JPH0460297A - Pipe joint with anti-corrosive end and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve productivity by composing a pipe joint of a main body of which internal and external surface arc coated with paint and a resin core which is injection moulded in a internal part of the main body and bonded by paint. CONSTITUTION:A T-shape resinous core 20 is formed, meeting an internal shape of a main body 11 in a cheese-type pipe joint 10. An internal and external surfaces of the main body is coated with paint. Melting resin is injection moulded in the internal part of the main body and bonded with paint 30 in the core 20. Main processed consist of a process of preparing paint by adding colorant to hot melt adhesive, a process of coating the internal and external surface of the main body with paint and a process of injection moulding melting resin to the internal part of the main body, melting adhesive by heat of melting resin and bounding the core to the main body. As a result, working efficiency increases remarkably by reduction of processes.

Description

[Detailed Description of the Invention] 1. Tojo Shokudo Mori Pipe Disaster The present invention relates to a pipe end corrosion-proof pipe joint for drinking water pipes, etc. that requires corrosion resistance, and is an adhesive for preventing the core from rotating within the joint body. It relates to a manufacturing method in which an internal coating process and an external surface coloring process for identification purposes can be performed simultaneously.

Causes of red water coming out due to rust caused by corrosion and extremely poor water flow include, for example, corrosion of the water pipes and pipe fittings themselves due to an increase in the amount of added chlorine due to deterioration of water quality. There's a problem.

Currently, as a corrosion prevention measure, pipes and pipe joints are commercially available in which only the inner peripheral surface or both inner and outer peripheral surfaces are lined by injection molding with molten corrosion-resistant resin.

FIGS. 2 and 3 show a socket-type pipe joint 1 and a cheese-type pipe joint 5 that have been subjected to corrosion-resistant treatment. In the case of the socket shown in Fig. 2, female threads 3 are provided on both sides of the inner circumference of the joint body 2,
There is a resin core 4 inside the main body 2 between the female screws 3 and 3 on both sides.
is provided.

The two pipe members to be connected are screwed into the female threads 3 from both sides of the main body 2, and are tightly engaged with the insertion portions 4a, 4a provided on both sides of the core 4.

Further, in the case of the cheese-shaped pipe joint 5 shown in FIGS. 3(a) and 3(b), the joint body 6 has female threads 7 on three sides, and a T-shaped resin core 8 is provided inside. Insertion portions 8a are provided on three sides of this core 8.

However, these two types of pipe joints such as pipe joint 1.5 generally have the following problems.

Most of the joint body 2 (6) is made of cast metal. Core 4 (8)
When injecting molten resin during molding.

Core 4 (8) after molding due to shrinkage as the molten resin cools.
There may be a slight gap between the main body 2 (6) and the main body 2 (6).

If the tube member is screwed into, for example, the socket-type pipe joint 1 shown in FIG. 2 with a gap created, there is a problem that the core 4 rotates with the tube member together with the inner circumferential surface of the main body 2. In addition, in the case of the cheese-type pipe joint 5 shown in Fig. 3, when a pipe member is screwed into the connection port 6B on one of the three sides, the other connection port 6B is screwed in due to the gap size as shown in Fig. 3(a). At the mouth 6A, the core 8 is brought to one side. Therefore, it may be difficult or impossible to screw the pipe member into the connection port 6A.

In order to deal with such problems, conventional methods have been used to apply an adhesive to a predetermined position inside the joint body 2 (6) before injection molding. That is, the molten resin is injection molded after the adhesive is applied, and the molten resin contracts as it cools, but the adhesive action prevents a gap from forming between the core 4 (8) and the main body 2 (5) after molding. It provides an adhesive force that prevents the pipe members from rotating even when they are screwed together.

On the other hand, in order to distinguish these pipe end corrosion-proof joints from other types of pipe joints, the outer surface is painted in a suitable color to distinguish them from other types.

However, in conventional pipe end corrosion-proof pipe joints, the core 4
(8) The process of internally applying the adhesive to bond it and the process of externally coloring it for external identification are carried out separately, and the process of applying the adhesive relies on brush painting, which makes each task complicated and costly. This leads to high production costs and reduces productivity.

Furthermore, when applying the adhesive with a brush, the coating surface becomes uneven, which causes a decrease in the adhesive strength of the core.

The present invention solves the above problems. The purpose of this invention is to provide a pipe end corrosion-proof pipe joint and its manufacturing method, mainly aimed at improving productivity.

The pipe end corrosion-proof pipe joint according to the present invention includes a joint body whose inner and outer surfaces are coated with a paint, and a joint body which is injection molded inside the joint body and which is bonded to the inner surface of the joint body with a paint. The core is made of resin.

In addition, the manufacturing method of this pipe end corrosion-proof pipe joint includes a process of adding a coloring agent to hot melt adhesive to create a coating agent, a coating process of coating the internal and external surfaces of the fitting body with a coating agent, and a coating process of coating the internal and external surfaces of the fitting body with the coating agent. Molten resin is injected into the inside of the core to form the core.
This process includes the step of melting the paint on the internal surface by the heat of the molten resin during injection and bonding the molded core to the joint body.

In this manufacturing method, it is possible to apply a coating agent to the inner and outer surfaces of the joint body by an electrostatic coating method or a fluidized dipping method.

Production - ■ The internal and external surfaces of the joint body are simultaneously coated using an electrostatic coating method or a fluidized dipping method using a coating agent prepared by adding a coloring agent to a hot melt adhesive. By painting the external surface of the joint body, it can be distinguished from other types of joints.

Molten resin is injected to form the core inside the joint body. At this time, the paint on the inner surface of the joint body is melted by the heat of the molten resin, and the core formed by the hot melt adhesive is adhered to the inner surface of the joint body. In other words, even if there is a slight gap between the joint body and the molten resin after cooling due to the difference in thermal contraction rate between the joint body and the molten resin, the strength of the bond will prevent the core from rotating together with the pipe member during screwing. do not have.

[5] Embodiments of the anti-corrosion pipe joint and its manufacturing method according to the present invention will be described with reference to the drawings.

FIG. 1 shows a cheese-shaped pipe joint 1 applied as an example.
Indicates 0. Connection ports 11A to IIC on three sides of the joint body 11
are each provided with internal threads 12 to 14, and a T-shaped resin core 20 is molded along the internal shape. Insertion portions 21 to 23 are provided on three sides of the core 20 corresponding to the connection ports 11A to 11C, respectively. The structure of such a pipe end corrosion-proof pipe joint is known. Further, as will be described in detail below, the inner and outer surfaces of the joint body 11 are coated with a colored paint 30, so that it can be visually distinguished from other types of pipe joints. The joint body 11 is often a cast product made of malleable cast iron or the like.

After being released from the mold, as a semi-finished product, the inner and outer surfaces are subjected to surface treatment such as sand polishing, and the three connection ports 11A to 11A.
Pretreatment such as deburring is performed on each end face of the IC. The treated joint body 11 is ready for a coating process using a coating agent 30 and for molding a core 20 by injecting molten resin into the interior.

The pipe joint 10 is manufactured using the joint body 11 processed as a semi-finished product through the following process. The main processes are: ■ Adding coloring agents to hot melt adhesives to create coatings.

■ A painting process in which the internal and external surfaces of the joint body are coated with a paint; ■ Molten resin is injected to form a core inside the joint body, and the heat of the molten resin during injection melts the paint on the internal surface. This is the step of bonding the core, which is molded using the same method, to the joint body.

The coating material 30 is created by coloring hot melt adhesive. As the hot melt adhesive, for example, powders of polyester resin, polyamide resin, etc. are used. Coloring agents include organic pigments.

In the next coating process, the inner and outer surfaces of the joint body 11 are simultaneously coated using the prepared coating agent 30. Electrostatic coating and fluidized dip coating are known as coating methods, and fluidized dip coating is employed here. That is, the joint body 11 is heated to a temperature higher than the melting temperature of the powdered coating agent 30, the heated joint body 11 is immersed in a dipping tank to coat the surface, and then dried by natural cooling.

Simultaneous coating with the coating agent 30 is the gist of the present invention, which aims to reduce process steps. The advantages of simultaneous coating more than compensate for the following considered wasteful effects. That is, although the external surface of the joint body 11 needs to be colored for the purpose of distinguishing it from other types of pipe joints, it is not necessary to have an adhesive effect using a hot melt adhesive. Conversely, it is not necessary to color the internal surface, but adhesive action by a hot melt adhesive is required.

After painting, the inner and outer surfaces of the joint body 11 are dried to prepare for the next core forming process. The painted joint body 11 is set in a mold, and an insert for molding the core 20 is inserted into the joint body 11. A molten resin of predetermined components is injected to form a core 20 having the shape shown in the figure. During molding of the core 2O, the coating agent 30 coated on the inner surface of the joint body 11 is melted by the heat of the molten resin, and the molded core 30 is adhered to the inner surface of the joint body 11 with the components of the hot melt adhesive.

By adhering the core 20 to the inner surface of the joint body 11, the injected molten resin contracts as it cools, and due to the difference in thermal contraction rate between the joint body 11 and the molten resin, a gap is created between the two. action can be prevented. Therefore, when the pipe joint 10 is used as an H product, there is no problem such as co-rotation due to screwing of the pipe member.

As explained above, the pipe end anti-corrosion pipe joint according to the present invention has the following features:
A hot melt adhesive with a coloring agent added is used as a coating agent, and by simultaneously painting this on the internal and external surfaces of the joint body, it is possible to use a hot melt adhesive to adhere the core to the internal surface as in the past. The coating process and the external coloring process for identification can be performed at the same time, which has the effect of significantly increasing work efficiency by reducing the number of processes.

In addition, by being able to use the fluidized dip coating method, the thickness of the coating layer is uniform, which increases the adhesive strength of the core and increases reliability, compared to the conventional method of applying adhesive to the internal surface with a brush. There are advantages to improving.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a pipe end corrosion-proof pipe joint obtained by the refining method according to the present invention. FIG. 2 and FIGS. 3(a) and 3(b) both show a side sectional view of a conventional socket-type pipe joint, and a plan sectional view and a side sectional view of a cheese-type pipe joint. 101. Pipe end anti-corrosion pipe joint, 110. Fitting body. 201. Core, 301, Painting agent (1 person) Figure procedure amendment July 31, 1990, Director General of the Ministry of Land, Infrastructure, Transport and Tourism, Toshi Uematsu Case, 1990 Patent Application No. 170085 Title of the invention: Pipe end protection Food pipe joint and its manufacturing method 3 Relationship with the case of the person making the amendment Patent applicant

Claims (3)

[Claims] (1) The joint body includes a joint body whose inner and outer surfaces are coated with a paint agent, and a resin core injection molded inside the joint body and adhered to the inner surface of the joint body with a paint agent. Features a corrosion-resistant pipe fitting at the end of the pipe. (2) Process of adding a coloring agent to hot melt adhesive to create a coating agent: Coating process of coating the internal and external surfaces of the joint body with a coating agent: Injecting molten resin into the interior of the joint body to form a core. 1. A method for manufacturing a pipe end corrosion-resistant pipe joint, comprising: molding the core, melting the paint on the internal surface by the heat of the molten resin during injection, and bonding the molded core to the joint body. (3) The manufacturing method according to claim (2), which includes the step of painting the internal and external surfaces of the joint body with a coating agent by electrostatic coating or fluidized dipping.