Abstract: There is provided a control apparatus for stopping a large grinding mill driven by two synchronous motors coupled to the mill through respective air clutches. The control includes a clutch actuator control which applies a predetermined amount of pressure of predetermined duration to the clutches sufficient to at least partially close the clutches but insufficient to fully close and lock-up the clutches. The control apparatus further includes an enable control which periodically enables the clutch actuator control to apply the predetermined amount of pressure. The enable control enables the clutch actuator control for a predetermined time duration sufficient to stop motion of the mill and synchronous motors. The present invention provides a system for bringing a mill to a stop relatively quickly without adding significant costs to the mill controls.

Abstract: Ramp signals having rounded starts and finishes are provided through the method of producing an electrical voltage signal comprised of approximately circular portions and approximately straight line portions wherein the straight line portions are approximately tangential to the circular portions. In achieving the desired ramp signals, suitable circuitry is provided in which, in one embodiment, a high gain amplifier is selectively fed a step input voltage to initiate the ramp signal. The amplifier has a voltage limited output and is series connected to a first integrator. The first integrator has a voltage limited output and is series connected to a second integrator which produces the required ramp signal. The circuit also contains two feedback loops. The output from the first integrator is fed to the input of the high gain amplifier via an inverting amplifier. The output of the second integrator is fed to the high gain amplifier via a resistor.