WO2009156084A1

WO2009156084A1 - Method and device for separating the needle and the looper threads on double-thread lockstitch sewing machines having a looper revolving about a horizontal plane

Info

Publication number: WO2009156084A1
Application number: PCT/EP2009/004353
Authority: WO
Inventors: Franz Gries; Hermann Rutz
Original assignee: Pfaff Industriesysteme Und Maschinen Ag
Priority date: 2008-06-24
Filing date: 2009-06-16
Publication date: 2009-12-30
Also published as: ATE540151T1; DE102008030620B3; EP2300654B1; EP2300654A1

Abstract

The invention relates to a method and a device for separating the needle and looper threads on double-thread lockstitch sewing machines having a looper revolving about a horizontal plane, wherein after completing the seam the stitched product is moved further along by means of the feeder device by an amount that is shorter than the stitch length forming the seam, whereby in this position of the stitched product at least one further stitch (knotting stitch) is formed with the feeder device inactive, and in the unchanged position of the stitched product the needle thread loop is expanded by the looper during the formation of a partial stitch (cutting stitch), wherein the catch-thread device (14) is moved from an idle position positioned laterally behind the needle (5) to a movement reversing position along a movement path extending between the piercing hole (13) and the lateral walls (16) of the looper (1), and the catch-thread point (17) penetrates into the expanded needle thread loop such that both the arm of the needle thread loop for guiding the stitched product and the region of the looper thread extending from the looper to the stitched product are laterally deflected, and in the movement reversal position of the catch-thread device (14) are both grasped by a barbed hook (18) disposed thereon and guided to the region of the piercing hole (13).

Description

Method and device for cutting the needle and the

Hook thread on lockstitch sewing machines with looper revolving in a horizontal plane

The invention relates to a method and a device for cutting the needle and the looper thread on lockstitch sewing machines with gripper rotating in a horizontal plane and a feed device with a needle or top feed device by means of a thread cutting device, and a sewing machine for carrying out the method.

In DE 197 22 395 C1 discloses a method and an apparatus for severing the needle and the looper thread of the same type lockstitch sewing machines, wherein at the beginning of a thread cutting process provided with a cutting edge yarn catcher from a rest position to a reversal position and both a knife, as well as a clamp for the looper thread in a stitch hole of the throat plate adjacent cutting or receiving position are brought. For detecting the looper thread and the leg of the needle thread leading leg of the thread catcher is moved in a first step in an intermediate position in which the needle thread loop is pulled up to this. In a second step, the thread catcher is moved back to its rest position, during which movement of the thread catcher first withdrawn thread from the looper thread and inserted into the thread clamp. Thereafter, in the interaction of the thread catcher with the movable knife of the needle and the looper thread in the vicinity of the stitch hole are severed. Subsequently, the thread clamp and the knife are also moved back into their rest position, wherein the thread clamp subtracts further looper thread from the thread supply.

Due to the fact that the knife is guided from a rest position into a cutting position located in the region of the stitch hole of the throat plate and after cutting needle and hook thread back to its rest position, this solution is in view of the fact that both the thread catcher, and the Each knife must be brought from a rest position into an operative position and from there back to the rest position, in terms of design very complex and requires both the thread catcher and the knife each have their own drive, the movements of the two drives must be coordinated.

Thus, the short length of the yarn side yarn ends is achieved primarily by not only the yarn catcher is brought from a rest position to a reversal position and from there back to the rest position, but also the knife from a remote from the stitch hole rest position in a stitch hole adjacent cutting position

A with respect to their structure and operation of the thread cutting device according to DE 197 22 395 C1 similar thread cutting device for generic same lockstitch sewing machines is disclosed in DE 10 2007 045 598 A1.

This also has a about a gripper shaft directed parallel shaft pivoting motion sensor, on its underside in the region of its front end a barb-shaped yarn thread catching part and a cutting edge part are formed. The movement of the knife is movable from its rest position along a trajectory extending through the needle path center in a reversal position. During the return movement of the movement knife to the rest position of the thread catching part first expands the needle thread loop formed by the gripper and then cuts through the needle and the hook thread in cooperation with a cutting blade, at the front end of a cutting edge portion is formed. For this purpose, it is also necessary to move the cutting blade from its rest position to its cutting position before performing the cutting process.

Thus, it is necessary to achieve only a small length sewing thread side yarn ends also in this thread cutting device, not only to move the moving knife with its cutting edge part of a rest position in a reversal position and from there back to the rest position, but also the cutting blade of one of Stitch hole remote rest position in a stitch hole adjacent cutting position and be moved from there back to its rest position. Although in both thread cutting devices to achieve short Nähgutseitiger thread ends of the thread catcher and the knife or the moving knife and the cutting blade are moved, and the respective movements time and motion must be precisely coordinated with each other, their cutting result is so far not optimal, as the relative position of the respective interfaces From needle or looper thread to the stitch hole and thus the length of the yarn side thread ends of the exact mutual coordination of the movements of thread catcher and knife or of motion and cutting knife is dependent.

The invention is therefore based on the object for lockstitch sewing machines with rotating in a horizontal plane gripper and a feed device with a needle or top feed device to provide a method for severing needle and looper thread, in conjunction with a simple trained, a thread catcher and having a knife having thread cutting device optimally short thread-side yarn ends results, but only requires the movement of either the thread catcher or the knife.

This object is achieved by a method according to claim 1 and an apparatus according to claim 4.

By the measures to move after the completion of the seam, the material to be moved by the feed by an amount and in this position of the material at ineffective feed device at least one further stitch (knotting stitch) to form, it is first achieved that the seam formed despite the very It is very difficult to put up with short yarn ends on the thread side.

In this case, the further measure to move the thread catcher from a laterally located behind the needle rest position along a running between the tap hole and the side wall of the gripper trajectory in a motion reversal position in which leading to the fabric leg of the needle thread loop together with the looper thread through the on Thread catcher trained barbs are detected, the ability to guide the detected threads in the field of stitch pattern and cut there. This has the further advantage that both the leg of the needled needle to be cut denschleife and the looper thread can be severed in the immediate area of the stitch image location, and thus optimally short thread side thread ends are reached.

The fact that the two threads to be cut can be guided through the thread catcher in the immediate area of the stitch pattern and cut there, the counter knife cooperating with the formed on the thread catcher cutting edges counter knife can be attached directly to the feed dog and thus arranged stationary, so that for between the Cutting edges of the thread catcher and the counter knife relative movement to be achieved, the movement of the yarn catcher is sufficient, and thus a drive for moving the counter knife is not required.

In order to obtain an optimally short distance between the interface of the threads and the stitch hole formed on the feed dog, it is expedient to position the feed dog before the movement of the thread catcher in the reverse position so that the needle hole is centered to the trajectory of the needle.

A structurally favorable and space-saving solution for the movement of the thread catcher is achieved when it is pivotable about an axis parallel to the gripper shaft, and the trajectory of the catcher tip between the cam of the needle plate on the one hand and the needle hole of the feed dog on the other hand. As a result, the thread catcher can be made relatively flat and move within a horizontal plane above the gripper from its rest position to the reverse position and from there back to its rest position.

A compact design for the thread catcher is achieved when the barbs is formed by a provided on its outer side surface incision, which is downstream of the tip of the thread catcher and the thread catcher on its upper side a tip also subordinate groove for receiving the to be separated Has threads that opens into the incision. As a result, the regions of needle and hook thread to be severed can be received within the groove and separated by cutting edges formed at the outlet of the groove without the aid of a movable counter knife. Although this achieves extremely short thread-side thread ends be obtained, the thread supply-side ends, characterized in that they lead from the interface first to the incision and thence along the underside of the thread catcher to the respective thread supply, sufficient to form the initial stitches of the next sewing cycle sufficient length.

If the tip-side end region of the groove is delimited by a bore passing through the thread catcher, the dividing edges of the thread catcher formed thereby can be produced relatively easily and can also be sharpened slightly.

In order to avoid during the movement of the yarn catcher from the rest position in the reverse position, a collision of the yarn catcher with the counter blade or its cutting edge, a vertical mobility limiting stop is provided on the underside of the throat plate in the region of the trajectory of the yarn catcher.

Further details and advantages of the invention will become apparent from the following description of an embodiment of the invention shown in the accompanying drawings.

It shows:

Fig. 1: A perspective view of a gripper housing a lockstitch sewing machine with a rotating in a horizontal plane gripper and the thread cutting device;

Fig. 2: An illustration of the thread catcher, the feed dog, the counter knife and the needle plate;

Fig. 3: A perspective view of the thread cutting device after the penetration of the catcher tip into the needle thread loop widened by the gripper;

Fig. 4: An illustration corresponding to Figure 3 shortly before the cutting process. In Fig. 1 serving for receiving a gripper 1 a lockstitch sewing machine housing 2 is shown, which can be used in a conventional manner in the base plate of a corresponding sewing machine. The gripper 1 is arranged on a shaft (not shown) running parallel to the path of movement of the needle, which in turn is driven via a corresponding gear by a stub shaft 4, which is in driving connection with the machine main shaft. The gripper 1 works to form lockstitches with a thread-guiding needle 5, which is received by a needle bar, which is also in a corresponding drive connection with the machine main shaft.

The circulating in a horizontal plane gripper 1 is provided with a hook tip 6 and has in a known manner to a thread supply receiving coil 7, which is secured by means of a between two cams 8 of a housing 2 attached to the throat plate 9 stopping piece 11 against rotational movement. To enable the stitch formation, a capsule fan 12 is provided in the housing 2 in a conventional manner, the movements of which are also derived from the stub shaft 4.

The sewing machine has a feed device with a needle and / or an upper transport device. Accordingly, the also driven by a corresponding gear from the stub shaft 4 feed dog 13 is provided in a conventional manner for the passage of the needle 5 with a stitch hole 13.

The sewing machine also has, in a manner known per se, a stopping device which makes it possible to stop the machine main shaft in certain angular positions.

The thread cutting device has a thread catcher 14, which is arranged on a parallel to the gripper shaft shaft 15, which also receives its drive via a corresponding gear from the main machine shaft. The thread catcher 14 having a substantially "L" shape in plan view is laterally behind the needle 5 in its rest position and is in a horizontal plane from its rest position along a trajectory extending between the stitch hole 13 and the side wall 16 of the gripper 1 Moving reversible position and pivotable from this along the same trajectory back to the rest position feasible. At its end facing away from the shaft 15 of the thread catcher 14 a catcher tip 17 is formed on this, which is a barb 18 downstream. To form the barbs 18, an incision 21 is formed on the outer side surface 19 of the suture catcher 14, which is arranged downstream of the catcher tip 17.

On its upper side 22, the thread catcher 14 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 regions of the groove 23 merging into the bore 24 form a semicircular cutting edge 25 of the thread 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. In a preferred embodiment, the counter knife 26 is arranged on the underside of the feed dog 13 of the sewing machine and firmly connected thereto.

In order to avoid a collision of the thread catcher 17 with the counter knife 26 or its cutting edge during the movement of the yarn catcher 17 from the rest position in the reverse position, at the bottom of the throat plate 9 in the region of the trajectory of the yarn catcher 17 a stop 28 limiting its vertical mobility arranged.

The operation of the thread trimmer is as follows:

After completion of the seam, the fabric is moved by the feed device in the feed direction by an amount that is less than the stitch length with which the seam is formed. As a result, the feed dog 10 is positioned such that its tap hole runs centrally to the movement path of the needle 5. In this position of the sewing material at ineffective (ie set to a stitch length "zero") feed device at least one further stitch (knotting stitch) is formed, which serves to secure the seam against being pulled. In still unchanged position of the material, the needle thread loop is widened by the gripper during the formation of a partial stitch (cutting stitch), after which the thread catcher 14 from a laterally located behind the needle 5 rest position along a between the stitch hole 13 and the side wall 16 of the gripper extending trajectory is moved in a motion reversal position. While the needle and gripper continue to move during the penetration of the suture catcher 14 into the widened needle thread loop, however, since the needle thread loop is caught by the suture catcher 14 and passed therethrough, the initiated stitch can not be properly completed. The formation of this "stitch" thus serves only to allow the penetration of the catcher tip (17) in the expanded needle thread loop and laterally deflect both their leading to the fabric leg and extending from the gripper to the fabric portion of the looper thread.

In the movement reversal position of the thread catcher 14, the leg of the needle thread loop leading to the sewing material and the hook thread are grasped by the barb 18 formed on the thread catcher 14 and guided into its rest position into the region of the stitch hole 3 during the first part of the return movement of the thread catcher 14. During the further movement of the thread catcher 14 from the region of the stitch hole to its rest position of leading to the fabric leg of the needle thread loop and the looper thread into the thread catcher 14 formed groove 23 and are -so soon the semi-circular cutting edge 25 has reached the area of the counter knife 26 - In the interaction of the cutting edge 25 of the thread catcher 14 with the cutting edge 27 of the counter knife 26 severed.

Since the recorded in the groove 23 areas of needle and looper thread from the interface directly to the fabric, the yarn ends remaining at this optimally short, while leading to the respective thread supply ends of needle and looper thread one to form the initial stitches of the next sewing cycle have sufficient length.

Claims

claims

I.Verfahren for cutting the needle and the looper thread to form short Nähgutseitiger thread ends in double stitch sewing machines with a rotating in a horizontal plane gripper and a feed device with a needle or a top feed device, and a thread cutting device with a thread catcher with a catcher tip formed thereon and a cutting edge cooperating with a counter knife, comprising the following steps:

a.) after completion of the seam, the fabric is moved by the feed device by an amount that is less than the stitch length with which the seam is formed;

b) in this position of the sewing material, at least one further stitch (knotting stitch) is formed when the feeding device is ineffective,

c) with unchanged position of the sewing material, the needle thread loop is widened by the gripper during the formation of a partial stitch (cutting stitch);

d) the thread catcher (14) is moved by a laterally behind the needle (5) located inoperative position along a movement path between the taphole (13) and the side wall (16) of the gripper (1) in a movement reversal position, wherein the catcher tip (17 ) penetrates into the widened needle thread loop and laterally deflects both its leg leading to the sewing material and the region of the hook thread running from the gripper to the sewing material;

e) in the movement reversal position of the thread catcher (17), the leg of the needle thread loop leading to the sewing material and the hook thread are grasped by a barb (18) formed on the thread catcher (14) and guided into the area of the stitch hole (3);

f) during the further movement of the thread catcher (14) from the region of the stitch hole to its rest position of the Sewing material leading leg of the needle thread loop and the looper thread of the in the region of the stitch hole (13) of the feed dog (10) arranged counter knife (26) in cooperation with the cutting edge (25) of the thread catcher (14) severed.

2. A method for severing the needle and the looper thread according to claim 1, characterized in that prior to the movement of the thread catcher (14) in the reverse position of the feed dog (10) is positioned such that the needle hole (3) centrally to the trajectory of the needle (5) runs.

3. A method for severing the needle and the looper thread according to claim 1, characterized in that after detecting the looper thread through the thread catcher (14) withdrawn by this looper thread from the thread supply and between the jaws one in the trajectory of the thread catcher (14, respectively . Of the looper thread) arranged thread clamp is guided.

4. Sewing machine for carrying out the method according to claim 1, comprising:

a) a needle bar for receiving a thread-guiding needle (5);

b) a cooperating with this for the formation of lockstitch seams and rotating in a horizontal plane gripper (1);

c) a device for stopping the needle bar or the gripper (1) in predeterminable angular positions of the gripper (1) or the machine main shaft;

d) a feed device with a Nadeltransport- and / or an upper transport device with a tap hole (13) having feed dog (10);

e) a thread cutting device with a thread catcher (14) which is movable along a trajectory between the stitch hole (13) of the feed dog (10) and a side wall (16) of the gripper (1) from a rest position to a reversal position, and a catcher tip (17), which during this movement in the expanded by the gripper (1) needle thread penetrates both their leg leading to the fabric, as well as the looper thread for detection by a on the catcher tip (17) formed barbs (18) deflects laterally, so that the barbs (18) detected threads during the return movement of the thread catcher (14 ) in its rest position in the region of the stitch hole (13) of the feed dog (10) in the interaction of an arranged in this area counter knife (26) with the thread catcher (14) formed cutting edges (26) of the thread catcher (14) are severed.

5. Sewing machine according to claim 4, characterized in that the thread catcher (14) about an axis parallel to the gripper shaft is pivotable, and the trajectory of the catcher tip (17) between the cams (8) of the needle plate (9) on the one hand and the needle hole (13 ) of the feed dog (10) on the other hand runs.

6. Sewing machine according to claim 4, characterized in that the barbs (18) of the thread catcher (14) from one of the outer side surface (19) provided for recess (21) is formed, which is arranged downstream of the catcher tip (17).

7. Sewing machine according to claim 6, characterized in that the thread catcher (14) on its upper side 22) has a tip (17) downstream of the groove (23) for receiving the threads to be separated, which opens into the recess (21).

8. Sewing machine according to claim 7, characterized in that the boundary edge of the groove (23) forms the cutting edge (25) of the thread catcher.

9. Sewing machine according to claim 4, characterized in that the counter knife (26) in the immediate region of the feed dog (10) and its cutting edge (27) is directed at an acute angle to the feed direction of the sewing material.

10. Sewing machine according to claim 9, characterized in that the counter knife (26) on the feed dog (10) is attached.

11. Sewing machine according to claim 4, characterized in that on the underside of the throat plate in the region of the movement path of the Yarn catcher (17) whose vertical mobility limiting stop (28) is provided.