AN ARRANGEMENT FOR PRODUCING AN ELONGATED FIBROUS OBJECT

Abstract: The invention includes an arrangement for manufacturing an elongated object (4) comprising, inter alia, a fibrous material, by compressing (7, 8) a quantity of fibrous material provided with a binding agent and drying the compressed fibrous material by passing the material between the electrodes of a high-frequency drier (5). One electrode (12), preferably both electrodes (12, 13) of the drier is/are arranged to co-act with an electrode-heating device (16).

Description: TITLE OF THE INVENTION: An Arrangement for produc ing an elongated fibrous ob ject . TECHNICAL FIELD The present invention relates to an arrangement for produ¬ cing an elongated object which is comprised, inter alia, of a fibrous material, and relates more specifically, although not exclusively, to an arrangement of the kind in which the elongated fibre-containing object is produced by compressing a quantity of fibrous material provided with a moist binder and drying the compressed fibrous material/binder mixture, by passing said mixture between the electrodes of a drier which is active at high frequencies. BACKGROUND PRIOR ART Swedish Patent Specification published under publication number 415 547 teaches an arrangement for producing an elon¬ gated object or product, in which fibre material provided with a binder is compressed, by feeding a proportion of the total amount of fibre material for the whole object to a compression chamber provided with compressing means. The compressing means are then activated such as first to compress said proportion of fibre material and then push said material into a matrix, the compression means then being withdrawn from the compression chamber so that a fur¬ ther proportion of fibre material can be delivered thereto and compressed and displaced by the compressing means. According to the above mentioned Swedish patent specifica¬ tion, the matrix shall ' include a plurality of wall sections and at least one of those wall sections shall be arranged for- movement relative to the object, with said relative movement being directed in the direction of the longitudinal axis of the object or in the production direction. The US Patent Specification 4,673,345 teaches the use of a heating arrangement in the form of a drier which is active at high frequency with an arrangement of the kind taught by the aforesaid Swedish patent specification. SUMMARY OF THE INVENTION TECHNICAL PROBLEMS When considering the present state of the art as described above " it will be realized that when the heating arrangement comprises a high-frequency active drier, a technical problem resides in the provision of conditions which will avoid or at least substantially prevent the precipitation of conden¬ sation on cold surfaces, particularly when starting up the drier, such condensation being found to impair the working of the drier and also likely to render the drier components defective. When considering the above technical problem, it will be seen that a further technical problem resides in realizing that said problem can be solved by preheating the electrodes. Another technical problem is one of realizing that a heating arrangement which is used to preheat the electrodes can also be used to impart smoother surfaces to the finished product. It will also be seen that a technical problem resides in the provisipn of an electrically operated, electrode-heating device in a high-frequency active drier while creating con¬ ditions which will reduce the effect from the generation of voltage which the drier will produce as a result of the electrical conductors serving the heating arrangement and located in the electromagnetic field. Another technical problem is one of providing means for removing by suction air laden with water vapour from a cavi- ty enclosed by the electrodes and a cavity surrounding the electrodes, in a manner such that while enabling moisture containing air to be removed from said cavities the electro¬ des will not be ' cooled to an undesirable extent in the pro¬ cess. This implies that the quantity of water vapour removed by suction shall be adapted to the water vapour (steam) generated at that moment in time. ~~ A further technical problem is one of being able to orienta¬ te a plurality of heating devices in the immediate vicinity of the electrodes while, at the same time, enabling the electrodes to be supported against an insulating glass com¬ posite material. When using a composite glass material, which is intended to support the electrodes and 'to form two mutually opposing matrix walls, it will be seen that a technical problem is one of providing for suitable displacement of the matrix walls and the electrode within the drier relative to the material produced, such that said displacement is effected in response to the movement of a piston or plunger intended for compression of the binder-containing fibrous material. A further technical problem is one of creating in a high- frequency active drier which operates in conjunction with an arrangement for producing an elongated Object or product conditions which will enable the drier to be screened elec- tromagnetically from the surroundings. SOLUTION The present invention can be considered to be based- on an arrangement for manufacturing an object comprised of, inter alia, a fibrous material, by compressing sequential quanti¬ ties of fibre material containing a moist binder, and drying the compressed fibrous-material quantities by passing the same between the electrodes of a drier which is active at high frequencies, in accordance with the teachings of the aforesaid US Patent Specification. In accordance with the invention it is now proposed that one electrode, preferably both electrodes, incorporated in the drier is/are arranged to co-act with an electrode-heating device which is constructed to heat the electrode and ele¬ ments located therearound to a temperature which will pre¬ vent condensation of the water present, prior to commencing the start of the object manufacturing process. Furthermore, it is proposed that a facility is provided which will enable air laden with water vapour to be removed by suction from a cavity or space which is partly enclosed by the electrodes and which partly surrounds the electrodes. The volume of air removed per unit of time is preferably adapted to or substantially adapted to the amount of water vapour generated in the drier. When the electrode-heating device is powered by electrical energy, the energy is supplied over an inductance. In accordance with one embodiment, a plurality of heating devices are positioned between electrically insulating glass composite material and in the immediate vicinity of the electrode. The electrical energy for powering the heating device is supplied to the one electrode, namely the electrode which is connected to earth in the system. The provision of an electrode-heating device will normally require a temperature on an electrode-sensing thermostat, and this sensing will also take place via an inductance. In accordance with one exemplifying embodiment of the pre¬ sent invention there is proposed the use of a glass compo¬ site material, and particularly the use of a glass composite material to form side walls in the drier and to support the drier electrodes, and in this context it is further proposed that the lower electrode shall be arranged to accompany the movement of a plunger or piston intended for compression of a quantity of binder-containing fibrous material, and that the two adjacent side walls comprising electrically insula¬ ting material are arranged to be displaced linearly in a manner to generate sufficient friction to join said quanti¬ ties. For the purpose of screening the high frequency drier, it is proposed that the electrodes and the glass composite mate¬ rial hav-e spaced therearound an electrically conductive layer which is effective in screening the high-frequency electro-magnetic field. In this regard, it is proposed that first rods made of glass composite material are arranged along two mutually opposite sides for abutment with the compressed quantities of fibrous material, and that a plurality of .second rods made of glass compos.ite material are arranged for supporting abutment with the electrodes along two mutually opposite sides. ADVANTAGES Those advantages primarily associated with an arrangement constructed in accordance with the present invention reside in the provision of conditions whereby at least one elec¬ trode can be heated prior to starting the process for manu¬ facturing the elongated object, so that said process can be commenced without water vapour condensing on the high-fre¬ quency drier electrodes or in the vicinity thereof. The primary characteristic features of an arrangement con¬ structed in accordance with the present invention are set forth in the characterizing clause of the following Claim 1, BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment having features characteristic of the present invention will now be described in more detail with reference to the accompanying drawings, in which Figure l.is a side view, highly simplified, showing the principle construction of an arrangement according to the present invention for manufacturing an elongated object; Figure 2 is a sectional view of a preferred high-frequency drier used in the arrangement of Figure 1; Figure 3 illustrates a simplified technical coupling arran¬ gement for the electrodes incorporated in a high-frequency drier, to permit adaptation of the power emission; and Figure 4 illustrates a simplified coupling circuit for supp¬ lying electrical energy to an electrode-heating device. DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a highly simplified side view of an arrangement 1 for manufacturing an elongated object 4 in accordance with the present invention. The arrangement illustrated in Figure 1 includes a hydraulic piston-cylinder device 10, with associated piston and piston rod 9. The piston rod is reciprocatingly movable and co-acts with a compressing device 8, which has the form of a plunger and extends somewhat into a compression chamber 7 and forms a part of said chamber, namely a rear wall part thereof. In addition to said rear wall part, the compression chamber 7 is also defined by a bottom part and two side parts, and also by the latest compressed quantity of fibrous material. Arranged immediately above the compression chamber 7 is a device 6. The upper part of the device 6 may be configured with a space for receiving fibrous material and a space for receiving moist binding agent, the fibrous material and bin¬ ding agent being mixed into portions of pre-determined size and moisture content in a mixing station not shown, where¬ after the resultant proportions are fed to a lower space 6a of the device 6. A proportion, or quantity, of the total fibre material required for the whole of the object 4 is dispensed to the compression chamber 7 from the aforesaid lower space, with the aid of dispensing or portioning devi¬ ces not shown. A particularly suitable alternative, however, is to use a ready mixture of fibrous material and moist binder, and to supply this ready mix directly to the device 6, where said proportion or quantity is measured by a weighing device and a compression plunger or filling plunger presses a weighed quantity of said mix into the compression chamber 7 and forms therewith the upper part of the compression chamber 7. As will be understood, as an alternative to using a fibre suspension which is mixed with a binding agent, the elonga¬ ted object can be formed by spraying or moistening a fibrous material with binding agent, in which case, and particularly in the latter case, the material is fed directly to the com¬ pression chamber 7 and there subjected to pressure. The fibrous material may comprise cutter shavings, paper waste, plastics materials, sawdust and like materials. The compressing device 8, which has the form of a plunger, is moved reciprocatingly by the aforesaid hydraulic piston- cylinder device 10, with associated piston and piston rod 9. In Figure 1 the compressing device 8 is shown in a side view, in a non-compressing position and therewith withdrawn from the compression chamber. When the compressing device occupies its illustrated position, the space located for- wardly of the compressing device is filled with fibre mate¬ rial from the device 6. This feed of material from said device can be effected by causing the compressing device 8 to expose an opening upon movement of said compressing devi¬ ce to the position shown in Figure 1, thereby ensuring that the space or compression chamber thus formed can be filled with the aid of a further plunger, not shown in the Figure. When the compressing device 8 is displaced linearly to the right in Figure 1, the fibre material or fibre-material quantity located in the compression chamber will be compres¬ sed against the preceding quantity of material, which has previously been compressed, so as to build-on a further quantity of material in the production of the complete object 4. During this described displacement of the compressing means 8, the filling or charging plunger is in its lower position. Thus, sequential proportions or quantities of material will be compressed in the compression chamber 7 and displaced in the form of an integral unit to a heating section, via a matrix. There is nothing to prevent this heating section from also including the compression chamber 7, particularly when the heating section utilizes a drier which is active at high frequency, since in this case it is only necessary for the electrodes to be allowed to pass the compression chamber 7 and to provide in the upper electrode an aperture which will accommodate the charging or filling plunger used to introduce a further, weighed quantity of fibre material into the compression chamber 7. The compressed fibre material, supplied with moist binder, is now introduced into the heating section and there treated with heat by means of a high-frequency heating device, whereafter the dried elongated object 4 can be discharged through a part 5b. The finished object is referenced 4. The object 4 may also conceivably be transferred directly to a treatment plant 3 , in which the outer surfaces of the object are treated with an impregnating liquid, or coated with paint, varnish or the like-. The arrangement illustrated in Figure 1 also includes a con¬ trol means 2 which controls the times at which reciprocating movement of the compressing device 8 is initiated. The con¬ trol means also controls material and binding agent and the device proportioning the volumes of individual quantities of material, and the device 6 containing the fibre material and pressing means associated with said device, together with other operational functions of the arrangement 1. The speci¬ fic electric circuitry of the control means 2 has not been illustrated, since the construction of said control means will be readily apparent from the following functional description. According to the present invention, the control means 2 also includes requisite electrical circuits for operating a dryer which is active at high frequencies. Figure ' 2 is a sectional view of a high-frequency dryer 5 constructed in accordance with the present invention. Figure 2 illustrates the orientation of the elongated binder-containing fibrous object 4 as it passes through a matrix, the upper surface of which is formed by the one electrode 12 of the high-frequency system, whereas the lower surface is formed by the second, the earthed electrode 13 of said high-frequency system. The two side surfaces of the matrix are formed by two rods 14, 15 which comprise a glass composite material and which are fitted in between the electrodes 12, 13. In accordance with the invention one electrode 12, although preferably both electrodes 12, 13, is arranged to co-act with one or more electrode-heating devices 16, the illustra¬ ted embodiment having four such devices 16 arranged to co-act with the upper electrode and four similar devices arranged to co-act with the lower electrode 13. These electrode-heating devices are intended to heat, prior to initiating the manufacturing process, not only the eleσ»- trodes 12, 13 but also elements peripheral of said electro¬ des, such as the rods 14,15 and rods 17,18, and also other elements, such as a top cover plate, to a temperature such as to avoid condensation of the water vapour generated onto cold surfaces. It can be mentioned in this connection that water vapour is generated when drying the quantities of mixed fibre-binder, materials at the very moment of starting up the drier. This water vapour normally rises and if it condenses on cold surfaces it is liable to cause electric discharges. This is particularly applicable when the electrode and the electrode surroundings are " not earthed in the system. It is also proposed that air laden with water vapour is removed through a pipe 19 from a space enclosed by the electrodes 12, 13 and the rods 14 and '15, and also from a space 20 which surrounds the electrodes. The space 20 communicates with the pipe 19 via openings 21. The volume of air thus extracted is preferably adapted, with the aid of a fan means not shown, such that said air volume per unit of time is commensurate with or essentially commensurate with the amount of water vapour generated in the drier. It should be noted in particular that if the volume of air withdrawn by suction is set to exceed the volume of water vapour generated, only an insignificant amount of air will be able to pass in through the infeed side 5a, so that no wall portions will be cooled. Air which-passes in through the outfeed side 5b will also have a cooling effect and should be avoided. In order to ensure that sufficient heat is obtained on the infeed side 5a, hot air may be directed onto the compression chamber 7 and elements located therein. In this case, the volume of air extracted by suction should be increased, so that the hot air will pass into the matrix and around said matrix and the electrodes. It is also proposed in accordance with the present invention that the lower system-earth electrode or the lower electrode 13 is firmly connected, via electrically insulating glass composite rods 18, to a bottom plate 22 which is joined to the plunger 8 and thus moves together with said plunger. The glass composite rod 14 is firmly connected to a plate 23 and the glass composite rod 15 is connected firmly to a plate 24, which are arranged to be displaced linearly by hydraulic piston-cylinder devices (not shown) corresponding to the piston-cylinder device 9, 10. The upper electrode 12 is connected firmly to a plate 25 via rods 17 which comprise a similar glass composite material. The plates 22, 23, 24 and 25 are made of an electrically conductive material. Located above the upper plate 25 is a heat insulating mate¬ rial 26, while located above said material 26 is a space 27 through which air laden with water vapour is conducted to a pipe or outlet 19 and from there away from the system. The inner surfaces of the plates or elements 22, 23, 24 and 25 are coated with a copper layer intended for screening the electromagnetic field. Since a given degree of relative movement will take place between the element 22 and the ele¬ ments 23 and 24, and between the elements 23 and 24 and the element 25, copper rails 30, 31 are arranged between said elements 22, 23 and 24 respectively, while copper rails 32, 33 are arranged between the element 25 and the elements 23 and 24. The aforesaid glass composite material comprises a material retailed under the trade mark "ARCLEX". Figure 3 illustrates a connection 36 for supplying energy to the high-frequency dryer. The connection 3 is connected to the upper electrode 12 which is connected through a connec¬ tion 37 to the bottom electrode 13, which in turn is connec¬ ted by an electrical conductor to system earth 38. The electrodes 12 and 13 are also connected electrically to a respective plate 34 and 35 of a capacitor, the capacitance of which can be varied by altering the distance "<i ,r between said plates. This variation in distance "d_" can best be effected by mounting the plate 3 for movement along a guide, towards and away from the plate 35. This possibility of adjusting the aforesaid distance "d_" enables the high-frequency circuit to be tuned to pre-selec- ted operating conditions. In the case of certain applications it may be necessary to adapt the system in a manner which is not contingent on the plate 34 and 35, but which requires the use of different lengths of the connection 37. It is possible with the aid of solely one, or with the aid of both adapting possibilities to change and move the volta¬ ge distribution, and therewith the drying effect along indi¬ vidual length sections of the electrodes 12 and 13. Figure 4 illustrates an exemplifying circuit for the supply of electrical energy to the heating device 16, said supply being effected over an inductance 40, 41 and with four capa¬ citances 42 and 42a, 43 and 43a connected to system earth 38 for the high-frequency system. This circuit, or coupling, is intended to reduce the generation of voltage occurring in the device 16 as a result of the high-frequency circuit and of the cable connections. The capacitances are intended to dampen induced voltage peaks. As will be seen from Figure 2, a plurality, four, heating- devices 16 are arranged between electrically . insulating, glass composite materials 17, each of said devices being supplied with energy through a Figure 4 circuit. The supply of electrical energy to the device 16 located adjacent the bottom electrode 13 can be effected directly to' said electrode, without passing through the Figure 4 cir¬ cuit, since the electrode 13 is connected to system earth 38. In the case of the illustrated embodiment, respective devices are surrounded by a screening tube which extends out of the electromagnetic field. It should be noted, however, that in this case the device 16 shall be fully encompassed in a screening tube, a copper tube, which extends completely through the electromagnetic field. Although not shown in the drawings, the arrangement includes a temperature sensing thermostat which is connected to the upper surface of the electrode 12 and which senses through an inductance and with the aid of a plurality of capacitan¬ ces, in the manner indicated in Figure 4. As previously mentioned, the bottom electrode 13 shall move together with the plunger 8, by means of which a quantity of fibrous material provided with a moist binder is compressed, while the two side walls, made of an electrically insulating material, are moved simultaneously through approximately half of said movement. -The relative displacement between the stationary electrode 12 and the side walls 14, 15, and the relative displacement between the movable electrode 13 and the side walls is adap¬ ted so that there is generated thereby sufficient friction to join the separate fibre quantities together and to impart a smooth surface to said quantities. It will also be seen from Figure 2 that the first rods 14, 15 of glass composite material are arranged to abut the com¬ pressed quantities along two mutually opposite sides of the object 4, and that one or more second rods 17, 18 made of glass composite material are arranged to supportingly abut the electrodes 12, 13 along two mutually opposite sides. The electrodes and rods extend from the compression chamber 7 to said end part 5b. Although the compression chamber 7 of the illustrated exem- plifying embodiment is located within the dryer 5, the upper electrode 12 being provided with an aperture through which the fibre-binder mixture can be passed, it also lies within the scope of the invention to provide a compression chamber which is separate to and spaced from the dryer. This latter alternative can be expected to afford somewhat simpler mea¬ sures in respect of the drier. It will be understood that the invention is not restricted to the illustrated and described embodiment, since modifica¬ tions can be carried out within the scope of the invention defined in the following claims.

Claims: CLAIMS 1. An arrangement for manufacturing an elongated object which comprises, inter alia, fibrous material, by compress¬ ing a quantity of fibrous material provided with a binder and drying said compressed fibrous material bypassing said material between the electrodes of a drier which is active at high frequencies, characterized in that the one electro¬ de, preferably both electrodes, of the drier are arranged for co-action with an electrode-heating device. 2. An arrangement according to Claim 1, characterized in that the electrode-heating device is constructed to heat the electrode and elements peripheral of said electrode prior to the start of an object manufacturing process, to a tempera¬ ture at which condensation of water vapour is prevented. 3. An arrangement according to Claim 1 or 2, characterized in that air laden with water vapour is removed by suction from a space enclosed by the electrodes and surrounding the electrodes. 4. An arrangement according to Claim 3, characterized in that the volume of air extracted by suction per unit of time is commensurate or essentially commensurate with the amount of water vapour generated in the drier. 5. An arrangement according to Claim 1, characterized in that electrical energy is supplied to the heating device over an inductance. 6. An arrangement according to Claim 1, characterized in that the heating device is located between electrically insulating, glass composite material. 7. An arrangement according to Claim 1 or Claim 5, characte¬ rized in that electrical energy is supplied to the heating device of one electrode directly. 8. An arrangement according to Claim 1, characterized in that a temperature sensing thermostat sense over an induc¬ tance. 9. An arrangement according to Claim 1, characterized in that the bottom electrode moves together with a plunger intended for compressing a quantity of fibrous material pro¬ vided with a binding agent, and in that two side walls made of electrically insulating material are arranged to be dis¬ placed in a manner such as to thereby generate sufficient friction to join contiguous quantities of fibrous material together. 10. An arrangement according to Claim 1, characterized in that the electrodes are each surrounded in spaced relation¬ ship by an electrically conductive layer effective in scree¬ ning the high-frequency electromagnetic field. 11. An arrangement according to Claim 1, characterized in that first rods formed from a glass composite material are arranged to abut the compressed quantities along two mutual¬ ly opposite sides, and in that a plurality of second rods formed from a glass composite material are arranged to sup¬ porting abut the electrodes along two mutually opposite sides.

Inventors: ANDERSSON KURT, ANDERSSON, KURT
Applicants: ANDERSSON KURT, ANDERSSON, KURT
Application year: 1988
Main classification: B27N3
IPC codes: B27N3, B29C35, B29C47, D21J3, F26B3, H05B6