JPS588222Y2 - sewing machine tension device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tension device for a sewing machine, and more particularly to a tension device for a sewing machine that automatically determines the tension of an upper thread.

Conventionally, the tension of the upper thread has been manually set by a seamstress while observing the degree of intertwining of the seams and the balance between the tensions of the upper thread and the lower thread each time the sewing is performed.

On the other hand, the needle thread tension is determined by various factors such as the thickness of the cloth to be sewn, the weave of the cloth, the material of the sewing thread, the thickness of the sewing thread, the type of pattern to be sewn, and the sewing speed.

Among these factors, the thickness of the fabric, the material of the sewing thread, and the way the fabric is woven are important determinants of needle thread tension.

That is, even if the fabrics are made of the same material, the frictional force between the fabric and the thread becomes large when the thread is pulled up in the thread line process where the fabric is thick.

If the coefficient of friction between the cloth and the thread is large, it is necessary to increase the needle thread tension.

The optimal tension also changes depending on how the cloth is woven.

If you classify commonly used fabrics, for example, plain weave.

Twill or stockinette weave can be considered.

For fabrics with a weak waist, such as mesh weave, the tension must be relatively weak to prevent puckering (stitch wrinkles), compared to relatively stiff fabrics such as plain weave or twill weave. No.

Therefore, attempts have been made to automatically adjust the tension of the upper thread.

However, all of the conventional automatic tension devices are mechanical or mechanical, and if they incorporate all of the many factors that determine needle thread tension as described above, they will have a very complicated structure. Moreover, it is difficult to obtain the desired tension due to stiffness or deflection of mechanical parts or wobbling between parts, and it is also impossible to detect whether the desired tension pressure is applied to the tension plate.

Therefore, there is a need for an automatic tension device for a sewing machine that can reliably set the upper thread tension appropriately.

Therefore, the main purpose of this invention is to provide a tension device for a sewing machine that can reliably and appropriately set a desired needle thread tension.

In summary, this idea connects a solenoid plunger to one of two tension plates, and multiplies or adds voltages depending on factors such as the right bank, the weave of the cloth, and the material of the thread that determines the tension. The tension of the sewing machine is such that a solenoid is energized by a voltage, the pressure of the tension plate is detected by a pressure sensitive element such as a strain gauge, and the output of this pressure sensitive element is fed back to the solenoid energizing voltage for correction. It is a device.

The above objects and other objects and features of the present invention will become clearer from the following detailed description with reference to the drawings.

In lock stitch sewing machines, the knot formed by the upper thread and bobbin thread is formed at a position where the tension of the upper thread and the lower thread are balanced, and between the semi-fixed bobbin tension and the knot and the fabric. The position of the knot is determined primarily by the frictional forces that occur and the corresponding variable upper thread tension.

Therefore, the main factor that determines needle thread tension is the relationship between the fabric and the thread, and among these, the thickness of the fabric,
The frictional force between the cloth and the thread and the amount of thread consumed have a major influence.

The graph in Figure 1 was created based on data obtained from experiments showing the relationship between the frictional force between the cloth and thread, which comes mainly from the thickness of the cloth and the materials of the cloth and thread, and the needle thread tension. , the tension of the needle thread, the horizontal axis the thickness of the cloth, and the relationship between the frictional force between the cloth and the thread [y-f(X)].

In this graph, as the thickness of the fabric and the frictional force between the fabric and thread increase, the tension of the upper thread needs to be increased.
The diagram is a curved line sloping upward to the right in FIG.

As mentioned above, with the needle thread tension as the determining factor, y
= f ( In this way, the most preferable needle thread tension is determined by integrating needle thread tension determining factors that are relatively unrelated to other factors that determine needle thread tension.

FIG. 2 is a schematic block diagram of this invention.

For example, the right bank sensor 1 including a potentiometer derives an electrical signal (voltage or current) depending on the cloth thickness.

This right bank correlated electric signal from the right bank sensor 1 is sent to a multiplier 2
given to.

Further, this multiplier 2 is supplied with a voltage from a switch 3 .

This switch 3 is connected to one end of each of the semi-fixed resistors 41 to 4m of the cloth quality-thread quality correlation voltage generating means 4.

The other ends of these semi-fixed resistors 41 to 4m are commonly connected to the reference voltage source 5.

Therefore, by switching the switch 3, the multiplier 2 is provided with a voltage that correlates with the selected fabric/yarn quality.

Then, in this multiplier 2, the function y=f (X) is
Calculation is performed using the heavy correlation voltage and the cloth quality-thread quality correlation voltage.

The output of this multiplier 2 is given as an input to an adder 6.

The input of this adder 6 is further supplied with a voltage from a switch 7 .

This switch 7 selectively switches semi-fixed resistors 81 to 8n included in means 8 for setting the weave of the cloth.

The other ends of the semi-fixed resistors 81 to 8n are commonly connected to the reference voltage source 9.

Therefore, by switching this switch 7, a voltage correlated to the weave of the cloth is selectively applied to the adder 6.

Then, in this adder 6, the output voltage C from the multiplier 2
'! = f (

This switch 13 is for switching between automatic mode A and manual mode M, and the contact point M for the manual mode is
receives the output of variable resistor 11 as a manual tension regulator.

This variable resistor 11 is connected to a reference voltage source 12.

The movable contact O of the changeover switch 13 is connected to the adder 1.
Connected to 4.

The output of the adder 14, that is, the voltage from the adder 6 or the voltage from the variable resistor 11 as a manual tension regulator, is applied to an actuator 16 including, for example, a solenoid via a driving power amplifier 15.

This actuator 16 is connected to one of two tension plates (not shown), and is adapted to press this one tension plate.

The pressure in the tension plate is therefore regulated by the voltage from the adder 6 or by the voltage from the manual tension regulator 11.

Further, the pressure of the tension plate is detected by a sensor 17 including a semiconductor element such as a strain gauge.

This sensor 17 derives an electrical signal (voltage, current, etc.) that correlates with the pressure in the tension plate.

The pressure-correlated electric signal from the sensor 17 is applied to the adder 14 via a buffer amplifier 18.

That is, the sensor 17 and the buffer amplifier 18 constitute a feedback loop.

The above is a basic explanation of this invention, and more detailed examples will be described below.

FIG. 3 is a structural diagram showing an example of the right bank sensing mechanism used in this invention.

In the configuration, a needle bar 10 is provided at the tip of the sewing machine arm 101.
2 is connected to an upper shaft (not shown).

A sewing needle 103 is attached to the lower end of this needle bar 102.

A presser bar 104 is further housed in the sewing machine arm 101 so as to be freely displaceable so that its tip protrudes.

A block 10 is placed in the center of this presser bar 104.
7 is fixedly attached.

A spring 106 for applying presser pressure is provided between the block 107 and the locking portion.

The presser pressure of this spring 106 is adjusted by a presser pressure regulator 105 provided at the upper end of the presser bar 104.

A presser foot 108 is swingably attached to the lower end of the presser bar 104.

Therefore, the cloth 111 is attached to the throat plate 109 and this presser foot 108.
and is fed by the feed dog 110.

A rack 114 is formed on the side edge of the block 107.

A bracket 112 is attached to the sewing machine arm 101 in close proximity to the block.

A pinion 115 that meshes with the rack 114, a gear 116 that is integrally attached to the pinion 115, and a gear 117 that meshes with the gear 116 are housed inside the bracket 112.

Further, the gear 117 is connected to a rotating shaft of a potentiometer PM supported by a bracket.

Therefore, block 1 is lifted by the presser foot lifting lever 113.
07 and therefore, when the presser bar 104 is displaced in the vertical direction, the displacement causes the rack 114. Pinion 115. Gear 116. It is transmitted via gear 117 as rotation of potentiometer PM.

In other words, presser bar 104 and therefore presser foot 108
The amount of displacement is given as the amount of rotation of the potentiometer PM at a certain ratio.

Therefore, this potentiometer PM is connected to the presser foot 108.
It will be understood that the resistance value is determined according to the thickness of the cloth 111 sandwiched between the needle plate 109 and the throat plate 109.

FIG. 4 shows the tension mechanism used in this idea, FIG. 4a is a plan view of the tension mechanism, and FIG.

In configuration, this tensioning mechanism is a solenoid SQL
including.

The plunger 201 of the solenoid SQL has a screw 202.
One end of the adjustment plate 203 is connected by.

An adjustment plate 204 is provided on the adjustment plate 203, which cooperates with the adjustment plate 203 to adjust the moving length of the plunger 201 by the solenoid SQL.

This pair of adjustment plates 203 and 204 are connected to two screws 205.
and 206 are connected so that their lengths can be adjusted.

The other end of the adjusting plate 204 is connected to the connecting plate 2 by a screw 207.
It is rotatably connected to one end of 08.

The other end of the connecting plate 208 is connected to a bracket 210 by a screw 209.

This bracket 210 is fixedly attached to the sewing machine arm by screws 211.

A push plate 215 is attached to the bottom of the bracket 210 so as to be slidable in the longitudinal direction of the bracket 210.

A pin 215a is integrally attached to the push plate 215 in a protruding manner.

This pin 215a contacts a contact portion 208a formed at the other end of the connecting plate 208.

Furthermore, long holes 216 and 217 are bored in the push plate 215, and screws 213 and 21 attached to the bracket 210 are inserted into the long holes 216 and 217.
4 is inserted.

Then, the end of this push plate 215 is bent and connected to the push plate 218.

This pushing plate 218 is for pushing the tension plate 219 in the direction of the tension plate 220 provided oppositely.

Furthermore, a pressure sensor PS is provided behind the tension plate 220 to detect the pressure of the tension plate 219 applied to the tension plate 220.

These pressure sensor PS, tension plate 220.
219. Holding plate 218. The push plate 215 is the bracket 22
It is loosely inserted into a pin 222 protrudingly attached to 1.

In such a configuration, when the solenoid SOL is energized and the nib plunger j201 is attracted in the direction of arrow A, the adjustment plate 203 and therefore 204 are similarly displaced in the direction of arrow A.

Accordingly, the contact portion 208a of the connecting plate 208 rotates in the direction of arrow B about the screw 209 as a fulcrum.

Therefore, the pin 215 that comes into contact with this contact portion 208a
A is pushed in the direction of arrow B.

Therefore, the press plate 215 is pushed in the direction of the arrow B, and the press plate 218 connected to the tip thereof, and therefore the tension plate 219, are pushed in the direction of the arrow B.

Therefore, the tension plates 219 and 220 come into strong contact, and the tension of the thread (not shown) passing between them increases.

Further, at this time, the pressing force of the tension plate 219 is detected by a pressure sensor PS provided, for example, from a semiconductor pressure sensitive element.

As the pressure sensor PS, a strain gauge is used which changes its resistance value depending on the pressure between the tension plate 219 and 219 and 220.

FIG. 5 is an electrical circuit diagram showing an embodiment of this invention.

This embodiment is constructed according to the basic block diagram shown in FIG.

In the configuration, the heavy sensor 1 includes a potentiometer PM as shown in FIG.
is connected between resistors R1 and R2, and its slider is applied to one input of operational amplifier OAI via resistor R3.

Further, the resistor R1 is connected to the power supply +V, and the resistor R2 is grounded.

The other input of the operational amplifier OAI is grounded, and a resistor R4 is connected between the output terminal and the one input.

Therefore, the resistance value of this potentiometer PM is the third
Depending on the thickness of the cloth 111 shown in the figure, that is, the presser bar 104
, the output voltage of the operational amplifier OA1 changes accordingly.

The output voltage of the heavy sensor 1, that is, the operational amplifier OAI, is applied to the multiplier 2 via a resistor R5.

The input of this multiplier 2 is further supplied with a cloth quality-thread quality correlation voltage from a switch 3, as shown in FIG.

Then, the output of the multiplier 2 is sent to the adder 6 via the resistor R6.
The signal is applied to one input of the operational amplifier OA2 constituting the circuit.

A resistor R7 is further connected to one input of the operational amplifier OA2.
A voltage related to the weave of the cloth from said switch 7 is applied via.

The other input terminal of the operational amplifier OA2 is grounded, and a resistor R8 is connected between its output terminal and the one input terminal.

The output of this adder 6, that is, the operational amplifier OA2, is connected to one of the variable resistors 10 for fine adjustment.

The output voltage of the operational amplifier OA2 is applied to the automatic mode contact A of the changeover switch 13.

A manual mode contact M of this changeover switch 13 is connected to a manual tension regulator, that is, a variable resistor 11.

Furthermore, the movable contact O of this changeover switch 13 is connected to one input of an operational amplifier OA3 as an adder 14 via a resistor R9.

The other input of the operational amplifier OA3 is grounded, and its output is connected to the one input via a resistor RIO and to the base of a transistor T1 constituting the power amplifier 15 via a resistor R11.

The base of this transistor T1 is grounded via a resistor R13 and connected to the power supply +■ via a resistor R12.

The collector of this transistor T1 is connected to one end of a solenoid SOL as shown in FIG. 4, and is also connected to the collector of a transistor T2.

The emitter of transistor T1 is connected to the base of transistor T2.

The emitter of transistor T2 is connected.

The other end of the solenoid SQL is connected to the 10V power supply.

Furthermore, a diode D is connected in parallel in opposite directions to both ends of this solenoid SQL.

Therefore, it can be seen that this solenoid SQL acts as the actuator 16 shown in FIG. 2.

Pressure sensor PS constitutes a bridge circuit together with resistors R14, R15, and R16, and is included in sensor 17.

Note that the variable resistor VR included in this bridge circuit 7 is for fine adjustment.

The slider of this variable resistor VR is connected to one input of an operational amplifier OA4 constituting the buffer amplifier 18.

One end of the bridge circuit is connected to a fixed power supply Vc, and the other end is grounded.

The connection point between the pressure sensor PS and the resistor R15 is connected to the other input of the operational amplifier OA4 and also to its output.

The output of this operational amplifier OA4 is connected to one input of the operational amplifier OA3 via a resistor R17.

In operation, first, the case where the changeover switch 13 is switched to automatic mode will be described.

In the automatic mode, presser foot lifting lever 113 is operated to sandwich cloth 111 between presser foot 108 and throat plate 109.

Then, the presser foot lifting lever 113 is pushed down, and the presser foot 108 presses the cloth 111.

In response to the operation of this presser foot lifting lever 113, the presser bar 10
4 is displaced and the potentiometer PM changes its resistance value.

As a result, the resistance value of the potentiometer PM corresponds to the thickness of the cloth 111 to be sewn.

Therefore, the output voltage of the Ichihara sensor 1, that is, the operational amplifier OAI, also corresponds to its resistance value and, therefore, the thickness of the cloth 111.

In addition, semi-fixed resistors 41 to 41 serve as cloth quality/thread quality setting means.
Within 4m, switch terminals are provided corresponding to the combinations of sewing thread and cloth material used, such as polyester, cotton, silk, etc., and each semi-fixed resistor connected to this terminal is connected to the value obtained by the solid line. Let the correlated resistance values be,
By switching this switch 3 according to the material of the cloth and thread to be sewn, a predetermined voltage corresponding to the cloth quality-thread quality is applied from the switch 3 to the multiplier 2.

Then, the multiplier 2 calculates the function Y=f(x) and provides it to the adder 6, that is, the operational amplifier OA2.

Furthermore, the switch 7 is switched according to the weave of the cloth, such as plain weave, twill weave or stockinette weave.

Accordingly, a voltage correlated to the weave of the cloth is derived from the switch 7 and is applied to the operational amplifier OA2.

In other words, the multiplier 2 multiplies the electrical signals based on the factors that have a correlation among the factors that determine the needle thread tension to obtain an electrical signal corresponding to the function y, and this electrical signal is applied to the An adder 6 adds factors that independently determine tension, such as weaving, and an electrical signal that can be used.

Therefore, the output of the adder 6, that is, the operational amplifier OA2, becomes an electric signal (voltage) for determining the tension in this invention.

This tension determining electric signal is then applied to an operational amplifier OA3 as an adder 14 via a variable resistor 10 for fine adjustment and a changeover switch 13 or a resistor R9.

Therefore, the output of the operational amplifier OA3, ie, the base of the transistor T1, is supplied with a voltage for adjusting the tension.

Adjust the tension on the base of transistor T1! When a voltage is applied, this transistor T1 becomes conductive to a depth corresponding to the voltage.

Therefore, the transistor T2 connected to this transistor T1 is likewise conductive at a depth depending on the voltage and therefore the width.

Therefore, current flows from the power supply +■ to the solenoid SQL, and the solenoid SQL is energized.

It should be noted that it is easily understood that the biasing strength of the solenoid SQL at this time is in accordance with the above-mentioned Ichihara.

When the solenoid SQL is energized and the plunger 201 shown in FIG. 4 is pulled in the direction of arrow A, the tension plate 219 is pressed against the tension plate 220 as described above.

At this time, the resistance value of the pressure sensor PS provided at the rear of the tension plate 220 changes depending on the pressure contact force.

The balance of the bridge circuit including this pressure sensor PS on one side changes.

That is, the difference between the output voltage on the side of this bridge circuit composed of resistor R14, variable resistor VR, and resistor R15 and the output voltage on the side composed of pressure sensor PS and resistor R15 is detected by this operational amplifier OA4. , is fed back to the operational amplifier OA3 via the resistor R17.

Therefore, the solenoid SQL is energized according to the pressure, and this solenoid SQL is energized and maintained in this state until the pressure between the tension plates 219 and 220 becomes appropriate.

In this way, the tension of the thread passing between tension plates 219 and 220 can be set automatically.

In manual mode, changeover switch 13 is set to contact M
Switch to

At this time, the operation differs from the automatic mode described above only in that instead of the tension adjustment voltage from the adder 6, the output voltage from the manual tension regulator 11 is applied.

Therefore, detailed explanation of its operation will be omitted.

As described above, according to this invention, the tension plate is directly pressed by the solenoid actuator (actuation mechanism), and the pressing pressure is fed back to the actuator drive system, so the tension setting is accurate. and can be made to any desired value.

Note that the fine adjustment variable resistor 10 performs fine adjustment in automatic mode.

In other words, in automatic mode, the needle thread tension is automatically determined, as is clear from the above explanation, but for example, if you are using a special thread or sewing, you may want to change the tension a little more than the tension depending on the fabric. be.

Therefore, if the variable resistor 10 is adjusted in such a case, a more appropriate needle thread tension can be obtained.

In the above-mentioned embodiment, the weight sensor is linked to the presser foot bar, but this sensor is installed separately in a part of the sewing machine bed, and measures only the right bank before starting sewing. It is also possible to manually issue an electric signal depending on the right bank.

In addition to the potentiometer method explained in the example, such a heavy-duty sensor also uses a differential transformer method, a magnetic flux change method (eddy current change method), a resistance wire strain method (semiconductor pressure sensor method), a charging method (pass-through method), etc. Of course, a method such as a method of changing the area of the light beam flux) or a method of changing the capacitance may also be adopted.

Further, in the above embodiment, the function y=f in the multiplier 2
We have only explained the right bank and thread quality - fabric quality as factors for (X), but this multiplier also includes the friction coefficient between the needle thread and the tension plate, the thread consumption per stitch or per pattern cycle. , bobbin thread tension, etc. may be provided, and signals from these voltage sources may be provided.

That is, the multiplier 2 may be supplied with electrical signals of factors that are correlated with each other in order to determine the upper thread tension.

Furthermore, although the adder 6 is configured to add only the weave of the cloth, if necessary, it may also add a constant correction value unique to the sewing machine.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between a function and tension to explain the principle of this invention. FIG. 2 is a basic block diagram of this invention. FIG. 3 is an illustrative diagram showing the right bank sensing mechanism used in this invention. FIG. 4 is an illustrative diagram showing the tension mechanism used in this invention. FIG. 5 is an electrical circuit diagram of one embodiment of this invention. In the figures, the same reference numerals indicate the same or equivalent parts, 1 is a thick sensor, 2 is a multiplier, 3 and 7 are switches, and 4
10 is a fine adjustment means; 11 is a manual tension adjuster; 13 is a changeover switch; 6.14 is an adder; 15 is a power amplifier; is an actuator, 17 is a sensor,
18 is a buffer amplifier, PM is a potentiometer, SO
L is a solenoid, and PS is a pressure sensor.

Claims (3)

[Scope of utility model registration request] (1) Sandwich the thread with at least two or more tensions,
In a sewing machine that adjusts the tension of the thread by the pressure, means for generating a related electrical signal based on various factors related to the tension, and generating a tension determining electrical signal for calculating the related electrical signal and adjusting the tension. a drive amplifier for amplifying the tension-determining electric signal; a solenoid whose electromagnetic force is controlled by the magnitude of the output of the drive amplifier; an actuation mechanism for moving at least one of the tension amounts by the electromagnetic force of the solenoid; A sewing machine comprising a pressure sensing element that detects a certain amount of pressure and generates a pressure-correlated electrical signal, and a feedback loop that feeds back the pressure-correlated electrical signal from the pressure sensing element to the tension determining electrical signal generating means. tension device. (2) The tension device for a sewing machine according to claim (1), wherein the operating mechanism is a lever whose displacement is controlled by the electromagnetic force of the solenoid. (3) The feedback loop includes a bridge circuit that includes the pressure-sensitive element on one side, and a buffer amplifier that applies the output of the bridge circuit to the tension determining electric signal generating means. A tension device for a sewing machine according to item (2).