Method for controlling voltage and providing temperature compensation in a thermal printer

Claim 1

An apparatus for controlling a thermal printer having a plurality of exothermic printing elements and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, comprising driving circuit means for selectively applying driving pulses to said exothermic elements and control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said control circuit means including a pulse generation circuit operably couplable to receive said power source output voltage for producing an oscillatory signal, said pulse generation circuit including voltage sensitive means including a varistor independent of said plurality of exothermic elements for adjusting the period of said oscillatory signal in response to the level of said output voltage so that the period of said oscillatory circuit is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage, said oscillatory signal being applied to said driving circuit means for determining the width of said driving pulses.

Claim 2

An apparatus for controlling a thermal printer having a plurality of exothermic printing elements and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, comprising driving circuit means for selectively applying driving pulses to said exothermic elements and control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said control circuit means including a pulse generation circuit operably couplable to receive said power source output voltage for producing an oscillatory signal, said pulse generation circuit including voltage sensitive means including a varistor independent of said plurality of exothermic elements for adjusting the period of said oscillatory signal in response to the level of said output voltage so that the period of said oscillatory circuit is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage, said oscillatory signal being applied to said driving circuit means for determining the width of said driving pulses.

Claim 7

A method for driving an exothermic printing element by means of a voltage source the output voltage of which may vary and wherein printing is effected on a heat sensitive paper by a paper advance means comprising providing a plurality of exothermic printing elements; selectively applying a pulse of current to selected of said exothermic printing elements sufficient to elevate the temperature of said selected exothermic printing elements to a printing temperature to define a predetermined character; detecting the output voltage of said power source; adjusting the pulse width of said driving current pulse in response to variations in the output voltage of said voltage source so as to narrow said pulse width in response to increases in output voltage and widen said pulse width in response to decreases in output voltage; selectively applying driving pulses to said paper advance means to effect advancement of said paper; and adjusting the pulse width of said paper advance driving pulses in response to said detected output voltage so that the width of the paper advance driving pulses is widened in response to a lowering of the output voltage of the power source and narrowed in response to an increase in the output voltage of the power source.

Claim 8

A method for driving an exothermic printing element by means of a voltage source the output voltage of which may vary and wherein printing is effected on a heat sensitive paper by a paper advance means comprising providing a plurality of exothermic printing elements; selectively applying a pulse of current to selected of said exothermic printing elements sufficient to elevate the temperature of said selected exothermic printing elements to a printing temperature to define a predetermined character; detecting the output voltage of said power source; adjusting the pulse width of said driving current pulse in response to variations in the output voltage of said voltage source so as to narrow said pulse width in response to increases in output voltage and widen said pulse width in response to decreases in output voltage; selectively applying driving pulses to said paper advance means to effect advancement of said paper; and adjusting the pulse width of said paper advance driving pulses in response to said detected output voltage so that the width of the paper advance driving pulses is widened in response to a lowering of the output voltage of the power source and narrowed in response to an increase in the output voltage of the power source.

Claim 12

An apparatus for controlling a thermal printer having at least one exothermic printing element and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, said thermal printer being adapted to effect printing on temperature sensitive paper and including paper advance means, comprising driving circuit means for selectively applying driving pulses to said exothermic elements; control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said driving circuit means being further adapted to selectively apply driving pulses to said paper advance means to effect advancement thereof, said control circuit means being further adapted to adjust the width of said paper advance means driving pulses in response to the level of said output voltage of said power source so that the width of said paper advance means driving pulse is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage.

Claim 13

An apparatus for controlling a thermal printer having at least one exothermic printing element and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, said thermal printer being adapted to effect printing on temperature sensitive paper and including paper advance means, comprising driving circuit means for selectively applying driving pulses to said exothermic elements; control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said driving circuit means being further adapted to selectively apply driving pulses to said paper advance means to effect advancement thereof, said control circuit means being further adapted to adjust the width of said paper advance means driving pulses in response to the level of said output voltage of said power source so that the width of said paper advance means driving pulse is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage.

Claim 14

An apparatus for controlling a thermal printer having at least one exothermic printing element and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, comprising driving circuit means for selectively applying driving pulses to said exothermic elements and control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said control circuit means including a pulse generation circuit operably couplable to receive said power source output voltage for producing an oscillatory signal, said pulse generation circuit including voltage sensitive means including a varistor for adjusting the period of said oscillatory signal in response to the level of said output voltage so that the period of said oscillatory circuit is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage, said oscillatory signal being applied to said driving circuit means for determining the width of said driving pulses, said pulse generation circuit further including a free-running multivibrator circuit means having first and second R-C circuit means for controlling the period of oscillation thereof, one of said first and second R-C circuit means including said varistor.

Claim 15

An apparatus for controlling a thermal printer having at least one exothermic printing element and adapted to be energized for printing by a current pulse produced in response to the output voltage of a power source, comprising driving circuit means for selectively applying driving pulses to said exothermic elements and control circuit means connected for detection of said power source output voltage and operatively coupled to said driving circuit means for adjusting the width of the driving pulses applied to said exothermic printing elements in response to the level of said power source output voltage so that the width of said driving pulses is increased in response to a decrease in said output voltage and is decreased in response to an increase in said output voltage, said control circuit means including a pulse generation circuit operably couplable to receive said power source output voltage for producing an oscillatory signal, said pulse generation circuit including voltage sensitive means including a varistor for adjusting the period of said oscillatory signal in response to the level of said output voltage so that the period of said oscillatory circuit is increased in response to a decrease in said output voltage and decreased in response to an increase in said output voltage, said oscillatory signal being applied to said driving circuit means for determining the width of said driving pulses, said pulse generation circuit further including a free-running multivibrator circuit means having first and second R-C circuit means for controlling the period of oscillation thereof, one of said first and second R-C circuit means including said varistor.