Abstract:
A plastic closure device ( 1 ) with a lower part ( 2 ) is disclosed which can be fastened in a non-releasable and integrally bonded manner by means of ultrasonic welding to a plastic film or a plastic patch. A flange ( 20 ) of the lower part ( 2 ) is connected by an underside thereof to the plastic layer in an integrally bonded manner by means of introducing ultrasonic energy of a sonotrode into the flange ( 20 ). An energy-introducing arrangement, comprising a plurality of energy-introducing ribs ( 23 ), is used to introduce the ultrasonic energy into the flange ( 20 ), as a result of which the weld parts are welded under the action of a static joining force. Owing to the design according to the invention of the energy-introducing arrangement, a desired connection can be achieved in spite of a reduced static joining force, a reduced ultrasonic energy and, in general, with the use of a reduced welding power by comparison with prior art methods.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention describes a plastic closure device for tubular bags, having a bottom part, comprising a discharge outlet and a flange having a flange bottom side on which there is disposed an energy-introducing arrangement which can be connected to a plastic layer by means of ultrasonic welding. 
         [0002]    Plastic closure devices for tubular bags, which in technical language are generally referred to as pouches, are known in different embodiments. 
         [0003]    The plastic closure devices generally comprise a bottom part, fastened directly on the tubular bag, and a screw cap, releasably fastenable on the bottom part, for closing off a discharge outlet in the bottom part. For the fastening of the plastic closure device, a flange of the bottom part is fastened on the plastic film material of the tubular bag in a non-releasable, integral manner by ultrasonic welding. This welded joint is realized either directly between the flange bottom side and the plastic film of the tubular bag, or between the flange bottom side and a plastic patch which closes a punched opening in the plastic film of the tubular bag. 
         [0004]    As is made clear in the diagrams according to the prior art, the ultrasonic welding of plastic in the region of a joining zone of the flange as the weldment by means of a sonotrode leads to the non-releasable connection of the flange to the tubular bag or the plastic patch. In order that a static joining force can be applied perpendicularly to the flange, the sonotrode is pressed with a defined joining force against a so-called anvil. This anvil is not represented in the figures. 
         [0005]    In order to achieve a sufficiently firm and liquid-tight connection between the bottom side of the flange and the tubular bag, according to the prior art an energy-introducing rib, which runs all the way round the flange, has been disposed on the bottom side of the flange. According to the appended figure, an energy-introducing rib which is as blunt as possible and points with a flat face in the direction of the tubular bag and which withstands the high static joining forces that are necessary for optimal welding, has been provided. The energy-introducing rib is made as blunt as possible with sufficient thickness, so that the static joining force can be evenly applied to as large a surface area as possible. 
         [0006]    The mechanical ultrasonic vibrations are transferred under pressure to the flange in the region of the energy-introducing rib, wherein, by molecular and boundary friction, the heat which is necessary for the plasticization of necessary heat is generated on the basis of pressure threshold loading and an approximately homogeneous welding of the surface of the energy-conducting rib in a large region ensues, in that the blunt energy-conducting rib is plasticized and provides a large-area connection. 
         [0007]    The method according to the prior art delivers satisfactory results with low welding times, wherein, due to the thickness of the energy-introducing rib, a liquid-tight, large-area welding is achieved. The efficiency of the fastening method is open to improvement, however, since a total power of several thousand Watts for the entire connecting operation by ultrasonic welding is necessary in order to achieve the desired liquid-tight, non-releasable connections. According to the prior art, the necessary static joining force in respect of film thicknesses of, say, 125 μm, is about 400 N and must be applied, as far as possible, perpendicularly to the flange surface. Integral connections between the plastic closure device and the plastic film are thereby achievable in such strength that the connection withstands tensile forces of about 0.2 to 0.5 N/mm2. 
         [0008]    Depending on the application and loading of the tubular bag, this achievable strength is insufficient. In order to create an optimal plasticization of the energy-introducing ribs and hence a sufficiently strong connections, a structured anvil was used. The drawback of a structured anvil is the possibility that bacteria will hide in the structured surface, or that the structure of the anvil will damage the plastic film of the tubular bag, including next to the welding point. 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the present invention is to provide a plastic closure device which, in comparison to known plastic closure devices known from the prior art, can be fastened on the tubular bags by means of lower static joining forces, lower amplitudes, lower welding energies, and thus, in total, by means of lower welding powers. Due to the high quantities, a more cost-effective fastening of each individual plastic closure devices leads to enormous savings worldwide in the region of billions of dollars per annum. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A preferred illustrative embodiment of the subject of the invention is described below in connection with the appended drawings. 
           [0011]      FIG. 1  shows a perspective view of a two-part plastic closure device, while 
           [0012]      FIG. 2  shows a view of the bottom side of the bottom part with the inventive energy-introducing arrangement. 
           [0013]      FIG. 3  shows a longitudinal section through a plastic closure device with mounted sonotrode, while 
           [0014]      FIG. 4  shows a sectional view of a detail of the flange in the region of the joining zone. 
           [0015]      FIG. 5   a  shows a diametrical vertical section through a bottom part, wherein the flange, in the outer marginal region after the outer energy-introducing rib, is of rounded construction, while 
           [0016]      FIG. 5   b  shows a section through a bottom part along the sectional line W-W according to  FIG. 2 . 
           [0017]      FIGS. 6   a  and  6   b  show a plastic closure device according to the prior art. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The inventive plastic closure device is denoted in its entirety by  1  and comprises a bottom part  2  onto which a screw cap  3  can be releasably fastened to form a seal. Optionally, the screw cap  3  can be fastened to the bottom part  2  by a guarantee band  4  as protection against prior opening, so that an intact guarantee band  4  is a sign of a plastic closure device  1  which has never previously been opened. The bottom part  2  comprises a normally cylindrically shaped discharge outlet  22 , on the outer face of which is arranged an external thread  21  and which is delimited by a flange  20 . The screw cap  3  has an internal thread (not represented), which can be brought into operative connection with the external thread  21 , whereby the plastic closure device  1  can be closed in a liquid-tight manner. 
         [0019]    The bottom part  2  can also be provided with a hinged cap, or a piercing element disposed in the bottom part  2 . It is only important that the plastic closure device  1  should have a bottom part  2  with discharge outlet  22  and a peripheral flange  20 . 
         [0020]    With the flange  20 , the bottom part  2  can be fastened directly or indirectly to a plastic film  5 , as shown in detailed representation in  FIG. 3 , wherein the plastic film  5  constitutes a part of a tubular bag (not represented). Depending on use, the tubular bag can be filled with different liquids, wherein the liquid can be extracted from the discharge outlet  22  from the tubular bag following the removal of the cap. The opening in the tubular bag which is necessary beneath the discharge outlet  22  can be produced either by a corresponding device to the abovementioned piercing element, for instance, or can be made directly in the plastic film  5  of the tubular bag. 
         [0021]    The bottom side  200  of the flange  20 , which is facing away from the cap  3 , for instance a screw cap  3 , has an energy-introducing arrangement in the form of a plurality of energy-introducing ribs  23 , which skirt the round flange  20  and project away from the bottom side  200  of the flange  20 . The energy-introducing ribs  23  are here preferably at least approximately parallel to one another and are arranged at such a distance from the inner diameter of the flange  20  or of the discharge outlet  22  that they lie outside the region of the cap  3 . 
         [0022]    A non-releasable connection of the bottom part  2  to the plastic film  5  of the tubular bag is effected by means of ultrasonic welding. After the bottom part  2  has been placed with the bottom side  200  of the flange  20  on the plastic film  5 , a sonotrode  6 , which is usually of rotationally symmetric configuration, is positioned on the flange top side  201 , which is facing away from the energy-introducing ribs  23 . The sonotrode  6  is advantageously configured as a rotary sonotrode  6 , which has a receiving space  60  into which the bottom part  2 , where necessary with mounted cap  3 , can be received, while the bearing edge  61  of the sonotrode  6  has direct contact with the flange top side  201 . The ultrasonic energy is introduced into the region of the joining zone Z at least approximately perpendicularly to the flange top side  201 , wherein the vibrational direction S of the sonotrode  6  is realized, say, longitudinally roughly parallel to the longitudinal axis of the bottom part  2  of the plastic closure device  1 . With an amplitude A, high-frequency mechanical vibrations, generated by a connected generator, are realized, which vibrations correspond to the working frequency of the sonotrode  6 . 
         [0023]    During the introduction of the mechanical ultrasonic vibrations, a static joining force F is applied at least approximately perpendicularly to the flange top side  201  during a welding time. The static joining force F points roughly in the vibrational direction S. The sonotrode  6  presses the bottom part  2  under the static joining force F against an anvil (not represented). 
         [0024]    As a result of the high-frequency ultrasonic vibration, the contact points between the plastic film  5  and the flange  20  is or are heated, whereby the integral connection between the bottom part  2  and the tubular bag or plastic film  5  ensues. The welded joint can be realized either directly between the flange bottom side  200  and the plastic film  5  of the tubular bag, or between the flange bottom side  200  and a plastic patch inside the tubular bag beneath the plastic film  5  of the tubular bag, wherein the ultrasonic vibration correspondingly introduces energy into the energy-introducing ribs  23 . 
         [0025]    After the actual welding operation also, the joining force F persists for a dwell time, wherein the flange  20  and the plastic film  5  cools under pressure. 
         [0026]    Tests have shown that the plurality of energy-introducing ribs  23  should be arranged over a width b on the bottom side  200 , wherein the flange top side  201 , spanning the width b, should be fully covered during the welding operation by the bearing surface, here the edge  61  of the sonotrode  6 , in order to ensure an optimal energy input. The energy-introducing ribs  23  should be arranged approximately parallel at a distance apart b′, wherein the energy-introducing ribs  23  and the flange bottom side  200  are distanced by a height h from the plastic film  5 . 
         [0027]    Tests have shown that two or more, preferably three, energy-introducing ribs  23  over the width b lead to optimal liquid-tight welded joints. In comparison to methods according to the prior art, the static joining force F which is to be expended, and the overall expended power, was able to be reduced, wherein welded joints of equivalent quality are achievable. 
         [0028]    The height h is determined by the distance between the flange bottom side  200  and the elevation maximum of the energy-introducing ribs  23 , and thus by the plastic film  5  which is to be welded on. Heights h of 0.2 to 0.4 mm were chosen. The energy-introducing ribs  23 , which in cross section are configured rounded into their end, have a radius r of 0.1 to 0.3 mm. The elevation maxima of the energy-introducing ribs  23  in the form of domes give rise, viewed in cross section, to roughly punctiform bearing surfaces against the plastic film  5 . The flanks of the energy-introducing ribs  23  enclose an angle α between 50° and 70°, preferably of 60°. The domes of the energy-introducing ribs  23  lie beneath the flange bottom side  200  on circular bearing lines or narrow bearing surfaces. 
         [0029]    The distance apart b′ of adjacent energy-introducing ribs  23  of the energy-introducing arrangement is chosen between 1 mm and 1.5 mm, depending on the flange width B and width of the bearing edge  61  of the sonotrode  6 , so that, in the case of three parallel, and thus non-intersecting energy-introducing ribs  23 , the width b of the energy-introducing arrangement is about 2.5 to 2.7 mm. Since thread flanks of the external thread  21  project partially over the flange top side  201 , the bearing edge  61  of the sonotrode  6  can usually be mounted onto the flange top side  201  such that it does not bear against the discharge outlet. It is important, however, that the edge  61  rests as flatly as possible on the flange top side  201 , lying opposite the energy-introducing arrangement on the flange bottom side  200 , wherein the ultrasonic energy can be optimally introduced by the sonotrode  6  into the flange  20  and the energy-introducing ribs  23 . In order to achieve a largest possible region of energy transfer to the flange  20 , the sonotrode  6  must be led as closely as possible past the thread flanks of the external thread  21 , so that a maximal contact surface on the flange top side  201  is covered. 
       Example 
       [0030]    In series of tests which have compared the welding method according to the prior art, where only one energy-introducing rib is used, with the use of a plastic closure device  1  having a plurality of energy-introducing ribs, a significant reduction in the necessary static joining force F, and, above all, in the maximally necessary power, was able to be measured. Here good results were manifested with the use of energy-introducing arrangements comprising two and three energy-introducing ribs  23 , wherein the best results were able to be achieved with three energy-introducing ribs  23 . 
         [0031]    The weld fastening of a bottom part of a plastic closure device according to the prior art is compared with a bottom part  2  with special energy-introducing arrangement comprising three energy-introducing ribs  23  on identical plastic films  5  each having a thickness of 5 mil, which corresponds to a thickness of (1 mil=25.4 μm) about 125 μm. The surface areas of the flange bottom sides  200  and flange top sides  201  of the known bottom part, as well as of the novel bottom part  2 , were identical, so that the results are comparable. 
         [0032]    In the case of more than three energy-introducing ribs, these must be reduced in thickness so as not to add further to the energy and power requirement. As a consequence, the volume of the material necessary for the welding would be too low, however, and the strength of the welded joint would be reduced. 
         [0033]    Table 1 shows the direct comparison of the method parameters for fastening the known bottom part and the novel bottom part  2  respectively. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Prior art 
                 Invention 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Welding time 
                 0.160 
                 s 
                 0.200 
                 s 
               
               
                   
                 Dwell time 
                 0.100 
                 s 
                 0.100 
                 s 
               
             
          
           
               
                   
                 Amplitude A 
                 95% 
                 90% 
               
             
          
           
               
                   
                 Static joining force F 
                 400 
                 N 
                 250 
                 N 
               
               
                   
                 Energy max. 
                 120 
                 J 
                 105 
                 J 
               
               
                   
                 Power max. 
                 3900 
                 W 
                 549 
                 W 
               
               
                   
                   
               
             
          
         
       
     
         [0034]    In addition to a near halving of the necessary static joining force F and a reduction in the necessary inputted ultrasonic energy in combination with approximately equal amplitude A, the power to be expended for the entire ultrasonic welding operation was able to be significantly reduced. 
         [0035]    Table 2 shows a comparison of the tensile force for the removal of a welded-on plastic closure devices according to the prior art and an inventive plastic closure device  1  or the bottom part  2 , with the use of three energy-introducing ribs  23 . The above-described bottom parts with identical surface areas of the flange bottom sides, after having been fastened on an identical plastic film  5 , were loaded after a while with the below-specified tensile forces under identical conditions. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Prior art 
                 Invention 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Tensile force (N) 
                 92.00 
                 144.33 
               
               
                   
                 Tensile force/unit of area (N/mm2) 
                 0.43 
                 0.67 
               
               
                   
                   
               
             
          
         
       
     
         [0036]    It can clearly be seen that the necessary tensile force or tensile force per unit of area for the detachment of the bottom parts, in the case of the bottom part  2  provided with the new energy-introducing arrangement, lies significantly above the comparison value of the traditional bottom part. 
         [0037]    As has been explained above, the present configuration of the bottom part  2  was able to bring about an improvement in the previously known welding methods, so that an energy-efficient, integral connection of bottom parts  2  of plastic closure devices  1  with plastic films  5  of tubular bags can be achieved, which connection additionally ensures a still stronger and more resistant connection between the bottom part  2  and the tubular bag. 
         [0038]    In order to enhance the welded joint, a situation in which the bottom side  200 , in the outer marginal region Y of the flange  20 , comes into contact with the plastic film  5  during welding should be avoided. In order to prevent a part of the energy from being introduced into the plastic film  5  outside the desired joining zone Z during the welding operation, the bearing of the bottom side in the marginal region Y of the flange  20  is avoided by virtue of the fact that bottom side  200  is guided after the outer energy-introducing rib  23  in the direction of the flange top side  201 . This is illustrated in  FIG. 5   a . The strongly rounded marginal region Y of the flange  20  is distinguished by the fact that the bottom side  200  merges into the flange top side  201 , wherein the distance of the bottom side  200  to the plastic film  5  corresponds to the height h of the energy-introducing rib  23  only directly at the outer energy-introducing rib  23 . As a result of the bottom side  200  in the marginal region Y, said bottom side being curved away from the plastic film  5 , the welding energy remains limited to the joining zone Z and thus no adhesion of the plastic film  5  occurs beneath the marginal region Y of the flange  20 . As a result of this concentration of welding energy, the necessary energy can be additionally reduced. 
         [0039]    In  FIG. 5   b , a section through the flange  20  along the sectional line W-W according to  FIG. 2  is represented. Here too, the bottom side  200  is curved after the outer, in this case second energy-introducing rib  23  strongly away from the plastic film  5  in the direction of the flange top side  201 , whereby the resulting marginal region Y after the outer energy-introducing rib  23  is strongly curved and is distanced from the plastic film  5 . That surface area of the flange bottom side  200  which lies opposite the plastic film  5  is thus minimized, whereby almost no welding is performed in this marginal region Y. The introduced energy is thus concentrated on the energy-introducing ribs  23 .