GB946270A - Control mechanism for lock stitch sewing machines - Google Patents

Abstract

946,270. Sewing machines. SINGER CO. Aug. 2, 1962 [Aug. 25, 1961], No. 29754/62. Heading D1G. A lock stitch sewing machine comprises a looptaker journalling a bobbin adapted to be wound in situ during normal operation of the needle and looptaker, and a manually-operable control member movable from an at-rest position in which the bobbin-winding means is rendered inoperative, to any one of a selected range of distances from the at-rest position, for both rendering the bobbin-winding means operative and also for rendering operative an indexing mechanism adapted to return the control member to the at-rest position at a rate proportional to the speed of operation of the drive means for the needle and looptaker. As shown, the cup-shaped body 50 of a rotory hook carried by a hollow vertical shaft 45 driven by gearing 40, 42, 44 and shafts 41, 43 from the arm shaft 17. A bobbin case 54, journalled within body 50, journals abobbin 58. A bobbin-winding member 61, fast on a shaft 62 journalled and axially slidable within shaft 45, is keyed to body 50 by a tongue 63. When shaft 62 is raised by means of a leaf spring 74 carried by a horizontal lever 72 fulcrummed at 73, a tongue 65 on member 61 clamps the needle thread against the loop-taking beak on body 50, and a stud 70 on member 61 enters one of a series of holes in bobbin 58 to rotate the latter, whereby thread is drawn through the eye of the reciprocating needle 15 and is deflected by a rib 67 on member 61 on to the bobbin 58, while a cam member 75, rigid with shaft 62, co-operates with a fixed abutment 76 to lower member 61 slightly during each revolution of shaft 62. Lever 72 is pivoted at 104 to an offset arm 103 at the lower end of a vertical bar 99 pivoted at its upper end to one end of a horizontal lever 100 which is fulcrumed at 101 and is pivoted at its other end to a downward bar 102, movement of which serves to release the tension at needle thread tensioner 18. Shaft 17 carries an eccentric 26 actuating a pitman 27 normally coupled to the feed lift shaft 30, for this purpose a spring 33 engaging a horizontal recess 31 in pitman 27 with a crank pin 28 carried by shaft 30. A knob 83, rigid with a shaft 82 journalled in a fired block 81, has a flange 84 provided with a scale 88 observable through a window 87. A boss 90, rigid with shaft 82, is formed with a notch 91 which, in the at-rest position of knob 83, is engaged by a shoulder 94 on a lever 92 which is pivoted at 93 to block 81 and has an arm 97 overlying a lateral arm 98 on bar 99. When knob 83 is turned sufficiently clockwise to position shoulder 91 on the periphery of boss 90, arms 97 and 98 co-operate to move bar 99 downwardly against the bias of a spring 107, whereby spring 74 raises member 61 to initiate bobbin winding, bar 102 is lowered to release the thread tension, and a finger 105 on bar 99 cooperates with a cam surface 106 on pitman 27 both to align a vertical slot 32 in the latter with pin 28 for immobilising the feed, and also to engage a pin 110, carried by pitman 27, with a slot 115 in a lever 113 fulcrumed on shaft 82. A pair of pawls 117, 118, pivoted at 116 on lever 113 and biased by respective springs 119, 120 into engagement with a ratchet wheel 121 rigid with shaft 82, thereby serve to rotate the latter clockwise until shoulder 94 re-engages notch 91. The amount of thread wound on the bobbin is thereby determined by the extent that the knob 83 is turned initially. Specification 931, 214 is referred to.