Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-10-14
2001-08-28
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S264000, C156S556000, C156S558000, C156S559000, C156S563000, C156S566000
Reexamination Certificate
active
06280560
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and plant for producing endless laminated veneer boards.
A method of this kind is disclosed by German Offenlegungsschrift 196 27 024. This method is based on the object of automatically and continuously assembling assemblies of layers of large-area veneer panels (or sheets) to give adequate mechanical interlinking, with the result that, given the subsequent continuous pressing operation, these veneer-assembly transitions have virtually the same physical strength properties in the finished laminated veneer boards, as the laminated veneer boards produced in accordance with the previous laminated veneer assemblies joined together in a sandwich construction. With this method, it is possible to produce laminate veneer boards of good quality if all the manufacturing and production parameters are matched to one another in an optimum manner and the plant operates accordingly. One disadvantage of this method is the high proportion of the costs accounted for by the plant.
According to another method that has been disclosed, the veneer panels are deposited in the appropriate laying position by means of a rolling belt. Here, the veneer panels are first of all moved into the deposition position by means of the rolling belt and are then unloaded as the belt projection moves back, as a result of which the veneer panel falls onto the conveyor belt or veneer assembly underneath it.
For a complete deposition cycle comprising the following steps:
a) taking over veneer panel onto a rolling belt,
b) moving veneer panel into a deposition position and
c) unloading and depositing veneer panel during return movement, it was previously possible to achieve cycle times of 5 s per veneer panel.
However, industrial-scale LVL production plants with a production capacity of about 250 m
3
per day must achieve cycle times of at least 2.5 s per veneer panel in order to keep up with the competition. For this reason, the laying operation in the laying stations is carried out on two levels to enable the required 24 veneer panels per minute to be achieved at a laying cycle of 5 s per veneer panel per level.
However, one disadvantage of these multi-level laying stations is that the laid veneer assemblies from the two levels must then be combined to give a veneer-panel strand. This necessarily requires sloping conveyor belts and corresponding kinks. At the transition from the horizontal to the slope and vice versa, stretching and compression effects occur which deform the veneer-panel strand or displace the veneer panels relative to one another. Since the veneer panels are already glued at this point in time, the displacements and deformations occur at undefined locations and lead to a change in the lengths of overlap between the veneer panels. The length of overlap must not fall below a minimum length in order to achieve the required bending strengths in the finished boards. Accordingly, any overlap tolerances must be compensated for by increasing the length of overlap and this results in a commercial disadvantage due to increased use of material.
The large number of drive elements in these plants also entails considerable susceptibility to faults, which impairs the availability of the overall production line.
SUMMARY OF THE INVENTION
An object of the present invention is to continuously produce good quality laminated veneer boards at a high throughput rate.
Another object of the present invention is to create a plant with an overall simple construction having fewer subassemblies and components in order to reduce plant costs.
According to one embodiment of the invention, in a continuous process, each veneer panel is passed through a glue application machine at a high speed equal to the operating and pressing speed, but in the process the veneer board is provided with a layer of glue only on its upper side. The application of glue ceasing in each case at the veneer panel intended as the covering layer. The veneer panels are then transferred from the glue application machine to a buffer acceleration belt with a higher speed and an accelerating reversing transfer projection. The veneer panel is transferred from the transfer projection to a supporting surface of a horizontally reversing laying device that can also be raised and lowered. The supporting surface circulates via two rollers, and the veneer panel is hence moved into the predetermined deposition position, while being guided on the upper level by its front edge until it reaches a first stop, where it stops, by means of an endless recirculating chain device which takes the supporting surface along. The supporting surface forms part of the recirculating-chain section with a second part that forms a fall-through gap for the veneer panel. After the veneer panel stops, the supporting surface then continues to run underneath it and releases the rear edge of the veneer panel. The veneer panel falls, rear edge first, through the fall-through gap into a second stop on the lower level of the recirculating chain device and hence also onto the supporting surface, which is now returning underneath it counter to the feed direction. After release from the second stop and by virtue of the supporting surface, which continues to run underneath it, the veneer panel falls front edge first onto a veneer-assembly laying belt running at the operating speed at the deposition position predetermined for it in accordance with the laying sequence and having the forward stepping effect as shown in FIG.
4
. The subsequent veneer panels are assembled to give a veneer assembly, in each case with a veneer overlap x with a forward stepping effect, by repeating the preceding steps which are synchronized and coordinated in terms of time, to the appropriately input traversing positions of the transfer projection of the buffer acceleration belt and of the laying device in the horizontal and vertical direction. A plurality of veneer assemblies is assembled one behind the other to give a veneer-panel strand by repeating the preceding method steps. The veneer-panel strand formed in this way is passed at operating speed from the veneer-assembly laying belt into a heated, continuously operating press for pressing and gluing.
According to a second embodiment of the invention, in a continuous process, each veneer panel is passed through a glue application machine a high speed equal to the operating and pressing speed, being in the process provided with a layer of glue only on its upper side, the application of glue ceasing in each case at the veneer panel intended as the covering layer. The veneer panel is then transferred from the glue application machine to a buffer acceleration belt with a higher speed and an accelerating reversing transfer projection. The veneer panel is transferred from the transfer projection to a supporting surface of a laying device that can be raised and lowered, the supporting surface circulating via two rollers, and is hence moved into the predetermined deposition position, in the process being guided on the upper level by its front edge until it reaches a first stop, where it stops, by means of an endless recirculating chain device which takes the supporting surface along, the supporting surface forming part of the recirculating-chain section and the second part forming a fall-through gap for the veneer panel. After the veneer panel stops, the supporting surface continues to run underneath it and releases the rear edge of the veneer panel, which falls, rear edge first, through the fall-through gap into a second stop on the lower level of the recirculating chain device and hence also onto the supporting surface, which is now returning underneath it counter to the feed direction. After release from the second stop and by virtue of the supporting surface which continues to run underneath it, the veneer panel falls front edge first onto a veneer-assembly laying belt running at the operating speed at the deposition position predetermined for it in accordance with the laying sequence and having the rearward stepping ef
Ball Michael W.
Foley & Lardner
Kilkenny Todd J.
Maschinenfabrik J. Dieffenbacher GmbH & Co.
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