US3759220A

US3759220A - Cleaning device in electrophotography

Info

Publication number: US3759220A
Application number: US00194956A
Authority: US
Inventors: T Saito; T Iida
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1970-11-04
Filing date: 1971-11-02
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18
Also published as: NL7118127A

Abstract

A cleaning device for an electrophotographic copying apparatus comprising a photosensitive medium having liquid collection grooves formed at the opposite end portions thereof, and a cleaning blade of resilient material having an edge adapted to bear against the surface of the photosensitive medium. The cleaning blade has projections formed at the opposite ends thereof so that when the blade is brought to its cleaning position, the inner side walls of the projections thereof may keep liquid-tight contact with the inner side walls of the liquid collection grooves. Thus, relative sliding movement between the blade and the photosensitive medium removes any amount of developing liquid remaining of the surface of the photosensitive medium after an image transfer has been completed.

Description

Saito et al.

Nov. 4, 1970 CLEANING DEVICE IN ELECTROPIIOTOGRAPIIY Inventors: Takashi Saito; Toshihide Iida,

both of Tokyo, Japan Assignee: Can on Kabushiki Kaisha, Tokyo,

Japan Filed: Nov. 2, 1971 Appl. No.: 194,956

Foreign Application Priority Data Japan 45/109363 l U.S. Cl 118/261, 117/37 LE, 118/102, 118/104, 1l8/DlG. 23 Int.,Cl..;.. 603g 13/00 Field'oi Search 117/37 LE; 118/100,

118/102, 104, 203, 261, 637, DIG. 23; 355/10, 15

1 References Cited UNITED STATES PATENTS 6/1968 Farrell 118/104 7/1952 Govan 198/1 Sept. 18, 1973 2,889,758 6/1959 Bolton 355/15 X 3,667,428 6/1972 Smith 118/637 3,368,566 2/1968 Matsumoto et al 1 18/637 3,552,850 1/1971 Royka et a1 355/15 Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Attorney-Joseph M. Fitzpatrick et al.

[57] ABSTRACT A cleaning device for an electrophotographic copying apparatus comprising a photosensitive medium having liquid collection grooves formed at the opposite end portions thereof, and a cleaning blade of resilient material having an edge adapted to bear against the surface of the photosensitive medium. The cleaning blade has projections formed at the opposite ends thereof so that when the blade is brought to its cleaning position, the inner side walls of the projections thereof may keep liquid-tight contact with the inner side walls of the liquid collection grooves. Thus, relative sliding movement between the blade and the photosensitive medium removes any amount of developing liquid remaining of the surface of the photosensitive medium after an image transfer has been completed.

4 Claims, 9 Drawing Figures I CLEANING DEVICE IN ELECTROPIIOTOGRAIIIY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in a cleaning device for a photosensitive medium used with an electrophotographic copying apparatus of the liquid development and transfer type, and more particularly to a cleaning device using a cleaning blade to wipe a photosensitive medium to thereby collect and remove any amount of residual developing liquid from the surface of the photosensitive medium.

2. Description of the Prior Art In the electrophotographic copying apparatus of the liquid development and transfer type, the surface of a photosensitive medium is wiped by a cleaning blade after image transfer, to gather the residual developing liquid near the blade, and then the developing liquid flows laterally along the cleaning blade and down along the periphery of the photosensitive medium at the opposite ends thereof or along grooves formed at such portions of the medium until it is collected for reuse.

The cleaning system of this type has often encountered a serious problem that part of the developing liquid collected near the opposite ends of the cleaning blade may flow around these ends and leak to the surface area of the photosensitive medium which is located behindthe cleaning blade. If a subsequent electrophotographic process proceeds with such leaking liquid still left on the surface of the photosensitive medium, no sufficient cleaning effect could be attained and stains or blots would be formed in the next image reproduction. In addition, the insulating characteristic of the surface of the photosensitive medium would be seriously reduced to attenuate electric charge and destroy the electrostatic latent image on the surface of the photosensitive medium, thus adversely affecting the resulting image formation.

SUMMARY OF THE INVENTION An object of the present invention'is to eliminate the above-described troubles by employing a cleaning blade of resilient material formed with projections at the opposite ends thereof, and a photosensitive medium formed with liquid collection grooves adjacent to the opposite ends thereof. The cleaning blade is installed in such a manner that the projections are received in the liquid collection grooves of the photosensitive medium with the inner side walls of the projections kept in close or liquid-tight contact with the inner side walls of the grooves. By doing so, any amount of developing liquid remaining on the photosensitive medium may be interrupted by the cleaning blade and directed to flow toward the opposite ends of the photosensitive medium, whereafter the liquid may flow along the projections of the blade and further along the grooves on the photosensitive medium for collection.

In the cleaning process as described above, the residual developing liquid on the photosensitive medium after image transfer may sometimes be solidified due to a low content of carrier liquid therein. Also, some of the developing liquid may remain unremoved in or adjacent to the area of contact between the photosensitive medium and the cleaning blade and solidfy due to evaporation of the carrier liquid when the copying apparatus is not in operation. Such solidified developer, i.e., solidified toner, which intervenes between the blade and the photosensitive medium, tends to injure the surface of the photosensitive medium once a subsequent copying cycle is entered. This tendency is is especially conspicuous at the beginning of the daily use of the copying apparatus.

It is therefore another object of the present invention to solve such a particular problem by designing the cleaning device so that except during a cleaning cycle the cleaning blade is retracted into contact with a body of carrier liquid so as to be kept wet with such liquid, thereby preventing the solidification of the developer and/or fixer sticking to the blade, and that the blade is moved again into contact with the photosensitive medium when a cleaning cycle starts. Means for retracting the cleaning blade away from the surface of the photosensitive medium and maintaining it wet with the carrier liquid may be of two alternative types, i.e., horizon tal movement type and rotational movement type.

The above and other features of the present invention will become fully apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows an electrophotographic copying apparatus of the liquid development and transfer type in which the cleaning device of the present invention is incorporated.

FIG. 2 is a perspective view of an embodiment of the photosensitive medium according to the present invention with the conventional cleaning blade applied thereto.

FIG. 3 shows an improved cleaning blade according to the present invention.

FIG. 4 is a perspective view of a photosensitive medium with the cleaning blade of FIG. 3 applied thereto.

FIG. 5 is a fragmentary perspective view showing another embodiment of the present invention.

FIGS. 6 and 7 are a cross-sectional view and a plan view, respectively, of an embodiment of the cleaning device in which the cleaning blade is rotatable to move into a carrier liquid reservoir.

FIGS. 8 and 9 show further embodiments of the present invention.

DESCRIPTIONOF THE PREFERRED EMBODIMENTS In order to eliminate the disadvantages described previously, the cleaning blade used with the copying apparatus as shown in FIG. 1 may preferably take the form as shown in FIG. 3, instead of the conventional form shown in FIG. 2. In FIG. 1, which shows a drum type electrophotographic copying machine including a drum type photosensitive medium 1 rotatable in the direction of arrow, primary charger 13, AC (or DC) corona discharger 14, light image exposure means 15, whole surface exposure means 17, liquid type developing means 116, post charger l8 and transfer means 21 and so on are arranged. In FIG. 1, the liquid type developing means 16 is shown, together with a blade type cleaning means 26. The developing liquid in a tank 12 may be utilized as cleaning liquid. When the main switch (not shown) is closed, a drive source 8 is energized to supply the developing liquid from the tank and centrifugal pump 11 or the like through distributor means 9 into a pipe terminating at a spray conduit 10, through which the developing liquid is applied to blade means 26 and to the surface of the photosensitive medium. The conventional blade means comprises a blade 24, as shown in FIG. 2. In this case, a part of the developing liquid collected near the opposite ends of the cleaning blade may flow around these ends and leak to the surface area of the photosensitive medium which is located behind the cleaning blade, which causes stains or blots in the next image reproduction. The cleaning blade 2 shown in FIG. 3 is formed of resilient material and has projections 2' formed at the opposite ends thereof. Where such a cleaning blade is to be used with a drum type photosensitive medium 1 as shown in FIG. 4, developing liquid collection grooves 3 are formed along the periphery of the drum adjacent to the opposite ends thereof and the cleaning blade 2 is mounted with its projections 2' received in the respective collection grooves 3. In this case, it is essential that the inner side wall of each projection 2' of the cleaning blade 2 shoud be in close contact with the inner side wall 4 of each collection groove 3. When the photosensitive drum 1 is rotated in the direction indicated by a curved arrow in FIG. 4, developing liquid flowing in the directions indicated by arrows 5 will be interrupted by the cleaning blade 2 and directed toward the opposite ends of the photosensitive drum 1 so that the liquid will further flow along the projections 2 of the blade 2 and into' the grooves 3 for collection, as indicated by arrows FIG. 5 shows an alternative form of the cleaning blade according to the present invention. As shown there, the cleaning blade 2 has no integral projection 2' but instead, employs separate guide members 7, only one of which is shown. The guide members 7 may be disposed at each end of the cleaning blade 2 in such a manner as to kee close contact with the surface of the blade 2 and with the inner side wall of the collection groove 3. With this arrangement, the developing liquid may be interrupted by the cleaning blade.2 and directed into the collection grooves 3 formed at the opposite ends of the photosensitive drum 1, whereby the developing liquid remaining on the surface of the photosensitive medium may be completely prevented from flowing past the blade to the surface area of the photosensitive medium which is located behind the cleaning blade.

FIGS. 6 and 7 show a device of the type in which the cleaning blade described above is maintained wet in a carrier liquid reservoir during the suspension of the cleaning operation. The cleaning blade used in this device is of the type which is rotatable to move between the photosensitive medium and the carrier liquid reservoir. In FIGS. 6 and 7, the photosensitive medium 1 is formed with developing liquid collection grooves 3 similar to those shown in FIGS. 4 and 5, and the blade 2 is formed of rubber such as NBR or the like having a high oil-resistivity. The blade 2 is supported by a blade holder 25 attached to a torque tube 28. The torque tube 28 is rotatably mounted on a shaft 30 which extends between and is secured to a frame 29. The torque tube 28 carries a pulley 31 at one end thereof. A spiral spring 32 is provided between the shaft 30 and the pulley 31 to bias the pulley 31, torque tube 28 and blade 2 in clockwise direction and thereby hold the blade 2 in the position as shown by imaginary lines in FIG. 6.

A wetting means, generally designated by numeral 33, is provided to prevent the blade 2 from drying up. The wetting means comprises a reservoir 35 filled with a body of developer carrier liquid 34 such as kerosene and a supply tank 36 for supplying such liquid to maintain the liquid in the reservoir 35 at a constant level. The supply tank 36 is interchangeable and may be of the chicken feed type. The reservoir 35 is formed with an opening 37 through which the blade 2 may pass into the carrier liquid 34 in the reservoir 35. Although not shown, a cover responsive to the movement of the blade 2 may be provided to close the opening 37 during a cleaning cycle. A motor 38 is provided to drive the torque tube 28 and blade 2 via belt 39 and pulley 31. The motor may start in response to the closing of an unshown power switch of the copying apparatus and stop in response to a signal from an unshown microswitch.

There are further provided electromagnets 40 which may be energized upon closing of the power switch of the copying apparatus to attract members 41 attached to the torque tube 28 when the blade 2 is brought to its cleaning position.

In operation, the power switch (not shown) of the copying apparatus is first closed to start the motor 38 and energize the electromagnets 40 at the same time. The motor 38 drives the belt 39 and pulley 31 to rotate the torque tube 28 and blade 2 counter-clockwise about the shaft 30 against the force of the spiral spring 32 so that the free end of the blade 2 comes out of the carrier liquid 34 in the wetting means 33 to approach the surface of the photosensitive medium 1. Thereupon, the energized electromagnets 40 attract the members 41 of the torque tube 28 so that the free end of the blade 2 resiliently bears against the surface of the photosensitive medium 1 to assume its cleaning position (FIGS. 6 and 7). Thereupon, the microswitch is opened to stop the motor 38 and wind up the spiral spring 32. When the power switch of the copying apparatus is opened after completion of a copying operation, the electromagnets 40 are deenergized to allow the blade 2 to be rotated clockwise by the return force of the spiral spring 32 until brought back to the opening 37 of the wetting means 33 and dipped in the carrier liquid therein. Thereupon, the microswitch is closed to enable the motor 38 to be energized at the initiation of the next copying cycle (see broken-line position in FIG. 6).

FIG. 8 shows another form of the mechanism for moving the cleaning blade in response to the closing of the power switch of the copying apparatus. As shown, a slide switch 42 and a pulley 43 are connected by a wire 44. From a pulley 45 mounted on a shaft common with the pulley 43, via a pulley 46 to a pulley 47, there extends a further wire 48. The pulley 47 is securely mounted on the torque tube 28 having the plate holder 25 attached thereto. With this arrangement, displacement of the switch 42 in the direction of arrow ON" may be utilized to rotate the blade 2 in the counterclockwise direction so as to assume its cleaning position for applying a predetermined cleaning pressure to the surface of the photosensitive medium with the aid of the return force of a spring (not shown) provided between the shaft 30 and the torque tube 28. Thereafter, upon completion of a copying cycle, the switch 42 may be moved in the direction of arrow OFF" to return the blade 2 into the wetting means 33, whereafter the blade 2 may be maintained in that position as by clip means (not shown).

Instead of the slide switch, use may be made of any lever switch which can provide an amount of displacement. Also, means'for moving the blade 2 is not limited to the shown pulley-wire system but the principle of lever motion may be utilized for the same purpose.

FIG. 9 shows a further embodiment of the cleaning device in which the cleaning blade 2 is adapted for horizontal movement. Upon completion of a copying cycle, the blade 2 may be moved horizontally from its cleaning position (solid-line position) to a scraper plate 50 for removing material 49 such as toner, fixer, etc., sticking to the free end of the blade 2. Thereafter, the blade 2 may rest on a pad 51 which is impregnated with carrier liquid 34, whereby the blade may be maintained wet with such liquid. The reservoir 35 of the wetting means 33 has a carrier liquid supply port 52. Although the mechanism for accomplishing the described horizontal movement of the blade 2 is not shown, such mechanism may be provided as by connecting the blade holder 25 through a rack-pinioq system to a drive source which is operable in a manner similar to the motor 38 shown in FIGS. 6 and 7.

Thus, according to the present invention, the cleaning blade is in contact with the surface of the photosensitive medium only during a cleaning cycle and, after completion of a copying cycle, the blade is separated from the surface of the photosensitive medium and maintained in wet condition so that any amount of toner and/or fixer sticking to the blade and existing between the blade and the surface of the photosensitive medium may be prevented from solidifying to injure the blade and/or the photosensitive medium during a subsequent operation.

We claim:

1. A cleaning device for an electrophotographic apparatus including a photosensitive medium, comprising means defining liquid collection grooves at the opposite end portions of said photosensitive medium, and a cleaning blade of resilient material having an edge adapted to bear against the photosensitive medium, said cleaning blade having projections formed at the opposite ends thereof so that the inner side walls of said projections may keep liquid-tight contact with the inner side walls of said liquid collection grooves, whereby relative sliding movement between said blade and said photosensitive medium removes any amount of developing liquid remaining on said photosensitive medium after an image transfer has been done,

2 A cleaning device as defined in claim 1, wherein said projections of said cleaning blade comprise guide members attached to the blade.

3. A cleaning device as defined in claim ll, further comprising means for moving said cleaning blade from the surface of said photosensitive medium into a carrier liquid reservoir to maintain said blade in wet condition during the suspension of cleaning operation.

4. A cleaning device as defined in claim 1, further comprising means for orienting said cleaning blade in a counter direction with respect to the direction of movement of said photosensitive medium.

Claims

1. A cleaning device for an electrophotographic apparatus including a photosensitive medium, comprising means defining liquid collection grooves at the opposite end portions of said photosensitive medium, and a cleaning blade of resilient material having an edge adapted to bear against the photosensitive medium, said cleaning blade having projections formed at the opposite ends thereof so that the inner side walls of said projections may keep liquid-tight contact with the inner side walls of said liquid collection grooves, whereby relative sliding movement between said blade and said photosensitive medium removes any amount of developing liquid remaining on said photosensitive medium after an image transfer has been done. CM,2Aning device as defined in claim 1, wherein said projections of said cleaning blade comprise guide members attached to the blade.

3. A cleaning device as defined in claim 1, further comprising means for moving said cleaning blade from the surface of said photosensitive medium into a carrier liquid reservoir to maintain said blade in wet condition during the suspension of cleaning operation.