FR2580063A1 - Apparatus for drying wood veneer - Google Patents

Abstract

Method for drying wood veneer, characterised in that it consists in routing the veneer to be dried along a sinuous path along which it follows a portion of the periphery of two heated drums driven round in reverse directions, so that it is dried by direct contact successively on its two faces.

Description

 The present invention relates to a new apparatus for drying thin wood veneers, making it possible to benefit both from an improvement in the quality of the product obtained and from an increase in energy efficiency.

 We know that the thin wood veneers used in the plywood and furniture industries are necessarily produced in sheets, 0.5 to 5 mm thick from very wet wood, which therefore requires a drying operation. before their implementation.

Currently, two techniques are used for this purpose.
- The first technique consists in operating continuously, by continuous scrolling of the veneers through an enclosure with circulation of hot air.

 The second, discontinuous technique consists in bringing the veneers step by step between the plates of a heating press.

 This second technique presents vis-a-vis the first the advantage of a higher energy yield, resulting from the direct contact of the veneers with the hot metallic surfaces. On the other hand, in addition to the disadvantage of being discontinuous, it has that of involving handling difficulties, as well as of causing rapid fouling of the material.

 The present invention relates to a method and an apparatus eliminating all the drawbacks of the aforementioned prior techniques, while benefiting from their advantages.

 This process essentially consists in continuously moving the veneers to be dried along a winding path along which they follow a portion of the periphery of two heated drums rotating in opposite directions, so as to be dried successively on their two faces.

 The apparatus for implementing this process comprises, in a thermally insulated enclosure, a pair of drums rotating in opposite directions around parallel axes, and two endless pressing strips made of wire mesh or similar material, having the dual role of apply the plating along each of its faces against each of said drums and ensure the evacuation towards the outside of the water vapor resulting from drying.

 This therefore benefits both from uniform and practically simultaneous drying on both sides of the veneer, and from the continuous nature of the process without any handling or cleaning problem, scraping or brushing accessories ensuring permanent cleaning and the elimination of deposits which may occur both on the drums and on the press belts.

 The invention will now be described in more detail, with reference to the accompanying drawing which illustrates the principle of the process.

 In this drawing, there are shown, housed in an enclosure 1, two drums 2 and 3, driven in rotation in opposite directions by means not shown around parallel axes 4 and 5, and into which is introduced a heating fluid bringing their lateral surface at a predetermined temperature.

 A veneer to be dried P runs in this enclosure between an inlet E and an outlet S, winding successively.

around each drum, on the surface of which it is pressed by two continuous pressing strips 6 and 7, guided and held in tension by return rollers C1 ... C4; for each of these bands, a jack exerts on one of these rollers, respectively C5 for the band 6 and C14 for the band 7, a traction, respectively a tension,. of shackle to ensure the appropriate tension on each band, resulting in an appropriate contact pressure between bands and drums.

 The wet veneer to be dried entering the enclosure 1 through the inlet E is caught by the strips 6 and 7 at the level of the return cylinder C1, then pressed by the strip 7 against the drum 3 between the return cylinders Cg and C13, then taken up and pressed against the drum 2 by the strip 6 between the return cylinders C3 and C4, and finally driven between the strips 6 and 7 to the outlet S of the enclosure 1.

 It should be noted that, the two drums 2 and 3 rotating in opposite directions in the portion of path Cg-Cl3, one face of the cladding is in contact with the metallic heating drum 3, while in the portion of path C3-C4, counts -due to the reversal of the direction of travel of the veneer, it is the other face of the veneer which is in contact with the metallic heating drum 2.

 The strips 6 and 7 are made of a flexible material resistant to elongation and to heat, and comprising perforations ensuring the evacuation of moisture from the panels, and preferably in wire mesh.

 Of course, the temperature and the speed of travel of the veneer, that is to say the speed of rotation of the drums, are adjusted as desired according to the initial humidity of the veneers to be dried, and the residual humidity. desired.

 In addition to the advantages already mentioned, it can be noted that this process ensures a practically total absence of wood shrinkage and flatness deformations.

Claims (3)

CLAIMS. 1. Method for drying the wood veneers, characteristic in that it consists in making the veneer to dry follow a sinuous path along which it follows a portion of 1 periphery of two heated drums rotating by motorization in opposite directions , so that it is dried by direct contact successively on both sides. 2. Apparatus for drying wooden veneers, characterized in that it essentially consists of two heated drums rotating by motorization in opposite directions around two parallel axes and around a portion of the periphery of each of the drums, the cladding being pressed by an endless band through which the moisture resulting from the heating of the cladding is removed, this by any suitable means, for example an extraction fan. 3. Apparatus according to claim 2, characterized in that the endless bands are made of wire mesh.