WO1990002641A1

WO1990002641A1 - A material compaction arrangement for use in the manufacture of rigid beams

Info

Publication number: WO1990002641A1
Application number: PCT/SE1989/000485
Authority: WO
Inventors: Curt Andersson
Original assignee: Curt Andersson
Priority date: 1988-09-12
Filing date: 1989-09-11
Publication date: 1990-03-22
Also published as: AU4226689A; FI911190A0; SE8803194L; SE464179B; EP0435899A1; SE8803194D0

Abstract

The invention relates to a material compacting arrangement for use in a plant intended for the manufacture of rigid, elongated structural elements (4) from binder-moistened loose material (2), comprising a compaction section (7), in which batches of binder-moistened loose material are compacted, a heating section (5) in which the compacted material batches are dried, and a transport arrangement which is intended to cause each of the material batches compacted in the compaction section to pass through the heating section (5). The compaction section (7) is constructed to impart to the front material batch (2a), as seen in the feed direction, over a short transport path, a higher degree of compaction than a following, pre-compressed material batch (2b) over a longer transport path, by using a screw compressor (10) for pre-compressing the material batch and a press roll for finally compressing, or compacting, (20) the batch.

Description

TITLE OF THE TNVFNTION : A material compaction arrangement for use in the manufacture of rigid beams

TECHNICAL FTELD

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, elongated structural elemnts, 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 subsequently 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 transporting arrangement by means of which each of the material batches compacted in the compaction unit is passed successively and in sequence, through the heating section.

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 no clearly defined interfaces can be considered to exist between two mutually adjacent batches.

The term "batch" is used primarily to provide a simple understanding of the discontinous production process taking place in a heating section provided with movable wall sections and bottom section.

BACKGROUND PRIOR AR T

A plant of the aforesaid kind is known from International Patent Application No. PCT/SE84/00303, which describes and illustrates an arrangement for producing an elongated element (a so-called beam), comprising a compaction or compaction section which includes compaction apparatus operative in sequentially displacing and compacting binder-moistened, mutually separate material batches which have been clearly defined by weighing, such that the compressed or compacted, separate material batches can be passed sequentially 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, codirectionally with the centre line of the heating section and the outfeed direction of the beam subsequent 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 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 compressed to the desired degree of compaction, all of the compressed material batches present in the heating section, including the last compressed 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 compressed material batches.

In each of the aforesaid known methods, the so-called beam is produced from separate, 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.

The following publications also disclose subject matter belonging to the prior art:

WO-A1 - 85/01243

SE-A-219 835

SE-A-183 492

DE-B2-22 55 712

AT-A-172 687 and Derwent's Abstract No. 26943 C/15 SU 679 420.

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 complicated 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 element produced in accordance with these known methods in the boundary region between two mutually adjacent compacted material batches. 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.

It will be also seen that a qualified technical problem resides in realizing that the aforesaid drawback can be eliminated by constructing the compaction section such that the material batches will never have the form of separate units, and such that said batches will merge more continuously with one another and will be compacted or compressed to increasing degrees of compaction as the batches pass through the compaction section. it will also be seen that a technical problem resides in the provision of a simple compaction section arrangement which will totally eliminate the previously occurring, sharply defined degrees of compaction and fibre movement between each batch and within each individual batch. It will also be seen that a technical problem resides in realizing that the latter technical problem can be solved in practice, by configuring the compaction section such as to enable a batch which has been pre-compacted to a pre-determined degree to be further compacted or compressed along an adapted, limited region of the longitudinal extension of the compaction section, where said pre-compaction can be terminated with a final, locally acting final compaction with the aid of a device which acts in one direction or also in a plurality of directions.

It will also be seen that a technical problem resides in realizing that with the aid of a screw conveyer, there can be obtained within said screw conveyer a region of successively increasing compaction, whereas at the end of the screw conveyer there is obtained a pre-determined degree of pre-compaction in a collection of binder- moistened material which is arcuate in cross-section and which is pressed into a rectilinear (rectangular) space, such as to change the shape of said collection and with the given degree of pre-compaction, and thereafter achieve a final degree of compaction with the aid of a roll or like device capable of producing a profiled cross-section with a profiled upper surface.

It will also be seen that a technical problem of creating conditions for discontinuous advance of material batches, despite the known realization that the weight per unit volume of the finished beam requires a portioning and weighing device for the separate batches of loose material used, without the occurrence of appreciable boundary regions between mutually adjacent batches, such that one batch cannot be distinguished from an adjacent batch, and therewith be able to eliminate the use of a plunger-charged portioning arrangement adjacent the compaction section.

It will also be seen that a technical problem resides in solving each of the aforesaid techincal problems related to a compaction section, and of realizing 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 with a pre-compaction and an immediately following, locally-acted final compaction in one direction, such as to form a finished outer surface for the manufactured beams within pre-determined regions, so that the beam will present pre-determined mechanical strength properties, for example beams which are able to fulfill the test results for accepted 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 screw conveyer is able, in practice, to impart an appropriate degree of pre-compaction to each of said material batches, whereas the final compaction of said batches can be effected with one or more rolls, and to create therewith conditions in which a reinforcing net or band can be applied to the top and/or bottom surface.

In the case of heating sections provided with movable walls, it will be seen that a technical problem resides in the ability to provide, with simple means, conditions which will eliminate rupturing tendencies or material- displacement tendencies of material batches located in the compaction section, even when the wall parts of the heating section are displaced back towards the compaction section, by imparting sufficiently high pre-com paction to said material batches.

SOLUTION

The present invention relates to the provision of a material-compaction arrangement capable of being used in a plant intended for the manufacture of rigid, elongated structural elements, so-called beams, from a binder- moistened loose material, said plant comprising a compaction section for the compaction of binder-moistened loose material batches, a heating section for drying the thus compacted material batches, and a transporting arrangement which is operative in causing each of the material batches compacted in the compaction unit to pass successively through said heating section .

The transporting arrangement utilizes, inter alia, the circumstance that the wall parts of the heating section are reciprocatingly movable in the direction of displacement of the material, and also employs the assistance of a conveyer.

For the purpose of solving one or more of the aforesaid technical problems, it is proposed in accordance with the invention that the compaction section is constructed such as to impart to the forwardly located material batch, as seen in the direction of feed, a higher degree of compaction than the compaction of a following material batch, among other things by utilizing a material transporter capable of imparting to the the following material batches a constant, or substantially constant degree of compaction.

It is also proposed as particularly suitable, optional developments that during its passage through said compaction section, a material batch is subjected to pre compaction with the aid of a screw conveyer.

It is also proposed that the degree of compaction concerned can be varied in dependence on the required density of the finished elongated element, and that when using a glue binder and a loose fibrous material in the form of cutter shavings or sawdust for instance, the final degree of compaction is at most 5:1. It is also proposed that the front batch is compressed to a final degree of compaction with the aid of a device which acts at least in one direction, preferably with the aid of one or more rolls.

A knife is positioned adjacent the final compaction stage, adjacent said roll, in order to prevent material from being picked-up by and accompanying said roll.

According to one embodiment of the invention, a following batch of material, compressed to a lower degreeof compaction, can be advanced in the form of a cylindrical body and, in such case, be 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 screw conveyer is preferably constructed such as to impart to subsequent material batches a degree of compaction, sufficiently great to prevent displacement of said walls from separating a forwardly located batch from a subsequent batch.

It is also proposed in accordance with the invention that a reinforcing mat, fibreglas mat, is past between the rolls and a finally compacted batch, such as to form a surface reinforcement. 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 primarily afforded by an arrangement constructed in accordance with the present invention reside in the provision of conditions which enable all mutually adjacent material batches are, as far as possible, compacted to mutually equal degrees of compaction, such as to eliminate thereby the occurrence of vertically extending, strength-impairing regions between mutually adjacent material batches .

When practising the present invention, it is also possible to profile and work the top surface of the socalled beam or elongated structural element during the final compaction stage.

--------------------------- The primary characteristic features of an arrangement constructed in accordance with the invention are set forth in the characterizing clause of the following Claim 1. --------------------------

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of a material compacting arrangement at present preferred and incorporated in a plant for the manufacture of elongated structural elements or socalled beams and presenting 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 prior art plant intended for the manufacture of elongated structural elements or so-called beams.

Figure 2 is a side view, partly in section, of a first embodiment of an inventive material compacting arrangement adapted for use with the plant shown in Figure 1; Figure 3 is a side view, partly in section, of a second embodiment of said arrangement; and

Figure 4 illustrates the driving influence of a screw conveyer in response to the displacement of the wall parts and bottom part of a heating section.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED

Figure 1 illustrates a plant 1 which is operative in producing a rigid, elongated element, or beam 4 from binder-moistened loose material 2, with the aid of a compaction section 7 and a heating section 5.

Thus, Figure 1 is a greatly simplified illustration, in side view, of a plant 1 for manufacturing an elongated element 4 or a beam. The plant illustrated in Figure 1 includes a hydraulic piston-cylinder device 10 having a piston and piston rod 9. The piston rod is reciprocatingly movable and coacts with a compaction device 8, having the form of a piston which extends somewhat into a compaction chamber 7', comprising a part, namely a rear wall part of said compaction section 7.

Located immediately above the compaction chamber 7' is a batch supply device 6. The upper part of the device 6 may be configured with a space for accommodating fibre material and a space for acommodating binder. The fibre material and binder are mixed together in specific proportions in a mixing station (not shown) and fed to a lower space. The total amount of fibre material required to produce a full beam is fed in batches from the lower space 6a to the compaction chamber 7', via a portioning and weighing arrangement not shown.

A ready-mix of fibre material and binder may alternatively be supplied to the arrangement 6 directly.

It will be understood, that instead of utilizing a fibre suspension mixed with binder, the elongated structural element can be formed by spraying or moistening fibrous material with binder, particularly in the latter case in which the 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, waste paper, textiles, sawdust, chips and like materials, or alternatively such a material admixed with plastic, bark and the like.

The compaction device 8 has the form of a piston and is activated by a hydraulic piston-cylinder device 10 having a piston and piston rod 9 capable of reciprocal movement. The compaction device 8 is shown 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 located in front of the compaction device is filled with a measured or weighed quantity of fibre material from the device 6, preferably with the aid of a vertically acting piston (not shown in the figure). This is effected by ensuring that the space or compaction chamber formed when the compaction device 8 is moved to the position illustrated in Figure 1 can be filled with said material batch upon said movement of the compaction device. When the compaction device 8 is moved to the right in Figure 1, the fibre material, or fibre batch, present in the compaction chamber will be compressed against the preceding material batch, such as to build upon one batch after another and thereby construct said beam. Thus, each of the 'sequentially located batches will be compacted in the compaction chamber 7' and displaced in the form of a unit to a following heating section 5. The finally compacted fibre 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 beam is discharged through the end part 5b of said section. The finished beam is referenced 4 in the drawings.

If desired, the beam 4 can be transferred directly to a processing plant 3 , in which the outer surfaces of the beam are coated with impregnating liquid, painted varnished or like treated.

The functions of the compaction device 8, the material and binder mixing and volume-proportioning arrangement, the fibre-material-containing plant 6 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 with guidance of the following functional description, the specific circuitry of said control means is not described here. In Figure 2, it is assumed that the compaction section 7 proposed in accordance with the invention also includes a pre-compacting device 10. This device is preferably capable of imparting a constant or substantially constant degree of compaction to material batches located in the space 11.

The following description is also intended to illustrate one such device in the form of a screw conveyer 18, 19. The device 10 is preferably constructed such as to impart to density-determined batches a degree of compaction of between 1.2:1 and 3:1, preferably 2:1 in a space 11 located at the end of the screw conveyer.

It will be understood that this compaction merely refers to pre-compaction of a material batch, such as to enable contemplated material batches to form, in sequence, an elongated configuration in the absence of appreciably marked border regions of mutually different degrees of compaction between mutually adjacent material batches, or in the absence of any such border regions whatsoever, It is true that the material conveyed by the screw conveyer 10, which is of known type, will be subjected to increasing compaction towards the space or section

11, but it will be understood that a constant degree of pre-compaction will preferably prevail in said space 11. The prevailing density of the glue-moistened fibrous material 2 can be evaluated with the aid of density- determining means (not shown in Figure 1) and when the registered density value is lower than a standard value, the force exerted by the screw conveyer, or the operating speed thereof, can be increased with the aid of control means not shown. The section 7 also includes a final compaction stage 12, in which the binder-moistened, pre-compressed material batches 2b are finally compressed, to form a finally compressed material batch 2a, preferably having a profiled top surface 2a'.

Thus, Figure 2 illustrates an inventive material compressing or compacting arrangement used in a plant intended for the manufacture of a rigid, elongated beam or structural element 4 from binder-moistened loose material 2, including the heating section 5 provided, in a known manner, with movable wall sections and in which the direction of movement conforms to the direction of movement of the material.

The Figure 2 illustration includes two vertical wall sections, which are made of electrical insulating material and of which only one, 15, is shown. Means (not shown) are provided for reciprocally moving the wall sections in the direction of the arrow 15a, and a bottom section 16 is similarly arranged for reciprocating movement, in the direction of arrow 16a, with the aid of means not shown in the drawing. The bottom section 16 is made of an electrically conductive material.

In Figures 2 and 3, the wall sections 15 and the bottom sections 16 are shown in their respective positions furthest to the left in said Figures.

In accordance with the present invention, the compaction section 7 is intended to impart to the front material batch 2a, as seen in the feed direction, over a very short displacement path, a higher degree of compaction than the compaction imparted to the pre-compressed material batches 2b located in the space 11.

This pre-compaction of material batches to a predetermined degree of compaction is achieved by utilizing the properties afforded by a screw conveyer 10, which comprises a tubular casing 17 which houses a helical screw 18 capable of being rotated by a shaft 19, and further comprises drive means not shown in the figure. The screw conveyer 10 has the dual purpose of feeding the material and pre-compressing the same.

The degree of this pre-compaction can be adjusted by adjusting the force acting on the screw helix and the pitch of said helix, and also the diameter of the tubular casing 17. Higher forces and smaller pitch will result in higher degrees of compaction. It is assumed that compaction in the tubular casing 17 takes place successively towards a desired degree of compaction and towards forwardly located material batches.

The front material batch 2a in the compaction section is finally compacted with the aid of a roll 20, Figure 2. The final degree of compaction is dependent on the degree of pre-compaction and the degree of final compaction, this latter determining the density of the manufactured beam. The smallest degree of pre-compaction is dependent on factors made apparent in the following.

The final compaction is dependent on the press depth of the roll, and it can be assumed that this roll will assist in imparting to the top surface 2a' a somewhat greater degree of compaction than the underlying parts.

A reinforcing net or reinforcing mat 12a can be passed through the roll 20, in each individual case, such as to provide surface reinforcement.

When desiring greater press depths, the roll will have a larger diameter than when desiring smaller press depths. The degree of final 'compaction should not exceed 5:1, but is dependent on the desired density of the manufactured beam.

Mounted beneath the roll 20 is a knife or doctor blade 21, which is flat when a flat top surface is required and profiled when a profiled top surface is required.

Although the illustrated embodiment includes only a single roll 20, it lies within the concept of the invention to use two or more rolls, or technically equivalent devices, so that final compaction of the material can be effected in stages.

As illustrated in Figure 2, material batches pre-compressed to cylindrical cross-section pass into a right- angled space 11, located immediately adjacent the final compaction stage, with the aid of the roll 20. lt will be understood, however, that the cylindrical, pre-compressed material batches can be fed directly to the final compaction stage, wherewith each subsequent material batch, with a lower degree of compaction, will be advanced through the space 11 in the form of a batch of cylinder configuration, and that this cylindrical batch will be transfigured to a polygonal cross-section