JPS6020030B2 - sewing machine tension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present 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.

In sewing machines, the tension of the needle thread has conventionally been adjusted by passing the needle thread through a tension plate.

The upper thread tension is adjusted by adjusting the pressure of the tension discs that sandwich the upper thread. Conventionally, the needle thread tension has been adjusted manually by the sewing person using a knob or the like. On the other hand, such needle thread tension depends on, for example, fabric thickness,
This is determined by the material of the cloth, the type or thickness of the sewing thread, the type (amplitude) of the pattern to be sewn, etc.
Among these, the thickness of the cloth to be sewn is an important determining factor for needle thread tension. Therefore, recently, attempts have been made to automatically adjust the pressure on the tension plate, that is, the needle thread tension, depending on the fabric thickness. however,
All of the conventional automatic tension devices are mechanical or mechanical, and their configurations are complicated.Also, with such mechanical devices, it is true that the pressing force of the tension plate is adjusted according to the thickness of the fabric. However, it is not known whether the pressure is set properly, that is, whether the pressure is surely appropriate for the thickness of the cloth. Therefore, none of the conventional attempts of this type have been put into practical use. Therefore, a main object of the present invention is to provide a tension device for a sewing machine that can automatically control needle thread tension.

Another object of the present invention is to provide a tension device for a sewing machine that can reliably set the needle thread tension in accordance with the thickness of the fabric.

In summary, this invention has a pressing spring that presses one of two tension plates toward the other, and a moving part that adjusts the elastic force of this pressing spring by the movement of the pressing spring, and this moving member. a cloth thickness sensor that generates a voltage according to the thickness of the cloth to be sewn, and a sensor that detects displacement of the moving member and generates a voltage corresponding to the displacement of the moving member; The energization is controlled by the voltage from the cloth thickness sensor and the feedback output voltage of the sensor.

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

FIG. 1 is a graph showing the relationship between cloth thickness and needle thread tension for explaining the principle of the invention.

That is, the thicker the fabric, the stronger the needle thread tension must be in proportion to it. Therefore,
The present invention attempts to adjust the needle thread tension, that is, the pressure of the tension plate, by detecting such cloth thickness. FIG. 2 is a schematic block diagram of the invention.

For example, a cloth thickness sensor 1 including a potentiometer derives an electrical signal (voltage or current) according to cloth thickness. The cloth thickness correlation electrical signal from the cloth thickness sensor 1 is applied to the contact A of the changeover switch 4 via the adjusting means 2. This switch 4 is for switching between automatic mode and manual mode, and its manual mode contact point M receives the output of the manual tension regulator 3. Then, the movable contact 0 of the changeover switch 4 is applied to the adder 5. The output of the adder 5, that is, the voltage from the cloth thickness sensor 1 or the voltage from the hand tension regulator 3, is applied to an actuator 7 including, for example, a reversible motor via a driving power amplifier 6. This actuator 7 is adapted to press one side of the tension plate via a spring, as will be described later. Therefore, the pressure on the tension plate is determined by the voltage from the fabric thickness sensor 1 or by the manual tension regulator 3.
regulated by the voltage from. The pressure in the tension plate is also detected by a sensor 8 which includes, for example, a potentiometer.

This sensor 8 derives an electrical signal (voltage, current, etc.) that correlates with the pressure of the tension plate. This pressure-correlated electrical signal from the pressure sensor 8 is applied to the adder 5 via a buffer amplifier 9. That is, the sensor 8 and the buffer amplifier 9 constitute a feedback loop. The above is the basic explanation of this invention, but below:
A more detailed example will be described. FIG. 3 is a structural diagram showing an example of a cloth thickness sensing mechanism used in the present invention.

In the configuration, a needle bar 10 is provided at the tip of the sewing machine arm 101.
2 connects a magnetic field groove (not shown) to the lower end of the needle bar 102. A presser foot 104 key is also displaceably housed in the lower end of the needle bar 102, with its tip protruding.

A block 10 is placed in the center of this presser bar 104.
7 is fixedly attached. This block 107
A spring 10 for applying presser pressure is provided between the locking portion and the locking portion.
6 is provided. The presser pressure of this spring 106 is determined by a presser pressure regulator I05 provided at the upper end of the presser bar 104.
adjusted by. A presser foot 1 is attached to the lower end of the presser bar 104.
08 is swingably attached. Therefore, the cloth 111 is sandwiched between the throat plate 109 and this presser foot 108, and is fed by the feed dog 1101. flock 107
A rack 114 is formed on the green side edge of the frame.

A bracket 112 is attached to the sewing machine arm 101 in close proximity to the block. Inside this bracket 112 are a pinion 115 adjacent to the rack 114, a gear 116 integrally attached to this pinion 115, and a gear 11 meshing with this gear 116.
7 is stored. Further, the gear 117 is connected to a rotating shaft of a potentiometer PMI supported by a bracket. Therefore, when the presser foot lifting lever 113 displaces the block 107 and therefore the presser bar 104 in the vertical direction, the displacement causes the rack 114, pinion 115
, the potentiometer P via the gear 116 and the gear 117.
It is transmitted as the rotation of MI. In other words, presser foot 10
4 and therefore the displacement of the presser foot 108 is given as the rotation of the potentiometer PMI in a certain ratio. Therefore, it will be understood that this potentiometer PMI has a resistance value that corresponds to the thickness of the cloth 111 sandwiched between the presser foot 108 and the wire 109. FIG. 4 shows a tension mechanism used in the present invention, FIG. 4a is a plan view thereof, and FIG. 4b is a side sectional view thereof. In the configuration, a worm gear 202 is connected to a rotating shaft 201 of the reversible motor RM. A worm wheel 203 that is integrally attached to a screw shank 204 is adjacent to this worm gear 202 . And Nejiha 20
4 is rotatably and fixedly supported in the axial direction by brackets 210 and 217. A metal fitting 205 having a screw hole into which the threaded rod 204 is screwed is inserted into one end (right side in the figure) of the threaded rod 204 .

A spring 206 is interposed between the metal fitting 205 and the worm wheel 203 to provide a resilient force to the metal fitting 205. The metal fitting 205 is connected to the slider 207 of the potentiometer PM2 by a screw 208. Also, on the pond end (left side in the figure) of the screw shank 204, there is a screw shank 204.
A block 209 is provided that has a screw hole that threads into the block 04.

This block 209 has a hole into which a bar 211 installed between brackets 210 and 217 is inserted. A presser plate 213 is inserted through the bar 211 so as to be freely displaceable in the length direction thereof. This presser plate 213
A presser spring 212 is inserted between the bar 211 and the block 209 and provides a resilient force to the presser plate. The presser plate 213 is, for example, a three-point presser, and the three points abut against the tension plate 214. Furthermore, the tension plate 21
The tension plate 215 is attached to the bracket 2 so that it faces M.
17. In such a configuration, when the reversible motor RM rotates, the worm gear 202
and by the worm wheel 203, the screw birch 204
rotates.

The block 209 is displaced in accordance with the rotation of the screw shank 204, and the force acting on the spring changes. Therefore, the elastic force of this spring changes, and the pressing force of the holding plate 213 and therefore the tension plate 214 also changes. That is, the rotation of the reversible motor RM changes the pressure between the tension plates 214 and 215, that is, the tension of the thread (not shown) passing between them. At the same time, due to the rotation of the screw shank 204, the metal fitting 205 is also displaced in its length direction, and the potentiometer P
M2 slider 207 is also displaced. Therefore, it will be understood that this potentiometer PM2 takes a resistance value depending on the position of the block 209 which determines the number of rotations of the reversible motor RM, that is, the pressure of the tension plate 214. In this embodiment, the amount of movement of the tension plate 214 is
The pitch of this movement is approximately a few steps, and it is difficult to detect this movement with high accuracy even if it is the movement of the slider of the potentiometer PM2 at the same pitch. Therefore, preferably screw shank 2
The pitch at which the block 209 of 04 is moved and the pitch at which the slider 207 of the potentiometer PM2 is moved are changed. That is, it is preferable that the movement of the tension plate is magnified and transmitted to the potentiometer PM2. In this invention,
The potentiometers PMI and PM2 described above control the energization of the reversible motor RM (which may be replaced with something like a solenoid).

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

This embodiment takes the configuration shown in the principle block diagram of FIG. 2 in its configuration. That is, the cloth thickness sensor 1 includes a potentiometer PMI shown in FIG. Half-time constant resistors VRI and VR2 for tuning are connected to both ends of the potentiometer PMI, respectively. This semi-fixed resistor VRI is connected to the power supply 10V, and the semi-fixed resistor VR2
is connected to the power supply -V. The slider of this potentiometer PMI is connected to the automatic mode terminal A of the automatic/manual changeover switch 4. The manual mode contact M of the changeover switch 4 is connected to the slider of the variable resistor of the manual tension regulator 3. This regulator and therefore the variable resistor 3 is connected at one end to 10V and at the other end to -V. Contact 0 of the changeover switch 4 is
It is applied to one input of an operational amplifier OA2 as an adder 5 via a DC amplifier OAI and a resistor RI. The other input of this amplifier OA2 is grounded, and its output is resistor R
Transistor TI constituting the power amplifier 6 via 2
and T2 as their respective base inputs.
The respective emitters of transistors TI and 2 are commonly connected and grounded by an emitter resistor R3. In addition, the collectors of transistors TI and T2 are each
It is connected to the bases of transistors T3 and T4, and to power supplies -V and +V via resistors R5 and R4. The transistors T3 and T4 are connected in series between the power supplies 1V and -V, and the series connection point is connected to the reversible motor RM (FIG. 4). One end of the potentiometer PM2 shown in FIG. 4 is connected to 10V, and the other end is connected to -V.

The slider is applied to one input of the operational amplifier OA2 via a DC amplifier OA3 serving as a buffer amplifier 9. Next, the operation of such a configuration will be explained. First, the case where the changeover switch 4 is set to automatic mode will be explained.

Raise the presser foot lifting lever 113 shown in FIG.
04, the cloth 111 to be sewn is passed between the presser foot 108 and the throat plate 109. Then, the presser foot lifting lever 113 is lowered and the cloth 111 is pressed by the presser foot 108. Such presser foot lifting lever 113 and therefore presser foot 10
4, a voltage is derived from the potentiometer PMI. At this time, the potentiometer PMI indicates that the needle thread tension dial of the slave is set, for example, from "1" to "9".
'', the voltage from the slider is set to 0 at a tension in the middle of these nine levels. If the slider is displaced toward the +V side of the power source, the tension will be stronger, and if the slider is displaced toward the −V side of the power source, the tension will be weaker. The voltage from the potentiometer PMI is applied to the changeover switch 4, the DC amplifier OA1, the resistor R1, and the operational amplifier OA.
2, applied to the bases of transistors TI and T2 via resistor R2. Here, the transistor TI is pnp
The transistor T2 is an npn transistor.

Therefore, the potential of the base of the transistor TI is (
1), and the transistor T2 is conductive when its base potential is (10). The thickness of the cloth 111 to be sewn is large, so when the voltage from the potentiometer PMI is (10), the transistor T2 conducts.
Power supply +V to bias resistor R4 - potentiometer T2
- Current flows to ground potential via resistor R3. Accordingly, P
The rlp transistor T4 becomes conductive, and a forward current flows from the power supply of 1 V to the reversible motor RM through the transistor T4. Therefore, in FIG. 4, the worm wheel or threaded rod 204 is rotated by the rotation of the reversible motor RM.
rotates, and the slide flock 209 is displaced to the left in the figure. Correspondingly, the pressure spring 212 is pressed by this slide block, and the pressure plate 213 and therefore the tension disc 214 are pressed even more tightly by this spring 212. Therefore, in this case, the tension plate 2
The pressing force between 14 and 215 becomes stronger, and the tension of the thread passing between them becomes greater. Also, the fabric to be sewn is 111
If the potential from potentiometer PMI is (1), the output of operational amplifier OA2 becomes (1) voltage, and transistor TI becomes conductive. Therefore, from the ground side, resistor R3 - transistor TI - bias resistor R5 A current flows to the power supply -V through the transistor T3.Accordingly, the npn transistor T3 becomes conductive, and a reverse current flows from the ground side to the power supply -V through the transistor T3 in the reversible motor RM. When the motor RM rotates, the slide block 209 is displaced to the right in the figure. Therefore, the presser spring 212 is extended in the direction of release, and the pressure on the presser plate 213 and therefore the tension plate 214 is reduced. Therefore, this tension The tension of the thread passing between the plates 214 and 215 becomes smaller.As mentioned above, when the reversible motor RM is rotated in the forward or reverse direction, the sliding movement of the potentiometer PM2 shown in FIG. The child will also be displaced.

This potentiometer PM2 is also the potentiometer P.
Similar to MI, for example, the output voltage is 0 at the middle tension among nine tension levels, and if the tension is stronger than that (10), a voltage is derived, and if it is weaker, (
-) voltage shall be derived. Therefore, the output of the potentiometer PM2 is substantially equal to the tension plate 21
It is proportional to the pressure of 4. By feeding back the output of the potentiometer PM2 to the drive circuit, an appropriate tension pressure can be always set according to the thickness of the cloth. In other words, this buffer amplifier OA
If the output of 3 and the output of DC amplifier OA1 (resistance RI) are not equal, the output of operational amplifier OA2 becomes 0 potential, transistors TI and T2 are both cut off, and no energizing current flows to reversible motor RM. Therefore, at this time, the needle thread tension is determined according to the fabric thickness.The semi-fixed resistor VRI or VR2 for tuning performs tuning in this automatic mode.

In other words, in automatic mode, as is clear from the above explanation, the upper thread tension is automatically determined, but in the case of special threads or stitches, if you want to change the tension slightly more than the one appropriate for the thickness of the fabric. There is. Therefore, in such a case, by adjusting the semi-fixed resistor VRI or VR2, a more appropriate needle thread tension can be obtained. Further, when the changeover switch 4 is switched to the manual mode, the reversible motor RM is energized and controlled by the voltage from the variable resistor 3 instead of the cloth thickness detection voltage from the cloth thickness sensor 1.

Naturally, a feedback loop including the potentiometer PM2 also operates at this time. FIG. 6 is an illustrative view showing another embodiment of the tension mechanism used in the present invention, FIG. 6a is a plan view thereof, and FIG. 6b is a side sectional view thereof. In construction, this embodiment is the same as that of FIG. 4, except for the following points. That is, in FIG. 4, the potentiometer PM2 is a slide type, but in this embodiment, the potentiometer PM2 is a multi-rotation type. For that purpose, threaded rod 2
04', a screw is formed only on the slide block 209 side, and a pin 218 is provided protruding from the potentiometer PM2 side. A coupling block 221 is attached to the tip of the rotating shaft 219 of the potentiometer PM2.
is fixedly attached by screw 2201. The coupling block 221 also has the screw shank 20.
A notch is provided so that a pin 218 formed at 4' can be engaged, thereby connecting the threaded rod 204' and the rotating shaft 209 so that they can rotate together. In this way, the rotation of the reversible motor RM is controlled by the potentiometer PM.
2, and this potentiometer PM2 is included in the feedback loop. As described above, according to the present invention, the needle thread tension is automatically set according to the fabric thickness, so complicated operations for setting the tension are not required.

Also, at this time, the tension is accurately set according to the thickness of the fabric due to the action of the feedback loop. In the above-described embodiment, the cloth thickness sensor is linked to the presser foot, but this sensor is installed separately, for example in a part of the sewing machine bed, and measures only the cloth thickness in advance before starting sewing. Thereby, an electric signal may be generated depending on the cloth thickness.

Furthermore, in addition to the potentiometer method described in the examples, such cloth thickness sensors can also be used, for example, a differential transformer method, a magnetic flux change method (eddy current change method), a resistance wire strain method (semiconductor pressure sensor method), a photoelectric method ( Of course, a method such as a method of changing the area of the passing light beam east) or a method of changing the capacitance may also be adopted.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between cloth pressure and tension for explaining the principle of this invention. FIG. 2 is a basic block diagram of the present invention. FIG. 3 is a scale diagram showing a cloth pressure sensing mechanism used in the present invention. FIG. 4 is an illustrative view showing the tension mechanism used in the present invention. FIG. 5 is an electrical circuit diagram of an embodiment of the present invention. FIG. 6 is an illustrative view showing another embodiment of the tension mechanism used in the present invention. In the figures, the same reference numerals indicate the same or equivalent parts, 1 is a cloth thickness sensor, 2 is a tuning means, 3 is a manual tension adjuster, 4 is a changeover switch, 5 is an adder, 6 is a power amplifier, 7
is the actuator, 8 is the sensor, 9 is the buffer amplifier,
PM1 and PM2 are potentiometers, and RM is a reversible DC motor. Matuzu koji zu kozu zu koji 6

Claims (1)

[Scope of Claims] 1. A tension device for a sewing machine that passes a thread between at least two tension discs and adjusts the tension by the pressure of the thread, which detects the thickness of the fabric to be sewn. a cloth thickness sensor that generates an electric signal in accordance with the cloth thickness sensor; a presser spring that presses one side of the tension plate against the other side; a moving member that changes the elastic force of the presser spring by its movement; a movement drive means for displacing the moving member in accordance with an electric signal; a movement amount sensor for detecting the movement amount of the moving member and deriving an electric signal according to the movement amount;
and a feedback loop for feeding back the output of the movement amount sensor to the movement drive means. 2. The fabric to be sewn is fed between a presser foot connected to the tip of the presser bar and a needle plate, and the fabric thickness sensor detects the amount of displacement of the presser bar. The tension device for the sewing machine described in Section 1. 3. The tension device for a sewing machine according to claim 1 or 2, wherein the cloth thickness sensor includes a potentiometer. 4. The tension device for a sewing machine according to any one of claims 1 to 3, wherein the movement amount sensor includes a potentiometer. 5. The tension device for a sewing machine according to any one of claims 1 to 4, wherein the moving drive means includes a reversible DC motor. 6. A threaded rod is connected to the reversible DC motor,
5. A tensioning device for a sewing machine according to claim 4, wherein said moving member is screwed onto said threaded rod and moves linearly. 7 Claims 1 to 6 further include a switch for switching between automatic mode and manual mode.
A tension device for a sewing machine according to any of paragraphs. 8. The tension device for a sewing machine according to claim 7, further comprising means for finely adjusting the output of the cloth thickness sensor in the automatic mode.