Connecting rods 3 and 4 are connected by turning pairs B and C to crank 1, turning about fixed axis A, and by turning pairs D and E to rocker arms 6 and 5 which turn about fixed axes G and F. Link 2 is connected by turninhg pair H to rocker arm 5 and by turning pair L to link 7 which, in turn, is connected by turning pair K to Tocker arm 6. When crank 1 turns about axis A, serrated member a has a complex motion in which it grips and advances the cloth being sewn.
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