GB420127A - Improvements in and relating to machines for operating upon webs or strips of material such as paper - Google Patents

Abstract

420,127. Feeding webs; electric control systems. BRITISH THOMSONHOUSTON CO., Ltd., Crown House, Aldwych, London. March 26, 1934, No. 9419. Convention date, March 30, 1933. [Class 100 (i)] A control system for a machine having an element operating on a strip of material and means for feeding the strip to the element comprises a variable-speed transmission gear between the feeding means and the element for varying their relative speeds, means controlled by the relative positions of the strip and the element for effecting a movement of the member to produce a relatively large temporary correction in the relative speeds of the strip and element, and means for subsequently reducing the amount of movement of the member to provide a small relatively permanent change in the relative speeds of the element and strip. The system preferably includes a light-sensitive control acting through the rotating contact device 49, valves 44, 45, and contactors 38, 40, which are similar to those of Fig. 1 in Specification 372,574. The contactors 38, 40 when in their upper closed positions serve respectively to complete the circuits of the field windings 36<a>, 36b of the reversible motor 36, which is therefore operated in the appropriate direction according to whether the cutter is operating early or late. The shaft of the cutter roll is driven from the feed roller 13 by variable-speed mechanism comprising cone pulleys 22, 23 and a belt 24 adjustable by a connection 25 and rod 27a hinged to a lever 26, which is provided with a control collar 26a pivotally connected to a nut 27 actuated in one direction or the other along a screw 28 when the latter is rotated by the motor 36. The lever 26 is fulcrumed in a member 30 attached to a plunger 32 moving in a dashpot 33, and is provided with springs 34, 35 to centre the lever 26 with respect to the nut 27. In operation, lack of register results in starting the motor 36, which rotates the screw 28 in the appropriate direction and displaces the nut 27 comparatively suddenly, with the result that the lever 26 pivots about the point 30 and produces a large movement o:F the belt shifter 25 and a correspondingly large temporary correction for the positional relationship of the knife and the web. The motor circuit is subsequently broken by a time-delayed relay 52. The effect of the adjustment is modified by the springs 34, 35 which are strained by the movement of the lever 26 and return to their normal condition under the control of the dashpot 33, the lever meanwhile pivoting about the point 27 and reducing the speed change which was suddenly introduced. The arrangement may be modified by omitting the dashpot and providing a further contact on each of the contactors 38, 40, which serve respectively to close the circuit of a solenoid, operating to swing the lever 26 in the appropriate direction about its pivot 27 to effect a large correction in the relation between the cutter and the web. At the same time, the motor 36 adjusts the position of the nut 27 to bring about a permanent speed change. The time-delayed relay then operates to stop the motor and also de-energizes the solenoid, whereon centring springs serve to restore the lever 26 to a vertical position.