Abstract:
A method and system for separating long unwound items like fiber, fiber strands, yarn, etc. into short lengths. The system has a backup roll, a blade roll, an idler roll, a new-strand starting mechanism and a set of pull rolls. The improvements include a second starting roll spaced from a first starting roll as part of the new-strand starting mechanism and a guide aid for the pull rolls

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 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 improved mechanisms and features. 
         [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, 4,551,160, 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, often or preferably driven, which the blades work against to effect the separation and which pulls the fibers or fiber strands and in some cases, 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 often the item most limiting the productivity of the processes. These processes typically operate continuously every day of the year, 24 hours each day, except for furnace rebuilds every 5-10 years. 
         [0003]    The above choppers must be serviced every few hours, shifts or days, depending on the type of material being chopped, to replace a worn backup roll, a blade roll, or both and sometimes other components of the chopper. These service shutdowns of the chopper often mean that all of the bushings being served by the chopper are not only disrupted, but do not produce any salable product until the chopper is again running and the strands from each of the bushings have been restarted into the chopper. It usually takes 10-15 or more minutes to stop and service the chopper and to restart all of the 5-14 bushings that are normally served by the chopper. The fiberizing bushings usually do not run well for the first hour or two after a chopper service shutdown because the bushings loose their temperature equilibrium and uniformity during the disruption and it takes a period of time to regain the desired equilibrium. During this time the productivity is also reduced and the manual labor demand is increased. 
         [0004]    Any improvement in the chopper that would allow the chopper to pull and chop faster and/or for longer times between service shutdowns, and/or to pull and chop more fibers or fiber strands at a time would have an extremely positive impact on productivity and production costs. The invention comprises improvements to the type of chopper shown in U.S. Pat. No. 4,551,160. Problems exist with this type of chopper that cause interruptions in production limiting productivity and causing higher than necessary manufacturing costs. Some of these problems are strand breakage in the chopper prior to chopping and resulting roll wraps. Each running strand, due to the high speed it is being pulled and the nature of the strand, is subject to being broken by interference from the loose end of a broken strand, fuzz clumps comprised of a web of chopped or broken fibers, and the worn, rough surface of the backup roll. When a strand breaks, the productivity of the fiberizing bushing is lost for a few minutes until the bushing beads down and the resulting new fiber strand is started back into the chopper. Also, too frequently, when a strand breaks at the chopper, an idler roll wrap or a strand guide roll wrap resulting in or requiring most or all of the strands to be broken out, the wrapped roll cleared of the wrapped strand or strands, and each of the fiber strands from each of the fiberizing bushings laced back into the chopper. Typical production time lost for the entire bushing leg from a roll wrap is about 10 minutes. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is an improved 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. 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, first by the peripheral surfaces of a pair of pull rolls and subsequently by a moving elastomer working layer having a peripheral working surface on the peripheral surface of a rotating backup roll. The latter carries the item(s) on into a nip between the elastomer working layer and a rotating blade roll of the chopper. The improvement of the chopper comprises one or any combination of the following:
       A) A second starter roll spaced from a first starter roll on a pivot arm for starting a new-item into said nip and for reducing roll wraps when starting a new-strand into the nip and   B) a strand guide aid for a set of pull rolls for new strands,       
 
         [0008]    The invention also includes a method of chopping items as described above using the improved chopper described above having novel improvements as described above to separate the items into short lengths while optimizing backup roll working layer and blade lives and increasing chopping speed and productivity. 
         [0009]    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 
         [0010]      FIG. 1  is an elevational perspective view of a portion of a prior art chopper. 
           [0011]      FIG. 2  is an elevation view of a portion of the chopper of the present invention showing the improvements described herein. 
           [0012]      FIG. 3  is an elevation view of a portion of the chopper showing the function of one feature of the present invention. 
           [0013]      FIG. 3A  is a partial elevation view of an arm  29  shown in  FIG. 3  and showing more detail of one feature on the arm  29 . 
           [0014]      FIG. 4  is a front view of one feature of the present invention, a guide aid with a set of pull rolls. 
           [0015]      FIG. 5  is side view of the guide aid shown in  FIGS. 2 and 4 . 
           [0016]      FIG. 6  is a plan view of the guide aid shown in FIGS.  2  and  4 - 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 1  shows a front elevation perspective view of a portion of a prior art chopper  2 , of the type shown in U.S. Pat. No. 4,551,160, and that is used in making chopped strand glass fiber. It comprises a front plate  3 , a blade roll  4  with spaced apart blades  5  contained in slots and projecting from the periphery of an integrated hub  6 , a backup roll  8  and a free-wheeling idler roll  9 . The blade roll  6  is usually made entirely of metal, but can be made using a thermoplastic material to hold spaced apart blades such as the blade rolls shown in U.S. Pat. Nos. 4,083,279, 4,249,441 and 4,287,799, the disclosures of which are herein incorporated by reference. 
         [0018]    The backup roll  8  is held on a spindle (not shown) with a hub  9  and also has a metal rim  11  on which is a notch and projection  12  for starting a new strand  7  of fibers into the chopper. The backup roll  8  is biased against the blade roll  4  until the blades  5  press into the working layer of the backup roll  8  a proper amount forming a nip  14  to break or separate fiber strands  1  into an array of short length or chopped strands  15 . 
         [0019]    One or more, usually five or more and up to 14 or more strands  1 , such as glass fiber strands, each strand containing 400-6000 or more fibers and usually having water and/or an aqueous chemical sizing on their surfaces, are pulled by the backup roll  8  into the chopper  2  and the nip  14 . The strands  1  first run under a grooved guide roll  16 , preferably with one or two strands  1  in each groove, and upward and over a working surface  13  of the backup roll  8 , i.e. the exposed peripheral surface of the backup roll  8  on which the running strands  1  lay against and are supported while being severed by blades  5  on the blade roll  4 . The working surface of the back up roll  8  is typically wider than the oscillating path of the glass fiber strands  1 . The strands  1  then pass under the outer surface of the free-wheeling idler roll  9 , which is located to provide sufficient contact of the strands  1  on the surface of the backup roll  8  to enable the latter to pull the glass fiber strands  1 . 
         [0020]    When a new strand  18  is ready to be started into the prior art chopper it is pulled to the front of the chopper  2  by the operator and pulled under the separator roll  16  and the idler roll  9  and up over a free-wheeling starter roll  19  attached to the end of a pivoting arm  20  and down between a nip of a pair of driven pull rolls, part of a conventional pull roll assembly  21 , that pull the new strand  18  at a first low speed and deliver the new strand into a scrap bin or scrap basement. After the new strand  18  is being pulled by the pull roll assembly  21  at a low initial speed, the pull rolls  21 , the pulling speed of the pull rolls  21  is ramped up to bring the new strand  18  to at least close to the speed of the strands  1  running into the chopper  2 . When that speed is reached, the pivot arm  20  is pivoted counterclockwise to start the new strand  18  into the chopper  2  in the manner disclosed in U.S. Pat. No. 4,551,160. 
         [0021]    The improvements to the chopper, according to the present invention, are shown in  FIG. 2  and in more detail in other figures described below. The chopper  22  comprises a frame  32 , a cabinet front wall  39  and outboard of the cabinet front wall are a backup roll  23  having a working layer with a working surface  41 , a blade roll  24  with a plurality of spaced apart blades  45 , in a position to discharge the chopped strands  7  in a generally horizontal direction, a free-wheeling idler roll  25 , a pivoting arm  20  and an optional first starter roll  27  and a second starter roll  28  located on a dog-leg arm  30  integral with or connected to the pivoting arm  29 . A set of pull rolls  31  is located upstream of the chopper  22  having an item starter guide aid  34 . 
         [0022]    The second startup roll  28  for starting a new strand  18  positioned close to a first conventional, now optional, first startup roll  27  on a dogleg arm  30  attached to or integral with the first arm  29  reduces roll wraps caused in the prior art chopper by the waste portion of the new-strand  18  contacts the working surface of the backup roll  23 . Instead of comprising a first startup roll  27  and a second startup roll  28 , the chopper  22  can comprise a single startup roll  28  located on the end portion of a longer pivot arm  29 . Both the first start up roll  27  and the second startup roll  28  can be free wheeling, but preferably are non rotating. In  FIG. 2 , the start up rolls  27 , 28 , are shown in a home position, i.e. the position where each new strand  18  is first laced into a start up sub-system of the chopper  22 . 
         [0023]    The invention will be described with the embodiment shown in  FIG. 2 . The start up sub-system of the chopper  22  is comprised the idler roll  25 , the optional first start up roll  27 , the second start up roll  28 , the pivoting arm  20 , the dogleg arm  30  and the conventional mechanism (not shown) that moves the arm  20  to move the start up rolls  27 , 28  in a counter-clockwise direction to generally a 12 o&#39;clock position above the backup roll  23  to start the new strand  18  into the nip between the backup roll  23  and the blade roll  24 , as seen in  FIG. 3 , and then returns the start up rolls  27 , 28  to the home position. 
         [0024]    When an item running into the chopper breaks out between the nip of blade roll  24  and the backup roll  23  of the chopper and the source of the item, it is necessary to start that item back into the chopper. For purposes of describing the starting procedure, a strand of fibers, e.g. glass fibers, will be used. Only one new-strand  18  is started at any one time into the chopper  22  and each new-strand  18  runs in a plane that is in front of the running strands  1  and thus does not interfere with the running strands  1 . A rod  60  in a vertical position holds the new-strand away from the running strands  1  and at the proper time is rotated out of the way by pivot shaft  60  in a known manner. This same procedure is used for starting each strand into the chopper when the chopper is first started up. 
         [0025]    Referring to  FIG. 2 , each new-strand  18  is started into the chopper  22  by first lacing the new-strand  18  around an outboard portion of the idler roll  25 , up over the first starter roll  27 , over the second starter roll  28  and then into the set of pull rolls  21  using the strand guide aid  34  feature of the invention. To protect the operator and others from accidentally getting clothing or fingers caught in the set of pull rolls  21 , the two pull rolls  21  are guarded with guards  38  shown in  FIGS. 4-6  (some shown in phantom). The strand guide aid  34  is comprised of a member  43  having an angled, strand (item) contacting, surface  44  that extends from above the top of, and at the front of, the pull roll that is closest to the chopper  22 , downwardly at an angle towards a nip  45  of the set of pull rolls and ending above the nip  45 , and a second, curved, member  46  having a curved, strand (item) contacting, surface  47 . The curved surface  47  begins above or close to the top and front of the pull roll closest to the chopper  22  and curves around towards the a point above the nip  45 . 
         [0026]    An optional third member of the strand guide aid  34  is a vertical member  49  attached at or near its base to a pull roll frame (not shown) or preferably to one of the guards  38 . Any two of the members  43 ,  46  and  49 , or all three members, can be integrated into one or two members, such as a continuous, bent, rod. Stainless steel is the preferred material of construction, but various plastics, brass or other materials used in the chopping environment are suitable. 
         [0027]    When the operator pulls each new-strand  18  over the first starter roll  27 , or the second starter roll  28 , and towards the set of pull rolls  21 , the strand guide aid  34  makes it easy for the operator and saves him time, in getting the new-strand  18  into the nip  45  between the set of pull rolls  21 . The strand guide aid  34  also keeps the new-strand  18  from catching or getting hung up on the guards  18 , thus avoiding a break or aborted start. This strand guide aid  34  substantially improves the productivity of the chopped strand process by reducing item startup time and avoiding aborted item startups. 
         [0028]      FIGS. 2-6  show how a new strand  18  is transferred from the arrangement shown in  FIG. 2  to become a running strand  1  being pulled by the rotating backup roll  23  and chopped at the nip  14  with a blade on the blade roll  24 . After a new backup roll  23  has been in chopping mode for a few hours, the working surface  41  becomes rough. With the prior art arrangement for starting a new strand using only one start-up roll  27 , a waste portion  47  of the new strand  18 , that portion between the start-up roll  27  and the pull rolls  21 , comes into contact with the working surface  41  and the rough surface frequently catches the waste portion  47  and breaks out the new strand  18  before it is completely transferred, thus frustrating the start-up of the new strand  18  and requiring the start-up procedure to be repeated. Also, occasionally the loose strand would wrap on the idler roll  25  causing a costly shut down of the chopper to clear the roll wrap. When this breaking out of the new strand  18  became too frequent, often after only about 10 hours of service on a backup roll  23 , it was necessary to shut down the chopper  2  and replace the backup roll  23  even though it was still chopping running strands satisfactorily. 
         [0029]    This problem is solved by one feature of the present invention because the second or repositioned start-up roll  28  keeps the waste portion  47  of the new strand  18  off of the working surface  41  of the backup roll  23 , as shown in  FIG. 3 , until the new strand  18  has been successfully transferred to the working surface  41  of the backup roll  23  by moving a contact rod  35  by pivoting a first member  39  around a pivot point  36  to press the new-strand  18  against the working surface  41  of the backup roll  23 .  FIG. 3A  shows more detail of how the contact rod  35 , supported by a first member  39  that pivots at  36 , is moved by a second member  40  connected to a rod end of a fluid cylinder  42  that can be activated at the appropriate time in a conventional manner to press the new-strand  18  against the working surface  41 . The cylinder  42  is attached to the arm  20 . 
         [0030]    Once the new-strand  18  contacts the working surface  41 , it is pulled by the working surface  41  to the nip  14  where it is severed by a blade  45  and becomes a running strand  1 . The waste portion  17  of the new-strand  18  is pulled away from the chopper  22  by the pull rolls  21  and delivered to a conventional scrap collection means as soon as the new-strand  18  is severed by a blade  45  of the blade roll  24 . Once the new-strand  18  has become a running strand  1 , it is then manually, or mechanically, placed into the appropriate groove in the strand guide  26  in a known manner, and the arm  29  is returned to the home position shown in  FIG. 2  to be ready for another new-strand  18  to be laced into the chopper  22 . The addition of the feature comprising the second roll  28  mounted on the dogleg arm  30  attached to or integral with the arm  29  has greatly reduced aborted starts of new strands and roll wraps, substantially increasing productivity of the chopper. 
         [0031]    Given the above disclosure many equivalents will be obvious to those of ordinary skill in the art and also many modifications that can be made from the preferred embodiments disclosed without changing the function or results except for possibly one of degree. Those equivalents and obvious modifications are included within the scope of the following claims.