US3745308A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Temperature control circuits
Assignee: Heinemann Electric Co
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Filing: 1971-07-01
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Granted: 1973-07-10
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Expires: 1991-07-01
Abstract
Abstract A system for applying electrical power to a heater element in response to a manual command, periodically monitoring changes in the temperature of the heater element by sensing its resistance during the heating process, and automatically disconnecting power from the heater when it reaches a preselected temperature. The system includes control circuits comprising an electrical bridge, including the heater element itself as one arm thereof, a comparator circuit for periodically sensing the output of the bridge at a time when the bridge is fully energized. The comparator generates a comparator signal each positive half cycle of the power source dependent upon the temperature of the heater element. A relay controls power to the bridge in response to a control signal generated by a bistable circuit. The bistable circuit is initially switched ''''on'''' in response to a manual command which results in power being applied to the bridge. Subsequently, the bistable circuit is switched ''''off'''' by each positive half cycle of power applied to the bridge circuit and ''''on'''' by the comparator signal at the end of each positive half cycle of power to the bridge circuit, so long as the temperature of the heater is below the preselected value. Each time the bistable circuit is switched ''''on,'''' a half wave of power is applied to the relay to maintain it in an energized condition. When the temperature of the heater reaches the predetermined value, the comparator signal ceases to switch the bistable circuit ''''on'''' and power is disconnected from the bridge and the heater.
Inventors
- 👤 P Lefferts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:17
CPC Classifications
G; G05; G05D; G05D23/00; G05D23/19; G05D23/20; G05D23/24; G05D23/2401
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
133 words
A system for controlling temperature comprising a source of pulsating electrical current, a heater element having a high temperature coefficient of resistance, an electrical bridge with said heater element connected as one arm thereof, said bridge being unbalanced with a first polarity output when said heater element is below a preselected temperature and unbalanced with a second polaRity output when said heater element is above said preselected temperature, circuit means for coupling said source to said bridge in response to an external command to begin the heating of said heater element, decoupling said source from said bridge in response to the change in the polarity of the output of said bridge during preselected time intervals, and inhibiting the recoupling of said source to said bridge until the subsequent occurrence of said external command.
Claim 2
Independent Claim
133 words
A system for controlling temperature comprising a source of pulsating electrical current, a heater element having a high temperature coefficient of resistance, an electrical bridge with said heater element connected as one arm thereof, said bridge being unbalanced with a first polarity output when said heater element is below a preselected temperature and unbalanced with a second polaRity output when said heater element is above said preselected temperature, circuit means for coupling said source to said bridge in response to an external command to begin the heating of said heater element, decoupling said source from said bridge in response to the change in the polarity of the output of said bridge during preselected time intervals, and inhibiting the recoupling of said source to said bridge until the subsequent occurrence of said external command.
Claim 3
Dependent Claim
106 words
The system recited in claim 1 wherein said circuit means comprises, a power relay including switching contacts in series with said source and said bridge, and a power relay coil, power relay energizing means for operating said power relay, including an electronic switch, first control circuit means for operating said electronic switch in response to said external command to permit energization of said power relay and the connection of power from said source to said bridge to begin the heating of said heater element, and second control circuit means for operating said electronic switch to de-energize said relay when said heater element reaches said preselected temperature.
Claim 4
Dependent Claim
70 words
The combination recited in claim 2 wherein said second control circuit means includes pulse generating means for alternately opening and reclosing said switch when said heater element is below said preselected temperature the time period during which said switch is open being insufficient to de-energize said relay and for opening said switch for a time period sufficient to de-energize said relay when said heater element rises above said preselected temperature.
Claim 5
Dependent Claim
129 words
The combination recited in claim 3 wherein said pulse generating means comprises turn off signal generating means for opening said switch at a preselected time during each cycle of power applied from said source to said bridge, and turn on means for generating a first signal for reclosing said switch subsequent to each of its openings by said turn off means after a sufficiently short time to maintain said power relay energized when said heater element is below said preselected temperature and for generating a second signal for permitting said switch to remain open subsequent to its opening by said turn off means when said heater element rises above said preselected temperature to permit the de-energization of said power relay and the disconnection of said source from said bridge.
Claim 6
Dependent Claim
75 words
The combination recited in claim 4 wherein said turn on means comprises a d.c. comparator for intermittently sensing the instantaneous output of said bridge and generating said first signal when its output is of a polarity to indicate that the temperature of the heater element is below said preselected temperature and for generating said second signal when the polarity of said output indicates that the temperature of the heater element is above the preselected temperature.
Claim 7
Dependent Claim
23 words
The combination recited in claim 5 further including means for activating said comparator and during alternate half cycles of current to said bridge.
Claim 8
Dependent Claim
68 words
The combination recited in claim 2 wherein said electronic switch comprises a bistable circuit, one stage of said bistable circuit being in series with said power relay coil, said one stage presenting a high impedence to the flow of current through said relay coil when in a first state and presenting a low impedence to the flow of current through said relay coil when in a second state.
Claim 9
Dependent Claim
55 words
The combination recited in claim 7 wherein said first control circuit means further includes a second switch connected in one arm of said bridge, and initiating means responsive to the closing of said switch for generating a pulse to switch said one stage of said bistable circuit from its first state to its second state.
Claim 10
Dependent Claim
60 words
The combination recited in claim 8 further including, a capacitor coupled to said bistable circuit and said switch, means for charging said capacitor when said switch is open, and means, including Said switch, for discharging said capacitor when said second switch is closed to trigger said one stage of said bistable circuit from its first state to its second state.
Claim 11
Dependent Claim
82 words
The combination recited in claim 5 wherein said comparator comprises a two stage semiconductor amplifier with positive feedback having two oppositely saturated states, said comparator having its input coupled to the output of said bridge and an output coupled to said switch, said comparator being driven to one of its oppositely saturated states by said first polarity output of said bridge to generate said first signal and to the other of its saturated states by said second polarity output of said bridge.
Claim 12
Dependent Claim
81 words
The combination recited in claim 6 wherein said means for activating said comparator comprises a gate circuit for maintaining said comparator deactivated when in a first state and for activating said comparator when in a second state, and means for controlling said gate circuit in response to the voltage across an arm of said bridge to switch said gate circuit from said first state to said second state when the voltage across said arm reaches a predetermined value greater than zero.
Claim 13
Dependent Claim
127 words
The combination recited in claim 11 wherein said gate circuit means includes a transistor device, said transistor device being conductive in said first state and non-conductive in said second state, said transistor device including a control terminal for conrolling the state of said transistor device in accordance with the voltage applied thereto, first biasing means for holding said control terminal at a potential to cause said transistor device to assume said first state, and second biasing means including a resistor connected in one of the arms of said bridge and coupled to said control terminal for applying a potential to said control terminal to switch said transistor device to said second state at a preselected magnitude and polarity of voltage across said resistor thereby activating said comparator.
Claim 14
Independent Claim
94 words
A system for controlling successive heating operations comprising, control circuit means responsive to a trigger signal for initiating the application of power from a source to a heater element in response to an external command, sensing circuit means for monitoring the rise in temperature of said heater element, and automatically disconnecting power from said heater element when it reaches a preselected final temperature, and means for simultaneously generating a trigger signal for operating said control means to initiate said heating cycle and selecting one of a plurality of final temperatures for said heater element.
Claim 15
Independent Claim
94 words
A system for controlling successive heating operations comprising, control circuit means responsive to a trigger signal for initiating the application of power from a source to a heater element in response to an external command, sensing circuit means for monitoring the rise in temperature of said heater element, and automatically disconnecting power from said heater element when it reaches a preselected final temperature, and means for simultaneously generating a trigger signal for operating said control means to initiate said heating cycle and selecting one of a plurality of final temperatures for said heater element.
Claim 16
Dependent Claim
74 words
The system recited in claim 13 wherein said means comprises, an electrical bridge with said heater element connected as one arm theroef, said heater element having a high temperature coefficient of resistance, another arm of said bridge comprising at least two parallel paths, said paths including resistance means for selecting a plurality of final temperatures for said heater element, and switch means for alternately connecting one of said paths in circuit with said bridge.
Claim 17
Dependent Claim
43 words
The combination recited in claim 14 wherein said switch means has three alternate positions, first and second positions for connecting said paths in circuit with said bridge, and a third position in which neither of said paths is in circuit with said bridge.
Claim 18
Dependent Claim
41 words
The combination recited in claim 15 further including heating cycle initiating circuit means response to the movement of said switch means to said first or second positions to generate a signal for initiating the application of power to said heater element.
Claim 19
Dependent Claim
52 words
The combination recited in claim 16 wherein said initiating circuit means comprises a capacitor coupled to said switch means and capacitor control means for charging said capacitor when said switch means is in said third position and discharging said capacitor when said switch means is moved to said first and second positions.
Claim 20
Dependent Claim
163 words
In a system comprising a heater element having a high temperature coefficient of resistance, an electrical bridge having said heater element in one arm thereof, and control circuit means for generating a signal for controlling the application of power from a source of alternating current to said bridge in accordance with the temperature of said heater element, said bridge means being unbalanced with a first polarity output when said heater element is below a preselected temperature and unbalanced with a second polarity output when said heater element is above said preselected temperature, the improvement comprising, first circuit means forming a portion of said control circuit means for sensing a change in the polarity of the output of said bridge and generating a control signal in response thereto, second circuit means responsive to said control signal for disconnecting power to said bridge, and timing circuit means for intermittently activating said circuit means on alternate half cycles of power to said bridge from said source.
Claim 21
Dependent Claim
163 words
In a system comprising a heater element having a high temperature coefficient of resistance, an electrical bridge having said heater element in one arm thereof, and control circuit means for generating a signal for controlling the application of power from a source of alternating current to said bridge in accordance with the temperature of said heater element, said bridge means being unbalanced with a first polarity output when said heater element is below a preselected temperature and unbalanced with a second polarity output when said heater element is above said preselected temperature, the improvement comprising, first circuit means forming a portion of said control circuit means for sensing a change in the polarity of the output of said bridge and generating a control signal in response thereto, second circuit means responsive to said control signal for disconnecting power to said bridge, and timing circuit means for intermittently activating said circuit means on alternate half cycles of power to said bridge from said source.
Claim 22
Dependent Claim
62 words
The combination recited in claim 18 wherein said circuit means comprises a detector circuit having two stable states, means for coupling said detector circuit to the output of said bridge, said detector circuit being driven to a first of said stable states in response to said first polarity and to a second of said stable states in response to said second polarity.
Claim 23
Dependent Claim
73 words
The combination recited in claim 18 wherein said timing means comprises control means for activating or de-activating said circuit means in response to a bias voltage applied thereto, and means coupled into an arm of said bridge for applying a voltage to said control means to activate said circuit means on alternate half cycles of power to said bridge upon the occurrence of a voltage of preselected magnitude and polarity of said bridge.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |