JPS5937993B2 - sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a needle fixed position stop device for a sewing machine, and more particularly, the present invention relates to a needle fixed position stopping device for a sewing machine, and in particular, it operates the sewing machine at high speed via a drive means based on the operation of the worker operating means from an inactive position. The needle of the sewing machine is configured to once shift the sewing machine to a low-speed operation state by returning to the non-working position, and then detect the needle's return to a predetermined position and actuate a brake means to stop the needle at a specific position. This invention relates to a fixed position stopping device.

Conventionally, in this type of device, an output is generated from a speed detection circuit such as a delay timer when the opening or closing time of a single detection switch that detects the stop position and speed of the hand exceeds a predetermined time. A needle fixed position stopping device is provided which operates a brake means thereby.

However, the set time of the delay timer or the like as the speed detection circuit is selected to be smaller than the opening or closing time of the detection switch in the low-speed operating state.

This is because the time at which output is generated from the delay timer changes due to fluctuations in power supply voltage or temperature changes, etc., and is not the same as the set value. This is to prevent such a situation from occurring, since when the sewing time is longer than the sewing time, the slow speed is not detected and the needle of the sewing machine is not stopped at a specific position.

Therefore, the output from the speed detection circuit is generated before the sewing machine is shifted to the low speed operating state.

FIG. 4 explains this situation, with the horizontal axis showing the passage of time and the vertical axis showing changes in the speed of the sewing machine.

The moment the foot pedal is released, the sewing machine is in high-speed operation, for example, 5000 rpm.
More rapidly decelerating and lower speed driving conditions e.g. 215 r
pm, but for the reasons mentioned above, the speed detection circuit generates an output at, for example, 330 rpm.

Therefore, just before a permanent magnet piece attached to the main shaft of the sewing machine or a member interlocked with the main shaft of the sewing machine for operating the detection switch operates the detection switch, the output from the speed detection circuit is caused by opening or closing of the detection switch. When the speed of the sewing machine falls below 33 Orpm, which is sufficient to cause this problem, the brake means will be operated at around 330 rpm, and conversely, the sewing machine will start operating immediately after the permanent magnet piece passes the detection switch. Rotation speed is 330 r
When the temperature drops below pm, there is some time before the detection switch is activated again, so the speed of the sewing machine is 215 r.m.
pm, at which point the braking means is activated.

Therefore, in reality, the brake means is activated at approximately 330 rpm, or at 215 rpm, resulting in a defect in which the needle stops at a different position each time, even when the needle is stopped at the same needle up or down position. was.

In particular, since the needle top stop position is usually taken as the top dead center of the balance, it is close to the fabric support surface, and if an error occurs in the needle stop position, the needle stop position will move even closer to the fabric support surface. This interfered with the handling of the cloth, caused injury to the worker's hands and fingers, and in extreme cases, the needle could even stop with the cloth pierced.

Furthermore, the fact that the needle up or down stops are the same but the stopping positions are different may cause confusion for the operator.

In view of these circumstances, the present invention has devised an attached position stopping device that allows the needle to always accurately stop at a fixed position.

An example will be explained below.

In the figure, 1 is a sewing machine having a thread cutting device (not shown), and has a main shaft 2 and a needle 3 that moves up and down in conjunction with the main shaft 2.

4 is a drive means for driving the sewing machine 1, and a flywheel 7 is fixed to a rotor shaft 6 of a solenoid main motor 5.

8 has a clutch disc 9 on the side facing the flywheel 7.
is a fixed output shaft, which is rotatably and axially slidably attached to the bracket of the main motor 5, and its end opposite to the flywheel 7 is connected to the main shaft 2 of the sewing machine 1 via a belt 10. is connected to.

Reference numeral 11 denotes a brake wheel rotatably supported around the output shaft 80, the 8th wheel faces the clutch disc 9, and a worm wheel 12 is formed on the other side.

Reference numeral 13 denotes a worm that meshes with the worm wheel 12, the shaft portion 14 of which extends on both sides, and a rotary disk 15 at one end.
is fixed, and the other end is formed as a spline shaft and a movable platen 16 is fitted therein.

A brake coil 17 is attached to the bracket of the main motor 5, and when it is energized, it attracts the movable platen 16 toward the fixed brake 18 and stops the rotation of the shaft portion 140.

Reference numeral 19 denotes an auxiliary motor, the end of whose rotor shaft 20 is formed as a spline shaft, and a movable plate 21 facing the rotary plate 15 is fitted therein.

22 is a clutch coil which, when energized, attracts the movable plate 21 toward the rotary plate 15 and transmits the rotation of the auxiliary motor 19 to the shaft portion 14.

Reference numeral 23 designates a clutch lever, which includes a main lever 25 whose intermediate portion is rotatably supported by a shaft portion 24 on the bracket of the main motor 5 and whose upper end is operatively connected to the output shaft 9; It consists of an auxiliary lever 27 whose intermediate portion is rotatably supported by a shaft portion 26 at the open end of the lever 25 .

A foot pedal 28 is connected to the auxiliary lever 27 of the clutch lever 23 via a connecting rod 29 and can be depressed in two directions from a neutral position about its support shaft 30.

Further, in the clutch lever 23, a normally open front depression switch 3 is provided which is closed by the auxiliary lever 27 which is rotated at the initial stage of depression of the foot pedal 28 on the toe side.
1, and a normally open rear depression switch 32 which is closed by an auxiliary lever 27 rotated by depression of the heel side of the foot pedal 28.

Note that even after the front depression switch 31 is closed, if the foot pedal 28 is depressed toward the toe side, the clutch lever 23
The entire body is rotated, and the clutch disc 9 comes to be engaged with the flywheel 7.

Also, when the pedal is released, the clutch lever 2
3 is moved by the action of a return spring 33, and its clutch disc 9 comes to be engaged with the brake wheel 11.

34 is a rotary plate fixed to the end of the main shaft 2, and one permanent magnet piece 35 is fixed thereto.

Reference numeral 36 denotes a normally open type first detection reed switch disposed corresponding to the upper position of the permanent magnet piece 350, and is closed by the permanent magnet piece 35 when the needle 3 reaches the upper position. .

37 is a normally open second detection reed switch disposed corresponding to the thread cutting position of the permanent magnet piece 35, and is closed by the permanent magnet piece 35 when the thread cutting device reaches the operating position. The first detection reed switch 36 is arranged approximately 180 degrees out of phase with respect to the first detection reed switch 36 with respect to the main shaft 2 as the center.
will be closed prior to.

This second detection reed switch 37 also functions to detect speed based on its closing time.

Separate detection reed switches may be used for the needle top detection function and speed detection function, respectively.

However, the detection reed switch 37 as a speed detection function, that is, the second detection reed switch 37 which also serves as thread trimming position detection in this embodiment, has a phase shift of an interval described later with respect to the first detection reed switch 36. It is necessary to shift it.

Reference numeral 38 denotes a normally open third reed switch disposed corresponding to the needle lower position of the permanent magnet piece 350, which is closed by the permanent magnet piece 35 when the needle 3 reaches the lower position. , the first and third detection reed switches 3
6 and 37.

Therefore, the phase of the second detection reed switch 37 is further shifted from that of the first detection reed switch 36.

Next, the electrical configuration will be explained with reference to FIG.

The configuration of this electric circuit is a configuration of a negative logic circuit in which a negative potential is a logical value of "1".

39 is the negative power line, 40 is the positive power line, 41
is a delay timer as a speed detection circuit, and includes the second detection reed switch 37 and the front depression switch 31.
When the needle 3 stops when the foot pedal 28 returns to the neutral position, the speed of the sewing machine 1 is reduced to just before the low speed operation state (operation state by the auxiliary motor 19) (approximately 330 rpm). ) Generates an output when the closing time of the second detection reed switch 37 exceeds a predetermined time.

As described above, the delay time of the delay timer 41 is determined by the delay time of the second detection reed switch 37 in the low speed operation state.
is set smaller than the closing time of approximately 330 rpm.
Output is generated when the sewing machine is decelerated to

Reference numeral 42 designates a first 7-lip flop as a storage circuit for storing the output from the delay timer 41 during transition to the low-speed operation state, and an OR circuit 43 which receives the output of the delay timer 41 as an input; Front press switch 31
The OR circuit 44 receives the output from the OR circuit 44 as an input.

45 is a changeover switch for selecting the stop position of the needle 3, which is connected to the first detection reed switch 36 as shown in the figure.
The hour hand 3 connected to the third reed switch 38 side can be stopped upward, and the hour hand 3 connected to the third reed switch 38 side can be stopped downward.

46 is an AND circuit having two input terminals, one input terminal of which is connected to one of the first and third detection reed switches 36 and 38 via the changeover switch 45;
The other input terminal is connected to the output side of the OR circuit 43 of the first flip-flop 42.

The interval between the second and first reed switches 37 and 36 is such that the first detection reed switch 36 is closed after an output is generated from the delay timer 41 and stored by the first flip-flop 42. The setting is such that the time required for the sewing machine to shift to the low speed operation state is sufficient for the sewing machine to be transferred to the low speed operating state.

Fortunately, the second reed switch 37 for detecting the thread trimming position is located in such a positional relationship, so the speed is detected by the second reed switch 37 for detection, but this speed detection function Alternatively, another reed switch may be used as described above.

Further, since the third detection reed switch 38 is further apart from the first detection reed switch 36 (along the rotational direction of the permanent magnet piece 35), the detection reed switch 38 At the time of detection, the sewing machine 1 is of course in a low speed operation state.

In other words, the first and third detection reed switches 36.
38 detects the position of the hand 3 even if the output of the delay timer 41 occurs near 330 rpm or 215 rpm.
Regardless of whether it occurs nearby, it is ensured that the sewing machine 1 is operated at a low speed of 215 rpm before the operation is performed.

47 is a second flip-flop, and the AND circuit 46
and an OR circuit 4 whose inputs are the output from the reset circuit 48 that generates a reset output of "1" only when the power is turned on.
9, and an OR circuit 50 whose input is the output from the front depression switch 31.

51 is an OR circuit which receives the output from the reset circuit 48 and the front press switch 31; 52 is a third flip-flop; an AND circuit 53 whose input is the output of , the OR circuit 44 of the first flip-flop 42 and the OR circuit 5
It consists of an OR circuit 54 which receives the output of 1 as an input.

55 is an AND circuit, and the third flip-flop 52
The AND circuit 53 and the second flip-flop 4
The outputs from the OR circuit 49 of No. 7 and the third detection reed switch 38 are input.

56 is the fourth flip-flop, and its AND circuit 55
an OR circuit 57 whose input is the output of the OR circuit 51;
The OR circuit 58 receives the output from the OR circuit 58 as an input.

Reference numeral 59 denotes a fifth flip-flop, which includes an AND circuit 60 which receives the outputs from the OR circuit 57 of the fourth flip-flop 56 and the first detection reed switch 36, and an output from the OR circuit 51. It consists of an OR circuit 61 which receives as input.

62 is an OR circuit which receives as input the outputs of the OR circuit 49 of the second flip-flop 47 and the AND circuit 60 of the fifth flip-flop 59; 63 is the AND circuit 53 of the third flip-flop 52; and an OR circuit whose input is the output of the AND circuit 60 of the fifth flip-flop 59; 64 is the OR circuit 62, 6;
A NAND power amplifier circuit that receives the output of No. 3 as an input controls whether the clutch coil 220 is turned on or off.

Reference numeral 65 denotes a Noah power amplifier circuit which receives the output of the NAND power amplifier circuit 64 as an input, and controls the energization/disconnection of the brake coil 17.

66 is an AND power amplifier circuit whose inputs are the second detection reed switch 37 and the output of the OR circuit 57 of the fourth flip-flop 56, and a thread cutting coil for putting the thread cutting device into operation. 670 controls power on/off.

Next, the operation of this device will be explained step by step.

(1) Turning on the power When the power is turned on, the main motor 5 and the auxiliary motor 19 rotate, and at this time the flywheel 7 and the movable platen 21 rotate idly.

At this time, an output of "1" appears from the reset circuit 48, which is sent directly to the second flip-flop 47 and also to the third, fourth, and fifth flip-flops 51 through the OR circuit 51.
2, 56, and 59 as inputs.

Therefore, the OR circuit 49 of the second flip-flop 47
The output of the third Noritsubu flop 520 is "11", the output of the OR circuit 54 is "11", and the output of the fourth flip-flop 5 is "1".
The output of the 60 OR circuit 57 becomes "0", and the output of the OR circuit 60 of the fifth flip-flop 59 becomes "0".

The "1" outputs of the OR circuits 49 and 54 of the second and third flip-flops 47 and 52 are respectively connected to the OR circuit 62.
, 63 as an input to the NAND power amplifier circuit 640, its output becomes "0" and the clutch coil 22 is energized, and the "0" output is inverted by the Noah power amplifier circuit 65 and the brake coil 17 is attached. Forced.

Due to the energization of the brake coil 17, the movable platen 16 is attracted by the fixed brake 17, and the rotation of the brake wheel 11 is stopped via the shaft portion 14, that is, the worm 13, and the worm wheel 12.

Also, since the clutch disc 9 is pressed against the brake wheel 11 by the return spring 33, the output shaft 8. belt 1
0, the main shaft 2 of the sewing machine 1 is also stopped from rotating.

Furthermore, since the AND power amplifier circuit 66 also has the output "0" of the OR circuit 57 of the fourth flip-flop 56 added as an input, its output is "O", and the thread cutting coil 67 is energized. There is.

(2) When the sewing motion foot pedal 28 is depressed toward the toe side, the auxiliary lever 27 is first rotated and the front depression switch 31 is closed.

Thereby, the OR circuit 5 of the second flip-flop 47
Since the input “1” is added to 0, the output is “0”.
'', and since the output of the AND circuit 60 of the fifth flip-flop 59 is also "0" as before, one input of the NAND power amplifier circuit 64 via the OR circuit 62 becomes "O". The output of the NAND power amplifier circuit 64 becomes "1", so that the clutch coil 22 is energized and, conversely, the brake coil 17 is energized.

Thereby, the movable platen 21 is pressed against the rotary plate 15, and the rotation of the auxiliary motor 19 is transmitted to the brake wheel 11 via the shaft portion 14, the worm 13, and the worm wheel 12.
The rotation of the brake wheel 11 causes the clutch disc 9, the output shaft 8,
is transmitted to the sewing machine 1 via the belt 10, and the sewing machine 1
will now be operated at low speed.

Furthermore, when the foot pedal 28 is depressed deeply toward the toe side,
The clutch lever 23 is rotated around the ring portion 24,
The clutch disc 9 is separated from the brake wheel 11 and becomes engaged with the flywheel 7.

As a result, the sewing machine 1 is driven by the main motor 5 at high speed.

During this time, the brake wheel 11 is rotating idly.

(3) Stopping the needle by releasing the toe side of the foot pedal: However, the changeover switch 45 is connected to the first detection reed switch 36 side.

After the required sewing is completed, when the foot pedal 28 is released from the toe side and returned to the neutral position, the clutch disc 9 is pressed against the brake wheel 11 by the action of the return spring 33.

At this time, due to the contact between the clutch disc 9, which is rotating at high speed due to inertia, and the brake wheel 11, which is rotating at low speed, the clutch disc 9, that is, the sewing machine 1, is rapidly decelerated until it is driven by the brake wheel 11. .

This situation is as shown in Figure 4, and approximately 5000 rp
The speed is reduced to 215 rpm.

Simultaneously with the release of the toe-side depression of the foot pedal 28, the front depression switch 31 is opened, and an input of "0" is applied to one input terminal of the delay timer 41, thereby causing the second detection reed switch 37 to close. A state is reached where an output of "1" can pass each time the signal is formed.

However, while the sewing machine 1 is in the process of decelerating, the delay timer 41 does not output because the opening time interval of the second detection reed switch 37 is short.

However, when the rotational speed of the sewing machine 10 reaches about 330 rpm, an output of "1" is generated from the delay timer 41, and the output of "1" is added to the OR circuit 43 of the first flip-flop 42, and the output is added to the OR circuit 43 of the first flip-flop 42. The output of 43 is “
1”.

The second detection reed switch 37 becomes open when the magnet piece 35 passes, but the first flip-flop 42 stores that there is an output from the delay timer 41.

Thereafter, the first detection reed switch 36 is closed by 350 rotations of the permanent magnet piece.
As is clear from FIG. 2, there is a phase difference of 180 degrees between the second detection reed switch 37 and the first detection reed switch 36 with the main shaft 2 in between. Since it takes time for the first detection reed switch 36 to close, the sewing machine 1
The speed of the motor is reduced from 330 rpm to 215 rpm, ie, until it is rotated by the auxiliary motor 19.

After being decelerated, the first reed switch 36 is closed by the permanent magnet piece 35, thereby causing the 11
'' is generated and is applied to one input terminal of the AND circuit 46.

Since the output "1" stored by the first flip-flop 42 is applied to the other input terminal of the AND circuit 46, when the first detection reed switch 36 is closed, AND circuit 46 generates an output of "1".

The output of "1" is added as an input to the OR circuit 490 of the second flip-flop 47, and the output of the OR circuit 49 becomes "1".

The output of "1" is applied as one input of the NAND power amplifier circuit 64 via the OR circuit 62.

Since the output "1" from the OR circuit 54 of the third flip-flop 52 is applied as an input to the other input terminal of the NAND power amplifier circuit 64, the output of the NAND power amplifier circuit 64 is The signal becomes "0", the clutch coil 22 is energized, and the brake coil 17 is energized.

Therefore, the sewing machine 10 needle 3 is immediately stopped at that position, that is, at the position above the needle 3.

In this way, just before the permanent magnet piece 35 passes the second detection reed switch 37, the speed of the sewing machine 1 reaches 33 Or
pm and the delay timer 41 generates an output, there is time until the first detection reed switch 36 is closed, so the sewing machine speed is 215 rpm.
The speed is reduced to m.

Further, the permanent magnet piece 35 is connected to the second detection reed switch 3.
When the speed of the sewing machine reaches 33 rpm after passing through 7, there is more time until output is generated from the delay timer 41 due to the rotation of the permanent magnet piece 350, so needless to say, at this time the speed is increased to 215 rpm. .

Therefore, the energization of the brake coil 17 is always 215 rp.
Since this is carried out at a distance of m, the stopping position of the needle 3 does not vary.

(4) Re-driving the sewing machine by pressing the heel of the foot pedal for thread trimming To perform thread cutting with the needle 3 stopped at the upper position, press the heel of the foot pedal.

As a result, the auxiliary lever 27 is rotated in the opposite direction to the above, and the rear depression switch 32 is closed.

As a result, the AND circuit 5 of the third flip-flop 52
Since all 30 inputs become "1" (the output of the first flip-flop 420 OR circuit 43 is already "1"), the state of the flip-flop 52 is reversed and the output of the OR circuit 54 becomes "1". 0".

Furthermore, since the output of the AND circuit 60 of the flip-flop 59 is "0", the output of the OR circuit 63 is "0".
0", and the NAND power amplifier circuit 640 input is "1".
, becomes "0" and its output becomes "11".

Therefore, at the same time as the clutch coil 22 is energized, the brake coil 17 is energized, and the needle 3 moves from the upper position to the lower position.

(5) Needle passes through the lower position and thread trimming operation When the needle 3 reaches the lower position, the third reed switch 38 is closed and one input of the AND circuit 55 becomes "1". .

The other two input terminals of the AND circuit 55 have already received an input of "1" from the AND circuit 53 of the third flip-flop 52 and the OR circuit 49 of the second 7-lip-flop 47. The output of the fourth flip-flop 560 OR circuit 51 becomes "1", which is transmitted to the AND power amplifier circuit 66 and the fifth flip-flop 5.
9 is applied to one input terminal of an AND circuit 60, respectively.

Therefore, when the needle 3 begins to rise from the lower position and the second detection reed switch 37 for thread trimming is closed, all inputs to the AND power amplifier circuit 660 become "1", and its output becomes "1". As a result, the thread cutting coil 67 is energized.

The thread cutting coil 67 is connected to the second detection reed switch 3.
When the thread cutting coil 67 is released, the thread cutting device is again energized, but once the thread cutting coil 67 is energized, the thread cutting device continues its operation to the end.

This is achieved, for example, by energizing the thread cutting coil 67 to connect a clutch between the hook shaft and the cutting device.

(6) When the needle 3 reaches the upper position after the needle is stopped following thread trimming and the first detection reed switch 36 is closed, the fifth flip-flop 5
Since all the outputs of the AND circuit 600A of 9 are "1", the output of the AND circuit 60 is "11".

The output of "1" is applied as one input of the NAND power amplifier circuit 64 via the OR circuit 63.

Since an input of "1" is applied to the other input terminal of the NAND power amplifier circuit 64 from the second flip-flop 47, the output of the NAND power amplifier circuit 64 becomes "0", and the clutch coil 22 The brake coil 17 is energized and the needle 3 is stopped at the upper position.

This type of fixed position stopping device, which stops the needle up when the pedal is released, and cuts the thread and stops the needle up by pressing the heel of the pedal, can be used when sewing the fabric once to a predetermined position and then shifting it and sewing again. used.

(7) Stopping the needle down by releasing the foot pedal At this time, the changeover switch 45 may be connected to the third detection reed switch 38 side.

When the foot pedal 28 is released after sewing is completed, the needle is stopped in the same way as when the needle is stopped up.

The only difference is which of the first and third detection reed switches 36 and 38 the changeover switch 38 is connected to, so the explanation will be omitted.

In the above embodiment, the first to third detection reed switches 36 to 38 are closed when detecting the upper and lower positions of the needle and the thread trimming position. Good too.

In that case, by simply adding a circuit for inverting the signal, the other parts may be exactly the same as in the above embodiment.

As described in detail above, the present invention includes a first detection switch for detecting the arrival of a needle at a predetermined position, and a first detection switch arranged at a distance from the first detection switch. A second detection switch is provided to detect the speed based on the detection time that is activated prior to the operation, so that when the needle stops when the operator operating means returns to the inactive position, the speed of the sewing machine remains in the low-speed operation state. When the speed is decelerated until just before and the detection time of the second detection switch exceeds a predetermined time, the speed detection means generates an output, and the first detection switch performs detection from the generation of the output from the speed detection means. The interval between the rain detection switches is set so that the sewing machine can shift to low speed operation during this time, and
Since the output generation from the opening speed detection means for transition to the low speed operation state is stored in the storage means, and the brake means is always operated when the stored output and the detection by the first detection switch occur. The braking means is to be operated when the sewing machine is in a certain low-speed operation state,
The stop position of the needle is always constant when the operator operating means returns to the inactive position.

Therefore, as in the past, for example, when the needle stops at the top, the needle stop position is close to the fabric support surface, making it difficult to handle the fabric, causing injury to the worker's fingers, and furthermore, the needle stops at the top stop position. It is possible to prevent the fabric from being pierced regardless of the position, and also to prevent the operator from being confused (even if the same needle is stopped at the top or bottom, the position is shifted). The effect is extremely unique, as it does not cause the child to wake up.

[Brief explanation of drawings]

FIG. 1 is a front view showing the mechanical configuration, FIG. 2 is a side view of the detector, FIG. 3 is a logic circuit diagram, and FIG. 4 is an explanatory diagram showing the stopping operation of the sewing machine. In the figure, 1 is a sewing machine, 2 is a main shaft, 3 is a needle, 4 is a driving means, 5 is a main motor, 7 is a flywheel, 8 is an output shaft, 9
is a clutch disk, 11 is a brake wheel, 17 is a brake coil, 19 is an auxiliary motor, 22 is a clutch coil, 23 is a clutch lever, 125 is a main lever, 27 is an auxiliary lever,
28 is a foot pedal, 31 is a front depression switch, 32 is a rear depression switch, 35 is a permanent magnet piece, 36 is a first detection reed switch, 37 is a second detection reed switch, and 38 is a third detection 39 is a negative power line, 40 is a positive power line, 41 is a delay timer, 42, 47, 52, 56° 59 are first to fifth flip-flops, 45 is a changeover switch, 46.55 48 is an AND circuit, 5L62 and 63 are OR circuits, 64 is a NAND power amplifier circuit, 65 is a NOR power amplifier circuit, 66 is an AND power amplifier circuit, and 67 is a thread trimming coil.

Claims (1)

[Scope of Claims] 1. The sewing machine is operated at high speed via the drive means based on the operation of the operator operating means from the inactive position, and the sewing machine is temporarily brought into a low speed operating state by returning the operator operating means to the inactive position. In a sewing machine that detects the arrival of the needle at a predetermined position after the needle has moved to a predetermined position and operates a brake means to stop the needle at a specific position, the detection operation is based on the operation of the main shaft of the sewing machine or a member interlocked with the main shaft of the sewing machine. a first detection switch for detecting the arrival of the needle at a predetermined position; and a first detection switch arranged at a distance from the first detection switch and activated for detection prior to the first detection switch. a second detection switch for detecting the speed by a second detection switch; and a second detection switch for reducing the speed of the sewing machine to just before the low speed operation state when the needle stops when the operator operating means returns to the inactive position; A speed detection means that generates an output when the detection time of the detection switch exceeds a predetermined time, and the interval between the rain detection switch is determined from the generation of the output from the speed detection means until the detection by the first detection switch. and storage means for storing the output generated from the speed detecting means during the transition to the low speed operation state. and a control means for operating the brake means when there is a memory output from the memory means and a detection by the first detection switch.