JPH0444147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a seat ring that is arranged and fixed around the outer periphery of a valve body of a butterfly valve.

[Prior Art] A seat ring is a pressure-tight member that is always attached to a valve, intervening at the contact area between the valve seat of the valve body and the valve body, and serving to seal the movement of fluid. be.
Tetrafluoroethylene (trade name: Teflon) is used in the parts of this seat ring that are exposed to fluid, that is, the parts that come in contact with liquid, to improve lubricity, heat resistance, and corrosion resistance. However, tetrafluoroethylene has poor elasticity and can only be formed into a thick wall using a single material, has almost no elastic deformation, and has poor sealing performance when fully closed. Furthermore, since the adhesiveness with elastic bodies such as synthetic rubber is not good, conventionally, a seat ring having a structure as shown in FIG. 4 has been used. In other words, the seat ring is made of a thick film (film thickness 1.5 mm to 2.0 mm) made of tetrafluoroethylene with a cylindrical cross section.
An elastic body that has been molded and added elasticity through heat vulcanization is inserted, and both ends are joined in a ring shape.
As shown in the figure, the entire circumference of the elastic body is covered with a tetrafluoroethylene skin layer. As shown in Fig. 4, the entire outer circumference of the valve body 1a is ground down to form a two-step difference on the half side, and the seat ring 3a is placed on this step and fixed by fitting into the remaining step. When the ring 10a is installed, the most conventional installation of a seat ring made of an elastic material whose surface in contact with liquid is coated with a tetrafluoroethylene skin layer is completed. Another conventional technique for improving the sealing performance of the seat ring is disclosed in Japanese Utility Model Publication No. 53-32886, as shown in FIG. As shown in the figure, the valve is connected to the tapered seat 9b of the valve box by sandwiching the Teflon sheet membrane 5b between the clamping groove (not shown) of the valve body and the cross-shaped iron core 104 having a protrusion 103 on the top. The main body is a seat ring whose surface is formed into a wave shape consisting of a cavity 102 and ridges 101a and 101b, and an elastic filler 6b such as silicone rubber or fluorinated rubber is placed inside.

As a result of this configuration, the elastic filler 6b having an H-shaped cross section raises the protruding ridges 101a and 101b on both sides by the compressing force of the air in the cavity 102 of the corrugated valve contact surface, thereby sealing the Teflon sheet membrane 5b. It describes its actions and effects as being able to improve sexual performance.

[Problems to be Solved by the Invention] However, in the conventional seat ring 3a, since the elastic body 6a is inserted and filled into the cortical layer 5a, it is not possible to prevent a sliding phenomenon between the two, and the cortical layer 5a Even if it makes contact with the valve box seat 9a, the rear elastic body 6a escapes in a direction that reduces the contact surface pressure generated at the contact area between the skin layer 5a and the valve box seat 9a, and the contact between the skin layer and the valve box seat 9a decreases. There is a problem that the contact surface pressure is small, resulting in poor sealing. Further, another conventional technique shown in FIG. 5 still has the same problem as the previous example in that the contact surface pressure of the seat ring is reduced. Cited Teflon sheet membrane 5b
As shown in the figure, it is too thick to be called a membrane in order to form a shape consisting of two side surfaces with two ridges and one hollow step, so it is too thick to be called a membrane.
It is difficult to mold unless the thickness is approximately 1.5 mm to 2.0 mm. Since the Teflon material itself has poor elasticity and almost no elastic deformation, even if a cortical layer of this thickness is applied from behind using an elastic body, the efficiency of deforming the cortical layer through the elastic deformation of the elastic body is extremely low.

Moreover, since the back of the filler 6b (elastic body) is reliably supported by the iron core 104 having a cross-shaped cross section, although the Teflon sheet membrane 5b does not cover the entire surface of the filler, in reality, This iron core supports the bottom surface of the filler, so the elastic body is thickly surrounded by an inflexible material, which is the same as the prior art shown in FIG. 4.

Therefore, even when the Teflon sheet membrane comes into contact with the tapered seat of the valve body, the elastic body escapes in a direction that reduces the contact surface pressure generated at the contact area between the two, and the contact surface pressure is small and there is a risk of seal failure. It's exactly the same.

The technical challenge of this idea is to integrate tetrafluoroethylene and an elastic body and eliminate the slippage between them.

[Means for Solving the Problems] The valve seat ring according to the present invention has a cortical layer with a thickness of
A very thin plate-like film with a thickness of 0.2 to 0.5 mm is formed integrally with a part of the elastic body, and when the seat ring is inserted into the annular groove recessed on the outer circumferential surface of the valve body, the contact that is exposed from the outer circumferential surface of the valve body is formed integrally with a part of the elastic body. The above-mentioned problem has been solved by the skin layer covering the elastic body only in the part that contacts the liquid part and a part of the side surface of the groove following the liquid part. In addition, as for this manufacturing method, a very thin film of 0.2 to 0.5 mm thick polytetrafluoroethylene is molded along the mold circumferential surface of the seat ring mold by heating to imitate the outer peripheral shape of the seat ring, and both ends are firmly connected. By attaching a plate-shaped thin film and press-fitting the unvulcanized soft rubber into the mold while heating and vulcanizing it, a layer of ethylene tetrafluoride is integrally formed on a part of the surface of the elastic body. It was also shown that it was formed.

[Function] For the sake of convenience, the manufacturing method will be described in the following steps. That is, 1. Tetrafluoroethylene film sheet (thickness
0.3mm (commercially available) to a size equivalent to the cortical shape and size.

2 While heating this, it is primarily formed into the shape and size of the cortical layer.

3. Adhesive treatment is applied only to the inner surface (surface activation and adhesive application).

4. Both ends are butted together, and the mating surfaces are connected using a piece of tetrafluoroethylene sheet for joints that has been adhesive-treated on both sides.

5 Place this in a rubber mold and set it along the circumference of the mold.

6. When filling with rubber, clamp one end of the tetrafluoroethylene sheet to prevent it from moving (mold structure).

7 While heating the unvulcanized rubber, it is press-fitted between the skin layer and the mold and integrally formed.

8 Take it out and cut off any excess burrs such as the fixing part of the sheet.

After going through these steps, the cortical layer and the elastic body on the back are completed as an endless seat ring that is tightly attached as if they were connected as one body. Fig. 1 shows the state in which this is attached to the valve. That is, when the seat ring 3 is fitted into the annular groove 2 recessed in the outer peripheral surface 4 of the valve body 1, both ends of the skin layer made of tetrafluoroethylene are sandwiched between the annular groove 2 and the elastic body 6 on the side surface 11 of the groove. to strengthen the tight contact with the elastic body 6, and the remaining part inside the annular groove 2 is covered with the elastic body 6.
is directly held in the annular groove 2 and integrated with the valve body 1. Because of this aspect, the liquid contact part 12
The characteristics of corrosion resistance and heat resistance of the seat ring 3 are inherited as they are, and due to the sliding phenomenon between the elastic body 6 and the skin layer 5, the elastic body 6 comes into contact with the skin layer 5 and the valve box valve seat 9. Rather, due to its own elasticity, the skin layer 5 of the elastic body 6 adheres closely to the surface of the valve seat 9 of the valve box, resulting in good sealing performance. It acts to become.

[Example] Fig. 1 shows an example in which the seat ring 3 is applied to an eccentric shaft type butterfly valve. A skin layer (sealing material) 5 made of tetrafluoroethylene in the form of a thin plate is integrally adhered to the surface of the elastic body 6. In addition, in practice, the thickness of the tetrafluoroethylene thin film used as the sealing material is
To smooth the elastic deformation of seat ring 1
A range of 0.2 mm to 0.5 mm is suitable.

Next, Fig. 2 (plan sectional view) and Fig. 3 (front sectional view) show another example of a concentric butterfly valve, in which the seat ring 3 is attached to the circumferential seal portion (second
In the figure), the area extends from the part that contacts the valve box seat 9 to the part sandwiched between the left and right valve bodies 1A, 1B, and around the valve shaft 8, from the part that contacts the valve box seat 9 to the left and right valve body 1A. , 1B and the valve stem 8, the skin layer (sealing material) 5 tightly adheres to the surface of the elastic body 6 and covers the entire liquid contact part. The valve body 1 in this embodiment consists of a pair of left and right discs 1A and 1B, and the left and right sides are fixed and hold a valve shaft 8 having a square cross section in a non-rotatable manner.

[Effects of the Invention] As described above, in the present invention, the corrosion-resistant and heat-resistant thin film that moves integrally with the elastic body that supports the back is directly exposed on the surface of the liquid-contacted part and performs the valve function. It can be guaranteed for a long time. In addition, with conventional covered seat rings, the elastic body is inserted into the thick-walled cylindrical skin layer, so this work is easily performed.
In order to prevent air from entering the gap between the two, the seat ring of the present invention was limited to a type in which the cross section of the seat ring did not change, that is, an eccentric shaft type butterfly valve (FIG. 1 of the first embodiment). Since the original shape of the cortical layer of the ring is not a cylindrical cross section but a plate shape, it is unrelated to changes in the cross section of the seat ring, and a butterfly valve with a concentric shaft in which the valve shaft passes through the seat ring (Second Embodiment, Fig. 2) It has the advantage that it can also be applied to Figure 3).

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention;
2 and 3 are a plan sectional view and a front sectional view showing another embodiment, FIG. 4 is a front sectional view showing a conventional technique, and FIG. 5 is a front sectional view showing another conventional technique. DESCRIPTION OF SYMBOLS 1... Valve body, 2... Annular groove, 3... Seat ring, 4... Outer peripheral surface, 5... Skin layer (sealing material), 6
...Elastic body, 11...Side surface of groove, 12...Liquid contact part.

Claims (1)

[Scope of Claims] 1. A valve seat ring made of an elastic body whose surface in contact with liquid is covered with a tetrafluoroethylene skin layer,
The skin layer is an extremely thin plate-like film with a thickness of 0.2 to 0.5 mm that is formed integrally with a part of the elastic body, and when the seat ring is inserted into the annular groove recessed on the outer circumferential surface of the valve body, the outer circumferential surface 1. A seat ring for a valve, characterized in that the skin layer covers an elastic body only in a portion contacting a liquid contact portion exposed from the liquid contact portion and a part of a subsequent groove side surface. 2.A very thin plate-shaped film of 0.2 to 0.5 mm thick of tetrafluoroethylene is attached along the mold circumferential surface of the seat ring mold by heat-forming to imitate the outer circumferential shape of the seat ring and firmly connecting both ends. A tetrafluoroethylene layer is integrally formed on a part of the surface of the elastic body by pressing and filling unvulcanized soft rubber into the mold while heating and vulcanizing it. A method for manufacturing a seat ring for a valve according to claim 1.