JPH0975429A - Disinfection device for inside of liquid tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disinfection device for the inside of a liquid tank, which is constructed small, excels in the liquid disinfecting effect, and is free from risk of damaging the liquid tank. SOLUTION: A disinfection device for the inside of a liquid tank is composed of a disinfection ray radiating unit 13 installed under the liquid 12 contained in a liquid tank 11 and a float 18 which is coupled with the unit and put buoyant under the liquid so as to support the unit. Accordingly the unit in the condition floating under the liquid at all times makes vertical motions together with the float in compliance with the liquid increment/decrement in the tank, and can always radiate ultraviolet rays into the liquid. This heightens the disinfecting effect with ultraviolet rays.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid tank sterilizer, and more particularly to a liquid tank sterilizer which has a small size and is excellent in liquid sterilizing effect and which does not damage the liquid tank.

[0001]

2. Description of the Related Art Conventionally, as a sterilizer in a liquid tank,
For example, there is one as shown in FIG. In FIG.
Reference numeral 1 denotes a liquid tank in which water or other liquid 2 is filled, 3 is a sterilization ray irradiation unit that is fixedly attached to the liquid tank and irradiates sterilization rays in the liquid, and 4 is a power supply that supplies power to the sterilization ray irradiation unit. And the power source is plug 5
Is connected to an AC circuit such as a power line. The sterilizing ray irradiation unit 3 is waterproofed and has a control box 6 containing therein a control member for generating sterilizing rays.
And an ultraviolet lamp 7 which is attached to the control box 6 and emits germicidal rays (which means ultraviolet rays which are electromagnetic waves having a wavelength of 253.7 nm (nanometers)).

In the conventional liquid tank sterilization apparatus having such a structure, when the switch of the sterilization ray irradiation unit 3 is turned on, electric power is supplied to the sterilization ray irradiation unit 3 to turn on the ultraviolet lamp 7 and the liquid 2 UV rays inside (Fig. 4
Medium UV). Bacteria, molds, bacteria, and algae in the liquid 2 are killed or their generation is suppressed by this ultraviolet ray, and the inside of the liquid tank is purified.

[0003]

However, in such a conventional liquid tank sterilization device, the sterilization ray irradiation unit 3 is fixedly attached to the liquid tank 1, and the ultraviolet lamp 7 is provided at the zenith portion of the liquid tank 1. Since it has a structure that extends downward from the minute, the ultraviolet lamp 7 must be properly used depending on the size of the liquid tank 1 in order to reach near the bottom of the liquid tank 1. It is uneconomical and costly. Further, the ultraviolet lamp 7 uniformly irradiates ultraviolet rays from the entire ultraviolet lamp 7 even when the liquid 2 is almost completely filled near the zenith in the liquid tank 1 or when the liquid level is low. Therefore, when the liquid surface is at a low level, most of the ultraviolet rays illuminate the air in the liquid tank 1, resulting in waste. Moreover, when the liquid tank 1 is made of plastic by irradiating the inside wall of the liquid tank 1 with ultraviolet light by irradiating the air with ultraviolet light, the plastic is deteriorated, and as a result, the liquid tank 1 above the waterline is There was a problem that the plastic was damaged more than specified. Further, since the ultraviolet rays illuminate the air in the liquid tank 1, a large amount of insects are attracted by the ultraviolet rays leaking through the small gaps at night and the like, and the ultraviolet rays are killed by the ultraviolet rays in the liquid tank 1 and are often lost. There was also the problem that the insects floated in the liquid.

The present invention has been made in view of the above problems, and a first object of the present invention is to provide a small-sized liquid tank sterilizing apparatus having an excellent liquid sterilizing effect.

A second object of the present invention is to provide a liquid tank sterilizer which does not damage the liquid tank.

A third object of the present invention is to provide an in-tank sterilizer which prevents insects or the like from entering from the outside and floating in the liquid tank.

A fourth object of the present invention is to provide a liquid tank sterilizer having excellent versatility which can be used for any liquid tank regardless of the size of the liquid tank.

[0008]

In order to solve the above-mentioned problems, the liquid tank sterilizing apparatus of the present invention basically comprises a sterilizing ray irradiation unit arranged in the liquid in the liquid tank, and a sterilizing ray irradiating unit. The sterilization ray irradiation unit is always connected to the irradiation unit and consists of a floating member that floats on the liquid and supports the sterilization ray irradiation unit, and moves the floating member up and down according to the increase or decrease of the liquid in the liquid tank. The gist is that the liquid is retained so that it exists in the liquid.

As an embodiment of such a liquid tank sterilizer, the liquid tank sterilizer is vertically movable in the liquid tank and is engaged with the guide member so as to be vertically movable. A slider member, a sterilization ray irradiation unit fixedly attached to the slider member and moving up and down integrally with the slider member, and a float which is connected to the slider member and floats on the liquid surface to hold the slider member and the sterilization ray irradiation unit in the liquid. The gist is that the slider member is moved up and down along the guide member according to the increase and decrease of the liquid in the liquid tank, and the sterilizing ray irradiation unit is always held in the liquid.

[0010]

[Operation] With the above configuration. As a basic operation, the liquid tank sterilization apparatus of the present invention has a floating member that moves up and down in response to an increase or decrease in the amount of liquid in the liquid tank. Therefore, the sterilization line supported by the floating member in the liquid is supported. The irradiation unit moves up and down integrally with the floating member while always being in the liquid regardless of whether the liquid surface is above or below. Therefore, the sterilization ray irradiation unit can always irradiate ultraviolet rays into the liquid and does not irradiate the outside of the liquid, that is, the air in the liquid tank, so that the sterilization efficiency by the ultraviolet rays in the liquid is improved. .

Further, according to the above-described embodiment, the liquid tank sterilization apparatus includes a guide member, a slider member movable along the guide member, a sterilization ray irradiation unit fixedly attached to the slider member, and a slider member. The sterilizing ray irradiating unit is arranged along the guide member according to the increase / decrease of the liquid in the liquid tank, since the sterilizing ray irradiating unit is connected to and floats on the liquid surface and holds the sterilizing ray irradiating unit in the liquid. It is constantly held in the liquid while moving up and down. As a result, the liquid in the liquid tank can be uniformly irradiated with ultraviolet rays, and the liquid can be entirely sterilized and purified. And since all of the ultraviolet rays are applied to the liquid, it does not deteriorate the inner wall of the liquid tank and shorten the life.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid tank sterilizer according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a configuration of a liquid tank sterilization apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part for explaining the configuration of the liquid tank sterilization apparatus in detail. In FIG. 1, reference numeral 11 is a liquid tank in which water or other liquid 12 is filled, 13 is a sterilization ray irradiation unit that is fixedly attached to the liquid tank and emits sterilization rays in the liquid, and 14 is a sterilization ray irradiation unit 13. It is a power supply member that supplies electric power,
The power supply member 14 is connected to an AC circuit such as a power line by a plug 15. In order to simplify the structure of the sterilizing ray irradiation unit 13, the control box part is incorporated in the power supply member 14, and only the ultraviolet lamp 27 part is installed in the liquid tank 11. As described in the above description of the conventional example, the ultraviolet lamp 27 is supplied with electric power from the power supply member 14 and sterilized (ultraviolet ray having a wavelength of 253.7 nm (nanometer)).
Occurs.

The sterilizer is provided with a liquid tank 11
A plurality of guide members 16 extending in the vertical direction and installed inside
A slider member 17 which is engaged with the guide member 16 and is movable in the vertical direction along the guide member 16, and a slider member 17 which is connected to the slider member 17 and floats on the liquid surface.
A float 18 as a floating member that holds the germicidal ray irradiation unit 13 in the liquid 12 and a stirring mechanism 30 that stirs the liquid 12 in the liquid tank 11 at a position below the guide member 16. Sterilizing ray irradiation unit 13
Is fixedly attached to the slider member 17 and can move up and down integrally with the slider member 17.

In this embodiment, the guide member 16 includes a first guide member 16a and a second guide member 16b.
Are installed in the liquid tank 11. At least the first guide member 16a of the first and second guide members 16a and 16b is formed of an elongated tubular body having openings at the upper end and the lower end. Second guide member 1
6b may have either a tubular structure or a rod-shaped structure. In addition, the first and second guide members 16a and 16b
Is coupled to the inner wall of the liquid inlet 11a of the liquid tank 11, and is attached and supported by a support beam member 26 extending in the diameter direction and suspended.

The slider member 17 includes an upper plate 19 and a lower plate 2.
0 and a side member 21 formed of a side plate having a cylindrical structure that connects the upper plate 19 and the lower plate 20 to each other, and has a cylindrical body structure such as a cylinder as a whole. The side member 21
As the above, it may be configured by a plurality of side bars (so-called bird cage structure) instead of the side plate having the above-mentioned tubular structure. The slider member 17 is for mounting and supporting the sterilization ray irradiation unit 13 in a state where it itself can move up and down, and the ultraviolet rays emitted from the sterilization ray irradiation unit 13 (in particular, its ultraviolet lamp 27) are introduced into the liquid 12. The UV lamp 27 should not be surrounded and shielded by the side member 21 since it must be illuminated. Therefore, when the side member 21 is constituted by a side plate having a cylindrical structure, a plurality of slits extending in the circumferential direction or the vertical direction are provided in this side plate, or a plurality of holes are opened in the side plate so that the ultraviolet rays are contained in the liquid 12. Need to reach the whole. When the side member 21 is composed of a plurality of side bars, it is not necessary to use a large number of side bars, and at most three or four side bars may be used to connect the upper plate 19 and the lower plate 20. Then, through holes 22 and 23 are formed in the upper plate 19 and the lower plate 20, respectively, and these through holes 22, 2 are formed.
The slider member 17 engages with the guide member 16 in a vertically movable manner by loosely fitting the guide member 16 into the guide member 3. In the central portion of the slider member 17, mounting holes 24 and 25 for mounting the sterilization ray irradiation unit 13 are formed in the upper plate 19 and the lower plate 20, respectively, and the sterilization ray irradiation unit is installed in these mounting holes 24 and 25. It is fixedly installed. As a result, the sterilization ray irradiation unit 13 and the slider member 17 are integrally connected.

The float 18 is made of a spherical body made of plastic or other material, and has gas injected therein to float on the liquid. Plural floats 18 are arranged in the slider member 17. The plurality of floats 18 may be disposed in the slider member 17 completely freely moveable, or the slider member 17 may be arranged.
May be fixedly attached to the upper plate 19 of the slider member 17 at a constant interval so as to support them in a well-balanced manner. Whether the float 18 is arranged in the slider member 17 so as to be freely movable or fixedly attached to the upper plate 19 of the slider member 17 may be determined according to the structure of the slider member 17, and for example, the slider member 17 may be used. When the side surface member 21 of 17 is composed of 3 to 4 side bars, it is preferable that the float 18 is fixedly attached to the upper plate 19 of the slider member 17 so as not to separate from the slider member 17.

Incidentally, the first and second guide members 16
A stopper member 28 is provided at the lower ends of a and 16b so that the slider member 17 does not come off from the guide member 16 when the liquid level in the liquid tank 11 drops significantly. Among the stopper members 28, the stopper member 28 attached to the first guide member 16a is the first guide member 1
It is attached so as not to block the opening at the lower end of 6a.

In this embodiment, the stirring mechanism 30 has a rotating shaft 31 which is attached so as to penetrate the inside of the first guide member 16a made of a tubular body, and the rotating shaft 31.
A stirring screw 32 that is attached to the tip (lower end in FIG. 4) of the liquid tank 11 that stirs the liquid 12 in the liquid tank 11, and a drive motor 33 that rotationally drives the rotating shaft 31. The first guide member 16a and the rotary shaft 31 are
Bearing bearings 34, 3 are provided at the upper end portion of the first guide member 16a and the lower end portion to which the stopper member 28 is attached.
5 are attached to each other, and the rotary shaft 31 is rotatably supported by the first guide member 16a via these bearing bearings 34 and 35, so that they are connected to each other.

Further, in this embodiment, the rotary shaft 31
Are driven by being directly connected to the drive motor 33. The drive motor 33 is waterproofed, and the drive motor 33 is connected to the power supply member 14 via the control unit 41. As shown in FIG. 3, the control unit 41 is connected to the sensor 35 for detecting the level change of the liquid level in the liquid tank 11, the power switch 14 and the sensor 35, and turns on the power supply based on the detection result from the sensor 35. A first timer switch 36 that shuts off, a limit switch 37 that is connected to the first timer switch 36 to perform an on / off operation, and a second timer switch 38 that performs an on / off operation according to the operation of the limit switch 37.
It is composed of The ultraviolet lamp 27 is connected to the power supply member 14 via the first timer switch 36, so that the lighting and extinguishing operations thereof are controlled. The drive motor 33 is connected to the power supply member 14 via the first timer switch 36, the limit switch 37, and the second timer switch 38, so that the on / off operation of the drive motor 33 is controlled.

In this embodiment, the first timer switch 36 receives the liquid level change signal from the sensor 35, and when the liquid level does not change for a certain time (for example, 12 hours or 24 hours), the first timer switch 36 is connected to the power supply member 14. The circuit is cut off to stop the power supply. That is, in the present invention, it is assumed that the liquid 12 in the liquid tank 11 is used almost entirely once a day, is filled up again at night, and is used again the next day. Therefore, for example, on Saturdays and Sundays that are closed on the second day of the week, the liquid level is constant for a long time, so the first timer switch 36 cannot receive the liquid level change signal from the sensor 35, and the first 1 timer switch 3
6 turns off and shuts off the power supply circuit. When the liquid level changes again, the first timer switch 36 is turned on to connect the circuit with the power supply member 14 and supply the power. The set time of the first timer switch 36 can be changed as necessary.

The limit switch 37, as shown in FIG. 2, is comparatively viewed from the entire liquid tank 11 of either the first or second guide member 16a or 16b (the first guide member 16a in this embodiment). It is attached to the outer surface at a high position. And this limit switch 37 is
The slider member 17 in the low position rises in the liquid surface due to liquid replenishment and the like, so that the first and second guide members 1
The upper plate 19 ascends along 6a and 16b, reaches the limit switch 37, and engages with the limit switch 37 to be turned on. The second timer switch 38 is turned on when the limit switch 37 is turned on, and drives the drive motor 33 for a predetermined time at regular time intervals. The fixed time interval for driving the drive motor 33 and the time during which the drive motor 33 is driven are preset in the second timer switch 38, and these set times can be changed as necessary.

The operation of the liquid tank sterilizer of the present embodiment having such a configuration will be described below. First, as a premise, it is assumed that the liquid tank 11 is filled with the liquid 12 in a substantially full state (that is, a prescribed amount), and in the control unit 41, the first timer switch 36 is turned on. In this case, the slider member 17 is the float 1
It is held at a high position in the liquid tank 11 by the action of 8. Then, when the switch of the sterilization ray irradiation unit 13 is turned on, electric power is supplied to the sterilization ray irradiation unit 13 from the power source member 14, the ultraviolet lamp 27 is turned on, and the liquid 12 is irradiated with ultraviolet rays. During the irradiation of the ultraviolet rays, the ultraviolet lamp 27 is always attached to the slider member 17 so as to be kept in the liquid 12. Therefore, almost all the ultraviolet rays emitted from the ultraviolet lamp 27 are in the liquid 12. To the outside of the liquid 12 (the space of the liquid tank 11). Then, the ultraviolet rays kill or suppress the generation of bacteria, mold, bacteria, and algae in the liquid 12, and clean the inside of the liquid tank. For sterilization, the normal sterilization ray irradiation unit 13 is always (day or night, that is, 24
It is turned on for a period of time) and the liquid is irradiated with ultraviolet rays.

On the other hand, regarding the stirring mechanism 30, the limit switch 37 of the control section 41 is engaged with the slider member 17 when the slider member 17 is in the high position, and is turned on. As a result, the second timer switch 38 is also in the ON operation, and at a fixed time interval (for example, every 2 hours), for a predetermined time (for example, 3 seconds).
The drive motor 33 is driven (for 0 minutes only). Drive motor 3
The rotation shaft 31 is rotated by driving 3 and the stirring screw 32 is rotated to stir the liquid 12 in the liquid tank 11. When the liquid 12 is stirred, bacteria, molds, bacteria, and algae floating in the liquid 12 are removed from the liquid 12.
Those that move inside and come closer to the UV lamp 27 are more sterilized. This is because the ultraviolet ray transmittance differs depending on the type of the liquid 12, and the closer to the ultraviolet lamp 27, the greater the bactericidal effect.

On the other hand, the liquid 12 in the liquid tank 11 has its liquid level lowered by the use of the liquid 12 (for example, as drinking water, as cooling water, or as cleaning water). When the liquid surface descends, the slider member 17 descends along the guide member 16 to reach the low position, and the ultraviolet lamp 27 also reaches the descending low position. Even when the slider member 17 descends in this way, the ultraviolet lamp 27 is still attached to the slider member 17 so that it is always in the liquid 12 as when the ultraviolet lamp 27 is in the high position. , This UV lamp 27
Almost all of the ultraviolet light emitted from the liquid 12 is applied to the liquid 12, and the outside of the liquid 12 (the space of the liquid tank 11) is not irradiated. Note that the sensor 3
Since 5 outputs the liquid level change signal, the first timer switch 36 is turned on, the circuit of the power supply member 14 is connected, and the ultraviolet lamp 27 and the limit switch 37 are kept on.

Here, regarding the agitating mechanism 30, the limit switch 37 of the control unit 41 moves the slider member 17 in the high position to the lower position as the liquid surface descends, thereby causing the slider member 17 to move. The engagement with and is released, and the off operation is performed. As a result, the second timer switch 38 is also turned off and the drive motor 33 is not supplied with electric power. Therefore, the drive motor 33 does not operate and the stirring screw 32 does not rotate. This means that the liquid level descending means that the liquid 12 is flowing out. Therefore, the liquid 12 in the liquid tank 11 slightly moves and stirs due to the descending motion of the liquid level accompanying the outflow of the liquid 12. This is because it is not necessary to perform the stirring operation by the stirring mechanism 30 because of the action. And then the liquid 12
If the liquid 12 is replenished with respect to the decrease of the liquid, the liquid level will rise. The float 18, which is a floating member, moves up and down as the liquid level rises and falls (that is, the amount of the liquid 12 in the liquid tank 11 increases and decreases), and the slider member 17 connected to the float 18 also follows the guide member 16. Up and down. As a result, the sterilization ray irradiation unit 13 is provided with the slider member 1
The slider member 17 is fixedly attached to the slider 7.
And move up and down together. Since the germicidal ray irradiation unit 13 is fixedly attached to the slider member 17 in a state of being in the liquid 12, the germicidal ray irradiation unit 1 is
3 is always held in the liquid.

From the above, the sterilization ray irradiation unit 13 can always irradiate the liquid 12 with ultraviolet rays, and since it is not irradiated outside the liquid 12, that is, in the air inside the liquid tank 11, the liquid 12 is not irradiated. The sterilization efficiency by the ultraviolet rays in is improved. Further, since the movement of the germicidal ray irradiation unit 13 in the liquid tank 11 is guided by the guide member 16, the germicidal ray irradiation unit 13 can be placed at a position (path) where the irradiation efficiency of ultraviolet rays is the highest. As a result, the liquid 12 in the liquid tank 11 can be uniformly irradiated with ultraviolet rays, and the liquid 12 can be entirely sterilized and purified. And all the ultraviolet rays are liquid 1.
Since it is irradiated during the period, the inner wall of the liquid tank 11 is not deteriorated and the life is not shortened. Further, since the germicidal ray irradiation unit 13 is in a state of floating in the liquid 12 in the liquid tank 11, it is not necessary to use a large lamp as the ultraviolet lamp 27, and it can be made small. In addition, what size the liquid tank 11 is,
It is possible to use the sterilization ray irradiation unit 13 having substantially the same size even if it has a shape, and it is possible to reduce the cost because it has versatility.

As long as the liquid 12 in the liquid tank 11 repeats increasing and decreasing at a rate of about once a day,
Since the sensor 35 outputs a liquid level change signal, the first
Since the timer switch 36 is in the ON state, and the ultraviolet lamp 27 and the limit switch 37 are also kept in the ON state, the sterilization operation by the sterilization ray irradiation unit 13 is continued, and the stirring operation of the liquid 12 is controlled at a constant level. Run below. On the other hand, on weekends or when there is a long break, the liquid 12 in the liquid tank 11 is not used and the liquid level is constant for a long time. Therefore, the first timer switch 36 sets the liquid level from the sensor 35. When the change signal is not received, the first timer switch 36 is turned off to cut off the power supply circuit. This first timer switch 3
By the OFF operation of 6, the ultraviolet lamp 27 is turned off, the limit switch 37 is also turned off, and the drive motor 33 is not driven. Then, when the liquid level changes again due to the use of the liquid 12 or the like, the first timer switch 36 is turned on to connect the circuit with the power supply member 14 to supply electric power to the ultraviolet lamp 27. The light is turned on and the limit switch 37 is turned on to drive the drive motor 33.

In the above embodiment, the stirring mechanism 30 has the rotating shaft 31 attached to the first guide member 16a and is directly connected to the drive motor 33 to be driven. The second guide member 16
You may make it carry out double stirring operation by attaching to b. A rotary shaft and a stirring screw are attached to the second guide member 16b, and a pulley and a belt for power transmission are provided between the first and second guide members 16a and 16b so that the power from the drive motor 33 can be supplied. You may make it transmit to the stirring mechanism by the side of the 2nd guide member 16b.

Further, although not shown in the drawing, the liquid tank 1
By installing a liquid purifying agent such as activated carbon in the vicinity of the liquid outlet 1 of FIG.
2 further remove impurities, or the above liquid 1
2 can contain minerals.

[0030]

As described above, according to the present invention,
Basically, the sterilization ray irradiation unit disposed in the liquid in the liquid tank and the floating member connected to the sterilization ray irradiation unit and floating in the liquid and supporting the sterilization ray irradiation unit sterilize the inside of the liquid tank. Since the device is configured, depending on the increase or decrease of the liquid in the liquid tank, the sterilizing ray irradiation unit can be moved up and down together with the floating member in the state where the sterilization ray irradiation unit is always present in the liquid, and it is possible to always irradiate the liquid with ultraviolet rays. it can. Therefore, the sterilization efficiency by the ultraviolet rays in the liquid is enhanced.

When the movement of the sterilizing ray irradiation unit in the liquid tank is guided by the guide member, the sterilizing ray irradiating unit can be placed at the position (route) where the irradiation efficiency of the ultraviolet rays is the highest, which allows The liquid in the liquid tank can be uniformly irradiated with ultraviolet rays, and the liquid can be entirely sterilized and purified. And since all of the ultraviolet rays are applied to the liquid, it does not deteriorate the inner wall of the liquid tank and shorten the life.

Further, since the germicidal ray irradiation unit is in a state of floating in the liquid in the liquid tank, it is not necessary to use a large lamp as an ultraviolet lamp, and it can be downsized. Further, regardless of the size and shape of the liquid tank, it is possible to use sterilization ray irradiation units of almost the same size, and it is possible to keep the cost low because of its versatility.

Further, since the germicidal ray irradiation unit always irradiates ultraviolet rays into the liquid in the liquid tank and does not leak the liquid to the outside of the liquid tank, insects and the like gather and die.
It does not float in the liquid and it is possible to keep the liquid more hygienic.

[Brief description of drawings]

FIG. 1 is a front view showing the configuration of a liquid tank sterilizing apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of main parts for explaining in detail the configuration of the liquid tank sterilizing apparatus according to the above embodiment.

FIG. 3 is a block diagram showing a control unit that controls ON / OFF operation of a drive motor.

FIG. 4 is a front view schematically showing a configuration of a conventional liquid tank sterilizer.

[Explanation of symbols]

 11 Liquid Tank 12 Liquid 13 Sterilizing Radiation Irradiation Unit 14 Power Supply Member 16 Guide Member 17 Slider Member 18 Float (Floating Member) 27 UV Lamp 30 Stirring Mechanism 32 Stirring Screw 41 Control Section

Claims (4)

[Claims] 1. A sterilization ray irradiation unit disposed in a liquid in a liquid tank, and connected to the sterilization ray irradiation unit,
It consists of a floating member that floats in the liquid and supports this germicidal radiation irradiation unit. The floating member moves up and down according to the increase or decrease of the liquid in the liquid tank, and keeps the germicidal radiation irradiation unit so that it always exists in the liquid. A liquid tank sterilization device characterized by: 2. A guide member extending vertically in the liquid tank, a slider member that engages with the guide member and can move in the vertical direction, and is fixedly attached to the slider member and integrally formed with the slider member. A sterilization ray irradiation unit that moves up and down, and a float that is connected to the slider member and floats on the liquid surface to hold the slider member and the sterilization ray irradiation unit in the liquid, depending on the increase or decrease of the liquid in the liquid tank. A sterilizing device in a liquid tank, which vertically moves along a guide member and holds the sterilizing ray irradiation unit at all times in the liquid. 3. The apparatus for sterilizing liquid in a liquid tank according to claim 2, wherein a stirring screw is arranged below the guide member to stir the liquid in the liquid tank. 4. The apparatus for sterilizing liquid in a liquid tank according to claim 2, wherein the sterilizing ray irradiation unit and the stirring screw are controlled in operation by time control.