EP2948581B1 - Embroidering machine with at least one rotating loop taker for two-thread lock stitch - Google Patents

Description

The invention relates to an embroidery machine with at least one embroidery head, which is provided with stitch-forming tools for stitch-forming an embroidered seam, the stitch-forming tools having a needle provided for guiding an upper thread and a rotating gripper that interacts with the needle to form embroidered seams, the gripper having a receptacle for Arrangement of a lower thread supply is provided and preferably more than twice around its axis of rotation during a stitch formation cycle, and movement means for performing relative feed movements between the needle and an embroidery material is provided.

In the case of embroidery machines, such as are used in particular for the industrial production of textiles, double lockstitch grippers are used in the majority of cases, as are also used in principle with sewing machines. In embroidery machines, such a lockstitch gripper performs two full revolutions per stitch formation period. In the DE 10 2010 013 016 A1 it is suggested that the lockstitch gripper perform more than two full revolutions during a stitch formation period. Such a stitch formation period, which can also be referred to as a stitch formation cycle, is characterized in that the main machine shaft driving the needle bar and needle completes a full 360° revolution.

Due to the different tasks of a sewn seam ("seam") on the one hand and an embroidered seam ("embroidery seam") on the other hand, there is a significant difference in the requirements for a sewing machine or an embroidery machine. While the sewn seam is essentially a connecting or fastening seam, with which two or more parts are usually firmly connected, the embroidered seam is an ornament (ornamental seam) applied to the embroidery base, which does not have to transmit any forces and is visible in the finished state is not charged.

The strength of the fastening seam is achieved by the fact that the thread loop that has fallen off the hook is pulled by the thread lever with relatively great force in the direction of the upper side of the sewing material, so that the looping of the needle and looper thread comes to rest in the middle between the layers of fabric to be sewn. The thread force of the looper thread is dimensioned accordingly.

The conditions when forming an embroidered seam are completely different. Since the needle thread (=embroidery thread) should only lie cleanly on the upper side of the embroidery material to achieve decorative effects, the thread tension during the embroidery process is kept as low as possible so that the embroidery thread is sufficiently secured in terms of position on the embroidery base, but no loose thread parts arise , and the entanglement between the needle and looper thread always comes to rest on the underside of the embroidery base.

With the invention of DE 10 2010 013 016 A1 as a solution to the problem that the minimum thread tension is undesirably high in embroidery machines with lockstitch rotary hooks, it is proposed to let the rotary hook rotate with at least three revolutions during a stitch formation period. As has been shown, these modified kinematics can prevent the aspects that lead to a system-related excessive thread tension in the case of double-rotating hooks. In this way, the gripper embroidery machine with typical sewing machine kinematics can be adapted to the special requirements of an embroidery machine. However, it has now also been shown that this measure means that the length of the lower thread corresponds approximately to the length of the upper thread for each stitch, especially in the case of satin stitches. Satin stitches, which have a zigzag seam, are mainly used to create surface patterns. The seam created with satin stitches typically shows a change in direction of the orientation of the upper thread after each stitch. The lower thread extends on the underside of the embroidery base from one needle puncture to the next needle puncture in the embroidery base. The lower thread thus runs from a thread that is arranged directly below a puncture Upper thread loop to the next upper thread loop, which is also arranged immediately below where the needle punctures the embroidery base.

Similar to lockstitch sewing machines, the lower thread is wound onto bobbins in such embroidery machines, which are usually inserted into the hook so that the hook tip rotates around the bobbin. As already explained above, it has been shown, particularly in the case of embroidery machines with triple or more rotating grippers, that the thread on these bobbins is quickly used up and therefore has to be changed frequently. This change must be made much more frequently than with the upper thread guided by the needle, since there is no gripper that restricts the size of the bobbin in bobbins for the upper thread. Upper thread spools are therefore usually significantly larger than lower thread spools. Frequent changing of the bobbin, especially the bobbin of the lower thread, means unproductive standstill of the embroidery machine for the duration of the change and should therefore be avoided as far as possible.

From the EP 0 756 031 A2 a so-called "Schiffli embroidery machine" is also already known, in which the lower or rear thread is guided by a "Schiffli", or also called shuttle. This is an element that is moved back and forth in an oscillating manner in a straight line. At its movement reversal points, the "Schiffli" always has the speed "zero". From here, the "Schiffli" and the lower or rear thread guided by it are accelerated in the direction of the other movement reversal point of the movement path. the EP 0 756 031 A2 is concerned with reducing the movement errors of the thread guides that are common in the prior art in machines with a large number of shuttles and their common drive for the upper thread guide. This is intended to improve the embroidery image of the individual embroidery processes carried out simultaneously by the machine through standardization. To solve this task, the EP 0 756 031 A2 proposes making the previously movable first thread guide immovable and allowing the second thread guide to perform a movement that corresponds to the earlier movements of the two thread guides that were previously movable. By tightening the lower thread or the With this type of embroidery machine, a parallel offset of the upper and lower threads of each stitch can also be achieved with the upper thread.

The invention is therefore based on the object of specifying a measure by which the change intervals for the lower thread bobbin can be extended in embroidery machines of the type mentioned.

This object is achieved according to the invention by the features of patent claim 1 in an embroidery machine of the type mentioned. means of the embroidery machine for the adjustable variation of at least one parameter of the stitch formation process, which result in different values of the parameter at least during one, preferably during each, stitch formation period from a large number of stitch formation periods of the embroidery seam, in order to thereby in relation to the position and length of the Lower and upper thread of a stitch of the embroidery seam on the top and bottom of the embroidery to produce a non-congruent arrangement of upper and lower thread on the embroidery. According to an aspect of the invention based on the same inventive idea, the object is also achieved by means for reducing a thread tension of the upper thread of the embroidery machine at a predeterminable point in time of the stitch formation cycle. The object is also achieved by an embroidery method according to claim 11 and by an embroidery product according to claim 14.

The invention overcomes the view that has long prevailed in connection with rapier embroidery machines that only their kinematics determine the amount of lower thread, particularly in the case of satin stitches. In contrast to this, as a consequence of the features mentioned in claim 1, the invention provides that at least one parameter of the embroidery process that can be influenced by the embroidery machine is changed during the execution of the embroidery process - in particular during each stitch formation cycle - on the basis of at least one control process of the embroidery machine. This change should be made in a predetermined manner that is performed by the machine itself, for example based on a setting previously made on the embroidery machine or due to appropriate programming. It is also conceivable that the setting is controlled or regulated on the basis of and as a function of a detection result, determined by the machine, of an ACTUAL value of the at least one parameter. The parameter of the embroidery process that is deliberately varied during a stitch formation cycle can advantageously be a thread tension or another influencing factor of the embroidery process that influences the thread tension. As has been shown, with unchanged kinematics of gripper embroidery machines, the lower thread length assigned to a specific stitch length can already be shortened simply by deliberately varying the size of instantaneous values of a parameter of the embroidery process in terms of time and amount. This can be done in particular by reducing values of at least one parameter during a phase of the stitch formation period compared to values of the respective parameter in a phase of the same stitch formation period that precedes this phase. By setting different values for the respective parameter when it varies during a stitch formation period, it is possible to achieve different lengths of the lower thread section assigned to a stitch length in a targeted manner. It is indeed preferred that the at least one parameter is always varied in an identical manner when a seam is formed. In principle, however, it is also possible for different stitches of the seam to be used To change the at least one parameter in different ways and in particular to forego a variation for certain stitches.

The means according to the invention thus act in such a way that, at the latest after the completion of the respective stitch formation, the upper thread loop receiving the lower thread is arranged on the underside of the embroidery base at a distance from the passage point of the upper thread through the embroidery material assigned to the respective upper thread loop. According to the invention, in the case of the finished satin stitch embroidery seam formed with a looper that rotates more than twice, the upper thread with its loop should no longer be arranged directly below the respective puncture point of the needle in the embroidery material. Rather, it is provided that the upper thread loop is arranged between two successive puncture points at the latest after the stitch or seam has been formed. As a result, the length of lower thread required for seam formation can be significantly reduced for each seam. With satin stitches, the lower thread no longer runs from puncture point to puncture point, but from an upper thread loop drawn in between two puncture points under the embroidery base to the next upper thread loop in stitch sequence, which is also drawn in in basically the same way under the embroidery base between two puncture points. The lower thread thus takes a path between two consecutive puncture points in the puncture sequence of the needle in the embroidery base that is shorter than the distance between the two consecutive puncture points (stitch length) in order to still be guided through the upper thread loop assigned to each puncture point. The measures according to the invention also mean that the respective lower thread section of the satin stitch embroidery seam, which runs between two upper thread loops that follow one another directly in the stitch sequence on the underside of the embroidery material, is not congruent with the corresponding upper thread section on the upper side of the embroidery material. As has been shown, the invention can also lead to advantages for reasons other than reducing the lower thread consumption, even with straight seams and also with loopers that only rotate twice per stitch formation cycle.

The measure provided according to the invention leads to a reduction in the amount of lower thread required for satin stitches. However, to compensate for this, it requires an increased amount of upper thread. However, the latter is of secondary importance due to the significantly larger and practically any size spool for the upper thread in relation to the length of the required change intervals for thread spools. Conventional upper thread spools allow a significantly larger amount of upper thread to be stored on the embroidery machine than is possible with lower thread spools. In addition to satin stitches, the invention can also be used to advantage for other types of stitches, especially when the upper thread sections of consecutive stitches or the associated puncture points do not lie on a straight line but enclose an angle deviating from 180°.

According to the invention, with satin stitches per stitch - and thus also per stitch length between two consecutive punctures of the needle, only one lower thread portion is required, in which the lower thread portion assigned to this stitch length is at most 80% of the stitch length, preferably at most 70%, also preferably at most 60 % and more preferably half the stitch length or less.

In a preferred embodiment of the invention, the means for reducing the thread tension have an upper thread brake, the braking effect of which on the upper thread can be reduced or completely canceled by the control of the embroidery machine at a predetermined, in particular at a variably predeterminable, time of seam formation. Instead of an actual absolute reduction in the upper thread tension, it is also conceivable in principle to reduce the ratio of the upper thread tension to the lower thread tension, for example by increasing the lower thread tension while the upper thread tension remains unchanged. By reducing the upper thread tension or the ratio between upper thread and lower thread tension, there is sufficient thread tension on the lower thread that is passed through the respective upper thread loop, so that the loop of the upper thread can pass through the Lower thread is pulled at least essentially in the direction of the respective subsequent puncture point of the needle in the embroidery material. The lower thread sections between the respective contact points of the lower thread with the upper thread loops that follow one another in the stitch sequence are thus significantly shorter than the distance between successive puncture points of the needle. In the case of satin stitches, which are produced with embroidery machines of the generic type according to the previously known generic method, the distances between successive puncture points correspond at least approximately to the lower thread sections.

It has proven to be particularly expedient if, during a stitch formation period, the thread tension is reduced or removed after a point in time after the thread feed of the needle thread has a value of zero or almost zero. The latter is the case when the pivoting movement of the thread lever for the upper thread, which is preferably provided in embroidery machines of the generic type, has reached its top dead center.

Furthermore, it has proven to be particularly advantageous if the reduction or cancellation of the upper thread tension triggered by the machine control takes place at a time when the embroidery base is already moving to the next stitch position. The upper thread tension should advantageously be reduced in particular between points in time of the respective stitch formation period at which the upper thread feed has a minimum value and before the embroidery base stops moving again after the movement has taken place.

The upper thread tension should preferably be increased again at a point in time when or after the needle has reached its greatest penetration depth during its subsequent penetration into the embroidery material, i.e. at point in time A in the machine diagram 3 .

Further preferred configurations of the invention result from the claims, the description and the drawing.

Fig. 1

eine Teilansicht eines vorderen Bereichs eines Stickkopfs mit einem Doppelsteppstich-Greifer;

Fig. 2

Eine Darstellung der Situation beim Stickvorgang, wie er zum Zeitpunkt B aus Fig. 3 gegeben ist;

Fig. 3

ein Weg-Zeit-Diagramm der Stichbildemittel und der Vorschubein-richtung;

Fig. 4

eine Darstellung der Situation beim Stickvorgang, wie er zum Zeitpunkt C aus Fig. 3 gegeben ist;

Fig. 5

eine Darstellung der Situation beim Stickvorgang, wie er zum Zeitpunkt D aus Fig. 3 gegeben ist;

Fig. 6

Eine Darstellung der Situation beim Stickvorgang, wie er beim erfin-dungsgemäßen Ausführungsbeispiel zum Zeitpunkt B aus Fig. 3 gegeben ist;

Fig. 7

eine Darstellung der Situation beim Stickvorgang, wie er beim erfin-dungsgemäßen Ausführungsbeispiel zum Zeitpunkt C aus Fig. 3 gegeben ist:

Fig. 8

eine Darstellung der Situation beim Stickvorgang, wie er beim erfin-dungsgemäßen Ausführungsbeispiel zum Zeitpunkt D aus Fig. 3 gegeben ist.

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

1

a partial view of a front area of an embroidery head with a lockstitch gripper;

2

An illustration of the situation during the embroidery process as it was at time B 3 given is;

3

a path-time diagram of the stitch-forming means and the feed device;

4

a representation of the situation during the embroidery process as it was at time C 3 given is;

figure 5

a representation of the situation during the embroidery process as it was at time D from 3 given is;

6

A representation of the situation during the embroidery process as it is in the embodiment according to the invention at time B 3 given is;

7

a representation of the situation during the embroidery process, as in the inventive embodiment at time C from 3 given is:

8

a representation of the situation during the embroidery process, as in the inventive embodiment at time D from 3 given is.

In 1 the front part 1 of a conventional embroidery head is shown in a sectional view, as in relation to its structural design in connection with the Invention can be applied. The front part has a lockstitch gripper 2, a table top 3 and a needle plate 4. The embroidery frame 5, which is freely movable in two axes and into which the embroidery base or the embroidery material is clamped, rests on the table top 3. The lockstitch gripper 2 is of conventional design and has a bobbin case carrier 6 for receiving a bobbin case 7 . In the bobbin case 7, the coil receiving the gripper supply is rotatably mounted. The double lockstitch gripper 2 is provided in the embroidery machine with an axis of rotation aligned parallel to the table top 3 or to the embroidery base.

The double lockstitch gripper 2 is assigned a needle bar 9 which carries a needle 8 and which interacts with the double lockstitch gripper 2 . The lockstitch gripper 2 and each needle 8 are components of stitch forming tools, each needle leading an embroidery thread, referred to below as the upper thread. The needle bars 9 are accommodated in a base frame 10 so that they can move vertically and are each driven in a manner known per se by a driver 11 which transmits the drive movement of the needle drive to the respective needle bar 9 . Also provided on the front part 1 of the embroidery head is a hold-down device 12 for each embroidery thread, which is arranged to be displaceable on the needle bar 9 and is driven by a driver 13 . Furthermore, on the front part 1 of the embroidery head, a thread lever 14 which is driven in a known manner and is pivotably mounted on an axis 15 which in turn is accommodated in the base frame 10 is arranged for each embroidery thread. Finally, for each of the upper threads, the embroidery head has a thread brake 16, known per se and adjustable in terms of its braking effect, which is fixedly attached to the front part 1.

The rear part of the embroidery head, not shown in detail, is firmly connected to the machine frame and carries the drives for the needle bar 9, the hold-down device 12 and the thread lever 14. The rear part of the embroidery head is also connected to the front part 1 via a straight guide, not shown in detail. so that this can be moved within a horizontal plane in the direction of alignment of the existing needle bars 9 above the lockstitch gripper 2, each a needle bar 9, a hold-down device 12 and a thread lever 14 are connected to the respective drive.

With the exception of the drive for the double lockstitch gripper 2, the aforementioned parts are driven by a main machine shaft (not shown) which performs a full, ie a 360° rotary movement per stitch formation period. Instead of mechanical synchronization with the machine main shaft, the aforementioned elements and parts could also be provided with separate drives that are electronically synchronized with one another. Such a coordinated, predetermined or predeterminable synchronization of the movements can be carried out in particular by the machine control. During, except for the solution according to the DE 10 2010 013 016 A1 , in the prior art the lockstitch gripper rotates at twice the speed, i.e. with n=2, in embroidery machines according to the invention the double lockstitch gripper 2 rotates with n>2, where n should be an integer other than zero. Accordingly, in the illustrated embodiment of the invention, a transmission with a transmission ratio of n=3 is provided between the machine main shaft and the lockstitch gripper 2 . Instead of a mechanical transmission, any other conceivable solution for a fixed or variable synchronization between the machine main shaft and the at least one lockstitch gripper 2 can be provided.

In the machine diagram 3 the kinematic relationships of the elements involved in stitch formation are shown for one stitch formation cycle or machine cycle, ie the stitch formation period mentioned at the outset. at 2 is the perspective, pictorial transfer of the abstract situation at time B from the machine diagram according to 3 .

To explain the invention is first on 2 received, in which a moment of the stitch formation process and several stitches of a satin stitch seam, which is made according to the method of DE 10 2010 013 016 A1 was generated are shown. This representation refers to time B in the diagram 3 . In 2 the needle 8 is in the region of a top dead center of its oscillating movement. The upper thread 25 she guides is connected by a immediately before the in 2 shown point in time generated puncture hole in the embroidery base 23 in the form of an upper thread loop and is located essentially directly below the puncture hole or the puncture point of the needle 8. The lower thread 24 is out of the hook 2 and the hook spool and passed through the upper thread loop 26. This entanglement is caused by the process of grasping the upper thread 25 by the rotating gripper 2 and inserting the lower thread 24 into the upper thread loop 26 widened by the gripper 2 and which is the basis of the double lockstitch principle. While the needle 8 moves out of the puncture hole 20, the thread lever 14 takes the upper thread with it during its pivoting movement, thereby reducing the upper thread loop 26 and laying it against the underside of the embroidery base 23.

The lower thread 24, which was thereby placed on the underside of the embroidery base 23, runs from the puncture hole 20 to the puncture hole 21 created immediately beforehand. At the puncture hole 21 of the previously created puncture point, the lower thread is also pulled through the upper thread loop 27 assigned to this puncture point, with the upper thread loop 27 is also arranged directly below the puncture hole 21. The length of the lower thread section between the two puncture points 20, 21 offset from one another in the longitudinal direction of the zigzag seam thus corresponds at least approximately to the distance between the two puncture points 20, 21 from one another or to the stitch length S At the beginning of the seam, the upper and lower threads 24, 25 run on the underside of the embroidery base in principle in the same way. On the upper side of the embroidery base 23, i.e. on the side of the embroidery base 23 facing away from the hook 2, the upper thread 25 runs approximately parallel to the lower thread 24, with approximately the same length as the lower thread 24 and also from each puncture point to the next in the stitch sequence puncture site.

In the situation of 2 the needle 2 and the fabric hold-down device 3 have almost reached the upper apex of their vertical movement perpendicular to the throat plate 1, what in the diagram of 3 represented by the graphs "Needle tip over needle plate" and "Fabric hold-down device over needle plate" at point in time B. the inside 2 Embroidered base 23 shown as a section, which is shown in 2 not shown embroidery frame is clamped, which in turn is displaceable by its own drive in two axes parallel to the surface of the needle plate 4, after the needle 8 and the hold-down device 12 have left it in the vertical direction, has practically not yet moved. The amount of thread feed after 2 is at said time B at zero. Therefore, below the embroidery base 23, the upper thread 25 forms only the comparatively small upper thread loop 26. This is the remainder of the previously considerably larger loop, which was guided around the non-rotating bobbin case carrier 6 of the rotary hook 2 shown in partial view. The stretched length of this large needle thread loop corresponds to the maximum value of the thread requirement 3 . Due to the continuously falling thread feed shortly before time B, the formerly large loop 26 (not shown) of the upper thread 25 was reduced to the said remainder by the upward pivoting movement of the thread lever 14 . In the 2 The small loop 26 of the upper thread 25 shown loops around the lower thread 24, which emerges approximately vertically from the bobbin case carrier and thereby passes through the throat plate bore 29 of the throat plate 4 and fixes the lower thread 24 on the underside of the embroidery base 23 directly at the last puncture point 20 of the needle 8 in the embroidery base 23. The upper thread 25, by the action of the in 1 illustrated needle thread brake 16, and the lower thread 24, because of the integrated in the bobbin case carrier 6, not shown lower thread brake, each under a defined tension.

4 gives the situation at time C in the machine diagram 3 again. The most important difference at the point in time B in the diagram is that the embroidery base 23 has started to move as a result of its drive. It moves over the surface of the throat plate 4 in the opposite direction to the next needle entry point of the zigzag seam and has already covered a significant distance of the stitch length. The thread feed (upper thread) is still at zero during this. Therefore the small loop 26 ( 2 ), which here through the section of the embroidery base 23 is covered, remains unchanged and continues to fix the lower thread 24 on the underside of the embroidery base 23.

The loop 26 moves further and further away from the needle plate bore 29 with the movement of the embroidery base 23. Between the small loop 26 and the upper edge of the needle plate bore 29, an additional thread requirement arises in the lower thread 24, the one in which the lower thread 24 over the upper edge the needle plate bore 29 slides, is compensated against the resistance of the lower thread brake from the supply of the hook spool 7.

In figure 5 is the time point D in the diagram 3 illustrated. Here the relative movement between the stick base 23 and the throat plate bore 29 has come to an end. The new puncture position of the needle 8 above the embroidery base 23 has been reached. The length of the part of the lower thread 24 that now lies between the upper edge of the throat plate bore 29 and the small loop 26 above the throat plate 4 practically corresponds to the distance that the embroidery base 23 has covered with its movement, i.e. the stitch length or the Lower thread consumption of the stitch. During the last phase of the movement of the embroidery base 23, the needle 8 and the fabric hold-down device 12 were progressively lowered vertically over the embroidery base 4. Therefore, the upper thread 25 comes between its anchoring point, on the top of the embroidery base 23 and the opening 18 in the fabric hold-down device 12, increasingly in an inclined position, which requires a slowly but steadily increasing thread requirement in the upper thread 5. This need is taken into account with the thread application, which begins slowly before time D, as can be seen from the diagram in FIG 3 emerges. The small loop 26 remains unchanged, as does its importance for the lengthening of the lower thread 24 during the complete movement phase of the embroidery base 23.

The reason for the lower thread consumption described thus lies in the kinematic interaction of the movement of the embroidery base with the thread feed during the movement of the embroidery base, as is shown in DE 10 2010 013 016 A1 is described, the disclosure content of which is hereby fully incorporated by reference.

The thread feed is a function of the pivoting position of the thread lever 14 about its pivot axis 15, in which the course of the upper thread 25 on its way from the thread brake 16 ( 1 ) to the embroidery base 23, depending on the pivoting position of the thread lever 14, is caused to detours of different lengths. In its uppermost pivoting position, this detour is greatest and the yarn feed is zero. The maximum thread feed occurs when the thread lever 14 is in the lowest pivoting position, with the slightest detour in the upper thread 25. The thread feed works in relation to the upper thread 25 in the same way as a buffer memory, from which the drive kinematics of the thread lever 14 for the needs of the stitch formation organs, i.e. the Needle 8 and especially the looper 2, temporarily additional upper thread 25 is provided with an excess. At the points in time D via A to B in the machine diagram 3 the thread feed enables the stitch formation, but does not influence it. At point in time B, the needle thread 25 borrowed from the thread dispenser is completely returned to the buffer. The thread feed is back to zero. Shortly before, however, the consumption of upper thread from the last movement of the stick floor was compensated for by the upward pivoting movement of the thread lever 14 against the resistance of the upper thread brake 16 from the supply spool of upper thread 25 . The state after 2 has arisen. Between times B and D, the drive kinematics of the thread lever 14, which is responsible for the thread feed, ensures that the small loop 26 of the upper thread remains unchanged during this period, see 4 and figure 5 .

So far it has been described why, according to the prior art, the embroidery product of a gripper embroidery machine, the rotary gripper 2 of which performs more than two revolutions per stitch cycle, when performing satin stitches, the lower thread length per stitch necessarily corresponds to the length of the stitch. This can be very useful, for example if the view of the lower thread is to be covered by the upper thread when the embroidery base is translucent. However, this is not the norm, which is why the high lower thread consumption is seen as a disadvantage in most applications.

The solution according to the invention is based on the previous knowledge that in gripper embroidery machines only their kinematics determines the amount of lower thread in satin or zigzag stitches and not the ratio between upper and lower thread tension, as will be described below.

6 shows the situation in the machine diagram based on the work result achieved according to the invention 3 at time B, ie at the time when the yarn feed reaches the value zero. This representation is in close analogy to 2 , whose description therefore in principle also applies 6 applies and is not repeated.

In 7 are the conditions in the machine diagram 3 shown at point in time C, ie at a point in time after the value zero of the yarn feed has been reached. 7 shows in principle the same process step as shown in 4 . As related to 4 was described, is taken between the times B and C by the movement of the embroidery base 4 lower thread from the bobbin supply of the lockstitch rotary hook 2.

In contrast to the previously known method sequence, in the exemplary embodiment of the method according to the invention and a device according to the invention discussed here, the effect is that from time C in 3 the thread brake 16 of the upper thread 25 is open. This happens, triggered by the machine control, by an electric actuator (not shown in detail), which acts on the thread brake and releases it. In principle, any previously known actuator is suitable as an actuator with which the embroidery machine is able to rotate according to the usual speeds of embroidery machines Machine shaft to open the thread brake 16 and then to close it again. Such an actuator can be a lifting magnet, a piezo element or a pneumatic element, for example, in a non-exhaustive list.

Due to the fact that from this point in the stitch formation period the thread tension previously applied by the thread brake 16 to the upper thread 25 is missing due to the removal of the latter small upper thread loop 26 on the underside of the embroidery base 4 is now lifted. Instead, the hitherto small upper thread loop 26 is now enlarged again as a result of the lower or no thread tension in the upper thread. Together with the thread tension and thread force present in the lower thread 24, this also pulls the upper thread 25 to the underside of the embroidery base 23.

8 shows how figure 5 the situation at time D in the machine diagram 3 . At this point in time D, the movement of the embroidery base 23 has ended. On its way between the times C and D, the formerly small upper thread loop 26 is enlarged to the now again larger upper thread loop 26a by the upper thread 25 being pulled onto the underside of the embroidery base 23 by the lower thread 24, which is still being braked. The piece of thread or thread section 24a of the lower thread 24 is significantly smaller than the stitch length S and represents the lower thread consumption between the last two stitches. However, the course of the upper thread 24 and the lower thread 24 on the embroidery material, separated by the embroidery backing 23, is no longer congruent , in contrast to the situation after 2 .

The lower thread length can be specifically influenced via the machine control. This influence can mainly be caused by variation of the in 3 be carried out at a specific point in time at the point in time C entered, for example. Depending on what point in time C is between points B and D in 3 the upper thread brake has been opened, the length of the upper thread pulled to the underside and thus the lower thread length required per stitch can be varied. If the opening happens earlier, the proportion of lower thread is lower and vice versa. Since the thread feed can assume the value zero or almost zero not only at a single point in time but during a time interval of the stitch formation period, point in time B can also be selected as a possible point in time from this interval.

The type of embroidery to be produced can now decide whether, for example, with a translucent embroidery base 23, the upper and lower threads should run congruently to one another - high lower thread consumption - or, if this is not necessary, what predetermined fraction of the stitch length the corresponding lower thread consumption has - low lower thread consumption . This option is not available on looper embroidery machines with a double rotating looper.

The overall sequence of stitch formation requires that the upper thread brake 16 is closed again. This is advantageously done at time A, ie at a time when the needle point has just passed through its lowest point and begins to move back towards the underside of the embroidery base and then out of the puncture point. In the preferred exemplary embodiment, this point in time A is thus in the subsequent stitch formation period, which follows the stitch formation period in which the thread brake was opened. <b>Reference List</b> 1 front part 21 puncture hole 2 Lockstitch Looper 23 embroidery ground 3 tabletop 24 bobbin thread 4 needle plate 24a piece of thread 5 embroidery hoop 25 upper thread 6 bobbin case carrier 26 upper thread loop 7 bobbin case 26a upper thread loop 8th needle 27 upper thread loop 9 needle bar 28 10 gripper frame 29 throat plate drilling 11 driver S stitch length 12 hold-down 13 driver 14 take-up lever 15 axis 16 yarn brake 18 Breakthrough of 12 20 puncture hole

Claims (14)

1. An embroidery machine comprising at least one embroidery head provided with stitch-forming tools for forming stitches of an embroidery seam, said stitch-forming tools comprising a needle (8) provided for guiding an upper thread (25) and a looper (2) cooperating with said needle (8) for forming embroidery seams the hook (2) is provided with a receptacle for arranging a supply of bobbin thread (24) and rotates more than twice about its axis of rotation during a stitch-forming cycle, and is provided with movement means for performing relative feed movements between the needle (8) and an embroidery material. characterized by means of the embroidery machine for the adjustable variation of at least one parameter of the stitch formation process, by means of which different values of the parameter result at least during one stitch formation period, preferably in each case during a plurality of stitch formation periods, of the embroidery seam, in order, in relation to the position and length of the lower (24) and upper (25) thread

   of a stitch of the embroidery seam on the upper side and lower side of the embroidery material to produce a non-coincident arrangement of upper thread (25) and bobbin thread (24) on the embroidery material, as a result of which a stitch length (S) provided between two successive insertion points (20, 21) of the needle (8) for forming an embroidery seam and a bobbin thread length assigned to this stitch length (S)

   is at most 80% of the stitch length, preferably at most 65% and particularly preferably less than or equal to half the stitch length (S).
2. Embroidery machine according to claim 1, characterized in that said means for adjustably varying at least one parameter of the stitch formation process comprise means for variably adjusting a ratio between upper-thread- and bobbin thread tension at least during one point in time of the stitch forming period.
3. An embroidery machine according to at least one of the preceding claims, characterized by means for reducing the upper thread tension comprising a thread brake (16) of the upper thread (25) adjustable such that, at each of a plurality of stitching image periods of the embroidery seam, the upper thread tension can be temporarily reduced compared to the lower thread tension.
4. Embroidery machine according to at least one of the preceding claims, characterized in that during at least one, preferably at each of a plurality of stitch pattern periods, each preferably comprising a
   When the needle (8) starts to penetrate the needle plate (4), the embroidery seam, both a reduction and an increase of the at least one parameter can be made.
5. Embroidery machine according to at least one of the preceding claims, characterized by means for reducing a thread tension of the upper thread of the embroidery machine, at least in relation to a thread tension of the lower thread, at a predeterminable or predetermined time of the stitch pattern cycle.
6. Embroidery machine according to claim 5, characterized in that the means for reducing the thread tension comprise a controllable thread brake (16), whose braking effect can be controlled by the machine control system during a stitch forming cycle.
7. Embroidery machine according to claim 5 or 6, characterized in that a point in time of a switching operation, which can be carried out by the machine control, for reducing the thread tension, and preferably also a duration, during which the thread tension is reduced can be set.
8. Embroidery machine according to any one of the preceding claims 5 to 7, characterized in that in a stitch pattern cycle the machine control reduces the thread tension of the upper thread (25) after the thread feed has reached its maximum value and during or after the thread feed has reached a The stitch pattern cycle preferably starts when the needle (8) enters the needle plate (4).
9. Embroidery machine according to any one of the preceding claims 5 to 8, characterized in that the reduction of the thread tension between time points occurs and is maintained for the duration of these time points, in which the thread feed in a stitch pattern cycle has a value of zero and a time point of a subsequent stitch pattern cycle, at which the needle (8) has passed through its lower low point.
10. Embroidery machine according to one of the preceding claims, characterized in that
    characterized in that the reduction of the upper thread tension takes place at a time when an embroidery frame (5) provided for receiving an embroidery base (23) moves relative to the needle (8).
11. Embroidery method for forming embroidery seams, in particular satin stitch embroidery seams, with a lock stitch embroidery machine, in which by means of a

    oscillating back and forth and guiding an upper thread (25) into the embroidery material, which can be moved in a zigzag manner at least in one plane relative to the needle (8) by means of moving means, by penetration of the needle (8) into the embroidery material below the point of penetration (20, 21) in the embroidery material, an upper thread loop (26, 26a, 27) is formed, and this loop (26, 26a, 27) is looped back into the embroidery material by means of a needle (8) guided by the needle (8) during the penetration (20, 21).

    stitch-forming period at least twice rotating looper (2) is detected and a bobbin thread (24) stored in the looper (2) is guided through the loop (26, 26a, 27), characterized in that at least during one, preferably during each of a plurality, of the stitch-forming periods of the embroidery seam, different values of a loop (26, 26a, 27) connected to the lockstitch embroidery machine are detected and the loop (26, 26a, 27) is guided through the loop (26, 26a, 27).

    of the stitch formation process can be adjusted in order to produce a non-coincident arrangement of the upper (25) and lower (24) threads on the embroidery material with respect to the position and length of the lower (24) and upper (25) threads of a stitch of the embroidery seam on the upper side and lower side of the embroidery material, as a result of which a non-coincident arrangement of the upper (25) and lower (24) threads on the embroidery material is produced between two successive stitching points. (20, 21) of the needle (8) for forming an embroidery seam and a bobbin thread length associated with this stitch length (S) of at most 80%.

    of the stitch length, preferably at most 65% and particularly preferably less than or equal to half the stitch length (S).
12. The embroidery method according to claim 11, characterized in that the at least one parameter after the upper thread loop (26, 26a, 27) is detected by the hook (2) and after an interlacing of the upper thread loop (26, 26a, 27) with the lower thread (24) is changed.
13. Embroidery method according to claim 11 or 12, characterized in that after the upper thread loop (26, 26a, 27) has been gripped by the looper (2) and the upper thread loop (26, 26a, 27) has been entangled with the lower thread (24) the thread tension of the upper thread (25) is reduced.
14. An embroidery material in which embroidery seams are formed from an upper thread (25) and a bobbin thread (24) using the embroidery method according to claim 12, characterized by the embroidery seam having an upper thread loop (26, 26a, 27) of the embroidery seam disposed below the embroidery material through which the

    lower thread (24) and which is arranged between two successive insertion points of the needle (8) in the embroidery material, a non-conforming arrangement of upper thread (25) and lower thread (24) being produced on the embroidery material with respect to the position and length of the lower thread (24) and upper thread (25) of a stitch of the embroidery seam on the upper side and underside of the embroidery material, and

    wherein the bobbin thread runs between two successive stitching points in the stitching sequence of the needle in the embroidery base along a path which is shorter than the distance between the two successive stitching points.

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