JPH0376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a presser foot lifting magnet control device for a sewing machine.

[Conventional technology]

FIG. 4 is a block diagram showing the configuration of a presser foot lifting magnet control device that uses a magnet to lift up the fabric in a conventional cycle sewing machine. , 2 is a starting means that generates a signal by operating a pedal of the sewing machine, 3 is a control means consisting of a microprocessor, ROM and RAM that store a control program, and 4 is a RAM that stores the duty set by the duty setting means 1. The duty reading means 5 is a magnet driving means for supplying magnet energizing current as a pulse to energize the magnet.

The conventional presser foot lifting magnet control device is constructed as described above, and the duty setting means 1 sets the duty during the presser foot lifting operation. However, from FIG. 7, duty [%] = t ₁ /(t ₁ +t ₂ ).

Next, the operation of the conventional presser foot lifting magnet control device will be explained according to the flowchart shown in FIG.

When the starting means 2 is turned on, the control means 3 reads the duty set by the duty setting means 1 from the duty reading means 4 and operates a magnetic drive so as to apply a pulse at the time of starting the presser foot lifting operation for a fixed time t seconds. controlling means 5;

When a predetermined pulse application time t seconds has elapsed, the control means 3 switches the magnet control pulse to the holding duty.

[Problem that the invention seeks to solve]

In the conventional presser foot lifting magnet control device as described above, the pulse application time at startup is matched to the lifting time of the presser foot when the duty is small, as shown in Figure 6B, so the pulse application time as shown in Figure 6A is When the duty is large, the presser foot rises quickly, so even after the lifting of the presser foot is completed, the duty pulse at startup is applied extra for Δt seconds.

As a result, the drive magnet generates heat, making the operation less effective than during normal operation.
This has the problem of shortening the useful life of the magnet and further reducing the safety to the human body of the sewing machine operator.

Conversely, if the pulse application time at startup is matched to the rise time of the presser foot when the duty is large, the rise of the presser foot will be slow when the duty is small, so the pulse during holding will be applied before the presser foot reaches the upper limit. It is clear from the above that since the sewing machine is switched, the spring that urges the presser foot downward causes the presser foot to fall, reducing the reliability of the operation of the presser foot and the human safety of the sewing machine operator.

This invention was made to solve this problem, and even when the duty at the start of the presser foot lifting operation is set variable, it provides an appropriate pulse application time to raise the presser foot. An object of the present invention is to obtain a presser foot lifting magnet control device that can perform the following functions.

[Means for solving problems]

The presser foot lifting magnet control device for a sewing machine according to the present invention includes a presser foot that presses the cloth at a lower position, is separated from the cloth at an upper position, and always receives a downward elastic force; In a sewing machine having a magnet that is raised against the
A drive circuit that applies a large amount of electricity to give a strong acting force to the magnet at a predetermined time in the initial stage of energization, and then a small amount of electricity that gives a weak acting force, and a drive circuit that adjusts and sets the large amount of electricity before the energization. It consists of a setting means and an adjusting means for changing the predetermined time based on the setting value of the setting means.

[Effect]

In this invention, a pulse with the above duty is applied for a predetermined pulse application time based on a set duty value.

〔Example〕

Examples of this invention are described in Japanese Patent Publication No. 51-4462, for example.
A cycle sewing machine having a thread cutting mechanism having a bobbin thread payout body as described in the above publication will be described.

FIG. 1 is a block diagram of a presser foot lifting magnet control device for a cycle sewing machine showing one embodiment of the present invention. 1 to 5 are completely the same as the conventional device described above. Reference numeral 6 denotes a pulse application time setting means consisting of a ROM that stores an arithmetic expression for setting a time corresponding to the duty set by the duty setting means 1.

FIG. 2 is a flowchart showing the operation of a presser foot lifting magnet control device according to an embodiment of the present invention, and FIGS. 3A and 3B are time charts showing the operation of the same device.

The operation of the above embodiment will be explained with reference to FIGS. 1, 2, 3A, and 3B. First, the duty setting means 1 sets the duty at the time of activation of the magnet control signal. Next, the starting means 2 sends a presser foot lifting command signal to the control means 3.

Therefore, the control means 3 reads the duty set by the duty reading means 4, calculates the pulse application time according to the read duty using the pulse application time setting means 6, and sets the value.

When you want the presser foot to rise quickly, increase the duty. As shown in Figure 3A, the presser foot will rise faster. Therefore, the appropriate pulse application time to raise the presser foot is short as _t1 . Set.

However, if this duty is too large and the presser foot rises too quickly, causing the bobbin thread to be cut by the thread pay-out body of the thread trimming mechanism, it is necessary to lower the duty.

Therefore, if the duty is made small, the lifting of the presser foot becomes slow as shown in FIG. 3B, so the appropriate pulse application time to raise the presser foot is set to be long, such as _t2 .

[Other Examples]

In the above embodiment, the control means 3 reads the set duty using the duty reading means 4, calculates the pulse application time according to the read duty using the pulse application time setting means 6, and sets the value. The pulse application time does not need to be calculated, but a table storing pulse application times corresponding to duties may be prepared in advance in the pulse application time setting means 6, and the pulse application time may be selected from the table.

〔Effect of the invention〕

According to the present invention, by applying the duty pulse for a predetermined pulse application time using the duty value set as described above, it is possible to apply a pulse appropriate for operating the presser foot lifter magnet.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a presser foot lifting magnet control device for a cycle sewing machine which is an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the same device which is an embodiment of the present invention, and FIG. 3A. FIG. 3B is a time chart showing the operation of the device which is an embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a conventional presser foot lifting magnet control device.
FIG. 5 is a flowchart showing the operation of the conventional device, FIGS. 6A and 6B are time charts showing the operation of the conventional device, and FIG. 7 is a pulse waveform diagram explaining the duty. In the figure, 1 is a duty setting means, 3 is a control means, 4 is a duty reading means, 5 is a magnet drive circuit, and 6 is a pulse application time setting means.

Claims (1)

[Scope of Claims] 1. A cloth presser that presses the cloth at a lower position, is separated from the cloth at an upper position, and always receives a downward elastic force, and a magnet that raises the cloth presser by force against the elastic force. a drive circuit that applies a large amount of electricity that applies a strong acting force to the magnet at a predetermined time in the initial stage of energization, and then applies a small amount of electricity that gives a weak acting force; A presser foot lifting magnet control device for a sewing machine, comprising: a setting means for adjusting and setting an amount of electricity; and an adjusting means for changing the predetermined time based on a setting value of the setting means.