Patent Application
20080302223
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.
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.
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.
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 ten minutes.
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 passing over an idler roll, a starting roll on a starting arm and on into a nip of opposed peripheral surfaces of a pair of pull rolls, and subsequently by a moving elastomer layer on a peripheral working surface of a rotating backup roll. The latter carries the item(s) on into a nip between the elastomer working layer and blades of a rotating blade roll. Both the blade roll and the backup roll are outboard of a front of a cabinet that contains the conventional drive and roll biasing members. The improvement comprises any one or any combination of; (A) a strand guide, preferably oscillating, for the running strands that is located upstream of the chopper, (B) a new improved, movable two part idler roll for avoiding roll wraps and increasing the chopping width on the backup roll, and (C) a shield located between the backup roll and the strand guide to protect the strand guide from stray flying separated item(s). Preferably at least two of the improved features are used and most preferably all three improvements are used on the chopper.
The invention also includes a method of chopping items as described above using the improved chopper described above having one or both of the improvements described above to separate the items into short lengths while optimizing backup roll working layer life and blade lives and increasing chopping speed and productivity.
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'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.
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.
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.
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 fixed, preferably non-freewheeling 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 conventional scrap processing system, 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.
The improvements to the chopper, according to the present invention, are shown in
The first improvement, designated A in
The axle 51 is held by an arm 54 in a fixed, non-rotating manner. An end portion 55 of the arm 54 is attached in a fixed, non-rotating manner to a piston rod 56 of a fluid, gas or liquid powered, cylinder 58. The hydraulic cylinder 58 is mounted behind the front wall 39 of the chopper 22 on a member 59 of the chopper frame 32. The piston rod 56 is supported by the hydraulic cylinder 58 and by a bushing 57 slideably surrounding the piston rod 56 and mounted in a hole (not shown) in the front wall 39 in a conventional manner. The hydraulic cylinder 58 can be operated with compressed air or other hydraulic fluid at elevated pressure in the normal manner. The hydraulic cylinder can also be replaced by various mechanical means, as one skilled in the art will recognize after reading this disclosure, that will move the idler roll 25 in the same or similar manner shown in
Once the new strand 18 has moved to the first section 50, the hydraulic cylinder 58 is energized to move the idler roll 25 to the position shown in
A clearance 53 between an inside diameter of the second section 52 and an outside diameter of the first section 50 is sufficient that when the first section 50 is being driven by running strands 1, its rapid rotation does not cause more than a very slow rotation of the second section 52 when no new strand 18 is on the second section 52. The clearance 53 should be at least about 0.05 cm and preferably about 0.038 cm. A smaller clearance can cause the second section 52 to rotate fast enough, due to friction with the rapid movement of air close to the surface of the outer surface of the first section 50, to jerk the new strand 18 when it comes into contact with the outer surface of the second section 52 to occasionally break out the new strand 18. The independence of the two sections 50,52 allows the first section 51 to rotate to produce a different surface speed than that of the second section 52. The still or only very slow rotation of the second section 52 produces superior performance in starting a new strand 18 because it does not jerk the slow moving new strand 18 when first contacting the surface of the second section 52 during lacing in of the new strand 18. A preferred material for the idler 25 is 440C stainless steel with a finish of about 30 microinches and a Rockwell C scale hardness of about 62.
The new strand 18 first runs, or moves, at a slower surface speed than the strands 1 are running, and then, after having been placed over the starter roll 19 and put into the pull rolls 21, is then accelerated up to at least close to the running speed of the running strands 1 prior to being transferred to the backup roll 23 and nip 14.
Another improvement involves removing the prior art oscillating strand guide roll 16 from the chopper and positioning an oscillating strand guide roll 26 upstream of the chopper 22 as shown in
The next improvement, designated C, is a shield 38 attached to the frame 32 or a side of the chopper 22 and located between the home position of the start up roll 19 and the strand guide 26 to prevent chopped strand 7, etc. from being thrown from the backup roll 23 onto strands 1 running into the chopper and to protect the operator when he positions each new strand 18, or repositions a running strand, on the strand guide 26, see
Many variations of the above improvements will be obvious to those of ordinary skill in the art given the above disclosure and these obvious variations and modifications are covered by the scope of the claims below.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10919570 | Aug 2004 | US |
| Child | 12228330 | US |
