaxed, and thread cutting can be performed from the entrance near the stepped portion 14.

1, 1a Counterbore T nut 10 Plate body 11 Main body 111 One end 112 Other end (tip)
1121 Part to be caulked 1122 Step part 113 Inner peripheral surface 114 Outer peripheral surface 115 Thread (inner thread)
116 Thread (external thread)
117 Folding back for caulking 12 Flange 13 Claw 14 Step portion 15 Enlarged portion 2 Tapping bolt 21 Thread 3 Furniture member 31 Plate material 32 Metal fittings 311, 321 Screw hole 33 Cushioning material

Claims (3)

A flange is provided at one end of the cylindrical body, the cylindrical body is formed by deep drawing of a plate-like body forming the flange, and the other end of the cylindrical body is provided with a thin-walled caulking portion. In the counterbore T-nut formed in
The main body is predetermined from the threads on the outer circumferential surface of the bolt to be screwed, and an inner circumferential surface having threads in which the tops of the crests and the bottoms of the valleys are formed into gentle curves, and the threads on the inner circumferential surface. A counterbore T-nut comprising: an outer circumferential surface having external threads of threads formed substantially parallel across a thickness. 2. The counterbore T-nut according to claim 1, wherein the flange is cut and raised to form a pawl that pierces the base material and prevents rotation of the cylindrical body around the axis. The T-nut according to claim 1 or 2, wherein the T-nut is a step barrel counterbore T-nut having an enlarged diameter portion on the flange side at a stepped portion.

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