8.5 Instantaneous door safety interlock 8.5.1 General characteristics Certain models with electronic control systems feature an instantaneous door safety interlock. In this case, the door can be opened as soon as the drum comes to a stop. 8.5.2 Operating principle 1. Solenoid protective PTC 2. Solenoid valve 3. Lever mechanism 4. Camme 5. Bi-metal PTC 6. Electrical contacts (main switch) 7. Locking latch When the appliance is switched on by pressing the ON/OFF button, the bi-metal PTC is powered; the camme is in a position that prevents the locking latch from moving outwards.
When the programme is started by pressing START/PAUSE, the main PCB sends a signal (duration 20 msec) to the solenoid (at least 6 seconds after switching on), which causes the camme to rotate one position. The latch which locks the lever of the door safety interlock is raised and, at the same time, the contacts of the main switch are closed, thus powering all the electrical components. At the end of the programme, the PCB sends two signals (at an interval of 200 msec) (duration 20 msec): - the first signal moves the camme by another position, though the latch is not released.
- the second signal (which is sent only if the system functions correctly) moves the camme by a further position, which causes the latch to retract, thus releasing the device; at the same time, the contacts of the main switch are opened. 8.5.2.1 "Door open" conditions The main PCB, before sending the door aperture signals, checks for the following conditions: The drum must be stationary (no signal from the tachymetric generator) The water level must not be higher than the lower edge of the door The temperature of the water must not be higher than 40є C.
8.5.2.2 Automatic release device In the event of a power failure, or if the appliance is switched off using the ON/OFF switch, or if there is a fault in the solenoid valve, the bi-metal PTC cools within a period of between 55 seconds and about 4 minutes (at a temperature of 65°C), thus releasing the door. SOI/DT 2002-05 eb 65 599 35 23-17