US 3843407 A
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Oct. 22, 1974 B. E. THORP BLADE CLEANING WITH REVERSE MOVEMENT Filed Aug. 24. 1973 :United States Patent Office 3,843,407 BLADE CLEANING WITH REVERSE MOVEMENT Bruce E. Thorp, Webster, N.Y., assignor to Xerox Corporation, Stamford, Conn. Filed Aug. 24, 1973, Ser. No. 391,197 Int. Cl. B08b 7/00 U.S. Cl. 134-6 9 Claims ABSTRACT F THE DISCLOSURE A method and apparatus for improving blade cleaning of an imaging surface in electrostatographic systems in which the imaging surface normally moves in only one direction, but intermittently stops, and is cleaned while it is moving in the normal direction by a contacting cleaning blade extending into the normal direction of movement of the imaging surface; comprising intermittently temporarily reversing the direction of movement of the imaging surface relative to this cleaning blade while maintaining the same contact of the cleaning blade with the imaging surface. Preferably the intermittent reversing is done automatically in response to the intermittent stopstopping of the imaging surface.
The present invention relates to an improved apparatus and method for electrostatographic imaging surface cleaning by cleaning blades.
Exemplary xerographic blade type dry toner cleaning apparatus, to which the present invention relates, is disclosed in U.S. Pats. 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 of interest include U.S. applications Ser. Nos. 356,985, led May 3, 1973, by Richard E. Smith and Ser. No. 356,986, iiled May 3, 1973, by Christ S. Hasiotis. Toner cleaning systems with a polyurethene cleaning blade are commercially embodied in the Xerox Corporation 4000 and 3100 xerographic copiers. The present invention is an improvement in this technology.
Several of the above references disclose chiseling type cleaning blades in which the blade extends into (towards) the direction of motion of the photoreceptor in its cleaning engagement therewith. This provides certain cleaning advantages, but also may render the blade more susceptible to localized failures, such as blade edge tuckunders. Contamination of the cleaning blade surface engaging edge becomes a critical factor contributing to increases in cleaning failures in this environment. f
The latter three issued U.S. patents cited above relate to apparatus for translating the blade laterally relative to the photoreceptor surface direction of movement in order to alleviate cleaning blade problems. They also teach that it can be helpful to continue for a time this lateral blade translation even after the photoreceptor has stopped moving.
While the above referenced blade cleaning structures are generally eifective, there is a particular problem in this environment of a build-up of removed toner, lubricants, paper lint and other contaminants along the blade cleaning edge affecting its cleaning seal with the photoreceptor. By the present invention, it has been found possible to break up and remove at least part of this build-up periodically, and, therefore, potentially reduces the likelihood of cleaning blade seal failures during machine operations. The method and apparatus for achieving this improvement is simple and inexpensive and does 3,843,407 Patented Oct. 22, 1974 not interfere with any other electrostatographic machine functions. It may be used either alone, or together with the lateral blade translation apparatus described above, to prevent blade edge build-up of contaminants. It involves simply occasionally reversing the relative motion of the photoreceptor and the cleaning blade, so that instead of the blade operating to scrape or wipe the photoreceptor the photoreceptor rubs backwards against the blade edge to break up and remove the pile up of toner and contaminants thereon. This function and result can be achieved by various simple structures without requiring any significant modification of existing electrostatographic apparatus.
An exemplary embodiment of the present invention is shown and described hereinbelow as incorporated in an otherwise conventional exemplary xerographic apparatus and process. Accordingly, said Xerographic apparatus and process need not be described in detail herein, since various printed publications and patents and publicly used machines are available which teach details of various suitable exemplary electrophotographic structures, materials and functions to those skilled in the art, in addition to the above-cited patents and machines. Some examples are disclosed in the books yEleczrophoitography by R. M. Schaffert, and X erography and Related Processes by John H, Dessauer and Harold E. Clark, both first published in 1965 by Focal Press Ltd., London, England; and the numerous patents and other references cited in these books. All of the references cited in this specification are hereby specifically incorporated by reference.
|Further objects, features and advantages of the present invention pertain to the particular steps, apparatus, and details 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 drawing forming a part thereof, wherein:
The single figure is a schematic perspective view of an exemplary electrostatographic blade cleaning system in accordance with the present invention.
Referring to the figure, there is shown therein an exemplary electrostatographic blade cleaning system 10 in accordance with the apparatus and method of the invention. `For improved clarity, only those details and elements of a conventional xerographic system are shown which relate to the specific improvement of the invention. These include a rotatable photoreceptor drum 12 having the electrostatographic imaging surface 14 moving thereon. The surface 14 is conventionally rotated in one direction during normal machine operations by a regular drum drive motor 16 through a conventional chain and sprocket drive connection to the drum 12 axis. The drive motor 16 is powered by a conventional electrical power source 18 through the conventional machine controls and switches (not shown). The normal direction of rotation of the drive motor 16 when it is being powered to drive the drum 12 is illustrated by the solid arrow 17 thereon.
The imaging surface 14 is shown being conventionally cleaned by a cleaning blade 20. It may be seen that the cleaning blade 20 is of the above-described scraping or chiseling type which contacts the imaging surface 14 at a cleaning edge 24 and extends toward the normal driven direction of motion of the surface 1'4, illustrated by the solid arrow 22. Thus, toner and any photoreceptor lubricant material on the imaging surface 14 will tend to accumulate on the cleaning edge 24 of the cleaning blade 20. This build-up of material can cause localized or total blade sealing failures, and, therefore, visible cleaning failures of the eventual copy.
Considering now the disclosed apparatus for eiecting the desired intermittent reversal of direction of the motion of the imaging surface 14 relative to the cleaning blade 20, it will be appreciated that the disclosed structure,
3 while effective, is only one of many other suitable structures for achieving the same steps and results. The illustrated exemplary structure utilizes a reversing motor 26 which is intermitently connected to the photoreceptor drum 12 to reverse its direction when the imaging surface 14 is stopped by the removal of power to the drive motor '16. This is accomplished here by having the reversing motor 26 mounted coaxially the shaft of the drive motor 16 adjacent its free end, i.e., opposite from the end which is connected to the drum sprocket drive. A conventional normally disconnected (free-running) electrical clutch 28 is mounted between the reversing motor 26 and the main drive motor 16 so as to connect the two motors together only upon an electrical input to the electrical clutch 28.
This electrical input to the clutch 28 occurs here only upon actuation of a control switch 30. It may be seen that the switch 30 normally connects a first contact 31 to provide electrical power to the main drive motor 16 and prevent any power input to the electrical clutch 28. However, upon movement of the control switch 30 to a second contact 32, power is removed from the drive motor 1'6 so that the imaging surface 14 cornes to a stop. This connection to the second contact 32 also provides electrical power input to the electrical clutch 28, thereby connecting the reversing motor 26 to the shaft of the drive motor 16, and therebyrcausing the drive motor 16 to run in a reverse direction shown by the dashed line 34 thereon. The reverse rotation of the drive motor 16 causes, through the same sprocket and chain drive connection normally used by the drive motor 16, the drum 12 to automatically reverse its direction of rotation and thereby change the direction of motion of the imaging surface 14 to the reverse direction illustrated by the dashed line 36. The blade 20 thereby changes from a scraping to a wiping mode.
This reversal movement of the imaging surface 414 need not be long to achieve the desired results of breaking up or removal of build-up on the cleaning blade 20. Only a partial rotation in a reverse direction of the imaging surface is sufficient. A wiping action of the surface 14 against the blade of only one-quarter to one-half inch has been found sufficient to temporarily reseal cleaning blade defects causing toner streaking on copies. This reversal movement is not required every time the imaging surface 14 is stopped. It may be provided only at intervals or periods determined by a number of machine stops or the like. However, it is preferred that the reversing occur automatically in response to the normal stopping of the imaging surface. Thereby there is no interruption of the normal machine operation.
It is believed that there may be at least three reasons yfor the surprising effectiveness of this reversal operation. First, any blade edge -tuckunders are relieved; secondly the thickness of the seal of toner and lubricant material at the blade edge can be reduced and made more uniform; and thirdly any contaminants present under the blade edge can be backed' out from beneath the blade.
. It may be seen that the above embodiment provides the desired functions, steps and results of the invention with simple conventional apparatus and only aminor modification of an existing xerographic system. Other suitable conventional apparatus which could be utilized to achieve the desired reverse rotation would be a conventional rotary solenoid, coupled to the drive motor 16 shaft, or a conventional slip clutch, or a conventional spring loaded over-running clutch which would be loaded in one direction with spring force by the normal rotation of the drive motor "16 shaft, and upon stopping of the drive motor 16 the stored spring force would act to rotate the motor 16 backwards for'a brief distance, thereby briefly rotating the imaging surface 14 backwards for a short distance, The amount of reverse rotation can be Y limited, if desired, by a mechanical stop or by reducing the reversal spring loading in this case. The solenoid or spring would provide the second or reversal driving force for such systems in place of a motor.
Numerous other variations and modifications within the purview of those skilled in the art can be made herein. The following claims are intended to cover all such variations and modifications as fall within the true spirit and scope of the invention.
What is claimed is:
1. In an apparatus for improved blade cleaning of 'an imaging surface in electrostatographic apparatus containing drive means 4for ynormally driving an imaging surface in a rst direction of motion and means for stopping said drive means for stopping said imaging surface, wherein said imaging surface is cleaned by a cleaning blade contacting said imaging surface and extending into said first direction of motion of said surface; the improvement comprising reversing means for rio intermittently reversing said direction of motion of said imaging surface while said cleaning blade is maintained in said same contact with said imaging surface.
2. The apparatus of Claim 1, wherein said reversing means is connected to said drive means.
3. The apparatus of Claim 1, wherein said reversing means operates automatically in response to said stopping of said imaging surface.
4. The apparatus of Claim 1, wherein said reversing means includes additional drive means connected to said drive means and operative automatically to reverse the direction of movement of said drive means in response to said stopping of said imaging surface.
S. The apparatus of Claim 4, wherein said reversing means includes normally disconnected clutch means for connecting said additional drive means to said drive means.
6. The apparatus of Claim 5, wherein said clutch r means is electrically actuated and operatively connects with said means for stopping said drive means.
7. A method for improving blade cleaning of an imaging surface in an electrostatographic system, which imaging surface normally moves in one direction of movement, but intermittently stops, comprising the steps of;
normally cleaning said imaging surfacerwhile said surface is moved in said one direction by contacting said surface with a cleaning blade extending into said one direction; and
intermittently temporarily reversing said one direction of movement of said imaging surface relative to said cleaning blade while maintaining said contact of said cleaning blade with said surface.
8. The method of Claim 7, wherein said intermittent reversing is done automatically in response to said intermittent stopping of said surface.
V 9. The method of Claim 8, wherein said imaging surface is normally fully rotated repeatedly in said one direction, and said intermittent reversing is for only a portion of a full rotation.
References Cited UNITED STATES PATENTS 4/ 1963 Ljungquist 15-256.51 ,4/1973, Shanly 355-15 X U.S. Cl. XR.