Ice maker control circuit

Claim 2

A solid state refrigeration control circuit for an automatic icemaker operative for sensing the presence of a finished slab of ice on a freezer plate and initiating an ice harvest cycle for the icemaker, means for refrigerating said plate to form an ice slab thereon, and means for defrosting the freezer plate and causing the ice slab to slide onto an ice cube cutting grid, said control comprising, in combination; a mercury ice thickness control thermostat switch; a normally open grid switch being operable upon the slab of ice sliding from the freezing plate onto the cutting grid to close; a transistor having a base, an emitter and a collector; a rectifier circuit for producing rectification of an AC power input, said rectifier circuit having one terminal connected to both said grid switch and said mercury thermostat switch, said rectifier circuit other terminal connected to the base of said transistor via biasing means; normally closed first switch means connecting said transistor base to said mercury thermostat switch; second switch means having a normally closed contact energizing the plate refrigerating means and a normally open contact for providing an electrical path when closed for energizing the freezer plate defrosting means; said mercury thermostat switch being positioned a preselected distance above the plate such that when a predetermined thickness of the ice slab is achieved the temperature of the ice slab is sensed by said mercury thermostat switch whereby said mercury thermostat switch opens causing said transistor to be triggered conductive; and transfer means operable, when energized by said conductive transistor, to open said normally closed first switch means and move said second switch means from its plate refrigerating contact to its freezer plate defrosting contact.

Claim 3

A solid state refrigeration control circuit for an automatic icemaker operative for sensing the presence of a finished slab of ice on a freezing plate and initiating an ice harvest cycle for the icemaker, means for refrigerating said plate to form an ice slab thereon, means for defrosting the freezing plate and causing the ice slab to slide onto an ice cube cutting grid, said control circuit comprising, in combination; a mercury ice thickness control thermostat switch; a grid switch being actuated upon the slab of ice sliding from the freezing plate onto the cutting grid; an NPN transistor having a base, an emitter and a collector; a bridge circuit for producing rectification of the AC power input; said bridge circuit having one terminal connected to a terminal of both said grid switch and said mercury thermostat switch, and its other terminal connected, at a junction point, to the base of said transistor through a biasing resistor; normally closed first switch contacts connecting said transistor base to the other terminal of said mercury thermostat switch, second switch means having a normally closed contact energizing the plate refrigerating means and a normally open contact for providing an electrical path when closed energizing the freezer plate defrosting means, said biasing resistor being of a value such that when a predetermined temperature of the ice slab is sensed by said thermostat mercury switch said thermostat switch opens directing the current flow through the base-emitter circuit of said transistor whereby said transistor is triggered conductive, and transfer means operable, when energized, to open said normally closed contact of said first switch means and close the normally open contact of said second switch means to energize said defrosting means and initiating the ice slab harvest cycle, said transfer means including a relay exciting coil connected, in series with the collector-emitter circuit of said transistor, between said junction point and said one terminal of said bridge circuit.

Claim 4

A solid state refrigeration control circuit for an automatic icemaker operative for sensing the presence of a finished slab of ice on a freezing plate and initiating an ice harvest cycle for the icemaker, means for refrigerating said plate to form an ice slab thereon, means for defrosting the freezing plate and causing the ice slab to slide onto an ice cube cutting grid, said control circuit comprising, in combination; a mercury ice thickness control thermostat switch; a grid switch being actuated upon the slab of ice sliding from the freezing plate onto the cutting grid; an NPN transistor having a base, an emitter and a collector; a bridge circuit for producing rectification of the AC power input; said bridge circuit having one terminal connected to a terminal of both said grid switch and said mercury thermostat switch, and its other terminal connected, at a junction point, to the base of said transistor through a biasing resistor; normally closed first switch contacts connecting said transistor base to the other terminal of said mercury thermostat switch, second switch means having a normally closed contact energizing the plate refrigerating means and a normally open contact for providing an electrical path when closed energizing the freezer plate defrosting means, said biasing resistor being of a value such that when a predetermined temperature of the ice slab is sensed by said thermostat mercury switch said thermostat switch opens directing the current flow through the base-emitter circuit of said transistor whereby said transistor is triggered conductive, and transfer means operable, when energized, to open said normally closed contact of said first switch means and close the normally open contact of said second switch means to energize said defrosting means and initiating the ice slab harvest cycle, said transfer means including a relay exciting coil connected, in series with the collector-emitter circuit of said transistor, between said junction point and said one terminal of said bridge circuit.

Claim 5

A solid state refrigeration control circuit for an automatic icemaKer operative for sensing the presence of a finished slab of ice on a freezing plate and initiating an ice harvest cycle for the icemaker, means for refrigerating said plate to form an ice slab thereon, a hot gas solenoid controlled valve operative for defrosting the freezing plate and causing the ice slab to slide onto an ice cube cutting grid, and pump means for distributing water on the freezing plate, said control circuit comprising, in combination; a mercury ice thickness control thermostat switch; a grid switch being actuated upon the slab of ice sliding from the freezing plate onto the cutting grid; an NPN transistor having a base, an emitter and a collector; a diode bridge rectifier for producing full wave rectification of the AC power input; said bridge rectifier having one terminal connected to a terminal of both said grid switch and said mercury thermostat switch, and its other terminal connected, at a junction point, to the base of said transistor through a biasing resistor; said other terminal also connected to one side of an exciting coil of a double pole-double throw relay, the other side of said exciting coil connected to said transistor collector, said relay including a first single pole section and a second double pole section, the normally closed contact of said single pole section connecting said transistor base to the other terminal of said mercury thermostat switch, the normally closed contact of said second double pole section operative for energizing the plate refrigerating means and the normally open contact thereof operative for providing an electrical path when closed energizing the freezer plate hot gas solenoid for defrosting the plate, the ohmic value of said biasing resistor being such that when a predetermined temperature of the ice slab is sensed by said thermostat mercury switch said thermostat switch opens directing the current flow through the base-emitter circuit of said transistor, whereby said transistor is triggered conductive to energize said exciting coil and open said normally closed contact of said first single pole section and close the normally open contact of said second double pole section of said relay to energize the hot gas solenoid and initiating the ice slab h harvest cycle.

Claim 6

A solid state refrigeration control circuit for an automatic icemaKer operative for sensing the presence of a finished slab of ice on a freezing plate and initiating an ice harvest cycle for the icemaker, means for refrigerating said plate to form an ice slab thereon, a hot gas solenoid controlled valve operative for defrosting the freezing plate and causing the ice slab to slide onto an ice cube cutting grid, and pump means for distributing water on the freezing plate, said control circuit comprising, in combination; a mercury ice thickness control thermostat switch; a grid switch being actuated upon the slab of ice sliding from the freezing plate onto the cutting grid; an NPN transistor having a base, an emitter and a collector; a diode bridge rectifier for producing full wave rectification of the AC power input; said bridge rectifier having one terminal connected to a terminal of both said grid switch and said mercury thermostat switch, and its other terminal connected, at a junction point, to the base of said transistor through a biasing resistor; said other terminal also connected to one side of an exciting coil of a double pole-double throw relay, the other side of said exciting coil connected to said transistor collector, said relay including a first single pole section and a second double pole section, the normally closed contact of said single pole section connecting said transistor base to the other terminal of said mercury thermostat switch, the normally closed contact of said second double pole section operative for energizing the plate refrigerating means and the normally open contact thereof operative for providing an electrical path when closed energizing the freezer plate hot gas solenoid for defrosting the plate, the ohmic value of said biasing resistor being such that when a predetermined temperature of the ice slab is sensed by said thermostat mercury switch said thermostat switch opens directing the current flow through the base-emitter circuit of said transistor, whereby said transistor is triggered conductive to energize said exciting coil and open said normally closed contact of said first single pole section and close the normally open contact of said second double pole section of said relay to energize the hot gas solenoid and initiating the ice slab h harvest cycle.