DE1093183B - Seam locking device for sewing machines - Google Patents

Description

The invention relates to a seam locking device for sewing machines with electromagnetic Switching from forward to backward stitch.

Such a locking device is already known, but in this case the reversal the sewing direction triggered by operating a toggle lever on a control roller with several Switch positions is effective. The sewing machine is first in the first switching position of the control drum Driven at reduced speed until after switching to the second detent position the shutdown takes place with the needle set in the upper or lower dead position by known means will. If the control roller is then switched to the third detent position, a reverse transport begins, also with reduced speed. Once the desired number of backtack stitches has been sewn, the seamstress has to release the knee lever, which then returns to its starting position.

In this known arrangement, the number of backtack stitches sewn depends only on the seamstress which makes it easier to count the stitches executed by reducing the speed. Of the The disadvantage of the known arrangement is that each seamstress can only operate one machine can and the workflow because of the necessary counting of backtack stitches only with considerable reduced speed can take place.

In order to accomplish this counting, a stitch number preselection device can be used, wherein in another already proposed and known version, one with a main drive and an auxiliary drive equipped sewing machine a number of stitches preselected via a dial at low speed sews and is then stopped in a certain position of the needle bar. With the help of such a It is therefore only possible to set up one after completing a certain number of stitches that can be set beforehand Trigger switching process, and only a one-time switching process. Beyond that, it is only possible to switch off the auxiliary drive. Practically only the time of the shutdown can be controlled Problem that does not arise with the present invention.

In another known sewing machine with an automatically controlled decorative stitch device it is possible, with the appropriate machine setting and use of a special roller, the change of the feed direction to operate. However, such a change option is for special machines for seam bartacking not suitable because the use of a molette at the high level usually given here Sewing speed leads to difficulties.

The invention has set itself the task of a

Seam bartacking device
for sewing machines

Applicant:

G. M. Pfaff A. G.,

Kaiserslautern, Königstr. 154

Karl Winz, Kaiserslautern,
has been named as the inventor

To create a seam locking device in which the bar production takes place automatically. Furthermore should the backtack stitches can be executed at normal sewing speed to avoid long delays to occur while sewing.

This object is achieved by the invention in that the automatic change of feed direction by means of a by a stitch counter actuated switching magnet takes place, the stitch counter from one of the Sewing machine inevitably operated pulse generator is controlled, which is in series with the contact of a relay is switched, the circuit is led over the last counting contact of the stitch counter, so that the Circuit of the pulse generator is interrupted when this last counting contact is reached.

With the counting contacts of the stitch counter, contacts of a preselector can be used to determine the Number of stitches in both sewing directions must be connected.

To reset the stitch counter to its starting position after a single pass, it is also necessary A reset circuit is advantageously provided for the stitch counter, the reset circuit from the series connection of the magnetic coil and the last counting contact of the stitch counter and one There is a switch that is actuated by a machine part moving after the machine has stopped.

The device allows both the implementation of the locking at the beginning and at the end of a Seam. In the latter case, it is only necessary to ensure that the stitch counter only starts at the beginning of the locking process can address. This is achieved by one in the excitation circuit of the solenoid of the Automatically controllable monitoring switch to control the point of use of the counting process.

The combination of electrical switching means according to the invention has made it possible for the first time the task of automation in sewing

009 648/141

machines for seam bartacking. Furthermore, the number of locking stitches can be arbitrary can be changed without the need to replace any machine parts.

The drawing shows the circuit diagram of an exemplary embodiment.

The drive motor 2 can be connected to voltage at the terminals R, S, T, Mp of the three-phase network by means of the main switch 1, the start-up being indicated by the signal lamp 3 lighting up. When the main switch 1 is closed, the rectifier 4 and the primary winding of the transformer 5 are also connected to voltage in separate circuits. The rectifier 6 is connected to the secondary winding of the transformer 5, so that a DC voltage is applied to its terminals 7 and 8 for feeding the control device described in more detail below.

The most important elements of this device are a stopping relay A with contact 1 a, a switch-on relay B with a contact 2 b for switching on the switching magnet 9, a preselector switch C with preselection contacts or contact groups Ic to 5c and a stitch counter D with contact blades 3J, 4 J and 5 J and the counter contacts 3dO to 3rf 10, 4JO to

As soon as the sewing machine is driven by the drive motor 2, the pulse generator 10, which is arranged in a known manner on the arm shaft, closes the excitation circuit for the magnetic coil 11 of the stitch counter D once during each revolution as follows:

I. Terminal 7, monitoring switch 12, terminal 13, pulse generator 10, contact la, terminal 14, solenoid 11, terminal 15, terminal 8.

The contact tongues 3 d, 4 d and 5 d initially on contact 0 of their contact path are switched to the next higher contact with each pulse.

Assume that three bartack stitches are required at the beginning of a seam. To do this, the seamstress must depress contact group 3c of preselector switch C.

After the pulse generator 10 has closed the excitation circuit I of the stitch counter D three times, the switching tongues are on the contacts 3 d 3, 4J3 and 5 J 3. A circuit for the switch-on relay B is closed via the contact 3 ti3 as follows:

II. Terminal 7, monitoring switch 12, terminal 13, switch-on relay B, contact 3 c, contact 3 J 3, contact tongue 3 d, terminal 15, terminal 8.

relay B interrupted again. The contact 2 b is opened, and the circuit III for the switching magnet 9 is interrupted. The transport is now moving forward again. As soon as the machine has sewn a total of ten stitches and accordingly the contact tongues 3 J, 4 J, 5 J are on the contacts 3J10, 4J10, 5J10, an excitation circuit for the stopping relay A is established as follows:

IV. Terminal 7, terminal 19, stopping relay A, resistor 20, contact 5J10, contact tongue 5 J.

Terminal 21, terminal 8 of rectifier 6.

After stopping response of the relay A opens its contact 1 α, and the circuit I of the stitch counter D remains until the stopping of the sewing machine interrupted. If the machine is stopped, for example when the presser foot is raised, a switch 22 coupled to it is closed, which briefly closes a reset circuit for the stitch counter D as follows:

V. Terminal 7, terminal 23, contact 4J10, contact tongue 4 J, switch 22, terminal 14, solenoid 11, terminal 15, terminal 8.

This resets the contact blades 3 d, 4 J, 5 J to the contacts 3 JO, 4JO, 5JO. A signal lamp 24 indicating the sewing readiness is energized via the contact 5 JO as follows:

VI. Terminal 7, terminal 23, terminal 19, terminal 25, signal lamp 24, resistor 26, terminal 5J0, contact tongue 5 d, terminal 21, terminal 8, rectifier 6.

The excitation circuit IV of the stopping relay A and the reset circuit V of the stitch counter D are interrupted.

If a different number of backtack stitches is to be sewn, e.g. B. five, the contact group 5 c of the preselector switch C is depressed, so that after five pulses, ie when the contact tongues 3 J run on the contact 3 d 5, the switch-on relay B and thus the switching magnet 9 are energized. These fall off again as soon as the contact tongue 3 J has passed over the contact 3 J 9.

If locking is to take place at the end of a sewing process, the monitoring switch 12 must remain open until shortly before the end of the sewing process. This can be done by a counter which, after executing a certain number of stitches, switches on the stitch counter D when the locking process is to begin.

The switch-on relay B closes its contact 2b, so that the switching magnet 9 is excited as follows:

III. Rectifier 4, terminal 16, contact 2b, changeover magnet 9, terminal 17.

A spark extinguisher 18 is connected in parallel with contact 2b. When the switching magnet 9 responds, the sewing machine is switched from forward to reverse transport in a known manner.

Since the sewing machine continues to run, the circuit I of the stitch counter D is closed once for the following three stitches via the pulse generator 10 and the contact tongue 3J is rotated further via the contacts 3J4, 3J5 up to the contact 3J6. The contact blades 4J and 5 J are set accordingly to the contacts 4J6 and 5 J6.

As soon as the contact tongue 3 J is on contact 3 J 6, the excitation circuit II of the switch-on

Claims (4)

Patent claims: 1. Seam locking device for sewing machines, characterized in that the automatic The feed direction is changed by means of a switching magnet operated by a stitch counter and that the stitch counter is from a pulse generator that is positively actuated by the sewing machine is controlled, which is connected in series with the contact of a relay whose circuit is via the last counting contact of the stitch counter is performed, so that the circuit of the pulse generator when reached this last counting contact is interrupted. 2. Seam locking device according to claim 1, characterized in that with the Counting contacts of the stitch counter Contacts of one Selector switch for determining the number of stitches in both sewing directions are connected. 3. Seam locking device according to claim 1 and 2, characterized by a reset circuit for the stitch counter (D), wherein the reset circuit consists of the series connection of the magnetic coil (11) and the last counting contact (4dlO) of the stitch counter (D) and a switch (22) that is actuated by a machine part that is moved after the machine has stopped. 4. Seam locking device according to claim 1 and 2, characterized by an im Excitation circuit of the magnet coil (11) of the stitch counter (D) , automatically controllable monitoring switch (12) to control the starting point of the counting process. Considered publications:
German Patent Nos. 914 458, 76 563;
German interpretation Sch 9796 VII / 52 (published on March 22, 1956); German utility model No. 1 682 040;
Austrian patent specification No. 17 276. 1 sheet of drawings © 009 648/141 11.60