Valve mechanism

A valve for use in draining a liquid system to prevent the liquid in the system from freezing under low ambient temperature conditions comprising:

• means providing a valve chamber connectable to the liquid system, said valve chamber having a drain outlet;
• a valve element cooperating with said drain outlet and movable from a first position towards a second position, the valve element in its first position closing the drain outlet and, during movement thereof towards its second position, opening the drain outlet;
• means in contact with the valve element for urging the valve element towards its second position;
• latch means connectable to the valve element for holding the valve element in its first position and releasable to permit the valve element to move towards its second position under the influence of the urging means;
• a temperature sensor including a temperature sensing element that is in thermal contact with the liquid in the liquid system when the valve is connected to said system, and means responsive to the temperature sensing element for releasing the latch means when the temperature of the sensing element falls below a predetermined level;
• means providing a heat-conductive housing surrounding at least a substantial part of the temperature sensing element, said means isolating the temperature sensing element from the ambient atmosphere substantially completely;
• and
• means for conducting heat from the liquid system to the heat-conductive housing when the valve chamber is connected to the liquid system;
• whereby the valve is prevented from opening while the liquid in the liquid system is warm, yet responds rapidly to a drop in the ambient temperature when the liquid in the liquid system is cool.