GB755733A - Improvements relating to electrical remote-control switch apparatus - Google Patents

Abstract

755,733. Controllers; retractive switches. DAVIS & SON, DERBY, Ltd., J., and DAVIS, W. B. Aug. 18. 1954 [Aug. 19, 1953], No. 22812/53. Classes 38(3) and 38(5) A controller comprises an operating lever 14 pinned to a shaft to which a drum 20 is fixed, another drum 21 being rotatable upon the shaft. The drum 20 carries a cam for operating a leaf spring contact lever 23 in a main starting switch 24 whilst the drum 21 has adjustable cams for operating auxiliary running switches 33, 34, by means of spring contact levers 33a, 34a. In the "off" position of the controller, a spring-loaded push-rod 36 carried by the drum 21 is aligned with a plunger 27 in the drum 20 so that the drums are locked together until the movement imparted by a cam profile 29 disengages them. Thus, movement of the handle 14 to operate the switch 24 causes the two drums to move together, the drum 21 being released after the starting switch has closed. A spring 39 then drives the drum 21 in the reverse direction under the control of time delay mechanism 41, the push-rod 36 being held in its retracted position by a leaf spring member 46 until the drum has nearly completed its return movement whereupon a plate 47 actuates the member 46 to free the push-rod. Not until this has been achieved can the drum 21 be re-coupled with the operating shaft. When the drum has fully returned the running connections are completed, but overriding control is effected by the switch 24 which is actuated directly by the handle when the handle is returned to the "off" position. The shaft of the controller operates under a snap action derived from telescopically extensible plungers 15, 15a, extended by spring 17, the plunger 15a being fixed to the drum 20. The controller may be used in conjunction with motors driving conveyers which work in a dangerous atmosphere, the running contacts being placed in a pilot circuit designed to prevent sparking. These arrangements generally have a number of safeguards which normally may be rendered ineffective by holding the controller handle continuously in the "starting" position. The isolation of the manual control member from the associated switch mechanism in the pilot circuit after the starting operation has been completed prevents this faulty operation of the controller. Specification 600,524 [Group XXX]. is referred to.