US3794896A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control circuit for cooling fans
Assignee: ZF International UK Ltd
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Filing: 1972-12-29
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Granted: 1974-02-26
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Expires: 1992-12-29
Abstract
Abstract A control circuit for an electrically driven cooling fan has a relay for switching the fan in and out. Associated with the relay is resistance means for reducing the differential between the on and off points of the fan.
Inventors
- 👤 W Holt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 19:32
CPC Classifications
F; F01; F01P; F01P7/00; F01P7/02; F01P7/08
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
170 words
A control circuit for an electrically driven cooling fan, comprising in combination a resistor the value of which is dependent in use on the temperature of an apparatus cooled by the fan, a relay winding having a contact which when the winding is de-energised serves to operate the fan, an amplifier coupled to said resistor and responsive to the value of said resistor, said amplifier having an output decreasing with rise in temperature of the apparatus whereby when the temperature of the apparatus falls to a predetermined level the amplifier output energises said relay winding, and resistance means which is coupled to the amplifier by way of the relay contact when the relay winding is energised, the resistance means serving when the relay is energised to reduce the current flowing in the relay winding by an amount insufficient to cause the relay winding to become deenergised, so reducing the required increase in the temperature of the apparatus before the relay winding is again de-energised to cause the fan to operate.
Claim 2
Dependent Claim
170 words
A control circuit for an electrically driven cooling fan, comprising in combination a resistor the value of which is dependent in use on the temperature of an apparatus cooled by the fan, a relay winding having a contact which when the winding is de-energised serves to operate the fan, an amplifier coupled to said resistor and responsive to the value of said resistor, said amplifier having an output decreasing with rise in temperature of the apparatus whereby when the temperature of the apparatus falls to a predetermined level the amplifier output energises said relay winding, and resistance means which is coupled to the amplifier by way of the relay contact when the relay winding is energised, the resistance means serving when the relay is energised to reduce the current flowing in the relay winding by an amount insufficient to cause the relay winding to become deenergised, so reducing the required increase in the temperature of the apparatus before the relay winding is again de-energised to cause the fan to operate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |