US3908133A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High-low level control circuit
Assignee: Hartley Controls Corp
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Filing: 1974-05-23
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Granted: 1975-09-23
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Expires: 1994-05-23
Abstract
Abstract A high level probe and a low level probe are mounted at corresponding locations within a container of dry granular or powdered material. The probes are selectively coupled via an input relay to the signal input of a multi-stage amplifier. An output relay is coupled in series with the D.C. power supply for the amplifier and is actuated when the amplifier''s total current drain reaches a predetermined value, which occurs when the dry material contacts the high level probe and increases the capacitance thereof. The output relay is coupled to the input relay via a transfer relay to switch the input from the high level probe to the low level probe when the output relay is actuated. The output relay remains actuated until the material level drops below the low level probe, at which time the output relay de-actuates, which switches the high level probe back to the amplifier input, and activates means for refilling the container with dry material. When the material reaches the high level probe again, the output relay actuates, which switches the refilling means off, and switches the low level probe to the amplifier input. The transfer relay switches between two calibrating rheostats, one of which is used to calibrate the output relay when the high level probe is connected in the circuit, and the other of which is used to calibrate the output relay when the low level probe is connected in the circuit. A third calibrating rheostat is coupled in series with the first mentioned rheostats to compensate for the distributed capacitance of the cables coupled to the two probes.
Inventors
- 👤 Nelson Hartley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:47
CPC Classifications
G; G05; G05D; G05D9/00; G05D9/12; G01; G01F; G01F23/00; G01F23/22; G01F23/26; G01F23/263; G01F23/265
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
255 words
A level responsive circuit for initiating a predetermined action in response to the level of material in a container, comprising a first probe located at a first predetermined level in said container, a second probe located at a second predetermined level in said container, an amplifier circuit having signal input terminals, switch means coupled between said first and second probes and said signal input terminals and operable to couple said first probe to said signal input terminals in a first position of the switch means and to Couple said second probe to said signal input terminals in a second position of the switch means, a current responsive device coupled to said amplifier circuit, said current responsive device having two different states and being switchable to its first state in response to a first level of current flow therethrough and being switchable to its second state in response to a second level of current flow therethrough, means coupled to said current responsive device for initiating said predetermined action in response to one state thereof and for terminating the action in response to the other state thereof, and means coupled between said current responsive device and said switch means for switching said switch means to its first state in response to the first state of said current responsive device and for switching said switch means to its second state in response to the second state of said current responsive device, thereby permitting one amplifier circuit and one current responsive device to be used for the both probes.
Claim 2
Dependent Claim
255 words
A level responsive circuit for initiating a predetermined action in response to the level of material in a container, comprising a first probe located at a first predetermined level in said container, a second probe located at a second predetermined level in said container, an amplifier circuit having signal input terminals, switch means coupled between said first and second probes and said signal input terminals and operable to couple said first probe to said signal input terminals in a first position of the switch means and to Couple said second probe to said signal input terminals in a second position of the switch means, a current responsive device coupled to said amplifier circuit, said current responsive device having two different states and being switchable to its first state in response to a first level of current flow therethrough and being switchable to its second state in response to a second level of current flow therethrough, means coupled to said current responsive device for initiating said predetermined action in response to one state thereof and for terminating the action in response to the other state thereof, and means coupled between said current responsive device and said switch means for switching said switch means to its first state in response to the first state of said current responsive device and for switching said switch means to its second state in response to the second state of said current responsive device, thereby permitting one amplifier circuit and one current responsive device to be used for the both probes.
Claim 3
Dependent Claim
104 words
The circuit of claim 1 and further comprising at least two variable impedance elements and additional switch means for selectively coupling said variable impedance elements in series with said current responsive device in such manner that one of said variable impedance elements is in series with said current responsive device in one state thereof and the other variable impedance element is in series with said current responsive device in the other state thereof, whereby each variable impedance element serves as a calibration device for said current responsive device when a corresponding one of said probes is coupled to the input of said amplifier circuit.
Claim 4
Dependent Claim
74 words
The circuit of claim 2 and further comprising a third variable impedance element coupled in series with both of said two variable impedance elements whereby said third variable impedance element serves as a calibration device for said current responsive device when either of said probes is coupled to the input of said amplifier circuit, thereby enabling said probes to be coupled to the input of said amplifier circuit by conductors of any desired length.
Claim 5
Dependent Claim
80 words
The circuit of claim 1 wherein said means coupled to said current responsive device to initiate said predetermined action comprises a relay coupled to said current responsive device and responsive to the state thereof, and refilling means for refilling said container with said material, said refilling means being coupled to said relay and being responsive thereto to initiate refilling in response to one state of said relay and to terminate refilling in response to the other state of said relay.
Claim 6
Dependent Claim
54 words
The circuit of claim 1 wherein said amplifier circuit has power input terminals, and further comprising a current source coupled in series with said power input terminals, and said current responsive device being coupled in series with said current source so as to be responsive to the total current drain of said amplifier circuit.
Claim 7
Dependent Claim
95 words
The circuit of claim 5 and also comprising two variable impedance elements and switch means for coupling one of said variable impedance elements in series with said current responsive device in one state thereof and for coupling the other variable impedance element in series with said current responsive device in the other state thereof, whereby said one variable impedance element serves as a calibration device for said current responsive device in one state thereof and said other variable impedance element serves as a calibration device for said current responsive device in the other state thereof.
Claim 8
Dependent Claim
73 words
The circuit of claim 6 and further comprising a third variable impedance element coupled in series with said current responsive device and in series with both of the first mentioned variable impedance elements, whereby said third variable impedance element serves as a calibration device for said current responsive device in both states thereof and enables said probes to be coupled to the input of said amplifier circuit by conductors of any desired length.
Claim 9
Dependent Claim
94 words
The circuit of claim 7 wherein said current source is a rectifier bridge and means for applying an A.C. voltage to the A.C. input thereof, the D.C. output of said rectifier bridge being coupled to the power input terminals of said amplifier circuit, and wherein said three variable impedance elements are rheostats, two of said rheostats being coupled in parallel with each other and in series with said current responsive device, and the third rheostat being coupled in series with said current responsive device and in series with both of the other two rheostats.
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) | 1978-09-22 | 1979-03-24 | 1979-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-22 | 1983-03-24 | 1983-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-22 | 1987-03-24 | 1987-09-23 | $7700.00 | Window Closed / Lapsed |