Patent GB-181556-A (GB)
Title: Sewing machines
IPC: D05B65/00
Filed: 1921-04-21
Abstract: 181,556. Fairweather, W., (Singer Manufacturing Co.). April 21, 1921. Button-hole sewing- machines.-In a sewing-machine for producing groups of stitches a thread severing device is employed which is mounted below the work plate and comprises a cutting edge and a pull-out arm which is actuated at the close of a stitching period to draw out a thread loop into contact with the cutting edge, and also preferably a nipping arm in advance of the cutting edge into contact with which the nipping arm draws out the free end of thread at the beginning of a stitching period. The threadcutting and nipping device is described as employed in a buttonhole sewing-machine of the kind described in Specifications 181,555 and 185,711, wherein a shifting frame 2 carries the stitch-forming devices and the needle is rotated at certain times synchronously with the rotation of a lower needle and looper mechanism carried in a revolving turret in the shifting frame. The looper mechanism is of a form modified from that described in Specification 185,711. Loop - stitching. - 'The looper l which spreads the loops of the needle n for the passage of the lower needle s is secured to an arm 29 pivoted in a block 32 having a stud 34 pivoted in the rotary turret 36. Roller studs 37 on the arm 29 and 38 on an arm 33 of the block enter cam grooves 39, 40 in the periphery and one of the ends of a cam-cylinder 41 pivoted on a shaft 42 mounted in the turret and actuated bv a rack 44 engaging a pinion 43 thereon. The rack is mounted on a block 45 fixed to a vertically reciprocating sleeve 47. The needle s is actuated by a link 50 pivoted to the head of the sleeve 47 and to the arm 51, pivoted at 52, on which the needle is mounted. The sleeve is actuated by mechanism for producing a dwell, including a pitman 58 and crankpins 59, 60 on the crank-plate 28 of the shaft 3 which drives the upper needle-actuating pitman 25. The means for rotating the needle and looper mechanism are described in Specification 185,711. Thread-cutters and thread-end holders.-Fixed nipping and cutting blades 83, 85 adjustably secured on the turret have lateral extensions 83<1>, 85<1> coacting with a pull-out blade 86, the supporting arm 89 of which is pivoted at 90 concentricallv with the blades 83, 85. The arm 89 is connected by a pin-and-slot mechanism to a. lever 94 pressed towards lower position by a spring 96. An extension 94<1> of the lever engages a segmental guideway 99 carried by a yoke comprising arms 101, 102 and secured to a sleeve 105 sliding on a post 14. A collar 106 on the sleeve 105 is formed with a tooth or projection 107, Fig. 7. The yoke is guided by a pin 109 and is pressed downwards by a spring 112. A stop-arm comprising a projection 117 cut away at one side to form a shoulder 118 is mounted in bearings 115 on a bracket fixed to the stationary cloth plate 113, Fig. 3. A spring 120 surrounding the endwise movable shaft 116 of the arm and connecting a collar 119 thereon to one of the bearings presses the arm towards the sleeve 105, the arrangement being such that in one position of the arm the tooth 107 may slide past the stop-arm and in another it will be engaged by the shoulder 118. A rockshaft 122 mounted in bearings on the base-plate 2 carries a tappet arm 124 to which is secured a lifting arm 126. The arm 124 lies in the path of a roller stud 127 mounted in the pitman 25, and when the arm 124 is actuated thereby the arm 126 is moved to engage the guide-way 99 and lift it and the sleeve 105, producing a loop-engaging movement of the pull-out blade 86. The sleeve and guideway then fall owing to the stud 127 travelling beyond the end of the arm 124, and the thread is drawn out by the retraction of the blade 6 by the spring 12. The tappet arm is normally held out of contact position with the stud 127 by a spring 128 which engages a split collar 130 with a lateral wing 131. An arm 133 of a spring-controlled three-armed lever bears against the wing 131 and is moved to shift the shaft 122 endwise by the engagement with a roller 136 carried by the lever of one of two spaced projections 141 on a cam-disc. The ensuing rocking movement of the shaft 122 caused by the stud 127 allows the nose of the arm 133 to snap beneath the wing 131 with retraction of the shaft 122. The nose remains beneath the wing until the withdrawal of the projection 141 from the roller permits the lever to return to initial position. The movements of the stop-lever 117, 118, produced owing to the traversing of the shifting frame and the movement of the lever 94 relatively to the guideway 99 produced by the rotation of the turret 36, co-operate with the lifting movement of the yoke and guideway 99 produced by the engagement of the stud. 127 with the arm 124 in such a manner that, at the start of a buttonhole-producing cycle, the first loop produced is engaged bv the pull-out 86 and drawn till the thread is nipned by engagement with the blade-end 83<1> and held till a few stitches have been made, after which, as the arm 94 rides out of the guideway 99, the blade is returned to initial position and releases the thread. At the completion of a buttonhole the tooth 107 is so situated relatively to the stop 117, 118 that the complete descent of the sleeve is not prevented by the shoulder 118, and the lever 94 is therefore moved by the spring 112 into extreme retracted position after engaging a loop which is then brought into contact with the cutting edge 85<1> and severed.