A thermal printing apparatus 41 that can transfer a colorant from a moving ribbon 66 onto printable areas 140a, 140b of a thermal print receptive sheeting 46. The apparatus 41 includes a thermal print head 44, a transport, a mechanism that can move the thermal print head 44 in a second direction x, a ribbon travel mechanism that is capable of supporting a ribbon 66, and a mechanism that allows colorant to be transferred to a thermal print receptive sheeting 46 while the ribbon travel mechanism is in operation and while the thermal print head 44 is moving in the second direction x. The ribbon 66 and the thermal print head 44 are in motion while the indicia is being printed on the thermal print receptive sheeting. The thermal print head 44 is elongate, has a length l of at least one centimeter, and extends substantially in a first direction y. An apparatus of this construction allows sheetings having a width greater than S to receive a thermally printed indicia without encountering a significant ribbon wrinkling problem because narrow ribbons may be employed in transferring the indicia onto the thermal print receptive sheeting. A single ribbon also can be used to print on sheetings of various widths.
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0. 13. A thermal printing apparatus that can transfer colorant from a movable ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
a. an elongate thermal print head with a row of heating elements that extends substantially in a first direction for a length l of at least one centimeter, the print head being movable in a second direction across the sheeting; b. a sheeting transport that can move the sheeting past the print head in the first direction; and c. a ribbon transport that can move the ribbon across the sheeting in the second direction as colorant is transferred to the sheeting.
0. 32. A thermal printing apparatus that can transfer colorant from a movable ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
a. an elongate thermal print head that extends in a first direction for a length l of at least about one centimeter and has means for providing localized heat to transfer the colorant to the sheeting, the print head being movable in a second direction across the sheeting; b. means for transporting the sheeting past the print head in the first direction; and c. means for transporting the ribbon across the sheeting in the second direction as colorant is transferred to the sheeting.
0. 25. A thermal printing apparatus that can transfer colorant from a movable ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
a. a thermal print head having a row of heating elements with a resolution of at least about 75 dots per lineal centimeter and a length l of at least about one centimeter that extends substantially in a first direction, the print head being movable in a second direction across the sheeting; b. a sheeting transport that can move the sheeting past the print head in the first direction; and c. a ribbon transport than can move the ribbon across the sheeting in the second direction as colorant is transferred to the sheeting.
1. A thermal printing apparatus that can transfer colorant from a moving ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
(a) a thermal print head that is elongate, the has a length l of at least one centimeter, that extends in a first direction, and that has a mechanism which provides localized heat for the transfer of colorant from a moving ribbon to a thermal print receptive sheeting; (b) a transport that can move the thermal print receptive sheeting past the thermal print head in the first direction; (c) a mechanism that can move the thermal print head in a second direction; (d) a ribbon travel mechanism that is capable of supporting the ribbon; and (e) a mechanism that allow allows such transfer of colorant from a moving ribbon to a thermal print receptive sheeting while the ribbon travel mechanism is in operation and while the thermal print head is moving in the second direction.
0. 18. A thermal printing apparatus that can transfer colorant from a movable ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
a. an elongate thermal print head with a row of heating elements that extends substantially in a first direction for a length l of at least one centimeter, the print head being movable in a second direction across the sheeting; b. a sheeting transport that can move the sheeting past the print head in the first direction; and c. a ribbon transport that can move the ribbon across the sheeting in the second direction as colorant is transferred to the sheeting wherein movement of the ribbon can cease when the print head encounters an area of sufficient size on the sheeting that is not destined to have colorant transferred to it and wherein the print head can continue to move across the sheeting in the second direction to an area that is destined to have colorant transferred to it.
0. 29. A thermal printing apparatus that can transfer colorant from a movable ribbon onto printable areas of a thermal print receptive sheeting, the apparatus comprising:
a. a thermal print head having a row of heating elements with a resolution of at least about 75 dots per lineal centimeter and a length l of at least about one centimeter that extends substantially in a first direction, the print head being movable in a second direction across the sheeting; b. a sheeting transport that can move the sheeting past the print head in the first direction; and c. a ribbon transport that can move the ribbon across the sheeting in the second direction as colorant is transferred to the sheeting wherein movement of the ribbon ceases when the print head encounters an area of sufficient size on the sheeting that is not destined to have colorant transferred to it and wherein the print head continues to move across the sheeting to an area that is destined to have colorant transferred to it.
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This is a continuation of application Ser. No. 08/241,756 filed May 12, 1994
In this invention, "thermal printing" refers to those processes that transfer colorant from a ribbon to a substrate by use of localized heat. Typically, thermal printing is accomplished by a non-impact system that transfers colorant by the simultaneous application of localized heat and pressure. A system that transfers colorant predominantly by impact would not be considered to generate a significant amount of localized heat during the impact to qualify as a thermal printing system. The term "colorant" is used herein to mean a media capable of providing an image or indicia on the surface of a thermal print receptive sheeting. The colorant may be a binder media that contains a pigment(s), a dye(s), or a combination thereof. The colorant is transferred to a thermal print receptive sheeting by a thermal print head that contains, for example, resistive elements, ribbon-contacting elements in a laser system, electronic elements, thermally activated valve elements, inductive elements, thermopile elements, and the like. The term "thermal print head" refers to the mechanism or mechanism that provide the localized heat for the transfer of colorant. A preferred mechanism for transferring colorant comprises heatable resistive elements in a thermal print head of a thermal mass transfer printing system. Using the method and systems of the invention, indicia may be formed which include alphanumeric characters, logos, or graphic information upon the thermal print receptive substrate.
Thermal print head 44 operates to transfer discrete areas of colorant to a thermal print receptive sheeting 46. The size of the colorant transfer area, or dot, can be determined by the area of each discrete heating element in print head 44, as is known in the art. Such dots are generally about 3.76×10-6 square centimeters, which is the area of a pixel. The resolution of indicia printed with print head 44 generally is from about 75 to about 250 dots per lineal centimeter.
An example of a print head that can be incorporated into print head assembly 50 of
Ribbon 66 may have a wax-based, resin-based or a combined wax/resin-based binder, although a preferred ribbon comprises a resin-based binder. The width of ribbon 66 may be substantially the same as or narrower than length L of print head 44. Ribbon 66 may be, for example, a ribbon sold under the trade name Printronix 2150 or 2200, or ribbon sold under the trade name Zebra No. 5030/5099 by Zebra Technologies Corporation of Vernon Hills, Ill. Alternatively, ribbons may be used which are sold under the trade names Sony brand No. 3021/3022/3023 by Sony Chemical Corporation of America, Wood Dale, Ill.
In the embodiment shown in
A print head linear motion mechanism moves a print head in a second direction (indicated by arrow x in
A print head motor may be, for example, a motor made by Airpax Corp., Chesire, Conn. and sold under the trade name Airpax 82900. Other suitable motors for actuating print head linear motion are, for example, a stepper motor, a DC brushless motor with an encoder, or an AC synchronous motor with encoder. Print head linear motion mechanisms that comprise one of these motors are known in the art.
A linear motor system, which combines a track mechanism, drive mechanism and positioning mechanism, may conveniently provide both linear motion mechanisms as well as position tracking devices, described below. Alternatively, a lead screw drive assembly actuator apparatus comprises linear motion mechanisms and print head alignment mechanisms in one readily obtainable item.
A print head sensor 78 may be mounted on print head assembly 50 by attachment to print head frame 52 that slidably engages a fixed, etched glass bar 80. Print head sensor 78 may be, for example, an optical sensor or a magnetic sensor, and is operably connected by a data line (not shown) to a mechanism such as computer 112 for comparing the position of print head 44 relative to the position of sheeting 46. Alternatively, print head sensor 78 may be a linear scale system made by Sony Corporation, which system comprises a bar and suitable sensor. Other print head position tracking devices known in the art also may be used.
A transport advances or transports thermal print receptive sheeting past a print head in a first direction, (indicated by arrow y in FIG. 3). In the embodiment depicted in
A preferred sheeting transport can comprises a tractor drive mechanism sold under the trade name Model ST-611, by Seitztec, Torrington, Conn. A friction drive assembly, however, may be substituted for a tractor drive mechanism if less graphic accuracy in the formed indicia is acceptable. A friction drive assembly has a lower cost and eliminates the need for drive holes in sheeting 46. It is possible in this invention, although typically less preferable, to use a manual transport of the sheeting.
An optional sheeting sensor may be employed to receive positional information regarding sheeting 46. In the embodiment shown in
Referring to
The number of print operation cycles necessary to complete colorant transfer to a thermal print receptive article depends upon the dimensions of the desired indicia relative to length L of a print head 44. When more than one print operation cycle is necessary to complete indicia formation, print head sensor 78 may be used to locate the position of print head assembly 50 relative to the position of sheeting 46, preferably with an accuracy of less than one colorant dot. Print operation cycles may be repeated as described above, until the desired indicia have been formed on sheeting 46. If one pass is sufficient to complete the formation of indicia on an article, a print head sensor 78 and an etched glass bar 80 may not be needed. A print head sensor generally is useful when producing articles demanding a high degree of graphic accuracy. For the production of articles requiring less graphic accuracy, or when using a stepper motor or other mechanisms discussed above, a print head sensor may not be necessary.
In the embodiment described above, sheeting transport during a print operation cycle occurs after movement of print head 44 to location 47. However, any particular timing of sheeting advancement in relation to a print operation cycle is within the scope of the invention.
Print head arrangement 40 may be positioned in a printing system such that the direction indicated by arrow x of
Thermal printing arrangements disclosed in this invention may be referred to as "cross web" systems, because colorant is applied across the width of the sheeting or web, in a direction generally normal to the length or direction of movement of the sheeting. As shown in
In another embodiment of the invention, indicia of more than one color can be applied to sheeting by adding additional printer heads, arranged in the same manner as described above, each head associated with a ribbon of a different color, i.e., red, green, blue, black and the like. As the sheeting is advanced past successive printer heads, colorant is applied from each successive ribbon. The print heads may be supported on the same assembly or each print head supported by a separate assembly. An apparatus having more than one print head is manufactured by Ring Corporation or Arlington Heights, Ill. It also is possible to apply more than one color with a single print head, by executing more than one printing operation and substituting a differently colored ribbon after each printing. In addition, ribbons having up to 4 strips of different colors are known, for example, red, green, yellow and black, and may be usefully employed in the print head arrangement and printing system disclosed herein to generate multi-color signage articles. The invention provides substantial ribbon savings in either a multi-color printing or multi-color process printing use, the latter normally using black, magenta, cyan, and yellow as transparent color overlays.
An operator loads indicia to be printed and various print and sheeting control commands into computer 112 for use with print head data processing mechanisms within cross web thermal printer 41. The operator input is assembled by software into code suitable for controlling actuation, disengagement and colorant transfer by print head 44, transport by sheeting transport mechanisms in a second direction and movement of print head 44 by linear motion mechanisms in a direction perpendicular to sheeting transport movement. Data from optical sensors 78 and 100 (shown in
Thermal printing systems of the invention may be used to produce signage articles in dispersed locations, rather than in large central facilities. Methods and systems of the invention may be used to form repeating (or incrementally changing) information or variable information such as alphanumeric characters, graphic images or bar codes. For example, such articles may be made from retroreflective polymeric sheeting materials that are directly printable upon the upper surface thereof, as disclosed in U.S. patent applications Ser. No. 08/033,627 filed Mar. 16, 1993 and U.S. patent application Ser. No. 08/186,751 filed Feb. 2, 1994, the disclosures of which art, respectively, incorporated here by reference.
A thermal printing system can be configured to produce signage articles such as highway signs. When an article such as a highway sign is desired to be formed, the sheeting onto which the thermally printed indicia is transferred may be a retroreflective sheeting or a polymeric layer that becomes secured to the front surface of the retroreflective sheeting. For purposes of this invention, it will be assumed that the indicia is transferred to or printed upon a retroreflective sheeting in those instances when there is a polymeric layer or layers disposed thereon. The retroreflective sheeting can be essentially any now known or later developed retroreflective sheeting. The retroreflective sheeting can be, for example, a cube corner element sheeting (see, for example, U.S. Pat. Nos. 3,684,348, 4,801,193, 4,895,428 and 4,938,563, the disclosures of which are incorporated herein by reference), or a beaded lens sheeting comprising exposed lens elements, encapsulated lenses, or enclosed lenses (see, for example, U.S. Pat. Nos. 2,407,680, 3,190,178, 4,025,159, 4,896,943, 5,064,272 and 5,066,098, the disclosures of which are incorporated herein by reference).
A thermal printing system of the present invention allows thermal printing on polymeric sheetings of varying widths, in particular, sheetings that are wider than 16 centimeters, wider than 38 centimeters, and even wider than 46 centimeters (FIG. 3). The thermal printing of the invention also may allow printing at various angles by moving the print head at the desired angle across the sheeting. A sheeting of width W (
Further advantages of the invention relate to ribbons used in thermal printing. Ribbons for thermal transfer printing are generally made with a 6 micrometer polyester backing and are generally 5 to 38 centimeters wide. Torsional and other stresses often cause the wider ribbons to flex, leading to ribbon wrinkling. Such wrinkling results in uneven transfer of colorant and poor quality indicia. The thermal printing system of the invention can overcome the problem of ribbon wrinkling by using a narrow width ribbon in a manner that provides full range ribbon capabilities normally attributed to wider ribbons, rather than trying to solve the wrinkling problem by redesigning the mechanical carriages. This preferred solution also results in more efficient ribbon use, as discussed in reference to FIG. 5.
A further advantage of the system disclosed herein is that only a single width of ribbon suffices for printing on varying widths of sheeting. Prior thermal printing systems required ribbon width to be essentially equal to print head length, necessitating that different ribbons be installed on each printing system of a particular length. In accordance with the present invention, a 60 centimeter wide sheeting and a 122 centimeter wide sheeting may be printed with the same ribbon, whereas such printing can not be accomplished with known systems because 60 or 122 centimeter wide ribbons are not available for down web thermal printing systems.
The system disclosed herein has yet another advantage, in that there is less waste of ribbon. Currently known thermal print head arrangements have a ribbon that is essentially the same width S (
The disclosed thermal printing systems may provide reduced cost compared to prior thermal printing systems, especially for printing on wide sheetings. In thermal printing systems, the ribbon support members, print head assemblies, support frames and the like must be sufficiently rigid to minimize torsional and other stresses on the ribbon as it travels between the print head and the media substrate. The rigidity required for a 38 centimeter wide print head can be more than four times greater than that required for a 15 centimeter wide print head. As a consequence, the cost of a 38 centimeter wide print head system generally may be significantly greater than the cost of a 15 centimeter wide print head system. Cross web thermal printing systems disclosed herein can utilize less rigid and narrower print heads to print signage articles as wide or wider than a 38 centimeter down web system, thereby reducing the overall cost of the system.
A further advantage relates to the system control mechanism for a printing system of this invention. The formatting memory in the print head computer mechanism required to control a single wide print head may require a relatively expensive data communication and system control mechanism. In contrast, the relatively narrower print head of the disclosed printing system may require less formatting memory in the print head computer mechanism and consequently may utilize a less expensive system control mechanism.
The thermal graphic printing systems and methods disclosed herein can be used in many applications. For example, barcode labels for packages, bottles, metal canisters and the like, sometimes require that item-specific labels have varying widths. Highway signs generally use screen printing production methods and systems, which can be time consuming, inconvenient, and may use quantities of organic solvents. The thermal printing system of this invention allows highway signs having varying widths to be made more conveniently, in less time and with smaller amounts of solvent than known systems. Small production runs such as "made-to-order" retail business signs also can be manufactured with the system described herein. Signage articles made by the method and system disclosed herein may have lower production costs and can be made more conveniently than hand lettered signs or signs pieced together from smaller width printed subsections, die cut-out characters, electronically cutout characters, or screening printing.
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