A PROCESS FOR FORMING FLOOR BOARDS ON A PLYWOOD BASE AND A BOARD THUS REALIZED

Abstract: The board for wooden floors consists of an upper layer (21) with viewable face, mostly of valuable wood, matched with a lower layer (23) having plywood construction; the valuable layer making up the viewable face, has a longitudi­ nal fibres pattern and the lower plywood layer has trans­ verse grooves (25) being thus at right angles to the fibres pattern of the upper layer (21); the external sheets (23A, 23B) of this lower plywood layer have their fibres at right angles to those of the valuable layer (21) and therefore, parallel to the grooves (25).

Description: The invention refers to a development of Italian prior patent No. 9456 A/84 filed by the same inventor on 11 July 1984. According to the prior patent, a board for wooden floors is made up of an upper layer with viewable face, mostly of valuable wood, matched with a lower layer having a plywood construction and thus with sheets having the fibres pattern both orthogonal and parallel to that of the valuable layer; the valuable layer _ intended to form the viewable face _ has a longitudinal fibres pattern and the lower plywood layer has transverse grooves being thus orthogonal to the fibres pattern of the upper layer. In the preferred embodiment of the prior invention patented with No. 9456 A./84, the support layer consists of a plywood structure whose external sheets have longitudinal fibers, parallel to those of the layer of prestige wood; it is understandable that in this condition both the layer of prestige wood and the top sheet of the support panel will deform in the same transverse direction with the result that the wood strip warps (where, by warping, the curving of the width of the strips is intended). It follows, that in the case of a particularly dry environment, this prejudical phenomenon may cause the strip of prestige wood to become convex, or alternatively, in a very humid environment, concave. The grooves were expected to improve the overall elasticity of this wooden strip with respect to possible excessive longitudinal strain. A panel disclosed in French patent No. 659803 is produced with a supporting composite structure on which a very thin sheet of covering is veneered whose fibres are orthogonal to those of the support panel itself. The parallel position of the fibres of the four sheets of this support layer, does not make the size of the support stable. According to the present invention, the lower layer has the fibres patterns of the external sheets on thicknesses perpendicular to those of the upper valuable layer and, therefore, parallel to the grooves. In a possible embodiment, the lower plywood layer has five sheets or thicknesses, the intermediate thickness and the two external ones of said lower plywood layer having fibres being transverse in respect to those of the upper valuable layer. According to another feasible embodiment, the lower plywood layer has the two outer thicknesses or sheets with a fibres pattern transverse in respect to that of the upper valuable layer, and the intermediate sheet _ single or double _ with a fibres pattern parallel to that of the upper valuable layer. The proposed solution is particularly suitable for boards being relatively wide in respect to their length. The above mentioned transverse grooves may be deeply cut to involve at least most of the thickness of the lower layer. More particularly, in the grooves may have a width of the order of a least 3 mm. and such a depth as never to penetrate the upper layer and not to indent the adhesive veil which unites the valuable wood board to the lower plywood layer. In case of boards having mounting joints, the side cogs and slots for the installation joint are formed in the lower plywood layer. The invention will be better understood by following the description and the attached drawing which shows a practical non-limitative exemplification of the same invention. In the drawing: Fig. 1 shows a perspective view of a board according to a first embodiment, with cutaway parts and without joints; and Fig. 2 shows a much enlarged and fragmentary cross section of a board according to a second embodiment, with a five-layer plywood. According to the drawing, a floor board is made up of an upper layer (21) of valuable wood and a lower layer (23) consisting of two external plywood sheets (23A, 23B) and two intermediate sheets (23C). The fibres pattern of the layer (21) and of the sheets (23C) is longitudinal, that is, lying in the direction fL of the board length; the fibres pattern of sheets (23A, 23B) is orientated in the transverse direction fT. In the drawing, the cross section taken on planes perpendicular to the fibres are conventionally squared and the cross-sections parallel to the fibres pattern show a wide, wavy hatching. In the plywood layer (23A, 23B, 23C, 23C), transverse grooves (25) are cut out parallel to the direction fT and suitably spaced apart for the function already pointed out. The depth of the grooves does not go beyond the glueing surface (27) between 21 and 23B, and may also not go beyond the glueing surface (29) between 23B and 23C. The boards have rib projections (30) and channel recesses (32) _ shown only in Fig. 2 _ to form the joints. Both the projections,and the channels are formed from the layer (23). Fig. 2 shows a five-layer plywood, a central layer (23E) being interposed between the thicknesses or sheets (23C); the sheet or thickness (23E) has the fibres pattern parallel to that of thicknesses (23A and 23B). The preparation of the above described material is similar to that point out in the above mentioned prior patent. It is understood that the drawing shows an exemplification given only as a practical demonstration of the invention, as this may vary in the forms and dispositions without departing from the scope of the idea on which the same invention is based, and as disclosed in the attached claims.

Claims: 1. A board for wooden floors consisting of an upper layer (21) with viewable face, mostly of valuable wood, matched with lower layer (23) having a plywood contruction and thus with sheet having the fibres pattern both orthogonal and parallel to that of the valuable layer (21), the valuable layer (21) intended to form the viewable face having a Iongitudinal fibres pattern and the lower plywood (23) having transverse grooves (25) being therefore orthogonal to the fibres pattern of the upper layer (21), characterized in that the lower layer (23) has external sheets or thicknesses (23A, 23B) with the fibres pattern perpendicular to those of the upper valuable layer (21) and thereby parallel to the grooves (25). 2. Board for floors according to the precedent claim, characterized in that the lower plywood layer (23) has five sheets or thicknesses, the intermediate thicknesses (23C) and the two external ones (23A, 23B) of said lower plywood layer (23) having fibres pattern transverse in respect to that of the upper valuable layer (21). 3. Board for floors according to claim 1, characterized in that the lower plywood layer (23) has the two external sheets or thicknesses (23A, 23B) with fibres pattern being transverse to that of the upper valuable layer (21), and the intermediate sheet or thickness (23C) _ single or double _ with a fibres pattern being parallel to that of the upper valuable layer (21). 4. Board for floors according to claims 1 to 3, characterized in that the grooves (25) have such a depth as to involve most of the thickness of the lower plywood layer (23). 5. Board for floors according to claim 1 to 4, characterized in that the grooves (25) have a depth of the order of a least 3 mm. and such a depth as never to pentrate the upper layer (21) and so as not to indent that adhesive veil which unites the board to the lower plywood layer (23). 6. Board according to claim 1 to 5, characterized in that the side clogs (30) and slots (32) for the installation joint are formed in the lower layer (23).

Inventors: GIORDANO, GUGLIELMO
Applicants: VIAROM S.R.L.
Application year: 1986
Main classification: E04F15
IPC codes: E04F15