JPS61241130A - Clamping of plastic molded parts - Google Patents

Abstract

PURPOSE:To lessen the stress developed by clamping by a method wherein a plastic molded part and another part are clamped with a bolt each other through flexible material. CONSTITUTION:At the clamping portion between a polycarbonate windshield and an ABS resin cowling, the windshield 1 and the cowling 2 are clamped together by a clamping bolt 4, which pierces through clamping holes 3 and 3' respectively bored on the windshield 1 and on the cowling 2. In addition, annular gaskets 5, which are made of synthetic rubber and the outside diameter of each of which is the dimension suitable for the outer diameter of the clamping bolt and the thickness of each of which is 3mm, are interposed on the part surface 1a of the windshield 1 and on the part surface 2a of the cowing 2. Further, an M-4 bolt 4 is clamped through metal washers 6 by the tightening torque of 15 kg.cm. The tensile strain on the surface of the polycarbonate windshield 1 clamped as described above is as small as 600mum. As a result of the investigation of the change on the clamped portion with time by the dripping and coating of gasoline, thinner and the like, no change such as the generation of crack or the like has been shown even after 30 days.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of fastening a plastic molded part and another part using fastening bolts.

[Prior Art] Plastic products are used in various fields because they have characteristics such as light weight, impact resistance, and easy processability. They may be used alone as molded products, but they are also often used as molded parts by being glued or fastened to other parts.In such plastic molded parts, polycarbonate molded parts have a tolerant polarity. Because the molecular structure has a chain of groups and dioxy groups, the intermolecular attraction is very strong, and the mechanical properties, thermal stability,
It is well known that it is one of the few engineering plastics that has good electrical properties. In particular, the spectral transmittance is at wavelength 300.
It is 90% or more in the visible part of 0 mg or more, and has excellent transparency.

Due to these excellent properties, polycarbonate molded products are
From the standpoint of use as a transparent member that requires impact resistance, for example, windshields of two-wheeled vehicles, windows, doors, and partitions of buildings, and housings for OA equipment.

It is widely used in fields such as safety glasses and various optical glasses, and recently there has been an increase in demand for it as a transparent material in place of glass.

Although polycarbonate can be molded by extrusion, compression, powder molding, etc., polycarbonate is generally molded by injection molding of dry pellets, and various molded parts and molded parts are obtained. Some of these molded members and molded parts are used alone, but in many cases they are used by being fastened to other members with a fastening device or bonded with an adhesive. When bonding with an adhesive, it is not easy to select the adhesive because the bonding surface of the polycarbonate molded part becomes cloudy and foams due to moisture in the atmosphere when the product is delivered. will be adopted. In the fastening method, when fastening is performed using fastening bolts, the fastening parts of the polycarbonate molded part and other parts are overlapped, and the fastening is carried out by, for example, tightening a bolt inserted into a fastening hole drilled in the part. The surfaces of the polycarbonate molded parts and other parts facing the overlapping surfaces are each fastened to bolts with metal washers interposed between them.

[Problems to be Solved by the Invention] In the injection molding of polycarbonate as described above, an important problem that occurs to polycarbonate molded parts is residual strain. Residual strain is also observed during the bending process. In addition, polycarbonate has a small cold claw, so even if residual strain occurs in the molded product, it will not cause dimensional changes such as deformation and alleviate the residual strain.
Over time, large stress may develop and cause cracks. This residual strain is caused by mechanical strain during injection molding, a part solidified on the cavity surface, and a molecular orientation strain that occurs at the fluid interface, that is, the weld part, and is caused by optimizing the injection molding conditions. Efforts have been made to reduce the distortion, but it is difficult to alleviate all the distortion.

It is generally known that when polycarbonate molded products have large residual strain, so-called chemical stress cracks such as bracing or cracking occur due to chemicals. Therefore, when a polycarbonate molded part and another part are fastened together using a fastening bolt with a metal washer interposed, if there is residual strain or distortion in the weld part in the polycarbonate molded part, the fastened part may be damaged even under weak fastening pressure conditions. A problem unique to polycarbonate molded parts is that they crack extremely easily when exposed to chemicals, gasoline, thinners, etc.

In particular, the use of metal washers tends to damage the surface of polycarbonate molded parts and other parts, and if the part has a curvature, the metal washer is difficult to change in proportion to the curvature, so the part is biased. There is also the problem that the fastening makes it easy for chemicals and the like to enter, and that it becomes biased and causes stress.

Therefore, at present, no suitable method has been found for fastening polycarbonate molded parts and other parts with fastening bolts, which can prevent chemical stress cracks in the fastened parts.

[Means for Solving the Problems] The present invention was made in view of the conventional problems as described above, and provides a method for fastening plastic molded parts, particularly polycarbonate molded parts, and other parts using fastening bolts. By fastening through flexible materials,
The purpose is to solve the above problems.

That is, the present invention relates to a method of fastening a plastic molded part and another part with a fastening bolt, which is characterized in that the fastening is performed with a flexible material interposed between the plastic molded part surface and/or the other part surface. This provides a method for fastening parts.

The present invention is particularly effective for plastic molded parts, such as polycarbonate, which are prone to residual strain during the molding process and which also cause chemical stress cracks due to chemicals.

In the present invention, it is preferable that the flexible material be a rubber-like material having 1 elasticity, but it is not necessarily limited to a rubber-like material, and any material having elasticity can be used. Examples of such flexible materials include natural rubber, butadiene rubber, butadiene styrene rubber, butadiene acrylonitrile rubber, butyl rubber, chloroprene rubber, imprene rubber, and urethane rubber.

Examples include synthetic rubbers such as fluororubber, silicone rubber, and sulfur-containing rubber, and synthetic resins such as polyacrylic acid, butyl polyacrylate, polyvinyl chloride, and polyvinyl acetate.

These flexible materials cover the polycarbonate molded part surface and/or
Alternatively, it is interposed between the surface of another component and the fastening bolt, and is fastened so that it adapts to the surface curvature of both parts, lowers the surface pressure on the part, and has the effect of relieving the fastening stress caused by fastening.

Therefore, if the hardness and thickness of the flexible material is large, it will not adapt to the curved surfaces of both parts and will not be effective.
Even if a flexible material such as crepe is firmly fastened with a fastening bolt, it may loosen over a long period of use, so it is preferable that the thickness be 1 to 5 mm. The flexible material is not limited to just one piece, and may be made of a combination of multiple pieces to achieve the same thickness.Also, there are no particular restrictions on its shape or outer diameter, but if the size is larger than necessary, it may cause damage. - When using a bonate molded part as a transparent member, it is not appropriate because it affects the transparent part, and if the dimensions are small, the effect of relieving the fastening stress cannot be obtained.The shape and external dimensions of the fastening bolt are It is desirable to be correspondingly so, so that it may also be a washer made of flexible material or a ring-shaped gasket made of flexible material.

The use of flexible materials in the present invention also has the effect of providing a liquid seal to the fastening holes drilled in the polycarbonate molded parts, preventing chemicals, gasoline, thinner, etc. from entering the holes. , it is possible to prevent the occurrence of chemical stress cracks from the pores.

The fastening device may be a normal fastening bolt, but it is preferable that the fastening torque be constant, and it is preferable to use a stepped bolt as such means. A flexible material is interposed between the fastening bolt and the surface of the polycarbonate molded part and/or another part to be fastened, but a metal washer or the like is further interposed on the flexible material surface on the fastening bolt side. In such a case, it is preferable in terms of uniformity of fastening stress on the surface of the polycarbonate molded part and the surface of other parts during fastening.

In the present invention, the polycarbonate molded parts include, as mentioned above, motorcycle windshields, military window and lighting lenses,
Partitions between windows and doors of buildings! ! ! Examples include parts molded by injection molding, injection compression molding, etc. for light weapon equipment bars, housings for OA equipment, hard hats, safety glasses, goggles, various optical members, and other parts.

The fastening method of the present invention has a remarkable effect on materials with poor chemical resistance such as polycarbonate molded parts, but it can also be used on other plastic molded parts such as polyacetal resin, polymethyl methacrylic resin, ABS resin,
It can also be applied to materials made of polyacetyl cellulose resin, polyvinyl chloride resin, polystyrene, etc. Of course, other parts may also be made of the various plastics mentioned above, or may be made of polycarbonate molded parts.

[Example] Hereinafter, a case where an example of the present invention is applied to a windshield of a two-wheeled vehicle will be described with reference to the drawings.

Embodiment 1 FIG. 1 is an enlarged cross-sectional view of a fastening portion between a polycarbonate windshield and an ABS resin cowling of a two-wheeled vehicle according to the fastening method of the present invention. In FIG. 1, the windshield l and the cowling 2 are Fastening holes 3 and 3' are bored therein, and fastening is performed by a fastening bolt 4 passed through the fastening holes. A ring-shaped gasket 5 is interposed on the component surface 1a of the windshield 1 and the cowling component surface 2a, which is made of synthetic rubber as a flexible material, has dimensions corresponding to the outer diameter of the fastening bolt, and has a thickness of 3 mm. Furthermore, an M-4 port 4 of a fastening bolt is fastened with a torque of 15 kg-c through a metal washer 6. The tensile strain on the surface of the polycarbonate windshield l thus fastened is 800 I.
When a small amount of gasoline, thinner, etc. was applied dropwise to the surface and the change over time was investigated at room temperature, no changes such as cracks were observed even after 30 days.

Examples 2-3 2 and 3 follow the fastening method of the present invention.

FIG. 2 is an enlarged sectional view of another fastening method for fastening a polycarbonate windshield of a two-wheeled vehicle to an ABS resin cowling. In FIG. A similar gasket 5 is interposed only on the component surface 1a of the windshield 1 and fastened, and in FIG. It has been concluded. The tensile strain on the surface of the polycarbonate windshield l that was fastened in this way was 800.
JLm was small, and when we investigated the change in room temperature over time after applying gasoline, thinner, etc., no changes such as the occurrence of cracks were observed even after 30 days.

Comparative Example 1 FIG. 4 is an enlarged sectional view of a fastened portion where a polycarbonate windshield of a two-wheeled vehicle and an ABS resin cowling are fastened together using a conventional fastening method, and shows the parts surface 1a of the windshield 1 and the parts of the cowling 2. The M-4 port 4 is 15 kg as a fastening bolt with only a metal washer 6 interposed on the surface 2a.
It is fastened with a torque of -c+s. The tensile strain on the surface of the polycarbonate windshield 1 thus fastened was 3000 p, m, and cracks were observed to occur approximately 1 hour after application of gasoline, thinner, etc., in an investigation of changes in room temperature over time.

Example 4 In Example 1, the centers of the fastening hole 3 of the polycarbonate windshield 1 and the fastening hole 3'' of the ABS resin cowling 2 were shifted by about one layer when fastening.

The tensile strain on the surface of the polycarbonate windshield l thus fastened was 11,000 IL, but no changes such as the occurrence of cracks were observed even after 30 days in an investigation of changes in room temperature over time after application of gasoline, thinner, etc. There wasn't.

[Effects of the Invention] As mentioned above, the fastening method of the present invention has the effect of alleviating the surface pressure caused by fastening and has excellent liquid sealing properties, and has the disadvantage of chemical resistance under fastening stress such as polycarbonate molded parts. This method has been found to be extremely effective as a method for fastening plastic molded parts made of materials with .

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a fastening portion between a polycarbonate windshield and an ABS4#l resin cowling of a two-wheeled vehicle according to Example 1 according to the fastening method of the present invention, and FIGS. Enlarged cross-sectional view of the fastened part according to the fastening method No. 3, No. 4
The figure shows an enlarged cross-sectional view of a fastening portion according to a conventional fastening method of Comparative Example 1. l...Polycarbonate windshield, 2...ABS resin cowling, 3.3゛...fastening hole, 4...fastening pole l-(M-4 bolt), 5...synthetic rubber Ring-shaped gasket, 6...Metal washer Clasp 1 Figure 2 Part 3

Claims (1)

[Claims] 1. In a method of fastening a plastic molded part and another part with a fastening bolt, the surface of the plastic molded part and/or
Or a method of fastening plastic molded parts, characterized by fastening the plastic molded parts with a flexible material interposed on the surface of another part. 2. The fastening method according to claim 1, wherein the plastic molded part is a polycarbonate molded part. 3. The fastening method according to claim 1, wherein the flexible material is a rubber material with a thickness of 1 to 5 mm.