JPH0134137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a socket part of a plastic pipe, which constitutes a joint part of the pipe.

Plastic pipes, which are widely used in various types of piping, are commercially available in the form of fixed-length unit pipes, and the unit pipes are shaped so that they can be easily joined together.

In the case of rigid PVC pipes for water supply, one end of the pipe is cut off, and the other end of the pipe is cut off.
As shown in FIG. 1, the pipe 1 is bulged and expanded in diameter to form the socket part 1a.
, a shoulder part A forming an inclined step part, a sleeve part B having a substantially straight tube shape or widening to the rear, a loading part C covering a sealing rubber ring (not shown), and a tip part D having a slightly larger diameter. That is, the diameter of the portion on the back side from the loading portion C is larger than the diameter of the tip portion D. The cut end of the adjacent pipe 2 is inserted into the inner hole of this socket 1a and connected, but as mentioned above, the sleeve part B on the back side has a larger diameter than the tip part D. The feature is that the mutual bendability of the pipe connection part is large because of the

Note that the unit pipes 1 and 2 are made of a straight pipe material cut into a fixed length from a long pipe, and a shape of a socket part 1a is formed on one end of the workpiece. The present invention relates to a method for molding the same or a method for molding plastic joints having a similar joint shape.

By the way, as a conventional technique for forming a socket part having a large-diameter sleeve part in the deep part of this type, a technique described in Japanese Patent Application Laid-open No. 103916/1983 has been proposed; This is a method in which one end of a pipe material softened by heating is pushed from the side into the gap between the core and the outer mold. Explain.

First, the push die used in this method includes a core 3 that forms the inner circumference of the socket, a fixed outer mold 4 that forms the outer shape of the socket, and a pipe as a workpiece. The side end portion 5a of the material 5, which is formed into the pipe socket, is formed thickly, and this is because, for example, during extrusion molding of a long pipe,
With a pitch interval equal to the standard size L, the thickness of the peripheral wall t ₀
The side end portion 5a with a thicker wall thickness _t1 is molded at the same time, and thus the long pipe is
Each pipe material 5 is cut on one side of the side end portion 5a.

Next, in the molding process of the pipe material 5, the side end portion 5a is heated and softened, and then the pipe material 5 is pushed into the gap 6 between the core and the outer mold from the right side in FIG. This molds the socket.

In the molding method prior to the conventional molding method disclosed in JP-A-55-103916,
Since this method does not preliminarily form a thickening part on the side end part of the pipe material, the part becomes extremely thin when the diameter of the part is expanded by pushing, and as a result, the softened side end part has to reach a predetermined wall thickness. In the process of pushing an excessive amount of increased thickness into the gap between the core and the outer mold, there was a drawback that wrinkles were formed on the outer surface of the sleeve part, which was supposed to have a large diameter at the upper part of the pipe socket part that became the product. . The technology proposed in the above-mentioned Japanese Patent Application Laid-open No. 103916/1988 is such that the reduction in tube volume due to diameter expansion and bulge on the outer periphery of the core is compensated for in advance by thickening _t1 , so that the outer diameter of the core is increased during diameter expansion. The gap between the mold and the mold is made as small as possible to minimize the amount of pushing required to increase the thickness. However, in the conventional proposed technology in which a thickened portion is formed in advance at the tube end, when the thickened end is pushed between the core and the outer mold, the inclined diameter enlarged portion in the pushing gap is Because the sliding resistance is large, the heat-softened portion of the pipe that has not yet been inserted is likely to buckle.Therefore, there are significant restrictions on the heating conditions for the pipe material and the insulation conditions for the core and outer mold. As a result, there is a drawback that the processing yield becomes poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to create a plastic pipe receiver that does not cause wrinkles on the outer periphery of the expanded diameter molded part and does not buckle during molding. An object of the present invention is to provide a method for forming a mouth part.

The present invention will be described below based on an illustrated embodiment.

As shown in FIG. 3, the molding means of the embodiment includes an inner mold 6 forming the inner periphery of the socket, and a split mold 6 (usually halved or three-piece) forming the outer periphery of the socket. An outer mold 7 is used, and the outer mold 7 is
It is formed so that it can be floated from the inner mold 6 by an appropriate distance d in the open state, and as shown in the figure, the outer mold 7 is in a floating position.

Moreover, the side end portion 8a of the pipe material 8 to be processed is
The increased wall thickness t ₂ is 10 to 15% of the peripheral wall thickness t ₀
It is molded to the size of t ₀ × 1.10 to 1.15.

Thus, the molding of the socket portion of the pipe material 8 is carried out in accordance with the process sequence described below.

Heating and pressing process (1) The pipe side end portion 8a is heated to the softening point, and the inner mold and outer mold 7 are heated to 75 to 85°C and 65°C, respectively.
Heated and kept at ~80℃.

(2) When the outer mold 7 is opened in the state shown in the third figure, the pipe material 8 is pushed to the left in the drawing along the axis of the mold, so that the side end portion 8a fits into the mold of the inner mold 6. It slides and moves to the tip of the mold while being pushed and spread by the surface.

Closing Step The outer mold 7 is squeezed toward the circumferential surface of the inner mold 6 to the closed position, as shown in FIG. At this time, in order to prevent the outer mold 7 from biting the side end portion 8a, there are particularly irregularities on the mold surface between the inner and outer surfaces of the side end portion 8a and the mold surfaces of both molds 6 and 7. There is a slight void d' along the section.

Re-Pushing Step As shown in FIG. 5, the pipe material 8 is pressed and urged again in the axial direction for a required period of time, during which time the side end portion 8a fills the void between the mold surfaces. In this case, the tube may be pushed onto the pipe material from the rear end side, the front end side, or both the front end and the rear end.

Cooling removal process: After being left for a certain period of time after the re-insertion process, first,
The outer mold 7 is opened, and then the side end portion transformed into the socket portion is cooled to a predetermined temperature by water cooling or air cooling.

Thereafter, the pipe material processed into the unit pipe is removed from the inner mold 6.

As described above, according to the method of forming a plastic pipe socket part according to the present invention, the outer mold is kept open until the shaping of the inner surface of the socket part is completed in the heating and pressing process of the end part of the pipe material. So,
Buckling of the heated part of the pipe that has not been inserted into the mold is prevented.
In addition, the thickness has been increased in advance so that there is a slight void inside the inner and outer mold surfaces.
Since the pipe end where d' is formed is filled into the mold in the re-pushing process, no bulges (indicated by broken lines in Figure 1) occur near the inner end of the sleeve part B, and the inner and outer surfaces of the sleeve part B are No wrinkles. Similarly, there are advantages such as wrinkles do not occur in the loading section C and the wall thickness of the sleeve section B becomes stable.Furthermore, due to these factors, the heating conditions of the pipe material and the heat retention conditions of the core and outer mold can be changed. There are excellent effects such as the loosening of constraints on the process and, as a result, improved processing yields.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a unit pipe socket, Fig. 2 is a partial sectional view of a processing die and pipe material used in a conventional method of forming a socket, and Fig. 3 is a partial sectional view of a pipe material according to the present invention. FIGS. 4 and 5 are partial cross-sectional views of a processing die and pipe material used in a method of forming a plastic pipe socket part showing one embodiment.
FIG. _t0 ... Thickness of peripheral wall, _t2 ... Increased thickness, 1... Unit pipe, 1a... Socket part, 6... Inner mold, 7... Outer mold, 8... Pipe material, 8a... As end part side end part.

Claims (1)

[Claims] 1. In a method for shaping a plastic pipe socket in which the diameter of the back side from the rubber ring loading part for sealing the pipe connection part is larger than the diameter of the tip, the shaping processing means for the pipe socket includes: An inner mold forming the inner peripheral shape of the socket and an outer mold forming a split mold forming the outer peripheral shape of the socket are provided, and the end of the pipe material to be molded into the socket is The end of the pipe material is formed thicker than the thickness of the peripheral wall of the pipe material, and the end portion of the pipe material is heated and softened during the heating pressing process with the outer mold in an open state. After being driven along the outer surface of
In the closing step, the outer mold is squeezed toward the circumferential surface of the inner mold to close it, and is almost sandwiched between the inner and outer mold surfaces, and in the re-pushing step, the outer mold is closed in the direction of the axis. A method for molding a plastic pipe socket, characterized in that the inner and outer mold surfaces are tightly filled between the surfaces of the inner and outer molds which are pressed and biased into the closed state.