JPS6223598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device for detecting a needle position of a sewing machine and stopping the sewing machine at a predetermined position when a needle position detecting means fails in an electric sewing machine.

Generally, as shown in FIG. 1, an electric sewing machine includes a clutch motor section 1 for driving and a sewing machine 8 driven by the clutch motor section 1. The clutch motor section 1 includes a motor 2, a clutch friction plate 16 attached to the shaft end of the motor, a clutch plate 3 disposed on the driven shaft opposite to the clutch friction plate 16, and a clutch plate 3 disposed on the driven shaft. The clutch plate 3 and the brake plate 4 have a fixed brake friction plate 17 provided opposite to the brake plate 4.
Pulley 18 attached to the outer end of the driven shaft attached to
is connected to a pulley 19 of the sewing machine 8 by a belt 20. Furthermore, the clutch motor section 1 has a clutch coil CL disposed close to the clutch plate 3 and a brake coil BR disposed close to the brake plate 4. Both of these coils are controlled to be energized by the control device 10 via transistors TR1 and TR2, and when the clutch coil CL is energized, the clutch plate 3 comes into contact with the clutch friction plate 16, and the brake coil BR comes into contact with the clutch friction plate 16. When the brake plate 4 is energized, the brake plate 4 comes into contact with the brake friction plate 17. On the other hand, on the shaft of the sewing machine 8, a detection means 13 is provided with a position detector 14 for detecting the upper or lower position of the sewing machine needle and a speed detector TG for detecting the rotation speed.
is installed, and the outputs of the position detector 14 and speed detector TG are input to the control device 10. Further, an operation command device 12 connected to a foot pedal of the sewing machine provides a command signal to the control device 10 to drive or stop the sewing machine at a predetermined speed in response to pedal operation.

In such an electric sewing machine, the motor 2 rotates at a constant speed, and when a drive command signal is issued from the operation command device 12, the control device 10 controls the clutch coil.
The clutch plate 3 contacts the clutch friction plate 16, and the rotation of the motor 2 is transmitted to the pulley 19 via the clutch plate 3, pulley 18, and belt 20, and the sewing machine 8 is driven. . At this time, the rotational speed of the sewing machine shaft is converted into an electrical signal by the speed detector TG and inputted to the control device 10, which controls the clutch coil CL and the brake so that the rotational speed of the sewing machine shaft reaches the set value. Controls the excitation of coil BR. Next, when a stop command signal is issued from the operation command device 12 (when the drive command signal disappears), the control device 10 monitors the position detection signal from the position detector 14 and controls the clutch coil CL and brake coil BR. , and when a position detection signal is output, the needle of the sewing machine 8 is stopped at a predetermined position.

In an electric sewing machine controlled in this way,
If the position detector 14 fails and future position detection signals are not input to the control device 10, the control device 1
0 does not work to stop the sewing machine needle 8. Therefore, in such a case, even if a stop command signal is issued from the operation command device 12, the sewing machine 8 continues to be driven, resulting in dangerous and wasteful sewing work (mistakes).

An object of the present invention is to prevent the sewing machine from continuing to rotate due to a failure of the needle position detection means in an electric sewing machine, and to prevent the sewing machine from continuing to rotate due to failure of the needle position detection means in an electric sewing machine. It is to provide safety equipment at the time.

In order to achieve this object, the present invention includes a speed detecting means that outputs a speed signal with a period corresponding to the rotation of the sewing machine, and a speed detecting means that counts the speed signal from the speed detecting means and resets the number of stitches using a needle position detection signal. The control means is equipped with a counting circuit that outputs an output when the content reaches a predetermined value or more, and when the needle position detection means fails and a needle position detection signal is not generated, the sewing machine is stopped by the output of the counting circuit. Features.

Embodiments of the present invention will be described in detail below with reference to FIGS. 2 to 4.

FIG. 2 shows a control circuit. The operation command device 12 is equipped with a command switch FSW that is linked to the foot pedal. When the foot pedal is depressed, the command switch FSW is turned on and the command signal FSWS is at a high (H) level (drive When the foot pedal is released or pressed back, the command switch FSW is turned off and the command signal FSWS becomes low (L) level (stop command). The position detector 14 sets the position detection signal DET to H level when the needle of the sewing machine reaches a preset position. speed detector
TG is a synchronous generator that outputs AC voltage according to the rotation of the sewing machine. The control device 10 includes a speed control circuit 32 and receives an output signal from the speed detector TG.
Input TGS and set the clutch coil CL and brake coil so that the rotation speed of the sewing machine becomes the set value.
Create acceleration signal DRIVES and deceleration signal BRAKES to control BR (set to high level). The circuit for the acceleration signal DRIVES is connected to the transistor TR1 via the AND gate AND2 to control the clutch coil CL, and the circuit for the deceleration signal BRAKES is connected to the transistor TR2 via the AND gate AND1 and the OR gate to control the brake coil BR.
be controlled. Sequence control circuit
The MC inputs the command signal FSWS and the position detection signal DET, and when the command signal FSWS is at H level, the drive signal DRIVE is set to H level, and the command signal FSWS is output.
is at L level and position detection signal DET is at H level, drive signal DRIVE is at L level, stop signal
Set BRAKE to H level. The circuit for the drive signal DRIVE is connected to the other input terminals of the AND gates AND1 and AND2 via the AND gate AND3. The circuit of the stop signal BRAKE is the above-mentioned OR gate.
Connected to other input terminals of OR. The pulse counting circuit 31 inputs the alternating current output signal TGS obtained from the speed detector TG, which is shaped by the waveform shaping circuit 30, to the input terminal I and counts it. When a preset count value is reached, the output signal at the output terminal O is LOCKed. H
It is used to set the level, and the counting contents are reset terminal R.
It is designed to be reset by the position detection signal DET input to the In a machine in which the position detection signal DET is output once per cycle of the sewing machine needle, the set count value of the pulse counting circuit 31 is determined by the number of output pulses of the waveform shaping circuit 30 generated during one cycle of the sewing machine needle movement. Set to a value that is equal to or greater than this, but close to this. The output terminal O of the pulse counting circuit 31 is connected to the other input terminal of the AND gate AND3 via the inverter INV.

In the above configuration, the normal operation will be explained with reference to FIG. When the command switch FSW is turned on and the command signal FSWS is at H level, the drive signal DRIVE of the sequence control circuit MC is at H level,
The stop signal BRAKE is at L level. Moreover, if the position detector 14 is normally outputting the position detection signal DET, the pulse counting circuit 31 is reset periodically and does not reach the set count value, so the output signal LOCK of the pulse counting circuit 31 is at the L level. The H level is input to the AND gate AND3 via the inverter INV, and therefore one input terminal of each AND gate AND1 and AND2 is at the H level. Therefore, the acceleration signal DRIVES and the deceleration signal output from the speed control circuit 32
BRAKES turns on and off transistors TR1 and TR2 through AND gates AND1 and AND2 to excite clutch coil CL or brake coil BR and drive sewing machine 8. Then, when the command switch FSW is turned off to set the command signal FSWS to L level at a given rotation angle θ1 of the sewing machine shaft, the sequence control circuit MC causes the position detection signal DET to go to H level at a predetermined rotation angle (predetermined sewing machine needle position) θ2. When this happens, the stop signal BRAKE is set to H level and the drive signal DRIVE is set to L level. As a result, the output of the AND gate AND3 becomes L level, so the AND gates AND1 and AND2 are closed and the acceleration signal DRIVES and deceleration signal BRAKES from the speed control circuit 32 are invalidated. Then, the stop signal BRAKE passes through the OR gate OR and turns on the transistor TR2, so that the brake coil BR is energized and the sewing machine stops at a predetermined needle position.

Next, the operation when the position detector 14 is abnormal will be explained with reference to FIG. At the rotation angle θ1 of the sewing machine shaft, turn off the command switch FSW and send the command signal.
When FSWS is set to L level, the sequence control circuit
MC outputs the drive signal while monitoring the position detection signal DET.
DRIVE is kept at H level. If the position detection signal DET is not input even when the predetermined rotation angle θ2 is reached, the drive signal DRIVE becomes H level and the stop signal
Since BRAKE remains at L level, the sewing machine does not stop. If this state continues for one cycle or more of the sewing machine needle movement and reaches the rotation angle θ3, the pulse counting circuit 31 is not reset either, so the pulse counting reaches the set counting value and the output signal LOCK goes to H level. . Therefore, since the L level is input from the inverter INV to the AND gate AND3, the AND gate AND3 is closed and the drive signal DRIVE from the sequence control circuit MC is invalidated (the output of the AND gate AND3 becomes L level).
As a result, the AND gates AND1 and AND2 are closed, and the signals DRIVES and DRIVES from the speed control circuit 32 are
BRAKES is disabled, clutch coil CL and brake coil BR remain demagnetized, and the sewing machine stops naturally. Such a natural stop similarly occurs if the position detection signal DET of the position detector 14 is not output within a predetermined period even if the command switch FSW is in the on state.

Therefore, if the position detector 14 fails, the sewing machine can be stopped to ensure the safety of the sewing operation and to prevent mistakes.

In addition, if you want to stop the sewing machine suddenly in the event of an abnormality like this, use the OR gate OR as a three-input terminal type and set the output signal LOCK of the pulse counting circuit 31 to the third terminal.
It is better to input it to the input terminal to excite the brake coil BR.

As explained above, according to the present invention, there is provided a speed detecting means for outputting a speed signal with a period corresponding to the rotation of the sewing machine, and a speed signal from the speed detecting means is counted, and the needle is reset by a needle position detection signal. The control means is equipped with a counting circuit that outputs an output when the number content reaches a predetermined value, and when the needle position detection means fails and the needle position detection signal is not generated, the sewing machine is stopped by the output of the counting circuit. It is possible to prevent the sewing machine from continuing to rotate due to a failure of the needle position detection means, reduce sewing errors, and perform safe sewing work.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an electric sewing machine to which the present invention is applied, Fig. 2 is a control circuit diagram of an electric sewing machine showing an embodiment of the invention, and Figs. 3 and 4 are an embodiment of the invention. FIG. 3 is an explanatory diagram of the operation of the safety device in normal and abnormal conditions. 1...Clutch motor section, 8...Sewing machine, 10
...Control device, 12...Driving command device, 14...
Position detector, 31... Pulse counting circuit, 32...
Speed control circuit, TG... speed detector, CL... clutch coil, BR... brake coil, FSW...
Command switch, MC...Sequence control circuit.

Claims (1)

[Claims] 1. A driving motor, a transmission means for driving the sewing machine by the driving motor, a stopping means for stopping the sewing machine, a needle position detection means for detecting the position of the needle of the sewing machine, and a command for driving and stopping the sewing machine. A safety device in case of a failure of the needle position detection means in an electric sewing machine, which includes an operation command means and a control means for driving or stopping the sewing machine at a predetermined position using a command signal from the operation command means, wherein the control means comprises: , a speed detection means for outputting a speed signal with a period corresponding to the rotation of the sewing machine; and a speed signal from the speed detection means is counted, reset by the needle position detection signal, and output when the count reaches a predetermined value or more. 1. A safety device in the event of a failure of a needle position detecting means in an electric sewing machine, comprising: a counting circuit, the stopping means being activated by the output of the counting circuit.