JPH06102108B2 - Square stitching method and device in flat stitch sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for sewing a bent portion of a seam when a seam that also serves as a decoration is formed on both front and back surfaces of a cloth by a flat stitch sewing machine. Relates to a method and an apparatus for corner sewing.

[Prior Art] A sewing method for a flat stitch sewing machine that performs the above-described square stitching has been proposed by the applicant of the present application and is disclosed in JP-A-63-186688. The sewing method of the flat stitch sewing machine disclosed herein is such that, when performing square stitching, after temporarily stopping the sewing operation of the sewing machine, the needle plate claw protruding into the needle drop hole is retracted in the direction opposite to the cloth feed direction, The needle plate claw is returned to the needle drop hole immediately after changing the direction of the cloth, and then the sewing operation is started again.

When corner sewing is performed by such a sewing method, the stitches are removed from the needle plate claws by moving the fabric, and then the direction of the fabric is changed. There is an effect that a loose thread is less likely to be generated between the two, the quality is improved, and the work can be simplified.

[Problems to be Solved by the Invention] However, when the needle plate claw is retracted to rotate the fabric as described above, as shown in FIG. 8A, the needle plate claw 101 is provided in the needle drop hole 111a. Needles 112,1 when
When the cloth X is rotated, the needle threads a1 and a2 descending directly below 13 are arranged on one needle side (for example, the needle 11) as shown in FIG. 8B.
3 side). For this reason, JP-A-63-186688
When the presser foot 109 is lowered immediately after the direction of the fabric is changed and the needle plate claw 101 is returned to the needle drop hole 111a, as shown in FIG. 8C, as shown in FIG.
When the thread a11 caught between the needle plate claw 101 and the needle plate claw 101 is generated, then when the needles 112 and 113 are lowered again by starting sewing again, the needle thread a1 is sandwiched between the needle thread a1 and the needle thread a11 as shown in FIG. 8D. There was a problem that it was pulled out by an extra amount. In such a case, when the lower looper 160 is subsequently pulled out, the extraly pulled out thread is not tightened but becomes looped and protrudes from the seam, which significantly impairs the quality of the product. become.

The present invention has been made in view of the above circumstances, and despite the fact that it is possible to rotate the cloth by retracting the needle plate claws, the looped out thread as described above is used. An object of the present invention is to provide a method and apparatus for square stitching in a flat stitch sewing machine that does not form a thread.

[Means for Solving the Problems] In order to achieve the above object, the method of square stitching in a flat stitch sewing machine according to the first aspect of the present invention achieves the above object by stopping a needle at an upper stop position from a normal operation state in which flat stitch sewing is performed on a cloth. Next, the needle plate claw protruding into the needle drop hole of the throat plate is retracted to the fabric feeding side and the presser foot is raised, and then the fabric is swung on the throat plate in a horizontal state with a predetermined angle, and then the presser foot is pressed. It is characterized in that after the foot is lowered to the cloth and the sewing machine is driven by several stitches, the needle plate claw is projected again into the needle drop hole, and then the sewing machine is normally operated.

Another square stitching method for a flat stitch sewing machine according to the second invention is the above first invention, wherein the needle plate claw after driving the sewing machine for a few stitches is re-projected into the needle drop hole.
The needle is temporarily stopped at the upper stop position before the needle plate claw is re-projected.

In order to achieve the above-mentioned object, a corner stitching device in a flat stitch sewing machine according to a third aspect of the present invention has a needle plate claw that can be retracted into a needle drop hole of a needle plate and a claw drive that moves the needle plate claw in a cloth feed direction. The sewing machine includes a mechanism, a rotation detector that detects a rotation state of a main shaft of the sewing machine, and a control unit that controls the pawl drive mechanism based on a detection signal of the rotation detector. When the needle plate claw is retracted from the needle drop hole based on the stop signal and the sewing machine is restarted after this retreat, the needle is detected after the rotation detector detects that the spindle has rotated for a predetermined number of stitches. It is characterized in that the pawl drive mechanism is controlled so that the plate pawl is projected into the needle drop hole.

[Operation] According to the square stitching method in the flat stitch sewing machine of the first invention, the sewing machine is in a state in which the needle plate claw is not returned to the needle drop hole even if each needle thread deviates to one needle side when the cloth is rotated. Even if the needle plate claw is returned to the needle drop hole again by driving the needle for a few stitches, no needle thread will be caught between the needle plate claw and the presser foot. . Therefore, even if the normal operation is performed thereafter, the loop-shaped protruding yarn does not occur.

According to the square stitching method in the flat stitch sewing machine of the second invention, it is possible to return the needle plate claw having a portion wider than the interval between the needles to the needle drop hole.

According to the angle stitching device in the flat stitch sewing machine of the third invention, after the fabric is rotated with the needle plate claw retracted, the rotation detector detects that the sewing machine spindle has rotated by a predetermined number of stitches. When this is detected, the needle plate claw is returned to the needle drop hole, and normal operation can be performed thereafter.

[Embodiment] FIG. 1 is a configuration diagram of a square stitching device in a flat stitch sewing machine of an embodiment. As shown in FIG. 1, this corner stitching device has a needle plate claw 1, which is movable in a direction parallel to the cloth feeding direction,
A claw drive mechanism 2 for driving the needle plate claw 1 is used to control the positions of needles 12, 13 and a presser foot (not shown) which will be described later by operating and to move the needle plate claw 1 in conjunction with these. A knee switch 3 for outputting a start signal, a rotation detector 4 for detecting the rotation of the main shaft of the flat stitch sewing machine, and a corner stitching control means 5 are provided. The corner stitching control means 5 is provided with a claw drive control means 5a, a sewing machine motor control means 5b, and a presser foot control means 5c.

As shown in FIG. 2, the needle plate claw 1 is normally directed to the needle feed hole 11a of the needles 12 and 13 formed in the needle plate 11 with the tip in the cloth feeding direction (arrow A direction in the figure). It is protruding. Further, the rear end side base portion 1a of the needle plate claw 1 passes below the needle plate 11 and extends to the cloth feeding side (arrow B side in the figure). The drive mechanism 2 is connected to the rear end side base 1a. Reference numeral 11b is a guide groove formed on the back side of the needle plate 11 for guiding the needle plate claw 1 in a direction parallel to the cloth feeding direction. Further, 10 is a bed of this sewing machine having the needle plate 11 fitted on the upper surface thereof.

As shown in FIG. 2, the drive mechanism 2 secures the intermediate portion of the drive lever 22 to the rotary shaft 21a of the rotary solenoid 21 and attaches the needle to the cylindrical pin 22a provided on the upper side surface of the drive lever 22. A notch 1aa formed in the base 1a of the plate claw 1 is engaged. A coil spring 23 is wound around the rotary shaft 21a, and the coil plate 23 constantly urges the needle plate claw 1 engaged with the drive lever 22 toward the cloth feeding direction A. . 24a is a stopper, and as shown in FIG. 3A, the protrusion amount of the needle plate claw 1 into the needle drop hole 11a by contacting the drive lever 22 above the fixed portion of the rotating shaft 21a. Are regulated. The drive mechanism 2 energizes the rotary soleoidoid 21 to rotate the rotary shaft.
By rotating 21a against the urging force of the coil spring 23, the needle plate claw 1 can be retracted in the cloth feeding direction B from the needle drop hole 11a, as shown in FIG. 3B. At this time, the stopper 24b comes into contact with the drive lever 22 below the fixed portion of the rotary shaft 21a, thereby restricting the retreat amount of the needle plate claw 1 described above. This needle plate claw 1
As shown in FIG. 3B, the amount of retreat of B is such that at least the tip of this retreat from the needle drop points N ₁ and N ₂ to the cloth feeding side B
Is set to be located at. A fixing lever 25 shown in FIG. 2 is fixed to the tip end of the operating knob 26. This fixing lever 25 is engaged with the base portion 1a of the needle plate claw 1 by operating the operating knob 26, and by doing so, the needle plate claw 1 does not move even when the rotary solenoid 21 is driven. I have to. Reference numeral 27 is a mounting member for mounting the rotary solenoid 21 and the like, and is fixed to the bed 10 by a bolt 28.

Of course, the pawl drive mechanism is not limited to the above-mentioned configuration, and for example, an air cylinder may be used as the drive source instead of the rotary solenoid. When the air cylinder is used as the drive source in this way, the needle plate claw 1 can be driven by only switching a small solenoid valve without the need for the stoppers 24a, 24b and the fixed lever 25 as described above, and therefore, it is simpler. It becomes a simplified nail drive mechanism.

By operating this, the knee switch 3 outputs a start signal necessary for moving the needle stopped at the lower stop position to the upper stop position. As shown in FIG. 1, the start signal is a sewing machine motor control means 5b for controlling the driving of the sewing machine.
When the start signal is input, the sewing machine motor control means 5b drives the sewing machine motor 6 to raise the needles 12, 13 in the lower stop position to the upper stop position. In addition, the sewing machine motor control means 5b thus
When 3 stops at the upper stop position, a lift command signal is output to the presser foot control means 5c to operate the presser mechanism 7, and
A backward movement command signal for the needle plate claw 1 is output to the claw drive control means 5a. Therefore, the presser foot 7 is raised by the presser mechanism 7, and the needle plate claw 1 moves the needle drop hole 11 by the claw drive mechanism 2.
Evacuated from a. In FIG. 2, the presser foot is omitted for convenience sake, and only the presser bar 29 to which the presser foot is attached is shown.

The rotation detector 4 is, for example, a well-known one that is constructed by embedding a magnet in the main shaft of a sewing machine and disposing a Hall element that detects the presence of the magnet around the main shaft, and outputs a hole every time the magnet is detected. The electromotive voltage of the element is used as the rotation detection signal. However, if there is an existing rotation detector 4 for knowing the number of hand movements, it can be used.

When the claw drive control means 5a receives the backward movement command signal from the sewing machine motor control means 5b, the lifter foot starts to move up due to the lift command signal issued from the presser foot control means 5c, and then the rotary foot is moved with a slight time lag. The solenoid 21 is operated to retract the needle plate claw 1 from the needle drop hole 11a. Further, the claw drive control means 5a drives the sewing machine with the needle plate claw 1 retracted from the needle drop hole 11a, so that the rotation detector 4 has several stitches, specifically, 1 to 3 stitches. When it is detected that the main shaft has rotated, the claw driving mechanism 2 is controlled based on the rotation detection signal so that the needle plate claw 1 again projects into the needle drop hole 11a.

Hereinafter, the method of square stitching in the flat stitch sewing machine of the present invention using the above-described square stitching device will be described with reference to the timing chart shown in FIG. In this embodiment, the sewing machine is driven by depressing the pedal.

First, at time t ₀ , the pedal is stepped forward from the neutral state. As a result, the motor of the sewing machine is rotated, and the normal flat stitch is performed on the cloth X. This flat stitching is performed until time t ₁ when the motor is stopped by returning the pedal to the neutral position, whereby a straight or gently curved stitch S ₁ as shown in FIG. 5A is formed.

When this flat stitch sewing machine is provided with a cutting device for the upper decorative thread, in order to loosen the thread prior to cutting, in general, when the motor is stopped, the needles 12 and 13 are stopped at a lower stop position below the needle plate 11. Has been Therefore, in order to make the cloth X rotatable, at the time t ₂ after stopping the motor, the needles 12, 13
Is moved to the upper stop position above the cloth X, and at the time t ₃ when this movement ends, the presser foot holding the cloth is raised. The movement of the needles 12 and 13 from the lower stop point to the upper stop point and the lifting of the presser foot can be started by the operator operating the knee switch 3, and These operations stop when the operation is canceled. However, the movement of the needles 12 and 13 and the lifting of the presser foot may be performed at a different timing from the above-mentioned case, for example.

In order to enable the rotation of the cloth X, in addition to raising the needles 12 and 13 and the presser foot as described above, it is necessary to remove the needle plate claw 1 from the stitch S ₁ . For this reason, there is a slight time lag after the presser foot starts to rise, for example, at time t after 100 msec.
_{In 4} , the needle plate claw 1 is retracted from the needle drop hole 11a toward the cloth feeding side, whereby the needle plate claw 1 is pulled out from the stitch S ₁ . Then, after pulling out, as shown in FIG. 5B, the cloth X is rotated by a desired angle around the bent portion of the seam.

Next, at time t ₅ after rotating the cloth X, the operation on the knee switch 3 is released, the presser foot is lowered, and the cloth X is sandwiched between the cloth and the needle plate 11. Then, at time t ₆ , the pedal is stepped forward again to drive the sewing machine with the needle plate pawl 1 retracted from the needle drop hole 11a.

In this way, when the sewing machine is driven with the needle plate claw 1 retracted, the rotation detector 4 detects the number of rotations of the driven spindle, thereby detecting the needle movement needle. Then, the number of hand movements is a predetermined number, specifically 1 to 3
When the needle is reached (time t ₇ ), the hand movement operation is temporarily stopped. Therefore, as shown in FIG. 5B, a few stitches S ₂ are formed in the bent portion of the stitch without the needle plate claw 1. In the timing chart of FIG. 4, the needle
It is designed to automatically stop 12, 13 at the upper stop position,
This back to the time t ₈ after the automatic stop of the pedal in neutral and stops driving of the sewing machine as.

Then, after a predetermined time since the driving of the sewing machine is stopped, to return, for example, in the time t ₉ after 40msec from the retracted state described above the needle plate nail 1 to the original position within the needle落孔11a.

After returning the throat plate claw 1 to the original position in this way, the sewing machine is driven by depressing the pedal again forward at time t _10, and then the normal flat stitching is performed.
As shown in FIG. 5C, a straight line or a seam S ₃ close thereto is formed.

In FIGS. 5A to 5C, N ₁ and N ₂ are needle drop holes 11a.
The needle drop portions are located on both sides of the needle plate claw 1 that protrudes in the direction.

When the corner stitching is performed by the above method, the cloth X is turned between the time t ₄ and the time t ₅ , whereby the needle threads a1 and a2 are twisted as shown in FIG. be gone biased below the needle, the number stitches of sewing operation in a state of retracting the needle plate claw 1 performed between time t ₇ from the time t _6, the needle thread a1 which has offset the fabric X tightening To be That is, when the above is done, when the needles 12 and 13 are lowered by the sewing operation of several stitches,
Since the twisted needle thread a1 is not caught between the needle plate claw 1 and the presser foot 8 as shown in FIG. 8C, it can be pulled out almost redundantly as shown in FIG. 6A. Without, first
As shown in FIG. 6B, when the looper 60 is pulled out, it is fastened to the cloth X. Therefore, even if the needle plate claw 1 at time t ₉ is been restored to the needle落孔11a, the needle thread is not present, which is sandwiched between the needle plate claw 1 and the presser foot was lowered earlier,
After the usual flat sewing of time t ₁₀ later, yarn squeeze-out of the loop is not generated by the thread loose.

By the way, as in the above-mentioned corner stitching method, the needle is automatically stopped at the upper stop position at time t ₇ , and then the needle plate claw is returned to the needle drop hole at time t ₉ . Even in the case of the needle plate claw 1'where the tips are thicker than the distance between the needles as shown in FIG. 7, it is possible to return to the original position in the needle drop hole 11a without any problem.

However, when the needle plate claw is not in the shape of a thick tip as shown in FIG. 7 but is in a general shape in which the width of any part is narrower than the distance between the needles, the timing chart shown in FIG. as described above, it may not be performed once stops the driving of the sewing machine in the automatic stop and time t ₈ at the stop position over the needle at time t _7. That is, such a case, if termination is hand movement of several needles in a state where the needle plate claw 1 is retracted at time t _7, it is returned to the original needle落孔11a remains needle plate nail 1 was driven sewing machine You can

By the way, when performing the square stitch as described above, when the needle plate claw 1 '(or 1) is retracted from the inside of the needle drop hole 11a as shown by the alternate long and short dash line in FIG. It is preferable that the movement of the yarn can be prevented so that the yarn does not move to the front side apart from the falling portions N ₁ and N ₂ . This is because, when the needle plate claw 1 '(1) is retracted, the both sides of the needle plate claw 1' (1) are brought into close contact with the needle plate 11, or the lower side of the passage of the needle plate claw 1 '(1). This is realized by forming a needle plate 11 and a constant yarn movement blocking portion on the. With this arrangement, the so-called skipping which prevents the stitches from being formed at the time of forming the next stitch does not occur due to the movement of the thread.

Although the above description has been made using the two-needle, flat stitch, sewing machine, it goes without saying that the present invention can also be applied to a multi-needle, flat stitch, sewing machine having three or more needles. Further, for example, in the case of three needles, the two needle plate claws arranged in parallel may be driven integrally or separately.

[Effect of the invention] According to the first aspect of the present invention, when performing square stitching in a flat stitch sewing machine, the sewing machine is driven by a few stitches while the needle plate claw is retracted. In addition to the advantage that the complexity of work such as removing the stitches is eliminated and that the fabric can be rotated without moving the position of the end of the stitch, the needle thread twisted during the rotation of the fabric causes a loop-shaped loop. It is also possible to eliminate the formation of the squeeze-out yarn and improve the quality of the product.

According to the second aspect, even in the case of the flat stitch sewing machine using the needle plate claw that cannot return to the needle drop hole when the needle is stopped at the lower stop position, the same effect as that of the first aspect can be obtained. be able to.

According to the third aspect, the needle plate claw can be retracted to rotate the cloth, and the needle plate claw can be returned to the original position after the twisted thread is tightened by this rotation. It is possible to produce a high-quality product in which no lumps or run-out yarns on loops are generated.

[Brief description of drawings]

FIG. 1 is a block diagram of a corner stitching device in a flat stitch sewing machine of an embodiment, and FIG. 2 is a perspective view of the same main portion, FIGS. 3A and 3B.
Fig. 4 is an explanatory view showing the operating state of the needle plate claw, Fig. 4 is a timing chart diagram of a square stitching method in a flat stitch sewing machine,
5A to 5C are explanatory views showing a process of square stitching by a flat stitch sewing machine, FIGS. 6A and 6B are schematic cross-sectional views of main parts for explaining a state of needle thread at the time of square stitching, and FIG. 7 is FIGS. 8A to 8D are plan views showing modified examples of the needle plate claws, and FIGS. 8A to 8D are schematic sectional views for explaining the state of the needle thread at the time of corner sewing by the conventional method. DESCRIPTION OF SYMBOLS 1 ... Needle plate claw 2 ... Claw drive mechanism 4 ... Rotation detector 5a ... Claw drive control means (control means) 8 ... Presser foot, 11a ... Needle drop hole 12, 13 ... Needle

Claims (3)

[Claims] 1. A normal operating state in which flat stitching is performed on fabric, a needle is stopped at an upper stop position, and then a needle plate claw protruding into a needle drop hole of the needle plate is retracted to the fabric feeding side and a presser foot is also provided. , And then the fabric is rotated on the needle plate at a predetermined angle in a horizontal state with the needle plate, and then the presser foot is lowered onto the fabric to drive the sewing machine for a few stitches, and then the needle plate claw is needled. A square stitching method in a flat stitch sewing machine, characterized in that the sewing machine is made to project again into the hole and then the sewing machine is normally operated. 2. When the sewing machine is driven by several stitches and then the needle plate claw is projected into the needle drop hole again, the needle is temporarily stopped at the upper stop position before the needle plate claw is re-projected. A square stitching method in a flat stitch sewing machine characterized by the above. 3. A needle plate claw capable of appearing and retracting in a needle drop hole of a needle plate, a claw driving mechanism for moving the needle plate claw in a cloth feeding direction, and a rotation detector for detecting a rotation state of a main shaft of the sewing machine. A control means for controlling the pawl drive mechanism based on a detection signal of the rotation detector, the control means retracting the needle plate pawl from the needle drop hole based on a rotation stop signal of the sewing machine, and When the sewing machine is restarted after this withdrawal, the pawl drive mechanism is controlled so as to project the needle plate pawl into the needle drop hole after it is detected by the rotation detector that the main shaft has rotated by a predetermined number of stitches. A corner stitching device in a flat stitch sewing machine characterized by the above.