JPS6337689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a socket for a plastic pipe, and more particularly to a method for molding a socket for a plastic pipe having a groove for inserting a sealing rubber ring on the inner surface.

As is well known, the shape of a plastic pipe socket is such that the opening has an inner diameter slightly larger than the outer circumference of the plastic pipe socket, and a rubber ring mounting groove is formed in the deep part of the opening with an enlarged inner diameter. At its deeper end, it is formed with an enlarged diameter section for insertion of the socket end, and a tapered section that reduces in diameter from this enlarged diameter section to a normal pipe diameter.

Therefore, the mold for forming the pipe socket is
Since it is impossible to pull out and release the mold, the core body and the outer mold are naturally splittable in the radial direction, and molding is carried out by pressing them into contact with the plastic tube from the radial direction. A type as shown in FIG. 1 or 2 is known.

The split mold X shown in Fig. 1 is a tube A divided by a pair of dividing planes B and B parallel to each other with respect to the diameter D of the pipe. The pipe shown in Fig. 2 is a pipe A divided by dividing planes B, which extend radially from the pipe axis A'. Then, the socket is formed by reducing the diameter of this, but in any of the above cases, when reducing the diameter of the split mold Since there is a gap between the dividing surfaces of the mold, the outer surface of the plastic tube is compressed into this gap, so-called bite marks H are formed along the dividing surface as shown in the figure, and the surface of the molded product is It became unsightly, and the socket was sometimes destroyed due to this bite.

In addition, as shown in Fig. 3, in order to form the rubber ring mounting groove G formed on the inner surface of the tube socket _A1 into a sharp shape with good molding accuracy, the outer mold X must be sufficiently tightened. It is necessary to bring A into close contact with the core E, but there is a problem in that if the outer mold is tightly tightened, the bite damage will become larger and the above-mentioned drawback will be significantly increased.

In view of the above-mentioned drawbacks, the present invention was made with the object of providing a method for molding a pipe socket for a plastic pipe in which no so-called bite damage occurs when a split mold is used for the outer mold. , the tube end of the plastic tube for forming the tube socket is fitted onto the outer peripheral surface of the core body for molding the inner surface of the tube socket, which can be reduced in diameter in the radial direction, and then an outer mold is formed to form the outer surface of the tube socket. A divided piece that is divided into four or more pieces in the circumferential direction, and the dividing plane is divided by a pair of planes parallel to the diameter, and the dividing plane is a parallel plane, and the dividing plane makes an intersecting angle. Among the outer mold pieces, which are made up of two types of split pieces with non-parallel faces, the diameter of the outer mold piece whose split faces are non-parallel is reduced, the outer periphery of the plastic tube is compressed, and then the split faces are parallel. This method is characterized by reducing the diameter of the remaining outer mold piece, which is a surface, and compressing the outer periphery of the plastic tube.

Next, the present invention will be explained using examples.

FIG. 4 and the following are explanatory diagrams showing the state of implementation of the present invention step by step.

In FIG. 4, the core body 1 is enlarged in diameter to form the inner surface of the tube socket, and the outer mold 2 is expanded to form a gap between the core body 1 and the surface of the core 1 so that the plastic tube 3 can be inserted sufficiently. A plastic tube 3, which has been enlarged in diameter and has been heated and made retroactive, is pushed out in the direction of arrow Y and fitted onto the core body 1.

Note that a heating device (not shown) is built into the core body 1 or the outer mold 2 as necessary.

As shown in Fig. 5, the outer mold 2 is divided into an even number of four or more (six in the case shown) parts whose inner diameter forms the outer surface of the plastic tube socket 3' when the diameter is reduced. The dividing surfaces 2A, 2A are
It is formed in a shape divided by a pair of planes parallel to each other with respect to the diameter 3D of the tube 3.

Therefore, the divided pieces 21 and 22 of the outer mold are divided into two types, 21 having parallel dividing surfaces and 22 having non-parallel dividing surfaces.

Next, in order to reduce the diameter of the outer mold 2 in order to mold the outer surface of the pipe socket, first, as shown in FIG. .

At this time, due to the pressing force of the divided piece 22, the material flows from the compressed part of the plastic tube 3 to the uncompressed part as shown by the arrow, and the uncompressed part rises slightly, and the divided part 22 after diameter reduction , 22, a space is formed in which the other divided pieces 21, 21 can slide in contact with each other without a gap.

Next, as shown in FIG.
The outer periphery of the plastic tube 3 is compressed by decreasing the diameter along the dividing plane between them.

At this time, there is no gap at all between the divided pieces 21, 21 of the outer mold and the other divided pieces 22, 22, and furthermore, the contact between the inner surface 21A of the divided pieces 21, 21 and the plastic tube 3 is limited to the above-mentioned material. Since it starts from the thicker part, there is no possibility that the plastic material will get caught between the contact surfaces of the divided pieces 21, 21.

Therefore, since the plastic tube 3 is molded into the shape of a socket between the core 1 and the outer mold 2 without being bitten by these molds, as shown in FIG. In order to increase the thickness of the plastic tube 3, it is also possible to apply a pressing force to the plastic tube 3 from the direction of the arrow M or N.

After forming the socket as shown above, plastic tube 3
The plastic tube is removed by cooling the tube, opening the outer mold, and reducing the diameter of the core.

As described above, in the case of reducing the diameter of an outer mold, this invention first reduces the diameter of the outer mold segment whose dividing surface is a non-parallel surface, and then reduces the diameter of the outer mold segment whose dividing surface is a parallel surface. Because of this structure, there is no biting of the plastic molded object into the dividing surface of the split die, and it is possible to mold a socket with an extremely smooth external shape, making it possible to make the quality of the socket high. In addition, since no bite damage occurs, it becomes possible to increase the thickness of the so-called plastic tube by pushing it into the mold, and it becomes possible to easily form the socket with high precision.

[Brief explanation of the drawing]

FIGS. 1 to 3 are explanatory diagrams of a conventional example, and FIGS. 4 to 8 are explanatory diagrams showing the state of implementation of the present invention. 1... Core body, 2... Outer mold, 2A... Divided surface of outer mold, 21, 22... Divided piece, 3... Plastic tube, 3'... Socket, 3D... Diameter.

Claims (1)

[Claims] 1. Fit the tube end of the plastic tube for forming the tube socket onto the outer peripheral surface of the core body for molding the inner surface of the tube socket, which can be reduced in diameter in the radial direction, and then A split piece that is a mold and is divided into an even number of 4 or more in the circumferential direction, and the split surfaces are parallel to the diameter, and the split surfaces are parallel surfaces. Among the outer mold pieces, which are made up of two types of split pieces each having a non-parallel surface having an intersecting angle, the diameter of the outer mold piece whose split surface is a non-parallel surface is reduced to compress the outer periphery of the plastic tube, and then the plastic tube is divided. A method for molding a socket for a plastic tube, which comprises reducing the diameter of the remaining outer mold piece having parallel surfaces to compress the outer periphery of the plastic tube.