Method and Apparatus for Manufacturing Container Having Bellows Bottom and Lid

The present invention generally relates to containers having a body of cardboard or any other material having equivalent strength properties, and the invention is more particularly directed to containers of the type which can be damaged when subjected to pressure changes, to the packed goods or to the ambient atmosphere, and in which the container comprises a container sleeve that has at least at one end a bellows bottom which in case of pressure changes in the packed goods or the ambient atmosphere can move outwards and inwards in the container thereby compensating for the pressure changes so that the cardboard container sleeve is maintained substantially unchanged, and in which the container has a protective lid exteriorly of the bellows bottom.

The invention also relates to a method and an apparatus for the manufacture of such a container. The apparatus comprises a carrier for the container sleeve and a piston means for pressing a bellows bottom blank and a lid blank respectively into the container tube, whereby a rim of the bellows bottom blank and of the rim blank respectively are folded upwards, and in which the piston means comprises a lower part and an upper part which are axially movable in relation to each other, and an expandable means between said movable piston parts which expandable means at the compression of the two piston parts is pressed radially outwards to the inner surface of the sleeve which in turn is pressed to the carrier. The carrier is formed with a welding ring for welding the rim of the bellows bottom and the lid respectively to the inside of the container sleeve.

Containers having so called bellows bottoms are previously known, for instance from the U.S. Pat. No. 3,627,171. The said previously known container having a bellows bottom is made of sheet metal or another form-stiff material, and the bellows bottom, which is flexible and made of a flexible material is connected by being folded between the container sleeve and the lid which as conventional in manufacturing of sheet metal tins are curled inwards to provide a seal lockseam. The bellows bottom alternatively can be replaced by a type of air balloon or a slidable means which is attached to the form-stiff container.

A problem in connection with containers having a body of cardboard or a similar material is that the containers change form when subjected to internal or external pressure changes and if the pressure changes are maintained for some time, for instance for some hours to some days, the container gets an undesired permanent change of form. In case of heavy pressure changes the cardboard container even break or become unsealed. Such problems normally do not appear in containers of sheet metal or other form-stiff or shape permanent materials.

In the said previously known type of container both the bellows bottom and the end or lid are connected to the container sleeve, and thereby a pressure chamber is provided between the bellows bottom and the lid. Such a sealed pressure chamber is not acceptable in containers of cardboard or a similar non-shaped permanent material, since a pressure change should lead to a change of the container both at the area inside the bellows bottom and in the area between the bellows bottom and the lid.

For different reasons some types of goods are packed in a hot state and when the said goods are cooled down the packing volume thereof is reduced. In case of such packaging it is important to compensate the pressure change by the action of the bellows bottom so that the form of the container sleeve is maintained unchanged. This is possible only if the bellows bottom can move unprevented by an exterior lid.

Further it is important that different types of goods, especially food stuffs, are packed aseptically and the filling and the closing of the container therefore preferably is made at the place where the goods are manufactured. Machines for manufacturing and closing of cans of metal, however, are so large, complicated and expensive that they generally are not suited for small or medium size manufacturers of food stuffs or other products. Cans of sheet metal also are very bulky and lately discussions also have come up as concerns composting problems and different types of environmental problems in connection with cans of sheet metal. Also for this reason a container of the type mentioned in the said U.S. patent is less suitable for some areas of packaging.

Therefore the invention relates to a canlike container having a body of cardboard or any other material having equivalent strength properties. For eliminating the deformation and damages of the container in case of internal or external pressure changes, for instance when goods packed in a hot state are being cooled, in case of air transportation of ready filled and sealed containers etc., the container is formed with an inner bellows bottom at least at one end thereof. The bellows bottom is provided so that it can be expanded or contracted depending on pressure changes while the container maintains its shape unchanged.

There are, however, certain problems in closing and sealing of cardboard containers, and the sealing problems are increased by inserting a bellows bottom in the container, especially since the manufacture, the filling and the closing of the containers must be accomplished quickly for a rational manufacturing process. A modern method for manufacture of cardboard containers of this type makes use of a welding tool by means of which the container is closed and sealed by high frequency heat or ultrasonic heat. For this the lid and the container sleeve on their meeting surfaces are formed with a weldable material, and the lid with a folded up all around extending rim is pressed down in the sleeve so that the rim of the lid is positioned straight in front of the welding tool, for instance the welding ring. When weld connecting a bellows bottom the welding operation also must be done right in front of the welding ring. In order to give the container an attractive appearance and in order to protect the bellow bottom the container must be formed with a further lid axially outwardly of the bellows bottom and preferably connected to the inner surface of the container sleeve. The said further lid ought to have air channels in which the air volume between the bellows bottom and the protective lid can be reduced and increased when the bellows bottom is moved outwards and inwards respectively. In order to provide the bellows bottom, the pressure piston which forms and forces the bellows bottom down in the container sleeve must be designed so that the bellows bottom is cup-shaped. This means that the press piston at the bottom surface thereof must be convexly formed. The protection lid cannot be inserted at the same time as the bellows bottom, and the introduction of the protection lid must be made in a separate operation, and in case the press piston has the above mentioned convexly bulged shape the protection lid cannot be formed, forced into the container sleeve and welded to the container sleeve in the same way as the bellows bottom. Also the protection lid cannot be welded to the container sleeve without moving the sleeve so that the protection lid comes in a position straight in front of the welding tool. It is expensive and complicated to execute the operation in two different machine stations and by means of two different press pistons.

The object of the invention therefore is to solve the problem of providing a method and an apparatus suitable for the manufacture of containers alternatively having or not having a bellows bottom and in which the container having a bellows bottom can be fully manufactured in one and the same machine station and by using one and the same press piston.

According to the invention the lower part of the press piston is formed with a bulge provided below the expandable means corresponding to the intended shape of the bellows bottom, and the carrier for the container sleeve is formed with means for supporting the sleeve at two different levels, viz. an upper level in which the bellows bottom is inserted and a lower level in which a protection lid is welded to the container sleeve above the bellows bottom. Preferably the bulge of the press piston is formed as a straight cylinder having a bellied, rounded or otherwise designed bottom surface so that the outer cylindrcial portion of the bulge can be used as a press surface when the protection lid is weld connected to the container sleeve. Thereby the protection lid can be formed with relatively low edges. The bulge of the press piston should be such that the bellows bottom can be moved both inwards and outwards if the outer pressure change is positive or negative respectively, and the bulge therefore may be a combination of convexly and concavely formed parts.

Further characteristics of the invention will be evident from the following detailed description in which reference will be made to the accompanying drawings.

In the drawings FIG. 1 is a cross section through the upper part of a cardboard container having a bellows bottom and manufactured in accordance with the invention.

FIG. 2 is a diagrammatic cross section view through an apparatus according to the invention.

FIG. 3 shows a part of the apparatus according to FIG. 2 on a larger scale and during the welding of the bellows bottom, and

FIG. 4 correspondingly shows the welding of the protection lid.

Thus the shown apparatus is intended for the manufacture of a container of cardboard or any material having equivalent stiffness or strength properties and comprising a container sleeve 1 which at the bottom can be sealed closed and which at the upper part is formed with an inner bellows bottom 2 which sealingly closes the container. Above the bellows bottom a protection lid 3 is connected to the container sleeve, and at its upper end 4 the container sleeve is formed with an inwardly curled edge 5. The container also can be formed with a bellows bottom and a protection lid both at the bottom and the top of the container.

The material of the container sleeve is a body 6 of cardboard or a similar stiff material, preferably an intermediate layer 7 adapted to absorb high frequency or ultrasonic energy, for instance an aluminum layer, and an inner layer 8 of a weldable plastic material like polyethylene. The protection lid preferably is made of the same material as that of the container sleeve or any other suitable material. The bellows bottom 2 should be made of such weldable material as is easily foldable and also is weldable. The bellows bottom is the gas seal of the container sleeve and therefore it is important that the bellows bottom carefully seals to the inner surface of the container sleeve. The bellows bottom can be made of a suitable laminated material like aluminum and polyethylene with the polyethylene layer facing the container sleeve. In the left hand part of FIG. 1 the container is shown in a partly ready state, and in the right hand part of the figure the container is shown in a final ready state.

The apparatus according to the invention, shown in FIG. 2, comprises a carrier 9 having a welding tool 10 in the form of a welding ring and an introduction piston or plunger 11 connected to known means 12 for moving the plunger 11 upwards and downwards and for providing a suitable pressure or weld connecting the edges of the bellows bottom to the inner surface of the sleeve as will be explained more in detail in the following.

The carrier 9 is intended for holding the sleeve 1 in contact with the welding ring 10 while the bellows bottom 2 and the protection lid 3 is introduced and weld connected to the inner surface of the sleeve. At the bottom edge the carrier is conically formed for providing a guide cone 13 for the sleeve which is introduced into the carrier from underneath. The weld ring 10 the is slightly conically widened in the direction upwards, for instance at an angle of about 3.degree.. Above the weld ring 10 carrier is formed as a straight cylinder the inner periphery of which coincides with the upper edge of the weld ring 10. At a location a predetermined distance above the weld ring the carrier cavity has a shoulder 14 defining the upper position of the sleeve 1. The introduction bore above the shoulder 14 should have such area that the plunger 11 together with the bellows bottom blank or a protection lid blank can be pressed down through the carrier and into the opened end of the sleeve 1. When the bellows bottom blank or the protection lid blank are pressed down as mentioned they are formed with an upwardly projecting rim which at a later stage is weld connected to the inner surface of the sleeve. For providing a good folding up of the outer edge of the bellows bottom or the protection lid a formation ring 15 having rounded edges 16 may be mounted above the carrier 9. It should, however, be noted, that it is also possible to form the bellows bottom and the protection lid respectively by pressing the same directly into the container sleeve, and the carrier may have or not have both the shoulder 14 and the formation ring 15. The widened part of the cavity existing above the welding ring 10 makes possible a slight widening of the upper edge of the sleeve when the bellows bottom blank and the lid blank are pressed down in the sleeve, whereby it is foreseen that the sleeve is protected against damages by the said blank or blanks.

The introduction piston or the plunger 11 comprises a lower part 17 and an upper part 18 which are axially movable in relation to each other. Between the upper part 18 and the lower part 17 there is an expandable means, for instance a rubber ring 19 which changes form and is pressed radially outwards when the upper plunger part and the lower plunger part are pressed together. The lower part 17 is formed with an outwards-downwards sloping surface 20 supporting the rubber ring 19, and below said sloping surface the lower plunger part has a bulge 21, the shape of which defines the final form of the bellow bottom. The bulge 21 has sides 22 in the shape of a straight cylinder and a bottom which preferably has an evenly rounded outer edge. For making the bellows bottom assimilate both above atmospheric pressure and below atmospheric pressure it must be movable both outwards and inwards, and for this purpose the bulge 21 may be formed with one or more cavities, for instance a central cavity 23 as shown in FIG. 3. For letting out air and/or for connecting the bellows bottom blank to said cavity 23 by a suction means an evacuation bore or a suction means 24 may be provided at the center of the cavity. The upper plunger part 18 is with easy slip fit displaceable outside the lower plunger part 17 and it has an outer area which is adapted for moving the plunger 11 down together with a bellows bottom blank or a protection lid blank in the carrier 9 and into the open end of the container sleeve 1. The actuation means are adapted to move the plunger 11 to an exactly predetermined position in which the rubber ring 19 is located just in front of the welding ring 10. In this position the lower plunger part 17 is stopped by a carrier pin 25 whereas the upper plunger part 18 can be moved some further distance in relation to the lower plunger part, whereby the rubber ring 19 is compressed axially and thereby expands in the radial direction.

At the upper side of the carrier 9 there may be a first support 26 for positioning a bellows bottom blank 27 and a second support 28 for positioning a (non illustrated) protection lid blank.

The operation of the apparatus is best evident from FIGS. 3 and 4 in combination with FIG. 2. A container sleeve 1 is from underneath moved to an upper position in the carrier 9. The said upper position for instance can be defined by the shoulder 14. A bellows bottom blank 27 is placed in the first support 26, and the plunger 11 is moved downwards by the actuation means 12, whereby the plunger forces the bellows bottom blank down through the upper part of the carrier 9 and into the open end of the sleeve. The bellows bottom blank is formed exactly to the shape of the plunger, and the plunger is adjusted so as to be stopped in a position in which the rubber ring 19 is located just in front of the welding ring 10. After the lower plunger part has been stopped by the carrier pin 25 the upper plunger part 18 is moved an exactly predetermined further distance down, whereby the rubber ring is compressed and expands in the radial direction, whereby the bellows bottom blank 27 is pressed to the inner surface of the sleeve 1. The sleeve in turn is pressed to the welding ring 10. When applying heat, high frequency or ultrasonic energy the heat is absorbed in the metal layer of the sleeve and/or the bellows bottom blank, whereby the weldable plastic layers of the sleeve and the bellows bottom rim melt together. Since the rubber ring is forcing the material towards the welding tool a very good weld contact is obtained, and since the bellows bottom blank is relatively thin a very good seal is obtained even if the bellows bottom blank has folds in the welding area. After the bellows bottom is weld connected the plunger 11 is retracted and a protection lid blank is placed in the second support 28. At the same time the container sleeve is moved a predetermined distance down so that the protection lid can be welded to the container sleeve at a predetermined distance above the bellows bottom weld. By moving the plunger 11 down it forms the protection lid blank to a lid plane 29 having an all around upwards extending rim 30. By forming the protection lid of a thicker material than the bellows bottom the lid will be pressed with sufficient force to the inner surface of the container sleeve for providing a tack welding only by the actuation of the sides 22 of the bulge 21. The plunger is thereby moved down so that the lower part of the straight bulging sides 22 is straight in front of the welding tool, and heat is supplied, whereby the protection lid is point by point or discontinuously weld connected to the sleeve. In this second stage the welding therefore is made without the actuation of the rubber ring 19. This is possible since the protection lid is made of a slightly thicker material than that of the bellows bottom and since the upwardly projection rim 30, owing to the elasticity of the material is being biassed outwards. There should not be a complete seal between the protection lid and the sleeve. On the contrary it is necessary that there is at least some perviousness between the sleeve 1 and the protection lid 3 so that air may pass the protection lid in both directions depending on pressure changes providing a movement outwards or inwards of the bellows bottom. Possibly the protection lid can be formed with one or more perforated holes or air channels.

By mounting the bulge 21 of the plunger 11 releasably one and the same plunger may be used for the manufacture both of containers having a bellows bottom as described above and for manufacture of containers without a bellows bottom, whereby the container lid is welded by the actuation of the rubber ring 19 in a position of the plunger 11 in which the rubber ring and the lid are straight in front of the welding tube 10 as described above in connection to the welding of the bellows bottom.

The moving of the sleeve 1 into two predetermined positions and the moving down of the plunger into two likewise determined positions is made by previously known means which need not be described in detail. Reference may be had to U.S. Pat. No. 3,346,435, issued Oct. 10, 1967 to R. Beck entitled "Apparatus For Forming Container From Synthetic Plastic Films" for a disclosure of known positioning means cooperable with a carrier to releasably confine a sleeve in an opening against axial displacement relative to the carrier.

It is to be understood that the above specification and the embodiment of the invention illustrated in the drawings are only illustrating examples and that different modifications may be presented within the scope of the appended claims.

Container having a bellows bottom and method and apparatus for manufacturing such container

1 container sleeve

2 bellows bottom

3 protection lid

4 upper edge

5 curled edge

6 cardboard body

7 aluminum layer

8 inner weldable layer

9 carrier

10 welding tool

11 plunger

12 actuation means

13 guide cone

14 shoulder

15 formation ring

16 rounded edges

17 lower plunger part

18 upper plunger part

19 rubber ring

20 sloping surface

21 bulging

22 sides (of 21)

23 central cavity

24 suction means

25 carrier pin

26 first support

27 bellows bottom blank

28 second support

29 lid plane

30 rim