JPH0376209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to improvements in joints of synthetic resin piping used in drainage pipes and the like.

[Prior art]

Conventionally, as this type of pipe joint, one shown in a half-sectional view in FIG. 4 is known. This joint connects an insertion tube 1 inserted into an expanded diameter socket 2 via a rubber ring 4 fitted in a groove 3 for fitting the rubber ring. Because there is a triangular step between the tip and the tip, there is a problem in that dirt, dirt, and other impurities accumulate in this area. Therefore, in order to solve this problem, a stopper ring 6 having a triangular cross section has been attached to the triangular step, but with this type of connection means, a stopper ring of a different size is attached for each different pipe diameter. It had to be prepared and ended up being expensive.

[Purpose of the invention]

The object of the present invention is to provide a method for manufacturing a pipe joint that is inexpensive to manufacture, can be easily manufactured, and does not create gaps or steps at the joint portion of the joint to prevent the accumulation of dirt and the like.

[Structure of the invention]

In order to achieve the above-mentioned object, in the present invention, a preliminary socket is formed at the end of a synthetic resin pipe with an enlarged step at a substantially right angle, and then this preliminary socket is heated and softened and placed in an outer mold. At the same time, an inner mold is inserted into the preliminary socket, the inner mold is held in close contact with the tip of the preliminary socket and the step, and the pressurized fluid is applied to the inner surface of the preliminary socket. , the preliminary socket is expanded until it comes into close contact with the outer mold to form an enlarged socket, and a groove for fitting a rubber ring is formed in the enlarged diameter socket.

〔Example〕

Next, an embodiment of the method for manufacturing a pipe joint of the present invention will be described.

First, as shown in FIG. 1, a preliminary socket 2 is formed at the end of a synthetic resin pipe 11.

By injection molding or by inserting a diameter expanding mold into the end of the tube 11, the inner periphery of the preliminary socket 12 is tapered from the end toward the back, and a step 13 is formed which will serve as a stopper for the insertion tube. The preform A is formed by forming a substantially right angle and chamfering the inner periphery 14 of the end face.

This preformed product A is, for example, a preliminary socket 12.
The inner diameter d ₁ of the end is slightly larger than the outer diameter of the insertion tube, and the inner diameter d ₂ of the inner part of the socket 12 is approximately the same as the outer diameter of the insertion tube.
The inner surface has a taper of d ₁ -d ₂ /l=1/50, the height d ₂ -d/2 of the step 13 is approximately the same as the thickness of the insertion tube, and the angle θ is approximately 90.6 degrees. It is preferable that the tube wall thickness of the preliminary socket 12 is equal to or greater than the tube wall thickness of the tube 11.

The thus formed preform A is blow molded as shown in FIG.

First, the preliminary socket 12 is heated to a temperature of 90° C. to 130° C. to soften it, and the inner mold 15 is press-fitted into the preliminary socket 12 to slightly expand the diameter of the preliminary socket 12. The outer mold 16 is closed, and a sealing material 17 such as a plate packing or an O-ring is interposed between the step 13 and the tip of the preliminary socket 12 and the inner mold 15 to keep the inside of the preliminary socket 12 airtight. do.

The outer mold 16 has a groove 16a for forming a groove for fitting a rubber ring and a step portion 1 for forming a substantially right-angled step.
6b, an air vent hole 16c, etc. are provided.

Then, approximately 10 kg/cm ² of pressurized fluid such as compressed air is injected from the air supply path 15a of the inner mold 15 through the air injection hole 18 until the preliminary socket 12 is in close contact with the outer mold. The product is expanded, cooled while maintaining pressure, and the mold is removed to complete blow molding.

When the insertion tube 19 is fitted to the enlarged diameter socket 2 formed in this way as shown in FIG. 3, it fully matches the step 13 of the enlarged diameter socket 2, and there is no gap or step on the mating surface, allowing insertion. The inner surface of the tube 19 and the inner surface of the tube 11 are flush with each other. In this case, the inner surface of the expanded diameter socket 2 is the insertion tube 1
The socket shoulder part 20, which is slightly larger than the outer diameter of the socket 9 and straight, and which is the outer surface of the enlarged diameter socket 2 and is most exposed to stresses such as tension and bending of the pipe, is thickened to increase strength.

In addition, in order to achieve high performance at low cost, the dimensions of the groove 21 for fitting the rubber ring are made small, and the width a of the rubber ring 22 is made small, and the inside diameter d ₃ of the rubber ring and the outside diameter d ₄ of the rubber ring are also made small. It is possible to keep the rate of thinning of the material small and improve dimensional accuracy. Furthermore, even if the insertion tube is deformed due to the smaller inner diameter d ₁ of the tip end of the socket, it will be difficult to insert it into the end face of the socket, so a slight chamfering process is applied to facilitate fitting.

〔Effect of the invention〕

As described above, in the present invention, the step that will become the stopper part is preformed at a substantially right angle, and then blow molded. Therefore, the stopper part of the socket can be easily made at a right angle at a low cost, and the height of the stopper part can be increased. can be made almost the same as the wall thickness of the insertion tube, so when used as a drainage conduit, there are no gaps or steps at the joints, so there is no accumulation of dirt, etc., and there is no obstruction to the flow. .

[Brief explanation of drawings]

Fig. 1 is a half sectional view of a preformed product before blow processing the pipe joint of the present invention, Fig. 2 is a sectional view of the main part showing the blow molded state, and Fig. 3 is a half sectional view of the finished product.
FIG. 4 is a half-sectional view showing an example of a conventional pipe joint. A is a preformed product, 2 is an expanded socket, 11 is a synthetic resin pipe, 12 is a preliminary socket, 13 is a step, 15 is an inner mold, 16 is an outer mold, 17 is a sealing material, and 18 is compressed air. The injection hole 21 is a groove for fitting a rubber ring.

Claims (1)

[Claims] 1. A preliminary socket is formed at the end of the synthetic resin pipe with an enlarged step at a substantially right angle, and then this preliminary socket is heated and softened and set in an outer mold, and an inner mold is placed inside the preliminary socket. After inserting the inner mold into close contact with the tip of the preliminary socket and the step and holding it airtight, pressurized fluid is applied to the inner surface of the preliminary socket, and the preliminary socket is brought into close contact with the outer mold. 1. A method for manufacturing a pipe joint, characterized in that a diameter-enlarged socket is formed by expanding the pipe joint until the diameter of the pipe joint is expanded, and a groove for fitting a rubber ring is formed in the diameter-expanded socket.