WO1996003263A1

WO1996003263A1 - Method and apparatus for manufacturing structures, especially boards, and the use of these boards

Info

Publication number: WO1996003263A1
Application number: PCT/FI1995/000406
Authority: WO
Inventors: Edgar Gudmundsson
Original assignee: Eela, Harri
Priority date: 1994-07-27
Filing date: 1995-07-26
Publication date: 1996-02-08
Also published as: BR9508442A; EP0796165B1; RU2162407C2; EP0796165A1; EE03957B1; EE9700027A; PT796165E; FI104240B1; NO970286D0; ES2173960T3; FI104240B; DE69525965D1; DE69525965T2; JPH10502027A; NO970286L; FI943519A; DK0796165T3; NO311709B1; ATE214655T1; AU2983695A

Abstract

The invention relates to a method and an apparatus for manufacturing cement flake boards (7) having hollow channels (10) arranged between outer board portions (8). A mix (11) comprising a fibre material and a cement binding agent is provided between outer press panel elements (5, 6), subjected to an outer pressure and rapidly cured under the influence of carbon dioxide gas. At least one separate core press expander element (3) is arranged between said outer press panel elements (5, 6), and prior to the curing said mix (11) is subjected to an inner pressure by expanding said core press expander element(s) (3) inside said mix (11) between said outer press panel elements (5, 6).

Description

METHOD AND APPARATUS FOR MANUFACTURING STRUCTURES ESPECIALLY BOARDS, AND THE USE OF THESE BOARDS.

The present invention relates to a method for manufacturing structures, especially for manufacturing boards having at least one, preferably a multiple of adjacent hollow channels arranged between outer board portions, said method comprising the providing of a mix mainly comprising a fibre material, a cement based binding agent and an activating liquid between outer press panel elements for subjecting said mix to an outer pressure, as well as a rapid carbon dioxide curing of said cement based binding agent by subjecting said mix to the in¬ fluence of carbon dioxide gas. The invention further relates to an apparatus for the manufacture of cement flake boards or the like of a hollow channel board type, said apparatus com¬ prising outer press panel elements suitably operable to com¬ press, between them, a mix mainly comprising a fibre material, a cement based binding agent and an activating liquid, which mix in a cured state defines said board, and carbon dioxide injection means for injecting carbon dioxide into said mix in order to perform a rapid curing of said cement binding agent. The invention also covers the use of a product manufactured in accordance with the invention.

Prior art defines several methods for manufacturing board like structures from concrete or the like stabilizing material. Such structures are used especially in the building industry for on-site erecting of buildings. Usually such methods com¬ prise molding wet concrete in a desired form, compacting the concrete using vibrating means for lowering the internal friction of the concrete, and curing the concrete simply by using sufficient time, alternatively by the addition of cer¬ tain curing additives or by increasing the temperature. The resulting product will usually have opposite planar surfaces. In some cases the product also will comprise hollow portions, for making the product lighter or for saving some concrete. In a hollow-core slab several adjacent hollow portions extend through the whole slab. In some cases such hollow portions are filled with insulating material and/or used as lead-through passages for piping or the like.

The object of the present invention is to achieve such a pro¬ duct in a manner, whereby the product may be manufactured in a very rapid process, the resulting structure still having all the necessary properties needed especially in the erecting of buildings, such as one family houses or the like, preferably of a modular size. A special object of the invention is a complete building system comprising modular type hollow ele¬ ments made of a cement-woodchips mix, which may preferably be produced from readily available materials in most countries. The system comprises the use of hollow slab type elements preferably having a full wall height of about 2.4 meters in arbitrary lengths of up to some 10 to 15 meters. The thickness of such an element is preferably about 200 mm, and the element itself is of a hollow frame type having composite plates forming generally homogeneous outer/inner surface portions interconnected by relatively thin transverse webs. In order to meet any structural demands it should be possible to pre-deter- min the exact position and extent of the hollow channels, so that the wall thickness and the location of the intercon¬ necting webs at any time can be prearranged in accordance with the results of any necessary structural calculations. The arrangement should further be such that the position of the neutral axes of the respective mix portions constituting the main parts of the structure can remain essentially in their original positions, which feature is especially important when a rapidly setting mix is used.

According to the inventive system an entire building, in¬ cluding floor, ceiling and roof, consists preferably of one single type of a hollow slab element. Said elements are inter¬ connected only along the sides thereof, making the erection process a very simple one. All openings in the elements, e. g. for doors and windows etc. may be cut out on site. In a cor¬ responding manner any special structural details may be manu¬ factured by cutting portions from standard size hollow slab elements according to the invention.

The invention makes use of a process utilizing a mix of wood chips, e. g. from waste timber or the like, and cement, which mix is formed and consolidated in a special type press. For the consolidation of the mix the inventive system utilizes a special process more closely described e. g. in EP patent 189 127, which process uses carbon dioxide for speeding up the consolidation of the mix. Said EP patent, the whole content of which is included herein by reference, also teaches how special advantages may be achieved by compressing a mix of a fiber material and cement in connection with the injection of carbon dioxide.

Injecting excess carbon dioxide gas into such a material facilitates a rapid carbonization of a part of the cement binding agent, mainly by the process CaO + CO.. => CaCθ3. Such processes are earlier described e. g. in US Patents 109, 669, 3,462,993, 4,362,679, 4,093,690, SE Patent 110 792, GB Patent 1 460 284 and CH Patent 584 666. According to said documents the process has to be performed in fully closed process chambers, which is considered quite a serious drawback in industrial production scale.

The special process referred to comprises a method for harden¬ ing cement bonded panels and sections of fibre material, where the fibre material and cement in known composition and with water as activating agent is carbonized with carbon dioxide gas. According to the process such fibre material with its accompanying substances is laid between pressure plates of a pressing machine. Since the fibre material is slightly com¬ pressible a high amount of carbon dioxide gas can be injected, whereafter the material is compressed into the final dimen¬ sions of the structure to be manufactured. Said European Patent 189 127 describes how the use of a fully closed process chamber can be avoided by pressing the edges of the material into a higher density, which constitutes a gas barrier re¬ placing said fully closed chamber. The present invention uti¬ lizes some of the features of said EP Patent, and achieves, in a quite new concept, several advantages totally unknown in the prior art. The present invention utilizes the compression of a mix of fibre material and binding agent for obtaining, prior to compression, a very high gas injection rate in the relatively loose mix. In the next step the material is com¬ pressed to its final dimensions and the rapid curing or con¬ solidation of the binding agent, e. g. cement or the like, takes place. In the process according to the present invention the use of both fully closed process chambers, as disclosed in the earlier prior art, and especially compressed portions, as disclosed in said EP Patent can be avoided.

The characterizing features of the present invention are evident from the appended claims.

Thus, the inventive apparatus is characterized in that said apparatus comprises special core press expander elements to be located in said mix or mortar between said outer press panel elements for forming internal channels in said board manu¬ factured between said outer press panel elements. The in¬ ventive method is characterized in arranging said core press expander elements between said outer press panel elements, and subjecting, before the curing of said cement based binding agent, said mix located between said outer press panel ele¬ ments to an additional inner pressure by expanding said core press expander elements essentially uniformly inside said mix between said outer press panel elements. In at least one direction the expansion rate of said core press elements generally correspond to the press rate of said outer press panels, in which case the neutral axes can remain essentially in their original positions. The core press expander elements according to one embodiment of the invention comprise movable portions co-acting with corresponding portions of adjacent core press expander ele¬ ments or with said outer press panel elements. In an expanded position said core press expander elements compress between them the intermediate portions of said mix uniformly while essentially maintaining the neutral axes of said intermediate portions in their original positions with respect to the longi¬ tudinal axis of the respective core press expander element. Said core press expander elements further comprise means for maintaining a controlled migration of carbon dioxide and/or air within said mix. In order to obtain full control of the pressing procedure said core press expanders normally comprise several rigid elements arranged in a special manner according to the inventive concept so that said core press means are able to expand essentially uniformly without any local deformations due to uneven internal pressure or load dis¬ position in the junction portion between the expander and the raw mix material constituting the element walls and webs.

According to the invention an excellent hollow cement slab, resulting from the above mentioned raw material, is formed in one single or multi-stage press operation, including hardening of the raw material mix or mortar. Basically the inventive apparatus is a press mold composed of two presses, one of which is a horizontal flat press, consisting of upper and lower press boards movable within surrounding edgings. According to the invention the inventive press mold further comprises separate expanding core presses located between said horizontal press boards.

A typical board product would comprise an about 200 mm thick slab element having two about 20 mm thick panels interconnected by equally thick webs on central distances of about 400 mm. All these elements, i. e. said panels and said interconnecting webs, are formed in one single operation by simultaneously applying inside and outside pressure to the mix, throughout a very short hardening or consolidation process. Thus, the normal axis of each respective connecting web will be maintained essentially in its original position throughout the hardening process. Any adverse stresses and strains in the final product will thus be reduced already^' during the curing period. During the hardening process pressurized carbon dioxide gas is injected into the mortar, e. g. a woodchips-cement-water mix hereafter referred to as the CFB mix. Due to the use of excessive carbon dioxide the complete hardening process takes only some 4 to 5 minutes, while an ordinary cement consolidating process takes initially 8 to 10 hours. The complete manufacturing cycle for one board element may thus be performed within some 10 minutes.

Cement flake boards (CFB) are very advantageous for the in¬ ventive concept. The CFB element may be used equally well indoors and outdoors, since it is weather resistant, water¬ proof and non-frost susceptible. The CFB production process contributes to environment protection by binding carbon dioxide into a non-polluting product. The CFB is fairly fire resistant and has relatively good acoustic qualities, since it contains a high degree of sound insulation.

The production of full dimension hollow slab elements is the key operation in the inventive system, and this is utilized in the special inventive press mold arrangement discussed in detail below. In this respect it is also important for the process, that carbon dioxide can be effectively distributed throughout the complete slab material, in order to facilitate the rapid curing of the cement, in accordance with the prin¬ ciples disclosed in the above mentioned EP-patent 189 127.

The method according to the present invention provides a hollow slab structure comprising a ready made double wall element having spaced apart webs connecting said walls to each other. By pressing the mixed material from both outside sur¬ faces and simultaneously also from the inside a totally new mold concept is achieved. The neutral axis, i. e. the functional centre of gravity for each wall portion of the mixed material, is thus essentially maintained unmoved from the unprocessed to the pressed stage.

The invention will now be discussed in greater detail with reference to the appended drawings which disclose some pre¬ ferred embodiments of the invention. In the drawings

Fig 1 schematically shows a perspective view of a building erected using hollow slabs according to one embodiment of the invention,

Fig 2 shows a general exploded view of a mold arrangement according to one embodiment of the invention,

Figs 3 and 3a show a schematic view of a section of a portion of two alternative arrangements of the press mold appa¬ ratus, wherein the dotted sections indicate a CFB mix prior to compression and the hatched sections indicate the CFB mix in compressed and cured state,

Fig 4 shows a schematic sectional view of a double action press arrangement according to a special embodiment of the invention,

Figs 5a and 5b show schematic views of the carbon dioxide injection principle according to one embodiment of the invention,

Fig 6 shows a more detailed view of a partial transverse section through a wedge type core press expander ac¬ cording to one embodiment of the invention,

Fig 7 shows a schematic sectional view through an expanded core press expander according to an especially preferred embodiment of the invention, and Fig 8 shows the core press expander of Fig 7, in retracted state and still positioned within the hollow channel portion of a finished CFB board.

Referring now to Figure 1 a building according to the in¬ vention basically comprises a floor element A, wall elements B, B' and roof elements C. In said wall elements B, B' there are openings for doors D, windows E and the like. According to the inventive concept all said basic building elements A to C comprise hollow slab elements produced in a press arrangement as indicated in Figure 2, said press arrangement generally comprising a horizontal lower press panel arrangement 1, a horizontal upper press panel arrangement 2 and intermediate core press elements 3 arranged horizontally between said lower and upper press panel arrangements 1, 2, the longitudinal axis of one core press element 3 being indicated as F-F. Said press panel arrangements preferably comprise wall portions 4, 4a partially disclosed in Figures 2 and 4, and separate hori¬ zontal lower and upper press panels 5, 6, at least one of which is movable against the opposite one. Between the essentially rigid surface portions 5a, 6a of said lower and upper press panels 5, 6 there is arranged one or several core press elements 3. Said core press elements 3 are expandable and comprise essentially rigid surface portions 3a which are arranged for exerting a pressure at the inner portions of a CFB mix or the like provided between said press panel arrangements 1, 2. Since the relative movement of said lower and upper press elements 5, 6 normally is directed vertically, i. e. transversely with respect to the general horizontal extent of the element to be produced, the surface of the final element can be made in any desired shape, for example planar, corrugated or comprising a decorative pattern.

According to Figures 3 and 3a each hollow slab board element 7 comprises outer panel portions 8 interconnected by transversal web portions 9. Since one of the favorable properties of CFB boards is the relatively easy workability, the inventive con¬ cept enables making all openings in the board elements consti¬ tuting the final building (see Figure 1), such as said openings for doors D, windows E and the like, as well as any special structural details e. g. details of non-rectangular shape or of small dimensions, in the CFB board elements 7 after their manufacture in the inventive press arrangement. Thus, said boards 7 can be manufactured as essentially identi¬ cal ones, which considerably facilitates the production.

According to the inventive concept said CFB boards are gene¬ rally manufactured in standard sizes. A typical element board 7 intended for a one family home house, as disclosed in Figure 1, has an overall width of about 2.4 meters and a length of up to 10 to 15 meters. The thickness of the element board is suitably about 200 mm. In section, as disclosed in Figures 3 and 3a, each complete element board 7 comprises adjacent hollow channel portions 10 running through the whole extent of said element board 7. Said hollow channel portions 10 are surrounded by said web portions 9 and said panel portions 8. In Figures 3 and 3a the neutral axes G-G, G' -G' of each portion 8, 9 are shown in phantom. Here Figure 3 shows a preferred embodiment where said neutral axes G-G, G' -G' remain essentially in their original absolute positions due to generally uniform compression, while Figure 3a shows a section of a final product where a non-uniform compression has been applied. In an element disclosed in Figures 3 and 3a said web and panel portions 8, 9, suitably have a thickness of about 20 mm, and the c/c distance between said webs 9 is suitably about 400 mm, but in other embodiments and applications different measurements may, of course, be used within the scope of the invention.

According to Figures 3 and 3a a CFB mix 11 (shown in dotted section) is provided between said outer press elements 5 and 6 (of which only sections are shown for clarity reasons) within said wall portions 4, 4a preferably surrounding the assembly (see Figures 2 and 4). Essentially centrally between said press elements 5 and 6, and thus surrounded by said CFB mix 11, there are several adjacent core press elements 3 (one of which is shown in Figure 2) arranged in a fixed spaced pre-determined relationship. Prior to compression the distance between the respective surfaces of adjacent core press ele¬ ments 3 and between any core press element and said outer press elements 5, 6 corresponds to the uncompressed extent of said CFB mix 11. Typically, for a CFB board of the above dimensions the free distance between each two of said press elements 3 and 5, 6, respectively, would be about 60 mm prior to the compression. In fully compressed state each pair of opposite surfaces of said press elements 3, 5 and 6 would have moved about 20 mm each, thus giving for each mix portion 11 a total compression rate of about 65 % distributed suitably essentially equally on each pair of said outer and inner press elements 3, 5 and 6, respectively. In this connection and especially referring to Figure 2 it can be seen that due to the fixed arrangement of the press elements 3, 5 and 6 the mutual disposition of the press surfaces of each press element at the end stage of the pressing motion and thus the location of the hollow channel portion 10 in the end product can be very exactly pre-determined. This is a very important feature considering the accuracy of the strength calculations.

According to the invention the process comprises the steps of pressing the uncured CFB mix from a generally loose state, as indicated in dotted section in Figures 3, 3a, to a compressed state as indicated in hatched section in said Figures. General¬ ly the total compression rates would be in the range of 30 to 80 %, usually 50 to 75 % depending on the mix used. Thus, in the favorable embodiment disclosed in the Figures the exerted pressure would compress the mix from 60 to 20 millimeters. In the web portion 9 between each two of said core press expander elements 3 the total compression usually would be distributed to an equal amount on each expander element 3. In the panel portions 8 the internal distribution of the total compression between the press surface of each outer press element 5, 6 and the correspondingly opposite surface of the core press expander element 3 is chosen taking in account the technical features of the respective presses, the mix used, as well as the desired position of the neutral axis. In all cases the core press expander element 3 is expanded at least a few milli¬ meters in order to facilitate the easy removal thereof. In practice, the portion of compression, which is applied by the internal core press expander element 3 may vary, within the inventive concept, ranging from some 5 % up to some 80 % of the total compression, usually at least 25 %, and in one pre¬ ferred embodiment about 50 %, i. e. when both surfaces move essentially equally towards said mix 11. The compressed state generally corresponds to the final extensions of the manu¬ factured CFB board 7. The compression is made immediately prior to the curing of the cement binding agent in the CFB mix, and will in most cases correspond to a pressure in the range of 15 to 50 bar.

According to a preferred embodiment the compression procedure comprises two steps, which are performed within a few seconds. In a first step the adjacent core press elements 3 are expanded to give the hollow channel portion 10 inside the board 7 its proper dimensions. Simultaneously they compress the CFB mix in order to give it the special favorable features indicated in said EP patent 189 127. Normally, for an element having the general dimensions indicated above, the expansion would be about 20 mm to each web side and about 3 mm to each panel side. The expanded core press element 3 and the resulting hollow channel portion 10 is thus at least in two dimensions slightly larger than the said core press element 3 in its retracted state, and thus the removal of the core press elements 3 from the hollow channel portions 10 of the final board 7 will be easy. This fact can more clearly be seen in Figure 8. Since the expansion of all core press elements 3 is performed simultaneously the respective neutral axes G' -G' at each web portion 9 will remain essentially in its original location, i. e. very little internal movement in the CFB mix will take place.

In a subsequent pressing operation, which will take place in immediate connection to the first one discussed above the^' outer press panel elements 5, 6 are pressed towards each other for pressing the panel surface portions of said CFB mix 11. This pressing takes place on both sides of said core press elements 3 and can be performed by pressing both outer press elements 5, 6 towards each other and towards stationary core press elements 3. In a preferred embodiment said core press elements 3 are movable in the pressing direction of one outer press element so that only one, usually the upper one 6 of said outer press elements will move against a stationary lower outer press element 5. In this case the complete core press element 3 assembly will simultaneously be moved about half the amount of movement of the upper press element 6.

In a preferred embodiment the mold arrangement comprises a separate matrix element (not shown), which comprises at least a bottom plate as well as positioning means for keeping said core press elements 3 in position. In certain embodiments said positioning means further comprise means for moving said press elements vertically, in order to achieve the movement dis¬ cussed above. The matrix element may preferably further com¬ prise side wall portions surrounding said matrix bottom plate. In use said matrix is filled with CFB mix, and the filled assembly is then fed in between said outer press elements 5, 6 which may be essentially stationary and arranged only for the actual pressing movement on the upper and/or lower sides of said matrix element.

In an especially preferred embodiment disclosed in Figure 4 one single movable central "outer" press element 6' is arranged between two essentially stationary outer press ele¬ ments 5' , 5". In this embodiment two boards 7 can be manu¬ factured semi-simultaneously, i. e. one board is being pressed and cured while the other, already finished board is being unloaded and raw CFB mix is being provided in place thereof. Thus, the capacity of the apparatus will be considerably in¬ creased.

Due to the special method for curing the cement based binding agent in said CFB mix in about 5 minutes, the complete process cycle comprising loading the CFB mix, pressing the mix and curing the binding agent therein will take only about 10 minutes. For this reason a preferred arrangement of the carbon dioxide injection system is most important for the arrangement according to the invention.

According to the invention the core press elements 3 extending in the centre of the CFB mix 11 represent a favorable channel for injecting carbon dioxide gas into the CFB mix. Thus said core press elements 3 comprise, in accordance with a preferred embodiment of the invention, interconnecting carbon dioxide gas channels 13 as well as a suitable perforation in the outer surfaces (not separately shown) allowing said gas to emanate into the CFB mix surrounding said core press elements 3.

In a preferred embodiment, which is disclosed in Figures 5a and 5b, the injection of carbon dioxide gas into the CFB mix is arranged as a two step operation, which principle is known per se from the above mentioned EP-patent 189 127. In a first step (see Figure 5a) a gas mixture of carbon dioxide and air is pumped via said outer press elements into said CFB mix, as indicated by arrows 14 towards said mix. This creates an overpressure of carbon dioxide in said CFB mix. In this connection a vacuum or reduced pressure is maintained in said core press elements 3, as indicated in Figure 5a by arrows 15 directed towards the centre of said core press element 3. This vacuum facilitates the passage of said gas mixture through said CFB mix and increases the amount of carbon dioxide contacting the cement binding agent especially in the mix constituting the outer panel portions in the final CFB board. In a second step, as disclosed in Figure 5b, suitably every second one of said core press elements 3 is also pressurized with said gas mix, which pressurization is indicated with arrows 16. This second step facilitates a corresponding pas¬ sage of said gas through the intermediate wall portions 9 located between the hollow channel portions in the final CFB board and, thus, practically all free air inhibiting the curing process can be replaced by an especially composed mix¬ ture of carbon dioxide, which remarkably decreases the curing time.

For most cases it has, however, proven sufficient to perform the introduction of carbon dioxide in one single step by blowing said gas directly into said core press elements 3. Actually, this method is preferred, since maintaining a gas flow in only on direction, i. e. into said core press elements 3 will keep them and especially the gas channels 13 to be dis¬ cussed later free from any kind of impurities.

The core press elements 3 constitute a most central part of the invention. Figure 6 shows a core press element 3 according to one embodiment of the invention. Figure 6 shows a partial section of such an element 3 in a direction transversely to the longitudinal axis F-F of said element. Generally the core press elements 3 are oblong elements having wall portions which are movable in directions perpendicular to said longi¬ tudinal axis F-F. Thus, said elements 3 are expandable in both lateral directions thereof and can exert a pressing force against the surrounding CFB mix, which will be compressed between adjacent core press elements 3 and/or between such an element 3 and one of said outer press elements 5, 6.

In the core press element 3 according to Figure 6 the mold press surfaces comprise preferably essentially planar or at least generally smooth surface elements 17 and special corner elements 18. In Figure 6 said corner elements 18 are shown in an extended position, from which said elements 18 are r, - tractable to a position where they allow edges 19 of adjacent planar essentially rigid surface elements 17 to maintain a mutual contact. Said corner elements 18 have a wedge surface 21 interacting with a corresponding inner wedge inclined sur¬ face 20 at said planar surface elements 17. At each corner the dimensions of said core press element 3 may thus be extended and retracted by an amount corresponding to the width (indi¬ cated as "a" and "b" ) of the corner portions of said corner elements 18 by moving said corner elements 18 with respect to said planar side surface elements 17. The necessary movement is achieved e. g. by hydraulic or the like means or preferably, as indicated in Figure 6, by interacting wedge means 22, 23. Figure 6 also discloses that gas channels 13 are arranged within said core press element 3 and lead trough said planar side surface elements 17 for contact with a CFB mix 11 pro¬ vided outside said core press element 3.

Preferably said wedge means comprise successive wedges 22 attached to said planar side surface elements 17 as well as successive wedges 23 attached to a central actuator bar 24 suitably extending through the whole extent of said core press element 3. By moving said actuator bar 24 in the direction of the longitudinal axis F-F of said element 3, all wedges 23 will move and simultaneously press the respective wedges 22 outwards, which movement will accomplish a uniform lateral movement of said planar side surface elements 17 and said corner elements 18. Thus the dimensions of said core press element 3 may be altered between a fully retracted position having essentially closed corners between said planar side surface elements 17 and an fully expanded position, where said corner elements 18 will fill up the corner portions between said planar surface elements. In both positions the core press element will constitute a closed mold structure having es¬ sentially sharp corners. Said corners may also easily be slightly rounded, which will give somewhat rounded inner corners 25 in the hollow channel portions 10 of said boards 7, as indicated in Figure 3a. In some embodiments also the outer surface of said surface elements 17 may actually be rounded, which in some special cases may generate a nearly oval sectional shape.

Figures 7 and 8 show an especially preferred core press ele¬ ment 3 according to an alternative embodiment of the in¬ vention. In this embodiment the main mold and press surfaces comprise generally L-shaped wall portions 26 and wedge means 27, 28 for moving said generally L-shaped wall portions 26. For clarity reasons said L-shaped wall portions are here shown as strictly orthogonal pieces, but their actual sectional shape of can, of course, be subject to rather free alternations in accordance with the desired sectional shape of the hollow channel. Figure 7 shows said core press element 3 in expanded position and Figure 8 the same element 3 in retracted position within the hollow channel portion 10 of a board 7. In both Figures the right portion is a section through actuating or expander means 29 exerting a pushing force on said wedge means 27 for pressing one end of opposite pairs of said L-shaped wall portions 26 outwards-sideways. Simultaneously guiding wedges 28 interact with inclined counter surfaces 30 arranged at a central beam 31 and urge the remaining free ends 32 of said L-shaped wall portions 26 outwards. Thus a pressure can be exerted upon a CFB mix 11 outside the core press element 3.

The left portion of said Figures 7 and 8 show a section through retractor means 33 for retracting said L-shaped wall portions 26 after the completion of the molding operation and prior to the removal of said core press element 3 from hollow channel portion 10 of the final board 7, a section of which is shown in Figure 8. As indicated, there will be a space 12 between the inner wall of said hollow channel portion 10 and the retracted core press element, which will facilitate the removal of said element 3 from said board 7. Normally expander means 29 and retractor means 33 are arranged successively so that between each two expanders 29 there is a retractor 33. In the embodiment according to Figures 7 and 8 the expander 29 comprises a preferably hydraulic piston 34 moving in cylinder means and having bolts 35 pressing against a common pressure plate 36 holding said wedge means 27, which in this case are pressure cones or the like extending into the wedge shaped space between two adjacent ones of said L-shaped wall portions 26. Said pressure plate 36 urges said wedge means 27 in between said L-shaped wall portions 26 and thus forces them to move apart at said wedge shaped space. When said pressure plate 36 reaches the inner front surfaces of said L-shaped wall portions 26 the movement of said pressure plate 36 further will urge said L-shaped wall portions 26 to move forwards, and then said guiding wedges 28 will move along said inclined counter surface 30 and also force said free ends 32, i. e. the central portion of one side of said core press 3, outwards against said CFB mix 11.

The retractor means 33, on the other hand, suitably comprise spring means 37, 38 acting against the force of said expander means 29 and pulling said pressure plate 36 inwards when said expanders 29 are out of action. Said pressure plate 36 is suitably movable against an inner sill element 39 arranged at each of said L-shaped wall portions 26, and thus the inwards movement of said pressure plate 36 will force said L-shaped wall portions 26 away from the inner surface of the hollow channel portion 10 of said CFB board 7 and bring about said space 12, the extent of which corresponds to the extent of the compression of said CFB mix 11.

In order to maintain a smooth inner surface of said hollow channel portion 10 in the final board 7 said L-shaped wall portions preferably are at least partially covered with one or several layers of essentially rigid covering plates 40, 40' , which preferably in at least one central region 41 at said free ends 32 of said L-shaped wall portions 26 comprise interdigitated tongue elements between adjacent covering plates 40, 40' . This central region 41 is preferably supported by a separate support plate 42. In the embodiment shown in Figure 7 the short ends of said L-shaped wall portions 26 do not need any interdigitated tongue arrangements, since said cone or wedge means 27 suitably extends in between covering plates 43, 43' at said ends and fills the space between them. In another embodiment the arrangement at said short end is similar to the arrangement at the long ends and comprises corresponding interdigitated tongue arrangements. In this case said wedge means 27 can be located also at the outer portions of said pressure plate 36, preferably as an integrated part thereof. Thus, one preferred embodiment comprises pressure plates 36 having wedge shaped sides which co-act with wedges located at the repective inner corners of said L-shaped wall portions 26.

As in the embodiment disclosed in Figure 6 the embodiment according to Figures 7 and 8 also comprises channels 13 for carbon dioxide gas or the like to be injected into said CFB mix. Said channels 13, some of which are disclosed in the Figures, are supplemented by a suitable perforation in said covering plates 40, 40' , 43 and 43' . Thus the gas mixture used for the curing of the cement binding agent may freely move from the inner portions of said central bar 31 through the whole core press element 3 to the CFB mix 11 outside. In certain embodiments said channels 13 and said supplementary perforation are also used for the retraction of air, as more closely discussed in connection with Figures 5a and 5b.

Above some of the preferred embodiments of the invention have been discussed. This discussion, however, should be seen as an example only, and for an expert it is clear, that the in¬ vention may be altered in many other ways within the scope of the appended claims. Thus, all or some of the above mentioned hydraulic means may in some embodiment be replaced by means activated by the pressure of said carbon dioxide gas. Further the core press element 3 may comprise other types of prass elements, such as a tube like press element having expandable inner bag like means to be filled with a pressurized fluidum, as well as outer surface means having telescopic properties in directions transverse to the longitudinal axis of said element 3. The inventive concept may further be utilized for the manu¬ facture of different kinds of structures, i. e. for culvert elements or the like tube shaped structures.

Claims

1. A method for manufacturing structures, especially for manu¬ facturing boards (7) having at least one, preferably a mul¬ tiple of adjacent hollow channels (10) arranged between outer board portions (8), said method comprising providing a mix (11) mainly comprising a fibre material, a cement based binding agent and an activating liquid between outer press panel elements (5, 6), and moving at least one of said outer press panel elements (5, 6) against said mix (11) for sub¬ jecting said mix (11) to an outer compression, as well as rapid carbon dioxide curing of said cement based binding agent by subjecting said mix to the influence of carbon dioxide gas, c h a r a c t e r i z e d by said method further comprising the arrangement of at least one separate core press expander element (3) between said outer press panel elements (5, 6), and subjecting, before the curing of said cement based binding agent, said mix (11) located between said outer press panel elements (5, 6) also to an internal compression by expanding said core press expander element(s) (3) inside said mix (11) between said outer press panel elements (5, 6), for pressing corresponding essentially rigid surface portions (3a, 17, 40) of said core press expander element (3) towards said elements (5, 6) and towards any adjacent core press expander elements (3).

2. A method as defined in claim 1, c h a r a c t e r i z e d by expanding said core press expander element(s) at least in one direction to an amount generally corresponding to the compression exerted by said outer press elements (5, 6), suitably so, that the total compression of said mix in at least one direction is 30 to 80 %, especially 50 to 75 % and most suitably about 65 %, the internal distribution of said total compression between the surface of said core press expander element (3) and the opposite press surface of each corresponding outer press element (5, 6) and/or an adjacent core press expander element (3) ranging between 5 to 80 %, preferably about 50 %.

3. A method as defined in claim 1 or 2, c h a r a c t e ¬ r i z e d by expanding at least two adjacent core press expander elements (3) spaced apart within said mix (11) in such a manner, that the neutral axes (G' -G' ) of said mix (11) located between each two ones of said adjacent core press expander elements (3) will remain essentially in its original position with respect to the longitudinal axis (F-F) of the respective core press expander element (3).

4. A method as defined in claim 3, c h a r a c t e r i z e d in subsequently activating at least one of said outer press panel elements (5, 6) and pressing said mix (11), preferably so that the neutral axis (G-G) of said mix (11) located between said core press elements (3) and preferably the lower one (5) of said outer press panel elements (5, 6) remains essentially in its original position.

5. A method according to any one of claims 1 to 4, c h a ¬ r a c t e r i z e d in that said method further comprises the injection of carbon dioxide gas through said core press ex¬ pander elements (3).

6. A method according to claim 5, c h a r a c t e r i z e d in that said method further comprises the providing of a partial vacuum within said core press expander elements (3) prior to said carbon dioxide injection.

7. A method as defined in claim 5 or 6, c h a r a c t e ¬ r i z e d in that carbon dioxide and/or a partial vacuum is applied at alternating pressures within adjacent ones of said core press expander elements (3).

8. The use of a board product (7) manufactured by a method according to claims 1 to 7 as construction element for erecting complete buildings or the like.

9. An apparatus for the manufacturing of cement flake boards (7) or the like of a hollow channel board type, said apparatus comprising outer press panel elements (5, 6) suitably operable to compress, between them, a mix (11) mainly comprising a fibre material, a cement based binding agent and an activating liquid, which mix (11) in a cured state defines said board (7), and carbon dioxide injection means (13) for injecting carbon dioxide into said mix (11) in order to perform a rapid curing of said cement binding agent, c h a r a c t e r i z e d in that said apparatus further comprises at least one inner core press expander element (3) to be located in said mix (11) between said outer press panel elements (5, 6) for forming at least one internal channel (10) in said board (7) manufactured between said outer press panel elements (5, 6), said core press expander element(s) (3) comprising movable portions (17, 21, 26, 27, 40) co-acting with corresponding portions of adja¬ cent core press expander elements (3) and/or with said outer press panel elements (5, 6), for compressing, in an expanded position, the intermediate portions of said mix (11) between the essentially rigid portions (3a, 5a, 6a, 17, 40) of said elements (3, 5, 6), said core press expander element(s) (3) further comprising means (13) for maintaining a controlled migration of carbon dioxide and/or air within said mix (11).

10. An apparatus as defined in claim 9, c h a r a c t e ¬ r i z e d in that each of said core press expander elements (3) is a longitudinally extending element having in the longi¬ tudinal direction preferably four movable press wall portion elements (17, 26) defining, in a section transversal to the longitudinal extent of said core press expander element (3), a rectangle which in the expanded position of said core press expander element (3) extends to the position of the final inner surfaces of said internal hollow channel (s) (10), said core press expander element(s) (3) further comprising ele¬ ments, preferably wedge means (21, 22, 23, 27, 28), for pres¬ sing said wall elements (17, 26) into said expanded position within said mix (11), preferably while essentially maintaining the neutral axes (G-G, G' -G' ) of said intermediate portions of said mix (11) in their original positions with respect to the longitudinal axis (F-F) of the respective core press expander element (3).

11. An apparatus as defined in claim 10, c h a r a c t e ¬ r i z e d in that at least some of said wedge means (21, 27) are adapted for filling up spaces formed between said wall elements (17, 26) and constituting, in said expanded position of said core press expander element (3), a part of the mold surface defining said channels (10) in said board (7).

12. An apparatus as defined in any one of claims 9 to 11, c h a r a c t e r i z e d in that central wedge support means are arranged within said core press expander element(s) (3), said wedge support means comprising wedge carrier beams (24, 31, 36) and, optionally, sliding wedge surfaces (23, 30), for positioning said wedge portions (22, 28) for urging said wall portions (17, 26) outwards from the central longitudinal axis (F-F) of said core press expander element (3) along an exactly defined path, and further preferably comprising actuator means (29), preferably hydraulic or pneumatic cylinders (34) or the like, for moving said wedge carrier beams (24, 36) and initiating the expansion of said core press expander ele¬ ment(s) (3).

13. An apparatus as defined in claims 11 or 12, c h a r a c ¬ t e r i z e d in that said movable press wall portions are generally flat elements (17), and that said wedge means (21) in said expanded position of said core press expander elements (3) extend into the open corners between edges (19) of adja¬ cent ones of said movable press wall portions (17).

14. An apparatus as defined in claims 11 or 12, c h a r a c - t e r i z e d in that said movable press wall portions are, in section, generally L-shaped wall portions (26) each covering a corner of said channel (10), wedge means (27) being adapted for pressing said L-shaped wall portions (26) towards the respective corners of said channel (10), and that means (40, 40' , 41) are arranged for covering the longitudinal openings formed, upon the expansion of said core press expander ele¬ ment(s) (3), on the flat surfaces between adjacent ones of said L-shaped wall portions (26).

15. An apparatus as defined in claim 14, c h a r a c t e ¬ r i z e d in that at least some of said means for covering said longitudinal openings are separate sliding overlapping cover means (40, 40' ) arranged within and/or between and/or outside said L-shaped wall portions (26).

16. An apparatus as defined in claim 14, c h a r a c t e ¬ r i z e d in that at least some of said wedge means (17, 27) simultaneously act as said means for covering said longi¬ tudinal openings.

17. An apparatus as defined in claim 14, c h a r a c t e ¬ r i z e d in that said central wedge support means (24, 31) further comprises means (33) especially adapted for retracting said wall portions (16, 26) of said core press expander ele¬ ment(s) (3) from the wall surfaces of said channels (10) in said board (7).

18. An apparatus as defined in any one of claims 9 to 17, c h a r a c t e r i z e d in that said means for maintaining a controlled migration of carbon dioxide comprise intercon¬ necting channels (13) arranged in the inner portions of said core press expander elements (3), as well as perforated por¬ tions arranged at the outermost surfaces (40, 40' , 41, 43, 43' ) of said core press expander elements (3) and connected to said interconnecting channels (13).

19. An apparatus as defined in any one of claims 9 to 18, c h a r a c t e r i z e d in that said outer press panel elements (5, 6) comprise two fixed press elements (5' , 5") and a movable intermediate press element (6' ) arranged there¬ between, and that the apparatus further comprises means for urging, in an alternating motion, said intermediate press element (6' ) towards a respective one of said fixed press elements (5' , 5"), and that further means are arranged for moving a corresponding layer of core press expander elements (3) located between said movable intermediate press element (6' ) and said respective one of said fixed press elements (5' , 5" ) to an extent corresponding to generally half the extent of the movement of said intermediate press element (6' ).