21—the Design and Dynamics of Non-Linear Cams for Use in High-Speed Weft-Knitting Machines Part Iii: The Analysis of Knitting-Yarn Tensions With Non-Linear Cams and Positive Feed

Lau, Thomas; Knapton, J. J. F.

doi:10.1080/00405007808631438

Cited by 6 publications

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“…The relation between the magnitude of RB and other relevant variables must be affected by the dynamic nature of knitting zone geometry in a manner different from that if the geometry were just static. In the course of this paper, we have subjected this aspect to a preliminary analysis.Various authors have suggested models for working out yam tension in the knitting zone as well as robbing back [ 1,5,7,9,13 ], but they have invariably ignored the effect of loops cast off in the cycle prior to the one under consideration. We designed the simple experiments described here with a view to establishing whether the assumption that the cast-off loop has an insignificant effect on RB is valid.…”

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“…Knitting cam setting seems to have a marginal effect [ 6 ] , whereas the extent to which fabric take-down tension affects RB is governed by the geometry of the knitting zone [ 4,12,13 ] . This geometry, a function of coordinates of needle hooks and sinkers, has generally been viewed in a static frame [1,5,8,9,13,14], but it is apparent that as a needle slides down the wall of a stitch cam, the geometry assumes a dynamic character. The relation between the magnitude of RB and other relevant variables must be affected by the dynamic nature of knitting zone geometry in a manner different from that if the geometry were just static.…”

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Mechanics of the Single Jersey Weft Knitting Process

Ghosh

Banerjee

1990

Textile Research Journal

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A study of the mechanics of the single jersey weft knitting process is initiated with experiments designed on two different small diameter, circular bed machines. The results highlight the role of the dynamic geometry of the knitting zone and the dynamic equilibrium of forces on the needle hook, as well as the importance of cast-off loops hanging around the yam, pulled in by needles inside knitting zone, on the loop formation process.During the process of loop formation, an interaction takes place between various yarn variables X; (rigidities, coefficient of friction, diameter, etc.), knitting machine variables Yj (speed, diameter, gauge, cam shape, needle and sinker shape, etc.), and knitting process variables Zk ( yarn input tension, fabric take-down tension, cam setting, etc.) [3][4][5][6][7][11][12][13] . Studies on the mechanics of the loop formation process are in principle aimed at determining this interaction both qualitatively and quantitatively. Investigations of the mechanics of single jersey loop formation have revealed that the phenomenon of robbing back plays an important role in determining loop length [ 6,7 ] . Robbing back is, in effect, a manifestation of the interaction between the X;, Yj, and Zk variables. Consequently, it appears that a detailed investigation relating to robbing back should be the first step in a study of the mechanics of the loop formation process.The magnitude of robbing back (RB) can be calculated from experimental results but cannot as yet be predicted, even though some of the factors governing RB have been well researched. Thus, the yarn input tension, the yarn-metal coefficient of friction, and the geometry of the knitting zone are known to have a decisive influence on the value of RB. Knitting cam setting seems to have a marginal effect [ 6 ] , whereas the extent to which fabric take-down tension affects RB is governed by the geometry of the knitting zone [ 4,12,13 ] . This geometry, a function of coordinates of needle hooks and sinkers, has generally been viewed in a static frame [1,5,8,9,13,14], but it is apparent that as a needle slides down the wall of a stitch cam, the geometry assumes a dynamic character. The relation between the magnitude of RB and other relevant variables must be affected by the dynamic nature of knitting zone geometry in a manner different from that if the geometry were just static. In the course of this paper, we have subjected this aspect to a preliminary analysis.Various authors have suggested models for working out yam tension in the knitting zone as well as robbing back [ 1,5,7,9,13 ], but they have invariably ignored the effect of loops cast off in the cycle prior to the one under consideration. We designed the simple experiments described here with a view to establishing whether the assumption that the cast-off loop has an insignificant effect on RB is valid. Finally, we closely observed needle and yarn movements along the rising side of the stitch cam, because they play an important role in determining the location of the robbing oppos...

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