Safety electromagnetic relay

Abstract

A safety electromagnetic relay includes two pairs of contact sets, each pair including a load-driving contact set and a control contact set, and each contact set including a fixed contact and a movable contact spring. The two load-driving contact sets are normally-open contacts and may be connected in series and included in an external load circuit which requires safe interruption. The contact springs of each of the first and second pairs are ganged by a coupling member which is movable independently of a relay armature. The ganged pairs of contact springs are actuated by the armature in such a manner that when one of the load-driving contact sets should become welded in the closed condition, the other load-driving contact set will still open when the armature moves to the inoperative position, but the control contact set associated with the welded load-driving contact set is prevented from returning to its condition corresponding to the inoperative position of the armature. The status of the control contact set may be utilized to signalize failure of the relay. Specifically, the control contact set may be a normally-closed contact which, when the associates load-driving contact set has welded, is retained in its open condition, thereby preventing recharging of a capacitor that may be required for re-energization of the relay coil.