Thermal printer

• US 4,591,876 A
• Filed: 09/27/1982
• Issued: 05/27/1986
• Est. Priority Date: 10/02/1981
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Uchikata, Yoshio, Asakura, Osamu, Nozaki, Mineo, Nagashima, Masasumi
• Primary Examiner(s): Goldberg, E. A.
• Assistant Examiner(s): PRESTON, GERALD
• Application Number:
  US06/424,410
• Time in Patent Office: 1,338 Days
• Field of Search: 346/76 PH, 219/216, 400/120
• US Class Current: 347/189
• CPC Class Codes: B41J 2/365 by compensation for variation in temperature

Abstract

A thermal transfer printer includes a thermal head having plural heat generating elements, a thermal head driver connected to a character generator for controlling the thermal head by supplying drive currents to the heat generating elements of the thermal head in response to print information, and control circuit for controlling the drive currents from the thermal head driver in response to the ambient temperature. Therefore, the thermal transfer printer is capable of constantly providing an optimum transfer density regardless of the ambient temperature, thus ensuring a satisfactory print quality.

Claims

1. A thermal printer comprising:

a thermal head of one of at least two types having a plurality of heater elements and respective different operating characteristics, said thermal head being removably mountable to the printer;

driver means operable in response to a print signal for driving said heater elements;

detection means for detecting the type of said thermal head mounted to the printer; and

control means for controlling the heating of a first type of said thermal head in dependence on a first ambient temperature vs. power characteristic curve when said detection means detects that said first type of thermal head is mounted to the printer and for controlling the heating of a second type of said thermal head in dependence on a second ambient temperature vs. power characteristic curve when said detection means detects that said second type of thermal head is mounted to the printer so that said first and second types of thermal head print with substantially the same print density.

2. A thermal printer according to claim 1, wherein said control means includes a plurality of temperature sensors.

3. A thermal printer according to claim 2, wherein said detection means includes switch means operable in response to the type of said thermal head mounted to the printer.

4. A thermal printer according to claim 3, wherein said control means includes means for selecting among said temperature sensors depending on the operation of said switch means.

5. A thermal printer according to claim 1, further comprising an ink ribbon having an ink layer melted by heat generated by said thermal head.

6. A thermal printer comprising:

first thermal head means of a first type having a plurality of heater elements and being removably mountable to the printer;

second thermal head means of a second type having a plurality of heater elements and being removably mountable to the printer;

driver means operable in response to a print signal for driving said first and second thermal head means;

detection means for detecting which of said first or second thermal head means is mounted to the printer;

first control means for controlling the heating of said first thermal head means in dependence on a first ambient temperature vs. power characteristic curve when said detection means detects that said first thermal head means is mounted; and

second control means for controlling the heating of said second thermal head means in dependence on a second ambient temperature vs. power characteristic curve when said detection means detects that said second thermal head means is mounted so that said second thermal head means can print with substantially the same print density as said first thermal head means.

7. A thermal printer according to claim 6, wherein said first control means includes a first temperature sensor.

8. A thermal printer according to claim 6, wherein said second control means includes a second temperature sensor.

9. A thermal printer according to claim 6, wherein said detection means includes switching means operable in response to mounting said first and second thermal head means on the printer.

10. A thermal printer according to claim 6, further comprising an ink ribbon having an ink layer melted by heat generated by said thermal head mounted to the printer.

11. A thermal printer comprising:

thermal head means for printing characters in a first character size and a second character size different from the first character size;

switch means for changing between the first and second character sizes; and

control means responsive to said switch means for controlling the heating of said thermal head means in dependence on a first ambient temperature vs. power characteristic curve for the first character size and in dependence on a second ambient temperature vs. power characteristic curve for the second character size so that substantially the same print density can be obtained with either of the first and second character size.

12. A thermal printer according to claim 11, further comprising an ink ribbon having an ink layer melted by heat generated by said thermal head means.