Abstract:
A disc chipper for crushing lumpy feed material. The disc chipper has a crushing rotor driven by a drive unit, rotating about an axle, including a rotor shaft and a chipping disc connected in a rotationally fixed manner with the rotor shaft. The chipper disc includes chipping knives, which are transversely aligned in the disc plane to the rotational direction and which cooperate with stationary counter knives for the comminution of the feed material. The drive unit include a primary drive and a secondary drive, which drive the crushing rotor via a transmission, wherein the primary drive is in active operative connection with the crushing rotor during the crushing operation, and the secondary drive during the acceleration process or when readjusting the crushing rotor for purposes of maintenance and repair.

Description:
[0001]    This nonprovisional application claims priority under 35 U.S.C. §119(a) to German Patent Application No. 10 2015 005 859.2, which was filed in Germany on May 11, 2015, and which is herein incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a disc chipper for crushing lumpy feed material, particularly wood. 
         [0004]    2. Description of the Background Art 
         [0005]    Disc chippers are generally known and are used to produce wood chips from lumpy feed material such as timber or residual wood chips in order to produce wood chips as raw material for further industrial use. A large proportion of the produced wood chips is supplied to a thermal utilization system, i.e., the wood chips are burned as renewable fuel in thermal power stations or private households. In addition, the use of the wood chips for the production of high-quality wood products such as MDF and chipboard is of interest. A prerequisite for this is that the chips thus produced meet predetermined quality features in terms of size, shape and surface texture of the wood chips. 
         [0006]    From the German disclosure 2 031 635, a disc chipper is known with a chipping disc rotating within a housing and equipped with knives. The chipper disc is seated rotationally fixed on a shaft, which is driven by an electric motor via a reduction gear. The feed material is fed to the chipping disc over lateral chutes at an acute angle to the disc plane. 
         [0007]    In DE 42 38 089 A1, which corresponds to U.S. Pat. No. 5,293,917, a disc chipper for the production of chips is described, having as a comminution unit a cutting disc with knives which rotates about a horizontal axis. The feed material is supplied to the disc in a feed angle of a maximum of 34° in order to obtain an improved chip quality. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore an object of the invention to provide a disc chipper with which high-quality chips can be cost-effectively produced. 
         [0009]    A first advantage of a disc chipper according to the invention results from a drive unit with a primary drive, which is responsible for driving the crushing rotor during the crushing operation, and a secondary drive, which drives the rotor in all other cases. In this way, it is possible to align in a targeted manner the primary drive to the specific needs of the crushing operation. For example, the primary drive can have an output of between 450 kW and 1500 kW, preferably between 900 kW and 1400 kW, in order to guarantee a constant rotation also of large chipping discs. 
         [0010]    By contrast, the secondary drive assumes the drive during acceleration, deceleration or the gradual adjustment of the rotor, and in turn can be adapted to the specificities of these operations. For the acceleration of the chipping disc, a secondary drive with an output between 25 kW and 75 kW is preferred, in particular between 35 kW and 55 kW, so that the secondary drive can be selected to be comparatively small with the advantage of lower costs. 
         [0011]    With regard to an exemplary embodiment of the invention, a ratio of power of the primary drive to the output of the secondary drive in a range between 10 and 35, preferably between 20 and 3, has been found to be beneficial. 
         [0012]    Particularly in chipping discs with large diameters and large weight, this advantage is particularly evident, since due to the inertia of the rotor, the acceleration and deceleration forces are enormous. Such chipping discs may, for example, have a diameter of more than 2 m and/or a weight of more than 5,000 kg, in particular more than 7,500 kg, preferably more than 10,000 kg. 
         [0013]    The secondary drive can comprise a hydraulic motor, which already during starting of the rotor provides a maximum torque and allows for an exact positioning of the rotor during readjustment of the rotor for maintenance and repair work, for example, during the gradual adjustment of the rotor into the blade changing position for changing the chipping knives. For braking the chipping disc, the hydraulic motor can pump the hydraulic oil in the circuit, which allows for wear-free braking. 
         [0014]    In an embodiment of the invention, the transmission can have a drive shaft to which both the primary drive and the secondary drive are coaxially arranged and on which both drives act directly. The construction cost of the drive unit is thereby simplified, with the advantage that the manufacturing cost of a disc chipper according to the invention is kept as low as possible and a compact design is obtained. 
         [0015]    The transmission can be a gear transmission, which enables the transfer of large forces with low wear. In another embodiment, the transmission is formed by a belt transmission, which can be produced relatively inexpensively. A transmission ratio can be between 5:1 and 6:1, in order to operate the primary drive in the optimum range at the predetermined rotational speed of the chipping disc. 
         [0016]    To transmit the driving force from the rotor shaft to the chipping disc, the rotor shaft according to the invention comprises a bearing seat for the chipping disc, having a polygonal cross section. In connection with a complementary-shaped centric through-hole in the chipping disc, the existing drive torque is transmitted over large areas of contact. This has the advantage that even very high drive and/or acceleration forces can be transmitted without overtaxing the materials in the contact area. This creates power reserves in the contact area, which can be advantageously used to increase the engine power and consequently to improve the efficiency of a disc chipper according to the invention. To this end, bearing seats with point or axisymmetric cross sections have proven to be advantageous, such as square, pentagonal, hexagonal or octagonal cross-sections, which cause a uniform power transmission over the circumference of the bearing seat. 
         [0017]    The bearing seat can have a peripheral bearing flange against which the back of the chipping disc is clamped for attachment to the rotor shaft. The bearing flange thereby forms a spatially defined reference surface, starting from which the blades of the chipping knives are adjusted to a common cutting plane. In this way, it is possible to reproduce uniform geometric relationships during the chipping process for all chipping knives, which results in the wood chips being uniform in size and shape and therefore being characterized by a very high quality. 
         [0018]    In order to be able to adjust the geometric conditions on the stator side that are relevant to the chipping process, the stationary counter blades are mounted in rigid receptacles and there, are indirectly supported on stop surfaces in the receptacles via an adjustment device. In this way, it is possible to accurately adjust the axial gap between the chipping knives and the counter knives. By maintaining the optimum cutting geometry, chips with an excellent surface quality can be produced. 
         [0019]    A simple yet very robust and reliable type of counter knife adjustment involves the use of spacer plates that are inserted in suitable thickness and number between stop surface and counter knife. A continuous adjustment of the counter knives is carried out according to an alternate embodiment of the invention using adjustment screws that determine the distance between counter knife and stop surface, depending on their insertion depth. 
         [0020]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
           [0022]      FIG. 1 a    a side view of an inventive disc chipper with a closed housing, 
           [0023]      FIG. 1 b    illustrates the disc chipper shown in  FIG. 1  with open housing, 
           [0024]      FIG. 2  is a section through the disc chipper shown in  FIG. 1 , along the local line II-II. 
           [0025]      FIG. 3  is a plan view of the disc chipper shown in  FIG. 1 , including the drive unit, 
           [0026]      FIG. 4 a    is a view of the front side of the chipping disc of the disc chipper shown in  FIG. 1 , 
           [0027]      FIG. 4 b    is a view of the back side of the chipping disc shown in  FIG. 4 a   , and 
           [0028]      FIG. 5  a detailed view of the region marked in  FIG. 2  with V. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIGS. 1 a , 1 b   ,  2  and  3  show a disc chipper  1  according to the invention in different views and sections. The disc chipper  1  has a housing  2 , which is composed of a lower part  3  and a hood-like upper part  4 . The housing  2  has a front wall  5  and a rear wall  6  plane-parallel thereto, which are connected via a cylindrical housing shell  7  and in this manner enclose a downwardly open comminuting chamber  9  which extends along an axis  8 . The housing upper part  4  is formed of a housing segment  10  via a sector-shaped portion, which, driven by a cylinder-piston assembly  11 , can be pivoted about the axis  12  in order to open the housing  2 , for example, for maintenance or repair work. The lower housing part  3  is reinforced by a number of rib-shaped stiffening plates  13 . 
         [0030]    In the transition area between the lower part  3  and the upper part  4 , in each case a console  14  is secured on the outside front wall  5  and the rear wall  6 , on each of which a pivot bearing  15 ,  16  is positioned for receiving a crushing rotor  17  that rotates about the axis  8 . The crushing rotor  17  has a rotor shaft  18 , which shaft end associated with the front wall  5  is supported by the local pivot bearing  16 , and which other end is passed through the pivot bearing  15  and attached to a drive described in particular in more detail in  FIG. 3 . 
         [0031]    The shaft section extending within the housing  2  forms a bearing seat  19  for a chipping disc  20  oriented perpendicular to the axis  8 , which, for example, may comprise a diameter of about 2.5 m and a weight of about 10,000 kg. The chipping disc  20  has a centric through-hole  21  with which it is mounted on the bearing seat  19 . For exact axial positioning of the chipping disc  20 , the bearing seat  19  has a bearing flange  22  encircling the shaft circumference, which seat delimits the axial insertion depth of the chipper disc  20 . The chipping disc  20  is clamped against the bearing flange  22  by means of the screws  23  ( FIGS. 2 and 4   a ). 
         [0032]    To transmit the torque from the rotor shaft  18  to the chipping disc  20 , the bearing seat  19  is designed as a hexagon and the through-hole  21  of the chipping disc  20  has an outline complementary thereto. In this way, relatively large force transfer surfaces result that are also capable of transferring great driving forces as they occur especially in chipping discs with large weight and large diameter, without overstressing the material. 
         [0033]    The more precise design of the chipping disc  20  is also shown in  FIGS. 4 a  and 4 b   . The chipping disc  20  has a number of linearly extending passage gaps  24  reaching from the disc front side  25  to the disc back side  26  and which extend star-shaped from the near-axial inner disc portion to the near outer disc portion ( FIG. 4 b   ). On the disk front side  25  along each passage gap  24 , a chipping knife  27  is arranged which with a predetermined blade projection protrudes from the plane of the chipping disc  20  and guides the freshly obtained chips into the passage gap  24 . The blades of all chipping discs  27  thus lie on a common plane, plane-parallel to the disc plane. For producing high-quality wood chips, it is important that the chipping knives rotate in exactly this plane. 
         [0034]    For the loading of the disc chipper  1  with feed indicated by arrow  34 , a housing opening  28 , into which a horizontal feed chute  29  opens extending at an acute angle to the disc plane, is disposed at the front wall  5  of the housing  2  approximately centrally below the pivot bearing  15 . Opposite the housing opening  28 , the feed chute  29  has an opening  30 , which is closable by a pivotable flap  32  about an axis  31 . The opening and closing of the flap  32  is carried out by means of a cylinder-piston unit  33 , which is hinged both on the housing  2  and on the flap  32 . 
         [0035]    Counter knives  35  cooperating with the chipper knives  27  extend along the lower horizontal edge and the vertical edge of the housing opening  28  that adjoins in the direction of rotation  45 . As shown particularly in  FIG. 5 , for this purpose receptacles are provided in these areas, which are each welded in the form of a rigid bearing beam  36  with the front wall  5  of the housing  2  and of which the side facing the housing opening  28  is formed by an inclined bearing surface  37 . Along the edge of the bearing surface  37  facing away from the housing opening  28 , a strip-shaped extension  39  extends to form a stop surface  38 . 
         [0036]    The counter knife  35  rests with its planar side full-surface on the bearing surface  37  and is fixed via a clamping strip  40  and a number of clamping screws  41  on the bearing beam  36 . So that the counter knives  35  are arranged at the exact axial distance from the chipping knives  27 , an adjusting device is provided on the back side of the counter knives  35  facing the stop surface  38 , said adjusting device being supported by the stop surface  38 . In the present embodiment, the adjusting device includes two adjusting screws  42  arranged at a lateral distance, each engaging with its threaded portion in threaded holes at the rear side of the counter knives  35 , and each being supported by their screw head on the stop surface  38 . By a suitably wide screwing-in or unscrewing of the adjustment screws  42 , the distance between the counter knives  35  from the stop surface  38  and thus the distance of the blades of the counter knife  35  from the chipping knives  27  can be adjusted. Setting the correct insertion depth of the adjustment screws  42  can be done via a lock nut or a suitable number of spacer plates between the back side of the counter knives  35  and the screw head. 
         [0037]    Accessibility to the horizontal counter knives  35  near the bottom  43  of the feed shaft  29  is ensured there by a provided opening, which is filled by a removable first cover plate  44 . With its front edge, the first cover plate  44  joins gap-free to the counter knife  35 , while the opposite rear edge is supported on the opening edge. To support the first cover plate  44  perpendicular to the display plane, a supporting plate  46  approximately centrally supporting the first cover plate  44  is provided on the support beam  36 , and the rear edge of the first cover plate  44  is reinforced by arranging a rib  47 . 
         [0038]    In the region of the vertical counter knives  35 , these are protected by a second removable cover  48  which is integrated in the flap  32  and in the course of opening the flap  32 , releases the vertical counter knives  35 . The second cover  48  includes a plate that is rigidly welded to the outside of the flap  32  along the flap edge facing the hinge region, perpendicular to the flap plane, and that in the course of closing the housing opening  28  covers the vertical counter knives  35 . 
         [0039]    An inventive drive unit as shown in  FIG. 3  in a plan view drives the chipping disc  20 . The drive unit comprises an electric motor  49  as a primary drive, which shaft is aligned coaxially to the drive shaft  51  of a transmission  52  and acts directly via a first clutch  50  on the drive shaft  51 . The output shaft  53  of the transmission  52  is in turn coupled via a second coupling  54  with the rotor shaft  18  that is driving the chipping disc  20 . The two clutches  50  and  54  are each composed of two coaxially opposed clutch discs, at which sides facing each other resilient carriers and openings are alternately arranged. Through a mutual offset of the clutch plates in the circumferential direction, when merging the clutch plates, the carriers of the one clutch disc position themselves in the openings of the other clutch disc. Because of the toothing thereby formed, torques can be transmitted. Within the transmission  52 , the rotational speed of the electric motor  49  is decelerated at a ratio of 5:1 to 6:1 into a rotational speed of about 300 rev/min on the output side, which corresponds to the speed of the chipper disc  20 . The output of the primary drive thereby amounts to 1400 kW. 
         [0040]    On the opposite side of the transmission  52 , a hydraulic motor  55  is arranged as a secondary drive, which shaft that is coaxial to the drive shaft  51  is directly coupled to the drive shaft  51 . The hydraulic motor  55  is connected via hydraulic lines  56  to a hydraulic unit  57  having pumps and an oil tank. The output of the secondary drive amounts to 45 kW. 
         [0041]    In order to bring the inventive disc chipper  1  into the operating state, the chipping disc  20  is accelerated by means of the secondary drive to the rotational speed at which the disc chipper  1  is later operated in the chipping operation. During acceleration, the primary drive is turned off, that is, the rotor of the electric motor  49  remains passive and is only set in rotation by the hydraulic motor  55  together with the chipping disc  20 . When the predetermined operating speed is reached, the secondary drive is switched off and the primary drive is switched on. Thus, during the chipping operation, the secondary drive is driven by the primary drive, without participating in driving the chipping disc  20 . Only in the braking phase of the chipping disc  20  is the hydraulic motor  55  again turned on, after the primary drive has been previously switched off. The hydraulic oil pumped in the circuit by the hydraulic motor  55  carries out the braking process. 
         [0042]    If maintenance or repair work are to be done on the chipping disc  20 , for example, when worn chipping knives  27  must be replaced by sharpened ones, the secondary drive can also be used for the gradual adjustment of the chipping disc in the respective blade change position without the need for the primary drive to be enabled. 
         [0043]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.