EP3399089A1 - Method and sewing machine for generating a bobbin thread end of a seam with a predetermined protrusion - Google Patents

Abstract

To produce a seam end lower thread with a desired seam protrusion of at most 10 mm, a sub-conveyor (17) is switched from a sewing operation position to a cut-off position displaced with respect to this along a sewing direction (x) before cutting off a lower thread (35) at one end of a seam , Subsequently, the lower thread (35) is cut off at the end of the seam. A sewing machine for carrying out this method has a controller for driving a displacement drive, which is designed such that it controls the displacement drive for shifting the Untertransporteurs (17) from the Nähbetriebsstellung in the cutting position synchronized at the end of a Nahterzeugung. The result is a production method for a seam Endunterfaden with predetermined target seam projection, in which the seam Endunterfaden and thus also the desired seam projection can be made shorter, and a sewing machine for performing the method.

Description

The present invention takes priority of the German patent application DE 10 2017 207 626.7 claim, the contents of which are incorporated herein by reference.

The invention relates to a method for producing a seam end lower thread with a predetermined desired seam projection. Furthermore, the invention relates to a sewing machine for carrying out such a method.

A sewing machine, with which a seam Endunterfaden can be generated with a predetermined target seam projection, is known from the EP 1 847 641 B1 and from the EP 2 330 241 B1 ,

It is an object of the present invention to develop a method for producing a seam end lower thread with a predetermined desired seam projection in such a way that the seam end lower thread and thus also the desired seam projection can be made shorter.

This object is achieved by a production method having the features specified in claim 1.

According to the invention, it has been recognized that the position of a sub-conveyor after forming a seam and before cutting the lower thread at the seam end can be displaced so that a lower thread path between the last stitch of the seam and a cut-off position can be shortened. This results in a correspondingly shortened seam end lower thread. This shortening is exactly reproducible due to the clearly definable position of the bottom conveyor in the cutting position, so that, depending on the position of the lower transporter, a predetermined target seam projection results. Simultaneously with the generation of a seam end lower thread with a desired seam projection, a seam end upper thread with a comparable desired seam projection, for example of at most 10 mm, can also be produced. The upper thread can be cut simultaneously with the lower thread in the production process. By switching the Untertransporteurs from the Nähbetriebsstellung in the cutting position then a top thread path between the last stitch of the seam and the cutting position can be shortened before cutting the upper thread, resulting in a correspondingly shortened seam Endoberfaden. The result is a correspondingly predetermined target seam projection of the seam end upper thread depending on the position of the Untertransporteurs. By corresponding conversion of the undertread into a cut-off position in which a lower thread path and / or a upper thread path is extended between the last stitch of the seam and the cut-off position, a seam end lower thread and / or a seam end upper thread with an extended nominal seam projection can also be targeted , for example, significantly more than 10 mm, are generated. This can be useful for certain sewing tasks where longer seam end threads are desired. The sub-feed dog may be a feed dog. The sub-feed dog can work together with stitching tools of the sewing machine, ie a sewing needle and a gripper, synchronized and / or periodically. The sub-feed provides a component that transports the fabric by frictional contact from below in the sewing direction. In this case, the sub-feed dog engages with the sewing material during a stitching period during a period of time and is out of engagement with the sewing material for a further period of time.

A short stitch before cutting according to claim 2 causes a produced with the cutting seam end lower thread and a seam Endoberfaden from the fabric to the cutting position take a comparatively long way and therefore are practically the same length due to the last short stitch.

A changeover according to claim 3, depending on the configuration of the sewing machine lead to an advantageous shortening of the lower thread path between the last stitch and the cut-off position. As a cut-off position for the sub-feed dog, the position "Reverse stitch" can be selected.

A changeover according to claim 4 can be integrated into the normal operation of a sewing machine. An additional changeover can then be omitted.

Another object of the invention is to provide a sewing machine for carrying out the method according to the invention.

This object is achieved by a sewing machine with the features specified in claim 5.

The advantages of the sewing machine correspond to those which have already been explained above with reference to the method according to the invention. The drive for displacing the Untertransporteurs can then represent the actuating means of a transport company.

The control for controlling the displacement drive can be designed programmable to specify a residual bobbin thread length at the seam end. The remaining bobbin thread length can be preselected by means of a control element on the sewing machine.

A Stichstellergetriebe according to claim 6 is particularly suitable as a controllable displacement drive for switching the Untertransporteurs from the Nähbetriebsstellung in the cutting position. The Stichstellergetriebe can be designed in particular as a plate gear. Such a suitable Stichstellergetriebe is known from the EP 2 330 241 B1 ,

A rotary actuator according to claim 7 represents a particularly simple drive for switching the Untertransporteurs from the Nähbetriebsstellung in the cut position. The pivot drive can be designed as a stepper motor. Alternatively, the rotary actuator can be designed as a solenoid or as a pneumatic cylinder. The rotary actuator can cooperate with at least one stop to specify at least one Untertransporteurstellung. The stop can be adjustable. Also, several such attacks can be provided.

Fig. 1

eine Vorderansicht einer Doppelsteppstichnähmaschine;

Fig. 2

eine Draufsicht auf einen Ausschnitt der Nähmaschine in vergrößertem Maßstab entsprechend dem Sichtpfeil II in Fig. 1;

Fig. 3

eine innere Details freigebende Stirnansicht auf einen Ausschnitt der Nähmaschine entsprechend dem Sichtpfeil III in Fig. 1 in vergrößertem Maßstab;

Fig. 4

eine perspektivische Darstellung eines Fadenziehmessers;

Fig. 5

einen Schnitt gemäß Linie V-V in Fig. 1 in einer Momentanposition eines Untertransporteurs und eines Fadenziehmessers beim Abschneiden eines Unterfadens an einem Ende einer Naht zur Erzeugung eines Naht-Endunterfadens mit einem Soll-Nahtüberstand nach dem Stand der Technik;

Fig. 6

in einer zur Fig. 5 ähnlichen Darstellung einer Momentanposition des Untertransporteurs und des Fadenziehmessers beim Abschneiden des Unterfadens am Nahtende zum Erzeugen des Naht-Endunterfadens mit Soll-Nahtüberstand von höchstens 10mm; und

Fig. 7

schematisch eine Aufsicht auf eine mit der Nähmaschine genähten Naht zur Veranschaulichung eines erzeugten NahtEndunterfadens mit einem vorgegebenen Soll-Nahtüberstand.

Embodiments of the invention will be explained in more detail with reference to the drawing. In this show:

Fig. 1

a front view of a lockstitch sewing machine;

Fig. 2

a plan view of a section of the sewing machine in an enlarged scale corresponding to the viewing arrow II in Fig. 1 ;

Fig. 3

an inner details releasing front view of a section of the sewing machine according to the viewing arrow III in Fig. 1 on an enlarged scale;

Fig. 4

a perspective view of a thread-pulling knife;

Fig. 5

a section along line VV in Fig. 1 in an instantaneous position of a bottom transporter and a thread-pulling knife in cutting a bottom thread at one end of a seam to produce a seam end thread with a desired seam overhang of the prior art;

Fig. 6

in a to Fig. 5 similar representation of an instantaneous position of the lower transporter and the thread-pulling knife when cutting the lower thread at the seam end to produce the seam end lower thread with nominal seam projection of at most 10 mm; and

Fig. 7

schematically a plan view of a stitched seam with the sewing machine to illustrate a generated seam end underneath thread with a predetermined target seam projection.

A sewing machine 1 designed in particular as a lockstitch sewing machine has a base plate 2 with a stand 3 extending upward therefrom and an angled arm 4. The latter ends in a head 5. In the arm 4, an arm shaft 6 is rotatably mounted. This drives in the head 5 a crank mechanism 7 with a thread lever 8 at. The crank mechanism 7 is drivingly connected to a needle bar 9 axially slidably mounted in the head 5 in connection. This has at its lower end a needle 10. The needle 10 is moved by the crank mechanism 7 on a vertical axis 11 up and down. The needle 10 leads in an eye from a spool 12 via a thread tensioning device and the thread lever 8 supplied needle thread 13, which is also referred to as needle thread.

The base plate 2 carries a screw-mounted support plate 14, on which a two-ply workpiece 15 rests. The support plate 14 is formed with a recess 16 for the passage of a feed dog 17, which is also referred to as Untertransporteur. The latter has a tap hole 18 for the passage of the needle 10th

The feed dog 17 with respect to the fabric part 15 opposite a presser foot 17a is arranged.

To clarify positional relationships, a Cartesian xyz coordinate system is used below. The x-direction, which runs along a sewing direction, runs in the Fig. 1 perpendicular to the drawing plane into this. The y-direction runs in the Fig. 1 to the left. The z-direction, along which the axis 11 extends, runs in the Fig. 1 up. The feed dog or sub-feed 17 transports the workpiece 15 during a sewing along the sewing direction in the positive x-direction.

The feed dog 17 is in a known manner in drive connection with a arranged below the base plate 2 thrust and screw jack. Such a gear for the sub-feed dog 17 can be designed as a stitch actuator gear and in particular as a link gear, like in the EP 2 330 241 B1 described. Such Stichstellergetriebe represents a Transporteurgetriebe, on which in particular a transport length of the Untertransporteurs 17 can be adjusted, so a stitch length in the seam production. The Stichstellergetriebe is part of a drive for displacing the Untertransporteurs 17 along the sewing direction x. The displacement drive is in the Fig. 1 shown schematically at 18a. The displacement drive 18a acts as well as the other driven components of the sewing machine 1 with a in the Fig. 1 schematically shown central control device 18b together. For this purpose, the control device 18b is in direct connection with these components of the sewing machine 1 to be controlled, and in particular with the displacement drive 18a in a manner not shown. Part of the displacement drive 18a is a swivel drive for a stitcher shaft of the stitch actuator transmission. Such a Stichstellerwelle is particularly in connection with the Fig. 2 of the EP 2 330 241 B1 described, the contents of which are hereby incorporated by reference. Depending on the swivel angle of the Stichstellerwelle results in a stitch length and also a relative position of the Untertransporteurs 17 along the x-direction relative to the base plate fixed components of the sewing machine 1. The pivot drive is thus an adjusting the Stichstellergetriebes for a transport length of the Untertransporteurs 17th

Below the platen 14 is a gripper 19 having a gripper body 20 with a gripper tip 21. In the gripper body 20, a cup-shaped coil housing 22 is mounted for receiving a looper thread supply. A looper thread is also referred to below as a lower thread.

The gripper 19 is rotatable about a vertical gripper axis 23. A sewing operation direction of rotation 24 runs in Fig. 2 in the clockwise direction around the gripper axis 23 extending along the z-direction. The gripper body 20 is fixedly connected to a shaft 25, which runs coaxially with the gripper axis 23. The shaft 25 is rotatably mounted in a bearing block 26 screwed to the base plate 2. In this, a drive shaft 27 is mounted, which is connected to a arranged in the interior of the bearing block 26 gear transmission. The gear transmission has a gear ratio of 1: 2, so that in one revolution of the drive shaft 27 located on the shaft 25 gripper body 20 rotates twice. The drive shaft 27 is drivingly connected to the arm shaft 6 via a belt drive 28.

To cut off the looper thread, a thread-pulling knife 29 is used. The thread-pulling knife 29 is located between an in Fig. 2 illustrated basic position and a thread detection position about a parallel to the gripper axis 23 pivot axis 30 pivotally. The thread-pulling knife 29 has one in the view Fig. 2 reminiscent of a sickle basic form, the free end in the basic position in the view after Fig. 2 extends around the coil housing 22 around. In the thread detection position of the thread pulling knife 29, the stitch hole 18 is adjacent to a detection groove 31 (see FIG. Fig. 4 ) of the thread-pulling knife 29 with a groove bottom-side cutting edge 32. The detection groove 31 is executed in a right angle with respect to a horizontally extending base body 32a angled edge portion 32b of the thread-pulling knife 29. An extended free end portion 32c of the thread-pulling knife 29 is shown in FIG Fig. 2 executed rounded end.

Fixed to the base plate 2 on a boom is a fixed counter knife 33 (see. Fig. 3 ), which cooperates with the cutting edge 32 of the thread-pulling knife 29 for cutting the thread during the pivoting of the thread-pulling knife 29 from the thread-detecting position into the basic position.

A counter-cutting edge 34 of the counter knife 33, which cooperates with the cutting edge 32 of the thread-pulling knife 29 during thread cutting, extends vertically along the z-direction.

The Fig. 5 and 6 each show an instantaneous position of components of the sewing machine 1 on the one hand in a position "short forward stitch" ( Fig. 5 ) and on the other hand in the "reverse stitch" position ( Fig. 6 .). Both current positions after the Fig. 5 and 6 show cutting positions, so are reproduced at the time immediately before the cutting of the upper thread 13 and the lower thread 35 between the cutting edge 32 of the thread pulling knife 29 and the counter knife 34 of the counter knife 33. Also shown is the course of the upper thread 13 and on the other hand, the lower thread 35 during the Last stitches S ₁ to S ₅ in the fabric 15. The sub-feed 17 is also shown broken in the area of the stitch hole 18 to allow the view of underlying sections of the thread-pulling knife 29 and the counter knife 33. The Fig. 5 and 6 also show details of a movement guidance of the undertread 17 with a bottom feed carrier 36, a feed shaft 37, via which a transport stroke extending along the x direction is transmitted to the bottom feed dog 17, and a feed dog stroke 38, via which a feed unit acting along the z direction or Austauchhub is exerted on the sub-feed 17. The displacement drive 18a, the one in the Fig. 5 and 6 invisible Stichstellerwelle acts, is in the Fig. 5 and 6 not shown.

Fig. 5 shows the current position in a normal operation of the sewing machine 1, are generated with the short seam end threads. The stitch regulator gear is changed with the displacement drive 18a before formation of the fifth stitch S ₅ to the "Short forward stitch", so that this last stitch S ₅ is shorter than the stitches previously generated S ₁ to S. ₄ After knotting the fifth stitch S ₅ , both the upper thread 13 and the lower thread 35 extend toward the cut-off position between the cutting edge 32 and the counter knife cutting edge 34. Here, in particular, the lower thread 35 runs along an approximately U-shaped course around a section delimiting the stitch hole 18 39 of the Untertransporteurs 17 around.

Fig. 6 shows the corresponding components of the sewing machine 1 in the stitch regulator gear position "reverse stitch", also after formation of the executed as a short stitch stitch S _5th In this position, the Stichstellergetriebes a conversion is carried out by appropriate control of the displacement drive 18a.

Due to the position "reverse stitch" is the conveyor shaft 37 in the Fig. 5 in comparison to Fig. 6 pivoted further counterclockwise, so that the feed dog 17 compared to the instantaneous position Fig. 5 in the current position Fig. 6 in the positive x-direction, ie in sewing direction, is shifted. This results in that the feed dog section 39 immediately before the cutting of the upper thread 13 and the lower thread 35 relative to the cutting stitch position of these threads 13, 35, which is independent of the stitch regulator gear and basically frame-fixed the cutting edge 32 and the counter blade 34 in the Fig. 6 is also displaced in the positive x-direction. When changing over to the "reverse stitch" position, the feed dog section 39 moves relative to the sewing material part 15. The sewing material part 15 is held stationary by the presser foot 17a relative thereto. A path between the last stitch S ₅ and the cutting position between the cutting edges 32, 34 is now for the threads 13, 35 and in particular for the lower thread 35 at the instantaneous position Fig. 6 not as long as in the current position Fig. 5 , so that after the cutting of the threads 13, 35 smaller seam end threads on the fabric part 15 and in particular a shorter seam Endunterfaden results with a nominal seam projection of at most 10 mm.

Fig. 7 shows a seam 40 which is produced with the sewing machine 1. The seam Endunterfaden 41 stands at the seam 40 from the last stitch S ₅ with a nominal seam projection A of at most 10 mm.

The method for producing such a seam end underneath with a nominal seam projection of at most 10 mm includes sewing the seam with the stitches Si, wherein prior to cutting the lower thread 35 at the seam end of the sub-conveyor 17 from the Nähbetriebsstellung, eg. From a position "Short Forward stitch "in a relation to this along the sewing direction x displaced cutting position, so for example the position" reverse stitch "is shifted. Subsequently, the lower thread 35 and the upper thread 13 are cut at the end of the seam with the thread-pulling knife 29 by cooperation of the cutting edges 32, 34.

The Untertransporteur 17 can in comparison to the cutting position after Fig. 5 be displaced in a further cut position, which is displaced in the negative x-direction, so that a path on the one hand of the lower thread 35 and on the other hand, the upper thread 13 to the cutting position between the cutting edges 32, 34 extended even further. In this position of the Untertransporteurs 17 may be the position "maximum forward stitch length". This results in correspondingly elongated seam end threads 13, 35.

A stitch shortening, for example, the last stitch S ₅ is not mandatory. It can therefore be sewn to the last stitch with normal stitch length, in which case immediately a change over of the Stichstellergetriebes from the position "normal forward stitch" in the cut position for the Untertransporteur 17, ie, for example, in the "backward stitch" position.

The controller 18b is designed such that, synchronized at the end of sewing production, it controls the displacement drive 18a in such a way that the sub-conveyor 17 is displaced from the sewing operating position to the cutting position. The controller 18b is programmable to specify a residual bobbin thread length formed at the seam end.

The displacement drive 18a is designed as a stepper motor. Alternatively, it is possible to design the displacement drive as a lifting magnet or as a pneumatic cylinder. In this case, at least one stop can be provided in order to specify a position of the stitch actuator transmission with activated lifting magnet or pneumatic cylinder. Such a stop can be made adjustable. It can also be more than one such attack be provided.

Claims (7)

A method for creating a seam end underneath with a nominal seam protrusion of at most 10 mm with the following steps - sewing a seam; - before cutting off a lower thread (35) at one end of the seam: converting a Untertransporteurs (17) from a Nähbetriebsstellung in a relation to this along a sewing direction (x) displaced cut-off position; - Cutting the lower thread (35) at the end of the seam. A method according to claim 1, characterized in that prior to cutting when sewing a stitch with shortened stitch length occurs. A method according to claim 1 or 2, characterized in that when switching the sub-feed dog (17) in the sewing direction (x) is displaced. Method according to one of claims 1 to 3, characterized in that the changeover of the Untertransporteurs (17) by controlling an actuating means (18a) of a transporting operation for a transport length of the Untertransporteurs (17). Sewing machine (1) for carrying out a method according to one of claims 1 to 4, with stitching tools (10, 19) for sewing a seam with an upper thread (13) and a lower thread (35), with a subtransfer (17) displaceable along a sewing direction (x), - With a thread knife (29) for cutting the lower thread (35) at the seam end, - With a drive (18 a) for displacing the Untertransporteurs (17) along the sewing direction (x), - With a controller (18 b) for driving the displacement drive (18 a), wherein the controller (18 b) is designed such that synchronized at the end of a seam production, the displacement drive (18 a) such that the sub-conveyor (17) from the Nähbetriebsstellung in the cut-off position is shifted. Sewing machine according to claim 5, characterized by a Stichstellergetriebe for specifying a transport length of the Untertransporteurs (17). Sewing machine according to claim 6, characterized in that the displacement drive (18b) has a pivot drive for a stitcher shaft of the Stichstellergetriebes.

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