JPH04194485A - Pipe joint - Google Patents

Abstract

PURPOSE:To avoid damage in an external thread part and a trouble of new thread cutting on the external thread part by providing a lining layer, formed of resin, over a joint main unit end part and an internal surface from a position in the vicinity of a start end of the thread part in a joint main unit peripheral surface. CONSTITUTION:In a pipe joint 1, a lining layer 3, formed of resin, is provided over a joint main unit internal surface 2d from a position in the vicinity of a start end of external thread parts 2b, 2b, that is, from an external surface of protrusive parts 2c, 2c in a joint main unit 2. By this lining layer 3, metal parts of the internal surface 2d of the joint main unit 2 and the external surface of the protrusive parts 2c, 2c are prevented from coming into contact with water. Since fold back parts 3a, 3a of the lining layer are provided only to the vicinity of thread ridges 2b1, 2b1 so as to not overlap with the external thread parts 2b, 2b of a joint main unit peripheral surface further with an external diameter Do of each fold back part 3a almost equal to the external diameter of a valley part 2b2 in a start end side of the external thread part, interference of an internal thread part with each fold back part 3a is avoided at the time of screwing with the internal thread part of a mate member to be connected.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a pipe joint used for piping for water supply, hot water supply, air conditioning, etc.

[Conventional technology]

For example, when metal pipes are used for water supply pipes or hot water supply pipes, the inner metal parts of the pipes may corrode and generate red water. In order to prevent the occurrence of such red water,
Internally resin-coated pipes (hereinafter referred to as corrosion-resistant pipes), which are metal pipes whose inner surfaces are coated with corrosion-resistant resin, are used, but when this type of corrosion-resistant pipes are connected to metal pipe fittings, the pipe ends, the inner surfaces of the fittings, etc. If the metal part of the pipe comes into contact with a liquid such as water or hot water (hereinafter simply referred to as water) in the pipe, corrosion will occur in that part. In order to cope with corrosion at the connecting portion of such a corrosion-proof pipe, there has conventionally been a nipple in which the inner surface of a metal nipple body is coated with a synthetic resin. However, the resin layer formed by coating cannot be made as thick as the resin layer formed by lining, so in the above nipple, water penetrating the resin coating layer corrodes the metal part on the inner surface of the nipple. As a result, there is a problem in that the coating layer causes peeling and blistering, thereby impeding the pipe function. In order to deal with such problems, for example, Japanese Patent Application Laid-Open No. 139986/1986 proposes a nipple having a non-water-contact structure in which a predetermined area is coated with resin. This is because, as shown in FIG. 6, in the nipple A in which the male threaded portions a1 and al are formed on the outer peripheral surface of the nipple body a,
Inner surface a2 and both end surfaces a3, a3 of the nipple body a
is coated with a synthetic resin with a thickness equal to or thicker than the lining layer of the mating member (not shown) to be connected, and the male threaded portion al of the nipple body a is coated on the outer peripheral surface of both ends of the resin coating.
This is a configuration in which male threaded portions S, b, continuous with the sal are formed. According to this, the inner surface a2 of the nipple body a2 is already coated with a thick synthetic resin film to provide sufficient waterproofness, and both end surfaces a3 and a3 of the nipple body a are also coated with a synthetic resin film. Because of this provision, it is possible to prevent the metal portions of both end surfaces a3, a3 of the main body from coming into contact with water.

[Problem to be solved by the invention]

However, in the nipple A described in the above-mentioned publication, the male threaded portions al, al are also formed on the outer circumferential surface of the resin coating covering both ends of the nipple body a, which causes the following problem. That is, when the resin male threaded part a1 is screwed into the metal female threaded part of a mating member to be connected (for example, a cast joint), the resin male threaded part a1 comes into contact with the mating metal part and the metal part a1 contacts the mating metal part. The tip of the male threaded portion a1 may be chipped, resulting in problems such as poor fitting and deterioration of anti-corrosion performance. In addition, if the nipple A and the mating member are screwed in with their axes not aligned, a new thread will be cut in the resin male thread a1 on the nipple side by the metal female thread of the mating member. There is a problem in that both cannot be connected in a predetermined state. The present invention addresses the above-mentioned problems in a pipe joint for corrosion-resistant pipe connection in which a threaded portion (male threaded portion) is provided on the outer circumferential surface of the joint body. It is an object of the present invention to provide a pipe joint that can ensure the properties of the pipe joint and prevent screwing failure and connection failure when screwing into a threaded part (female threaded part) of a mating member to be connected.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a pipe joint in which a threaded portion is provided on the outer circumferential surface of a metal joint main body, and is characterized in that it is configured as follows. That is, a lining layer made of resin is provided over the outer surface and inner surface of the end of the joint body located near the starting end of the threaded portion so as not to overlap the threaded portion. Here, as the resin constituting the above-mentioned lining layer, polyvinyl chloride, polyethylene, polyvinylidene fluoride,
Thermoplastic resins such as cross-linked polyethylene and polybutene are most suitable. In addition to this type of resin, if a reinforced resin containing glass fiber, carbon fiber, etc. (for example, polyvinylidene fluoride, polyamide, polyetherimide, etc.) is used,
This is preferable because expansion and contraction of the resin portion due to temperature changes in the water within the pipe can be suppressed.

[For production]

According to the above configuration, since the lining layer made of resin is provided from the position near the starting end of the threaded portion, that is, the male threaded portion, on the outer circumferential surface of the joint body to the end portion of the joint body and the inner surface, the lining layer Not only the inner metal portion of the tube but also the metal portion of the outer surface and end surface of the end of the main body are no longer in contact with the water in the pipe. In that case, instead of a thin coating layer (film thickness),
By being considered as a lining layer that is originally formed thickly,
Since moisture penetration into the metal surface such as the inner surface of the joint body is reliably prevented, problems such as corrosion of the metal surface and blistering and peeling of the resin layer due to moisture penetration are also eliminated. Moreover, according to the above configuration, the lining layer on the outer surface of the end of the joint main body exists only up to a position near the starting end of the threaded part on the outer peripheral surface of the main body so as not to overlap the threaded part on the outer circumferential surface of the main body. (female threaded part) when screwed together,
It is possible to prevent the female threaded portion from interfering with the outer lining layer. This may cause damage to the male threaded part due to the female metal threaded part of the mating member coming into contact with the male resin threaded part at the end of the pipe fitting, or the possibility that a new thread may be cut on top of the male threaded part. It is possible to eliminate the problem and, in turn, prevent a poor connection with the mating member.

【Example】

The present invention will be explained in detail below. This embodiment relates to a case where the present invention is applied to a nipple-shaped pipe joint, and as shown in FIG.
has a cylindrical metal joint body 2 with a non-threaded portion 2a at the center of the outer circumferential surface, and male threaded portions 2b, 2b are provided on both left and right sides of the non-threaded portion 2a on the outer circumferential surface of the main body. It is. These male threaded parts 2b, 2b are respectively tapered threads in which the thread diameter on the end side of the joint body 2 is smaller than the thread diameter on the center side. Further, male threads are not formed at both ends of the joint body 2, and protrusions 2c, 2 protrude outward along the axial direction.
c are provided respectively. These protrusions 2c, 2c are threaded threads 2b located at the starting ends of each male threaded portion 2b, 2b,
, 2b, and the outer diameter of each male threaded portion 2b,
The dimension is set to be smaller by a predetermined amount than the outer diameter of the trough portion 2b2 on the starting end side in 2b (see FIG. 2). In this pipe joint 1, as a characteristic part of the present invention, the entire inner surface 2d of the joint body 2 is moved from the outer surface of the protruding parts 2c, 2c so as not to overlap the male threaded parts 2b, 2b on the outer peripheral surface of the joint body 2. A resin lining layer 3 is provided to cover the. In this case, the outer diameter of the folded portions 3a, 3a of the lining layer 3 covering the outer surfaces of the protrusions 2c, 2c is as shown in an enlarged view in FIG. It is desirable to set the diameter so that it is approximately equal to or slightly smaller than the outer diameter of the valley portion 2b on the starting end side of the male threaded portion. According to the pipe joint 1 configured as described above, the joint body 2
Since the lining layer 3 made of resin is provided near the starting ends of the male threaded portions 2b, 2b, that is, from the outer surface of the protruding portions 2c, 2c to the inner surface 2d of the joint body, the lining layer 3 allows the joint body 2 to Inner surface 2d and protrusion 2c
, 2c (the outer surface and end surface of the end of the joint body) are prevented from coming into contact with water. In this case, the resin layer covering a predetermined portion of the joint body 2 is not a thin coating layer, but a lining layer that is originally thick, so the joint body This will reliably prevent moisture from penetrating into the metal surfaces such as the inner surface 2d. Therefore, problems such as corrosion of the metal surface of the joint body and blistering and peeling of the resin layer due to moisture penetration are eliminated. Further, according to this pipe joint 1, the folded portions 3a, 3 of the lining layer covering the outer surfaces of the protruding portions 2c, 2c are
a does not overlap with the male threaded portions 2b, 2b on the outer circumferential surface of the joint main body, and exists only in the vicinity of the starting ends of the threaded portions 2b, 2b, that is, in the vicinity of the screw threads 2b, , 2b, and in addition, each folded portion 3a The outer diameter dimension D0 is the trough 2 on the starting end side of the male thread part.
Since the outer diameter of bz is approximately equal to or slightly smaller than the outer diameter of
interference with can be avoided. Therefore, the metal female thread of the mating member may come into contact with the resin male thread on the outer surface of the pipe fitting end, causing damage to the male thread, or cutting a new thread onto the male thread. Problems can be resolved and poor connection with the mating member can be prevented. The resin lining layer 3 is most preferably formed by injection molding, but as shown in FIG. The folded portion 3a may be formed by molding it so as to protrude by a predetermined length from the base and heating the protruding portion 3a'. In addition, when forming by injection molding, a hot melt adhesive is applied to the inner surface of the joint body in advance, and the adhesive is melted by the resin heat of the molten resin during injection molding. The resin lining layer may be brought into close contact with the inner surface of the joint body by cooling and solidifying. In this way, it is possible to improve the adhesion between the lining layer and the inner surface of the joint body. In addition, like the pipe joint 11 of the second embodiment shown in FIG.
It is preferable to form the recesses 12e, 12e on the inner surface 12d of the joint body 12, since it is possible to suppress expansion and contraction of the resin lining layer 13 provided on the inner surface 12d, etc. In this case, the recesses 12e, 12e only need to be provided on the inner surface 12d so as to be concave with respect to the axial direction of the joint body 12, and other positions and shapes are not particularly limited. Furthermore, although the above-mentioned first and second embodiments apply the present invention to nipples, the pipe joints to which the present invention is applied are not limited to nipples, for example, as shown in FIG. 5 as the third embodiment. It may be something. In the pipe joint 21 of this third embodiment, the joint body 22
A male threaded portion 22b is provided at one end (smaller diameter side), and a female threaded portion 22f is provided at the other end (larger diameter side). Then, the threaded portion 2 is made so as not to overlap the male threaded portion 22b.
Joint main body end (protrusion) 22 located near the starting end of 2b
A resin lining layer 23 is provided from the outer surface of C to the inner surface 22d of the small diameter side of the main body, and is further divided into a double cylindrical shape inside the large diameter side, the outer part 23b of which is connected to the female threaded portion 2.
The large-diameter inner surface 22d is continuous with 2f. The inner portion thereof extends toward the large-diameter opening end to form a cylindrical portion 23c. According to the pipe joint 21 of this third embodiment, the male threaded portion 2
2b and the female threaded portion (not shown) of the mating member connected thereto is of course prevented in the same manner as in each of the above embodiments. By closely contacting the cylindrical portion 23c with the inner surface of the end of the pipe or pipe joint connected to the tube, the end can also be protected from corrosion.

【Effect of the invention】

As described above, according to the pipe joint of the present invention, since the lining layer made of resin is provided from the position near the starting end of the threaded part on the outer circumferential surface of the joint body to the end of the joint body and the inner surface, it is possible to This avoids problems such as damage to the male threaded part caused by the metal female threaded part of the component coming into contact with the resin male threaded part at the end of the pipe fitting, and problems such as a new thread being cut on top of the male threaded part. That will happen. In addition, as mentioned above, the resin layer that covers the predetermined parts of the joint body is not a thin coating layer, but a lining layer that is originally thick, so that the inner surface of the joint body, etc. Since moisture penetration into the metal surface is reliably prevented, problems such as corrosion of the metal surface and flaking and peeling of the resin layer due to moisture penetration can be solved at the same time. This ensures sufficient waterproofness on the inner surface and end surface of the joint body, and also prevents poor screwing and poor connection when screwing together with the threaded part of the mating member to be connected, which in turn improves corrosion resistance at the pipe connection. It will be improved.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention. FIG. 1 is a partially cutaway front view of a pipe joint showing the first embodiment, FIG. 2 is a partially enlarged view thereof, and FIG. 3 is the above-mentioned FIG. 4 is a partial sectional view showing a method of forming a resin lining layer at the end of a pipe joint, FIG. 4 is an axial half-sectional view of a pipe joint according to a second embodiment, and FIG. 5 is a partial cross-sectional view of a pipe joint according to a third embodiment. It is a partially cutaway front view. Moreover, FIG. 6 is an axial sectional view showing a conventional pipe joint. 1.11.21... Pipe joint, 2. 12. 22...
・Joint body, 2b, 22b...threaded part (male threaded part),
2c, 22c... Joint body end (projection), 2d, 1
2d, 22d...Inner surface of the joint body, 3, 13.23...
・Resin lining layer. Patent applicant: Sekisui Chemical Co., Ltd. 1st wl. Figure 2. Figure 5 Figure 6

Claims (1)

[Claims] (1) In a pipe fitting in which a threaded portion is provided on the outer circumferential surface of the metal fitting body, from the outer surface of the end of the fitting body located near the starting end of the threaded portion so as not to overlap the threaded portion, A pipe joint characterized in that a resin lining layer is provided over the entire length.