JPS5936553B2 - Needle fixed position stop device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for stopping a sewing needle at a predetermined position, for example, at a needle-up position in response to a stop operation of a manual operation switch for starting and stopping a sewing machine motor. This invention relates to a needle fixed position stopping device.

Conventionally, when stopping a sewing needle at a predetermined position, the sewing machine motor was operated at a constant low speed, and when the needle position detector detected that the sewing needle had arrived at the predetermined position, the power to the sewing machine motor was cut off. It has been common practice to stop the rotation of the sewing machine motor.

However, due to its inertia, the sewing machine motor cannot stop rotating at the same time as the power is cut off, and the sewing needle may stop moving out of its designated position, or if the sewing machine motor's rotational speed is high. The sewing needle stops after making one more rotation.

This happens because the rotational speed of the sewing machine motor is set to a relatively high speed while the sewing needle is stopped at a fixed position. When sewing thick work cloth, the sewing needle cannot penetrate the work cloth, and the sewing machine motor locks with the sewing needle stuck in the work cloth, and in some cases, the sewing machine motor may burn out.

As mentioned above, if the speed of the sewing machine motor is set to a low speed during the fixed position stopping operation in order to accurately stop the sewing needle at a predetermined position, it will not be possible to sew thick work cloth; If set too high, the sewing needle will not be able to stop accurately in a predetermined position.

Therefore, the present invention has been made to solve the above contradictory problems all at once.The present invention has been made to solve the above-mentioned contradictory problems at once. When sewing thick work cloth, set the sewing speed to a relatively high speed, and set it to a low speed when the sewing needle passes through the work cloth and moves to the specified position. It is an object of the present invention to provide a fixed position stopping device that can accurately perform fixed position stopping operations.

An embodiment embodying the present invention will be described below with reference to the drawings.

1, 2, and 3 are automatic return type speed selection switches for setting the operating speed of the sewing machine motor to "low speed,""mediumspeed," or "high speed," which will be described later.These switches are connected to the positive power terminal +VCC. and a zero potential terminal via resistors 4, respectively.

5 is a latch with a 2-bit configuration, each latch input terminal is connected to the anti-zero potential side contact of each of the speed selection switches 1 and 2, and its clock input terminal ck is a falling trigger type monostable multivibrator. It is connected to the output terminal of 6.

7 is a multi-input NOR circuit whose input terminals are connected to the anti-zero potential side contacts of each of the speed selection switches 1, 2, and 3, and whose output terminal is connected to the input terminal of the monostable multivibrator 6. .

8 is a multiplexer whose input terminals A1 and B1 are connected to receive each output bit of the latch 5 via lines LA and LB, and whose input terminal C1 is connected to a zero potential terminal.

When a high level signal is applied to the gate terminal G of the multiplexer 8, the input terminals A1, B1, CI
Activate the input signal to each input terminal AI
, Bl, and output terminals A3 . B3.
When a low level signal is output from C3 and is applied to the gate terminal G, the signals input to the other input terminals A2, B2, and C2 are enabled and applied to the respective input terminals A2, B2, and C2.
The output terminals A3.B2 and C2 are in husband-and-wife correspondence.
B3. Output from C3.

Now, 9 is a manually operated switch connected through a resistor 10 in series between the positive power supply terminal 10 VCC and the zero potential terminal, and when this is manually pressed, the two contacts are opened, and the press is released. The structure is such that when the contact is closed, both contacts are returned to closed state.

Reference numeral 11 denotes a rising trigger type T flip-flop (corresponding to the stop command signal generating means of the present invention), whose clock input terminal T is connected to the anti-zero potential side contact of the manual operation switch.

This T flip-flop 11 is triggered every time the signal input to its clock input terminal T rises, or in other words, every time the manual operation switch 9 is pressed, and the output from its output terminal Q is at a high level. The activation command signal consisting of the signal “
This configuration reversibly inverts between "H" and a stop command signal consisting of a low level signal.

The T flip-flop 11 is cleared in synchronization with the power-on of the sewing machine, and when cleared, the output from its output terminal Q becomes a stop command signal.

12 is a monostable multi-biplane connected to receive the output signal from the output terminal Q of the T flip-flop 11 via the line L1. It is triggered at the moment the output signal reverses from the start command signal H to the stop command signal, and outputs an unstable pulse.

13 is an OR circuit, one input terminal of which is connected to the output terminal QKi of the T flip-flop 11, and the other input terminal is connected to the output terminal Q through a delay circuit 14 with a delay time of about 1 to 2 seconds. It is connected to the.

Note that the output from the output terminal Q of the T flip-flop 11 is also given to the gate terminal G of the multiplexer 8 via the line L1.

Now, 15 is a first position detection circuit that generates a first position signal when the sewing needle reaches a predetermined stop position.
Specifically, as shown in Figure 2, 1 indicated by a straight line
When 6 is the sewing machine bed surface and 11 shown by a curve is the vertical movement locus of the sewing needle tip, the sewing needle is at a predetermined stop position Y1, for example, the sewing needle is in the needle-up position above the sewing machine bed surface 16. A first position signal NP that falls and rises during a predetermined period is generated.

Reference numeral 18 denotes a second position detection circuit that generates a second position signal when the sewing needle reaches a predetermined constant position Y2 between the position where the sewing needle penetrates the work cloth and the stop position Y1. Specifically, as shown in FIG. 2, the sewing needle rises after a predetermined period of time after it has been displaced from the needle-up position above the sewing machine bed surface 16 to the needle-down position below the sewing machine bed surface 16.
In addition, a second position signal RP that falls immediately after the stitch y@ is displaced from the needle down position to the needle up position is generated.

Incidentally, FIG. 2 shows signal waveforms at each point indicated by b to i in FIG. 1.

19 and 20 are AND circuits, one input terminal of which is connected separately to receive the first 0 position signal NP and second position signal RP, respectively, and the other input terminal of each of which is connected to the OR circuit 13; Commonly connected to the output terminals.

Reference numeral 21 denotes a falling trigger type monostable multivibrator, the input terminal of which is connected to the output terminal of the AND circuit 20 via an inverter 22.

23 is a rising trigger type T flip-flop.
The clock input terminal T is connected to the output terminal of the AND circuit 19, and the clear terminal CL is connected to the output terminal of the monostable multivibrator 21, so that the clock input terminal T is connected to the output terminal of the AND circuit 19, and the clear terminal CL is connected to the output terminal of the monostable multivibrator 21. A corresponding discrimination circuit 24 is configured.

The T flip-flop 23 outputs a high level signal from one of its output terminals Q and Q, and a low level signal from the other.
It is triggered at the rising edge of the signal input to the output terminal Q, and when triggered, the outputs from the output terminals Q and Q are mutually inverted.

Also, this T flip-flop 23 has its clear terminal CL.
is cleared when an astable pulse from the monostable multivibrator 21 is applied to the output terminal Q.
The output is a high level signal.

Therefore, the activation command signal H from the T flip-flop 11 is output from the OR circuit 13, and the AND circuits 19 and 2
When the second position signal RP rises in the state where the second position signal RP is applied to each of the input terminals 0 to 10,000, the monostable multivibrator 21 is triggered, and its output, an unstable pulse, is passed through the T flip-flop 23. Since the output terminal Q is applied to the clear terminal of the output terminal Q, the output from the output terminal Q becomes a low level signal, and the output from the output terminal becomes a high level signal.

Further, when the first position signal NP rises thereafter, the T flip-flop 23 is triggered and the outputs from its output terminals Q and Q are inverted, and the output terminal Q
A high level signal and a low level signal are output from Q and Q, respectively.

(Thus, the discrimination circuit 24 determines whether the sewing needle is in a first state in which it moves from the stop position Y1 to the fixed position Y2 or in a second state in which it moves from the fixed position Y2 to the stop position Y1.) the first and second position signals NP and RP
As shown in FIG. 2 f2g, when in the first state, a high level signal is output from the output terminal Q of the T flip-flop 23, and a low level signal is output from the output terminal Q, and at the same time, when the T flip-flop 23 is in the second state, , the above output terminal Q
It outputs a low level signal from the output terminal and a high level signal from the output terminal.

25 is the multiplexer 8, AND circuits 26 and 27;
These AND circuits 26 and 21 have one input terminal connected to the output terminals Q and Q of the T flip-flop 23, respectively, and the other input terminals of the AND circuits 26 and 21, which will be described later. They are commonly connected to the output terminal Q of the R-S flip-flop 28, and each output terminal is connected to the input terminals B2 and C2 of the multiplexer 8, respectively.

29 is a timer circuit connected to receive as an input the astable pulse output from the monostable multivibrator 12; It is configured to be triggered at the moment a command signal is output, thereby performing a timing operation for a preset period of time, for example, 0.6 to 0.8 seconds.

The timer circuit 29 normally outputs a low level signal from its output terminal, but during timekeeping operation it outputs a high level signal. Therefore, the timer circuit 29 outputs a stop command signal from the T flip-flop 11. It outputs a timer pulse Pi (see second diagram) that rises for a set time every time the signal is output.

Reference numeral 30 denotes an AND circuit connected to its input terminal to receive the first position signal NP and timer pulse P1 directly or via an inverter 31, and whose output terminal is connected to the falling trigger type monostable multivibrator 32. connected to the input terminal.

The output terminal of the monostable multivibrator 32 is connected to the reset input terminal R of the R-S flip-flop 28, and the set input terminal S of the R-S flip-flop 28 is connected to the input terminal S of the monostable multivibrator 12. The R-S flip-flop 28 and the timer circuit 29 are connected to receive stable pulses as input.
The blocking means 33 is constituted by the above.

Note that the R-S flip-flop 28 is a rising trigger type.

34, 35 and 36 are AND circuits connected to each input terminal to receive the timer pulse P1 from the timer circuit 29 via the inverter 31, and each other input terminal is connected to the output terminal A3 of the multiplexer 8. ,
It is connected to B3 and C3 separately.

The respective output terminals of the AND circuits 34, 35 and 36 are connected to the cathodes of the light emitting diodes DA, DB and DC, respectively, and the respective output terminals of the light emitting diodes DA.

The anodes of DB and DC are connected to the positive power supply terminal VCC via a resistor 37, respectively.

T.A. TB and TC are the light emitting diodes DA, respectively.

A phototransistor constitutes a photocoupler with DB and DC, and each emitter is commonly connected to the anode of a diode 38 via a line L2, and each collector is connected to a sliding terminal of a variable resistor 40 via a resistor 39, respectively. It is connected to the.

Additionally, four resistors 4 are connected between the emitters of the phototransistors TA, TB, and TC and the anode of the diode 38.
1 are connected in series, and a resistor 42 is connected between the common connection point between each resistor and each collector of the phototransistors TA, TB, and TC, so that the phototransistors TA, TB, TC, and the resistor 39 .41, 42, etc. constitute a D-A converter 43 having a well-known configuration.

The photo coupler constituted by the light emitting diode DB and the phototransistor TB is connected to the sewing machine motor 5, which will be described later.
1 at a low speed, and generates a relatively low voltage at the output terminal P of the DA converter 43 by turning off only the phototransistor TB, and is the first control of the present invention. It corresponds to the means.

In addition, the light emitting diode DC and the phototransistor T
The photocoupler constituted by C operates to operate the sewing machine motor 51 at an extremely low speed, and the output terminal P is turned off by turning off only the phototransistor TC.
It generates an extremely low voltage, and corresponds to the second control means of the present invention.

Reference numeral 44 denotes an AC power source, both output terminals of which are connected to busbars 48 and 49, respectively, via a noise prevention filter 41 consisting of an induction coil 45 and a capacitor 46.

Between the busbars 48 and 49, there is a series circuit of a sewing machine motor 51, which is operatively connected between the anode and cathode of a thyristor 50 for phase control and to a main shaft of the sewing machine (not shown), for example, consisting of a commutator motor excited by a permanent magnet; resistance 52,
The variable resistor 40, the resistor 53, and a series circuit of a diode 54 having the illustrated polarity are connected to each other, and the anode of the diode 54 is connected to the cathode of the diode 38.

A resistor 55 is connected between the gate and cathode of the Sairisk 50.
A parallel circuit consisting of a capacitor 56 and a capacitor 56 is connected, and a varistor 51 for protecting the thyristor 50 is connected in parallel between the anode and cathode of the thyristor 50.
A capacitor 58 is connected in parallel with the series circuit of the variable resistor 40 and the resistor 53.

59 is a transistor for triggering the thyristor 50, whose base is connected to the output terminal P of the DA converter 43, and whose collector is connected to the connection point between the resistor 52 and the variable resistor 40; The emitter is divided into two parts, one branch end of which is connected to the gate of the thyristor 50 via a diode 60 of the illustrated polarity, and the other branch end connected to the anode of the diode 54 via a resistor 61.

Next, in explaining the operation of the above configuration, for convenience, a high level signal will be described with a logic value of 1, and a low level signal will be described with a logic value of 0.

Prior to starting operation of the sewing machine, the power to the sewing machine is turned on, and speed selection switches 1, 2 are set according to the operator's wishes.
3, for example, the selection switch 3 corresponding to "high speed" is operated to suppress it, and then the manual operation switch 9 is operated to suppress it.

Then, T flip-flop 1 cleared when the power was turned on.
1 is triggered when the manual operation switch 9 is pressed, and a start command signal H is output from its output terminal Q, and this is supplied to the gate terminal G of the multiplexer 8 via the line L1. Terminal AI
, B1°C1 is enabled.

On the other hand, when the speed selection switch 3 is operated to suppress, the line LA is transferred from the latch 5.

Since a logic value 1 signal is supplied to both LB, the result and LC
1 to input terminals AI and B1°C1 of multiplexer 8, respectively.
．． i, 0 signals are input, and these are sent to multiplexer 8.
output terminal A3. B3. AND circuit 34.35 from C3
．． 36 input terminals.

Thus, the activation command signal H from the T flip-flop 11
When is output, monostable multivibrator 12
Since the timer circuit 29 is not triggered, the timer circuit 29 is in a non-operating state, and the logic value 0 signal (low level signal) from its output terminal is inverted by the inverter 31 to a logic value 1 signal (high level signal), and the logic value 0 signal (low level signal) from its output terminal is inverted to the logic value 1 signal (high level signal). , 35° and 36, respectively.

Therefore, since the AND circuits 34 and 35 output a 1 signal, and the AND circuit 36 outputs an O signal, only the light emitting diode DC is lit.

As a result, the phototransistor T in the D-A converter 43
Only C is turned on and a relatively high DC voltage is output from the output terminal P of the D-A converter 43, and this DC voltage is applied to the base of the transistor 59, so that transistor 59 is turned on and a relatively high DC voltage is output from the output terminal P of the D-A converter 43. A collector current flows.

Then, the emitter potential of the transistor 59 becomes relatively high and is applied to the gate of the thyristor 50 via the diode 60, so that the thyristor 50 starts the phase control operation with its firing conduction angle relatively large. , the sewing machine motor 51 receives a relatively large amount of power and rotates at high speed.

The rotation of the sewing machine motor 51 causes the sewing needle to reciprocate up and down, and also causes the feeding movement of the feed dog to impart feeding movement to the workpiece cloth, thereby forming a predetermined stitch on the workpiece cloth. Ru.

Next, in the following, we will discuss the case where the manual operation switch 9 is pressed to stop the stitch forming operation during the above-mentioned stitch forming operation. The case where the operation switch 9 is pressed will be described.

At the moment when the manual operation switch 9 is pressed, a stop command signal is output from the output terminal Q of the T flip-flop 11 to which the start command signal H had been output until then (see Figure 2 a). When the vibrator 12 is triggered, the timer circuit 29 starts a time counting operation, and the timer pulse P1 from the timer circuit 29 rises to 1 signal only for a predetermined period of time, that is, a period of timings T1 to T2 shown in FIG.

Then, at timings T1 to T2, the 1 signal from the timer circuit 29 is inverted to a 0 signal by the inverter 31, and is applied to one input terminal of each of the AND circuits 34, 35, and 36 and one of the AND circuits 30 in the cutoff circuit 33. added to the input terminal.

Therefore, the outputs of the AND circuits 34, 35, and 36 all become O signals, so that the light emitting diodes DA, DB, and DC all light up.

As a result, the phototransistor T in the D-A converter 43
A.

TB and TC are all turned on and the D-A converter 43
The DC voltage output from the output terminal P of the transistor 59 is turned off, and the thyristor 5
Since the ignition voltage is no longer applied to the gate of 0, the thyristor 50 stops its phase control operation.

Therefore, the sewing machine motor 51 rotates inertia while the power supply is cut off during the period between timings T1 and T2.

On the other hand, the start command signal H is applied to the AND circuits 19 and 20 in the discrimination circuit 24 via the delay circuit 14 and the OR circuit 13 even after timing T1, and each AND circuit 19 and 20 Passage of the first and second position signals NP and RP from the second position detection circuits 15 and 18 is allowed.

Therefore, the discrimination circuit 24 determines whether the sewing needle is in the first state in which it moves from the stop position Y1 to the fixed position Y2, as described above, or in the second state in which it moves from the fixed position Y2 to the stop position Y1. is determined according to the first and second position signals NP and RP, and signals in the states shown in FIG. 2 f and g are outputted from the output terminal Q of the T flip-flop 23 and each other, respectively.

Moreover, the R-S flip-flop 28 in the cutoff circuit 33 is
At timing T1 when the stop command signal is output, the set input terminal S receives an unstable pulse from the monostable multivibrator 12, so the output terminal Q
1 signal is now output from (see Figure 2 i),
AND circuits 26 and 27 are respectively T flip-flops 23
This allows outputs from output terminals Q and Q to pass through.

After that, for example, the timing T when the sewing needle shifts to the needle down position in a state where it is stuck into the workpiece cloth.
2, when the timer circuit 29 completes its timekeeping operation and the timer pulse P1 falls to the 0 signal, 1 signal is applied to each input terminal of the AND circuits 34, 35, and 36, and each AND Circuits 34, 35, 36 respectively connect output terminals A3. The output from B3°C3 is allowed to pass through, and one signal is applied to one input terminal of the AND circuit 30, so that the AND circuit 30 receives the first signal from the first position detection circuit 15. The passage of the position signal NP is now allowed.

Then, at timing T2, as shown in FIG. 2 fsg, 0 is output from the output terminal Q of the T flip-flop 23.
A signal is output, and one signal is output from the output terminal Q, which passes through AND circuits 26 and 21 and is supplied to input terminals B2 and C2 of the multiplexer 8, respectively.

At this point, the multiplexer 8 has the stop command signal applied to its gate terminal G and input terminals A2 and B2.

Since C2 is enabled, as a result its output terminal A
3. B3. Signals of 0, 0, and 1 are output from C3, respectively.

This causes the light emitting diode DA. DB is lit, phototransistors TA and TB are turned on, and the D-A converter 43 is turned on.
Since an extremely low DC voltage is output from the output terminal P of the transistor 59, the transistor 59 is turned on and an extremely small collector current flows.

Then, the emitter potential of the transistor 59 becomes extremely low (the thyristor 50 starts its phase control operation with its firing conduction angle extremely small, and the sewing machine motor 51 receives an extremely small power supply and rotates at an extremely low speed). do.

After that, when the sewing needle comes out of the workpiece cloth and moves to the stop position Y1, the first position signal NP from the first position detection circuit 15 falls at timing T3, so that until then one signal was output. The AND circuit 30 outputs a 0 signal, triggering the monostable multivibrator 32, and the astable pulse is transmitted to the R-S flip-flop 2.
8 is supplied to the glue set input terminal R.

At this time, a 0 signal is applied to the set input terminal of the R-S flip-flop 28 based on the fact that the unstable pulse from the monostable multivibrator 12 has already disappeared, and therefore the R-S flip-flop The O signal is outputted from the output terminal Q of 28 after timing T3 (see FIG. 2i).

As a result, a 0 signal is applied to one input terminal of each of the AND circuits 26 and 27, so that the outputs from the output terminals Q and Q of the T flip-flop 23 are applied to the AND circuits 26 and 21.
, the AND circuits 26 and 21 both output a 0 signal, and as a result, the output terminals A3 . B3. The output from C3 is made into an all 0 signal.

Therefore, the outputs of the AND circuits 34, 35, and 36 become 0 signals, and the light emitting diodes DA, DB, and DC all light up, and as described above, the thyristor 50 stops the phase control operation, and the power to the sewing machine motor 51 is reduced. Be cut off.

In this case, since the sewing machine motor 51 was rotating at an extremely low speed until just before the power was cut off as described above, its inertial force is extremely small, and the sewing machine motor 51 stops rotating almost at the same time as the power is cut off.

Therefore, the sewing needle does not stop at a predetermined stopping position unlike the conventional sewing machine, and the operation of stopping the sewing needle at a fixed position can be performed accurately.

In contrast to the above case, if the manual operation switch 9 is pressed at timing T4 when the sewing needle is at the needle-down position during the stitch forming operation described above, the manual operation switch 9 is pressed in the same way as described above. At the moment it is pressed, a stop command signal is output from the output terminal Q of the T flip-flop 11, the timer circuit 29 starts timing operation, and the timer pulse P1 from the timer circuit 29 is output for a predetermined time, that is, the timing shown in FIG. The signal rises to a high level only during the period T4 to T5.

As a result, the outputs of the AND circuits 34, 35, and 36 all become 0 signals, and the light emitting diodes DA, DB, and DC all light up, and the sewing machine motor 51 cuts off the power supply during the period from timing T4 to T5, as described above. rotates due to inertia.

Further, since the operations of the discrimination circuit 24, cutoff circuit 33, etc. that occur when the manual operation switch 9 is pressed are the same as those described above, the explanation of the operations will be omitted.

Thereafter, for example, the counting operation of the timer circuit 29 ends at timing T5 when the sewing needle moves to the needle-up position after being pulled out from the workpiece cloth, and when its output falls to the 0 signal, the above-mentioned Similarly, the AND circuit 34,3
5.36 are output terminals A3 and B of multiplexer 8, respectively.
3, the output from C3 is allowed to pass, and the AND circuit 30 also allows the first position signal NP from the first position detection circuit 15 to pass.

At timing T5, as shown in FIG. 2, the 1 signal is output from the output terminal Q of the T flip-flop 23, and the O signal is output from the output terminal Q. and are supplied to multiplexer 80 input terminals B2 and C2, respectively.

At this point, the multiplexer 8 has its input terminals A2, B2.

Since C2 is enabled, as a result its output terminal A
3. B3. Signals of husbands 0 and 1.0 are output from C3.

This causes the light emitting diode DA. DC is turned on, phototransistors TA and TC are turned on, and a relatively low DC voltage (higher than when the aforementioned phototransistors TA and TB are turned on) is output from the output terminal P of the DA converter 43. , transistor 59 is turned on and a relatively small collector current flows.

Then, the emitter potential of the transistor 59 becomes relatively low, and the thyristor 50 starts its phase control operation with a relatively small firing conduction angle, and the sewing machine motor 51 receives a relatively small power supply and operates at a low speed ( faster than the ultra-low speed)
Rotate with.

Therefore, the rotational speed of the sewing machine motor 51 is relatively high when the sewing needle pierces the workpiece cloth, so that even when sewing thick workpiece cloth, the sewing needle can reliably penetrate the workpiece cloth. Unlike the conventional sewing machine, the sewing machine motor 51 does not lock due to the sewing needle sticking into the workpiece cloth (it is possible to reliably prevent the sewing machine motor 51 from burning out).

Then, when the second position signal RP rises at timing T6 after the sewing needle pierces the work cloth, the monostable multivibrator 21 is triggered and its output is supplied to the clear terminal CL of the T flip-flop 23. The T
The output from the output terminal Q of the flip-flop 23 is inverted to the O signal, and the output from the output terminal Q is inverted to the 1 signal.

As a result, a 0 signal is input to the input terminal B2 of the multiplexer 8, a 1 signal is input to the input terminal C2, and as a result, the output terminal A3. Signals of 0, 0, and 1 are output from B3°C3, respectively.

Therefore, from then on, the sewing machine motor 51 is rotated at a very low speed in the same manner as described above, and when the first position signal NP falls at timing TI, the power to the sewing machine motor 51 is cut off, and the power to the sewing machine motor 51 is cut off. The sewing needle stops rotating substantially at the same time as this, and the sewing needle is thereby accurately stopped at a predetermined stop position Y1.

It goes without saying that the same effect as described above can be obtained even if the manual operation switch 9 is depressed at any timing to stop the stitch forming operation while the sewing machine is in the stitch forming operation.

According to the present invention, as is clear from the above description, the speed of the sewing machine motor during the operation of stopping the sewing needle in a fixed position is set to a relatively high speed when the sewing needle pierces the workpiece cloth. When the sewing needle passes through the workpiece fabric and moves to the specified position, by setting the speed to a low speed, the sewing needle can be accurately stopped at the specified position even when sewing thick workpiece cloth. A fixed position stop device can be provided.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a diagram showing an electrical configuration, and FIG. 2 is a timing chart. In the figure, 8 is a multiplexer, 9 is a manual operation switch, 1
1 is a T flip-flop (stop command signal generating means);
5 is a first position detection circuit, 18 is a second position detection circuit,
NP is a first position signal, RP is a second position signal, 24 is a discrimination circuit (discrimination means), 25 is a logic circuit (work means),
29 is a timer circuit, 33 is a cutoff circuit (cutoff means), 4
3 is a DA converter, 50 is a thyristor, 51 is a sewing machine motor, and DA. DB and DC are light emitting diodes, and TA, TB and TC are phototransistors.

Claims (1)

[Scope of Claims] 1. A manual operation switch for starting and stopping a sewing machine motor operatively connected to the main shaft of the sewing machine, and a switch that generates a °C stop command signal in response to a stop operation of the manual operation switch. a stop command signal generating means for erasing the stop command signal in response to a starting operation of the sewing needle; and a first position detection circuit for generating a first position signal when the sewing needle reaches a predetermined stop position. a second position detection circuit that generates a second position signal when the sewing needle reaches a predetermined constant position between the position where the sewing needle penetrates the work cloth and the stop position; and the sewing machine motor. a first control means for operating the sewing machine motor at a low speed; a second control means for operating the sewing machine motor at a predetermined ultra-low speed lower than the low speed; It is determined whether the state is in the first state of moving to the fixed position or the second state of moving from the fixed position to the stop position.
and a discriminating means for discriminating according to a second position signal, and when the discriminating means discriminates that the sewing needle is in the first state while the stop command signal is generated, the first control means is activated. actuating means for actuating the second control means when the determining means determines that the sewing needle is in the second state while the stop command signal is being generated; and the stopping means. and shutoff means for disabling said actuating means and cutting off power to said sewing machine motor in response to a first position signal generated while a command signal is being generated. 2. The cutoff means includes a timer circuit that operates in response to the generation of the stop command signal, and cuts off power to the sewing machine motor for a time set by the timer circuit regardless of the operation of the actuation means. operating the sewing machine motor according to the operation of the logic circuit after a set time has elapsed;
2. The needle fixed position stopping device according to claim 1, wherein power to the sewing machine motor is cut off again in response to the first position signal that is generated for the first time after the set time has elapsed.