Abstract:
A device for comminuting feed material has a rotary blade ring rotating about an axis of rotation. A comminution chamber is enclosed by the rotary blade ring and receives the feed material in an axial direction parallel to the axis of rotation. A counter abutment projects in the axial direction into the comminution chamber. The rotary blade ring is moveable in a radial advancing direction against the counter abutment and applies a pressing force relative to the counter abutment to effect comminution of the feed material in a working position of the counter abutment. The counter abutment has an effective surface facing the feed material and the effective surface is supported so as to be moveable such that, upon surpassing a predetermined value of the pressing force, at least the effective surface performs an escape movement relative to the rotary blade ring in an escape direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a device for comminuting material, in particular, material in the form of trunk wood and residual wood as well as wood material combined to a packet, comprising a comminution chamber surrounded by a rotary blade ring into which the material is fed in the axial direction, wherein, for the purpose of comminution, the rotary blade ring is movable in the radial direction against an abutment projecting axially into the comminution chamber. 
     2. Description of the Related Art 
     Devices of the aforementioned kind for comminution of material are known, for example, from DE 35 05 077. Such devices have a horizontally movable carriage on a stationary frame. On the carriage a comminution apparatus is arranged which is comprised substantially of a rotary blade ring surrounding a comminution chamber. The cutting edges of the comminution tools project with a short projecting length from the inner side of the rotary blade ring into the comminution chamber. For providing an abutment during the comminution process, the device of the aforementioned kind has a stationary abutment which projects axially into the comminution chamber. 
     For comminuting the feed material, the feed material is fed axially into the comminution chamber and secured within as well as outside of the comminution chamber. By horizontally moving the carriage and thus also the rotating blade ring, the material is compressed between the counter abutment and the rotary blade ring and at the same time comminuted by the cutting edges of the rotary blade ring. By means of the continued advancing movement of the rotary blade ring in the direction toward the abutment, the pressing force required for comminution is maintained. After completion of a working stroke, with which a section of the feed material corresponding to the depth of the comminution chamber has been processed to chips or cuttings, the carriage together with the rotary blade ring moves back into its initial position, and the material is then advanced farther by the length of a further section into the comminution chamber. In this way, a cycled comminution of the feed material by the depth of the comminution chamber, respectively, is achieved. 
     Such devices have proven very successful in practice. Problems occur only when the material is contaminated by hard foreign bodies. The hard foreign bodies can be, for example, broken-off parts of woodworking tools of previous processing stations or shrapnel dating back to the World Wars I and II that have penetrated into the trunk wood. They are engaged during the course of the comminution of the material by the comminution tools of the rotary blade ring and cause increased wear, and, in more serious cases, even destruction of machine parts. 
     In order to overcome this problem, it has been suggested to test the material with regard to foreign bodies by means of detectors. According to this method, feed material contaminated by foreign bodies can already be sorted out prior to processing. However, experience has shown that, actually, this is achieved only unsatisfactorily so that a residual risk is still present for the devices of the aforementioned kind. 
     In order to prevent this residual risk, it is also already known to provide a device of the aforementioned kind with a monitoring and control system. It monitors, on the one hand, the drawing of current at the drive side of the device and, on the other hand, the operating pressure of the cylinder-piston unit which provides the feed action of the rotary blade ring. A sudden increase of the current draw and/or a sudden increase of the operating pressure of the cylinder-piston unit indicates a foreign body within the feed material. In order to protect the comminution device, the cylinder-piston unit which provides the feed action is then switched to a pressureless state for reducing the pressing force between the comminution tool and the foreign body. Parallel to this, braking and stopping of the rotary blade ring can be realized. 
     Both alternatives, however, have the disadvantage that a reaction in response to the signal indicating the foreign body can be provided only with some temporal delay. This is caused, on the one hand, by the large mass of the rotating blade ring and the resulting great kinetic energy as well as the inertia of the hydraulic advancing or feeding system. Possibly, the rotary blade ring cannot be protected from damage as a result of the temporally delayed counter measures. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to development the devices of the aforementioned kind such that feed material contaminated with foreign bodies cannot cause any damage during operation of such a device. 
     In accordance with the present invention, this is achieved in that at least the effective surface of the counter abutment facing the feed material is moveably supported so that, upon surpassing a predetermined value of the pressing force caused by the advancing of the rotary blade ring, at least the effective surface of the counter abutment will yield to or perform an escape movement relative to the rotary blade ring. 
     The invention takes an entirely new direction for solving the aforementioned object in that it no longer changes the pressing force acting on the comminution blades indirectly via the control of the cylinder-piston unit driving the carriage but reduces directly the pressing force required for an effective comminution. This is realized by providing an escape movement of the counter abutment in the advancing direction of the rotary blade ring. 
     With this inventive concept, the pressing force onto the comminution tools is reduced directly without any intermediate action so that a very fast response for protecting the device according to the invention is realized. This escape movement of the counter abutment is effected by the pressing force which is present within the comminution chamber so that for this purpose no additional force expenditure is required. Moreover, the parts which are to be moved for damage control have relatively small dimensions with a corresponding minimal weight so that their minimal inertia further improves a quick response. 
     The escape movement of the counter abutment can be realized in different ways. Preferred is a parallel movement of the surface of the counter abutment facing the rotary blade ring in the advancing direction or feed direction of the rotary blade ring. 
     As a result of the specific weight and primarily of the entrainment effect of the comminution tools, the foreign bodies will collect preferably in the area of the counter blade, i.e., in the lower area of the comminution chamber. An escape movement of the effective surface of the counter abutment in this area can also be made possible by a pivot movement of the effective surface about an axis extending horizontally in the upper area of the counter abutment. 
     A preferred embodiment of the invention provides for a substantially two-part configuration of the counter abutment. In this connection, on a stationary part of the counter abutment, which receives the abutment forces occurring during operation, a movable attachment is provided which is facing directly the feed material. This embodiment reduces the number and the weight of the movable parts of the counter abutment to a minimum so that this embodiment ensures very short response times. The movability between the rigid part and the attachment is ensured by guide elements which are aligned in the advancing direction. 
     In other preferred embodiments the counter abutment is a rigid or stiff structure which is movably supported on the remaining stationary structure of the device outside of the comminution chamber. In this way, larger moving masses are obtained but this configuration has the advantage of an improved accessibility of the moveable support and the drive. A further advantage of this configuration is based on the simple configuration of the part of the counter abutment projecting into the comminution chamber which can be formed with minimal thickness as a result of its unitary configuration. In this connection, for identical rotary blade ring size an enlargement of the comminution chamber results so that it can receive and process more feed material. In this embodiment, the movability of the counter abutment is realized by means of a sliding support on the stationary structure of the device. 
     Further advantages result from a combination of the aforementioned embodiments in which a counter abutment with attachment is additionally moveably secured by means of its support arm on the stationary structure external to the comminution chamber. The two systems for providing an escape movement can cooperate in this connection such that a first quick escape movement is realized via the attachment on the support arm and a further escape movement is realized by a movement of the support arm. 
     In a simplified embodiment of the invention, the counter abutment is secured by means of a spring element in its nominal or working position. The spring force corresponds in this connection to a predetermined value of the pressing force for which the presence of foreign bodies does not yet cause appreciable damage. Upon surpassing this pressing force value, the counter abutment moves back with compression of the spring element and prevents greater damage. 
     An especially preferred embodiment of the invention has a monitoring and control system as well as at least one cylinder-piston unit which secures the counter abutment in its nominal or working position. Upon reaching a predetermined value of the pressing force, which signals the presence of foreign bodies at the comminution tools, the cylinder-piston unit is switched to a pressureless state in order to thus initiate an escape movement of the counter abutment. 
     This embodiment has the advantage that the starting point for the escape reaction can be controlled very precisely. Since the feed material to be comminuted is present in a compressed state within the comminution chamber, the switching of the cylinder-piston unit into a pressureless state provides a relaxation possibility for the feed material which effects the restoring force for the escape movement of the counter abutment. 
     According to further embodiments of the invention, this restoring force can be actively enhanced for accelerating the escape movement in that double-acting cylinder-piston units and/or pre-stressed spring elements are used. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
     FIG. 1 is a vertical longitudinal section of the device according to the invention along the line I—I illustrated in FIG. 2; 
     FIG. 2 is a horizontal longitudinal section of the device according to the invention along the line II—II illustrated in FIG. 3; 
     FIG. 3 is a vertical cross-section of the device according to the invention along the line III—III illustrated in FIG. 1; 
     FIG. 4 is a cross-section on a large scale of the counter abutment in the area of the comminution chamber; 
     FIG. 5 is a longitudinal section of the counter abutment illustrated in FIG. 4 along the line V—V illustrated therein; 
     FIG. 6 is a horizontal longitudinal section of a further embodiment of the device according to the invention along the line VI—VI illustrated in FIG. 7; 
     FIG. 7 is a vertical longitudinal section of the device illustrated in FIG. 6 along the line VII—VII shown therein; 
     FIG. 8 is detail view of the device illustrated in FIGS. 6 and 7; 
     FIG. 9 is a cross-section of the counter abutment illustrated in FIG. 8 along the line IX—IX shown therein; 
     FIG. 10 is a detail of the device illustrated in FIG. 8 along the line X—X shown therein; and 
     FIG. 11 is a plan view onto the device illustrated in FIGS. 8 through 10. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1,  2 , and  3  a comminution device according to the invention is illustrated in essential section views. They show a frame  1  fixedly anchored to the ground which has two horizontal and parallel rails  2  and  3  at its upper side which are slightly projecting from the surface of the frame  1 . The frame  1  serves for receiving a movable carriage  4  which is supported on wheels  5  and  6  and can be moved by means of the advancing cylinder  7  along the rails  2  and  3 . 
     The carriage  4  is comprised substantially of a basic frame forming a platform on which a comminution apparatus  8  and its drive unit  9  are arranged so as to be movable therewith. 
     The central component of the comminution device  8  is a rotary blade ring  10  which rotates about a horizontal axis  12  extending transversely to the rails  2  and  3 . The rotary blade ring  10  is formed by two annular discs  13  and  14  which are coaxial to one another and spaced apart at a distance from one another. They are rigidly connected to one another by means of a plurality of blade carriers  15  which are axially arranged at the circumference. The comminution or chipping blades which are fastened on the blade carriers  15  project with their cutting edge projection into the interior defined by the rotary blade ring  10  and thus define the cutting edge circle during operation. 
     The annular disc  13  which is positioned deeper within the comminution chamber  16  is coupled with its outer annular surface  2  to a support disc  17  which is also coaxially positioned and, in turn, is connected to a drive shaft  18  whose free end supports a multi-groove pulley  19 . 
     A housing  20  surrounds the rotary blade ring  10  with ample space and makes possible the removal of the comminuted material by means of a lower outlet  21 . In the area of the drive shaft  18  the housing  20  has two bearing groups  22  and  23  which receive the drive shaft  18 . At the front side of the comminution apparatus  8 , a feed opening  24  which corresponds substantially to the size of the rotary blade ring  10  and is positioned opposite thereto is provided via which the feed material is supplied to the comminution tools. 
     The inner space of the comminution apparatus  8  which is surrounded by the rotary blade ring  10  has a comminution chamber  25  whose upper side is delimited by a horizontally extending cover plate  26  which projects with both ends into close vicinity of the cutting edge circle. The cover plate  26  has a top segment  27 . The underside is formed by a massive bottom plate  28  which also extends into close vicinity of the cutting edge circle. At the backside the comminution chamber  25  is delimited by a closure wall  29  which provides a depth stop for the feed material and covers the rotating support disc  17 . 
     Parallel to the axis  12  a counter abutment  30  projects through the feed opening  24  into the interior. This will be explained in more detail in connection with FIGS. 4 and 5. The counter abutment  30  covers on one side of the comminution chamber  25  the portion of the rotary blade ring  10  extending between the cover plate  26  and the bottom plate  28 . In contrast to the other parts delimiting the comminution chamber  25  which follow the advancing movement  72  of the carriage  4 , the counter abutment  30  is stationarily attached to a portal structure (support structure)  31  positioned opposite the feed opening  24  (FIGS.  2  and  3 ). The portion of the rotary blade ring  10  positioned horizontally opposite the counter abutment  30  forms the comminution zone where the feed material is brought into engagement with the comminution or chipping tools. In the area of the comminution zone the bottom plate  28  is provided with a wear-resistant counter blade  32 . 
     For securing the feed material during the comminution process, two pressing blades  33  and  34  project from the top segment  27  in two radial planes. They are arranged in a comb-like arrangement on a common blade support  35  and can be pivoted about the bearing axle  35  into the comminution chamber  25 . For this purpose, the cover plate  26  has corresponding cutouts. 
     Laterally adjacent to the comminution or chipping chamber  25  in the area of the comminution zone a planar protective shield  38  is arranged at the front side of the housing  20 . The front side of the protective shield  38  is positioned in the plane of the separating cut and thus moves during the course of the working stroke into a position in front of the end faces of the feed material that have just been cut or chipped. Accordingly, the movement path of the comminution apparatus  8  is protected against pieces of wood that could penetrate into the movement path and thereby impair the operation of the comminution device. 
     The rotary blade ring  10  is rotated by a drive unit  9  which is mounted at a short lateral spacing adjacent to the comminution apparatus  8  on the carriage  4 . The drive unit  9  is comprised substantially of an electric motor  36  which is connected by a drive belt  37  to the multi-groove pulley  19 . 
     Moreover, FIGS. 2 to  3  show directly in front of the comminution chamber  25  a stationary portal structure  31  whose support surface  39  projects slightly relative to the bottom plate  28  of the comminution chamber  25  by a minimal amount. Above the pressing surface  39  and at a spacing matching the height of the comminution chamber  25 , pressing elements  40  in the form of weights are arranged which can be lowered and which secure the feed material directly in front of the comminution chamber  25  during the comminution (chipping) process. 
     A trough-shaped feed gutter  41  adjoins directly the rear side of the portal structure  31  and has a bottom formed by a conveyor belt  42  which provides transportation of the feed material to the comminution apparatus  8 . The drive for the conveyor belt  42  is indicated at  11 . 
     The precise configuration of the first embodiment of the counter abutment  30  can be seen in FIGS. 4 and 5. The counter abutment  30  has first a stationary support arm  43  projecting axially into the comminution chamber  25  which is connected with its end projecting out of the comminution chamber  25  by a head flange rigidly to the portal structure (support structure)  31 . During the radial advancing movement  72  of the carriage  4  and thus of the comminution apparatus  8 , the support arm  43  thus provides a stationary reference point within the comminution chamber  25 . 
     The outer side  15  of the support arm  43  is matched in the form of a polygon to the radius of the cutting edge circle and has at the upper and lower edge areas two bores  44 , respectively, spaced relative to one another and arranged in the direction of the advancing movement. A bolt  45  is slidably guided in the bores  44 , respectively. At the front side of the support arm  43  the upper and lower edge areas are provided with a recess in which foamed material strips  46  are provided as a protection of the sliding seals between the bores  44  and the bolts  45 . 
     In additional bores  47 , which are arranged diagonally opposite from one another, hydraulically operated cylinder-piston units  48  are arranged whose movable pistons project from the front side of the support arm  43 . In an alternating arrangement thereto bores  49  are provided in which the spring elements  50  are inserted. 
     In addition, the counter abutment  30  has an attachment  51  which is positioned opposite the inner side of the support arm  43  at a spacing of approximately 5 cm. The attachment  51  has a convexly curved surface  68  which is facing the comminution chamber  25 . The oppositely positioned rear side of the attachment  51  follows the contour of the inner side of the support arm  43 . In an axial direction the attachment  51  projects approximately from the closure wall  29  to the front side of the machine housing  20 . The attachment  51  is secured by the bolts  45  in the nominal position which for this purpose at its end face is provided with a pin  52  which is anchored in a corresponding bore  53  of the attachment  51 . In a corresponding way, the spring elements  50  are connected with the attachment  51 . 
     For providing and maintaining a predetermined spacing between the support arm  43  and the attachment  51  during regular operation of the comminution or chipping device according to the invention, the pistons of the cylinder-piston units  48  are extended and accordingly press on the inner side of the attachment  51  and move it along the guided bolt  45  away from the support arm  43 . In this connection, the spring element  50  is pre-stressed in that a pressure spring  54  between the base of the bore  44  and the widened bolt head  55  is compressed. 
     The second embodiment of the invention is illustrated in more detail in FIGS. 6 to  11 . With the exception of the counter abutment and its connection to the portal structure  31 , the device illustrated therein is substantially identical to the previous embodiment so that the above description applies accordingly. 
     The second embodiment differs from the previously described embodiment substantially in that the counter abutment  56  is of a unitary (one-part) configuration wherein it has both sides provided with convexly curved surfaces  69 ,  70  (FIG. 9) positioned in a radial cross-sectional plane. The end of the counter abutment  56  projecting out of the comminution chamber  25  is fastened with its end face on the inner side of a jaw  57 . The outer side of the jaw  57  has a horizontal upper guide bushing  58  which is aligned in the advancing direction  72  and a guide bushing  59  arranged underneath and parallel thereto. The bushings  58 ,  59  represent the movable part of a sliding guide. A vertical reinforcement element  60  connects the two guide bushings  58  and  59  and is welded, in turn, with its longitudinal side to the outer side of the jaw  57 . 
     The stationary part of the sliding guide is fastened on the portal structure  31  and is comprised substantially of guide elements in the form of horizontal sliding rods  61 ,  62  which are secured at their ends in the bearings  63  and  64  as well as  65  and  66  and are thus rigidly connected with the portal structure  31 . The arrangement of the guide bushings  58 ,  59  on the sliding rods  61 ,  62  provides for the counter abutment  56  to be movable between the bearings  63 ,  65  and  64 ,  66  in the horizontal direction. The advancing force required for this purpose is provided by a hydraulically operated cylinder-piston unit  67  which engages with its movable piston  71  the reinforcement element  60  parallel between the sliding rods  61 ,  62  and is supported with its stationary cylinder on the portal structure  31 . 
     The function of the device according to the invention is as follows: 
     During the regular comminution operation the effective surface  68 ,  69  on the counter abutment  30  or the entire counter abutment  56  is positioned in a forward operating position moved by a predetermined amount into the comminution chamber  25 . This state is illustrated in FIG.  4  and FIG.  11 . 
     A monitoring and control unit examines continuously the comminution or chipping operation in regard to whether irregularities indicate the presence of foreign bodies in the feed material. For this purpose, the monitoring and control unit can be furnished as desired individually or in combination with sensors which detect the current draw of the drive unit  9 , the vibrations and/or noise development at the rotary blade ring  10  or the operating pressure at the advancing cylinder  7  and compare these values with predetermined nominal values. When unusual deviations of the measured values relative to the nominal values indicate the presence of foreign bodies, for example, an excessive increase of the current draw of the electric motor  36  or an increased operating pressure of the advancing cylinder  7 , the monitoring and control unit initiates immediately countermeasures which effect a receding or escape movement of the effective surface  68 ,  69  of the counter abutment  30 ,  56 . 
     In the case of the first embodiment of the invention such measures are the immediate stopping of the advancing movement of the rotary blade ring  10  and/or switching of the cylinder-piston unit  48  to a pressureless state. As a result of the pressing force which is applied onto the effective surface  68  by the compressed feed material, the attachment  51  escapes suddenly in the direction of the support arm  43  so that the foamed material strips  46  are compressed. This escape movement is assisted and continued by the spring elements  50  which are pre-stressed in the working position and which now relax. As a result of the escape movement of the attachment  51 , the feed material with foreign bodies contained therein is no longer pressed against the comminution tools and the risk of damage is thus eliminated. 
     In the case of the second embodiment of the invention, the advancing movement of the rotary blade ring  10  is stopped also. At the same time, in the case of the double-acting cylinder piston unit  67  a thrust reversal is initiated which effects an active return of the entire counter abutment  56  along the sliding rods  61  and  62 . The resulting volume increase of the comminution chamber  25  allows for a relaxation of the compressed feed material so that the pressing force of the feed material acting on the rotary blade ring  10  decreases and, in this way, the comminution device is protected against damage. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.