GB639817A - Improvements in or relating to switch control devices for dynamically braked, electrically driven machines - Google Patents

Abstract

639,817. Control of motors; mechanical switches. MASON, J. A., and MOLINS MACHINE CO., Ltd. June 9, 1948, No. 15595. [Classes 38 (iii) and 38 (v)] [Also in Group XXIV] A switch control device, for use with dynamically-braked, electrically-driven machines comprising variable speed gearing for driving the machine, has means for adjusting the switch relatively to the cam or the like which operates it so as to vary the instant of disengagement of the contacts and initiation of dynamic braking in accordance with variations in the adjustment of the variable speed gearing. In a packet-wrapping machine the packets are moved by pusher-pieces 1 on a conveyer 2 which is driven by an electric motor 3. The motor is controlled by means of a timing- switch 4 which is adapted to initiate dynamic braking and to stop the machine in a predetermined position, as described in Specification 628,299. The motor drives pulleys 15 and 16, the latter being geared to the main shaft 21 of the conveyer. The member 15 comprises two separate parts (see Group XXIV) which are relatively movable to alter the effective diameter of the pulley, this adjustment being effected by means of a worm 29 coupled by flexible cable 30 to a movable knob or handle 31. The worm-shaft has a threaded portion co-operating with a nut which is coupled through bell-crank 34 and link 37 to a lever 12 which is fixed to a spindle of the switch 4. The switch comprises contacts 7, 8, which are mounted on switch body 9 and which co-operate with a plunger 6 coacting with a cam 5 driven from shaft 21. When the member 31 is moved to alter the speed of the machine, the switch body is correspondingly adjusted relatively to the cam 5 and the moment at which contacts 7, 8 are opened is determined by the speed at which the machine is running. The lever 12 may be in the form of a quadrant to allow for adjustment to compensate for different operating conditions. A belt 25 is held taut during adjustment of the variable speed drive by means of a spring 39 and quadrant 20. The pulley 16 may be slidable in splines in order to align the belt correctly.