Electrical load control circuit useful in liquid level control systems

Claim 1

Apparatus for maintaining the level of liquid in a chamber between upper and lower levels, comprising, in combination: a pump for causing flow of liquid with respect to the chamber; an electric motor energizable to cause operation of said pump; and means for controlling the energization of said motor including a relay, having a winding and a set of normally open contacts which are closed and opened, after short delays, upon energization and deenergization respectively of said winding, first switch means and second switch means responsive respectively to the presence of liquid at upper and lower levels in said chamber, first circuit means for supplying electrical energy from a source to said winding and said motor through said first switch means and said second switch means in series, and a second circuit means for supplying electrical energy from said source to said motor and said winding through one of said first and second switch means and said contacts of said relay, said second circuit means connecting said contacts in parallel with the other of said first and second switch means, so that initial energization of said motor and relay as said liquid reaches one of said levels is accomplished by the closing of said first and second switch means in series and initial deenergization of said motor and relay as said liquid reaches the other of said levels is accomplished by the opening of said one of said switch means, with both said energization and deenergization occurring during said delays by said switch means rather than by said contacts.