Title of Invention

METHOD AND DEVICE FOR MECHANICALLY SEWING A DOUBLE CHAIN STITCH SEAM

Abstract

ABSTRACT "METHOD AND DEVICE FOR MECHANICALLY SEWING A DOUBLE CHAIN STITCH SEAM" The present invention relates to a double chain stitch is made has by first pushing a needle carrying a needle thread down through goods to be seamed to from below a lower face of the goods a needle-thread loop and then passing a looper carrying a looper thread transversely to a stitching direction parallel to the face through the loop below the lower face to pass the looper thread through the needle-thread loop. Then the looper thread and needle-thread loop are gathered on an element below the lower face and the element is moved with the gathered needle and looper threads away from the needle and looper generally parallel to the face while advancing the goods in the direction to form with the needle-thread loop and looper thread a window. Thereafter the needle is again passed through the window and the gathered needle and looper threads are released from the element so that they engage around the most recently formed needle loop. The steps are then repeated. (Fig 1&Fig 2)

Full Text

METHOD AND DEVICE FOR MECHANICALLY SEWING A DOUBLE CHAIN STITCH SEAM The invention concerns a method for mechanically sewing a double chain stitch seam, whereby the double chain stitch is produced by means of an industrial sewing machine with a sewing needle and needle thread as well as a main looper and looper thread, whereby the needle thread locks needle loops laid in a chain on the underside of the material being sewn, whereby during the stitch formation process the main looper which in particular moves at right angles to the direction of the seam, takes up the needle thread loop in the needle rise position of the sewing needle and carries the looper thread through the loop while the needle thread loop slides past the main looper, whereby the looper thread and the needle thread loop are formed into a thread triangle through which the needle passes at the next downstroke. In industrial sewing of lengths of fabric or individual pieces of textile, particularly in sewing the seams, this same sewing process is used to produce a straight double chain stitch seam. The use of a double chain stitch is among other things advantageous, because it obviates the need for a bottom spool and for spooling the looper thread. The thread guidance take place on the one hand by means of the sewing needle which carries the needle thread and passes through the sewing plane (the material being sewn) and forms a thread loop behind the sewing plane as the needle is withdrawn, whereby on the other hand a main looper is mounted below the sewing plane which carries the looper thread and threads it through the loop of the needle thread. When sewing in a straight seam direction the forming of the double chain stitch seam poses no problems. With conventional industrial sewing machines stitching speeds of more than 4,000, even more than 6,000 stitches per minute are achieved. This brings about that when sewing takes place in the direction of the seam, the transport alone of the material being sewn results in the formation of a thread triangle from the thread loop and the looper thread which the sewing needle perforates during the downstroke. This achieves the locking of the thread loops. Of course, if the thread triangle is not properly formed or not formed in the right position, faulty stitches occur which result in the seam coming undone. Such faulty stitches can e.g. occur when the successive entry points or the needle are very close together, because then the area of the thread triangle is very small. If instead of a straight type of the double chain stitch seam, another type of seam, e.g. a zigzag seam, a cross seam or similar must be produced, it cannot be ensured with traditional devices that the thread triangle is formed in such a way that the needle at each subsequent downstroke perforates the area surrounded by the triangle. A particular problem is also the locking when a seam is being completed whereby sewing takes place against the direction of the seam. In such a case it is not possible to form a thread triangle through the transport of the material alone. In the state of the art attempts have already been made to grab the threads underneath the sewing plane and to form a thread triangle with a looper finger to ensure locking. Such devices have not stood the test, because with automatic operation it was not possible to ensure proper sewing against the direction of the seam e.g. for completion of the seam. Also the mechanical stability of the relevant components was not adequate. Furthermore there was considerable risk of thread breakage with such devices, particularly at high speeds. Additionally, there was a high incidence of faulty stitches with these devices so that they proved unsuitable. From US-A-3 867 891 a multineedie double-chain stitching machine is known. With this known machine the object is to create a machine with which it is possible to stitch in a direction at a right angle to the direction movement of the loopers and specifically both to the right and the left. To achieve this a spreader with a spreader finger is provided there which engages the lower thread (looper thread) and, if the transport movement of the fabric or the like to be sown deviates from a rectilinear movement, deflects the looper thread to the side of the needle axis of the sewing needle away from the looper. With this machine the looper thread is therefore shifted sideways by means of the spreader to bring the looper thread behind the needle. This is disadvantageous, because only the looper thread is grabbed by the spreader so that there is a considerable risk of this thread breaking. A particular disadvantage of this design is that stitch formation can only happen in the transport direction and in directions at right angles to it in cases where the last formed stitch hole is not further forward than the next to be made. This design does not make it possible to form stitches if e.g. for the purpose of finishing a seam, the sewing direction is reversed against the direction of the seam. Also in the case of stitches positioned closely together it is not possible to create a thread triangle of sufficient size for the needle to perforate and so avoid faulty stitches. Against the background of these problems, the purpose of the invention is to create a method and a device of a similar type with which the locking of a double-chain stitch seam is ensured in a simple way and with great precision even at high sewing speeds, particularly if the seam does not run straight and if to finish the seam the sewing direction is reversed against the direction of the seam. To meet this purpose the invention proposes that to avoid faulty stitches, a driven auxiliary component is used as a means to bring the needle thread loop and the looper thread together below the sewing plane in the area between the main looper and the sewing plane at a distance from the sewing needle and the main looper and that they are held and moved in such a manner that the thread triangle is formed which the sewing needle perforates at the downstroke. The method proposed by the invention ensures that the thread triangle required for locking, which triangle the sewing needles perforates at the downstroke, is in every case formed and aligned so that the needle perforates the area enclosed within the thread triangle. With a normal straight seam the auxiliary component may not have a function or may even be turned off. If the stitches to be sewn are very close together, the thread triangle can be enlarged accordingly, because the forming of the triangle is not dependent on the amount of travel of the material, but depends solely on the movement of the auxiliary component. Proper locking is possible also for seams not running straight, e.g. a zigzag seam, a cross seam or the like, because here too the auxiliary component forms the thread triangle precisely in the area where the sewing needle enters at the downstroke. Additionally it is preferably provided that for completion of the double chain stitch seam, the sewing direction is reversed, that after reversal of the sewing direction and synchronised with the up and down movement of the sewing needle, the thread loop formed by the sewing needle underneath the fabric is taken up by the main looper, then by means of the driven auxiliary component the needle thread forming the thread loop is brought together in the direction of the seam underneath the sewing plane with the looper thread at a distance from and in front of the needle and the main looper and is held there and the thread assembly is moved in the direction of the seam and a thread triangle, consisting of the needle thread forming the loop, the looper thread area parallel to the main looper and the looper thread area leading to the thread assembly area, is formed, which the sewing needle perforates and whereupon the thread assembly area is released by the auxiliary component. This ensures that even when the sewing direction is reversed against the direction of the seam, e.g. for the completion of the seam, a thread triangle of suitable size is formed for the needle to perforate at the downstroke. Preferably it is provided that the auxiliary component is driven synchronously with the sewing machine or with the stitching rhythm of the sewing needle. In some cases it may also be provided that the auxiliary component is driven by the sewing machine. The auxiliary component can e.g. be coupled to the drive of the sewing machine by means of a belt drive so that a common drive for both elements is sufficient. However, it may preferably also be provided that the auxiliary component is driven by a separate drive. There may thereby be provision for the auxiliary component to be driven by a servo drive. Additionally it may hereby be provided that the separate drive is only activated when the auxiliary part must be in operation. A separate drive makes it possible to use conventional sewing machines and operate them with the method as per invention without the need to rebuild or modify the sewing machine itself. Moreover the separate drive, particularly in the form of a servo drive, offers the possibility of adapting the drive exactly to the particular seam production requirements or also of only activating the drive when operation of the auxiliary component is necessary. Additionally it may preferably be provided that after take-up of the thread loop by the main looper, the auxiliary component then pushes the thread loop onto the main looper against the working direction of the looper. This further improves the sewing certainty, because it prevents the thread loop from slipping off the main looper and moreover the pushing of the thread loop onto the main looper increases the area of the thread triangle. Subject of the invention is further a device for the mechanical sewing of a double chain stitch seam, whereby the double chain stitch is formed with the aid of an industrial sewing machine with a sewing needle and needle thread and also a main looper and looper thread, whereby the needle thread locks needle loops laid in a chain on the underside of the material being sewn, whereby during the stitch formation process the main looper which in particular moves at right angles to the direction of the seam, takes up the needle thread loop in the needle rise position of the sewing needle and carries the looper thread through the loop while the needle thread loop slides past the neck of the main looper, whereby the looper thread and the needle thread loop are formed into a thread triangle which the needle perforates at the next downstroke. To meet the purpose mentioned above, it is proposed that to avoid faulty stitches, the thread needle loop and the looper thread are brought together underneath the sewing plane by a driven auxiliary component in the area between the main looper and the sewing plane at a distance from the sewing needle and the main looper and are held and moved in such a way that the thread triangle is formed which the needles perforates at the downstroke. Preferred further developments thereof are set out in the sub-claims. The design as per invention ensures that also for seams not running straight or in the case of a very short distance between the entry points of the sewing needle or also when sewing against the direction of the seam, e.g. for completion of the seam, there is — even at high sewing speed - a simple and precise formation of the thread triangle which the sewing needle can perforate at the downstroke so that proper locking of the double chain stitch seam and also proper completion of the seam can be achieved. In addition, the method and the design of the device as per invention result in gentle handling of the threads by the auxiliary component so that the risk of thread breakage is reduced to a minimum. If the auxiliary component is coupled to the drive of the sewing machine there is automatic synchronous movement of the elements so that a high seam precision is achieved. Particularly also when working on the seam against the actual direction of the seam, e.g. for its completion, early intervention in the sewing process guarantees suitable thread guidance. In particular the method and device as per invention achieve that the intervention of the auxiliary part commences immediately at the take-up of the thread loop by the main looper and only ends at the release of the thread loop at a definite point in time when the locking of the double chain switch is complete. When considering a fully completed double chain stitch it is seen that the thread loop taken up spends more than 90% of the total time required to complete the stitch on the main looper. Within this period the thread loop assumes at certain times accurately predetemiinable positions in order to correctly form the thread triangle and to guarantee correct locking without the production of faulty stitches which would lead to the seam coming undone. The fact that the auxiliary component has several functional surfaces and functional edges makes it possible, in concert with the kinetic sequence of the auxiliary part, to place the thread loop in defined time-related and spatial positions critical to the sewing process and to accurately position the thread triangle both in terms of size and location. This ensures in particular that even under high-speed automatic operating conditions a double chain stitch seam, whether straight or othenwise, and also when the sewing direction is reversed, is produced. The functional edge referred to in the claims can be of any design e.g. by angling a formed part. It may also be a smooth bar or the like with a groove or a similar element. What is only essential for its function is that the functional edge holds the needle thread and the looper thread together at one point so that through the motion of the auxiliary component the required thread triangle can be formed. The invention is explained in more detail below with reference to the diagrams. Illustrations: Fig. 1 is a diagrammatic front view of the elements under discussion; Figures 2 and 3 show a top view of the essential elements in different functional positions. The illustrations only show the parts essential to the invention. The essential elements of the industrial sewing machine producing double chain stitches are the sewing needle 1 with a hole 2 at the needle tip to hold the needle thread 3 which is the top thread and a main looper 5 underneath the sewing plane 4 driven synchronously with the sewing needle 1 and whose working direction is indicated at 6. The sewing needle 1 carries out movements in the direction of arrow 7. The main looper 5 carries the looper thread 8 which exits at a hole 9 of the main looper. For the sake of simplicity the drawing does not show a needle plate or the like for supporting the length of fabric in the sewing plane 4, nor a possibly mounted presser which in the sewing plane 4 presses the fabric against the needle plate or against a possibly mounted fabric feed (also not shown). While in Figure 1 the viewing direction of the illustration is oriented parallel to the transport direction of the material to be sewn in the sewing plane 4, the viewing direction in Figures 2 and 3 is orthogonal to the sewing plane 4 and, specifically, underneath the sewing plane 4. The normal transport direction of the material to be sewn is indicated by an arrow at 10. This direction is the normal direction of the seam, whereas the opposite direction indicates a reversal of the direction of the seam. For the creation of a double chain stitch seam during sewing against the direction of the seam 10, an auxiliary component 11 becomes active (the method of operation will be explained below) which can be inactive during sewing in the direction of the seam 10, if the movement of the material to be sewn alone is sufficient to form the thread triangle which will be described later. Figures 2 and 3 show the thread triangle formed by the looper thread 8 and the loop of the needle thread 3, which triangle is perforated by the needle 1 with the continuous needle thread 3.During sewing in the direction of the seam 10 this thread triangle is formed independently by the fabric transport alone so that the perforation of the descending needle 1 in the area surrounded by the thread triangle automatically takes place correctly. In the case of deviations from the direction of the seam 10, especially also during sewing against the direction of the seam 10, the auxiliary component 11 ensures that the thread triangle is set up in such a way that the area enclosed by the triangle is hit by the needle 1 at the downstroke. The auxiliary component is shown in various positions, i.e. in the operating positions 1 to iV, whereby the auxiliary component 11 executes a movement deviating from the circular, curving, self-contained, beginning from Position I via Position II to Position III and then to Position IV and then back to Position I. When sewing in a direction other than the direction of the seam 10, in particular also when sewing against the direction of the seam 10, the main looper 5 takes up the thread loop of the needle thread 3 formed by the sewing needle 1 as is shown particularly in Figure 1. Hereby the main looper 5 moves at right angles to the direction of the seam 10 in the direction of the arrow 6. In this position the auxiliary component 11 moves from Position I to Position II (as shown in Figures 1 and 2) so that with the first functional surface 12, e.g. an edge, the needle thread 3 forming the loop is taken up and pushed onto the main looper 5 against its working direction and is held to prevent the loop from slipping off the main looper 5 and to form a sufficiently large thread triangle. This happens by a relatively fast movement of the auxiliary component 11 against the working direction 6 of the main looper 5 from Position I to Position II. To prepare the needle thread 3 and the looper thread 8 for the formation of the thread triangle, the auxiliary component 11 is then shifted from Position II to Position III until the needle thread 3 and the looper thread 8 reach the edge 13, e.g. a corner area, an angular area or rounded corner area of the auxiliary component 11 and are held there. In this way a thread triangle is formed between the area of the needle thread loop held on the main looper 5, the free looper thread 8 and the main looper 5, which triangle is perforated by the sewing needle 1 at the downstroke. The needle thread 3 and the looper thread 8 are carried on the corner area 13 until the sewing needle has securely perforated the thread triangle. The second functional surface 14, e.g. an edge, takes the thread assembly area down from the main looper 5, whereby the thread triangle as its area decreases remains open until the next loop formation by the needle thread 3 begins. By fast withdrawal of the functional surface 14 the locked stitch can slip off the looper 5 and the sewing process can start anew. This is clarified by the illustration in Fig. 3, Position IV, from which position the auxiliary component 11 resumes Position I. The main looper 5 thereby moves back again to its initial position against the working direction 6. In the embodiment the auxiliary component 11 is represented by an L-shaped angle. The cross-section of the shanks is preferably round to exclude damage to the threads. The shape of the auxiliary component 11 is, however, not necessarily L-shaped, but any shape is possible as long as at least the corresponding functional surfaces and functional edges are retained. The actuation of the auxiliary component can be through a separate drive. However, actuation can also be by means of an eccentric drive, whereby through the eccentric design the retarded and accelerated movements of the auxiliary component 11 are easy to realise. It is of course also possible to couple the auxiliary component to the drive of the sewing machine so that synchronization follows automatically. WE CLAIM: 1. A method of double-chain stitching comprising the steps of sequentially: a) pushing a needle carrying a needle thread down through goods to be seamed to form below a lower face of the goods a needle-thread loop; b) passing a looper carrying a looper thread transversely to a stitching direction and generally parallel to the face through the loop below the lower face to pass the looper thread through the needle-thread loop; c) gathering the looper thread and needle-thread loop on a catching element below the lower face; d) moving the element in the stitching direction with the gathered needle and looper threads away from the needle and looper generally parallel to the face while advancing the goods in the direction to form with the needle-thread loop and looper thread a window; e) repeating step a) with the needle passing through the window; f) releasing the gathered needle and looper threads from the element so that they engage around the needle loop formed in step e); and g) repeating steps b), c), d), e), f), and g). 2. The double-chain stitching method as claimed in claim 1 wherein the direction in which the goods is moved is reversed. 3. A method of double-chain stitching comprising the steps of sequentially: a) pushing a needle carrying a needle thread down through goods to be seamed to form below a lower face of the goods a needle-thread loop; b) passing a looper carrying a looper thread transversely to a stitching direction and generally parallel to the face through the loop below the lower face to pass the looper thread through the needle-thread loop; c) gathering the looper thread and needle-thread loop on a catching element below the lower face; 5. An apparatus for double-chain stitching, the apparatus comprising: a needle (l)carrying a needle thread(3); needle-drive means (15)for pushing the needle (l)down through goods(4) to be seamed to form below a lower face of the goods (4)a needle-thread (3)loop; a looper (5)carrying a looper thread(8); looper-drive means for moving the element in an annular path in a plane parallel to the goods (4)through the loop below the lower face to pass the looper thread(8) through the needle-thread (3)loop; a catching element(l 1) between the lower face and the looper(5); element-drive means for gathering the looper thread (8)and needle-thread (3)loop at the lower face on an element below the lower face, pulling the element with the gathered needle and looper threads away from the needle (l)and looper (5)generally parallel to the face while advancing the goods (4)in the direction to form with the needle-thread (3)loop and looper thread (8)a window(w), and releasing the gathered needle and looper threads from the element (ll)so that they engage around the needle loop. 6. The apparatus as claimed in claim 5 wherein the drive means(15,16) are all interconnected for synchronous movement of the needle(l), looper(5), and element(ll). 7. An apparatus for double chain stitching, the apparatus comprising: a needle(l) carrying a needle thread(3); needle-drive means (15)for pushing the needle(l) down through goods (4)to be seamed to form below a lower face of the goods (4)a needle-thread (3)loop; a looper (5)carrying a looper thread(8); looper-drive means for pushing the looper (5)transversely to a stitching direction parallel to the face through the loop below the lower face to pass the looper thread (8)through the needle-thread (3)loop; a catching element (1 l)between the lower face and the looper (5)and having a pair of generally parallel engagement surfaces meeting at a comer(13); element-drive means for gathering the looper thread (8)and needle-thread (3)loop at the lower face on an element below the lower face, pulling the element with the gathered needle and looper threads away from the needle(l) and looper (5)generally parallel to the face while advancing the goods (4)in the direction to form with the needle-thread (3)loop and looper thread (8)a window(w), and releasing the gathered needle and looper threads from the element (ll)so that they engage around the needle loop.

Documents:

in-pct-2002-1052-che abstract duplicate.pdf

in-pct-2002-1052-che abstract.pdf

in-pct-2002-1052-che claims duplicate.pdf

in-pct-2002-1052-che claims.pdf

in-pct-2002-1052-che correspondence-others.pdf

in-pct-2002-1052-che correspondence-po.pdf

in-pct-2002-1052-che description (complete) duplicate.pdf

in-pct-2002-1052-che description (complete).pdf

in-pct-2002-1052-che drawings duplicate.pdf

in-pct-2002-1052-che drawings.pdf

in-pct-2002-1052-che form-1.pdf

in-pct-2002-1052-che form-19.pdf

in-pct-2002-1052-che form-26.pdf

in-pct-2002-1052-che form-3.pdf

in-pct-2002-1052-che form-5.pdf

in-pct-2002-1052-che pct.pdf

in-pct-2002-1052-che petition.pdf