WO1997033741A1

WO1997033741A1 - Method and apparatus for forming containers

Info

Publication number: WO1997033741A1
Application number: PCT/EP1997/001188
Authority: WO
Inventors: Andrea Bartoli
Original assignee: Unifill International A/G
Priority date: 1996-03-12
Filing date: 1997-03-10
Publication date: 1997-09-18
Also published as: ITMO960031A1; IT1287409B1; AU2154397A

Abstract

A method for forming containers envisages subjecting a pair of sheets (3) to the action of a forming fluid to obtain from them pairs of opposed shells (5) in a forming mould (1) closed with sufficient force to prevent substantially any leakage of the forming fluid, avoiding, however, welding the sheets (3) together; the deformed sheets (3) are subsequently passed through a welding station (2) in which substantial parts of the outlines of the shells are welded by means of the combined action of heat and pressure.

Description

METHOD AND APPARATUS FOR FORMING CONTAINERS

The invention concernes a method and apparatus for forming containers .

FR-A-1199371 describes a method for forming containers in heat formable and heat weldable material in which a pair of sheets of the said material is progressively made to pass through a heating station to soften corresponding areas of the material, a welding and forming station for welding the outline of these areas with open profiles corresponding to the outlines of the containers, and for deforming the same areas by means of injection from inside, and/or by means of external suction, a filling station, a sealing and cutting station to separate the formed and filled containers from the sheets.

EP-A-0479152 describes an analogous forming method in which, however, the first station is a station for welding the edges of the outlines and is followed by a heating station, a blowing station, a filling station and a sealing station. WO 94/08852 also describes a method in which a pair of sheets are fed to a heating station and then to a welding and preliminary expansion station, where the sheets are welded along the outlines of pockets which are expanded by means of the injection into them of a forming fluid, and thence to a final expansion station.

US-A-3423902 describes an apparatus for forming containers from a pair of sheets of thermoplastic material in which the pair of sheets is introduced into a single die where it is welded along the outlines of the embryonic containers and these are expanded to form containers that are then filled and sealed while the die is oscillated vertically to advance the sheets.

In US-A-3245197, the system includes a thermofor ing station at which two strip-form sheets have formed therein respective rows of cavities, followed by a welding and filling station at which the outlines of the pairs of cavities are welded together except at filling openings and the containers thus obtained are filled. The welding and filling station is followed by a closing station at which the filling openings are sealed.

At the thermoforming station is a stationary mould member which is wedge-shaped, has its narrow side facing downwardly, and has its two opposed inclined mould faces facing towards respective mould faces of two turnable mould members. The stationary member has compressed air outlet apertures opening through its opposed inclined faces to supply jets of air to force the sheets into contact with the mould faces of the movable members .

Electrical heates may be provided in the stationary member to keep the sheets at the proper temperature for pressure moulding.

The sheets may be pre-heated at respective heating stations preceding the thermoforming station. Each movable member is pivotally mounted on a rod which also serves as a support of a sheet-guiding roller. During indexing of the sheets through the stations, the movable members extend vertically downwards from the respective rods. At the end of each step of advance of the sheets, the movable members are swung into fluid-tight contact with the sheets and clamp them against the stationary member. For swinging the movable member to-and-fro, they are pivotally connected to respective, horizontal, hydraulic piston-and-cylinder devices. At the filling and welding station are two harizontally reciprocable sealing blocks formed with respective rectangular recesses receiving the containers with clearance except at interrupted sealing rims thereof.

DE-A-1801966 discloses a system in which, at a single station, two thermoplastic sheets are introduced to between a pair of mould dies and are temporarily attached to the respective dies by suction, a heating element is introduced to between the sheets, the mould parts are closed to clamp the sheets to the heating element, the sheets are thermoformed into respective mould cavities by suction and/or blowing, the heating element is removed, and the thermoformed shells welded together by pressing them between the mould dies.

In an alternative version, the sheets are temporarily attached to the heating element by suction and then introduced therewith to between the dies.

GB-A-533502 disclosed a method comprising holding together between two mould dies the edges of plies of wrapping material, for example rubber hydrohalide, which is rendered stretchable by heating and, while the plies are so held, injecting a substance, such as confection, soap, cosmetic or wax, through a needle to between the plies with sufficient pressure to expand the wrapping material and thus to form a package. The substance is plastic so that it can be forced into the wrapper. The needle is withdrawn and the package is removed from the mould and undergoes a final sealing operation in which blunt-edged, heated dies weld the wrapping material plies together under heat and pressure to provide a permanent, air-tight, sealed joint. The sealing operation not only welds the plies together, but also pinches off surplus wrapping material and thus trims the package. In an example, the package is a lollipop and the sustance is candy which is forced in while hot and thus molten; it is hard and adheres to the wrapping material when removed from the mould. The wrapping may be stripped from the lollipop by pulling a loose skirt or tab which remains unattached around a stick of the lollipop.

According to one aspect of the present invention, there is provided a method of forming containers in which at least one sheet of a pair of sheets is subjected to the action of a forming fluid to obtain shells, the sheets of said pair of sheets also being welded together along the outlines of the shells to form containers, characterised in that said at least one sheet is subjected to deformation by the said fluid while held between two parts of a forming mould with a closing force that is sufficient substantially to prevent leakage of the said forming fluid and in that the sheets are subsequently conveyed into a welding station, in which the sheets are welded together around substantial parts of the respective outlines of the said shells.

According to another aspect of the present invention, there is provided an apparatus for forming containers, comprising a forming station in which at least one sheet of a pair of sheets is subjected to the action of a forming fluid to obtain shells, supplying means for supplying said forming fluid at said forming station, a forming mould at said forming station and comprised of two parts which are closable with a force that is sufficient substantially to prevent leakage of said forming fluid and at least one of which has cavities for moulding the shells, and a welding station in which the sheets are welded together around substantial parts of respective outlines of the said shells, characterized in that said welding station follows said forming station.

Owing to the invention, it is possible to keep the sheets relatively independent of each other at the outlines of the shells during forming thereof. The forming fluid may be the product to be contained by the containers; however, it is much prefered that the forming fluid should other than that product, for example should be air, since otherwise, if the product constitutes the forming fluid, then it needs to be fluid during forming and relatively solid between the forming and welding stations (otherwise it might leak from the shells) and the change of the product from its fluid phase to its solid phase would make the method relatively slow.

Keeping the sheets relatively independent of each other at the outlines of the shells during forming is particulary advantageous when the product contains relatively penetrative components, for example solvents, essential oils or detergents, which can penetrate thinnings in sheets at or immediately beyond the outlines is not so greatly prevented from moving to within the outlines during forming of the shells as it would be if the sheets were to be welded together at the outlines. Such inward movement of such material of the sheets is particulary facilitated if the sheets are in face-to-face contact with each other during forming of the sheels, rather than with some separator between the sheets.

The sheets may be two separate strips of thermoplastic material or may be provided by a single strip folded longitudinally of itself. Moreover, the shells may be formed in both or only one of the sheets. In the event that the shells are formed in only one of the sheets, the other sheets need not be thermoformable and may be peelable or non-peelable, as required.

To facilitate mass-production of containers in groups, at least one of the mould parts at the forming station may be formed with grooves inteconnecting the cavities, whereby at least one of the sheets is formed with inflation channels interconnecting the sheels.

If desired, at the forming station there may be a distributor plate, having its major faces substantially parallel to each other, for distribuing the forming fluid. The plate is positioned between the two sheets at the forming station and has its two major faces formed with holes for supplying the cavities with the forming fluid. An advantage of employing a plate for such distribution is that the mould parts can be driven in simple reciprocatory motions perpendiculary to the sheets and the plate. Some embodiments of the invention are illustrated, purely by way of example, in the eight sheets of drawing attached, in which:

Figure 1 is a longitudinal schematic section through container forming and welding stations in apparatus for blow thermo-forming with compressed air as the forming fluid; PC17EP97/01188

6 Figures 3, 4 and 5 are, respectively, sections III-III, IV- IV and V-V of Figure 2;

Figure 6 is a section as in Figure 2, but in a version with a single, central conduit for injecting the forming fluid; Figure 7 is a section as in Figure 2, but in a version with a distributor plate for the forming fluid; Figure 8 is section VIII-VIII of Figure 7;

Figure 9 is a section as in Figure 8, but in a version with mechanical forming of conduits interconnecting the containers;

Figures 10 and 11 are, respectively, sections X-X and XI-XI of Figure 8;

Figure 12 is section XII-XII of Figure 9.

The forming apparatus comprises a forming station 1 for forming containers, in groups or individually, in which a pair of sheets 3 in heat-formable and heat-weldable material is introduced between a corresponding pair of transversaly reciprocable dies of a forming mould 4 to form shells 5 by means of the injection of the forming fluid by injector devices 6 positioned between the pair of sheets at a location preceding the mould 4 on a path of indexing advance of the sheets 3. A pre-heating station for the sheets 3 may also precede the mould 4.

The forming fluid is injected through the devices 6 into the mould so as to cause the moulding of the shells 5 against the opposed cavities in the dies of the mould itself.

To this end, the dies are mantained at a temperature which enables the material to be softened; however, that temperature has to be low enough not to cause the welding together of the sheets 3 in the areas held between the dies of the mould 4. For the same reason, the closing force of the mould 4 should be high enough to prevent leakage of the forming fluid, without causing the sheets 3 to weld to each other. After the forming station 1 there is a welding station 2 in have been indexed to the station 2, the welding of the shells is carried out around substantial parts of the respective outlines 7 to obtain the respective containers, or groups of containers.

As shown in Figure 2, the shells 5 are connected with each other by means of communication conduits 10 created by means of corresponding opposed grooves in the dies of the forming mould 4.

The conduits 10 communicate, by means of a transverse conduit 12, with a pair of lateral conduits 11, extending longitudinally with respect to the sheets 3 between the transverse conduit 12 and the devices 6.

The transverse conduit 12 intersects all of the communication conduits 10 in a group of pairs of shells 5 in such a way as to be positioned between the two consecutive rows of pairs of shells 5 in the group. The welding station 2 comprises a pair of welding dies 8 with cavities 9 in which the already formed shells 5 are lodged. The areas of contact of the welding dies 8 with the sheets 3 may be limited to the outlines 7 of the shells 5. The welding dies 8, as opposed to the forming dies 4, do not have grooves to accomodate the lateral conduits 11; in this way, when the welding dies 8 are closed on the sheets 3, the conduits 11 are squashed and disappear. The welding dies 8 may be made in such a way that outlines 13 and 14, respectively, of the transverse conduit 12 and of the communication conduits 10 in the sheets 3 are also welded.

In this way, the groups of containers exiting from the welding station 2 are in an hermetically sealed condition and ready to be opened by cutting along the transverse conduit 12, for subsequent filling and final sealing. Figure 6 shows how there may be a single longitudinal conduit 15 which leads from an injection device 6 and which intersects the communication conduits 10 of a group of pairs of shells 5. This enables the quantity of the PC EP97/01188

8 sheets 3 is no longer required in the proximity of the edges to create the lateral conduits 11.

Figures 7 and 8 show how a distributor plate 16 of the pressurised forming fluid may be inserted between the sheets 3 in the forming mould 4, having distributor conduits 17 with terminal portions 18 opening out into the cavities of the dies in which the forming of the shells 5, as well as the conduits 10 and 12, is carried out. As shown in Figure 7, the transverse conduit 12 may be omitted, it being consequently envisaged that only the communication conduits 10 are formed. In this case, after the welding of the edges 7, 13, the groups of containers defined by the pairs of shells 5 are separated from the sheets 3 in such a way that their interiors remain isolated from the outside environment, and they are subsequently opened by cutting along a line intersecting the conduits 10 for filling through the portions of the conduits 10. This enables the quantity of discaded material to be significantly reduced.

As seen in Figure 9, the distributor plate 17 may be provided with projections 19 in its central part acting as presses for forming the communication channels 10, or possibly, for forming parts of the sheels 5. In this way it is possible to carry out the forming of the shells 5 and of the relevant channels, in part pneumatically, that is, with a pressurised forming fluid, and in part mechanically, that is, by the projections 19 of the plate 16 co-operating with corresponding grooves in the dies 4.

Operation is as follows: the continuous sheets 3 of the heat-formable and heat-weldable material are advanced in the direction of the arrow F and arrive at the forming station 1 between the forming dies 4 which are then closed upon the sheets 3 with a force no higher than necessary to prevent leakage of forming fluid from between the sheets 3. The sheets are then expanded, by means of the action of the pressurised forming fluid, into the cavities and grooves in the dies 4 to create the shells 5 and the communication conduits 10, as well as any other conduits 11, 12, 15 envisaged. The injection of the forming fluid may be achieved by means of the device (s) 6 positioned between the sheets 3, or by means of the distributor plate 16 and its distributor conduits 17, 18.

On exiting from the welding station 2, the groups of containers formed by the pairs of shells 5 are separated from the sheets 3, for example, along the dashed lines as in Figures 2 and 6, and subsequently opened transversely at the conduits 10, for example at one of the channels 12 if present, for filling with a fluid product through the residual portion of each communication conduit 10. After they have been filled, the containers are sealed and trimmed for dispatching.

In practice, the materials, dimensions and the details of execution may be different from, but techically equivalent to those described.

Claims

1. Method of forming containers in which at least one sheet of a pair of sheets (3) is subjected to the action of a forming fluid to obtain shells (5) , the sheets of said pair of sheets (3) also being welded together along the outlines (7) of the shells (5) to form containers, characterised in that said at least one sheet (3) is subjected to deformation by the said fluid while held between two parts (4) of a forming mould (1) with a closing force that is sufficient substantially to prevent leakage of the said forming fluid and in that the sheets (3) are subsequently conveyed into a welding station (2) , in which the sheets (3) are welded together around substantial parts of the respective outlines (7) of the said shells (5) .

2. Method according to claim 1, characterized in that the sheeets (3) of said pair are in contact with each other while held between said two parts (4) with said closing force and in that, after the forming of the shells (5), the shells (5) are filled with product.

3. Method according to claim 2, characterized in that the shells (5) are filled with said product after the sheets (3) are welded together about said respective outlines (7) .

4. Method according to any preceding claim, characterized in that, in the forming mould (1), channels (10, 12, 15) are formed in said at least one sheets (3) interconnecting said shells (5) .

5. Method according to claim 4, characterized in that, in the welding station (2), while the outlines (7) of the shells (5) are being welded, the respective edges (13, 14) of said channels (10, 12, 15) are also welded in order to isolate said channels (10, 12, 15) from the outside environment.

6. Method according to claim 4 or 5 as appended to claim 2, characterized in that, after the welding station (2) , said sheets (3) are cut to open the channels (10) and said (10) .

7. Apparatus for forming containers, comprising a forming station (1) in which at least one sheet of a pair of sheets

(3) is subjected to the action of a forming fluid to obtain shells (5), supplying means (6) for supplying said forming fluid at said forming station (1), a forming mould (1) at said forming station (1) and comprised of two parts (4) which are closable with a force that is sufficient substantially to prevent leakage of said forming fluid and at least one of which has cavities for moulding the shells

(5), and a welding station (2) in which the sheets (3) are welded together around substantial parts of respective outlines (7) of the said shells (5), characterized in that said welding station (2) follows said forming station (1) .

8. Apparatus according to claim 7, characterized in that filling means is disposed after said forming station (1) and serves to fill said shells (5) with product.

9. Apparatus according to claim 8, characterized in that said filling means is disposed after said welding station (2) .

10. Apparatus according to any one of claims 7 to 9, characterized in that the at least one of said two parts

(4) having cavities is formed with grooves interconnecting said cavities.

11. Apparatus according to any one of the claims 7 to 10, characterized in that a distributor plate (16) for distributing said forming fluid is positioned between said sheets (3) in the forming station (1) and is provided with holes for supplying said cavities with the forming fluid.

12. Apparatus according to claim 11 as appended to claim 10, characterized in that said holes (18) open out into said grooves.

13. Apparatus according to claim 11 or 12, characterized by projections (19) on said distributor plate (16) for forming channels (19) in said sheets interconnectiong said shells (5) .