Theoretical And Experimental Study On The Twist Inside The Rotor In Rotor Spinning

A theoretical and experimental study on the twist inside the rotor in rotor spinning is carried out in this thesis. What is covered in this thesis can be summed as: the present status of researches on the twisting mechanism of rotor spinning, the experimental study on twist measuring method of rotor spun yarn and the development of twist lowering device of rotor spinning with theoretical analysis. The three mentioned constitutional parts are to be detailed in six chapters with a preface as follows:The preface introduces the macro background of the subjects which are going to be described in the following.Chapter 1 serves as an overview of current status of researches on both the twist measuring methods of rotor spun yarn and the twist lowering device of rotor spinning. The overview of twist measuring methods introduces both the available methods which were used for estimating the actual twist level of rotor spun yarn and the experimentalresults with theoretical analysis resulting from those methods. Theoverview of twist lowering device of rotor spinning shows that the navel, the twist blockage device and so on are the main devices which affects the twist level of rotor spinning most. It is also in this chapter that we listed the subjects of this thesis.In Chapter 2, the mechanism of twist to break method is introduced in detail with an assessment of this method's validity for rotor spun. yarn. The twist measuring device developed according to the principle of that method is used to measure the actual twist level of rotor spun yarn. Theexperimental results obtained from this device shows that this method works better than the untwist-retwist method for estimating the actual twist level of rotor spun yarn., and that the measured twist deviates only maximum 5% from the actual twist of rotor spun yarn.In Chapter 3, The "Virtual Twist Blockage" in the yarn arm near the peeling point is studied by means of modeling, and its influence on spinning stability and twist level at the peeling point is clarified theoretically. Prompted by this theory, we developed a flange-grooved navel which can be used to weaken the effect of the "Virtual Twist Blockage". The experiments directed to verify the theory and to observe the flange-grooved navel's effect OB yarn quality show that: the effect of the "Virtual Twist Blockage55 can be weakened either by proper match of rotor spinning parameters or by applying the flange-grooved navel;The flange-grooved navel lowers the twist level by 4.5% or so; The quality comparisons made between the yarns spun at lower twist level with the flange-grooved navel and the yarns spun at higher twist level with a normal smooth-surfaced navel show that the flange-grooved navel improves neps, thin places and strength uniformity of yarns without change of yarn evenness., and that the flange-grooved navel increases yarn hairiness and thick places with a slight decrease of yarn strength.In Chapter 4, the twist blockage factor of arbitrary surfaced twist blockage device is modeled. The twist blockage mechanism is clarified further by numerical simulating the twist blockage factor of common curve surfaced twist blockage device, This model shows that the surface curvature of the twist blockage device doesn't affect twist blockage factor, but the deviation angle has an important influence on twist blockage factor. Under the guide of this model, four types of twist blockage device are designed. Tlie experimental results obtained from that four types of twist blockage device coincided well with the theory.The experimental results also show that both three-traverse-banked and three-oblique-banked twist blockage device lowered the twist level up to 20%. Quality of the yarns produced at lowered twist levels by the above two types of twist blockage device is tested to make a comparison with normal high twist rotor-spun yarn without the twist blockage device. It can be seen from the statistical analysis of the testing results that either of the two types of twist blockage device incr...