Patent GB-416668-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1933-03-10
Abstract: 416,668. Sewing-machines. UNITED SHOE MACHINERY CORPORATION, 140, Federal Street, Boston, U.S.A.-(Assignees of Ashworth, F.; Wenham, Massachusetts, U.S.A.) March 10, 1933, No. 7270. Convention date, March 11, 1932. [Class 112.] A McKay lockstitch sewing- machine of the type described in Specification 347,269 is modified by having an arrangement for lifting the presser foot and releasing the thread from the thread lock to prevent the latter from being opened when the presser is lifted by thick work, and for locking the presser against lifting when work of unusual thickness is being sewn. Normally inoperative means are provided for raising the presser foot clear of the work and opening the thread lock when the machine is stopped to permit removal of the work. The stitch-forming mechanism, horn and feed mechanism are the same as described in the above Specification. Stopping - mechanism.-The connections from the stopping and starting treadle 16 for actuating the latch 32 to disconnect the needle from the actuating lever 30 comprises a rod 44 connecting the treadle with an arm 46 fixed on one end of a cross shaft 48 mounted in the head of the machine. This arm is provided with a lug 50 projecting laterally beneath a rearward extension of an arm 52 loosely mounted in the shaft 48 and connected at its forward end by a link 54 to operate on a rock shaft 56 upon the forward end of which an upwardly extending needle locking lever 58 is secured. A heavy coiled spring (not shown) surrounds the shaft 48 and tends to turn it clockwise as viewed from the left of the machine. While the machine is running, the treadle 16 is depressed and the lug 50 is held out of engagement with the arm 52. This arm is swung in an anti-clockwise direction when the treadle is lowered by a spring which through the arm 52 and link 54, swings the locking lever 58 in a clockwise direction. On release of the treadle, the clutch 8 is first operated to disconnect the motor 4 from the machine and the arm 46 swings upwardly to cause the lug 50 to engage the rear of the arm 52. The arm 46 turns the arm 52 and moves the locking lever 58 to disengage the latch 32 from the lever 30 and lock the needle at the upper limit of its stroke. Presser bars with periodic control; lifting devices; threads controlling otherwise than in stitchforming.-The presser foot 60 is secured to a block 62 on the presser bar 64. The foot is forced downwards by a spring 66 surrounding the presser bar and also by a spring 68 surrounding the shaft 70. The spring 68 tends to rotate the shaft 70 which carries an arm 76 having a pin-and-slot connection with the presser bar as in the above Specification. As the work is fed by the awl 78, the presser is intermittently lifted as described in the above Specification. When work of unusual thickness is being sewn, however, the resistance to the passage of the needle may be sufficient to overcome the action of the springs 66, 68 and so raise the presser. In the presser machine, this is overcome by presser locking devices comprising pawls 94 engaging a toothed segment 96 attached to the presser foot arm 76. The pawls are of slightly different length to engage a single tooth in the segment in slightly different positions of the arm 76 and are pivoted on the sleeve 97. They are pressed into engagement with the segment by springs 100. They are disengaged intermittently when the needle reaches the upper portion of its stroke by a lever 102 which has an arm with a cam surface cooperating with a roll 108. The usual hand lever 120 is provided to enable the presser to be lifted by the operator at any time regardless of the position of the needle. A lever 126 is loosely mounted on the shaft 70 and has a T-shaped lug 128 acted upon by a hook-shaped presser foot lifting member 130 and a relating member 132 to open the thread look. Connections are also provided for operating the thread lock in the base of the horn to release the thread when the machine is stopped in order to remove the work. These connections comprise an arm 160 pivoted on a bolt 162 engaging an enlargement on the lever 126, a link 166 connected to the arm 160 and to a lever 168. A thread tension 172 is provided and the thread lock is the same as described in the above Specification.