Incremental printing of symbolic information – Thermal marking apparatus or processes – Platen or engaging means therefor
Reexamination Certificate
2000-02-29
2001-05-15
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Platen or engaging means therefor
C400S648000, C400S649000
Reexamination Certificate
active
06232995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to multi-color printing devices and, more particularly, to a multi-color printing device which saves printing film by only applying a particular color to the printing medium when that color is needed for printing on the medium.
2. Discussion of the Related Art
Currently available thermal transfer printing heads generally comprise a plurality of thermal elements. The heating elements are generally provided on one side of a flat substrate of ceramic or like material along with the requisite electronic circuitry for controlling the activation of the heating elements.
The thermal transfer printing head is typically used in conjunction with a roller platen assembly and ink transfer printing film or ribbon which carries a thermally transferable printing ink. During printing, a web of material to be printed are oriented between the thermal elements of the printing head and the roller platen of the roller platen assembly such that the printing ribbon is adjacent to the print head and the material to be printed is adjacent to the roller platen. The roller platen and printing head are moved against each other so that the printing ribbon and the material to be printed are pressed against the printing head such that when selected thermal elements of the printing head are heated, ink from the ink transfer printing ribbon is transferred to the surface of the material.
Typical thermal transfer printers can include one or more printing heads, each of which are capable of printing in a different color. If more than one printing head is employed, the printing heads are generally arranged in line with each other, with each printing head having a roller platen assembly associated therewith.
In typical multi-color thermal transfer printers, each printing head and roller platen assembly is associated with a printing film of a particular color. During the printing process, the media to be printed is passed between the head and roller platen of each roller platen assembly along with the printing film of each assembly. For simplicity, the printing media referred to in this application is a series of labels serially attached on a continuous web. When a particular color is to be printed on a label, the printing head is activated, thus transferring the ink from the film to the label.
In one type of prior art thermal transfer printer, the film is wound off of a supply roll and through the roller platen assembly at the same rate that the label web is fed through the assembly. While this ensures that a fresh portion of printing film is always in contact with the label when the printing head is activated, it also wastes a great deal of the film, especially if a particular color is used sparingly for a particular print job. Since the label web and the printing films are fed through the printing apparatus at a 1:1 ratio, for each length of a label, an identical length of printing film is used. Therefore, in a system which uses four printer assemblies to print four colors on a label, for each label printed, four times as much film is used.
In an attempt to reduce the amount of film used in this printing process, prior art printing devices have been developed in which the printing head of a particular printing assembly is lowered against the roller platen only when the particular color associated with that printing assembly is to be applied to the printing media. When the color is not being applied, the printing head is raised away from the roller platen. Therefore, the printing film is only fed through the printing assembly while that particular color is being printed. While this type of device effectively reduces the amount of film used, it presents other problems. Specifically, when the printing head is mechanically urged downward onto the roller platen, by, for example, a motor-powered drive mechanism, the impact of the printing head against the roller platen causes printing irregularities, such as smudging, blurring and color darkness inconsistencies. Furthermore, the impact of the printing head against the roller platen shortens the effective life of the printing head.
Therefore, what is needed is a printing mechanism which conserves the amount of printing film used for a particular printing process, while also reducing printing errors which can occur in the prior art printing mechanisms.
SUMMARY OF THE INVENTION
The present invention provides a printing device in which the printing head of a printing apparatus is biased against the associated roller platen for transferring ink from a printing film to a label mounted on a media web as it passes between the printing head and the roller platen. At the instances when ink is not to be transferred onto the label, the print head is pushed away from the roller platen to stop the transfer of ink to the label. When printing is to resume, the print head is controllably released to allow it to come into contact with the roller platen, thus causing ink to be transferred to the label. In this manner, since the print head is brought into contact with the roller platen in a controlled manner, the printing inconsistencies associated with the prior art printing devices are eliminated.
According to one embodiment of the invention, an apparatus for applying images to a strip of print media is disclosed. The apparatus comprises a printing mechanism having a platen and a thermal print head mounted on a mounting bar, for biased engagement with the platen, the strip passing intermediate the thermal print head and the platen, a thermal printing film passing intermediate the strip and the thermal print head and a print head lifting mechanism which is movable between a first position, in which the print head lifting mechanism is disengaged from the mounting bar, thereby allowing the print head to be biased into engagement with the platen, and a second position, in which the head lifting mechanism engages the mounting bar, thereby lifting the print head out of engagement with the platen. The mounting bar is biased toward the platen by a spring mechanism which applies a constant biasing force to the mounting bar, thereby biasing the print head into engagement with the platen with the constant biasing force.
The head lifting mechanism comprises at least one finger mounted on a shaft and an actuation device, the activation device being operative for rotating the shaft to move the at least one finger between the first position and the second position. The actuation device is a piston which, when activated, rotates the shaft to move the at least one finger from the second position to the first position, and which, when deactivated, rotates the shaft to move the at least one finger from the first position to the second position.
Other features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.
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Astro-Med Inc.
Salter & Michaelson
Tran Huan
LandOfFree
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