Buttonhole sewing machine

Details Buttonhole sewing machine Buttonhole sewing machine

2000-03-31

2001-05-01

Nerbun, Peter (Department: 3741)

Sewing

Special machines

Buttonhole

C112S447000, C112S451000

Reexamination Certificate

active

06223664

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a buttonhole sewing machine capable of forming a stitched buttonhole having a pair of left and right zigzag stitch portions placed at both sides of a defined buttonhole and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions on a work cloth.
2. Description of Related Art
A conventional buttonhole sewing machine typically includes a feed bracket that feeds a work cloth, a sewing device that creates stitches on the work cloth, and a sewing controller that controls the feed bracket and the sewing device to form a stitched buttonhole having a pair of left and right zigzag stitch portions placed at both sides of a buttonhole to be formed and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions. In such a buttonhole sewing machine, the sewing controller controls the feed bracket and the sewing device, the work cloth is fed and stitches are made thereon. Thus, a stitched buttonhole
70
(which will be later described in detail), as shown in
FIG. 6
, can be created.
However, the buttonhole sewing machine does not provide for minute settings regarding buttonhole shapes. For example, the stitch width of the needle to sew the zigzag stitch portions
71
,
72
(hereinafter referred to as a zigzag width) was fixed to a predetermined value. In short, the buttonhole sewing machine provides for the settings of the size of the stitched buttonhole
70
and the stitch pitch, but the settings of the shape of the stitched buttonhole
70
and the balance between the left and right zigzag stitch portions
71
,
72
and between the front and rear bar-tack stitch portions
73
,
74
were not taken into consideration. As a result, problems have occurred. For example, the widths of the left and right zigzag stitch portions
71
,
72
are usually set so as to be equal to each other. According to the tension of the needle thread, the finish looks as though the widths of the left and right zigzag stitch portions
71
,
72
are different. However, the buttonhole sewing machine could not correct the balance by means of adjustment. Similarly, it could not correct the balance between the front and rear bar-tack stitch portions
73
,
74
as if the finish looks as though their widths are different.
When this kind of stitched buttonhole is formed on the work cloth, double sewing, in which the finished stitched buttonhole is sewn again so as to overlap the needle thread on the work cloth, is performed in some cases. However, in double sewing, the needle thread already sewn into the stitches may be broken because the second sewing is made on the same needle points where the first sewing is made. In addition, when double sewing is partially made, a part where double sewing is made and another part where double sewing is not made are different in thickness. Because the conventional sewing machine was provided for a fixed stitched buttonhole pattern only, it could not make the adjustment in proportion to the difference in the stitch thickness.
SUMMARY OF THE INVENTION
The invention was made in consideration of the above circumstances. A first object of the invention is to provide a buttonhole sewing machine capable of minutely setting the shape of a stitched buttonhole. A second object of the invention is to provide a buttonhole sewing machine that can prevent the needle thread from being cut when double sewing is performed. A third object of the invention is to provide a buttonhole sewing machine that can easily adjust the balance of thickness of a stitched buttonhole.
The buttonhole sewing machine, which is intended to accomplish the first object, comprises a feed bracket that feeds a work cloth; a sewing device that forms stitches on the work cloth; a sewing controller that controls the feed bracket and the sewing device so as to form a stitched buttonhole having a pair of zigzag stitch portions placed at both sides of a buttonhole and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions; and a zigzag stitch width setting device that enables the left and right zigzag stitch widths to be set separately; wherein the sewing controller controls the sewing device based on the zigzag stitch width set by the zigzag stitch width setting device so as to cause the sewing device to form the stitched buttonhole having the set zigzag stitch width. Therefore, the buttonhole sewing machine can not only change the shape of the stitched buttonhole, but can also adjust the balance of the left and right zigzag stitch portions.
In a preferred aspect of the invention to accomplish the first object, a buttonhole sewing machine comprises a feed bracket that feeds a work cloth; a sewing device that forms stitches on the work cloth; a sewing controller that controls the feed bracket and the sewing device so as to form a stitched buttonhole having a pair of zigzag stitch portions placed at both sides of a buttonhole and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions; a stitch width setting device that enables a width for the pair of zigzag stitch portions and a width for the front or rear bar-tack stitch portions to be set separately, wherein the sewing controller controls the sewing device based on the zigzag stitch width set by the zigzag stitch width setting device so as to cause the sewing device to form the stitched buttonhole having the set zigzag stitch width. Therefore, the buttonhole sewing machine can minutely change the shape of the stitched buttonhole by separately setting the width for the pair of zigzag stitch portions and the width for the front or rear bar-tack stitch portions. In addition, it can adjust the balance between the front and rear bar-tack stitch widths of the stitched buttonhole.
In another preferred aspect of the invention to accomplish the first object, a buttonhole sewing machine comprises a feed bracket that feeds a work cloth; a sewing device that forms stitches on the work cloth; a sewing controller that controls the feed bracket and the sewing device so as to form a stitched buttonhole having a pair of zigzag stitch portions placed at both sides of a buttonhole and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions; a bar-tack stitch length setting device that enables a length for each of the pair of bar-tack stitch portions to be set separately; wherein the sewing controller controls the sewing device based on the bar-tack stitch portion length set by the bar-tack stitch length setting device and causes the sewing device to form a stitched buttonhole having the set bar-tack stitch lengths. Therefore, the buttonhole sewing machine can minutely change the shape of the stitched buttonhole by setting the length for each of the pair of bar-tack stitch portions separately. In addition, it can adjust the balance between the front and rear bar-tack stitch lengths of the stitched buttonhole.
To accomplish the second object, a buttonhole sewing machine comprises a feed bracket that feeds a work cloth; a sewing device that forms stitches on the work cloth; a sewing controller that controls the feed bracket and the sewing device so as to form a stitched buttonhole having a pair of zigzag stitch portions placed at both sides of a buttonhole and a pair of bar-tack stitch portions disposed at both ends of the zigzag stitch portions; wherein the sewing controller disposes needle points at the start of sewing and needle points at the end of sewing so as not to overlap each other when the start and the end of the stitched buttonhole are disposed on either of the front or rear bar-tack stitch portions and the front and rear bar-tack stitch portions are doubly sewn. Thus, the needle points at the end of sewing do not agree with those at the start of sewing. As a result, the buttonhole sewing machine prevents the needle thread that is already sewn into stitches, from being cut when double sewing is performed.
To accomplish the third object, a buttonhole sewing machine comprises

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