Abstract:
A mobile shredder comprises a truck having a truck body defining an enclosure and including a partition in the enclosure that divides a storage volume from the remainder of the enclosure for storage of shredded material in the storage volume, a single-shaft rotary shredder mounted in the enclosure outside the storage volume, the rotary shredder comprising a rotor having cutters rigidly mounted thereon, a bin lift and dump mechanism operable to transport material to be shredded from outside to inside the enclosure so as to deliver material to the rotary shredder, and a discharge conveyor operable to transport shredded material from the rotary shredder through the partition to the storage volume. The floor of the storage volume can comprise a walking floor, and the enclosure can have rear doors that are openable to allow shredded material to be discharged through the open rear doors when the walking floor is operated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to mobile shredders for shredding documents and other materials at customer sites.  
         [0002]     With the increasing incidence of identity theft and other misuse of private or proprietary information, the desirability and necessity of protecting such information is becoming increasingly important. In recent years, laws have been passed in various jurisdictions regulating the use and protection by businesses, health care providers, and other entities, of sensitive or private information on customers, patients, and the like. At the federal level in the United States, the HIPAA and Gramm-Leach-Bliley laws require specific measures, such as document shredding, in order to comply with the laws&#39; provisions for protecting certain designated types of information.  
         [0003]     Discarding of sensitive documents in an unshredded state is risky because identity thieves, investigative journalists, and other unscrupulous individuals often engage in “dumpster diving” to retrieve documents from trash dumpsters or garbage cans. Accordingly, the demand for document shredding has surged. For entities having a small amount of documents requiring shredding, personal-sized shredders that are purchased or leased may be adequate. However, for many businesses and other organizations, the large volume of documents and other materials to be shredded makes such an approach impractical. Accordingly, document-shredding service providers have arisen to meet the increasing demand for large-volume shredding.  
         [0004]     In the early history of document-shredding services, typically the documents to be shredded were picked up by the service provider and transported to a central facility for shredding. This form of shredding service still represents the prevalent one today. Central document shredding certainly can accomplish its intended purpose, if carried out properly. The drawbacks to central shredding include the necessity of strictly safeguarding the documents against theft or unauthorized access throughout the entire chain of custody from the time the documents are picked up from the customer to the time they are shredded, the necessity of properly documenting the chain of custody and the measures taken to safeguard the documents, and the fact that the users cannot independently verify that the documents were in fact shredded. This latter factor can give rise to a general sense of unease among some users of central shredding services.  
         [0005]     Consequently, there is now a trend toward on-site document shredding using mobile shredders. A mobile shredder generally consists of a truck having a shredder mounted therein, and a storage volume for storing the shredded material. Typically, the users place the materials to be shredded in bins or “toters” that usually have wheels for rolling the bins to a location for pickup, such as a curbside location on a street. Mobile shredders typically have some type of bin lift and dump mechanism, such as those commonly employed on garbage collection trucks, for lifting the bins and emptying them into the shredder.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The present invention is aimed at improving upon various aspects of mobile shredders. In accordance with one embodiment of the invention, a mobile shredder for shredding documents and other materials comprises a truck having a truck body defining an enclosure and including a partition in the enclosure that divides a storage volume from the remainder of the enclosure for storage of shredded material in the storage volume, a single-shaft rotary shredder mounted in the enclosure outside the storage volume, the rotary shredder comprising a rotor having cutters rigidly mounted thereon, a bin lift and dump mechanism operable to transport material to be shredded from outside to inside the enclosure so as to deliver material to the rotary shredder, and a discharge conveyor operable to transport shredded material from the rotary shredder through the partition to the storage volume. In a preferred embodiment, the floor of the storage volume comprises a walking floor, and the enclosure has rear doors that are openable to allow shredded material to be discharged from the storage volume through the open rear doors when the walking floor is operated.  
         [0007]     In another preferred embodiment, a controller is operatively coupled to the walking floor and to the discharge conveyor, and is operable to control compaction of the shredded material in the storage volume by alternately operating in a first mode wherein the discharge conveyor is operated and the walking floor is stationary, and a second mode wherein the discharge conveyor is operated and the walking floor is operated to carry shredded material away from the discharge conveyor.  
         [0008]     The bin lift and dump mechanism in one embodiment of the invention includes a bin-engaging member structured and arranged to grasp a bin that contains material to be shredded, and a powered lift device coupled with the bin-engaging member and operable to lift the bin-engaging member from a first position generally vertically upward to a second position that places the bin in a generally upright orientation adjacent the rotary shredder, and operable then to move the bin-engaging member to a third position that tips the bin so as to dump the material to be shredded from the bin into the rotary shredder. Advantageously, the mobile shredder includes a load sensor associated with the rotary shredder and operable to provide a signal indicative of a load level of the shredder, and the bin lift and dump mechanism further comprises a controller operatively coupled with the load sensor and with the lift device of the lift and dump mechanism. The controller is operable to automatically operate the lift device through a cycle from the second position to the third position and then back to the second position, and is further operable to suspend the cycle to prevent the bin from being emptied into the rotary shredder when the load level indicated by the load sensor exceeds a predetermined limit and to resume the cycle to empty the bin into the rotary shredder when the load level falls below the limit.  
         [0009]     In one preferred embodiment, the rotary shredder has a single rotor having an outer surface formed generally as a surface of revolution about an axis, the shredder further including a counter knife arranged in opposition to the outer surface of the rotor, a space being defined between the counter knife and the outer surface of the rotor for passage of material being shredded, and a plurality of cutters rigidly affixed to the outer surface of the rotor, the cutters and counter knife cooperating to shred material. The rotary shredder also advantageously includes an infeed hopper disposed for receiving material to be shredded, and a hydraulic ram positioned beneath the hopper and operable to advance material to be shredded into the space between the rotor and counter knife.  
         [0010]     The rotary shredder can be driven in various ways. In one embodiment, a hydraulic drive is coupled to the rotor of the shredder and is operable to receive pressurized hydraulic fluid and drive the rotor, and the mobile shredder includes a hydraulic pump that supplies pressurized hydraulic fluid to the hydraulic ram and to the hydraulic drive of the shredder. The truck comprises an engine including a drive train, and a power takeoff unit is coupled between the drive train and the hydraulic pump for driving the hydraulic pump. The mobile shredder includes a programmed controller operable to control operation of the hydraulic pump and associated valves, and a sensor system in communication with the controller and operable to monitor a plurality of operating parameters of the rotary shredder and truck, the controller being programmed to provide an alarm indication when one or more of the operating parameters is outside a predetermined normal range. Preferably, the controller is operable to provide a relatively low level of alarm when the sensor system indicates an abnormal condition of the rotary shredder or associated components, and to provide a relatively higher level of alarm when the sensor system indicates an abnormal condition of the truck.  
         [0011]     The sensor system can monitor a level of fuel remaining in a fuel tank for the engine, and the controller can provide a first type of alarm indication when the level of fuel falls below a predetermined first value (e.g., one-eighth of a tank). For example, the first type of alarm indication can be effected by causing the vehicle horn to sound intermittently with a relatively low frequency (e.g., the horn can sound for half a second, once every five seconds). The controller can provide a second type of alarm indication (e.g., the horn can sound for half a second, once every second) when the level of fuel falls below a predetermined second value (e.g., one-sixteenth of a tank). Alternatively or additionally, the controller can be operable to shut down the engine when the level of fuel falls below a predetermined level so as to avoid running out of fuel; this is particularly advantageous for diesel trucks wherein running out of fuel is a major event.  
         [0012]     The power takeoff unit preferably is selectively engageable with and disengageable from the drive train, and the mobile shredder preferably includes a programmed controller operable to control operation of the hydraulic pump and to control engagement and disengagement of the power takeoff unit with the drive train. The mobile shredder can include various sensors for monitoring conditions and detecting when it is safe or unsafe to engage or disengage the power takeoff unit or to shut down the hydraulic pump. For example, in one embodiment, an engine RPM sensor can measure engine RPMs, and the controller can prevent the power takeoff unit from being engaged with or disengaged from the drive train when the engine RPMs are above a predetermined limit. It is also possible to employ a transmission sensor to detect whether or not a transmission of the drive train is in a neutral gear, and the controller can prevent the power takeoff unit from being engaged with the drive train unless the transmission is in a neutral gear.  
         [0013]     In another embodiment, the mobile shredder includes a pump sensor operable to measure a load level of the hydraulic pump, and the controller is operable to prevent the hydraulic pump from being shut down when the load level measured by the pump sensor is above a predetermined limit.  
         [0014]     In accordance with a further aspect of the invention, a mobile shredder includes a bin lift and dump mechanism operable to lift a bin that contains material to be shredded and to tip the bin to dump the material into the rotary shredder, the bin lift and dump mechanism comprising a lift device traversable upwardly and downwardly within a channel defined in one side of the truck body, the channel being open along an outer surface of the one side of the truck body. A movable door is connected to the truck body and is movable between a closed position closing the channel and an open position permitting access to the channel so that a bin can be lifted by the bin lift and dump mechanism. The mobile shredder includes an actuator coupled with the door for opening and closing the door.  
         [0015]     Preferably, a door sensor system is operable to detect whether the door is in the open position or in the closed position, and a programmed controller in communication with the door sensor system is operable to control operation of the rotary shredder and to control operation of the actuator for the door.  
         [0016]     In another embodiment, a programmed controller is operable to control operation of the rotary shredder, and an operator control panel is coupled with the controller and includes a plurality of operator controls manipulable by an operator, the operator controls including at least a start control for initiating operation of the bin lift and dump mechanism. Preferably, the controller is operable to operate the bin lift and dump mechanism in either an automatic mode wherein the bin lift and dump mechanism goes through a complete cycle of lifting a bin, dumping the material from the bin into the rotary shredder, and lowering the bin back down without continuous operator intervention, or a manual mode allowing an operator to control operation of the bin lift and dump mechanism. The controller preferably is programmed to operate in the automatic mode upon an operator continuously depressing the start control for at least a predetermined minimum amount of time.  
         [0017]     In yet another aspect of the invention, a mobile shredder includes a sensor system comprising sensors for measuring a plurality of operating parameters associated with the mobile shredder, a programmed controller coupled with the sensor system and operable to control operation of the rotary shredder and the bin lift and dump mechanism, an operator interface coupled with the controller and including operator controls manipulable by an operator to cause the controller to execute routines programmed in the controller, and a visual display for displaying information for an operator. The controller includes a memory storing an event history file and is operable to record significant events in the history of operation of the mobile shredder in the event history file, and the operator interface is operable to display the event history file on the visual display. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       [0018]     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:  
         [0019]      FIG. 1  is a top elevation of a mobile shredder in accordance with one embodiment of the invention, partially broken away to show internal features of the mobile shredder;  
         [0020]      FIG. 2  is a road-side elevation of the mobile shredder, along line  2 - 2  in  FIG. 1 ;  
         [0021]      FIG. 3  is a curb-side elevation of the mobile shredder, along line  3 - 3  in  FIG. 1 ;  
         [0022]      FIG. 4  is a perspective view of the mobile shredder, generally from curb-side;  
         [0023]      FIG. 5  is a view along line  5 - 5  in  FIG. 3 , showing the bin lift and dump mechanism being operated through a lift and dump cycle;  
         [0024]      FIG. 6  is a detailed perspective view of the bin-engaging part of the bin lift and dump mechanism;  
         [0025]      FIG. 7A  is a perspective view of the bin lift and dump mechanism, showing a bin being lifted from ground level to a raised level;  
         [0026]      FIG. 7B  is a perspective view showing the bin being tipped to dump its contents into the shredder;  
         [0027]      FIG. 8  is a cross-sectional view along line  8 - 8  in  FIG. 5 , showing the infeed hopper, ram, shredder, and discharge auger in accordance with one embodiment of the invention;  
         [0028]      FIG. 9  is a perspective view showing details of the movable door for closing the channel of the bin lift and dump mechanism;  
         [0029]      FIG. 10  is a rear perspective view of the mobile shredder, showing the rear doors open in preparation for discharging shredded material from the storage volume;  
         [0030]      FIG. 11  is a top elevation of the walking floor, with the slats partially broken away to show the hydraulic drive arrangement;  
         [0031]      FIG. 12  is a cross-sectional view along line  12 - 12  in  FIG. 11 ;  
         [0032]      FIG. 13  is a perspective view of a clamp member for one group of slats of the walking floor;  
         [0033]      FIG. 14  is a schematic diagram of the hydraulic system of the mobile shredder;  
         [0034]      FIG. 15A  depicts the controls panel for the mobile shredder;  
         [0035]      FIG. 15B  shows a portion of a touch screen of the controls panel;  
         [0036]      FIG. 16  depicts a main maintenance manual menu displayed on the touch screen;  
         [0037]      FIG. 17  depicts a main troubleshooting menu displayed on the touch screen when selected from the main menu of  FIG. 15A /B;  
         [0038]      FIG. 18  depicts a mobile shredder inputs and outputs page displayed on the touch screen when selected from the main troubleshooting menu of  FIG. 17 ;  
         [0039]      FIG. 19  shows a job setup page displayed on the touch screen when selected from the main menu of  FIG. 15A /B;  
         [0040]      FIG. 20  depicts an event history page displayed on the touch screen when selected from the main troubleshooting menu of  FIG. 17 ; and  
         [0041]      FIG. 21  shows a machine operation page displayed on the touch screen when selected from the main menu of  FIG. 15A /B. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]     The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.  
         [0000]     Overall System Description  
         [0043]     A mobile shredder  100  in accordance with one embodiment of the invention is depicted in  FIGS. 1-4 . The mobile shredder  100  comprises a truck having a cab  102  for accommodating a driver and passenger, and a truck body  104  of generally box-shaped construction. The truck body has a floor  106 , a road-side wall  108 , a curb-side wall  110 , a ceiling  112 , a front wall  114 , and a pair of rear doors  116 . The walls  108 ,  110 ,  114  and ceiling  112  and rear doors  116  can comprise various materials, but advantageously comprise a fiber-reinforced polymer (FRP) material such as fiber glass or the like, for high strength-to-weight ratio.  
         [0044]     The truck body defines an interior space that is subdivided into two portions by a partition  118  that extends between the two side walls  108 ,  110  at a location axially spaced behind the front wall  114 . As further described below, the space between the partition  118  and the rear doors  116  defines a storage volume  120  for storage of shredded material. The space forward of the partition defines a location for the primary working components of the mobile shredder.  
         [0045]     Thus, in the forward space of the truck body, a single-shaft rotary shredder  130  is mounted on the floor  106 . The structure and operation of the rotary shredder  130  are described in detail below in connection with  FIG. 8 , but for present purposes it is sufficient to note that the rotary shredder receives material to be shredded, shreds the material into small flake-like pieces, and passes the shredded material to a discharge conveyor  140 , which advantageously can comprise an auger as shown. The discharge conveyor is located forward of the partition  118  and is arranged to convey the shredded material through an opening in the partition into the storage volume  120  as shown in  FIG. 2 .  
         [0046]     Also located forward of the partition  118  is a bin lift and dump mechanism  150  operable to lift a bin B containing material to be shredded and to tip the bin to dump the contents of the bin into the rotary shredder  130 . The structure and operation of the bin lift and dump mechanism  150  are described below in connection with  FIGS. 5, 6 ,  7 A, and  7 B.  
         [0047]     The floor of the storage volume  120 , in one embodiment of the invention, comprises a “live” or “walking” floor  180  as further described below in connection with  FIGS. 11 through 13 . The walking floor  180  is operable to discharge the shredded material out the rear end of the storage volume  120  when the rear doors  116  are opened.  
         [0000]     Single-Shaft Rotary Shredder  
         [0048]     The single-shaft rotary shredder  130  is generally of the type described in U.S. Patent Application Publication No. US 2004/0118958A1 and in European Patent EP 419 919 B1, the entire disclosures of which are incorporated herein by reference. With primary reference to  FIGS. 1 and 8 , the single-shaft shredder comprises a rotor  131  that carries cutters as further described below, and a counter knife  132  that works in conjunction with the rotor to grind up or shred material fed into the space where the rotor and counter knife converge. The counter knife is generally stationary, although it can be flexibly supported so that it can “give” to some extent when a very hard object (e.g., a piece of metal or a rock) is inadvertently fed into the space between the rotor and counter knife, the flexibility thereby tending to prevent damage to the machine. The ground up or shredded material exits through a screen  133  having apertures suitably sized to regulate the size of the pieces of shredded material. The shredder  130  also includes a hopper  134  for receiving material to be shredded, and a hydraulic ram  135  or the like for feeding the material into the space between the rotor and counter knife.  
         [0049]     The rotor  131  is generally cylindrical in form, but the outer surface of the rotor defines a series of circumferential ridges or ribs (not shown) that project radially outwardly. Each rib can have opposite side faces that are conical and oppositely inclined to the rotor axis, and a radially outermost surface that is parallel to the rotor axis. Thus, in the axial direction along the rotor, the outer surface defines a series of alternating peaks (where the ribs are) and valleys between the peaks. The counter knife  132  has a series of teeth (not shown) that are axially aligned with the valleys between the ribs of the rotor, there being one such tooth for every valley in the rotor surface. Correspondingly, there are V-shaped recesses between the teeth of the counter knife that are axially aligned with the ribs of the rotor; thus, the rotor surface and the counter knife are complementary in configuration.  
         [0050]     Rigidly mounted to the outer surface of the rotor  131  are a plurality of cutters  136  that are axially aligned with the ribs and with the V-shaped recesses in the counter knife. Material that is fed into the space between the rotor  131  and counter knife  132  is cut by the cutters  136  as they mesh with the counter knife. Various configurations can be used for the rotor surface, the cutters, and the counter knife, depending on the nature of the materials to be shredded. Where plastic film may constitute some of the materials to be shredded, the shredder design described in the aforementioned U.S. Patent Application Publication No. 2004/0118958A1, having both V-shaped cutters and flat cutters, is particularly advantageous. Where the materials to be shredded constitute substantially entirely paper documents and the like, alternative designs such as that described in the aforementioned EP 419 919B1 can be used.  
         [0051]     In operation, materials to be shredded are dumped into the infeed hopper  134  of the rotary shredder. The hydraulic ram  135  is operated to push the materials into the space between the rotor  131  and counter knife  132 . The materials are shredded and pass through the screen  133  into the discharge conveyor  140 .  
         [0052]     The rotary shredder  130  is hydraulically driven. A hydraulic drive  137  receives pressurized hydraulic fluid from a hydraulic pump  190  ( FIG. 14 ) and drives the rotor  131 . The hydraulic ram  135  also is driven by pressurized hydraulic fluid from the pump  190 . The supply of hydraulic fluid to the hydraulic drive  137  and hydraulic ram  135  is controlled by suitable electrically controlled valves  202  ( FIG. 14 ) or the like, the operation of which is controlled by a computer controller as further described below.  
         [0000]     Discharge Conveyor  
         [0053]     The discharge conveyor  140  is best seen in  FIG. 8 . It comprises an auger  142  having helical flights  144  mounted on a central shaft  146 . The auger  142  is disposed within a cylindrical casing  147  that defines an opening therein for receiving shredded material from the rotary shredder. The auger is driven by a hydraulic drive  148  that receives pressurized hydraulic fluid from the pump  190 ; suitable valves  202  ( FIG. 14 ) are employed for controlling the supply of hydraulic fluid to the drive  148 . The cylindrical casing  147  communicates with an opening through the partition  118  so that shredded material is fed by the auger  142  through the opening into the storage volume  120  of the truck.  
         [0000]     Bin Lift and Dump Mechanism  
         [0054]     The bin lift and dump mechanism  150  is now described with primary reference to  FIGS. 5, 6 ,  7 A, and  7 B. The bin lift and dump mechanism comprises a bin-engaging member  151  structured and arranged to grasp a bin B that contains material to be shredded, and a powered lift device coupled with the bin-engaging member  151  and operable to lift the bin-engaging member from a first position (e.g., ground level as shown in solid lines in  FIGS. 5 and 7 A) generally vertically upward to a second position (the middle position shown in phantom lines in  FIG. 5 ) that places the bin in a generally upright orientation adjacent the rotary shredder  130 , and operable then to move the bin-engaging member  151  to a third position (the top position in  FIG. 5 ) that tips the bin so as to dump the material to be shredded from the bin into the rotary shredder.  
         [0055]     As best seen in  FIG. 6 , the powered lift device includes a pair of spaced chains  152  arranged in vertically extending loops about drive sprockets  153  and idler sprockets  154  ( FIG. 7A ). A drive shaft  155  connects the two drive sprockets  153  of the respective chains  152 , and the drive shaft is coupled to a hydraulic drive  156  that receives pressurized hydraulic fluid from the hydraulic pump  190  ( FIG. 14 ) for driving the shaft and hence the drive sprockets so that the chains rotate. A transverse rod  157  is attached at its opposite ends to the chains  152 . Adjacent each end of the rod  157 , the lower end of a link arm  158  is pivotally mounted to the rod; the upper end of each link arm  158  is pivotally connected to the lower end of a generally L-shaped link arm  159 . The upper ends of the L-shaped link arms  159  have rollers  160  mounted thereon, and the rollers are arranged to roll along respective vertical track members  161  each located adjacent one of the chains  152 . Rollers  160  are also affixed to the L-shaped link arms  159  at positions proximate the lower ends of the arms, for rolling along the track members  161 . The vertex of each L-shaped link arm  159  is non-pivotally attached to a respective end of a transversely extending mounting portion  162  of the bin-engaging member  151  at an upper end of the bin-engaging member.  
         [0056]     The track members  161  define upper stops (not shown) that limit how far the upper rollers  160  of the L-shaped link arms can travel vertically upward. When the hydraulic drive  156  is operated to drive the chains  152  so as to lift the transverse rod  157  vertically upward, the link arms  158  push the L-shaped link arms  159  upward, and both pairs of rollers  160  roll along the track members until the upper pair of rollers are stopped from further upward travel by the stops. However, the transverse rod  157  can continue to travel upwardly; this further upward travel is accommodated by rotation of the L-shaped link arms  159  about the upper pair of rollers  160 , which causes the lower pair of rollers  160  to leave contact with the track members  161 . This rotation of the L-shaped link arms  159  about the upper rollers  160  causes the bin-engaging member  151  to be pivoted to tip the bin B and dump its contents into the rotary shredder as shown in the top position in  FIG. 5 .  
         [0057]     The lift and dump mechanism  150  is located in an opening or channel  163  in the curb-side wall  110  of the truck body. A movable door  164  is provided for covering the channel  163  when the lift and dump mechanism is not being used, such as when the mobile shredder is traveling on the road. The door  164  is shown in its closed position in solid lines in  FIGS. 1, 3 , and  5 , and is shown in its open position in phantom lines in  FIGS. 1, 3 , and  5 , and in solid lines in  FIGS. 4, 7A ,  7 B, and  9 . The door  164  is supported by arms  165  that are mounted on a rotatable vertical shaft  166  coupled to a rotary pneumatic actuator  167  ( FIG. 9 ) or the like. The shaft  166  and actuator  167  are mounted to the truck body, recessed within the channel  163 . Rotation of the actuator  167  in one direction opens the door  164 , and rotation in the other direction closes the door. Advantageously, a sensor associated with the actuator  167  detects when the door is open or closed, and the computer controller is operable to prevent operation of the rotary shredder unless the door is open.  
         [0058]     The operation of the lift and dump mechanism  150  is also controlled by the computer controller, which regulates operation of the hydraulic drive  156  by controlling suitable electrically controlled valves  202  ( FIG. 14 ) so as to control the supply of hydraulic fluid to the drive. Advantageously, the controller is programmed to control the lift and dump mechanism in such a way as to avoid overloading the rotary shredder  130 . More particularly, the controller is programmed to prevent the lift and dump mechanism from tipping a bin to dump its contents into the rotary shredder whenever a load level of the shredder, as detected by a suitable sensor  138  ( FIG. 14 ), is above a predetermined limit.  
         [0059]     In one embodiment, an operator control panel  170  ( FIG. 15A ) is coupled with the controller and includes a plurality of operator controls manipulable by an operator, the operator controls including a start button  171   a  for initiating operation of the bin lift and dump mechanism. Preferably, the controller is operable to operate the bin lift and dump mechanism in either an automatic mode wherein the bin lift and dump mechanism goes through a complete cycle of lifting a bin, dumping the material from the bin into the rotary shredder, and lowering the bin back down without continuous operator intervention, or a manual mode allowing an operator to control operation of the bin lift and dump mechanism. The controller preferably is programmed to operate in the automatic mode upon an operator continuously depressing the start button  171   a  for at least a predetermined minimum amount of time.  
         [0060]     In an automatic mode cycle, once the start button  171   a  has been depressed for at least the predetermined minimum amount of time, the controller takes over control of the lift and dump mechanism. With reference to  FIG. 5 , the controller then operates the lift and dump mechanism to lift the bin B from ground level up to a raised holding level (middle position in  FIG. 5 ). If the load level of the rotary shredder is above the predetermined limit, the bin is held at this holding level until the load level falls below the limit; the bin is then lifted farther up and tipped to dump its contents into the rotary shredder. The controller then turns the control of the lift and dump mechanism back over to the operator for manual control.  
         [0061]     In the manual or operator-controlled mode of operation, with the bin at the holding level, the start button  171   a  can be depressed to cause the bin to be tilted once again to empty the bin into the shredder. This can be necessary, for example, if some of the contents remain in the bin after the automatic dumping cycle. Alternatively, with the bin at the holding level, the operator can press the stop button  171   b  to cause the bin to be lowered back to the ground.  
         [0062]     The operator control panel  170  preferably is arranged behind a door  172  that can be closed to prevent access to the panel. The door  172  can comprise a flexible material that is foldable and slides in tracks  173  similar to an automobile sun roof. The door can be opened and closed by an electric motor (not shown). In one embodiment, the computer controller is operable to prevent operation of the rotary shredder when the controls door  172  is in the closed position.  
         [0000]     Walking Floor  
         [0063]     The walking floor  180  is now described with primary reference to  FIGS. 11 through 13 . The walking floor comprises a plurality of axially extending, parallel slats arranged in three groups  182   a ,  182   b ,  182   c  that alternate in “a, b, c, a, b, c . . . ” fashion.  
         [0064]     The slats advantageously are generally I-shaped in cross-section, having depending dovetails  183  that are clamped in clamp members  184   a ,  184   b ,  184   c , respectively, for the three groups of slats. All of the first clamp members  184   a  are affixed to a transversely extending support plate  185   a  so they move together as a unit, and likewise the second group of clamp members  184   b  are affixed to support plate  185   b , and the third group of clamp members  184   c  are affixed to support plate  185   c . Thus, each group of slats is independently movable, as a unit. Each group of slats is driven by its own hydraulic cylinder  186   a ,  186   b ,  186   c , respectively, that form a drive unit  187 . Thus, the hydraulic cylinder  186   a  is coupled with the support plate  185   a  for the first group of slats  182   a , and likewise the other two hydraulic cylinders  186   b  and  186   c  are respectively coupled with the support plates  185   b  and  185   c . The hydraulic cylinders are operated in unison so that all of the slats  182   a, b, c  are advanced rearwardly at the same time so as to move the shredded material resting on the walking floor toward the rear of the truck. Then one hydraulic cylinder is operated at a time to slide each group of slats forward; thus, all of the first slats  182   a  are slid forward as shown by the arrows in  FIG. 11 , then all slats  182   b  are slid forward, and finally all slats  182   c  are slid forward. When one group at a time is moved, the pile of shredded material atop the walking floor tends to stay in place because of the friction between the material and the two stationary groups of slats. Thus, the material is “walked” rearwardly to gradually move the shredded material out the open rear doors  116  of the truck.  
         [0000]     Power Takeoff and Hydraulics  
         [0065]      FIG. 14  is a schematic diagram of the hydraulic system of the mobile shredder in accordance with one embodiment of the invention. As noted, a hydraulic pump  190  supplies pressurized hydraulic fluid to various hydraulically driven components of the mobile shredder. A pump sensor  191  monitors a load level of the pump; advantageously, the computer controller is programmed to prevent the pump from being shut down when the load is above a predetermined level. The hydraulic pump is driven by a power takeoff unit  192  that is selectively engageable and disengageable. The power takeoff unit&#39;s engagement with and disengagement from the transmission  194  is controlled by the mobile shredder&#39;s computer controller. A transmission sensor  195  can detect whether or not the transmission is in a neutral gear; advantageously, the controller is programmed to prevent engagement of the power takeoff unit with the transmission if the transmission is not in neutral.  
         [0066]     Hydraulic fluid is contained in a reservoir  198 ; temperature of the hydraulic fluid in the reservoir is monitored by a temperature sensor  199 . The reservoir also includes a breather cap  200  and a fluid level sensor  201 . The hydraulic pump  190  supplies pressurized hydraulic fluid to the rotary shredder drive  137 , to the walking floor drive  187 , to the bin lift and dump drive  156 , to the hydraulic ram  135 , and to the discharge auger drive  148 . The pressurized hydraulic fluid is supplied to these components via a plurality of electrically controllable valves (e.g., spool valves controlled by solenoids or the like), collectively designated by reference number  202 . The valves  202  are coupled with the computer controller, which controls the valves to supply hydraulic fluid or discontinue supply of hydraulic fluid to each of the various components as needed. Hydraulic fluid is returned to the reservoir  198  via an oil filter  204  and a thermal transfer cooler  206 .  
         [0000]     Operator Controls  
         [0067]     The operator controls for the mobile shredder are now described with primary reference to  FIGS. 15A, 15B , and  16 - 21 . As already noted, the mobile shredder includes a controls panel  170 , as depicted in  FIGS. 15A and 15B . The controls panel includes control buttons for controlling the various components of the mobile shredder. The control buttons include: the previously described lift and dump start button  171   a , and a lift and dump stop button  171   b  for interrupting operation of the lift and dump mechanism during an automatic cycle; a walking floor start button  174   a  and a walking floor stop button  174   b ; a total system start button  175   a  and a total system stop button  175   b ; a system reset button  176   a  and an emergency stop button  176   b ; and a rotary shredder start button  177   a  and a rotary shredder stop button  177   b . There are no separate start and stop controls for the discharge auger, as the auger starts and stops with the system, and thus is effectively controlled by the system start and stop buttons  175   a,b . The controls panel also includes a number of gauges for monitoring hydraulic pressure in the various hydraulically driven components, including: a lift and dump pressure gauge  171   c ; a walking floor pressure gauge  174   c ; a total system pressure gauge  175   c , which monitors the hydraulic pressure delivered by the hydraulic pump; a discharge auger pressure gauge  176   c ; a rotary shredder pressure gauge  177   c ; and a hydraulic ram pressure gauge  178   c.    
         [0068]     The controls panel  170  also includes a touch screen  210  operable to display various types of information to an operator and further operable to allow the operator to interact with the computer controller in various ways. The touch screen includes a number of regions  212 ,  214 ,  216 ,  218  that constitute interactive touch control buttons which, when touched, cause the computer controller to execute various tasks. The computer controller is programmed to display text and/or graphics in registration with one or more of the buttons to signify to the operator what operation will be carried out when each button is touched. For example, the touch screen can display a main menu ( FIG. 15B ) on which the button  212  displays the text “Maintenance Manual” (or alternatively displays a graphical icon); when the button  212  is touched on the main menu, the computer controller is caused to display on the touch screen a maintenance manual menu ( FIG. 16 ) allowing the operator to bring up any of various maintenance manuals for the various systems of the mobile shredder; the maintenance manual is stored in a memory device (e.g., a hard disk drive or the like) connected with the computer controller. The maintenance manuals can include digital video clips illustrating various maintenance procedures, in addition to text (in searchable or non-searchable form). The maintenance manual menu can include various buttons or icons for different mobile shredder systems manuals, such as a truck manual icon, a shredder manual icon, a truck body manual icon, and the like.  
         [0069]     The main menu of the touch screen can also display the text “Troubleshooting” or the like in registration with the button  214  such that when the button  214  is touched, the computer controller causes the touch screen to display a troubleshooting menu ( FIG. 17 ) that draws on a knowledge base stored in the memory device connected to the controller so as to provide the operator with information to assist in determining possible causes for various malfunctions of the mobile shredder. The troubleshooting menu can include buttons or icons allowing the operator to display other pages such as an input/output (I/O) page ( FIG. 18 ), an event history page ( FIG. 20 ), a troubleshooting guide (not shown), and the like.  
         [0070]     When the event history icon on the troubleshooting menu of  FIG. 17  is selected, an event history page as shown in  FIG. 20  is displayed on the touch screen  210 . The event history page displays a list of all significant events in the history of the operation of the mobile shredder, as detected by various sensors and as recorded in a memory device connected with the computer controller, along with the date and time of each event. If any alarm was triggered, it is also recorded in the event history file stored in the memory device.  
         [0071]     The main menu can further display the text “Job Setup” or the like in registration with the button  216  such that when the button  216  is touched, the computer controller causes the touch screen to display a job setup menu ( FIG. 19 ) that allows the operator to select, add, delete, and edit various information regarding customers.  
         [0072]     The main menu can also display the text “Machine Operation” or the like in registration with the button  218  so that when the button  218  is touched, the computer controller causes the touch screen to display a machine operation page ( FIG. 21 ) that allows the operator to selectively view text and/or graphics and/or digital video of various aspects of operating the mobile shredder. The machine operation page also displays certain key operating parameters such as hydraulic fluid temperature, system hydraulic fluid pressure, shredder hydraulic fluid pressure, auger hydraulic fluid pressure, machine run hours, shredder or cutter hours, and the like. The machine operation page also includes icons allowing the operator to perform certain operations such as manual ram reversal, manual shredder rotor reversal, reset the cutter hours (e.g., after an overhaul), and printing of a certificate for a customer indicating how much material was shredded, the date and time of shredding, and other information.  
         [0000]     System Alarms  
         [0073]     The computer controller advantageously is programmed to detect, via suitable sensors connected to the controller, various abnormal conditions of the mobile shredder and to initiate different levels of alarm depending on the abnormal condition that is detected. The alarm system advantageously includes relatively low-level alarms for certain conditions and higher-lever alarms for other more-serious conditions. For example, in one embodiment of the invention, the controller is operable to provide a relatively low level of alarm when the sensor system indicates an abnormal condition of the rotary shredder  130  or associated components (shredder drive  137 , hydraulic ram  135 ), and to provide a relatively higher level of alarm when the sensor system indicates an abnormal condition of the truck.  
         [0074]     One type of abnormal truck condition that can generate an alarm is low fuel level. Thus, based on a fuel level sensor, the computer controller can cause a relatively low-level alarm to be given (e.g., by causing the truck&#39;s horn to sound intermittently at a relatively low frequency, such as once every 5 seconds) if the fuel level falls below a certain value (e.g., one-eighth of a tank). A higher level alarm (e.g., causing the horn to sound once every second) can be initiated if the fuel level falls to a dangerously low level (e.g., one-sixteenth of a tank). Alternatively or additionally, the controller can be operable to shut down the engine when the level of fuel falls below a predetermined level (e.g., one-sixteenth of a tank) so as to avoid running out of fuel; this is particularly advantageous for diesel engines wherein running out of fuel is a major event requiring re-priming of the engine to restart it. Other alarms can also be generated for other types of malfunctions, and any alarm states can be stored in the event history file, as previously noted, which can assist the operator or maintenance personnel in diagnosing and repairing the mobile shredder as needed.  
         [0075]     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.