The invention is explained in greater detail using an illustrated exemplary embodiment. Shown are:
Reference character 1 references the outline of a household sewing machine. On the sewing machine 1 only the essential parts for understanding the invention are shown. In the upper arm 3 there is a needle thread bobbin 5 rotatably positioned on a bobbin mandrel 7. The needle thread 9 directly or indirectly leads from the needle thread bobbin 5 to a thread tension device 11 of conventional design, for example, comprising two discs 13 compressible by an axially effective spring, between which the needle thread 9 is guided through. From here, the thread 9 runs into a monitoring device, device 15 for short, for monitoring the needle thread 9. The device 15, which is the object of the invention, is explained in greater detail using
From the device 15, the thread 9 further extends to the thread lever 17 and from there, after being suitably deflected, to the eye 19 of the needle 21.
In the enlarged representation of the device 15 for the needle thread 9, a regulator spring 25 is unilaterally held in a rotation-proof manner at a mounting plate 2, which may be a component of the housing of the sewing machine 1. The regulator spring 25 comprises a helically bent section 27 as well as a leg 28 tangentially facing away from the section 27. The free end 31 of the leg 29 of the regulator spring 25, embodied as a thread deflector, is preferably laterally guided in a guidance device 33. The guidance device 33 may comprise two parallel extending plates or wires 35, which ensure the lateral inlet and outlet of the needle thread 9. The helically shaped section 27 of the regulator spring 25 encompasses a shaft stump 37, on which a cam switch 39 in the form of a circular segment is pivotally supported. The cam switch 39 is connected in a fixed manner to the leg 29 and follows its oscillations during changes of thread tension and/or thread motion. The changes of thread tension and thread motion may for example be caused by a change of the thread consumption per stitch. On the periphery of the cam switch 39 light/dark or black/white areas (not shown) and/or protrusions 41 having a meandering contour or other detectable areas are arranged. These areas/protrusions 41 are embodied on a cylinder casing segment 43, axially protruding from the level of the cam switch 39. The cylinder segment 43 passes, in a pivotal motion of the cam switch 39, through a sensor 45, in which two or more serially arranged sensor areas a, b, c, are inserted. Light bars, proximity switches, or the like can be used as sensors and/or sensor areas, by which the presence of the cam switch 39, its present location and/or its present pivotal angle as well as its direction of motion and/or the speed of motion can be exactly detected.
In the following, the operation of the device 15 is explained. By the changes of thread tension and/or thread motion as well as changes of the thread consumption of the needle thread 9, guided through the hook-shaped end 31 of the regulator spring 25, the regulator spring 25 in
Summarizing, conclusions can be drawn, for example, regarding
sewing errors (thread balls, skip stitches, failed stitch formation, etc.)
material thickness
stitch length
thread quality
etc.
Number | Date | Country | Kind |
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01230/06 | Jul 2006 | CH | national |