Sewing – Elements – Frames
Patent
1991-01-03
1992-01-07
Nerbun, Peter
Sewing
Elements
Frames
112273, 112275, 112317, D05B 6918, D05B 6922, D05B 6936
Patent
active
050780689
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a process and an apparatus for making a seam which is uninterrupted on a side facing the needle of a sewing machine in which, during the preparation of the seam, the operation of the sewing machine is interrupted in the case of a shuttle thread disturbance and a new shuttle thread is fed in.
BACKGROUND OF THE INVENTION
West German Patent Specification No. DE-PS 2,028,027 discloses a sewing machine on whose housing a guide groove is provided in close proximity to the shuttle, and a cutting device is arranged at the end of the guide groove facing away from the shuttle. The guide groove serves to receive the end of the old shuttle thread coming from the fabric being sewn and, after changing the bobbin, to receive the beginning of the new shuttle thread. After the shuttle threads extending in the guide groove have been shortened by the cutting device, the sewing process is continued, and the new shuttle thread is knotted with the needle thread during the first stitching and pulled to the stitch formation site, while the old shuttle thread is gradually pulled out of the guide groove by the feed motion of the fabric being sewn.
Since the needle thread in the sewing machine is not cut when the shuttle thread has come to its end, a seam whose top side is made without interruption is obtained. However, since the needle thread is connected only to the old shuttle thread at the time of the last stitch prior to the change of the bobbin and only to the new shuttle thread at the time of the first stitch after bobbin change, the lower side of the seam has an interruption, which is a weak point under stress.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to provide a process and a sewing machine for making a seam, in which the needle thread extends uninterrupted and both the knotting with the old shuttle thread and the knotting with the new shuttle thread are to be accomplished in a reliable manner, so that the strength of the seam is not reduced.
According to the invention, a process and sewing machine arrangement are provided for making a seam which is uninterrupted on a side facing the needle of the sewing machine. The arrangement provides that in the case of a disturbance of the shuttle thread during the preparation of the seam, the operation of the sewing machine is interrupted and a new shuttle thread is fed in. The process includes stopping the sewing machine in the position in which the needle is in its bottom most position after the appearance of a shuttle thread disturbance and after the completion of a stitch formation cycle which has already begun. A stitch length regulating mechanism is set for reversing stitching. The sewing machine is then brought into a position in which the needle is in its top position. A stitch length regulating mechanism is then set to zero. After the elimination of the disturbance, at least one stitch is formed to knot the new shuttle thread with the needle thread in the insertion hole in which the needle was located prior to the appearance of the shuttle thread disturbance. Subsequently, stitch formation is continued with the original stitch length.
The apparatus according to the invention provides a sewing machine including means for detecting the appearance of a shuttle thread disturbance and means for stopping the sewing machine in a position in which the needle is in its bottom most position upon the appearance of the shuttle thread disturbance after the stitch formation cycle which has been begun is completed. A control arrangement is provided for setting the stitch length regulating mechanism for reverse stitching subsequent to machine stoppage and the control mechanism brings the sewing machine into a position which the needle is in its top position at which point a stitch length regulating mechanism is set to zero. After the elimination of the thread disturbance, at least one stitch is formed to knot the new shuttle thread with the needle thread in the insertion hole in which the ne
REFERENCES:
patent: 4195582 (1980-04-01), Novick et al.
patent: 4336761 (1982-06-01), Magnan
patent: 4345532 (1982-08-01), Eguchi
patent: 4934292 (1990-06-01), Mardix et al.
Dobner Reinhold
Hager Walter
Nerbun Peter
Pfaff Industriemaschinen GmbH
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