Abstract: A device for detecting a thickness variation of a piece of fabric passing under the presser foot of a sewing machine. The device includes a transmitter and receiver between which the fabric passes. The receiver stores maximum and minimum signals in memory units generated when the fabric passes between the transmitter and receiver. A computing unit calibrates the thresholds as a function of the stored maximum and minimum signals. A comparator compares the incoming signals with the calibrated thresholds and sends a signal to a logic unit to control the sewing operations accordingly.

Abstract: A device for detecting the passage of the edge (4a) of a piece of material (4), not parallel to the advancing direction (A) of the material for a sewing machine including a presser foot (2), a needle (1) and a needle plate (3). The device comprises a sensor (7) for generating a magnetic field and a sensor (10) responsive to this magnetic field. A magnet is coupled to the presser foor (2) so that it is on the one hand, applied to the piece of material (4) at a point situated at a distance and in front of the needle (1) of the sewing machine relatively to the advancing direction (A) of the material, and on the other hand, is moved with respect to the presser foot (2) in a direction substantially perpendicular to the plane of the needle plate (3). The sensor is mounted opposite the magnet and fixedly in the sewing machine, under the needle plate (3).

Abstract: The invention provides a method and device for automatically carrying out an end portion of stitching so that this latter is finished at a constant distance from the edge of the material whose passage in front of a fixed point is detected by a sensor (20, 21). In accordance with the invention, during a recording operation, the number of pulses (33) counted on the appearance of the signal delivered by the sensor (20, 21) as well as the final number of pulses are recorded and during reproduction, the number of pulses recorded (33) when the signal appears from the sensor (20, 21) is substituted for the number of pulses (37) counted and the number of pulses thus reinitialized are compared with the final number of pulses (35) for controlling the sewing machine (10) forming complete stitches and possibly a last reduced stitch depending on the results of the comparison.

Abstract: Sewing operations are automated, at least partially, using a controllable sewing machine. In an intial recording phase for the sewing operation to be effected, there are put into memory the instantaneous values of three sensed parameters, i.e. the elapsed time of sewing, the position of a sewing speed control element and the length of the sewing, at each time the position of the speed control element changes under the action of the operator. Then, in a reproduction phase, the time is detected in continuous fashion, as is the distance sewn, and the position of the speed control element is changed at each moment for which the time detected is equal to a time recorded, or for which the length sewn is equal to the length recorded.