US3751631A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Temperature control systems
Assignee: Dunlop Ltd
•
Filing: 1972-02-14
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Granted: 1973-08-07
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Expires: 1992-02-14
Abstract
Abstract A heater control system, particularly for temperature unbalance arising in the currents flowing in three heater elements supplied from a three-phase power supply. The current unbalance may be created as a result of a short-circuit, or may in a temperature control circuit be dependent on changes in the resistance of one heater element having a different temperature coefficient from that of the other elements.
Inventors
- 👤 B Seager
- 👤 G Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 03:04
CPC Classifications
G; G05; G05D; G05D23/00; G05D23/19; G05D23/20; G05D23/24; G05D23/2401
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
124 words
A control system for an electrical multi-phase heating system, comprising: a heater element for each phase of such multi-phase heating system, a primary winding of a current balance transformer operatively connected to said heater element so that the current flowing in said primary winding is directly dependent on the current flow in said heater element, a secondary winding of the same said transformer providing a signal dependent on the algebraic sum of the currents in the heater elements, a control circuit operatively connected to said secondary winding and arranged to respond to said signal, and means operatively connected to said control circuit for regulating the supply of power to the heater elements in response to an unbalance of current flowing in said heater elements.
Claim 2
Dependent Claim
124 words
A control system for an electrical multi-phase heating system, comprising: a heater element for each phase of such multi-phase heating system, a primary winding of a current balance transformer operatively connected to said heater element so that the current flowing in said primary winding is directly dependent on the current flow in said heater element, a secondary winding of the same said transformer providing a signal dependent on the algebraic sum of the currents in the heater elements, a control circuit operatively connected to said secondary winding and arranged to respond to said signal, and means operatively connected to said control circuit for regulating the supply of power to the heater elements in response to an unbalance of current flowing in said heater elements.
Claim 3
Dependent Claim
76 words
A control system according to claim 1 wherein the heater elements form part of the control system, at least part of one heater element having a different coefficient of change of resistance with teMperature from that of the remaining heater elements, the control circuit being arranged to actuate the means for regulating the supply of power so as to supply power to the heater elements when the currents in the heater elements are out of balance.
Claim 4
Dependent Claim
65 words
A control system according to claim 2 wherein the means for regulating the supply of power comprises load switch means and the control circuit comprises a null detector circuit arranged to receive a signal proportional to the out-of-balance current in the heater windings and to respond to a null signal by actuating the load switch means to cut off the supply to the heater elements.
Claim 5
Dependent Claim
63 words
A control system according to claim 3 wherein the null detector circuit incorporates a differential amplifier arranged to compare the input signal with a reference signal, and an output stage arranged to regulate the supply of trigger pulses to the load switch means, the load switch means comprising solid state load switches connected in series with a power supply to the heater elements.
Claim 6
Dependent Claim
43 words
A control system according to claim 4 wherein an oscillator is provided to generate trigger pulses for the solid state load switches, the oscillator output being connected to a trigger circuit through means controlled by the output stage of the null detector circuit.
Claim 7
Dependent Claim
34 words
A control system according to claim 2 wherein a gross current unbalance detector circuit is provided to cut off the supply of power to the heater elements in the event of gross current unbalance.
Claim 8
Dependent Claim
99 words
A control system according to claim 6 wherein the gross current unbalance detector circuit comprises a differential amplifier arranged to compare an input signal proportional to the out-of-balance current with a reference signal, and an output stage, and means for regulating the supply of power to the heater elements comprising solid state load switches connected in series with a power supply to the heater elements and operated by trigger pulses from a source of trigger pulses, the differential amplifier being arranged to cut off the supply of trigger pulses to the solid state load switches when gross unbalance arises.
Claim 9
Dependent Claim
52 words
A control system according to claim 7 wherein an oscillator is provided to generate trigger pulses for the solid state load switches, means being provided, controlled by the output stage of the gross current unbalance detector circuit, to inhibit the operation of the oscillator whenever a gross current unbalance condition is detected.
Claim 10
Dependent Claim
45 words
A control system according to claim 4 wherein the control circuit incorporates a reset circuit arranged to re-apply power to the heater elements after a predetermined time interval following any operation of the output stage to prevent trigger pulses from passing to the load switches.
Claim 11
Dependent Claim
43 words
A control system according to claim 1 wherein the control circuit comprises a current unbalance and null detector circuit arranged to provide an input to a logic circuit, the logic circuit being arranged to control the supply of power to the heater elements.
Claim 12
Dependent Claim
85 words
A control system according to claim 10 wherein the logic circuit incorporates a first monostable circuit which can be actuated by the input signal so as to operate through associated gates to switch on power to the heater elements and to disconnect power from the heater elements and which has a timed reset function which enables the power supply to be reconnected to the heater elements to test automatically for current balance conditions at a predetermined time after the heater current has been switched off.
Claim 13
Dependent Claim
59 words
A control system according to claim 11 wherein the logic circuit incorporates a second monostable circuit having a second timed reset function which is arranged to operate through associated gates to disconnect the power supply after a predetermined time interval following reconnection of the power supply to the heater elements by the first monostable circuit when current balance exists.
Claim 14
Dependent Claim
78 words
A control system according to claim 10 wherein a gross current unbaLance detector circuit is arranged to cut off the supply of power to the heater elements in the event of gross current unbalance, the output from the gross current unbalance detector circuit being passed through an associated logic circuit arranged to latch-on any output signal from the gross current unbalance detector circuit which is such as to effect disconnection of the power supply from the heater elements.
Claim 15
Dependent Claim
77 words
A control system according to claim 13 wherein the output from the logic circuit associated with the gross current detector circuit is connected to one input terminal of an AND gate, the other input terminal of the AND gate being connected to receive the output from the logic circuit associated with the current unbalance and null detector circuit, and the output from the AND gate being arranged to control the supply of power to the heater elements.
Claim 16
Dependent Claim
42 words
A control system according to claim 14 wherein the output from the AND gate is arranged to actuate an output stage to connect trigger pulses from an oscillator to a trigger circuit for solid state load switches associated with the heater elements.
References Cited (Backward Citations)
US3159736A
Cited
US3475588A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-06 | 1977-02-05 | 1977-08-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-06 | 1981-02-05 | 1981-08-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-06 | 1985-02-05 | 1985-08-07 | $7700.00 | Window Closed / Lapsed |