Patent Application
20140237848
The invention relates to the field of dryers, and in particular, to dryers that actively generate airflow when drying printed media.
Businesses or other entities having a need for volume printing typically purchase a production printer. A production printer is a high-speed printer used for volume printing (e.g., one hundred pages per minute or more). Production printers are typically continuous-form printers that print on webs of print media that are stored on large rolls.
A production printer typically includes a localized print controller that controls the overall operation of the printing system, and a print engine (sometimes referred to as an “imaging engine” or as a “marking engine”). The print engine includes one or more printhead assemblies, with each assembly including a printhead controller and a printhead (or array of printheads). An individual printhead includes multiple tiny nozzles (e.g., 360 nozzles per printhead depending on resolution) that are operable to discharge ink as controlled by the printhead controller. A printhead array is formed from multiple printheads that are spaced in series across the width of the print media.
While the production printer is in operation, the web of print media is quickly passed underneath the printhead arrays while the nozzles of the printheads discharge ink at intervals to form pixels on the web. Some types of media used in inkjet printers are better suited to absorb the ink, while other types are not. Thus, a radiant dryer may be installed downstream from the printer. The radiant dryer assists in drying the ink on the web after the web leaves the printer. A typical radiant dryer includes an array of lamps that emit light and heat. The light and heat from the lamps helps to dry the ink as the web passes through the dryer.
In order to facilitate drying of the web, air may be actively forced through the dryer so that moisture-saturated air is driven out of the dryer, while dry air is brought into the dryer. However, active air flow can cause flutter at the web, which can result in warps and tears along the web, and may even break the web. Thus, it is undesirable to implement any active airflow that directly strikes the web. Furthermore, rollers are rarely used within the interior of a dryer to tension the web and prevent such flutter, because when tensioned rollers are heated to the operating temperature of the dryer, the rollers increase the risk of igniting the portion of the web that they are in contact with. Thus, web flutter in dryers that actively exchange air remains a problem.
Embodiments described herein provide flow generators in a dryer that drive opposing jets of gas (e.g., air) onto opposite sides of a web of printed media as the web travels through a dryer. The jets balance out forces from each other that would otherwise warp or bend the web. The jets also move the air inside of the dryer along the direction of travel of the web and towards an exit.
One embodiment is dryer for a printing system. The dryer includes a heating element, a top flow generator, and a bottom flow generator. The heating element is within an interior of the dryer, and heats a web of printed media as the web travels across the interior. The top flow generator is within the interior, and directly projects a first jet of gas onto a top side of the web. The first jet of gas deflects air proximate to the web. The bottom flow generator is within the interior, and directly projects a second jet of gas onto an opposing side of the web. The second jet strikes the web at substantially the same location as the first jet, and compensates orthogonal force applied to the web by the first jet. Furthermore, the top and bottom flow generators are both oriented to project the jets partially in the direction of travel of the web.
Another embodiment is a method. The method includes driving a web of printed media through an interior of a dryer, and operating a heating element within the interior of the enclosure to heat a web of printed media as the web travels across the interior. The method also includes directly projecting a first jet of gas onto a top side of the web that deflects air proximate to the web within the interior. Further, the method includes directly projecting a second jet of gas onto an opposing side of the web that deflects air proximate to the web within the interior. The second jet strikes the web at substantially the same location as the first jet and compensates orthogonal force applied to the web by the first jet, and the first and second jets are projected partially in the direction of travel of the web.
Other exemplary embodiments (e.g., methods and computer-readable media relating to the foregoing embodiments) may be described below.
Some embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings.
The figures and the following description illustrate specific exemplary embodiments of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope of the invention. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the invention is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.
Drying system 100 has been enhanced to include flow generators 140, which project impinging jets of gas directly onto web 120 as web 120 travels through drying system 100. One flow generator 140 is located above web 120 and projects a jet downward onto web 120, while another flow generator 140 is located below web 120 and projects a jet upward into substantially the same location on web 120.
The jets increase the rate at which air is exchanged with within drying system 100. This ensures that air within the dryer that is already saturated with moisture is quickly cycled out of drying system 100. Additionally, the forces applied by the complementary jets can tension web 120 while web 120 is within drying system 120, without placing a roller within the interior of drying system 100 and thereby increasing the risk of fire.
Gas source 150 provides a supply of gas to flow generators 140, and may comprise a compressor or pressurized container. Flow controller 160 manages the rate at which gas is supplied to flow generators 140 from gas source 150. For example, flow controller 160 may comprise a manual valve. In some embodiments, flow controller 160 comprises an electronically implemented controller (e.g., a circuit, or a processor implementing programmed instructions), that is capable of actively controlling the rate at which gas travels to flow generators 140. Flow controller 160 may further provide a different rate of flow to top flow generator 140 than to bottom flow generator 140. This may be done, for example, in response to detected variations in pressure from gas source 150, to compensate for any other conditions that may change the flow characteristics between the top and bottom flow generators 140, or for any other reason as desired.
Illustrative details of the operation of drying system 100 will be discussed with regard to
In step 202, web 120 is driven through drying system 100. For example, in one embodiment tensioned roller 130 drives web 120 through an interior of drying system 100. In step 204, heating elements 112 are operated to heat web 120 as web 120 travels across the interior of drying system 100.
In step 206, the airflow generator 140 (located above web 120) directly projects a top jet of gas onto web 120. The jet of gas extends into the page in
The top jet is oriented/angled so that it is partially projected in the direction of travel of web 120, and is partially projected orthogonal to web 120. This means that orthogonal force applied to web 120 by the top jet, if not compensated for, will deform web 120 downward.
In step 208, the airflow generator 140 (located below web 120) projects a bottom jet of gas onto web 120 that also deflects air proximate to web 120 while web 120 is within the interior of drying system 100. The bottom jet is applied at the same time as the top jet to substantially the same portion of web 120 as the top jet (but on a different side), and applies a compensating orthogonal force upward to balance the orthogonal force applied by the top jet. The bottom jet, like the top jet, is partially projected in the direction of travel of web 120.
By utilizing method 200 described above, a dryer can achieve multiple benefits at once. First, drying system 100 can enhance the flow of air along the interior, and can specifically disrupt laminar boundary layer flow for air proximate to a web of printed media. This means that new air which is not saturated with moisture can engage in convective mass transfer with marked portions of web 120. Second, because flow generators 140 apply complementary orthogonal forces to web 120, web 120 is not deformed by the jets of gas. Third, complementary flow generators 140 are oriented to apply substantially balancing orthogonal forces to web 120, which ensures that web 120 is properly positioned within drying system 100 without resorting to rollers, which may increase the risk of fire. Fourth, complementary flow generators 140 direct the flow of air along the direction of travel of web 120, and therefore towards an exit of drying system 100. This means that air is not driven towards marking engine 102, which would reduce print quality.
Flow generators 140 may comprise air knives that have a nozzle width (W) into the page that substantially matches the width of web 120. The nozzles of flow generators 140 may also have a length (L), and the nozzles may be located a distance (D) away from web 120. In one embodiment, the ratio of L to D is about 1:7. Flow generators 140 may project any suitable gas such as air, carbon dioxide, nitrogen, argon, etc.
In the following examples, additional processes, systems, and methods are described in the context of a dryer that processes a printed web of media.
In one particular embodiment, software is used to direct a processing system of flow controller 160 to dynamically regulate the amount of gas flow supplied to one or more flow generators (e.g., based on a determined speed of a web of print media).
Computer readable storage medium 512 can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor device. Examples of computer readable storage medium 512 include a solid state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Current examples of optical disks include compact disk - read only memory (CD-ROM), compact disk-read/write (CD-R/W), and DVD.
Processing system 500, being suitable for storing and/or executing the program code, includes at least one processor 502 coupled to program and data memory 504 through a system bus 550. Program and data memory 504 can include local memory employed during actual execution of the program code, bulk storage, and cache memories that provide temporary storage of at least some program code and/or data in order to reduce the number of times the code and/or data are retrieved from bulk storage during execution.
Input/output or I/O devices 506 (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled either directly or through intervening I/O controllers. Network adapter interfaces 508 may also be integrated with the system to enable processing system 500 to become coupled to other data processing systems or storage devices through intervening private or public networks. Modems, cable modems, IBM Channel attachments, SCSI, Fibre Channel, and Ethernet cards are just a few of the currently available types of network or host interface adapters. Presentation device interface 510 may be integrated with the system to interface to one or more presentation devices, such as printing systems and displays for presentation of presentation data generated by processor 502.
Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.
