JPH01193584A - Method and device for vacuum drying - Google Patents

Abstract

PURPOSE:To evaporate liquid, adhered to an article efficiently, by a method wherein, the article to be dried is received in a first vacuum vessel, a second vacuum vessel is evacuated and both of the vacuum vessels are communicated to evacuate the first vacuum vessel rapidly and disperse the liquid adhered to the article under ebullition, further, the first vacuum vessel is evacuated to vaporize the liquid. CONSTITUTION:An article 17 to be dried is received in a first vacuum vessel 18, a first solenoid opening and closing valve 23 is closed and a second solenoid opening and closing valve 24 is opened to evacuate a second vacuum vessel 21 by a vacuum pump 5. When a pressure is reduced to a pressure P4, the solenoid opening and closing valve 24 is closed and the solenoid opening and closing valve 23 is opened to evacuate the vacuum vessel 18. The vacuum vessel 18 is evacuated to a pressure near a pressure P2, then, the vacuum pump 5 is stopped and the solenoid opening and closing valve 24 is opened. A pressure in the vacuum vessel 18 is reduced suddenly and liquid, adhered to the article 17 to be dried is subjected to ebullition while the liquid, not evaporated yet, is separated from the article 17 to be dried. When the pressures in both vacuum vessels 18, 21 have achieved an equilibrium at a pressure P3, the solenoid opening and closing valve 24 is closed and the vacuum vessel 18 is evacuated further. The liquid, remaining on the surface of the article 17 to be dried, is evaporated from the article 17 to be dried.

Description

[Detailed Description of the Invention] a1 Purpose of the Invention (Field of Industrial Application) The present invention provides a method for drying an article such as a metal to which liquid such as water is attached during cleaning work or the like. To provide a vacuum drying method and device, which are particularly effective for drying articles that have complicated internal voids and in which liquid such as cleaning liquid remains. It is.

(Prior Art) Various drying methods and devices have been proposed and used in the past in order to dry various objects that remain wet from liquids such as water by cleaning metal objects. .

Such conventionally known drying methods and devices include, for example, a method of using an air blower to blow away the liquid attached to the object to be dried, a method of drying the object to be dried with hot air, or a method of drying the object to be dried with hot air. A method of boiling and evaporating a liquid adhering to an object to be dried by heating with far infrared rays is known.

However, in drying methods using air blow, if there are complex voids inside the object to be dried, such as porous metals, it is not possible to blow away the liquid that has entered the object. Therefore, sufficient drying cannot be performed.

Also, in the case of drying methods that use hot air or far infrared rays, it takes a long time to dry the liquid that has entered the inside of the material to be dried, and the temperature of the material to be dried increases. In some cases, after the drying process is completed, before moving on to the next process,
A process of cooling the material to be dried is required.

In order to eliminate the above-mentioned disadvantages, a so-called vacuum drying method has been proposed and is actually used, in which the material to be dried is dried in a vacuum container under reduced pressure.

FIG. 3 schematically shows an apparatus for implementing such a vacuum drying method, and the vacuum drying method will be explained below based on FIG. 3.

Reference numeral 1 denotes a vacuum container, and the vacuum container 1 is composed of a bottomed cylindrical main body 2 with an open upper end, and a lid 3 that can freely open and close the upper end of the main body 2. The upper end edge of the main body 2 and the lower end edge of the lid body 3 each have an outward flange-shaped portion 2a,
3a, and these outward flange-like portions 2a,
A backing 4 is provided between 3a so that the top opening of the vacuum container 1 can be hermetically closed with the lid 3.

5 is a vacuum pump, and one end of a tube 6 is connected to the vacuum pump 5, and the other end of a tube 6 is tightly connected to the inside of the vacuum container 1.

When drying an object to be dried using the vacuum drying apparatus configured as described above, first, the object to be dried 1 is placed inside the main body 2 of the vacuum container 1.
7 is housed and the lid body 3 is closed, the vacuum pump 5 is operated to exhaust the air inside the vacuum container 1 through the tube 6, and the pressure inside the vacuum container 1 is reduced.

As a result, the boiling point of the liquid adhering to the material to be dried 17 decreases,
This liquid takes heat from the material to be dried 17 and evaporates.

The temperature of the material to be dried 17 decreases by the amount of heat taken away as the liquid evaporates, so the material to be dried 17 after drying is finished.
The temperature becomes lower than the temperature before drying, and after the drying operation is completed, the next operation (dimensional inspection, assembly, etc.) can be started immediately without performing the cooling operation.

Incidentally, FIG. 4 shows an example of a washing/drying apparatus in which washing and drying operations can be performed within the vacuum container 1 by combining the above-mentioned vacuum drying apparatus and washing apparatus.

In this washing/drying apparatus, nozzles 7.7 are provided at the top and bottom of the vacuum container 1 and eject washing liquid and rinsing liquid.
Then, connect one end to the cleaning liquid tank 8, connect the other end of the connecting pipe 9 branched in the middle, and connect the other end of the connecting pipe 9a, which has one end connected to the rinsing liquid tank 14, to the middle of the connecting pipe 9. In connection, the nozzle 7.7 can be supplied with cleaning or rinsing liquid. In Fig. 4, 12.12a is a liquid sending pump, 15.15a is a heater for heating the cleaning liquid and rinsing liquid, and 16.16a is the amount of current applied to the heater 15.15a by detecting the temperature of the cleaning liquid and rinsing liquid. It is a controller that controls the

When cleaning and drying articles using the cleaning and drying apparatus configured as described above, the articles to be cleaned are placed in the vacuum container 1, the lid 3 is tightly closed, and then the connecting tube 9. With the valve provided in the middle of 9a opened and closed appropriately, the liquid feeding pump 12
is operated, and the cleaning liquid is jetted from the nozzle 7.7 to clean the article.

After cleaning the article, stop the liquid pump 12,
After the cleaning liquid in the vacuum container 1 is discharged, the valve is opened and closed appropriately again to operate the liquid supply pump 12a, and the rinsing liquid is spouted from the nozzle 7.7, and the article is rinsed in the same manner as in the case of the above-mentioned cleaning liquid. Do this.

After rinsing the article, the rinsing liquid is discharged from the vacuum container 1, the on-off valves 11a and 13a are closed, and the next drying process is started.

In this drying step, as described above, the vacuum pump 5 is operated to exhaust the air in the vacuum container 1, and under the reduced pressure state, the liquid adhering to the article (in this case) is removed by the heat of the article itself. This is done by evaporating the rinsing liquid.

During this drying process, the article is deprived of the heat of evaporation (heat of vaporization) for the evaporation of the liquid attached to the article, so the temperature of the article after drying becomes lower than the temperature of the article before drying. . Therefore, by appropriately controlling the pressure inside the vacuum container 1 and the temperature of the article before drying, it is possible to bring the temperature of the article after drying to a desired temperature.

(Problems to be Solved by the Invention) However, even in the vacuum drying method as described above, a large amount of liquid may adhere to the object to be dried (article to be dried) 17, or the object to be dried may have a large amount of liquid attached to it. If the temperature is not too high,
The liquid cannot be completely evaporated and drying tends to be insufficient.

That is, if a large amount of liquid adheres to the material to be dried 17,
The amount of heat given by the material to be dried 17 is less than the amount of heat required to evaporate all of the liquid, and unless the vacuum pump 5 continues to operate for a long time, the liquid cannot be completely evaporated.

Furthermore, even when the temperature of the material to be dried 17 is low, it is difficult to completely evaporate the liquid adhering to the material to be dried 17 for the same reason. In particular, as in the case of the conventional drying method described above, when the material to be dried 17 has minute voids inside, such as sintered metal, and it is necessary to dry the inside of these voids, the liquid is likely to remain in this void.

The present invention solves the above-mentioned disadvantages and provides a vacuum drying method and apparatus that can efficiently evaporate liquid adhering to an article to be dried.

b. Structure of the invention (means for solving the problem) Among the vacuum drying method and apparatus of the present invention, the vacuum drying method includes:
Storing the article to be dried in a first vacuum container, and
After the pressure inside the second vacuum container is reduced, the first and second wing containers are communicated with each other to rapidly reduce the pressure inside the first vacuum container, causing the liquid to bump and scatter.

When the pressure in the first vacuum container and the pressure in the second vacuum container reach equilibrium, the pressure in the first vacuum container is further reduced, and the liquid is evaporated by the heat of the article.

In addition, the vacuum drying apparatus used to carry out the above method connects a first vacuum container having a lid whose opening can be closed airtight and a second vacuum container by a connecting pipe, and The pipe leading to the vacuum pump is branched from the middle of the pipe to provide communication between the first and second vacuum containers, communication between the vacuum pump and the first vacuum container, and communication between the vacuum pump and the second vacuum container. It is constructed by providing a valve mechanism that switches between communication and communication.

(Function) In order to dry an object to be dried using the vacuum drying apparatus of the present invention configured as described above, the following procedure is performed.

First, the valve mechanism is switched to a state where the vacuum pump and the second vacuum container are communicated with each other, and the vacuum pump is operated to reduce the pressure inside the second vacuum container.

Next, based on switching of the valve mechanism, the first and second winged empty containers are communicated with each other, and the pressure inside the first vacuum container is rapidly reduced. As a result of the sudden drop in the pressure in the first vacuum container containing the object to be dried, the liquid adhering to the object to be dried causes bumping, and the unevaporated liquid is blown away by the force.

When the pressure in the first and second double-winged empty containers reaches equilibrium, the vacuum pump is operated with the first vacuum container and the vacuum pump communicating with each other, and the inside of the first vacuum container is further increased. Apply vacuum to completely evaporate the liquid.

(Example) Next, the present invention will be explained in more detail while explaining the illustrated embodiment.

FIG. 1 is a schematic longitudinal sectional view showing a vacuum drying apparatus of the present invention.

The first vacuum container 18 that stores the material to be dried 17 is composed of a bottomed cylindrical main body 19 with an open upper end and a lid 20 that airtightly closes the upper end opening of the main body 19. Similar to the vacuum container of the drying device, the backing 4 is provided between the outward flange-like part 19a formed at the upper end of the main body 19 and the outward-directed flange-like part 20a formed at the lower end of the lid body 20, and the lid body 20 is closed. The aim is to maintain airtightness when
- 21 is a second vacuum container, which is connected to the first vacuum container 18;
It has a larger internal volume.

These first vacuum container 18 and second vacuum container 21 are
They are connected to each other by a connecting pipe 22, which has a cross-sectional area large enough to rapidly introduce the negative pressure in the second vacuum container 21 into the first vacuum container 18. have.

In the middle of this connecting pipe 22, a first electromagnetic on-off valve 23 and a second electromagnetic on-off valve 24, both of which have a fast opening speed, are provided in order from the first vacuum vessel 18 side. A vacuum pump 5 is connected between the valve 23 and the second electromagnetic on-off valve 24 via a pipe 6.

In the figure, 25 is a suction pipe, and 26 is a third electromagnetic on-off valve, which introduces outside air into the first and second wing containers 18.21 and returns the insides of the wing containers 18.21 to atmospheric pressure. used for.

When drying an object to be dried using the vacuum drying apparatus of the present invention configured as described above, it is carried out as follows.

First, the material to be dried 17 is placed in the main body 19 of the first vacuum container 18.
The opening of the main body 19 is hermetically closed with a lid 20.

Next, with the first electromagnetic on-off valve 23 closed, the second electromagnetic on-off valve 24 is opened, and the vacuum pump 5 is operated to reduce the pressure inside the second vacuum container 21. At this time, the second vacuum container 2
While observing the pressure gauge 27 provided in
The pressure inside the second vacuum container 21 is reduced to a predetermined pressure P4 that is lower than the vapor pressure of the liquid (P2 in FIG. 2) at the temperature of the liquid adhering to the liquid (in section T1 in FIG. 2). (See dashed line a).

When the pressure inside the second vacuum container 21 drops to P4, the second electromagnetic on-off valve 24 is closed, and the first electromagnetic on-off valve 23 is closed.
The vacuum pump 5 is operated in an open state to reduce the pressure inside the first vacuum container 18.

In this case, as in the case of reducing the pressure inside the second vacuum vessel 21, while observing the pressure gauge 28 provided in the first vacuum vessel 18, the vapor pressure is reduced to about the above-mentioned vapor pressure P2 (see Fig. 2). , the pressure inside the first vacuum container 18 is reduced (section T2 in FIG.
(See the solid line entry).

Once the pressure inside the first vacuum container 18 has been reduced to around pressure P2, the vacuum pump 5 is stopped and the second electromagnetic on-off valve 24 is opened to reduce the negative pressure inside the second vacuum container 21 to the first level. Vacuum container 1
It will be introduced within 8.

Connecting pipe 2 connecting the first and second wing empty containers 18.21
2 has a sufficiently large inner diameter, the negative pressure in the second vacuum container 21 is quickly introduced into the first vacuum container 18, and as a result, the negative pressure in the first vacuum container 18 is Pressure drops rapidly. Since the liquid adhering to the dried material 17 in the first vacuum container 18, which had been previously depressurized to around pressure P2, was on the verge of boiling, the pressure in the first vacuum container 18 further decreased from P2. As a result, the liquid adhering to the material to be dried 17 bumps, and the unevaporated liquid is also separated from the material to be dried 17 and scattered around (see section T in FIG. 2).

When the first and second wing empty containers 18 and 21 reach equilibrium at the pressure P3, the second electromagnetic on-off valve 24 is closed and the vacuum pump 5 is operated to further reduce the pressure inside the first vacuum container 18. do.

As the vacuum pump 5 operates, the pressure inside the first vacuum container 18 gradually decreases as shown by the solid line in section T4 in FIG. The remaining liquid removes heat from the material to be dried 17 and evaporates.

As described above, the vacuum drying apparatus of the present invention first scatters the liquid adhering to the material to be dried 17 by bumping, and then evaporates the liquid under reduced pressure, similar to conventional vacuum drying, so it The liquid adhering to the object to be dried 17, including the liquid present inside the object to be dried 17, can be reliably evaporated, and the object to be dried 17 can be completely dried.

Furthermore, since the heat for evaporating the liquid adhering to the drying object 17 is obtained from the drying object 17, the drying object 1 after drying is completed.
The temperature at No. 7 is lower than that before drying. Therefore, if the temperature of the material to be dried 17 before drying is determined appropriately in advance,
After completion of drying, the material to be dried 17 can be immediately sent to the next work step without performing cooling work.

When the drying process of the material to be dried 17 is completed, the vacuum pump 5 is stopped, the third electromagnetic on-off valve 26 is opened, and the suction pipe 2 is opened.
Atmospheric air is introduced into the first vacuum container 18 from 5.

In the case of the illustrated embodiment, by providing two electromagnetic on-off valves 23 and 24 in the middle of the connecting pipe 22, communication between the insides of the first and second vacuum vessels 18 and 21 and both vacuum vessels 18 are established. ．．
21 and the vacuum pump 5, but instead of the two electromagnetic on-off valves, the connection pipe 22 and the pipe 6 are connected.
One electromagnetic three-way valve may be provided at the branching point between the two.

Further, a nozzle 7.7 as shown in FIG. 4 is provided in the first vacuum container 18, and the article is configured to be washed, rinsed, and further dried in the first vacuum container 18. You can also do it.

C1 Effects of the Invention The vacuum drying apparatus of the present invention is configured and operates as described above, so even if the article to be dried has complex internal voids, it is possible to quickly remove liquid adhering to the article. In addition, after the drying work is completed, the next work can be carried out immediately without cooling work.

[Brief explanation of the drawing]

FIG. 11 is a schematic vertical sectional view showing one example of the vacuum drying apparatus of the present invention, FIG. 2 is a diagram showing pressure changes in both the first and second vacuum containers, and FIG. FIG. 4 is a schematic longitudinal cross-sectional view showing a vacuum drying device; FIG. 4 is a schematic vertical cross-sectional view showing a washing and drying device using the vacuum drying device of FIG. 3; 1: Vacuum container, 2: Main body, 2a + outward flange, 3
．． Lid body, 3a: outward flange-shaped portion, 4: packing, 5
: Vacuum pump, 6/pipe, 7: Nozzle, 8: Cleaning liquid tank, 9.9a: Connection pipe, 12.12a: Liquid pump, 14
: Rinse liquid tank, 15.15a/heater, 16.16
a: Controller, 17: Material to be dried, 18: First vacuum container,
19: Main body, 19a: Outward flange-shaped part, 20: M body,
20a: outward flange, 21: second vacuum container, 2
2: Connection pipe, 23: First electromagnetic on-off valve, 24: Second electromagnetic on-off valve, 25: Suction pipe, 26: Third electromagnetic on-off valve, 2
7.28: Pressure gauge. Patent applicant: Chiyoda Seisakusho Co., Ltd. Managing Director: Kinzo Koyama (and one other person) Figure 1, Figure 2

Claims (2)

[Claims] (1) After storing the article to be dried in the first vacuum container and reducing the pressure in the second vacuum container, the first and second vacuum containers are communicated with each other, and the first vacuum container is By rapidly reducing the pressure inside the container, the liquid adhering to the above items can be brought to boiling point.
After the liquid is dispersed and the pressures in both the first and second vacuum containers reach equilibrium, the pressure inside the first vacuum container is further reduced to evaporate the liquid. (2) The first vacuum container and the second vacuum container, each having a lid whose opening can be closed airtight, are airtightly connected by a connecting pipe, and a pipe is connected from the middle of the connecting pipe to the vacuum pump. A valve mechanism is provided that branches the first and second vacuum containers and switches communication between the first and second vacuum containers, communication between the vacuum pump and the first vacuum container, and communication between the vacuum pump and the second vacuum container. Vacuum drying equipment.