JPH04156888A - Bobbin thread breakage detecting device for sewing machine - Google Patents

Abstract

PURPOSE:To increase the reliability of bobbin thread breakage detection by bringing a detecting piece into contact with a bobbin thread, and efficiently applying the tension change given to the bobbin thread to the detecting piece. CONSTITUTION:The contact piece 58a of a detecting piece 58 is brought into contact with a bobbin thread Y between the outer periphery of an outer shuttle 32 and a shuttle support 50, the contact piece 58a is pushed to the right in the figure each time tension is applied to the bobbin thread Y by a bulge section 34, the detecting piece 58 is rotated to the virtual line position in the figure against the elastic force of a spring 62, and it is again returned to the solid line position in the figure by the elastic force of the spring 62 when the tension applied to the bobbin thread Y by the bulge section 34 is released. The detecting piece 58 repeats reciprocating motion as far as the bobbin thread Y is properly delivered from a bobbin thread bobbin 46, and preset pulse signals are outputted from a magnetic sensor 70. When the thread breakage of the bobbin thread Y occurs, the signals transmitted from the magnetic sensor 70 are interrupted, thereby a bobbin thread breakage detection signal is generated, and the drive of a sewing machine is stopped.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a bobbin thread breakage detection system for detecting when the bobbin thread in a sewing machine is broken or when the bobbin thread is used up. Regarding equipment.

[Conventional technology]

The hook, which is generally placed below the throat plate of a sewing machine, has the function of a thread catcher, and an overhang formed on the outer peripheral end surface of the outer hook, which is rotationally driven through the hook shaft, is attached to the inside of the inner hook. When passing through the part of the lower thread that has been pulled out from the set lower thread bobbin, it functions to let out the lower thread from the bobbin. Therefore, each time the bobbin thread is unwound from the bobbin by the overhanging portion, it is subjected to tension from the thread guide of the bobbin to the sewing portion on the throat plate.

A device has already been proposed that detects thread breakage by utilizing the fact that tension is repeatedly applied to the bobbin thread in order to unwind it. For example, JP-A-64-176
In Publication No. 86, the tension applied to the bobbin thread that comes into contact with the bobbin thread between the protruding part of the outer hook and the sewing part on the throat plate, that is, between the outer periphery of the outer hook and the lower surface of the throat plate. A detector is provided which rotates depending on the change in. A sensor can also be used to detect whether the detector continues to rotate or has stopped. When the rotation of the detector stops, it can be treated as if the bobbin thread has broken or the thread has been used up.

[Invention or problem to be solved]

In the bobbin thread breakage detection device disclosed in the above publication,
When the bobbin thread at the point in contact with the detector is subjected to tension at the protruding portion of the outer hook, the bobbin thread tilts significantly diagonally from its almost vertical position due to the gap between the outer periphery of the outer hook and the needle hole of the throat plate. . For this reason, the tension applied to the bobbin thread does not act efficiently on the detector,
In other words, the rotation of the detector due to changes in the tension of the bobbin thread becomes inaccurate, reducing the reliability of thread breakage detection.

In addition, when the tension applied to the bobbin thread due to the sewing operation is originally large, such as with a sewing machine that sews cords or tape-like embroidery material in a continuous manner, the tension applied to the bobbin thread due to the sewing operation is due to the action of the overhang of the outer hook. Regardless of whether tension is applied to the bobbin thread or released, there is little change in the tension of the bobbin thread relative to the detector. Therefore, in this case as well, the mouth movement of the detector becomes inaccurate, causing false detection.

Furthermore, when the sewing work is finished, as is well known, a movable scalpel for cutting the lower thread and upper thread advances into the gap between the outer periphery of the outer hook and the lower surface of the throat plate. Therefore, in order to avoid interference with the moving knife when cutting the thread, the record-resistant detector must be retracted from the outer periphery of the outer hook, and a mechanism for this purpose is required.

The technical problem of this invention is to increase the reliability of bobbin thread breakage detection by efficiently applying changes in the tension applied to the bobbin thread to the detector, and to retract the detector even when the movable knife cuts the thread. An object of the present invention is to provide a bobbin thread breakage detection device for a sewing machine that does not require any operation.

[Means to solve the problem]

In order to solve the above problem, the bobbin thread breakage detection device of the present invention is configured as follows.

That is, a hook having an outer hook that is driven to rotate and an inner hook that is assembled inside and does not rotate is arranged below the throat plate,
The bobbin thread pulled out from the bobbin thread bobbin in the bobbin case incorporated inside the inner hook passes from the thread guide of the bobbin case, passes through the needle hole of the throat plate, and reaches the sewing part on the throat plate. In the sewing machine of the type in which the open bobbin thread from the thread guide to the sewing section is fed out from the bobbin thread bobbin under tension due to the action of an overhang formed on the end surface of the outer periphery as the outer hook rotates, The tension of the bobbin thread changes between when the bobbin thread is brought into contact with the bobbin thread between the thread guide of the bobbin case and the outer periphery of the outer hook, and the bobbin thread is paid out from the bobbin by the action of the overhang, and at other times. It includes a detector that repeatedly rotates back and forth, and a sensor that detects whether the detector continues to rotate or has stopped.

[For production]

The bobbin thread located between the thread guide of the bobbin thread bobbin and the outer periphery of the outer hook is given more tension by the overhang than the bobbin thread extending from the outer periphery of the outer hook to the sewing section on the throat plate. Even in the tilted state, the tilt is maintained at a low level. This is because, as a matter of course, both the thread guide and the outer hook section 8 are located on the end face (front) side of the hook, and the relative positional deviation in the direction along the hook axis is small, whereas the overhang section This is because the amount of misalignment between the needle hole and the needle hole of the throat plate is quite large.

By bringing the detector into contact with the bobbin thread with a small inclination between the thread guide and the outer periphery of the outer hook, the tension applied to the bobbin thread by the overhang can be applied to the detector efficiently ( Therefore, the detector repeatedly rotates accurately as the tension of the bobbin thread changes.

In addition, since the contact part of the detector with the bobbin thread is located inside the outer periphery of the outer hook (towards the center of rotation), there is no interference with the moving knife when cutting the thread, and this detector No evacuation mechanism is required.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

First, FIG. 1 shows a plan view of the structure of a hook base including a bobbin thread breakage detection device, and FIG. 2 shows a cross-sectional view taken along the line ■--■ in FIG. In these drawings, a throat plate 22 is fixed to the upper surface of the hook base lO, and this throat plate 22 has a needle hole 24 into which the tip of a sewing needle (not shown) enters during sewing work of the sewing machine.

Further, in a part of the hook base 10, a hook shaft 12 or a bearing is rotatably supported by a metal 14 below the throat plate 22 (see FIG. 2). A gear 16 is fixed to one end of the hook shaft 12 (the left end in the drawing).
meshes with a drive gear 20 of a drive shaft 18 disposed perpendicular to the shuttle shaft 12.

Front: A hook 30 is attached to the other end of the hook shaft 12 (the right end in the drawing). FIG. 3 shows an enlarged cross section of the pot 30 in a state corresponding to FIG. 2, and FIG. 4 shows an end face of the pot 30. As is mainly clear from these FIGS. 3 and 4, the hook 30 includes an outer hook 32 fixed to the hook shaft 12 and rotationally driven, and an inner hook 36 built into the outer hook 32. It is equipped with The inner hook 36 is rotatable relative to the outer hook 32 around the axis of the hook shaft 12, and has a support shaft 38 coaxial with the hook shaft 12.

Also, inside the inner pot 36, as shown in FIG.
A hobbin case 42 in which a bobbin thread bobbin 46 is set is incorporated in a state where it is supported by the support shaft 38. A thread kite 44 is fixed to the bobbin case 42 on the front side of the hook 30 (on the right side in FIG. 3). During the sewing operation of the sewing machine, as shown in FIG. It passes through and reaches the stitched part A on the throat plate 22.

A locking recess 40 is formed in the upper end surface of the inner pot 36, and a convex portion 52 of a hook support 50 is engaged therein.

This hook support 50 is fixed to the hook base 10 as shown in FIGS. 1 and 2. This hook support 50 holds the inner hook 36 together with the bobbin case 42 in the attitude shown in the drawing, regardless of the rotation of the outer hook 32.

Furthermore, a projecting portion 34 is formed on the outer circumferential end surface of the outer hook 32 in a part of its circumferential direction that extends toward the front side of the hook 30 (to the right in FIG. 3).

When this projecting portion 34 passes through the location of the bobbin thread Y between the thread guide 44 of the bobbin case 42 and the sewing portion on the throat plate 22 due to the rotation of the outer hook 32 (see FIG. 3), It functions to apply tension to the lower thread Y and let it out from the lower thread bobbin 46.

Next, the bobbin thread breakage detection device will be explained. First, as shown in FIGS. 1 and 2, a support bracket 56 fixed to the hook base 10 at the lower part of the throat plate 22 has a detector 58 formed in a planar shape or approximately L-shape. A middle portion of the shaft 60 is rotatably attached to the shaft 60. One end of this detector 58 is connected to a gap between the hook support 50 and the outer periphery of the outer hook 32 (the portion having the projecting portion 34), as shown in FIGS. 3 and 4. The contact piece 58a enters into the lower thread Y and comes into contact with the bobbin thread Y.

The other end of the detector 58 is connected to the support bracket 5.
Detection unit 7 of magnetic sensor 70 fixed on the top surface of 6
2 (see FIGS. 1 and 2). As shown in FIG. 2, the detector 58 receives a biasing force in the direction of the arrow in FIG. It's stopped. In this state, the contact piece 58a has entered the gap between the hook support 50 and the outer periphery of the outer hook 32 to its maximum extent.

In the above configuration, the hook shaft 12 of the sewing machine during the sewing operation is continuously rotated in one direction together with the outer hook 32 of the hook 30 in response to the rotation of the drive shaft 18. This rotation of the outer hook 32 performs a well-known thread catching function.

In addition to this thread catching function, the projecting portion 34 on the outer periphery of the outer hook 32
Each time the thread passes directly under the needle hole 24 of the throat plate 22, the bobbin thread Y located between the thread guide 44 and the needle hole 24 of the throat plate 22 is moved by the protrusion 34 as shown in FIG. It is pulled as shown, and a predetermined tension is applied to the bobbin thread Y. Due to this tension, the lower thread Y is let out from the lower thread bobbin 46.

Now, the contact piece 58a of the detector 58 is in contact with the bobbin thread Y between the outer periphery of the outer hook 32 and the hook support 50, and tension is applied to the bobbin thread Y by the overhang 34. Each time, the contact piece 58a is pushed to the right in FIGS. 1 to 3.

As a result, the detector 58 rotates against the elastic force of the spring 62 to the imaginary line position shown in FIG. Then return to the solid line position in Figure 1 again. Therefore, the bobbin thread Y
As long as the bobbin thread is properly unwound from the bobbin 46, the detector 58 repeats the above-mentioned reciprocating rotation, and the detected piece 5
8b repeatedly approaches and moves away from the detection section 72 of the magnetic sensor 70. As a result, the magnetic sensor 70 outputs a predetermined pulse-like signal.

When the bobbin thread Y breaks or the thread in the bobbin thread bobbin 46 is used up, the detector 58 remains stopped at the solid line position in FIG. 1. Then, the signal transmitted from the magnetic sensor 70 changes or is interrupted, and this becomes a bobbin thread breakage detection signal, and the driving of the sewing machine is stopped.

Note that the lower thread Y located between the outer periphery of the outer hook 32 and the hook support 50 has a relatively small inclination even when tension is applied by the projecting portion 34. Therefore, the tension applied to the bobbin thread Y acts efficiently on the contact piece 58a of the detector 58. Also, due to the arrangement of the detector 58, when the sewing machine finishes sewing, a moving knife (not shown) for optical cutting can advance into the gap between the outer periphery of the outer hook 32 and the lower surface of the throat plate 22. However, the detector 58 does not pose any obstacle to the movement of the moving scalpel at this time.

〔Effect of the invention〕

In this way, the present invention allows the detector to contact the bobbin thread with a small inclination located between the thread guide and the outer circumference of the outer hook.
Changes in the tension applied to the bobbin thread can be applied to the detector efficiently, increasing the reliability of bobbin thread breakage detection regardless of the strength of sewing tension on the bobbin thread based on the type of sewing. , it is possible to eliminate the need for a retracting operation of the detector even when cutting the thread with the moving knife.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view showing the configuration of a hook base including a bobbin thread breakage detection device, and FIG.
3 is an enlarged sectional view of the pot, and FIG. 4 is an end view of the pot. 22... Throat plate 24... Needle hole 30... Hook 32... Outer hook 34... Overhang portion 36... Inner hook 42... Bobbin case 44... Thread kite 46.・Bobbin thread bobbin 58 ・Detector 70 ・Sensor Y ・Bobby thread A ・Sewing section Applicant Tokai Kogyo Sewing Machine Co., Ltd.

Claims (1)

[Claims] A hook having an outer hook that is rotationally driven and an inner hook that is built into the inner hook and does not rotate is arranged below the throat plate, and a bobbin case that is built into the inner hook. The lower thread pulled out from the lower thread bobbin passes from the thread guide of the bobbin case, passes through the needle hole of the throat plate, and reaches the sewing part on the throat plate. In a sewing machine of the type in which the bobbin thread from the thread guide to the sewing section is fed out from the bobbin thread bobbin under tension due to the action of an overhang section, the thread guide of the bobbin case and the outer periphery of the outer hook are connected to each other. a detector that contacts the bobbin thread between the parts and repeats reciprocating rotation due to changes in the tension of the bobbin thread when the bobbin thread is paid out from the bobbin by the action of the overhanging portion and at other times; A bobbin thread breakage detection device for sewing machines equipped with a sensor that detects whether rotation continues or stops.