JPH0748235Y2 - Bobbin presser for sewing machine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bobbin pressing device for a sewing machine, which prevents the lower thread bobbin from idling during the thread cutting operation of the sewing machine.

[0002]

2. Description of the Related Art A lockstitch sewing machine, etc., in which a stitch is formed by cooperation of a sewing needle and a sewing machine hook, is currently or automatically semi-automatically lowered in a non-sewing operation state in which the sewing machine hook is stopped. A device having a thread cutting mechanism for cutting a thread is known. Generally, various thread cutting mechanisms have been proposed and implemented, but basically, in order to keep the length of the movable blade, the fixed blade and the bobbin thread (bobbin thread feeding amount) at a constant length. The lower thread plucking arm is provided below the needle plate, and the movable blade and the lower thread plucking arm move horizontally to capture the upper thread from the bobbin to the needle hole of the needle plate and to the side from the ascending / descending path of the sewing needle. The lower thread is pulled out and cut between the fixed blade. Further, after the cutting operation, the movable blade returns to the standby position and holds the cut end portion of the lower thread between the fixed blade and the leaf spring.

It is extremely important to keep this bobbin thread feeding amount properly in order to properly form a stitch at the start of the next sewing. That is, when the amount of the bobbin thread drawn from the bobbin thread bobbin at the start of sewing is insufficient, the cut end of the bobbin thread comes off the knot at the start of sewing, and the problem that the stitch is not formed occurs. In addition, when the thread is pulled out excessively, the needle thread tension and bobbin thread tension are not balanced, the knot position is biased to the upper surface side of the cloth, and the excess thread sticks out of the seam. There is a problem that causes deterioration. Therefore, in this type of thread trimming mechanism, by setting the thread cutting position by the movable blade, the bobbin thread hoisting arm and the fixed blade to an appropriate position, an appropriate bobbin thread feeding amount at the start of sewing is ensured. There is.

However, an appropriate amount of bobbin thread may not be secured simply by setting the bobbin thread cutting position as described above. This is because the bobbin thread bobbin that rotates with the bobbin thread reeling operation of the bobbin thread winding arm idles due to its inertial force, and the bobbin thread is excessively paid out, or the bobbin thread that has idled is once paid out. This is because the bobbin thread is wound up again and a shortage of the bobbin thread occurs.

Therefore, in order to prevent the bobbin thread bobbin from idling, a bobbin pressing device as shown in FIG. 4 has been conventionally proposed. In FIG. 4, reference numeral 2 is a pressing member rotatably supported by a fulcrum shaft 4, and a tip portion 2 a thereof can be brought into contact with and separated from an outer surface of a collar portion 1 a of the bobbin bobbin 1, and a spring 3 is used. The tip portion 2a is biased so as to come into pressure contact with the collar portion 1a. The pressing member 2 is configured to be forcibly moved and held at a position separated from the collar portion 1a against the urging force of the spring 3 by a predetermined moving means, and at the time of sewing, the moving means is moved. Is held at a position separated from the collar portion 1a, and during thread cutting operation, the collar portion 1a is pressed against the collar portion 1a to press the collar portion 1a of the bobbin 1 with a constant pressing force. Therefore, at the time of thread cutting, a resistance force is applied to the rotation of the bobbin 1, the idling due to the inertial force of the bobbin 1 is suppressed, and the bobbin thread can be prevented from being unnecessarily paid out to some extent. ing.

[0006]

However, in the above-mentioned conventional bobbin pressing device, since the pressing force of the pressing member 2 against the collar portion 1a of the bobbin 1 is always constant, the bobbin winding device of the bobbin bobbin 1 is wound. Depending on the amount, problems such as yarn breakage occurring at an improper position and idling of the bobbin bobbin 1 were not sufficiently prevented occurred.

That is, as shown in FIG. 5, the lower thread bobbin 1
When the amount of bobbin winding is small, the distance from the bobbin thread feeding point P to the center of rotation of the bobbin bobbin 1 is small, and the angular acceleration of the bobbin 1 at the beginning of rotation is large. A large torque is required to rotate the bobbin 1, and excessive tension is applied to the bobbin thread I to cause thread breakage at an inappropriate location, or a large amount of bobbin thread is wound on the bobbin thread bobbin 1. If so, there were cases where a sufficient slip prevention effect could not be obtained.

This invention has been made in view of the above-mentioned problems, and always realizes stable feeding of the bobbin thread in the thread cutting operation regardless of the change of the bobbin thread winding amount in the bobbin thread bobbin. The purpose of the present invention is to provide a bobbin presser for a sewing machine.

[0009]

According to the present invention, a bobbin bobbin accommodated in a sewing machine hook is reciprocated in a movement path from a position where the bobbin wound around the lower thread winding portion is joined to a non-interference position with the sewing machine hook. A bobbin presser movably supported, a spring body for urging the presser member toward the joining position, and a holding member by moving the presser member to a non-interference position with the sewing machine hook when the thread trimming mechanism is not operating. In addition, a pressing movement mechanism that releases the pressing member when the thread trimming mechanism operates is provided.

[0010]

In the present invention, the pressing member is constantly urged by the spring body toward the peripheral surface of the lower thread winding portion of the lower thread bobbin, and during the thread cutting operation, the pressing member is wound around the lower thread bobbin by the urging force of the spring body. The loaded bobbin thread is pressed to prevent the bobbin thread bobbin from idling. Therefore, when a large amount of the bobbin thread is wound around the bobbin thread bobbin, the biasing force of the spring body increases, and conversely, when the amount of the bobbin thread wound around the bobbin thread bobbin is small. Therefore, the biasing force of the spring body is reduced. Therefore, the bobbin bobbin is provided with a resistance force that is in inverse proportion to the bobbin thread amount, so that a good tension can be always applied to the bobbin thread, and idling and thread breakage at an inappropriate position are prevented. be able to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
It will be explained based on. In the drawing, reference numeral 10 denotes a sewing machine hook. The sewing machine hook 10 includes an outer hook 11 that rotates in synchronization with a lifting operation of a sewing needle, and an inner hook 12 that is rotatably fitted in the outer hook 11. The bobbin case 13 is detachably mounted in the inner hook 12. In addition, in the bobbin case 13, the bobbin winding portion 1
A bobbin thread bobbin 14 (see FIG. 2) having a 4a and a collar portion 14b is rotatably accommodated. These are almost the same as those conventionally used,
The bobbin case 13 is different from the conventional one in that an insertion hole 13a (see FIG. 2) for inserting a pressing member described later is formed on the peripheral surface of the bobbin case 13.

A pressing member 15 is rotatably supported by a fulcrum shaft 20, and a tip portion 15a of the pressing member 15 can be inserted into and removed from the insertion hole 13a of the bobbin case 13. 16 is the other end 15 of the holding member 15.
The pressing member 15 is constantly urged in the direction a by a coil-shaped tension spring stretched between b and the machine frame of the sewing machine, and the tip end portion 15a of the pressing member 15 is urged by the urging force. The lower thread I wound around 14 can be pressed against the peripheral surface.

Reference numeral 17 denotes a presser moving mechanism for forcibly moving the presser member 15 in the b direction and holding it at a position where it does not interfere with the sewing machine hook 10. This presser moving mechanism is the same as the presser member 1 described above.
5 is provided with a movable body 18 that can move forward and backward and a cylinder 19 that moves the movable body. The cylinder 19 releases a thread-cutting foot pedal that operates a thread-cutting mechanism (not shown). , Operates according to the depression operation,
When the operation is disabled, the moving body 18 is moved in the c direction to forcibly hold the pressing member 15 in the non-interference position with the sewing machine hook 10.

Next, the operation will be described based on the above configuration.
During the sewing operation, the cylinder 19 is in the operating state because the operator releases the thread-cutting pedal that operates the thread-cutting mechanism. Therefore, the moving body 18 moves in the c direction and the pressing member 15 is forcibly held in the non-interference position with the sewing machine hook 10.

When the sewing operation is completed and the operator depresses the thread-cutting foot pedal, the thread-cutting mechanism starts the thread-cutting operation and the cylinder 19 becomes inoperative (moves in the direction d). The holding of the pressing member 15 by the moving body 18 is released. For this reason, the pressing member 15 rotates in the a direction around the fulcrum shaft 20 by the urging force of the pulling spring 16, and the tip portion 15a thereof penetrates the insertion hole 13a and projects into the bobbin case 13 to be attached to the bobbin bobbin 14. The bobbin thread I wound around is pressed.

As a result, the pressing force of the pressing member 15 acts as a resistance force against the rotation of the lower thread bobbin 14 associated with the lower thread delivering operation by the lower thread winding arm of the thread cutting mechanism. The pressing force of the pressing member 15 increases or decreases as follows depending on the amount of bobbin winding of the bobbin bobbin 14. That is, FIG.
As shown in (a), when the lower thread winding amount of the lower thread bobbin is relatively small, the lower thread bobbin 14 is pressed against the lower thread I at a position relatively close to the rotation center of the lower thread bobbin 14. The amount of extension of the pulling spring 16 is small, the urging force applied to the pressing member 15 is small, and a relatively small resistance force is applied to the lower thread bobbin 14.

Further, as shown in FIG. 2B, when a relatively large amount of the bobbin thread I is wound around the bobbin thread bobbin 14, the pressing member 15 is moved from the rotation center of the bobbin thread bobbin 14. Since the bobbin thread I is pressed into contact with the bobbin thread I at a relatively distant position, and the extension amount of the pulling spring 16 increases accordingly, the biasing force applied to the pressing member 15 becomes relatively large, and the bobbin thread bobbin 14 has a large resistance force. Will occur.

On the other hand, the torque required at the beginning of the rotation of the bobbin bobbin and the inertial force after the rotation increase or decrease in inverse proportion to the bobbin winding amount, as described in the prior art. Therefore,
At the time of the thread trimming operation, the rotational force that is inversely proportional to the bobbin winding amount,
A resistance force proportional to the bobbin thread winding amount is applied to the bobbin thread bobbin, and as a result, a constant resistance force always acts on the bobbin thread bobbin 14 regardless of the bobbin thread winding amount. Therefore, the bobbin bobbin 14 can be reliably prevented from idling irrespective of the variation of the bobbin thread winding amount, and the bobbin thread I can be reliably prevented from being excessively or insufficiently paid out, and an appropriate tension can be stably applied to the lower thread. It is possible to prevent yarn breakage at an inappropriate position.

In the above embodiment, the holding member 1
Although the pulling spring 16 is used as the spring body for applying the urging force to 5, it is also possible to use a push spring, a torsion coil spring, or the like, in which the compression amount increases or decreases in accordance with the increase or decrease in the bobbin winding amount. It is also possible to use a spring body other than the coil spring, such as a leaf spring. Further, an actuator other than the cylinder can be used as the moving means for moving the pressing member. For example, the moving member may be moved by a solenoid, or the moving member may be linked to a foot pedal or the like without using any actuator. It is not limited.

[0020]

As described above, in the bobbin pressing device of the sewing machine according to the present invention, the pressing member urged by the spring body is pressed against the bobbin thread wound around the bobbin thread bobbin during thread cutting operation, Since the bobbin bobbin is given an appropriate resistance force according to the bobbin winding amount, it is possible to reliably prevent the bobbin bobbin from idling during the thread cutting operation, and the required bobbin thread amount set in advance by the thread trimming device. There is an effect that the bobbin thread can be obtained without excess and deficiency, an excessive tension can be prevented from being applied to the bobbin thread, and the bobbin thread can be cut at an appropriate position by the thread cutting mechanism.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment according to the present invention.

FIG. 2 is a side view showing a bobbin case and a bobbin thread bobbin applied to the embodiment.

FIG. 3 is a front view showing an operation state of the thread cutting operation of the one shown in FIG. 1, (a) shows a case where the bobbin winding amount of the bobbin bobbin is small, and (b) shows many. The case where the lower thread is wound around the lower thread bobbin is shown.

FIG. 4 is a side view showing a bobbin pressing device of a conventional sewing machine.

FIG. 5 shows a state in which a thread is unwound from a lower thread bobbin,
(A) shows the case where the amount of winding of the lower thread wound around the lower thread bobbin is small, and (b) shows the case where a large amount of the lower thread is wound.

[Explanation of symbols]

 10 sewing machine hook 11 outer hook 12 inner hook 13 bobbin case 13a insertion hole 14 bobbin thread bobbin 15 pressing member 16 tension spring (spring body) 17 moving mechanism

Claims (2)

[Scope of utility model registration request] 1. A needle thread and a bobbin thread inserted through the sewing needle by the cooperation of a sewing hook that rotatably accommodates a bobbin thread bobbin wound with a bobbin thread and a sewing needle that moves up and down. For a sewing machine having a stitch forming means for knotting a bobbin thread fed from a bobbin and a thread cutting mechanism for guiding the bobbin thread laterally and cutting it when the stitch forming means is in an inoperative state, A bobbin retainer supported so as to reciprocate along a movement path from a position where the lower thread bobbin is joined with the peripheral surface of the lower thread winding portion to a position where the bobbin is not interfering with the sewing machine hook. A spring body for urging and a bobbin presser mechanism for moving and holding the bobbin presser to a position where the bobbin presser does not interfere with the sewing machine hook when the thread trimming mechanism is not operated and for releasing the bobbin presser when the thread trimming mechanism is operated are provided. Bobbin presser foot of a sewing machine characterized by Place 2. A bobbin bobbin is rotatably accommodated in a cylindrical bobbin case detachably mounted on a sewing machine hook, and an insertion hole for inserting a bobbin retainer is formed on a peripheral surface of the bobbin case. The bobbin pressing device for a sewing machine according to claim 1, wherein: