There are three methods of forming the newly-fed yarn into the shape of a needle loop:
1. (Fig. 1) – by sinking the yarn into the space between adjacent needles usingloop forming sinkers or other elements which approach from the beard side.Theaction of a straight bar frame is illustrated. (Other obsolete circular bearded needle machines such as the sinkerwheel and loopwheel frame employ the sametechnique.) The distance SL, which the catch of the sinker moves past the beardside of the needle, is approximately half the stitch length,
|Fig. 1 Action of the loop-forming sinker.|
2. (Fig.2) – by causing latch needles to draw their own needle loops down through the old loops as they descend, one at a time, down the stitch cam. This method is employed on all latch needle weft knitting machines.The distance SL that the head of the latch needle descends below the knock-over surface (in this case, the belly of the knock-over sinker) is approximately half the stitch length, and
Fig. 2 Action of the knock-over sinker.
3. (Fig. .3) – by causing a warp yarn guide to wrap the yarn loop around the needle. The lapping movement of the guide is produced from the combination of two separate guide bar motions:
- A swinging motion which occurs between the needles from the front of the machine to the hook side and return.
- A lateral shogging (or racking) motion parallel to the needle bar on the hook side and also on the front of the machine.
|Fig. 3 Loop forming by warp guides.|