An improved yarn bobbin and yarn snagger including a core, a groove formed in the wall of the core and a yarn-engaging insert housed within the groove. The width of the groove opening is narrower than the width of the groove base while the width of the top portion of the insert is similarly narrower...http://www.google.es/patents/US5791574?utm_source=gb-gplus-sharePatente US5791574 - Yarn bobbin with improved snagger
