GB505153A - Improvements in or relating to electric switches with automatic trip mechanism - Google Patents

Abstract

505,153. Electrically - released switches. PATENTVERWERTUNGS-GES. HERMES. Aug. 23, 1938, No. 24829. Convention date, Aug. 26, 1937. [Class 38 (v)] An automatic switch for consumers' installations is provided with a single-part fireproof insulating base member having the trip mechanism and thermal trip device mounted on the front thereof. A recess in the front surface of the base constitutes a spark-chamber for the contacts, and a recess in the back surface receives an overload current trip magnet and armature. The arrangement enables a reduction in height to be obtained in switches having the parts arranged one above the other so as to reduce the area of the base. The Figures show the invention applied to a switch having its contacts, tripping and resetting mechanism, bimetal element 14, and manual release arranged generally as in Specification 481,407. The base 1 is recessed at 2 to receive the spirally-wound, strip-conductor coil 3 and its spool 4, also an iron core 7 apertured to receive a trip rod 9 on which is adjustably mounted the pot-shaped, spring-controlled armature 6. The core 7 is retained by an iron plate 12 which is secured by a screw 13 in a recess on a boss on either side of which is mounted a fixed contact, the fixed contacts being adapted to be bridged by the movable contact 36. The top of the spark-chamber recess 15 housing the contacts is closed by an iron plate 16, which serves as a stop for the open position of contact 36 and co-operates with plate 12 to produce a blow-out field, the quenching being further aided by providing 16 with an inner lining plate of fibre or other deionizing-gas evolving material impregnated, if desired, with an ammonia compound. A cap 19 of pressed material is secured to the base 1 by a screw 32 and nut 33 pressed into the cap, the screw 32 passing through a tubular rivet 31 by means of which the coil and spool, the plate 16, and side plates 29 housing the mechanism proper, are secured to the base. The manual trip link 24 has lateral projections (not shown) to prevent its falling out of the cap. Four connecting terminals 49 are inserted in a slot 50 formed in the base 1 by the intersection of discs during pressing, and are provided with fixing screws 53 and screws 51, 52 for the external and internal connections, respectively, Fig. 4. This arrangement may be modified to reduce the base area by closing the recess 2 in the back of the base 54, Fig. 12, by an insulating member into which terminals 56 are screwed, the member being secured by a metal stay 57 secured to the base 54 by screws 58 engaging nuts 59 located in slots 60 in the base. Alternative shapes of latching projection to that B of Fig. 1 are shown, providing varying angles between the toggle-pivots, and accordingly varying bearing pressures between B and the latch 51, the minimum pressure, and hence minimum tripping force, being obtained when these pivots are substantially collinear, Fig. 7b (not shown).