Patent Publication Number: US-11027287-B2

Title: Gyratory crusher including a variable speed drive and control system

Description:
BACKGROUND 
     The present disclosure generally relates to a rock crushing machine, such as a rock crusher of configurations commonly referred to as a gyratory crusher. More specifically, the present disclosure relates to a gyratory crusher that includes a variable speed drive and control system for controlling the operation of the gyratory crusher to optimize the discharge flow rate from the gyratory crusher. 
     Rock crushing machines break apart rock, stone or other materials in a crushing cavity formed between a downwardly expanding conical mantle installed on a mainshaft that gyrates within an outer upwardly expanding frustoconically shaped assembly of concaves inside a crusher outer shell. The conical mantle and the mainshaft are circularly symmetric about an axis that is inclined with respect to the vertical outer shell assembly axis. These axes intersect near the top of the rock crusher. The inclined axis is driven circularly about the vertical axis thereby imparting a gyrational motion to the mainshaft and mantle. The gyrational motion causes points on the mantle surface to alternately advance toward and retreat away from stationary concaves mounted to the outer shell. During retreat of the mantle, material to be crushed falls deeper into the cavity where it is crushed when motion reverses and the mantle advances toward the concaves on the outer shell. 
     Gyratory crushers typically include a discharge hopper that is located at the discharge end of the gyratory crusher to accumulate the material after the material has passed through the gyratory crusher. The size of the discharge hopper must be sufficient to accumulate the material after passing through the gyratory crusher before the material is discharged by a feeder onto a conveyor assembly. Since the operational speed of the feeder and conveyor assembly is typically constant while the feed of material into the gyratory crusher is generally uncontrolled, the discharge hopper must be large enough to accumulate material during high flow rates from the gyratory crusher. In some embodiments, the discharge hopper has a height of 6-8 meters. 
     The size of the discharge hopper is a significant variable in the cost of creating a rock crushing system that includes the gyratory crusher. The present inventor has identified a desire to reduce the size of the discharge hopper by optimizing the operation of the gyratory crusher, resulting in a smaller rock crushing system and reducing the cost associated with the discharge hopper and the energy consumption of the rock crushing system 
     To increase the efficiency of the crushing process, the operation of the gyratory crusher can be adjusted. In typical gyratory crushers, the operation of the crusher can be adjusted by controlling the size of the crushing gap by moving a mainshaft vertically with respect to the frame of the crusher. This adjustment modifies the size of the discharge particles from the gyratory crusher. Another adjustment possible in a gyratory crusher is to modify the gyratory speed of the mantle. In currently available gyratory crushers, adjusting the gyratory speed is limited based upon the drive motor used to create the gyrational movement. The inventor has recognized that an improvement in the drive of the gyratory crusher will increase operational efficiency. 
     SUMMARY 
     The present disclosure relates to a gyratory crusher that includes a variable drive and control system for controlling the operation of the gyratory crusher to optimize the discharge flow rate from the gyratory crusher. 
     The gyratory crusher of an exemplary embodiment of the present disclosure operates to reduce the size of material that is fed into an open feed end of the gyratory crusher. The gyratory crusher includes a stationary outer shell and a mainshaft that has a mantle. The mainshaft includes an eccentric that is positioned around a portion of the mainshaft such that the eccentric creates rotation of the mainshaft within the gyratory crusher. Material is trapped between an inner surface of the outer shell and an outer surface of the mantle within a crushing gap. Rotation of the mainshaft within the outer shell crushes material as the material enters into the crushing gap. 
     The gyratory crusher further includes a variable frequency drive that is directly or indirectly coupled to the eccentric to create rotation of the eccentric and the mainshaft. In one exemplary embodiment, the variable frequency drive includes an electric motor and a variable frequency controller. The variable frequency controller outputs a control signal to the electric motor which adjusts the rotational speed of the electric motor. In this manner, the variable frequency drive can dynamically adjust the rotational speed of the mainshaft within the stationary outer shell. 
     The gyratory crusher further includes a control system that can operate to control the rotational speed of the eccentric through control of the variable frequency drive. In one embodiment of the disclosure, a camera is positioned to detect the particle size of the material fed into the dump hopper. Another sensor can be used to detect the amount of material contained within the dump hopper. The control system can dynamically adjust the rotational speed of the eccentric through the variable frequency drive. In addition, the control system can adjust the vertical position of the mainshaft within the outer shell to change the size of the crushing gap. 
     In another contemplated embodiment, the gyratory crusher can include an outflow sensor that monitors the flow rate of crushed material from the gyratory crusher. Information from the outfeed sensor is fed to the control system such that the control system can modify the operation of the electric motor of the variable frequency drive to dynamically control the output feed from the gyratory crusher. The control system can modify the rotational speed of the eccentric such that the outflow feed from the gyratory crusher closely corresponds to the flow of material from a discharge hopper. 
     The present disclosure further relates to a method of controlling a rock crushing system that includes a gyratory crusher having a stationary outer shell that includes an interior crushing surface and a mainshaft that has a mantle including an exterior crushing surface. The interior crushing surface and exterior crushing surfaces create a crushing gap. Material is supplied to an dump hopper that is positioned above the gyratory crusher. The size and the amount of material within the dump hopper are determined, such as through the use of a camera. 
     Based upon the size and amount of material within the dump hopper, a variable frequency drive is operated to rotate an eccentric mounted to the mainshaft to create gyratory movement of the mantle within the outer shell. The rotational speed of the eccentric is dynamically controlled to control a flowrate of crushed material from the gyratory crusher. By controlling the flow rate of crushed material from the gyratory crusher, the size of a discharge hoper used to accumulate crushed material can be reduced. 
     Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate the best mode presently contemplated of carrying out the disclosure. In the drawings: 
         FIG. 1  is a schematic illustration of a gyratory rock crusher utilized as part of a rock crushing system; 
         FIG. 2  is a partial section view of the gyratory crusher including a variable frequency drive of the present disclosure; 
         FIG. 3  is a graph illustrating the relationship between eccentric speed and volumetric output of a gyratory crusher; and 
         FIG. 4  is an illustration of the movement of material through the crushing gap of the gyratory crusher. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates the general use of a rock crushing system  11  of the present disclosure. As illustrated in  FIG. 1 , a gyratory rock crusher  10  is positioned within a dump hopper  12  having a bottom wall  14 . The dump hopper  12  receives a supply of material  16  to be crushed from various sources, such as a haul truck  18 . The material  16  deposited into the dump hopper  12  is directed toward the open, upper feed end  20  of the gyratory crusher  10 . During operation of the rock crushing system  11 , the dump hopper  12  may accumulate a supply of material  16  which feeds through gravity into the upper feed end  20  of the gyratory crusher  10 . 
     The material  16  enters the crushing cavity and passes through a concave assembly positioned along the stationary outer shell  22 . Within the outer shell  22 , a crushing mantle (not shown) gyrates and crushes the material within the crushing cavity. The crushed material created a flow of crushed material that exits the gyratory rock crusher  10  and enters into a discharge hopper  24 . The discharge hopper  24  is shown in  FIG. 1  as having a sloped inner wall  26  that directs the crushed supply of material onto a discharge conveyor assembly  28 . The discharge conveyor assembly  28  operates to move the crushed material away from the rock crushing system  11  where the material can be further processed either through an additional crushing step or by being transported away from the mining site. Typically, the discharge conveyor assembly  28  operates at a constant rate and crushed material from the discharge hopper  24  is discharged onto the discharge conveyor assembly in a metered manner. 
     As can be understood in  FIG. 1 , the height H of the discharge hopper  24  dictates the amount of material that can be accumulated within the discharge hopper  24  before it is discharged onto the conveyor assembly  28 . The height H of the discharge hopper  24  thus has a direct impact on the oversize height X of the rock crushing system  11 . During construction of the rock crushing system  11 , estimates for the cost to create the rock crushing system  11  are often specified by the overall height X of the rock crushing system  11 . Thus, reducing the height H of the discharge hopper  24  will reduce the overall cost of the rock crushing system  11 . 
     As described above, the volume, and thus the height H, of the discharge hopper  24  must be sufficient to accumulate material within the discharge hopper  24  before the material is removed by the conveyor assembly  28 . In typical gyratory crusher feed systems, the amount of material  16  fed into the gyratory crusher  10  is controlled by the number of haul trucks  18  and the size of the truck bed  30 . Typically, the truck bed  30  carries between 200 and 400 tons of rock. In some cases, a large supply of material may accumulate within the dump hopper  12  before the material can be crushed by the gyratory crusher  10 . In other cases, only a very small supply of material may be within the dump hopper  12 . In prior systems, the speed of the gyratory crusher  10  remains generally constant such that the flow rate of material from the gyratory crusher  10  and thus the volume of material within the discharge hopper  24  can vary drastically. In many embodiments, the size of the discharge hopper  24  is designed to be two to four times the capacity of the truck bed  30  in order to accumulate enough material so that the gyratory crusher  10  can operate at a constant speed while still feeding a constant flow of crushed material onto the discharge conveyor assembly  28 . 
       FIG. 2  illustrates one exemplary embodiment of the gyratory crusher  10  that can be utilized within the rock crushing system shown in  FIG. 1 . Although a representative gyratory crusher  10  is illustrated, it should be understood that various different embodiments of the gyratory crusher could be utilized while operating within the scope of the present disclosure. The gyratory crusher  10  shown in  FIG. 2  includes a mainly vertical mainshaft  32  that includes an eccentric  34  mounted thereto. The mainshaft  32  includes a mantle  36  that creates a crushing gap  38  between the outer surface  43  of the mantle  36  and an inner surface  42  of an outer shell assembly  40 . The inner surface  42  of the shell assembly  40  includes a single piece concave or rows of concaves that define the generally tapered frustoconical inner surface  42  that directs material from the open top end  20  downward through a converging crushing cavity to the crushing gap  38 . Material is crushed over the height of the crushing cavity between the inner surface  42  of the outer shell and the outer surface  43  of the mantle. 
     The upper end  44  of the mainshaft  32  is supported by a bushing  46  contained within the center hub of a spider  48 . In  FIG. 2 , one half of the spider  48  along with the shield  50  and top cap  52  are removed to facilitate understanding. Although the exemplary embodiment shown in  FIG. 2  includes the spider  48 , other embodiments of the gyratory crusher would not include a spider and the related supporting structure. Such embodiment would also fall within the scope of the present disclosure. As the material  16  moves through the crushing chamber, the size of the material is reduced such that a discharge flow of material  54  is created. 
     In the embodiment shown in  FIG. 2 , the rotation of the mainshaft  32  is controlled through a rotating pinion shaft  56  and pinion gear  58  that meshes with a gear  55  mounted to the eccentric  34  in a conventional manner. The pinion  56  is directly or indirectly coupled to a variable speed drive (VFD)  60  in accordance with the present disclosure. The variable frequency drive  60  operates to rotate the pinion  56  as illustrated by the rotational arrow  63  shown in  FIG. 2 . The variable frequency drive  60  is coupled to a control system  64 . 
     In accordance with the present disclosure, the variable-frequency drive (VFD) is a type of adjustable speed electro-mechanical drive system that controls the operating speed of an electric motor  66  by varying the motor input frequency and voltage. In the embodiment shown in  FIG. 2 , the variable frequency drive  60  includes the AC motor  66  and a variable frequency controller  68 . The variable frequency controller  68  has a power electronics conversion system that submits an output signal to the AC motor  66  along control line  69  to control the operation of the AC motor  66 . Through the control of the frequency of the output signal from the variable frequency controller  68 , the variable frequency controller  68  can control the operational speed of the AC motor  66 . In the embodiment shown in  FIG. 2 , a control system  62  for the gyratory crusher  10  is in further communication with the variable frequency controller  68  such that the operational controls for the gyratory crusher are able to control the speed of the AC motor  66  through the variable frequency controller  68 . 
     As can be understood by the description in  FIG. 2 , the variable frequency drive  60  allows the operational speed of the eccentric  34  to be adjusted by modifying the frequency of the control signal from the variable frequency controller  68 .  FIG. 3  provides a graphic illustration relating the eccentric speed  70  to the volume output  72  from the crusher. It should be understood that the values shown in  FIG. 3  are representative values for one type of crusher and are not meant to be limiting and are for illustrative purposes only. In the chart shown in  FIG. 3 , the operational speed of prior art gyratory crushers that utilized a conventional diesel powered drive motor is shown by point  74 . Point  74  illustrates that at an eccentric speed of approximately 150 RPM, the volume output of the gyratory crusher is approximately 3,500 tons per hour. In accordance with the present disclosure and through the use of the variable frequency drive  60  shown in  FIG. 2 , the eccentric speed can be adjusted between the point  74  and an upper point  76 . The two points  74  and  76  create a sub-critical zone  78  where the variable frequency drive  60  will operate the AC motor  66  to create the desired eccentric speed  70 . 
     The graph of  FIG. 3  further illustrates a critical speed  80 . When the eccentric is operated at a speed greater than the critical speed  80 , the volumetric output of the gyratory crusher begins to decrease. Thus, it is desired to operate the gyratory crusher at a speed within the sub-critical zone  78  to optimize the operation of the crusher. 
       FIG. 4  is a graphical illustration to describe the sub-critical speed and critical speed shown in  FIG. 3 . In the illustration of  FIG. 4 , a round ball  82  is shown located within the crushing gap  38  defined by the inner surface  42  of the shell  40  and the outer surface  43  of the mantle  36 . As an illustrative example, if the crusher were at rest, the round ball  82  would become wedged between the crushing surfaces on the closed side of the crushing gap. As the eccentric begins to rotate the crushing head, the ball  82  will begin to slide down the chamber as the gap at that point in the chamber begins to widen from the closed side to the open side position. The ball will begin to slide down the head but does not free fall because the size of the ball is larger than the gap. Once the head is at the open side, the gap begins to compress the ball and the ball deflates until the diameter of the ball is equal to the closed side crushing gap. This will be repeated until the ball exits the crusher. 
     As the rotational speed of the eccentric increases, the ball  82  will be able to freefall within the expanding gap until the rotational speed matches the freefall speed of the ball. This point is referred to as the critical speed. If the rotations frequency is further increased, the head returns faster than the ball drops and the crusher will be operating at a super-critical speed. As indicated above, the critical speed  80  is the fastest speed desired for the rotation of the eccentric. 
     Referring back to  FIG. 2 , the control system  62  is further designed to include a camera  90  that is positioned to detect the size of the material  16  being fed into the open feed end  20  of the gyratory crusher  10 . The camera  90  can be a video camera or a still camera or any other type of device that creates a visual image of the material. The camera  90  provides visual images to the control system  62  such that the control system  62  can detect the typical particle size distribution of the material  16  being fed into the gyratory crusher  10 . Another sensor (not shown) can be positioned within the dump hopper provide an indication of the level of material in the dump hopper. Based upon the size of the particles being fed into the open end  20  of the gyratory crusher, the control system  62  can automatically adjust the size of the crushing gap  38  by moving the vertical position of the mainshaft  32 . In currently available gyratory crushers, the size of the crushing gap  38  can be adjusted utilizing a hydraulic assembly to adjust the vertical position of the mainshaft  32 . A similar arrangement would be utilized within the gyratory crusher of  FIG. 2 . However, in accordance with the system of  FIG. 2 , the control system  62  can automatically adjust the vertical position of the mainshaft based upon the size of the material  16 , as sensed by the camera  90 . 
     In addition to measuring the product size, the camera  90  can also be used to detect the flow of material into the open feed end  20  of the gyratory crusher  10 . The flow of material into the dump hopper will cause material to accumulate above the gyratory crusher  10  until the gyratory crusher can act on the material to crush the material. 
     In the embodiment shown in  FIG. 2 , a flow rate sensor  92  can be positioned near the discharge outlet of the gyratory crusher  10 . The flow rate sensor  92  can detect the flow of material out of the gyratory crusher  10  and into the discharge hopper. Based on this detected output flow rate as well as the level of material in the discharge hopper, the control system  62  can dynamically adjust the speed of the electric motor  66  to optimize the flow rate from the gyratory crusher  10 . As indicated above, the relationship between the output flow rate and the rotation speed of the eccentric is shown by the graph of  FIG. 3 . It is desirable to operate the gyratory crusher in the sub-critical zone  78 . 
     As can be understood above, the use of the variable frequency drive  60  with the gyratory crusher  10  allows the control system  62  to dynamically optimize the operation of the gyratory crusher. The control system  62  can measure the feed to the crusher along with other crusher operating parameters, including hydraulic pressure, temperature and available power from the AC motor  66  such that the control system  62  can adjust the crusher eccentric speed to reach the highest capacity and/or lowest wear rates on the crusher linings. 
     As an illustrative example, the control system  62  can cause the AC motor  66  to operate at a faster speed to increase production when the feed into the gyratory crusher is suitable. Alternatively, if the feed rate into the gyratory crusher is small, the speed of the AC motor  66  is reduced to reduce wear rates on the wear components within the gyratory crusher. It is desirable to maintain operation of the gyratory crusher with material such that the gyratory crusher operates as infrequently as possible with no material present. By optimizing the operational speed of the eccentric within the crusher, less material needs to be accumulated in the discharge hopper, which allows the size of the discharge hopper to be reduced. 
     In one exemplary embodiment, the control system  62  can operate the variable frequency drive in an attempt to closely match the output flow rate from the gyratory crusher  10  to the flow rate of material on the conveyor assembly. In this manner, the amount of material accumulated within the discharge hopper can be minimized, which will allow the volume, and thus the height H, of the discharge hopper to be reduced. Although it is desirable to have some amount of material within the discharge hopper at all times, reducing the amount of material within the discharge hopper will allow the size of the discharge hopper to be reduced. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.