A MATERIAL COMPACTION ARRANGEMENT FOR USE IN THE MANUFACTURE OF RIGID BEAMS

Abstract: The invention relates to a material-compacting apparatus for use in a plant in which a rigid elongated element or beam (4) is manufactured from loose material (2) moistened with a binder. The apparatus comprises a compaction section (7) in which batches of loose material moistened with binder are compacted, a heating section (5) in which the compacted batches are dried, and a transport arrangement which functions to move each compacted material-batch (2b'', 2b''', 2a) through the heating section (5). The compaction section (7) has mounted therein a rod-like member (23) whose end surface, or cross-sectional surface, is such that the member (23) will compact the foremost material-batch and hold the batch such that the foremost material-batch (2a) will not tend to separate from a nearest following material-batch (2b''') when the walls (15) of the heating section are displaced.

Description: TITLE OF THE INVENTION; A material compaction arrange¬ ment for use in the manufac¬ ture of rigid beams TECHNICAL FIELD The present invention relates generally to material compacting apparatus, and more particularly, but not exclusively, to material compacting apparatus which can be used in plants for the manufacture of rigid, elon¬ gated structural elements, so-called beams. The starting material used with such apparatus comprises loose, fibrous material moistened with binder, for instance such materials as cutter chips or shavings and sawdust, although it may also comprise other suitable materials, and is compacted in said apparatus and subseguently dried in a heating section, to form said beam. The invention also relates to simple material compacting apparatus adapted for use in a plant for the aforesaid purpose, and comprising a material compaction section or unit, in which batches of binder-moistened, loosely packed fibrous material are compacted. The plant also includes a heating section, in which the sequentially compressed material batches are dried, and a transport¬ ing arrangement by means of which each of the material batches compacted in the compaction unit is passed successively and in sequence, through the heating sec¬ tion. In order to understand the present invention, it is important to note that by "material batches" is not meant mutually separate and well defined quantities of material, but a plurality of such batches or material quantities required to form an elongated beam, and that measures are taken to ensure .that no clearly defined interfaces exist between mutually adjacent batches. The term "batch" is used primarily to provide a simple understanding of the discontinuous production process taking place in a heating section which is provided with linearly movable wall-sections and a bottom section. BACKGROUND PRIOR ART A plant of the aforesaid kind is known from Interna- . tional Patent Application No. PCT/SE84/00303, which describes and illustrates an arrangement for producing an elongated element (here referred to lossely as a beam) , comprising a compaction section which includes compaction apparatus which functions to displace and compact sequentially binder-moistened, mutually separate material batches, the volumes of which have been clearly defined by weighing, such that the compressed or co - pacted, individual material batches can be passed se¬ quentially through a high-frequency heating section. The apparatus described in the aforesaid publication includes a compaction section in which a piston is reciprocatingly movable in a horizontal direction, co- directionally with the centre line of the heating sec¬ tion and with the outfeed direction of the beam, subse¬ quent to its passage through the heating section. When the piston is located in a first position, the piston-retracted position, a batch of loose material, moistened with binder, falls into a compaction chamber, or alternatively is pushed into said chamber with the aid of a piston or plunger, whereafter the chamber is closed and the horizontal piston is moved towards the heating section and the material batch located in the compaction chamber is compressed or compacted against the immediately forwardly located previous batch of material, and subsequent to being compacted to the desired degree of compaction, all of the compacted material batches present in the heating section, inclu¬ ding the last compacted batch, are displaced forwards to an extent equal to the axial length of the batch last compacted, whereupon the piston is returned to its retracted position and a further batch of binder- moistened, loose material falls into said chamber, in front of the piston. The apparatus described and illustrated in Swedish Patent Specification 415 547 (Patent Application 7809708-4) also forms part of the prior art, this known apparatus including a heating section whose walls are reciprocatingly movable in a horizontal direction and function, in part, as means for transporting compacted material batches. In each of the aforesaid known methods, the so-called beam is produced from individual, well-defined material batches which are clearly separated from one another by a section or border region of material which has been compressed to varying degrees of compaction and also the fibre directions of which have been displaced vertically in relation to one another, to some extent. SUMMARY OF THE INVENTION TECHNICAL PROBLEMS When considering the state of the prior art as described in the aforegoing, it will be seen that a highly compli¬ cated technical problem is one of providing, with simple means, conditions which will eliminate the reduction in the mechanical strength of a so-called beam or elongated structural element produced in accordance with these known methods in the boundary or interface region be¬ tween two mutually adjacent compacted material batches, where this interface region or boundary region can be considered to be due to the fact that the forwardly located material batch presents a highly compacted surface to the piston, whereas the subsequent batch is introduced vertically and is compacted to some extent prior to being subjected to horizontal compaction with a pronounced difference in compaction against the surface of the preceding batch, without needing to forego the advantages of being able to used well-defined, indivi¬ dual material-batches which can be readily weighed. It will also be seen that a qualified technical problem resides in the realization that the aforesaid drawback can actually be eliminated, even when the compaction section is constructed such that the material-batches are delivered in separate units, when compaction of said material can be effected in a manner which will enable the material-batches to merge with one another more continuously and to impart to respective material- batches an increase degree of compaction in several stages, preferably while breaking-down the interface, as the batches pass through the compaction section. Another technical problem is one of realizing that despite compacting the material-batches in several stages and despite the resultant pronounced reduction in the mechanical strength of the interface, the mechanical strength in the interface between mutually adjacent batches can be considerably improved when the extent to which compaction is effected in each stage is selected such that a relatively high degree of compaction is effected in the last compaction stage. Another technical problem is one of realizing, in this respect, that it is necessary to compact the material to the smallest possible extent upstream of or before the last compaction stage, but that this degree of compac- tion shall nevertheless be sufficiently great to enable the material-batches to be pressed and moved through the last compaction stage. It will also be seen that a technical problem is one of modifying an earlier known compaction section in a simple fashion, such as to eliminate, or at least great¬ ly reduce, the occurrence of locally defined, separate degrees of compaction and fibre movement between each material batch experienced with the earlier techniques. Another technical problem is one of realizing that the aforesaid technical problem can be solved by construc¬ ting the compaction section in a manner such that the material-batches are compacted stepwise to a pre- determined degree of pre-compaction, with the aid of a rod-like device or ram located in a limited region of the longitudinal extension of the compaction section kand operative to compact material in a later stage of the pre-compaction process. It will also be seen that a further technical problem is one of utilizing the knowledge that the weight per unit volume of a finished beam, or elongated structural member, requires the provision of a metering and weigh- ing device for establishing the weight and moisture content of each of the individual batches of loose material used, while still creating conditions by means of which there can be produced a beam which lacks pro¬ nounced interfaces between mutually adjacent material- batches, while feeding said material-batches discon- tinuously into the apparatus, so that the material strength of one material-batch will not differ from the material strength of an adjacent batch. It requires qualified perception to solve this technical problem while still being able to use a weight-based metering device coupled to the compaction section. It will also be seen that having provided a compaction section which solves each and every one of the aforesaid technical problems, a further problem is one of realiz¬ ing that in the case of an adhesive binder and a loose material in the form of cutter chips or sawdust, the final degree of compaction must be achieved subsequent to a multi-stage pre-compaction process and an immedi- ately following, locally-acting final compaction, pre¬ ferably in solely one direction, such as to form on the manufactured beams a finished outer surface, so that the beams will exhibit pre-determined mechanical strength properties, for example beams or elongated structural which are able to fulfill the test requirements pre¬ scribed for loading-pallet constructions. It will also be seen that a technical problem resides in the provision of a principle solution to one or more of the aforesaid technical problems, by realizing that a piston-operating metering device is able to pre-compact the material batches to the requisite extent, without the occurrence of pronounced interfaces or boundaries, by permitting an initial pre-compaction to act against a surface of the pre-compacted batch which has disinte¬ grated as a result of pre-compaction. When the heating section comprises movable wall-parts, it will be seen that a further technical problem resides in the provision of conditions, with the aid of simple means, which will eliminate the tendency of the material-batches located in the compaction section to break-up or to be displaced, especially when the wall- parts of the heating section are moved back towards the compaction section, for instance by providing a rod-like device or ram which has a cross-sectional surface area, of such size as to bear against a pre-compacted material batch and hold said batch effectively against movement with the wall-parts. SOLUTION The present invention relates to material-compacting apparatus which can be used in plants for the manufac- ture of rigid, elongated structural elements, so-called beams, produced from loose, fibrous material moistened with binder, and comprising a compaction section in which batches of binder-moistened material are compac¬ ted; a heating section in which the compacted material- batches are dried; and a transporting arrangement which functions to cause material-batches compacted in the compaction unit to pass successively through the heating section. The transporting arrangement utilizes, inter alia, the circumstance that the wall-parts of the heating section are reciprocatingly movable in a direction parallel with the direction of the material-batches. For the purpose of solving one or more of the aforesaid technical problems, it is proposed in accordance with the invention that the material-batches are pre- compacted to a compaction value which is greater than the compaction value required to feed the thus lightly pre-compacted material-batches through apparatus in which said batches, pre-compacted in varies stages, are finally compacted prior to feeding the batches into the heating section. It is also proposed in accordance with the invention that pre-compaction of the material batches is effected in a small number of stages, comprising a first stage of greater batch-compaction and subsequent stages in which the material-batches are compacted to a lesser extent, and that the batches are then compacted to a high degree of final compaction. The degree of pre-compaction of material batches in the first stage corresponds to, or substantially corresponds to, twice the degree of compaction in the final compac¬ tion zone. The degree of pre-compaction in the first stage is much greater than the degree of pre-compaction in the second stage or than the total compaction in the remaining pre- compaction stages. The material-batches are compacted to their ultimate degree of compaction from one side of the batches, namely the side considered to be the right-side of the elongated member, so as to provide a finished surface. In accordance with one embodiment of the invention, the compaction chamber has arranged therein a reciproca- tingly movable rod-like device, or ram, which moves parallel with the longitudinal extension of the elon¬ gated member or beam, and the cross-sectional area of which is such that the member will be held pressed against material-batches in their respective positions and move said batches towards the heating section, even when one side-wall part, normally both side-wall parts, and/or the bottom part of the heating section is dis¬ placed towards the compaction section. In accordance with preferred embodiments of the inven¬ tion, it is proposed that the compaction section is constructed so as to impart to the foremost material- batch, seen in the direction of feed, a considerably higher degree of compaction than the degree to which the following material-batch is compacted. Each material-batch may comprise a definite, weighed quantity of material. The material-batches are pre-compacted in a second compaction stage by means of a horizontally movable piston which is configured with a surface inclined to the horizontal plane, said surface defining an angle of from 40-60° . The end-face of the rod-like member has an area which equals 20% of the cross-sectional area of the compacted batch, preferably between 30 and 40%. In its position nearest the heating section, the end- face of the rod-like member terminates short of the foremost, finally compacted material-batch. The rod-like member extends through a pre-compacting section and forms in an adjacent and forwardly located material-batch a cavity which is located adjacent a boundary layer or interface between two mutually ad¬ jacent material-batches. The distance travelled by the horizontally movable piston is shorter than the distance travelled by the rod-like member. It is also proposed that the degree of compaction of individual material-batches can be varied in dependence on the desired density of the elongated member finally formed, although when the binder used is glue and the loose fibrous material comprises cutter chips or saw- dust, the ultimate degree of compaction is at most 5:1. It is also proposed that the foremost batch is com¬ pressed or compacted with the aid of a device which acts in at least one direction, preferbly a device comprising one or more rolls. According to one embodiment, a knife or doctor blade is positioned adjacent the final compaction stage, in order to prevent material from being picked-up by and carried with the roll. According to one embodiment of the invention, a follow¬ ing batch of material, compressed to a lower degree of compaction is advanced in the form of a cylindrical body and subjected to a final shape change in the final compaction stage. Particularly during those time periods in which the walls of the heating section are displaced towards the compaction section, the free cross-sectional surface of the rod-like member is effective to impart to subsequent material-batches a degree of compaction sufficiently great to prevent the movement of the walls from separa- ting a forwardly located compacted material-batch from a following finally pre-compacted material-batch. According to one embodiment of the invention, a rein¬ forcing mat, fibreglass mat, is passed between the rolls and a finally compacted material-batch, such as to form a surface reinforcement on the elongated member pro¬ duced. Practical experiences have shown that in the case of large press depths, the final compaction roll should have a larger diameter than in the case of smaller press depths (in order to achieve the final degree of compaction) . ADVANTAGES Those advantages primarly afforded by an arrangement constructed in accordance with the present invention reside in the provision of conditions which, despite the fact that the material is metered in batches, will enable the boundary layer between all mutually adjacent material-batches to be compacted to equal degrees of compaction to the highest possible extent, so as to reduce or totally eliminate the earlier drawback of the occurrence of vertical, strength-reducing layers between mutually adjacent batches, even when utilizing material- batches which comprise individual quantities of weighed material, by compacting the material batches in a plura¬ lity of particularly chosen stages. When practicing the present invention, it is also pos¬ sible to profile and work the top surface of the elon¬ gated member, or beam, during the final compaction stage. The primary characteristic features of an arrangement constructed in accordance with the present invention are set forth in the characterising clause of the following Claim 1. BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of a material-compacting arrange¬ ment included in a plant for manufacturing elongated members, or beams, and having features characteristic of the present invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a highly simplified illustration, in side view, of a known plant machinery intended for the manu¬ facture of elongated members, or so-called beams, and illustrating one embodiment of a compaction section for stepwise compaction of material-batches; Figure 2 is a side view, partly in section, of a mate- rial-compacting arrangement suited for use in the plan shown in Figure 1, said arrangement being shown in a first operational state; Figure 3 is a side view, partly in section, of the arrangement illustrated in Figure 2, and shows the arrangement in a second operational state; and Figure 4 illustrates the proposed time-related activa tion of a rod-like member in dependence on the pre- compaction sequence and the displacement of side-wall parts and bottom-part of a heating section. DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED Figure l illustrates plant machinery 1 which is opera¬ tive produce a rigid, elongated element, or beam 4 from binder-moistened loose material 2, and which includes a compaction section 7 and a heating section 5. Thus, Figure 1 is a highly simplified illustration, in side view, of a plant 1 for manufacturing an elongated element or beam 4. The plant machinery illustrated in Figure 1 include a hydraulic piston-cylinder device 10 having a piston rod 9 which co-acts with a compacting device 8, which has in the form of a piston or plunger. The piston rod 9 is reciprocatingly movable and func- tions to move the piston, which extends slightly into a compaction chamber 7' . The front or leading surface 8a of the piston 8 forms a rear side-wall part of the compaction section 7. Located immediately above the compaction chamber 7' is a material-batch supply device 6. The upper part of the device 6 may be configured with a space for accommo¬ dating fibre material and a space for accommodating binder. The fibre material and binder are mixed together in specific proportions in a mixing station (not shown) , whereafter the mixture is fed to a lower space. The total amount of fibre material required to produce a complete elongated member or beam is fed to the compac¬ tion chamber 7' , via a portioning and weighing arrange- ent not shown in Figure 1. Alternatively, a ready-mix of fibre material and binder may be supplied directly to the batch-supply device 6. It will be understood, that instead of utilizing a fibre suspension mixed with binder, the elongated element can be formed by spraying or moistening fibrous material with binder, particularly in the case when the fibrous material is fed directly to the compaction chamber 7 - and there subjected to pressure. The material is primarily non-conductive electrically, e.g. such material as cutter shavings, wastepaper, textiles, sawdust, chips and like materials or alter- natively such a material which is admixed with plastic, bark and the like. As before mentioned, the compaction device 8 has the form of a piston and is moved reciprocatingly by means of a hydraulic piston-cylinder device 10 having a piston and piston-rod 9. The compaction device 8 is illustrated in side view in Figure 1 in a non-compacting position in which it leaves the compaction chamber open. When the compaction device 8 is located in this position, the space in front of the compacting device is filled with a metered quantity of fibrous material from the device 6, optionally with the aid of a vertically acting plunger, not shown. This is effected by ensuring that the compac¬ tion chamber will be filled with batch material as the compacting device 8 is withdrawn to its position shown in Figure 1 and thus exposes an opening, through which the material is dispensed. When the compacting device 8 moves to the right in Figure 1,. the material-batch located in the compaction chamber is compacted against the rear-face of the preceding material-batch, such as to build upon one batch after another and thereby con¬ struct the elongated element or beam. Thus, each of the sequentially located batches will be compacted in the compaction chamber 7' and displaced in the form of a coherent unit to a following heating section 5. The finally compacted material, provided with binder, is introduced through the end part 5a of the heating section and is subjected to heat treatment in said section with the aid of a known high-frequency plant, not shown in detail, whereafter the finished elongated-element or beam is discharged through the end part 5b of said section. The finished beam is referenced 4 in the drawings. If desired, the elongated element 4 can be transferred directly to a processing plant 3, in which the outer surfaces of the beam are coated with an impregnating liquid, paint, varnish or the like. The functions of the compaction device 8, the material- and-binder mixing and volume-proportioning arrangement, the feed arrangement 6 containing said fibrous material, and the press means, together with other functions of the arrangement 1 are activated and initiated by a control means referenced 1' in Figure 1. Since this control means can be constructed readily from the following functional description, the specific circuitry of said control means is not described here. Figure 1 illustrates in side view, and in principle, a fibre-compacting unit in which the compaction of fibrous material is effected in three stages. Loose fibre material 2b, such as sawdust, moistened with binder, and agglomerated to form a material-batch in a portioning and weighing arrangement (not shown) is fed to a space located beneath a plunger 21 in a known manner. In a first compaction stage, this batch of material is compacted from one side thereof to a compaction ratio of 2.5:1, therewith imparting to said material-batch a first degree of compaction. The compacting surface of the plunger 21 is then moved to the position 21a shown in Figure 1. The material-batch compacted to said first degree of compaction in the first compaction stage is then co - pacted to a second degree of compaction in a second compaction stage. The material-batch is compacted only to a relatively small extent in the second stage and this further compaction of the material-batch in said stage is solely intended to ensure that the material batch is compacted sufficiently to enable said batch to be passed through a third stage. Preferably, the material-batch is compacted in the second compaction stage at a ratio of 1:1 to about 1.5:1, suitably a ratio of 1.1:1. This secondary compaction is effected by displacing the piston 8 so that the surface 8a is moved to the illus¬ trated position 8a". The material-batch compacted to said second degree of compaction in the second compaction stage is then com¬ pacted in a final or third compaction stage 12 from one side of said batch to a compaction ratio of 1.3:1. The thus compacted material-batch is then passed to the heating section. In the case of the Figure 2 embodiment, the compaction section 7 includes a piston 21 which functions to pre- compact a material-batch 2b (Figure 3) in a first com¬ paction stage. Compaction of the thus pre-compacted material-batch is effected in the second stage 2b" and the third stage 2b' ' ' with the aid of the compacting device 8 and a rod-like member 23. Subsequent to pre-compacting the material-batch in said three compaction stages, the material-batch is finally compacted by a roll 12, to form finally-compacted batches 2a. As will be seen from Figures 2 and 3, the aforesaid rod¬ like member 23 is mounted for reciprocating movement in the compaction space 22, in a direction parallel with the longitudinal axis of the elongated element or beams 4. The end face 23a of the rod-like member 23 is con¬ figured so that it is able to hold and retain the com¬ pacted material-batches 2a, 2b' ' ' and displace said material-batches towards the heating section in their respective positions, even when a side-wall part 15, normally both side-half parts, and/or the bottom-part 16 of the heating section are displaced towards the com¬ paction section. It is known to displace the side parts and/or the bottom part of a heating section towards the compaction sec- tion, and this movement of the heating-section parts does not form part of the present invention and will not therefore be described. It can be mentioned, however, that the side-wall parts 15 are illustrated in section in Figure 2 and that these side-wall parts actually pass by the compaction chamber 7' for lateral connection to the piston 8. The rod-like member 23 is driven by means of a hydraulic drive (not shown). As before mentioned, the foremost material-batch 2a is finally compacted to a degree of compaction hjigher than the degree of compaction of the ollowing material- batches 2b' '', 2b" and 2b' respectively. This final compaction is effected with the aid of compacting means, such as a roll 12. It should be observed in this respect that each material-batch pre-compacted in the aforesaid three stages comprises, in this case, a metered, specifically proportioned quantity of material which is introduced into the space 22 and there compacted in a first stage by the piston 21, which moves from the position illu¬ strated in Figure 3 to the position illustrated in Figure 2. The material-batch 2b is in this way pre-compacted to 2b' in a first compaction stage. In accordance with the present invention, the thus pre- compacted material-batch is then further compacted in a second stage, by movement to the right in the drawing of the horizontal piston 8. The piston 8 has a surface 8a which is inclined to the horizontal plane and the upper part of which lies closer to the heating section 5 and the lower part of said surface, said surface preferably being inclined at an angle of from 40-60°. Compaction of the material-batch in the second stage is effected by moving the piston 8 to the right, from position 8a to the position 8a' shown in the drawing. This displacement of the piston 8 results in simul¬ taneous displacement of the rod-like member 23. The material-batch can be further compacted, by causing the rod-like member 23 to be moved to the right after the piston 8 has stopped in the position 8a'. The side-wall parts 15, the bottom-parts 16, the mate¬ rial-batch 2b" and the rod-like member 23 are then moved to the right, as seen in the drawing, so that the mater¬ ial-batch 2b" will occupy the position previously oc¬ cupied by the material-batch 2b'' ' . This movement will result in movement of the material-batch 2b" to the final compaction stage, where said batch is compacted to form the illustrated material-batch 2a. The cross-section of the rod-like member 23 must be precisely dimensioned, and it is proposed in accordance with the invention that the end face, or end cross- section surface, of the rod-like member will cover more than 20% of the cross-section of the compacted material- batch, preferably between 30 and 40% of said cross- sectional area. When the rod-like member 23 occupies its position nearest the heating section, this position being shown in chain lines in Figure 2, the end-surface 23a of said member will be located at a small distance from the foremost material-batch 2a. The rod-like member is intended to extend through the pre-compacting section to an extent such as to be able to form in an adjacent material-batch, the material- batch located immediately adjacent the finally-compacted material-batch 2a, a cavity 24 which is located immedi¬ ately adjacent a boundary or interface layer between two mutually adjacent material-batches, this interface layer being obliquely formed. Figure 3 illustrates clearly a material-batch 2b"*, which has been pre-compacted in two stages and in which one such cavity 24 has been formed in an oblique boundary layer 25. As will be understood, when subsequent batches are pre-compacted in said first stage, the boundary layers 25' of preceding batches will disintegrate and fall into the cavity 24. The material-batch 2b' com¬ pacted by the piston 21 will now fill the space 22 and pre-compaction of the material-batch in the following second compaction stage will cause the boundary layer to crumble such that no pronounced boundary layer or inter¬ face will exist between the material-batches 2b''' and 2a. The rod-like member 23 is moved forward simultaneously with the piston 8, and it is proposed that when the piston 8 has reached its forward terminal position, to the right in the figure, the rod-like member 23 is caused to move forward slightly, into the material-batch 2b" so as to subject said batch to final pre-compaction. Figure 2 shows that two vertical side-wall parts, made of an electrically insulating material, of which only one is referenced 15, can be moved backwards and for¬ wards in the direction of the arrow 15a, while a bottom- part 16 can similarly be moved in the direction of the arrow 16a, by means not shown. The bottom-part 16 is made of an electrically conductive material. Figure 2 shows the side-wall parts and the bottom-part 16 in their far-left position in the beam-forming appar¬ atus. The illustrated side-wall parts 15 and the bottom-part 16 are intended to move in conformity with the piston 8 and the frequency of said piston. It lies within the scope of the invention, however, for the side-wall parts and the bottom-parts to move through shorter distances and to move more quickly, in vibratory movement. In the case of the illustrated embodiment, the compac- tion section 7, over a very short displacement path, is intended to impart to the foremost material-batch 2a a higher degree of compaction than the following pre- compacted material-batches 2b'" located in the space 11. Pre-compaction of the material-batches in the different compaction stages can be regulated in dependence on the force acting on the pistons 21 and 8 and on the rod-like member 23. The foremost material-batch 2a located in the compaction section is finally compacted by means of a roll, i.e. the roll 12 shown in Figure 2. The degree of final compaction is dependent on the degree of pre-compaction, and the extent to which the material-batch is finally compacted will determine the density of the elongated element or beam. The smallest degree of pre-compaction of the material- batch 2b''' is contingent on factors which will be apparent from the following. The degree of final compaction is dependent on the press-depth of the roll, and it can be assumed that the roll will contribute in imparting a somewhat higher degree of compaction to the upper surface 4a' than to the underlying parts of the elongated element. In the case of the illustrated embodiment, a reinforcing net or reinforcing mat 12a is passed through the nip defined between roll 12 and the material-batch, so as to provide a surface reinforcement. When a greater press-depth is desired, the roll 12 will have a larger diameter than when a smaller press-depth is required. The degree of final compaction will preferably not exceed 5:1, although the extent to which the batches are compacted will depend on the desired density of the finished elongated element or beam. A knife 21 is arranged beneath the roll 12, said knife being flat when a flat upper beam-surface is desired and ** profiled when a profiled upper beam-surface is desired. 5 Although only one roll 12 is shown, it will be under¬ stood that two or more such rolls may be used for finally compacting respective material-batches stepwise, or other equivalent means may be used which provide the same or similar results. 10 Since the present invention is based on the assumption that the side-wall parts 15 and the bottom-parts 16 of the heating section 5 are displaceably mounted, it is intended that the side-wall parts 15 and the bottom-part 15 16 accompany the movement of the material-batches 2b''' as they pass beneath the roll 12 and are finally com¬ pacted thereby, as the finally pre-compacted material is successively fed to the area 11. 20 When the side-wall parts 15 and the bottom-parts 16 have been moved to their terminal position to the right as seen in the drawing, forward movement of the material- batches 2b", 2b' " and 2a ceases, so as to enable the side-wall parts 15 and the bottom-parts 16 to be moved 25 back to their terminal position to the left of the figure. During this return movement of said parts 15 and 16, there is a tendency for the material-batches located in the space 11 to separate from one another and to form cracks, due to the friction which prevails between the 30 material-batches 2a and 2b"' and respective wall and bottom parts 15, 16. As will be understood, the extent to which the batches 2b"' are pre-compacted and the counter-pressure exerted by the rod-like member 23 must be sufficiently large to prevent such cracks from forming. When the apparatus is such that the side-wall part 15 and the bottom-part 16 are moved simultaneously with one another, the material-batches must be pre-compacted to a greater extent than when solely one of said parts is moved at a time, and similarly the surface area of the rod-like member must also be greater. Consequently, it is therefore proposed that solely either the side-wall parts or solely the bottom-part are/is, returned to its left-terminal position while the end face 23a of the rod-like member 23 bears against the material-batch. Thus, the material-batches are compacted within the area 11 to an extent at which the formation of cracks is reliably eliminated. At the same time, or immediately thereafter, one or both side-wall parts 15 can be moved to their left-terminal position as seen in the drawing. The apparatus is then ready to finally compact material- batches 2b"', during which the side-wall parts 15 and the bottom-part 16 accompany the movement and a finally- compacted batch 2a passes into the heating section 5. This time-related procedure is described in more detail below with reference to Figure 4. When the heating section 5 comprises a high-frequency plant, the side-wall parts 15 are preferably made from an electrically insulating material and the bottom-part 16 from an electrically conductive material, said bot¬ tom-part being earthed. It should be observed (referring back to Figure 2) that the provision of a plurality of rolls 12 will, on the one hand, provide a longer friction path, which can be desirable per se, although a longer friction path will result in a smaller degree of compaction, and conse¬ quently these factors should be taken into account when practicing the invention. The cross-sectional shape of the rod-like device 23 and the configuration of its end face 23a are preferably such that sufficient counterpressure will be obtained to prevent the formation of cracks when the side-wall parts 15 and the bottom-part 16 are moved to the right, as seen in the figure. It should also be observed that the cross-section should be chosen so that disintegration of the boundary layer or interface (25') will be effective, which means that the cavity 24 must be relatively large. Figure 4 illustrates an appropriate time-related example of the intermittent manufacturing procedure, and how this procedure is time-related to the movements of the side-wall parts 15 and the bottom-part 16. The Figure 4 diagramme has a starting point from the moment at which the piston 21 has pre-compacted a material-batch 2b' , comprising cutter chips and adhe¬ sive, in the space 22, i.e. pre-compaction in the first compaction stage, and the side-wall parts 15 and the bottom-part 16 are located in their left-terminal posi¬ tion. This also applies to the rod-like member 23. The rod-like member 23 and the piston 8 move simultaneously as the piston is moved to the right in Figure 2 to a position in which a material-batch 2b" is pre-compacted in the second compaction stage. It is assumed that movement of the piston 8 is stopped at the time point tl, whereas movement of the rod-like member 12 con¬ tinues, so that said member is forced into the material- batch 2b" to effect compaction in a third stage at time point t2. At time point t3, the side-wall part 15 and the bottom-part 16 are moved to the right, at the same time as the piston 8 and the member 23 move the material-batch 2b" to the position of the material-batch 2b". This step is terminated at time point t4. During the time-sections t 5 - t g , the side-wall parts 15 are moved back to the left in the figure, whereas during the time-sections t ? - t β , the bottom-part 16 is re- turned while the surface 23a of the rod-like member 23 bears against the batch 2b'" , so as to prevent the formation of cracks between the batches 2b"' and 2a. At time point t g , the rod-like member 23 is returned and at the time point t.- the piston 8 is returned to the Figure 2 position. This movement is terminated at time point t^.. At time point t.. , the rod-like member is returned to its far-left position, whereafter the piston 21 is raised at time point t 12 and a weighed quantity of material is metered to the space 22 during t 12 ~ t i3 * At time point t , the piston 21 is lowered and reaches the position illustrated in Figure 2 at time point t Q , when the material-batch 2b' located in the space 22 is pre-compacted in the first-compaction stage. Compaction of the material-batch is then effected in the manner described and illustrated from the time point t_ and onwards. By the reference "movement towards the compaction section", is meant movement to the left in Figure 2. It will be understood that the invention is not restricted to the illustrated and described exempli¬ fying embodiment thereof and that modifications can be made within the scope of the following claims.

Claims: CLAIMS 1. A material-compacting apparatus for use in a plant in which a rigid, elongated element or beam is manufac- tured from loose material moistened with binder, com¬ prising a compaction section in which batches of loose material moistened with binder are compacted; a heating section in which the compacted material-batches are dried, and a transport arrangement which functions to pass each of the material-batches compacted in said compaction section through said heating section, said transport being effected, inter alia, by movement of the walls of the heating-section in the direction of move¬ ment of the material-batches; characterised in that the apparatus is constructed to pre-compact the material- batches to a value exceeding the value required to feed such pre-compacted material-batches through an arrange¬ ment in which said batches are finally compacted prior to feeding the batches, compacted in a plurality of stages, into the heating section. 2. Apparatus according to Claim 1, characterised in that pre-compaction of the batches is effected in two stages, a first stage of relatively high compaction and a second stage of low compaction. 3. Apparatus according to Claim 1 or 2, characterised in that the degree of pre-compaction achieved in the first stage corresponds to, or substantially corresponds to,- twice the degree of compaction achieved in the final compaction stage. 4. Apparatus according to Claim 2, characterised in that the degree of pre-compaction in the first stage is much greater than the degree of compaction in the second stage. 5. Apparatus according to Claim 1 or 2, characterised in that compaction of the material-batch for the purpose of obtaining a final degree of compaction is effected from one side of the batch, namely the side considered to be the right side of the elongated element. 6. Apparatus according to Claim 1, characterised in that mounted in the compacting space is a reciproca- tingly movable rod-like member which moves in a direc¬ tion parallel to the longitudinal axis of the elongated element; in that the cross-sectional surface of the rod- like member is configured such as to hold and retain the compacted material-batches displaced towards the heating section in their respective positions, even when a side- wall part, normally both side-wall parts, and/or the bottom-part of the heating section is/are displaced towards the compaction section. 7. Apparatus according to Claim 6, characterised in that the compaction section is constructed so that, when seen in the feed direction, a foremost material-batch will be compacted to a higher degree of compaction than a following material-batch. 8. Apparatus according to Claim 1 or 6, characterised in that each material-batch comprises a specific quan- tity of weighed material. 9. Apparatus according to Claim 1 or 6, characterised by a horizontally movable compacting-piston provided with a surface which is inclined to the horizontal plane. 10. Apparatus according to Claim 9, characterised in that said surface is inclined at an angle of from 40-60°. 11. Apparatus according to Claim 6, characterised in that the compacting end-face of the rod-like member is has an area which is more than 20%, preferably between 30 and 40% of the cross-sectional area of the compacted material-batch. 12. Apparatus according to Claim 6 or 7, characterised in that the rod-like member, when in its terminal posi¬ tion nearest the heating section, terminates short of the foremost material-batch in the line of material- batches. 13. Apparatus according to Claim 12, characterised in that the rod-like member extends through a pre- compacting section and is operative to form a cavity in an adjacent material-batch in the vicinity of a boundary layer or interface between two mutually adjacent material-batches. 14. Apparatus according to Claim 6, characterised in that the horizontally movable piston is intended to move through a shorter distance than the rod-like member. 15. Apparatus according to Claim 1, characterised in that final compaction of loose cutter chips or sawdust admixed with wood glue is effected to a ratio of at most 5:1. 16. Apparatus according to Claim 1, characterised in that the foremost material-batch located in the compac- tion section is finally compacted with the aid of a device, such as a roll, which acts in solely one direc¬ tion. 17. Apparatus according to Claim 16, characterised in that the degree of final compaction is chosen in depen¬ dence on the desired density of the elongated element produced. 18. Apparatus according to Claim 17, in which final compaction is effected with the aid of a roll, characterised in that a knife-like device is mounted adjacent the foremost material-batch. 19. Apparatus according to Claim 1, characterised in that a following material-batch having a lower degree of compaction, is advanced in the form of a cylindrical body and formed to its final shape in the final compac¬ tion stage. 20. Apparatus according to Claim 6, characterised in that during those time periods in which the side-walls of the heating section are displaced towards the compac¬ tion section, the cross-sectional surface of said rod- like member functions to compact each material-batch following the foremost material-batch and to exert a counterpressure of such magnitude as to prevent any tendency of the foremost material-batch from separating from the nearest following batch during said movement of said side-wall part. 21. Apparatus according to Claim 16, characterised in that a reinforcing net or mat is passed between the roll and a finally compacted material-batch. 22. Apparatus according to Claim 16, characterised in that the roll has a larger diameter when greater press depths are desired.

Inventors: ANDERSSON CURT, ANDERSSON, CURT
Applicants: ANDERSSON CURT, ANDERSSON, CURT
Application year: 1989
Main classification: B27N3
IPC codes: B27N3, B30B11