Incremental printing of symbolic information – Ink jet – Controller
Patent
1995-11-30
1998-03-03
Metjahic, Safet
Incremental printing of symbolic information
Ink jet
Controller
347 86, B41J 2195, B41J 2175
Patent
active
057240760
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet print head for printers, facsimiles, plotters, and word processors and to an out-of-ink detector for ink jet printers.
2. Description of the Related Art
Ink jet printers incorporating an ink jet print head are well known. These ink jet printers are of such a type that fine ink particles are jetted against a medium to be printed on, with a print head being out of contact with it. Thus these type of printers are advantageous in that the medium to be printed on have relaxed technical limits, and that they are capable of high-speed printing.
FIG. 12 schematically illustrates the basic principle of a Kaiser type piezoelectric head unit. As shown in the FIG. 12, an ink feed passage 102, a pressure chamber 103, and a nozzle 104 are provided in series on a substrate 101. A vibration plate 105 is provided on a surface of the substrate 101, outside the vibration plate 105 a piezoelectric element 106 is installed opposite to the pressure chamber 103. To apply voltage to the piezoelectric element 106, both of the element 106 sides are connected to a signal source 107. An ink container 109 is connected through a pipe 108 with the ink feed passage 102.
In the above configuration, the piezoelectric element 106 warps the vibration plate 105, thereby jetting ink 110 in the pressure chamber 103 in the form of ink droplets 110a through the nozzle 104 against recording medium for recording when the signal source 107 applies a voltage to the piezoelectric element 106. When voltage application to the piezoelectric element 106 is stopped after jetting ink, the vibration plate 105 returns to its original condition, so that the same amount of ink as has been jetted is fed under the capillary action of the nozzle from the ink container 109 through the ink feed passage 102 and the pipe 108.
Conventional ink jet print heads are provided with an ink tank from which ink is fed to their head substrates.
As shown in FIG. 10 and FIG. 11 showing a partial cross section of a conventional ink tank of FIG. 10, taken on line X--X, two electrodes 52a and 52b have been installed in an ink tank 50 to detect an out-of-ink condition by measuring the resistance between the electrodes 52a and 52b. When the ink tank 50 is filled with ink, a resistance of a few megohms can be measured because the two electrodes 52a and 52b are electrically connected with each other through the ink. On the other hand, when no ink is in the ink tank, the electrodes are not electrically connected together.
In FIG. 11, an ink outlet 54 is internally fitted with a filter 53 and externally fitted with an O-ring 55.
As described above, for out-of-ink detectors used with conventional ink jet print heads, the ink tank 50 must be provided with two electrodes, so that the detectors have posed problems of high electrode cost and a complicated structure of the ink tank 50.
It is an object of the present invention, in order to solve the problems, to provide an out-of-ink detector which allows the number of electrodes installed in an ink tank to be reduced, and the electrode cost to be reduced, and the ink tank to be structurally simplified.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an out-of-ink detector which detects the out-of-ink condition of an ink jet print head having an ink jet head unit with a plurality of nozzles, through which the unit selectively jets ink, and having an ink tank feeding ink to the unit, the detector comprising a pair of electrodes and one of the two detection electrodes is electrically conductive film formed on the vibration plate of the ink jet head unit constituting a common electrode.
According to a second aspect of the present invention, in the detector of the first aspect, the electrically conductive film for the common electrode is the electrode on a ground side.
According to a third aspect of the present invention, in the detector of the first or second aspects, the ink tank has another detecti
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patent: 5488395 (1996-01-01), Takayanagi et al.
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Chizmar John
Metjahic Safet
Rohm & Co., Ltd.
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