JPH0137275Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pipe joint used when connecting metal pipes whose inner surfaces are coated with synthetic resin.

For metal pipes used in pipelines for drinking water, chemicals, etc., internally coated metal pipes are generally used to prevent corrosion, and when connecting these internally coated metal pipes, the structure shown in Figure 1 is used. pipe fittings are widely used.

That is, 1 is an inner-coated metal tube whose inner surface is lined with a synthetic resin such as epoxy resin to form a lining layer 2 of a predetermined thickness, and 3 is a flange portion 4 that covers the end surface of the metal tube 1. The anti-corrosion core 3 is internally fitted to the end of the inner-coated metal tube 1 via a liquid packing to protect the end surface of the inner-coated metal tube 1 from fluid corrosion. As described above, the internally coated metal tube 1 with the tube end anti-corrosion core 3 fitted inside is connected by screwing a tapered female thread of a predetermined length on the outer peripheral surface of the end and the inner peripheral surface of the end. A structure in which a tapered male thread that is threaded into the tapered female thread of the joint body 5 consisting of the pipe end is screwed continuously up to the outer circumferential surface of the flange portion 4 of the pipe end anticorrosion core 3, and the connection is made by tightening both of these tapered female and male threads. It was hot.

By the way, according to the results measured by the inventor,
Due to the manufacturing tolerance of the male and female taper screws, the pipe joint with the above structure will not allow the end of the internally coated metal pipe 1 and the joint body 5 to connect when tightened at the same torque.
In the case of a 20A metal pipe, there is an error of ±2 peaks in the relative position with the tapered female thread part, and the larger the diameter of the metal pipe, the
It was confirmed that the error becomes large.

Due to the above-mentioned error, when connecting using a conventional pipe joint, the end face of the inner-coated metal pipe 1 into which the pipe end anti-corrosion core is fitted is usually located in the middle of the tapered female thread of the joint body 5. However, in some cases, the tapered female thread may be penetrated (dotted chain line in FIG. 1).

That is, in the case of the former (solid line in Figure 1), the tapered female threaded portion of the end of the joint body 5 that does not engage with the tapered male threaded portion of the end of the inner-coated metal tube 1 is exposed and comes into contact with the fluid. However, there was a drawback that corrosion at this portion was much faster than corrosion at the inner circumferential surface of the joint body 5. The latter (dotted chain line in Figure 1)
In this case, the tapered male thread at the end of the inner-coated metal tube 1 is exposed and comes into contact with the fluid, as in the former case, and corrodes, and in addition, the inner-coated metal tube 1
The fluid gradually infiltrates the liquid packing interposed between the end portion and the tube end anti-corrosion core 3, and the tube end anti-corrosion core 3 may eventually come off from the end of the inner-coated metal tube 1, or the tube may become damaged due to the water hammer phenomenon. There was a drawback that the end anti-corrosion core 3 came off and the end of the internally coated metal tube 1 was exposed and corroded due to contact with the fluid.

The present invention was developed in an attempt to eliminate the drawbacks of the above-mentioned screw-in type pipe joints, and it forms an inner flange with a tapered female thread on the inner circumferential surface of the end, and the inner circumferential surface in contact with this inner flange. The joint body is partially coated with a synthetic resin layer forming a female thread that is continuous with the tapered female thread of the inner flange, and the inner surface is composed of a synthetic resin layer having a tapered male thread threaded onto the outer peripheral surface of the end portion to be screwed into the tapered female thread. A cylindrical pipe end anti-corrosion core that is fitted into an end of a resin-coated metal pipe via a liquid packing and has a male thread continuous with the tapered male thread on the outer peripheral surface of a flange covering the end face of the metal pipe. The pipe joint is constructed such that the female thread of the synthetic resin layer and the male thread of the flange portion of the pipe end anticorrosion core are screwed together when connected.

The present invention will be explained below based on an embodiment shown in FIG.

In the drawings, reference numeral 11 denotes a joint body, and an inner flange 12 having a tapered female thread of a predetermined length is formed on the inner peripheral surface of the end portion of the joint body 11.
The inner circumferential surface in contact with the inner flange 12 is coated with a synthetic resin layer 13 made of, for example, epoxy resin or vinyl chloride, and the end of the synthetic resin layer 13 is provided with a tapered female thread threaded onto the inner flange 12. A continuous internal thread is formed.

Reference numeral 14 denotes a metal tube coated with a synthetic resin on the inner surface and having a tapered male thread threaded onto the outer circumferential surface of the end thereof to be screwed into the tapered female thread, and a cylindrical synthetic resin pipe is inserted into the end of the metal pipe 14 via a liquid packing An end anti-corrosion core 15 is fitted inside. On the outer circumferential surface of a flange portion 16 that extends to one end of the pipe end corrosion protection core 15 and protects the end surface of the metal pipe 14 from corrosion by fluid,
A male thread is formed that is continuous with the tapered male thread. Note that 17 is a synthetic resin layer coated on the inner peripheral surface of the metal tube 14 whose inner surface is coated with synthetic resin.

The joint body 11 of the pipe joint according to the present invention may be of any type as long as it can connect pipes, such as an elbow, a tee,
It can be applied to any object such as a cloth.

In addition, in this embodiment, a pipe joint for connecting inner-coated metal pipes has been described, but the invention is not limited to this. When connecting metal pipes coated on both the inner and outer surfaces, the joint body 11 is attached to the outer surface of the inner diameter pipe. is the same as or slightly smaller in diameter than the outer diameter of the joint body 11, and an outer synthetic resin coating layer is formed whose end face protrudes from the end face of the joint body, and the inner surface of the protruding outer synthetic resin coating layer and the outer coating layer of the coated metal tube It is optional to change the design such that a gasket such as an O-ring can be inserted between the two.

When a metal pipe coated with synthetic resin on the inner surface is connected using the pipe joint according to the present invention constructed as described above, the inner thread is formed on the female thread formed at the end of the synthetic resin layer coated on the inner surface of the joint body. The external thread formed on the outer periphery of the flange of the pipe end anti-corrosion core that is fitted internally into the end of the coated metal pipe will be screwed together, and any fluid flowing inside the pipe will not flow through the joint body or the inner surface of the synthetic resin coated metal pipe. No contact with metal parts,
There is no corrosion of metal parts due to fluid.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a main part showing an embodiment of a conventional pipe joint, and FIG. 2 is an enlarged cross-sectional view of a main part showing an embodiment of a pipe joint according to the present invention. 11 is a joint body, 12 is an inner flange, 13 and 17 are synthetic resin layers, 14 is an inner surface of a metal tube coated with synthetic resin, 15
16 is the pipe end anticorrosive core, and 16 is the flange.

Claims (1)

[Scope of utility model registration request] An inner flange with a tapered female thread is formed on the inner circumferential surface of the end part, and the inner circumferential surface in contact with the inner flange is partially coated with a synthetic resin layer having a female thread continuous with the tapered female thread of the inner flange. a joint body consisting of a joint body; and a metal tube which is internally fitted via a liquid packing onto an end of a metal tube whose inner surface is coated with a synthetic resin, the inner surface of which has a tapered male thread threaded onto the outer peripheral surface of the end portion to be screwed into the tapered female thread. a cylindrical pipe end anti-corrosion core having a male thread continuous with the tapered male thread formed on the outer circumferential surface of the flange covering the end face, the tip surface of the flange of the pipe end anti-corrosion core being at least on the inner circumferential surface of the joint body; A pipe joint characterized by being screwed into a female threaded portion of a coated synthetic resin layer.