BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a non-asbestos gasket of Embodiment 1;
FIG. 2 is a section view of the non-asbestos gasket of FIG. 1;
FIG. 3 is a section view of main portions showing a bolt attaching portion of the non-asbestos gasket of FIG. 1;
FIG. 4 is a front view of a non-asbestos gasket of Embodiment 2;
FIG. 5 is a section view of main portions showing a bolt attaching portion of the gasket of FIG. 4;
FIGS. 6A and 6B are front and section views of a non-asbestos gasket of Embodiment 3, respectively;
FIGS. 7A and 7B are views of a non-asbestos gasket of Embodiment 4 showing a free state and a state after fastening, respectively;
FIG. 8 is a graph showing compression and restoration characteristics;
FIG. 9 is a graph showing helium-gas sealing characteristics after a heat cycle;
FIG. 10 is a front view showing a non-asbestos gasket (another embodiment) having a substantially elliptical shape; and
FIG. 11 is a perspective view showing a conventional metal gasket and the mounting situation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the non-asbestos gasket of the invention will be described with reference to the accompanying drawings. FIGS. 1 to 3 show Embodiment 1, FIGS. 4 and 5 show Embodiment 2, FIG. 6 shows Embodiment 3, and FIG. 7 shows Embodiment 4. FIGS. 8 and 9 show various characteristic graphs, and FIG. 10 is a front view of a non-asbestos gasket of another embodiment.
Embodiment 1
FIGS. 1 to 3 show a non-asbestos gasket A of Embodiment 1. The non-asbestos gasket A has a three-layer structured sealing portion S configured by: a core layer 1A which is made of a plate of a metal such as stainless steel, and which is formed into a concentric circle-like (an example of a concentric shape) corrugated shape having an axis P; and surface layers 2, 3 which are made of expanded graphite, and which are stacked on the front and back faces of the core layer 1A, respectively. The sealing portion S is configured by a corrugated portion 4 having a corrugated shape, and inner- and outer-circumferential flange portions 5, 6 which are formed continuously with the inner and outer diameter sides of the corrugated portion, respectively. The inner- and outer-circumferential flange portions 5, 6 are placed on the identical plane with the lower side which is one end of the thickness direction of the corrugated portion 4, and on the same side.
Namely, the sealing portion is formed so that the peaks of the lower crests y of the corrugated portion 4, and bottom faces 5a, 6a of the inner- and outer-circumferential flange portions 5, 6 are included in the same virtual plane m. In FIG. 3, an end face 11A of a first flange pipe 11 which is on the lower side corresponds to the virtual plane m. FIG. 3 shows a free state of the non-asbestos gasket A where the upper and lower crests y are in light contact with end faces (sealed surfaces) 11A, 12A of first and second flange pipes 11, 12 each having an internal flow path r, or the non-asbestos gasket A is not compressed between the end faces 11A, 12A, but simply interposed between the end faces.
In an outer circumferential end of the sealing portion S, i.e., an outer circumferential end of the outer circumferential flange portion 6, the core layer 1A is slightly protruded from the front and back surface layers 2, 3 toward the outer diameter side. Namely, the outer diameter of the core layer 1A is slightly larger than the outer diameters of the front and back (upper and lower) surface layers 2, 3, and the metal portion is exposed. In an inner circumferential end of the sealing portion S, i.e., an inner circumferential end of the inner circumferential flange portion 5, the front and back surface layers 2, 3 are more protruded than the core layer 1A toward the inner diameter side, and processed in a direction (vertical direction) along which the surface layers are in close contact with each other. As a result, the inner circumferential end is configured so that the core layer 1A is not exposed but covered.
The inner and outer diameters of the non-asbestos gasket A are set so that, when the non-asbestos gasket A is in the free state, as shown in FIG. 3, the diameter of the inner circumferential end of the inner-circumferential flange portion 5 is slightly larger than that of the flow path r, and a distinct radial gap exists between the outer circumferential end of the outer-circumferential flange portion 6, i.e., the outer circumferential end of the core layer 1A, and fastening bolts 7. In a state (not shown) where the fastening bolts 7 are fastened with a specified torque and the non-asbestos gasket A is compressed, the gasket is slightly inflated in the inner and outer diameter sides, and hence the diameters are set so that displacement occurs in which the diameter of the inner circumferential end of the inner-circumferential flange portion 5 coincides or substantially coincides with that of the flow path r, and the outer circumferential end of the core layer 1A is in light contact with the fastening bolts 7 or a very small gap is formed therebetween.
Therefore, the core layer 1A which is made of a metal material is not exposed in the flow paths r, r of the flange pipes 11, 12 which are connected to each other through the non-asbestos gasket A, and hence a fluid which must avoid a contact with a metal, such as a chemical solution or a wash solution can be used. The core layer 1A which is made of a metal material is exposed on the outer circumference. When the non-asbestos gasket A is in contact with the fastening bolt 7 in the case of assembling or the like, only the core layer 1A is in contact with the fastening bolt. Therefore, it is possible to achieve a preferred effect that a fear that the surface layers 2, 3 which are made of expanded graphite bump against the fastening bolt 7 and collapse, and this adversely affects the sealing property is avoided. The non-asbestos gasket A of Embodiment 1 is configured by only the circular sealing portion S.
The above-described non-asbestos gasket A of Embodiment 1 has the following various features. The features will be briefly described in a supplemental manner. Items of the features are structure and feature, characteristics (compression and restoration characteristics, helium-gas seal test after a heat cycle), etc.
[Structure and Feature]
The gasket is a semi-metallic gasket in which the core layer 1A that is a core member and a thin metal plate (for example, a stainless steel material that is a standard pipe material) is formed into a corrugated shape, and the expanded graphite sheets 2, 3 which have a sealing property and a heat resistance are stacked on the both faces of the layer. According to the configuration, a local fastening pressure can be set to be high by forming a concentric circle-like seal loop. Even in a low-torque fastened state in a process of fastening a bolt, therefore, the gasket exhibits an excellent sealing property. Furthermore, the amount of compression of the gasket in bolt fastening can be set to be large, and hence the gasket is excellent in conformability to the flange surface, and in following property with respect to the surface accuracy of the flange. Since the gasket has such features, there is an advantage that, in a place where an asbestos joint sheet gasket is conventionally used, a sealing property equivalent to or more than that obtained by the asbestos joint sheet gasket can be obtained without changing the manner of the fastening management.
[Compression and Restoration Characteristics]
FIG. 8 shows an example of the compression and restoration characteristics of the non-asbestos gasket A of Embodiment 1, in the form of a graph for comparison to an asbestos joint sheet gasket. As seen from the graph, the amount of compression of the non-asbestos gasket A is ensured to be about 5 times that of an asbestos joint sheet gasket.
[Helium-Gas Seal Test after a Heat Cycle]
FIG. 9 shows an example of the helium-gas sealing characteristics after a heat cycle of the non-asbestos gasket A of Embodiment 1, in the form of a graph for comparison to an asbestos joint sheet gasket. As seen from the graph, as compared with an asbestos joint sheet gasket, in the non-asbestos gasket A, the sealing property in the use at a high temperature can be stabilized at a high level.
Embodiment 2
As shown in FIGS. 4 and 5, the non-asbestos gasket A of Embodiment 2 comprises a gasket main portion 1 configured by: the core layer 1A; and projection pieces 1B which are formed integrally at four places of the outer circumferential side of the core layer, respectively. The other configuration is identical with that of the non-asbestos gasket A of Embodiment 1. Therefore, components which are identical with those of the non-asbestos gasket A of Embodiment 1 are denoted by the same reference numerals.
The four projection pieces 1B are arranged about the center P of the gasket at intervals of equal angle (90 deg.), and formed to be in the identical plane with the outer-circumferential flange portion 6. Preferably, the fastening bolts 7 are placed in four places between adjacent projection pieces 1B, 1B, respectively as shown in FIG. 4. The projection pieces 1B can function as nip portions for positioning in assembling the non-asbestos gasket A, or carrying the gasket, and therefore is convenient.
Embodiment 3
As shown in FIG. 6, the non-asbestos gasket A of Embodiment 3 is formed at an irregular pitch in which the interval of crests which are adjacent to each other in a radial direction of the corrugated portion 4, i.e., the radial intervals between the crests y is smaller as more advancing toward the inner diameter side of the corrugated portion 4. Specifically, when the intervals of adjacent crests y, y are indicated as dn (n=1, 2, 3, . . . ) in the sequence beginning with the inner-diameter side, the relationships of d1<d2<d3< . . . <dn−1<dn are established. The other configuration is identical with that of the non-asbestos gasket A of Embodiment 1.
Embodiment 4
In the non-asbestos gasket A of Embodiment 4, as shown in FIG. 7, an outer diameter side end of the inner-circumferential flange portion 5 is positioned on an identical (or substantially identical) plane with the lower end (an example of one end) in the thickness direction of the corrugated portion 4, and the inner-circumferential flange portion is formed into a tapered face in a state where the face is closer to the lower side (an example of the side remote from another end in the thickness direction) as more advancing toward an inner diameter side end. The other configuration is identical with that of the non-asbestos gasket A of Embodiment 1. Therefore, components which are identical with those of the non-asbestos gasket A of Embodiment 1 are denoted by the same reference numerals.
In a free state where only the inner end 5a of the inner-circumferential flange portion 5 is in contact with the end face 11A of the first flange pipe 11, the fastening bolts 7 are turned to compress the non-asbestos gasket A of Embodiment 4, and then the inner-circumferential flange portion 5 is deformed so as to be folded back about the inner end 5a toward the horizontal plane. In the side of the gasket bottom face, therefore, the butting pressure of the inner end 5a is gradually raised by the elasticity due to the downward bending of the inner-circumferential flange portion 5. In this case, the lower surface layer 3, i.e., the expanded graphite is in direct contact with the end face 11A, and a coefficient of friction which is higher than that in the case where the core layer (metal) 1A is in contact with the end face is produced. Therefore, a frictional drag against the force by which the corrugated portion 4 tries to perform the radial expanding displacement due to the compression acts at a higher degree than that in the case where a metal is in contact with the end face.
As a result, the reduction ratio that is a ratio at which the inner end 5a is moved toward the inner diameter side when the fastening bolts 7 are fastened with a specified torque is reduced as compared with the case of a gasket configured only by a metal. Therefore, it is possible to obtain advantages that the measure of diameter differences in the case where the diameter of the inner end 5a in the free state is set to be slightly larger than the diameter of the internal flow path r in anticipation of the diameter reduction deformation due to the gasket compression can be reduced, and that a failure in which a fluid flow is disturbed by an unexpected protrusion of the inner end 5a into the internal flow path r hardly occurs.
Other Embodiments
The gasket of the invention may be the non-asbestos gasket A comprising the core layer 1A made of a metal plate which has a concentric and substantially elliptical shape, and which is formed into a corrugated shape as shown in FIG. 10. This gasket is identical with the non-asbestos gasket A of Embodiment 1 except that the shape in a front view is different, and the corresponding components are denoted by the corresponding reference numerals. As the concentric or substantially concentric shape, various shapes such as elliptic, oval, rectangular, and polygonal shapes may be employed.
Patent Application
20080036161
