8.4 Door safety interlock (traditional version) 8.4.1 General characteristics The electromechanical door safety device performs the following functions: When powered, the voltmetric safety interlock closes the contacts of the main switch that powers the electrical components of the appliance (only if the door is closed). During operation, the lever is blocked mechanically, preventing opening of the door when the appliance is in operation. When the power supply is disconnected, the door remains locked for 2- 3 minutes to ensure that the drum comes to a stop before the door is opened. In more complex versions, the safety interlock also performs the following functions:
By means of a pneumatic actuator it maintains the latch closed when there is water in the tub. It also acts as a support for the door aperture levers when aperture is effected using the pushbutton. The "door closed" pilot lamp may also be fitted using a special support. 1. P.T.C. 2. Bi-metal strips 3. Contact in rest position 4. Contact closed The PTC is a ceramic resistor whose internal resistance increases with the temperature. In this device, the PTC is used to heat the bi-metal strips. The temperature deforms the two strips (from A to B ), thus moving the lever which closes the contact of the main switch.
At the same time, the latch, which is actioned by the contact plate, moves outwards to block the lever in position. This procedure takes place within 5 seconds after power is supplied. When the power supply is disconnected, the PTC cools (1 - 2 minutes), and the strips return to their original position, thus opening the contact and releasing the lever. 1. Latch 2. Lever 8.4.1.1 Version with door aperture system On certain models, the door can be opened by pressing a button on the control panel. In this case, the safety device is fitted with a series of levers that release the latch. SOI/DT 2002-05 eb 63 599 35 23-17