Controller functions
RES-445
Page 47
10.19.8 Preheating (with time control)
If time control is active, the preheating temperature
(
!
Kap. 10.10 „"PREHEAT" signal (preheating without
time control)“ auf Seite 37 is only deactivated during
the heating phase. Preheating is active during the
starting delay and the cooling phase.
The ACTUAL temperature consequently cannot fall
below the set preheating temperature during the
cooling phase.
The temperature which is set for the end of the cooling
phase (
!
Kap. 10.19.5 „Setting the cooling value“ auf
Seite 44) must always be higher than the preheating
temperature. If not, the end of the cooling phase is
never reached, i.e. the internal timeout does not
elapse.
If the cooling temperature is required to be lower than
the preheating temperature, the "PREHEAT" signal
must be deactivated until the end of the cooling phase
and then activated again.
10.19.9 Example
The example below illustrates the basic design of a
pneumatically operated L-sealer with a solenoid valve.
The heatsealing process is started by means of a foot
switch.
The functional sequence is as follows:
1. The controller receives the "START" signal for
internal time control via the foot switch.
2. The heating process must begin immediately –
without a starting delay.
3. When the ACTUAL temperature reaches 95% of the
SET temperature (T = 180°C), the normally open
contact of relay K1 must close. The solenoid valve
is then energized and the sealing jaws are closed.
The heatsealing time (t
2
= 1s) begins
simultaneously.
4. The heatsealing bands are not heated any further at
the end of the heatsealing phase (i.e. at the end of
the heatsealing time). The cooling phase begins.
5. The cooling phase must end when the ACTUAL
temperature of the heatsealing bands falls to
T
≤
80°C. The sealing jaws are still closed (the
normally open contact of relay K1 is also still
closed).
6. The normally open contact of relay K1 opens again
at the end of the cooling phase. The sealing jaws
are also opened again.
7. End of the heatsealing process.
Controller
Relay K1
Start
U
Film
Film
Heatsealing band
Heatsealing bar
Retainer
Cylinder
Solenoid valve
Foot contact
