JPS5896511A - Method of molding receptacle of end of plastic pipe - Google Patents

Abstract

PURPOSE:To make the thickness of the pipe wall of a receptacle approximately equal to the thickness of the resin pipe, by inserting the synthetic resin pipe end between a core mold and an outer mold, and extending a horizontal section of a packing mounting groove thereby forming a semi-molded receptacle. CONSTITUTION:The heated synthetic resin pipe end (P) is inserted in a molding space between the core mold 4 and the outer mold 5 that comprise extended section forming mold parts 4a, 5a retained at 90-100 deg.C and mold parts 4b, 5b retained at 70-80 deg.C, and the semi-molded receptacle having an extended section 340 extended from the horizontal section 34 of the packing mounting groove is molded. Then after the outer mold 5 is removed, the mold 4 is removed forcibly against the tapered section of the receptacle enlarged section 2, and the extended section 340 is caused to shrink by heat. Then using another mold 6, the extended section 340 is molded into a tapered section 35 and an opening section 30, and after a packing mounting groove section 300 is molded, the outer mold 61 is removed, and the diameter of a mold part 620 of the inner mold 62 under a rubber packing mounting groove 3 is reduced to forcibly remove the inner mold 62.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the method of molding a socket at the end of a plastic tube.

BACKGROUND ART As a method for molding a socket at the end of a plastic tube, it is known to heat the end of the plastic tube and press-fit a tongue (hereinafter referred to as a core mold) into the heated end.

When molding a socket with a backing groove, a core mold with an annular protrusion for forming the backing groove is used, but the deformation rate of plastic heated to a certain temperature is low. If the core mold is at a high speed, it exhibits elastic properties that restore it to its original dimensions, so that the core mold can be tightly press-fitted into the heated plastic tube end despite the presence of its annular protrusion, and thus Even sockets with rubber ring mounting grooves can be molded with excellent dimensional accuracy.

On the other hand, when removing the core mold, what is the temperature of the molded socket and the escape velocity of the core mold as described above? If properly selected, there will be an undercut rubber backing installation groove.

The core mold can be removed from the socket while keeping the rubber backing mounting groove in an elastic state that allows it to return to its original size and shape. It is.

By the way, as shown in FIG. 1, as a socket for a plastic pipe, there is a well-known socket which has a reverse tapered shape so as to make the socket part 2 deeper than the backing mounting groove 3, that is, the socket deeper. be.

According to this socket, it is possible to increase the rotation angle of the tip of the socket within the pocket, and it is possible to join the pipes using the so-called socket-button method with excellent flexibility.

However, if the forcible extraction method described above is used to manufacture this socket (hereinafter referred to as an improved socket), the rubber ring mounting groove part will not undergo forced deformation due to its own undercut as described above. Moreover, following this deformation, the rubber ring mounting groove is subjected to unreasonable deformation by the mold portion for molding the pocket, so that dimensional deformation of the rubber ring mounting groove and eventually damage are inevitable. Therefore, it is extremely difficult to apply the forcible extraction method to the improved socket shown in FIG.

The first invention according to this patent application provides a method for molding a socket at the end of a plastic pipe, which makes it possible to manufacture the above-mentioned improved socket by removing the core mold without reducing its diameter. an enlarged diameter portion whose diameter is expanded in a downwardly tapered shape after passing through the tapered portion;
In the method of molding a socket at the end of a plastic pipe, the socket has a backing mounting groove consisting of at least an ascending tapered section, a horizontal section, and a descending tapered section in front of the enlarged diameter section, and an opening connected to the descending tapered section. A semi-molded socket is formed by press-fitting the end of the plastic pipe into the core mold, and the core mold is inserted into the core mold from the semi-molded socket as described above. of the enlarged diameter part. This method is characterized in that the downwardly tapered portion is forcibly extracted, and then the extended portion is formed on the downwardly tapered portion of the backing mounting groove and the mouth portion.

The second invention according to the present patent application is the first invention, which includes:
The present invention provides a socket molding method for the end of a plastic pipe that improves the efficiency of molding the extended portion and ensures the thickness of the opening. The end of the plastic tube is press-fitted between the mold and the mold.

In this molding, the mold part that molds the extended shape part is kept at a higher temperature than the other mold parts, and after the molding, the outer mold is removed, and the core mold is replaced with the expanded diameter part. Then, under the residual heat, insert the extended shape part into the downward taper part of the backing mounting groove and the mouth part using a mold different from the above mold. This method is characterized by molding.

The main parts of the first invention are included in the second invention, and the second invention will be explained below, and then the first invention will be referred to.

Figure 1 shows an example of the shape of the socket formed according to the present invention, and shows an enlarged diameter part 2 whose diameter is expanded into a gentle downward taper shape through an ascending taper part 1, and a rubber ring mounting groove in front of the enlarged diameter part 2. 3, and a mouth portion 30 that connects to the rubber ring mounting groove, and the rubber ring mounting groove 3 includes a first ascending tapered portion 31, a first upwardly tapered portion 31,
horizontal part 32, second ascending teniper part 33, second horizontal part 34,
It is composed of a downwardly tapered portion 35.

The first ascending tapered part 31 and the first horizontal part 32 are omitted,
It is also possible to extend the enlarged diameter portion 2 to these portions, and hereinafter, the horizontal portion in the backing mounting groove refers to the second horizontal portion 34.

To carry out the present invention, first, as shown in FIG. 2A,
A heated plastic tube is inserted into the molding space between the core valley mold 4 and the outer mold 5 with a semi-molded socket having an extension shape 340 of the horizontal part 34 of the backing mounting groove in front of the horizontal part 34. (For example, a vinyl chloride pipe) is molded by press-fitting the end P.

In this case, the mold part 4a for molding the extended shape part 340
, 5a is kept at 90 to 100°C, and the temperature of mold parts 4b and 5b for molding other parts is kept at 70 to 80°C. This temperature of 70 to 806 C is a temperature that has been empirically established in order to achieve the predetermined purpose in the above-mentioned overexertion.

After forming the semi-formed socket, as shown in Fig. 2B, the outer mold 5 is
After demolding, the core mold 4 is immediately inserted into the socket enlarged diameter part 2.
Forcefully pull it out against the downward taper (reverse taper). The mold temperature of the part P1 other than the tip of the semi-formed socket is set at 70 to 80°C, which is suitable for forced removal, so the downwardly tapered enlarged diameter part 2 is suitable for forced removal. \Although,
Due to its elastic properties, it can hold the molded shape well.

The tip of the semi-molded socket, that is, the above-mentioned extended shape portion 3
Since the temperature of No. 40 is 90 to 100°C, it shrinks due to heat.

Immediately after demolding the core mold, as shown in FIG. 2, an extended portion is molded into the downwardly tapered portion 35 and the mouth portion 3o using a mold 6 different from the above. This molded part is
The mold part 4a at the stage of forming the semi-formed socket shown in FIG. 2A above.

5a, the temperature is as high as 9ON100'C, so it can be sufficiently molded at that temperature.

Therefore, the downwardly tapered portion 35 and the mouth portion 30 can be formed without reheating the extended portion.

In this shaping, it is desirable to simultaneously shape the groove portion 30CO excluding the downwardly tapered portion 35 of the backing mounting groove 30 and the mouth portion 30, as shown in FIG. 2C.

After molding the downward taper portion 35 and the mouth portion 3o, the outer mold 6
1 is removed from the mold, and then the inner mold is forcedly removed while the downward taper portion 35 and the mouth portion 30 are at the above-mentioned forced removal temperature, that is, about 70 to 80°C. This inner mold has smaller dimensions than the core mold described above, and even if it is a reduced diameter type, the disadvantages in terms of mold structure, cost, etc. are relatively small, so it is shown in Figure 2. Similarly, it is also possible to reduce the diameter of the mold portion 620 below the rubber ring mounting groove of the inner mold 62 and allow the inner mold 62 to escape.

The second invention according to this patent application has the above-mentioned configuration; on the other hand, in the first invention, an appropriate method may be used as long as a core mold is used for forming the semi-formed socket. The core mold is forcedly punched out in the same manner as in the second invention, and the extended portion after the forced punching can be formed into the downwardly tapered portion and the mouth portion by an appropriate method.

The method of molding the end of a plastic tube according to the present invention is as described above, and in the production of the improved socket as described above, it is necessary to forcefully remove Since this method can be applied, a low-cost non-reduced diameter core mold can be used for the large-sized core mold used for this molding. In addition, the rubber ring mounting groove is formed by reducing the diameter of the extended portion of the semi-formed socket, and in this molding stage, diameter expansion molding that involves thinning the pipe wall is eliminated, so the rubber ring mounting groove The tube wall thickness can also be made sufficiently thick.

In particular, in the second invention, the diameter expansion molding is performed by press-fitting the end of the plastic tube into the gap between the core mold and the outer mold, so the thickness of the gap is increased (the thickness of the plastic tube is increased). is the thickness of the plastic pipe), the wall thickness of the socket can be made equal to the wall thickness of the plastic pipe (y), and furthermore, since the extended portion is kept at a sufficiently high temperature during molding of the semi-formed socket,
There is an advantage that after the core mold is forcibly removed from the semi-forming socket, the extended portion can be molded directly without reheating.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing a known socket shape, Figure 2A,
FIG. B, FIG. 2C, and the second diagram are explanatory diagrams showing the working procedure of the method for molding a socket at the end of a plastic pipe according to the present invention. In the figure, P is the plastic pipe end, 1 is the ascending tapered part, 2 is the enlarged diameter part, 3 is the backing mounting groove, 33 is the ascending taper part, 34 is the horizontal part, 35 is the descending tapered part, 30 is the mouth part, 340 is an extended shape portion.了lΣ n dimension

Claims (2)

[Claims] (1) An enlarged diameter part whose diameter expands into a downwardly tapered shape via an ascending tapered part, a backing mounting groove consisting of at least an ascending taper part, a horizontal part, and a descending tapered part in front of the enlarged diameter part, and the descending tapered part. In the method of molding a socket having an opening connected to a plastic pipe end, a semi-formed socket having a shape in front of the horizontal part of the backing mounting groove as an extension of the horizontal part is molded into a plastic core mold. The pipe end is formed by press-fitting, and the core mold is forcefully removed from the semi-formed socket against the descending taper part of the enlarged diameter part, and then the extended part is inserted into the backing mounting groove. A method for molding a socket at the end of a plastic pipe, the method comprising molding the socket at the downwardly tapered part of the pipe and at the mouth part. (2) An enlarged diameter part whose diameter is expanded into a downwardly tapered shape after passing through an ascending tapered part, a backing mounting groove consisting of at least an ascending tapered part, a horizontal part, and a descending tapered part in front of the enlarged diameter part, and the descending tapered part. In the method of molding a socket having a lotus-shaped mouth part at the end of a plastic pipe, a half-formed socket with a part in front of the horizontal part of the backing mounting groove shaped as an extension of the horizontal part is molded into a core mold and an outer part. Molding is performed by press-fitting the end of the plastic tube between the mold and the mold, and in this molding, the mold part that molds the extended shape part is
The temperature is kept at a higher temperature than other mold parts, and after the above molding, the outer mold is demolded, and the core mold is forcefully extracted against the downwardly tapered part of the expanded diameter part, and then, A method for molding a socket at the end of a plastic pipe, comprising molding the extended portion into the downwardly tapered portion of the backing mounting groove and the mouth portion using a mold different from the mold under residual heat. .