Patent Publication Number: US-2002008170-A1

Title: Shredder

Description:
[0001] The invention relates to a shredder for brushwood or other organic waste and particularly to, but not exclusively limited to, a shredder for brushwood or other organic waste mounted on a trailer to be towed behind the vehicle.  
       [0002] Shredders for shredding brushwood of other organic waste are known and are generally used by tree surgeons and local authority operatives to dispose of all forms of organic waste such as cuttings from trees and other plants. Material shred by the shredder can then be used as a mulch or can be composted for reincorporation into the soil.  
       [0003] Most shredder machines operate on a flail principal. That is to say, individual flail cutters are freely pivoted to a shaft which is rotated at a substantial speed to cause the cutters to fly out centrifugal to the shaft. The waste material is then fed into the path of the cutters. The power requirement for those machines is high and the noise level is also high.  
       [0004] An alternative form of shredder is disclosed in our co-pending European Patent Application Number 0903182. That shredder has a shaft carrying a helical array of cutting/shredding discs.  
       [0005] There is a requirement for shredders having increased capacity to handle larger volumes of material.  
       [0006] It is an object of the invention to provide an improved shredder.  
       [0007] According to the invention there is provided a shredder for brushwood or other organic waste comprising a shaft having first and second sets of cutters, each set of cutters being arranged around the shaft along respective helical paths so as to feed cut material along the shaft, the first set being arranged to feed cut material towards one end of the shaft and the second set being arranged to feed cut material towards the other end of the shaft.  
       [0008] In that way a larger capacity machine can be provided since twice the volume of material can be inserted into the shredder described above and the cut material is fed in opposite directions towards the ends of the shaft for expulsion from the shredder.  
       [0009] Preferably the first set of cutters feeds cut material from the centre of the shaft towards said one end and the second set feeds material from the centre of the shaft towards said other end. In an alternative embodiment, the first set of cutters has an outer end towards said one end of the shaft and an inner end towards the centre of the shaft, the second set of cutters has an outer end towards said other end of the shaft and an inner end towards the centre of the shaft and the inner ends of the first and second sets overlap slightly. In a still further embodiment, a central cutter may be provided to slice material hat bridges the centre of the shaft  
       [0010] Expulsion means may be provided at each end of the shaft. Preferably each expulsion means comprises at least one generally radial by extending web carried by the shaft arranged in a chamber at respective ends of the shaft arranged so as to provide an airflow to exhaust tangentially from the chamber so as to expel the shredded material. An elongate exhaust tube may be provided from the chamber so as to direct the exhausted cut material away from the shredder. The exhaust tube is preferably rotatable. The exhaust tube may be tiltable up and down.  
       [0011] The shredder may further include a feed rotor which is arranged to pull material into the shredder and force it in the direction of the cutters. The feed rotor preferably includes a series of teeth on the periphery thereof The feed rotor may be moveable from a non-feed position to a feed position.  
       [0012] The shredder may include a hopper for loading material to be shredded. In such a case, the feed rotor is arranged at one end of the hopper. The feed rotor in that case is moveable from a position above the material to be cut in the hopper to a position engaging the material to be cut. The hopper may include a sensor to determine the presence of a “non-suitable object”. Examples of “non-suitable object” would be material which is likely to damage the shredder such as concrete or metal or the limbs of an operator.  
       [0013] The shredder is preferably located on a trailer which can be hitched behind a vehicle. The trailer preferably carries a motor for driving the drive shaft and, where provided, the feed rotor. 
     
    
    
     [0014] One embodiment of shredder will now be described in detail by way of example and with reference to the accompanying drawings, in which:  
     [0015]FIG. 1 is a perspective view of a shredder in accordance with the invention, and  
     [0016]FIG. 2 is an elevation of part of the shredder of FIG. 1 with the hopper removed for clarity. 
    
    
     [0017] In FIG. 1 the shredder assembly  10  forms part of a trailer  12  intended To be towed behind a vehicle to an intended place of use. The trailer  12  comprises a conventional hitch  14 , trailer wheels  16  and a jockey wheel  18  for use in manoeuvring the trailer when disconnected from the vehicle. The trailer  18  also carries a drive engine  20  with associated fuel tank. coolant system, starter motor gearing etc. (not shown). The motor  20  drives the shredder assembly  10 .  
     [0018] The shredder assembly  10  comprises a hopper  22 , a feed mechanism  24 , a shredder mechanism  26  and an exhaust assembly  28 . The hopper  22  comprises two slanted side walls  30 ,  32  and a slanted end wall  34 . Side and end walls,  30 ,  32 ,  34  define an open base and open other end The end wall  34  is arranged forward most of the trailer relative to the rest of hopper. The “free ends” of side walls  30 ,  32  abut an enclosure for the feed and shredder mechanisms,  
     [0019] The feed mechanism  24  comprises a conveyor belt  36  arranged beneath the open base of the hopper  22 . The conveyor  36  has chevron shaped ribs  38  formed on the surface thereof. The conveyor  36  is driven to feed material loaded thereon towards the open end of the hopper  22 . A curtain  40  comprising slats of resilient material such as rubber is arranged across the open mouth of the enclosure for the feed rotor and shredder mechanism. The curtain  40  is provided to prevent cut material being thrown back towards the hopper from the shredder.  
     [0020] Feed mechanism  24  further comprises a feed rotor  42 . The feed rotor  42  comprises a driven shaft carrying four sets of teeth  44  running longitudinally of the shaft and regularly equally spaced about the periphery thereof. The feed rotor  42  is located in guide tracks  46 , the ends of the rotor  42  extending through the guide tracks  46  and being carried by pivotal arms  48 . One end of the rotor  42  is connected to a drive  50 , such as a hydraulic drive. The arms  48  are pivotally mounted at a point remote from the feed rotor  42  so as to enable up and down movement of the rotor  42  along the guide track  46  by pivotal movement of the arms  48 . The arms  48  may be positioned by means of hydraulics to attain certain positions. Alternatively, the position of the arms may be adjusted manually. Still further, the rotor may be arranged simply to “float” up and down the guide track  46  so as to accommodate different sizes and volumes of material to be cut The weight of the rotor itself acts with sufficient downward force to allow feeding to occur when rotating of the feed rotor commences.  
     [0021] The shredder mechanism  26  is best illustrated in FIG. 2. The shredder mechanism  26  comprises shaft  52  which carries first and second sets  54 ,  56  of cutters  58 . The shaft  52  further carries flywheels  60 ,  62  at opposite ends hereof. The flywheels  60 ,  62  include radial vanes  64  as shown in FIG. 1.  
     [0022] The cutters  58  in the first set  54  are arranged in a helical pattern around the shaft whereby rotation of the shaft in a clockwise direction as viewed in FIG. 1 will feed cut material cut by the cutters  58  from the middle of the shaft  52  towards the end of the shaft which carries the flywheel  60 . Likewise, that same rotation will cause the cutters  58  in the second set  56  of cutters to cut material and to feed the cut material to the end of the shaft  52  which carries flywheel  62 . In the embodiment illustrated there are sixteen cutters  58  in each set. The cutters  58  are substantially similar to those described in EP-A-0903182. A central cutting blade  59  is mounted on the shaft  52  between the first and second sets  54 ,  56  of cutters  58 . The central cutting blade cuts lengthy material which bridges the two sets of cutters.  
     [0023] The exhaust assembly  28  comprises the radial vanes  64  carried by the flywheel,  60 ,  62  on the shaft  52  of the shredder mechanism. The vanes  64  are enclosed within a chamber  66 . The chamber  66  has an inlet  68  Through which cut material from the shredder mechanism  26  is received and an outlet  70  is arranged tangentially of the path of the radial vanes  64  through which cut material is exhausted. The exhaust assembly  28  further comprises exhaust tubes  72  which are connected to the exhaust outlet  70  of the respective exhaust enclosure  66 . The exhaust tubes  72  are inclined towards the horizontal from the exhaust outlet  70 . The tubes  72  are rotatable from side to side and are also preferably pivotable up and down to enable more accurate exhausting of shred material  
     [0024] In use, the material to be shred is loaded into the hopper  22  and the conveyor belt  36  is activated. The conveyor  36  forces material towards the feed rotor  42  which “floats” on the surface of the incoming woody material. The rotor  42  is driven in rotation and the teeth  44  separate sections of infed material and pass those sections to the shredder mechanism  26 . The shredder mechanism shreds the material by means of the cutters  58  and the helical arrangements of the cutters  58  feeds the shred material towards the end of the shaft  52  of the shredder mechanism  26 . The rotation of the shaft  52  also drives The vanes  64  of the exhaust assembly which blow the cut material out of the shredder through the exhaust tube  72 .  
     [0025] By way of example, the shredder  10  may have a shredding width of 400 mm, 600 mm, 850 mm or 1400 mm. Alternatively to the exhaust assembly  28 , the cart and feed material may drop onto a conveyor which can be arranged to convey the material to a container.  
     [0026] The present invention provides a large capacity shredding machine which is not prone to blockage and which does not require larger, and thus more expensive, shredder parts.