Patent Application
20100110117
This disclosure relates generally to ink jet printers, and in particular, to maintenance methods for use with such ink jet printers.
Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a melt reservoir. The melt reservoir is configured to maintain a quantity of melted ink in liquid or melted form and to communicate the melted ink to one or more printheads as needed.
In order to prevent the ink storage and supply assembly of the imaging device from exhausting the available supply of ink, the reservoirs of the ink storage and supply assembly may be provided with ink level sensors. Recently, ink level sensors have been developed that enable a continuous measurement of the level of ink in the reservoirs of the printer. These ink level sensors include a lower probe positioned near a lower portion of the reservoir, an upper probe that extends upward form the lower probe toward the top of the reservoir, and an outer probe. To detect the level of ink in an ink reservoir, an AC signal is driven to the outer probe. The ink in the reservoir conducts the AC signal to the lower probe and to the upper probe. A current flow is detected from the outer probe through the ink to the lower probe and from the outer probe through the ink to the upper probe. Assuming that the ink temperature and conductivity remains relatively consistent, a substantially constant current flow is detected via the lower probe. Varying levels of current flow are detected via the upper probe as more or less of the upper probe's surface area is covered or uncovered in ink. A continuous measurement of the height of ink in the ink reservoir may then be determined by comparing the varying current flow in the upper probe to the constant current flow in the lower probe.
The ink level sensor described above is robust to variation in ink conductivity that may result due to normal variation in the manufacturing processes of the ink and/or due to natural variation in the ink components. For example, due to variation inherent in the manufacture of ink from raw components, a moderate variation in the conductivity of the ink may be expected from batch to batch and accounted for accordingly. However, if ink having a conductivity that exceeds the range of reliable operation of a level sensor enters the reservoir, the level readings generated by the level sensor for that reservoir may not be accurate or the level sensor may fail altogether resulting in various printhead failures, including introduction of air which causes jetting failure, and weeping of jets which can contaminate the drum.
In response to the difficulties posed due to ink conductivity variations, an ink recovery operation mode has been developed that enables the restoration of ink conductivity of a reservoir ink volume to a nominal range of operational conductivity in response to the ink conductivity being outside of the nominal range. In one embodiment, a method for restoring ink conductivity of ink in an ink reservoir comprises detecting an ink conductivity of an ink volume in an ink reservoir, and comparing the detected ink conductivity to a predetermined ink conductivity operational range. A flush routine is performed in response to the measured ink conductivity being outside of the predetermined ink conductivity operational range. The flush routine includes: disabling ink supply operations to the ink reservoir; emptying the ink reservoir of ink; refilling the ink reservoir with ink; measuring an ink conductivity of an ink volume in the refilled ink reservoir; and comparing the detected ink conductivity to the predetermined ink conductivity operational range. The imaging device is returned to a normal operating mode in response to the measured ink conductivity being within the predetermined ink conductivity operational range after a flush routine has been performed.
In another embodiment, a system for use with an imaging device comprises an ink conductivity sensor positioned in an ink reservoir of an imaging device. The ink conductivity sensor is configured to generate a signal indicative of an ink conductivity of a volume of ink in the ink reservoir. The system includes a controller configured to receive the signal from the ink conductivity sensor and to compare the ink conductivity indicated by the signal to a predetermined ink conductivity operational range. The controller is configured to implement a flush routine in response to the ink conductivity being outside of the predetermined ink conductivity operational range. The flush routine includes disabling print operations of the imaging device and ink supply operations to the ink reservoir; purging ink through the at least one printhead until the ink reservoir is empty of ink; enabling the ink supply to refill the emptied ink reservoir with an ink volume; detecting an ink conductivity of an ink volume in the refilled ink reservoir; and comparing the detected ink conductivity to a predetermined ink conductivity operational range. In response to the detected ink conductivity being within the predetermined ink conductivity operational range after a flush routine has been performed, the controller is configured to return the imaging device to normal operating mode.
In yet another embodiment, a method of operating an imaging device comprises measuring an ink conductivity of an ink volume in an ink reservoir of an imaging device. The ink reservoir is configured to receive ink from an ink supply and to deliver the received ink to at least one printhead of the imaging device. The measured ink conductivity is compared to a predetermined ink conductivity operational range. Print operations of the imaging device and ink supply operations to the ink reservoir are disabled in response to the measured ink conductivity being outside of the predetermined ink conductivity operational range. Ink is then purged through the at least one printhead until the printhead is empty of ink. The printhead is then refilled with ink from the ink reservoir. The purging and refilling steps are repeated until the ink reservoir is empty of ink. Ink supply operations to the ink reservoir from the ink supply are then enabled to refill the ink reservoir in response to the ink reservoir being emptied. An ink conductivity of an ink volume in the refilled ink reservoir is measured and compared to the predetermined ink conductivity operational range. Print operations are enabled in response to the measured ink conductivity being within the predetermined ink conductivity operational after the ink reservoir has been refilled. This process may be repeated several times depending on the measured results.
For a general understanding of the system disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the word “printer,” “imaging device,” “image producing machine,” etc. encompasses any apparatus that performs a print outputting function for any purpose, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, etc.
Referring now to
The high-speed phase change ink image producing machine or printer 10 also includes a phase change ink system 20 that has at least one source 22 of one color phase change ink in solid form. Since the phase change ink image producing machine or printer 10 is a multicolor image producing machine, the ink system 20 includes for example four (4) sources 22, 24, 26, 28, representing four (4) different colors CYMK (cyan, yellow, magenta, black) of phase change inks. The phase change ink system 20 also includes a phase change ink melting and control assembly 100 (
As further shown, the phase change ink image producing machine or printer 10 includes a substrate supply and handling system 40. The substrate supply and handling system 40 for example may include substrate supply sources 42, 44, 46, 48, of which supply source 48 for example is a high capacity paper supply or feeder for storing and supplying image receiving substrates in the form of cut sheets for example. The substrate supply and handling system 40 in any case includes a substrate handling and treatment system 50 that has a substrate pre-heater 52, substrate and image heater 54, and a fusing device 60. The phase change ink image producing machine or printer 10 as shown may also include an original document feeder 70 that has a document holding tray 72, document sheet feeding and retrieval devices 74, and a document exposure and scanning system 76.
The printer 10 may include a maintenance system for periodically performing a maintenance procedure on the printhead assembly. Maintenance procedures typically include purging ink through the print head, and wiping the faces of the printheads to remove ink and debris. The purging of ink through the printheads of the printhead assembly may be accomplished in any suitable manner as known in the art. The wiping of the printheads may be performed using at least one wiper blade (not shown) as is known in the art that is moved relative to the nozzle plates of the printheads to remove ink residue, as well as any paper, dust or other debris that has collected on the nozzle plate. As seen in
Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic subsystem (ESS) 80. The ESS or controller 80 for example is a self-contained, dedicated mini-computer having a central processor unit (CPU) 82, electronic storage 84, and a display or user interface (UI) 86. The ESS or controller 80 for example includes sensor input and control means 88 as well as a pixel placement and control means 89. In addition the CPU 82 reads, captures, prepares and manages the image data flow between image input sources such as the scanning system 76, or an online or a work station connection 90, and the printhead assemblies 32, 34, 36, 38. As such, the ESS or controller 80 is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the machine's printing operations.
In operation, image data for an image to be produced is sent to the controller 80 from either the scanning system 76 or via the online or work station connection 90 for processing and output to the printhead assemblies 32, 34, 36, 38. Additionally, the controller determines and/or accepts related subsystem and component controls, for example from operator inputs via the user interface 86, and accordingly executes such controls. As a result, appropriate color solid forms of phase change ink are melted and delivered to the printhead assemblies. Additionally, pixel placement control is exercised relative to the imaging surface 14 thus forming desired images per such image data, and receiving substrates are supplied by anyone of the sources 42, 44, 46, 48 and handled by means 50 in timed registration with image formation on the surface 14. Finally, the image is transferred within the transfer nip 92, from the surface 14 onto the receiving substrate for subsequent fusing at fusing device 60.
Referring now to
The ink delivery system 100 includes a melter assembly, shown generally at 102. The melter assembly 102 includes a melter, such as a melter plate, connected to the ink source for melting the solid phase change ink into the liquid phase. In the example provided herein, the melter assembly 102 includes four melter plates, 112, 114, 116, 118 each corresponding to a separate ink source 22, 24, 26 and 28 respectively, and connected thereto. As shown in
The melter plates 112, 114, 116, 118 can be formed of a thermally conductive material, such as metal, among others, that is heated in a known manner. In one embodiment, solid phase change ink is heated to about 100° C. to 140° C. to melt the phase change ink to liquid form for supplying to the liquid ink storage and supply assembly 400. As each color ink melts, the ink adheres to its corresponding melter plate 112, 114, 116118, and gravity moves the liquid ink down to the drip point 134 which is disposed lower than the contact portion. The liquid phase change ink then drips from the drip point 134 in drops shown at 144. The melted ink from the melters may be directed gravitationally or by other means to the ink storage and supply assembly 400.
In one embodiment, the ink storage and supply system 400 may incorporate a dual reservoir system.
The secondary reservoirs 410 comprise high pressure reservoirs (HPR). Each HPR 410 includes at least one discharge outlet 420 through which molten ink may flow to an ink routing assembly (not shown) for directing ink to one or more printheads (not shown) of the printhead assembly. Each HPR may include a plurality of discharge outlets 420 for supplying ink to a plurality of printheads. For example, in a system that includes four printheads for each color of ink, each HPR may include four discharge outlets, each outlet being configured to supply ink to a different printhead. When charging a printhead with ink, pressure is applied to the ink in a corresponding HPR using, for example, an air pump 424 through a dosing valve 428 or other suitable pressurization means to causing the ink to discharge through the one or more discharge outlets 420 of the HPR. The discharge outlet(s) of the HPR may include check valve(s) 430 or other suitable backflow prevention means that are configured to open to permit the flow of molten ink from the secondary reservoir to the printhead when the HPR is pressurized while preventing backflow of the ink through the opening 420 back into the HPR 410. In addition, the valve 418 in the opening 414 is configured to prevent backflow of ink from the secondary reservoir to the primary reservoir when the secondary reservoir is pressurized.
In order to prevent the ink storage and supply assembly 400 of the imaging device from exhausting the available supply of ink, the reservoirs 404 of the ink storage and supply assembly 400 may be provided with ink level sensors 200.
During operation, the ink level controller 204is configured to maintain a substantially consistent amount of melted ink in the reservoirs available for delivery to the printheads. Accordingly, during operations, the controller 204 is configured to monitor the ink level sensors 200 to determine when the ink level of a reservoir reaches one or more predetermined threshold levels. For example, when a level sensor 200 indicates that the ink level in a reservoir has fallen below a “start fill” level, the controller is configured to signal the corresponding ink melter 112, 114, 116, 118 to begin melting and supplying ink to the ink reservoir. The controller 204 is configured to monitor the ink level sensor in the reservoir as the melted ink is being supplied to the reservoir to determine when a “stop fill” level is reached at which point the controller is configured to signal the appropriate melter to stop supplying ink to the reservoir. Detecting an ink supply deficiency, melting the solid ink in response to the deficiency, and refilling the reservoir to a supply level with the melted ink may be referred to as an “ink melt duty cycle.” In addition to the start fill and stop fill levels, the controller is configured to monitor the ink levels as the reservoir is being filled to determine when a “last dose” level is reached at which point the controller may pause operations until the reservoir has been replenished. The last dose level corresponds to the level of ink at which continued printing operations run the risk of running the reservoir dry.
The ink level sensors 200 of the present embodiment are configured to measure the level of ink in each of the reservoirs 404 in a substantially continuous manner. As explained in more detail below, the ink level sensors of the present disclosure are configured to sense or detect the height of ink in a reservoir by detecting or measuring a base line conductivity of the ink present in the reservoir with a lower probe 248, shown in
Level sensor positioning support members 208 are operably connected to the level sensors 200 and the ink storage and supply system 400 to locate or position the level sensors in their respective reservoirs 404. As depicted in
Referring now to
The probe support 254 may be formed of any suitable material that is capable of providing the desired electrically isolating properties, such as a plastic material. As shown in
The lower 248 and upper probe 246 of each level sensor 200 may be made integral with the support frame by positioning the lower and upper probes in predetermined positions with respect to each other in a molding tool having the desired final shape of the insulating support frame and over molding the lower and upper probes in the molding tool with a suitable insulating material such as plastic. The support frame may be molded with suitable features that enable the outer probe to be assembled to the molded frame without using adhesive or additional parts. For example, the probe support frame 254 may include standoffs 280 (best seen in
The gap between the outer probe 250 and the upper 246 and lower probes 248 may be any suitable distance that allows the ink to flow freely between the probes while maximizing signal transmission through the ink from the outer probe to the upper and lower probes. A gap that is too small between the outer probe and the upper and lower probes may cause the ink to move sluggishly between the probes, due to surface tension effects. This sluggish movement, especially as the ink drains off the probe, may cause inaccurate level readings, as the ink between the two probes may be of a higher level than the ink in the reservoir. Any suitable means or method, however, may be used to attach the outer probe to the probe support frame to provide the predetermined gap between the outer probe and the upper and lower probes. Molding the support frame around the upper and lower probes enables accurate and repeatable positioning of the probes relative to one another and to the frame.
Each of the upper 246, lower 248, and outer probes 250 of each ink level sensor 200 is operably connected to an ink level controller 204. The ink level controller 204 may be implemented in the circuit board 210, or alternatively, may be in communication with the circuit board 210 via a suitable connection device such as a pin connector (not shown). Each of the upper 246, lower 248, and outer probes 250 includes a connection point, or tab, that extends upward through the top portion of the insulating support assembly for connection to the signal transmitting/receiving member. For example, the outer probe includes tab 256, lower probe includes tab 260, and upper probe includes tab 262 that each extends upward through the top portion of the probe support. The tabs of the probes of the level sensors are operably coupled to the circuit board via a suitable signal transmitting/receiving member. The signal transmitting/receiving members may comprise any suitable device or method that enables signal transmission between the probes of the level sensors and the ink level controller.
As depicted in
To detect the level of ink in an ink reservoir, an AC signal 230 is driven, or input to the tab 256 of the outer probe 250. The ink 290 conducts the AC signal to the lower probe 248 and to the upper probe 246. Controller 204 shown in
As depicted in
The upper probe 246 is electrically connected to the negative input 240 of op/amp 242 in controller 204. This negative input 240 forms a virtual ground by connecting the positive input 244 of op/amp 242 to ground and also connecting the negative input 240 of op/amp 242 through a resistor to the output of the op/amp 242. This virtual ground circuit eliminates any stray currents that can arise due to conductivity from the probes and associated traces and wires to electrical ground (i.e., reservoir body and other metal structures). Responsive to the current flow from the outer probe 250 through the ink 290 to upper probe 246, op/amp 242 outputs a voltage Vupper that is an expression of a conductance of the ink 290 contacting the surface area of the upper probe 246. As the level of the ink 290 varies in reservoir 40, that amount of surface area of upper probe 246 immersed in the ink 290 varies resulting in a varying conductance.
The controller 204 calculates the ratio of the variable Vupper to the base value of Vlower. The ratio calculation can be accomplished by connecting the outputs of the virtually grounding op/amps 242, 238 to analog-to-digital converters (not shown) and dividing the two digital values within controller 204. Any other methods of calculating ratios of voltages commonly known in the art are contemplated to be within the scope of this disclosure. This ratio gives a continuous measurement of the level of ink 290 in reservoir 404. The conductance of ink varies over types of inks and even within the same type of ink at different temperatures. The two probes 246, 248, along with virtually grounding op/amps 242, 238, and controller 204, result in a ratio of two conductivities. Thus, no matter what type of ink or what temperature the ink, within the physical limitations imposed by components such as the resistors, a ratio of conductance is measured which correlates to ink fluid level within the reservoir chamber.
Phase change ink printers including the level sensors above are typically optimized for use with ink having a particular conductivity or having conductivity within a nominal range. Phase change inks of different formulations, including color, typically have unique inherent conductivities. Therefore, contaminated ink including ink having a color or formulation not intended for use with a particular reservoir or batches of ink with extreme conductivity may cause the conductivity of the ink volume in one or more of the reservoirs to vary beyond a range that is acceptable to performance when that conductivity is used. Due to variation inherent in the manufacture of ink from raw components, a moderate variation in the conductivity of the ink may be expected from batch to batch and accounted for accordingly. For example, the level sensor described above may be considered to functioning accurately so long as the ink conductivity detected by the lower probe remains within a nominal range. The nominal range may be predetermined and corresponds to the range of ink conductivity at which the ink level sensors described above may be considered to be functioning accurately. If ink having a conductivity that exceeds the range of reliable operation of a level sensor enters the reservoir, the level readings generated by the level sensor for that reservoir may not be accurate or the level sensor may fail altogether resulting in various printhead failures, including introduction of air which causes jetting failure, and weeping of jets which can contaminate the drum.
In response to the difficulties posed due to contaminated ink, an ink recovery operation mode has been developed that enables the restoration of ink conductivity of a reservoir ink volume to a nominal range of operational conductivity in response to the ink conductivity being outside of the nominal range. As described above, the present system is configured to monitor the ink conductivity of the ink in the reservoirs during the level sensing process. In one embodiment, the ink recovery operation mode involves monitoring the conductivities of the ink volumes in the melt reservoirs and to determine when the ink is contaminated, i.e., has a conductivity that exceeds the operational range of the level sensor in the reservoirs. The operational range may be any suitable range of ink conductivities at which the level sensor is capable of providing substantially accurate level readings. Due to the ink conductivity differences that may be exhibited by inks of different colors or shades, the operational range for a given melt reservoir may be different than the operational ranges for the other melt reservoirs. When it is determined that the ink conductivity of the ink volume in a reservoir is outside of the operational range of ink conductivity for the level sensor of the reservoir, the reservoir is considered contaminated and a flush routine is initiated that involves emptying and refilling the contaminated reservoir until the contaminant is no longer present in the reservoir in debilitating amounts.
In one embodiment, the ink recovery operation mode is implemented as a software controlled algorithm in the controller. The control software is configured to recognize a contamination event by monitoring a nominal ink conductivity sensor positioned in each melt reservoir in the imaging device. As mentioned above, the lower probe of the level sensor assemblies described above may be used to detect the ink conductivity of the ink volume in the melt reservoirs. Accordingly, in one embodiment, the nominal ink conductivity sensor for a melt reservoir corresponds to the lower probe of the level sense probe assembly for the reservoir. However, a conductivity probe or sensor other than the ink level sensors described above may be utilized.
The control software is configured to compare the ink conductivity levels indicated by the nominal ink conductivity sensors for the melt reservoirs to a nominal operational value or value range for the level sensors of the melt reservoirs. The comparison of the ink conductivity level of a melt reservoir may be performed at any suitable frequency. In one embodiment, the control software is configured to compare the ink conductivity level of the ink volume in a melt reservoir to the nominal operational value or value range at a frequency of approximately 2.5 Hz although any suitable frequency may be used.
The control software recognizes a contamination event if the monitored ink conductivity of an ink volume in a melt reservoir exceeds or falls below the nominal operational value or value range. The control software may also be configured to compare the monitored ink conductivities of ink volumes in the melt reservoirs to minimum and maximum threshold values. Detected ink conductivity levels that fall below the minimum or exceed the maximum threshold values may be indicative of a fault condition that may not be correctable by flushing the ink from the reservoirs and that may require maintenance that goes beyond the capabilities of the maintenance system of the imaging device. If the control software determines that the ink conductivity level of a melt reservoir falls below the minimum or exceeds the maximum threshold value, the control software may be configured to disable print operations and alert a user that a fault has occurred and that a service call may be required.
The control software may also be configured to recognize a contamination event in response to the rate of change of the ink conductivity of the ink volume in a melt reservoir exceeding a predetermined operational rate of change. For example, the controller may be configured to determine a rate of change of the ink conductivity for the ink volume in a melt reservoir by comparing current ink conductivity readings of an ink volume in a melt reservoir to previous ink conductivity readings for the ink volume. The control software may then be configured to compare the determined rate of ink conductivity change for a melt reservoir to a predetermined rate or rate range of ink conductivity change. The control software may be configured to recognize a contamination event if the monitored ink conductivity change rate of a melt reservoir exceeds or falls below the predetermined rate or rate range.
In response to the recognition of a contamination event, the control software is configured to cause the system to enter a flush mode. In the flush mode, a flush routine is implemented in which printing and ink supply operations are stopped or disabled, and the maintenance system is activated to purge ink through the printheads to the waste tray. Purging ink through the printheads while the ink supply is disabled acts to empty or flush the ink from the melt reservoirs. Ink supply operations may then be enabled so that the emptied or flushed melt reservoir may be refilled with ink. The control software may then determine whether the ink conductivity of the ink volume in a melt reservoir has returned to the nominal operational range or if the ink conductivity is still outside of the operational range at which point the process may be repeated. The flush routine may be repeated any suitable number of times. If, however, the detected ink conductivity of ink in a melt reservoir has not returned to the nominal operational range after a predetermined number of flush routines, the control software may be configured to recognize a fault condition and disable print operations and alert a user that a fault has occurred and that a service call may be required. For example, in one embodiment, the control software may be configured to declare a fault if the conductivity of the ink has not returned to the normal operational range after the melt reservoir has been flushed and refilled three times.
In one embodiment, the flush routine is operated in an open loop scenario in which no feedback is given via the melt reservoir level sensors. Accordingly, in the flush mode, the initiating of melt cycles to supply melted ink to the reservoirs in response to detected ink levels is disabled. Instead, level sensors in the printheads are used to monitor the presence of ink, or lack thereof, in the printheads. Accordingly, in the flush mode, the printheads are purged which empties the printheads of ink. The melt reservoir then supplies ink to the printheads until the printhead level sensor indicates that the printhead has been refilled. Once full, the printheads are once again emptied by purging. This process, also referred to as flushing the printhead, is repeated until the printhead level sensors do not register the presence of ink in the printhead after the printhead has had a chance to be refilled. When the printhead level sensors indicates that no ink is present in the printhead, the melt reservoir may be considered to be emptied at which point the ink supply and level sense may be enabled. Accordingly, a melt duty cycle is initiated in which the melt plates are heated up and melted ink is supplied into the melt reservoir until the reservoir level sensor indicates that the melt reservoir is full, or a timer has expired, whichever comes first. The conductivity of the ink volume supplied to the melt reservoir may then be detected and compared to the predetermined nominal ink conductivity or conductivity range to determine if the ink conductivity has returned to normal operational values. If the detected ink conductivity of the melt reservoir indicates that the ink conductivity again falls below or exceeds the nominal ink conductivity range, the process described above may be repeated.
Referring now to
Those skilled in the art will recognize that numerous modifications can be made to the specific implementations of the ink conductivity recovery methods described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
