N. D. Burns

15—TRANSDUCERS FOR THE PRECISION MEASUREMENT OF WEFT-KNITTING FORCES. PART I: A CAM-FORCE TRANSDUCER

A description is given of a transducer, with its associated instrumentation, that has been developed to measure the dynamic forces between a latch needle and the stitch and guard cams during the formation of a knitted loop. Such forces are referred to as ‘cam forces’.

24—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART I: THE THEORY OF STITCH-CAM IMPACT

Before a transducer could be designed to measure the reaction force between the stitch cam and a needle at the instant of contact, it was necessary to estimate the pulse shape, frequency, and magnitude of the force. An analytical method is here described for determining the nature of the force pulse.

37—THE FRICTIONAL FORCES BETWEEN YARNS AND WEFT-KNITTING ELEMENTS

Modifications are made to equations proposed by earlier workers so that they more closely approximate to new measurements made under simulated practical conditions with small knitting elements. The tensioning-measuring technique is described and the statistical basis for the mathematical equations outlined, and some typical results are included.

31—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART VIII: THE EFFECT OF SOME KNITTING PARAMETERS ON GUARD-CAM IMPACT

The effects of certain knitting parameters on the impact force between the needle and the guard cam are described. It is found that increasing the stitch-cam incidence angle increases the guard-cam impact magnitude. The use of much steeper guard-cam angles tends to extend the duration of impact, as expected, but this is accompanied by higher impact-force magnitudes and more frequent needle-butt fractures. Progressively increasing the clearance between the cam and cylinder causes small but clearly discernible reductions in impact magnitude. Reducing the mass of the needle has a large effect in reducing the magnitude of impact but has little effect on its duration. Although no modifications to the shape of the needle butt conclusively reduce guard-cam impact conditions, they indirectly serve to spotlight the adverse effects of slight surface imperfections in the stitch cam. The heavy addition of lubricating oil to the cylinder tricks decreases the impact magnitude and causes the initial impact to occur at a...

25—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART II: A STITCH-CAM IMPACT TRANSDUCER

The design of a transducer for measuring the rapid force fluctuation existing between the needle and the stitch cam at the instant of contact is outlined. The device uses semi-conductor strain gauges and was constructed so that needle bounce on the cams could also be recorded. Typical results are given.

17—TRANSDUCERS FOR THE PRECISION MEASUREMENT OF WEFT-KNITTING FORCES. PART III: THE EXPERIMENTAL MEASUREMENT OF CAM AND YARN FORCES

Selected experimental results of dynamic forces recorded during knitting are reported. These were obtained by using a cam-force transducer designed to measure the dynamic forces between a latch-needle and the stitch and guard cams (see Part I) and a yarn-force transducer designed to measure the forces exerted upon the sinker and needle by the yarn during the formation of the knitted loop (see Part II).

20—DYNAMIC FORCES IN WEFT-KNITTING: PART I: A COMPARISON OF MEASURED NON-KNITTING CAM FORCES WITH MATHEMATICALLY PREDICTED VALUES

Non-knitting cam forces are the dynamic forces between the knitting cams and the latch needle when the needle passes down the stitch cam and along the guard cam but does not draw a yarn loop. Good agreement is shown between theoretical predictions of the forces and the experimental measurement of them.

26—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART III: SOME MEASUREMENTS OF STITCH-CAM IMPACT

A comparison is made of the results of experiments designed to investigate the effects of various knitting parameters on the impact force between the stitch cam and the needle with theoretical values obtained by analytical procedures detailed in earlier papers. The agreement is shown to be reasonably good. As machine speed, cam angle, and needle mass are each increased, the impact force also increases. Consideration is also given to the effect of trick resistance on measured and calculated values of impact force.

30—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART VII: THE INFLUENCE OF YARN TENSION AND MACHINE SPEED ON GUARD-CAM IMPACT

The results of experiments designed to investigate the effects of yarn-loop-drawing tension and machine speed upon the impact force between the needle and the guard cam are compared with theoretical values obtained by analytical procedures detailed in Part V, and the agreement is shown to be reasonably good. The impact force increases in direct proportion to the machine speed; increasing the yarn-loop-drawing tension delays the onset of the impact and reduces the magnitude of the impact force.

28—CAM-TO-NEEDLE IMPACT FORCES IN WEFT-KNITTING PART V: GUARD-CAM IMPACT

The significance of guard-cam impact with respect to needle damage is briefly discussed, and a simplified theoretical analysis of guard-cam impact is derived.