Brother PT-2420PC Service Manual page 14

(2) Adhesive Base Tape Feeding (only for laminated tape cassettes)
A laminated tape cassette contains both a transparent laminate tape roll and a separate
adhesive base tape roll.
When a transparent laminate tape and adhesive base tape pass through the contact point
(between the tape feed roller and tape feed sub roller), they are then bonded together into a
single, printed tape. The ink printed on the laminate tape is, therefore, sealed up with the
adhesive base tape.
(3) Ink Ribbon Feeding (except for non-laminated thermal film tape cassettes)
As the DC motor rotates, the ribbon drive cam located at the middle of the gear train rotates
counterclockwise. When fitted on the ribbon drive cam, the ribbon take-up roll in the tape
cassette also rotates to take up the ink ribbon.
To apply proper tension to the ink ribbon between the platen and the ribbon drive cam, the
feed amount of the ribbon drive cam is slightly greater than that of the tape feed gear. The
difference between the tape feed speeds at the platen and at the ribbon drive cam is
absorbed by the clutch spring which is integrated in the ribbon drive cam and allows the cam
to slip.
This way, the ink ribbon is kept tense, which enables the ribbon to clearly separate from the
tape at the stabilized angle after printing.
Adhesive base tape
Tape idle gear
Tape feed sub roller
Tape idle gear
Platen
Fig. 2.1-6 Ribbon Feeding Mechanism
II-6
Thermal head
Roller holder ASSY
DC motor
Ribbon drive cam
P idle gear
Transparent laminate tape
Ribbon take-up roll
Ink ribbon
Chassis