Patent Grant
8543048
This application is related to the following co-pending applications, each of which is hereby incorporated by reference in its entirety: “Cleaning Edge Modification For Improved Cleaning Blade Life And Reliability”, U.S. Ser. No. 12/840,798, filed herewith, by Bruce Thayer et al; “Long Life Cleaning System With Reduced Stress For Start Of Cleaning Blade Operation”, U.S. Ser. No. 12/840,729, filed herewith, by Bruce Thayer et al.
This disclosure relates in general to copier/printers, and more particularly, to cleaning residual toner from an imaging device surface with cleaning blades and the like that have a unique bevel surface profile to increased blade life and reliability.
In a typical electrophotographic printing process, a photoreceptor or photoconductive member is charged to a uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This process records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. Toner particles attracted from the carrier granules to the latent image form a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. Heating of the toner particles permanently affixes the powder image to the copy sheet. After each transfer process, the toner remaining on the photoconductor is cleaned by a cleaning device.
Blade cleaning is a technique for removing toner and debris from a photoreceptor or photoconductive member or other suitable surface within the marking process. In a typical application, a relatively thin elastomeric blade member is supported adjacent to and transversely across the photoreceptor with a blade edge that chisels or wipes toner from the surface. Toner accumulating adjacent to the blade is transported away from the blade area by a toner transport arrangement or by gravity. Blade cleaning is advantageous over other cleaning systems due to its low cost, small cleaner unit size, low power requirements, and simplicity. The contacting edge of a cleaning blade has the most influence on blade life and reliability. The bulk of the blade is basically a beam to support the cleaning edge and transmit forces to load the blade against the cleaning surface. The cleaning edge is obviously important for removal of particles from the cleaning surface, but it must also withstand cyclic stresses induced by starts and stops of the cleaning surface and printing/environmental conditions that generate high friction. Success of the blade is determined by how long it retains enough of the original cleaning edge shape to maintain a functional cleaning seal against the cleaning surface. In addition to the stress, photoreceptor surface coatings while improving photoreceptor life typically result in far higher blade wear rates due to friction. Frictional forces cause the blade to stick and slip or chatter as it rubs against the photoreceptor surface. As the blade rubs over the photoreceptor, the blade sticks to the photoreceptor because of static frictional forces. This stick-slip interaction or chatter is a significant cause of blade failure and very disruptive of the printing process. A lubrication film or lubricating particles between the rubbing surfaces reduces the intensity of the stick-slip (chatter) generated by the relative motion, but adverse interactions with other electrophotographic systems may occur.
Cleaning blades are typically designed to operate at either a fixed interference or fixed blade load as disclosed in U.S. Pat. No. 5,208,639 which is included herein by reference. Because of blade relaxation and blade edge wear over time, part and assembly tolerance, and cleaning stresses from environmental conditions and toner input, the cleaning blade is initially loaded to a blade load high enough to provide good cleaning at extreme stress conditions for all of the blade's life. However, a higher than required blade load for nominal stress conditions causes the blade and charge retentive surface to wear more quickly. Overcoated charge retentive surfaces have been developed to reduce the wear rate. While an overcoat protects the charge retentive surface, the overcoats increase the wear rate of the blades due to both physical and chemical interactions.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification there is need in the art for apparatus, and/or methods that increases the reliability of cleaning blades by changing the geometry of the leading edge of the blade.
According to aspects of the embodiments, there is provided an apparatus comprising a cleaning unit with a blade holder that rotates about a pivot point, the cleaning blade is coupled to the blade holder and is positioned to chisel excess toner from a photoreceptor surface. Geometrical changes produce a blade having a slanted surface that reduces cyclic fatigue stress at the blade tip and reduces blade edge wear. The blade has a sharp leading side, a trailing side, and a working end comprising a slanted surface. When the slanted surface is formed at an angle, between 93 degrees to 97 degrees, a stiffer tip is produced and wears resulting from blade and photoreceptor surface contact is reduced.
In accordance with various aspects described herein, systems and methods are described that facilitate cleaning a photoreceptor surface in a xerographic imaging device using cleaning blades. In order to greatly reduce blade stress incurred during the cleaning operation blades with at least one slanted surface is formed at angles ranging from 93 degrees to 97 degrees. The slanted surface produces a blade with a stiffer tip. The stiffer tip slows the creation of fatigue cracks, produced from a combination high contact pressure and high wear due to tucking stresses during high friction conditions, which tend to form near the edge of the blade. This narrow cut angle range is optimum for longer blade life and improved blade reliability.
Aspects of the disclosed embodiments relate to a process for producing a cleaning blade with increased blade life and reliability for a printing system comprising selecting a flexible, substantially rectangular, material formed from at least one of cast sheets, molded urethane or elastomer having a first major exterior surface opposite and parallel to a second major exterior surface and a first marginal end region opposite and parallel with a second marginal end region; shaping the first marginal end region at an obtuse angle to form a new sloping surface adjacent to the first major exterior surface and the second major exterior surface, wherein an edge region formed by the sloping surface and the second major exterior surface is capable of engaging a surface to remove particles therefrom; and joining the second marginal end region to a blade holder having a blade positioning mechanism to move the shaped blade into a working position.
In yet another aspect the disclosed embodiments includes an image forming machine comprising a moving surface; a blade with a free end having at least a first plane and a second plane, the first plane being adjacent to the second plane defining an obtuse angle therebetween, the free end further defining a blade tip between the first plane and the second plane; and a blade positioning mechanism connected to the blade to move the blade into a working position wherein the blade tip engages the moving surface to remove particles therefrom; wherein the defined blade tip between the first plane and the second plane reduces blade wear resulting from blade and moving surface contact.
In yet another aspect the disclosed embodiments includes an image forming machine comprising a moving surface; a blade with a free end having at least a first plane and a second plane, the first plane being adjacent to the second plane defining an obtuse angle therebetween, the free end further defining a blade tip between the first plane and the second plane; and a blade positioning mechanism connected to the blade to move the blade into a working position wherein the blade tip engages the moving surface to remove particles therefrom; wherein the defined blade tip between the first plane and the second plane reduces blade wear resulting from blade and moving surface contact.
In still another aspect the image forming machine disclosed embodiments wherein the blade tip comprises a line where the first plane and the second plane meet.
In still another aspect the image forming machine disclosed embodiments wherein the obtuse angle ranges from 93 degrees to 97 degrees.
In still another aspect the image forming machine disclosed embodiments wherein the moving surface is at least one of drum rotating in an operational direction, a flat surface moving in an operational direction, or a belt moving in an operational direction.
In still another aspect the image forming machine disclosed embodiments disclosed embodiments wherein the blade positioning mechanism comprises a supporting member having a rotational axis and being configured to hold the blade.
In still another aspect the image forming machine disclosed embodiments further include a controller to cause the blade positioning mechanism to move the blade within a position to create a minimum blade load so as to remove particles from the moving surface.
In still another aspect the image forming machine disclosed embodiments wherein the moving surface is a drum that rotates in an operational direction and the blade tip extends transversely across the flat surface.
In still another aspect the image forming machine disclosed embodiments wherein the moving surface is a belt moving in an operational direction and the blade tip extends transversely across the belt.
In still another aspect disclosed embodiments includes cleaning station in an electrophotographic marking system, the system comprising in an operative arrangement, a movable photosensitive surface and a cleaning blade in a holder, the blade having a top edge, a bottom edge and an end edge opposite the holder, a blade tip to clean the photosensitive surface, and a bevel on the end edge of the blade that provide lower blade tip wear, wherein the bevel forms an obtuse angle with the bottom edge.
Embodiments as disclosed herein may also include computer-readable media for carrying or having computer-executable instructions or data structures stored thereon for operating such devices as controllers, sensors, and eletromechanical devices. Such computer-readable media can be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of computer-executable instructions or data structures. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or combination thereof) to a computer, the computer properly views the connection as a computer-readable medium. Thus, any such connection is properly termed a computer-readable medium. Combinations of the above should also be included within the scope of the computer-readable media.
The term “print media” generally refers to a usually flexible, sometimes curled, physical sheet of paper, plastic, or other suitable physical print media substrate for images, whether precut or web fed.
The term “image forming machine” as used herein refers to a digital copier or printer, marking system, electrographic printer, electrophotographic printing process, bookmaking machine, facsimile machine, multi-function machine, or the like and can include several marking engines, as well as other print media processing units, such as paper feeders, finishers, and the like. The term “electrophotographic printing machine,” is intended to encompass image reproduction machines, electrophotographic printers and copiers that employ dry toner developed on an electrophotographic receiver element.
The term bevel, bevel surface, first plane, sloping surface as used herein refers to the portion of the blade that forms the surface between the leading edge of the blade and the trailing side of the blade and is typically the working surface of the blade when performing cleaning operations.
In
As seen from table 350 the angle formed between the bevel surface 330 and the second plane 320 correlate to the life and reliability of the blade. Additionally, the table shows that for certain range of angles (Φ1, Φ2, Φ3) such as for acute cut angles (Φ1), right cut angles (Φ2), and obtuse cut angles (Φ3) there are points where the blade life and reliability are maximized. Experiments were conducted with a series of blade cut angles to determine an optimum cut angle for maximum blade life and reliability. The experiments were performed on blade life fixtures. Upon completion of each test, edge wear was measured on the blades. The distributions of blade wear at each cut angle were examined to select the optimum cut angle to minimize blade wear failures.
Table 350 shows the projected life distribution of a few blade cut angles at the ten (10) and five (5) percent failure rate as shown in columns labeled 352. Using cumulative probability the 5% and 10% can be transformed to indicate the blade population that should survive to the intended life for the given cut angle. For example, 95% of the blades with a cut angle of 95 degrees are expected to be cleaning satisfactorily at 850 kc. In contrast, 95% of the conventional blade cut angle (90 Degrees) blades would only survive to 276 kc. As a general rule the blade wear rates are converted to blade lives by choosing a blade wear failure threshold value, WearTHRESHOLD. The failure threshold can be a predetermined number of prints or cycles or it can be a time period. Blade life is calculated by dividing the wear failure threshold by wear rate (BladeLife=WearTHRESHOLD/Wear Rate). Continuing with the tabular information, all of the 95° cut angle blades are expected to last for at least 500 kc in the blade life fixtures. The other cut angle blades (60, 90, and 100 Degrees) shown in Table 350 are expected to have some early blade failures because they all have some portion of their blade wear rate distributions extending to high wear rates. Blades cut at 95 degrees achieve a balance between high wear due to high contact pressure and high wear due to tucking stresses during high friction conditions. This balance results in a narrow cut angle optimum for longer blade life and improved blade reliability.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine. Moreover, while the present invention is described in an embodiment of a single color printing system, there is no intent to limit it to such an embodiment. On the contrary, the present invention is intended for use in multi-color printing systems as well, or any other printing system having a cleaner blade and toner. It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the followings claims.
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