Patent Description:
Generally, in these panels the wooden plate is made up of two or more layers of the same type of wood, which are arranged with the fibers of the wood of which they are made that are oriented in a nonparallel direction, i.e. crossed each other and between the individual layers.

Typically these layers of wood are made up of birch wood which has a relatively high weight of about <NUM>/m3.

Said panels are builded, for example in a support structure, one at a time and must be handled manually by the personnel. Therefore, there is a need to limit the overall weight of each panel.

This weight limit constitutes a conflicting need with other characteristics of the panel which are mainly the fact of presenting a certain mechanical resistance to bending under the action of the mass of material to be contained and at the same time of presenting a surface extension, i.e. dimensions in width and lengths that are relatively large so as not to penalize the installation and dismantling times of the containment structures and also to avoid the formation of too many junction areas between the individual panels. Depending on the conformation of the support frames of the panels, these junction areas can constitute areas of misalignment between the edges of mutual contact of the panels which therefore leave imprints of the same on the material of the casting once hardened or even areas in which containment losses occur and therefore seepage of the most liquid part of the pouring mass.

To date, conditions of equilibrium have been found between the various conflicting requirements described here, which have, among other things, also imposed relatively thin thicknesses of the panels and therefore also of the wooden plates that make them up.

The reduction in thickness has on the one hand contributed to a limitation of weight, but on the other hand has also led to a reduction in mechanical strength due to the limitation of the number of layers of wood having crossed orientations of the fibers of the wood from which they are made.

The reduction in thickness has also further limited the possibilities of providing for integrating systems of constraint to the load-bearing structure in the panels which could make the combination of panel main structure such as to synergistically strengthen the mechanical resistance of the combination main structure and panels to higher values than those supplied by the individual separate parts. Panels combining softwood and hardwood layers with a coating are for example known from<NPL>) or <CIT>.

There is therefore an unsatisfied need to improve the conditions of mediation of the contrasting characteristics set out above, allowing to have better performing panels for the same weight or even with lower weights than those currently known.

According to an embodiment, the present invention relates to a panel for making containment walls of formwork for concrete pouring, in particular for containment formwork for making concrete slabs or the like, as defined in claim <NUM>, which panel consists of at least one plate of wood or comprising wood, which plate of wood is coated in at least some areas, preferably on its outer faces and/or along the edges, with a waterproofing coating and wherein the plate of wood is formed of at least one layer of birch wood which is arranged in relation to the longitudinal and width directions of the panel with the wood fibers in a first direction and at least one layer of fir wood which is arranged in relation to the longitudinal and width directions of the panel with the wood fibers in a second direction, said two layers of wood being coupled together by chemical/physical adhesion along the faces of mutual contact.

According to one embodiment, said wooden plate can be made of at least three layers of which at least one central layer of fir wood positioned with the fibers of the wood in said second direction to which it is applied by chemical/physical adhesion on each of the two opposite faces of said central layer, at least one layer of birch wood positioned with the fibers of the wood in said first or third direction.

The choice of the orientation of the fibers of the different layers of fir and birch wood relative to the longitudinal orientation of the panel can be defined according to the conditions of use and therefore the mechanical stresses to which the panel is subjected.

In one embodiment, the orientation of the wood fibers of the central fir wood layer corresponds to the longitudinal direction of the panel, i.e. to the direction parallel to the longest side edge.

The orientation of the fibers of at least one of the birch wood layers, or the aforementioned first direction, can be parallel or not parallel to the orientation of the fibers of said central fir wood layer.

When two layers of birch wood are provided, each coupled to one face of the central layer of fir wood, the aforementioned first direction and the aforementioned third direction of orientation of the wood fibers of the first and second layer of birch wood respectively they can be parallel or not parallel to each other, and at the same time said first and said third directions can be parallel or not parallel with respect to said second direction of orientation of the wood fibers of said central layer of fir wood.

This configuration of the wooden plate in the form of at least two layers of a different wood and with the direction of the fibers parallel or not parallel to each other from layer to layer allows to increase the mechanical resistance of the wooden plate and at the same time increase the thickness and reduce the weight of the plate with the same thickness and/or mechanical resistance.

In fact, fir wood has a specific weight which is of the order of about <NUM>/m3 and is therefore of the order of about a third less than the specific weight of birch wood which is about <NUM>/m3 as further mentioned above.

The increase in thickness contributes not only to an increase in the intrinsic mechanical resistance of the plate and therefore of the panel, but at the same time allows the panel to be equipped with further accessories which, as will be seen below, improve the connection of each panel to a main structure and thanks to which a better and more rigid connection is generated a synergistic structural reinforcement of the mechanical resistance of the whole with respect to the mechanical resistance of the individual parts separated from each other.

Although the preferred embodiment described above provides for a single central layer of fir wood with the wood fibers oriented according to a second direction with respect to the longitudinal direction of the panel, i.e. parallel to the longest lateral edge of the same, different executive variants are possible thanks to which it is possible to combine different weights, different thicknesses and different mechanical resistances of the plate and therefore of the panel.

The external waterproofing coating of the wooden plate according to one or more of the embodiments described above can be made according to what is currently known in the state of the art.

An embodiment can provide for the waterproofing and/or scratchresistant coating of the panel thanks to a varnish, a lacquer or the like applied on the external faces and/or along the edges of the wooden plate.

A variant may provide that at least some of the edges and/or at least part of some of the perimeter edges or all the perimeter edges of the wooden plate are coated towards outwardly with a layer of plastic material applied by means of chemical-physical and/or also mechanical adhesion either to said edges or to said portions of edges and having a predetermined width and a predetermined elasticity.

Another possible alternative can provide that the waterproofing of the wooden plate takes place thanks to the application to the two external faces of the same of a plate or a layer of resin coupled by chemical-physical adhesion and/or other processes such as spreading or the like. Perimeter extensions of the said resin plate/s or of the said resin layer/s can be folded against the perimeter edges of the wooden plate or against part thereof and fixed to the material of the wooden plate of the said edges and/or between them by chemical-physical adhesion.

Alternatively, said layers of resin or plastic material or said plates of resin or plastic material coupled to the faces of the wooden plate are combined and fixed by means of chemical-physical and liquid-tight adhesion to coating layers in resin and/or plastic material of the edges of the wooden plate.

Said panel has at least one or more points of the extension on the faces at least one engagement seat in the form of a hole being provided in conjuction with each hole a corresponding locking pin having an externally threaded stem and being the diameter of the hole and the diameter of the corresponding pin and of the external thread commensurate with each other in such a way as to tighten said pin in said hole by screwing.

In a possible variant, the hole can be at least partially provided with an internal thread corresponding to the external one of the pin.

In a variant embodiment, since the plate is made of wood, the threading of the pin is of the self-tapping type, that is, which notches upon screwing the internal thread in the walls of the hole, the diameter of the hole being commensurate with the minor diameter of the external threading of the pin.

One embodiment provides at least one hole for at least one pin in correspondence with each corner area of the panel and in a recessed position with respect to the perimeter edges of the panel to a predetermined extent.

According to one aspect of the present invention, the containment formworks for concrete pouring are known and are formed by a plurality of panels which together form the concrete containment walls with the desired shape and dimensions and which panels are mounted so as to form said containment walls in a main structure.

The formworks are generally provided with a metal main structure in the form of frameworks made up of uprights, spars and crossbars, according to various geometries and on which the panels are arranged side by side so as to form a continuous containment wall for the mass of concrete.

Each panel is rested in one or more areas thereof on support brackets, while the panels are currently fixed in position by means of traditional screws or nails.

These traditional type screws or nails ensure that the individual panels are held in position, however they do not generate a mechanically rigid fastening between each panel and the main structure, such that the panel and the structure synergistically cooperate to increase the resistance mechanical than they would have if considered separately or constrained in the mildest mechanical way according to the state of the art.

According to a further aspect of the present invention, a formwork according to claim <NUM> is provided.

According to one embodiment, a hole is provided in the panel in each of the corner areas and in a recessed position towards the center of the panel in a predetermined distance with respect to the perimeter edges of the panel which form said corner area.

Said pin has an enlarged head with respect to the hole in the panel and in the corresponding support bracket, and said enlarged head is superimposed on a perimetric delimiting band of said through hole in said support bracket.

The diameter of the threaded stem of said pin is about <NUM>, while the depth of penetration of the same into the panel is expected to be about <NUM> and the thickness of the panel is therefore greater than said depth of penetration.

According to a preferred embodiment, said formwork is provided in combination with a panel made according to one or more of the embodiments and variants described above.

In one embodiment the formwork is provided in combination with a panel for the construction of containment walls which panel is composed of a base body constituted by a sheet-like element cut to size and having a perimeter edge surface along which perimeter edge surface is provided with a protective perimeter edge of plastic material.

Preferably, said protective perimeter edge is made in the form of a single continuous piece.

Said peripheral protective edge can extend along all the perimetric edges of the panel or only along some of them and possibly also along only some areas of said perimetric edges.

Said edge can be made for example according to what is described in document <CIT>.

According to another feature, the invention comprises a combination of at least one panel and a main structure for panels for making containment walls for concrete pouring, in particular for concrete slabs or the like, in which the panel/s are made according to one or more any combination of the embodiments and variants described above, while the panels are arranged directly adjacent to each other and with the outer surfaces of the protective edges in contact with each other so as to form a wall containment essentially continuous, without signatures of the contact areas between adjacent panels and with substantial sealing of the concrete mass.

According to one embodiment, the framework is of the type comprising a main structure constituted by a plurality of vertical uprights for supporting a combination of parallel longitudinal beams and/or crossbars and main frames intended to rest with at least two opposite sides on two adjacent spars and/or crossbars parallel to each other and on which frames are respectively fixed in position a panel, each frame being provided with support elements for the corresponding panel which support elements come into contact with areas of one of the faces of the panel which are provided at a certain distance from the perimeter edges of the panel, while in the assembled condition the panels adjacent to each other in the longitudinal and/or transversal direction come into contact with each other and in a liquid-tight manner with the facing perimeter edges and then with the corresponding protective edges.

Thanks to the aforementioned characteristic, the panels are supported by the structure with their perimetric edges protruding outwards with respect to the supporting structures of the same and therefore they come into direct contact with each other along the facing edges.

In one embodiment, each or only some of the spars or crossbar for supporting a panel or alternatively all or only some support brackets, or only the spars or only the crossbar, or only the support brackets are provided in at least one point, preferably in two points spaced apart along said side member or said cross member, of a hole coinciding with a hole provided in the panel being for each through hole in the cross member and/or in the side member and for each - each coinciding hole in the panel provides a threaded pin for tightening said crossbar and/or said spar against said panel.

The invention has further characteristics which are the subject of the subclaims.

The characteristics of the invention and the advantages deriving from them will become clearer from the following description of a non-limiting executive example illustrated in the attached drawings, in which:.

With reference to <FIG> and <FIG>, a panel according to the present invention for making containment walls of formwork for concrete pouring, in particular for containment formwork for making concrete slabs or the like comprises a body of base <NUM> which consists of a shaped piece with predetermined dimensions and plan shape of an essentially flat plate. The base body has a multilayer structure which will be described below with reference to <FIG> and <FIG> and consists of a combination of wood layers which are made up of different types of wood and which are arranged oriented relative to each other with the prevailing direction of the wood fibers according to pre-established directions parallel to each other or crossed, i.e. not parallel, or perpendicular.

The base body <NUM> has a predetermined thickness d1 (<FIG>) and has a peripheral edge surface globally indicated with <NUM>. A protective edge <NUM> is applied along the peripheral surface <NUM> of the base body which adheres to an internal surface <NUM> to the edge surface <NUM> of the base body <NUM> with a shape fit and by chemical/physical adhesion.

The protective edge <NUM> is made as a single piece, i.e. the material of which it is made does not substantially present a solution of continuity and does not consist of different parts joined together upon application to the base body and/or even in an earlier moment.

The thickness S of the protective edge <NUM> is such that the outer surfaces of said essentially flat protective edge <NUM> extend at a certain distance from the surfaces <NUM> of the edge of the base body <NUM> and complete the shape of the base body to the shape essentially rectangular finished panel.

In the embodiment illustrated but not by way of limitation, the base body <NUM> can have corner areas shaped in such a way as to be recessed with respect to the rectangular plan shape that would be obtained by extending the straight sides of the edge of the base body <NUM> up to reciprocal point of incidence of the same. In this way, in the corner area, the protective edge <NUM> has a greater thickness than that S present in the straight sections.

The increase in thickness in the corner areas is made in order to increase the absorption by the protective edge of the impact forces in the event of the panel falling. The areas of greatest stress are those at the corners of the panel and therefore in these areas a greater thickness of the protective edge in the direction parallel to the faces of the panel ensures that the material of the protective edge can compensate for the deformations induced by the impact forces.

According to a further improvement, in the corner areas, while the protective edge <NUM> forms a vertex of a right angle, the edge of the base body <NUM> is rounded with a predetermined radius of curvature. As indicated by the circle C in <FIG>. This characteristic allows to generate a surface of progressive deflection of forces with the major component oriented in a perpendicular direction with respect to the edge surface of the base body <NUM> in forces in which part of the energy is deflected by the said component perpendicular to a component parallel or tangent to the surface <NUM> of the base body in the arcuate corner region.

With reference to a further characteristic which appears from <FIG>, the mutual contact surfaces <NUM> and <NUM> are shaped so as to have non-flat fronts of the surfaces of the edges of the base body <NUM> and of the protective edge <NUM>.

<FIG> shows a preferred embodiment, in which the cross section of the surface of the edge <NUM> of the base body <NUM> which is wedge-shaped and preferably symmetrically to a median plane of the base body <NUM> which is parallel to the faces thereof.

The protective edge <NUM> has a contact surface <NUM> with the surface of the edge <NUM> of the base body which has an exactly corresponding shape so as to also generate a precise shape coupling between the base body <NUM> and the protective edge <NUM> and therefore has a wedge-shaped groove of dimensions and shape exactly identical to the protruding one of the surface of the edge <NUM> of the base body <NUM>.

According to a first variant of the illustrated shape, the wedge-shaped shaping has a flattening at the vertex, i.e. at the tip of the wedge-shaped shape, both of the protruding part of the surface of the edge <NUM> of the base body <NUM>, and of the groove which forms the corresponding contact surface on the protective edge <NUM>.

According to another characteristic, protruding ridges or ribs <NUM> are provided along one or more of the mutual contact surfaces <NUM>, <NUM> between the protective edge and the peripheral edge of the base body <NUM> which protrude from the surface <NUM> of the edge of the base body <NUM> and which engage with precise shape coupling in corresponding recesses in the walls of the groove present in the protective edge <NUM>.

The ribs or teeth can vary both in number and in shape and help to give a mechanical gripping coupling of the protective edge <NUM> to the edge of the base body <NUM>. They can be different in areas both in size and in number and/or in shape and can be continuous and/or discontinuous. Of course, this therefore also applies to the corresponding recesses of the contact surface of the protective edge <NUM>.

The difference in thickness in the direction perpendicular to the edge of the base body <NUM> and parallel to the faces of the same, between the thinner area S1 of the protective edge <NUM> and the peripheral area of greater thickness S in correspondence with the faces of the base body <NUM> can be such that the area of greater thickness S is from <NUM> to <NUM> times the thickness of the area of lesser thickness S1, preferably from <NUM> to <NUM> times said thickness S1.

It should be noted that this feature also contributes to improving the protection of the edges at the two opposite faces of the panel since the inclined surfaces of the wedge-shaped of the edge <NUM> of the base body eliminate areas of high deformability such as edges and partially deviating the perpendicular components into shear components with respect to the edge, i.e. into components perpendicular to the panel faces.

As appears from <FIG>, the panel according to the present invention can include, in any combination with the characteristics previously described, also the characteristic according to which the thickness of the protective edge <NUM> is greater than the thickness of the base body <NUM> in a direction perpendicular to the faces of the same at least for part of the extension of the protective edge <NUM> both in the longitudinal direction of the thickness and in the direction perpendicular to the edge <NUM> of the base body <NUM>.

The greater thickness is distributed symmetrically with respect to the central median plane of the base body which is parallel to the faces of the same and determines that the protective edge <NUM> protrudes for at least part of its extension in measure d2 from both faces of the base body <NUM>. As is evident, the protruding surfaces of the protective edge <NUM> with respect to the faces of the base body <NUM> extend along a more external peripheral band of the protective edge <NUM> and for a thickness S1 in the perpendicular direction of the edge and parallel to the faces of the base body <NUM> which is an integer submultiple of the maximum thickness S of the protective edge <NUM>. The section included between the innermost limit of the protruding edge in measure d2 of the protective layer <NUM> and the edge of the base body <NUM> is made inclined and is indicated with <NUM>, while the external edge along which the protective edge <NUM> protrudes in measure d2 beyond the corresponding face of the base body <NUM> is indicated with <NUM>.

According to another characteristic, the thickness S1 of the bands <NUM> substantially corresponds to the thickness S1 of the protective edge <NUM> at the bottom of the coupling groove to the wedge-shaped shape of the edge <NUM> of the base body <NUM>.

Still according to an advantageous feature, <NUM> indicates cavities produced in the thicker region of the protective edge <NUM>. These cavities can advantageously be obtained by known gas injection technologies, as will be described in more detail below.

Thanks to these recesses the weight is lightened, the protective edge is made more elastically flexible and the material costs are reduced.

The cavities can be continuous or discontinuous and differ from each other in different regions of the protective edge <NUM>, both in terms of shape and size.

With reference to <FIG> and <FIG>, these show a panel which has an improved structure with respect to the panel of the state of the art. The base body <NUM> of the panel is composed of a wooden plate <NUM> which is made of a plurality of layers, at least two of different types of wood.

In the illustrated executive example, the wooden plate comprises a central layer of fir wood <NUM> to whose two faces a layer of wood <NUM> of birch wood is coupled.

The coupling of the wooden layers <NUM> and <NUM> to each other can take place using any type of adhesive which can be used according to what is known in the state of the art.

According to one embodiment, the layer <NUM> and/or one or both layers <NUM> can be made of solid wood or can be made of plywood layers or layers with a structure of the so-called lamellar type.

According to another embodiment, within each of the layers <NUM> and/or <NUM> the wood fibers of respectively fir and birch are oriented substantially uniformly according to a main direction, while between layer and layer <NUM>, <NUM> the wood fibers can be provided oriented in mutually parallel directions or in mutually not parallel directions, i.e. also crossed or perpendicular directions.

In combination with the above, it is also possible to provide that the fiber directions in the layer combinations are different between the birch wood layers <NUM> and the fir wood layer <NUM>, or that also the fiber directions of the two layers of birch wood <NUM> are different from each other.

According to still possible variants, it is possible to provide a greater number of layers which takes the form of an alternating arrangement of layers of different wood, for example, of three or more different woods, each with a predetermined direction of the wood fibers within the layer and identical to or different from the direction of the wood fibers relatively to one or more or all of the other layers.

As appears from <FIG> and <FIG>, the plate <NUM> is covered along its two external faces by a coating layer <NUM> which can be a waterproofing and protective coating, such as a lacquer, a resin, a varnish or combinations of these or which it can be a layer of a plastic material coupled by chemical/physical adhesion to the corresponding face of the wooden plate <NUM>.

Said coating layer/s <NUM> are connected by chemical-physical adhesion or by covering to the peripheral protective edges <NUM> which frame the perimeter edges of the central plate <NUM> and of the protective and sealing coating layers <NUM>.

Thanks to the provision of a laminated structure using different types of wood for the wooden plate <NUM> it is possible to obtain functional advantages of the panel aimed at optimizing mutually contrasting characteristics, such as weight, mechanical resistance to load and therefore to bending under load and the thickness of the plate.

In fact, each panel is installed by manual lifting and positioning and therefore must necessarily weigh as little as possible or in any case the weight must be limited to a maximum bearable value within the scope of safety regulations by human personnel.

However, the material to be contained, in particular for the construction of slabs, has relatively high specific weights, whereby the load resistance of the panel must be such as it prevents the panel from arching downwards under the action of the load.

By providing several layers of different types of wood, it is possible to provide layers with wood fibers oriented in different directions, even if not parallel to each other.

Preferably the central fir wooden layer <NUM> has a main direction of the fibers in the direction of the longitudinal axis of the panel itself, while the main direction of the fibers within at least one of the birch wood layers <NUM>, preferably both said layers are oriented perpendicularly to the main direction of the fibers within the central layer of fir wood.

Furthermore, since birch wood has a specific weight of about <NUM>/m3 while fir wood has a specific weight of about <NUM>/m3, it is possible to obtain a stratification of the plate <NUM> with several layers of wood each having a predetermined main orientation of the fibers which can be set so as to modify the mechanical resistance characteristics of the panel according to the required needs.

Furthermore, with the same mechanical strength with other panels, not only can the weight be lower, but by maintaining the same weight of the panel with respect to the panels of the state of the art, the panel according to the present invention can have a wood plate thickness <NUM> greater than that of state-of-the-art panels.

As it appears evident from <FIG>, this increase in thickness allows to obtain a better mechanical coupling of each panel to the support structure thanks to fastening means which can exert clamping forces such as to generate a mechanically rigid connection between the panels and the support structure.

<FIG> shows a structure for making a containment wall for formwork for concrete pouring, in particular for containment formwork for making concrete slabs or the like, of the type known in the state of the art and which comprises a main frame indicated by <NUM> in <FIG> and which comprises uprights <NUM> of which only the end part is shown and which support a combination of spars and crossbar. In <FIG> the structure has spars <NUM> which rest on a plurality of uprights <NUM> while the crossbars are part of an essentially rectangular frame <NUM> comprising head sides <NUM> parallel to the spars <NUM> and which are intended to rest on said spars by engaging with a support foot in an engagement seat <NUM>.

As it appears evident, each spar cooperates with a pair of sideby-side frames <NUM>, each of which rests with its head side <NUM> on the spar <NUM>. Each frame <NUM> carries a panel <NUM> fixed on its upper side according to one or more of the variants described with reference to the previous ones figures. The panels are arranged side by side and adhere flush against each other and sealed with respect to the poured concrete along the facing contact edges directly with the protective edges.

For this purpose the frames <NUM> are made of dimensions smaller than the external dimensions of the panels <NUM>, both in the longitudinal and in the transversal direction and are mounted on the corresponding frame essentially in a central position with respect to the same so as to protrude to a predetermined extent on all the four sides and to a substantially identical extent by the frame <NUM>, at least on the two mutually opposite sides.

In the assembled condition, therefore, the panels <NUM> form a continuous containment plane by adhering directly to each other and thanks to this they reduce the traces or imprints of the joints between panel and panel which, on the other hand, occur in currently known formworks.

As it appears evident, that the structure comprising the combination of frame and panel can also be very different in terms of configuration of the individual parts, the only essential characteristic being the dimensional relationship between the panel and the support frame of the same and the panel and the spans between the support beams of the panel when for example a frame <NUM> is not provided, but the panel is mounted directly on a frame.

<FIG> and <FIG> show the improvement of said structure according to <FIG> in combination with panels of increased thickness according to the present invention.

As it appears evident, each panel is provided in correspondence with the elements <NUM> for supporting the frame <NUM> with an engagement seat for a threaded pin <NUM> for tightening the panel against said support element <NUM>. In particular, the support element has a through hole or opening which coincides with the clamping seat of the pin <NUM> and which hole or which opening has a diameter smaller than the diameter of a head <NUM> of the corresponding looking pin <NUM>. The latter has an engagement stem <NUM> which cooperates with the seat in panel <NUM>.

The pin is made as a threaded pin with a threaded stem <NUM> and an enlarged head <NUM>. The stem <NUM> having an external diameter smaller than the through hole in the corresponding support element <NUM> and commensurate with the seat in the panel <NUM>.

Said seat is an engagement hole of the threaded stem <NUM>, which hole can have a diameter corresponding to the smaller diameter of the stem <NUM> and whose wall has no internal thread, being the threaded pin <NUM> of the self-tapping type,.

Alternatively, the engagement hole of the threaded pin <NUM> can be provided with a pre-established internal thread and commensurate with the external thread of the threaded pin <NUM>.

A combination of a through hole coinciding with an engagement seat in the panel <NUM> for a looking pin <NUM> can be provided in each support element <NUM> or more than one through hole coinciding with an engagement seat in the panel <NUM> for a looking pin tightening <NUM> can be provided for each support element <NUM>, this substantially depending on the configuration of the frame <NUM> in relation to the shape, number and dimensions of the support elements <NUM>.

As it appears evident, the increased thickness thanks to the combination of layers of different woods for the plate <NUM> allows a combination of orientations of fibers within the thickness of the panel which is functional to optimizing the mechanical behavior of the panel in relation to the load resistance, moreover, the possibility of increasing the thickness without increasing the weight of the panel is obtained, allowing the use of clamping screws with which each panel is mechanically fixed in a rigid manner to the support structure.

Differently from what occurs for known panels, in which the panels are simply connected to the main structure by means of nails or screws which generate a position constraint, but not a mechanically rigid connection, in the case of the panel of the present invention, the increased thickness allows engage a threaded pin with a sufficient tightening force to generate said rigid mechanical constraint between the panel and the support, since the greater thickness allows a greater number of thread turns to bite the wooden material of the plate <NUM>, thus dividing the pressure load and the forces on a greater number of threads and therefore to maintain the stress below the limit force beyond which a breakage of the internal thread of the hole is caused.

According to one embodiment, the birch wooden layers <NUM> consist of birch multilayer in the form of with birch wood layers of <NUM> thickness which are coupled with their main direction of the fibers cross each other and in which the layers are glued together, forming a defined final thickness.

An example provides that the <NUM> birch multilayer plates have thicknesses of about <NUM> to <NUM>.

Thanks to the central layer <NUM> in fir wood, an increased thickness has been obtained, without increasing the weight or keeping the increase in weight limited, and allowing metal pins with a diameter of approximately <NUM> to be inserted on at least four perimeter points of the panel and with a depth of approximately <NUM> which have been anchored in the wooden panel for tightening the metal frame to it, with the function of resisting a shear force between the metal frame and the wooden panel which synergistically increased the resistance metal to the load compared to that of the individual separate parts, especially as regards the load resistance of the panel.

This action is also added to the action of fixing the panels in position obtained by means of traditional screws.

As it appears evident from the figures, and as previously indicated, the combination of at least one layer of birch wood with at least one layer of fir wood, and in the preferred embodiment, of a central layer of fir wood which is coupled on its two opposite faces to at least one layer of birch wood, allows the wooden part of the panel to be given greater mechanical strength in relation to engagement with the threading of the pins. In fact, the external thread of the pin bites both at least birch wood, which is a relatively hard wood, and fir wood, which is a relatively soft wood, at the same time.

Thanks to this, the resistance to a stripping of the internal thread made in the wood is reduced since part of the mechanical tightening force discharged on the threads is expected in the area of the birch wood and for the entire thickness of at least one layer of said wood.

When the fir wood layer has a greater thickness than the birch wood layer, the lower mechanical strength of the internal thread of the furnace part extending into the thickness of the fir layer can be compensated by a greater thickness of this layer. Thanks to the lower weight of fir wood, compared to birch wood, this greater thickness can guarantee excellent mechanical resistance of the thread in the condition of engagement with the external thread of the pin and at the same time a containment of the overall weight below the weight that the panel would present if it were made entirely of two layers of birch wood with the same thickness.

In the embodiment which provides two layers of birch wood which are coupled respectively to one of the two opposite faces of a central layer of fir wood, as shown in <FIG> and <FIG>, the screw engagement hole of the pin can extend for a depth such as to pass through a layer of birch wood, the central layer of fir wood and penetrate at least for part of the thickness of the same into the second layer of birch wood on the opposite face of the central layer of fir wood, ending at a predetermined distance from the face seen of said second layer of birch wood and therefore remaining embedded in the same.

Claim 1:
Panel for the construction of containment walls of formwork for concrete pouring, in particular for containment formwork for the construction of concrete slabs or the like, which panel comprises at least one wooden plate (<NUM>) or one plate comprising wood, which wooden plate (<NUM>) or which plate comprising wood is coated in at least some areas, preferably on their outer faces and/or along the edges with a waterproofing and/or protective coating (<NUM>, <NUM>) and wherein the wooden plate (<NUM>) or the plate comprising wood is formed of at least one layer (<NUM>) of birch wood which is arranged in relation to the longitudinal and width directions of the panel with the wood fibers in a first direction and at least one layer (<NUM>) of fir wood which is arranged in relation to the longitudinal and width directions of the panel with the wood fibers in a second direction, said two wooden layers (<NUM>, <NUM>) being coupled together by means of chemical/physical adhesion along the faces of mutual contact and the said first and said second direction can be parallel or not parallel to each other and
wherein said panel has in one or more points of one extension of the faces of the panel, at least one engagement seat in the form of a hole, being provided in combination with each hole a corresponding locking pin (<NUM>) having a stem (<NUM>) threaded externally and the diameter of the hole and the diameter of the corresponding pin (<NUM>) and of the external thread of the stem (<NUM>) being commensurate with each other in such a way as to tighten the said pin in said hole by screwing, while said pin (<NUM>) has at one end of the threaded stem (<NUM>), a head (<NUM>) which is radially enlarged with respect to the threaded stem (<NUM>) and/or to the engagement hole in the panel,
and
said hole is at least partially provided with an internal thread corresponding to the external one of the pin or the thread of the pin (<NUM>) is of the self-tapping type, that is, which notches upon screwing the internal thread in the walls of the hole, the diameter of the said hole being commensurate with the minor diameter of the external thread of the pin and
the diameter of the threaded stem of said pin is approximately <NUM>, while the depth of penetration of the same into the panel is approximately <NUM> and the thickness of the panel is greater than said depth of penetration.