The present invention generally relates to a cleaning device for a transfer type electrostatic copying apparatus, and more particularly, to a cleaning device which cleans off developing material remaining on a photosensitive material or photoreceptor by a magnetic brush.
Conventionally, in the known cleaning device of the above described type in which the cleaning is effected by the use of magnetic brush, as described in EP-Al-1413, since the developing material remaining on the photoreceptor is strongly attracted onto the surface of said photoreceptor, it is difficult to remove such developing material by the magnetic brush as it is, and therefore, it has been practice to effect an operation to weaken the adhesion of the developing material by a charge erasing lamp and the like before the cleaning by the magnetic brush. However, the conventional arrangement as described above has such a disadvantage that, since the portions to be erased for charge are located behind the remaining developing material, the cleaning efficiency has been undesirably low.
Accordingly, it is a primary object of the present invention to provide a cleaning device for use in an electrostatic copying apparatus in which cleaning efficiency by the magnetic brush has been improved by solving the technical problems as described above.
It is another object of the invention to provide a cleaning device which is arranged to feed the developing material removed by the magnetic brush positively into a developing material receptacle container.
According to the invention there is provided a cleaning device for transfer type electrostatic copying apparatus which comprises magnetic brush cleaning means for cleaning off a magnetic toner remaining from the photosensitive receptor surface (3) of a rotatable photosensitive drum after transfer, the bristle length of the magnetic brush being restricted by means of a restricting member, and a developing material receptacle for receiving toner removed from the photosensitive receptor surface of the rotatable drum; characterized in that the cleaning device comprises a brush roller disposed upstream of the direction of rotation of the drum with respect to the magnetic brush cleaning means and downstream with respect to an image transfer zone, the brush roller having a construction that the brush is provided on a peripheral surface of a cylindrical member made of material which transmits light except for light having wavelength adversely affecting the photosensitive material of the drum; being driven for rotation in the opposite direction to the direction of rotation (5) of the photosensitive drum (4) at such a rotational speed that possible damage to the surface of the photosensitive material, or scattering of the remaining developing material is prevented and being in contact with the photosensitive material; a charge eraser lamp secured within the cylindrical member; a rotary shaft disposed upstream of the direction of rotation of the magnetic brush with respect to the restricting member, the shaft being driven to rotate about an axial line parallel with the axis of rotation of the magnetic brush; transporting means of non-magnetic material secured to the rotary shaft at a right angle, for transporting developing material prevented from passage by the retricting member by movement due to rotation of the rotary shaft; the developing material receptacle being arranged to receive the developing material falling from the transporting means when the transporting means rotates downwardly, the receptacle having an opening facing upwardly on the opposite side of the magnetic brush with respect to the rotary shaft; and a passage formed between the magnetic brush cleaning means and the developing material receptacle.
According to the foregoing arrangement, since the developing material remaining on the photosensitive material or photoreceptor is positively deviated or shifted by the hair brush roller before the cleaning process by the magnetic brush, while the portions from which the developing material has been removed by the shifting are subjected to the light projection by the charge eraser lamp for erasing the charge thereat, the photoreceptor is almost completely erased with respect to the charge, and consequently, the cleaning efficiency is markedly improved owing to the facilitated removal of the developing material through cleaning by the magnetic brush. The direction of rotation of the brush- roller is opposite to the direction of rotation of the photosensitive drum in order to ensure that any toner particles loosened from the drum completely will tend to be released upwardly towards the magnetic cleaning brush and the collection means for the toner rather than being flicked downwardly generally to dirty the lower part of the interior of the copying machine with consequent contamination of copy papers.
Preferably there is further provided a switching means for alternating a switching mode in accordance with the weight of the developing material stored in a developing material receptacle when the weight has reached a predetermined value. Since there is provided the switching means whose state of switching is altered by the weight of developing material when the developing material accumulated in the developing material receptacle container has reached a preliminarily set weight, it is readily detected that the developing material receptacle container has been filled up by the developing material, and overflowing of the developing material from the developing material receptacle container may be advantageously prevented.
A detailed description of the invention will be made with reference to the accompanying drawings for a better understanding of the invention. In the drawings:
Referring now to the drawings, there is shown in Fig. 1 a schematic side sectional view of a transfer type electrostatic copying machine according to one preferred embodiment of the invention. The copying apparatus of Fig. 1 includes a photosensitive or photoreceptor drum 4 having a photosensitive material or photoreceptor 3 provided on the entire peripheral surface of a drum 2, and rotatably mounted at approximately a central portion of a machine housing 1. Around the photoreceptor drum 4, there are sequentially disposed, along the rotational direction indicated by the arrow 5, a charging corona discharger 6 for preliminarily charging the photoreceptor 3, a developing device 7 for visualizing an electrostatic latent image formed on the photoreceptor 3 into a visible toner image, a transfer corona discharger 8 for transferring the toner image thus formed on the photoreceptor 3 onto a copy paper sheet, and a cleaning device 9 for cleaning off the toner remaining on the photoreceptor 3 after the transfer process.
Above the photoreceptor drum 4, there is provided an exposure device 10 for projecting light- wise image of an original to be copied (not shown) onto the photoreceptor 3 in a position between the charging corona discharger 6 and the developing device 7 as shown by the dotted arrows. At the upper portion of the machine housing 1, an original carrier 11 is provided on which the original to be copied is horizontally placed for reciprocating movement as indicated by the arrows. In the exposure device 10, a light projecting means 12 for projecting light onto the original through the original carrier 11, further includes an exposure lamp 13, a reflector plate 14a and an auxiliary reflector plate 14b. The light projected towards the original placed on the original carrier 11 is focussed onto the photoreceptor 3 through a single focal point lens 15 to form the image of the original thereon, and thus, the electrostatic latent image is formed on the photoreceptor 3.
Along a copy paper transport passage 16 shown by the dotted line, the copy paper sheets stacked and accommodated in a paper feeding cassette 17 are fed, one sheet by one sheet, by a paper feeding roller 18 from the paper feeding cassette 17. The copy paper sheets are transported by a pair of feeding and transporting rollers 21 and 22 through upper and lower guide plates 19 and 20 in pair. The copy paper sheet fed into a transfer region 25 through another pair of upper and lower guide plates 23 and 24 is caused to closely adhere to the surface of the photoreceptor drum 4 confronting the transfer corona charger 8. After the transfer process, the copy paper sheet is held, at its one edge in the direction of width thereof, between a separating roller 26 and an auxiliary separating roller 27 so as to be peeled off the surface of the photoreceptor drum 4, and is fed into a heat fixing device 31 having a pair of heat fixing rollers 29 and 30 through a guide plate 28. In this heat fixing device 31, the toner image on the surface of the copy paper sheet is fixed. After the fixing process as described above, the copy paper sheet is discharged onto a copy paper tray (not shown) through pair of discharging rollers 32 and 33.
Referring also to Fig. 2 showing a schematic side sectional view of the copying machine of Fig. 1 as viewed from the reverse side thereof for illustrating its driving system, to an output shaft 35 of a motor 34, there is secured a sprocket wheel 36, around which a first endless chain 37 is directed or passed. The chain 37 is sequentially passed around a sprocket wheel 38, a sprocket wheel 39 coupled to the feeding and transporting roller 22 and a sprocket wheel 40 connected to the copy paper feeding roller 18 along its running direction indicated by the arrow. Meanwhile, around another sprocket wheel (not shown) secured to the output shaft 35 so as to be one unit with the sprocket wheel 36, a second endless chain 41 is passed. The chain 41 is sequentially passed around sprocket wheels 42 and 43, two sprocket wheels 44 and 45 for driving the original carrier 11, and sprocket wheels 46 and 47 along its running direction indicated by the arrow. The gear (not shown) to be rotated as one unit with the sprocket wheel 43 is engaged with a gear 48 connected to the heat fixing roller 29. The sprocket wheel 44 is connected to a gear 49 through a clutch which is not shown, while the sprocket wheel 45 is coupled to a gear 50 and a pulley 51 through a clutch which is not shown, with the gears 49 and 50 being in mesh with each other. A wire 160 connected, at its one end, to the right side end of the original carrier 11 in Fig. 2 is further passed around a pulley 51 from a pulley 161, and again around the pulley 161 so as to be connected at its other end, to the left side end of the original carrier 11 in Fig. 2. By the changeover of a clutch (not shown), the pulley 51 is subjected to forward or reverse rotation, according to which the original carrier 11 is reciprocated in the directions shown by the arrows. By the functions of the two clutches as described above, when the original carrier 11 is driven by the driving force from the sprocket wheel 44, said original carrier 11 is caused to run at a comparatively high speed, while when the original carrier 11 is driven by the driving force from the sprocket wheel 45, it is caused to move at a comparatively low speed.
A gear 52 mounted on the same shaft as the sprocket wheel 46 is connected to a gear 57 through gears 53, 54, 55 and 56. The gear 56 is secured to a rotary shaft 58 of the cleaning device 9, while the gear 57 is concentrically fixed to a sleeve 120 of the cleaning device 9. A gear 60 to be rotated as one unit with the sprocket wheel 47 is connected through a gear 61 to a gear 62 which is coupled to a cylindrical member 128 of the cleaning device 9. Meanwhile, the gear 60 is connected to a gear 64 associated with the separating roller 26 through a gear 63. Furthermore, the gear 60 is connected to a gear 65 which is integral with the photoreceptor drum 4, while the gear 65 is engaged with a gear 69 through gears 66, 67 and 68, with the gear 69 being connected to a developing sleeve 71 of the developing device 7.
Reference is made to Fig. 3 showing, on an enlarged scale, a cross sectional view in the vicinity of the cleaning device 9. The cleaning device 9 generally includes a magnetic brush cleaning means 122 having a permanent magnet member 121 fixedly provided within a hollow sleeve 120 of non-magnetizable material which is driven for rotation, a restricting member 123 for restricting the bristle length of the magnetic brush to be formed on the peripheral surface of the sleeve 120, a toner receptacle 124 for receiving therein the toner removed by the magnetic brush cleaning means 122, a feed-in means 125 for forcibly feeding the remaining toner restricted by the restricting member 123 into the toner receptacle 124, a hair brush roller 126 provided at the upstream side of the magnetic brush cleaning means 122 along the rotational direction of the photoreceptor drum 4, and a charge eraser lamp 127 provided within the hair brush roller 126.
Referring further to Fig. 4 showing part of the arrangement in the vicinity of the hair brush roller 126 as viewed from the cross section taken along the line IX-IX of Fig. 3, the hair brush roller 126 is composed of a cylindrical member 128 of light transmitting material, for example, glass or the like, and a large number of brush bristles or brush hairs 129 of flexible material, for example, acrylic resin filled on the outer peripheral surface of said cylindrical member 128, and is disposed in a parallel relation with respect to the axis of the photoreceptor drum 4. As shown in Fig. 5, the brush bristles 129 are filled on the outer peripheral surface of the cylindrical member 128 in a spiral configuration at a predetermined width d, with light transmitting portions 131 being formed between the neighboring bristle-filled portions 130 as shown. The length of the brush bristles 129 is so determined as to contact the peripheral surface of the photoreceptor drum 4 by a length 6 from the free end of said bristles (Fig. 3). The length 6 should suitably be in the region from 1 to 5 mm.
The opposite ends of the cylindrical member 128 are journalled by side plates 133 of a frame 132 of the cleaning device 9 through corresponding plain bearings 134. Within the cylindrical member 128, a charge eraser lamp 127 having a length longer than said cylindrical member 128 is coaxially extended, while the opposite ends of the charge eraser lamp 127 are secured by supporting means (not shown). To the one end of the cylindrical member 128, there is secured the earlier described gear 62, which is engaged with the gear 60 mounted on the same shaft as the sprocket wheel 47 through the gear 61. By the driving force transmitted from the sprocket wheel 47, the cylindrical member 128 is driven for rotation in the direction of the arrow 135 in Fig. 8. The speed of rotation of the hair brush roller 126 is so selected that the peripheral speed at the portion contacting the surface of the photoreceptor drum 4 becomes larger by 0 to 500 m/H, and more preferably, by 100 to 300 m/H, than the peripheral speed of the photoreceptor drum 4. By selecting the rotational speed of the hair brush roller 126 as described above, possible damage to the surface of the photoreceptor 3 by the sliding contact of the hair brush roller 126 with the photoreceptor drum 4 or undesirable scattering of the mono-component magnetizable toner over the photoreceptor 3 may be advantageously prevented.
Furthermore, by rotating the hair brush roller 126 at the peripheral speed difference as described earlier, the position of the mono-component magnetizable toner remaining on the photoreceptor 3 is deviated or shifted in the circumferential direction by the hair brush roller 126, whereby, upon projection of light of the charge eraser lamp 127 onto the surface of the photoreceptor 3 through the light transmitting portions 131, the light is directed onto the portion of the photoreceptor 3 where the mono-component magnetizable toner is absent through the displacement, and the portion is erased for charge, and thus, the cleaning by the magnetic brush cleaning means 122 at the downstream side with respect to the hair brush roller 126 along the rotational direction 5 of the photoreceptor drum 4 is effectively carried out.
It is to be noted here that by filling flexible and electrically conductive fine carbon fibers on the outer peripheral surface of the cylindrical member 128, triboelectrical charging due to sliding contact between the hair brush 129 and photoreceptor 3 may be prevented. Meanwhile, it may be so arranged that a material capable of cutting off light having wavelength adversely affecting the photoreceptor 3 is employed for the cylindrical member 128, whereby the cylindrical member 128 may also serve as a filter of the charge eraser lamp 127.
In the foregoing embodiment, since the hair brush 129 is spirally filled on the cylindrical member 128, the amount of light projection by the charge eraser lamp 127 onto the photoreceptor 3 may be properly determined by suitably setting the intervals of the light transmitting portions 131, number of revolutions of the hair brush roller 126, and contact length 6 of the hair brush roller 126 with respect to the photoreceptor 3.
Reference is also made to Fig. 6 showing a simplified cross section taken along the line XI-XI in Fig. 3, the magnetic brush cleaning means 122 is disposed at a position close to the photoreceptor 3 in a relation parallel to the axis of the photoreceptor drum 4. One end of the permanent magnet member 121 extending through one end of the sleeve 120 through a bearing 140, is secured to a support member 141 fixed to the side plate 133. Meanwhile, to the other end of the sleeve 120 which extends through the side plate 133 via a bearing 142, the gear 57 is fixed. The other end of the permanent magnet member 121 is supported by the sleeve 120 through a bearing 143. The permanent magnet member 121 is magnetized by a magnetic pole equally spaced in the circumferential direction, with the neighboring magnetic poles directed to have alternately opposite polar orientation.
As described earlier with reference to Fig. 2, the power is transmitted to the gear 57, whereby the sleeve 120 is rotated in the direction indicated by the arrow 144. (Refer to Fig. 3.) Accordingly, the magnetic brush having the predetermined bristle length is formed by the restricting member 123 so as to be in contact with the photoreceptor drum 4. As a result, the mono-component magnetizable toner remaining on the photoreceptor 3 is attracted onto the sleeve 120 through the magnetic attracting force of the permanent magnet member 121, and thus, removed from the surface of the photoreceptor 3.
As was also explained with reference to Fig. 4 and 10, the toner remaining on the photoreceptor 3 is displaced over the peripheral surface of the photoreceptor 3 through action of the hair brush roller 126, while the entire peripheral surface of the photoreceptor 3 has been erased for charge, since the light from the charge eraser lamp 127 is projected thereonto through the light transmitting portions 131. Therefore, in the magnetic brush cleaning means 122, the toner on the photoreceptor 3 is readily attracted onto the sleeve 120, with a further improvement of the cleaning efficiency by the magnetic brush cleaning means 122.
Referring back to Fig. 3, in the magnetic brush cleaning means 122, at the side remote from the photoreceptor drum 4, the restricting member 123 is fixed to the frame 132 in a position close to the peripheral surface of the sleeve 120. By this restricting member 123, the bristle length of the magnetic brush on the sleeve 120 is restricted, while the feed-in means 125 is provided for feeding the surplus toner thus restricted into the toner receptacle 124. Still with reference to the magnetic brush cleaning means 122, at the side remote from the photoreceptor drum 4 and at a position lower than that of the magnetic brush cleaning means 122, the toner receptacle 124 open at its upper portion is provided, and between the magnetic brush cleaning means 122 and the toner receptacle 124, there is formed a passage 145 for feeding-in the toner. The toner feed-in means 125 is provided at the upstream side with respect to the restricting member 123 along the rotational direction 144 of the sleeve 120 at an opening 145a of the passage 145 at the side of the cleaning means 122. The feed-in means 125 includes the rotary shaft 58 supported, at opposite ends thereof, by the corresponding side plates 133 through bearings 147, and a toner transport member 148 of non-magnetizable material provided as one unit with the rotary shaft 58. To the rotary shaft 58, the gear 56 is fixedly mounted, and by the driving force to be transmitted to the gear 56, the rotary shaft 58 is rotated in the direction indicated by the arrow 149. (Refer to Fig. 3.) The toner transport member 148 is arranged to extend in a relation parallel to the rotary shaft 58, with opposite ends thereof pressed at right angles, into the rotary shaft 58 for being secured thereat. The rotational direction 149 of the rotary shaft 58 is selected to be opposite to that of the sleeve 120, whereby the surplus mono-component magnetizable toner restricted by the restricting member 123 is transported by the toner transport member 148 so as to be positively brought into the passage 145. The mono-component magnetizable toner thus fed into the passage 145 falls in the passage 145 by its own weight and fed into the toner receptacle 124.
Still referring to Fig. 3, the toner receptacle 124 is placed on a microswitch 150 as a switching means, which is set to be rendered conductive when the mono-component toner to be accommodated in the toner receptacle 124 reaches a predetermined weight. The microswitch 150 as described above is connected to a toner collection indicating means such as a pilot lamp or the like, and is arranged to illuminate the pilot lamp when the weight of the mono-component magnetizable toner within the toner receptacle 124 has reached a predetermined level. Accordingly, it is readily detected that the toner receptacle 124 has been filled with the mono-component magnetizable toner.
Referring to Fig. 7, there is shown a top plane view of a modified hair brush roller 151 according to the present invention, by which the hair brush roller 126 in the embodiment of Figs. 1 to 6 may be replaced. As shown in the modified hair brush roller 151 of Fig. 7, the hair brush roller may be formed by filling the hair brush 129 on the peripheral surface of the cylindrical member 128 in a lattice-like pattern.
Reference is further made to Fig. 8 showing a cross section of the arrangement for the toner receptacle according to a still further embodiment of the present invention. As shown in the arrangement of Fig. 8, the toner receptacle 124 may be so arranged as to be placed on the frame 132 through a spring 152 so that, when the spring 152 is compressed by the weight of the mono-component magnetizable toner accumulated within the toner receptacle 124 and the amount of the mono-component magnetizable toner has reached a predetermined value, the microswitch 150 is rendered to be conductive, by which arrangement the detection weight can be adjusted by the adjustment of the spring force of the spring 152.