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Title:
METHOD FOR MANUFACTURING AN ARTICLE COMPRISING A SHEET OF PLASTIC WELDED TO ITSELF OR TO AT LEAST ONE OTHER SHEET OF PLASTIC AND INFLATABLE ARTICLE
Document Type and Number:
WIPO Patent Application WO/2019/174920
Kind Code:
A1
Abstract:
Method for manufacturing an article (1), preferably an inflatable article, comprising a sheet of plastic (2) welded to itself or to at least one other sheet of plastic (2), the method comprising a welding step in which a first sheet of plastic (2 ) is welded to itself or to a second sheet of plastic (2), whereby a first deformation step takes place before the welding step, wherein in the first deformation step the first sheet of plastic is plastically deformed and is preformed into a first sheet of plastic (2) which cannot be spread out flatly. The invention further concerns an inflatable article (1 ) comprising a first sheet of plastic (2) welded to itself or to a second sheet of plastic (2), whereby in non-inflated condition, the first sheet of plastic (2) is plastically deformed and preformed into a sheet of plastic (2) that cannot be spread out flatly.

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Inventors:
BEYERS, Koen (p/a Bijkhoevelaan 32c, 2110 Wijnegem, 2110, BE)
SORGELOOS, Kristof (p/a Bijkhoevelaan 32c, 2110 Wijnegem, 2110, BE)
VERLEIJE, Bart (p/a Bijkhoevelaan 32c, 2110 Wijnegem, 2110, BE)
Application Number:
EP2019/054929
Publication Date:
September 19, 2019
Filing Date:
February 28, 2019
Export Citation:
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Assignee:
VOXDALE BVBA (Bijkhoevelaan 32c, 2110 Wijnegem, 2110, BE)
International Classes:
B29D22/00; A61G7/10; A63B5/00; A63G31/12; B29C33/00; B29C49/02; B29C51/26; B29C65/00; B29C65/02; B29D22/02; B32B3/02; B32B3/26; B32B3/28; B32B5/14; B32B7/04; B32B7/05; B32B27/08; B32B37/00; B32B38/12; B66F3/35; B29C49/00
Foreign References:
US20120234467A12012-09-20
US20110224059A12011-09-15
Other References:
None
Attorney, Agent or Firm:
KAMPHUIS, Albertus Johannes (Slachthuisstraat 120 bus 3, 2300 Turnhout, 2300, BE)
Download PDF:
Claims:
Claims

1. Method for manufacturing an article (1 ) comprising a sheet of plastic (2) welded to itself or to at least one other sheet of plastic (2), the method comprising a welding step in which a first sheet of plastic (2 ) is welded to itself or to a second sheet of plastic (2), characterized in that a first deformation step takes place before the welding step, wherein in the first deformation step the first sheet of plastic is plastically deformed and is preformed into a first sheet of plastic (2) which cannot be spread out flatly.

2. Method according to claim 1 , characterized in that the article is an inflatable article (1 ).

3. Method according to one of the preceding claims, characterized in that the method comprises a positioning step for positioning in a desired position a first to be welded part (4) of the first sheet of plastic (2) relative to a second to be welded part of the first sheet of plastic or relative to a to be welded part (4) of the second sheet of plastic (2), the positioning step taking place before the welding step, the positioning step taking place after the first deformation step, wherein in the positioning step a bottom mould (12) ) is used with a cavity (13) and a surface (14) around the cavity, a preformed, non-flat, part of the first sheet of plastic (2) being placed in the cavity and a first to be welded part (4) of the first sheet of plastic (2) being placed on the surface (14) around the cavity (13) and wherein a to be welded part (4) of the second sheet of plastic (2) or the second to be welded part of the first sheet of plastic is placed on the first to be welded part (4) of the first sheet of plastic (2).

4. Method according to claim 3, characterized in that the cavity (13) has a shape which is complementary to the shape of said preformed, non-flat, part of the first sheet of plastic (2).

5. Method according to one of the preceding claims, characterized in that the method comprises a second deformation step which takes place before the welding step, wherein in the second deformation step a second sheet of plastic is plastically deformed and preformed into a second sheet of plastic (2) which cannot be spread out flatly, and wherein in the positioning step a preformed, non-flat part of the second sheet of plastic (2) is placed in the cavity (13), and wherein in the welding step the first sheet of plastic (2) is welded to the second sheet of plastic (2).

6. Method according to one of the preceding claims, characterized in that said preformed, non-flat, part of the first sheet of plastic (2) and/or of the second sheet of plastic (2) is inserted into the cavity (13) by placing the respective non-flat preformed part over a complementary shaped stamp (11 ) and to bring the stamp (1 1 ) together with the preformed, non-flat, part into the cavity (13).

7. Method according to one of the preceding claims, characterized in that said preformed, non-flat, part of the first sheet of plastic (2) is inserted into the cavity and/or held therein by applying a negative pressure between the first sheet of plastic (2) and the bottom mould (12).

8. Method according to claim 7, characterized in that the bottom mould is provided with at least one channel (15) which opens into the cavity (13) and which is connected to a device for applying a negative pressure.

9. Method according to any one of the preceding claims, characterized in that the first deformation step is carried out by means of vacuum forming.

10. Method according to any one of the preceding claims, characterized in that, before the positioning step, the first sheet of plastic (2) is adapted to have different stretching behaviour at different locations. 11. Method according to claim 10, characterized in that, before the positioning step, the first sheet of plastic (2) is adapted to have different stretching behaviour at different locations by plastically stretching at said different locations the first sheet of plastic (2) at varying degrees to a different thickness (d 1 , d2, d3).

12. Method according to claim 2 and claim 10 or 1 1 , characterized in that said adjustment of the first sheet of plastic (2) takes place on the basis of predetermined guide values for the stretching behaviour at the said different locations, wherein these predetermined guide values have been determined to obtain a desired inflation behaviour of the inflatable article

(1 ), wherein these predetermined guide values have been determined experimentally and/or determined on the basis of numerical modelling.

13. Inflatable article (1 ) comprising a first sheet of plastic (2) welded to itself or to a second sheet of plastic (2), characterized in that, in non-inflated condition, the first sheet of plastic (2) is plastically deformed and preformed into a sheet of plastic (2) that cannot be spread out flatly.

14. Inflatable article according to claim 13, characterized in that the first sheet of plastic (2) has a different stretching behaviour at different locations.

15. Inflatable article according to claim 13 or 14, characterized in that the first sheet of plastic (2) has a different thickness (d 1 , d2, d3) at different locations.

Description:
METHOD FOR MANUFACTURING AN ARTICLE COMPRISING A SHEET OF PLASTIC WELDED TO ITSELF OR TO AT LEAST ONE OTHER SHEET OF

PLASTIC AND INFLATABLE ARTICLE The present invention relates to a method for manufacturing an article comprising a sheet of plastic which is welded to itself or to at least one other sheet of plastic and an inflatable article.

On the one hand, the invention relates to an inflatable article wherein the volume of the article in inflated condition is at least twice, and preferably at least four times, the volume of the article in non-inflated condition. On the other hand, the invention also relates to an inflatable article which does not or hardly expand when inflated to a usable pressure. Many types of such inflatable articles are known which are mainly formed from flexible sheets of plastic, for example beach balls, inflatable boats, bouncy castles, air mattresses and air cushions for raising and/or supporting loads.

The known inflatable articles are made from sheets of plastic which are flat, and which are welded together to obtain an article which extends in three dimensions.

This is an easy way to manufacture an inflatable article, both in terms of cutting the various sheets of plastic, as well as for welding the various sheets of plastic together.

However, the well-known inflatable articles also have disadvantages.

For example, they have a relatively large number of seams, which is necessary to obtain the desired shape, but which is laborious to apply and which always entails a risk of leakage.

The flat shape of the sheets of plastic also cause an article with curved surfaces to have, non-homogenous stresses to arise in the material after inflation. The flat shape of the sheets of plastic also means that complex shapes of the inflatable article cannot, or can only with difficulty, be realized after inflation.

Furthermore, when inflated above atmospheric pressure, the inflation behaviour of inflatable articles produced in such a way cannot be controlled: the article will expand approximately equally in all directions, whether this is desirable or not.

The article will also exert a tensile stress due to its own expansion on any surface that is in contact with the article during inflation.

The article will also increasingly assume a rounded shape, as it becomes more inflated, whether this is desirable or not. With air cushions for lifting or supporting loads, this rounded shape will also cause the load not to be uniformly supported over the entire contact surface.

The objective of the present invention is to provide a solution for the aforementioned and other disadvantages and, to this end, provides an inflatable article comprising a first sheet of plastic which is welded to itself or to a second sheet of plastic, the first sheet of plastic being plastically deformed and preformed into a sheet of plastic that cannot be spread out flatly to thereby obtain a controlled shape of the inflatable article upon inflation to atmospheric pressure. Preferably, both sheets of plastic are plastically deformed and preformed.

Alternatively, the invention relates to an inflatable article comprising two or more flexible sheets of plastic which are welded to each other, at least one of the sheets of plastic being plastically deformed and preformed into a sheet that cannot be spread out flatly to thereby obtain a controlled shape of the inflatable article upon inflation to atmospheric pressure. Preferably, both sheets of plastic are plastically deformed and preformed.

In this way, the preformed sheet of plastic has a naturally preferred shape which, due to the flexibility of the inflatable article, can be deformed when the article is not inflated and which will only be attained upon inflation to atmospheric pressure and which corresponds to the desired shape of the particular part of the inflatable article. This is best evaluated in non-inflated condition, because the plastic deformation is then most easily visible. In other words, the preformed sheet of plastic is preformed in such a way that it extends in three dimensions.

These inflatable articles can be made with more complex shapes and/or with a higher accuracy and/or with fewer welding edges than the currently known inflatable articles.

There are also fewer stresses in the material when inflating.

In a preferred embodiment, the first sheet of plastic has different stretching behaviour at different locations, to thereby expand in a controlled manner upon inflation to a pressure of more than atmospheric pressure. This is preferably obtained because the first sheet of plastic has a different thickness at different locations. This has the advantage that a preferred expansion in certain directions is possible, whereby for instance a more constant pressure distribution can be exerted on the surface of an object that is to be carried or lifted, and whereby no or less space is required for the inflatable article in directions other than the direction of the preferred expansion. This also makes it possible to keep a surface of the article relatively flat, which results in the reduced risk that items located on this surface will slide off.

A locally different stretching behaviour can easily be obtained by local differences in thickness of the sheet, but also by local physico-chemical changes, such as a polymer crystallization and/or a pre-stretching to a plastic deformation in a particular direction and/or a heating followed by a sudden cooling step and/or a partial polymer decomposition.

Forming sheets of plastic before welding them can easily be performed by means of vacuum forming. Hereby, the local thickness of the sheets of plastic can also be controlled according to known techniques in the field of vacuum forming by controlling the local temperature of the sheet of plastic and/or by controlling the length of time during which the sheet of plastic can be locally stretched by means of the speed of applying vacuum and by means of the shape and temperature of the mould used.

In a preferred embodiment the inflatable article is suitable for being inflated to 5 KPa above atmospheric pressure, and preferably to 10 KPa above atmospheric pressure. This is evaluated on the article itself, independently of other articles, and particularly in circumstances in which the article can freely expand and is not limited in an expansion by another object. This implies a certain tensile strength of the wall material and of existing welds.

Preferably, the inflatable article is a beach ball or an inflatable boat or a bouncy castle or an air mattress or an air cushion for raising and/or supporting a load, the invention particularly focusing on this latter embodiment.

The invention further relates to the use of such an inflatable article to raise and/or support a load, in other words an object with a weight.

In a preferred variant, the invention relates to the use of such an inflatable article as an actuator in a positioning table.

The invention also comprises a method for manufacturing an article, in particular an inflatable article according to the invention, which comprises a sheet of plastic which is welded to itself or to another sheet of plastic, the method comprising a welding step in which a first sheet of plastic is welded to itself or to a second sheet of plastic, wherein before the welding step a first deformation step takes place, wherein in the first deformation step the first sheet of plastic is plastically deformed and preformed into a first sheet of plastic which cannot be spread out flatly.

Alternatively, this can be described as a method for manufacturing an article, preferably an inflatable article according to the invention, comprising two or more sheets of plastic welded to each other, in which a first sheet of plastic and a second sheet of plastic are welded together in a welding step, wherein, before the welding step is carried out, a first deformation step takes place, wherein in the first deformation step the first sheet of plastic is plastically deformed and preformed into a sheet which cannot be spread out flatly.

The advantages of this are analogous to the above-described advantages of the inflatable article.

The welding step can be carried out by means of any welding technique, such as ultrasonic welding, laser welding, hot bar welding and high-frequency welding, the latter welding technique being preferred.

The deformation step and the welding step are preferably carried out in separate machines or at separate locations in the same machine. As a result, both the welding step and the deformation step can optimally be carried out.

Preferably, the first sheet of plastic has a temperature of 45 ° or lower at any time between the deformation step and the welding step.

In a preferred variant of the method, it comprises a positioning step to place in a desired position a first to be welded part of the first sheet of plastic relative to a second to be welded part of the first sheet of plastic or relative to a to be welded part of the second sheet of plastic, wherein the positioning step takes place before the welding step, the positioning step taking place after the first deformation step, wherein in the positioning step uses a bottom mould with a cavity and a surface around the cavity, wherein in the positioning step a preformed, non-flat, part of the first sheet of plastic is placed in the cavity and a first, to be welded, part of the first sheet of plastic is placed on the surface around the cavity and wherein in the positioning step a to be welded part of the second sheet of plastic or the second to be welded part of the first sheet of plastic is placed on the first to be welded part of the first sheet of plastic.

Standard welding techniques for sheets of plastic are intended to attach flat sheets to one another. When the sheets are not flat, as in the present invention, with the existing techniques they cannot be properly positioned to produce a reliable weld. It is particularly difficult to place the to be welded parts correctly and flat on each other before starting the actual welding step. There is also a risk that the preformed, non-flat parts of the sheets interfere with the movements of the welding machine.

In this preferred variant, a bottom mould, or in other words a mould, with a cavity is used for placing the preformed part, so that the parts of the sheets to be welded can be neatly and non-deformed placed on each other, and such that movements of the welding machine can not touch the preformed, non-flat parts.

For the sake of clarity, it is noted that the positioning step takes place in the machine which is used for performing the welding step.

The positioning step is suitable for all articles comprising sheets of plastic that are welded together. More generally the invention therefore relates to a method for manufacturing an article comprising two or more sheets of plastic welded together, wherein a first sheet of plastic and a second sheet of plastic are welded together in a welding step, wherein, before the welding step is carried out, a positioning step is carried out to place the first sheet of plastic and the second sheet of plastic in a desired position relative to each other, wherein in the positioning step a mould, or die, is used with a cavity and a surface around the cavity, wherein at least a part of the first sheet of plastic is placed in the cavity of the mould and another, to be welded part of the first sheet of plastic to is placed on the surface and wherein a to be welded part of the second sheet of plastic is placed onto the to be welded part of the first sheet.

In a preferred variant, the method comprises a second deformation step which takes place before the welding step, wherein in the second deformation step a second sheet of plastic is plastically deformed and is preformed into a second sheet of plastic which cannot be spread out flatly, and wherein in the positioning step a preformed, non-flat, part of the second sheet of plastic is placed in the same cavity, and wherein in the welding step the first sheet of plastic is welded to the second sheet of plastic. In a preferred variant the said preformed, non-flat part, of the first sheet of plastic and/or of the second sheet of plastic is introduced into the cavity by placing the relevant non-flat preformed part over a complementary shaped stamp and to bring the stamp into the cavity together with the preformed, non-flat part. The stamp can either be retracted while leaving behind said preformed, non-flat, part of the first sheet of plastic and/or of the second sheet of plastic in the cavity, or can remain in the cavity during the welding step.

In yet another preferred variant the said preformed, non-flat, part of the first sheet of plastic is placed into the cavity and/or held therein by applying a negative pressure between the first sheet of plastic and the bottom mould.

To this end, preferably the bottom mould is provided with at least one channel which opens into the cavity and which is connected to a device to apply a negative pressure.

Preferably, the first and/or the second deformation step is carried out by means of vacuum forming, and more preferably by means of vacuum forming on a minimally partially but preferably completely convex mould.

In a preferred variant, before the positioning step, the first sheet of plastic is adapted from a first sheet with a uniform stretching behaviour into a first sheet with a different stretching behaviour in different places. As a result the inflation behaviour of an inflatable article to be manufactured can be better controlled.

This preferably happens by plastically stretching the first sheet of plastic to varying degrees at the previously mentioned different locations to a different thickness but can also be obtained through local physico-chemical changes, such as polymer crystallization and/or a pre-stretching into a plastic deformation in a particular direction and/or a heating followed by a sudden cooling step and/or a partial polymer decomposition. The said adjustment of the first sheet of plastic is preferably done during the deformation step.

In a further preferred variant, said adjustment of the sheet of plastic takes place on the basis of predetermined guide values for the stretching behaviour at the said different places, wherein these predetermined guide values are determined to obtain a desired inflation behaviour of the inflatable article, wherein these predetermined guide values have been determined experimentally and/or have been determined on the basis of modelling.

The said sheets of plastic can in principle be any plastic, such as PVC, Polyurethane, TPU, PET, PET-G and PET-GAG foil, but are preferably sheets of polyurethane foil.

In order to clarify the invention a preferred embodiment of an inflatable article according to the invention and of a method for manufacturing this article are described below, with reference to the following figures, in which:

Figure 1 shows in perspective an inflatable article according to the invention in a first inflated condition;

Figure 2 shows a part of the inflatable article of Figure 1 in cross-section according to ll-ll;

Figure 3 shows in side view the inflatable article of Figure 1 in non-inflated condition;

Figure 4 shows in side view the inflatable article of Fig. 1 in the condition of Figure 1 ;

Figure 5 shows in side view the inflatable article of Figure 1 in a second inflated condition;

Figure 6 shows a first step in the manufacturing of the inflatable article of Figure 1 ;

Figure 7 shows a second step in the manufacturing of the inflatable article of Figure 1 ;

Figure 8 shows a part of a device used in the manufacturing of the inflatable article of Figure 1 ;

Figure 9 shows a third step in the manufacturing of the inflatable article of Figure 1 ; and Figure 10 shows an application of the inflatable article of Figure 1.

Figures 1 to 5 show an inflatable air cushion 1. The air cushion consists of two identical preformed sheets of flexible polyurethane foil 2 and a valve 3. The preformed sheets of polyurethane foil 2 are each provided with a welding edge 4 and are welded together at the location of this welding edge 4. The mentioned valve 3 is also welded into the welding edges 4 that are welded together.

The preformed sheets of polyurethane foil 2 are preformed in a cylindrical shape, and have a different thickness at different locations, namely a thickness d1 of approximately 1.5 mm at the top wall or bottom wall 5, a thickness d2 of approximately 1.0 mm at the side walls 6 and a thickness d3 of approximately 0.5 mm at the location of the welding edge 4. The preformed sheets of polyurethane foil 2 are not flat and, because they are preformed in the described shape, cannot be spread out flatly.

The air cushion 1 can be brought into a compact condition, as shown in Figure 3, by compressing the air cushion 1 while the valve 3 is open.

When the air cushion 1 is inflated via the valve to atmospheric pressure, as shown in Figures 1 and 4, it takes its natural shape, wherein the sheets of polyurethane foil 2 are not under any stress.

It is clear that during inflation of the compact condition as shown in Figure 3, to the condition of Figure 4, expansion of the air cushion 1 occurs substantially in vertical direction.

When the air cushion 1 is inflated via the valve 3 to a pressure above atmospheric pressure, as shown in Figure 5, where the air cushion 1 is inflated to 0.3 bar above atmospheric pressure, it expands, and the preformed sheets of polyurethane foil 2 are stretched.

Hereby, the expansion substantially takes place at the side walls 6, because these are thinner than the top wall 5 and bottom wall 5. The top wall 5 and bottom wall 5 hereby remain relatively flat. Such an air cushion 1 can be manufactured as follows.

Flat sheets of polyurethane foil 7 are plastically deformed in a deformation step by means of the known technique of vacuum forming. Hereby, a mould 8 is used which is equipped with channels 9 to apply a vacuum.

Above this mould 8 a flat sheet of polyurethane foil 7 of 1.5 mm thickness is stretched and heated, after which a vacuum is applied between the mould 8 and the sheet of polyurethane foil 7, whereby the sheet of polyurethane foil 7 plastically deforms around the mould 8 and takes on the shape of the mould 8.

This is shown in Figure 6.

Excess material is cut away, after which the previously mentioned cylindrically preformed sheets of polyurethane foil 2 with a welding edge 4 are obtained which are ready to be welded.

Hereby, a different thickness d1 , d2, d3 at different locations of the preformed sheet of polyurethane foil 2 is obtained, because the polyurethane can only plastically deform as long as it is not in contact with mould 8, because after contact with the mould 8, it is cooled by the mould 8.

The obtained thickness d1 , d2, d3 can be controlled by many known techniques that are known in the art of vacuum forming, such as local additional heating or cooling of the flat sheet of polyurethane foil 7 before applying the vacuum or by physically and/or chemically treating the flat sheet of polyurethane foil 7 before the vacuum forming so that a sheet of polyurethane foil is obtained that is not homogeneous across its surface.

Two such preformed sheets of polyurethane foil 2 are now welded together.

Before this can happen, however, they must be correctly positioned relative to each other, with their welding edges 4 neatly flat and without folds on top of each other. This positioning step is carried out in the final welding device 10, namely in this case a welding device for high-frequency welding.

In first instance, the preformed sheets of polyurethane foil 2 are applied over a stamp 11. This stamp 11 has a shape corresponding to the shape of the preformed sheets of polyurethane foil 2 and may be made of, for example, wood or plastic. This is shown in Figure 7.

The stamp 1 1 with the preformed sheets of polyurethane foil 2 is then turned over and placed in a specially formed bottom mould 12 of the welding device 11. This bottom mould 12 is made of aluminium and is shown in Figure 8. The bottom mould 12 is provided with a cavity 13 which corresponds to the shape of the preformed sheets of polyurethane foil 2, and has a flat surface 14 around this cavity 13.

Furthermore, this bottom mould 12 is provided on its bottom side with channels 15 which are connected to a vacuum pump (not shown).

The two to be welded preformed sheets of polyurethane foil 2 are placed together in the cavity with the aid of the stamp 1 1.

Hereby, the welding edges 4 of the preformed sheets of polyurethane foil 2 lie neatly flat together on the flat surface 14 around the cavity 13. Subsequently, a vacuum is applied by means of the channels 15, whereby the lower preformed sheet of polyurethane foil 2 is even better placed in the cavity 13, and is also held in this position during the subsequent welding step.

The use of a stamp 1 1 and the application of vacuum are not both necessary here. Also with either of the above means a sufficiently good placement of the preformed sheets of polyurethane foil 2 in the cavity 13 can be obtained, although the combined use is preferred if the shape of the preformed sheets of polyurethane foil 2 is suitable for this purpose. Depending on the circumstances, it may be desirable to retract the stamp 1 1 , leaving behind the preformed sheets of polyurethane foil 2 in the cavity 13, but this is not necessary in the current method. The preformed sheets of polyurethane foil 2 are now ready to be welded together. This situation is shown in Figure 9.

The actual welding step is carried out in a known manner by lowering an upper plate 16 in the welding device 10, which is provided with a properly formed welding electrode 17, until the welding electrode 17 exerts some pressure on the welding edges 4 of the preformed sheets of polyurethane foil 4, wherein a high frequency alternating voltage is applied between the welding electrode 17 and the bottom mould 12, whereby the polyurethane at the location of the welding electrode 17 heats up and melts, such that a weld is formed.

Hereby, a small part of the welding edge 4 is not welded, because the valve 3 must be welded herein later, according to techniques known in the art. After this has been done, the inflatable air cushion 1 is ready for use. A possible use of the air cushion 1 is shown in Figure 10. This relates to a positioning table 18 in which, between a base 19 and a table top 20, a number of such air cushions 1 is arranged. By individually adjusting the pressure in each of the air cushions 1 , the height and the orientation of the table top 20 can be adjusted. The air cushions 1 thus act as actuators.

Traditionally, such positioning tables are equipped with metal actuators. As a result, they are heavy and cannot be used in situations where the presence of metal can be disturbing, such as in various medical and non-medical scanning techniques or in other situations in which a strong magnetic or electric field is present.

Due to the air cushion 1 according to the invention, such positioning tables 18 can be embodied light-weight and metal-free.