Patent Application
20170120626
The present invention relates to the technical field of sign manufacturing, and in particular manufacture of signs that are ADA compliant, such as Braille signs that conform to ADA rules on dot spacing, height, and finish. Previously known technologies in the art include use of photopolymer, engraving/routing, and similar techniques and technologies.
In general, greater printing height and dot placement accuracy are desirable. Printing height is generally limited by the type of ink used, as low-viscosity inks may wet out across the printing substrate. Likewise, dot placement accuracy may be negatively affected by wetting of the printed ink. Known technologies utilize UV curable ink, which may be dispensed easily and cured on the substrate.
A printer includes a substrate and at least one print head. The at least one print head is movable in a print direction. The print head includes an ink jet dispenser configured to jet UV-curable ink toward the substrate in a target region. The at least one print head further includes a UV curing system behind the ink jet dispenser in a following direction opposite the print direction. The UV curing system is configured to emit UV irradiance in a radiation field that covers the target region and provides sufficient intensity to at least pin the UV-curable ink in the target region.
An improved printer is described herein that reduces or eliminates several inefficiencies of previously known Braille printers. For example, printers incorporating the invention can produce ADA-compliant signage using fewer passes, resulting in faster printing. Furthermore, by reducing the number of passes of the print head, accuracy of dot placement of Braille or other ADA-compliant signage can be increased.
Print head 1 can be used to generate printed materials such as ADA-compliant and/or Braille signage. Dot spacing, height, and finish of printed material are dependent on the capabilities of print head 1. Print head 1 is capable of producing signage with accurate dot spacing, using a controlled number of passes to create a desired height.
UV system 2 is a curing system used to cure a UV ink (not shown) dispensed from print nozzles 3. For clarity, only some of print nozzles 3 are shown in
Print nozzles 3 can be, for example, piezo dispensers, or more particularly micro piezo dispensers. Micro piezo technology is based on the phenomenon of piezoelectricity where materials like crystals and ceramics (known as “piezoelectric materials”) react physically by bending, vibrating or expanding when an electrical charge is applied to them. Micro piezo print heads feature microscopic piezoelectric actuators that are built behind the print nozzles. When an electrical charge is applied to them, the piezoelectric elements bend backward, drawing precise amounts of ink from the ink chamber into the firing chamber. When the electrical pulse is reversed, the piezoelectric elements bend the opposite way very rapidly, propelling the ink out of the nozzles at high speed. Micro piezo technology is able to precisely eject ink droplets of up to five different sizes by controlling minute variations in the charge applied to the piezoelectric actuators of the print heads.
UV system 2 includes a UV source. In the embodiment shown in
In alternative embodiments, UV system 2 may include more than one UV source. For example, UV system may comprise two UV LED lamps, positioned in the following direction from associated print nozzles.
The effect of side mirror 5a, following mirror 5b, and/or a print direction mirror (not shown) is to intensify the dosage of UV irradiation 8 that is incident upon recently printed UV-curable ink from print nozzles 3. By preventing the diffusion of UV irradiance 8 from UV bulb 4, more curing is possible on each pass of print head 1. In the embodiment shown in
UV bulb 4 is not as wide as print head 1. In order to ensure that all of the UV ink dispensed by print nozzles 3 is at least “pinned,” or cured sufficiently to prevent undesirable running or bleeding, angled mirror 5c is employed to extend the area cured by UV bulb 4. Angled mirror 5c is angled compared to side mirror 5a and following mirror 5b. In particular, angled mirror 5c extends at an angle that does not deflect as much UV irradiation 8 as is deflected by side mirror 5a or following mirror 5b. Thus, UV irradiation 8 is predominantly redirected towards those targets 7 over which UV bulb 4 would not otherwise pass during one printing pass.
Target 7 is the location where UV ink from ink nozzles 3 falls upon substrate 6. Each nozzle 3 is associated with a separate target 7, though only one target 7 is pointed out particularly in
In operation, print head 1 moves along the print direction. During the movement of print head 1, UV system 2 emits UV irradiation that is focused and directed by the mirrors 5a-5c. UV curable ink dispensed from nozzles 3 is exposed to irradiance from UV bulb 4 immediately after contact with substrate 6 at target 7. Side mirror 5a and following mirror 5b cooperate to intensify the dosage of UV irradiance 8 that is incident upon the UV curable ink that is dispensed onto targets 7 that UV bulb 4 passes directly over. Furthermore, angled mirror 5c directs a portion of UV irradiance 8 towards those targets 7 that UV bulb 4 does not pass directly over. In this way, all of the UV ink is at least pinned Immediate curing (at least pinning or partial curing) provides for greater dot height on each pass of print head 1, as well as greater accuracy of dot placement.
Because UV irradiation 8 is intensified by side mirror 5a and following mirror 5b, print nozzles 3 can dispense large quantities of UV curable ink onto targets 7. Print head 1 can be configured, for example, to print “inline ” Inline printing may consist of first printing out a white base from those print nozzles 3 that are arranged furthest in the print direction. The white base may be a textured layer, such as the base of a Braille sign. A second set of print nozzles 3 that are arranged closer to the following direction can then print colored UV curable ink on the textured layer. All of the dispensed ink can then be cured as UV system 2 passes over the targets 7 that were just printed to. This process can be completed in a single pass. A second pass (or additional passes) of print head 1 may be used to add height or additional color or features.
In alternative embodiments, the nozzles 3 may be configured in the opposite way; that is, those print nozzles 3 arranged furthest in the print direction may dispense colored ink (e.g., black ink or a multitude of colors) in order to set up the base, textured portion, and the print nozzles 3 that are arranged furthest in the following direction may be used to print white ink over that. In either case, because of the intensity-increasing effect of mirrors 5a-5b, and the extension of range of angled mirror 5c, cure or pin all of the dispensed UV curable ink. Additional inline printing methods are described in more detail with respect to
Thus, the orientations of side mirror 5a, following mirror 5b, and angled mirror 5c facilitate printing Braille signage with very few passes. For example, in one exemplary system, print head 1 may be used to produce a sign having pictograms and/or text that are a minimum of 0.079375 cm. (0.03125 in.) in height and Braille that is between 0.0635-0.09398 cm (0.025-0.037 in.) in height, using only two passes of print head 1 over substrate 6. In other exemplary systems, this level of height and precision, or other levels of height and precision defined by laws of other countries or regulations of other governing associations, may be achieved with different numbers of passes.
Print head 1 is movable relative to the rest of inkjet printer 10 both away from table 12 and across table 12 (i.e., perpendicular to rails 16). Because both table 12 and print head 1 are movable relative to the rest of inkjet printer 10, inkjet printer 10 can be controlled to modify the position of table 12 and height of print head 1 from table 12. Print head 1 may be set to a standard height above substrate 6. In the embodiment shown in
A UV LED ink curing process and various other control features necessary for multi-layer printing operation, including the control of registration repeatability, can be controlled. For example, the print engine sub-system may consist of a standard photo quality printer control system and components capable of resolutions ranging from 360 DPI up to 5760 DPI. Inkjet printer 10 may dispense a single layer or multiple layers of ink onto print media.
Inkjet printer 10 of
A second method of using inkjet printer 10 of
In alternative embodiments, print head 1 may be kept stationary and table 12 may be moved instead. In fact, movement of one, the other, or both of print head 1 and table 12 are possible, so long as there is relative movement of print head 1 to table 12 that permits for dispensing and curing UV ink in a satisfactorily precise manner
Inkjet printer 10 includes table 12, linear cars 14, rails 16, base beam 18, lead screw 20, anti-backlash screw threaded nut 22, screw mount block 24, lead screw drive end 26, roller ball bearing 28, support blocks 30a and, drive sub plate 32, and motor 34.
Table 12 is shown in exploded view, removed from the other components that make up inkjet printer 10. In the embodiment shown, table 12 is a precise aluminum cast jig plate with a complete surface flatness less than 0.025 cm (0.010 in) and a dimensional square tolerance less than 0.005 cm (0.002 in). This allows printed media to be positioned flat and square to a print head (e.g., print head 1 of
In operation, linear cars 14 generally do not have any head space under the four points of contact with table 12, as shown in
Base beam 18, which may be made of a relatively inflexible material such as Aluminum, is aligned with rails 16 and is mounted to be substantially flat, and aligned to each other within the desired tolerance in all directions.
Table 12 is driven via lead screw 20 and anti-backlash lead screw threaded nut 22. Anti-backlash lead screw nut 22 is a three prong spring loaded split nut to accomplish anti backlash by eliminating thread space engagement. Anti-backlash lead screw threaded nut 22 may be adjusted so that it is centered with lead screw 20 throughout its length of travel. Lead screw 20 is parallel to rails 16, and rails 16 are parallel to one another, within dimensional tolerances determined by the desired finished printed product.
Anti-backlash lead screw threaded nut 22 is positioned in screw mount block 24, which has a dimensional square tolerance less than the desired printing tolerance previously described with respect to
Lead screw drive end 26 is configured to be driven by motor 34. On the opposite end of lead screw 20 from drive end 26, lead screw 20 is arranged on roller ball bearing 28, allowing free rotation of lead screw 20.
Support blocks 30a and 30b hold lead screw 20 and include roller ball bearings pressed into common bearing supports. Support blocks 30a and 30b are attached to drive sub plate 32 and on the idler end of inkjet printer 10. Dimensional tolerances are set as appropriate so that tolerance stackups do not affect the alignment of the parallelism of lead screw 20 with rails 16.
Drive sub plate 32 is coupled to rails 16 via base beam 18. Furthermore, drive sub plate 32 provides support for motor 34.
When motor 34 is driven, lead screw 20 is caused to rotate. Table 12 is coupled to lead screw 20 via screw mount block 24. Thus, when lead screw 20 is driven, table 12 will move along rails 16.
In alternative embodiments, additional rails 16 may be used and adjusted so that no more than 20% variance of measured drag is experienced throughout the travel distance of aligned table 12 mounted to four linear cars 14 which are in turn mounted onto rails 16. One of rails 16 may be mounted to determine the positional datum first, then a second rail 16 may be mounted such that the measurement from the datum to be aligned is within a desired tolerance. For ADA-compliant signage, for example, a tolerance of 0.013 cm (0.005 in.) may be used to ensure necessary accuracy of signage printed by inkjet printer 10.
Inkjet printer 10 provides a highly accurate work surface (table 12) that may be translated along one axis while providing a datum representative of the position of the work surface.
Mechanical sub plate frame 40 is a stable mounting platform for the other components of printer following subassembly 37. Print engine DC motor 38 is mechanically coupled to mechanical sub plate frame 40 via adjustable mount 44.
Brake 46 is a magnetic brake. While brake 46 as shown in
Encoder disc 48 is a rotatable disc that passes through a sensing region of encoder sensor 50. Encoder disc 48 is mounted to encoder shaft 52, which is supported by two ball bearings (not shown). In the embodiment shown in
Encoder shaft 52 is driven by timing belt 54. Timing pulley 56 is mounted on encoder shaft 52, adjacent to encoder disc 48 Timing pulley 56 is connected to motor 38 via timing belt 54. Adjustable mount 44 may be adjusted to modify the tension of timing belt 54. The angle and position of adjustable mount 44 is adjusted with screws 60. Screws 60 may be adjusted to move overlapping lock plate 58. Overlapping lock plate 58 can be adjusted to move adjustable mount 44 when screws 60 are loose, resulting in a change in both position and angle of DC motor 38, as desired.
The process begins with the design of the sign. According to one embodiment, the process uses an ADA design module, where the user can create ADA compliant Text and Braille. In alternative embodiments, various design modules may be used that correspond to other printing specifications. There are options for; raised text, visual text, visual with raised text and Braille only. Once the text and Braille components are complete the pictogram can be imported, or designed by the user. After the design is complete a priming function is used to distinguish between the variations in height of the pictogram, text and Braille. These different components have different height requirements. The default settings will produce a sign with a Pictogram and Text that are a minimum of 0.079375 cm (0.03125 in.) in height and Braille that is between 0.0635-0.09398 cm (0.025-0.037 in.) in height. In other embodiments, alternative minimum and maximum heights may be defined by the laws of other countries or the regulations of other governing associations.
After the design of the sign is complete, the setup menu allows the user to control the trapping and bleeding of the different layers of the image. This insures that there is no color but the one that is printed in the final layer showing on the sign. The trap and bleed values can easily be changed to achieve different widths.
The file is then sent to the RIP (Raster Image Processing) software. The file is received as a .PS (postscript) file. Postscript files have the ability to handle line-art which makes the processing time from the design software to the RIP almost instantaneous, cutting down on overall workflow time. The RIP uses a Queue based system which categorizes the different file qualifications. There are separate Queues for ADA printing. These Queues have a very specific set of parameters; while the user has the ability to manipulate the job further, none are necessary.
The ADA queue is set up to print two layers or passes (e.g., with printer 10 as previously described), with an automatic rewind of the flat-bed table between the passes. Vertical offsets, which change the y-axis start points, are used to account for the variations between a standard 2880×1440 print (first pass) and an inline 1440×1440 print (second pass). The layer profile feature keeps the process simple, multiple printer settings can be chosen on different layers and therefore the software only requires one image to be sent. The layer profile will do the layer breakdown interpretation from that point forward. If additional graphics are desired the user can perform other passes to do so.
At step 102, table position is calibrated. As previously described with respect to
At step 104, a first layer of ink is applied. The ink dispensed in this first pass may, for example, be strictly intended for building height. Variable dot profiling can be turned off, allowing for the maximum amount of ink to jet from the piezo-electric ink jet dispensers. Through the use of separation curves, the amount of ink volume is precisely controlled and can be easily adjusted to produce a variation in height. This layer can print in both a uni-directional (left to right) mode or a bi-directional mode. Often, the first pass comprises inline printing; that is, those nozzles positioned furthest upstream on the print head dispense sufficient ink to form the desired printed texture, for example including raised dots or platforms. Nozzles that are positioned further downstream dispense a top coating over the printed texture, such as a white priming layer.
At step 106, the printer is reset for a second pass, as previously described with respect to step 100.
At step 108, a second pass is used to print additional UV curable ink. The overall height of the ink applied in the second pass may vary. For example, a second layer can be printed at a resolution of 1440×1440 Bi-Directional and covers all areas with the desired color. Bi-Directional printing greatly increases throughput time. Also, Bi-Directional printing with a higher head height allows for the CMYK to cover both sides of the high first layer. Only a small amount of clear ink is used in the second pass to help with surface cure but keep the gloss level down at the same time. During the second pass, a smaller quantity of UV curable ink can be dispensed from each of the print nozzles. In this way, a rough approximation of the finished product can be generated in the first pass (i.e., step 104) and more detailed work can be done during the second pass (i.e., step 108). This allows printing at the resolution needed for fine detail and/or accurate color rendering.
As previously described with respect to step 104, the first pass can utilize inline printing to form a desired printed texture, which is covered by a background color ink. In that case, the second pass may be used to further increase the height of textured areas, and/or to add a desired color selectively. For example, textured areas that correspond to raised text on a sign may have a color added to them, or Braille dots that were created in the first pass may have an ink with a desired texture printed on top.
At step 110, the next row is printed, if required. This generally requires moving the print head relative to the table in the direction perpendicular to what has heretofore been referred to as the print direction. In this way, additional rows of raised printed material may be created. Some overlap of the rows may be present, for example to ensure any pinned UV ink is fully cured. Upon moving to the new row, the table position and print head position are re-calibrated at step 102 and the process continues until the desired sign is complete.
Although the printing processes described above are generally explained in relation to printing in two passes, it should be understood that the printing processes may be achieved in a single pass or in three or more passes in other embodiments, by either eliminating the second pass, or by repeating the passes multiple times.
The relative size of UV curing system 202 and of the extent of a target width that is cured by the UV radiation field produced thereby may vary.
In one particular embodiment, the emitting window of the UV curing system may be 20×28 mm, and may be located 7 mm from the surface of the substrate being printed. In another particular embodiment, the emitting window of the UV curing system may be 25×10 mm, and may be located 1.5 mm from the surface of the substrate being printed. Other sizes and heights of the emitting window of the UV curing system are possible in other embodiments, depending on the application for which the printing system is to be used.
The location of the UV curing system with respect to the nozzles of a print head may vary in different embodiments. For example, in the embodiment shown in
The number of passes used for the printing of a Braille sign may be selected based on the nature of the sign and the desired use of the printing system. For example, a sign to be printed may include a contrasting background, contrasting raised letters, and Braille dots. For a sign of this nature, it may be desirable to print the background, letters and dots in multiple passes. Alternatively, particularly for a system in which multiple ganged print heads are employed, it may also be possible to print such a sign in a single pass, using leading print heads to print the initial layer(s) and trailing print heads to print the subsequent layer(s), for example. Multiple passes may also be used in some applications to build up texture in an initial pass, with white and color being printed over the texture structure in subsequent passes. It should be understood by those skill in the art that the printing system disclosed herein allows for the number of passes to be selected, between one and three or more passes, while achieving the speed and accuracy needed for a number of printing applications.
In the description above, reference has been made to a number of “passes” in the process of printing a Braille sign. In the context of the present application, a “pass” refers to a complete traversal of all printable points of a substrate by the print head(s) of a printer. In some embodiments, the same point on the substrate may be traversed by the print head(s) multiple times during the same pass, such as by allowing the print head(s) to move across the width of the substrate in two opposite directions before stepping to the next row to be printed, or by employing multiple ganged print heads that each pass over the same point during a pass, for example.
In one particular embodiment, the UV curing system may provide a minimum power density of 4-6 Watts/cm2, and the printing speed on the X axis for the print head (or for multiple print heads or print head units) may be 534 mm/second. In such a system, it is possible to fully print a 6 inch×8 inch sign with the Braille text “MEN” and an accompanying flat pictogram image, such as is standard for a restroom sign, with no background, in about 3 minutes and 40 seconds. Similarly, a 3 inch×2.675 inch room sign with a full color background and Braille text may be printed in about 54 seconds. The time that is needed to print a particular sign is based on a number of factors, including the intensity/power density of the UV curing system, the printing speed, the chemistry of the ink, the height and spacing of the features of the sign to be printed, and others. The configurations described herein provide a printing system with excellent speed and dot placement accuracy for a variety of applications.
While the majority of the description above refers to ADA-compliant and Braille signage based on standards set in the United States, it should be understood that the printing systems and methods described herein are applicable to achieve three-dimensional sign printing according to other standards around the world. For example, signs compliant with the requirements of the Building Code of Australia (BCA) may be printed using the system(s) and method(s) described above, which requires tactile characters to be raised 1.0-1.5 mm, and includes other requirements of size and spacing.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
This application is a continuation-in-part of U.S. application Ser. No. 14/780,346 filed Mar. 26, 2014, which in turn is the national phase of PCT Application No. PCT/US2014/031865 filed Mar. 26, 2014, which in turn claims the benefit of U.S. Provisional Application No. 61/805,263 filed Mar. 26, 2013. The aforementioned U.S. application Ser. No. 14,780,346, PCT Application No. PCT/US2014/031865 and U.S. Provisional Application No. 61/805,263 are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61805263 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14780346 | Sep 2015 | US |
| Child | 15358111 | US |
