JPS609478B2 - Sewing machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewing machine control device that reliably stops the sewing machine needle directly above the sewing machine.

This type of secondary device is constructed using a relay, but as is well known, relays have large variations in attracting current and release voltage, so it is important to always ensure that the needle stops directly above the thread after thread trimming. In addition, when used in equipment with large vibrations such as sewing machines, failures occur frequently and the lifespan of the equipment is short (poorly practical, and relays operate for a long time, so even if you try to improve work efficiency, the This was a major time constraint.

This invention has been made to eliminate the drawbacks of the conventional devices described above, and is to construct the device using a non-contact circuit without using relays, thereby obtaining a device that improves both accuracy and reliability. be.

An embodiment of the present invention shown in FIG. 1 will be described below.

In the figure, 1 is a switch that is closed directly below the needle in synchronization with the needle movement of the sewing machine, 2 is a switch that moves when the treadle of the sewing machine (not shown) is operated, and is closed when the sewing machine is in high-speed operation, and 3 is the switch mentioned above. Similarly to switch 1, a switch is synchronized with the movement of the needle of the sewing machine and is closed when the needle is in the upper position; 4 is a switch that is linked to the operation of a treadle (not shown) of the sewing machine and is closed when the treadle is pressed back during thread trimming; 6 is controlled by the above-mentioned switches 1 and 2, and its output becomes L level when the sewing machine is operating at high speed, and changes from L level to H level when the sewing machine reaches the set low speed rotation speed and the needle is lowered. 6, 7, 8 are transistors, 9 is a DC power supply, 10 is a diode, 11 is an output terminal, R, to R, .
is resistance. Next, the operation of the apparatus constructed as described above will be explained based on FIG.

First, by depressing the footboard of the sewing machine (not shown), the switch 2 is activated and the control circuit 5 is set to the L level.

In this state, a base current is supplied to the transistor 6 from the DC power supply 9 via the resistors R, , R3, R4, and R5. Next, when the footboard is bounced back, the switch 2 is opened and the switch 4 is closed, the base current of the transistor 6 is cut off, and the transistor 6 is cut off.

On the other hand, at the same time as the switch 4 is closed, the rotational speed of the sewing machine begins to decrease, and when the rotational speed of the sewing machine falls below the set rotational speed (approximately 20 pm) and the needle becomes lower, the output of the control circuit 5 changes from the L level to the H level. Therefore, the diode 10 is cut off and the collector of the transistor 6 becomes H level at the same time. Further, when the collector of the transistor 6 becomes H level, the base current is supplied to the subsequent transistor 8 via the resistors R7 and R8, and as a result, the transistor 8 becomes conductive and its collector, that is, the output terminal 11 becomes It becomes L level. Next, when the transistor 8 becomes conductive, the transistor 7 is made conductive by the resistors R9, R, and o, and its collector current becomes the base current of the transistor 8 via the resistors R, R2. That is, the transistors 7 and 8 form a self-holding circuit, which holds the collector of the transistor 8, that is, the output terminal 11, at the L level until the switch 3 directly above the needle is closed. That is, the above operation will be explained based on the time chart shown in FIG. 2. First, when the treadle is depressed, switch 2 is closed as shown in the opening of FIG. 2, and the sewing machine starts and rotates at high speed.

On the other hand, since the switch is synchronized with the needle movement, it becomes as shown in FIG. 2C. (Potential at point ■ in Figure 1) In this state, the output of the control circuit 5 (potential at point ■ in Figure 1) is at L level as shown in Figure 2, and the switch 3 is synchronized with the needle movement. Therefore, the result is as shown in FIG. (Fig. 1 ◎ point potential) Next, when the treadle is bounced back, switch 4 is closed and the sewing machine rotation speed decreases. When the sewing machine reaches the set rotation speed, the output of the control circuit changes from the L level as shown in Fig. 2 2. In this state, the output of the switch 4 becomes valid, and the collector of the transistor 8, that is, the output terminal 11 changes from the H level to the L level, as shown in FIG. The needle is self-retained to the upper layer, and this period becomes a signal that gives a period during which thread trimming is possible.

As described above, according to the embodiment, even if the treadle is turned back and the switch 4 is closed in order to perform thread trimming when the sewing machine is operating at high speed, the diode 10 causes the output of the control circuit 5 to Unless the output of the switch 4 is discriminated and the output of the control circuit 5 changes from the L level to the H level, in other words, the thread trimming operation cannot be performed unless the number of revolutions of the sewing machine falls below a predetermined set number of revolutions. This is highly effective in preventing accidents such as needle breakage when thread trimming is performed while the sewing machine is operating at high speed. In FIG. 1, switches 1 to 4 are configured as contact switches, but it goes without saying that magnetic or photoelectric type non-contact switches may also be used.

As described above, according to the present invention, there is a control circuit that detects and controls the lower layer of the needle of the sewing machine and the rotation speed of the sewing machine, a detection circuit that detects the upper layer of the needle of the sewing machine, and a control circuit that detects and controls the lower layer of the needle of the sewing machine, and a control circuit that responds to the thread trimming operation. By discriminating the output of the control circuit, the number of rotations of the sewing machine reaches a predetermined set number of rotations, and after the needle is in the lower layer, the detection circuit is operated to trim the thread of the sewing machine and remove the needle. Since the needle is reliably stopped directly at the upper position, the series of thread trimming operations described above and the needle's upper position stop can be performed reliably without any consideration of failure or operation time due to the use of relays as in the past. It is possible to improve both workability and reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the apparatus shown in FIG. In the figure, 1 is a switch for detecting the lower needle layer, 2 is a switch that is closed when the treadle is depressed, 3 is a switch for detecting the needle upper position, 4 is a switch that is closed when the treadle is turned back, and 5 is a switch that is closed when the treadle is pressed down.
1 is a control circuit, 6, 7, and 8 are transistors, 9 is a DC power supply, 10 is a diode, and 11 is an output terminal. Figure 1 Figure 2

Claims (1)

[Claims] 1. A thread equipped with a position detector having one or more detection signals for detecting the needle position of a sewing machine, an operation signal that responds to the depression of the treadle, and a thread trimming signal that responds to the rebound of the treadle. In a cut-off sewing machine, a first circuit detects the lower position and rotational speed of the needle of the sewing machine, which is disabled while the treadle is being depressed, and becomes effective when the treadle is neutral or rebounds, and a second circuit that detects the upper position of the needle. The circuit includes a third circuit that responds to a thread trimming operation due to the rebound of the treadle, and is configured such that the third circuit can respond after the output of the first circuit, and after the third circuit responds. A control device for a sewing machine, characterized in that the thread cutting operation is performed until the output of the second circuit is generated, and the sewing machine is stopped at the above-mentioned needle-up position. 2. A discrimination circuit is provided for discriminating the outputs of the first and second circuits, and this discrimination circuit performs the thread trimming operation up to the output of the second circuit, which is generated after the first circuit, and also allows the sewing machine to be positioned above the needle. The control device for a sewing machine according to claim 1, characterized in that the control device is adapted to stop the sewing machine.