Patent Grant
8965245
U.S. patent application Ser. No. 13/152,555, filed Jun. 3, 2011 by Leighton et al. and entitled “SINGLE BTR ROLL AT STRIPPER FOR CONTINUOUS WEB TRANSFER is incorporated herein by reference in its entirety.
This disclosed device and method relates generally to a transfer station used in electrostatographic or xerographic printing.
The basic process steps of electrostatographic printing, such as xerography or iconography include creating an image with the toner particles which is transferred to a print medium, which is typically a sheet of paper but which could be any kind of substrate, including an intermediate transfer belt or continuous web. This transfer is typically carried out by the creation of a “transfer zone” of electric fields where the print sheet is in contact with, or otherwise proximate to, the photoreceptor. Devices to create this transfer zone are well known in the prior art.
For example, the use of BTR (Biased Transfer Roll) foam rollers to either pull an image from a PR (Photoreceptor) belt or drum to an intermediate belt or from an intermediate belt to paper are often used. Typically, in such transfer operations, as shown in U.S. Pat. Nos. 7,242,894 and 7,158,746, a biased transfer roll is disposed in contact with a portion of a photoreceptor, thus forming an image transfer nip. An image-receiving sheet passes through the nip between the photoreceptor and transfer roll. At the nip itself, a toner image on the photoreceptor is transferred to the sheet by a combination of physical pressure at the nip, caused at least in part by the transfer roll, and an electrical bias placed on the transfer roll by suitable circuitry.
However, if the paper or substrate being fed is not a cut sheet, but rather a continuous roll of sheet paper or label media, the standard transfer process is inadequate. The conversion of a high speed, high volume Xerographic machine with a cut sheet paper supply to a continuous paper roll feed for label or book production requires an entirely new transfer area, that will not disturb the unfused toner either by lateral or process direction shear forces resulting from velocity mis-matches or from air breakdown while the media makes contact to the belt. Various events must be considered such as the skipping of the photoreceptor (PR) belt seam and skipping various other images on the belt such as test patches, in order that the pitch to pitch distance of images transferred to the paper and paper roll feed is held consistent. The new system must also be configured such that air break down does not occur disturbing the image by reducing the nip area, pre-wrapping the PR assist roll, and sufficient attack exit angle.
In web feeding, the image substrate material is typically fed from large rolls of paper in a defined width as previously stated. A difficulty, however, in printing from an endless belt type photoreceptor printing engine onto a continuous web substrate is the fact that belt type photoreceptors typically have a belt seam where the two ends of the belt are fastened to one another to form a continuous loop. Typically, it is either impossible or undesirable to form images overlying this belt seam, resulting in asynchronous or irregularly spaced image production. This, in general, can be a significant problem to the transfer of those images to a substrate. The problem is more severe, in particular, in the synchronization of images with a continuous web substrate.
Heretofore, it has been difficult or impractical to rapidly start and stop paper webs running through a printing system at high speeds because of the danger of web tearing, slippage, or misregistration, and/or the large moment and mass of the paper roll. As disclosed in U.S. Pat. No. 5,970,304, buffer loops and dancer rolls are known for the buffering of web speed variations and also the separation of the web from the nip to adjust the relationship of the photoreceptor belt and web for facilitating the transfer of images from the belt to the web.
It would also be desirable to provide other possible advantages to prior continuous paper feed systems such as better registration error control, and a smaller transfer nip. For example, a BTR transfer zone is typically only 3-5 mm, which makes it easier to insure good image quality and low shear area due to either web velocity mis-match errors or lateral position error moments. Also, it may be desirable to fully strip the web with the image prior to the seam before disengaging the web from the photoreceptor.
Thus, in order to maintain the continuous paper web feed pitch and compensate for occurrences such as the need to avoid the seam on the PR belt, a BTR roll is provided at the transfer zone or station and the paper web separated from the BTR nip. The continuous paper web is driven backwards and then accelerated to position the paper web at exactly the correct location prior to the paper web and PR belt uniting at the BTR roll nip. This is known as a ‘Pilgrim step’ in the converting industry.
In operation, according to the disclosure, a suitable BTR roll, often a soft foam roll, when engaged with an auxiliary or stripper roll will produce a nip of 3-5 mm wide for generating a transfer field and depositing a positive tacking charge to the backside of the paper. The toner is negative and is drawn to the paper from the photoreceptor belt. The coordination of web tension, auxiliary roll, and BTR roll will provide controllable belt engagement and defined timing of transfer of image without destructive uncontrolled air breakdown to the image. The timing of the auxiliary roll and BTR roll engagement after reversing will allow for synchronization of the turn on of the field in the gap between images without creating toner disturbances.
U.S. Pat. No. 4,611,901, issued Sep. 16, 1986 to Kohyama et al. and entitled “ELECTROPHOTOGRAPHIC METHOD AND APPARATUS”;
U.S. Pat. No. 4,660,059, issued Apr. 21, 1987 to O'Brien and entitled “COLOR PRINTING MACHINE”;
U.S. Pat. No. 4,833,503, issued May 23, 1989 to Snelling and entitled “ELECTRONIC COLOR PRINTING SYSTEM WITH SONIC TONER RELEASE DEVELOPMENT”;
U.S. Pat. No. 5,970,304, issued Oct. 19, 1999 to Stemmle and entitled “TWO SIDED IMAGING OF A CONTINUOUS WEB SUBSTRATE WITH A SINGLE PRINT ENGINE WITH IN LINE TRANSFER STATIONS”;
U.S. Pat. No. 7,158,746, issued Jan. 2, 2007 to Swift and entitled “XEROGRAPHIC PRINTER HAVING A SEMIRESISTIVE ROTATABLE BRUSH IN THE TRANSFER ZONE”; and
U.S. Pat. No. 7,242,894, issued Jul. 10, 2007 to Kuo et al. and entitled “XEROGRAPHIC TRANSFER STATION USING A BELT” are all incorporated herein by reference in their entirety.
In one embodiment of this disclosure, described is a continuous feed image marking apparatus comprising an image transfer belt including one or more developed images for transfer to a media web at an image transfer zone including a nip, the image transfer belts driven by a Drive Roll and an Assist Roll; the Drive Roll and Assist Roll driving the inside surface of the image transfer belt; and a Bias Transfer Roll (BTR) and one or more media web support rolls operatively associated with transferring the one or more developed images from the image transfer belt to the media web, the BTR and one or more web support rolls configured to provide a selectably engageable/disengageable nip for transferring the one or more images from the image transfer belt to the media web, the BTR and one support roll selectably camming the media web to engage/disengage the nip for transferring the one or more images from the image transfer belt to the media web, wherein, there is substantially zero wrap of the media web on the BTR during an engagement of the media web with the image transfer belt.
In another embodiment of this disclosure, described is an electrostatographic printing apparatus, comprising a charge receptor including an endless belt; a transfer nip including a BTR roll; a continuous media supplied to a transfer zone including the BTR roll, the BTR adapted for systematic engagement and disengagement with the continuous media for synchronization of image transfer from the charge receptor to the continuous media provided to the transfer zone, wherein there is substantially zero wrap of the continuous media on the BTR during the image transfer.
In still another embodiment of this disclosure, described is an electrostatographic printing apparatus, comprising a charge receptor; a transfer nip in contact with the charge receptor at a transfer zone, the transfer nip including an Assist Roll and a BTR Roll and a source of continuous media provided to the transfer zone, wherein there is substantially zero wrap of the continuous media on the BTR, a method of systematic engagement and disengagement of the continuous media in the transfer nip for synchronization of image transfer from the charge receptor to the continuous media comprising the steps of recognizing a requirement for the transfer nip to disengage from the continuous media, disengaging the continuous media from the nip, and reengaging the media with the nip.
In accordance with this disclosure, a system is provided that uses a continuous web of stock or paper instead of cut sheet media. Various process patches on the PR (Photoreceptor) belt create inconsistencies with the media feed, for example, a label dimension or seam that require timing and coordination. A BTR roll provides a relatively small nip at the transfer zone or station and the paper web is separated from the BTR nip. The well-defined nip edges allow for accurate timing of the registration between the PR belt and web media. The web is stopped and reversed, then reversed again to reunite with the PR belt. The timing of the BTR roll engagement after reversing allows for synchronization of the turn on of the field in the gap between images without creating toner disturbances due to air breakdown. The web reversal is known as a Pilgrim Step in the label industry because the imaging drums have image seams that must be avoided to keep the labels at an even pitch.
Provided is a novel design for the control of the geometry of the media web in the transfer zone of a continuous feed label press. Conventionally, the transfer nip design includes the media web wrapping around the biased transfer roller (BTR). Since the media is under tension, and the BTR consists of a thick, conformable conductive foam layer surrounding an electrically connected rigid metal shaft, the foam will compress due to the forces applied through the shaft assembly. It is proposed here that this compression will be non-uniform and may negatively impact the uniformity of the width of the contact nip when the BTR brings the media into pressured contact with the photoreceptor belt. In addition, it is proposed here that this may lead to image and motion quality non-uniformities. To solve this problem, the disclosed image transfer design for a continuous web includes a media web not wrapping on the BTR foam, thereby eliminating the foam compression due to the tension in the media web.
According to one exemplary embodiment, a contiguous label press requiring the marriage of a PR continuous polyimide belt with a label stock (paper release/paper label or polymer release/polymer label) open loop web is described. The transfer of the xerographic image from the PR belt to the paper occurs at the PR belt assist drive roller. The PR belt has a seam that cannot be imaged. Therefore, a periodic retraction/engagement-disengagement of the web is necessary to skip the seam which requires the paper to reverse and reengage to maintain a uniform gap label pitch between labels. Otherwise, a significant amount of waste will occur in the final label product stream. When the BTR is engaged to the PR assist roll it must perform only one function, that is to transfer the image from the PR belt to the paper. If the exit web exerts any Tension/BTR Radius pressure on the foam the nip will be unstable causing motion/banding artifacts.
To maintain a uniform nip width, this disclosure provides the geometry and entrance and exit angles to provide functional isolation of the BTR foam/label media/PR belt interface. The field exerted on the toner at transfer is related to the mechanical width of the nip as well as other electrostatic material conductive properties. If the label web is wrapped on the BTR and tension variations exist between the vacuum pull roll and the metering roll due to eccentricities, tension and velocity control in the web path, the T/R pressure changes on the BTR. If the BTR foam roller has a small wrap angle, this T/R pressure is 2 psi at 1 pli web tension. The nip pressure generated is ˜8 psi. Therefore, more load will need to be applied to create the 3 mm nip for the transfer nip to balance the T/R pressure and tighter control of the tension will be required to prevent the foam nip from deflecting/changing while printing.
To print a continuous stream of labels with a constant gap between labels, this gap could be as small as 3 mm. In order to achieve this, a skip pitch problem arises due to the PR belt seam. To eliminate excessive material waste due to the PR seam, the web is required to periodically retract via a ‘pilgrim step movement’ disengage BTR, decel, reverse, accel, and engage BTR from the PR belt so that the seam will not be “printed” on the web. This coordinated motion of the label web will ensure that the gap is constant between labels. The goal of the pilgrim step registration is the industry standard of ±150 um in both process and cross track directions. In order to achieve the registration careful control of the tension is essential. This disclosure and the exemplary embodiments provided herein address the tension control by keeping the web span lengths the same during the pilgrim step motion.
However, it will be appreciated that the disclosed systems could also be employed in non-xerographic color printers, such as ink jet printers, or in “tandem” xerographic or other color printing systems, typically having plural print engines transferring respective colors sequentially to an intermediate image transfer belt and then to the final substrate. Thus, for a tandem color printer it will be appreciated the image bearing member on which the subject registration marks are formed may be either or both on the photoreceptors and the intermediate transfer belt, and have MOB sensors and image position correction systems appropriately associated therewith. Various such known types of color printers are further described in the above-cited patents and need not be further discussed herein.
Referring to the exemplary printer 10 of
In embodiments, developer units 50A-50D are used to develop black, cyan, yellow, and magenta, respectively. These separate color images (usually called color separations) are developed successively with appropriate time delays so that they become overlapped on the photoreceptor belt before being transferred to a sheet of paper.
The belt 12 has a conventional drive system 16 for moving it in the process direction shown by its movement arrows. A transfer station 18 is illustrated for the transfer of the composite color images to the final substrate, a continuous media web, which then is fed to a fuser 19 and outputted.
Referring to
One of the exemplary configurations of an image transfer station is shown in
The disclosed image transfer mechanisms address the geometry of the vacuum roll and support roll wrap angles, entrance and exit spans to ensure that all the wrap occurs on the PR assist roll and zero wrap on the BTR roll. By wrapping only the PR assist roll there are no T/R pressures exerted on the foam.
Notably, the natural design tendency is to place the vacuum pull roll lower such that it is below the PR belt plane. This allows for less displacement of the transfer deck system when the PR module slides to the right and comes out of the module for belt replacement. Enforcing a zero wrap condition on the BTR roller during printing puts the vacuum pull roll higher and the support roll lower. A swing away mechanism must drop further to miss the PR module. Therefore, the BTR roller's only function is to create a nip and will not be required to manage a T/R pressure force exerted by the web during printing.
With reference to
The system, as shown in
It should be noted that, generally, a bias transfer roll 120 is provided for establishing a directional force field capable of attracting toner particles from a photoconductive surface to a copy substrate, such as a continuous media web, that is subsequently transported to a fusing station. The bias transfer roll electrically attracts charged toner particles from the photoconductive surface such as a PR belt, to transfer the developed images on the photoconductive surface of the belt to the continuous web positioned in the transfer nip. The BTR roll is generally formed of an open cell foam which is electrically conductive. An electrical biasing device in the form of a constant current or voltage supply source is generally electrically coupled to the conductive core for providing the electrical bias. The bias is either a constant current or a constant voltage source.
PR drive assist stripper roll 118 and BTR roll 120 form a nip to receive an imaging medium such as a continuous paper web 130, driven by a vacuum roll drive 124 and low lateral force or idler roll 128 conveying the continuous paper web 130 to the transfer station nip 118, 120. The low lateral force roll 128 with suitable strain gauge along with vacuum roll drive 124 provide suitable tension 1 to 1.5 pli on the continuous paper feed roll to convey the paper through the transfer nip to receive images from the belt 130.
The vacuum roll drive 124 applies suitable vacuum pressure to pull the paper against the roll and the images on the web 130 are then carried to a suitable fuser station 126. The web 130 makes contact roughly 2 mm prior to the field from the BTR 120 to prevent pre-nip breakdown. At this point, the wringer roll 122 is up and the wrap angle of the web 130 around the BTR 120 at the exit of the nip is about 1.5 degrees.
With reference to
With reference to
With reference to
With reference to
Another embodiment of the BTR transfer is shown in
With references to
It should be understood that the above disclosure for the handling of a web seam is merely exemplary of different situations such as avoiding test patches and different formats for label printing and the disclosure is intended to cover a wide range of applications and teachings dealing with continuous web printing and adjustment for situations requiring a deviation from routine operation.
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be 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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4611901 | Kohyama et al. | Sep 1986 | A |
| 4660059 | O'Brien | Apr 1987 | A |
| 4833503 | Snelling | May 1989 | A |
| 5970304 | Stemmle | Oct 1999 | A |
| 7158746 | Swift | Jan 2007 | B2 |
| 7242894 | Kuo et al. | Jul 2007 | B2 |
| 20110013950 | Furuya et al. | Jan 2011 | A1 |
| 20120301186 | Yang et al. | Nov 2012 | A1 |
| Entry |
|---|
| U.S. Appl. No. 13/152,555, filed Jun. 3, 2011, Leighton et al. |
| Number | Date | Country | |
|---|---|---|---|
| 20130142544 A1 | Jun 2013 | US |
