Lamp configuration and controller for a radiant dryer unit of an inkjet printer

Systems and methods for a dryer unit of a printer. In one embodiment, a dryer unit includes a light source having a plurality of lamps. The dryer unit further includes a controller that associates a target output power with each of the lamps of the light source. When in operation, the controller determines a speed of a printable medium that passes through the dryer unit. The controller is able to vary an intensity of light generated by the light source based on the speed of the printable medium by varying which of the lamps of the light source are energized to their target output power.

FIELD OF THE INVENTION

The invention relates to the field of production printing systems and, in particular, to a radiant dryer unit of a printer.

BACKGROUND

Businesses or other entities having a need for volume printing typically purchase a production printing system. A production printing system comprises a high-speed printer used for volume printing, such as 100 pages per minute or more. The production printing systems are typically continuous-forms printers that print on paper or some other printable medium that is stored on large rolls. Some continuous-forms printers are able to print on paper up to 20 inches wide or more.

A production printing system typically includes a localized print controller that controls the overall operation of the printing system, and one or more print engines (sometimes referred to as an “imaging engine” or as a “marking engine”). The print engines include a printhead controller and arrays 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. The printhead array is formed from multiple printheads that are spaced in series along a particular width, such as 20 inches.

When in operation, the printable medium is passed underneath the printhead arrays while the nozzles of the printheads discharge ink at particular intervals to form pixels on the medium. Some of the media used in inkjet printers is better suited to absorb the ink, while others are not. Thus, printing systems may be implemented with a radiant dryer unit that assists in drying the ink on the medium after the print engine discharges ink on the medium.

A typical dryer unit includes an array of lamps that emit light and heat to dry the ink onto the medium. The power applied to the lamps typically varies based on the speed of the medium as it passes through the dryer unit. As the speed of the medium increases, a higher intensity light is needed to dry the medium. In a traditional dryer unit, the power applied to the lamps of the array would increase as the speed of the medium increases. By increasing the power applied to the lamps, the intensity of the light produced by the array likewise increases to dry the medium. As the speed of the medium decreases, a lower intensity light is needed to dry the medium. Thus, the power applied to the lamps of the array would decrease as the speed of the medium decreases. By decreasing the power applied to the lamps, the intensity of the light produced by the array likewise decreases to dry the medium.

Printer manufacturers are continually trying to improve the effectiveness of radiant dryer units.

SUMMARY

Embodiments described herein provide an improved radiant dryer unit that more effectively dries a recording liquid (e.g., ink) onto a moving medium. There is an optimal light intensity and/or wavelength that can be used within a dryer unit for a specific medium/recording liquid combination. In a traditional dryer unit that varies the power applied to an array of lamps, the characteristic wavelength of the light emitted by the lamps varies as the power applied varies. Therefore, a traditional dryer unit may not be operating at the optimal wavelength at all times. In the embodiments described herein, each of the lamps of the dryer unit is energized to create a target output power. The target output power for a lamp is selected to produce at or near the optimal wavelength for drying a recording liquid onto a medium. To vary the overall intensity of the light source as the speed of the medium varies, different combinations of the lamps are energized to their target output power. For example, if low intensity light is desired in the dryer unit, then a first array of lamps may be energized to create a first target output power. If medium intensity light is desired, then a second array of lamps may be energized (instead of the first array) to create a second target output power. If high intensity light is desired, then both the first array and the second array may be energized with their respective target output powers. Even though the overall intensity of the light source varies, the wavelength of light emitted by each array stays constant at the optimal wavelength because a target output power is used for each lamp. This improves the operation of the dryer unit.

One embodiment is a dryer unit of a printer. The dryer unit includes a light source having a plurality of lamps. The dryer unit further includes a controller configured to associate a target output power with each of the lamps of the light source. The controller is further configured to determine a speed of a printable medium that passes through the dryer unit. The controller is further configured to vary an intensity of light generated by the light source based on the speed of the printable medium by varying which of the lamps of the light source are energized to create their target output power.

In another embodiment, the controller is further configured to determine a target intensity of light for the light source based on a measured speed of the printable medium, to select a combination of lamps in the light source that provides the target intensity when the lamps are energized to their target output powers, and to energize the lamps of the selected combination to their target output powers.

Another embodiment is a method of operating a dryer unit of a printer, where the dryer unit includes a light source comprising a plurality of lamps. The method includes associating a target output power with each of the lamps of the light source. The method further includes determining a speed of a printable medium that passes through the dryer unit. The method further includes varying an intensity of light generated by the light source based on the speed of the printable medium by varying which of the lamps of the light source are energized to their target output power.

The invention may include other exemplary embodiments described below.

DETAILED DESCRIPTION

FIG. 1illustrates a printing system100in an exemplary embodiment. Printing system100comprises any continuous-forms printer used to mark a printable medium102. In this embodiment, printing system100comprises a production printing system that uses a recording liquid, such as ink, to mark printable medium102. Although not specifically shown inFIG. 1, printing system100includes a print controller and one or more print engines. The print engines include a print head controller and arrays of print heads that discharge the recording liquid onto medium102as it passes under the print heads. After a print engine discharges the recording liquid onto medium102, printing system100may include a radiant dryer unit that assists in drying the recording liquid on medium102.

FIG. 2illustrates a dryer unit200in an exemplary embodiment. Dryer unit200is installed in printing system100after the print heads to dry the recording liquid that is printed on medium102. Dryer unit200includes a light source202that projects light onto medium102. For example, light source202may comprise one or more arrays of lamps or light bulbs. The light waves from light source202are illustrated as dotted arrows inFIG. 2. The radiant energy in the light waves helps to dry ink on medium102as the medium102passes through dryer unit200. Some of the light waves may pass through or pass by medium102during the drying process. Thus, dryer unit200may also include a reflector element206that is opposite light source202(i.e., on the other side of medium102). Reflector element206acts to reflect the light waves that pass through or around medium102back towards medium102to assist in the drying process.

FIG. 3illustrates light source202for dryer unit200in an exemplary embodiment.FIG. 3is a top view showing medium102passing underneath light source202. In this embodiment, light source202includes a first array302of lamps that spans across the width of medium102. Light source202also includes a second array304of lamps that spans across the width of medium102. A lamp as described herein comprises any element that produces light. One example of a lamp is an infrared light bulb.

Each of the lamps in array302may have similar characteristics, and each of the lamps in array304may have similar characteristics. However, the lamps in array302may have different characteristics than the lamps in array304. For example, array302may include lamps that produce light at an intensity I1having a wavelength of λ1with an applied power of P1. Array304may include lamps that produce light at an intensity I2having a wavelength of λ1with an applied power of P2. Thus, even though different powers are applied to arrays302and304, the lamps are able to produce light having the same wavelength of λ1.

The lamps utilized in arrays302and304may have a tubular shape as illustrated inFIG. 3. When tubular lamps are used, they may be positioned at an angle with respect to medium102, which is illustrated inFIG. 3. Instead of the major axes of the lamps being parallel or perpendicular to the direction of travel of medium102, the major axes are at an acute angle to the direction of travel of medium (which is illustrated by an arrow inFIG. 3). This angled configuration (between 0 and 90 degrees) of the lamps provides a more even temperature across medium102. The angled configuration is just one embodiment, and lamps may be perpendicular or parallel to the direction of travel of the medium in other embodiments.

Dryer unit200also includes a controller that controls the operation of light source202.FIG. 3shows controller310connected to light source202. Controller310is configured to vary the overall intensity of the light generated by light source202based on the speed of medium102as it passes through dryer unit200. There is an optimal intensity of light for drying the recording liquid on medium102that is based on the speed of medium102. Therefore, controller310is able to vary the overall intensity of light generated by light source202as the speed of medium102changes.

To vary the intensity, controller310selectively energizes lamps of light source202. Each lamp of light source202has a target output power that is set by controller202. The target output power for a lamp represents the power that is used to energize the lamp when it is switched on. A lamp is energized solely according to its target output power in this embodiment. Thus, if a lamp is turned on (or energized), then the lamp is energized to create its target output power. Each lamp has an effective operating power range (generally between 70-100% of full power) where the characteristic wavelength output is acceptable for the ink being applied. Therefore, a power range can be associated with each lamp as the “target output power” for that lamp. The output power can be adjusted by an operator within the power range, but does not substantially affect the lamp's characteristic output wavelength. Adjusting the output power outside of the target range is undesirable as the output wavelength would no longer be optimal for the ink.

Controller310includes a processor312and a memory314. Memory314may store information, such as a table, that relates the speed of a medium to an optimum intensity of light for a light source. Memory314may also store information on the target output power of each lamp in light source202. Memory314may further store information on the intensity of light emitted by each lamp (or array of lamps) when energized to create its target output power. Processor312executes the desired operational steps of controller310, which is further illustrated inFIG. 4.

FIG. 4is a flow chart illustrating a method400of controlling light source202in an exemplary embodiment. The steps of method400will be described with reference to dryer unit200inFIGS. 2-3, although method400may be performed in other systems. The steps of the flow chart described herein are not all inclusive and may include other steps not shown. The steps may also be performed in an alternative order.

In step402, controller310associates a target output power with each of the lamps in light source202. For example, controller310may access a table stored in memory314to locate the associations between the lamps and a target output power that is preconfigured or pre-set for the lamps. In step404, controller310determines a speed of medium102that passes through dryer unit200. Controller310may be connected to a sensor or some other measurement device that measures or estimates the speed of medium102. In step406, controller310varies the intensity of light generated by light source202based on the speed of medium102by varying which of the lamps of light source202are energized (or turned on) to create their target output power. Thus, controller310is able to control the overall intensity of light generated by light source202by controlling which (e.g., how many) lamps are switched on to their target output power. For example, if controller310energizes the lamps in array302, then controller310will apply power to a lamp to create an output power P1for each of the lamps in array302. The output power P1of the lamps is fixed within a target range. If controller310energizes the lamps in array304, then controller310will apply voltage/current to a lamp to create an output power P2for each of the lamps in array304. The output power P2of the lamps is fixed within a target range.

Method400is continually repeated so that the intensity of light generated by light source202is changed as the speed of medium102changes. One exemplary operation for varying the intensity of light generated by light source202is shown inFIG. 5. Assume that a speed measurement is taken for medium102at some point in time.FIG. 5is a flow chart illustrating a method500of varying the intensity of light from light source202in an exemplary embodiment. In step502, controller310determines a target intensity of light based on the speed of medium102. This information may be stored in a table of memory314. In step504, controller310selects a combination of lamps in light source202that provides the target intensity when the lamps are energized to create their target output powers. As described above, each lamp in light source202has an associated target output power. Therefore, controller310can determine how much each lamp will contribute to the overall intensity of light source202according to their target output power, and select the combination accordingly. In step506, controller310energizes the lamps of the selected combination by applying their target output powers.

FIG. 6illustrates a pattern of light produced by arrays302and304across the width of medium102in an exemplary embodiment. Lamps302a,302b,302c, and302dbelong to array302. Lamps304a,304b,304c, and304dbelong to array304. As can be seen inFIG. 6, lamps302a,302b,302c, and302dare offset from lamps304a,304b,304c, and304d. Thus, light emitted from array302overlaps with light emitted from array304. For example, light emitted from lamp304aoverlaps with light emitted from lamps302aand302b. Therefore, if the light emitted from lamp302ahas an intensity of Ix and the light from lamp304ahas an intensity of Iy, the combined intensity from the two lamps is Ix+y in the area where the light overlaps.

FIG. 7is a graph illustrating the speed (V) of medium102in relation to the overall intensity (I) of light generated by light source202in an exemplary embodiment. When the speed of medium102is V1, controller310may energize the lamps of array302to create a target output power P1for the lamps of array302. When only array302is turned on to create the target output power P1, the overall intensity of light generated by light source202is I1. When the speed of medium102increases to V2, controller310may energize the lamps of array304to create a target output power P2for the lamps of array304. Controller310also turns off the lamps of array302. When only array304is turned on to create the target output power P2, the overall intensity of light generated by light source202is I2. When the speed of medium102increases to V3, controller310may energize the lamps of array302to create an output power P1for the lamps of array302, and may also energize the lamps of array304to create an output power P2for the lamps of array304. When both arrays302and304are turned on to create their target output powers P1and P2, respectively, the overall intensity of light generated by light source202is I1+2. Thus, the intensity of light source202is changed by selectively energizing array302, array304, or both.

In order to increase the overall intensity of light generated by light source202above I1+2, additional arrays of lamps may be installed in light source202. Controller310may then turn on different combinations of the arrays when the speed of medium102increases to Vn to achieve a target intensity of In.

By selecting which lamps to turn on as shown in the above embodiments, controller310can change the intensity radiated onto medium102by light source202. Because a target output power created by the lamps when they are energized, the wavelength of light emitted onto medium102remains substantially constant at an optimal value even though the intensity changes. Therefore, the effectiveness of dryer unit200is optimized for drying the recording liquid onto medium102.

The controller described herein can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In one embodiment, the controller is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc.FIG. 8illustrates a computing system800in an exemplary embodiment.

Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium812providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium812can be any apparatus that can contain, store, communicate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.

A data processing system suitable for storing and/or executing program code will include one or more processors802coupled directly or indirectly to memory804through a system bus850. The memory804can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code is retrieved from bulk storage during execution.

Input/output or I/O devices806(including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers, as can a presentation device interface (I/F)810.

Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems, such a through network interfaces808, or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters.