Patent GB-694765-A (GB)
Title: Improvements in or relating to apparatus for controlling a refiner
IPC: D21D1/22
Filed: 1951-10-04
Abstract: 694,765. Control of two motors. BLACK-CLAWSON CO. Oct. 4, 1951 [Oct. 14, 1950], No. 23127/51. Class 38 (iii) [Also in Group II] An electric motor 11 for rotating the tapered plug 12 of a conical refiner 10 for paper pulp (see Group II) is connected by means of electric circuits to an electric motor 30 for moving the plug axially within its shell 13 so that when the load on the motor 11 varies from a constant predetermined value, the motor 30 is energised to cause the plug to move axially until the load on the motor 11 is restored to its predetermined value. These circuits include a manuallyoperable selector switch 75 which, as shown, is shifted to its contact 76 for automatic control of the refiner which is effected by means of a watt sensitive relay 80 including a movable armature 81 carrying a switch arm 82 movable between upper and lower contacts 83, 84 and an intermediate neutral position. The relay also includes a fixed voltage coil 86, a movable current coil 90, and a fixed compensating current coil 91. The current to the coils is controlled by a theostat 95 in accordance with the desired input power to the motor 11. With the switch 75 set for automatic operation, as long as a constant load condition on the motor 11 continues, a signal light 110 is lighted through the upper pairs of contacts of two normally de-energised relays 111, 112. In the event of a change, e.g. variation in the consistency of the stock passing through the refiner, there will be a corresponding change in the load conditions on the motor 11. This affects the relay 80 resulting in upward or downward movement of the armature 81 and hence of the switch arm 82 with respect to the contacts 83, 84. When the switch arm engages the contact 83, corresponding to a decrease in the load on the motor 11, circuits will be completed through a reversing switch 70 to energise the motor 30 to cause the plug 12 to move inwardly of the shell 13 to restore the desired load condition on the motor 11. The relay 111 is also energised to break the circuit to the signal light 110 and at the same time a circuit is completed to a signal light 115 which remains on as long as the motor 30 is operated in the direction to move the plug inwardly of the shell. When there is an increase in the load on the motor 11, the switch arm engages the contact 84 causing the plug to back off from the shell. The motor 30 will then operate until the changed setting of the plug restores the desired load condition on the motor 11 or until the plug has backed off so far that a limit switch is opened. During this operation, a third signal light 116 will be lighted and the lights 110, 115 will be off. When the refiner is used for a batch refining operation, a timing circuit including a timer 125 is provided through the contact 78 of the switch 75 to effect backing off movement of the plug at the end of the operation to prevent overloading of the motor 11 at the start of the next operation. Switches 100, 101 are provided to prevent damage to the refiner in the event of stoppage of the motor 11 or of failure of the stock pressure as supplied to the refiner. Means, Fig. 5 (not shown), are provided for automatically driving the plug-adjusting motor to compensate for variations in the web conditions as registered by a vacuum gauge for the suction roll of the paper-making machine. A current sensitive relay, Fig. 6 (not shown), may be provided to replace the watt sensitive relay.