Riso RP-255, Technical Manual

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MASTER MAKING SECTION
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4. Thermal Print Head Elevation Mechanism
Thermal print head elevation
When the system is on standby or when winding the master onto the print drum after master making, the
thermal print head is raised from the write roller. Conversely, for master making and during transport, the
thermal print head is lowered and pressed onto the write roller.
The thermal print head is raised and lowered by the pressure release cam [B], which is driven by the
thermal pressure motor [A].
The pressure release cam [B] is an eccentric cam, which raises and lowers the TPH pivot plate [C] as it
rotates. The raised and lowered stop positions for the motor are detected by the TPH pressure sensor
[E], which is blocked by the pressure detection disc [D]. The sliding plate [F] and blade link [G] are also
moved by the vertical action of the thermal head.
Thermal print head raised position
In the thermal print head raised position, the load roller No. 1 [H] and load roller (top) [I] also rise.
At the same time, the blade cushion [J] descends, and applies back tension to the master while it is
being wound onto the print drum to prevent creases in the master.
Thermal print head lowered position
In the thermal print head lowered position, the load roller No. 1 (top) [H] and load roller (top) [I] also
descend to allow the master to be transported. At the same time, the blade cushion [J] rises.
Initialization
This moves the thermal print head to the pressure release (raised) position when power is switched on,
or when everything is reset.
Loading guide plate operation
• In the clamp plate master release operation at the start of master ejection, the front edge of the
loading guide plate is raised by the master release bar to prevent it from obstructing the leading edge
of the freed master on the drum.
• In the clamp plate master clamping operation at the start of master loading, only the front edge sheet
of the loading guide plate is raised by the clamp plate, so as to prevent it from obstructing the master
loading operation.
• During master loading, the master being loaded is back-tensioned by the sponge fitted to the bottom of
the front edge sheet of the loading guide plate.