Method and device for drying, modelling and/or thermally modifying wooden parts

Abstract

The invention relates to a method for drying, modelling and/or thermally modifying wooden parts, comprising the steps of: a) arranging the wooden parts in a bath; b) filling the bath with a liquid, for instance paraffin or (linseed) oil, wherein the wooden parts are sealed from the ambient air by the liquid; c) the liquid being heated for some time, preferably between 100 C. and 300 C., for the purpose of drying, modelling and/or thermally modifying the wooden parts; d) removing the wooden parts from the bath. The invention also relates to a device for performing the method according to the invention for drying, modelling and/or thermally modifying wooden parts, comprising:a bath adapted to receive the wooden parts, which bath is intended to receive a liquid such as paraffin or (linseed) oilheating means for heating the liquid. Finally, the invention relates to a covering and rack as parts of the device according to the invention.

Claims

1. A method for heat treatment of wooden parts by transmitting heat to wooden parts in a low-oxygen environment, comprising the steps of: a) arranging the wooden parts in a bath; b) filling the bath with a liquid; c) the liquid being heated for some time for the purpose of drying or thermally modifying the wooden parts; d) removing the wooden parts from the bath; wherein, step a) comprises the sub-steps of: a1) placing a liquid-excluding covering with an open underside of heat-conducting solid material over the wooden parts; a2) holding the covering in position during steps b), c) and (d); and step b) comprises the sub-step of: b1) enclosing the open underside of the covering with the liquid thereby creating a liquid level under the covering that encloses a volume of air under the covering, whereby the volume of air is contained under the covering by the liquid and the covering such that an air pressure is created under the covering which ensures that contact between the liquid and the wooden parts is avoided during steps b), c) and d).

2. A method as claimed in claim 1, wherein in step a1) the wooden parts are first placed on an elevation.

3. A method as claimed in claim 1, wherein step a1) comprises the further steps of: a1-2) placing further wooden parts on a positioned covering; a1-3) placing a further covering over the further wooden parts of step a1-2); a1-4) performing steps a1-2) and a1-3) repeatedly until a desired height has been reached; and wherein in step a2) all coverings are held in position during steps b), c) and d).

4. A method as claimed in claim 1, wherein in step a1): a covering is in each case chosen wherein the upper side of the covering has a shape corresponding to the upper side of the placed wooden parts; and the upper side of the covering lies against the upper side of the wooden parts.

5. A method as claimed in claim 1, wherein in step a1): a covering is in each case chosen wherein the upper side of the covering has a shape corresponding to the underside of the placed wooden parts; and the upper side of the covering lies against the underside of the wooden parts.

6. A method as claimed in claim 1, wherein in step c) the shrinkage of the wood is taken into account when holding the covering in position.

7. A method as claimed in claim 1; wherein in step c) the sides of one or more coverings are pressed against the wooden parts placed under the covering.

8. A method as claimed in claim 1, wherein a profile and/or profiling is placed against one or more sides of the wooden parts.

9. A method as claimed in claim 1, wherein the liquid is cooled in controlled manner before step d) is performed.

10. A method as claimed in claim 9, wherein gas is injected into the bath under the wooden parts during cooling.

11. A method as claimed in claim 10, wherein steam is injected into the bath under the wooden parts during cooling.

12. A method as claimed in claim 9, wherein cool liquid is introduced into the bottom of the bath during cooling and hot liquid is discharged at the top of the bath.

13. A method as claimed in 1, wherein in step a2) holding the covering in position during steps b), c) and d) is achieved by placing a sufficiently heavy weight on the uppermost covering.

14. A method as claimed in claim 1, wherein in step a2) holding the covering in position during steps b), c) and d) is achieved by a clamping device.

15. A method as claimed in claim 14, wherein the clamping force is also used for the purpose of modelling the wooden parts, arranging a profile on the wooden parts, preventing splitting in the wooden parts and/or compacting the wood structure of the wooden parts.

16. A method as claimed in claim 1, wherein knots are first sunk into the wooden parts before step a).

17. A method as claimed in claim 1, wherein in step c) the liquid is heated to between 100 C. and 300 C.

18. A method as claimed in claim 1, wherein the liquid used in step b) is paraffin or oil or linseed oil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be further described with reference to a number of figures, in which:

(2) FIG. 1 shows a preferred embodiment of the device according to the invention in which the wooden parts have been placed in the device;

(3) FIGS. 2A, 2B, 2C and 2D show different views and embodiments of the covering according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(4) FIG. 1 shows a preferred embodiment of device 1 according to the invention in which the wooden parts W have been placed in device 1. The device comprises a bath 3 adapted to receive the wooden parts W. Bath 3 is provided with supply opening 4 for supplying liquid F and discharge opening 5 for discharging liquid F. The liquid F used cannot combust of itself and has a low evaporation, such as paraffin or (linseed) oil. Device 1 also comprises heating means for heating the liquid F. These are however not drawn, since the heating of liquid is a commonplace operation for the skilled person. The heating means can be adapted to heat the liquid directly. The heating means can also be arranged in or inside the one or more coverings, for instance thermal plates placed between the wooden parts. Device 1 comprises an elevation V which is arranged in optionally releasable manner on the bottom of bath 3. The elevation V is preferably manufactured from a grating such that liquid F can enter the space in elevation V. The first series of wooden parts W to be dried, modelled and/or thermally modified is placed on elevation V. Once the first series of wooden parts W has been placed, a covering 2 is placed over this series. Further series of wooden parts W are then placed alternating with further coverings 2. This is preferably repeated until the resulting stack reaches the vicinity of the edge of bath 3. Arranged on uppermost covering 2 are means for holding the placed coverings 2 in position, for instance a heavy weight P. Bath 3 is then filled with liquid F via supply opening 4.

(5) Because the coverings are liquid-excluding, no liquid can penetrate into the space in covering 2, although air cannot escape from this space either. The result is that the air pressure under covering 2 ensures that the wooden parts W do not come into contact with the liquid F.

(6) The liquid F is then heated to a known temperature and for a known period of time using means known in the field for the purpose of drying, modelling and thermally modifying wooden parts.

(7) Once the drying, modelling and/or thermal modifying of the wooden parts has been completed the wooden parts W are cooled, wherein the hot liquid F is discharged via discharge opening 5 and cool liquid F is simultaneously supplied via supply opening 4. The cool liquid F will absorb the heat still present in the wood W. This heat can then be reused.

(8) Following cooling of the wooden parts W all liquid F is removed from bath 3 via discharge opening 6. After the weight P has been removed, all coverings 2 and wooden parts W can then be taken out of device 1.

(9) FIG. 2A is a top view of the preferred embodiment of the covering according to the invention. The top view is formed by the upper side T, two downward sloping long sides S1 and two downward sloping short sides S2.

(10) FIG. 2B shows a cross-section of the preferred embodiment of the covering according to the invention along the line in FIG. 2A. This cross-section shows the upper side T and two downward sloping long sides S1.

(11) FIG. 2C is a perspective view of the preferred embodiment of the covering according to the invention in which the upper side T and the sides S1 and S2 are shown. The upper side T is preferably manufactured from a thin-walled metal which is easily deformable, such as aluminium or soft copper.

(12) It is recommended that the transitions between S1 and S2, between S1 and T and between S2 and T are gas and liquid-tight so that no air can escape from the space under the covering and no liquid can enter this space while the method according to the invention is being performed.

(13) FIG. 2D shows an embodiment of the covering in which the covering is provided with discharge pipes. These discharge pipes are arranged on the underside of the covering and have a height such that the discharge pipe protrudes above the liquid level. This largely prevents the gases coming out of the wooden parts from contaminating the liquid in the bath. There is a random number of discharge pipes. The discharge pipe can also be provided with a non-return valve for the purpose of preventing return flow of possibly condensed, contaminated gases.

(14) The above developed embodiment shows a single layer with wooden parts under a covering. The patent application is not however limited hereto. It is expressly also possible for the wooden parts to be stacked under the covering. It is also possible here for (thermal) plates to be placed between the wooden parts.

(15) The inventive method produces a homogeneously dried, modelled and/or thermally modified wood, whereby the method qualifies for known certification, such as KOMO certification.

(16) Using the inventive method and device it is possible to thermally modify thick wooden parts without the wooden parts being deformed or the liquid being absorbed into the wooden parts. The method hereby produces for instance wood suitable for manufacturing door/window frame parts, wherein the wooden parts may not be warped, must have a relatively great thickness, the wooden parts must preferably have a high durability class (for instance durability class 1 or 2 in accordance with NEN-EN 350-1) and must be suitable for painting.

(17) In an economic preferred embodiment of the device according to the invention the one or more baths for application of the method according to the invention are provided with heat-exchanging means for absorbing the heat of the bath, wherein the heat-exchanging means comprise a heat-absorbing liquid or a gas. The liquid in the one or more baths can have a differing temperature, but can also have the same temperature. The wooden parts which have undergone a heat treatment in a bath are placed with covering in a subsequent bath for cooling purposes, wherein the liquid in this bath has a lower temperature than the liquid in the preceding bath. The heat of the wooden parts is hereby transmitted in simple manner to the liquid in the bath, which then transmits the heat to the heat-exchanging means.

(18) The heat-exchanging means are preferably formed by a heat-exchanging bath filled with a heat-absorbing liquid or a gas. The baths are placed in the heat-exchanging bath.

(19) In addition, the heat-exchanging means can be formed by one or more conduits and/or reservoirs which are placed round or in the one or more baths. The conduits and/or reservoirs here comprise the heat-absorbing liquid.

(20) In another economic preferred embodiment of the device according to the invention, wherein energy is also recovered, the device is provided with a plurality of successive baths, wherein the liquid in the subsequent bath has a higher temperature than in the preceding bath. By immersing the wooden parts with covering in successive baths, the wooden parts will in each case absorb heat and become warmer. After drying and/or modification/modelling has taken place at higher temperatures (between for instance 100 and 300 degrees), the wooden parts with covering can be immersed in increasingly colder baths so that the heat absorbed by the wooden parts is returned to the liquid in the baths, whereby an enormous energy-saving is realized. It has been found in practice that the energy-saving increases with the number of baths.

(21) Each bath is preferably provided with two compartments separated by liquid-tight separating walls, wherein both compartments are filled with a liquid. The first compartment is preferably filled with a cheaper liquid than the second compartment. The first compartment is adapted to heat the wooden parts with covering placed in the first compartment. The second compartment is adapted to cool the wooden parts with covering placed in the second compartment. The liquid-tight separating walls are adapted here to transmit the heat absorbed by the liquid from the second compartment to the first compartment.

(22) Each bath is preferably provided with heat-exchanging means as is described above.

(23) The steam and possible other gases released during drying and/or thermal modifying of the wooden parts can be recycled within and/or outside the process using known heat exchanger techniques.

(24) In a further preferred embodiment of the covering according to the invention the covering is provided with one or more supply pipes for adding gases (for instance acetic anhydride) to be suctioned in via the underside of the covering and/or to keep the pressure high enough during cooling so as to avoid liquid contact.

(25) During the process of drying and/or thermal modifying of the wooden parts reservoirs with means for supplying gas, such as acetic anhydride or paraffin, floating under the covering or arranged on the inner side of the covering, can also supply vapour to be suctioned into the wooden parts.