The manufacture of reverse loop sliver knit fabric using a circular sliver knitting machine for producing a pile fabric is well known in the art. Typically, a doffer roll is used to receive the sliver fiber from a card unit. Needles mounted on a rotatable cylinder receive the sliver fibers from a doffer roll as hooks on the needles enter the fillet wire of the doffer roll and draws sliver fibers after the needles have risen to a clearing level along a predetermined wave-like path. The hooks of the needle also pick up a yarn which is used to anchor or secure the sliver fibers such that free ends of the sliver fibers project from one side of the fabric. Examples of this approach to knitting pile fabric may be seen in U.S. Pat. Nos. 3,299,672 and 3,710,597 to Schmidt.
A variation on this approach is set forth in U.S. Pat. No. 3,226,952 to Cassady which discloses the use of a jet of air to position sliver fibers and hold it in position by means of a sinker nib for forming a single-faced pile fabric. As shown in Cassady, the air nozzle is located radially outward of the needle cylinder and at a position diagonal to the sinkers and needles.
In U.S. Pat. No. 2,280,535 Moore introduced the use of a suction nozzle in an attempt to obtain a two-faced pile fabric. In Moore, the suction nozzle was positioned radially inward from the needles for drawing the free ends of the sliver fiber inward between shanks of the plurality of needles and below the held loops, which, in combination with the rotation of the needle cylinder, tended to wind the free ends about the shank of the needles resulting in two-faced pile fabric.
Schaab et al. in U.S. Pat. Nos. 4,244,198 and 4,245,487 which have been assigned to the Assignee of the present invention disclose a method and apparatus for making reverse loop sliver knit fabric which is a significant departure from the traditional manufacturing techniques described above. The traditional manufacturing method reverse loop sliver knit fabric resulting in a single knitting of the sliver fibers into the base fabric. This results in a pile fabric which is both long and has an uneven length. It is therefore necessary to finish the product by shearing the pile to the desired height and napping or brushing the sheared pile to minimize any flaws in the fabric.
Schaab et al. knit the sliver fabric into a typical J-loop or U-loop on the first pass of the needles in accordance with the previously described techniques. However, unlike previous methods, Schaab, et al. use an air nozzle which is positioned radially inward from the needles and sinkers. The purpose of the air nozzle is to turn the free ends of the sliver, previously knitted into the base fabric during the first pass of the needles, over the sinkers so that the remaining free ends, assuming that they are of sufficient length, will be knitted a second time or interlaced into the fabric. The result is that the length of the free ends remaining after the second pass is shortened and as a consequence, the pile will be shorter, therefore, less waste will occur as result of shearing.
Unfortunately, the arrangement of the air nozzle used in Schaab et al. is such that the free ends of the sliver can be blown radially backward causing the free ends of the sliver to stand almost vertically in the area between the needles and the sinker units. This vertical orientation makes it difficult for the needles to capture and retain the free ends of the sliver for purposes of interlacing them into the fabric. As a consequence, the resultant fabric does not have a uniform length and still requires shearing of a large portion of the pile prior to use. The ability to control the orientation and positioning of the free ends of the sliver over the sinkers so that the free ends of the sliver may be knit a second and possibly a third time is important to manufacturing a consistent and uniform reverse loop sliver knit fabric.
In addition, by using an air jet similar to the one disclosed by Schaab et al., much of the fiber waste generated by the knitting process is blown away from the centrally located exhaust unit and outside of the circular sliver knitting machine. Consequently, much of the fiber waste is blown into the atmosphere rather than being collected. An unclean environment surrounding the machine occurs, which may result in fiber waste being interlaced with the sliver fibers causing the quality of the fabric to decrease because of the impurities.