Sewing – Special machines – Darning
Patent
1985-08-07
1986-10-14
Nerbun, Peter
Sewing
Special machines
Darning
112254, 112314, D05B 2100, D05B 4704
Patent
active
046165835
DESCRIPTION:
BRIEF SUMMARY
TECHINICAL FIELD
This invention relates to a thread tightening control apparatus for tightening upper and under threads by the relative movement between a needle and a fabric holding body in an automatic sewing machine in which a seam of a predetermined shape is formed while the fabric holding body holding an article to be stitched is moved horizontally relative to a needle and then halted.
PRIOR ART
In a sewing machine of this kind, the fabric holding body is moved a predetermined amount during a period of time from an instant (t.sub.0), at which the tip of the needle is raised to a point above the needle plate, to an instant (t.sub.1), at which the tip of the needle is again lowered to a point below the needle plate, as shown in FIG. 6. In particular, in order to perform thread tightening fully, timing for completion of fabric feed (fabric holding body movement) is brought close to the instant t.sub.1. That is to say, when a needle 4 is at a great height at completion of movement of a fabric W in a direction F, as shown in FIG. 2, the length of the thread from an immediately preceding needle descent point to the next needle descent point becomes excessively large. Then, when the needle is lowered to stitch the seam followed by raising a take-up lever, the upper thread fails to be taken up fully by the lifting of the upper thread performed by the take-up lever. The result is diminished thread tightening. Accordingly, unsatisfactory thread tightening is prevented by adopting a fabric feed completion timing (feed tightening) that will result in the lower end of the needle 4 coming as close as possible to the fabric surface.
When fabric feed completion timing is constant in the above-described arrangement, the needle contacts and, hence, damages the fabric prior to completion of fabric feed if the fabric is thick. For a thin fabric, on the other hand, thread tightening is unsatisfactory for the above-mentioned reasons. Accordingly, it is necessary to adjust the fabric feed timing in dependence upon fabric thickness. In order to perform this adjustment in the conventional arrangement, however, an adjustment screw disposed inside the sewing machine is tightened or loosened to move a prescribed adjustment member. This operation requires a high level of technical knowledge and skill. Another drawback is that the adjustment takes time owing to the complexity thereof.
SUMMARY OF THE INVENTION
Object of the Invention
An object of the present invention is to provide a thread tightening apparatus in a cycle sewing machine adapted to establish relative movement between a needle and a fabric holding body by electrical drive means such as stepping motors, which apparatus makes it possible to adjust the timing of the relative movement between the needle and the fabric holding body, which are to perform the feed tightening, by a manually operable switch with ease and without the need for a high level of technical knowledge.
Another object of the present invention is to provide a thread tightening control apparatus of an automatic sewing machine which makes it possible to perform uniform and highly satisfactory thread tightening even when there is a change in the thickness of a fabric being stitched.
The present invention has been devised to attain the foregoing objects and provides a thread tightening control apparatus of an automatic sewing machine comprising:
a needle rod having a needle secured to a lower end thereof and movable up and down in operative association with a spindle;
a fabric holding body for holding a fabric at a lower end thereof and movable along a horizontal direction relative to the needle rod;
drive means coupled to the fabric holding body and operated by elecrical drive pulses for driving the fabric holding body in a horizontal direction with respect to a needle descent point;
memory means for storing feed data which determine the amount of movement of the fabric holding body for each and every seam;
pulse generating means synchronized to the spindle for generating pulse signals of a constan
REFERENCES:
patent: 4370938 (1983-02-01), Bergvall
patent: 4377980 (1983-03-01), Hanyu et al.
patent: 4566396 (1986-01-01), Sakuma et al.
Nukushina Masanori
Takano Kunio
Nerbun Peter
Tokyo Juki Industrial Co. Ltd.
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