JPS62248623A - Joining method for thermoplastic pipes having diameters different from each other - Google Patents

Abstract

PURPOSE:To constitute the title method so that deformation of a form is not generated by strengthening joining force between a first and second pipes, by joining the first and second pipes through weld to each other by starting fusion by bringing the top of a protrusion of the first pipe into contact with the inside of the second pipe at the time of a rotation of the first pipe. CONSTITUTION:A first pipe 1 is turned at high speed over the tip of which a second pipe 2 is fitted in a state wherein the second pipe doesn't turn. The inside of the second pipe 2 comes into contact with the top of a protrusion 6, to begin with, frictional heat is generated on a contacting part and fusion starts from this part. First contact is either linear or point contact. The diameter of the second pipe 2 is expanded slightly through pressing-in of the first pipe 1 and moved so as to wrap the protrusion 6 in the same. The major part of the protrusion 6 is fused and the fused part 3 flows in a gap between both the pipes l, 2 in a moving direction of the second pipe 2. In other words, the fused part 3 is dispersed so as to involve the same in a joint face. Thus the fused part 3 spreads over the joint face uniformly, a part of which forms a protrusion 7 by coming out through the tip of the second pipe 2.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for joining thermoplastic pipes of different diameters.

<Prior art> Spin welding is known as a method for connecting two types of thermoplastic molded products (for example,
``Plastic Reader,'' published by the Japan Revised 9th Edition, edited by Osaka Municipal Industrial Research Institute, Plastic Reader Editorial Committee, and Plastics Technology Association, page 246).

In this method, one molded product is fixed, the other molded product is rotated at high speed, the two molded products are brought into contact, and the contact surfaces are melted by frictional heat to join the two molded products.

<Problems to be Solved by the Invention> When this spin welding method is applied to the connection of pipes of different diameters made of thermoplastic plastics, the following problems arise.

FIGS. 4(A) and 4(B) show an example of this, in which a first pipe l made of a thermoplastic plastic such as polypropylene is used.
This is an example in which the pipe 2 is connected to the second pipe 2, which is also made of polypropylene. Here, the outer diameter of the first pipe l is the second
This approximately corresponds to the inner diameter of the pipe 2. As shown, the first
When the pipe 1 is rotated and inserted into the second pipe 2, the outer peripheral surface of the first pipe 1 and the inner peripheral surface of the second pipe 2 come into contact, and frictional heat is generated on the contact surface. and melt it. 3
indicates the melted part. However, since the two are in surface contact, substantially the entire fitting portion of the first pipe 1 generates heat and becomes soft, making it impossible to maintain rotational force and deforming. If such deformation occurs, further insertion becomes impossible and adhesion becomes insufficient.

In addition to the improved crime example, if the first pipe 1 is fixed, the second pipe 2 is rotated, and the two are pressed together, the contact part of the second pipe 2 will heat up and soften, causing the rotation. The diameter expands due to centrifugal force, making it impossible to bond. Therefore, in order to connect two types of pipes of different diameters, it is necessary to rotate the small diameter pipe.

5(A) and 5(B) show another example of solving the above problem, in which a protruding portion 4 is formed near the inner tip of the second pipe 2, and while the first pipe 1 is rotated, the protruding portion 4 is When the first pipe 1 is inserted into the second pipe 2, the first pipe 1 first comes into line contact with the top of the protrusion 4, and melts from this part.

With such a structure, the strength of the first pipe 1 is maintained,
Although it can be inserted into the second pipe 2 by a predetermined dimension and the welding strength is sufficient, the molten part 3 protrudes from the tip of the first pipe 1, creating a protruding part 5 and narrowing the inner diameter of the pipe. In this case, another problem occurs, which is that it becomes blocked.

Means for Solving the Problems> The present invention was made in view of the above circumstances, and includes two types of pipes, both of which are made of thermoplastic plastic, a first pipe 1 having a small diameter, and a first pipe 1 having a small diameter. When joining the second pipe 2, which has an inner diameter approximately equal to the outer diameter of the first pipe 1, by spin welding, a protrusion 6 is formed near the tip of the outer circumferential surface of the first pipe 1. While rotating the first pipe 1, it is fitted into the second pipe 2, and the top of the protruding part 6 is brought into line contact or point contact with the inner surface of the second pipe 2, and the melting of the protruding part 6 causes the first and The second pipe 1.2 is welded and joined.

<Function> The function of the embodiment of the present invention will be explained based on FIGS. 2(A) to 2(D).

(A) The first pipe 1 is rotated at high speed, and the second pipe 2 is fitted into the tip thereof without rotating.

CB) The inner surface of the second pipe 2 first contacts the top of the protrusion 6, generates frictional heat in the contact area, and starts melting from this area. The first contact is a line contact or a point contact, not a surface contact. The diameter of the second pipe 2 expands slightly due to the pushing of the first pipe 1, and the second pipe 2 moves so as to wrap around the protrusion 6.

(C) Most of the protrusion 6 is melted, and the melted portion 3
flows through the gap between both pipes 1.2 in the direction of movement of the second pipe 2 (to the left in the figure). That is, the molten portion 3 is spread around the joint surface.

(D) Thus, the molten portion 3 spreads evenly over the joint surface, and a portion thereof comes out from the tip of the second pipe 2 to form a protruding portion 7.

<Example> In FIG. 1, 1.2 are the aforementioned first pipe and second pipe, respectively, and the outer diameter of the first pipe 1 is the same as that of the second pipe.
This approximately corresponds to the inner diameter of the pipe 2. Here, "approximately matching" includes the case where the outer diameter of the first pipe 1 is slightly larger than the inner diameter of the second pipe 2, and these pipes 1.2 are:
Made of thermoplastics such as polyethylene and polypropylene. 8 is a small diameter part formed at the tip of the first pipe 1 by several minutes, and is formed slightly smaller than the outer diameter of the other main part of the first pipe 1, and is difficult to fit into the second pipe 2. It's easy. 6 is the aforementioned protrusion formed near the tip of the first pipe 1, that is, following the small diameter portion 8;
It is formed on the circumference and slightly protrudes from the outer circumference of the first pipe l. When the first pipe 1 is rotated and the protrusion 6 is inserted into the second pipe 2, the top of the protrusion 6 is
First, it comes into linear contact with the inner surface of the second pipe 2 and starts melting.

FIG. 3 shows another embodiment in which a plurality of protrusions 6a, 6b
... are formed near the tip of the first pipe 1. In such a case, the tops of the protrusions 5a, 5b, . . . first come into contact with the inner surface of the second pipe 2 in a dotted manner, and begin to melt. In the illustrated example, the protrusions 6 and (ia, 5b...
In this example, the top portion is approximately spherical, but it may also be a corner.

The joining method according to the present invention is effective for joining, for example, a cap of a radiator reserve tank of an automobile and a pipe-like hose fixed to this camp.

<Effects of the Invention> According to the present invention, when two types of pipes of different diameters, both of which are made of thermoplastic plastic, are fit-joined using spin welding, a small pipe of zero diameter (the first pipe) is rotated, and forming a protrusion near the tip of the first pipe;
Upon contact with the inner surface of the second pipe, the protrusion starts to melt from line contact or point contact, and the melting of the protrusion causes the melted portion to spread between both pipes in the direction of movement of the second pipe. , is a thing. Therefore, (1) The centrifugal force generated in the first pipe and the opposing force of the second pipe create pressure on the contact surfaces of both pipes, and the joining force becomes strong. ■Since the melting of the first pipe and the second pipe starts from line contact or point contact at the protrusion,
The two pipes are mainly joined by melting the protrusions. This causes almost no deformation of the first and second pipes. (2) The melted portion from the protrusion moves in the direction of movement of the second pipe, that is, in the direction of the exit (tip) of the second pipe. Thereby, there is no risk that the molten portion will flow into the second pipe (in the opposite direction to the above-mentioned direction) and cause the protruding portion described in the conventional example, and therefore there is no risk that the molten portion will block the pipe.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the shapes of the first and second pipes in the embodiment of the present invention, Figs. 2 (A) to (D) are sectional views showing the above embodiment in the order of steps, and Fig. is a perspective view showing the shapes of the first and second pipes in other embodiments, and FIG. 4(A) (+3) and FIG. 5(A)(B) illustrate the problem to be solved by the present invention. FIG. 3 is a cross-sectional view for explaining the points. ■...First pipe 2...Second pipe 3.
...Melted part 5.7...Protruding part 6.5
a, 5b...Protrusion part 8...Small diameter part

Claims (1)

[Claims] (1) A first pipe made of thermoplastic plastic,
A method of rotating and fitting the first pipe into a second pipe made of thermoplastic plastic and having an inner diameter approximately equal to the outer diameter of the first pipe, and melting and joining the contact portion of both pipes by frictional heat. A protrusion is formed near the tip of the outer peripheral surface of the first pipe, and the top of the protrusion comes into line or point contact with the inner surface of the second pipe when the first pipe rotates. A method for joining thermoplastic plastic pipes of different diameters, characterized in that the first and second pipes are joined by welding by melting the protrusion.