WO2014005608A1

WO2014005608A1 - Inkjet printer

Info

Publication number: WO2014005608A1
Application number: PCT/EP2012/002864
Authority: WO
Inventors: Raimon Castells De Monet; Jesus Garcia Maza; David Claramunt Morera
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2012-07-06
Filing date: 2012-07-06
Publication date: 2014-01-09

Abstract

A printer (300) and a method of printing on a printing media by an inkjet printer. The inkjet printer has at least one print-head (210) for printing on the printing media (112), a media transport mechanism (124, 132) arranged to advance the printing media in a media-advancing direction, a printing carriage (200) arranged to be driven in a swath direction across the printing media and provided with at least one print-head-holding pocket for the at least one print-head for holding and referencing the print-head. To compensate for a media-advance error which corresponds to a deviation of the measured media movement from a nominal media movement for a desired printing result, the movement of the printing media in a media-advancing direction is measured and a media-advance-error signal representing the media-advance error is calculated, and the print-head is displaced relatively to the print-head carriage by means of a print-head-displacement device (230) arranged between the print-head and the print-head-holding pocket in a direction parallel to the media-advancing direction in response to the media-advance-error signal.

Description

INKJET PRINTER

BRIEF DESCRIPTION OF THE DRAWINGS

Examples will be described, by way of example only, with reference to the accompanying drawings in which corresponding reference numerals indicate corresponding parts and in which:

Figure la is a schematic illustration of a side view of an inkjet printer, which may be a wide- format printer, according to one example;

Figure lb is a schematic illustration of a side view of an inkjet printer according to another example;

Figure lc is a schematic diagram of a controller which is part of the printer according to one or more examples;

Figures 2a and 2b are enlarged schematic illustrations of examples of a printing carriage which can be part of the printer shown in Figure la or lb according to examples;

Figure 3 is a perspective view of a printing carriage of the printer according to one example;

Figure 4 is an enlarged perspective view of a part of the printing carriage shown in Figure 3, wherein some parts or elements shown in Figure 3 are omitted for the purpose of explanation;

Figures 5a and 5b are schematic illustrations which show a principle of correcting two types of media-advance errors in accordance with examples, wherein a part of a printing media and a printing carriage are schematically shown in top view.

The drawings and the description of the drawings refer to examples of the invention and not to the invention itself. DETAILED DESCRIPTION OF EMBODIMENTS

Figures la and lb are schematic illustrations of an inkjet printer which for example is a wide- format printer. The printer 300 includes a printing carriage 200 which is arranged for moving in a reciprocating type of movement across a substrate or printing media 1 12. The direction of this reciprocating movement across the printing media 112 usually is called the main scanning direction or swath direction, the movement is often simply called swathing, and it is in a direction perpendicular to the drawing plane of Figure la, as indicated by the double-ended arrow. The printing carriage 200 includes at least one print-head 210 for printing on the substrate or printing media 112. UV radiation sources for ink curing or ink drying sources may be attached to or near the printing carriage 200 and may move in the same reciprocating movement as the printing carriage 200 or may have separate drives or may also be stationary.

A feed-path for the flexible substrate 112 includes a substrate supply-roll 116, a substrate drive-roll 124 and, associated with the substrate drive-roll 124, a first or drive-roll pressure- roll 128. Spaced apart from the drive-roll 124 a substrate tension-providing-roll 132 is arranged and, associated with the substrate tension-providing-roll 132, a second pressure-roll 136. The drive-roll 124, the first pressure-roll 128, the tension-providing-roll 132 and the second pressure-roll 136 span, in the printing media or substrate advance direction, at least a part of the substrate 112 on which printing is performed.

Also shown in Figures la and lb, there is a support surface 150 for the flexible substrate 112. This support surface 150 usually is a flat surface, although it may also be a curved surface, or a surface which is assembled from separate segments, over which printing takes place and which includes a printing area wherein printing is performed by the print-head 108 on the substrate or printing media 112.

The printing media 112, after having been printed, may be collected on a collection-roll 154, or it may directly be ejected and fall freely, e.g. in an output tray, or the like.

The printer 300 further includes a control unit 158 which is arranged for controlling the operation the printer 300, including the rotation speed of all the rolls, operation of UV- radiation sources or drying-heat-emitting sources, synchronization of all units, and the printing process itself, i.e. receiving, processing and generating image-representing data and forwarding them to the print-heads 210, and controlling the movement of the printing carriage 200. An example of the control unit 158 and its main components is shown in Figure lc.

Figure lc is a diagrammatic representation of a computer system as it may be arranged to provide the functionality of the controller 158 in Fig. la or in Fig. lb. The computer system is configured to execute a set of instructions so that the controller 158 is able to perform the described tasks for the printer. The computer system includes a processor 101 and a main memory 102, which communicate with each other via a bus 104. Optionally, the computer system may further include a static memory 105 and/or a non-transitory memory 106 which may be a solid-state memory or a disk-drive unit. A video display 107, an alpha-numeric input device 108 and a cursor-control device 109 may form a user interface. Additionally, a network-interface device 103 may be provided to connect the computer system to an Intranet or to the Internet. A set of instructions (i.e. software) 1 10 embodying any one, or all, of the controller tasks, may reside completely, or at least partially, in or on a machine-readable medium, e.g. the main memory 102 and/or the processor 10.1. A machine-readable medium on which the software 110 resides may also be a data carrier 111 (e.g. a solid-state data drive, a non-removable magnetic hard disk or an optical or magnetic removable disk) which is part of the data drive unit 106. The software 110 may also be transmitted or received as a propagated signal via the Intranet or the Internet through the network interface device 103, e.g. for updating the software or for other purposes.

Referring back to Figures la and lb, the printing media 112, as a web, is threaded through the substrate feed-path from the substrate supply-roll 116, on which the printing media or substrate 112 is stored, through the first pressure-roll 128 and the substrate drive-roll 124 and over the support surface 150 where the printing takes place in the printing area. Typically, in operation, the substrate drive-roll 124 is caused to rotate at a first speed, and the tension- providing-roll 132 is caused to rotate at a second, different speed which is higher than the first rotation speed, and the difference in the rotation speed of the two rolls 124, 132 generates a constant tension (back tension) as a force which keeps the printing media 112 flat in the printing area on the support surface 150. The web of printing media 1 12 is pulled over the support surface 150 past the tension-providing-roll 132 and the second pressure-roll 136, as shown by the arrow in Figure la, towards the substrate collection-roll 154. In the course of printing, at each pass or swath of the printing carriage 200 which includes the one or more print-heads 210, the printing media 112 is advanced in a step- wise manner wherein the step nominally is equal to the width of each pass or swath of the at least one print- head 210. The surface 150 supports the tensioned web of printing media 112 in the printing area. The width of a pass or swath of the at least one print-head 210 in the printing carriage 200 is nominally equal to the print-head assembly width and has constant value. When the value of the printing media 112 advance does not match the print-head assembly width, artifacts are formed in the printed image.

Figures 5a and 5b show such artifacts. The printing media advance direction is indicated by a block arrow, and the scanning or swathing direction of the printing carriage 200 is perpendicular to that. Figure 5a shows a case where the printing media 112 advance does not match the printing carriage 200 swath in that the advance is larger than the swath width, i.e. an over-advance error has occurred in the form of a gap between two subsequent printed swaths. By contrast, as shown in Figure 5b, if the printing media 112 advance does not match the printing carriage 200 swath in that the advance is smaller than the swath width, an under- advance error occurs in the form of overlapping printed swaths.

Figures la and lb, respectively, show two examples of a media-advancing measurement system which are arranged for measuring the movement of the printing media in the media- advancing direction, and for calculating and outputting a media-advance-error signal representing a media-advance error which corresponds to the deviation of the measured media movement from the nominal media movement as required for a desired printing result. The media-advance-error signal indicates whether there is a correct matching of the stroke width and the media advance or whether there is an over-advance error, as shown in Figure 5 a, or an under-advance error, as shown in Figure 5b, and it indicates the magnitude und the direction of such an error.

In the example shown in Figure la, associated with the substrate drive-roll 124 and the substrate tension-providing-roll 132, encoders 304 and 308 are arranged for measurement of the media advance in the media-advance path. These encoders 304 and 308 may be coupled to the rolls 124 and 132, respectively, or the encoders 304' and 308' may be provided separately from the rolls 124 and 132, as shown by dashed circles. Instead of two encoders 304 and 308; 304' and 308' of which the encoder 304; 304' is arranged upstream of the printing area 150, and the encoder 308; 308' is provided downstream of the same, there also only one encoder 304; 304' or 308; 308' may be provided, either upstream or downstream of the printing area 150. The measurement of the at least one encoder 304; 304' and/or 308; 308' is output to the control unit 158 as a signal representing the movement of the printing media 1 12 in the media-advancing direction, and by comparing it to the nominal value of the media advance per one printing carriage swath for calculating the media-advance-error signal.

In accordance with another example which is shown in Figure lb, instead of encoders for measuring the media advance, an optical media-advance sensor 404 is provided in the region of the printing area 150. The optical media-advance sensor 404 outputs a measurement indicating the printing media 112 advance to the control unit 158 where the media-advance- error signal is calculated by comparing the measured media advance with the nominal media advance. All other parts of components of the printer 300 shown in Figure lb correspond to the respective ones of the printer shown in Figure la.

As shown in Figures la and lb, at least one print-head displacement device 230 is provided for displacing the print-head 210 relatively to the printing carriage 200 in a direction parallel to the media-advancing direction in response to the media-advance-error signal which is calculated and output by the control unit 158 forming a part of the media-advancing measurement system. The print-head-displacement device 230 is arranged to compensate for the media-advance error in response to the media-advance-error signal.

Figures 2a and 2b show examples of the print-head-displacement device 230. In these examples, the print-head-displacement device is arranged between the print-head 210 and a pocket 220 which holds and references the print-head 210 within the printing carriage 200.

The print-head-displacement device 230 includes an actuator 232 which is arranged, in the shown example, in a fixed position with reference to the print-head-holding pocket 220, and a displacing element 234 which engages the print-head 210 in order to displace it relatively to the print-head-holding pocket 220 in the direction parallel to the media-advancing direction, as indicated by the double-ended arrows. In the example shown in Figure 2a, the print-head-displacing device 230 is arranged and coupled to the print-head 210 so as to displace the same back and forth parallel to the media- advancing direction.

In the example shown in Figure 2b, the print-head 210 abuts on a resilient element 238 arranged at an end of the print-head 210 opposite to the print-head-displacing device 230, and the print-head displacing device 230 is arranged to displace the print-head 210 in one direction parallel to the media-advancing direction against the resilient element 238 in response to the media advance error signal, and the resilient element 238 is able to push back the print-head 230 in the opposite direction.

According to one example, the actuator 232 of the print-head-displacement device 230 is a piezoelectric actuator.

Figures 3 and 4 show an example in a perspective view wherein a printing carriage 200 includes a plurality of print-heads 210 (one of them indicated in isolated manner in Fig. 4) each of which is held and referenced by a print-head-holding pocket 220. The print-head- holding pocket 220 includes a holding-pocket base 222 which is attached to a bottom part 205 of the printing carriage 200 and which has an opening 223 through which an ink-ejecting region 215 of the print-head 210 faces the printing media 112. Connecting elements 260 are provided for electrical connection of the print-heads 210 to the printer control system. In the example shown in Figure 3, the printing carriage 200 has attached first and second mounting and connecting elements 240, 250 for connecting and coupling the printing carriage 200 to an appropriate guiding and driving mechanism which is arranged for guiding and driving the printing carriage 200 in a main scanning direction accross the printing media 112 and which is known in the art per se. The advance direction of the printing media 112 which is, in the perspective views of Figures 3 and 4, to be imagined as located under the printing carriage 200, is as shown by the block arrow in Figure 3. The advance direction of the printing media 112 also is called a subscanning direction.

As shown in Figure 4, the displacing element 234 of the displacing device 230 extends into the holding-pocket-base opening 223 to engage the print-head 210 near the ink ejecting region 215. Each of the print-head-holding pockets 220 is associated with a respective print-head- displacement device, as examplified in Figures 1 and 2, only one displacement element 234 of these print-head-displacement devices being shown for the print-head-holding pocket base 222 of Figure 4. Each of the print-head-holding pockets 220 has a print-head-holding latch 224 for holding down the print-head 210 onto the print-head-holding pocket base 222.

As explained above with reference to the Figures la, lb and lc, the controller 158 which forms a part of the media-advancing measurement system calculates and outputs the media- advance-error signal representing a deviation of the measured media movement in the media- advance direction from a nominal media movement for a desired printing result. In general, the controller 158 provides a corresponding drive signal to the print-head-displacement device 230 of each associated print-head 210.

According to one example, the controller 158 is configured to provide an individual print- head-displacing signal to each print-head-displacement device 230. This individual print- head-displacement signal represents the displacement to be carried out by the respective print- head 210. This may include first and second portions or contributions, of which a first portion corresponds to an individual referencing measure for the individual print-head 210, i.e. an amount of generally fixed displacement from a basic position, to reference the respective print-head 210 with regard to the other print-heads, and the second portion corresponds to the displacement to compensate for the media advance error, which typically is common to all print-heads 210 in the printing carriage.

Now, some more general points of examples as described herein will be discussed:

As described, inkjet printing on a printing media is performed by an inkjet printer comprising at least one print-head for printing on the printing media, a media-transport mechanism for advancing the printing media in a media-advancing direction, and a printing carriage which is arranged to be driven in a swath direction across the printing media and which is provided with at least one print-head-holding pocket for the at least one print-head for holding and referencing the print-head. A media-advancing measurement system measures the movement of the printing media in the media-advancing direction and calculates and outputs a media- advance-error signal. The media-advance-error signal represents the media-advance error which corresponds to a deviation of the measured media movement from a nominal media movement for a desired printing result. At least one print-head-displacement device displaces the print-head relatively to the print-head carriage in a direction parallel to the media- advancing direction in response to the media-advance-error signal in order to compensate for the media-advance error. The displacing of the print-head is performed by a print-head- displacement device which is arranged between the print-head and the print-head-holding pocket.

According to one example, the print-head-displacement device which is arranged between the print-head and the print-head-holding pocket is a piezoelectric device.

The print-head-displacement device may include an actuator which is arranged fixed with reference to the print-head-holding pocket and a displacing element engaging the print-head in order to displace the same relatively to the print-head-holding pocket in the direction parallel to the media-advancing direction.

According to one example, the print-head-displacing device is arranged and coupled to the print-head for displacing the same back and forth parallel to the media-advancing direction in response to the media-advance-error signal.

Alternatively, the print-head may abut on a resilient element, and a print-head-displacing device is arranged to displace the print-head in one direction parallel to the media-advancing direction against the resilient element in response to the media-advance-error signal, and the resilient element pushes back the print-head in the opposite direction.

According to one example the actuator is a piezoelectric actuator.

According to one example the print-head-holding pocket includes a holding-pocket base which is attached to a bottom part of the printing carriage, and has an opening through which an ink-ejecting region of the print-head faces the printing media, wherein the displacing element of the displacement device extends into the holding-pocket base opening for engaging the print-head near the ink-ejecting region.

According to another example the print-head abuts on a resilient element, and the print-head- displacing device is arranged to displace the print-head in one direction parallel to the media- advancing direction against the resilient element in response to the media-advance-error signal, and the resilient element pushes back the print-head in the opposite direction. The resilient element may be arranged opposite the displacing element with regard to the ink- ejecting region.

The printer may comprise two or more print-heads for printing on the printing media, and the printing carriage is provided with two or more print-head holding pockets for the two or more print-heads, and each print-head-holding pocket may be associated with a respective print- head-displacement device.

According to one example the printer comprises a controller arranged to control operation of the printer, wherein the controller is configured to provide an individual print-head-displacing signal to each print-head-displacement device, which individual print-head-displacement signal represents a print-head-displacement which includes first and second portions of which the first portion corresponds to an individual referencing measure for the individual print- head, and the second portion corresponds to a print-head-displacement to compensate for the media-advance error common to all print-heads.

We also describe a method of printing on a printing media by means of an inkjet printer comprising at least one print-head for printing on the printing media, a media transport mechanism for advancing the printing media in a media-advancing direction, a printing carriage which is arranged to be driven in a swath direction across the printing media and which is provided with at least one print-head-holding pocket for the at least one print-head for holding and referencing the print-head. The method includes measuring the movement of the printing media in a media-advancing direction and calculating a media-advance-error signal representing a media-advance error which corresponds to a deviation of the measured media movement form a nominal media movement for a desired printing result, displacing the print-head relatively to the print-head carriage by means of a print-head-displacement device which is arranged between the print-head and the print-head-holding pocket in a direction parallel to the media-advancing direction in response to the media-advance-error signal in order to compensate for the media-advance error.

According to one example the method comprises that the print-head is displaced relatively to the print-head carriage by means of a piezoelectric device which is arranged between the print-head and the print-head-holding pocket. According to another example the method is carried out with a printer comprising two or more print-heads for printing on the printing media, and the printing carriage being provided with two or more print-head-holding pockets for the print-heads, and each print-head-holding pocket is associated with a respective print-head-displacement device, wherein an individual print-head-displacing signal is provided to each print-head-displacement device.

According to one example of the method the individual print-head-displacement signal represents a print-head displacement which includes first and second portions, of which the first portion corresponds to an individual referencing measure for the individual print-head, and the second portion corresponds to a print-head displacement to compensate for the media- advance error common to all print-heads.

Although certain products and measures constructed in accordance with the teachings of the invention have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all embodiments of the teachings of the invention fairly following within the scope of the attended claims either literally or under the doctrine of equivalents.

Claims

1. An inkjet printer comprising

- at least one print-head arranged to print on a printing media,

- a media-transport mechanism arranged to advance the printing media in a media- advancing direction,

- a printing carriage arranged to be driven in a swath direction across the printing media and provided with at least one print-head-holding pocket holding and referencing the print-head, and

- a media-advancing measurement system arranged to measure movement of the media in the media-advancing direction and to calculate and output a media-advance- error signal representing a media-advance error which corresponds to a deviation of the measured media movement from a nominal media movement for a desired printing result,

- at least one print-head-displacement device arranged to displace the print-head relatively to the print-head carriage in a direction parallel to the media-advancing direction in response to the media-advance-error signal in order to compensate for the media-advance error,

- wherein the print-head-displacement device is arranged between the print-head and the print-head-holding pocket.

2. The inkjet printer of claim 1, wherein the print-head-displacement device includes an actuator, which is arranged fixedly with reference to the print-head-holding pocket, and a displacing element which engages the print-head and is arranged to displace it relatively to the print-head-holding pocket in the direction parallel to the media- advancing direction.

3. The inkjet printer of claim 1 or 2, wherein the print-head-displacing device is arranged and coupled to the print-head to displace the print-head both back and forth parallel to the media-advancing direction.

4. The inkjet printer of any one of claims 1 to 3, wherein the print-head abuts on a resilient element at one end of the print-head, and the print-head-displacing device is arranged to displace the print-head in a direction parallel to the media-advancing direction against the resilient element, and the resilient element is arranged to push back the print-head in the opposite direction.

5. The inkjet printer of any one of claims 2 to 4, wherein the actuator is a piezoelectric actuator.

6. The inkjet printer of any one of claims 2 to 5, wherein the print-head-holding pocket includes a holding-pocket base which is attached to a bottom part of the printing carriage and which has an opening through which an ink-ejecting region of the print- head faces the printing media, wherein the displacing element of the displacement device extends into the opening of the hoiding-pocket base at one end in the direction parallel to the media-advancing direction for engaging the print-head near the ink- ejecting region.

7. The inkjet printer of claim 6, wherein the print-head-displacing device is arranged and coupled to the print-head to displace the print-head back and forth parallel to the media- advancing direction.

8. The inkjet printer of claim 6 or 7, wherein the print-head abuts to a resilient element which is arranged at one end of the holding-pocket base opening, and the print-head- displacing device is arranged to displace the print-head in one direction parallel to the media-advancing direction against the resilient element, and the resilient element is arranged to push back the print-head in the opposite direction.

9. The inkjet printer of any one of claims 1 to 8, wherein the printer comprises two or more print-heads for printing on the printing media, and the printing carriage is provided with two or more print-head-holding pockets for the print-heads, and wherein each print-head-holding pocket is associated with a respective print-head-displacement device.

10. The inkjet printer of claim 9, wherein the printer comprises a controller arranged to control operation of the printer, wherein the controller is configured to provide an individual print-head-displacing signal to the displacement device of each print-head, which individual print-head-displacement signal represents a print-head displacement including first and second portions of which the first portion corresponds to an individual referencing measure for the individual print-head, and the second portion corresponds to a displacement to compensate for the media-advance error which is common to all print-heads. 1. A method of printing on a printing media by means of an inkjet printer comprising

- at least one print-head arranged to print on the printing media,

- a printing carriage arranged to be driven in a swath direction across the printing

media and which is provided with at least one print-head-holding pocket for the at least one print-head for holding and referencing the print-head,

the method comprising

- measuring the movement of the printing media in a media-advancing direction and calculating a media-advance-error signal representing a media-advance error which corresponds to a deviation of the measured media movement from a nominal media movement for a desired printing result,

- displacing the print-head relatively to the print-head carriage by means of a print- head-displacement device which is arranged between the print-head and the print- head-holding pocket in a direction parallel to the media-advancing direction in response to the media-advance-error signal in order to compensate for the media- advance error.

12. The method of claim 1 1 , wherein the print-head is displaced relatively to the print-head carriage by means of a piezoelectric device which is arranged between the print-head and the print-head-holding pocket.

13. The method of claim 1 1 or 12, wherein the printer comprises two or more print-heads for printing on the printing media, and the printing carriage is provided with two or more print-head-holding pockets for the print-heads, and each print-head-holding pocket is associated with a respective print-head-displacement device, wherein an individual print-head-displacing signal is provided to each print-head-displacement device. The method of claim 13, wherein the individual print-head-displacement signal represents a print-head-displacement which includes first and second portions, of which the first portion corresponds to an individual referencing measure for the individual print-head, and the second portion corresponds to a print-head displacement to compensate for the media-advance error common to all print-heads.