Automatic fail-safe valve control for boiler flues - uses discharge of condenser to energise electro-magnet and correctly set valve flap of flue upon mains electricity failure

摘要

The fail-safe device brings about a mechanical action when the mains electricity supply fails. In normal operation the relay coil (20) is energised by the full-wave rectified d.c. output of a low voltage mains transformer (16). A condenser (25) is kept charged by the d.c. supply by the relay contact (24) being held in the normally on position (23). Mains failure causes the release of the contact and the condenser discharges through the coil of an electromagnet (13). This causes a mobile bolt to activate a motor - disengaging mechanism. The automatic draw valve in a boiler flue is disconnected from its control motor drive. A return spring then rotates the vein into a safe position.