Patent US582265A successfully refreshed from Google Patents.
Patent US3899896A successfully refreshed from Google Patents.
US3899896A
Expired / Lapsed
US
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Automatic defrosting control system
Assignee: Texas Instruments Inc
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Filing: 1974-10-15
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Granted: 1975-08-19
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Expires: 1994-10-15
Abstract
Abstract An automatic defrosting control system for a refrigeration system having an evaporator or the like for absorbing heat from a zone to be cooled and a cold control to maintain the zone substantially at a preselected temperature. The control system comprises means for causing defrosting of the evaporator and two thermostats.
Inventors
- 👤 Samuel T Bryant
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 20:10
CPC Classifications
F; F25; F25D; F25D17/00; F25D17/04; F25D17/06; F25D17/062; F25D17/065; F25D21/00; F25D21/002; F25D2317/00; F25D2317/06; F25D2317/065; F25D2317/0653; F25D2400/00; F25D2400/04
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
339 words
An automatic defrosting control system for a refrigeration system having cooling means for absorbing heat from a zone to be cooled and thermostatic means for periodically energizing the cooling means to maintain the zone substantially at a preselected temperature, said cooling means being subject to the accretion of frost thereon, said control system comprising: means for causing defrosting of said cooling means; a first thermostat adapted to be positioned adjacent and in heat-exchangE relation with both said defrosting and said cooling means and adapted for connection in a control circuit, said first thermostat having a first switching position for terminating operation of said defrosting means and a second switching position for enabling operation of said defrosting means, said first thermostat switching from its first to its second position in response to its temperature falling to a predetermined level and switching to its first position in response to its temperature rising to a predetermined level; and a second thermostat adapted to be positioned adjacent said cooling means but in a poorer heat-exchange relation therewith than is said first thermostat, said second thermostat adapted for connection in said control circuit, said second thermostat having a first switching position for permitting energization of said cooling means and a second switching position for energizing said defrost means and preventing operation of the cooling means, said second thermostat switching from its first to its second switching position in response to its temperature falling to a predetermined level whereby as frost tends to build up on the cooling means the temperatures of both thermostats are reduced until after a first time delay due to the thermal lag between the temperature of said cooling means and that of the first thermostat the latter is cooled sufficiently to switch to its second position and after a second and longer time delay, due to the greater thermal lag between the temperature of the cooling means and that of the second thermostat, the second thermostat thereafter cools sufficiently to switch to its second position thereby energizing the defrosting means.
Claim 2
Dependent Claim
339 words
An automatic defrosting control system for a refrigeration system having cooling means for absorbing heat from a zone to be cooled and thermostatic means for periodically energizing the cooling means to maintain the zone substantially at a preselected temperature, said cooling means being subject to the accretion of frost thereon, said control system comprising: means for causing defrosting of said cooling means; a first thermostat adapted to be positioned adjacent and in heat-exchangE relation with both said defrosting and said cooling means and adapted for connection in a control circuit, said first thermostat having a first switching position for terminating operation of said defrosting means and a second switching position for enabling operation of said defrosting means, said first thermostat switching from its first to its second position in response to its temperature falling to a predetermined level and switching to its first position in response to its temperature rising to a predetermined level; and a second thermostat adapted to be positioned adjacent said cooling means but in a poorer heat-exchange relation therewith than is said first thermostat, said second thermostat adapted for connection in said control circuit, said second thermostat having a first switching position for permitting energization of said cooling means and a second switching position for energizing said defrost means and preventing operation of the cooling means, said second thermostat switching from its first to its second switching position in response to its temperature falling to a predetermined level whereby as frost tends to build up on the cooling means the temperatures of both thermostats are reduced until after a first time delay due to the thermal lag between the temperature of said cooling means and that of the first thermostat the latter is cooled sufficiently to switch to its second position and after a second and longer time delay, due to the greater thermal lag between the temperature of the cooling means and that of the second thermostat, the second thermostat thereafter cools sufficiently to switch to its second position thereby energizing the defrosting means.
Claim 3
Dependent Claim
45 words
A system as set forth in claim 1 wherein the predetermined level to which the second thermostat must fall to switch to its second position is a lower temperature level than that to which the first thermostat must fall to switch to its second position.
Claim 4
Dependent Claim
53 words
A system as set forth in claim 1 further comprising a heating means in heat-exchange relation with said second thermostat, said heating means adapted for connection in said control circuit for energization when said first thermostat is in its first position and for deenergization when said first thermostat is in its second position.
Claim 5
Dependent Claim
36 words
A system as set forth in claim 3 wherein said heater is 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 6
Dependent Claim
70 words
A system as set forth in claim 3 in which the cooling means includes an electrically energized compressor for connection across an electrical power source, said second thermostat when in its first switching position serially connecting said thermostatic means and the compressor across the a.c. power source, said thermostatic means being responsive to close therby to operate the compressor when the temperature in the zone rises above a preselected level.
Claim 7
Dependent Claim
64 words
A system as set forth in claim 5 in which the cooling means further includes an evaporator coil, and which further includes a bracket thermally associated with the evaporator, said first and second thermostats being mounted on said bracket with the thermal conductivity between the evaporator and the second thermostat being substantially less than the thermal conductivity between the evaporator and the first thermostat.
Claim 8
Dependent Claim
52 words
A system as set forth in claim 6 which further includes a second heating means serially connected with the first heater means for energization when the second thermostat is in its first switching position, said second heating means being positioned in heat-exchange relationship with said bracket thereby to heat it when energized.
Claim 9
Dependent Claim
31 words
A system as set forth in claim 7 wherein the first and second heater means are serially connected with the thermostatic means for energization only when the latter means is closed.
Claim 10
Dependent Claim
14 words
A system as set forth in claim 7 wherein said heating means are resiStors.
Claim 11
Dependent Claim
39 words
A system as set forth in claim 9 wherein at least one of said resistors is a self-regulating, self-heating positive coefficient resistor having a relatively low initial resistance which increases abruptly as its temperature rises above a given level.
Claim 12
Dependent Claim
50 words
A system as set forth in claim 7 wherein the second heating means is shunt-connected across contacts of said second thermostat whereby when the latter is in its second switching position the second heater means is shunted and deenergized and the energization level of the first heating means is increased.
Claim 13
Dependent Claim
32 words
A system as set forth in claim 5 in which said first thermostat is single pole-single throw and operates when in its second position to shunt said heater means to deenergize it.
Claim 14
Dependent Claim
44 words
A system as set forth in claim 6 wherein the predetermined level to which the second thermostat must fall to switch to its second position is a lower temperature than that to which the first thermostat must fall to switch to its second position.
Claim 15
Dependent Claim
49 words
A system as set forth in claim 13 wherein the temperature to which said first thermostat must rise to switch from its second to its first switching position is lower than that temperature to which the second thermostate must rise to switch from its second to its first position.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |