FIELD OF THE INVENTION 
     This invention relates to machines and techniques for crimping textile threads and more particularly, although not necessarily exclusively, to such machines and techniques providing increased throughput while maintaining regularity of crimping. 
     BACKGROUND OF THE INVENTION 
     Commonly-owned U.S. Pat. No. 5,074,016 to Meyer details a widely-used machine, known as a “stuffer box,” for crimping textile threads. Described as part of the machine are a compression chamber, a decompression chamber, and pivoting paddles defining an evacuation, or holding, chamber. Spring blocks or similar structures may bias the paddles to a normally-closed position, initially closing the outlet. 
     Textile thread introduced into the machine via drive pulleys (e.g. nip rolls) packs into the compression chamber, with the act of compression facilitating crimping of the threads. Additional thread forced into the machine drives crimped thread from the compression chamber into the decompression chamber, where the crimped thread is subjected to an atmosphere of hot steam (or other appropriate fluid). Subjecting the thread to vapor in this manner assists in fixing the crimps in the thread. 
     Thereafter, the fixed, crimped thread is forced into the evacuation chamber. Doing so counteracts force provided by the spring blocks so that the paddles open slightly. As the paddles open, thread may exit the machine for further processing or to be wound onto a winding machine or other device. 
     Machines detailed in the Meyer patent function well in use. Desirably, however, these machines could provide increased throughput of crimped threads. One possible way of increasing throughput is to increase the height of the machine, thereby increasing the volumes of the compression, decompression, and evacuation chambers. Increasing the volumes of the chambers obviously increases the amount of thread positionable in each chamber. Unfortunately, however, it also decreases the uniformity of the crimping, an undesirable result. 
     Another possible technique for increasing throughput is to expand the width of the machine. Enlarging the width of the stuffer box allows for relatively uniform crimping of the threads, thus avoiding the problem associated with increasing the height of the machine. Regrettably, though, a width increase mandates a corresponding resizing of the nip rolls. Such resizing exacerbates the ability of one thread to slide relative to another, producing different entry speeds of threads into the stuffer box. The different entry speeds in turn create exit difficulties associated with the threads and their subsequent winding. 
     SUMMARY OF THE INVENTION 
     The present invention provides an alternate manner of increasing throughput of machines such as (but not limited to) that of the Meyer patent. Rather than increasing the height or width of the stuffer box, the present invention reconfigures the nip rolls so as to group the threads in one (preferably central) region of the roll faces. This grouping reduces tendency of the threads to spread across the faces and slide relative to each other—or off the faces entirely—promoting uniformity of entry speed and correspondingly increasing throughput. 
     A presently-preferred version of the invention incorporates a circumferential groove in a central region of the face of at least one nip roll. The groove beneficially is concave in shape, although it need not necessarily be so. An eyelet or other thread-focusing means optionally may be provided upstream of the nip rolls. If such an eyelet is utilized, it preferably will have diameter less than or equal to the width of the groove. 
     It thus is an optional, non-exclusive object of the present invention to provide improved apparatus and methods for crimping textile threads. 
     It also is an optional, non-exclusive object of the present invention to provide crimping machines configured to allow greater thread throughput than generally commercially available. 
     It is another optional, non-exclusive object of the present invention to provide greater thread throughput without changing the height or width of the stuffer box. 
     It is a further optional, non-exclusive object of the present invention to provide machines in which at least one nip roll is grooved to group threads entering the machines. 
     It is, moreover, an optional, non-exclusive object of the present invention to provide an eyelet upstream of the grooved roll (or rolls) to condense the threads into the region defined by the groove (or grooves). 
     Other objects, features, and advantages of the present invention will be apparent to those skilled in the appropriate field with reference to the remaining text and drawings of this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematicized view of a pair of nip rolls as conventionally configured as part of a textile thread-crimping machine. 
         FIG. 2  is a schematicized view of the nip rolls of  FIG. 1  as modified consistent with the present invention. 
         FIG. 3  is a perspective view of a portion of a crimping machine incorporating the nip rolls of  FIG. 2 . 
         FIG. 4  is a perspective view of the interior of part of the crimping machine shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Illustrated in  FIGS. 1-4  is a pair of drive pulleys, preferably in the form of nip rolls  10 A-B, for a stuffer box or other crimping machine  14 . As detailed in the Meyer patent, rolls  10 A-B introduce thread into machine  14  to commence the crimping operation. In particular, respective drive faces  18 A-B of rolls  10 A-B are spaced slightly (by a small distance D 1  in  FIG. 1 ), creating an area in which the thread may be positioned. Generally, positioning the thread in the central regions  22 A-B of faces  18 A-B (i.e. remote from edges  26 A-B and  30 A-B) produces greater regularity of crimping, both by centering the thread for entry into compression chamber  34  and by reducing likelihood of the thread sliding from between rolls  10 A-B and thereby losing its drive force.  FIG. 1  shows a conventional mass of thread T 1  entering machine  14  when rolls  10 A-B are spaced by distance D 1 . 
       FIG. 2 , by contrast, illustrates a centrally-grouped (and probably larger) mass of thread T 2  entering machine  14  notwithstanding maintenance of the minimum spacing of drive faces  18 A-B at distance D 1 . This result may be achieved by creating (circumferential) groove  38  in central region  22 A of drive face  18 A of roll  10 A. Thread may fill groove  38  during operation of machine  14 , allowing a more centrally-bunched grouping of thread to enter machine  14  at all times. In effect, creation of groove  38  both centers thread T 2  for entry into machine  14  and reduces likelihood of the thread T 2  sliding from between rolls  10 A-B or relative to each other. Rolls  10 A-B retain their ability to drive thread T 2  into machine  14 , however, so no material sacrifice of performance occurs. Consequently, use of groove  38  may increase throughput of machine  14  without adverse results. 
     As shown in  FIG. 2 , groove  38  is semi-circular or otherwise concave in shape. Groove  38  need not necessarily be concave, however, but rather may have any shape desired or suitable for its intended purposes. Further, although only one groove  38  is depicted in  FIGS. 2-4 , more than one groove may be utilized consistent with the present invention. For example, central region  22 B of drive face  18 B likewise could be grooved, or either of drive faces  18 A or  18 B could have multiple grooves  38 . However, because incorporating multiple grooves  38  into a single drive face  18 A or  18 B might create multi-modal crimping characteristics, doing so is not presently preferred. 
     Also depicted in  FIGS. 3-4  is optional eyelet  42 . If present, eyelet  42  preferably is located upstream of rolls  10 A-B, so that thread encounters it before encountering the rolls  10 A-B. Consequently, eyelet  42  may function to consolidate, or focus, the thread toward central areas  22 A-B of drive faces  18 A-B. The diameter of eyelet  42  preferably is equal to or less than the width of groove  38 . Eyelet  42  need not necessarily be so sized, however, and may if desired be shaped differently than as shown in  FIGS. 3-4 . 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention. The contents of the Meyer patent are incorporated herein in their entirety by this reference.
Thread-crimping machines with enhanced throughput are detailed. One or more drive rolls forming parts of the machines may be grooved to group centrally the entering threads without materially adversely impacting driving and crimping operations of the machines. Thread-focusing components also may be employed upstream of the inlet areas.