EP2714979B1 - Sewing machine having a thread clamp - Google Patents

Description

The invention relates to seam forming means for a sewing machine, comprising thread guide means, such as a needle and / or a gripper, for guiding at least one thread provided for seaming, and a thread clamping device which is provided with a thread clamp, in particular for the formation of a seam beginning a thread can be inserted, clamped and re-executed. Moreover, the invention relates to a sewing machine provided with such seaming means.

Sewing machines form using an oscillating reciprocating needle that guides a thread. Seams. Chain stitch sewing machines use only one thread. In lockstitch sewing machines, the needle feeds a needle thread which is entangled with a bobbin thread supply for a bobbin thread for the lockstitch seam. The coil is in this case in a revolving gripper, which performs relative to the coil rotational movement, detected at each stitch of the needle into the fabric the upper thread and devoured with the lower thread.

To form a complete seam, this entanglement must take place at each stitch. For a long time, however, in particular at the beginning of the seam, there is the problem that this entanglement is not produced reliably and reproducibly here. In particular, depending on different materials and thicknesses of the sewing material, it may take some stitches, especially at the seam beginning, until the gripper can devour the lower thread with the upper thread. For this reason, thread clamps have already become known, in which the lower thread is introduced for the beginning of the seam and subsequently torn out again during the seam formation. It is in such thread clamps to a clamping spring plate, which cooperates with a fixed counter-holder. Although these thread clamps often lead to an improvement in the formation of seams, they can still not guarantee sufficiently satisfactory start of seaming.

From the DE-C-197 22 395 is a sewing machine with a thread cutting device for cutting the sewing threads of lockstitch sewing known. The latter is provided in the region of the gripper and the thread cutting device with a thread clamp, which is formed from one end of a leaf spring and a portion of an arm of a thread catcher. The thread clamp is closed by the thread catcher achieved by its backward movement, an overlap with the leaf spring. To release the thread again, this is pulled out against the clamping force of the thread clamp from this.

From the US 3,173,393 , of the DE-A-23 44 720 , of the DE-A-43 31 746 and the US Pat. No. 3,599,588 In each case thread cutting devices emerge whose thread clamps are opened and closed at a given time. These solutions, too, can not guarantee a reliable seam beginning, especially with different sewing conditions.

The invention is therefore based on the object to provide a measure by which an improvement in terms of a reliable seam formation can be achieved even at the beginning of a sewing process.

This object is achieved with seam forming means of the type mentioned according to the invention by an operable thread clamp which can be closed by means of a controllable actuating means for clamping and / or by means of the actuating means can be opened. In the context of the invention it has been shown that can achieve a significantly safer seam formation with such controlled thread clamps. The inventively provided controlled thread clamp, which can be closed by actuation at a certain time of the sewing process for thread take-up or clamping, allows for each sewing reproducible conditions and thus a reliable seam formation, in particular between a lower and an upper thread. The inventively provided thread clamp should u can be opened at a certain time to release the thread, so that the thread is also released at a certain time. In this context, under "Open" not only an active Separating the clamping parts of the thread clamp are understood, whereby they are arranged at a distance from each other. As an "opening" in the context of the present invention, a removal or reduction of the applied to the thread clamp for clamping load on the actuating means can be understood. An opening in the context of the invention is therefore already at a release of the thread clamp by an actuating means, which is sufficient to be able to bring out the previously not removable from the thread clamp thread now in particular by the sewing process from the thread clamp.

By such a controlled thread clamp the thread can be taken safer and more reliable than before for a designated period in the thread clamp and held there and subsequently released at determinable times again. As a result, a tension can be reliably applied to the thread for the then proceeding section of the seam-forming process, which makes it easier to ensure reproducible conditions even at the beginning of seam formation, which is conducive to secure seam formation.

An inventive thread clamp can be provided with advantage as a lower thread clamp, as it can be used in connection with lockstitch sewing machines. However, it is within the scope of the invention underlying idea to form a thread clamp according to the characterizing part of claim 1 also for an upper thread of the needle, either for an upper thread of a lockstitch or a chain stitch sewing machine.

A suitable possible embodiment of an operable thread clamp of the seam-forming means according to the invention may comprise at least two clamping parts, of which at least one is designed to be movable. The two clamping parts can preferably be brought from a position (opening position) in which they are spaced apart in a position (closing and clamping position) in which the clamping parts are pressed against each other and vice versa. In the closing and clamping position, the clamping parts are able to clamp a thread between them. Preferably, at least one of the two movements, namely the transfer of the clamping parts in the opening position or the closing and clamping position is carried out by a driven movement which can be generated by a drive means. In principle, the opening movement and / or the closing movement may be a movement driven by a drive means. As opening position and positions of the two clamping parts come into consideration, in which they indeed abut against each other but can be opened by a brought up to the thread clamp thread.

As drive means of actuating means of the thread clamp come in a non-exhaustive list, for example, pneumatic actuators, electric drives or magnets into consideration. If only one of the two movements is designed as a driven movement, the respective other of the two movements can advantageously be configured as a return movement, which is generated against the action of a return element, such as a spring element, which is tensioned in one of the two movements.

In a further preferred embodiment of the invention, the time at which the thread clamp is closed for clamping the thread, by a control of the thread clamp predetermined or can be predeterminable by this. Advantageously, the opening time or an opening movement of an actuating means of the thread clamp provided for this purpose by the controller is predetermined or predeterminable. The controller may be a central sewing machine controller. This makes it particularly easy to coordinate the movements of the thread clamp on movements of other sewing machine components and coordinate with them. So it may be to achieve a high reliability of advantage if the thread is already inserted and clamped in the controlled thread clamp during the end of the previous sewing operation. This has the advantage that the thread is still in a sewing process and thus present for the clamping reproducible conditions. Only after the thread has been inserted into the clamp is the thread cut in the embodiment of the invention discussed here. For cutting the thread may advantageously be provided a thread cutting device, as for example in the DE 10 2008 030 620 B3 is described. The thread remains clamped even after completion of the sewing process in the thread clamp and is thereby arranged and clamped at the beginning of each subsequent sewing process in a particularly simple manner already in the targeted and predetermined operable thread clamp.

In addition, it is also possible in this way to determine particularly simple times at which the thread clamp is closed. The closing operation can be derived with advantage from a cutting operation performed by the thread cutting device. The clamping operation can thus be triggered in the cutting process, which is usually triggered by an operator of the sewing machine, by pressing a button or a switch. When the cutting process is triggered, the clamping operation of the thread is thus advantageously carried out first by receiving the thread in the thread clamp and only then by the cutting operation.

In the embodiment according to the invention, at least the time of opening or the release of the thread clamp - and thus the release of the thread - variably adjustable. Such adjustability may be advantageously provided depending on an adjustable predetermined number of first stitches of a sewing operation. This makes it possible to reduce the duration of the Clamping until the thread clamp is opened again and releases the thread to adjust to the given sewing conditions, such as the type of thread used, the material of the fabric and its thickness.

Further preferred embodiments of the invention will become apparent from the claims, the description and the drawings.

Fig. 1

eine Doppelsteppstichnähmaschine in einer teilweise geschnittenen Vorderansicht;

Fig. 2

eine Baugruppe "Greifervorrichtung" der Nähmaschine aus Fig. 1 in einer perspektivischen Darstellung;

Fig. 3

ein mögliches Beispiel für Teile einer Fadenschneideinrichtung;

Fig. 4

eine gesteuerte und betätigbare Fadenklemmeinrichtung der Nähmaschine in einer perspektivischen Darstellung, wobei die Fadenklemme nicht betätigt aber geschlossen ist;

Fig. 5

die Fadenklemmeinrichtung aus Fig. 4 mit einer nicht betätigten aber geöffneten Fadenklemme;

Fig. 6

die Baugruppe "Greifervorrichtung" mit gezeigtem Unterfaden nach dem Erfassen des Unterfadens durch einen Fadenfänger und nach Einführung des Unterfadens in die Fadenklemme, aber vor einem Schneiden des Unterfadens;

Fig. 7

die Situation aus Fig. 6, dargestellt aus einem anderen Blickwinkel;

Fig. 8

die Baugruppe "Greifervorrichtung" mit gezeigtem Unterfaden nach einem Schneiden des Unterfadens und mit Anordnung des Unterfadens in der Fadenklemme;

Fig. 9

die Situation aus Fig. 8, dargestellt aus einem anderen Blickwinkel.

The invention will be explained in more detail with reference to embodiments shown purely schematically in the figures, in which:

Fig. 1

a lockstitch sewing machine in a partially cut front view;

Fig. 2

a module "gripper device" of the sewing machine Fig. 1 in a perspective view;

Fig. 3

a possible example of parts of a thread cutting device;

Fig. 4

a controlled and operable thread clamping device of the sewing machine in a perspective view, wherein the thread clamp is not actuated but closed;

Fig. 5

the thread clamping device Fig. 4 with a non-actuated but open thread clamp;

Fig. 6

the assembly "gripper device" with shown lower thread after the detection of the lower thread through a thread catcher and after insertion of the lower thread in the thread clamp, but before cutting the lower thread;

Fig. 7

the situation Fig. 6 presented from a different angle;

Fig. 8

the assembly "gripper device" with shown lower thread after cutting the lower thread and with the lower thread in the thread clamp;

Fig. 9

the situation Fig. 8 , presented from a different angle.

In Fig. 1 an example of a designed as a lockstitch sewing machine 1 is shown in a highly schematic manner, the housing 1 has a lower housing-shaped so-called base plate 2, from which a stand 3 extends substantially vertically upwards. At an upper end of the stator, an arm 4 connects, which runs approximately parallel to the base plate 2.

The sewing machine has a mounted in the arm 4 arm shaft 7, which as well as the following other basic components of the sewing machine in Fig. 1 possibly only partially or highly schematically represented. The arm shaft 7 drives an oscillating up and down movable needle bar 5, to the needle holder, a needle 6 for receiving an upper thread (not shown) can be attached. In the base plate 2, a gripper device 8 is arranged, whose rotational movement is synchronized with the oscillating movement of the needle bar 5. A lower thread is located on a spool 11, which is arranged in a multi-part bobbin case carrier. In this case, the gripper device 8 guides the upper thread guided by the needle 6 around the bobbin case carrier in a manner known per se so that it can form a seam together with the bobbin thread. Usually, the needle bar 5 and the gripper device 8 are driven by a common drive, namely a non-illustrated servo electric motor whose rotary drive movement is tapped to the needle bar 5 and the gripper device 8 from a machine main shaft and translated in a certain ratio.

The sewing machine also has a non-illustrated feeding device with a needle and / or top feed device. Accordingly, the also driven by a corresponding gear from the machine main shaft feeders for the passage of the needle 6 is provided with a stitch hole.

Fig. 2 shows a representation of the arranged in the base plate 2 assembly of the gripper device 8, located in the base plate immediately below a throat plate 9 (FIG. Fig. 1 ) is located. The gripper device 8 has a rotatable in a horizontal plane gripper 12, which is provided with a hook tip 12a and in the known manner, the thread supply receiving coil 11 is inserted. The coil 11 is secured in a manner known per se against rotational movements.

As in Fig. 2 as well as the Fig. 6-9 can be seen, the gripper device 8 is provided with a thread cutting device 13, which is provided for detecting and for the separation of the lower and the upper thread. After completion of a seam formation, the thread cutting device 13 can be used either automatically or by actuation of an arranged on or in the vicinity of the sewing machine actuating means.

The thread cutting device 13 may, for example, according to the in the DE 10 2008 030 620 B3 be formed, whose content, in particular with regard to the structural design and achievable functions, is hereby incorporated by reference. In the Fig. 3 by way of example and purely schematically partially shown thread cutting device 13 has a thread catcher 14, which is arranged on a shaft 15 parallel to the gripper shaft and oscillates about this over a certain angular range in opposite directions of rotation. The thread cutting device 13 receives its drive movement from the machine main shaft to the shaft 15 via a corresponding gear. The thread catcher 14 is located in its rest position laterally behind the needle 6 and is for a cutting operation in a horizontal plane from the rest position along a running between the stitch hole 13 and the side wall of the gripper path of movement in the movement reversal position and from this along the same trajectory again can be returned to the rest position.

At its end facing away from the shaft 15 of the thread catcher 14 a catcher tip 17 is formed on this, which is arranged downstream of a barb. For education of the barb 18, an incision 21 is formed on the outer side surface of the thread catcher, which is arranged downstream of the catcher tip 17.

On its upper side, the thread catcher for receiving the threads to be separated on a catcher tip 17 downstream groove 23, which opens at one end into the recess 21 and the other end in a thread catcher 14 passing through bore 24. As a result, the end region of the groove 23 merging into the bore 24 forms a semicircular cutting edge 25 of the catch catcher 14.

To cut off the thread leading to the leg of the needle thread loop and the looper thread, a cooperating with the thread catcher 14 stationary arranged counter knife 26 is provided in the immediate area of the stitch pattern, the cutting edge 27 is directed to achieve a pulling cut at an acute angle to the feed direction of the material. The counter knife 26 can also be arranged on the underside of a feed dog of the sewing machine and be firmly connected thereto.

A thread clamping device 28 is located in the immediate vicinity of the thread cutting device 13 in the region of the circumference of the gripper 12 (FIG. Fig. 2 and 6-9 ). With regard to the direction of rotation of the gripper, the thread clamping device is arranged directly behind the thread cutting device. The thread clamping device 28 has a thread clamp 29, which is provided with two cooperating clamping parts 30, 31. The upper clamping member 30 is in this case arranged rigidly on a carrier 32 and projects beak-like and curved away from the carrier 32. The lower clamping part 31 is formed angularly and is located immediately below the upper clamping member 30. The lower clamping member 31 also has a beak-like and approximately to the gripper curved course of a substantially horizontal clamping leg 31a. The lower clamping part 31 is pivoted on the carrier by means of a shaft 33, the pivot axis 33a is oriented horizontally. The shaft 33 is in this case in a in the Fig. 4 and 5 not shown manner held by the carrier 32. In addition, the lower clamping member 31 is force-loaded with a spring, also not shown. The direction of action and spring force of the spring is provided so that the lower clamping member 31 with a force only slightly exceeding its own force against the upper Clamping part 30 is pressed. Finally, a screw 35 is screwed below the shaft 33 in the vertical leg of the lower clamping part and this also passed through the carrier 32. The screw 35 protrudes with its screw head 35a on the side remote from the lower clamping part 31 side of the carrier 32 at a distance from the latter. The threaded other end of the screw protrudes from the vertical clamping leg 31 b of the lower clamping member 31, in which case a nut 35b is screwed onto the end of the screw, which rests against the vertical clamping leg 31b.

On the support 32, a pneumatic flat cylinder 36 is also attached by screwing. In Fig. 2 At the rear end of the flat cylinder a pneumatic connection of the cylinder can be seen. The free end of the piston 38 of the pneumatic cylinder 37 is located directly opposite the screw head 35a, wherein a longitudinal axis of the stroke movement of the piston 38 and the longitudinal axis of the screw 35 are parallel to each other. By a stroke movement of the piston 38, this comes into abutment against the screw head 35a and moves it in the direction of the carrier 32 to. As a result, the lower clamping member 31 performs a rotational movement about the pivot axis 33a of the shaft 33, whereby the lower clamping member 31 is pressed against the upper clamping member 30 with a greater force than can exert the spring. Like that Fig. 4 and 5 can be removed, clamping surfaces of the clamping members 30, 31 profiled in cross-section, in particular triangular in shape, resulting in particularly good clamping effects at comparatively low clamping forces required.

• Der Einsatz der Fadenklemmeinrichtung 28 wird durch Betätigen einer nicht näher dargestellten Taste für die Auslösung des Fadenschneidvorgangs ausgelöst. Wird diese Taste am Ende der Erzeugung einer Naht betätigt, so wird zunächst in an sich bekannter Weise im Nähgut ein Verknotungsstich gebildet, der der Sicherung der Naht gegen ein Aufziehen dient. Ein solcher Verknotungsstich kann mit der Stichlänge "Null" und beispielsweise in der in der DE 10 2008 030 620 B3 beschriebenen Weise erfolgen. Bei weiterhin unveränderter Lage des Nähguts wird während der Bildung eines Teilstiches (Schneidstich) die Nadelfadenschlaufe durch den Greifer 12 aufgeweitet, wonach der Fadenfänger 14 von einer seitlich hinter der Nadel gelegenen Ruhestellung entlang einer kreisbogenförmigen Bewegungsbahn in eine Bewegungsumkehrposition bewegt wird. Diese Bewegung erfolgt in den Darstellungen von Fig. 2 und 6-9 im Gegenuhrzeigersinn. Der Fadenfänger dringt mit der Fängerspitze 17 in die aufgeweitete Nadelfadenschleife ein, erfaßt diese und führt sie weg.

The operation of the described seam forming means of the sewing machine is as follows:

• The use of the thread clamping device 28 is triggered by pressing a button not shown for triggering the thread cutting operation. If this key is actuated at the end of the production of a seam, a knotting stitch is first formed in a known manner in the sewing material, which serves to secure the seam against being pulled on. Such a knotting stitch can with the stitch length "zero" and for example in the in the DE 10 2008 030 620 B3 done manner described. While still unchanged position of the fabric is during the formation a partial stitch (cutting stitch), the needle thread loop widened by the gripper 12, after which the thread catcher 14 is moved from a laterally located behind the needle rest position along an arcuate movement path in a movement reversal position. This movement takes place in the representations of Fig. 2 and 6-9 in the counterclockwise direction. The thread catcher penetrates with the catcher tip 17 in the expanded needle thread loop, detects them and leads them away.

In the movement reversal position of the thread catcher 14 leading to the fabric leg of the needle thread loop and in the Fig. 6-9 Gripper thread 40 shown detected by barbs 18. The needle thread loop and the looper thread 40 can be detected here by different areas of the barbs 18, for bobbin thread and upper thread different grooves are provided on the barb for this purpose. During the further movement of the thread catcher 14 to its rest position of leading to the fabric leg of the needle thread loop and the looper thread 40 in each case on the thread catcher trained for them groove and - as soon as there trained cutting edge has reached the area of the respective counter knife 26, 41 - severed in cooperation of the cutting edge of the yarn catcher with the cutting edge of the counter knife.

Before the severing of the threads has taken place, the path of movement of the thread catcher 14 past the thread clamp 29. By the movement of the thread catcher 14, the lower thread 40 is inserted between the two clamping parts 30, 31 of the thread clamp 29. The thread clamp 29 can hereby be slightly opened against the spring force by the abutting against it lower thread 40 Now the control of the sewing machine actuates the flat cylinder 36. The pressurization of the cylinder 36 leads to an extension of the piston 38, which now presses against the screw head 35a, thereby causing a pivoting movement of the lower clamping member 31 by a small angular amount, whereby the two clamping members 30, 31 are pressed against each other with the lower thread 40 arranged therebetween. The lower thread 40 is thus securely held between the clamping parts 30, 31. In this state, the already described severing of the lower thread 40 ( Fig. 8 and 9 ) and the upper thread. The sewing material with it arranged sewing-side ends of lower and upper thread can now be removed. This seam formation is completed.

For the seam to be subsequently formed, the lower thread 40 is thus still clamped in the thread clamp 29 and, as in, for example, FIG Fig. 8 and 9 shown guided by the coil 11 from this to the thread clamp 29. The piston 38 continues to press against the screw head 35a at the beginning of this seaming, as a result of which the lower thread 40 in the thread clamp 29 is held securely. The new sewing process can be started, whereby the needle 6 cooperate in a conventional manner with the gripper 12 and can produce one or more stitches of the seam to be formed from the beginning process reliable. The number of stitches during which the thread clamp 29 continues to clamp the lower thread 40 can preferably be adjusted via the controller. Good results with secure seaming start are achieved, for example, with a clamp of the lower thread 40 during a number of stitches ranging from one to 10, preferably from one to four stitches. However, it can also be advantageous to be able to set a larger number of stitches beyond this, during which the lower thread 40 is still clamped in the thread clamp 29 and thus predetermined conditions defined for the lower thread are created.

After each set predetermined number of first stitches of a seam with clamped lower thread 40 are processed by the sewing machine, the control of the sewing machine controls the flat cylinder 36 so that the piston 38 moves back and the lower clamping part 31 of the thread clamp 29 is released from the piston. The lower thread can hereby be led out of the thread clamp 29 due to the thread tension and the continuous sewing process and the seam can be formed from now on without thread clamping. At the end of this seam formation can be introduced by pressing a switch or button for the thread cutting process or by an automatic triggering of the thread cutting operation of the lower thread in the manner already described again in the thread clamp 29 and clamped there and cut. <B> LIST OF REFERENCES </ b> 1 sewing machine 28 Thread clamp 2 baseplate 29 thread clamp 3 stand 30 Upper clamping part 4 poor 31 lower clamping part 5 needle bar 31a horizontal clamping leg 6 needle 31b vertical clamping leg 7 arm shaft 32 carrier 8th gripper device 33 wave 9 needle plate 33a swivel axis 11 Kitchen sink 35 screw 12 grab 35a screw head 12a hook tip 35b mother 13 Thread cutter 36 flat cylinders 14 thread catcher 37 pneumatic connection 15 Shaft thread catcher 38 piston 17 taker point 40 looper thread 18 barb 41 against knife 21 incision 23 groove 24 drilling 25 cutting edge 26 against knife

Claims (12)

1. Seam-forming means for a sewing machine, comprising thread-guiding means such as, for example, a needle and/or a grippe, for guiding at least one thread that is intended for forming a seam, and a thread-clamp installation (28) which is provided with a thread clamp (29) into which a thread, in particular for forming a seam start may be introduced, in which said thread may be clamped, and from which said thread may be guided out again,
   characterized
   by an activatable thread clamp (29) which by means of a controllable activation means is closable for clamping and/or by means of the activation means is openable, and in which at least a point in time for opening or releasing the thread clamp (29) is variably adjustable.
2. Seam-forming means according to Claim 1, characterized in that the activation means comprise drive means by way of which an opening movement and/or a closing movement of the thread clamp (29) is generatable.
3. Seam-forming means according to Claim 1 or 2, characterized by a control by means of which points in time for opening and/or closing the thread clamp (29) are adjustable depending on a specific or on a determinable number of stitches.
4. Seam-forming means according to Claim 3, characterized in that a number of stitches of the seam start is adjustable as a point in time of opening the thread clamp (29), after which number of stitches the thread clamp (29) is opened, wherein the number of stitches is selectable in particular from a range from 1 to 15 stitches, preferably from a range from 1 to 6 stitches.
5. Seam-forming means according to at least one of the preceding claims, characterized in that the thread clamp (29) has at least two interacting clamp parts (30, 31) of which at least one in relation to the other camping part (30, 31) is configured as an activatable movable clamp part (30, 31) for an opening and/or clamping mouvement of the thread clamp (29).
6. Seam-forming means according to Claim 5, characterized in that clamping of a thread, in particular of a bobbin thread (40), is generatable by means of a drive means that acts on the at least one movable clamp part (30, 31).
7. Seam-forming means according to at least one of the preceding claims, characterized by a springloaded clamp part (30, 31) of the thread clamp (29) that is movable about a pivot axis (33a).
8. Seam-forming means for a sewing machine, according to at least one of the preceding claims, characterized in that the thread-guiding means comprise a needle (6) for guiding a needle thread, and a grippe device (8) having a gripper (12) that revolves about a rotation axis, in particular about a vertical rotation axis, in which gripper (12) a reserve for a bobbin thread is disposable and unwindable.
9. Sewing machine that is provided with seam-forming means, characterized by seam-forming means according to one of or a plurality of Claims 1 to 8.
10. Sewing machine according to Claim 9, characterized by a sewing-machine controller on which a number of stitches is adjustable, during which the thread clamp (29) is activated.
11. Method for seam-forming by means of seam-forming means of a stewing machine (1), in which for seam-forming at least one thread is incorporated in a sewn article, wherein at the commencement of seam-forming the at least one thread is already disposed or is being disposed in a thread clamp (29), and after one or a plurality of stitches of the seam to be produced is guided out of the thread clamp (29), characterized in that the thread clamp (29), for clamping the thread and/or for guiding out the thread, by means of activation means may be closed and/or opened or released, and that at least a point in time for opening or releasing the thread clamp (29) is variably adjustable.
12. Method according to claim 11, characterized in that the thread is introduced into the thread clamp (29) and cut during a preceding seam formation, is clamped in the thread clamp (29) up to the commencement of the subsequent seam formation, and escapes the thread clamp (29) only after a first stitch of the subsequent seam formation by virtue of the thread clamp (29) being released or opened.

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