Patent GB-420763-A (GB)
Title: Improvements in and relating to control systems for machines operating upon lengths of material such as paper
IPC: B26D5/34
Filed: 1933-07-20
Abstract: 420,763. Feeding webs. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Shoults, D. R. ; 318, Charles Street, Scotia, New York, U.S.A.) July 20, 1933, No. 20534. Convention date, July 21, 1932. [Class 100 (i)] In a control system for a machine having an element such as a cutter operating upon a strip of material fed continuously to the cutter, the drive to the cutter or the feeding means is transmitted through epicyclic gearing of the differential type having a rotatable reaction member, and correcting means are provided operative when the strip becomes out of register with the cutter for changing the relation between the speeds of the cutter and the feeding means, and for rotating the reaction member of the epicyclic gearing to apply a correction to the relative positions of the cutter and the feeding means. The invention is applied to the system described in Specification 372,574, and in one form the apparatus shown in Fig. 1 of that Specification is modified in the following respects. (a) The differential is prov:.ded between the shaft of the cone 26 and the shaft of the cutter roller 15, and is actuated to introduce an appropriate change in the relative positions of the web 13 and the cutter when these are out of register by means of an electric motor, of which the field coils are connected in parallel with the field of the motor 29, the direction of the change introduced being: dependent upon which of the contacts 34, 35 is closed. (b) The rotating contact maker 78 is replaced by a switching device having a magnetic circuit which provides a time element in its drop-out operation, and which is more particularly described below. In a second modification, the differential 66, Fig. 2, which drives the cutter shaft and is actuated by the motor 15 driving the feed rollers 13, is controlled by a motor 71 and generators 72, 73. The generator 72 is driven from a motor 74, while the generator 73 is connected to the driving motor 15 through suitable gearing and normally when the web is in register no current flows in the field coil 72<a> of the generator 72. Closing the main switch 87 energizes the coil 71<a> of the motor 71 and also energizes the operating coil of the time element relay 55, which closes its contact to connect to the positive side of the supply the anodes of the two valves 38, 40 in series with the operating coils of the contactors 78, 79, which correspond to the contacts 34, 35 of Fig. 1 of Specification 372,574, previously referred to. When the web and cutter become out of register, one or other of the valves 38, 40 is operated and causes a contactor 78 or 79 to close. If the contactor 79 is so operated (a) the armature winding and the portion 82<a> of the split field winding of a motor 82 are energized; and (b) the field coil 72<a> of the generator 72 is energized and supplies current to the motor 71 which rotates the third element of the differential and thereby introduces an additional movement in the rotation of the cutter so as to effect a space correction in the relative positions of the web and the knife. The motor 82 meanwhile rotates a screw 81 which moves a contactor arm 80<c> to the left whereby a suitable voltage is connected to the field winding 73<a> of the generator 73 ; for this purpose, the winding 73<a> is connected as shown with the reversible variable rheostat 80, having two sections 80<a>, 80<b>, connected in parallel and the contact arm 80<c>, such that when the arm occupies the central position indicated by the dotted line 84 no voltage is applied to the winding 73<a>. As the arm 80<c> moves to the left, to the position shown in the Figure, the resistance in circuit with the winding 73<a> is reduced, whereby the current which the generator 73 is supplying to the motor 71 is increased and effects a corresponding change in the relative speed of the strip and the rotary cutting-knife. At the end of a predetermined interval, the time element relay 55 interrupts the anode circuit of the valve 40, the contactor 79 is de-energized, the motor 82 stops, and generator 72 ceases to supply current to the motor 71. No further correction in the space relationship of the web and the knife is therefore made, but owing to the position which the arm 80<c> now occupies, the generator 73 continues to drive the motor 71, and the cutter is rotated at the increased speed necessary to compensate for the error which first caused the lack of register. A similar action takes place in connection with the contactor 78, but operating to effect changes in the opposite direction. The differential and/or the change-speed mechanism of the first modification or the differential of the second modification may be applied to the feed rolls instead of to the cutter.