Method of manufacturing a can lid composed of a composite material

Abstract

A method of manufacturing a can lid composed of a composite material comprising at least one sheet metal part, in particular an aluminum part or a tin plate part, and at least one plastic part, in particular composed of polypropylene or polyethylene terephthalate, wherein the plastic material and the sheet metal part are joined together by pressing together and by inductive heating to effect a stable connection with an effort and a manufacturing time that are as small as possible.

Claims

1. A method of manufacturing a can lid for a can, wherein the can lid is composed of a composite material comprising at least one sheet metal part and at least one plastic part, wherein the at least one sheet metal part has an upper side facing an exterior of the can and a lower side facing an interior of the can, wherein the at least one plastic part is joined to the lower side of the at least one sheet metal part by a joining process including pressing together and inductive heating, wherein a cross-sectional height profile of the at least one plastic part is adapted to a cross-sectional height profile of the at least one sheet metal part before the joining process, and wherein the at least one plastic part includes a plastic film.

2. The method in accordance with claim 1, wherein at least one of the sheet metal part and the plastic part is coated with a bonding agent before the joining process.

3. The method in accordance with claim 2, wherein the bonding agent includes a same plastic as the plastic part to be connected to the sheet metal part.

4. The method in accordance with claim 1, wherein the at least one sheet metal part further includes a closure element disposed on the upper side of the at least one sheet metal part, and wherein the closure element covers an opening region of the can lid.

5. The method in accordance with claim 4, wherein both joining processes take place in one workstep.

6. The method in accordance with claim 4, wherein the closure element is composed of an injection molded plastic.

7. The method in accordance with claim 6, wherein the injection molded plastic comprises one of polypropylene and polyethylene terephthalate.

8. The method in accordance with claim 1, wherein a press is used for the joining process having a top tool and a bottom tool as well as a hollow conductor for supplying an electromagnetic alternating field into a region of the can lid for its inductive heating, with the top tool having a shape reciprocal to a top side of the can lid and the bottom tool having a shape reciprocal to a bottom side of the can lid.

9. The method in accordance with claim 8, wherein the hollow conductor comprises a section that is disposed opposite a reception region of the can lid to be joined.

10. The method in accordance with claim 9, wherein the top tool located proximal to the hollow conductor comprises largely shape-stable material, and the bottom tool comprises elastic material.

11. The method in accordance with claim 10, wherein the top tool comprising largely shape-stable material is associated with the plastic film.

12. The method in accordance with claim 9, wherein the hollow conductor comprises a ring-shaped region in a marginal region of the can lid and a spiral region disposed within the ring-shaped region and having two, three, or more windings in a middle region of the can lid.

13. The method in accordance with claim 1, wherein the at least one sheet metal part and the at least one plastic part are held together by vacuum during the joining process.

14. The method in accordance with claim 1, wherein the at least one sheet metal part comprises one of an aluminum part and a tin plate part.

15. The method in accordance with claim 1, wherein the at least one plastic part is composed of one of polypropylene and polyethylene terephthalate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the invention is represented in the drawing and will be described in the following. There are shown, schematically in each case:

(2) FIG. 1 is a sectioned, perspective view of a press for use in a method in accordance with the invention;

(3) FIG. 2 is a sectioned side view of a part of the press in accordance with the invention;

(4) FIG. 3 is a perspective view of an inductor to be used in the apparatus of FIG. 1;

(5) FIG. 4 is a side view of the inductor of FIG. 3;

(6) FIG. 5 is a plan view of the inductor of FIG. 3;

(7) FIG. 6 is a plan view of a can lid,

(8) FIG. 7 is a cross-section through the can lid of FIG. 6;

(9) FIG. 8 is a detail B of FIG. 7;

(10) FIG. 9 is a detail C of FIG. 7; and

(11) FIG. 10 is a detail D of FIG. 7.

DETAILED DESCRIPTION

(12) The press 1 shown in FIG. 1 comprises a lower rack 2 and an upper press part 3 movable relative thereto as well as guide cylinders 4 for guiding the upper press part 3 on the opening and closing of the press. A bottom tool 5 is provided at the upper side of the lower rack 2 and a top tool 6 is provided at the lower side of the upper press part 3. The bottom tool 5 comprises an elastomeric material and has a cavity 7 for receiving a closure element 18 (see FIG. 6) of a can lid 9. In another respect, the bottom tool 5 replicates the shape of the upper side of the can lid 9. The top tool 6 comprises a largely stable-shape plastic and replicates the lower side of the can lid 9.

(13) An inductor 10 is arranged in the region of the press. Hollow conductors 11 for supplying an electromagnetic alternating field are guided into the region of the top tool 6 starting from the inductor 10. As can in particular be seen in FIGS. 3 to 5, the hollow conductors that in particular consist of copper are shaped to form an outer ring 12 and a spiral 13 arranged within the ring and having a plurality of windings. As can in particular be seen in FIG. 2, the outer ring 12 and the spiral 13 are arranged above the top tool 6. They thereby lie opposite the surface of the can lid 9 to be joined. The copper hollow conductors 11 are in particular water-cooled.

(14) The can lid 9 shown in FIGS. 6 to 9 comprises a base body 14 composed of a sheet metal, in particular aluminum or tin plate. The base body 14 comprises a fixed metallic end region 15 and an upwardly pivotable opening section 16 to release an opening region 8. As can in particular be seen in FIGS. 8 and 9, the lower side of the can lid 9 is laminated with a plastic film 17. In contrast, a closure element that comprises a sealing frame 19 and a closure unit 20 is arranged on the upper side of the can lid 9. The sealing frame 19 is connected to the fixed end region 15 and the closure unit 20 is connected to the upwardly pivotable opening section 16.

(15) The method in accordance with the invention can be used to manufacture the can lid 9 shown in FIGS. 6 to 9 while using the apparatus shown in FIGS. 1 to 5. For this purpose, the closure element 18 that is in particular produced in one piece in a deep-drawing process is placed into the bottom tool 5 such that the side facing the can lid 9 faces upward. The base body 14 that had previously had the plastic film 17 applied to its lower side is placed onto the closure element 18. The press 1 is then closed and the induction heating 10 is switched on.

(16) The metallic base body 14 is heated by the supplied energy in that electromagnetic eddy currents are produced therein. The heated base body 14 in turn heats the plastic film 17 and the closure element 18 that are thereby partially melted. A plastic weld connection is thereby produced between the metallic base body 14 and the plastic film 17, on the one hand, and the closure element 18, on the other hand, with a bonding agent preferably being used to improve the plastic weld connection. The bonding agent can here include the same plastic that is used for the plastic film 17 or for the closure element 18. It can here in particular be polypropylene or polyethylene terephthalate.

(17) The top tool 6 can additionally have ribs which are not recognizable here and by which a weakening line is introduced into the plastic film 17 during the pressing and joining procedure. In addition, indentations can be provided in the top tool 6 to generate free spaces between the plastic film 17 and the metallic base body 14. Enclosed air can hereby be collected in predefined regions of the can lid 9, in particular in regions in which air bubbles are not disruptive such as in the region between the margin of the can lid and its opening region 8. Additionally or alternatively, the press 1 can be provided with a vacuum supply that, on the one hand, holds the parts to be joined together and, on the other hand, can at least largely prevent an enclosure of air. With can lids having a microgap between the fixed end region 15 and the opening section 16 that can be pivoted open, this applies to both sides of the can lid.

(18) A rotary indexing table can be provided for the equipping of the press 1 that has a plurality of stations for putting together the individual parts of the can lid. However, a linear supply for the press 1 can also be provided instead of a rotary indexing table.

(19) After the welding of the plastic film 17 and the closure element 18 to the metallic base body 14 has taken place, the press is opened and the finished can lid 9 is removed.

REFERENCE NUMERAL LIST

(20) 1 press 2 lower rack 3 upper press part 4 guide cylinder 5 bottom tool 6 top tool 7 cavity 8 opening region 9 can lid 10 inductor 11 hollow conductor 12 outer ring 13 spiral 14 base body 15 fixed end region 16 opening section 17 plastic film 18 closure element 19 sealing frame 20 closure unit