Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-09-29
2001-10-09
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06299291
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fluid jet devices, and more particularly, to ink jet apparatus and ink jet printer heads, and methods of operating the same.
BACKGROUND OF THE INVENTION
Ink jet printers are known as a type of non-impact printer which has no physical contact with the surface on which it is printing. As the name “ink jet” suggests, an ink jet printer projects a jet of ink out of the print head through free air onto a surface to be printed. Due to its ability to print on various shaped and textured surfaces without contact, the ink jet technology finds new applications daily, especially in all types of industries which rely upon product marking, coding, dating or identification. Ink jet printing (text and graphic) has also developed considerably.
Ink jet technology falls into two main categories. One is continuous ink jet technology, according to which a stream of ink is continuously circulating from the body of the printer through the print head and back to the body of the printer. The ink is broken into drops at the nozzle and then deflected by electric charge to either reach the target or end up in a return block. The other technology is drop-on-demand, according to which droplets of ink are forced out of the nozzle only when needed, at an appropriate time. In some cases, the ink is ejected by heating a resistor which causes an air bubble to expand. When the bubble collapses, the droplet breaks off and the system returns to its original state. In other cases, the ink is ejected under pressure pulses caused by mechanically induced volumetric changes in the ink.
A typical drop-on-demand type ink jet printing system of the latter case is disclosed in U.S. Pat. No. 4,459,601 to Howkins. In Howkins, the volume of an ejection chamber is varied by a piezoelectric transducer that communicates with a moveable wall of the ejection chamber. The transducer expands and contracts to drive ink out through an orifice. A printing control voltage is applied to electrodes placed across the piezoelectric transducer to induce the expanding or contracting movements of the transducer.
Generally, in the above Hawkins structure, the transducers are placed in predetermined positions through an adhesive agent or the like to attach to the ejection chambers. Particularly in high quality printers, it is desirable to design an increased number of the nozzles for ejecting ink drops in an ink jet printer head. Since the dimension of the ink jet printer head is limited, the transducers, arranged in a densely packaged array, must be as small as possible. Therefore, in the case of a high-density ink-jet recording apparatus having a large number of nozzles, there is a limitation from the viewpoint of accuracy in aligning and bonding the transducers to their respective moveable walls. The adhesive layer interposed between the moveable wall and the piezoelectric transducer may lower the driving efficiency of the ink jet apparatus as well.
In addition, the conventional ink jet apparatus utilizes a separate transducer for each channel. A pair of electrical electrodes must also be formed individually in each transducer. Accordingly, to construct such a printer head, a large number of individual parts must be used, and a large number of steps are required to assemble the array. For these reasons, it has heretofore been impractical to manufacture a very high density ink jet printer head.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an ink jet apparatus which tolerates some degrees of misalignment between the transducer and the chamber without sacrificing accuracy.
It is a further object of the present invention to provide an ink jet apparatus which eliminates the need for a physical adhesive bond between the transducer and the chamber, thus, improving the driving efficiency of the ink jet apparatus.
It is a further object of the present invention to provide an ink jet apparatus which utilizes common transducers and chambers yet achieves the above objects.
It is a further object of the present invention to provide an ink jet printer head in which a single transducer can be shared among several channels, thus reducing the number of parts to be used and simplfying the assembling process in the manufacture of the ink jet printer head.
These and other objects of the present invention are achieved by the use of electrostatic attraction to bind the moveable wall of the ejection chamber to the transducer. In accordance with an aspect of the invention, a fluid jet apparatus comprises a fluid chamber and an actuator. The fluid chamber has a nozzle and a flexible wall capable of vibrating to alter a volume of the fluid chamber. The actuator generates mechanical movements according to a control signal. The flexible wall and the actuator are coupled by electrostatic coupling arrangements, thereby the mechanical movements of the actuator are transformed into vibrations of the flexible wall.
The foregoing objects of the present invention are also achieved by an ink jet apparatus comprising an ink chamber and an actuator. The ink chamber includes a nozzle, an inlet, and a flexible wall. Electrostatic coupling arrangements are provided for creating an electrostatic bond between the flexible wall and the actuator. Thus, when the actuator moves, the flexible wall is deformed to force ink out through the nozzle and to draw ink in through the inlet. In accordance with an aspect of the invention, the electrostatic coupling arrangements comprises a pair of electrodes which are attached directly or indirectly to an edge of the actuator and to the outer surface of the flexible wall.
The foregoing objects of the present invention are also achieved by an ink jet printer head comprising a plurality of ejection chambers, at least one motion driving element, and a coupling control circuit. Each ejection chamber has a nozzle, an inlet, and a flexible wall. There is a plurality of first electrostatic coupling members each associated with one flexible wall. At least one second electrostatic coupling member is also provided for the at least one motion driving element. The coupling control circuit selectively generates electrostatic bonds between selected first electrostatic coupling members and the at least one second electrostatic coupling member. Therefore, when the at least one motion driving element moves, only the flexible walls associated with the selected first electrostatic coupling members are deformed to force ink out through their nozzles and to draw ink in through their inlets. In accordance with an aspect of the invention, the electrostatic coupling members are electrodes which are attached directly or indirectly to an edge of the at least one motion driving element and to the outer surfaces of the flexible walls.
The foregoing objects of the present invention are also achieved by a method of operating an inkjet apparatus. The ink jet apparatus includes an ink chamber with a flexible wall, and an actuator. In accordance with the method, an electrostatic bond is generated between the flexible wall and the actuator. Next, the flexible wall is deformed in response to a movement of the actuator in a first direction. In accordance with an aspect of the invention, the flexible wall then returns to its original state either in response to a movement of the actuator in a second direction, or when the electrostatic bond is removed.
The foregoing objects of the present invention are also achieved by a method of operating an ink jet printer head. The inkjet printer head includes a plurality of ejection chambers, and at least one actuator. In accordance with the method, electrostatic bonds are selectively generated between flexible walls of selected ejection chambers and the at least one actuator. Next, selected flexible walls are deformed in response to a movement of the at least one actuator in a first direction. In accordance with an aspect of the invention, the selected flexible walls then return to their original states either in response to a movement o
Breh Donald J.
Croll Mark W.
Gordon Raquel Yvette
Illinois Tool Works Inc.
Soltis Lisa M.
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