Fasteners and methods for securing fasteners

Abstract

A fastener that can be easily machined to be fixed to a hole provided in a molded member made of thermoplastic resin, and a method for fixing the fastener are provided. [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), and a tip 5. The tip 5 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 6 as a through thread from the end face a to the tip 5.

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 the 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 peripheral 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 on November 8, 2023, for a fixture in the shape of a nut with a through screw processed in a hole provided in a molded member of a thermoplastic resin.

[0004] However, the fixture with a through screw processed in the shape of a nut described in the above application has a problem that the cutting process is complicated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] As described above, the fastener with a nut-shaped through-thread for fixing into a hole in a molded thermoplastic resin component, for which an application was filed on November 8, 2023, had the problem of being difficult to machine. The object of this invention is to provide a fastener and a method for fixing the fastener that are easy to machine for fixing into a hole in a molded thermoplastic resin component. [Means for solving the problem]

[0007] Therefore, the present invention relates to a metal fastener with a through-thread processed into a nut shape, which is fixed by heating and pressurizing into 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 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, and a tip portion provided at the tip on the outer circumferential surface of the cylindrical body adjacent to the plug 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 hole diameter, a plug portion adjacent to the head 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, and a tip portion provided at the tip of the outer circumferential surface of the cylindrical body adjacent to the plug portion, and when the fastener is inserted into the hole provided in the molded thermoplastic resin member and the head of the fastener is heated and pressurized, the tip of the fastener melts the bottom of the hole, and the molten resin flows into the numerous uneven grooves on the outer circumferential surface of the plug portion and the threads of the through-thread and solidifies, thereby fixing the fastener in the hole. [Effects of the Invention]

[0008] The present invention makes it possible to provide a fastener that is easy to cut and fix to a hole provided in a molded thermoplastic resin component, 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), and a tip portion 5.

[0011] 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.

[0012] The outer diameter of the plug body 4 is machined to be a predetermined value smaller than the outer diameter of the head. This is done to prevent the thermoplastic resin melted from the tip 5 from flowing into the head 3, as will be explained in more detail later. The tip portion 5 is chamfered. The tip portion 5 is also used to melt the bottom of the hole in the molded thermoplastic resin component, which will be described later, and can be made into various shapes depending on the size of the fastener. For example, the tip portion may be made to have a smaller diameter than the outer diameter of the plug portion. The main body 2 is provided with a through-thread female screw 6 from end face a to tip 5.

[0013] The fastener 1 in this embodiment is machined to a precision of 1 / 100 mm. For example, the dimensions of fastener 1 are as follows: the total length (from end face a to tip 5) is 12.00 mm, the outer diameter of the head 3 is 6.00 mm and the length is 6.00 mm, and the outer diameter of the plug body 4 is 5.00 mm and the length is 6.00 mm, all machined to this size. The female thread 6 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, the fastener 1 of the present invention does not cut the circumferential surface of the hole in the molded product member as in the conventional method, but rather, as will be described in detail later, melts the bottom of the hole 13 from the tip portion 5 and embeds itself in the bottom of the hole and solidifies. 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. Another feature of this invention is that the molten resin from the tip 5 flows to the female thread 6 and solidifies on the threads, thereby maintaining the pull-out strength of the fastener 1 against the hole 13.

[0016] Next, in such a configuration, a method for fitting and fixing the fixture 1 into the hole 13 of the molded part member 11 will be described. That is, this fitting and fixing method involves pressurizing the fixture 1 while heating it and fitting it into the hole 13 of the molded part member 11. First, the fixture 1 is supplied to the hole 13 of the molded part 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 placed in a temporary state in the hole 13 of the molded part member 11.

[0017] As shown in FIG. 3, the tip portion 5 of the fixture 1 is placed 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 bottom of the hole 13 melts out from the tip portion 5, enabling the fixture 1 to enter the hole 13. That is, the melting of the resin at the bottom of the hole that contacts the knurled circumferential surface side and the female thread 6 side of the plug body portion 4 from the tip portion 5 starts due to the heated fixture 1, and pressure is also applied to accelerate the melting.

[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 part member 11. Since the total length of the fixture 1 is 12.00 mm and the depth of the hole 13 is 10.00 mm, the fixture 1 is pressurized until it reaches a position 2 mm (predetermined position) where it is buried. As a result, the end face a of the fixture 1 and the end face b of the molded part member 11 are flush and in the same plane (predetermined position). Conversely, by pressurizing while heating until the end face a of the fixture 1 and the end face b of the molded part member 11 are flat and in the same plane (in the embodiment, the difference between the total length of the fixture 1 of 12.00 mm and the depth of the hole 13 of 10.00 mm is 2.00 mm), the portion up to 2.00 mm from the tip portion 5 of the plug body portion 4 is buried in the bottom of the hole 13. When the portion up to 2.00 mm from the tip portion 5 of the plug body portion 4 is buried in the bottom of the hole 13, the resin corresponding to that volume flows to the knurled circumferential surface side of the plug body portion 4. As a result, as shown in FIG. 4, the resin d on the knurled circumferential surface is pushed up and solidifies. However, the resin c that has flowed and entered the female thread 6 side does not become a clean state as shown in the drawing, and it is inevitable in terms of structure that the resin filling the thread reduces the movable range of the M4 bolt.

[0019] In this way, the resin at the bottom of the hole 13, which has been melted by the plug portion 4 from the tip portion 5, flows into the knurled circumferential surface side of the plug portion 4 and also into the female thread 6 side, so that 2.00 mm from the tip portion 5 of the plug portion 4 is embedded 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 c that melts on the female thread 6 side, penetrates the threads, and hardens. Furthermore, the fastener 1 can also ensure torsional strength (rotational torque) by the resin d that penetrates and hardens on the knurled surface of the plug body 4. Furthermore, since there is no expansion pressure from inside the boss hole 13 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. In addition, it is thought that cracks due to aging deterioration of the boss 12 can also be avoided.

[0020] As described above, according to the embodiments of the invention, it is possible to provide a fastener that is easy to cut and fix 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... Tip, 6... 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 and a part of the plug body having numerous uneven grooves on its outer circumferential surface, which is provided adjacent to the tip, melt the hole bottom and fill it with the hole bottom, and the molten resin flows into the numerous uneven grooves on the outer circumferential surface of the plug body and the threads of the through screw and solidifies, thereby fixing the fastener.

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