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Phase-Locked Loop Emitter Processor and Method of Monitoring Emitter Pulse Rates for Band Printers

IP.com Disclosure Number: IPCOM000040435D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Barcomb, JG: AUTHOR [+3]

Abstract

Hardware and software improvements are used to reduce registration errors arising from discrepancies in the detection of the precisely spaced emitter openings in a print band and the corresponding generation of electric emitter pulses by an optical sensor. Referring to the figure, the printer band 1 includes a row of precisely spaced and shaped apertures to ultimately trigger a "fire" pulse or a "home" pulse. The apertures are optically sensed as they move by a detector 2, which generates a series of electric signals. The hardware improvements include inputting these electric signals on line 3 to a phase-locked loop (PLL) pulse generator 4, which generates pulses that are logically processed by processor 5. The processor outputs home or fire signals on lines 6 and 7 to the actuator control 8.

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Phase-Locked Loop Emitter Processor and Method of Monitoring Emitter Pulse Rates for Band Printers

Hardware and software improvements are used to reduce registration errors arising from discrepancies in the detection of the precisely spaced emitter openings in a print band and the corresponding generation of electric emitter pulses by an optical sensor. Referring to the figure, the printer band 1 includes a row of precisely spaced and shaped apertures to ultimately trigger a "fire" pulse or a "home" pulse. The apertures are optically sensed as they move by a detector 2, which generates a series of electric signals. The hardware improvements include inputting these electric signals on line 3 to a phase-locked loop (PLL) pulse generator 4, which generates pulses that are logically processed by processor 5. The processor outputs home or fire signals on lines 6 and 7 to the actuator control 8. The actuator control signals the hammer driver 9 to actuate the hammers in the hammer bank 10, and fires selected hammers at a frequency based upon the signals from the detector. The PLL 4 operates as a frequency multiplier and generates multiple virtual fire pulses for each emitter slot at a frequency dependent upon the desired number of dots to be printed per inch. Changes in the frequency of the signals from the detector results in corresponding changes in the frequency of the output signals from the PLL. If a signal from the detector is absent, due to band contamination or some other reason, the PLL continues to operate at substantially the same frequency, and the fire pulses are generated based upon this presumed presence of an emitter aperture at the proper location. Thus, infrequent or minor variations in the frequency of the detector signal have little effect. On the other hand, more significant changes, such as a change in the print band speed or blockage of several emitter openings, will change the frequency of the PLL to match the band speed. Frequent detection of small changes in frequency may also be used to alert an operator that the band should be cleaned. Assuming a single optical detector is used to sense the emitter openings and the wider home slot, the decoding circuit 5...