JP2647768B2 - Sewing machine thread tensioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread tensioner for a sewing machine in which a sewing thread is clamped by a pair of opposed thread tension plates in order to generate a predetermined tension on the sewing thread during sewing. , Which relates to the optimization of the thread clamping force.

[0002]

2. Description of the Related Art In a sewing operation by a sewing machine, in order to properly maintain a thread tightening and a sewing condition of a stitch, a tension of a sewing thread, particularly, a tension of a sewing machine upper thread (hereinafter, simply referred to as an upper thread) is properly adjusted. It is necessary to keep it. For this reason, conventionally, a thread tensioner as shown in FIG. 3 is provided on a side surface of a sewing machine arm.

[0003] In the drawing, a spindle 2 is projected from a sewing machine arm Ma via a mounting base 1, and two thread tension discs 3, 4 opposed to each other are arranged on the spindle 2 along the axial direction. It is inserted movably. A thread tension knob 5 is screwed into the tip of the spindle 2, and a thread tension spring 6 is press-fitted between the thread tension knob 5 and one thread tension 4. The pressing force of the spring 6 causes the thread tension discs 3 and 4 to clamp the upper thread and to apply a resistance to the movement of the upper thread to generate tension.

[0004] The holding force of the thread by the thread tension discs 3 and 4 can be appropriately changed by rotating the thread tension knob 5. That is, if the length of the thread tension spring 6 is reduced by rotating the thread tension knob 5 toward the machine frame side, the clamping force can be increased, and the thread tension knob 5 can be moved in the opposite direction. By rotating, the holding force can be reduced.

[0005]

However, in the above conventional thread tensioner, a coil-shaped thread tension spring 6 is press-fitted between a thread tension plate 4 and a thread tension knob 5. As a result, a uniform pressing force could not be applied to the thread tension disc 4, and the holding state of the upper thread was biased. That is, the pressing force applied to the thread tension disc 4 is the strongest at the joint with the end portion 6a of the thread tension spring 6 as shown in FIG.
The further away from here, the lower the pressing force. That is, the pressing force applied to the portion a becomes the smallest. As a result of the non-uniform pressing force applied to the thread tension disc 4 as described above, in the conventional thread tensioner, if the upper thread clamping portion of both thread tension discs 3 and 4 is slightly changed, the clamping force is changed. There has been a problem that the thread tension fluctuates and the thread tightness and the sewing condition vary. Further, since the adjustment range of the clamping force of the thread tension discs 3 and 4 is determined by the elastic coefficient of the thread tension spring 6, there is a problem that the adjustment range cannot be made large and lacks versatility.

The present invention has been made in view of the above problems, and a stable state of holding the upper thread can be always obtained by a pair of thread tension discs, and the adjusting range of the upper thread holding force can be set in a wide range. It is an object of the present invention to provide a thread tension plate of a sewing machine that can perform the operation.

[0007]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. That is, (a), the first and second thread tension discs are movably supported by a spindle protruding from the outer surface of the sewing machine frame, and the thread tension knob screwed to the spindle and the second thread tension knob. The first and second permanent magnets, which generate repulsive force from each other, are movably supported by the support shaft between the tensioner and the thread tension plate, and the first permanent magnet is generated by the repulsive force generated between the two permanent magnets. A second permanent magnet was pressed against the second thread tension plate against the thread tension knob, respectively, and the second permanent magnet was inserted between the two thread tension plates by a pressing force of the first thread tension plate against the second thread tension plate. By holding the sewing thread and rotating the first thread tension knob to change the facing gap between the two permanent magnets,
The pinching force of the sewing thread by the two thread tension discs is adjusted.

(B) The first and second thread tension discs and the first permanent magnet are movably supported on a support shaft projecting from the sewing machine frame so as to be sequentially movable. A second permanent magnet for generating a repulsive force is supported by the support shaft, and a coil for generating a magnetic force is provided on at least one of the first and second permanent magnets, and the coil is provided on the coil. Is applied to generate a repulsive force with respect to the permanent magnet facing the permanent magnet, and the first permanent magnet is pressed against the tension plate by the repulsive force against the first permanent magnet. A sewing thread inserted between the sewing machines is clamped. Further, in the thread tensioner described in (b), the current supplied to the coil may be changed by the current control means in accordance with the sewing conditions of the sewing machine.

[0009]

In the thread tension as described in the above (a), a uniform pressing force can be applied to the second thread tension disc by using the repulsive force generated in both permanent magnets. The thread tension tray can clamp the sewing thread with a uniform force regardless of the clamping position, and can generate a stable tension on the sewing thread. When adjusting the thread holding force, the thread engagement position of the thread tension knob with respect to the support shaft may be changed. That is, when the thread tension knob is moved, the second permanent magnet pressed against the thread tension knob is also moved, and the distance between the second permanent magnet and the first permanent magnet changes. As a result, a repulsive force is applied to the second permanent magnet in accordance with the distance between the second permanent magnet and the second permanent magnet, and the thread clamping force by both thread tension discs is adjusted.

Further, in the thread tensioner described in (b) above, the thread clamping force can be adjusted by adjusting the current flowing through the coil. In other words, the repulsion generated between the two permanent magnets is generated by the total magnetic force of the magnetic force of their own and the magnetic force of the coil,
By adjusting the current flowing through the coil to increase or decrease its magnetic force, the repulsive force generated between the two permanent magnets, that is, the yarn clamping force can be adjusted. In addition, if the current value flowing through the coil is increased or decreased at any time according to the sewing conditions such as the sewing speed and the thickness of the sewing product, even when the sewing conditions change during one sewing operation, a stable sewing is always performed. Quality can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing an upper half portion vertically cut off with reference to a center axis L. In the figure, reference numeral 11 denotes a cylindrical mounting base fitted to the front of the sewing machine arm Ma;
Reference numeral 12 denotes a support shaft fixed to the center of the mount 11, which protrudes from the front surface of the sewing machine arm Ma. The support shaft 12 is formed with a bifurcated portion 12a that is bifurcated into a predetermined range from the distal end, and a thread groove 12a1 is formed on the outer peripheral surface of the bifurcated portion. Note that 12
b indicates a portion (hereinafter, referred to as a shaft portion) other than the forked portion 12a in a portion protruding from the front surface of the sewing machine arm Ma.

Reference numeral 13 denotes a disk-shaped first member which is inserted into the shaft portion 12b of the support shaft 12 so as to be movable along the axial direction thereof.
The movement of the thread tension plate toward the sewing machine arm is restricted by contact with the opening edge of the mounting base 11. Reference numeral 14 denotes a disk-shaped second thread tension plate which is also inserted through the shaft portion of the support shaft 12, and is provided to face the first thread tension plate 13. Reference numeral 15 denotes a headed tubular dish holding member fixed to the front surface of the second thread tension dish 14, and a shaft portion 12a of the support shaft 12 is inserted into a through hole 15a formed in the center of the head. ing. Reference numeral 16 denotes an annular first permanent magnet fixed to the outer surface of the head of the plate holding member, and the support shaft 12 is inserted through the center of the first permanent magnet.

Reference numeral 18 denotes a cylindrical iron core movably inserted in the support shaft 12 along the axial direction thereof, and a coil 19 formed by winding a copper wire is fitted on the outer periphery of the cylindrical iron core. Further, the rear end face of the iron core 18 has an annular second shape.
The permanent magnet 17 is fixedly opposed to the first permanent magnet 16, and the support shaft 12 is inserted through a through hole formed in the center thereof. This second permanent magnet 17 and the first
The magnetic poles generated on each opposing surface of the permanent magnet 16 have the same polarity, and a repulsive force is generated in each of the permanent magnets so as to move them in the opposite direction along the axial direction of the support shaft 12. It is supposed to.

Reference numeral 20 denotes a cylindrical thread tension knob that is screwed to the forked portion 12a of the support shaft 12, and is provided to face the front end surface of the iron core 18. 21 is the thread tension picker 2
This is a rotation stopper interposed between 0 and the front end face of the iron core 18, and is non-rotatably inserted into the forked portion 12 a of the support shaft 12. Reference numeral 22 denotes a thread take-up spring wound around the support shaft 12, and acts by removing an unnecessary thread slack by applying an upper thread to its free end 22a.

In the sewing machine thread tensioner constructed as described above, the iron core 18 is moved by the thread tension knob 20 by the repulsive force generated between the first permanent magnet 16 and the second permanent magnet 17.
Is pressed against the rear end face of the
Is pressed toward the mounting base 11 together with the second thread tension plate 13, and the pressing force puts both thread tension plates 13 and 14 into a pressed state. Therefore, a predetermined tension can be generated in the upper thread by inserting the upper thread fed from the upper thread supply source between the two thread tension discs 13 and 14.

The needle thread tension can be adjusted by rotating the thread tension knob 20 to move the position of screwing with the support shaft 12 in the axial direction. That is, when the thread engagement position of the thread tension knob 20 is moved, the iron core 18 also moves in the same direction, and the interval between the first permanent magnet 16 and the second permanent magnet 17 increases or decreases. And
By increasing or decreasing the distance, both permanent magnets 13,
14 is reduced or increased, and the thread tension disc 1
The needle thread clamping force by the threads 3 and 14 also decreases or increases.

On the other hand, the needle thread clamping force can be further increased by applying a current to the coil 19.
That is, when a current is applied to the coil 19,
Magnetic lines of force passing through the iron core 18 and the second permanent magnet 17 are generated. By setting the current direction so that the direction of the magnetic field lines is the same as the direction of the magnetic field lines generated from the second permanent magnet 17, the magnetic force generated from the coil 19 is applied to the first permanent magnet 16. Acts as a repulsive force. Accordingly, a repulsive force is generated between the permanent magnets 16 and 17 by combining the repulsive force generated by their own magnetic force and the repulsive force generated by the magnetic force of the coil 19. The clamping force is coil 1
9 is increased as compared with the case where 9 is turned off.

As described above, in this embodiment, the first,
A uniform pressing force can be applied to the second thread tension tray 14 by the magnetic force generated in the second permanent magnet and the coil. Even if the position is moved, the upper thread can always be clamped with a constant clamping force. For this reason, the upper thread tension is stable, and the desired thread tightness and thread tension can be obtained.

In the case where the upper thread is clamped by using the magnetic force of the coil 19 as described above, the current supplied to the coil 19 is controlled, so that the upper thread can be further adjusted in addition to the adjustment by the thread tension knob 20. The thread clamping force can be adjusted. Therefore, if the current flowing through the coil 19 is automatically controlled in accordance with a change in sewing conditions or the like, it is possible to always perform sewing with an appropriate sewing tightening or sewing condition, and to achieve excellent sewing product quality. Obtainable.

This can be realized, for example, by using a control system circuit of the sewing machine as shown in FIG. In the figure, reference numeral 31 denotes a CPU as current control means, and the coil 19 is connected to the CPU 31a via a drive circuit 19a. Also, this CPU 3
An input device 34 for setting sewing conditions such as a sewing pitch and a sewing condition, a cloth thickness detector 35 for detecting a cloth pressure, and a predetermined number of pulses by one rotation of the main shaft of the sewing machine. An encoder 36 for transmitting a signal is connected, and various drive control circuits (not shown) such as a sewing machine motor drive circuit 37 are connected to the output side in addition to the drive circuit 19a. ing. A ROM 32 stores sewing data and the like, and a RAM 33 temporarily stores input data and the like.

In such a control system circuit, the CPU 3
When the sewing operation is started, the sewing speed is calculated based on the pulse signal output from the encoder 36, and the sewing speed is calculated based on the sewing speed and the cloth thickness data sent from the cloth thickness detector. The initial current value set at the beginning of the start is appropriately corrected, and the current value flowing through the coil is changed. In this way, by controlling the current flowing through the coil based on sewing conditions such as the cloth pressure and the sewing speed of the sewn product, when there is a step in the sewn product or when the sewing speed changes. In addition, an appropriate tension can always be applied to the upper thread, and excellent sewing product quality can be obtained.

In the above embodiment, the second permanent magnet 1
8 can move along the axial direction of the support shaft 12 together with the iron core 18, but the second permanent magnet 17 is fixed to the support shaft 12 and the needle thread clamping force is changed only by changing the magnetic force of the coil. It is also possible to make an adjustment, in which case the thread tension knob 20 can be omitted.

In the above embodiment, the case where the coil 19 is provided only on the second permanent magnet 17 side has been described.
It is also possible to provide a coil on the first permanent magnet 16 side, and conversely, without providing a coil at all,
The upper thread may be clamped only by the repulsive forces of 3, 14 and the present invention is not particularly limited to the above embodiment. Further, the thread tensioner according to the present invention is not limited to a lockstitch sewing machine, and can be applied to any other types of sewing machines.

[0024]

As described above, in the thread tensioner of the sewing machine according to the present invention, the repulsive force of a pair of permanent magnets provided opposite to each other, or the total of the repulsive force and the repulsive force generated in the coil. By applying such a repulsive force to the pair of thread tension discs, the joining state of both thread tension discs can be equalized. For this reason, even when the upper thread clamping position changes in both thread tension discs, the sewing thread can always be clamped with a constant force, and a stable tension can be generated in the sewing thread, and The adjustment range of the needle thread clamping force is also expanded as compared with the case where a conventional thread tension spring is used, and excellent versatility can be obtained. Furthermore, if the current value flowing through the coil is gradually increased or decreased according to the sewing conditions such as the sewing speed and the thickness of the sewing product, the entire sewing range can be maintained even when the sewing state changes during one sewing operation. In this manner, it is possible to always obtain a good thread tightening and sewing condition over the entire range, and to realize more excellent sewing product quality.

[Brief description of the drawings]

FIG. 1 is a partial vertical sectional side view showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a control system circuit of the sewing machine applied to this embodiment.

FIG. 3 is a partially longitudinal side view showing a conventional thread tensioner.

FIG. 4 is a partially longitudinal side view showing a state in which a thread tension spring is pressed against a thread tension disc in the one shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Support shaft 12a1 Thread groove 13 First thread tension disc 14 Second thread tension disc 16 First permanent magnet 17 Second permanent magnet 19 Coil 31 CPU (current control means) Ma Sewing arm

Claims (1)

(57) [Claims] 1. A spindle protruding from an outer surface of a frame of a sewing machine, a first thread tension plate supported on the spindle so as to be movable along an axial direction thereof, and a first thread tension plate. A second thread tension plate movably supported by the spindle along the axial direction between the spindle tip and the spindle; and a support between the second thread tension plate and the spindle tip. A first permanent magnet supported by a shaft so as to be movable along the axial direction thereof; and a first permanent magnet supported between the first permanent magnet and the support shaft tip by the support shaft. A second permanent magnet for generating a repulsive force with the magnet, a coil for generating magnetic force provided on at least one of the first and second permanent magnets, and a current flowing through the coil according to sewing conditions of the sewing machine. Current control means for changing the current control means. A current from the step is passed to generate a repulsive force on the permanent magnet opposed to the permanent magnet provided with the coil, and the first permanent magnet is pressed against the tone plate by the repulsive force on the first permanent magnet, and the pressing force is applied by the pressing force. A thread tensioner for a sewing machine, wherein a sewing thread inserted between the thread tension discs is clamped.