WO2022081172A1

WO2022081172A1 - Controllers and printers

Info

Publication number: WO2022081172A1
Application number: PCT/US2020/056068
Authority: WO
Inventors: Dorkaitz Alain VAZQUEZ FERNANDEZ; Joan Albert MIRAVET JIMENEZ; Ana Oropesa Fisica
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2022-04-21

Abstract

Example implementations provide a controller to control gas purging of gas associated with an ink supply channel of a printer; the controller comprising: an input to receive a signal output by a pressure sensor; the signal being indicative of ink pressure associated with the ink supply channel, and a monitor to determine from a characteristic of the signal whether or not a gas purging system is fluidically coupled to the ink supply channel.

Description

BACKGROUND [0001] Ink jet printing can provide a high image quality given the resolution and colours of the ink drops ejected from the printheads. Anomalies associated with the printhead or ink 5 delivery system can reduce image quality. For example, fluid, such as air, ejected from a printhead can adversely affect image quality. The air may be within the ink delivery system and eventually be ejected by printhead. Furthermore, the presence of air in the printhead could lead to printhead failure due to ink starvation in which the printhead nozzles have insufficient ink to eject correctly, which is known as a dry fire. Consequently, the energy 10 that would be otherwise used to eject the ink via respective resistors is not transferred to the ink, but increases the printhead temperature. Therefore, printers can be provided with a gas purging system that is arranged to purge the printer of air or gas from the ink delivery system and, therefore, prevent adverse effects on image quality from manifesting. [0002] At initialisation, an ink delivery system of a printer can be purged of gas via the gas 15 purging system. The gas purging system allows air or any other gas to be evacuated from the ink delivery system. Additionally, printheads can be shipped containing a shipping fluid that is also purged, using a different mechanism, before printing commences. [0003] However, the effectiveness or otherwise of the gas purging system depends on the gas purging system being properly, that is, fluidically, connected to the ink delivery system. 20 The gas purging system can be connected to the ink delivery system at the time of manufacture of the printer or at the time of assembly of the ink delivery system. If the gas purging system is not connected to the ink delivery system, such as, for example, when a user or operator prematurely removes the gas purging system prior to completing a purge operation or prior to completing the start-up of the ink delivery system, the gas may not be 25 adequately removed from the ink delivery system. Any residual gas can be ingested by the printhead, which can lead to premature printhead failure, printer performance issues and reduced image quality. [0004] BRIEF INTRODUCTION TO THE DRAWINGS [0005] Examples implementations are described below with reference to the 30 accompanying drawings, in which: [0006] figure 1 shows a schematic diagram of a printer according to some examples; [0007] figures 2A and 2B illustrate ink delivery systems according to example implementations; [0008] figure 3 depicts a graph of variation of ink pressure with time according to some examples;

[0009] figure 4 shows a further graph of variation of ink pressure with time according to some examples;

[0010] figure 5 illustrates a flowchart according to some examples; and

[0011] figure 6 shows machine-readable storage and machine executable instructions according to some examples.

[0012] DETAILED DESCRIPTION

[0013] Figure 1 illustrates a schematic plan view of a printer 100. The printer 100 comprises: a working area 102 in which a printed plot or drawing can be produced. The working area is an example of a printing region. The printer 100 further comprises a medium actuator 104. The medium actuator 104 moves a medium 106 on which a printing liquid is to be deposited in between print traversals of a printhead carriage 108. A print traversal is a movement of the printhead carriage 108 from one side of the working area 102 to the other side of the working area.

[0014] The printhead carriage 108 comprises one or more than one printhead 110 for printing one or more than one printing liquid. A printhead 110 can comprise one or more than one channel 110a, 110b for receiving and expelling printing liquid during a print traversal. Examples can be realised in which the printhead carriage 108 comprises a number of such printheads 110. The printheads 110 are arranged to deposit respective printing liquids onto the medium 106. The one or more than one printing liquids can comprise one or more printing liquids associated with a respective colour process. Such a colour process can comprise a single tone or multiple tones. For example, a six-colour process, involving magenta, yellow, cyan, red and two blacks, can be used. Similarly, a nine-colour process could be used. In the example shown, each printhead 110 comprises two channels 110a, 110b for printing liquid. The example implementation shown uses a six-colour process with the colours being ejected from respective channels 110a, 110b of the three printheads 110. Examples can be realised in which a nine-colour process can be accommodated via 5 printheads.

[0015] The printhead carriage 108, in this example, is arranged to traverse the working area 102 in a reciprocating manner. While traversing the working area 102, the printheads 110 can print printing liquids onto the medium 106. The printheads can deposit printing liquid onto the medium 106 in either one direction, or both directions, of traversal. The printheads 110 can use an array of nozzles (not shown) to deposit the printing liquids. Depositing the printing liquids can use a thermal technique in which a heating element is arranged to heat the printing liquid rapidly so that printing liquid is ejected from a nozzle orifice associated with the heating element.

[0016] A stowage area 112 can be provided to one side of the working area 102. The printhead carriage 108 can be stowed in the stowage area 112 between printing traversals. [0017] A maintenance area 114 can be provided to another side of the working area 102. The maintenance area 114 is an example of a maintenance region. The maintenance area 114 can comprise a spittoon 116 for receiving one or more than one printing liquid during a maintenance operation. Examples can be provided in which a maintenance operation can comprise ejecting or expelling printing liquid from one or more than one of the printheads 110. Maintenance operations such as, for example, spitting a printing liquid, purging a printing liquid, printing a printing liquid, flushing a printing liquid, wiping a printing liquid, taken jointly and severally in any and all permutations, are examples of such ejecting or expelling printing liquids.

[0018] Although the examples have been, or are, described with reference to separate stowage 112 and maintenance 114 areas, examples can alternatively be realised in which the stowage 112 and maintenance 114 areas are the same, which means a single such area can be provided as opposed to two such areas.

[0019] A controller 118 is provided for controlling one or more aspects of the printer and/or printer operations. The printer operations can comprise one or more of printing operations, maintenance operations or other operations.

[0020] The controller 118 comprises an input interface 120 for receiving an image 122 to be printed. The controller 1 18 can control the printing operations used to print the image 122 on the medium 106 via printing control logic 124.

[0021] The printer 100 also comprises an ink delivery system 126 and a fluid or gas purging system 128. The ink delivery system 126 has been illustrated using a single line with a solidus; the solidus indicating multiple printing liquid supply channels in which each supply channel carries a respective printing liquid such as one of the inks of any of the above-described colour processes. The terms ink and printing liquid are used synonymously. The gas purging system 128 comprises a number of gas purgers 130 that are fluidically coupled to the ink delivery system 126 to vent or otherwise purge the ink delivery system of air or other gas. In the illustrated example, each printhead 110 has a respective gas purger 130. In the example shown in figure 1 , there are six gas purgers; one for each of the dual printing liquid channels. It will be appreciated that the gas purging system 128 can be installed and invoked or otherwise used to purge the ink delivery system 110. However, example implementations can be realised in which both the gas purging system 128 and the printheads 110 are installed simultaneously.

[0022] The controller 1 18 also comprises logic or circuitry 132 to detect 'whether or not the gas purging system 128 is fluidically coupled to the ink delivery system 126 to be able to vent gas from within the ink delivery system 128. The logic or circuitry 132 is an example of a monitor to determine from a characteristic of a pressure profile derived from one or more than one signal whether or not a gas purging system is fluidically coupled to the ink supply channel. The logic or circuitry 132 is responsive to at least one signal 134 from at least one transducer 136. Each transducer or the transducer 136 can be a pressure sensor. Each pressure sensor 136 is arranged to provide an indication of printing fluid pressure in a respective one of the supply channels via respective signals 134. Again, a solidus is used to indicate one or a number of signals 134 output by a respective transducer or respective transducers 136.

[0023] The logic or circuitry 132 can comprise a signal processor 138 that is arranged to process any pressure signals to determine whether or not they exhibit any characteristic or characteristics indicative of the gas purging system 128 being present or not, that is, being fluidically coupled to the ink delivery system 126 or not. If the determination is that a signal exhibits one or more characteristics indicative of a respective gas purger not being fluidically coupled to the ink delivery system, or to a respective supply channel of the ink delivery system 126, an output 140 to that effect is generated and output by the controller 118. The output 140 can comprise a message displayed on a screen (not shown) that can be viewed by the user or operator. It 'will be appreciated that each colour process or supply channel will have a respective transducer 136 producing a respective pressure signal that is processed to determine whether or not a respective gas purger 130 is fluidically coupled to a respective supply channel.

[0024] Referring to figure 2A, there is shown a view of an ink delivery system 200A according to an example implementation. The ink delivery system 200A is an example of the above-described ink delivery system 126. The ink delivery system 200A comprises an ink supply channel 202A. The ink supply channel 202A is an example of any of the abovedescribed ink supply channels. The ink supply channel 202A is arranged to supply a printing liquid to a printhead 204A. The printhead 204A is an example of any of the above described printheads 110. The ink supply channel 202A supplies printing liquid to print nozzles 206A of the printhead 204A. A gas purger 208A is illustrated as being fluidically coupled to the ink supply channel 202A. The gas purger 208A is an example of any of the above-described gas purgers 130. The gas purger 208A is arranged to vent gas within the ink supply channel 202A when the gas purger 208A is fluidicaily coupled to the ink supply channel 202A. The ink supply channel 202A is coupled to a pump 210A. The pump 210A is used to draw printing liquid from a printing liquid supply 212A.

[0025] A transducer 214A such as a pressure sensor is arranged within or is fluidicaily coupled to, or is otherwise influenced by, the pressure of the printing liquid within, the ink supply channel 202A. The transducer 214A is an example of any of the above-described transducer or transducers 136. The transducer 214A is arranged to output a signal 216A. The signal 216A is indicative of, or otherwise associated with, the pressure of the printing liquid in the ink supply channel 202A. The signal is an example of any of the abovedescribed signal or signals 134. The controller 1 18 is arranged to use the output signal 216A in determining whether or not the gas purger 208A is fluidicaily coupled to the ink supply channel 202A according to one or more characteristics of the output signal 216A.

[0026] The example implementation depicted in figure 2A additionally comprises an intermediate tank 218A for storing printing liquid. The intermediate tank 218A is maintained at a preset pressure to ensure correct printing operation. Furthermore, prior to installing or using the gas purging system 128 to purge the ink supply system 126 of gas, the intermediate tank can be pressurised to prevent gas that should be purged from the ink supply system 126 from entering the intermediate tank 218A. The preset pressure is maintained using a pressure sensor 220A in conjunction with a value 222A and an air pump 224A. The value 222A is used to vent air from the intermediate tank 218A when it is being primed with printing liquid from the ink supply or printing liquid supply 212A in preparation for printing. As the printing liquid level varies during printing the pressure sensor 220A and air pump 224A are responsive to maintain the printing liquid within the intermediate tank 218A at a desired pressure.

[0027] Referring to figure 2B, there is shown a view of a further ink delivery system 200B according to an example implementation. The ink delivery system 200B is an example of the above-described ink delivery system 126. The ink delivery system 200B comprises an ink supply channel 202B. The ink supply channel 202B is an example of any of the abovedescribed ink supply channels. The ink supply channel 202B is arranged to supply a printing liquid to a printhead 204B. The printhead 204B is an example of any of the above described printheads 110. The ink supply channel 202B supplies printing liquid to print nozzles 206B of the printhead 204B. A gas purger 208B is illustrated as being fluidicaily coupled to the ink supply channel 202B. The gas purger 208B is an example of any of the above-described gas purgers 130. The gas purger 208B is arranged to vent gas within the ink supply channel 202B when the gas purger 208B is fluidicaily coupled to the ink supply channel 202B. The ink supply channel 202B is coupled to a pump 21 OB. The pump 21 OB is used to draw printing liquid from a printing liquid supply 212B.

[0028] A transducer 214B such as a pressure sensor is arranged within or is fluidically coupled to, or is otherwise influenced by, the pressure of the printing liquid within, the ink supply channel 202B. The transducer 214B is an example of any of the above-described transducer or transducers 136. The transducer 214B is arranged to output a signal 216B. The signal 216B is indicative of, or otherwise associated with, the pressure of the printing liquid in the ink supply channel 202B. The signal is an example of any of the abovedescribed signal or signals 134. The controller 118 is arranged to use the output signal 216B in determining whether or not the gas purger 208B is fluidically coupled to the ink supply channel 202B according to one or more characteristics of the output signal 216B. [0029] Referring to figure 3, there is shown a graph 300 of variation of a pressure output signal 302 with time when a gas purger is not fluidically coupled to a respective ink supply channel. The pressure output signal 302 is an example of any of the above described signals such as, for example, output signal 134 output from a respective pressure sensor such as, for example, pressure sensor 136. The pressure output signal 302 is indicative of the printing liquid pressure within a respective printing liquid supply channel. While there is a gas within the ink supply channel or ink supply system, in particular, while there is a gas in contact with the pressure sensor, the pressure output signal is relatively low. In the illustrated example, the pressure is approximately -5750 mPsi (-39.64 kPa). However, there is a small sharp increase in pressure at point 304 when the printing liquid within the ink supply channel contacts the pressure sensor. Thereafter, the pressure reaches a short plateau 306.

[8830] It can be appreciated that the subsequent variation in pressure has at least one characteristic indicative of the gas purger not being fluidically coupled to the ink supply channel. The at least one characteristic can comprise one or more than one of [0031] - a progressive increase in pressure 308, [0032] - a relatively high initial time derivative of pressure 310, [0033] - a rate of change of ink pressure with time, [0034] - a predetermined ink pressure threshold 312, [0035] - an ink pressure profile, [0036] - an ink pressure profile associated with a respective ink, [0037] - an ink pressure profile of a number of possible ink pressure profiles each associated with respective inks, [0038] - a relatively low time derivative of pressure 314, [0039] a relatively low time derivative of pressure 314 after a respective period of time since one or more of the end of the plateau 306, since the increase 316 in pressure 304 or since some other point in time, or

[0040] - a relatively smooth variation of pressure 308 with time having relatively low frequency harmonics in the frequency domain,

[0041] taken jointly and severally in any and all permutations.

[0042] It will be appreciated that frequency harmonics are example implementations of frequency components. It will be appreciated that the end of the plateau 306, the rapid increase in pressure 316 or the reference to some other point in time are each examples of a datum.

[0043] In the example depicted, the pressure varies from an initial value of about -5750 mPsi, (-39.64 kPa) to a -4000 mPsi (-27.57 kPa) plateau when the ink contacts the pressure sensor and then progressively climbs to about 1000 mPsi (6.89 kPa) over about a 20 second period.

[0044] Referring to figure 4, there is shown a graph 400 of variation of a pressure output signal 402 with time when a gas purger is fluidicaliy coupled to a respective ink supply channel. The pressure output signal 402 is an example of any of the above described signals such as, for example, output signal 134 output from a respective pressure sensor such as, for example, pressure sensor 136. The pressure output signal 402 is indicative of the printing liquid pressure within a respective printing liquid supply channel. While there is a gas within the ink supply channel or ink supply system, in particular, while there is a gas in contact with the pressure sensor, the pressure output signal is relatively low. In the illustrated example, the pressure is approximately -5750 mPsi (-39.64 kPa). However, there is a small sharp increase in pressure at point 404 when the printing liquid within the ink supply channel contacts the pressure sensor. Thereafter, the pressure reaches a short plateau 406. It can be seen, however, that the pressure level corresponding to the plateau is lower compared to the pressure level corresponding to the plateau when the gas purger is not fluidicaliy coupled to the ink supply channel. In the illustrated example, the pressure level at the plateau is approximately -4250 Psi (-29.30 kPa).

[0045] It can be appreciated that the subsequent variation in pressure has a respective profile bearing at least one characteristic indicative of the gas purger being fluidicaliy coupled to the ink supply channel. The at least one characteristic can comprise one or more than one of

[0046] - a relatively low further increase in pressure 408,

[0047] - a relatively low time derivative of pressure 410, [0048] - a rate of change of ink pressure with time,

[0049] - a predetermined ink pressure threshoid 412,

[0050] - an ink pressure profile,

[0051] - an ink pressure profile associated with a respective ink,

[0052] - an ink pressure profile of a number of possible ink pressure profiles each associated with respective inks,

[0053] - a relatively low time derivative of pressure 414,

[0054] - a relatively low time derivative of pressure 414 after a respective period of time since one or more of the end of the plateau 406, since the increase 416 in pressure 404 or since some other point in time, or

[0055] - a relatively irregular variation of pressure 408 with time having relatively higher frequency harmonics in the frequency domain compared to the frequency harmonics of the signal without the gas purger being fluidically coupled to the ink supply channel, [0056] taken jointly and severally in any and all permutations.

[0057] It 'will be appreciated that frequency harmonics are example implementations of frequency components, it will be appreciated that the end of the plateau 406, the rapid increase in pressure 416 or the reference to some other point in time are each examples of a datum.

[0058] For example, it the first time derivative of the signal, such as the pressure signal, has a value that is less than or equal to a respective threshold value, it can be concluded or assumed that the gas purger system is fluidically coupled to at least one of the transducer or ink supply system. Conversely, if the first time derivative of the signal, such as the pressure signal, is greater than or equal to a respective threshold value, it can be assumed or concluded that the gas purger system is not fluidically coupled to at least one of the transducer or ink supply system.

[0059] It will be appreciated that the events representing the end of the plateau 406, the increase in pressure 404 or some other point in time are each examples of a datum.

[0060] In the example depicted, the pressure varies from an initial value of about -5750 mPsi, (-39.64 kPa) to a -4250 mPsi (-27.30 kPa) plateau when the ink contacts the pressure sensor and then progressively climbs in an irregular manner to about -1750 mPsi (-12.06 kPa) over about a 20 to 30 second period.

[0061] Referring to figure 5, there is shown a view of a flowchart 500 according to an example implementation. At 502, the controller 118 receives a pressure sensor signal. The pressure sensor signal is an example of any of the above-described pressure signals such as, for example, signal 134. [0062] A determination is made at 504 based on at least one characteristic of the pressure signal whether or not a gas purger is fluidically coupled to a respective ink supply channel associated with a transducer giving rise to the pressure sensor signal. If the determination at 504 is that a gas purger is not fluidically coupled to the ink supply channel, an output signal or an alarm to that effect is generated at 506. The output signal or alarm is an example of the above-described output 140.

[0063] If the determination at 504 is that a gas purger is connected to the respective ink supply channel, normal printer operations commence at 508. The normal printer operations can comprise additional start-up or printer initialisation operations. For example, once the ink supply system 126 has been purged, the printhead or printheads can be installed via a fluid Interconnect located on the carriage 108 whereupon a servicing routine is triggered to purge the printhead. Purging the printhead can comprise spitting any shipping fluid, or other liquid, contained with the printhead through the nozzles and replacing the shipping fluid with printing liquid.

[0064] Example implementations can be realised in the form of machine executable instructions arranged, when executed by a machine, to implement any or all aspects, processes, activities or flowcharts, taken jointly and severally in any and all permutations, described or claimed in this application. Therefore, implementations also provide machine- readable storage storing such machine instructions executed or implemented by a machine. The machine-readable storage can comprise non-transitory machine readable storage. The machine can comprise one or more processors or other circuitry for executing or implementing the instructions. For example, the controller 118 can process any such machine executable instructions. The signal processor 122 can be realised using such instructions.

[0065] Therefore, referring to figure 6, there is shown a view 600 of implementations of at least one of machine executable, or machine implemented, instructions or machine- readable storage. Figure 6 shows machine-readable storage 602. The machine-readable storage 602 can be realised using any type of volatile or non-volatile storage such as, for example, memory, a ROM, RAM, EEPROM, optical storage and the like. The machine- readable storage 602 can be transitory or non-transitory. The machine-readable storage 602 stores or implements machine executable, or machined implemented, instructions (MEIs) 604. The MEIs 604 comprise instructions that are executable, processed, interpreted or implemented, by a processor or other instruction execution circuitry 606. The processor or other circuitry 606 is responsive to executing the MEIs 604 to perform any and all activities, operations, methods described and claimed in this application. The processor or other circuitry 606 is an example of the above-described controller 118.

[0066] The processor or other circuitry 606 can receive one or more than one signal 608 for determining whether or not one or more gas purgers are fluidically coupled to one or more than one respective ink supply channel. The signal 608 is an example of any of the above described signals 136. The signal 608 is output by a respective transducer 610. The transducer 610 is an example of any of the above described transducers 134.

[0067] The controller 118 can be an implementation of the foregoing processor or other circuitry 606 for executing any such MEIs 604.

[0068] The MEIs 604 can comprise instructions for realising a controller, printer or to implement any method described and/or claimed in this application.

[0069] Any and all example implementations can be realised with or within a printer such as the printer described with reference to figure 1 . The printer can be a multipass printer that is capable of printing at least one, or both, of bidirectionally or unidirectionally.

[0070] Although the above implementations have been described within a TIJ printing context, example implementations are not limited to such a technology. Any and all example implementations can be used for controlling printheads realised using technology other than TIJ technology such as, for example, piezoelectric printheads.

[0071] It will be appreciated that example implementations can be realised using page- wide printheads. Some printers have one or more than one printhead that spans the medium to be printed, that is, some printer have one or more than one page-wide printhead. Such printers are known as page-wide array printers. Page-wide array printers can have static printheads, that is, the carriage bearing the printheads does not traverse the medium rather the medium moves relative to the one or more than one printhead. It will be appreciated that some page-wide printers use multiple printheads to space the full width of the printer and other printers use a single printhead with an array of nozzles to space the full width of the printer.

[0072] Throughout the description and claims of this application, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components or integers. Throughout the description and claims of this application, the singular encompasses the plural unless the context otherwise dictates. Where the indefinite article is used, the specification is to be understood as contemplating the plural as well as the singular, unless the context requires dictates.

[0073] Although example implementations have been described with reference to 2D printers, examples are not limited to such an arrangement. 3D printers use a variety of liquids in defining a 3D printed product. Example implementations can be realised in which the channels used to carry printing liquids used in 3D printers are purged of gas using gas purgers as described above.

[0074] Example implementations can be realised as follows:

[0075] Clause 1 : A controller to control gas purging of gas associated with an ink supply channel of a printer; the controller comprising: an input to receive a signal output by a pressure sensor; the signal being indicative of ink pressure associated with the ink supply channel, and a monitor to determine from a characteristic of the signal whether or not a gas purging system is fluidically coupled to the ink supply channel.

[0076] Clause 2: The controller of clause 1 , in which the characteristic is associated with one or more than one of: a time derivative of ink pressure, a rate of change of ink pressure with time, a predetermined ink pressure threshold, or an ink pressure profile of a number of possible ink pressure profiles each associated with a respective ink taken jointly or severally in any and all permutations.

[0077] Clause 3: The controller of clause 2, in which the rate of change of ink pressure with time is above a predetermined gradient that is indicative of the gas purging system not being fluidically coupled to the ink supply channel or in which the rate of change of ink pressure with is below a further predetermined gradient that is indicative of the gas purging system being fluidically coupled to the ink supply channel.

[0078] Clause 4: The controller of any preceding clause, in which the monitor is arranged to determine the characteristic after a prescribed time period measured from an datum.

[0079] Clause 5: The controller of clause 4, in which the prescribed time period is measured from an increase in ink pressure.

[0080] Clause 6: Machine readable storage storing machine instructions arranged when executed or implemented to: receive a pressure signal derived from a pressure transducer; the pressure signal being associated with an ink pressure within an ink delivery system; and process the received pressure signal to determine whether or not a gas purger is fluidically coupled to the pressure transducer.

[0081] Clause 7: The machine readable storage of clause 6, in which the instructions to process the received pressure signal to determine 'whether or not a gas purger is fluidically coupled to the pressure transducer comprise instructions to determine from a gradient, or other feature , of the pressure signal output by the transducer whether or not the gas purger is fluidically connected to the pressure transducer. [0082] Clause 8: The machine readable storage of clause 6, in which the instructions to process the received pressure signal to determine whether or not a gas purger is fluidically coupled to the pressure transducer comprise instructions to determine variability of pressure with time and instructions to determine from the variability of pressure with time whether or not the gas purger is fluidically coupled to the pressure transducer.

[0083] Clause 9: The machine readable storage of any of clauses 6 to 8, in which the instructions to process the received pressure signal to determine whether or not a gas purger is fluidically coupled to the pressure transducer comprise instructions to determine frequency components of the pressure signal time, and instructions to determine from the frequency components whether or not the gas purger is fluidically coupled to the pressure transducer.

[0084] Clause 10: The machine readable storage of any of clauses 6 to 9, comprising instructions arranged to measure a pressure reading associated with the pressure transducer an elapsed period of time from an event such as, for example, an ink contact with the pressure transducer.

[0085] Clause H : A printer comprising a printhead, an ink delivery system for transporting ink to the printhead from an ink supply, a pressure transducer for determining an ink pressure, a gas purging system to purge gas from at least the ink delivery system; the gas purging system being selectively fluidically couplable to and decouplable from the ink delivery system, and a controller arranged to determine from an output signal associated with the pressure transducer whether or not the gas purging system is at least one of coupled to or decoupled from the ink delivery system.

[0086] Clause 12: The printer of clause 11 , in which the controller is arranged to process the output signal to determine at least one characteristic of the output signal and to determine from the at least one characteristic whether or not the gas purging system is coupled to or decoupled from the ink delivery system.

[0087] Clause 13: The printer of clause 12, in which the at least one characteristic comprises one or more of a rate of change of ink pressure with time, a predetermined ink pressure threshold, an ink pressure profile of a number of possible ink pressure profiles each associated with a respective ink.

Claims

CLAIMS A controller to control gas purging of gas associated with an ink supply channel of a printer; the controller comprising: a. an input to receive a signal output by a pressure sensor; the signal being indicative of ink pressure associated with the ink supply channel, and b. a monitor to determine from a characteristic of the signal whether or not a gas purging system is fluidicaliy coupled to the ink supply channel. The controller of claim 1 , in which the characteristic is associated with one or more than one of: a. a rate of change of ink pressure with time, b. a predetermined ink pressure threshold, c. an ink pressure profile of a number of possible ink pressure profiles each associated with a respective ink. The controller of claim 2, in which the rate of change of ink pressure with time is above a predetermined gradient that is indicative of the gas purging system not being fluidicaliy coupled to the ink supply channel or in which the rate of change of ink pressure with is below a further predetermined gradient that is indicative of the gas purging system being fluidicaliy coupled to the ink supply channel. The controller of claim 1 , in which the monitor is arranged to determine the characteristic after a prescribed time period measured from an datum. The controller of claim 4, in which the prescribed time period is measured from an increase in ink pressure. Machine readable storage storing machine instructions arranged when executed or implemented to: a. receive a pressure signal derived from a pressure transducer; the pressure signal being associated with an ink pressure within an ink delivery system; b. process the received pressure signal to determine whether or not a gas purger is fluidicaliy coupled to the pressure transducer. The machine readable storage of claim 6, in which the instructions to process the received pressure signal to determine whether or not a gas purger is fluidicaliy coupled to the pressure transducer comprise instructions to determine from a gradient, or other feature, of the pressure signal output by the transducer whether or not the gas purger is fluidicaliy connected to the pressure transducer. The machine readable storage of claim 6, in which the instructions to process the received pressure signal to determine whether or not a gas purger is fluidically coupled to the pressure transducer comprise a. instructions to determine variability of pressure with time, and b. instructions to determine from the variability of pressure with time whether or not the gas purger is fluidically coupled to the pressure transducer. The machine readable storage of claim 8, in which the instructions to process the received pressure signal to determine 'whether or not a gas purger is fluidically coupled to the pressure transducer comprise: instructions to determine frequency components of the pressure signal, and instructions to determine from the frequency components whether or not the gas purger is fluidically coupled to the pressure transducer. The machine readable storage of claim 6, comprising instructions arranged to measure a pressure reading associated with the pressure transducer an elapsed period of time from an event. A printer comprising a. a printhead, b. an ink delivery system for transporting ink to the printhead from an ink supply, c. a pressure transducer for determining an ink pressure, d. a gas purging system to purge gas from at least the ink delivery system e. ; the gas purging system being selectively fluidically couplable to and decouplable from the ink delivery system, and f. a controller arranged to determine from an output signal associated with the pressure transducer whether or not the gas purging system is at least one of coupled to or decoupled from the ink delivery system. The printer of claim 11 , in which the controller is arranged to process the output signal to determine at least one characteristic of the output signal and to determine from the at least one characteristic 'whether or not the gas purging system is coupled to or decoupled from the ink delivery system. The printer of claim 12, in which the at least one characteristic comprises one or more of a. a rate of change of ink pressure with time, b. a predetermined ink pressure threshold, c. an ink pressure profile of a number of possible ink pressure profiles each associated with a respective ink.