EP1089140A2

EP1089140A2 - Apparatus for removing print substance from a sheet

Info

Publication number: EP1089140A2
Application number: EP20000121442
Authority: EP
Inventors: Atsuto c/o Minolta Co. Ltd. Hirai
Original assignee: Minolta Co Ltd
Current assignee: Minolta Co Ltd
Priority date: 1999-09-30
Filing date: 2000-09-29
Publication date: 2001-04-04
Also published as: JP2001100607A

Abstract

The present invention provide a sheet cleaning apparatus that comprises a sheet cleaner for removing print material from printed sheets, a stacker on which the printed sheets are set, a sheet feeder for feeding the printed sheets set on the stacker to the sheet cleaner. The apparatus further comprises: a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and a controller for starting warming-up of sheet cleaning when the sheet quantity detector detects a predetermined quantity or more of the printed sheets.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a sheet cleaning apparatus for removing print material on a printed sheet.
Conventionally, there has been proposed a sheet cleaning apparatus for removing print material such as toner on a recording member or a sheet, on which characters or images are recorded by an electrophotographic apparatus or the like.
In the above mentioned sheet cleaning apparatus, necessary power is almost same in either the case of treating a small number of sheets or the case of treating a large number of sheets. Generally, when some printed sheets are collected, user sets the sheets on the sheet cleaning apparatus. However, it is not efficient to conduct the cleaning process at every time when the sheets are set.
In the sheet cleaning apparatus in which swelling layer formed on the surface of the sheet is swelled in swelling liquid to remove print material and then the sheet is dried by dryer means, it is necessary to maintain the swelling liquid in a predetermined temperature and maintain the dryer means in a predetermined condition. However, it leads to loss of energy to hold the apparatus energized condition independently of cleaning in order to maintain the swelling liquid and the dryer means.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sheet cleaning apparatus that can efficiently conduct sheet cleaning process and can save energy.
According to one aspect of the present invention, there is provided a sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets, a stacker on which the printed sheets are set and a sheet feeder for feeding the printed sheets set on the stacker to the sheet cleaner, characterized in that the apparatus further comprises: a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and a controller for starting warming-up of sheet cleaning when the sheet quantity detector detects a predetermined quantity or more of the printed sheets.
Preferably, the controller activates the sheet feeder to feed the printed sheets from the stacker to the sheet cleaner after completion of the warming-up of sheet cleaning.
Preferably, the sheet quantity detector detects the number of the printed sheets or the weight of the printed sheets.
Preferably, the sheet cleaner includes: a swelling tank for containing swelling liquid at the operating time of the sheet cleaner; and a swelling liquid recovery tank for recovering the swelling liquid from the swelling tank at the non-operating time of the sheet cleaner, and wherein the warming-up of sheet cleaning is transferring the swelling liquid stored in the swelling liquid recovery tank to the swelling tank.
Preferably, the sheet cleaner further includes: a liquid quantity sensor for detecting the quantity of the swelling liquid in the swelling tank; and a heater for heating the swelling liquid contained in the swelling tank, and wherein the heater starts heating the swelling liquid after the liquid quantity sensor detects a predetermined quantity of the swelling liquid transferred from the swelling liquid recovery tank.
Preferably, the sheet cleaning apparatus further comprises: a drier for drying the sheets after sheet cleaning; wherein the warming-up of sheet cleaning is starting operation of the drier.
Preferably, the sheet cleaning apparatus further comprises: a manual start switch for forcedly starting the cleaning process, wherein, when the manual start switch is ON, the controller starts the warming-up of sheet cleaning irrespectively of the quantity of printed sheets detected by the sheet quantity detector.
Preferably, the controller activates the sheet feeder to feed the printed sheets from the stacker to the sheet cleaner after completion of the warming-up of sheet cleaning.
Preferably, when the manual start switch is OFF, the controller stops feeding the printed sheets to the cleaner by the sheet feeder irrespectively of the quantity of printed sheets detected by the sheet quantity detector and then conducts final process of sheet cleaning after completion of cleaning process of the printed sheet that have been fed at the time of stop of feeding.
Preferably, the sheet cleaner immerses the printed sheet into swelling liquid to swell the swelling layer formed on the printed sheet and removes the print material by applying blush roller to the printed sheet.
According to another aspect of the present invention, there is provided A sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets and a sheet feeder for feeding the printed sheets set on a stacker to the sheet cleaner, characterized in that the apparatus further comprises: a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and a controller for conducting final process of sheet cleaning when a predetermined time has passed after the sheet quantity detector detects no printed sheet.
Preferably, the sheet cleaner includes: a swelling tank for containing swelling liquid at the operating time of the sheet cleaner; and a swelling liquid recovery tank for recovering the swelling liquid from the swelling tank at the non-operating time of the sheet cleaner, and wherein the final process of sheet cleaning is transferring the swelling liquid contained in the swelling tank to the swelling liquid recovery tank.
Preferably, the sheet cleaner includes: a heater for heating the swelling liquid contained in the swelling tank, wherein the final process of sheet cleaning is stopping heating the swelling tank contained in the swelling tank by the heater.
Preferably, the sheet cleaner further includes: a filter disposed in a transferring route between the swelling tank and the swelling liquid recovery tank, the filter filtrates the swelling liquid at the time of transferring the swelling liquid.
Preferably, the sheet cleaning apparatus further comprises: a drier for drying the sheets after sheet cleaning; wherein the final process of sheet cleaning is stopping operation of the drier.
Preferably, the predetermined time is a time required to finish the cleaning process of one of the printed sheets.
Preferably, the predetermined time can be set by user.
According to still another aspect of the present invention, there is provided a sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets and a sheet feeder for feeding the printed sheets set on a stacker to the sheet cleaner, characterized in that the apparatus further comprises: a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and a controller for prohibiting operation of the sheet cleaner when the sheet quantity detector detects a predetermined quantity or less of the printed sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which:
Fig. 1 is a schematic view of a sheet cleaning apparatus according to the present invention;
Fig. 2 is an enlarged view of Fig. 1 showing an operation for delivering a sheet to a print-material removing portion from a tray;
Fig. 3 is a flowchart showing an operation of sheet cleaning apparatus according to the present invention;
Fig. 4 is a flowchart continued from Fig. 3; and
Fig. 5 is an enlarged view of Fig. 1 showing an operation for delivering a sheet to a print-material removing portion from a tray.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 shows a sheet cleaning apparatus 1 according to the present invention. A sheet 2 on which print material or toner is removed by the sheet cleaning apparatus 1 is so-called a reusable sheet or reusable OHP sheet, on the surface of which a swelling layer made of water swelling resin is formed. The print material such as toner on the sheet 2 can be removed by swelling the swelling layer to weaken adhering force of the print material to the swelling layer.
The sheet cleaning apparatus 1 is provided with a sheet feed portion 3 for feeding the printed sheet 2 to the inside of the apparatus. The sheet cleaning apparatus 1 has a function for automatically starting the cleaning process when a predetermined number of sheets 2 are set on the sheet feed portion 3.
The sheet 2 fed to the inside of the apparatus by the sheet feed portion 3 is conveyed to a tray 5 disposed in a swelling tank 4 and then immersed in swelling liquid 6 contained in the swelling tank 4. Thus, the surface (swelling layer) of the sheet 2 becomes wet and swells.
The sheet 2 of which swelling layer swells is delivered to a print material removing portion 8 by the sheet conveying mechanism 7 to remove the print material. The sheet 2 of which print material is removed is then taken out of the swelling tank 4 and washed down by a washing mechanism 10. Subsequently, the sheet 2 is heated at a sheet drying portion 11 and then discharged in a dried condition to a discharge tray 12.
In addition, the sheet cleaning apparatus 1 is provided with a recovery tank 13 for recovering the swelling liquid 6 contained in the swelling tank 4 in a non-cleaning state.
Hereinafter, detail construction of each portion of the sheet cleaning apparatus 1 will be described.
The sheet cleaning apparatus 1 is equipped with a operation portion 14 on the top of the apparatus. The operation portion 14 is provided with a liquid crystal display portion 15 on the front surface for indicating operation state of the sheet cleaning apparatus 1. The operation portion 14 includes a power switch 16, an automatic cleaning process switch 17 for automatically starting the cleaning process and a manual cleaning process switch 18 for the user to arbitrarily start the cleaning process.
The sheet cleaning apparatus 1 is also equipped with a control unit 19 inside thereof for controlling all portions and elements of the sheet cleaning apparatus 1, i.e., the sheet feed portion 3, the swelling tank 4, the sheet conveying mechanism 7, the washing mechanism 10, the sheet drying portion 11 and so on.
The sheet feed portion 3 is provided with a tray 20 as a stacker in which a number of printed sheets 2 are contained. The tray 20 is biased upward by springs 21 so that the uppermost sheet 2 comes into contact with a feed roller 22 disposed above the sheet feed portion 3. Upon rotation of the feed roller 22, the sheet 2 can be fed on a guide plate 24 through a sheet feed opening 23 formed on the side wall of the apparatus.
There is disposed a photoelectric sensor 25 as a sheet quantity detector above the tray 20 so that the number of the sheet 2 set on the tray 20 can be detected and the detected result can be outputted to the control unit 19. Alternatively, the number of sheet 2 may be detected by weighing the sheets 2.
At the downstream end of the guide plate 24 in a sheet conveying direction, there are disposed a pair of conveyer rollers 26 and guide plates 27 so that the sheet 2 fed on the guide plate 24 is sent to the guide plates 27 by the pair of conveyer rollers 26. The guide plates 27 are slanted so that the downstream ends of them in the sheet conveying direction are positioned above a tray 5 provided in the swelling tank 4 so that the sheet 2 passing through the guide plates 27 is received in the tray 5. The tray 5 has a size possible to receive fifty sheets 2 in a stacked condition.
The sheet conveying mechanism 7 comprises a sheet pressing portion 29 positioned above the tray 5 and a conveyor roller 31 which comes into contact with the sheet 2 contained in the tray 5 through an opening 30 formed on the bottom of the tray 5.
The sheet pressing portion 29 comprises, as shown in Fig. 2, a press roller 32 for pressing the uppermost sheet 2 contained on the tray 5 and a cam mechanism 33 to have the press roller 32 advance and retreat with respect to the tray 5. The cam mechanism 28 comprises a guide 36 for supporting the press roller 32, a plate cam 38 which is possible to rotate in a condition that it comes into contact with the guide 36 so as to press down the guide 36 and a spring 37 for biasing the press roller 32 against the plate cam 38.
The sheet pressing portion 29 is so constructed that the press roller 32 presses the uppermost sheet 2 to delivery the bottommost sheet 2, upon rotation of the conveyor roller 31 in a direction of arrow 34, to the print material removing portion 8 through an outlet opening 40 formed on the side wall of the tray 5. The outlet opening 40 is necessary to have a height for one sheet 2 to pass therethrough because the print material removing portion 8 has to treat the sheet 2 one by one. In the embodiment, however, the outlet opening 40 has a height substantially corresponding to the thickness of two sheets 2 in order to prevent paper jam in the outlet opening 40.
The print material removing portion 8 includes a pair of brush rollers 41. Each brush roller 41 comprises hair-like members set in a shaft in a density of 400/cm². Each hair-like member is made of nylon and has a diameter of 0.1 mm and a length of 8 mm. The shaft has a diameter of 14 mm. The distance between the shafts of the brush rollers 41 is set to 24.2 mm. The brush rollers 41 are rotatable in the same direction (arrow 44) as the rotational direction (arrow 34) of the conveyor roller 31 so that when passing through between the brush rollers 41 the print material on both surfaces of the sheet 2 is removed by the hair-like members, while the sheet 2 is given a conveyance force.
At the downstream side of the print material removing portion 8 in the sheet conveying direction, there are disposed a pair of conveyer rollers 42 and a guide 43 in order to discharge the sheet 2 of which print material is removed by the brush rollers 41 from the swelling tank 4.
The swelling tank 4 is provided with a swelling liquid heating heater 47 with a temperature sensor built-in so that the swelling liquid 6 contained in the swelling tank 4 and added with surfactant can be heated in a predetermined temperature. The swelling liquid recovery tank 13 is disposed beneath the swelling tank 4 and has a size enable to recover the swelling liquid 6 contained in the swelling tank 4. The top plate of the swelling liquid recovery tank 13 and the bottom plate of the swelling tank 4 are connected each other via recovery pipe 48. In the middle portion of the recovery pipe 48 is fitted an electromagnetic valve 49 having a built-in filter so that the swelling liquid 6 contained in the swelling tank 4 is filtrated and recovered to the recovery tank 13.
To the side wall of the swelling tank 4 is connected a replenishment pipe 50 the end of which is inserted into the inside of the recovery tank 13 just above the bottom thereof. To the end of the replenishment pipe 50 is connected a pump 51 for forcing the swelling liquid 6 recovered in the recovery tank 13 to the swelling tank 4. Above the swelling tank 4 is disposed an photoelectric sensor 52 as a liquid quantity sensor so that the liquid surface of the swelling liquid contained in the swelling tank 4 can be detected.
At the end of the guide 43, there are disposed a pair of conveyor rollers 56 for conveying the sheet 2 discharged along the guide 43 toward a cleaning mechanism 10. The cleaning mechanism 10 comprises a guide 57 disposed at the downstream side of the conveyor rollers 56 in the sheet conveying direction, a swelling liquid recovery mechanism 58 disposed under the guide 57 and a spray nozzle 59 disposed above the guide 57.
The swelling liquid recovery mechanism 58 comprises a funnel 60 disposed beneath the guide 57 and a recovery tank 62 containing cleaning liquid (water) 61. The funnel 60 is connected to a recovery pipe 64 having a filter 63. The end of the recovery pipe 64 is inserted into the recovery tank 62 through the upper opening thereof. The spray nozzle 59 is connected to a feed pipe 66. To the end of the feed pipe 66 is fixed a pump 65 which is inserted into the recovery tank 62 so that the cleaning liquid 61 sucked by the pump 62 is sprayed by the spray nozzle 59 to the sheet 2 moving on the guide 57.
At the downstream side of the spray nozzle 59 in the sheet conveying direction, there are disposed a pair of squeezing rollers 67 for pressing the sheet 2 passing therethrough to squeeze the liquid contained in the sheet 2. At the downstream side of the squeezing rollers 67 in the sheet conveying direction are disposed a sheet drying portion 11 and a guide 69. The sheet drying portion 11 comprises a pair of drying rollers 70 with built-in heater for heating the sheet 2 passing therethrough to discharge it on the discharge tray 12 through the guide 69.
Method for using the sheet cleaning apparatus 1 having above construction will be described hereinafter with reference to the flowchart as shown in Figs. 3 and 4.
The sheet cleaning apparatus 1 has a function (automatic cleaning process) for automatically starting and stopping the cleaning process and a function (manual or forced cleaning process) for enabling to conduct the cleaning process irrespective of the number of the sheets 2 set on the sheet feed portion 3.
Firstly, the automatic cleaning process will be described. By the user who desires to conduct the automatic cleaning process, the power switch 16 is operated to activate the sheet cleaning apparatus 1 (Step S1). Then, the automatic cleaning process switch 17 is ON (Step S2). The number of the sheets 2 contained in the sheet feed portion 3 is detected to confirm that the sheets 2 more than predetermined number are set (Step S3). If YES, the controller 19 starts the warming-up of sheet cleaning. That is, the pump 51 is driven to transfer the swelling liquid 6 to the swelling tank 4 from the swelling liquid recovery tank 13 (Step 4). The predetermined number of the sheets 2 in the present embodiment is 50.
When the photoelectric sensor 52 detects that the predetermined quantity of the swelling liquid 6 is contained in the swelling tank 4, the swelling liquid heating heater 47 is energized to heat the swelling liquid 6. The heater built-in the heating roller 70 is also energized (Step S5). When the swelling liquid 6 and the heating roller 70 are maintained in predetermined temperatures respectively (Step S6), the cleaning process is started (Step S7). The operation of the cleaning process will be explained in detail hereinafter.
Then, it is decided whether or not the sheets in the sheet feed portion 3 is empty (Step S8). If YES, each portion of the apparatus is OFF and held as it is for a predetermined time (Step S9). The predetermined time may be set as such a time that the sheet 2 fed finally can pass through each portion of the apparatus or that a series of cleaning processes are completed. The predetermined time may also be such a time, for example, 10 min., 30 min. and 1 hour that is decided considering sheet receiving condition, time required for starting the apparatus and energy. The predetermined time may be set by the user.
After the predetermined time has passed, it is decided again whether or not the sheet is not contained in the sheet feed portion 3 (Step S10). When it is confirmed that the sheets is not contained in the sheet feed portion 3, the controller 19 conducts final process of sheet cleaning. That is, the power supply to both the swelling liquid heating heater 47 and the heating roller 70 is shutoff to stop the heating (Step S11).
Consequently, the electromagnetic valve 49 is operated to discharge the swelling liquid 6 contained in the swelling tank 4 to the swelling liquid recovery tank 13 (Step S13). When the swelling liquid 6 is recovered to the swelling liquid recovery tank 13 (Step S13), the power switch 16 is operated to shutoff the power (Step S11).
As described above, when the photoelectric sensor 25 detects the predetermined quantity of the sheets 2, the warming-up of sheet cleaning is started. Therefore, it is not necessary to frequently switching the sheet cleaning apparatus between the energizing condition and the non-energizing condition, enabling to save electric power.
Because the swelling liquid 6 is recovered when stopping the sheet cleaning process, the swelling liquid 6 is prevented from decrease due to vaporization. Therefore, it is not necessary to frequently replenish the swelling liquid 6, allowing the maintenance of the sheet cleaning apparatus 1 to become easy. Even if the sheet cleaning apparatus 1 falls down due to an accident, the swelling liquid is prevented from leaking, reducing the cleaning of the sheet cleaning apparatus 1 itself and the environment around the sheet cleaning apparatus 1.
Next, the manual cleaning process will be described. If the automatic cleaning process switch 17 is not ON at step S2 and the manual cleaning process switch 18 is ON at step S12, then the manual sheet cleaning process is started irrespectively of the number of the sheets 2 set on the sheet feed portion 3. Consequently, the same operation as in the automatic sheet cleaning process is conducted. Thus, in the manual sheet cleaning process, it is possible to conduct the sheet cleaning process when the prompt cleaning is desired.
When the manual sheet cleaning process switch 18 is OFF, it is also possible to stop newly feeding the sheets and finish the sheet cleaning process of the sheets under the cleaning and then forcedly stop the cleaning apparatus.
Next, operation in the sheet cleaning process by the sheet cleaning apparatus 1 will be explained.
In the sheet cleaning apparatus 1, the sheets 2 contained in the tray 20 of the sheet feed portion 3 are fed to the tray 5 one by one by the rotation of the feed roller 17 to stack them on the tray 5.
At this time, by rotating the plate cam 38 of the sheet pressing portion 29 to move the press roller 32 upward, a gap possible to stack the predetermined number of the sheets 2 is formed between the press roller 32 and the bottom of the tray 5. When a predetermined time elapses after the predetermined number of the sheets 2 are received in the tray 5, the plate cam 38 is rotated to move the press roller 32 downward, thereby the whole of the stacked sheets 2 is pressed in a predetermined pressure.
With reference to Figs. 2 and 5, operation of delivering the sheets 2 contained in the tray 5 to the print material removing portion 8 will be described hereinafter. The bottommost sheet 2 among the sheets pressed by the press roller 32 comes into contact with the conveyor roller 31 through the opening 30. Rotation of the conveyor roller 31 in the direction of arrow 34 creates a conveyance force in a direction of arrow 76, causing the bottommost sheet 2 to move and pass through the outlet opening 40.
Since the outlet opening 40 has a height substantially corresponding to the thickness of two sheets 2 as described above, a second sheet 2 from bottom which is superimposed on the bottommost sheet 2 (hereinafter, former is referred to as a sheet 2a, while later is referred to as a sheet 2b) is conveyed through the outlet opening 40 in a overlaid condition on the bottommost sheet 2a. Thus, the sheets 2a and 2b are delivered to between the pair of brush rollers 41.
When the sheet 2a is conveyed out of the tray 5, by rotating the plate cam 38 of the sheet pressing portion 29 to move the press roller 32 upward, a gap is formed between the press roller 32 and the uppermost sheet 2 for allowing the sheet 2 to enter therebetween. Subsequently, the sheet 2 is fed on the uppermost sheet 2 in the tray 5 from the sheet feed portion 3. Thus, the sheet 2 is fed to the tray 5 from the sheet feed portion 3 every time when the sheet 2 is discharged from the tray 5, which makes the swelling of sheet 2 efficient, vanishing the swelling time superficially.
Thus, the sheet 2 discharged from the outlet opening 40 passes through the pair of rotating brush rollers 41, whereby the print material of the sheet 2 is removed. Then, the sheet 2 is conveyed to the conveyor rollers 42 and discharged from the swelling tank 4 through the guide 43. The conveyor rollers 42 can be interchanged with the brush rollers 41 so that the conveyor rollers 42 apply a conveyance force in the direction of arrow 78 that the sheet 2 is drawn back to the tray 5 to the sheet 2b.
The sheet 2 discharged from the swelling tank 4 is conveyed to the cleaning mechanism 10 by the conveyance rollers 56. The print material adhering to the sheet 2 is washed away on the guide 57 by the cleaning liquid 61 jetted from the nozzle 59. Subsequently, the sheet 2 passes through the pair of squeezing rollers 67 to squeeze the water from the sheet 2. The cleaning liquid 56 used to clean the sheet 2 and squeezed from the sheet 2 flow into the funnel 60, wherein the print material in the cleaning liquid 61 is captured. Then, the cleaning liquid is recovered into the recovery tank 62.
The sheet 2 with the print material removed and with the water squeezed is heated and dried by passing through the pair of drying rollers 70 in the sheet drying portion 11 and then discharged to the discharge tray 12.
The sheet cleaning apparatus to which the present invention is applied is not limited to the cleaning apparatus 1 which cleans the sheet 2 on which surface the swelling layer is formed. The present invention can be applied to any kind of sheet cleaning apparatus for removing the print material from the sheet, for example, sheet cleaning apparatus which removes the print material with the use of solvent.
Although the present invention has been fully described by way of the examples with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the spirit and scope of the present invention, they should be construed as being included therein.

Claims

A sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets, a stacker on which the printed sheets are set and a sheet feeder for feeding the printed sheets set on the stacker to the sheet cleaner, characterized in that the apparatus further comprises:

a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and

a controller for starting warming-up of sheet cleaning when the sheet quantity detector detects a predetermined quantity or more of the printed sheets.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the controller activates the sheet feeder to feed the printed sheets from the stacker to the sheet cleaner after completion of the warming-up of sheet cleaning.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the sheet quantity detector detects the number of the printed sheets.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the sheet quantity detector detects the weight of the printed sheets.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the sheet cleaner includes:

a swelling tank for containing swelling liquid at the operating time of the sheet cleaner; and

a swelling liquid recovery tank for recovering the swelling liquid from the swelling tank at the non-operating time of the sheet cleaner, and wherein the warming-up of sheet cleaning is transferring the swelling liquid stored in the swelling liquid recovery tank to the swelling tank.
The sheet cleaning apparatus as claimed in Claim 5, characterized in that the sheet cleaner further includes:

a liquid quantity sensor for detecting the quantity of the swelling liquid in the swelling tank; and

a heater for heating the swelling liquid contained in the swelling tank, and wherein the heater starts heating the swelling liquid after the liquid quantity sensor detects a predetermined quantity of the swelling liquid transferred from the swelling liquid recovery tank.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the apparatus further comprises:

a drier for drying the sheets after sheet cleaning; wherein the warming-up of sheet cleaning is starting operation of the drier.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the apparatus further comprises:

a manual start switch for forcedly starting the cleaning process, wherein, when the manual start switch is ON, the controller starts the warming-up of sheet cleaning irrespectively of the quantity of printed sheets detected by the sheet quantity detector.
The sheet cleaning apparatus as claimed in Claim 8, characterized in that the controller activates the sheet feeder to feed the printed sheets from the stacker to the sheet cleaner after completion of the warming-up of sheet cleaning.
The sheet cleaning apparatus as claimed in Claim 8, characterized in that, when the manual start switch is OFF, the controller stops feeding the printed sheets to the cleaner by the sheet feeder irrespectively of the quantity of printed sheets detected by the sheet quantity detector and then conducts final process of sheet cleaning after completion of cleaning process of the printed sheet that have been fed at the time of stop of feeding.
The sheet cleaning apparatus as claimed in Claim 1, characterized in that the sheet cleaner immerses the printed sheet into swelling liquid to swell the swelling layer formed on the printed sheet and removes the print material by applying blush roller to the printed sheet.
A sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets and a sheet feeder for feeding the printed sheets set on a stacker to the sheet cleaner, characterized in that the apparatus further comprises:

a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and

a controller for conducting final process of sheet cleaning when a predetermined time has passed after the sheet quantity detector detects no printed sheet.
The sheet cleaning apparatus as claimed in Claim 12, characterized in that the sheet cleaner includes:

a swelling tank for containing swelling liquid at the operating time of the sheet cleaner; and

a swelling liquid recovery tank for recovering the swelling liquid from the swelling tank at the non-operating time of the sheet cleaner, and wherein the final process of sheet cleaning is transferring the swelling liquid contained in the swelling tank to the swelling liquid recovery tank.
The sheet cleaning apparatus as claimed in Claim 13, characterized in that the sheet cleaner includes:

a heater for heating the swelling liquid contained in the swelling tank, wherein the final process of sheet cleaning is stopping heating the swelling tank contained in the swelling tank by the heater.
The sheet cleaning apparatus as claimed in Claim 13, characterized in that the sheet cleaner further includes:

a filter disposed in a transferring route between the swelling tank and the swelling liquid recovery tank, the filter filtrates the swelling liquid at the time of transferring the swelling liquid.
The sheet cleaning apparatus as claimed in Claim 12, characterized in that the apparatus further comprises:

a drier for drying the sheets after sheet cleaning; wherein the final process of sheet cleaning is stopping operation of the drier.
The sheet cleaning apparatus as claimed in Claim 12, characterized in that the predetermined time is a time required to finish the cleaning process of one of the printed sheets.
The sheet cleaning apparatus as claimed in Claim 12, characterized in that the predetermined time can be set by user.
A sheet cleaning apparatus, the apparatus comprising a sheet cleaner for removing print material from printed sheets and a sheet feeder for feeding the printed sheets set on a stacker to the sheet cleaner, characterized in that the apparatus further comprises:

a sheet quantity detector for detecting the quantity of the printed sheets set on the stacker; and

a controller for prohibiting operation of the sheet cleaner when the sheet quantity detector detects a predetermined quantity or less of the printed sheets.