EP2369046A1 - Device for preparing a sewing thread - Google Patents

Abstract

The device has a thread puller (13) arranged between a thread tensioner (6) and a sewing needle (11). The thread puller has a cylinder (16) comprising a piston rod (15) with a free end (17), at which a thread (2) is fed such that the thread is lengthened during a determined movement of the piston rod. The thread puller has a central pin for forming an eyelet (18) arranged between pins so that the thread arranged between the pins and the central pin is forced by shifting the central pin from a straight line into a roughly U-shaped curve.

Description

The present invention relates to a device for providing a sewing thread of a defined length on a sewing or embroidery machine.

1. 1. Bei einem zu kurzen Annähfaden rutscht der Faden bei Beginn des Nähvorgangs aus der Nadel. Mit dem Ausfädeln des Oberfadens bricht die Nähmaschine den Nähvorgang mit einer Fehlermeldung an das Wartungspersonal ab, das zur Störungsbeseitigung eingreifen muss.
2. 2. Bei zu langem Annähfaden kann es zu Beginn des neuen Nähvorgangs zu der sog. Nestbildung kommen. Hier werden in den ersten Stichen Schlaufen des Oberfadens und/oder ein Anfangsfaden zu einem losen Knoten verbunden. Neben einer unschönen Optik kann sich eine solche als "Nest" bezeichnete Fadenverknotung auch lösen, da die zwischen Ober- und Unterfaden gebildeten Knoten nicht ausreichend fest zusammengezogen werden.

From the prior art, the problem is known that in thread processing machines of the aforementioned type at the beginning of a new sewing process a sewing thread of a certain length must be present on the needle. This length of the sewing thread depends on a particular application and is limited by the occurrence of two error situations or malfunctions:

1. 1. If the sewing thread is too short, the thread will slip out of the needle at the beginning of the sewing process. With the unthreading of the upper thread, the sewing machine aborts the sewing process with an error message to the maintenance personnel who must intervene to eliminate the fault.
2. 2. If the sewing thread is too long, the so-called nest formation may occur at the beginning of the new sewing process. Here in the first stitch loops of the upper thread and / or a starting thread are connected to a loose knot. In addition to an ugly appearance, such as "nest" called Fadenverknotung can also solve, since the nodes formed between upper and lower thread are not tightened sufficiently tight.

There are therefore known from the prior art. Thread catcher and wiper devices in particular for sewing machines. The former catch the upper thread when finishing a previous one Sewing process and secure it by clamping, so as to hold after the cutting of the thread to start a new sewing process a sewing thread of a defined length. Devices of the latter type wipe the upper thread below a raised sewing needle and over a sewing clamp laterally before separation of the upper thread, thereby to keep after sewing a Nähähfaden certain length ready. The upper thread is usually cut under tension. In addition to a very complex structure and a certain susceptibility to failure during operation, a suture wiper is also subject to design limitations, especially since he has to work in a narrow space in the area under a raised sewing needle and a sewing clamp and in particular during operation of a sewing machine despite space competition and usually more complex Kinematics must not collide with a thread hot cutter.

Another way treads the DE 20 2007 009 565 U1 in that here a thread puller is provided, which is arranged between a thread tensioning nut and a thread tensioner on the sewing machine. The thread puller reduces at the moment of completion of a previously to be produced seam the remaining thread in the needle area.

Next is from the DE 21 03 791 B2 a thread puller known, which is arranged between a thread tensioner and a sewing needle. The thread passes alternately through two movable via a push rod and a rigid hook. By a displacement of the movable against the rigid hook a thread elongation is caused.

It is the object of the present invention, a known thread-pulling device with simplification while further increasing the operational reliability of the device in the sense of an improved adjustment accuracy of the length of a sewing thread training to form a well retrofittable unit with low additional space requirements.

This object is achieved in that a thread-pulling between the second thread tensioner and the sewing needle is arranged and controlled with a common control of a thread cutter such that the thread puller is operated prior to cutting the threads on a finished seam, the thread puller movable rod having a free end on which the thread is guided so that the thread is elongated in the course of a certain movement of the rod, wherein the thread puller comprises at least one pin and past the pin or between the pin through a on the rod arranged center pin is slidably arranged to form a kind of eyelet, so that a thread arranged between the pin and the center pin is forced by the displacement of the center pin of a straight line in an approximately L-, U-shaped course.

The present invention is based on the finding that thread catcher and thread clamping devices can be saved if a design and provision of sewing thread length is carried out before the thread is cut off. As long as the thread is not cut off, the finished seam itself holds the needle thread in the needle. Thus, each pre-measured sewing thread length can be reliably deducted from an upper thread roll and made available as far as possible avoiding nest formation for the beginning of a new seam. Also, when cutting a thread that is not under tension, a cut with the desired quality can be realized at any time. Other known devices of the type mentioned above, in particular thread wipers, can be completely eliminated when using a device according to the invention.

Advantageous developments and structural embodiments of a device according to the invention are the subject of the dependent claims. Accordingly, the at least one rigid pin is advantageously arranged fixed on a mounting plate. In the mounting plate, at least one guide groove extends between the pins along a travel path of the rod, into which in each case the at least one center pin arranged at the free end of the rod engages. The entire compact thread puller is only fixed by a screw in the area of the mounting plate on the sewing machine near the needle.

Due to the good availability of compressed air on a sewing machine, the rod is the piston rod of a pneumatic cylinder, wherein the length of a loose thread loop is substantially adjustable via a stop on the piston rod.

A U-shaped course of a loose thread loop with secure storage in a thread puller according to the invention is preferably effected as a bracket in one piece with two connected pins. For the same purpose more than two pins are bridged by a plate bridged together, in particular screwed.

Under largely free scalability of a thread puller according to the invention n center pins are arranged movable meshing against n + 1 rigid pins, preferably the stop is formed as Aufraabel the piston rod on two or more free ends for fixing the respective center pin to a meandering course of the upper thread and safe storage of the towed, and after shipment of the rod in to create the starting position of loose upper thread in a compact unit and small space requirement for all moving parts.

• Figur 1a: eine Darstellung einer Ausführungsform eines Fadenziehers in einer Ausgangssituation und in einem darüber geblendeten ersten Schritt;
• Figur 1b: eine Darstellung eines zweiten Teilschrittes analog der Darstellung von Figur 1a;
• Figur 1c: eine Darstellung weiteren Ausführungsform eines Fadenziehers in einer Ausgangssituation und in einem darüber geblendeten ersten Schritt analog Figur 1a;
• Figuren 2a und 2b: eine Darstellung einer zweiten Ausführungsform der Erfindung analog der Darstellungen der Figuren 1a und 1b;
• Figur 3: eine Nähmaschine unter prinzipieller Darstellung bekannter Ansätze zur Bereitstellung eines Annähfadens im Vergleich zu einer erfindungsgemäßen Anordnung;
• Figuren 4a bis 4d: Ansichten der Ausführungsform gemäß der Figuren 2a und 2b;
• Figur 5: eine perspektivische Zusammenbauzeichnung der Ausführungsform gemäß der Figuren 2a und 2b bzw. 4a - 4d;
• Figur 6: eine Darstellung einer dritten Ausführungsform eines Fadenziehers in einer Ausgangssituation;
• Figur 7a und 7b: eine Darstellung einer ersten Phase der Bereitstellung eines bei geringem Zylinderhub deutlich verlängerten Annähfadens analog zu der Abbildungen der Figuren 4a und 4b und
• Figur 7c: eine Darstellung der kämmend angeordneten Umlenkungselemente der dritten Ausführungsform analog zu der Abbildung von Figur 4a in einer zweiten Totpunkt-Stellung mit skizziertem Verlauf eines gezogenen Oberfadens.

Hereinafter, embodiments of the invention, illustrating further features and the resulting advantages with reference to the figures of the drawing will be explained in more detail. In the drawing, in sketched representation:

• FIG. 1a FIG. 2 is an illustration of an embodiment of a thread puller in a starting situation and in a first step blended therewith; FIG.
• FIG. 1b a representation of a second sub-step analogous to the representation of FIG. 1a ;
• Figure 1c : An illustration of another embodiment of a thread puller in an initial situation and in a blinded first step analog FIG. 1a ;
• FIGS. 2a and 2b FIG. 2: an illustration of a second embodiment of the invention analogous to the representations of FIG FIGS. 1a and 1b ;
• FIG. 3 a sewing machine with a basic representation of known approaches for providing a sewing thread compared to an inventive arrangement;
• FIGS. 4a to 4d : Views of the embodiment according to the FIGS. 2a and 2b ;
• FIG. 5 FIG. 3: an assembled perspective drawing of the embodiment according to FIG FIGS. 2a and 2b or 4a-4d;
• FIG. 6 a representation of a third embodiment of a thread puller in an initial situation;
• FIGS. 7a and 7b FIG. 2: an illustration of a first phase of providing a sewing thread, which is significantly extended with a small cylinder stroke, analogously to the illustrations of FIG FIGS. 4a and 4b and
• FIG. 7c FIG. 2: a representation of the combing deflection elements of the third embodiment analogous to the illustration of FIG FIG. 4a in a second dead center position with sketched course of a drawn upper thread.

Uniformly, the same designations and reference numbers are used across the figures for the same components, elements, method steps or assemblies.

The picture of FIG. 3 shows a sewing machine 1 with a known arrangement for retracting a thread residue as a measure to prevent the so-called nest formation at the beginning of a new seam. Usually, a needle thread 2 runs on a sewing machine 1 from a thread spool (not shown) via a thread tension nut 4 through at least one thread hook 5 to a thread tensioner 6 and from there via a thread hook 7 to a vertically movable thread lever 8 and from there via a further thread guide 9 to a holder 10 with a Sewing needle 11. For this purpose, a thread puller 13 is provided as an extension in the above roughly described path of the upper thread 2. The thread-puller 13 according to FIG. 3 is disposed between the thread tension nut 4 and the thread tensioner 6 in a position A, as in DE 20 2007 009565 U1 disclosed. Here, the upper thread 2 extends in a guide 14 via a piston rod 15 of a pneumatic cylinder sixteenth

From the prior art, in addition to the outlined position A, an arrangement of a thread puller 13 at a position B is known, for example from the DE 41 32 991 C1 , According to the above teachings, the thread tensioners are supportive in the sense of these respective disclosures. In contrast, a thread puller 13 is arranged as a unit in the form of a small attachment in a position C.

This position C is located between the thread tensioner 6 and the sewing needle 11 relatively close to a sewing needle and will now be with reference to the FIGS. 1a, 1b with the representation of a first embodiment of the invention described in more detail. The thread puller 13 holds the thread 2 in a guide 14. The guide is part of a unit of a piston rod 15 and a pneumatic cylinder 16 and is arranged there at a free end 17 of the piston rod 15. Here, this guide 14 as - not graphically illustrated - simple eyelet 18 executed with a quenched surface, through which the upper thread 2 is threaded through when setting the sewing machine 1. The thread runs before passing through the eyelet 18 on a pin 19 over.

In the manner shown in the manner outlined, a seam 20 on a sewing material 21 is completed, and after raising the sewing needle 11 into a rest position, a sewing plate 22 is also raised. Now, however, before cutting the upper thread 2 the thread puller 13 is actuated so that the upper thread 2 is pulled by the piston rod 15 toward the cylinder 16, as in FIG FIG. 1a indicated by the dashed line with respect to the original thread course in a solid line. The pin 19 now causes an approximately L-shaped deflection of the thread 2 such that the upper thread 2 sweeps across the triangular area shown hatched. The upper thread 2 is thus extended or drawn by this thread puller 13 between the needle 11 and the thread lever 8 so that a secure sewing can subsequently be carried out with a short sewing thread on the sewing needle 11.

In a second step, the piston rod 15 after FIG. 1b again from the cylinder 16 in the starting position of FIG. 1a moved out, so that at least one loose thread loop 23 is available near the top of the sewing needle 11. In contrast to the cited prior art, this thread loop 23 is after FIG. 1b in an area without further deflection or friction points and thus is largely tension-free already at the first stitch of a new seam available.

Only in the just above to FIG. 1b described relaxed or tension largely free situation, the thread 2 is cut by a device not shown. Thus leaded - without a different pronounced elastic recoil of a commonly in the art under tension thread - a sewing thread defined adjustable length near the tip of the sewing needle 11. This sewing thread now only needs to ensure that the upper thread 2 at the beginning of a first stitch of a new seam does not slip out of the needle 11. Another thread supply is also available near the sewing needle 11 in the form of the at least one loose thread loop 23. Advantageously, however, this thread supply is now in a manner that substantially eliminates the undesirable nesting and, moreover, with sufficient certainty avoids unthreading of the sewing thread from the sewing needle even using short sewing threads.

The picture of Figure 1c shows an alternative embodiment analogous to the representation of FIG. 1a , Here, the pin 19 is now - viewed from the mounting position - arranged below the free end 17 of the piston rod 15. For the same operation of the pneumatic cylinder 16 and thus the same displacement of the piston rod 15, the upper thread 2 now passes over a much smaller triangular surface. The length of the additionally drawn upper thread 2 is compared to the first described alternative, although slightly lower, the hatched, triangular area is also significantly smaller and is completely in the closed housing of the sewing machine 1. Within the hatched area are all moving Parts of a thread puller 13 according to the invention, so that a smaller area can also be interpreted as an indication of a lower probability of failure by incorrectly protruding parts and lower injury potential for maintenance personnel.

The pictures of the FIGS. 2a and 2b show a second embodiment of the invention analogous to the illustrations of FIGS. 1a and 1b , Here, the thread puller 13 has been extended by a mounting plate 24, not visible here, which carries two rigid pins 25. Between the pin 25 passes along a travel path of the piston rod 15 of the cylinder 16, a guide groove 26. A arranged at the free end 17 of the piston rod 15 center pin 27 engages end into the guide groove 26 or even therethrough. The eyelet 18 of the embodiments of Figures 1a - 1c is now through the pin 25, the piston rod 15, the center pin 27 and the mounting plate 24 in the function of a thread 2 enclosing eyelet 18 is formed.

Like the transition from FIG. 2a on FIG. 2b shows, the pins 25 form a kind of comb structure, through the gap of the center pin 27 is moved therethrough. Thus, the upper thread 2 is forced from a straight line into an approximately U-shaped course. This detour of the thread 2 or the loose thread loop 23 formed therefrom is approximately twice as long as the travel path of the center pin 27 that can be adjusted on the piston rod 15 via a stop 28.

Also, this thread-puller still shown in detail forms a small attachment as a unit, compared to the first embodiment, this design is more precisely adjustable and promotes more thread or length of upper thread 2 per used for the displacement piston length. In this case, a loose loop of thread 23 near the needle tip 11 is still freely available without further deflection, friction or braking points for the upper thread 2 would be available. In addition, this is in FIG. 2b hatched drawn, all movable elements comprehensive triangle also compared to the embodiment of Figure 1c again significantly reduced, but now a significantly greater length of upper thread 2 is pulled.

Hereinafter, this second embodiment will be illustrated and explained in detail with reference to a practical example. In this case, a description and reference to standard technical components, such as connections and mechanical fixing elements, beyond the illustrations in the drawing out only in exceptional cases, since they are known in the art.

The FIGS. 4a to 4d show the compact structure of the embodiment according to the FIGS. 2a and 2b as a structural unit of a retrofittable to existing sewing machines 1 thread-puller 13 in three technical views and in perspective view. Based on these figures, the small additional space requirement of such a thread puller 13 on a sewing machine 1 becomes clear. It is therefore already apparent from this illustration that such a thread-pulling device 13 can be combined with a hot-end cutter on a sewing machine 1 simply.

The picture of FIG. 5 is an perspective assembly drawing of the embodiment according to the FIGS. 2a and 2b or 4a to 4d. A thread-pulling device 13 according to this embodiment consists of comparatively few different individual parts and is fixed only by the screw 30 on the sewing machine 1 near the needle 11. Thus, this thread-puller 13 on each sewing machine 1 is easy to retrofit. The mechanical load during operation is low, and at other terminals only the illustrated pneumatic connections are connected to a controller, not shown. Space problems can also be largely excluded in this area near the needle 11.

FIG. 6 shows a representation of a third embodiment of a thread puller in a starting situation analogous to the figures of FIGS. 1a . 1c and 2a , In contrast to the second embodiment, three rigid pins 25a, 25b, 25c are now provided here, between which two center pins 27a, 27b fixed to the piston rod 15 are displaceable. For this purpose, the piston rod 15 now extends into two free ends 27a, 27b, on which the center pins 27a, 27b are arranged. In this case, the area C is also sufficient for this thread-puller 13 in terms of the space available, due to the now feasible additionally drawn length of upper thread 2 at the same time a free stroke of the piston rod 15 could be reduced. In principle, a structure of the type described above could be continued as desired, that is to say with n central spigots 27,... 27n, which are arranged so as to be movable in a meshing manner against n + 1 rigid spigots 25,..., 25 (n + 1). In practice, in the case of very short strokes and compact design of the cylinder 16, a limit for such designs will probably be reached in the area of three movable and four rigid pins.

Figure 7a shows a representation of a first phase of providing a low cylinder stroke significantly extended sewing thread analogous to the figures of FIG. 4a , Furthermore, a screw 30 for fixing the now slightly enlarged plate 24 may be sufficient as a central mechanical support element. The plate 24 now carries two guide grooves 26 for the center pin 27a, 27b displaceable therein. The stop 28 has now been modified here to Aufgabelung the piston rod 26 on two free ends for the fixation of the center pin 27a, 27b. In addition, the pins 25a, 25b, 25c are interconnected by a plate 31 screwed in this example, as in FIG FIG. 7b indicated. The plate 31 is shown only in outline in the drawing for reasons of clarity. In the embodiment of the FIGS. 2a, 2b . 4a to 5 can be used instead of a plate 31 by means of a U-shaped integrally connected pin 25 or bracket.

FIG. 7c is a representation of the meshing arranged deflecting elements of the third embodiment analogous to the figure of FIG. 4a in a second dead center position with outlined meandering course of a pulled upper thread 2. Accordingly, when the piston rod 15 is moved or displaced by an amount Δl, the upper thread 2 is lengthened by approximately 4 * Δl. Even with movement of the piston rod 15 by a small amount .DELTA.l, as it can occur directly on the housing of a sewing machine 1 due to restrictions on the free space, comparatively much upper thread 2 is pulled in this embodiment with small-sized pneumatic unit or another drive. This additional upper thread length of about 4 * .DELTA.l is after the retraction of the piston rod 15 in the position Figure 7a in the form of loosely and in the compactly constructed thread puller 13 against any knotting stored loops when sewing directly available.

LIST OF REFERENCE NUMBERS

1

sewing machine

2

upper thread

3

4

Thread-clamping nut

5

thread hook

6

yarn tensioner

7

thread hook

8th

up lever

9

thread guide

10

holder

11

sewing needle

12

13

thread puller

14

guide

15

piston rod

16

pneumatic cylinder

17

free end

18

Guide / eyelet

19

spigot

20

seam

21

workpiece

22

sewing plate

23

loose thread loop

24

mounting plate

25

rigid pin

26

guide

27

center pin

28

attack

29

30

screw

31

Plate for connecting the pins 25

A

Position on a sewing machine 1

B

Position on a sewing machine 1

C

new position of a thread puller on a sewing machine

.DELTA.l

Displacement of the piston rod 15th

Claims (9)

Device for providing a stitching of a defined length on a sewing or embroidery machine,
wherein between a thread tensioner (6) and a sewing needle (11) a thread puller (13) is arranged and
the thread-pulling device (13) is controlled with a thread cutter such that the thread-pulling device (13) can be actuated prior to cutting at least one thread (2) on a finished seam (20),
characterized,
in that the thread-pulling device (13) comprises a movable rod (15) with a free end (17) on which the thread (2) is guided in such a way that the thread (2) is elongated in the course of a specific movement of the rod (15) in that the thread puller (13) comprises at least one pin (19, 25) and displaceably past the pin (19) or between the pins (25) a center pin (27) arranged on the rod (15) to form a kind of the thread (2) enclosing eyelet (18) is arranged so that a between the pin (19) or the pin (25) and the center pin (27) arranged thread (2) by the displacement of the center pin (27) of a rectilinear is forced into an approximately L- or U-shaped course. Device according to the preceding claim, characterized in that the at least one pin (19, 25) is arranged on a mounting plate (24). Apparatus according to the preceding claim, characterized in that in the mounting plate (24) between the pin (25) along a travel path of the rod (15) has a guide groove (26) into which the at the free end (17) of the piston rod (25). 15) arranged center pin (27) intervenes. Device according to one of the three preceding claims, characterized in that the rod (15) is the piston rod of a pneumatic cylinder (16) and the length of a loose thread loop (23) via a stop (28) on the piston rod (15) is adjustable. Device according to one of the preceding claims, characterized in that the thread-pulling device (13) is fixed to the sewing machine (1) near the needle (11) only by means of a screw (30) in the region (C) of the mounting plate (24). Device according to one of the preceding claims, characterized in that two pins (25) are formed as a bracket integral with each other. Device according to one of claims 1 to 5, characterized in that more than two pins (25) by a plate (31) bridging connected to each other and in particular are screwed. Device according to one of claims 1 to 5 and 7, characterized in that n center pins (27a, 27b) are arranged to mesh with n + 1 rigid pins (25a, 25b, 25c) movable. Device according to one of claims 1 to 5 and 7 to 8, characterized in that the stop (28) as Aufraabelung of the piston rod (26) on two or more free ends (17) for the fixation of center pin (27a, 27b) is formed ,

Images