Air dryer device for compressed air system of vehicle

An air dryer device for a compressed air system of a vehicle, said compressed air system having a compressor for supplying suppressed air, an air reservoir for restoring the compressed air and an air governor for feeding a pneumatic signal, said air dryer device comprising:

• (a) a housing;
• (b) a dryer mounted within said housing and containing a desiccant for drying the compressed air from the compressor, said dryer being connectable to the air reservoir for feeding the dried compressed air thereto;
• (c) a drain valve mounted within said housing, said drain valve including (i) a valve body having a valve port and a valve seat disposed adjacent to said valve port, (ii) a hollow elongated control piston mounted within said valve body for movement along an axis thereof, said control piston having a bore extending along its axis (iii) a valve element mounted on said control piston, and (iv) means for normally urging said valve element into sealing engagement with said valve seat to close said valve port, said control piston being responsive to the pneumatic signal from the air governor for being moved along its axis to bring said valve element out of sealing engagement with said valve seat to open said drain valve, thereby communicating the interior of said housing with the atmosphere;
• and
• (d) an elongated heater member mounted at one end thereof on said valve body for generating heat, said heater member being received in said bore of said control piston, the other end of said heater member being disposed close to said valve element to transmit the heater of said heater member to said valve element and said valve seat, a projection being formed on the inner surface of said bore of said control piston adjacent to said valve element, and said heater member engaging said projection and being spaced from said inner surface of said bore.