JP3349532B2 - Liquid level control device for storage tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for supplying a liquid to a liquid storage tank when the liquid level in the liquid storage tank falls below a liquid supply start level. The present invention relates to a liquid level control device for a storage tank that stops supplying a liquid when the liquid supply stop level is raised to recover the liquid supply stop level.

[0002]

2. Description of the Related Art A conventional liquid level control device for a liquid storage tank, for example, a ball tap, attaches a float which is displaced up and down in accordance with the liquid level in the liquid storage tank to a free end of a lever to lower the liquid level. When the float is displaced downward, the float opens the valve that closes the spout via the lever and starts water supply by weight.When the liquid level rises and the water supply stop level is restored, the float uses its own buoyancy to discharge the spout. The lever is pushed up against the water coming out, and the spout is closed with a valve.

[0003]

For this reason, since the float has a large buoyancy, the float and the lever have to be made strong, so that the weight becomes heavy. In addition, since the ball tap is fixed to the upper part of the side wall in the liquid storage tank, it is difficult to perform inspection and repair. In addition, if there is an earthquake when the valve is at the full water level with the valve closing the water discharge port due to the buoyancy of the float, the liquid surface will wave up and down and displace, and the liquid surface will displace downward and move away from the float, The float uses the lever to release the valve from the spout to supply water, and then the liquid level displaces upward, causing the valve to close the spout again. Cause failure.

[0004] Further, since the flow rate of the water supply due to the chattering phenomenon is very small, the water meter is often not sensed. In such a case, a water supply company (mainly a local public entity)
There was an inconvenience in that it was not possible to collect the fee while actually supplying water. The present invention has been made in order to solve the above-mentioned inconvenience, and is small and bulky, can be installed anywhere on the ceiling wall of the liquid storage tank, and can be easily removed from outside the liquid storage tank for maintenance and inspection. It is an object of the present invention to provide a liquid level control device for a liquid storage tank which can eliminate the chattering phenomenon when the liquid level is full.

[0005]

A liquid level control device for a storage tank according to the present invention opens and closes a main discharge port, and supplies a liquid from a liquid supply pipe connected when the main discharge port is opened. A back pressure chamber into which a part of the liquid from the liquid supply pipe flows through a small-diameter first liquid passage hole provided in the main valve body while incorporating a main valve body to be supplied into the storage tank. The main valve cylinder, the back pressure chamber and the sub-discharge port are communicated with a sub-liquid supply path, and the liquid flowing from the sub-discharge port is supplied to the upper space or the middle space by the buoyancy and gravity of the float, A sub-valve with a built-in sub-valve supplying the liquid flowing from the sub-discharge port into the upper space into the liquid storage tank, wherein the sub-valve moves up and down inside the sub-valve A sub-valve shaft, an upper sub-sliding valve attached to the sub-valve shaft and sliding inside the upward sub-bar portion of the sub-valve, and a lower portion of the sub-valve A lower sub-sliding valve that slides inside the sub-cylinder portion, and the upper space of the sub-valve cylinder above the back pressure chamber and the upper sub-sliding valve in a state where the sub-valve is lowered. In the sub-supply passage, and the middle space of the sub-valve cylinder between the back pressure chamber and the upper sub-sliding valve and the lower sub-sliding valve in a state where the sub-valve is raised. And a second liquid passage hole, which has one end opened to the upper space and the other end opened to the peripheral surface below the lower sub slide valve, in the sub valve shaft. And the float is attached to the sub-valve shaft at the lower end of a downward extension extending downward from the lower end of the downward sub-cylinder.

[0006]

The liquid level control device for a liquid storage tank according to the present invention is constructed as described above. Therefore, when the liquid level in the liquid storage tank is lowered and buoyancy does not act on the float, the gravity of the float is reduced. By acting on the valve element, the sub-valve element is lowered, and the liquid is supplied from the sub-discharge port to the upper space of the sub-valve, so that the liquid flows into the liquid storage tank. For this reason, since the pressure in the back pressure chamber of the main valve cylinder which communicates with the upper space and the sub-supply passage is lowered and the main valve moves, the main valve opens the main discharge port,
Liquid is supplied from the main discharge port into the liquid storage tank.

When the liquid level rises due to the supply of the liquid into the liquid storage tank, the sub-valve rises due to the buoyancy of the float and closes the sub-discharge port in the middle space, so that the pressure in the back pressure chamber rises. As the main valve moves to close the main discharge port, the supply of liquid from the main discharge port into the storage tank stops.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a liquid level control device for a liquid storage tank according to a first embodiment of the present invention when water supply is stopped. FIG. 2 is a cross-sectional view of a liquid level control device for a liquid storage tank shown in FIG. FIG. 3 is a cross-sectional view showing a state in which the sub water outlet of the liquid level control device of the liquid storage tank shown in FIG. 1 is closed and water is supplied from the main water outlet. In each of the following embodiments, the case where the liquid is water will be described.

In these figures, reference numeral 10 denotes a main valve cylinder which is fixed at the lower end around the opening 2 of the ceiling wall 1 of the liquid storage tank and stands outside the liquid storage tank, and a water supply pipe 3 as a liquid supply pipe. And a main water supply passage 11 as a main water supply passage to which the main water supply passage 1 is connected.
An upward main cylinder portion 1 concentrically connected to the tip of the first vertical direction 1
2 and a downward main cylinder 13 having a main water outlet 14 as a main discharge port having a smaller diameter than the upward main cylinder 12. The upper end of the upward main cylinder 12 is closed by an upper lid 12 '. I have.

Reference numeral 21 denotes a series of main valve shafts which move up and down at the centers of the upwardly directed main cylinder portion 12 and the downwardly directed main cylinder portion 13 of the main valve cylinder 10. A main slide valve 22 that slides inside the main valve, and a main pressing valve 23 that opens and closes an upward valve seat around the main water discharge port 14 from above is attached to a lower end portion of the main valve shaft 21, the main slide valve 22. The main valve body 20 is constituted by the main pressing valve 23 and the main pressing valve 23. The main sliding valve 22 is provided with a first water passage hole 24 as a first liquid passage hole having a small diameter, for example, a diameter of about 1 mm to 1.5 mm, and is formed in a vertical direction.

The diameter of the main pressing valve 23 is substantially equal to the inner diameter of the downward main cylinder portion 13, and when the main valve body 20 moves up and down in the main valve cylinder 10, the main sliding valve 22 and the main pressing valve 23 Guide with. If necessary, a cutout for water passage may be provided in the peripheral portion of the main pressing valve 23.

Numeral 30 denotes a sub-valve whose lower end is fixed to the periphery of the opening 2 of the ceiling wall 1 of the storage tank and stands outside the storage tank,
It is much smaller in diameter than the main valve barrel 10. The sub-valve 30 is provided with an upward sub-tube portion 31 and a downward sub-tube portion 32 having an inner diameter smaller than that of the upward sub-tube portion 31 vertically and concentrically. A step 33 is provided at the boundary with the sub-water outlet 34 as an auxiliary liquid outlet having a small diameter.

Reference numeral 41 denotes a sub-valve shaft that moves up and down at the center of the sub-valve cylinder 30. The sub-valve shaft 41 has a large-diameter portion 41a whose lower end abuts against the step 33, and a lower-diameter portion of the large-diameter portion 41a. And a small diameter portion 41b extending downward. And the large diameter part 4
An upper O-ring 42 as an upper sub-sliding valve that slides up and down across the sub water outlet 34 is attached to the inside of the upward sub-cylinder 31 at 1a, and the downward sub-cylindrical portion is attached to the small diameter portion 41b. A lower O-ring 43 serving as a lower sub-sliding valve that slides inside 32 is attached, and a sub-valve 40, an upper O-ring 42 and a lower O-ring 43 constitute a sub-valve element 40,
The O-rings 42 and 43 form a middle space 37 inside the upper and lower sub-valve cylinders 31 and 32.

The sub valve shaft 41 has a downward extension 41 'extending downward from the open lower end of the downward sub cylinder portion 32 and reaching the inside of the liquid storage tank. , A float 44 is attached to the lower end. The downward length of the downward extension 41 'is determined according to the full water level in the liquid storage tank. Further, the back pressure chamber 2 above the main sliding valve 22 in the upward main cylinder portion 12
5 and a sub water discharge port 34 of the upward sub cylinder part 31 are communicated with a sub water supply passage 35 as a sub liquid supply passage.

In the case of the first embodiment shown in FIGS. 1 to 3 in which the main valve barrel 10 and the sub-valve cylinder 30 are integrally formed in parallel, the sub-water supply passage 35 is formed at the time of molding. Also, the upward sub-cylinder 3
In order to allow the upper space 36 above the upper O-ring 42 in 1 to communicate with the atmosphere, a second end is opened at the upper end of the sub-valve shaft 41 and the other end is opened at the peripheral surface below the lower O-ring 43. A second water passage hole 38 is provided as a liquid passage hole.

Further, usually, on the ceiling wall 1 of the liquid storage tank,
As shown in FIG. 4, the ventilation cylinder 7 is erected, and the surface of the liquid in the liquid storage tank is communicated with the atmosphere through a filter provided in the ventilation cylinder 7 for preventing intrusion of insects and dust. , Upper space 36
Communicates with the space above the liquid level in the liquid storage tank through the second water hole 38. The total cross-sectional area of the sub water outlet 34 and the second water hole 38 may be slightly larger than the first water hole 24 of the main sliding valve 22.

Next, the operation will be described. The water level in the storage tank shown in FIG. 1 is a full water level, the float 45 is immersed in water, the buoyancy causes the sub-valve shaft 41 to rise, and the space between the upper O-ring 42 and the lower O-ring 43 The middle space 37 is connected to the sub water outlet 34 and closes the sub water outlet 34. And the tap water from the water supply pipe 3 is the main valve cylinder 1
0, the space between the main sliding valve 22 and the main pressing valve 23 is filled, and a part of the tap water is passed through the first water hole 24 to the back pressure chamber 2.
5. Fill the sub water supply passage 35 and the middle space 37.

When the back pressure chamber 25, the sub-water supply passage 35, and the middle space 37 are filled with water, equal water supply pressure acts on the main sliding valve 22 located in the upward main cylinder 12 from above and below. , The main valve body 20 uses its own weight and water supply pressure to make the main pressing valve 2.
3 is pressed against the valve seat around the main water discharge port 14 from above, and the main water discharge port 14 is closed. Further, the main pressing valve 23 is connected to the main water discharge port 1.
In order to ensure that the valve 4 is closed from above, a weak spring 26 may be accommodated in the back pressure chamber 25, and the main valve body 20 may be lightly reduced in pressure by the spring 26.

Then, when the water level in the liquid storage tank falls and the float 45 loses buoyancy, as shown in FIG.
5 and the sub-valve element 40 are lowered by their own weight, and the large-diameter portion 41 a abuts the step portion 33, and the upper O-ring 42 is located below the sub-water outlet 34. When the upper O-ring 42 is located below the sub water outlet 34, the back pressure chamber 25, the sub water supply passage 35,
The water filling the upper space 36 falls into the liquid storage tank through the second water hole 38, and a part of the tap water from the water supply pipe 3 flows into the back pressure chamber 25 through the first water hole 24. ,
Similarly, it falls into the liquid storage tank.

In this way, the auxiliary water outlet 34 is opened, and the back pressure chamber 25 is opened.
Is released, the main sliding valve 22 having a large pressure receiving area and the main pressing valve 23 having a smaller pressure receiving area are instantaneously released.
The main valve body 20 rises due to the pressure difference based on the difference in the pressure receiving area, and the main pressing valve 23 opens upward from the valve seat around the main water discharge port 14 to open the main water discharge port 14, and most of the water from the water supply pipe 3. Tap water falls from the main spout 14 into the storage tank. That is, the water supply into the liquid storage tank is performed from both the main water discharge port 14 and the sub water discharge port 34.

When the water level in the liquid storage tank rises due to the supply of water into the liquid storage tank, first, as shown in FIG.
2 is positioned above the sub water outlet 34 and the middle space 37
Is connected to the sub water outlet 34, and the stopper 44 abuts against the lower end of the downwardly facing sub cylindrical portion 32, thereby closing the sub water outlet 34. When the sub water outlet 34 is closed in this way, the sub water outlet 34
Although the supply of water to the liquid storage tank is stopped, the main pressure valve 23 keeps the main water discharge port 14 open by the above-described differential pressure, and the water supply from the main water discharge port 14 into the liquid storage tank continues.

Then, a part of the tap water from the water supply pipe 3 flows into the back pressure chamber 25 through the first water hole 24, and the back pressure chamber 2
5. Middle space 37 with sub water supply passage 35 and sub water outlet 34 closed
When the condition is satisfied, the water pressure acting on the main sliding valve 22 from above and below becomes equal. When the water pressures acting on the main sliding valve 22 from above and below become equal, the main valve body 20 is gradually lowered by its own weight or by its own weight and the spring force of the spring 26, as shown by a broken line in FIG. When the volume of the back pressure chamber 25 increases due to the lowering of the main valve body 20, the tap water from the water supply pipe 3 fills the back pressure chamber 25 whose volume has increased from the first water hole 24. As shown in FIG. 1, the main pressing valve 23 closes the main water discharge port 14 from above by the feed water pressure acting from above and the own weight of the main valve body 20, or the own weight and the spring force of the spring 26, and the main pressurizing valve 23 is connected to the liquid storage tank. Stop water supply completely. At this time, the water level in the liquid storage tank becomes the full water level.

The time from when the float 45 pushes up the sub-valve element 40 by buoyancy, when the middle space 37 closes the sub-water outlet 34, and when the main pressing valve 23 closes the main water-out port 14 is the back pressure chamber 25. , The total capacity of the sub water supply passage 35 and the middle space 37, the supply flow rate of the tap water supplied from the water supply pipe 3, and the diameter of the first water passage hole 24. The above-mentioned total capacity is set so that the full water level is higher by about 10 cm than the water level WL when the float 45 closes the sub water discharge port 34 in the middle space 37 according to the supply flow rate.

As a result, since the float 45 is immersed in water deeper than the water level WL, even if there is an earthquake when the water level is full and the liquid surface undulates, since the float 45 is immersed in the water, the secondary water discharge port is provided. The occurrence of the chattering phenomenon can be prevented without opening the valve. When a check valve 27 that allows water to flow from bottom to top and prevents water flow from top to bottom is attached to the first water passage hole 24 on the upper surface of the main sliding valve 22, Since the water in the pressure chamber 25 does not flow backward, the water hammer and the vibration of the main valve body 20 can be prevented.

Further, a threaded rod 15 may be vertically penetrated through the upper lid 12 'of the upwardly directed main cylinder portion 12, and the threaded rod 15 may be moved up and down so that the highest position of the main valve body 20 can be adjusted. desirable. The stopper 16 is provided on the main valve body 20.
So that the main slide valve 22 is located below the upper end opening of the sub water supply passage 35 even when the main valve body 20 is raised to the maximum. Further, as shown in FIG. 2, an L-shaped pipe 17 is connected to the lower end of the downward main cylinder portion 13,
It is preferable to deflect the water flowing down from the float 45.

FIG. 4 is an explanatory view showing a second embodiment of the liquid level control device for a liquid storage tank according to the present invention, which is installed on a ceiling wall of the liquid storage tank. Are given the same reference numerals and description thereof is omitted. In FIG. 4, one or more auxiliary floats which vertically overlap with the float 45 or float integrally with the float 45 or the downward extension 41 'of the sub-valve shaft 41, and in the second embodiment, two auxiliary floats 46A which are upper and lower , 46B are connected by a string-like connecting tool 47 such as a chain.

The upper and lower auxiliary floats 46A, 46A
As a guide 48 that vertically overlaps and floats B below the float 45, a guide shaft is attached to the float 45 downward, and auxiliary floats 46A and 46B are skewed to the guide shaft so as to be movable in the vertical direction. Instead of the guide shaft, a water-flowing cylinder surrounding the float 45 and the auxiliary floats 46A and 46B is provided vertically around the opening 2 of the main valve cylinder 10 or the ceiling wall 1 as shown by a broken line. 45, the auxiliary floats 46A and 46B may be moved up and down.

With the configuration shown in FIG. 4, even if the liquid level in the liquid storage tank is lowered and the float 45 comes out of the liquid level and loses buoyancy, the liquid level is further lowered and the upper auxiliary float 46
Even if A rises above the liquid level and loses buoyancy, the auxiliary water outlet 34 is closed in the middle space 37, the liquid level becomes a drought level near the bottom of the storage tank, and the lower auxiliary float 46B loses buoyancy. For the first time, the sub-valve element 40 is lowered by the total weight of the three floats 45, 46A, 46B, and the water supply can be started by positioning the upper O-ring 42 below the sub-water outlet 34.

In this case, due to the continuation of the water supply, the lower auxiliary float 46B first floats below the upper auxiliary float 46A, and the upper and lower auxiliary floats 46A and 46B are integrally placed below the float 45. Only when the three floats 45, 46A, 46B float together, the sub-valve 40 rises and the sub-water outlet 3
Close 4. In this way, the start of water supply can be freely set, for example, when the liquid level in the liquid storage tank reaches the drought water level.

FIG. 5 is a sectional view of a third embodiment of the liquid level control device for a liquid storage tank according to the present invention when water supply is stopped. The same reference numerals are given to the same parts as in FIGS. I do. In FIG. 6, the main valve body 10 and the sub valve body 30 are formed separately from each other, and the main valve body 10 and the sub valve body 30 are connected to each other by a small-diameter tube or the like so as to communicate with each other. Road 35. The diameter of the opening 2 provided in the portion of the ceiling wall 1 for fixing the lower end of the sub-valve 30 is made larger than the float 45, and the sub-valve 30 is removed from the ceiling wall 1 during maintenance and inspection, and the float 45 is removed. Be able to go outside.

FIG. 6 is a cross-sectional view of a fourth embodiment of the liquid level control device for a liquid storage tank according to the present invention when the water supply is stopped. The same parts as those in FIGS. I do. In FIG. 6, reference numeral 50 denotes a main valve cylinder whose lower end is fixed to the periphery of the opening 2 of the ceiling wall 1 of the liquid storage tank and stands outside the liquid storage tank. Main water supply channel 51 as main liquid supply channel provided with main water discharge port 51 'as a main liquid discharge port
And an outer cylindrical portion 52 formed concentrically outside the main water supply channel 51 and having an open end, and connected to a side portion of the outer cylindrical portion 52 to form the main water supply channel 51 and the outer cylindrical portion 52. And a communication cylinder portion 53 for communicating the space formed by the inside of the liquid storage tank with the end of the outer cylinder portion 52.
Closed at 2 '.

Reference numeral 61 denotes a diaphragm as a main valve body for opening and closing the main water discharge port 51 '. The periphery of the diaphragm 61 is fixed to a step inside the outer cylindrical portion 52 by a lid 52'. In the diaphragm 61, a first water passage hole 62 as a first liquid passage hole having a small diameter, for example, about 1 mm to 1.5 mm is formed in the left-right direction. Reference numeral 63 denotes a back pressure chamber formed by the diaphragm 61 and the lid 52 '. The back pressure chamber 63 is communicated with the sub-valve 30 through the sub-water supply passage 35.

Reference numeral 64 denotes a spring mounted between the diaphragm 61 and the lid 52 '. When the left and right pressures become equal, the diaphragm 61 closes the main water discharge port 51' by its own elastic force. Is for applying a biasing force for the diaphragm 61 to reliably close the main water discharge port 51 '. Reference numeral 65 denotes a check valve for preventing water in the back pressure chamber 63 from flowing back to the first water hole 62.

With the configuration shown in FIG. 6, the operation is the same as that of each of the above embodiments, and the description of the operation is omitted. In the fourth embodiment shown in FIG. 6, the same effects as in the previous embodiments can be obtained.

In the first and second embodiments, the main valve cylinder 1
In the third and fourth embodiments, the main valve body 10 or the main valve body 50 and the sub valve body 30 are separated from each other. In order to install 50 and the sub-valve 30 on the ceiling wall 1, as shown in FIG.
A bolt 4 is erected around the opening 2 with a nut 5, and a hole in a flange at the lower end of the valve cylinder is fitted to the bolt 4 and the nut 5 to form the main valve cylinder 10 or the main valve cylinder 50 and the sub valve cylinder 30. The ceiling wall 1
After standing on the top and fitting the washer from above to the bolt 4, the nut 6
It can be easily installed because it only has to be screwed from above and tightened.

Then, by removing the nut 6 from the bolt 4, the float 45 or each of the floats 45 and 46 is removed.
Since the main valve body 10 or the main valve body 50 and the auxiliary valve body 30 can be removed from the ceiling wall 1 for each of the A and 46B, inspection and repair can be easily performed. Further, the main valve body 10 of the first, second and third embodiments may be horizontal, and the main valve body 5 of the fourth embodiment may be horizontal.
0 indicates that the outer tubular portion 52 and the communicating tubular portion 53 are formed concentrically,
It may be mounted vertically on the ceiling wall 1.

Further, in the fourth embodiment, the float 4
5 may be configured as in the third embodiment, or the main valve cylinder 50 and the sub-valve cylinder 30 may be integrated. Further, the liquid is not limited to water, and it is needless to say that another liquid having fluidity like water may be used.

[0038]

As described above, the liquid level control apparatus for a liquid storage tank according to the present invention controls the start and stop of the liquid supply by the vertical displacement of the float without using the lever. The float is operated by the sub-valve that moves up and down in the sub-valve, whose diameter can be made very small as compared with the main valve cylinder, so that the float may be small and lightweight. Therefore, it is possible to provide a small and non-bulky liquid level control device for the liquid storage tank.

Further, the float can be easily installed anywhere on the ceiling wall of the storage tank, and the float can be easily removed from the ceiling wall by work outside the storage tank during maintenance and inspection. Further, after the sub-discharge port of the sub-valve is closed by the sub-valve by floating of the float, the supply of liquid continues until the main discharge port of the main valve cylinder closes, and the float is turned into the liquid of the full liquid level. Since it is soaked deeply, even if there is an earthquake when the liquid level is full, the chattering phenomenon does not occur, so that no failure occurs and no dead water supply which is not detected by the water meter or the like is performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid level control device for a liquid storage tank according to a first embodiment of the present invention when water supply is stopped.

FIG. 2 is a cross-sectional view of the liquid level control device for a liquid storage tank shown in FIG. 1 when water is supplied.

FIG. 3 is a cross-sectional view showing a state in which a sub water outlet of the liquid level control device of the liquid storage tank shown in FIG. 1 is closed and water is supplied from a main water outlet.

FIG. 4 is an explanatory view showing a second embodiment of the liquid level control device for a liquid storage tank according to the present invention, which is installed on a ceiling wall of the liquid storage tank.

FIG. 5 is a sectional view of a liquid level control device for a liquid storage tank according to a third embodiment of the present invention when water supply is stopped.

FIG. 6 is a sectional view of a liquid level control device for a liquid storage tank according to a fourth embodiment of the present invention when water supply is stopped.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceiling wall 2 Opening 3 Water supply pipe 4 Bolt 5, 6 Nut 7 Vent cylinder 10 Main valve cylinder 11 Main water supply channel 12 Upward main cylinder part 13 Downward main cylinder part 14 Main water outlet 20 Main valve body 21 Main valve shaft 22 Main slide Valve 23 Main press valve 24 First water hole 25 Back pressure chamber 26 Spring 30 Sub-valve 31 Up-side sub-tube 32 Down-side sub-tube 33 Step 34 Sub-water outlet 35 Sub-water supply path 36 Upper space 37 Middle space 38 Second water passage hole 40 Sub-valve 41 Sub-valve shaft 41a Large diameter portion 41b Small diameter portion 41 'Downward extension portion 42 Upper O-ring 43 Lower O-ring 45 Floats 46A, 46B Auxiliary floats 47 String-like connecting tool 48 Guide 50 Main Valve cylinder 51 Main water supply passage 51 ′ Main water discharge port 52 Outer cylinder part 52 ′ Lid 53 Communication cylinder part 54 Fixture 61 Diaphragm 62 First water hole 63 Back pressure chamber 64 Spring

Claims (4)

(57) [Claims] A main valve body for opening and closing a main discharge port and supplying a liquid from a liquid supply pipe connected to the main discharge port into the storage tank when the main discharge port is opened. A main valve cylinder having a back pressure chamber into which a part of the liquid from the liquid supply pipe flows through a small-diameter first liquid hole formed in the valve body; The liquid that is communicated with the liquid supply path and is supplied from the sub-discharge port to the upper space or the middle space by the buoyancy and gravity of the float, and the liquid that flows from the sub-discharge port into the upper space is stored in the liquid. A sub-valve that incorporates a sub-valve to be supplied into the tank, wherein the sub-valve is a sub-valve that moves up and down inside the sub-valve, An upper sub-sliding valve that slides inside the upward sub-cylinder and a lower sub-sliding valve that slides inside the downward sub-cylindrical portion of the sub-valve; A state in which the back pressure chamber and the upper space of the sub-valve above the upper sub-sliding valve are communicated with the sub-supply in a state where the sub-valve is lowered, and the sub-valve is raised. In the back pressure chamber, while communicating with the middle space of the sub-valve cylinder between the upper sub-sliding valve and the lower sub-sliding valve in the sub-supply passage, the sub-valve shaft, One end is open in the upper space,
A second end whose other end is opened on a peripheral surface below the lower auxiliary slide valve;
A liquid level control device for a liquid storage tank, wherein a liquid passage hole is provided, and the float is attached to a lower end of a downward extension extending downward from a lower end of the downward sub cylinder portion on the sub valve shaft. 2. The liquid level control device for a storage tank according to claim 1, wherein the main valve barrel and the sub-valve are integrally formed around an opening formed in a ceiling wall of the storage tank. A liquid level control device for a liquid storage tank, being attached and standing outside the liquid storage tank. 3. The liquid level control device for a storage tank according to claim 1, wherein the main valve barrel and the sub-valve are separated from each other around an opening formed in a ceiling wall of the storage tank. A liquid level control device for a liquid storage tank, wherein the liquid level control apparatus is individually attached to the liquid storage tank and stands outside the liquid storage tank. 4. The liquid level control device for a liquid storage tank according to claim 1, wherein the float or the sub-valve shaft vertically overlaps and floats integrally with the downward extension of the sub-valve shaft. A liquid level control device for a liquid storage tank, wherein one or a plurality of auxiliary floats are connected by a string-like connecting tool.