JPH0331264Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Technical Field] This invention relates to an upper thread feeding device for a sewing machine.

[Conventional technology]

FIG. 1 is a perspective view of the main parts of a needle thread unwinding device of a sewing machine equipped with a conventional automatic thread tensioning device.
Reference numeral 1 denotes a sewing machine, which includes a main shaft (not shown) that is rotated in conjunction with a drive source, and a needle 2 through which the upper thread T is threaded.
A needle bar 3 is fixed to the lower end and moved up and down in conjunction with the main shaft, and the needle thread T is supported between the needle 2 and the bobbin spool 4 as a needle thread supply source, and the needle thread T is tensioned and relaxed. This is a well-known device equipped with a balance 5 that is interlocked with the main shaft and reciprocated between two positions, and the positional relationship between the needle bar 3 and the balance 5 with respect to the rotation angle of the main shaft is shown in FIG. That's right.

The first holding means 6 and the second holding means 7 are attached to the balance 5.
The first solenoid 8 and the second solenoid 9 are arranged separately on the needle thread path between the bobbin spool 4 and the bobbin thread take-up 4 in the upper thread supply direction from the bobbin spool 4 to the thread take-up take-up 5. It consists of a pair of holding plates 10 and 11, which hold the upper thread T so that it cannot move, and are released so that the upper thread T can move when it is not excited.

The feeding section 12 is interlocked with an eccentric cam 13 that rotates in conjunction with the main shaft, and can swing a certain amount around a shaft 14, and its free end is connected to the upper thread path between the two holding means 6 and 7. When the needle 2 is positioned below the bed surface as shown in FIG. When the upper thread T is tensioned, it is associated with the movement of the needle 2 and the thread take-up 5 in such a way that it is kept to a minimum length.

Further, the rotating body 15 is arranged between the holding means 6 and 7 so that it can rotate in proportion to the moving distance when the needle thread T is moved along its path.

Conventionally, when the needle thread is being paid out in this type of automatic thread tensioning device of a sewing machine, the operation of the feeding section 12 causes the thread holding means 6, 7 to be removed from the bobbin 4.
After the balance has been paid out by the planned length,
If the upper thread T, which has been let out by the action of Later, it is further fed out by the action of the thread take-up lever 5, and if sewing is started with this sag present, a seam with poor thread tightness will be formed, and a sewn product with commercial value will not be obtained, and the sewing material will be damaged. The disadvantages were that materials were wasted and work efficiency was low.

[Summary of the idea]

This invention was made to improve this drawback, and it calculates in advance the number of stitches to be formed (number of stitches) until the upper thread slack is consumed at the beginning of sewing.
There is provided a needle thread feeding device for a sewing machine that prevents sewing defects at the beginning of sewing by stopping feeding of the needle thread until the calculated number of stitches is formed, thereby producing a high-quality sewn product. It is something that

[Example of idea]

FIG. 3 is a block diagram showing an upper thread unwinding device of a sewing machine according to a first embodiment to which this invention is applied, and FIG. 4 is a block diagram of the same operation.

In the figure, 16 is a one-chip microcomputer that is a calculation system, and this one-chip microcomputer 1
6 includes an input unit (not shown), a CPU, a RAM,
It has a built-in ROM and an output section, and these functions are well known.

When a sewing machine is about to start sewing, a slack L is left on the upper thread T. If you start sewing in this state, a stitch with poor thread tightness will be formed, so stop supplying the needle thread T until the needle thread equivalent to the length L is consumed by sewing. Then, when this slack L is exhausted, the upper thread can be normally fed out.

In one embodiment of this invention, in order to consume such an excessive amount of needle thread, first, a message is sent to the input section of the one-chip microcomputer 16 so that the thread length L of the needle thread can be assumed to be constant at the feed-out section 12 of the sewing machine. , this constant value L, the sewing pitch P at which the cloth is sewn, the thickness d of the cloth to be sewn, the sewing pitch coefficient k1 and the cloth thickness that are selected in advance based on the type of cloth, the cloth thickness, etc. Coefficient k2 is input. Here, assuming that the needle thread payout length required to sew the cloth for each stitch matches the calculated value obtained by the calculation formula k ₁ p + k ₂ d, from the actual sewing results, Both coefficients k ₁ and k ₂ are determined.

In this way, L data, p data, d data, k ₁
data, k ₂ data, one-chip microcontroller 16
When inputted to , the calculated value obtained by the calculation formula k ₁ p + k ₂ d is calculated, the number of stitches is calculated as the ratio of the above-mentioned sag amount L and this calculated value, and this number of stitches is converted into a pulse. , this pulse is input from the one-chip microcomputer 16 to the needle thread pay-out section 12 as an output pulse.

In this way, the needle thread slack amount L is determined and set experimentally in advance, and this value is the needle thread trimming end signal (which may also be the sewing machine start signal after pattern selection or thread trimming operation). When this occurs, the setting value is input to the counter.Then, when the sewing machine is started, the amount of needle thread required each time one stitch is formed is calculated, and this calculated thread value is input to the counter. , this value is subtracted from the set value of the counter, and when the set value becomes negative, the upper thread payout calculator is activated by the output of the counter. In other words, when the set value of the counter is positive, the needle thread payout calculator is inactive and its output is prohibited.
When the set value of the counter is made negative, the inhibition of the output of the needle thread pay-out calculator is canceled.

According to the method of this invention, after the supply of the needle thread corresponding to the amount of slack is stopped, the needle thread is normally paid out, and it is possible to prevent sewing defects when sewing is started.

The first embodiment described above is for a sewing machine in which the length of the sag is constant, but the case of a sewing machine in which the length of the sag is not constant will be explained in the following second embodiment.

FIG. 5 is a perspective view showing a second embodiment of this invention, in which numerals 1 to 15 are the same as those of the conventional device. In the figure, the feeding unit 12 includes a stepping motor 17 and a driving roller 1 that is interlocked with the stepping motor 17.
8, and a driven roller 21 pivotally supported by an arm 20 which is always urged by a spring 19 to rotate in the direction of arrow a. 23 is presser foot 2
A light emitting device is provided at the lower part of the sewing machine arm 24 at a predetermined distance l from the needle bar 3 on the front side of the sewing machine arm 2.
5 is the sewing machine bed 2 facing this light emitter 23.
6, and the cloth A is transmitted through the light emitter 2.
A light receiver generates a current corresponding to the intensity of light received from the light emitter 23, and together with the light emitter 23, a fabric thickness detection signal 27, which is a fabric thickness detection unit, is configured, 28 is a feed adjustment dial, and 29 is an upper thread. It is a guide.

6 and 7 are explanatory diagrams of the control relationship of the sewing machine, and in the second embodiment of this invention, the length of the sag is not constant and the thickness of the fabric needs to be detected, so 30. The cloth thickness detecting section for this purpose is a device that uses light transmittance, a device that uses reflection of ultrasonic waves, or a mechanical method, and 31 is an A/D converter.

The main shaft detector 32 calculates the number of stitches from the time when the cloth thickness is detected by the cloth thickness detector 30 until the cloth is moved directly below the needle bar 3. 3
3 is a pattern control unit, and 34 is a logic unit, which is built into a microcomputer 35 which is a calculation system, and since the distance l from the fabric thickness detection device 27 to the needle bar 3 is known, the fabric thickness is detected. The information of the pattern control unit 33 is used to calculate in advance the set nth stitch of the needle bar between the distances, and further calculations are performed to compare the nth stitch and the Nth stitch of the needle bar of the main shaft detection unit 32. That is, at the point in time when n=N, the stepped portion of the fabric A or the portion where the thickness of the fabric changes will be directly below the needle bar 3. The feeding section 12 supplies the amount of needle thread necessary for the cloth thickness and sewing pitch at the time when the logic section 34 calculates the amount.

After the cloth thickness is detected, the main shaft detection section 32 calculates the set number N of stitches expected to be sewn during the distance l. This is because the sewing pattern from the circuit of the pattern control section 33 has already been stored in the main memory of the logic section 34, so P ₁ , P ₂ , P ₃ , ... P _o , P _o + ₁ are changed to the fabric thickness D
_{Assuming that the} sewing _{pitch is} expected to be _sewn after the _detection of The number of stitches n that satisfies the condition is set by the microcomputer 35, and this number of stitches n is further compared with the above expected number of stitches N, and when n=N, the fabric thickness corresponds to the changed fabric thickness _D2 . The needle thread pay-out amount S is calculated, and the necessary amount of the needle thread T is paid out, taking into consideration the sewing pitch P and cloth thickness _D2 before sewing.

As explained above, in another embodiment to which this invention is applied, the number of sewing stitches corresponding to a certain distance from the needle bar to the front side is calculated in advance, and the number of sewing stitches from the time of cloth thickness detection is calculated in advance. When the number of needle threads matches the set number of stitches, the required amount of needle thread is supplied, so that sewing defects due to excess or insufficient supply of needle thread can be prevented.

[Effect of idea]

As described above, this device actively unwinds the needle thread required for each stitch formation from the bobbin winder and supplies it to the thread take-up, based on the stitch pitch and fabric thickness. The amount of needle thread is determined by calculation, and the number of stitches until the slack amount of the needle thread that already exists before sewing starts is determined by calculation. Since normal feeding starts with the determined amount of needle thread, the supply of needle thread at the beginning of sewing after the thread trimming operation is not excessive, making it possible to form stitches with good thread tightness from the first stitch, improving the quality of the sewing. It has the effect of improving.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the main parts of a needle thread pay-out device of a sewing machine equipped with a conventional automatic thread tension device, Fig. 2 is a motion diagram of the same, and Fig. 3 is a first embodiment to which this invention is applied. FIG. 4 is a block diagram showing the signal transmission system of the sewing machine, FIG. FIG. 7 is an explanatory diagram of the input/output related to the control. In the figure, 12 is a feeding section, 16 is a one-chip microcomputer, 30 is a cloth thickness detection section, and 35 is a microcomputer. Note that the same reference numerals in each figure represent the same or equivalent parts.

Claims (1)

[Claims for Utility Model Registration] A sewing machine equipped with a thread trimming device that is activated in response to a thread trimming signal and cuts the upper thread below the fabric, which includes terms corresponding to the fabric feed pitch and fabric thickness. A memory device that stores an arithmetic expression that can calculate the needle thread length required to form one stitch and the length of slack in the needle thread at the start of sewing that has been determined experimentally, and a first calculation device that calculates the needle thread length necessary for stitch formation based on the calculation formula and generates a thread amount signal corresponding to the needle thread length; and a memory of the needle thread length calculated by the first calculation device. a second calculation device that calculates and outputs the number of sewing days in which needle thread is consumed corresponding to the slack length of the needle thread from the slack length of the needle thread stored in the device; and a start operation signal after the thread trimming signal; Related to this is a counter that counts the number of stitches formed and outputs a release signal when the number of stitches formed reaches the output of the second calculation device, and a counter that operates based on the thread amount signal from the first calculation device to wind the upper thread. a control circuit that prohibits the output of a thread amount signal from the first computing device in response to a starting operation signal of the sewing machine and releases the inhibition in response to a release signal; An upper thread feeding device for a sewing machine, characterized in that it is equipped with the following.