Universal electrical plug adapter
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electrical adapter and more particularly to a three-prong grounding adapter for adapting three-prong household plugs to OSHA three-prong twistlock connectors. 
     2. Brief Summary of the Invention 
     Several different systems of three-prong electrical connectors are in current use for low-power single-phase appliances. It sometimes is necessary to make electrical connections between electrical outlets, power cables and electrical appliances having different types of prongs which are incompatible with each other. It is an object of this invention to provide an adapter for interconnecting three-prong grounding household connectors and OSHA (Occupational Safety and Health Administration) three-prong twistlock connectors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a universal plug adapter shown in accordance with the present invention; 
     FIG. 2 is a cross-sectional view of the embodiment of the invention shown in the retracted position; 
     FIG. 3 is a cross-sectional view with the male household prongs extended, and 
     FIG. 4 is a cross-sectional view with the male OSHA prongs in the extended position. 
    
    
     DETAILED DESCRIPTION 
     As illustrated by the exploded view of the invention in FIG. 1, electrical male household prongs 1aand 1b are electrically connected to male OSHA prongs 2a and 2b, respectively, through an insulating block 3. Ground prong 4 on the household plug is electrically connected to ground prong 5 on the OSHA plug through the insulating block 3. The assembly comprising the prongs and the insulating block is housed in a hollow cylindrical housing 6 and is free to slide back and forth therein. On the side of the household plug, there is provided an end plate 7 with openings matching the pattern of a three-prong household plug, and the end plate 7 is secured to the end of the housing 6. On the side of the OSHA plug, there is similarly provided an end plate 8 having openings matching the pattern of a three-prong OSHA plug, this end plate being secured to the opposite end of the housing 6. To prevent rotation of the prong assembly within the housing, the household prongs are guided by alignment clips 9 which are fastened to the end plate 7, which are made of a nonconducting material, and within which the household prongs are free to slide back and forth. 
     Two coil springs 10 and 11 are disposed inside the housing 6, spring 10 between the end plate 8 and the insulating block 3, and spring 11 between the end plate 7 and the insulating block 3. 
     Referring to FIG. 3, when an OSHA male plug is connected to the adapter, being inserted through the openings in end plate 8, the prong assembly is pushed toward the end plate 7 and the household prongs 1a, 1b and 4 protrude from the openings in end plate 7. Referring to FIG. 4, when a household male plug is inserted through the openings in end plate 7, the prong assembly is pushed toward the end plate 8 and the OSHA prongs 2a, 2b and 5 protrude from the openings in end plate 8. A male OSHA plug is thus converted to a male household plug, and vice versa. 
     While various changes may be made in the detail construction, it is understood that such changes will be within the spirit and scope of the present invention, as is defined by the appended claims.