GB540237A - Improvements in or relating to thermally operated release means, applicable to electric switches - Google Patents

Abstract

540,237. Thermostats ; electrically released switches TURNER, L. V. (Talbot, F. A.). July 2, 1940, No. 11163. [Class 38 (v)] [Also in Group XIII] A thermal release, described in connection with a circuit breaker comprises two similar heat sensitive elements each having one end free to deflect, which ends are inter-engaged, one element being displaceable relative to the other to effect a release action of the engaged ends solely under conditions of thermal difference between the elements. In the example, as applied to a switch, the elements comprise helical bi-metallic strips, 5, 17, one, 5, secured at its lower end to the frame 3, the other 17 on a plate 22 sliding on a rod 18, co-axial with a release rod 11 and resting in a socket at its lower end. Rotation of the plate 22 is prevented by a lug 24 riding in a vertical slot in the frame. A spring 21 presses upwards the top plate 16 of the element 17. The rod 11 has a boss 12 at its lower end from which depend two lugs 14 against which the plate 16 is pressed in engaged position. Upon relative rotation of the rod 11, such as on undue heating of the element 5, by an overload heating-coil 41, the lugs 14 slip off the edges of ears 15 on the plate 16, Fig. 7, and the element 17 is pushed upward to disengage contacts 23 on the plate 22 from fixed contacts. To reset on cooling, a bar 33 of insulating material is pressed down against the action of a spring 35, a projection 34 on its lower end bearing on the lug 24 of the contact plate 22 until the ears 15 re-engage below the lugs 14. Just previously the lower end of the bar 33 has pressed on the extension 31 of a spider plate 26, arms 30 on which hold the contacts open until the bar 33 is allowed to rise again.