Textile yarn cores, i.e., yarn winding tubes, yarn carriers or bobbins, are employed in the textile industry for winding and supporting yarn packages. In the package forming process, a moving yarn line is strung up onto a rapidly rotating empty core. The moving yarn line is brought into tangential contact with the rotating empty core. Typically, a start-up (or pick-up) groove is provided in the surface of the core, normally adjacent one end of the core. The yarn line is directed into the groove which grips and breaks the yarn line, thereby initiating the wind-up process.
Multiple width start-up grooves in yarn cores have been provided in an effort to improve the yarn pick up propensities of the groove. In the multiple width pick up grooves, one longitudinal, i.e., lengthwise, portion of the groove is relatively wide while an adjacent longitudinal portion is relatively narrow. The core is rotated so that the wide portion of the groove forms the leading portion; the narrow portion of the groove forms the trailing portion. The transition portion of the groove, between the wide and narrow portions, then forms a “nip” for gripping and catching the yarn. The initial strands of the yarn that are caught by the groove during the initial few turns of the automatic winding operation are commonly referred to as the “transfer bunch.” When the yarn is removed from the package, the last few strands of the transfer bunch often remain in the groove.
The string-up efficiency, defined as the percentage of successful string-ups over time as compared to the total attempted number of string-ups, is reduced with repeated use of a yarn winding tube. This reduction is partly due to the compression of the fiber fibrils of a paper tube, for example, that assist in the catching of the yarn and which are further damaged when the transfer bunch is removed from the groove. The efficiency reduction is also partly due to the portion of the transfer bunch that remains in the groove and diminishes the ability of the groove to further catch yarn.
A missed string-up, even in one yarn carrier, results in a significant loss of production, since yarn carriers are used in multiple carrier winders (e.g., 2, 4, . . . 10) per shaft. A missed string-up requires human intervention in re-stringing up of the position, sometimes requiring wiping of the spinneret face. When one in a gang of yarn carriers fails to string-up, this process may result in a loss of 10-30 minutes of production time.
It is desirable to reduce manufacturing costs by maintaining a high string-up efficiency and to reduce part costs by re-using yarn carrier tubes. These are often conflicting goals because the string-up efficiency of a tube deteriorates with repeated use of a yarn carrier tube due to damage cause by removal of yarn from the groove and due to yarn remaining in the groove.
It is often difficult to remove all the remaining strands of the transfer bunch from the groove without damaging the tube, especially when the tube is made of paper. This is because typical yarn catching grooves are very difficult to clean due to the very tight grip imparted by the walls of the groove on the yarn. Removal of the yarn usually results in broken filaments being retained in the groove.
One method of removing yarn from the groove, vacuuming, may not damage the tube but typically does not remove all the yarn from the groove. As the carrier is reused, accumulation of broken filaments and wall deterioration increases, further decreasing string-up efficiency. Other methods, such as using a knife to clean the groove, may remove the transfer bunch from the groove but may also damage the surface of the tube or the groove, thereby making the tube unsuitable for further use.
Reuse of the groove is thus limited due to the deterioration of the groove surface and to the collection therein of broken filaments. As a result, yarn carriers are often discarded with little or no reuse rather than incur the increased cost of production that results from a low string-up efficiency.