Process for automated sewing of decorative seams

Abstract

Method for sewing decorative seams with the following process steps: - the sewing dress (12) is positioned in the sewing machine (10) in such a way that the seam stub (28) of the functional seam (24), which is approximately teardrop-shaped in cross-section, runs in a seam groove (40) of the sewing machine (10), - the sewing garment (12) is fixed in the seam trench (40) by a seam sword (54) which is placed on the functional seam (24) from the side (56) of the sewing garment (12) opposite the seam trench (40), - the two reference elements (20, 22) of the sewing dress (12) connected by the functional seam (24) are brought into a position approximately perpendicular to the functional seam (24) by a presser set (50) of the sewing machine (12) and held there, - at least one decorative seam is applied parallel to the functional seam (24) by means of a sewing needle (58) positioned laterally next to the seam blade (54), - characterized in that - the seam stub (28) of the functional seam (24) is fixed approximately at the level of the functional seam (24) on both sides by a taper (48) at the upper edge area of ​​the seam trench (40).

Description

TECHNICAL FIELDThe invention relates to a method for the automated sewing of decorative seams. Decorative seams are designated as high-expression seams which regularly serve for the optical activation of a surface by placing accents and emphasizing contours. Decorative seams are increasingly considered to be signs of particular product quality and represent, in particular in the interior of automobiles and in upholstery, a decorative element of the molded parts which are regularly laminated with leather or artificial leather.PRIOR ARTIn particular in the automobile industry, the components are laminated more frequently and over a larger area in the interior sector in order to decorate them in particular with leather or with leather designs and to give them a higher quality appearance. Laminating is understood to mean the joining of several plies of identical or different materials by suitable laminating means, in particular by adhesive. The lamination can protect or decorate a material.For laminating carrier parts, usually a sewing line, also called a cover, is first made by connecting two or more reference elements to one another via a functional seam. The functional seams form a seam stub on the underside of the sewing line. These suture stubs can be inserted into a seam trench of the carrier part designed for this purpose. Parallel to the functional seam, decorative seams can be regularly applied on the front side of the sewing line, which are a decorative element.For this purpose, after the functional seam sewing, the decorative seams are usually sewn on both sides of the functional seam manually in a decorative seam sewing machine provided for this purpose in a separate working step. For this purpose, the sewing cloth must be positioned manually in the decorative seam sewing machine. For this purpose, the sewing cloth is positioned in the sewing machine in such a way that the functional seam points with its seam stub downwards, so that the seam stub can be guided through the sewing machine in a slight groove of the sewing machine. The groove of the sewing machine is only for the purpose that the seam stub can embed itself flat relative to the throat plate. For this purpose, the sewing machine has a seam blade which presses into the functional seam from above in the region of the functional seam and thus represents a simple guide. On each side of the seam blade, a trigger assembly is provided on each side, which holds apart the two reference elements provided on the right and on the left of the functional seam and holds them in a position arranged approximately perpendicular to the seam stub of the functional seam. The sewing cloth is transported by the upper and lower transport of the sewing machine. The actual sewing of the decorative seams is effected by means of one or two needles which are arranged on both sides of the seam blade. For this purpose, the sewing cloth must be held and guided manually by a person skilled in the art. After completion of a sewing line, the latter must be removed from the sewing machine and a new sewing line inserted into the sewing machine from the supply.The sewing of decorative seams has hitherto been carried out completely manually, which requires the use of formed approaches. These can operate only a single sewing machine, since the sewing lines must be permanently guided during the sewing process. Changing a finished sewing line to a new sewing line is relatively time-consuming and may take the same time as actually sewing the decorative lines.Therefore, the machine time cannot be optimally utilized. This results in high personnel costs for producing decorative seams.Corresponding methods for sewing decorative seams are known, for example, from DE 10 2009 013 863 A1, DE 10 2009 013 862 A1, U.S. Pat. No. 3,407,420 A or EP 1 377 705 B1.In addition, it is also possible to bend the two ends of the seam stub apart again in order to suture the decorative seam and to fasten these to the covering material from below by means of the decorative seams. Corresponding processes are known, for example, from DE 10 2006 003 423 A1. In this way, further molded parts can also be fastened to the underside of the sewing cloth, as is known, for example, from DE 10 2004 053 133 A1.DE 10 2012 100 891 A1 discloses a seam tape which can be used to reinforce a seam.SUMMARY OF THE INVENTIONProceeding from this prior art, the object of the invention is to specify an improved method for sewing decorative seams, which method can be executed at least partially in an automated manner.The method according to the invention is given by the features of the main claim 1. Meaningful further developments of the method are the subject matter of further claims which follow the main claim 1.The method according to the invention for sewing decorative seams makes use of the fact that an approximately drop-shaped cross section of the seam stub of the functional seam can result from the use of an additional soft insert. Such a seam stub can be held and guided in the seam trench of the sewing machine if this seam trench narrows at its upper edge region. The functional seam of the seam stub comes to lie in the region of the taper. The tapering thus prevents the suture stub from slipping out of the suture trench.The soft insert can be, in particular, felt, leather, plastic, silicone, cardboard, cardboard, paper, rubber, granules, wood or foam. The soft insert can be designed, for example, as a textile insert made of synthetic or natural materials. The hardness and the thickness and the strength of the soft insert can vary depending on the application. The seam stub of the sewing line can preferably be surrounded by a seam tape which is fixed by the functional seam. The soft insert can in principle be present between the seam tape and the seam stub or also on the outer side of the seam tape. In particular, the soft insert can be arranged only in the region of the seam stub, but not in the region of the functional seam. The optical seam image of the functional seam thus remains as far as possible non-significant and a switch position cannot be accidentally visible in the region of the functional seam. In addition, the functional seam is given more stability by the sewn-in seam tape and thereby runs visually closed, rectilinear and calmer, so that a closed seam pattern is achieved. The seam stub surrounded by soft insert and optionally also by seam tape can thereby have an approximately drop-shaped cross section, in which the functional seam forms a taper.As an alternative to a single soft insert, two soft inserts can also be present on the seam tape, which are arranged parallel to one another and at a certain distance from one another. As a rule, the two soft inserts can be present on the same side of the seam tape. However, it would also be possible to provide two or more soft inserts on different sides of the seam tape. In this case, a part of the soft inserts could be present between the seam tape and the seam stub of the sewing line after sewing, while another part of the soft inserts would be arranged on the outside of the seam tape. As a result, it would also be possible to provide the individual soft insert with different surfaces, so that a well-slipping soft insert or a soft insert with an anti-slip effect could be used in a targeted manner.Alternatively, it would also be conceivable to pass the sewn suture stub through a silicone dipping bath, a plastic dipping bath or a rubber dipping bath in order to achieve a suitable drop shape. It would also be possible to spray a plastic sheathing onto the suture stub.To produce such a seam stub, the soft insert can first be fixed to the edge regions of the covering elements and then the functional seam can be produced-if appropriate using a seam tape. Preferably, the soft insert can already be present pre-fixed on the seam tape, so that during the production of the functional seam the seam tape can be sewn in directly with the soft insert and thus the drop-shaped cross section of the seam stub is formed.Due to the drop-shaped cross section of the seam stub of the functional seam, the functional seam can serve as a guide element. As a result, the seam stub can be guided and also steered on the decorative seam sewing machine in the region of the throat plate without the risk of the seam stub slipping.Such a narrowing can be realized in particular by a hold-down device which is present above the needle plate of the sewing machine having the seam trench. In this case, the holding-down device can project on both sides a certain distance into the clear cross section of the seam trench, so that a corresponding tapering is formed. Such a holding-down device can be positioned subsequently on the throat plate of the sewing machine as an apparatus or tool and can optionally also be fixed there. This would allow simple manual adjustment of the sewing machine, which could also be disassembled again if necessary by removing the holding-down device. However, it would also be possible to integrate the hold-down devices into the throat plate of the bottom clothing of the sewing machine.The method according to the invention can be carried out with great process safety. In addition, the method is significantly faster than the completely manual method from the prior art and thus also more effective. The sewing lines are guided independently and the speed for sewing the decorative seams can be programmed according to the complexity. For the first time, it is possible with the method to suture decorative seams without a trained operator, i.e. without trained closer. This leads to a reduction in the personnel costs and to planning the production independently of persons. Also, no closer teaching needs to be performed. The method according to the invention can thus increase the degree of utilization of a sewing machine. The processing capability is also increased by the safe and guided guiding of the functional seam in the apparatus. As a result, the internal waste can be significantly reduced.In a particularly preferred embodiment, a plurality of sewing clothes are connected in a row by means of an endless sewing belt. This can be done when several sewing clothes are sewn on successively with the endless sewing belt during the upstream functional seam sewing. The individual sewing lines should be spaced apart by a small distance and not immediately follow one another. The distance can be in particular between 2 and 5 millimeters. The stitched clothes arranged in rows can be guided continuously through the apparatus so that after completion of a first stitched clothes, the subsequent stitched clothes are automatically threaded into the guide of the apparatus. The locking at the beginning and at the end of each sewing line can be effected fully automatically by means of a detection, for example by means of a light barrier or by means of a laser. Due to the spatial arrangement of the tapered seam trench, the individual sewing lines already align themselves when approaching the sewing machine in such a way that the drop-shaped seam stub is guided directly into the tapered seam trench.This eliminates the time-consuming insertion of the sewing lines into the sewing machine. The machine time is optimally utilized, since decorative seams can be produced practically uninterruptedly. This also leads to a reduction in the personnel costs, since now an operator can operate a plurality of sewing machines. By using an endless belt, a fully automated process with endless seams is thus possible. The trim seams can thus be sewn without manual intervention by an operator. Only for changing the supply after the endless belt has been used up or for changing the suture material at the end of the yarn bobbins is the aid of an operator necessary.In order to further facilitate the threading of the successive sewing lines into the sewing machine, a new sewing line can initially strike an expanding element of the sewing machine before the beginning of the sewing operation and the sliding of the seam stub into the tapered seam trench of the sewing machine. The spreading element can enter between the two covering elements of the sewing cloth still lying on top of each other and spread and fold these open in such a way that they are present approximately perpendicular to the suture stub. In this position, the reference elements can enter the gap between the throat plate and the presser set of the sewing machine. The spreading element can be static and be arranged spatially in front of the sewing machine. It would also be possible to use a movable spreading element, by means of which the two reference elements are actively pressed apart.The locking at the beginning and at the end of each sewing process can be effected by a recognition at the sewing machine. For this purpose, a sensor can be present which detects the end of a sewing cloth and automatically initiates the locking process. Similarly, a locking process can also be initiated by the sensor of the sewing machine at the beginning of a new sewing line. Such a locking process usually comprises two stitches backwards and subsequent two stitches forwards. The locking is necessary so that the decorative seams cannot open again at the beginning and at the end of the seam.The method according to the invention can always be used when decorative seams are to be applied or when another refinement of a covering is to be carried out by seams. Applications in all modular systems of the automotive industry, aeronautical industry or furniture industry, for example, are thus possible. The method can be used in particular for applying decorative seams to center consoles, instrument carriers, doors or seats.Further advantages and features of the invention can be taken from the features further specified in the claims and from the exemplary embodiments below.BRIEF DESCRIPTION OF THE DRAWINGSThe invention is described and explained in more detail below with reference to the exemplary embodiment shown in the drawing. The following are shown: FIG. 1 is a cross-section through a sewing machine with a tapered seam trench during sewing of two decorative seams next to a functional seam.WAYS OF CARRYING OUT THE INVENTIONFIG. 1 shows a cross section through a sewing machine 10 in the region of the needle plate, into which an exemplary embodiment of a sewing cloth 12 is inserted. The sewing cloth 12 has two reference elements 20, 22, which are fastened to one another by means of a functional seam 24. The two reference elements 20, 22 are made of leather or artificial leather in the present example, but other materials of the reference elements 20, 22 are also conceivable in principle. A seam stub 28 is formed on the underside 26 of the sewing line 12 by the functional seam 24, and the seam stub 28 is surrounded in the present example by a soft insert 30 and by a seam tape 32. The seam tape 32 is present here sewn directly into the functional seam 24. The width of the soft insert 30 is selected such that no soft insert 30 is present in the region of the functional seam 24. This ensures a harmonic and optically smooth functional seam 24.The seam tape 32 may be 0.2 to 10.0 millimeters thick. Preferably, the seam tape 32 is between 0.2 and 0.5 millimeters thick, so that the seam tape 32 is not marked in the region adjoining the functional seam 24 in the finished sewing line 12. The soft pad 30 may be between 0.3 and 10.0 millimeters thick. The soft insert 30 can be present glued onto the seam tape 32. Alternatively, the soft pad 30 could also be sewn onto the seam tape 32. Other fastening possibilities of soft insert 30 and seam tape 32 would also be possible in principle. Soft insert 30 and seam tape 32 do not necessarily have to be connected to one another even before being attached to the functional seam 24.Both in the seam tape 32 and in the soft insert 30, a perforation, for example in the form of a plurality of apertures or slits, can be present centrally along the longitudinal axis of the seam tape 32, so that the seam tape 32 or the soft insert 30 can be bent particularly easily along its longitudinal axis. This facilitates the sewing of the seam tape 32 and the soft insert 30 into a functional seam, since the seam tape 12 folds better in the intended gripping aid of the sewing machine. The perforation can be adapted to the respective circumstances, for example to the material of the sewing cloth to be sewn or to the width or the material of the soft insert and the sewing tape.The seam stub 28 of the sewing line lies in a seam groove 40 of the sewing machine 10. the seam groove 40 is present in the throat plate 42 of the sewing machine 10, so that the seam stub 28 is bounded laterally by the under-transport 44 of the sewing machine 10 and from below by the central web 46 of the throat plate. At the upper edge region of the seam trench 40, a respective hold-down device 48 is provided on both sides. The hold-downs 48 each protrude on both sides a certain distance into the clear cross section of the seam trench 40, so that a tapering of the seam trench 40 is formed. The hold-downs 48 are arranged approximately at the height of the functional seam 24, so that the seam stub 28 cannot slide upward out of the seam trench 40 due to its drop-shaped cross section. The hold-down 48 can be mounted in front of the needle bar, parallel to the needle bar or else subsequently on the needle plate.The two reference elements 20, 22 are held apart by a respective presser assembly 50 and are held in an approximately horizontal position. In addition to the trigger clothing 50, an upper transport 52 is provided on each side, which ensures a uniform advance of the sewing cloth 12 through the sewing machine 10 in addition to the lower transport 44. In addition, as is already customary in the prior art, the suture stub 28 is fixed by a suture blade 54 which rests on the front side 56 of the suture lining 12 as an additional guide. At a certain distance from the seam blade 54, a sewing needle 58 is provided on each side. In the present example, the sewing needle 58 is arranged one piece before the top transport 52. The two sewing needles 58 each suture a decorative seam, which thus run exactly parallel to one another.As an alternative to the embodiment shown in FIG. 1, the suture stub with the holding-down device and the integrated suture trench can be brought up to the actual needle plate in an apparatus which has been mounted in front of the needle plate. If, as described here, an apparatus is mounted or placed on, it is mounted directly before the top transport. There is then only one seam groove which has been milled from the throat plate of the sewing machine. The apparatus is mounted from above on the throat plate / sewing machine table before the top transport and the trigger clothing. The apparatus contains a seam trench and a holding-down device on both sides in order to bring the sewing material to the sewing machine, the top transport and the trigger clothing in a positionally accurate manner. The pre-assembled apparatus brings the sewing stub and the sewing material directly in front of the upper / lower conveyor in order to guide the sewing material and the sewing stub further into the needle plate of the sewing machine. The groove in the needle plate of the sewing machine is machined in correspondence with the stud and can have additional holding-down devices.FIG. 1 illustrates the position in the throat plate of the sewing machine. If an apparatus is to be plugged on, the principle is similar. A seam trench and hold-down device are located on the apparatus. The seam blade comes from behind and is mounted on the sewing machine. The needle plate of the sewing machine has a seam trench, possibly additional holding-down devices.Due to the drop-shaped cross section of the seam stub 28 and the taper 48 of the seam trench 40 of the sewing machine 10, the sewing cloth 12 can be transported through the sewing machine 12 without manual guidance, merely by means of the under-transport 44 and the upper transport 52.

Claims

Method for sewing decorative seams, comprising the following method steps: - the sewing line (12) is positioned in the sewing machine (10) such that the seam stub (28) of the functional seam (24), which is approximately drop-shaped in cross section, runs in a seam trench (40) of the sewing machine (10), - the sewing line (12) is fixed in the seam trench (40) by a seam blade (54), which is placed on the functional seam (24) from the side (56) of the sewing line (12) opposite the seam trench (40), - the two reference elements (20, 22) of the sewing line (12) connected by the functional seam (24) are brought into a position approximately perpendicular to the functional seam (24) by a trigger assembly (50) of the sewing machine (12) and held there, at least one decorative seam is applied parallel to the functional seam (24) by means of a sewing needle (58) positioned laterally next to the seam blade (54), characterized in that - the seam stub (28) of the functional seam (24) is fixed on both sides, approximately at the height of the functional seam (24), by a respective taper (48) on the upper edge region of the seam trench (40).Method according to claim 1, - characterised in that - a plurality of sewing clothes are fastened to one another by means of an endless sewing belt enveloping the functional seam, - the endless sewing belt is passed through the tapered seam trench, so that - a plurality of sewing clothes are provided with decorative seams one after the other.Method according to Claim 2, - characterized in that - a new sewing cloth, before the beginning of the sewing operation, meets a spreading element of the sewing machine which travels between the two reference elements of the sewing cloth which are still located one on top of the other, - the spreading element spreads the two reference elements in such a way that they come to lie between the needle plate having the sewing trench and the presser sets.

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