Patent Application
20150307235
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.
Plastic closure devices for tubular bags, which in technical language are generally referred to as pouches, are known in different embodiments.
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.
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.
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.
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.
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.
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.
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.
A preferred illustrative embodiment of the subject of the invention is described below in connection with the appended drawings.
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
b shows a section through a bottom part along the sectional line W-W according to
a and 6b show a plastic closure device according to the prior art.
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.
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.
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
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
Table 1 shows the direct comparison of the method parameters for fastening the known bottom part and the novel bottom part 2 respectively.
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.
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.
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.
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.
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
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 003 019.8 | Mar 2010 | DE | national |
| 10 2010 003 268.9 | Mar 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/050778 | 1/20/2011 | WO | 00 | 3/28/2013 |
