Packaging apparatus for closing a can with a membrane

Abstract: A packaging apparatus for closing a can (202) with a membrane (214) by means of heat-sealing comprises an inner, heat-sealing die (190) and an outer, sealing ring (180) wherein an outer surface of the heat-sealing die (190) and an inner surface of the sealing ring (180) are beveled slightly in mating fashion.

Description: Background of the Invention The invention relates to a packaging apparatus for closing a can with a membrane. In general, cans as referred to herein differ from boxes or cartons in that cans are hermetically sealed, i.e., the contents are sealed in liquid-tight and preferably gas-tight fashion. Boxes or cartons, on the other hand, are typically closed simply by means of tabs or flaps or folded-in corner portions that do not provide for such tight, hermetic sealing. A can is usually sealed with at least one closure member at a first end thereof. By connecting the can body to the closure member, the cylinder is given the desired shape cross-section, at least in the region of the closure element. After the can is filled, a further closure member may be sealed to the opposite end of the lateral surface or body member so that the can is completely sealed and the cylinder has a desired shape at the second end as well. In case of a folded cylinder having at least two folding edges, the folding edges are formed (in particular bent and/or fluted) and circumferentially located in such a way that the lateral wall or body-forming portion of the can can be collapsed flat before insertion of a closure member. In the flat state, the volume of the cylindrical, body-forming member corresponds essentially to the material volume. In other words, essentially no empty volume is transported during transportation from the cylinder factory to the filling line. The foldable cylinder then is unfolded -- preferably just before filling -- and is sealed in the manner described above. The closure members are initially completely separate from the lateral surface portion of the can body. They are, in general, formed as a single piece and comprise a closing surface, which is the same as the can cross-section, and an annular contact region by which they can be sealed tightly to the inside lateral can surface around the entire can circumference. (For purposes of the invention all continuous (i.e., unbroken), closed surfaces will be referred to as annular regardless of whether their contour is circular, oval, or polygonal and regardless of whether they are formed with straight or curved lines.) Cans having a cardboard lateral surface are frequently cylindrical with the lateral surface being formed as a wound cardboard tube. In the case of a foldable cylinder having just two folding edges, the cross-section can become increasingly flat with increasing distance from a closure member, depending on the method of unfolding. Therefore, in order to achieve a better approximation to the desired circular cross-section along the length of the can, more folding edges can be provided, and a circular closure member be applied. In addition, the cylinder can be spread apart by a shaping means during unfolding, and/or the folding edges can be flattened out. The final shape of the can also depends on the filling and on the second closure member. High resistance to deformation or crushing of the middle region of the can is achieved if the can cross-section is as circular as possible. However, elliptical closure members, those which comprise circular segments or parts of ellipses, or polygonal closure members (particularly having an even number of sides that are of the same length, and preferably having rounded corners) may also be provided instead of circular closure members. With said can, it is also possible to provide unusual shapes in a simple manner. Specifically, the folding lines need not be flattened out, but can be used as the edges of a polygonal can cylinder. Accordingly, the closure members or the bottom and the lid would also be polygonal, i.e., the number of folding edges and the number of corners of the closure members would correspond. In particular, tetragonal, preferably hexagonal or even octagonal to dodecagonal cans can be provided with closure members according to the invention. Since the "closed" (i.e., continuous) or annular contact surface of each of the closure members presses tightly against the inside of the lateral surface, the can or the foldable cylinder has excellent stability and seal tightness. Closure members having high tensile strength - e.g., closure membranes which are firmly connected to the inside of the lateral surface or body member in a tensioned state - may be used. The membrane comprises a plastic film or paper sheet, but preferably an aluminum foil, and is hermetically sealed to the internal lateral can surface. If the closure member is firmly connected to a free cylinder edge along the edge, the cylinder is given the desired shape or cross-section at least in the region of the closure member. After filling, another closure member is mounted at a second, opposite region of the cylinder so that the can is closed and the cylinder is given the desired shape in the second end region as well. For the insertion and sealing of closure members, preferably by means of a hot-melt adhesive, it is possible to use press apparatuses which press against the annular contact surfaces of the closure member and the cylinder from within and without (optionally from only one side) and supply heat to the contact surfaces during heat-sealing. Depending on the particular arrangement of the contact surfaces, the sealing surfaces lie either in the interior of the cylinder or along a separate sealing surface of the foldable cylinder. Conventional apparatus for insertion of the closure member may be used for this purpose, e.g., a standard can closing machine, such as a press apparatus having at least one radially adjustable press surface. With such an apparatus, the press surface can be pressed against the contact surfaces after introduction of the apparatus. In the case of pressing from the inside of the cylinder, at least one press part (but preferably a plurality of press parts) having a convex press surface must be capable of being moved from a feed position in which it has a smaller press surface circumference to a pressing position in which it has a larger circumference. In the case of pressing from the outside of the cylinder, at least one press part (but preferably a plurality of press parts) having a concave press surface must be capable of being moved from a feed position in which it has a larger press surface circumference to a pressing position in which it has a smaller circumference. The parts which can be moved from the outside of the cylinder into their pressing positions may be dimensioned so that they form a step-free, closed (i.e., non-broken) circumferential line when they rest against one another. However, such press apparatuses are mainly useful for cylindrically shaped can bodies having a circular cross-section. For non-circular shapes, such press appartuses become rather complicated, and if the cross-section becomes polygonal, a tight sealing in the corner edges is difficult to achieve. EP-A-74343 discloses an apparatus for closing the open end of a can with an inner end closure by means of heat-sealing along bevelled surfaces. Summary of the Invention It is one object of the invention to provide a packaging apparatus for closing a can with a membrane, especially (but not only) for a can which can be transported and stored in a compact folded manner and which can be provided as an unfolded fillable can that is hermetically sealed at the filling site at low cost. It is a further object of the invention to provide a more universally applicable apparatus for closing a can with a membrane, which apparatus can be applied to can bodies having a circular cross-section but is especially advantageous to apply to non-circular cross-sections, especially to polygonal ones. Said objects are achieved by expediently sealing the closure membrane to the cylinder by means of a double cone sealing apparatus as mainly claimed in claim 1 and as described below Description of the Drawings The invention will be described in detail with reference to the following drawings in which: Figs.1A and 1B are schematic views demonstrating the sealing one opening of a can according to the invention by sealing-in a closure membrane 214. Detailed Description of Preferred Embodiments According to Figs.1A and 1B, a thermoformed membrane film 214 which has a collar 213 that projects over the upper edge of the can cylinder 202, rests with the collar on the edge of the cylinder. A heated, outer sealing ring 180 having a slightly (e.g. by 2°) beveled inner surface 180' moves from an upper, waiting position (Fig.1A) to a lower, sealing position (Fig.1B) in which it seals the membrane collar 213 onto the outside of the cylinder and/or the axial part 214' of the membrane film 214 onto the inside surface of the cylinder. The inner heat-sealing die 190 has a complementarily slightly (e.g. by 2°) beveled outer surface 190' against which the sealing ring 180 presses when in the sealing position. It will be apparent that the invention is not restricted to the embodiment shown. Any desired closure member with any desired connection to the can cylinder can be used. Moreover, by using suitable hot-melt adhesives, it is possible, in certain circumstances, to connect together the abutting cylinder web edges without using connecting strips. Other embodiments are deemed to be within the scope of the following claims.

Claims: Packaging apparatus for closing the open end of a can (214) with a membrane by means of heat-sealing, said packaging apparatus comprising a heat-sealing die (190) with an outer surface and a heat sealing ring (180) with an inner surface (180) for contacting and heat sealing said membrane to said end along the periphery of said membrane, said surfaces extending annularly around a central axis and being slightly bevelled with regard to said axis, said ring being located around said die and being displaceable relative to said sealing die in the direction of said axis thereby enabling said surfaces to be positioned adjacent to each other in mating fashion, and wherein both the outer diameter of said die (190) and the inner diameter of said ring (180) get smaller towards said can end in sealing position. The apparatus of claim 1, wherein said outer and inner surfaces are each beveled by approximately two degrees.

Inventors: GRABHER WERNER, GRABHER, WERNER
Applicants: GRABHER WERNER, GRABHER, WERNER
Application year: 1997
Main classification: B31B17
IPC codes: B65D5, B31B17, B65D3