Movement 477

477. Steam trap for shutting in steam, but providing for the escape of water from steam coils and radiators (Hoard & Wiggin’s patent). It consists of a box, connected at A with the end of the coil or the waste-pipe, having an outlet at B, and furnished with a hollow valve, D, the bottom of which is composed of a flexible diaphragm. Valve is filled with liquid, and hermetically sealed, and its diaphragm rests upon a bridge over the outlet-pipe. The presence of steam in the outer box so heats the water in valve that the diaphragm expands and raises valve up to the seat, a, a. Water of condensation accumulating reduces the temperature of valve; and as the liquid in valve contracts, diaphragm allows valve to descend and let water off.