Sewing – Method of sewing – Stitch forming
Reexamination Certificate
2000-01-11
2001-03-06
Izaguirre, Ismael (Department: 3765)
Sewing
Method of sewing
Stitch forming
C112S235000
Reexamination Certificate
active
06196148
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a sewing method and a sewing machine for sewing on a piece to be sewn such as a flexible cover, a stitch consisting of threads, known as auxiliary threads, of the type which form a passage which extends in the direction of sewing (oversewing, zig-zag, etc), with a thread, known as the tension thread, which is guided and put into position relative to the stitch in the passage, simultaneously with picking up of the auxiliary threads, such that this tension thread can slide longitudinally and/or laterally in this passage, the tension thread not being picked up by the auxiliary threads which form the stitch.
DESCRIPTION OF THE RELATED ART
EP-0 223 312 and U.S. Pat. No. 4,732,097 describe a method and a sewing machine which make it possible in particular to oversew by means of auxiliary threads, and to guide a tension thread, and put it into position into a passage of this oversewing, as this oversewing is being carried out.
This method and this machine are entirely satisfactory. However, it has since been attempted to automate the sewing operations. In fact, this would make it possible to carry out all of the covering method automatically, using a robot.
These sewing operations, which are particularly problematic, still require the presence of a qualified person.
In particular, at the beginning and end of sewing, it is necessary to start and end the oversewing neatly and accurately, and to leave strands of the tension thread which extend beyond the ends of the oversewing, of a sufficient length, and conventionally more than 10 cm, in order subsequently to be able to exert traction on these strands which extend, and then to lock these strands which extend, after traction, by knotting and/or fastening. For this purpose, a large number of manual operations must be carried out before sewing, at the start and end of sewing, and after sewing (release of the strands of tension thread which extend during the oversewing, and cutting off the excess length of oversewing).
In addition, at the beginning and end of sewing, the oversewing must be carried out beyond the piece to be sewn, around the tension thread, for lengths which correspond to the said strands of tension thread which extend, and are to be left free, and these unnecessary excess portions of oversewing are cut off, after the piece has been sewn and has been released from the machine. In addition to the fact that these oversewing operations constitute a waste of thread, time and labour (which can assume substantial proportions within the context of mass production implemented by this method and this machine), sewing of excess portions of oversewing, without a piece to be sewn, corresponds to abnormal functioning of the machine, which gives rise to malfunctioning, interruption of the production pace, and loss of adjustment, or even deterioration of the machine (in particular of the drive lugs which are in direct contact with the foot, in the absence of material). In particular, it should be noted that the assembly of the tension thread and oversewing cannot be guided downstream from the means for picking up, with the same accuracy as when there is a piece to be sewn.
In addition, in some applications, it is also sometimes desirable to be able to release portions of tension thread from the oversewing in certain parts, whilst sewing is taking place, for example in order to form loops to hook the sliding tension thread.
The same problems are posed with other stitches and/or in other applications in which there is laying of a thread, such as a tension thread, simultaneously with sewing of a stitch formed from auxiliary threads other than the tension thread, this tension thread not being an auxiliary sewing thread, and not being picked up, i.e. passed through by the auxiliary threads. For example, the passage for the tension thread can be formed (far less efficiently but satisfactorily in some applications in which the tension thread is not subjected to tension, or is subjected to little tension), by a zig-zag stitch.
Throughout the text, the expression “tension thread” thus covers any thread-type component (including cord, thin cord, large cords, military braid, clothing braid, etc), which may or may not be elastic, other than auxiliary threads used to form the stitch, which is guided and put into position in the passage simultaneously with picking up of the stitch, without being passed through by the auxiliary threads, such that it can slide longitudinally and/or laterally in this passage.
The object of the invention is thus to provide a solution to the above-described problems, and its objective is to provide a sewing method which makes it possible to form, at the start of sewing, and/or whilst sewing is taking place, and/or at the end of sewing, strands of tension thread which are released from the passage formed by the stitch, in particular strands which extend beyond the ends of the passage formed by the stitch, in a simple, quick and reliable manner.
SUMMARY OF THE INVENTION
The object of the invention is in particular to provide a method of this type which can be put into practice in an entirely automated manner, by means of a command from a programmed control device (robot, automaton, computer system, etc), without requiring human intervention.
The object of the invention is thus to permit production, in particular entirely automatically, of strands of a tension thread which extend at the start and end of sewing, at each end of a passage of a stitch, such as an oversewing stitch, in which the tension thread is put into position simultaneously with picking up of the stitch, such as to be able to slide longitudinally and/or laterally in the passage.
The object of the invention is thus to permit production, and in particular entirely automatically, of loops of the tension thread which are released from the said passage whilst sewing is taking place.
The object of the invention is in particular to provide a method of this type which permits full automation of a method for covering an object, such as seat upholstery, by a flexible cover, as described by EP-0 223 312 and/or U.S. Pat. No. 4,732,097. In this respect, the object of the invention is to permit increases in productivity, and saving of labour and raw materials.
The object of the invention is also to make it possible to achieve the aforementioned objectives simply and economically, by means of a simple, cheap modification made to a known sewing machine, and in particular an oversewer as described by EP-0 223 312 and/or U.S. Pat. No. 4,732,097.
The object of the invention is thus to provide a sewing machine which permits implementation of a method according to the invention.
The object of the invention is more particularly to provide a sewing machine of this type which can be obtained by means of a simple modification made to a known sewing machine, and in particular an oversewer as described by EP-0 223 312 and/or U.S. Pat. No. 4,732,097, after production of the machine.
Throughout the text, the terms “upstream” and “downstream” are used with reference to the direction of sewing by the means for picking up of the machine, and to the direction of movement of the piece by these means for picking up, which is thus moved from upstream in the downstream direction. The direction of sewing and movement of the piece is assumed to be horizontal, for reasons of clarity, although this arrangement, which is the most common one in practice, is not strictly essential within the context of the invention. Similarly, “transverse” displacement signifies any displacement relative to the direction of sewing and movement, which has at least one component in a transverse plane perpendicular to the direction of sewing and movement by the means for picking up. “Lateral” displacement signifies any transverse displacement which has at least one horizontal component, i.e. which is parallel to the piece to be sewn, and to the work-holder plate, or in other words, at right angles to the direction of displacement of a needle of the means for picking u
Guilhem Christian
Guilhem Marc
Izaguirre Ismael
Young & Thompson
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