Abstract: A material level sensing device for detecting when the level of unprocessed material has reached a predetermined threshold includes a contact-type probe extending from a housing into a retaining bowl where unprocessed material is collected before processing. Within the housing is disposed a proximity sensor. The housing itself is suspended from an overhanging support. When the material level reaches the predetermined threshold, the material displaces the material level sensor, which displacement is sensed by the proximity sensor. The proximity sensor then sends a signal to an external system indicating that the material has reached the threshold.

Abstract: A first stage of a rock crushing plant is controlled by controlling the feed rate supplied to a primary rock crusher and by indicating to haul vehicles bringing rock to the plant from a quarry when the load being hauled can be dumped in to a hopper supplying the feeder for the primary rock crusher. Non-material contacting level sensors, such as ultrasonic transducers are used to sense the level of rock within the hopper and within the cavity of the rock crusher. Further, the load of the motor driving the primary rock crusher and the motor driving an output conveyor that receives the discharged rock from the primary rock crusher is monitored. The output signals from the level and load sensors are compared with preset values to adjust the feed rate of rock being delivered to the primary crusher in order to optimize the throughput of rock in the first crushing stage of the plant.

Abstract: A control system for a rock crusher in a rock crushing plant operates the crusher at optimum efficiency for increasing the throughput of the crusher. The horsepower of the motor that drives the crusher is sensed, and the level of rock within the crusher bowl is sensed, and these sensed conditions are inputted into a programmable logic controller. The programmable logic controller correspondingly adjusts the feed rate of a feeder that supplies rock to the crusher. The controller also commands a bypass component positioned between the feeder and crusher adjacent the mouth of the crusher for providing an immediately responsive control of the feed rate being delivered to the crusher.