Patent GB-347269-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1930-01-25
Abstract: 347,269. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd., Union Works, Belgrave Road, Leicester.- (United Shoe Machinery Corporation; 205, Lincoln Street, Boston, U.S.A.) Jan. 25, 1930, No. 2629. [Class 112.] Lock stitching by shuttles; starting and stopping- gear.-Machines of the McKay type as described in Specification 285,487, [Class 112, Sewing &c.], with a horn and straight barbed needle, have a presser-foot raised from the work during each cycle a uniform distance irrespective of the thickness of the work and an improved presser-foot feed mechanism. The machine has a presser-foot 14, straight hook needle 16, and horn 18 carrying a whirl 20 for threading the needle. A shuttle 22 has a hook 24 and a loop spreader 26. The whirl 20 is driven through connections to the vertical shaft 32, which is driven from the main shaft 46 through shafts 36, 34. An electric motor 38 drives the main shaft through a clutch controlled by a foot pedal 40 on a lever 42. The shaft 36 drives the sewing cam shaft 50. The needle 16 is secured in the lower end of the needle bar 52, mounted in bearings 54, 56, and actuated by a crank pin 58 on the end of the shaft 50 through connections which allow the needle to be disconnected from its driving mechanism at the top of its stroke. These parts comprise a lever 60 on a rock shaft 62 connected to a bracket 66 on the bar 52 by a link 64. A crank lever 68 loosely mounted on the shaft 62 is given a continuous reciprocating movement by the engagement of the pin 58. To cause the lever 60 to oscillate with the lever 68, the shaft 62 and sleeve 72 of the crank lever are connected by a coiled spring 74. The levers 60, 68 are also held rigidly together during the operation of the machine, by a latch 80. To disconnect the needle from its actuating mechanism at the top of its stroke, a locking lever 86 is forced to the left against the spring 100 by connection controlled by the stopping and starting treadle 40 as described in Specification 285,487. This lever has a slot 90 engaging a roller 93 on the end of the needle-actuating lever 60. The slot is off-set at the top so that in one position of the lever 86, the roller can move freely up and down the vertical part of the slot and in the other, is held out of operation at the top of its stroke. A hook 110 is provided on an upwardly extending arm of the latch 80 to engage an abutment 106 on the locking lever 86 to prevent the spring 74 from moving the needle downwards, when the machine is re-started, before the lever 60 is operatively connected to the crank lever 68. Presser-bars with periodic control.-The presserfoot is adjustably secured in a groove in the lower face of a block 114 at the lower end of the vertically movable presser-bar 116. The foot is forced on to the work by a spring 118. The foot is lifted slightly during each cycle of operations to permit feeding, by mechanism comprising a cam lever 132 loose on a fixed horizontal bearing shaft 134 carrying a cam roll 136 riding on a cam 138 on the shaft 50. At its free end, the cam lever 132 is linked to an arm 146 on a rock shaft 148 which has a U-shaped frame 150 to permit free play for a shuttle lever. A presser-foot lifting lever 152 is secured to the shaft 148 and is given a reciprocating movement of constant amplitude from the cam 138. Set screws 156 permit adjustment of the limits of movement of the presser lifting lever. To cause the presser-foot to be lifted a predetermined amount regardless of the thickness of the work, a cam-shaped member 160 rotatably mounted on a bracket 162 on the presser-bar 116 engages a pin 164 rigidly secured to the end of the lifting lever 152. The cam-shaped member is adjusted in accordance with the thickness of the work by a rack 168 sliding in a slot 170 in the presser-bar and engaging a pinion 172 on the shaft of the member 160. The rack 168 is moved in its slob 170 to adjust the member 160 for various thickness of work by a second pinion 174 in a lever 176 pivoted to the frame. A second rack 180 on the bracket 162 engages the opposite side of the pinion 174. In operation, as the presser-foot moves downwards into contact with the work, the lever 176 and pinion 174 are held rigidly in position by the engagement of the abutment 192 with the set screw 194, and the downward movement of the second rack 180 with the presser-bar 116 will cause the pinion 174 to rotate about its axis and move the rack bar 168 upwardly in its slot 170, thus causing the cam-shaped member 160 to rotate about its pivot. The final position of the member 160 therefore depends on the distance through which the presser-foot is depressed before it comes into contact with the work. Feed by devices engaging upper surface of work.- The feeding-mechanism comprises a feed-point 196 adjustably clamped in a holder on the lower end of a vertical carrier 198. The carrier is mounted for vertical movement in a frame 200 pivoted at 202 on the machine frame. The carrier is oscillated about its pivot to impart work-feeding movements to the point 196 by a feed-lever 204 loosely mounted on the hub of the needle-locking lever 86 at the forward end of the rock shaft 88. The feed-lever is a bell crank having a cam-shaped slot 208 in its vertical arm engaged by a roll 93 on the end of the needle-actuating lever 60 so that the feeding and needle operating movements are in timed relation. The length of feed is adjusted by a pin 216 adjustably clamped in a slot 219 in the arm 212 connected to the feed-lever 204. The limit of the feeding movement of the feed-point is maintained constant for different adjustments of the pin 216 by bring- ing the feed-arms 210, 212 to a parallel position. Vertical movements are imparted to the feed-point 196 and its carrier through connections from the shaft 148 for actuating the presser-foot lifting lever. These connections comprise a link 220 pivoted to the carrier 198 and to a bell-crank lever 224 pivoted on the arm 128. The other arm of the bell-crank lever 224 is secured to the U-shaped frame 150 at the outer end of the rock shaft 148. The frame 200 which imparts feeding movements to the feedpoint is pivoted on the machine frame so that its position is unaffected by any change in the thickness of the work. Threads, controlling otherwise than in stitchforming.-The shuttle casing 248, Fig. 3, is discoidal and is open at the forward end to receive the thread holder 250. This holder is arranged to allow the thread to be drawn from a cop. The thread passes through a hole 257 between the inner surface of an arm 258 and a plunger 254, thus being subjected to sufficient pressure to produce the necessary tension. The thread case is securely locked in position in the shuttle casing 248, for easy removal, by a flange 260 engaging a slot in the casing, and the arm 258 engaging a groove 262.