Patent Publication Number: US-7222805-B1

Title: Shredder with cage relief

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention is generally related to apparatus for grinding and granulating various types of waste material which may contain hard to grind stray materials, and in particular, to an adaptation to a materials processing system which is adapted to protect the grinding and driving components of the system from damage when such hard to grind stray materials becomes trapped or jammed within the grinding components. 
     In conventional apparatus configured for the processing of material by grinding, shredding, or crushing, there is a constant problem associated with the intake of material which is either to large or to hard for the apparatus to effectively reduce. Such material, commonly referred to as “tramp material”, can become trapped or jammed within the grinding, shredding, or crushing components, resulting in severe damage or destruction to these components or any associated drive mechanisms before the driving motors can be shut down. The high operational speeds of conventional material grinding, shredding, or crushing apparatus make it especially difficult to timely shut down the driving motors when such tramp materials are encountered. 
     One solution to which reduces the risk of damage to the grinding, shredding or crushing components of a materials processing apparatus is set forth in U.S. Pat. No. 5,743,472 to Williams, Jr. et al. The &#39;472 Williams, Jr. et al. patent discloses an electrical safety cutoff circuit means which is operative upon the loss of a shear pin support means for a sizing screen and shredding cutter for stopping the electrical current supply to a drive motor of the materials processing apparatus. Essentially, the &#39;472 Williams, Jr. et al. patent discloses an automatic cutoff system for the drive mechanism of the materials processing apparatus which is triggered by the loss of a shear pin support means due to trapped or jammed tramp material exerting an excess load on the sizing screen. In the &#39;472 Williams, Jr. et al. system, once the shear pin support means is lost, tripping the electrical safety cutoff, the materials processing apparatus is completely shut down until an operator manually replaces the lost shear pin and restarts the system. This can result in a significant interruption in the materials processing system, due to the time required to replace the shear pin and re-start the associated materials feed systems, drive systems, and processed materials removal systems. 
     Accordingly, there is a need in the industry for an apparatus which is adapted to protect the grinding and driving components of a materials processing system from damage when such hard to grind stray materials becomes trapped or jammed within the grinding apparatus, and which is capable of being automatically reset, thereby eliminating the need for an operator to manually replace frangible parts and restart the system. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the present invention sets forth an improved materials processing system adapted for the shredding and grinding reduction of materials. The processing system includes a materials feed portion configured to convey metallic materials for shredding and grinding to a mill portion. The mill or shredder portion includes a motor driven rotor in close running fit with a cage mounted screen through which reduced material is discharged onto a screen conveyer mechanism. In order to guard against damage to the materials processing system due to the presence of tramp material and the associated destruction, the cage of the improved system is biased to a closed operating position by one or more hydraulic rams. A feedback mechanism including a speed sensor operatively coupled to the motor driven rotor is configured to regulate a flow of hydraulic fluid to and from the hydraulic rams, thereby controlling the opening and closing of the cage in response to slowed or stopped rotation of the motor driven rotor. The feedback mechanism is further configured to regulate the operation of the new materials feed portion to suspend material feed during opening of the cage. 
     In the event hard to grind tramp material is fed into the processing system, the force imposed on the material by the rotor may cause damage to the mill. Simultaneously, continued feed of additional material may result in a backlog and jamming of material in the mill. Preventing the occurrence of mill damage and material jam is of utmost importance and the provision of the feedback mechanism to open and close the cage and simultaneously regulate material feed in response to rotor rotational speeds achieves the desired result, allowing the cage to open and discharge any hard to grind tramp material while precluding the addition of new material before the system is cleared. 
     A method of the present invention provides for controlling material input and releasing trapped or jammed tramp material from a materials processing system adapted for the shredding and grinding reduction of metallic materials. During operation of the materials processing system, materials to be reduced are conveyed by a material feed to a grinding or shredding mill containing a motor driven rotor in close running fit with a cage assembly including a discharge screen. Materials which are reduced in size by the motor driven rotor are passed through the discharge screen and onto a screen conveyer mechanism for further separation or are returned to the material feed for additional reduction. A speed sensor switch monitors the rotational speed of the rotor in the grinding or shredding mill. Upon detection of a substantial reduction or cessation in rotor rotation the speed sensor switch signals the material feed to slow or cease delivery of materials to be reduced, and signal motive components to open the cage assembly, thereby evacuating trapped or jammed tramp material from the grinding or shredding mill. Upon resumption of a normal rotational speed of the rotor, as detected by the speed sensor switch, signals are provided to direct the closure of the cage assembly and to resume normal delivery of materials to the mill. 
     The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification: 
         FIG. 1  is a block diagram of an improved material processing system of the present invention; 
         FIG. 2  is a vertical partial sectional view of an alternate embodiment of the material grinding and shredding mill of the present invention, with the cage mounted screen in the closed operating position; and 
         FIG. 3  is a vertical partial sectional view of alternate embodiment of the material grinding and shredding mill of  FIG. 2 , with the cage mounted screen in the open tramp material release position. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
     Turning to  FIG. 1 , the improved materials processing system of the present invention is shown generally at  10 . A material feed  12  delivers material to be processed to a material inlet  13  of a grinding or shredding mill  14 . Within a housing  15  of the mill  14 , a rotor  16  having cutters or hammers reduces the delivered material by grinding or shredding. Rotor  16  is driven by a primary drive unit  18 , such as a diesel motor, and is coupled to the primary drive unit  18  through a fluid coupler or clutch  20 . The fluid coupler or clutch  20  permits a disconnect to occur between the rotor  16  and the primary drive unit  18  in the event the rotor  16  becomes jammed with material. One embodiment of the material grinding and shredding rotor is seen in greater detail in U.S. Pat. No. 5,911,372, hereby incorporated by reference. 
     At the base  22  of the mill housing  15 , a cage assembly  23  is provided to retain material delivered to the mill  14  adjacent the grinding or shredding elements of the rotor  16 . The cage assembly consists of a pivoting cage  24  and a grate or discharge screen  26  for sizing ground or shredded material within the mill  14 . If the material has been reduced to a predetermined size, it is passed through the grate or discharge screen  26 , through a discharge outlet  27  in the housing  15 , and onto a screen conveyer mechanism  28  for further sorting or for return of larger materials to the input of the mill  14  for further reduction. 
     The improvements of the present invention reside in the safety provisions and feedback systems associated with the cage assembly  23  and material feed  12 . The pivoting cage  24  is coupled to the mill housing  15  by a hinge or pivot pin  30  disposed on a first side, and is configured to pivot away from the rotor  16  about the hinge or pivot pin  30 . Movement of the pivoting cage  24  is regulated by one or more associated hydraulic rams  32  disposed on a second side of the pivoting cage  24 , opposite the hinge or pivot pin  30 . Each hydraulic ram  32  is of conventional design, and consists of a ram arm  32 A and a fluid cylinder  32 B hydraulically coupled to a fluid reservoir  36  through a hydraulic circuit  38  including a hydraulic pump  40 . 
     In a first operating position, the hydraulic rams  32  maintain the pivoting cage  24  in a closed and operational position adjacent the rotor  16 , thereby maintaining material to be reduced adjacent the cutting, shredding, or grinding surfaces of the rotor  16 . In a second operational position, the hydraulic rams  32  pivot the pivoting cage  24  about the hinge or pivot pin  30  away from the rotor  16  to effect the discharge of trapped or jammed tramp material from the mill  14  onto the screen conveyer mechanism  28 . 
     The operational position of the hydraulic rams  32  is regulated through a feedback mechanism utilizing a speed sensor switch  42 , preferably a “zero-speed” switch. The speed sensor switch  42  is operatively coupled to the rotor  16 , and configured to measure the rotational speed of the rotor  16 . In the event tramp material becomes trapped or jammed in the mill  14  during operation, the rotational speed of the rotor  16  will slow or stop. 
     Upon detection of the rotational speed of the rotor  16  either falling below a predetermined threshold, or stopping completely, speed sensor switch  42  provides a signal to the hydraulic circuit  38  to alter the flow of hydraulic fluid, moving the hydraulic rams  32  to the second operational position in which the pivoting cage  24  pivots about the hinge or pivot pin  30  to move away from the rotor  16 , resulting in the discharge of trapped or jammed tramp material from the mill  14 . In addition to communicating the signal to the hydraulic circuit  38 , the speed sensor switch  42  communicates the signal to the material feed  12 . The material feed  12  is configured to respond to the signal by slowing or ceasing delivery of material to the input of the mill  14 . 
     Upon detection of the rotational speed of the rotor  16  either rising above a predetermined threshold, or stopping completely, speed sensor switch  42  provides a signal to the hydraulic circuit  38  to alter the flow of hydraulic fluid, moving the hydraulic rams  32  to the second operational position in which the pivoting cage  24  pivots about the hinge or pivot pin  30  to move away from the rotor  16 , resulting in the discharge of trapped or jammed tramp material from the mill  14 . In addition to communicating the signal to the hydraulic circuit  38 , the speed sensor switch  42  communicates the signal to the material feed  12 . The material feed  12  is configured to respond to the signal by slowing or ceasing delivery of material to the input of the mill  14 . 
     Those of ordinary skill in the art will recognize that the signals may either be provided directly by the speed sensor switch  42  as described, or may be provided to the hydraulic circuit  38  and the material feed  12  by a control system  41 . The control system  41  may optionally include a microprocessor or logic circuit configured to interpret signals received from the speed sensor switch  42 , and to control at least the hydraulic circuit  38  and the material feed  12 . 
     In a first embodiment, show in  FIG. 1 , the arms hydraulic rams  32  are in the first operational position when each ram arm  32 A is extended, exerting a pushing force on the pivoting cage  24  to maintain it in the closed and operational position. To maintain the first operational position, the hydraulic pump  40  provides hydraulic fluid from the reservoir  36  to each fluid cylinder  32 B, through the hydraulic circuit  38 . Upon receiving a signal from the speed sensor switch  42  or control system to release and open the pivoting cage  24 , the hydraulic pump  40  is reversed, drawing fluid from each fluid cylinder  32 B and returning it to the reservoir  36 . Alternatively, hydraulic pump  40  is disengaged, and a fluid return bypass is opened, permitting fluid to drain from each fluid cylinder  32 B back to the reservoir  36 . As fluid is withdrawn or drained from each fluid cylinder  32 B, each ram arm  32 A retracts, drawing the pivoting cage  24  away from the rotor  16 , and into an open position for discharge of the trapped or jammed tramp material. 
     In a second embodiment, show in  FIGS. 2 and 3 , the arms hydraulic rams  32  are in the first operational position when each ram arm  32 A is retracted, exerting a draw force on the pivoting cage  24  to maintain it in the closed and operational position. To maintain the first operational position, the hydraulic pump  40  draws hydraulic fluid from each fluid cylinder  32 B, through the hydraulic circuit  38 , and stores it in the reservoir  36 . Upon receiving a signal from the speed sensor switch  42  or control system to release and open the pivoting cage  24 , the hydraulic pump  40  is reversed, drawing fluid from the reservoir  32  and supplying hydraulic fluid under pressure to each fluid cylinder  32 B. As the hydraulic fluid is pumped into each fluid cylinder  32 B, the associated ram arms  32 A extend, moving the pivoting cage  24  to an open configuration shown in  FIG. 3  for the discharge of the trapped or jammed tramp material. 
     Those of ordinary skill in the art will recognize that the hydraulic circuit  38  may be configured with a variety of conventional hydraulic components in addition to the hydraulic pump  40  described above, including flow dividers, valves, and pressure regulators. The addition or replacement of conventional hydraulic components within the hydraulic circuit  38  to achieve the controlled opening and closing of the pivoting cage  24  in response to signals from the speed sensor switch  42  or control system does not depart from the scope of the present invention. 
     During operation, the improvement of the present invention provides for controlling material input and releasing trapped or jammed tramp material from the materials processing system  10  adapted for the shredding and grinding reduction of metallic materials, such as scrap metal. Initially, materials to be reduced are conveyed by the material feed  12  to the input of the grinding or shredding mill  14 . Within the mill  14  rotor  16  is rotationally driven by a primary drive unit  18 , in close running fit with the pivoting cage  24  and associated grate or discharge screen  26 . Materials which are reduced in size by the action of the rotor  16  are passed through the grate or discharge screen  26  and onto a screen conveyer mechanism  28  for further separation, or are returned to the input of the mill  14  for additional reduction. 
     The rotational speed of the rotor is monitored by the speed sensor switch  42 . Upon detection of a substantial reduction or cessation of rotor rotation by the speed sensor switch  42  or an associated control system, a signal is provided to the material feed  12  to slow or terminate delivery of materials to be reduced, and simultaneously, to the components of the hydraulic circuit  38  to open the pivoting cage  24 , thereby evacuating trapped or jammed tramp material from the grinding or shredding mill. Upon detection by the speed sensor switch  42  of a resumption of normal rotor rotation following evacuation of the trapped or jammed tramp material, a signal is provided to the hydraulic circuit  38  to close the pivoting cage  24  and to the material feed  12  to resume normal delivery of materials. 
     The present invention can be embodied in-part in the form of computer-implemented processes and apparatuses for practicing those processes. The present invention can also be embodied in-part in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or an other computer readable storage medium, wherein, when the computer program code is loaded into, and executed by, an electronic device such as a computer, micro-processor or logic circuit, the device becomes an apparatus for practicing the invention. 
     The present invention can also be embodied in-part in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented in a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.