GB1179964A - Thread Trimming Mechanism for Sewing Machines. - Google Patents

Abstract

1,179,964. Sewing machines. SINGER CO. 3 July, 1967 [5 July, 1966], No. 30507/67. Heading D1G. A lock stitch sewing machine comprises a movable thread-catching element adapted to engage and extend loops of needle and bobbin thread, and a movable cutter element adapted to sever at least one limb of each of said extended loops. A rotary hook 10, carried by a shaft 11, journals a bobbin case 12 restrained from rotation by a finger 13. A rod 18, formed with a thread-catching hook 19, is connected by a bar 22 to a hollow plunger 23 slidable in a bracket 21 rigid with the sewing machine frame, plunger 23 being biased outwardly by an internal spring 24. When the needle is in its lowest position, a solenoid 60, mounted on the sewing machine stand 56, is energised, whereby the armature 61 shifts plunger 23 inwardly to position hook 19 within a notch (20) formed in bobbin case 12, plunger 23 being retained in its innermost position by the engagement of a notch 27 therein with a pivoted latch 28 biased against plunger 23 by a spring 29. As the needle rises, a lug 31, rigid with the feed advance shaft 32, engages one end of a slidable bar 30, the other end of which is pivoted to latch 28 for releasing the latter from notch 27. Spring 24 then moves plunger 23 outwardly whereby hook 19 draws out loops of needle and bobbin thread, the limbs of said loops extending to the work being located under finger 13. When the needle thread loop is cast off the rotary hook, the thread extending from hook 19 to the needle is located above finger 13. A ring 42, journalled on a bearing 53 for shaft 11, carries a knife (41) positioned between the rotary hook and the throat plate 39, and also carries a pin 44 engaging a notch in a lug 51 at one end of a lever 46 pivoted at 48 on bracket 21. The other end of lever 46 has a lug 49 abutting the armature 64 of a solenoid 63 rigid with solenoid 60. When the needle is in its uppermost position and the take-up (17) acts to tighten the threads for setting the previous stitch, solenoid 63 is energised, whereby armature 64 pivots lever 46 and the latter pivots ring 42 to move knife (41) across the limbs of bobbin and needle thread extending from hook 19 to the work. On deenergisation of solenoid 63, a spring 50 restores lever, 46 and ring 42 to their initial positions. The solenoids may be energised by manuallyoperable switches. The specification describes an arrangement in which energisation of the solenoids is combined in the control system for positioning the needle either up or down as described in Specification 774610.