Control apparatus for an on-demand ink jet printing element
First Claim
1. A printing apparatus having at least one on demand ink jet printing element comprising a container made of insulating material for containing an electrically conductive ink, said container having a nozzle, a first electrode in contact with the ink, and a second electrode located adjacent the outlet edge of said nozzle, said apparatus also comprising printing control means for generating voltage pulses between said first electrode and said second electrode to create an electric current in the ink so as to cause a drop of ink to be expelled through the nozzle, wherein said printing control means include:
- a signal generator for generating a logic signal for each drop to be expelled,a first circuit directly responsive to said logic signal for generating a first voltage pulse having such a duration as to raise the temperature of the ink into the nozzle up to close to the vaporization point of the ink,a delay circuit connected to said signal generator for outputting a signal delayed with respect to said signal a predetermined time,a second circuit responsive to said delayed signal for generating a second voltage pulse so as to suddenly create a bubble of vapor in the nozzle to expel a drop of ink, andadjusting means substantially responsive to the ink temperature for controlling said first circuit so as to alter the duration of said first voltage pulse an amount inversely proportional to the variations of said ink temperature.
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Accused Products
Abstract
In an ink jet printing element in which the drop is expelled by generating a current pulse through the ink in the nozzle, in order to reduce the control voltage, a first pulse (Tr) for heating the ink is generated, followed by a vaporization pulse (Tv) with a delay such as to make the printing position independent of the direction of movement of the element with respect to the paper. The heating pulse (Tr) is generated by a circuit (31) controlled by a temperature sensor (34) so that the duration of the heating pulse has a negative temperature coefficient. The vaporization pulse (Tv) is generated by a circuit (32) manually controlled (potentiometer 39) to determine the pulse duration on the basis of the desired strength of the printing. The delay between the two pulses is controlled by a delay circuit (38), e.g. a monostable circuit. The two pulses are applied to a transformer (35) which generates the voltage between the electrodes. The two circuits (31, 32) may be constituted by one monostable circuit with separate RC networks sequentially enabled for determining the durations of the heating and vaporization pulses.
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Citations
10 Claims
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1. A printing apparatus having at least one on demand ink jet printing element comprising a container made of insulating material for containing an electrically conductive ink, said container having a nozzle, a first electrode in contact with the ink, and a second electrode located adjacent the outlet edge of said nozzle, said apparatus also comprising printing control means for generating voltage pulses between said first electrode and said second electrode to create an electric current in the ink so as to cause a drop of ink to be expelled through the nozzle, wherein said printing control means include:
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a signal generator for generating a logic signal for each drop to be expelled, a first circuit directly responsive to said logic signal for generating a first voltage pulse having such a duration as to raise the temperature of the ink into the nozzle up to close to the vaporization point of the ink, a delay circuit connected to said signal generator for outputting a signal delayed with respect to said signal a predetermined time, a second circuit responsive to said delayed signal for generating a second voltage pulse so as to suddenly create a bubble of vapor in the nozzle to expel a drop of ink, and adjusting means substantially responsive to the ink temperature for controlling said first circuit so as to alter the duration of said first voltage pulse an amount inversely proportional to the variations of said ink temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification