JPH04263897A - Needle threading device of sewing machine - Google Patents

Abstract

PURPOSE:To prevent the generation of damage of parts even if a user executes an erroneous operation by constituting the device so that a threading work to a needle eye of a needle of a sewing machine can be executed simply. CONSTITUTION:The device is provided with a threading hook 12 which can be moved into a needle eye from a home position by a manual operation, and a member 14 which works by interlocking with a rotation of a sewing machine, and also, prevents the threading hook 12 from moving to the needle eye except the time when a needle bar 16 is in a position being suitable for threading. Also, in addition thereto, threading to the needle eye of the left and the right threads 13 is selected by sliding the upper part of a threading arm 20 which has the threading hook 12 in the tip and hangs down along a left and right needle switching device 19 installed horizontally by positioning the left side in the rear a little.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for threading thread through the needle of a sewing machine such as a household lock sewing machine.

0002

2. Description of the Related Art As a needle threading device attached to a household lock sewing machine, the one shown in FIGS. 3 and 4 is known (see Japanese Patent Laid-Open No. 2-104391).

[0003] This needle threading device is attached to a shaft 101 provided perpendicular to the cloth feeding direction and a threading arm 102 fixed to this shaft 101, and penetrates into and escapes from a hole in a needle 103. It has a thread hook 104, a knob 105 fixed to the end of the shaft 101, a first positioning member 106 fixed to the shaft 101, and a second positioning member 108 fixed to a hand wheel 107.

[0004] In this device, when the needle 103 is at a predetermined position above the throat plate and the knob 105 is turned by hand to rotate the first positioning member 106 and engage it with the second positioning member 108, the , the threading needle 104 penetrates into the hole of the needle 103. The engagement between the first positioning member 106 and the second positioning member 107 at this time prevents malfunction and ensures safety.

[0005]

[Problem to be solved by the invention] Although it is very important to attach a needle threader to a sewing machine to facilitate threading work and make it easier to use, the needle threader is simply It is not enough just to fulfill the purpose; it is also necessary to have a safety mechanism that will not break even if the user accidentally operates it.

However, although the aforementioned malfunction prevention mechanism of the conventional threading device has no problem when the handwheel 107 is operated by hand, problems arise in the following two operations.

(a) If the knob 105 is turned to engage the first positioning member 106 and the second positioning member 108 and the controller is continued to be depressed, the hand wheel 107 will not rotate, so the amount of energy that should become kinetic energy becomes thermal energy, causing burnout of the motor's rotor windings. In the worst case, it may lead to a fire.

(b) If the knob 105 is turned while the sewing machine is rotating, the rotation of the hand wheel 107 will be abruptly stopped, and parts such as the hand wheel, the first positioning member 106, the second positioning member 107, etc. will be damaged.

SUMMARY OF THE INVENTION An object of the present invention is to provide a needle threading device for a sewing machine that can easily thread the thread into the needle hole and prevent parts from being damaged even if the user malfunctions. It is said that

0010

[Means for Solving the Problems] In order to achieve the above object, the needle threading device for a sewing machine of the present invention includes a threading hook that can be moved from a home position into the needle hole by manual operation, and a threading hook that is linked to the rotation of the sewing machine. and a member that prevents the threading hook from moving to the needle hole unless the needle bar is in a position suitable for threading. It is lowered and installed horizontally, and the upper part of the threading arm, which has a threading hook at the tip and hangs down, slides along the left and right needle switching device to select threading into the needle holes of the left and right needles. It is.

[0011]

[Operation] In the needle threading device of a sewing machine configured as described above, the threading hook is manually moved into the hole of the needle at a position suitable for threading, and the needle is inserted into the threading hook. Needle threading is done by threading the thread,
When you release your hand, the threading hook returns to its home position. Unless the needle bar is in a position suitable for threading operation, the threading hook does not move toward the needle because the threading hook is prevented from moving in the direction of the needle. Also, for example, when the upper part of the threading arm is slid to the left along the left/right needle switching device, the threading hook at the hanging end of the threading arm will move to the left,
It also moves slightly backwards. As a result, the radius of the movement locus of the threading hook becomes slightly smaller, and the position of the threading hook can be adapted to the needle hole of the left needle which is located above the needle hole of the right needle.

0012

[Embodiment] An example in which the needle threading device of the present invention is applied to a lock sewing machine will be explained with reference to FIGS. 1, 2, and 5 to 8. It can also be applied to sewing machines. In addition, what is shown by the dashed-dotted line in FIG. 1 and FIG. 2 is the external shape of the lock sewing machine.

A hole is made in the frame 2 of the lock sewing machine body above the upper knife drive shaft 1, and a bush 4 for inserting and guiding the drive shaft 3 is driven in and fixed. The frame 2 further includes a shift gate plate 5 having a guide groove 6 for controlling the rotation and axial sliding movement of the drive shaft 3.
to be fixed.

A guide pin 7 that engages with a guide groove 6 of the shift gate plate 5 is fixed to the right end circumferential surface of the drive shaft 3 with a screw. The guide pin 7 can be moved from home position A to positions B, C, and D, as shown in FIG.

A return spring 8 is provided between the E-ring 9 fixed to the drive shaft 3 and the right end of the bush 4, surrounding the drive shaft 3.
Another return spring 1 is also provided between the lower protrusion 10 of
1 is provided so that the threading device can be returned to the home position A after the threading operation is completed. The return spring 8 transfers the return force in the thrust direction to the return spring 1.
1 applies a return force in the rotational direction to the drive shaft 3, respectively.

If the needle threading operation is performed at a position other than the top dead center of the needle bar, there is a risk of damage to the needle 13 and the threading hook 12, so the threading operation is performed at the needle bar top dead center. The positional relationship between the threading hook 12 and the hole of the needle 13 is set. A shift lock plate 14 having a cross-sectional shape as shown in FIG. 2 is screwed to the upper knife drive shaft 1, which reciprocates in synchronization with the vertical movement of the needle bar, with a screw 14a. The guide groove 6 of the gate plate 5 can be moved in and out of the B position. The upper knife drive shaft 1 is pivotally supported at both ends by a frame at the position shown in FIG. The free end of the shift lock plate 14 is located at 14 except when the rod 16 is at the top dead center.
As shown in ', the guide groove 6 of the shift gate plate 5
Move to a position where it is blocked. In this state, the operation lever 17
Even if an attempt is made to operate the guide pin 7 in the guide groove 6 from position B to direction C or D, the free end of the shift lock plate 14 restricts the movement of the guide pin 7 in the guide groove 6, resulting in a situation where the needle 13 and threading hook 12 come into contact with each other. does not occur.

A support arm 18 is fixed near the position where the operating lever 17 is fixed on the drive shaft 3, a left/right needle switching device 19 is fixed to the supporting arm 18, and a left/right needle switching device 19 is fixed to the supporting arm 18.
A threading arm 20 having a threading hook 12 and a needle guide plate 21 fixed to its tip is slidably attached to the.

The left/right needle switching device 19 has a structure as shown in FIGS. 5 and 6. FIG. 5 is a view of the left/right needle switching device 19 seen from above the sewing machine, and FIG. 6 is a diagram showing how the device is operated by the operator. It is a view seen from the side (front). As clearly shown in FIG. 5, the left side of the left and right hand switching device 19 is located slightly rearward.

The threading arm 20 has an operation knob 20a.
is formed, and a window 19a on the side wall of the left/right needle switching device 19 is formed.
It sticks out from the outside. A plate body 22 is fixed to the support arm 18, and a threading arm 20 is held in a gap between the plate body 22 and the plate body 22 inside the left/right needle switching device 19. By manually moving the operating knob 20a, the threading arm 20 can be slid left and right. A leaf spring 23 is further fixed to the support arm 18, and the tip with the protrusion 23a is
A window 22a formed in the plate body 22 is used as the window 22a. On the other hand, two recesses 20L and 20R are formed in the longitudinal direction on the upper surface of the portion of the threading arm 20 that is held between the plate members 22. By operating the operation knob 20a left and right, the recesses 20L and 20R can be selectively engaged with the protrusion 23a of the leaf spring 23. In FIGS. 5 and 6, the threading arm 20 indicated by a solid line and the threading arm 20' indicated by a chain line are used when threading the right needle and the left needle, respectively. As shown in FIG. 5, since the left side of the left and right needle switching device 19 is located slightly backward, the position of the threading arm 20 is better when threading the left needle than when threading the right needle. will move backwards slightly to the left.

As described above, the tip position of the threading arm 20 is slightly moved back when threading the left needle than when threading the right needle, so that the center of rotation O of the threading arm 20 (of the drive shaft 3) Although the axis (axis) remains unchanged, the radius R2 of the movement trajectory of the threading hook 12 is slightly smaller than the radius R1 of the movement trajectory of the threading hook 12 when threading the right needle. As a result, the position of the threading hook 12 can be shifted to fit the needle hole 13L of the left needle located above the needle hole 13R of the right needle.

Finally, the relationship between the manual operation of the operating lever 17 and the movement of the threading hook 12 at the tip of the threading arm 20 will be explained.

First, when the operating lever 17 is rotated backward, the guide pin 7 fixed to the right end of the drive shaft 3 to which the operating lever 17 is fixed moves from the home position A to B in the guide groove 6. move to position. Next, when the operating lever 17 is pulled to the left as it is, the guide pin 7 moves in the guide groove 6 from the B position to the C position. Further, when the operating lever 17 is rotated backward, the guide pin 7 moves in the guide groove 6 from the C position to the D position. As the guide pin 7 moves from the A position to the B position, the threading hook 12 moves forward via the support arm 18, the left/right needle switching device 19, and the threading arm 20, and the guide pin 7 moves from the B position to the C position. By the movement of , the threading hook 12 moves behind the needle selected by the left/right needle switching device 19, and by moving from the C position to the D position, the threading hook 12 moves forward into the needle hole of the selected needle. do. When the thread is passed through the threading hook 12 in this state and the operating lever 17 is turned back in the opposite direction, threading to the needle is completed. Switch the left and right needle switching device 19,
By repeating this operation, threading the two needles is completed.

[0023]

[Effects of the Invention] Since the present invention is constructed as described above, it produces the following effects.

In other words, threading the needle into the needle hole can be easily carried out, and even if an erroneous operation is performed, the threading hook is prevented from moving in the direction of the needle, thereby preventing damage to parts such as the needle. Now you can work safely without any problems. In addition, unlike conventional sewing machines, there is no need to mechanically stop the rotation of the sewing machine to ensure safety, so there is no risk of burning out the motor or damaging parts.

[Brief explanation of the drawing]

FIG. 1 is a front view of a lock sewing machine equipped with a needle threading device of the present invention.

FIG. 2 is a right side view as well.

FIG. 3 is a side view of a needle threading device of a conventional lock sewing machine.

FIG. 4 is a perspective view of a malfunction prevention mechanism in the needle threading device.

FIG. 5 is a plan view of the left and right needle switching device.

FIG. 6 is a front view of the left and right needle switching device.

FIG. 7 is a side view illustrating the state when the threading arm enters the respective needle holes of the left and right needles.

FIG. 8 is a front view showing the positional relationship between the guide groove of the shift gate plate and the free end of the shift lock plate.

[Explanation of symbols]

1 Upper knife drive shaft 5 Shift gate plate 6 Guide groove 7 Guide pin 8 Return spring 11 Return spring 12 Threading hook 13 needle 14 Shift lock plate 16 Needle bar 19 Left and right needle switching device 20 Threading arm

Claims (2)

[Claims] 1. A threading hook that can be moved from a home position into the needle hole by manual operation, and a threading hook that operates in conjunction with the rotation of the sewing machine and that can be used only when the needle bar is in a position suitable for threading. A needle threader for a sewing machine, comprising a member that prevents the needle from moving to the needle hole. Claim 2: The left and right needles are installed horizontally with the left side slightly lowered backwards, and the left and right needles are moved by sliding the upper part of the hanging threading arm, which has a threading hook at the tip, along the left and right needle switching device. 2. The needle threading device for a sewing machine according to claim 1, wherein threading into a needle hole is selected.