Abstract:
A stripper blade system has been developed for high throughput inkjet printers. The stripper blade system includes a metallic blade having a leading edge that is less than 0.06 mm in thickness, a blade holder to which the metallic blade is mounted, and an actuator that is associated with the blade holder to move the metallic blade into and out of contact with an intermediate imaging member.

Description:
TECHNICAL FIELD 
     This disclosure relates generally to printers having an intermediate imaging member and, more particularly, to the components and methods for facilitating removal of media from an offset imaging member or other cylindrical roller, such as a fuser roller. 
     BACKGROUND 
     In known printing systems having an intermediate imaging member, the print process includes an imaging phase, a transfix phase, and an overhead phase. In inkjet printing systems, the imaging phase is the portion of the print process in which the ink is expelled from the print head in an image pattern onto a print drum or other intermediate imaging member. The transfix phase is the portion of the print process in which the ink image on the print drum is transferred from the intermediate imaging member to the recording medium. The image transfer typically occurs by bringing a transfix roller into contact with the imaging member to form a nip. A recording medium arrives at the nip as the print drum rotates the image through the nip. The pressure in the nip helps transfer the malleable image inks from the print drum to the recording medium. In the overhead phase, the trailing edge of the recording medium passes out of the nip and the transfix roller is released from contacting the imaging member. The removal of the transfix member helps release the media from the intermediate imaging member. In some intermediate imaging printers, a stripper blade may be moved into position to intervene between the leading edge of a media leaving the transfix nip and the intermediate imaging member to facilitate separation of the media from the intermediate imaging member. 
     Inkjet printers that use intermediate imaging members, sometimes called offset printers, have been developed with higher throughput rates. Some of these printers have intermediate imaging members that have larger circumferences than previously known printers. The high transfix load pressure and the speed of the intermediate imaging member in higher throughput printers lead to high adhesive forces between the media and the intermediate imaging member. These adhesive forces make stripping the media from the intermediate imaging member with known stripping systems more difficult. A system that separates media with a higher adhesion force from an intermediate imaging member benefits the field of offset printing. 
     Other known cylindrical roller systems are used to fuse toner onto media after transfer of an image to the media. These fuser rollers can generate high pressure to enable the use of lower roller temperatures. When media passes through a fusing nip generating high pressure, the media can adhere to the roller and make media stripping a challenge. A system that separates media with high adhesion force from a high pressure fuser roller benefits the field of high pressure fusing. 
     SUMMARY 
     A stripper blade system has been developed that reliably strips media from an intermediate imaging member in an inkjet printer. The stripper blade system includes a metallic blade having a leading edge that is less than 0.06 millimeters in thickness, a blade holder to which the metallic blade is mounted, and an actuator that is associated with the blade holder to move the metallic blade into and out of contact with an intermediate imaging member. 
     The stripper blade system may be adapted for use in a xerography system to strip media from a fuser roller. The stripper blade system for a xerography system includes a metallic blade having a leading edge that is less than 0.06 millimeters in thickness, a blade holder to which the metallic blade is mounted, a stop member mounted proximate a fuser roller, and an actuator that is associated with the blade holder to move the metallic blade into and out of contact with the stop member to bias the leading edge of the metallic blade against the fuser roller to enable stripping of media from the fuser roller after the media exits a nip formed with the fuser roller. 
     A method that may be implemented with the stripper blade system includes moving a blade holder attached to a stainless steel blade having a leading edge with a thickness of no more than 0.06 millimeters to a position that enables the leading edge of the stainless steel blade to contact a cylindrical roller to facilitate separation of a leading edge of media on the cylindrical roller from the cylindrical roller, and moving the blade holder after expiration of a predetermined time period to disengage the leading edge of the stainless steel blade from the cylindrical roller. 
     A printer includes a print drum for receiving ink ejected by a print head, a transfix roller located proximate to the print drum, a stripper blade system, and a controller. The stripper blade system includes a metallic blade having a leading edge that is less than 0.06 millimeters in thickness, a blade holder to which the metallic blade is mounted; and an actuator that is associated with the blade holder to move the metallic blade into and out of contact with the print drum. The controller is configured to operate the transfix roller to form a transfix nip with the print drum selectively and to move the blade holder to contact the print drum with the leading edge of the metallic blade with the print drum to facilitate removal of media from the print drum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of an inkjet printer implementing a stripper blade system are explained in the following description, taken in connection with the accompanying drawings, wherein: 
         FIG. 1A  is a side view of a stripper blade system where the leading edge of a metallic stripper blade is in contact with a print drum. 
         FIG. 1B  is a side view of a stripper blade system where the leading edge of a metallic stripper blade is removed from a print drum. 
         FIG. 2  is a perspective view of a stripper blade. 
         FIG. 3  is a cross-sectional view of an alternative stripper blade. 
       FIG.  4 Ais a front side view of a print drum with a media sheet and a stripper blade with a uniform leading edge. 
         FIG. 4B  is a front side view of a print drum with a media sheet and a stripper blade with a tapered leading edge. 
         FIG. 5  is a flow diagram of a process for controlling a stripper blade system. 
         FIG. 6  is a side view of a stripper blade system that engages a fuser roller to enable separation of media from the fuser roller after the media exits a nip between the fuser roller and a pressure roller. 
         FIG. 7  is a side view of a prior art inkjet printer. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 7 , there is shown a side view of a prior art inkjet printer  10  that may be modified to include a stripper blade system that reduces undesirable ink transfer during the printing process. The reader should understand that the embodiment of the print process discussed below may be implemented in many alternate forms and variations. In addition, any suitable size, shape or type of elements or materials may be used. 
     As shown in  FIG. 7 , the inkjet printer  10  may include an ink loader  40 , an electronics module  44 , a paper/media tray  48 , a print head  50 , an intermediate imaging member  52 , a drum maintenance subsystem  54 , a transfix subsystem  58 , a wiper subassembly  60 , a paper/media preheater  64 , a duplex print path  68 , and an ink waste tray  70 . In brief, solid ink sticks are loaded into ink loader  40  through which they travel to a melt plate (not shown). At the melt plate, the ink stick is melted and the liquid ink is diverted to a reservoir in the print head  50 . The ink is ejected by piezoelectric elements to form an image on the intermediate imaging member  52  as the member rotates. Member  52  is called an intermediate imaging member because an ink image is formed on the member and then transferred to media in the transfix subsystem. This printing process is a type of offsetting printing. The intermediate imaging member may also be called a print drum. 
     An intermediate imaging member heater is controlled by a controller to maintain the imaging member within an optimal temperature range for generating an ink image and transferring it to a sheet of recording media. A sheet of recording media is removed from the paper/media tray  48  and directed into the paper pre-heater  64  so the sheet of recording media is heated to a more optimal temperature for receiving the ink image. A synchronizer delivers the sheet of the recording media so its movement between the transfix roller in the transfer subsystem  58  and the intermediate image member  52  is coordinated for the transfer of the image from the imaging member to the sheet of recording media. 
     The operations of the inkjet printer  10  are controlled by the electronics module  44 . The electronics module  44  includes a power supply  80 , a main board  84  with a controller, memory, and interface components (not shown), a hard drive  88 , a power control board  90 , and a configuration card  94 . The power supply  80  generates various power levels for the various components and subsystems of the inkjet printer  10 . The power control board  90  regulates these power levels. The configuration card contains data in nonvolatile memory that defines the various operating parameters and configurations for the components and subsystems of the inkjet printer  10 . The hard drive stores data used for operating the inkjet printer and software modules that may be loaded and executed in the memory on the main card  84 . The main board  84  includes the controller that operates the inkjet printer  10  is configured in accordance with an operating program executing in the memory of the main board  84 . The controller receives signals from the various components and subsystems of the inkjet printer  10  through interface components on the main board  84 . The controller also generates control signals that are delivered to the components and subsystems through the interface components. These control signals, for example, drive the piezoelectric elements to expel ink from the print heads to form the image on the imaging member  52  as the member rotates past the print head. The printer depicted in  FIG. 7  is merely exemplary of a printer suitable for adaptation with a stripper blade system, and the stripper blade system described herein may be used in a variety of printers with alternative components and configurations. Furthermore, the stripper bade system described herein can also be used in other printer subsystems such as roll fusers, belt fusers, etc. 
     A stripper blade system configured to remove print media from an intermediate imaging member or other cylindrical roller, such as a fuser roller or an unheated roller that contacts printed media, is depicted in  FIGS. 1A and 1B .  FIG. 1A  shows the stripper system  100 A with the stripper blade  112  biased against the surface of an intermediate imaging member, herein embodied as a print drum  108 .  FIG. 1A  and  FIG. 1B  show the print drum configured to rotate in a counterclockwise direction shown by arrow  102 . In the embodiment of  FIG. 1A , the stripper blade  112  is biased against the surface of the print drum  108  at location  148  with a pressure of approximately 0.033 lb/in to about 0.083 lb/in. The stripper blade  112  is deformed by the biasing force, and the acute angle formed at location  148  between the print drum  108  and stripper blade  112  is between approximately 10 and 14 degrees. This angle is also known as the “angle of attack”, and in the example embodiment these angle of attack ranges facilitate separating a print medium from the print drum  108 . The deformation results in the stripper blade  112  having a curvature when biased against the print drum  108 . The curvature allows the leading edge of stripper blade  112  to engage the print drum  108  uniformly. The stripper blade  112  has at least one metallic layer, which may be formed from stainless steel, although other materials may be used. The surface of print drum  108  is also metallic, typically being anodized aluminum. Generally, the stripper blade has a thickness of about one-half the thickness of the media most commonly used in the printer. In one embodiment, the media has a thickness of about 0.1 mm so the stripper blade has a thickness of about 0.06 mm. 
     The stripper blade  112  is attached to a blade holder  116 . The blade holder  116  may be formed from a polymer compound, such as a thermoplastic adapted to secure the stripper blade  112 , although other suitable materials may be used. The blade holder  116  engages a support arm  124  that is rotatably attached to a pivot  120  at one end and a spring  136  at the other end. The spring  136  is further attached to an actuator arm  132 . The actuator arm  132  is controlled by an actuator  128 , which is typically an electromechanical device such as a servo or solenoid. In the configuration of  FIG. 1A , the actuator arm  132  is in a retracted position, pulling the spring  136 , support arm  124  and blade holder  116  towards a stop member  140 . The stop member  140  applies a reverse bias against the blade holder  116 . The forces from actuator  128  and stop member  140  maintain the biasing pressure of approximately 0.033 lb/in to 0.083 lb/in as the print drum  108  rotates and the stripper blade  112  engages media sheets. 
       FIG. 1B  depicts a stripper blade system  100 B with the stripper blade  112  removed from the print drum  108 . In this disengaged position, a gap  152  is formed between the stripper blade  112  and print drum  108 . The actuator  128  extends actuator arm  132 , pivoting support arm  124  and blade support  116  away from mechanical stop  140 . As the blade support  116  moves away from the print drum  108 , the end of the arm  116  furthest away from the print drum  108  moves to encounter the stop member  144 . Thus, stop member  144  limits the travel of the blade support  116  during disengagement of the blade  112  from the drum  108  and the stop member  140  limits the travel of the blade support  116  during engagement of the blade  112  with the drum  108 . 
     In both  FIG. 1A  and  FIG. 1B  the transfix roller  104  is positioned to form a transfix nip  110  with print drum  108 . The transfix roller  104  may be moved into the nip position or removed from the nip position by rotation of a transfix roller actuator  156 . The transfix roller  104  rotates freely about a central axis  164  in response to the rotation of the print drum  108 , allowing media sheets to pass through the transfix nip  110 . In the embodiment of  FIG. 1A  and  FIG. 1B , the transfix roller actuator  156  engages the transfix roller  104  using at least one armature  160 , although alternative embodiments may use other means of moving the transfix roller such as belts or a gearing system. The transfix roller actuator  156  is typically an electromechanical device such as an electric motor. The transfix roller actuator  156  may also rotate armature  160  and transfix roller  104  to a position removed from the transfix nip  110  when the printer is not transfixing an image to a print medium. When the transfix nip  110  is formed, the print drum  108  rotates in direction  102 , carrying a media sheet through the transfix nip  110  towards the stripper blade  112 . If the stripper blade  112  is engaged as show in  FIG. 1A , the media sheet is separated from the print drum  108  starting at location  148 . 
     The actuator  128  and transfix roller actuator  156  are both configured to operate in response to signals received from a controller (not shown). The controller may be a general purpose microprocessor that executes programmed instructions that are stored in a memory. The controller also includes the interface and input/output (I/O) components for receiving status signals from the printer and supplying control signals to the printer components. Alternatively, the controller may be a dedicated processor on a substrate with the necessary memory, interface, and I/O components also provided on the substrate. Such devices are sometimes known as application specific integrated circuits (ASIC). The controller may also be implemented with appropriately configured discrete electronic components or primarily as a computer program or as a combination of appropriately configured hardware and software components. 
     A stripper blade that may be used in the embodiment of  FIG. 1A  and  FIG. 1B  is depicted in  FIG. 2 . The stripper blade  200  is formed from a single sheet of a flexible material such as stainless steel. In the example embodiment of  FIG. 2 , the stripper blade  200  has a leading edge  204  adapted to contact an intermediate imaging member such as a print drum, which is typically made of anodized aluminum, although other materials may be used. The leading edge  204  depicted in  FIG. 2  is 30 mm wide, although different lengths may be used in alternative embodiments. For the embodiment of  FIG. 2 , the stripper blade  200  has a thickness  208  of approximately 0.05 mm, and a length  212  of 12 mm. These dimensions provide the stripper blade  200  with sufficient strength and flexibility to be biased against a print drum for the purpose of stripping a media sheet from the print drum as shown in  FIG. 1A . The length  212  is also sufficient to permit the stripper blade  200  to be held by a stripper blade holder such as the stripper blade holder  116  depicted in  FIG. 1A . In alternative embodiments, the precise dimensions of the stripper blade  212  may vary according to the desired width of the leading edge  204 , the desired angle of attack for the stripper blade, and material used to form the stripper blade. While the leading edge  204  of stripper blade  200  is depicted as a straight edge, alternative shapes such as a tapered edge forming a point in the leading edge are also envisioned. 
     A cross sectional view of an alternative embodiment of a stripper blade suitable for use with the system of  FIG. 1A  and  FIG. 1B  is depicted in  FIG. 3 . The stripper blade  300  has a metal layer  312  laminated to a first polymer layer  308 . In the example embodiment of  FIG. 3 , the metal layer  312  is typically formed from a sheet of metal such as stainless steel, and is 26 mm in length and is up to 0.051 mm thick. The first polymer layer  308  is typically formed of Mylar, and is recessed from the leading edge  314  such that metal layer  312  extends approximately 1 mm beyond the first polymer layer  308 . The first polymer layer  308  is 0.076 mm thick and is 25 mm wide. The second polymer layer  304  is also formed from Mylar and is approximately 0.229 mm thick and 22 mm wide. The second polymer layer is further recessed from the leading edge of the first polymer layer  308  by 3 mm. The polymer layers  304  and  308  are constructed with sufficient deformation range to allow the attached metal layer  312  to engage the print drum with a desired contact load and angle of attack, while providing enough stiffness to overcome force applied by print media being stripped from the print drum. As with the stripper blade  200  depicted in  FIG. 2 , the stripper blade  300  may be biased against the print drum, and is configured to deform into a curved shape with an angle of attack between approximately 10 and 14 degrees when biased against the print drum. In the curved shape, the leading edge  314  of metal layer  312  contacts the print drum first, with polymer layer  308  and  304  contacting the print drum after the metal layer  312 . 
     While the stripper blades of  FIG. 2  and  FIG. 3  are described in detail, these are only examples of stripper blade configurations that are adapted for use in printers, and various alternative embodiments are envisioned. For example, the thickness of a stripper blade may vary according to multiple factors including the desired degree of blade deformation and the thickness of media sheets that are expected to pass through the printer. For printers configured to print to thicker media, such as cardboard, the preferred thickness for a stripper blade may be thicker than the precise embodiment disclosed above. The angle of attack and biasing pressure may also be adjusted in printers having differing print drum diameters and rotational speeds. Various appropriate materials, such as aluminum or alternative polymers, may be substituted for use in the stripper blade in alternative printer designs as well. 
       FIG. 4A  and  FIG. 4B  depict frontal views of two alternative stripper blade arrangements suitable for use with the stripper blade system depicted in  FIG. 1A  and  FIG. 1B . In  FIG. 4A , the stripper blade  416  has a horizontally uniform leading edge and is held by blade holder  412 . The print drum  404  rotates, carrying a media sheet  408  towards the stripper blade  416 . If the stripper blade  416  is biased against the print drum  404 , the stripper blade  416  separates the media sheet  408  from the surface of print drum  404  when the leading edge of the media sheet  410  meets the edge of the stripper blade  416 . In the alternative embodiment of  FIG. 4B , the stripper blade  420  also engages the leading edge  410  of the media sheet  408 . In  FIG. 4B , the stripper blade  420  has a tapered leading edge with an apex point  424  that engages the media sheet  408  first. As the print drum  404  carries media sheet  408  towards the stripper blade  420 , the tapered leading edge gradually engages the entire media sheet edge  410 , separating the media sheet  408  from the print drum  404 . In both  FIG. 4A  and  FIG. 4B  the stripper blade is approximately the same width as the print drum  404 . Either of the stripper blades exemplified in  FIG. 2  or  FIG. 3  may be adapted for use in  FIG. 4A  or  FIG. 4B . The blade holder  412  may engage with an electromechanical actuator in the manner depicted in  FIG. 1A  and  FIG. 1B . 
     A method for controlling a stripper blade system such as the system depicted in  FIG. 1A  and  FIG. 1B  is shown in  FIG. 5 . The stripper blade control process  500  starts by moving the blade holder into the contact position (block  504 ). Moving the stripper blade holder causes the attached stripper blade to come in contact with an intermediate imaging member, such as a print drum. The stripper blade is biased against the intermediate imaging member prior to the arrival of the leading edge of a media sheet at the location where the stripper blade engages the intermediate imaging member (block  508 ). The biasing is accomplished by moving the stripper blade holder against a stop member, such as stop member  140  from  FIG. 1A . The biasing force is applied for a predetermined period of time (block  512 ) where the stripper blade is held in the biased position (block  516 ). This predetermined period of time may vary depending upon factors such as the speed of the intermediate imaging member and the physical dimensions of the media sheet. The time should be sufficient to separate at least a leading portion of the media sheet from the intermediate imaging member such that the remaining portion of the media sheet will also separate from the intermediate imaging member. After the predetermined time period expires, the blade holder is moved to a remote position (block  520 ), removing the stripper blade from contact with the intermediate imaging member. 
     In operation, ink is ejected from at least one print head onto the surface of the print drum, forming a latent image. The transfix roller is moved into a transfix nip position with the print drum, and the print drum rotates, carrying a media sheet through the transfix nip to transfer the latent image from the print drum to the media sheet. The stripper blade is biased against the surface of the print drum at a position ahead of the leading edge of the media sheet after the leading edge of the media sheet emerges from the transfix nip. The stripper blade remains biased against the print drum for a predetermined amount of time allowing at least the leading portion of the media sheet to separate from the rotating print drum. At least a portion of the media sheet surface that was in contact with the print drum contacts the stripper blade as the media sheet separates from the print drum. The stripper blade is removed from contact with the print drum after sufficient time has passed to separate the media sheet from the print drum. The transfix roller is removed from the transfix nip after the media sheet has passed through the transfix nip. The process recited above may be repeated for multiple media sheets in a printer. Although the embodiments discussed above related to a stripper blade interacting with an intermediate imaging member, such as a print drum, the stripper blade may be used to facilitate the separation of printed media from other cylindrical rollers, such as heated rollers, i.e., fuser rollers, and unheated rollers in the media path. 
     In known xerography imaging systems, toner is attracted to electrical charge forming a latent image on an intermediate imaging member. The image is transferred to media and then the toner image on the media is fused to the media by passing the media with the toner image through a fusing nip formed between a fuser roller and a pressure roller. A fuser roller  604  and a pressure roller  608  are shown in  FIG. 6 . In a typical xerography imaging system, the fuser roller is heated to a temperature in a range of about 80 degrees to about 120 degrees Celsius and the pressure generated in the nip is in a range of about 0.3 N/mm 2  to about 1 N/mm 2 . In previously known xerography systems, plastic fingers were used to strip media from the fuser roller. Metal blades having a width as wide as the fuser roller were not used because the relatively high temperature differences to which the full width metal blades were exposed induced severe process direction buckling. This buckling affected consistent placement of the leading edge of the stripper blade at a position relative to the nip position that was effective for stripping the media from the fuser roller. To overcome that issue, relatively narrow plastic fingers were used to strip the media from the fuser roller. 
     The stripper blade system  600  shown in  FIG. 6  enables metallic blades to be used for stripping media from a fuser roller and still maintain consistent placement of the leading edge of the blade against the fuser roller. In the system  600 , the stripper blade  612  is biased against the surface of the fuser roller  604 , which is rotating in a counterclockwise direction shown by arrow  602 . As shown, the stripper blade  612  is biased against the surface of the fuser roller  604  at location  648  with a pressure of approximately 0.033 lb/in to about 0.083 lb/in. The stripper blade  612  is deformed by a biasing force supplied by the blade holder  616  being urged against stop member  640  by support arm  624  that is rotatably attached to a pivot  620  at one end and a spring  636  at the other end. An actuator  628 , which is typically an electromechanical device, such as a servo or solenoid, moves an actuator arm  632  to extend a spring  636  to urge the support arm  624  and blade holder  616  against the stop member  640 . The forces from actuator  628  and stop member  640  maintain a biasing pressure of approximately 0.033 lb/in to 0.083 lb/in as the fuser roller  604  rotates and the stripper blade  612  engages media sheets at an acute angle formed at location  648  between the fuser roller  604  and stripper blade  612 . In one embodiment, this angle is between approximately 10 and 14 degrees. This angle is also known as the “angle of attack”, and in the example embodiment, the angle of attack range facilitates separation of media bearing a toner image from the fuser roller  604 . The biasing of the stripper blade  612  curves the blade  612  and enables the leading edge of the stripper blade  612  to engage the fuser roller  604  uniformly. The stop member  644  operates to limit the range of motion for the blade holder  616  when the actuator  628  releases the spring  636 . 
     The stripper blade  612  has at least one metallic layer, which may be formed from stainless steel, although other materials may be used. The surface of the fuser roller  604  may also metallic, typically being anodized aluminum, although elastomer coated rollers may be used. Generally, the stripper blade has a thickness of about one-half the thickness of the media most commonly used in the xerography system. In one embodiment, the media has a thickness of about 0.1 mm so the stripper blade has a thickness of about 0.06 mm. The stripper blade  612  is attached to a blade holder  616 , which may be formed from a polymer compound, such as a thermoplastic adapted to secure the stripper blade  612 , although other suitable materials may be used. 
     In the embodiments described above, a single stripper blade has notable advantages over a plurality of discontinuous fingers for a number of reasons. For one, the discontinuous fingers may not successfully remove media if the media between the fingers remains adhered or substantially adhered to the roller. The single metallic blade is also better able to handle variable loading that varies with the degree to which the media is adhered to the roller from which the media is being removed. Additionally, the biasing and stop members enable the blade to engage the roller adequately for media removal without damaging the roller or the blade, particularly in metal-on-metal contact. The biasing force also enables a single metal blade to be used in a fuser environment without buckling occurring. Thus, the single metal blade and biasing mechanism provide reliable media stripping in a variety of imaging environments. 
     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. 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.