EP2550387B1 - Two-thread lock stitch sewing machine or multi-head sewing machine with rotating shuttle - Google Patents

Description

The invention relates to single-head or multi-head embroidery machines with stitch imaging tools which are each formed by a needle cooperating with a lockstitch gripper for producing stitches, and have a feed device for achieving relative movements between the embroidery bottom and the stitch pattern tools.

The lockstitch gripper, which is predominantly used here, is a revolving gripper which executes two full revolutions per stitching period, as it is used a hundred thousandfold in sewing machines as a "standard gripper" and has also proven itself very well here. This lockstitch gripper requires a certain size of the thread tension for the stitch formation, in particular for the Sticheinzug.

Due to the different tasks of a sewn seam ("sewing seam") on the one hand and an embroidered seam ("stitching") on the other hand, a significant difference in the requirements for a sewing machine or an embroidery machine is justified. While the sewing seam essentially represents a connecting or fastening seam with which usually two or more parts are firmly connected to each other, the embroidered seam represents an embroidery (ornamental seam) applied to the embroidery floor, which has no forces to transmit.

The strength of the fastening seam is thereby achieved that the fallen from the gripper thread loop is pulled by the thread lever with relatively large force in the direction of the top of the fabric, so that the knotting of needle and hook thread comes to rest in the middle to be sewn fabric layers. Accordingly, the thread force of the looper thread is to be measured.

Completely different are the conditions in the formation of an embroidered seam. Since here the needle thread (= embroidery thread) to achieve decorative effects on the top of the embroidery material should rest only clean, the thread tension is kept as low as possible during the embroidery process, that the embroidery thread on the embroidery floor positionally is sufficiently secured, but still no loose thread portions arise, and the knot between needle and looper thread always comes to rest on the underside of the embroidery base.

For this reason, a much lower tension of the needle thread is sought for sewing machines compared to sewing machines.

Since in the acquisition of per stitch pattern two turns exporting lockstitch gripper in the embroidery machine whose kinematics has not been adjusted accordingly, even with the current embroidery machines, the advancing movement for the embroidery floor already at a time at which the stitching process is not yet complete. This is very disadvantageous in so far as this has shifted the embroidery bottom at the time of the beginning of the thread feed through the thread lever by a considerable amount compared to its position during the insertion of the needle into the embroidery floor. As a result, the leg of the thread loop leading from the stitch hole to the thread supply experiences an additional deflection both at its exit from the stitch hole and immediately after it has passed through the embroidery base. The two deflections cause when pulling the thread through the thread lever an additional resistance that forcibly leads to the undesirable increase in the minimum size of the thread tension.

This situation affects embroidery machines as a whole in so far, particularly disadvantageous, as they work against sewing machines generally both with much larger stitch lengths, as well as extending in different directions feed directions.

From the US 2008/0216722 A1 For example, there is known a zig-zag sewing machine provided with a needle feed for placing a needle of a sewing machine in right and left needle positions. Due to the needle transport made during a seam-forming operation, synchronization difficulties between the gripper of the sewing machine and its needle result in its two positions. The US 2008/0216722 A1 suggests to vary the rotational speed of the transmission of the gripper to correct for the synchronization deviations resulting in different left / right positions of the needle.

In the DE 197 51 083 A1 a sewing machine is described with a driven by a main shaft needle bar and with a mechanically independent of the main shaft drive motor which drives a looper of the sewing machine. The drive of the main shaft and the drive motor of the loop taker are synchronized with each other, but are not mechanically connected to each other in operative connection. Due to certain conditions of use, such sewing machines may experience synchronization discrepancies. The the DE 197 51 083 A1 The underlying invention is intended to prevent this synchronization discrepancy. For this purpose, sensors are provided with which state information of the main shaft, the sewing motor, the loop taker and the loop taker drive motor are detected. With a synchronization control unit, a speed correction is determined on the basis of the determined state information, by which a synchronization of the main shaft and the loop taker can be achieved.

Also in the US 4,690,081 a sewing machine is disclosed in which a separate drive is provided for a plurality of different driven components of the sewing machine, for example needle bar, gripper, presser foot, transport means or thread tensioning device. With each of the separate drives each drive movement should be generated, which is independent of drive movements of the other drives. As a result, a substantial adjustability of the sewing machine to different applications should be possible, for example, to be able to set the sewing machine to different materials to be processed, number of sewing material layers to be sewn together and the like.

The invention is therefore based on the object to provide a solution that makes it possible to keep the minimum thread tension in the desired much lower range in embroidery machines with lockstitch circular grippers.

The invention is based on the recognition that at lockstitch gripper embroidery machines, the stitch formation on the one hand and the feed movement of the embroidery on the other hand at least partially overlap such that the advancing movement of the embroidery already begins when the stitching is not complete is completed, ie the needle thread is not completely retracted by the thread lever.

To solve the above problem, it is proposed to avoid the temporal overlap of stitch formation with the advancing movement of the embroidery base, to let the lockstitch gripper rotate at a speed that corresponds to n times the speed of the main shaft of the embroidery machine, wherein <"n" a whole Number is greater than the number "2">.

Because the lockstitch gripper revolves with <"n" equal to 3 ">, for example, the stitch formation-corresponding to the greater angular speed of the lockstitch gripper resulting from the main machine shaft-is earlier than at <" n The time window in which the stitch formation and the feed movement of the embroidery base are active at the same time is thus minimized.

Since per double stitching lockstitch grippers produce absolutely satisfactory results in the area of the so-called high-speed stitches, it is obvious that the increase in the speed of the lockstitch gripper according to the invention negatively affects neither the quality of the seams produced nor the mechanical durability.

While in the above-described solution the lockstitch gripper rotates at a constant <"n-fold"> speed of the machine main shaft, a further solution of the object underlying the invention is to see the lockstitch gripper periodically with respect to the main shaft of the machine circulating variable angular velocity, wherein the angular velocity of the lockstitch gripper during its working revolutions has the larger and during its idle revolutions the other hand, smaller value.

The invention is explained below with reference to an embodiment with corresponding diagrams.

• Fig. 1 : Einen Teilschnitt des vorderen Bereiches eines üblichen Stickkopfes mit einem Doppelsteppstich-Greifer;
• Fig. 2 : Ein Weg / Zeit Diagramm der Bewegungen der Stichbildewerkzeuge und der Vorschubeinrichtung nach dem Stand der Technik, mit sich zeitweise überlappenden Zeitfenstern für die Stichbildung und die Vorschubbewegung;
• Fig. 3 : Ein Weg / Zeit Diagramm der Bewegungen der Stichbildewerkzeuge und der Vorschubeinrichtung gemäß der Erfindung;
• Fig. 4 : Die Situation der Fadenschlinge beim Durchgang an der Verdrehstütze (Anhaltestück) des Spulenkapselträgers des Doppelsteppstich-Greifers entsprechend dem Zeitfenster 31 in Figur 2- gemäß dem Stand der Technik;
• Fig. 5 : Wie Fig 4, jedoch dargestellt für eine andere Richtung der Vorschubbewegung des Stickrahmens.
• Fig. 6 : Die Situation der Fadenschlinge beim Durchgang an der Verdrehstütze (Anhaltestück) des Spulenkapselträgers des Doppelsteppstich-Greifers - entsprechend dem Zeitfenster 31 in Figur 3 - gemäß der Erfindung.

It shows:

• Fig. 1 : A partial section of the front portion of a conventional embroidery head with a lockstitch gripper;
• Fig. 2 : A path / time diagram of the movements of the stitch pattern tools and the advancing device according to the prior art, with temporally overlapping time windows for the stitch formation and the advancing movement;
• Fig. 3 : A path / time diagram of the movements of the stitching tools and the feed device according to the invention;
• Fig. 4 : The situation of the thread loop when passing at the twist support (stopper piece) of the bobbin case carrier of the lockstitch rapier corresponding to the time window 31 in FIG FIG. 2 - According to the prior art;
• Fig. 5 : How Fig. 4 , but shown for a different direction of the advancing movement of the hoop.
• Fig. 6 : The situation of the thread loop when passing the twist support (stopper piece) of the bobbin case carrier of the lockstitch rapier - corresponding to the time window 31 in FIG FIG. 3 - According to the invention.

In Fig. 1 the front part 1 of a conventional embroidery head is shown in sectional view, which has a lockstitch gripper 2, a table top 3, and a throat plate 4. On the table top 3 is the freely movable in two axes embroidery frame 5, in which the embroidery bottom is clamped. 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 bobbin thread supply receiving coil is rotatably mounted.

The cooperating with the lockstitch gripper 2 and a needle 8-bearing needle bar 9 is vertical in a base frame 10 movably received and is driven in a conventional manner by a driver 11, which transmits the drive movement of the needle drive to the needle bar 9. At the front part 1 of the embroidery head, a hold-down 12 is further provided per embroidery thread, which is arranged displaceably on the needle bar 9 and is driven by a driver 13. Furthermore, on the front part 1 of the embroidery head per embroidery thread in a known manner driven thread lever 14 is arranged, which is pivotally mounted on an axis 15, which in turn is received in the base frame 10. Finally, the embroidery head in a known manner adjustable yarn brake 16 which is fixedly attached to the front part 1.

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

The drive of the aforementioned parts is done with the exception of the drive of lockstitch gripper 2 by a machine main shaft, not shown, which performs a full, ie a 360 ° comprehensive rotational movement per stitch forming period. While in the prior art the lockstitch gripper 2 rotates at twice the speed, that is with <"n = 2">, according to the invention the lockstitch gripper 2 runs with <"n = an integer greater than the number" 2 > around.
Accordingly, in the illustrated embodiment of the invention between the machine main shaft and the lockstitch gripper 2, a transmission gear with a transmission ratio "n = 3" is provided.

To understand the invention is first on Fig. 2 which shows the typical movement diagram of the known kinematic interaction of the needle 8 with a lockstitch 2, which rotates twice according to the prior art, as well as the feed device and the hold-down device 12, not shown, over one revolution of the machine main shaft.

The graph 17 illustrates the movement of the tip of the needle 8 to the surface of the needle plate. The needle tip emerges at the time 18 through the tap hole below the surface of the throat plate 4 and rises again at time 19 on this.

The graph 20 illustrates the lifting movement and the distance of the underside of the blank holder 12 on the stitch plate 4 from.

The graph 21 indicates the progress of the embroidery frame movement relative to the last needle drop point at the time point 18 on the embroidery bottom.

The start of the embroidery frame movement takes place at the time 22 and thus shortly after the time 19, which corresponds to the time of exit of the needle 8 from the throat plate 4. The end of the embroidery frame movement coincides with the end of the diagram.
All values of this motion function are scaled linearly with the variable stitch length (= distance from the last insertion point 18 to the future needle entry point) as a constant factor.

The graph 23 represents the thread requirement of the needle 8, beginning at time 24, when its eye descends below the embroidery bottom surface. At time 25, the top of the lockstitch gripper 2 enters the needle thread loop formed by the needle 8, whereby the lockstitch gripper 2 takes control of the needle thread. Its yarn requirement is represented by the graph 26. The tip of the lockstitch gripper 2 first expands the thread loop presented to it by the needle 8 and then guides it around the bobbin case 7 arranged inside the lockstitch gripper 2. Thereafter, the thread requirement of the lockstitch gripper 2 decreases again until the gripper closes Needle thread at time 27 completely releases again. The lockstitch gripper 2 is therefore only in the time between the points 25 and 27 in contact with the needle thread. This corresponds to a maximum of 180 ° of the 360 ° stitch pattern period, the rest of the time, the lockstitch gripper 2 moves empty, d. H. the lockstitch gripper 2 comes again in contact with the needle thread in the next stitch forming period next.

The thread requirement of needle 8 and lockstitch gripper 2 is opposed by the threading according to graph 28. It is a function of the pivotal position of the thread lever 14 about its axis 15. The threading according to the graph 28 points opposite to the Thread requirement (23, 26) on a surplus. This serves as a reserve, from which the stitch length-dependent thread consumption is taken from the previous stitch cycle.

The threading 28 is reduced by the amount of this thread consumption, so that the effective threading with the graph 29 is identical. The said thread consumption is only deducted in the time range between the time 30 and thread lever OT by the thread lever 14 from the needle thread stock while the system thread length (= entire length of the needle thread between the thread brake 14 to the throat plate 4, at the highest pivot position of the thread lever 14 again compensated ,

A difference to the diagram of a sewing machine relates to the length of the time window for the movement of the embroidery frame. For the sewing machine this is approx. 120 °. In the gripper embroidery machine but 180 ° and more. The beginning of the embroidery frame movement at the time 22, therefore, according to the prior art, according to temporally advanced. Although this is a necessary concession to the numerically controlled embroidery frame drive, which is independent of the embroidery mechanism, it leads to a not inconsiderable embroidery disadvantage with regard to the size of the required thread tension.

The temporal advancing the beginning of the advancing movement of the embroidery frame in the area well before the time of completion of the thread take-up by the thread lever 14 to complete the initiated stitch causes the embroidery floor is moved relative to the stitch plate 4 before the conclusion of the thread take-up.

In FIG. 4 it can be seen that to secure the bobbin case 6 against rotation on this a radially directed groove 34 is provided, into which a stationary stop piece 35 engages with a nose, so that the needle thread between the stop piece 35 and the lateral boundary surface 36 of the groove 34 are moved therethrough can.
If, with stitch lengths greater than 2 mm, the last insertion point of the needle 8 is displaced more than one millimeter to the middle of the stitch hole by the embroidery bottom movement according to graph 21 in the time domain 31, two deflections 32, 33 (FIG. Fig. 4 ) of the needle thread on the way between the thread lever 14, the groove 34 and the stop piece 35. The directed in the needle thread above the embroidery base to the thread lever 14 towards thread force F1 is first reduced at the deflection 32 and then again at the deflection 33 in a total of 2 steps by the thread friction. What remains is the force F2. This is the force required to open the thread passage between the stopper piece 35 and the lateral boundary surface 36 of the groove 34.

The magnitude of the force F2 is given by the stitch formation process and therefore can not be changed. So that this again reaches the value specified by the system, the thread force F1 must be increased even with favorable material pairings with a factor "K" of approx. 2.5. In unfavorable material pairings (cotton thread / embroidery bottom of cotton), this factor "K" tends to the value of 4. The thus increased thread force F1 corresponds to the minimum retention force of the thread brake 16 when thread feeding through the thread lever 14th

In Fig. 5 the conditions for the time window 31 are shown, in which the thread lever 14 attracts the thread loop and the thread passage between the nose of the stop piece 35 and the lateral boundary surface 36 of the groove 34 opens, wherein the advancing movement of the embroidery base against the advancing movement in Fig. 4 is reversed and in the direction of the arrow in Fig. 5 he follows. This corresponds approximately to the situation in which the so-called loop stitches occur during sewing or embroidering. In this case, the needle thread is devoured not only with the looper thread 37, but also with itself. In the sewing machine, this transport direction and situation hardly occurs.

However, in the case of the hook-and-loop embroidery machine, it arises regularly. Due to the more intensive wrapping at the Fadenumlenkstelle 32, the factor "K" increases further. After the needle thread loop has passed the thread passage, the needle thread tension drops to almost zero. The thread lever 14 further reduces the needle thread loop until it is completely minimized at the point 30. On the way there, the needle thread part 38, which was previously lying flat on the embroidery base, is built up by friction of the needle thread on the knot 39 with itself, to form a thread loop 40 which rises above the embroidery bottom. This must be retracted in the time range 30 to thread take-up (TDC). This works the better the steeper the needle thread thread part 41 strives for the needle eye and thereby leaves the surface of the embroidery base. This steepness decreases with the distance of the embankment transport (at the point of view of the graphene 21, that is already 75% of the stitch length), according to trigonometric laws. Depending on the coefficient of friction the needle thread used is the safe collection of the thread loop 40 only up to a corresponding maximum stitch length possible.

As from the description of the FIGS. 4 and 5 As can be seen, the circumstances that increase the necessary thread tension are due to the fact that the thread passage between the stop piece 35 and the lateral boundary surface 36 of the groove 34 does not occur until the middle of the current, already advanced feed movement of the embroidery base. This is the consequence of the temporal overlap of the activities of the gripper or the stitch formation with those of the embankment transport or the feed device.

Thus, it is obvious that the advancement of the start of the advancing movement of the embroidery frame into the time range of the pulling up of the needle thread by the thread lever 14, leads to an unavoidable increase in the thread tension. This is exactly what is undesirable for embroidery machines.

This in Fig. 3 According to the invention shown diagram of the movement of the stitch pattern tools corresponds with the exception of the movement of the lockstitch gripper 2 and the dependent course of the thread requirement and the thread release graph 26, 28 and 29 the diagram Fig. 2 ,

Due to the fact that the lockstitch gripper revolves with <"n" equal to 3 ">, for example, the stitching takes place earlier than in the case of <" n-based on the angle of rotation returned by the machine main shaft, in accordance with the resulting greater angular velocity of the lockstitch gripper This means that the release of the thread loop by the lockstitch gripper 2 -related to the rotation angle of the machine main shaft- occurs earlier than with the double-circumference lockstitch gripper, and thus the loop release the lockstitch gripper marking time 27 relative to its position in the diagram according to Fig. 2 in the diagram according to Fig. 3 is shifted to the left.

Thus, the movement of the thread lever 14 for the insertion of the formed entanglement of needle and looper thread-related to the rotation angle of the machine main shaft-use at a corresponding earlier time, so that the thread lever 14 reaches the top dead center (TDC) of its trajectory accordingly earlier, and thus the stitch formation - related to the rotation angle of the machine main shaft - completed earlier accordingly. Stitch formation and feed are now temporally unbound. The result is in Fig. 6 which shows the situation of the thread loop just before the thread lever (OT) when the rest of the thread loop passes through the thread passage between the stop piece 35 and the lateral boundary surface 36 of the groove 34. The case of the thread to be overcome resistance represents the systemic minimum thread force (= voltage) when using a rotary gripper.

In comparison with the FIGS. 4 and 5 are the respective Fadenumlenkstellen on the needle plate and in the embroidery ground and in the direction of the needle-striving leg of the thread loop no longer available. Accordingly, eliminates due to the omission of the thread deflections and the high friction forces and thus the previously required increase the thread retention force by a factor of 2.5 to 4 compared to the minimum thread force. Thus, the present invention allows the operation of a gripper embroidery machine with a thread tension, which is only slightly above the systemic minimum voltage for reasons of reliability of the stitch formation.

Claims (3)

1. Single-head or multi-head embroidery machine having stitch-forming tools which are each formed by a thread-guiding needle (8) which for forming stitches interacts with a double-lockstitch gripper (2), and an indexing installation for achieving relative movements between the embroidered goods and the stitch-forming tools, said relative movements being performed depending on the movements of the needle,
   characterized in that
   in order for a temporal overlap between the stitch-forming phase and the indexing movement of the stitched goods to be reduced, the double-lockstitch gripper (2) revolves at a rotation speed which corresponds to n-times the rotation speed of the main shaft, wherein "n" equals "3", and wherein a step-up gear unit having a gearing ratio of 1:3 is disposed between the main machine shaft and the double-lockstitch gripper (2).
2. Single-head or multi-head embroidery machine according to Claim 1, characterized in that an embroidery base of the single-head or multi-head embroidery machine, prior to a thread being completely drawn in, is movable in relation to the needle plate (4).
3. Single-head or multi-head embroidery machine according to Claim 1 or 2, characterized in that the double-lockstitch gripper (2) revolves at a constant rotation speed of 3 times the rotation speed of the main machine shaft.

Images