Sewing – Method of sewing – Material sensing
Patent
1998-02-10
1999-08-24
Nerbun, Peter
Sewing
Method of sewing
Material sensing
112153, 112306, 112320, 11247007, 271227, D05B 2100, D05B 2714
Patent
active
059411872
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a device for guiding flexible textile material (woven or knitted fabric etc) able to be sewn on a sewing machine of the traditional type comprising a work carrier plate and a claw mechanism for advancing the material, associated with at least one needle; hereinafter this mechanism and its accessories will be designated by the expression "presser foot". The invention extends to a method for the automatic sewing of material, implemented by means of a sewing machine equipped with such a guidance device. It also extends to improved sewing machines equipped with one or more guidance devices according to the invention.
BACKGROUND OF THE INVENTION
In making up, the operations of sewing pieces of woven or knitted fabric generally aim to sew two pieces together along one of their edges or to form a hem at the border of one piece, or again to fix a tape, a piece of elastic, a waistband etc along one edge of a piece. In order to attempt to save on labour and make gains in productivity, guidance systems have been proposed which move the woven or knitted fabric in the transverse direction upstream of the needle in order to constantly bring the area to be sewn facing the needle; these systems generally comprise wheels or caterpillars with rollers, disposed in the transverse direction upstream of the needle in the direction of driving, and which are driven in rotation in one direction or the other so as to be able to move the material transversely (at right angles to the direction of driving) in both directions in order to make suitable position corrections. However, these systems are little used since they result in imperfect sewing and frequent defects. This is because the flexible material driven by the presser foot level with the needle is braked upstream of the latter by the guidance system and has a tendency to roll on itself, to become folded or to wrinkle in a random fashion, which is incompatible with obtaining an even quality stitching; this defect is particularly serious for stretch or "soft mesh" knitwear which it is impossible to sew with these known systems; in the case of two pieces to be joined edge to edge; offsets of one edge with respect to the other occur, and joining imperfections which are prejudicial to the quality of the product produced. In addition, the majority of existing systems can be used only for materials with a defined thickness.
Subsequently (patents FR 2 585 683 and EP 0 216 644), a guidance device was proposed which comprises a spherical wheel coming into abutment against the material upstream of the presser foot and turning in a single direction of rotation in order to drive and guide the material upstream of the stitching area. This device has a radically different principle from the other prior systems since, in these patents, the spherical wheel is offset laterally, drives the material in the same direction as the presser foot, but is mounted so as to pivot about a vertical axis so as to be able to orient it by virtue of a control of the proportional analogue type in different driving directions enabling the material to be brought into the required position. In the device to which these patents relate, the spherical wheel is driven in rotation by friction by means of a roller which comes into abutment on one side thereof in the horizontal plane containing the axis of the wheel.
However, such a system comes up against a serious practical difficulty in implementation. To afford satisfactory driving of the spherical wheel by means of the roller, it is necessary for the surfaces of these components to roll without sliding against each other and therefore to have a sufficient coefficient of friction; when the spherical wheel pivots about the vertical axis in order to adopt another orientation, the abutment of the roller on this wheel describes a segment of a great circle and this movement is transverse with respect to the roller (parallel to the axis of the roller and perpendicular to the tangential velocity), so that the friction of th
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patent: 4813364 (1989-03-01), Boser
patent: 4836119 (1989-06-01), Siraco et al.
patent: 5054409 (1991-10-01), Schips
patent: 5493980 (1996-02-01), Nishimori et al.
patent: 5497720 (1996-03-01), Kawasaki
Rouleau Alain
Rouleau Patrick
Touret Jean-Pierre
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