Patent Application
20120291642
The disclosure relates to direct inking to a digital offset plate. In particular, the disclosure relates to ghostless inking systems for direct inking of, for example, an anilox roll to a digital offset plate.
Inking systems are designed to transfer ink to offset plates. An inking system may be a keyed or key-less type. An inking system may be a regular offset-type printing system, or a digital offset plate printing system.
Related art inking systems can suffer from ghosting issues. In inking systems, transferred ink may be deposited in a layer. The layer may have areas of varying thickness. Ghosting can result from an ink layer being thinner in a particular area where an image has been previously transferred. Areas of thinner ink in ink layers typically cause corresponding lighter areas in image prints.
In related art systems, and particularly in, e.g., regular offset systems, ghosting issues may be addressed by using inker rolls that each have about the same diameter. Such an arrangement causes a repeating image to always be on the same location on the rolls, and circumvents the effects of ghosting.
For digital offset, however, a key-less inker having reduced ghosting issues is desirable. An inking system that is effective in reducing ghosting issues is provided. For example, methods, apparatus, and systems accommodate inking directly from an anilox roll to a digital offset plate with reduced occurrence of ghosting. An embodiment of methods may include depositing ink from an ink chamber onto an inking member. The inking member may include ink wells for containing inking deposited from an ink chamber. Methods may include leveling the ink on the inking member. The ink may be leveled by applying a doctor blade to a surface of the inking member. The doctor blade may be configured to remove excess ink from the inking member surface, and/or an ink well of the inking member.
An embodiment of methods includes transferring the deposited ink directly to a conformable digital offset member, e.g., plate. Another embodiment may include removing fountain solution transferred from the conformable digital offset plate to the inking member. The fountain solution may be removed by e.g., a doctor blade or an air knife, or a combination of removal mechanisms including at least an air knife and/or a doctor blade.
An embodiment of a digital offset inking system may include an ink chamber, an inking member, and an ink chamber doctor blade configured to remove excess ink from the inking member. The ink chamber may be configured to deposit the ink on a surface of the inking member. In an embodiment of systems, the inking member may be configured to include one or more wells for holding ink deposited by the ink chamber. The inking member may be, for example, an anilox roll. The ink wells may be one of a tri-helical or quad-channel type arranged about a surface of the roll. In alternative embodiments, the wells may be configured to have any shape that is suitable for carrying ink from an inking chamber to an offset surface for transfer thereto.
In an embodiment of systems, an imaging member includes a conformable offset surface. The inking member may be configured to contact the imaging member. For example, the inking member may be a rotatable member configured to bring ink deposited from an ink chamber into contact with the imaging member. The ink deposited from the ink chamber, and in embodiments, leveled to remove excess ink, may be transferred from the inking member directly to the conformable offset surface.
During transfer, fountain solution from the imaging member may be transferred to a surface of the inking member. In an embodiment of systems, a fountain solution system may be configured to remove the fountain solution from the surface of the inking member. In an embodiment, the fountain solution removal system may be a doctor blade. In another embodiment, the fountain solution removal system may be an air knife. In yet another alternative embodiment, the fountain solution removal system may be a combination of a doctor blade and an air knife. At least one of the doctor blade and the air knife may be configured to remove fountain solution from a surface of the inking member.
In another embodiment of systems, a digital offset inking system may include an inking chamber for depositing ink. The inking system may include an inking member for carrying ink deposited by the ink chamber. The inking member may including a doctor blade for removing excess ink, e.g., leveling the ink deposited from the ink chamber. In another embodiment, the inking chamber may include a chamber blade for containing the ink in the ink chamber, e.g., in combination with a portion of the inking member and/or a doctor blade.
In an embodiment, the digital offset inking system may include an imaging member for receiving ink transferred from the inking member. The imaging member may include a conformable surface, e.g., the imaging member may be a conformable offset plate. A fountain solution on a surface of the imaging member may be transferred to the inking member during transfer of a ink or an ink layer from the inking member to the imaging member. The inking system may include a fountain solution removal system configured to remove fountain solution from the inking member, e.g., after ink transfer.
Exemplary embodiments are described herein. It is envisioned, however, that any system that incorporates features of apparatus and systems described herein are encompassed by the scope and spirit of the exemplary embodiments.
Exemplary embodiments are intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the apparatus and systems as described herein.
Reference is made to the drawings to accommodate understanding of methods, apparatus, and systems for direct inking to a digital offset plate. In the drawings, like reference numerals are used throughout to designate similar or identical elements. The drawings depict various embodiments and data related to embodiments of illustrative methods, apparatus, and systems for inking directly from an inking member to an imaging member.
Methods, apparatus, and systems of embodiments are preferably key-less and accommodate ghostless inking directly to a digital offset plate.
In an inking step 300, ink may be transferred from an inking member to the surface of the central imaging cylinder. The transferred ink adheres to portions of the surface of the central imaging cylinder where a fountain solution has been evaporated. In a partial cure step 400, the transferred ink may be partially cured by irradiation, for example, UV cure. In an image transfer step 500, the transferred ink may be transferred to media such as paper at a media transfer nip.
In a step 600, a surface of the central imaging cylinder may be cleaned by a cleaning system. For example, trace cleaning rollers may be used to clean the surface of the central imaging cylinder. In embodiments, the surface of the central imaging cylinder is conformable. The surface of the central imaging cylinder may be made of, for example, silicone.
Ink may be transferred to a central imaging cylinder, as shown in inking step 300 of
For example, the ink chamber may be associated with a doctor blade or similar suitable structure. The doctor blade may be configured to doctor excess ink deposited in a cell of the inking member from the surface of the inking member. A chamber blade may be associated with the ink chamber. The chamber blade and the doctor blade may be configured to contain ink within the chamber. For example, the chamber blade, inking member, and doctor blade, in combination, may be configured to contain ink inside the ink chamber. Ink containment may be further facilitated by seals such as side seals.
The inking member, which may be an anilox roll, for example, may be configured to translate rotatably about a central longitudinal axis. Ink may be deposited by the ink chamber into one or more cells of an inking member when the inking member is at a first position. The inking member may be rotated to a second position at which the deposited ink is transferred directly to an imaging member, e.g., a digital offset transfer plate. The imaging member may be a central imaging cylinder, such as that diagrammatically shown in
During transfer of the deposited ink from the inking member to the imaging member, fountain solution from the surface of the inking member may be transferred to the inking member. In embodiments, the inking member may then be rotated to a third position at which the fountain solution may be removed from a surface of the inking member. A fountain solution removal system may be configured to remove fountain solution. For example, a fountain solution removal system may include a doctor blade that is configured to remove fountain solution. In an alternative embodiment, the fountain solution removal system may include an air knife that is configured to evaporate fountain solution from a surface of the inking member.
In another alternative embodiment, the fountain solution removal system may include a combination of at least a fountain solution doctor blade and an air knife for removing fountain solution transferred from the imaging member to the inking member.
For example, the inking member 205 may include a surface having one or more wells or cells configured to hold ink deposited by the ink chamber 207. The cells may be structured to have a tri-helical shape, or a quad-channel shape, or similarly structured for preferably permitting smoother solids and better ink fluidity and transfer for high viscosity inks, e.g., about 400,000 cps. Such high viscosity inks are a typical selection for digital offset applications. The cells may be mechanically or laser-engraved.
The ink chamber 207 may be associated with a chamber blade 210 and a doctor blade 215. The chamber blade 210 may be configured to contain ink within the ink chamber 207. Ink containment may be enhanced with the combination of doctor blade 215 and chamber blade 210.
The fountain solution transferred to the inking member 205 may be removed by a fountain solution removal system. For example, the inking member 205 may be rotatable from an ink transfer position to a fountain solution removal position as shown in
In another embodiment, the fountain solution removal system may include a combination of at least a fountain solution doctor blade and an air knife for removing fountain solution transferred from the imaging member to the inking member.
For example, the inking member 305 may include a surface having one or more wells or cells configured to hold ink deposited by the ink chamber 307. The cells may be structured to have a tri-helical shape, or a quad-channel shape, or similarly structured for preferably permitting smoother solids and better ink fluidity and transfer for high viscosity inks, e.g., about 400,000 cps. Such high viscosity inks are a typical selection for digital offset applications. The cells may be mechanically or laser-engraved.
The ink chamber 307 may be associated with a chamber blade 310 and a doctor blade 315. The chamber blade 310 may be configured to contain ink within the ink chamber 307. Ink containment may be enhanced with the combination of doctor blade 315 and chamber blade 310.
The fountain solution transferred to the inking member 305 may be removed by a fountain solution removal system. For example, the inking member 305 may be rotatable from an ink transfer position to a fountain solution removal position as shown in
As discussed above, the inking member may be an anilox roll, for example. The ink used in the inking system may be a high viscosity ink. For example, the ink may have a viscosity on the order of 400,000 cps. To facilitate inks of this viscosity and similar viscosities, the anilox roll may be configured to include a surface that defines cells having high-viscosity ink-accommodating patterns. For example,
It has been found that ghosting is significantly reduced when direct inking from an inking member such as an anilox roll to a digital offset plate where the surface of the digital offset plate is conformable. Traditional key-less inking systems, which may include an anilox roll followed by a conformable transfer roll typically suffer from ghosting. Transient tests show that there is an ink thickness transient that occurs in an ink transfer roll. Tests show that it takes about three to four revolutions of an ink transfer roll for the transient to arrive at a steady-state ink thickness.
For example,
While apparatus and systems for digital offset inking are described in relationship to exemplary embodiments, many alternatives, modifications, and variations would be apparent to those skilled in the art. Accordingly, embodiments of apparatus and systems as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the spirit and scope of the exemplary embodiments.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art.
