Abstract:
The present invention relates to an adjustable air shield for skewed godet rolls. The air shield can be any blocking type plate with or without perforations. Furthermore, these air shields may be placed in close proximity to the pair of skewed, relax rolls in the relax zone of a fiber producing process. The plates are positioned on the inside of the threadline so that the airflow is substantially reduced around the threadline on the skewed rolls. The preferred embodiment of the present invention is one or more skewed godet rolls in the relax area of the fiber production process with air shields positioned on the inside of the fiber string up (threadline) between the pair of skewed rolls, such that the gap between any roll and any air shield is uniform and constant.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (1) Field of the Invention 
         [0002]    The present invention relates to an adjustable air shield for skewed godet rolls in a relax zone during yarn production. Both the adjustable air shield and the adjustable skewed godet rolls are incorporated into a relax zone in the production of yarn to increase the stability of the yarn on the relax rolls, especially at process speeds greater than about 4,000 meters per minute. The skew is changed to accommodate processes that have different deniers (width of filament band on the rolls) and a different number of wraps on the rolls. Typical processes that have apparatus for relaxing the yarn during production are spin-drawing, draw-twisting, draw-winding, and draw-bulking processes. There is thus a need for a design of adjustable air shields to accommodate changes in roll skew. 
         [0003]    (2) Prior Art 
         [0004]    The following patents relate to employing an air shield during yarn production. Generally these patents teach employing an air shield near a pair of godet roll. None of these patents teaches employing adjustable air shields. 
         [0005]    Japanese Patent 58-26767 to Ishihara Masatoshi, et al. assigned to Toray Industries, Inc., describes air shield plates used to prevent yarn vibration thereby enhancing the quality of the wound yarn in high speed winding applications. This patent employs restricting guides as well as the air shield plates in FIG. 2 of JP 58-26767. 
         [0006]    Japanese Patent 62-116477 to Ohata Takahiro, et al. assigned to Teijin Seiki Company, Ltd., discloses an air shield plate positioned between a pair of godet rolls to prevent the occurrence of vibration of the yarn. 
         [0007]    Korean Patent Applications 94-4689 and 94-4690 by Baek, et al. and assigned to Cheil Synthetics, Inc., both relate to employing multi-hole air shield plates near the first godet roll to be used at high speeds above 6,000 meters per minute to prevent air flow thereby reducing fiber breakage and ensure high productivity of the process. 
         [0008]    Japanese Patent 2761789 to Takashi Inoue, and assigned to Teijin Seiki, Co., Ltd., describes an air shield type device. Specifically, two godet rolls are employed where yarn moves excessively on the roll surfaces. Each godet pair consists of a driven roll and a separator roll. The air shield is a single plate mounted between the rolls with one edge in close proximity to the driven godet roll surface. The plate is perforated with multiple holes which break up the deflected air stream that bounces off the plate and reduces the incidence of roll wrap. 
         [0009]    Published PCT application PCT US02/00153 filed Jan. 3, 2002 discloses at least a pair of godet rolls with at least one air shield. There is no teaching of adjustability of the air shields with respect to the skewed rolls. This patent application has a common inventor and is commonly assigned. 
         [0010]    The fixed shields, relative to the godet rolls, in the prior art devices do not allow for the skew of the rolls to be changed (or adjusted) without changing the geometry and thus the efficiency of the air shields. The skew is changed to accommodate processes that have different deniers (width of filament band on the rolls) and a different number of wraps on the rolls. There is thus a need for a design of adjustable air shields to accommodate changes in roll skew. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention relates to an adjustable air shield for skewed godet rolls. The air shield can be any blocking type plate with or without perforations. Furthermore, these air shields may be placed in close proximity to the pair of adjustable skewed, relax rolls in the relax zone of a fiber producing process. The plates are positioned on the inside of the threadline so that the airflow is substantially reduced around the threadline on the skewed rolls. The preferred embodiment of the present invention is one or more skewed godet rolls in the relax area of the fiber production process with air shields positioned on the inside of the fiber string up (threadline) between the pair of skewed rolls, such that the gap between any roll and any air shield is uniform and constant. 
         [0012]    In the broadest sense, the present invention comprises, for use in a relaxation zone of a fiber production process, an adjustable air shield and a pair of skewed godet rolls. 
         [0013]    Likewise, the present invention relates to a process for producing fibers in a relax zone having a pair of skewed godet rolls, comprising the step of introducing an adjustable air shield adjacent at least one of the skewed rolls (relax rolls) in the fiber relaxation zone. Thus when the skew of the rolls is reset to accommodate different yarns, the air shield is adjusted such that the gap between any roll and any air shield is uniform and constant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The drawings are to aid one skilled in the art in understanding the present invention and its related concepts as well as the scope of the invention. However, the drawings are in no way meant to limit the scope of the invention or impose any limitation on the invention beyond that set forth in the claims. 
           [0015]      FIG. 1  shows a schematic of a pair of adjustable air shields and a pair of skewed godet rolls, with the air shield positioned inside the threadline between the two skewed rolls. 
           [0016]      FIG. 2  shows a second schematic of two pairs of air shields and a pair of skewed godet rolls, where all air shields are inside the threadline. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The present invention is directed to adjustable air shields and skewed godet rolls in a relax zone of a yarn production process. By godet rolls, the inventors are referring to any pair of rolls that has a threadline wound around them. Sometimes the industry refers to a godet roll and a separator roll, or one or more relax rolls. All of these various references are included under the phrase “godet rolls”. Current processes such as a spin draw process, draw twisting process, draw-winding process, or draw bulking process include a relax zone and thus the process and apparatus of the present invention can be employed in such a relax zone. 
         [0018]    Any melt-spun polymer employed with any of the above processes such as polyesters, polyamides (nylons), polyolefins, polyketones, polyetherketones, polyphenylene sulfide, and polyarylates can be employed with the present invention. Typical polyesters are polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, or a mixture of any of these, or copolymers of any of these polyesters with up to about 15% by weight of other comonomers, such as isophthalic acid. Typical nylons are nylon 6 and nylon 66. Typical polyolefins are polyethylene, polypropylene, polybutylene, or a mixture of these. Combinations of any of these polymers, or any one of these polymers with other polymers like polyethylene or polypropylene, in the form of a bicomponent or heterofil fiber are also within the scope of the present invention. 
         [0019]    As the relax level increases, yarn tension in the relax zone decreases, and this causes the yarn to become unstable, especially on skewed godet rolls in or downstream of the relax zone. As process speeds increase, instability becomes worse at a constant relax ratio, due to the increase in centrifugal force on the yarns on the skewed relax rolls. Thus as process speeds are increased, relax level must be decreased to maintain stability. Unstable yarn is defined as yarn moving, or swaying across the roll surface of the skewed godet rolls due to low tension. Highly unstable yarn can lead to a reduction in mechanical quality, and in severe cases, to breakouts (yarn breakage). The skew for godet rolls is different for different process conditions, such as denier of the yarn, process speed, amount of relax, and type of synthetic yarn, for example. Therefore, the skew of godet rolls may be varied to accommodate running different products on the same equipment. 
         [0020]    When the process or apparatus of the present invention is used in any of the yarn production processes having a relax zone, a higher level of relax and a resulting lower hot air shrinkage can be achieved as compared to conventional processes and apparatus having no air shields. By using the present invention at higher processing speeds one can achieve the same level of relax under high speed conditions versus more conventional low speed conditions, or one could maintain the process speed but increase the level of relax such that the hot air shrinkage is greatly improved (reduced), or both can be done simultaneously. 
         [0021]      FIG. 1  schematically illustrates the present invention comprising the adjustable air shields and skewed rolls. Referring to  FIG. 1 , reference  10  generally indicates the apparatus of the present invention positioned in a relax zone of a fiber production process. The relax zone has a pair of spaced apart, skewed, godet rolls  12 ,  14 . Generally these rolls are adjustable such that the skew angle can be varied. The details of this adjustability are not essential to understanding the present invention since there are several solutions to vary the angle of the rolls. These rolls may be the same size, different sizes, and constructed of the same or different materials. A fiber threadline  16  is wrapped multiple times around the rolls  12 ,  14 . Each roll has an air shield  18  mounted adjacent the rolls  12 ,  14  and are spaced approximately 1 to 5 mm (preferably 1 to 2 mm) from the rolls. The shields  18  may be perforated or solid as known in the art. The air shield  18  is supported by a support frame or bar  20  that may be secured to the supporting framework  22 . Preferably the connection between the frame or bar  20  and the framework  22  includes a swivel joint  24  so that the bar  20  can be positioned at any angle to the framework, and preferably parallel to its related skewed roll. It is also preferred that the framework  22  includes an elongated slot  26  that the swivel joint is positioned within, so that the air shield may be further adjusted relative to the roll it is associated with. Depending upon the string-up conditions and the production parameters, the skew of the rolls  12 ,  14  to one another may be changed. With the preferred use of a swivel joint  24  and an elongated slot  26 , maximum flexibility can be obtained by allowing the adjustment of the air shields to the rolls. 
         [0022]    The air shield is positioned inside of the threadline  16  so that airflow is blocked from blowing across the threadline and creating movement on the skewed rolls  12 ,  14 . The air shield  18  comprises at least one plate (thin and flat substantially two dimensional) and preferably a pair of plates are employed, one per roll as shown. The plates may be made from any material capable of being perforated or being solid such as metal, like aluminum or copper for example (virtually any metal will perform equally well); plastic capable of withstanding the heat generated during the relaxation stage of the fiber making process, like polycarbonate, polyester, polyamide, all of which are well known in the art; wood, rubber; or a combination of these. The air shield may be any shape, not necessarily rectangular or square, because the rolls  12 ,  14  are skewed. Preferably the spaced apart plates  18  are positioned between the skewed rolls  12 ,  14  and within each tangent line connecting the outer surface of each roll, and thus within the threadline  16 . When one air shield is used per roll as shown in  FIG. 1 , the air shield  18  is positioned on the threadline discharge side of the roll. The air shields block the flow of air generated by the rotation of the skewed rolls  12 ,  14  and any airflow caused by fans or blowers in a production facility, for example. By virtue of the fact that the air shield  18  is positioned approximately 1 to 5 mm (preferably 1 to 2 mm.) from rolls  12 ,  14  and are also about the same distance from the threadline  16 , a quiescent zone adjacent each air shield  18  is created thus significantly reducing any disruption of the movement of the threadline on rolls  12 ,  14  induced by air currents. 
         [0023]    In operation of the  FIG. 1  device, a threadline  16  coming from the draw stage (not shown), for example, is wrapped multiple times about the pair of skewed rolls  12 ,  14 . The function of the rolls  12 ,  14  is not a part of the present invention and depends upon the type of process in which the relax zone is present (the relax zone includes the rolls  12 ,  14 ). Therefore the rolls  12 ,  14  could be in a spin-drawing process, or in a draw-twisting process, or in a draw-winding process, or a pair of rolls in a draw bulking process. The threadline is wrapped multiple times about the rolls  12 ,  14  and exits the rolls to further processing or winding. Because the air shields  18  are positioned inside of the threadline  16 , created by the multiple wraps of the yarn or fiber  16 , the air shields  18  do not interfere with string-up, for example. 
         [0024]      FIG. 2  illustrates a modification of  FIG. 1  of the present invention in which two pairs of air shields are employed per skewed roll. All references to numerals in  FIG. 1  apply equally to  FIG. 2 . To further reduce air currents around the skewed rolls  12 ,  14 , each roll has a pair of air shields  18  are positioned inside the threadline and are between the rolls  12 ,  14  so that the air is blocked from the treadline  16  upon both entering a roll and leaving a roll. Thus even less instability of the treadline is present in the  FIG. 2  device as compared to the  FIG. 1  device. 
         [0025]    The operation of the  FIG. 2  device is substantially similar to that of the  FIG. 1  device. 
         [0026]    Those skilled in the art may recognize that a larger diameter roll like roll  12  would create more air currents at its larger surface than a smaller diameter roll like  14 . Thus its within the present invention to have 3 air shields where the larger roll has a pair of shields while the smaller roll has only a single air shield. Likewise, it is within the skill of the artisan to provide only one air shield at the exit side of the threadline adjacent the larger roll, and no air shield on the smaller roll. 
         [0027]    Thus it is apparent that there has been provided in accordance with the invention a process and an apparatus that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and the broad scope of the claims.