US3660720A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic grounding switch
Assignee: ABB Inc USA
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Filing: 1970-10-20
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Granted: 1972-05-02
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Expires: 1990-10-20
Abstract
Abstract Designed for use with electrically grounded power distribution systems, the switch is operable with replaceable propellent cartridges in association with a current limiting fuse. Upon receipt of an electrical signal indicating the presence of an overcurrent fault, a small surge of energy is provided to fire the cartridge and, in turn, propel its plunger into direct contact with a ''''hot'''' terminal of the switch, establishing a conducting path to ground. The magnitude of the resulting short circuit currents to ground are limited by the current limiting fuse.
Inventors
- 👤 Ralph W Samm
- 👤 E Robert Perry
- 👤 David S Dodge
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 15:27
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/093; H02H3/02; H02H3/021; H02H3/023
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
187 words
In conjunction with an electrical power distribution system having a primary current carrying conductor, the combination comprising: a current limiting fuse coupled to said conductor; an electrically conductive striker operatingly cooperative with one terminal of said current limiting fuse; rupturable means for electrically insulating said striker and said one terminal; first means coupled to said power distribution system conductor for storing a voltage representative of the peak current value in said conductor; second means coupled to said first means for generating a firing signal; delay means coupled to said first means for activating said second means after a predetermined time delay which is inversely proportional to the magnitude of current in said conductor; ignition means coupled to said first means and responsive to said firing signal for firing said conductive striker to rupture said rupturable means and make electrical contact with said current carrying conductor to effect current limiting flow through said cooperative fuse and to automatically ground said fuse in the presence of overcurrent conditions; said first and second means and said ignition means all being powered exclusively by the current in the conductor being monitored.
Claim 2
Dependent Claim
187 words
In conjunction with an electrical power distribution system having a primary current carrying conductor, the combination comprising: a current limiting fuse coupled to said conductor; an electrically conductive striker operatingly cooperative with one terminal of said current limiting fuse; rupturable means for electrically insulating said striker and said one terminal; first means coupled to said power distribution system conductor for storing a voltage representative of the peak current value in said conductor; second means coupled to said first means for generating a firing signal; delay means coupled to said first means for activating said second means after a predetermined time delay which is inversely proportional to the magnitude of current in said conductor; ignition means coupled to said first means and responsive to said firing signal for firing said conductive striker to rupture said rupturable means and make electrical contact with said current carrying conductor to effect current limiting flow through said cooperative fuse and to automatically ground said fuse in the presence of overcurrent conditions; said first and second means and said ignition means all being powered exclusively by the current in the conductor being monitored.
Claim 3
Dependent Claim
85 words
The combination of claim 1 wherein said current carrying conductor is maintained in a first housing, and wherein said conductive striker is maintained in a second housing in alignment with an aperture of said first housing but which is normally closed off therefrom by said rupturable means which is comprised of an insulating disc included within said second housing, and through which said striker is propelled in response to said electrical signal generation to contact said current carrying conductor to effect said current limiting action.
Claim 4
Dependent Claim
28 words
The combination of claim 1 wherein said first housing and said insulating disc are constructed of acrylic material and said second housing is constructed of a steel component.
Claim 5
Dependent Claim
76 words
The combination of claim 2 wherein said first means comprises an electronic overcurrent relay circuit adjustable to provide at least the value of signal current needed to fire the electrically conductive striker to contact said current carrying conductor and wherein said relay circuit includes a toroidal current transformer inductively coupled to said primary current conductor; a capacitor and a diode coupLed across said transformer for storing the peak value of the voltage developed by said transformer.
Claim 6
Dependent Claim
47 words
The combination of claim 4 in which said second means further includes a relaxation oscillator coupled to said transformer for generating the ignition firing signal and having an adjustable conduction point so as to vary the response time of the oscillator to meet different anticipated overcurrent conditions.
Claim 7
Dependent Claim
34 words
The combination of claim 5 in which there is also included neon tube means coupled across said toroidal current transformer to protect the overcurrent relay circuit against transients and heavy primary system current faults.
Claim 8
Dependent Claim
24 words
The combination of claim 5 wherein said delay means further comprises a resistor-capacitor circuit including an adjustable resistor for adjustably controlling the time delay.
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) | 1975-05-02 | 1975-11-01 | 1976-05-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-02 | 1979-11-01 | 1980-05-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-02 | 1983-11-01 | 1984-05-02 | $7700.00 | Window Closed / Lapsed |