JPH08168584A - Thread cutter for sewing machine - Google Patents

Abstract

PURPOSE: To provide a thread cutter for a sewing machine with which the durability of a blade can be satisfactorily improved. CONSTITUTION: Upper and lower threads fed out of a shuttle 11 are held at any positions so as to be abutted to a blade top 13a of a cylindrical blade 13 and when a motor 21 and a first solenoid 27 are electrified in such a state, the cylindrical blade 13 is moved forward while being rotated. Then, that blade top 13a is continuously rotated in the lengthwise direction of the blade while being abutted to the upper and lower threads. With this operation, the upper and lower threads are cut.

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 of a sewing machine which cuts a thread arranged between a needle hole and a shuttle.

[0002]

2. Description of the Related Art Conventionally, as this type of device, for example, one shown in FIG. 4 has been considered. That is, the thread trimming device 51 of FIG. 4 has a fixed blade 55 fixed to a sewing machine frame (not shown) above the shuttle 53 and a movable blade 57 that moves when a thread cutting signal is generated. All of them are not shown) and are configured as follows. The lower shaft 61, to which the shuttle 53 is fixed at the tip, is provided with a disk-shaped movable blade holder 63 adjacent to the end surface of the shuttle 53 on the side of the lower shaft 61. This movable blade holder 63
Is swingably provided with respect to the lower shaft 61, and the movable blade 57 is fixed to one end thereof. When a thread cutting signal is generated, the rotational force of the lower shaft 61 is transmitted to the movable blade holder 63 via a link mechanism (only part of which is shown) 65. Then, in response to this, the movable blade holder 63 swings to a position where the movable blade 57 opposes the fixed blade 55. Therefore, the upper thread and the lower thread sandwiched between the movable blade 57 and the fixed blade 55 are cut.

[0003]

However, in this type of thread cutting device 51, the positions where the upper thread and the lower thread contact the movable blade 57 and the fixed blade 55 are substantially constant. Moreover, in general, the blade becomes unsharp after being used many times, and the blade edge must be re-sharpened or the blade itself must be replaced. The movable blade 57 and the fixed blade 55 are
Since the cutting is always performed at substantially the same position, only the abutting positions of the upper thread and the lower thread are repeatedly used.
Therefore, the durability of the movable blade 57 and the fixed blade 55 is limited.

Therefore, the present invention has been made for the purpose of providing a thread cutting device for a sewing machine which can improve the durability of the blade.

[0005]

In order to achieve the above object, the invention according to claim 1 is a cylindrical blade having a cylindrical shape surrounding a shuttle and having a cutting edge formed all around the needle hole side end edge. And a moving means for moving the cylindrical blade in the central axis direction between a contact position of the thread arranged between the needle hole and the shuttle and a non-contact position of the thread, A thread cutting device for a sewing machine, comprising: a rotation driving unit that continuously rotates the cylindrical blade about its central axis when at least the cylindrical blade moves to a contact position with the thread. Is the gist.

According to a second aspect of the present invention, when the cylindrical blade moves to the contact position with the yarn, a part of the yarn is contacted with the cylindrical blade and the remaining yarn is retained. A thread cutting device for a sewing machine according to claim 1, characterized in that thread separating means is provided at positions where they cannot contact the cylindrical blade.

According to a third aspect of the present invention, the rotation driving means includes a first gear formed around the cylindrical blade, and the first gear.
A thread cutting device for a sewing machine according to claim 1 or 2, further comprising: a second gear that meshes with the gear, and a rotary actuator that rotates the second gear.

[0008]

In the invention according to claim 1 having such a structure, when the cylindrical blade is moved to the contact position with the yarn by the moving means and is continuously rotated by the rotation driving means, The blade edge contacts the thread, and the blade edge continuously moves with respect to the thread in the blade crossing direction. Therefore, the thread is cut.

Here, the blade tip is formed on the entire circumference of the end edge of the cylindrical blade on the needle hole side, and by the rotation of the cylindrical blade, the blade tip abuts the yarn evenly. Therefore, in the present invention, the durability of the blade can be improved satisfactorily. Therefore, it is possible to reduce the number of times of blade replacement and re-sharpening. When the thread is not cut, the cylindrical blade may be moved to the non-contact position with the thread by the moving means. Then, the blade tip and the thread do not come into contact with each other, and the thread is not cut.

In addition to the configuration of the invention described in claim 1, the invention described in claim 2 further comprises a yarn separating means. When the cylindrical blade moves to the abutting position with the yarn, the yarn separating means positions a part of the yarn at a position where the cylindrical blade can contact the cylindrical blade and the remaining yarn at a position where the cylindrical blade cannot contact the cylindrical blade. , Respectively.
Therefore, the cylindrical blade cuts only the above-mentioned part of the threads and does not cut the remaining threads. That is, in the present invention, in addition to the effect of the invention described in claim 1, the effect that only part of the yarn can be cut is obtained.

If the above-mentioned part of the yarns to be cut are properly set, the following effects can be further obtained. When all the yarns arranged between the needle hole and the shuttle are cut, the yarns forming the loop with the cut surface therebetween become wastes. Therefore,
For example, if only a part of the thread forming the loop is cut, the generation of thread waste can be prevented. Further, if the needle thread disposed between the needle hole and the shuttle is cut away from the needle, the thread remaining on the needle side after the thread cutting operation becomes long. In this case, it is possible to prevent the needle thread from coming off the sewing needle due to the operation of the balance.

According to another aspect of the present invention, the rotation driving means includes a first gear formed around the cylindrical blade, a second gear that meshes with the first gear, and a rotary actuator that rotates the second gear. Is equipped with. What is a rotary actuator?
For example, it can be configured by a motor, an air turbine, or the like. When such a structure is adopted, the structure of the rotation driving means can be integrated in the vicinity of the cylindrical blade, and the structure can be made compact as compared with the conventional link mechanism. Therefore, in the present invention, in addition to the effect of the invention described in claim 1 or 2, the effect that the entire configuration of the thread cutting device can be made compact can be obtained.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration of a thread cutting device 1 of a sewing machine of an embodiment, and FIG. 2 is a sectional view showing a configuration near a lower shaft 19 of the thread cutting device 1 of the sewing machine.

As shown in FIG. 1, a bobbin around which a lower thread 3 is wound can be mounted, and around a well-known shuttle 11 which forms a seam 7 between the lower thread 3 and the upper thread 5, A cylindrical blade 13 having a shape surrounding the shuttle 11 is provided. The edge of the cylindrical blade 13 on the side of the needle hole (hereinafter referred to as the front side) has a cutting edge 13 over the entire circumference.
a is formed, and the first gear 15 is formed on the outer periphery of the rear edge. Further, on the outer circumference of the cylindrical blade 13 on the front side of the first gear 15, a groove portion 17 is formed over the entire circumference.

As shown in FIG. 2, the cylindrical blade 13 is fitted and supported on the outer peripheral surface of a ring-shaped slide bearing 18 fixed to the sewing machine body 16 on the outer side of the lower shaft 19, and the outer periphery of the slide bearing 18 is fixed. The surface of the shuttle 11 is rotatable about the central axis of the lower shaft 19 and is movable along the lower shaft 19 within a certain range.

Returning to FIG. 1, the first gear 15 is meshed with a second gear 23 driven by a motor 21 as a rotary actuator. The second gear 23 is formed longer than the first gear 15 in the direction of the lower shaft 19, and even if the first gear 15 moves along with the cylindrical blade 13 along the lower shaft 19 as long as it is within the movement range. The meshed state with the first gear 15 is maintained. Further, a tip 25a of a rod 25 arranged in parallel with the lower shaft 19 is engaged with the groove portion 17, and the rod 25 has a first solenoid 27 as a moving means.
It moves forward according to the energization of. The motor 21 and the first solenoid 27 are fixed to a sewing machine frame (not shown).

Therefore, when the motor 21 is driven, the second
The driving force is transmitted via the gear 23 and the first gear 15, and the cylindrical blade 13 rotates on the peripheral surface of the slide bearing 18 about the central axis of the lower shaft 19. In addition, the first solenoid 27
When energized, the driving force is transmitted through the rod 25,
The cylindrical blade 13 moves forward.

Further, on the outer periphery of the front end of the shuttle 11, a yarn separating device 31 as a yarn separating device is provided so as to be swingable around the central axis of the lower shaft 19. The thread separation 31 has a lower shaft 19
Is swingably connected to the tip of a rod 33 disposed orthogonally to the shaft via a support shaft 33a. And this rod 3
3 moves in the longitudinal direction according to the energization of the second solenoid 35 fixed to the machine frame of the sewing machine. Therefore, in response to the energization of the second solenoid 35, the yarn separating device 31 swings around the lower shaft 19. In addition, when the cylindrical blade 13 is moved forward, the yarn separating member 31 is arranged inside the cylindrical blade 13.

Furthermore, the thread cutting device 1 of the present embodiment is provided with a third solenoid 39 that causes the columnar grindstone 37 to project in response to energization. The third solenoid 39 is mounted on the sewing machine frame so that when the cylindrical blade 13 is retracted by stopping energization of the first solenoid 27 and the whetstone 37 is projected, the whetstone 37 abuts on the cutting edge 13a. Positioning is fixed.

Next, with reference to FIG. 3, the construction of the thread separating device 31 and the operation of the thread cutting device 1 as a whole will be described. Note that FIG. 3 is a side view of the vicinity of the cylindrical blade 13 of the thread cutting device 1 as viewed from the second solenoid 35 side. As shown in the drawing, the sewing needle 43 is attached to the hook 1 at the upper end edge of the thread separating device 31.
The notch 45 is provided at the position facing the upper thread 5 up to 1
Notches 47 are formed at positions facing the upper thread 5 and the lower thread 3, which are formed and sent out from the shuttle 11, respectively. The cutout portion 45 is formed in a shape that is bent forward, and its tip end 45a reaches a position where it does not overlap with the blade edge 13a (illustrated by a chain double-dashed line) that has moved the furthest forward. The cutout portion 47 is formed at a position where it can overlap the cutting edge 13a. For this reason, when the second solenoid 35 is energized to swing the thread separating device 31 (upward in the figure), the sewing needle 43 moves the needle 1
The upper thread 5 reaching 1 is located at a position where it cannot abut the blade edge 13a of the cylindrical blade 13, and the upper thread 5 and the lower thread 3 sent from the shuttle 11
Are held at positions where they can contact the cutting edge 13a.

Next, the operation of the thread cutting device 1 of the sewing machine of this embodiment having the above-mentioned structure will be described. When a thread trimming signal is generated by operating a foot pedal or the like (not shown), first, the second solenoid 35 is energized. Then
As described above, the thread stopper 31 swings, and the sewing needle 43 moves from the hook 1 to the hook 1.
The upper thread 5 reaching 1 is located at a position where it cannot abut the blade edge 13a of the cylindrical blade 13, and the upper thread 5 and the lower thread 3 sent from the shuttle 11
Are held at positions where they can contact the cutting edge 13a.

Subsequently, the motor 21 and the first solenoid 27 are energized. Then, as described above, the cylindrical blade 13 moves forward while rotating. And the cutting edge 1
3a keeps rotating in the blade crossing direction while contacting the upper thread 5 and the lower thread 3 fed from the shuttle 11. For this reason,
After a predetermined time has elapsed, the upper thread 5 and the lower thread 3 are cut.

When a preset drive time that is longer than the predetermined time has elapsed, the energization of the first solenoid 27 is stopped, and then the energization of the second solenoid 35 is stopped. Then, the cylindrical blade 13 retreats, and then the thread separation 3
1 returns to its original position. After the cylindrical blade 13 retreats,
The solenoid 39 is energized for several seconds. At this time,
Since the motor 21 continues to be energized, the grindstone 37 contacts the rotating blade edge 13a to polish the blade edge 13a. After the energization time of the above several seconds elapses, the third solenoid 39
Then, the power supply to the motor 21 is stopped, and the thread cutting operation is completed.

As described above, in the present embodiment, the thread slitting 31
The upper thread 5 from the sewing needle 43 to the shuttle 11 by the cylindrical blade 13
The upper thread 5 and the lower thread 3 sent from the shuttle 11 are cut at a position where they cannot come into contact with each other. The upper thread 5 is
A loop is formed from the needle hole to the needle hole again via the shuttle 11. When the upper thread 5 between the needle hole and the shuttle 11 is completely cut off, the upper thread 5 cut off at both ends is threaded. Although it becomes waste, by cutting only one upper thread 5 in this way, it is possible to prevent the generation of thread waste. Further, since the upper thread 5 is cut away from the sewing needle 43, the upper thread 5 remaining on the sewing needle 43 side becomes longer after the thread cutting operation. For this reason,
The needle thread 5 causes the needle 4 to
It is possible to prevent falling out of 3. Therefore, it is possible to easily restart the sewing work.

Further, in this embodiment, the blade edge 13a is formed on the entire circumference of the front edge of the cylindrical blade 13, and the cylindrical blade 13 rotates so that the blade edge 13a evenly contacts the upper thread 5 and the lower thread 3. Contact. Therefore, the durability of the cylindrical blade 13 is extremely superior to that of the conventional blade. Therefore, the cylindrical blade 13
The number of replacements and re-sharpening can be reduced. Furthermore, in the present embodiment, since the cutting edge 13a is ground by the grindstone 37 at the end of the thread cutting operation, the durability of the cylindrical blade 13 can be further improved and the number of times of replacement of the cylindrical blade 13 can be further reduced. .

Further, in this embodiment, the first gear 15 is formed around the cylindrical blade 13, and the second gear 23 is formed on the first gear 15.
The driving force of the motor 21 is transmitted via the. Therefore, a mechanism for rotating the cylindrical blade 13 (first gear 1
5, the second gear 23, the motor 21: the rotation driving means) can be integrated near the cylindrical blade 13. Therefore, the thread cutting device 1 as a whole can be made more compact than a thread cutting device using a conventional link mechanism. Further, since the rotation speed of the motor 21 is easy to control, the rotation speed of the cylindrical blade 13 can be easily controlled to a desired speed.
Therefore, the upper thread 5 and the lower thread 3 can be cut more reliably.

It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the gist of the present invention. For example, in the above-described embodiment, as the moving means for moving the cylindrical blade 13 along the lower shaft 19, the swinging means for swinging the thread separating device 31, and the whetstone moving means for bringing the grindstone 37 into contact with the cutting edge 13a, respectively. , Solenoids 27, 35, 39 are used, but these means may be constituted by an air cylinder or a link mechanism. In particular, when the grindstone 37 is brought into contact with the blade tip 13a by an air cylinder, it becomes easy to control the contact pressure of the grindstone 37 to the blade tip 13a constant regardless of the wear of the grindstone 37. Therefore, the cutting edge 13
The polishing amount of a can be controlled appropriately. Also, the second
Even if the gear 23 is driven by an air turbine or the like, the rotation speed of the cylindrical blade 13 can be well controlled.

Further, the cylindrical blade 13 is moved forward by a preset drive time to cut the upper thread 5 and the lower thread 3, but a plurality of drive times are set and the upper thread is selected by a selection switch or the like. 5 and the thickness of the lower thread 3 may be selected so that a desired driving time can be selected. According to this structure, the driving time can be set to a time necessary and sufficient for cutting the upper thread 5 and the lower thread 3.
Therefore, the time of the thread cutting operation is shortened to improve the efficiency of the sewing work, and the driving time of the motor 21, the first solenoid 27, and the second solenoid 35 is shortened to save the power of the thread cutting device 1. be able to.

Further, when the upper thread 5 and the lower thread 3 are cut, the cylindrical blade 13 sharply moves forward. Therefore, the movement of the cylindrical blade 13 may be detected and the energization of the solenoids 27 and 35 may be stopped when the movement sharply forward. In this case, the driving time can be further shortened to further improve the efficiency of the sewing work and the power saving of the thread trimming device 1. For example, when the cylindrical blade 13 moves abruptly, the reactance of the first solenoid 27 changes abruptly. Therefore, when the differential coefficient of the reactance of the first solenoid 27 exceeds a predetermined value, the energization of the solenoids 27 and 35 may be stopped. In this case, it is possible to further improve the efficiency of the sewing work and reduce the power consumption of the thread trimming device 1 without adding a new configuration for detecting the movement of the cylindrical blade 13.

In the above embodiment, the third solenoid 39 is energized for a few seconds each time the thread cutting operation is completed, and the cutting edge 1
Although 3a is polished, it may be polished in accordance with another switch operation. In this case, the operator can grind the cutting edge 13a according to how the upper thread 5 and the lower thread 3 are cut. Therefore, it is possible to further improve the durability of the cylindrical blade 13 by making the polishing amount of the blade edge 13a necessary and sufficient. Further, the cylindrical blade 13 has the upper thread 5 and the lower thread 3
It is also possible to integrate the time (proportional to the amount of wear of the blade edge 13a) rotated while abutting against, and perform polishing every time the integrated time reaches a predetermined time. In this case, the polishing amount of the cutting edge 13a can be automatically made necessary and sufficient. Therefore, the durability of the cylindrical blade 13 can be further improved.

Further, among the upper thread 5 and the lower thread 3, which thread 3, 5 is to be cut is determined by the cutout portions 45, 4 of the thread trimmer 31.
It can be freely set as desired by changing the design of 7.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing the configuration of a thread cutting device for a sewing machine according to an embodiment.

FIG. 2 is a cross-sectional view showing a configuration near a lower shaft of a thread cutting device for a sewing machine according to an embodiment.

FIG. 3 is a side view schematically showing the configuration and operation of the thread cutting device of the sewing machine of the embodiment.

FIG. 4 is a perspective view schematically showing a configuration of a conventional thread cutting device for a sewing machine.

[Explanation of symbols]

1 ... Thread trimming device 11 ... Kettle 1
3 ... Cylindrical blade 15 ... First gear 21 ... Motor 2
3 ... 2nd gear 27 ... 1st solenoid 31 ... Thread separation 3
5 ... Second solenoid

Claims (3)

[Claims] 1. Having a cylindrical shape surrounding a pot,
Between a cylindrical blade having a cutting edge formed all around the needle hole side end edge, a contact position with a thread arranged between the needle hole and the shuttle, and a non-contact position with the thread, Moving means for moving the cylindrical blade in the direction of its central axis, and rotation driving means for continuously rotating the cylindrical blade about its central axis when at least the cylindrical blade has moved to the contact position with the thread. And a thread trimming device for a sewing machine. 2. When the cylindrical blade moves to the contact position with the yarn, a part of the yarn is contacted with the cylindrical blade, and the remaining yarn is contacted with the cylindrical blade. 2. The thread cutting device for a sewing machine according to claim 1, further comprising thread separating means provided at positions where they cannot come into contact with each other. 3. The rotation driving means includes a first gear formed around the cylindrical blade, a second gear meshing with the first gear, and a rotary actuator for rotating the second gear. The thread trimming device for a sewing machine according to claim 1 or 2, characterized in that.