EP0011689A1 - Method and device for overedge seaming with the aid of a zig-zag sewing machine - Google Patents

Abstract

A method of forming an overlock seam using a zigzag sewing machine. After forming a first interlacing (1) of needle and looper thread in a first stitch position (I) of the needle bar (22), the needle thread (NF) is loosened and the needle bar (22) is moved into a second stitch position (II) in which a further thread entanglement (2) takes place. After at least one straight stitch has been formed in the second overstitch position, the connecting thread between the two first thread loops is pulled out into the first overstitch position (I) to form a loop (S), the needle (26) sticks into the loop (S), whereupon the latter is released. The seam formed in this way is a firm connecting seam, by means of which the material to be sewn is not drawn together between the thread entanglements. The method is carried out on a device which contains an oversewing mandrel, which, in order to achieve two successive movement phases, is assigned one in the pendulum movement path of the needle bar (22) and one in the axial movement path for the first overstitch position (I) arranged thrust bracket (47 or 48) and in the path of which a loop wiper (51) protrudes. The needle bar thus controls pulling out and throwing off the connecting thread between the first two thread loops.

Description

From DE-OS 28 11 455 a method for forming a seam that can be used as an edge seam on a zigzag sewing machine is known, after which of three forward stitches the third takes place under a change of upper stitch position, followed by two reverse stitches in this overstitch position, whereupon four forward stitches are sewn of which the first is sewn with a change of stitch position, the two following are sewn in this stitch position and the fourth again with a change of stitch position etc., whereby the stitches which are at a distance from the fabric edge are sewn while reversing the feed direction. As a result, the needle and looper thread are intertwined each time the needle is inserted, both at the outer edge of the fabric and at a distance from it - that is to say in both needle stitch positions. All overstitching is carried out in the feed direction.

Since this seam is only formed by controlling the stitch movements of the needle and the feed movements of the fabric pusher, which means that it is a pure zigzag seam, it suffers from the disadvantage of all known zigzag seams that it has a thread tension of needle which is significantly reduced compared to a straight seam. and looper thread must be sewn in order to keep the unavoidable contraction of the seam and thus also the material to be sewn in the seam area as inevitable when the stitch is drawn in, which is particularly noticeable in the manufacture of an edge retaining seam. This can be avoided entirely the manufacture of one, however, if a proper and still sufficiently tight interlacing of needle and looper thread is to be achieved by the stitch feed.

In the transition from sewing a zigzag seam to sewing a straight seam and vice versa, a re-adjustment of the tension of the needle and looper thread cannot be avoided. However, the tension is usually not reset immediately, but only after a few changes in tension and subsequent close tests. That means having to put up with a considerable loss of time.

In the manufacture of feston and decorative seams, it is known to use a two-needle sewing machine (DF-PS 285 182) which is equipped with a thread puller by which the thread of one needle is pulled out and the other needle is presented for puncture in order to withstand a bending stress to avoid the needle. To control the thread puller, a relatively complicated gear is required, which is built into the machine. As a result, the machine becomes a special machine for producing two parallel seams, in which the thread of one needle is merely intertwined with that of the other needle. As a single-purpose machine, it cannot be used in private households at all.

The invention has for its object to develop a method for forming an overlock seam, by means of which a seam can be produced, by means of which the material to be sewn - for example two layers of fabric - is sewn to one another firmly and durably and is not contracted in the seam area, so that the Seam is suitable for sewing together and edging edges of particularly thin materials, knitwear and knitwear as well as similar elastic textiles.

This object is achieved by the method steps specified in the characterizing part of claim 1.

In order to keep the stretching stress of the thread to be pulled out into a loop as low as possible, it is further proposed to pull out the needle thread into the first overstitch position while reversing the material feed direction.

A device which is particularly easy to control for carrying out the method according to the invention results from the features specified in the characterizing part of patent claim 3.

The sub-claims 4 and 5 relate to advantageous details of the device.

• Fig. 1 eine schaubildliche Darstellung der Vorrichtung zur Durchführung des neuen Verfahrens in vergrößertem Maßstab;
• Fig. 2 eine Vorderansicht der an der Stoffdrückerstange einer nur angedeuteten Zickzack-Nähmaschine angebrachten Vorrichtung etwa in natürlicher Größe;
• Fig. 3 eine stark vergrößerte schaubildliche Darstellung einer nach dem neuen Verfahren hergestellten Oberwendlichnaht an der Randkante eines Stoffstückes und die
• Figuren 4 bis 6 in Draufsicht verschiedene überwendlichnähte, ebenfalls stark vergrößert, zum Aufzeigen der Stichfolge bei der Nahtbildung nach dem neuen Verfahren, wobei Fig. 6 die Oberseite der in Fig. 3 dargestellten Naht zeigt.

The new method and the device for its implementation are described in the following with reference to the attached drawing. Show it:

• Figure 1 is a diagrammatic representation of the device for performing the new method on an enlarged scale.
• Figure 2 is a front view of the device attached to the presser bar of a zigzag sewing machine, only indicated, approximately in natural size;
• Fig. 3 is a greatly enlarged diagrammatic representation of an Oberwendlich seam produced by the new method on the edge of a piece of fabric and the
• Figures 4 to 6 in plan view various overlock seams, also greatly enlarged, to show the sequence of seams according to the new method, with Fig. 6 showing the top of the seam shown in Fig. 3.

In the head 2U of the zigzag sewing machine, with the aid of which the method is to be carried out, the presser stands 21, which are under spring action, and the needle bar 22 are arranged. At the lower end of the needle bar 22, a needle holder 23 is arranged, in which the needle 26 is fastened by means of a fastening screw 25 having a cylinder head 24 and which cooperates with a thread-guiding gripper 28 arranged under the needle plate 27 for stitch formation. The needle bar 22 are issued in a known manner, vertical up and down movements and optionally transverse movements between the top stitch positions designated 1 and II.

The needle plate 27, which is attached to the fabric support plate 29 of the sewing machine 20 and has a passage slot (not shown) for the needle 26, has two longitudinal slots 30 through which the toothed webs 31 of the fabric slide 32, which performs a square motion in the usual manner, for moving the fabric upward pass.

A fabric presser sole 33, which is articulated on a shaft 34, works together with the above webs 31 of the fabric slide 32. The shaft 34 is fastened by means of a wing screw 35 to the lower end of the presser bar 21, which is acted upon downwards by a presser spring, not shown. The shaft 34 is extended to one side and is formed into a bearing bracket 36 with two angularly bent bearing webs 37 and 38, in which a shaft 39 is rotatably and longitudinally displaceably mounted.

An angle lever 40 is attached to the lower end of the shaft 39, which protrudes outward through the bearing web 38, the free end of which points in the direction of the material feed (arrow V) and forms an upper seam 41. A spacer bush 42 and a torsion spring 43, which has two free legs 44, 45, are arranged on the shaft 39 between the two bearing webs 37 and 38. The shaft 39 is axially secured via the straight end 46 of the thrust bracket 47 which is guided by a transverse bore in the shaft 39 and is in contact with the bush 42 and which in the upper stitch position I of the needle bar 22 moves into motion path of the cylinder head 24 of the needle fastening screw 25 protrudes. In a transverse bore in the upper end of the shaft 39, a pin 48 with a tight fit is pressed, which has a bent free end 49, which is arranged in the pendulum movement path of the needle bar 22 and serves as a thrust bracket for the needle bar.

One free leg 44 of the torsion spring 43 is supported on the bearing bracket 36, while its other free leg 45 engages the thrust bracket 47. By this arrangement of the torsion spring 43, the shaft 39 with the parts arranged thereon is normally held in the position shown in the drawing.

On the presser sole 33, a loop stripper 51 is fastened by means of a screw 50, which extends from its attachment point on the sole 33 in an arc to the upper sewing mandrel 41 and whose front edge is arranged in the path of movement of the mandrel 41.

It should also be mentioned that a recess 52 is provided in the presser sole 33 for the passage of the needle 26, and that in the sole 33. one with its free end extending in the material feed direction (arrow V) extends into a groove (not shown) on the Stitch-forming tongue 53 protruding underside is attached.

Implementation of the method and operation of the device.

It is assumed that the sewing material W is placed on the fabric support plate 29 and the throat plate 27 so that the right edge K extends right up to the puncture point of the needle 26 in the overstitch position I of the needle bar 22, through the usual fabric pressure rod spring on the Shaft 34 arranged presser sole 33 on the throat plate 27 Dzw the webs 31 of the fabric pusher 32 are pressed on and the needle bar 22 is in the overstitch position with the needle 26 outside the sewing material W, the shaft 39 during the panning movement of the needle bar 22 into the overstitch position I via the one interacting with the needle bar 22 as a starting bracket for this serving pin 48/49 is twisted so that the overspring 41 assumes its loop pull-out position, such as. 8. in Fig. 3.

If the sewing machine is switched on as a starting point, the needle 26 first pierces in point 1, FIGS. 4 to 6, and a tangle of needle and looper thread is formed. To achieve a seam as shown in FIG. 4, the needle bar 22 - without the Nangut W being shifted - changes to the overstitch position 11. The thrust bars 47 and 48 are released and the shaft 39 with the upper sewing mandrel 41 by the torsion spring 43 into the one shown in FIG 1 and 2 position shown is rotated. During this pendulum movement of the needle bar 22, the needle thread NF is placed over the overlocking mandrel 41, so that it has a greater length than the distance 1-2. The needle 26 sticks into the sewing material at point 2 and the next interlacing of needle thread NF and hook thread GF takes place. In the upper stitch position II, the sewing material W is now shifted by a stitch length in the feed direction, arrow V, while the needle 26 is outside the sewing material W during its axial movement. The next puncture of the needle 26 is then in point 3. After forming the interlacing of needle thread NF and hook thread GF in point 3, the needle bar 22 also executes a pendulum movement in the overstitch position I to puncture the needle 26 at point 4 during its axial movement. During this pendulum movement, the thread overlying the sewing mandrel 41 is pulled out between points 1 and 2 to form a loop S, in that the needle bar 22 first strikes the bent end 49 of the pin 48 and rotates the shaft 39 with the top sewing mandrel 41 so that the Loop S of the needle 26 is bent for the puncture at point 4. When the needle 26 has pierced the loop S, the shaft 39 with the upper mandrel 41 is further rotated by the cylinder head 24 of the needle fastening screw 25 which strikes the starting bracket 47 during the further downward movement of the needle bar 22 such that the loop S in cooperation with the upper sewing mandrel 41 with the loop stripper 51, on the front edge of which the sewing mandrel 41 is moved past, is stripped from the oversewing pin. By looping needle thread NF and hook thread GF in point 4, the loop S enclosing the fabric edge is tied off. The thread interlacing in point 4 simultaneously forms the first thread interlacing 1 'of a further sequence 1' - 4 'with loop S', the binding of sequence 1 "- 4" with loop S "is connected to this in point 4 ' a loose overlock seam is formed, which is at the same time a stretchable and yet maintainable seam with the straight stitches 2 - 3, 2 '- 3', 2 "- 3". The stretchability results from the fact that the straight stitches mentioned are not directly behind each other in the feed direction, but instead are each connected via the part of the needle thread loops S, S 'and S "lying transversely to the feed direction, arrow V.

5 is based on the same principle as the formation of the seam according to FIG. 4, with the only difference that the feed movements of the fabric pusher 32 are controlled differently, namely that the material to be sewn W is the same as in point 1 Intertwining of the needle and looper thread in the overstitch position I of the needle bar 22 is shifted by a stitch length in the feed direction, arrow V, and at the same time the needle bar 22 is moved into the overstitch position II. This is followed by a straight stitch (2-3) after the second thread interlacing in point 2, whereupon the change of the needle bar 22 to the upper stitch position I and the pulling out of the needle thread NF to the loop S to insert the needle 26 in point 4 in the overstitch position I. is done by reversing the feed direction. As a result, a further loosening of the thread placed over the overlocking mandrel 41 is achieved. Saw there Strip the tied loop S from the overlocking mandrel 41 in the same way as in the manufacture of the seam according to FIG. 4. The further sequences 1 '- 4' and 1 "- 4" are formed like the sequence 1-4.

3 and 6 differs from the seam according to FIG. 5 only in that after the needle bar 22 has been changed from the first interlacing of needle and looper thread in point 1 to the upper stitch position II and the thread interlacing in point 2 two Straight stitches are sewn in the overstitch position II. The pulling out of the loop S into the upper face position I for the insertion of the needle 26 into this loop at point 5 is again done by reversing the direction of advance and the loop S is dislodged from the mandrel 41 as in the formation of the seam according to FIGS. 4 and 5.

The control of the needle bar pendulum movements and the movements of the fabric pusher is carried out by appropriate actuation of the zigzag stitch actuator and the feed stitch actuator of the sewing machine, expediently by means of a separate cam disc using a suitable linkage.

Claims (5)

1. A method for forming an upper seam with the help of a zigzag sewing machine, characterized in that after forming a first interlacing (1) of needle and looper thread in a first stitch position (I) of the needle bar (22) and after loosening the needle thread (NF) After the needle bar (22) has been changed to a second upper stitch layer (II), another thread interlacing (2) takes place, after which at least one straight stitch is formed in the second overstitch layer (II), leading from the first (1) to the second (2) thread interlacing Needle thread (NF) is drawn into the first stitch position (I) to form a loop (S), the loop (S) of the needle (26) is presented to the next stitch (4) and then released. 2. The method according to claim 1, characterized in that the pulling out of the needle thread (NF) in the first topstitch layer (I) takes place with reversal of the direction of the material feed. 3. Device for carrying out the method according to claim 1, characterized by an oversewing mandrel (41) which, in order to achieve two successive movement phases, has a thrust bracket (1) arranged in the pendulum movement path of the needle bar (22) and an axial movement path for the first stitch position (I). 47 or 48) and a loop wiper (51) protrudes in its path of movement. 4- Device according to claim 3, characterized in that the upper sewing mandrel (41j is arranged on a shaft (39) which carries the thrust bracket (47, 48). 5. Apparatus according to claim 3 and 4, characterized in that the shaft (39) is monetized on the presser foot of the sewing machine.

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