This Utility Patent Application is a U.S. National Stage filing under 35 U.S.C. §371 of PCT/US11/28030, filed Mar. 11, 2011 incorporated by reference herein.
In an offset press or in a portion of a digital offset press, an image is transferred to a media on a color-by-color basis in which each color for an image is applied separately. In this arrangement, a given media sheet will pass through an image-transfer nip multiple times before the entire image is formed onto the media sheet.
However, several factors can cause distortion of the media sheet as each color is successively applied to the media sheet. For instance, sometimes distortion can result from pressure and/or temperature that are used to facilitate transfer of the image onto the media sheet upon each pass of the media sheet through the image-transfer nip. Moreover, distortion also can result from variables associated with how the media sheet is fed into and settles in a gripper mechanism of the impression cylinder that carries the media sheet during printing. Unfortunately, because these factors can cause the media sheet to become distorted slightly from one color separation to the other, print quality can suffer because the registration between colors will vary from print to print.
One conventional approach used for an offset press to overcome color plane mis-registration due to these distortions relies on calibration and preventing stresses. Another conventional approach used for digital offset presses includes adding one idle cycle, which improves the initial paper settling on the impression cylinder, which in turn, improves color plane registration. On the other hand, adding an idle cycle is undesirable because it decreases press productivity.
For at least these reasons, conventional approaches still fall short of achieving consistent color plane registration without compromising press productivity.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
Embodiments of the present disclosure ensure proper color plane registration between a media sheet (carried by an impression cylinder) and an image (carried by a blanket cylinder—an intermediate cylinder covered with blanket) via a roller assembly that flattens the retained media sheet, prior to a nip between the blanket cylinder and the impression cylinder. In one embodiment, a press comprises a blanket cylinder, an impression cylinder, and a conditioning roller selectively engageable against the impression cylinder to apply to pressure to the secured media sheet passing between the conditioning roller and the impression cylinder. The impression cylinder rollingly engages the blanket cylinder to form an image-transfer nip. The impression cylinder includes at least one gripper configured to selectively secure an end of a media sheet relative to the impression cylinder. The conditioning roller is selectively engageable against the impression cylinder to apply to pressure to the secured media sheet prior to its passage through the image-transfer nip. In one aspect, the location at which this pressure is applied via the conditioning roller is an area that is free from ink.
In some embodiments, in addition to applying pressure to the media sheet, the conditioning roller also applies heat simultaneous with the applied pressure. The heat enhances ink adhesion when the image is transferred to the media sheet.
With this arrangement, prior to the media sheet entering the image-transfer nip, a conditioning roller flattens the media sheet to overcome any introduced deformations, and thereby achieve color plane registration throughout the different color separations without decreasing overall press productivity.
These embodiments, and additional embodiments, are described in association with
One embodiment of a press 15 is illustrated in
While not shown in
In preparation to receive an image, imaging cylinder 30 receives a charge from charging station 32 (e.g., a charge roller or a scorotron) in order to produce a uniform charged surface on electrophotographic surface 31 of imaging roller 30. Next, as imaging roller 30 rotates (as represented by directional arrow A), laser imager 20 projects an image via beam 22 onto the surface 31 of imaging cylinder 30, which discharges portions of the imaging cylinder 30 corresponding to the image. These discharged portions are developed with ink via developing station 34 to “ink” the image. As imaging cylinder 30 continues to rotate, the image is transferred onto the electrically biased blanket 44 of the rotating blanket cylinder 40. Rotation of the blanket cylinder 40 (as represented by directional arrow B), in turn, transfers the ink image onto a media 60 that will pass through the pressure nip 58 between blanket cylinder 40 and impression cylinder 50.
Impression cylinder 50 is configured to releasably secure media 60 about surface 52 of impression cylinder 50 so that media 60 is wrapped around impression cylinder 50 as media 60 passes through the pressure nip 58. In one embodiment, impression cylinder 50 includes one or more grippers 54 configured to selectively hold an end of a media sheet to releasably secure the media sheet relative to surface 52 of impression cylinder 50. While grippers 54 are shown schematically for illustrative purposes, one skilled in the art will be familiar with a variety of gripper mechanisms, including those shown in Wieland U.S. Pat. No. 4,253,396, among many others.
Press 15 also includes a feed mechanism 65 configured to feed media sheets 60, one at a time, to impression cylinder 50. While not shown for illustrative clarity, it will be understood that feed mechanism 65 includes appropriate guides to direct transport of media sheets 60 so that a first end 61 of media sheet 60 becomes positioned to be retained via one of the grippers 54 on impression cylinder 50.
Press 15 also includes a conditioning roller 70 positioned for selective engagement directly against impression cylinder 50 to condition media sheet 60 prior to its passage through nip 58, as will be described in more detail throughout
As shown in
It will be understood that the degree to which portion 64 is raised from surface 52 as depicted in
Unlike conventional systems, embodiments of the present disclosure include a conditioning roller 70 which is positioned and arranged to engage media sheet 60 to ensure proper color plane registration relative to blanket 44 of blanket cylinder 40.
In particular, as impression cylinder 50 further rotates to move media sheet 60 toward nip 58, conditioning roller 70 is moved (from its spaced position) toward impression cylinder 50 until conditioning roller 70 directly contacts surface 52 of impression cylinder 50, as shown in
As further shown in
Rotation module 102 controls and implements a generally continuous rotation of conditioning roller 70 so that conditioning roller 70 is always ready to engage impression cylinder 50. In one aspect, rotation module 102 causes conditioning roller 70 to rotate such that, at the point of contact, conditioning roller 70 exhibits substantially the same velocity as impression cylinder 50 and in a direction (shown via arrow T) compatible with the rotation of impression cylinder 50.
Translation module 104 of control assembly 101 controls and implements a translational movement of roller 70 toward and away from impression cylinder 50. In one aspect, movement of roller 70 toward impression cylinder 50 (as represented by directional arrow L) causes engagement of roller 70 against impression cylinder 50 while movement of roller 70 away from impression cylinder 50 (as represented by directional arrow M) causes roller 70 to move to a rest position spaced apart from impression cylinder 50 (for example, see
Pressure module 105 of control assembly 101 controls and implements an application of pressure (as represented by directional force arrow F) by roller 70 against impression cylinder 50 while roller 70 rotates in contact against impression cylinder 50. As further described below, this applied pressure flattens media sheet 60 (against surface 71 of media-conditioning roller 70) as sheet 60 passes through nip 78 between impression cylinder 50 and media-conditioning roller 70.
The respective modules (rotation module 102, translation module 104, and pressure module 105) comprise software, firmware, and/or hardware, including a combination of components such as circuitry, actuators, guides, motors, etc. as known to those skilled in the art, to carry out the functions described above for conditioning roller 70. In addition, it will be understood that while control assembly 101 forms a part of roller assembly 100 depicted in
As shown in
Eventually, with the on-going rotation of impression cylinder 50 relative to the rotating blanket cylinder 40, media sheet 60 enters image-transfer nip 58. However, unlike conventional systems, media sheet 60 has been flattened, via pressure applied via roller 70, prior to entry into nip 58. This flattening action ensures that media sheet 60 will be generally free of any raised portions across its width or along its length, which in turn, ensures proper color plane registration of media sheet 60 with the image (carried on blanket cylinder 40) that is being transferred onto media sheet 60 and with images previously transferred onto media sheet 60.
As further shown in
After second end 62 of media sheet 60 has advanced beyond conditioning roller 70 (as shown in
It will be understood that after the image (on blanket cylinder 40) has been completely transferred onto media sheet 60, in some instances, controller 38 of system 15 releases media sheet 60 from gripper 54 and media sheet 60 is further guided through system 15 to a finishing station or media output module. Accordingly, in this example media sheet 60 will make a single pass through nip 58 and conditioning roller 70 acts to condition media sheet 60 before any ink is applied to media sheet 60.
However, in other embodiments, media sheet 60 will make multiple passes through image-transfer nip 58 to receive the image as expressed in different color separations. In these embodiments, regardless of whether a slightly different deformation is introduced into media sheet upon each cycle, conditioning roller 70 acts to flatten media sheet 60 to ensure proper color plane registration.
With this arrangement, both heat and pressure is applied to media sheet 60 prior to nip 58 (between intermediate blanket cylinder 40 and impression cylinder 50) at which an image is transferred onto media sheet 60. The heat, when accompanying the applied pressure, enhances ink adhesion.
Embodiments of the present disclosure ensure proper color plane registration of a blanket cylinder with a media sheet (carried by an impression cylinder) by applying pressure to the media sheet via a conditioning roller positioned prior to the nip between the blanket cylinder and the impression cylinder. In some embodiments, heat is applied via the conditioning roller simultaneous with pressure. This arrangement achieves high quality printing while minimizing additional steps or complex mechanisms sometimes associated with conventional systems for achieving color plane registration.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2011/028030 | 3/11/2011 | WO | 00 | 8/30/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/125136 | 9/20/2012 | WO | A |
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CN Office Action, May 12, 2014, 10 pages. |
Number | Date | Country | |
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20130333580 A1 | Dec 2013 | US |