The invention relates to a laminated veneer lumber product made from veneer panels which are glued and pressed to one another in a plurality of layers, at least one layer having a plurality of veneer panels which butt against one another and, at the butt joints, have a respective scarfing zone in which the thickness of the veneer panel decreases in the direction of an outer periphery of the scarfing zone, said periphery at the same time forming the edge of the veneer panel, and which is delimited in the inward direction by an inner periphery from which the veneer panel has its full thickness.
DE 887 702 C discloses a method of scarfing veneer panels from which laminated veneer lumber products will then be formed. When forming the laminated veneer lumber products, the veneer panels which belong to the same layer are butted against one another such that they overlap with their scarfing zones. In this way, a good joint between veneer panels is achieved without that, on the other hand, the material becomes too thick in the overlapping zone.
It is an object of the invention to further improve the homogeneity of laminated veneer lumber products.
In order to achieve this object, according to the invention, at least the inner periphery of the scarfing zone, as seen in plan view, runs in an undulating manner.
In conventional laminated veneer lumber products, the inner periphery of the scarfing zone extends straight and in uniform distance from the outer periphery which is also straight. Since, at the inner periphery of the scarfing zone, the flat surface of the main part of the veneer panel joins the downwardly slanting surface of the scarfing zone, the inner periphery of the scarfing zone forms a knuckle line at which the inclination of the surface of the veneer changes abruptly. When the veneer panels are pressed, the parts of the veneer panels that are superposed one upon the other are abruptly kinked at the knuckle points, so that the certain discontinuities are created in the product. Because the inner periphery of the scarfing zone runs in an undulating manner according to the invention, a gradual transition from the main part of the veneer panel to the scarfing zone is obtained instead of a sharp knuckle line. Moreover, the scarfing zone has an undulating profile also in the thickness direction, which profile is at least partly smoothened out again when the veneer panels are pressed. In this way, a greater compressibility of the veneer and, therewith, a better distribution of mechanical strains within the product is achieved and the formation of local stress concentrations is avoided. Also, when the veneer panels are laid, a larger tolerance in view of positional deviations is achieved, because gaps or material doublings, which may be produced in the laying process because the outer edge of the one veneer panel does not coincide exactly with the inner periphery of the scarfing zone of the other veneer panel, are mitigated by the wavy shape of this periphery.
More specific optional features of the invention are indicated in the dependent claims.
The invention relates also to methods and apparatus for forming laminated veneer lumber products according to the invention.
In one embodiment, the scarfing zones having the wavy periphery are formed by so-called wet scarfing already during the peeling of the veneer. In another embodiment, the scarfing zones are formed by so-called dry scarfing by means of a milling or grinding tool only after the veneer panels have been dried.
Embodiment examples will now be described in conjunction with the drawings, wherein:
It is a particular feature of the veneer panel T that the inner periphery R of the scarfing zone Z is not straight but has a wavy shape. This has the effect that the position P at which the bottom surface of the veneer panel has a kink varies periodically along the periphery S of the veneer panel.
As is shown in
Each veneer panel has two scarfing zones Z, namely one at the leading edge in the transport direction of the conveyor F and another one at the trailing edge. Typically, due to the manufacturing process, those scarfing zones are formed on the same side of the veneer panel, other than has been shown in
An apparatus and a method for manufacturing the scarfing zones Z with the wavy periphery R will now be described by reference to
Extending in parallel to the round timber 20, there is provided a knife bar 22 having a peeling knife 24 that is disposed on the back side of the knife bar 22 and is not visible in
A pressure roll unit 28 is arranged above the round timber 20, and two sets of pressure rollers 30 are rotatably supported at the pressure roll unit. The pressure rollers 30 are arranged on a bottom side of a carrier 32 which is suspended on a drive mechanism (not shown) and is movable relative to the frame 10 in vertical direction. By means of the drive mechanism, the pressure roll unit 28 is pressed against the round timber 20 such that the pressure rollers 30 roll on the periphery of the round timber and absorb a part of the reaction force that the peeling knife 24 exerts upon the round timber.
By means of the drive system which has not been shown and which acts upon the sleeves 18 and/or the pressure rollers 30, the round timber 20 is rotated about its longitudinal axis while the peeling knife 24 has its cutting edge set against the peripheral surface of the round timber such that an endless veneer web 36 is peeled-off from the round timber. The veneer web 36 is withdrawn in a position above the base 16, in a direction towards the viewer in
Whereas the pressure rollers 30 are arranged at a certain spacing from the side walls of the frame and from the ends of the round timber 20, the carrier 32 is extended beyond the pressure rollers towards the side wall 12 and carries, in the extended part, a milling head unit 38 having a milling head 40 that can be driven for rotation. The milling head 40 has a conical scarfing tool 42 which increases in diameter in the direction towards the side wall 12. More precisely, the scarfing tool is formed by knives which have not been shown in detail and the cutting edges of which are contained in a common enveloping surface with a conical shape. A radially projecting groove-forming tool 44 joins the outer end of the scarfing tool 42, which end has the largest diameter.
The milling head 40 and an associated drive system 46 are mounted on a free end of a rocker 48 the opposite end of which, facing away from the viewer in
Above the rocker 48, the carrier 32 forms an arm that projects in parallel with the rocker, and, between the free end of this arm and the free end of the rocker 48, there is arranged a compression spring 54 which biases the milling head unit 38 downwards and holds the follower roll 52 and the milling head 40 in engagement with the peripheral surface of the round timber 20.
The groove-forming tool 44 forms a groove 56 at a small distance from the end of the round timber 20, and adjoining the inner edge of this groove, there is a conical scarfing zone 58 which is formed by means of the scarfing tool 42 and merges into the peripheral surface of the round timber.
When a peripheral portion of the round timber 20 which has been processed with the milling head 40 in this way reaches the peeling knife 24, an outer peripheral layer is peeled-off, which layer forms the veneer web 36. The thickness of the veneer is smaller than the depth of the groove 56, so that, during peeling, a seam that is located beyond the groove 56 is separated from the main part of the veneer web. In this way, a neat butting edge 60, which is formed by one of the two sides of the previously formed groove 56, is formed at the main part of the veneer web 36. From this butting edge, the thickness of the veneer increases linearly in the scarfing zone 58 until the full thickness of the veneer is finally reached.
In
In the amount in which the radius of the round timber 20 decreases as the peeling of the veneer web 36 proceeds, the peeling knife 24 must be moved upwards, whereas the pressure roll unit 28 moves downwards by the same amount, so that the pressure rollers 30 stay engagement with the peripheral surface of the round timber 20. In this way, the correct position of the milling head unit 38 relative to the round timber 20 is maintained.
In a preferred embodiment, two milling head units 38 are arranged symmetrically at opposite ends of the carrier 32, and both are jointly adjusted by means of the pressure roll unit 28 in accordance with the decreasing radius of the round timber.
Further details of the apparatus described above are explained in the earlier utility model application DE 20 2015 102 518.
In a later processing step which has not been shown here, the veneer web 36 is divided into the individual veneer panels T, such that the scarfing zone 58 shown in
A slightly modified embodiment of the method has been shown in
A method and an apparatus according to another embodiment will now described by reference to
The scarfing apparatus 110 has a rail-like frame 116 which extends transverse to the transport direction over the entire width of the belt conveyor at the end of this belt conveyor 112. A carriage 118 is guided on guide rails 120 and adapted to move along the frame 116.
An upper profile portion of the frame 116 forms a support 122 that is flush with the top side of the belt conveyor 112.
In the example shown, a camera 124 for detecting the time of the passage of the leading (outer) edge S of the veneer panel T is disposed above the belt conveyor 112. Then, the drive system for the belt conveyor 112 is controlled such that the veneer panel T is pushed beyond the end of the belt conveyor onto the support 122 until its periphery S slightly projects beyond the support 122.
A trimming device 128 and a grinding tool 130 are arranged on the carriage 118.
In the example shown, the trimming device 128 is a slitting saw having a circular saw blade 132 that is driven via a belt drive 134 and a rotating drive disk 132. Optionally, the trimming device may also be a chopper which completely chops the strip of material that is cut away.
The grinding tool 130 has an endless grinding belt 138 running over a pulley 140 and a corresponding cylindrical section 142 of the drive disk 132.
In a start position, the carriage 118 is located in an end portion of the frame 116, on the left end in
Subsequently, the pressure shoe 144 is lifted again, the veneer panel T is slightly withdrawn by means of the belt conveyor 112 and is then lifted by means of a suction device (not shown) and transferred onto a laying line on which a multi-layer string of veneer panels is laid as has been shown in
It can be seen in
The trimming device 128 having the circular saw blade 132 can be seen in
Further details of the device described above have been explained in the earlier patent application DE 10 2015 117 931.
In the cross-sectional view in
Optionally, the trimming device 128 can be set such that one obtains a scarfing zone with the configuration shown in
Number | Date | Country | Kind |
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10 2016 113 548.8 | Jul 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/066829 | 7/5/2017 | WO | 00 |