Photoelectric ice level sensor

Claim 2

A control circuit for a current activated thermostatic appliance control switch comprising: means for supplying an indication of a predetermined external condition intended to initiate actuation of the thermostatic switch; means for supplying an AC voltage including first and second input terminals; a trigger SCR and a voltage dropping resistor connected in series across said input terminals, the trigger SCR adapted to be responsive to said external condition indication means to change its conduction state in response to a predetermined change in said external condition; a thermostatic heater current control SCR coupled across the input terminals and having a control gate terminal; a transistor having its base-emitter junction connected from the anode of the trigger SCR to the control gate of the control SCR and having its base-collector junction connected across the anode-cathode terminals of the trigger SCR; whereby, non-conduction of the trigger SCR causes a gating current to flow by zener action of the transistor base-emitter junction to the gate terminal of the control SCR during positive half cycles of the AC supply and reverse current during negative half cycles of the AC supply is provided by diode action of the transistor base-collector junction.

Claim 3

A control circuit as recited in claim 1, wherein the indication means comprises a beam of radiant energy and the trigger SCR is a photo-sensitive SCR adapted to be responsive to said beam.

Claim 4

A control circuit as recited in claim 1 wherein the transistor is a PNP transistor.

Claim 5

A control circuit for a current activated thermostatic appliance control switch comprising: photoelectric triggering means, including a source providing a beam of radiant energy, for supplying an indication of a predetermined external condition intended to initiate actuation of the thermostatic switch; means for supplying an AC voltage including first and second input terminals; a photo-sensitive trigger SCR and a voltage dropping resistor connected in series across said input terminals, the trigger SCR adapted to be responsive to said photoelectric triggering means to change its conduction state in response to a predetermined change in said external condition; a thermostatic heater current control SCR coupled across the input terminals and having a control gate terminal; a PNP transistor having its emitter-base junction connected from the anode of the trigger SCR to the control gate of the control SCR and having its collector-base junction connected across the anode-cathode terminals of the trigger SCR.

Claim 6

A control circuit for a current activated thermostatic appliance control switch comprising: photoelectric triggering means, including a source providing a beam of radiant energy, for supplying an indication of a predetermined external condition intended to initiate actuation of the thermostatic switch; means for supplying an AC voltage including first and second input terminals; a photo-sensitive trigger SCR and a voltage dropping resistor connected in series across said input terminals, the trigger SCR adapted to be responsive to said photoelectric triggering means to change its conduction state in response to a predetermined change in said external condition; a thermostatic heater current control SCR coupled across the input terminals and having a control gate terminal; a PNP transistor having its emitter-base junction connected from the anode of the trigger SCR to the control gate of the control SCR and having its collector-base junction connected across the anode-cathode terminals of the trigger SCR.

Claim 7

In combination with an automatic ice making system of the type having an ice maker, an ice storage receptacle and electrical control means Including a heater and a thermostatic switch adapted to be responsive to the heater to control the operation of the ice maker as a function of the level of ice pieces in the receptacle, a control circuit for actuating the thermostatic switch comprising: means for supplying an AC voltage including first and second input terminals; photoelectric triggering means supplying an indication of the level of ice pieces in the receptacle intended to initiate actuation of the thermostatic switch, said triggering means including a source, connected across said input terminals, providing a beam of radiant energy positioned so as to traverse the receptacle at a predetermined level; a heater current control SCR for controlling actuation of the heater, said SCR being coupled across said input terminals and further having a control gate terminal; a gating circuit for gating the heater current control SCR into conduction when the quantity of ice pieces in the receptacle reaches a predetermined level, including a photo-sensitive trigger SCR and a voltage dropping resistor coupled in series across said input terminals, said trigger SCR adapted to be responsive to the photoelectric triggering means so as to be switched to the non-conduction state when the quantity of ice pieces is above the predetermined level, and a PNP transistor having its emitter-base junction connected from the anode of the trigger SCR to the control gate of the control SCR and having its collector base junction connected across the anode-cathode terminals of the trigger SCR; whereby, when the trigger SCR is switched to the non-conduction state, during the positive half cycle of the AC supply, a gating current is caused to flow by zener action of the base-emitter junction of the PNP transistor to the control gate of the control SCR, causing the control SCR to be switched into the conduction state, allowing current to flow to actuate the heater, which in turn actuates the thermostatic switch, thereby de-activating the ice maker.

Claim 8

In combination with an automatic ice making system of the type having an ice maker, an ice storage receptacle and electrical control means Including a heater and a thermostatic switch adapted to be responsive to the heater to control the operation of the ice maker as a function of the level of ice pieces in the receptacle, a control circuit for actuating the thermostatic switch comprising: means for supplying an AC voltage including first and second input terminals; photoelectric triggering means supplying an indication of the level of ice pieces in the receptacle intended to initiate actuation of the thermostatic switch, said triggering means including a source, connected across said input terminals, providing a beam of radiant energy positioned so as to traverse the receptacle at a predetermined level; a heater current control SCR for controlling actuation of the heater, said SCR being coupled across said input terminals and further having a control gate terminal; a gating circuit for gating the heater current control SCR into conduction when the quantity of ice pieces in the receptacle reaches a predetermined level, including a photo-sensitive trigger SCR and a voltage dropping resistor coupled in series across said input terminals, said trigger SCR adapted to be responsive to the photoelectric triggering means so as to be switched to the non-conduction state when the quantity of ice pieces is above the predetermined level, and a PNP transistor having its emitter-base junction connected from the anode of the trigger SCR to the control gate of the control SCR and having its collector base junction connected across the anode-cathode terminals of the trigger SCR; whereby, when the trigger SCR is switched to the non-conduction state, during the positive half cycle of the AC supply, a gating current is caused to flow by zener action of the base-emitter junction of the PNP transistor to the control gate of the control SCR, causing the control SCR to be switched into the conduction state, allowing current to flow to actuate the heater, which in turn actuates the thermostatic switch, thereby de-activating the ice maker.