For the manufacturing of terry cloth, it is necessary to use single-bed circular knitting machines equipped with special sinkers featuring a longer nose than standard sinkers and special thread guides which feed simultaneously two yarns, one called ground yarn and the other one called face yarn, into the same needle.
During the stitch formation, the sinkers move forward and position themselves between the two yarns. The ground yarn fits under the sinker nose, inside the throat, and carries out a standard stitch formation cycle, while the face yarn is positioned above the sinker nose. Therefore, as the fabric is knitted, the face yarn forms a loop pile, leaving the other yarn to serve as the ground. As a result, the face yarn always appears on the face and the ground yarn always on the back of the cloth.
If the sinker is not pushed forward to reach its maximum forward position, the two yarns fed are both tucked under the nose, with the consequent formation of a double knit stitch of standard length. By exploiting the possibility of moving the sinkers forward completely or only partially, it is possible to create sculptured terry effects, i.e. flat zones alternated with terry knit zones.
Picture 108 -Terry sinker
Picture 108 -Terry sinker
The terry formation steps can be described as follows:
STEP A: the sinkers reach their maximum forward position towards the centre of the cylinder and are momentarily stopped. During this step, they must retain the previous loop on the needle stem and allow the needle to rise, reach the knitting position, and prepare to receive the two yarns fed by the yarn guide. In this starting position the face yarn is on the sinker nib and the interloop is in the throat.
STEP B: the sinkers start their backstroke to allow the yarn guide to feed the needle with the two yarns at different heights. The ground yarn, fed in the lower part of the needle hook, is inserted into the sinker throat while the face yarn, fed in the upper part of the hook, is laid on the sinker nib.
STEP C: the sinkers move toward the centre of the cylinder and the needle starts lowering. During this step, the two yarns remain on the nib and in the throat of the sinkers.
STEP D: the sinkers reach their maximum forward position and stand still; the needle lowers and completely knocks over the previous stitch on the new stitch which has just formed. The new stitch is made up by two yarns (ground yarn and face yarn), while the face yarn of the stitch previously formed is on the sinker nib and the ground yarn forming the interloop is in the sinker throat.
Many manufacturers offer terry knitting machines with a 40-inch bed diameter and up to 60 feed systems to carry out both terry and plating, with gauge range from E 14 to E 28.
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