High frequency ultrasonic cleaning of ink jet printhead...

Incremental printing of symbolic information – Ink jet – Ejector mechanism

Reexamination Certificate

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Details

C347S035000

Reexamination Certificate

active

06196656

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to high frequency ultrasonic transducer for cleaning of ink jet printhead cartridges wherein the high frequency ultrasonic transducer is in physical contact with the orifice plate.
BACKGROUND OF THE INVENTION
Typically, an ink jet printer has at least one printing cartridge from which droplets of ink are directed towards a receiver. Within the cartridge, the ink may be contained in a plurality of channels and energy pulses are used to cause the droplets of ink to be ejected on demand or continuously, from nozzles or orifices in a plate in an orifice structure.
In a thermal ink jet printer, the energy pulses are generally provided by a set of electrical resistors, each located in a respective one of the channels, each one of them is individually addressable by current pulses to instantaneously heat and form a droplet or bubble in the channels which contact the resistors.
Operation of thermal ink jet printer is described in details in U.S. Pat. Nos. 4,849,774; 4,500,895; and 4,794,409.
On the other hand, a piezoelectric ink jet printing system includes a body of piezoelectric material defining a plurality of parallel open topped channels separated by walls. The walls have metal electrodes on opposite sides thereof to form shear mode actuators for causing droplets to expel from the channels. An orifice structure comprising at least one orifice plate defining the holes through which the ink droplets are ejected is bonded to the open end of the channels. The electrical energy pulses are applied to the parallel electrodes causing the channels to shear actuating the expulsion of droplets from the orifice plate. Operation of piezoelectric ink jet print heads is described in details in U.S. Pat. Nos. 5,598,196; 5,311,218; and 5,248,998 .
Ink jet printing cartridges, whether it is of thermal or piezoelectric kind, use a variety of functional components, all of which must cooperate in a precise manner to achieve maximum efficiency. One of the most important components is an orifice plate having a plurality of orifices or nozzles therein.
The nozzles are usually circular in cross section and the diameter of the nozzles may vary from 10 to 100 &mgr;m as required by the specification of the printer.
Higher the resolution of the printed output, smaller is the ink droplet thereby requiring smaller diameter nozzles or orifices. Ink is ejected through these openings during printing operation. To obtain defect-free printing output, the orifice plates and all the nozzles must be kept clean and free of debris and any kind of obstructions to ink flow at all times. If the orifice plate and nozzles are not clean, many problems can occur thereby undermining the performance of the printer. As for example, paper fibers and other debris accumulated on the orifice plate surface and inside the nozzles can affect the quality of the printed images.
Similarly, debris can be dried ink crusts and paper dust on the orifice plate as well as in the ink channels and the nozzles can cause the printer to perform poorly.
The foregoing problems are overcome, as described in U.S. Pat. No. 5,300,958 to Burke et al, by providing “maintenance or service stations” within the main printer unit. The maintenance stations are designed such that when the printhead ink cartridge is not operating and is in a “parked” position, the cartridge is situated in the maintenance station outside the printing zone for the purpose of routine cleaning of the cartridges. The maintenance station has many components which are designed to serve many functions. These functions include: (a) priming the printhead cartridge, (b) capping the orifice plate and nozzles (orifices) therein when the printhead is not in operation, (c) wiping contaminants from the orifice plate, (d) preventing ink from drying out in the openings of the orifice plate, and (e) providing a receptacle for discarding the cleaned debris.
To accomplish this cleaning, the U.S. Pat. No. 5,103,244 discloses a structure in which a multi-blade wiper is used. The desired cleaning is performed by dragging a printhead (cartridge) across the selected wiper blade.
The wiper mechanism also includes a plurality of resilient blades each having an octagonal shape and rotatable about an axis.
Another cleaning structure disclosed in U.S. Pat. No. 5,300,958, includes a printhead wiper unit consisting of a single or dual members positioned against each other to form a capillary pathway therebetween. The cartridge includes a compartment having an opening therethrough and an absorbent member impregnated with cleaning solution.
Still another cleaning structure is disclosed in U.S. Pat. No. 5,287,126 which includes a vacuum cleaner to help clean the orifice plate. The vacuum cleaner is comprised of a top cover plate, having a plurality of air passages, that is located over a channel surface by spacers. A pressure differential in the defined volume between the top cover plate, the channel surface, and the spacers below the external pressure, so that air is drawn into the defined volume through the air passage. The resulting air flow removes ink, dust and debris from the vicinity thereby keeping the cartridge clean.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide improved cleaning of ink jet printhead cartridges.
It is another object of the present invention to provide a more efficient printhead cartridge cleaning system which permits a controlled dislodging of debris accumulated in the nozzles and the orifices of the orifice structure, discarding the debris without contaminating and damaging the cartridges and thereby cleaning the printhead cartridges efficiently.
It is another object of the present invention to provide an apparatus for cleaning an ink jet printhead cartridge which is compact, robust and efficient.
It is yet another object of the present invention to provide a cleaning apparatus which does not abrade or damage the ink jet cartridges.
These objects are achieved in an ink jet printing apparatus for receiving an ink cartridge defining an orifice structure having at least one orifice plate with a plurality of nozzles for ejecting ink droplets onto a receiver to form an image, means for cleaning the orifice structure of debris, comprising:
(a) at least one actuable high frequency ultrasonic transducer in physical contact with the orifice structure and operatively associated with and spaced from the nozzles; and
(b) means for actuating the actuable high frequency ultrasonic transducer to cause such actuable high frequency ultrasonic transducer to produce ultrasonic sound waves which impinge upon the orifice structure and loosens debris.
Advantages of the invention include:
Overcoming many of the disadvantages of the existing technology, such as damage of the orifice plates due to wear, abrasion and distortion;
Cost-effective electronic integration of the high frequency actuable high frequency ultrasonic transducer to clean ink jet printhead cartridge;
Use of solvents and other undesirable chemicals can be avoided;
The active surface of the actuable high frequency ultrasonic transducer is flat so that it comes in intimate physical contact with a flat orifice plate of an ink jet cartridge; and
Use of a replaceable blotting element that effectively removes and dries the surface of the orifice plate.
It is an important feature of the present invention to involve at least one actuable high frequency ultrasonic transducer to be in physical contact with the orifice plate of an ink jet cartridge for effectively cleaning the ink jet printhead cartridge of debris.


REFERENCES:
patent: 4500895 (1985-02-01), Buck et al.
patent: 4794409 (1988-12-01), Cowger et al.
patent: 4849774 (1989-07-01), Endo et al.
patent: 5103244 (1992-04-01), Gast et al.
patent: 5212496 (1993-05-01), Badesha et al.
patent: 5248998 (1993-09-01), Ochiai et al.
patent: 5287126 (1994-02-01), Quate
patent: 5300958 (1994-04-01), Burke et al.
patent: 5311218 (1994-05-01), Ochiai et al.
patent: 5598196 (1997-01-01), Braun
patent: 5757396 (1998-05-01), Bruner

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