Brother TD-4000, Service Manual

Page: 8 / 139

II - 1
CHAPTER II THEORY OF OPERATION
2.1 OUTLINE OF MECHANISMS
2.1.1 Print Mechanism
■
Structure of Thermal Head
This machine adopts direct thermal printing system. The thermal head consists of
1296 pieces of heating elements arrayed in vertical single row as shown in the Fig.
2.1-1.
The dimension of each heating element is vertical length 0.0847(0.0847mm pitch) x
horizontal width 0.13mm.
Figure 2.1-1 Heating Elements of Thermal Head
■ Printing Process
A thermal tape is pressed against the thermal head in the printing process by the
force comes from a nip between the cylindrical rubber platen and the thermal head.
At this timing, voltage is applied selectively to 1296 pieces of heating elements
arrayed on the thermal head. By this voltage application, the heating elements
generate heat and the thermal tape develops dots by itself at heat sensing points.
After application of voltage the thermal tape is fed to the next printing position by the
platen (0.0847mm).
This printing cycle is repeated and characters and geometries are printed on the tape.
One time travel distance (0.0847mm) is shorter than the width of a heating element
(0.13mm), so that continuous printing cycle can print characters and geometries on a
tape by developing dots with no gap.
Pitch 0.0847mm
0.13mm