Patent Publication Number: US-6209298-B1

Title: Process for the manufacture of a dipped tire cord fabric made of organic fiber cords including cord joint portions

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a process for the manufacture of a dipped tire cord fabric made of organic fiber cords including cord joint portions, and more particularly to a process for the manufacture of a dipped tire cord fabric made of organic fiber cords, at least one of which cords including a cord joint portion therein. Particularly, the invention relates to a process for the manufacture of a dipped tire cord fabric made of organic fiber cords including cord joint portions and having a high quality wherein the productivity for connecting ends of two cords to each other is excellent, and a size of the joint portion is thinner than the conventional one and becomes approximately equal to a diameter of a non-connected portion of the cord and a tensile strength of the joint portion is high and the fabric is particularly suitable as a reinforcing member for pneumatic tires or conveyor belts. 
     2. Description of Related Art 
     The organic fiber cord used as a reinforcing member for the conveyor belt or the pneumatic tire is so-called two or three strand cord formed by subjecting two or more bundles of organic multifilaments to cable twisting and ply twisting. In case of producing this type of the organic fiber cord before dipping, it is unavoidable to vary lengths of the resulting organic fiber cords and also the organic fiber cord having a very long length is sometimes required, so that it is necessary to conduct work or operation of connecting the organic fiber cords to each other. 
     As general means for connecting the organic fiber cords by hand labor, there is a sewing connection through an electric sewing machine. In such a sewing connection, end portions Ae, Be of two different cords A, B are sewn by means of the electric sewing machine at a state of simply overlapping these end portions with each other as shown in FIG. 5, so that even if the sewing work is conducted more carefully, free end threads not sewn always come out at both ends of a knot portion C between the cords. 
     These free end threads are required to deliberately cut off from the knot portion by means of scissors or the like. In this case, there is caused a problem that the cords A and B existing in the knot portion are injured or a part of the filaments in these cords is cut off. And also, there is caused an inconvenience that during the manufacture of the tire cord fabric, the free end threads of the knot portion C are caught on other cords adjacent thereto, a dropper pin, a held wire and the like to cause a temporary stop of operation in an apparatus for the manufacture of the tire cord fabric or the cord breaking-up. Furthermore, since the electric sewing machine itself is big, there are caused secondary inconveniences that it is difficult to move the electric sewing machine in a factory having a limited space, and a power feeding cable for the electric sewing machine becomes cumbersome and the like. 
     In addition to the above means, there is a method of connecting the cords with an apparatus called as a knotter. According to this method, the connecting time required for the completion of, for example, a single joint cord is required to be about five minutes, which is inefficient, and also the untwisting work is required after the connection through the knotter. The latter work tends to depend on the sixth sense and the gist by a skilled worker. Therefore, this method is at variance with the reality. 
     In order to solve the above problems in the connection between mutual cords, JP-T-6-505,222 discloses a method of connecting ends of two assemblages (cords) wherein an end of one of the assemblages (two or three strand cord) each made of two or more multifilament threads is untwisted to separate the threads at such an end, and an end of the other assemblage is untwisted to separate the threads at such an end likewise the above case, and a pair of these assemblages are placed side by side and also untwisted thread parts in each of the assemblages are placed side by side to obtain junction regions shifted axially from each other, and filaments of the two threads in each junction region are assembled together by air splicing. 
     Since this connection method need not use the electric sewing machine, the knotter or the like, it is possible to shorten the connecting time and there is not feared the generation of the free end filaments at the knot portion. And also, the junction regions are shifted axially from each other and dispersed in each of the assemblages, so that it is sure to have a merit capable of making the bulge of the knot portion small. 
     In this method, however, it is necessary that the two or more strand cord is specially separated into the multifilament threads, and such a separation is kept so as not to return it, and the untwisting is carried out every the multifilament thread, and the twisting operation is carried out every the multifilament thread after the completion of the connecting work, so that the method takes labor and requires 2-3 minutes for completing a single joint cord and hence the operability for connecting the cords still stands improvement. For this end, it should be noticed to adopt the connection between the cords as a dipped tire cord fabric made of organic fiber cords without sticking only the connection between the two cords. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the invention to provide a process for the manufacture of a dipped tire cord fabric made of organic fiber cords including a joint portion, which is advantageously applicable to articles such as pneumatic tire and conveyor belt, by supposing an initial connection of cords each formed by twisting two or more fiber bundles of organic multifilaments and a finish connection as a tire cord fabric of organic fiber cords wherein the end portions of two cords before the dipping are surely connected in a short time at the initial connection and an excellent quality is given to the tire cord fabric at the finish connection. 
     According to the invention, there is the provision of a process for the manufacture of a dipped tire cord fabric made of organic fiber cords including cord joint portions, which comprises steps consisting of: 
     (a) a step that end portions of two organic fiber cords, each formed by subjecting two or more bundles of organic multifilaments to cable twisting and ply twisting, after untwisting prior to a dipping treatment are placed in a box provided in its bottom with a jetting port of a pressure gas and having a circumferential wall and a cover for receiving a jetted gas so as to cross these end portions with each other at a position of the jetting port or in the vicinity of the jetting port together with ends of these end portions, and filaments in the crossed end portions of the two cords are untwisted by jetting the pressure gas through the jetting port into the inside of the box as a jet stream to simultaneously engage these untwisted filaments with each other, whereby an initial connection is completed to form a continued cord; and 
     (b) a step that a tire cord fabric is made from many organic fiber cords including the thus continued cord after the completion of the initial connection, and passed through a dipping solution, and subjected to a heat treatment at a high temperature lower by 10-30° C. than a melting point of the organic multifilament under a given tension to decrease a size of a joint portion in the continued cord to thereby complete a finish connection. 
     In a preferable embodiment of the invention, the two cords including their free ends are clamped at both side positions sandwiching the box there-between so as to hold the crossing of the two cords in the box, and portions of the two cords near to their ends are cut off in the box or at a position near to the box and then subjected to the initial connection. 
     In another preferable embodiment of the invention; the pressure gas is a compressed air of 8-11 kgf/cm 2 . 
     In the other preferable embodiment of the invention, a connecting length in the initial connection is within a range of 5-15 mm. 
     In a still further preferable embodiment of the invention, the bundle of organic multifilaments is selected from a nylon fiber bundle, a polyester fiber bundle, a rayon fiber bundle and a Kevlar fiber bundle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein: 
     FIG. 1 is a diagrammatically plan view of an outline in an apparatus for connecting two cords according to the invention; 
     FIG. 2 is a diagrammatically section view taken along a line II—II of FIG. 1; 
     FIG. 3 is a schematic view illustrating a joint portion between two cords prior to a dipping treatment; 
     FIG. 4 is a diagrammatically side view of an outline in an apparatus for treating a tire cord fabric made of organic fiber cords; and 
     FIG. 5 is a schematic view illustrating a joint portion of two cords by the conventional connection through an electric sewing machine. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Firstly, the connection of two untreated cords will be described with reference to FIGS. 1-3. 
     As shown in FIG. 1, a connection apparatus  1  comprises a base  2 , four clamping devices  3 - 1 A,  3 - 1 B,  3 - 1 C and  3 - 1 D in total arranged thereon, a cord connecting box  4  showing a side view in FIG. 2 (an outer profile line and a recess portion as mentioned below are shown in FIG.  1 ), and a pair of cutters  5 A and  5 B located on both sides of the cord connecting box  4  and near thereto. 
     Each of the clamping devices  3 - 1 A,  3 - 1 B,  3 - 1 C or  3 - 1 D is composed of a first clamp member having a compression coil spring and a second clamp member receiving a pushing force of the first clamp member and is a simple device capable of manually performing the clamping operation. When each of the clamping devices  3 - 1 A,  3 - 1 B,  3 - 1 C or  3 - 1 D is kept at a released state, the first clamp member having the compression coil spring is rendered into a compressed state by hanging on a lock member (not shown). Besides this device, there may be used a clamping device using a small-size double-action cylinder (not shown), wherein the clamping operation and releasing operation can be carried out semi-automatically. 
     As shown in FIG. 2, the cord connecting box (hereinafter abbreviated as a box)  4  is provided on a side of a main body  4   a  with a recess portion  4   b  having a space enough to completely accommodate two cords  8 A and  8 B as mentioned later, and comprises a lid  4   c  connected to the main body  4   a  through a hinge (not shown) and freely moving in a direction shown by an arrow in FIG.  2  and an inlet hole  6  for a pressure gas communicating with a through-hole  2   h  formed in the base  2  of the connection apparatus  1  and opening in a bottom of the recess portion  4   b.  The sectional shape of the inlet hole  6  may be either a circle or an ellipse. The connection between end portions  8 Ae and  8 Be of the two cords  8 A and  8 B will be described below. 
     Firstly, end portions  8 A e  and  8 B e  of two untreated cords  8 A,  8 B to be connected are fed to the connection apparatus  1 . The term “untreated cord” used herein means an organic fiber cord of, for example, 840D/2, 1000D/2, 1260D/2, or 1890D/2 obtained by subjecting a bundle of organic multifilaments having a given denier such as 840D, 1000D, 1260D, or 1890D to cable twisting and then subjecting two or more of such cable twisted bundles to ply twisting. The untreated cord is so-called green cord state before a treatment with a dipping solution as mentioned later and is hereinafter abbreviated as a green cord. As a material of the organic multifilaments, there are nylon-6, nylon-66, polyester, rayon, aramid (Kevlar) and the like. 
     When the two green cords  8 A and  8 B are fed to the connection apparatus  1 , the end portion  8 A e  of the green cord  8 A is passed through a concave portion  9 A c  of an untwisting device  9 A, the clamping device  3 - 1 A of the released state and the recess portion  4   b  of the box  4  and is clamped at its end by the clamping device  3 - 1 B, while the end portion  8 B e  of the green cord  8 B is passed through a concave portion  9 B c  of an untwisting device  9 B, the clamping device  3 - 1 C of the released state and the recess portion  4   b  of the box  4  and is clamped at its end by the clamping device  3 - 1 D. 
     In this case, the end portions  8 A e  and  8 B e  of two green cords  8 A and  8 B are crossed with each other at a very small crossing angle α in the recess portion  4   b  of the box  4  to form a flat X-shape, wherein the crossing position is a position of the inlet hole  6  for the pressure gas opening to a bottom of the recess portion  4   b  of the box  4  or in the vicinity thereof. By such a crossing can be conducted the simultaneous cut-off of extra parts of the end portions  8 A e  and  8 B e  of the cords as mentioned later, which contributes to shorten the connection time. The crossing angle α between the end portions  8 A e  and  8 B e  is preferably within a range of 15-45°. After the completion of the above clamping, an initial tension T in the direction shown by an arrow in FIG. 1 is applied to the green cords  8 A and  8 B, respectively. In this case, the lid  4   c  of the box  4  is naturally at an opened state. 
     Next, the untwisting devices  9 A and  9 B are rotated in a direction shown by an arrow (i.e. direction of untwisting the cord) at the crossed state of the end portions  8 A e  and  8 B e,  whereby the twisting of these end portions  8 A e,    8 B e  is untwisted. The operation of the untwisting devices  9 A,  9 B may be performed by hand, but it is effective and advantageous to rotate the untwisting devices  9 A and  9 B by a given number through an electric driving means. In this case, the lid  4   c  of the box  4  may be at either opening or closing state. 
     After the completion of the untwisting by the given number, the clamping devices  3 - 1 A and  3 - 1 C for the end portions  8 A e  and  8 B e  kept at the released state are actuated to strongly clamp the end portions  8 A e  and  8 B e.  At this state, the cutters  5 A and  5 B are moved in a direction shown by an arrow by hand or by means of a moving device to cut off an extra end portion existing between the cutter  5 A and the clamping device  3 - 1 B and an extra end portion existing between the cutter  5 B and the clamping device  3 - 1 D. As a result, cut ends of the cord end portions  8 A e  and  8 B e  subjected to tension Ta larger than the initial tension T by the working of the clamping devices  3 - 1 A and  3 - 1 C are accommodated in the recess portion  4   b  of the box  4 . 
     After the lid  4   c  of the box  4  is closed, the pressure gas such as the compressed air is jetted as a jet stream gas through the through-hole  2   h  formed in the base  2  of the connection apparatus  1  and the inlet hole  6  opening in the bottom of the recess  4   b  of the box  4 . The compressed air is favorable to have a pressure of 8-11 kgf/cm 2 . And also, the jetting time of the jet stream gas is preferable to be within a range of 8-16 seconds. 
     In this case, the recess portion  4   b  of the box  4  indicates a semi-closed state with the bottom and side wall faces of the box and the lid  4   c,  while only a part of the end portions  8 A e  and  8 B e  at the enter and delivery sides of the recess portion is released into the outside of the box, so that the jet stream gas untwists the bundles of the multifilaments in the cord end portions  8 A e  and  8 B e  accommodated in the recess portion  4   b  of the box  4  inclusive of their free cut ends. At the same time, the jet stream gas strikes against each surface of the recess portion  4   b  under the semi-closed state to form a high-speed turbulence, which engages the untwisted multifilaments of the cord end portions  8 A e  and  8 B e  with each other and finally the end portions  8 A e  and  8 B e  of the cords are strongly connected to each other. The connecting length is substantially determined by the length of the recess portion  4   b  (the length is measured along the left and right direction of FIG.  1 ), but is practically suitable within a range of 5-15 mm. 
     As seen from the above, the connection between the end portions  8 A e  and  8 B e  of the green cords  8 A and  8 B takes only a time of setting the end portions  8 A e  and  8 B e  in the connection apparatus  1 , a time of untwisting by the given number, a time of cutting the extra portions through the cutters  5 A and  5 B, and a time of untwisting and engaging through the pressure gas. Therefore, the connection between the green cords  8 A and  8 B is not required to take a long time and is about 30 seconds irrespectively of the material of the green cord as previously mentioned, so that the connection productivity between the two cords is considerably excellent as compared with the productivity by the conventional method. In FIG. 3 is shown an embodiment of the joint portion  8 C between the green cords  8 A and  8 B. 
     In the joint portion  8 C shown in FIG. 3, there is observed no filament portions indicating the loosened state corresponding to the free end threads at the knot portion observed in the example using the electric sewing machine. As a result of repetitive investigations whether or not the size of the joint portion  8 C forms an obstruction factor in the manufacture of the tire cord fabric inclusive of the cord having the joint portion according to the usual manner, there is found no inconvenience on the manufacture of the tire cord fabric. Furthermore, it has been confirmed that the tensile strength of the joint portion  8 C is larger than the tensile strength of the unconnected portion of the cord. 
     The manufacture of the dipped tire cord fabric made of organic fiber cords inclusive of the above green cord having the joint portion  8 C will be described below. 
     In an apparatus  10  for the treatment of a tire cord fabric made of organic fiber cords shown in FIG. 4, an elongated tire cord fabric  11  made of organic green fiber cords inclusive of the green cord having the joint portion  8 C is fed out from a take-up motion  12  wound with the elongated tire cord fabric in a direction shown by an arrow, subjected to a dipping treatment by immersing in a dipping solution  13   b  in a tank  13   a  of a dipping device  13  under a guidance of various rolls (shown by circles in FIG.  4 ), successively passed through a drying zone (dry)  14 , a hot-treating zone (heat-stretch)  15  and a hot-relaxing zone (heat-relax)  16 , and thereafter cooled to form a finish dipped tire cord fabric  17 , which is wound on a take-up reel to obtain a large-size finish wound fabric  18 . 
     In the dipping device  13 , the dipping solution is a known mixed solution (RF/L) of resorcin-formaldehyde condensate/rubber latex having an optimum compounding recipe capable of ensuring the adhesion between the organic fiber cord as previously mentioned and rubber. Moreover, a given tension is applied to the tire cord fabric  11  and the dipped tire cord fabric before and after each treatment by pull rolls  19   a,    19   b,    19   c,    19   d,    19   e  over a region ranging from a position just before the dipping device  13  to a position just before the finish wound fabric  18 . 
     In the dry zone  14 , the dipping solution adhered to the tire cord fabric  11  is merely dried by treating at a relatively high temperature under the application of a given tension (although the tension differs by the material of the cord and the denier number, it is usually 1500-4500 gf/cord). 
     In both the heat-stretch zone  15  and the heat-relax zone  16 , the tire cord fabric  11  is subjected to a heat treatment at a temperature lower by 10-30° C., desirably 10-25° C., particularly 10-20° C. than a melting point of the filament of the organic fiber cord under an action of a proper tension (gf/cord). After such a heat treatment at the high temperature under the proper tension, the size of the heat-treated joint portion  8 C t  (not shown) is decreased so as to be approximately equal to a diameter of the unconnected green cord  8 A,  8 B though the diameter of the joint portion  8 C before the heat treatment is about 1.3-1.6 times the diameter of the unconnected green cord  8 A,  8 B, while the heat-treated joint portion  8 C t  has a tensile strength higher by about 1.2-1.3 times than a tensile strength of the joint portion  8 C before the heat treatment. 
     On the other hand, the heat-treated joint portion  8 C t  has a tensile strength higher by about 0.9-1.1 times and a diameter higher by about 0.9-1.1 times than those of unconnected cord portions  8 A t  and  8 B t  after the above heat treatment. The effect of decreasing the diameter and the effect of increasing the tensile strength through the heat-treated joint portion  8 C t  have been confirmed based on the following examples. 
     The above effects are clear to be based on the fact that the excellent joint portion  8 C can be obtained between the green cords  8 A and  8 B and the filaments of the organic fiber cord are not melted by the above high-temperature heat treatment but indicate just like a state of adhering these filaments with each other by tackiness just before the melting. 
     The following examples are given in illustration of the invention and are not intended as limitations thereof. 
     In Table 1 are shown the material and denier number of the cord, the heating temperature (°C.) every the cord, the tension (gf/cord) applied to the cord, and the heat treating time (sec) as examples. In the material of the cord shown in Table 1, 6N is nylon-6, 66N is nylon-66 and PE is polyester. Moreover, a melting point of nylon-6 filament is 220° C., and a melting point of nylon-66 filament is 250° C., and a melting point of polyester filament is 260° C. Incidentally, a melting point of rayon filament not described in Table 1 is 260 280° C. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Heat stretch zone 
                 Heat relax zone 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Tem- 
                   
                   
                 Tem- 
                   
                   
               
               
                 Cord Denier 
                 pera- 
                   
                   
                 pera- 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Ma- 
                   
                 ture 
                 Tension 
                 Time 
                 ture 
                 Tension 
                 Time 
               
               
                 terial 
                 Denier 
                 (° C.) 
                 (gf/cord) 
                 (sec.) 
                 (° C.) 
                 (gf/cord) 
                 (sec.) 
               
               
                   
               
               
                  6N 
                  840D/2 
                 200 
                 1500˜ 
                 30 
                 200 
                 800˜860 
                 30 
               
               
                   
                   
                   
                 1700   
               
               
                   
                 1260D/2 
                 200 
                 2100˜ 
                 35 
                 200 
                 1100˜1200 
                 35 
               
               
                   
                   
                   
                 2400   
               
               
                   
                 1890D/2 
                 200 
                 3400˜ 
                 40 
                 200 
                 2000˜2200 
                 40 
               
               
                   
                   
                   
                 3700   
               
               
                 66N 
                  840D/2 
                 230 
                 1400˜ 
                 35 
                 230 
                 700˜800 
                 35 
               
               
                   
                   
                   
                 1600   
               
               
                   
                 1260D/2 
                 230 
                 2500˜ 
                 35 
                 230 
                 1300˜1500 
                 35 
               
               
                   
                   
                   
                 2700   
               
               
                   
                 1890D/2 
                 230 
                 4300˜ 
                 35 
                 230 
                 2600˜2800 
                 35 
               
               
                   
                   
                   
                 4500   
               
               
                 PE 
                 1000D/2 
                 250 
                 1700˜ 
                 60 
                 250 
                  800˜1000 
                 60 
               
               
                   
                   
                   
                 2300   
               
               
                   
                 1500D/2 
                 250 
                 2400˜ 
                 60 
                 250 
                  900˜1200 
                 60 
               
               
                   
                   
                   
                 2700   
               
               
                   
               
            
           
         
       
     
     As to a heat-treated joint portion  8 C t  between cords  8 A t  and  8 B t  sampled from a finish wound fabric  18  treated under the temperature, tension and treating time disclosed in the columns of “heat-stretch zone” and “heat-relax zone” of Table 1, there are obtained the tensile strength and diameter as previously mentioned. As seen from the above, the diameter of the heat-treated joint portion  8 C t  is not so increased in the finish wound fabric  18  including the heat-treated joint portion  8 C t,  so that the end count (number of cords per unit width as measured in a direction perpendicular to the cord extending direction) can be made sufficiently large. And also, the heat-treated joint portion  8 C t  has a sufficient strength. Therefore, such a finish wound fabric has a satisfactory quality as a reinforcing member for the pneumatic tire or belt conveyor. 
     According to the invention, the organic fiber cords before the treatment can be connected to each other in a short time, and the tire cord fabric can be manufactured by using the cord having such a joint portion together with the other organic fiber cords without causing inconveniences, and the joint portion has substantially the same diameter and tensile strength as those of the unconnected cord portion when the resulting tire cord fabric is subjected to a dipping treatment and subsequent high-temperatured heat treatment under a given tension, so that there can be provided a process for the manufacture of the tire cord fabric including the joint portions and possessing both high productivity and high quality.