Continuous Blade Cleaner

Abstract

An electrostatographic cleaning system for cleaning imaging material from the imaging surface by two cleaning edges of an endless belt which continuously moves transversely across the imaging surface. Providing a Mobius (one-half) twist in the belt, and appropriate supports, causes the two belt edges to continuously switch relative to the imaging surface. Cleaning and/or lubricating of the cleaning edges can be provided spaced from the imaging surface.

Description

This invention relates to electrostatographic imaging systems and, more particularly, to an improved translating blade cleaning apparatus for cleaning electrostatographic image developer material from an imaging surface.

The general development and cleaning of imaging materials on a re-usuable imaging surface in electrostatography is well-known. In xerography, for example, a latent electrostatic image is optically formed on a photoconductive imaging surface and developed by depositing on the latent image a charged finely divided dry electroscopic visible image developer material known in the art as toner. This toner image may then be electrostatically transferred and permanently fixed to a support surface such as paper. However, after such transfer, residual toner remains on the photoreceptor, which for re-use thereof must be removed by a cleaning operation at a cleaning station. This cleaning of residual toner from the photoreceptor must be accomplished rapidly and thoroughly yet without damage to the delicate photoreceptor, and the removed toner must be appropriately disposed of. The residual toner is tightly retained on the photoconductive surface and is difficult to remove. This retention is believed to be caused both by electrical charge attractions and by Van der Waals forces that prevent complete transfer of the toner to the support surface. Also, a small percentage of the toner can be wrongly charged, or uncharged, either initially or by virtue of the cleaning operation. Thus, cleaning of the imaging surface is one of the more difficult technical problems in practical xerography. Conventional photoreceptor cleaning devices are brush type cleaning apparatus, web type cleaning apparatus, or blade type cleaning apparatus.

Exemplary xerographic photoreceptor blade type dry toner cleaning apparatus is disclosed in U.S. Pat. Nos. 3,438,706, issued Apr. 15, 1969, to H. Tanaka et al; 3,552,850, issued Jan. 5, 1971, to S. F. Royka et al; 3,634,077, issued Jan. 11, 1972, to W. A. Sullivan; 3,660,863, issued May 9, 1972, to D. P. Gerbasi; 3,724,019, issued Apr. 3, 1973, to Alan L. Shanly; 3,724,020, issued Apr. 3, 1973, to Henry R. Till; and 3,740,789, issued June 26, 1973, to Raymond G. Ticknor. Pending applications include U.S. Applications Ser. No. 356,985, filed May 3, 1973, by Richard E. Smith and Ser. No. 356,986, filed May 3, 1973, by Christ S. Hasiotis. Toner cleaning systems with a reciprocally translating polyurethane cleaning blade are commercially embodied in the Xerox Corporation "4000" and "3100" xerographic copiers. The present invention represents a development in the above-cited technology, and accordingly these references are all hereby incorporated by reference in the present specification.

One problem in the use of cleaning blade systems for cleaning moving xerographic photoreceptor imaging surfaces of imaging material has been the tendency of blade edge sealing failures, such as localized truck-unders, to occur at points where the blade edge is being repeatedly struck at the same point by the same defects on the imaging surface being repeatedly rotated past the blade edge while the blade edge is stationary. Cyclic translation movement of the cleaning blade transverse the direction of the photoreceptor has been previously found to avoid most of these problems, especially if the translation continues after the imaging surface stops and a short dwell-time drive cam or eccentric multiple lobe drive cam is used. Lubrication of the imaging surface has been generally provided. U.S. Pat. Nos. 3,724,019, 3,724,020 and 3,740,789 cited above relate to such translation mechanisms. However, if reciprocal lateral translation during machine operation is used, there will be end dwell positions on the photoreceptor at which the blade stops to reverse in each translation cycle. Thus, in these dwell points the blade is not fully protected by translation from the above-described single point multiple impacts from the same defects on the photoreceptor. Also, as a practical matter, the usable length of a reciprocating cleaning blade edge is limited to the width of the imaging surface.

The present invention provides a solution to the above-described problems by a simple means allowing fully continuous blade translation relative to the photoreceptor, and substantially increased effective cleaning blade length without a corresponding increase in the cleaning system dimensions, thereby providing an increased effective lifetime for the blade. The present cleaning system also allows cleaning and/or lubricating of the blade cleaning edge at a convenient position spaced away from the photoreceptor.

Various doctor or cleaning blade structures are, of course, known in the non-electrostatographic arts. For example, U.S. Pat. No. 2,664,792, issued Jan. 5, 1954, to E. P. Cook discloses pealing paper from a roll by a steel doctor blade which is wound between reels spaced at each side of the roll, where it is also cleaned and lubricated. Canadian Pat. No. 562,364, issued Aug. 26, 1958, to Howard E. Roscoe teaches removing liquid from a film web with an endless metal band continuously moving transversely the web, guided by grooved supports. The band is supported by pulleys at each side of the web and cleaned by wipers.

Further features and advantages of the present invention pertain to the particular apparatus and functions whereby the above-mentioned aspects of the invention are attained. Accordingly, the invention will be better understood by reference to the following description and to the drawings forming a part thereof, which are substantially to scale, wherein:

FIG. 1 is a plan view of an exemplary embodiment of the present cleaning blade system; and

FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1.

Referring now to the drawings, FIGS. 1 and 2, there is shown therein an exemplary cleaning system 10 in accordance with the present invention for cleaning toner from the moving photoreceptive imaging surface 12 of a xerographic drum 14. The photoconductive surface 12 is cleaned by a contacting cleaning blade 16 extending transverse the direction of movement (rotation) of the imaging surface 12. It may be seen that the blade 16 is in the form of a flexible endless belt having two continuous opposite edges 18 and 20. Both of these edges are adapted to clean the imaging surface 12. However, only one edge at a time is held against and transversely moved across the imaging surface in cleaning engagement therewith.

The blade or belt 16 here contains a mobius twist in a portion of the belt which is spaced away from the imaging surface. That is, one flight of the blade 16 has a one-half turn twist. This has the effect of turning the belt over and thereby reversing the two blade edges 18 and 20 in each rotation or cycle of the endless blade 16. This provides an automatic reversal in each cycle of the belt movement of the edge of the blade which is in cleaning engagement with the imaging surface. The endless loop form of the belt 16 doubles the effective length of the cleaning blade edge relative to its overall length, and the reversal changes the edges as well.

The blade 16 is rotatably supported at its opposite ends by and between two identical cylindrical pulleys 22 and 24. Preferably the blade 16 is held in tension between these two pulleys. The blade 16 is also supported by an appropriate linear guide 26 in that portion of the belt which is in cleaning engagement with the imaging surface. The guide 26 here is an exemplary linear, continuous, sliding support channel in which the edge 20 of the belt (the outside edge of the blade 16) is slidably retained for proper cleaning engagement with the imaging surface. The inside of the channel 26 may, of course, be coated with any suitable lubricant material. Preferably the channel 26 also includes a structure for flexibly deforming the blade 16 against the imaging surface. This is illustrated in FIG. 2, where it may be seen that here there is an extending lip 28 of the channel 26 which continuously forcibly engages the rear central portion of the blade 16 to flexibly press the extending edge 18 of the blade against the imaging surface. The channel 26 and the pulleys 22 and 24 together maintain the lower flight of the blade 16 in a constant position (except for its linear motion transverse direction of motion of the imaging surface. It will be noted that the only twist in the belt 16 is that in the upper flight of the belt between the two pulleys, i.e., the flight which is spaced away from the imaging surface. The lower (cleaning engagement) flight of the belt is substantially fully planar between the two pulleys.

One or both the pulleys 22 and 24 may be conventionally driven by an electric motor as shown, or other suitable conventional drive means, at the desired blade translation speed. Since the blade motion is preferably continuous and unidirectional a complex drive mechanism is not required.

With the disclosed structure a cleaning station can be provided for cleaning the edges of the belt at a single small area spaced from the imaging surface. This is exemplified hereby a cleaning brush 30 engaging the edge 20 of the blade 16. This cleaning brush 20 need only encompass the one edge 20. Since the edges 18 and 20 reverse in each rotation of the belt, both edges can be cleaned by a single small cleaning brush 30 at this one location. It may also be seen that the cleaning brush 30 is (desirably) spaced away from the imaging surface by the full width of the belt. This is enabled by the mobius nature of the blade 16 and its continuous undirectional motion. The cleaning brush 30 is located here off to one side of the imaging surface 12, adjacent the pulley 22. However, it will be appreciated that other locations may be provided which will also allow continual cleaning without any interference or contact with the imaging surface. Since the cleaning station may be located at a single point for the entire belt, a simple single point toner removal system (not shown) may also be utilized in connection therewith. Thus, a trough and auger system extending the full length of the cleaning blade, as utilized in some of the above cited prior art structures is not required.

Remote lubrication of the cleaning blade edges is exemplified here by a stick or bar lubricant applicator 32 for applying a suitable imaging surface lubricant for the blade edges, such as zinc stearate or the like. As shown, this may be applied directly to the cleaning corner edge of the blade edge 18 immediately prior to its engagement with the imaging surface. Other lubricant applicator locations may be utilized, all of which can take advantage of the ability to apply the lubricant at a position spaced away from the imaging surface. Thus, with this arrangement the lubricant can be applied only as needed to only the cleaning blade edge and does not need to be applied over the imaging surface itself or with the imaging material (toner).

As may be seen from FIG. 2 the exemplary blade structure 16, shown here in cross section is preferably a thin steel strap central portion or material to which two continuous elastomer material cleaning tips are mounted. The cleaning edges are preferably made by forming sharp edges on these elastomer tips to engage the imaging surface. This basic preferred structure is described in further detail (but for a single edge blade) in the above cited U.S. Pat. applications, Ser. Nos. 356,985 and 356,986. However, other suitable cleaning blade structures, such as a monolithic band of polyurethane rubber, with or without reinforcing materials, may be utilized.

In conclusion, it may be seen that there has been provided by the above disclosed structure an improved cleaning system in which the cleaning blade can move continuously to avoid any dwell points, and has an increased effective length, for increased blade life and improved cleaning. Although the exemplary embodiment described herein is presently considered to be preferred, various other modifications or improvements will be apparent to those skilled in the art. The following claims are intended to cover all such variations and modifications as fall within the true spirit and scope of the invention.

Claims

What is claimed is:

1. In electrostatographic apparatus, the improvement in the cleaning system for cleaning imaging material from an imaging surface with a cleaning blade comprising:

an endless belt having two opposite edges,

said edges being adapted to clean said imaging surface;

support means for continuous motion of said belt including continuously moving a portion of one said edge of said belt transversely across said imaging surface in cleaning engagement with said imaging surface;

and a mobius twist in said belt spaced from said imaging surface for automatically reversing said one edge of said belt with the other said edge of said belt into cleaning engagement with said imaging surface.

2. The apparatus of claim 1 including linear guide means parallel to said imaging surface for guiding a portion of said belt linearly across said imaging surface in engagement therewith.

3. The apparatus of claim 2 wherein said linear guide means is a continuous sliding support channel and includes means for flexibly deforming said belt against said imaging surface.

4. The apparatus of claim 3 wherein said belt has a thin metal central portion and said edges comprise an elastomer material mounted to said central portion.

5. The apparatus of claim 1 including cleaning means for cleaning one said edge of said belt at a position spaced from said imaging surface.

6. The apparatus of claim 5 wherein said cleaning means engages the edge of said belt opposite from the edge engaging the imaging surface.

7. The apparatus of claim 1 including lubricating means for lubricating one said edge of said belt at a position spaced from said imaging surface.

8. The apparatus of claim 1 wherein said support means further includes two parallel pulleys located respectively at opposite sides of said imaging surface, said belt being mounted on and extending between said pulleys.

9. The apparatus of claim 1 wherein said belt has a thin metal central portion and said edges comprise an elastomer material mounted to said central portion.