Automatic control for a clothes dryer

An automatic control system for a clothes dryer of the type having a clothes drum, an air flow system for passing drying air through the drum and a heater for heating the air at the inlet side of the drum to enhance the drying effect of the air during the drying cycle, the drying cycle having an initial warm-up period, followed by a period of a relatively constant moisture removal rate followed by a period of a decreasing moisture removal rate, the control system comprising:

• means for sensing the drum inlet air temperature;
• means for sensing the drum outlet air temperature;
• air flow control means for holding the volumetric flow rate of air through the drum normally at a first predetermined rate for the duration of the drying cycle and being responsive to the inlet air temperature sensing means to increase the volumetric air flow rate through the drum, only during the warm-up and constant moisture rate periods, when the inlet air temperature exceeds a predetermined elevated temperature level corresponding to a maximum safe operating condition for fabrics in the drum;
• means responsive to the inlet and outlet temperature sensing means and to the air flow control means for controlling the heater to normally supply a predetermined high rate of heat to the dryer air and for reducing the heat rate when the inlet air temperature reaches said predetermined elevated temperature level, said heat rate reduction adapted during the warm-up and constant moisture removal rate periods to occur only when increased air flow rate exists but fails to hold inlet air temperature below said elevated temperature level;
• and means for terminating the dryer operation at the conclusion of the drying cycle.