JPS5949822B2 - Sewing machine thread tension display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a sewing machine equipped with a thread tension device that can apply tension of different strength in accordance with each operation position by manual operation. The present invention relates to a thread tension display device for a sewing machine that can display a proper operating position.

Conventionally, in order to form stitches with good thread retrieval on cloth using a sewing machine, for example, in a lockstitch sewing machine, the tension of the upper and lower threads must be set to a predetermined strength. As seen in Japanese Patent Publication No. 2870, etc., tension is applied by adjusting the pressing force of the leaf spring of the bobbin thread bobbin case with screws, etc., and tension is applied to the upper thread.
The thread tension device found in No. 065 etc. is used to apply tension corresponding to the bobbin thread tension, and normally the same type of sewing thread is used for the upper and lower threads to form a stitch, but the sewing thread is The degree of slippage (frictional resistance), degree of elongation, etc. will vary depending on the thread tension, and therefore the actual thread tension will vary depending on the frictional resistance, etc. that the thread receives when passing between the tension discs of the thread tension device or between the leaf springs of the bobbin case. Varies depending on the type.

According to the applicant's experiments, for example, as shown in Figure 6,
When using sewing thread A as the upper and lower threads, if the bobbin case leaf spring is set so that the bobbin thread tension is, for example, 15 g, the optimal needle thread tension at this time is, for example, 180 g.
However, if you change the type of upper and lower threads and use the sewing thread with this setting, the actual lower thread tension will be, for example, 10 g because the slippage and elongation will be different from sewing thread A, and the optimal needle at this time will be The thread tension is, for example, about 130 g, and if a sewing thread port is used in the same way, the actual bobbin thread tension is 6 g, and the optimal needle thread tension is about 110 g.

Therefore, when changing the type of sewing thread, it is necessary to adjust the tension of the upper thread to a tension suitable for the type of sewing thread as the tension of the bobbin thread changes, but conventionally, when changing the type of sewing thread,
Since the tension of the needle thread was adjusted by relying on the experience and intuition of the operator, the adjustment was inappropriate and the end of the sewing thread became unsightly, resulting in a disadvantage of lowering the quality of the product.

The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional devices.

An embodiment of the present invention will be described with reference to the drawings. On the path of the needle thread 1 between a needle (not shown) and a thread spool 18 removably arranged on a spool pin 17 on the sewing machine head, An auxiliary conditioner 2 is placed on the front side and a main conditioner 3 is placed on the rear side of the path.

The main conditioner 3 is movable on a shaft 5 in the axial direction relative to the machine frame 4.
One plate 6a, fixed to the shaft 5, is loosely fitted onto the shaft 5, and the other plate 6b, fixed to the machine frame 4, is constantly pressed by the force of the spring 7, and one fixed plate is concentric with the shaft 5. It has a well-known structure in which a spring 7 expands and contracts to adjust the pressing force of the plates 6a and 6b in relation to the rotational position of an operation dial 8 supported on the machine frame so as to be manually rotatable about an axis. On the circumferential surface of the operation dial 8, marks "01" to "91" are engraved to indicate the rotational position along the direction of rotation, and an arrow (not shown) is provided on the machine frame near the scale. This is so that the pressing force applied by the plates 6a, 6b to the needle thread 1 increases in proportion to the increase in the scale indicated by the arrow.

The auxiliary tension device 2 has a pair of plates 9a and 9b, which are pressed against each other with an elastic force substantially equal to the pressure applied by the leaf spring of the bobbin thread bobbin case and extremely small with respect to the elastic force of the spring 7 of the main tension device 3.

A support shaft 10 having an axis perpendicular to the axial direction of the shaft 5 is fixed to the machine frame, and a movable body 11 is supported so as to be slidable in the axial direction with respect to the support shaft 10. The pulley 12 is rotatable around parallel axes of the auxiliary tensioner 2 and the main tensioner 3, and supports a pulley 12 that passes around the needle thread 1 between the auxiliary tensioner 2 and the main tensioner 3.A working shaft 13 along the support shaft 10 is fixedly supported at the lower end. The coil spring 14 causes one axial direction away from both tone regulators (the second
・Receives an elastic force toward the left side of the figure).

The working shaft 13 is arranged in relation to a potentiometer] 5 fixed to the machine frame, and the potentiometer 15 generates a different voltage output depending on the movement position of the working shaft in association with the movement of the moving body 11. do.

These devices constitute a sewing thread detection means, and the needle thread 1 passed through the auxiliary tensioner 2, pulley 12, and main tensioner 3 is pulled toward the needle and fed out each time a stitch is formed by the sewing machine. When the pulley 12 between the main tension device 3 and the auxiliary tension device 2 around which the thread 1 is wrapped around, the pulley 12 in the axial direction of the support shaft 10 (right side in FIG. 2) is approximately proportional to the tension of the auxiliary tension device 2.
The moving body 11 moves against the acting force of the coiled spring 14 due to this acting force, and comes to rest when the tension of the auxiliary tension device 2 and the elastic force of the coiled spring 14 are balanced.

That is, when the force F that the pulley 12 receives from the needle thread 1 is balanced, the needle thread tension T = F (kx) (k is the spring constant of the coiled spring 14, and X is the amount of extension of the coiled spring 14), and this formula is x
=T/, and the amount of extension of the coiled spring 18, that is, the amount of displacement of the moving body 11, can be determined by the change in T.

Since the pressure contact force of the main tension device 3 is extremely larger than the pressure contact force of the auxiliary tension device 2, T is due to the thread tension approximately equal to the bobbin thread tension caused by the auxiliary tension device 2, and this thread tension depends on the type of sewing thread mentioned above. Determined by

Therefore, the moving position of the moving body 11 corresponds to the type of sewing thread.

Thread spool detector 16 placed inside the sewing machine frame (Figure 3)
has a switch 16a that protrudes from a hole 19 provided in the machine frame, and when the thread spool 18 is attached to the thread stand pin 17, the switch 16a is
It turns on when pressed.

Next, the electric circuit will be explained.

G1. G2 is a well-known IC gate circuit.

W1 to W3 are well-known one-shot circuits, one-shot W1 is triggered by turning on the switch 16a of the thread spool detector 16 and generates an H-level output for a predetermined time, and one-shot W2 is triggered by the rise of the output of gate G2. The sewing machine generates an H level output for the time it takes to sew 5 to 6 stitches at low speed, and one shot W3 is triggered by one shot I'.
Triggered by the fall of the output of W2, it remains high for a predetermined time.
Generate level output.

PW is a reset circuit that generates an H level signal with a predetermined pulse width when the power is turned on.

SW is a start/stop switch, which generates an H level signal with a predetermined pulse width in connection with manual operation.

Fl, F2 are flip-flops;
It is reset by the H level output of the flip-flop G1 to bring the Q terminal to the L level, and is preset by the H level output of the one shot W3 to bring the Q terminal to the H level.

A/D is an analog/digital converter that converts the analog output of the potentiometer 15 into a digital output, and L
T is a latch circuit that reads, outputs, and holds the output of the A/D at the fall of the H level output of the one shot W2.

The ROM is a memory circuit in which the tension of the upper and lower threads corresponding to the type of sewing thread is stored in advance as data divided into three types: high, medium, and low (Fig. 6) based on the graph of Fig. 6, and the latch circuit The data is read out in accordance with the output content of the LT, and a corresponding 6-bit output is generated.

Reference numeral 20 denotes a well-known seven segment display device, which is connected to a power supply 1 through the emitter and collector of a switching transistor TR, and a flip-flop F connected to the base of the transistor TR through an inverter IN and a resistor R.
Connect the Q terminal of 2.

Then, the I transistor TR is turned on by the H level output of the Q terminal of the flip-flop F2, and the display device 20 displays "8" corresponding to the content of the 'output of the decoder DEC, for example, if the needle thread tension is "high". , if it is “medium” then “5”
”, “Mr. Lee”, “2” is displayed.

VC is a motor drive circuit that drives the sewing machine motor M in relation to the H level output of the Q terminal of the flip-flop F1, and in particular, while the H level output is generated from the one shot W2, the sewing machine motor M is driven at a predetermined level. Drive at low speed.

The present invention has the above-mentioned configuration, and its operation will be explained next.

To explain the case where sewing thread A is used as the upper and lower threads and is replaced with sewing thread C, the setting of the main tension regulator 3 and the leaf spring of the bobbin case is the appropriate tension for sewing thread A, and when the needle thread is 18.
0g, and the bobbin thread is 15g (see Figure 6).

When the lower thread bobbin in the bobbin case is replaced with one for sewing thread and the thread is pulled out through the leaf spring, the tension on the lower thread becomes 10 g (Fig. 6) due to slippage of the sewing thread.

When a new thread spool 18 is attached to the spool pin 17 in order to replace the needle thread 1, the switch 16a of the thread spool detector 16 is turned on, so that the output of the one-shot W1 remains at H level for a predetermined period of time, and the gate G1 is turned on. The output goes to H level, flip-flop F2 is reset, and its Q terminal goes to H level, but when the power is turned on, the reset circuit PW resets it in advance and the Q terminal of flip-flop F1 is at L level. The output remains at the L level, and the one-shot W2 does not operate.

Insert the sewing thread of the thread spool 18 into the needle via the auxiliary tension device 2, the pulley 112, and the main tension device 3, place the cloth on the upper surface of the needle plate (not shown), and operate the start/stop switch SW.
The Q terminal of flip-flop F1 becomes H level, which starts the sewing machine, and at the same time, the Q terminal of flip-flop F1 becomes H level.
Since W2 has already been reset, its Q becomes H level, and the output of W2 becomes H level (one shot), and the drive circuit VC drives the sewing machine motor M at a low speed.

On the other hand, when the sewing machine is driven, the needle thread 1 is pulled toward the needle each time a stitch is knotted in cooperation with the bobbin thread. The movable body 11 with the pulled pulley 12 moved to the right in the axial direction (FIG. 2) on the support shaft 10 to a position corresponding to the sewing thread C, whereby the potentiometer 15 outputs an analog output corresponding to the moved position. This analog output is converted into a digital code by an A/D converter.

The elastic force of the spring 7 of the main tension device 3 is the same as that of the plate 9 of the auxiliary tension device 2.
Since it is sufficiently larger than the pressure contact force of a and 9b, the moving position of the movable body 11 is almost constant regardless of the rotational position of the operation dial 8, and therefore the analog output of the potentiometer 19 depends only on the type of sewing thread.

After the sewing machine has started and 5 to 6 stitches have been formed, the output of one shot W2 falls, and this causes the latch circuit LT to
reads the output of the A/D converter, holds it, and outputs it to the ROM, and according to the output of the latch circuit LT, the ROM stores the needle thread tension data corresponding to the sewing thread C, that is, the "medium tension" (
The needle thread tension data (see Fig. 6) is output to the display device 20 via the decoder DEC, and one shot W3 is further triggered by the falling edge of one shot W2, and its output remains at H level for a predetermined period of time. Since the flip-flop F2 is preset and its Q terminal becomes H level, the resistor TR is turned on and the display device 20 is turned on.
displays "5" based on the output of the decoder DEC.

Therefore, when the start/stop switch SW is operated, the Q terminal of the flip-flop F1 goes to L level, thereby stopping the driving of the sewing machine.

After rotating the operation dial 8 to set the scale to "5", the start/stop switch SW is operated to enable normal stitch formation.

Similarly, when the upper thread and lower thread are replaced at the sewing thread opening, the tension of the lower thread becomes 6 g (3 strands) (Figure 6) due to slippage of the sewing thread opening.

When the thread spool 18 is replaced with the one at the sewing thread port and the sewing thread port is inserted and sewing begins as described above, the needle thread tension at the sewing thread port is measured by the potentiometer 15 and its value is transmitted via the A/D converter. Information stored in the ROM is read out in relation to the value held in the latch circuit LT, and the display device 20 displays "2".

Next, a second embodiment controlled by a microcomputer will be described.

The mechanical configuration is the same as the present embodiment and will be omitted.

In the electric circuit (FIG. 5), parts that are the same as those in this embodiment are designated by the same numbers and explanations thereof will be omitted.

RD is a rotation angle detection means arranged in relation to the main shaft of the sewing machine and generates a rotation signal at a predetermined rotation angle for each revolution;
MC is a microcomputer (microcomputer) consisting of a control section CPU and a storage section ROM.
In addition to storing needle thread tension data corresponding to the type of sewing thread, a program for displaying the needle thread tension based on the flow shown in FIG. 7.8 is also stored.

In the above configuration, the effect of this second embodiment is as follows.
This will be explained according to the flow shown in FIG.

When the power is turned on, the motor and thread tension flags are reset. At this time, it is determined whether the switch 16a of the thread spool detector 16 is on or not. If it is off, the thread tension flag is reset, and the next If the thread tension flag is set, the state of the switch 16a is again judged, and if it has been reset, the motor flag is judged.

If the motor flag is set, the sewing machine is driven at low speed and the potentiometer 15 is set when the main shaft of the sewing machine rotates at a large speed.
The output is read, and the display device 20 displays a display corresponding to the tension of "high", "medium", or "low" in relation to the output value, sets the thread tension flag, and sets the thread spool again. Return to the "judgment" of the switch.

Figure 8 shows the flow when operating the start/stop switch SW after the power is turned on. When the start/stop switch SW is operated, the motor flag is "judged" and if it is set, the sewing machine motor M is stopped. and reset the motor flag.

When the sewing machine motor M is reset, the sewing machine motor M is driven and a motor flag is set.
As shown in the flowchart of the figure, if the thread tension flag is reset, the needle thread tension is read, and if the thread tension flag is set, the needle thread tension is not read.

In the second embodiment, the "judgment" of the thread spool detector 16
However, the presence or absence of the output of the potentiometer 15 may be "determined" instead.

Further, in the first and second embodiments, a tone disc was used as the auxiliary tone device 2, but other means such as a leaf spring may be used.

In addition, in the first and second embodiments, a potentiometer was used as the sewing thread tension detection means, but a strain gauge is placed on the sewing thread path between the main tension device and the auxiliary tension device, and the output of the strain gauge is monitored. Alternatively, a linear type encoder may be used instead of the combination of a potentiometer and an A/D converter.

Furthermore, although the first and second embodiments are shown for a lockstitch sewing machine that uses top and bottom threads, similar results can be obtained for a chainstitch sewing machine that uses top and bottom threads or a chainstitch sewing machine that uses only needle threads. The tension to be applied to the needle thread based on experimental data may be stored as data in the ROM, read out using a detection signal from the detection means 15, and displayed on the display device.

Furthermore, in the first and second embodiments, the sewing thread detection means was arranged in the needle thread path, but as shown in FIG. In the path of the bobbin thread 24, for example, a strain gauge 2'6 is fixed to the lower end surface of the needle hole 25a of the throat plate 25, and the output of the strain gauge 2'6 causes the R
Data may also be read from OM.

Furthermore, in the first and second embodiments, the detection and display of sewing thread tension was divided into three levels: "high,""medium," and "low." However, the present invention is of course not limited to this, and the levels can be further divided. It may also be possible to set minute sewing thread tension.

Furthermore, in the first and second embodiments, the sewing thread tension is displayed digitally by a seven-segment display device, but it is displayed analogously by, for example, a well-known meter with a movable pointer via a D/A converter. You may also do so.

As described above, according to the present invention, the needle thread tension detection means is provided, and corresponding data is read out from the storage means in relation to the detection signal of the detection means, and appropriate tension is applied to the needle thread of the thread tension device. Since the operation position is displayed, the operator can always apply the appropriate needle thread tension to the sewing thread by operating the thread tension device according to this display, which will result in beautiful stitches with good thread take-up. This has the effect of improving product quality.

[Brief explanation of drawings]

Fig. 1 is a side view of the main tension regulator of this embodiment, Fig. 2 is a diagonal/main view of the thread tension detection means, Fig. 3 is the thread spool detection means, Fig. 4 is the electric circuit, and Fig. 5 is the diagram of the thread tension detection means. The electric circuit of the second embodiment, Fig. 6 is a graph showing an example of the relationship between the tension of upper and lower threads corresponding to the type of sewing thread, and Figs. 7 and 8 are flow charts showing the needle thread tension display frame of the second embodiment. , FIG. 9 is a side view showing an embodiment in which a thread tension detection means is arranged in the bobbin thread path.

Claims (1)

[Scope of Claims] 1. It is arranged on the needle thread path between the thread supply source and the needle to enable manual operation, and it clamps the needle thread with different strengths depending on the operating position, so that the needle thread can be properly adjusted during sewing. A main tension device 3 for applying tension, an auxiliary tension device 2 for applying a constant tension weaker than the tension by the main tension device to the needle thread between the thread supply source and the main tension device, and during sewing. a detection means 15 that detects the tension generated in the needle thread between the auxiliary tensioner and the main tensioner and generates a different detection signal in accordance with the strength; and a state in which a specific passing resistance is applied to the needle thread. a storage means ROM which stores in advance the operating position of the main tone controller corresponding to the type of needle thread calculated from experimental data of detecting the strength of tension generated in the needle thread during sewing; A sewing thread tension display device for a sewing machine, comprising a control means that can read a corresponding data from a storage means, and a display device 20 that displays an operating position of a main regulator based on the read data.