US3765008A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for the prevention of theft of electrically operated articles
Assignee: Individual
•
Filing: 1972-06-23
•
Granted: 1973-10-09
•
Expires: 1992-06-23
Abstract
Abstract Apparatus for the prevention of theft of electrically operated articles includes a detection system and an alarm system. The detection system is activated by interruption of electrical power to the gate of a programmable unijunction transistor which then becomes conducting and completes a circuit to the gate of a thyristor. The triggered thyristor is thus converted from an off position to an on position, thereby allowing current to flow therethrough, which current activates an alarm system. The alarm system may be visual or audible or a combination of both. Interruption of the electrical power to the detection system is caused by unplugging the input power cord to the electrically operated article to be protected, or by cutting said cord or by interrupting or interfering with the input power cord in any way such as in an attempted theft of the article.
Inventors
- 👤 R Lowry
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 00:51
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/02; G08B13/14; G08B13/1409
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
229 words
Apparatus for the prevention of theft of electrical appliances of the type having a power cord connectible to an electric outlet, said apparatus comprising: a voltage source disposed at said electrical appliance, said source capable of supplying a continuous voltage output as long as said power cord is connected to an energized AC electric outlet; a detection system and an alarm system; said detection system comprising an input, a rectifier, a programmable unijunction transistor, a thyristor, a capacitor, means for applying a positive voltage to the anode of said transistor and means for maintaining a charge on said capacitor, the output of said voltage source being connected to the input of said detection system, said rectifier being so electrically disposed between said input and the anode gate of said transistor that a positive DC voltage is applied to said anode gate as long as said voltage source supplies a continuous voltage to said input of said detection system, the relationship between the positive voltages on said anode gate and said anode being such that said transistor is in an off condition as long as said continuous voltage is supplied, said capacitor being so electrically connected that upon cessation of said continuous voltage said capacitor will discharge through said transistor and apply a triggering current to the gate of said thyristor and whereupon said thyristor will activate said alarm system.
Claim 2
Dependent Claim
229 words
Apparatus for the prevention of theft of electrical appliances of the type having a power cord connectible to an electric outlet, said apparatus comprising: a voltage source disposed at said electrical appliance, said source capable of supplying a continuous voltage output as long as said power cord is connected to an energized AC electric outlet; a detection system and an alarm system; said detection system comprising an input, a rectifier, a programmable unijunction transistor, a thyristor, a capacitor, means for applying a positive voltage to the anode of said transistor and means for maintaining a charge on said capacitor, the output of said voltage source being connected to the input of said detection system, said rectifier being so electrically disposed between said input and the anode gate of said transistor that a positive DC voltage is applied to said anode gate as long as said voltage source supplies a continuous voltage to said input of said detection system, the relationship between the positive voltages on said anode gate and said anode being such that said transistor is in an off condition as long as said continuous voltage is supplied, said capacitor being so electrically connected that upon cessation of said continuous voltage said capacitor will discharge through said transistor and apply a triggering current to the gate of said thyristor and whereupon said thyristor will activate said alarm system.
Claim 3
Dependent Claim
32 words
The apparatus of claim 1 wherein said voltage source is a step-down transformer, the primary of which is connected to said power cord and the secondary of which supplies said continuous voltage.
Claim 4
Dependent Claim
34 words
The apparatus of claim 1 wherein said means for applying a positive voltage to the anode of said transistor is a battery, which is also the means for maintaining said charge on said capacitor.
Claim 5
Dependent Claim
23 words
The apparatus of claim 3 wherein said alarm system includes an indicator light and said battery supplies the power to energize said light.
Claim 6
Dependent Claim
41 words
The apparatus of claim 1 wherein said alarm system includes an audible alarm in series with a silicon controlled rectifier, said silicon controlled rectifier being so electrically connected to said detection system that it is fired when said thyristor is triggered.
Claim 7
Dependent Claim
38 words
The apparatus of claim 1 wherein said alarm system includes a switch, said switch being normally closed and being so electrically connected that activation of said alarm system requires opening of said switch to deactivate said alarm system.
References Cited (Backward Citations)
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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) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |