Abstract:
A knife assembly ( 10 ) particularly adapted for coupling with an extruder barrel ( 26 ) is provided having a knife shaft ( 16 ) supporting a knife unit ( 14 ), with the knife shaft ( 16 ) axially rotatable and axially shiftable through fore and aft limits. The assembly ( 10 ) may be adjusted during operation without interrupting the axially rotation of shaft ( 16 ), using adjustment mechanism ( 24 ) located in a safely remote position from knife unit ( 14 ). The preferred assembly ( 10 ) includes axial shift limiting structure ( 114, 116, 124 ) serving to limit the extent of fore and aft axial movement of shaft ( 16 ). The mechanism ( 24 ) allows fine adjustment of the position of knife unit ( 14 ) relative to the extruder barrel ( 26 ), and also permits monitoring of the wear of knife unit ( 14 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with improved knife assemblies of the kind commonly used with extruders to cut extrudate on a continuous basis. More particularly the invention is concerned with such knife assemblies and corresponding methods wherein the knife assemblies include an adjustment mechanism allowing easy and safe axial adjustment of the cutting knives relative to an extruder die. 
     2. Description of the Prior Art 
     Extruder systems for the production of comestible and other products typically include an elongated extruder barrel with an internal, axially rotatable auger serving to subject materials to be processed to high levels of shear and temperature. The barrel is equipped with an endmost extrusion die which serves to shape the materials as they are extruded. It is also common to provide a rotating knife assembly adjacent the die end of such an extruder barrel, in order to cut the extrudate to desired lengths. Such cut products then fall by gravity onto a conveyor belt or other similar equipment to transport the product away from the system. 
     The conventional knife assemblies in use today are deficient in several respects. First of all, it can be difficult and even hazardous to change the axial position of the rotating knives during operation. Indeed, in many cases it is necessary to stop the knife assembly and thus the entire system in order to adjust the knife position. Some on-the-go knife adjustment mechanisms have been proposed, but these are generally very complex and costly. For example, hydraulic devices have been tried, but these are not really satisfactory. Furthermore, some prior knife adjustment mechanisms were of the rotating type, i.e., the adjustment components normally rotate at knife speed. 
     In addition, it is sometimes difficult to properly gauge and determine the extent of knife wear during operation of conventional knife assemblies. This is important in that over-worn knives become inefficient and damage to the knife assembly can occur if the blades are excessively worn. 
     There is accordingly the need in the art for an improved knife assembly of the type used in extruder systems and wherein the knife assembly may be adjusted during and without interfering with cutting operations, and which make use of non-rotating adjustment components which can be manually manipulated by the operator. Furthermore, there is a need for such a knife assembly which can monitor the extent of blade wear during operation. 
     The following references are indicative of the state of the art. U.S Pat. Nos. 2,594,894; 3,029,466; 3,196,487; 3,266,090; 3,337,913; 3,353,213; 3,564,650; 3,673,298; 4,151,241; 4,184,833; 4,249,879; 4,285,652; 4,529,370; 4,728,276; 5,059,103; 5,146,831; 5,360,585; 5,836,225; 6,332,765; 6,604,929; US Publication No. 2007/0172533; German Patents Nos. 3436394; 3437495; European Patent No. 001576881; Great Britain Patents Nos. 0016891; 0848596; Japanese Patent No. 54-072261; and Russian Patent No. 0514707. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above and provides an improved knife assembly equipped with an adjustment mechanism located at a remote position relative to the knives thereof, and which permit on-the-go axially adjustment of the knives, manual manipulation of a non-rotating mechanism. Broadly speaking, the invention comprises a knife assembly comprising an elongated, axially rotatable knife shaft supporting at least one knife adjacent an end thereof. A motor is operably coupled with the knife shaft for powered axial rotation thereof. The knife shaft is supported by an elongated bushing which permits such powered axial rotation while also permitting fore and aft axial movement of the knife shaft and supported knife. A bearing is secured to the end of the shaft remote from the knife, and a non-rotatable bearing support receives the bearing. An adjustment mechanism is operably coupled with the bearing support and is operable to permit axial adjustment of the knife shaft to individual positions without interrupting the axial rotation of the knife shaft. 
     In preferred forms, the knife assembly of the invention also has axial shifting limit structure operably associated with the knife shaft in order to limit the fore and aft axial movement of the knife shaft between fore and aft limits. The non-rotating adjustment mechanism can then be used to axially fine adjust the knife shaft to individual positions within the fore and aft limits. 
     The preferred adjustment mechanism includes a biasing spring operably engaging the end of the bearing support, together with a preloader engaging the end of the spring remote from the bearing support. A lock to secure the preloader at selected positions thereof whereby the preloader may be moved in order to vary the force exerted by the spring against the bearing support. In particular, the adjustment mechanism includes an elongated, threaded rod secured to the bearing support and extending through the preloader, with the lock threaded onto the threaded rod. In further preferred forms, the knife assembly includes a sensor assembly operable to determine the fore and aft position of the knife blade. A display is connected with the sensor assembly in order to display the fore and aft position of the knife shaft in small increments. In this manner, the operator can readily determine when the blades of the knife assembly require replacement owing to wear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of a knife assembly in accordance with the invention; 
         FIG. 2  is a bottom perspective view of the knife assembly; 
         FIG. 3  is a plan view of the knife assembly; 
         FIG. 4  is a side view of the knife assembly partially in section to illustrate internal components thereof; 
         FIG. 5  is a vertical sectional view of the knife assembly; 
         FIG. 6  is a fragmentary, enlarged sectional view depicting the components of the remote adjustment mechanism of the knife assembly; 
         FIG. 7  is a vertical sectional view taken along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is an exploded, perspective view of the components of the remote adjustment mechanism; and 
         FIG. 9  is a perspective view of the knife assembly support structure and die apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, a knife assembly  10  is illustrated in perspective in  FIGS. 1 and 2 . Broadly speaking, the assembly  10  includes a mounting and support assembly  12 , a rotatable knife unit  14  mounted on elongated knife shaft  16 , a motor  18 , housing  20 , display  22 , and a knife adjustment mechanism  24  (see  FIGS. 4-6  and  8 ). As explained below, the knife assembly  10  is typically secured to the output end of an extruder barrel  26 , in order to cut extrudate emerging from the extruder 
     In more detail, mounting and support assembly  12  has a generally U-shaped main body  28  including an apertured end plate  30  and marginal side plates  32  and  34 . The side plate  32  has a pair of vertically spaced hinge pin mounts  36  whereas plate  34  includes a pair of locking eyes  38 . In addition, a terminal mounting plate  40  is provided with a central opening  42 . The end of plate  40  adjacent side plate  32  has a pair of hinge pin mounts  44  aligned with the hinge pin mounts  36 . A removeable hinge pin  46  serves to hingedly connect terminal plate  40  with side plate  32 . The opposite end of plate  40  also has a pair of hinge pin mounts  48  as well as locking eyes  50 . An intermediate plate  52  is hingedly connected with terminal plate  40 , by means of hinge pin mounts  54  and a removeable hinge pin  56 . The plate  52  carries an extruder die assembly  58  including an apertured plate member  60  and flow-directing bullet  62 ; the assembly  58  is secured to plate  52  by bolts  63 . 
     As illustrated, the motor  18 , housing  20 , and display  22  are secured to the face of plate  30  remote from side plates  32 , 34 . When the assembly  10  is used with the extruder barrel  26 , the intermediate plate  52  is positioned so that the die assembly  58  mates with opening  42 , and the die assembly  58  and plate  52  are attached to plate  40  and barrel  26  using through bolts  65  ( FIG. 9 ). The main body  28  is positioned with the locking eyes  50  in registry with locking eyes  38 . A removable connector pin  64  is used to secure the assembly  10  together. 
     The knife unit  14  includes a circular knife head  66  which supports a plurality of radially outwardly extending cutting knives  68 . In operation, the knives  68  are in engagement with or closely proximal to the plate member  60  so as to cut extrudate passing through the plate member  60  into a desired length. 
     The outer end of shaft  16  is threadably connected to and supports the knife unit  14 . Referring to  FIGS. 6 and 8 , it will be observed that the inner end  16   a  of the shaft  16  remote from unit  14  is provided with a pair of opposed keys  70 . Furthermore, the end  16   a  has a double roller bearing  72  secured by a locking ring  74 . The shaft  16  is both axially rotatable and axially shiftable. To this end, an elongated tubular bushing  76  receives shaft  16  and has a pair of opposed internal keyways  78  which slidable receive the keys  70 . The bushing  76  is supported by a pair of spaced apart bushing mounts  80  and  82 , with mount  80  secured to housing  20  and mount  82  secured to end plate  30 . A cog wheel  84  is secured to bushing  76  by means of a hub  86  and key  87 . 
     The motor  18  is a conventional electrical motor having an output shaft  88  with an attached cog wheel  90  below and in alignment with cog wheel  84 . As illustrated, the motor  18  is bolted to housing  20 . A cog belt  92  is trained about the wheels  84  and  90  in order to drivingly rotate knife shaft  16 . 
     The housing  20  is generally L-shaped in configuration, presenting a dome top  94  equipped with a lifting eye bolt  95 , a pair of depending L-shaped sidewalls  96  and  98 , bottom wall  100 , and intermediate and terminal apertured bulkhead walls  102 ,  104 . As shown, the bushing mount  80  is secured to bulkhead wall  102  by connectors  106 . A bail-type handle  108  is pivotally coupled to the sidewalls  96 ,  98  by bolts  110 , and is releaseably secured in the illustrated position by spring pins  112 . 
     The knife adjustment mechanism  24  is designed to permit gross and fine adjustment of the position of knife shaft  16  and knife unit  14  relative to die assembly  58 . Furthermore, and very importantly, the mechanism  24  allows adjustment of the knife position during the operation of assembly  10  without interruption, and from a location adjacent knife shaft end  16   a , so that the adjustment can be readily and safely carried out. The mechanism  24  includes a flanged cup-shaped mounting housing  114  secured to bulkhead wall  104  and having a pair of opposed cam slots  116  and a sensor arm slot  118 ; the slots  116 ,  118  have fore and aft ends  116   a ,  116   b , and  118   a ,  118   b , respectively. In the present embodiment, the axial travel distance between the fore and aft ends  116   a ,  116   b  is two inches. More broadly, a distance of travel of at least about ½ inch, and more preferably from 1-3 inches, is adequate. The open end of housing  114  carries a annular bearing support  120  which receives roller bearing  72  and locking ring  75 . The support  120  has a threaded bore  122  and carries a pair of opposed cam follower screws  124  slideable within cam slots  116  and an oblique sensor arm  126  slideable within slot  118 . 
     The mechanism  24  further includes a threaded collar shaft  128  which is threaded into bore  122  and secured therein by means of lock nut  130 . An elongated, tubular, externally threaded preloader  132  is telescoped over shaft  128  and carries a stop washer  134  and spring washer  136 . A biasing spring  138  is captively retained on shaft  128  between washer  136  and the adjacent face of bearing support  120 . A locking nut  140  is threaded onto the preloader  132  and bears against the face of mounting housing  114 . A handle  142  is also threaded onto shaft  128  and bears against the head of preloader  132 . Finally, a cap nut  144  is threaded onto shaft  128  and bears against handle  142 . 
     In order to sense the axial position of shaft  16  and knife unit  14 , a sensor element  146  is secured to bulkhead wall  102  and has a spring-loaded plunger  148 . The end of plunger  148  bears against sensor arm  126 . The output from sensor element  146  is transmitted by line  150  to display  22 . Accordingly, the axial position of knife shaft  16  and knife unit  14  is transmitted to and displayed by display  22 . 
     Operation 
     In use, a selected die assembly  58  having appropriately sized die apertures is mounted on plate  52  when the mounting and support assembly  12  is in the swung-away position thereof as illustrated in  FIG. 9 . Thereupon, the plate  52  is pivoted inwardly until the assembly  58  comes into registry with the opening  42  of plate  40 , and the die assembly  58  and plate  52  are secured to extruder barrel  26  by means of through bolts  65 . Next, the body  28  is pivoted inwardly until locking eyes  38  mate with locking eyes  50 , and connector pin  64  is used to complete the assembly. In this orientation the extruder is operated in the normal fashion so that extrudate passes from the barrel  26  and through the apertured plate member  60  of die assembly  58 . The motor  18  is actuated to rotate knife shaft  16  and knife unit  14 , thereby serving to cut the extrudate into a desired length. 
     In initial setup operations, the body  28  is swung open and collar shaft  128  and handle  142  are threaded back into abutment with cap nut  144 . The knife shaft  16  is then shifted within housing  114  until cam screws  124  abut the fore ends  116   a  of the slots  116 . Next, the preloader  132  is shifted towards handle  142  until a zero spring force is achieved, but without allowing the spring to loosen completely. In the illustrated embodiment the spring  138  has a 52 lb/inch rating. The locking nut  140  is then rotated to abut one face of preloader  132 , securing it in place. The handle  142  is then rotated until it snugly abuts the other face of preloader  132 . This position is then noted from the output of display  22 . The display is then zeroed and the handle  142  is rotated clockwise until a reading of 0.750 inches is displayed (which is equivalent to 21 full rotations of handle  142 ). This serves to compress spring  138  and moves the knife shaft  16  and knife unit  14  leftwardly as viewed in  FIG. 6 . The cap nut  144  is then rotated against the face of handle  142 . The main body  28  with the pre-adjusted mechanism  24  is then rotated into position until the locking eyes  38  register with locking eyes  50 , and the pin  64  is inserted through the locking eyes. At this point, the knives  68  should be about ¼ inch away from the face of plate member  60 . 
     The motor  18  is then actuated and runs to its normal operating speed. The handle  142  is rotated counterclockwise to allow the knives  68  move up to the surface of the plate  60 . Each ⅛th revolution of the handle  142  causes about 0.004 inches of movement of the knife shaft  16  and knife unit  14 . At this point the handle  142  will spin free once the knives  68  come into contact with plate  60 . The spring  138  will be compressed about ½ inch and will create about 25 pounds of force between the knives  68  and the plate  60 . The cap nut  144  is then rotated counterclockwise for about ¼ inch of travel, whereupon handle  142  is similarly rotated until about ⅛th inch clearance is provided between the handle  142  and the adjacent face of preloader  132 . This establishes a predetermined set point as to how the knives  68  can wear before requiring replacement. This is also a way to protect the knife unit  14 , by preventing complete wear of the knives  68 . The display  22  is then zeroed so that plate wear can be monitored in 0.001 inch increments. 
     If more knife force is needed, it is only necessary to loosen the locking nut  140  to unlock preloader  132 , whereupon the preloader  132  is rotated clockwise until the desired cut of extrudate is achieved. The preloader  132  is then locked in place using nut  140 . If less knife force is desired, the nut  140  is loosened, preloader  132  is rotated counterclockwise and the nut  140  is used to relock the preloader  132 . In the event that a small clearance is desired between the knives  68  and plate  60 , the cap nut  144  is loosened and handle  142  is rotated clockwise until its abuts preloader  132 . The handle  142  is then further rotated clockwise until the desired clearance is achieved. If at any time there is a need to pull the knife unit  14  away from the plate  60 , it is only necessary to grasp  142  and pull the mechanism  24 , shaft  16 , and knife unit  14  leftwardly as viewed in  FIG. 6 . 
     It will be appreciated that a key element of the simplicity and functionality of the knife assembly  10  resides in the use of the bearing  72  within bearing support  120 . This construction handles all thrust loads and, in conjunction with cam screws  124  and cam slots  116  of housing  114 , eliminates any rotational movement from that point back through the remainder of the assembly.