Study On Fiber Mechanical Properties In The Ring Spinning Triangle

As one traditional yarn spinning method, ring spinning is used most widely at present, in which the fiber strands coming from the draft zone were twisted by the rotation of the spindle. Recently, there have appeared some new spinning methods with high efficiency and short process, such as rotor spinning, air-jet spinning. However, comparing with these new spinning methods, ring spinning still has some advantages on the applicability of the raw materials and spun yarn comprehensive qualities. Therefore, ring spinning is still the most widely used spinning method. Spinning triangle is a critical region in the spinning process of yarn. Its geometry influences the fiber tension distribution and thus affects the properties of spun yarns. It has attracted great interest by taking appropriate measures to change the geometry of spinning triangles in order to improve the qualities of yarn. However, at present, the effects of spinning triangle on yarn qualities are often studied by experiments or qualitative analysis, and the theoretical analysis is less. According to this, in the paper, theoretical studies of fiber tension in the spinning triangle were presented.In the paper, by using the principle of stationary total potential energy, firstly, when one roving was feeding for yarn spinning, the fiber tension distributions in the spinning triangle, yarn torque caused by the fiber tension were studied. The theoretical relation model between the fiber tension and geometry parameters of spinning triangle was given. Then, spinning experiments were taken by using a pair of offset device invented by our group, which is installed between the front roller and the yarn guide and can be moved in the scale locating slot freely in order to change the horizontal offset continuously. Secondly, when multi-roving was feeding for yarn spinning, fiber tension distributions and yarn torque caused by the fiber tension were analyzed when multi-roving was feeding on the same plane and feeding on the space with uniform angle, respectively. Then, taking the Sirospun spinning as an example, spinning experiments were taken by using an airflow false twisting device which can change spinning triangle parameters. Finally, for the multi-roving feeding yarn spinning, according to analysis of the two-strand yarn spinning, the convergence point of the Three-strand Yarn Spinning was given by introducing a series of virtual intermediate variables, and then the system of the general Multi-strand yarn spinning composed of n strands was present.For the one roving feeding yarn spinning, the spinning triangles are often supposed as symmetric. However, in the practical spinning, the spinning triangles are often asymmetric. On the one hand, the spinning triangles are asymmetric due to the frictional contacts of fibers with the bottom roller, which interferes with the twist propagation into the spinning triangle zone, and thus leads to the migration of the axis fiber at the front roller nip. On the other hand, the yarn spinning tension has an obvious angle with the vertical axis perpendicular to the nip line. According to this, in the paper, a theoretical model of the fiber tension distributions in the general spinning triangle has been proposed by considering both the inclination angle of the spinning tension and the migration of the axis fiber at the front roller nip according to the principle of minimum potential energy firstly. Then, under the assumption that all the fibers are ideally packed in the yarn cross-section in concentric circular rings, the model of yarn torque caused by the fiber tension was given. Secondly, by using a pair of offset device invented by our group, corresponding spinning experiments were taken. The device is installed between the front roller and the yarn guide and can be moved in the scale locating slot freely in order to change the horizontal offset continuously. According to the given theoretical model and the spun yarn qualities, the effects of spinning triangle geometric parameters on spun yarn qualities were analyzed qualitatively. Finally, based on the spinning principle of Solospun technology, a kind of multi-level division device was employed and installed on the front of front roller nip. When the fiber strands coming from the draft zone, the fiber strand was divided into several parts by the first level division, and several strands were formed under the first twist, and corresponding several small first primary triangles were produced. Then, the strands were divided by the multi-level division successively, and corresponding primary triangles were produced, and finally the yarn was formed under the final twist, and corresponding one final triangle was produced. In the paper, the theoretical model of the fiber tension distributions in this spinning process were given, and the effects of parameters of division proportions and number of primary triangles on fiber tension distributions were analyzed mainly.For the multi-roving feeding yarn spinning, based on the spinning principle of Sirospun technology, multi-roving was feeding form the back roller simultaneously. When the multi fiber strands come from the draft zone and enter the nip of the front roller, a primary twist is imposed to those substrands, where several smaller primary triangles are produced. Then, those substrands are twisted into a Sirospun yarn by a final twist, and corresponding final triangle is produced. In the paper, according to the principle of minimum potential energy, theoretical model of yarn torque was given by linking the fiber tension in the spinning triangle to yarn torque under the assumption that the arrangement of fibers(substrands) in the substrands(yarn) is hexagonal close packing firstly. The effects of division proportions and number of feeding roving on spun yarn torques are analyzed theoretically mainly. Then, for the 1-5 roving feeding on the space with uniform angle, the theoretical model of fiber tension in the spinning triangle was given, and then theoretical models of yarn residual torque due to the fiber tension were presented under the assumption that the arrangement of fibers is assumed as hexagonal close packing with a single core fiber, two core fibers, three core fibers, four core fibers, five core fibers at the center respectively. Finally, the convergence point of the Multi-strand yarn spinning was present. The complete convergence point state was given for two-strand yarn spinning. Then, according to analysis of the two-strand yarn spinning, the system of the three-strand yarn spinning and general Multi-strand yarn spinning composed of strands was present by introducing a series of virtual intermediate variables.