Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-09-21
2001-02-13
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000, C347S019000, C347S068000
Reexamination Certificate
active
06186610
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to imaging apparatus and methods and more particularly relates to an imaging apparatus capable of suppressing inadvertent ejection of a satellite ink droplet therefrom and method of assembling same.
An imaging apparatus, such as an ink jet printer, produces images on a receiver medium by ejecting ink droplets onto the receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the ability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
One such ink jet printer is disclosed in commonly assigned U.S. patent application Ser. No. 09/036,012, titled “Printer Apparatus Capable Of Varying Direction Of An Ink Droplet To Be Ejected Therefrom And Method Therefor” filed Mar. 6, 1998 in the name of Xin Wen. The ink jet printer of the Wen disclosure includes a piezoelectric print head capable of varying direction of an ink droplet to be ejected from the print head. A pair of sidewalls belonging to the print head define an ink channel therebetween containing ink. The print head includes addressable electrodes attached to the side walls for actuating (i.e., moving) the sidewalls, so that the ink droplet is ejected from the ink channel. In this regard, a pulse generator applies time and amplitude varying electrical pulses to the addressable electrodes for actuating the sidewalls.
More specifically, when the side walls of the Wen device inwardly move due to the actuation thereof, a pressure wave is established in the ink contained in the channel. As intended, this pressure wave squeezes a portion of the ink in the form of the ink droplet out the channel. However, as the pressure wave ejects the ink droplet, the pressure wave impacts the sidewalls defining the channel and is reflected therefrom. The pressure wave reflected from the sidewalls establishes a reflected pressure wave in the channel, this reflected pressure wave being defined herein as a “reflected portion” of the incident pressure wave. Of course, if the time between actuations of the sidewalls is sufficiently long, the reflected portion dies-out before each successive actuation of the sidewalls.
However, the reflected portion of the pressure wave may be of amplitude sufficient to inadvertently eject an unintended so-called “satellite droplet” that follows ejection of the intended ink droplet but that occurs before the reflected portion dies-out. Satellite ink droplet formation is undesirable because such inadvertent satellite ink droplet formation interferes with precise ejection of ink droplets from the ink channels, which leads to ink droplet placement errors. These ink droplet placement errors in turn produce image artifacts such as banding, reduced image sharpness, extraneous ink spots, ink coalescence and color bleeding. Thus, a problem in the art is satellite ink droplet formation leading to ink droplet placement errors.
In addition, as stated hereinabove, if the time between actuations of the sidewalls is sufficiently long, the reflected portion of the pressure wave eventually dies-out. Thus, printer speed is selected such that electrical pulses are applied to the addressable electrodes at intervals after each reflected portion dies-out. Such delayed printer operation is required in order to avoid the unintended reflected portion interfering with the intended pressure wave. Otherwise allowing the reflected portion to interfere with the intended pressure wave may result in the aforementioned ink droplet placement errors. However, operating the printer in this manner reduces printing speed because ejection of ink droplets must await the cessation of the reflected portion of the pressure wave. Therefore, quite apart from the aforementioned problem of satellite droplet formation, another problem in the art is reduced printer speed due to presence of the reflected portion of the intended pressure wave.
Therefore, there has been a long-felt need to provide an imaging apparatus capable of suppressing inadvertent ejection of a satellite ink droplet therefrom while maintaining printing speed, and method of assembling the apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an imaging apparatus capable of suppressing inadvertent ejection of a satellite ink droplet therefrom while maintaining printing speed, and method of assembling the apparatus.
With this object in view, the invention resides in an imaging apparatus, comprising a transducer defining a chamber therein, said transducer capable of inducing a first pressure wave in the chamber, the first pressure wave having a reflected portion; and a deflectable sensor coupled to the chamber for sensing the reflected portion and connected to said transducer for actuating said transducer in response to the reflected portion sensed thereby, so that said transducer actuates to induce a second pressure wave in the chamber damping the reflected portion, said sensor capable of deflecting as said sensor senses the reflected portion.
According to one embodiment of the present invention, an imaging apparatus, with pressure sensor, is provided that is capable of suppressing inadvertent ejection of a satellite ink droplet from an ink body residing in the imaging apparatus. The imaging apparatus comprises a print head defining a chamber having the ink body disposed therein. A transducer (e.g., a piezoelectric transducer) is in fluid communication with the ink body for inducing a first pressure wave in the ink body, which first pressure wave has a reflected portion of a first amplitude and a first phase sufficient to inadvertently eject satellite droplets. In this regard, a waveform generator is connected to the transducer for supplying a first voltage waveform to the transducer, so that the transducer induces the first pressure wave in the ink body. In addition, a sensor is in fluid communication with the ink body for sensing the reflected portion of the first pressure wave and for generating a second voltage waveform in response to the reflected portion sensed by the sensor. Moreover, a feedback circuit is connected to the sensor for receiving the second voltage waveform generated by the sensor. The feedback circuit converts the second voltage waveform to a third voltage waveform. The amplitude and phase of the third voltage waveform are chosen by the feedback circuit to rapidly drive the reflected portion and thus the second voltage waveform to zero. The third voltage waveform is transmitted to the transducer, so that the transducer controllably actuates in response to the third voltage waveform supplied thereto. This third voltage waveform induces a second pressure wave in the ink body. The second pressure wave has a second amplitude and a second phase which damps the amplitude of the reflected portion of the first pressure wave in order to suppress inadvertent ejection of satellite ink droplets. This is so because the amplitude and phase of the third voltage waveform are chosen by the feedback circuit to rapidly drive the reflected portion and thus the second voltage waveform to zero, as previously mentioned.
The imaging apparatus further comprises a switch capable of switching between a first operating mode and a second operating mode. When the switch switches to the first operating mode, the switch connects the waveform generator to the transducer for actuating the transducer in order to produce the first pressure wave in the chamber. When the switch switches to the second operating mode, the switch connects the feedback circuit to the sensor and transducer for sensing the reflected portion of the first pressure wave and for damping the reflected portion in the manner mentioned hereinabove.
A feature of the present invention is the provision of a sensor coupled to the chamber for sensing the reflected portion of the first pressure wave.
Another feature of the present invention is the provision of a feedback circuit connected to the sensor for control
Delametter Christopher N.
Kocher Thomas E.
Lubinsky Anthony R.
Moghadam Omid A.
Barlow John
Eastman Kodak Company
Hallacher Craig A.
Stevens Walter S.
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