Patent GB-1485670-A (GB)
Title: Method and apparatus for regulating mining machines
IPC: E21C35/24
Filed: 1975-05-16
Abstract: 1485670 Automatic control EICKHOFF MASCHINENFABRIK U EISENGIESSEREI mbH Gebr 16 May 1975 [4 June 1974] 20934/75 Heading G3N  In a mining machine having an electric motor or respective motors for driving a drum cutter tool and a winch wherein the winch speed is automatically controlled in dependence upon the measured load current of the cutter driving motor, the cutting power is optimized to obtain the maximum amount of mineral material for the power input. This is effected automatically by regulating the cutting speed of the cutter in a sense so as to reduce toward zero a control variable corresponding to a differential quotient - d(N wa )/d(V Wi2 ) where N wa  is the cutting drum power and V Wi  is the winch speed i.e. feedrate. In a control arrangement Fig. 1 for a machine having a cutter drum tool motor 1 and a winch driving motor 2, the speeds of the motors are regulated by phase control of thyristors in the respective A.C./D.C. converter bridges 34 and 19, 19' . The converter 19 is driven by trigger pulses from a pulse generator 18 when the winch motor is to operate in one direction and bridge converter 19' is driven by pulses from a generator 18' to move the winch motor in the other direction. Parallel connected shunts 4, 5, continuously supply D.C. voltages proportional to load current in respective motors 1, 2 to an OR gate 8 which passes only the higher of the two voltages to a limit unit 15. If this voltage exceeds a limit value dependent upon max. permissable load current in motors 1, 2, it will influence the output from a controller 14 to adjust the trigger angle of the thyristors thereby to reduce the speed of the winch motor 2 until the overload on the cutting tool or the winch has disappeared. The winch motor speed reference is a pre-set constant voltage selected by a switch 9, the winch direction being set by the sign of this voltage. A difference unit or comparator 10 compares the set voltage with an actual speed signal from a tachogenerator 11 and the resulting difference value is applied to an amplifier/controller 14 and via the limit unit 15 and switching unit 17 to the operating trigger pulse generator. The cutter tool motor 1 speed is controlled by a controller 27 operating on a trigger pulse generator 33 to vary the firing angle of thyristors 34. A differential quotient computer 29 receives the output signal of the winch motor tachogenerator 11 and a D.C. voltage signal proportional to the cutter motor load current from a shunt 4. The computer output is fed to a storage register 30 and briefly stored. A comparator 31 compares two successive values of the stored signal and the resultant difference signal is fed via an amplifier 32 to the controller 27. Initially the controller 27 acts to raise the cutter speed irrespective of the differential quotient, speed control variable. This results in instant change of the quotient output to storage register 30. If the difference detected by comparator 31 remains positive or becomes positive, the motor 1 speed is further increased until the difference becomes zero; and vice versa if the difference. detected is negative. In an embodiment Fig. 2 (not shown), a single A.C. motor drives fluid pumps which power fluid motors on the winch and cutter head. An electrical signal proportional to measured winch power input is derived and subtracted from the measured power input to the motor to give cutting power. A differential quotient computer produces a speed control variable as before.