EP3289132B1 - Multi-needle chain-stitch sewing machine - Google Patents

Description

The invention relates to a multi-needle chainstitch sewing machine with several needles provided for receiving one needle each leading an upper thread, the several needles being arranged along a straight line at a distance from one another and being movable synchronously with one another, and the line being aligned at least essentially orthogonally to the intended feed direction of a sewing material transport , with a thread guide for the several upper threads to lead each upper thread from its thread supply to the needle assigned to it, with several driven grippers each leading to the guidance of a lower thread, the grippers being arranged at a distance from one another and movable synchronously with one another by the movements the looper and the needles each have an upper thread and a lower thread can be looped with one another in order to thereby simultaneously create several parallel seams in the sewing material, with one arranged in the sewing material in the feed direction of the sewing material without offset to one another to generate stitching points of the needles and a drive device having at least one motor with which the stitching movements of the needles and the gripper can be generated in a predetermined manner and coordinated with one another.

Chain stitch seams are often used in the industrial production of sewing goods, among other things, for the seams of trousers, in particular of jeans. In contrast to lockstitch seams, chainstitch seams have a higher elasticity, which is why chainstitch seams are often preferred for such applications. In particular with jeans and other articles of clothing made of denim, but not only with denim, seams running parallel and at a distance from one another are provided, for example double or triple seams.

Two different types of machines have already become known for this purpose. One of the two machine types is known as a crossline, the other machine type as an inline chainstitch machine. The two machine types differ primarily in the arrangement of the multiple needles to one another and in relation to the intended feed direction of the material transport. In crossline machines, the multiple needles are arranged along a line that corresponds to the direction of fabric transport includes an angle other than 90 °, usually an acute angle; for example 45 °. Due to the offset of the needles with respect to the intended direction of material transport, this type of machine is particularly suitable for applications in which the needles can also have a small distance from one another with respect to the direction of material transport. With this type of machine, due to the principle-related offset of the stitch-forming tools in the seam-forming direction, there is little risk that threads will be caught by adjacent stitch-forming tools and that this will result in seam malformations.

In the case of the inline chain stitch sewing machines already mentioned at the outset, however, the needles are arranged in a line which runs perpendicular to the intended direction of material transport. There is no offset of the needles and the other stitch-forming tools in the direction of material transport. In particular, the upper thread loops can come into conflict here with the respective adjacent gripper or grippers and, in particular, can be grasped by them. This results in errors in the stitch formation, which at least lead to optical errors, but usually to seams that do not fulfill their function. For this reason, the distance between adjacent needles of inline chain stitch sewing machines is limited. For the production of seams running parallel to one another in a single operation, which have a particularly small distance from one another, crossline chain-stitch sewing machines have therefore primarily been used up to now. However, these have the inherent disadvantage that the stitch points of the individual needles in the sewing material and thus also the seams are offset from one another in their longitudinal direction. This is often undesirable.

From the US 2007/261620 A1 a multi-needle chain stitch sewing machine is known which is provided with a plurality of needles arranged in a line but at a large distance from one another. This multi-needle chain stitch sewing machine is intended to topstitch large textiles, such as bedspreads, with regard to their surface extension. In order to produce the individual quilting cells, a comparatively large distance between adjacent needles of the sewing machine is therefore absolutely necessary. After coming out of the sewing machine US 2007/261620 A1 the seam formation is completed and the thread only remains must be cut off, a pusher 405 is pushed onto the upper thread in order to deflect it, thereby tensioning the thread and thereby being able to cut it off better.

Furthermore describes the U.S. 5,816,175 a two-needle chainstitch sewing machine whose two needles each lead an upper thread and these two upper threads are intertwined by a common lower thread to form a double seam. The two-needle chain stitch sewing machine has a thread brake for each upper thread, which thus acts on a different upper thread in each case. Only at the end of the seam formation, which is determined by detecting the end of the textile part to be sewn, is one of the thread brakes switched from a passive to an active mode of operation in order to vary the thread tension of one of the upper threads so that the last stitching process at the end of the seam ensures a reliable chain of both upper threads with the common bobbin thread takes place through secure chain stitch formation.

The invention is therefore based on the object of providing a sewing machine which is able to produce chain stitch seams running parallel to one another in one operation, which are at a small distance from one another and in which the stitching points of the seams are not offset in relation to their longitudinal direction .

This object is achieved according to the invention by a multiple needle chain stitch sewing machine with the features of claim 1. Here, a sewing machine has At the outset, a thread tightening means arranged in the area of the thread guide for at least one of the upper threads, with which at least one of the upper threads can be provided with an additional thread tension in the area between the thread tightening means and the needle assigned to the at least one upper thread. An "additional thread tension" can be understood to mean a thread tension component which results at least temporarily due to the action of the thread tightening means on the upper thread or threads and which is added to a thread tension that may be present even without such a thread tightening means.

In previous multi-needle chain stitch sewing machines, the thread guide was usually provided with a thread brake and a thread take-up lever (usually also referred to as a thread take-up lever) for each thread, which keep the upper thread under tension, provide the respective needle with a sufficient supply of thread and the thread of the thread loop as the needle moves upwards retract to a limited extent between the needle and the thread take-up lever after bottoming out. According to the invention, a separate thread tightening means is now preferably also provided, with which the respective upper thread is passively or actively pulled at a certain point in time in addition to the thread take-up device and preferably at a point other than that of the thread take-up device in the course of the upper thread. With the tightening of the at least one upper thread, preferably all of the upper thread, an additional tensioning force can be applied to the respective upper thread, at least temporarily. The object is also achieved by method claim 16.

With these measures according to the invention, even with a significant reduction in the needle spacing of multi-needle inline chain stitch sewing machines, a plurality of chain stitch seams arranged close to one another can be formed in a functionally reliable manner. This even applies to the so-called "linking" in which, for example, chain stitch seams are formed at the end of a seam formation without sewing material. Because of the lack of resistance for the upper threads through the sewing material, the seam formation of closely spaced chain stitch seams is particularly critical and prone to errors. As has been shown, the measures according to the invention lead to safe even under these conditions Seams without seaming tools from adjacent seams engaging threads from other than their own seams.

In connection with the present invention, it is therefore possible to provide significantly smaller needle spacings from mutually adjacent needles of inline multiple needle chain stitch sewing machines than before. These needle distances can be selected from a range from 4.4 mm to 2.6 mm, preferably from 4.2 mm to 2.8 mm and particularly preferably from a range from 3.8 mm to 3.0 mm.

In an advantageous embodiment of the invention, the at least one thread tightening means can preferably be arranged between the thread brake and the thread tightening lever (thread feeder). At this point, the intended thread tightening can be carried out particularly effectively and functionally reliable.

A particularly advantageous embodiment of the invention can provide that only one common thread tightening means is provided for the upper threads of several needles, preferably for all needles. The several upper threads assigned to this only one thread tightening means should be located or guided in an area of action of the thread tightening means so that the thread tightening means can act on the upper threads for a thread tightening. The plurality of upper threads are preferably passed through the only one thread tightening means. With this embodiment according to the invention, the thread suit can be realized in a particularly economical manner.

In a further preferred embodiment of the invention, the thread tightening means can be passively movable in order to exert a force on the at least one upper thread. The design as a passively moved element means that expensive drives for the thread tightening means can be avoided. In this advantageous embodiment of the invention, the thread tension present in the upper threads can be used to make different thread suits in different stitch formation phases. In addition, an automatically resetting of the thread tightening means can be carried out with little effort.

Furthermore, it is preferred that the thread tightening means is designed as a mechanical spring element, or as a pneumatically acting element or as a cam-controlled element which is movably coupled to a drive device of the sewing machine.

It has also been shown to be particularly advantageous that, during a stitch formation cycle, the thread tightening means provides a force that is variable in relation to the level of the force exerted on at least one upper thread. This makes it possible in particular to exert a particularly suitable force adapted to the upper threads for the respective stitch formation phase in order to generate thread tensions that are as suitable as possible in the upper threads, which can be used for the controlled upper thread loop formation of each needle and / or for controlled intertwining between one upper and one lower thread .

It has proven to be beneficial if the thread tightening means during a stitch formation phase, ie from the top dead center of the needles until the needles reach the top dead center again, at least two, preferably at least three, at least local maximum values of the maximum values exerted by the thread tightening means on the at least one upper thread Force going through. These multiple local maximum values can have different sizes or be of the same size. Likewise, it can advantageously be provided that the thread tightening means repeatedly reaches at least local minimum values of the force exerted by the thread tightening means on the at least one upper thread during a stitch formation phase. These minimum values can also have different values or be of the same size. This makes it possible, at least for certain times or phases of stitch or seam formation, to adapt the force with which the thread tightening means acts on at least one, preferably on all, upper threads. This makes it possible, in particular, to apply an increased force to one or more upper threads compared to other times when the needles are at least approximately in one of the two dead centers of their movement, that is to say in the upper or lower dead center. In the bottom dead center, the needles begin to form and release their respective upper thread loop through their subsequent upward movement. To prevent loops that are too large from forming, especially one that is too large Have expansion in the direction of adjacent grippers, an increased thread tension can have a beneficial effect on the upper threads at these times.

At the top dead center phase of the needles, a new stitch-forming process begins, with the loops formed in the immediately preceding stitch-forming process still on the hooks and the hooks beginning their backward movement, during which the previously formed upper thread loops are released by the hooks due to the backward movement. So that these upper thread loops can be controlled and released as loops that are not too large, a thread tightening can have a favorable effect, for example at the beginning of the backward movement of the hook. In particular, together with the subsequent downward movement of the needle and the subsequent material transport, which also contribute to tightening the upper thread loops on the grippers, the upper thread loops can thus be kept taut and thus sufficiently small until the intended jump from the grippers. Since the loops therefore rest largely tightly against their grippers during the backward movement of the grippers, the loops are also released at the predetermined phases and at least largely with a predetermined geometric shape.

In a further preferred embodiment of the invention, the force exerted by the thread tightening means on one or more upper threads can then have at least local minimum values when the needles are between their upper and lower dead centers. The minimum values of the thread tightening means can be provided in particular when the needles penetrate the sewing material and / or leave the sewing material again. During the downward movement of the respective needle, a large thread supply can be provided for the respective upper thread while the needle penetrates the sewing material by opening a thread brake, which thread supply should not be reduced if possible by the thread tightening means. The upward movement of the respective needle with the upper thread leads to the formation of loops, which are not prevented by the thread tightening means due to excessive thread tensions, but should be controlled by a slight action of the thread tightening means in order to avoid too large upper thread loops.

In order to further increase the functional reliability of the chain stitch formation of a multi-needle chain stitch machine according to patent claim 1, it can further be provided that the loop stroke is reduced in comparison to the loop stroke values customary up to now. It has proven to be advantageous if the loop stroke has a value from a range from 4 mm to 2.5 mm and preferably from a range from 3.5 mm to 2.7 mm. The loop stroke can be understood to mean the distance between a bottom dead center of the respective needle and the point along the longitudinal axis of the needle at which the gripper intersects the longitudinal axis of the needle during its movement. The shortening of the loop stroke leads to a reduction in the size of the upper thread loop formed by the needle and thus to a reduction in the risk that neighboring hooks will grip the upper thread loop of a needle.

In the same way, a reduced length of a spreader evasive movement compared to previous movement lengths can also support the measures according to patent claim 1 in order to achieve reliable stitch formation despite a small needle spacing. It has proven to be advantageous here if the spreader evasive movement has a length from a range of preferably 4.5 mm to 4.7 mm.

Each of the grippers can be arranged on a rotary shaft with which the respective gripper executes a driven alternating pivoting movement. The eccentricity that generates the alternating pivoting movement can preferably be reduced in the case of embodiments according to the invention compared to the otherwise usual eccentricities for driving the pivoting movement of the grippers. With the smallest needle spacing of 4.8 mm that has been customary up to now, the eccentricity is approximately 4.9 mm. For example, values from a range from 4.0 mm to 4.6 mm, preferably 4.4 mm, can now be provided. This enables shorter swiveling paths of the grippers to be achieved. As a result, the loop picked up by the gripper is not overstretched and drawing in of the upper thread is thus improved.

Further preferred embodiments of the invention emerge from the claims, the description and the drawing.

Fig. 1

eine erfindungsgemäße Mehrnadelkettenstichnähmaschine in einer Vorderansicht, die eine Inline-Nadelanordnung aufweist und mit einem Fadenanzugsmittel versehen ist;

Fig. 2

eine erfindungsgemäße Mehrnadelkettenstichnähmschine gemäß der Darstellung von Fig. 1 in einer anderen Stichbildephase;

Fig. 3

eine erfindungsgemäße Mehrnadelkettenstichnähmschine gemäß der Darstellung von Fig. 1 in einer weiteren Stichbildephase;

Fig. 4

eine erfindungsgemäße Mehrnadelkettenstichnähmschine gemäß der Darstellung von Fig. 1 in noch einer weiteren Stichbildephase;

Fig. 5

Eine perspektivische Ausschnittsdarstellung der Stichbildewerkzeuge der Nähmaschine aus Fig. 1, in der sich die Nadeln näherungsweise in ihrem unteren Totpunkt befinden;

Fig. 6

Die Stichbildewerkzeuge aus Fig. 5, die sich ausgehend von Fig. 5 in einer Aufwärtsbewegung befinden;

Fig. 7

Die Stichbildewerkzeuge aus Fig. 5, die sich ausgehend von Fig. 5 in einer Aufwärtsbewegung befinden;

Fig. 8

Die Stichbildewerkzeuge gemäß Fig. 5, die sich näherungsweise in einem oberen Totpunkt befinden;

Fig. 9

Die Stichbildewerkzeuge gemäß Fig. 8, die sich ausgehend von Fig. 8 in einer Abwärtsbewegung befinden;

Fig. 10

Die Stichbildewerkzeuge gemäß Fig. 8, die sich ausgehend von Fig. 9 in einer weiteren Phase der Abwärtsbewegung befinden;

Fig. 11

Ein Ausführungsbeispiel für ein als mechanische Feder ausgebildetes Fadenanzugsmittel;

Fig. 12

ein Diagramm, in dem in einem Graph eine Position einer Nadelspitze über der Zeit und in einem zweiten Graph eine von dem Fadenanzugsmittel auf zumindest einen Oberfaden ausgeübte Spannkraft abgetragen sind;

Fig. 13

eine perspektivische Darstellung eines von einer Maschinenhauptwelle angetriebenen Exzenterantriebs der Greifer.

The invention is explained in more detail with reference to exemplary embodiments shown purely schematically in the figures, which show:

Fig. 1

a multi-needle chain stitch sewing machine according to the invention in a front view, which has an in-line needle arrangement and is provided with a thread tightening means;

Fig. 2

a multi-needle chain stitch sewing machine according to the invention as shown in FIG Fig. 1 in another stitch formation phase;

Fig. 3

a multi-needle chain stitch sewing machine according to the invention as shown in FIG Fig. 1 in a further stitch formation phase;

Fig. 4

a multi-needle chain stitch sewing machine according to the invention as shown in FIG Fig. 1 in yet another stitch formation phase;

Fig. 5

A perspective detail view of the stitching tools of the sewing machine Fig. 1 , in which the needles are approximately in their bottom dead center;

Fig. 6

The stitch-forming tools Fig. 5 based on Fig. 5 are in an upward movement;

Fig. 7

The stitch-forming tools Fig. 5 based on Fig. 5 are in an upward movement;

Fig. 8

The stitch-forming tools according to Fig. 5 which are approximately in a top dead center;

Fig. 9

The stitch-forming tools according to Fig. 8 based on Fig. 8 are in a downward motion;

Fig. 10

The stitch-forming tools according to Fig. 8 based on Fig. 9 are in another phase of downward movement;

Fig. 11

An embodiment of a thread tightening means designed as a mechanical spring;

Fig. 12

a diagram in which a position of a needle tip over time is plotted in a graph and a tensioning force exerted by the thread tightening means on at least one upper thread is plotted in a second graph;

Fig. 13

a perspective view of an eccentric drive of the gripper driven by a machine main shaft.

In Fig. 1 a multi-needle chain stitch machine 1 according to the invention is shown, which has a housing, shown partially open, with an upper part 1a and a lower part 1b. In the front view, the housing 1 has a U-shape that is tilted by approximately 90 °. In the upper part 1 a of the housing 1 there is in particular a drive unit in order to drive several needles 2 which can be moved synchronously. The needles 2 are arranged in a common needle holder, which in turn is attached to a needle bar. The needle bar is operatively connected to the drive unit in the upper part 1a of the housing, so that a drive movement leads to an oscillating straight up and down movement of the needle bar. In other exemplary embodiments, each needle 2 could also be attached to its own needle bar which is assigned to it.

In the lower part 1b of the housing 1, a further drive unit is provided, which is provided for the likewise synchronous drive of grippers 3. Both the grippers 3 and the needles 2 belong to stitch-forming tools of the multi-needle chain stitch machine. As is already known per se, the two drive units for the needles 2 and the grippers 3 can have a common motor which drives an arm shaft, which in turn provides and transmits drive movements for each of the two drive units. The basic structure of the two drive units can correspond to previously known multiple needle chain stitch sewing machines be constructed. In other embodiments, the needles and the grippers could be driven by several separate motors.

In the area of the front side of the upper part 1 a, a thread guide 4 for upper threads is provided, with which an upper thread 5 for each needle 2 is guided from a thread supply 6 of the respective upper thread 5 to the corresponding needle 2. The thread guide 4 has, as seen in the feed direction of the upper threads 5, for each upper thread 5 an adjustable thread brake 7 which is assigned only to this upper thread and through which the respective upper thread 2 is guided. The upper threads 5 are then jointly guided through a guide eye 8. From here the upper threads 5 jointly reach a thread tightening means 10 and are passed through the thread tightening means 10. In the further course, the upper threads 5 are again guided jointly through only one thread dispenser 11. Each upper thread 5 then arrives at its needle 2 and is passed there through the respective needle eye. Each upper thread 5 executes its oscillating movement together with the needle 2 and forms an upper thread loop required for the formation of the chain stitch seam with each movement cycle.

In the two representations of the Fig. 11 a possible embodiment for a thread tightening means 10 is shown. Here the thread tightening means 10 is designed as a thread tightening spring device. This has a carrier 14 with which the thread tightening means 10 can be fastened to the upper part 1 a of the housing of the sewing machine and which carries the guide of the thread and a helical spring 15. The helical spring 15 is pushed onto a shaft of the carrier 14 and is arranged thereon. A front end 15a of the coil spring 15 is fixed in place. A housing-side end of the helical spring is designed as a bracket 15b.

The several grippers 3 arranged in the lower part 1b of the housing are arranged together on a gripper carrier 16, which in turn is driven by the drive unit in the lower part 1b of the housing. This drive movement leads to a jointly and synchronously executed alternating tilting or swiveling movement of all grippers 3. The grippers 3 present in the same number as the needles 2 can move back and forth between two end positions along a predetermined curved path. The curved or The curved path of the grippers 3 can be, for example, an arc of a circle or an arc of an ellipse. As in Fig. 13 is shown, the grippers 3 are driven by means of an eccentric drive 17 which, in the case of the exemplary embodiment, in turn receives its rotary drive movement from the arm shaft. The eccentric drive 17 comprises a shaft 18 which is driven in rotation by the arm shaft (not shown in detail) and on which an eccentric 19 is arranged. The eccentric 19 acts in the manner of a roller or cam drive and causes the alternating tilting movement of the gripper carrier 16. The size of the eccentricity E determines the size of the pivoting angle of the grippers 3 during their alternating pivoting movement. Compared to the size of previous eccentric drives for grippers, a smaller eccentricity is provided in the exemplary embodiment, namely 4.4 mm.

The several identically designed grippers 3 each have a U-shape that is approximately 90 ° tilted. Each gripper is fastened to a gripper carrier 16 with the lower leg 3a of the tilted U-shape. Each of the grippers 3 has an upper leg 3b, which is provided with a recess 24 from its rear end 22 to its hook tip 23, which for receiving and passing the only one lower thread 25 assigned to the respective gripper 3 through the upper leg 3b to to the gripper tip 23 is provided. In the area of its free end, each gripper 3 tapers approximately conically to its gripper tip 23. The bobbin threads 25 coming from a supply of bobbin threads are passed individually through one of the recesses 27 of a bobbin thread separation aid 28. From here, each lower thread reaches the area of the connecting leg 3c of the U-shape of the respective gripper 3 and is introduced here into the inlet opening of the recess 24 designed as a passage. The bobbin thread 25 then exits upwards in the area of an upper side of the hook tip 23 and is guided away upwards to the underside of the sewing material (not shown in detail).

In the exemplary embodiment with three needles 2, a total of three grippers 3 are provided, which are aligned parallel to one another. In other exemplary embodiments, a different number of grippers 3 can also be present, with the number of grippers 3 always corresponding to the number of needles 2 provided. In particular, a number of grippers from a range from 2 to 10 can be provided be. Like needles 2 that are adjacent to one another, grippers 3 that are adjacent to one another are preferably at the same distance from one another, preferably the same spacing as the needles 2 assigned to grippers 3. In the exemplary embodiment, neighboring gripper tips are 3.2 mm apart. Likewise, the longitudinal axes of needles 2 that are adjacent to one another, preferably all of the needles 2 that are spaced apart from one another, are each provided with a spacing of 3.2 mm. The needles 2 are arranged along a straight line which is intersected by each of the longitudinal axes of the needles 2 and to which the longitudinal axes are perpendicular. The line also runs perpendicular to the direction of sewing material transport. In the representation of Fig. 1 the line is in the plane of the drawing Fig. 1 or parallel to this plane of the drawing. The material transport direction, however, is perpendicular to the plane of the drawing Fig. 1 aligned.

In the area between the two legs, a needle guard 35 is attached to the gripper carrier 16. This has several struts 36 which are arranged at a distance from one another and which are arranged and aligned in such a way that they represent a guide for the needles 2. If needles 2, for example due to particularly stiff sewing material, show a tendency to bend and deviate from their target path, this deviation is limited by the struts 36 and the needles are forced to at least approximately maintain their target orientation. This also ensures that the position of the upper thread loops 37 is in each case in the area of the one looper 3 assigned to the respective upper thread loop 37 and thus each upper thread loop 37 can be grasped by its respective looper 3.

Finally, in the area of the grippers 3, there is also a carrier 38 for several spreader elements. In the exemplary embodiment discussed here, the spreader elements can be designed as spreader pins 39. With each spreader pin 39, the respective lower thread 25 of the respective spreader pin 39 associated with a lower thread 25 is grasped at a certain point in time in order to then deflect it laterally by a spreader evasive movement of predetermined length and direction. The spreader evasive movement preferably takes place in a direction transverse to the needle movement.

In the Figures 5 to 10 the processes involved in the formation of stitches or seams in the area of stitch formation tools are shown. For a discussion of the processes involved in stitch and seam formation, the following is also referred to FIGS. 1 to 4 Reference is made, in particular in order to explain the thread tightening means 10, which acts on the respective upper thread 5 and is designed as a thread tightening spring, and its function. In Fig. 5 the three needles 2 and the corresponding three grippers 3 are shown. Each needle 2 guides an upper thread 5 which is guided through the respective needle eye and each of the loops 3 guides a lower thread 25 which is guided through the upper limb 3b of each looper. In the representation of Fig. 5 the needles 2 moving synchronously with one another are in the area of their bottom dead center and begin to reverse their direction of movement towards their top dead center. The three grippers 3 are on their way to their end position with their gripper tips in front of the needles 2 and at this point in time of the stitch formation phase are arranged in front of the plane formed by the three needles. The grippers 3 are in their rear end position, ie in their reversal point of the direction of movement, where they are at the greatest distance from the needles. Shortly before reaching this position, a previously generated thread loop 37 of the upper thread, which was entwined with the associated lower thread 25, has jumped off the hooks 3 due to the movement away from the needles 2. This process will be discussed in more detail below for the next interlacing between the respective upper thread 5 and the associated respective lower thread 25.

This stitch formation phase also includes the display of Fig. 3 . As can be seen here, at the point in time at which the needles 2 are in their bottom dead center, the thread dispenser 11 is also arranged in its bottom dead center. The thread take-up spring 10 has now moved with its bracket 15b from its stop 40 on the left in the illustration in the direction of its upper stop 41, in which it exerts the greatest spring tension on the respective upper thread. The passive thread take-up spring 10 has been transferred into this position by the latter due to an increasing thread tension in the upper threads 5.

In Fig. 6 all needles have moved a little further up along their respective longitudinal axis in the direction of their upper dead center or their upper position, which also determines the loop stroke, and have already started to release an upper thread loop 37. The grippers 3 have here in a pivoting movement, in the illustration of Fig. 6 moved to the right, towards the needles 2 and approached the latter. The thread dispenser 11 is likewise in an upward movement. The thread take-up spring 10 is relieved of tension in the upper threads due to the upward movement of the needles 2, also in the area of the thread take-up spring 10. The spring force of the thread tightening spring 10 therefore causes a pivoting movement of the bracket 15b of the thread tightening spring in the direction of its first stop 40, in which the thread tightening spring 10 has the lowest spring force.

On the way from their position in Fig. 6 to their position in Fig. 7 the grippers 3 have already passed the longitudinal axes of the needles 2. How out Fig. 7 As can be seen, the grippers 3 are already passed with their respective tips through the only one loop 37 assigned to them. The bobbin thread 25 emerging from the hook point is hereby already guided with a section through the loop 37 assigned to it. The thread feeder 11 executes a synchronous movement with respect to the needles 2 and is also in an upward movement. The thread take-up spring 10 is further relieved due to the decreasing upper thread tensions and is still on its way to its first stop 40, in which the thread take-up spring 10 has the lowest spring force

In Fig. 8 the grippers 3 have moved on their predetermined curved path, in the exemplary embodiment here on a circular arc path, further to the end position on the gripper tip side and are shown in FIG Fig. 8 in this movement reversal position. The grippers 3 have received the loop 37 as far as possible on their upper legs 3b, the loops 37 each being designed to be taut, ie with the least possible lateral deflection. A section of the upper leg 3b of the respective gripper is arranged with the gripper tips in this position below the spreader pins 39. The grippers 3 each have their lower thread 25 on a specific side of the due to their pivoting movement Spreader pins 39 arranged, namely the side in the direction of which the spreader pins 39 will subsequently move. In the representation of Fig. 8 the lower threads are thus each guided behind one of the spreader pins 39. The needles 2 are now in the position of their top dead center, in which their upper thread loop is at its largest.

To the stitch formation phase of the Fig. 8 Also includes the representation of the front view of the sewing machine from Fig. 1 . How out Fig. 1 As can be seen, at this point in time the thread dispenser 11 as well as the needles 2 are in their top dead centers. The needle and thread dispenser movements as well as the feed movement of the sewing material lead to an increase in the thread tension in the upper threads 5, which is why the thread tension spring 10 with its bracket 15b is loaded to the maximum by the upper threads 5. The thread tightening spring 10 is therefore held in its upper, second end position 41 with the spring force resulting from the tensions of the upper threads 5 and rests with its bracket 15b on the upper threads with this spring force. The thread take-up spring 10 thus ensures that the upper thread loops 37 are tightened and have a slight lateral deflection.

Fig. 9 shows a current position of the spreader pins 39, in which the spreader pins 39 have already begun their lateral deflection movement and have grasped the one bobbin thread assigned to them. The carrier 38 of the spreader elements is together with the spreader pins 39 held and moved by it - with reference to the illustration of FIG Fig. 9 and its drawing plane - has been moved backwards. During this movement, the spreader pins have entrained the bobbin thread 25, which is arranged immediately in front of each spreader pin 39, and thereby deflected it in the direction of movement of the corresponding spreader pin 39. The needles 2 have already left their position in their upper dead center and are again on their way towards their lower dead center, but are still arranged above the upper legs 3 b of the grippers 3. Needle 2 have just pierced the material to be sewn. The grippers 3 now move in a direction opposite to the previously assumed direction of movement towards the second end position of the grippers facing away from the gripper tips. The needles 2 happen - due to the deflection of the bobbin threads 25 and - with reference to the illustration of FIG Fig. 9 , each assigned to the needle and emerging from this gripper 3 Lower thread 25, namely before this lower thread 25. The needles 2 then begin to form the subsequent upper thread loop 37a. The upper thread loop 37 formed immediately before is still gripped by the respective gripper 3, as shown in FIG Fig. 9 and also in Fig. 10 is shown.

In the representation of Fig. 10 the needles 2 have moved further in the direction of their bottom dead center and have also passed the grippers 3. The thread feeder 11 guiding the upper threads 5 continues to move synchronously with the needles 2 and also in the direction of its bottom dead center. Furthermore, the grippers 3 have covered a further section in the direction of their second end position facing away from the gripper tips, which is shown in the illustration of FIG Fig. 10 located on the left. Each lower thread 25 is also deflected by a respective spreader pin 39. As a result, the bobbin threads 25 come into abutment in each case against the needle 2 assigned to them. During a subsequent upward movement of the needles 2, the bobbin threads 25 jump off the needles 2 or are released from the needles and a loop between each bobbin thread 25 and a loop 37 of one of the upper threads 5 then takes place.

With regard to the stitch formation phases according to Fig. 9 and 10 , in which the needles 2 are in their downward movement towards their common bottom dead center, the thread take-up spring 10 pivots from its previously assumed upper end position 41, in which it is loaded with its maximum spring force, to its left-hand end position 40 in which it has the lowest spring force and thus can apply at least almost no tensile force to the upper threads 5. The upper thread loops 37 that are still on the respective gripper 3 and formed in the previous stitch-forming process are each held taut on their respective grippers 3. By relieving the thread tension spring 10, tension is applied to the upper thread, which is otherwise relatively slightly tensioned or even almost loose compared to other thread conditions.

In Fig. 12 is to illustrate a possible and advantageous basic course of the force exerted by the thread tightening means 10 for the invention, in the case of the exemplary embodiment a spring force. In other embodiments, the force provided for pulling the thread can also be done in other ways than by a spring to be provided. This force acting on the at least one, preferably on all upper threads simultaneously, is variable during a stitch formation cycle, that is, from a position of the needle tips in their top dead center to the subsequent reaching of the top dead center again. As from the diagram of Fig. 12 it is preferred here if the force exerted by the thread tightening means assumes a maximum value several times during the aforementioned stitch-forming cycle, at least one local maximum value each time. Likewise, the force of the thread tightening means can assume a minimum value several times during a stitch formation cycle, at least one local minimum value each time. It has proven to be advantageous here if at least local maximum force values acting on the upper threads are set in the upper and lower dead center of the needles. Minimum force values can be present in particular when the needles pierce the material to be sewn and / or when the needle tip leaves the material to be sewn in the upward movement. Just like the path of the needles, the course of the force of the thread tightening means can also correspond to a cosine curve or a cosine function. As in Fig. 12 shown, the respective minimum value can be a positive value of the force other than zero. It is also possible for at least one of the minimum values to have the value zero during a stitch formation phase.

As shown in the embodiment discussed here, despite a very small needle spacing from adjacent needles 2, which are arranged according to the inline principle of a multi-needle chain stitch sewing machine, the invention enables a reliable seam formation of seams running parallel to one another at a small distance will. In particular, it can be avoided that adjacent stitch-forming tools, ie those belonging to an adjacent seam, grasp an upper thread and thus prevent a seam from being formed.

List of reference symbols

1 Multi-needle chainstitch machine 18th wave 1a Top 19th eccentric 1b Lower part 22nd rear end 2 needle 23 Hook point 3 Grapple 24 Recess 3a lower thigh 25th Bobbin thread 3b upper thigh 26th Bobbin thread reserve 3c Connecting leg 27 Recess 4th Thread guide upper threads 28 Lower thread separation aid 5 Upper thread 35 Needle guard 6th Thread reserve 36 strut 7th Thread brake 37 Upper thread loop 8th Guide eye 37a subsequent upper thread loop 10 Thread attracting means 11 Thread dispenser 38 carrier 14th carrier 39 Spreader pin 15th Coil spring 40 left stop 15a front end 41 upper stop 15b hanger 16 Gripper carrier E. eccentricity 17th Eccentric drive

Claims (16)

1. Multi-needle chain-stitch sewing machine having a plurality of needles (2) which are provided for guiding in each case one top thread (5), wherein the plurality of needles are in each case disposed so as to be mutually spaced apart along a straight line and movable conjointly in synchronous manner, and the line is aligned so as to be at least substantially orthogonal to the envisaged advancing direction of transporting a material to be sewn; having a thread guide (4) for the plurality of top threads so as to guide each top thread (5) from the thread supply (6) thereof to the needle assigned to said top thread (5), having a plurality of driven grippers (3) which guide in each case one bobbin thread (25), wherein the grippers (3) are disposed so as to be mutually spaced apart and movable conjointly in a synchronous manner; wherein, as a result of the movements of the grippers (3) and of the needles (2), one top thread (5) and one bobbin thread (25) are in each case able to be intertwined so as to, as a result, generate simultaneously a plurality of seams that run so as to be mutually parallel in the material to be sewn, having piercing locations of the needles that are disposed in the material to be sewn without any mutual offset in the advancing direction, and having a drive installation which has at least one motor and by way of which the movements of the needles and of the grippers are able to be generated in a predetermined and mutually adapted manner, characterized in that, in order for the seam to be reliably formed, a thread tautening means (1) for at least one of the top threads (5) is present in the region of the thread guide, between a thread brake and a thread take-up (11), and provided additionally to the thread take-up (11), at least one of the top threads by way of said thread tautening means (10) being able to be provided with an additional thread tension in the region between the thread tautening means (10) and that needle (2) that is assigned to the at least one top thread (5).
2. Multi-needle chain-stitch sewing machine according to Claim 1, characterized in that the at least one thread tautening means (10) in terms of a profile of top threads (5) is disposed between at least one thread brake (7) of these top threads (5) and that thread take-up (11) that moves conjointly with the needles (2).
3. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that a common threat tautening means (10) by way of which the plurality of top threads (5) can be simultaneously acted on is provided for a plurality, preferably for all, of the top threads (5).
4. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10) is a passively moved element that acts on at least one of the top threads.
5. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized by a thread tautening means (10) which is provided for bearing on at least one, preferably all, of the top threads (5).
6. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10) is configured as a mechanical spring element, or as a pneumatically acting element, or as cam-controlled element which is movably coupled to a drive installation of the sewing machine.
7. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10) during a stitchforming cycle exerts on at least one of the top threads a force that is variable in terms of magnitude.
8. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10), during a stitchforming cycle in which the needles move from the top dead centre thereof to a bottom dead centre and back to the top dead centre, has at least two, preferably at least three, at least local maximum values of the force that is exerted on the at least one top thread (5) by the thread tautening means.
9. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10), during a stitchforming cycle in which the needles move from the top dead centre thereof to the bottom centre thereof and back to the top dead centre, has at least two, at least local, minimum values of the force that is exerted on the at least one top thread by the thread tautening means (10).
10. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10) exerts in each case an at least local maximum force on at least one of the top threads (5) when the needles (2) pass the top dead centre thereof and the bottom dead centre thereof.
11. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the thread tautening means (10), on the path of the needles (2) between the top dead centres and bottom dead centres thereof as well as on the path between the bottom dead centres and the top dead centres thereof, has in each case at least one at least local minimum value.
12. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that the needle spacing of mutually adjacent needles (2) is selected from a range from 4.4 mm to 2.6 mm, preferably from 4.2 mm to 2.8 mm, and particularly preferably from a range from 3.8 mm to 3.0 mm.
13. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that a spreader deflection movement is selected from a range from 4.5 mm to 4.7 mm.
14. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized in that an eccentricity of a roller or cam drive of at least one, preferably of all, of the grippers is selected from a range from 4.8 mm to 4.0 mm, preferably having a value of 4.4 mm.
15. Multi-needle chain-stitch sewing machine according to at least one of the preceding claims, characterized by a needle spacing of longitudinal axes of mutually adjacent needles from a range from 3.8 mm to 3.0 mm, preferably from 3.6 mm to 3.1 mm, and particularly preferably having a value of 3.2 mm.
16. Method for simultaneously generating chain-stitch seams that are disposed next to one another by means of a multi-needle chain-stitch sewing machine having a plurality of needles (2) which are provided for guiding in each case one top thread (5), wherein the plurality of needles are in each case disposed so as to be mutually spaced apart along a straight line and movable conjointly in synchronous manner, and the line is aligned so as to be at least substantially orthogonal to the envisaged advancing direction of transporting a material to be sewn; wherein the plurality of top threads in the multi-needle chain-stitch sewing machine are guided by means of a thread guide (4) so as to guide each top thread (5) from the thread supply (6) thereof to the needle assigned to said top thread (5), and a plurality of bobbin threads (25) which are in each case guided by means of one of a plurality of driven grippers (3) are provided, wherein the grippers (3) are disposed at a mutual spacing and moved conjointly in a synchronous manner and, as a result of the movements of the grippers (3) and of the needles (2), one top thread (5) and one bobbin thread (25) are in each case intertwined so as to, as a result, generate simultaneously a plurality of seams that run so as to be mutually parallel, having piercing locations of the needles that are disposed in the material to be sewn without any mutual offset in the advancing direction; wherein
    movements of the needles and of the grippers which are mutually adapted in a predetermined manner are generated by means of at least one motor of a drive installation, characterized in that, in order for the seam to be reliably formed, a thread tautening means (10) for at least one of the top threads (5) is present in the region of the thread guide between a thread brake and a thread take-up (11) and additionally provided to the thread take-up (11), wherein at least one of the top threads by way of the thread tautening means (10) is provided with an additional thread tension in the region between the thread tautening means (10) and that needle (2) that is assigned to the at least one top thread (5).

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