JPH07167303A - Manufacture of fluororesin-coated gasket - Google Patents

Abstract

PURPOSE:To easily manufacture a gasket which has satisfactory sealability and hardly generates liquid reservoir with a low cost by forming an outer film connection body composed of a plurality of outer film units, extracting it from a case, cutting it into the outer film units, and mounting an elastic circular center body to the outer film unit. CONSTITUTION:A tube-like pulson is housed in a case 14 having circular recessions and projections alternatively on its inner periphery. Pressure is applied to an inner portion of the pulson, for expanding to the outer peripheral side and bringing into close contact with an inner peripheral surface 14a of the case 14. The figure indicates this condition. An outer film connection body T is extracted from the case 14, and cut into outer film units (t). It is thus possible to easily obtain a plurality of hourglass fluororesin-coated gasket forming thin outer films. Since an elastic circular center body is mounted to the outer film unit (t) by adhesive, the fluororesin gasket having excellent sealability is obtained with a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gasket which is incorporated in a flange joint used for towers such as tanks or pipes, and which prevents leakage of internal fluid, and more specifically, it is extremely contaminated. The present invention relates to a method for manufacturing a gasket, which is used as a gasket for so-called sanitary used in a pipe or the like through which a fluid that dislikes oil flows, and in which the surface of an elastic annular core is covered with a thin fluororesin.

[0002]

BACKGROUND OF THE INVENTION In manufacturing plants for chemicals, foods, semiconductors, etc., pipes through which fluids that are extremely resistant to contamination circulate are used. Fluoroethylene resin (hereinafter PT
A gasket whose surface is covered with a film made of a fluororesin such as FE) is used.

In this fluororesin-coated gasket, for example, as shown in FIG. 6, the inner peripheral wall of the bore portion 2 of the elastic annular core 1 and the front and back surfaces 3 and 4 have a U-shaped half section ( In some cases, it is covered with a thin outer skin 5 formed in a V shape.

The ring-shaped core 1 functions as a cushioning material, and the material to be used differs depending on the application, but a single rubber, a composite of organic or inorganic fibers and rubber, a felt mat, a woven cloth, or the like is used. Used alone or in combination.

On the other hand, since the outer skin 5 is a portion which is in direct contact with the flange 6 or the flowing fluid, it is desirable that the outer skin 5 has excellent heat resistance and chemical resistance, and that it also has appropriate elasticity. Therefore, a fluororesin such as the above-mentioned PTFE is used.

When such a fluororesin-coated gasket G is mounted between the flanges 6 of the flange joint, the elasticity of the annular core 1 is transmitted to the flange 6 side through the PTFE outer cover 5. Since the sealing property is improved, the outer skin 5 is preferably relatively thin. If the outer skin 5 is thick, the elasticity of the annular core 1 is difficult to be transmitted to the flange 6 side, and the sealing property is deteriorated.

However, if the outer skin 5 is too thin,
The outer skin 5 cannot prevent the state (indicated by the broken line in FIG. 6) in which the inner peripheral wall of the bore portion 2 of the annular core 1 swells inwardly. There is a risk of accumulation.

Further, when the annular core 1 is covered with the PTFE outer cover 5, conventionally, a PTFE thin film having a predetermined width is folded in two so that the release side end is on the outer peripheral side of the annular core 1. In addition, it is plastically deformed into a circle.

However, in this way, the thickness is 0.2
Since the outer peripheral side of the PTFE thin film having a thickness of mm or less is forcedly stretched, a crack may occur on the outer peripheral side. Therefore, the PTFE thin film used as the outer skin must have a certain thickness.

When manufacturing the outer skin, it is possible to mechanically cut the PTFE block to manufacture an outer skin having a substantially uniform thickness, but in that case, a relatively thin-walled outer skin is produced. The cutting process is difficult, and the material is wasted, which is disadvantageous in terms of cost.

[0011]

The object of the present invention is that it can be used for pipes through which a fluid extremely dislikes contamination flows and has a good sealing property.
It is an object of the present invention to provide a method for producing a fluororesin-coated gasket, which is suitable for sanitary use with almost no liquid pool, can be easily produced, and is advantageous in terms of cost.

[0012]

SUMMARY OF THE INVENTION In the method for producing a fluororesin-coated gasket according to the present invention, a tube-shaped parson is placed in a mold in which annular concave portions and convex portions are alternately formed on the inner peripheral surface, By applying pressure to the inner wall of the bore, which has a large wall thickness, and the outer wall of the front and back whose wall thickness gradually decreases from the inner wall of the bore toward the outer circumference After forming a body and taking out the outer skin connected body from the mold, cutting the outer skin alone into individual thin skins, and using this outer skin single body as a thin-walled outer skin, mounting an annular annular core body in the outer skin simple substance. Is characterized by.

In the present invention, protrusions may be formed on the front and back surfaces of the annular core body (see FIGS. 2 and 3). In addition, the thin-walled skin of the fluororesin-coated gasket is
It is also possible to cover not only the inner peripheral wall and the front and back surfaces of the bore of the annular center core but also the outer peripheral wall (see FIG. 3).

Such a thin-walled outer cover may be adhered to the annular core body. Since the method for producing a fluororesin-coated gasket according to the present invention is performed by using so-called blow molding, the thickness of the U-shaped bottom portion that is the outer shell for the bore is large because of its molding characteristics. In addition, it is possible to easily form the outer cover connecting body in which a large number of outer cover single bodies whose thickness is gradually reduced from the bottom toward the outer peripheral side are connected, which is advantageous in terms of cost.

In the fluororesin-coated gasket manufactured by such a method, the inner peripheral wall of the bore of the annular core having elasticity and at least the front and back surfaces of the core are covered with a thin outer coat made of fluororesin. The thickness of the outer skin for the bore covering the inner peripheral wall of the bore portion is thick, and the thickness of the outer skin for the front and back surfaces covering the front and back surfaces of the annular core is gradually thinner from the bore side toward the outer peripheral side. Has become.

In the fluororesin-coated gasket manufactured according to the present invention as described above, the thickness of the outer skin for the bore covering the inner peripheral wall of the bore is large, and the thickness of the outer skin for the front and back surfaces is thin. Therefore, even if this gasket is attached to a flange joint and tightened, the inner bore wall side of the gasket does not deform, and it is possible to prevent the accumulation of internal fluid.
The outer skin on the outer peripheral side sensitively transmits the elasticity of the ring-shaped core body to the flange, and has an excellent sealing property. With normal fittings,
Since the tightening force on the outer peripheral side is smaller than the tightening force on the bore side, in the fluororesin-coated gasket, the elasticity of the annular core body effectively acts and the sealing property becomes excellent. In particular, it is extremely advantageous as a gasket for a clamp type joint that cannot obtain a large tightening force.

Further, in the fluororesin-coated gasket having protrusions formed on the front and back surfaces of the annular core, the protrusion is compressed when the fluororesin-coated gasket is mounted between the members, and the bore side of the protrusion is repulsed by the repulsive force. It is pressed toward the flange side, which further prevents liquid pooling between the gasket and the flange.

Furthermore, the fluororesin-coated gasket (see FIG. 3) manufactured so as to cover the inner peripheral wall, the front and back surfaces and the outer peripheral wall of the bore of the annular core is also suitable for cleaning by removing the gasket. Since the ring-shaped core body is in a hermetically sealed state, it does not deteriorate, and if the outer cover is made of a fluororesin, it also does not deteriorate by washing.

[0019]

DETAILED DESCRIPTION OF THE INVENTION A method for producing a fluororesin-coated gasket according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a half sectional view of a fluororesin-coated gasket obtained according to an embodiment of the present invention, and FIGS. 2 and 3 show fluororesin-coated gaskets obtained according to other embodiments of the present invention. Half-sectional views and FIGS. 4 and 5 are cross-sectional views showing the main parts of the manufacturing method of the present invention. The same members as those shown in FIG. .

Fluororesin-coated gasket 1 shown in FIG.
0 is a thin outer skin 1 made of a fluororesin for the inner peripheral wall of the bore 2 of the annular core 1 having elasticity and at least the front and back surfaces 3 and 4.
It is covered with 1.

The outer skin 11 has a thicker outer skin 11a for the bore which covers the inner peripheral wall of the bore 2, and a larger outer skin 11b for the front and back surfaces which covers the upper and lower surfaces 3, 4 of the annular core 1. Is gradually reduced from the side of the bore portion 2 toward the outer peripheral side.

In the present invention, it is preferable to manufacture such a fluororesin-coated gasket 10 by a blow molding method. The method for manufacturing the fluororesin-coated gasket according to the present invention will be described in detail below. [Manufacture of Fluororesin-Coated Gasket] In the present invention, for example, as shown in FIG. 4, first, a tubular Parson (not shown) is formed with annular concave and convex portions alternately formed on the inner peripheral surface thereof. Put it in the mold 14.

A fluororesin is used as such a Parson material. The type of fluororesin is not particularly limited, and polytetrafluoroethylene (PTFE), PFA which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and copolymerization of tetrafluoroethylene and hexafluoropropylene It is widely used such as FEP which is a combination, or EPE which is a copolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether.

Next, pressure is applied to the inside of the Parson to bulge the outer periphery thereof and the inner peripheral surface 14 of the mold 14 is expanded.
Adhere to a. FIG. 4 shows a state in which the outer periphery of the Parson is swollen and brought into close contact with the inner peripheral surface 14a of the mold 14. When such blow molding is performed, the parson is pulled outward toward the outer peripheral side of the swollen parson and becomes thin, which is preferable for forming the outer cover 11.
That is, the outer skin simple substance t (see FIG. 4) thus obtained has a substantially U-shaped half-section, and the thickness of the U-shaped bottom portion (on the central axis side of the bulging Parson) is large and The wall thickness gradually decreases from the bottom toward the outer circumference (a position away from the central axis of the bulging Parson in the circumferential direction). Moreover, the outer skin simple substance t is connected in large numbers to form the outer skin connected body T. In other words, when the Parson blow molding is performed as described above, the inner wall of the thick bore portion (U-shaped bottom portion) is thickened.
Then, the outer skin connected body T is formed in a state in which a large number of outer skin single bodies t are connected to each other, the outer skin for front and back surfaces having the thickness gradually decreasing from the inner peripheral wall of the bore portion toward the outer peripheral side. The thicknesses of the outer and outer skins 11 thus bulged in the inner and outer diameter sides are not particularly limited, but preferably 0.5 respectively.
It is -1.0 mm and 0.01-0.5 mm.

By removing the outer skin connecting body T from the mold 14 and then cutting it into individual outer skins t, a large number of drum-shaped thin outer skins 11 for forming a fluororesin-coated gasket can be easily obtained.

The outer shell thus obtained is used as a thin outer shell for producing a fluororesin-coated gasket, and the elastic annular core 1 is mounted in the outer shell alone.
A fluororesin-coated gasket is obtained.

When the ring-shaped central body 1 is mounted on the thin-walled outer skin 11, the thin-walled outer skin 11 and the annular core body 1 may be bonded with an adhesive. In order to perform this adhesion, for example, the inner surface of the outer skin 11 is roughened with an ammonia solution of sodium, the thin outer skin 11 thus roughened is covered on the rubber material of the annular core 1, and then , Heated in a mold under pressure to vulcanize the rubber and to form a thin outer shell 11 and an annular core 1
Just glue and.

The material of such an annular core 1 is not particularly limited as long as it has elasticity, and for example, rubber,
Light plastic is used. The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways.

As shown in FIG. 5, protrusions may be formed on a part of the mold used for blow molding to form the fluororesin-coated gasket 10 as in the embodiment shown in FIG. . [Fluorocarbon Resin-Coated Gasket] The fluorocarbon resin-coated gasket 10 shown in FIG. 1 manufactured in this manner has fluorine at least the inner peripheral wall of the bore 2 of the annular core 1 having elasticity and at least the front and back surfaces 3 and 4. It is covered with a thin skin 11 made of resin.

The outer skin 11 has a thicker outer skin 11a for the bore covering the inner peripheral wall of the bore 2, and a larger outer skin 11b for the upper and lower surfaces 3 and 4 of the annular core 1. Is gradually reduced from the side of the bore portion 2 toward the outer peripheral side.

The thickness of the outer skin 11 on the inner diameter side and the outer diameter side is
Although not particularly limited, each is preferably 0.5 to 1.
It is 0 mm and 0.01 to 0.5 mm. Also, the outer skin 11
Examples of the fluororesin and the ring-shaped core body 1 constituting the above are the same as those mentioned above.

According to such a gasket, when the gasket 10 is tightened by the flange, the thick outer skin 11a for the bore prevents the gasket 10 from being deformed toward the bore portion 2 side.

Therefore, it is possible to prevent a so-called liquid pool, in which a part of the gasket bulges or deforms to stagnate a part of the fluid flowing inside. Also, the outer skin 11
b, the elasticity of the annular core 1 is sensitively transmitted to the flange 6,
It has excellent sealing properties. Since the normal joint has a smaller tightening force on the outer peripheral side than on the bore portion 2 side, in this fluororesin-coated gasket 10, the elasticity of the annular core body 1 effectively acts and the sealing property is excellent.

Therefore, it is extremely advantageous as a gasket for a clamp type joint which does not provide a large tightening force. In addition, as shown in FIG. 2, the projection 1 is formed on the front and back surfaces of the annular core 1 at substantially the center of the inner and outer diameters.
In the fluororesin-coated gasket 10 in which 2 is formed, when the fluororesin-coated gasket 10 is attached to the flange joint, the protrusion 12 is compressed by this flange, and the bore portion 2 side of the protrusion 12 is pressed toward the flange side by the repulsive force. As a result, liquid pooling is less likely to occur. Further, such a protrusion is preferably annular.

As shown in FIG. 3, the thin outer skin 11
Is the inner peripheral wall of the bore portion 2 of the annular core 1 and the front and back surfaces 3, 4
Not only the outer peripheral wall 13 may be covered. By doing so, even when the gasket 10 is removed and washed, the annular core body 1 is in a sealed state, so that it does not deteriorate, and if the outer cover 11 is also a fluororesin, this also deteriorates due to cleaning. There is an advantage of not doing it.

[0037]

As described above, the method for producing a fluororesin-coated gasket according to the present invention is carried out by utilizing so-called blow molding. The U-shaped bottom portion has a large thickness and the outer skin coupling body in which a large number of outer skins whose thickness gradually decreases from the bottom portion toward the outer peripheral side are connected can be easily formed, which is advantageous in terms of cost.

Further, in such a manufacturing method of the present invention,
Since the blow molding is performed, the core body and the outer skin can be reliably bonded. In addition, the conventional PTFE thin film with a predetermined width is
In the method of forming the outer cover by folding it in half, the adhesion between the core body and the outer cover is likely to be incomplete, and there is a risk of peeling.

In the fluororesin-coated gasket obtained according to the present invention, the outer skin for the bore covering the inner peripheral wall of the bore has a large thickness, and the outer skin for the front and back surfaces has a small thickness. Even when installed and tightened, the inner peripheral wall side of the gasket does not deform, liquid pool of the internal fluid can be prevented, and the outer peripheral skin sensitively transmits the elasticity of the annular core to the flange, which is excellent in sealing performance. It becomes a thing. In a normal joint, the tightening force on the outer peripheral side is smaller than that on the bore side, so in the fluororesin-coated gasket,
The elasticity of the ring-shaped core effectively acts, and the sealing property becomes excellent. In particular, it is extremely advantageous as a gasket for a clamp type joint that cannot obtain a large tightening force.

Further, in the fluororesin-coated gasket obtained by the present invention, the thickness of the front and back surfaces of the outer skin is gradually reduced, and moreover, the front and back surfaces are arranged in a symmetrical state with substantially the same thickness, so that a uniform thickness is obtained. Can be tightened. If this is not the same thickness, the tightening will be non-uniform and it will be necessary to re-tighten after tightening.

When the fluororesin-coated gasket obtained by the present invention has protrusions formed on the front and back surfaces of the annular core of the gasket, the fluororesin-coated gasket is mounted between members. In this case, the protrusion is compressed, and the bore side of the protrusion is pressed against the flange side by the repulsive force, which further prevents liquid pooling between the gasket and the flange.

Furthermore, in the fluororesin-coated gasket of the present invention, if the inner peripheral wall of the annular core, the front and back surfaces, and the outer peripheral wall of the annular core are also covered, the annular core is sealed even when the gasket is removed and washed. Therefore, if the outer skin is made of a fluororesin, it will not deteriorate even if it is washed.

[Brief description of drawings]

FIG. 1 shows P obtained according to an embodiment of the present invention.
It is a half cross-sectional view of a TFE resin-coated gasket.

FIG. 2 is a half sectional view showing a PTFE resin-coated gasket obtained according to another embodiment of the present invention.

FIG. 3 is a half sectional view showing a PTFE resin-coated gasket obtained according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the main parts of the manufacturing method of the present invention.

FIG. 5 is a cross-sectional view showing the main parts of the manufacturing method of the present invention.

FIG. 6 is a half cross-sectional view of a conventional fluororesin-coated gasket.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Annular core body, 2 ... Bore part, 3, 4 ... Front and back surfaces, 10 ... Gasket, 11 ... Outer skin, 11a ... Bore outer skin, 11b ... Front and back outer skin, 12 ... Protrusion, 13 ... Outer peripheral wall, 14 ... type, t ... outer skin simple substance, T ... outer skin connected body.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29L 31:26

Claims (1)

[Claims] 1. A tube-shaped parson is placed in a mold in which annular concave portions and convex portions are alternately formed on the inner peripheral surface, and pressure is applied to the inside of this parson so that the inside of a thick bore portion is thickened. An outer skin connecting body is formed in which a plurality of outer skin units each including a peripheral wall and an outer skin for front and back surfaces whose thickness gradually decreases from the inner peripheral wall of the bore portion toward the outer peripheral side are formed, and the outer skin connecting body is formed in the mold. A method for producing a fluororesin-coated gasket, characterized in that the outer shell is cut into individual pieces, the outer shell is used as a thin outer shell, and an elastic annular core is mounted in the outer shell alone.