Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
307 words
An automatic defrosting control system for a refrigeration system having cooling means for absorbing heat from a zone to be cooled to a predetermined temperature level, said cooling means being subject to the accretion of frost thereon, said control system comprising: means for causing defrosting of said cooling means; a thermostat adapted to be positioned in heat-exchange relation with both said cooling means and said defrosting means and adapted for connection in a control circuit for said refrigeration system and having a first switching position for terminating operation of said defrosting means and a second switching position for enabling operation thereof, said thermostat switching from its first to its second position in response to its temperature falling to a lower predetermined level and switching to its first position in response to its temperature rising to a higher predetermined level; a thermal time-delay relay adapted to be positioned in heatexchange relation with said cooling means and adapted for connection in said control circuit and having a first switching position for permitting operation of said cooling means and a second switching position for energizing said defrosting means and preventing operation of said cooling means, said relay switching from its first switching position to its second position in response to its temperature falling to a lower predetermined level and switching to its first position in response to its temperature rising to a higher predetermined level; and heating means adapted for connection in said control circuit for energization during at least a portion of the period that said relay is in its second position thereby to heat said relay to its higher predetermined temperature level whereby upon the temperature of said thermostat falling to its lower predetermined level and said relay cooling to its lower predetermined temperature level said thermostat and relay will switch to their second positions thereby initiating defrosting.
Claim 2
Dependent Claim
307 words
An automatic defrosting control system for a refrigeration system having cooling means for absorbing heat from a zone to be cooled to a predetermined temperature level, said cooling means being subject to the accretion of frost thereon, said control system comprising: means for causing defrosting of said cooling means; a thermostat adapted to be positioned in heat-exchange relation with both said cooling means and said defrosting means and adapted for connection in a control circuit for said refrigeration system and having a first switching position for terminating operation of said defrosting means and a second switching position for enabling operation thereof, said thermostat switching from its first to its second position in response to its temperature falling to a lower predetermined level and switching to its first position in response to its temperature rising to a higher predetermined level; a thermal time-delay relay adapted to be positioned in heatexchange relation with said cooling means and adapted for connection in said control circuit and having a first switching position for permitting operation of said cooling means and a second switching position for energizing said defrosting means and preventing operation of said cooling means, said relay switching from its first switching position to its second position in response to its temperature falling to a lower predetermined level and switching to its first position in response to its temperature rising to a higher predetermined level; and heating means adapted for connection in said control circuit for energization during at least a portion of the period that said relay is in its second position thereby to heat said relay to its higher predetermined temperature level whereby upon the temperature of said thermostat falling to its lower predetermined level and said relay cooling to its lower predetermined temperature level said thermostat and relay will switch to their second positions thereby initiating defrosting.
Claim 3
Dependent Claim
37 words
A system as set forth in claim 1 wherein said heating means comprises a self-regulating self-heating positive temperature coefficient resistor having a relatively low initial resistance which increases abruptly as its temperature rises above a given level.
Claim 4
Dependent Claim
35 words
A system as set forth in claim 1 wherein said heating means is an electric resistance heater parallel-connected across said relay thereby to be shunted and deenergized when said relay is in its first position.
Claim 5
Dependent Claim
42 words
A system as set forth in claim 1 wherein said refrigeration system includes a door for access to the cooled zone and a door-operated switch connected in said circuit for energizing said heating means during the time periods said door remains open.
Claim 6
Dependent Claim
29 words
A system as set forth in claim 1 wherein the thermostat is a single-pole single-throw switch and is open in its first position and closed in its second position.
Claim 7
Dependent Claim
48 words
A system as set forth in claim 5 wherein the heating means is an electrical resistance heater shunt-connected across said thermostat whereby the heating means is only energized during the period when the thermostat is in its first position and the relay is in its secoNd switching position.
Claim 8
Dependent Claim
144 words
A system as set forth in claim 1 wherein the thermal time-delay relay comprises a thermostatic switch having first and second switching positions, heat-responsive means for actuating said switch to its first position in response to a temperature rise to a first predetermined level and moving said switch to its second predetermined level, a thermal reservoir in heat-exchange relation with said heat-responsive actuating means, a positive temperature coefficient electrical resistance heater in heat-exchange relation with said thermal reservoir for effecting rapid heating thereof to the first temperature level, and a thermally insulating housing enclosing the switch, actuating means, thermal reservoir and heater whereby the time required for heating said means from its second temperature level to its first temperature level is much less than the time required for the temperature of said actuating means to fall from the first level to the second level.