Connecting rods 3 and 4 are connected by turning pairs B and C to crank 1, turning about fixed axis H, 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 turning pair A to rocker arm 5 and by turning pair L to link 7 which, in turn, is connected by turning pair K to rocker arm 6. Link 2 has slotted end b sliding along sliding member c which turns about axis A. Sliding member c can be set at various positions along slotted end b and clamped. This changes the length A͞L of link 2, thereby regulating the stroke length of member a. When crank 1 turns about axis H, serrated member a, mounted on link 2, has a complex motion in which it grips and advances the cloth being sewn.
$891$LW,FD$