Plug and grounding means

July 17, 1962

3,045,201

W. D. HALL

PLUG AND GROUNDING MEANS

Filed Oct. 8, 1959

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William D. Hall

United States Patent Office _p ., ,³ ®!⁵,²®¹

Patented July 17, 1962

3,045,201

PLUG AND GROUNDING MEANS William D. Hall, 5112 Westpath Court, Montgomery County, Md.

Filed Oct. 8, 1959, Ser. No. 845,119 5

Claims. (Cl. 339—14)

This invention relates to plugs that have grounding means and has for its main object the provision of a third wire grounding means in devices using certain types j o of plugs.

Air conditioners have frequently employed thermostats. For air conditioners which did not have thermostats as original equipment, for a number of years there have been available on the market thermostats which could 15 be attached to the air conditioner. One form of such thermostats included a series plug and socket which was inserted in the wall and the air conditioner was plugged into the socket of the series plug. However, the arrangements were of such character that it was impossible 20 to add or provide for the third wire grounding prong on the plug of the air conditioner. The present invention overcomes this difficulty and provides for grounding of the third wire prong.

The same thermostat that is used on air conditioners 25 is often used for other articles such as electric fans where the third prong is not needed, and one object of the present invention is to provide an arrangement whereby the plug on the end of the thermostat has universal application. It can be used to receive an air conditioner 30 plug with three prongs irrespective whether the wall socket has a third prong or not. If it has, provision is employed to use it. Moreover, the thermostat and series plug of this invention may receive a plug with only two prongs even though the wall socket may have provision 35 to receive three. If the plug of the air conditioner should have three prongs but the wall socket only has provision to receive two, here again the device is applicable.

Other objects and advantages of the invention will ap- 40 pear as this description proceeds.

In carrying out the aforesaid objects, said series plug is of rectangular shape but not thick enough to interfere with the normal position of the third prong on the plug of the air conditioner. In addition to the series ⁴⁵plug there is a pin with a socket on the rear end which is separate from the plug and which may be inserted in the wall socket and will receive the third prong of the plug of the air conditioner.

In the drawings: ³⁰

FIGURE 1 is a side view of the invention.

FIGURE 2 is a top detailed view of the invention.

FIGURE 3 is a further detailed view of the invention.

FIGURE 4 is a view partly in cross-section of the supplemental plug used in connection with this invention. ⁵⁵

In the drawings a three-wire electric cord 10 leading to an air conditioner is fed by a three-prong plug 11. As is customary on air conditioners such a plug has two flat blades 12 and 13 for transmitting the electric current and a third prong 14 acting as a grounding pin. The ⁶⁰wall socket 15 has the usual sockets 16 and 17 for the blades and a third socket 18 for the grounding pin. A series plug 19 has blades 20 and 21 respectively adapted to be inserted in sockets 16 and 17. This plug also has sockets 22 and 23 to receive the blades 12 and 13 of ⁶⁵the plug 11. Blade 21 is electrically connected directly to socket 22. Blade 20, however, connects to wire 24;

and socket 23 connects to wire 25 and these two wires pass to the thermostat 26 which may be mounted on the air conditioner. As a result, when the series plug 19 is inserted in the wall socket 15 and the plug 11 is inserted in the rear end of the series plug 19, the thermostat 26 is directly in series with the air conditioner. The apparatus shown in FIGURE 4 includes a socket element 27 for receiving the pin 14 and a prong 28 for insertion in the third socket 18 of the wall socket 15. By making the series plug 19 relatively thin it does not interfere with the third prong 14 on the plug 11, whereby the socket member 27 may be placed on that prong and also inserted in socket 18 for grounding purposes. In event the wall plug 15 does not have provision for a third socket 18, the apparatus can still be used without mutilating the plug 11 of the air conditioner, by simply omitting the member 27, 28 which is in a separate piece from the series plug 19. In event the thermostat is used to control a fan or other appliance which has a plug 11 with only two instead of three prongs, the member 27, 28 may be discarded and the plug 19 used irrespective of whether the wall outlet has two or three socket elements.