System and method for stripping media from an offset imaging member in an inkjet printer

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.

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.

DETAILED DESCRIPTION

Referring toFIG. 7, there is shown a side view of a prior art inkjet printer10that 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 inFIG. 7, the inkjet printer10may include an ink loader40, an electronics module44, a paper/media tray48, a print head50, an intermediate imaging member52, a drum maintenance subsystem54, a transfix subsystem58, a wiper subassembly60, a paper/media preheater64, a duplex print path68, and an ink waste tray70. In brief, solid ink sticks are loaded into ink loader40through 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 head50. The ink is ejected by piezoelectric elements to form an image on the intermediate imaging member52as the member rotates. Member52is 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 tray48and directed into the paper pre-heater64so 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 subsystem58and the intermediate image member52is coordinated for the transfer of the image from the imaging member to the sheet of recording media.

The operations of the inkjet printer10are controlled by the electronics module44. The electronics module44includes a power supply80, a main board84with a controller, memory, and interface components (not shown), a hard drive88, a power control board90, and a configuration card94. The power supply80generates various power levels for the various components and subsystems of the inkjet printer10. The power control board90regulates 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 printer10. 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 card84. The main board84includes the controller that operates the inkjet printer10is configured in accordance with an operating program executing in the memory of the main board84. The controller receives signals from the various components and subsystems of the inkjet printer10through interface components on the main board84. 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 member52as the member rotates past the print head. The printer depicted inFIG. 7is 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 inFIGS. 1A and 1B.FIG. 1Ashows the stripper system100A with the stripper blade112biased against the surface of an intermediate imaging member, herein embodied as a print drum108.FIG. 1AandFIG. 1Bshow the print drum configured to rotate in a counterclockwise direction shown by arrow102. In the embodiment ofFIG. 1A, the stripper blade112is biased against the surface of the print drum108at location148with a pressure of approximately 0.033 lb/in to about 0.083 lb/in. The stripper blade112is deformed by the biasing force, and the acute angle formed at location148between the print drum108and stripper blade112is 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 drum108. The deformation results in the stripper blade112having a curvature when biased against the print drum108. The curvature allows the leading edge of stripper blade112to engage the print drum108uniformly. The stripper blade112has at least one metallic layer, which may be formed from stainless steel, although other materials may be used. The surface of print drum108is 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 blade112is attached to a blade holder116. The blade holder116may be formed from a polymer compound, such as a thermoplastic adapted to secure the stripper blade112, although other suitable materials may be used. The blade holder116engages a support arm124that is rotatably attached to a pivot120at one end and a spring136at the other end. The spring136is further attached to an actuator arm132. The actuator arm132is controlled by an actuator128, which is typically an electromechanical device such as a servo or solenoid. In the configuration ofFIG. 1A, the actuator arm132is in a retracted position, pulling the spring136, support arm124and blade holder116towards a stop member140. The stop member140applies a reverse bias against the blade holder116. The forces from actuator128and stop member140maintain the biasing pressure of approximately 0.033 lb/in to 0.083 lb/in as the print drum108rotates and the stripper blade112engages media sheets.

FIG. 1Bdepicts a stripper blade system100B with the stripper blade112removed from the print drum108. In this disengaged position, a gap152is formed between the stripper blade112and print drum108. The actuator128extends actuator arm132, pivoting support arm124and blade support116away from mechanical stop140. As the blade support116moves away from the print drum108, the end of the arm116furthest away from the print drum108moves to encounter the stop member144. Thus, stop member144limits the travel of the blade support116during disengagement of the blade112from the drum108and the stop member140limits the travel of the blade support116during engagement of the blade112with the drum108.

In bothFIG. 1AandFIG. 1Bthe transfix roller104is positioned to form a transfix nip110with print drum108. The transfix roller104may be moved into the nip position or removed from the nip position by rotation of a transfix roller actuator156. The transfix roller104rotates freely about a central axis164in response to the rotation of the print drum108, allowing media sheets to pass through the transfix nip110. In the embodiment ofFIG. 1AandFIG. 1B, the transfix roller actuator156engages the transfix roller104using at least one armature160, although alternative embodiments may use other means of moving the transfix roller such as belts or a gearing system. The transfix roller actuator156is typically an electromechanical device such as an electric motor. The transfix roller actuator156may also rotate armature160and transfix roller104to a position removed from the transfix nip110when the printer is not transfixing an image to a print medium. When the transfix nip110is formed, the print drum108rotates in direction102, carrying a media sheet through the transfix nip110towards the stripper blade112. If the stripper blade112is engaged as show inFIG. 1A, the media sheet is separated from the print drum108starting at location148.

The actuator128and transfix roller actuator156are 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 ofFIG. 1AandFIG. 1Bis depicted inFIG. 2. The stripper blade200is formed from a single sheet of a flexible material such as stainless steel. In the example embodiment ofFIG. 2, the stripper blade200has a leading edge204adapted 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 edge204depicted inFIG. 2is 30 mm wide, although different lengths may be used in alternative embodiments. For the embodiment ofFIG. 2, the stripper blade200has a thickness208of approximately 0.05 mm, and a length212of 12 mm. These dimensions provide the stripper blade200with 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 inFIG. 1A. The length212is also sufficient to permit the stripper blade200to be held by a stripper blade holder such as the stripper blade holder116depicted inFIG. 1A. In alternative embodiments, the precise dimensions of the stripper blade212may vary according to the desired width of the leading edge204, the desired angle of attack for the stripper blade, and material used to form the stripper blade. While the leading edge204of stripper blade200is 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 ofFIG. 1AandFIG. 1Bis depicted inFIG. 3. The stripper blade300has a metal layer312laminated to a first polymer layer308. In the example embodiment ofFIG. 3, the metal layer312is 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 layer308is typically formed of Mylar, and is recessed from the leading edge314such that metal layer312extends approximately 1 mm beyond the first polymer layer308. The first polymer layer308is 0.076 mm thick and is 25 mm wide. The second polymer layer304is 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 layer308by 3 mm. The polymer layers304and308are constructed with sufficient deformation range to allow the attached metal layer312to 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 blade200depicted inFIG. 2, the stripper blade300may 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 edge314of metal layer312contacts the print drum first, with polymer layer308and304contacting the print drum after the metal layer312.

While the stripper blades ofFIG. 2andFIG. 3are 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. 4AandFIG. 4Bdepict frontal views of two alternative stripper blade arrangements suitable for use with the stripper blade system depicted inFIG. 1AandFIG. 1B. InFIG. 4A, the stripper blade416has a horizontally uniform leading edge and is held by blade holder412. The print drum404rotates, carrying a media sheet408towards the stripper blade416. If the stripper blade416is biased against the print drum404, the stripper blade416separates the media sheet408from the surface of print drum404when the leading edge of the media sheet410meets the edge of the stripper blade416. In the alternative embodiment ofFIG. 4B, the stripper blade420also engages the leading edge410of the media sheet408. InFIG. 4B, the stripper blade420has a tapered leading edge with an apex point424that engages the media sheet408first. As the print drum404carries media sheet408towards the stripper blade420, the tapered leading edge gradually engages the entire media sheet edge410, separating the media sheet408from the print drum404. In bothFIG. 4AandFIG. 4Bthe stripper blade is approximately the same width as the print drum404. Either of the stripper blades exemplified inFIG. 2orFIG. 3may be adapted for use inFIG. 4AorFIG. 4B. The blade holder412may engage with an electromechanical actuator in the manner depicted inFIG. 1AandFIG. 1B.

A method for controlling a stripper blade system such as the system depicted inFIG. 1AandFIG. 1Bis shown inFIG. 5. The stripper blade control process500starts by moving the blade holder into the contact position (block504). 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 (block508). The biasing is accomplished by moving the stripper blade holder against a stop member, such as stop member140fromFIG. 1A. The biasing force is applied for a predetermined period of time (block512) where the stripper blade is held in the biased position (block516). 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 (block520), 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 roller604and a pressure roller608are shown inFIG. 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/mm2to about 1 N/mm2. 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 system600shown inFIG. 6enables 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 system600, the stripper blade612is biased against the surface of the fuser roller604, which is rotating in a counterclockwise direction shown by arrow602. As shown, the stripper blade612is biased against the surface of the fuser roller604at location648with a pressure of approximately 0.033 lb/in to about 0.083 lb/in. The stripper blade612is deformed by a biasing force supplied by the blade holder616being urged against stop member640by support arm624that is rotatably attached to a pivot620at one end and a spring636at the other end. An actuator628, which is typically an electromechanical device, such as a servo or solenoid, moves an actuator arm632to extend a spring636to urge the support arm624and blade holder616against the stop member640. The forces from actuator628and stop member640maintain a biasing pressure of approximately 0.033 lb/in to 0.083 lb/in as the fuser roller604rotates and the stripper blade612engages media sheets at an acute angle formed at location648between the fuser roller604and stripper blade612. 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 roller604. The biasing of the stripper blade612curves the blade612and enables the leading edge of the stripper blade612to engage the fuser roller604uniformly. The stop member644operates to limit the range of motion for the blade holder616when the actuator628releases the spring636.

The stripper blade612has at least one metallic layer, which may be formed from stainless steel, although other materials may be used. The surface of the fuser roller604may 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 blade612is attached to a blade holder616, which may be formed from a polymer compound, such as a thermoplastic adapted to secure the stripper blade612, 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.