Patent GB-613052-A (GB)
Title: Improvements in automatic electric control systems for material-winding or reeling apparatus
IPC: B65H23/18
Filed: 1946-01-30
Abstract: 613,052. Automatic systems for control of winding tension. WINTHER, M. P. Jan. 30, 1946, No. 2963. Convention date, May 4, 1944. [Class 38 (iv)] In material winding or reeling apparatus, e.g. for a rolling mill or calendering machine, of the type in which a motor drives the reel through an electric slip coupling, the winding of an eddy current slip coupling is fed from a circuit comprising a grid-controlled rectifier which is controlled in accordance with the conductivity of a further gridcontrolled valve, these valves being connected with a main reference voltage circuit so that normally the slip coupling is energized by the rectifier discharging through it, the control valve having a grid which is controlled by a transformer-fed rectifying valve, and the primary winding of the transformer being fed from an A.C. supply driving the winding motor, whereby increased current delivered to the motor under increased load biasses the control valve towards firing and thus biasses the rectifier to a condition of lower output. This reduces the energization of the clutch coil and introduces slip to correct incipient increase in tension in the material being wound. The material to be processed is drawn from a pay-off reel UW-1, Fig. 1, by the processing machine P which is driven by a three-phase induction motor PM, the tension in the material acting to rotate the reel UW-1. The processed material is wound upon a reel WP-1 connected by a shaft OP-2 to one part F-2 of the eddy-current slip clutch, the part EA-2 of which is driven clockwise by a three-phase induction motor WM. The coil of the slip clutch is energized through slip rings CB-3 fed from a control unit CB-1 which embodies the aforesaid valve system and derives part of its control current from tachometer generators GN-1, GN-2, respectively driven by the processing machine P and wind-up reel WP-1. A similar system comprising an eddycurrent slip clutch CC-W, with an armature driven anti-clockwise by a motor PW provides a braking effect on the pay-off reel UW-1, otherwise the arrangement is similar to that for the winding reel. Control unit. Fig. 2 shows the arrangement of the control unit CB-1 for the winding reel WP-1, that for the pay-off reel UW-1 being similar. The clutch coil CL is normally energized by the conduction of a pair of gasfilled triodes 1, 2 of the thyratron type arranged in a full-wave rectifying circuit with their anodes connected across the secondary winding of a transformer T-1 and their grids connected over limiting resistances R-1 to the anodes of a twin triode 3. Resistances R-2, R-3 connected to the grid leads of the thyratrons are included in a bridge circuit with resistances R-4, R-5 and valve 3, across which a fullwave power supply rectifier 5 is connected, the thyratron grids being at a positive potential when valve 3 is non-conducting, so that the thyratrons conduct alternately. The conductivity of the control valve 3 is determined by the potentials of its grids G-3, G-4 which are connected across the secondary winding of a centre-tapped transformer T-4, the primary of which is energized from a feeder transformer T-2 connected to A.C. supply leads L-1, L-2, phase displaced by 120 degrees relative to the leads L-2, L-3 to transformer T-1 connected to the thyratron anodes. Superimposed on the A.C. voltage applied to the grids G-3, G-4 is a D.C. controlling voltage derived from one or more of four control circuits IV-VII, of which circuits IV and V are voltage accumulative, but act in opposition to circuits VI and VII, which are also voltage accumulative. Circuit IV comprises a bridge arrangement fed by a full-wave rectifier 7 connected to a mainsenergized transformer, and includes a preset potentiometer R-8 and an adjustable potentiometer R-8A which are introduced alternatively by means of a switch SW-3 controlling contacts 28, 29A and 30A. Circuit V comprises a rectifier 8 energized by a transformer T-7 fed from tachometer generator GN-1 driven by the processing machine, and is thus operative only when that machine is running. The voltage derived from circuits IV and V, aided by that derived over a connection to a point 29 in the power circuit II, is applied over a resistance R-10 and variable resistance R-11 (or switch SW-2A) to the grids G-3, G-4 of the control valve 3, the grids being thus given a negative bias, so that that valve is non-conducting and the positive bias is maintained on the grids of the thyratrons 1, 2 with the result that the clutch coil CL is energized. This action is opposed by circuits VI and VII, of which circuit VI includes a full-wave rectifier 9 transformer fed from tachometer generator GN-2 driven with the winding reel WP-1 by the slip clutch which, in turn, is driven by the three-phase motor WM. Circuit VII is dependent on the current taken by the motor WM, and includes a full-wave rectifier 10 fed by a transformer T-9 which receives from a system comprising transformers T-10, T-11 a voltage which is substantially a straight-line function of the torque delivered by the motor WM; this system is described in the Specification, and forms the subject-matter of divisional Specification 613,096. The torque is required to increase in a direct proportion, from a low value when the material starts at the core WP-C, to a higher value at the rim. Operation. In starting a winding operation, switch SW-1 is closed to cut-out circuit V, and the torque control circuit VII is disconnected by switch SW-2. Resistance R-8A of circuit IV is introduced temporarily and the machine drive and processing machine P started at a low threading speed to enable the material to be applied to the winding reel WP-1. After a few revolutions, resistance R-8 is substituted for R-8A in circuit IV to give increased speed to the winding reel, the processing machine is brought up to running speed, and circuits V and VII are connected by manual operation of their relative switches. Any incipient variation in tension on the windup reel produces corresponding variation in the current taken by motor WM, which reacts through circuit VII to vary the conductivity of valve 3 and thus of valves 1 and 2 to adjust the current through the clutch coil CL to regulate the tension on the material. Decrease in reel speed due to increasing diameter of the wound material WU reacts through tachometer generator GN-2 to produce from circuit VI a reduced control action which results in a tightening of the clutch coupling and. increases the torque delivered from the motor according to the increasing " moment arm of the winding roll. As the material wound on the roll increases in diameter, the control voltage from circuit VI decreases and that from VII increases proportionally.