Ink jet recording apparatus

An ink jet recording apparatus having at least one ink tank for containing therein a substantial amount of ink, a nozzle connected to said ink tank for discharging the ink within the ink tank to the outside of said ink tank, an electrode supported in position in spaced relation to said nozzle, means connected to said nozzle and said electrode for applying a voltage between said nozzle and said electrode for establishing an electric field between said nozzle and said electrode, said nozzle and voltage applying means having a shape and applying a sufficient voltage for producing an electric field having an intensity which is symmetrical with respect to the center of the nozzle for causing the ink droplets to travel straight from the nozzle and having a strength for causing the ink to be drawn out of the nozzle due to the field alone, means connected to said nozzle for moving the nozzle relative to a recording medium with the tip of the nozzle spaced a predetermined distance from the recording medium, velocity detecting means associated with said nozzle and said recording medium for detecting the velocity of said relative movement of the nozzle and the recording medium for generating an output signal indicative of the detected velocity, and means for controlling the amount of ink jetted from the nozzle towards the recording medium for drawing lines of predetermined width, said controlling means comprising;

• pressure control means connected to said tank for controlling the static air pressure acting on the surface of the ink within the ink tank to an amount less than that necessary to jet ink from the nozzle solely by the air pressure and for varying the static air pressure and for varying the amount of ink jetted from the nozzle in proportion to the air pressure;
• pressure sensor means connected to said tank for detecting the air pressure acting on the surface of the ink within the ink tank and for generating an output signal indicative of the value of the pressure thus detected;
• comparison means connected to said pressure sensor means and said velocity detecting means for comparing the output signal from the pressure sensor means with the output signal from the velocity detecting means and for generating an output signal indicative of any difference therebetween;
• and
• operating means connected between said comparison means and said pressure control means for operating the pressure control means in response to the output signal from said comparison means, whereby the ink jetted from the nozzle is controlled in accordance with the variance of the relative velocity of the nozzle and the recording medium.

An ink jet recording apparatus having at least one ink tank for containing therein a substantial amount of ink, a nozzle connected to said ink tank for discharging the ink within the ink tank to the outside of the ink tank, an electrode supported in position in spaced relation to said nozzle, means connected to said nozzle and said electrode for applying a voltage between the nozzle and the electrode for establishing an electric field between the nozzle and the electrode, said nozzle and voltage applying means having a shape and applying a sufficient voltage for producing an electric field having an intensity which is symmetrical with respect to the center of the nozzle for causing the ink droplets to travel straight from the nozzle and having a strength for causing the ink to be drawn out of the nozzle due to the field alone, means connected to the nozzle for moving the nozzle relative to a recording medium, and means for controlling the amount of ink jetted from the nozzle towards the recording medium, said controlling means comprising;

• pressure control means connected to said tank for controlling the static air pressure acting on the surface of the ink within the ink tank to an amount less than that necessary to jet ink from the nozzle solely by the air pressure and for varying the static air pressure and for varying the amount of ink jetted from the nozzle in proportion to the air pressure;
• pressure sensor means connected to said tank for detecting the pressure acting on the surface of the ink within the ink tank and for generating an output signal indicative of the pressure thus detected;
• means associated with said nozzle and the recording medium for detecting the velocity of relative movement of the nozzle and the recording medium and for generating an output signal proportional to the detected velocity;
• comparison means connected to said pressure sensor means and said velocity detecting means for comparing the output signal from the velocity detecting means for generating an output signal indicative of any difference therebetween;
• and
• means connected between said comparison means and said pressure control means for operating the pressure control means in response to the output signal from said comparing means;
• said pressure control means having a pulse motor, the angle of rotation of which is controlled by the output signal from the operating means, motion translator means connected to the pulse motor for translating the rotation of the pulse motor into a linear motion, an air pump including a sealed cylinder and a piston operatively accommodated within said cylinder for adjusting the volume of the interior of said cylinder, means connected between the motion translator means and the piston for transmitting the linear motion to the piston, and a flexible tubing having its ends connected to the ink tank and the cylinder, respectively, for transmitting the pressure evolved within the cylinder by said piston to the ink tank whereby the ink jetted from the nozzle is controlled in accordance with the pressure transmitted to the ink tank.