JPS5946196B2 - How to feed fabric on a sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fabric feeding method for a sewing machine, and in particular, the present invention relates to a fabric feeding method for a sewing machine, and particularly to a looper thread that continues to the fabric on the lower surface of the throat plate after the sewing machine is stopped near the needle top dead center, and a fabric side thread that is loose in the needle thread that is attached to the looper. This invention relates to a cloth feeding method for a double chainstitch sewing machine equipped with a thread cutting mechanism for cutting the threads.

A double chainstitch sewing machine having this kind of thread cutting mechanism is well known, but this sewing machine has the following drawbacks.

That is, as shown in Fig. 1, when the needle 1 is stopped near the top dead center, the double sewing stitch S has a looper thread extending from the last stitch knot to the long needle plate 2 in the cloth feeding direction. The needle thread T continues from the needle hole 3 to the looper 40 and the thread hole 5, and the needle thread T passes through the fabric from the seam knot to the looper 4, and the needle side thread TN passes through the fabric from the seam knot to the looper 4. The needle has reached needle 1.

The outer side of the movable knife 7 having the hook part 6 of the thread trimming mechanism is located between the lower surface of the throat plate 2 and the upper part of the looper 4, and when it moves forward, the fabric side thread is close to the looper threader and the needle side thread TN of the needle thread T. TC, and during the backward movement, these looper threads and the fabric side thread TC close to the needle side thread TN are captured by the hook portion 6 and cut between them and the fixed knife 8.

However, the distance between the fabric side thread TC and the needle side thread TN of the needle thread T wound on the looper 4 is extremely narrow as shown in FIG. In relation to the length, the loop of the needle thread T that hangs over the looper 4 tends to rise upward in proportion to the cloth feed amount, and as the cloth feed amount decreases, these cloth side threads TC and needle side threads TN
As the distance between the threads and the threads approaches, it becomes difficult for the hook portion 6 of the movable knife 7 of the thread trimming mechanism to capture only the fabric side thread TN.

For this reason, for example, after sewing with a normal cloth feed amount, in order to prevent the seam from fraying and strengthen the seam at the end of the seam formation, the multiple needle cloth feed amount is reduced, the stitch pitch is reduced, and the stitch pitch is reduced. When the sewing machine is stopped and the thread trimming mechanism is activated, the looper 4
As shown in Figure 5, the hooked needle thread loop is connected to the fabric side thread TC.
Since the needle side thread TN and the needle side thread TN are close to each other, an accident occurs in which the hook 6 of the movable knife catches and cuts both needle threads, and as a result, the needle side thread TN from the needle thread hole to the cut end is The remaining length of needle thread may become too short and the end of the needle thread may slip out of the needle thread hole at the beginning of the next stitch, making it impossible to form a stitch, or it may be necessary to stop the sewing machine and pass the needle thread through the thread hole. This has the disadvantage of reducing work efficiency.

In this invention, after the needle comes out of the fabric, the sewing machine is stopped near the top dead center of the needle, and the looper thread connected to the fabric and the fabric side thread of the needle thread loop caught on the looper are removed from the bottom surface of the throat plate. In a double chainstitch sewing machine with a thread cutting mechanism that reciprocates to cut the thread, the amount of cloth fed immediately before stopping the sewing machine to cut the thread is made larger than the amount of cloth fed before that. The purpose is to eliminate shortcomings.

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. A needle hole 3 that is long in the direction is formed.

Reference numeral 4 denotes a looper which forms a thread hole 5 through which the looper thread is passed, and works in conjunction with the sewing machine mechanism to form a double stitch with an elongated tip that moves an elliptical locus in cooperation with the drawing needle.

Reference numeral 7 designates a movable knife, which has a hook 6 formed at its tip and is linked to an appropriate knife operating mechanism (not shown) to remove the looper thread and the loop of the needle thread T caught on the looper 4 during its forward movement. It intersects with the side thread TC, captures both threads during the backward motion, and cuts these two threads in cooperation with the fixed knife 8.

Reference numeral 10 denotes a U-shaped adjustment link whose free ends are rotatably supported on the machine frame 11 of the sewing machine by a shaft 12.

Reference numeral 13 denotes a U-shaped two-pronged link, the base of which is rotatably supported by a shaft 14 at the base of the adjustment link 100.

Reference numeral 15 denotes a feed adjuster whose central portion is rotatably supported with respect to the machine frame by a shaft 16, and has a slope 17a in the forward feed direction and a slope 17b in the reverse feed direction, which are formed facing each other in opposite directions at the front. Form.

Reference numeral 18 denotes an adjustment knob, the tip of which is screwed into the machine frame 11, and the tip 19 is fed to a slope 17a in the forward/reverse feed direction of the adjuster;
A knob 20 is formed on the outside of the machine frame and facing b.

21 is a connecting rod whose upper end is rotatably connected to the rear of the feed adjuster 15 by a shaft 22, and whose lower end is connected to the forked link 13.
It is rotatably connected to a shaft 14 which is a 0-rotation fulcrum, and a pin P that protrudes laterally is installed in the center.

23 is a vertical rod whose upper end is loosely fitted onto the outer periphery of an eccentric cam 25 provided on the main shaft 24.

Reference numeral 26 denotes a horizontal feed shaft rotatably supported on the sewing machine frame 11, the base of an arm 27 is fixed to one end, and although not shown, the other end of the horizontal feed shaft 26 swings to feed the cloth as is well known. The teeth are connected to provide horizontal cloth feeding motion.

A connecting link 28 has one end rotatably connected to the tip of the arm 27, and the other end rotatably connected to the free end of the two-pronged link 13 together with the lower end of the vertical rod 23 via a shaft 29.

Reference numeral 30 denotes a feed conversion shaft rotatably supported on the machine frame 11. The center portion of the connecting arm 31 is fixedly supported inside the machine frame, and the base of the feed conversion lever 32 is fixed to the projecting end on the outside of the machine frame.

One end of the connecting arm 31 is formed with a two-pronged portion 33 that loosely fits on the pin P of the connecting rod 21, and the other end is provided with the upper end of a spring 34, which is fixed to the machine frame 11 at the lower end. The acting force rotates the feed adjuster 15 clockwise around the shaft 16 via the fork 33, the pin P, and the connecting rod 21,
The slope 17a is pressed against the tip of the adjustment knob 18, and the feed converting shaft 30 receives a rotational force in the counterclockwise direction, so that the tip of the feed converting lever 32 is maintained at the upper position.

35 is an air cylinder, the upper end of which is rotatably supported by the tip of a support 36 fixed to the upper surface of the machine frame 11, and the lower end of a rod 37 is rotatably connected to the tip of the feed conversion lever 32. The air cylinder is controlled by a solenoid valve which will be described later, and the rod 37, which is lowered by the action of the air cylinder, has its lowering position defined by a stopper provided inside.

Reference numeral 38 shown in FIG. 1 is a sensor provided on the machine frame surface on the right side of the throat plate 2.

FIG. 2 is a seam diagram formed by this embodiment,
The cloth 39 fed in the direction of the arrow is sewn with a relatively large seam up to point B, and from point B near the rear end 40 of the cloth to points C and D, the seams must be strengthened and the double sewn seams should be prevented from fraying. In order to prevent this, the cloth feed amount is reduced to form a reduced stitch, and at point E, where the thread is cut from point D, the cloth feed amount is returned to its original size.

FIG. 3 is a block diagram showing a control circuit for controlling the sewing machine of FIG. 1 to perform the stitching shown in FIG. 2.

AND inputs the sewing (sewing machine drive) signal and the fabric edge detection signal, and generates an output signal when the sewing signal and the fabric edge detection signal when needle 1 is at point A in Figure 2 are input. do.

The sewing end position timer T2 is set at time t1 in Fig. 2 when the fabric is sent from point A to point B after the AND output signal is generated.
An output signal is generated at point B with a delay of

The stitch reduction timer T2 generates an output signal for the time t2 required for the fabric to be fed from point B to point 0 in FIG. Activate the solenoid valve.

The timer T3 starts the air cylinder 3 after the output signal of the stitch reduction timer T2 disappears and the solenoid valve becomes inactive.
The output signal is generated with a delay of time t3 from point C to point D in FIG. 2 until the rod 37 of No. 5 returns to its original raised position.

When the needle up position signal is input next to the output signal of timer T3, the motor is stopped, the sewing machine stops at the needle up position, a thread trimming signal is generated, and an appropriate thread trimming mechanism operating member is activated to move the sewing machine as shown in FIG. Move the knife 7 back and forth.

The present invention has the above configuration, and its operation will be explained next.

First, when the adjustment knob 20 is rotated and the tip 19 is placed in an appropriate position as shown in FIG.
Via the connecting rod 21 the shaft 14 of the adjustment link 10 is maintained in position.

When the sewing machine is driven from this state, a double chain stitch is formed by the cooperation of the needle and the looper, and as is well known, the eccentric cam 25 moves the vertical rod 23 up and down to move the fork link 13 to the shaft 14. Swings to the center.

This swinging of the two-pronged link 13 imparts movement in the horizontal direction to the connecting link 28 via the shaft 29, and further swings the horizontal feed shaft 26 via the arm 27.

The swing of the horizontal feed shaft 26 (not shown) imparts a horizontal movement to the cloth feed tooth, and in cooperation with the swing of another well-known vertical feed shaft (not shown), the cloth feed dog is moved four times to feed the cloth in the forward direction. As a result, a double chain seam with a pitch P1 shown in FIG. 2 is formed on the cloth.

When the fabric is fed and the trailing edge 40 of the fabric 39 passes the sensor 38, a fabric edge detection signal is generated, which causes the pitch P1 to reach point B during the time t1 in FIG. 2 set by the sewing end position timer T1. Form a seam.

When point B is reached, an output signal from the sewing end position timer T1 is generated, which activates the solenoid valve to lower the rod 37 of the air cylinder 35 in FIG. 1 by a predetermined distance determined by a stopper (not shown). .

This lowering causes the connecting arm 31 to rotate clockwise against the spring 34 via the feed converting lever 32 and the feed converting shaft 30, and the first The feed adjuster 15 shown in FIG. 4 is rotated counterclockwise about the shaft 16.

The rotating position of the feed adjuster 15 defined by the air cylinder 35 is the position indicated by the two-dot chain line in FIG. is maintained opposite the tip 19 of the adjustment knob 15, therefore, the cloth feed direction is the positive direction and the cloth feed amount is a pitch P2 smaller than the pitch P1 shown in FIG.
t in Fig. 2 determined by the stitch reduction timer T2.
2. Form a reduction seam in the fabric.

Next, when the signal from the stitch reduction timer disappears at point 0 in FIG. The slope 17a of the feed adjuster 15 is returned to the original position indicated by the solid line in FIG. 4 via the rod 21, and the cloth feed amount is returned to the state of P1.

When the time t3 shown in FIG. 2 required for the air cylinder 35 to recover has elapsed, an output signal is generated from the timer T3 shown in FIG. When the needle moves and the sewing machine needle approaches top dead center, the needle up position signal generated causes the sewing machine to stop at needle top dead center, and the looper thread and needle thread become as shown in Figure 6. The distance between the cloth side thread TC and the needle side thread TN of the needle thread applied to the looper 4 is wider than when the pitch of the cloth feed amount shown in FIG. 5 is P2.

Thereafter, the movable knife 7 shown in FIG. 1 moves forward and intersects the looper thread and the cloth side thread TC shown in FIG. disconnect between.

As described above, this invention feeds the fabric after the needle comes out of the fabric, stops the sewing machine near the top dead center of the needle, and removes the looper thread connected to the fabric and the needle thread loop caught on the looper from the bottom of the throat plate. In a double chainstitch sewing machine that has a thread cutting mechanism that moves back and forth to cut the thread, the fabric feed is adjusted so that the fabric feed amount immediately before stopping the sewing machine to cut the thread is larger than the fabric feed amount before that. By converting, the looper thread to be cut and the fabric side thread TC are separated from the needle side thread TN of the needle thread on the looper 4 when the sewing machine is stopped, so the cut thread can be captured by the moving knife. This has the effect of reliably cutting the specified thread, and also prevents the thread from being removed from the needle at the start of the next sewing, which is caused by cutting both the fabric side thread TC and needle side thread TN. There are no problems such as the formation of stitches, the sewing work is stable, and there is no need to stop the sewing machine or thread the thread in order to fix a loose thread, which improves work efficiency.

In the above embodiment, as shown in Fig. 2, a stitch is formed at a large pitch P1, a reduced stitch is formed at a small pitch P2 near the rear end of the cloth, and then the sewing machine is stopped at a large pitch P1. I showed you what to do to cut the thread, but the seventh
A similar effect can be obtained by continuously forming stitches at a small pitch P2 as shown in the figure, and then setting the stitches at a large pitch P1 when the sewing machine stops for thread trimming.

This embodiment is shown in FIG. 8, in which the feed regulator 15 is similar to that of FIG. 1, with the spring 34 being mounted directly on the feed regulator 15 for convenience.

The lever 41 is rotatably provided at the center by a vertical step screw 42, and on the left side thereof is a positive slope 17 of the feed adjuster 15.
A cam portion 43 is formed facing the step screw 42 and has gradually different distances from the center axis of the stepped screw 42, and a forked portion 44 is formed at the right end of the lever 41.

45 is an air cylinder whose base is fixed to the machine frame, and the tip of the rod 46 is connected to the lever 41 via a pin 47.
It is connected to the forked part 44 of.

In the state shown in FIG. 8, the air cylinder 450 rod 46 is protruding, and in this state, the feed regulator 1
The needle surface 17a in the normal feed direction of No. 5 is the cam portion 43 of the lever 41.
If the sewing machine is operated in this state, the 7th
Stitches are formed at the small pitch P2 shown in the figure.

Then, when the air cylinder 45 acts at the same timing as when the air cylinder 35 is inactive in the embodiment described above and the rod 46 moves a predetermined distance to the right, the lever 41 rotates counterclockwise around the step screw 42. The cam part 4
The small diameter portion of No. 3 faces the forward slope 17a of the feed adjuster 15.

As a result, the feed adjuster 15 rotates clockwise following the outer peripheral displacement of the cam portion 33 due to the force acting on the spring 340, the cloth feed amount increases to the pitch P1, and the stitching thread is in the state shown in FIG. Then, the thread cutting mechanism is activated to cut the thread.

Further, the same effect can be obtained by using a mechanism for holding the cloth and moving it in the X and Y directions by changing the feed using the feed dog of the sewing machine, as in the above-mentioned embodiment.

Furthermore, each timer in FIG. 3 can be replaced with a counter for counting stitches.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view of the sewing machine mechanism, Fig. 2 is a plan view showing the reduced stitch at the end of the cloth, Fig. 3 is a block diagram of the control circuit, Fig. 4 is a side view of the feed adjuster, Fig. 5 is a state diagram showing the state of the thread when the sewing machine is stopped when the amount of fabric feed is small, and Fig. 6 is a state diagram similar to Fig. 5 when the amount of fabric feed is large.
FIG. 7 is a plan view showing a seam at the end of the cloth in another embodiment, and FIG. 8 is a perspective view showing a feed adjustment control mechanism for forming the seam shown in FIG.

Claims (1)

[Claims] 1. After the needle comes out of the fabric, feed the fabric and stop the sewing machine near the top dead center of the needle to separate the looper thread connected to the fabric and the fabric side thread of the needle thread loop caught on the looper. In a double-stitch sewing machine that has a thread cutting mechanism that moves reciprocatingly under the throat plate to cut the thread, the fabric feed amount just before stopping the sewing machine to cut the thread is made larger than the previous fabric feed amount. The sewing machine's cloth feed method to convert the cloth feed to .