Abstract:
An apparatus for chipping material, particularly wood, includes a plurality of knife carriers are arranged around a mutual axis that form the boundaries of a cutting chamber while forming a comminution path. On the knife carriers, the slicing knives, under inclusion of a cutting angle δ, are detachably attached to the comminution path. The blades of the slicing knives uniformly project into the cutting chamber. To adjust the cutting angle δ so as to adapt it to the prevailing conditions, a control element for determining the cutting angle δ is detachably arranged between the slicing knives and the knife carriers.

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) on German Patent Application No. 103 23 769.0-23 filed in Germany on May 22, 2003, which is herein incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus for chipping materials having an adjustable cutting angle. 
   2. Description of the Background Art 
   Devices of this class are known from a wide variety of models. DE 101 25 922 A1, for example, has a knife ring chipper for timber. Its chipping unit has a chipping chamber around which a ring of knives are arranged. The chipping unit includes two ring wheels, which are concentrically arranged around an axis of rotation, the ring wheels being connected to axis-parallel knife carriers, which are distributed around a perimeter of the ring wheels in a circular fashion. With their base facing the axis of rotation, the knife carriers form the boundary of the chipping chamber. Due to the spacing between the knife carriers, axis-parallel slots are formed. Each knife carrier has a bearing surface that is angled towards its base for an accurate incorporation of the slicing knife. In this position, the slicing knife extends through the axial slot with a predetermined blade length projecting into the chipping chamber, and with the backside of the preceding knife carrier forms a comminution channel for the passage of the chipped material. The angle of inclination between the slicing knife and the base of the knife carrier is equal to the cutting angle, which typically is in the range of approximately 30° to 45° and is immutably determined by the geometry of the knife carrier. 
   A similar device is known from DE 198 48 233 A1, which also discloses a knife ring chipper, and in which small-particle material is fed in an airflow to the knife ring. For the comminution of the material, a striker wheel acts jointly with the knife ring, both of which rotate in opposite directions and thus move the small-particle material past the blades of the slicing knives. Apart from counter-rotating chipping tools, simpler models are also known, whereby the knife ring is stationary and only the striker wheel rotates, or whereby only the knife ring rotates and the blades are moved past a stationary counter-knife. All of these devices have in common that the structure of the knife ring is basically as previously described, in particular, that the knife carriers have a rigid bearing surface for the slicing knives that determines the cutting angle. 
   Conventional cutting disks have a comminution unit that includes a rotating disk with an opening that is arranged in a semi-radial direction along which the knife carriers with slicing knives are arranged. The knife carriers, in turn, have a bearing surface that is inclined towards the disk plane for attaching the slicing knife, whose inclination determines the cutting angle. Such a cutting disk is known from DE 100 48 886 C1, for example, wherein a cutting disk is used in a first stage of comminution. The special feature of this device is the combination with a second stage of comminution, which is formed from a ring of knives as previously described. 
   All of the conventional art previously described have in common that the position of the slicing knife in relation to the chipping chamber, and therefore the cutting angle, are immutably determined by the fixed geometry of the knife carrier. In many areas of application, this constant cutting angle may be sufficient. However, increased demands regarding the quality of the chips and the economical operation of comminution devices make it imperative to continue to improve devices of this class. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to improve the quality of the chips while simultaneously increasing the efficiency of the chipping apparatus. 
   The invention is based on the idea to adjust a cutting angle of a chipping apparatus, based on prevailing conditions, by arranging a control element between a slicing knife and a knife carrier. This is accomplished by designing the control element in such a way that its two surfaces incline towards each other. Preferably, the shape of the control element is always the same. Therefore, for each inclination change, a suitable set of control elements is available, with which all knife carriers of a knife ring and/or a cutting disk can be fitted. 
   The prevailing conditions depend in a large measure on the characteristics of the material that is to be processed. For example, if the material are tree trunks, the type of wood is the deciding factor for the comminution process since the type of wood determines the physical characteristics of the material. Essential factors are the hardness and moisture content of the wood, the time of year when the trees were logged (summer or winter wood), fast or slow growth of the trees, freshly-cut or stored wood, etc. 
   Machine-dependent factors, which influence the chipping process, are first of all an engagement direction of the chipping tools, namely vertical or parallel to the direction of the grain, the possibility of chip removal, as well as the required chip quality and chip geometry. Additional factors are the maximum energy input and the comminution output resulting therefrom, as well as the maximum permissible temperature during the chipping process. 
   Using a control element specially designed for the characteristics of the material to be processed allows for an optimal adjustment of the cutting angle, which sets the best possible conditions for the comminution process. From the equipment side, this computes into lower energy use and reduced wear and tear, which reduces the need for replacement parts, lowers maintenance costs and energy demands. Altogether, there is less wear and tear during the comminution process on a chipping device that is optimally tuned. 
   With respect to the final product, a substantially increased chip quality can be observed. The right cutting conditions lead to smooth chip surfaces and overall uniform size. This material is especially well suited for the production of high-quality intermediate products like, for example, OSB boards (Oriented Strand Boards), which are strewn on a band and are glued together, under high pressure, in the direction of the grain and with as few minute particles as possible. 
   According to a beneficial embodiment of the invention, the control element is plate-shaped in order to provide the slicing knife or the knife package as great of a large-surface support as possible. Through the non-parallelity of the upper side and the lower side of the plate-shaped control element, a wedge shape is formed that leads to a setting of a cutting angle δ depending on the degree of the mutual inclination ε. This non-parallel nature can be such that the control element&#39;s profile is tapered towards the chipping chamber. In this way, the cutting angle δ is increased by the degree of an angle ε starting at the inclination of the bearing surface of the knife carrier. The non-parallel feature can also lead to a steady widening of the control element&#39;s profile towards the chipping chamber. In this case, the cutting angle δ is decreased by the degree of the angle ε. In this way, by using a suitable control element, the best comminution conditions can be achieved for each application. 
   Depending on the prevailing conditions during the comminution process, particularly the characteristics of the feed material, a setting range of the angle δ of 20° to 50° using the control element of this invention is preferred to allow consideration of all possible areas of application. In some instances cutting angles δ ranging from 25° to 45° or even from 30° to 40° are also sufficient if the feed material in view of its characteristics do not vary too much. 
   Since the cutting angle δ is derived from the inclination of the knife carrier and the inclination ε of the control element&#39;s surfaces towards each other, by a customary knife carrier inclination of, for example, 35°, an angle ε ranging between 0° and 15° is desirable, a range of 0° and 10° is preferred, and a range of 0° and 5° is most preferred in order to achieve the above-mentioned ranges for the cutting angle δ. 
   To exchange the control elements, the control elements must be detached from the knife carrier. A screw connection is preferred therefor, which is simple in design and safe in operation. Additionally, according to a particularly beneficial embodiment of the invention, a toothing is formed in the contact surface between the control element and the knife carrier, for example, in the form of a nut and spring connection. The primary purpose of the toothing is to center the control element plate in relation to the knife carrier and to absorb additional forces in the contact surface. 
   When using knife packages that are composed of the slicing knife and the knife retaining plate, a partially gradated surface of the control element is preferred to achieve an adaptation to the contours of the knife package. In this way, the knife package is supported on the full surface of the control element. 
   When using the control element of this invention with a knife package or with only a slicing knife, it is beneficial to screw the control element to the knife package and/or the slicing knife. The unit resulting therefrom can be assembled outside of the knife ring so that there is no interruption in the comminution operation. The knife exchange itself is done by exchanging only the unit, which, when compared with a knife exchange without control elements, does not require additional time and, therefore, does not add to the down time caused by the changing out of knives. 
   Because the knife packages are to function with different control elements, it is beneficial to provide a backstop at a rearward longitudinal edge of the knife package that is adjustable horizontally to the edge and takes into account the changed geometry when the cutting angle δ is adjusted, and particularly takes the blade projection across from the base of the knife carrier into consideration. 
   By arranging receptacles for slitting elements, the chips produced with a device of this invention can be made of a predetermined length. 
   Through a change of the cutting angle δ a displacement of the blade of the slicing knife in relation to the knife ring occurs, thus pressure lips that are located in the direction of rotation at the rearward side of the knife carriers are exchangeable, according to a further advantageous embodiment this invention. By using a suitable pressure lip in combination with a certain control element, the cutting conditions for the operation of a chipping device can be further optimized. 
   The invention is explained in more detail below with an embodiment illustrated in the drawings. The embodiment shows a knife ring chipper for timber, without limiting the invention to this embodiment. The invention also includes knife ring chippers with stationary or rotating opposing knives as well as cutting disks, all of which have knife carriers, which hold a slicing knife in a predetermined cutting angle to the comminution material. 
   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  is a schematic diagram of a chipping apparatus according to a preferred embodiment of the present invention; 
       FIG. 2  is a partial cross-section of a knife ring of a the chipping apparatus according to the invention; 
       FIGS. 3   a - 3   c  are a top view and two cross sectional vies, respectively, of a control element illustrated in  FIG. 2 ; 
       FIG. 4  is a cross section of a chipping apparatus according to an alternate embodiment of the invention; and 
       FIG. 5  is an illustration of a blade of a slicing knife. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a knife ring chipper of this invention for chipping timber. To start with, there is shown 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  that can be rotated freely around a horizontal axis. A rearward wall of the housing  10  is closed and serves as a storage place for a drive shaft (not shown) of the knife ring  11 , the front of the housing  10  has a circular opening, through which the chipping chamber  12  is freely accessible. Towards its top, the chipping chamber  12  is bound by a circular arc segment  13 , a bent side of which extends in close proximity to the knife ring  11 . In the lower region, a bracing floor construction  14  forms the boundary of the chipping chamber  12  and is, like the circular arc segment  13 , 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 stationarily 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, which is in the form of 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  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 holding-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 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 knife ring  11  includes two concentric ring wheels arranged with a space there between, of which in  FIGS. 1 and 2 , due to the layout of the sectional view, only the rear one marked with the reference numeral  17  is visible. The inner sides of the two ring wheels are connected by axially-oriented knife carriers  18 , which are evenly distributed around the perimeter, thereby resulting in a rigid knife ring  11  unit. 
     FIG. 2 , illustrates a section of a knife ring  11 . Again, the reference numeral  17  marks the hub-lateral ring wheel, from the inner side of which the knife carriers  18  extend perpendicular. The left half of the drawing shows, in the direction of rotation  19 , the front part of a knife carrier  18 , whereas the right half of the drawing illustrates the rear part of a preceding knife carrier  18 , also in the direction of rotation  19 . 
   The knife carrier  18  is box-shaped, whereby its bottom side is formed by a curved wear shoe  20  that forms a boundary of the chipping chamber  12 . The rearward side of the knife carrier  18  is formed of a radially oriented wall element  21 , to which a slat-shaped pressure lip  22  having a trapezoid cross section is screwed. Of the two sidewalls, only the one allocated to the rear ring wheel  17  and identified with the reference numeral  23  is visible. The two sidewalls  23  are rigidly connected to the ring wheels  17  by screws  24 . 
   A front side of the knife carrier  18  is formed by a slanted base plate  25 , which extends at an angle of approximately 35° tangentially to the chipping chamber  12 . This results in a knife carrier  18  that is tapered in the direction of rotation  19  towards the chipping chamber  12 . In the area of its longitudinal edge located across from the wear shoe  20 , the base plate  25  has a longitudinal groove  26  extending vertically to the illustration plane. The parts forming the knife carrier  18  are all welded together and are made of wear-resistant materials, for example, Hardox 400. This results in an extremely robust and rigid construction. 
   As an alternative to the box-shaped design of the knife carrier  18 , a massive type of construction with hardened or armor-plated parts being provided in zones with high wear and tear would also be possible. 
   The base plate  25  forms a support surface for a control element  27 , which in the illustrated embodiment includes a wedge-shaped plate with a top  28  and a bottom  29 . A more detailed construction of the control element  27  is illustrated in  FIGS. 3   a - 3   c.    
   The bottom  29  of the control element  27  is formed so as to be flat in order to ensure as large a support surface as possible and features only at the rear longitudinal edge a slat-shaped projection  30 , which, together with the longitudinal groove  26 , creates a positive locking in the base plate  25 . The function of this positive locking is both for a power derivation and for a centering of the control element  27 . The top  28  of the control element  27  is gradated, the result of which is a first larger partial surface  31 , a second striated partial surface  32 , and finally, a third, also striated partial surface  33 . The transition between the second partial surface  32  and the third partial surface  33  serves to form a stop surface  34 . In this way, a surface profile is created, which is ideally suited for accommodating a knife package  35 . 
   The wedge shape of the control element  27  is formed by the inclination of the top  28  compared to the bottom  29 , which in the illustrated embodiment includes an angle ε of approximately 5°. 
   The mounting of the control element  27  to the knife carrier  18  is done with the aid of screws  36 , as illustrated in  FIG. 4 . Their distribution can be viewed in  FIG. 3 , where the arrangement of the bores  37  for the screws  36  is illustrated. Extensions of the bores  37  are found in screw thread bores in the base plate  25  ( FIG. 4 ). 
   The top  28  of the control element  27  carries a knife package  35 , which is formed by a knife retaining plate  38 , onto which the slicing knife  39  is mounted with screws  40  ( FIG. 4 ), which are adjustable within elongated holes, as is commonly known. This allows the adjustment of the knife package  35  to a predetermined width outside the knife ring  11 . 
   When installed, the bottom side of the slicing knife  39  rests evenly on the first partial surface  31 . The thickness of the slicing knife  39  is equal to the height differential to the second partial surface  32 , and the heads of the screws  40  lie within grooves  54  ( FIGS. 3 and 4 ) of the partial surface  31 . As a result, the knife retaining plate  38  comes to rest evenly on the second partial surface  32 . The knife retaining plate  38  pushes with its rear longitudinal edge against the stop surface  34 , which forms a zero position for setting the projection of the slicing knife  39  into the chipping chamber  12 . The knife package  35  is fastened with screws, which extend through the knife package  35  to threaded bores  42  in the control element  27  ( FIG. 3 ). 
   In this way, in an operative mode, the slicing knives  39  are brought into a position that is parallel to the pressure lip  22 , or slightly diverging and at a distance therefrom so that a passage slot  43  is created, through which the chipped material in the course of the comminution passes from the chipping chamber  12  to the peripheral areas of the knife ring  11 . 
     FIG. 5  shows, in a simplified illustration, the chipping process. What can be seen is the tip of the slicing knife  39  with a blade  44  engaged in the processing of material in the form of wood, for example, a tree trunk  16 . A top side  45  of the material corresponds thereby with the bottom part of the wear shoe  20  that bounds the chipping chamber  12 . The projection  46  of the blade  44  of the slicing knife  39  beyond the bottom of the knife carrier  18  defines the thickness of the chip  47  to be cut. 
   During the chipping process, the following geometric relations and angle designations occur. Enclosed by a back  48  of the slicing knife  39  and a perpendicular to the top  45  of the material is an angle of the chip γ. The angle formed by the back  48  of the slicing knife  39  and the top  45  of the material is referred to as cutting angle δ; the tapering angle of the blade  44  is referred to as wedge angle β. Between the blade  44  and the top  45  of the material, setting angle α arises. 
   As can be easily seen in  FIG. 2 , with knife ring chippers and also with disk cutters, the cutting angle δ is formed by the inclination of the base plate  25  and the additional inclination of the slicing knife  39  that is determined by the shape of the control element  27 , the inclination in the illustrated embodiment being formed by the wedge shape. The wedge shape is created by the inclination in opposite directions of the top  28  and bottom  29  of the control element  27 , which include an angle ε and thereby form a joint cutting line L. In the embodiment illustrated in  FIG. 2 , the cutting line L is inside the chipping chamber  12  with the result that the cutting angle δ, which is determined by the base plate  25  of the knife carrier  18 , is increased by the measure ε. 
   For other application purposes, the wedge shape of the control element  27  can be tapered in the opposite direction so that the cutting line L lies outside of the chipping chamber  12 . In this instance, the cutting angle δ is decreased by the measure ε. 
   A third possibility is illustrated in  FIG. 4 , whereby the top  28  and bottom  29  of the control element  27  extend parallel to one another and thus do not form a cutting line L. In this case, the cutting angle δ is equal to the inclination angle of the base plate  25  to the bottom of the wear shoe  20 . 
   In this way, by using a suitable control element  27 , it is possible to adjust the cutting angle δ to the prevailing conditions with respect to material, chip geometry, chip quality etc. without having to exchange the complete knife ring  11 . 
     FIG. 4  shows a modified embodiment of the invention, whereby, as previously mentioned, the control element  27  does not alter the cutting angle δ determined by the knife carrier  18  due to the top  28  extending parallel to the bottom  29 . 
   In comparison to the embodiment of the invention illustrated in  FIG. 2 , the modified version in  FIG. 4  has an adjustable backstop  49  on the rearward longitudinal edge of the knife retaining plate  38 . The adjustable backstop  49  includes a screw  50  with a stop surface  34  concurring with a disk  51 , which can be screwed into the rearward longitudinal side of the knife retaining plate  38 . Preferably, such an adjustable backstop  49  is arranged in two separate locations on the knife retaining plate  38 . 
   Between the disk  51  and the longitudinal edge of the knife retaining plate  38 , a predetermined number of thin inlay lamellae  52  is inserted. The number of the inlay lamellae  52  thereby determines the relative position of the disk  51  with respect to the knife retaining plate  38  and thus determines the position of the backstop  49 . Thus, an adjustment of the knife package  35  to differently shaped control elements  27  and the varying geometry resulting therefrom can be achieved in a simple way. 
   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.