GB1078993A - Improvements in or relating to sewing machines - Google Patents

Abstract

1,078,993. Sewing machines. NECCHI S.p.A. Feb. 5, 1965 [Feb. 13, 1964], No. 5011/66. Heading D1G. Mechanism in a sewing machine for cutting the threads and for stopping the machine with the needle bar in a predetermined position, comprises a control member connected by kinematic means to a thread cutter, the control member being constituted by cam means controlling the initial movement of the thread cutter, and restraint means adapted, at the end of the action of the cam means and when the control member is in an angular position corresponding to said predetermined position of the needle bar, to effect a rigid coupling between the control member, kinematic means and thread cutter, whereby forward rotation of the control member is accompanied by cutting of the thread and disconnection of the sewing machine drive, the control member then being returned by resilient means to said angular position. A control member in the form of a disc 2 is provided on its outer face with a cam 3, and is rigid with a shaft 8 coupled by 2 to 1 reduction gearing 10, 11 with a shaft 9 carrying a rotary hook 12 rotating twice for each reciprocation of the needle 13. A pin 5, adapted to cooperate with the edge 4 of cam 3, is carried by one arm of a bell crank lever 6 pivoted at 24 to a lever 25. The other arm of lever 6 has a slot 22 engaged by the armature 23 of a solenoid M. A spring 24' biases pin 5 towards disc 2. The lower ends of lever 25 and a lever 26 are pivoted together at 7. The upper end of lever 26 is pivoted at 27 to the machine frame, and a spring 39 biases lever 26 against a fixed abutment 41. The upper end of lever 25 carries a pin 31 engaged in a slot in a bar 29. One end of the latter is slidable in a fixed bearing 33, and the other end carries a rack 36 meshing with a pinion 37 adapted to actuate a pair of thread-cutting blades 38. When the machine is driven normally by a motor C, solenoid M is energised to withdraw pin 5 from disc 2. The arrangement is such that when a press button switch is actuated to stop the machine, the speed of the latter is automatically reduced and solenoid M is deenergised, whereby pin 5 engages the starting print 15 of said cam 3. The initial part of cam 3 has a progressively increasing radius, whereby bar 29 is moved leftwards against the bias of a spring 34 and one of the blades 38 deflects the bobbin thread. Cam 3 next has a dwell surface, whereat the needle descends and rises between the blades 38, when a loop of needle thread is cast about the other blade and the threads are concatenated. The cam radius then progressively increases to an abutment 19 coincident with a hole in disc 2. Pin 5 thereby enters said hole, whereby, on further rotation of disc 2, levers 6, 25 and 26 rock as a unit about pivot 27 to move bar 29 leftwards, until blades 38 cut both threads and the end 40 of bar 29 actuates a microswitch P' for disconnecting the drive from motor C. Spring 39 then returns lever 26 to abutment 41. The initial movement of the blades 38 serves to draw off sufficient needle and bobbin thread to ensure correct commencement of the next seam.