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Patent US3790914A successfully refreshed from Google Patents.
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US3790914A Expired / Lapsed US ⏱️ 0.0 years remaining

Double lock electric plug

Assignee: Individual
•
Filing: 1973-05-10
•
Granted: 1974-02-05
•
Expires: 1993-05-10
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Abstract

Abstract A cylindrical body of di-electric material, having an axial bore with an electric cable received therein, and comprising; a first ring, having on one face, a tubular axial extension, and having on the other face, three conductive prongs, including a ground prong, for being received in a conventional power outlet, said prongs being connected to the wires of said cable; a second ring rotatable on said extension and a third ring on said extension, which serves as a thrust bearing for the second ring and a retainer for said cable. The ground prong has a bifurcated, or split, outer wall in which lies a rotatable cam rod, which extends through the first ring and into a cam slot formed in the second ring. The cam rod has at one end a flat coin-like locking head, which when rotated in one direction, expands the walls of said ground prong to prevent withdrawal of the plug from the socket. At the other end of said cam rod is a cam for axially rotating the said rod, when the second ring is rotated on the said axial extension. Each said first and second ring has a perforated tab thereon for receiving a padlock, to prevent rotation of the two rings, with respect to each other, when said cam rod is in locking position.

Inventors

  • 👤 D Hough

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-28 04:56
CPC Classifications
H; H01; H01R; H01R13/00; H01R13/62; H01R13/639

Claims Analysis

Total Claims: 6
Claim 1
Independent Claim 165 words
In a device of the character described, a plurality of axially aligned, non-conductive rings, having an electric cable received therein, conductive prongs on one of said rings and connected to the wires of said cable, said first ring having an axial extension thereon which serves as a bearing for a second and third ring, one of said conductive prongs being a laterally expandable ground prong, a cam rod in said ground prong, said rod having a flat head portion at one end and a cam at its opposite end, said cam being received in a cam slot carried by said second ring and arranged to rotate said cam rod and said flat head to open said ground prong when said second ring is rotated relative to said first ring, each of said first and second rings having perforated locking tab thereon, said perforated tabs being arranged to receive a padlock when brought together by the rotation of said second ring relative to said first ring.
Claim 2
Dependent Claim 165 words
In a device of the character described, a plurality of axially aligned, non-conductive rings, having an electric cable received therein, conductive prongs on one of said rings and connected to the wires of said cable, said first ring having an axial extension thereon which serves as a bearing for a second and third ring, one of said conductive prongs being a laterally expandable ground prong, a cam rod in said ground prong, said rod having a flat head portion at one end and a cam at its opposite end, said cam being received in a cam slot carried by said second ring and arranged to rotate said cam rod and said flat head to open said ground prong when said second ring is rotated relative to said first ring, each of said first and second rings having perforated locking tab thereon, said perforated tabs being arranged to receive a padlock when brought together by the rotation of said second ring relative to said first ring.
Claim 3
Dependent Claim 63 words
The structure of claim 1, in which said second ring has a bore in which is received a low voltage electric bulb, which is electrically connected to two of said prongs, the light from said bulb being visible through the walls of said second ring to indicate the flow of current through said device, when the device is received in a power outlet.
Claim 4
Dependent Claim 69 words
The structure of claim 1, being arranged to be received in a power outlet and further arranged to be first locked in said power outlet upon the expansion of said ground prong by the rotation of said second ring, and arranged to be second locked by a padlock which is received in the perforations of said tabs, which padlock prevents the rotation of said rings relative to one another.
Claim 5
Dependent Claim 39 words
The structure of claim 1, in which said second ring is rotatable on the said extension of said first ring and said third ring serves as a thrust bearing for said second ring and a support for said cable.
Claim 6
Dependent Claim 40 words
The structure of claim 1, including means to expand said ground plug, means to prevent the rotation of said rings relative to one another and visible means in said second ring to indicate that said ground plug is properly expanded.

References Cited (Backward Citations)

US1771757A Cited
US3345605A Cited
US3390404A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-02-04 1977-08-06 1978-02-05 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-02-04 1981-08-06 1982-02-05 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-02-04 1985-08-06 1986-02-05 $7700.00 Window Closed / Lapsed

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