Abstract:
A cover tape is applied before welding onto the edge region of two subjects which are to be welded or bonded to one another by ultrasound. The cover tape covers uncleanly cut edge regions, seals the seam and prevents the delamination with multi-layered material along the seam.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The subject-matter of the invention is a method for manufacturing a seam connection between two textile sheet by ultrasonic welding or ultrasonic bonding and an ultrasonic welding device.  
         [0002]     Seam connections, in particular on textiles, may be produced by way of a thread seam or by way of a bonding seam or weld seam. With the present invention it is the case of the production of a weld seam or bonding seam, which is produced by an ultrasonic welding device. Ultrasonic welding devices for textile sheet formations or technical films are known. They comprise an anvil and a sonotrode. For the production of long or curved seam connections one uses rollers for the anvil as well as for the sonotrode, which may be pressed against one another by way of suitable means and with a suitable force.  
         [0003]     In order to be able to produce and optically aesthetic seam formation, it is necessary to cut to size the edges of the textile sheet formation to be connected in a very exact manner, i.e. to avoid fibers projecting out of the edges of the sheet formation. In order to achieve this, the cut part of such a sheet formation may not be effected in a conventional manner by way of punching, but on cutting for example a suitable temperature increase at the cut edge must be simultaneously effected in order to seal this. This leads to the high cost of cut parts.  
       SUMMARY OF THE INVENTION  
       [0004]     It is the object of the present invention to provide a method with which conventional cut parts are sufficient in order, despite this, to produce clean undetachable seam connections.  
         [0005]     A further object of the invention lies in providing a device for carrying out the method.  
         [0006]     By way of the simultaneous application of a tape which may be welded to the surfaces of the two textile sheet formations to be connected and which laterally overlaps the edge region of the seam, it is possible on the one hand to cover unclean cut edges and at the same time create a direct connection between the surfaces of the two textile sheet formations or films which are connected to one another by the seam. The seam may be designed in a waterproof manner depending on the material of the tape used for covering. If a tape is used whose color differs from the color of the textile sheet formation, then the seams may be optically emphasized. For invisible coverings, the tapes of the same material as the visible surfaces of the sheet formation may be used.  
         [0007]     The cover tape may be simultaneously fed and welded to the surfaces with the device according to the invention for producing the connection seam between the textile sheet formations i.e. in the same working step and on a conventional welding device. As a result of this no additional working costs arise, and the positioning of the cover tape is effected in an extremely precise manner and parallel to the course of the edge regions of the seam. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The invention is explained in more detail by way of an illustrated embodiment example. There are shown in:  
         [0009]      FIG. 1 a  perspective representation of an ultrasonic welding device (only anvil roller and sonotrode roller are shown),  
         [0010]      FIG. 2 a  front view of the device according to  FIG. 1 ,  
         [0011]      FIG. 3 a  lateral view of the device and  
         [0012]      FIG. 4 a  cross section enlarged several times, through a connection seam of two multi-layered textile sheet formations with cover tapes deposited on both sides. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     In  FIG. 1 , which shows an ultrasonic welding device  1  only schematically and only with regard to those parts which are essential to the invention, a sonotrode roller  3  is visible at the bottom, which is seated on a drivable shaft mounted laterally of the sonotrode roller  3 . The sound generator and the mounting of the sonotrode roller  3  have been omitted for the purpose of an improved overview. A drive motor is indicated at M. An anvil roller  7  is mounted on a shaft which is not shown, above the sonotrode roller  3 . The anvil roller  7  is displaceably mounted in the vertical and is pressed with a settable force F against the sonotrode roller  3  by way of means which are not shown.  
         [0014]     Two textile sheet formations, subjects  11 ,  13  for short, which are to be connected to one another lie on a table which is only indicated and provided with reference numeral  9 , which forms a working and rest surface for the subjects  11 ,  13  and comprises a recess (not shown) which is in the region of the sonotrode roller  3  arranged below the table  9  and through which the apex of the sonotrode roller  3  projects into the plane of the table  9 . The subjects  11 ,  13  overlap mutually by an amount a, e.g. 6 mm (cf.  FIG. 4 ) which is dimensioned in dependence on the subject property in order to ensure a permanent undetachable connection of the two subjects  11 ,  13 . A bonding aid  15  may lie between the two subjects  11 ,  13  in the region of their overlapping, for example a tape which may be melted on by way of heat. Such a tape is optional and is applied when the materials of the two subjects  11 ,  13  have insufficient properties for a direct mutual welding by way of heat. The insertion of an adhesive aid  15  between the subjects  11 ,  13  on ultrasonically welding sheet formations such as pieces of clothing, in particular rainwear, or also technical textiles such as rain protection coverings, tarpaulins etc. is not described in more detail. The bonding aid  15  is schematically shown in the  FIGS. 1 and 3 .  
         [0015]     A protective and cover strip is indicated with the reference numeral  17  which in the examples according to  FIGS. 1 and 3  by way of suitable means is led up to the periphery of the anvil roller  7  tangentially from above, or directly into the gap between the anvil roller  7  and the subjects  11 ,  13  and is deposited by these exactly at the desired location on the edge region  19 . The width of the cover tape  17  may be a few millimeters so that for example in each case only two millimeters are covered on both sides of the edge  25  of the upper-lying subject  11  which is to be covered. The cover tape  17  may of course also be significantly wider and project more beyond the seam edge (cf.  FIG. 4 , shown in broken lines). The cover tape  17  on production of the welding or bonding of the two subjects  11 ,  13 , in the clamping gap between the sonotrode roller  3  and the anvil roller  7  is placed onto those surfaces of the subjects  11 ,  13  which face the tape  17  and is connected by way of the effect of the sonotrode  3  to the surfaces of the subjects  11 ,  13  with their mutual welding or bonding. I.e. the subjects  11 ,  13  and the tape or tapes  17  are simultaneously connected to one another and amongst one another.  
         [0016]     In  FIG. 4  it is shown in a schematic and enlarged manner how the cover tape  17  covers the edge region  19  also at the end-face so as to form a textile sheet formation arrangement comprising both subjects  11 ,  13  and the cover tape  17 . Any fibers  27  projecting at the edge region  19  are covered and bonded by way of the cover tape  17 . The edge region  19  and the cover tape  17  are pressed together by way of the effect of pressure and heat, so that the thickness of the seam with the cover tape  17  is significantly lower than double the thickness of the subjects  11 ,  13  and of the cover tape  17 . As is further evident from  FIG. 4 , the cover tape  17  may not only be deposited onto the upper side of the connected subjects  11 ,  13  but also on their lower side. For this a second cover tape  17  is fed to the periphery  23  of the sonotrode roller  3 , and likewise during the welding of the two subjects  11 ,  13  is undetachably connected to their surfaces.  
         [0017]     In a preferred design of the invention, the cover tape  17  consists of the same material and the same color as the outer-lying layer  21  of the subjects  11 ,  13 . The cover tape  17  may be transparent, and the color of the outer layer  21  may shine through or complementarily or reflecting colors may be applied in order to optically highlight the seams. The cover tape  17  not only covers unclean subject edges  19 ; but also the requirements with regard to an exact positioning of the bonding aid  15  between the two subjects  11 ,  13  may be reduced. Should the bonding aid  15  happen to be pressed out laterally over the edge region  19  on welding or bonding, then it is rendered invisible by the cover tape  17 , i.e. it is covered.  
         [0018]     With subjects  11 ,  13  of multi-layer material, a delamination on loading due to friction or washing may be completely prevented with the cover tape  17 . The cover tape  17  furthermore increases the waterproofing of the seam, since no water may penetrate into the edge region  19  at the end-face.  
         [0019]     The small thickness of the cover tape  17  of for example a few hundredths of millimeters as a result does not increase the thickness of the seam design. By way of the welding, the edges of the cover tape  17  are pressed flatly in a manner such that an almost stepless transition to the subject surface arises.  
         [0020]     The cover tape  17  may smooth the wave formation along a welded seam which is often present.  
         [0021]     Preferably the cover tape  17  overlaps the subject  13  lying at the bottom more than the object  11  lying at the top by the thickness of the subject. By way of this it is ensured that a sufficiently large contact surface to the subject  11  lying at the bottom is achieved.