US4967302A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Safety barriers for 2-wire transmitters
Assignee: MEASUREMENT TECHNOLOGY Ltd POWER COURT LUTON BEDFORDSHIRE LU1 3JJ ENGLAND A BRITISH Co
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Filing: 1988-05-31
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Granted: 1990-10-30
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Expires: 2008-05-31
Abstract
Abstract A single-channel shunt-diode safety barrier for energizing a 2-wire transmitter, particularly for use in process control, incorporates within the barrier a floating d.c. power supply or its equivalent to enable the barrier to deliver into an earthed load a direct current substantially equal to that which it draws from the transmitter. The floating d.c. power supply is preferably derived from an external d.c. power source via a transformer or diode-pump circuit within the barrier itself. The barrier is enabled to pass superimposed digital or frequency signals in both directions to and from the transmitter.
Inventors
- 👤 Ian C. Hutcheon
- 👤 David J. Epton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:39
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/008; G; G08; G08C; G08C19/00; G08C19/02
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
83 words
A safety barrier for energizing a two-wire transmitter, the barrier including floating DC power supply means adapted to enable the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which the floating DC power supply means is derived from an external DC source, with means to generate the floating power supply means being located within the barrier and comprising an oscillator, a voltage step-up transformer, and a rectifying and smoothing circuit.
Claim 2
Dependent Claim
83 words
A safety barrier for energizing a two-wire transmitter, the barrier including floating DC power supply means adapted to enable the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which the floating DC power supply means is derived from an external DC source, with means to generate the floating power supply means being located within the barrier and comprising an oscillator, a voltage step-up transformer, and a rectifying and smoothing circuit.
Claim 3
Dependent Claim
54 words
A safety barrier according to claim 1, in which said means to generate the floating power supply within the barrier comprises an oscillator and at least one diode-pump circuit driven by the oscillator, the at least one diode-pump circuit driving the load with a current equal to that which it draws from the barrier.
Claim 4
Dependent Claim
30 words
A safety barrier according to claim 2, which includes at least one switched inductor associated with said at least one diode-pump circuit to boost the peak-to-peak voltage of said oscillator.
Claim 5
Dependent Claim
31 words
A safety barrier according to claim 3, in which said at least one inductor is controlled by switch means, with the on-time of said switch means providing the desired voltage boost.
Claim 6
Dependent Claim
17 words
A safety barrier according to claim 4, in which the on-time is one quarter of a cycle.
Claim 7
Dependent Claim
27 words
A safety barrier according to claim 3, in which said at least one switched inductor directly provides an ac drive for the at least one diode-pump circuit.
Claim 8
Dependent Claim
80 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means adapted to enable the barrier to deliver into a grounded load a direct currently substantially equal to that which it draws from the transmitter, and including means for maintaining a constant voltage across the barrier, said means including a voltage compensating circuit having voltage regulator means that does not modify the transmitter current connected between the floating DC power supply means and the load.
Claim 9
Dependent Claim
80 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means adapted to enable the barrier to deliver into a grounded load a direct currently substantially equal to that which it draws from the transmitter, and including means for maintaining a constant voltage across the barrier, said means including a voltage compensating circuit having voltage regulator means that does not modify the transmitter current connected between the floating DC power supply means and the load.
Claim 10
Dependent Claim
68 words
A safety barrier for energizing a two-wire transmitter, the barrier including floating DC power supply means to enable the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which compensation for variations in the voltage across the load is delayed in time so that the barrier will pass superimposed digital or frequency signals in both directions.
Claim 11
Dependent Claim
68 words
A safety barrier for energizing a two-wire transmitter, the barrier including floating DC power supply means to enable the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which compensation for variations in the voltage across the load is delayed in time so that the barrier will pass superimposed digital or frequency signals in both directions.
Claim 12
Dependent Claim
79 words
A single-channel shunt-diode safety barrier for energizing a two-wire transmitter, comprising a floating DC power supply means for delivering into a grounded load a direct current substantially equal to that which it draws from the transmitter, the floating DC power supply means being located within the barrier and including oscillator means and at lest one diode-pump circuit means driven by the oscillator means for driving the load with a current equal to that which it draws from the barrier.
Claim 13
Dependent Claim
79 words
A single-channel shunt-diode safety barrier for energizing a two-wire transmitter, comprising a floating DC power supply means for delivering into a grounded load a direct current substantially equal to that which it draws from the transmitter, the floating DC power supply means being located within the barrier and including oscillator means and at lest one diode-pump circuit means driven by the oscillator means for driving the load with a current equal to that which it draws from the barrier.
Claim 14
Dependent Claim
33 words
A safety barrier according to claim 9, which includes at least one switched inductor means associated with said at least one diode-pump circuit means to boost the peak-to-peak voltage of said oscillator means.
Claim 15
Dependent Claim
29 words
A safety barrier according to claim 10, in which said at least one switched inductor means directly provides an AC drive for the at least one diode-pump circuit means.
Claim 16
Dependent Claim
36 words
A safety barrier according to claim 10, in which said at least one inductor means is controlled by switch means producing a periodic on-time of said switch means with the on-time providing the desired voltage boost.
Claim 17
Dependent Claim
16 words
A safety barrier according to claim 12, ion which the on-time is one-quarter of a cycle.
Claim 18
Dependent Claim
73 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, including a voltage-compensating circuit means comprising voltage regulator means that does not modify the transmitter current connected between the floating DC power supply and the load for maintaining a constant voltage across the barrier.
Claim 19
Dependent Claim
73 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, including a voltage-compensating circuit means comprising voltage regulator means that does not modify the transmitter current connected between the floating DC power supply and the load for maintaining a constant voltage across the barrier.
Claim 20
Dependent Claim
68 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which the barrier is polarized to pass signals of negative polarity with respect to ground and the current delivered to the load is positive with respect to ground.
Claim 21
Dependent Claim
68 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, in which the barrier is polarized to pass signals of negative polarity with respect to ground and the current delivered to the load is positive with respect to ground.
Claim 22
Dependent Claim
114 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, including at least one regulating circuit means for holding the voltage applied to the barrier automatically at a level below the level at which the barrier starts to conduct and for compensating the variations in the supply voltage and the voltage drop across the load, and in which compensation for variations in the voltage across the load is delayed in time so that the barrier will pass superimposed digital or frequency signals in both directions.
Claim 23
Dependent Claim
114 words
A safety barrier for energizing a two-wire transmitter, the barrier incorporating floating DC power supply means for enabling the barrier to deliver into a grounded load a direct current substantially equal to that which it draws from the transmitter, including at least one regulating circuit means for holding the voltage applied to the barrier automatically at a level below the level at which the barrier starts to conduct and for compensating the variations in the supply voltage and the voltage drop across the load, and in which compensation for variations in the voltage across the load is delayed in time so that the barrier will pass superimposed digital or frequency signals in both directions.
Claim 24
Dependent Claim
20 words
A safety barrier according to claim 16 in which the at lest one regulating circuit means comprises a switching regulator.
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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) | 1993-10-29 | 1994-04-30 | 1994-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-29 | 1998-04-30 | 1998-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-29 | 2002-04-30 | 2002-10-30 | $7700.00 | Window Closed / Lapsed |