US3708650A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical heating apparatus
Assignee: Tronicair International Ltd
•
Filing: 1971-01-18
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Granted: 1973-01-02
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Expires: 1991-01-18
Abstract
Abstract Electrical heating apparatus comprises first and second electric heater means. First means are provided in a control means for deriving from a source of electric power a first derived voltage consisting of first pulses all of the same polarity and for applying the first derived voltage pulse only to the first heater means. Second means are provided in the control means for deriving from the source of electric power a second derived voltage consisting of second pulses all being of opposite polarity to the first derived pulses and for applying the second derived voltage pulses to only the second heater unit. The first and second pulses occur alternately in time and do not overlap. The heater units each comprise at least one heating element comprising elongated resistive conductors adapted to dissipate heat and which have a maximum cross-sectional area equal to that of a circular conductor of a diameter not greater than 0.015 inches. The heating apparatus may comprise a forced circulation air heater with the conductors of the first and second heater units exposed to direct contact by the air stream. Alternatively, the apparatus can be used to heat a liquid, in which case the conductors may be embedded in refractory material and immersed in the liquid.
Inventors
- 👤 G Smillie
- 👤 F Johnstone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:31
CPC Classifications
H; H05; H05B; H05B3/00; H05B3/10; H05B3/16; F; F24; F24C; F24C7/00; F24C7/08; F24C7/087; F24H; F24H3/00; F24H3/02; F24H3/04; F24H3/0405; F24H3/0411; G; G05; G05D; G05D23/00; G05D23/19; G05D23/1906; G05D23/1909; H03; H03K; H03K17/00; H03K17/51; H03K17/56; H03K17/72; H03K17/725
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
28 words
Apparatus as claimed in claim 1 wherein there are in each element a multiplicity of said elongated conductors in parallel for each kilowatt of rated electrical power input.
Claim 2
Dependent Claim
29 words
Apparatus as claimed in claim 1 wherein the elements comprise: conductors having a cross-sectional area equal to that of a circular conductor of diameter not greater than 0.0076 inches.
Claim 3
Dependent Claim
14 words
Apparatus as claimed in claim 1 comprising heat-resisting insulating structure for supporting the conductors.
Claim 4
Dependent Claim
14 words
Apparatus as claimed in claim 4 wherein the structure comprises rods of glass fiber.
Claim 5
Dependent Claim
16 words
Apparatus as claimed in claim 1 comprising a printed circuit terminal board whereat the conductors terminate.
Claim 6
Dependent Claim
36 words
Apparatus as claimed in claim 1 wherein the apparatus is apparatus for heating liquid, the heating elements being embedded in material chosen from the group consisting of refractory material, fibrous mineral material and particulate mineral material.
Claim 7
Dependent Claim
29 words
Apparatus as claimed in claim 7 wherein the elements comprise conductors of diameter 0.006 inches or less, and/or non-circular conductors of cross-sectional area equal to that of such conductors.
Claim 8
Dependent Claim
150 words
Apparatus as claimed in claim 1 wherein the apparatus is adapted to operate from a source of AC electrical power, the said first and second means comprising meaNs to derive and apply the first and second derived voltages to the first and second elements by connecting the first element to the source during part cycles of the source waveform of one polarity and by connecting the second element to the source during part cycles of the source waveform of opposite polarity, the first and second elements respectively being disconnected from the source during part cycles of opposite and one polarities respectively, the said first and second means effecting said connection and disconnection whilst the instantaneous power being drawn or about to be drawn from the source by the element being disconnected or connected is small compared to the mean power drawn by the said element when connected to the source.
Claim 9
Dependent Claim
35 words
Apparatus as claimed in claim 9 wherein the said first means comprises a first unilaterally conductive means and the second means comprise a second unilaterally conductive means oppositely directed to the first unilaterally conductive means.
Claim 10
Dependent Claim
17 words
Apparatus as claimed in claim 10 wherein the said unilaterally conductive means are switchable unilaterally conductive means.
Claim 11
Dependent Claim
70 words
Apparatus as claimed in claim 11, wherein the unilaterally conductive means are adapted to be rendered operative in response to a control signal, there being a resistance-capacitance circuit for modifying the control signal so that in operation the elements are connected to and disconnected from the source when the said instantaneous power about to be drawn, or being drawn by the elements is small compared to the said mean power.
Claim 12
Dependent Claim
36 words
Apparatus as claimed in claim 12 wherein there is a temperature sensing element adapted to sense the temperature of a medium heated by the apparatus, and to provide said control signal according to the sensed temperature.
Claim 13
Dependent Claim
37 words
Apparatus as claimed in claim 10 comprising a bilaterally conductive electronic switch to which the first and second unilaterally conductive means are connected in parallel, the switch being arranged to conduct in response to a control signal.
Claim 14
Dependent Claim
53 words
Apparatus as claimed in claim 9 comprising control means for controlling the said second means so that the second element is connected to the source during a given part cycle of said opposite polarity only if the first element was connected to the source during the immediately preceding part cycle of said polarity.
Claim 15
Dependent Claim
53 words
Apparatus as claimed in claim 15 wherein the control means comprises a capacitor arranged to be charged during said immediately preceding part cycle and to discharge during said given part cycle of opposite polarity thereby to permit the second means to connect the second element to the source during said given part cycle.
Claim 16
Dependent Claim
30 words
Apparatus as claimed in claim 1 comprising means for increasing the peak amplitude of the voltage pulses above the peak amplitude of the voltage of the source of electrical power.
Claim 17
Dependent Claim
60 words
Apparatus as claimed in claim 1 comprising means defining a duct, the elements being disposed in the duct, a fan being provided to pass air downsardly through the said duct, a thermal cut-out being disposed in said duct whereby in operation if the fan fails, the cut-out senses an increased temperature and disconnects the elements from the source of power.
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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) | 1976-01-02 | 1976-07-03 | 1977-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-02 | 1980-07-03 | 1981-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-02 | 1984-07-03 | 1985-01-02 | $7700.00 | Window Closed / Lapsed |