US3624449A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intrinsically safe transmitter system
Assignee: Combustion Engineering Inc
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Filing: 1970-08-24
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Granted: 1971-11-30
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Expires: 1990-08-24
Abstract
Abstract A DC regulator-type transmitter in a hazardous area is connected by a pair of electrical barriers to a DC source in a safe area to define a closed DC loop in which the current is controlled by the transmitter in proportion to a variable condition in the hazardous area. One barrier limits the voltage with respect to ground of metering resistance in the safe area of the loop connected to the source side grounded in the safe area. The other barrier limits the source voltage with respect to ground. Voltage drop across the metering resistance provides a measure of the variable condition.
Inventors
- 👤 Martin J Morgan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 20:35
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/008
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
372 words
An intrinsically safe system having a DC regulator constructed and arranged for location in a hazardous area, said regulator having a pair of first terminals and being responsive to a variable condition for causing DC to flow from one said terminal to the other said terminal in proportion to the magnitude of said condition: Said system also having a DC source constructed and arranged for location in a safe area, said source having a pair of second terminals, and said system also having first DC conductive means interconnecting one said first terminal and one said second terminal, and second DC conductive means interconnecting the other said first terminal and the other said second terminal, for defining a closed circuit including said source and said regulator in series with each other, with DC flowing in said circuit via DC conductive means and in proportion to said magnitude; said first DC conductive means being defined by metering resistance having one end directly connected to said one said second terminal and additional resistance having one end connected to the other end of said metering resistance, said additional resistance having its other end connected to said one said first terminal; said second DC conductive means being defined by further resistance interconnecting said other first terminal and said other said second terminal; said one said second terminal being connected to ground, and said first terminals being normally isolated from said ground save through the resistances of said DC conductive means and through the resistance of said source; and the improvement comprising first zener diode means interconnecting a point on said second conductive means and said ground, and having a zener voltage value corresponding to a voltage at said point that is substantially the largest voltage at that point as can be tolerated for intrinsically safe electrical conditions to obtain in said hazardous area with respect to said regulator; and second zener diode means interconnecting said other end of said metering resistance and said ground and having a zener voltage value that is substantially the value of the largest voltage at said other end of said metering resistance as can be tolerated for intrinsically safe electrical conditions to obtain in said hazardous area with respect to said regulator.
Claim 2
Dependent Claim
372 words
An intrinsically safe system having a DC regulator constructed and arranged for location in a hazardous area, said regulator having a pair of first terminals and being responsive to a variable condition for causing DC to flow from one said terminal to the other said terminal in proportion to the magnitude of said condition: Said system also having a DC source constructed and arranged for location in a safe area, said source having a pair of second terminals, and said system also having first DC conductive means interconnecting one said first terminal and one said second terminal, and second DC conductive means interconnecting the other said first terminal and the other said second terminal, for defining a closed circuit including said source and said regulator in series with each other, with DC flowing in said circuit via DC conductive means and in proportion to said magnitude; said first DC conductive means being defined by metering resistance having one end directly connected to said one said second terminal and additional resistance having one end connected to the other end of said metering resistance, said additional resistance having its other end connected to said one said first terminal; said second DC conductive means being defined by further resistance interconnecting said other first terminal and said other said second terminal; said one said second terminal being connected to ground, and said first terminals being normally isolated from said ground save through the resistances of said DC conductive means and through the resistance of said source; and the improvement comprising first zener diode means interconnecting a point on said second conductive means and said ground, and having a zener voltage value corresponding to a voltage at said point that is substantially the largest voltage at that point as can be tolerated for intrinsically safe electrical conditions to obtain in said hazardous area with respect to said regulator; and second zener diode means interconnecting said other end of said metering resistance and said ground and having a zener voltage value that is substantially the value of the largest voltage at said other end of said metering resistance as can be tolerated for intrinsically safe electrical conditions to obtain in said hazardous area with respect to said regulator.
Claim 3
Dependent Claim
102 words
The system of claim 1, including additional zener diode means interconnecting a point on said additional resistance and said ground, said additional zener diode having a zener voltage corresponding to said second zener diode means'' said zener voltage, insofar as are concerned said intrinsically safe electrical conditions, but slightly lesser in value; and also including further zener diode means interconnecting a point on said further resistance and said ground, said further zener diode means having a zener voltage corresponding to said first zener diode means'' said zener voltage, insofar as are concerned said intrinsically safe electrical conditions, but slightly lesser in value.
Claim 4
Dependent Claim
57 words
The system of claim 2 wherein the first said point on said additional resistance is separated by part of said additional resistance from the second said point on said further resistance; and the first said point on said resistance also being separated by part of said further resistance from the second said point on said further resistance.
Claim 5
Dependent Claim
69 words
The system of claim 2, wherein said additional resistance includes a first fuse means and a further resistance includes a second fuse means; and said first fuse means being located between the first said point on said additional resistance and the said other end of said metering resistance; said second fuse means being located between said other said first terminal and the first said point on said first resistance.
Claim 6
Dependent Claim
47 words
The system of claim 1 wherein said additional resistance includes first fuse means between said other end of said metering resistance and said point on said additional resistance; and said further resistance including second fuse means between said other second terminal said point on said further resistance.
Claim 7
Dependent Claim
315 words
An intrinsically safe system having a DC regulator constructed and arranged for location in a hazardous area, said regulator having a pair of first terminals and being responsive to a variable condition for causing DC to flow from one said terminal to the other said terminal in proportion to the magnitude of said condition; said system also having a DC source constructed and arranged for location in a safe area, said source having a pair of second terminals, and said system also having first DC conductive means interconnnecting one said first terminal and one said second terminal, and second DC conductive means interconnecting the other said first terminal and the other said second terminal, for defining a closed circuit including said source and said regulator in series with each other, with DC flowing in said circuit via said DC conductive means and in proportion to said magnitude; said first DC conductive means being defined by metering resistance having one end directly connected to said one said second terminal and additional resistance having one end connected to the other end of said metering resistance, said additional resistance having its other end connected to said one said first terminal; said second DC conductive means being defined by further resistance interconnecting said other said first terminal and said other said second terminal; said one said second terminal being connected to ground, and said first terminals being normally isolated from said ground save through the resistances of said DC conductive means; and the improvement comprising a first barrier forming part of said additional resistance for preventing conduction of electrical energy, by said first conductive means, above a given level, and a second barrier forming part of said further resistance for preventing conduction of electrical energy, by said second conductive means, above said given level; and the resistance of said first barrier being large with respect to said second barrier.
Claim 8
Dependent Claim
315 words
An intrinsically safe system having a DC regulator constructed and arranged for location in a hazardous area, said regulator having a pair of first terminals and being responsive to a variable condition for causing DC to flow from one said terminal to the other said terminal in proportion to the magnitude of said condition; said system also having a DC source constructed and arranged for location in a safe area, said source having a pair of second terminals, and said system also having first DC conductive means interconnnecting one said first terminal and one said second terminal, and second DC conductive means interconnecting the other said first terminal and the other said second terminal, for defining a closed circuit including said source and said regulator in series with each other, with DC flowing in said circuit via said DC conductive means and in proportion to said magnitude; said first DC conductive means being defined by metering resistance having one end directly connected to said one said second terminal and additional resistance having one end connected to the other end of said metering resistance, said additional resistance having its other end connected to said one said first terminal; said second DC conductive means being defined by further resistance interconnecting said other said first terminal and said other said second terminal; said one said second terminal being connected to ground, and said first terminals being normally isolated from said ground save through the resistances of said DC conductive means; and the improvement comprising a first barrier forming part of said additional resistance for preventing conduction of electrical energy, by said first conductive means, above a given level, and a second barrier forming part of said further resistance for preventing conduction of electrical energy, by said second conductive means, above said given level; and the resistance of said first barrier being large with respect to said second barrier.
Claim 9
Dependent Claim
20 words
The intrinsically safe system of claim 6, wherein at least one said barrier is of the type limiting current therethrough.
Claim 10
Dependent Claim
22 words
The intrinsically safe system of 6, wherein at least one said barrier is of the type limiting voltage due to current therethrough.
Claim 11
Dependent Claim
22 words
The intrinsically safe system of 6, wherein at least one said barrier is of the type limiting voltage due to current therethrough.
Claim 12
Dependent Claim
26 words
The intrinsically safe system of claim 6, wherein at least one said barrier is of the type limiting current therethrough and voltage due to said current.
Claim 13
Dependent Claim
30 words
The intrinsically safe system of claim 6, wherein at least one said barrier is of the type connected to ground for diverting current to ground if said level is exceeded.
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) | 1974-11-29 | 1975-05-31 | 1975-11-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-29 | 1979-05-31 | 1979-11-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-29 | 1983-05-31 | 1983-11-30 | $7700.00 | Window Closed / Lapsed |