Protecting an icemaker against overcurrent damage

A control system for a refrigerator icemaker comprising:

• (a) an electrically operated coil adapted for actuation of an electromagnetically actuated coil for controlling ice maker waterfill, said coil having a known impedance and defining an armature receiving cavity and having a plurality of turns of relatively fine wire chosen such that the turns increase in temperature and successively short out in the event a normal operating current continues to flow for a time greater than a predetermined normal waterfill cycle time, said shorted coils operative to decrease the impedance of said coil and the magnetomotive force sufficient to cause said valve to be electromagnetically deactuated and operative to permit current greater than a normal operating current to flow therethrough;
• (b) heater means electrically series connected with said coil and operative to perform an ice melting function upon flow of a normal operating current therethrough, said heater means operative as a voltage divider with said coil having an impedance higher than said coil such that said heater acts as a current limiter for said coil and said coil upon said coil shorting continues flow of greater than normal current and is prevented from overheating and acting as a fuse;
• (c) current terminating means electrically series connected with said heater means, said terminating means operative to create an open circuit only when a predetermined limit current above normal operating current flows in said heater means;
• and,
• (d) controller means, operative to effect switching of current to said coil for normal ice maker waterfill.

An appliance control system comprising:

• (a) a solenoid coil having an impedance and defining an armature receiving cavity and having a plurality of turns of relatively fine wire chosen such that, upon flow of a normal operating current therethrough a magnetomotive force is provided sufficient for effecting a first operating function, said coil turns, upon said normal current flowing continuously beyond a predetermined threshold interval of time, subject to shorting out of successive turns, whereupon said coil impedance drops and said coil becomes inoperative to effect said first appliance function;
• (b) heater means electrically series connected with said coil and, upon flow of said normal operating current therethrough for a time interval less than said threshold, said heater means operative to effect a second appliance function, said heater means and said coil forming a voltage divider whereby when said coil impedance drops current through said heater continues and increases to a greater than normal level;
• (c) fusing means electrically series connected with said heater means and coil and operative to maintain current in said heater means as said coil impedance drops and to go open circuit only when the current in said heater means reaches an unacceptable level;
• and,
• (d) controller means connected in circuit with said coil, said heater means and said fusing means, said controller means operative to switch power to said heater means, coil and fusing means in a predetermined program for effecting said first and second appliance functions.