JPH0460280A - Metallic gasket - Google Patents

Abstract

PURPOSE:To reduce the generation of the creep deformation of a gasket when baked and prevent the lowering of the bearing of a sealed face for obtaining a reliable metallic gasket by making the material near the part, with which the blade of a flange is brought into contact, of material whose hardness is lower than that of the material around the part. CONSTITUTION:The vacuum seal between a gasket 4 and flange 13 is performed by letting the blade 11 of the flange 13 cut into the sealing member of the gasket. When baking is done to reduce the quantity of gas discharging from a vacuum container, the temperature of a vacuum flange section rises, and since clamping force works to the cutting edge of the flange cut into the sealing member 1 of the gasket 4 due to the clamping bolt 12 of the flange 13, the creep deformation of the gasket 4 progresses. This deformation lowers the clamping force of the clamping bolt 12, which causes leak generation. Since, however, the internal peripheral surface, external peripheral surface, and bottom surface of the sealing member 1, into which the blade 11 of the flange cuts, is enclosed by a base member 2 whose hardness is higher than that of the sealing member 1, the deformation of the sealing member 1 is bound so that creep may not easily be generated, which reduces the generation of creep deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a metal gasket used for vacuum sealing between flanges.

(Prior Art) Conventionally, as a metal gasket, a gasket made of oxygen-free copper used for an ICF flange or a metal hollow O-ring made of stainless steel has been used.

The reason why a metal gasket is used for vacuum sealing is to bake the vacuum container at a high temperature and reduce outgas inside the vacuum container. However, in order to perform vacuum sealing with a gasket, a predetermined surface pressure is required on the contact surface between the sealing surface of the gasket and the flange. Figure 3 shows a case where a vacuum seal is maintained by an ICF flange and a gasket.The flange 13 is secured with a tightening bolt 12 so that the blade 11 of the flange is inserted into the gasket 4 and a predetermined surface pressure is generated on the contact surface. It's tightening.

(Problem to be solved by the invention) When a gasket is tightened at room temperature, a certain surface pressure is generated on the sealing surface, but when baking is performed, the gasket undergoes creep deformation due to this surface pressure, and as a result, the surface pressure is reduced. This can cause leaks to occur. An example in which the gasket is made of a composite material is described in US Pat. No. 3,989,285, and its outline will be explained with reference to FIG. This is a configuration in which a material with high hardness is used at the center of the gasket's cross section, and the periphery is covered with a material with low hardness. In order to suppress creep deformation during baking, it is necessary to suppress the deformation of the gasket in the radial and thickness directions, but the gasket shown in Figure 4 only restrains the deformation in the thickness direction; There is no action to restrict deformation.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly reliable metal gasket that reduces creep deformation of the gasket during baking and prevents a decrease in surface pressure on the sealing surface. .

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, a harder material is used around the gasket which receives the pressing force from the flange,
The metal gasket of the present invention is a metal gasket that is interposed between two flanges and maintains a vacuum by the pressing force of the blades of the flanges, in which the vicinity where the blades of the flanges come into contact is made of a material with lower hardness than the surrounding area. It is.

(Function) With the above configuration, the periphery of the gasket (four circumferences and bottom surface) that the flange blade comes into contact with is made of a harder material than the gasket, so during baking, the contact pressure between the sealing blade and the gasket surface is applied. Creep changes that occur are inhibited and the occurrence of creep is prevented.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view showing the configuration of the first embodiment. 1st
The gasket of the embodiment is donut-shaped, and includes a ring-shaped sealing member 1 that holds the seal near the contact of the flange blade.
are embedded in the upper and lower surfaces of the ring-shaped foundation member 2, respectively, so that the inner peripheral surface, outer peripheral surface, and bottom surface are in contact with each other, and are metallurgically joined to the foundation member 2. The hardness of the base member 2 is higher than that of the seal member 1. Further, the thickness of the sealing member 1 is greater than the depth into which the blade of the flange bites.

FIG. 2 is a diagram showing a state in which the gasket of the first embodiment is attached to a flange. In FIG. 2, the flange 13
has a vertically symmetrical shape, and the blade 11 of the flange contacts the gasket 4. The upper and lower flanges 4 are tightened with bolts 12, and the blades 11 of the flanges bite into the sealing member 1 of the gasket 4 to perform vacuum sealing.

Next, the operation of the first embodiment will be explained. gasket 4
Vacuum sealing between the flange 13 and the flange 13 is achieved by the blade 11 of the flange biting into the sealing member 1 of the gasket 4. When baking is performed to reduce the gas released from the vacuum container, the temperature of the vacuum flange increases and the gasket 4
Since a tightening force is applied by the tightening bolt 12 of the flange 13 to the cutting edge of the flange that has bitten into the seal member 1, the creep deformation of the gasket 4 progresses. In other words, the tightening force causes the cutting edge of the flange to dig deeper into the gasket 4 than when it is at room temperature. This deformation reduces the tightening force of the tightening bolt 12, causing leakage. However, in this embodiment, the sealing member 1 into which the flange blade 11 bites has the inner peripheral surface, outer peripheral surface, and bottom surface of the sealing member 1.
Since the sealing member 1 is surrounded by the base member 2 having a higher hardness, deformation of the sealing member 1 is restrained, and the structure is such that creep is less likely to occur, and creep deformation is small. According to the first embodiment, the reduction in the tightening force to the gasket due to creep deformation of the gasket during baking is reduced, and the reliability of the vacuum seal is improved. In the case of complex vacuum vessels, baking is performed after the equipment is assembled, but baking causes gasket creep and cannot prevent leaks, so improving the reliability of the vacuum seal is extremely effective for vacuum equipment. .

Next, a second embodiment will be explained. In the second embodiment, the hardness of the gasket is changed smoothly so that the hardness of the gasket is low at the part where the blade of the flange makes contact and becomes high at other parts. In this case, metallurgical connections between different materials are not required, and the creep characteristics of the gasket can be varied.

Next, a third embodiment will be described. In FIG. 1, the material of the base member 2 is ceramic. This makes it possible to obtain an insulating gasket that insulates the gap between the blades of the two flanges that contact the gasket. By using insulating bolts as the tightening bolts of the flanges, it is possible to insulate between the flanges.

[Effects of the Invention] As is clear from the above description, in the present invention, the members that come into contact with the blade of the flange and the members in the vicinity thereof are made to have lower hardness than the surrounding members, so that the members are restrained by the surrounding members, It is possible to provide a highly reliable gasket with less creep deformation during baking and vacuum sealing.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the first embodiment of the present invention, Figure 2 is a diagram showing the first embodiment attached to a flange, and Figures 3 and 4 are diagrams of a conventional gasket attached to a flange. It is. 1... Seal member, 2... Foundation member, 4...
Gasket, 11... Flange blade, 12... Tightening bolt, I3... Flange. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A metal gasket that is interposed between two flanges and maintains a vacuum by the pressing force of the blades of the flanges, characterized in that the vicinity where the blades of the flanges come into contact is made of a material with lower hardness than the surrounding area.