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Velocity Control for Ink Jet Printers

IP.com Disclosure Number: IPCOM000088220D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Dohanich, GJ: AUTHOR

Abstract

Referring to Fig. 1, pump driver 10 has two inputs: a fixed frequency, fixed pulse-width digital signal, shown as drive rate, and an analog control signal. Pump driver 10 mixes these two inputs and has as its output a fixed frequency, fixed pulse-width variable amplitude output. The output amplitude is proportional to the analog input. The output from pump driver 10 is applied to pump 11, which is connected to reservoir 12 to supply printing ink under pressure to nozzle 13 to cause a continuous stream of ink drops 14 to be projected toward a print medium (not shown). The pump 11 is assumed to be such a design that it is responsive to the amplitude control input such that the output stream velocity is proportional to the input amplitude.

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Velocity Control for Ink Jet Printers

Referring to Fig. 1, pump driver 10 has two inputs: a fixed frequency, fixed pulse-width digital signal, shown as drive rate, and an analog control signal. Pump driver 10 mixes these two inputs and has as its output a fixed frequency, fixed pulse-width variable amplitude output. The output amplitude is proportional to the analog input. The output from pump driver 10 is applied to pump 11, which is connected to reservoir 12 to supply printing ink under pressure to nozzle 13 to cause a continuous stream of ink drops 14 to be projected toward a print medium (not shown). The pump 11 is assumed to be such a design that it is responsive to the amplitude control input such that the output stream velocity is proportional to the input amplitude. Further, ink reservoir 12 has a sufficiently long time constant that it is not responsive to the switching input. That is, there is a low ripple content due to the non-DC input.

An electromechanical vibrator 15 is attached to nozzle 13 to be operated at a fixed frequency to produce the stream of droplets 14 whose velocity is determined by the analog input to pump driver 10 and whose wavelength is the ratio of velocity and the excitation frequency.

Two drop sensors 16 and 17 are spaced an integral number of desired wavelengths apart at a fixed distance from nozzle 13 such that when the correct stream velocity exists, detection signals from the sensors 16 and 17 occur simultaneously. For velocities other than the desired velocity, but near the desired velocity, the sensor output detection signals are time-displaced.

A phase detector circuit 18 continuously monitors the output detection signals from sensors 16 and 17 and converts their relative times of occurrence into outputs Q and Q independently of input pulse width, but of varying output pulse width proportional to the time difference of occurrence of the signal outputs from sensors 16 and 17. It is assumed that the drop excitation rate applied to the electromechanical vibrator 15 far exceeds the pump drive rate applied to pump driver 10.

The two low-pass filters R(1Q)-C(1) and R(2)-C(2) average the phase information contained at the outputs Q and Q of detector 18 This averaged analog data is converted into digital data by comparator 19 and applied to the up/down control of up/down counter 20. The averaging by the low-pass filters is desired to prevent the system from reacting to stream jitter.

As seen in Fig. 3, the operation of this portion of the system shows that if the velocity is low, the wavelength of the drops 14 will be less than the desired wavelength for the desired velocity. This condition will result in a detection signal output from sensor 16 occurring before the detection signal from sensor 17. If sensor 16 is connected to the set input of...