Patent GB-526088-A (GB)
Title: Improvements in and relating to electric control systems for classifying sheet material according to thickness
IPC: G05D5/03
Filed: 1939-03-08
Abstract: 526,088. Gauging apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. March 8, 1939, No. 7543. Convention date, March 8, 1938. [Class 106 (ii)] [Also in Group XXXVIII] Relates to electric control systems for classifying sheet material according to thickness of the type described in Specification 478,448, in which a conveyer for delivering sheet material to receiving units is provided with diverting units operated according to the movement of gauging devices, timing devices securing a delay action between gauging and diverting ; and consists in an electromagnet having an operating coil controlled by the gauging device for actuating the diverting device and an opposing coil to which a voltage varying with the speed of the conveyer is supplied for varying the time of the delay. Sheet material from a reel 11 passes through pinch rolls 12 and gauging rolls 25 to a flying shear 13 which severs it into lengths. A sheet conveyer having sections 17 ... 21 delivers the sheets to a lot counter and stagger piler (not shown). These machines are driven at constant speed by individual direct current motors supplied from an adjustable voltage generator so as to work in step. Conveyer sections 18, 20 are pivoted about the forward edge to act as diverters and are controlled by solenoids 22, 23. These are under the control of a gauge of the variable gap transformer type worked according to the separation of the gauge rolls 25. Relative movement of the rolls is transmitted to a movable member 26 in known manner and causes a centre reading needle 29 of a milliammeter to contact one or other of two contacts 30, 31 which may be set to " under " or " over size positions depending on the tolerance allowed. Devices 32, 33 interpose a time delay between the closing of contacts 29, 30 or 29, 31 and the operation of diverters 18 or 20. The time delay relays 32, 33, 34, 35 have U-shaped case members 32a ... 35a upon which are mounted coils 32b ... 35b. The relays also have movable contact members 32c ... 35c biased by springs to the positions shown. As the speed of the drive may be varied, the time setting of the relays must automatically accommodate itself to these conditions. To this end, coils 32d ... 35d are supplied from a voltage generator 36 driven from the rolls 12. These coils are arranged on the case of the time relay so that their magnetomotive force opposes that of the coils 32b ... 35b. The field winding 36a is excited from the supply 37. Adjustable resistors 39, 40 are included between the armature of the generator 36 and the bucking coils 33d, 32d, and similar resistors 41, 42 are provided for the other relay. An adjustable calibrating resistor 36b is provided in the field circuit 36a. Suitable valves 43, 44, as shown, of the threeelectrode type, are provided to amplify the current from the microammeter 28 and control relays 46, 46, 47, 48 for sequencing the opening and closing of the time delay relays. The valves are supplied from an A.C. source 49 to which they are connected through a power transformer 50 having a primary winding and three secondary windings 50a, 50b, 50c. The cathodes are heated from winding 50b, cathodeanode circuits supplied from winding 50a, and grid circuits from winding 50c. Suitable protective means 51 illustrated as a contactor having normally open contacts in the cathodeanode circuits and a thermostatic member 51b in circuit with the operating coil of the contactor maintain circuits open until the cathodes are heated to the correct temperature.