CA1053555A - Method of and apparatus for the continuous production of chipboard, fibreboard or like panels - Google Patents
Method of and apparatus for the continuous production of chipboard, fibreboard or like panelsInfo
- Publication number
- CA1053555A CA1053555A CA214,837A CA214837A CA1053555A CA 1053555 A CA1053555 A CA 1053555A CA 214837 A CA214837 A CA 214837A CA 1053555 A CA1053555 A CA 1053555A
- Authority
- CA
- Canada
- Prior art keywords
- press
- roller
- zone
- pressure
- drum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
- B27N3/08—Moulding or pressing
- B27N3/26—Moulding or pressing characterised by using continuously acting presses having a heated press drum and an endless belt to compress the material between belt and drum
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
- Press Drives And Press Lines (AREA)
- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The continuous production of chipboard panels is effected by depositing a ribbon of chips provided with a binding agent onto an endless belt, passing the endless belt and ribbon of chips through a heated press zone including a press drum and a press roller of substantially the same diameter and in pressure contact with the press drum through the endless belt and the ribbon of chips, and subjecting the ribbon of chips in the heated press zone alternately to high and low pressure. The heated press zone includes a zone of high pressure formed by a line of pressure between the press drum and the press roller, the pressure being approximately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow; the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone. The invention enables one to manufacture chipboard panel webs having up to 20 mm. in thickness.
The continuous production of chipboard panels is effected by depositing a ribbon of chips provided with a binding agent onto an endless belt, passing the endless belt and ribbon of chips through a heated press zone including a press drum and a press roller of substantially the same diameter and in pressure contact with the press drum through the endless belt and the ribbon of chips, and subjecting the ribbon of chips in the heated press zone alternately to high and low pressure. The heated press zone includes a zone of high pressure formed by a line of pressure between the press drum and the press roller, the pressure being approximately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow; the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone. The invention enables one to manufacture chipboard panel webs having up to 20 mm. in thickness.
Description
163S~555 The invention relates to a method and apparatus for the continuous production of chipboard, fibreboard or like panels.
In one previously proposed method, a ribbon of chips incorporating a binding agent is fed onto an endless belt and passes along a heated moulding zone in whi~h it is alternately subjected to high and lower pressures. As this happens, the ribbon of chips is pressed between the endless belt and a press drum against which a plurality of presser rollers additionally press. The looping angle relevant to the length of the heated pressing zone amounts to approximately 270, so that the emerging chipboard panel therefore has again to be guided around a reversing roller, through 180. Thick chipboard panels cannot be produced on this plant.
In a second previously proposed method, the ribbon of chips passes between two endless belts, through a system of successive mutually staggered rollers which press against one another. Large angle bends in the chipboard panels are largely avoided in this method, but the durability of the two endless 20 belts is rendered unsatisfactory by reason of the increased -alternating bending loading.
In a third method it has been proposed to pass the ribbon of chips without any change in direction, between two rollers which act under high pressure directly on the chip ribbon. However, this third method provides only a preliminary pressing and an intermittently operated panel press provided downstream of the pair of rollers is also required. ~`
A fourth previously proposed method for the continuous production of chipboard panels utilises a press drum, around which a belt is partially looped, to diminish bends, the chipboard panels emerging from the pressing zone being fed in the form of a loop of reversed curvature to an intermittently 105~5S5 operating saw. This fourth method is suitable only for relatively thin chipboard panels, because, while the fèed is stopped upstream of the saw, the loop serves as a store for the web of chipboard panels which are being constantly supplied.
According to the invention, there is provided a method for the continuous production of chipboard panels, which comprises depositing a ribbon of chips provided with a binding agent onto an endless belt, passing the endless belt and ribbon of chips through a heated press zone including a press drum and a press roller of substantially the same diameter and in pressure contact with the press drum through ; the endless belt and said ribbon of chips, and subjecting the ribbon of chips in the heated press zone alternately to high and low pressures. The heated press zone includes a zone of high pressure formed by a lir.e of pressure between the press drum and the press roller, the pressure being approximately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow;
the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone.
The mean temperature in the press zone is preferably about 170C.
Due to this zone of high pressure and the length of the line of pressure, the ribbon of chips is so compressed that any increase in its volume is diminished, which formerly was a problem due to the moisture contained in the chips. If moisture is present, the ribbon tends to spriny back so that the glue bridges formed in the press zone may be partially broken. Due to the high oressure ... .
.. . ~
(about 600 kp/cm) and the length of the pressure line (at least 7 cm), the tearing open of the glue bridges formed in the high pressure reqion is prevented, in accordance with the invention.
The present invention also provides an apparatus for carrying out the above method, which comprises an endless belt, means for depositing a ribbon of chips onto the endless belt, a heated press zone for subjecting the ribbon of chips in the heated press zone alternately to high and low pressures, the heated press zone including a press drum, a press roller having a diameter substantially the same as the diameter of the press drum, a presser roller spaced from the press roller and being relatively smaller in diameter, and an inlet roIler spaced from and of similar diameter to the presser roller.
The endless belt is looped partially around the inlet roller, presser roller, press drum and press roller and defines therewith the heated press zone, the press roller being arranged as the last drum within the circle of the endless - belt in the direction of movement of the belt; the inlet roller, presser roller and press roller are in pressure contact with the press drum through the endless belt and the ribbon of chips. The heated press zone includes a zone of high pressure formed by a line of pressure between the press drum and the press roller, the pressure being approxi-mately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow; the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone. The alternate high and low pressures in the heated press zone are provided respectively by the lines of pressure between the inlet roller, presser roller , ~,...
lOS35S5 and press roller against the ~)ress drum and the intervening zone areas where the pressure is maintained only by the endless belt.
In a preferred embodiment of the apparatus of the invention, the press drum and the press roller have diameters of such a value and offer such a mutual pressure on the belt extending between them and carrying the ribbon of chips, that the product of pressure, in kp/cm of chipboard panel width, and diameter, of one of the press drum and the press roller, exceeds 1,000 kp-m/cm. This product of pressure and diameter is preferably about 1,800 kp-m/cm.
Preferred embodiments o the invention will now be described in ~reater detail with reference to the accompanying drawings, wherein:
Figure 1 : shows one embodiment of apparatus for carrying out the method of the invention;
Figure 2 : shows a pair of rollers to achieve the high-pressure regions in the apparatus of Figure l;
Figure 3 : shows a pair of rollers according to Figure 2 for achieving a broad pressure line; ,~"~
Figure 4 : shows a pair of rollers for achieving a narrow pressure line; and Figure 5 : shows an alternative embodiment of apparatus for carrying out the method of the invention to that shown in Figure 1.
Referring to the drawings, Figure 1 shows a machine wit,h a moulding station 1, for example comprising a sprinkling arrangement of known kind, an endless belt 2 made from steel or like material, an inlet roller 3, a press drum 4, a press roller 5 and a clamping roller 6. Between the inlet roller 3 and the press roller 5, it is possible also to provide one or more presser rollers 7 which are adjustable in the direction of the press drum and which produce additional high-pressure .- ~,~ . .
~B ~ 4 _ lQ5,3555 regions in a press ~one which lies between the inlet roller 3 and the press roller 5. The inlet rollex 3 and the press roller 5 are, to permit adjustment to the thickness of chipboard panel desired, likewise adjustable in a radial direction with :. /
/
:'' /
/
_ _ . _ _ . ~ - 4a -l~53cjs5 respect to the press drum 4. The press drum 4 and the press roller 5 are su~tantially of the same dimensions and have a dia~
meter of approximately 3 m.
The inlet roller 3 has a substantially smaller diameter than the press drum 4. The inlet roller 3 is so disposed that the endless belt 2 enters the gap formed between press drum 4 and inlet roller 3 at an angle of between 20 and 40 and prefer-ably 37.5. This has the advantage that the structure of the sprinkled chip ribbon is not altered upon entry into the press zone.
At the outlet formed between the press drum 4 and the press roller 5, the endless belt 2 emerges at an angle of 4~
to 100. With regard to the exit, the most favourable angle of emergence varies according to the intended thickness of the completed chipboard panel. In the case of the example illustrat-ed, the angle amounts to approximately 75. After emerging, the endless belt 2 is looped around the upper side of the press roller 5 together with the ribbon of chips or the web of chip-board panel and is then fed back to the clamping roller 6.
Associated with the upper side of the press roller 5 are one or a plurality, in the example illustrated there are two, presser rollers 8 which in this example act on that side of the chipboard panel web which bears against the press drum 4 with-- in the press zone. On the one hand, these presser rollers 8 produce a calibration of the chipboard panel web and on the other, they can by choice of varying speed with respect to the speed of the press roller 5, be utilised fcr polishing purposes. It is also possible for these presser rollers to eliminate faults in the surface.
Furthermore it is possible to introduce, via these presser rollers 8, films for covering the chipboard panel we~
. .
~ ~ --5--1~53555 ~ wo guide rollers 9 and a linear slide path 10 are provided to carry away the completed, possibly covered chipboard panel web 11.
The press roller 5 and the two presser rollers 8 are driven. With regard to the press roller 5, this has the advan-tage that by reason of the considerable area of contact between the belt 2 and the press roller 5, the endless belt 2 can be more gently driven than if it was driven by a smaller r~ller, for example the clamping roller 6. The driving of the presser rollers 8 has the advantage that together with calibration, polishing and fault correction can be effected.
Between the rollers 3, 7, 5 and 8, additional heating means may be provided. These heating means, not shown, are preferably infra-red radiators, if they act on the endless belt, and heating coils if they act directly on the web of chipboard , panel.
The press drum 4 and the rollers 3, 5, 7 as well as the rollers 8, if provided, are maintained at a temperature of 170C for example by means of a steam heating system. The infra-red heaters, if provided, between the rollers 3 and 5 producea temperature of approximately 200C.
During the return path of the endless belt 2 from the roller 7 to the moulding station 1, the belt cools sufficiently for there to be no premature hardening of the binder contained in the chip ribbon, during the spreading-on process. If necessa-ry, the clamping roller 6 and prossibly also the belt 2 in the region of the clamping roller 6 may be cooled.
The various rollers act with the following pressures on the relevant counter-rollers or on the press drum 4 (or on the ribbon of chips, as the case may be):
Inlet roller 3 (against press drum 4): 340 kp/cm roller length Presser roller 7( " " "): 550 kp/cm " "
11~535SS
Press roller 5 ( " " ~ 600 kp~cm Presser roller 8( against press roller 5~;
each 125 kp/cm roller length The diameters of the various rollers and the drum are dimensioned as follows :
Press drum 4, press roller 5 : each 3,000 mm Inlet roller 3, presser roller 7 : each 1,600 mm Clamping roller 6 : 1,600 mm Presser rollers 8 : each 800 mm The machine described thus far operates as follows ;
In the moulding station 1, a ribbon of chips comprising chips provided with a binding agent, is fed onto a substantially plane portion of the endless belt 2 which runs at continuous speed around the rollers 3, 7, 5, 6 lying on the belt 2, the chip rib-bon runs into the intake between the roller 3 and the press drum 4 in which, by reason of the optimum angle of intake, it is not distorted but is pressed, as desired, During the course of the overall press zone, between the intake (at the nip between the inlet roller 3 and the press drum 4) and the outlet (at the nip between the press drum 4 and the press roller 5), the chip ribbon is subjected to alternately high and low pressures. I'he high-pressure is applied by the rollers pressing against the drum 4 the lower pressure is ap-plied by the endless belt 2 which is tensioned against the press drum 4. With the entrance into the press zone between the press drum 4 and belt 2, thechip ribbon additional~y passes into a - region of high temperature by which the thermoplastic adhesive is activated. It has been found that the combined application of a high pressure and of a relatively high temperature has favour-able consequences on the pressing and solidification of the chip xibbon.
-7~
F'igure 3 symbolically shows tl~e entry o~ ~ still thic~
chip ribbon into the gap between a pair of rollers, as shown the press drum 4 and the press roller 5. For ease of observation, the chip ribbon 11 is shown fed linearly to the gap between the drum 4 and the roller 5 and without the belt 2. As soon as the still tick chip ribbon 11 contacts the periphery of the drum 4 and roller 5, the drum and roller produce a compression with a considerable rise in pressure. This pressure rise is effected in the case of rollers of smaller diameter, for example the press-er roller 7 shown in Figute 2 which acts on the drum 4, consider-ably later, because the ribbon of chips does not strike the apex of the roller 4 until shortly before the middle of the gap.
Since the ribbon of chips leaves the outlet of the pair of rollers in a pressed condition, the width of the pressure line acting on the chip ribbon between the two rollers is not symmet-rical. Without regression, the pressure line extending transver-sely to the direction of feed would extend from the point of contact of the chip ribbon 11 and press roller 5 as far the point of least gap thickness. As the pressure line patterns shown in Figures 3 and 4 for two roller diameters (although these are symmetrically illustrated), the pressure rise between two large rollers is considerably broader than between a large roller and a small roller.
Over the course of the press zone, the ribbon of chips lies directly on the periphery o~ the press drum 4. Therefore, this acts more intensively on the chip ribbon than do the other rollers associated with the press zone, which act on the chip ribbon onlyvia the endless belt~. The gluebridges formed during solidification of the binder as it passes through the press zone are therefore more s017 d at the outlet of the press zone on the face of the chipboard adjacent the roller 4 than are the glue ~ridges which are directed towards the endless belt 2.
;.' - , , :
This gives rise to the danger that the completed chip~oard panels may be curved. This danger is diminished in many ways in the case of the rn~chine of Figure 1.
By the introduction of zones of alternately high and low pressures at relatively high temperature, particularly the region having a broad pressure line between the pressdrum 4 and the press roller 5, the freedom of the chipboard panel web from regeneration is achieved already after a relatively small loop-ing angle. This is favoured by the possibility of providing the high-~ressure zone not only with a longer action time (broad line of pressure), but also with a substantially higher pressure.
By the choice of press drums or press rollers of large diameter such as is required to achieve the broad pressure line, there is at the same time an increase in the pressure loading capacity of these two rollers or drums including the belt 2 which is passed between them. However, this is not only more favour-able to the pressure, temperature and pressure line factors which are essential for the hardening of the ribbon of chips, by reason of the greater diameters of the rollers, also the ribbon of chips is above all less curved in the press zone.
Any residual curvature can easily be compensated during the hardening phase while the web of chipboard panel is still heated. For this purpose, the web of chipboard panel emerging - from between press drum 4 and press roller 5 is guided on with opposite curvature ~round the periphery of the press roller 5.
The side which faces the belt 2 continues to rest thereagainst and continues to receive heat from the heated press roller 5 where it can, under the pressure of the presser rollers 8, achieve correspondingly more solid glue bridges.
With the machine according to Figure 2, therefore, there is a bilateral hardening which is important particularly _g_ for thicker chipbo~lrd panels. At the same time, the presser rollers 8 which are significant for this purpose perform a calibration of the chipboard panel web.
The rollers 9 associated with the outlet from the calibration arrangement serve to hold and guide the chipboard panel weh 11 to the linear discharge zone lO.
The length of the treatment zone, that is to say the press zone and the hardening zone, extending between the intake constituted by the nip between the press drum 4 and the inlet roller 3 and the outlet formed by the nip between the final press-er roller 8 and the press roller 5 is for chipboard panel webs of 15 to 20 mm thickness, chosen to be 5.60 m, of which some 60 %
represents the press zone. The looping angles around the press drum 4 and press roller 5 are 120 and 90 respectively. For still thicker chipboard panels, the looping angle of the press drum 4 can for the same angle of run-on, be made larger so that `the chipboard panel emerges more steeply from the exit between the press drum 4 and the press roller 5. The looping angle of the press roller 5 can then be madecorrespondingly larger so that particularly in the case of thicker chipboard panels, that side of the chipboard panel which is less influenced by the press drum 4 can be hardened by extended looping around the heated roller 5.
In contrast to the construction of the machine according to Figure 1, the inlet rcller 3 may also have a diameter corres-ponding to the press drum 4 and may be operated at a correspond-ingly high pressure.
~-~ This construction may either be provided in addition to the press roller 5 constructed according to Figure 1 or ins-;` tead of this construction. This would have the advantage that the ideal combination of pressure and temperature is effective along a broad line of pressure already at the commencement of . . , , --10--lOS3S55 the press zone. In the case of thin chipboard panels, this would have the advantage that the chipboard panels could be taken off already at the low point of the press drum without the need for any nota~le cou~ter-curvature.
In the case of a machine with the dimensions given above the rotary speed of the press roller 5 is so chosen that the endless belt 2 moves at a speed of 15 m/min, the ribbon of chips being passed at this speed through the press zone including the regions of high and lower pressure. The indicated roller diameters, the pressure of the two rollers 4 and 5 on the ribbon of chips, the temperature of the press zone (particularly in the high-pressure region), the speed of the belt 2 and thus the period of dwell in the high-pressure region are so attuned to one another and possibly to the activation and hardening time of - the binder, that there is at the outlet from the press zone a substantially regression-free web of chipboard panel which has hardened without twisting by the time it emerges from the hard-ening zone at the roller 5. The width of the line of pressure between the press drum 4 and press roller 5, in the case of the dimensions used, amounts to 8 to 12 cm, the dwell time in this - zone amounting to 0.32 to 0.48 seconds according to the original thickness of the ribbon of chips entering the line of pressure.
~uring this period of dweel of the chip ribbon in the zone of the pressu~e line, the ribbon of chips is subject to a pressure of 600 kp/cm of roller length. The temperature o~ approximately 170C which is intensively active at this stage is, in conjunc-tion with the high pressure, of particular importance. A measure of the action on the chip ribbon is the product of dwell time, pressure and temperature, which in the case of the present example is 0.32 to 0 o48 sec. 600 kp/cm and 170C.
32,640 to 48,960C. sec. kp/cm.
' - : , . , , . . :
l~Ci3S55 It is true that the temperature may be raised above 170C but it doe~ not bring the advantages as does the raising of the pressure and increasing of the pressure zone, because the surface of the ribbon of chips could be damaged by that would then be excessive heat.
In the embodiment of Figure 5, a moulding station 1, an endless belt 2, an inlet roller 3, a first press drum 4, a press roller 5, a clamping roller 6, and at least one presser roller 7 are provided as in the embodiment of Figure 1. The endless belt 2 is looped thereby around the rollers 6, 3, 5, 7 and enclose a part of the periphery of the press drum 4 to form a press zone, In order to achieve a further zone having a sur-face pressure exerted on the ribbon of chips, there is disposed around the press drum 4 an endless pressure belt 12 which is additionally in direct contact therewith, which is partially looped around the pressure roller 5 and which can be tensioned by a roller 13 which is adjustable in position. Presser rollers 14help to maintain the pressure per unitof surfacearea generated by the taut belt 12 or even to increase it. The ribbon of chips enters the press zone at the nip between the inlet roller 3 and the press drum 4, It does not, however, come into direct contact with the periphery of the press drum 4, but lies between the two endless belts 2 and 12. m e ribbon of chips remains between these belts until it emerges at the nip between the press drum 5 and the presser roller 13.
In one previously proposed method, a ribbon of chips incorporating a binding agent is fed onto an endless belt and passes along a heated moulding zone in whi~h it is alternately subjected to high and lower pressures. As this happens, the ribbon of chips is pressed between the endless belt and a press drum against which a plurality of presser rollers additionally press. The looping angle relevant to the length of the heated pressing zone amounts to approximately 270, so that the emerging chipboard panel therefore has again to be guided around a reversing roller, through 180. Thick chipboard panels cannot be produced on this plant.
In a second previously proposed method, the ribbon of chips passes between two endless belts, through a system of successive mutually staggered rollers which press against one another. Large angle bends in the chipboard panels are largely avoided in this method, but the durability of the two endless 20 belts is rendered unsatisfactory by reason of the increased -alternating bending loading.
In a third method it has been proposed to pass the ribbon of chips without any change in direction, between two rollers which act under high pressure directly on the chip ribbon. However, this third method provides only a preliminary pressing and an intermittently operated panel press provided downstream of the pair of rollers is also required. ~`
A fourth previously proposed method for the continuous production of chipboard panels utilises a press drum, around which a belt is partially looped, to diminish bends, the chipboard panels emerging from the pressing zone being fed in the form of a loop of reversed curvature to an intermittently 105~5S5 operating saw. This fourth method is suitable only for relatively thin chipboard panels, because, while the fèed is stopped upstream of the saw, the loop serves as a store for the web of chipboard panels which are being constantly supplied.
According to the invention, there is provided a method for the continuous production of chipboard panels, which comprises depositing a ribbon of chips provided with a binding agent onto an endless belt, passing the endless belt and ribbon of chips through a heated press zone including a press drum and a press roller of substantially the same diameter and in pressure contact with the press drum through ; the endless belt and said ribbon of chips, and subjecting the ribbon of chips in the heated press zone alternately to high and low pressures. The heated press zone includes a zone of high pressure formed by a lir.e of pressure between the press drum and the press roller, the pressure being approximately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow;
the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone.
The mean temperature in the press zone is preferably about 170C.
Due to this zone of high pressure and the length of the line of pressure, the ribbon of chips is so compressed that any increase in its volume is diminished, which formerly was a problem due to the moisture contained in the chips. If moisture is present, the ribbon tends to spriny back so that the glue bridges formed in the press zone may be partially broken. Due to the high oressure ... .
.. . ~
(about 600 kp/cm) and the length of the pressure line (at least 7 cm), the tearing open of the glue bridges formed in the high pressure reqion is prevented, in accordance with the invention.
The present invention also provides an apparatus for carrying out the above method, which comprises an endless belt, means for depositing a ribbon of chips onto the endless belt, a heated press zone for subjecting the ribbon of chips in the heated press zone alternately to high and low pressures, the heated press zone including a press drum, a press roller having a diameter substantially the same as the diameter of the press drum, a presser roller spaced from the press roller and being relatively smaller in diameter, and an inlet roIler spaced from and of similar diameter to the presser roller.
The endless belt is looped partially around the inlet roller, presser roller, press drum and press roller and defines therewith the heated press zone, the press roller being arranged as the last drum within the circle of the endless - belt in the direction of movement of the belt; the inlet roller, presser roller and press roller are in pressure contact with the press drum through the endless belt and the ribbon of chips. The heated press zone includes a zone of high pressure formed by a line of pressure between the press drum and the press roller, the pressure being approxi-mately 600 kp/cm and the length of the line of pressure being at least 7 cm measured along the peripheries of the press drum and press roller in the direction of ribbon flow; the product of pressure and temperature in the high pressure zone is substantially higher than that in adjacent zones of the heated press zone. The alternate high and low pressures in the heated press zone are provided respectively by the lines of pressure between the inlet roller, presser roller , ~,...
lOS35S5 and press roller against the ~)ress drum and the intervening zone areas where the pressure is maintained only by the endless belt.
In a preferred embodiment of the apparatus of the invention, the press drum and the press roller have diameters of such a value and offer such a mutual pressure on the belt extending between them and carrying the ribbon of chips, that the product of pressure, in kp/cm of chipboard panel width, and diameter, of one of the press drum and the press roller, exceeds 1,000 kp-m/cm. This product of pressure and diameter is preferably about 1,800 kp-m/cm.
Preferred embodiments o the invention will now be described in ~reater detail with reference to the accompanying drawings, wherein:
Figure 1 : shows one embodiment of apparatus for carrying out the method of the invention;
Figure 2 : shows a pair of rollers to achieve the high-pressure regions in the apparatus of Figure l;
Figure 3 : shows a pair of rollers according to Figure 2 for achieving a broad pressure line; ,~"~
Figure 4 : shows a pair of rollers for achieving a narrow pressure line; and Figure 5 : shows an alternative embodiment of apparatus for carrying out the method of the invention to that shown in Figure 1.
Referring to the drawings, Figure 1 shows a machine wit,h a moulding station 1, for example comprising a sprinkling arrangement of known kind, an endless belt 2 made from steel or like material, an inlet roller 3, a press drum 4, a press roller 5 and a clamping roller 6. Between the inlet roller 3 and the press roller 5, it is possible also to provide one or more presser rollers 7 which are adjustable in the direction of the press drum and which produce additional high-pressure .- ~,~ . .
~B ~ 4 _ lQ5,3555 regions in a press ~one which lies between the inlet roller 3 and the press roller 5. The inlet rollex 3 and the press roller 5 are, to permit adjustment to the thickness of chipboard panel desired, likewise adjustable in a radial direction with :. /
/
:'' /
/
_ _ . _ _ . ~ - 4a -l~53cjs5 respect to the press drum 4. The press drum 4 and the press roller 5 are su~tantially of the same dimensions and have a dia~
meter of approximately 3 m.
The inlet roller 3 has a substantially smaller diameter than the press drum 4. The inlet roller 3 is so disposed that the endless belt 2 enters the gap formed between press drum 4 and inlet roller 3 at an angle of between 20 and 40 and prefer-ably 37.5. This has the advantage that the structure of the sprinkled chip ribbon is not altered upon entry into the press zone.
At the outlet formed between the press drum 4 and the press roller 5, the endless belt 2 emerges at an angle of 4~
to 100. With regard to the exit, the most favourable angle of emergence varies according to the intended thickness of the completed chipboard panel. In the case of the example illustrat-ed, the angle amounts to approximately 75. After emerging, the endless belt 2 is looped around the upper side of the press roller 5 together with the ribbon of chips or the web of chip-board panel and is then fed back to the clamping roller 6.
Associated with the upper side of the press roller 5 are one or a plurality, in the example illustrated there are two, presser rollers 8 which in this example act on that side of the chipboard panel web which bears against the press drum 4 with-- in the press zone. On the one hand, these presser rollers 8 produce a calibration of the chipboard panel web and on the other, they can by choice of varying speed with respect to the speed of the press roller 5, be utilised fcr polishing purposes. It is also possible for these presser rollers to eliminate faults in the surface.
Furthermore it is possible to introduce, via these presser rollers 8, films for covering the chipboard panel we~
. .
~ ~ --5--1~53555 ~ wo guide rollers 9 and a linear slide path 10 are provided to carry away the completed, possibly covered chipboard panel web 11.
The press roller 5 and the two presser rollers 8 are driven. With regard to the press roller 5, this has the advan-tage that by reason of the considerable area of contact between the belt 2 and the press roller 5, the endless belt 2 can be more gently driven than if it was driven by a smaller r~ller, for example the clamping roller 6. The driving of the presser rollers 8 has the advantage that together with calibration, polishing and fault correction can be effected.
Between the rollers 3, 7, 5 and 8, additional heating means may be provided. These heating means, not shown, are preferably infra-red radiators, if they act on the endless belt, and heating coils if they act directly on the web of chipboard , panel.
The press drum 4 and the rollers 3, 5, 7 as well as the rollers 8, if provided, are maintained at a temperature of 170C for example by means of a steam heating system. The infra-red heaters, if provided, between the rollers 3 and 5 producea temperature of approximately 200C.
During the return path of the endless belt 2 from the roller 7 to the moulding station 1, the belt cools sufficiently for there to be no premature hardening of the binder contained in the chip ribbon, during the spreading-on process. If necessa-ry, the clamping roller 6 and prossibly also the belt 2 in the region of the clamping roller 6 may be cooled.
The various rollers act with the following pressures on the relevant counter-rollers or on the press drum 4 (or on the ribbon of chips, as the case may be):
Inlet roller 3 (against press drum 4): 340 kp/cm roller length Presser roller 7( " " "): 550 kp/cm " "
11~535SS
Press roller 5 ( " " ~ 600 kp~cm Presser roller 8( against press roller 5~;
each 125 kp/cm roller length The diameters of the various rollers and the drum are dimensioned as follows :
Press drum 4, press roller 5 : each 3,000 mm Inlet roller 3, presser roller 7 : each 1,600 mm Clamping roller 6 : 1,600 mm Presser rollers 8 : each 800 mm The machine described thus far operates as follows ;
In the moulding station 1, a ribbon of chips comprising chips provided with a binding agent, is fed onto a substantially plane portion of the endless belt 2 which runs at continuous speed around the rollers 3, 7, 5, 6 lying on the belt 2, the chip rib-bon runs into the intake between the roller 3 and the press drum 4 in which, by reason of the optimum angle of intake, it is not distorted but is pressed, as desired, During the course of the overall press zone, between the intake (at the nip between the inlet roller 3 and the press drum 4) and the outlet (at the nip between the press drum 4 and the press roller 5), the chip ribbon is subjected to alternately high and low pressures. I'he high-pressure is applied by the rollers pressing against the drum 4 the lower pressure is ap-plied by the endless belt 2 which is tensioned against the press drum 4. With the entrance into the press zone between the press drum 4 and belt 2, thechip ribbon additional~y passes into a - region of high temperature by which the thermoplastic adhesive is activated. It has been found that the combined application of a high pressure and of a relatively high temperature has favour-able consequences on the pressing and solidification of the chip xibbon.
-7~
F'igure 3 symbolically shows tl~e entry o~ ~ still thic~
chip ribbon into the gap between a pair of rollers, as shown the press drum 4 and the press roller 5. For ease of observation, the chip ribbon 11 is shown fed linearly to the gap between the drum 4 and the roller 5 and without the belt 2. As soon as the still tick chip ribbon 11 contacts the periphery of the drum 4 and roller 5, the drum and roller produce a compression with a considerable rise in pressure. This pressure rise is effected in the case of rollers of smaller diameter, for example the press-er roller 7 shown in Figute 2 which acts on the drum 4, consider-ably later, because the ribbon of chips does not strike the apex of the roller 4 until shortly before the middle of the gap.
Since the ribbon of chips leaves the outlet of the pair of rollers in a pressed condition, the width of the pressure line acting on the chip ribbon between the two rollers is not symmet-rical. Without regression, the pressure line extending transver-sely to the direction of feed would extend from the point of contact of the chip ribbon 11 and press roller 5 as far the point of least gap thickness. As the pressure line patterns shown in Figures 3 and 4 for two roller diameters (although these are symmetrically illustrated), the pressure rise between two large rollers is considerably broader than between a large roller and a small roller.
Over the course of the press zone, the ribbon of chips lies directly on the periphery o~ the press drum 4. Therefore, this acts more intensively on the chip ribbon than do the other rollers associated with the press zone, which act on the chip ribbon onlyvia the endless belt~. The gluebridges formed during solidification of the binder as it passes through the press zone are therefore more s017 d at the outlet of the press zone on the face of the chipboard adjacent the roller 4 than are the glue ~ridges which are directed towards the endless belt 2.
;.' - , , :
This gives rise to the danger that the completed chip~oard panels may be curved. This danger is diminished in many ways in the case of the rn~chine of Figure 1.
By the introduction of zones of alternately high and low pressures at relatively high temperature, particularly the region having a broad pressure line between the pressdrum 4 and the press roller 5, the freedom of the chipboard panel web from regeneration is achieved already after a relatively small loop-ing angle. This is favoured by the possibility of providing the high-~ressure zone not only with a longer action time (broad line of pressure), but also with a substantially higher pressure.
By the choice of press drums or press rollers of large diameter such as is required to achieve the broad pressure line, there is at the same time an increase in the pressure loading capacity of these two rollers or drums including the belt 2 which is passed between them. However, this is not only more favour-able to the pressure, temperature and pressure line factors which are essential for the hardening of the ribbon of chips, by reason of the greater diameters of the rollers, also the ribbon of chips is above all less curved in the press zone.
Any residual curvature can easily be compensated during the hardening phase while the web of chipboard panel is still heated. For this purpose, the web of chipboard panel emerging - from between press drum 4 and press roller 5 is guided on with opposite curvature ~round the periphery of the press roller 5.
The side which faces the belt 2 continues to rest thereagainst and continues to receive heat from the heated press roller 5 where it can, under the pressure of the presser rollers 8, achieve correspondingly more solid glue bridges.
With the machine according to Figure 2, therefore, there is a bilateral hardening which is important particularly _g_ for thicker chipbo~lrd panels. At the same time, the presser rollers 8 which are significant for this purpose perform a calibration of the chipboard panel web.
The rollers 9 associated with the outlet from the calibration arrangement serve to hold and guide the chipboard panel weh 11 to the linear discharge zone lO.
The length of the treatment zone, that is to say the press zone and the hardening zone, extending between the intake constituted by the nip between the press drum 4 and the inlet roller 3 and the outlet formed by the nip between the final press-er roller 8 and the press roller 5 is for chipboard panel webs of 15 to 20 mm thickness, chosen to be 5.60 m, of which some 60 %
represents the press zone. The looping angles around the press drum 4 and press roller 5 are 120 and 90 respectively. For still thicker chipboard panels, the looping angle of the press drum 4 can for the same angle of run-on, be made larger so that `the chipboard panel emerges more steeply from the exit between the press drum 4 and the press roller 5. The looping angle of the press roller 5 can then be madecorrespondingly larger so that particularly in the case of thicker chipboard panels, that side of the chipboard panel which is less influenced by the press drum 4 can be hardened by extended looping around the heated roller 5.
In contrast to the construction of the machine according to Figure 1, the inlet rcller 3 may also have a diameter corres-ponding to the press drum 4 and may be operated at a correspond-ingly high pressure.
~-~ This construction may either be provided in addition to the press roller 5 constructed according to Figure 1 or ins-;` tead of this construction. This would have the advantage that the ideal combination of pressure and temperature is effective along a broad line of pressure already at the commencement of . . , , --10--lOS3S55 the press zone. In the case of thin chipboard panels, this would have the advantage that the chipboard panels could be taken off already at the low point of the press drum without the need for any nota~le cou~ter-curvature.
In the case of a machine with the dimensions given above the rotary speed of the press roller 5 is so chosen that the endless belt 2 moves at a speed of 15 m/min, the ribbon of chips being passed at this speed through the press zone including the regions of high and lower pressure. The indicated roller diameters, the pressure of the two rollers 4 and 5 on the ribbon of chips, the temperature of the press zone (particularly in the high-pressure region), the speed of the belt 2 and thus the period of dwell in the high-pressure region are so attuned to one another and possibly to the activation and hardening time of - the binder, that there is at the outlet from the press zone a substantially regression-free web of chipboard panel which has hardened without twisting by the time it emerges from the hard-ening zone at the roller 5. The width of the line of pressure between the press drum 4 and press roller 5, in the case of the dimensions used, amounts to 8 to 12 cm, the dwell time in this - zone amounting to 0.32 to 0.48 seconds according to the original thickness of the ribbon of chips entering the line of pressure.
~uring this period of dweel of the chip ribbon in the zone of the pressu~e line, the ribbon of chips is subject to a pressure of 600 kp/cm of roller length. The temperature o~ approximately 170C which is intensively active at this stage is, in conjunc-tion with the high pressure, of particular importance. A measure of the action on the chip ribbon is the product of dwell time, pressure and temperature, which in the case of the present example is 0.32 to 0 o48 sec. 600 kp/cm and 170C.
32,640 to 48,960C. sec. kp/cm.
' - : , . , , . . :
l~Ci3S55 It is true that the temperature may be raised above 170C but it doe~ not bring the advantages as does the raising of the pressure and increasing of the pressure zone, because the surface of the ribbon of chips could be damaged by that would then be excessive heat.
In the embodiment of Figure 5, a moulding station 1, an endless belt 2, an inlet roller 3, a first press drum 4, a press roller 5, a clamping roller 6, and at least one presser roller 7 are provided as in the embodiment of Figure 1. The endless belt 2 is looped thereby around the rollers 6, 3, 5, 7 and enclose a part of the periphery of the press drum 4 to form a press zone, In order to achieve a further zone having a sur-face pressure exerted on the ribbon of chips, there is disposed around the press drum 4 an endless pressure belt 12 which is additionally in direct contact therewith, which is partially looped around the pressure roller 5 and which can be tensioned by a roller 13 which is adjustable in position. Presser rollers 14help to maintain the pressure per unitof surfacearea generated by the taut belt 12 or even to increase it. The ribbon of chips enters the press zone at the nip between the inlet roller 3 and the press drum 4, It does not, however, come into direct contact with the periphery of the press drum 4, but lies between the two endless belts 2 and 12. m e ribbon of chips remains between these belts until it emerges at the nip between the press drum 5 and the presser roller 13.
Claims (17)
1. A method for the continuous production of chipboard panels, which comprises depositing a ribbon of chips provided with a binding agent onto an endless belt, passing said endless belt and ribbon of chips through a heated press zone including a press drum and a press roller of substantially the same diameter and in pressure contact with said press drum through said endless belt and said ribbon of chips, and subjecting said ribbon of chips in said heated press zone alternately to high and low pressures, said heated press zone including a zone of high pressure formed by a line of pressure between said press drum and said press roller, said pressure being approximately 600 kp/cm and the length of said line of pressure being at least 7 cm measured along the peripheries of said press drum and press roller in the direction of ribbon flow, the product of pressure and temperature in said high pressure zone being substantially higher than that in adjacent zones of said heated press zone.
2. The method of claim 1, wherein the mean temperature in said press zone is approximately 170°C.
3. The method of claim 1, wherein said endless belt enters said press zone at an angle of about 37.5°C to the horizontal, and emerges from said press zone at an angle of about 70° to the horizontal.
4. The method of claim 1, wherein said ribbon of chips traverses a small portion of the periphery of said press drum and said press roller, with the ribbon being reversely bent while passing around said press roller so as to eliminate any curvature which may have been formed in the chipboard panel web while passing around said press drum.
5. Apparatus for the continuous production of chipboard panels comprising an endless belt, means for depositing a ribbon of chips onto said endless belt, a heated press zone for subjecting said ribbon of chips in said heated press zone alternately to high and low pressures, said heated press zone including a press drum, a press roller having a diameter substantially the same as the diameter of said press drum, a presser roller spaced from said press roller and being relatively smaller in diameter, and an inlet roller spaced from and of similar diameter to said presser roller, said endless belt being looped partially around said inlet roller, presser roller, press drum and press roller and defining therewith said heated press zone, said press roller being arranged as the last drum within the circle of the endless belt in the direction of movement of said belt, said inlet roller, presser roller and press roller being in pressure contact with said press drum through said endless belt and said ribbon of chips, said heated press zone including a zone of high pressure formed by a line of pressure between said press drum and said press roller, said pressure being approxi-mately 600 kp/cm and the length of said line of pressure being at least 7 cm measured along the peripheries of said press drum and press roller in the direction of ribbon flow, the product of pressure and temperature in said high pressure zone being substantially higher than that in adjacent zones of said heated press zone, the alternate high and low pressures in said heated press zone being provided respectively by the lines of pressure between said inlet roller, presser roller and press roller against said press drum and the intervening zone areas where the pressure is maintained only by said endless belt.
6. The apparatus of claim 5, wherein said press drum and said press roller have diameters of such a value and offer such a mutual pressure on said belt extending between them and carrying the ribbon of chips, that the product of pressure, in kp/cm of chipboard panel width, and diameter, of one of said press drum and said press roller, exceeds 1,000 kp.m/cm.
7. The apparatus of claim 6, wherein said product of pressure and diameter is about 1,800 kp.m/cm.
8. The apparatus of claim 5, wherein said press drum, said inlet roller and said press roller are so disposed that said endless belt enters said press zone between said inlet roller and said press drum at an angle of about 37.5° to the horizontal, and emerges from said press zone between said press drum and said press roller at an angle of about 70° to the horizontal.
9. The apparatus of claim 5, further including at least one additional presser roller in pressure engagement with said press roller downstream of said press drum.
10. The apparatus of claim 9, wherein the chipboard panel web emerging from said press zone is so guided in contact with a portion of the periphery of said additional presser roller that it is calibrated between said additional presser roller and said press roller.
11. The apparatus of claim 9, further including means for feeding to said additional presser roller finishing layers for coating said chipboard panel web.
12. The apparatus of claim 9, wherein said press roller and said additional presser roller rotate at different speeds.
13. The apparatus of claim 5, further including means for heating said press drum, said inlet roller, said presser roller and said press roller.
14. The apparatus of claim 13, wherein said heating means maintains said press drum, said press roller,inlet and presser rollers at a temperature of about 170°C.
15. The apparatus of claim 5, further including guide rollers to receive chipboard panel from said press roller and convey it away.
16. The apparatus of claim 5, wherein, in operation, the pressure between said press drum and said press roller is approximately twice as great as the pressure between said press drum and said inlet roller.
17. The apparatus of claim 5, further including a second endless belt looped around both said press drum and a second presser roller, and wherein said zone of high pressure is produced by a pressure line between said press drum and said press roller, said zone of high pressure being formed by the first recited endless belt and a peripheral portion of said press drum around which said first endless belt is passed, the second of said endless belts being guided around said press drum and said second presser roller, said second endless belt in the region of said press zone being disposed between the periphery of said press drum and said first endless belt, said second endless belt together with said first endless belt being looped around a part of the periphery of said press roller, said ribbon of chips being pressed between said two endless belts thereby to extend the press zone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19732360141 DE2360141C3 (en) | 1973-12-03 | 1973-12-03 | Device for the continuous production of an endless chipboard web, fibreboard web or the like |
| DE2415650A DE2415650A1 (en) | 1974-04-01 | 1974-04-01 | Continuous chipboard mfg. process - has a controlled pressure length after high-pressure zone to prevent expansion |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1053555A true CA1053555A (en) | 1979-05-01 |
Family
ID=25766189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA214,837A Expired CA1053555A (en) | 1973-12-03 | 1974-11-28 | Method of and apparatus for the continuous production of chipboard, fibreboard or like panels |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS50112473A (en) |
| CA (1) | CA1053555A (en) |
| CS (1) | CS187451B2 (en) |
| FR (1) | FR2252918B1 (en) |
| GB (1) | GB1485025A (en) |
| IT (1) | IT1032148B (en) |
| NO (1) | NO744323L (en) |
| SE (1) | SE7415157L (en) |
-
1974
- 1974-11-19 GB GB50143/74A patent/GB1485025A/en not_active Expired
- 1974-11-28 CS CS748137A patent/CS187451B2/en unknown
- 1974-11-28 CA CA214,837A patent/CA1053555A/en not_active Expired
- 1974-11-29 IT IT54297/74A patent/IT1032148B/en active
- 1974-12-02 FR FR7439434A patent/FR2252918B1/fr not_active Expired
- 1974-12-02 JP JP49137082A patent/JPS50112473A/ja active Pending
- 1974-12-02 NO NO744323A patent/NO744323L/no unknown
- 1974-12-03 SE SE7415157A patent/SE7415157L/xx unknown
Also Published As
| Publication number | Publication date |
|---|---|
| SE7415157L (en) | 1975-06-04 |
| JPS50112473A (en) | 1975-09-03 |
| CS187451B2 (en) | 1979-01-31 |
| IT1032148B (en) | 1979-05-30 |
| FR2252918B1 (en) | 1979-02-23 |
| GB1485025A (en) | 1977-09-08 |
| FR2252918A1 (en) | 1975-06-27 |
| NO744323L (en) | 1975-06-23 |
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