Fasteners and methods for securing fasteners

Abstract

The present invention provides a fastener having a nut-like through-thread that is fastened to a hole provided in a molded thermoplastic resin member, and a method for fastening the fastener. [Solution] The fastener 1 of the present invention comprises a short cylindrical body 2, a head 3 provided on the outer peripheral surface having an end face a, a plug body 4 provided on the outer peripheral surface with knurling (uneven stripes), a small diameter portion 5, and a tip portion 6. The tip portion 6 is chamfered. The outer diameter of the plug body 4 is machined to be smaller than the outer diameter of the head by a predetermined amount. The body 2 is provided with a female thread 7 as a through-thread from the end face a to the tip portion 6.

Description

Technical Field

[0001] The present invention relates to a fixture suitable for being fitted and fixed to a molded member of a thermoplastic resin and a method for fixing the fixture.

Background Art

[0002] Conventionally, when a screw hole is formed in a member made of a molded product of a thermoplastic resin and a bolt or the like is screwed and fixed, the screw hole is deformed or destroyed when subjected to tensile, torsional, vibrational or other external forces, or when the bolt or the like is repeatedly attached and detached, and it becomes unusable. Therefore, a nut-shaped metal fixture (insert) has been put into practical use that can be stably fixed to a bolt or the like by fitting and fixing it to a hole provided in a molded member and can withstand repeated attachment and detachment. Further, a method has been proposed in which a roll-shaped or other unevenness is provided on the outer circumferential surface of the fixture so that such a fixture bites into the hole of the molded member and is fixed with sufficient strength (for example, Patent Documents 1 and 2).

[0003] When fitting such a fixture into a molded member, the fixture is heated (around 200°C) and pressed into a boss hole provided in the molded member. Utilizing the properties of this thermoplastic resin, the inventor has filed an application for a fixture suitable for mass production on November 4, 2,023.

[0004] However, the nut-shaped fixture applied for above has a problem that it cannot be processed unless it is a closed-end screw and cannot be processed with a through screw.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] As described above, the nut-shaped fastener filed on November 4, 2023, had the problem that it could only be manufactured with closed-end threads and could not be manufactured with through-threads. The purpose of this invention is to provide a nut-shaped fastener with a through-thread for fixing into a hole provided in a molded thermoplastic resin member, and a method for fixing the fastener. [Means for solving the problem]

[0007] Therefore, the present invention provides a metal fastener with a through-thread processed into a nut shape, which is fixed by heating and pressurizing a hole provided in a molded thermoplastic resin member, comprising a cylindrical body with a head having the same outer diameter as the hole diameter, a plug portion adjacent to the head and having numerous grooves on the outer circumferential surface of the cylindrical body and having an outer diameter smaller than the outer diameter of the head, a small-diameter portion adjacent to the plug portion and provided on the outer circumferential surface of the cylindrical body and having an outer diameter smaller than the outer diameter of the plug portion, and a tip portion adjacent to the small-diameter portion and provided on the outer circumferential surface of the cylindrical body and having an outer diameter larger than the outer diameter of the small-diameter portion. Furthermore, the present invention relates to a method for fixing a metal fastener, which is processed with a through-thread in the shape of a nut, into a hole provided in a molded thermoplastic resin member, and is fixed by heating and pressurizing the fastener, wherein the fastener has a cylindrical body with a head having the same outer diameter as the diameter of the hole, a plug portion adjacent to the head and having numerous uneven grooves on the outer circumferential surface of the cylindrical body and having an outer diameter smaller than the outer diameter of the head, a small-diameter portion adjacent to the plug portion and provided on the outer circumferential surface of the cylindrical body and having an outer diameter smaller than the outer diameter of the plug portion, and a tip portion adjacent to the small-diameter portion and provided on the outer circumferential surface of the cylindrical body and having an outer diameter larger than the outer diameter of the small-diameter portion, wherein when the fastener is inserted into a hole provided in the molded thermoplastic resin member and the head of the fastener is heated and pressurized, the tip portion and the small-diameter portion of the fastener melt and fix to the bottom of the hole. [Effects of the Invention]

[0008] The present invention makes it possible to provide a fastener with a nut-shaped through-thread for fixing to a hole provided in a molded thermoplastic resin member, and a method for fixing the fastener. [Brief explanation of the drawing]

[0009] [Figure 1] A cross-sectional view of one side showing an example of a fastener to which the first embodiment of the present invention can be applied. [Figure 2] A cross-sectional view showing the shape of a molded product member to which the first embodiment can be applied. [Figure 3] This diagram shows the fastener temporarily placed in the hole of the molded product component. [Figure 4] A diagram showing the fastener fixed in the hole of the molded product component. [Modes for carrying out the invention]

[0010] Embodiments of this invention will be described in detail below with reference to the drawings. Figure 1 is a one-sided cross-sectional view showing a fastener 1 called an insert according to a first embodiment of the present invention. Specifically, this fastener 1 is provided with a short cylindrical body 2, a head 3 provided on the outer circumferential surface having an end face a, a plug body portion 4 provided on the outer circumferential surface and having knurling (recessed grooves), a small diameter portion 5, and a tip portion 6. Head 3 is machined to have the same outer diameter as the hole diameter of the molded thermoplastic resin component described later. The head is designed according to the size of the fastener, with "hole diameter of molded component ≥ outer diameter of head". This is to allow for changes in the design dimensions when necessary to remove air from inside the hole when the fastener is heated and pressurized into the hole. Therefore, the head may be made a predetermined value smaller than the hole diameter of the molded component depending on the size of the fastener.

[0011] The outer diameter of the plug body 4 is machined to be a predetermined value smaller than the outer diameter of the head. As will be explained in more detail later, this is done by designing the tip portion 6 and the small diameter portion 5 so that the molten thermoplastic resin does not flow into the head portion 3.

[0012] The main body 2 is provided with a through-thread female screw 7 from end face a to tip 6. Furthermore, the tip portion 6 is intended to provide the pull-out strength of the fastener from the hole, and can be made into various shapes depending on the size of the fastener.

[0013] The fastener 1 in this embodiment is machined to a precision of 1 / 100 mm. For example, the dimensions of the fastener 1 are as follows: overall length (from end face a to tip 6) is 11.00 mm, head 3 has an outer diameter of 6.00 mm and a length of 6.00 mm, plug body 4 has an outer diameter of 5.60 mm and a length of 4.00 mm, small diameter 5 has an outer diameter of 4.60 mm and a length of 0.50 mm, and tip 6 has an outer diameter of 5.20 mm and a length of 0.50 mm, all of which are machined to this size. The tip 6 is chamfered. The female thread 7 is machined to M4. In this embodiment, brass is used for the fastener 1, but other metals such as stainless steel, carbon steel, aluminum, and zinc may also be used.

[0014] Figure 2 is a cross-sectional view showing an example of the structure of a molded product member 11 made of thermoplastic resin. The molded product member 11 is formed by providing a hole 13 in a boss 12 and providing an end face b on the upper surface of the boss 12. The hole 13 has an inner diameter of 6.00 mm and a depth of 10.00 mm.

[0015] Next, we will explain the configuration of fastener 1 in more detail. As described above, the fastener 1 is provided with a plug portion 4, which serves as a guide when fitting it into the hole 13 provided in the molded product member 11 of thermosetting resin. Furthermore, in the present invention, the plug portion 4 of the fastener 1 does not cut the circumferential surface of the hole in the molded product member as in the conventional invention. Rather, as will be described in detail later, the tip portion 6 and the small diameter portion 5 melt the bottom of the hole 13 and embed themselves in the bottom of the hole and solidify. This is a completely novel approach that differs from the conventional idea of ​​forcibly fitting a fastener with an outer diameter larger than the inner diameter of the hole.

[0016] Next, in such a configuration, a method of fitting and fixing the fixture 1 into the hole 13 of the molded member 11 will be described. That is, this fitting and fixing method is to fit the fixture 1 into the hole 13 of the molded member 11 while heating and pressurizing it. First, the fixture 1 is supplied to the hole 13 of the molded member 11 by a parts feeder or the like. At that time, the plug body portion 4 of the fixture 1 serves as a guide and is temporarily placed in the hole 13 of the molded member 11.

[0017] As shown in FIG. 3, the tip of the tip portion 6 of the fixture 1 rides on the bottom of the hole 13. In this state, the fixture 1 is pressurized while being heated from above (in the drawing), and the tip portion 6 melts the bottom of the hole 13 of the hole 13 to allow the fixture 1 to enter the hole 13. That is, the melting of the resin at the bottom of the hole starts from the tip portion 6 by the heated fixture 1, and pressure is also applied to accelerate the melting. The melted resin at the bottom of the hole flows into the knurled circumferential surface of the plug body portion 4 via the small diameter portion 5 from the tip portion 6.

[0018] FIG. 4 shows the state after the fixture 1 has been heated and pressurized. The fixture 1 is fitted and fixed in the hole 13 of the molded member 11. The fixture 1 is pressurized and stopped until the entire length of the tip portion 6 + the small diameter portion 5, which is 1.00 mm, is buried in the bottom of the hole 13 of the hole 13 (predetermined position). As a result, the end face a of the fixture 1 and the end face b of the molded member 11 are flat and coincide in the same plane (predetermined position). Conversely, by heating and pressurizing until the end face a of the fixture 1 and the end face b of the molded member 11 are flat in the same plane (in the embodiment, 1.00 mm corresponding to the entire length of the tip portion 6 + the small diameter portion 5), the tip portion 6 and the small diameter portion 5 will be buried in the bottom of the hole 13. When the tip portion 6 and the small diameter portion 5 are buried in the bottom of the hole 13, the resin corresponding to the volume of that portion flows to the knurled circumferential surface of the plug body portion 4. As a result, as shown in FIG. 4, it is pushed up to approximately half of the knurled portion and solidifies (resin c).

[0019] In this way, the resin at the bottom of the hole 13 melted by the tip portion 6 and the small diameter portion 5 flows into the knurled circumferential surface of the plug body portion 4, and the tip portion 6 and the small diameter portion 5 are in a state of being buried in the bottom of the hole 13. The fastener 1 maintains tensile strength (pull-out strength) of the molded product member 11 into the hole 13 by the resin d that melts and solidifies between the tip portion 6 and the small diameter portion 5. Furthermore, the fastener 1 can also ensure torsional strength (rotational torque) by the resin c that flows into and solidifies on the knurled surface of the plug portion 4. In addition, since there is no expansion pressure from inside the hole 13 of the boss due to the insertion of the fastener 1 described above, it is possible to avoid cracks that sometimes occur on the upper part of the boss 12. Furthermore, it is thought that cracks due to aging deterioration of the boss 12 can also be avoided.

[0020] As described above, according to the embodiment of the invention, it is possible to provide a fastener having a through-thread processed into a nut shape for fixing to a hole provided in a molded thermoplastic resin member, and a method for fixing the fastener.

[0021] Furthermore, the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. The embodiments may also be combined as appropriate, and the combined effects can be obtained. Moreover, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the multiple disclosed constituent elements. For example, if several constituent elements are deleted from all the constituent elements shown in an embodiment, and the problem described in the section on the problem the invention aims to solve is solved and the effects described in the section on the effects of the invention are obtained, then the configuration with these deleted constituent elements can be extracted as an invention. The present invention is applicable to fasteners with an outer diameter of 30 mm or less. [Explanation of symbols]

[0022] 1... Fastener, 2... Main body, 3... Head, 4... Plug body, 5... Small diameter part, 6... Tip, 7... Female thread, 11... Molded part, 12... Boss, 13... Hole.

Claims

[Claim 1] A method for fixing a metal fastener having a cylindrical body with a nut-shaped through-thread, which is fixed by heating and pressurizing into a hole with a bottom provided in a molded thermoplastic resin component, A method for fixing a fastener, characterized in that when the fastener is inserted into a hole having the hole bottom, the fastener is heated and pressurized so that the tip of the fastener melts the hole bottom, the tip and a smaller diameter portion adjacent to the tip having a smaller outer diameter than the tip are embedded in the hole bottom, and as the tip and the smaller diameter portion are embedded in the hole bottom, the resin that is melted and extruded from the hole bottom flows into the circumferential surface of a plug body portion adjacent to the smaller diameter portion, which has a larger outer diameter than the smaller diameter portion and has numerous uneven grooves on its outer circumferential surface, and the molten resin hardens on the tip, the smaller diameter portion and the circumferential surface of the plug body portion, thereby fixing the fastener.

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