JPS5951838B2 - Needle thread unwinding device for sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an upper thread unwinding device for a sewing machine that operates during thread cutting by a thread cutting means that cuts off an upper thread continuous between a needle and a cloth to unwind the upper thread from a thread supply source. It is related to the device.

Conventionally, in a cycle sewing machine such as a bar tack sewing machine, after the -cycle sewing is completed, the needle bar is stopped at an upper stop position in which the needle tip is raised upward from the fabric, and the needle bar is stopped at the top stop position where the needle tip is raised upward from the fabric, so that there is no space between the top surface of the fabric and the needle. Since the continuous needle thread is cut, the needle thread protruding from the threading hole of the needle becomes shorter after cutting the needle thread, and when the next sewing starts, the upper and lower needle threads of the needle bar are cut. Because the timing of the up and down movement of the thread take-up is slightly delayed relative to the movement of the needle, when the needle bar descends from the top dead center, the vertical distance between the thread take-up and the threading hole of the needle increases. The needle thread, which is under tension on the side of the needle thread supply source rather than the threading hole, will come out of the threading hole of the needle when the needle descends, so to prevent this, tension is applied to the needle thread. An engaging body that can be engaged is provided, and before cutting the needle thread, the engaging body is engaged with the needle thread in advance to feed the needle thread from the thread supply source to the needle side.

However, in the conventional device described above, the engagement between the engaging body and the needle thread is released in the needle thread path from the thread take-up to the needle after the needle thread is let out. This resulted in some shortcomings.

In other words, the upper thread is bent or twisted as it is sent through the thread tension device and thread take-up, giving it a heft. When a large synthetic thread is used as the needle thread, when the engagement between the engaging body and the needle thread is released after the needle thread is let out, the needle thread returns and comes out from the needle. , is the drawback?
there were.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks with a simple configuration.

Hereinafter, the present invention will be described in detail with reference to the drawings.Although not shown, this sewing machine feeds the cloth W so as to form a stitch of a predetermined shape to a needle N that moves up and down at a fixed position while sandwiching the cloth W. This is a known cycle sewing machine having a cycle drive mechanism in which the needle N automatically stops at a predetermined position above the cloth W just before the top dead center after forming the stitch.

The needle bar 1 is supported on the jaw machine frame of the sewing machine so as to move up and down in conjunction with a main shaft (not shown), and has a needle bar thread guide formed with a guide hole 2a through which a needle N and upper thread S can be inserted. 2 and is supported at the lower end.

The balance 3 is of a circumferential type that moves up and down at a predetermined phase with respect to the needle bar 1 in conjunction with the main shaft.

The thread tension device 4 is a well-known device that has a tension plate and a thread take-up spring and applies a certain tension to the upper thread.

Thread guide 5 (i', needle bar thread guide guide hole 2a from thread take-up 3
This is for guiding the upper thread S.

The air cylinder 7 is supported at the tip of a support rod 6 fixed to the lower part of the front end of the sewing machine's jaw, and the rod 7h of the air cylinder 7 is placed in the non-working position (wooden line in Figure 1) and the working position (two points in Figure 1). It is always held in the non-active position by elastic force and moves from the active position of the air cylinder 7 to the working position.

At the end of the rod 7a, the thread shaft supports a body 8 rotatably around the shaft edge of the rod 7a, and the thread hook is connected to the body 8 by the rod 7a.
The rod 7a has an abbreviated shape consisting of a parallel portion 8a extending along the axial direction of the rod 7a and an engaging portion 8b extending in a direction crossing the axial direction of the rod 7a.

For the thread hook, the needle thread path should pass between the thread take-up lever 3 and the guide hole 2a of the needle bar thread guide 2 in the 8th L length of the body. When 7a is the exit from the position of the solid line to the position of the two-dot chain line, the parallel part 8a of the thread hook body 8 intersects the upper thread S, and the upper thread of the length consumed in one stitch is paid out. Do it like this.

In addition, the support body 6 has elasticity, and the thread hook is attached to the engaging portion 8b of the body 8.
A holding body 9 formed with a bent portion 9a that removably fits and holds the rod 7a of the air cylinder 7 in the direction of the working position is fixed, and when the rod 7a of the air cylinder 7 is in the non-working position, the thread hook is placed in the body. 8 to the horizontal state (the position shown in FIG.
The needle thread path between the thread take-up lever 3 and the needle bar thread guide 2 is fitted into the bent portion 9a of the body 8. When parallel = ts8a and the engaging part 8b are in the standby position where they do not engage the needle thread, and when the rod 7a is brought to the working position by the action of the air cylinder 7, the engaging part 8b of the body 8 is connected to the holder 9. By pulling out the thread from the bent part 9a of
The screws 1 to 1 fixed to the holding body 6 are rotated so as to lower them.
It is held in the lowered position (FIG. 3) by engagement with a knob (not shown).

As will be described later, this lowered position is located at the upper thread S, which is pulled up by the thread take-up when the needle N descends to knot the stitch in the first stitch of the next sewing after three threads are trimmed. The needle thread S is further pulled up by the thread take-up 3 to fit the engaging part 8b into the bent part 9a of the holder 9. It will be raised to the waiting list.

Reference numeral 10 indicates a thermal thread cutting means having a nichrome wire 10a, which is detailed in Japanese Patent Application No. AS55-151181 filed by the present applicant, and is connected to an air cylinder (not shown). After the nichrome wire 10a is energized, the nichrome wire 10a is held between the needle N and the cloth W as shown in FIG. It descends to the thread cutting position where it intersects the continuous upper thread.

Next, the operating circuit of the air cylinder 7 and the air cylinder connected to the thread cutting means will be explained.

In Fig. 6, SW is a switch connected to the drive/cutoff device (not shown) for the main shaft of the sewing machine, and is attached to the machine frame so that it is always off and turned on when the main shaft of the sewing machine is cut off. Place related.

One terminal of the switch SW is grounded, and a positive voltage Vc is applied to the other terminal via a resistor R1, and the base of the transistor TRI is connected via a resistor R2.

The emitter of the transistor TRI is grounded, and a positive voltage Vc is applied to the collector through the resistor R3. When the switch SW is turned on, the transistor TR1 is turned off, and the switch S
The configuration is such that the transistor TRI is turned on when W is turned off.

MSI and MS2 are one-shot multivibrators (hereinafter referred to as one-shot), and the one-shot MSI is triggered by the change of the transistor TR1 from on to off, and outputs an H level signal for a predetermined time T1.

The one-shot MS2 is triggered by the fall of the output of the one-shot MSI and outputs an H level signal for a predetermined time T2.

The transistor TR2 is connected to the air valve of the air cylinder 7, and the solenoid SQ opens the air valve when turned on.
This is to turn on and off L1, and a positive voltage Vc is applied to the collector through the coil of solenoid SQL1 and its flywheeling diode D1, and the emitter is grounded, so that the output of the one-shot MSI is high. Depending on the level, current flows through the amplifier A1 to the base, turning on the transistor TR2.

The transistor TR3 is connected to an air valve of an air cylinder (not shown) connected to the thread cutting means 10, and is used to turn on and off a solenoid SQL2 which opens the air valve when turned on.
A positive voltage Vc is applied through the L2 coil and its flywheeling diode D2, and the emitter is grounded, and the H level of the one-shot MS2 output causes current to flow to the base via the amplifier 0A2, turning on the transistor TR3. Make it so that

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

Air cylinder 7 is inactive, i.e. its rod 7a is in the first
In the position shown by the solid line in the figure, the thread hook holds the body 8 in the waiting position by manually lifting the body 8 and engaging the bent portion of the holding means 9.

Next, the thread tension device 4, the thread take-up lever 3, the threader 5, and the thread hook are the synthetic fibers with the highest looseness in the order of the parallel part 8a of the body 8, the guide hole 2a of the needle bar thread guide 2, and the threader hole of the needle N. (For example, Tetron (registered trademark) thread) S is inserted and sewing is started.

When one predetermined cycle of sewing is completed, the drive/cutoff device connected to the main shaft performs a cutoff operation, and the needle bar 1
The drawer stops at a predetermined upper position just before the raised top dead center.

When the switch SW (Fig. 5) is turned on due to this cutoff operation, the transistor TRI is turned off, which triggers the one-shot MS1 and its output becomes H level, which turns on the transistor TR2 and connects the solenoid 5QL1. to strengthen

Then, the air valve of the air cylinder 7 is opened and the rod 7
a moves to the working position, and the thread hook body 8 separates from the bending part 9a of the holder 9 and moves together with the rod 7a toward the working position while rotating by its own weight to the lowered position. As shown in Fig. 5), the thread hook engages with the engaging part 8a of the body 8 and is pulled to the left (Fig. 5), and one needle's worth of needle thread is let out, and the needle thread path is directed to the parallel part 8a. bends downward due to

When time T1 elapses and the output of one-shot MSI falls to L level, transistor TRI is turned off and solenoid SQL 1 is deenergized, so air cylinder 7
The air valve of is closed, and the rod 7a returns to the inactive position shown by the solid line in Figure 1, but the thread hook body 8 remains hanging down in the lowered position due to its own weight, so the path of the upper thread S is still
The thread hook remains bent at the parallel part 8a of the body 8, and the thread take-up remains bent at the parallel part 8a of the body 8.
Since tension is applied to the needle thread S passed between the thread hook body 8 and the thread hook body 8, the needle thread S does not loosen and return.

Further, the one-shot MS2 is triggered by the fall of the output of the one-shot MS1 and its output becomes H level, so that the transistor TR3 is turned on, the solenoid 5QL2 is energized, and the output connected to the thread cutting means 10 is turned on. The air cylinder air valve is opened.

As a result, the thread cutting means 10 cuts the nichrome wire 10a into the needle N.
At the same time, the nichrome wire 10a is turned on and the upper thread S is fused and cut by heat.

When time T2 elapses and the output of MS2 falls to the L level, the transistor TR3 is turned off and the air valve of the air cylinder connected to the thread trimming means 10 is closed. Return to position.

When the cloth W is moved and sewing is started again, the needle bar 1 is lowered, but at this time, the guide hole 2a of the needle bar thread guide 2 and the thread hook are connected to the body 8.
Between the air cylinder 7 and the vertical part 8a of the needle N, the needle thread of one stitch length is let out by the thread letting out by the body 8, so the needle thread is pulled out from the needle N. Never.

When the needle N descends to knot the stitch, the upper thread is threaded at body 8.
When the upper thread is pulled up by the rise of the thread take-up lever 3, the thread hook body 8 is pulled upward on the parallel part 8a by the action force (tension) of the upper thread, and the thread hook body 8 is pulled upwards on the parallel part 8a. 9 and is held in the waiting position by engaging with the bent portion 9a, so that no action is exerted on the upper thread path during the subsequent sewing (FIG. 4).

In the above embodiment, the rod 7a supporting the body 8 is moved by an air cylinder, but for example, an electromagnetic solenoid may be used instead of the air cylinder.

Further, in the above embodiment, a thread cutting means using heat rays is used especially for synthetic fiber threads, but the thread cutting means is of course not limited to such a means, as shown in, for example, Japanese Unexamined Patent Application Publication No. 52-118363 filed by the present applicant. A thread cutting device with a scalpel may also be used.

As described above, according to the present invention, the needle bar is stopped at a fixed position after the needle has been removed from the cloth after completing a predetermined sewing process,
In a sewing machine that lets out the needle thread in advance and then cuts the needle thread that runs from the needle to the fabric, the thread hooker places its body on the needle thread path from the thread take-up thread take-up to the needle bar thread guide, and lets out the needle thread. After that, the thread hook moved its body to bend the needle thread path, and the thread hook applied tension to the needle thread from the thread take-up to the body. Even if a thread with a high rebound property is used as the needle thread, the tension is maintained by the tension and the needle thread does not curl back up, so the needle thread will not shrink and come out of the needle.
Work efficiency can be improved since the need to rethread the needle is eliminated.

1 Brief description of the drawings Figure 1 is a perspective view of the front part of the sewing machine, Figure 2 is a diagram with the needle bar stopped at a fixed position after sewing is finished, Figure 3 is a diagram with the thread trimmed after the thread has been let out, Figure 4 is a diagram showing the state in which the thread take-up lever is raised after sewing is restarted, Figure 5 is a diagram showing the operation of taking out the upper thread edge, and Figure 6 is a diagram showing the upper thread edge pulling-out operation.
The figure is a diagram of an operating circuit for opening and closing an air valve of an air cylinder.

1...Needle bar, 10...Thread cutting means, 8
... Thread hook is body, 9... Holding body, 7...
...Operating means, TR1.

TR2, TR3, MSI, MS2...control circuit.

Claims (1)

[Scope of Claims] 1. The needle is fixed at the lower end and has a needle bar thread guide 2 formed with a guide hole 2a through which the needle thread can be inserted between the needle and the thread take-up, and is movable up and down in conjunction with the main shaft. It has a needle bar supported on a frame, and a thread cutting means disposed above the throat plate that cuts the needle thread running between the needle and the fabric by its action, leaving a predetermined length from the needle, and the needle is removed from the fabric. In a sewing machine in which the needle bar is stopped at a predetermined upper position after the needle bar has been raised, and a thread trimming means is activated, the actuating means is installed in the sewing machine frame and is movable horizontally between an activated position and a non-activated position by an electric signal. a holder 9 disposed close to the actuating means and extending vertically and having a bent portion 9a; and an engaging portion 8b having a base rotatably supported on the actuating means and extending in a direction intersecting the moving direction of the actuating means. and a parallel part 8a extending from the tip of the engaging part 8b in the moving direction of the actuating means. When the actuating means moves to the operating position, the engaging portion 8b of the thread hook body 8 separates from the holder 9 and crosses the upper thread S between the thread take-up lever and the needle bar thread guide 2. Then, the needle thread S is let out, and by cutting the needle thread by the thread cutting means, the thread hook body 8 is rotated in one direction around the base by a single fold with its parallel portion 8a in contact with the needle thread,
The parallel part 8a is lifted by the tension of the needle thread when tying the next stitch at the start of sewing and rotates in the opposite direction around the base, and the engaging part 8b engages and locks with the bent part 9a of the holder. An upper thread feeding device for a sewing machine, characterized in that: