Patent GB-288552-A (GB)
Title: Improvements in or relating to cutting attachments for sewing machines
IPC: D05B13/00
Filed: 1928-04-10
Abstract: 288,552. Bates Valve Bag Corporation, (Assignees of Krasa, A.). April 11, 1927, [Convention date]. Cutting.-In a machine for sewing a continuous seam across a number of articles such as sacks a cutting means for severing the seam between the articles is brought into action by a clutch mechanism governed by a feeler contacting with the edge of the article. The seam is preferably reinforced by tape. A trip arm 67 has a feeler 70 contacting the edge of the article being sewn. When the article is completely sewn and fed away, the feeler can move across the seam. Springs 87, 92 can then pull down pawls 81. 88<1> on arms 83, 90 of a shaft rocking on a pivot 85, causing arms 79, 80 to rock the shaft 75 which was held by a forked arm 74 thereon engaging a pin 72 on one arm of the bell crank lever 71, 67 carrying the feeler. The pawl 81 rocks the threearmed lever 83, 90, 97 about its pivot 85, causing the arm 97 to lift a stop 66 and free the tail 65 of a spring-pressed dog pivoted on the eccentric 59 of the cutting shaft 39 to allow its nose 62 to engage either of a pair of recesses 63 on a flange 46 of a collar 45 resiliently connected to a cog wheel 42 operated from the main shaft by another cog in the revolution ratio 1 : 2, so clutching the cutting shaft 39 with the main shaft. The shaft 39 then works a rod 36 through an eccentric 38 to rock a shaft 34 which reciprocates the movable cutting blade 30 to and from the fixed blade 26, through an arm 33, link 32, and rod 31, cutting the seam between the articles. As the shaft 39 rotates to reciprocate the cutting blade, an eccentric 107 on the boss 55 carrying the eccentric 59 rocks the forked arm 108 of a lever pivoted at 110 to cause pins 113 on a cross-arm 111 to lift the pawls 81, 88<1> back out of engagement with the arms 83, 90 which then allow the arm 97 to drop the stop 66 under the action of the spring 127, back into the path of the dog 60, which is then engaged thereby, as it rotates, to de-clutch the boss 55 from the collar 45, rendering the shaft 39 and the cutting mechanism inactive. The lifting of the pawls 81, 88<1> rocks the shaft 75 and brings the feeler 70 back into position for contacting the edge of the articles. The cutting operation is performed while the feed dogs 123, 124 is moving back ready for their next forward stroke. To prevent the cut seam following the knife, a resilient member 120 is attached to the presser foot 115 to keep it down. In order to prevent continued running of the cutting mechanism when de-clutched, due to momentum when the machine is running at high speeds, the cam 59 is provided with a recess 128 into which the roller 102 engages when the dog de-clutches the cutting shaft. The spring 104 is strong enough normally to prevent movement of the shaft 39, but if the momentum is such as to overcome the spring, the roller 102 merely rides up the incline of the recess 128 until the excess of momentum is exhausted, when the spring 104 restores it to the bottom of the recess. A trimming knife may also be incorporated between the feed dogs in known manner. Feed by dogs.-The two feed dogs 123, 124, Fig. 14, move parallel to each other and the dog carrying member oscillates at a point below the dogs so that the dog 124 grips the work slightly sooner than the dog 123 and thus effects a separation of the parts of the cut seam.