# US 8,739,714 B2 · Method for operating a chain stitch sewing machine and chain stitch sewing machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,739,714 B2 - Document ID: US8739714B2 - Status: Granted - Kind: B2 - Application number: 13/524,079 - Filed: 2012-06-15 - Published: 2013-04-18 - Granted: 2014-06-03 - Earliest claimed: 2011-07-01 - Assignees: Nahmaschinenfabrik Emil Stutznacker GmbH & Co. KG - Applicants: Harmut Klapp - Inventors: Harmut Klapp - Web page: https://patentgrep.com/patent/US8739714B2 ## CPC - D05B 1/00: General types of sewing apparatus or machines without mechanism for lateral movement of the needle or the work or both - D05B 1/10: Double chain-stitch seams - D05B 57/02: for chain-stitch sewing machines, e.g. oscillating - D05B 65/02: controlled by the sewing mechanisms {(D05B65/006 takes precedence)} - D05B: SEWING (appliances for the tailoring trade A41H; sewing tables A47B29/00; sewing in bookbinding B42B2/00; sewing machines modified for knitting D04B39/08) ## Abstract A method for operating a chain stitch sewing machine and a chain stitch sewing machine, the chain stitch sewing machine having a pair of sewing members comprising a needle which pierces a sewing material and a gripper disposed below a sewing material rest, which can be moved along a movement path, where an upper thread is guided with the needle through the sewing material resting on the sewing material rest, which is linked to a lower thread. The lower thread is fed to a retaining element and is held in said element that is moved with regard to its direction of movement and/or speed of movement to the sewing material rest according to a movement path of a pivoting movement of the gripper in particular along a circular-arc-segment-shaped movement path. ## Claims ### Claim 1 A method for operating a double chain stitch sewing machine, which comprises a pair of sewing members comprising a needle which pierces a sewing material and a gripper disposed below a sewing material rest, which can be moved along a movement path, wherein an upper thread is guided with the needle through the sewing material resting on the sewing material rest, which is linked to a lower thread, characterized in that the lower thread is fed as required to a retaining element and is held in said element, that is moved with regard to its direction of movement and/or speed of movement to the sewing material rest according to a movement path of a pivoting movement of the gripper, in particular along a circular-arc-segment-shaped movement path and in that the lower thread is arranged tensioned between gripper and retaining element. ### Claim 2 (depends on 1) The method according to claim 1, characterized in that the lower thread is disposed substantially anti-parallel to the longitudinal axis of the gripper running between its tip and the retaining element. ### Claim 3 (depends on 1) The method according to claim 1, characterized in that the lower thread is fed to the retaining element before or during a cutting process executed with a cutting tool, in particular of the lower thread. ### Claim 4 (depends on 3) The method according to claim 3, characterized in that the cutting tool is moved during the cutting process into the area of the lower thread, in particular until at least one cutting surface abuts against the lower thread, and the cutting process is executed by a movement of the sewing material relative to the sewing material rest and/or by an additional movement of the cutting tool. ### Claim 5 (depends on 3) The method according to claim 3, characterized in that the cutting tool is moved jointly with the gripper and the retaining element. ### Claim 6 (depends on 3) The method according to claim 3, characterized in that the cutting tool, the gripper and the retaining element are moved during the sewing process on a circular-arc-segment shaped movement path into a region in which the cutting tool does not come in contact with the lower thread and that in order to execute the cutting process, cutting tool, gripper and retaining element are moved along the movement path with the same direction of movement beyond the region. ### Claim 7 A double chain stitch sewing machine, which comprises a pair of sewing members comprising a needle which pierces a sewing material and a gripper disposed below a sewing material rest, which can be moved along a movement path, wherein the needle guides an upper thread through the sewing material resting on the sewing material rest and the upper thread is linked to a lower thread, characterized by a retaining element for holding the lower thread as required in a tensioned way between gripper and retaining element which retaining element can be moved with regard to its direction of movement and/or speed of movement to the sewing material rest according to a movement path of a pivoting movement of the gripper, in particular along a circular-arc-segment-shaped movement path. ### Claim 8 (depends on 7) The sewing machine according to claim 7, characterized in that the retaining element is disposed on the gripper, in particular in the area of section of the gripper that can be connected to a gripper shaft. ### Claim 9 (depends on 7) The sewing machine according to claim 7, characterized in that the retaining element is disposed in the longitudinal axial direction of the gripper between the gripper and a cutting tool, wherein the cutting tool can be moved together with the gripper. ### Claim 10 (depends on 7) The sewing machine according to claim 7, characterized in that the retaining element is disposed with respect to the gripper in such a manner that the retained thread extends substantially anti-parallel to a leg of the approximately L-shaped gripper. ### Claim 11 (depends on 7) The sewing machine according to claim 7, characterized in that the retaining element consists of a base body that can be connected to a gripper holder, the gripper shaft and/or the gripper and a spring-elastic element fastened thereon, which is connected at a first end to the base body and the second end thereof can be moved relative to the base body and abuts against the base body. ### Claim 12 (depends on 11) The sewing machine according to claim 11, characterized in that the spring-elastic element is formed from spring steel. ### Claim 13 (depends on 7) The sewing machine according to claim 7, characterized in that the retaining element has a guide surface over which the lower thread is guided into a retained position depending on the angular position of the gripper relative to the sewing material rest. ### Claim 14 (depends on 9) The sewing machine according to claim 9, characterized in that cutting tool, retaining element and gripper are disposed in such a manner with respect to one another that the lower thread is disposed in the retaining element before reaching the cutting tool.