Abstract:
An apparatus for comminuting materials includes a rotating or stationary ring of knives that is arranged around a chipping chamber. The ring of knives is has a plurality of knife carriers, which are distributed around the knife ring axis in a circular shape, each knife carrier having a bearing surface. The bearing surface is a receptacle for a knife package that is comprised of a knife retaining plate and a slicing knife, and which is held in an operational position at a predetermined angle and a predetermined blade projection by fasteners. The knife carrier has a reference surface, which interacts with the knife package, and based on which the blade projection is determined. The slicing knife has at least one recess that originates in a rearward longitudinal edge, whereby the reference surface is arranged on the projection inside the recess, the projection extending vertically to the bearing surface.

Description:
This nonprovisional application claims priority under 35 U.S.C. § 119(a) on German Patent Application No. DE 10 2004 004 877 filed in Germany on Jan. 30, 2004, which is herein incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus for comminuting materials, the apparatus including a ring of knives that is arranged around a chipping chamber. 
   2. Description of the Background Art 
   Chipping devices of this class are known, for example, as knife ring chippers with an interior striker wheel system, whereby chips are comminuted into fine shavings, which serve as a base material for the production of particle boards. In addition, there are timber chippers, whereby the stationary material is turned into large-size chips by a rotating and transversely-operating knife ring, the chips being further used for manufacturing OSB ( O riented  S trand  B oard) products. 
   In such devices, the actual comminuting is done by slicing knives that are assembled, together with a knife retaining plate, outside of the chipping apparatus and within a template to form a knife package. The knife packages are held by knife carriers, which are arranged in a circular shape between two carrier rings around an axis of rotation, thus forming a ring of knives. To make it easier to attain the required blade projection, the knife carrier has a stop surface as a reference surface that extends along the entire length of the knife carrier, the reference surface interacting with a oppositely located blade located of the pre-adjusted knife package. This stop surface, which also serves as a reference surface, is also the zero position for the knife packages because from it the control value for the position of the blade of the slicing knife is taken. The main rule for the installation of knife packages is that all blades of the slicing knives travel in the same cutting circle. 
   However, as a consequence of tolerances generated during production, the stop surfaces of the knife carriers, and thus the reference surfaces for the blade cutting circle of the slicing knives, are not all positioned on one and the same circumferential line in relation to the axis of the knife ring. This leads to uneven blade projections of the slicing knives and thus, to chips of an inferior quality. 
   For this reason, it is already known from DE 26 28 764 to adjust the reference surface with the aid of an adjustment device to compensate for tolerances generated during production. In DE 26 28 764, the reference surface is formed by an adjustment and set screw, which can be screwed into the knife carrier, or unscrewed therefrom, coplanar to the knife package. The adjustment and set screw thereby serves as a stop for a continuous counter-pressure, and is tightly screwed to the knife package. 
   A disadvantage of the conventional constructions is that a maximal usable width of the slicing knife is fixed by the distance between the blade of a slicing knife and the reference surface, to which the slicing knife abuts with its rearward longitudinal edge. In view of longer operating times of the wear-prone slicing knives, the use of the widest possible slicing knives would be desirable. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide slicing knives with a usable width that is larger than has been previously possible. 
   The invention is based on the idea to design the reference surface on the knife carrier, which interacts with the knife package, in a basically punctiform shape. In conjunction with slicing knives, which each have in the area of the reference surfaces a recess extending from the rearward edge, a constructive development of a knife carrier is thus achieved, whereby the reference surfaces are within the recesses. Thus, making it possible for the rearward edge of the slicing knives to extend beyond the reference surface. The reference surface can thereby be formed by a fixed stop, but also by an adjustable element that is adjustable coplanar to the knife package. 
   Thanks to the invention, the operator of chipping devices of this invention will have the advantage to be able to use wider slicing knives than before. Due to their greater usable width, these slicing knives have a longer life span, which makes the chipping devices of this invention more economical all around. 
   Furthermore, the structure of a knife carrier according to this invention makes a shifting of the reference surface towards the middle of the knife carrier possible. This results in a more compact construction of the individual knife carriers, which opens up the possibility to accommodate more knife carriers on a circumferential line than before. A modified knife ring such as this is capable of a much higher chipping output. 
   In a simple embodiment of the invention, the reference surface is formed from one stop on the knife carrier for the knife package. The special merit of an embodiment such as this is its simplicity of construction, but it is only effective in the direction of the stop, that is, a knife package has to be held against the stop until it is screwed onto the knife carrier. 
   In a further embodiment of the invention, an interlock is created between the knife carrier and the knife package, for example, through the formation of a plug connector. This has the advantage that the knife package is already fixed in a control position when the knife package is placed on the bearing surface of the knife carrier, and only needs to be screwed on. Although it is more complex to manufacture an embodiment such as this, it contributes to greater safety in regards to maintaining the necessary blade projection. 
   A preferred plug connector of the invention is the slot and key principle. It is even more beneficial when the slot is arranged in the knife retaining plate and the fitting key in the knife carrier. This allows a compact design of the knife carrier with simple construction. A slot that is longer in relation to the fitting key makes it easier to thread the fitting key into the slot and allows minor position corrections in the direction of the slot after assembly. 
   Although the invention also includes chipping devices with fixed reference surfaces, embodiments that allow a setting of the reference surface and thus an adjustment of the zero position of the knife packages are preferred. In an example embodiment, the reference surface is part of the adjustment device, which preferably is arranged on the knife ring. This allows the knife package, which has to be removed every time the knives are being exchanged, to be reduced to only those parts that are absolutely necessary. The parts needed for an adjustment are thus protected in the knife carrier and are not inadvertently misadjusted. 
   A simple, but very effective and reliable type of an adjustment device includes an adjustment screw, which can be screwed to the knife carrier, with the insertion of small spacers in between. It is thereby possible that the head of the adjustment screw also functions as the reference surface for the knife package. As an alternative thereto, it is possible to attach a centering peg with the adjustment screw to the knife carrier, which interacts with the knife retaining plate, by the interposition of small spacers. 
   Particularly when knife carriers with an adjustment device are used, the arrangement of recesses on the knife carrier is an advantage. By arranging the adjustment device in the recess, the adjustment device disappears into the cross section of the knife carrier. This makes it possible to keep the chip removal channel free of contractions of the cross section, which is always a source of danger in regards to clogging. Thus, the chipping devices of this invention also have the benefit of increased reliability and operational safety. 
   In a further embodiment of the invention, the bearing surface of the knife carrier has a base, on which the knife retaining ring rests during operation. Arranging the reference surface or the adjustment device in the area of the base has the advantage that from a statical point of view, the base itself has the effect of a stabilizing element for the reference surface. 
   Additionally, the invention includes a ring of knives, which is also marketed as an independent part of a device of this invention. To such a knife ring, the previously made statements also apply. 
   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 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 
     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: 
       FIG. 1  shows a vertical longitudinal section through a timber chipper with a rotating knife ring; 
       FIG. 2  shows a partial cross section along the line II-II through the knife ring illustrated in  FIG. 1 ; 
       FIG. 3  shows a top view of a slicing knife of this invention; 
       FIG. 4  shows a top view of a knife retaining plate of this invention; 
       FIG. 5  shows a front view of a knife carrier of this invention; 
       FIG. 6  shows cross sections along the lines VIa-VIa and VIb-VIb through the knife carriers illustrated in  FIG. 2 ; 
       FIG. 7  shows a partial view along the line VII-VII through the knife carrier illustrated in  FIG. 6 ; 
       FIG. 8  shows a partial cross section along the line VIII-VIII through the knife carrier that is illustrated in  FIG. 6 ; and 
       FIG. 9  shows a cross section of an alternate embodiment of a knife carrier of this invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a knife ring chipper according to a preferred embodiment of the present invention for chipping timber. To clarify the invention, a chipper for making wood chips with a knife ring and an interior striker wheel, whereby the knife ring can be stationary as well as rotating, can be utilized to illustrate this invention.  FIG. 1  shows a stationary substructure  1  having rails  2  arranged along its upper side in plan view. The rails  2  serve as a track for the base frame  3  of the engine, which is cross-slidingly arranged on wheels  4  in the direction of the arrow  5 . A cylinder piston unit  6  is fixedly connected to the substructure  1 , its moving piston  7  activating the base-frame  3  of the engine, thus causing a lateral movement of the base frame  3  of the engine. Furthermore, the base frame  3  has a platform  8 , which carries an electric motor  9 . Additionally, a hood-shaped housing  10  is attached to the base frame  3 , which serves as a receptacle for a knife ring  11  than can be rotated freely around a horizontal axis. Whereas the rear wall of the housing  10  is closed and serves as a storage for a drive shaft of the ring of knives  11 , the front of the housing  10  has a circular opening, through which the chipping chamber  12  can be freely accessed. Towards the top, the chipping chamber  12  is bound by a circular arc segment  13 , a bent side of which extends in close proximity to the ring of knives  11 . In the lower region, a bracing floor construction  14  forms the boundary of the chipping chamber  12  and, like the circular arc segment  13 , is fixedly connected with the housing  10 . The left boundary area of the chipping chamber  12 , from an illustration view point, is formed by a counter-stop  15 , which extends axially into the chipping chamber  12 , is convex in cross section, and is fixedly arranged opposite the substructure  1  of the apparatus and thus does not follow the lateral movements of the base frame  3  of the engine. The opposite side of the chipping chamber  12  is formed by a segment of the inner side of the knife ring  11  and forms a comminution path. 
   The material to be processed, that is, logs  16 , as well as the counter-stop  15  extend with an unencumbered part of their length axially into the chipping chamber  12 . The part of the logs  16  that is located outside the chipping chamber  12  is in a feeder device (not shown), at which end it is firmly clamped together for the comminution process. Additionally, there are hold-down clamps (not shown) in the chipping chamber  12 , which hold the logs  16  in place during the comminution process. The comminution of the logs  16  is done by lateral movement of the base frame  3  of the engine in the direction of arrow  5  while the knife ring  11  is rotating, whereby the logs  16 , due to the stationary counter-stop  15 , are pressed against the comminution path, where they are engaged by the chipping tools. 
   The detailed construction of the knife ring  11  is illustrated in  FIG. 2 . Basically, the ring of knives  11  includes two concentric ring wheels  17  and  18  that are arranged with an axial space in between, and which are connected to knife carriers  19 , the knife carriers being distributed axis-parallel and annular around the axis of rotation in a circular shape. Whereby, the upper front sides of the knife carriers  19  and the inner sides of the ring wheels  17  and  18  are screwed together. Each knife carrier  19  can function as a receptacle for the chipping tools in their required operational position, which is accomplished by mounting them in mounting planes A. In the illustrated example, the chipping tools include knife packages  20 , each knife package  20  including a knife retaining plate  21  and a slicing knife  22 . The individual elements of such a unit, that is, the slicing knife  22 , the knife retaining plate  21  and the knife carrier  19 , are illustrated in  FIGS. 3 to 5 . Their respective arrangement during operation is clearly illustrated in  FIG. 6 . 
   The slicing knife  22  illustrated in  FIG. 3  extends in a distinct longitudinal direction, whereby the front longitudinal edge, in  FIG. 3  the lower longitudinal edge, forms a blade  23 . The edge segments of the rearward longitudinal edge  24  of the slicing knife  22  are provided with a slit-shaped recess  25  with a rounded bottom and an extension that is transverse to the longitudinal extension direction. Additionally, there are two threaded bores  26  between the front upper side and the recess  25 . 
   A knife retaining plate  21  that is suitable for forming a knife package  20  is illustrated in  FIG. 4 . Basically, the layout of the knife retaining plate  21  is, in principal, the same as the slicing knife  22 , having a rearward longitudinal edge  27  and a front longitudinal edge  28 . In the illustration a lower portion of the front longitudinal edge  28  tapers to a pointed longitudinal edge. Each of the two mounting planes A is provided with a tapered bore  29 , which extends through the thickness of the knife retaining plate  21 . The tapered bore  29  has a larger diameter on a top side  30  and a smaller diameter on a bottom side  31  of the knife retaining plate  21 . 
   Between the tapered bores  29  and the rearward longitudinal edge  27 , there are grooves  32  that are arranged on the bottom side  31  in the area of the mounting planes A, the grooves extending parallel to the longitudinal extension direction and their depths equaling about one half of the thickness of the knife retaining plate  21 . 
   In addition, a longitudinal hole  33  is arranged between the tapered bores  29  and the upper front sides of the knife retaining plate  21 , which is tapered in a way similar to the tapered bores  29 . The longitudinal holes  33  extend transversely to the longitudinal extension direction. 
   The slicing knife  22  illustrated in  FIG. 3  and the knife retaining plate  21  illustrated in  FIG. 4  are combined outside the ring of knives  11  in a specially provided template to form a knife package  20 . The template provides for a predetermined width of the knife package  20 , which, starting from a defined zero position on the knife carrier  19 , results in a desired blade projection into the comminution chamber  12 . Depending on the condition of attrition of the slicing knife  22 , the slicing knife  22  and the knife retaining plate  21  are thereby placed on top of each other, transversely to the longitudinal extension direction of the knife retaining plate  21  and with the required overlap, and are connected with screws (not shown). The threaded part of the screws thereby extends through the longitudinal holes  33  into the threaded bores  26  of the slicing knife  22 . The final location of the screw heads is in the longitudinal holes  33  so that they do not protrude beyond the top side  30  of the knife retaining plate  21 . The illustrated extension of the longitudinal hole  33  being transverse to the longitudinal axis of the knife retaining plate  21  allows readjusting, and thus an adjustment of the knife package  20  to the current condition of wear and tear of the respective slicing knife  22 . 
   The knife packages  20  thus adjusted to a predetermined width are subsequently fastened to a knife carrier  19 , as illustrated in  FIG. 5 , for example. As can be particularly seen in  FIGS. 5 and 6 , the knife carrier  19  is rod-shaped and has a triangular cross section. On the side facing the chipping chamber, a wear shoe  34  is arranged. 
   The side of the knife carrier  19 , which in a direction of rotation  47  is the front side, forms a bearing surface  35  for the knife package  20 . The side, which in a direction of rotation  5  is the rearward side  36  of the knife carrier  19 , forms, in conjunction with the knife package  20  of a subsequent knife carrier  19 , a chip removal channel  37 , through which the chipped material is radially removed to the outside by centrifugal force. 
   A more detailed illustration of the bearing surface  35  is shown in  FIG. 5 , where it can be seen that the bearing surface  35  extends basically in a plane direction to accommodate the back of the slicing knife  22 . Perpendicular to the bearing surface  35 , there is a threaded bore  38  in each of the mounting planes A, with which fastening screws  39  ( FIGS. 6 and 7 ) engage. Between the threaded bore  38  and the rearward longitudinal edge of the knife carrier  19 , there is a base  40 , each having a width that fits into the recess  25  of the slicing knife  22 . The height of the base  40  substantially equals the thickness of the slicing knife  22 , whereby the surface of the base  40  forms a support for the bottom side  31  of the knife retaining plate  21  when the screws  39  are tightened. This is particularly illustrated in  FIG. 6 . 
   The rearward longitudinal edge of the knife carrier  19  is provided in both mounting planes A with a niche  41 , which is rectangular in cross section, the bottom  44  of the niche and the base  40  forming a flush connection. The niche  41  serves as a receptacle for an adjustment device  42 . For this purpose, a threaded bore is provided in the bottom  44  of the niche  41 , with which an adjustment screw  43  engages. The head of the adjustment screw  43  tightens a cuboid centering peg  45  against the bottom  44  of the niche  41 , with the insertion of one or several small spacers  46  in between. With a narrow side, the centering peg  45  extends beyond the surface of the base  40  and due to appropriately calculated measurements, engages free of play and transversely to the longitudinal extension direction of the knife carrier  19  with the groove  32  on the bottom side  31  of the knife retaining plate  21 . 
   In this way, the centering peg  45  forms a reference surface, which fixes the relative position of the knife package  20  against the knife carrier  19 , and thus the blade projection. 
   Since tolerances generated during production can result in minor deviations of the reference position of the knife carriers  19  in the ring of knives  11 , an insertion of a corresponding number of small spacers  46  between the centering peg  45  and the bottom  44  of the niche  41  makes it possible to compensate for these production tolerances. 
   As can be clearly seen in  FIG. 7 , and particularly in  FIG. 8 , the application of slicing knives  22  with a greater width is possible due to the invention-characteristic arrangement of the reference surface in the form of the centering peg  45  inside the projection of the recess  25  of the slicing knife  22 , the projection extending vertically to the bearing surface  35 . Thereto, the rear longitudinal edge  24  can coincide with or project above the corresponding longitudinal edge of the knife carrier  19 . 
   Due to the provision of niches  41  for the adjustment device  42 , it is possible to keep the chip removal channel free of components that may obstruct the chip removal, even if the structure of the cross section of the knife carrier  19  is compact. 
   The illustration in  FIG. 9  is to demonstrate that the invention is not limited to the embodiments illustrated in  FIGS. 1 to 8 , in which the reference surface can be adjusted by using an adjustment device  42  that is located on the knife carrier  19 . Rather, a plurality of embodiments and combinations are possible within the scope of the invention, whereby the adjustment device or the centering plug alone is mounted to the knife retaining plate, for example. 
   The knife carrier illustrated in  FIG. 9  has a mostly plane bearing surface  51 , which only in the mounting planes A is interrupted by a respective base  52 . The base  52  is two-tiered, with a first deeper surface and a second higher surface that connects to the rearward longitudinal edge of the knife carrier  50  and is located opposite the support surface  51 , 
   The support surface  51  serves as a receptacle for the knife package  54 , which is formed by a slicing knife  55 , which is basically the same as the one described in  FIG. 3 , and a knife retaining plate  56 , which is a modification of the one described in  FIG. 4 . 
   In comparison to the example embodiments described in  FIGS. 1 to 8 , the knife retaining plate  56  has an adjustment device  57 , which is arranged at the rearward longitudinal edge of the knife retaining plate  56  in the area of the corresponding recesses of the slicing knife  55 . The adjustment device  57  in turn includes a adjustment screw  58 , which engages with a threaded bore in the rearward longitudinal edge of the knife retaining plate  56 . In its turn, the head of the adjustment screw  58  tightens a stop element  59  against the rearward longitudinal edge of the knife retaining plate  56 , with the insertion of one or several small spacers  60  in between. 
   In fastening the knife package  54  onto the knife carrier  50 , the tiers between the first, deeper surface of the base  52  and the second, higher surface serve as a reference, that is, a stop surface for the stop element  59  of the knife package  54 . By inserting the appropriate quantity of small spacers  60 , the required blade projection can be set. 
   Since the extension of the base  52  in the longitudinal direction of the knife carrier  50  does not exceed the recess in the slicing knife  55 , the slicing knives  55  can also have a greater width than conventional knives according to this embodiment of the invention. This allows the rearward longitudinal edge of the slicing knife  55  to extend to the rearward longitudinal edge of the knife carrier  50 . 
   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.