JPH03107674A - Fluorine resin-coated gasket and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain satisfactory sealing property and prevent the formation of a liquid pool by thickening a bore outer skin covering the bore part inner circumferential wall, and gradually thinning the surface and back surface outer skins covering both surfaces of a ring core body from the bore side toward the outer circumference. CONSTITUTION:In a gasket 10, the inner circumferential wall of the bore pare 2 of an elastic ring core body 1 and at least both surfaces 3, 4 are coated with a thin outer skin 11 made of fluorine resin. For the outer skin 11, a bore outer skin 11a covering the inner circumferential wall of the bore part 2 is thickened, and surface and back surface outer skins 11b covering both the upper and lower surfaces 3, 4 are gradually reduced from the bore part 2 side toward the outer circumference. When the gasket 10 is fastened by a flange, the outer skin 11a prevents the deformation of the gasket 10 toward the bore part 2, so that a so-called liquid pool in which a part of the gasket is swollen or deformed to retain part of the liquid running in its inner part is prevented. The outer skin 11b sensitively transmits the elasticity of the core body 1 is sensitively transmitted to the flange, improving sealing property.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a gasket that is incorporated into a flange joint used for towers and vessels such as tanks or piping to prevent leakage of internal fluid. This gasket is used as a so-called sanitary gasket, which is used in piping through which fluids that are sensitive to contamination flow, and the surface of the elastic annular core is covered with a thin fluororesin, and it relates to a method for manufacturing the gasket.

Technical Background of the Invention In manufacturing factories for pharmaceuticals, foods, semiconductors, etc., piping is used through which fluids that are extremely sensitive to contamination flow, and recently, polytetrafluoroethylene A gasket whose surface is covered with a film made of a fluororesin such as resin (hereinafter referred to as PTFE) is used.

As shown in FIG. 6, for example, this fluororesin-coated gasket has a U-shaped half cross section (in some cases, It is covered with a thin outer skin 5 formed in a 7-shaped shape.

This annular core body 1 functions as a cushioning material, and the material used varies depending on the purpose, but it can be made of rubber alone,
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 part that comes into direct contact with the flange 6 or the flowing fluid, it is desirable that it has excellent heat resistance and chemical resistance, and it is also preferable that it has some degree of elasticity. , a fluororesin such as the aforementioned PTFE is used.

However, such a fluororesin-coated gasket G is
When installed between the flanges 6 of a flange joint, the elasticity of the annular core body 1 is transmitted to the flange 6 side through the PTFE outer skin 5, which improves the sealing performance. Thin ones are preferred. If the outer skin 5 is thick, the elasticity of the annular core 1 is difficult to be transmitted to the flange 6 side,
Seal performance is poor.

However, if the outer skin 5 is too thin, the outer skin 5 will not be able to prevent the inner circumferential wall of the bore 2 of the erotic core 1 from expanding inward (as shown by the broken line in FIG. 6). There is a risk of internal fluid pooling due to inward bulge.

Furthermore, when covering the annular core body 1 with the PTFE outer skin 5, conventionally, a PTFE thin film of a predetermined width is folded in half, and a circular shape is formed so that the open end is on the outer circumferential side of the annular core body 1. It is plastically deformed.

However, if you do this, P with a thickness of 0.2 mm or less
Since the TFE thin film is forcibly stretched on the outer circumferential side, there is a risk that cracks will occur on the outer circumferential side. Therefore, the PTFE thin film used as the outer skin must have a certain degree of thickness.

In addition, when manufacturing the outer skin, it is possible to mechanically cut a PTFE block to produce an outer skin with a substantially uniform thickness, but in that case, cutting of a relatively thin outer skin is possible. Not only is it difficult to do this, but it is also disadvantageous in terms of cost since materials are wasted.

Purpose of the Invention The present invention can also be used in pipes through which fluids that are extremely sensitive to lr5 staining flow, and has good sealing properties and almost no liquid pools, making it suitable for sanitary applications.
Moreover, it is an object of the present invention to provide a fluororesin-coated gasket that can be easily manufactured and is advantageous in terms of cost, and a method for manufacturing the same.

(Summary of the invention) The fluororesin corrugated gasket according to the present invention is a fluororesin-coated gasket in which the inner circumferential wall of the bore portion of an elastic annular core body and at least the front and back surfaces are covered with a thin outer skin made of fluororesin. The outer skin for the bore that covers the inner peripheral wall of the bore portion is thickened, and the outer skin for front and back surfaces that covers the front and back surfaces of the annular core body is gradually thinned from the bore side toward the outer peripheral side. do.

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

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

Such a thin outer skin may be adhered to the annular core.

Further, in the method for manufacturing a fluororesin-coated gasket according to the present invention, a tube-shaped Parson is placed in a mold in which four annular portions and convex portions are alternately formed on the inner peripheral surface, and pressure is applied inside the Parson. In addition, the outer skin 1 is made up of a thick inner circumferential wall of the bore portion and an outer skin for the front and back surfaces whose thickness gradually decreases from the inner circumferential wall of the bore portion toward the outer circumferential side.
A connected outer skin is formed by connecting a large number of 11 bodies, and after taking out the connected outer skin from the mold, the outer skin is cut into individual outer skins, and this single outer skin is used as a thin outer skin. It is characterized by being equipped with an annular core having elasticity.

According to such a fluororesin-coated gasket according to the present invention, the thickness of the outer skin for the bore that covers the inner circumferential wall of the bore portion is increased;
Since the wall thickness of the outer skin for the front and back surfaces is thin, even when this gasket is attached to a flange joint and tightened, the inner peripheral wall of the gasket's bore will not deform, preventing the internal fluid from pooling. The outer skin sensitively transmits the elasticity of the annular core to the flange, resulting in excellent sealing performance. In a normal joint, the tightening force on the outer peripheral side is smaller than on the bore side, so in the fluororesin-coated gasket, the elasticity of the annular core acts effectively, resulting in excellent sealing performance. In particular, it is extremely advantageous as a gasket for clamp-type joints where large tightening forces cannot be obtained.

In addition, in the fluororesin-coated gasket according to the present invention, when protrusions are formed on the front and back surfaces of the annular core, the protrusions are compressed when the fluororesin-coated gasket is inserted between members. The bore side is pressed toward the flange side by the repulsive force, which partially prevents liquid pooling from forming between the gasket and the flange.

Furthermore, in the fluororesin-coated gasket of the present invention, if the inner peripheral wall of the bore part, front and back surfaces, and outer peripheral wall of the annular core are also coated, the annular core will remain in a sealed state even when the gasket is removed and cleaned. Since it is made of fluorine resin, it will not deteriorate, and if the outer skin is also made of fluororesin, it will not deteriorate even after washing.

Furthermore, since the method for manufacturing the fluororesin-coated gasket according to the present invention utilizes so-called blow molding, due to the molding characteristics, the thickness of the bottom of the U-shape that serves as the outer skin for the bore is limited. It is possible to easily form an outer skin connected body in which a large number of 114 shells are connected, which is thick and whose wall thickness gradually decreases from the bottom toward the outer periphery, which is advantageous in terms of cost.

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 one embodiment of the present invention, FIGS. 2 and 3 are half-sectional views showing other embodiments of the present invention, and FIGS. 6A and 6B are cross-sectional views showing essential parts of the manufacturing method of the present invention, and members common to those shown in FIG. 6 are denoted by the same reference numerals, and some explanations are omitted.

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

This outer skin 11 is made by increasing the thickness of the bore outer skin 11a that covers the inner peripheral wall of the bore portion 2, and by increasing the thickness of the outer skin 1.1b for front and back surfaces that covers both upper and lower surfaces 3.4 of the annular core 1. gradually decreases from the bore portion 2 side toward the outer circumferential side. The thickness of the outer skin 11 on the inner diameter side and the outer diameter side is not particularly limited, but is preferably 0, 5 to 1, 0 mm, 0, respectively.
, 01-0, 5 mm.

Further, the fluororesin constituting the outer skin 11 is not particularly limited, or may be polytetrafluoroethylene (PTFE).
), PFA which is a copolymer of tetrafluoroethylene and fluoroalkyl vinyl ether, FEP which is a copolymer of tetrafluoroethylene and hexafluoropropylene, or tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl Fluorine resins such as EPE, which is a copolymer with 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 bore outer skin 1.1
a prevents the gasket 10 from deforming toward the bore portion 2 side.

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

Therefore, it is extremely advantageous as a gasket for a clamp-type joint that does not require large tightening force.

As shown in FIG. 2, a protrusion 12 may be formed at approximately the center of the inner and outer diameters on the front and back surfaces of the annular core body 1. In this way, this fluororesin-coated Gaskera I-10
When attached to a flange joint, the projection 12 is compressed by the flange, and the bore portion 2 side of the projection 12 is pushed toward the flange by a repulsive force, thereby making it difficult for liquid pooling to occur. Moreover, it is preferable that such a protrusion is annular.

As shown in FIG. 3, the thin outer skin 11 may cover not only the inner circumferential wall and front and back surfaces 3, 4 of the bore portion 2 of the annular core 1, but also the outer circumferential wall 3.

In this way, even when the gasket 10 is removed and cleaned, the annular core 1 remains in a sealed state.
It does not deteriorate, and if the outer skin 11 is also made of fluororesin, it has the advantage that it will not deteriorate even after cleaning.

Note that the thin outer skin 11 may be bonded to the annular core 1 with an adhesive. To perform this adhesion, for example, the inner surface of the outer skin 1 is roughened with a sodium ammonia solution, placed on the rubber fabric of the annular core 1, heated under pressure in a mold, and then The outer skin 11 and the annular core 1 may be bonded together during vulcanization.

To manufacture such a fluororesin-coated gasket 10,
Preference is given to using blow molding methods.

For example, as shown in FIG. 4, first, a tubular Parson is placed in a mold 14 in which four annular portions and convex portions are alternately formed on the inner peripheral surface. Next, pressure is applied to the inside of this Palson to bulge the outer periphery, thereby forming the inner peripheral surface 14a of the mold 1-4.
Closely contact. When such blow molding is performed, the outer peripheral side of the bulged Palson is pulled,
This results in a thinner wall, making this a preferred molding method for forming the outer skin 11- described above.

According to such blow molding, the outer skin t-shaped body t( (See Figure 4)
It is possible to obtain a connected outer skin body T in which a large number of are connected.

Finally, by taking out the outer skin connected body T from the mold 14 and cutting it into individual outer skins t, a large number of thin outer skins 11 can be easily obtained.

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

As shown in FIG. 5, a protrusion may be formed on a part of the mold used during blow molding to form a fluororesin-coated gas Kent 10 like the embodiment shown in FIG. 2.

As described in detail, according to the present invention, the thickness of the outer skin for the bore that covers the inner circumferential wall of the bore portion is made thicker, and the thickness of the outer skin for the front and back surfaces is made thinner, so that this gasket can be used as a flange joint. Even when attached and tightened, the inner circumferential wall of the gasket bore does not deform, preventing the internal fluid from pooling, and the outer 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 periphery side is smaller than on the bore side, so in the fluororesin-coated gasket, the elasticity of the annular core acts in an a-effect, resulting in excellent sealing performance.

In particular, a gasket for a clamp-type joint that cannot be tightened to a large extent is extremely useless.

Further, in the gasket according to the present invention, the thickness of the front and back surfaces of the outer skin gradually decreases, and since the front and back surfaces have approximately the same thickness and are arranged symmetrically, uniform tightening is possible. If the thickness is not the same, uneven tightening will occur, and additional tightening will be required later.

In addition, in the fluororesin-coated gas container/soto according to the present invention,
When protrusions are formed on the front and back surfaces of the annular core, the protrusions are compressed when the fluororesin-coated gasket is inserted between the members, and the bore side of the protrusions is pressed against the flange side by repulsive force, causing This makes it difficult for liquid to pool between the gasket and the flange.

Furthermore, in the fluororesin wave-covered gas gasket/soto according to the present invention, if the inner circumferential wall of the bore part, front and back surfaces, and outer circumferential wall of the annular core are covered, the annular core will remain airtight even when the gasket is removed and cleaned. Since it is in the same state as before, it will not deteriorate, and if the outer skin is also made of fluororesin, it will not deteriorate even after washing.

Furthermore, since the method for manufacturing the fluororesin-coated gasket according to the present invention utilizes so-called blow molding, due to the molding characteristics, the thickness of the bottom of the U-shape that serves as the outer skin for the bore is limited. It is possible to easily form a connected outer skin body in which a large number of outer skins 11i which are thick and whose wall thickness gradually decreases from the bottom toward the outer periphery are connected, which is advantageous in terms of cost.

Further, in the manufacturing method of the present invention, since blow molding is performed, the core and the outer skin can be reliably attached. In the conventional method of forming an outer skin by folding a PTFE'/Tj membrane of a predetermined width in half, the connection between the core and the outer skin tends to be incomplete, and there is a risk of peeling.

[Brief explanation of drawings]

Fig. 1 is a half-sectional view of a PTFE resin overcoating sheet according to an embodiment of the present invention, Fig. 2.3 is a half-sectional view showing another embodiment of the present invention, and Fig. 45 FIG. 6 is a cross-sectional view showing essential parts of the manufacturing method of the present invention, and FIG. 6 is a half-sectional view of a conventional fluororesin-coated gasket. DESCRIPTION OF SYMBOLS 1... Annular core body, 3.4... Front and back surfaces, 11... Outer skin, 1, 1 b... Outer skin for front and back surfaces, 13... Outer peripheral wall, t... Outer skin alone, 2... Bore part, 10... Gasket, 1, 1.8... Outer skin for bore, 12... Projection, 14... Type, T... Outer skin connection body.

Claims (1)

[Scope of Claims] 1) In a fluororesin-coated gasket in which the inner circumferential wall of the bore portion of an elastic annular core body and at least the front and back surfaces are covered with a thin outer skin made of fluororesin, a gasket for use in a bore that covers the inner circumferential wall of the bore portion. A fluororesin-coated gasket characterized in that the thickness of the outer skin is increased, and the thickness of the outer skin for front and back surfaces that covers the front and back surfaces of the annular core body is gradually thinned from the bore side toward the outer circumferential side. 2) The fluororesin-coated gasket according to claim 1, wherein a protrusion is formed at approximately the center of the inner and outer diameters of the front and back surfaces of the annular core. 3) The thin outer skin covers not only the inner circumferential wall of the bore portion and both upper and lower surfaces of the annular core body but also the outer circumferential wall of the annular core body.
The fluororesin-coated gasket described in section. 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. 5) A tubular 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 the Parson to form a thick inner circumferential wall of the bore portion. A connected outer skin body was formed by connecting a large number of single outer skins, each consisting of a front and back outer skin whose wall thickness gradually decreased from the inner circumferential wall of the bore portion toward the outer circumferential side, and this connected outer skin body was taken out from the mold. A method for manufacturing a fluororesin-coated gasket, characterized in that the outer skin is then cut into individual outer skins, each of which is used as a thin outer skin, and an annular core having elasticity is mounted inside this single outer skin.