Abstract:
A material reducing apparatus comprising a feed conveyor, for conveying material to be reduced, and a feed roller cooperating with the feed conveyor. An upwardly rotatable rotor carrying a plurality of strikers which facilitate reduction of the material to be reduced and an anvil cooperating with the plurality of strikers to facilitate further reduction of the material to be reduced. A grate assembly, located adjacent an arcuate path of the rotor, which permits sufficiently reduced material to pass therethrough. The material reducing apparatus further includes a failsafe system which comprising an accelerometer supported by the rotor and coupled to a control system such that the accelerometer, upon detection of the rotor contacting a hard material, sends a signal to the control system. If the signal indicates a sufficiently large material, the control system reverses a rotational direction of the feed roller so that the feed roll rotates to withdraw the hard material from contact with the rotor. A section of the grate assembly may also be moved away from the rotor, by a release device, upon the release device receiving a command from the control system.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a failsafe system for a material reducing apparatus or machine that essentially prevents damage from occurring to the material reducing apparatus or machine when the failsafe system detects an attempted reduction, e.g., a conversion of a large piece of material into smaller, more convenient pieces of material for subsequent handling and recycling purposes, of a “hard” material, such as tramp metal, by the material reducing apparatus or machine. 
       BACKGROUND OF THE INVENTION 
       [0002]    A variety of different materials reducing machines and apparatuses are known in the art which receive large bulky materials, e.g., logs, tree stumps, brush, yard waste, pallets as well as other materials, and process the same for recycling or disposal, for example. Typically a large rotor, containing a plurality of replaceable blades, knives, teeth, hammers or strikers on a peripheral surface thereof, is rotated at relatively high speed so as to strike the incoming material in either a downward or an upwardly arcing path and produce a shearing action of the material to be reduced which assists with conversion of material into smaller pieces which are more convenient for subsequent disposal, handling, recycling, etc. 
         [0003]    A feed conveyor is generally provided for feeding material into the downward or the upwardly rotating rotor. A screen generally surrounds a major periphery of the rotating arc of the rotor to assist with the conversion of the large pieces of material into particles of a desired smaller size for subsequent handling and recycling. 
         [0004]    A prevalent problem associated with prior art material reducing apparatus is that metal, or some other hard material, tends to be intermixed with the debris, logs, tree stumps, brush, yard waste, pallets or other material to be recycled. If any hard material is attempted to be reduced by the material reducing apparatus, this normally causes the anvil(s), the hammer(s), the striker(s) and/or other internal components within the material reducing apparatus to be dented, chip, fracture and/or break. Prior art attempts to compensate for this have been to provide shear arrangements which allow one or more components to be pivotally supported by shear pins and break away when a hard material is attempted to be reduced by the material reducing apparatus. The problem with such shear arrangements is that, although they are somewhat effective in minimizing damage to the material reducing apparatus, they still result in some damage occurring to the material reducing apparatus which, in turn, leads to costly down time while the material reducing apparatus is shut down so that the chipped, fractured or broken part(s) can be repaired or replaced. 
       SUMMARY OF THE INVENTION 
       [0005]    Wherefore, it is an object of the present invention to overcome the above mentioned shortcomings and drawbacks associated with the prior art. 
         [0006]    Another object of the present invention is to provide a failsafe system which when the system detects that the rotor initially strikes or contacts a hard material, such as metal, the failsafe system, substantially immediately upon detecting such contact, reverses the rotational direction of the top feed roller while also reducing the speed of the engine driving the rotor. 
         [0007]    Yet another object of the present invention is to provide a failsafe system with a further safety feature which, when the failsafe system detects that a hard material, such as metal, is in the process of actually being reduced by the material reducing apparatus, facilitates an extremely rapid opening of a grate assembly so as to permit the rotation of the rotor to discharge the hard material on to the discharge conveyor before any shearing and/or damage can result to any of the internal components of the material reducing apparatus, e.g., the screen, the anvil(s), for example. 
         [0008]    A further object of the present invention is to affix an accelerometer, to a bearing housing supporting the shaft which supports the rotor, such that the accelerometer detects generated vibrations when any of the supported hammers or strikers impacts against a hard material, such as metal, and the accelerometer generates an output signal which is immediately forwarded to main control system which, provided that the detected vibrations is sufficiently large, automatically reverses the rotational direction of the top feed roll to withdrawn the hard material or metal away from the arcing path of the rotor while, at the same time, slowing down the rotational speed of the rotor and also possibly actuating the grate assembly so as to sufficiently space the grate assembly away from the rotating rotor and prevent damage to the internal components of the material reducing apparatus. 
         [0009]    Yet a further object of the present invention is to ensure hydraulic actuation of the grate assembly, radially away from a periphery of the rotor, within a time period of about 200 milliseconds or less, and most preferably within a time period of about 20-30 milliseconds following detection of the rotor initially striking or contacting a hard material, such as metal. 
         [0010]    A further object of the present invention is to provide a failsafe system which maximizes throughput of the material reducing apparatus while minimizes the possibility of any significant damage occurring to internal grinding/shearing components during operation. 
         [0011]    Another object of the present invention is to mount the top feed roller to a pivotal clamshell assembly which facilitates improved access to the hammers or the strikers, the striker or hammer support blocks, the rotor the and the screen or grate, etc., to facilitate servicing and/or replacement of such components. 
         [0012]    The present invention also relates to a material reducing apparatus comprising a feed conveyor for conveying material to be reduced; a feed roller cooperating with the feed conveyor for assisting with conveying the material to be reduced; an upwardly rotatable rotor carrying a plurality of strikers which facilitate reduction of the material to be reduced; an anvil cooperating with the plurality of strikers to facilitate further reduction of the material to be reduced; and a grate assembly, located adjacent an arcuate path of the rotor, which permits sufficiently reduced material to pass through openings provided therein; wherein in the material reducing apparatus further includes a control system which comprising an accelerometer supported by the rotor and coupled to the control system, and the accelerometer transmits vibrations signals to the control system, and the control system, when it receives a signal above a threshold, reverses a rotational direction of the feed roller so that the feed roll rotates to withdraw the hard material from contact with the rotor 
         [0013]    The present invention also relates to A material reducing apparatus comprising: a feed conveyor for conveying material to be reduced; a feed roller cooperating with the feed conveyor for assisting with conveying the material to be reduced; an upwardly rotatable rotor carrying a plurality of strikers which facilitate reduction of the material to be reduced; an anvil cooperating with the plurality of strikers to facilitate further reduction of the material to be reduced; a grate assembly, located adjacent an arcuate path of the rotor, which permits sufficiently reduced material to pass therethrough, the grate assembly comprises a pivotally mounted upper grate assembly and a fixed lower grate assembly; a release device connected for actuation of the uppergrate assembly; and a discharge conveyor for receiving material which passes through the grate assembly to facilitate conveyance thereof; wherein the material reducing apparatus further includes a control system which comprising an accelerometer supported by the rotor and coupled to the control system, and the accelerometer, upon detection of vibration, sending a signal to the control system and the control system, when the controls systems determines that the signal is of a sufficient magnitude, reverses a rotational direction of the feed roller and the feed conveyer so that the feed roll and the feed conveyer rotate to withdraw the hard material from contact with the rotor and the release device pivots the pivotally mounted upper grate assembly radially away from the rotor 
         [0014]    As used within this patent application, a “hard” material generally refers to a material which has a hardness comparable to that of metal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
           [0016]      FIG. 1  is a diagrammatic front elevational view of material reducing apparatus according to the present invention; 
           [0017]      FIG. 1A  is a diagrammatic left side elevational view of material reducing apparatus of  FIG. 1 ; 
           [0018]      FIG. 2  is a diagrammatic top plan view of the material reducing apparatus with the discharge conveyer shown in a stored transport position; 
           [0019]      FIG. 2A  is a diagrammatic cross section view along section line  2 A- 2 A of  FIG. 2 ; 
           [0020]      FIG. 3  is a diagrammatic front elevational view of hog box of the material reducing apparatus shown in the closed operative position; 
           [0021]      FIG. 3A  is a diagrammatic front elevational view of hog box of the material reducing apparatus shown in the opened, servicing position; 
           [0022]      FIG. 4  is a diagrammatic view showing the accelerometer supported by the bearing housing for the rotor; 
           [0023]      FIG. 5A  is a diagrammatic view showing the normal grinding/reducing operation of material reducing apparatus; 
           [0024]      FIG. 5B  is a diagrammatic view showing reversal of the feed roller upon the accelerometer detecting contact of the rotor with a hard material;; 
           [0025]      FIG. 5C  is a diagrammatic view showing both reversal of the feed roller and actuation of the release device upon the accelerometer detecting contact of the rotor with a hard material; 
           [0026]      FIG. 6  is a diagrammatic view of hydraulic system for actuating the release device; and 
           [0027]      FIGS. 7  is diagrammatic front elevational view showing the horseshoe shaped protectors for protecting the bolt heads secure the upper grate to the upper grate assembly,  7 A is a right side elevation view thereof, and  7 B is a perspective view thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Turning now to  FIGS. 1 ,  1 A,  2  and  2 A, a brief description concerning the various components of the present invention will now be briefly discussed. As can be seen in  FIG. 1 , a material reducing apparatus  2  is diagrammatically shown therein. The material reducing apparatus  2  is arranged to reduce materials such as debris, logs, tree stumps, tree limbs, brush, yard waste, pallets and the like into particles having a desired smaller particle size. According to this embodiment, the material reducing apparatus  2  includes a chassis or frame assembly  4  having a pair of tracks  6  which facilitate travel and maneuverability of the material reducing apparatus  2  to a desired location of a particular work site or onto a transportation trailer. It is conceivable that the chassis or frame assembly  4  may instead include a plurality of rotatable wheels and have a conventional hitch which facilitates connection to a conventional towing unit for towing the material reducing apparatus  2  to a desired site or location. The material reducing apparatus  2  is readily transportable to a site where materials to be reduced have accumulated, 
         [0029]    The material reducing apparatus  2  has a receiving bin  8  which includes a feed end  10  for receiving deposited materials that are to be reduced by the material reducing apparatus  2 . The receiving bin  8  has a pair of opposed upstanding sidewalls  12  which facilitate containment of the material that is deposited therein. A known feed conveyor  14 , such as a belt-type conveyor, extends along a length of the receiving bin  8 , e.g., the conveyer  14  has a length of about 18 feet for example, and is provided for conveying the materials to be reduced, which are deposited within the receiving bin  8 , toward a material reducing rotor  16  which is positioned adjacent a discharge end of the receiving bin  8 . During operation, the conveyor  14  conveys the deposited materials along the feed conveyer  14 , in the direction indicated by arrow  15 , toward the upwardly rotating rotor  16 . 
         [0030]    A top feed roller  18 , (see  FIG. 2 ) which assists with holding down the material being feed to the rotor  16 , is positioned at the discharge end  20  of the feed conveyor  14  immediately adjacent but preceding the rotor  16 . Normally, the rotational speed of the feed roller  18  will be automatically controlled, via a main control system  22 , depending upon the load of the engine  24  driving the rotor  16 . The feed roller  18  normally assists with compaction or crushing of the material to be reduced and also assists the feed conveyor  14  with conveying the material to be reduced into the rotational path of the rotor  16 . It is to be appreciated that the materials fed into the rotor  16  are partially reduced when such materials are impacted by the strikers or hammers  26  which are mounted to the peripheral surface of the rotor  16 . To assist with further reduction of the material, at least one anvil(s)  28  is strategically positioned along a width of the rotor  16 , but slightly radially spaced therefrom, such that the strikers or hammers  26 , carried by the rotor  16 , will pass closely adjacent to the anvil(s)  28 , without contacting the anvil(s)  28 , and the material is further sheared/reduced in a conventional manner into smaller particles by such interaction of the strikers or hammers  26  rotating past and slightly underneath the anvil(s)  28 . 
         [0031]    A conventional grate assembly  30 , such as a screen or grate, is located after the anvil(s)  28  and this grate assembly  30  only allows material of up to a specified size, i.e., determined by the size of the holes or openings  32  provided in the grate assembly  30 , to pass through the grate assembly  30  and onto a discharge conveyer  34 . The material that is reduced, by the material reducing apparatus  2 , to or less than the specified size readily passes through openings  32  in the grate assembly  30  and is deposited on the discharge conveyor  34  located vertically under the grate assembly  30 . The grate assembly  30  in combination with the strikers or hammers  26  produce a conventional shearing action of the material which assists with further reduction of the material. The discharge conveyor  34  then conveys the screened material either to a desired container or merely onto a storage pile. Separated conventional power or drive sources (not shown or described in further detail) provide driving power to both the feed and the discharge conveyors as well other components of the material reducing apparatus  2 . 
         [0032]    As previously mentioned, the feed conveyor  14  extends along the length of the receiving bin  8  and conveys the material that is deposited into the receiving bin  8  toward the rotor  16 . The feed roller  18  is positioned adjacent to the discharge end of the conveyor  14  and a first end of a pair of arms  36  (see  FIG. 3A ) support the feed roller  18  while an opposite end of the pair of arms  36  are pivotally supported by the chassis or frame assembly  4 . The pivot point or location of the pair of arms  36  is designated as element  38  and is located generally forward of a vertical plane P which extends through and bisects the rotor  16  into two halves, i.e., the pivot point  38  is located between the vertical plane P and a rotational axis A of the feed roller  18 . The feed roller  18  is thus simultaneously pivotable toward and away from both the rotor  16  and the discharge end  20  of the feed conveyor  14 . Such pivotal movement of the feed roller  18  is generally indicated by double arrow  39 . 
         [0033]    The pair of arms  36  also support a shroud or hood  40  which encloses a portion of the feed roller  18  and assists with channeling and redirecting all of initially impacted material toward the anvil(s)  28  where such material may be further reduced by a shearing action between the strikers or hammers  26  and the anvil(s)  28 . A drive mechanism  42  for the feed roller  18  may either by carried by the chassis or frame assembly  4  or is preferably mounted to the arms  36  and provides additional weight for biasing the feed roller  18  downwardly toward the feed conveyer  14  as this generally assists with holding down the material to be reduced as such material is being impacted by the strikers or hammers  26  of the rotor  16 . The exterior surface of the feed roller  18  typically has a plurality of nubs or other protrusions  44  which provide a gripping action that assists with conveying the material as the feed roller  18  normally rotates in its forward feed direction. 
         [0034]    The weight of the feed roller  18 , the drive mechanism  42 , the arms  36  and the associated components mounted to the arms  36  along with the rotation of the feed roller  18  assist with forcing the material under the feed roller  18  where such material is initially crushed/compacted between the feed roller  18  and the feed conveyor  14  as the material is continuously fed to the rotor  16 . Normally the arms  36  of the feed roller  18  are at least hydraulically actuated by a pair of hydraulic feed roller actuators  46  to assist with raising and lowering the feed roller  18  away from and toward the feed conveyer  14 . The pair of hydraulic feed roller actuators  46  respectively couple the chassis or frame assembly  4  to the pair of arms  36  to facilitated pivoting movement of the feed roller  18  about its pivot point  38 . The main control system  22  controls operation of the pair of hydraulic feed roller actuators  46  to allow infinite adjustment of the downward pressure that the feed roller  18  can exert on the material to be reduced. 
         [0035]    The main control system  22  controls the feed roller  18  so that it rotates at a rate such that its peripheral speed is either the same as or greater than a travel speed or rate of the feed conveyor  14 . When the feed roller  18  rotates at a higher rotational speed, any material that may be piled high in the receiving bin  8 t e.g., tree, branches, limbs, brush, pallets, etc., is pushed down and into the entrance of the rotor  16  at a more rapid rate than the conveyor speed  14 . This speed difference tends to relieve any congestion at the entrance as long as the material is rapidly cleared away from the entrance to the rotor  16  which is normally accomplished by the rotor  16  rotating at a speed of between 1,000-1,800 rpms, for example. 
         [0036]    As is conventional in the art, a periphery of the rotor  16  has a plurality of spaced apart striker or hammer support blocks  48  mounted to the exterior surface of the rotor and each striker or hammer support block  48  supports a replaceable striker or hammer  26 . Typically, the striker or hammer support blocks  48 , e.g., about 24 striker or hammer support blocks, are strategically arranged, e.g., in an offset helix layout, for maximum grinding efficiency. Each striker or hammer support block  48  supports a striker or hammer  26  to the rotor  16  in a conventional manner, via at least one bolt for example, such that the strikers or hammers  26  rotate at a relatively high rate of speed for impact against the material that is being conveyed into the rotor  16  by the feed roller  18  and the feed conveyor  14 . As noted above, a conventional engine  24  drives the rotor  16  in an upward rotational direction, as indicated by arrow  21 . Since the rotor  16  is driven at a much higher rotational speed than both the feed roller  18  and the feed conveyer  14 , the strikers or hammers  26  effectively reduce the material by an impact cutting action. The particles thus reduced by the strikers or hammers  26  are propelled and redirected by the shroud or hood  40  toward the anvil(s)  28 . The particles then impact against the anvil(s)  28  which, in combination with the striker or hammer  26 , further reduce the particles through shear cutting action. 
         [0037]    The anvil(s)  28  is fixedly mounted to a portion of a pivotal clamshell assembly  50  which is pivotal relative to a remainder of the chassis or frame assembly  4  to facilitated maintenance and/or servicing of the internal components. As a result of such arrangement, the anvil(s)  28  is fixedly mounted to cooperate with the strikers or hammers  26 , during operation, and shear or reduce the material. The interaction of the strikers or hammers  26  with the anvil(s)  28  typically shear the material, that was initially partially reduced by impact with the strikers or hammers  26 , to further reduce the material to a size that will readily pass through the openings in the grate assembly  30 . It is to be appreciated that the openings  32  in the grate assembly  30  can have any desired size so that the material can be reduced to anywhere from a course particle end product to a more uniform very fine end product. 
         [0038]    The grate assembly  30  generally has a curved profile, which closely conforms to the rotational path of the rotor, and has a plurality of openings therein. A first end of the grate assembly  30  is mounted adjacent the anvil(s)  28  and receives the material as such material is reduced by the shearing action. The material that is substantially reduced but still too large to readily pass through the openings  32  in the grate assembly  30  will be forced by the strikers or hammers  26  against the grate (located in close proximity to the rotor teeth) to further break up the material typically to a size that will pass through the openings. As will be noted from  FIGS. 5A-5C , the grate assembly  30  generally extends from the anvil(s)  28  around the periphery of the rotor to the position adjacent the discharge end  20  of the conveyor  14 . The material passing through the grate assembly  30 , at any point between the anvil(s)  28  and the discharge end of the conveyor  14 , is normally deposited on the discharge conveyor  34  for transfer. 
         [0039]    The grate assembly  30  generally comprises two mating sections  60 ,  62  which, when mated together, form the grate assembly  30  which extends from the anvil(s)  28  around the periphery of the rotor  16  to the position adjacent the discharge end  20  of the conveyor  14 . The upper section  60  of the grate assembly  30  is normally pivotally connected, at pivot point  64 , to the chassis or frame assembly  4  to allow the upper section  60  of the grate to be pivoted radially away from the rotating strikers or hammers  26  and the rotor  16  in the event that a hard material or metal is in the process of being reduced. The upper section  60  is coupled to a high speed release device  78  which rapidly, e.g., within less than about 200 milliseconds, moves/pivots the upper section  60  of the screen assembly  30 , about its pivot point  64 , to adequately space the screen or grate  104  of the upper section  60  away from the strikers or hammers  26  of the rotor  16  and prevent any damage from occurring to the internal components of the material reducing apparatus  2 . A further discussion concerning operation of the high speed release device  78  will follow below. 
         [0040]    The lower section  62  of the grate assembly  30  is supported, in normally a fixed manner, adjacent the strikers or hammers  26  of the rotor  16 . However, a number of shear pins  68  connect the lower section  62  to the chassis or frame assembly  4  so that in the event that the lower section  62 , for some reason, is impacted significantly by a hard material, one or more of the shear pins  68  will shear away, in a conventional manner, and allow the lower section  62  to pivot or fall, due to gravity, away from the rotor  16 . A hook or stop feature  66  is provided so as to prevent the lower section  62  from falling too far away from the rotor  16  and inadvertently causing damage to the lower section  62 . This break away arrangement thus minimizes the amount of damage which may otherwise occur to the internal components of the material reducing apparatus  2 . 
         [0041]    Instead of the release device  78  for the uppergrate assembly  60 , the upper grate assembly  60  may be mounted so as break away when subjected to a significant impact, e.g., at least one shear pin (not shown) may be provided for retaining the upper grate assembly  60  in a normally fixed operational position. In the event that the upper grate assembly  60  is struck by a relatively hard material, then such impact against the upper grate assembly  60  causes the shear pins, which retains the upper grate assembly  60  in a fixed position, to shear or break and minimize damage to the internal components. This safety feature generally minimizes undesired jamming or significant damage to the internal components, such as the rotor  16 , the strikers or hammers  26 , the striker or hammer support blocks  48  and/or the anvil(s)  28  during operation. 
         [0042]    Alternatively, instead of having a substantially fixed anvil(s)  28 , the anvil(s)  28  may be mounted so as break away along with the upper grate assembly  60  when subjected to a significant impact, e.g., at least one shear pin (not shown) may be provided for retaining the anvil(s)  28  and the upper grate assembly  60  in a fixed operational position. That is, both the anvil(s)  28  and the upper grate assembly  60  are mounted so as to shear one or more pivot pins, when subjected to a significant impact, and pivot about a pivot axis or point  64 . As a result of such arrangement, in the event that the anvil(s)  28  and/or the upper grate assembly  60  is struck by a relatively hard material that is not readily shearable by the strikers or hammers  26  and the anvil(s)  28 , then such impact against the anvil(s)  28  causes the shear pins, which retains the anvil(s)  28  and the upper grate assembly  60  in a fixed position, to shear or break and minimize damage to the internal components. This safety feature generally prevents undesired jamming or significant damage to the internal components, such as the rotor  16 , the strikers or hammers  26 , the striker or hammer support blocks  48  and/or the anvil(s)  28  during operation. 
         [0043]    The shaft  70  of the rotor  16  is provided with an accelerometer  76  (see  FIG. 4 ) which is mounted to a bearing housing  72  of the shaft  70  supporting the rotor  16 . The accelerometer  76  detects the impact of the strikers or hammers  26  with any hard material or object, such as metal, e.g., and the vibrations transmitted to the rotor  16  and the shaft  70  caused by the strikers or the hammers  26  impacting against a hard material. Depending upon the sensitivity of the accelerometer  76 , the accelerometer  76  can be adjusted to detect contract of the strikers or hammers  26  with virtually any material having a specific hardness. When the accelerometer  76  detects such contact, the accelerometer  76  generates an output signal which is sent to the main control system  22  for evaluation. 
         [0044]    In the event that the main control system  22  determines that the strikers or hammers  26  contacted a material having a specific hardness (see  FIG. 5A ), e.g., the detected vibration is above a certain level and/or the rotor  16  experiences a specified load, the main control system  22  immediately sends a signal to reverse the rotational direction of the feed roller  18  so that the feed roller  18  immediately rotates in an opposite rotational direction, i.e., rotates in a direction which withdraws the material from the rotational path of the rotor  16  (see  FIG. 5B ). The rotational direction of the feed conveyer may also be automatically reversed as shown in  FIG. 5B . 
         [0045]    In combination with such reversal motion of rotational direction of the feed roller  18 , the control system  22  also slows down the engine  24  which drives the rotor  16 , or may possibly completely stop rotation of the rotor  16 . Once this occurs, an operator can then shut down any other operating components and inspect the material reducing apparatus  2  and undertake any necessary corrective action, e.g., remove any metal or other hard material from the material reducing apparatus  2  before such hard material can cause any damage to the internal components of the material reducing apparatus  2 . 
         [0046]    In the event that multiple signals are detected by the accelerometer  76  within a short duration of time, the main control system  22  can undertake more drastic corrective action such as (see  FIG. 5C ), in addition to reversing the rotational direction of the feed roller  18  and reducing the rotational speed of the rotor  161  the control system  22  can also hydraulically actuate and pivot the upper grate assembly  60  radially away from the rotation path of the strikers or hammers  26 . This is accomplished by very quickly actuating the release device(s)  78  to move the upper grate assembly  60  radially away from the rotor  16  within a response time of about 200 milliseconds or less and most preferably moving the upper grate assembly  60  radially away from the rotor  16  within a response time of about 20 to 30 milliseconds following generation of the signal by the accelerometer  76 . 
         [0047]    As can be seen in  FIG. 6 , a hydraulic pump  80  operates when the material reducing apparatus  2  is initially started. This pump  80  pumps hydraulic fluid from a sump  82  to a release manifold  84  where the supplied hydraulic fluid is stored in a primary accumulator  86  as potential energy for actuating the release device  78 . When a sufficiently large “hard” piece of material, such as metal, contacts a striker(s) or hammer(s)  26  of the rotor  16 , this vibration generated by such contact travels through the rotor  16  and the shaft  70  to the accelerometer  76  where the vibration is detected and measured. The accelerometer  76  will, in turn, generate a signal indicative of the detected vibration(s) and transmit this signal to the control system  22  where the signal is analyzed, in a conventional manner, to determine the potential size and/or type of material which was contacted by the striker(s) or the hammer(s)  26  or the rotor  16 . If the received signal is determined to be too high, e.g., above a desired threshold, then the control system  22  determines that the striker(s) or the hammer(s)  26  contacted a “large” piece of hard material or metal M and immediately sends a signal to the release manifold  84 . Through internal valving, not shown in detail, the release manifold  84  releases the stored hydraulic fluid stored within the primary accumulator  86  and this energy is rapidly conveyed to an input side  88  of one or more cylinders  90  of the release device  78  which rapidly bias the respective internal piston  92  away from the pivotal upper grate assembly  60 . As the upper grate assembly  60  is respectively connected to the internal pistons  92  via a linkage arm  94 , such movement also causes the upper grate assembly  60  to be carried away from the rotating path of the rotor  16 . The entire release operation, which sufficiently spaces the upper grate assembly  60  radially away from the rotating path of the rotor  16  by at least a few inches or so, occurs within about 170 milliseconds. It is to be appreciated that the upper grate  60  assembly must be adequately spaced from the rotating path of the rotor  16  so as to allow sufficient clearance for the large “hard” piece of material M to pass between the upper grate assembly  130  and the rotor  16 , without causing any significant damage to the internal components of the material reducing apparatus  2 , and be ejected onto the discharge conveyor  34 . 
         [0048]    While the hydraulic fluid is rapidly conveyed to the input side  88  of the release cylinders  90  from the primary accumulator  86 , hydraulic fluid is also rapidly conveyed from an opposite side  96  of the release cylinders  90 , via internal valving not shown in detail, and this hydraulic fluid is collected and stored in a restoring accumulator  98  so that the large rush of hydraulic fluid, from the release cylinders  90 , is adequately controlled. The hydraulic fluid which collects and is stored in the restoring accumulator  98  can be utilized to rapidly return the upper grate assembly  60  to its normal operational position adjacent the rotating path of the rotor  16  or, alternatively, may be subsequently dumped into the sump  82 . 
         [0049]    To facilitate such rapid actuation of the upper grate assembly  60 , the primary accumulator  86  is typically able to supply of about 30 gallons per second of the hydraulic fluid to the release device  78 . In addition, restoring accumulator  98  is generally able to accommodate removing of about 150 gallons per second of hydraulic fluid from the opposite side of the release cylinders  90 . By transferring such high volumes or hydraulic fluid to and removing hydraulic fluid from the release device  78 , the release device  78  responds very rapidly and is thus able to substantially instantaneously pivot the uppergate assembly  60  about its pivot point  64  to sufficiently space the upper grate assembly  60  away from the strikers or hammers  26  and thereby minimize the possibility of any damage occurring to the internal components as a result of a hard material or metal being reduced within the material reducing apparatus  2 . 
         [0050]    As can be seen in  FIGS. 7-7B , the upper grate assembly  60  normally has a number of bolts  102  which secure the screen or grate  104  (e.g., 1 to 1½ inch thick plate metal which has a plurality of rectangular holes  108  burnt therethrough and bent into a generally curved profile) to the upper grate assembly  60 . Typically eight bolts  102  are utilized to secure the screen or grate  104  to the upper grate assembly  60  and a mating horseshoe shaped protective shrouds  106  are utilized to protect the heads of the bolts  102  as well as prevent rotation thereof while also preventing premature wear of the bolt heads. 
         [0051]    The upward cutting action of the strikers or hammers  26  induces a flow pattern that is beneficial for discharging the reduced material through the grate assembly  30 . The strikers or hammers  26 , as they impact and then sever the material being fed by the conveyor  14  and the feed roller  18 , is normally propelled upwardly along the shroud or hood  40  and thus essentially will be flowing in an air flow through the grate assembly  30 . 
         [0052]    Since certain changes may be made in the above described failsafe system for a material reducing apparatus or machine, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.