US3733576A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reversible safety ground plug
Assignee: Individual
•
Filing: 1971-07-28
•
Granted: 1973-05-15
•
Expires: 1991-07-28
Abstract
Abstract An electric plug having a pair of alternative retractable prongs for insertion into an electrical receptacle connected with a source of electrical power. The electrical plug is arranged with a pair of contact blades which are inserted into appropriate slots in the electrical terminal or receptacle and also with a pair of ground prongs, one of which can be inserted in the ground opening of the receptacle assuming it is a three opening receptacle. The two round ground plugs are retractable into the housing for the plug. Both of the ground plugs are connected to the ground of the appliance. The appliance may be a refrigerator, television set, recreational vehicle or other vehicle or power tool or any other type of appliance with which the plug is designed to cooperate. One of the two blade contacts is connected to the positive side of the appliance and the other blade contact is connected to the neutral or negative side of the appliance. The neutral lead has a Y formed therein and a lead is provided from the end of the Y through a resistance, a small neon light, and a buzzer and back to the ground terminal of the cable leading to the plug. Means are provided for manually retracting either of the ground prong contacts, the means consisting of a button attached to each one of the ground prongs.
Inventors
- 👤 J Cooper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 23:05
CPC Classifications
H; H01; H01R; H01R27/00; H01R13/00; H01R13/66; H01R13/70; H01R13/713
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
279 words
An electric plug comprising in combination: a. a casing; b. means in said casing for connecting a source of electric power to an electrical apparatus comprising: 1. a pair of spaced blade electrical contacts supported by and projecting out from said casing, said blade electrical contacts being provided for insertion into the positive and neutral slots of a receptacle connected to opposite poles of a source of electric power; 2. a pair of movable electrical prong contacts both electrically connected to the ground wire of said cable and each arranged to extend at times outward from said casing and at times to be retracted within said casing; and 3. a three wire electrical cable having one end of each wire electrically connected to an electrical appliance and having the opposite end of one said wire connected to both of said prong contacts, having the opposite end of another of said wires connected to one of said blade contacts, and having the opposite end of said third wire connected to the other of said blade contacts; and c. signal means included within said casing for indicating that the polarity of a receptacle into which the blade contacts are inserted is reversed as to the polarity of the appliance; and d. means for converting the operable condition of said plug to one in which the polarity of the connections from source to said appliance is corrected: comprising 1. mechanism for moving one of said prong contacts to and from said projecting position from and to a retracted position; and 2. mechanism for moving the other of said prong contacts to and from said projecting position from and to a retracted position.
Claim 2
Dependent Claim
279 words
An electric plug comprising in combination: a. a casing; b. means in said casing for connecting a source of electric power to an electrical apparatus comprising: 1. a pair of spaced blade electrical contacts supported by and projecting out from said casing, said blade electrical contacts being provided for insertion into the positive and neutral slots of a receptacle connected to opposite poles of a source of electric power; 2. a pair of movable electrical prong contacts both electrically connected to the ground wire of said cable and each arranged to extend at times outward from said casing and at times to be retracted within said casing; and 3. a three wire electrical cable having one end of each wire electrically connected to an electrical appliance and having the opposite end of one said wire connected to both of said prong contacts, having the opposite end of another of said wires connected to one of said blade contacts, and having the opposite end of said third wire connected to the other of said blade contacts; and c. signal means included within said casing for indicating that the polarity of a receptacle into which the blade contacts are inserted is reversed as to the polarity of the appliance; and d. means for converting the operable condition of said plug to one in which the polarity of the connections from source to said appliance is corrected: comprising 1. mechanism for moving one of said prong contacts to and from said projecting position from and to a retracted position; and 2. mechanism for moving the other of said prong contacts to and from said projecting position from and to a retracted position.
Claim 3
Dependent Claim
16 words
The structure of claim 1, in which the means for moving said prong contacts are independent.
Claim 4
Dependent Claim
21 words
mechanism for moving the other of said prong contacts to and from said projecting position from and to a retracted position.
Claim 5
Dependent Claim
21 words
mechanism for moving the other of said prong contacts to and from said projecting position from and to a retracted position.
Claim 6
Dependent Claim
38 words
a pair of movable electrical prong contacts both electrically connected to the ground wire of said cable and each arranged to extend at times outward from said casing and at times to be retracted within said casing; and
Claim 7
Dependent Claim
38 words
a pair of movable electrical prong contacts both electrically connected to the ground wire of said cable and each arranged to extend at times outward from said casing and at times to be retracted within said casing; and
Claim 8
Dependent Claim
26 words
The structure of claim 1, in which the means for moving said prong contacts are interconnected so that as one is extended, the other is retracted.
Claim 9
Dependent Claim
126 words
a three wire electrical cable having one end of each wire electrically connected to an electrical appliance and having the opposite end of one said wire connected to both of said prong contacts, having the opposite end of another of said wires connected to one of said blade contacts, and having the opposite end of said third wire connected to the other of said blade contacts; and c. signal means included within said casing for indicating that the polarity of a receptacle into which the blade contacts are inserted is reversed as to the polarity of the appliance; and d. means for converting the operable condition of said plug to one in which the polarity of the connections from source to said appliance is corrected: comprising
Claim 10
Dependent Claim
126 words
a three wire electrical cable having one end of each wire electrically connected to an electrical appliance and having the opposite end of one said wire connected to both of said prong contacts, having the opposite end of another of said wires connected to one of said blade contacts, and having the opposite end of said third wire connected to the other of said blade contacts; and c. signal means included within said casing for indicating that the polarity of a receptacle into which the blade contacts are inserted is reversed as to the polarity of the appliance; and d. means for converting the operable condition of said plug to one in which the polarity of the connections from source to said appliance is corrected: comprising
Claim 11
Dependent Claim
28 words
The structure of claim 1, in which when an electrical prong contact is extended outward from said casing it is in substantial parallel relationship with said blade contacts.
Claim 12
Dependent Claim
40 words
The structure of claim 4, in which the extended positions of said electrical prong contacts are on opposite sides of a plane intersecting the longitudinal axes of said blade contacts and are at a substantial equal distance from said plane.
Claim 13
Dependent Claim
37 words
The structure of claim 1, in which the prong contacts are retracted by sliding along their longitudinal axis into said casing and are projected by sliding in a reverse direction along said axis out of said casing.
Claim 14
Dependent Claim
74 words
The structure of claim 1, in which: one wire of said three-wire electrical cable connects one of said blade electrical contacts to the positive side of an electrical appliance; a second wire of said three-wire electrical cable conNects the other of said blade electrical contacts to the neutral side of an electrical appliance; and said electrical signal means interposed in a wire connected between said second wire and one of said electrical prong contacts.
Claim 15
Dependent Claim
14 words
The structure of claim 7, in which the signal means is an electric light.
Claim 16
Dependent Claim
14 words
The structure of claim 7, in which the signal means is an electric buzzer.
Claim 17
Dependent Claim
14 words
The structure of claim 7, in which the electric appliance is a recreational vehicle.
Claim 18
Dependent Claim
23 words
The structure of claim 7, in which the third electrical lead has a resistor interposed between said signal means and said neutral lead.
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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) | 1976-05-14 | 1976-11-13 | 1977-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-14 | 1980-11-13 | 1981-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-14 | 1984-11-13 | 1985-05-15 | $7700.00 | Window Closed / Lapsed |