Sewing – Stitch forming – Overseaming
Patent
1996-11-27
1998-09-15
Nerbun, Peter
Sewing
Stitch forming
Overseaming
112168, 112254, D05B 114, D05B 4704
Patent
active
058064486
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an overlock sewing machine, and more particularly, it relates to an overlock sewing machine which can readily switch from an ordinary over-edge chain stitch to a rolled seam.
BACKGROUND TECHNIQUE
In general, a rolled seam is formed by employing an overlock sewing machine with one needle and three threads or an overlock sewing machine with one needle and two threads comprising a hook looper, replacing a presser foot and a needle plate with those for the rolled seam, and increasing the tension of a lower looper thread or a looper thread (hereinafter referred to as a bobbin thread) while reducing the feed rate. FIG. 1 shows an ordinary over-edge chain stitch which is formed by a conventional overlock sewing machine with one needle and three threads, and FIG. 2 shows a conventional rolled seam which is formed by increasing bobbin thread tension (to about twice that in an ordinary over-edge chain stitch) and reducing the feed rate for retracting an upper looper thread to the back side of cloth while reducing the seam pitch. Referring to FIGS. 1 and 2, the over-edge chain stitch part and the rolled seam part are formed by needle threads 101, upper looper threads 102 and lower looper threads 103.
Such a rolled seam is generally employed for an over-edge chain stitch for a handkerchief or the like since the cloth edge is rolled and beautified on the upper part.
In most of conventional general overlock sewing machines, it has been necessary to replace parts such as a presser foot and a needle plate with those which are dedicated for a rolled seam while strengthening tension of a bobbin thread in the case of forming the rolled seam, as hereinabove described. In this adjustment of the tension, there has been such a problem that an adjustment operation for attaining preferable tension balance is not easy due to a seam by complicated intertwinement of a plurality of threads, and a considerable time is required as the result. This also applies to the case of returning the operation from the rolled seam to an ordinary over-edge chain stitch, and there has been such a problem that the presser foot and the needle plate are changed to ordinary standard parts while a complicated adjustment operation for attaining preferable tension balance which is suitable for the over-edge chain stitch is required.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an overlock sewing machine which can readily perform switching from an over-edge chain stitch to a rolled seam or reverse switching without carrying out a complicated tension adjustment operation.
The overlock sewing machine according to the present invention comprises a main thread tensioner for providing a bobbin thread with thread tension which is necessary for forming an ordinary over-edge chain stitch, and an auxiliary thread tensioner for providing the bobbin thread with thread tension which is necessary for forming a rolled seam along with the main thread tensioner. Thus, it is not necessary to carry out adjustment of the thread tension for forming a rolled seam or returning the rolled seam to an ordinary over-edge chain stitch and tension balance which is once attained may not be changed, whereby switching from the over-edge chain stitch to the rolled seam or reverse switching is simplified. Further, tension adjustment ranges can be narrowed in both of the main thread tensioner and the auxiliary thread tensioner as compared with that carrying out tension adjustment in a wide range from the over-edge chain stitch to the rolled seam with one thread tensioner by one thread tensioner, whereby the degree of freedom in design of the thread tensioners is advantageously increased.
In the overlock sewing machine according to the present invention, the bobbin thread is guided along the main thread tensioner and the auxiliary thread tensioner for the rolled seam to be provided with thread tension from the two thread tensioners, while the bobbin thread is guided along only the main thread tensio
REFERENCES:
patent: 5216970 (1993-06-01), Sakuma
Matsuo Osamu
Suzuki Yoshikazu
Jaguar Co., Ltd.
Nerbun Peter
LandOfFree
Overlock sewing machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Overlock sewing machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Overlock sewing machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-77773