Controller functions
42
RES-430
10.19.1 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 signal for energizing
relay K1 via the foot switch. The solenoid valve is
then energized and the sealing jaws are closed.
2. The switch for the "START" signal is activated when
the sealing jaws reach their end position. This starts
the timeout for internal time control.
Relay K1 must then be energized immediately by
the time control (the foot switch can then be opened
again but the jaws remain closed).
3. The heating process must begin immediately – wit-
hout a starting delay.
4. The heatsealing time (t
2
= 1s) must begin when the
ACTUAL temperature reaches 95% of the SET tem-
perature (T = 180°C).
5. 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.
6. The cooling phase must end when the ACTUAL
temperature of the heatsealing bands falls to
T
≤
80°C. The sealing jaws are still closed (relay K1
is also still closed).
7. Relay K1 opens again at the end of the cooling
phase. The sealing jaws are also opened again.
8. End of the heatsealing process.
r
Relay K1
FOOT SWITCH
U
Film
Film
Heatsealing band
Sealing bar
Retainer
Cylinder
Solenoid valve
FOOT SWITCH
START
contact
contact
START
