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Quick Step Servo Scheme for Aspirated Ink Jet Printers

IP.com Disclosure Number: IPCOM000052736D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Damon, BW: AUTHOR [+2]

Abstract

In an aspirated ink jet printer, the air and ink stream travel at approximately the same velocity through a tunnel before the ink (in the form of ink drops) strikes the paper. In order to achieve correct air and ink stream velocity through the tunnel, it is typical to ""servo'' the system from time to time not only for ink stream and air start-up but to compensate, during printing, for environmental changes. Because during the servo time the printer is inoperable with regard to the machine operator, it is desirable to reduce the time required to servo the air and ink stream. The present scheme relates to a method of reducing the time for such servo operation.

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Quick Step Servo Scheme for Aspirated Ink Jet Printers

In an aspirated ink jet printer, the air and ink stream travel at approximately the same velocity through a tunnel before the ink (in the form of ink drops) strikes the paper. In order to achieve correct air and ink stream velocity through the tunnel, it is typical to ""servo'' the system from time to time not only for ink stream and air start-up but to compensate, during printing, for environmental changes. Because during the servo time the printer is inoperable with regard to the machine operator, it is desirable to reduce the time required to servo the air and ink stream. The present scheme relates to a method of reducing the time for such servo operation.

The time required to servo in an ink jet system is highly dependent upon the response time of the ink and air systems. For a step change at the electrical input to the ink pump or blower, the output changes exponentially from one operating point to another. The exponential change in output is of the form: P (t) = P(O) + delta P (1-e/-t/tau/) where P(O) is the initial output value, delta P is the difference between the initial and final values, and tau is the system's characteristic time constant. A plot of this response is shown in Fig. 1. As may be seen from Fig. 1, the time for the system to fall within 5% of the final value is approximately 3 time constants (3 tau).

A quick step servo provides an input step that is 1 1/2 times the desired step size. A...