1. Field of the Invention
The present invention relates to a bearded needle for bookbinding stitching machines, embroidery machines and other similar machines. The needle includes a needle shank followed by a crimp or neck portion and a needle head which has an essentially conical needle tip. The needle head supports a beard which, together with the shank portion, forms the needle eye. The needle eye on the side facing the needle tip, is delimited by a rounded fillet.
2. Discussion of the Prior Art
Bearded needles are used to pull a threaded loop through a workpiece and for example the workpiece may be the pages of a book to be sewn together. German Pat. No. 642,703 discloses a conventional configuration where the operation of a bookbinding stitching machine operating with bearded needles is briefly described. In principle, bearded needles are used in such a manner that the previously perforated or unperforated workpiece is pierced by them until their beard is exposed on the other side and is able to catch a thread which is then pulled in the form of a loop through the workpiece. In particular, if the workpiece is hard as in the case of a book where the pages are stitched together, the thread is subjected to considerable stress when the loop is pulled through the workpiece. The prior art bearded needles develop high frictional forces between the thread and the paper resulting in considerable stresses in the region of the needle tip. The result of these stresses is damage to the thread which adversely affects the stability of the stitching. In embroidery machines, these stresses also produce a sloppy appearance of the finished workpiece. The difficulties naturally become greater as the operating speed of the bearded needles become greater to a point where the thread may even break. Consequently the operating speed is limited by the stress on the thread.