Description

METHOD FOR WINDING UNDER-THREAD OF SEWING MACHINE AND BOBBIN WOUND WITH UNDER-THREAD

USING THE METHOD

Technical Field

[1] The present invention relates to a method for winding an under thread of a sewing machine and a bobbin wound with the under-thread by the same method, and more particularly to a method for winding an under thread of a sewing machine on a bobbin in order to secure under thread remains and the bobbin wound with the under thread by the said method.

[2] According to the present invention, thus, a separate sensing device adopted to sense the distal end of an under thread, can completely prevent sewing defects occurring when an under thread is finished during the sewing operation. That is because the present invention gives an alarm when it senses the predetermined length of under thread remains enough to finish the sewing.

[3]

Background Art

[4] Sewing machines, which are used for the whole processes of sewing products or woven fabric, generally need an upper thread and an under thread, wherein the under thread is wound around a bobbin and supplied by an under thread supplying device holding the bobbin.

[5] The bobbin wound with a under thread is often replaced, as the under thread is supplied by predetermined length wound around the bobbin. Besides, difficulty in expecting an under thread's finish as the under thread is placed under the sewing plate , causes problem in an under thread supply.

[6] Thus, there have been developed various kinds of devices for sensing the distal end of the under thread. However, most of the devices just raise an alarm when the under thread remains from the end by a length between about lcm and 40cm, and moreover they are of high price. In addition, they give no good results during real sewing by failing to accurately sense the distal end of an under thread, thereby providing no good effects. For example, when the alarm sounds for warning the distal end of the under thread still remaining about 100cm sewing, the operation should be resumed, which makes the alarm useless.

[7] The problem in sensing the distal end of an under thread causes another problem of backstitching without an under thread. When resumption of sewing results from back- stitching without an under thread, the backstitched thread must be cut off and the

sewing operation is resumed. Furthermore, the sewing operation has to be restarted at the hole previously made by a needle, which needs work with a high degree of concentration. Thus, undesirably, the working time increases and the fatigues of the operator become also severe.

[8] Besides, in spite of the said re-sewing, if the sewing operation is restarted at a hole not corresponding to the hole made by the needle in previous backstitching, defective products 'having unnecessary needle holes' are produced. Thus, the disposal of defective products results in increase of costs of materials, labor and production, and increase of additional work time for making up for the short supply caused by the disposal.

[9] In addition thereto, the backstitching without an under thread makes the operator feel overburdened, so that he or she comes to have a low degree of concentration on his or her sewing operation, and it gives bad influences on the quality of products and the productivity.

[10] On the other hand, if the said re-sewing is not done, a connected sewing should be performed, wherein the sewing is continued with the second under thread replaced after the finish of the first under thread. However, this connected sewing may cause a problem that the connected portion of the first under thread and the second under thread is opened in case of a product requiring high tension. Such products requiring high tension includes air bags, footwear, swimwear, and the like.

[H]

Disclosure of Invention

Technical Problem

[12] It is an object of the present invention to provide a method for winding an under thread of a sewing machine on a bobbin in order to secure a predetermined desired length of an under thread remains by easy sensing of its distal end and the bobbin wound with the under thread using the said method.

[13]

Technical Solution

[14] The object of this invention is attained by a method for winding an under thread of a sewing machine so as to easily sense the distal end of the under thread during a sewing operation, the method including the steps of: (a) winding a given length of under thread around a part of the surface of a bobbin, the under thread being left for the purpose of giving the alarm of the under thread reaching its finish; and (b) winding a under thread continuing the said under thread around the remaining surface of the bobbin except the said part of the surface of the bobbin wound with the said under- thread at the step (a), this under- thread also being used to sense the distal end of the

under thread.

[15] The object of this invention is also attained by a bobbin having an under thread wound around so as to easily sense the distal end of the under thread during a sewing operation, the under thread comprising: a first under thread wound around a part of the surface of a bobbin, the first under thread being left by a given length around the bobbin, for the purpose of giving the alarm of the under thread reaching its finish; and a second under thread being continuously wound around the remaining surface of the bobbin except the said part of the surface of the bobbin wound with the said first under thread, the second under thread also being used to sense the distal end of the under thread.

[16]

Advantageous Effects

[17] The present invention providing a method for winding an under thread of a sewing machine and a bobbin wound with the under thread using the said method can secure under thread remains by a desired length enough to finish a sewing operation, thereby preventing backstitching done with no under thread. [18] Besides, the present invention is applicable for sewing middle or large-sized products wherein the under thread remains for sensing its finish are over 40cm. [19] Furthermore, the present invention has the under thread for sensing its finish wound with multistage around a bobbin divided into plural sections by a different length, thereby enhancing the efficiency of sensing the distal end of the under thread, and has merits to efficiently perform a sewing work requiring different length of under threads by securing various length of under thread remains. [20] In addition, the present invention adopts a bobbin of which the inner or outer surface has a plurality of concavo-convex protrusions formed, thereby improving the optical sensitivity in sensing the finish of the under thread. [21]

Brief Description of the Drawings [22] FIG.1 is a view showing a method for winding an under-thread of a sewing machine according to the present invention; [23] FIG.2 is a view showing a sequence of winding an under thread according to the method for winding an under thread of the present invention; [24] FIG.3 is a view showing a sensing operation for sensing under thread remains according to the method for winding an under thread of the present invention; and [25] FIG.4 is a view showing examples of the bobbin employed according to the method for winding an under thread of the present invention. [26]

[27] <Explanation on the reference numerals in the main parts of the drawing>

[28] 100: bobbin 110: first section 121: second section

[29] 122: third section 123: fourth section 130: fifth section

[30]

Mode for the Invention

[31] The terms and the words used in the specification and the claims should not be limitedly construed with ordinary or lexical meaning. Rather, they should be construed with the meanings and the conceptions according to the idea of the present invention, abiding by the principle that an inventor can properly define the conception of terms so as to describe his or her own invention with the best manner.

[32] While the present invention has been described with reference to particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

[33] Hereinafter, an explanation on a preferred embodiment of the present invention will be given in detail with reference to the attached drawings.

[34] FIG.1 is a view showing a method for winding an under-thread of a sewing machine according to the present invention. Referring to FIG.l, when an under thread is wound around a bobbin (100), it is wound by a necessary length from its end around a first section (110) defined by a given length of the bobbin (100), and next it is all wound around the remaining length of the bobbin (100).

[35] In this case, the remaining length of the bobbin (100) can be divided into several sections like a second section (121), a third section (122), and a fourth section (123). That is, an under thread wound through several steps around the bobbin (100), and the under thread remains detected section by section by a separate sensing device of finish of under thread (which is not shown) make it possible to control of sensing the remaining length of an under thread.

[36] For example, when the length of a bobbin (100) is divided into three sections and the length of an under thread wound around each section of the bobbin (100) is 100cm, the length of an under thread wound around the three sections is 300cm. Thus, when the under-thread wound around the outermost section of a bobbin(lOO) is finished to make the surface of the section of a bobbin (100) naked, the length of an under thread wound around the remaining two sections of a bobbin (100) becomes 200cm. Accordingly, when the under thread wound around the second section of a bobbin (100) is finished, the remaining under thread is 100cm. That is, an operator can sense each step of 200cm section and of 100cm section through the separate sensing device of the

finish of an under thread. In the same way, when the length of an under thread wound around each section of the bobbin (100) is 50cm, not 100cm, each step of 100cm and of 50cm can be sensed as a result of the finish of the under thread wound around each section. In the said manner, the remaining length of an under thread enough to finish a work can be controlled to be sensed by various lengths.

[37] A bobbin (100) is an 'H'-shaped tube or a straight tube and is made of a transparent material or an opaque material coated with a reflective material. If a sensing device of the finish of an under thread is of a transmission type, a bobbin (100) made of a transparent material is desirable, and contrarily, if a sensing device is of a reflection type, a bobbin (100) made of an opaque material is desirable. In case of a reflection type sensing device, a bobbin (100) can be coated with silver foil as a reflective material.

[38] FIG.2 is a view showing a sequence of winding an under thread according to the method for winding an under thread of the present invention. Referring to FIG.2, according to FIG.l an under thread is wound around the first section (110) of a bobbin (100) by a desired length to be left on the last alarm. The length of the under thread wound around the first section(l 10) is sufficient enough to satisfy necessary under thread remains in various sewing operations, which help produce various size of many items.

[39] Next, the under thread for sensing its finish is wound around the second to fourth sections (121, 122, and 123) of a next section (120) of the bobbin. That is, when the under thread wound around the fourth section (123) is finished during a sewing operation, a first alarm is raised for warning of the under thread reaching its end. Sequentially, when the under thread wound around the third section (122) and the second section (121) is all consumed, the second and the third alarms are given for warning of the under thread reaching its end. Therefore, the remaining under thread wound around the first section (110) after the consumption of the second to fourth sections (121, 122 and 123) prevent backstitching without an under thread, and the remaining sewing operation can be finished.

[40] After the under thread is wound around the second to fourth sections (121, 122 and

123), it is wound around a fifth section (130) as a section for an initial use. The fifth section (130) is defined along the entire sections of a bobbin (100) and is for a general use of an under thread, not the use for sensing its end.

[41] As an under thread is wound step by step around the second to fourth sections (121,

122 and 123) and is consumed in reverse order, the surface of a bobbin (100) is completely exposed step by step, which ensures the high accuracy of the sensing device to sense the distal end of the under thread. This is different from the existing method where the initial winding of an under thread around the bobbin is of an

'S'-shaped waveform to have the surface of the bobbin irregularly exposed through the clearances of the under-thread wound therearound.

[42] In a different way, the other section of a bobbin for sensing the finish of an under thread than the first section (110) for the under thread remains after the last alarm can be divided into more than two sections, not limited to be divided into the second to fourth sections (121, 122 and 123) when applied in various embodiments. Also, the section for sensing the finish of the under thread can be extended up to the first section (110).

[43] FIG.3 is a view showing a sensing operation for sensing under thread remains according to the method for winding an under thread of the present invention. Referring to FIG.3, the under thread wound around the first and second sections (110 and 121) remaining after the consumption of the under thread around the third and fourth sections (122 and 123) is sensed by using an optical sensor. In here, the bobbin (100) is an embodiment formed of a transparent material adapted for the transmission type of sensing device of the finish of under thread (which is not shown).

[44] If light is radiated to a bobbin (100) wound with an under thread, it cannot transmit the first and second sections (110 and 121) wound with an under thread. However, the light transmits the surface of the third and fourth sections (122 and 123) of the transparent bobbin (100) exposed after the consumption of the under thread wound therearound and it is sensed by means of the optical sensor (a light-detecting part). Therefore, it is possible to sense the finish of an under thread, that is, the length of an under thread remains sufficient to finish a sewing operation.

[45] FIG.4 is a view showing examples of the bobbin employed according to the method for winding an under thread of the present invention. Referring to FIG.4, a plurality of concavo-convex reflective protrusions are formed around a transparent bobbin (100) adopted for a transmission type of sensing device, so that the light radiated for sensing the finish of an under thread wound around the bobbin (100) is diffusely reflected, thereby enhancing the optical sensing effects.

[46] In this case, the concavo-convex reflective protrusions formed for diffused reflection can be disposed around the inner or outer periphery of a bobbin in a waving round or triangular shape.

[47] Although a preferable embodiment have been described above in considerable detail, embodiments are not limited to the said embodiment, and numerous variations and modifications are possibly made by those skilled in the art within the scope not deviating from the purpose of the present invention and the equivalence of the following scope of claims.