EP0914527A1

EP0914527A1 - Method and apparatus for manufacturing hollow channel boards

Info

Publication number: EP0914527A1
Application number: EP97930548A
Authority: EP
Inventors: Edgar Gudmundsson; Harri Eela
Original assignee: Geca EHF
Current assignee: Geca EHF
Priority date: 1996-07-23
Filing date: 1997-07-23
Publication date: 1999-05-12
Also published as: JP2000514739A; FI101054B; CN1231711A; FI962942A0; FI962942A; CN1103846C; AU3446597A; WO1998003747A1

Abstract

The invention relates to a method for manufacturing structures having at least one hollow longitudinal channel arranged between outer board portions. Compressible and curable matrix material (4) is arranged between outer press panels (1, 2, 3) and separate core press expander means (6, 6a) are arranged in said material (4). Pressure is applied to said material by said core press expanders and said press panels (1, 2, 3). Said curable matrix material (4) contains a heat curable glue agent and said method further comprising the providing of a heat impact to said glue agent. The invention also relates to an apparatus for the manufacturing of a board or the like. Said apparatus comprises an arrangement of outer press panels (1, 2, 3) as well as channel core press expander means (6, 6a) located therebetween, for compressing said matrix material (4) to the final dimensions of said board (5). Means are arranged for transporting a pressurized hot fluid through channels, for contacting with said matrix material (4).

Description

Method and apparatus for manufacturing hollow channel boards

The invention relates to a method for manufacturing structures, especially for manufacturing boards, having at least one, preferably a multiple of adjacent hollow longitudinal channels arranged between outer board portions. Said method comprises the steps of providing a compressible and suitably curable matrix material between outer press panels and arranging, for each hollow channel, a separate core press expander means into said curable matrix material, and further expanding said core press expander elements to correspond to the final sectional dimensions of said channels while compressing said press panels to obtain the final outer dimensions of said structure, i.e. said board. The invention also relates to an apparatus for the manufacturing of a board made of a compressible matrix material and having one or preferably several adjacent, essentially longitudinal channels therein, said apparatus comprising an arrangement of outer press panels as well as channel core press expander means located there between, said core press expander means comprising wall portions which are movable outwards in an essentially parallel disposition with respect to a central axis of said expander means, for compressing said matrix material to the final dimensions of said board.

From Finnish patent application No. 943519 an arrangement is known, wherein a special press arrangement is used for manufacturing cement flake boards. Said arrangement comprises retractable core press expanders for forming hollow channels in the board to be manufactured and carbon dioxide is fed through said core press expanders for rapidly curing the cement binding agent .

Hollow channel cement flake boards are excellent for many structural purposes, but in some case there is a demand for a wood based material which is easier e.g. to cut and fix together using normal carpenter's tools and methods. Therefore wood chip boards of all kinds have their established position among carpenters and other craftsmen.

A common wood chip board comprises a mix of wood chips and a glue agent, and this matrix material is compressed between hot press panels to form a board having generally smooth opposite surfaces, the interior of said board being more or less compressed and coherent. The glue used for the production of wood chip board was earlier generally a formaldehyde based glue agent which was cured by heating, but nowadays less harmful glue components are used for the same purpose. Normally such wood fiber boards will have a thickness of 6 to 32 millimeters. Thicker boards constitute a problem since it is difficult to direct the impact of opposite press panels into the central portions of a relatively thick board, and thus a thick board will become structurally instable due to ins^*-ιfficient compression and bonding between the wood chips in the central portion of said board.

The purpose of the present invention is to widen the range of board types by introducing a wood chip board having hollow channels extending in the longitudinal direction between said opposite board surfaces. This also and especially includes boards having a relatively long distance between said opposite board surfaces, say e.g. 100 to 300 millimeters.

The object of the invention is achieved by using a method and an apparatus as described in the appended claims. The in^¬ vention generally comprises a modification of the arrangement described the above mentioned said Finnish patent application so that a glue agent is used instead of said cement based binding agent, and by introducing heating means for rapidly curing said glue agent while compressing said matrix material to the final shape of said board. Thus, the inventive method is characterized in that said curable matrix material comprises a heat curable glue agent and said method further com- prises the providing of a heat impact to said glue agent, for rapidly curing said glue agent prior to the removal of said core press expander means .

The invention will now be described in more detail with reference to embodiments disclosed the appended drawings, wherein

Figure 1 shows a schematic view of an arrangement in accordance of one embodiment of the invention,

Figure 2 shows a sectional view of a board manufactured in an alternative embodiment, wherein the core press expanders have a triangular cross section,

Figure 3 shows one embodiment of a core press expander means for making triangular hollow portions in accordance with Figure 2,

Figure 4 shows how the core press expander means according to Figure 3 is located within the matrix material prior to extracting said expander from a manufactured board,

Figure 5 shows an alternative embodiment of a core press expander means, and

Figure 6 shows the core press expander means in a retracted position within the matrix material.

Referring to Figure 1, the inventive arrangement generally comprises a lower press element 1, an upper press element 2, and, suitably, side press elements 3, 3a, for pressing, between the surfaces of said elements 1, 2, 3 and 3a, a curable matrix material 4 to form a hollow core board 5. Figure 1 further generally discloses multiple adjacent core press expanders 6, 6a arranged within said matrix 4 to form, upon consolidation of said curable matrix material , hollow core portions 7, 8 extending essentially longitudinally through said board 5 (see also Figure 2} .

The embodiment disclosed in Figure 1 comprises hollow core portions or channels of a generally rectangular sectional shape. An especially favorable embodiment of the invention, however, which is especially useful for structural purposes, comprises hollow channels 7, 8 having a generally triangular sectional shape, as disclosed in Figure 2. This triangular channel shape gives intermediate wall portions 9, 10 which are in pairs, respectively, inclined. The inclination of said wall portions 9, 10 actually gives the board an exceptionally high resistance against shearing, and thus such a board can advantageously be used for numerous structural purposes.

According to the invention said curable matrix comprises a basic material, which favorably is constituted of wood chips or the like material which preferably can be relatively easily worked with hand tools. During the inventive process, a heat curable glue agent is mixed into said basic material and thereafter cured so as to form, with said basic material, a coherent material. The inventive curing procedure thus comprises the step of heating the glue and/or the basic matrix to a considerably high temperature, while simultaneously applying pressure to said matrix material, for bringing said wood chips or the like into a close mutual contact and simultaneously compressing said material to its final shape.

The pressure is normally obtained by moving said upper press panel 2 towards said lower press panel 1. In this respect the press force generally corresponds to the forces normally used for manufacturing wood fiber boards. As such, the reference to 'upper' and 'lower', respectively, is intended only to be a simplifying statement for better understanding of Figure 1, and in some embodiments the main press panels may actually be arranged and orientated in a different manner, for example vertically. In the embodiment disclosed in Figure 1 said upper press panel 2 favorably is pressed towards said lower press panel 1 until it reaches side press panels 3, 3a. At this stage said side press panels 3, 3a are moved inwards to form, between them, the edge portion of said board 5. In the embodiments shown in Figures 1 and 2 said board edges favorably comprise groove and tongue formations 11, 12 as known per se .

The inner portion of said board obtains its hollow core structure using adjacent core press expander elements 6, 6a as known per se from said Finnish patent application No. 943519, but differing from said application the curing procedure now comprises heating at least said matrix material 4 to a considerably high temperature, for rapidly curing said glue agent interconnecting said wood chips. Typically the heat applied would be in the range of 100 to 200 °C, preferably about 180 to 190 °C.

As such, the heat can be applied in different manners, most of which actually also comprise a heating of at least the surface portions of some of said press means 1, 2, 3, 3a and 6, 6a. Said heating should be applied essentially simultaneously with said pressing. Depending on the glue agent the procedure actually is very rapid, usually about 5 to 10 seconds, favorably about 8 seconds, for each sectional millimeter of wall material. Thus, even a board having comparatively thick wall portions, i.e. a wall thickness of 32 millimeters, would demand a heating/pressing time only of about 3 minutes.

In practice there are several methods of applying heat to the matrix. Thus, one embodiment comprises heating means arranged in each of said press elements 1, 2, 3, 3a and 6, 6a. Said heating means are generally indicated by reference number 13 and may comprise electrical heating means, hot air blowing means or steam heating means or the like. One problem with the heating of only said pressure means 1, 2, 3, 3a and 6 is that external heating applied to said matrix material 4 also tends to dry up the matrix material and thus affect the consolidation of said glue agent in an unfavorable manner. Therefore an embodiment is preferred, wherein the necessary heat is applied by actually blowing a hot f--uid, for example hot air or steam, preferably supersaturated steam, into and preferably through said matrix material 4. This can be done, until the glue agent has set, suitably by pressing said fluid though the inner portions of at least every second core press expander 6 and suitably by retracting said fluid via the outer press elements and e.g. via the intermediate every second core press expanders 6a.

By using supersaturated steam for this purpose the temperature can be kept at a high level, while simultaneously enabling the adding of a liquid, e.g. water or an activating agent necessary for the consolidation process of the glue agent . According to a special embodiment of the invention said matrix material constitutes, at the beginning of the process, mainly wood chips or the like easily compressible base material, while components vital for curing the glue agent, in certain embodiments even at least some components of the actual glue agent itself, is fed into said matrix material in connection with said heating fluid.

While the core press expanders known from said Finnish patent application No. 943519 are useful as such for boards having hollow core channels of considerable dimensions, e.g. of the order 100 to 300 millimeters, said devices are unnecessarily complicated and sturdy for manufacturing boards of lesser dimensions. Figures 3 to 6 show examples of embodiments of core press expanders used for small diameter core channels. In these embodiments the main interest resides not actually in a high pressing force but in an easy contractibility of said expander from said hollow core channel after the consolidation of the board material. Thus, Figure 3 discloses a triangular core press expander element comprising wedge means 14, 15 which interact with wall elements 16 and corner wedges 17. Preferably said corner wedges 17 comprise a rounded end portion for smooth impact on said matrix mixture and for avoiding unnecessary strains in the final board product. Figure 3 further discloses channels 18 connecting the interior of said core expander element with the outside thereof. A fluid which is pressed into said interior, or extracted therefrom, will then pass through said channels 18. Since an absolute smoothness of the interior wall of the small size longitudinal hollow core channels 7, 8 of a board 5 usually is of minor importance there are, in accordance with one embodiment of the invention, generally longitudinal distribution channels 19 arranged at the outermost surface of said core press element. A central wedge beam 20 favorably also comprises a central bore and channels 21 interconnecting said bore to a space 22 between said wedges and said wall elements 16.

Figure 4 shows the core press of Figure 3 as positioned in a matrix material 4. According to the Figure the core press is shown in a contracted state and ready for withdrawal from the board 5. This stage of the procedure appears when said matrix material 4 has been consolidated. In the disclosed embodiment said central wedge beam 20 has been moved longitudinally with respect to the general extent of the core press expander. Thus the outermost parts are retracted from the inner walls constituting the hollow core portion 7, 8 of said board 5, as can be seen in the Figure. In one embodiment the retraction is facilitated by counter wedge means located suitably in connection with said wedges 15. When the core press expander is in its contracted state it can be withdrawn from the board 5.

The core press element disclosed in Figure 5 comprises, on the other hand, collapsible wall portions 23 which are interconnected via hinge means 24, 25 arranged at the corners and in the middle of the wall field. Said wall portions are slightly tiltable due to central rotatable eccentric means 26 acting e.g. directly on the inner surfaces of said wall portions 23, while flexible pushing means 27, for instance spring means or rubber bumpers, force said collapsible wall portions 23 to bend away from the hollow core walls when the eccentric pressing force is removed, thus facilitating the removal of said core press expander. This wall portion position is shown in Figure 6.

When hot steam is used as heating fluid the supplying of said fluid is favorably effected through the central portions of said core press expanders. Figure 5 discloses one embodiment wherein channels 28 connect the inner portions of the expander with the outer wall surfaces, thus facilitating the passage of heating and/or curing fluid from the inner of the core press expander to the surrounding matrix material, and, in a reverse direction, the passage of an overpressure generated e.g. by an adjacent core press expander into a core press expander having an underpressure. In the corner portions these effects are preferably achieved using generally loose fit hinge structures .

In another embodiment (not shown) the fluid is supplied through bores in the outer press panel elements 1, 2, 3 and 3a, the core press expanders acting as suction channels for maintaining underpressure conditions within the matrix material. In order to secure the applying of heat also to the wall portions located between adjacent core expanders an arrangement is then considered favorable, where at least every second core press will, at least momentarily, also supply hot fluid under overpressure.

In some embodiments it is considered sufficient only to maintain a stream of hot fluid directly through said core press expanders, e.g. through longitudinal bores 29, some of which are disclosed in Figure 5, without actually forcing any fluid into the actual matrix material . In such an embodiment said core press expanders can favorably be wrapped in a flexible socking made of rubber or the like material, for preventing any matrix material from entering into the press mechanism. In another embodiment of the invention the whole press apparatus is kept within hot overpressure conditions.

The inventive concept will produce a quite new type of boards, which as such can be used especially for structural purposes like erecting walls, for floors, ceilings and the like. The invention avoids the need of connecting of separate simple two-dimensional boards to form generally three dimensional structures. Still the advantage of easy workability can be maintained .

The board manufactured in accordance with the invention will also have a special advantage of high strength combined with light weight. Further, the dimensions of the board can be rather freely altered to suit the corresponding purpose. Thus, one favorable embodiment comprises a board which as such has the dimensions and strength directly adapted for a floor structure, the overall thickness being about 300 millimeters. Another board can, on the other hand, show dimensions suitable for general use as a wall element, wherein the thickness can be less than 100 mm.

It is to be observed that the specification above is only intended to give an example of favorable embodiments, and that the invention may be altered in many ways within the scope of the appended claims.

Claims

1. A method for manufacturing structures, especially for manufacturing boards (5), having at least one, preferably a multiple of adjacent hollow longitudinal channels (7, 8) arranged between outer board portions, said method comprising the steps of providing a compressible and curable matrix material (4) between outer press panels (1, 2, 3) and arranging, for each hollow channel (7, 8) , a separate core press expander means (6, 6a) in said curable matrix material (4) , and expanding said core press expander means (6, 6a) to correspond to the final sectional dimensions of said channels (7, 8) while applying a pressure on said press panels (1, 2, 3) to obtain the final outer dimensions of said structure, i.e. said board (5), c h a r a c t e r i z e d in said curable matrix material (4) containing a heat curable glue agent and said method further comprising the providing of a heat impact to said glue agent, for rapidly curing said glue agent prior to the removal of said core press expander means (6, 6a) from said hollow channels (7, 8) .

2. A method as defined in claim 1, c h a r a c t e r i z e d in that a mixture of wood chip material or the like and a glue agent is used as said compressible and curable matrix material

(4) , said glue agent favorably being a heat curable wood glue based, for example, on formaldehyde or corresponding components .

3. A method as defined in claim 1 or 2, c h a r a c t e r i z e d in maintaining, at least at the surface of said matrix material (4) , a temperature of 100 to 200 °C, preferably 180 to 190 °C, favorably for a period corresponding to 5 to 10 seconds, preferably about 8 seconds, for each millimeter of material in the compressed state corresponding to the final dimensions of said structure, i.e. said board (5) .

4. A method as defined in any one of claims 1 to 3, c h a r a c t e r i z e d in that said heat impact is effected at least partly via said press panels (1, 2, 3) and/or said core press expander means (6, 6a), suitably via the press wall portions (16, 23) of said means.

5. A method as defined in any one of claims 1 to 4 , c h a r a c t e r i z e d in that said heat impact is effected by blowing a hot fluid through the body of said curable matrix material (4) , and preferably extracting surplus fluid through at least some surface portions of said press panels and/or said core press expander means.

6. A method as defined in claim 5, c h a r a c t e r i z e d in forming said curable material in an essentially dry matrix state and adding humidity to said dry matrix at or after the compression procedure, suitably by utilizing the humidity of said fluid, favorably so that said glue agent and/or a hardener is fed in connection with or included in said fluid.

7. A method as defined in claim 6, c h a r a c t e r i z e d in using hot air and/or steam, preferably supersaturated steam as said fluid.

8. A method as defined in any one of claims 1 to 7 , c h a r a c t e r i z e d in performing at least a part of the procedure under overpressurized conditions.

9. An apparatus for the manufacturing of a board (5) or the like made of a compressible and curable matrix material (4) and having one or preferably several adjacent, essentially longitudinal channels (7, 8) therein, said apparatus comprising an arrangement of outer press panels (1, 2, 3) as well as channel core press expander means (6, 6a) located there between, said core press expander means comprising wall portions (16, 23) which are movable outwards and inwards in an essentially parallel disposition with respect to a central axis (A-A) of said expander means (6, 6a), for compressing said matrix material (4) to the final dimensions of said board (5), c h a r a c t e r i z e d in that means are arranged for transporting a pressurized hot fluid through said channels (7, 8) , for contacting with said matrix material (4) in order to activate and/or accelerate the curing process of a glue type curing agent interconnecting the individual particles or groups of particles of said matrix material (4) .

10. An apparatus as defined in claim 9, c h a r c t e r i z e d in that said transporting means are arranged for feeding and/or extracting said hot fluid through openings (18, 19, 22, 28) in the walls of said core press expander means (6, 6a) and/or through openings in the walls of said outer press panels (1 , 2 , 3) .