JPH0231278B2 - KANTANMEN BOSEISHORIHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for anticorrosion treatment of the end surfaces of metal pipes such as water pipes and gas pipes.

[Prior Art and Problems] Conventionally, the inner circumferential surface of a metal pipe is coated with a synthetic resin such as nylon, polyethylene, vinyl chloride, etc. to prevent the inner circumferential surface from rusting. However, even with metal pipes whose inner peripheral surfaces are coated with synthetic resin, when cutting the metal pipes to an appropriate length in order to connect them to joints, elbows, etc., the cutting may cause damage. Metal skin is exposed on the end face of the pipe, and since the fluid flowing inside the pipe comes into contact with that part, the occurrence of rust is unavoidable. For this reason, water pipes were becoming a social problem in and of themselves, with rust getting into tap water, making it unhygienic and potentially harmful to the human body.

[Object and Structure of the Invention] The present invention has been made in view of the above, and is intended to effectively prevent rust on the end surface of a tube. In order to achieve this object, the present invention is a synthetic material in which the inner peripheral surface of a metal tube is coated with a cylindrical fitting member formed so that one end has a slightly smaller diameter and a flange portion is integrally formed at the larger diameter end. The synthetic resin is formed of a synthetic resin having a melting temperature similar to that of the resin, and the fitting member is press-fitted into the metal tube while rotating, thereby covering the outer circumferential surface of the fitting member and the inner circumferential surface of the metal tube. are fused by the frictional heat, and the flange portion is crimped onto the end surface of the metal tube.

[Example] In the figure, reference numeral 1 denotes a circular metal tube, and synthetic resins 2 and 3 are coated over the entire length on both the inner and outer peripheral surfaces of the metal tube.
(in this case nylon 12). Reference numeral 4 denotes a cylindrical fitting member whose outer peripheral surface is tapered and one end 4' has a small diameter, and a flange portion 5 is integrally formed at the larger diameter end. It is formed from a synthetic resin having a melting temperature similar to that of the synthetic resin 2 that coats the inner peripheral surface of the metal tube 1 (that is, preferably nylon 12, which is the same material as the synthetic resin coating 2). The synthetic resin 2 that covers the inner peripheral surface of the metal tube 1 may be made of various materials such as nylon 12, polyethylene, vinyl chloride resin, or polyester resin, but the fitting member 4 is preferably made of the same resin. Otherwise, resin materials with similar melting temperatures are selected and molded into a predetermined shape. The inner circumferential surface of the fitting member 4 has a large number of engaging pawls 6, 6, . . . formed at regular intervals in the shape of an internal gear.

However, when fitting the fitting member 4 to the metal tube 1, the metal tube 1 is fixed by an appropriate means such as a chuck, and the fitting member 4 is inserted into the tube end from its narrow diameter end 4'. The rotating shaft of an impact wrench, which has a spline groove formed on the outer periphery that engages with the engaging claws 6, 6, is inserted into the fitting member 4, and the fitting member 4 is press-fitted into the metal tube 1 while rotating. . In this way, frictional heat is generated between the outer circumferential surface of the fitting member 4 and the synthetic resin 2 covering the inner circumferential surface of the metal tube 1, and the mutual contact surfaces are melted by the heat. Then, the flange portion 5 is press-fitted into the metal tube 1 until it comes into pressure contact with the end surface 1'. By doing so, the fitting member 4 and the metal tube 1 are strongly integrated by the fusion of the synthetic resin.

Note that although an example in which an impact wrench is used to rotate the fitting member has been described above, an electric drill or a thread cutting tool may be used without necessarily using an impact wrench.

In the case shown in FIG. 4, a threaded groove 7 is cut on the outer periphery of the metal tube 1 into which the fitting member 4 is fitted as described above so as to extend to the flange portion 5 of the fitting member 4.
The ends of these tubes are connected to each other by a joint tube 8. In this example, thread grooves 9, 9 are formed on the inner peripheral surface of the metal joint pipe, respectively.
When the metal tube 1 and the joint tube 8 are screwed together, the flange portion 5 and the synthetic resin 10 are coated over approximately 2 pitches of the thread grooves 9 and 9 connected thereto. The metal skin of the joint pipe 8 is prevented from being exposed on the inner surface by being in close contact with the joint pipe 8 to prevent rust. In this way, in the present invention, even if the thread groove 7 is cut after the fitting member 4 is fitted into the metal tube 1, the fitting member 4 is strongly integrated with the metal tube 1 as described above, so that it will not work. Therefore, the fitting member 4 will not come off.

[Effects of the Invention] By press-fitting the fitting member into the metal tube while rotating it, the fitting member fuses with the synthetic resin on the inner peripheral surface of the metal tube and becomes integrated, and the flange portion is strongly crimped to the end surface, so that the end surface Since the pipe is covered by the flange portion and no metal skin is exposed inside the pipe after connection, rust can be reliably prevented. Therefore, the present invention is extremely useful because it can reliably prevent rust from forming inside the pipe even during long-term use.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
The figure is a vertical cross-sectional view of the fitting member, Figure 2 is a perspective view of the metal pipe and the fitting member, Figure 3 is a vertical cross-sectional view when they are fitted together, and Figure 4 is a joint tube between metal pipes. FIG. DESCRIPTION OF SYMBOLS 1... Metal tube, 1'... End surface, 2... Synthetic resin covering the inner peripheral surface of the metal tube, 4... Fitting member, 4'...
...Small diameter side end of the fitting member, 5...Flange portion.

Claims (1)

[Claims] 1. A cylindrical fitting member formed with a slightly smaller diameter at one end and a flange integrally formed at the larger diameter end is heated to a melting temperature similar to that of the synthetic resin covering the inner peripheral surface of the metal tube. The fitting member is made of synthetic resin and press-fitted into the metal tube while being rotated, so that the outer peripheral surface of the fitting member and the synthetic resin covering the inner peripheral surface of the metal tube are fused by their frictional heat, A method for rust-preventing a pipe end surface, characterized in that the flange portion is crimped onto the end surface of the metal pipe.