Sewing machine for sewing groups of stitches

The sewing machine (1), especially for sewing in groups of stitches, has a clutch (11) to give a selective engagement/disengagement between the arm shaft (6) and drive wheel (5), operated by a pneumatic clutch switch drive (16). A stop/positioning unit (25) has a brake (42) connected to the arm shaft (6), with a friction brake surface and a positioning arm and a swing lever (26) for braking and positioning. A pneumatic brake drive (31) acts on the swing lever (26) to press the arm against the brake. A control system has a control valve (56) to give a pneumatic control for the clutch switch drive (16) and a brake control valve (57) for pneumatic control of the brake drive (31). A control cam (50) is at the arm shaft (6), rotating with it, with a clutch control cam (54) to trip the clutch control valve (56) and a brake control cam (55) to act on the brake control valve (57).