WO2021216064A1

WO2021216064A1 - Combination of thermal and piezoelectric ejection devices

Info

Publication number: WO2021216064A1
Application number: PCT/US2020/029338
Authority: WO
Inventors: Maria Elizabeth Zapata; Pere Esterri Pedra; Lluis ABELLO ROSELLO; Maria Isabel BORRELL BAYONA; Rafael ULACIA PORTOLES
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-04-22
Filing date: 2020-04-22
Publication date: 2021-10-28

Abstract

A printing apparatus comprises a first depositing device and a second depositing device. The first depositing device is operable to deposit a first print fluid on a print medium by applying heat to the first print fluid to cause the first print fluid to thermally expand through a first passage towards the print medium. The second depositing device is operable to deposit a second print fluid on the print medium by applying a mechanical vibration to move the second print fluid through a second passage towards the print medium.

Description

COMBINATION OF THERMAL AND PIEZOELECTRIC EJECTION DEVICES

BACKGROUND

[0001] The inkjet technology allows for the deposition of a print fluid onto a print medium. In addition or alternatively to reproducing an image on the print medium, the inkjet technol ogy may be used to apply any suitable material on a substrate provided as print medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. l is a schematic diagram of a printing apparatus according to an example.

FIG. 2 is a schematic diagram of a depositing device according to an example. FIG. 3 shows schematic diagrams of depositing devices according to further examples. FIG. 4 is a schematic diagram of a printing apparatus according to another example. FIG. 5 is a schematic diagram of a printing apparatus in a perspective view according to a further example.

FIG. 6 is a schematic diagram of a carriage in a bottom view according to an example FIG. 7 is a schematic diagram of the carriage in a cross-sectional side view FIG. 8 a schematic diagram of a service device according to an example FIG. 9 is a schematic diagram of a print bar according to an example FIG. 10 is a schematic diagram of print bars according to an example.

FIG. li is a flow diagram of a method according to an example. DETAILED DESCRIPTION

[0002] In the following detailed description, same reference numerals and letters are used to refer to the same, similar or related features in different examples. Wherever the same ref erence numeral or letter is used, the respective structural or functional features of the other example also apply to the currently described example, unless otherwise indicated.

[0003] FIG. 1 shows a printing apparatus 100 operable to deposit any one or both of a first print fluid Fi and a second print fluid F2 on a print medium P. The printing apparatus 100 may comprise a first depositing device 110 to deposit the first print fluid Fi on the print medium and a second depositing device 120 to deposit the second print fluid F2 on the print medium P. The first depositing device 110 may be operable to apply heat to the first print fluid Ft to cause the first print fluid Ft to thermally expand through a first passage 112 towards the print medium P. The second depositing device 120 may be operable to apply a mechanical vibration to move the second print fluid F2 through a second passage 122 towards the print medium P. The example as shown in FIG. 1 is illustrative. In some examples, the printing apparatus too may comprise a plurality of first depositing devices 110. Further, the printing apparatus may comprise a plurality of second depositing devices 120. Any of the first and second depositing devices 110, 120 may comprise a respective ejection device.

[0004] The printing apparatus too may further comprise a mount device 130 on which the first depositing device 110 and the second depositing device 120 may be mounted. In some examples, the mount device 130 may be a carriage which may be movable over and across the print medium P, see also FIG. 5. In other examples, the mount device 130 may be a print bar which extends over and across the print medium P, see also FIG. 9. Furthermore, the printing apparatus too may comprise a print bar, a carriage or both.

[0005] The printing apparatus too may further comprise an image processor 140. The im age processor 140 may be operable to control the first depositing device 110, or the second depositing device 120, or both. In some examples, the image processor 140 may control the first depositing device 110 in a first color space of the first print fluid Ft and control the second depositing device 120 in a second color space of the second print fluid F2, wherein the first and second color spaces are separate color spaces. The color space may refer to an entirety of colors that can be reproduced using the respective print fluid Ft, F2 and the respective depositing device 110, 120. In examples where the first print fluid Ft or the second print fluid F2 is a material other than process colors, the color space of this print fluid may refer to an entirety of the deposition intensity (e.g. deposition thicknesses) that is reproducible using the respective depositing device no, 120.

[0006] For example, image processor 140 may control the depositing of the second print fluid F2 by the second depositing device 120 as a spot color that is independent from a color space available for depositing the first print fluid Fi by the first depositing device no. In such an example, the first print fluid Fi maybe a process color, for example cyan, magenta, yellow or black. In some examples, the deposition of the second print fluid F2 by the second depositing device 120 maybe controlled based on a standard raster image processor (RIP). In such exam ples, the second print fluid F2 maybe deposited according to a Halftone technique. The depo sition of the second print fluid F2 may be assisted by any suitable known algorithm, such as Matrix Halftone and Error Diffusion.

[0007] In some examples, a backend-pipeline maybe provided to the controlling of the dep osition of the second print fluid F2, wherein the backend-pipeline may support 2-bits per pixel for multi-drop capability. The backend-pipeline may further control nozzle alignment correc tions for the second depositing device 120 with a single slot and different number of nozzles and different printing resolution.

[0008] In some examples, a single encoder device may control the deposition of both the first print fluid Ft and the second print fluid F2 by driving the first depositing device 110 and the second depositing device 120, respectively. The use of the single ensure may help synchro nizing of the deposition processes by both of the depositing devices 110, 120 and further help aligning the deposition on the print medium P.

[0009] The mount device 130 may house electronic components and logic devices including drivers for the first and second depositing devices 110, 120. The electronic parts may include nozzle data protocol, waveform generation to drive piezoelectric elements as described below, DAC drivers, FPGA, microcontrollers and power sources. Some of the electronic components and logic devices maybe used for both of the first and second depositing devices 110, 120, and other electronic components and logic devices may be provided separately for the first and second depositing devices 110, 120.

[0010] The printing apparatus too may comprise or be a part of a single printing device or a printing system. For example, the printing apparatus too maybe an inkjet printing apparatus operable to propel any of the print fluids Ft, F2 onto the print medium P. The printing appa ratus too may be a drop-on-demand apparatus.

[0011] The print medium P may be a solid material providing a surface on which either of the print fluids Fi, F2 maybe deposited. The print medium P maybe provided as a continuous sheet or as a single sheet. The print medium P may comprise paper, textile, fabric, synthetic material, web material or woven material, or any combination thereof. The print medium P may be or comprise a substrate.

[0012] The first depositing device 110 may be operable to deposit the first print fluid Fi on the print medium P by applying heat to the first print fluid Fi. The first depositing device 110 may comprise a thermal inkjet ejection device. For example, the first depositing device 110 may comprise or be connected to a power source and a heating resistor. The first depositing device 110 may apply an electric voltage to the heating resistor, thereby generating heat. The first print fluid Fi may be provided such to evaporate in response to the heat applied by the first depos iting device 110 and thereby generate a bubble, i.e. a volume of the gaseous phase within the liquid phase of the first print fluid Fi. The evaporation leads to an increase of volume, i.e. ex pansion, of the first print fluid Fi and thus to an increase of the pressure within the first de positing device 110. As a result, a certain amount of the first print fluid Fi is pushed through a first passage 112 that opens to the outside of the first depositing device 110. If the print medium P is positioned under the first passage 112 as shown in FIG. 1, the operation leads to the first print fluid Ft expanding through the first passage 112 towards the print medium P.

[0013] FIG. 2 schematically shows an example of the first depositing device 110. The first depositing device 110 may comprise the first passage 112. In some examples, the first print fluid Ft may be stored within the first depositing device 110. Alternatively or additionally, the first depositing device 110 may be connected to an external reservoir (not shown) providing the first print fluid Ft. The reservoir may comprise a container storing the first print fluid Ft or a supply device for delivering the first print fluid Ft to the first depositing device 110, or a combination thereof. In FIG. 2, a delivery passage 116 symbolizes a supply path of the first print fluid Ft from such a container or a delivery device.

[0014] The first depositing device 110 may comprise a chamber 114 which receives the first print fluid Ft from the reservoir. The first print fluid Ft may be received by the first depositing device 110 and stayed in the chamber 114 until discharged from the first depositing device 110. When viewed along a delivery direction of the first print fluid Ft as indicated in FIG. 2, a cross section of the first passage 112 maybe smaller than a cross section of the chamber 114. The first passage 112 may be referred to as a nozzle.

[0015] In some examples, the pressure in the chamber 114 may be regulated such to main tain the first print fluid Ft in the chamber 114. For example, the pressure in the chamber 114 is decreased below the ambient pressure regulated such to prevent external air ingestion through the first passage 112 during or in between the deposition operation of the first depositing device 110. The pressure regulation may help to prevent drooling of the first print fluid Fi through the first passage 112. In alternative examples, the first depositing device 110 may passively provide a pressure regulation.

[0016] The first depositing device 110 may further comprise a heating device 118. The heat ing device 118 may be provided partly integrated in the first depositing device 110. The heating device 118 may comprise a heating resistor and a power source (both not shown). In this ex ample, both of the heating resistor and the power source may be integrated in the first depos iting device 110. In some other examples (not shown), any of the heating resistor and the power source may be provided separately from the first depositing device 110. The heating resistor may be arranged adjacent to the chamber 114. The power source may apply an electric pulse to the heating resistor to generate heat in the chamber 114. In response, the first print fluid Fi partly evaporates and expands within the chamber 114. As a result, a portion of the first print fluid Fi is discharged from the first depositing device nothrough the first passage 112. Accord ingly, the first print fluid Ft may be thermally deposited on the print medium P (see FIG. 1) using the first depositing device 110.

[0017] The print fluid Ft may comprise a process color for a color inkjet printing process. For example, the first print fluid may be or comprise one of cyan, magenta, yellow and black process colors. Additionally or alternatively, the print fluid Ft may comprise another process color, a pre-treatment fluid or an overcoat fluid, or any combination thereof. The pre-treat ment fluid may contain a substance to facilitate the printing on a given target substrate, for example on a garment. The overcoat fluid may contain a substance to protect a printing prod uct, for example by covering it with a hydrophobic layer.

[0018] The first print fluid Ft may be designed to be thermally expandable through the first passage 112 of the first depositing device 110 under heat. For example, the first print fluid Ft may be prepared such to have any of a melting point, thermal expansion coefficient and ther mal capacity according to the specifics of the first depositing device 110.

[0019] In some examples, the first depositing device 110 may comprise a memory device 119 to store information about calibration, information about an operational event, infor mation about malfunction of the first depositing device 110 or any combination thereof. Addi tionally or alternatively, the memory device 119 may be used to store information about cali bration, information about an operational event, information about malfunction the second depositing device 120 or any combination thereof. For example, the information stored in the memory device 119 may be used to determine debugging information, counters of the respec tive print fluid and warranty of the respective depositing device. The memory device 119 may be provided as any known digital data store device, for example a solid-state memory device or EEROM. In some examples, the first depositing device 110 may comprise a process color car tridge, and the memory device 119 may be provided as a memory chip integrated therein.

[0020] The second depositing device 120 may be operable to generate a mechanical vibra tion. The second depositing device 120 may comprise a piezoelectric inkjet ejection device. For example, the second depositing device 120 may comprise a piezoelectric element. The second depositing device 120 may be provided, integrally or separately, with electrodes, a power source and a signal generator (not shown) to apply an electric signal to the piezoelectric ele ment. The electric signal may be generated in a pulsed waveform, i.e. as a time-limited surge of voltage. Applying the electric signal to the piezoelectric element may cause the piezoelectric element to vibrate and physically deform. The piezoelectric element may be arranged such that its deformation may induce a decrease of a volume within the second depositing device 120 containing the second print fluid F2. As a result, the second print fluid F2 may discharge from the second depositing device 120 through a second passage 122 which opens to the outside of the second depositing device 120. Accordingly, the piezoelectric element may generate a pres sure gradient across the second depositing device to control a deposition process of the second print fluid F2.

[0021] The second depositing device 120 may comprise the second passage 122. In some examples, the second print fluid F2 may be stored within the second depositing device 120. Alternatively or additionally, the second depositing device 120 maybe connected to an external reservoir (not shown) providing the second print fluid F2. The reservoir may be a container storing the second print fluid F2, a supply device for delivering the first print fluid F2 to the second depositing device 120 or a combination thereof.

[0022] FIG. 3 illustrates some examples of the second depositing device 120. For all the examples shown in FIG. 3, the second depositing device 120a - i2od may comprise a chamber 124 to receive the second print fluid F2 from a reservoir. The second print fluid F2 may be received by the second depositing device 120 and stayed in the chamber 124 until discharged from the second depositing device 120. When viewed along a delivery direction of the second print fluid F2 as indicated via arrows in FIG. 3, a cross section of the second passage 122 may be smaller than a cross section of the chamber 124. The second passage 122 may be referred to as a nozzle. [0023] In some examples, the pressure in the chamber 124 may be regulated such to main tain the second print fluid F2 in the chamber 124. The pressure regulation may help to prevent drooling of the second print fluid F2 through the second passage 122.

[0024] Furthermore, the second depositing device 120a - i2od may each comprise a piezo electric element 126 to perform a mechanical vibration in response to an electric signal applied. The mechanical vibration causes a physical deformation 127 of the piezoelectric element 126 as schematically illustrated in FIG. 3. The physical deformation 127 may reduce a volume avail able for the second print fluid F2 in the chamber 124, and thus create a pressure gradient across the second passage 122 which opens to the outside of the second depositing device 120. As a result, the second print fluid F2 may discharge from the second depositing device 120 through the second passage 122.

[0025] In one example shown in FIG. 3, the piezoelectric device 126 of the second depositing device 120a is arranged adjacent to a surface of the chamber 124 opposite to the second passage 122. When an electric signal is applied to the piezoelectric element 126, the piezoelectric ele ment 126 performs a deformation 127 into the chamber 124, thereby pushing the second print fluid F2 inside the chamber 124 towards the second passage 122. As a result, the second print fluid F2 may be discharged from the second depositing device 120a through the second passage 122. The second depositing device 120a maybe referred to as a push-type inkjet ejection device.

[0026] In another example, the second depositing device 120b comprises a channel 128 through which the second print fluid F2 is delivered to the chamber 124. In some examples, the channel 128 maybe considered as a part of the chamber 124. The piezoelectric element 126 is arranged adjacent to the channel 128. When an electric signal is applied to the piezoelectric element 126, the volume of the channel 128 is reduced due to the deformation 127 of the pie zoelectric element 126. As a result, the second print fluid F2 maybe discharged from the second depositing device i2oba through the second passage 122. The second depositing device 120b maybe referred to as a bend-type inkjet ejection device.

[0027] In a further example, the second depositing device 120c comprises two piezoelectric elements 126 arranged on both sides of the chamber 124. When an electric signal is applied to the piezoelectric elements 126, the piezoelectric elements 126 may bend into the chamber 124 and reduce its volume. As a result, the second print fluid F2 may be discharged from the second depositing device 120c through the second passage 122. The second depositing device 120c maybe referred to as a squeeze-type inkjet ejection device. [0028] Yet another example I20d is shown in FIG. 3 in a schematic top view. In the second depositing device i2od, multiple chambers 124 and multiple piezoelectric elements 126 are arranged in an alternating manner. When an electric signal is applied to the piezoelectric ele ments 126, the piezoelectric elements 126 may bend into the respectively adjacent chamber 124 and reduce its volume. As a result, the second print fluid F2 may be discharged from the second depositing device i2od through second passages 122 that may extend in a perpendicular direc tion to the plane of FIG. 3. The second depositing device i2od may be referred to as a shear- type inkjet ejection device.

[0029] The second depositing device 120 of the printing apparatus 100 may be any of the herein described types of the second depositing device 120a to i2od, but is not limited thereto. The printing apparatus 100 may comprise any of the second depositing device 120a - i2od or any combination thereof.

[0030] The second print fluid F2 may comprise a primer, an overcoat, a varnish, a fluores cent agent, a metallic ink, a UV curable agent or a pre-treatment agent, or any combination thereof. Furthermore, the second print fluid F2 may comprise a conductive ink or non-water- based fluids. In addition or alternatively, the second print fluid F2 may comprise any process color or a combination of process colors.

[0031] As shown in an example in FIG. 4, the printing apparatus too may comprise a recir culation device 150 and a reservoir 160 providing the first print fluid Ft to the first depositing device 110. Alternatively or additionally, the reservoir 160 may provide the second print fluid F2 to the second depositing device 120. The recirculation device 150 maybe operable to gen erate and to maintain a circulation circuit of the first print fluid Ft between the reservoir 160 and the first depositing device 110. Additionally or alternatively, the recirculation device 150 may be operable to generate and to maintain a circulation circuit of the second print fluid F2 between the reservoir 160 and the second depositing device 120. Accordingly, the recirculation device 150 may provide a respective circulation circuit of the first print fluid Ft and the second print fluid F2. Further the printing apparatus too may comprise multiple recirculation devices 150 each for a respective one of the first print and second print fluids Ft, F2. In some examples, the circulation circuit may comprise a loop of the respective print fluid Ft, F2.

[0032] The reservoir 160 may be a container storing the first print fluid Ft. Alternatively or additionally, the reservoir 160 may be a container storing the second print fluid F2. Accord ingly, the reservoir 160 may provide either one or both of the first print fluid Ft and the second print fluid F2. Additionally or alternatively, the reservoir 160 may be connected to an external supply that provides the respective print fluid Fi, F2 via a delivery device (not shown). In some examples, the printing apparatus may comprise multiple reservoirs (not shown in the draw ings) each providing a respective one of the first and second print fluids Fi, F2.

[0033] In some examples, the recirculation device 150 may generate and maintain the cir culation circuit of the respective print fluid Fi, F2 during or in between the operation of the respective depositing device 110, 120. For example, the recirculation device 150 maybe opera ble to generate the circulation circuit and stopping the same within a response time and an operation duration of 1 to 10 seconds. Accordingly, the recirculation device 150 may help to prevent settling of components or other mixture issues. In order to generate and maintain the circulation circuit, the recirculation device 150 may be provided with a flow controller (not shown).

[0034] As for example shown in FIG. 4, the recirculation device 150 may be fluidly con nected to the respective depositing device 110, 120 and the reservoir 160. The recirculation device 150 may comprise a first manifold 152 to receive and collect the respective print fluid Ft, F2 from the respective depositing device 110, 120. The first manifold 152 maybe connected at a downstream position of the chamber 124 of the respective depositing device 110, 120 and at an upstream position of the reservoir 160 in terms of the flow of the respective print fluid Ft, F2. Further, the first manifold 152 maybe arranged at or directly upstream of the respective passage 112, 122. The first manifold may 152 may be arranged to receive and collect the respec tive print fluid Ft, F2 from the respective depositing device 110, 120 while the respective de positing device 110, 120 is not depositing the respective print fluid Ft, F2.

[0035] In some examples, the first manifold 152 may be operable to receive and collect the respective print fluid Ft, F2 from multiple depositing devices. For example, the printing appa ratus too may comprise a plurality of first depositing devices 110, a plurality of second depos iting devices 120 or both. In such example, the first manifold 152 may be arranged such to receive and collect the respective print fluid Ft, F2 from the first and second depositing devices 110, 120.

[0036] In some examples, the recirculation device 150 may comprise a second manifold 154 arranged downstream of the reservoir 160 and upstream of the respective depositing device 110, 120 in terms of the flow of the respective print fluid Ft, F2. The second manifold 154 may be used to distribute the respective print fluid Ft, F2 that is received from the reservoir 160 to the respective depositing device 110, 120. [0037] In some examples, the second manifold 154 may be operable to distribute the re spective print fluid Fi, F2 to an additional depositing device in addition to the respective de positing device 110, 120. For example, the printing apparatus 100 may comprise a plurality of first depositing devices 110, a plurality of second depositing devices 120 or both. In such exam ple, the second manifold 154 may be arranged such to direct the first or second print fluid Fi, F2 to some or all of the first and second depositing devices 110, 120.

[0038] In some examples, the printing apparatus 100 may further comprise a flush device 170. The flush device 170 may be operable to discharge the first print fluid Fi or the second print fluid F2 from the circulation circuit, which is maintained by the circulation device 150 between the reservoir 160 and the respective depositing device 110, 120, through the respective passage 112, 122. For example, the discharging and flushing by the flush device 170 may be performed to clean the first depositing device 110, the second depositing device 120 or both before the respective depositing device 110, 120 enters an idle state. For example, the discharg ing and flushing by the flush device 170 may be performed before exchanging the first print fluid Ft or the second print fluid F2 with another print fluid.

[0039] The flush device 170 may be arranged upstream of the respective depositing device 110, 120 in terms of the delivery of the respective print fluid Ft, F2. The flush device 170 may be fluidly connected to the respective depositing device 110, 120 and operable to flush the re spective print fluid Ft, F2 from the respective depositing device 110, 120. For example, the flush device 170 may introduce a flushing fluid, which is different from the first print fluid Ft or the second print fluid F2, into the respective depositing device 120 under pressure to remove the respective print fluid Ft, F2 from the respective depositing device 110, 120. For example, the flush device 170 may be connected with a supply providing the flushing fluid.

[0040] Accordingly, the flush device 170 may be operable to flush and discharge either one or both of the first print fluid Ft and the second print fluid F2 from the respective depositing device 110, 120 through the respective passage 112, 122. For example, the flush device 170 may be fluidly connected to either one or both of the first depositing device 110 and the second depositing device 120, and operable to introduce the flushing fluid into the respective deposit ing device 110, 120.

[0041] In some examples, the printing apparatus too may comprise a recovery tank 172. For example, the recovery tank 172 may be provided as a component of a service device which is described in detail below. In other examples, the recovery tank 172 may be provided sepa rately from such a service device. The recovery tank 172 may be arranged such to receive any of the first print fluid Fi and the second print fluid F2 flushed and discharged by the flush device 170 from the respective depositing device 110, 120 through the respective passage 112, 122. In addition or alternatively, the recovery tank 172 may be moved to a position below an outlet of either or both of the first passage 112 and the second passage 122. The respective de positing device 110, 120 and the recovery tank 172 may be maintained in said positions during the flushing operation to collect the discharged print fluid Fi, F2 along with the flushing fluid. The recovery tank 172 may be contain or redirect the collected discharged fluid for recycling or for waste disposal.

[0042] In some examples, the recovery tank 172 is provided as a separate component from a service device. In such examples, the second depositing device 120 maybe movable by means of a carriage 130a between an engaging position with the service device and an engaging posi tion with the recovery tank 172. For example, the service device and the recovery tank 172 may be arranged on opposite sides of a printing zone over which the carriage 130a crosses during operation. The position of the recovery tank 172 may be referred to as a flushing station or as a left carriage overtravel, in which the carriage 130a may decelerate coming from above the printing zone and reaccelerate towards the printing zone.

[0043] In some examples, the recovery tank 172 may comprise a funnel, a capping unit or a combination thereof to direct the flushed and discharged fluid from the second depositing de vice 120 into the recovery tank 172 through gravity. In such examples, the recovery tank 172 may be further assisted by a suction pump to collect the discharged fluid from either one or both of the first depositing device 110 and the second depositing device 120. In some examples, the printing apparatus too may comprise multiple recovery tanks (not shown in the drawings) each provided to collect a respective one of the first and second print fluids Ft, F2.

[0044] The recovery tank 172 may provide a spittoon or a capping unit for any of the first depositing device 110 and the second depositing device 120. In some examples, the recovery tank 172 may be provided to collect both the first print fluid Ft and the second print fluid F2, and the spittoon or the capping unit may serve colleting waste print fluid from both of the depositing devices 110, 120. In some examples, the recovery tank 172 may collect the flushed fluid from the second depositing device 120 while providing spitting or capping services to the first depositing device 110, or vice versa. In such examples, a driver for a decision between the spittoon or the capping unit may be an total flush operation time of the flush device 170.

[0045] The use of the recirculation device 150 may help increasing an image quality of a printing product by preventing occurrences of a deterioration. The operation of the flush device 170 may help to clean any of the first depositing device 110 and the second depositing device 120 from remainders of the respective print fluid Fi, F2.

[0046] Furthermore, any of the recirculation device 150, the flush device 170 and the recov ery tank may be used for both the first print fluid Fi from the first depositing device 110 and the second print fluid F2 from the second depositing device 120, thereby reducing a space oc cupancy, material and energy costs of the printing apparatus.

[0047] FIG. 5 is a schematic perspective diagram of a further example of the printing appa ratus 100. In the example of FIG. 5, the printing apparatus 100 may comprise a carriage 130a on which the first depositing device 110 and second depositing device 120 are mounted. In some examples, the carriage 130a may be provided with electronic devices, including the image processor 140 as described above, to control the first and second depositing devices 110, 120. In further examples, the printing apparatus 100 may in addition comprise a print bar as shown in FIG. 9 or 10, wherein each of the print bar and the carriage may support some of the first and second depositing devices 110, 120.

[0048] The printing apparatus 100 may further comprise a cover frame 102, a rail 104 and a compartment 106. The cover frame 102 may be part of a housing covering and thereby pro tecting the mechanical and electric parts of the printing of the printing apparatus 100. The cover frame 102 has an opening having a substantially conformal shape to a sidewise projection (e.g. along direction M in FIG. 5) of the carriage 130a to allow the carriage 130a to pass through.

[0049] The side cover frame 102 as shown in FIG. 5 may substantially correspond to a boundary between a service position (or service station) above the compartment 106 as de scribed below and a printing zone of the printing apparatus too. In the printing zone, any of the print fluids Ft and F2 may be deposited on the print medium P while the carriage 103 moves over and across the print medium P.

[0050] The carriage 130a may be mounted on the rail 104 such that the carriage 130a is movable along the rail 104 as indicated by arrow M in FIG. 5. In some examples, the printing apparatus too is operable to convey the print medium P in a direction perpendicular to the moving direction M of the carriage 130a. In other words, the rail 104 may be arranged perpen dicular to the conveying direction of the print medium P by the printing apparatus too.

[0051] In FIG. 5, the first depositing device 110 and the second depositing device 120 are arranged on a bottom side of the carriage 130a in the orientation of FIG. 5, as indicated by dashed lines. The depositing devices 110, 120 may be arranged such that the first passage 112 and the second passage 122 open downwards in the orientation of FIG. 5 to deposit the respec tive print fluid Fi, F2 on the print medium P that is conveyed below the carriage 130a.

[0052] FIG. 6 shows an arrangement of the first and second depositing devices 110, 120 in the carriage 130a according to an example. In the example of FIG. 6, the printing apparatus 100 comprises six first depositing devices 110 and four second depositing devices 120 arranged in parallel and in a staggered manner. The numbers are examples and maybe varied arbitrarily according to the individual specifications of the printing apparatus 100.

[0053] Each of the first depositing devices 110 may be operable to deposit a respective first print fluid by applying heat to cause a thermal expansion of the respective first print fluid through a respective passage. The first print fluids of the depositing devices 110 may include process colors, a pre-treatment fluid and an overcoat fluid. The first depositing devices 110 may comprise a thermal inkjet ejection device. In some examples, the first depositing devices 110 may be thermal inkjet ejection devices.

[0054] Each of the second depositing devices 120 may be operable to deposit a respective second print fluid on the print medium by applying a mechanical vibration to move the respec tive second print fluid through a respective passage. The second print fluids of the second de positing devices 120 maybe selected from: a primer, an overcoat, a varnish, a fluorescent agent, a metallic ink, a UV curable agent and a pre-treatment agent. Furthermore, the second print fluids may comprise a conductive ink or non-water-based fluids. The second depositing devices 120 may comprise a piezoelectric inkjet ejection device. In some examples, the second depos iting devices 120 maybe piezoelectric inkjet ejection devices.

[0055] Accordingly, the carriage 130a may carry a combination of thermal inkjet ejection devices and piezoelectric inkjet ejection devices. The print fluids that are used with the depos iting devices 110, 120 as well as the total number of the print fluids may be configured accord ing to the specification of the printing apparatus too and the specifications of the individual printing job. In addition, parameters of the deposition, such as a width and length of a swath, by the first and second depositing device maybe individually configurable.

[0056] FIG. 7 schematically shows a cross-sectional side view of the carriage 130a. The first depositing devices 110 and the second depositing devices 120 are arranged such to overlap one another in the side view of FIG. 7. In some examples, any of the first depositing devices 110 and the second depositing devices 120 may be provided as cartridges. The cartridges of the first depositing devices 110 and the second depositing devices 120 may have similar physical di- mensions such to occupy similar volumes. Here, the term similar may indicate a relative dif ference of less than 10%, less than 5% or less than 2% relative to the dimensions or the volume of one of the first and second depositing devices 110, 120. For example, the first depositing devices 110 and the second depositing devices 120 may be provided as removable cartridges. In such examples, the cartridges of the first depositing devices 110 and the second depositing devices 120 may have similar, compatible, or substantially identical form factors in terms of the spatial dimensions, as illustrated in FIG. 7. The form factors may refer to a specific set of normed dimensions of the cartridges. In such examples, the first and second depositing devices 110, 120 may have similar sizes, thereby facilitating the designing and construction of the com bination of the depositing devices.

[0057] In a specific example, the printing apparatus 100 may have a staggered array of ther mal inkjet ejection devices as first depositing devices 110, as for example shown in FIG. 6. In further examples, the thermal inkjet ejection devices (first depositing devices 110) maybe ar ranged in a row or in a column (not shown). In addition, the printing apparatus too may com prise a staggered array of piezoelectric ejection devices as second depositing devices 120, see for example FIG. 6. In further examples, some of the piezoelectric inkjet ejection devices (sec ond depositing devices 120) may be arranged in a row or in a column (not shown).

[0058] Referring back to FIG. 5, the compartment 106 may house a service device 180. The service device may provide different services to the depositing devices 110 and 120 at the same time. The carriage 130a may be movable over the service device 180 as shown in FIG. 5 before and after moving into and from the printing zone.

[0059] In some examples, the service device 180 may comprise an absorber device, a spit ting tray, a wiping device, a pressure dimple, a capping member, a print fluid collector or a wetting device, or any combination thereof. Some examples of the components of the service device 180 include a web wipe, a rubber wiper, active wetting device of wipers and a ejection device primer. The first depositing devices 110 and the second depositing devices 120 may be movable over the service device 180 to interact with any of the components of the service device 180. The service device 180 may further feature a drop detection system operable with both the first depositing devices 110 and the second depositing devices 120.

[0060] The components of the service device 180 may assist the depositing devices 110, 120 to dispose of dried out print fluid residues and also to moisturize openings of the passages 112, 122 by discharging excess print fluid Ft, F2 through the respective passage 112, 122. The com ponents may be used to remove and collect the excessive print fluid and the removed dried out print fluid residues, thereby preventing a deterioration of the printing quality.

[0061] As shown in FIG. 5, the service device 180 may comprise two separate service as semblies 182, 184 respectively for the two different types of depositing devices 110 and 120. The carriage 130a carrying the first depositing devices 110 and the second depositing devices 120 may be movable over the service device 180 such that the first depositing devices 110 may interact with the first service assembly 182 and the second depositing devise 120 may interact with the second service assembly 184.

[0062] The service assemblies 182, 184 may be configured accordingly to the respective print fluids Fi, F2 and the individual specifications of the depositing devices 110 and 120. Any of the service assemblies 182, 184 may be provided as a cassette that is exchangeable, thereby facilitating a reconfiguration of the second depositing devices 120, e.g. for use with a new sec ond print fluid F2.

[0063] FIG. 8 shows a schematic diagram of an example of the service device 180 compris ing a first service assembly 182 for the first depositing devices 110 and a second service assem bly 184 for the second depositing devices 120. In some examples, the first and second service assemblies 182, 184 may each comprise an absorber device 186a, 186b, a spitting tray 188a, 188b, a wiping device 190a, 190b, a pressure dimple 192a, 192b, a capping member 194a, 194b, a print fluid collector 196a, 196b or a wetting device 198a, 198b, or any combination thereof. The components 186-198 may differ for the first and second depositing devices 110, 120. The first service assembly 182 may have a set of components different from the second service as sembly 184. In further examples, some or all of the components 186a - 198a may be used for both the first depositing device 110 and the second depositing device 120. In the herein de scribed examples, any of the components i86a-i98a and i86b-i98b may be omitted, combined with another component, or present in multiple numbers.

[0064] FIG. 9 shows an example in which the printing apparatus 100 comprises a print bar 130b instead of or in addition to the carriage 130a as shown in FIG 5 to 7. The print bar 130b may be arranged such to extend over and across a width W of the print medium P in the print ing zone. In the example of FIG. 9, an array of first depositing devices 110 and an array of second depositing devices 120 are mounted on the print bar 130b. The area below the print bar, i.e. underneath the nozzles of the depositing devices 110, 120 arranged in the print bar 130b, may establish a printing zone of the printing apparatus 100. The print medium P maybe transported through the printing zone of the printing apparatus 100 in a direction perpendic ular to the width W. The print fluids may be deposited from the first and second depositing devices no, 120 while the print medium P is moved below the print bar 130b.

[0065] In further examples, the printing apparatus 100 may comprise multiple print bars. FIG. 10 shows the printing apparatus 100 according to such example comprising a first print bar 130c and a second print bar i3od. An array of first depositing devices no maybe mounted on the first print bar 130c. An array of second depositing devices 120 may be mounted on the second print bar i3od. The print bars 130c, i3od may be arranged adjacent to each other or separate from each other along a transport direction of the print medium P. In further exam ples not shown in the drawings, the printing apparatus may comprise additional print bars each supporting an array of first depositing devices 110 or an array of second depositing devices 120. In some examples, the printing apparatus 100 may in addition comprise a carriage, for example the above described carriage 130a, on which any of the first and second depositing devices 110, 120 maybe mounted.

[0066] FIG. 11 shows a flow diagram of a method 200 according to an example. The method 200 may be carried out to operate or use the printing apparatus 100 described above. The method 200 may be carried out to deposit a first print fluid and a second print fluid on a re spective print medium or on a same print medium using a single printing apparatus. The print medium or print media according to the method 200 may correspond to the print medium P as described above.

[0067] According to the method 200, at 202, a first print fluid is deposited by a printing apparatus, for example by the above described printing apparatus 100, on a print medium P by applying heat to cause a thermal expansion of the first print fluid Fi through a first passage 112. The first print fluid Fi according to the method 200 may correspond to the first print fluid Ft as described above with respect to the printing apparatus too. The application of the heat and the first passage 112 according to the method 200 may correspond to the operation of the first depositing device 110 and the first passage 112, respectively, as described above with re spect to the printing apparatus too.

[0068] At 204, a second print fluid F2 is deposited by the printing apparatus, which may be the printing apparatus too as described above, on a different print medium or the same print medium P by applying a mechanical vibration to move the second print fluid F2 through a second passage 122. The second fluid F2 according to the method 200 may correspond to the second print fluid F2 as described above with respect to the printing apparatus too. The appli cation of the mechanical vibration and the second passage 122 according to the method 200 may correspond to the operation of the second depositing device 120 and the first passage 122, respectively, as described above with respect to the printing apparatus 100.

[0069] Further in the method 200, the first print fluid may comprise a process color. The second print fluid may be selected from a primer, an overcoat, a varnish, a fluorescent agent, a metallic ink, a UV curable agent and a pre-treatment agent.

[0070] The operations 202, 204 of the method according to the example may be performed in an arbitrary order or simultaneously. Further, any one or both of the operations 202, 204 maybe repeated according to specifications of a particular print job and the printing apparatus. Moreover, instances of the deposition of the first print fluid Fi using a thermal inkjet ejection device and deposition of the second print fluid F2 using a piezoelectric inkjet ejection device maybe combined in terms of order and the composition of the used print fluids Fi, F2.

[0071] In a specific example of the method 200 and of the printing apparatus 100, a pre treatment agent may be deposited on a print medium P by applying mechanical vibration to move the pre-treatment agent, which maybe one second print fluid F2, through a second pas sage 122. The deposition of the pre-treatment agent may be performed by using one example of the second depositing device 120 as described above, for example by a piezo inkjet ejection device. After depositing the pre-treatment agent on the print medium P, a process color, which may be one first print fluid Fi, may be deposited on the print medium P by applying heat to cause thermal expansion of the process color through a first passage 112. The deposition of the process color may be performed by one example of the first depositing device 110 as described above, for example by a thermal inkjet ejection device. Next, an overcoat maybe deposited on the print medium P by applying mechanical vibration to move the overcoat through a second passage 122, which maybe the same second passage 122 for depositing the pre-treatment agent or different therefrom. The deposition of the overcoat may be performed by one example of the second depositing device 120 as described above, for example by a piezoelectric inkjet ejection device. According to this example, a single printing apparatus loomay allow for depositing the pre-treatment agent, process color and overcoat on the same print medium P. Accordingly, a print product may be obtained that has the image quality of thermal inkjet ejection devices and is pre-treated and overcoated using piezoelectric inkjet ejection devices.

[0072] The above described printing apparatus too and the method 200 allow for using a thermal depositing device, i.e. thermal inkjet ejection device, in combination with a piezoelec tric depositing device, i.e. piezo inkjet ejection device, in a single printing device or single print ing system. The thermal inkjet ejection device may provide for implementing a high density of nozzles and thus perform an increased image quality and throughput. Also, the thermal inkjet ejection device maybe simple and cheap in terms of maintenance. On the other hand, the piezo inkjet ejection device may exhibit an increased durability, may allow for adjust a drop weight of the deposited print fluid and may be usable with a wide range of different print fluids in cluding specific deposition materials apart from colorants, pigments or dyes. Accordingly, the printing apparatus 100 and the versatility of the method 200 as disclosed herein combine the characteristics from both of the thermal inkjet ejection devices and piezo inkjet ejection de vices.

[0073] Accordingly, the piezo inkjet ejection device may allow for depositing a relatively large drop weight at an increased deposition frequency. A combination of the thermal and pi ezo inkjet ejection devices may have a synergistic effect on increasing the productivity of the printing apparatus when a large amount of print fluid is to be deposited for a given printing job, which may include a pre-treatment or post-treatment.

[0074] Moreover, the detailed examples described above provide means to overcome tech nical challenges occurring when combining a thermal depositing device and a piezoelectric de positing device in a single apparatus or single system. The present disclosure therefore facili tates the implementation and the use of a combination of thermal and piezoelectric depositing devices.

Claims

1. A printing apparatus, comprising: a first depositing device to deposit a first print fluid on a print medium by applying heat to the first print fluid to cause the first print fluid to thermally expand through a first passage towards the print medium; and a second depositing device to deposit a second print fluid on the print medium by applying a mechanical vibration to move the second print fluid through a second passage towards the print medium.

2. The printing apparatus of claim l, wherein the first depositing device and the second depositing device are provided as removable cartridges having similar physical dimensions to occupy similar volumes.

3. The printing apparatus of claim l, further comprising: a carriage to move over and across the print medium, wherein the first depositing device and the second depositing device are mounted on the carriage.

4. The printing apparatus of claim l, further comprising: a print bar arranged extending over and across the print medium, wherein the first depositing device and the second depositing device are mounted on the print bar.

5. The printing apparatus of claim l, further comprising: a piezoelectric element to generate a pressure gradient across the second passage of the second depositing device to control a deposition process of the second print fluid.

6. The printing apparatus of claim l, further comprising: a reservoir to provide one or both of the first print fluid and the second print fluid to the second depositing device; and a recirculation device to generate and to maintain a circulation circuit between the reservoir and the second depositing device.

7. The printing apparatus of claim 6, further comprising: a flush device to flush one or both of the first print fluid and the second print fluid from the respective depositing device and to discharge from the circulation circuit between the reservoir and the respective depositing device through the respective passage.

8. The printing apparatus of claim l, further comprising: a service device comprising an absorber device, a spitting tray, a wiping device, a pressure dimple, a capping member, a print fluid collector or a wetting device, or any combination thereof, wherein the first depositing device and the second depositing device are movable over the service device to interact with the service device.

9. The printing apparatus of claim l, wherein the first print fluid comprises a process color, wherein the second print fluid comprises a primer, an overcoat, a varnish, a fluorescent agent, a metallic ink, a UV curable agent or a pre-treatment agent, or a combination thereof.

10. The printing apparatus of claim l, further comprising: an image processor to control the first depositing device and the second depositing device in separate color spaces.

11. The printing apparatus of claim l, wherein the first depositing device comprises a memory device to store information about calibration, information about an operational event, information about malfunction of the first depositing device and the second depositing device, or a combination thereof.

12. A printing apparatus, comprising first depositing devices each to deposit a respective first print fluid on a print medium by applying heat to cause a thermal expansion of the respective first print fluid through a respective passage; and second depositing devices each to deposit a respective second print fluid on the print medium by applying a mechanical vibration to move the respective second print fluid through a respective passage, wherein first print fluids of the first depositing devices comprise process colors, wherein second print fluids of the second depositing devices are selected from: a primer, an overcoat, a varnish, a fluorescent agent, a metallic ink, a UV curable agent and a pre-treatment agent.

13. The printing apparatus of claim 12, wherein the first depositing devices comprises a thermal inkjet ejection device, wherein the second depositing devices comprises a piezoelectric inkjet ejection device.

14. A method of printing on a print medium, comprising: by a printing apparatus, depositing a first print fluid on a print medium by applying heat to cause thermal expansion of the first print fluid through a first passage; and by the printing apparatus, depositing a second print fluid on the print medium or on another print medium by applying mechanical vibration to move the second print fluid through a second passage, wherein the first print fluid comprises a process color, wherein the second print fluid is selected from: a primer, an overcoat, a varnish, a fluorescent agent, a metallic ink, a UV curable agent and a pre-treatment agent.

15. The method of claim 14, comprising, in the following order: by the printing apparatus, depositing a pre-treatment agent on a print medium by applying mechanical vibration to move the pre-treatment agent through one second passage; by the printing apparatus, depositing a process color on the print medium by applying heat to cause thermal expansion of the process color through the first passage; and by the printing apparatus, depositing an overcoat on the print medium by applying mechanical vibration to move the overcoat through one other second passage.