JPH04129733A - Terminal protective structure of resin coated metal pipe - Google Patents

Abstract

PURPOSE:To certainly protect a male screw part from rust or damage by coating the male screw part formed to the terminal of a metal pipe with the same resin as other part and utilizing the release slit formed to the resin layer at the time of use to remove the resin layer applied to the male screw part. CONSTITUTION:A male screw is cut in the outer periphery of the terminal of a metal pipe 10 such as a steel pipe to form a male screw part 12 and a protective jig 30 having a flanged cylndrical shape and composed of a synthetic resin is fitted in the end part of the metal pipe 10. A resin layer 20 composed of a vinyl chloride resin is applied and formed to the outer periphery of the metal pipe 10 containing the protective jig 30 and the male screw part 12 and a plurality of release slits 40-44 are formed to the outer surface of the resin layer 20. The release layer 20 is raised up from the release slit 42 using an electric knife and peeled off along the circumferencial slits 40, 44. When the same operation is carried out on both sides of the release slit 42, the resin layer 20 is cut open left and right to be peeled from the metal pipe 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a terminal protection structure for a resin-coated metal tube, and more specifically, a resin-coated metal tube that is used as a conduit or the like and has a male thread cut at the terminal for connection. The present invention relates to a terminal protection structure for protecting metal pipes from rust, etc. until they are installed.

[Conventional technology]

Resin-coated metal pipes are made by coating the outer periphery of metal pipes such as steel pipes with synthetic resin such as polyvinyl chloride, and have the advantage of being resistant to rust and having a good appearance. Widely used as pipes and fluid piping for water, gas, etc.

When using a resin-coated metal tube, a male thread is often cut at the end and the male thread is screwed into a female threaded pipe joint or a joint of a structural member. However, it is troublesome to machine a male thread on each end of the resin-coated metal pipe at the construction site, so in advance, at a manufacturing factory, etc. There is a problem in that the parts are susceptible to rust. Further, as rust progresses on the male threaded portion, it becomes difficult to connect it with a pipe joint or the like. Furthermore, if another object hits the male threaded portion during transportation or storage, the threads may be damaged, making it difficult to make a screw connection.

Therefore, it is necessary to protect the male threaded portion formed at the end of the resin-coated metal tube from rust and damage.

Conventionally, a method shown in FIG. 4 has been adopted as a method for protecting the male threaded portion of the terminal.

As shown in FIG. 4 (δ), after coating the entire outer periphery of the metal tube P with resin to form a resin layer C, the end of the metal tube P is machined with a male thread from above the resin layer C to form a male thread. form S. Then, as shown in Fig. 4 (bl), the male threaded part S with the exposed metal surface is covered with a terminal cap T made of synthetic resin or the like to protect the male threaded part S. When using a coated metal tube, the terminal cap T can be removed.

[Problem to be solved by the invention]

However, the conventional terminal protection structure for the resin-coated metal tube described above has a problem in that the metal tube P is not sufficiently protected.

That is, since the terminal cap T is simply placed over the male threaded portion S, moisture enters the gap between the terminal cap T and the male threaded portion S, and rust is likely to occur in the metal material. During transportation and storage of the resin-coated metal tube, the end cap T tends to come off, making it impossible to protect the male threaded portion S from rust and damage.

Therefore, the object of this invention is to solve the above-mentioned problems of the terminal protection structure of the conventional resin-coated metal tube, and to reliably protect the male end of the metal tube from rust and damage. The object of the present invention is to provide a terminal protection structure for a resin-coated metal tube that is easy to manufacture and handle.

[Means to solve the problem]

A terminal protection structure for a resin-coated metal tube according to the present invention that solves the above problems is a metal tube having a male tap cut at the terminal.
The outer periphery including the male threaded portion is coated with resin, and a peeling slit is formed at the boundary between the resin layer on the end side including the male threaded portion and the resin layer on the center side.

Metal pipes, like ordinary resin-coated metal pipes, are made of steel pipes and other metal materials.
Any resin can be used, such as vinyl chloride and other thermoplastic resins that are used in ordinary resin-coated metal pipes. As a method for coating the metal tube with resin, a method employed in the production of ordinary resin-coated metal tubes, such as a method of applying a heated and melted thermoplastic resin liquid to the outer periphery of the metal tube, is used.

Before the metal tube is coated with resin, a male thread is cut at the end thereof, and the entire outer periphery of the metal tube including the formed male threaded portion is coated with resin. Therefore, since the male threaded portion is covered with resin, it is not exposed to the outside at all. Note that if the male threaded portion is coated with a protective coating before being coated with resin, the male threaded portion can be better protected in addition to the protection provided by the resin.

Of the resin layers formed as described above, to peel off the resin layer on the end side at the boundary between the resin layer on the end side including the male threaded part and the other part of the metal tube, that is, the resin layer on the center side. A peeling slit is formed. The peeling slit may have a groove shape, such as a 7-shape or a U-shape, formed in the thickness direction from the outer surface of the resin layer, and may be cut more easily than the surrounding resin layer. As the means for forming the peeling slits, any means capable of forming groove-shaped slits in synthetic resin, such as a normal cutter or a heat cutter, can be used. The deeper the peeling slit is, the easier the peeling becomes, but in practical terms, it is preferable that the tip of the slit completely penetrate the resin layer and reach or not reach the metal tube.

When using a resin-coated metal tube, the peeling slit is formed in two areas: the area where the resin layer must be removed at the end to expose the male thread, and the area where the metal tube is left covered with the resin layer. Set the boundary line between in particular,
It may be aligned with the end of the male thread, it may be set slightly closer to the center than the end of the male thread, or it may be set slightly closer to the center than the end of the male thread, as long as it does not interfere with the function of the male thread. It is also possible to set some settings on the terminal side.

It is preferable to form the peeling slit in a circumferential shape over the entire circumference of the resin-coated metal tube to ensure separation between the resin layer on the terminal side and the resin layer on the center side. As long as separation is possible, part of the peeling slit may be interrupted or may be formed intermittently in the form of perforations.

If there is a peeling slit like the one above, the resin layer on the terminal side can be reliably separated from the resin layer on the center side, and the separated resin layer on the terminal side can be twisted off from the male thread part while keeping the cylindrical shape. However, in order to easily peel off the resin layer on the terminal side, in addition to the peeling slit, a
Furthermore, it is preferable to additionally form a peeling slit. Specifically, by forming a peeling slit that axially traverses the resin layer on the terminal side, the cylindrical resin layer can be cut and peeled off in the form of a band or strip. When the pipe diameter is large, a plurality of axial peeling slits may be provided at intervals in the circumferential direction. By providing a circumferential peeling slit, the resin layer can be divided into thin pieces. If a helical peeling slit is provided,
Ij! while the entire resin layer on the terminal side remains continuously connected!
! It can be peeled off in a zonal pattern.

In order to peel off and remove the resin layer on the terminal side using the peeling slit, a part of the resin layer on the terminal side may be lifted or peeled off using a suitable tool such as an electric knife or pliers.

A protective device can be attached to the end of the resin-coated metal tube. Protective equipment is made of synthetic resin or metal, and fits onto the inner periphery of the end of a metal tube, covering the end surface or inner periphery of the end, preventing the metal material in this area from being exposed, and preventing rust and damage. protect from If the protective equipment is attached to the end of the metal pipe before coating the metal pipe with resin, and the outer periphery of the protective equipment is coated with resin at the same time as the metal pipe, the protective equipment will be integrated with the metal pipe. There is no need to worry about the protective equipment coming off while handling resin-coated metal pipes.

If the protective equipment is coated with a resin, it is preferable to remove the protective equipment at the same time as peeling off the resin layer on the terminal side. For this purpose, if you connect the resin layer covering the metal tube and the resin layer covering the protective equipment and leave a connecting part, that is, a part that is not separated by the peeling slit, the resin layer on the terminal side The whole is peeled off and removed.

[For production]

If the male threaded part formed at the end of a resin-coated metal tube is covered with a resin layer, it should be protected from rust or damage from collision with other objects. I can do it. Since the resin layer on the male threaded portion can be formed simultaneously with the resin coating the entire outer periphery of the metal tube, the processing steps are not more complicated than in the past.

Next, if a peeling slit is formed at the boundary between the resin layer on the end side including the male thread part and the resin layer on the center side, when using the resin-coated metal tube, use the peeling slit as a cut. If you separate the resin layer on the terminal side and the resin layer on the center side,
The two can be easily separated, and by removing the separated end, the male threaded portion can be exposed.

[Embodiments] Next, embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 (al (bl) and Figure 2 show the terminal protection structure of a resin-coated metal tube.
A male thread portion 12 is formed by cutting a male thread on the outer periphery of the end of the wire.

A protector 30, which has a cylindrical shape with a flange and is made of synthetic resin or the like, is fitted to the end of the metal tube 10.

The protective device 30 is attached so that the cylindrical portion 32 at the tip fits into the inner periphery of the metal tube 10 and the collar portion 34 at the rear end abuts against the end surface of the metal tube 10. In the illustrated embodiment,
The entire protective device 30 has a cylindrical shape with a space in the center, but if the collar portion 34 of the protective device 30 is disc-shaped and the end face is closed, the inside of the metal tube 10 can be completely sealed.

Next, the metal tube 1 including the protector 30 and the male threaded portion 12 is
0 is coated with a resin layer 20 made of vinyl chloride resin or the like. In the illustrated embodiment, the external thread 1
Although the resin layer 20 is formed on the outer periphery of the threads of the male thread part 2, the resin layer 20 that covers the male thread part 12 may penetrate into the valleys of the thread threads of the male thread part 12.

When coating the outer periphery of the metal tube 10 with resin, a connector having a structure in which the protectors 30 are integrated back to back is used, and the metal tube 10 is connected to both ends of this connector to form a long continuous piece. By constructing 10 rows of metal tubes and continuously applying molten thermoplastic resin to the 10 rows of metal tubes, the resin coating work can be performed efficiently. The 10 rows of resin-coated metal tubes are cut at the center of the connector to obtain individual resin-coated metal tubes, and protectors 30 are attached to both ends of the resin-coated metal tubes. Become. Such a method is based on the patent application filed in 1986 by the inventors of the present application.
No. 2-70689 and the like.

A plurality of peeling slits 40 to 4 are provided on the outer surface of the resin layer 20.
4 is formed. First, the peeling slit 40 is formed in a circumferential manner over the entire circumference at a position slightly closer to the center than the male threaded portion 12 on the end side of the metal tube 10 . Therefore, the resin layer 20 is
The resin layer A on the center side and the resin layer B on the terminal side are separated. A peeling slit 42 extending in an axial direction orthogonal to the peeling slit 40 is provided in the resin layer B on the terminal side. Further, a circumferential peeling slit 44 connected to the end of the peeling slit 42 is formed at the boundary between the end of the metal tube 10, that is, the tip of the male threaded portion 12, and the protector 30. As shown in FIG. 1 (bl), this circumferential peeling slit 44 is not formed over the entire circumference, but has an interrupted part, and the resin layer 20 covering the male threaded part 12 protects the externally threaded part 12. It serves as a communication part 22 that connects the resin layer 20 covering the tool 30.The forming range of the peeling slit 44 may be about 1/2 to 3/4 of the circumference, and the remaining part becomes the communication part 22. .

The resin-coated metal tube is manufactured to have the above-described structure, and is transported, stored, and handled in this state.

Then, at the stage of using the resin-coated metal tube, the protective structure is removed to expose the male threaded portion 12. In Figure 1, use an electrician's knife or pliers to open the peeling slit 4.
2 to form a resin layer 20. The resin layer 20 is peeled off along the circumferential peeling slints 40, 44 on both sides. When the same operation is performed on both sides of the peeling slit 42, the resin layer 20 is cut left and right and peeled off from the metal tube 10. Since the peeling slit 40 is formed over the entire circumference, the resin layer A on the terminal side and the resin layer B on the center side
It is completely separated from the However, since a part of the peeling slit 44 is interrupted, the male screw 12
The side resin layer 20 and the resin layer 20 of the 30 protective devices remain connected.

As shown in FIG. 3, when the protective device 30 is pulled out from the end of the metal tube 10, the resin layer 20 covering the protective device 30,
Then, the resin layer 20 covering the male threaded portion 12 connected to this resin layer 20 through the communication portion 22 is removed as a whole. As a result, the male threaded portion 12 is exposed and can be connected to a joint or various structural members. The resin layer 20 left on the metal tube 10 at the center side of the peeling slit 40 can protect the metal tube 10 well. [Effects of the Invention] The resin coating according to the present invention described above According to the terminal protection structure for a metal tube, the male thread formed at the end of the metal tube is coated with the same resin as the other parts, and when used, the male thread is removed using a peeling slit formed in the resin layer. Since the resin layer covering the part is removed, the male thread part can be reliably protected from rust and damage, and the protection can be easily removed to expose the male thread part when in use.

In particular, since the male threaded portion can be coated with resin at the same time as other parts in the same process, the manufacturing process is not complicated and the male threaded portion can be protected extremely efficiently. If it is coated with resin, unlike conventional terminal caps, there will be no gaps between the terminal cap and the metal material, and the terminal cap will not come off during handling, so the protection performance for the male thread is much greater. improves.

In addition, as a means to release the protection of the male threaded part, it is only necessary to provide a peeling slit in the resin, so processing is simple and can be done in a short time.When in use, simply peel off the resin covering the male threaded part. Can be removed. Unless the peeling slit is peeled off with a tool or the like, the resin covering the male threaded portion will not come off, so there is no worry that the resin will peel off during handling such as transportation and storage.

[Brief explanation of drawings]

FIG. 1 (al (b)) shows an embodiment of the present invention;
Figure (a) is a perspective view, Figure 1 (b) is a perspective view with the previous bottom side facing up, Figure 2 is an enlarged sectional view, Figure 3 is a sectional view with protection released, Figure 4 (a) and (b) show the conventional example, and Fig. 4 (a) is a sectional view before installing the terminal cap.
Figure (bl is a sectional view of the installed state. 10...Metal tube 12...Male thread part 20...Resin layer 40...Peeling slit agent Patent attorney Takehiko Matsumoto

Claims (1)

[Claims] 1 The outer periphery of a metal tube with a male thread cut at its end, including the male thread, is coated with resin, and a peeling slit is formed at the boundary between the resin layer on the end side, including the male thread, and the resin layer on the center side. A terminal protection structure for a resin-coated metal tube.