FR2630227A1 - Cleaning device for image forming apparatus - Google Patents

Abstract

The invention relates to a cleaning device 30 placed near a sensitised drum 11 on which a latent electrostatic image corresponding to the image of a document is formed. The cleaning device comprises a cleaning blade 43 intended to be placed in contact with the sensitised drum or to be removed therefrom. When a predetermined number of copying operations have been carried out, or alternatively when the electricity supply is turned on, the cleaning blade is brought into contact with the drum, then the drum rotates in the direction opposite to that for forming the image, so that the toner and the paper dust adhering to the cleaning blade can be removed.

Description

The present invention relates to an image forming apparatus having a cleaning device which places a blade in contact with a sensitized drum and removes it from it and, more specifically, it relates to improvements in
The blade and drum cleaning operation.

 In conventional copying machines, an original is exposed and scanned so as to form an electrostatic image, corresponding to the image of the original, on a sensitized drum.

The electrostatic image on the sensitized drum is then developed into an image of an inking agent, or toner, which is transferred to a copy paper and is melted, so that an image corresponding to the image of the original is formed on paper.

 After the toner image has been transferred to the copy paper, residual foreign matter, such as toner and paper dust, is removed from the drum by scraping with a cleaning device; in preparation for the next electrostatic image to be formed on the drum.

 More specifically, the cleaning device is provided with a cleaning blade and is placed near the drum, the blade being brought into contact with the surface of the drum rotating in a certain direction in order to scrape off the residual toner from the drum and paper dust adhering to it after transferring the toner image to the copy paper.

 When the copy operation ends and the sensitized drum stops rotating, the drum cleaning blade must be removed to prevent the drum from being deformed.

Then, the drum is rotated, by a predetermined angle, in the opposite direction, so that when the blade is brought back into contact with the drum, it makes contact with a part of the drum which has been previously cleaned. . This ensures that the drum is properly cleaned and prevents the formation of unwanted images on the drum.

 In this type of cleaning device, in which paper is used, the fibers of which are liable to be damaged, paper dust produced in the paper feed section and in the paper transport section sticks to the drum and is transported to the cleaning device.

This foreign material, which is paper dust, will also be removed from the drum by scraping using the cleaning blade together with the residual toner, in the normal state, as above indicated. However, a part of the paper dust can adhere strongly to the end of the blade and not be removed from it. A gap will then form between the drum and the blade, which will result in faulty cleaning and the formation of unwanted images.

 To solve this kind of problem, measures can be taken to reduce the friction of the paper in the paper feeding section and the paper transport section of a copying machine, but this cannot be achieved from sufficiently complete. Another possibility is to provide the copying machine with a device specialized in removing paper dust. In this case, the copying machine becomes of a complex and expensive structure.

 It is therefore an object of the invention to provide an image forming apparatus having a cleaning device provided with a contacting and removal function of the slide, which ensures appropriate and complete cleaning of the means. image transport, which prevents unwanted images from forming.

 The object of the invention is achieved using a cleaning device for an image forming apparatus comprising: means for transporting an image; means for driving the means of transport in a certain direction; means for applying a development agent to the image carried by the transport means, to form a developed image; means for transferring the developed image to a copy medium; means for removing residues from the conveyance, the removal means being adapted to be in contact with or removed from the surface of the conveyor; and means for causing the drive means to move the transport means in the opposite direction at a predetermined time, the removal means being in contact with the transport means.

 According to the invention, while the image transport means is being driven in the first direction by the drive means, the removal means is brought into contact with the image transport means . Then, by driving the image transport means in the opposite direction while the removal means is in contact with the latter, paper dust and the like which adhere to the removal means are scraped off by means of the friction force created by the mutual contact of the removal means and the image transport means. In this way, the paper dust which adheres to the removal means can be removed without the need to provide a removal device; particular, which ensures the formation of good images.

-The following description, designed to illustrate
The invention aims to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which:
- Figure 1 is a simplified diagram of a copying machine provided with a cleaning device constituting an embodiment of the invention;
- Figure 2 is a cross-sectional view of the cleaning device of Figure 1;
- Figure 3 is a block diagram of a control circuit used in the copying machine of Figure 1;
- Figure 4 is a flow chart for explaining the operation of the control circuit of the figure;
- Figure 5 is a block diagram of another control device which can be used in place of that of Figure 3;
- Figure 6 is a flow chart for explaining the operation of the control circuit of Figure 5;
- Figure 7 is a flow chart for explaining the operation of the control circuits of Figures 3 and 5 at the time of switching on the electric power source; and
- Figures 8 and 9 are diagrams used to explain the operation of the cleaning device.

 As can be seen in Figure 1, a copying machine 1 has, at its upper part, a document tray 2 consisting of a transparent glass plate on which a document to be copied must be placed. An optical system 3 is arranged below the document-holding tray 2 and comprises an exposure lamp 4, mirrors 5, 6 and 7, a block 8 of magnification change lenses and a fixed mirror 9. The lamp d exposure 4 and the mirrors 5, 6 and 7 are driven so as to move along the document holder plate 2 in the directions indicated by the arrows. The film placed on the document tray 2 is exposed and scanned by the exposure lamp 4, so that an image is formed on the surface of a sensitized drum 11.

 The sensitized drum 11 rotates in the direction indicated by the arrow and is first charged by an electrostatic charging device 12. Next, the image of the document is exposed by a slit using the optical system 3, so that an electrostatic latent image is formed on the surface of the drum 11. The latent image is developed (toner is attracted to the image) by a developing unit 13, so that the latent image is made visible, then it is discharged by a charge removal lamp 14 before being transferred to copy paper.

 The copying machine also has an upper paper supply cassette 15 and a lower paper supply cassette 16, both of which can be removed. You can choose one or the other cassette via a control panel placed on the top of the copying machine, and each contains a transfer paper P. Advance cylinders 17 and 18 are placed in the immediate vicinity of the upper cassette 15 and the lower cassette 16, in order to advance the transfer paper P at the rate of one sheet at a time. The paper P is transported to a matching cylinder 21, via a paper guide section 19 or 20, then advances, under the action of a cylinder 21, in a transfer section 22. The paper P which has been brought into the transfer section 22 comes into contact with the surface of the drum II at a transfer charging device 23, and a toner image, which is formed on the drum, is transferred to the paper P. The paper carrying the transferred toner image is then separated from the drum II by a separation loading device 24, and is conveyed to a fixing device 26 by a conveyor belt 25, where the toner image is fixed to the paper P. Finally, the paper P carrying on it the fixed image is transported to an outlet 28 by paper discharge cylinders 27, then is evacuated hos from the copying machine, on an output tray 29 , which communicates with exit 28, and stacks there.

 After the image has been transferred, all that remains is to remove the residual toner carried by the sensitized drum 11 using the cleaning device 30, after which any residual image is erased using the lamp. load removal 31. In this way, the drum was returned to the initial state. The copying machine 1 is further provided with a control device 32 used to control the general operation of the machine.

 FIG. 2 shows the cleaning device 30 according to the invention. A container 40 has an opening 40A located opposite the sensitized drum 11, and it contains a cleaning blade 41 comprising a support 42 and a blade itself 43. An intermediate part of the support 42 is held by an axis of rotation 44, a - First end of the support 42 being fixed to a plunger 45A driven by a solenoid 45, and its other end being fixed to one end of the blade 43, which is formed for example of urethane. The length of the blade 43 is such that it covers the entire width of the drum 11, and it comes into contact with the surface of the drum 11 through the opening 40A of the container 40. The container 40 also contains a recovery blade 46 disposed in the vicinity of the blade 43, and the end of the blade 46 being in contact with the surface of the drum 11 permanently, in order to prevent that the toner which is removed from the drum 11 by scraping using of the blade 43 does not escape outside the container 40.

Depending on whether the solenoid 45 is activated or not, the blade 43 is brought into contact with the surface of the drum 11 or else, respectively, is removed from this surface. More specificaly; when solenoid 45 is activated, plunger 45A is pulled into
The solenoid 45, so that the support 42 rotates in the direction of arrow E so as to bring the anterior end of the blade 43 into contact with the drum 11. Conversely, when the solenoid 45 ceases to be activated, the plunger 45A is pulled out of the solenoid 45, so that the support 42 rotates in the direction of the arrow Fi so as to separate the blade 43 from the drum 11.

 FIG. 3 represents the general arrangement of the control device 32. In FIG. 3, only the parts necessary for the explanation of the embodiment are shown.

 A control section 50 is formed by a central processing unit (CPU) 50A comprising a microcomputer and a memory 508. The memory 50B contains the program necessary for the operation of the CPU 50A. The control section 50 reads information from various parts of the copy machine 1 and sends various instructions to its various parts.

 To the control section 50 is connected an excitation or driving device 51, which is itself connected to a pulse motor 52 serving to drive the drum 11. In response to an instruction from the control section 50, the drive device 51 excites the pulse motor 52 using a predetermined number of pulses so as to rotate the drum 11 in the positive direction or in the opposite direction to the positive direction, then it L 'stopped.

 Another control device 50 is connected to the control section 50, which is itself connected to the solenoid 45 for driving the cleaning blade 41.

In response to an instruction from the control section 50, the drive device 52 energizes the solenoid 50 so as to bring the blade 41 into contact with the drum II or to separate therefrom.

A control panel 50 is connected to the control section 50.
command 55 which has a copy key 55A used to provide a copy instruction, and a decimal keyboard 55B used to set the number of copies and designed to apply to the copy section
commands 50 the information necessary for the copy operation. For
count the number of copies fixed by the ten-key keyboard 55B, a copy counter 55 is connected to the control section 50.

In addition, to provide electrical power to the various parts of the control section 50 and the copying machine 1,
the power supply switch 57 is connected to the control section 50.

We will now describe the operation in relation to Figure 4. First, we place a document to copy on
the document holder tray 2, then the keyboard 55 is actuated to fix the number of copies. When, next, the copy key 55A is pressed, the control section 50 erases the content of the copy counter 51 during a step S1. Then the section of
control 50 provides the drive device 51 with a forward rotation instruction to rotate the sensitized drum 11 forward, i.e. in a positive direction
(in the direction of arrow A in FIG. 2) during Step 52. The drive device 51 responds to the instruction by exciting the pulse motor 52, so that the drum 11 rotates in the direction positive. Then, the control section 50 sends an instruction to the drive device 53 in order to bring the blade 43 of the cleaning device 30 into contact with
the drum 11, during step S3. As a result, the drive device 53 activates the solenoid 45 so as to rotate
The cleaning blade 41 in the direction of arrow E in FIG. 2.

The blade 43 is thus brought into contact with the drum 11.

In this situation, the copy operation begins to
step S4. Thus, the document placed on the document holder tray 2 is scanned by the optical system 3 and an electrostatic latent image corresponding to the document is formed on the drum 11, as described above. The latent image is developed. by the developing device 13 to form the toner image. The toner image is transferred to the paper P by the transfer section 22, then is fixed by the fixing device 26, to be finally discharged on the output tray 29.

 After the transfer of the toner image to the paper P, the residual toner and the paper dust on the drum 11 are removed by the blade 43 of the cleaning device 30, then the residual image is erased by the lamp 31 so as to return the copy machine to the initial state. A copy cycle is thus completed.

 Then, the content of the copy counter 56 is incremented by one in step S5, then a check is made to determine whether or not the content of the copy counter 56 has reached the number of copies which has been set at using the keyboard 55B of the panel 48, during step S6. Consequently, when the number of copies has not been reached, the flowchart returns to step e4 so as to repeat the above operation.

 If the number of copies has been reached in step S6, then the control section 50 applies a stop instruction to the drive device 51, in step S7. In response to this, the drive device 51 stops the pulse motor 52, so that the drum 11 stops.

 Then, the control section 50 delivers to the drive device 51 an instruction of rotation in the opposite direction, which rotates the drum 11 by a predetermined number of pulses in the opposite direction (the direction of the arrow B of the figure 2), during step S8. In response to this instruction, the drive device 51 rotates the pulse motor 52 in the opposite direction so that the drum 11 rotates by the predetermined number of pulses in the reverse direction. At this time, the paper dust which may have adhered to the end of the blade 43 falls therefrom under the effect of the friction exerted between the drum 11 and the blade 43. The control section 50 then delivers to the device drive 53 an instruction to separate the blade 43 from the drum 11, during step S10. The drive device 53 then deactivates the solenoid 43. Consequently, the cleaning blade 41 rotates in the direction of arrow F in FIG. 2, so that the blade 43 separates from the drum 11.

As described above, the toner and the paper dust adhering to the end of the blade 43 can therefore fall into the container 40 under the effect of the rotation of the drum 11 in the opposite direction while the blade 43 is in contact. with the drum 11 at a predetermined time, for example once ten copy cycles have been completed. Thus, since it is possible to remove foreign materials such as toner and paper dust adhering to the blade 43 by simple control of the drum 11 and the
Cam 43 makes it possible to safely clean the drum there and thus obtain clean copies.

 Figure 5 shows another general arrangement of the control device. In FIG. 5, the same reference numbers are used as in the figure. 3 to designate corresponding parts, and the description which will be given will relate to these different parts.

 In this other arrangement, a general counter 58 is connected to the control section 50. A reference number RN of copies is stored beforehand in the memory 508. The general counter 58 counts the number of copies according to an instruction from the control section 50.

 The operation of this other arrangement of the control device will now be described in relation to FIG. 6.

When the ten-key keyboard 558 of the control panel 55 is operated to set the desired number of copies and then the copy key 55A is pressed, the copy counter 56 is cleared during step Sîl and the drum 11 is rotated in the forward direction, in step S12. In this situation, the solenoid 45 is activated so as to rotate the cleaning blade 41 to bring the blade 43 into contact with the drum 11, in step S13. Then, the document is copied to the S14 stage and,
When a copy cycle has ended, the copy counter 56 and the general counter 58 are incremented. of a unit, in step S15.

After that, it is checked whether or not the number of copies entered using the keyboard 55B of the control panel 56 has been reached by the counter 56, in Step S16. If not, the copy operation starts again.

 On the other hand, when the value of the copy counter 56 has reached the set number of copies, it is then checked whether the reference number RN stored in the memory 50B has been reached by the general counter 58 or not. from step S17. As a result, when the reference number RN has not yet been reached, the drum 11 stops at step S18 and the blade 43 is separated from the drum 11, at step S19. The flowchart then goes to a final stage.

 When the reference number RN has been reached by the general counter 58, then the drum Il is stopped, in step S20.

After that, the drum 11 is rotated in opposite directions to a predetermined angle while the blade 43 is brought into contact with the drum 11, in step 521. Then, the total counter 58 is cleared, in step 522. The flowchart then proceeds to a final stage.

 This embodiment of the control device can offer the same advantages as the previous embodiment.

 We will now describe, in relation to FIG. 7, the operation carried out when the electrical supply is applied to the copying machine 1. In this case, this operation is common to the control device of FIGS. 3 and 5.

When the electric power switch 57 is closed so as to electrically supply the copying machine 1, an instruction is issued by the control section 50 to the drive device 53 so as to bring the blade 43 into contact with the drum 11, during step S31. The drive device 53 therefore activates the solenoid 43 in order to rotate the cleaning blade 41. As a result, the blade 43 is brought into contact with the drum 11. After that, the control section 50 supplies the drive device 51 an instruction to rotate in the opposite direction for the drum 11, during step S32. The drive device 51 rotates the pulse motor 52 in the opposite direction so that the drum It is rotated in the opposite direction. Then, the control section 50 provides the drive device 53 with an instruction to separate the cleaning blade 41 with respect to the drum 11, during the step
S33. The drive device 53 then deactivates the solenoid 43 so as to rotate the cleaning blade 41. Then, the blade 43 is separated from the drum 11 and the control section 50 goes into the ready state.

 According to the embodiment presented above, when the electrical power is supplied to your copying machine 1, the blade 43 is brought into contact with the drum 11 and the drum 11 rotates in opposite directions so that the drum 11 and the blade 43 are cleaned. Thus, even at the start of the copying operation, unwanted images due to the existence of residual toner can be prevented, so that clean images are formed.

 The number of pulses used to rotate the drum 11 in the opposite direction during steps S8, S21 and S32 can be fixed so as to allow reaching a point C of contact between the drum 11 and the blade 43 such that, when the drum 11 stops, it returns substantially halfway between the blade 43 and the recovery blade 46, as shown in FIG. 8. According to another possibility, the number of pulses used for the rotation in direction reverse of the drum, it can be fixed so as to bring the contact point C further than the recovery blade 46 in the direction of arrow B, as shown in FIG. 9.

In this case, foreign materials such as paper dust can be removed from the drum 11 by scraping with the aid of the recovery blade 46, which makes it possible to remove foreign materials more surely.

 The invention has been described in relation to a copying machine using a sensitized drum. According to another possibility, the invention can also be applied to a laser printer using a sensitized drum.

 Of course, those skilled in the art will be able to imagine, from the device whose description has just been given by way of simple illustration and in no way limitative. various variants and modifications not departing from the scope of the invention.

Claims (4)

 1. A cleaning device for an image forming apparatus comprising transport means (11) for transporting an image; drive means (51) for driving said transport means in a certain direction; training means (13) for applying a development agent to the image carried by said transport means to form a developed image; transfer means (23) for transferring the developed image to a copy medium; characterized in that it includes  means (41) for removing residues from said image transport means, said removal means (41) being adapted to be brought into contact with the surface of said image transport means (11) or to be separated from it; and  means (50) for causing said drive means (51) to move said transport means (11) in the opposite direction at a predetermined time, said removal means (41) being then contacted with said means transport.  2. Cleaning device according to claim 1, characterized in that said displacement means (50) comprises:  means (55B) for setting the number of transfers to be made by said transfer means (24); means (56) for counting the number of transfers made by said transfer means; and means (50) for controlling said drive means (51) to move said transport means (11) in the opposite direction while said removal means (41) has been brought into contact with said transport means when the counting value of said counting means reaches the number of transfers fixed by said fixing means.  3. Cleaning device according to claim 1, characterized in that said displacement means (50) comprises: means (50B) serving to store in advance the number of transfers that said transfer means must perform; means (58) for counting the number of transfers made by said transfer means; and means (50) for controlling said drive means to move said conveying means in the opposite direction while said removing means has been placed in contact with said conveying means when the count value of said counting means reaches the number of transfers stored in said storage means.  4. Cleaning device according to claim 1, characterized in that said displacement means (50) comprises: an electrical power switch (57) serving to supply The power supply to said means of movement; and means (50) for controlling said drive means to move said transportation means in the opposite direction while said removal means has been contacted with said transportation means when said power switch is turned on. in closed position