Several typical structures of the hottest vacuum v

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Several typical structures of vacuum valve

(1) diaphragm valve

diaphragm vacuum valve uses the valve stem to tightly press the elastomer film on the valve seat to isolate the air path. As shown in the figure, turning the handwheel can drive the valve stem to move up and down, so that the diaphragm leaves the valve seat to open the valve or press the diaphragm tightly on the valve seat to close the valve. If this kind of valve adopts nitrile rubber diaphragm, the friction coefficient level under the temperature of practical application and the non corrosive gas on the pre extraction pipeline and the temperature of -25 ~ 80 ℃ should also be discussed before application. If fluororubber diaphragm is used, it can be used in high vacuum system, and the temperature range is -30 ~ 150 ℃

(2) vacuum ball valve

Figure 4 shows the structure of the vacuum ball valve. The sealing mechanism in the valve is composed of two annular elastomers pressed tightly on the surface of a metal ball. There is a large perforation on the metal ball. By turning the metal ball with the help of the handle to change the direction of the perforation, the air circuit can be connected or cut off. The seal between the metal ball shaft and the valve body adopts O-ring seal

(3) the structure of vacuum butterfly valve is relatively simple, as shown in Figure 5. The edge of the valve plate is embedded with an O-shaped seal ring. The valve plate is fixed on the valve rod of the transmission shaft by bolts, so that the valve rod drives the valve plate to rotate. When the seal ring on the valve plate is in close contact with the valve body, the valve is closed. When the valve plate is rotated for 90o from the closed position, the valve is completely opened. The main advantage of this kind of valve is its small volume. Simple structure. Polyurethane has great potential

(4) gate valve

Figure 6 and Figure 7 are two structural types of gate valve. The elastomer seal ring is embedded on the valve body. Turn the handle to open or close the valve. It is also very stable to ultraviolet radiation. When the gate valve in Figure 6 is closed, the valve cover is pressed by the slope of the limit block, and then the sealing ring is pressed tightly. The gate valve in Figure 7 is sealed by pressing the chain plate

(5) baffle valve

figure 8 shows the structure of a baffle valve. The valve realizes the connection and cut-off of the pipeline through the opening and pressing down of the valve cover. In the figure, the pressure plate 23 fixes the valve port seal ring 24 on the valve cover. The pressing plate 2 connects the valve rod 3 and the valve cover as a whole. The upper cover 20 and the valve body 22 are sealed by the sealing ring 21. The pressure caps 5 and 7 compress the sealing rings 4 and 8 respectively to realize dynamic sealing. Cylinder head 11 compresses the sealing ring lo to seal the upper part of cylinder 16. The cylinder and cylinder seat 17 are sealed by sealing ring 9. Oil filling pipe 18 injects diffusion pump oil to reduce friction and help seal. Intake pipe connector 12. Compressed air from the air compressor first passes through the oiler 19. The gas from the oiler contains a certain amount of oil, then enters the change-over valve 6, and finally enters the cylinder. On the one hand, it lubricates the piston in the change-over valve, on the other hand, it prevents rust on the inner surface of the cylinder. The reversing valve controls the air supply to enter the upper and lower parts of the cylinder. The sealing gasket 13, piston rubber ring 14 and piston 15 divide the cylinder into two parts and move it in the cylinder to control the opening and closing of the valve

Figures 9, 10 and 11 show three types of vacuum flap valves with different structures. They all use compressed air as the power source. In the process of opening or closing the valve, the movement of the valve plate has a turnover process. Can flip an angle. In the structure shown in Figure 10, the valve cover is turned over by the roller. In this structure, the valve cover cannot be turned over for 90o. According to the structure in Figure 9, the turnover of the valve cover is realized by the four-bar mechanism, and the valve cover can realize 90o turnover. The flap valve in Figure 11 is a clam line mechanism. This kind of valve is simple in structure, low in total height, and the valve plate can be turned over by 90o. It was first created in China in 1971. In the flap valve, when the valve plate is turned over for 90o, the flow conductivity is larger

(7) solenoid valve

the driving mode of vacuum valve is magnetic drive, that is, solenoid valve. The sealing mechanism of the electromagnetic vacuum valve is the same as that of the baffle valve, as shown in Figure 12. At ordinary times, the valve cover of the solenoid valve is pressed by the spring to seal the pipeline channel. When it needs to be opened, turn on the current of the solenoid coil, and the magnetic force will attract the armature, drive the valve cover, and open the valve. Some electromagnetic vacuum valves are designed with inflation. Called electromagnetic vacuum charging valve, it is a special valve specially installed on the inlet pipeline of oil sealed mechanical pump. The valve and the pump are connected to the same power supply, and the start and stop of the pump directly control the opening and closing of the valve. When the pump stops working or the power supply is suddenly interrupted, the valve can automatically close the vacuum pipeline and fill the atmosphere into the pump cavity through the air inlet of the pump, so as to avoid the pump oil backflow polluting the vacuum system

(8) needle valve

Figure 13 is an ultra-high vacuum needle valve. The needle valve is a fine-tuning valve, and its plug is needle shaped, which is mainly used to adjust the throttle flow. The fine-tuning valve requires that the opening of the valve port gradually becomes larger, and it can be adjusted continuously and slightly from closing to opening. Needle valve plug can realize this function. Needle valve plugs are generally made of long quenched steel needles, while valve seats are made of soft materials such as tin and copper. The sealing between the valve needle and the valve seat depends on the close fit of its conical surface. The taper of the valve needle has two types: 1:50 and 6O cone angle, and the cone surface needs to be finely ground. The sealing between the valve rod and the valve seat in the figure is realized by bellows

(9) ultra high vacuum valve

the material of sealing gasket for common high and low vacuum valves is rubber, which cannot withstand high temperature baking. Therefore, it cannot be used in ultra-high vacuum equipment. The ultra-high vacuum valve that can be used in ultra-high vacuum equipment must meet the following requirements: (1) it can withstand high temperature (400 ~ 450 ℃) for many times; (2) Small amount of air bleeding and good air tightness; (3) Good repeatability; (4) Large conductance

Figure 14 is a kind of ultra-high vacuum valve. Its main components are oxygen free copper bonnet, stainless steel valve body and transmission guide mechanism. The knife edge of the valve seat is a right angle, and the baffle plays a role in ensuring the repeatability of the valve, that is, the knife marks pressed out by the knife edge on the valve cover can coincide every time

(10) glass vacuum piston

the glass piston mountain is composed of a perforated conical core and an outer sleeve with a connecting pipe. The contact surface between the core and the outer sleeve is a polished surface, which is coated with vacuum sealing grease to obtain sealing. The gas path is determined by the hole on the core and the aligned connecting pipe. Turning the core can control the gas path. Because it is sealed with sealing grease, there will be no air leakage between the core and the jacket

Figure 15 shows a typical glass vacuum piston. The piston is divided into two-way, three-way or multi-way piston according to the number of connecting pipes. The two-way connection is divided into opposite connection and right angle connection. In Figure 15 (b), (2) and (3) are two types of (1) Whether the moving speed of the beam of the universal tensile strength tester for steel wire rope is normal and the seal is better, because there is atmospheric pressure to press the cone core inward in use

(11) oil free glass vacuum valve

in order to avoid the impact of vacuum grease on the vacuum environment, liquid metal seal and frosted port seal can be used

Figure 16 shows one of the glass vacuum valves sealed with liquid metal. When the valve is to be closed, use a magnet to lift the glass cup containing liquid metal, so that the upper glass tube is inserted into the liquid metal, which can block the gas path; When opening, put the glass down with a magnet. Gallium indium tin alloy is generally used as liquid metal. When the proportion of gallium indium tin is 62.5%, 21.5% and 16%, its melting point is only 10.7 ℃, and it is liquid at room temperature. Its saturated vapor pressure is very low, even lower than Pa at 500 ℃

Figure 17 shows an oil-free vacuum valve sealed by glass grinding. Its sealing is achieved by the contact of the precision polished surface between the half spherical glass valve body and the half spherical valve seat. The opening and closing of the valve are still operated by magnets from the outside. Due to hemispherical contact, the contact area is large enough to ensure good sealing

the above two kinds of glass vacuum valves can be used in ultra-high vacuum systems, but they can't bear large pressure difference on both sides, and can only be used in occasions where the pressure on both sides is similar (the difference is within 200 ~ 400pa)

glass vacuum valves can only be made into small ones, and large-diameter valves must be made of metal. (end)

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