Multicolor thermal printing apparatus

Information

  • Patent Grant
  • 6262755
  • Patent Number
    6,262,755
  • Date Filed
    Tuesday, December 23, 1997
    26 years ago
  • Date Issued
    Tuesday, July 17, 2001
    22 years ago
Abstract
An apparatus and method for multi-color printing on plastic cards, such as credit cards, identification cards, and the like. The printing apparatus includes a rotatably driven cylinder having a smooth, high friction outer surface, and a plurality of color print stations spaced circumferentially about the cylinder. A receptor web supply roll is mounted adjacent to the cylinder and supplies an uninterrupted length of a receptor web to the outer surface of the cylinder. The receptor web is frictionally engaged with the outer surface of the cylinder such that the web rotates therewith when the cylinder is rotated. A stepper motor and gearing assembly is connected to the cylinder for rotating the cylinder, and therefore the receptor web that is disposed on the outer surface thereof, to position the receptor web relative to the color print stations. The stepper motor and gearing assembly allow precise positioning of the cylinder and the receptor web relative to each print head, to ensure precise print registration.
Description




FIELD OF THE INVENTION




This invention relates to color printers, and more particularly to a multicolor thermal printer to perform color printing on a receptor web material that is then mated with a plastic card so that the color image on the receptor material can be transferred onto the card.




BACKGROUND OF THE INVENTION




In a traditional color printer for plastic cards, a ribbon having three different color segments is passed by a single print head and the card is moved back and forth into position relative to the print head to allow each color to be printed. A problem with this type of printer is the relatively low throughput caused by the numerous back and forth movements of the card. Further, the numerous back and forth movements results in a printing process that is not smooth. In addition, a printer of this type cannot print to the edge of the card.




U.S. Pat. No. 5,440,328 to Nardone et al discloses a compact color printer that utilizes three non-driven platen rollers arranged in an arc, with three color print heads disposed around the rollers to print onto a receptor media. Output drive rollers are used to pull the receptor media through the printer, with the printed receptor media being output through an output slot in the printer. The receptor media is output from the printer in its final form and is not applied to a card to transfer the printed image onto the card.




SUMMARY OF THE INVENTION




The present invention provides an apparatus and method for multi-color printing on plastic cards, such as credit cards, identification cards, and the like. The present invention provides a printing apparatus that is compact and able to perform precise single pass, multi-color printing onto a receptor web, with the web then being mated with a plastic card to permit transfer of the color image from the web onto the card. The present invention eliminates the numerous back and forth movements of the prior art, thereby increasing the throughput of the printer, as well as smoothing the printing operation. Further, by printing initially onto a receptor web and then transferring the image to the card, the entire image can be printed on the web, eliminating the problem of printing at the edge of the card.




A preferred embodiment of the printing apparatus in accordance with the principles of the present invention includes a rotatably driven cylinder having a smooth, high friction outer surface, and a plurality of color print stations spaced circumferentially about the cylinder. A receptor web supply roll is mounted adjacent to the cylinder and supplies an uninterrupted length of a receptor web to the outer surface of the cylinder. The receptor web is frictionally engaged with the outer surface of the cylinder such that the web rotates therewith when the cylinder is rotated. An incremental digital drive mechanism, such as a stepper motor and gearing assembly, is connected to the cylinder for rotating the cylinder, and therefore the receptor web disposed on the outer surface thereof, to position the receptor web relative to the color print stations. The incremental digital drive mechanism allows precise positioning of the cylinder and the receptor web relative to each print head, thereby ensuring precise registration between the receptor web and the print beads.




The invention further includes a method of multi-color printing on a card including providing a rotatably driven cylinder having an outer, high friction surface and a plurality of color print stations spaced circumferentially about the cylinder. An uninterrupted length of a receptor web is supplied to the outer surface of the cylinder and is in frictional engagement therewith such that the web moves with the cylinder. The cylinder is then rotated to position the receptor web relative to a first one of the color print stations, and the first color print station then prints onto the receptor web. The cylinder is repeatedly rotated to position the web relative to each color print station until the entire printed image is printed on the receptor web. The receptor web is then mated with the card to thereby transfer the printed image from the receptor web onto the card.




These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objects attained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying description, in which there is described a preferred embodiment of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a diagrammatic view of the printing apparatus and a mating and image transfer station.





FIG. 2

is a detailed view of one of the print stations.





FIG. 3

is an exploded view showing the receptor web supply roll.





FIG. 4

illustrates the drive mechanism for driving the cylinder.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




Referring now to the drawings, the printing apparatus in accordance with the principles of the present invention is generally referred to by the numeral


10


. With reference to

FIG. 1

, the apparatus


10


includes a rotatably mounted cylinder


12


, and a plurality of color print stations


14




a-e


disposed at spaced locations around the cylinder


12


. The cylinder


12


includes an outer surface that is preferably formed by a silicon coated rubber material to provide a high friction gripping surface, as well as chemical resistance to the coloring used in the color print stations


14




a-e


. The silicon coated rubber material is preferably soft and compliant to assure compliance between the printhead, print ribbon, and the receptor web.




A receptor web supply roll


16


is rotatably mounted adjacent the cylinder


12


for supplying a receptor web


18


to the outer surface of the cylinder. The roll


16


is freely rotatable, i.e. not driven, with the web


18


extending from the roll


16


to the high friction outer surface of the cylinder


12


, whereby the feeding of the web


18


from the roll


16


is caused by the rotation of the cylinder


12


. The web


18


extends around, and is integral with, the majority of the outer surface of the cylinder, and finally separates from the outer surface past the last print station


14




e


, with the web then extending to a mating and image transfer station


20


, where the receptor web


18


is mated with the plastic cards to thereby permit transfer of the printed image from the receptor web to the plastic cards.




The receptor web


18


is of conventional three-layer construction including a carrier layer, a topping layer, and an ink receptor layer. In use, the topping layer and the ink receptor layer are intended to be laminated onto the card, thereby transferring the image onto the card. Other receptor web materials could be used if desired, as long as the receptor web permits printing of the image thereon and permits subsequent transfer of the image to the card. The mating and image transfer station


20


is a conventional arrangement suitable for mating the receptor web with one of the cards, and for causing transfer of the image from the receptor web onto the card. For instance, a pair of conventional heated pressure rollers could be used, between which the receptor web and card pass to cause the topping layer and the ink receptor layer to be laminated onto the card, thereby transferring the image onto the card.




Since the outer surface of the cylinder


12


is highly frictional, the receptor web is gripped by the outer surface and moves integrally therewith as the cylinder is driven in rotation, with no slippage occurring between the web


18


and the outer surface. Thus feeding of the receptor web from the roll


16


is caused by the rotation of the cylinder, with the cylinder being used to position the receptor web relative to each print station


14




a-e


using a drive mechanism


130


explained in more detail below.




With reference to

FIG. 2

, the details of the print station


14




a


are illustrated, it being understood that each of the other print stations


14




b-e


are identical in construction to the print station


14




a


. The color print station


14




a


includes a print head


22


, a color print-ribbon


24


, a print-ribbon feed roll


26


, a print-ribbon take-up roll


28


, and a pair of print-ribbon guides


30




a-b


. The print head


22


, shown diagrammatically in

FIG. 2

, is preferably a thermal print head, although other types of print heads can be used if desired.




The print-ribbon


24


is fed from the feed roll


26


, around the guide


30




a


, past the print head


22


, past the guide


30




b


, and onto the take-up roll


28


. The print head


22


is mounted so as to be moveable in a radial direction relative to the cylinder


12


between a non-print position, at which no printing takes place, and a print position, at which printing occurs. The mounting of print heads to permit such movement is conventional in the art, and therefore no description of the details of the mounting will be specifically described herein.




Each guide


30




a-b


is preferably a smooth, elongated stationary post, with the guides being located so as to guide the print-ribbon


24


to and from the print head


22


. Additionally, the feed roll


26


is rotatably mounted on a fixed shaft


32


, with the feed roll being undriven. The feed roll


26


includes an uninterrupted length of the print-ribbon


24


thereon. The mounting of the feed roll


26


on the shaft


32


is such that rotation of the feed roll is slightly resisted to prevent unwinding of the print-ribbon


24


until a sufficient pulling force is applied to the print-ribbon.




The take-up roll


28


is rotatably mounted on a shaft


34


that is disposed on one end of an L-shaped support arm


36


, with the other end of the support arm including a handle


38


connected thereto. The support arm


36


is pivotally mounted at the central portion thereof to a support base


40


, to permit pivoting movements of the support arm. A cylindrical capstan


42


is rotatably mounted adjacent the take-up roll


28


, with the capstan


42


being rotatably driven through a suitable connection to a drive means, such as a separate drive motor or the drive motor for the cylinder


12


. The take-up roll


28


is biased into contact with the capstan


42


by a spring


44


that is connected between the support base


40


and the support arm


36


to continuously bias the take-up roll toward the capstan.




Since the take-up roll


28


is biased into contact with the capstan


42


, rotation of the capstan causes rotation of the take-up roll, thereby taking-up, or winding, the print-ribbon


24


onto the take-up roll


28


. Thus, when the capstan


42


is rotated, the take-up roll


28


rotates, thereby pulling the print-ribbon


24


from the feed roll


26


, past the print head


22


, and to the take-up roll


28


. As the print-ribbon


24


is being taken up on the take-up roll


28


, the diameter of the take-up roll increases, thus causing the roll to pivot about the axis of the support arm


36


, away from the capstan


42


. When the take-up roll


28


is full (i.e. when the feed roll


26


is empty), the take-up roll and feed roll need to be replaced. Replacement of the take-up roll


28


is accomplished by grasping and pulling the handle


38


to pivot the support arm


36


so that the take-up roll moves sufficiently away from the capstan


42


to permit the take-up roll to be removed and replaced with a new, empty take-up roll. The empty feed roll


26


is also removed from the shaft


32


and replaced with a full feed roll. Obviously, the feed roll and take-up roll can be constructed so as to be interchangeable, whereby a full take-up roll can be replaced by the empty feed roll, and vice-versa, thereby making replacement easier.




The apparatus


10


functions by printing spaced images on the receptor web


18


. The first print station


14




a


begins the printing of one of the images onto the web. During this time the cylinder


12


is rotated, thereby moving the web


18


relative to the printhead


22


so that the first print station


14




a


can print the first color at the desired location(s) over the entire extent of the intended image. Once the first print station is finished printing, the first image is brought into registration with the second print station


14




b


. Simultaneously, the first print station is ready to start printing a second image onto the web, with the second image being spaced from the first image. The second print station performs printing on the first image in the second color, and then the first image is then brought into registration with the third print station. This process is repeated until the first image is brought into registration with each remaining print station so that the desired color image is completely printed onto the web. The use of multiple print stations


14




a-e


disposed around the cylinder allows a plurality of images to be printed at the same time, thereby increasing the throughput of the printer.




Once printing of the first image is completed, the first image is then mated with a card in the mating and image transfer station


20


, to permit transfer of the topping layer and the ink receptor layer of the web onto the plastic card, thereby transferring the image onto the card. It should be apparent to a person having ordinary skill in the art that the length of each printed image on the web should be chosen so that the image is able to fit completely onto the card.




Turning to

FIG. 3

, an exploded view of the receptor web supply roll


16


is shown, illustrating how the supply roll


16


is rotatably mounted. A shaft


46


is fixed at one end thereof within a base block


48


using a fastener


50


or the like, with the shaft


46


extending vertically therefrom. A first, generally cylindrical bottom spindle


52


is disposed over the shaft


46


and includes an enlarged bottom portion


54


defining a tapered shoulder


56


. A central passage


58


extends longitudinally through the spindle


52


having a diameter greater than the diameter of the shaft


46


to allow passage of the shaft. A bearing


60


fits within the bottom of the passage


58


for rotatably mounting the spindle


52


onto the shaft


46


.




A top spindle


62


includes a small diameter section


64


that closely fits within the central passage


58


of the spindle


52


to allow the top spindle


62


to be fitted onto the bottom spindle


52


. A large diameter section


66


of the spindle


62


includes three spaced fingers


68




a


,


68




b


,


68




c


extending axially therefrom. The fingers


68




a-c


are flexible and each finger includes a tapered shoulder


70


on the outside surface thereof. The spindle


62


also includes a central passage


72


extending therethrough having a diameter greater than the diameter of the shaft


46


, and a bearing


74


, similar to the bearing


60


, is disposed within the passage


72


so as to rotatably mount the spindle


62


to the shaft


46


.




In use, the two spindles


52


,


62


are fit together and disposed around the shaft


46


so as to rotate relative thereto. The receptor web supply roll


16


, with the receptor web


18


thereon, is then disposed around the spindles


52


,


62


, between the tapered shoulder


56


of the enlarged bottom portion


54


and the tapered shoulders


70


of the fingers


68




a-c.






In order to fix the supply roll


16


in place, a cam mechanism


76


is disposed around the top end of the shaft


46


within the diameter defined by the fingers


68




a-c


so as to selectively bias the fingers outward and into contact with the roll


16


. The cam mechanism


76


includes a cylindrical body portion


78


with the base end thereof having a plurality of spaced cam surfaces


80


defined thereon. The number of cam surfaces


80


corresponds with the number of fingers


68




a-c


, with the spacing between the cam surfaces corresponding with the spacing between the fingers. The cam surfaces


80


are designed so as to contact the fingers and bias them outward into engagement with the roll


16


based upon the rotational position of the body portion


78


. In order to bias the fingers outward into contact with the roll, the cam mechanism


76


is rotated so that the cam surfaces


80


engage the fingers


68




a-c


, thus biasing them outwardly, such that the tapered shoulders


70


on the fingers engage the roll


16


, whereby the roll is sandwiched between the shoulders


70


and the shoulder


56


. Rotation of the cam mechanism in the opposite direction releases the outward bias on the fingers, to thereby permit the roll


16


to be replaced by slipping the roll off of the spindles


52


,


62


. A threaded bolt


82


engages with a suitably provided threaded hole


84


in the end of the shaft


46


to secure the cam mechanism


76


in place. Further, a coil spring


86


is disposed between the bearing


74


and the bottom of the cam mechanism


76


to bias the cam mechanism outward, so as to facilitate gripping by a users fingers or with a suitable tool when rotation of the cam mechanism is desired. A similar arrangement can be used in order to mount the feed roll


26


and the take-up roll


28


on their respective shafts.




The supply roll


16


is preferably provided with a tensioning mechanism for applying a tension to the web


18


as it is being unwound from the roll


16


by the cylinder


12


. The tensioning mechanism includes a cup-shaped friction disk


88


disposed around the shaft


46


below the spindle


52


. The friction disk


88


is cup-shaped and includes a cylindrical side wall


90


and a bottom wall


92


. The bottom wall


92


has a centrally located hole


94


therein permitting free passage of the shaft


46


, and an arcuate slot


96


formed between the hole


94


and the side wall


90


, the purpose of which will become apparent later in the description. First and second notched disks


98




a


,


98




b


are disposed below the friction disk


88


and alternate with first and second washers


100




a


,


100




b


. The washers


100




a,b


include central apertures


102


that are shaped such that the washers are fixed to the shaft


46


to prevent rotation of the washers on the shaft, but are axially slideable thereon. The notched disks


98




a,b


each include three spaced notches


104


in the outer circumference thereof, with pins


106


connected to and extending from the bottom wall


92


of the friction disk


88


engaging in the notches so that the notched disks are fixed to and rotate with the friction disk


88


. A cylindrical compression spring


108


, such as a helical coil spring, is disposed around the end of the shaft


46


, and rests upon the base block


48


and engages the bottom of the second washer


100




b


. The spring


108


biases the washers


100




a,b


and notched disks


98




a,b


upward into engagement with each other and the bottom of the friction disk


88


, such that when the friction disk


88


rotates, which causes the notched disks to rotate, friction is created between the notched disks and the stationary washers, thus resisting rotation of the roll


16


and thereby applying a tension to the web


18


.




In order to cause the friction disk


88


to rotate, the enlarged bottom portion


54


includes a pin


110


connected thereto and extending downward toward the disk


88


and through arcuate slot


96


. Since the pin


110


is fixed to the spindle


52


, it rotates therewith. The pin


110


and slot


96


arrangement permits limited rotational movements of the spindle


52


relative to the disk


88


within the range defined by the slot


96


. However, once the pin


110


contacts the end of the slot


96


, the disk


88


then rotates with the spindle


52


, which causes the notched disks


98




a,b


to rotate relative to the washers


100




a,b


, thereby creating the frictional tension force on the web


18


.




In order to sense the amount of rotational movement of the roll


16


, a notched disk


112


with a plurality of circumferentially spaced radial fingers


114


is disposed around the shaft


46


under the spindle


52


. The disk


112


includes a central aperture


116


permitting passage of the shaft, and an offset aperture


118


through which the pin


110


extends so that the disk


112


rotates with the spindle


52


. A sensor assembly


120


is secured to the top of the base block


48


and is disposed relative to the disk


112


for sensing the passage of the fingers


114


as the disk


112


rotates with the roll


16


, thereby providing an indication of the amount of rotation of the roll


16


.




A torsion spring


122


is disposed about the shaft


46


between the disk


112


and the friction disk


88


. The spring


122


is preferably a coiled spring of conventional construction and includes a first finger


124


that engages the pin


110


, and a second finger


126


that engages a pin


128


that is connected to and extends from the bottom wall


92


of the friction disk


88


. The torsion spring


122


maintains tension on the web


18


once feeding of the web


18


to the cylinder is stopped, i.e. once rotation of the cylinder


12


stops.




The drive mechanism


130


for driving the cylinder


12


is illustrated in FIG.


4


. The drive mechanism


130


forms an open loop positional control for the cylinder


12


. As shown, the cylinder


12


is driven by a motor


132


, preferably a stepper motor, through a gearing assembly


134


to achieve precise positioning of the cylinder and the receptor web


18


frictionally engaged therewith relative to the print stations


14




a-e


. Although the drive mechanism is described as being a stepper motor and gearing assembly, other incremental digital drive mechanisms can be used if desired.




The gearing assembly


134


includes a first pinion gear


136


that is driven by the motor


132


, and an intermediate gear


138


engaged with and driven by the first pinion gear


136


. A shaft


140


extends from the intermediate gear


138


, and a second pinion gear


142


is fixed on the end of the shaft


140


so as to rotate with the gear


138


. A large diameter gear


144


is connected to the cylinder


12


and is driven by the second pinion gear l


42


.




As shown in

FIG. 4

, the diameter of the gear


144


is made to be large relative to the sizes of the other gears


136


,


138


,


142


. For instance, the diameter of the gear


144


can be approximately equal to the diameter of the cylinder


12


, however the diameter of the gear


144


can be either larger or smaller than the diameter of the cylinder. The large diameter of the gear


144


minimizes the effects of eccentricities and other errors in the gear


144


, so that the errors have minimal or no effect on the positioning of the web


18


relative to the print stations


14




a-e.






The diameter of the second pinion gear


142


is selected so that the pinion gear


142


rotates exactly twice during the printing operation on each segment, thereby canceling out any eccentricity errors in the gears


138


,


142


, so that such errors do not effect the alignment of the web with the print stations. Further, the effects due to errors in the gears


136


,


138


are reduced by the reduction ratio of the gear


142


to the gear


144


. Therefore the gearing assembly


134


is specifically designed so that the effects of errors in the gears


136


,


138


,


142


,


144


on the positioning of the cylinder


12


and web


18


are minimized. Further, the drum


12


is preferably sized so that it is an integer value of the motor resolution. A drag brake or the like can also be provided on the gear assembly


134


in order to reduce backlash and load variations.




It is to be understood that while certain embodiments of the present invention have been illustrated and described, the invention is not limited to the specific forms or arrangements of the parts described and shown.



Claims
  • 1. A method of color printing on a card, comprising:a) providing a rotatable cylinder having an outer surface and a plurality of color print stations spaced circumferentially about the cylinder; b) supplying an uninterrupted length of a receptor web to the outer surface of the cylinder and in frictional engagement therewith; c) rotating the cylinder to thereby position the receptor web relative to one of the color print stations, and printing onto the receptor web using the one color print station to form a printed portion, wherein rotating the cylinder comprises using a pinion gear that rotates twice during the printing operation on each segment; and d) mating the printed portion of the receptor web with the card.
  • 2. The method of color printing according to claim 1, wherein the step of supplying the receptor web comprises applying tension to the receptor web.
  • 3. The method of color printing according to claim 1, wherein the step of rotating the cylinder comprises connecting a stepper motor to the cylinder, and actuating the stepper motor to rotate the cylinder.
  • 4. The method of color printing according to claim 1, including repeating step c) for at least one of the other color print stations.
  • 5. The method of color printing according to claim 1, including repeating step c) for each of the remaining color print stations.
  • 6. A multi-color printing apparatus, comprising:a rotatable cylinder having an outer surface; a plurality of color print stations spaced circumferentially about the cylinder; an uninterrupted length of a receptor web frictionally engaged with the outer surface of the cylinder such that the web is rotatable therewith; and a drive mechanism connected to the cylinder for rotating the cylinder and the receptor web disposed on the outer surface thereof to thereby position the receptor web relative to the color print stations; wherein said drive mechanism comprises a drive motor and a gearing assembly connected between the drive motor and the cylinder; wherein said gearing assembly includes a first gear connected to the cylinder, and a second, pinion gear engaged with the first gear and in driving engagement with the drive motor, the diameter of said first gear being greater than the diameter of the second pinion gear; and further including a mating and image transfer station for receiving the receptor web.
  • 7. The multi-color printing apparatus according to claim 6, wherein said drive motor comprises a stepper motor.
  • 8. The multi-color printing apparatus according to claim 6, wherein the printing apparatus prints onto segments of the receptor web; and said second, pinion gear is configured such that the second gear revolves twice as one of the segments of the receptor web moves from a first one of said plurality of color print stations to a last one of said color print stations.
  • 9. A multi-color printing apparatus, comprising:a rotatable cylinder having an outer surface; a plurality of color print stations spaced circumferentially about the cylinder; wherein each said print stations include a printhead, a color print-ribbon, a print-ribbon feed roll, a print-ribbon take-up roll and print ribbon guides; further including a capstan mounted adjacent each said take-up roll, and biasing means for biasing said take-up roll against said capstan; an uninterrupted length of a receptor web frictionally engaged with the outer surface of the cylinder such that the web is rotatable therewith; and a drive mechanism connected to the cylinder for rotating the cylinder and the receptor web disposed on the outer surface thereof to thereby position the receptor web relative to the color print stations; and further including a mating and image transfer station for receiving the receptor web.
  • 10. The multi-color printing apparatus according to claim 9, wherein each said take-up roll is rotatably mounted, and each said capstan is rotatably driven and causes rotation of the respective take-up roll.
  • 11. The multi-color printing apparatus according to claim 9, further including support arms supporting each said take-up roll, said support arms being pivotally mounted within the printing apparatus; and further comprising a handle connected to each said support arm.
  • 12. The multi-color printing apparatus according to claim 11, wherein each said support arm includes first and second portions extending perpendicular relative to each other.
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Entry
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