Primary crushing stage control system

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.

FIELD OF THE INVENTION 
The invention relates to a system for controlling the first stage of a rock 
crushing plant. 
BACKGROUND OF THE INVENTION 
Rock that is removed from a quarry is typically hauled to a rock crushing 
plant. Within the rock crushing plant, there are usually three stages of 
crushing: primary crushing, secondary crushing, and tertiary crushing. 
Some of the rock removed from the quarry is of a sufficient size to enter 
the secondary and tertiary crushing stages directly. The remainder of the 
rock removed from the quarry must pass trough a primary crushing stage so 
that it is reduced in size, typically to 8 inches in diameter or less. 
All of the rock removed from a quarry or other location is dumped by a 
hauling vehicle into a hopper or bin. This includes the rock that is 
already of a sufficient minimum size to be introduced into the secondary 
and tertiary crushing stages directly. The rock is emptied out of the 
hopper by a feeder across screening bars that allow the sufficiently small 
sized rock to pass through to a conveyer that transfers the smaller 
diameter rock to the other crushing stages in the plant. The remainder of 
the rock is fed to a primary crusher, such as a Jaw Crusher or a Gyratory 
Crusher. 
The throughput of the primary crusher therefore governs the amount of rock 
that can be introduced into the secondary and later stages of crushing. 
Accordingly, when the primary crushing stage is unable to deliver enough 
rock to the secondary and later stages of crushing within the rock 
crushing plant, the overall efficiency of the plant is greatly reduced. 
Conversely, when the feeder of the primary crusher is operated at a flow 
rate that produces a large volume of crushed rock being discharged to an 
output conveyer, the output conveyer or other output side equipment 
becomes overloaded so the feeder rate needs to be decreased. If the output 
conveyer reaches an overloaded condition, then the motor driving the 
conveyer trips off in response to an overload prevention circuit. This 
creates unwanted down time and the likelihood of material spillage. 
Ordinarily, an operator is required to regulate the feed rate of rock being 
supplied to the primary crusher and to supervise the dumping of rock into 
the hopper that is delivered by the haul vehicles returning from the 
quarry. The operator relies upon his experience to vary the feed rate in 
order to maintain a constant supply of rock to the primary crusher and to 
keep the hopper full without overfilling it. The output of the primary 
crusher, therefore, is controlled by the operator. The operator has no way 
to determine whether the first stage crushing operation is at optimum 
efficiency other than to depend on his experience in operating the 
equipment. Further, the operator usually runs the primary crusher feeder 
at a rate that prevents an unwanted overload from ever occurring, and thus 
also prevents the throughput of the primary crusher from ever reaching an 
optimum throughput. 
It has been known to automate secondary and tertiary crushing stages in a 
rock crushing plant by controlling the feed rate of a feeder delivering 
rock to the secondary or tertiary crushers being used. For example, U.S. 
Pat. No. 4,804,148 discloses that control systems are known wherein a 
programmable logic controller has been used to vary the feed rate to a 
secondary or tertiary crusher in accordance with signals received from a 
horsepower sensor and level sensor so that an optimum feed rate for the 
conditions being sensed can be determined and set for the crusher feeder. 
According to the known methods, however, a material contacting level 
sensor is required to extend within the bowl of the crusher in order to 
determine the level of rock within the crusher bowl. The level sensing 
probe that has been used is of a design that is able to withstand the 
harsh environment encountered in a rock crushing bowl of a secondary or 
tertiary crusher material contacting level sensor. It is not known, 
however, to sense the level of rock within a crushing cavity for a primary 
crusher, because the rock that enters a primary crusher is much larger 
than the rock entering a secondary or tertiary crusher thus creating an 
even harsher environment for the level sensor. Accordingly, no attempts 
have been made to automate a primary crusher, so an operator has always 
been used to regulate the feed rate delivered to a primary crusher and to 
signal the driver of a haul vehicle when to dump his load. 
SUMMARY OF THE INVENTION 
It is an object of the invention to automate a primary crushing stage of a 
rock crushing plant in order to optimize the throughput of the primary 
crushing stage so that a maximum amount of rock is available for delivery 
to the secondary and later stages of crushing. 
It is an object of the invention to provide an indicating system for a 
driver of a haul vehicle who intends to dump a load of rock into a hopper 
supplying rock to a primary crushing stage of a rock crushing plant. 
It is an object of the present invention to automate the operation of 
primary rock crusher by controlling the feed rate of rock delivered to the 
crusher such that the throughput of the crusher is optimized and the 
output conveyer and other output side equipment is not overloaded by an 
excessive amount of crusher throughput. The other output equipment that 
should not be overloaded includes downstream screens, conveyors, and 
crushers for the secondary stage of crushing. 
It is an object of the invention to automate the operation of a primary 
rock crusher by sensing the level of rock within the cavity of the rock 
crusher with a non-material contacting level sensing transducer by 
controlling the feed rate of rock delivered to the primary rock crusher so 
that a minimum level of rock within the cavity is maintained while a 
maximum level of rock within the cavity is not exceeded. It is a further 
object of the invention to maintain the feed rate within a desired range 
so that the load on an engine driving the primary crusher is maintained 
within an optimum efficiency range. 
It is an object of the invention to provide an indication to a driver of a 
haul vehicle that the load of the haul vehicle can be dumped into the 
hopper by sensing the level of rock contained in the hopper with a 
non-material contacting level sensing transducer. The driver receives an 
indication that the load can be dumped when the level of rock within 
hopper is less than a predetermined level so that the load being dumped 
does not overfill the hopper. 
It is an object of the invention to provide a control system for indicating 
to an operator of a haul vehicle when the load of the haul vehicle can be 
dumped into a hopper and for controlling the feed rate of a feeder 
delivering rock from the hopper to a primary rock crusher in accordance 
with the load placed on the motor driving the output conveyer such that 
the load on the output conveyer motor doe not exceed a predetermined 
amount that corresponds to a load placed on the motor when the maximum 
material handling capacity of the conveyer is reached. It is a further 
object to run the feeder of the crusher while monitoring other first stage 
crushing halting conditions that when sensed command the feeder to stop. 
The feeder is commanded to stop by the control system, for example, when 
the level sensed within the hopper is less than a predetermined amount so 
that the hopper is never emptied by the feeder. The control system further 
commands the feeder to stop when conditions such as a plugged chute, 
insufficient primary lubrication for the primary crusher and other like 
conditions are sensed that would cause spillover or damage to the rock 
crushing equipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a diagram of a typical first crushing stage in a rock crushing 
plant. A hopper 10 is provided for receiving rock from a haul vehicle 12 
that is brought to the plant from a quarry. Ordinarily, a driver does not 
leave the vehicle to determine whether or not the hopper will hold the 
load he is hauling because it is to dangerous, so a plant operator informs 
the driver about whether the hopper can hold the load. By the present 
invention, lights 14 and 15 are provided to visually indicate to the 
driver whether or not the load can be dumped into the hopper so the need 
for an operator is obviated. Of course, other suitable ways of signaling 
the driver that a load can be dumped may be provided that include, for 
example, providing audible signals or a movable gate in front of the 
hopper. Lights 14 and 55 are shown for purposes of illustrating a 
preferred embodiment of the invention, but only one light is sufficient to 
indicate either a dump or no-dump condition. Lights 14 and 15 are shown as 
green and red lights respectively to indicate the dump and no-dump 
conditions. 
The signaling of the lights 14 and 15 is controlled by controller 40 in 
accordance with the level of rock sensed within hopper 10 by a level 
sensor 19. When the level of rock within the hopper is less than a 
predetermined level such that a load of rock can be dumped into the hopper 
without risking overfilling the hopper, then the appropriate light 14 is 
illuminated to indicate to the driver of the haul vehicle that a dump 
condition is present. 
Level sensor 19 is a non-material contacting level sensor, and any type of 
non-material contacting level sensor can be used to determine the level of 
rock within the hopper. Preferably, level sensor 19 is an ultrasonic 
transducer that receives an echo that is proportional in time to the 
distance between the face of the transducer and the average level of rock 
within the hopper. An ultrasonic control box 20 is provided to compare the 
signal of the ultrasonic transducer with a preset value that corresponds 
with the level that allows for dumping of another load of rock into the 
hopper. The value of the ultrasonic transducer signal increases as the 
level of rock is lowered because the distance between the transducer and 
the rock level increases as the hopper is emptied. When a comparison shows 
that the signal of the ultrasonic transducer exceeds the preset value, 
then controller 40 lights the dump light 14, otherwise the no-dump light 
15 is illuminated. Also, the controller 40 commands the feeder 22 to stop 
when the output signal of transducer 19 exceeds a value representing a 
near empty load of hopper 10. 
The rock brought from the quarry is dumped into the hopper and fed to a 
primary crusher 30 by a feeder 22. Some of the rock within the hopper will 
be of a sufficiently small size in diameter so that is does not need to be 
crushed in primary crusher 30, so feeder 22 has screening bars 24 that 
allow the smaller sized rock to fall out from the feed path and slide down 
chute 25 onto an output conveyer 26. The rock that is crushed within 
primary crusher 30 is discharged onto output conveyer 26. The rock 
traveling on conveyer 26 is transported to the secondary and later stages 
of crushing in the rock crushing plant. 
The amount of rock delivered by conveyer 26 to the secondary and later 
stages of crushing in the rock crushing plant depends upon the amount of 
rock dumped into hopper 10 and crushed in primary crusher 30. Accordingly, 
the control system of the invention is provided to maintain the hopper in 
a full state by providing an indication of when rock can be dumped into 
the hopper and to keep the cavity 3 of the primary crusher full with rock 
as well by keeping the load on motor 32 driving the primary crusher within 
a predetermined optimum efficiency range. Further, in order to deliver the 
most rock to the later stages of rock crushing, the output conveyer must 
be kept running at a maximum capacity. 
To sense the level of rock within cavity 31 of the primary crusher, a 
non-material contacting level sensor 29 is provided that, like level 
sensor 19, is preferably an ultrasonic level sensing transducer. Level 
sensor 19 is shown as being connected to the ultrasonic transducer control 
box 20. The output of the transducer 29 also increases as the rock level 
goes down in the cavity. As a result, the feeder rate is increased when 
the output signal of transducer 29 exceeds a first set value, representing 
minimum cavity capacity and the feeder rate is decreased when the output 
signal is less than another preset value representing a maximum cavity 
capacity of crusher 30. Also, a load sensor 33 is provided on the 
conductor supplying the power for motor 32 in order that the load on the 
motor can be monitored. The level of rock within the cavity 32 and the 
horsepower load on motor 32 are received as inputs by controller 40. 
Feeder 22 is, for example, a Grizzly vibrating feeder that s driven by a 
motor 16, which is of variable speed. The feeder is positioned at the 
bottom of the hopper, as shown in FIGS. 1 and 2. The feeder pan 23 is 
shown in FIG. 2. The feeder has a variable feed rate that is controlled by 
changing the speed of motor 16. It is necessary to control the speed of 
the motor driving the feeder to control the material flow rate into the 
primary crusher. Another factor to consider is if the motor setting 
remains constant, then the feed rate being delivered to the crusher will 
vary depending upon the level of rock within the hopper and the ratio of 
small and large diameter rocks within the hopper. 
FIG. 1 shows that a typical motor for driving a primary crusher feeder is a 
wound rotor motor having grid resistors 18 in the rotor circuit and a drum 
switch for varying the resistance in the rotor circuit (not shown). In 
order to vary the resistance in the rotor circuit by using controller 40, 
the drum switch is connected in parallel with a plurality of shunting 
contactors 17, which are opened and closed progressively to provide the 
same result as achieved by a drum switch. Alternatively, the feeder may be 
driven by a motor that is controlled by a potentiometer or rheostat, which 
can be driven by a low RPM motor. On existing equipment, the controls for 
varying the speed of the motor driving the feeder are intended for 
operation by a plant operator, and these controls may vary from plant to 
plant. Any suitable method therefore, for controlling the existing 
variable feed rate controls that are provided with the equipment can be 
used to implement the control system of the invention. The circuit 
including shunting contractors 17 is shown as a preferred embodiment for 
controlling the speed of a wound rotor motor through a programmable logic 
controller, such as controller 40. 
In order to maintain a maximum supply of rock for the later crushing 
stages, the load on motor 27 that drives output conveyer 26 is monitored 
by a load sensor 28. An indication of whether or not the feed rate can be 
increased without exceeding the maximum capacity of the conveyer can be 
determined by comparing the sensed load on motor 27 to a preset value 
representing the maximum load the motor can handle without reaching an 
overload condition that causes the motor to trip off. If the load on the 
motor has not reached the maximum operating range, then the feed ate can 
be increased. Ordinarily, a plant operator would hesitate to increase the 
feed rate to the crusher for fear of overloading the output conveyer, but 
as a result of controlling the feed rate while monitoring the load on 
motor 27, the risk of overloading the conveyer is overcome, and the 
throughput of the primary crushing stage is greatly increased. 
Under certain conditions, it is necessary to stop the feeder 22, so 
controller 40 is provided with additional inputs that monitor various 
conditions that might need to be monitored depending upon the specific 
equipment and installation. For example, the lubrication system for the 
primary crusher can be monitored in order to determine whether or not the 
crusher is adequately lubricated. The lubrication system can be monitored 
by using a pressure transducer in the lubricant flowpath, for example. In 
this case, however, should the lubrication system fail, then the feeder 
and the primary crusher would both be turned off. 
FIG. 3 shows a flow chart of the operation of the control system of the 
present invention. The control system is designed to be used as an 
alternative to the manual control system that is provided on existing 
equipment. Therefore, at a first step 50, the determination is made 
whether or not the automatic/manual mode switch is in the automatic mode. 
If it is not, then the control system disables all of the controlled 
outputs so that manual operation can be exercised over the equipment. If 
the automatic mode has been selected, then the controller 40 determines 
whether or not any externally monitored control systems, such as the 
lubrication system for the primary crusher, are not in condition for 
supporting operation of the equipment. If any of the monitored conditions 
are not ready to support operation of the system, then the feeder is 
disabled and an alarm is sounded at step 51. Otherwise, the controller 
proceeds to a step 52 to determine whether the hopper 10 will hold a load 
by comparing the hopper level sensor 19 with a preset level that is 
determined in accordance with the size of the hopper and the size of the 
dump body of the haul vehicles supplying the rock. If the hopper will hold 
the load, then light 14 is illuminated to indicate a dump condition, but 
if the hopper will not hold a load then light 15 is illuminated to 
indicate a no-dump condition. 
If the hopper is not near empty, then the feeder 22 and primary crusher 30 
are started. The control system continues to monitor the dump hopper 
level, energizing the dump and no-dump lights respectively and further 
monitors the dump hopper level in step 53 to determine whether the level 
of the hopper is below a predetermined level or near empty. If the dump 
hopper is nearly empty, then the feeder is stopped so that a minimum level 
of rock is maintained within the hopper. In this way, when another load of 
rock is dumped into the hopper, the remaining layer of rock buffers the 
impact of the dumped load so that a minimum amount of damage occurs to the 
bottom of the hopper and bottom feeder pan 23. 
If the dump hopper is not near empty, then the feeder is started and the 
level of rock within crusher cavity 31 is monitored by level sensor 29 at 
a step 54. If the level of rock within the crusher cavity 31 is below a 
preset minimum level, then the feeder rate is increased. If the crusher 
level is above a minimum preset level, the control system further 
determines whether the crusher level is above a maximum preset level at 
step 55. If it is, then the feed rate of the feeder 22 is slowed down. The 
maximum an minimum levels are set as desired to establish an efficient 
working range. 
At the same time the rock level in the crusher cavity 31 is monitored, the 
load of motor 32 driving the primary crusher is monitored through load 
sensor 33. First, the controller 40 determines at a step 56 whether the 
load of motor 32 is above a minimum desired operating level. If it is not, 
then the feeder rate is increased. If it is, then the controller 40 is 
further programmed to determine whether or not the load of motor 32 is 
above a maximum preset level as step 57. If it is above the maximum level, 
then the feeder is commanded to slow down the feed rate. 
An additional condition being monitored is the load of output conveyer 
motor 27. At a step 58, the controller compares the signal from load 
sensor 28 to a predetermined minimum operating range value and commands 
the feeder to increase the feed rate to the crusher if the load on motor 
27 is below the preset value. If the load is within the operating range, 
then at step 59 the load signal is compared to another preset value 
representing the maximum load within the desired working range. The feeder 
is commanded to decrease the feed rate if the load signal exceeds the 
maximum preset value. Otherwise, the feeder continues to run within the 
established working range. 
By presetting maximum and minimum operation levels of rock within the 
crusher cavity 31 and maximum and minimum loads on the crusher motor 32 
and the output conveyer motor 27, the primary crusher 30 is operated in an 
optimum range of efficiency without the need for an operator to vary the 
feed rate of feeder 22. Further, controller 40 can receive other inputs 
from transducers monitoring external conditions at a step 60 to determine 
whether or not the monitored conditions exceed a desired level that 
requires the feeder to be stopped. For example, the controller decides at 
step 58 whether or not chute 25 is clogged or whether or not excessive 
belt drift is occurring in conveyer belt 26, or other belts. If any of 
these conditions exists, then the feeder is stopped or slowed down 
depending on the severity of the problem and the likelihood of the problem 
to cause damage to the equipment or to cause spillage. Controller 40 is 
preferably programmable to set the maximum and minimum levels that are 
desired for the level of rock within crusher cavity 31, and the maximum 
and minimum load levels for the crusher motor 32 and conveyer motor 27. 
Further, the controller can be programmed to accept a variety of inputs 
for comparing the inputs to set values in order to determine whether or 
not the crushing system is working properly. In this way, the need for an 
operator is reduced from a full-time need to a part-time need, and the 
required experience level of the operator is reduced while the efficiency 
of the primary crushing stage of the plant is optimized. 
It can be appreciated that the foregoing invention can be practiced by 
substituting other non-material contacting level sensors for the 
ultrasonic transducers disclosed and by substituting other types of 
indicating systems for the lights that are disclosed without departing 
from the scope of the invention. Further, other equipment on the output 
side of the primary crusher can be monitored other than the output 
conveyer, such as screens and feeders in the secondary crushing stage of 
the plant. Accordingly, the invention may be practiced within the scope of 
the spirit of the appended claims.