CA1259930A

CA1259930A - Container, particularly for milk products and machine for manufacturing such container

Info

Publication number: CA1259930A
Application number: CA000460352A
Authority: CA
Inventors: Gerard Charpentier
Original assignee: Monoplast SA France
Current assignee: Monoplast SA France
Priority date: 1983-08-05
Filing date: 1984-08-03
Publication date: 1989-09-26
Also published as: DE3470725D1; JPS6077857A; IE55396B1; DK160018C; MX161189A; FR2550169B1; DK373284D0; ATE33809T1; EP0133834A1; ES8600723A1; DK373284A; ES534639A0; EP0133834B1; BR8403906A; AU2650588A; AU3132784A; IE842014L; FR2550169A1; JPH0212814B2; DK160018B

Abstract

ABSTRACT OF THE DISCLOSURE:
A container at least partially made of plastic, and in particular a container for milk products. The contai-ner is made by ultrasonically welding together components including at least a tubular side wall which is extruded in the form of a rectangular sheet and which has its short sides welded together; and two end closure members closing respective ends of the tubular side wall. The end closure members constituting a bottom and a lid, and each of said end closure members including a groove for receiving a respective one of the long sides of said rectangular sheet, and extending substantially perpendicularly to the axis of the side wall tube, said long sides being ultrasonically welded in place in said grooves.

Description

"3~) A CONTAINER, I~ PA~TICULAR FOR MILK PRODU~S, AND
A MACH~NE ~'OR ~AKING SUCH A CONTAINER.
The present invention relates to a container made of plastics material ~hereinafter referred to as "plastic" for short) and intended particular]y, but not exclusively1 for packaging fresh milk products such as yoghurt, and to a ~achine for maklng containers of this t;ype.
BACKGROU~D 0~ T~E INV~NTION
Pots made of plastic have to a very large extent replaced pots made of waxed card or of glass as goghurt containers.
Compared with glass pots~ plastic pots have the advan-tages of being lighter, less fragile, and more suitable for having marking printed directly on the pot. Unfortunately, plastic containers (which are generally made of polystyrene or of po]ypropylene) do not provide some of the advantages that glass containers provide in use: in particular they do not provide such good isolation from the surrounding medium. Thus, plastic, and in particular polystyrene~ is relatively porous to gases normally present in the atmosphere, such as oxygen, carbon dioxide, and water vapor. These gases can diffuse through the wall of the container and spoil the quality of the product, even during its normal shelf life. As a result the taste is rapidly degraded.
Preferred embodiments of the present invention provide a container which enables the quality of the product to be fully conserved during its shelf life.
Also, conservation of the product contained in the container depends in part on the precautions taken when the container is filled. Preferred embodiments of the invention 3 pro~ide a container which can be sterilized by purely physical means, which is in line with present trends in regulations.
~ urther, currently used containers are constituted by a hollow body which is closed by a lid or cap that is sealed or clamped in place. Pots may thus be manufactured by blowing or by injection making use of the properties of plastics.
Unfortunately, since the site of container manufacture is generally distant from the site of product manufacture and ~5~ 3 .
container filling, the empty containers need ~o be transported (eg. by road), which results in considerable empty space being transported in spite of various container stacking techniques.
Preferred embodiments of the invention provide a container which is formed immediately before being filled, thereby improving transport efficiency and facilitating perfectly sterile filling conditions.
Suzuki's US patent N 4 187 768 describes the manufacture of a container made of paper which has one face covered in a thermoplastic film. ~he container is built up from a bottom component and a side wall component which are welded together ultrasonically. The periphery of the bottom component is ~olded in such a manner that the fold is surrounded by another fold in the bottom of the side wall. The top of the container is hemmed. The method described in the said patent is long given the need to perform the folding and the fact that it always takes longer to weld plastic to paper than it does to weld plastic to plastic. ~he weld is performed by relative displacement between the container and an ultrasonic probe which further increases the manufacturing time. An additional factor is that the bigger the container the longer it takes to manufacture using the method described in the said US patent.
Preferred implementations of the present invention also enable containers of any cross section to be manufactured at a rate which is substantially independent of the size of the containers.
Finally, for practical purposes, milk products are generally packed in individual or unit portions. Both for practical purposes and for commercial reasonsS it is desirable for such unit portions to be grouped in twos, fours 9 eights or twelves, and it may also be desirable for the milk products in such groups to be varied, ie. with adjacent containers containing different products. Dividing the product up into unit portions and bringing together different products into a single group both add to the cost of packaging. ~urthermore, for reasons of mechanical strength, such groups generally need additional overall packaging which is usually a carton.

~59{3~

PreEerred embodimen-ts of -the present inven-t.ion provide a container which is easily grouped ~Ji-th other :Like containers without requiring a group formed in -this manner -to be packed in a car-ton, -thereby considerably reducing overall costs.

SUMM~RY OF TEtE INVENTION

According to the present invention, there is provided a container adapted to receive flowable contents at a site and forrned by -three discrete components each adapted to be transported to said site in a substantially Elat condition; said three componen-ts lncluding a wall portion formed by a substantially Elat sheet of rectan-gular ma-terial having means including opposing end por-tions for forming a cyl.indrical por-tion having opposite open ends upon sealing said end por-tions -together at said site, and two preformed closure portions each having re-spective means for sealingly engaging a respective one of said open ends at said site, said container being formed of thermoplastic materials sealed together ultrasonically, the internal face oE the wall portion being embossed and its external face being smooth, said container including a lid having an external face com-plementary to an external face of a bottom of a secondcon-tainer in such a manner that said second container may be stacked on said con-tainer by interfitting -the bot-tom of the second container on the lid of said container, and that af-ter such stacking, the wall portions of said containers are aligned and in thrust transmi-tting contact via said interfi-tting of the bottom of the second con-tainer on -the lid of said container.
Thus, the components are posi-tioned relative to one another somewhat automatically by -the edges of ., ~599~
- 3a -the end walls being received in the grooves. Once properly placed, they are relatively easily welded in order to seal -the joint. It may be noted -tha-t the assembled com~
ponen-ts for welding have the advantage oE concentrating ultrasounds, and -the resulting weld is of good quality.
PreEerably, the end closure members are consti-tuted by a bottom and a lid which are made by injection molding, while the sheet which is made up into the side wall is preferably extruded.
The present invention also provides a machine for manufacturing such containers, said machine com-prising:
means Eor unstacking the side wall constitu-ting sheets, and the respective end closure members;
means for s-terilizing -the unstacked components;
means for folding the shee-ts to constitute the side walls, and means for welding the folded shee-ts to constitute side wall tubes;
means for applying a bottom end closure member to a side wall tube;

. . _ _ _ . . . _ _ . _ ~ .. .
, . . : .~

~;~5'3'~

a weldine head for ultrasonically welding the sidé wall to the bottom applied thereto;
means for filling the container with a portion of product;
means for snap fittin~, the top end closure means to the ~ide wall of the filled container; and a welding head for welding the side wall to the lid.
All the components are thus fed to the machine in flat or sheet form. This greatly facilitates sterilization of the components, eg. by means of ultraviolet radiation or the like, and the subsequent operations can readily be performed under an inert atmosphere.
Making the side walls by extruding sheet material has several advantages~ ~'irstly, a plurality of layers or plies may be extruded simultaneously. The resulting composite sheet can be made impermeable to gas by including an impermeable layer, thereby improving storage of the product in the container. Secondly there is no difficulty in marking the external faces of the container by printing. Thirdly, there is no need for any waste m~terial, which is of considerable importance when dealing with composite sheets, since it is di-fficult to recycle ~ultilayer offcuts.
When fresh milk products are transported, the vibrations due to the transport have a pumping effect on the products such that serum separates from the mass of the yoghurt or other product. A prior technique for reducing this drawback consists in using generally conical containers with their larger diameter ends at the bottom. This shape prevents the yoghurt from moving upwards against the shrinking diameter of the container. Unfortunately such containers do not lend them-selves to nesting when empty nor to stacking when full.
Containers in accordance with the present invention are preferably straight sided with the side walls ex-tending perpendicularly to the end closure members. This ensures that the resulting structure is mechanically strong enough for several layers of full containers to be stacked on top of one another. In order to reduce the above-mentioned "pumpingl' effects, the interior -faces of the straight sided walls are ~'3<3~() advantageously embossed during extrllsion of the side wall sheet 80 as to "key" the yoghurt to the wall and thus prevent it from movin~ relative to the container during transport.
BRIE~ DESCRIPTION OF THE DRAWINGS
An embodiment of the invention is described by way of example with reference to the accompanying drawings, in which:
~igure 1 is an exploded ,perspective view of a group of containers in accordance with the invention;
~igures 2 and ~ are respectively a front view and a vertical section through a single container;
~igure 4 is a perspective view of a single extruded sheet for making up into the side walls of a container;
~igure 5 is a cross section through multilayer wall material;
~igure 6 is a diagrammatic perspective view of an extruder for extruding side wall sheet;
Figure 7 is a block diagram of a container forming machine;
~igure 8 is a perspective diagram of the ~igure 7 container forming machine;
~igure 9 is a partially cut-away perspective view of a machine for shaping the side wall; and Figure 10 is a partially cut-away perspective view of means for advancing containers through a fillel machine.
MORE DETAI~ED DESCRIPTION
~igure 1 is an exploded perspective view of a group of four containers, each of the t~pe shown in a front view in ~igure 2 and in cross section in ~igure ~. In accordance with the invention, each container comprises three portions, a side wall 1, a cover or lid 3, and a bottom 4. The bottom 4 and the lid ~ have grooves 10 which receive the bottom and the top edges respectively of the side wall 1 and which are ultra-sonically welded thereto. This method of welding is preferred over other known methods because of its speed and because it conser~es the organoleptic characteristics of the container.
The side wall 1 is obtained by lap welding the ends of a plastic sheet 2 (see ~igure 4) in which fold lines or creases 6a are preformed during extrusion.

`3 , As can be seen more clearly in ~i~ure 3, the lid 3 has a bottom 1~ which i6 lower than the top edge of the æide wall 1.
~he bottom closure member 4 has a bottom 13 which projects beyond the bottom edge of the side wall 1. Thus the lid is concave and the bottom is convex in the embodiment shown. The opposite arrangement could be used with a convex lid and a concave bottom. The profiles of the lid 3 and the bottom 4 are complementary so that the convex bottom of one container can be received in the concave lid of a another container,.-thereby stacking the containers with their side walls 1 accurately aligned. This ensures maximum mechanical strength for such a stack, and normal stacking and handling loads are adequately supported. The lid 3 and the bottom ~ have rims defining the grooves 10 in such a manner that the top and bottom edges of the side wall 1 are securely received therein, and may be even snap fitted thereto, prior to the above-mentioned welding.
This ensures accurate assembly of the three parts.
In the drawings, the containers are shown as pots of square section. This is an advantageous configuration in that it enables compact groups of containers to be obtained, thereby not wasting space; ~owever, other cross sections are possible, and in particular a circular section could be used.
~ igure 4 is a perspective view of a sheet 4 prior to folding into the shape of the side wall 1. The sheet has an internal face ~ and an external face 7 (relative to the assembled container). The external face 7 is smooth and is intended to receive decoration and/or information concerning the product contained in the container. The internal face 5 is embossed with a checkered pattern of projecting ribs 6.
3o Although it is known to use ribs on the walls of containers, this has previously been for the purpose of strengthening the container walls, rather than for providing the container with means for gripping the product, ieO for keying the product to the wall. This gripping or keying function is enhanced by using a diagonal pattern as shown, but other patterns could alternatively be used. The advantage of allowing a "thick"
product such as yoghurt to grip the walls is that it remains ~ ~t~3~

, homogenous inside the container in spite'of the ~hocks as~ociated with tran~porting the containers after they have been fillea. The embossing does also contribute to overall strength of the container, but its resistance to vertical crushing lies principally with its side wall being disposed vertically and with the welding to the end parts (the lid 3 and the bottom 4) giving the structure adequate rigidity.
The sheet 2 is made by extrusion9 and if the side wall 1 is to be of polygonal cross section, crease marks 6a are 10 ' preformed in the sheet during extrusion to facilitate subsequent folding. 'i'he crease marks 6a are advantageously slightly curved in shape.
As mentioned above, it is necessary for unit portions to be grouped together into convenient sized units for commerciali~ation. An example of such a grouping is shown in I~`igure 1. Grouping is generally achieved by associating the top and/or bottom end members in groups of at least two~ In the example shown, four lids 3 are associated. This association is obtained at the same time as the lids are formed, eg. by hot pressing or by injection molding. Tear-off strips 8 are provided between adjacent associated lids. The ~ strips 8 extend over a portion only of the facing sides of the ;~ lids, and in -the arrangement of four lids shown in ~igure 1, a central hole 9 is left empty. Such a hole enables a handling tool (not shown) such as a barbed rod to be passed through several layers of stacked groups of containers, thereby ensuring that the layers are maintained relative to one another. The central hole can also be used when transporting a - single group of containers by hand.
Naturally, on arrival at their final destination, the containers must be easy to open. A line of weakness 14 is thus provided in each lid 3 to delimit a cap 11 which can be removed from the lid. To facilitate its removal 9 the cap incorporates a pull tab (not shown).
Given the shape of the end members ~ and 4, and the strength of the side walls 1 against vertical crushing, several groups of containers may be superposed so as to constitute a 3 ~ 3 uniform assembly. This arrangement greatly i~proves the , e~iciency with which vehiclc-s and storage areas can be ~illed, for example up to 2.2 times as much milk product may be stored in a given volume compared with prior art contai~ers. Further, the containers no longer need to be packed into a ~arton, thereby considerably reducing cost. Once a predetermined quantity of containers have been brought together both horizontally and vertically, they may simply be strapped together to prevent t,hem coming apart. In the example described, vertical assembly and positioning is due to the convex bottoms bei~g received in -the concaYe lids. The opposite could just as well be true with c,onvex lids being received in concave bottoms. ~he essential point is to ensure that vertical forces are directly transmi-tted from side wall to vertlcally adjacent side wall.
~ igure 5 is a cross section through the sheet 2 or through a lid or a bottom. As mentioned above, preferred embodiments o~ the present invention improve conservation o~ the product stored in the container. This is achieved by improving the impermeability of the walls to gases. ~o do this, merely increasing the thickness of the walls rapidly encounters practical manufacturing limits. Gas impermeability i8 better obtained by making the walls of the container from a layered material including at least one layer which is impermeable to the gases that ought not to be allowed to diffuse into the container, eg. oxygen. The structure of such a layer constitutes a barrier to the dif~usion of one or more gases through the wall. Suitable barrier materials include co-polymers of ethylene-vinyl-alcohol (EVA~) and polyvinylidenes (PVDC). ~igure 5 is a cross section through such a multilayer material including an external layer 7, an internal layer 5, and a middle layer 15. In some cases other materials are added to these main layers to ensure proper adhesion between the layers. The internal and external layers 5 and 7 may be constituted by polystyrene or polypropylene, with the middle layer 15 being made o~ EVAL or PVDC.

~5~:3~3~0 The barrier made in this manner conserve~ the taste "old fashioned" products throughout *he Ghelf life without requiring anti-oxidizin~ chemical preservatives and while using modern materials that can be extruded rather than being blown.
Figure 6 shows the process for extruding the side walls 1.
~hree extruders 16, 17, and 18 deliver three streams of pasty material to a shaping die 19 which outputs three layers of material 5, 7 and 15. A set of roll9 20 provide the embossing 6 of the internal surface (ie. the surface inside the finished container). ~he three-layer sheet ib then cooled at 21 and its external face 7 receives printing from an inking roll 23 and a printing roll 22. The printed face is then dried in an oven 24 and the sheet 2 is cut to size by a guillotine 25 which ClltS
off lengths of sheet ~ equal to the desired height of the containers. The width of the sheet coming from the die 19 is equal to the perimeter of the finished side wall plus the welding overlap. The lengths of sheet 2 are counted, stacked and packaged at 26, It may be observed that there is no wastage of material in the manufacture of the sheets 2, which is of particular importance for a multiple layer material.
The lids 3 and the bottoms 4 may be shaped from the same material as the side walls 1, or they may be made from some other material. They may be hot pressed or they may be injection molded. Depending on requirements they may be of di-fferent colors so that if a mixture of products is offered in the same group of containers, then each product may be identified by color coding one or both ends of the containers.
As men-tioned above, the lids 3 are made in groups of two, four, eight or twelve and the containers are welded thereon without breaking the grouping. The bottoms 4 may likewise be made in groups~ or else they may be individually applied. Alternatively the bottoms may be grouped for the purposes of grouping containers and the lids may be applied individually.
By way of typical example, the machines that fill the containers with individual portions operate at a rate of about ; 40,000 portions an hour. It is thus desirable for the machines which make the packaging to operate at a similar rate. ~igures 7 ~3~

and 8 are respectively a b~ock diagram and an exploded perspective view of a machine for m,aking containers in accordance with the invention and intended to occupy the same premises that a,re used for making the content. As mentioned above the components for making the containers are made elsewhere and are delivered flat and in sheet form which makes the loading of trucks for transport highly efficient in comparison with the transport of fully formed empty containers. As shown in ~igures 7 and 8, a machine includes three unstacking stations 27, 28 and 29 for the sheets 2, the bottoms 4 and the lids 3 respectively. Each unstacking station is followed by a respective sterilizer 34, eg. using ultraviolet radiation, with the components being sterilized while still flat. The sheets 2 as unstacked at 27 are conveyed to a shaplng stage 30 where they are folded in four and welded along a generator line. In parallel with this operation, a set of bottoms 4 is delivered to a statior 30 and is assembled to the tops of the tubular side walls 1 of a group of pots. Pressure is applied to ensure that the edge5 of the side walls 1 penetrate into the grooves 10. This assembly then passes an ultrasonic welding head 31 thus completing the pots per se. The pots are then turned over and delivered to a filling station 3? which is followed by means for applying lids or groups of lids thereto and then means 35 for welding the lids 3 to the pots~ A station 36 automatically places groups of filled pots onto a pallet~
~ igure 9 is a partially cut away perspective view of a station for making the side walls 1 from the sheets 2~ q`he unstacking station 27 is of conventional type. After passing through the ultraviolet radiation at 34 the sides of the side wall are folded by a combination of guides 39 and 41 and they are welded along the join line by an ultrasonic probe 40.
There is a small overlap where the sides are welded together.
~ igure 10 is a partially cut away perspective view of the station 35 for filling the pots. After the pots have been turned the right way up, they enter a housing 45. ~hey are driven along the housing 45 by an endless belt 51 which is caused to advance stepwise by a roll 42 which is driven from a ~5~3~() ', 11 drive shaft 44 via a Maltese cross type of cam 43. The purpose of such ætepwise advance i8 to ensure that the pots are stationary during filling and during subsequent welding of the lid. The pots are simultaneously pushed by a piston 46 which is driven from a gear wheel 49 which co-operates with an excentric arrangement 48 includin~ a cam 50 which is connected to the piston 46 by a lever which is hinged about a fixed shaft 47. The assembly is designed so that the stroke o~ the piston 46 i9 substantially equal to the step size of the endless belt 0 51 as driven by the roll 42.
Given the structure of the containers, the container manufacturing machine i9 advantageously modular comprising the following main modules:
side wall shaping;
bot-tom placement;
product filling; and lid placement.
Secondary modules may include, for example, automatic stack insertion modules; automatic quality control modules (shown diagrammatically at 52 in ~igure 8) for obtaining statistics;
and an automatic pallet loading module. The movements of the various operations for packaging the product do not require a continuously moving assembly line. The movements are of small amplitude and do not require high torque. The accuracy which can be obtained on the components means that the complex positioning means of conventional machinery can be avoided. In the machine described above, each pot constitutes its own positioning means~ This considerably simplifies sterilization and and the maintenance of sterile conditions along the entire ~0 production line, thus saving on equipment costs. Costs are also kept down by the items used in the line, such as the ultrasonic welding probes and the pot filling machines, being standard commercially available items.
The present invention may be used for packaging products which are in powder, pasty, or liquid form, and which need not be food products. It provides the following novel combination o~ characteristics: good product conservation; no additional ~'3~39~ 3 .
packaging carton for groups of containers; excellent marking due to information and decoration being printed on ~urface~
while they are flat; ease of grouping containers and subsequently of breaking up the groups; the product is itself keyed to the walls of the container.

,

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A container adapted to receive flowable contents at a site and formed by three discrete components each adapted to be transported to said site in a substantially flat condition; said three components including a wall portion formed by a substantially flat sheet of rectangular material having means including opposing end portions for forming a cylindrical portion having opposite open ends upon sealing said end portions together at said site, and two performed closure portions each having respective means for sealingly engaging a respective one of said open ends at said site, said container being formed of thermoplastic materials sealed together ultrasonically, the internal face of the wall portion being embossed and its external face being smooth, said container including a lid having an external face complementary to an external face of a bottom of a second container in such a manner that said second container may be stacked on said container by interfitting the bot-tom of the second container on the lid of said container, and that after such stacking, the wall portions of said containers are aligned and in thrust transmitting contact via said interfitting of the bottom of the second con-tainer on the lid of said container.

2. A container according to claim 1, wherein the external face of one of the closure portions is con-cave and the external face of the other closure portion is convex relative to the adjacent ends of said wall por-tion.

/