Fluid sprinkling – spraying – and diffusing – With means to vibrate or jiggle discharge – By electric transducer
Reexamination Certificate
1999-07-22
2001-02-06
Hook, James (Department: 3752)
Fluid sprinkling, spraying, and diffusing
With means to vibrate or jiggle discharge
By electric transducer
C347S094000
Reexamination Certificate
active
06182907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique to drive a liquid jet unit for jetting droplets from a liquid surface, and more particularly to a technique to jet droplets by providing vibration to a liquid having a surface limitedly exposed by an opening.
2. Description of the Background Art
There has been a technique of depositing ink onto printing paper in a form of droplet to draw images and characters, i.e., ink jet printing. In this description, for distinction, a term “jet” is used when a plurality of ink droplets are simultaneously generated and a term “discharge” is used when droplets are sequentially generated one by one.
To faithfully reproduce tone of an image proposed is a technique of ultrasonically providing ink with vibration to obtain droplets from an ink surface. For example, Japanese Patent Application Laid Open Gazette No. 2-303849 discloses a technique of controlling the length of period for continuously providing ink with ultrasound to control the amount of ink to be discharged. Japanese Patent Application Laid Open Gazette No. 10-128968 discloses a technique of providing ink with ultrasonic burst including a certain number of pulses repeatedly a plurality of times to control the amount of ink to be jetted with the repeat number.
In the technique of controlling the length of period for continuously providing ink with ultrasound to control the amount of ink to be discharged, however, in order to discharge a large amount of ink, it is necessary to provide ink with continuous ultrasonic supply for a long time. That causes a marked rise of the level of ink surface from the opening with a radiation pressure as discussed later, resulting in an unstable discharge of droplets.
The technique of providing ink with ultrasonic burst repeatedly a plurality of times is superior in not providing continuous radiation pressure. Since the ink jet printing, however, requires depositing of ink on printing paper with different tones for dots, it is necessary to adjust the timing of sending the printing paper and that of disposing ink for every dot. The length of period while no continuous ultrasonic is supplied varies from dot to dot in the technique of providing ink with ultrasonic burst repeatedly a plurality of times as well as in the technique of controlling the length of period for continuously providing ink with ultrasound. Since the length of period while a radiation pressure is provided therefore varies from dot to dot, the rise of ink level from the opening varies from dot to dot. This variation causes an unstable jetting of droplets, and further causes deterioration in graininess in terms of printing quality and difficulty in controlling gradation.
SUMMARY OF THE INVENTION
The present invention is directed to a liquid jet driving device. According to a first aspect of the present invention, the liquid jet driving device comprises: a liquid jet unit having a jet surface provided with an opening to limitedly expose a surface of liquid to be jetted out and a vibration exciter provided on an opposite side to the jet surface with the liquid interposed therebetween for providing the liquid with vibration; and a driving unit for providing the vibration exciter with a suppressing signal and a jet burst signal consisting of a pulse train of a first frequency to drive the vibration exciter. In the device of the first aspect, vibration provided for the liquid by the vibration exciter which is driven with the jet burst signal is sufficient for the liquid to jet out from the jet surface and vibration provided for the liquid by the vibration exciter which is driven with the suppressing signal is not sufficient for the liquid to jet out from the jet surface.
According to a second aspect of the present invention, in the liquid jet driving device according to the first aspect, the suppressing signal is a suppressing burst signal consisting of a pulse train of the first frequency and has less pulses in number than the jet burst signal.
According to a third aspect of the present invention, in the liquid jet driving device according to the first aspect, the suppressing signal is a suppressing burst signal consisting of a pulse train of the first frequency which has a smaller amplitude than those of the jet burst signal.
According to a fourth aspect of the present invention, in the liquid jet driving device according to the first aspect, the vibration exciter is driven with the jet burst signal to provide the liquid with a first radiation pressure, the liquid makes free vibration caused by the first radiation pressure in a mode specific to the shape of the opening, the suppressing signal is supplied for the vibration exciter near at least one timing when the free vibration takes an amplitude of extreme value, and the vibration exciter is driven with the suppressing signal to provide the liquid with a second radiation pressure which works in a direction to suppress the free vibration.
According to a fifth aspect of the present invention, in the liquid jet driving device according to the first aspect, the vibration exciter has a first vibration exciter supplied with the jet burst signal and a second vibration exciter supplied with the sup pressing signal.
According to a sixth aspect of the present invention, in the liquid jet driving device according to the fifth aspect, the first vibration exciter is driven with the jet burst signal to provide the liquid with a radiation pressure, the liquid makes free vibration caused by the radiation pressure in a mode specific to the shape and size of the opening, the suppressing signal is supplied for the second vibration exciter near at least one timing when the free vibration takes an amplitude of extreme value, and the second vibration exciter is driven with the suppressing signal to provide the liquid with a pressure which works in a direction to suppress the free vibration.
According to a seventh aspect of the present invention, in the liquid jet driving device according to the sixth aspect, the suppressing signal is supplied for the vibration exciter at the point of time when a liquid level of the liquid in the opening takes an extreme value near the side of the vibration exciter in the free vibration.
According to an eighth aspect of the present invention, in the liquid jet driving device according to the fifth aspect, the second vibration exciter is driven with the suppressing signal in a period while the jet burst signal is supplied for the first vibration exciter, to provide the liquid with a pressure having a direction opposite to that of a radiation pressure provided for the liquid by the first vibration exciter driven with the jet burst signal.
According to a ninth aspect of the present invention, in the liquid jet driving device according to the first aspect, the jet burst signal and the suppressing signal are supplied for the vibration exciter repeatedly with a second frequency.
According to a tenth aspect of the present invention, in the liquid jet driving device according to the ninth aspect, the second frequency is a frequency with which the liquid makes free vibration in a mode specific to the shape of the opening.
According to an eleventh aspect of the present invention, in the liquid jet driving device according to the first aspect, the jet burst signal is supplied for the vibration exciter repeatedly during a period required for a to-and-fro movement of a surface wave in the opening, which is excited on the basis of a radiation pressure to push the liquid out from the opening in a period while the vibration exciter is driven.
According to a twelfth aspect of the present invention, the liquid jet driving device comprises: a liquid jet unit having a jet surface provided with an opening to limitedly expose a surface of liquid to be jetted out and a vibration exciter provided on an opposite side to the jet surface with the liquid interposed therebetween for providing the liquid with vibration; a driving unit for providing the vibration exciter with a jet burst signal consisting of
Aizawa Jyun-ichi
Fukumoto Hiroshi
Nakagawa Hiroyuki
Ozaki Yasuhiko
Hook James
Hwu Davis
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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