KR20050064922A - A device for detecting water level of ink in ink supplying device for printer - Google Patents

Abstract

The present invention relates to a water level sensing device for an ink supply system of a printer, wherein a level sensing unit having a water level detecting terminal is installed in an ink reservoir in which ink is stored, and a sensing signal is output from each control unit through each terminal of the level sensing unit. It is configured to determine the level, so that the ink level can be accurately detected. Therefore, according to the present invention, since the valve operates only at exactly the required time point in the ink supply system, unnecessary operation is eliminated and the number of on / off operations is reduced, thereby preventing frequent operation of the valve, thereby reducing noise. This makes it possible to extend the life of the valve, reduce power consumption and maintain a stable output.

Description

A water level detection device for an ink supply system of a printer {A device for detecting water level of ink in ink supplying device for printer}

The present invention relates to a level sensor for an ink supply system of a printer, and more particularly, to a level sensor for an ink supply system of a printer capable of accurately detecting the level of ink stored in a predetermined storage location in the ink supply system. It is about.

In general, a printer is a device for outputting computer-generated data on an output paper, and there are various types of printing output methods, but a laser printer for printing data on paper using a laser beam and toner / drum, and a nozzle Inkjet printers for directly injecting ink onto paper sheets are widely used.

In recent years, due to the widespread use of large-scale due diligence, wide color, banners, etc., there is a growing demand for large inkjet printers such as plotters in order to output them, and such large inkjet printers are becoming larger.

In addition, such a large-size inkjet printer, it is common to embody the color of the output in a color of 2 degrees or more in order to attract people's eyes when printing.

Therefore, in the large-size inkjet printer, as shown in FIG. 1, a plurality of ink cartridges 2 storing ink for each color to supply ink to one side of the printer main body 1 to the print head are provided in the cartridge case 3. ), The ink cartridges 2 are detachable individually.

Each ink cartridge 2 has a storage pack filled with ink therein, a rectangular box-type case for protecting the storage pack, and is attached to one side of the storage pack to touch a separate sensing switch when ink is consumed. It consists of a working plate to notify the replacement time of the cartridge.

This ink cartridge 2 is a single use, and when the ink filled in the storage pack is consumed, it should be separated from the printer and replaced with a new cartridge.

By the way, when the ink cartridge 2 is replaced every time, wasteful wasteful and uneconomical, even if ink is consumed in any one of the ink cartridge (2) during printing, all the operation of the print is stopped, it takes a lot of work time.

In particular, when a new ink cartridge 2 is replaced during the printing of a large-scale print, the work is stopped and serious defects are generated in the printed output, which in turn causes considerable financial damage as well as the inconvenience of reprinting.

As another conventional example to solve this disadvantage, Korean Patent No. 10-0387551 has been proposed, such Patent No. 10-0387551 as shown in Figures 2 and 3 (a) and (b) , An ink cartridge 30, an ink refill tank 40, and a solenoid valve 50.

The ink cartridge 30 is installed inside the case 31 provided in a rectangular box shape, and the ink is filled therein, and the ink discharge port 32 and the ink inlet 33 are integrally formed at the front and rear ends thereof, respectively. The storage pack 34, the operation plate 60 installed on one side of the lower side of the case 31 and integrally formed on one surface of the storage pack 34, and the operation plate as ink is replenished in the storage pack 34. When the 60 moves, it includes a limit switch 70 that is on / off operation in accordance with the movement of the operation plate (60).

The ink replenishment tank 40 has a supply tube 41 connected to the ink inlet 33 of the storage pack 34, stores a predetermined amount of ink therein, and the storage pack (through the supply tube 41). 34) is disposed at a position relatively higher than the ink cartridge 30 so as to continuously replenish the ink by the natural dropping method.

The solenoid valve 50 is provided in the supply tube 41 to open and close the supply tube 41 by the limit switch 70.

That is, the above patent 10-0387551 further includes an ink refill tank 40, a supply tube 41, and a solenoid valve 50 to transfer the ink of the ink refill tank 40 to the ink cartridge 30. By replenishing, the trouble of replacing the ink cartridge 30 was eliminated and ink was consumed during the print job so that the job was not interrupted.

By the way, in the manner of employing the refill ink tank as described above, the solenoid valve is opened as the ink is consumed in the storage pack in the ink cartridge and the operating plate contacts the limit switch, so that the ink in the ink refill tank is supplied to the ink cartridge. Even if the storage pack expands slightly due to the supply of ink, the solenoid valve is closed by releasing the contact between the operating plate and the limit switch, and the solenoid valve is opened while the operating plate contacts the limit switch again even when a small amount of ink is consumed.

In other words, it is not a method of controlling the valve by accurately detecting the level of ink, but simply controlling the valve according to the contact between the operation plate and the limit switch. The operation plate is limited during a print job in which ink of the ink cartridge is continuously consumed. The gap between contact and release of the switch is narrow, so the solenoid valve opens and closes very frequently.

As the solenoid valve is frequently opened and closed in this way, intermittent sound is periodically generated due to the opening and closing of the valve, causing discomfort to the user, shortening the service life of the solenoid valve, and increasing power consumption. There is a need for the development of a water level detection device capable of accurately detecting the ink level of a cartridge.

In addition, the conventional technique as described above has a problem in that the remaining amount of ink is detected by the operation plate of the mechanical mechanism, and there is a problem that low precision and frequent malfunctions occur. Therefore, the precision mechanism is high and the malfunction is eliminated. There is a demand for the development of a level sensor which does not occur.

Accordingly, the present invention has been made in order to meet the demand of the above-described technology development, the ink supply system can accurately detect the ink level of the ink storage location, more precise and malfunction does not occur for the ink supply system of the printer The purpose is to provide a water level sensing device.

The water level sensing device for an ink supply system of a printer according to the present invention for achieving the above object is a water level sensing unit having a plurality of detection terminals are inserted and installed in the place where the ink is stored in the ink supply system and the height difference; And a control unit for sensing the ink level through each detection terminal of the level detection unit and outputting a result signal according to the detected ink level.

In addition, the present invention, the plurality of detection terminals of the water level detection unit, the lower end is arranged to be located at a predetermined low water level detection height, and the low point detection signal input terminal for inputting the detection start signal input via the ink to the controller; A high point detection signal input terminal for inputting a detection start signal inputted through ink to the controller, the lower end of which is disposed at a preset high point detection height, the low point detection signal input terminal and the high point detection signal; The input terminal is a signal output terminal which is arranged to be in electrical contact with each other when the ink is in contact with the ink, and outputs a detection start signal applied from the control unit.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a configuration diagram illustrating an ink supply apparatus of a printer to which the present invention is applied. As can be seen from the same view, the ink supply apparatus of the printer to which the present invention is applied includes an ink cartridge 110 and an ink refill container 120. ), The valve 130, the water level detecting unit 140, the control unit 150, and the alarm generating unit 160 may be configured.

The ink cartridge 110 includes a main body 111 filled with ink therein, an ink discharge port 112 and an ink inlet 113 formed on the left side and the upper side of the main body 111, respectively.

The ink refill container 120 is disposed at a relatively higher position than the ink cartridge 110 to supply ink by a natural dropping method, and there is ink stored therein, and a lid 121 at an upper portion thereof and a lower portion thereof. The connection pipe 122 connected to the ink inlet 113 of the ink cartridge 110 is provided.

The valve 130 is installed in the connection pipe 122 to open and close the connection pipe 122 by turning on / off (ON / OFF) according to the control signal of the controller 150, such a valve 130 As long as it can operate in accordance with a control signal, any kind of material developed to date can be used, for example, a solenoid type solenoid valve can be used.

The water level detecting unit 140 is inserted into and fixed to the ink cartridge 110 through an upper surface of the main body 111 of the ink cartridge 110, and as illustrated in FIG. 5, a plurality of detection terminals. (141-143) is provided.

These detection terminals 141 to 143 are lead type terminals formed by processing a long conductor, and the double terminals 141 are positioned at a low set level Hb at the lower end of the low level detection height. Arranged and output through the signal output terminal 143 below from the control unit 150 is a low point detection signal input terminal for inputting the sensing signal input via the ink to the control unit 150, the terminal 142 has a lower end The control unit 150 is disposed to be located at a high setting level Ht, which is a high water level detection height, and is output from the control unit 150 through the signal output terminal 143 to be input via ink. It is a signal input terminal for high point detection.

In addition, the terminal 143 is disposed to contact the ink together when the low point detection signal input terminal 141 and the high point detection signal input terminal 142 contact ink, respectively, and receive a detection signal from the controller 150. Output signal output terminal.

In addition, the water level detection unit 140, each terminal (141 ~ 143) is fixed to the conductive pattern (not shown) of the connection portion 146 on the printed circuit board 144, respectively, It is configured to be connected to the control unit 150 through a signal cable 145 connected to 144.

The control unit 150 outputs a detection signal to the signal output terminal 143 and checks whether the detection signal is input through the low point detection and high point detection signal input terminals 141 and 142 of the water level detection unit 140. By detecting the water level in the ink cartridge 110, and generates a control signal for operating the valve 130 on / off (ON / OFF) according to the detected water level.

Here, the controller intermittently outputs the detection signal to the signal output terminal 143 of the water level detection unit 140 according to a setting cycle.

In addition, the controller 150 counts the time during the on-operation of the valve 130 and outputs a control signal to generate an alarm indicating an ink shortage when the counted time exceeds the set time limit TL.

In addition, the controller 150 further includes an alarm reset switch 151 and a valve blocking switch 152. When an ON signal is input from the alarm reset switch 151 at the time of an alarm, the controller 150 stops generating an alarm. When the ON signal is input from the cutoff switch 152, the ink supply is stopped for the set time.

As the alarm reset switch 151 and the valve blocking switch 152, a push button type switch in which an ON signal is generated only while the user presses the button is used.

Here, the controller 150 may be configured to control only a single ink cartridge, but may also be configured to control all of the plurality of ink cartridges for each color. In this way, the control method when controlling the plurality of ink cartridges, Same as when controlling a single ink cartridge, but applied individually to each ink cartridge.

The alarm generating unit 160 generates an alarm according to a control signal output from the control unit 150. For example, the alarm generating unit 160 may be configured to flash a lamp indicating an ink shortage or output a warning sound. have.

An operation example of the present invention configured as described above will now be described with reference to the accompanying drawings.

First, the controller 150 outputs detection signals to the signal output terminal 143 of the water level detection unit 140. At this time, the output detection signals are intermittently generated according to a setting cycle, and the waveforms represent pulse shapes. do.

As such, the control unit 150 intermittently generates the detection signal in consideration of a special environment in which the detection target is ink, and at least one of the signal input terminals 141 and 142 of the water level detection unit 140 is applied to the ink. Continuously flowing current to the signal output terminal 143 while in contact may cause electrolysis, which may adversely affect the quality of the ink. In order to prevent this, the signal is set to flow only for a very short time. will be.

The controller 150 checks a signal input through the low point detection and high point detection signal input terminals 141 and 142 of the water level detection unit 140, and the signal input terminals 141 and 142 for low point detection and high point detection. When no detection signal is input, the low point detection and high point detection signal input terminals 141 and 142 do not come into contact with ink, and the ink in the ink cartridge 110 has a low point detection signal input terminal ( 141) Since it is lower than the lower height, that is, the low set water level Hb (S20), a control signal for turning ON the valve 130 is generated.

In response to a control signal generated from the controller 150, the valve 130 is turned on to open the connection pipe 122, whereby the ink of the ink refilling container 120 is naturally dropped in the connection pipe 122. It is supplied to the inside of the ink cartridge 110 through.

If the detection signal output through the signal output terminal 143 is input to both the low point detection and high point detection signal input terminals 141 and 142, the signal point input terminals 141 and 142 for low point detection and high point detection. Are all in contact with the ink, and since the ink in the ink cartridge 110 is higher than the lower height of the high point detection signal input terminal 141, that is, the high point set water level Ht, the valve 130 is turned off. Generates a control signal for operation.

In response to a control signal generated from the controller 150, the valve 130 is turned off to close the connection pipe 122, thereby stopping the ink supply to the ink cartridge 110.

Here, the valve 130 operates ON / OFF according to the low set water level Hb and the fixed set water level Ht detected by the water level detecting unit 140, and operates only at a precisely necessary time point. Therefore, unnecessary operation is eliminated and the number of on / off operations is reduced.

Meanwhile, the water level detection unit 140 shown in FIG. 5 may be manufactured in various forms by designing different arrangements and shapes of the conductor pattern of the connection unit 146 and the printed circuit board 144. A number of preferred embodiments will be described, and hereinafter, additional symbols are given.

First, as shown in FIG. 6, the water level detection unit 210 of the first embodiment has a low input signal input terminal for detecting a low point on a plurality of conductor patterns 212 to 214 formed on the lower surface of the printed circuit board 211. 215, the high point detection signal input terminal 216 and the signal output terminal 217 are connected to each other and fixed by soldering 212a to 214a.

In this case, the plurality of conductor patterns 212 to 214 are formed to have a height difference with each other, which is a distance between the conductor patterns 212 to 214, so that the ink is agglomerated between the respective conductor patterns 212 to 214. To prevent it.

That is, the ink cartridge 110 is filled with ink so that a part of the printed circuit board 211 of the water level sensing unit 210 is immersed in ink, and then the ink of the ink cartridge 110 is exhausted so that the printed circuit board 211 is ink. Part of the ink remains on the surface of the printed circuit board 211 even if it is not immersed in the ink. When the distance between the conductor patterns 212 to 214 is close, the ink is agglomerated between the conductor patterns 212 to 214. It may be shorted by the moisture of the ink.

As such, when the conductor patterns 212 to 214 are shorted together, the controller 150 cannot properly detect the ink level, thereby blocking the possibility of short circuit by making the distance between the conductor patterns 212 to 214 far.

Next, as shown in FIG. 7, the water level sensing unit 220 according to the second embodiment has a low point sensing signal input terminal on a plurality of conductor patterns 222 to 224 formed on the lower surface of the printed circuit board 221. 225, the high point detection signal input terminal 226 and the signal output terminal 227 are connected to each other and fixed with solder 222a to 224a.

At this time, the lower end of the printed circuit board 221 is located between the low point detection signal input terminal 225 and the signal output terminal 227, and between the signal output terminal 227 and the high point detection signal input terminal 226. Grooves 228 and 229 are formed in corresponding portions, respectively, in which the ink is agglomerated between the terminals 225 to 227 with a distance and a space between the terminals 225 to 227 on the printed circuit board 221. To prevent this from happening.

That is, the ink cartridge 110 is filled with ink so that a part of the printed circuit board 221 of the water level sensing unit 220 is immersed in ink, and then the ink of the ink cartridge 110 is exhausted so that the printed circuit board 221 is ink. Even if it is not immersed in the ink, some moisture of the ink remains on the surface of the printed circuit board 221. When the distance between the terminals 225 to 227 is close, the ink is agglomerated between the terminals 225 to 227. Can be shorted.

As such, when the terminals 225 to 227 are shorted together, the controller 150 may not properly detect the ink level. Thus, a distance and a space between the terminals 225 to 227 may not be sufficient to shorten the possibility of a short circuit due to ink moisture. To block.

Next, as shown in FIG. 8, the water level detecting unit 230 of the third embodiment has a signal input terminal for low point sensing on the plurality of conductor patterns 232 to 234 formed on the lower surface of the printed circuit board 231. 235, the high point detection signal input terminal 236 and the signal output terminal 237 are connected to each other and fixed by soldering 232a to 234a.

At this time, a lower end of the printed circuit board 231 is disposed between the low point detection signal input terminal 235 and the signal output terminal 237, and between the signal output terminal 237 and the high point detection signal input terminal 236. Grooves 238 and 239 are formed in corresponding portions, respectively, in which the ink is agglomerated between the terminals 235 to 237 with a distance and a space between the terminals 235 to 237 on the printed circuit board 231. To prevent this from happening.

In addition, the plurality of conductor patterns 232 to 234 are formed to have a height difference with each other, which prevents ink from agglomerating between the conductor patterns 232 to 234 by providing a distance and a space between the conductor patterns 232 to 234. Is intended.

That is, the ink cartridge 110 is filled with ink so that a part of the printed circuit board 231 of the water level sensing unit 230 is immersed in ink, and then the ink of the ink cartridge 130 is exhausted so that the printed circuit board 231 is ink. Even if it is not immersed in, some moisture of the ink remains on the surface of the printed circuit board 231, when the distance between the terminals 235 to 237 is close, and the distance between the conductor patterns 232 to 234 is close. In this case, ink may be agglomerated and short-circuited between the terminals 235 to 237 and between the conductive patterns 232 to 234.

As such, when the terminals 235 to 237 or the conductor patterns 232 to 234 are short-circuited, the controller 150 cannot properly detect the ink level, and thus the resistance value between the terminals 235 to 237 may be reduced. The distance and space between the conductor patterns 232 to 234 may be used to block the possibility of short circuit caused by ink moisture.

Next, as shown in FIG. 9, the water level detection unit 240 of the fourth embodiment has a low input signal input terminal for detecting a low point on a plurality of conductor patterns 242 to 244 formed on the lower surface of the printed circuit board 241. 245, the signal input terminal 246 for high point detection, and the signal output terminal 247 are connected, respectively, and are fixed by soldering 242a-244a.

At this time, a groove 248 is formed at the lower end of the printed circuit board 241, and the conductive patterns 242 to 244 are disposed on the left side, the right side, and the upper side between the grooves 248, which is printed. This is to prevent the ink from agglomerating by placing a distance between the terminals 245 to 247 and a distance and a space between the conductor patterns 242 to 244 on the circuit board 241.

That is, the ink cartridge 110 is filled with ink so that a part of the printed circuit board 241 of the water level sensing unit 240 is immersed in ink, and then the ink of the ink cartridge 130 is exhausted so that the printed circuit board 241 is ink. Even if it is not immersed in the ink, some moisture of the ink remains on the surface of the printed circuit board 241. When the distance between the terminals 245 to 247 is close, the distance between the conductor patterns 242 to 244 is close. In this case, ink may be agglomerated and short-circuited between the terminals 245 to 247 and between the conductive patterns 242 to 244.

As such, when the terminals 245 to 247 or the conductor patterns 242 to 244 are short-circuited, the controller 150 cannot properly detect the ink level, and thus the resistance value between the terminals 245 to 247 may be reduced. The distance, space and height difference between the conductor patterns 242 to 244 prevent the possibility of short circuit due to ink aggregation.

On the other hand, in the above-described embodiment shown in Figs. 5 to 9, the case where the lead type terminal of the water level sensing unit is fixed by soldering to the conductor pattern of the printed circuit board has been described as an example. As shown in FIG. 10, the water level detecting unit is configured to use a conductor pattern formed on a printed circuit board as a detection terminal without using a separate lead-type terminal.

That is, the water level detection unit 250 according to the fifth embodiment of the present invention forms a plurality of conductor patterns 252 to 254 on the printed circuit board 251 in the vertical direction, and the conductor patterns (between them). 252 is used as a signal output terminal, the upper conductor pattern 253 is used as a high point detection signal input terminal, and the lower conductor pattern 254 is used as a low point detection signal input terminal.

However, the water level detecting unit 250 according to the fifth embodiment uses a conductor pattern instead of a lead as a detection terminal, so that when ink remains on the surface of the printed circuit board 251, each pattern is short-circuited and the water level is short. It becomes difficult to detect. Therefore, in the state where the printed circuit board 251 is not immersed in ink, the surface of the printed circuit board 251 is subjected to a surface treatment for enhancing watertightness or a material having high watertightness is used for the surface layer of the printed circuit board 251. It is preferable that the moisture of the ink remains on the surface of the printed circuit board 251 so that the ink does not aggregate between the patterns 252 to 254.

In still another embodiment, the conductor pattern may be formed by being disposed in the vertical, left, and right directions in addition to the vertical direction.

The present invention is described above by illustrating specific embodiments, but the present invention is not limited to the above embodiments. Those skilled in the art can easily make various changes and modifications to the present invention, and it should be noted that such variations or modifications are included within the scope of the present invention as long as the features of the present invention are used.

Particularly, in the above-described embodiment of the present invention, the case where the water level sensing unit is installed inside the ink cartridge has been described as an example, but this is only one possible example, and the water level sensing unit of the present invention is an ink level such as an ink refill container in addition to the ink cartridge. It can be installed wherever it needs to be detected.

In addition, in the above-described embodiment of the present invention, the control unit has been described as an example of only the case of controlling the on / off valve according to the ink level detected through the water level detection unit, which is the result of the control unit detects the ink level through the water level detection unit As an example of the output according to the control unit, the controller outputs the ink level to another controller according to the detected ink level, a signal for indicating the ink level, a signal for generating an alarm, a signal for printing the ink level, and the like. It can be set to output various result signals.

As described above, the present invention is configured to determine the level of ink by installing a level detecting unit having a level detecting terminal in an ink reservoir in which ink is stored and outputting a detection signal from each control unit through each terminal of the level detecting unit. The ink level can be detected accurately.

Therefore, according to the present invention, since the valve operates only at exactly the required time point in the ink supply system, unnecessary operation is eliminated and the number of on / off operations is reduced, thereby preventing frequent operation of the valve, thereby reducing noise. This makes it possible to extend the life of the valve, reduce the power consumption, and eliminate the mechanical mechanism in detecting the ink level, so that there is an effect of high accuracy and prevention of malfunction.

In addition, when using the present invention, since the operating plate is not used, there is no need to use an ink storage pack therein, so that there is no durability problem by using the storage pack in the ink cartridge as in the prior art, and the configuration of the ink cartridge is simplified. It is easy to replace, low replacement cost, and the cartridge body can be composed of a transparent material or a transparent window can be installed, it is easy to see the deposits and foreign matter inside the ink cartridge with the naked eye. In particular, since the correct water level can be maintained, the ink discharge can be stabilized and the print quality can be improved.

1 is a perspective view showing the back of a conventional general inkjet printer,

2 is a cross-sectional view showing another conventional ink supply apparatus;

(A) and (b) of Figure 3 is a view showing the operating state of the storage pack, the operation plate and the limit switch inside the ink cartridge shown in Figure 2,

4 is a configuration diagram illustrating an ink supply apparatus of a printer to which the present invention is applied;

5 is an enlarged view of the water level detecting unit of the present invention shown in FIG. 4;

6 is a view showing a first embodiment of the water level detecting unit shown in FIG. 5;

7 is a view showing a second embodiment of the water level detecting unit shown in FIG. 5;

8 is a view showing a third embodiment of the water level detecting unit shown in FIG. 5;

9 is a view showing a fourth embodiment of the water level detection unit shown in FIG. 5;

10 is a view showing a water level detection unit according to a fifth embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

110: ink cartridge 120: ink replacement

122: connector 130: valve

140: water level detection unit 141: signal input terminal for low point detection

142: signal input terminal for high point detection 143: signal output terminal

150: control unit 151: alarm reset switch

152: valve blocking switch 160: alarm generating unit

Claims (11)

In the ink supply system of the printer, A water level sensing unit having a plurality of detecting terminals having a height difference and inserted in a place where ink is stored in the ink supply system; And a control unit which detects the ink level through each detection terminal of the level detection unit and outputs a result signal according to the detected ink level. The method of claim 1, wherein the plurality of detection terminals of the water level detection unit, A low point detection signal input terminal arranged to have a lower end at a predetermined low point detection height and inputting a detection start signal inputted through ink to the controller; A high point detection signal input terminal arranged to have a lower end positioned at a preset high point detection height and inputting a detection start signal inputted through ink to the controller; And a signal output terminal arranged to be electrically connected to the ink when the low point detection signal input terminal and the high point detection signal input terminal are in contact with ink, respectively, and output a detection start signal applied from the controller. Ink supply apparatus of the printer, characterized in that. The water level detecting unit of claim 2, A plurality of detection terminal connection patterns are formed and include a printed circuit board connected to the control unit through a signal line, And a plurality of detection terminals are fixedly connected to a plurality of conductor patterns on the printed circuit board, respectively. 4. The water level sensing apparatus for an ink supply system of a printer according to claim 3, wherein the plurality of conductor patterns are formed so as to have a height difference with each other. 4. The water level sensing apparatus for an ink supply system according to claim 3, wherein a groove is formed at a lower end of the printed circuit board at a portion between the detection terminal and the detection terminal. The method of claim 3, wherein the plurality of conductor patterns are arranged to have a height difference with each other, And a groove is formed at a lower portion of the printed circuit board at a portion between the detection terminal and the detection terminal. 4. The water level sensing apparatus for an ink supply system according to claim 3, wherein a groove is formed in a lower end of the printed circuit board, and the groove is formed by arranging a conductor pattern on the left side, the right side, or the upper side. 8. The water level sensing device for an ink supply system according to any one of claims 3 to 7, wherein each terminal is a lead type terminal formed by processing a conductor long. The water level sensing device for an ink supply system according to claim 1 or 2, wherein the plurality of detection terminals of the water level sensing unit are conductor pattern type terminals formed on a printed circuit board. The water level sensing apparatus for an ink supply system of claim 1, wherein the result signal generated from the control unit is a signal for controlling on / off of a valve for ink supply. 3. The water level sensing apparatus for an ink supply system according to claim 2, wherein the detection start signal output from the control unit to the signal output terminal of the water level sensing unit is intermittently generated at every setting cycle.