EP2218847A2

EP2218847A2 - Panel for concrete castings

Info

Publication number: EP2218847A2
Application number: EP10153206A
Authority: EP
Inventors: Luca Doimi
Original assignee: Amaro Timber Ltd
Current assignee: Amaro Timber Ltd
Priority date: 2009-02-11
Filing date: 2010-02-10
Publication date: 2010-08-18
Also published as: ITGE20090007A1; IT1394199B1

Abstract

A panel for concrete castings is composed of at least a supporting layer made of wood which is at least partly externally coated with one or more sealing layers and wherein the supporting layer is in turn composed of at least two layers made of wood strips or sheets which are glued together and whose wood fibres for each layer have the same and parallel orientation said strips or sheets being oriented with reference to the peripheral edges of the panel such that at the end edges and at the longitudinal edges of said supporting layer a portion of the wood fibres are parallel and a portion of the wood fibres are transverse to said side. At the longitudinal sides the wood fibres ending perpendicular to or transverse to said sides are not covered from the environment for an amount not greater than 40% of the overall surface of said longitudinal edges of the supporting layer, while at least a part of one end side of the panel that is at least a side transverse to said longitudinal sides of the panel has or is composed of a sealing edge which is made of plastic material, and it overlies said end side of the supporting layer and/or of the sealing/protective layer or layers along at least said part of said end side and it is fastened to said end side of the panel by chemical/physical bonding and it seals it from the environment.

Description

The invention relates to a panel for making formwork retaining walls for concrete castings, particularly for retaining formworks for making concrete slabs or the like, which panel is composed of at least a supporting layer made of wood which is at least partly externally coated with one or more moisture and/or water sealing and/or protective layers,
the supporting layer in turn being composed of at least two layers made of wood sheets or strips
said strips or sheets being made such that the direction of the wood fibres of said sheets or strips has a predetermined orientation with respect to a predetermined direction or axis of said strips or sheets;
said strips or sheets are glued together such to form said at least two layers,
said strips or sheets with reference to the peripheral edges of the panel are oriented such that at the end edges and at the longitudinal edges of said supporting layer a portion of the wood fibres are parallel and a portion of the wood fibres are transverse to said side.
Retaining formworks for concrete castings are known and are made of a plurality of panels which form together the walls retaining the concrete with the desired shapes and dimensions and which panels are mounted such to form said retaining walls in a load-bearing structure.
As mentioned above each panel is composed of at least a wood supporting layer having such length, width and thickness dimensions to withstand the concrete stress without being deformed, while ensuring easy handling thereof by the operators that transport and mount the formwork. Such dimensions, especially as regards the thickness, are substantially fixed. Therefore currently there is the drawback of increasing the load resistance of panels without changing the thickness and particularly without increasing their thickness.
Panels of said type having at least a layer with a strip structure are known and strips are mainly made of resinous wood. While panels made of resinous wood strips guarantee the weight to be reduced with respect to panels made mainly of hardwood and therefore of a more solid wood, these panels do not allow sufficient mechanical strength characteristics to be obtained according to safety standards in the building industry for reduced thickness and weight.
In order to give a greater mechanical strength to the panel it is known to make the wood part, i.e. the supporting layer, in the form of two or more layers, wherein strips of one layer and strips of the adjacent layer are in crossing relationship as regards the direction of the wood fibres.
It is known to protect the wood supporting layer along at least some side edges and/or portions of some side edges as well as also along at least a part of at least one of the faces with a coating layer made of impermeable material such as resins, films or layers made of plastic materials or the like.
Particularly when making slab formworks walls, panels have to show a sufficient bending strength under the weight of the concrete. In wood strips, their resistance is higher in the longitudinal direction of wood fibres than in the transverse direction. Moreover, the cost of the panel and the weight have to be reduced, therefore unnecessary processing steps should be limited. Since the absorption of fluids and particularly of water and moisture within the wood through surfaces oriented parallel to the direction of the orientation of fibres is considerably lower than through the surfaces oriented transverse to fibres, exploiting the fact that shapes of the panels provide rectangular shapes, these characteritics have been used in some known panels to make panels with a supporting layer having a strip structure wherein strips are made with their longitudinal axes oriented in the direction of the wood fibres, while transverse end edges of strips extend transverse to the orientation of wood fibres. In this case possible sealing and protective layers are provided on the two faces of the panel, i.e. of the supporting layer and along transverse edges thereof, strips being oriented with their longitudinal axis parallel to the longitudinal axis of the panel and therefore fibres oriented parallel to the longitudinal axis of the panel. Therefore the supporting layer is composed of a plurality of adjacent strips arranged at least on one layer, i.e. coplanar one to the other and oriented with longitudinal axes parallel to wood fibres and parallel to the longitudinal direction of the panel, the adjacent strips being arranged side by side and being joined by chemical/physical bonding, that is by gluing them at the mutually contacting longitudinal edges.
However, even with this panel, the load mechanical strength in the direction transverse to the longitudinal axis of the panel is not enough with reference to what required by the safety standards of the sector, whereby the supporting layer has to be made of several layers of strips, therefore a solution to drawbacks in common to other known panels is not obtained.
Panels having a sealing edge throughout the extension of the perimetral edges of the panel are also known. In this case, the panel is completely sealed allowing fibres transverse to the the longitudinal edges of the panel to be provided without having a moisture infiltration. At the same time the peripheral edges of the panel would be completely protected, i.e. for the overall length thereof and especially along corners against mechanical damages because of the sealing materials. However, since in the building industry, the outer sealing layers can be damaged, for example holes can be made therein by nails, even with these panels moisture infiltration can occur. However in such case, the complete sealing effect, especially along the perimetral edges is a serious drawback preventing moisture from effectively transpiring to the environment and therefore the natural drying process does not occur. Therefore moisture is trapped within the panel causing it to be progressively damaged considerably decreasing the panel life.
The invention aims at making a panel of the type described hereinbefore which, by simple and inexpensive arrangements, can exhibit characteristics of the resistance to stress on panel which, with the panel having the same thickness, are better than those of the existing panels, while effectively obviating drawbacks of existing panels and that is affording effective protection of the panel against both mechanical damages and damages to the seal against water or moisture infiltrations, without increasing costs or without requiring too complex structures and without increasing manufacturing steps mainly concerning the supporting layer being sealed against moisture infiltrations.
The invention achieves the above aims by providing a panel of the type described hereinbefore and that is a panel for making formwork retaining walls for concrete castings, particularly for retaining formworks for making concrete slabs or the like, which panel has four perimetral edges oriented in pairs parallel one another the edges of a pair being called end sides or edges, oriented transverse to the edges of the other pair which are called longitudinal sides or edges and which panel is composed of at least a wood supporting layer at least partly externally coated with one or more sealing and/or protective layers against moisture and/or water,
the supporting layer in turn being composed of at least two layers made of wood strips or sheets
said strips or sheets being made such that the direction of the wood fibres composing said strips or sheets has a predetermined orientation with respect to a predetermined axis or direction of said strips or sheets;
said strips or sheets are glued together such to form said at least two layers,
said strips or sheets are oriented with reference to the peripheral edges of the panel such that at the end edges and at the longitudinal edges of said supporting layer a portion of wood fibres is parallel to and a portion of wood fibres is transverse to said side and
which panel is characterized in that at the longitudinal sides the wood fibres ending at said sides and oriented perpendicular to or transverse to said sides are exposed to the environment for not more than 40% of the overall surface of said longitudinal edges of the supporting layer;
while at least a part of an end side of the panel that is of at least a side transverse to said longitudinal sides of the panel has or is composed of a sealing edge made of plastic material, and it overlies said end side of the supporting layer and/or of the sealing/protective layer or layers along at least said part of said end side and it is fastened to said end side of the panel by chemical/physical bonding and sealing it from the environment.
Preferably wood fibres of the supporting layer are oriented perpendicular to or transverse to said longitudinal sides of the panel or of the supporting layer and are exposed for a part not greater than 30% of the overall surface of the edges along said longitudinal sides.
Advantageously at least the wood layers forming the supporting layer and whose fibres run transverse to and particularly perpendicular to the longitudinal edges of the panel are made of hardwood.
A variant provides the whole supporting panel to be made of hardwood.
The term hardwood means woods such as Maple, Alder, Birch, Hickory, Hornbeam or white Beech, Chestnut, Beech, Ash, Walnut, Sycamore, Poplar, Cherry, Willow, Oak, Basswood, Elm and also tropical woods such as Kauri pine, Iroko, Red pine, Palisander, Brazilian Rosewood, Ebony, African Mahogany, Mansonia, Balsa, Nyatoh, Afrormosia, Meranti, Teak, Limba, Ayous.
As regards the protection and sealing of the panel, that is of the supporting layer against moisture penetration, said supporting layer is advantageously coated on one or both faces with a layer made of a protective material and particularly a sealing material, a groove or channel being provided, at least along a portion of the panel sides along which the sealing edge is provided, which channel extends directly under the side of the protective layer or layers adherent to the supporting layer of the panel and which channel is delimited on at least one side by said face of the corresponding protective layer, while the sealing edge extends also inside said channel adhering also to the bottom and to the side walls of the channel by chemical/physical bonding.
An embodiment provides the channel to run throughout the overall thickness of the supporting layer and it is delimited on the two sides by the two opposite protective layers the end side of the supporting layer being recessed with respect to the end sides of the two protective layers.
A further variant embodiment provides the channel to have a thickness corresponding to a part of the thickness of the supporting layer and to be laterally delimited, on one side by the corresponding protective layer and on the other side by the surface parallel to the protective layer of a stepped recess which is made along the corner area of the face of the supporting layer which directly underlies the protective layer, while the bottom of said channel is formed of the step of said stepped recess provided in the thickness of the supporting layer.
Essentially, the protective layer externally covers the stepped recess, leaving a perimetral band corresponding to the depth of the milling or of the stepped recess exposed or accessible from the channel.
The sealing edge has a filling extension for said channel and it adheres by chemical/physical bonding to the channel walls formed of the material of the supporting layer and of the protective layer.
According to an improvement when the supporting layer is coated with a protective layer on each one of the two opposite faces, then a channel of the above type is provided having a partial thickness with respect to the overall thickness of the supporting layer directly under each one of the two protective layers and along the sides provided with the sealing edge, in this case the sealing edge being provided with filling extensions for each one of said two channels which extensions adhere by chemical/physical bonding to the materials of the walls delimiting the channels.
According to a further improvement the protective layer or layers are made of a plastic material and the sealing edge adheres in a watertight manner against the end side of said protective layer or layers and to the side of said protective layer or layers constituiting the side wall of the corresponding channel.
By such arrangement, a band for bonding the plastic material of the sealing edge to the plastic material of the protective layer or layers is created in a simple way which extends beyond the simple thickness of said layers. This guarantees the path necessary for moisture or water to penetrate from the outside into the supporting layer made of wood or the like to be longer and to run from the outer side of the joint between the sealing edge and the protective layer to the bottom of the channel for a length corresponding to the depth of said channel.
Again according to a further advantageous improvement the sealing edge is made by injection molding on the corresponding side or sides of the assembly composed of the supporting layer or of the protective and/or coating layer or layers, particularly made of PU, therefore the filling extensions for the channel or channels are absolutely unproblematic.
According to a further characteristic, the panel has a supporting layer interposed between two protective layers which adhere to one face of the supporting layer respectively, the supporting layer being provided with a tongue which is in a central position with reference to the overall thickness of said supporting layer and having a thickness smaller than the overall thickness of the supporting layer, which tongue projects out beyond the corresponding perimetral side of the protective layer or layers and which tongue is embedded into the sealing edge the latter covering it on the sides parallel to the panel faces and possibly also on the end side, complementing the panel thickness till to the overall thickness of the protective layers and of the supporting layer.
According to an improvement when the panel has a groove or channel directly under each one of the protective layers, which grooves or channels are composed of perimetral stepped recesses of the supporting layer, said tongue is composed of a peripheral extension of the part of the supporting layer interposed between the two stepped recesses, whereby surfaces of said tongue which are parallel to the panel faces extend flush with the corresponding surfaces of the stepped recesses forming said grooves or channels.
According to an improvement, there are provided means for the mechanical connection between the sealing edge and the material of the protective layer, which means are composed of complementary interlocking means for the material of the sealing edge and the material of the supporting layer.
A further adventageous characteristic provides said tongues and particularly the surfaces parallel to the panel faces to be provided with holes or apertures which are blind or extend throughout the thickness of said tongue, while the sealing edge penetrates therein or therethrough with bridges or ridges of material which connect the two layers of material of said edge which cover the two faces of said tongues parallel to the panel faces.
By such arrangement a chemical/physical and also mechanical connection between the sealing edge and the material of the protective layer occurs. Transverse bridges made of the material of the sealing edge filling the through holes are a kind of mechanical retaining nails promoting the mechanical connection between the supporting layer and the sealing edge. This is synergistically reflected on the connection between the sealing edge and the protective layers forming the watertight joint. The mechanical connection between the sealing edge and the supporting layer prevents any movements of this edge with respect to the edge and therefore tears or cracks in the joint between the sealing edge and the material of the protective layers.
Again according to a further improvement, the stepped recess forming the channel or channels allowing the sealing edge to penetrate under the protective layer or layers has a bottom or riser surface which is concave in shape. This optimizes the absorption of thrusts when injecting the material of the sealing edge preventing high injection pressures from lifting the protective layer or layers.
The sealing edge can be provided along all the sides or along any side of the panel.
According to an embodiment the panel provides the sealing edges to be provided along the end sides of the panel oriented transverse to the direction of orientation of wood fibres of the supporting layer, and particularly of strips, for at least a part or the overall thickness of the panel and/or for at least a part or the overall surface of the end layers of the panel.
When, as in said case, the wood layer edge provided with the sealing edge is oriented transverse to wood fibres for at least a part of its thickness, the surface along said edge is rough or anyway porous and uneven, therefore a greater mutual penetration between said wood surface and the plastic material of the sealing edge is achieved therefore improving not only the mechanical connection, but also the sealing effect, generating a barrier against moisture having a certain penetration depth into the wood layer.
According to a further characteristic the wood supporting layer has recessed corner areas which are filled with inserts made of plastic material having such a shape that the perimetral profile of the panel is complemented to obtain an ideal shape that might be envisaged without said recessed areas.
It is possible to provide the channel or channels under the protective layer or layers, and the tongue of the protective layer, if any, with or without through holes even along said chamfered corner areas and along the initial recessed portion of the longitudinal sides of the panel which are directly adjacent to said corner areas.
As regards protective layers these can be composed of thin films of resins, varnishes, or the like or of layers of plastic material for example of the type composed of polypropylene filled with vegetable flours and for example known under the name of Wood-Stock®. Said protective layers can be joined in a watertight manner by chemical/physical bonding to the sealing edges thus generating a plastic or resin skin sealing the inner wood layer and which is tigthly closed on all sides by said chemical/physical bonding for example welding, gluing or the like.
In the case of the above mentioned examples, the sealing edge is applied on the panel already provided with the wood layer and with a coating or protective layer on at least one side, such that during the molding process the material of the sealing edge overlies the end surface of the wood panel edge and of the corresponding thickness of the edge of the coating and/or protective layer.
Again according to a further characteristic, between the protective layer or layers and the supporting layer a fibre layer can be provided which fibre layer can also extends into the corresponding groove or channel, whereby the material of the sealing edge adheres to the protective layer indirectly with said fibre layer interposed between the material of the sealing edge and the protective layer.
In order to easily dismantle the panels, particularly when are used for supporting frames for making retaining forms, i.e. for concrete formworks, the sealing edge can have reinforced inserts for the connection of tools for lifting or dismantling the panels, such as levers or crowbars or the like.
For making said reinforced inserts for the connection of tools, inserts of stiff material possibly provided with slots and indentations for engaging said lifting tools are embedded into the sealing edge.
According to a further characteristic, said connection inserts can be composed of thicker areas of the sealing edge with reference to its thickness in a direction parallel to the panel faces.
Considering that water or moisture absorption from the surfaces of a strip that are oriented parallel to wood fibres are negligible, as well as the absorption through the wood sheet or sheets or veneers of hardwood even when they have wood fibres transverse to or perpendicular to said surfces, then in some cases, the sealing against moisure and/or water penetration can be necessary only along said two edges of the panel that have or are composed of the end sides of strips, while the longitudinal sides or the longer sides of the panel can be exposed.
Considering dimensions of panels currently used for making formworks and having dimensions with a typical width of 500mm and with length of 1000mm, 1500 mm, 2000mm, 2500mm, the panel with the supporting layer according to the present invention allows hardwood veneer shapes available on the market to be better used.
The above panel therefore has a protective and/or sealing coating on the two opposite faces, and a coating of plastic material along the shortest peripheral sides and i.e. sides oriented transverse to the longitudinal extension of panels. Along the longitudinal edges, the moisture absorption is reduced by the combination of the use of hardwood for the wood layers of the supporting panel whose fibres end transverse to the longitudinal edges and by the factthat by reducing the surface of said edge having said fibre orientation to a maximum amount of 40% of the overall surface of the longitudinal edges, the moisture absorption is reduced and it is such that the moisture-induced deterioration of the panel material along the longitudinal sides of the panel is such to guarantee an average life of the panel greater than that resulting from the handling for assembling and dismantling it and from mechanical damages due to the panel being handled during use. In the building industry materials are subjected to treatments that generally are not much careful.
Therefore the present invention is based on the optimization of sealing and transpiration properties of the panel as regards moisture such that said opposing properties are optimized in order to guarantee to the panel an average life due to moisture effects which is surely greater than that of the panel if considering use conditions. Typically a panel according to what described above has an average life of about five years if moisture effects are only considered, while the average life of the panel when used and so when subjected also to handling effects and to other stresses generally is about three years.
According to an improvement the panel can have a protective coating also along said longitudinal sides. Suh coating acts for protecting said longitudinal sides mainly against mechanical damages, since with reference to the moisture absorption, it is very reduced due to the above mentioned choice made about the orientation of the fibres of the material constituting the supporting layer.
Particularly, in order to allow moisture possibly penetrated into wood layers to transpire and so to achieve the results of the invention while reducing the moisture absorption through said longitudinal sides, said longitudinal sides being the only parts of the wood material not covered by protective or sealing layers, the invention provides the panel along said longitudinal sides to have a stepped recess along each corner between the longitudinal side and one of the two faces of the panel, which stepped recess is filled such to complement the cross-section of the panel at said longitudinal sides with a filling of plastic material extending by one side flush with the corresponding longitudinal side of the panel and by the other side flush with the corresponding face of the panel, thus forming a longitudinal protective small edge along each longitudinal corner of the panel.
Essentialy the invention provides longitudinal corners of the panel to be composed of a protective small edge made of plastic material for a certain depth in the direction of the thickness and for a certain depth in the direction of the width of the panel.
Particularly said stepped recess is filled with plastic material by injection molding, that is the small edge of plastic material at longitudinal corners of the panel, is made by injection molding.
Preferably when the panel has an outer sealing and/or protective layer on one or both the faces, the corresponding stepped recess extends, in the direction of the panel thickness, also for the thickness of the corresponding sealing and/or protective layer, whereby the small protective edge made of plastic material forming the corresponding corner of the panel covers also the end edge of the sealing and/or protective layer.
Again according to a further characteristic, the overall dimension of the protective small edges at the two longitudinal corners of each longitudinal side of the panel in the direction of the thickness of the panel is smaller than the overall thickness of the panel.
In order to have a better bonding of protective small edges, the stepped recess at the side oriented in the direction of the panel thickness has a groove or channel running under the corresponding sealing and/or protective layer, said channel on one side being delimited by the face of the sealing and/or protective layer faced towards the supporting layer of the panel, whereby the protective small edge extends also for a predetermined amount into said channel directly under a longitudinal peripheral band of the sealing and/or protective layer of the corresponding panel face.
According to a variant, protective small edges are provided along the longitudinal sides at least for a part of the areas of the longitudinal edges where wood fibres of the supporting layer are oriented transverse to or perpendicular to said longitudinal edge.
Areas absorbing most moisture which are those wherein fibres of wood forming the supporting layer of the panel are oriented transverse to or perpendicular to the corresponding longitudinal edge are coated and sealed, at least for a portion, while areas of said longitudinal edges of the supporting layer where wood fibres are oriented parallel to said edges are exposed, thus allowing the moisture possibly penetrated into the panel for example through holes made by nails or other apertures or cracks of the protecting layers to transpire and consequently to be discharged. At the same time the provision of the protective small edges along the corners makes panel corners more resistant to mechanical damages and so it protects the outer shape and the integrity of the panel against mechanical actions in locations generally more sensitive to such actions.
In this case, at said areas, of the longitudinal edges, channels or recesses in the wood are made wherein the sealing small edge is housed.
Particularly such sealing small edge of said areas of the longitudinal edges is made similarly to and/or possibly also contemporaneously to said sealing and protective small edges at the corners of the longitudinal edges of the panel and particularly by injection overmolding or similar processes.
In combination with the above, it is possible to provide the supporting layer to have a special structure able to guarantee the greatest efficacy both as regards the mechanical strength and as regards the optimization between impermeability and transpiration along the longitudinal edges.
According to such improvement, the supporting layer is made of wood layers wherein each layer has wood fibres oriented according to only one direction i.e. they are all parallel each other, layers being joined together with a crossed orientation as regards the direction of the wood fibres of said layers, whereby said supporting layer has layers with wood fibres oriented alternately parallel to and perpendicular to the longitudinal edges of the panel and the outermost layers of the protective layer, i.e. those forming the faces of the protective layer to which a sealing and protective layer is applied being provided with wood fibres oriented perpendicular to the longitudinal edges of the panel, the thickness of the protective small edges along the two longitudinal corners of the longitudinal edges of the panel being such that they overlie at least partly or completely the thickness of said outermost wood layers.
Moreover as already mentioned above a sealing small edge can be provided also for completely or partly cover some or all the intermediate wood layers between said outermost layers which have the wood fibres oriented perpendicular to said longitudinal edges of the panel, while layers having wood fibres parallel to said longitudinal edges remain exposed.
The intermediate layers having wood fibres perpendicular to the longitudinal edges end in a recessed position along said edges with respect to the layers having fibres parallel to said longitudinal edges and the sealing small edges abut against the recessed longitudinal edges of said layers and complement them by being extended flush with the longitudinal edges of the layers having fibres parallel to the longitudinal edges of the panel.
In the embodiment wherein the supporting layer is composed of at least three material layers, of which two outermost layers are composed each one of a second material layer made of at least a wood sheet, while an intermediate layer is arranged therebetween which is composed for example of a first material layer made of a plurality of strips, said three layers being joined together in a superposed position one on the other by gluing, the stepped recesses along the corners of the longitudinal sides extend, in the direction of the panel thickness, for a depth at least equal to the thickness of said outermost layers composed of one or more wood sheets.
By this arrangement, the protective small edges of the longitudinal sides of the panel, allow moisture possibly penetrated into the panel to transpire, since they leave a portion of the thickness of the longitudinal sides exposed wherein the wood of the supporting layer is not covered and so directly exposed to the environment, but they also seal the longitudinal sides of the wood sheets of the two outermost layers, whose fibres extend transverse to the longitudinal direction and therefore are favorably exposed to moisture absorption. Therefore contemporaneously to the effective protection and to the transpiration ability of the panel, as a third advantage the longitudinal sides of the layers having fibres oriented transverse to said sides are also sealed.
It has to be noted that it is possible to provide the sealing edges to be applied on the end sides and at corner areas and the protective small edges along the corners of the longitudinal sides of the panel by contemporaneously injection molding the same plastic material or different plastic materials along said longitudinal sides and end sides and along the corner areas connecting said sides one to the other such that a protective and/or sealing frame as one piece is made extending all along the perimeter of the supporting layer. Contemporaneously to the application of the small edges by injection molding it is possible to apply also the protective inserts by embedding them by overmolding in a single injection molding step.
Since the longitudinal sides of the panel are protected with a longitudinal small edge made of plastic material only at longitudinal corner areas and the protection occurs mainly only against mechanical damages, it is possible for the longitudinal edges of the panel to swell at least in the central area not covered with the plastic material of the protective small edges due to a moisture absorption even though reduced through the wood of said exposed central part of the longitudinal edge. Such swelling substantially occurs as an outwardly convex bulge . Therefore when two panels are put side by side it is possible that due to the swelling of at least one of the facing longitudinal contacting edges of the two adjacent panels lower watertight areas and/or even grooves can be generated causing projecting webs to be made on the concrete article once panels are removed. The effect is greater when panels are used for horizontal retaining walls.
Therefore the invention provides the longitudinal edges of the panel, i.e. the edges along which the protective small edges made of plastic material are provided only along the areas of the two longitudinal corners where a wood central band of the supporting layer is left exposed therebetween, to have a recessed configuration and particularly a concave configuration.
In this case, the concavity can be extended for a part of the panel thickness. Particularly for a part or the entire thickness of the supporting layer of the panel along the longitudinal edges.
The maximum depth of the concavity along the longitudinal edges of the panel is adapted to the possible swelling and the amount can be defined by empiric tests.
According to an improvement, the depth of the concavity is provided of such an amount that the slot made remains under the ports not allowing the material to be retained to spontaneously infiltrates due to capillarity effects with reference to the viscosity of the material to be retained.
The invention provides several specific embodiments that are different one another as regards the structure of the supporting layer.
According to one embodiment, the invention provides a panel for making formwork retaining walls for concrete castings, particularly for retaining formworks for making concrete slabs or the like, which panel is composed of at least a supporting layer made of wood which is at least partly externally coated with one or more moisture and/or water sealing and/or protective layers, the supporting layer in turn being composed of at least two layers, at least a first layer thereof being composed of a plurality of strips having a predetermined length, wood fibers of such strips being all oriented in the longitudinal direction of the strips and which strips are glued together in order to form said first layer wherein their longitudinal axes are oriented in a substantially parallel direction one with the other, the end sides of the supporting layer and of the panel being oriented in a direction transverse to the wood fiber orientation of strips and/or to the longitudinal extension of strips, while the side longitudinal edges of the supporting layer and then of the panel are oriented in a direction parallel to the wood fiber orientation of strips and/or to the longitudinal extension of strips, wherein at least the second layer of wood forming the supporting layer is composed of a wood sheet, whose fibers are oriented in a direction transverse to the longitudinal extension of the panels or strips and/or transverse to the wood fiber orientation of strips the two layers being coupled together by gluing process and at least a portion of one end side of the panel oriented in a direction transverse to the direction of wood fibers of strips forming the first layer being made of a sealing edge made of plastic, and overlying the end side of the supporting layer and/or of the sealing and/or protective layer or layers along at least said portion of said end side and it is fastened to said end side of the panel by chemical/physical bonding and sealing it from the environment.
A first advantageous variant embodiment provides the supporting layer to be composed of three material layers of which: two first material layers composed each one of a plurality of strips and forming the outermost material layers and a second material layer is interposed between said two first material layers. Said three material layers are joined together in a superposed position one on the other by gluing or by other chemical/physical bonding means.
A further variant embodiment likewise provides the supporting layer to be composed of three material layers but in this case two material layers are composed each one of a second material layer made of at least a wood sheet, while an intermediate layer is interposed therebetween which is composed of a first material layer made of a plurality of strips, said three layers being joined together in a superposed position one on the other by gluing or other chemical/physical bonding means.
Advantageously the wood sheet forming the second material layer or layers of the supporting layer is made of hardwood.
According to a further characteristics said sheet forming the second material layer or layers of the supporting layer has the wood fibres oriented substantially parallel one another along the overall surface extension of the sheet and parallel to or substantially parallel to at least one of the peripheral edges and/or transverse to a further peripheral edge respectively.
According to a preferred characteristic, the wood sheet forming the second material layer or layers of the supporting layer has a thickness lower than the one of the first material layer of the supporting layer, i.e. it is lower than the thickness of strips forming said first material layer.
A specific embodiment provides said wood sheet to have thicknesses falling within the range from 1 to 8mm, preferably from 1 to 4 mm.
The second material layer or layers can be composed of at least two wood sheets glued together in such a relative position that wood fibers are crossed one with respect to the other.
In this case, the orientation of the wood fibres for one of said sheet is transverse to the one of the wood fibres in the layer composed of the strips, while as regards the other sheet the wood fibres are oriented substantially parallel to the wood fibres of the strips.
Wood sheets can be be made according to different techniques.
According to a preferred embodiment wood sheets are the so called veneers, that is they are obtained from a trunk by the veneer cutting process.
Due to the above characteristics the invention allows considerable advantages to be achieved:

The hardwood thin layer or layers, that is said wood sheets or said veneers, guarantee a resistance to transverse bending, since at least one of said layers has the wood fibres parallel one to the other and oriented in the transverse direction of the panel. The thickness of the layers composed of sheets, that is veneer, being equal, the resistance to transverse bending is particularly high and anyway greater than the one that can be obtained with strip wood layers even with structures having two or three strip wood layers wherein strips of the different layers are oriented transverse one to the other with reference to the direction of the wood fibres. The above is applied both with thickness being equal and also with thicknesses of the supporting layer according to the present invention lower than those of the supporting layers of known panels.

Moreover, considering fixed overall thicknesses, as regards the arrangements made of strip wood, the surface of the transverse end fibers is such to cause water to be highly absorbed, whereas by using a veneer layer or several layers according to the present invention, both the water absorption along the longitudinal edges is reduced, and at the same time the resistance to transverse bending is increased the thickness being equal to the corresponding layers in panels completely made of strips.
In addition to that the use of hardwood sheets, that is of hardwood layers, led to unexpected results as regards the torsional strength of the panel. Such strength is greater that the one that can be obtained by using only layers with a strip structure both with the thickness being equal and with thicknesses of the supporting layer according to the present invention lower than those of supporting layers of known panels.
Moreover as regards the mechanical properties the supporting layer provided in the panel according to the present invention guarantees a dimensional stability greater than the panels with strip supporting layers and than panels with supporting layers made of plywood.
With reference to the absorption, due to the fact that layers made of one or more wood sheets such as veneers or the like are mode of hardwood, the moisture absorption through such layers at the edges of said layers oriented transverse to the direction of orientation of fibres is very low and negligible. The fact that wood sheets are thin causes the absorption to be further reduced. That allows the edges of said sheets to be oriented transverse to the direction of orientation of the fibres and to be coincident with the longitudinal edges of panels which are sealed only along the transverse end edges and not along the longitudinal edges of the panel, without suffering from a greater absorption with respect to the portion of said longitudinal edges of the panel made of strips having the wood fibres oriented parallel to said longitudinal edges of the panel.
In this case it is advantegous and preferable for the fibres of the strips to be oriented at 100% in a direction parallel to the longitudinal axis of the strips and therefore to the longitudinal axis and to the longitudinal edges or longest sides of the panel.
An alternative embodiment, provides the supporting layer to be composed by superposed wood sheets such as a plywood or the like, each sheet being composed of wood whose fibres are oriented parallel one to the other and the wood sheets being joined and particularly glued one on the other one with such an arrangement that the wood fibres of one sheet are oriented transverse to or perpendicular to the wood fibres of adjacent sheets, while the longitudinal edges of the panel are composed of the edges of the supporting layer which have the smallest portion of the thickness of said edge where wood fibres are transverse to or perpendicular to the edge and particularly which have transverse or perpendicular fibres for a portion not greater than 40% of the overall surface of said edges.
Obviously it is possible to provide also combinations of said two embodiments, wherein one or more strip layers are alternated with one or more layers of single-layered or multi-layered wood sheets the characteristics of the invention being clearly available for any structure of the wood supporting layer and in addition leaving out of consideration also the configuration of the outer layers protecting and sealing the two panel faces which are connected to the outer faces of the wood supporting layer.
Further improvements are the object of dependant claims and are described below in greater details.
Characteristics of the invention and advantages deriving therefrom will be more clear from the following description of a non limitative embodiment shown in annexed drawings, wherein:

Fig.1 is a schematic plan view of an embodiment of the panel according to the present invention wherein the sealing edge is provided only along the end sides transverse to wood fibres of strips which form at least a layer of a supporting layer of the panel and about corner areas, as well as at the initial portions of the longitudinal sides adjacent to said corner areas.
Figure 2 is a perspective view of an embodiment of the supporting layer composed of two layers each one composed of wood strips arranged with their longitudinal axes and/or with wood fibres oriented parallel to each other and parallel to the strip longitudinal direction and of an intermediate layer composed of at least a sheet, preferably a continuous wood sheet whose fibres are oriented transverse to wood fibres of strips.
Figure 3 is a cross-sectional view of a panel according to figure 2 and wherein outer layers protecting and sealing the two faces of the supporting layer are also shown and wherein the variant concerning two wood intermediate sheets is shown by a broken line.
Figure 4A is a perspective view of a variant embodiment of figures 2 and 3, wherein the supporting layer is composed of two layers each one made of at least a wood sheet whose fibres are oriented transverse to wood fibres of strips of an intermediate layer compose of wood strips arranged with their longitudinal axes and/or with wood fibres oriented parallel to each other and parallel to the strip longitudinal direction as well as parallel to the lengthwise extension of the panel.
Figure 4B is a cross-sectional view of the panel according to figure 4A the two further protective layers being also shown each one of them being superimposed on one of the faces of the supporting layer respectively.
Figure 5 to 10 are cross-sectional enlarged views of details of an end side of the panel where a sealing edge is provided according to different variant embodiments of the invention.
Fig. 11 is a plan view of the transverse end edge of the panel according to figures 1 and 5 showing the perimetral tongue of the supporting layer projecting beyond the perimetral edge of the protective layer and showing through holes provided in said tongue, the sealing edge being shown with broken lines.
Fig. 12 is a variant embodiment of the panel according to figure 8 in which the profile of the peripheral edge of the supporting layer and the protective layers has recesses adapted for use as connection areas for panel dismantling tools.
Figure 13 is a detail of one end side of the panel provided with a sealing edge in which connection inserts for panel dismantling tools are incorporated by being embedded therein.
Fig. 14 is a perspective view of a panel according to Fig. 13 with said tool connection inserts being incorporated by embedding them in its sealing edge and which inserts have tool engagement cavities that are open at the end side of the sealing edge.
Fig. 15 is a plan view of a panel face according to an improvement of the present invention.
Figure 16 is a cross-sectional view of the area of a longitudinal side of the panel according to figure 15.
Figure 17 likewise figure 16 is a variant embodiment of the improvement according to figure 15.
Fig. 18 is an enlarged view of a cross-section of the area of one of the longitudinal sides of a panel according to a further variant embodiment.
Figures 19 and 20 are views like those of figures 16 and 17 of a variant embodiment of the panel according to the present invention.
Figures 21 to 23 are a variant embodiment of the invention wherein the supporting layer is composed of a plurality of layers each one made of a wood sheet and wherein each wood sheet has wood fibres oriented according to only one direction, while sheets are coupled one to the other in such a relative position that fibres of one sheet are oriented in crossing relationship to fibres of adjacent sheet or sheets.

With reference to figure 1, it shows a panel particularly for slab formworks, or the like made according to the invention.
It has to be noted that the examples of the present description shall be intended without limitation and that they are only some specific choices among different variant embodiments, in which the configuration of the panel is a preferred configuration or a configuration which best illustrates the inventive teaching.
Generally panels for making formworks are about one to three meters long and about 0.5 to 1.5 meters wide, length being greater than width (thereby having a rectangular shape) and have a thickness that changes depending on materials and structure from a few centimeters to a maximum of ten centimeters. These maximum and minimum sizes change depending also on the configuration of the bearing frame or skeleton in which the panels are mounted in a side-by-side position for forming the retaining walls of formworks.
The thickness of the panels may fall in a range of thicknesses from about one or a few decimeters to about one or a few centimeters.
Therefore with reference to figure 1 it shows a panel according to a first embodiment of the invention wherein the panel shows the simplest configuration as regards the number of layers and the number of constructional parts.
According to such embodiment, the panel is composed of at least a wood supporting layer 1 which is covered on both faces by a protective and/or waterproofing layer 2 and which also has, along at least the two opposite sides transverse to the longitudinal axis of the panel and/or to the orientation of wood fibres of the supporting layer 1 a sealing edge 4 which adheres by chemical-physical bonding, to the supporting layer 1 and to the protective layers 2, while wrapping in a moisture-and/or watertight manner the corresponding end side of the supporting layer of the panel.
The sealing edges 4 extend to the corner areas of the assembly composed of the intermediate supporting layer 1 and of the two opposite protective layers 2 and also along the two longitudinal sides of the panel for a certain length by two extensions 104.
The coating and protective layers 2 can be composed of varnish or resin films or of plastic layers in the form of sheets applied to the wood layer by gluing or another type of adhesion or bonding. Particularly the coating and protective layer or layers 2 can be composed of sheets made of polypropylene filled with vegetable flours for example sheets made of a material known under the tradename Wood-Stock®.
The coating and protective layers 2 of the intermediate supporting layer 1 can also be composed of several material layers joined together and attached to faces of the intermediate supporting layer 1 which can be also composed of several layers as mentioned above. The thickness of coating and/or protective layers 2 fall, for example, within a range from a few tenths of a millimeter to a few millimeters and it can also have values smaller or greater than the above ones depending on the type of coating layer that is used among those listed above.
In the case of the protective and/or coating layer composed of sheets made of polypropylene filled with inerts, or the like the thickness of such layers ranges from a few tenths of a millimeter to a few millimeters.
The protective and coating layers 2 can be attached to the supporting layer 1 once that each of them has been made by joining together further layers or all the layers forming the panel.
In such cases, the protective and coating layer or layers 2 are applied before applying the sealing edge or edges 4, so that when these sealing edges 4 are applied said sealing edges 4 overlie the end sides of the edges of the protective and coating layers 2 and are connected thereto such to generate a watertight joint. Therefore the protective and coating layers 2 adhere in a watertight manner to the sealing edges 4 by chemical-physical bonding between the plastic materials said parts are made of.
Sealing edges can be applied by different techniques. A particularly advantageous method is injection molding of the sealing edge material on the corresponding end side of the assembly composed of the supporting layer 1 and the protective and/or coating layer or layers applied thereon.
Figures 2 and 3 show a first embodiment of the invention. This is a preferred embodiment but it shall be intended without limitation due to possible variant embodiments resulting therefrom. As it is shown in figure 2, the wood supporting layer can be composed of three superposed wood layers 1A, 1B, 1C each one having a predetermined sructure. The outermost layers 1A and 1B have a strip structure that is they are made of a plurality of strips adjacent one another such to form a continuous layer. Wood strips can extend continuously throughout all the length of the wood layer or can be shorter than the wood layer 1A, 1B, the wood strips being side-by-side both laterally and longitudinally.
Wood strips 3 of individual layers 1A and 1B are arranged with their longitudinal axes oriented parallel to each other, unlike prior art layer. Each layer of strips 1A, 1B is composed of laterally contiguous strips attached together at mutually contacting side surfaces by chemical-physical bonding. When the length of the strips corresponds to the dimension of the wood layer in such direction of the strips, then there are no contiguous strips in the longitudinal direction. Otherwise, strips are also longitudinally contiguous, the end contact surfaces oriented transverse to their longitudinal axis being offset with respect to end contact surfaces of two subsequent strips laterally adjacent to the first ones.
Moreover, the two layers 1A and 1B made of wood strips can be vertically aligned one with the other with the mutually contacting longitudinal side surfaces 103 of the strips of one layer 1A arranged laterally offset and in a position coinciding with an intermediate longitudinal axis of the strips of the layer 1B such as shown in figure 3 or with mutually contacting longitudinal side surfaces 103 of the strips of one layer 1A arranged vertically coinciding or coplanar one another with the mutually contacting longitudinal side surfaces 103 of the strips of the layer 1B such as shown in figure 2.
Individual layers 1A and 1B made of wood strips as well as the wood strips 3 are glued together in a manner known to the person skilled in the art.
According to an advantageous feature, strips are made with their longitudinal axes oriented in the direction of the fibres and therefore of the wood grain. Due to such feature, each strip and therefore the panel has an improved load resistance with reference to the longitudinal extension of the strips and so of the panel since wood has a higher resistance to stress in the direction of the fibres and grains.
On the contrary the intermediate layer 1C is composed of at least a sheet, preferably a continuous sheet, i.e. in a seamless manner throughout the surface extension of the panel and of the supporting layer 1. Said wood sheet has a thickness smaller than the thickness of the layers 1C and 1B made of strips and it falls within a range from 1 to 8 mm, preferably from 1 to 4 mm.
The thin wood sheet can be composed of a so called veneer. According to a feature of the invention, wood fibres of the wood sheet are oriented parallel one another and transverse to the longitudinal extension L of the panel.
Said intermediate layer can also be composed of two or more superposed and attached sheets such as for example multi-layered plywood sheets or the like. In this case, when the intermediate layer 1C is composed of at least two wood sheets, the latter are arranged such that the direction of fibre orientation within one sheet is transverse to the one of fibers within the other sheet. In such case therefore a sheet has fibres oriented transverse to the longitudinal sides of the panel or the supporting layer 1, while the other one has fibres oriented substantially parallel to said longitudinal sides.
The two or more sheets which can form the intermediate layer 1C are attached together by chemical/physical bonding such as for instance gluing. This is also for the attachement of the three layers 1A, 1B and 1C one to the other.
Preferably fibres of the strips forming the layers 1A and 1B are all oriented, that is 100% in the direction of the longitudinal axis of strips such that longitudinal side surfaces of the strips forming a part of the longitudinal edges of the supporting layer have a very low absorption coefficient of liquid and particularly of moisture.
As regards the sheet or sheets forming the intermediate layer 1C, they are very thin with respect to the thickness of the strips and they have also a low moisture absorption due to the fact that said sheets or veneers are made of hardwood.
The term hardwood is a specific technical term in the art and examples of hardwood are woods such as Maple, Alder, Birch, Hickory, Hornbeam or white Beech, Chestnut, Beech, Ash, Walnut, Sycamore, Poplar, Cherry, Willow, Oak, Basswood, Elm and also tropical woods such as Kauri pine, Iroko, Red pine, Palisander, Brazilian Rosewood, Ebony, African Mahogany, Mansonia, Balsa, Nyatoh, Afrormosia, Meranti, Teak, Limba, Ayous.
Due to the fact that the wood fibers of the intermediate layer are oriented parallel one another and transverse to fibres of the strips forming the layers 1A and 1B, i.d. transverse to the longitudinal edges of the panel, the supporting layer 1 and therefore the panel have optimal mechanical strength characteristics both in the longitudinal direction and in the transverse direction, and this with overall thicknesses smaller than supporting layers of known panels as well as with considerably more light weights.
Inexpensive and not so much heavy resinous woods can be used for the strips, while hardwoods for the intermediate layer allow moisture absorption to be reduced in an acceptable manner along the longitudinal edges of the panel and allow mechanical strength to be given in the transverse direction of the panel.
The fact of using strips having 100% of wood fibres oriented in the longitudinal direction of the panel in combination with small thicknesses of the sheet or sheets forming the intermediate layer 1C and the particular type of wood used such as hardwood allows at least the longitudinal edges of the supporting layer 1 made of wood not to be coated, since the absorption or penetration of moisture through the surfaces of the strips oriented parallel to the wood fibres and grain is considerably lower than the absorption and penetration of moisture through the surfaces oriented transverse to the direction of the wood fibres.
Therefore the wood layer sides transversely oriented, i.e. oriented in the panel width direction, for a considerable portion of the thickness consist of the end sides of the strips oriented transverse to the wood fibres and grain.
The sealing edge 4 is applied to said transverse edges of the wood panel.
Their construction is similar to what already described above. The sealing edge 4 applied particularly by over-molding to the end sides of the strips oriented transverse to the wood fibres causes, due to the higher porosity of such surfaces, the plastic material forming the sealing edges 4 to penetrate by a predetermined amount into pores and between wood fibres, thereby causing an effective sealing action against moisture penetration and furthermore a better attachment of the sealing edge 4 to the surface of the wood layer edge that, in addition to the intrinsic chemical/physical bonding of the plastic material generates also a mechanical bonding due to the mutual penetration of said plastic material and the wood fibres.
As already mentioned hereinbefore with reference to figures 2 and 3, the wood layer 1 or the superposed layers 1A, 1B, 1C can be coated by a coating and/or protective layer 2 on their outward faces. The coating and protective layer or layers 2 can be of different type and for example they are composed of varnish, resin or plastic material in the form of films or sheets which are joined by chemical/physical bonding to the faces of the supporting layer 1 and i.e. in this case to the outward faces of the two strip layers 1A and 1B. The sealing edge 4 also overlies the end surface of the edge of said coating and protective layers 2 at the edge of the wood layer or layers 1, 1A, 1B with said coating and protective layers 5 attached thereto, said sealing edge 4 being connected in a watertight manner to the corresponding edge of said coating and protective layers 5 by chemical/physical bonding.
Obviously there's nothing to prevent a sealing edge from being provided also at the longitudinal edges of the wood layer or layers 1, 1A, 1B.
The panel structure in figure 3 is complemented by the provision of said schematically shown protective layers 2, while 101C denotes a sheet forming the intermediate layer 1C and 101C' denotes a second sheet that together with the sheet 101C forms the intermediate layer and which can be provided or not and therefore it is shown by a broken line. Such broken line has to be intended to schematically shown the fact that the intermediate layer can be composed also of more than two superposed sheets attached together by chemical-physical bonding, such as for example multi-layered plywood or the like.
Figures 4A and 4B like figures 2 and 3 show a variant embodiment, wherein the wood supporting layer 1 is composed of three layers too which are denoted with 10A, 10B, 10C, unlike the previous embodiment the outermost layers 10A and 10B being made like the intermediate layer 1C of the previous embodiment of figures 2 and 3, while the intermediate layer 10C has a structure like the structure of layers 1A and 1B. Again the supporting layer 1 on the two opposite faces is coated with a protective and/or coating layer 2 and as regards mechanical properties and moisture absorption, the panel according to this embodiment has characteristics substantially equal to those of the panel according to the previous example. As regards the moisture absorption remarks made for the previous embodiment are applied also in this case. The two outer layers 10A and 10B can be made of one or more wood sheets 101A and 101A', 101B and 101B' as the intermediate layer 1C of the previous example even in this case the wood fibres of at least one of the sheets being oriented transverse to the longitudinal edges of the panel.
In both cases the supporting layer and therefore also the finished panel in addition to a higher mechanical strength in the transverse direction of the panel with thicknesses smaller than those of conventional panels have also a higher torsional strength. This is absolutely unexpected since generally wood fibres can be easily divided in a direction transverse to their longitudinal extension and just by a torsional stress, as one can easily personally observed. Contrary to expectations, the panel according to the present invention and according to the above embodiments has a considerable torsional strength overcoming that of conventional panels even with thicknesses smaller than thicknesses of said conventional panels.
In order to make the watertight joint between the sealing edge 4 and the protective or coating layers 2 of the panel even more reliable against moisture or water penetration, the invention provides the size of the mutually contacting and watertight chemical/physical bonding surface between the sealing edge 4 and the protective and/or coating layers 2 to be increased along the part that has said sealing edge extending thereon and in the water penetration or path direction from the outside to the inside of the panel through the joint between the sealing edge and the protective and/or coating layers 2.
In the following figures, for simplicity reasons the structure of the supporting layer 1 is omitted but it has to be considered as being provided and made according to one embodiment among those described above. Moreover the channel or channels provided immediately under the protective layers 2 can have such a size in the direction of the thickness of the supporting layer 1 to be extended only for at least a part or all the thickness of the outermost layers 1A and 1B or even for a part or all the thickness of the intermediate layer 1C. This is applied also in the case of the tongue 301 made of a portion of the thickness of the intermediate layer 1C or all the thickness of said layer 1C or also of a portion of the thickness of one or both the two outermost layers 1A and 1B.
According to a first embodiment shown in figure 5, along the contact end side between the sealing edge 4 and the panel, the intermediate supporting layer 1 ends in a recessed position to a predetermined amount with respect to the corresponding edge of the coating and/or protective layer or layers 2. Thus a peripheral groove is made whose bottom is made of the end side 101 of the intermediate supporting layer 1 made of wood or the like and whose delimiting side walls are made of the perimetral bands 102 of the protective layers 2 projecting outwards beyond the end side 101 of the intermediate supporting layer 1.
Therefore the sealing edge 4 has an extension or rear tongue 204 by which it engages with said peripheral channel of the panel completely filling the cavity thereof and adhering by chemical/physical bonding to the end side 101 of the supporting layer 1 and to the free surface of the protective layers 2 faced towards the intermediate supporting layer 1 and which is provided along the protruding perimetral bands 102 of the supporting layers 2. The adhesion against the bands 102 of the supporting layers is such that a moisture- or water-tight attachment is generated extending for each protective and coating layer 2 through the thickness of said layer and for the width of the peripheral band 102 forming the side wall of the peripheral channel of the panel which is filled by the rear tongue 204 of the sealing edge 4. Thus between the protective or coating layers 2 and the sealing edge 4 a watertight attachment area is generated which is very large in the direction of the water penetration path with reference to the thickness of said protective layers 2.
In the variant of figure 6, the end side of the supporting layer 1 is shaped such to have two individual channels instead of one channel, each one of them extending flush with the contact surface of one of the faces of the intermediate supporting layer with the respective protective layer 2 and along the area of the corresponding corner of the end side of said supporting layer 1. Particularly, each of the two channels is made by a stepped recess made along the area of the corresponding end corner of the intermediate supporting layer, whereby the channel leaves the face of the corresponding protective layer 2 facing towards the supporting layer 1 exposed through a width corresponding to the depth of the channel and of the stepped recess provided in the supporting layer 1. This surface forms one of the two side walls of the channel and is denoted by 102, having the same function as in the previous example. The opposite side surface of the channel is formed by the parallel surface 201 of the stepped recess, whereas the bottom of the channel is made of the end side of the stepped recess 101'.
In this case, the thickness of each of the two channel is smaller than the overall thickness of the supporting layer 1 and for example it is of a few millimeters or it is as thick as the corresponding protective layer 2.
Like the solution of the previous example even in this variant, the sealing edge 4 has rear tongues 104 each of which penetrates into one of the two channels and adheres by chemical-physical bonding both to the material of the supporting layer 1 and to the material of the protective layers 2 and in this case along the end side thereof and along surface bands 102 outwardly delimiting the corresponding channel.
In this case a smaller amount of expensive material is used and moreover the channel filling volume is also reduced, so drawbacks related to injection defects are avoided. Advantages concerning the sealing are the same described in the previous example.
A further constructional variant shown in figure 7 is different from the one of figure 6 in that while in the example of figure 6, the end side of the remaining portion of the thickness of the supporting layer 1 provided between the two channels extends flush with end sides of the protective and/or coating layer or layers 2, in the example of figure 7, said remaining portion of the thickness of the supporting layer 1 extends beyond the end sides of the protective and/or coating layers 2. This causes a further reduction of the amount of material necessary to make the sealing edge which in this case is composed only of a wood tongue or the like coated along the end side and along the two faces parallel to the faces of the panel with a layer of plastic material forming a sealing enclosure with a substantially inverted U-shaped section and joined by chemical-physical bonding to the material of the supporting layer 1 and to the material of the protective layer or layers 2 generating a watertight attachment therewith.
Thus in addition to the enlargement of the contact surface between the material of the sealing edge 4 and the material of the protective layer or layers 2, an enlargement of the contact surface between the material of the sealing edge and the material of the supporting layer 1 is also achieved. This guarantees a better watertight effect in combination with a better attachment of the sealing edge 4 to the supporting layer of the panel 1 whereby said edge is more strongly attached to the panel.
Figure 8 shows again a further variant of the panel according to figure 7 in this case the variant provides the end extension or protuberance 301 of the end side of the supporting layer 1 made of wood or similar materials, to be provided with one or more rows or through holes 401 within which the material of the sealing edge penetrates forming mechanical anchor through members 304 with a function similar to fastening pins or nails but which are made as one piece with the remaining portion of the sealing edge 4. Therefore in this embodiment in addition to the mechanical connection of the sealing edge due to the chemical/physical bonding of the material of the sealing edge 4 to the panel and particularly to the supporting layer, said sealing edge has a mechanical shape fit with the supporting layer 1.
In order to understand the importance of the above it has to be noted that since the attachment between the sealing edge 4 and the protective or coating layer or layers 2 is intended to provide above all a watertight effect against the penetration of moisture or water, they have to be subjected to minimal mechanical stress, said mechanical fastening or retaining function of the sealing edge 4 being provided by the attachment thereof with the supporting layer 1. Therefore in this embodiment the increased mechanical strength of the sealing edge-supporting layer attachment further reduces the mechanical stresses acting on the attchment between said sealing edge and the protective layer or layers.
Fig.9 shows a further variant embodiment, wherein the bottom of the groove has a curved cross-section, so the groove has an inverted U-shaped cross-section. This allows pressures by the material of the sealing edge 4 to be better distributed during injection molding preventing strong pressures acting on a corner area from causing the protective layer 2 to be lifted from the corresponding face of the supporting layer 1.
Finally figure 10 shows again a variant wherein the protective or coating layer or layers 2 are applied on the supporting layer 1 by interposing one or more additional layers, such as for example fibre layers, in the form of fabrics, mats, nonwovens, or other type. In this case, the free perimetral band projecting out of the protective layer denoted by 102 does not directly adheres to the material of the sealing edge 4, but by the interposition of additional layer or layers denoted by 5.
While such alternative is shown with reference to the variant of figure 9, it can be provided in combination with one or more of any variant embodiments described above. Moreover what said with reference to the variant embodiment of figure 10 also applies to the variant embodiment of figure 9.
Figure 11 shows a detail of an end side of a panel according to the embodiment of figure 8 and possibly also of figures 9 and/or 10. The sealing edge is shown by broken lines. The figure clearly shows the extension 301 of the end side of the supporting layer 1 beyond the end side of the protective or coating layer 2. Moroever the row of through holes 401 into said extension 301 can be seen. With reference to said holes, instead of through holes a further variant can provide a row of blind holes or indentations on only one or both the opposite faces of the extension 301 of the end side of the supporting layer 1.
With reference to figure 11 moreover the panel has a chamfer or a recessed or removed area at each of the two corner areas of the end side thereof and also for a certain length along the portion of the longitudinal edges directly adjacent to said corner areas, whereby the sealing edge extends also along said corner areas and by portions 104 along said portions of the longitudinal edges. At corner areas the sealing edge 4 complements the shape of the assembly made of the supporting layer 1 and of the protective layer or layers 2 such to give the finished panel a rectangular shape, while along recessed portions of the two longitudinal sides the sealing edge portions 104 end flush with said longitudinal sides of the panel composed of the longitudinal sides of the supporting layer 1 and of the protective or coating layer or layers 2.
Advantageously the assembly of the supporting layer 1 and of the protective or coating layers 2 and the longitudinal edge are shaped according to one or more of the alternatives described and shown with reference to figures 2 to 10 even along the chamfered corner area and along the recess of the initial portion of longitudinal sides.
Advantageously, the peripheral edge of the assembly of the supporting layer 1 and coating layer or layers along the end sides along the corner area and along initial portions of longitudinal sides has a rounded and curvilinear arrangement at the corner areas and at the end areas of the recessed portions along the longitudinal sides.
Again according to an improvement that can be provided in any combination with one or more of the previous variant embodiments, the panel can be provided with reinforced areas for connection of dismantling tools, such as for example levers or crowbars or the like. In this case for example when panels are used for retaining floor castings or the like, they are dismantled by being lifted or removed with said tools which are introduced at the end sides of said panels and that is of the sealing edge.
In a first embodiment, in order to prevent the panel to be damaged by the mechanical action along the sealing edge, which might cause it to be removed or a weakening of the attachment to the panel, at said attachment areas the perimetral edge of the assembly of layers composed of the supporting layer 1 and of the protective or coating layer or layers 2 has one or more recesses 6 arranged along the lengthwise direction thereof and which are filled with the material of the sealing edge 4 which in said areas has a greater thickness in the direction of the distance between the outer edge of the sealing edge and the edge of the assembly of the supporting layer 1 and protective layers 2. In the embodiment of figure 12, there are provided three recesses 6 one is a central recess in the end side and two are side recesses at the ends of the recessed portions of the longitudinal sides of the assembly made of the supporting layer 1 and of the protective or coating layer or layers 2. It has to be noted that the shape of the peripheral edge of the supporting layer and of the protective or coating layer or layers 2 also run seamlessly along said recesses 6.
Figures 13 and 14 show a variant wherein areas for the connection of mounting tools denoted by 7 are composed of elements made of plastic material or other material incorporated by being embedded and/or overmolding or anyway embedded or trapped into the material of the sealing edge 4.
In this embodiment said connection areas 7 are composed of elements such as blocks or the like having an open cavity at one of the sides and particularly at the end side of the sealing edge 4. This allows the end of the lever or of another similar tool to be grasped better and more safely avoiding a force to be directly exerted on the sealing edge and preventing the connection end of the tool against the panel from damaging it for example due to an accidental slipping or disengagement thereof. As denoted by the central element 7 in figure 13 which is shown in broken line, it is possible to provide one or more of said elements 7 at different locations of the peripheral edge of the sealing edge 4.
With reference to the shape of the peripheral edge of the assembly of the supporting layer 1 and the protective or coating layer 2 having a chamfer at the corner area and a recess along the initial portions adjacent to said corner area of the longitudinal sides, as shown in embodiments of figure 1 and of figures 11 and 12, the function of such arrangement is to protect the corner areas which are the most exposed to damages.
According to an improvement shown in variants of figures 15 to 18, the panel according to one or more of the embodiments mentioned above has a protective coating also along said longitudinal sides. Such coating acts for protecting said longitudinal sides mainly against mechanical damages and it is made such that the moisture possibly penetrated into the wood layers can transpire through the longitudinal sides.
As it results in figures, along each longitudinal side and at the corners of the panel, it is made of protective small edges 8 made of plastic material particularly of the same plastic material as the edges of the transverse sides of the panel.
With reference to figure 16, said protective small edges 8 are composed of plastic material filling a stepped recess 108 provided along each corner between the longitudinal side and one of the two faces of the panel. Said stepped recess 108 is filled with the protective small edge 8 such to complement the cross-section of the panel at said longitudinal sides. Each protective small edge extends by one side flush with the corresponding longitudinal side of the panel and by the other side flush with the corresponding face of the panel.
Therefore as it results from figure 16, at each corner of the two longitudinal sides of the panel, the protective small edges 8 extend for a certain depth in the direction of the thickness and for a certain depth in the direction of the width of the panel. The overall thickness of the protective small edges is smaller than the overall thickness of the panel and therefore a median wood band is left exposed along each longitudinal side.
Particularly the protective small edges 8 are made by injection overmolding of the longitudinal sides of the panel. Such process can be carried out contemporaneously when making edges 4 of plastic material along the transvers sides of the panel.
When the panel has an outer sealing and/or protective layer 2 on one or both the faces, the corresponding step 108 extends, in the direction of the thickness of the panel, also for the thickness of the sealing and protective layer 2, whereby the protective small edge 8 made of plastic material forming the corresponding corner of the panel covers even the end edge of the sealing and/or protective layer 2 adhering thereto by chemical-physical bonding and in a watertight manner.
The portion 208 of the supporting layer 1 projects outwards with respect to the sealing and protective layers and it forms a side of the step at the corner.
Moreover such as shown in figures 17 and 18, in order to have a better bonding of the protective small edges 8, the stepped recess 108 at the side oriented in the direction of the thickness of the panel has a groove or channel extending under the corresponding sealing and/or protective layer 2, said channel being delimited at one side by the face 102 of the sealing and/or protective layer 2 facing towards the supporting layer of the panel, whereby the protective small edge 8 extends also for a predetermined amount into said channel directly under a longitudinal peripheral band 102 of the sealing and/or protective layer 2 of the corresponding panel face.
With reference to figure 18, likewise other embodiments already described above about the edges at the transverse end sides of the panel, even for the longitudinal sides said channel in the bottom or riser side of the stepped recess, i.e. at the side in the direction of the panel thickness, can have a bottom side with a curved or rounded cross-section.
In the embodiment of figure 2 wherein the supporting layer 1 is composed of three material layers 10A, 10B, 10C, of which two outermost layers 10A and 10B are composed each one of a second material layer made of at least a wood sheet, while an intermediate layer 10C is arranged therebetween which is composed of a first material layer made of a plurality of strips, said three layers being joined one to the other in a superposed position one on the other one by gluing, the stepped recesses 108 along the corners of the longitudinal sides of the panel extend, in the direction of the panel thickness, for a depth at least equal to the thickness of said outermost layers 1A, 1B composed of one or more wood sheets.
In figure 17 the depth of the stepped recesses 108 is greater than the thickness of layers 1A and 1B, while in figure 18 said depth is substantially equal to the thickness of the layers 10A and 10B of the supporting layer 1 of the panel.
By this arrangement, the protective small edges 8 of the longitudinal sides of the panel, allow moisture possibly penetrated into the panel to transpire, since they leave a portion of the thickness of the longitudinal sides exposed wherein the wood of the supporting layer is not covered and so directly exposed to the environment, but they also seal the longitudinal sides of the wood sheets of the two outermost layers 10A and 10B, whose fibres extend transverse to the longitudinal direction and therefore are favorably exposed to moisture absorption. Therefore contemporaneously to the effective protection and to the transpiration ability of the panel, as a third advantage the longitudinal sides of the layers having fibres oriented transverse to said sides are also sealed.
Figures 19 and 20 show views similar to the ones of figures 16 and 17 of a variant embodiment of the panel according to the present invention.
Such variant provides the longitudinal edges of the panel, i.e. the edges along which the protective small edges 8 made of plastic material are provided only along the areas of the two longitudinal corners and where a wood central band 208 of the supporting layer of the panel is left exposed therebetween, to have a recessed configuration and particularly a concave configuration.
In this case, the concavity can be extended for all the central band 208 of the longitudinal edges where the supporting layer made of wood is exposed and also for at least a portion of the height or thickness of the protective small edges 8 at the corners of the panel.
As an alternative the concavity can be extended, such as shown, for all the thickness of the panel between two longitudinal corners.
The maximum depth of the concavity along the longitudinal edges of the panel is adapted to the possible swelling and the amount can be defined by empiric tests.
According to an improvement, the depth of the concavity is provided of such an amount that the slot made remains under the ports not allowing the material to be retained to spontaneously infiltrates due to capillarity effects with reference to the viscosity of the material to be retained.
The provision of such concave arrangement of the longitudinal side edges of the panels has the following result: since the longitudinal sides of the panel are protected with a longitudinal small edge made of plastic material only at longitudinal corner areas and the protection occurs mainly against mechanical damages, it is possible for the longitudinal edges of the panel to swell at least in the central area not covered with the plastic material of the protective small edges due to a moisture absorption even though reduced through the wood of said exposed central part of the longitudinal edge. Such swelling substantially occurs as an outwardly convex bulge . Therefore when two panels are put side by side it is possible that due to the swelling of at least one of the facing longitudinal contacting edges of the two adjacent panels lower watertight areas and/or even grooves can be generated causing projecting webs to be made on the concrete article once panels are removed. The effect is greater when panels are used for horizontal retaining walls.
Figure 21 shows a variant embodiment of the panel according to the present invention. Here, the supporting layer 10 is composed of several wood layers in the form of multi-layered plywood or multi-layered veneer.
In this case several wood sheets or layers 10A, 10B, 10C, 10D are joined together in a superposed position by gluing. Each layer has a predetermined thickness which has not to be necessarily equal to the other layers and is composed of a certain type of wood which has not to be necessarily equal to the one of other layers too. The wood of each layer 10A, 10B, 10C, 10D has fibres oriented in the same direction within said layer and layers are superposed each one with such an orientation that the orientation of wood fibres of one layer is transverse to or specifically perpendicular to the orientation of wood fibres of the adjacent layers. In Figure 21 and in following figures 22 and 23 the orientation of fibres within layers is denoted with broken lines which are continuous and parallel to lines delimiting the layers one with respect to the other when fibres are parallel to the shown side, while when fibres are perpendicular to the shown side they are denoted by filling the thickness of the edge of the corresponding layer with a plurality of dots.
According to the invention, by acting on the thickness and on the arrangement of the wood layers the longitudinal edges of the panel are provided along the edges of the multi-layered supporting layer which have a portion of the overall surface of the edge wherein fibres end perpendicular to or transverse to said edge which is not greater than, i.e. at most 40% of the overall surface of the longitudinal edge.
Figure 20 is only approximate, but it shows that if the edge parallel to the sheet is considered as the transverse edge of the panel, and the one shown in perspective as the longitudinal edge, the overall surface of the layers 10E and 10D having fibres transverse to or perpendicular to the longitudinal edge is lower than 40% of the overall surface of the layers 10A, 10B and 10C whose fibres are parallel to the shown longitudinal edge.
The sealing and protective layer on the two faces of the supporting layer is shown by a grey section and is denoted with numeral 2. It can be made according to one or more of the variants described for the previous example in figures 1 to 20.
Also as regards such type of supporting layer one or more of the variants or constructional characteristics provided and described with reference to figures 1 to 20 and in the several listed combinations or subcombinations can be provided.
As already mentioned above, by providing a surface of the longitudinal edges wherein fibres are oriented transverse to or perpendicular to said edges, even with the panel not sealed along the longitudinal edges, but only along the transverse ones, the moisture absorption along the exposed longitudinal edges of the supporting layer is reduced to such an amount that the dynamics between absorption and transpiration and therefore drying leads to a panel life, due to only the moisture effect, which considerably overcomes the average life provided during the practical use of the panel where the panel is subjected also to high mechanical stresses when handling it. Also as regards the deformation due to a possible swelling it is very reduced and completely negligible.
However by using one or more of the constructional characteristics provided according to the invention and already described with reference to the previous example of figures 1 to 20, and particularly by sealing even partially the longitudinal edges, it is possible to further improve the life and to further optimize or at least change the balance between moisture absorption and drying ability due to the moisture being transpired i.e. removed through not sealed parts of the longitudinal edges.
Particularly, figures 22 and 23 show two variants that substantially correspond to the embodiments of figures 16 and 17 referred to the previous example of the panel.
As it is clear, in such figures, like what described above there are provided two sealing and protective small edges along corners which are denoted by 8.
Again like what described above the small edges along the corners can be made into a stepped recess which comprises also the thickness of the sealing and protective layers 2. As further shown in figure 23 at the bottom of the stepped recess a groove or channel can be provided allowing the protective and sealing small edge to extend by the protuberance 108 under the corresponding sealing and protective layer 2.
Advantageously when sealing small edges are provided along the corners of the longitudinal sides it is suitable to make the supporting layer with such an amount of layers that the outermost layers 10A and 10B have wood fibres oriented perpendicular to or transvese to the longitudinal edges as shown in figures 22 and 23.
Thus even by providing the surface portion of the longitudinal edges at which wood fibres are oriented transverse or perpendicular to said layers to be greater than 40% of the overall surface of the longitudinal edges, such value can be obtained again since the sealing small edges cover a portion of the surface of the longitudinal edges provided with transverse or perpendicular fibres by sealing it from the environment thus reducing the portion of said surface of the longitudinal edges provided with transverse or perpendicular fibres which is really exposed to moisture to a value within provided limits.
Then by acting on thicknesses it is also possible by the sealing and protective small edges 8 along the longitudinal corners to reduce the really exposed portion of the surface of said longitudinal edges provided with transverse or perpendicular fibres within very low values and widely below the maximum limit of 40% of the overall surface of the longitudinal edges.
Such as shown when there are provided several layers having fibres oriented transverse to or perpendicular to the longitudinal edges of the panel it is possible according to an intermediate not shown variant to seal from the environment only a portion of the areas of the longitudinal edges where wood fibres are transverse to or perpendicular to said longitudinal edges. For example by providing only sealing and protective small edges 8 along corners of the longitudinal edges.
As an alternative it is possible to provide a sealing small edge at at least one or a part of one or more of the additional layers (10G and 10F) whose fibres are oriented transverse to or perpendicular to the longitudinal edges.
Moreover a complete variant is the one shown in figures 22 and 23 wherein sealing and protective small edges denoted with 8' are provided also along the longitudinal edges and for the overall thickness of the intermediate layers 10G and 10F.
The sealing might occur by spreading or by a mutual penetration of a sealing or waterproofing plastic material.
As an alternative it is possible to provide, such as shown, the longitudinal edges of the layers 10F and 10G with fibres transverse to or perpendicular to said longitudinal edges to end in a recessed position with respect to the longitudinal edges of the layers 10C, 10D, 10E whose fibres are parallel to said longitudinal edges. Due to that grooves or channels housing the sealing small edges of the layers 10G and 10F are obtained whose fibres are transverse to or perpendicular to the longitudinal edges, where said sealing small edges 8' can be housed.
Said recesses or channels can be made by milling process like stepped recesses for the sealing and protective small edges 8 along the corners of the longitudinal edges. In case, they can be made contemporaneously as the stepped recesses along the longitudinal corners by means of suitable milling machines.
Likewise the sealing small edges 8' can be made as the protective and sealing small edges 8 along the longitudinal corners by injection molding of a plastic material. Such operation can be carried out contemporaneously to the injection molding of the sealing and protective small edges along the longitudinal corners using the same plastic material or different plastic materials.
With reference to the shown examples it is clear to the person skilled in the art that it is possible to provide also combined arrangements of the structure of the supporting layer alternating one or more layers composed of strips to one or more single-layered or multi-layered sheet layers made of wood it being possible to apply the characteristics of the invention according to one or more of the combinations described above to said layers.

Claims

Panel for making formwork retaining walls for concrete castings, particularly for retaining formworks for making concrete slabs or the like, which panel is composed of at least four perimetral edges oriented in pairs parallel one another the edges of one pair being called end sides or edges, oriented transverse to the edges of the other pair which are called longitudinal sides or edges and which panel is composed of at least a supporting layer made of wood which is at least partly externally coated with one or more moisture and/or water sealing and/or protective layers,
the supporting layer in turn being composed of at least two layers made of wood sheets or strips
said strips or sheets being made such that the direction of wood fibres of said sheets or strips has a predetermined orientation with respect to a predetermined direction or axis of said strips or sheets;
said strips or sheets are glued together such to form said at least two layers,
said strips or sheets with reference to peripheral edges of the panel are oriented such that at the end edges and at the longitudinal edges of said supporting layer a portion of wood fibres are parallel and a portion of wood fibres are transverse to said side and
which panel is characterized in that at the longitudinal sides the wood fibres ending at said sides and oriented perpendicular to or transverse to said sides are exposed to the outside for not more than 40% of the overall surface of said longitudinal edges of the supporting layer;
while at least a part of an end side of the panel that is of at least a side transverse to said longitudinal sides of the panel has or is composed of a sealing edge made of plastic material, and it overlies said end side of the supporting layer and/or of the sealing/protective layer or layers along at least said part of said end side and it is fastened to said end side of the panel by chemical/physical bonding and seals it from the environment.
Panel according to claim 1, wherein the wood fibres of the supporting layer are oriented perpendicular to or transverse to said longitudinal sides of the panel or of the supporting layer and are exposed for a part not greater than 30% of the overall surface of the edges along said longitudinal sides
Panel according to claims 1 or 2, characterized in that at least the wood layers forming the supporting layer and whose fibres run transverse to and particularly perpendicular to the longitudinal edges of the panel are made of hardwood.
Panel according to one or more of the preceding claims, characterized in that sealing edges are provided along the end sides of the panel oriented transverse to the direction of orientation of the wood fibers of the supporting layer, through at least a part of or the whole thickness of the panel and/or over at least a part or the whole surface of end layers of the panel.
Panel according to one or more of the preceding claims, characterized in that it has a protective coating also along the longitudinal sides which coating covers at least a part of the surface of said longitudinal edges where the wood fibres of the layers forming the supporting layer end and which are oriented perpendicular to said longitudinal edges.
Panel according to claim 5, characterized in that at least for the thickness of one or more of the layers forming the supporting layer of the panel and whose fibres are oriented perpendicular to a longitudinal edge of the panel, the correspondiong edge of said layer is recessed with respect to the edge of the layers whose fibres are parallel to the longitudinal edge of the panel a recess being made which is sealed by a sealing small edge made of plastic material filling said recesses and which ends flush with the longitudinal edge of the layers whose fibres are oriented parallel to the longitudinal edge of the panel, such that the surface of the longitudinal edges of the panel where wood fibres are provided transverse to or perpendicular to said longitudinal edges which are not covered or sealed from the environment is lower than 40%, preferably than 30% of the overall surface of said longitudinal edges.
Panel according to one or more of the preceding claims, characterized in that at least along said longitudinal edges the panel has a stepped recess along each corner between the longitudinal side and one of the two faces of the panel, which stepped recess is filled such to complement the cross-section of the panel at said longitudinal sides with a plastic material filling extending by one side flush with the corresponding longitudinal side of the panel and by the other side flush with the corresponding face of the panel, thus forming a protective longitudinal small edge along each longitudinal corner of the panel.
Panel according to claim 7, characterized in that the panel has a stepped recess along each corner between the transverse side and one of the two faces of the panel, which stepped recess is filled such to complement the cross-section of the panel at said transverse sides with a plastic material filling extending by one side at least flush with the corresponding transverse side of the panel and by the other side flush with the corresponding face of the panel, thus forming a protective longitudinal small edge at least along each transverse corner of the panel.
Panel according to claims 7 or 8, characterized in that it has an outer sealing and/or protective layer on one or both the faces, while the corresponding stepped recess extends, in the direction of the panel thickness, also for the thickness of the corresponding sealing and/or protective layer, whereby the protective small edge made of plastic material forming the corresponding corner of the panel covers also the end edge of the sealing and/or protective layer.
Panel according to claim 9, characterized in that in order to have a better bonding of protective small edges, the stepped recess at the side oriented in the direction of the panel thickness has a groove or channel running under the corresponding sealing and/or protective layer, said channel on one side being delimited by the face of the sealing and/or protective layer faced towards the supporting layer of the panel, whereby the protective small edge extends also for a predetermined amount into said channel directly under a longitudinal peripheral band of the sealing and/or protective layer of the corresponding panel face.
Panel according to claim 10, characterized in that the bottom of the recess has a concave shape with the concavity faced towards the corresponding transverse and/or longitudinal peripheral edge of the panel.
Panel according to one or more of the preceding claims, characterized in that at least along the end edges the panel has means for mechanically connecting the sealing edge and the material of the supporting layer, which means are composed of complementary interlocking means for the material of the sealing edge and the material of the supporting layer.
Panel according to claim 12, characterized in that along the end edges of the panel the two stepped recesses along the corners of said edges form a tongue, the surfaces of said tongue parallel to the panel faces being provided with holes or apertures which are blind or extend throughout the thickness of said tongue, whereas the sealing edge penetrates therein or therethrough with ridges or bridges of material which connect the two layers of material of said edge that cover the two faces of said tongues parallel to the faces of the panel.
Panel according to one or more of the preceding claims, characterized in that the supporting layer made of wood has recessed corner areas filled with inserts made of plastic material having such a shape to complement the perimetral profile of the panel to obtain the ideal shape that might be envisaged without said recessed areas.
Panel according to claim 14, characterized in that the channel or channels under the protective layer or layers, and the tongue of the protective layer, if any, with or without through holes are provided even along said chamfered corner areas and along the initial recessed portion of the longitudinal sides of the panel directly adjacent to said corner areas.
Panel according to one or more of the preceding claims, characterized in that the protective and/or sealing small edges and/or corner areas are made of plastic material by injection molding preferably contemporaneously along all the perimeter of the panel.
Panel according to one or more of the preceding claims, characterized in that at least the longitudinal edges of panels, have a recessed configuration and particularly a concave one.
Panel according to claim 17, characterized in that the concavity extends for the whole band at least of the longitudinal edges formed of the thickness of the supporting layer.
Panel according to claim 17 or 18, characterized in the maximum depth of the concavity along the longitudinal edges of the panel is adapted to the possible swelling and said amount being defined by empiric tests.
Panel according to one or more of the preceding claims, characterized in that the supporting layer is made of at least three wood layers wherein each layer has wood fibres oriented according to only one direction i.e. they are all parallel each other within the corresponding layer, layers being joined together with a crossed orientation as regards the direction of the wood fibres of said layers, whereby said supporting layer has layers with wood fibres oriented alternately parallel to and perpendicular to the longitudinal edges of the panel and the outermost layers of the protective layer, i.e. those forming the faces of the protective layer to which a sealing and protective layer is applied being provided with wood fibres oriented perpendicular to the longitudinal edges of the panel, while the further one or more wood intermediate layers have wood fibres oriented alternately for each layer parallel and perpendicular to said longitudinal edges, the protective small edges and the corresponding stepped recesses housing said small edges provided along each one of the two longitudinal corners of the two longitudinal edges of the panel being made with such a thickness that they overlie at least partly or completely the thickness of said outermost wood layers.