JPS6373311A - Control method for water level of liquid bath - Google Patents

Abstract

PURPOSE:To evade a state that a water level stays at an intermediate level for a long time, by stopping the operation of a pump when the water level arrives at the lower limit of the water level, then starting up a timer, and operating the pump by the operation of the timer after the lapse of a set time, even without detecting the water level by an upper limit switch, in a liquid bath to be used in a drainage facility. CONSTITUTION:An underwater pump 12 with built in a motor 12a is sunk in the liquid bath 10 to be used in the drainage facility, and a lifting pipe 12b which stands upright from the base part of the pump is bent at its upper part, and it pierces through the roof of the liquid bath 10, then is introduced to a drain groove 13. Also, floating switches 14 and 15 for detecting the upper limit and the lower limit of the water level, are provided at the underwater pump 12, and the upper limit HL, and the lower level LL of the water level are detected, respectively, and the pump 12 is operated by those detecting signals. At this time, a relay 19 and the timer 20 are provided on the pump 12 through a transformer 18, and the pump is stopped when the water level arrives at the LL, and afterwards, the pump 12 is stopped even when the water level does not arrive at the HL, after the lapse of the set time of the timer 20, then drainage is accelerated, thereby, the decay of water can be evaded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention detects the upper limit water level and the lower limit water level in a liquid tank.
The present invention relates to a method for controlling the water level of a liquid tank so as to start and stop the pump, respectively.

(Prior Art) Conventionally, in drainage equipment for liquid tanks, water level detection means (for example, electrodes,
A float switch, etc.) is installed, and when the water level rises to the upper limit water level, a pump installed in the liquid tank or on land is operated to drain the water, and when the water level falls to the lower limit water level, the pump operation is stopped.

This method of controlling the water level of the liquid tank is implemented by a control circuit as shown in FIG. That is, in FIG. 4, 1 is a pump motor connected to a three-phase AC power source AC consisting of R-3-T phases, 2 is a transformer inserted between RT and T of the power source AC, 3.4・5 is an upper limit water level switch of the upper limit water level detection means connected in series to the secondary side of the transformer 2 ・A lower limit water level switch of the lower limit water level detection means (any water level switch 3
・Relay 5a is a normally open contact of the relay 5 connected in parallel with the lower limit water level switch 4, and 5b and 5C are connected to the S and T terminals of the power supply AC. This is the normally open contact of the relay 5.

Now, when the water decreases due to pump operation and the liquid tank reaches the lower limit water level, the lower limit water level switch 4 closes, and since the upper limit water level switch 3 is already closed, the relay 5 is energized and the normally closed contacts 5b and 5C open. At the same time, the normally open contact 5c closes, forming a self-holding circuit and stopping the operation of the pump. Next, when water flows into the liquid tank from the outside and rises, the lower limit water level switch 4 is first opened (but the relay 5 is kept energized by the closing of the normally open contact 5C, and when the water increases further and reaches the upper limit water level, the upper limit water level switch 4 is opened). Since the water level switch 3 is also opened, the relay 5 is demagnetized, the normally open contact 5a is opened, and the normally open contacts 5b and 5C are closed, causing the pump to operate (circuit state shown in FIG. 5).

(Problem to be Solved by the Invention) In the case of using the water level control method of the liquid tank as described above, the pump stops operating when the water level of the liquid tank reaches the lower limit water level, and even if the water increases, the liquid tank stops midway. If the flow of water into the tank is severely reduced or stopped altogether, the water in the tank will remain at the intermediate level for a long time, causing the water to rot and emit a foul odor.

(Means for Solving Problems) The water level control method for a liquid tank according to the present invention operates the pump when the water level rises to the upper limit water level, stops the operation of the pump when the water level decreases to the lower limit water level, and starts a timer. The pump is characterized in that when the water level is between an upper limit water level and a lower limit water level, the pump is operated when the timer is activated for a predetermined set time.

(Function) When the water level in the liquid tank reaches the lower limit water level, the pump stops operating and the timer starts. When the predetermined time set in the timer elapses until the water level reaches the upper limit water level from the lower limit water level, the pump is operated by the operation of the timer even if the upper limit water level switch 3 does not detect the water level. Therefore, there is no need to worry about the water level in the liquid tank remaining in the middle for a long time, causing the water to corrode and emit a bad odor.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 4.

10 is a liquid tank into which water W flows from an inlet 11.

A submersible pump 12 with a built-in electric m12a is installed at the bottom of the liquid tank 10.
The water pump 12b of the submersible pump 12 rises upward, penetrates through the upper part of the liquid tank 10, and opens into a drain 13 outside the liquid tank 10.

Reference numerals 14 and 15 denote float switches for detecting an upper limit water level and a lower limit water level, which are attached to the upper and lower parts of the submersible pump 12 via suitable brackets, respectively, and each has an upper limit contact 14a and a lower limit contact 15a built-in.
15a is closed by the float switches 14 and 15 hanging downward under their own weight when the water level to be detected has not yet been reached, and when the float switches 14 and 15 reach their respective water levels and float upwards, It is designed to open. In FIG. 1, the water level at which the contact 14a changes from closed to open is shown as the upper limit water level IL, and the water level at which the contact 15a changes from open to closed is shown as the lower limit water level LL. For convenience, the water level is intermediate water level M
It is shown as L.

Reference numeral 16 denotes a control panel installed outside the liquid tank 10, which has a built-in control circuit 17. A cable CB led out from this panel is connected to the upper terminal plate 12C of the submersible pump 12, and is used to supply power to the motor 12a and both float switches. - Wiring to notches 14 and 15 is done. FIG. 2 shows the state of the control circuit 17 when the water level reaches the upper limit water level HL and the submersible pump 12 is in operation. To explain the configuration of the control circuit 17, the electric motor 112a is connected to a three-phase alternating current power supply AC consisting of R, S, and T phases. 18 is a transformer, the primary winding 18
a is connected between the RT and T phases of the power supply AC, and the secondary winding 18
Both ends of b are connected by parallel connections vAρ1 and λ2. The upper limit contact 14a, lower limit contact 15a, and relay 19 are connected in series to one wiring l, and the other wiring I! A timer 20 is connected to 2. 19a
・19b is the normally closed contact of the relay 19 interposed between the power supply AC17) ST phase, and 19C is the lower limit contact 15a.
The normally open contact 19d of the relay 19 connected in parallel with the timer 20 is the normally open contact of the relay 19 connected in series with the timer 20. 20a is a normally closed contact of a timer 20 connected in series with the relay 19. A predetermined set time t is set in the timer 20, and the normally closed contact 20a is opened when the set time t has elapsed since the timer 20 started.

Therefore, if water W is flowing into the liquid tank 10 from the inlet 11 while the submersible pump 12 is not operating, the water level in the liquid tank 10 will rise. When the water level reaches the upper limit water level HL, the float switch 14
floats upward and opens the upper limit contact 14a, so the relay 19 is demagnetized and the normally closed contacts 19a and 19b of the relay 19
is closed, thereby driving the electric motor 12a and operating the submersible pump 12. Due to the demagnetization of the relay 19, the normally open contacts 19c and 19d open, so the timer 20 is demagnetized.
Its normally closed contact 20a is closed. Further, the lower limit contact 15a remains open because the float switch 15 stands upward in the water.

By operating the submersible pump 12, the water W in the liquid tank 10 is drained into the drain groove 13, and the water level is lowered. As the water level decreases, the float switch 14 hangs downward under its own weight, and the upper limit contact 14a closes again, but since the lower limit contact 15a and the normally open contact 19C are open, the relay 19 remains demagnetized. The ice pump 12 continues to operate.

When the water level reaches the lower limit water level LLI, the float switch 15 also hangs downward due to its own weight, so the lower limit contact 1
5a is closed, the upper limit contact 14a and the normally open contact 20a
Coupled with the closed state, the relay 19 is energized. Therefore, by energizing the relay 19, its normally closed contacts 19a and 19
b opens, cutting off the power supply to the electric motor 12a, and submersible pump 1
Stop operation of 2. Also, since the normally open contacts 19C and 19d close due to the excitation of the relay 19, a self-holding circuit for the relay 19 is formed and the timer 20 is started (
(Situation shown in Figure 3). However, even if the timer 20 starts, the normally closed contact 20a does not open until the set time t has elapsed.

- When the operation of the submersible pump 12 is stopped, the liquid tank 1
When the water rises, the float switch 15 is turned upward again, so the lower limit contact 15a opens, but the self-holding circuit keeps the relay 19 in the energized state, that is, the submersible pump 12
maintain the stopped state.

Now, if for some reason the inflow of water W from the inlet 11 is extremely reduced or completely stopped, the water level of the liquid tank 10 will not reach the upper limit water level HL and will remain at the intermediate water level, and the submersible pump 12 will not reach the upper limit water level HL. It will remain out of operation. If the water level is at the intermediate water level MLI and the set time t of the timer 20 has elapsed, the normally closed contact 20a
opens, the relay 19 demagnetizes, and the normally closed contacts 19a and 19b
is closed, and the pump 12 operates without the water level reaching the upper limit water level. By demagnetizing the relay 19, the normally open contact 19c
・19d opens, the timer 20 also demagnetizes, and the normally closed contact 20
a closes again. Even if the normally closed contact 20a is closed, both the lower limit contact 15a and the normally open contact 19C are open, so that the relay 19 is kept in a demagnetized state, that is, the submersible pump 12 is maintained in an operating state.

The state of the control circuit 17 in FIG. 4 is such that the normally closed contact 20a is about to close due to demagnetization of the timer 20.

The water level decreases due to the operation of the submersible pump 12 at the intermediate water level MLI, and when it reaches the lower limit water level LL2, the control circuit 17 enters the state shown in FIG. 3 and stops the operation of the submersible pump 12. After that, the water in the liquid tank 10 increases and the timer 2
When the water level reaches the upper limit water level HL2 within the set time of 0, the control circuit 17 enters the state shown in FIG. 2, as described above, and the submersible pump 12 starts operating again.

The submersible pump 12 may be replaced with a pump installed on land, and although the float switches 14 and 15 were used as water level detection means in the embodiment described above, other detection means such as electrodes may also be used.

(Effects of the Invention) As explained above, according to the method for controlling the water level of a liquid tank according to the present invention, the timer is started when the pump stops operating, and when the timer is activated for a predetermined set time, the water level is set to the upper limit water level. Since the pump is operated even before the liquid tank reaches the water level, there is no risk that the water in the liquid tank will remain at the intermediate water level for a long time, causing the water to rot and emit a bad odor, and the environment around the liquid tank can be protected.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention. Figure 1 is a sectional view of a liquid tank in which a submersible pump is installed, and Figures 2 and 3 are state diagrams of the control circuit at the upper and lower water levels, respectively. , FIG. 4 is a state diagram of the control circuit when the timer operates at an intermediate water level. FIG. 5 is a state diagram corresponding to FIG. 2 of a control circuit employing a conventional water level control method. In the figure, 10 is a liquid tank, 12 is a submersible pump, 12a is an electric motor,
14 is a float switch for detecting the upper limit water level, 14a is the upper limit contact, 15 is a float switch for detecting the lower limit water level, 15a
17 is a control circuit, 19 is a relay, and 20 is a timer.

Claims (1)

[Claims] When the water level rises to the upper limit water level, the pump is operated; when the water level decreases to the lower limit water level, the pump is stopped and a timer is started; and when the water level is between the upper limit water level and the lower limit water level, the timer operates according to a predetermined value. A pump operation control method characterized in that the pump is operated when a set time has elapsed.