JPH076578B2 - Fluororesin coated gasket and method for manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a gasket that is incorporated in a flange joint used in tower tanks such as tanks or pipes, for example, and prevents leakage of internal fluid. In particular, the present invention relates to a gasket used for so-called sanitary gaskets used in pipes and the like through which a fluid that dislikes contamination flows, and in which the surface of an elastic annular core is covered with a thin fluororesin.

Technical 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. Recently, however, polytetrafluoroethylene has been used in the joints of such pipes. A gasket whose surface is covered with a film made of fluororesin such as resin (hereinafter referred to as PTFE) is used.

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

The annular core body 1 functions as a cushioning material, and although the material to be used is different depending on the application, a single rubber body,
Composites of organic or inorganic fibers and rubber, felt mats, woven fabrics, etc. are used alone or in combination.

On the other hand, since the outer skin 5 is a portion that 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 is preferable that it has appropriate elasticity. A fluororesin such as PTFE is used.

Then, such a fluororesin-coated gasket G is
When the flange joint is mounted between the flanges 6, when the elastic force of the annular core body 1 is transmitted to the flange 6 side through the PTFE outer cover 5, the sealing property is improved.
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 annular core body 1
The outer skin 5 cannot prevent the state where the inner peripheral wall of the bore portion 2 swells inward (indicated by the broken line in FIG. 6), and this inner swelling may cause a pool of internal fluid. There is.

Further, when the annular core 1 is covered with the PTFE outer skin 5, conventionally, a PTFE thin film having a predetermined width is folded in two and the release side end portion is located on the outer peripheral side of the annular core 1 so as to have a circular shape. It has been plastically deformed.

However, in this case, the PTFE thin film having a thickness of 0.2 mm or less is forced to be stretched on the outer peripheral side, which may cause cracks on the outer peripheral side. Therefore, the PTFE thin film used as the outer cover must have a certain thickness.

It should be noted that, when manufacturing the outer skin, it is possible to mechanically cut from the PTFE block to manufacture an outer skin with a substantially uniform thickness as a whole, but in that case, a relatively thin-walled outer skin is cut. In addition to being difficult, the material is wasted, which is disadvantageous in terms of cost.

OBJECT OF THE INVENTION The present invention can be used for pipes through which a fluid that extremely dislikes pollution flows, has good sealing properties, is suitable for sanitary use with almost no liquid pool, and is easily manufactured. It is an object of the present invention to provide a fluororesin-coated gasket that is capable of being produced and is advantageous in terms of cost.

SUMMARY OF THE INVENTION The fluororesin-coated gasket according to the present invention is a fluororesin-coated gasket obtained by coating the inner peripheral wall of a bore portion and at least the front and back surfaces of an elastic annular core body with a thin outer skin made of a fluororesin. The outer skin for the bore covering the peripheral wall is thickened, and the outer skin for the front and back surfaces covering the front and back surfaces of the annular core is gradually thinned from the bore side toward the outer peripheral side.

In the fluororesin-coated gasket according to the present invention, protrusions may be formed on the front and back surfaces of the annular core body.

Further, the thin-walled outer skin of the fluororesin-coated gasket according to the present invention may cover not only the inner peripheral wall and the front and back surfaces of the annular core, but also the outer peripheral wall.

Such a thin skin may be bonded to the annular core body.

According to such a fluororesin-coated gasket according to the present invention, the thickness of the outer skin for the bore covering the inner peripheral wall of the bore portion is increased,
Since the outer and outer skins are thin, even if this gasket is attached to a flange joint and tightened, the inner wall of the gasket bore will not be deformed, and it is possible to prevent pooling of the internal fluid. The outer skin of the ring has a good elasticity because the elasticity of the annular core body is sensitively transmitted to the flange. In a normal joint, the tightening force on the outer peripheral side is smaller than that on the bore side. Therefore, in the fluororesin-coated gasket, the elasticity of the annular core body effectively acts and the sealing property is 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 according to the present invention, when the projections are formed on the front and back surfaces of the annular core, the projections are compressed when the fluororesin-coated gasket is mounted between the members, and the bores of the projections are compressed. The side is pressed against the flange side by the repulsive force, which further prevents the liquid pool from being generated between the gasket and the flange.

Further, in the fluororesin-coated gasket according to the present invention, if the inner peripheral wall of the annular core, the inner peripheral wall, the front and back surfaces and the outer peripheral wall are also covered, the annular core becomes a closed state even when the gasket is removed and washed. Therefore, it does not deteriorate, and if the outer skin is made of a fluororesin, it does not deteriorate by washing.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a half sectional view of a fluororesin-coated gasket according to an embodiment of the present invention, FIGS. 2 and 3 are half sectional views showing other embodiments of the present invention, and FIGS. It is sectional drawing which shows the principal part of the manufacturing method of this invention, respectively, and attaches | subjects the same code | symbol to the member common to the member shown in FIG. 6, and abbreviate | omits a part of description.

In a fluororesin-coated gasket 10 shown in FIG. 1, a thin outer skin 11 made of fluororesin covers the inner peripheral wall of the bore portion 2 of the annular core 1 having elasticity and at least the front and back surfaces 3 and 4.

The outer skin 11 is an outer skin for a bore that covers the inner peripheral wall of the bore portion 2.
The wall thickness of 11a is made thicker, and the wall thickness of the front and back outer skin 11b that covers the upper and lower surfaces 3, 4 of the annular core 1 is gradually reduced from the bore portion 2 side toward the outer peripheral side. Inner and outer diameter skin 11
The inner thickness of is not particularly limited, but preferably 0.
It is 5 to 1.0 mm and 0.01 to 5 mm. The fluororesin forming the outer skin 11 is not particularly limited, but includes polytetrafluoroethylene (PTFE), PFA which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and tetrafluoroethylene and hexafluoropropylene. A fluororesin such as FEP which is a copolymer of EPO, or EPE which is a copolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether can be widely used.

The material of the annular core is not particularly limited as long as it has elasticity, and for example, rubber, light plastic, etc. are used.

According to such a gasket, when the gasket 10 is tightened by the flange, the thick wall skin 11a 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 swells or deforms to stagnate a part of the fluid flowing inside. Further, the outer skin 11b on the outer peripheral side sensitively transmits the elasticity of the annular core 1 to the flange 6 and has excellent sealing properties. In a normal joint, since the tightening force on the outer peripheral side is smaller than that 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 becomes excellent.

Therefore, it is extremely advantageous as a gasket for a clamp type joint in which a large tightening force cannot be obtained.

As shown in FIG. 2, a protrusion 12 may be formed on the front and back surfaces of the annular center core 1 substantially at the center of the inner and outer diameters. With this configuration, when the fluororesin-coated gasket 10 is attached to the flange joint, the flange 12 causes the protrusion 12
Is compressed, and the bore portion 2 side of the projection 12 is pressed against the flange side by the repulsive force, so that the liquid pool hardly occurs. Further, such a protrusion is preferably annular.

As shown in FIG. 3, the thin-walled outer shell 11 has an annular core body 1.
Not only the inner peripheral wall and front and back surfaces 3 and 4 of the bore portion 2 but also the outer peripheral wall 13
You may coat even.

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 skin 11 is also a fluororesin, this also deteriorates due to cleaning. There is an advantage of not doing it.

The thin outer skin 11 may be bonded to the annular core body 1 with an adhesive. To perform this adhesion, for example, the outer skin 11
Roughened the inner surface of the with an ammonia solution of sodium,
Cover the rubber material of the ring-shaped core 1, press and heat in the mold,
The outer skin 11 and the annular core 1 may be bonded together with the vulcanization of the rubber. In order to manufacture such a fluororesin-coated gasket 10, it is preferable to use a blow molding method.

For example, as shown in FIG. 4, first, a tube-shaped parson is put into a mold 14 in which annular concave portions and convex portions are alternately formed on the inner peripheral surface. Next, a pressure is applied to the inside of this Parson to bulge the outer periphery to bring it into close contact with the inner peripheral surface 14a of the mold 14. When such blow molding is performed, the parson is pulled closer to the outer peripheral side of the swollen parson and becomes thinner, which is a preferable molding method for forming the outer cover 11.

According to such blow molding, the half-section has a substantially U-shape, the thickness of the U-shaped bottom is large, and the thickness of the outer skin t gradually decreases from the bottom toward the outer peripheral side. (See figure)
It is possible to obtain the outer skin connected body T in a state in which a large number of are connected.

Finally, if the outer skin connected body T is taken out from the mold 14 and then cut into individual outer skin units t, a large number of thin outer skins 11 can be easily obtained. This outer shell is used as a thin outer shell 11 of a fluororesin-coated gasket, and an annular central body having elasticity within the outer shell alone (that is, inside the thin outer shell)
When 11 is attached, the fluororesin-coated outer gasket according to the present invention can be obtained. 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 a mold used for blow molding to form a fluororesin-coated gasket 10 as in the embodiment shown in FIG.

EFFECTS OF THE INVENTION As described above, according to the present invention, the thickness of the outer skin for the bore covering the inner peripheral wall of the bore portion is increased, and the thickness of the outer skin for the front and back surfaces is reduced. Even when tightened by tightening it on the inner surface of the gasket, the inner peripheral wall side of the gasket is not deformed and 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,
It has excellent sealing properties. In a normal joint, the tightening force on the outer peripheral side is smaller than that on the bore side. Therefore, in the fluororesin-coated gasket, the elasticity of the annular core body effectively acts and the sealing property is 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 gasket according to the present invention, the thicknesses of the front and back surfaces of the outer skin are gradually reduced, and moreover, since the front and back surfaces are arranged symmetrically with the same thickness, uniform tightening is possible. If this is not the same thickness, the tightening will be uneven
After tightening, it is necessary to retighten again.

Further, in the fluororesin-coated gasket according to the present invention, when the projections are formed on the front and back surfaces of the annular core, the projections are compressed when the fluororesin-coated gasket is mounted between the members, and the bores of the projections are compressed. The side is pressed against the flange side by the repulsive force, which further prevents the liquid pool from being generated between the gasket and the flange.

Further, in the fluororesin-coated gasket according to the present invention, if the inner peripheral wall of the annular core, the inner peripheral wall, the front and back surfaces and the outer peripheral wall are also covered, the annular core becomes a closed state even when the gasket is removed and washed. Therefore, it does not deteriorate, and if the outer skin is made of fluororesin, it does not deteriorate by washing.

[Brief description of drawings]

FIG. 1 is a half sectional view of a PTFE resin-coated gasket according to an embodiment of the present invention, FIGS. 2 and 3 are half sectional views showing other embodiments of the present invention, and FIGS. FIG. 6 is a sectional view showing a main part of a method for manufacturing a PTFE resin-coated gasket according to an embodiment of the present invention, and FIG. 6 is a half sectional view of a conventional fluororesin-coated gasket. 1 ... Annular core, 2 ... Bore part, 3,4 ... Front and back, 10 ... Gasket, 11 ... Outer skin, 11a ... Bore outer skin, 11b ... Front and back outer skin, 12 ... Protrusion, 13 ... Outer wall, 14 ... Model, t ... Outer skin unit, T ... Outer skin connection body.

Claims (4)

[Claims] 1. A fluororesin-coated gasket comprising an inner peripheral wall of an annular core having elasticity and at least the front and back surfaces thereof covered with a thin outer cover made of fluororesin, wherein the outer skin for the bore covers the inner peripheral wall of the bore. A fluororesin-coated gasket, characterized in that the thickness is made thicker, and the thickness of the front and back skins covering the front and back surfaces of the annular core is gradually reduced from the bore side toward the outer peripheral side. 2. The fluororesin-coated gasket according to claim 1, wherein a protrusion is formed at substantially the center of the inner and outer diameters on the front and back surfaces of the annular core body. 3. The fluororesin-coated gasket according to claim 1, wherein the thin outer skin covers not only the inner peripheral wall and the upper and lower surfaces of the annular core, but also the outer peripheral walls. 4. The fluororesin-coated gasket according to any one of claims 1 to 3, wherein the thin outer skin is bonded to an annular core body.