JPH0518553Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an expansion pipe joint for connecting pipes that expand and contract in the axial direction or the like.

Technical background of the invention and its problems Piping through which relatively high-temperature, high-pressure fluid flows may undergo thermal expansion or be subject to various vibrations, so it is necessary to expand and contract in the axial direction to connect the pipes. Expansion joints are used.

Fig. 5 shows this expansion joint, which has a bellows body 3 provided between flanges 5 for connection to a pipe through which a fluid flows. The bellows body 3 is composed of an inner bellows 1 made of synthetic resin, which is chemically resistant to the fluid flowing inside the pipe, and an outer bellows 2 made of metal, which is physically strong in terms of durability and strength, and is fitted around the outer periphery of the inner bellows 1. The two bellows 1, 2 are simply fitted together without being bonded with an adhesive or the like so that they can exhibit independent expansion and contraction properties. Both axial ends of the bellows body 3 are attached to flanges 5 provided with insertion holes 4 into which the bellows body 3 is fitted, and the amount of expansion and contraction of the bellows body 3 is adjusted by a plurality of connecting rods 6 installed between the two flanges 5.

Therefore, this expansion pipe joint is not only used to connect pipes through which high-temperature, high-pressure fluid flows, but in some cases, it may also be used for negative pressure pipes. In such a case, a reinforcing ring 7 (ring-shaped spring steel coated with synthetic resin) is provided in the peak Y of the bellows body 3 to prevent the bellows body 3 from collapsing radially inward even under vacuum. It prevents you from doing so.

Here, in manufacturing the bellows body 3, a metal tube is coated around the outer periphery of a cylindrical synthetic resin tube, and after this is set in a mold, both are pressurized from the inside using fluid pressure or the like. , the entire body is shaped into a bellows shape. For this reason, in the bellows body 3 after molding, due to its structure, it is difficult to bring both bellows 1 and 2 into complete contact with each other, and air may remain or exist between both bellows 1 and 2. be.

If an expansion pipe joint using such a bellows body 3 is used to connect pipes that flow not only the high-temperature, high-pressure fluid described above but also high-temperature, ultra-low-pressure fluid, the air existing between both bellows 1 and 2 will be heated to a high temperature. The bellows body 3 expands due to the ultra-low pressure inside the bellows body 3.
The internal bellows 1 is pressed by the air, deforms, and may even collapse inward in the radial direction, which is a serious situation.

Therefore, in order to allow the air between the inner and outer bellows 1 and 2 to escape, a small air vent is provided in a part of the metal outer bellows 2, so that both bellows 1 and 2 can escape even under the above-mentioned high temperature and ultra-low pressure conditions. It is also conceivable that the air existing therein moves between both bellows 1 and 2 and escapes to the outside through this through hole.

However, creating such a through hole after molding the bellows body 3 involves extremely difficult work, and if the through hole is provided in the metal tube before molding the bellows body 3, the above-mentioned custom molding will be required. When doing so, a new problem arises in that cracks form from this through-hole portion. For this reason, the reality is that there is still no expansion pipe joint provided with such a through hole.

Purpose of the invention The present invention was made in order to solve the drawbacks and problems associated with the prior art described above, and includes a bellows body in which an outer bellows made of metal is fitted around the outer periphery of an inner bellows made of synthetic resin. An air vent hole is provided in the external bellows of the expansion pipe joint to ensure that the air existing between the inner and outer bellows can be exhausted, and the expansion pipe does not cause any problems in manufacturing the bellows body. The purpose is to provide fittings.

Summary of the invention In order to achieve the above object, the present invention has a bellows body consisting of an internal bellows made of synthetic resin and an external bellows made of metal fitted around the outer periphery of the internal bellows, and both ends of the bellows body in the axial direction. In the expansion pipe joint, the expansion pipe joint has a fitting hole into which the flange is fitted, and a flange for connecting with a pipe through which fluid flows, and the external bellows at a position facing the circumferential wall of the fitting hole of the flange is provided with an air vent. The flange is characterized in that a through hole is opened and an air exhaust passage is provided in the flange to communicate with the through hole and guide the air existing between the internal bellows and the external bellows to the outside from the through hole. be.

In the present invention having such a configuration, the through hole is formed in the flange attachment part of the metal external bellows with the air vent opening at the end, so that this part is not plastically deformed during molding. Since this is the part with the least amount of air, cracks will not occur when forming the bellows body, and even if the air existing between both bellows expands, it will pass through the air exhaust passage of the flange from the through hole.
This means that it can be reliably discharged to the outside.
The internal bellows will not deform or cave in.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a side view showing a half part of the embodiment shown in Fig. 1, Fig. 3 is an enlarged sectional view of the main part of Fig. 1, and Fig. 4 is a half sectional view showing the molded state of the bellows body of the same embodiment. The same members as those shown in FIG. 5 are given the same reference numerals.

As shown in FIG. 1, the expansion pipe joint 10 includes an internal bellows 1 made of a synthetic resin such as polytetrafluoroethylene (PTFE) having excellent properties such as heat resistance and chemical resistance. A bellows body 3 is formed of an external bellows 2 made of a metal having excellent mechanical strength such as stainless steel coated on the outer periphery, and a fitting hole 4 is provided into which both axial ends of the bellows body 3 are fitted. A plurality of connecting rods 6 are installed between the two flanges 5, and the amount of expansion and contraction of the bellows body 3 is thereby adjusted.

Note that this connecting rod 6 is connected to the through hole 11 of the flange 5.
The expansion pipe joint 1
The amount of expansion and contraction of 0 is regulated.

Note that the reference numeral 12 in the figure is a through hole for connecting pipes.

In particular, in this embodiment, as shown in detail in FIG.
3 is opened, and air existing between the internal bellows 1 and external bellows 2 is removed from the through hole 1.
The flange 5 is provided with an air exhaust passage 14 that leads from the flange 3 to the outside.

This flange 5 has a lower end portion 5a fitted into a groove portion formed by the mountain portion Y and the side end flange portion 1a, and an upper region 5 of this lower end portion 5a.
A notch 15 is formed in b so that it does not come into contact with the mountain portion Y, so that the air that has passed through the air exhaust passage 14 can escape to the outside.

In order to mold the bellows body 3 constructed in this way, first, as shown in FIG. A synthetic resin tube 17 (for example, PTFE), which is longer than the tube 16, is installed inside the tube 17 in a substantially intimate state. Then, both ends of the tube 17 are bent back while being heated to form the flange portion 1a.

A flange 5, in which a passage 14 is previously bored, is set on the flange portion 1a of the metal/synthetic resin composite pipe formed in this manner so as to be in close contact with the flange 5, and the flange 5 and the metal pipe 16 are fixed by welding or the like. do. Note that the hole 13 and the passage 14 may be opened after this welding.

After setting the mold rings 19 aligned at a predetermined interval between both flanges 5 via spacers 18, a jig 20 is attached vertically, and a large number of small holes are formed inside this jig 20. Set the core 22 in which the core 21 is opened.

Here, the tips of the individual mold rings 19 are curved and tapered, but this is so that the space formed by both the mold rings 19 forms the above-mentioned peak Y. This is to make it approximately semicircular.

The thus prepared product is set between the press molds 23 and 24, and pressing force is applied to the jig 20.
For example, high-pressure steam of about 150° C. is passed through the small hole 25 opened in the hole 25 . This steam is blown out from the small hole 21 of the core 22, and together with the pressing force from the press, the synthetic resin tube 17 and the metal tube 1
6 is bulged outward as shown by the broken line in the figure.

By performing such an expansion action in stages, both the tubes 16 and 17 are bent and formed into a shape along the inner circumferential surface of the metal ring 19, that is, into a bellows shape.

In this case, even if air exists between the two tubes 16 and 17, the air will flow through the through hole due to the repeated expansion molding.
3 and will be expelled from the outside.

In this way, in this embodiment, the air vent hole 1
3 is provided at the end of the metal tube 16 at a position facing the insertion hole 4 of the flange 5, so that even when the bellows body 3 is press-formed, it is welded and fixed to the flange 5, and there is almost no plastic deformation. Therefore, the through hole 13 portion of the metal tube 16 is not stretched, and no cracks are generated in the metal tube 16 during molding.

When the bellows main body 3 formed in this way is used in the expansion pipe joint 10, even if air exists in both the bellows 1 and 2, this air expands thermally and fills the gap between the bellows 1 and 2. move through,
The gas is discharged from the through hole 13 to the outside through the passage 14, and there is no possibility that the internal bellows 1 will bulge inward in the radial direction or collapse.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways.

For example, RTFE is the material for the internal bellows.
However, other fluororesins, engineering plastics such as polyamide polyether ketone (PEEK), polyphenylene sulfide (PPS), or other synthetic resins can be used.

Further, according to the present invention, a pressure regulating means for regulating the air pressure existing between the internal bellows 1 and the external bellows 2 is connected to the air discharge passage provided in both flanges 5, 5, and the pressure regulating means is connected to the air discharge passage provided in both flanges 5, 5. By means of
The air pressure between the bellows 1 and 2 may be controlled so as to approach the pressure of the fluid flowing inside the bellows. For example, specifically, a conduit is connected to the air exhaust passage, and this conduit is connected to a vacuum pump, so that both bellows 1,
It is also possible to forcibly exhaust the air between the two. In that case, there is no pressure difference between the inside and outside of the internal bellows 1, and it becomes possible to more effectively prevent the internal bellows 1 from collapsing inward in the radial direction.

Effects of the invention As described above, according to the invention, an air vent hole is provided in the external bellows at a position facing the peripheral wall of the insertion hole of the flange, and a hole is provided between the internal bellows and the external bellows. Since the flange is provided with an air exhaust passage that guides the existing air to the outside through the hole, cracks will not occur when the bellows body is molded, and even if the air existing between the bellows expands, the air passage will be removed. This means that the air can be reliably discharged to the outside through the hole through the air discharge passage of the flange, resulting in an excellent effect that the internal bellows will not be deformed or caved in.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a side view showing a half of the embodiment shown in Fig. 1, and Fig. 3 is an enlarged sectional view of the main part of Fig. 1. 4 is a half-sectional view showing the molded state of the bellows body of the same embodiment, and FIG. 5 is a sectional view showing a conventional expansion pipe joint. 1... Internal bellows, 2... External bellows, 3
... Bellows body, 4 ... Fitting hole, 5 ... Flange, 6 ... Connecting rod, 13 ... Air vent hole,
14...Air exhaust passage.

Claims (1)

[Scope of utility model registration request] A bellows body consisting of an internal bellows made of synthetic resin and an external bellows made of metal fitted to the outer periphery of the internal bellows, and a fitting hole into which both ends of the bellows body in the axial direction are fitted, and a fluid flows through the bellows body. In an expansion pipe joint having a flange for connecting to a pipe to be connected, an air venting hole is opened in the external bellows at a position facing the peripheral wall of the fitting hole of the flange, and the through hole communicates with the An expansion pipe joint characterized in that the flange is provided with an air exhaust passage that guides air existing between the internal bellows and the external bellows to the outside from the through hole.