Apparatus for indicating level of liquid in tank

Abstract: An apparatus for indicating information concerning the level of a liquid (41) contained in a tank (42) includes a tank (42), at least one exhaust pipe (51-53) having a transparent portion (51c-53c), a light source (51-63) for emitting light to the transparent portion (51c-53c) of each of the exhaust pipes (51-53), a photodetector (71-73) for detecting light reflected by or transmitted through the transparent portion (51c-53c) of each of the exhaust pipes (51-53) and outputting electric signals corresponding to the detected light, and a liquid level measuring portion (80) for indicating information concerning the level of liquid (41) contained in the tank (42) from the electric signals output from the photodetector (71-73). The transparent portion (51c-53c) of the exhaust pipe (51-53) is formed at least as a part thereof, the exhaust pipe (51-53) having a first end (51a-51c) thereof installed to be connected to the tank (42) and a second end (51c-53c), horizontally displaced from the first end (51a-53a) and connected to a set supply path (54) and/or the tank (42) so that liquid (41) can be collected. The exhaust pipe (51-53) is installed at a predetermined height vertically from a bottom surface (42a) of the tank (42) to obtain information on the level of liquid (41) contained in the tank (42). Thus, developer can be prevented from adhering to the transparent portion (51c-53c) of the exhaust pipe (51-53) installed at the tank (42) at a height to be indicated so that an error in measuring the level of liquid (42) can be reduced.

Description: The present invention relates to an apparatus for indicating the level of a liquid in a tank adopted in a liquid electrophotographic printer, and more particularly, to an apparatus for indicating the level of a liquid in a tank adopted in a liquid electrophotographic printer so that an error in measuring the level of a liquid due to solidification of developer can be reduced. In general, liquid level detectors for detecting the liquid level inside a tank are known from JP-A-60 169 720 or DE-A-33 08 695. An apparatus for indicating the level of a liquid contained in a tank is adopted in a liquid electrophotographic printer such as a laser printer or a copier using developer to provide information about the amount of developer remaining in the tank. The liquid electrophotographic printer informs a user to add developer at an appropriate time by displaying a message requesting refilling of developer using information on the amount of remaining developer provided by the liquid level indicating apparatus. Thus, by requesting a supply of developer appropriately by means of the liquid level indicating apparatus, an incomplete print process or interruption of a print task during printing due to a lack of developer can be avoided. Figure 1 shows the structure of a general liquid electrophotographic printer. Referring to the drawing, a printer using developer includes a plurality of rollers 11, 12 and 13, a photoreceptor web 14, a reset unit 15, four laser scanning units 16, four development units 30, a drying unit 18, and a transfer unit 20. The reset unit 15 includes an exposure unit 15a for emitting light to the photoreceptor web 14 to remove an electrostatic latent image and a charging unit 15b for charging the photoreceptor web 14 to a predetermined electric potential. Reference numeral 39 denotes a waste developer collection tank. The four laser scanning units 16 scan information of yellow (Y), magenta (M), cyan (C) and black (B) colors. The four development units 30 supply developer of yellow (Y), magenta (M), cyan (C) and black (B) colors. The development unit 30 includes a developer supply tank 32 for supplying developer to the photoreceptor web 14 and a development tank 31 for collecting developer falling from the photoreceptor web 14. The development tank 31 includes a development roller 36, a brush roller 37 for removing developer adhering to the development roller 36, a squeegee roller 34 for separating a liquid carrier component of the developer supplied to the photoreceptor web 14 which is not used for image formation, and a plate 35 for collecting the carrier component flowing along the outer circumferential surface of the squeegee roller 34 into the development tank 31. The developer supply tank 32 is provided with a liquid carrier component, norpar (N), which is a solvent, and toner which is a development substance, or highly concentrated developer from a developer supply portion 38 and is provided with the developer from the development tank 31. The developer contained in the developer supply tank 32 is supplied between the development roller 36 and the photoreceptor web 14 by a pump P. In the printing process of the liquid electrophotographic printer having the above structure, the laser scanning unit 16 scans light to a predetermined area of the photoreceptor web 14 circulating past the reset unit 15. An electrostatic latent image is formed on the photoreceptor web 14 by the scanned light and the electrostatic latent image is developed by developer supplied from the developer supply tank 32 of the development unit 30. A color image is formed on the photoreceptor web 14 by the laser scanning units 16 for scanning light of different color information and the development units 30 for performing development with developer of a corresponding color. Most of the liquid carrier component that is not used for image development of the developer supplied to the photoreceptor web 14 from the development unit 30 during development is collected in the development tank 31. As the photoreceptor web 14 continues to rotate, the color image formed on the photoreceptor web 14 with toner which is a development substance is first transferred to a transfer roller 21 rotating in engagement with the photoreceptor web 14, passing the drying unit 18 for absorbing and removing the liquid carrier component remaining on the photoreceptor web 14. Subsequently, the image on the transfer roller 21 is transferred to a sheet of paper 23 by the rotation of the transfer roller 21 and the fixation roller 22 which rotate in engagement with each other interposing the paper 23 inserted and make the paper 23 proceed. There is a known conventional apparatus for indicating the level of developer contained in the developer supply tank 32 by detecting the change in the amount of transmitted or reflected light with respect to the developer supply tank 32. The liquid level indicating apparatus includes a light source (not shown) for emitting light at the height corresponding to the level of liquid to be measured with respect to the developer supply tank 32, and a photodetector (not shown) for detecting light transmitted or reflected light in a direction which is the same as or opposite to the light projecting direction with respect to the developer supply tank 32. The developer supply tank 32 is made of a material such as plastic in order to prevent easy breakage. However, most developer supply tanks made of plastic have a strong affinity to the developer. As a result, an error occurs in the measurement of the level of liquid due to developer adhering to an inner wall of the plastic developer supply tank giving false readings. As another example of liquid level measuring apparatus, there is known a float (not shown) installed in a tank and a sensor (not shown) for detecting the positional displacement of the float. For example, a permanent magnet is built-in the float and a Hall sensor responding to a magnetic force is adopted. In such a liquid level measuring apparatus, a movement channel having a width which is slightly greater than the outer diameter of the float is vertically positioned in the tank to minimize any horizontal positional displacement of the float as the float follows its vertical movement path. However, in this case, the width of the movement channel of the float can become reduced so as to be less than the outer diameter of the float due to developer fluid fixedly adhering to the interior of the channel so that errors can occur in measuring the level of liquid. Also, the float must be manufactured according to the specific gravity of the developer subject to the test, which is inconvenient. Meanwhile, there is another conventional method of measuring the level of liquid by installing two electrode plates (not shown) in a tank and detecting the change in electrostatic capacitance measured by the electrode plates corresponding to the change in the level of the developer. However, in this method, when the developer fixedly adheres to the electrode plate, an error can occur in measuring the level of liquid. With a view to solve or reduce the above problems, it is an aim of embodiments of the present invention to provide an apparatus for indicating information concerning the level of liquid contained in a tank which can reduce the problems of developer adhering to positions where the level of liquid is to be measured so that an error in indicating level can be reduced. According to a first aspect of the present invention, there is provided an apparatus for indicating information concerning the level of liquid contained in a tank comprising: a tank; at least one exhaust pipe including a transparent portion in at least a part thereof, having a first end thereof connected to the tank and a second end, said second end being horizontally displaced from said first end and, connected to a supply path and/or the tank so that liquid can be collected, said exhaust pipe being installed at a predetermined height vertically from a bottom surface of the tank; a light source for emitting light to the transparent portion of the at least one exhaust pipe; a photodetector for detecting light reflected by or transmitted through the transparent portion of the exhaust pipe and outputting electric signals corresponding to the detected light; and a liquid level measuring portion for indicating information concerning the level of liquid contained in the tank from the electric signals output from the photodetector. Preferably, the transparent portion is a glass pipe. Preferably, the second end of the exhaust pipe is connected to a developer supply pipe through which developer fluid contained in the tank can be supplied to a photoreceptor medium. Preferably, there are provided first to third exhaust pipes the first exhaust pipe being installed at a first predetermined height from the bottom surface of the tank to provide information concerning a "low level" of liquid, the second exhaust pipe being installed at a height higher than that of the first exhaust pipe to provide information concerning a "medium level" of liquid, and the third exhaust pipe being installed at a height higher than that of the second exhaust pipe to provide information concerning a "full level" of liquid. Preferably, the second end of the first exhaust pipe is connected to a developer supply pipe through which developer fluid contained in the tank can be supplied to a photoreceptor medium. Preferably, the second ends of the second and third exhaust pipes are connected to a developer supply pipe. Preferably, the second ends of the first, second and third exhaust pipes are connected to one another. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1 is a view showing the structure of a general liquid electrophotographic printer; and Figure 2 is a sectional view showing a part of a liquid electrophotographic printer adopting an apparatus for indicating information concerning the level of liquid in a tank according to the present invention. In the description below, elements having the same functions as those described in Figure 1 are labeled with the same reference numerals. Referring to Figure 2, a first exhaust pipe 51, a second exhaust pipe 52 and a third exhaust pipe 53 are sequentially installed horizontally (direction X) on a side surface of a developer supply tank 42 at predetermined vertical intervals (direction Y) from a bottom surface 42a of the developer supply tank 42. First end portions 51a, 52a and 53a of the first, second and third exhaust pipes 51, 52 and 53, respectively, are connected to the developer supply tank 42 and second end portions 51b, 52b and 53b thereof are connected to a developer supply pipe 54. The first, second and third exhaust pipes 51, 52 and 53 are provided with transparent portions 51c, 52c and 53c, respectively, a part of or the entire part of which is formed of a transparent material, preferably, a glass tube exhibiting the features of having a low affinity to the developer 41 and making the developer 41 being easily separated therefrom as liquid flows. A pump 55 is for supplying the developer 41 in the developer supply tank 42 to the photoreceptor web 14 which is a photoreceptor medium. When the other end portions 51b, 52b and 53b of the first, second and third exhaust pipes 51, 52 and 53 are connected to the developer supply pipe 54 as described above, the developer 41 is exhausted toward the developer supply pipe 54 through the first, second and third exhaust pipes 51, 52 or 53 located below the level of the developer 41 contained in the developer supply tank 42 by being driven by the pump 55 during printing. Thus, it is advantageous that the developer 41 does not easily adhere to the transparent portions 51c, 52c and 53c. The positions of the first, second and third exhaust pipes 51, 52 or 53 from the bottom surface 42a of the developer supply tank 42 are appropriately determined according to the level of the developer 41 to be checked. In the case in which only an empty state, a supplement requiring state and a full state according to the amount of developer 41 remaining are needed, as shown in the drawing, the first, second and third exhaust pipes 51, 52 or 53 are installed at the set heights for a low level, a mid level and a full level. The transparent portions 51c, 52c and 53c of the first, second and third exhaust pipes 51, 52 or 53 are respectively provided with light sources 61, 62 and 63 and photodetectors 71, 72 and 73 for receiving light rays emitted from the light sources 61, 62 and 63 and passing the transparent portions 51c, 52c and 53c. The photodetectors 71, 72 and 73 may be installed so as to be capable of receiving light rays emitted from the light sources 61, 62 and 63 and reflected by the transparent portions 51c, 52c and 53c. The photodetectors 71-73 may be installed on opposing sides of the transparent portions 51c-63c so as to face the light sources 61-63, or they may be installed on the same side of the transparent portions 51c-53c as the light sources 61-63. A liquid level measuring portion 80 receives electric signal levels output from the respective photodetectors 71, 72 and 73 installed to face the transparent portions 51c, 52c and 53c of the first, second and third exhaust pipes 51, 52 or 53 and compares the received electric signal levels with data, obtained through experiments for the cases in which the transparent portions 51c, 52c and 53c are full, partially filled and completely empty, and recorded therein, so that the level of the developer 41 can be measured. In the process of measuring the level of liquid by the liquid level measuring apparatus having the above structure, first, the liquid level measuring portion 80 controls a valve 33 provided on an exhaust pipe between the development tank 31 and the developer supply tank 42 to open periodically or at an appropriate time to restrict the developer 41 from adhering to the first, second and third exhaust pipes 51, 52 or 53. Then, the liquid level measuring portion 80 drives the pump 55 so that the developer 41 in the developer supply tank 42 is preferably circulated to be collected after passing the developer supply pipe 54 and the development tank 31. Here, as an example of driving the pump 55 at an appropriate time, the pump 55 is driven for a predetermined time when, in a print ready state in which a print job is not performed, the level of developer 41 contained in the developer supply tank 42 is maintained as high as one of the first, second and third exhaust pipes 51, 52 or 53 and a corresponding signal is input from the photodetector 71, 72 or 73. When the developer 41 is circulated in a print ready state, the developer 41 can be prevented from adhering to the transparent portions 51c, 52c and 53c of the first, second or third exhaust pipe 51, 52 or 53. Also, the level of the developer 41 containing in the developer supply tank 42 can be measured from signals output from the photodetectors 71, 72 and 73 during or after a developer circulating process. When an electric signal corresponding to a state in which the developer 41 in the developer supply tank 42 is below the first exhaust pipe 51 is input from the photodetector 71 installed at the first exhaust pipe 51, the liquid level measuring portion 80 controls the developer supply portion (38 of Figure 1) such that highly concentrated developer and/or a liquid carrier component can be supplied from the developer supply portion. The liquid level measuring apparatus as above can be adopted to any type of tank capable of containing liquid and supplying the contained liquid through a predetermined path. As described above, according to the apparatus for measuring a level of liquid in a tank according to the present invention, developer can be prevented from adhering to the transparent portion of the exhaust pipe installed at the tank at the height to be measured so that an error in measuring the level of liquid can be reduced. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s), but is defined by the appended claims.

Claims: An apparatus for indicating information concerning the level of liquid contained in a tank comprising: a tank (42); at least one exhaust pipe (51-53) including a transparent portion (51c-53c) in at least a part thereof, having a first end (51a-53a) thereof connected to the tank (42) and a second end (51b-53b), said second end being horizontally displaced from said first end (51a-53a) and, connected to a supply path (54) and/or the tank (42) so that liquid can be collected, said exhaust pipe (51-53) being installed at a predetermined height vertically from a bottom surface (42a) of the tank (42); a light source (61-63) for emitting light to the transparent portion (51c-53c) of the at least one exhaust pipe (51-53); a photodetector (71-73) for detecting light reflected by or transmitted through the transparent portion (51c-53c) of the exhaust pipe (51-53) and outputting electric signals corresponding to the detected light; and a liquid level measuring portion (80) for indicating information concerning the level of liquid contained in the tank (42) from the electric signals output from the photodetector (71-73). The apparatus as claimed in claim 1, wherein the transparent portion (51c-53c) is a glass pipe. The apparatus as claimed in claim 1 or 2, wherein the second end (51b-53b) of the exhaust pipe (51-53) is connected to a developer supply pipe (54) through which developer fluid (41) contained in the tank (42) can be supplied to a photoreceptor medium (14). The apparatus as claimed in claim 1, 2 or 3, wherein there are provided first to third exhaust pipes (51-53), the first exhaust pipe (51) being installed at a first predetermined height from the bottom surface (42a) of the tank (42) to provide information concerning a "low level" of liquid, the second exhaust pipe (52) being installed at a height higher than that of the first exhaust pipe (51) to provide information concerning a "medium level" of liquid, and the third exhaust pipe (53) being installed at a height higher than that of the second exhaust pipe (52) to provide information concerning a "full level" of liquid. The apparatus as claimed in claim 4, wherein the second end (51b) of the first exhaust pipe (51) is connected to a developer supply pipe (54) through which developer fluid (41) contained in the tank (42) can be supplied to a photoreceptor medium (14). The apparatus as claimed in claim 4 or 5, wherein the second ends (52b, 53b) of the second and third exhaust pipes (52, 53) are connected to a developer supply pipe (54). The apparatus as claimed in claim 4, 5 or 6, wherein the second ends (51b-53b) of the first, second and third exhaust pipes (51-53) are connected to one another.

Inventors: EOM YOON-SEOP, EOM, YOON-SEOP
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO. LTD.
Application year: 1999
Main classification: G01F23
IPC codes: G03G15, G01F23