Patent Publication Number: US-4649722-A

Title: Open warp knit fabric

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to warp knitted fabrics, and more particularly to warp knitted fabrics having a nonelastomeric yarn knit in an open stitch construction in the front bar and an elastomeric yarn knit in a closed stitch construction in the back bar. 
     Open warp knit technology which incorporates open loops or a combination of open and closed loops in the stitch formation is disclosed in Research Disclosure, Article No. 24338, July 1984. The stated advantages were high luster, silk-like aesthetics and crepe-like frosty visual appearance. It has now been discovered that using this technology with elastomeric yarns in combination with nonelastomeric yarns provides a warp knit structure that imparts greater resistance to distortion and growth compared to conventional elastomeric/nonelastomeric Jersey warp knit structure which uses closed stitch construction exclusively in commercial fabrics. 
     SUMMARY OF THE INVENTION 
     This invention provides a warp knitted fabric that includes at least two sets of threads either, partial or full sets, knitted in courses according to a stitch pattern forming spaced wales of knitted loops. The improvement comprises back bar threads of elastomeric, such as spandex, yarn with a (1-0, 1-2 or 1-2, 1-0, or 2-4, 0-2, or 3-6, 3-0) stitch pattern and front bar threads of nonelastomeric, such as nylon, yarn knit with a (3-2, 0-1 or 0-1, 3-2 or 0-1, 2-3, 5-4, 3-2 or 0-2, 4-2 or 0-3, 6-3) stitch pattern. Double and triple needle stitches should use partial threading (e.g., 0-2, 4-2, and 0-3, 6-3 use guide bar threading, one end in and one end out; and one end in and two ends out, respectively). 
     This novel fabric construction eliminates crossover points, or pinch points between the elastomeric and nonelastomeric yarns, thus giving the elastomeric yarns more freedom to move which is not possible when the elastomeric yarns are pinched between the nonelastomeric yarns as with the prior art warp knit fabrics of elastomeric and nonelastomeric yarns. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a stitch pattern diagram of a prior art warp knit fabric. 
     FIGS. 1B-1I are stitch pattern diagrams for the fabrics of this invention. 
     FIG. 2A is a loop diagram of a portion of the knitted loops of the prior art fabric shown in FIG. 1A. 
     FIG. 2B is a loop diagram of a portion of the knitted loops of a fabric of this invention shown in FIG. 1E. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The invention is best defined in terms of stitch patterns as shown in FIGS. 1B to 1I. FIG. 1A being noted as prior art for warp knit fabrics of elastomeric combined with nonelastomeric yarns. For each of the Figs. represented a single needle-bar is normally employed, being fed from a front bar of nonelastomeric knitting yarns such as nylon yarn designated 20 and a back bar of elastomeric knitting yarns such as spandex yarn designated 21. Knitting needle positions for each of two successive courses are represented in the diagrams by horizontal lines of dots, the top line representing the course formed immediately after the course represented by the bottom line. Only one front-bar end and one back-bar end are shown in each instance, it being understood that one end of each is knitted on each knitting needle for every course. More particularly, referring to FIG. 1A, the stitch construction of the fabric is notationally set out and shows that the threads of the front bar, one of which is indicated at 20, have back and forth movement to nonadjacent needles in successive courses as indicated by the numbers 2-3, 1-0 and that the threads of the back bar, one of which is indicated as 21, having similar movements as indicated by the numbers 1-0, 1-2. 
     The back bar threads of elastomeric yarn 21 are closed loops while the front bar threads of nonelastomeric yarn 20 are open loops in the stitch constructions of the instant invention as depicted in FIGS. 1B through 1I. The movements to needles to excessive courses are indicated below each diagram by their numbers as set forth in Table I below. 
     
                       TABLE I                                                     
______________________________________                                    
FIG. No.      Front Bar      Back Bar                                     
______________________________________                                    
1A            2-3, 1-0       1-0, 1-2                                     
1B            0-1, 3-2       2-4, 2-0                                     
1C            0-2, 4-2       2-4, 2-0                                     
1D            0-1, 3-2       3-6, 3-0                                     
1E            3-2, 0-1       1-0, 1-2                                     
1F            0-3, 6-3       1-2, 1-0                                     
1G            0-1, 2-3, 5-4, 3-2                                          
                             1-2, 1-0                                     
1H            0-2, 4-2       1-2, 1-0                                     
1I            0-1, 2-3, 5-4, 3-2                                          
                             1-0, 1-2                                     
______________________________________                                    
 
    
     To illustrate the structure and functional advantage of this invention versus the prior art Jersey warp knit construction loop diagrams of FIG. 1A and FIG. 1E have been constructed as FIGS. 2A and 2B, respectively. Referring now to FIGS. 2A and 2B the nonelastomeric yarn is again designated 20 and the elastomeric yarn is designated 21. As illustrated in these figures float A of the nonelastomeric yarn 21 pulls generally upward and float B of this yarn pulls generally downward as indicated by the direction arrows. These floats in conjunction with the designated loop of nonelastomeric yarn sandwich the elastomeric yarn 21 between the two nonelastomeric yarns at locations or crossing points designated 30 through 36. At location 40 the float loops pinch the elastomeric yarn against the top of loop D in FIG. 2A by comparison while eight crossing points 30 through 36 are retained in the stitch construction of this invention. The pinch point is eliminated to provide more freedom for the elastomeric yarns to move in the fabric of this invention. 
     EXAMPLE 
     A 28-gauge tricot knitting machine is used to produce three fabrics as identified in Table II. The control fabric has the knit structure of the prior art as shown in FIG. 1A. The finishing procedures for the fabrics are outlined in Table III. The test methods for determining thickness, bulk, static extension, air permeability and power are detailed below. 
     Test Methods 
     Thickness is measured according to ASTM D1777-64 using apparatus commercially available from Customer Scientific Instruments, Inc., Whippany, NJ. Thickness is measured in inches. 
     Bulk (specific volume) is calculated according to the formula: ##EQU1## wherein T=Thickness (inches) 
     W=Weight (g/cm 2 ) 
     Static Extension Test determines fabric elongation and growth. Measurements are made using a Model C5138 static extension tester available form Customer Scientific Instrument Co., Kearny, NJ. 
     Test Stretch is the length of a fabric sample while under a load of 2 lb. per inch fabric width expressed as a percentage of original relaxed length. 
     Growth is measured by holding a fabric sample at 180% of its relaxed length for two hours, then measuring its relaxed length after one minute and again after one hour. Growth is expressed as percentages of original relaxed fabric length. 
     Air Permeability is the rate of air flow though the fabric under a differential pressure between the two fabric surfaces and expressed in cubic feet of air per minute per square foot of fabric. It is measured in accordance with ASTM method D737-75. 
     
                                           TABLE II                                
__________________________________________________________________________
FABRIC CONSTRUCTION AND GREIGE FABRIC PROPERTIES                          
Fabric                                                                    
     Type                                                                 
Number                                                                    
     Fabrics  Front Bar//Back Bar                                         
                               Stitch-F.B//B.B.                           
__________________________________________________________________________
4955-68A                                                                  
     Jersey (Control)                                                     
              40-13 T865 Nylon//40 den Spandex                            
                               2-3, 1-0//1-0, 1-2                         
4955-68C                                                                  
     Del-Jersey                                                           
              40-13 T865 Nylon//40 den Spandex                            
                               3-2, 0-1//1-0, 1-2                         
4955-68I                                                                  
     Del-Atlas                                                            
              40-13 T865 Nylon//40 den Spandex                            
                               0-1, 2-3, 5-4, 3-2//1-0,                   
__________________________________________________________________________
                               1-2                                        
         Guide Bar Threading                                              
                        Knit                                              
                             Runners - Inch                               
                                     ##STR1##                             
Fabric Number                                                             
        F.B.//B.B. Gauge                                                  
                       Quality                                            
                            F.B.//B.B.                                    
                                    gms/3 ends                            
__________________________________________________________________________
4955-68A                                                                  
        full//full 28  7.5&#34; 58&#34;//24&#34;                                      
                                    81/2                                  
4955-68C                                                                  
        full//full 28  7.5&#34; 60&#34;//24&#34;                                      
                                    83/4                                  
4955-68I                                                                  
        full//full 28  7.5&#34; 601/2&#34;//24                                    
                                    73/4                                  
__________________________________________________________________________
        Greige Fabric              Boiled Off Fabric                      
                Count   Hand Stretch                                      
                                   Weight                                 
Fabric Number                                                             
        Weight oz/yd                                                      
                WPI CPI % Wale                                            
                             % Course                                     
                                   oz/yd.sup.2                            
__________________________________________________________________________
4955-68A                                                                  
        5.5     64  100 150  100   7.8                                    
4955-68C                                                                  
        5.3     64   96 130  100   8.2                                    
4955-68I                                                                  
        5.5     56  120 160   85   7.5                                    
__________________________________________________________________________
FINISHED FABRIC PROPERTIES                                                
Fabric     Weight                                                         
               Count  Thickness                                           
                            Bulk                                          
                                Hand Stretch                              
Number    oz/yd.sup.2                                                     
               WPI × CPI                                            
                      BSI   cc/g                                          
                                % Wale                                    
                                      % Course                            
__________________________________________________________________________
4955-68A (Control)                                                        
          4.8  63 × 100                                             
                      .031  4.89                                          
                                150   120                                 
4955-68C  4.7  65 × 94                                              
                      .032  5.10                                          
                                150   100                                 
4955-68I  4.5  56 × 100                                             
                      .029  4.88                                          
                                170   100                                 
__________________________________________________________________________
STATIC EXT. TEST                                                          
Fabric    % Test Stretch                                                  
                  % Growth 1 Min.                                         
                           % Growth 1 Hr.                                 
                                    Air Per. cu.                          
Number    Wale × Course                                             
                  Wale × Course                                     
                           Wale × Course                            
                                    ft. min/ft.sup.2                      
__________________________________________________________________________
4955-68A (Control)                                                        
          173 × 133                                                 
                  28 × 26                                           
                           21 × 15                                  
                                    329                                   
4955-68C  170 × 143                                                 
                  20 × 24                                           
                           14 × 15                                  
                                    417                                   
4955-68I  203 × 118                                                 
                  32 × 18                                           
                           26 × 12                                  
                                    382                                   
__________________________________________________________________________
 
    
     
                       TABLE III                                                   
______________________________________                                    
FINISHING PROCEDURE                                                       
______________________________________                                    
Step 1   Steam the fabrics.                                               
Step 2   Heat set the fabrics on the Pin Tenter at 375°            
         4 boxes - 50 secs. 7% overfeed and 7% over                       
         with the greige fabric                                           
Step 3   Beck scour and dye the fabrics                                   
Step 4   Dry on the Pin Tenter at 290° F. 30 yds/min and           
         set the Pin Tenter at the fabric&#39;s wet width.                    
______________________________________