Abstract:
A method and apparatus for chopping long unwound items like fiber, fiber strands, yarn, etc. having an idler roll for pressing the item(s) against a backup roll for pulling the item(s) into the chopper, the idler roll being an assembly allowing the idler roll to pivot around a pin inside the idler roll assembly to keep the surface of the idler roll in proper contact with the items being chopped.

Description:
BACKGROUND  
       [0001]     The present invention involves an improved chopper for chopping continuous or very long loose items such as fiber, fiber strands, yarn, wire, string, ribbon, tape and the like by pulling the item(s) into the chopper while the loose items are held tightly against the surface of a rotating backup roll with a rotating idler roll biased against the backup roll and carrying the item(s) on into a nip between a rotating blade roll and the rotating backup roll where they are separated into short pieces. More specifically the present invention involves a chopper having an improved idler roll which allows the idler roll to reliably self align with the surface of a back up roll to more reliably and more effectively hold down and pull item(s) being pulled and chopped such as loose wet or dry strands of glass fibers with, or without, a chemical sizing thereon.  
         [0002]     It has long been known to chop continuous fibers or fiber strands into short lengths of about 3 inches or shorter. Billions of pounds of such product including chopped glass fibers and fiber strands are produced each year in process and chopping apparatus such as disclosed in U.S. Pat. Nos. 5,970,837, 4,398,934, 3,508,461, and 3,869,268, the disclosures of which are incorporated herein by reference. The choppers disclosed in these patents comprise a blade roll containing a plurality of spaced apart blades for separating the fibers into short lengths, a backup roll, usually driven, which the blades work against to effect the separation and which pulls the fibers or fiber strands and an idler roll to hold the fibers or fiber strands down onto the surface of the backup roll. In the chopped fiber processes disclosed in these patents, the chopper is usually the most productivity limiting equipment in the processes that are round the clock, 24 hours per day, type processes. Therefore, improvements in the chopper, which allow the chopper to pull and chop faster, for longer times between maintenance shutdowns, and/or to pull and chop more fibers or fiber strands at one time, have an extremely positive impact on productivity and production costs.  
         [0003]     In the published prior art the idler roll has been mounted and held against the surface of the back up roll in a generally rigid manner and with a variable force such as a force applied by an air or hydraulic cylinder. The working surface of the idler roll has been knurled and chrome plated in the past to better grip the fibers or fiber strands to prevent the fibers or fiber strands from sticking to the roll and wrapping and to avoid having to shut the chopper down to remove the wrap. Normally several strands, up to 14 or more, are fed into the chopper, each strand containing 2000 or more fibers. As more fiber strands and fibers are fed into the chopper it becomes more difficult to pull all of the strands and fibers at the same speed, so more pressure is applied to the cylinder pushing the idler roll against the backup roll with more force. If all of the strands or fibers are not pulled at the same speed, the slower strands and fibers will have a greater fiber diameter which is unacceptable and the bushings of the slower strands frequently will not operate at the proper temperature causing more frequent breakouts and/or additional fiber diameter variations, both of which are unacceptable. Also, fiber slippage can cause some of the fibers to be cut to shorter lengths than desired resulting in an unacceptable product.  
         [0004]     As the pulling speed is increased, and/or as the number of strands and fibers are increased, above about 3000-4000 ft./min. (FPM), depending on the product, the present state of the art choppers begin to vibrate and the idler roll begins to allow one or more of the strands to slip some thus reducing the pulling speed of one or more of the strands. Also, if all of the strands are not pressed between the idler roll and the elastomer layer of the backup roll, a strand can slip partially out of the nip leaving some of the fibers unchopped, producing double cuts and stringers in the chopped product and causing the product to be scrapped. This condition worsens as the backup roll and blades become worn with use, typically about 6-24 hours following a chopper rebuild in which the blade roll is replaced with a roll having new blades and the backup roll is replaced with either a refurbished or new backup roll. The backup roll has a working layer of polyurethane at least about a half inch thick on the surface of a metal wheel. As the chopper life increases the surface of the backup roll becomes chopped up due to the blades pressing and cutting into the polyurethane.  
         [0005]     Periodically the backup roll must be removed and either the polyurethane layer turned down on a lathe or sander or must be replaced with a new layer of polyurethane. It would be very desirable to be able to run the chopper at higher speed without vibration and strand slippage to make good chopped fiber than is possible with the current state of the art choppers because the remainder of the process is capable of producing fiber that can be pulled much faster in terms of speed and pounds of fiber per hour than is currently possible. Also, in the preferred state of the art chopper the idler roll mount is exposed to broken fiber and sizing being thrown from the various rolls on the chopper and must be frequently cleaned to avoid serious malfunction at current speeds.  
         [0006]     An improved idler roll mount is disclosed in U.S. Pat. No. 6,723,670, and this mount works very well but requires the entire yoke to pivot to keep the idler roll in the desired alignment and this added inertia is a disadvantage, especially at high pulling speeds above about 3000 FPM. It is known that the reason for certain strands slipping on the idler/backup roll of the current choppers is the manner in which the idler roll is mounted, the manner in which the force is applied to hold the idler roll onto the surface of the backup roll and the fact that the peripheral surface of a new and used backup rolls often have a slight taper from side-to-side or misalignment with the idler roll, either initially or after the new backup roll has been in use for a few hours. A mechanism that would achieve at high pulling speeds with the same desired alignment now achieved at lower pulling speeds with this device would be highly desirable and valuable.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention includes a chopper having an improved idler roll assembly for a chopper for separating long lengths of one or more unwound items selected from a group consisting of fibers, fiber strands, wires, strings, tape(s), strip(s) and ribbon(s) into short lengths while one or more of, preferably a plurality of, the long lengths of material are pulled into the chopper in an unwound form at speeds exceeding 1,000 FPM, preferably at speeds exceeding 2000 FPM by a rotating idler roll pressing the item(s) against the peripheral surface of an elastomer layer on the peripheral surface of a rotating backup roll which carries the item(s) on into a nip between the elastomer layer and a rotating blade roll. The item(s) being chopped can be either dry or wet with or without a chemical sizing on the surface of the item(s). The chopper having an improved idler roll mount assembly comprises a blade roll having a plurality of spaced apart blades in its peripheral surface, a backup roll having an elastomeric working layer on its periphery, and an idler roll, preferably having a knurled surface.  
         [0008]     The chopper for separating long lengths of unwound item(s) selected from the group consisting of fibers, fiber strands, string, yarn, wire, tape and ribbon into short pieces comprising a frame having a front plate on an outboard, operating side of the chopper, a rotatable backup roll outboard of the front plate, the backup roll having an elastomeric peripheral working surface, a rotatable blade or cutter roll outboard of the front plate, a rotatable idler roll mounted outboard of the front plate for pressing the item(s) against said working surface of the backup roll and an idler roll mount for holding the idler roll and applying a force to press the idler roll against the item(s) to be chopped and the working layer on the backup roll as the latter rotates. The improved chopper has an idler roll assembly comprising an idler roll, a hub and pin for pivotally attaching to the axle and at least one bearing between the idler roll and the hub to permit the idler roll to rotate around the hub while the hub is free to pivot to keep the idler roll in contact with the items on the working surface. The improved chopper can also optionally further comprise an idler roll mount assembly comprising a support arm for mounting the idler roll assembly. The idler roll assembly can optionally further comprise a biasing member for impeding the idler roll from pivoting downwardly when the idler roll is raised off of the working surface of the backup roll. The improved chopper can also optionally further comprise a fluid purge system that forces a fluid through the interior of the idler roll assembly to prevent foreign matter from entering the idler roll assembly and impeding pivoting and/or rotation of the idler roll and also optionally through a portion of the idler roll mount assembly to prevent foreign matter from getting into moving parts exposed to the atmosphere outside the chopper. This fluid purge system would also provide some cooling effect to help increase the longevity of rotating idler roll components.  
         [0009]     The invention also includes an idler roll assembly for a chopper comprising an idler roll, a hub and pin for pivotally attaching to the axle and at least one bearing between the idler roll and the hub to permit the idler roll to rotate around the hub while the hub is free to pivot to keep the idler roll in contact with the items on the working surface. The idler roll assembly can optionally further comprise a biasing member for impeding the idler roll from pivoting downwardly when the idler roll is raised off of the working surface of the backup roll. The idler roll assembly can optionally further comprise a fluid purge system that forces a fluid through the interior of the idler roll assembly for some cooling effect and to prevent foreign matter from entering the idler roll assembly and impeding pivoting and/or rotation of the idler roll. The idler roll assembly can further comprise at least one bearing, typically two bearings, located between the hub and the idler roll.  
         [0010]     The invention also comprises a method of separating long lengths of unwound item(s) selected from the group consisting of fibers, fiber strands, string, yarn, wire, tape and ribbon into short pieces comprising feeding one or more of said item(s) into a chopper, the chopper being those described in a previous paragraph of this section and containing an idler roll assembly as described above.  
         [0011]     When the word “about” is used herein it is meant that the amount or condition it modifies can vary some beyond that so long as the advantages of the invention are realized. Practically, there is rarely the time or resources available to very precisely determine the limits of all the parameters of one&#39;s invention because to do so would require an effort far greater than can be justified at the time the invention is being developed to a commercial reality. The skilled artisan understands this and expects that the disclosed results of the invention might extend, at least somewhat, beyond one or more of the limits disclosed. Later, having the benefit of the inventors disclosure and understanding the inventive concept and embodiments disclosed including the best mode known to the inventor, the inventor and others can, without inventive effort, explore beyond the limits disclosed to determine if the invention is realized beyond those limits and, when embodiments are found to be without unexpected characteristics, those embodiments are within the meaning of the term about as used herein. It is not difficult for the skilled artisan or others to determine whether such an embodiment is either as might be expected or, because of either a break in the continuity of results or one or more features that are significantly better than reported by the inventor, is surprising and thus an unobvious teaching leading to a further advance in the art. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a front view of a chopper of the present invention with a portion cut away to show a part of a mount assembly for the idler roll assembly of the invention.  
         [0013]      FIG. 2  is a plan view of the mount assembly shown in  FIG. 1 .  
         [0014]      FIG. 3  is an end view of the idler roll mount assembly shown in  FIGS. 1 and 2 .  
         [0015]      FIG. 4  is a back view of the idler roll mount assembly shown in  FIG. 1 .  
         [0016]      FIG. 5  is a plan view of an arm and axle for the idler roll assembly of the invention.  
         [0017]      FIG. 6  is an end view of the arm and axle; shown in  FIG. 5 , for the idler roll assembly of the invention.  
         [0018]      FIG. 7  is a cross sectional view of the idler roll assembly of the invention, including the axle shown in  FIGS. 5 and 6 .  
         [0019]      FIG. 8  is a cross sectional view of the idler roll assembly along lines  8 - 8  of  FIG. 7 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIG. 1  shows a chopper  2  for separating long items such as fibers, fiber strands, strings, wires, tape(s) or ribbon(s)  1  into short lengths  3 . Typically the short lengths are about 4 or 5 inches or less, but can be longer if the diameter of the blade roll  12  and the backup roll  4  are more than about one meter. For purposes of describing the invention an improved chopper  2  for separating long fiber strands, such as glass fiber strands, is illustrated. Such a chopper typically comprises a backup roll  4  having an elastomer layer  6  on its outer periphery and mounted on a rotating spindle  8  and held on with a large washer  9  and nut  10 , a blade roll  12  having blades  14  spaced apart around its outer periphery and mounted on a rotating spindle  16  in a similar manner as the backup roll  4 . The typical chopper also comprises a front plate  5 , which preferably is an element of a conventional chopper frame (not shown) and a rotating idler roll  20  having a knurled surface that is pressed against the fiber strands  1  and the elastomer layer  6  of the backup roll  4 . The idler roll  20  serves the purpose of pressing the fiber strands  1  against the rotating backup roll  4  which will help pull the fiber strands  1  at the desired speed into the chopper  2 . Typically a strand separator and guide roll  18  mounted on or off the chopper is used to separate the fiber strands  1  and to guide them to the desired location on the backup roll  4 . The improved chopper  2  of the present invention comprises a novel idler roll assembly  20  and an idler roll mount assembly  22 . The front plate  5  is partially cut away in  FIG. 1  to show the parts of the idler roll mount assembly  22  that are behind the front plate  5 .  
         [0021]     A typical idler roll mount assembly  22 , illustrated in  FIGS. 1-5  and, supports the idler roll assembly  20 , shown in  FIGS. 6-8 , of the present invention. A support arm  26 , that can be a part of either the roll mount assembly  22  or the idler roll assembly  20 , surrounds and is held fast onto an outer portion  60  of a main shaft  55  with a quick disconnect pin  62 , such as a unit identified by McMaster-Carr™ as 190 90293A313 stainless steel positive locking quick release T-handle pin, to allow the exposed idler roll parts to be quickly removed and replaced without opening the housing of the chopper  2 . The main shaft  55  is a part of, or attached to, a torque arm  43  (see  FIG. 4 ) of the idler roll mount assembly  22  that will be described later. The support arm  26  can be all one piece, or as shown, can be made from two or more pieces that are than attached together in any suitable manner. The support arm shown in  FIG. 5  comprises an arm  28  with a passage  29  down its axis, an axle  30  having an axis  24 , the axle  30  attached to a first surface  31  of the arm  28  near an optional first end  32  of the arm  28 , and a socket  33  attached to a second end  34  of arm  28 . The axle  30  has a cavity  35  in its unattached end and a round hole  36  running completely through the axle  30  perpendicular to the axis  24  of the axle  30 . The hole  36  is located in the axle  30  such that a portion of the surface of the hole  36  is near a bottom of the cavity  35  and spaced a substantial distance from the first surface  31  of the arm  28 .  
         [0022]     The socket  33  is cup shaped having a smooth cylindrical cavity  15  therein and is attached to the arm  28  by any suitable method, such as by welds  7 . A side of the cup shaped socket  33  adjacent the support arm  28  contains a passage  21  that links up with the passage  29  in the support arm  28 , both passages being for carrying a cooling fluid like air or water to bearings in the idler roll assembly  20  and to pressurize the interior of the idler roll assembly  20  to provide exhaust of the fluid out of all small openings in the idler roll  20  to prevent water, binder, and dirt from entering and reaching moving parts in the idler, roll assembly  20 . The axle  30  has a passage  13  along its axis  24  for a portion of its length. The passage aligns and communicates with a passage  37  in the arm  28 , the passage  37  oriented generally perpendicularly, and communicating, with the passage  29 . The other end of the passage  13  communicates with a generally perpendicular passage  17  that extends entirely through the axle  30  generally perpendicular to the axis  24 . One or more passages  19  communicate with the passage  17  and extend to the surface of the unattached end of the axle  30 , lying between the cavity  35  and the outer circumferential surface of the axle  30 . The arm  28  optionally has a removable first end  32  that bolts onto the arm  28  with bolts  23  (see  FIG. 6 ). An outboard end portion  60  of the main shaft  55  fits into the cavity  15  of the socket  33  and is held fixed to the socket  33  with a quick release pin  62  (see  FIG. 2 ).  
         [0023]     The idler roll mounting assembly  20  is shown in  FIGS. 1-4 . An inboard portion  38  of a main shaft  55  is preferably held generally horizontally in a rotatable manner by an inboard housing  39  attached to an interior surface of the frame or front plate  5  of the chopper  2 , the housing  39  having a cylindrical opening  40  therethrough, an axis of which aligns with an axis of the cup shaped socket  33 . The housing  39  is of a length to allow an inboard portion  38  of the main shaft  55  to extend beyond an inboard end of the housing  39  at least about 0.5 inch to permit any means of applying a torque to the main shaft  55 , such as a first end  41  of a torque arm  43  to be fixedly attached to the inboard portion  38  of the main shaft  55  in any suitable manner, such as by a key  52  in a slot or keyway as shown in  FIG. 4  and a tightening bolt  88  shown in  FIGS. 2 and 4 . A first bushing  53  and a second bushing  56 , preferably both being lubricated bushings, with a gap  57  therebetween surround the main shaft  55  in the cylindrical opening  40  of the housing  39  to allow free and stable rotation of the main shaft  55 .  
         [0024]     A fluid cylinder  44 , preferably an air cylinder, is located inside the chopper  2  housing on the inboard side of the plate  5  by any suitable means, such as with a cylinder mount  50 , with the cylinder rod  49  attached to a clevis  46  attached to a second end portion  45  of the torque arm  43  opposite the first end portion  41 . Air or other fluid is fed to the cylinder  44  via either one of a first line  47  or a second line  48  depending on whether the idler roll assembly  20  is being pressed against the elastomer working layer  6  or backed away from the working layer  6 . A first fluid pressure regulator  51  is connected to line  47 , which is used to regulate the amount of force applied to the torque arm  43  which in turn regulates the force the idler roll assembly  20  applies to the working layer  6  and the item being chopped such as strands  1 . The force on the idler roll assembly is applied via the outboard end portion  60  of the main shaft  55 , residing inside the cavity  15  of the cup shaped socket  33  and held fixed to the socket  33  with a locking pin  62  running through the walls of the socket  33  and through a hole in the main shaft  55 . Thus, when the torque arm  43  rotates the main shaft  55 , the latter in turn moves the support arm  26  to force the idler roll assembly  20  against the working layer  6 , or to lift the idler roll assembly  20  off of the working layer  6 .  
         [0025]     The idler roll assembly  20  is shown in detail in  FIGS. 7 and 8 . The idler roll  63  can pivot vertically, in one dimension, as shown by the phantom lines, to adapt to any taper on the working surface  6  of the backup roll  4 , a taper that frequently develops during the life of the working surface  6 . A pin  64  passes through the hole  36  and acts as a pivot for the idler roll assembly  20  mounted on the axle  30 . The idler roll assembly  20 , including the axle  30 , has the ability to pivot up to at about plus or minus 1 to 2 degrees. The idler roll pin  64  is held in place with an inboard retainer surface  60  of cylindrical frame  70  and an outboard retainer plate  68  with bolts  67  passing through both plates and threaded into a cylindrical frame  70 . Tapered circumferential surfaces  72 , 74  on the interior ends of the idler roll  64  match up with tapered, outer circumferential surfaces on the retainer plates  66 , 68  to hold the idler roll  64  firmly in place when the bolts  67  are tightened into the cylindrical frame  70 . The cylindrical frame  70  mounts over an inboard bearing  75  and an outboard bearing  76  spaced from the inboard bearing  75 , both bearings  75 , 76  in contact with a cup shaped hub  73 . This embodiment uses tapered bearings, but most typically ball bearings are used to minimize noise and heat.  
         [0026]     The hub  73  fits around the axle  30  and is held in a pivoting way with the pin  64  that passes through holes in the hub  73  and through the hole  36  in the axle  30 . The inside diameter of the hub  73  is greater than the outside dimension of the axle  30  forming a gap  78  that permits the hub  73  to pivot the desired amount with respect to the axle  30 . The hub  73  optionally has a top hat  77 , that part that is adjacent to the cavity  35  in the axle  30 , an extension having a hole through which a coil spring or elastomeric biasing member  79  can be inserted to extend at least part way into the cavity  35 . The diameter of the biasing member  79  should be approximately equal to the interior diameter of the cavity  35  and that of at least some of the hole in the optional top hat  77  so that the biasing member  79  fits snuggly into the cavity  35  and the hole in the top hat  77 . The biasing member  79  can be held in place in many ways and in the embodiment shown in  FIG. 7 , it is held in place with a threaded bolt  82  that engages a threaded portion  81  of the top hat  77 .  
         [0027]     The purpose of the optional biasing member  79  is to impede the idler roll  63  from dropping down, pivoting down, when the idler roll  63  is raised off of the working surface  6  with the idler roll mounting assembly  22 , usually to replace the backup roll  4  or idler roll assembly  63  when needed. The biasing member provides sufficient bias to support the effective weight or force tending to pivot the idler roll axis with respect to the axis of the axle  30 . The idler roll can still be caused to pivot with an external force, but most typically will not pivot of its own accord. As is conventional, the surface of the idler roll  63  is knurled and this knurling wears in operation to a degree that fibers or fiber strands begin to stick and wrap on the idler roll  63 . When this happens, or is likely to happen, the chopper is stopped and the idler roll assembly  20  is replaced by removing the quick release T-handle pin  62  and replacing with a new or reconditioned idler roll assembly  20  followed by reinstalling the quick release pin  62 . This is more easily accomplished if the idler roll is held in a neutral position with the biasing member  79 . Also, this biasing helps keep the idler roll axis properly oriented to allow quick replacement of the backup roll  4  with reduced encumbrance or interference by contact with the idler roll assembly  20 .  
         [0028]     Optionally, the idler roll mount assembly  22  and the idler roll assembly  20  can also be equipped with a fluid purge system, typically an air purge system, shown in  FIGS. 2 and 3 , to prevent water, chemical sizing and fiber dust that are prevalent in the air surrounding the idler roll assembly  20  and the idler roll mount assembly  22  from entering the bushings in the housing  39 , the socket  33  and/or the bearings  75 , 76 , and reducing the freeness of rotation of the moving parts in the assemblies. Circular seals  80  are effective in preventing most material from getting to the bearings  75 , 76 , but positive air pressure inside the idler roll assembly  20  improves the interior environment. The air purge system comprises a purge air line  54  connected to the end of the inboard portion  38  of the main shaft  55  where it aligns with a first channel  65  that runs through the interior of the main shaft  55  and empties into the interior of socket  33 , cavity  15 , and into passage  29  in the support arm  26 . Purge air flows through passages  29  and  37  into the axle  30  and on into the gap  78  between the axle  30  and the hub  73  and some exits out small holes at the rear of the idler roll assembly  20  in the inboard cap plate  66  and also optionally through a hole  71  in the outboard cap plate  68 . The proper air pressure to achieve these results while conserving high-pressure air is regulated with a second pressure regulator  80  in the second air line  54 .  
         [0029]     While a most typical purge air system of the present invention has been shown, once given this concept, it will be obvious that many modifications can be made to this system to get the air, or other fluid such as water or other gas, to the desired locations to achieve the same or similar result. Other modifications to the idler roll assembly  20  will also be obvious given the disclosure above.  
         [0030]     When the knurled surface of the idler roll  63  becomes worn it becomes necessary to replace the idler roll  63  with a new or rebuilt one. To do this the above described procedure can be followed, but to do so more quickly, the removable pin  62  removed and the sub-assembly comprising the support arm  26  and the idler roll assembly  20  is removed and replaced with a new or reconditioned sub-assembly.  
         [0031]     In the embodiment disclosed herein, many of the parts of the novel idler roll mount assembly  22  are contained within the chopper cabinet behind the front plate  5  to protect the parts from the hostile environment on the outside of the chopper. However, if one wanted to put up with the problems caused by the environment outside the chopper cabinet in front of the front plate  5  more or all of the novel idler roll mount assembly could be located outside the chopper cabinet.  
         [0032]     It will be obvious to chopper artisans that the embodiments and structures disclosed herein can be modified in several ways without significantly changing the result. For example, instead of an air purge system, a lubricating system using a lubricant compatible with the chopped fiber product can be used. Also, different bearings, biasing members and fastening means than those disclosed can be used. All such modifications are within the concept and scope of the present invention described in the following claims.