WO2019226165A1

WO2019226165A1 - Purging shipping fluid from a printhead

Info

Publication number: WO2019226165A1
Application number: PCT/US2018/034295
Authority: WO
Inventors: Antonio GRACIA VERDUGO; Andreu VINETS ALONSO; Mauricio SERAS FRANZOSO
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-05-24
Filing date: 2018-05-24
Publication date: 2019-11-28

Abstract

A printing apparatus comprises a printhead receptacle to accommodate a printhead comprising fluidic structures filled with a shipping fluid, and a controller. The controller performs a purging process to expel the shipping fluid from the printhead. The controller monitors a temperature of the printhead during the purging process and detects whether there is an abnormality of the purging process using the monitored temperature. If there is an abnormality of the purging process, the controller changes firing conditions of the purging process, and checks whether the abnormality is removed by changing the firing conditions. The purging process is continued if the abnormality is removed by changing the firing conditions.

Description

Purging Shipping Fluid from a Printhead

BACKGROUND

Printing apparatuses form printed images by ejecting liquid from nozzles of a printhead. Thereby, liquid is applied onto a print medium for printing a pattern of individual dots at particular locations. Some printheads, such as thermal inkjet printheads, are filled with a special shipping fluid during storage or shipping. Upon installing the printhead into a printing apparatus and before starting the regular printing operation, the shipping fluid is to be discharged or expelled from the printhead. Generally, the shipping fluid is more stable to shipping conditions, such as temperature and humidity, and the shipping fluid is more stable to large periods of storage time, when compared to regular printing liquids. Shipping fluids are generally denser, with higher viscosity and surface tension when compared to regular printing fluids, used in the printer to form printed images. Upon inserting the printhead into the printing apparatus, the shipping fluid is purged and replaced by the regular printing liquid, such as ink.

Generally, methods for purging shipping fluids from printheads may involve firing of the shipping fluids through the nozzles of the printheads using firing frequencies higher than that of regular printing and using printhead temperatures increased when compared to regular printing.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples will now be described, by way of non -limiting examples, with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram of a printing apparatus according to an example;

Fig. 2 is a block diagram of a controller according to an example;

Fig. 3 is a flow diagram of an example of a method of performing a purging process; Figs. 4 and 5 are diagrams showing temperature profiles of a printhead during a purging process; and

Fig. 6 is a flow diagram of an example of a method to perform a purging process.

DETAILED DESCRIPTION

Generally, methods of purging shipping liquids from a printhead may involve firing of shipping fluids through printhead nozzles of a printhead. Due to the chemical properties of the shipping fluid, the recommended firing conditions may be much more aggressive when compared to those used in regular or normal printing with the printing liquid, such as ink. Such firing conditions may involve higher firing frequencies, higher printhead temperatures and higher fluid volumes to be expelled when compared to regular printing. Such firing conditions in the process of purging shipping fluid may introduce some challenges and risks. For example, it was recognized that one such risk may be purging shipping fluid from the printhead through nozzle firing in presence of small quantities of air that may be present within the printhead. Presence of air within the printhead during the discharge of shipping fluid may result in an increase in temperature of the printhead. This may result in thermal shutdown errors, printhead early permanent damages and user dissatisfaction at the first time of installation of a printhead.

Examples of the present disclosure provide a printing apparatus comprising a printhead receptacle to accommodate a printhead comprising fluidic structures filled with a shipping fluid, and a controller. An example of a printing apparatus 10 comprising a printhead receptacle 12 is shown in Fig. 1. The receptacle is to accommodate a printhead 14, wherein the printhead 14 comprises fluidic structures 16 including a nozzle array 18. The nozzle array indudes nozzles through which shipping fluid and regular printing fluid may be ejected. The printing apparatus 10 indudes a controller 20. Upon installing printhead 14 into receptacle 12, electrical interfaces of printhead 14 are connected to controller 20. This is indicated by a connection 22 in Fig. 1. In addition, at least one fluidic interface of printhead 14 is connected to at least one mating fluidic interface of printing apparatus 10. Each nozzle of nozzle array 18 has associated therewith an actuator, which may be a resistor to heat liquid over the resistor. Controller 20 it to control components of the printing apparatus 10 and printhead 14, such as the actuators associated with the nozzles, upon installation of printhead 14 in receptacle 12. Each printhead 14 may include one or more printhead dyes. Each printhead dye may be controlled separately to perform the purging process. In examples, monitoring a temperature of the printhead 14 may include monitoring a temperature of each printhead die of the printhead 14. In examples, if the temperature of a printhead die shows an abnormality, the methods described herein are performed for this printhead die. In examples, if the temperature of a printhead shows an abnormality, the methods described herein are performed for each printhead die of the printhead.

Controller 20 may be to provide the functionality described herein and to execute methods described herein. Controller 20 may be implemented, for example, by one or more discrete modules (or data processing components) that are not limited to any particular hardware and machine-readable instructions configuration. Controller 20 may be implemented in any computing or data processing environment, including in digital electronic circuitry, e.g., an application-specific integrated circuit, such as a digital signal processor (DSP) or in computer hardware, device driver, or machine-readable instructions. In some implementations, the functionalities are combined into a single data processing component. In other implementations, the respective functionalities may be performed by a respective set of multiple data processing components. As shown in Fig. 2, controller 20 may comprise a processor 24 and a memory device 26 accessible by processor 24. Memory device 26 may store process instructions (machine- readable instructions, such as computer software) for implementing methods executed by controller 22. Memory device 26 may store instructions to control components of the printing apparatus to perform the purging processes described herein. Memory device 26 may include one or more tangible machine-readable storage media. Memory devices suitable for embodying these instructions and data include all forms of computer-readable memory, including, for example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices, magnetic disks such as internal hard disks and removable hard disks, magneto-optical disks, and ROM/RAM devices. Routines and processes applied to printhead 14 to perform the methods described herein may be stored in memory device 26.

Before installing printhead 14 into receptacle 12, the fluidic structures 16 are filled with a shipping fluid. Shipping fluids are generally denser, with higher viscosity and surface tension when compared to regular printing fluids which are used in the printer to form printed images. Upon installing printhead 14 into receptacle 12, in examples of the present disclosure, printing apparatus 10 is to perform a method as shown in Fig. 3. At 30, a purging process is performed to expel the shipping fluid from printhead 14. At 32, the temperature of printhead 14 is monitored during the purging process. At 34, it is detected whether there is an abnormality of the purging process using the monitored temperature. At 36, if there is an abnormality of the purging process, firing conditions of the purging process are changed and it is checked whether the abnormality is removed by changing the firing conditions. At 38, the purging process is continued if the abnormality is removed by changing the firing conditions. Thus, according to examples of the present disclosure, abnormal purging sequences are identified, which may include purging sequences obtained due to presence of air in a printhead when purging shipping fluid from printheads. Changing firing conditions upon detecting an abnormality may help to prevent printer errors and early printhead damages when expelling shipping fluid from a printhead. Changing firing conditions of the purging process and continuing the purging process if the abnormality is removed by changing the firing conditions one or several times may permit finishing the purging of shipping fluid even in case purging using the initial firing conditions would result in printhead damages due to high temperatures or in thermal shutdowns. Examples of the present disclosure may help in troubleshooting dead on arrival printhead errors in the field.

In examples, the controller is to perform the purging process in discrete periods, wherein the operations of monitoring the temperature, of detecting whether there is an abnormality of the purging process and of changing firing conditions and checking whether the abnormality is removed by changing the firing conditions are performed for each period of the purging process. The discrete periods may be separated by rest periods.

Fig. 4 shows a diagram of the printhead temperature over time during a purging process.

The diagram in Fig. 4 shows the temperatures of a plurality of printheads of the same kind. Fig. 4 shows a sequence of fourteen discrete purging periods separated by respective rest periods. Generally, a specific volume of the shipping liquid, such as 1 ml_, may be expelled during each purging period using a specific firing frequency. A specific number of firings may be performed for each nozzle in each purging period, such as sixteen consecutive firings. During the purging periods, the printhead temperature is controlled to a specific elevated temperature, such as a temperature between 55°C and 65°C, for example 60°C. In either case, the temperature to which the printhead is heated during the purging periods is lower than a upper threshold temperature, such as 70°.

The temperature diagram of Fig. 4 does not show any abnormality. As can be seen in Fig. 4, foe purging periods are well under temperature control limits starting at 55^eC and not above 70°C. As can be seen from Fig. 4, the temperature falls from a highest temperature at the beginning of a purging period to a lowest temperature at foe end of the purging period. Thus, there is a negative slope of the temperature between the highest temperature at the beginning of the purging period and foe lowest temperature at foe end of the purging period.

Fig. 5 shows temperature diagrams of a plurality of printheads of the same kind during purging, wherein one printhead shows an abnormal temperature behavior. To be more specific, the temperature behavior designated by“x” in Fig. 5 represents an abnormality. The temperature designated by“x" is associated with one of the printheads, while the other curves designated by“y” in Fig. 4 are associated with printheads not showing an abnormality. As it is shown in Fig. 5, the purging process is performed in discrete purging periods separated by respective rest periods. In the example shown in Fig. 5, the printhead is heated to a printhead temperature of about 60°C during the purging process. Due to the purging process, the temperature rises to about 62°C during the purging periods and, in case of no abnormality, remains substantially constant during the purging periods. In case of an abnormality indicated by ^*x” in Fig. 5, the printhead temperature rises above 70°C in the fifth purging period and the purging periods following the fifth purging period. This may end up with thermal shutdown errors in foe printing apparatus. The temperature behavior shown at V in Fig. 5 may be linked to the fact that some air is in the printhead area under foe nozzles of the printhead. As it is shown in Fig. 5, foe abnormality“x” may result in a temperature increase above a threshold temperature. In addition, the abnormality may result in a different slope of foe temperature when compared to foe normal case. In examples, foe slope may be positive in case of an abnormality and negative in a normal case. In example, foe slope may be zero or positive below a slope threshold in a normal case and may be higher than the slope threshold in an abnormal case.

In examples, detecting whether there is an abnormality comprises detecting whether a characteristic of foe monitored temperature reaches a threshold. In examples, foe characteristic of the monitored temperature is the magnitude of the monitored temperature. In examples, the characteristic of the monitored temperature is the slope of the magnitude of the monitored temperature over time. In examples, the controller is to compare the magnitude of the monitored temperature to an upper threshold and to determine that there is an abnormality in case the temperature readies the upper threshold. In examples, the controller is to alternatively or additionally compare the slope of the temperature to a threshold and to determine that there is an abnormality in case the slope readies a slope threshold. The slope threshold may be any slope threshold indicating an abnormality, such as a slope of zero if the slope is negative in the normal case, or such a slope of a specific positive value if the slope is lower than this specific value in the normal case. In examples, an abnormality is determined in case one of the characteristics reaches a threshold. In examples, an abnormality may be determined in case more than one characteristic, such as magnitude and slope, of the monitored temperature reach a threshold. If an abnormality is determined, the controller is to change firing conditions of the purging process and to check whether the abnormality is removed by changing the firing conditions. In examples, changing the firing conditions comprises lowering a printhead temperature to which the printhead is heated for purging. In examples, changing the firing conditions of the purging process comprises lowering a frequency with which nozzles of the printhead are fired for purging. In examples, changing the firing conditions of the purging process comprises lowering a fluid volume of shipping fluid expelled during a period of tiie purging process. Changing the firing conditions aims to lower the maximum printhead temperature during purging, such as during the next purging period. Each of the above-measures may cause the maximum temperature during purging to decrease. Thus, examples may permit finishing the complete purging process even if an abnormality is detected under specific firing conditions.

In examples, the controller is to repeatedly change the firing conditions and check whether the abnormality is removed, if the preceding change of the firing conditions does not remove the abnormality. If repeatedly changing the firing conditions does not remove the abnormality, the purging process may be stopped and a warning may be output. In examples, repeatedly changing the firing conditions may comprise changing the same or different firing parameters. In examples, the firing parameters are the printhead temperature to which the printhead is heated for purging, the frequency with which nozzles of the printhead are fired for purging, and a fluid volume of shipping fluid expelled during a period of the purging process. In examples, one or more of these parameters may be changed in a first repetition. The same or different of these parameters may be changed during another repetition. Thus, examples of the present disclosure permit different changings of firing conditions to be checked. In examples, repeatedly changing the firing conditions includes progressively lowering the same parameter or the same parameters so that moderate changings having a reduced influence to the purging time may be checked in the beginning and stronger changings having a stronger influence to the purging time may be checked if the moderate changings are not sufficient.

In examples, the controller is to check whether changing the firing conditions results in an improvement of the characteristic of the monitored temperature before checking whether the abnormality is removed by changing the firing conditions. If changing the firing conditions does not result in an improvement of the characteristic of the monitored temperature, the firing conditions may be repeatedly changed and, if repeatedly changing the firing conditions does not result in an improvement of the characteristic of the monitored temperature, the purging processes may be stopped and a warning may be output. The fact that changing the firing conditions once or repeatedly does not result in an improvement of the characteristic of the monitored temperature means that the abnormality is not removed. In examples, checking whether changing the firing condition results in an improvement of the characteristic of the monitored temperature includes checking whether the maximum temperature since the last change of firing conditions has decreased by a specific amount. In examples, an improvement of the characteristic of the monitored temperature is detected if the slope of the temperature has changed by at least a specific amount.

In examples, the controller is to continue the purging process without changing firing conditions of the purging process if an abnormality of the purging process is not detected. In example, the controller is to change the firing conditions by increasing a fluid volume of shipping fluid to be expelled during the next period of the purging process if an abnormality has not been detected during the present and any preceding period of the purging process. In examples, such a change of firing conditions by increasing the fluid volume of shipping fluid to be expelled during the next period of the purging process is performed if the actual period is the initial period. Accordingly, examples of the present disclosure may use printhead thermal logs to detect an abnormal thermal escalation. In principle, such a thermal escalation may be caused by the presence of some air in the printhead. However, such a thermal escalation may be indicative of some other issues of the printhead as well. In example, such issues may be mitigated or resolved by adjusting the firing conditions under which shipping fluid is purged from the printhead.

Referring to Fig. 6, another example of a method of purging shipping fluid from a printhead is described. At 100, shipping fluid is purged in an initial period by firing a specific fluid volume at high frequency and at an initial printhead temperature set to a specific temperature. For example, the specific fluid volume may be 1 mL and the initial printhead temperature may be in a range from 55°C to 65°C. “High firing frequency” means that the frequency is higher than the frequency for normal printing, i.e., printing to produce images on a medium. At 102, the printhead temperature during firing is monitored and a temperature characteristic is evaluated. The temperature characteristic may be the temperature magnitude or the thermal escalation slope. At 104, it is determined whether there is an abnormality. In examples, there is an abnormality if the temperature reaches a temperature threshold or if the temperature slope reaches a slope threshold. If it is determined at 104 that there is no abnormality, it is checked whether a determined purging volume has been purged at 106. If a determined purging volume has been purged, the process ends at 108 and the printing apparatus is ready for normal printing. The fact that a determined purging volume has been purged means that the shipping fluid has been completely replaced by normal printing fluid, such as ink.

If foe determined purging volume has not been purged, the process proceeds with the next purging period at 110. From 110, the process jumps to 102, where the printhead temperature is monitored again and the temperature characteristic is evaluated.

If an abnormality is detected at 104, the process jumps to 112, where the firing conditions for the next firing period are changed. As explained above, changing the firing conditions may include at least one of lowering the printhead temperature, lowering the firing frequency, or lowering foe fluid volume fired. Thereupon, the temperature characteristic is re-evaluated. At 114 it is checked whether an improvement of the temperature characteristic took place by changing the firing conditions. If an improvement of the temperature characteristic took place, the process jumps to 104 and it is checked again whether there is still an abnormality. If there is no improvement of the temperature characteristic, the firing conditions are changed again at 112 if the number of non- improved periods does not exceed a predetermined number. This is checked at 116. If foe number of non-improved periods exceeds the predetermined number, such as three, the process jumps to 118 where a warning is output. The warning may indicate to a user that the printhead has been detected as failed, such as due to detected air inside the printhead. If the check at 116 reveals that step 112 has not been repeated for the predetermined number of time without improvement of the temperature characteristic, the process jumps back to 112.

As indicated in Fig. 6 by a broken arrow 120, in alternative examples, the process may jump back from block 112 directly to block 102, where re-evaluation of the temperature characteristic may take place. In such examples, upon determining an abnormality at 104, the process may check whether repeatedly changing the firing conditions at 112 did not remove the abnormality. If so, i.e. if repeatedly changing the firing conditions did not remove the abnormality, a warning may be output to the user. In examples, if three times changing the firing conditions at 112 did not remove the abnormality, an warning may be output.

Thus, according to examples of the present disclosure, abnormal purging sequences are detected when discharging shipping fluid from shipping fluid filled printheads. Upon detecting abnormal purging sequences, firing conditions, i.e., purging parameters, are changed so that undesired consequences due to aggressive firing conditions during purging may be avoided and so that dead on arrival printhead errors may be detected.

Examples relate to a non-transitory machine-readable storage medium encoded with instructions executable by a processing resource of a computing device to perform methods described herein.

Examples described herein can be realized in the form of hardware, machine-readable instructions or a combination of hardware and machine-readable instructions. Any such machine-readable instructions 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 foe form of memory, such as, for example, RAM, memory chips, device or integrated circuits or an optically or magnetically readable medium, such as, for example, a CD, DVD, magnetic disk or magnetic tape. 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. Ml of the features disclosed in the specification (including any accompanying claims, abstract and drawings), and/or all the features of any method or progress described may be combined in any combination (including any claim combination), except combinations where at least some of such features are mutually exclusive. In addition, features disclosed in connection with a system may, at the same time, present features of a corresponding method, and vice versa.

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

The foregoing has described the principles, examples and modes of operation. However, the teaching herein should not be construed as being limited to the particular examples described. The above-described examples should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those examples by workers skilled in the art without departing from the scope of the following claims.

Claims

1. A printing apparatus comprising:

a printhead receptacle to accommodate a printhead comprising fluidic structures filled with a shipping fluid; and

a controller to:

perform a purging process to expel the shipping fluid from the printhead, monitor a temperature of the printhead during the purging process,

detect whether there is an abnormality of foe purging process using the monitored temperature.

if there is an abnormality of the purging process, change firing conditions of foe purging process, and check whether the abnormality is removed by changing foe firing conditions; and

continue the purging process if the abnormality is removed by changing the firing conditions.

2. The printing apparatus of claim 1 , wherein the controller is to perform foe purging process in discrete periods and to perform the monitoring, detecting, changing and checking for each period of the purging process.

3. The printing apparatus of claim 1 , wherein detecting whether there is an abnormality comprises detecting whether a characteristic of foe monitored temperature reaches a threshold.

4. The printing apparatus of claim 3, wherein the characteristic of the monitored temperature is a magnitude of the monitored temperature or a slope of foe magnitude of foe monitored temperature over time.

5. The printing apparatus of claim 1 , wherein changing the firing conditions of the purging process comprises at least one of:

lowering a printhead temperature to which the printhead is heated for purging; lowering a frequency with which nozzles of the printhead are fired for purging; and lowering a fluid volume of shipping fluid expelled during a period of the purging process.

6. The printing apparatus of claim 1 , wherein the controller is to: if changing the firing conditions does not remove the abnormality, repeatedly change file firing conditions and check whether the abnormality is removed, and

if repeatedly changing the firing conditions does not remove file abnormality stop the purging process and output a warning.

7. The printing apparatus of claim 3, wherein the controller is to:

before checking whether the abnormality is removed by changing the firing conditions, check whether changing the firing conditions results in an improvement of the characteristic of file monitored temperature,

if changing the firing conditions does not result in an improvement of the characteristic of the monitored temperature, repeatedly change file firing conditions, and if repeatedly changing the firing conditions does not result in an improvement of the characteristic of file monitored temperature stop the purging process and output a warning.

8. The printing apparatus of claim 2, wherein the controller is to:

if an abnormality has not been detected during file actual period and any preceding period of file purging process, change the firing conditions by increasing a fluid volume of shipping fluid to be expelled during the next period of the purging process.

9. A method of performing a purging process to expel shipping fluid from a printhead, comprising:

monitoring a temperature of the printhead during the purging process, detecting whether there is an abnormality of the purging process using file monitored temperature,

if there is an abnormality of the purging process, changing firing conditions of the purging process, and checking whether the abnormality is removed by changing the firing conditions; and

continuing the purging process if the abnormality is removed by changing file firing conditions.

10. The method of claim 9, wherein the purging process is performed in discrete periods and wherein monitoring, detecting, changing and checking is performed for each period of the purging process.

11. The method of claim 10, wherein detecting whether there is an abnormality comprises detecting whether a characteristic of the monitored temperature reaches a threshold, wherein the characteristic of the monitored temperature is a magnitude of the monitored temperature or a slope of the magnitude of the monitored temperature over time.

12. The method of claim 10, wherein changing the firing conditions of the purging process comprises at least one of:

lowering a printhead temperature to which file printhead is heated for purging; lowering a frequency with which nozzles of file printhead are fired for purging; and lowering a fluid volume of shipping fluid expelled during a period of file purging process.

13. The method of daim 12, comprising:

if changing the firing conditions does not remove the abnormality, repeatedly changing the firing conditions and check whether the abnormality is removed, and

if repeatedly changing the firing conditions does not remove file abnormality stopping the purging process and outputting a warning.

14. The method of daim 11 , comprising:

before checking whether the abnormality is removed by changing the firing conditions, checking whether changing the firing conditions results in an improvement of the characteristic of file monitored temperature,

if changing the firing conditions does not result in an improvement of the characteristic of file monitored temperature, repeatedly changing the firing conditions, and if repeatedly changing the firing conditions does not result in an improvement of the characteristic of file monitored temperature stopping file purging process and outputting a warning.

15. A non-transitory machine-readable storage medium encoded with instructions executable by a processing resource of a computing device to perform a purging process to expel shipping fluid from a printhead, the purging process comprising: monitoring a temperature of the printhead during the purging process, detecting whether there is an abnormality of the purging process using file monitored temperature. if there is an abnormality of the purging process, changing firing conditions of the purging process, and checking whether the abnormality is removed by changing the firing conditions; and

continuing the purging process if the abnormality is removed by changing the firing conditions.