Variable control circuit having a timed bypass

Claim 1

A variable speed control system for fans having spring loaded mechanical louvers comprising: AC voltage source; fan blades mounted adjacent to said spring loaded mechanical louvers; a spring connected to said mechanical louvers for urging said mechanical louver to an open position but having insufficient strength to hold said mechanical louvers in an open position; AC motor connected to said fan blades for turning said fan blades upon turning said motor by said AC voltage source; control circuit located between a first side of said AC voltage source and said AC motor, a second side of said AC voltage source being connected to said AC motor, said control circuit further comprising: single armature means actuated by an uppermost and a lowermost movement of a toggle lever for a positive ON and a positive OFF, respectively, through contacts on said single armature means; switching means connected between one of said contacts of said single armature and said AC voltage source, said switch means having a gate; first variable resistance means and first capacitor means in series across said switching means and having gating means connected therebetween to said gate; bridge means connected between one side of said switching means to said gate to shunt said gating means for a predetermined time interval, said bridge means having an RC network thereacross to set said predetermined time interval of sufficient duration to bring said fan blades to near full speed to open said louvers before slowing said AC motor for intermediate positions of said toggle lever by eliminating said shunt.