JPS6030327A - Welding method of plastic hollow body - Google Patents

Abstract

PURPOSE:To provide the titled hollow body having high bonding strength by arranging a heating element in an external surrounding of the jointed surface of a pair of synthetic resin constituent parts in an opposed position and melting and jointing the constituent parts with a gas heated by the heating element and caused to be sucked into the parts. CONSTITUTION:A pair of synthetic resin constituent parts are attached inside the cavities 7A and 8A of a pair of retaining mold 7 and 8 provided in the upper and lower parts, opposed to each other in such a manner that the jointed surfaces 2A and 2B of a pair of synthetic resin constituent parts are set in an opposed position and the open part 5 of the constituent part fits the suction part 13 of the retaining mold 7. The retaining mold sucks a gas from numerous perforations 7B and 8B to retain the constituent part. Next hydraulic cylinders 11 and 12 are actuated to shift the retaining molds 7 and 8 toward a heating element 9, so that the jointed surfaces 2A and 3A of the constituent part come in the proximity of up to 2-10mm. to the heating element. Then a gas in the interior 6 of the constituent part is sucked from a suction port 5 and is again introduced into the interior 6' of the constituent part through a tip 9C after being heated by the heater 9B of the heating element 9. After this process, the jointed surfaces 2A and 3B are heated into fusion and then the cylinders 11 and 12 are actuated to shift the retaining mold 7 and 8, thus pressing the jointed surfaces 2A and 3B into adhesion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for welding a hollow plastic body by heating, melting, and press-bonding the joining surfaces of a pair of plastic members.

Conventionally, hot plate welding has been known as a welding method for plastic hollow bodies in which the joint surfaces of a pair of plastic members are heated and melted and crimped. Because of the heating process, the heat conduction efficiency is poor and the time required for heating and melting is long, and the heat transfer efficiency to the joint surface is greatly influenced by the temperature of the outside air, resulting in uneven welding.

On the other hand, a hot air welding method is known as a welding method that improves heat conduction efficiency. The conventional hot air welding method places a nozzle that sprays hot air into the gap between the joining surfaces of a pair of plastic members, and blows hot air from a large number of small diameter nozzles to heat and melt the joining surfaces, which improves heat transfer efficiency. However, on the other hand, since the hot air is injected toward the contact surface from many small diameter nozzles, it is difficult to equalize the amount of heat of the hot air injected from each small diameter nozzle, and the welding condition may be uneven. There was a drawback that it was uniform. In addition, configuring many nozzles with the same diameter or configuring a hot air jet nozzle according to the shape of the joining surface of the welded parts itself requires extremely high precision, and the disadvantage is that the equipment itself is complicated and expensive. there were.

The present invention solves the above-mentioned drawbacks, and makes it possible to obtain a plastic hollow body with good heat conduction efficiency and excellent welding strength, and to transfer a uniform amount of heat to the joint surface using relatively simple equipment and processes. The object of the present invention is to provide a method for welding plastic hollow bodies that can uniformly heat and melt the joint surfaces.

The method for welding plastic hollow bodies according to the present invention basically includes a first step of arranging a pair of plastic members, a second step of heating and melting the joint surfaces of the plastic members, and a second step of heating and melting the joining surfaces of the plastic members. The third step consists of crimping the joint surfaces.

In view of the fact that in the conventional hot air welding method, the reason why uniform welding cannot be achieved is that when heating and melting the joint surface, hot air is sprayed at positive pressure from a large number of injection nozzles onto the joint surface, We focused on the fact that it is effective to generate a flow of hot air using negative pressure without using a large number of injection nozzles in order to uniformly contact the hot air over the entire circumference of the joint surface. That is, the present invention sucks the gas inside the plastic member, which is the member to be welded, through an opening provided in advance, so that the gas passes from the outer periphery of the joint surface through the gap between the joint surfaces and through the inside of the member. Generates a flow of gas that moves outward from the opening, and heats and melts the joint surface by contacting the joint surface with the gas heated by a heat source placed close to the outside of the joint surface. It is characterized by

Hereinafter, one embodiment of the present invention will be described based on the drawings.
In the figure, / is a plastic hollow body (hereinafter referred to as hollow body) obtained by the welding method according to the present invention, and the hollow body /
It is integrally constructed by welding a pair of plastic members (hereinafter referred to as "members") and 3 at their joint surfaces with 2 people and 3A. Also, G is the opening, S is the plastic member,
This is a flange formed on the opposing welded portions of the hollow body 3, and the opening G is formed so as to communicate between the hollow part B in the hollow body and the outside of the hollow body.

Next, a welding device will be explained based on an example.

FIG. 1 is a front view schematically showing the entire welding device, and FIGS. 3 and 3 are sectional views of essential parts of the welding device.

As shown in the drawing, the welding device includes a pair of holding molds 71g which are vertically opposed to each other and which hold a pair of members λ, 3 (3); Placed in the middle. Heat source body 9 that heats gas
The holding mold 71g and the heat source body 9 are mounted on the stand frame 1.
It is supported at 0. The upper and lower holding molds 71g are each hydraulic cylinders.

/, 2, and is configured to move freely forward and backward in the direction of the heat source body. In addition, members λ,
Capity 7 is recessed in a shape that is approximately the same as the external shape of 3.
A and gA, and a suction port 13 is formed in a part of the cavity 7A of the holding mold 7.

The suction port/3 is connected to a suction device lll.

In addition to the suction port/3, the holding mold 71g also includes a member 2.
A cooling unit Cj, 70 is formed to suck and hold 3 into the cavity 7h, gA, and a cooling unit Cj, 70 is formed to cool the member 3. Gas intake that can be removed? A, a heating part 9B that heats the introduced gas, and a tip part C that introduces the heated gas into the interior of the member λ, 3 are formed.

Next, a welding method will be explained based on Examples.

(ll) Fig. 2 shows the step of arranging a pair of members λ so that their joint surfaces 2A and 3A face each other, and Fig. 3 shows the arranged joint surfaces 2A and 3A.
A...? A are brought close to each other at an appropriate interval, and the bonding surface -A
, 3A is placed close to the outer periphery of the heat source body 9 and then heated and melted. FIG. 7 shows the step of crimping the heated and melted joint surfaces.

First, as shown in Figure 1, with the holding mold 70g fully open, two people hold a pair of parts 3 on their joint surfaces.

Cavity 7A1g of holding mold 71g so that 3A faces
After being installed in A, the members 3 are held in a large number of small holes 7 by suction from gA.

At this time, the opening S of the member is arranged so as to match the suction port of the holding mold. Next, the hydraulic cylinder //, /J
, move the holding mold 3 in the direction of the heat source, and
As shown in the figure, the joint surface of the upper part 3, 2A, ? A are placed close to each other at an appropriate interval, for example, 2 to 10 mm, and a heat source 9 is placed close to the joint surface, 2A, and the outer periphery of 3 people. At this time, the tip 9c of the heat source 9 is the joint surface, 2A
, 3A so that it does not enter the gap. Then, the suction device /ll is activated to suck the gas inside the member from the suction rotor of the holding mold 7. As a result, gas passes through the heating part 9B and the tip part qG from the gas intake qA of the heat source body W, passes through the gap from the outer periphery of the joint surfaces IA and 3h, passes through the inside of the member B1, and enters the opening S. A flow of gas is generated that moves from the suction port/11 to the outside.

Then, the gas heated in the heating part 9B formed in the heat source body Wa passes through a passage/S formed between the heat source body Wa and the holding mold 71g, and joins at the tip part 9G, and the joining surface 2A,
,,? A, and the heat of the contacting gas heats and melts the joining surfaces of members A and 3, 2A and 3A. Next, the hydraulic cylinder //, /, 2. is operated to move the holding mold λ, 3, and as shown in the figure, the heated and melted joint surfaces uA,
,? Crimp A and stop the suction device. After crimping, the parts 3 are cooled down using the cooling unit 7B, gB, and then the hydraulic cylinders //, /, 2 are operated to open the holding molds λ, 3, and the parts are sucked and held through the small holes 7A, gA. The first
The hollow body as shown in the figure is taken out by stopping the suction of the small holes 7h and gA.

According to the inventor's experiments, the joint surface, 2A, ? The temperature of the gas when passing through the gap A varies depending on the type of plastic ivy that makes up the members λ and 3, but it ranges from -30°C to θθ
℃ range. For example, in the case of high-density polyethylene, about 3
The time required for melting and softening at a suitable temperature of 0θ°C is about 73 seconds, and in the case of nylon, it is about 1 second. When the gas temperature is below J5θ℃, the time required to melt and soften the joint surfaces 2A and 3A becomes extremely long;
o ``C or more, the bonding surfaces λA, ', ?A tend to deteriorate,
The appearance of the joints is also poor.

The present invention can be applied as a method for welding various plastic hollow bodies made of thermoplastic plastics such as polyethylene, polypropylene, nylon, polystyrene, ABS resin, etc., used for tanks, bottles, ducts, and other mountain vehicle parts 1 and de-energizing parts. . In addition, in the present invention, when heating and melting the joint surface, it is necessary to generate a gas flow from the heat source to the joint surface by suctioning the gas inside the member through girder openings provided in advance in the member. ,at least(
7) One member requires an opening. The opening may be an inlet, an outlet, an air blower, etc. for the final product, but other openings may be closed in the final product by an appropriate means.

The present invention is not limited to the one embodiment described above, but includes many embodiments.

First, in the embodiment, a pair of members are attached to the holding mold 72g.

By moving the holding mold 71g after holding 3,
Joint surface JA...? Although the heat source was placed close to A,
A pair of members λ, 3 are held in advance at an appropriate interval,
Then, the heat source body may be moved and brought into close proximity. At this time, the heat source body 9 can also be configured in a split type. In addition, the holding molds 71g may be arranged not only to face each other in the vertical direction but also to face each other in the left and right directions. It is also possible to use known means such as actively fitting or engaging the 3 into the cavities 7A and IA of the holding mold 71g and pushing them out with a knock bottle or the like when taking them out. Also,
In the embodiment, if the gas supply passage is configured so that the gas discharged from the inside (g) of the member to the outside via the suction aiii is supplied again to the gas intake port qA of the heat source body W, the gas can be used once. By reusing the relatively high temperature gas, the energy required for heating can be saved. Also, in the example, is the gas heated part?
Although the gas was heated at point B, the tip portion C of the heat source body 9 is heated, and the gas can be heated by the tip portion C which has reached a high temperature.

According to the present invention, it is possible to easily obtain a hollow body that is complex and requires precision, such as threaded portions, ribs, and protrusions, due to the problems of mold removal and moldability of conventional molding molds. For example, injection molding and blow molding of various parts.

Since a hollow body can be obtained by forming the hollow body in advance by rotational molding or compression molding and welding a pair of members in an appropriate combination, the shape of the hollow body can be configured freely. In addition, according to the present invention, unlike conventional hot air welding, a large number of injection nozzles are used, and instead of using positive pressure to spray hot air onto the joint surface, a negative pressure generates a flow of hot air, so that the flow of hot air is uniformly applied to the joint surface. Heat is transmitted and uniform welding can be achieved. That is,
By suctioning the gas inside the member through an opening provided in the member in advance, the gas flows from the outer periphery of the joint surface, passes through the gap between the joint surfaces, and moves from the opening to the outside through the inside of the member. Since the gas generated and heated by a heat source placed close to the outside of the joint surface comes into contact with the joint surface, the joint surface can be uniformly heated and melted. In addition, in both conventional hot plate welding and hot air welding, members such as the heating plate and hot air jet nozzle are placed in the gap between the joint surfaces held opposite each other, so they are However, as shown in the embodiment of the present invention, the heat source is placed close to the outside of the abutment surface, as shown in the embodiment of the present invention. In addition, by arranging the tip of the heat source so that it does not enter the gap between the joint surfaces, the above problem can be solved, the process can be simplified, the apparatus can be simplified, and the molding cycle can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of a plastic hollow body obtained by the welding method according to the present invention, Fig. 2 is a schematic front view of the entire welding device, and Figs. 3 and 7 are the heating melting process and the crimping process. FIG. 2 is a cross-sectional view of main parts of the welding device. /Plastic hollow body, 3 plastic members, 2A
, 3A joint surface opening 7, g retention type heat source body patent applicant Kyoraku Co., Ltd.

Claims (1)

[Claims] A step of arranging a pair of plastic members so that their joining surfaces face each other at an appropriate interval, and arranging a heat source close to the outer periphery of the joining surfaces; A step of generating a gas flow from the heat source to the joint surface by suctioning the gas, and heating and melting the joint surface by the gas heated by the heat source coming into contact with the joint surface and passing into the inside of the member. A method for welding a hollow plastic body, comprising the steps of: crimping the melted joint surfaces.