JPS61142374A - Vacuum device - Google Patents

Abstract

PURPOSE:To achieve vacuum condition easily without employing He gas by roughly evacuating a vacuum container then leading low saturation steam pressure gas thereafter roughly evacuating again and condensating/removing said gas. CONSTITUTION:When evacuating a vacuum container 1 arranged in a container 2, valves 7, 9 are opened at first to drive a rotary pump 3 thus to roughly evacuate the vacuum container 1 and a liquid nitrogen trap 5. Then the valve 7 is closed while a valve 8 is opened to lead CO2 gas from CO2 gas cylinder 4 into the vacuum cylinder 1 and to close the valve 8 upon reaching of the inner pressure in vacuum container 1 to predetermined level. Thereafter, the valve 7 is opened again to roughly evacuate through a rotary pump 3 and the valve 7 is closed to inject the liquid nitrogen through the valve 23 into a tank 14 of liquid nitrogen trap 5. Consequently, the tank 14 is cooled to condensate and remove CO2 gas molecules thus to bring high vacuum in the vacuum container 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust vacuum device for obtaining a vacuum, and is applicable to containers for vacuum storage, various vacuum devices, and the like.

[Conventional technology]

Conventionally, diffusion pumps, Talio pumps, and the like have been mainly used to obtain high vacuum. However, the diffusion pump
Since a small amount of oil flows into the vacuum container, the Talai-o-bump is now often used to obtain a clean high vacuum. Talio pumps generally use helium gas as a refrigerant gas, but not only is helium gas expensive, but in Japan most of the gas is imported.

[Problem that the invention seeks to solve]

Therefore, the problem to be solved by the present invention is to provide a new vacuum device that obtains a high vacuum without using helium gas.

[Means for solving problems]

As a means for solving the above-mentioned problems, the present invention provides a vacuum container, an exhaust means for exhausting the gas in the vacuum container to the outside, and a device for introducing a low saturated vapor pressure gas into the vacuum container. a storage means for storing the gas in the vacuum container; and a cooling condensing means for cooling the low saturated vapor pressure gas in the vacuum container to a temperature at which its saturated vapor pressure becomes a high vacuum, and condensing and removing the low saturated vapor pressure gas. It is characterized by comprising:

[Effect]

According to the above means, the gas in the vacuum container is first evacuated by a pump, and then the low saturated vapor pressure gas stored in the storage means is introduced into the vacuum container. Then, by evacuating the gas in the vacuum container again using the pump, the partial pressure of the gas other than the low saturated vapor pressure gas is lowered. Thereafter, the low saturated vapor pressure gas in the vacuum container is cooled to a temperature at which the saturated vapor pressure becomes high vacuum by the cooling condensing means, and the gas is condensed and removed. Then, the inside of the vacuum container becomes a gas having a low partial pressure (about 10-6 Torr) other than the low saturated vapor pressure gas and the gas having a low saturated vapor pressure (about 10-6 Torr), resulting in a so-called vacuum state.

In addition, the high vacuum referred to here is 10-3 to 1O-7 Torr.
Say something about the degree.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIG.

The blade element container 1 is made of a material with a low gas release rate, such as stainless steel, and is surrounded by another container 2 on the outside. 1st
In the figure, the vacuum container 1 is located below the container 2, and the bottom plate is shared. The vacuum container 1 is provided with a lid 1a, a baking heater 16, a storm gauge 6, and holes 18, 19, and 20. The boat 18 is connected via an operating valve 8 to a storage means, ie, a CO2 cylinder 4, for storing CO2 gas, which is a low saturated atmospheric pressure gas.The port 19 is connected to a rotary pump 3, which is an exhaust means, via an operating valve 7. Each is connected via an operating valve 9 to a liquid nitrogen trap 5 which is a cooling and condensing means. Further, the baking heater 16 is connected to a heater power source 17. The second container 2 has a lid 2a,
A boat 21 is attached, and a port 22 is provided on the lid 2a. The port 21 receives CO2 via the operating valve 10.
The cylinder 4 and the hose 1-22 are connected to the atmosphere via an operating valve 1). The control unit 15 receives the signal from the vacuum gauge 6 and operates the operating valve 7.8.9.10.1)
and outputs a control signal to the heater power source 17. The operating valves 7.8.9.10.1) are driven by motors, solenoid valves, air cylinders, etc. Note that the power supply for the control unit 15 is omitted in the figure. liquid nitrogen trap 5
is composed of a liquid nitrogen inlet vibrator 12, a nitrogen outlet vibrator 13, and a tank 14. The tank 14 is provided with fins 14a.

The operation will be explained below based on the above configuration.

First, the initial state when starting the operation of this device will be described. Vacuum container 1 and container 2 contain air at atmospheric pressure,
All valves are closed. The tank 14 of the liquid nitrogen trap 5 does not contain liquid nitrogen.

First, the vacuum container 1 and the liquid nitrogen trap 5 are evacuated to 1X10-2 Torr using the rotary pump 3 by opening the valve 7.9 (rough evacuation). Vacuum container 1 is placed at atmospheric pressure (7
60Torr), the main composition of the air is 78.09% N2 and 2% 02.
0.95%, Ar 0.93%, co2 0.03% (
total 100%), so the partial pressure of CO2 gas when exhausted to lXl0-2Torr is lX1O-2X0.03X10-2=3X10-6or
r, and the partial pressure of gases other than CO2 gas is 1x10-2-
3x10-6=9.997xlO-3'["or
It becomes r.

Next, the valve 7 is closed, and the valve 8 is opened to introduce C02 gas from the pump 4 into the vacuum container 1.

Attach a pressure regulator (not shown) to the CO2 cylinder to remove CO2.
The pressure of the two gases was set to about 0.1 atmosphere in gauge pressure. The internal pressure of the vacuum container l was monitored with the vacuum gauge 6, and the pressure was 760.
When the temperature reaches T o r r, close valve 8 and release CO.
Complete the introduction of 2 gases. At this time, CO2 in the vacuum container
The partial pressure of components other than gas is the aforementioned 9.997xlO-3
Torr, and the partial pressure of CO2 gas is 760-9.99
7xlO-3=759.990003 Torr.

Next, open valve 7 again and use rotary pump 3 to
Exhaust to -2 Torr. With this operation, the partial pressure of components other than C02 gas is 9.997xlO-3x (1xlO-2/760) =
1.3×10-'Torr.

Next, close the valve 7 and close the tank 14 of the liquid nitrogen trap 5.
Then open the valve 23 and inject liquid nitrogen. These valve operations are controlled by signals from the control unit 15. In addition, liquid nitrogen is supplied by a liquid nitrogen supply device (not shown).
The water is sent from there to the valve 23 via the vibrator 12. Liquid nitrogen tank 14 and fin 1 are removed by injection of liquid nitrogen.
The temperature of 4a is cooled to approximately liquid nitrogen temperature (77K),
CO2 gas molecules are condensed out in the tank and fins. 7
The saturated vapor pressure of CO2 gas at 7 is approximately 1 x 10-8T.
It's o r r. Therefore, most of the CO2 gas in the vacuum container is condensed and removed. The pressure inside the vacuum container 1 is co
The partial pressure of components other than the two gases, i.e. the above 1.3X10
-'Torr. By the above operations, the pressure inside the vacuum container can be set to 1.3X10-'Torr. It goes without saying that a higher vacuum can be achieved by repeating the introduction, exhaust, and condensation removal of CO2 gas.

Note that if left as it is, the pressure inside the vacuum container will gradually increase due to the release of gas from the inner wall of the vacuum container 1;
The degree of this varies depending on the material of the vacuum container 1 and the method of surface treatment. The degree of pressure increase is illustrated by the following example. For example, according to data from Y, 5trausser, when baking stainless steel at 150°C for 24 hours, the gas release rate is 4xlQ-12Torr-6-3-"
Clm-2 (Gen Horikoshi, Vacuum Technology, P127)
. Although this value can only be achieved by paying close attention to surface treatment, it is useful as a tentative target value. The volume of the vacuum vessel 1 is v (n?), the inner surface area is A (coil), and the gas release rate is q ('l'or
r・j2-3-'-cn+-2), the pressure is P(Torr
), then the pressure P inside the vacuum container is the total amount of released gas Q=
A-q CTorr-1-5-') multiplied by dt waiting time corresponds to the pressure increase, so Q-dt=V-d
p, and from this the following equation can be obtained.

dp/d t=Q/V (To r r/S) If the initial pressure is Po, then the pressure P after 2 seconds can be calculated by integrating the above formula: P= (Q/V) t +P o (To r r )
becomes. For example, for vacuum container 1, the length of the − side is 1 m.
Considering the cube of A=6X10'c+d, the amount of gas released is, using the value of q,
X10'x4xl O-12=z, 4xto-' (T
orr-1/S) The initial pressure Pa is the above pressure 1.3X1
0' Tarr, the pressure P after seconds is ■=
1×106cI1)-1×1031! P = (Q/V)xt+P.

= (2,4XIO=')/ (IXIO3)xt+1
．． 3X10-' (Torr). From the above formula, the time t for P to rise to 5×1O-5Torr is calculated as t=(5-cross 10-5-1.3xlO-')/(2,4X
, 1O-10) =2. lX105 (seconds) = 58 (hours), and it is possible to maintain a sufficiently long internal vacuum.

Even if the vacuum container 1 is brought to a high vacuum by the method described above, the pressure inside the container gradually increases over a long period of time.

At this time, high vacuum can be obtained again by performing the same operation as above, but there are some operations that are required, so we will describe them. This is the operation of the valve 9 and liquid nitrogen trap 5. If liquid nitrogen remains in the tank 14, first close the valve 9 and open the valve 8 to introduce CO2 gas. Next, valve 8 is closed and valve 7 is opened for rough exhaust.

After rough exhaust is completed, valve 7 is closed and valve 9 is opened.

In this case, since liquid nitrogen is contained in the liquid nitrogen trap 5, CO2 gas is condensed and removed, resulting in a high vacuum.

On the other hand, if the liquid nitrogen has run out, the operation described first may be sufficient (that is, there is no need to operate the valve 9).

Although a high vacuum can be obtained by the method described above, it is necessary to open the vacuum container 1 to take things in and out. If the vacuum container 1 is exposed to the atmosphere at this time, various molecules constituting the air and water vapor will adhere to the inner wall of the vacuum container.
Baking is required to obtain high vacuum again. To prevent this, the vacuum container 1 is placed within a second container 2 filled with CO2 gas. To be more specific, CO2 gas is heavier than air, so CO2 gas flows from the bottom of the second container 2 through the valve 10 and port 21 from the pump 4.
The interior of the second container 2 is filled with CO2 by introducing CO2 and expelling the air via the port 22 at the top of the container 2, valve 1). By taking things in and out of the vacuum container 1 via the container 2, the inside of the vacuum container 1 is always free of CO.
2 atmosphere can be maintained, and the inner wall of the vacuum container 1 is filled with CO2.
Since only two gases are attached, most of the gas released from the inner wall of the vacuum container 1 becomes CO2, and therefore a high vacuum can be easily obtained by the method described above. In addition, when loading and unloading items from the vacuum container 1 to the second container 2, use the lid 2a and the lid 1a.
Just open it gently and move the items. Because the container 2 is deeper than the vacuum container 1 and CO2 is heavier than air and water vapor, the area around the vacuum container 1 is CO2.
2, air and water vapor will not enter the vacuum container 1 if the lid 1a is gently opened.

Next, other embodiments (application examples) will be described.

By providing a plurality of the devices around the third container and operating them in sequence, it is possible to prevent a pressure increase in the third container and maintain a high vacuum permanently unless the devices break down. A schematic diagram in this case is shown in FIG. In the case of FIG. 2, in order to create and maintain a high vacuum inside the third container 1', the vacuum container 1 with an exhaust device is attached to both sides via valves 30. The vacuum containers 1 on both sides are connected to C02 as described above.
By alternately creating a high vacuum depending on the introduction method, opening and closing the valves 30 alternately, and communicating with the third container 1' located in the center, the third container 1' can be maintained at a high vacuum at all times.

In the above-mentioned embodiment, a rotary pump was used as the evacuation means, but it goes without saying that a device capable of rough evacuation of about 10 -2 to 10 -3, such as a mechanical booster pump, may also be used.

In addition, CO2 gas was used as a low saturated vapor pressure gas, but
Low saturated vapor gas refers to a gas whose saturated vapor pressure is lower than about 1O-6 Torr at the cooling temperature of the cooling and condensing means (the cooling temperature of the liquid nitrogen trap in the above example is 77K), and which H2S5Cj! 2.S.O.
2, Br 2, etc.

In the above-mentioned embodiment, CO2 gas was used because it is an inert gas, but it goes without saying that the low saturated vapor pressure gas may be selected as appropriate depending on the purpose for which the present device is used. Furthermore, as a cooling and condensing means, a cooling device using Freon gas (Polycojd's C
The o1d Trap Chiller has a cold odor temperature of 123.
(degree) may be used. However, in this case, it is necessary to use 2 gas as a low saturated vapor pressure gas, which may be inappropriate for general use.

〔Effect of the invention〕

As described above, by roughly evacuating the inside of the vacuum container, introducing a low saturated vapor pressure gas into the vacuum container, and after roughly evacuating the inside of the vacuum container again, the gas is condensed and removed by the cooling condensing means. The inside of the vacuum container can be brought into a vacuum state. Therefore, there is an excellent effect that a vacuum state can be easily obtained without using expensive helium gas.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG. 2 is a schematic diagram showing another application example. ■... Vacuum container, 2... Second container, 3... Rotary pump (exhaust means), 4... CO2 cylinder (storage means), 5... Liquid nitrogen trap (condensing means).

Claims (4)

[Claims] (1) a vacuum container, an evacuation means for evacuating the gas in the vacuum container to the outside, and a storage means for introducing a low saturated vapor pressure gas into the vacuum container and storing the gas; 1. A vacuum apparatus comprising a cooling and condensing means for cooling a low saturated vapor pressure gas in a vacuum container to a temperature at which its saturated vapor pressure becomes a high vacuum, and condensing and removing the low saturated vapor pressure gas. (2) The vacuum device according to claim 1, wherein the low vapor pressure gas stored in the storage means is carbon dioxide (CO_2) gas. (3) The vacuum apparatus according to claim 1, wherein the cooling and condensing means is a liquid nitrogen trap that condenses the low saturated vapor pressure gas with liquid nitrogen. (4) The vacuum device according to claim 1, wherein the vacuum device is disposed within a second container filled with a low vapor pressure gas stored in the storage means.