JPH08233109A - Gasket - Google Patents

Abstract

PURPOSE: To provide a gasket which exercises a high sealing property even in a low pressure fastening condition, so as to prevent the leakage of a fluid. CONSTITUTION: High density areas 2 and 3 with no permeability which are continued in the peripheral direction, and the thickness is higher than that in a low pressure fastening condition; and low density areas 7 and 8 which are continued in the peripheral direction, the thickness is higher than that of the high density areas 2 and 3, and the surfaces are made the same to the high density areas 2 and 3 in the low pressure fastening condition; are formed in a porous sheet 5. And the high density areas 2 and 3 are formed at least one side of the inner periphery or the outer periphery of the sheet 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket for sealing a joint portion of a fluid device and a pipe flange portion.

[0002]

2. Description of the Related Art Conventionally, a gasket has been manufactured by punching a sheet having a constant thickness into a ring shape such as a round shape or a square shape. As a gasket material, a porous sheet made of polytetrafluoroethylene (hereinafter referred to as PTFE) is widely used instead of conventional asbestos because of its low pollution. Further, when it is used to connect a glass tube or a plastic tube, it cannot be tightened with a high tightening pressure, so it is necessary to connect the tubes with a low tightening pressure. Therefore, the porous sheet is required to have high sealing properties.

[0003]

[Problems to be Solved by the Invention]
As shown in FIG. (A), the normal porous sheet 40 has a permeability through which a fluid passes in the non-tightened state (the fluid passage path is indicated by an arrow), but as shown in FIG. Even when this product is tightened at a low pressure, a considerable amount of voids remain inside, so that there is a drawback that the fluid permeates into the porous sheet 40 and leaks to the outside, as described above.

As a method of improving the sealability of a gasket using such a porous sheet, a method of applying a sealant capable of imparting impermeability to the surface of the ring-shaped gasket or the vicinity of the inner periphery thereof, and the gasket is locally applied. There is a method in which a high-density region that is impermeable in the circumferential direction is formed by applying a positive pressure. The former method requires another member in addition to the porous sheet, which is not preferable because of an increase in cost. Further, in the latter method, although it is possible to reduce the leakage of the fluid to the outside through the inside of the gasket due to the local pressurization to some extent, the leakage cannot be completely prevented. That is, as shown in FIG. 14 (a), in the porous sheet 41 in which both ends are pressed to form the compression parts 42, 42, so-called penetrating leakage that passes through the compression part 42 can be prevented. As shown in (b), since the step portion cannot be eliminated with a low tightening pressure, leakage occurred through this step portion.

In order to prevent such a step from remaining, it is conceivable to reduce the pressure applied to the compression section 42 so that the thickness of the compression section 42 becomes closer to that of the non-compression section 43. Then, the significance of providing the compression portion 42 is substantially lost, and the penetration preventing effect cannot be achieved.

The present invention has been made to eliminate the above-mentioned problems, and provides a gasket capable of exhibiting a high sealing property even in a low pressure tightened state and preventing fluid leakage. With the goal.

[0007]

The gasket of the present invention comprises:
A gasket made of a porous sheet, which has an impervious high-density region which is continuous in the circumferential direction and whose thickness is larger than the thickness in the low-pressure tightened state, and which is continuous in the circumferential direction and whose thickness is the above-mentioned high density. It is characterized in that a low density region which is larger than the region and which is flush with the above high density region in a low pressure tightened state is formed.

Further, the high-density region is formed on at least one of the inner peripheral portion and the outer peripheral portion.

[0009]

15 (a) and 15 (b) conceptually show the operation based on the above-described structure of the present invention. As shown in FIG. 3A, when the high density areas 45, 45 are formed at both ends of the porous sheet 44, since the high density areas 45 are impermeable, in the non-tightened state, no pressure is applied. The fluid permeates through the step formed between the low density area 46 (shown by an arrow). However, the thickness of the high density region 45 is
Since the thickness is larger than the thickness in the low pressure tightening state and the step between the high density region 45 and the low density region 46 is relatively small, in the low pressure tightening condition, as shown in FIG. As a result of making the low density region 46 flush with each other, it becomes possible to prevent the fluid from permeating through the step portion.

It is preferable that the high-density regions 45 are provided on the inner peripheral portion and the outer peripheral portion of the ring-shaped gasket, respectively.
This makes it possible to prevent the fluid from penetrating into the gasket and also to prevent the fluid from leaking from the gasket to the outside. Further, by providing such high-density regions 45 on the inner and outer peripheral portions, respectively, the inner and outer peripheral portions of the gasket are reinforced, and dimensional change can be prevented. In addition, if necessary, high density area 4
5 may be provided only on one of the inner peripheral portion and the outer peripheral portion of the ring-shaped gasket.

As described above, the high-density region 45 needs to have a sufficiently high density so as to be impermeable, and if it is not high density, the fluid may penetrate. Therefore, it is not sufficient to simply press and compress as in the past. Various methods can be adopted to form such a high-density region 45 (for example, a method of laminating and adhering the same porous sheet to a part of the porous sheet and press-molding), but in the present invention. By drawing at least one of the inner peripheral portion and the outer peripheral portion of the porous sheet, and then molding,
A high-density area can be easily formed.

In another gasket of the present invention, adjacent portions of the porous sheet are depressed in opposite directions from both sides to at least half the thickness of the porous sheet to form a pair of depressed portions. Since the passage of the fluid is blocked and the space between the depressions becomes extremely high, the effect of preventing the fluid from permeating is ensured. At this time, if the protrusions are provided, the protrusions are compressed by tightening, and the depressed portions have a higher density and become impermeable.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. 1 and 2 are a plan view and a sectional view taken along line II-II of the gasket of this embodiment.
As shown in these figures, the ring-shaped gasket 1 is
Impermeable high-density regions 2 and 3 which are continuous in the circumferential direction and have a thickness larger than the thickness in the low pressure tightened state are formed in the inner peripheral portion and the outer peripheral portion, respectively. Further, a compression portion 4 continuous in the circumferential direction is formed between them, and low density areas 7 and 8 continuous in the circumferential direction are provided between the high density areas 2 and 3 and the compression portion 4. Has been formed.

Such a gasket comprises a porous sheet made of PTFE or the like. This porous sheet usually has a thickness of 0.1 to 3.0 mm and a density of 0.5 to 1.0 g.
It is about / cm ³ . On the other hand, the thickness t ₁ and the density of the high density regions 2 and 3 are 0.5 to 1.5 mm and 1.0, respectively.
It is preferably about 2.2 g / cm ³ . When the thickness t ₁ of the high density regions 2 and 3 is smaller than the above range, the step portion between the low density regions 7 and 8 remains when the gasket is tightened at a low pressure, so that the fluid penetrates from there. , There is a risk of leakage from the inside of the gasket to the outside. Further, when the density of the high density regions 2 and 3 is smaller than the above range, a large number of voids remain inside, so that the fluid easily penetrates into the gasket and the sealing property becomes insufficient.

The compression section 4 is formed by compressing and compressing the porous sheet 5, and by making the thickness t ₂ smaller than the thickness t ₁ of the high density regions 2 and 3, The density is set to be approximately the same as that of the high density regions 2 and 3 to prevent passage of the fluid.

Next, a method of manufacturing the gasket of this embodiment will be described with reference to FIGS. First, a porous sheet as a material is punched into a ring shape. At this time, as shown in FIG. 3, the inner diameter d ₁ of the punched porous sheet 5 is smaller than the inner diameter of the normal gasket 6 (shown by the one-dot chain line in the figure), and the outer diameter d ₂ thereof is smaller than that of the normal gasket. It is formed larger than the outer diameter.

This porous sheet 5 is put into a drawing die (not shown), and the inner peripheral edge portion A and the outer peripheral edge portion B are bent in the same direction as shown in FIG. By such drawing, the inner diameter and the outer diameter of the porous sheet 5 are adjusted to be equal to those of the target gasket.

Then, the porous sheet 5 is put into the mold 9 shown in FIG. 5 and molded into the shape shown in FIGS. 1 and 2. The mold 9 comprises a bottom mold 91, a core mold 92, an outer mold 93 and a pressing mold 94, and two grooves 95, 95 are formed in parallel on the upper surface of the bottom mold 91 and the lower surface of the pressing mold 94, respectively. A projection 96 for molding the compression portion 4 is provided between the grooves. Molding is performed by at least one of heating and pressing.

As shown in FIG. 6, the thus obtained gasket of this embodiment has flanges 10 and 1 facing each other.
It is inserted between 1 and it is tightened at low pressure (usually about 150-300 kg / cm ² ). At this time, the thickness t _{2 in} FIG.
When tightened up to, the gasket has no stepped portion, and the high density areas 2 and 3 of the inner and outer peripheral parts maintain a higher density than other parts, so simply press and compress as in the past. Compared to the above, the fluid is completely prevented from permeating and passing, and the fluid does not leak. That is, if the material is simply pressed and compressed without being drawn, the whole has a uniform density by tightening, so that fluid leakage is likely to occur especially in the case of low pressure tightening.

In the gasket of the present invention, the high density regions 2 and 3 are provided on the inner and outer peripheral portions, respectively, as shown in FIG. 11, without providing the compression portion 4 and the depressed portion shown in these embodiments. Of course, the gasket may be a free gasket.

Another gasket of the present invention is shown in FIGS.
Each is illustrated in the figure. That is, in the gasket shown in FIG. 7, adjacent portions on both sides are strongly pressed and / or heated from opposite directions to compress each other to form two V-shaped depressions 12a and 12b in cross section, thereby allowing fluid to permeate. The paths are blocked and the depressions 12a and 12b are formed.
A high-density impervious portion 14 is provided between them to prevent bypass of the fluid. At this time, the depth of the depressions 12a, 12b needs to be formed to be half or more than the thickness of the porous sheet, and the depressions 12a,
When the depth of 12b does not reach half of the thickness of the porous sheet, not only blocking of the flow path of the fluid but also the density of the impermeable portion 14 becomes low, which is insufficient for preventing the permeation of the fluid. The first
The same components as those in FIG. 2 and FIG. 2 are designated by the same reference numerals and their description is omitted.

The gasket shown in FIG. 8 has a recess 1 having a rectangular cross section.
3a and 13b are formed in the same manner as described above, and a high density impervious portion 15 is provided between them, which is the same as that shown in FIG.

FIG. 9 is a modification of FIG. 7, in which projections 1 are formed on the opposite surface when forming V-shaped depressions 16a and 16b in cross section.
7a and 17b are projected. In this case, the impervious portion 18 is formed over almost the entire thickness of the gasket, and the protrusion 17 is compressed at the time of tightening to have a high density, so that the effect of preventing fluid permeation is further improved. Become. FIG. 10 shows depressions 19a, 19b having a rectangular cross section and projections 20a, 20b formed on the opposite side. The protrusions 17a, 17b, 20a, 20b may be provided on only one of the two surfaces.

Next, the gasket of the present invention will be described with reference to experimental examples. Example 1 Porous sheet with a thickness of 3 mm and a density of 06 g / cm ³ (PTF
E) was cut into an inner diameter of 32 mm and an outer diameter of 78 mm. Then, as shown in FIG. 4, the porous sheet is drawn to have an inner diameter of 35 mm and an outer diameter of 74 mm, and then molded with a mold 9 shown in FIG. A gasket as shown was obtained. The gasket has a thickness of 1.4 mm and a density of 18
A high density area of g / cm ³ was formed, and a compressed portion having a thickness of 1.0 mm and a density of 18 g / cm ³ was formed between them. Example 2 A gasket having a special shape was formed into a shape shown in FIG. The height of the protrusion was 0.5 mm and the depth of the depression was 2.2 mm. Example 3 A gasket shown in FIG. 10 was obtained in the same manner as in Example 2 except that the mold surface shapes of the bottom mold and the pressing mold were changed. In this product, the height of the protrusion was 0.5 mm and the depth of the depression was 2.0 mm.

Gas Leakage Test A sample gasket was inserted between flanges and tightened, nitrogen gas was flowed at 21 kg / cm ² , and the sealing performance of the sample gasket was evaluated from the leakage amount. The sample gasket used was the gasket of Example 1, and the following Comparative Examples 1 and 2 were used as comparative samples. Comparative Example 1-Ring cut piece of porous sheet (inner diameter 35 m
m, outer diameter 74 mm, thickness 3 mm) Comparative Example 2—Thickness 1.
Gasket compressed to 0 mm with a density of 1.8 g / cm ³ . The test results are shown in FIG. From the figure, it can be seen that the gasket of Example 1 has excellent sealing performance at low tightening pressure. That is, 300 kg / cm in the gasket technical field
We think that a tightening pressure of up to ² is low, and 200kg in Example 1.
With a low tightening pressure of / cm ^2, the amount of leakage could be reduced to 0.01cc / min or less. In addition, the gaskets of Examples 2 and 3 also obtained almost the same results as in Example 1.

[0026]

The gasket of the present invention is formed with a high density region having a thickness larger than that in the low pressure tightened state, and the high density region and the low density region are flush with each other in the low pressure tightened state. Therefore, leakage to the outside due to fluid permeation is prevented. When such a high-density region is provided on at least one of the inner peripheral portion and the outer peripheral portion of the gasket, it is possible to prevent fluid from permeating into the gasket and / or leaking from the inside of the gasket to the outside. The part and / or the outer peripheral part is reinforced, and the dimensional change can be prevented.

When the gasket of the present invention is manufactured, for example, at least one of the inner peripheral portion and the outer peripheral portion of the porous sheet is drawn and then molded to easily form an impermeable high density region. can do.

[Brief description of drawings]

FIG. 1 is a plan view of a gasket according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a cross-sectional view of a porous sheet used for manufacturing the gasket of the present invention.

FIG. 4 is a cross-sectional view of a drawn porous sheet.

FIG. 5 is a cross-sectional view of a molding die used for manufacturing the gasket of the present invention.

FIG. 6 is a cross-sectional view showing a tightened state of the gasket according to the embodiment of the present invention.

FIG. 7 is a sectional view showing a gasket according to another embodiment of the present invention.

FIG. 8 is a sectional view showing a gasket according to another embodiment of the present invention.

FIG. 9 is a sectional view showing a gasket according to another embodiment of the present invention.

FIG. 10 is a sectional view showing a gasket according to another embodiment of the present invention.

FIG. 11 is a sectional view showing a gasket according to another embodiment of the present invention.

FIG. 12 is a graph showing the results of a fluid leakage test of gaskets of Examples and Comparative Examples of the present invention.

FIG. 13 is an explanatory diagram for explaining the operation of a conventional gasket.

FIG. 14 is an explanatory diagram for explaining the action of another conventional gasket.

FIG. 15 is an explanatory diagram for explaining the action of the gasket of the present invention.

[Explanation of symbols]

 1 Gasket 2,3 High Density Area 4 Compressed Part 5 Porous Sheet 6 Gasket 7,8 Low Density Area 9 Mold 17a, 17b, 20a, 20b Protrusion

Claims (2)

[Claims] 1. A gasket made of a porous sheet, which has an impervious high-density region which is continuous in the circumferential direction and whose thickness is larger than the thickness in a low-pressure tightened state, and which is continuous in the circumferential direction and has a large thickness. Is smaller than the high-density region, and a low-density region that is flush with the high-density region in a low-pressure tightened state is formed. 2. The gasket according to claim 1, wherein the high-density region is formed on at least one of an inner peripheral portion and an outer peripheral portion.