WO2004058483A1

WO2004058483A1 - Method of manufacturing a vessel, as well as such a vessel

Info

Publication number: WO2004058483A1
Application number: PCT/NL2002/000875
Authority: WO
Inventors: Johan Arie Brambach
Original assignee: Euro Maintenance Lease Produktie B.V.
Priority date: 2002-12-30
Filing date: 2002-12-30
Publication date: 2004-07-15
Also published as: AU2002360014A1

Abstract

The invention relates to a method of manufacturing a vessel from at least two plastic parts. These parts comprise circumferential walls (3, 6) having substantially similarly shaped circumferential edges (4, 7), each comprising a circumferential flange (5, 8) projecting away from the circumferential wall. The circumferential flanges of these circumferential edges are positioned in an abutting relationship and are attached to each other. Then the circumferential flanges are moved to one side and laid flat against one of the circumferential walls, and the vessel is then finished. The circumferential flanges are attached to each other such that a subsequently exerted force on the connection will cause the circumferential flanges to be laid flat against one of the circumferential walls. The invention also includes such vessel made from at least two parts.

Description

Method of manufacturing a vessel, as well as such a vessel

The invention relates to a method of manufacturing a vessel in accordance with the preamble of claim 1. The invention further relates to a vessel in accordance with the preamble of claim 14.

There are various ways of manufacturing vessels of plastic material. If the vessels are made in one piece, blow- moulding and injection-moulding techniques may be used. These methods require large investments in apparatus and moulds, it is true, but they are inexpensive when large numbers are produced .

Vessels that are made in one piece have a drawback in that the storage and/or transport of these vessels require a great deal of space and is expensive, therefore. Especially if the vessels must be transported to another location for further treatment, the large volume constitutes a drawback.

In order to obviate this drawback, the vessels may be made of two parts, which parts can usually be nested, so that they take up much less space. The individual parts of the vessels can be manufactured by vacuum moulding, for example, which is an accurate and reliable manufacturing method. In that case provisions must be made for joining said parts, however. In the present case said provisions are comprised of circumferential flanges, which can be attached to each other .

US-A-3 , 198, 683 discloses a method and a vessel in accordance with the preamble of claims 1 and 14. With this known method, the circumferential flanges of the vessel parts are attached to each other by heat welding, after which the vessel is moved down through a special mould, causing the joined flanges to be laid flat. The circumferential flanges may be pressed firmly against the cooled mould as a result of an internal pressure in the vessel, thus fixing the circumferential flanges in position. The object of the present invention is to provide a new method of manufacturing a vessel of the kind referred to in the introduction, as well as such a vessel.

In order to accomplish that objective, the method according to the invention comprises the features defined in the characterising portion of claim 1, and the vessel according to the invention comprises the features defined in the characterising portion of claim 14.

According to the invention the circumferential walls are formed in such a manner and the circumferential flanges are attached together in such a manner that the force exerted on the vessel parts in a direction away from each other causes the circumferential flanges to "turn over", so that they will no longer project.

According to a simple manner of generating the pulling force which is advantageous in particular when manufacturing pressure vessels, the joint between the circumferential flanges is made airtight and the pulling force on the joint is effected by pressurising the vessel internally.

This embodiment of the method is very advantageous when manufacturing pressure vessels, which manufacture involves the winding of a fiber round the plastic vessel parts. This must take place in the pressurised condition of the vessel, so that said turning over of the circumferential flanges and said winding can take place directly after each other. It may be necessary, however, to slightly increase the pressure for the winding operation.

According to one method of laying flat the circumferential flanges, the circumferential flanges are joined together in such a manner that the circumferential walls are arranged slightly out of alignment, with the pulling force on the joint exerting a moment on the joint, which moment causes the flanges to pivot and be laid flat against the circumferential wall.

In this way the turning over of the flanges takes place in a very simple manner without any help from outside. The turning over of the circumferential flanges is further facilitated if a weakening is formed at the location of the joint between the circumferential flanges and the associated circumferential walls. Basically, a film hinge is formed about which the flanges can pivot . The integrity of the wall of the vessel is a matter to be considered in this connection, taking into account the loads that will be exerted on the wall of the vessel.

In an alternative method according to the invention, one of the circumferential flanges is connected to the circumferential wall of the associated vessel part in such a manner that it can readily bend, whilst the other circumferential flange exhibits greater bending stiffness, in which the associated vessel part is formed such that the shape of said vessel part is different from the shape of the vessel part in the position of use, and that deformation of the vessel part to the position of use involves a movement of the associated circumferential flange to the abutting position of the two circumferential flanges.

It is advantageous if the circumferential wall of the vessel part having the relatively stiff circumferential flange is pivoted upon deformation from the position reached after joining the circumferential flanges to the position of use, at least in the area adjacent to said circumferential flange, through an angle which is at least equal to the angle between the relatively flexible circumferential flange and the adjoining circumferential wall of the vessel part in question.

According to a first possibility of this method, the circumferential wall of the vessel part having the relatively stiff circumferential flange extends at least substantially inwardly of the circumferential wall of the other vessel parts after said joining of the two circumferential flanges but prior to said deformation, being turned over upon deformation to the position of use, whilst on the other hand the circumferential wall of the vessel part having the relatively stiff circumferential flange may only extend in a direction towards the other vessel part over a small portion of the section of the one vessel part after said joining of the circumferential flanges but prior to said deformation, in which case only said small portion is turned over upon deformation to the position of use.

As already said before, the invention also relates to a vessel which is characterized in that the circumferential flanges are joined together in such a manner that the force exerted on the joint via the circumferential walls exerts a moment on the joint, which moment causes the flanges to turn and to be laid flat against the circumferential wall.

The invention also includes a semi-manufacture for a vessel according to claim 19. This embodiment has the advantage that the place of manufacture of the vessel parts and their attachment can be separated from the place of further treatment of the vessel, such as winding, without causing transport problems. Then, the semi-manufactures are nestable as a result of their shape, enabling a small volume stacking of the semi-manufactures for storage and further transport .

The invention will be explained in more detail hereinafter with reference to the drawings, which show embodiments of the invention.

Figs. 1 - 4 are very schematic cross-sectional views of the various stages of the manufacture of a vessel from two vessel parts.

Figs, la - 4a are larger-scale views of the details A of Figs. 1 - 4.

Figs. 5, 6 are very schematic cross-sectional views of two stages of the manufacture of the vessel from two vessel parts according to a second embodiment of the invention.

Figs. 5a, 6a are larger-scale views of the details A of Figs . 5 and 6.

Figs. 7 and 8 are sectional views corresponding to Figs. 5 and 6 of another embodiment of the invention.

Figs. 7a and 8a are larger-scale views of the details A of Figs. 7 and 8. The drawings, and in the first place Figs. 1 - 4, show an embodiment of a method of manufacturing a vessel, in this case consisting of two vessel parts 1 and 2, each forming substantially one half of the vessel to be formed. The vessel to be formed may be a pressure vessel, for example a vessel of the kind disclosed in EP-A-0 862 535, whose contents are considered to be incorporated herein by reference. The vessel parts 1 and 2 may be flexible to a smaller or greater extent, but the vessel parts 1 and 2 may also be more or less stiff. The vessel parts are preferably made of a thermoplastic plastic material, such as polypropylene, polyethylene (HDPE) , PET, polycarbonate, nylon, but also all kinds of other thermoplastic and thermosetting plastics are conceivable.

The vessel part 1 comprises a circumferential wall 3 having a circumferential edge 4 on the open side, and a circumferential flange 5 adjoins said circumferential edge. Said circumferential flange 5 extends in a direction away from the wall, in this case substantially perpendicularly thereto, but it may also extend at an angle to the circumferential wall 3. The vessel part 2 similarly comprises a circumferential wall 6, a circumferential edge 7 and a circumferential flange 8. The circumferential flanges 5 and 8 are preferably configured such that they abut flat against each other when the vessel parts 1 and 2 are placed into contact with each other. As is shown in Fig. la, the transitional area between the circumferential flange 5 and the circumferential wall 3, i.e. at the location of the circumferential edge 4, is slightly weakened. This implies that the wall thickness at that location is slightly smaller than at the location of the circumferential wall 3 and the circumferential flange 5. As a result, a film hinge is formed, as it were, which facilitates pivoting of the circumferential flange 5 with respect to the circumferential wall 3.

In Fig. 2 the vessel parts 1 and 2 are positioned in abutting relationship, and the circumferential flanges 5 and 8 of the vessel parts 1 and 2 are joined. If the vessel parts 1 and 2 are made of a thermoplastic plastic material, for example by vacuum moulding, the circumferential flanges 5 and 8 may be joined by heat welding. In particular in the case of thermosetting plastics it is possible, however, to use an adhesive or the like for joining the circumferential flanges 5 and 8 together.

Said heat welding may be carried out by using the high-frequency welding method. On the other hand it is possible to use a heated tool (chuck) , in which case said tool is also used for forming a portion of reduced thickness at the transitional area between the circumferential flange 8 and the circumferential wall 6 of the vessel part 2, which portion is comparable with a portion of reduced thickness at the circumferential edge 4 of the vessel part 1.

As the figures furthermore show, the circumferential edge 4 and thus the adjoining circumferential wall 3 are positioned slightly out of alignment, in particular inwardly, with respect to the circumferential edge 7 and the adjoining circumferential wall 6 of the vessel part 2. In this way a radial distance is created between the walls 3 and 6, the function of which will be explained in more detail yet hereinafter.

The method for manufacturing a vessel according to this embodiment is carried out as follows.

In Fig. 1 the vessel parts 1 and 2 are placed one above the other, with their central axes aligned. The diameter of the circumferential edge 4 is slightly smaller than the diameter of the circumferential edge 7 of the other vessel part 2, so that the circumferential edge 4 and the adjoining circumferential wall 3 are positioned slightly radially inwardly of the circumferential edge 7 and the adjoining circumferential wall 6 of the vessel part 2.

Figs. 2 and 2a show the circumferential flanges 5 and 8 to be joined by heat welding, using a heat-welding tool (not shown) which has formed a portion of reduced thickness in the wall at the location of the circumferential edge 7. The portion of reduced thickness at the circumferential edge 4 of the vessel part 1 is positioned inwardly of the welded area.

In Fig. 3 the vessel, which is provided with a closable opening (not shown) , is pressurised, as a result of which a tension is generated in the circumferential walls 3 and 6. Said force will be exerted both perpendicularly to the wall and within the wall, and thus also in a direction away from the joint between the two wall parts 1 and 2, as is illustrated by means of arrows for the walls 3 and 6 in Fig. 3a.

Since the walls 3 and 6 are not aligned but rather spaced apart, the illustrated forces in the walls will provide a moment which attempts to move the two circumferential walls into alignment. This is indicated by means of an arrow in the shape of a circular segment .

Figs. 4 and 4a show that said moment has caused the circumferential flanges 5 and 8 to turn over in the direction of the vessel part 2 at the location of the joint between the vessel parts 1 and 2, i.e. in the direction of the radially outward vessel part . The movement of the flanges 8 and 5 is a pivoting movement at the location of the portion of reduced thickness near the circumferential edges 4 and 7. As a result of said pivoting movement, the circumferential walls 3 and 6 have moved more into alignment with each other at the location of the circumferential edges 4 and 7.

In this position of the flanges 5 and 8, said flanges can be attached to the circumferential edge 6 of the vessel part 2 , for example by glueing or by applying adhesive tape. In a next step, winding of the joined vessel parts 1 and 2 can take place either directly or after the flanges 5, 8 have been fixed in position, with the windings directly keeping the circumferential flanges 5 and 8 in position if this has not been arranged yet .

After said winding of the vessel parts 1 and 2, the vessel may be immersed in an adhesive or other fixing agent so as to fix the fiber windings with respect to each other and possibly with respect to the vessel parts 1 and 2. As a result, a very strong envelope of the vessel is obtained. Figs . 5 and 6 show a second embodiment of the method of manufacturing a vessel from two vessel parts. In Fig. 5, the vessel part 1 is concave rather than convex in comparison with the vessel part 2, so that the circumferential wall 3 of the vessel part 1 extends inwardly of the circumferential wall 6, and in the case of two substantially equal vessel parts 1 and 2 the circumferential wall 3 extends at least substantially parallel to the circumferential wall 6.

In Fig. 5a, the circumferential edge 7 between the circumferential flange 8 and the circumferential wall 6 has a portion of reduced thickness so as to render the circumferential flange 8 flexible relative to the circumferential wall 6, but a similar portion of reduced thickness or weakened portion is not present at the circumferential edge 4. Consequently, said circumferential edge 4 is relatively stiffer than the circumferential edge 7.

This difference in bending stiffness might be small as long as it allows a turn-over of the flanges.

In the position shown in Fig. 5A the vessels may be nested in order to be stored and/or transported in a space saving manner. If, in this position, the pressure in the space between the vessel parts 1 and 2 is increased, the circumferential wall 3 of the vessel part 1 will at some point "turn over" completely to the position that is shown in Fig. 6. The circumferential wall 3 will thus exert a bending force on the circumferential flange 5. As a result of the relatively great bending stiffness of the circumferential edge 4 and the relatively small bending stiffness of the circumferential edge 7, the circumferential flange 5 will pivot along with the circumferential wall 3, thus carrying along the circumferential flange 8, so that said circumferential flange 8 will move into abutment with the adjoining circumferential wall 6. The obtained position will be at least substantially comparable to the position that is shown in Fig. 4, therefore. The relatively stiffer circumferential edge 4 will yield eventually, and consequently the circumferential flange 5 will be more or less aligned with the circumferential wall 3. Upon comparison of Figs. 5 and 6 it appears that the angle through which the circumferential wall 3 adjoining the circumferential flange 5 has pivoted upon turning over is considerably greater than the angle through which the circumferential flange 8 has pivoted upon being placed into abutment with the circumferential wall 6, so that a proper abutment and pressing together will be obtained. Preferably, the flanges 5 and 8 have passed a dead center after their rotation causing the flanges to remain in their turned-over position, thereby avoiding that the vessel has to remain under pressure for further treatment or avoiding that the flanges have to be (directly) attached to the wall of the vessel.

Figs. 7 and 8 show another embodiment, which essentially represents a kind of intermediate form of the two preceding embodiments. The first part of the circumferential wall 3 of the vessel part 1 adjacently to the circumferential edge 4 extends inwardly in the direction of the vessel part 2, but the circumferential wall 3 then bends back to a convex part of the circumferential wall 3. When the interior of the vessel is pressurised, the same phenomenon will occur as in the embodiment of Figs. 5 and 6, i.e. the circumferential wall 3 adjoining the circumferential flange 5 will turn over and exert a bending force or a bending moment on the circumferential flanges 5 and 8 through a sufficiently large angle, causing said flanges to abut against the circumferential wall 6 of the vessel part 2.

Fig. 7a shows the shape of the flanges 5 and 8 to be slightly curved already, conforming to the curvature of the adjoining circumferential wall 6 of the vessel part 2, thus facilitating the abutment.

The vessel manufactured in accordance with the various methods is very suitable for several applications, for example for containing all kinds of end products and intermediate products, such as beer and other liquids and food (emulsions) . The vessel is also very suitable for containing all kinds of gasses and gas containing liquids. In particular in those cases in which an inner bag is used, the vessel forms a system which prolongs the shelf life of its contents, since the contents of the inner bag of the vessel do not come into contact with air. This renders the vessel highly suitable for all kinds of perishable goods, such as foodstuffs. When the vessel is used for storing a gas, the inner bag ensures the maintenance of the quality of the gas, especially if the pressure in the inner bag can be kept constant by introducing gas into the space between the vessel wall and the inner bag. Also other applications, in which an inner bag may or may not be used, are conceivable. The bag may comprise one or two connections for airtight connection to inlet or outlet means.

This connection or connections may be provided in a connecting element which may possibly be arranged in the opening which is used for pressurizing the vessel during the manufacture thereof. An inner bag may be positioned inside the vessel before or possibly also after attachment and expansion of the vessel parts . The vessel may have various dimensions. Generally its capacity will be more than 10 litres, and it may amount to several dozen litres. The shape of the vessel may vary, and the vessel parts need not have the same shape or dimension. Preferably, the individual vessel parts are nestable so as to obtain the aforesaid advantage as regards the storage thereof .

The invention is not restricted to the embodiment as described above and shown in the drawings, which can be varied in various ways within the scope of the invention as defined in the claims. Thus it would be possible according to the invention to exert an (additional) force on the circumferential flanges from outside so as to assist in positioning the flanges into abutment with the circumferential wall. The vessel may be designed for single or multiple use.

Claims

1. Method of manufacturing a vessel from at least two plastic vessels parts, which vessel parts comprise circumferential walls having substantially similarly shaped circumferential edges, each comprising a circumferential flange projecting away from the circumferential wall, in which the circumferential flanges of said circumferential edges are positioned in an abutting relationship and are attached to each other to form a connection, after which the circumferential flanges are moved to one side and laid flat against one of the circumferential walls, whereupon the vessel is finished, characterized in that the circumferential flanges are attached to each other in such a manner that a force which is subsequently exerted on the connection between the circumferential flanges will cause the circumferential flanges to be laid flat against one of the circumferential walls.

2. Method according to claim 1, wherein the joint between the circumferential flanges is made airtight and the pulling force on the joint is effected by pressurising the vessel internally.

3. Method according to claim 1 or 2 , wherein the circumferential flanges are joined together in such a manner that the circumferential walls are arranged slightly out of alignment, with the pulling force on the joint exerting a moment on the joint, which moment causes the flanges to pivot and be laid flat against the circumferential wall.

4. Method according to claim 3 , wherein a weakening is formed at the location of the joint between the circumferential flanges and the associated circumferential walls .

5. Method according to claim 4, wherein the vessel parts are made of a thermoplastic plastic material, whilst the circumferential flanges are joined together by heat welding, in which at least one of the transitional areas between the circumferential flange to the circumferential wall is reduced in thickness by the chuck which is used in heat welding the circumferential flanges.

6. Method according to claim 1 or 2 , wherein one of the circumferential flanges is connected to the circumferential wall of the associated vessel part in such a manner that it can readily bend, whilst the other circumferential flange preferably exhibits greater bending stiffness, in which the associated vessel part is formed such that the shape of said vessel part is different from the shape of the vessel part in the position of use, and that deformation of the vessel part to the position of use involves a movement of the associated circumferential flange to the abutting position of the two circumferential flanges.

7. Method according to claim 6, wherein the circumferential wall of the vessel part having the relatively stiff circumferential flange is pivoted upon deformation from the position reached after joining the circumferential flanges to the position of use, at least in the area adjacent to said circumferential flange, through an angle which is at least equal to the angle between the relatively flexible circumferential flange and the adjoining circumferential wall of the vessel part in question.

8. Method according to claim 7, wherein the circumferential wall of the vessel part having the relatively stiff circumferential flange extends at least substantially inwardly of the circumferential wall of the other vessel parts after said joining of the two circumferential flanges but prior to said deformation, being turned over upon deformation to the position of use.

9. Method according to claim 7, wherein the circumferential wall of the vessel part having the relatively stiff circumferential flange may only extend in a direction towards the other vessel part over a small portion of the section of the vessel part after said joining of the circumferential flanges but prior to said deformation, and wherein only said small portion is turned over upon deformation to the position of use.

10. Method according to one of the preceding claims, wherein the circumferential edges move through a dead center when they are being laid flat against one of the circumferential walls, and remain in the flat lying position when the exerted force is taken away.

11. Method according to any one of the preceding claims, wherein a plastic fiber is wound round the vessel, using a winding method, after said joining of the vessel parts .

12. Method according to claim 6, wherein said winding is carried out in the pressurized condition of the vessel .

13. Method according to claim 6 or 7, wherein the vessel is put under a (higher) pressure (anew) after said winding, and the vessel is immersed at said pressure in an adhesive so as to adhere the windings at least to each other.

14. Vessel consisting of at least two plastic vessel parts, which vessel parts comprise circumferential walls having substantially similarly shaped circumferential edges, each comprising a circumferential flange projecting away from the circumferential wall, in which the circumferential flanges of said circumferential edges are attached to each other to form a connection and are moved to one side into abutment with one of the circumferential walls, characterized in that the circumferential flanges are joined together in such a manner that a force exerted on the joint via the circumferential walls causes a moment a moment to be exerted on the joint, which moment causes the flanges to pivot into abutment with the circumferential wall.

15. Vessel according to claim 14, wherein the circumferential edge of the circumferential wall of one vessel part is positioned inwardly of the circumferential edge of the other vessel part .

16. Vessel according to claim 14 or 15, wherein the transitional area between the circumferential flange and the circumferential wall is weakened so as to form a film hinge.

17. Vessel according to any one of the claims 14-16, wherein the shape of said circumferential flanges and/or said one circumferential wall is adapted to enable flat abutment of the circumferential flanges.

18. Vessel according to any one of the claims 14-17, wherein the circumferential flanges are fixed to the circumferential wall in question by glueing and/or by means of adhesive tape.

19. Vessel according to any one of the claims 14-18, wherein said vessel parts are half shells.

20. Vessel according to one of the claims 14-19, comprising an inner bag and a closable filling opening arranged in the vessel wall and communicating with the interior of the inner bag, said inner bag being suitable for containing gasses, liquids containing gas or not and/or emulsions, wherein preferably a second filling opening is arranged in the vessel wall opening into the space between the inner bag and the vessel wall.

21. Semi-manufacture for a vessel from at least two plastic vessel parts, which vessel parts comprise circumferential walls having substantially similarly shape circumferential edges, each comprising a circumferential flange projecting away from the circumferential wall, in which the circumferential flanges of said circumferential edges are attached to each other for forming a connection, and may be positioned against one of the circumferential walls to one side, characterised in that the vessel parts of the semi- manufacture are shelves, preferably substantially halve shelves, which are at least partially be nested and of which the circumferential flanges are preferably attached to each other such that when the vessel parts are moved away from each other there is exerted a momentum on the circumferential flanges which causes the circumferential flanges to turn and to be laid flat against the circumferential wall.