Isothermal package and method for producing it

The present invention relates to the field of packaging isotherms. The invention relates more particularly to a device isothermal packaging designed for temperature-sensitive products, materials hazardous, infectious, biologically active products, etc. used including biotechnology, chemistry, pharmacy or any other type of Product tolerant only a very small change in temperature.

It is known in the prior art packaging with walls include ice packs components. It is well known WO 00/03931 a container package incorporating a foam insulating polyethylene forming a plurality of internal walls of the container and an outer wall made of polyethylene. This type of packaging is bulky and ineffective. Moreover the polyethylene foam does not constitute the insulating more efficient.

The use of polyurethane contiguous plates is also known to form a simpler insulation means. However, the effectiveness devices incorporating this system is much less, many losses heat being generated at the junction of polyurethane plates.

It is known in the prior art by patent application FR 2664 240, an insulated body formed from a sheet with walls and cover include rigid polyurethane foam injected under low pressure. This fund has good insulation qualities but requires a complicated manufacturing method. Prior to forming is required for this fund, including a multiplicity of folds card is tedious and can not be automated. The manufacturing method This fund remains artisanal. For these known products using cardboard or like sheets, an additional disadvantage is the bridging / thermal leaks caused by folding sheets or the junction with the lid.

So far, injection of polyurethane foam under high pressure was not considered for inexpensive packaging since materials commonly used, such as cardboard, do not resist this high pressure. The thrust generated by the swelling of the foam reaches in effect about 1 kg / cm².

There is therefore a need for a packaging that is both economic, obtained by an industrial mode of production and semi-automated, and adapted to enable a very good thermal insulation products to be kept at a substantially constant temperature.

The present invention therefore aims to overcome one or more of drawbacks of the prior art by defining a reliable, industrial process of manufacturing an isothermal packing device which allows to inject, to inside of this device, a high density polyurethane foam under high pressure with enhanced thermal insulation performance.

To this end, the invention relates to a method of manufacturing a isothermal packing device formed of a container and a lid, comprising an injection phase of a polyurethane foam in said container, characterized in that it comprises the following steps:<ul><li>erecting an inner envelope having a face open at one end,</li><li>erecting an outer envelope open at both ends and having flaps,</li><li>establishment, on an inner mold shaping, of the inner casing previously set volume,</li><li>positioning on the surface adjacent to the mold opening the inner shell of a sealing ring thermally insulating,</li><li>establishment of said outer shell around said sealing ring,</li><li>establishing a first outer enclosure conformation Coming surround the outer envelope, </li><li>injecting a given volume of polyurethane foam under high pressure in the volume formed between said peripheral the inner shell and the outer shell, said volume foam being calculated as a function of said peripheral volume and the final desired density foam,</li><li>closing said peripheral volume by the flaps of the envelope external located on the side opposite the opening of the envelope inner and closing of said first enclosure,</li><li>expansion of the foam in said peripheral volume.</li></ul>

In another feature, the method of the invention comprises a demolding said container, said lid being removable and suited to said container.

In another feature of the invention, said inner envelope is shaped to form the bottom and sides of a housing open within said container, said outer envelope being shaped to form the outer bottom and outer walls of said container, said housing being sealed via a stopper returning from thermally insulating sealing cover.

In another feature, the method according to the invention comprises a cutting step of said sealing ring and a step use of the central part of this division as said cap sealing returning forming the base of said cover, the walls said outer cover being held by a bending of a sheet, the internal volume thus delimited being filled with polyurethane foam under high pressure injected before positioning of the plug and returning closing a second outer enclosure enclosing conformation said cover during expansion of the foam thus injected.

In another feature, the polyurethane foam volume injected inside the lid is calculated as a function of said internal volume to complete and the final desired density foam.

In another feature of the invention, the inner envelopes and external of the container each comprise a sheet cut cardboard or packaging material with similar properties, folded and glued to form a regular volume with horizontal bottom and vertical walls, folding the inner casing (10) having recoveries removing any point potential leakage of foam on the edges of the inner bottom.

In another feature of the invention, the bottom of said housing is rectangular and formed by successive folding of a first flap covering at least the entire bottom of two adjacent flaps said first flip and a last flap with an insertion tab under said two flaps adjacent.

In another feature of the invention, said container is placed in an inverted position on said forming mold, said mold being fixed and comprising a base on which is arranged the sealing ring, said first enclosure being mobile and comprising walls dimensionally stable.

In another feature, said first enclosure, mounted sliding on rails, comprises at least two movable walls around a axis closing over said outer shell and fastening means closed position of said movable walls, the closing of said walls mobile being carried out before the expansion of the polyurethane foam so that the recovery of said outer envelope by said first speaker is total.

In another feature, the second outer enclosure conformation comprises at least two mobile partitions around an axis closing the cover and securing means in the closed position said movable partitions, closing said movable partitions being carried out before the expansion of the polyurethane foam so that the covering the lid with said second chamber is total.

In another feature, said container is rectangular and the bottom of said outer casing is formed by at least two flaps, said injection of polyurethane foam being followed at least by the closing of a mobile wall of said first enclosure conformation for folding said bottom flap of the envelope external position horizontal.

In another feature, said mold is made of wood, metal or alloy resistant.

In another feature, said first and second enclosures conformation comprise metallic materials or wood.

In another feature, the additional cover is developed following a series of steps including:<ul><li>setting volume by folding a paperboard or sheet material of similar packaging, the volume formed by this sheet cardboard corresponding substantially to the volume of said lid,</li><li>positioning said sheet in a second enclosure external conformation determined Volume wrap lid,</li><li>positioning at least one sealing element, located in the base of said lid, whose shape corresponds to the opening between the inner walls of said container to form a plug returning sealing,</li><li>an injection of a given volume of polyurethane foam high pressure in the interior volume of the lid,</li><li>total and sealing said second enclosure to the Following injection,</li><li>the opening of said second enclosure after a sufficient time for the expansion of the polyurethane foam fills the interior volume of the lid delimited by said element sealing and said cardboard sheet.</li></ul>

In another feature, the container is developed following a series of steps including:<ul><li>the volume formatting said inner shell from a first piece of formable packaging material, the volume formed by the inner envelope corresponding substantially to volume of a head of the forming mold, said mold comprising a base integral with said head,</li><li>the upturned positioning of said inner envelope on the head of the shaping mold,</li><li>insertion of the sealing ring between the base of the mold and the edge walls of said housing,</li><li>the upturned positioning of said outer envelope around the base and the head of said mold, said outer envelope being obtained from a second piece of packaging material formable, said outer bottom has not yet formed,</li><li>the advance of said first chamber to encircle said outer shell,</li><li>an injection of a given volume of polyurethane foam under high pressure into said peripheral volume,</li><li>the total and sealed closing of said first enclosure to the Following injection, said outer bottom of the outer shell being formed during the folding at least one movable wall said first enclosure,</li><li>the opening then withdrawal of said first enclosure after a sufficient time for the expansion of the foam polyurethane fills said peripheral volume</li><li>demoulding of the container.</li></ul>

An object of the invention is to define a device isothermal affordable package having a foam Insulation in high density high pressure injected polyurethane.

To this end, the invention relates to an isothermal packaging device intended for thermosensitive products comprising a container and a removable lid, the container and said lid each comprising a piece of polyurethane foam, characterized in that said container comprises: <ul><li>a shaped inner shell to form the bottom and inner walls of a housing,</li><li>a one-piece layer of polyurethane foam density greater than the density achieved by free expansion, adhering to the bottom and walls of said housing,</li><li>a thermally insulating sealing ring overlapping the edge of the walls of the housing and said foam layer polyurethane,</li><li>an outer casing, having flaps covering at least said layer of polyurethane foam and surrounding said sealing ring, said polyurethane foam layer adhering to the outer shell.</li></ul>

In another feature of the invention, the cover includes:<ul><li>a thermally insulating seal dimensions corresponding to the shape of the opening between the walls domestic housing to constitute a returning stopper sealing,</li><li>a shaped sheet to form the volume of the cover,</li><li>a one-piece layer of polyurethane foam density greater than the density achieved by free expansion, injected into the internal volume formed by said sheet and adhering both said plug and returning to said sheet.</li></ul>

In another feature, said density obtained by expansion free is approximately 31 kg / m³Said polyurethane being integral of density between 38 and 51 kg / m³.

In another feature, said plug and said returning crown sealing have a thickness of between 5 and 20 mm, and are consist of a polyolefin foam.

In another feature, the inner envelope (10), the envelope outer (11) and said sheet (20) of the lid each comprise of cardboard or a packing material with similar properties, to a thickness of between 0.5 and 10 mm.

In another feature, the inner and outer envelopes containing each have a single cut sheet of cardboard or extruded plastic, folded and glued to form a regular volume up horizontal and vertical walls.

In another feature, the bottom of the inner shell forming said housing is rectangular and comprises, from top to bottom, a first flap covering at least the entire bottom, two adjacent flaps audit first flap and a top flap with an insertion tab under said two adjacent flaps.

According to another embodiment, the outer shell of the container is formed integrally from a single rectangular strip divided into a row of four folding portions to constitute in particular the four outer walls of the container, these four folding parts each having upper and lower flaps to close respectively the top and bottom of the container, the height of the outer shell being sufficient for the cover to be inserted in said upper flaps.

In another feature, said foil lid is formed one piece from a rectangular strip secured flaps, said rectangular strip forming the top of the lid, the flaps forming other walls and each having a bend from end above said returning sealing plug, at least one of said flaps having additional intermediate foldable portions to form a tongue gripping the lid.

The invention, with its features and advantages, will become clearly on reading the description made with reference to the drawings attached in which:<ul><li>1 shows a perspective view of an embodiment of embodiment of the isothermal packing device according to the present invention, </li><li>2 shows an exploded view of various elements constitute an isothermal packing device according to the invention,</li><li>3 schematically represents an inner mold formatting and a shaper for the manufacture of device according to the invention,</li><li>4 shows an example of cardboard blank which can be used to form the outer shell of the container,</li><li>5 shows an example of cardboard blank which can be used to form the walls of the lid,</li><li>6 shows a piece of cardboard for example can be used to form the inner casing of the container,</li><li>7 shows schematically the injecting step of polyurethane foam in the peripheral volume of containing</li><li>8A and 8B schematically show the step expansion of the polyurethane foam in the volume Device containing, respectively, in the volume inside the cover,</li><li>9 shows an example of shaping structure used in the invention.</li></ul>

The invention will now be described with reference to Figures 1 and 2.

Isothermal packing device according to the invention consists of a container (1) and a cover (2). As illustrated in Figure 1, the lid (2) is removable by example and may include a gripping tab (21) to facilitate opening of the device. The container (1) and the lid (2) each comprise a one-piece layer of polyurethane foam sandwiched between two walls. In one embodiment of the invention, the polyurethane foam density reaches a value between 38 and 51 kg / m³This value being reached by overpopulation of high-pressure polyurethane foam. The different walls of the lid (2) and the container (1) are for example cardboard-based. The thickness of these walls can vary between 0.5 and 10 mm. other packaging materials with similar properties can be considered in the instead of cardboard, for example paper, a polyolefin such as polyethylene or polypropylene or any other plastic material not foam obtained by extrusion.

As illustrated in Figure 1, the container comprises a casing inner (10) and an outer envelope (11) of cardboard, foam polyurethane being interposed between these two envelopes (10, 11). The inner envelope (10) is shaped to form the bottom and sides interior of a housing (L) for receiving one or more products to be kept at constant temperature. Similarly, the envelope external (11) in particular forms the outer bottom and outer walls of container (1). In the embodiment of Figures 1 and 2, the envelope inner (10) is cuboid and has an opening rectangular on top. A sealing ring properties thermal insulation, formed for example of a polyolefin foam or other synthetic material with similar properties, open borders of the inner casing (10). This sealing ring has a width determined for sealing the peripheral volume (V1) between the envelope inner (10) and the outer casing (11) of the container (1). said volume device (V1) is fully filled with the polyurethane foam. This foam has a closed cell structure and has a coefficient very efficient thermal insulation, approximately 0,021 K / (mK). Density this foam from 38 to 51 kg / m³, Is greater than the density obtained by free expansion which amounts to about 31 kg / m³. In alternative embodiment, the inner casing (10) can form a housing (L) not cuboid. Opening the slot (L) can obviously have a different form, adapted to the type of product to maintain temperature constant.

The lid (2) is formed by a sheet (20) of cardboard or other of formable packaging material and a seal positioned at the base said cover (2), as shown in Figure 2. A one-piece layer of polyurethane foam, the same type as that used for the container (1) occupies the entire internal volume (V2) of the lid (2) formed by said sheet (20) and the seal. This seal, in the same type material that for the sealing ring (12) is a retractable stopper (22) in the housing opening (L). In one embodiment of the invention, returning said plug (22) is obtained during the cutting of said rim sealing (12). The insulating material constituting the sealing ring (12) and returning the plug (22) is for example a foam flexible polyethylene, with a thickness between 5 and 20 mm. this foam polyethylene may be colored in blue or any other color. The adhesive properties of the polyurethane foam make the joints sealing (12, 22) used in the container (1) and the lid (2) adhere polyurethane foam in one piece. In a variant of embodiment, the thickness of the outer shell (11) can be of the order of 2 mm, while the thickness of the inner casing (10) and said sheet the lid (2) is of the order of 1 mm.

In one embodiment of the invention, the lid (2) has a thickness substantially corresponding to the surplus of height (H) the outer shell (11) relative to the level of the sealing ring (12) bordering the opening of the housing (L). The lid (2) can thus be covered by the upper flaps (14) of the outer casing (11) container (1). In alternative embodiments, the outer shell (11) can be devoid of upper flaps (14). The lid (2) can be attached to container (1) by fasteners of a known type. These fasteners are then mounted the side of the outer casing (11) so as to maintain a very high thermal insulation.

The invention will be now described with reference to Figures 3 to 6.

To contain the thrust generated by the polyurethane foam during the expansion phase which amounts to about 1 kg / cm²The walls cardboard or the like surrounding expanding foam must be watertight and stiffened. For this, the manufacture of the container (1) involve first shaping enclosure (6) for holding the envelope external (11) and to contain the thrust of the polyurethane foam, as illustrated schematically in Figure 3. A shaping inner mold (5) is also used to hold the inner casing (10) and the sealing ring (12) and contain the thrust of the foam when expansion. In one embodiment of the invention the mold (5) comprises a head (51) mounted on a base (52). This head (1) has a volume substantially equal to the volume of said housing (L). The sealing ring (12) can be placed on the base (52) and caught by the inner casing (10) positioned on the head (51) of the mold. According to variants, the head of mold corresponds to a parallelepiped or another regular volume.

In the embodiment of Figure 3, said first chamber (6) is positioned against the outer shell (11), movable walls (61, 62) of this chamber (6) closing in a sealed manner on the top and on one side of the container (1) during manufacture. To ensure good sealing during the expansion of the polyurethane foam, the inner envelope (10) and outer (11) can each be formed a single cut sheet in conventional packing material, folded and eventually stuck. Regular volume formed by the inner casing (10) should not have leaks, especially at the folds between the horizontal bottom and vertical walls.

6 shows an exemplary piece of cardboard or material analogous packaging format to form the envelope inner (10). In this embodiment, the bottom of the casing inner (10) is rectangular and comprises, from top to bottom, a first flap (100) covering at least the entire bottom, two flaps (102) adjacent to said first flap (100) and a last flap (103) having a insertion tab (104) under said two flaps (102) adjacent. A Folding of this type of the different flaps (100, 101, 102, 103) of the envelope inner (10) to form the bottom makes it possible to effectively fill the points leakage may be caused in the edges of the bottom, so that sealing is ensured. The folding of the inner envelope (10) comprises and one or more laps at the bottom edges. thus the polyurethane foam can not run away and join the inner mold (5) the release is no problem. As illustrated in Figure 4, the outer shell (11) may be formed integrally from a single rectangular strip divided into a row of four parts collapsible (111, 112, 113, 114) to constitute in particular the four walls exterior of the container (1). Said four folding portions (111, 112, 113, 114) each of the upper flaps (14) and lower (13) to respectively close the top and bottom of the container (1). The outer shell (11) can be closed by gluing a strip of collage (110). It can go the same for the inner envelope (10), via a bonding web (105). Other embodiments analogs are naturally conceivable for said casings (10, 11). A facing can be added inside the inner casing (10) and / or outside of the outer casing (11).

5 shows an example of a sheet (20) of cardboard or analogous to shape the packaging material to form the coating of the lid (2). Said sheet (20) of the lid (2) is formed in one piece from a rectangular strip (200) integral with flaps (201). This rectangular strip (200) form the top of the lid (2) and the flaps form the other walls. In the embodiment of Figure 5, the end flaps has, by folding, to be inserted into the top of the cap returning sealing (22). At least one of said flaps includes portions Additional folding intermediates (202) to form a tongue (21) or a handle of the lid (2).

The invention will be now described with reference to Figures 7, 8A, 8B and 9.

As shown in FIG 7, the injection of the mouse of polyurethane is carried out using a spray gun (4) for injecting a medium or injector known equivalent. The polyalcohol and isocyanate precursors are under pressure in containers (3) adapted to be subsequently mixed and injected so as to form the polyurethane foam. The gas for the expansion is for example air or other gas / gas mixture expansion known to the skilled artisan. The container (1) can be returned to inverted position, as shown in Figures 7 and 8 during the injection of the foam. Polyurethane is liquid when it comes out of the gun (4) injector and remains in this state a period of time, on the order of twenty seconds. It is applied to the bottom of the volume (V1) reversed to complete. Then the exothermic reaction begins and the foam swells with thrust of about 1 kg / cm²So that it completely fills the volume device (V1) of the container (1). The volume of initial injection is naturally calibrated for this filling with a density of foam of the order of 38-51 kg / m³ in the preferred embodiment of the invention.

Injection of a pressurized polyurethane foam between two envelopes (10, 11) of cardboard, plastic or customary packing material requires a good sealing of the envelopes (10, 11) for the foam no glue or the inner mold (5) or the outer wall of conformation (6). As illustrated in Figure 7, the injection conditions in the process of manufacture according to the invention can guarantee such a seal. The outer shell (11) is disposed against one of the outer enclosure conformation (6) and the inner shell (10) wife inside the mold (5) formatting. The top flaps (14) of the outer casing (11) can be folded outwards. Naturally one can consider variants with flaps (14) folded within the enclosure (6) conformation or variations without flaps. One can also consider to use several inner envelopes in alternative embodiments, ensuring the perfect seal of the bottom of the housing (L). The envelope External (11) is shaped to form the exterior bottom walls external and optionally the top of the container (1). A box classic exterior, for example of American envelope or polychrome envelope, may be considered as external envelope (11).

In the embodiment of Figure 7, the container (1) parallelepiped has an outer bottom formed by at least two flaps (13). The injection of polyurethane foam is followed by the closure of a wall movable (61) of the shaping enclosure (6) for folding said flaps (13) bottom of the outer casing (11) in horizontal position. The crown sealing (12) is disposed before injection leading to the expansion of polyurethane foam, between the mold (5) and the edge walls of said housing (L) to form a closure element of the volume (V1) device between the inner casing (10) and the outer shell the container (1). In one embodiment of the invention, the mold Interior (5) is made of wood, of metal or alloy and the outer enclosure (6) conformation includes metallic material or wood or a combination of these materials. The outer enclosure (6) conformation, adapted to the volume of the outer casing (11) contains the foam and prevents leakage of the foam. Due to its elasticity, the foam is thus sandwiched and fills the entire peripheral volume (V1) to form a single piece.

The lid manufacturing process (2), as for the embodiment of the container (1), involves a shaping enclosure (7) adapting to the shape of the lid (2). As illustrated in Figure 8B, the enclosure (7) shaping the cover (2) can be wrapped completely the cover (2). Returning the seal forming the plug (22) of the lid (2) is wedged between the walls of the enclosure (7) and the sheet (20) folded from cover (2). This seal is affixed after injection of the foam in the internal volume (V2) of the cover formed by the sheet (20). At least one moving partition the shaping enclosure (7) is then closed before the beginning of the expansion of the foam so that said chamber (7) contains substantially uniformly the pressure of the foam. Use a single sheet (20) of cardboard or the like is inexpensive and allows prevent leaks in the corners. In alternative embodiments the cover (2) can also be formed by an assembly of several sheets overlapping at least partially and not generating such leaks.

This simple manufacturing process can be adapted to different housing forms and sizes for the outer shell (11). he is a straightforward matter of simply changing the layout inside the mold. Moreover it is easy to choose different thicknesses of cardboard or other usual packaging material, a thin millimeter can be agreed with that process.

In one embodiment of the invention, the inner mold (5) for the container (1) is fixed while the enclosure (6) of the conformation container (1) is movable, as shown in Figure 9. This first (6) shaping chamber, for example slidably mounted on rails via pads comprises at least two movable walls (61, 62) about an axis and being closed on the outer casing (11) of the container (1). Mobile walls (61, 62) may for example be built around elements (64) of hinge. This chamber (6) comprises a structure can be formed by metal profiles and panels with a sufficient thickness to be dimensionally stable, for example of the order of 2 mm in the case of panels made of aluminum. The chamber (6) comprises fastening means (63) in the closed position of said movable walls (61, 62). Closing of the movable walls (61, 62) can be performed before the expansion of the polyurethane foam so that the cover said outer shell (11) with the enclosure (6) is total. In variants embodiment, this speaker can be mobile in rotation, for example on rollers or feed vertically on the mold (5) and the container (1) by an elevator system. The second shaping enclosure (7) used for the cover comprises analogously at least two partitions mobile (not shown) about an axis and a member closing on the cover (2). It may be fixed and includes fixing means in the closed position of the movable walls, so that the recovery of lid (2) by said second enclosure (7) is total.

During injection, the possible upper flaps (14) of the envelope external (11) are folded on the outside along the outer walls (111, 112, 113, 114) side. Similarly, the gripping tab (21) is folded against the outer walls of the lid when closing the corresponding shaping enclosure (7). The bottom flaps (13) the outer shell (11) are four, the cutting of these flaps (13) being such that the expanding foam can come to adhere and stick each of these flaps (13). Thus, in the method according to the invention, after of the expansion phase schematically illustrated in Figures 8A and 8B gets finished and it just remains to remove the cover (2) and the container (1) to assemble them.

It will be appreciated, in one embodiment of the invention, the container (1) can be obtained according to the following succession of steps:<ul><li>erecting of the inner shell (10), the volume formed by this inner casing (10) corresponding to the volume of the head (51) of the mold,</li><li>reversed positioning of said inner envelope (10) on the head (51) of the mold,</li><li>insertion of the sealing ring (12) between the base (52) mold (5) and the edge of the inner walls,</li><li>reversed positioning of said outer envelope (11) around the base (52) and the head (51) mold, the outer bottom of the container (1) is not yet formed,</li><li>Advanced said first enclosure (6) moving to encircle said outer shell (11),</li><li>injecting the high pressure polyurethane foam in said peripheral volume (V1) of the container (1),</li><li>total and sealingly closing said first enclosure (6), the bottom outside of the container (1) being formed when folding at least one movable wall (61) of said first enclosure (6),</li><li>the opening then withdrawal of said first enclosure (6) after a sufficient time for the expansion of the foam polyurethane fills said peripheral volume (V1),</li><li>demolding the container (1).</li></ul>

In one embodiment of the invention, also include that the cover (2) can be obtained according to the succession of steps following:<ul><li>erecting by folding a cardboard or like sheet (20), the internal volume (V2) formed by said sheet (20) corresponding substantially the volume of said lid (2),</li><li>positioning said sheet (20) into a second enclosure (7) Outdoor conformation determined Volume wrapping said cover (2),</li><li>positioning at least one sealing element, located in the base of said lid (2) to form a re-entrant plug sealing (22),</li><li>injecting the high pressure polyurethane foam in the inner volume (V2) of the lid (2),</li><li>total and sealing said second enclosure (7),</li><li>opening of said second enclosure (7) after a time sufficient for the expansion of the polyurethane foam fills said inner volume (V2).</li></ul>

One advantage of the invention lies in the simplicity of manufacturing isothermal packaging device. The manufacturing process can be easily industrialized, the shape of the housing (L) which can be very easily modified. In addition, the use of envelopes of cardboard or other conventional packaging material of small thickness and therefore low weight economically advantageous.

Another advantage of the invention lies in the fact that with a integral polyurethane foam of high density, of for example, from 38 to 51 kg / m³The insulation performance is greatly increased. The thermally insulating piece completely envelope the housing (L) and there is no thermal bridge despite the use of a material as light as cardboard. The invention therefore provides an optimized solution for packaging temperature-sensitive products. Reports by packaging known, the manufacturing process provides a packaging device coefficient of high performance thermal insulation.

An additional advantage of the invention is that the process, which can be easily industrialized, is particularly suited to meet to mass production requirements.

It should be obvious to those skilled in the art that the present invention allows embodiments under many other specific forms without departing from the scope of the invention as claimed. Therefore, the present methods of realization should be considered illustrative, but can be modified in the field defined by the scope of the appended claims, and the invention should not be limited to the details given above.