JPS6144052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of expanding the diameter of the end of a thermoplastic resin pipe to form a tapered socket.

Conventionally, in order to connect thermoplastic resin pipes or joints, it has been done to expand the diameter of their ends and provide taper sockets, but conventional taper sockets have a taper socket at the tip of the main body P, as shown in Figure 8. Tapered part T
Since an enlarged taper socket S is formed through the socket, when another pipe is inserted into the socket and connected, the insertion end of this pipe enters too far into the taper part T, causing stress on the shoulder of the taper socket. There are increasing drawbacks.

JP-A-51-134769 proposes a method of forming a stopper part (vertical stepped surface) perpendicular to the tube axis at the back end of a tapered socket. A thickened part is provided over a predetermined width on the inner circumferential surface of the pipe, and this thickened part is first expanded in diameter into a tapered shape, and then this tapered surface is deformed to form a stopper part perpendicular to the pipe axis. , there was a problem that it was time-consuming. Moreover, this socket molding requires a mold having a special structure, and has the disadvantage that the mold apparatus becomes expensive.

The present invention eliminates the drawbacks of the conventional molding method as described above, and includes a cylindrical part at the end of a thermoplastic resin tube having an outer diameter approximately equal to the inner diameter of the tube, and a tapered part having an outer diameter larger than the cylindrical part. In order to form a tapered socket with an enlarged diameter by inserting a mold consisting of a stepped portion connected with a step that is substantially orthogonal to the pipe axis, the pipe end side is first placed on the inner circumferential surface of the pipe corresponding to the shoulder of the tapered socket. An annular protrusion is provided that has a steep slope towards the bottom and a gentle slope towards the back.
The tube end is heated and softened, the mold is inserted, and the cylindrical portion inverts the annular protrusion onto the outer circumferential surface of the tube, and the steep slope stands up almost perpendicular to the tube axis; A gentle slope is formed flush with the inner circumferential surface of the pipe at the part, and a stopper part is formed by bringing the stepped part of the mold into contact with a steep slope that stands up in an almost vertical state, and the tapered part of the mold is made to form a stopper part flush with the inner circumferential surface of the pipe. A method for molding a thermoplastic resin pipe into a socket, which is characterized by expanding the diameter of the pipe end on the distal end side to form a tapered socket.

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a state in which a thermoplastic resin pipe is molded and an annular protrusion is provided on its inner peripheral surface. In the figure, 1 is a die ring, and 2 is a mandrel, and the mandrel 2 has a tapered surface 3 that is gradually tapered toward its tip. Reference numeral 4 denotes an outer mold connected to the tip of the die ring 1, and a cooling jacket 41 for circulating cooling water is provided inside the outer mold 4. The synthetic resin pipe 5 extruded from between the die ring 1 and the mandrel 2 is cooled by contacting the outer mold 4, and is taken by a take-off machine (not shown) to be continuously molded. In this tube forming process, when the take-up speed is stopped or decelerated or the extrusion speed is increased, the excess thermoplastic resin rises along the tapered surface 3 of the mandrel 2, and the surface in contact with the tapered surface 3 becomes a gentle slope 61. Thus, an annular protrusion 6 whose raised end surface forms a steep slope 62 is formed. After cutting this synthetic resin pipe 5 at a predetermined position, a tapered socket is formed at the end of the pipe.

Although the above-mentioned molding method has been described in which an annular protrusion is provided on the inner circumferential surface of the tube at the same time as the thermoplastic resin tube is molded, the present invention is not limited to this.
After the thermoplastic resin tube is molded, an annular protrusion may be provided on the inner peripheral surface of the tube. For example, as shown in FIG. 2, a heat-softened thermoplastic synthetic resin 5
is pushed between the inner mold 8 and the outer mold 9, and an annular groove formed by a gentle slope 81 and a steep slope 82 provided in the inner mold 8 is filled with resin to form an annular protrusion 6 on the inner peripheral surface of the tube 5. It is also possible to provide one. At this time, it is preferable that the gentle slope 81 and the steep slope 82 be formed on surfaces that are substantially perpendicular to each other, and after opening the outer mold 9 while the tube 5 is in a softened state, It can be easily removed by pulling it out in the direction.

After the annular protrusion 6 is provided on the inner peripheral surface of the synthetic resin pipe 5 as described above, as shown in _{FIG .} Then, as shown in FIG. 4, a mold 10 for forming a taper socket is placed therein.
Insert. At this time, molding can be performed more easily by inserting the mold 10 while secondary heating the portion corresponding to the shoulder of the taper socket as shown by arrow _Y3 . This mold 10 includes a cylindrical part 11 having an outer shape comparable to the inner diameter of the tube 5, and a stepped part 1 having a diameter larger than that of the same part and forming a curved surface having a dogleg shape in cross section toward the rear.
2 and a tapered portion 13 that widens from this stepped portion.
and a taper 10a at the end of the columnar part 11.
The angle α between the circumferential surface 11b of the cylindrical portion and the lower slope 12a of the doglegged curved surface is set to α≦90°, and a flange 14 is provided at the end of the tapered portion 13.

By inserting the mold 10, the cylindrical portion 11 is formed into the tube 5.
As shown in FIG. 4, the annular protrusion 6 provided on the inner circumferential surface of the tube is inverted and raised, and the gentle slope 61 is flush with the original inner circumferential surface of the tube. At the same time, the steep slope 62 rises in a vertical state almost orthogonal to the tube axis, and at the same time, the curved surface of the mold step part 12 contacts the steep slope 62 of the annular protrusion 6, and the mold taper part 13 expands the diameter of the tube end. The end of the tube flares out.

Next, as shown in FIG. 5, the tube 5 or the mold 10 is surrounded by an outer mold 15, and the curved surface of the mold step 12 is brought into pressure contact with the steep slope 62 on the inner circumference of the tube. the flange 14 of. Then, the steep slope 62 standing vertically and substantially perpendicular to the tube axis becomes a curved surface recessed in a dogleg shape by the doglegged curved surface protruding from the mold step 12. Therefore, by removing the outer mold 15, cooling and solidifying it, and then removing the mold 10, a product as shown in FIG. 6 can be obtained. In this product, a tapered socket 16 is formed at the end of the tube 5, and a stopper part 17 having a dogleg-shaped curved surface facing forward is formed on the inner circumferential surface of the socket, and a protruding peripheral edge 18 facing forward is formed.

When the pipe 19 is inserted into the taper socket 16 and pressed, the end surface of the pipe 19 comes into contact with the protruding peripheral edge 18 at the inner part of the taper socket 16 and stops as shown in FIG. 5 and does not act to widen the inner part of the taper socket, and there is no risk of increasing stress in this part.

In addition, in the above embodiment, the cylindrical part 11 and the tapered part 1
Although the mold 10 is exemplified in which a stepped portion 12 having a curved surface with a doglegged cross section is formed at the boundary between the two and It is sufficient if a vertical surface is formed.

As described above, when forming a tapered socket in which the end of a synthetic resin pipe is enlarged in diameter, the inner circumferential surface of the pipe corresponding to the shoulder of the tapered socket is formed with a steep slope toward the pipe end and a deep slope. An annular protrusion with a gentle slope toward the end is provided, and when inserting a mold to expand the diameter of the tube end, this annular protrusion is reversely raised on the outer circumferential surface of the tube to create a gentle slope inside the tube. Since the tube is made flush with the circumferential surface and the steep slope serves as the stopper, it is possible to extremely easily mold the stopper that is substantially perpendicular to the tube axis using a mold having a simple structure. Further, since the annular protrusion is inverted and raised on the outer circumferential surface to form the shoulder of the tapered socket, a socket with good appearance and excellent strength can be obtained.

Therefore, when a pipe is inserted into this taper socket and connected, it will not be damaged due to the stress applied to the shoulder of the taper socket, and the end surface of the connecting pipe will be in close contact with the stopper part at the back end of the taper socket, creating a gap. Therefore, there is no risk of clogging the pipes.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIGS. 1 and 2 are longitudinal sectional views showing two types of embodiments in which protrusions are formed on the inner circumferential surface of a pipe, and FIG. 3 is a longitudinal sectional view showing an inner circumferential protrusion. Fig. 4 is a longitudinal sectional view of the pipe shown in Fig. 3 with a mold for forming a taper socket inserted into the pipe.
Figures 5 through 5 are longitudinal cross-sectional views showing the steps from molding to die cutting of the taper socket, Figure 6 is a vertical cross-sectional view showing the completed taper socket, and Figure 7 is a vertical cross-sectional view showing the pipe connected to the taper socket. , FIG. 8 is a longitudinal sectional view showing a conventional taper socket. 1... Dairing, 2... Mandrel, 3...
Gentle tapered surface, 4... Outer mold, 5... Thermoplastic resin pipe, 6... Annular protrusion, 61... Gentle slope, 62
... Steep slope, 7 ... End surface, 8 ... Inner mold for forming annular protrusion, 9 ... Outer mold, 10 ... Mold for forming socket, 1
DESCRIPTION OF SYMBOLS 1... Cylindrical part, 12... Step part, 13... Taper book, 15... Outer mold, 16... Taper socket, 1
7... Stopper part, 18... Projection edge, 19...
connecting pipe.

Claims (1)

[Claims] 1. A structure in which a cylindrical portion having an outer diameter approximately equal to the inner diameter of the tube and a tapered portion having an outer diameter larger than the cylindrical portion are connected at the end of a thermoplastic resin pipe by a stepped portion substantially orthogonal to the tube axis. When forming a tapered socket with an enlarged diameter by inserting a mold, an annular protrusion is formed in advance on the inner circumferential surface of the pipe corresponding to the shoulder of the taper socket, which forms a steep slope toward the tube end and a gentle slope toward the inner part. A section is provided, the tube end section is heated and softened, the mold is inserted, and the cylindrical section is used to invert and bulge the annular protrusion on the outer circumferential surface of the tube, and to make the steep slope substantially perpendicular to the tube axis. and forming a gentle slope flush with the inner circumferential surface of the pipe at the cylindrical part, and forming a stopper part by bringing the stepped part of the mold into contact with the steep slope rising almost vertically;
A method for molding a socket of a thermoplastic resin tube, which is characterized by expanding the diameter of the tube end on the distal side of the annular protrusion in a tapered section of a mold to form a tapered socket.