JPH06126834A - Butt fusion method for thermoplastic resin moldings having tubular ends - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a butt fusion method capable of butt fusion welding a thermoplastic resin tube with sufficient fusion strength without causing beads inside the tubular end. In a butt fusion method, the tubular ends 1a, 1b of a thermoplastic resin molded product are heated by a heater 3 until they are melted, and then the melted tubular ends 1a, 1b are butted against each other at a predetermined pressure. , Both of the tubular ends 1a, 1b are formed in a shape inclining inwardly of the tubular ends 1a, 1b from the inner edge to the vicinity of the center of the wall thickness and from the vicinity of the center of the wall thickness to the shape perpendicular to the pipe axis At the time of heating, the portions from the inner edges of the tubular ends 1a and 1b to the vicinity of the central portion of the wall thickness are arranged to be farther from the heater 3 as they are closer to the inner edge side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of butt-melting thermoplastic resin molded products having tubular ends, such as pipes and joints, in which the molded product is formed of a material having a high melting point. If you are in the right way.

[0002]

2. Description of the Related Art A method of butt-fusing is known in which the tubular ends of a thermoplastic resin molded product are brought into contact with a heater and heated until they are melted, and then the fused tubular ends are butted against each other at a predetermined pressure and fused. (See, for example, German Patent Application Publication No. 2212055).

However, in this method, the tubular ends of both thermoplastic resin molded products are formed at right angles to the pipe axis, and the entire tubular ends are melted almost uniformly and then fused.
The fusion pressure resulted in the molten resin being extruded both inside and outside the tubular end, with beads being formed there. The bead generated inside has a disadvantage that it obstructs the flow of fluid, and therefore it is strongly desired to minimize it. In particular, in the case of a clean application, it becomes an accumulation part of water, which causes inconvenience.

In order to meet such a demand, a method as disclosed in Japanese Patent Laid-Open No. 1-110128 has been invented.

According to this method, the tubular end of the thermoplastic resin molded product is inclined inward so that when it is heated, it is gradually melted from the outer edge close to the heater, and when the tubular ends are butted, they are fused from the outer edge. I am trying. Then, the fusion pressure causes the molten resin to be extruded to the outside, and the bead hardly occurs inside.

By the way, when the synthetic resin molded product is made of a material having a high melting point and the heater has to be heated to 300 ° C. or higher, there is no heater coating material and the releasability deteriorates. Heater temperature is 4
It is customary to perform non-contact heating at a temperature of 00 degrees or more.

[0007]

However, in the above-mentioned conventional butt fusion method, when the temperature of the heater is raised to perform non-contact heating, the outer edge of the tubular end starts to melt and then the tubular end is melted. Until the inner edge is melted, the vicinity of the outer edge, which is close to the heater, is excessively heated and decomposed, and there is a problem that the required fusion strength may not be obtained.

In the present invention, attention is paid to the above problems, and it is possible to butt and fuse thermoplastic resin pipes with sufficient fusion strength while preventing beads from forming inside the tubular ends. The purpose is to provide a method of fusion welding.

[0009]

In order to achieve the above object, in the butt fusion method for a thermoplastic resin pipe having a tubular end of the present invention, the tubular end of the thermoplastic resin molded product is melted by a heater. After heating, the butt fusion method in which the melted tubular ends are butted against each other at a predetermined pressure and fused, at least one tubular end is inclined toward the inside of the tubular end from the inner edge to the vicinity of the center of the wall thickness. The outside from the vicinity of the central portion of the wall thickness is formed to be at right angles to the tube axis, and when heating, the portion from the inner edge of the tubular end to the vicinity of the central portion of the wall is further away from the heater as it is closer to the inner edge side.

[0010]

In the butt fusion welding method of the present invention, the tubular end heated by the heater first begins to melt in the portion outside the vicinity of the central portion of the wall thickness, and then from the outside in the portion inside the central portion of the wall thickness. It gradually begins to melt inward. Therefore, as compared with the conventional method in which the entire tubular end is gradually melted from the outer edge to the inner edge, the time from the start of melting of the outer edge to the completion of melting of the inner edge can be shortened, so that the outer edge is excessively heated. It can be prevented from disassembling.

Further, the tubular ends abutted at a predetermined pressure are
First of all, since the part outside the central part of the wall thickness is fused,
The molten resin near the outer edge is extruded to the outside of the tubular end by the fusion pressure at that time.

Further, the tubular end has the deepest melting depth in the outer portion than in the vicinity of the central portion of the wall thickness, and the melting depth gradually decreases from the central portion of the wall thickness to the inner edge toward the inner edge. Therefore, when the fusion pressure is continuously applied, the molten resin near the outer edge is further pushed out to the outside of the tubular end, and the inner edge side is gradually fused from the vicinity of the central portion of the wall thickness.

[0013]

Embodiments of the present invention will be described in detail below with reference to the drawings. First, the butt fusion welding method of the first embodiment will be described with reference to FIGS.

First, both the tubular ends 1a and 1b to be fusion-bonded are processed into a shape as shown in FIG. That is, the portion from the inner edge to the vicinity of the thickness center (a = 0.4t is preferable) is inclined to the inside of the tubular ends 1a and 1b, and the portion from the vicinity of the thickness center to the outside is perpendicular to the pipe axis. To

Next, the two tubular ends 1a and 1b are clamped by the clamps 2a and 2b, respectively, and the clamps 2a and 2b are clamped.
The heater 3 provided between b heats until it melts. At this time, as shown in FIG. 2, the portion from the inner edge to the vicinity of the center of the wall thickness is further away from the heater 3 as it is closer to the inner edge side, and the portion outside the vicinity of the center of the wall thickness is parallel to the heating surface of the heater 3. To do so.

Then, in the tubular ends 1a and 1b heated by the heater 3, first, the portion outside the vicinity of the central portion of the wall thickness begins to melt, and then the portion inside the portion near the central portion of the wall thickness is directed from the outside to the inside. And gradually begins to melt. Therefore, as compared with the conventional method in which the entire tubular end is gradually melted from the outer edge toward the inner edge, the time from the start of melting of the outer edge to the completion of melting of the inner edge can be shortened, so that the outer edge is excessively heated. It can be prevented from disassembling.

If the tubular ends 1a and 1b are made of a material having a high melting temperature such as PPS and the temperature of the heater 3 must be set to 400 ° C. or higher, the heater 3 and the tubular ends 1a and 1b can be set. A gap of about 1 mm is provided between the and, or they are brought into contact with each other without pressure.

Then, as shown in FIG. 3, the clamp 2
The heater 3 is removed from between a and 2b, and one or both clamps 2a and 2b are slid until the melted tubular ends 1a and 1b are butt-fused at a predetermined pressure.

At this time, the tubular ends 1a and 1b abutted with each other at a predetermined pressure are first fused on the outer side of the vicinity of the central portion of the wall thickness, so that the molten resin near the outer edge is tubular due to the fusion pressure at that time. It is extruded to the outside of the ends 1a and 1b.

Further, the tubular ends 1a and 1b have the deepest melting depths in the outer portion than in the vicinity of the central portion of the wall thickness, and the melting depth gradually decreases from the central portion of the wall thickness to the inner edge as the inner edge approaches. Therefore, when the fusion pressure is continuously applied, the molten resin near the outer edge is further pushed out to the outside of the tubular ends 1a and 1b, and the portion near the center of the wall thickness to the inner edge is gradually fused.

As described above, in the butt fusion method of this embodiment, the outer edges of the tubular ends 1a and 1b can be prevented from being excessively heated and decomposed during heating. Since the beads 4 can be extruded to the outside of the ends 1a and 1b, the bead 4 is minimally formed on the inner surface of the tubular ends 1a and 1b, while a sufficient welding area is ensured to provide a necessary welding strength. Obtainable.

Table 1 below shows the results of comparison of the height of the inner surface bead between the conventional method and the method of this embodiment (a = 0.4t).

[0023]

[Table 1] Next, a butt fusion welding method according to the second embodiment will be described with reference to FIGS.

In the method of this embodiment, the tubular ends 5a and 5b are processed and heated in the same manner as the butt fusion welding method of the first embodiment.
Although it is a method of fusion bonding, first, in the processing step, one tubular end 5a is inclined from the inner edge to the vicinity of the center of the wall thickness to the inside of the tube end 5a, and from the vicinity of the center of the wall thickness to the outside. This is different from the first embodiment in that the portion of is processed at a right angle to the tube axis, and the other tubular end 5b is processed at a right angle to the tube axis as a whole.

In the next heating step, the tubular end 5b, which is at a right angle to the tube axis, is moved closer to the inner edge side by the heater 7
It is different from the first embodiment in that it is heated away from.
That is, as shown in FIGS. 4 and 5, the heater 7 is
One heating surface is formed like a mortar. The diameter d of the bottom of the mortar is substantially the same as the inner diameter of the tubular end 5b, and the diameter D of the mortar is slightly larger than the outer diameter of the tubular end 5b. Furthermore, the angle θ of the inner surface of the mortar is 2
5 to 35 degrees is preferable. Heated tubular ends 5a, 5b
Gradually begins to melt from the outside in. The heater 7 may have a mortar-shaped portion of a cartridge type, or may be integrally formed by casting.

In the next fusion step, as in the first embodiment, the heater 7 is removed from between the clamps 6a and 6b, and the clamps 6a and 6b are welded until the melted tubular ends are butt-fused at a predetermined pressure. Slide one or both of 6b.

At this time, the tubular ends 5a and 5b abutted with each other at a predetermined pressure are first fused at the portions outside the vicinity of the central portion of the wall thickness, so that the molten resin near the outer edge is tubular due to the fusion pressure at that time. It is extruded to the outside of the ends 5a and 5b.

Further, in both of the tubular ends 5a, the melting depth of the outer portion is deepest from the vicinity of the central portion of the wall thickness, and the melting depth becomes gradually shallower from the central portion of the wall thickness to the inner edge toward the inner edge. However, since the melting depth of the tubular end 5b becomes gradually shallower as the whole is closer to the inner edge, if the fusion pressure is continuously applied, the molten resin near the outer edge will be further outside the tubular ends 5a and 5b. It is extruded, and the inner edge side is gradually fused from the vicinity of the center of the wall thickness.

As described above, in the butt fusion method of this embodiment, the outer edges of the tubular ends 5a and 5b can be prevented from being excessively heated and decomposed during heating, and the molten resin is tubular during fusion. Since the beads 8 can be extruded to the outside of the ends 5a and 5b, the bead 8 is minimally formed on the inner surfaces of the tubular ends 5a and 5b, and a sufficient welding area is ensured to provide a necessary welding strength. Obtainable. Further, in the butt fusion welding method according to the present embodiment, the workability is improved because the one tubular end 5b does not have to be provided with the inclined surface.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention. For example, in the second embodiment, one tubular end is processed so as to be perpendicular to the tube axis, but an outer surface may be provided with an outward inclination. In addition, in the second embodiment, a mortar-shaped heater was used in order to move away from the heater as the tubular end is closer to the inner edge side. However, the above object is achieved by providing the heater with a temperature gradient. Good.

[0031]

As described above, in the butt fusion method for the thermoplastic resin molded product having the tubular end of the present invention, the outer edge of the tubular end is not excessively heated and decomposed during heating. Since the molten resin can be extruded to the outside of the tubular end at the time of fusion, a sufficient fusion area is secured while ensuring a minimum fusion bead inside the tubular end. The effect that can be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional shape of a tubular end according to a first embodiment.

FIG. 2 is a sectional view showing a heated state of a tubular end in the first embodiment.

FIG. 3 is a sectional view showing a butt fusion state of tubular ends in the first embodiment.

FIG. 4 is a cross-sectional view showing a heated state of a tubular end in the second embodiment.

FIG. 5 is a side view showing a heater.

FIG. 6 is a sectional view showing a butt fusion state of tubular ends according to a second embodiment.

[Explanation of symbols]

 1a, 1b tubular end 3 heater 5a, 5b tubular end 7 heater

Claims (1)

[Claims] 1. A butt fusion method in which the tubular ends of a thermoplastic resin molded article are heated by a heater until they are melted, and then the fused tubular ends are abutted and fused at a predetermined pressure in at least one tubular shape. From the inner edge to the center of the wall thickness, the end is formed into a shape that is inclined inside the tubular end and from the center of the wall thickness to the outside at a right angle to the pipe axis. A butt fusion method for thermoplastic resin molded articles, characterized in that the closer to the inner edge side the portion up to the central portion is, the farther it is from the heater.