DE1260941B - Stitch group lockstitch sewing machine - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

D05b

German class: 52 a - 38/02

Number:
File number:
Registration date:
Display day:

D 46066 VII a / 52 a
December 15, 1964
February 8, 1968

The invention relates to a lockstitch sewing machine with a control and workpiece feed device to form a stitch group, e.g. B. a buttonhole bar, and with one below their fabric support surface arranged thread cutting device for separating the sewing threads the last time the needle pierced the workpiece.

As is known, a knot is formed at the end of the stitch group on such stitch group sewing machines formed by two consecutive fastening stitches in the same place, i.e. i.e., twice Piercing the sewing needle into the same piercing hole on the workpiece. This arises in cooperation Use the looper to knot the bobbin thread and the upper thread, and if a correct one is used Knotting is to be achieved, so-called roll stitches must act.

After completing the fastening roll stitches, the sewing needle sticks into the puncture hole a third time the fastening stitches. This third puncture of the sewing needle into the same puncture hole serves the purpose, the tip of the knife of the thread cutting device into the upper thread loop formed with the aid of the gripper to allow the needle thread together with the bobbin thread after going up the sewing needle behind the knotted fastening stitches. At the same time, a A sufficiently long piece of upper thread has been pulled through, which is necessary to start sewing the next group of stitches is.

If the upper thread is retrieved by the thread take-up device during this third stitch, then this is effected this train as a result of the deflection of the upper thread around the fishing tip of the knife that the through the The knot formed in the workpiece in the previous fastening stitches is pulled down and out of the material to be sewn will. Furthermore, there is also the risk that the double looping of the upper thread The knot formed around the bobbin thread loosens again because the upper thread and the bobbin thread in this third one Stitch are pulled in the same direction with the insertion of the needle thread puller, that is from the workpiece down away.

The disadvantage of this known type of formation of a fastening stitch is that the The knot is pulled down from the sewing material, creating an unclean seam finish, or, if the knot loosens, the sewn stitch group is not secured against unraveling. In addition, the Verkno stitch group lockstitch sewing machine can also be used when severing the threads by means of the thread cutting device

Applicant:

Dürkoppwerke

Company with limited liability,

4800 Bielefeld, Niederwall 29

Named as inventor:
Kurt Biermann, 4805 Brake

with detached when they are at the bottom of the workpiece protrudes.

The inventive design of the control and workpiece feed device of a stitch group lockstitch sewing machine eliminates these deficiencies, namely by the fact that the workpiece after forming the fastening roll stitches and before the last Penetration of the needle a feed movement is given. The last penetration of the needle takes place so not, as previously known, in the same place as the fastening stitches, but at one point, which lies in the vicinity next to the piercing hole of the fastening stitches, so that the needle thread of the Thread cutting device presented on the detour over the top of the workpiece for severing will. It follows that when the needle thread is drawn, the knotting as a result of the twofold Deflection, namely on the one hand over the top of the workpiece and on the other hand over the air-termination tip of the knife of the thread trimmer, not downwards out of the workpiece, but the the opposite of how it is drawn into the workpiece with normal stitch delay. In this way a clean seam finish is created and the knotting of the lower thread and the needle thread in one Brought a protected position within the workpiece, as with the chaining of the threads in normal Double lockstitch.

The sequence of the formation of such a fastening stitch is described below with reference to a known one Lockstitch stitch group sewing machine shown with a cam-controlled fabric clamp for the fabric feed and a controlled thread trimmer for the upper and lower thread is equipped and their stitch-forming tools in cooperation with the fabric feed on the one hand produce normal lockstitch and on the other hand so-called roll stitches.

809 507/172

To carry out the last puncture of the sewing needle following the fastening stitch, which according to the invention is set next to the puncture hole of the fastening stitch, is a corresponding training the control cam of the feed device required, such that the workpiece according to the forming the fastening roll stitches and a feed movement before the needle is inserted for the last time is granted. This last needle penetration is expedient. in the stitch group of the stitch group placed, with only a short distance from the previous knotting stitch. That has The advantage is that the needle thread stitching on the top of the sewing material is barely visible and the upper thread is held particularly firmly in the stitch bandage. It will also go further avoided that the end of the upper thread cut below the throat plate after the The surface of the sewing material runs through, which is in terms of a neat appearance of the surface the stitch group is desired.

The workflow for forming the knotted fastening roll stitches, e.g. on a buttonhole bartack, is the following:

Due to the relative position of the needle and hook, the stitch group in the association on the one hand normal lockstitch and on the other hand roll stitches generated. For the fastening stitches roll stitches are required and for this reason the fastening stitches are on the roll stitch side of the stitch group by inserting the needle twice in a row in the same place. If these two roll stitches are warped, a Knotting the bobbin thread and needle thread.

Before the thread trimmer comes into action, the needle has to make another puncture perform, which according to the invention is preceded by a movement of the workpiece. After the puncture has taken place the gripper pulls the loop ejected by the needle, and the tip of the knife the The thread trimmer takes the from the last stitch to the lower thread bobbin or to the upper thread supply leading thread legs of the two threads. After the needle has gone up and the needle thread has been tightened by the thread take-up device, the knotted fastening roll stitches by the two-fold deflection of the needle thread, namely firstly over the top of the workpiece and secondly over the tip of the knife, into the workpiece are drawn in, the thread cutting device comes into action and separates the threads tightly on the underside of the workpiece. Damage or loosening of the knot will affect this Wise, safely prevented.

Claims (1)

Claim: Stitch group lockstitch sewing machine with a control and workpiece feed device, which is designed so that after making the stitch group by piercing several times the sewing needle formed knotted fastening roll stitches in the same puncture hole on the workpiece whereupon the needle pierces the workpiece one more time and with a thread cutting device arranged below the fabric support surface of the sewing machine the sewing threads are cut off after the needle is inserted into the workpiece for the last time, characterized by such a design of the control and workpiece feed device, that the workpiece is fed with a feed movement after the fastening roller stitches have been formed and before the needle is pierced for the last time is granted. 809 507/172 1.68 © Bundesdruckerei Berlin