Keying system for low profile connector

Claim 1

In an electrical connector having a plug and receptacle matable along a mating axis, each plug and receptacle including a housing having electrical contacts therein wherein each contact of said plug mates with a corresponding contact of said receptacle, and a first keying arrangement for polarizing to assure proper orientation of said plug with said receptacle during mating thereof, a second keying arrangement for inhibiting said mating except for mating a plug to a designated receptacle, comprising: (a) a polygonal opening formed in said plug housing and a corresponding polygonal opening formed in said receptacle housing each defining a key-receiving axis therealong parallel to the mating axis so that when said housings are in mated engagement said polygonal opening in said plug housing is in axial alignment with said corresponding polygonal opening in said receptacle housing; (b) two keys having body sections having polygonal shaped outer surfaces that are sized to slip fit into said polygonal openings in each of a plurality of unique angular positions, each said key being in a respective one of said polygonal openings of said plug and receptacle housings and having an offset half polygonal portion extending forwardly of the respective said body section to extend outwardly from said one of said polygonal openings into said corresponding aligned polygonal opening when said plug and receptacle housings are mated; and (c) retainer means for holding each said key in its respective polygonal opening, at least one said retainer means defines on both said key and said respective polygonal opening and including a first surface and an opposite second surface spaced axially from said first surface along each side wall of a respective said polygonal opening, and further including at least one flange projecting from a respective said key and arranged to overlie said first surface and a locking tab projecting from each key and arranged to underlie said second surface thereby retaining said key within its respective said polygonal opening upon insertion of said key into said polygonal opening, wherein each said key is arranged in one of said plurality of angular positions so that said plug and receptacle housings will mate only when said off-set portions of the axially aligned keys are in mating alignment, and at least one of said keys is securable in its polygonal opening upon insertion thereinto and without other securing means.