JPH0740386Y2 - Sewing machine bobbin thread remaining amount detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a lower thread remaining amount detecting device for optically detecting a lower thread remaining amount wound around a lower thread bobbin of a sewing machine.

[Prior Art] As is well known, the amount of bobbin thread that can be wound around a bobbin thread bobbin in a lockstitch sewing machine is relatively small and consumed in a short time. If the sewing operation is performed without doing so, there is a possibility that defective sewing may occur due to insufficient bobbin thread.

Therefore, conventionally, as shown in FIG. 5, a detecting device for automatically detecting the amount of the lower thread wound around the lower thread bobbin has been proposed and implemented.

This detection device faces the bobbin case 3 mounted on the middle hook 2 of the sewing machine which is fitted with the outer hook 1, and is provided with a light projecting section 4a and a light receiving section
While the reflection type sensor 4 composed of 4b is arranged, an opening 3b is formed on the side surface 3a of the bobbin case 3 and a through hole 5a1 is formed on one of the collars 5a of the bobbin bobbin 5. The light emitted from the light projecting portion 4a is peeled off and radiated to the through hole 5a1, and when the bobbin thread amount of the bobbin thread bobbin 3 becomes a certain amount or less, the light emitted from the light projecting portion 4a is moved downward. The other collar 5b of the thread bobbin 3 reflects the reflected light, and the reflected light is received by the light receiver 4b.

That is, when a certain amount or more of the lower thread is wound around the lower thread bobbin 5, the light incident path R1 from the light projecting section 4a to the collar section 5b through the opening section 3b and the through hole 5a1 is formed by the lower thread. It is always shut off, and the output signal of the light receiving section 4b is turned off. Further, when the lower thread amount of the lower thread bobbin 5 becomes a certain value or less, when the through hole 5a1 of the lower thread bobbin 5 coincides with the opening 3b of the bobbin case 3, it is opened from the incident path R1 and the collar portion 5a. Portion 3b and through hole
Since the reflection path R2 is formed through the light receiving portion 4b via 5a1, an ON signal is sent from the light receiving portion 4b by reflected light.

Then, the ON signal drives a buzzer, a lamp, or the like to notify the operator that the remaining amount of the lower thread is insufficient.

[Problems to be Solved by the Invention] As described above, the one that optically detects the remaining amount of the bobbin thread by using the light emitting / receiving units 4a and 4b can be realized with a relatively inexpensive and simple configuration. However, it is more frequently used than other means, for example, one using magnetism, but there is a problem that the detection performance gradually deteriorates with use.

This is because minute thread scraps generated during sewing, oil scattered from the hook, etc. adheres to the front surface of the light projecting section 4a and the light receiving section 4b, which reduces the light projecting quantity and the light receiving quantity. ing.

This invention was made in view of the above conventional problems, and can prevent dust from adhering to the front surfaces of the light projecting portion and the light receiving portion.
An object of the present invention is to provide a bobbin thread remaining amount detecting device for a sewing machine that can always obtain good detection performance.

[Means for Solving the Problem] The present invention provides a light projecting portion that emits light through a through hole formed in one collar portion of a bobbin bobbin and a light reflected by the other collar portion of the bobbin bobbin. In a bobbin thread remaining amount detection device of a sewing machine having a light receiving section for receiving light, a shield plate covering the vicinity of the front surfaces of the light projecting section and the light receiving section is connected to a solenoid for operating a thread cutting mechanism, and the thread cutting operation by the solenoid is performed. Only at this time is the shielding plate retracted from the vicinity of the front faces of the light projecting portion and the light receiving portion.

Further, the shield plate may be provided with a sliding contact body that makes sliding contact with the light transmitting surface and the light receiving surface when the shield plate is moved.

[Operation] In the bobbin thread remaining amount detection device of the sewing machine according to the present invention, during the sewing operation period when dust and oil are most likely to adhere to the light projecting portion and the light receiving portion, the moving body moves near the front surface of the light projecting portion and the light receiving portion. The movable body is retracted only during a slight thread cutting operation performed after the end of the sewing operation, and the lower thread remaining amount is detected by the light projecting unit and the light receiving unit.

Therefore, almost no dust or oil adheres to the light projecting unit and the light receiving unit, and good detection performance can be maintained for a long period of time.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 and 2.

1 to 3 are views showing an embodiment of the present invention.

In the figure, 11 is an outer hook that rotates in conjunction with the lifting operation of a sewing needle (not shown), 12 is an inner hook that is rotatably fitted to the outer hook 11, and 13 is removable from the inner hook 12. A bobbin case 14 to be fitted is a lower thread bobbin rotatably housed in the bobbin case 13.

The lower thread bobbin 14 is a lower thread winding shaft 14a for winding a lower thread.
And an annular collar portion 14b, which is provided at both ends of the flange portion so as to face each other,
A through hole 14b1 is formed in one of the flange portions 14b, 14c, which is made of 14c (see FIG. 2).
Means that when the bobbin thread wound around the bobbin thread winding shaft 14a becomes less than the length (required shortest amount) consumed by one sewing operation, the light incident from the through hole 14b1 is lowered. It is formed at a position where the yarn is not irradiated, that is, at a position where the distance t1 from the axis of the lower thread winding shaft 14b is slightly larger than the required minimum amount of the lower thread I radius R1.

The inner surface of the other flange 14c is at least the through hole 1
The portion 14c1 facing the 4b1 is mirror-finished.

In addition, the bobbin case 13 has a collar portion 14 b of the lower thread bobbin 14.
There is formed an opening 13a capable of exposing the through hole 14b1 formed in.

15 is a reflection type sensor having a light projecting portion 15a and a light receiving portion 15b,
It is provided at a position facing the opening 13a of the bobbin case 13, and the light receiving portion 15b is reflected by the inner surface of the other flange 14c of the bobbin case 13, and the through hole 14b1 and the opening 13a.
It is arranged so that it can receive light that has passed through.

On the other hand, 16 is a solenoid that operates a thread trimming mechanism (not shown).

This solenoid 16 is adapted to move the cylinder rod 16a in the direction of arrow A during the thread cutting operation by a signal output from the sewing machine controller after the sewing operation is completed.
During the other period, the cylinder rod 16a is kept protruding in the arrow B direction.

By moving the cylinder rod 16a in the direction of arrow A, the thread cutting mechanism (not shown) is connected to the sewing machine lower shaft 17, and the movable blade moves while the lower shaft 17 makes one rotation (the aforementioned thread cutting period). The needle plate and the outer shuttle 11 are horizontally reciprocated to cut the upper thread and the lower thread between them and the fixed blade.

Reference numeral 18 is a link rotatably connected to the tip end of the cylinder rod 16a, and 19 is an L having one end pivotally attached to the other end of the link 18.
The pivotal link has a character shape, and an intermediate portion thereof is rotatably supported by a support shaft 20.

Next, the operation will be described based on the above configuration.

When the sewing operation is completed, the solenoid rod 16a of the solenoid 6 is moved in the arrow A direction from the position shown in FIG. 1 by the signal sent from the sewing machine control device, and the thread cutting operation is started.

Further, since the solenoid rod 16a moves in the arrow A direction and the rotation link 19 rotates in the C direction, the shield plate 21 moves in the arrow E direction.
And moves away from the vicinity of the front surfaces of the light projecting portion 15a and the light receiving portion 15b. Here, the light projecting unit 5a is operated by the sewing machine controller and emits light toward the opening 13a of the bobbin case 13.

Further, during the thread cutting operation, the bobbin thread is fed from the bobbin thread bobbin 14, so that the bobbin thread supplementary blade 14 rotates in the bobbin case 13.

The light that has passed through the opening 13a at the time when the through hole 14b1 formed in the flange portion 14b is exposed through the opening 13a further passes through the through hole 14b1. At this time, if the amount of bobbin thread wound on the bobbin bobbin 14 is shorter than the required minimum amount,
The light that has passed through the through hole 14b1 further reaches the inner surface of the other flange portion 14c of the bobbin case 13, and is reflected by the rear through hole 14b1 and the opening portion 13a to be received by the light receiving portion 15b.

Then, a predetermined signal is output from the light receiving unit 15b to drive the buzzer or the lamp. On the other hand, when the bobbin thread amount wound around the bobbin thread bobbin 14 is equal to or more than the required minimum as shown by R2 in FIG.
Since the light passing through 14b1 is blocked by the lower thread, no signal is sent from the light receiving section 15b, and the buzzer or lamp is not driven.

In this way, the bobbin thread remaining amount is detected along with the thread trimming operation, and when the solenoid rod 16a of the solenoid 16 returns in the direction of arrow B, the link 18 also moves in the same direction and the rotary link 19 Rotates in the direction of arrow D. As a result, the shielding plate 21 moves in the direction of the arrow F, and the one side surface 21a thereof causes the light projecting portion 15a.
And covers the vicinity of the front surface of the light receiving unit 15b.

The light projecting unit 15a stops its operation at the same time when the solenoid rod 16a starts moving backward.

Since the covering state of the light projecting portion 15a and the light receiving portion 15b by the shielding plate is maintained until the next sewing operation is completed, the thread scraps and oil droplets scattered at the time of sewing the light projecting portion 15a and the light receiving portion 15b.
It can be surely prevented from adhering to the front surface of the.

Further, in the above-described embodiment, the shielding plate 21 is used as the light emitting / receiving unit 15
Although it is located in front of a and 15b to prevent the adhesion of dust, as shown in FIG.
A flexible member (contact body) 23 that contacts the front surfaces of the light emitting / receiving portions 15a and 15b, for example, flocked hair, sponge, etc., is provided and slidably contacts the front surfaces of the light emitting / receiving portions 15a and 15b when the shield plate moves. By doing so, it is possible to remove even a very small amount of dust that adheres when the remaining amount of the lower thread is detected.

[Effects of the Invention] As described above, in the lower thread remaining amount detecting device of the sewing machine according to the present invention, the shielding plate that covers the vicinity of the front surfaces of the light projecting section and the light receiving section is provided only when the thread cutting operation is performed. Since the remaining amount of bobbin thread is detected by retracting the bobbin thread from the section, the front surfaces of the light projecting section and the light receiving section can be shielded from dust during a sewing operation in which the largest amount of thread waste and oil droplets scatter. Good detection performance can be maintained throughout. Furthermore, by performing the detection operation for each thread trimming operation, the operator can confirm whether the remaining amount of the bobbin thread is sufficient before starting the next sewing operation. It is possible to prevent the occurrence of poor sewing due to.

Further, if a contact body is provided on one side surface of the shield plate in contact with the front surfaces of the light projecting portion and the light receiving portion, the contact body can be used for moving the shield plate to remove a small amount of dust attached to the light projecting portion and the light receiving portion. Since it can also be removed, better detection performance can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 (a) is a perspective view showing a bobbin case and a bobbin in the same embodiment, and FIG. 2 (b) is a bottom view shown in FIG. FIG. 3 is a side view of the thread bobbin, FIG. 3 is a partially longitudinal front view of the thread bobbin shown in FIG. 1, FIG. 4 is an enlarged perspective view of an essential part of another embodiment of the present invention, and FIG. 5 is a conventional sewing machine. FIG. 3 is a vertical sectional front view showing the lower thread remaining amount detection device. 11 …… Outer hook 12 …… Interior hook 14 …… Bottom thread bobbin 14a …… Bottom thread winding shaft 14b …… Ball 14b1 …… Through hole 14c …… Ball 15 …… Reflective sensor 15a …… Emitter 15b: Light receiving part 16: Solenoid 17: Lower shaft 21: Shielding plate 23: Contact body

Claims (1)

[Scope of utility model registration request] 1. A sewing machine comprising: a sewing machine hook provided on a lower shaft that rotates in conjunction with an upper shaft of the sewing machine; and a pair of collar portions facing opposite ends of a lower thread winding shaft for winding the lower thread. In addition to being rotatably held in the hook, a lower surface is formed with a through hole in the one flange portion, and a reflecting surface is formed in at least a portion of the inner surface of the other flange portion facing the through hole. A thread bobbin, a light projecting portion that emits light toward the through hole, and a reflected light that has passed through the through hole from the light projecting portion and is reflected by the inner surface of the other flange portion to receive a predetermined electric power. A lower thread remaining amount detecting device for a sewing machine, comprising: a light receiving section for transmitting a signal, and detecting the lower thread remaining amount depending on whether or not the light receiving section receives the reflected light from the inner surface of the other collar section. In, the retracted position for exposing the front surfaces of the light projecting portion and the light receiving portion and the vicinity of the front surface of the light projecting portion and the light receiving portion are covered. A shield plate that can move between the shield position and the shield position is provided, and the shield plate is connected to a solenoid that activates a thread cutting mechanism in response to a thread cutting command. A bobbin thread remaining amount detecting device for a sewing machine, wherein the device is retracted from the vicinity of the front surface of the light section and the light receiving section.