Patent GB-728171-A (GB)
Title: Improvements in or relating to work feeding mechanisms for sewing machines
IPC: D05B27/08
Filed: 1952-12-17
Abstract: 728,171. Sewing-machines. UNION SPECIAL MACHINE CO. Dec. 17, 1952 [Dec. 19, 1951], No. 31925/52. Class 112. In a sewing-machine having a rotary shaft driving stitch-forming means and also driving work-feeding means embodying differentially acting four-motion feed dogs, the feed strokes of the latter can be simultaneously varied at will during the continued operation of the machine by means capable of being freely operated by a knee press, foot control or the like. The main drive shaft 15 is inclined to the work support 14 and carries eccentrics 23, 24, 25 and 26. Eccentric 23 is adapted to rock a lever 36 pivoted to the machine frame at 37; and a link 97, connected at its respective ends to the lever 36 and a block 51, serves to impart lifting and lowering motion to a pair of feed dogs 43 and 44. The main feed dog 43 is secured to the block 51 which is connected by a bar 52 to block 50, and the latter is connected by an arm 46 to a rocker 47 journalled on a stationary shaft 48. The auxiliary feed dog 44 is secured to a rod 62 slidably mounted in the blocks 50 and 51. A block 65, secured adjustably to rod 62, is provided with a pin 68 journalled in one end of a link 69 the other end of which carries a bolt 70 extending through an arcuate slot 71 formed in a bracket 72 secured to the rocker 47. The feed strokes of the dogs are altered with respect to each other by varying the position of the bolt 70, the latter being locked in adjusted position by means of a nut 74 serving to clamp an extension 75a of a washer 75 against the side of the slot 71. Eccentric 26 is connected adjustably to the rocker 47 for imparting feed and return movement to the dogs. A link 30 connects eccentric 26 to a ball member 94 carried by a rocker 82 journalled on a fixed shaft 85. A bolt 84 is slidably mounted in an arcuate slot 83 formed in an arm 81 of the rocker 82, and is connected by a link 77 to an arm 76 of the rocker 47. The position of bolt 84 may be varied during operation of the machine by means of a linkage, for simultaneously altering the feed strokes of the dogs. A link 100 is secured at one end to bolt 84 and is pivoted at its other end to an arm 102, the latter being fixed to one end of a shaft 103 journalled in the machine frame. An arm 105 is fixed to the other end of shaft 103 and is connected by a link 109 to an arm 111 fixed to one end of a shaft 112 journalled in the machine frame. An arm 115, fixed to the other end of shaft 112, passes between stops 123, 124 adjustably set in a calibrated vertical slot 122 of a fixed bracket 120. A chain 118, attached to arm 115 connects the latter to a knee press pad or treadle. A coil spring 114 is adapted to bias the arm 115 against the upper stop 123. Downward movement of arm 115 carries bolt 84 nearer the pivoted axis of rocker 82 to decrease the magnitude of the feed strokes. Eccentric 24 and its associated link 28 co-act with devices (not shown) to operate an under looper 40, and eccentric 25 with its link 29 co-act with other devices (not shown) to operate an overedge looper 41. The eccentrics are lubricated from an oil reservoir 31 by tubes 33 containing wicking 34. Arm 36 carries at its face end a work-trimming blade 35.