US3893022A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sealed envelope examining device for detecting the presence of metal
Assignee: Individual
•
Filing: 1974-02-28
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Granted: 1975-07-01
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Expires: 1994-02-28
Abstract
Abstract A device for detecting the presence of metal in sealed flat envelopes, whereby the presence of ''''letter bombs'''' and similar destructive devices can be sensed and an alarm device actuated. The device includes a base of generally rectangular configuration containing a detecting circuit including a pair of coils, one of said coils being mounted within said base, and the other said coil supported on a bridge-like structure extending transversely above said base to define an interstice through which envelopes pass. The presence of metal changes the electromagnetic field existing between the coils, resulting in a change in impedance sufficient to actuate the alarm.
Inventors
- 👤 Herbert S Kulik
- 👤 Jacob Schachter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 22:21
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/104; G01V3/105
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
155 words
A sealed envelope examining device comprising: a base element forming a housing, a metal-sensitive oscillating detector circuit at least partially disposed within said housing, said circuit including first and second coils developing an electromagnetic field therebetween and an alarm device; said base element including a planar upper wall and a pair of side walls on either side thereof, a bridge structure supported by portions of said walls and extending over said upper wall to define an interstice therebetween for the passage of an envelope therethrough, one of said coils being supported by said bridge structure, the other of said coils being supported by said base element on opposite sides of said interstice; a slideable drawer element supported by said base element and passing beneath said bridge structure, and a pivotally mounted cover element selectively overlying said base element and having means maintaining said drawer element against movement when said cover element is in overlying position.
Claim 2
Dependent Claim
155 words
A sealed envelope examining device comprising: a base element forming a housing, a metal-sensitive oscillating detector circuit at least partially disposed within said housing, said circuit including first and second coils developing an electromagnetic field therebetween and an alarm device; said base element including a planar upper wall and a pair of side walls on either side thereof, a bridge structure supported by portions of said walls and extending over said upper wall to define an interstice therebetween for the passage of an envelope therethrough, one of said coils being supported by said bridge structure, the other of said coils being supported by said base element on opposite sides of said interstice; a slideable drawer element supported by said base element and passing beneath said bridge structure, and a pivotally mounted cover element selectively overlying said base element and having means maintaining said drawer element against movement when said cover element is in overlying position.
Claim 3
Dependent Claim
40 words
Structure in accordance with claim 1, including means for mounting said upper wall of said base element at an angle relative to horizontal, whereby envelopes placed upon said upper wall may slide under the force of gravity through said interstice.
References Cited (Backward Citations)
US2966582A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-30 | 1978-12-30 | 1979-07-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-30 | 1982-12-30 | 1983-07-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-30 | 1986-12-30 | 1987-07-01 | $7700.00 | Window Closed / Lapsed |