Electronic control of compressor unloader and air dryer purge

An air compressor system comprising:

• a reservoir
• an air compressor connected to supply compressed air to said reservoir when loaded and to not supply compressed air when unloaded;
• a pressure transducer connected to be responsive to the pressure in said reservoir and providing an electrical output signal indicative of the reservoir pressure;
• an air dryer connected between said reservoir and said air compressor including a desiccant for removing moisture and also including a purge control valve which when activated vents the desiccant bed to initiate purging;
• compressor control means connected to receive the electric signal from said pressure transducer for unloading said air compressor when the reservoir pressure exceeds a first pressure and for loading the air compressor when the pressure in said reservoir falls below a second pressure;
• purge control means connected to receive the electric output signal from said pressure transducer for causing purging of said air dryer when said air compressor is unloaded and the pressure in said reservoir is above a third pressure, which is intermediate the first pressure and the second pressure, and for stopping purging of said air dryer when the pressure in said reservoir falls below the third pressure.

An air compressor system having a compressor, which is loaded and unloaded in response to a pneumatic signal, for supplying compressed air to a reservoir through an air dryer, which includes a purge means responsive to a pneumatic signal for purging the air dryer to atmosphere and which also includes a desiccant bed, the improvement comprising:

• a compressor control solenoid valve disposed in a pneumatic connection between the compressor and the reservoir to provide the pneumatic signal to load or unload the compressor;
• an air dryer purge solenoid valve disposed in a pneumatic connection between the air dryer and the reservoir to provide a pneumatic signal to said purge means;
• a pressure transducer mounted to sense the pressure in the reservoir and provide an output electrical signal indicative of the pressure in the reservoir;
• controller means for receiving the output electrical signal from said pressure transducer and for providing a first electrical output to said compressor control solenoid valve to unload the compressor when a first pressure is reached and to load the compressor when the reservoir pressure falls below a second pressure and a second electrical output to said air dryer purge solenoid valve to cause purging of the air dryer when the air compressor is unloaded and pressure in the reservoir is above the second pressure.