US 5,690,437 A · Method and apparatus for controlling the thermal head drive

Abstract

The present invention provides a method and an apparatus for driving and controlling a thermal head used in a printing device, such as a tape printer, in response to the temperature variations of the printing device environment and the thermal head. According to the present invention, in the printing operation of the tape printer, measurements are made of the initial temperature T1 immediately after the power is switched on, the temperature prior to printing T2, and the ambient temperature of the thermal head each time the thermal head prints T3 (i). If the temperature difference between the initial temperature T1 and the temperature prior to printing T2 is small, the duration of the current signals provided to the thermal head is controlled in accordance with the temperature prior to printing T2, which is the most recently measured thermal head ambient temperature best reflecting the printing device environmental temperature. If the difference is large, the duration is controlled in accordance with the initial temperature T1 which then best reflects the environmental temperature. If the rate of the increase in temperature during printing T3(i) is large, the duration is controlled in accordance with the initial temperature T2 to reduce the duration. If the temperature during printing T3(i) exceeds a temperature which indicates overheating, the printing operation is aborted. Thus, the present invention allows for controlling the thermal head drive by means of the measured thermal head temperature excluding the effect of the heat generation of the thermal head and in accordance with the thermal state of the thermal head.

Claims27

Dependent claims

A method for driving and controlling a thermal head of a printing device, said thermal head including a plurality of heat elements to which current signals are supplied, the method comprising the steps of:

(a) measuring an ambient temperature of said thermal head to obtain an initial temperature T1 immediately after the power to the printing device is switched on;
(b) measuring an ambient temperature of said thermal head to obtain a temperature prior to printing T2 just before said thermal head starts printing on a recording medium;
(c) calculating a temperature difference between the initial temperature T1 and the temperature prior to printing T2;
and
(d) if the temperature difference is less than a predetermined first threshold value Ta, controlling the duration of the current signals provided to the heat elements of said thermal head in accordance with the temperature prior to printing T2.

2 more elements

An apparatus for driving and controlling a thermal head of a printing device, said thermal head including a plurality of heat elements to which current signals are supplied, the apparatus comprising:

means for measuring an ambient temperature of said thermal head to obtain an initial temperature T1 immediately after the power to the printing device is switched on, and for measuring an ambient temperature of said thermal head to obtain a temperature prior to printing T2 just before said thermal head starts printing on a recording medium;
means for calculating a temperature difference between the initial temperature T1 and the temperature prior to printing T2;
and
control means for controlling the duration of the current signals provided to the heat elements of said thermal head, said control means controlling the duration of the current signals in accordance with the temperature prior to printing T2 if the temperature difference is less than a predetermined first threshold value Ta.

1 more element

A printing device, comprising:

a thermal head having a plurality of heat elements;
drive means for providing current signals to said heat elements of said thermal head;
and
means for driving and controlling said thermal head, comprising:
means for measuring an ambient temperature of said thermal head to obtain an initial temperature T1 immediately after the power to the printing device is switched on, and for measuring an ambient temperature of said thermal head to obtain a temperature prior to printing T2 just before said thermal head starts printing on a recording medium,
means for calculating a temperature difference between the initial temperature T1 and the temperature prior to printing T2, and
control means for controlling the duration of the current signals provided to the heat elements of said thermal head, said control means controlling the duration of the current signals in accordance with the temperature prior to printing T2 if the temperature difference is less than a predetermined first threshold value Ta.

4 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling the thermal head drive

Life of this patent

Method and apparatus for controlling the thermal head drive

Life of this patent

Abstract

Claims27