Method and apparatus for digital printing

Abstract
A printing device for digital printing on a print medium is comprised of a wheel rotatable by a motor, a liquid dispenser for depositing a quantity of liquid on the wheel along the outer edge, and an air jet positioned adjacent the outer edge for removing the liquid from the outer edge and directing the liquid toward the print medium as the wheel rotates through the air jet. The outer edge includes a plurality of teeth transport the paint from the dispenser to the air jet. An electronically controlled motor is used to selectively rotate the wheel through the air jet thereby removing a desired amount of liquid from the wheel. The liquid is transported by the air jet toward the print medium. By employing a plurality of such printing devices, a full color digital image can be reproduced on any print medium.
Description




BACKGROUND




1. Field of the Invention




This invention relates generally to a method and apparatus for digital printing and, more specifically, to a method and apparatus that employs a metering device for metering a quantity of paint to be deposited on a surface to be painted and that deposits the metered quantity of paint on the surface.




2. Background of the Invention




Large format printing, such as the printing of billboard signs and building drapes, has generally followed printer technologies used in smaller scale printers, such as thermal and piezoelectric ink jet technologies. Such technologies, when employed for large scale printing, are relatively expensive, with large format thermal ink jet printers costing the range of about $250,000 to $350,000 and large format piezoelectric printers costing about $700,000 to $800,000.




Such ink jet printers work by depositing small droplets of ink in various colors, typically cyan, magenta, yellow and black, on a print medium to form a color image. Conventional thermal ink jet printing heads include a plurality of nozzles and thermal elements. Ink is expelled from the nozzles in a jet by bubble pressure created by heating the ink by the thermal elements while the nozzles and thermal elements are in close proximity. One such ink jet printing head, as described in U.S. Pat. No. 5,121,143 to Hayamizu, includes a thermal head member having at least one thermal element consisting of a plurality of thermal dot elements and a plurality of electrodes of different widths connected to each thermal element whereby different widths of heated portions of the thermal element are obtainable to vary the amount of ink jetted in one dot. Another such ink jet printing head is described in U.S. Pat. No. 4,731,621 to Hayamizu et al.




Another type of print head is disclosed in U.S. Pat. No. 4,764,780 to Yamamori et al. in which an ink ejection recording apparatus includes a plurality of ink ejection heads connected to an ink tank, each of the ink ejection heads having an ink nozzle through which minute ink droplets are discharged in accordance with an electric signal and an air nozzle opposing the ink nozzle and adapted for forming an air stream which accelerates the ink droplets toward a recording medium.




Typical desk top ink jet printers for home or office use are relatively inexpensive but are usually limited to printing on standard office size sheets of paper, such as 8½×11 or similar standard sizes. Some wide format printers, however, are able to accommodate 16 feet or wider substrates such as films, paper, vinyl, and the like and can print 300 ft


2


per hour, depending on the resolution of the print. Such machines sometimes employ piezoelectric printhead technology utilizing several printheads per color with numerous nozzles per printhead to deposit ink onto the print medium.




In addition to the cost of the machine itself, which employs relatively small orifices, valves and nozzles for depositing the desired quantity and color of ink on the print medium, very fine grade inks are required in which particle sizes of the pigments within the inks are kept to a minimum to help keep the orifices, valves, and nozzles of the ink system from becoming clogged. Such inks are expensive and thus result in billboard sized prints to be rather expensive. Despite the high quality and expense of ink products, clogging of the printhead is still a problem with current printer technologies.




Many large format printers also use water-based inks that may not be suitable for outdoor use. Accordingly, special waterproofing systems and techniques must be employed such as treating the printing medium with a substance that binds with the ink once deposited to form a waterproof mark or laminating the print with a weatherproof film. These weatherproofing techniques and processes add expense to the cost of each print.




There are some applications for digital printing where the resolution is not a significant issue. These applications include very large signage such as large billboard signs or building drapes as were used in the 2002 Salt Lake City Winter Olympics. Billboards, which are typically about 14 feet×48 feet do not require extremely sharp resolution as the viewing distances are typically more than 100 feet away. Another application in which lower resolution imaging may have significant usefulness is in stadium graphics such as printing on football field end zones (both grass and artificial turf), grass infields of race car tracks and foul territories and warning tracks of baseball fields. Military applications include applying camouflage painting schemes to ship hulls, decks and structures, as well as tanks and large decoys. Other applications may include the printing of imagery on freeway embankments, roadways, and roof tops. Still other applications may include printing on carpet and other textiles. To obtain sufficient image coverage, large quantities of pigmented paint or sublimating dye are very desirable to produce a highly visible image. In situations where the media is a building drape, a rocky embankment, plush carpeting, or a grass field, such large quantities of paint are necessary to fill voids in media so that the desired image is visible. The volumes of paint needed to produce such images are much greater than ink jet technology could ever reasonably deliver. As such, current methods of painting football end zones include hand painting with rollers and other conventional paint application devices to produce a desired image. Such methods are extremely time consuming and require significant manpower to accomplish.




In the case of building drapes, such as those used in the 2002 Winter Olympics in Salt Lake City, the fabric was a screen-type material that would allow air to easily pass through the fabric. Because of the difficulty in applying paint to such materials using current state of the art techniques, the building drapes were not only of quite low resolution, but were generally washed out in both vibrancy and color.




Thus, it would be advantageous to provide a method and apparatus for producing images on virtually any medium including highly porous media or media having significant voids where large quantities of paint are necessary to produce a desired image. Furthermore, it would be highly advantageous to provide a method and apparatus for digital printing that is compatible with any paint including fast drying paints such as all surface acrylic enamels. It would be a further advantage to provide a method and apparatus for digital printing that is compatible with extremely inexpensive paints, such as common house paints. Digital printing with sign type ink jet inks can run up to $0.50 per square foot. Typical ink prices run $0.20 per square foot. Cheap house paint can result in digital imaging paints costing between 2 and 3 cents per square foot. Such capability is very significant in large signage applications which are now near commodity based pricing.




SUMMARY OF THE INVENTION




Accordingly, a paint injector is provided comprising at least one air nozzle that directs a jet of air across a moving member, the member having ink, paint, or other similarly pigmented liquid material disposed thereon. The air jet blows or pulls the paint off of the member and onto a print medium, such as paper, vinyl, film, grass, dirt, rock, asphalt, carpet, fabric or other textiles, or other print media known in the art. The moving member is comprised of a wheel having paint disposed on the outer rim or edge thereof.




In one embodiment, a relatively small saw-type blade or gear may be used as a miniature gear pump to meter paint for digital printing. The edge or teeth of the gear or blade grab paint within the gap between each tooth from a paint reservoir. The blade is advanced between a pair of air jets and the paint in the gap is blown off from both sides of the blade. As the blade continues to rotate it interlocks with a second blade having substantially the same teeth spacing and configuration. The engagement of the teeth between the first and second blades causes any paint remaining between each tooth of the first blade to be forced out by the interlocking nature of the blades. As the paint is removed from the teeth of the first blade, small scrapers are used to remove dried paint from the edges and surface of the blades.




The paint reservoir is comprised of a block having a slit therein for receiving a portion of the blade in one side thereof, the slit is in fluid communication with an internal reservoir containing paint. As the blade rotates through the slit, paint contained in the reservoir is received and maintained between the teeth of the blade as the portion of the blade containing paint is rotated out of the block. As the blade continues to rotate, the teeth containing paint pass through one or more air jets directed at the teeth which remove the paint from between the teeth and transport the paint onto a print medium.




In another embodiment, a toothless wheel is provided in which paint is applied to the outer edge or rim of the wheel. The paint may be applied by a roller or other metering device. As the paint coated portion of the wheel passes through one or more air jets, the paint is blown from the edge of the wheel and onto the print medium.




While the air jets can be configured to remove nearly all of the paint from the blade, wheel or gear, for some quick drying paints or materials, there may be a need to provide a means of removing paint from the side surfaces of the blade, wheel or gear. As such, various scrapers may be positioned proximate or in contact with the surface of the blade to be cleaned so that upon rotation of the blade, the scraper can remove any paint deposited thereon. Such paint removal keeps the blade, wheel or gear, as the case may be, in a clean condition to ensure that the amount of paint being metered by the blade, wheel or gear is relatively precisely controlled.




Digital painting in each color occurs by using a computer to selectively control the advancing a paint coated blade or wheel through an air stream to remove the paint and project it onto a surface. The air stream remains relatively constant. Paint modulation for digital printing is achieved by the controlled advancement of the wheel through the air stream. By including multiple blades or wheels associated with multiple paint colors and controlling the position of each blade or wheel relative to the medium, digital painting can be accomplished to reproduce a preselected digital image onto a selected medium.




The present invention may be employed to apply paint to various medium regardless of the porosity of such medium. For example, grass fields, carpets and building drapes can be digitally painted with the printing device and techniques of the present invention.




It is also contemplated that the present invention may be employed to deposit other liquid, liquid-based or bondable materials onto or toward a surface in a relatively precise and controlled manner. That is, there is often a need to apply oils, finish materials, such as acrylics or polyurethanes to a surface in a controlled manner to produce a desired result, such as film thickness. Additionally, the present invention may be employed to apply such materials as etchants for glass applications as well as materials that may be employed in various masking operations, such as photo resists. The present invention, while being described with reference to “digital printing” by way of example may employ such instruments and techniques to other applications in various other fields of art.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a front view of a first embodiment of a paint injector in accordance with the present invention;





FIGS. 1A

,


1


B and


1


C are side, partial side and cross-sectional views, respectively, of an air manifold in accordance with the principles of the present invention;





FIG. 1D

is a partial, close-up side view of a bladed wheel in accordance with the principles of the present invention;





FIG. 2

is a partial side cross-sectional view of the printing device of

FIG. 1

;





FIGS. 2A

,


2


B,


2


C and


2


D are bottom, end, top and side cross-sectional side views, respectively of a paint reservoir in accordance with the principles of the present invention;





FIG. 3

is a partial end view of the printing device shown in

FIG. 1

;





FIG. 4

is a top view of the printing device shown in

FIG. 1

;





FIG. 5

is an end view of the printing device shown in

FIG. 1

;





FIGS. 6A

,


6


B, and


6


C are top, front and side views, respectively, of a first embodiment of a partially assembled print head in accordance with the principles of the present invention;





FIGS. 7A

,


7


B and


7


C are top, front and side views, respectively, of a further assembled print head of the print head shown in

FIG. 6A

;





FIGS. 8A

,


8


B and


8


C are top, front and side views, respectively, of a further assembled print head of the print head shown in

FIGS. 6A and 7A

;





FIGS. 9A

,


9


B,


9


C and


9


D are bottom, front, side and top views, respectively, of a further assembled print head of the print head shown in

FIGS. 6A

,


7


A and


8


A;





FIGS. 10A

,


10


B and


10


C are top, front and side views, respectively, of a further assembled print head of the print head shown in

FIGS. 6A

,


7


A,


8


A and


9


A;





FIGS. 11A

,


11


B and


1


C are top, front and side views, respectively, of a further assembled print head of the print head shown in

FIGS. 6A

,


7


A,


8


A,


9


A and


10


A;





FIG. 12

is a front view of a wall printer assembly in accordance with the principles of the present invention;





FIGS. 13A and 13B

are side and partial front views of a carpet printer assembly in accordance with the principles of the present invention;





FIG. 14

is a partial side view of a second embodiment of a bladed wheel in accordance with the principles of the present invention;





FIGS. 15A and 15B

are front and side views of a second embodiment of a printing device in accordance with the principles of the present invention;





FIG. 15C

is a front view of a third embodiment of a printing device in accordance with the principles of the present invention;





FIG. 15D

is a partial top view of the application wheels of

FIG. 15D

;





FIG. 16

is a partial side view of a third embodiment of a wheel in accordance with the principles of the present invention;





FIG. 17

is a partial side view of a fourth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 18

is a partial side view of a fifth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 19

is a partial side view of a sixth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 20

is a partial side view of a seventh embodiment of a wheel in accordance with the principles of the present invention;





FIG. 21

is a partial cross-sectional side view of an eighth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 22

is a partial cross-sectional side view of an ninth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 23

is a partial cross-sectional side view of a tenth embodiment of a wheel in accordance with the principles of the present invention;





FIG. 24

is a partial cross-sectional side view of an eleventh embodiment of a wheel in accordance with the principles of the present invention; and





FIG. 25

is a partial cross-sectional side view of an twelfth embodiment of a wheel in accordance with the principles of the present invention.











DETAILED DESCRIPTION




Referring to

FIG. 1

, a printing device, generally indicated at


10


, in accordance with the present invention is illustrated. The printing device


10


is comprised of a rotatable wheel


12


mounted relative to a frame assembly


11


. The use of the term “wheel” herein is intended to encompass any such like structure including one or more disks, blades and spoke-like structures that have an outer edge that can carry a liquid in accordance with the principles of the present invention. The wheel


10


is in fluid communication with a liquid dispenser


14


having a base member


16


and a liquid reservoir


18


. The wheel


10


is partially inserted into the base member


16


and in fluid communication therewith for receiving a liquid, such as one of paint, ink, die, etchant, solvent, oil, acrylic, and polyurethane. While such materials can be applied utilizing the printing device


10


of the present invention, the remainder of the discussion will focus upon the use of the printing device


10


to apply paint, knowing that a simple substitution of materials may be employed to apply such other materials.




The liquid dispenser


14


also includes a liquid source


19


, in this example, a tube containing paint


20


coupled to a fitting


21


that is in turn coupled to the base member


16


. The paint


20


contained in the reservoir


18


is applied to the outer edge


22


of the wheel


12


as the outer edge


22


passes through the base member


16


. As the wheel rotates in a counter-clockwise direction, the paint coated portion of the wheel


12


rotates between a pair of air jets


25


emanating from a pair of pressurized tubes, only one tube


24


of which is visible. The air jet removes the paint


20


from the outer edge


22


and blows the paint toward a print medium


26


.




As further shown in

FIGS. 1A-1C

, the tube


24


is provided with a flat portion


2


so as to allow clearance for the wheel


12


. Proximate the flat portion


2


is orifice set


6


. The orifice set


6


shown in

FIG. 1B

, comprises three orifices


9


,


13


and


15


. The orifices extend through the side wall of the tube


24


so that pressurized air within the tube


24


creates air jets emanating from the orifices


9


,


12


and


15


. Each set of orifices is configured to remove paint from one side of a particularly associated wheel containing paint thereon. In addition, multiple orifices in each orifice set is configured to not only remove the paint from the wheel, but to focus the paint toward a single point on the print medium. Thus, the orifice


15


, for example may be directed at the wheel to remove paint in a purely radial direction, while the orifices


6


and


13


are angled above the air jet created by orifice


15


to help eliminate conical divergence of the paint as it is pulled from the surfaces of the wheel. For a print head assembly comprising a plurality of printing devices, as will be described herein, a longer tube with a plurality of orifice sets will be provided, with one orifice set provided for each wheel of the print head.




A freely rotatable cleaning wheel


30


is secured proximate the wheel


12


and engages the outer surface thereof. In the case where the wheel


12


is provided with a plurality of teeth along the outer edge


22


, the cleaning wheel


30


is also provided with a plurality of teeth along its outer edges having a size and pitch to substantially match the size and pitch of the teeth of the wheel


12


. As the wheel


12


rotates, the cleaning wheel


30


is caused to rotate therewith in a gear mating arrangement. This meshing of teeth of the two wheels


12


and


30


causes any residual paint contained in interstices between adjacent teeth to be forced out prior to reentry of the teeth into the reservoir


18


. As such, the quantity of paint contained in the teeth of the wheel


12


during each revolution remains relatively constant without the possibility of dried paint clogging the gaps between teeth.




As shown in

FIG. 1D

, which shows a partial close-up view (not to scale) of the wheel


12


, the paint


20


is held in the interstices or gaps between adjacent teeth


32


by surface tension in the paint. Moreover, the paint


20


covers a portion of the side surface of the wheel


12


above the teeth


32


as well as the side surfaces of the teeth


32


. Thus, in order to remove substantially all of the paint


20


from the wheel, the air jet is directed at a point P above the line L representing the edge of the paint


20


on the wheel


12


. As the paint


20


is pulled from the side surfaces of the wheel


12


by the air jet, the paint in the gaps between teeth


32


is also pulled therefrom such that the wheel is substantially cleaned as it passes the air jet. Moreover, flow of air over the edges formed by the teeth


32


causes any paint


20


to be pulled from all surfaces of the wheel


12


, even those surfaces at the bottom of the teeth


32


. Sharp edges of the teeth


32


also facilitate atomization and release of paint from the wheel


12


.




The wheel


12


and the cleaning wheel


30


may be formed from two slitting saw blades, with the wheel


12


used as a miniature gear pump to meter paint for digital printing. The edge of the wheel


12


grabs paint within the gap of each tooth from the paint reservoir


18


. The wheel


12


is advanced in front of an air jet and the paint in the gap is blown off from both sides. As the wheel


12


continues to rotate, it interlocks with the cleaning wheel


30


. Any paint remaining between each tooth is forced out by the interlocking nature of the blades. Small scrapers may also be used to remove dried paint from the edges and/or side surfaces of the wheels


12


and


30


.




Air being blown from the tubes through their respective nozzle orifice disperses or pulls paint from the wheel


12


to the print medium


26


. Depending on the viscosity of the paint, the width of the wheel


12


and the radial width of the paint proximate the outer edge of the wheel, a relatively precise amount of paint can be effectively metered by advancing the motor and thus rotating the wheel


12


a relatively precise fraction of a rotation. Such an apparatus may produce images having a resolution of approximately 10 dpi or better, which is more than adequate for large signs such as billboards, grass painting and the like.




While an air stream has been described as the preferred vehicle for transporting the paint from the wheel to a print medium, it is also contemplated that other fluid streams, such as thinner, steam, or other materials known in the art, may be employed or mixed with air or another gas to transport the paint from the wheel


12


to a print medium.




As shown in

FIG. 2

, the plurality of teeth


32


along the outer edge


34


of the wheel


12


mesh with the plurality of teeth


36


disposed around the cleaning wheel


30


. The size and spacing or pitch of the teeth


32


are substantially the same as the teeth


36


on the cleaning wheel to allow engagement of the teeth


32


and


36


in a gear-like manner. Moreover, depending upon the diameter of the wheel


12


and the diameter of the cleaning wheel


30


, the several teeth


32


and


36


on each wheel


12


and


30


, respectively, can simultaneously mesh together to provide a range of engagement


38


. As the wheel


12


rotates as in a counter-clockwise direction as indicated by the arrow and teeth


32


and


36


mesh together, the teeth


36


of the cleaning wheel force out any paint residue that may be contained within the interstices


40


between adjacent teeth


32


of the wheel


12


. This occurs after the outer edge


34


has passed through the air jets (not shown) but before the outer edge


34


has entered the paint dispenser


14


.




As further shown in

FIGS. 2A-2D

, as the outer edge


34


and thus the teeth


32


of the wheel


12


enter the reservoir


14


, they enter into a slot or channel


42


formed in the base member


16


of the dispenser


14


. The base member


16


is formed from a single block of material, such as aluminum. The slot


42


has a bottom curved surface


43


that matches the radius defined by the outer tips


44


of the teeth


32


. Indeed, the slot


42


may be formed by inserting the wheel into the block


16


as it rotates, thus cutting its own slot to provide relatively tight tolerances between the surfaces of the slot, both side walls and bottom, and the surfaces of the wheel


12


that enter the slot


42


.




The reservoir


18


of the dispenser


14


is comprised of a primary chamber


46


which feeds a secondary chamber


48


. The secondary chamber


48


is in fluid communication with the slot


42


and exposes a section of teeth


50


therein into which paint


20


contained in the reservoir


18


can flow. As the section of teeth


50


rotate out of the secondary chamber


48


, the contact between the surfaces of the wheel


12


and the surfaces of the slot


42


cause paint not contained within the interstices


40


between teeth


32


to remain with the secondary chamber


48


. In addition, a raised sections


45


and


47


proximate the opening into the secondary chamber


48


extending toward the wheel


12


are provided about the slot


42


to further scrape paint from the sides of the wheel


12


as the wheel rotates relative thereto to clean the side surfaces of the wheel


12


. The raised portions


45


and


47


are positioned on the entry side of the slot


42


, that is the side of the slot


42


that the wheel


12


first enters as it rotates. Such scraping maintains the amount of paint applied to the wheel


12


on each rotation so that the amount of paint applied to the wheel


12


along the outer edge


44


is substantially metered. Also, depending upon the fit between the wheel


12


and the slot


42


, more or less paint


20


can be allowed to be applied to the outer edge


44


and the side surfaces of the wheel


12


proximate the outer edge


44


. Thus, in situations where initiated paints, such as thermal-setting paints or UV curable paints that require exposure to dry, more paint can be deposited for the same amount of wheel


12


rotation, the gap between the wheel


12


and the slot


42


can be widened by either providing a block


16


with a wider slot


42


, utilizing a thinner wheel


12


, or utilizing a wheel with a slightly smaller outer diameter.




As further illustrated in

FIG. 3

, the wheel


12


is attached to the shaft of a motor (not visible) with a hub


52


concentrically attached to the center of the wheel


12


. The wheel


12


passes between a pair of tubes


54


and


56


that are positioned adjacent to the outer edge


22


of the wheel


12


each include at least one transversely extending bore


58


and


60


, respectively, through a side wall thereof that are angled inwardly toward the wheel


12


and outwardly toward the outer edge


22


. The bores


58


and


60


form nozzle orifices for producing air jets when the inside of the tube is pressurized. As the tubes


54


and


56


are pressurized with air (or other gaseous or liquid substance) to form air jets


62


and


64


, respectively. The tubes


54


and


56


are coupled to an a manifold assembly


77


(as shown in

FIG. 4

) that provides air to and between air each printing device


10


. The air jets


62


and


64


are oriented to contact the side surfaces


66


and


68


, respectively, of the wheel


12


at a point away from the outer edge


22


of the wheel


12


. This provides a flow of air over a portion of the side surfaces


66


and


68


proximate the outer edge


22


to remove paint not only being carried on the outer edge


22


of the wheel


12


, but also being carried on the side surfaces


66


and


68


. As the air jets


62


and


64


travel over the side surfaces


66


and


68


and past the outer edge


22


of the wheel


12


, paint is pulled from the surfaces


66


and


68


and the outer edge and carried in the air jets


62


and


64


toward a desired print medium (not shown).




Referring now to

FIGS. 4 and 5

, a motor


70


is secured to the frame member


11


to rotate the wheel


12


. The motor is comprised of a 2-phase high torque stepper motor. For example, the stepper motor may be a HT23-400-D stepper motor from Applied Motion. The HT23-440-D motor is a Nema 23 style motor, high torque, double shaft motor with 8 leads, 1.8 degree step angle, 187 oz-in, a motor length of 2.99″, 2 Amps, and 4.5 Volts. Alternatively, a micro-stepping drive could be coupled to the 2-phase stepper motor to further resolve the 1.8 degree step angle into smaller steps.




A motor damper


71


, such as an Oriental Motor D6CL-6.3 damper, is attached to the distal end


73


of the motor


70


. Such a damper is provided with a 0.25″ shaft size is 3.46 oz. and has a 1.01 oz.-in×in. rotational inertia. The damper


71


allows for higher speed printing. That is, the printing process in accordance with the present invention provides that the paint from the printing device is quickly started and stopped depending upon the desired color to be deposited. Thus, because the print head passes over the media surface at a uniform speed, each color motor is required to quickly accelerate and decelerate through a variety of speeds. This can result in torsional resonances in the motor and motor stalling. The damper


71


eliminates most of these problems by preventing resonance within the motor


70


. Alternatively, while typically being more expensive, a 5-phase motor could be used to bypass the torsional resonance problems. Alternatively, a servo motor could be used to bypass the resonance problems.




The motor


70


is electronically coupled to a computer


75


that controls rotational operation of the motor, both in number of rotational steps and timing. Separate control of each individual paint motor


70


allows for digital printing in multiple colors, with each printing device


10


printing a particular color. The computer


75


is provided with software to control not only rotation of the motor


70


, but also position of the printing device


10


relative to a print medium (not shown). Thus, once input into the computer


75


, a digital image can be reproduced by the printing device


10


, and as will be described in more detail, herein, by utilizing multiple printing device


10


together, a full color digital image can be reproduced on virtually any print medium.




The rotation of the shaft of the motor


70


with the controller or computer


75


is accomplished by converting digital signals from the computer into alternating phase currents for causing one or more rotational steps of the motor


70


. Such signals are discrete signals to instruct selective rotation of the shaft of the motor


70


. In the case where the motor


70


is a stepper motor, the signals are sent in the form of electrical pulses, each pulse designating a single step or micro-step that the shaft of the stepper motor


70


is to rotate. A typical stepper motor provides 200 steps per revolution with each step being activated by a current in the range of several amperes, depending on the current requirement of the motor. Thus, if it is desired to deposit the quantity of paint deposited on the wheel


12


in one half of a revolution of the wheel


70


, 100 pulses would be sent by the computer


75


with each pulse converted by circuitry into alternating phase currents depending on the current requirements of the stepper motor


70


sufficient to cause the stepper motor


70


to rotate its shaft one step, and the shaft would rotate 100 steps.




One way of driving the motor


70


is to perform all shaft advances for the printing device by time calculations made thereby eliminating the need of a calculating device within the printing device itself. Thus, all wheel


70


advances for the same color of paint, in addition to spatial motions of the printing devices relative to a print medium for depositing a metered paint at relatively precise locations, can be made by the computer


75


.




If a DC servo motor is employed, the signal sent from the computer


75


would be converted into a voltage by the circuitry necessary to rotate the shaft of the DC motor a desired portion of a rotation. A feedback device, such as an optical encoder, would be employed to control the precise rotation of the shaft of the motor


70


. It is also contemplated that a crude metering of paint could be accomplished by simply providing a timed duration of power to a direct current, induction, air, or other similar motor without feedback.




A pair of air feed tubes


72


and


74


supply pressurized air to the tubes


54


and


56


. This pressurized air is used to blow the paint from the wheel


12


at the desired location and in the desired quantity on a print medium. The paint dispenser


14


sits atop the wheel


12


and is aligned such that a portion


50


of the wheel


12


extends into the base


16


of the dispenser


14


for receiving paint therefrom.




If paint accumulates on the wheel


12


, various scrapers, in the form of threaded fasteners


76


and


78


, are positioned to having their distal ends in contact with or close to both side surfaces of the wheel


12


. By placing the scrapers


76


and


78


at the point of contact or near the point of contact between the wheel


12


and the cleaning wheel


30


, the scrapers


76


and


78


not only keep paint from accumulating on the side surfaces of the wheel


12


, but keep the wheel


12


and the cleaning wheel


30


in lateral alignment relative to each other.




Referring now to

FIGS. 6A

,


6


B and


6


C, in order to achieve digital printing in multiple colors, a print head assembly, generally indicated at


100


, is comprised of a plurality of individual printing devices in accordance with the present invention. While a four color print head may be sufficient for printing on white print media, a five color print head


100


as illustrated includes white as a color to allow printing on non-white surfaces, such as green grass. The print head


100


is provided with five printing devices


102


,


104


,


106


,


108


and


110


. The five printing devices


102


,


104


,


106


,


108


and


110


are provided with one of yellow, magenta, cyan, black and white. With these five colors, the print head


100


can produce virtually any color in the color spectrum.




In order to better describe the components of the print head


100


, the following drawings show the print head in various stages of assembly. As shown in

FIGS. 6A-6C

, the print head


100


is first assembled by attaching five motors


111


-


115


to a frame member


116


, in this example an elongate plate having various holes and apertures formed therein for attaching and allowing access to the various components of the print head


100


. Each motor


111


-


115


is provided with its own dampener


121


-


125


as previously described. The motors


111


-


115


are attached to the frame member


116


with a plurality of bolts


117


and


119


such that the motor is positioned on the back side of the frame member


116


with the shaft


121


of each motor extending through the frame member


116


to the front side thereof. Various scrapers


118


,


120


and


122


may also be attached to the frame member


116


. Two bolt heads and a set screw are locked in place to form scraping and alignment functions for each wheel or blade. These screws are placed at various radiuses from the motor shaft


121


to cause the dried paint to be plowed away from the air jet structure. Dried paint is disposed of as it falls out of the mechanism and on the floor or into a tray (not shown). The height of the bolt heads and set screw are adjusted to just make contact with the wheel or blade. As dried paint builds on the blade it is scraped away as the blade rotates and the paint makes contact with the fixed screw heads and set screw.




While the presently described print head


100


shows use of a different motor with each printing device, it is also contemplated that a single motor could be used for more than one printing device. For example, a transmission-type gear system could be employed to switch the motor between printing devices so that the motor drives the desired printing device as needed. Such a system, however, would likely be more complicated than the present embodiment which utilizes direct drive with a single motor for each printing device.




As further shown in

FIGS. 7A

,


7


B, and


7


C, the next step in the assembly process is to attached a wheel or blade


131


-


135


to each motor shaft. Each wheel


131


-


135


is mounted to a hub


136


that allows each wheel


131


-


135


to be mounted to its respective motor shaft. The hub may be attached to the wheel with metal bonding epoxy or other suitable attachment means such as welding or mechanical attachments known in the art. As shown in

FIG. 7C

, the wheel


131


is placed on the shaft


121


so that the back side of the wheel just contacts the scraping device


122


. Thus, the hub


136


is attached to the shaft


121


at a point where the blade


131


is flush and in contact with the screw heads and set screw


122


discussed herein. This is repeated for each of the other wheels


132


-


135


. A commonly available blade that works well with the present invention is blade part number 03296100 available from MSC Industrial Supply Co. and described as a high speed steel jewelers saw with a 2.5″ outer diameter, a ½ inch hole, a thickness of 0.010 inch and 240 teeth disposed around its outer edge.




Thicker blades can be utilized for carrying more paint than thinner blades. The blade is concentric and perpendicular to the motor shaft. Supporting mounts


140


and


142


are attached to the back side


144


of the frame member


116


that, as will be described herein, are used to attach the print head


100


to the printer carriage. In

FIGS. 8A

,


8


B and


8


C, a second blade


151


-


155


is mounted so that the teeth of the second blades


151


-


155


mesh perfectly with the teeth of the first blades


131


-


135


, respectively. The second blades


151


-


155


may be of a smaller diameter than those of the first blades


131


-


135


to conserve space. Such a blade is available as part number 03289121 from MSC Industrial Supply Co. and described as a high speed steel jewelers saw with a 1.0 inch outer diameter, ¼ inch center hole, a thickness of 0.012 inch and 98 teeth. By calculating the tooth pitch of the first and second blades, the blades can be matched to ensure that the teeth will properly mesh. A slightly thicker second blade can be used to ensure complete cleaning of the interstices formed between blade teeth of the first blade. Different combinations of blades and tooth pitches can be also be utilized. For example, part number 03296233 HSS Jewelers Saws with a 2.5 inch diameter, a hole diameter of ½ inches, a 0.023 inch thickness, and 190 teeth can be used to interface with part number 03289329 HSS Jewelers Saw with a one inch diameter, a ¼ inch hole, a thickness of 0.032 inches and 76 teeth.




As previously discussed, the height of the second or cleaning blade is kept aligned with the first blade by the set screw


122


. As will be described herein, the outer edges of the blades will be sandwiched between a set screw mounted on the opposite side. The cleaning blade rotates on a shaft


157


formed from water-hardening tool steel drill rod, letter size ‘D’, 0.246 inch diameter. Black oxide steel set screw type shaft collars


158


and


159


with bore diameters of ¼ inch, outside diameters of ½ inch, and widths of {fraction (5/16)} inch are used to hold the cleaning blade


151


in position. The drill rod extends through an oblong hole in the frame member


116


plate. Utilizing two set screws


147


and


148


, the second blade


151


is differentially held while the blade


151


can be moved relative to the oblong hole so that the blade


151


can be brought into substantially precise radial alignment with the blade


131


. In addition, the differential set screws can be adjusted for blade wear. The collars


158


and


159


that sandwich the cleaning blade


151


are set so that there is about a 0.001 inch gap between the blade and the collars. This gap allows the blade


151


to rotate freely on the drill rod.




As shown in

FIGS. 9A

,


9


B,


9


C, and


9


D, an air system, generally indicated at


160


is mounted to the frame member


116


. The air system


160


is comprised of a pair of tubes


162


and


164


, such as elongate brass tubes. The tubes


162


and


164


are held and supported in position to sandwich the blades


131


-


135


blades with the tubes


162


and


164


forming a gap


166


therein between. The gap


166


is formed by milling flat sides on the sides of the tubes


162


and


164


facing the blades to provide additional clearance.




At least five holes are drilled into the side of each tube, at least one for each blade. The holes are angled so that they point at the blade teeth closest to the media. The holes may be approximately 0.025 inch in diameter. An air supply feeds each of the tubes


162


and


164


at about 30 psig. The holes are positioned to blow air at the same point on opposite sides of each blade. The air supply provides constant pressure within the tubes


162


and


164


so as to provide continuously blowing air jets from the tubes


162


and


164


, even when the blades are not rotating. As the blade is rotated, paint captured between adjacent teeth is brought to a point where the two air jets are focused. The captured paint is pulled from the blade and blown on to the media. The resulting air vector from the pair of air jets on each blade radially extends from the blade. Additional holes may be provided in the tubes


162


and


164


to serve to collimate the paint beam to provide a higher resolution and sharper edges on the media surface.




Referring now to

FIGS. 10A

,


10


B, and


10


C, an alignment member


170


, in this example, an elongate bar is added to the side opposite the frame member


116


. The alignment member


170


is provided to attach threaded fasteners


171


-


175


thereto. The fasteners or screw ends are positioned opposite the scraper set screws attached to the frame member


116


as previously described. The screw ends scrape the opposite sides of each blade to remove any dried paint therefrom. The screw ends also provide alignment of the small and large blades as they sandwich the edges of the blades together.




In

FIGS. 11A

,


11


B and


11


C, a paint dispenser/reservoir


181


-


185


is added to apply paint to each blade


131


-


135


. In this example, the paint reservoirs


131


-


135


has a length of ¾ inch diameter vinyl tubing


191


-


195


, respectively. The length is such to provide sufficient paint for a period of printing. It is also contemplated that a feeder mechanism can be added to the printer to add more paint to the reservoir automatically. Furthermore, a built-in software alarm can be provided to alert an operator to manually add more paint if paint is needed.




The tubes


191


-


195


fit on a nylon barbed fitting, such as fitting


196


shown in

FIG. 11C

, that is held in place with a set screw on an aluminum block


197


attached to the frame member


116


. The only exit for paint in the block


197


is a slit or slot (as previously described) on the bottom side of the block


197


. The slot is aligned with the first blade with the block


197


is mounted and the slot is cut so that the blade slices into the block slot. The slot may be machined so that there is perhaps only 0.001 inch of clearance between the blade and the slot and yet the blade will rotate freely as it is lubricated by the paint and the pumping action suspends the blade therein. The purpose of the slot is to cause the only paint exiting the slot to be that paint between the teeth of the blade. Dried paint on the surface of the slot furthers this purpose by forming a seal between the blade and the slot. The paint in the tube may be gravity fed or have a head pressure, for example one to eight inches or more.




As shown in

FIG. 12

, the print head


100


is mounted to a vertical flat bed printing mechanism, generally indicated at


201


. The print head


100


may be mounted to print on a wall ceiling or floor. Only the various paint reservoirs comprised of vinyl tubing may need to be reoriented so that the fitting is positioned atop the block and the paint can flow by gravity into the block of each printing device. In the case where the paint is pressurized, such reorientation may not be needed as the paint pressure will maintain the paint within the block as needed for depositing on the blade. If desired, a mechanism for blowing or otherwise removing accumulated dried paint from the print head may be incorporated.




To selectively move the carriage


200


in an x-direction, the carriage


200


is mounted on a rectangular beam


230


in a track and trolley arrangement with a motor


232


provided to selectively control horizontal movement of the carriage


200


relative to the beam


230


. The motor


232


may be a stepper or servo motor computer controlled to control the position of the carriage


200


relative to the beam


230


. The motor


232


engages a timing belt (not visible) laid along the top of the beam


230


and secured at each end of the beam to the right and left frame members


268


and


270


, respectively. The timing belt wraps around a pair of idlers and a timing belt sprocket in a manner similar to the sprockets


248


,


252


and


254


with the motor


232


fixedly attached to the carriage


200


. The beam


230


is secured between right and left vertical drive assemblies, generally indicated at


234


and


236


, respectively. Each drive assembly


234


and


236


is comprised of a computer controlled drive motor


240


coupled to a drive system


242


. A belt


244


couples the output of the drive motor


240


to the input


246


of the drive system


242


. A worm gear (not shown) attached to the input


246


meshes with another gear (not shown) to rotate the drive sprocket


248


. The drive sprocket


248


engages with the links of the chain


250


to raise and lower the beam


230


upon rotation of the drive sprocket


248


. The motor


240


is either a stepper motor or a servo motor so as to allow precise control of the rotation of the shaft of the motor


240


. By employing a micro-stepping device or gearing ratios between the output of the motor


240


and the sprocket


248


, the vertical movement of the carriage


200


for each step of the motor


240


can be increased or decreased to likewise decrease or increase the line resolution of the printing as desired.




Idler sprockets


252


and


254


are provided to wrap the chain


250


around the drive sprocket


248


to provide engagement of a sufficient number of teeth of the drive sprocket


248


with links of the chain


250


so that disengagement of the drive sprocket


248


and the chain


250


is highly unlikely.




The chain


250


is tensioned between an upper mounting device


260


and a lower mounting device


262


. Likewise, the right and left drive assemblies


234


and


236


are held in tensioned relative to one another with cable


266


coupled between the right and left frame members


268


and


270


, respectively, to which the beam


230


and sprockets


252


and


254


, and drive assembly


242


are mounted.




The drive right and left assemblies


234


and


236


move in unison up or down to precisely control the vertical position of the carriage


200


and thus the precise position of each printing device


191


-


195


. It is also contemplated that the motor


240


could be mounted so as to directly drive the sprocket


248


without use of the on either the left assembly


236


or right assembly


234


or some other structure to lower the mass of the carriage


200


. Such a motor would then drive a moveable chain or belt to position the carriage


200


at the desired location.




The print head


100


may be mounted to the carriage


200


at a slight angle allowing the paint colors within injectors or printing devices


191


-


195


to be applied in a predetermined overlapping order during bi-direction printing. For example, the first pass of the print head


100


over the media


280


might apply white paint to the first line. The second pass of the print head over the media might apply white paint to the second line and black paint to the first line over the white paint thereon. The third pass might apply white paint to the third line, black paint to the second line and cyan paint to the first line, an so on. Thus, by printing only four extra passes of the print head, the paint could always be printed in a predetermined order such as white on the bottom, black on top of the white, cyan on top of the black, then magenta and finally yellow, with the print head printing bi-directionally (i.e., right-to-left and left-to-right) on alternating lines so as to speed up overall printing.




Thus, to selectively move the carriage


200


in a z-direction, the entire beam


230


, carriage


200


and right and left drive assemblies


234


and


236


are suspended with the chains


250


to an overhead structure such as a ceiling


272


with bracket assemblies


260


and


261


.




In order to keep the carriage


200


from swaying either away from a print medium


280


or from side to side, a track


282


may be vertically oriented and secured to the a support structure, such as a wall or frame, to which the print medium


280


is permanently or temporarily secured. The track


282


may have a J-shaped cross-section into which a guide attached to the frame member


270


can engage and slide relative to thereto. Such a guide member may comprises a threaded bolt having its head retained by the track


282


and its shaft secured to the frame member


270


. Accordingly, movement of the left assembly


236


is restricted from moving away from the print medium


280


or toward the right assembly


234


. Similarly, a second track, having an opposite orientation to the track


282


, may be secured to the wall to restrict movement of the right assembly from moving away from the print medium


280


or toward the left assembly


236


during printing. Those skilled in the art will recognize that other track and guide member assemblies could be employed to maintain the beam


230


in its appropriate horizontal position relative to the print medium


280


, such as a single C-shaped track and retaining member arrangement.




In operation, the print medium


280


is attached to a wall or support frame and positioned between the wall or support frame and the carriage


200


. A controller


286


, such as a computer, sends signals to the individual motors of the printing devices


191


-


195


to control dispersion of paint as well as sends signals to the motors


232


and


240


to control relative position of the carriage


200


to the print medium


280


. Such control of each color and the position of deposit of such color on the print medium allows for the formation of a digital image on the print medium


280


. Thus, signals from the controller


286


are sent to the motors


232


and


240


which in turn cause movement of the sprockets


248


along the chains


150


corresponding to the desired vertical or z-direction position of the print head


100


. Likewise, signals from the controller


286


are sent to the motor


232


which in turn drives the carriage


200


along the beam


230


corresponding to the desired horizontal or x-direction position of the print head


100


. The controller


286


also individually controls each of the paint injectors


191


-


195


to deposit the desired color and quantity of paint on the print medium


280


at the desired location. Thus, the printable image size of the wall printer assembly of

FIG. 12

is only limited by the length of the chains


250


and the length of the beam


230


.




The present invention also contemplates that the print head


100


and/or individual printing devices


191


-


195


could be employed with other digital printing devices known in the art for digital painting purposes. For example, the print head


100


could be employed in a device where movement of the print head is along an x-axis while a roll of print medium, such as vinyl, building drape material or carpet, is selectively advanced relative to the print head


100


to affect movement along the y- or z-axis. With such a device, the size of print medium may only be limited by the size of the roll of print medium. Likewise, a rigid frame to which the print head, according to the present invention, can be mounted and upon which the print head could be selectively moved could also be employed to allow z- and x-direction movement or x- and y-direction movement of the print head, depending on the orientation of the frame.




As shown in

FIGS. 13A and 13B

, a carpet printer assembly, generally indicated at


300


, is illustrated. The carpet printer assembly is comprised of a print head, generally indicated at


302


, in this case comprised of four printing devices


311


-


314


. The print head


302


rides on a welded box beam


316


. As compared with the print head


100


shown in

FIG. 12

, the printing devices


311


-


314


have be rotated ninety degrees such that the printing blades, such as blade


318


, rotates in a direction in line with the direction of feeding of the carpet


320


.




The carpet


320


is fed from a feed roll


322


, drawn over a round mandrel


324


to expose the nap, and wound on a take-up roll


326


driven by a take-up drive assembly


328


. The orientation of the blades


316


in line with the direction of the carpet feed, as indicated by the arrow, allows the blades


316


to print a wider area while keeping sharper resolution in the transverse direction, i.e., along the width of the carpet. When the fibers of the carpet nap close as it becomes flat after passing over the mandrel


324


, the resolution is automatically enhanced in the roll or feed direction of the carpet


320


.




As the print head


302


moves back and forth along the beam


316


, a portion of a digital image is reproduced on the carpet


320


. A transverse pass of the print head


302


occurs for each line of printing as needed to reproduce that portion of the digital image. The carpet


320


is then incrementally advanced to provide exposure of the next section of carpet


320


for receiving the next corresponding line of printing. The consistency of the distance or length of carpet advanced for each line of printing can be maintained by calculating the diameter changes, by an encoder on the nap spreading mandrel, or by a diameter measuring system which might be mechanical or optical. As such, the carpet printer


300


ensures that the width of each step of carpet


320


passing across the mandrel remains constant regardless of the diameter of the take-up roll


326


.




By positioning the print head


302


further away from the carpet the carpet


320


at the location of printing, it is less likely that fibers released from the carpet


320


as it passes over the mandrel


324


will collect in the print head


302


. Fiber or lint accumulation may be disposed of by various disposal means known in the art. For example, a vacuum system and/or an automatic cleaning system might be employed. Moreover, it may be desirable, depending upon the nature of the paint or ink and its relative drying time to providing a drying system to dry the paint before it is wound on the take-up roll


326


so as to prevent the paint or ink from depositing on the back of later layers of carpet on the roll


326


or causing such layers to stick to one another from the paint or ink. With fabric dies in particular, a steam system might be employed to set the fabric dyes prior to becoming rolled on the take-up roll


324


.




While the print head devices of the present invention have been described as a single integrated unit, it is also contemplated that each of the individual printing devices and/or components thereof may be incorporated into a replaceable cartridge assembly, which includes various components as desired. For example, a replaceable cartridge could simply include the paint reservoir with a particular color and type of paint included. Unlike conventional ink jet type ink cartridges, once the reservoir emptied, the user could easily refill the reservoir with the desired paint. Likewise, the cartridge may include the paint reservoir and associated wheel in a snap in type assembly. In this example, the moving part (e.g., the wheel) and parts in which the wheel are in contact as the wheel rotates that may wear over time can be simply and easily replaced with a new cartridge. In addition, should the wheel and paint reservoir become clogged with paint, the wheel and paint reservoir cartridge could simply be replaced. Because of the simplicity of the components, however, and their relative availability and/or ease of manufacturing, such components of the present invention may be easily replaced without the use of a separate replaceable cartridge.




As shown in

FIG. 14

, a blade


400


, a portion of which is illustrated, may include teeth


402


that have had their tips removed to produce flattened top or outer edges


404


. Because paint applied by the present invention tends to deposit on the blade


400


, not only in the gaps between adjacent teeth


402


but also along a portion of the side surface of the blade


400


proximate the teeth


402


, printing is more continuous. One might expect very digital type printing as paint is pulled from between the teeth in discrete droplets. As it happens, however, the paint, while primarily being held between teeth


402


, also flows over a small radial surface of the blade


400


. Because of this feature, it is also contemplated that a simple disk may be employed in accordance with the present invention.




As shown in

FIGS. 15A and 15B

, a smooth edge wheel or disk


500


is used to transport paint


502


to the air jets


504


and


506


so as to be blown off to the media surface


508


. The disk


500


rides in an annular or circumferential groove


512


formed in an application wheel or disk


514


. The transfer disk


500


causes the grooved application disk


514


to rotate as the edge


516


of the transfer disk


500


rides on the bottom of the groove


512


and turns the grooved disk


514


as the transfer disk


500


rotates The groove


512


in the grooved disk


514


is slightly wider than the transfer disk


500


so as to cause paint within the groove


512


to be transferred to the sides of the transfer disk


500


proximate the outer edge


516


by wetting the edge


516


and using surface tension. A third wheel or disk


520


, being thicker than the transfer disk


500


, also rides within the groove


512


of the grooved disk


514


. The third disk


520


has a width that is just slightly smaller than the width of the groove


512


while still allowing relatively easy rotation of the grooved disk


514


. As the third disk


520


engages the groove


512


and rotates caused by rotation of the grooved wheel


514


, the third disk


520


dislodges dried paint within the groove


512


of the grooved disk


514


. Both the grooved disk


514


and the thicker disk


520


are contained with the reservoir


502


of paint and ride on axils attached to side walls thereof. The bottom edge


522


of the grooved disk


514


is exposed to the transfer disk


500


and the groove


512


and a portion of it is exposed to both the interior of the paint reservoir


514


and the exterior of the paint reservoir


514


.




Likewise, as shown in

FIGS. 15C and 15D

, various other means of applying paint to a transfer disk


550


may be devised. For example, a smooth edge wheel or disk


550


is used to transport paint


552


to the air jets


554


and


556


so as to be blown off to the media surface


508


. The disk


550


rotates between a pair of freely rotatable paint application wheels


558


and


560


. The wheels


558


and


560


are held within a paint dispenser


562


coupled to a paint feed tube


564


. The dispenser


562


defines a paint feed chamber


566


that is in fluid communication with both the feed tube


564


and the wheels


558


and


560


to allow paint to flow from the feed tube


564


to the wheels


558


and


560


as needed. Rotation of the transfer disk


550


causes rotation of the application wheels


558


and


560


with the rotation of the application wheels


558


and


560


causing paint to be applied to the outer edge of the transfer disk


550


. Depending upon the position of the transfer disk


550


relative to the wheels


558


and


560


, a strip of paint can be applied along the sides of the transfer disk


550


up to the thickness of the application wheels


558


and


560


.




Both or one application wheels


558


and


560


may be contained with the dispenser


562


and ride on axils attached to side walls thereof. The outer circumferential surfaces


568


and


570


of the application wheels


558


and


560


, respectively, are provided with a plurality of transversely extending grooves. These grooves provide small gaps in the wheels


558


and


560


for paint to reside prior to being applied to the transfer disk


550


. The grooves also help to some extent to grip the sides of the transfer disk


550


so that the wheels


558


and


560


rotate as the transfer disk rotates


550


. It should be noted that by using a single application wheel and one air jet, paint applied to a single side of the transfer disk could be adequately removed with a single air jet air jet.




Further examples of transfer disk or wheel profiles are shown in

FIGS. 16

,


17


,


18


,


19


and


20


. In

FIG. 16

, a gear-type wheel


600


is shown with the teeth


602


,


603


and


604


performing similar to the bladed wheel described herein.




In

FIG. 17

, a wheel


610


with notches or transverse grooves


612


is illustrated. The grooves


612


provide places for paint to be deposited and held with surface tension on the outer edge


614


of the wheel


610


. It should be noted that the groove


612


shown may be of any width from a width similar to the spacing of teeth on the blades described above to much smaller slits that very closely spaced.





FIG. 18

shows a smooth edged disk or wheel


620


as described with reference to

FIGS. 15A and 15B

. As illustrated, the paint


622


is deposited in a band


623


proximate the outer edge


624


of the wheel


620


.




In

FIG. 19

, a wheel


630


has an outer edge


632


that defines a plurality of semicircular transverse grooves


634


,


636


and


638


that form a serrated outer edge


632


. Each channel or groove


624


,


636


and


638


provides a pocket for holing paint as the wheel rotates through the air jet of the present invention.




The wheel


640


of

FIG. 20

is similar to that of

FIG. 19

with the grooves


642


,


644


and


646


spaced apart to provide edge plateaus


643


and


645


along the outer edge


647


.




Likewise, as shown in

FIGS. 21

,


22


,


23


,


24


and


25


, various cross-sectional profiles of wheels may be employed in accordance with the present invention, with each profile providing some additional benefit, such as ease of cleaning with the air jets or paint holding capability.




As shown in

FIG. 21

, the wheel


700


may have a simple rectangular profile. Likewise, a wheel


702


may have a peaked profile. As shown in

FIG. 23

, the desired profile of a wheel


704


may be achieved by combining a pair of wheels


706


and


708


abutted together to form the desired profile, in this case forming a circumferential channel


710


to hold paint therein.




In reverse, the wheel


712


of

FIG. 24

provides a dome shaped outer edge


714


to facilitate paint removal therefrom as the air can easily flow over the surfaces of the outer edge


714


to pull paint therefrom.




Finally, as shown in

FIG. 25

, a pair of wheels


716


and


718


can be combined to form a circumferential V-shaped groove


720


extending around the wheel


722


.




Each of the forgoing cross-sectional profiles shown in

FIGS. 21-25

could be incorporated with any of the blade profiles shown in

FIGS. 16-20

or the blade configurations previously described.




It should also be noted that while one and three nozzle or orifice configurations have been illustrated and discussed, various other nozzle or orifice configurations may be equally effective for removing the paint from the wheel while reducing spray, spattering or divergence of the paint within the air stream and are thus contemplated within the scope of the present invention.




Spatter created by the paint impacting the print medium and by turbulent flow of air around the wheel may be controlled by controlling the pressure of air supplied to the orifice, and thus the velocity of the air stream. For example, an air pressure of approximately 10 psi would be sufficient to direct some paints and dyes toward the print medium and substantially clean the wheel while minimizing spatter. Higher pressures of 80 psi or more may have equal utility depending on the distance of the wheel from the print medium, the quantity of paint on the wheel, and the diameter of the air jet orifices.




It should be noted that having white paint added to the mix of colors, however, allows painting on any color of print medium. It is contemplated, however, that more or fewer paint injectors may be included with various colors contained therein depending on the desired colors of print produced.




Those of skill in the art will appreciate, after an understanding of the present invention, that various modifications to the present invention may be made without departing from the spirit and scope thereof. For example, the wheel or blade may have various configurations in addition to those specifically described. Moreover, there may be various ways of applying or depositing paint onto the wheel or blade.




In general, the invention comprises digitally controlling the rotation of a wheel in which the advancement causes paint or other liquid material to be deposited on the wheel. Once at least partially coated, further rotation of the wheel moves the liquid coated portion in front of a stream of fluid, such as air, to remove the liquid from the wheel and deposit it onto a print medium. It is noted that while references are made to paint in the specification and claims, the term is intended to encompass, inks, dyes, and any other liquid pigmented material that can be deposited on a surface for printing or painting purposes. Furthermore, the present invention clearly has application in other fields where liquid materials are to be applied to a surface at discrete and relatively controlled locations. In addition, it is to be understood that the above-described embodiments are only illustrative of the application of the principles of the present invention. Numerous modifications and alternatives may be devised by those skilled in the art, including combinations of the various embodiments, without departing from the spirit and scope of the present invention. The appended claims are intended to cover such modifications, alternative arrangements, and combinations.



Claims
  • 1. An apparatus for depositing a liquid on a medium, comprising:at least one wheel having an outer edge selectively rotatable by a motor; a liquid dispenser for depositing a quantity of liquid on said wheel proximate said outer edge; and at least one air jet positioned proximate said outer edge for directing a flow of air at said outer edge, said flow of air removing at least a portion of said quantity of liquid and carrying the at least a portion of said quantity of liquid toward the print medium as said wheel rotates through said flow of air.
  • 2. The apparatus of claim 1, wherein said outer edge of said wheel is comprised of a plurality of teeth.
  • 3. The apparatus of claim 1, wherein said motor comprises one of a stepper motor and a servo motor electronically controlled by a computer for selectively controlling the rotation of said at least one wheel and thus the quantity of paint removed by said at least one air jet.
  • 4. The apparatus of claim 1, wherein said liquid dispenser comprises a reservoir in fluid communication with said outer edge for depositing a quantity of liquid on said outer edge.
  • 5. The apparatus of claim 4, wherein said reservoir comprises a base member having a slot therein in fluid communication with an interior of said reservoir for receiving an edge of said wheel.
  • 6. The apparatus of claim 5, wherein said wheel fits at least partially within said slot in close tolerance thereto to allow the wheel to rotate within the slot with the slot cleaning the side surfaces of the wheel.
  • 7. The apparatus of claim 1, wherein said at least one air jet comprises a first air jet positioned on a first side of said wheel and a second air jet positioned on a second side of said wheel, said first and second air jets oriented toward a position proximate said outer edge of said wheel at an angle thereto to remove liquid on said wheel and direct the liquid away from the outer edge of the wheel.
  • 8. The apparatus of claim 7, wherein said first and second air jets each comprise primary and secondary air jets, said primary air jets positioned to remove liquid from said wheel in a direction radially extending from the center of said wheel and said secondary air jets angled toward said primary air jet to focus said liquid in line with the direction of flow of the primary air jets.
  • 9. The apparatus of claim 1, wherein said wheel is coupled to a shaft of the motor.
  • 10. The apparatus of claim 1, wherein said liquid dispenser comprises at least one second wheel rotatable by said at least one wheel, said at least one second wheel in fluid communication with a liquid reservoir and engaging said outer edge of said at least one wheel.
  • 11. The apparatus of claim 10, wherein said at least one second wheel comprises an annular groove for receiving said outer edge of said at least one wheel, wherein said annular groove of said at least one second wheel receives liquid from said liquid dispenser and rotation of said at least one wheel allows liquid within said annular groove to be deposited on said outer edge of said at least one wheel.
  • 12. The apparatus of claim 10, wherein said at least one second wheel comprises a serrated outer edge.
  • 13. The apparatus of claim 10, wherein said at least one second wheel comprises a pair of wheels oriented approximately ninety degrees to said at least one first wheel and each of said pair of wheels engaging opposite sides of said at least one first wheel proximate said outer edge.
  • 14. The apparatus of claim 1, wherein said liquid is comprised of at least one of paint, ink, die, etchant, solvent, oil, acrylic, and polyurethane.
  • 15. The apparatus of claim 2, further comprising at least one second wheel having teeth configured to match the pitch of the teeth on said at least one wheel, wherein rotation of said at least one wheel causes rotation of said at least one second wheel and wherein said at least one second wheel cleans the teeth of the at least one wheel.
  • 16. The apparatus of claim 15, further comprising at least one scraper for removing material cleaned by said at least one second wheel.
  • 17. An apparatus for depositing a liquified material on a surface, comprising:stream means for providing a fluid stream; wheel means for advancing a material disposed on at least an outer edge thereof through said stream means, said stream means oriented for removing said material from said wheel means; application means for applying said material onto said wheel means; and control means for selectively rotating said wheel means relative to said stream means and thus controlling the quantity of material removed from said wheel means by said stream means.
  • 18. The apparatus of claim 17, wherein said wheel means comprises at least one wheel having an outer edge, said application means comprises a dispenser for depositing a quantity of material on said wheel proximate said outer edge, said stream means comprises at least one air jet positioned proximate said outer edge for removing at least a portion of said quantity of material and directing the material toward a medium as said wheel rotates through said at least one air jet, and said control means comprises at least one of a stepper motor and a servo motor.
  • 19. The apparatus of claim 18, wherein said outer edge of said wheel is comprised of a plurality of teeth.
  • 20. The apparatus of claim 18, wherein said control means further comprises a computer for selectively controlling the rotation of said at least one wheel and thus the quantity of paint removed by said at least one air jet.
  • 21. The apparatus of claim 18, wherein said dispenser comprises a reservoir in fluid communication with said outer edge for depositing a quantity of liquid on said outer edge.
  • 22. The apparatus of claim 21, wherein said reservoir comprises a base member having a slot therein in fluid communication with an interior of said reservoir for receiving an edge of said wheel.
  • 23. The apparatus of claim 22, wherein said wheel fits at least partially within said slot in close tolerance thereto to allow the wheel to rotate within the slot with the slot cleaning the side surfaces of the wheel.
  • 24. The apparatus of claim 18, wherein said at least one air jet comprises a first air jet positioned on a first side of said wheel and a second air jet positioned on a second side of said wheel, said first and second air jets oriented toward a position proximate said outer edge of said wheel at an angle thereto to remove liquid on said wheel and direct the liquid away from the outer edge of the wheel.
  • 25. The apparatus of claim 24, wherein said first and second air jets each comprise primary and secondary air jets, said primary air jets positioned to remove liquid from said wheel in a direction radially extending from the center of said wheel and said secondary air jets angled toward said primary air jet to focus said liquid in line with the direction of flow of the primary air jets.
  • 26. The apparatus of claim 18, wherein said wheel is coupled to a shaft of the motor.
  • 27. The apparatus of claim 18, wherein said liquid dispenser comprises at least one second wheel rotatable by said at least one wheel, said at least one second wheel in fluid communication with a liquid reservoir and engaging said outer edge of said at least one wheel.
  • 28. The apparatus of claim 27, wherein said at least one second wheel comprises an annular groove for receiving said outer edge of said at least one wheel, wherein said annular groove of said at least one second wheel receives liquid from said liquid dispenser and rotation of said at least one wheel allows liquid within said annular groove to be deposited on said outer edge of said at least one wheel.
  • 29. The apparatus of claim 27, wherein said at least one second wheel comprises a serrated outer edge.
  • 30. The apparatus of claim 27, wherein said at least one second wheel comprises a pair of wheels oriented approximately ninety degrees to said at least one first wheel and each of said pair of wheels engaging opposite sides of said at least one first wheel proximate said outer edge.
  • 31. The apparatus of claim 18, wherein said liquid is comprised of at least one of paint, ink, die, etchant, solvent, oil, acrylic, and polyurethane.
  • 32. The apparatus of claim 19, further comprising at least one second wheel having teeth configured to match the pitch of the teeth on said at least one wheel, wherein rotation of said at least one wheel causes rotation of said at least one second wheel and wherein said at least one second wheel cleans the teeth of the at least one wheel.
  • 33. The apparatus of claim 32, further comprising at least one scraper for removing material cleaned by said at least one second wheel.
  • 34. An apparatus for digital painting, comprising:a frame; a plurality of printing units secured to said frame, each of said printing units comprising: at least one wheel having an outer edge selectively rotatable by a motor; a liquid dispenser for depositing a quantity of liquid on said wheel proximate said outer edge; at least one air jet positioned proximate said outer edge for removing at least a portion of said quantity of liquid and directing the liquid toward the print medium as said wheel rotates through said at least one air jet.
  • 35. The apparatus of claim 34, wherein said outer edge of said wheel is comprised of a plurality of teeth.
  • 36. The apparatus of claim 34, wherein each of said plurality of printing units further comprises a stepper motor electronically controlled by a computer for selectively controlling the rotation of said at least one wheel and thus the quantity of liquid removed by said at least one air jet.
  • 37. The apparatus of claim 34, wherein said liquid dispenser comprises a reservoir in fluid communication with said outer edge for depositing a quantity of liquid on said outer edge.
  • 38. The apparatus of claim 37, wherein each of said reservoirs contain a different color of paint.
  • 39. The apparatus of claim 34, further comprising a support structure comprises a left support assembly and a right support assembly, said frame being mounted and moveable between said left support assembly and said right support assembly.
  • 40. The apparatus of claim 39, wherein said right and left support assemblies are configured to allow movement of said frame along said right and left support assemblies.
  • 41. The apparatus of claim 37, wherein said reservoir comprises a base member having a slot therein in fluid communication with an interior of said reservoir for receiving an edge of said wheel.
  • 42. The apparatus of claim 41, wherein said wheel fits at least partially within said slot in close tolerance thereto to allow the wheel to rotate within the slot with the slot cleaning the side surfaces of the wheel.
  • 43. The apparatus of claim 34, wherein said at least one air jet comprises a first air jet positioned on a first side of said wheel and a second air jet positioned on a second side of said wheel, said first and second air jets oriented toward a position proximate said outer edge of said wheel at an angle thereto to remove liquid on said wheel and direct the liquid away from the outer edge of the wheel.
  • 44. The apparatus of claim 43, wherein said first and second air jets each comprise primary and secondary air jets, said primary air jets positioned to remove liquid from said wheel in a direction radially extending from the center of said wheel and said secondary air jets angled toward said primary air jet to focus said liquid in line with the direction of flow of the primary air jets.
  • 45. The apparatus of claim 34, wherein said wheel is coupled to a shaft of the motor.
  • 46. The apparatus of claim 34, wherein said liquid dispenser comprises at least one second wheel rotatable by said at least one wheel, said at least one second wheel in fluid communication with a liquid reservoir and engaging said outer edge of said at least one wheel.
  • 47. The apparatus of claim 46, wherein said at least one second wheel comprises an annular groove for receiving said outer edge of said at least one wheel, wherein said annular groove of said at least one second wheel receives liquid from said liquid dispenser and rotation of said at least one wheel allows liquid within said annular groove to be deposited on said outer edge of said at least one wheel.
  • 48. The apparatus of claim 46, wherein said at least one second wheel comprises a serrated outer edge.
  • 49. The apparatus of claim 46, wherein said at least one second wheel comprises a pair of wheels oriented approximately ninety degrees to said at least one first wheel and each of said pair of wheels engaging opposite sides of said at least one first wheel proximate said outer edge.
  • 50. The apparatus of claim 34, wherein said liquid is comprised of at least one of paint, ink, die, etchant, solvent, oil, acrylic, and polyurethane coating.
  • 51. The apparatus of claim 35, further comprising at least one second wheel having teeth configured to match the pitch of the teeth on said at least one wheel, wherein rotation of said at least one wheel causes rotation of said at least one second wheel and wherein said at least one second wheel cleans the teeth of the at least one wheel.
  • 52. The apparatus of claim 51, further comprising at least one scraper for removing material cleaned by said at least one second wheel.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 10/155,884, filed on May 24, 2002, which is a continuation of U.S. patent application No. 08/878,650 filed on Jun. 19, 1997, now U.S. Pat. No. 5,972,111.

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Continuations (1)
Number Date Country
Parent 08/878650 Jun 1997 US
Child 10/155884 US
Continuation in Parts (1)
Number Date Country
Parent 10/155884 May 2002 US
Child 10/165017 US