Method of knitting a fabric having improved non-run and elasticity characteristics
FIELD OF THE INVENTION 
     The present invention relates to the formation of single-knit fabrics having improved non-run, elasticity, soft hand and drapeability characteristics and more particularly to an improved method of producing such fabrics. 
     BACKGROUND OF THE INVENTION 
     It is well known to produce a knit fabric having elasticity of double plain jersey loops of a ground yarn and an elastic yarn. One example of such a knitting method includes raising all needles to the knitting level where the old loops clear the latches on the needles and feeding both the ground yarn and the elastic yarn to the needles. As the needles descend, the sinkers withdraw so that the old loops knock over at the sinker tops and double loops are formed by the needles and sinkers of the ground yarn and the elastic yarn in each loop. 
     While producing knit fabrics of excellent elasticity, this prior method has difficulties and deficiencies. For example, the elastic yarn causes the fabric to contract in both the course and wale directions which results in deformed loops. The resulting fabric has a hard hand and poor drapeability. Also, elastic yarn breakage is difficult to correct during knitting of such fabric. 
     Another example of a prior method of producing knit fabric having double jersey loops is disclosed in U.S. Pat. No. 2,379,649. While producing a single-knit fabric of double jersey loops which overcomes the difficulties and deficiencies of the aforementioned method, the method of this prior patent has other difficulties and deficiencies. For example, the needles of the knitting machine are arranged in two groups and the two yarns are alternately fed to the front and the back of the hooks of the knitting needles in the two groups. To accomplish this, the group of needles to the back of which a yarn is being fed must rise sharply at the back of the first yarn guide. This type of yarn feeding is difficult and inaccurate and frequently results in less than desirable quality. 
     SUMMARY OF THE INVENTION 
     With the foregoing in mind, it is an object of the present invention to provide a method of producing easily and accurately fabrics having a soft hand and much elasticity and in which no elastic yarn is used and no special yarn feeding units are required. 
     The object of this invention is accomplished by a method of knitting fabric on a circular knitting machine in which double jersey loops are formed by having the needles arranged in groups of alternate and intervening needles and feeding a ground yarn to alternate groups at each yarn feed. The needles that do not receive a ground yarn at a particular yarn feed move to the next yarn feed while holding any previous yarn fed thereto in the hooks thereof until two ground yarns are received in the hooks thereof and then double loops of two ground yarns are formed at that knitting station. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some of the objects and advantages of the present invention having been stated, others will appear as the description proceeds when considered in conjunction with the accompanying schematic drawings, in which: 
     FIG. 1 is a schematic view of the knitting processes of the present invention; 
     FIG. 2 is a schematic view of the needle selection and operating cam for the high butt knitting needles of the circular knitting machine utilized in the method of the present invention; 
     FIG. 3 is a schematic view similar to FIG. 2 of the needle selection and operating cam for the low butt needles; 
     FIG. 4 is a fragmentary enlarged sectional view taken substantially along line 4--4 in FIG. 1; 
     FIG. 5 is a fragmentary sectional view similar to FIG. 4 taken substantially along line 5--5 in FIG. 1; 
     FIG. 6 is a sectional view similar to FIGS. 4 and 5 taken substantially along line 6--6 in FIG. 1; 
     FIG. 7 is a sectional view similar to FIGS. 4 through 6 taken substantially along line 7--7 in FIG. 1; 
     FIG. 8 is a sectional view similar to FIGS. 4 through 7 taken substantially along line 8--8 in FIG. 1; 
     FIG. 9 is a sectional view similar to FIGS. 4 through 8 taken substantially along line 9--9 in FIG. 1; 
     FIG. 10 is a sectional view similar to FIGS. 4 through 9 taken substantially along line 10--10 in FIG. 1; 
     FIG. 11 is a sectional view similar to FIGS. 4 through 10 taken substantially along line 11--11 in FIG. 1; and 
     FIG. 12 is a fragmentary schematic view of a fabric knit in accordance with the method of the present invention. 
     FIG. 13 is a cross sectional view of a knitting machine for forming the knit fabric of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more particularly to the drawings and specifically to FIG. 13, there is illustrated the knitting elements of a circular knitting machine generally indicated at 20. Circular knitting machine 20 is of the single knit type and includes a needle cylinder 21, sinker cap 22, yarn carrier 23 and cam holder 24. The needle cylinder 21 has multiple needle slots extending vertically in the outer periphery thereof. The needle slots have needles 25 and 26 slidably mounted therein. Needles 25 are high butt needles and are mounted in alternate needle slots in cylinder 21, while needles 26 are low butt needles mounted in intervening needle slots in cylinder 21. 
     A sinker dial 30 is fixed to the top of cylinder 21 for rotation therewith. Sinker dial 30 has multiple radial slots therein and a sinker 31 slidably mounted in each sinker slot. Sinkers 31 have a sinker nose 31a, a sinker throat 31b and a sinker top 31c. Preferably, the difference in height between the top of the sinker nose 31a and the sinker top 31c is between 1.5 mm and 2.2 mm. A sinker cam 32 is carried by sinker cap 22 for controlling and operating sinkers 31. 
     Cam holder 24 mounts a pair of cams 33, 34 for controlling and operating the cylinder needles 25, 26. Preferably, cams 33 and 34 are of the closed type as shown in FIGS. 2 and 3. Cam 33 controls and operates the high butt cylinder needles 25, and cam 34 controls and operates the low butt needles 26. 
     The needle cams 33 and 34 and sinker cam 32 control the needles 25 and 26 and sinkers 31 in a first process a, a second process b, a third process c and a fourth process d. Cam 33 has the closed cam track thereof divided into cam sections 33a, 33b, 33c and 33d corresponding to the first through fourth processes a through d, inclusive. Cam 34 has the closed cam track thereof divided into sections 34a through 34d, inclusive, corresponding to the third process c, fourth process d, first process a and second process b, respectively. In FIG. 1, the solid line 35 represents the operation or performance line of the high butt cylinder needles 25; the phantom line 36 represents the operation or performance line of the low butt cylinder needles 26; and the dash line 37 represents the operation or performance line of the sinkers 31. 
     The function or performance of high butt needles 25 is the same in the first and second processes a, b as the function or performance of the low butt needles 26 in the third and fourth processes c, d and the function or performance of the low butt needles 26 in the first and second processes a, b is the same as the function or performance of the high butt needles 25 in the third and fourth processes c, d. 
     In the first process a, a yarn carrier 23a feeds a first ground yarn G 1  to the cylinder needles 25, 26. A yarn carrier 23b feeds a second ground yarn G 2  to the needles 25, 26 in the third process c. 
     In the first process a, cam section 33a of cam 33 raises the high butt needles 25 to the knitting level (FIGS. 1 and 4) and the old double yarn loops OL clear the latches of the needles 25. At the same time, yarn carrier 23a feeds ground yarn G 1  to the high butt needles 25. As the needles 25 descend to a first welt position (FIG. 5), the old loops OL close the latches of the needles 25 thereby capturing the ground yarn G 1  in the hooks thereof and catching the ground yarn G 1  on the nose 31a of the sinker 31. 
     In the second process h, the sinkers 31. withdraw to the outside and the ground yarn G 1  drops off the nose 31a of the sinker 31 (FIG. 6). The cylinder needles 25 are then lowered by cam section 33b of cam 33 to a second welt position in which the hooks thereof are at the level of the sinker throat 31b and the sinkers 31 are advanced so that the old loops OL and the ground yarn G 1  are received in the sinker throat 31b (FIG. 7). 
     Cam section 33c raises the cylinder needles 25 in the third process c to the tucking level (FIG. 8) in which the old loops OL are held on the shanks of the needles 25 by the sinkers 31 and the ground yarn G 1  is held on the needles 25 above the latches thereof. Yarn carrier 23b feeds second ground yarn G 2  to the needles 25. 
     Needles 25 are then lowered to the third welt position while catching the second ground yarn G 2  in the hooks thereof. The old loops OL close the latches of the needles 25 and a new double yarn loop NL is formed of both of the first and second ground yarns G 1  and G 2  with the first ground yarn G 1  riding over the sinker top 31c and the second ground yarn G 2  riding over the sinker nose 31a. 
     Once the needles 25 have drawn the new loops NL, the sinkers 31 withdraw outside and the second ground yarn G 2  drops off of the sinker noses 31a (FIG. 10). Then, the sinkers 31 advance and the old loop OL and the ground yarns G 1  and G 2  are received and held in the sinker throat 31b as the needles 25 move on to the first process a again. 
     The intervening cylinder needles 26 are controlled and operated by cam 34 in the same manner as cam 33 operates needles 25 except that cam 34 raises needles 26 to the knitting level in the third process and to the tucking level in the first process. Accordingly, the description of the operation or performance of cylinder needles 26 will not be described further, but reference is made to the description of needles 25 herein. 
     The resulting fabric is shown in FIG. 12 and includes a plurality of alternate needle wales 25 and intervening needle wales 26 formed of stitch loops formed of ground yarns G 1  and G 2  as described above. The stitch loops in needle wales 26 are offset by one-half course from the stitch loops in needle wales 25. The ground yarn G 1  is knit in the stitch loops of all of the needle wales 25 and 26 in a course while a particular ground yarn G 2  is knit in the stitch loops of only the needle wales 26 while the ground yarn G 2  from the next adjacent course is knit into the stitch loops of the needle wales 25. This fabric structure provides increased elasticity, particularly in the wale direction, without distortion in the stitch loops or between stitch loops. Further, the fabric has a soft hand and greatly improved drapeability. 
     In the drawings and specifications, there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.