Field of the Invention: The present invention monitors the amount of thread in the shuttle of a sewing machine.

Description of the Prior Art: Generally, common sewing machines in use have an unavoidable defect. Because the amount of thread in a shuttle is limited, if the thread in a shuttle is used up during sewing, improper sewing without thread causes the quality of the piece sewn to be inferior.

Since one cannot frequently check the amount of remaining thread, it causes a decrease in the sewing capacity and productivity.

In order to solve these problems, many conventional techniques that indicate that it is time to change the thread in the shuttle, thus enabling one to sew more efficiently, are already known.

Among those censors which indicate whether or not there is thread in the bobbin using electro-optic technology, the censor that uses light reflected from thread, as shown

in the case of international open number w088/07099, causes many errors in the fluidity and grist of thread, so it is difficult to use in general multi-use sewing machines.

Also, as in the case of patent open number 96-34515, when the remaining thread is identified by the revolutions of the bobbin, it can be used in sewing machines for partially limited, continuous, batch-processed sewing. But, it is not always appropriate for use in all sewing machines.

And, in the case of patent open number P-1999-0069253, because light-channels are placed on all the components of the thread-providing device, the channel from the light- sending LED to the light-receiving part is different from the theoretical channel. Therefore, it is problematic due to the potential for error.

The shaftless shuttle of utility model number 20-2001-0030286 (Title: sewing machine that has a thread censor in the shuttle) is also problematic, since, when it is attached to a sewing machine and operated, the shuttle shakes so that the possibility of sewing errors such as needle breakage, etc. is very high.

Consequently, it is believed that the current devices which indicate the amount of remaining thread can be applied only to a limited range of sewing machines and are not for general use. Therefore, the present invention is an improvement over the existing thread- providing devices which can ensure correct operation and contribute to increased productivity.

The technical tasks that the present invention seeks to accomplish

The present invention is devised not only to prevent the inferior quality of sewn goods due to improper sewing without thread by monitoring whether or not there is thread remaining in the shuttle of a sewing machine by means of optic technology, but also to provide a thread monitor in the shuttle of a sewing machine that improves its endurance so that the sewing efficiency can be maximized.

The present invention which was devised to fulfill the above mentioned purposes has the following characteristics: a shuttle case is installed on the inside of the rolling bag; a thread winding bobbin, a light-sending LED that irradiates light to the thread-providing device in which the shuttle is installed, and a photo detector that senses the irradiated light are installed in the above mentioned shuttle case, so that, when there is no thread remaining, it can be indicated. in this thread monitor in the shuttle of a sewing machine, the above photo detector is installed in the shaft of the shuttle case; the electrode connected to the photo detector is installed at the outer edge of the above mentioned shaft, so that signals can be transferred through the outer edge; the (elastic) part which comes into contact with the above electrode is installed in the above rolling bag, so that signals can be transferred to the outside; the above mentioned bobbin is made of transparent materials; the inside part of the rolling bag, that is, the part that comes into contact with the photo detector electrode is elastic so that thread can pass through it.

SUMMARY OF THE INVENTION When one knows the amount of thread remaining in the shuttle case of a sewing

machine, he can prevent high quality materials from being of inferior quality due to their being improperly sewn without thread. The present invention which informs the user when the when the volume of thread in a shuttle is low, is a monitoring mechanism which prevents material from being wasted. It has the following characteristics: a photo detector (22) which is affixed to the shaft (21) of the shuttle case (2); electrodes (23) are made so that the light which is irradiated from outside a light-sending LED (60) passes the transparent bobbin (30) and reaches the photo detector when the amount of thread remaining in the bobbin of the shuttle reaches a marginal level. The photo detector's internal resistance then decreases rapidly so that a censor-controlling circuit (51) begins to work; and then, the circuit which indicates"no-thread" (50) begins to operate; this indicates, by various means, such as a warning light, buzzer or by turning off the power, that it is time to add more thread. At the same time, the power is automatically turned off so that a loss of materials can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein: Fig. 1 components of common thread-providing devices.

Fig. 2 components of the present invention's thread-providing device Fig. 3a represents the connecting part affixed to the rolling bag.

Fig. 3b represents the photo detector installed in the shuttle case shaft Fig. 4 represents the composition of the thread-providing device, and describes in detail the manner in which the light that is irradiated from the light-sending LED (60) of the thread-providing device reaches the photo detector (22), and is developed by the present invention.

DETAILED DESCRIPTION OF PARTS 1-rolling bag 2-shuttle case 3-bobbin 4-shuttle 41-shuttle shaft 10-rolling bag that has electrodes both on the inside and outside 11-connecting part of electrodes that is on the inside and outside of rolling bag 12-contact part of outer electrode 13- (elastic) contact part to shuttle case 20-shuttle case that has a photo detector 21-shaft of shuttle case 22-photo detector 23-photo detector electrode 30-transparent bobbin to wind thread (made of transparent materials) 40-newly developed shuttle that has a hole in its shaft (light from light-sending part passes it into photo detector) 50-"no-thread"indicating circuit (operates a warning light, buzzer and interrupter of motor, etc.) 51-censor-controlling circuit and contacting part of electrode 52-circuit which controls the emission of light and light-emitting LED DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention monitors the amount of thread in the shuttle of a sewing machine.

The structure and function of the present invention The example below is a detailed description of the desirable mode of use of the present invention. Please refer to the attached figures.

As shown in Fig. 1, although one intends to ascertain the amount of remaining thread optically, there are three hindrances due to the structural characteristics where light is insulated by the shaft (21) of the shuttle case (2), bobbin (3) and the shaft (41) of the shuttle. The present invention removes these hindrances, so that the photo detector (22) installed in the shaft (21) of the shuttle case (2), that the censor signals are transferred to electrode (23) so that they are transferred through the (elastic) contacting part (13) with the shuttle case of the improved outer rolling bag (10), that the signals which are transferred to the censor-controlling circuit (51) can operate the"no-thread"indicating circuit (50) thus reminding the user of the thread status through use of the warning light or buzzer and by turning off the motor, so that he can replace the thread.

Describing the present invention using Figures 2, 3a and 3b we can see that the elastic part (13) which comes into contact with the electrode (23) of the photo detector (22) in the shaft of the shuttle case is inside the rolling bag (10) which is always

rotating. The rolling bag (10) has been improved and the electrode (12) of its outer contact part is connected to the outer censor-controlling circuit (51). The shuttle case (20) in which the electrode (23) is connected with the contacting part (13) of the rolling bag (10) has been improved by installing a photo detector (22) inside the shuttle case (21).

The photo detector (22) has a maximum resistance in the absence of light. Once light is irradiated, its resistance is reduced to a minimum so that it can monitor whether or not there is remaining thread.

Also, the above mentioned transparent bobbin (3) is wound using the above mentioned thread and is made of transparent materials so that it can insulate the light from the light-sending LED (60).

The above mentioned shuttle is an improved one which has a hole in it through which the light from the light-sending LED (60) can penetrate into the photo detector (22).

The above mentioned components are assembled in such a way that, if the transparent bobbin (30) is wound using thread, the light which is irradiated from the light- sending circuit (60) is insulated so that the photo detector's resistance value increases and does not work. However, if the thread is used up, light from the light-sending circuit (60) irradiated on the photo detector (22), passes through the transparent bobbin (30) and the improved shuttle (40), so that the censor's resistance value is radically decreased. The signal of this decreased resistance value is transferred via electrode (23) to the electrode (13) of the inner (elastic) contact part and the electrode (12) of outer contact part of the rolling bag (10). And then, it is transferred to the electrode (51) of the censor- controlling circuit and contacting part, to the"no-thread"indicating circuit (50) so that it

can indicate to the user that there is no thread by warning light, buzzer, turning off the motor, etc. Thus, the user can replace the thread.

That is to say, its entire structure is composed of the following components: the improved shuttle case (20) in which electrodes and shaft (21) of shuttle case (2) that a photo detector is installed are fixed; the electrode of elastic inside contacting part on which the signals (decreased resistance value) from the improved shuttle case are transferred; the improved rolling bag (10) in which the electrode of outer contact part (12) is made; the outer light-sending circuit; the thread-winding transparent bobbin (30) which can prevent light irradiated from the light-sending LED (60) from being insulated; the thread-providing device which is composed of the improved shuttle (40) that its shaft (41) of shuttle (4) is drilled; as shown in Fig. 4, the light-sending circuit and light-sending LED (60); the censor-controlling circuit and electrode (51) of contact part that is devised to analyze the signals from the photo detector (22) inside the thread-providing device; "no-thread"indicating circuit (50).