Patent Publication Number: US-7721983-B2

Title: Crusher

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a crusher capable of efficiently crushing target materials to be crushed. 
     2. Description of the Related Art 
     For the purposes of mainly promoting reuse of waste materials and reducing the volume thereof, crushers are employed to crush various kinds of materials to be crushed. Some of those crushers are used to crush primarily cut limbs and timbers from thinning, which are generated with land development, maintenance and other operations made in forests, branches generated by trimming trees cut in forests, and scrap woods generated with pulling-down of wooden houses, etc. 
     One known such crusher includes a feed conveyor for conveying target materials, which are loaded to be crushed, toward a crushing chamber, a pressing roller for pressing the target materials to be crushed from above, which are conveyed on the feed conveyor, a crushing bit for crushing the target materials introduced by cooperation of the feed conveyor and the pressing roller, and a screen (sieve member) for discharging the materials having been crushed outward of the crushing chamber while selecting the grain size of the crushed materials. Further, in one example of that type of crusher, the crushing bit smashes against the target materials to be crushed from below, which are introduced to the crushing chamber while being gripped by the feed conveyor and the pressing roller, thereby crushing the target materials (see, e.g., U.S. Pat. No. 5,947,395). 
     SUMMARY OF THE INVENTION 
     With the crushing method of smashing the crushing bit against the target materials to be crushed from below as in the above-described technique, the target materials can be crushed into finer chips when a point (support point) where the target materials to be crushed are pressed and supported from above at the time of smashing by the crushing bit is positioned closer to a point (smashing point) where the crushing bit smashes against the target materials to be crushed. In the above-described technique, the support point where the target materials to be crushed are supported is a contact point between the pressing roller and the target materials. In trying to position the support point closer to the smashing point, however, there is a limit because of the problem with mechanical layout, e.g., the arrangement of the pressing roller and a crushing rotor. With the above-described technique, therefore, the support point and the smashing point tend to locate away from each other, whereby the target materials cannot be finely crushed and are roughly crushed by the crushing bit. Accordingly, in some cases, a longer time is required until the roughly-crushed target materials are finely crushed, and the crushed materials having relatively large sizes are discharged through the screen as they are. This may result in lowering of the crushing efficiency and a reduction in grain size quality of the crushed materials. 
     An object of the present invention is to provide a crusher capable of efficiently producing crushed materials with good grain size quality. 
     To achieve the above object, according to a first aspect, the present invention provides a crusher comprising a crushing rotor being rotatable and having a crushing bit to crush target materials to be crushed; a feed conveyor for conveying the target materials toward the crushing rotor; and a pressing feeder unit including a pressing roller disposed above the feed conveyor and introducing the target materials on the feed conveyor toward the crushing rotor while pressing the target materials from above, and a fixed bit disposed at a position which is closer to the crushing rotor than a point where the pressing roller presses the target materials and which is outward of the crushing rotor in the radial direction, the fixed bit having a bumping surface, against which the target materials bump, disposed in an opposed relation to the rotating direction of the crushing bit, thereby crushing the target materials introduced toward the crushing rotor. 
     According to a second aspect, in the crusher according to the first aspect, the bumping surface of the fixed bit is preferably arranged at a level not lower than the height of a lower end portion of the pressing roller during crushing operation. 
     According to a third aspect, in the crusher according to the first aspect, the fixed bit is preferably replaceable with another type of fixed bit. 
     According to a fourth aspect, in the crusher according to the third aspect, a gap size from a part of the fixed bit closest to the crushing rotor to a maximum locus of rotation of the crushing bit is preferably adjustable by replacing the fixed bit with another type of fixed bit. 
     To achieve the above object, according to a fifth aspect, the present invention provides a crusher comprising a crushing rotor being rotatable and having a crushing bit to crush target materials to be crushed; a feed conveyor for conveying the target materials toward the crushing rotor; and a pressing feeder unit including a pressing roller disposed above the feed conveyor and introducing the target materials on the feed conveyor toward the crushing rotor while pressing the target materials from above, and a support-point constituting portion disposed at a position closer to the crushing rotor than a point where the pressing roller presses the target materials, the support-point constituting portion acting, when the crushing bit smashes against the target materials introduced toward the crushing rotor, to press the target materials toward the feed conveyor side. 
     To achieve the above object, according to a sixth aspect, the present invention provides a crusher comprising a crushing rotor being rotatable and having a crushing bit to crush target materials to be crushed; a feed conveyor for conveying the target materials toward the crushing rotor; a pressing feeder unit including a pressing roller disposed above the feed conveyor and introducing the target materials on the feed conveyor toward the crushing rotor while pressing the target materials from above, and a first fixed bit disposed at a position which is closer to the crushing rotor than a point where the pressing roller presses the target materials and which is outward of the crushing rotor in the radial direction, the first fixed bit having a bumping surface, against which the target materials bump, disposed in an opposed relation to the rotating direction of the crushing bit, thereby acting, when the crushing bit smashes against the target materials introduced toward the crushing rotor, to press the target materials toward the feed conveyor side for crushing of the target materials; and a second fixed bit disposed at a position downstream of the first fixed bit in a direction in which the target materials are forced to move and which is outward of the crushing rotor in the radial direction, the second fixed bit having a bumping surface, against which the target materials bump, disposed in an opposed relation to the rotating direction of the crushing bit, thereby further crushing the target materials having been crushed by the first fixed bit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a crusher according to a first embodiment of the present invention; 
         FIG. 2  is a plan view of the crusher according to the first embodiment of the present invention; 
         FIG. 3  is a side view showing a structure in the vicinity of a crushing apparatus provided in the crusher according to the first embodiment of the present invention; 
         FIG. 4  is a side view showing a state of the structure shown in  FIG. 3  during the crushing operation; 
         FIG. 5  is a side view showing a structure in the vicinity of the crushing apparatus provided in a crusher according to a modification of the first embodiment of the present invention; 
         FIG. 6  is a side view showing a state of the structure shown in  FIG. 5  during the crushing operation; 
         FIG. 7  is a side view showing a structure in the vicinity of the crushing apparatus provided in a crusher according to a second embodiment of the present invention; 
         FIG. 8  is a side view showing a structure in the vicinity of the crushing apparatus provided in a crusher according to a first modification of the second embodiment of the present invention; 
         FIG. 9  is a side view showing a structure in the vicinity of the crushing apparatus provided in a crusher according to a second modification of the second embodiment of the present invention; 
         FIG. 10  is a side view showing a structure in the vicinity of the crushing apparatus provided in a crusher according to a third embodiment of the present invention; and 
         FIG. 11  is a side view showing a structure in the vicinity of the crushing apparatus during crushing operation provided in a crusher according to a fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of a crusher according to the present invention will be described below with reference to the drawings. 
       FIG. 1  is a side view showing an overall structure of a crusher according to a first embodiment of the present invention,  FIG. 2  is a plan view of the crusher shown in  FIG. 1 , and  FIG. 3  is a side view showing a structure in the vicinity of a crushing apparatus  13  (described later) provided in the crusher shown in  FIG. 1 . Note that, in the following description, directions corresponding to the left and right in  FIG. 1  are assumed to represent respectively the rear and front of the crusher or one side and the other side thereof. 
     The crusher shown in  FIGS. 1 to 3  comprises mainly a travel body  1  capable of being self-propelled, a crushing function structure  2  installed on the travel body  1  and crushing target materials loaded to be crushed, a discharge conveyor  3  for conveying the materials having been crushed in the crushing function structure  2  and discharging the crushed materials to the exterior of the crusher, and motive power equipment (power unit)  4  including a power source, such as an engine, for various components mounted in the crusher. 
     The travel body  1  comprises a track frame  5 , a drive wheel  6  and a driven wheel  7  disposed respectively at longitudinal opposite ends of the track frame  5 , a driving unit (hydraulic motor for travel)  8  having an output shaft coupled to a shaft of the drive wheel  6 , and a crawler (caterpillar belt)  9  looped over the drive wheel  6  and the driven wheel  7 . A body frame  10  is disposed on the track frame  5 . The body frame  10  supports the crushing function structure  2 , the discharge conveyor  3 , the power unit  4 , etc. 
     The crushing function structure  2  comprises a hopper  11  for receiving the loaded target materials, a feed conveyor  12  (see  FIG. 2 ) serving as feed means for feeding the target materials loaded into and received by the hopper  11 , a crushing apparatus  13  (see  FIG. 3 ) for crushing the target materials introduced by the feed conveyor  12 , and a pressing feeder unit  14  (see  FIG. 3 ) for pressing the target materials, which are going to be introduced to the crushing apparatus  13 , against the feed conveyor  12  at a position in front of the crushing apparatus  13 . 
     The feed conveyor  12  conveys the target materials toward a crushing rotor  15  (described later), and it comprises a sprocket-like drive wheel  16  (see  FIG. 3 ) disposed on the side close to the crushing rotor  15  (described later), a driven wheel (not shown) disposed on the opposite side (i.e., on the rear side of the wood crusher), and running members (i.e., conveyor belts or chain belts)  17  which are looped between the drive wheel  16  and the driven wheel at opposite ends of the feed conveyor  12  in the feed direction and which are disposed in plural rows (four in this embodiment, see  FIG. 2 ) side by side in the transverse direction. The driven wheel is supported by a bearing  19  (see  FIG. 1 ) mounted to a rear portion of a side wall  18  (see  FIG. 1 ) of the hopper  11 , and the drive wheel  16  is supported by a bearing (not shown) mounted to a side cover  20  of the crushing apparatus  13 , the side cover  20  being provided forward of the side wall  18 . Thus, the feed conveyor  12  is disposed to substantially horizontally extend from a lower position inside the hopper  11 , i.e., the inner side of the side wall  18  of the hopper  11 , to a position near the crushing rotor  15  (described later) such that the feed conveyor  12  is entirely accommodated within the hopper  11  and the side cover  20  of the crushing apparatus  13 . A rotary shaft  21  of the drive wheel  16  of the feed conveyor  12  is coupled through, e.g., a coupling to an output shaft of a driving unit (not shown) that is provided externally of the bearing in the transverse direction. By rotating the not-shown driving unit, the feed conveyor  12  is driven to move the conveyor running members  17  between the drive wheel  16  and the driven wheel in a circulating manner. 
     The pressing feeder unit  14  is provided adjacently rearward of the crushing rotor  15  (described later) above the feed conveyor  12  in an opposed relation to its conveying surface. With such an arrangement, the pressing feeder unit  14  introduces the target materials on the feed conveyor  12  toward the crushing rotor  15  while pressing the target materials from above. On that occasion, an anvil (first fixed bit)  70  (described later) presses the target materials toward the feed conveyor  12  side for crushing of the target materials. 
     The pressing feeder unit  14  comprises a support member (arm)  23  which has a rotary shaft  22  supported above the crushing apparatus  13  by a bearing provided in the side cover  20  such that the support member  23  is rotatable in a vertical plane (i.e., swingable up and down), a pressing roller  24  provided rotatably relative to the support member  23  and introducing the target materials to be crushed toward the crushing rotor  15  while pressing the target materials on the feed conveyor  12  from above, and the anvil  70  disposed at a position which is closer to the crushing rotor  15  than a point where the pressing roller  24  presses the target materials and which is outward of the crushing rotor  15  in the radial direction. The anvil  70  has a bumping surface  71 , against which the target materials bump, disposed in an opposed relation to the rotating direction of a crushing bit  36  (described later). 
     The support member  23  comprises an arm portion  25  provided with the rotary shaft  22 , and a bracket portion  26  provided at the distal end side of the arm portion  25  and supporting the pressing roller  24 . A lower end surface of the arm portion  25  is formed to curve in a circular-arc shape, and a curved plate  28  defining a part of a crushing chamber  27  (described later) is attached to the curved lower end surface of the arm portion  25 . On the other hand, a mount area of the bracket portion  26  to which the pressing roller  24  is mounted is formed in a circular-arc shape having a smaller diameter than the pressing roller  24  such that an outer circumferential surface of the pressing roller  24  projects out of the bracket portion  26 . 
     The dimension of the pressing roller  24  in the transverse direction (i.e., in the direction perpendicular to the drawing sheet of  FIG. 3 ) is set equal to or larger than the width of the conveying surface of the feed conveyor  12 . Though not specifically shown, the pressing roller  24  includes a driving unit mounted within its barrel. The pressing roller  24  is rotated by the not-shown driving unit substantially at the same circumferential speed as the feed speed of the target materials which are conveyed on the conveying surface of the feed conveyor  12 , thereby introducing the pressed target materials on the feed conveyor  12  toward the crushing chamber  27  (described later) in cooperation with the feed conveyor  12 . 
     The bracket portion  26  has a projected portion  80  which is projected into the crushing chamber  27  in a direction toward the crushing rotor  15  (described later). The projected portion  80  includes a wall  81  which is extended in the transverse direction of a crusher body and covers the pressing roller  24  from the crushing chamber  27  side, and also includes a recess  82  formed at the lower end (at the side closer to the feed conveyor  12 ) of the wall  81  so as to face the crushing chamber  27 . A bracket  84  having a protrusion  83  (see  FIG. 4 ) is mounted to the recess  82 , and the anvil  70  is mounted to the bracket  84 . 
     The anvil (first fixed bit)  70  has a bumping surface  71  against which the target materials bump, the bumping surface  71  being disposed in an opposed relation to the rotating direction of the crushing bit  36  (described later), a recess  72  (see  FIG. 4 ) to which is fitted the protrusion  83  of the bracket  84 , a side surface  73  (see  FIG. 4 ) formed continuously with the wall  81  and positioned on the side closer to the crushing rotor  15 , and an edge  74  (see  FIG. 4 ) formed by the bumping surface  71  and the side surface  73 . The anvil  70  thus constituted operates such that, when the crushing bit  36  smashes against the target materials introduced toward the crushing rotor  15 , the anvil  70  presses the target materials toward the feed conveyor  12  side for crushing of the target materials. A normal line n represents a normal direction of the bumping surface  71  on the side opposite to the recess  72 . The anvil  70  is mounted to the bracket  26  in a replaceable manner by bolts, for example, while the recess  72  is fitted to the protrusion  83  of the bracket  84 . Thus, because of the fitting between the recess  72  and the protrusion  83 , the anvil  70  has a structure being durable against an impact. In particular, the anvil  70  has superior durability against external forces acting in the outward radial direction of the crushing rotor  15 . Additionally, when the anvil  70  is mounted to the bracket portion  26 , it may be directly mounted to the recess  82  instead of using the bracket  84  as in the above-described example. 
     The anvil  70  will be described in more detail below with reference to  FIG. 4 . 
       FIG. 4  shows a state of the structure shown in  FIG. 3  during the crushing operation. In  FIG. 4 , the same components as those in  FIGS. 1-3  are denoted by the same reference numerals (such notation is similarly applied to other drawings described later), and a description of those components is omitted here. 
     Referring to  FIG. 4 , target materials  90  to be crushed are woods loaded into the crusher and have a height h in the direction of height of the crusher body. The pressing feeder unit  14  holds a posture (crushing posture) in which it is rotated upward by the target materials  90  about the rotary shaft  22  and is pushed upward to a level corresponding to the height h of the target materials  90 . The pressing roller  24  contacts the target materials  90  at a contact portion  91  located at the lower end of the pressing roller  24  in the crushing posture, thereby pressing the target materials  90  toward the feed conveyor  12  side at the contact portion  91  by the dead weight of the pressing roller  24 . 
     The bumping surface  71  of the anvil  70  is disposed at a level not lower than the height of the contact portion  91  (i.e., not lower than a position above the conveying surface of the feed conveyor  12  by the height h), and it is arranged such that, in the crushing posture, the normal line n is directed to the rear side of the crusher body (i.e., the lower left direction in  FIG. 4 ) in an opposed relation to the rotating direction of the crushing bit  36 . By thus mounting the anvil  70  to the bracket portion  26  with the normal line n directed to the rear side of the crusher body during the crushing operation, the edge  74  of the anvil  70  becomes more prominent and can more sharply crush the target materials  90 . 
     Also, the anvil  70  is preferably mounted to the bracket portion  26  such that, during the crushing operation, a part of the bumping surface  71  is positioned at a level of the height h. With such an arrangement, when the crushing bit  36  smashes against the target materials  90  introduced to the crushing chamber  27 , the anvil  70  restricts the target materials  90  from being raised upward, whereby energy of the bumping can be efficiently utilized as crushing energy. Hence the crushing efficiency is increased. 
     Returning to  FIGS. 1-3 , a hydraulic cylinder (arm drive means)  29  is rotatably coupled at its bottom-side end to a bracket  30  through a pin  31 , the bracket  30  being fixed to the crusher side cover  20 . Also, the hydraulic cylinder  29  is rotatably coupled at its rod-side end to a bracket  32  through a pin  33 , the bracket  32  being provided at an end of the arm portion  25  on the rear side (i.e., the left side as viewed in  FIG. 3 ). The hydraulic cylinder  29  rotates the pressing feeder unit  14  about the rotary shaft  22  such that the pressing feeder unit  14  can be raised and lowered relatively to the feed conveyor  12  (i.e., the crushing apparatus  13 ) (namely, the pressing feeder unit  14  is movable away from and closer to the crushing apparatus  13 ). 
     The crushing apparatus  13  is mounted substantially on a central portion of the body frame  10  (see  FIG. 1 ) in the longitudinal direction. As shown in  FIG. 3 , the crushing apparatus  13  comprises the crushing rotor  15  rotating within the crushing chamber  27  at a high speed, an anvil (second fixed bit)  34  disposed outward of the crushing rotor  15  in the radial direction and having a bumping surface (described later) arranged in an opposed relation to the rotating direction (also called the forward rotating direction, as required, i.e., the clockwise direction in  FIG. 3 ) of the crushing rotor  15 , and the anvil (first fixed bit)  70  provided on the pressing feeder unit  14  as described above. 
     The crushing rotor  15  is rotatably supported by bearings (not shown) each of which is mounted to, e.g., the side cover  20  of the crushing apparatus  13  (or a not-shown support member separately provided on the body frame  10 ). A plurality of support members  35  and crushing bits (i.e., smashing plates or crushing blades)  36  mounted respectively to the support members  35  are provided on an outer circumferential surface of the crushing rotor  15 . The crushing bits  36  are arranged such that their edge faces precede the corresponding support members  35  when the crushing rotor  15  is rotated in the forward direction. Also, the crushing bits  36  are fixed to the support members  35  by bolts  37  or the likes, and therefore they are easily replaceable when worn out. 
     Outward of the crushing rotor  15  in the radial direction, the curved plate  28 , the anvil  34 , and a screen (sieve member)  38  are successively disposed in this order from a point where the target materials to be crushed are introduced toward the crushing rotor  15  (i.e., from a position near the surrounding of the pressing roller  24 ) in an upstream-to-downstream direction in which the target materials are carried (i.e., in the forward rotating direction of the crushing bits  36 ). The crushing chamber  27  is a space substantially defined by the curved plate  28 , the anvil  34 , the screen  38 , etc. The crushing chamber  27  is opened at the same side as both the feed conveyor  12  and the pressing feeder unit  14  (i.e., the left side as viewed in  FIG. 3 ) to provide a target-material receiving area. 
     The anvil (second fixed bit)  34  has a surface (bumping surface)  60  against which the target materials introduced to the crushing chamber  27  bump, and it is mounted to a holding member  40  such that the bumping surface  60  is positioned in an opposed relation to the rotating direction of the crushing rotor  15 . The holding member  40  has a rotary shaft  41  and is coupled through a shear pin  43  to a support member  42  fixed to the side cover  20 . For example, when an impact load exceeding an allowable value of the shear pin  43  is applied to the anvil  34 , the shear pin  43  is broken and the holding member  40  is released from a restricted state. Thus, the holding member  40  is rotated about the rotary shaft  41  to retreat from the crushing chamber  27 . 
     The screen (sieve member)  38  has discharge holes (not shown) for discharging the materials having been crushed outward of the crushing chamber  27  while selecting the grain size of the crushed materials, and it is held at a position around the crushing rotor  15  by a frame-like screen holding member (screen holder)  44 . The screen holding member  44  has a rotary shaft  45  provided at one end of the screen holding member  44  on one side (i.e., the left side as viewed in  FIG. 3 ) in the circumferential direction thereof (i.e., in the circumferential direction of the crushing rotor  15 ), and also has a support member  46  mounted to the other end of the screen holding member  44  on the other side (i.e., the right side as viewed in  FIG. 3 ) in the circumferential direction thereof. During the crushing operation, the screen holding member  44  is held in a posture, shown in  FIG. 3 , by the support member  46 . However, when the screen holding member  44  is released from the state restricted by the support member  46 , it is rotated about the rotary shaft  45 . With the rotation of the screen holding member  44 , the screen  38  is also released from a restricted state, whereby the screen  38  can be replaced. 
     The discharge conveyor  3  mainly comprises a frame  50 , a conveyor cover  51  disposed over a conveyor belt (not shown) looped between a drive wheel (not shown) and a driven wheel (not shown) which are disposed at opposite ends of the frame  50  in the longitudinal direction thereof, a driving unit  52  (i.e., a hydraulic motor for the discharge conveyor) for rotating the drive wheel. A portion of the discharge conveyor  3  on the discharge side (i.e., its portion on the front side or the right side as viewed in  FIGS. 1 and 2 ) is supported in a suspended state by a support member  53  projecting from the power unit  4 . Also, another portion of the discharge conveyor  3  on the opposite side (i.e., its portion on the rear side or the left side as viewed in  FIGS. 1 and 2 ) is supported by a support member  54  in a state suspended from the body frame  10 . Thus, the discharge conveyor  3  is supported by the support members  53  and  54  so as to pass under the crushing apparatus  13  and the power unit  4 , and to further extend externally forward of the crusher while inclining upward. By rotating the driving unit  52 , the conveyor belt is driven to circulate between the drive wheel and the driven wheel. 
     The power unit  4  is mounted on an end portion of the body frame  10  on the other side in the longitudinal direction (i.e., on the right side as viewed in  FIGS. 1 and 2 ) through a support member  55 . Behind the power unit  4 , a cab  56  is provided in an area on one side (i.e., the lower side as viewed in  FIG. 2 ) in the transverse direction. A control lever  57  is disposed in the cab  56  for traveling and operating the crusher. A console  58  is disposed under the cab  56  to perform other operations, setting, monitoring, etc. 
     The operation of the crusher according to the first embodiment will be described below. 
     When target materials to be crushed are loaded into the hopper  11  by a heavy machine (such as a hydraulic excavator) equipped with an appropriate working device, e.g., a grapple, the target materials are dropped to be put on the running members  17  of the feed conveyor  12  while being guided by a spreading portion of the hopper  11 . Then, the target materials are substantially horizontally conveyed toward the front side of the crusher with circulating motion of the running members  17 . When the target materials on the feed conveyor  12  are conveyed to a position near the pressing feeder unit  14 , they come into under the pressing roller  24  and push up the pressing feeder unit  14 . Then, the target materials pushing up the pressing feeder unit  14  are introduced to the crushing chamber  27  while they are pressed toward the feed conveyor  12  side under the action of dead weight of the pressing feeder unit  14 . At that time, the target materials are projected into the crushing chamber  27  in a cantilevered state with their ends gripped between the pressing roller  24  and the feed conveyor  12  to serve as support points. 
     The projected material portions are smashed from below by the crushing bits  36  of the rotating crushing rotor  15  rotating at a high speed, whereby the target materials are going to be pushed up. At that time of smashing, the anvil  70  positioned above the target materials acts as not only a support point for restricting the smashed target materials from being moved upward and for pressing the target materials toward the feed conveyor  12  side, but also as a fixed bit for crushing the target materials by shearing in cooperation with the crushing bits  36 . Accordingly, the target materials are finely crushed, i.e., subjected to primary crushing. 
     The target materials having been thus subjected to the primary crushing are forced to move through the crushing chamber  27  in the rotating direction of the crushing rotor  15  until the anvil  34 . The target materials are further finely crushed, i.e., subjected to secondary crushing, by the anvil  34 . The target materials having been thus subjected to the secondary crushing are forced to pass through a space formed between the anvil  34  and the crushing rotor  15  with the rotation of the crushing rotor  15 , and to reach a position near the screen  38 . 
     Of the target materials having reached the screen  38 , those materials having sizes smaller than the diameter of the discharge holes are discharged at once from the crushing chamber  27  through the screen  38 , while those materials having sizes larger than the diameter of the discharge holes continue to circulate in the crushing chamber  27  and are repeatedly smashed by the crushing bits  36  and bumped against the anvil  34  and an inner wall surface of the crushing chamber  27  so that the target materials are gradually crushed into target grain sizes (i.e., tertiary crushing). The crushed materials (crushed chips) discharged from the crushing chamber  27  are dropped onto the conveyor belt of the circulating discharge conveyor  3  through a chute (not shown). The crushed materials having dropped onto the conveyor belt are conveyed toward the front side (i.e., the right side as viewed in  FIGS. 1 and 2 ) of the crusher and are accumulated there. 
     The advantages of the crusher according to the first embodiment will be described below. 
     For easier understanding of the advantages of the first embodiment, a crusher in which the pressing feeder unit includes no fixed bit corresponding to the anvil  70  used in the first embodiment is assumed to be a comparative example. Generally, in crushers, along with the crusher of the first embodiment, using the crushing method of smashing the crushing bit against the target materials to be crushed from below, which are introduced by the running members of the feed conveyor or the like, the target materials can be crushed into finer chips when a point (support point) where the target materials to be crushed are pressed and supported from above is positioned closer to a point (smashing point) where the crushing bit smashes against the target materials to be crushed. In the crusher of the comparative example, the support point where the target materials to be crushed are supported is a contact point between the pressing roller and the target materials (which corresponds to the contact portion  91  in the first embodiment). In trying to position the support point closer to the smashing point, however, there is a limit because of the problem with mechanical layout, e.g., the arrangement of the pressing roller and the crushing rotor. Thus, in the crusher of the comparative example, because of a limit in trying to position the support point and the smashing point closer to each other, a difficulty arises in crushing the target materials into chips finer than a certain level with the primary crushing by the crushing bit, and the target materials tend to be roughly crushed. In some cases, a longer time is required until the roughly-crushed target materials are finely crushed, and the crushed materials having relatively large sizes are discharged through the screen as they are. This may result in lowering of the crushing efficiency and a reduction in grain size quality of the crushed materials. 
     In contrast, in the crusher of this first embodiment, the pressing feeder unit  14  has the anvil  70  which is disposed at a position closer to the crushing rotor  15  than the contact portion  91  where the pressing roller  24  presses the target materials, and which is disposed at a position outward of the crushing rotor  15  in the radial direction. The bumping surface  71  of the anvil  70  against which the target materials bump is arranged in an opposed relation to the rotating direction of the crushing bits  36 . Further, when the crushing bits  36  smash against the target materials introduced toward the crushing rotor  15 , the anvil  70  presses those target materials toward the feed conveyor  12  side for crushing thereof. With such an arrangement, the anvil  70  acts not only as a fixed bit at an inlet of the crushing chamber  27 , but also as a support point for pressing the target materials at a position closer to the crushing rotor  15  than the contact portion  91  of the pressing roller  24 . Therefore, the support point and the smashing point can be located closer to each other than the case of the comparative example, and the crushed materials having smaller grain sizes can be obtained even in the primary crushing. As a result, the target materials can be more effectively crushed by the crushing bits  36 , and the crushed materials having good grain size quality can be produced with higher efficiency. 
     Also, in the crusher of this first embodiment, the target materials crushed by the anvil  70  are further crushed, as described above, by the anvil  34  disposed downstream of the anvil  70  in the direction in which the target materials are forced to move in the crushing chamber  27 . Accordingly, the target materials can be even more efficiently crushed by the interaction of both the fixed bits. 
     A modification of the first embodiment will be described below. 
     The modification of the first embodiment described below is featured in that the bumping surface  71  of the anvil  70  is arranged to have a difference posture during the crushing operation from that in the crusher of the first embodiment. 
       FIG. 5  is a side view showing a structure in the vicinity of the crushing apparatus  13  provided in a crusher according to the modification of the first embodiment of the present invention, and  FIG. 6  shows a state of the structure shown in  FIG. 5  during the crushing operation. 
     Referring to  FIG. 5 , the bracket portion  26  has a recess  82 A, and an anvil  70 A is mounted to the recess  82 A in a replaceable manner by bolts, for example. Referring to  FIG. 6 , the bumping surface  71  of the anvil  70 A is disposed at a position not lower than the height of the contact portion  91  and is arranged to be substantially horizontally held in the crushing posture while a normal line n with respect to the bumping surface  71  is directed vertically downward (i.e., downward as viewed in  FIG. 6 ). 
     By mounting the anvil  70 A to the bracket portion  26  with the normal line n being directed vertically downward during the crushing operation as shown in  FIG. 6 , the target materials  90  can be pressed by the entirety of the bumping surface  71 , and energy of the bumping can be more efficiently utilized as crushing energy. Also, since the height of the conveying surface of the feed conveyor  12  and the center of rotation of the crushing rotor  15  are positioned substantially at the same level as seen from  FIG. 6 , the bumping surface  71  is arranged in an exactly opposed relation to the rotating direction of the crushing bits  36  at the smashing point where the crushing bits  36  smash against the target materials. That arrangement also contributes to more efficiently utilizing the bumping energy as the crushing energy. Hence the crushing efficiency can be further increased. 
     As another modification similar to the above-described modification, the anvil may be mounted such that the normal line n with respect to the bumping surface  71  is directed forward of the crusher body in the crushing posture. Such an arrangement is particularly advantageous in that, when the target materials are loaded, they can be smoothly introduced into the crushing chamber  27  without being caught by the edge of the anvil. 
     A second embodiment of the present invention will be described below. As compared with the first embodiment, the second embodiment is featured in that the anvil (first fixed bit) has two or more bumping surfaces.  FIG. 7  is a side view showing a structure in the vicinity of the crushing apparatus  13  provided in a crusher according to the second embodiment of the present invention. 
     Referring to  FIG. 7 , an anvil  70 B having two bumping surfaces is mounted to the recess  82  of the bracket portion  26 . More specifically, the anvil  70 B has a bumping surface  71   a  positioned closer to the rear side of the crusher body, a bumping surface  71   b  positioned to continuously extend from the bumping surface  71   a  toward the front side of the crusher body, a first edge  74   a  formed by the bumping surfaces  71   a  and  71   b , and a second edge  74   b  formed by the bumping surface  71   b  and the side surface  73 . In the posture during a state other than the crushing operation, the first edge  74   a  is positioned lower than the second edge  74   b.    
     By performing the crushing operation with the thus-constituted anvil  70 B mounted in place, when the crushing bits  36  smash against the target materials, the target materials are first crushed by the first edge  74   a  and are then crushed by the second edge  74   b . Thus, since the target materials are crushed in two steps by the anvil  70 B, the crushing efficiency is increased. 
     Another example of the anvil having two bumping surfaces is shown in  FIG. 8  as a first modification of the second embodiment.  FIG. 8  is a side view showing a structure in the vicinity of the crushing apparatus  13  provided in a crusher according to the first modification of the second embodiment of the present invention. Referring to  FIG. 8 , an anvil  70 C having two bumping surfaces is mounted to the recess  82  of the bracket portion  26 . As in the above-described anvil  70 B, the anvil  70 C has two bumping surfaces and two edges. However, the bumping surfaces  71   a  and  71   b  jointly form a bumping surface which is “downwardly projected” in the state other than the crushing operation. Such an arrangement can also provide a similar advantage to that described above. In addition to the illustrated first modification, the similar advantage can be further obtained by constituting the anvil such that the edge positioned closer to the rear side of the crusher body (i.e., the first edge  74   a ) is positioned lower than the edge positioned closer to the front side of the crusher body (i.e., the second edge  74   b ). 
     An example of the anvil having three bumping surfaces is shown in  FIG. 9  as a second modification of the second embodiment and is described below.  FIG. 9  is a side view showing a structure in the vicinity of the crushing apparatus  13  provided in a crusher according to the second modification of the second embodiment of the present invention. Referring to  FIG. 9 , an anvil  70 D having three bumping surfaces is mounted to the recess  82  of the bracket portion  26 . More specifically, the anvil  70 D has a bumping surface  71   a  positioned closer to the rear side of the crusher body, a bumping surface  71   b  positioned to continuously extend from the bumping surface  71   a  toward the front side of the crusher body, a bumping surface  71   c  positioned to continuously extend from the bumping surface  71   b  toward the front side of the crusher body, a first edge  74   a  formed by the bumping surfaces  71   a  and  71   b , a second edge  74   b  formed by the bumping surfaces  71   b  and  71   c , and a third edge  74   c  formed by the bumping surface  71   c  and the side surface  73 . 
     By forming three bumping surfaces as described above, a plurality of edges (particularly, the first edge  74   a  and the third edge  74   c ) are also formed, and therefore the target materials can be crushed in plural steps substantially in a similar manner to that described above. Further, by forming bumping surfaces in number over three, e.g., four bumping surfaces, so as to provide two angular protrusions, a plurality of edges can be formed appropriately as in the above-described example. Thus, even in the case of three or more bumping surfaces, it is possible to crush the target materials in plural steps and to increase the crushing efficiency. 
     A third embodiment of the present invention will be described below. This third embodiment is featured in having a support-point constituting portion which positively acts on the target materials as a support point, instead of the anvil  70  which acts as the support point and the fixed bit in the above-described first embodiment.  FIG. 10  is a side view showing a structure in the vicinity of the crushing apparatus  13  provided in a crusher according to the third embodiment of the present invention. 
     Referring to  FIG. 10 , a support-point constituting portion  75  is mounted to the recess  82  of the bracket portion  26  such that, when the crushing bits  36  smash against the target materials introduced to the crushing rotor  15 , the support-point constituting portion  75  presses the target materials toward the feed conveyor  12  side. More specifically, the support-point constituting portion  75  has a side surface  73  and a curved surface  76  which is formed to have a “downwardly projected” shape in the posture during the state other than the crushing operation. When the crushing bits  36  smash against the target materials, the curved surface  76  comes into contact with the target materials to act as a support point for pressing the target materials toward the feed conveyor  12  side. Accordingly, the support-point constituting portion  75  acts on the target materials as a support point which is positioned closer to the crushing rotor  15  than the contact portion  91 . As compared with the case of pressing the target materials by only the contact portion  91 , therefore, the target materials can be more finely crushed. Further, since the support-point constituting portion  75  has the curved surface  76 , the target materials can be smoothly introduced to the crushing chamber  27  even when the target materials conveyed on the feed conveyor  12  contact the support-point constituting portion  75  during the crushing operation. The support-point constituting portion  75  is not limited to the above-described structure. A similar advantage to that described above can also be obtained by forming a curved surface at least in an area of the support-point constituting portion  75  which comes into contact with the target materials when the crushing bits  36  smash against the target materials. 
     A fourth embodiment of the present invention will be described below. This fourth embodiment is featured in making, in the anvil  70  of the first embodiment, adjustable a distance (hereinafter referred to as a “gap size D”) from an inner end of the anvil in the radial direction of the crushing rotor  15  to a maximum locus R (described later) of rotation of the crushing bits  36 .  FIG. 11  is a side view showing a structure in the vicinity of the crushing apparatus  13  during the crushing operation provided in a crusher according to the fourth embodiment of the present invention. 
     Referring to  FIG. 11 , an anvil  70 E is mounted to the recess  82  of the bracket portion  26 . The anvil  70 E is capable of adjusting the gap size D, i.e., the distance from its part closest to the crushing rotor  15  to the maximum locus R of rotation of the crushing bits  36  when one type of anvil is replaced with the other type. The remaining structure is the same as that in the modification of the first embodiment. 
     The anvil  70 E has a side surface  73 E which is projected into the crushing chamber  27  in the position during the crushing operation, shown in  FIG. 11 , to a larger extent than the side surface  73  of the anvil  70 A shown in the modification of the first embodiment, a bumping surface  71 E, an edge  74 E formed by the bumping surface  71 E and the side surface  73 E. The maximum locus R of rotation of the crushing bits  36 , shown in  FIG. 11 , represents a locus along which the outer ends of the crushing bits  36  in the radial direction of the crushing rotor  15  rotate. In the anvil  70 E of this fourth embodiment, its part closest to the crushing rotor  15  (i.e., the inner end of the anvil  70 E in the radial direction of the crushing rotor  15 ) is the edge  74 E. The edge  74 E is positioned on the inner side than the edge  74  of the anvil  70 A in the radial direction of the crushing rotor  15  to form a gap with the size D between the edge  74 E and the maximum locus R of rotation of the crushing bits  36 . 
     Further, in the crusher of this fourth embodiment, in addition to the above-described anvil  70 E having the edge  74 E, there are prepared other plural types of anvils (not shown) which have edges with different distances (sizes D) up to the maximum rotation locus R. In the crusher of this fourth embodiment, the gap size D can be adjusted by replacing the plural types of anvils from one to another as required. Thus, since the gap size D can be adjusted to a value suitable for the desired grain size of the crushed materials, it possible to improve the grain size quality of the crushed chips and to increase the crushing efficiency. The above description has been made in connection with the case of adjusting the distance from the edge  74 E to the maximum rotation locus R in the posture during the crushing operation. However, when another part of the anvil is positioned closest to the maximum locus R of rotation of the crushing bits  36  in the radial direction of the crushing rotor  15 , a similar advantage to the above-described one can also be of course obtained by adjusting the gap size D on the basis of such a part of the anvil. 
     Moreover, the above description has been made of, by way of example, the case where the present invention is applied to a self-propelled crusher, but the present invention is not limited to such an application. As a matter of course, the present invention is also applicable to, e.g., a mobile crusher capable of traveling with traction, a transportable crusher capable of being lifted by, e.g., a crane for transportation, and a stationary crusher installed as a fixed machine in a plant or the like. Any of those applications can also provide similar advantages to those obtainable with the above-described embodiments. In addition, the crusher of the present invention can be used to crush woods, waste plastics, waste tatami (straw matting), bamboos, etc. as target materials, and can provide similar advantages to those described above regardless of the type of target materials to be crushed.