JPH0378485B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixing device suitable for embedding and fixing in a molded article of thermoplastic synthetic resin, particularly polycarbonate. If a screw hole is formed in a synthetic resin molded member and a bolt or the like is screwed in to fix it, the screw hole can be easily opened when subjected to tension, torsion, vibration, or other external forces, or when the bolt or the like is repeatedly attached and detached. deformed or destroyed and become unusable. Therefore, a large number of uneven stripes are provided that protrude on the outer circumferential surface of the cylindrical body, and when embedded into the hole formed in the member, the uneven stripes and the synthetic resin bite into each other and become engaged, allowing bolts etc. A metal fastener has been proposed that can be stably fixed and can withstand repeated attachment and detachment. In order to fix such a fixing tool into a hole in a member made of thermoplastic synthetic resin, the fixing tool is passed with an electric current to generate electrical resistance heat or ultrasonic vibration is applied to generate frictional heat to soften the area around the hole. Furthermore, if the component is melted and embedded, if the component is made of a synthetic resin that tends to crack when heated and then cooled, such as polycarbonate, the synthetic resin that has flowed into the recesses of the uneven stripes will be particularly susceptible to damage. Tends to crack when cooled. This is because the uneven stripes are formed in a straight line, and stress is generated in one direction.When the synthetic resin that has bitten into the concave portions of the uneven stripes cracks, it immediately loosens or detaches from the member due to external forces such as tension. This causes the inconvenience of slipping out. As a countermeasure to this problem, Japanese Patent Application Laid-Open No. 50-85756 proposes a method of canceling out stress by providing multiple stages of uneven stripes inclining in one direction in the axial direction and making the inclination direction of the uneven strips of each stage opposite. However, since the stress caused by the uneven stripes in one step is aligned in one direction, cracks are likely to occur, and no improvement in tensile strength can be expected. In the present invention, a large number of uneven stripes are provided protruding from the outer peripheral surface of a cylindrical main body, and the synthetic resin around the hole is softened or melted and embedded in the hole of a molded product made of thermoplastic synthetic resin. This method eliminates the above-mentioned disadvantages of fixing devices that fix the materials by biting them into each other, and it is possible to use a member made of a thermoplastic synthetic resin molded product such as polycarbonate that is prone to cracking when cooled. The purpose of this device is to provide a fixing device that can be firmly and stably fixed. It is characterized by being formed in a curved shape so that the curved lines are inclined in opposite directions. When the uneven stripes are formed into such a shape, the stress generated when the synthetic resin that has flowed into the valleys of the uneven strips is cooled will be directed in slightly different directions along the curve, and will be different between the proximal end and the distal end. The directions intersect, so that stress is effectively dispersed and the proximal and distal sides cancel each other out to prevent cracking. Next, embodiments of the present invention will be described based on the drawings. The fixing device shown in FIGS. 1 and 2 is made to protrude onto the outer peripheral surface of a short cylindrical main body 1, and the tangential direction of the central part is parallel to the axis, and the proximal and distal sides are A large number of concave and convex strips 2 of an appropriate length are curved in such a way that the tangent line is inclined in the opposite direction.
is provided around the entire circumference, a plug 3 with a slightly larger diameter than the outer diameter is formed at the tip of the main body 1, and a female threaded hole 4 is provided passing through from the proximal end surface to the distal end surface, The valleys of the concavo-convex strips 2 are located on a circle whose diameter is slightly larger than the outer diameter of the main body 1. The fixing device shown in FIGS. 3 and 4 consists of two sets of appropriate lengths that protrude from the outer peripheral surface of a short cylindrical main body 11 and are curved in the same curved shape as in the previous embodiment. Concave and convex strips 12 and 13 are provided along the entire circumference at intervals, and a female threaded hole 14 is provided penetrating from the proximal end surface to the distal end surface, with a slight interval across the center of the main body 11. The concavo-convex strips 12 and 13 are curved in opposite directions, and their valleys are located on the outer diameter of the main body 11. The fixing tool shown in FIG. 5 has a large number of concavo-convex strips 22 that protrude from the outer peripheral surface of a short cylindrical main body 21 and are curved in the same curved shape as in the previous embodiment, extending over the entire circumference of the main body. 21, and a male threaded rod 23 is integrally formed at the proximal end thereof, and the valleys of the concavo-convex strips 22 are located on the outer diameter of the main body 21. In these embodiments, the uneven strips 2, 12, 1
Reference numerals 3 and 22 have triangular cross-sections, and the apexes of the convex portions are particularly sharp, and the entire members are made of a relatively hard metal such as carbon steel, stainless steel, or zinc. Further, depending on the purpose, an electrical connection terminal, a square shaft, etc. may be provided protruding from the base end. 6, 7, and 8 show an example of the work order for embedding and fixing the fasteners shown in FIGS. 3 and 4, in which a member 30 made of a thermoplastic synthetic resin molded product is molded. At this time, the tip of the main body 11 is fitted into the hole 31 formed in advance. The hole 31 is formed to have a diameter equal to the outer diameter of the main body 11 and a depth almost equal to the entire length of the main body 11, and is fitted into the hole 31 until the distal end surface of the uneven strip 12 on the distal side touches the entrance edge of the hole 31.
is placed on the center line of Next, the main body 11 is pushed into the hole 31 while applying ultrasonic vibration.
The synthetic resin around the main body 1 softens and melts due to frictional heat, allowing the uneven strips 12 and 13 to enter, and when the hole reaches the bottom and is stopped, the synthetic resin in a fluid state wraps around the main body 1 and melts the uneven strips 12 and 13. The fixing tool is fixed by cooling and hardening while filling the concave portion 13. The fastening tools of other embodiments are also pushed in and fixed in the same manner, but an electric current is passed through the fastening tool to generate electrical resistance heat, which softens the synthetic resin around the hole and presses it down with mechanical pressure. In some cases, the fixing tool is sufficiently heated in advance to soften it while being pushed in, or the periphery of the hole in the member is heated and softened and then pushed in to fix it. In this way, when a concave-convex strip is formed in a curved shape in which the tangential direction of the central part is parallel to the axis and the tangent line is inclined in the opposite direction toward the proximal and distal sides, the synthesis that flows into the trough is formed. When the resin cools, stress is generated in slightly different directions depending on the location along the curve, and at the same time, the directions cross between the proximal end and the distal end, so that stress is effectively dispersed without being concentrated. At the same time, the proximal end and the distal end act to offset each other, allowing embedding in the synthetic resin without causing cracks. Here, we will discuss the results of a tensile test between the fastener shown in FIGS. 3 and 4 of the present invention and the conventional fastener shown in FIG. The fixing devices are all made of brass, and have an axial length of 4.0 mm, a thread diameter of 8.4 mm, and an M6 x 1.0 female screw hole along the entire length.
Two sets of concave and convex stripes with a valley diameter of 7.8 mm and 25 peaks are provided at an interval of 1.5 mm across the center of the main body. The angle of inclination of the uneven stripes with respect to the axis is 30° at both ends in the product of the present invention, and 40° in the conventional product. On the other hand, as shown in Fig. 9A and B, a boss with a diameter of 16.0 mm and a height of 14.0 mm is provided at the center of the base with a diameter of 30 mm and a thickness of 3.0 mm, and a hole with a diameter of 8.0 mm and a depth of 14.0 mm is provided at the center of the boss. The base material was made of polycarbonate.
A fixing tool heated to 230 to 250°C was embedded in this hole so that the end surface was flush with the top surface of the boss, the bolt was completely screwed into the female threaded hole, and after the polycarbonate had hardened, the bolt was pulled to measure the tensile load. . Measurements were made five times each for the load when the base was fixed and the top surface of the boss was held down and the tensile fixing tool came off, and the load when the tension boss broke with the base fixed and the boss not restrained. Obtained the results in the table. The figures are in kgf.

[Table] From the test results, the product of the present invention has a higher pull-out load, that is, tensile strength, and a higher boss breaking load than the conventional product, so the effect of stress on the polycarbonate is small, and cracks do not occur or do not occur. It is assumed that even if As described above, the tangential direction of the central part is parallel to the axis, and the tangential lines are in opposite directions toward the proximal end and the distal end. According to the present invention, the synthetic resin is formed into a curved shape that is inclined to the side, by softening the periphery of the hole and pushing it into the hole of a member made of thermoplastic synthetic resin, thereby filling the concave portion of the uneven strip with the synthetic resin. In addition, when the convex part is inserted into the hole wall and fixed, when the synthetic resin that has flowed into the troughs of the uneven stripes cools, stress is generated in a slightly different direction depending on the location along the curve, and the stress changes from base to base. The directions of the end side and the distal end side intersect, so that stress is effectively dispersed without being concentrated, and the proximal end side and the distal end side act to cancel each other out. Therefore, it can be firmly and stably embedded into materials made of synthetic resins such as polycarbonate, which tend to crack when cooled, and even if the length of the uneven strips in the axial direction is shortened, it is comparable to conventional products. It has the advantage that the entire structure can be made short and compact because it has a high tensile strength.

[Brief explanation of drawings]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a front view showing a different embodiment, Fig. 4 is a plan view thereof, and Fig. 5 is a further different embodiment. Figures 6, 7, and 8 are explanatory diagrams showing the work order of embedding and fixation, and Figures 9A and B
FIG. 2 is a diagram illustrating a comparative test between a product of the present invention and a conventional product. 1, 11, 21...Main body, 2, 12, 13, 2
2... Concave and convex stripes.

Claims (1)

[Scope of Claims] 1. A large number of uneven stripes are provided protruding from the outer peripheral surface of a cylindrical body, and a synthetic resin for the periphery of the hole is softened or melted into a hole formed in a thermoplastic synthetic resin molded product. In a fixing tool that is embedded in the grooves and fixed by biting the uneven strips and the synthetic resin into each other,
The uneven stripes are formed in a curved shape such that the tangential direction of the central portion is parallel to the axis, and the tangential lines are inclined in opposite directions toward the proximal end and the distal end. Fastener. 2. The fixing device according to claim 1, wherein a female screw hole is provided passing through from the proximal end surface to the distal end surface of the main body. 3. The fixing tool according to claim 1, wherein a male threaded rod is provided protruding from the base end of the main body.