Thermal printer with print density control

Details Thermal printer with print density control Thermal printer with print density control

1982-04-30

1984-04-10

Reynolds, B. A.

Electric heating

Heating devices

Combined with diverse-type art device

346 76PH, 400120, H05B 300

Patent

active

044423420

ABSTRACT:
There is disclosed a print density control for use in a thermal printer, which control is responsive to variation in a supply voltage for assuring a uniform print density. The control includes a voltage-to-frequency converter for varying the frequency of an output signal in accordance with the amplitude of the supply voltage to the print head. An enabling voltage is applied to the print head until a count characteristic of the frequency of the output signal from the voltage-to-frequency converter reaches a predetermined value. By controlling the conduction duration of the print head in response to variations in the supply voltage, the thermal energy conveyed from the print head to a heat sensitive sheet is fixed to thereby assure uniform print density. In a preferred form, there are further provided a control circuit for permitting voltage supply to the print head until the count reaches the predetermined value and for varying the current conduction duration of the print head as a function of variations in the supply voltage to the print head. Accordingly, the strength of thermal energy being supplied to the print head is kept constant regardless of variations in the supply voltage to the print head.

REFERENCES:
patent: 3934695 (1976-01-01), Kovalick
patent: 3975707 (1976-08-01), Ito et al.
patent: 4113391 (1978-09-01), Minowa
patent: 4168421 (1979-09-01), Ito

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