Corona generator cleaning apparatus

[57] ABSTRACT

An improved apparatus is provided for cleaning the discharge electrode or electrodes of a corona generating device. The apparatus includes a cleaning element which is adapted to traverse the operative length of the electrode. An edge of the cleaning element engages the electrode to provide an effective scraping action on the surface thereof to clean the debris such as dust particles and toner particles therefrom. Preferably, the element cocks in operation to provide a first edge for scraping the electrode when the element is traversed in a first direction and a second edge for scraping the electrode when the element is traversed in an opposing direction. Preferably, the cleaning element also includes means for cleaning the shield of the corona generator. An electrostatographic reproducing apparatus incorporating the aforenoted cleaning apparatus also forms part of the instant invention.

Claims, 8 Drawing Figures

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PATENTED oct 151974

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PATENTED Ki 15BM

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PATENTED OCT1 51374

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PATENTED OCT 151274

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CORONA GENERATOR CLEANING APPARATUS

BACKGROUND OF THE INVENTION

This invention relates to a corona generator cleaning apparatus and to an electrostatographic reproducing machine incorporating the cleaning apparatus.

Corona generating devices are employed for a variety of purposes in electrostatographic reproducing machines including, for example, charging of the electrostatic imaging plate; electrostatic transfer of a developed image to an image receiving member; removal of background toner particles from a developed electrostatic latent image; and cleaning of the electrostatic imaging plate by neutralizing the charge on residual toner particles.

One particularly useful type of cornoa generating device is described in detail in U.S. Pat. No. 2,836,725 issued to Vyverberg. This device is usually comprised of at least one corona discharge electrode or coronode wire which is partially surrounded by a conductive shield.

Although this corona generating device is adapted to provide a uniform electrostatic charge on the desired surface, dust particles, toner particles, or other debris accummulating on or about the coronode wire and shield can cause non-uniform generation of corona current along the length of the coronode wire and may reduce the magnitude of the corona current generated.

A variety of techniques have been devised to reduce or remove such contamination such as those set forth in U.S. Pat. Nos. 3,324,291, 3,339,069, 3,382,360, 2,471,965, 3,483,372, 3,496,352 and 3,499,143. One particularly useful approach for cleaning the electrodes has been to wipe the electrodes so as to remove dust and toner particle contamination. Examples of this approach are set forth in U.S. Pat. Nos. 2,614,901, 2,811,135 and IBM Technical Disclosure Bulletin, Vol. 8, No. 8, Jan. 1969, by Voit, Jr.

It is particularly desirable for a charging corona generator to deposit a uniform layer of electrostatic charges on the surface of the electrostatic imaging plate in order to provide high quality images. Contaminated coronode wires provide non-uniform corona generation along their length and, therefore, non-uniform charge deposition on the imaging plate.

The creation of a corona current is predominately determined by the potential difference between the coronode wire and the shield. Dust particles and toner particles which accumulate on the inner walls of the shield produce deleterious effects, particularly for a grounded metal shield. These particles are comprised of dielectric material which can store the charged ions communicated thereto from the coronode wire. As the charge builds up on these particles, a voltage is provided on the contaminated portion of the inner wall of the surrounding shield resulting in a non-uniform potential difference between the coronode wire and the shield with consequent variations in corona discharge along the length of the corona generator. This latter problem is particularly associated with corona generating devices employing a metallic shield. For corona generating devices employing a dielectric shield constructed, for example, of a plastic material such as Teflon or Mylar the accumulation of such particles on the shield has no appreciable effect on the corona generated current uniformity.

SUMMARY OF THE INVENTION

In accordance with this invention an improved apparatus is provided for cleaning the discharge electrode of a corona generating device. Contrary to the approaches of the prior art in accordance with this invention the cleaning is accomplished by scraping the discharge electrodes. The apparatus in accordance with this invention includes a cleaning element which is adapted to traverse the operative length of the electrode. An edge of this cleaning element engages the electrode to provide an effective scraping action on the surface of the electrode to clean debris such as dust particles and toner particles therefrom.

Preferably the element cocks in operation to provide a first edge for scraping the electrode when the element is traversed in a first direction and a second edge for scraping the electrode when the element is traversed in an opposing direction. Preferably the cleaning element also includes means for cleaning the shield of the corona generator.

The discharge electrode preferably comprises a coronode wire. Due to the cocking action of the cleaning element the coronode wire is normally deflected so that it is biased into contact with the scraping edge of the cleaning element. Therefore, the cleaning element preferably is disengaged from the wire in the home position to allow the wire to assume its proper undeflected position.

It is also preferred in accordance with this invention to provide a spring biased return means for returning the cleaning element to the home position. An electrostatographic reproducing apparatus incorporating the aforenoted cleaning apparatus also forms a part of the instant invention.

Accordingly, it is an object of this invention to provide an apparatus for cleaning the discharge electrode or electrodes of a corona generating device.

It is a further object of this invention to provide an apparatus as above which is effective to remove contaminants from discharge electrodes by a scraping action.

It is a further object of this invention to provide an apparatus as above further including means for cleaning the shield associated with the corona generating device.

It is a still further object of this invention to provide an electrostatographic reproducing machine incorporating the aforenoted corona generator cleaning apparatus.

These and other objects will become more apparent from the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically an electrostatographic reproducing machine in accordance with this invention.

FIG. 2 is a perspective view of a corona generator cleaning apparatus in accordance with this invention.

FIG. 3 is a partial cross-sectional view of the cleaning apparatus of this invention at the home position.

FIG. 4 is a partial cross-sectional view of the cleaning apparatus of this invention traversing in a first direction.

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FIG. 5 is a partial cross-sectional view of the cleaning apparatus of this invention traversing in an opposing direction.

FIG. 6 is a perspective view of an alternative embodiment of a cleaning apparatus in accordance with this invention.

FIG. 7 is a bottom view of the device of FIG. 6 showing the cocking action.

FIG. 8 is a front view of a cleaning member in accordance with a preferred embodiment of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 there is shown by way of example an electrostatographic reproducing machine 1 which incorporates the improved corona generator cleaning apparatus 2 of the present invention. The reproducing machine 1 depicted in FIG. 1 illustrates the various components utilized therein for xerographically producing copies from an original. Although the cleaning apparatus of the present invention is particularly well adapted for use in an automatic xerographic reproducing machine 1 it should become evident from the following description that it is equally well suited for use in a wide variety of electrostatographic systems and is not necessarily limited in its application to the particular embodiment shown herein.

The reproducing machine illustrated in FIG. 1 employs an image recording drum-like member 10, the outer periphery of which is coated with a suitable photoconductive material 11. One type of suitable photoconductive material is disclosed in U.S. Pat. No. 2,970,906, issued to Bixby in 1961. The drum 10 is suitably journaled for rotation within a machine frame (not shown) by means of a shaft 12 and rotates in the direction indicated by arrow 13, to bring the image retaining surface thereon past a plurality of xerographic processing stations. Suitable drive means (not shown) are provided to power and coordinate the motion of the various cooperating machine components whereby a faithful reproduction of the original input scene information is recorded upon a sheet 14 of final support material such as paper or the like.

The practice of xerography is well-known in the art, and is the subject of numerous patents and texts, including Electrophotography by Schaffert, published in 1965, and Xerography and Related Processes, by Dessauer and Clark, published in 1965. The various processing stations for producing a copy of an original are herein represented in FIG. 1 as blocks A to E. Initially the drum 10 moves photoconductive surface 11 through charging station A. In charging station A an electrostatic charge is placed uniformly over the photoconductive surface 11 of the drum 10 preparatory to imaging. The charging may be provided by corona generating device of a type described in U.S. Pat. No. 2,836,725, issued to Vyverberg in 1958.

Thereafter, the drum 10 is rotated to exposure station B where the charged photoconductive surface 11 is exposed to a light image of the original input scene information, whereby the charge is selectively dissipated in the light exposed regions to record the original input scene in the form of a latent electrostatic image. A suitable exposure system may be of the type described in U.S. Pat. application, Ser, No. 259,181, filed June 2, 1972, or U.S. Pat. No. 3,330,181 issued to

Jakobson in 1967. After exposure, drum 10 rotates the electrostatic latent image recorded on the photoconductive surface 11 to development station C wherein a conventional developer mix is applied to the photoconductive surface 11 of the drum 10 rendering the latent image visible. A suitable development station is disclosed in U.S. Pat. No. 3,707,947 issued to Reichart in 1973. The patent describes a magnetic brush development system utilizing a magnitizable developer mix having carrier granules and a toner colorent. The developer mix is continuously brought through a directional flux field to form a brush thereof. The electrostatic latent image recorded on photoconductive surface 11 is developed by bringing the brush of developer mix into contact therewith.

The developed image on the photoconductive surface 11 is then brought into contact with a sheet 14 of final support material within a transfer station D and the toner image is transferred from the photoconductive surace 11 to the contacting side of the final support sheet 14. The final support material may be paper, plastic, etc., as desired. After the toner image has been transferred to the sheet of final support material 14 the sheet with the image thereon is advanced to a suitable fuser 15 which coalesces the transferred powder image thereto. One type of suitable fuser is described in U.S. Pat. No. 2,701,765, issued to Codichini, et al. in 1955. After the fusing process the sheet 14 is advanced by rolls 16 to catch tray 17 for subsequent removal therefrom by the machine operator.

Although a preponderance of the toner powder is transferred to the final support material 14, invariably some residual toner remains on the photoconductive surface 11 after the transfer of toner powder image to the final support material 14. The residual toner particles remaining on the photoconductive surface 11 after the transfer operation are removed from the drum 10 as it moves through cleaning station E. Here the residual toner particles are first brought under the influence of a cleaning corona generating device 18 adapted to neutralize the electrostatic charge remaining on the toner particles. The neutralized toner particles are then mechanically cleaned from the photoconductive surface 11 by conventional means as, for example, the use of a resiliently biased knife blade as set forth in U.S. Pat. No. 3,660,863, issued to Gerbasi in 1972. It is preferred in accordance with this invention that the sheets of final support material 14 processed in the automatic xerographic reproducing machine will be stored in the machine within a removable paper cassette 19. A suitable paper cassette as set forth in U.S. Pat. application, Ser. No. 208,138 field Dec. 15, 1971.

The copier in accordance with this invention can also have the capability of accepting and processing copying sheets of varying lengths. The length of the copy sheet, of course, being dictated by the size of the original input scene information, recorded on the photoconductive surface 11. To this end the paper cassette 19 is preferably provided with an adjustable feature whereby sheets of varying length and width can be conveniently accommodated therein. In operation the cassette 19 is filled with a stack of final support material of preselected size and the cassette 19 is inserted into the machine in operable relationship with a pair of feed rolls 20. When properly positioned in communication with the feed rolls 20 the top most sheet 21 of the stack is

3,842,273 separated and forwarded from the stack into the transfer station D by means of registration rolls 22.

It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an automatic xerographic copier 1 which can embody the teachings of the present invention.

Referring now to FIG. 2 there is shown by way of example a specific embodiment of a corona generator cleaning apparatus 2 in accordance with this invention. The corona generator 30 shown in FIG. 2 comprises the charging corona generator A of the apparatus 1 of FIG. 1. The generator 30 comprises a partially surrounding shield 31 and a coronode wire 32. The coronode wire 32 acts as a corona discharge electrode. While only one discharge electrode is shown, the corona generator may have any desired number of electrodes. The shield 31 is formed of metal and is connected to ground potential. The coronode wire 32 is connected to a suitable source of high voltage (not shown) by means of wire 33. The wire 32 in the embodiment shown is stationary and is supported at both of its ends by means of clamps 34. The wire 32 is held taut between the clamps 34 so that it is uniformly positioned at a proper distance from the photoconductive surface 11. As previously noted, the environment in an electrostatographic reproducing machine is not sufficiently clean to maintain the shield 31 and coronode wire 32 free from contamination by dust particles, toner particles or other debris. In the embodiment shown, a slot 35 is provided in the back portion 36 of the shield 31 to provide for communication with a cleaning means 37. The cleaning means 37 is positioned within the shield 31 and about the coronode wire 32 so that it can be traversed along the operative length of the wire and shield. The cleaning means is operative to clean the coronode wire 32 and preferably also the shield 31.

The cleaning means 37 in accordance with this invention comprises a movable member 38 or cleaning element having a body portion 39 with a slot 40 therein so that the element may be fit about the coronode wire 32. Two legs 41 project outwardly from the body portion 39 in parallel alignment on either side of the slot 40. A carriage member 42 having a slot 43 therein adapted to pivotably receive the legs 41 of the element 38 is provided which is adapted to shuttle back and forth in substantial axial alignment with the coronode wire 32. The legs 41 of the cleaning element 38 are preferably pivotably secured within the slot 43 of the carriage member 42 by means of pin 44 so that the cleaning element may cock in one or the other directions of travel. The legs 41 of the cleaning element 38 protrude through the slot 35 in the back of the shield 31. The slot 35 is in axial alignment with the wire 32 and is operative to guide the cleaning element 38 along the wire.

The cleaning element 38 is driven to and fro along the wire 32 by means of a cable drive 50. In the embodiment shown, the cable drive 50 comprises a first cable portion 51 connected between a first tab 52 of the carriage member 42 and an automatic return means 53 via pulley 54. The return means 53 preferably comprises a spring loaded rewind mechanism of conventional design. A second cable portion 55 is provided which is connected via pulley 56 between a second tab 57 of the carriage member 42 and a means 58 for actuating the cleaning means 37. The actuation means 58 shown in FIG. 2 comprises a knob which permits the operator to manually pull on the cable 55 to thereby cause the cleaning means 37 to traverse the wire 32 and shield 31 in a first direction over the operative lengths thereof. Upon releasing the knob 58 the cleaning means 37 is caused to traverse the wire 32 and shield 31 in the opposing direction automatically by operation of the spring biased rewind mechanism 53. The length of the slot 35 governs the distance over which the cleaning means 37 may be traversed. The length which is employed is at least as great and preferably greater than the operative length of the wire 32 and shield 31. Operative length of the wire 32 and shield 31, as the term is used herein, refers to that portion of the length of the wire and shield which is operative to charge the desired surface such as photoconductive surface 11.

The cleaning element 38 shown in FIG. 2 includes a means 60 for cleaning the inside portion 61 of the shield 31. The cleaning means 60 preferably comprises brushes formed of any desired material and having any desired structure such as, for example, fiberous or foam-like. One particularly useful material is sold under the trademark Velcro by the Heartwell Corporation, 9035 Dennis Boulevard, Los Angeles, Calif. This material consists of loop-type fibers 62 as better shown in FIG. 8, which are formed of a material such as nylon. This type of brush 60 has proved to be highly effective since the fibers 62 have increased stiffness by virture of their looped nature.

The shield 31 as shown in FIG. 2 has a structure designed to provide improved strength in consideration of the slot 35 which is provided in it. The shield 31 preferably comprises a member of rectalinear cross-section having a channel defined by surface 61 of substantially hemospherical cross-section formed therein.

Referring now additionally to FIGS. 3 through 5, the operation of the cleaning apparatus 2 in accordance with this invention will be more clearly set forth. FIG. 3 shows the cleaning apparatus 2 in the home position H. The home position as the term is employed in accordance with this invention, comprises the starting position or rest position for the cleaning element 38 when it is not actuated. The home position of the shield 32 is provided with ramps 70 which contact the shoulders 71 (FIG. 8) of the cleaning element 38 to force the element out of engagement with the coronode wire 32. It is desirable to maintain the distance between the wire 32 and the photoreceptive surface 11 substantially constant along the length of the wire, and, therefore, when the cleaning apparatus 2 is not in use it should be disengaged from the wire so as to avoid any deflection thereof.

Upon pulling the knob 58 in FIG. 2, and the cable 55 associated therewith out from the machine, the carriage 42 and cleaning element 58 are caused to traverse the coronode wire 32 in a first direction as shown by arrow 80 in FIG. 4 toward the end of travel position 73 of the slot 35. Since the cleaning element 38 is pivoted in the carriage 42, it cocks away from the direction of travel during traverse so that at least one first edge 81 of the cleaning element is caused to engage the wire 32 and scrape its surface clean of any contaminants. The engagement provided in accordance with this invention is unique as compared to the prior art devices in that an edge of the cleaning member is caused to scrape rather than just wipe the wire to remove contaminants. Scraping is highly effective for cleaning the wire 32.

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Therefore, in the broadened Sense in accordance with this invention there is provided an effective cleaning apparatus 2 which comprises an element 38 having at least one edge 81 which is operative to scrape the wire 32 to remove contaminants therefrom.

The cleaning element 38 traverses the wire 32 until it reaches its end of travel position 73 which is near the end of the wire 32 and outside the operable zone of the wire. At this time the knob 58 is released and the cleaning element is caused to traverse the wire 32 in the opposing direction as shown by arrow 82 in FIG. 5 back towards the home position H under the action of the spring rewind mechanism 53. Upon changing directions the cleaning element 38 cocks longitudinally away from the direction of travel so that at least one second edge 83 is caused to engage the wire 32.

This is a particulary effective cleaning apparatus since one edge 81 of the cleaning element 38 scrapes the wire 32 during the initial traverse from the home position H to the end of travel position 73 and a different edge 83 is caused to scrape the wire during the return traverse to the home position. Therefore, any particles or contaminants accumulated on the first edge 81 during the initial traverse do not interfere with the further cleaning during the return traverse.

It is preferred in accordance with this invention in order to achieve the optimum cleaning action that the cleaning element 38 engage the wire 32 so as to deflect it and thereby be biased against it during the cleaning operation as shown in FIGS. 4 and 5.

Preferably the slot 40 width is selected to provide the best scraping action for the largest portion of the circumference of the wire 32. Therefore, the slot 40 size is selected such that the width of the slot is about the same as the diameter of the wire 32. Preferably the width of the slot is within about +0.000 inch and -0.005 inch of the diameter of the wire 32. The bottom of the slot 40 as shown in FIG. 8 preferably conforms to the shape of the wire 32 which in the embodiment shown is circular.

The rest position of the wire is shown as the dashed line R in FIGS. 4 and 5. The amount of deflection shown is exaggerated for purposes of illustration. The actual deflection of the wire would generally be less than about 0.060 inch and preferably less than about 0.025 inch.

While is is preferred to have the slot 40 width conform as closely as possible to the diameter of the wire 32, the slot width may be set as desired. The preferred slot 40 width provides for the optimum cleaning action for the greatest portion of the circumference of the wire. For some applications, however, it may be desirable to employ a larger slot 40 width and thereby only scrape clean that portion of the wire 32 which faces the surface being charged. The edges 81 and 83 are effective to clean this latter surface irrespective of the slot 40 width. This latter approach also would provide less wear on the wire due to cleaning. The preferred approach, however, provides the best cleaning, and, therefore, the most uniform charge distribution from the cleaned wire.

The shield cleaning means 60 is effective to wipe the shield 31 clean during both the initial traverse and the return traverse of the cleaning element 38.

Referring now to FIGS. 6 and 7 there is shown an alternative embodiment of this invention wherein the carriage 42' is connected to the cables 51 and 55 at points 52' and 57' spaced apart transverse to the direction of travel and the wire 32 axis such that the cleaning element 38 is caused to be cocked transverse to the direction of travel and the wire axis. This cocking action may be provided in place of the previously described action with reference to FIGS. 4 and 5 by rigidly mounting the cleaning element 38 to the carriage 42' or alternatively a combination of cocking actions both in the transverse and longitudinal directions with reference to the wire 32 axis and the direction of travel may be provided by allowing the cleaning element 38 to pivot in the carriage 42' as shown. The carriage 42' includes the slot 43' which is adapted to receive the legs 41 of the cleaning element 38. The legs 41 are pivotably secured within the slot 43' by means of the pin 44'. The corona generator 30 shown in FIG. 6 is a partial view of the one shown in FIG. 2 and the means 58 for actuating the cleaning means 37 and the means 53 for returning the cleaning means to its home position would be arranged substantially as set forth in FIG. 2.

Referring specifically to FIG. 7 the transverse cocking action of the cleaning element 38 of FIG. 6 is illustrated. By cocking the cleaning element 38 transverse to the axis of the wire 32 at least a first pair of edges 90 and 91 are caused to scrapingly engage the wire during its initial traverse. During its return traverse at least a second pair of edges 92 and 93 are urged into scraping engagement with the wire 32. As shown, the wire 32 is deflected laterally in different directions on the opposing sides 94 and 95 of the cleaning element 38. It should be recognized that this type of transverse cocking action would provide an effective cleaning action by providing more than one edge 90 and 91 or 92 and 93 to scrapingly engage the wire 32.

The combination of transverse and longitudinal cocking action would provide an improved cleaning action by virtue of the increased circumferential area of the wire 32 which would be scraped by the element 38. As with the previously discussed embodiment the cleaning means 37 also includes brushes 60 adapted to clean the shield 31. The advantages previously noted with respect to providing a first edge or edges for cleaning during the initial traverse and a different edge or edges for cleaning during the return traverse are also enjoyed by the embodiment of FIGS. 6 and 7.

Referring to FIG. 8 there is shown an alternative embodiment of the cleaning element 38 in accordance with this invention. In accordance with the embodiment of FIG. 8 the body 39 of the cleaning element 38 includes two slots 100 which serve to define two arms 101 for supporting the brushes 60 which is adapted to clean the shield 31. By making the outer periphery 102 of the brushes 60 on the cleaning element 38 larger than the inner periphery 61 of the shield 31, the arms 101 serve to act as cantilevers to increase the bias between the brushes and the shield and thereby provide improved cleaning of the shield 31.

Preferably, in accordance with this invention the cleaning element 38, the brushes 60, the carriage 42, the pin 44, the pulleys 54 and 56, and the cables 51 and 55 are all constructed of non-conductive materials such as, for example, nylon, which will not breakdown at the potentials employed for corona generation.

While the invention has been described with reference to the use of a corona generator 30 employing a single wire 32, it is equally applicable to a generator

3,842,273 employing a plurality of wires by merely providing a corresponding number of slots 40 in the cleaning element 38. For some applications a double corona generator is employed wherein the shield 31 includes two cavities 61 with at least one wire 31 in each of the cavities. It should be apparent that the cleaning apparatus 2 of this invention is equally applicable to such a double corona generator or other combination generators. For example, one could merely employ two cleaning elements 38 projecting through two slots 35, one in each of the generators with a carriage 42 designed to accept the arms 41 from each of the respective elements 38. Otherwise, the apparatus would be similar in all respects to that shown. The invention is applicable to corona generators in general and is not limited to charging generators.

The term scraping as employed in the present application refers to the removal of material from the surface of the discharge electrode by stroking with an edged element as described above. The material which forms the edge should preferably be relatively hard, as for example, have a hardness of about 80 Shore A durometer. The scraping action described herein is distinguishable from the wiping action of prior art devices since wiping comprises rubbing with a relatively soft material rather than stroking with a relatively hard edged element.

The patents, patent applications and texts specifically set forth in the detailed description are intended to be incorporated by reference into the description.

The term electrostatography as employed in the present application refers to the formation and utilization of electrostatic charge patterns for the purpose of recording and reproducing patterns in viewable form. Electrostatography specifically includes, while not being limited to, electrography wherein an insulating medium is employed to form without the aid of electromagnetic radiation latent electrostatic charge patterns for producing a viewable record and electrophotography which employs a photoresponsive medium to form with the aid of electromagnetic radiation, latent electrostatic charge patterns for producing a viewable record.

It is apparent that there has been provided in accordance with this invention an effective corona generator cleaning apparatus and an electrostatographic reproducing machine incorporating the same which fully satisfies the objects, means and advantages set forth hereinbefore. While the invention has been described in conjunction with specific embodiments therefor, it is evident that may alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.