Patent Publication Number: US-9844964-B2

Title: Decoloring apparatus and method for operating the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. patent application Ser. No. 14/614,590, filed on Feb. 5, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a decoloring apparatus and a method for operating the decoloring apparatus. 
     BACKGROUND 
     An image forming apparatus forms an image with decoloring toner. A decoloring apparatus erases a toner image on a sheet printed by such an image forming apparatus by heating the toner image. Such a decoloring apparatus consumes energy to heat the toner image. Efficiently operating the erasing apparatus to reduce the amount of energy consumed is desired. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate an embodiment of the invention and together with the description, serve to explain the principles of the invention. 
         FIG. 1  illustrates a decoloring apparatus, which includes an image forming function, according to a first embodiment. 
         FIG. 2  is a block diagram of a decoloring control system of the image forming apparatus according to the first embodiment. 
         FIG. 3  is a partial cross-sectional view of a heating member in an image erasing unit of the decoloring apparatus according to the first embodiment. 
         FIG. 4  is a block diagram of an entire control system of the decoloring apparatus according to the first embodiment. 
         FIG. 5  illustrates a time detector of the decoloring apparatus according to the first embodiment. 
         FIG. 6  illustrates an accumulation quantity detector of the decoloring apparatus according to the first embodiment. 
         FIG. 7  is a flowchart of an operation carried out by the decoloring apparatus according to the first embodiment. 
         FIG. 8  illustrates a decoloring apparatus according to a second embodiment. 
         FIG. 9  is a block diagram of a control system of the decoloring apparatus according to the second embodiment. 
         FIG. 10  illustrates a time detector of the decoloring apparatus according to the second embodiment. 
         FIG. 11  illustrates an accumulation quantity detector of the decoloring apparatus according to the second embodiment. 
         FIG. 12  illustrates a relation between a second detection unit, a controller, and an image erasing controller of the decoloring apparatus according to the second embodiment. 
         FIG. 13  is a flowchart of an operation carried out by the decoloring apparatus according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a decoloring apparatus includes an erasing unit configured to generate heat so as to erase an image formed on a sheet with an erasable material, a sheet storing unit to store one or more sheets, each having the image formed thereon with the erasable material, a sheet conveying unit configured to convey the sheets from the sheet storing unit to the erasing unit, a quantity sensor configured to detect a quantity of the sheets stored in the sheet storing unit, and a control unit configured to determine whether or not the detected quantity is greater than a predetermined value, and control the sheet conveying unit to convey the sheets and the erasing unit to generate heat, when the detected quantity is determined to be greater than the predetermined value. 
     Reference will now be made in detail to the present embodiment of the invention, and example of which is illustrated in the accompanying drawing. 
     Hereinafter, the present embodiment will be described with reference to the drawings. The same reference numbers are used in the following description, with respect to the same configuration and function. 
     First Embodiment 
       FIG. 1  illustrates a decoloring apparatus (image forming apparatus) according to a first embodiment. As illustrated in  FIG. 1 , a document platen  2  for supporting a document, which is formed of a transparent material, such as a sheet of glass, and an operation panel  2   p  above the document platen  2  are provided on an upper part of an image forming apparatus  1 . The operation panel  2   p  displays an operational state of the image forming apparatus  1 , is, for example, a touch panel, such that an operator may touch and select one option that is displayed and may input various data thereto, and is disposed such that a direction of a display screen may be changed. A sheet according to the embodiment is a sheet on which a toner image is formed with decolorable toner that is decolorable through heating. 
     In addition, an auto document feeder (ADF)  3  that continuously transports original document sheets is disposed in an openable and closable manner to cover the document platen  2 . A scanner  4  that optically scans an image on a document placed on the document platen  2  is provided on the lower surface side of the document platen  2 . 
     The scanner  4  includes, for example, a carriage  6  that includes an optical source  5  that irradiates the document with a light beam, reflective mirrors  7   a ,  7   b , and  7   c  that reflect the light beam emitted from the optical source  5  and reflected by the document, a magnifying lens block  8  that magnifies the reflected light beam, and a charge coupled device (CCD)  9 . The carriage  6  is provided such that it can reciprocate along the lower surface of the document platen  2 . 
     The carriage  6  irradiates the document placed on the document platen  2  with a light beam while the carriage  6  reciprocates and the optical source  5  is turned on. An image formed with a light beam reflected by the document and guided by the reflective mirrors  7   a ,  7   b , and  7   c  and the magnifying lens block  8  is incident on the CCD  9 . 
     The CCD  9  outputs a digital-encoded image signal corresponding to the optical image obtained from the document to an image process circuit. The image signal on which an image data processing is appropriately performed by an image data processing circuit is output to a laser unit  11  of an image forming unit  10 . The image forming unit  10  executes an image forming process in which a toner image corresponding to the image signal output from the CCD  9  is formed on a recording medium P, such as a sheet. 
     The image forming unit  10  includes an image carrier  12  that has an organic photoconductor (OPC) on the front surface thereof, a corona charger  13  for uniformly charging a surface of the image carrier  12 , the laser unit  11  for forming an electrostatic latent image on the image carrier  12 , a developing device  14  that has a developing roller for developing the electrostatic latent image on the image carrier  12  by supplying a developer, a transfer roller  15 , a cleaner  16  for removing and collecting residual toner or the like, and a discharge lamp  17  for removing charge on the image carrier  12  after the transfer. 
     The image carrier  12  includes the organic photoconductor (OPC) on its surface, and rotates in an arrow O direction at a circumferential velocity of 136 mm/sec. The corona charger  13 , the laser unit  11 , the developing device  14 , the transfer roller  15 , the cleaner  16 , and the discharge lamp  17  are disposed in this order around the image carrier  12  in the rotational direction of the image carrier  12 . 
     The corona charger  13  is a scorotron-type corona charger and uniformly charges the surface of the image carrier  12  to have a negative polarity. Scanning exposure with a laser beam (semiconductor laser)  11   a  from the laser unit  11  is performed on the uniformly charged image carrier  12  by 600 dpi resolution according to the image signal obtained by the scanner  4 , and, as a result, an electrostatic latent image is formed on the image carrier  12 . 
     Two-component developer charged to have a negative polarity is stored in the developing device  14 . Two-component toner is formed of, for example, a mixture of decolorable toner having a volume average particle size of 5 μm to 12 μm and a magnetic carrier having a volume average particle size of 30 μm to 80 μm. The developing device  14  develops an electrostatic latent image on the image carrier  12  with the decolorable toner, and as a result a toner image is formed. 
     A toner concentration sensor for detecting toner concentration of the stored developer is provided in the developing device  14 , and the decolorable toner is supplied to the developing device  14  from a toner cartridge according to a detection output of the toner concentration sensor. 
     The transfer roller  15  is a conductive roller, to which a transfer bias voltage is applied by a high-voltage power supply to have a positive polarity from. The toner image formed on the image carrier  12  is transferred, by the transfer roller  15  that has the transfer bias, onto the recording medium P that is supplied from sheet feeders  32 ,  33 , and  34  and is transported in a predetermined timing by a resist roller  18 . The toner image transferred onto the recording medium P is fixed by an image fixing unit  40 . Then, the recording medium P is discharged to an external discharged sheet accumulation unit  45  by a sheet discharge roller  31 . 
     The cleaner  16  includes a cleaning blade  16   a  that is in contact with the front surface of the image carrier  12 , and causes the cleaning blade  16   a  to scrape and sweep off toner remaining on the image carrier  12  after the transfer. The discharge lamp  17  removes a charge remaining on the surface of the image carrier  12 . The image carrier  12  from which the charge is removed is used to form a subsequent electrostatic latent image. 
     A sheet feeder having a cassette includes the sheet feeder  32  that stores an unused sheet or a reusable sheet by image decolorization (collectively referred to as a usable sheet) P 1 , and the sheet feeder  33  that stores a used sheet (sheet having a fixed toner image) P 2 . In addition, the manual sheet feeder  34  that supplies a sheet from the outside of the apparatus is provided. 
     The selection of these sheet feeders may be set through the operation panel  2   p , and a sheet is fed from the sheet feeders  32  and  33  by pick-up rollers  321  and  331  and sheet separation/transport rollers  35  and  36 , respectively. In addition, a sheet is fed from the manual sheet feeder  34  by a pick-up roller  341 . 
     After a fixed toner image on the used sheet P 2  is erased by an image erasing unit  20 , the used sheet P 2  fed from the sheet feeder  33  is transported to the image forming unit  10  by a transport roller  39  and the resist roller  18 , and used for forming an image. A conveying unit to reverse the side of the sheet is provided in the image forming apparatus  1  according to the present embodiment, but not illustrated in the drawings. 
     A main control system of the image forming apparatus  1  is illustrated in  FIG. 2 . The image forming apparatus  1  includes a time detector  50  that detects that a predetermined time comes, an accumulation quantity detector  60  that detects a quantity of the stored used sheets P 2 , a sensor unit  70  that detects a peripheral condition around the image forming apparatus  1 , an image erasing controller  200  that erases an image on the used sheet P 2  under a predetermined condition, a decoloring temperature controller  300  that controls a decoloring (erasing of an image) temperature for the used sheet P 2 , a fixing temperature controller  400  that controls a fixing temperature, and a controller  88  that controls the entire system. 
     The used sheet P 2  is stored in the sheet feeder  33 . When the time preset by the time detector  50  comes, the image erasing unit  20  is operated and an image erasing (decoloring) process is performed on the used sheets P 2  stored in the sheet feeder  33  one by one, and the sheets subjected to the image erasing process are discharged from the sheet discharge roller  31  through a transport route, and stacked on the discharged sheet accumulation unit  45 . 
     Image Erasing Unit  20   
     The image erasing unit  20  is controlled by the image erasing controller  200 . The image erasing controller  200  causes the image erasing unit  20  to operate when the time detector  50  detects that the predetermined time comes. The image erasing unit  20  includes a heating unit that includes a first heating roller  21  and a second heating roller  22 . The first heating roller  21  serves as a first member that heats aside (hereinafter, also referred to as “image side”) on which a toner image is formed on the pre-used sheet P 2  has a diameter of 40 mm, and has a halogen lamp  23  as an inside heat source, The second heating roller  22  serves as a second member that heats a side opposite to the image side (hereinafter, also referred to as “pressurized side”), has a diameter of 40 mm, has a halogen lamp  24  as a heat source similar to the first heating roller  21 , and is in press contact with the first heating roller  21 . A length of a nip formed between the first heating roller  21  and the second heating roller  22  is about 10.8 mm, and a time during which the sheet passes the nip is about 0.08 seconds. 
     On the first heating roller  21  and the second heating roller  22 , temperature sensors (thermistors)  30   a  and  30   b  that measure temperatures of surfaces thereof are provided, respectively. The temperature sensors  30   a  and  30   b  output detected information to the decoloring temperature controller  300 . The decoloring temperature controller  300  controls a value of a current supplied to the halogen lamps  23  and  24 , based on the input information, such that the surface temperatures of the first heating roller  21  and the second heating roller  22  become a predetermined temperature. 
     Here, the predetermined temperature is a temperature preset in a range of a decoloring start temperature to an offset start temperature of the decolorable toner. The preset temperature is randomly set in terms of decoloring stability and offset of the decolorable toner. In addition, it is preferable that the first heating roller  21  and the second heating roller  22  be set to substantially the same temperature, for a similar reason. Specifically, when decolorable toner has the decoloring start temperature of 90° C., the surface temperatures of the first heating roller  21  and the second heating roller  22  are controlled to be 120° C. 
     An enlarged view of the first heating roller  21  and the second heating roller  22  is illustrated in  FIG. 3 . The first heating roller  21  that heats the image side includes a silicone rubber layer having a thickness of about 1.2 mm as an elastic layer  21   b  on an aluminum roller base  21   a  having a thickness of about 1.5 mm, and a fluororesin PFA (tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer) layer of about 30 μm as a release layer  21   c.    
     Similarly, the second heating roller  22 , which is a second member to heat the pressurized side, includes a silicone rubber layer having a thickness of about 1.2 mm as an elastic layer  22   b  on an aluminum roller base  22   a  having a thickness of about 1.5 mm, and a fluororesin PFA layer of about 30 μm as a release layer  22   c . The first heating roller  21  is driven by a drive source, and the second heating roller  22  follows the rotation of the first heating roller  21  ( FIG. 1  and  FIG. 3 ; arrow S) 
     The elastic layer  22   b  may not be provided on the second heating roller  22 . The elastic layer  22   b  is particularly effective when the used sheets P 2 , each having a toner image on one side thereof, are stored in the sheet feeder  33  randomly with respect to the side thereof, or when the used sheet P 2  that has toner images on both sides is stored in the sheet feeder  33 . 
     Image Fixing Unit  40   
     The image fixing unit  40  has a function of fixing a transferred image on the recording medium P, and includes a heating roller  42  that heats the image side of the usable sheet P 1  and a pressure roller  43  that presses the rear surface of the usable sheet P 1 . A halogen lamp  44  is disposed inside the pressure roller  43 . The image fixing unit  40  is controlled by the fixing temperature controller  400 . 
     The image fixing unit  40  includes the heating roller  42  that has a diameter of 45 mm and has the halogen lamp  41  as a heat source inside thereof and the pressure roller  43  that is in pressure contact with the recording medium P at a side opposite to the toner image side of the recording medium P. The heating roller  42  serves as a third member that heats a side of the recording medium P on which an unfixed toner image is formed. 
     A temperature sensor (thermistor)  30   c  and a temperature sensor (thermistor)  30   d , which measure surface temperatures of the heating roller  42  and the pressure roller  43 , are provided on the heating roller  42  and the pressure roller  43 , respectively. The temperature sensor  30   c  and the temperature sensor  30   d  output the detected temperature information to the fixing temperature controller  400 . 
     The fixing temperature controller  400  controls a current supplied to the halogen lamps  41  and  44 , based on the input information, such that the surface temperatures of the heating roller  42  and the pressure roller  43  become a predetermined temperature. 
     Here, the predetermined temperature is a temperature preset in a range between a lower limit fixing temperature and a decoloring start temperature of the decolorable toner. The preset temperature is randomly set in terms of decoloring characteristics and fixing characteristics of the decolorable toner. 
     Here, an entire electrically connected configuration of the image forming apparatus is illustrated in  FIG. 4 . The image forming apparatus  1  includes a display operation unit  82  that has the operation panel  2   p , a document scanning unit  83  that supplies an original document sheet and performs scanning, a sheet accommodation and transport unit  84  that performs accommodation and transportation of the sheet, a printing unit  85  that forms a latent image and performs transferring and fixing of the toner image, a decoloring unit  86  that performs the decoloring process under a predetermined condition when the sheet is a used sheet, a communication unit  87  that performs communication through a network, a controller  88  that controls these units as a whole, and a power supply unit  89  of the apparatus. 
     The document scanning unit  83  includes the ADF  3  and the scanner  4  in  FIG. 1 . The sheet accommodation and transport unit  84  corresponds to the sheet feeders  32  and  33  that store a sheet, and a transport roller or the like that performs transportation during printing. 
     The printing unit  85  includes the image forming unit  10 , the developing device  14 , and the image fixing unit  40  in  FIG. 1 . The decoloring unit  86  includes the time detector  50 , the accumulation quantity detector  60 , and the sensor unit  70  illustrated in  FIG. 2 , in addition to the image erasing unit  20 . The controller  88  includes a processor (CPU) and a memory unit  88   m , and the memory unit  88   m  includes a read-only memory (ROM) and a random access memory (RAM). The power supply unit  89  is turned off when the image forming apparatus  1  is shut down by an operator or when a predetermined time elapses after a normal operation has been finished. 
     Here, each component illustrated in  FIG. 2  is described further. Configuration of the time detector  50  is illustrated in  FIG. 5 . The time detector  50  includes a clock  52  that shows current time, a time setting section  54  on which time to perform the decoloring process may be set through an external operation, and a time comparator  56  that compares the current time from the clock  52  with the time set by the time setting section  54 , and outputs a predetermined time detection signal when the set time comes. 
     The setting of the predetermined time on the time setting section  54  is performed by direct inputting of time through the operation panel  2   p  illustrated in  FIG. 1  by an operator, or by causing the current time to be displayed and to be changed up and down from the current time and then determining the set time. It is possible to suppress electricity charge when the set time is in the middle of night when the electricity rate is lower. 
       FIG. 6  illustrates configuration of the accumulation quantity detector  60  that determines whether or not a predetermined amount of the used sheets P 2  are stacked. The accumulation quantity detector  60  includes a weight measuring section  62  that measures the weight of a tray  33   t , a weight setting section  64  on which an operator inputs and sets a quantity of the used sheets in advance, and a weight comparator  66  that compares the set weight and the measured weight of the used sheets P 2  measured by the weight measuring section  62 . 
     The accumulation quantity detector  60  measures weight of the used sheets by subtracting the self-weight of the tray  33   t  from weight of the tray  33   t  on which the used sheets P 2  are stacked, that is, a total weight of the used sheets P 2  and the tray  33   t . It is determined whether or not a predetermined quantity or more of the used sheets are stacked by comparing the measured weight with the predetermined value set in advance to perform the decoloring process. 
     The accumulation quantity detector  60  may not detect the weight of the used sheets that is to be decolorized, rather may measure a thickness of the stacked sheets by using, for example, an optical sensor, and calculate the number of sheets by converting the thickness into the number of sheets. When the number of sheets is set, the calculated number of sheets is compared to the number that is input and set in advance, and it is determined whether the predetermined number or more of the used sheets are stacked. 
     An operation according to the embodiment is described with reference to a flowchart illustrated in  FIG. 7 . The above-described image forming apparatus  1  normally uses the usable sheet P 1 , that is, unused or reusable sheet, which is stored in the sheet feeder  32 . An image formed by the image forming unit  10  is transferred, fixed, and printed on the sheet, and then the sheet is stacked on the discharged sheet accumulation unit  45 . The used sheets P 2  that have been used are stacked in the sheet feeder  33 . 
     The operator set appropriate time in advance as time for the decoloring process in the time setting section  54  of the time detector  50 . In the image forming apparatus  1  in which the predetermined time is set by the time setting section  54 , it is detected that the time set in the clock  52  comes (A701). It is determined that whether or not the set time comes by the time comparator  56  comparing the current time shown by the clock  52  with the time set by the time setting section  54 . 
     When it is detected that the set time comes (Y in A701), it is determined whether or not the image forming apparatus  1  is currently stopped based on the operation or operation-stop of the power supply unit  89 , in following A702. When the image forming apparatus  1  is not stopped (power-off state, minimum required operation) (N in A702), the decoloring process is not performed. Meanwhile, when it is detected that the image forming apparatus  1  is stopped in A702, the power supply unit  89  of the image forming apparatus  1  turns on in following A703, and the apparatus is operated. 
     It is determined whether or not the predetermined quantity or more of the used sheets P 2  are stacked in A704. The quantity is measured by the weight measuring section  62  in  FIG. 6 . The detection is performed by the weight comparator  66  comparing the weight of the used sheets P 2  obtained by subtracting the weight of the tray  33   t  from total weight measured by the weight measuring section  62  with the weight set in advance by the operator in the weight setting section  64 . 
     When it is determined that the predetermined quantity or more of the used sheets P 2  are stacked (Y in A704), the decoloring process is collectively performed on the used sheets P 2  in A705. Specifically, the image erasing process is performed on the used sheets stacked by the image erasing unit  20  under control of the image erasing controller  200 . Then, the power supply unit  89  of the image forming apparatus  1  turns off and no power is supplied except for a power needed for a stand-by operation (A706). Then, the process returns to A701 and is on standby until the set time comes. 
     When it is determined that less than the predetermined quantity of the used sheets are stacked in A704, the decoloring process is not performed, the image forming apparatus  1  is turned off in A706, and the process returns to A701. That is, even when the predetermined time set to perform the decoloring process comes, the decoloring process is not executed on the used sheets when the predetermined quantity of the used sheets is not stacked. 
     According to the embodiment, the apparatus is turned off until the preset decoloring start time comes, and the decoloring process is not executed when the used sheets are less than the preset quantity. 
     According to the embodiment, the operator sets, in advance, time to perform the decoloring process in the time setting section, but the time may also set through setting of termination time of the power-saving mode of the image forming apparatus. Accordingly, while the image forming apparatus is turned on, the decoloring process may be performed on the used sheets subsequent to the printing process. 
     Second Embodiment 
     Next, another embodiment as a decoloring apparatus will be described. A configuration of the decoloring apparatus according to a second embodiment is illustrated in  FIG. 8 . 
     A decoloring apparatus  100  performs a “decoloring process” in which a color of an image formed with a decolorable color material, such as decolorable toner or decolorable ink, is erased from a sheet. 
     The decolorable color material contains a coloring compound, a developer, and a decoloring agent. An example of the coloring compound includes leuco dye. Examples of the developer include phenols. An example of the decoloring agent includes a substance that is compatible with the coloring compound when the substance is heated, and that does not have affinity for the developer. The decolorable color material generates color by an interaction between the coloring compound and the developer, and since the interaction between the coloring compound and the developer is cut off through heating to a decoloring temperature or higher, the decolorable color material is decolorized. 
     The decoloring apparatus  100  includes a sheet feeding tray  102 , a sheet feeding member  104 , a reading unit  106 , a decoloring device  108 , a first tray  110 , a second tray  112 , discharge rollers  114  and  116 , a first transport path  118 , a second transport path  120 , a third transport path  122 , a first branch member  124 , a second branch member  126 , and an operation unit  128 . 
     The sheet feeding tray  102  is loaded with reusable sheets. The sheet feeding tray  102  is loaded with sheets of various sizes, such as A4, A3, B5, or the like. The sheet with which the sheet feeding tray  102  is loaded is a sheet having an imaged formed with a decolorable colorant that is decolorized by being heated to a predetermined temperature or higher. The sheet feeding member  104  includes a pick-up roller, a sheet supply roller, and a separation roller disposed to face the sheet supply roller, and supplies the sheets on the sheet feeding tray  102  one by one to the first transport path  118  inside the decoloring apparatus  100 . 
     In addition, the sheet feeding tray  102  includes a detection sensor  103  that detects presence or absence of a sheet on the sheet feeding tray  102 . The detection sensor  103 , for example, may be a microsensor or a microactuator. The first transport path  118  is a transport path from the sheet feeding tray  102  toward the first tray  110 . The fed sheet is conveyed through the first transport path  118  to the reading unit  106  or the first tray  110 . 
     The reading unit  106  is disposed along the first transport path  118  downstream with respect to the sheet feeding tray  102  in a sheet transport direction. The reading unit  106  is, for example, a charge coupled device (CCD) scanner or a CMOS sensor. 
     According to the present embodiment, the reading unit  106  reads images on a first surface and a second surface of a sheet that is transported. That is, the reading unit  106  has a first reading unit  106   a  and a second reading unit  106   b  which are disposed along the first transport path  118  between which the transport path is formed, and may read images on both surfaces of the sheet that is transported. 
     A position where the reading units of the reading unit  106  read images on the sheet is referred to as a reading position. Image data of the image read by the reading unit  106  is stored in a storage unit  210  (see  FIG. 9 ). For example, the image data of the image on the sheet which is read by the reading unit  106 , before the decoloring process, is digitalized and stored in the storage unit. When data of the decolorized image is required later, it is possible to output the image data. In addition, a controller  201  determines whether or not the image on the sheet is decolorable, or whether or not the sheet may be reusable, based on the image read by the reading unit  106 . 
     The first branch member  124  as a switching unit is disposed downstream with respect to the reading unit  106 . The first branch member  124  switches a transport direction of the sheet. The first branch member  124  guides the sheet that is transported through the first transport path  118  to the second transport path  120  or to the first tray  110 . The second transport path  120  starts in a branch point where the first branch member  124  is disposed and where the first transport path  118  branches. The sheet is conveyed through the second transport path  120  that starts from the branch point, to the decoloring device  108 . 
     In addition, the second transport path  120  joins the first transport path  118  at a junction  121  upstream with respect to the reading unit  106  in the sheet transport direction. That is, the second transport path  120  joins the first transport path  118  at a junction  121  between the sheet feeding tray  102  and the reading unit  106 . 
     Thus, the second transport path  120  enables the sheet transported from the reading unit  106  to be transported back to the reading unit  106  through the decoloring device  108 . In other words, the decoloring apparatus  100  controls the first branch member  124  to cause the sheet fed from the sheet feeding member  104  to be transported the reading unit  106 , the decoloring device  108 , and the reading unit  106  in the order. 
     The first transport path  118  includes a second branch member  126  downstream with respect to the first branch member  124 . The second branch member  126  guides the sheet transported from the first branch member  124  to the first tray  110  or to the third transport path  122 . The sheet is transported through the third transport path  122  to the second tray  112 . 
     The decoloring device  108  erases a color of the image on the sheet that is transported. For example, in a state in which the decoloring device  108  is in contact with the sheet that is transported, the decoloring device  108  heats the sheet to a predetermined decoloring temperature, thereby performing the decoloring of the image formed on the sheet with the decolorable colorant. 
     For example, the decoloring device  108  of the decoloring apparatus  100  according to the present embodiment includes two decoloring units  108   a  and  108   b  for decoloring the first and second surfaces of the sheet. The decoloring units  108   a  and  108   b  are disposed to face each other interposing the second transport path  120  therebetween. The decoloring unit  108   a  comes into contact with and heats the sheet from the one surface side of the sheet. 
     The decoloring unit  108   b  comes into contact with and heats the sheet from the other surface side of the sheet. That is, the decoloring device  108  performs the decoloring of the images on both surfaces of the sheet that is transported, during a single transport. The position where the decoloring units  108   a  and  108   b  heat the sheet, that is, the position where a heating section (not illustrated) that is included in the decoloring units  108   a  and  108   b  provides heat to the sheet and erases a color of the image, is referred to as the decoloring position. 
     In the decoloring device  108 , the decoloring units  108   a  and  108   b  have temperature sensors  109   a  and  109   b , respectively, each of which detects the temperature of the heating section. The temperature sensors  109   a  and  109   b  may be of a contact type or a non-contact type. 
     The operation unit  128  disposed on the upper part of a main body of the decoloring apparatus  100  includes a touch panel display section and various operation keys, which are, for example, disposed on the upper part of the decoloring apparatus main body. The operation keys include, for example, a numeric keypad, a stop key, and a start key. A user instructs a functional operation of the decoloring apparatus  100 , such as a decoloring start or reading of the image of the sheet on which the decoloring process is performed, through the operation unit. 
     The operation unit  128  displays setting information or operational status, or log information of the decoloring apparatus  100 , or an message to the user. 
     The discharge rollers  114  and  116  discharge the sheet to the first tray  110  and the second tray  112 , respectively, which are disposed vertically on the lower part of the main body. The second tray  112  is loaded with unused sheets or reusable sheets on which the decoloring process is performed. For example, the reusable sheet on which the image remains and the decoloring process is performed is loaded in the first tray  110 . When a predetermined time comes, the used sheet loaded in the first tray  110  is transported from the first tray  110 , and collectively decolorized by the decoloring device  108  and stacked onto the second tray  112 . Thus, the discharge roller  114  is also capable of rotating reversely, and not only the sheet passed through the reading unit  106 , but also the used sheet temporarily stored in the first tray  110  is transported from the first tray  110  to the second transport path  120  and passes through the decoloring device  108 . 
     According to the embodiment, the used sheets stored in the first tray  110  and the used sheets stored in the sheet feeding tray  102  pass through the decoloring device  108 , and thus it is possible to perform the decoloring process on the sheets. The quantity of the used sheets may be the sum of quantities of the sheets in the first tray  110  and in the sheet feeding tray  102 . 
     Here, the first tray  110  is described as a reuse tray for reusable sheets, and the second tray  112  is described as a tray of usable sheets. The sheets stored in the first tray  110  and the second tray  112  may be switched. 
       FIG. 9  is a block diagram of a functional units of the decoloring apparatus  100 . The decoloring apparatus  100  includes a controller  201 , a storage unit  210 , a detector  212 , a second detector  213 , a communication interface (communication I/F)  214 , a transport unit  216 , the reading unit  106 , the decoloring device  108 , the operation unit  128 , and an image erasing controller  290 . Each component of the decoloring apparatus  100  is connected through a bus  218 . The second detector  213  includes a time detector  250 , an accumulation quantity detector  260 , a sensor unit  270 , and an apparatus operation detector  280  (see  FIG. 12  to be described later). 
     The controller  201  includes a processor  202  that includes a central processing unit (CPU) or a micro processing unit (MPU), and a memory  204 . The controller  201  controls the reading unit  106 , the decoloring device  108 , and the operation unit  128 . 
     The memory  204  is, for example, a semiconductor memory, and includes a read-only memory (ROM)  206  that stores various control programs, and a random access memory (RAM)  208  that provides the processor  202  with a temporary operation region. For example, the ROM  206  stores a printing ratio that is a threshold value for determining whether a sheet is reusable or not, a concentration threshold value for determining whether or not an image on a sheet is decolorized, or the like. The RAM  208  may temporarily retain the image data generated by the reading unit  106 . 
     The decoloring apparatus  100  has, for example, a reading process, a decoloring process, and classifying process. The controller  201  of the decoloring apparatus  100  controls the reading unit  106 , the decoloring device  108 , and other configurations according to the set process. 
     In the reading process, the controller  201  controls the first reading unit  106   a  and the second reading unit  106   b  to read the images that are printed on both surfaces of the sheet. The controller  201  retains the image data generated by the reading unit  106  in the storage unit  210  (see  FIG. 9 ). 
     In the decoloring process, the controller  201  controls the decoloring device  108  to erase the images on the sheet. That is, the images printed on both surfaces of the sheet are erased by the decoloring units  108   a  and  108   b  of the decoloring device  108 . 
     In the classifying process, the controller  201  determines where the sheet is conveyed to the first tray  110  or to the second tray  112  depending on the presence or absence of an image on the sheet. The controller  201  determines whether or not an image is present, based on the image data generated by the reading unit  106 . When an image is present, the sheet is conveyed to the first tray  110 . When the image data generated by the reading unit  106  indicates that the image on the sheet is erased by the decoloring device  108 , the sheet is conveyed to the second tray  112 . 
     Configuration of the second detector  213  and a relation between the controller  201  and the image erasing controller  290  are illustrated in  FIG. 12 . The second detector  213  includes the time detector  250 , the accumulation quantity detector  260 , the sensor unit  270 , and the apparatus operation detector  280 . 
     As illustrated in  FIG. 10 , the time detector  250  includes a clock  252  that tells current time, a time setting section  254 , and a time comparator  256 . Appropriate time to perform the decoloring process is set on the time setting section  254  by an operator through an external operation. The time comparator  256  compares the current time shown by the clock  252  with the time of the time setting section  254 , and when the set time comes a decoloring instruction control signal is output. 
     As illustrated in  FIG. 11 , the accumulation quantity detector  260  detects the quantity of accumulation of the used sheets by measuring the weight of the used sheets. The accumulation quantity detector  260  is configured to have a weight measuring section  262  that detects the weight of the used sheets in the first tray  110 , a weight setting section  264  in which the weight of the used sheets is set, and a weight comparator  266 . 
     The sensor unit  270  includes a human sensor (motion detector)  272  that detects that a person is present near the human sensor  272 , and a brightness sensor  274  that detects the brightness around the decoloring apparatus  100 . The human sensor  272  may be a sensor that detects motion of an object. In addition, the brightness sensor  274  may compare luminance with a predetermined threshold value, and determines whether it is bright or dark. The detection by these human sensor and brightness sensor may be applied to the first embodiment in a similar manner. 
     The controller  201  controls each configuration inside the apparatus, based on a signal from the detector  212 . The detector  212  includes the detection sensor  103  illustrated in  FIG. 1 , the temperature sensors  109   a  and  109   b , sheet detection sensors  130  to  136 , and a detection sensor that detects the quantity of the sheets in the first tray  110  and the second tray  112 . The controller  201  determines the presence or absence of the sheet on the sheet feeding tray  102  based on a signal from the detection sensor  103 . 
     In addition, the controller  201  recognizes temperatures of the heating sections of the decoloring units  108   a  and  108   b  using the temperature sensors  109   a  and  109   b , and controls the temperatures of the heating sections of the decoloring units  108   a  and  108   b . In addition, the controller  201  recognizes a position of the sheet in the first to third transport paths  118 ,  120 , and  122 , using the sheet detection sensors  130 ,  131 ,  132 ,  133 ,  134 ,  135 , and  136 . For example, the controller  201  recognizes the sheet that passed the reading unit  106  by using the sheet detection sensor  130  in the vicinity of the downstream with respect to the reading unit  106 . 
     The storage unit  210  stores an application program and an OS. The application program includes a program to achieve a function that the decoloring apparatus  100  has, such as a reading function by the reading unit  106 , and a decoloring function of the decoloring unit. The application program further includes an application (Web browser) for a Web client or other applications. 
     The storage unit  210  retains the image data generated by the reading unit  106 . In addition, the storage unit  210  stores the number of sheets processed by the decoloring apparatus  100 . Examples of the storage unit  210  may be a hard disk drive or other magnetic storage devices, an optical storage device, a semiconductor memory device, such as a flash memory, or any combination thereof. 
     The communication I/F  214  is an interface to connect the decoloring apparatus  100  to an external device. The communication I/F  214  communicates with an external apparatus on a network via an appropriate wireless or wired access, such as Bluetooth (registered trademark), an infrared access, an optical access, for example, IEEE802.15, IEEE802.11, IEEE802.3, IEEE3304. The communication I/F  214  may further include a USB connector to which a connection terminal compatible with a USB standard is connected, a parallel interface, or the like. 
     The transport unit  216  includes a plurality of transport rollers that are disposed on the first transport path  118 , the second transport path  120 , and the third transport path  122 , and a transport motor that drives the transport roller. The controller  201  controls the drive of the transport motor of the transport unit  216  so as to control a transport speed of sheets. 
     Here, a speed of a sheet conveyed through the reading unit  106  so that an image on the sheet is read is referred to as a reading speed, and a speed of a sheet conveyed through the decoloring device  108  so that a color of an image on the sheet is erased is referred to as a decoloring speed. 
     Next, a loading unit of the decoloring apparatus  100  will be described. The loading unit includes the first tray  110 , which is a reuse tray in which the used sheet to be subject to the decoloring process is stored, and the second tray  112  in which the usable sheet is stored. The unused sheet that is usually used or the sheet on which the decoloring process has been performed is stored in the second tray  112 . The sheet stored in the first tray  110  is subject to the decoloring process by the decoloring device  108 . 
     Next, an image erasing operation according to the second embodiment is described based on a flowchart illustrated in  FIG. 13 . When the scheduled decoloring time preset to perform the decoloring process comes (Y in 1301), a control signal indicating that the time has come is transmitted to the controller  201  from the time detector  250 . When the controller  201  receives a scheduled decoloring time control signal, first, in A1302, a question whether the decoloring apparatus  100  is normally operated is transmitted to the apparatus operation detector  280  (A1302). When the decoloring apparatus  100  is normally operated, the process is on standby until the following set time. 
     When the decoloring apparatus  100  is not normally operated (N in A1302), the controller  201  transmits a signal of a question whether or not there is a person around the human sensor  272  of the sensor unit  270 . When there is a person around (N in A1303), the process returns to A1301 and is on standby until the following set time. 
     Meanwhile, when there is no person therearound (Y in A1303), the controller  201  transmits a question of the brightness around the decoloring apparatus  100  to the brightness sensor  274  of the sensor unit  270 . 
     When it is bright around (Y in A1304), it is highly probable that there is a person around. Therefore, the process returns to A1301 and is on standby until the following decoloring set time. Meanwhile, when it is dark around the apparatus (N in A1304), the process proceeds to the following A1305. In A1305, the controller  201  controls the accumulation quantity detector  260  to detect whether the preset quantity or more of the used sheets are stacked on the first tray  110 . 
     When the preset quantity or more of the used sheets are stacked (Y in A1305), the controller  201  transmits the image erasing instruction signal to the image erasing controller  290 , and erasing (decoloring) of the image is performed by the decoloring device  108 . Meanwhile, when less than the predetermined quantity of the used sheets are stacked (N in A1305), the process returns to A1301 and is on standby until the following set time for the decoloring process. 
     According to the embodiment, when the decoloring set time comes, the decoloring apparatus  100  stops normal operation. When there is no person around, it is dark around, and the predetermined quantity of the used sheets is stacked, the image erasing operation is performed. It is possible to stop the decoloring process when at least one condition of the human sensor and the brightness sensor is not met. For example, when the human sensor detects a person around, the decoloring process is not performed even at the predetermined time. Alternatively, when the brightness sensor detects a predetermined brightness around, the decoloring process is not performed even at the preset time. 
     According to above-described embodiments, the used sheets are subject to the decoloring process, but the technology may be applied to any used medium that may be printed decolorably other than the sheets. 
     According to the above-described embodiment, a document decoloring management apparatus and a decoloring management method are obtained, in which it is possible to efficiently erase an image on a sheet, such as a document, on which printing is performed. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.