GB212601A - Improvements relating to electric motor starters - Google Patents

Abstract

212,601. Hirst, J. A., and Brook, Hirst, & Co., Ltd. Nov. 8, 1922. Controllers with overload relense.-In a motor starter operated by an intermittently advancing shaft and ratchet or like handle gear, and provided with overload release control, the sensitiveness of the overload device, during the starting period, is reduced by means mechanically connected to the shaft, which is arranged so that the condition of reduced sensitiveness cannot persist if the handle is prematurely released. A slight further movement beyond the full running position of the shaft is required in order that the apparatus can be left in the condition of normal sensitiveness. The reduction of sensitiveness may be brought about, as shown in Fig. 1A, by applying the force of a spring s<3> to assist in holding down the core o<20> of an overload magnet o, the spring pressure being taken off when a cam W attached to the starting handle gear reaches its final position. In an alternative construction, Fig. 1c, the core of the. overload magnet is lowered while the cam W is passing through the starting positions and is raised again when the cam reaches the final position. In order to ,prevent the mechanism from being accidentally left in the condition of reduced sensitiveness, the release of the starting handle before it has reached its final position effects the tripping open of a main circuit breaker which cannot be reset except by returning the handle to its initial position, the mechanism being similar to that described in Specification 207,232. Specification 166,084 is referred to in one of the Provisional Specifications.