Abstract:
A method for crimping yarn wherein the yarn is fed into a compaction channel of a stuffer box to obtain uniform crimping, and the crimped yarn is pre-set and guided to the outlet of the stuffer box by a pre-setting fluid. A pre-setting and guiding chamber of the stuffer box has a cross-section of generally polygonal shape that is larger than that of the compaction channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 60/346,559 filed Jan. 8, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the textile industry, in particular to the treatment of yarns by crimping, and relates to a method of crimping yarns. The invention also relates to a device for carrying out this method.  
         BACKGROUND OF THE INVENTION  
         [0003]    The crimping of textile fibers or yarns using devices generally referred to as stuffer boxes is carried out by a known method. This method consists in directing the yarns to be crimped between two driving rollers that force the yams into a compaction channel. This compaction channel is usually equipped, at the opposite end to the rollers, with a flapper for compacting the yarns inside the stuffer box. The aim of the flapper or similar device is to increase the friction of the fibers or yarns against the walls of the compaction box to the point where the material to be crimped will lose, as it emerges from the driving rollers, its appearance in a longitudinal form and take on an undulating appearance created by the yarns rubbing downstream against the walls of the stuffer box.  
           [0004]    The undulation obtained is referred to as primary crimping and this crimping may be very uniform, but if the compaction chamber is of inappropriate volume or geometry, the primary crimping will tend to become secondary crimping which will have the effect of compacting the material differently and, consequently, will tend to make the primary uniform crimping disappear.  
           [0005]    In general, stuffer boxes use a thermal fluid, namely steam, to achieve all or part of the crimping. This steam is injected via orifices situated in the walls of the compaction chamber in such a way that the material to be crimped has a tendency to be pushed out of the stuffer box. This results in the need to apply an even more considerable braking force at the outlet of the stuffer box, so the material tends to acquire even more secondary crimping and consequently lose even more primary crimping.  
           [0006]    Crimping machines for carrying out such a method are known in particular from FR-A-2 652 359 and U.S. Pat. No. 5,647,109. In these machines, it is impossible to create and maintain the uniform crimping of the fibers or yarns, owing to the fact that the geometry of the compaction box and/or the system of heat treatment cause its destruction.  
         SUMMARY OF THE INVENTION  
         [0007]    The object of the present invention is to overcome these drawbacks by proposing a method and a device for crimping yarns which results in perfectly uniform crimping, without the formation of secondary or parasitic crimping.  
           [0008]    For this purpose, the method of crimping yarns includes the steps of making the yarns pass through an initial compaction zone of a stuffer box to obtain uniform crimping, then, in a second zone, in causing pre-setting of the resultant uniform crimping as well as guidance of the yarn to the outlet of the stuffer box by means of a pre-setting fluid.  
           [0009]    The invention also relates to a device for carrying out this method, in the form of a stuffer box equipped with a compaction chamber comprising driving rollers working in cooperation with doctor blades and a pre-setting and guiding chamber for the crimped yarns, wherein the cross-section of the compaction chamber is adjustable and the pre-setting and guiding chamber has a cross-section greater than that of the sliver of resultant crimped yarns such that one or more spaces are defined around the sliver being related to the delivery means for the pre-setting fluid.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The invention will be better understood from the following description which relates to a preferred embodiment, given as a nonrestrictive example and explained with reference to the accompanying diagrammatic drawings in which:  
         [0011]    [0011]FIG. 1 is a partial view illustrating a device according to one embodiment of the invention;  
         [0012]    [0012]FIG. 2 is a partial view in perspective on a larger scale, illustrating the outlet of the compaction chamber and the pre-setting and guiding chamber for the resultant sliver, this latter chamber being only partially illustrated;  
         [0013]    [0013]FIG. 3 is a partial view in perspective, on a larger scale and in section, of the compaction chamber linked to the inlet of the pre-setting and guiding chamber;  
         [0014]    [0014]FIG. 4 is a diagrammatic view from above illustrating the adjustment of the cross-section of the compaction chamber;  
         [0015]    [0015]FIG. 5 is a partial view in perspective illustrating the means for initial adjustment of the crimping; and  
         [0016]    FIGS.  6  to  13  are views in cross-section illustrating different geometries of the pre-setting and guiding chamber. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]    The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.  
         [0018]    [0018]FIG. 1 of the accompanying drawings illustrates, as an example, a device for crimping textile fibers or yarns in the form of a stuffer box equipped with a compaction chamber  1  comprising driving rollers  2  working in co-operation with doctor blades  3  (FIGS. 3 and 4) and pre-setting and guiding chamber  5  for crimped yarns  6 .  
         [0019]    According to the invention, this device employs a method which consists substantially in making the yarns  4  pass through an initial compaction zone of a stuffer box to obtain uniform crimping  6 , then in causing, in a second zone  5 , pre-setting of the resultant uniform crimping  6 , as well as guidance thereof, to the outlet of the stuffer box by means of a pre-setting fluid. As those skilled in the art will understand, steam constitutes a suitable pre-setting fluid.  
         [0020]    According to a characteristic of the invention, the adjustment and the initial formation of the crimping are produced by retention of the ends of the fibers or yarns engaged in the stuffer box, downstream of the compaction chamber  1 . In this way the fibers or yarns, which pass between the driving rollers  2  and are pushed between the doctor blades  3 , are initially retained in the pre-setting and guiding chamber  5  in order to produce initial crimping which corresponds to the desired crimping characteristics. The fiber or yarn retention time for the start of the crimping of a sliver is determined according to the mechanical characteristics of the fibers and yarns themselves and those of the desired crimping and are advantageously listed in a table or a chart which allows a rapid adjustment of the stuffer box for each type of textile fiber or yarn.  
         [0021]    According to a further characteristic of the invention, the pre-setting of the resultant uniform crimping  6 , as well as the guidance thereof to the outlet of the stuffer box, are advantageously produced by means of the presetting fluid which acts on at least part of the section of resultant crimped sliver, in a free space of the pre-setting and guiding chamber.  
         [0022]    For carrying out this method, the device in the form of a stuffer box is characterized in that the cross-section of the compaction chamber  1  is adjustable and in that the pre-setting and guiding chamber  5  has a cross-section greater than that of the compaction chamber and therefore greater than that of the sliver of resultant crimped yarns  6 , the supplementary space or spaces defined around the sliver  6  being related to the delivery means of the pre-setting fluid.  
         [0023]    The compacting chamber  1 , which is made up of driving rollers  2  and doctor blades  3 , is adjustable in its cross-section owing to the provision of means  7  and  8  which allow, on one hand, a coming together of the two doctor blades  3  and, on the other hand, a displacement of the inlet section of the doctor blades  3  in the direction of or away from the driving rollers  2 . The adjusting means  7  which allows the coming together of the two doctor blades  3  is illustrated in FIG. 4 of the accompanying drawings in the form of a reverse threaded element or screwed element, but may also very well be in the form of a pair of synchronized jack screws or an articulated control rod assembly bringing together or spreading apart the doctor blades  3 .  
         [0024]    The means  8 , which is intended to produce the displacement of the doctor blades inlet in the direction of the driving rollers  2  or in the opposite direction to these driving rollers  2 , is illustrated simply in FIG. 4 by a center line and may equally well be either in the form of a screw and nut drive acting on a guidance and support means common to the doctor blades  3 , or individual synchronized drives of the doctor blades.  
         [0025]    Preferably, the adjustment in spacing of these doctor blades  3  and the adjustment thereof in relation to the driving rollers  2  are carried out by a centralized control unit synchronizing the two adjusting movements. In fact, it is necessary to carry out simultaneously or almost simultaneously the adjustment of the opening of the doctor blades  3  and their positioning in relation to the driving rollers  2 , in order to quickly have available the best adjustment thereof.  
         [0026]    The compaction chamber  1  opens into the pre-setting and guiding chamber  5  for the resultant uniform crimping  6 , which has an internal cross-section greater than that of said crimping  6  and is equipped on its internal faces with delivery means for the pre-setting fluid, in the form of nozzles or the like, not illustrated. Preferably, the internal cross-section of the chamber  5  is arranged in such a way as to define on at least one side of the sliver of resultant crimped yarns  6  a free space  5 ′, of any geometry. This space  5 ′ allows expansion of the pre-setting fluid without the latter exerting a strong pressure on the sliver of crimped yarns  6 , this pressure being, however, sufficient to guide said sliver dynamically in the chamber  5 , that is to say to further its progression in said chamber toward the outlet thereof on a conveying or receiving device  9  (FIG. 1).  
         [0027]    As shown in FIGS.  6  to  13  of the accompanying drawings, the internal cross-section of the chamber  5  may be of the regular or irregular polygon type and define a space  5 ′ on only one side of the sliver of crimped yarn  6  or on both sides of this sliver. Preferably, the internal cross-section of the chamber  5  will have such a configuration that the spaces  5 ′, of slightly smaller height than the height of the sliver of crimped yarns  6 , are defined on either side of said sliver  6  so that they rest edgewise against the corners thereof (FIGS. 8 and 11).  
         [0028]    According to a further characteristic of the invention, not illustrated in the accompanying drawings, the cross-section of sliver of crimped yarns may equally well be adjustable in height by the provision, in the region of the doctor blades  3 , of movable guide means sliding between said doctor blades, in the direction of their vertical axis. In the foregoing, reference is made to a vertical axis of the doctor blades which corresponds, in fact, to the direction of the axes of the driving rollers  2 . Obviously, this concept of the verticality of the doctor blades is solely intended to explain the positioning and the displacement of the adjusting means for the height of the sliver of crimped fibers  6  in relation to the width of this sliver, given that the stuffer box may equally well have a vertical orientation of the axes of the driving rollers as a horizontal one.  
         [0029]    According to a further characteristic of the invention, the device is additionally equipped, at the end of the pre-setting and guiding chamber  5  opposite the one connected to the compaction chamber  1 , with a retaining means  10  for the fibers or yarns, at the beginning of a crimping process. This means  10  may advantageously be made in the form of a flapper (FIG. 5) installed in front of the outlet of said chamber  5  and able to be activated by means of a driving device not illustrated, the triggering of which to open and close is preferably produced by means of a programmable controller and/or a manual control. Such a driving device may be in particular in the form of a rotating jack screw or a jack screw acting on the axis of the flapper by means of a lever or also in the form of an electric stepping motor. The programmable controller able to control such a flapper is also of a type known to a person skilled in the art and may, for example, take into consideration numerical data predetermined by a learning adjustment means. Thus, it is sufficient, in the first stage, to produce a preliminary crimping test for each type of product used, in order to determine the adjustment characteristics which will produce the crimping values desired according to the yarn count of the product to be treated and the advancing speed of the yarns and to list these data on a table or chart and then simply program the machine according to the product data and the data of the final material to be obtained. The preliminary adjustment may, for example, be produced by activating the flapper  10  by means of a manual control.  
         [0030]    At the beginning of the crimping process for yarns or fibers, the machine starts up automatically with the flapper  10  in the closed position for a predetermined length of time corresponding to the production of primary initial crimping corresponding to the crimping to be obtained, then said flapper  10  is automatically opened and the crimping process may proceed as normal.  
         [0031]    In addition, in order to avoid the formation of condensation following the starting up of the machine, the upper and lower walls of the pre-setting and guiding chamber  5  may advantageously be equipped with an integrated electric or hot fluid circulation heating means.  
         [0032]    In order to allow quality control of the sliver of crimped yarns  6 , at least a part of the wall of the pre-setting and guiding chamber  5  can comprise transparent material. In this way, it is possible to carry out visual monitoring of the sliver  6  and to monitor the consistency of the product characteristics.  
         [0033]    According to a characteristic of the invention, not illustrated in the accompanying drawings, the transparent wall may also be equipped with an optical means of monitoring of the resultant product, working in cooperation with an electronic comparison device. Such an optico/electronic monitoring installation, which uses means known to a person skilled in the art, is not disclosed in more detail. This installation makes it possible to carry out verifications by comparison with data stored in an electronic memory and linked to a programmable controller or a computerized monitoring and central control system to act on the working parameters of the machine.  
         [0034]    Thanks to the invention, it is possible to carry out crimping of yarns in a stuffer box with perfect control of the uniformity of the crimp, the crimp being exposed during part of its passage through the stuffer box to pre-setting fluid, which simultaneously guides the sliver of crimped yarns dynamically to the outlet of the stuffer box, all this while using a space occupied exclusively by pre-setting fluid.  
         [0035]    In addition, the geometry of the pre-setting and guiding chamber  5  allows perfect preservation of the primary crimp created in the compaction chamber  1 .  
         [0036]    However, the invention also makes it possible, by specifically controlled use of the flapper  10  forming the retention means during crimping, to produce a non-uniform crimp, namely primary and secondary crimp, as it is possible with currently known machines.  
         [0037]    Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.