Improvements in or relating to control systems for electric apparatus more particularly gate-end boxes for coal mining machinery

摘要

537,240. Protective cut-out arrangements, electromagnetic switches. SCARF, C: T., HESKETH, H., HEATON, P. R., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Dec. 12, 1939, No. 32066. [Class 38 (v)] In a control system of the type in which a circuit-interrupter remotely disposed from the apparatus controlled is operated through a pilot circuit from a control switch which may be located at or near the apparatus, an example of which is the arrangement described in Specification 378,180 and applicable to remote control of mining machinery, abuse of the circuitinterruptor by repeated rapid operation of the control switch when the apparatus is heavily loaded, is prevented by a time-delay device imposing a few-seconds interval before the opened interrupter can again be closed. The invention is shown in its application to an existing arrangement in which the interrupter-contacts are mounted on a rock shaft connected to the closing armatures of the main relay, a knock-off device for manually opening the contacts. being pivoted to a lever on the shaft. Such a device is shown at 101 in the form of a vertically-slidable rod the upper end of which extends through the gate-end box wall. When the shaft (not shown) rotates to open the interrupter, the rod 101 falls and a latch 103 urged anticlockwise by spring 104, engages the end 106 of a lever 107 pivoted to a bracket 109 at 108, so raising contact 110 clear of a pair of contacts 111, which may be in the circuit of the closing coil or of one of its controlling relays such as 19 in the above-mentioned Specification. The return of the lever 107 and contact 110 is retarded by a dashpot or ratchet- and-clockwork mechanism in a case 114 pivoted in bracket 115. the undersurface of the arm-end 106 being bevelled to allow the latch 103 to move past in the closing stroke.