JPH1066797A - Thread cutting device of sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit a thread cutting device to become maintenance-free by eliminating a mechanism for retreating bobbin thread when cutting only needle thread, for a reduction in the number of part items, and eliminating the need for timing adjustment, etc. SOLUTION: This thread cutting device, which includes a fixed knife 42 and a movable knife 36 rotation moving back and forth in response to power from a predetermined drive source (pulse motor) 58, and which cuts a thread by capturing using the movable knife 36 the thread to be cut and moving it to a position where it crosses the fixed knife 24, is designed so that the angle of rotation of the movable knife 36 caused by the drive source 58 can be different when both needle and bobbin threads are cut and when only the needle thread is cut, so that when only the needle thread is cut, the rotation angle of the movable knife 36 is regulated to the range in which the bobbin thread is not captured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting device for a sewing machine in which a selection of cutting both an upper thread and a lower thread and cutting only an upper thread is planned.

[0002]

2. Description of the Related Art As a thread cutting device for a sewing machine of this type,
For example, a technique disclosed in Japanese Patent Application Laid-Open No. 8-38773 is known. This technique includes a thread cutting mechanism including a fixed knife and a movable knife, and a drive source such as a motor that applies a driving force to the movable knife, and also includes a lower thread retracting mechanism. In other words, this retraction mechanism is not operated when cutting both the upper thread and the lower thread, but is activated when the movable knife drives the lower thread by operating the retraction mechanism when cutting only the upper thread. Have been evacuated.

[0003]

However, the retracting mechanism has a lever member for hooking and retracting a lower thread.
A driving source such as a solenoid, an interlocking mechanism for transmitting power from the driving source to the lever member, and the like.
The number of components for configuring the thread cutting device of the sewing machine increases. Further, maintenance such as adjusting the operation timing of the thread trimming mechanism and the lower thread retracting mechanism is required.

An object of the present invention is to eliminate the mechanism for retracting the lower thread when cutting only the upper thread, reduce the number of parts, and eliminate the need for timing adjustments, thereby enabling maintenance-free operation. is there.

[0005]

According to the first aspect of the present invention,
It has a fixed knife and a movable knife that reciprocates and rotates upon receiving power from a predetermined drive source. The movable knife captures the yarn to be cut and moves it to a position that intersects with the fixed knife to cut the yarn. A thread cutting device, wherein a rotation angle of the movable knife by the drive source can be changed between a time when both the upper thread and the lower thread are cut and a time when only the upper thread is cut; When cutting only the movable knife, the turning angle of the movable knife is restricted to a range in which the lower thread is not caught.

According to the present invention, by changing the rotation angle of the movable knife, it is possible to select between cutting both the upper thread and the lower thread or cutting only the upper thread. The mechanism can be abolished. As a result, the number of components as the yarn cutting device is reduced, and maintenance-free operation becomes possible.

According to a second aspect of the present invention, in the sewing machine thread cutting device according to the first aspect, the rotation angle of the movable knife is changed by controlling a driving amount of a driving source thereof. And By controlling the driving amount of the drive source of the movable knife in this manner, it is easy to change the rotation angle of the movable knife when cutting both the upper thread and the lower thread and when cutting only the upper thread. , And accurately.

[0008]

Embodiments of the present invention will be described below. FIG. 1 is a plan view showing a thread cutting device of the sewing machine, and FIG.
FIG. 2 is a front view showing a thread cutting device of the sewing machine. As shown in these drawings, the needle plate 1
4 is fixed, and below the needle plate 14, a shuttle 12 is provided. The shuttle 12 is driven to rotate in a known manner in conjunction with the rotation of the shuttle drive shaft 16.

The pot base 10 is provided with the pot 12 and the needle plate 1.
4, a thread cutting mechanism 20 is provided. 3 is a disassembled perspective view of the thread cutting mechanism 20, and FIG. 4 is a partially enlarged view of FIG.
A fixed knife 24 and a movable knife 36 are provided for the knife table 22 fixed to the pot base 10, respectively. The fixed knife 24 has a thread holding spring 28 on its lower surface and a thread protector 30 on its upper surface, and is provided with two mounting holes 26, 29, 32 and screws 34, each of which is individually formed. Each is fixed to the knife table 22. The distal end of the fixed knife 24 is a blade 25 having a sharp cross section.

The movable knife 36 includes a thread cutting member 36A and a thread dividing member 36B. A vertical knife shaft 47 is rotatably supported on the knife table 22. The movable knife 36 has a thread cutting member 36A.
With the thread dividing member 36B disposed on the lower surface of the female shaft 4, the female shaft 4
7 is fixed to the upper end. This female shaft 47 is
As shown in FIGS. 1 and 2, the drive shaft 48 disposed below the hook base 10 is reciprocally slid and connected via a link 49 so as to reciprocate around the axis. The thread cutting member 36A has a blade portion 39 at the tip end thereof, and the thread splitting member 36B has a thread catching portion 44 formed.

As shown in FIGS. 1 and 2, a picker 50 (a thread hook) is attached to the hook
It is attached so that it can rotate from the position shown in FIG. That is, the base end of the picker 50 is fixed to a shaft 53 rotatably supported on the side wall of the pot base 10 as shown in FIG. 2, and this shaft 53 is mounted on the outer surface of the side wall of the pot base 10. The linear solenoid 52 is connected through a link to the plunger.

The picker 50 receives a predetermined spring force and is normally held at a pivot position in which the forked portion 51 is separated from the front surface of the shuttle 12 as shown in FIGS. Then, when the linear solenoid 52 is turned on,
The picker 50 rotates against the above-mentioned spring force, and the forked portion 51 reaches the upper front surface of the bobbin 13 in the shuttle 12 as shown in FIG.

Next, a knife driving device 54 for applying a driving force to the movable knife 36 will be described with reference to FIGS.
First, a pulse motor 58 which is a driving source of the knife driving device 54 is attached to a base 56 of the knife driving device 54. An interlocking shaft 64 disposed in parallel with the output shaft 60 of the pulse motor 58 is rotatably supported on the base 56. A drive gear 62 is fixed to an output shaft 60 of the pulse motor 58,
A driven gear 66 meshed with the drive gear 62 is fixed to the interlocking shaft 64. A pin 67 is fixed to the front end surface of the driven gear 66.

On the front side of the driven gear 66, the base 5
Slide shaft 68 slidably supported with respect to
Is arranged coaxially with a drive shaft 48 of the movable knife 36 and is coupled to the drive shaft 48. A block 70 is fixed on the axis of the slide shaft 68, and a pin 71 is fixed on a side of the block 70 facing the driven gear 66. The pin 71 of this block 70
And a pin 67 of the driven gear 66 are connected by a link member 72. Therefore, the pulse motor 5
When the driven gear 66 is reciprocally rotated by the drive control of FIG.

The thread cutting mechanism 20 includes a knife driving device 54
By controlling the driving amount of the pulse motor 58, which is the driving source of the above, the rotation angle of the movable knife 36 can be changed between when cutting both the upper thread and the lower thread and when cutting only the upper thread. It has become. That is, the end position when the movable knife 36 is moved forward (separating operation) is set to the imaginary line A1 in FIG. 4 when cutting both the upper thread and the lower thread, and in FIG. Virtual line A2.

Next, the operation of the yarn cutting device configured as described above will be described. First, FIG. 6 shows a state in which the shuttle 12 has captured the upper thread by its point and has been rotated substantially 180 °. As shown in this drawing, the upper thread T1 is separated into a cloth-side upper thread T1a and a needle-side upper thread T1b at the upper part of the shuttle 12 with respect to the front-rear direction.
Reference numeral 2 stands up toward a needle hole (not shown) of the needle plate 14. Here, the upper thread T1a on the cloth side is changed to the upper thread T1b on the needle side.
6 is located on the left side of FIG. 6 for the following reason.

That is, the rotation of the picker 50 is controlled as described above prior to the start of the forward movement of the movable knife 36,
The forked portion 51 of the picker 50 approaches the upper front surface of the bobbin 13 as described above. Therefore, as shown in FIG. 5, the upper thread T1a on the cloth side is
And is located on the left side of the needle-side upper thread T1b. FIG. 5 shows a state in which the shuttle 12 has been rotated substantially once (360 °).

A description will now be given of the case where only the upper thread T1 is cut. FIG. 7 shows a state immediately after the movable knife 36 has begun to move forward.
The thread dividing member 36B of No. 6 has entered between the cloth-side upper thread T1a and the needle-side upper thread T1b, and the thread dividing of the upper thread T1 has started. The end position of the forward movement of the movable knife 36 at this time is shown in FIG. 8 (corresponding to the imaginary line A2 in FIG. 4). In the forward movement amount (rotation angle) of the movable knife 36 at this time,
The lower thread T2 remains in contact with the arc-shaped leading edge of the thread dividing member 36B and does not come off from the thread dividing member 36B (FIG. 8).

When the movable knife 36 starts moving backward from the position shown in FIG. 8 to the original position shown in FIGS. 4 and 6, FIG.
As shown in the figure, the yarn catching portion 44 of the yarn dividing member 36B
Only the upper thread T1a on the cloth side is captured by the
It is carried towards. The blade 39 of the thread cutting member 36A in the movable knife 36 is
And crosses the cloth, the upper thread T1a on the cloth side is cut. When the movable knife 36 is rotated to the original position shown in FIGS. 4 and 6, the upper thread T1a on the cut cloth side is cut.
Is held between the distal end of the thread holding spring 28 and the lower surface of the thread dividing member 36B in a state suitable for the next sewing start.

Next, a case where both the upper thread T1 and the lower thread T2 are cut will be described. Also in this case, the movable knife 3
6 reaches the end position of the forward movement shown in FIG. 10 (corresponding to the imaginary line A1 in FIG. 4) after the thread splitting of the upper thread T1 by the thread splitting member 36B. At this time, the lower thread T2 is out of the arc-shaped leading edge of the thread dividing member 36B, and when the movable knife 36 starts the backward movement as described above, the thread of the thread dividing member 36B as shown in FIG. The upper thread T1a and the lower thread T2 on the cloth side are both captured by the capturing section 44 and carried toward the fixed knife 24.

Therefore, the blade 39 of the thread cutting member 36A of the movable knife 36 is fixed to the blade 25 of the fixed knife 24.
, Both the upper thread T1a and the lower thread T2 on the cloth side are cut. Also in this case, when the movable knife 36 rotates to the original position shown in FIGS. 4 and 6, the upper thread T1a and the lower thread T1 on the cut cloth side are cut.
2 are held between the tip of the thread holding spring 28 and the lower surface of the thread splitting member 36B.

In this manner, the driving of the pulse motor 58 in the knife driving device 54 is controlled to
Of the upper thread T1 (the upper thread T1a on the cloth side) and the lower thread T2, or only the upper thread T1 can be selected without employing a special mechanism by changing the rotation angle of the upper thread T1. Becomes As a result, the number of components of the yarn cutting device can be reduced, and operations such as timing adjustment are not required.

The means for changing the turning angle of the movable knife 36 can be easily set by controlling the driving amount of a pulse motor 58 which is a driving source of the knife driving device 54. Accuracy will be higher, but other means,
For example, a configuration in which two types of driven gears having different numbers of teeth are selectively engaged with the drive gear 62 shown in FIGS.

[Brief description of the drawings]

FIG. 1 is a plan view showing a thread cutting device of a sewing machine.

FIG. 2 is a front view showing a thread cutting device of the sewing machine.

FIG. 3 is an exploded perspective view showing a thread cutting mechanism.

FIG. 4 is an enlarged plan view showing a part of FIG. 1;

FIG. 5 is an enlarged view of the shuttle seen from the front.

FIG. 6 is a plan view showing the thread cutting mechanism in a state where the shuttle has been rotated by approximately 180 °.

FIG. 7 is a plan view showing the thread cutting mechanism immediately after the movable knife starts moving forward.

FIG. 8 is a plan view showing the end position of the forward movement of the movable knife when cutting only the upper thread.

FIG. 9 is a plan view showing a movable state of the movable knife when only the upper thread is cut.

FIG. 10 is a plan view showing the end position of the forward movement of the movable knife when cutting both the upper thread and the lower thread.

FIG. 11 is a plan view showing a returning state of the movable knife when cutting both the upper thread and the lower thread.

[Explanation of symbols]

 24 Fixed knife 36 Movable knife 54 Knife drive 58 Pulse motor (drive source) T1 Upper thread T1a Upper thread on fabric side T1b Upper thread on needle side T2 Lower thread

Claims (2)

[Claims] 1. A fixed knife and a movable knife reciprocatingly rotated by receiving a power from a predetermined driving source, wherein the movable knife captures a thread to be cut and moves to a position intersecting with the fixed knife. A thread cutting device for a sewing machine that cuts a thread by rotating the movable knife by the driving source.
When both the upper thread and the lower thread are cut and when only the upper thread is cut, it can be changed, and when cutting only the upper thread, the rotation angle of the movable knife is set in a range where the lower thread is not captured. A thread cutting device for a sewing machine, characterized in that it is regulated to 2. The thread cutting device for a sewing machine according to claim 1, wherein the rotation angle of said movable knife is changed by controlling a driving amount of a driving source thereof. apparatus.