EP0341250B1

EP0341250B1 - A process and apparatus for applying bonding agent and a process for forming reconsolidated wood product

Info

Publication number: EP0341250B1
Application number: EP88900559A
Authority: EP
Inventors: Robin David Sealey; Maxwell George Campbell
Original assignee: South Australian Timber Corp
Current assignee: South Australian Timber Corp
Priority date: 1986-12-24
Filing date: 1987-12-22
Publication date: 1994-03-30
Anticipated expiration: 2007-12-22
Also published as: ZA879646B; AU1102288A; ES2006013A6; JPH02501724A; NZ223047A; EP0341250A1; BR8707929A; WO1988004983A1; EP0341250A4; DE3789510T2; DE3789510D1; AU591022B2; CA1278961C

Abstract

Process and apparatus for introducing bonding agent in an improved manner to flexible open lattice work web of naturally interconnected wood strands, a substantial proportion of which are substantially discrete but incompletely separated from each other. The web with bonding agent applied may be compressed above or with others to form a reconsolidated wood product. The application of bonding agent is performed using at least one applying roller pair (102, 104) in which one or more rollers is corrugated to thereby allow better infiltration of the agent. Squeeze rollers (118) advantageously remove excess bonding agent. The applying rollers are preferably disposed in a bath (126) and the bonding agent, for example a foam, may be applied in the bath to be carried upstream by the rotation of the applying rollers. Conveniently a shroud (148) is provided beneath the applying rollers to guide bonding agent upstream.

Description

This invention relates to a process and apparatus for applying bonding agent and to a process for forming a reconsolidated wood product as well as to a reconsolidated wood product formed by the latter process.
Australian Patent Specification 510,845 describes a reconsolidated wood product formed from at least one flexible open lattice work web of naturally interconnected wood strands generally aligned along a common grain direction, a substantial proportion of the strands being substantially discrete but incompletely separated from each other,and the web having been consolidated by compression whilst substantially maintaining the wood strands aligned along the common grain direction and the strands being bonded together to hold them in juxtapositions assumed pursuant to the consolidation.
That patent specification also describes a process for forming a reconsolidated wood product from a flexible open lattice work web of naturally interconnected wood strands, the web being formed by partially rending natural wood so that the strands are generally aligned along a common grain direction, a substantial proportion of the strands being substantially discrete but incompletely separated from each other, and the process comprising compressing the web to consolidate the strands whilst maintaining them such as to substantially extend in the original grain direction and bonding the strands together to hold them in juxtapositions assumed pursuant to the consolidation.
One of the difficulties associated with the process of Australian Patent Specification 510,845 is satisfactorily introducing the bonding agent to the web of naturally interconnected wood strands. That patent specification proposed introducing a foamed bonding agent to the compression mould or spraying or otherwise applying the bonding agent during or after the formation of the web, but a particularly preferred proposal was to dip the web into a bath of liquid resin.
Patent Specification WO 85/02368 proposes coating the aforementioned webs with bonding agent on a continuous or semi-continuous basis by applying bonding agent to the or each web prior to its passage through a pair of applying rollers and removing excess bonding agent from the web downstream of said applying roller pair and, in a process for forming a reconsolidated wood product, superposing the webs, compressing the superposed webs to consolidate the strands and using the bonding agent to bond the strands and webs together.
Patent Specification WO 85/02368 also proposes apparatus for applying bonding agent to the aforementioned webs on a continuous or semi-continuous basis, comprising a pair of applying rollers adapted to receive the web therethrough, means for supplying bonding agent for impregnation by passage of the web through the applying roller pair and a pair of squeeze rollers for removing excess bonding agent from the web.
It has been found to be particularly important in the formation of a reconsolidated wood product of the type disclosed in Patent Specifications AU 510,845 and WO 85/02368 to ensure that the bonding agent is thoroughly dispersed through the web.
According to the present invention there is provided a process for applying bonding agent to a flexible open lattice work web of naturally interconnected wood strands as described herein with reference to WO 85/02368 wherein at least one roller of the pair of applying rollers is corrugated whereby a portion of the web passing through the applying rollers at any one time is spread laterally without substantial further separation of the strands and in that the bonding agent is applied to said portion of the web immediately prior to said portion being spread or while said portion is spread by the pair of applying rollers.
Further according to the present invention there is provided apparatus for applying bonding agent to a flexible open lattice work web of naturally interconnected wood strands as described herein with reference to WO 85/02368 wherein at least one of the rollers of said applying roller pair has a corrugated outer surface whereby to define an extended path for the web across the width thereof and to thereby open the web.
By the present invention, we have found that the lattice of the web is resiliently opened up as the web passes through the applying roller pair due to the increased lateral path defined by the or each corrugated roller, that is the increased surface length of the roller in the axial direction thereof. The bonding agent may accordingly more readily enter the body of the web and coat the strands. It is not necessary for the web to be substantially compressed between the nip of the applying rollers, merely that its effective surface area be increased by following the contour of the or each corrugated roller.
It is preferred that both rollers of the applying roller pair are corrugated in which case the peaks of the respective rollers should be offset, and may intermesh, to define a sinuous path between the applying rollers which is of greater length than the axial length of the rollers. As noted previously the nip between the rollers need not be substantially smaller than the depth of the web since it is important not to further break up the web by additional separation of the strands. The corrugations may take any desired shape and are conveniently substantially sinusoidal or sinusoidal but with lands between the peaks (i.e. the valleys are extended).
The applying rollers may take any suitable form and be made of, for example, metal, rubber or plastics. Cast iron, stainless steel and aluminium are preferred metal roller materials. Alternatively, the or each applying roller may be pneumatic, and it is preferred that, where only one of the rollers in the roller pair is corrugated, at least the other is pneumatic.
A second pair of applying rollers incorporating any one or more of the aforementioned features may be provided upstream or downstream of the first mentioned pair to facilitate infiltration of the bonding agent to the lattice work. The spacing between the two pairs of applying rollers may be minimal, for example in the range of 25-100 mm or less, preferably towards the lower end of the range. A support roller or other support means may be provided between the two pairs of applying rollers. The nip between the rollers of the two pairs of applying rollers may be substantially the same, but most advantageously the nip between the downstream pair of applying rollers is slightly smaller than that between the upstream pair. In a preferred embodiment where all four applying rollers are corrugated the apices of the peaks of the upstream pair of applying rollers lie in a common plane in the nip, while the apices of the peaks of the downstream pair of applying rollers intermesh in the nip.
The or each pair of applying rollers may be driven or non-driven, or one of the two pairs may be driven. If none of the applying rollers is driven it will be necessary to provide other means for displacing the web therethrough. Advantageously, a pair of cylindrical drive rollers is provided upstream of the one pair or both pairs of applying rollers whether or not the applying rollers are driven, and support means for example in the form of a single roller may be provided to guide the web from the drive rollers into the nip of the one pair or upstream pair of applying rollers.
The means for removing excess bonding agent from the web may take any suitable form, but as indicated hereinbefore preferably comprises a pair of squeeze rollers which are conveniently formed of rubber or are pneumatic. Such squeeze rollers are preferably plain rollers and may be mounted in a floating manner. The combination of at least one corrugated applying roller and the squeeze rollers is adapted to successively compress and relax the web primarily or substantially in the direction of the depth thereof and to permanently increase the width of the web without breaking the lattice-continuity. It has been found that deforming the web by means of the at least one corrugated applying roller such as to increase the width of the web in the range 15 to 35%, preferably about 25% is satisfactory for webs formed from young Pinus radiata trees.
A support roller or other carrier means may be provided between the one applying roller pair or the downstream applying roller pair and the means for removing excess bonding agent. Such carrier means and the aforementioned other optional support means are all intended to prevent small separated strands or splinters from separating from the web, but where they are in the form of rollers, and particularly if the bonding agent is applied as a foam, they may also serve the function of assisting to return excess bonding agent to a position upstream of the one pair or the upstream pair of applying rollers for re-use. A shroud at least beneath the one pair or each pair of applying rollers may be provided to assist the return of the excess bonding agent to a position upstream of the applying rollers, although excess bonding agent may also be carried back over the top of the applying rollers by the rotating action thereof.
The bonding agent may be of any suitable type that can be readily infiltrated into the web. For example a resin agent such as tannin may be dissolved in water and applied as a liquid either by immersion, or by flow through a curtain, or sprayed with air under pressure, or the liquid may be foamed with air or other gas and the foam infiltrated into the scrim web. The bonding agent may be metered onto the web on either or both major surfaces upstream of the or each corrugated roller pair where it is carried forward into the nip of the rollers and worked into the scrim web. Alternatively the bonding agent may be applied to the applying rollers and be carried by them into contact with the scrim web. Alternatively again, the bonding agent may be applied to a bath between the one pair or the downstream pair of applying rollers and the means for removing excess bonding agent, and be carried upstream by the rotating action of the applying rollers.
When the bonding agent solution (or emulsion) is applied as a foam, the foam may have a density of the order of 100 g/litre. However, the process has been operated satisfactorily with a foam density in the range 30 g/l to 160 g/l and heavier densities may be considered for specific applications. Foam density controls the pick up of resin and moisture if it is a solution. It is also anticipated that foamed liquid resins may be used neat.
Compression and consolidation of the web, for example by curing the bonding agent while the web is compressed on a non-, semi- or fully- continuous basis, occurs downstream of the application of bonding agent. Two or more of the webs may be superposed prior to compression and consolidation.
Further according to the present invention there is provided a process for forming a reconsolidated wood product from a plurality of superposed flexible open lattice work webs of naturally interconnected wood strands as described herein with reference to WO 85/02368 wherein at least one roller of the pair of applying rollers is corrugated whereby a portion of the web passing through the rollers at any one time is spread laterally without substantial further separation of the strands and in that the bonding agent is applied to said portion of the web immediately prior to said portion being spread or while said portion is spread by the pair of applying rollers.
Still further according to the present invention there is provided a reconsolidated wood product formed by the process described in the immediately preceding paragraph.
Two embodiments of apparatus and a process in accordance with the invention will now be described by way of example only with reference to the accompanying drawings in which:

FIGURE 1 is a diagram showing the steps in processing reconsolidated wood products in accordance with the invention described in the aforementioned Australian patent specification 510,845;
FIGURE 2 is a schematic diagram of one embodiment of apparatus used in practising the process of the present invention;
FIGURE 3 is a sectional side view of a second embodiment of apparatus used in practising the process of the present invention; and
FIGURE 4 is a fragmentary side view of an applying roller of the apparatus in Figure 2 or Figure 3.

Referring firstly to Figure 1, in the process of Australian Patent Specification 510,845 natural wood logs 10 are first partially broken down, being passed successively between rollers 12 of one or more roller pairs to induce cracking and thence to progressively open up the log structure to form it into a web of loosely interconnected splinter-like strands (called "splinters" in Patent Specification 510,845). The resultant web, shown at 14 in Figure 1 is of flexible open lattice work form, with individual strands being connected to each other and maintaining the original grain direction of the wood. Adhesive is then applied to the webs 14 such as by immersion in a suitable liquid adhesive in a bath 16 as shown. After removal of excess adhesive, for example by allowing the webs to drain, a plurality of webs 14 are assembled together, such as by laying them one over the other in a suitable mould 18. The assemblage of overlaid webs 14 is then compressed in mould 18 such as by compression between the base of the mould and an upper press element 20 as shown, and the adhesive is cured, to form the final product 22.
Product 22 is characterised in that it comprises a plurality of wood strands which remain naturally interconnected and which extend generally in the original grain direction of the wood. The strands are bonded together by the adhesive but are positioned in somewhat displaced relative locations as compared with the positions occupied in the original log 10. The product 22 has been found to be particularly satisfactory as it possesses good mechanical properties, due to the relatively small degradation of the original wood structure which is caused by the process, as well as good nailability and a generally pleasing appearance.
The process immediately before described is a batch type process and Figures 2 to 4 illustrate schematically two embodiments of apparatus for applying bonding agent to one or more webs 14 by a semi-continuous or continuous process in accordance with the present invention.
Referring now to Figure 2 apparatus 24 comprises a first pair of applying rollers 26 and a second pair of rollers 28 each mounted for rotation about an axis transverse to the direction of displacement of the web 14 through the applying rollers, shown by the arrow 30. The rollers 26 and 28 may each be driven or non driven and in the preferred apparatus, all of the applying rollers are driven to feed the web through the apparatus 24. The rollers may be mounted in a suitable frame or bath which for convenience has not been shown.
Each of the rollers 26 and 28 has the form shown in Figure 4, that is with a semi-sinusoidal outer periphery with peaks 32 interspaced by lands 34, and the peaks of each of the pairs of rollers 26 and 28 are offset so as to define a sinuous path between the rollers of each pair, that is with the peaks 32 of one roller of each pair overlying the lands 34 of the other roller in that pair. Each of the rollers has a keyed spindle 36 extending from each end of the roller body and is preferably formed in steel or cast iron. In a preferred embodiment, the roller body 38 has a length of about 440 mm and the peaks 32 and lands 34 have outside diameters of about 150 and 110 mm respectively. The typical length a of each land is 20 mm while the radius b of the apex 40 of each peak 32 is typically 3 mm and the angle α of each peak is typically 23°. The preferred range of thicknesses or depths of the web 14 are in the range 25 to 100 mm and the preferred minimum nip (i.e.. between the planes of the peaks) between the rollers of each pair 26 and 28 is in the range 0 to 20 mm with the nip between the first pair of rollers 26 being advantageously slightly greater than the nip between the second pair of rollers 28. The depth of the peaks 32 may be in the range 15 to 25 mm and it will be appreciated that the rollers of each pair 26 and 28 may intermesh to a small degree. Preferably only the rollers 28 do intermesh. Accordingly, there may be only a small degree of compression of the web 14 between either of the pairs of rollers 26 and 28 but the web 14 is stretched laterally, along the length of the rollers, by following the sinuous path defined by the nips so as to open up the lattice work of the discrete but not completely separated strands of the web 14.
Immediately upstream of the roller pair 26 in Figure 2 is provided means 42 for metering bonding agent onto the web 14. The means 42 is illustrated schematically and comprises respective foraminous tubes 44 disposed above and below the web and supplied with liquid bonding agent such as a tannin solution from a reservoir (not shown) through a metering device (not shown) and pipes 46. The tubes 44 are closed at each end and have a series of holes 49, such as shown in the lower tube 44 in Figure 2, opening towards the web 14. The application device 42 may be modified to discharge foam or vaporized bonding agent onto the web 14. The bonding agent is thus applied to the web 14 as or immediately before the lattice work of the web is opened up by the roller pair 26, such opening up permitting the bonding agent to infiltrate the lattice work. A sufficient infiltration may occur with just the roller pair 26, but the roller pair 28 may be provided, for example 25 mm downstream of the roller pair 26 to enhance the infiltration in much the same manner as the roller pair 26.
The successive pairs of rollers 26 and 28 may have their peaks in line but preferably to ensure optimum displacement of the strands of the web they are relatively displaced so that the peaks of the second roller pair are opposite the valleys of the first roller pair.
A pair of squeeze rollers 48 is mounted for rotation parallel to the rollers 26 and 28 to receive the web 14 as it is discharged from the second pair of rollers 28. The rollers 48 are shown schematically but preferably have a rubber or pneumatic body 50 which may be plain or gently corrugated. The rollers 48 should compress the web 14 without substantially breaking the interconnections between the strands of the web so as to squeeze excess bonding agent from the web.
It will be appreciated that the bonding agent may be applied between the first and second pairs of rollers 26 and 28 so that the bonding agent is applied to the open lattice work. Particularly, where the bonding agent is in the form of a foam, for example a tannin solution which is foamed with a suitable activator, it has been found that bonding agent applied downstream of the roller pair 26, or even downstream of both roller pairs 26 and 28, is carried upstream by the rotating surfaces of the rollers so as to also be applied to the web upstream of the first roller pair 26. Thus, the bonding agent may be applied directly to the web 14 between the second pair of rollers 28 and the squeeze rollers 48. Where the foamed bonding agent is applied in this manner, it is preferable that the rollers 26, 28 and 48 are disposed in a bath to contain the bonding agent.
Referring now to Figure 3, the apparatus 100 for applying bonding agent in much the same way as the apparatus 24 of Figure 2 includes two spaced pairs 102 and 104 of applying rollers which are each driven and are identical to the rollers described with reference to Figure 4 so including peaks 32 and lands 34. The rollers are supported for rotation about respective axes 36 and the axes of each pair 102 and 104 are vertically spaced. The peaks 32 of the roller pair 102 project into a common plane at the nip 106 so do not intermesh while the peaks of roller pair 104 do intermesh slightly as shown at the nip 108. The peaks 32 of the applying rollers in each pair are offset one relative to the other and the peaks of the rollers 102 are offset relative to the peaks of the rollers 104. The bottom rollers in each pair 102 and 104 rotate in a clockwise direction while the top rollers in each pair 102 and 104 rotate in an anti-clockwise direction so as to displace a web through the nips 106 and 108 from left to right in the drawing.
Upstream of the roller pair 102 is a pair of drive rollers 110 which are plain and supported for rotation about axis 112 to define a nip 114 which lies in a common plane with the nips 106 and 108. The drive rollers 110 are driven to rotate in the same respective directions as the roller pairs 102 and 104 and are intended to force the web into the nip 106.
Between the pair of drive rollers 110 and the pair of applying rollers 102 there is supported a support roller 116 for rotation about an axis parallel to the axes 36 and 112 but below the plane of the nips 114, 106 and 108. The support roller 116 is spaced from the lower drive roller 110 and the lower applying roller 102 by approximately 5 mm and may have a diameter in the range of for example 50 to 70 mm. The primary purpose of the support roller 116 is to prevent small separated strands from dropping out of the web between the roller pairs but it has a secondary function which will be described in due course.
Downstream of the applying roller pair 104 is a pair of squeeze rollers 118 which are also driven to rotate about respective axes 120 parallel to the axes 36 and 112 so that the nip 122 lies in the common plane of the nips 106, 108 and 114. The squeeze rollers 118 are also driven to rotate in the same respective directions as the applying rollers and the drive rollers and may otherwise be identical to the squeeze rollers 48 so will not be described further.
A second support roller 124 is mounted for rotation about an axis parallel to the other described axes and below the plane of the nips. The support roller 124 may have a diameter in the range 50 to 70 mm and is shown spaced from the bottom squeeze roller 118 by about 5 mm while almost touching the lower applying roller 104. Again, the primary function of the support roller 124 is to prevent small separated strands from dropping out of the web as it passes through the apparatus 100 but it has a secondary purpose which will be described hereinafter.
All of the pairs of rollers 102, 104, 110 and 118 and the support rollers 116 and 124 are supported for rotation in an open ended bath 126 having a bottom 128, sides 130 (only one shown) and at least a partial downstream end 132. The bath 126 is intended to contain the bonding agent, preferably in a foam form, as will be described in more detail hereinafter.
At the downstream end, a conveyor belt 134 shown only in part is supported for displacement on spaced rollers 136 (one only shown) to receive the coated and spread web from the bath 126 for onward processing for example as described with reference to Figure 1. The conveyor 134 is disposed within a housing 138 but this and the conveyor 134 may take any suitable form and will not be described further. A third support roller 140 is supported for rotation about an axis parallel to the other described axes between the lower squeeze roller and the adjacent conveyor roller 136. The purpose of the third support roller 140 is also to prevent small separated strands from dropping out of the coated and spread web.
As noted already, the bath 126 is primarily intended to take foam bonding agent which may be as previously described and this may be introduced to the bath in a batch manner or directly onto the web within the bath immediately upstream of the applying rollers 102 or elsewhere upstream of the squeeze rollers 118. The squeeze rollers 118 squeeze excess bonding agent out of the impregnated web and it is found that the excess is drawn by the anti-clockwise rotation of the upper rollers 102 and 104 over the top thereof back to upstream of the roller pair 102 where its return passage is blocked by a partial wall 142 extending across the bath above the plane of the nips. A similar movement of the excess bonding agent is caused between the bottom rollers 102 and 104 and the base 128 of the bath 126 and the return passage of this portion of the excess bonding agent is prevented by a partial wall 144 extending across the width of the bath between the base 128 and the first support roller 116. A well 146 in the base 128 of the bath allows a greater volume of bonding agent to be accommodated beneath the rollers 102 and 104.
It has been found that even better impregnation of the web is caused by the provision of a shroud 148 which extends across the width of the bath from immediately adjacent the first support roller 116, beneath and partly around the bottom applying roller 102 to between the bottom rollers 102 and 104, beneath and partly around the bottom roller 104 to adjacent the second support roller 124 and the bottom squeeze roller 118. The shroud 148 extends in close proximity to the lower arcs of the bottom rollers 102 and 104 but excess bonding agent is carried adjacent the shroud between the peaks 32 of the bottom applying rollers. A flared lip 150 defines a funnel to receive excess bonding agent from between the second support roller 124 and the bottom squeeze roller 118.
The roller pairs 102 and 104 are shown relatively closely spaced and in practice this spacing may be of the order of 25 mm. In a modification, the roller pairs 102 and 104 may be spaced by a rather greater distance such as the spacing between the drive rollers 110 and the applying rollers 102 and a similar support roller may be disposed between the bottom rollers 102 and 104.
The described method and apparatus have been advanced merely by way of explanation and many modifications and variations may be made thereto without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

A process for applying bonding agent (16) to a flexible open lattice work web (14) of naturally interconnected wood strands prior to compressing and consolidating said web (14) to form a reconsolidated wood product (22), said web (14) being formed by partially rending natural wood (10) so that said strands are generally aligned along a common grain direction with a substantial proportion of said strands being substantially discrete but incompletely separated from each other, applying bonding agent (16) to the web (14) prior to its passage through a pair of applying rollers (26,102) and removing excess bonding agent from the web (14) downstream of said applying roller pair (26,102), characterized in that at least one roller (26,102) of the pair of applying rollers is corrugated whereby a portion of the web (14) passing through the applying rollers (26,102) at any one time is spread laterally without substantial further separation of the strands and in that the bonding agent (16) is applied to said portion of the web (14) immediately prior to said portion being spread or while said portion is spread by the pair of applying rollers (26,102).
A process according to claim 1 wherein both rollers (26,102) of the applying roller pair are corrugated and the peaks (32) of the respective rollers (26,102) are offset.
A process according to claim 1 or claim 2 wherein at least one of the applying rollers (26,102) is pneumatic.
A process according to any one of the claims 1 to 3 wherein the or each corrugated roller (26,102) of the applying roller pair has substantially sinusoidal peaks (32) with lands (34) between the peaks.
A process according to any one of the preceding claims wherein a second pair of applying rollers (28,104) is provided upstream or downstream of the first-mentioned applying roller pair (26,102).
A process according to claim 5 wherein at least one roller (28,104) of the second pair of applying rollers is corrugated.
A process according to claim 6 wherein the peaks (32) of the at least one roller (28,104) of the second pair of applying rollers are offset from the peaks (32) of the at least one roller (26,102) of the first-mentioned pair.
A process according to any one of claims 5 to 7 wherein the nip (108) of the second pair (28,104) of applying rollers is less than the nip (106) of the first-mentioned pair (26,102).
A process according to claim 8 wherein both rollers (28,104) of the second pair of applying rollers are corrugated and the peaks (32) intermesh.
A process according to any one of the preceding claims wherein all of the applying rollers (26,28,102,104) are driven.
A process according to any one of the preceding claims wherein a pair of drive rollers (110) is provided upstream of the applying roller pair (102) or of the upstream applying roller pair (102).
A process according to claim 11 wherein a support roller (116) is provided between the drive roller pair (110) and the applying roller pair (102) or the upstream applying roller pair (102) to support the web (14) between the drive roller pair (110) and the applying roller pair (102) or pairs (102,104).
A process according to any one of the preceding claims wherein excess bonding agent is removed from the web (14) by a pair of squeeze rollers (48,118).
A process according to claim 13 wherein the squeeze rollers (48,118) are formed of rubber or are pneumatic.
A process according to claim 13 or claim 14 wherein a support roller (124) is provided between the applying roller pair (102) or the downstream applying roller pair (104) and the squeeze rollers (118) to support the web (14) between the applying roller pair (102) or pairs (102,104) and the squeeze rollers (118).
A process according to any one of the preceding claims wherein at least the or each applying roller pair (102,104) is mounted for rotation in a bath (126).
A process according to claim 16 wherein the bonding agent is introduced to the bath (126) downstream of the or each applying roller pair (102,104) and is carried upstream of the applying roller pair or pairs (102,104) by their rotation.
A process according to claim 16 or claim 17 wherein at least a bottom roller (102,104) of the or each applying roller pair is corrugated and a shroud (148) extends immediately beneath the or each said bottom roller (102,104) to guide bonding agent upstream of the rotating applying rollers (102,104).
A process according to any one of the preceding claims wherein the bonding agent is a foam.
Apparatus for applying bonding agent (16) to a flexible open lattice work web (14) of naturally interconnected wood strands formed by partially rending natural wood (10) so that said strands are generally aligned along a common grain direction with a substantial proportion of said strands being substantially discrete but incompletely separated from each other, said apparatus comprising a pair of applying rollers (26,102) adapted to receive the web (14) therethrough, means (42) for supplying bonding agent for impregnation by passage of the web (14) through the applying roller pair (26,102) and a pair of squeeze rollers (48,118) for removing excess bonding agent from the web, characterized in that at least one of the rollers (26,102) of said applying roller pair has a corrugated outer surface (38) whereby to define an extended path for the web (14) across the width thereof and to thereby open the web (14).
Apparatus according to claim 20 wherein both rollers (26,102) of the applying roller pair are corrugated and the peaks (32) of the respective rollers are offset.
Apparatus according to claim 20 or claim 21 wherein at least one of the applying rollers (26,102) is pneumatic.
Apparatus according to any one of claims 20 to 22 wherein the or each corrugated roller (26,102) of the applying roller pair has substantially sinusoidal peaks (32) with lands (34) between the peaks.
Apparatus according to any one of claims 20 to 23 wherein a second pair (28,104) of applying rollers is provided upstream or downstream of the first-mentioned applying roller pair (26,102).
Apparatus according to claim 24 wherein at least one roller (28,104) of the second pair of applying rollers is corrugated.
Apparatus according to claim 25 wherein the peaks (32) of the at least one roller (28,104) of the second pair of applying rollers are offset from the peaks (32) of the at least one roller (26,102) of the first-mentioned pair.
Apparatus according to any one of claims 24 to 26 wherein the nip (108) of the second pair (104) of applying rollers is less than the nip (106) of the first-mentioned pair (102).
Apparatus according to claim 27 wherein both rollers (104) of the second pair of applying rollers are corrugated and the peaks (32) intermesh.
Apparatus according to any one of claims 20 to 28 wherein all of the applying rollers (26,28,102,104) are driven.
Apparatus according to any one of claims 20 to 29 wherein a pair of drive rollers (110) is provided upstream of the applying roller pair (102) or of the upstream applying roller pair (102).
Apparatus according to claim 30 wherein a support roller (116) is provided between the drive roller pair (110) and the applying roller pair (102) or the upstream applying roller pair (102) to support the web (14) between the drive roller pair (110) and the applying roller pair (102) or pairs (102,104).
Apparatus according to any one of claims 20 to 31 wherein the squeeze rollers (48,118) are formed of rubber or are pneumatic.
Apparatus according to any one of claims 20 to 32 wherein a support roller (124) is provided between the applying roller pair (102) or the downstream applying roller pair (104) and the squeeze rollers (118) to support the web (14) between the applying roller pair (102) or pairs (102,104) and the squeeze rollers (118).
Apparatus according to any one of claims 20 to 33 wherein at least the or each applying roller pair (102,104) is mounted for rotation in a bath (126).
Apparatus according to claim 34 wherein the bonding agent is supplied to the bath (126) downstream of the or each applying roller pair (26,28,102,104).
Apparatus according to claim 34 or claim 35 wherein at least a bottom roller (26,28,102,104) of the or each applying roller pair is corrugated and a shroud (148) extends immediately beneath the or each said bottom roller to guide bonding agent upstream of the rotating applying rollers (26,28,102,104).
A process for forming a reconsolidated wood product (22) from a plurality of superposed flexible open lattice work webs (14) of naturally interconnected wood strands, each of said webs (14) being formed by partially rending natural wood (10) so that said strands thereof are generally aligned along a common grain direction, a substantial proportion of said strands of each web (14) being substantially discrete but incompletely separated from each other, said process comprising applying bonding agent (16) to said webs (14), superposing (18) the webs (14), compressing (20) the superposed webs (14) to consolidate the strands and curing the bonding agent (16) to bond the strands and webs (14) together, said application of bonding agent (16) comprising passing each web (14) through a pair of applying rollers (26,102) and applying bonding agent to the web (14) prior to its passage through the pair of applying rollers (26,102) and removing excess bonding agent from the web (14) downstream of said roller pair (26,102) characterized in that at least one roller (26,102) of the pair of applying rollers is corrugated whereby a portion of the web passing through the rollers at any one time is spread laterally without substantial further separation of the strands and in that the bonding agent (16) is applied to said portion of the web (14) immediately prior to said portion being spread or while said portion is spread by the pair of applying rollers (26,102).