US Patent 9543685 Tamper resistant receptacle with cam feature

A tamper resistant electrical receptacle for use with 20 A receptacles. A pair of pivoting shutter and trap doors biased in the same direction use a cam and cam follower that moves laterally a distance sufficient to allow passage of the perpendicular portion of a neutral blade of a 20 A electrical plug when simultaneous insertion of electrical plug tines overcome the spring bias of the springs to allow the tines to access the devices hot and neutral electrical contacts. Absent simultaneous insertion, the shutter and trap doors cannot operate in tandem to provide the tines passage to the electrical contacts.