Switch assembly having movable contact face configuration for penetrating frost or ice layer on adjacent contact surface

Claim 1

An automatic door operator having a control circuit connected to an electrically controlled motor means for controlling door movement in a freezing environment wherein frost forms on the surfaces within the environment, comprising a control switch adapted to be connected in said control circuit and having a pair of opposed electrical contacts, said contacts having opposed contact faces and said contacts solely moving on a line essentially perpendicular to said contact faces for opening and closing an electrical conductive path therebetween in response to the movement directly toward and away from each other on the line through said contacts, a first of said contacts having the contact face formed with a pimple and the other of said contacts having the contact face with a plurality of serrations defining a series of sharp contact peaks, said pimple defining a penetrating means to disrupt frost on said serrations of the other of said contacts and permit said pimple to move into conductive engagement with said second contact.