Variably controllable bobbin thread pull-off mechanism

In a sewing machine, a vertical axis looptaker including a drive shaft therefor, a non-rotatable bobbin case in the looptaker, a disc housed within the looptaker, a drive shaft for the disc concentric with the drive shaft for the looptaker, a thread carrying bobbin supported on the bobbin case for free rotation above the disc, means operably connected with the looptaker shaft for rotating the looptaker, means operably connected with the disc shaft and responsive to control input signals for causing the disc to be oscillated, between a fixed and a variably controllable position through an angle dependent upon the said signals, the disc being adapted to engage and pull thread from the bobbin according to said angle when the disc is moved in one direction, and to release the thread for use in the formation of a stitch when the disc is moved in the opposite direction.