The present invention relates to improvements in printing including improvements in printing machines and associated methods of printing.

Digital inkjet printing machines reproduce an image by jetting droplets of ink from a printhead (or printheads) onto a substrate. The printhead consists of a number of nozzles spread out over an addressable printable area. The maximum length of the printed image is limited only by the dimensions of the substrate.

In order to print an image where the width of the image is larger than the length of a printhead's printable area, there are two well-known solutions. The first of these solutions employs a fixed array of printheads, aligned so that their printable areas are adjacent to each other.

For example, if a single printhead has a printable width of 10 cm, with six printheads a printing machine is able to fully print on a substrate of up to 60cm in width

Printheads, however, are precision components which often make up a significant portion of the overall cost of an inkjet printing machine. The larger the width of the substrate, the less economically viable a full-width fixed array of printheads would be, for many applications. Furthermore, the scale of the problem is exacerbated with colour printing, which in its simplest form achieves a broad colour gamut by combining different proportions of the primary subtractive colours: cyan, magenta and yellow as well as black. Thus, continuing the example where six printheads with a 10cm printing width are required to fully print a 60cm substrate in monochrome, to print in colour on a substrate with a width of 60cm, twenty- four printheads are required.

The alternative prior art solution overcomes the problem of needing to increase the number of printheads in order to print on to larger substrates by placing one or more printheads for each colour into a moving carriage. With the printheads in this configuration, printing is achieved by shuttling the carriage across the full width of the image (the carriage axis), with each successive pass of the carriage resulting in the printing of a single swathe of the full image. In between passes, either the substrate or the carriage is moved along an axis perpendicular to the carriage axis (the substrate axis), so that the next swathe of the image is printed in the correct position on the substrate. Printers employing this printhead configuration and method of printing are referred to as scanning printers. Scanning printers benefit from being able to print any width by simply extending the carriage axis. However, this economical scalability is also coupled with a significant decrease in productivity. Whereas printers with printheads in a fixed position allow for continuous feeding of a substrate under the printhead carriage and consequent printing on the substrate, printing in a scanning mode requires repeated starting and stopping along both the printing axis and the substrate axis.

Comparing the productivity in terms of linear meters of substrate printed, the productivity achieved by a printer with a fixed array of printheads in minutes may take several hours to achieve on a scanning printer.

The present invention seeks to improve upon the prior art.

According to a first aspect of the present invention there is provided a printing machine comprising:

a printhead or printhead array arranged to print across a printable width oriented substantially perpendicular to a direction of travel of substrate when printing is occurring;

the machine being adapted to:

move the printhead or printhead array and / or substrate relative to each other so as to locate a printhead or printhead array of the printing machine in a substantially fixed position in relation to a width of substrate so as to print on a linear section extending along a length of substrate moved past the substantially fixed printhead or printhead array. By providing a machine as defined above a user is able to print on a single linear section of substrate if so desired, that linear section normally being selectable from a continuous range of linear sections spanning the width of the substrate. 'Substrate' may be part or whole of a single item of substrate or a plurality of items of substrate.

In some embodiments the printhead or printhead array is moveable so as to select the linear section of substrate to be printed on.

In some embodiments the machine is adapted to move the printhead or printhead array between a plurality of substantially fixed positions so as to allow a plurality of substantially linear sections of the same substrate to be printed on by the substrate moving past the printhead or printhead array a plurality of times.

In some embodiments the substrate is moveable so as to select the linear section of substrate to be printed on.

In some embodiments the machine is adapted to move the substrate between a plurality of substantially fixed positions so as to allow a plurality of substantially linear sections of the same substrate to be printed on by the substrate moving past the printhead or printhead array a plurality of times.

By providing a printing machine as defined above a user is able to print on linear sections of the same substrate by moving the substrate and / or by moving the printhead or printhead array only between print runs, thereby resulting in cost savings in comparison to fixed array printing machines (owing to the reduction in the number of printheads) and productivity savings in comparison to scanning printers (owing to the printhead not shuttling whilst printing is occurring).

In some embodiments a printhead array comprises a plurality of printheads arranged substantially linearly along the direction of travel of substrate.

In some embodiments a printhead array comprises a plurality of the same or differently coloured printheads. In some embodiments a printhead array comprises at least one cyan printhead, one magenta printhead, one yellow printhead and one black printhead.

By providing a printhead array with a plurality of printheads arranged substantially linearly along the direction of travel of substrate past the printhead array, and in particular by having in that array at least one cyan printhead, one magenta printhead, one yellow printhead and one black printhead, printing of a broad colour gamut may be achieved along the linear section of substrate being printed upon. In some embodiments the machine is configured to move at least 90% of the length of a single item of substrate past the printhead or printhead array before the substrate and / or printhead or printhead array are moved relative to each so as to select a new linear section of substrate to be printed on. In some embodiments the machine is configured to move substantially the full length of a single item of substrate past the printhead or printhead array before the substrate and / or printhead or printhead array are moved relative to each so as to select a new linear section of substrate to be printed on. In some embodiments the machine is capable of printing on a plurality of items of substrate before the substrate and / or printhead or printhead array are moved relative to each other so as to select a new linear section of substrate to be printed on.

In some embodiments a printing machine may comprise a plurality of moveable printheads or moveable printhead arrays.

In some embodiments a printing machine may comprise a plurality of independently moveable printheads or independently moveable printhead arrays. According to a second aspect of the present invention there is provided a method of printing on a printing machine comprising:

a printhead or printhead array arranged to print across a printable width oriented substantially perpendicular to a direction of travel of substrate when printing is occurring; the machine being adapted to:

move the printhead or printhead array and / or substrate relative to each other so as to locate a printhead or printhead array of the printing machine in a substantially fixed position in relation to a width of substrate so as to print on a linear section extending along a length of substrate moved past the substantially fixed printhead or printhead array; the method comprising the steps of:

i) locating a printhead or printhead array of the printing machine and / or the substrate in a first substantially fixed position in relation to the width of substrate;

ii) moving substrate past the printhead or printhead array so as to print on a first linear section of substrate.

In some embodiments the method comprises the further steps of:

iii) locating a printhead or printhead array of the printing machine and / or the substrate in a second substantially fixed position in relation to the width of substrate;

iv) moving the same substrate past the printhead or printhead array so as to print on a second linear section of substrate. In some embodiments the method comprises the further steps of:

v) locating a printhead or printhead array of the printing machine and / or the substrate in a further substantially fixed position in relation to the width of substrate;

vi) moving the same substrate past the printhead or printhead array so as to print on a further linear section of substrate.

In some embodiments the method comprises the further step of:

vii) repeating steps v) and vi). By repeating steps v) and vi) a user may print until all intended linear sections of the image or images have been printed on to the substrate.

In some embodiments the method comprises the further step of: viii) repeating steps v) and vi) until substantially the full length and width of substrate has moved under the printhead or printhead array.

In some embodiments the printhead or printhead array is moveable so as to select the linear section of substrate to be printed on.

In some embodiments the substrate is moveable so as to select the linear section of substrate to be printed on. In some embodiments both the printhead or printhead array and the substrate are moveable so as to select the linear section of substrate to be printed on.

In some embodiments a printhead array comprises a plurality of printheads arranged substantially linearly along the direction of travel of substrate past the printhead array when printing is occurring.

In some embodiments a printhead array comprises a plurality of the same or differently coloured printheads. In some embodiments a printhead array comprises at least one cyan printhead, one magenta printhead, one yellow printhead and one black printhead.

In some embodiments the machine is configured to move at least 90% of the length of a single item of substrate past the printhead or printhead array before the substrate and / or printhead or printhead array are moved relative to each other in a direction substantially perpendicular to the direction of travel of substrate when printing is occurring so as to select a new linear section of substrate to be printed on.

In some embodiments the machine is configured to move substantially the full length of a single item of substrate past the printhead or printhead array before the substrate and / or printhead or printhead array are moved relative to each other in a direction substantially perpendicular to the direction of travel of substrate when printing is occurring so as to select a new linear section of substrate to be printed on. In some embodiments the machine is capable of printing on a plurality of items of substrate before the substrate and / or printhead or printhead array are moved relative to each other in a direction substantially perpendicular to the direction of travel of substrate when printing is occurring so as to select a new linear section of substrate to be printed on.

In some embodiments a printing machine may comprise a plurality of moveable printheads or moveable printhead arrays.

In some embodiments a printing machine may comprise a plurality of independently moveable printheads or independently moveable printhead arrays.

According to a third aspect of the present invention there is provided a printing control unit adapted to operate the printing machine and/or method of the present invention. Such a printing control unit may include software, hardware or a combination of both.

In order that the invention may be more fully understood a specific embodiment will now be described with reference to the accompanying schematic drawings, of which: Figure 1 illustrates a prior art arrangement of a single fixed printhead printing in monochrome;

Figure 2 illustrates a prior art arrangement of a fixed array of printheads printing in monochrome;

Figure 3 illustrates a prior art arrangement of a fixed array of printheads printing in colour; Figure 4 illustrates a prior art arrangement of a moveable array of printheads installed in a moving carriage printing in colour;

Figure 5 illustrates an embodiment of a printing machine of the present invention having an array of printheads installed in a moveable carriage between substantially fixed positions printing in colour; and

Figure 6 illustrates how the printing machine of Figure 5 may print on two linear sections of substrate.

Referring to the drawings, Figures 1 to 4 illustrate prior art arrangements. Figure 1 illustrates how a fixed printhead 1 is capable of printing across main printable width B on substrate 2 as substrate 2 passes printhead 1 in direction of travel A when printing is occurring. Figure 2 illustrates how to solve the problem of printing on wide substrates using an array of fixed printheads. Fixed printheads 3a, 3b, 3c, 3d, 3e, 3f are capable of printing in monochrome across main printable width B on substrate 4 as substrate 4 passes printheads 3a, 3b, 3c, 3d, 3e, 3f in direction of travel A when printing is occurring. Figure 3 illustrates how in order to print in colour across printable width B on substrate 6.

When printing is occurring substrate 6 moves in direction of travel A and four separate arrays of printheads 5a, 5b, 5c, 5d (one array for each of cyan, magenta, yellow and black) are required.

Figure 4 illustrates an alternative prior art solution to printing on a wide substrate, in which solution a moving carriage 7 comprising four print heads (one of each of cyan, magenta, yellow and black) may print across the width of substrate 8 in linear sections each of printable width B.

Thus a first section Z is printed by carriage 7 traversing and printing across the width of substrate 8. Substrate 8 then moves forward the same distance as printable width B. Carriage 7 then again traverses and prints across the width of substrate 8 so as to print linear section Y. This process is again repeated to print linear section X, etc.

Figure 5 illustrates an embodiment of the present invention wherein a printing machine comprises a carriage 9 comprising a printhead array of four print heads 10a, 10b, 10c, lOd (one of each of cyan, magenta, yellow and black). At any one time carriage 9 is capable of printing across main printable width B.

Carriage 9 is moveable along carriage support 11 that extends across the path of substrate in the printing machine. Thus carriage 9 may be positioned at any location across the width of substrate 12 so as to define printable width C of the printing machine.

Substrate 12 may be considered to have its width extending in the direction of arrow C and its length extending in the direction of arrow A.

The printing machine comprises a substrate movement assembly (not shown) configured to move substrate 12 past the carriage 9. The direction of travel of substrate 12 when printing is occurring is indicated in Figure 5 by arrow A, which is substantially perpendicular to the longitudinal axis of carriage support 11 and substantially perpendicular to main printable width B of each of four print heads 10a, 10b, 10c, lOd. Print heads 10a, 10b, 10c, lOd are arranged substantially linearly along the direction of travel A of substrate 12 past carriage 9. Thus any part of substrate 12 that passes carriage 9 passes each of printheads 10a, 10b, 10c, lOd, thereby allowing for varying combinations of all colours to be printed on substrate 12 passing through the printable area B of carriage 9. Thus it can be seen that in comparison to the printhead carriage 7 of a prior art scanning printer as illustrated in Figure 4, carriage 9 of the present invention is essentially rotated by 90 degrees.

This means that instead of the printheads being substantially arranged linearly along the direction of travel of carriage 7, printheads 10a, 10b, 10c, lOd are arranged substantially linearly along the direction of travel A of substrate.

Thus instead of a printable width B being substantially parallel to the direction of travel A of substrate, as with carriage 7, a printing machine made in accordance with the present invention comprises a carriage 9 having a printable width substantially perpendicular to the to the direction of travel A of substrate, as may be clearly seen by comparing Figures 4 and 5. Turning to the present invention in use, and referring to Figure 6, a printing machine embodying the invention may locate carriage 9 in a first substantially fixed position and move substrate 12 in direction of travel A past carriage 9 such that it is printed upon as desired in the printed area indicated in Figure 6 by letter X.

Once the full length of an item or plurality of items of substrate have been printed upon carriage 9 may then be moved substantially perpendicularly to the direction of travel of substrate when printing is occurring to a second substantially fixed position, and the same substrate may then be moved in direction of travel A past carriage 9 such that it is printed upon as desired in the printed area indicated in Figure 6 by letter Y.

By using this technique the full width of an item or plurality of items of substrate may be printed upon by locating the carriage 9 in a minimal number of positions. Thus, if carriage 9 has a printable width of 10cm and substrate 12 is 60cm in width, then to print on the full length and width of substrate 12 carriage 9 can be located in just six positions.

Thus in contrast to prior art scanning printers carriage 9 does not need to shuttle while printing. Instead, during printing carriage 9 behaves like a fixed array of printheads, relocated only in-between print runs.

The productivity advantages when printing in this way are particularly apparent when considering longer print runs requiring thousands of linear meters to be printed in a single position. For printing in more than one position, the need to feed the material through the printer again for each additional position is more than compensated for by the timesaving provided by uninterrupted and continuous feeding and printing of the material in each position. This is particularly true where desired printing positions are located at each side of relatively wide substrates.

For example a prior art scanning printer must repeatedly move its printheads between each edge of the substrate so as to print at each edge, and time whilst the printheads are travelling between edges is wasted as no printing is occurring. In addition, whilst the carriage is moving, the substrate remains in a fixed position. In contrast a printing machine made in accordance with the present invention may locate its printheads at the first edge and continuously print on all substrate until the first edge is printed. The printing machine may then move its printheads such that they are located at the second edge and continuously print on all substrate until the second edge is printed.

Thus the present invention provides a printing solution with the build cost of a scanning printer but a capacity for production reaching up to the same levels as a printer with a traditional full-width, fixed array of printheads, depending upon the number of positions on a substrate in which printing is required.

Although in the present embodiment four printheads 10a, 10b, 10c, lOd, are provided in carriage 9, it will be appreciated that in other embodiments other numbers and combinations of printheads may be provided in a carriage.

For example, where printing is monochrome is desired a carriage may contain only a single printhead, or where bichrome printing is desired a carriage may contain only two printheads. Also additional set of printheads might be included in a carriage. For example eight printheads may be provided, with two sets of four printheads each being arranged substantially linearly along the direction of travel A of substrate 12 past carriage 9 so as to double the printable width of a carriage. Also in other embodiments a printing machine might comprise additional moveable carriages each containing a printhead or a printhead array.

For example a printing machine might comprise a plurality of moveable carriages that can each be located in substantially fixed positions whilst substrate is moved through the printing machine past the carriages before the carriages are moved to new positions and the same substrate is again moved through the printing machine past the carriages.

It should be noted that although a only discrete number of printing positions may be required to print across the full width of an item of substrate (for example six positions for a 10cm wide printhead to print across a 60cm substrate) in many embodiments a carriage will be locatable at any point along a carriage support, providing a continuous range of printing positions. A printing machine may comprise means to move substrate repeatedly past the printhead or printhead array.

For example, a printer may be configured to print on a single substrate at a time, for example a roll of substrate on two spools that is moved past a printhead array in a first direction of travel, the printhead array is then moved, and the substrate is moved past the printhead array in an opposite direction of travel.

In other embodiments a printing machine may be configured to print on a plurality of individual sheets of substrate that are repeatedly fed through the printing machine by means of one or more conveyors, with a printhead array moving positions between each print run.

In other embodiments manual intervention by a user may be required to feed substrate repeatedly though a printing machine made in accordance with the present invention

In the present embodiment a printhead array comprises one cyan printhead, one magenta printhead, one yellow printhead and one black printhead, but other embodiments may include other colours such as orange, green, violet, or red to broaden the reproducible colour space, or spot or special colours such as white, clear or metallic, which may, for example, be underprinted or overprinted with respect to the other colours in order to satisfy the requirements of certain applications. In addition, a printhead array may instead comprise of printheads for only one or a different number of colours.

In some embodiments the printing machine may itself comprise a substrate movement assembly to move substrate past the printhead or printhead array, whereas in other embodiments a substrate movement assembly may be provided as part of a second machine working in conjunction with a printing machine of the present invention. Although in the present embodiment carriage 9 is moveable between substantially fixed positions so as to select different linear sections of substrate 12 to be printed upon it will be apparent that in other embodiments substrate may be moved relative to a printhead or printhead array so as to select different linear sections of substrate to be printed upon. To select a new linear section of substrate the substrate would be moved in a direction substantially perpendicular to the direction of travel of substrate when printing is occurring.

Many variations are possible without departing from the scope of the present invention as defined in the appended claims.