Printhead comprising multiple types of drop generators

Details Printhead comprising multiple types of drop generators Printhead comprising multiple types of drop generators

2000-03-30

2001-12-11

Barlow, John (Department: 2853)

Incremental printing of symbolic information

Ink jet

Controller

Reexamination Certificate

active

06328405

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to inkjet printers and, in particular, to a printhead comprising multiple types of drop generators.
BACKGROUND OF THE INVENTION
Inkjet printers are well known in the art. A typical inkjet printhead comprises a silicon substrate, structures built on the substrate, and connections to the substrate to provide an array of drop generators. Such a printhead typically uses liquid ink (i.e., dissolved colorants or pigments dispersed in a solvent). Each drop generator comprises a precisely formed orifice or nozzle attached to the substrate that incorporates an ink ejection chamber that receives liquid ink from an ink reservoir. Each chamber is located opposite a nozzle so ink can collect between it and the nozzle. The ejection of ink droplets is typically under the control of a microprocessor, the signals of which are conveyed by electrical traces to ink ejectors (typically, resistor elements) on the substrate. When electric printing pulses activate the ink ejectors (i.e., heat a resistor element), a small portion of the ink next to it vaporizes and ejects a drop of ink from the printhead. Properly arranged drop generators form a dot matrix pattern. Properly sequencing the operation of each drop generator causes characters or images to be printed upon paper as the printhead moves past the paper.
Given current manufacturing technology, drop generators provided on silicon-based printheads of the type described above are currently capable of producing only a single drop weight. That is, the characteristics of each drop generator (i.e., chamber volume, orifice layer thickness, etc.) on a printhead are essentially identical. As a result, the drop weight or drop volume provided by each drop generator will be substantially identical. Furthermore, different types of inks have different dot gains, i.e., the amount of coverage provided for an equivalent ink drop volume. For example, different ink colors typically required different drop weights to produce equivalent amounts of coverage. In particular, black inks generally require a drop weight about twice that of color inks in that they have much different spreading characteristics to achieve substantially equal pixel coverage.
Given these circumstances, it is not currently possible to combine black and color architectures on a single printhead. One possible solution to this problem would be to provide equivalent drop generator structures for black and color inks and activate the black drop generators more frequently (i.e., twice as often) than the color drop generators, thereby providing similar coverage. However, this approach would effectively halve the expected reliability of black drop generators relative to color. Thus, the current approach to combine color and black inks in a single printer is to provide multiple print cartridges; one for each color (typically: cyan, yellow and magenta) and one for black. While this approach works, a cost and competitive advantage would be provided if black and color architectures could be combined into a single printhead and, therefore, a single cartridge.
SUMMARY OF THE INVENTION
The present invention provides a printhead having multiple types of drop generators, which types are differentiated according to at least the respective drop weights provided by each. Preferably, a first type of drop generator comprises at least two nozzles, whereas a second type of drop generator comprises a single nozzle. For the first type of drop generator, at least one ink ejector is associated with the at least two nozzles, which at least one ink ejector is controlled by a single firing signal. Preferably, each nozzle of the first type of drop generator has a uniquely corresponding ink ejector. In one embodiment of the invention, the first type of drop generators ejects a first type of ink and the second type of drop generators ejects a second type of ink. Preferably, the first type of ink is black ink and the second type of ink is color ink, such as cyan, yellow or magenta ink. Sets of drop generators are provided comprising both the first type and at least the second type. To prevent unwanted mixing of the black and color inks, a first orifice layer is provided separate and apart from a second orifice layer. The first and second orifice layers respectively define at least a first set of drop generators of the first type and at least a second set of drop generators of the second type. In this manner, a single printhead may be used for the delivery of both black and color inks. The printhead of the present invention may be provided as part of an inkjet cartridge and/or printing apparatus, thereby providing a competitive advantage over prior art devices.


REFERENCES:
patent: 5187500 (1993-02-01), Bohorquez et al.
patent: 5473351 (1995-12-01), Helterline et al.
patent: 5521622 (1996-05-01), Hock et al.
patent: 6183076 (2001-02-01), Childers et al.
patent: 361104856-A (1986-05-01), None
patent: 406008475-A (1994-01-01), None

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