WO1999031554A1

WO1999031554A1 - Continuous form printers and methods of forming images upon media

Info

Publication number: WO1999031554A1
Application number: PCT/US1998/026712
Authority: WO
Inventors: John D. Gillen
Original assignee: Output Technology Corporation
Priority date: 1997-12-16
Filing date: 1998-12-15
Publication date: 1999-06-24
Also published as: AU1829899A

Abstract

A continuous form printer with: printer (10), housing (14), media intake (18), media (22), and media supply (24).

Description

DESCRIPTION CONTINUOUS FORM PRINTERS AND METHODS OF FORMING IMAGES

UPON MEDIA Technical Field The present invention relates to continuous form printers and methods of forming images upon media. Background Art

Continuous form or continuous media printers are known in the art. The media typically comprises a plurality of connected individual sheets which may be supplied to the printer in a box or on a supply reel. Such printers are usually concerned with and designed for obtaining high printing throughputs.

Conventional continuous media printers are configured to operate at a single speed. Such printers feed the media into a processor which is operating at full speed. Conventional printers typically maintain the predetermined speed at a very high degree of accuracy.

The continuous media printers known in the art also typically provide rasterizing processors which are configured to rasterize the entire print job.

Such rasterizers pre-process the entire job prior to starting printing. Following complete processing of the job to be printed, the processed data is applied directly to the print engine of the printer at full speed.

Such conventional continuous form printers have numerous drawbacks. For example, complete rasterization of the print job requires a significant volume of storage capacity which incorporates associated hardware costs. In addition, prior art continuous form or continuous media printers have increased costs associated with the provision of maintaining the print speed at a target speed with a high degree of accuracy.

Therefore, there exists a need to provide a continuous form printer having variable print velocity capabilities. Brief Description of the Drawings Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

Fig. 1 is an isometric view of one embodiment of a printer in accordance with the present invention.

Fig. 2 is a cross-sectional view of the printer from an operator side thereof taken along line 2-2 of Fig. 1. Fig. 3 is a diagrammatic representation of an imaging assembly and the media travel path through the printer.

Fig. 4 is a diagrammatic representation of one embodiment of a drive system of the printer. Fig. 5 is a right-end view of the printer showing one embodiment of a heating/cooling assembly.

Fig. 6 is a functional block diagram of one embodiment of a control assembly of the printer.

Fig. 7 is a flow chart illustrating one process of ramping the velocity of media through the printer.

Fig. 8 is a flow chart illustrating one method of controlling process conditions of the printer. Best Modes for Carrying Out the Invention and Disclosure of Invention

This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U .S. Patent Laws "to promote the progress of science and useful arts" (Article 1 , Section 8) .

According to a first aspect of the present invention, a continuous form printer comprises a frame; a drive assembly coupled with the frame and configured to transport continuous form media along a media path within the printer at a plurality of velocities; an imaging assembly operably spaced adjacent the media path and configured to form images upon the continuous form media; and a control assembly coupled with the drive assembly and configured to control the velocity of the continuous form media.

A second aspect of the present invention provides a method of forming images upon continuous form media comprising providing continuous form media; providing a plurality of images; forming the plurality of images upon the continuous form media; outputting the continuous form media following the forming; and varying the rate of the forming of the images upon the continuous form media. Another aspect of the present invention provides a method of forming images upon media comprising receiving a plurality of first data descriptions corresponding to a plurality of images; converting the first data descriptions to a plurality of second data descriptions of the images; timing the converting of the first data descriptions to the second data descriptions; forming a plurality of images corresponding to the second data descriptions of the images upon the media; and selectively adjusting the rate of forming the images responsive to the timing.

In accordance with another aspect of the present invention, a method of forming images upon a continuous media comprises providing a plurality of images; providing a continuous form media at a first velocity; forming the images upon the continuous media at an initial rate; ramping the velocity of the providing of the continuous form media; and ramping the rate of the forming of the images.

The printer of the present invention is generally illustrated by the numeral 10 in Fig. 1. The illustrated printer 10 is a continuous form printer configured to form or print images upon plural sheets of media, such as paper, which are joined to form a continuous web.

The depicted embodiment of the printer 10 comprises a base portion 12 and housing 14 connected therewith. A control panel 16 which provides user control of several functions and other operational attributes of the printer 10 (which will be discussed in further detail hereinafter) is made integral with a front surface of housing 14 in the depicted embodiment.

A right side wall of housing 14 defines a media or substrate intake area 18. A wire form 20 is attached thereto and an intake aperture is formed therein (not shown). A suitable continuous form substrate or media 22 is taken from a media supply 24 provided adjacent the printer. Media 22 is applied across the wire form 20 and into the printer 10 for processing. Although illustrated as a box in Fig. 1 , media supply 24 can comprise other configurations, such as a supply wheel or roll, for example. A left side wall of housing 14 defines a media exhaust or outfeed area 26. A second wire form (not shown) is ideally attached to the left sidewall in the media exhaust area 26. The second wire form is operable to direct the processed substrate or media 22 to a downstream refolding area.

Referring now to Fig. 2, housing 14 defines a cavity and encloses a frame which is generally indicated by numeral 28. The frame 28 has two discreet sections only one of which is shown in the drawings. It is to be understood that the opposite section of the frame , which is spaced therefrom, will be substantially a mirror image of the same . The frame 28 has a top peripheral edge 30, a bottom peripheral edge 32 which rests on the base portion 12, a right peripheral edge 34, and a left peripheral edge 36. Still referring to Fig. 2, various assemblies of the printer 10 are shown and described hereafter in detail. A media propulsion assembly 40 is provided adjacent the intake area of housing 14 and right peripheral edge 34 of frame 28. Media propulsion assembly 40 is mounted with frame 28 and properly aligned with wire form 20 to receive continuous form media guided thereby. Media propulsion assembly 40 is operable to provide the media 22 into printer 10. Media propulsion assembly 40 comprises a tractor assembly in one embodiment of the invention including a motor 42 and tractors 41. Motor 42 is operable to drive the tractors 41 and propel the media 22 engaged thereby towards the internal components of the printer 10 for processing (printing) therein.

The preferred embodiment of media propulsion assembly 40 further includes a media tachometer 43 (shown in Fig. 4) . Tractors 41 are configured to guide media 22 into printer 10. Media tachometer 43 is coupled with tractors 41 and is operable to provide speed or velocity information of media 22 being inputted into printer 10.

In general, media propulsion assembly 40 operates in different modes corresponding to the various operational modes of printer 10. In one embodiment, a clutch is provided to selectively engage and disengage the motor 42 and tractors 41. During loading of media 22, motor 42 and tractors 41 are engaged to thread media 22 through an open pressure (i.e ., T_j) nip and pinch or outfeed rollers provided within printer 10 as discussed in detail below. Provision of media 22 into printer 10 via tractors 41 enables proper location and alignment of media 22 within printer 10 when printing is initiated. During printing, tractors 41 and motor 42 are disengaged in the described operation of printer 10.

The illustrated printer 10 additionally includes a media or substrate engagement assembly 44 secured upon the frame 40. Media engagement assembly 44 is located adjacent and downstream of media propulsion assembly 40. The media engagement assembly 44, as a general matter, is operable to direct the continuous substrate or media 22 along a given path of travel substantially defined thereby. In particular, media engagement assembly 44 receives media 22 from the media propulsion assembly 40 and guides the media 22 toward an internal imaging assembly 60 configured to provide the printed images upon the media. Media engagement assembly 44 has a support member 46 which has an upwardly facing surface which supports the media 22 which is to be printed. The support member 46 further has a first end mounted in close proximity to a first drum of the imaging assembly 60 and a second or opposite end located adjacent the media propulsion assembly 40.

A media preheating assembly 48 is mounted on the frame 40 and disposed in spaced, heat transferring relation relative to support member 46. Media heating assembly 48 includes a housing which encloses a heating element of conventional design. In one embodiment, the heating element of media heating assembly 48 comprises a 1 kW ceramic heater. The heating element is operable to impart heat energy to media 22 traveling nearby along support member 46, thereby increasing the temperature of the media 22. This heat energy facilitates the printing of images upon media 22.

The housing of media heating assembly 48 includes first and second shutters which are pivotally affixed to same . The individual shutters are operable to move along a path of travel between a first or open position and a second or closed position. In the first position, heat energy is imparted to the media 22 traveling adjacent heating assembly 48. In the second position, the shutters impair the transmission of heat to the underlying media 22. The media heating assembly 48 is typically employed when using substrates or media 22 which have high thermal absorption capacities. This heater imparts heat energy to media 22 in order to prevent melted toner from losing an excessive amount of heat energy too quickly to the substrate thereby interfering with the resulting toner fuse quality. As referred to above , printer 10 of the subject invention includes an imaging assembly 60 to form, print or otherwise provide the desired images upon media 22. The preferred embodiment of the printer 10 according to the present invention utilizes offset printing to provide the image upon media 22. In general, the imaging assembly 60 accepts data corresponding to the image, forms the received data as a latent electrophotographic image, develops the image with toner, and offsets the toner image onto printable media 22.

The illustrated imaging assembly 60 comprises a plurality of rotatable drums, a developer 64 and a print cartridge or head 62. The rotatable drums include a first or pressure drum 50, second or transfuser drum 52 and a third or imaging drum 54. The respective first, second, and third drums 50, 52, 54 have engagement areas or nips therebetween which are designated in Fig. 3 as T , and T₉, respectively. The amount of pressure existing in nip T , , also referred to as the pressure nip, is normally about 200 lbs. per square inch. The amount of pressure in nip T₇, also referred to as the imaging nip, is about 100 lbs. per square inch. These nip pressures may be adjusted. Further, the individual nips (T, and T₂) may be selectively opened.

A commercially available print head 62 may be secured from Delphax Systems, Inc. of Mississauga, Ontario, Canada. In particular, one suitable embodiment of print head 62 is described in U .S. Patent No. 4,891 ,656 to Kubelik, incorporated herein by reference. Such a print head is configured to provide electron deposition of a latent image . In general, print head 62 is a point charge generating device which comprises a plurality of alternating layers of electrodes and insulators which form a matrix of print points. Such a configuration enables the formation of individual dots anywhere along the media 22 at a resolution of 300 dots by 300 dots per inch. The latent image is developed following provision thereof upon imaging drum 54 by print head 62. One method of developing the latent image upon the imaging drum 54 includes applying toner via the developer 64. The "tonerized" image formed upon imaging drum 54 is transferred to transfuser drum 52 and subsequently to media 22. The transferring of the image from the imaging drum 54 to the transfuser drum 52 is permitted in the printing operational mode wherein drums 52, 54 are in contact at imaging (i.e ., T₂) nip. Media 22 supplied via support member 46 passes between transfuser drum 52 and pressure drum 50 at nip T_j . The toner image received upon the outer surface of transfuser drum 52 is transferred to the media 22. A pair of pinch or exit drums including first outfeed drum 56 and second outfeed drum 58 are mounted in spaced relationship relative to first or pressure drum 50. Following the printing, pinch or outfeed drums 56, 58 receive the printed media 22 and guide the media to the outfeed area 26. Referring to Fig. 3, media propulsion assembly 40, media engagement assembly 44, drums 50, 52 and outfeed drums 56, 58 generally define a media path. Media 22 is shown along the media path within printer 10 in Fig. 3. The path illustrates the path of travel of the continuous form media 22 through printer 10.

Print head 62 works in combination with the third or imaging drum 54 of imaging assembly 60 to electrostatically form a predetermined image thereon. This electrophotographic image formed upon the imaging drum 54 may be referred to as a latent image . In one embodiment, imaging drum 54 comprises a hard-coat anodized (dielectric) aluminum cylinder which receives the electrophotographic latent image from the print head 62.

A rotary tachometer is provided axially adjacent imaging drum 54 to provide rotational information thereof. In the described embodiment of printer 10, the rotary tachometer contains an infrared sensor configured to provide a resolution of 87.38 counts per lineal inch about the circumference of imaging drum 54. Such rotational information of imaging drum 54 is utilized to synthesize image resolution for positioning the latent image upon the imaging drum 54. Utilization of rotational information of imaging drum 54 permits variable speed printing. In addition, printer ID is preferably configured to provide variable resolution imaging. Details regarding variable resolution imaging of the latent image upon imaging drum 54 are described in a U.S. patent application entitled 'Printers and Methods of Forming an Image ," naming John D . Gillen as inventor, filed the same day as the present application, assigned to the assignee hereof, having attorney docket reference OU 1-038, and incorporated herein by reference .

As described above, a toner dispensing assembly or developer 64 is provided adjacent the outer surface of imaging drum 54. Developer 64 is configured to selectively deliver toner to drum 54 following the provision of the latent image upon the outer surface thereof. Providing toner to imaging drum 54 having the latent image thereon develops the image for subsequent offsetting of the image to the media 22.

Referring again to Fig. 2, developer 64 has a main body which defines a storage cavity 66 which receives a given amount of toner (not shown) to be dispensed. The storage cavity 66 has an intake end 63, and an opposite exhaust end 68 which is positioned operably adjacent the imaging drum 54.

Mounted in close proximity to exhaust end 68 is a distribution or toner roller assembly which facilitates the dispensing of the toner from the internal storage cavity 66. The distribution assembly includes a toner roller 70 configured to rotate opposite to the direct of rotation of imaging drum 54. On demand, small amounts of toner in hopper storage cavity 66 are sifted out to a metering chamber adjacent exhaust end 68. Toner roller 70 thereafter operates to apply toner from the metering chamber to image roller 54. One embodiment of toner roller 70 comprises a metal mantel or sleeve which is configured to rotate about a stationary magnetic roll. The magnetic roll is a bariu -ferrite cylinder which has been permanently magnetized in a polar array of eight magnetic poles. The magnetic poles attract magnetic toner to the metal sleeve . Transfer of the toner from the developer 64 to the imaging drum 54 occurs when the electrostatic force on the toner, induced by the static charge of the latent image on the imaging drum, is greater than the magnetic force of the toner roller 70. The latent image upon the imaging drum 54 becomes a "tonerized" or developed image following the transfer of toner.

In addition, developer 64 is preferably configured for operation in two modes. More specifically, developer 64 is movable between an appropriate toner dispensing relationship relative to the imaging drum 54 and a non-dispensing or spaced relationship relative to the imaging drum 54. Developer 64 is shown herein in the toner dispensing relationship with imaging drum 54.

When provided in the toner dispensing relationship, particles of toner are provided adjacent exhaust end 68 of developer 64. As the imaging drum 54 rotates as indicated in Fig. 2, particles of toner are attracted to the latent image formed upon imaging drum 54. The outer surface of imaging drum 54 picks up toner from the developer 64 as defined by the formed latent image thereon. The developed image is next transferred to transfuser drum 52.

In an exemplary embodiment, transfuser drum 52 comprises an aluminum cylinder core with a high-release silicone rubber coating for receiving and transferring the developed toner image . As described below, transfuser drum 52 is maintained at a temperature greater than imaging drum 54 to facilitate the transferring of toner.

Housing 14 provides imaging drum 54 and transfuser drum 52 in a contacting relationship when printer 14 is provided in an operational printing mode to effect the transfer of the developed image . Transfuser drum 52 is supported and movable by a movable lifting member and is selectively placed into contact with the first or pressure drum 50.

Transfuser drum 52 operates to offset the developed image to the media 22. Media 22 passes through pressure drum 50 and transfuser drum 52. Such passage of media 22 through drums 50, 52 provides the image onto media 22. Surface energy of media 22 tends to be higher than that of the silicone-rubber transfuser drum 52. In addition, special release agents such as silicone oil assist with the offsetting of the toner image from transfuser drum 52 to media 22. Further, the low viscosity of the toner and the preheating of certain types of media allow the toner to penetrate or "wick" into the media at the pressure nip (i.e ., T_| nip).

Following the formation of the images, the printed media 22 is guided to exhaust outfeed drums 56, 58 and outfeed area 26 of printer 10 following provision of the images thereon. Outfeed drums 56, 58 are configured to provide approximately a 5 lb. load on the media 22 as the media leaves the pressure nip. As shown in Fig. 4, an outfeed motor 59 is configured to drive outfeed drum 58.

Still referring to Fig. 4, an embodiment of a drive assembly 57 of the printer 10 is shown. The depicted drive assembly 57 includes a main drive motor 38 and a drive belt 55. In the described embodiment of printer 10, individual drums 50, 52, 54 are driven from main drive motor 38 and drive belt 55. Drive belt 55 engages the imaging drum 54. In particular, main drive motor 38 drives imaging drum 54 which in turn drives transfuser drum 52 which in turn drives pressure drum 50. The individual drums of imaging assembly 60 rotate in the direction as illustrated in Fig. 2.

Main drive motor 38 may also be utilized to power all print functions and primary media transport. Main drive motor 38 comprises a 1/4 horsepower, 36 Volt, 6.5 Amp (DC) three-phase brushless motor in one embodiment of the invention. As described below, main drive motor 38 is controlled via a media controller. Main drive motor 38 contains internal tachometry sensors providing rotational information to the media controller. Such rotational information permits media controller 112 to vary and control the speed of the main drive motor 38. During printing modes of operation, main drive motor 38 provides primary locomotion at the pressure nip (T_j) to transport media 22 through printer 10. During non-printing modes of operation, the pressure nip is opened thereby effectively disengaging the primary media transport from the media 22. Transport of media 22 is implemented by media propulsion assembly 40 during nonprinting modes of printer operation.

In addition to the foregoing, pressure drum 50, transfuser drum 52 and imaging drum 54 of imaging assembly 60 are maintained within predefined temperature ranges to optimize printing upon media 22. Such temperature ranges are maintained by heating or cooling devices during printing operations and selected standby operations. As described below, maintaining the imaging assembly drums 50, 52, 54 within the specified temperature ranges facilitates the printing process and transfer of toner.

Inasmuch as the illustrated embodiment of printer 10 is configured for offset printing, it is preferred to maximize the toner transferring capabilities of the imaging assembly 60 and especially the imaging drum 54 and transfuser drum 52 thereof. The print quality depends upon the ability of the imaging drum 54 and transfuser drum 52 to transfer the generated image to the media 22. Temperature conditioning of the toner aids with the transferring of toner from imaging drum 54 to transfuser drum 52. To maximize the transfer of toner from imaging drum 54 to transfuser drum 52, the temperatures of the two drums are regulated to "discourage " the gripping of toner via the imaging drum 54 and "encourage " the gripping of toner via the transfuser drum 52.

Surface materials of the imaging drum 54 and transfuser drum 52 additionally play an important role in maximizing the transfer of toner. In particular, the surface of imaging drum 54 is a relatively smooth hard anodized surface compared with the soft, rougher, silicone rubber surface of the transfuser drum 52. Thus, transfuser drum 52 has a tendency to "grip" and pull the toner from imaging drum 54.

Transfuser drum 52 is preferably provided at a temperature above 110°C to provide sufficiently tacky toner at the pressure (T₂) nip. Transfuser drum 54 is also ideally provided at a temperature less than 130°C to prevent premature provision of toner in a viscous state. Temperatures in excess of 130°C result in degradation of the toner image when the image is fused onto the media 22. More specifically, transfuser drum 52 is maintained in a predefined temperature range, such as 115°C - 125°C. Ideally, transfuser drum 52 is maintained at a temperature of approximately 120°C. This heat energy melts toner which adheres to the transfuser drum 52 thereby reducing it to a tar-like consistency. Such melting of the toner improves the transfer thereof from imaging drum 54 to transfuser drum 52. The temperature of imaging drum 54 is kept cooler than the transfuser drum 52 to retain the crystalline state of the toner at the toner/imaging drum interface. Ideally, imaging drum 54 is maintained at a temperature of less than about 70°C. However, imaging drum 54 is preferably maintained above a temperature of 55°C to prevent or minimize the formation of condensation upon the outer surface of the imaging drum 54. More specifically, imaging drum 54 is maintained within a predefined range of approximately 55°C - 65°C, and ideally maintained at the target temperature of approximately 60°C which is above ambient temperature and below the fusing temperature when the toner is applied to the media 22. Imaging drum 54 is ideally heated prior to printing (e .g., when printer 10 is in stand-by mode) and cooled during printing to maintain the temperature of the drum within the specified temperature range. Pressure drum 50 is maintained at a temperature of less than about 90°C. Maintaining pressure drum 50 below 90°C allows drum 50 to draw some of the heat from transfuser drum 52 at the pressure nip thereby reconditioning transfuser drum 52 for the image-to-transfuser offset. Temperature sensors 74, 76 shown in Fig. 3 are individually mounted in heat sensing relation relative to the respective transfuser and imaging drums 52, 54. The respective heat sensors 74, 76 are enclosed within a housing which maintains each of the heat sensors within a substantially constant temperature range of about 50°C to about 60°C. The temperature sensors 74, 76 are utilized to provide temperature information enabling temperature control of respective drums 52, 54.

Assemblies to maintain such operational temperatures are provided in heat transferring, or cooling, relation relative to the respective drums. As discussed below, a transfuser heating assembly is provided adjacent transfuser drum 52. Additionally, an imaging drum heating/cooling assembly is provided to control the temperature of imaging drum 54. An assembly for cooling pressure drum 50 is also described below.

Referring again to Fig. 3, transfuser drum heater or heating assembly 72 is provided in heat transferring relation to transfuser drum 52. More specifically, transfuser heating assembly 72 is provided between the imaging nip (T ) and pressure nip (T,). Transfuser drum heater 72 comprises at least one heat emitting device 73 and reflector 75 which is configured to direct emitted heat toward transfuser drum 52. Two devices 73 are shown in Fig. 3. Heat emitting device 73 of heating assembly 72 comprises a 2 kW infrared lamp in one embodiment of the invention. Toner received upon transfuser drum 52 receives a radiant boost of approximately 5°C via transfuser heating assembly 72. Such an increase in temperature reduces the viscosity of the toner prior to entry to the pressure nip and application to media 22.

A pressure drum fan 51 is provided adjacent pressure drum 50 as shown in Fig. 3. Pressure drum fan 51 is configured to cool pressure drum 50. Cooling pressure drum 50 allows the drum to draw some of the heat from transfuser drum 52 at the pressure nip .

Referring to Fig. 5, a right end view of printer 10 is shown. In this view, a heating/cooling assembly 80 for controlling the temperature of the imaging drum 54 is shown. As described above, the temperature at the surface of the imaging drum 54 is preferably maintained within a specified temperature range to prevent or minimize irregular print qualities upon media 22. Further, heating/cooling assembly 80 should be configured to increase or decrease the temperature at the surface of imaging drum 54 depending upon the mode of operation (e.g., standby or printing) of printer 10.

One embodiment of the imaging drum heating/cooling assembly 80 comprises a plenum or housing 82 below the media intake area 18. Housing 82 contains a central fan 84 and adjacent heaters 86. Fan 84 is preferably mounted adjacent an aperture 81 within housing 82 to draw ambient air therethrough.

Plural heating elements 86 are preferably mounted on either side of fan 84. Heating elements 86 in the described embodiment are helical wire heaters. Heating elements 86 are operable to selectively heat the air supplied to the imaging drum 54. In particular, heating of the supplied air is typically required when the printer 10 is in a standby mode of operation. Alternatively, cooled air is supplied to imaging drum 54 during printing to maintain an appropriate temperature at the surface of imaging drum 54. Exterior hoses 88 couple the housing 82 with both ends of imaging drum 54 and are configured to deliver conditioned air thereto. Imaging drum 54 is configured to circulate the received air across substantially the entire outer surface of drum 54 to assure even distribution of the air and maintain a substantially constant temperature across the outer surface thereof. In the described embodiment of the invention, imaging drum 54 comprises an aluminum extension mounted on a perforated hollow tube shaft. The perforations in the hollow tube allow air to circulate below the cylindrical surface of the imaging drum and out the ends thereof. One embodiment of a suitable imaging drum is described in a U .S. patent application entitled 'Imaging Drum," naming Benjamin Egbert, Paul Paroff and Mark Gaskievicz as inventors, filed August 28, 1997, assigned to the assignee hereof, having attorney docket reference OU 1-036, and incorporated herein by reference. The printer 10 according to the present invention includes a control assembly for supervising and controlling the operation of printer 10. The control assembly operates various printer functions. For example, the control assembly coordinates the speeds of rotation of the drums of the imaging assembly, and controls the media intake assembly and temperatures of the drums of the imaging assembly in order to facilitate the operation of the printer 10.

Referring now to Fig. 6, one embodiment of control assembly 100 is described below. The described embodiment of control assembly 100 of printer 10 includes an internal network 101. The internal network 101 operates as a serial master/slave multi-drop network in one embodiment of the invention.

The illustrated internal network 101 comprises a communication controller 06, which is connected via a data line 107 to a plurality of controllers.

Such controllers include an image controller 108, environmental controller 110, media controller 112, process controller 114, and a developer controller 116. Additionally, communication controller 106 is coupled with a raster image processor (RIP) 104 within printer 10. Raster image processor 104 receives image data from a host processor 102.

The controllers 106-116 comprise 8051 processors provided by Intel Corporation of Santa Clara, California, in accordance with one embodiment of the present invention. In the described embodiment, raster image processor 104 comprises a 960H processor also provided by Intel Corporation. Other microprocessors are utilized in other embodiments of the invention. The processors individually include an internal ROM which is configured to store operational and communications code . Operational code includes commands for operating associated printer components coupled with the individual processor. Communications code enables the individual processor to communicate with other processors of the control assembly 100 via communications network 101.

In the described embodiment, the individual controllers are electrically coupled with various components of the printer 10. More specifically, image controller 108 is coupled with print head 62 and an image drum tachometer for monitoring position and velocity of imaging drum 54. Environmental controller 110 is coupled with the heating and cooling assemblies. Media controller 112 is coupled with drive motor 38, media propulsion motor 42, and exhaust or outfeed motor 59. Further, media controller 112 is coupled with media tachometer 43 of media propulsion assembly 40 for monitoring the velocity and position of media 22 in printer 10.

Process controller 114 is coupled with accessories. For example, process controller 114 may be utilized to control supply and take-up rolls (not shown) for media 22. Developer controller 116 is coupled with developer 64. In particular, developer controller 116 is operable to control developer roller 70 for controlling the supply of toner to imaging drum 54.

During print operations, host processor 102 supplies a first description, such as a page description, of either a single image or a plurality of images to raster image processor 104. Raster image processor 104 of printer 10 is configured to receive image data from the host processor 102 via either a serial, parallel or I/O input interface.

Raster image processor 104 converts the images from the first description to a second description, such as a bit map of the image . Such conversion operations are referred to as rasterization of the incoming data images. Once a received image has been rasterized, raster image processor 104 sends a print request command to communication controller 106. Communication controller 106 recognizes the first print request and instructs the media controller 112 and image controller 108 to begin print operations. Media controller 112 provides the media 22 in position for printing through the utilization of media propulsion assembly 40. Media controller 112 is also configured to monitor top of form positioning of individual sheets of continuous form media 22. Media controller 112 outputs a top of form indication corresponding to the proper top of form positioning of a sheet of media 22. Media controller 112 closes the T₍ nip upon the media 22 to begin the print process. Additionally, media controller 112 is operable to open the T_t nip to disconnect transfuser drum 52 from media 22 at the end of a print job.

Image controller 108 waits for a top of form indication from media controller 112 to begin imaging. Image controller 108 interfaces with raster image processor 104 via communication controller 106 during printing. Image controller 108 is also coupled with a tachometer (not shown) upon imaging drum 54. The tachometer provides rotational velocity and position information of imaging drum 54. Such imaging drum 54 information may be utilized by image controller 108 and imaging assembly 60 during printing. Inasmuch as the print speed or velocity of printer 10 is variable, the formation of images via print head 62 is dependent upon the rotational velocity of imaging drum 54 in one embodiment of the invention.

One embodiment of image controller 108 comprises a data arranger. In general, the data arranger is configured to provide image data from the raster image processor 104 into a memory device such as a Video DRAM . The image data is outputted from the memory device to print head 62.

Once all data from the raster image processor 104 has been provided to image controller 108 and imaging has been completed, image controller 108 forwards an image stop command to communication controller 106 to finish printing. Alternatively, image controller 108 indicates an image stop command if raster image processor 104 is unable to keep up with the printing upon media 22. In the preferred embodiment, raster image processor 104 should complete the conversion from the first description of the next image to be imaged to the second description of the next image before print head 62 has imaged the last 25 scan lines of the image currently being imaged upon imaging drum 54. Image controller 108 issues an image stop command if controller 108 fails to receive the print ready command (indicating the next image has been rasterized) from raster image processor 104 before the imaging of the final 25 scan lines. Printer 10 is configured to operate at a variety of speeds in accordance preferred embodiments of the invention. Upon start-up, the printer 10 is configured to operate at a first or initial printing speed or velocity. During operation, the printer 10 ramps up in print speed to a preferred maximum print speed to provide maximum printing throughput capabilities. Referring now to Fig. 7, control operations of printer 10 are discussed in detail. More specifically, control operations regarding the regulation of the velocity or speed of media 22 through printer 10 are discussed with reference to the depicted flow chart.

Software or operational code to implement control operations of printer 10 is preferably stored within the ROMs of the respective controllers. In an alternative embodiment, flash memory is provided within the controllers and software code is downloaded into flash memory of the respective controllers upon initialization of printer 10. In yet a further embodiment of the invention, the control operations of printer 10 are implemented in hardware provided within the respective controllers of printer 10. The raster image processor 104 generates the print request command upon conversion of data received from host computer 102 from the first description to the second description. Raster image processor outputs the print request to the communication controller 106. As shown in step 150 of the flow chart, the printer 10 may be configured to idle in a stand-by mode of operation at step 153 until generation and receipt of the print request.

Upon receipt of the print request, the communication controller processor proceeds to step 151. At step 151 , the processor within communication controller 106 instructs media controller 112 and image controller 108 to begin printing at a predetermined initial print velocity. Media controller 112 outputs a top of form command once the top of a sheet of media 22 is received at the predetermined top of form location within printer 10 indicating media 22 is ready for printing.

Responsive to receiving the outputted top of form command, image controller 108 begins imaging the appropriate image received from raster image processor 104 upon the imaging drum 54. As indicated in step 151 , such initial printing operations occur at an initial velocity. In one embodiment of the invention, the initial velocity is approximately 6 inches per second (ips).

At step 152, communication controller 106 monitors for the reception of an image stop command from image controller 108. Image controller 108 typically issues an image stop command responsive to the end of a print request. As described above, image controller 108 may also issue an image stop command if the raster image processor 104 fails to convert the next image to be imaged in a sufficient amount of time. As indicated at step 152, if an image stop command is issued and received, communication controller 106 instructs other controllers of control assembly 100 to enter a printer standby or ready mode of operation at step 153.

For example, in the standby mode of operation, environmental controller 110 maintains printer 10 in a standby mode for quick resumption of printing. In particular, environmental controller 110 maintains imaging drum 54 at a proper process temperature . Alternatively, printer 10 may be configured to shut down once the standby mode is entered at step 153. In such an arrangement, the temperature of the drums is permitted to fall in such a power conserving mode of operation. Communication controller 106 proceeds to monitor the issuance of a print request command from raster image processor 104, as indicated at step 150, following entry into standby mode of operation. Referring again to step 152, if image controller 108 does not issue an image stop command, communication controller 106 monitors for the presence of a RIP slow request at step 154. In particular, raster image processor 104 measures the amount of time required to convert received images from the first description (i.e ., page description) thereof to the second description (i.e., bit map description) . If such measured value of time exceeds the rate at which the converted image must be applied to the image controller 108, raster image processor 104 issues a RIP slow request.

Communication controller 106 monitors for the assertion of a RIP slow request at step 154. If such a RIP slow request command is issued, communication controller 106 instructs media controller 112 to operate printer 10 at a lower print velocity, as indicated at step 155. Communication controller 106 continues to monitor for the presence of an image stop request at step 152. Communication controller 106 also continues to monitor for the presence of the RIP slow request from the raster image processor 104.

Raster image processor 104 de-asserts the RIP slow request command once it is converting incoming data images at a sufficient rate. Following the de- assertion of the RIP slow request or if no RIP slow request has been received, communication controller 106 proceeds to step 156. Printer 10 seeks to ramp the print velocity to maximum velocity at step 156. Communication controller 106 instructs the appropriate controllers via network 101 to increase speed to maximum velocity.

More specifically, media controller 112 operates main drive motor 38 to increase the rotational velocities of imaging drum 54, transfuser drum 52 and pressure drum 50. Such an increase in rotational velocities of the drums of the imaging assembly 60 increases the rate of imaging upon media 22.

Additionally, developer controller 116 increases the rotational speed of toner roller 70 to increase the deposition of toner upon imaging drum 54. Similarly, process controller 114, if provided, instructs accessories of the increased imaging rate of printer 10. For example, process controller 114 instructs supply and take-up reels of media 22 to operate at increased rates of supply and take- up.

Printer 10 ramps or increases the velocity of media 22 through printer 10 to a maximum velocity to provide increased printing throughput. Printer 10 continues to print images upon media 22 during fluctuations or changes in print velocity. In particular, the rate of forming the images is dependent upon the velocity of the media 22 through the printer 10. Print head 62 is configured to form latent images upon imaging drum 54 responsive to rotational velocity information from the tachometer monitoring the rotational speed of imaging drum 54. In the described embodiment of printer 10, the maximum velocity is approximately 12 inches per second (ips) although increased velocities are also considered.

To stay within the predetermined thermal characteristic ranges required upon the surfaces of drums of imaging assembly 60, temperature changes during changes in print velocity must be monitored. In particular, increased throughput of media 22 through printer 10 increases the removal of heat from internal components within printer 10. Therefore, temperature conditioning of the imaging assembly 60 may be necessary during changes in print velocity to assure proper toner transfer and quality image formation.

For example, during increased velocities, heat may be applied to transfuser drum 52 via transfuser heating assembly 72 to compensate for the increased amount of heat removed via media 22. Application of heat may be required to maintain transfuser drum 52 within an acceptable temperature range during variations in the media velocity and imaging rates. Similarly, less heat is supplied during lower printing velocities. Environmental controller 110 is configured to monitor the temperature of transfuser drum 52 via temperature sensor 74. Responsive to data received from sensor 74, environmental controller 110 may selectively increase or decrease the amount of heat supplied to transfuser drum 52 via transfuser heating assembly 72. Environmental controller also monitors the temperature of imaging drum 54 via sensor 76. Environmental controller 110 is configured to vary the temperature of imaging drum 54 via heating/cooling assembly 80.

Referring to Fig. 8, control operations of environmental controller 110 according to one embodiment of the present invention during a change in print speed or velocity are described below. Environmental controller 110 operates or controls components (e.g., heating or cooling assemblies) coupled therewith according to operational parameters defined by a particular band.

More specifically, a plurality of bands are provided which correspond to the print speeds or velocities of the printer 10. As the velocity or speed of the media 22 changes through printer 10, a different band may be accessed to provide appropriate operational parameters. Environmental controller 1 10 is configured to select the correct band corresponding to the current operating velocity of printer 10. Environmental controller 1 10 receives media speed from the media tachometer 43 provided within media propulsion assembly 40. Environmental controller 110 retrieves parameters from the selected band which corresponds to the current print speed. Therefrom, environmental controller 110 generates corresponding control signals for application to the heating and cooling assemblies for operation within a corresponding temperature range . For example , parameters included in the bands are utilized to control the heating and cooling of drums 50, 52, 54 of imaging assembly 60. The particular control signals applied to the heating and cooling assemblies depend upon the particular band to which the current printer speed or velocity corresponds.

Referring to Fig. 8, following the reception of a print command from communication controller 106, the processor of environmental controller 110 operates associated assemblies (e.g., heating, cooling) according to parameters provided within an initial or start-up band as shown at step 120. The environmental controller processor extracts the operational parameters from a memory device such as an ROM . The parameters are extracted from the initial band and the environmental controller processor applies corresponding control signals to the heating and cooling assemblies within printer 10.

Following application of control signals corresponding to the initial band, the environmental controller processor awaits a new speed indication from media tachometer 43. Once a new speed is received at step 122, the processor of environmental controller 110 proceeds to step 124 to determine whether the new speed is within the current operating band (e .g., the initial band). If the new speed is within the current operating band, the processor of environmental controller 110 continues to provide control signals according to parameters provided within the current band.

If at step 124, the new indicated speed is outside of the current operating band, the processor of environmental controller 110 proceeds to step 126. At step 126, the processor determines whether the new speed is in excess of speeds corresponding to the current band. If the new speed is in excess of the current band, the processor proceeds to step 128 where it selects an increased band and retrieves operational parameters from the increased band. Various environmental changes are effected within printer 10 responsive to the new band. For example, according to the operational parameters within the increased band, additional heat may be supplied to transfuser drum 52. Such increased heat is needed to offset the increased elimination of heat via media 22 passing through printer 10.

At step 126, if the new speed is less than the current band, the processor of environmental controller 1 10 proceeds to step 130. At step 130, the processor of environmental controller 110 decreases the current band and retrieves operational parameters from the selected band for operating heating and cooling assemblies. In accordance with the decreased band, less heat may be applied to transfuser drum 52 to maintain the drum within the proper operating temperature range . Accordingly, environmental controller 110 outputs control signals responsive to the new parameters to the transfuser heating assembly 72 to lower the temperature of transfuser drum 52. Following the decreased band operation at step 130, the processor of environmental controller 110 proceeds to step 122 to monitor the reception of a new speed indication from media tachometer 43.

In compliance with the statute , the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Claims

1. A continuous form printer comprising: a frame ; a drive assembly coupled with the frame and configured to transport continuous form media along a media path within the printer at a plurality of velocities; an imaging assembly operably spaced adjacent the media path and configured to form images upon the continuous form media; and a control assembly coupled with the drive assembly and configured to control the velocity of the continuous form media.

2. The printer according to claim 1 wherein the imaging assembly comprises a print head configured to provide a latent electrophotographic image .

3. The printer according to claim 1 wherein the imaging assembly comprises a print head and a plurality of drums.

4. The printer according to claim 3 wherein the imaging assembly further comprises a developer.

5. The printer according to claim 3 wherein the plurality of drums comprise an imaging drum configured to receive a latent image from the print head and a transfuser drum configured to receive the image from the imaging drum and offset the image onto the continuous form media.

6. The printer according to claim 5 wherein the latent image received upon the imaging drum is an electrophotographic image .

7. The printer according to claim 5 wherein the imaging assembly further comprises a developer configured to apply toner to the imaging drum to develop the latent image thereon, the developer being configured to vary the rate of application of the toner responsive to the velocity of the continuous form media.

8. The printer according to claim 1 further comprising: an input interface configured to receive a first description of an image ; and a processor configured to convert the first description of the image to a second description of the image.

9. The printer according to claim 8 wherein the control assembly is configured to control the velocity of the continuous form media responsive to a timing to convert the first description of the image to the second description of the image .

10. The printer according to claim 5 further comprising: an environmental control assembly; and plural heating assemblies individually configured to maintain the temperature of one of the imaging drum within a first predefined range and the transfuser drum within a second predefined range .

11. The printer according to claim 10 wherein the first predefined range is lower than the second predefined range.

12. The printer according to claim 10 wherein the first predefined range is approximately 55┬░C to approximately 65┬░C.

13. The printer according to claim 10 wherein the second predefined range is approximately 115┬░C to approximately 125┬░C.

14. The printer according to claim 1 wherein the control assembly operates the drive assembly to provide the continuous form media at an initial velocity and increase the velocity of the continuous form media during the formation of images upon the continuous form media.

15. The printer according to claim 1 wherein the control assembly comprises a plurality of controllers.

16. A method of forming images upon continuous form media comprising: providing continuous form media; providing a plurality of images; forming the plurality of images upon the continuous form media; outputting the continuous form media following the forming; and varying the rate of the forming of the images upon the continuous form media.

17. The method according to claim 16 wherein the providing the images comprises providing latent electrophotographic images.

18. The method according to claim 16 further comprising: converting the images from a first description to a second description; and timing the converting of the images.

19. The method according to claim 18 wherein the converting comprises rasterizing the images.

20. The method according to claim 18 wherein the varying is responsive to the timing.

21. The method according to claim 16 further comprising varying the velocity of the continuous form media.

22. The method according to claim 16 further comprising varying the velocity of the providing and outputting of the continuous media responsive to the varying the rate of the forming of the images.

23. The method according to claim 16 wherein the varying comprises: forming the images at an initial velocity; and increasing the rate of the forming of the images.

24. The method according to claim 16 wherein the providing of the images upon the continuous media comprises: forming a latent electrophotographic image upon an imaging drum; developing the latent electrophotographic image upon the imaging drum with toner, the developing providing a toner image; and offsetting the toner image to the continuous form media.

25. The method according to claim 24 wherein the developing comprises applying toner to the imaging drum at the latent electrophotographic image formed thereon.

26. The method according to claim 24 wherein the offsetting comprises: transferring the image from the imaging drum to the transfuser drum; and transferring the image from the transfuser drum to the continuous form media.

27. The method according to claim 24 further comprising maintaining the individual temperatures of the imaging drum and transfuser drum within respective predefined temperature ranges.

28. The method according to claim 24 further comprising adjusting the rate of the applying of toner to the imaging drum during the varying.

29. A method of forming images upon media comprising: receiving a plurality of first data descriptions corresponding to a plurality of images; converting the first descriptions to a plurality of second descriptions of the images; timing the converting of the first descriptions to the second descriptions; forming a plurality of images corresponding to the second descriptions of the images upon the media; and selectively adjusting the rate of forming the images responsive to the timing.

30. The method according to claim 29 wherein the forming the images comprises: providing a latent electrophotographic image upon an imaging drum; developing the latent electrophotographic image with toner; and offsetting the developed latent electrophotographic image to the continuous form media.

31. The method according to claim 30 wherein the offsetting comprises: transferring the developed image to a transfuser drum; and transferring the developed image to the media.

32. The method according to claim 31 further comprising maintaining the temperature of the transfuser drum within a predetermined range during the adjusting.

33. The method according to claim 30 further comprising maintaining temperature of the imaging drum within a predetermined range during the adjusting.

34. The method according to claim 29 wherein the converting comprises rasterizing.

35. The method according to claim 29 wherein the forming comprises forming an image upon an imaging drum.

36. The method according to claim 35 further comprising varying the amount of toner applied to the imaging drum responsive to the adjusting.

37. The method according to claim 29 wherein the selective adjusting comprises: forming the images at an initial velocity; and increasing the velocity of the forming of the images.

38. The method according to claim 29 wherein the media comprises continuous form media.

39. The method according to claim 29 wherein the selective adjusting comprises: receiving an operating velocity; determining if the operating velocity is within a predefined band; and selecting a new band responsive to the determining.

40. A method of forming images upon a continuous media comprising: providing a plurality of images; providing a continuous form media at a first velocity; forming the images upon the continuous media at an initial rate; ramping the velocity of the providing of the continuous form media; and ramping the rate of the forming of the images.

41. The method according to claim 40 wherein the providing the images comprises providing latent electrophotographic images.

42. The method according to claim 40 further comprising: converting the images from a first description to a second description; and timing the converting of the images.

43. The method according to claim 42 wherein the converting comprises rasterizing the images.

44. The method according to claim 40 wherein the ramping the rate of forming the images comprises: forming the images at an initial rate; and increasing the rate of the forming of the images.

45. The method according to claim 40 wherein the forming of the images upon the continuous media comprises: forming latent electrophotographic images upon an imaging drum; developing the latent electrophotographic images upon the imaging drum with toner, the developing providing a toner image; and offsetting the toner images to the continuous form media.

46. The method according to claim 45 wherein the developing comprises applying toner to the imaging drum at the latent electrophotographic image formed thereon.

47. The method according to claim 45 wherein the offsetting comprises: transferring the images from the imaging drum to the transfuser drum; and transferring the images from the transfuser drum to the continuous form media.

48. The method according to claim 45 further comprising maintaining the individual temperatures of the imaging drum and transfuser drum within respective predefined temperature ranges during the ramping of the velocity.

49. The method according to claim 45 further comprising adjusting the rate of the applying of toner to the imaging drum during the ramping the rate of forming the images.