45
Mechanical and electrical design
67
Drain valve
Description
The drain valve is a motor-operated membrane
valve having a large opening cross-section to
produce rapid emptying of the machine. The
rapid flow action produces a self-cleaning effect,
eliminating the necessity for a fluff filter.
The main parts of the valve are:
• Motor and gear
• Trapezoidal-threaded piston rod with piston
and return spring
• Rubber membrane
• Connections for water filling, overflow, drain
and level switch
When de-energised, the valve is open. In this
state, the piston, under the action of the return
spring, is at the bottom of its travel. The
membrane follows the piston downwards and the
valve is open.
Energizing the motor drives the piston upwards
through the action of the gear and the trapezoidal
thread, pressing the membrane against the valve
seat and closing the valve.
The overflow connection is connected to the
siphon breaker, so that water and foam are
discharged directly to drain if the inlet valve or
level switch should fail.
0919
Fig.
67
