GB605418A - An improved motor protection switch with quick release - Google Patents

Abstract

605,418. Automatic circuit-breakers. LANDIS & GYR, SOC. ANON. Dec. 21, 1945, No. 34789. Convention date, Dec. 23, 1944. [Class 38 (v)] The quick release in each phase of a multipole circuit-breaker, as described generally in Specifications 588,724, 588,738, 588,749 and 588,750, is applied to the moving contacts of a threephase motor protection switch, which is closed and held closed by an electromagnet 2 mounted on an insulating contact carrier 1. The moving contacts 8 are resiliently mounted on blade springs 12, which are latched forward on the carrier by pawls 10 engaging blade-spring latches 14. When the latch in any phase is tripped by the arm 17 of an overload-release magnet (not shown) the contact 8 is carried back from the fixed contact 6 by the blade spring 12, and the pin 10a strikes the common release-bar 22, thereby rocking the shaft 4 and bell-crank lever 35 so that a pin 34 thereon opens the contact 33 of an auxiliary switch in the coil circuit of the magnet 3. The trip is reset by depressing the knob 28 so that the slide 26 first carries back the blade spring 29, releasing the arm 38 so that the hook 39 is carried up by the blade 40 to engage a pin 42 on the carrier 1 and latch it in the open position. At the same time the contact 32 of the auxiliary switch is opened and the end of the recess 25 in the slide 26 engages the arm 24 to rock the shaft 4 so that the release-bar 22 bearing on the pin 10a forces the pawl 10 on to the catch 14. On releasing the button, the spring 29 carries the slide back to close the auxiliary switch, and at the same time bears on the arm 38 to unlatch the contact carrier. A bimetal strip 45 may be arranged to trip a catch 47 so that the spring-biassed lever 48 engages the extended contact arm 49 to open the auxiliary switch on overheating of the motor.