Encoder system for dot matrix line printer

Details Encoder system for dot matrix line printer Encoder system for dot matrix line printer

1983-11-10

1985-06-11

Sewell, Paul T.

Typewriting machines

Carriage or carriage-moving or movement-regulating mechanism

Carriage-feed mechanism

34087037, 364559, 400320, 4007051, B41J 1930

Patent

active

045225176

ABSTRACT:
A linear capacitive encoder is utilized for detecting and encoding the position of a movable member such as a print bar in a dot matrix impact printer. An eight-phase signal is capacitively coupled to one plate of a linear capacitor mounted on the movable print bar. When the print bar moves the phase of the coupled signal changes with respect to the phase of the signal on the other plate of the capacitor, producing an analog signal representing incremental movements of the print bar. The analog signal is amplified and filtered and then converted to a TTL signal representing the position of the print bar. Present position of the print bar is compared to previous position of the print bar to derive signals representing the present direction of movement, direction change and incremental movements of 0.001". Built-in error or hysteresis is added to the direction and direction change signals to prevent false direction changes due to noise. The 0.001" signal and the direction change signal input a microprocessor which generates print position command signals at a selected dot density based on data stored in an output table which takes into account print hammer flight time and compensates for the sinusoidal motion of the print bar. An absolute reference point is established by the processor at each direction change of the print bar motion.

REFERENCES:
patent: 3938113 (1976-02-01), Dobson et al.
patent: 3961318 (1976-06-01), Farrand et al.
patent: 4332492 (1982-06-01), Thern et al.
patent: 4423417 (1983-12-01), Tanaka et al.
IBM Tech. Disc. Bulletin, by D. R. Dobson et al, vol. 21, No. 1, Jun. 1978, pp. 242-243, 340-870.37, "Position Encoder".
Digital Design, "RF Technology for a Matrix Printer", by Robert Kulterman, vol. 6, No. 6, Jun. 1976, pp. 42-46, 400-322.

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