Sewing machine has needle position detector - controlling step motor to provide relative needle to material movement when needle retracted

摘要

The arrangement is intended for stitching materials using a sewing machine with reciprocating needle whilst the sewing machine is moved along the fixed material or vice versa. A detector unit responding to the position of the needle relative to the material produces signals which control a step motor to move the machine (or the material) such that this relative movement takes place whilst the needle is withdrawn from the material. The unit may comprise a disc on the driven main shaft of the machine, openings in the disc, and a fixed proximity switch responding to the openings to produce signal pulses which energise the motor driving the slidably supported machine (or feeding the material). Used for controlling relative movement between sewing machine and material being stitched. The arrangement prevents undesirable lateral forces on the needle and on the material. The operation can be easily changed by using interchangeable discs and the relative movements provided by the step motor automatically adapt to the (variable) drive speed of the sewing machine.