BRIEF DESCRIPTION OF THE DRAWINGS
Features of the present invention can be more clearly understood from the following detailed description considered in conjunction with the following drawings, in which the same reference numerals denote the same elements throughout, and in which:
FIG. 1 is a perspective view of an exemplary printer in accordance with this invention;
FIGS. 2A-2B are top plan views of the exemplary printer of FIG. 1;
FIG. 3A-3C are cross-sectional views of the printer of FIG. 2A along the line A-A in the direction of the arrows;
FIG. 4 is a bottom plan view of the support structure of FIG. 3A;
FIG. 5 is an enlarged view of a portion of the support structure of FIG. 4;
FIGS. 6A-6E are simplified views of an exemplary method of printing in accordance with this invention;
FIG. 7 is a bottom plan view of an alternative support structure in accordance with this invention;
FIG. 8 is a simplified view of the print head arrays of FIG. 7;
FIG. 9 is a bottom plan view of another alternative support structure in accordance with this invention;
FIGS. 10A and 10B are simplified views of the print head arrays of FIG. 9;
FIGS. 11A-11D are simplified views of an alternative exemplary method of printing in accordance with this invention;
FIGS. 12A-12B are simplified views of another alternative exemplary method of printing in accordance with this invention;
FIG. 13A-13B are simplified views of an exemplary method of interlaced printing in accordance with this invention;
FIG. 14 is a top plan view of an alternative exemplary printer in accordance with this invention;
FIG. 15 is a bottom plan view of the support structures of FIG. 14;
FIGS. 16A-16B are simplified views of an alternative exemplary method of interlaced printing in accordance with this invention;
FIG. 17 is a top plan view of another alternative exemplary printer in accordance with this invention; and
FIG. 18 is a top plan view of yet another alternative exemplary printer in accordance with this invention.
DETAILED DESCRIPTION
Referring to FIGS. 1-3, a first exemplary embodiment of a printer in accordance with this invention is described. Printer 10a includes base 12, conveyor 14 and support structure 16. Printer 10a has a width W aligned substantially parallel to an x-axis, and a length L aligned substantially parallel to a y-axis. Support structure 16 may be a rigid elongate structure that spans the width W of printer 12, and that is used to support one or more arrays 34 of ink jet print heads 24. Support structure 16 has an origin 18, and a long axis that is parallel to the x-axis. Conveyor 14 has an end 22 that is aligned with the y-axis. Printer 10a also may include one or more curing stations 17 coupled to support structure 16 and/or print head arrays 34.
In particular, support structure 16 may include curing stations 17a and 17b attached to first and second sides, respectively, of support structure 16 to cure or dry fluids deposited by print heads 24 on substrate 20 during printing. Curing stations 17 may include ultraviolet (“UV”) lamp systems, “cold UV” lamp systems, UV light emitting diode (“UV-LED”) lamp systems, infrared heat systems, electron-beam (“e-beam”) curing systems, hot air convection systems or other similar systems for curing or heating fluids.
A substrate 20 is disposed on conveyor 14, which is adapted to move in either direction along the y-axis. In particular, conveyor 14 is adapted to move substrate 20 under support structure 16 as ink jet print heads 24 deposit fluids on the substrate. Thus, as shown in FIG. 2A, during a first pass, conveyor 14 may move in a first direction so that print heads 24 deposit fluids across the width of substrate 20 from a first position P1 to a second position P2 on substrate 20. As shown in FIG. 2B, during a second pass, conveyor 14 may move in a second direction so that print heads 24 deposit fluids across the width of substrate 20 from second position P2 to first position P1 on substrate 20. Positions P1 and P2 may be any positions along the length of substrate 20.
While moving along the y-axis, conveyor 14 maintains substrate 20 at a fixed location along the x-axis. Thus, conveyor 14 may be a flexible “endless belt” disposed around a rigid vacuum table, a moveable vacuum table or other similar device for controlling the x- and y-axis locations of substrate 20. Substrate 20 has a width W0, and may be a metal, glass, wood, plastic, paper or other similar substrate or combination thereof.
Support structure 16 is disposed above substrate 20, and is adapted to control the x-axis location of print heads 24. In particular, as shown in FIG. 3A, support structure 16 may include arms 26 that are coupled to an actuator 28 and position detector 30. Actuator 28 may be a linear actuator or other similar device that may be used to provide linear motion to support structure 16. Position detector 30 may be a linear encoder or other similar device that may be used to accurately determine the x-axis location of support structure 16. A controller 32 may be coupled to actuator 28 and position detector 30 to precisely control the x-axis location of support structure 16. For example, controller 32 may direct actuator 28 to locate origin 18 of support structure 16 at a position x=X0. As illustrated in FIGS. 3B and 3C, controller 32 also may direct actuator 28 to move support structure 16 so that origin 18 is located at x=X0+Δ1 or x=X0−Δ2, respectively. Δ1 and Δ2 may be the same distance or may be different distances.
Referring now to FIGS. 4 and 5, an exemplary embodiment of support structure 16 is described. Support structure 16a includes an array 34 of print heads 24, each of which includes inkjet nozzles 36 that may be individually controlled to eject a fluid onto substrate 20. Fluids may be delivered to print heads 24 from a fluid reservoir system (not shown) via conventional tubing systems, via channels in support structure 16a that couple the print heads to the fluid reservoir system, or by other similar systems. Exemplary fluids that may be ejected by inkjet nozzles 36 include colored inks, such as cyan, magenta, yellow or black (“CMYK”) inks, as are commonly used in the printing industry. Colored inks also may include light cyan, light magenta, light yellow, light black, red, blue, green, orange, white, gray, spot colors, and other similar colored inks. The inks may be solvent-based inks, dye sublimation inks, cationic inks, UV curable inks, e-beam curable inks, or other similar inks. In addition, inkjet nozzles 36 also may be used to eject fluids other than colored inks, such as clear coat finishes, UV protective finishes, and other similar fluids.
Print head array 34 may include curing stations 17c and 17d attached to first and second sides, respectively, of print head array 34 to cure or dry fluids deposited by print heads 24 on substrate 20 during printing. Curing stations 17c and 17d may include UV lamp systems, cold UV lamp systems, UV-LED lamp systems, infrared heat sources, e-beam lamp systems, hot air convection systems or other similar systems for curing or drying fluids.
Array 34 in FIG. 4 includes twelve print heads 24, each of which includes eight inkjet nozzles 36. Persons of ordinary skill in the art will understand that print head arrays 34 in accordance with this invention may include more or less than twelve print heads 24, and each print head 24 may include more or less than eight inkjet nozzles 36. Inkjet nozzles 36 are spaced apart along the long axis of the print head 24 by a dot pitch D0. The resolution of each print head 24, referred to as the native resolution R0, equals the inverse of the dot pitch (i.e., 1/D0). The native resolution is typically specified in dots per unit length, such as 37.5 dots per inch (“DPI”).
Print heads 24 are disposed on array 34 such that the long axis of each print head 24 is aligned in parallel with the long axis of the array and with the long axis of support structure 16. Further, print heads 24 are staggered in the y-direction along the length L0 of print head array 34 so that the print head array has a continuous resolution R0 along the entire length L0. In this regard, if the length L0 of print head array 34 is substantially equal to the width W0 of substrate 20, print head array 34 may be used to print across the entire width W0 of substrate 20 at native resolution R0 without scanning across width W0 of substrate 20. Thus, in a single pass, printer 10a may print an image on substrate 20 at a continuous resolution R0 across the entire width W0 of substrate 20 without scanning across width W0 of substrate 20.
In addition, printer 10a may be used to print an image across the entire width of substrate 20 at resolutions greater than native resolution R0 without scanning across width W0 of substrate 20. In particular, referring to FIGS. 2 and 3, during a first pass, controller 32 positions origin 18 of support structure 16 at a first x-axis position (e.g., x=X0), and print head array 34 then prints a first image on substrate 20 as conveyor 14 moves substrate 20 in a first direction from P1 to P2. During a second pass, controller 30 positions origin 18 of support structure 16 at a second x-axis position (e.g., x=X0+Δ1), and print head array 34 then prints a second image on substrate 20 as conveyor 14 moves substrate 20 in a second direction from P2 to P1. If Δ1 is a fraction of dot pitch D0, this technique may be used to print an image across the entire width of substrate 20 at a composite resolution that is greater than the native resolution R0. For example, if Δ1=D0/2, printer 10a prints the image across the entire width of substrate 20 at a composite resolution of 2×R0. Further, if this process is repeated, and Δ1 is further decreased, printer 10a may be used to print at even higher composite resolutions.
For example, FIGS. 6A-6D illustrate how printer 10a may be used to print an image across the entire width of substrate 20 at a resolution of 4×R0. Persons of ordinary skill in the art will understand that the described process typically will be used with a print head array 34 that has multiple print heads 24 disposed along the length of the array, and that provides a continuous resolution R0 along the entire length L0 . To simplify the drawings, however, only a single print head 24 is illustrated in FIGS. 6A-6D. Exemplary print head 24 includes eight ink jet nozzles 36, which include two sets of ink jet nozzles, with each set adapted to print colored inks on substrate 20. Print head 24 has a native resolution R0 (e.g., 37.5 DPI).
As shown in FIG. 6A, during a first pass, print head 24 is located at a first x-axis position, x=X1, conveyor 14 moves substrate 20 in a first direction, and print head 24 prints a first image 38a on substrate 20. Next, as shown in FIG. 6B, during a second pass, print head 24 is located at a second x-axis position, x=(X1+D0/4), conveyor 14 moves substrate 20 in a second direction, and print head 24 prints a second image 38b on substrate 20. Next, as shown in FIG. 6C, during a third pass, print head 24 is located at a third x-axis position, x=(X1+D0/2), conveyor 14 moves substrate 20 in the first direction, and print head 24 prints a third image 38c on substrate 20. Finally, as shown in FIG. 6D, during a fourth pass, print head 24 is located at a fourth x-axis position, x=(X1−D0/4), conveyor 14 moves substrate 20 in the second direction, and print head 24 prints a fourth image 38d on substrate 20. Persons of ordinary skill in the art will understand that the fourth x-axis position alternatively could be x=(X1+3D0/4).
Thus, after four passes, print head 24 prints images 38a-38d across the entire width of substrate 20 at a composite resolution of 4×R0 (e.g., 150 DPI). In general, therefore, to print across the entire width of substrate 20 at a composite resolution of NR0, printer 10a prints in N passes, and shifts the x-axis position of support structure 16 (and therefore print heads 24) between each pass. The amount of each shift may be uniform or non-uniform. For example, as shown in FIGS. 6A-6D, support structure 16 is uniformly shifted by integer multiples of D0/N between each pass. Persons of ordinary skill in the art will understand that support structure 16 may be shifted by arbitrary amounts and/or non-uniformly between each pass. For example, FIG. 6E illustrates printing in four passes at a composite resolution of 4×R0, but shifting support structure by D0/5.6, D0/8, D0/3.111 and D0/2.667 between each pass.
Apparatus and methods in accordance with this invention also may print across the entire width of substrate 20 at a resolution greater than native resolution R0 without requiring multiple printing passes. In particular, multiple print head arrays 34 may be grouped on support structure 16, with each print head array 34 offset in the x-direction from adjacent print head arrays. For example, FIG. 7 illustrates an alternative exemplary support structure 16b that includes four print head arrays 34a-34d staggered in the y-direction, with each print head array 34 offset in the x-direction by D0/4 from adjacent print head arrays 34.
FIG. 8 illustrates a simplified view of FIG. 7, with a single print head 24a 24d from each of print head arrays 34a-34d, respectively. In this example, each print head array 34 has a native resolution R0=1/D0, and the group of print head arrays 34a-34d provides a continuous resolution of 4×R0 (e.g., 150 DPI) along the entire length L1 of support structure 16b. Thus, if L1 substantially equals width W0 of substrate 20, support structure 16b may be used to print across the entire width W0 of the substrate 20 at a composite resolution of 4×R0. Persons of ordinary skill in the art will understand that more than or less than four print head arrays 34 may be grouped together on support structure 16, depending on the desired composite resolution.
For example, FIG. 9 illustrates an alternative exemplary support structure 16c that includes three print head arrays 34a-34c staggered in the y-direction, with each print head array 34 offset in the x-direction by D0/3 from adjacent print head arrays 34. FIG. 10A illustrates a simplified view of FIG. 9, with a single print head 24a-24c from each of print head arrays 34a-34c, respectively. In this example, the group of print head arrays 34a-34c has a composite resolution 3×R0 (e.g., 112.5 DPI) along the entire length L1. Thus, support structure 16c may be used to print across the entire width W0 of the substrate 20 at a composite resolution of 3×R0.
In general, therefore, to print across the entire width of substrate 20 at a composite resolution of M×R0, support structure 16 includes M print head arrays 34, with each print head array 34 offset in the x-direction from adjacent print head arrays 34 by D0/M. Persons of ordinary skill in the art will understand, however, that other x-axis offset values may be used to achieve the same composite resolution, and that the x-axis offset values may be integer or non-integer fractions of D0 (e.g., D0/1.697, D0/14, D0/9.333, etc.), and may be uniform or non-uniform, such as illustrated in FIG. 10B.
The two techniques described above can be combined to further increase the resolution of printers in accordance with this invention. In particular, to print across the entire width of substrate 20 at a composite resolution of M×N×R0, printer 10a includes a support structure 16 that includes M print head arrays 34, with each print head array 34 offset in the x-direction by D0/M from adjacent print head arrays. The support structure 16 may then be used to print in N passes, with an x-axis shift of support structure 16 by multiples of 1/(NR0) between each pass.
For example, FIGS. 11A-11D illustrate exemplary apparatus and methods in accordance with this invention for printing an image across the entire width of substrate 20 at a resolution of 16×R0 (e.g., M=N=4). In particular, support structure 16b of FIG. 7 may be used, with four print head arrays 34a-34d staggered in the y-direction and offset from one another in the x-direction by D0/4. To simplify the drawings in FIGS. 11A-11D, each print head array 34a-34d is shown including only a single print head 24a-24d, respectively. Each exemplary print head 24a-24d includes eight ink jet nozzles 36, and has a native resolution R0 (e.g., 37.5 DPI). The group of print head arrays 34a-34c print across the entire width of substrate 20 at a composite resolution 4×R0 (e.g., 150 DPI).
As shown in FIG. 11A, during a first pass, the group of print head arrays 34a-34d is located at a first x-axis position, x=X1, substrate 20 moves in a first direction, and print heads 24a-24d print a first image 38a on substrate 20. Next, as shown in FIG. 11B, during a second pass, the group of print head arrays 34a-34d is located at a second x-axis position, x=(X1+D0/16), substrate 20 moves in a second direction, and print heads 24a-24d print a second image 38b on substrate 20. Next, as shown in FIG. 11C, during a third pass, the group of print head arrays 34a-34d is located at a third x-axis position, x=(X1+D0/8), substrate 20 moves in the first direction, and print heads 24a-24d print a third image 38c on substrate 20. Finally, as shown in FIG. 11D, during a fourth pass, the group of print head arrays 34a-34d is located at a fourth x-axis position, x=(X1−D0/16), substrate 20 moves in the second direction, and print heads 24a-24d print a fourth image 38d on substrate 20. Persons of ordinary skill in the art will understand that the fourth x-axis position alternatively could be x=(X1+3D0/16). Thus, after four passes, the group of print head arrays 34a-34d prints images 38a-38d on substrate 20 at a composite resolution of 4×4×R0 (e.g., 600 DPI) across the entire width of substrate 20.
Persons of ordinary skill in the art will understand that the sequence of printing steps may be modified from that shown in FIGS. 11A-11D. For example, image 38a may be printed during the first pass, image 38c may be printed during the second pass, image 38d may be printed during the third pass and image 38b may be printed during the fourth pass, and so on. Persons of ordinary skill in the art also will understand that print head arrays 34a-34d may be offset from one another in the x-direction by uniform or non-uniform amounts, and that the group of print head arrays 34a-34d may be shifted by arbitrary amounts and/or non-uniformly between each pass.
Persons of ordinary skill in the art will further understand that apparatus and methods of this invention may be used to print at non-integer multiples of the native resolution R0 of print head 24, and al l print heads 24 may not be used during each printing step. For example, as shown in FIG. 12A, during a first pass, the group of print head arrays 34a-34d is located at a first x-axis position, x=X1, substrate 20 moves in a first direction, and print heads 24a-24d print a first image 38a on substrate 20. Next, as shown in FIG. 12B, during a second pass, the group of print head arrays 34a-34d is located at a second x-axis position, x=(X1+D0/8), substrate 20 moves in a second direction, and print heads 24b and 24d print a second image 38b on substrate 20, while print heads 24a and 24c are inactive. Thus, after two passes, the group of print head arrays 34a-34d print images 38a and 38b on substrate 20 at a composite resolution of (8/3)×R0 (e.g., 100 DPI) across the entire width of substrate 20.
Apparatus and methods in accordance with this invention also may be used to print images on substrate 20 even if one or more inkjet nozzles 36 are defective or inactive. For example, FIG. 13A illustrates a group of print heads 24a-24d offset in the x-direction by D0/4 from adjacent print heads, for printing at a composite resolution of 4×R0. However, print head 24d includes one or more defective inkjet nozzles 36′ (shown in dashed lines). The multipass printing techniques of this invention may be used to compensate for such defective inkjet nozzles 36′.
In particular, as shown in FIG. 13A, during a first pass, the group of print heads 24a-24d is located at a first x-axis position, x=X1, substrate 20 moves in a first direction, and print heads 24a-24d print a first image 38a on substrate 20. Inkjet nozzles 36′, however, are deactivated, and do not print any portion of first image 38a. Next, as shown in FIG. 13B, during a second pass, the group of print heads 24a-24d is located at a second x-axis position, x=(X1−D0/4), substrate 20 moves in a second direction, and only inkjet nozzles 36a of print head 24c are used to print a second image 38b on substrate 20. In this regard, inkjet nozzles 36a of print head 24c may be used to fill in the portion of first image 38a that could not be completed because of the defective inkjet nozzles 36′ on print head 24d. Persons of ordinary skill in the art will understand that inkjet nozzles 36 from print heads 24a or 24b alternatively could have been used to compensate for defective inkjet nozzles 36′ by shifting the group of print heads 24a-24d to an appropriate x-axis position for the second pass.
In the embodiments described above, multiple print head arrays 34 are grouped together on a single support structure 16, and the group is collectively shifted along the x-axis. Referring now to FIGS. 14-15, an alternative exemplary printer in accordance with this invention is described in which each print head array 34 may be independently shifted along the x-axis. In particular, exemplary printer 10b includes multiple support structures 161-164, each of which spans the width W of printer 12 and is used to support one or more print head arrays 34. For example, support structures 161-164 may include print head arrays 34a-34d, respectively. Further, each support structure 161-164, may be independently shifted to control the x-axis location of print head arrays 34a-34d.
FIG. 16A illustrates a simplified view of FIG. 15, with a single print head 24a-24d from each of print head arrays 34a-34d, respectively. In this example, each print head array 34 has a native resolution R0=1/D0. Further, support structures 161-164 may be individually positioned so that print head arrays 34a-34d provide a continuous resolution of 4×R0 (e.g., 150 DPI). In addition, multipass printing techniques of this invention may be used to compensate for defective inkjet nozzles, such as inkjet nozzles 36′ on print head 24d.
In particular, during a first pass, support structures 161-164 are individually positioned so that print head 24d is at a first x-axis position, x=X1, and all other print heads 24b-24d are positioned to provide a continuous resolution of 4×R0. As substrate 20 moves in a first direction, print heads 24a-24d print a first image 38a on substrate 20. Inkjet nozzles 36′, however, are deactivated, and do not print any portion of first image 38a. Next, as shown in FIG. 16B, during a second pass, support structures 161-164 are individually positioned so that print head 24c is located at a the first x-axis position, x=X1. As substrate 20 moves in a second direction, only inkjet nozzles 36a of print head 24c are used to print a second image 38b on substrate 20. In this regard, inkjet nozzles 36a of print head 24c may be used to fill in the portion of first image 38a that could not be completed because of the defective inkjet nozzles 36′ on print head 24d. Persons of ordinary skill in the art will understand that inkjet nozzles 36 from print heads 24a or 24b alternatively could have been used to compensate for defective inkjet nozzles 36′ by shifting print heads 24a or 24b to an appropriate x-axis position for the second pass.
In the embodiments described above, one or more print head arrays 34 are disposed on one or more support structures 16, and the print head arrays are shifted individually or collectively along the x-axis to achieve a desired composite resolution that exceeds the native resolution of each print head. Referring now to FIG. 17, another exemplary printer in accordance with this invention is described in which print head arrays are rotated about an axis to achieve any desired print resolution. In particular, exemplary printer 10c includes support structure 16e that spans the width W of printer 12 and is used to support a print head array 34e that includes multiple print heads (not shown) that have inkjet nozzles 36 disposed to provide a continuous resolution of R0 across the entire width of substrate 20. In addition, print head array 34e is coupled to support structure 16e at pivot point 40, and may be rotated about the pivot point by an angle α. As a increases from 0 to 90°, the x-axis resolution increases. In this regard, by controlling the pivot angle α, any desired print resolution may be achieved.
FIG. 18 illustrates another exemplary printer in accordance with this invention that uses multiple pivotable print head arrays 34f-34o. In particular, exemplary printer 10d includes support structure 16f that spans the width W of printer 12 and is used to support print head arrays 34f-34o that each include multiple print heads (not shown) that have inkjet nozzles 36 disposed to provide a resolution R0 across the entire width of substrate 20. Print head arrays 34f-34o are coupled to support structure 16f at pivot points and may be individually rotated about their respective pivot points to provide any desired print resolution. Multiple print head arrays 34f-34o increase the printing width that may be achieved when using very high pivot angles.
The foregoing merely illustrates the principles of this invention, and various modifications can be made by persons of ordinary skill in the art without departing from the scope and spirit of this invention.
Patent Application
20070296757
