Background

[ 0001 ] image forming devices and systems may include printheads that are filled with a printing fluid and form images on a print medium. Some image forming devices may be refilled by providing additional printing fluid to a reservoir within the image forming device.

[0002 ] Figure 1 is a block diagram illustrating example components of a printing system as described herein.

[0003] Figure 2 Is a block diagram illustrating example components of a recharging system as described herein.

[0004] Figure 3 is a flow chart illustrating an example method to performing recharging of a printhead as described herein.

[0005] Figure 4 is a flow chart illustrating an exampie method to performing recharging of a printhead as described herein.

[0006] Figure 5 is a block diagram illustrating example components of a recharge system as described herein.

Detailed Description

[0007] Described herein are inkjet printing systems that incorporate printheads which eject printing fluid onto print media. The printhead pens have a capacity that is less than the expected lifetime throughput of the printhead, therefore, the inkjet printheads are refilled to continue printing, in some inkjet printing systems, the system may include an internal reservoir that supplies printing fluid to the printhead and is itself refilled from external supplies as needed. The systems described herein monitors the drive characteristics of refill pumps to determine if there is a fault or potentia! fault in the system.

[0008] This type of printing system is sometimes referred to as a continuous ink supply system (CISS for short), which can provide extended printhead lifetime that is not limited by the size of an associated pen capacity, in some examples, an internal reservoir of the printing system is used to deliver printing fluid to the inkjet pen to provide a continuous supply of printing fluid to the printheads. Furthermore, the internal reservoir may be refilled from an external bulk printing fluid supply. Of course, in various systems there may be additional intermediate reservoirs, or an external supply may be directly feeding into an inkjet pen.

[0009] The internal reservoirs ensure that jobs are complete and other reservoirs closer to the printhead are continually filled between refill from external supplies, in printing systems as described herein, the internal reservoirs are filled by a pump that extracts printing fluid from the external supply.

[0010] In order to prevent operation of a refill pump during a fault in fluid supply lines or other components of a fluid delivery system monitoring of pressures within the system may be used. In example printing systems as described herein, current supplied to the fill pump is used to estimate the pressure at which the fill pump is operating. For example, the pressure may be determined based on the current or changes from a baseline current measurement may be used to determine if there was a change in pressure that can be analyzed to predict a fault in a fluid delivery system.

[0011] In order to determine pressure based on the current, the refill pump is operated with a constant voltage drive. For example, the drive power may be a constant voltage signal or a pulse width modulated voltage signal that is provided at constant duly cycle and voltage. The current then changes based on the mechanical load of the refill pump.

[0012] The current signal received from a refill pump can reveal several faults in a fluid delivery system. For example, If the external supply is depleted, the inlet to the refill pump will act as If it is blocked. Accordingly, the pressure at the inlet will reduce and the refill pump will see less resistance to pumping. If the refill pump operates with the limited resistance, the fill pump may become damaged and the printing system may need service. Therefore, the fault monitoring system can stop operation of the refill pump and generate an alarm that the supply is depleted. In another example, a blockage may be present at the outlet of the refill pump. In this case, high pressures may be generated in fluid delivery system components. Therefore, the pump will encounter higher load and foe current supplied to maintain foe voltage to the pump will increase. To avoid creating leaks or other damage, the system can then stop operating foe motor, or reduce operation levels of the motor. In other examples, oscillating current levels, periodic current changes, or other current characteristics may be analyzed to determine other potential faults in a fault monitoring system.

[0013] Printing systems as used herein may include printers, copiers, fax machines, multifunction devices including additional scanning, copying, and finishing functions, all-in-one devices, pad printers to print images on three dimensional objects, and three-dimensional printers (additive manufacturing devices). Furthermore, print media may be used herein to describe plain paper or other suitable media or objects such as inflexible media, textiles, bulk objects, boxes, powdered build materials (for forming three-dimensional articles), or other suitable substrates. Printing fluids, including printing agents and colorants, may include ink, fusing agents, detailing agents, or other materials that may be applied to a substrate with printhead that includes a nozzle that utilizes a maintenance printing fluid scheduling system to provide consistent operation of a printhead. For example, thermal inkjet printhead, piezo inkjet printheads, or other printheads that eject printing fluids to a print media may be operated according to example systems and methods as described hereto.

[0014] Figure 1 is a block diagram illustrating example components of a printing system 100 as described hereto. The printing system 100 includes a bulk printing fluid supply 140, a fault detection system 110, a printhead 120, and an intermediary printing fluid tank 130. The fault detection system 100 analyzes a current sensor 115 that monitors the current used by a pump 102 that moves printing fluid from foe bulk printing fluid supply 140 to the intermediary tank 130.

[0015] The components of an image forming device shown in Figure 1 are a subset of components of a complete image forming device. In various examples foe image forming device may indude media handling components, media storage components, scanning components, output frays, or additional components to complete an image forming device. Furthermore, the fluid delivery system may indude additional pumps, valves, and monitoring devices to perform printing fluid delivery operations. For example, the printing system 100 may include an additional pump to provide the printing fluid from the intermediary supply 130 to the printhead 120. In some examples, the components shown may be incorporated into larger systems, such as three- dimensional printing systems, solid media printing (e.g., corrugated cardboard or the like), or other media printing, that utilize printing fluid ejection through a printhead having a porous media pen.

[0016] The bulk printing fluid supply 140 may be an external supply that is removably attachable to the printing system 100. During a refill operation, the bulk printing fluid supply 140 can be pumped to refill the intermediary tank 130. In some examples, the bulk printing fluid supply 140 may include a liner or other deflatable structure that collapses or evacuates as the pump 102 pulls printing fluid out.

[0017] The intermediary tank 130 is refilled by the bulk printing fluid supply 140 through the pump 102 and is then used to supply printing fluid to the printhead 120. In some examples, the intermediary tank 130 may have a vent 132, such as a spring-loaded normally closed valve or non-wetting membrane, that enables the release of air or other vapors to prevent accumulation within the printing system. Furthermore, as the intermediary tank 130 is depleted, the valve allows air to pass into the supply to replace printing fluid used by the system. The intermediary tank 130 is coupled to the printhead 120 by way of a fluidic channel that may be controlled by additional pumps, gravity fed, or other mechanisms not shown in Figure 1. The intermediary tank 130 may also indude a fill level gauge 134 that measures a fill level of the intermediary tank 134. Sensor readings from the fill level gauge 134 may be used to determine when to initiate a refill from the bulk printing fluid supply 140, when to stop a refill operation, or otherwise indicate a fluid level. In some examples, the fill level gauge 134 includes a number of electrodes at different depths that are probed to determine resistance readings. Those readings can be used to determine which electrodes are under the fill level of the intermediary tank 130. [0018] The refill pump 102 may be a multi-channel (one for each color printing fluid) or single channel positive displacement pump that can move a mix of fluids at system pressures including air, printing fluid, a mixture of air and printing fluid, froth, or other fluidic mixture. For example, based on agitation of the bulk printing fluid supply or introduction of air into the bulk printing fluid supply 140, the fluid may develop into a froth or other mix of air and fluid. Accordingly, the pump refill 102 may be designed to pass a variety of mixtures from the bulk printing fluid supply 140. The refill pump 102 may be a stogie direction pump or may have additional control valves to prevent back flow of printing fluid when not connected to a bulk printing fluid supply. In some examples, the refill pump 102 is a pump attached to a direct drive motor that is powered by a constant voltage source. Although described with relation to refilling, the disclosure is not limited to the refill pump 102 in the manner.

Rather, refill pump 102 represents fluid pumps in general that may be monitored through current draw to identify faults within a system.

[0019] The printhead 120 may include a pen that holds printing fluid for ejection on a print media. The printhead 120 may include a number of nozzles that may be thermal printheads, piezo printheads, or other types of fluid ejection devices that selectively activate to generate an image on a print media, in some examples, the printhead 120 may include a chamber that provides printing fluid to the nozzles, a porous media that holds printing fluid to provide to nozzles, microfluidic channels to provide printing fluid to nozzles, or other mechanisms for providing printing fluid for ejection.

[0020] The fault detection system 110 detects potential faults within toe printing system 100 based on readings from a current sensor 115 coupled to the refill pump 102. The current sensor 115 may comprise a current sensing resistor, a hall effect sensor, or another sensor that detects toe current used to operate refill pump 102. For example, the current sensor 115 may be coupled to a terminal of toe refill pump 102 or a drive motor that operates toe refill pump 102. In some examples, wherein the current sensor 115 is a current sensing resistor, the current sensing resistor may be placed at an input or an output terminal of the pump 102. The fault detection system 110 monitors toe current of the refill pump 102 during operation to identify potential faults within the fluid supply system. [0021] Figure 2 is a block diagram illustrating additional details of a fault detection system 200 as described herein. For example, the fault detection system 200 may be the same or similar to the fault detection system 110 described above with reference to Figure 1. As shown in Figure 2, the fault detection system 200 communicates with the refill pump 220. The fault detection system 200 includes a current sensor 202, a fault detector 204, an alert service 206, and a remediation service 208. In various implementations, the fault detection system 200 may include fewer or additional components or those components may be split or combined into other components. For example, the fault detection system 200 may operate without an alert service 206 or remediation service 208

[0022] The refill pump 220 may be the same or similar as toe refill pump 102 described with reference to Figure 1. For example, refill pump 102 may include a drive mechanism and a pump as described above. The refill pump 102 may be driven by a constant voltage source, either at a constant voltage or with a constant pulse width modulation. The current sensor 202 of the fault detection system monitors toe current Of the refill pump 220 during a refill operation. For example, the current sensor 202 may be one of a variety of options for current monitoring such as a current sensing resistor.

[0023] Based on the readings from the current sensor 202, the fault detector 204 determines whether toe system is operating properly or if there is a potential fault within the system. Example processes performed by toe fault detector 204 are shown further with regards to method 400 in Figure 4. Beginning in blot* 402, a refill operation is initiated by the system. For example, the refill system 200 may determine that toe refill operation begins in response to a change in current received from current sensor 202. In block 404, the fault detector 204 receives a current measurement from toe current sensor 202. Then, in block 406 the fault detector 204 determines whether toe current is out of range. For example, the fault detector 204 may have a baseline current measurement for toe refill pump 220. The baseline may be set by the system prior to installation or may be measured during an initialization or setup during a first filing operation of toe printing system. The current may be considered in range if it is within a threshold range of the baseline. In some examples, the high and low threshold values may be different than one another.

[0024] If the current is in range, the process may continue to b!ock 408 wherein if a desired fill is achieved, no error is generated in block 409 and the refill operation has ended. If the desired fill is not achieved, the process continues to receive another sensor reading in block 404. ih some examples, the readings may be taken periodically wherein there is a delay between current sensing. [0025] Back to block 406 if the current is determined to be out of range, the process continues to determine a cause of the current change. As an initial process in block 410, the refill system 200 may continue or stop the refill pump 220. For example, the remediation system 208 may instruct the printing system to stop actuating the refill pump 102.

[0026] In block 412, the fault detector 204 determines if the current was lower than the expected range. If the current was not outside a lower bound, then it was outside a higher bound and a high pressure response Is generated in block 414 by one or both of the alert service 406 and the remediation service 408.

For example, the alert service may provide an error code or request service. The remediation service 408 may initially reduce the drive voltage or the duty cycle of pulse width modulation to attempt to reduce the pressure within the system. For example, if there is a partial blockage, having a tower drive voltage may reduce the pressure to levels that won't cause leaks or damage.

[0027] If ih block 412 the fault detector 204 determines that the current is low, the fault detector may determine if the expected volume has been transferred from the external supply in block 416. For example, the volume may be determined based on a fluid level detector as described with reference to Figure 1 , a prediction of fluid moved by the pump 102, or a prediction of fluid moved by a flow monitor on the fluid delivery path. If the expected volume has been transferred, then no fault has occurred and the refill process can be ended. If the expected volume has not been transferred, then there may be a blockage at the supply and a tow pressure response is generated by on or both of the alert service 406 or remediation service 408 in block 420. For example, an error code may be generated or service may be requested. The refill operation may also be halted until service or replacement has been performed. In some examples, the printing system may continue to print using printing fluid in the intermediary tank, but will not continue to refill the intermediary tank,

[0028] In some examples, the fault detector 204 may further detect additional faults or potential future faults. For example, the current sensor may indicate a cyclical current reading or a frequency based oscillation. The cyclical current reading may indicate an issue with the refill pump 220 that indicates potential failure conditions of the refill pump 220. Accordingly, the remediation service 408 or alert service 406 may provide an alert or change operation to mitigate a failure event. The frequency based operation may indicate that air is being ingested by the system and there may be a leak in the fluid delivery system. Accordingly, the remediation service 408 or alert service 406 may provide an alert or change operation to mitigate or fix air intake.

[0029] While shown in Figure 4 as an ordered set of processes, it is understood that some of these processes may be performed in a different order or may be performed simultaneously. Furthermore, there may be fewer or additional processes performed to accomplish the processes described.

[0030] Figure 3 is a flow chart illustrating an example method 300 to monitor refilling of a print fluid tank as described herein. For example, the method may be performed by the components of systems as described with reference to Figures 1 and 2. In various examples, the processes described in reference to flow diagram 300 may be performed in a different order or the method may include fewer or additional blocks than are shown in Figure 3.

[0031] Beginning in block 302, the fault detection system receives an indication Of an operating current of a refill pump of a printing system. For example, the fault detection system may receive the indication from a current sensor coupled to the refill pump. In some examples, the reading may be received continuously, periodically, or at different intervals during various refill operations. [0032] In block 304, the fault detection system determines, based on the indication of the current measurement, that there is a fault condition within the printing system. For example, the fault detection system may determine that the indication of the current measurement is lower than a threshold value and generate a response to a low pressure fault in response to the current measurement, In another example, the fault detection system may determine that the indication of the current measurement is higher than a threshold value and generate a response to a high pressure fault in response to the current measurement. In various examples, the fault detection system may determine other operating faults or a normal operating condition baaed on the indication of the current measurement

[0033] In block 306, the fault detection system generates a response to tine fault condition within the printing system. For example, the fault detection system my generate an alert to an administrator, to a user, on a display screen or another alert The fault detection system may also stop operation of the refill pump, change operation of the refill pump, or provide other remediation operation to improve the operation of the printing system.

[0034] Figure 5 is a block diagram illustrating an example fault detection system 500 of printing system as described herein. Fault detection system 500 may indude at least one computing device that is capable of communicating with at least one remote system. In the example of Figure 5, fault detection system 500 includes a processor 510 and a memory 520. Although the following descriptions refer to a single processor and a single computer-readable medium, the descriptions may also apply to a system with multiple processors and computer-readable mediums. In such examples, toe instructions may be distributed (e.g., stored) across multiple computer-readable mediums and the instructions may be distributed (e.g., executed by) across multiple processors. [0035] Processor 510 may be a central processing unit (CPUs), a microprocessor, and/or other hardware devices suitable for retrieval and execution of instructions stored in memory 520. In toe example fault detection system 500, processor 510 may receive, determine, and send monitoring instructions 522 and control instructions 524 to monitor refilling of intermediary tanks within a printing system. As an alternative or in addition to retrieving and executing instructions, processor 510 may include an electronic circuit comprising a number of electronic components for performing toe functionality of an instruction in memory 521. With respect to toe executable instruction representations (e g., boxes) described and shown herein, it should be understood that part or ail of the executable instructions and/or electronic circuits included within a particular box and/or may be included in a different box shown in the figures or in a different box not shown.

[0036] Memory 520 may be any electronic, magnetic, optical, or other physical storage device that stores executable instructions. Thus, memory 521 may be, for example. Random Access Memory (RAM), an Electrically-Erasable Programmable Read-Only Memory (EEPROM), a storage drive, an optical disc, and the like. Memory may be disposed within fault detection system, as shown in Figures 1 and 2. In this situation, the executable instructions may be "installed" on the fault detection system 500.

[0037] Monitoring instructions 522 stored on memory 520 may, when executed by the processor 510, cause the processor 510 to monitor refill pump 520. For example, as discussed above, the fault detection system 500 may monitor operating current of a refill pump 530 to determine if there are potential faults within the system. Based on the results of monitoring by the fault detection system 500, the control instructions 524 may cause the processor 510 to determine when to change operation of refill pump 530 or generate an alert based on the operation. In addition to the operations discussed, memory 520 may include additional instructions that enable additional systems and operations as described herein. For example, those processes described with respect to Figures 1-4 may be performed based oh instructions stored on memory 520 or executed by processor 510 as described with reference to recharge system 500.

[0038] It will be appreciated that examples described herein can be realized in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as. for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are examples of machine-readable storage that are suitable for storing a program or programs that when executed, implement examples described herein. In various examples other non-transitory computer-readable storage medium may be used to store instructions for implementation by processors as described herein. Accordingly, some examples provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine-readable storage storing such a program.

[0039] The features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or the operations or processes of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes are mutually exclusive.

[0040] Each feature disclosed in this specification (including any accompanying claims, abstract, and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is an example of a generic series of equivalent or similar features.