Patent Application
20070006696
The present invention includes an oscillator assembly for oscillating rapidly moving items as the items run into all kinds of choppers. Each item can be a single fiber, filament, string, wire or ribbon, or each strand can contain a plurality of fibers, wires, ribbons or strips.
Choppers for separating long lengths or continuous items into short segments of various desired lengths are known as evidenced by various patents including U.S. Pat. Nos. 4,048,861, 4,398,934, 4,175,939, 4,347,071, 5,970,837. These choppers have a blade roll comprising a plurality of blades, each with a sharp edge, spaced apart around the periphery, a backup roll and some also have an idler roll. The idler roll runs against the backup roll the nip acts to hold the items being chopped It is known to oscillate the items being chopped back and forth to move the items back and forth along the cutting edge of the blades to attempt to lengthen the blade life, i.e. the running or chopping time of the blades in either time or in pounds of items chopped. When the blades become dull, the items are not completely chopped resulting in what is called “double cuts”, “triple cuts” and “stringers” (long incompletely chopped items). These longer than desired and incompletely chopped items result in defects in the products made from the chopped items, e.g. nonwoven fibrous mats, and cause costly results including scrap, more frequent downtime to replace the blade roll, and decreases in productivity. However, on choppers having idler rolls that use a high force to press running items against the working surface of a backup roll, oscillating the items being chopped has not resulted in as much added blade life as expected and desired and the reason has been elusive for many years.
The reason why the oscillation of the strand guide in the past, on choppers having an idler roll forcefully pressing against the running strands and the working surface of the backup roll, has not been nearly as effective as possible has now been discovered. The reasons are one or both of 1) that the strands of rapidly moving items had always been directed in a manner to contact the backup roll at or very near, i.e. within about 0.25 inch of the nip between the backup roll and the idler roll, and 2) the oscillation speed was too fast, not allowing time for the running strands to complete the oscillation prior to being contacted with a blade on a blade roll or contacting edge on a cutter roll. In this document the use of the term “blade” is intended to include a contacting edge on a cutter roll. Either one of these reasons limited the amount of oscillation and the best results are achieved when both of these reasons are addressed in the manner described below, or their equivalents. It has now been discovered that if the oscillating guide roll is located such as to make the rapidly moving items strike the peripheral surface of the backup roll at least about 0.75 circumferential inch or more upstream of this nip and more typically at least 1 or more circumferential inches, the oscillation will be much more effective in evening out the wear along the blade edges and lengthening the life, running time and pounds of items, of the blades in the blade roll. In this document the word “strands” means two or more of items, the items being fiber, filament, wire, string, ribbon or tape, and combinations of one or more of the items. This would include one or more strands of fibers such as glass fibers, and one or more wires, one or more strands of polymer fibers, and so on.
The invention comprises an oscillator assembly for moving one or more rapidly moving long or continuous items selected from a group consisting of fiber, filament, wire, string, strip, ribbon and strand back and forth in a direction generally perpendicular to the direction of the rapidly moving item(s), the oscillator comprising an item roll guide having a plurality of parallel, spaced apart grooves on its periphery, a motor for slowly rotating the roll guide, the motor being mounted on a platform having wheels, a reciprocating cylinder connected to the platform, a servo motor for driving the reciprocating cylinder and a control system for the servo motor. Typically, but not necessarily, the oscillator assembly also comprises a biasing member for maintaining the reciprocating cylinder under a bias throughout its reciprocating cycle to avoid backlash, prevent dwelling at the reversing points in its path or cycle, and also the use of a servo motor to drive the oscillation and a program for operating the servo motor, the program having the property of changing the speed of oscillation at the reversing points in the oscillation path. Most typically, the program stops the servo motor at the reversing points and pauses or permits the servo motor to remain still for several seconds, at least 5 seconds and more typically for 10 seconds or longer, even 30 seconds or longer, or until the running items have stopped moving laterally in the nip between the working surface and the idler roll. The dwell can be even longer, but it shouldn't be much longer or the wear will be excessive on the blades at the ends of the movement.
The invention also comprises a method of using the oscillator assembly for a strand guide in the process of chopping the long or continuous items in a chopper comprising a blade roll and a backup roll. Typically, but not necessarily, the chopper also has an idler roll whose periphery is in contact with the periphery of the backup roll and the items being chopped during operation. When used on choppers having an idler roll, the oscillator assembly is located such as to direct the running items onto the surface peripheral surface of the backup roll at a location at least about 0.5 inch upstream of the nip between the idler roll and the backup roll, more typically at least about 0.75 inch and most typically at least about 1 inch upstream of the nip. Most typically, the oscillator assembly has a servo motor and the servo motor that is operated such that the oscillator pauses for at least 5 seconds at two locations in the oscillating path, those locations being where the strand guide is stopped prior to reversing the direction of the movement of the strand guide.
The idler roll assembly 22 is also useful on choppers that do not have an idler roll to replace prior art oscillating assemblies. The use of the combination of the servo motor 50 and a programmable controller permits optimization of uniformity of wear of the chopping blades or a cutter roll. Also, the use of an electric ball and screw cylinder permits a more uniform wear pattern, and the use of a bias to maintain tension in one direction on the guide roll prevents springback at the turnarounds in the oscillating path.
When the word “about” is used herein it is meant that the amount or condition it modifies can vary some beyond that stated 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 any unexpected characteristics, those embodiments are within the meaning of the term “about” as used herein. It is not difficult for the artisan or others to determine whether such an embodiment is either as 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 comprised of a hub and spoke assembly 9 with an integral metal rim 10 on which is cast or mounted a working layer 11 of an elastomer or thermoplastic material such as polyurethane. The backup roll 8 is mounted on a second spindle 18 and held in place with a large nut 20. To operate the spindle 18 of the backup roll 8 is moved towards the spindle 17 of the blade roll 6 until the blades 7 of the blade roll 6 press into the working layer 11 of the backup roll 8 a proper amount forming a nip 14 to break or separate fiber strands 12 into an array of short lengths.
One or more, usually eight or more and up to 20 or more strands 12, 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, in cooperation with a knurled idler roll 13, into the chopper 2 and the nip 14. The strands 12 first run under a grooved oscillating, separator and guide roll 16, preferably with one or two strands in each groove, and upward and over the outer surface of the backup roll 8. The working surface of the back up roll 8 is typically wider than the oscillating path of the glass fiber strands 12. The strands 12 then pass under the outer knurled surface of the idler roll 13, which is pressed against the strands at a desired pressure to enable pulling of the glass fiber strands. The strands remain on the surface of the working layer 11 and next pass into the nip 14 between the backup roll 8 and the blade roll 6 where they are separated with the razor sharp blades 7 wherein the strands are usually cleanly cut or broken into an array of chopped strand 15 having the desired length.
Oscillator assemblies for oscillating item(s) back and forth to try to move the item(s) back and forth along the cutting edge of the blades on the chopper are known, but suffer deficiencies that gave rise to the invention. At least one of the known oscillator assemblies did not move the item(s) far enough, others suffered excessive dwell or lashback at the reversing points of their cycles. These and others did not provide adequate flexibility of adjustment and/or required excessive maintenance. Finally, the location of the prior art oscillator assemblies, particularly the item guide roll, was found to be substantially removed from the optimum location to provide optimum or near optimum blade life.
An embodiment of the oscillating assembly of the invention is shown in
In this embodiment, an end of the table 32 opposite the end closest to the guide roll 26 is U shaped, having an opening 38 therein for a clevis 40 pivotly secured to the table 32 with a rod or bolt 42 whose axis is most typically on the same plane as the axis of the wheels 34, or the centerline of the guide roll shaft 28. The rod or bolt 42 is secured to protruding opposed ears 44 protruding from the table 32 on opposite sides of the opening 38. Most typically the ears 44 are part of the table 32, but need not be. A cylinder rod 46 is attached to the clevis 40, the cylinder rod being a part of a reciprocating device, in this embodiment an electrically driven ball and screw cylinder 48 driven by an electric motor 50. Most any kind of reciprocating mechanism including a rack and pinion, fluid cylinder, eccentric drive, electric ball and screw drive and equivalents thereof can be used to drive the table 32 and guide roll 26 back and forth. The electric ball and screw drive 48,50 shown here is an Industrial Devices Corp., Model # EC2X-20-05B-150-MP2-FT1M-PB-SIE21X unit. This unit is capable of a reciprocating movement of about 150 mm, but not all of that is utilized. The amount of movement will depend upon the number of items being chopped and the width of the blades 7 in the blade roll 6. A typical blade width (cutting edge) is about 4-8 inches and a typical reciprocating distance with when using these blades is about plus and minus 1-3 inches from the center of the blades. The cylinder end of the ball and screw cylinder 48 is attached, typically pivotly attached, to a frame member 54 such as with a clevis 56 and a rod or pin 57. The frame member 54 can be part of the base plate 24 or can be a separate bracket, etc., most typically attached to the base plate 24. An optional cover 65, shown in phantom lines, is most typically held in place in any customary manner, such as with one or more bolts 66, to prevent liquid overspray and the item(s) typically present near the oscillator assembly 22 during operation from entering the works of the oscillator assembly 22.
An optional biasing means is most typically used to prevent uneven movement or lash back at the reversing points, i.e. the point in the cycle where the table 32 is deaccelerated, stopped and accelerated in the opposite direction. Due to slack in the parts, made worse with wear, a jerking action will often occur in the reversing process unless a biasing mechanism is used. In the embodiment shown in
As shown in
The embodiment shown in
In operation, a programmable controller runs the electric servo motor 50. The program is variable during the reciprocating cycle of the clevis 40 at the end of cylinder rod 46. In the most typical program, the electric servo motor 50 runs at a constant speed, when it is running, throughout the oscillating cycle, but the motor is paused at the ends, turn around points, of the oscillating cycle. As mentioned above, in the past the oscillating cycles used did not allow the strand guide 26 to pause for a substantial time at the turnaround points (two) in the cycle. The prior art had to cause the strand guide 26 to pause at each end, it was essential to reversing direction, but the pause was only instantaneous. In the present invention, the servo motor 50 is paused for at least 5 seconds at each turnaround point, usually longer such as at least 10 seconds with 30 seconds or more being more typical, to allow the strands 12 to move a maximum amount in the nip between the idler roll 13 and the working surface 11 of the backup roll 8, before the servo motor 50 is restarted to move the strands 12 in the opposite direction. This produces a substantial increase in the uniformity of blade wear and a substantial increase in blade life.
Most typically a controller is used to control the item oscillator or oscillator assembly for the strand guide, particularly the servo motor 50. The first parameter is the distance the strand guide is moved past a center point of its oscillating path in opposite directions, or plus or minus directions, from the center point. Most typically, this will be the maximum allowed by either the width of the blade, the width of the working surface or both. For example, for if the sharpened edge of the blade is 3.65 inches, that dimension is inserted into the controller and the controller will move the guide roll back and forth 1.6325 inches on either side of the center point of the oscillating path. The second parameter is the location of the center point of the oscillating path. The operator can insert the circumferential centerline of the working surface of the backup roll as the center point, or can offset the center point from the circumferential centerline of the working surface in either direction a desired amount. The next parameter is the incremental distance of movement of the oscillating assembly each time the motor 50 is energized, e.g. 6 mm, or more or less. The next parameter is the time intervals between the starting of the motor 50, i.e. if 60 seconds is entered, the oscillating assembly will move the strand guide 6 mm every 60 seconds. This time interval is a matter of choice, and should be sufficiently long to allow the items to move the maximum distance in the nip between the idler roll and the working surface and/or items being chopped. Most typically the time interval and speed of the servo motor 50 is set to travel about 25 mm in 30 seconds. The last parameter is the length of the delay at each turnaround point, most typically 30 seconds, more or less. Ideally, the pause is long enough to allow the running items to move laterally as far as they will move in the nip between the working surface 11 and the nip roll 13. Any significant longer dwell there will cause excessive wear on the blades at the ends of the oscillation path and any significant shorter dwell will fall short of optimizing the uniformity of wear, and the life, of the blades 7. However, if the life of the blades 7 is not at least twice the life of the working surface 11, it may not be necessary to completely optimize the life of the blades 7 because the cost of stopping
