Gripping device of sewing thread for bookbinding sewing machine with gas jet

A bookbinding sewing machine for sewing signatures into book blocks, wherein the bookbinding sewing machine comprises:

• one or more gripping devices each for gripping a sewing thread in the bookbinding sewing machine and each including
• a crochet having a hook for hooking the sewing thread, and
• a body having an abutment wall for the hook, the body and the crochet being slidable reciprocally along a longitudinal direction of the crochet between an open condition wherein the hook is distal from the abutment wall of the body for hooking the sewing thread and a closed condition wherein the hook is proximal to the abutment wall of the body for blocking the sewing thread, the body comprising one or more inlets for receiving a gas jet, one or more outlets at the abutment wall for directing the gas jet hook and one or more channels crossing the body between the inlets and the outlets for conveying the gas jet from the inlets to the outlets;
• and
• blasting means for providing the gas jet to each of the gripping devices.

A method for sewing signatures into book blocks in a bookbinding sewing machine, wherein the method comprises:

• forming, by one or more meddles and one or more further crochets, one or more stitchings between the signatures of each of the book blocks by corresponding sewing threads, the stitchings comprising one or more corresponding plain stitches formed by the needles and one or more corresponding looped stitches formed by the crochets concatenated to each other, each of the plain stitches comprising a single portion of the corresponding sewing thread extending between each pair of adjacent signatures, the looped stitches ending with corresponding free loops on a last one of the signatures of each completed one of the book blocks,
• bringing, by corresponding one or more shuttles, the sewing threads each downstream the corresponding plain stitches along a formation direction thereof to an intermediate position aligned with the corresponding free loop along an advancement direction of the book blocks during the sewing thereof,
• bringing, by one or more corresponding gripping devices, a closing portion of each of the sewing threads from the intermediate position through the corresponding free loop along the advancement direction, the closing portion consisting of a portion of the sewing thread downstream the corresponding plain stitches along the formation direction thereof,
• actuating the gripping devices each to block the corresponding sewing thread at a gripping point comprised in the closing portion thereof,
• cutting the sewing threads being blocked, by one or more corresponding cutters, each downstream the gripping point thereof along the formation direction of the plain stitches,
• moving the gripping devices, each blocking the corresponding sewing thread being brought through the corresponding free loop, to pull the sewing thread being cut away from the free loop thereby tightening the free loop around the sewing thread,
• bringing the gripping devices each to an open condition thereby releasing the corresponding sewing thread being pulled, and
• providing a gas jet to each of the gripping devices in the open condition, the gas jet being received by one or more inlets of the gripping device, being conveyed from the inlets to one or more outlets of the gripping device through one or more channels crossing a body of the gripping device between the inlets and the outlets, and being directed from the outlets towards a hook of the gripping device.