Note: Descriptions are shown in the official language in which they were submitted.
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Process and Plant for the Manufacture of Endless Veneer
Laminates
The invention relates to a process for the manufacture
of endless veneer laminates from a strand of veneer panels
made from several layers of veneer panels layered one above
the other and one behind the other by means of gluing and
pressing in a heated, continuously operating press, whereby
the strand of veneer panels passes through a prepress with
a preheating device before entering the press, and to a
plant for carrying out the process.
German Patent No. DE-OS 196 27 024 discloses a process
the object of which is to automatically bring lamination
assemblies of large-area veneer panels (or sheets)
continuously together into a sufficient mechanical
interlinking so that in the subsequent continuous pressing
operation these veneer panel transitional stages
demonstrate, in the finished veneer laminate, almost the
same physical strength characteristics as the traditional
veneer laminates built up from veneer laminate assemblies
on the sandwich principle. High-quality veneer laminate
panels can be manufactured using this process if all
production and manufacturing parameters are optimally
harmonized with each other and the plant operated
accordingly. The disadvantage is that only relatively
narrow veneer panels of approximately 1.2 m (4 feet) width
can be produced and thus the output of completed LVL panels
and veneer panels per plant is small.
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The object of the invention is to provide a process by
which a higher throughput can be achieved in the
manufacture of veneer laminates and to devise a plant for
the execution of the process according to the invention.
In accordance with one aspect of the present invention
there is provided a process for manufacturing endless
veneer laminates from a veneer panel strand of several
layers of veneer panels joined one above the other and one
behind the other by means of gluing and pressing in a
continuously operating press, wherein several veneer panels
of manufacturing width are brought together, each
overlapping the other, and are stitched on the connecting
edges into over-width veneer panels, following which
several of these over-width veneer panels are assembled
into a veneer panel strand in layers one above the other
and one behind the other and introduced into a heating
press and glued and pressed into a veneer laminate strand.
The plant for the execution of the process according to
the invention consists of a glue application machine for
the veneer panels, conveyers, a veneer panel laying device
and a continuously operating press, characterized in that
for the formation of overwidth veneer panels an
interleaving device with sewing machine is located upstream
of the veneer panel laying device, while downstream of the
continually operating press an appropriate number of
longitudinal edging and centre cut saws are located.
The joining together by stitching of the overlapped
1.2 m (4 feet) wide single veneer panels lying side by side
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and above and behind each other into an overwide veneer
panel strand provides the advantage that after pressing
immediately downstream of the continuously operating press
the 2x4 or 3x4 foot wide veneer laminates are once more
separated in such a way that the central separation cut
strip = R is significantly smaller in comparison to the
external longitudinal edging saw strip = S. In practice it
turns out to be about a quarter of S, that is, R is
approximately s~ S.
From this the following advantage is derived:
With an endlessly produced veneer laminate 2x4 feet wide
with a central seam for 8 foot width, which after pressing
is separated through the central cut R, waste material of
only VTm will be produced:
VTm - ( (2.S) + (1.R) ) - 2~ S.
This advantage will increase further in the case of a
3x4 foot wide veneer laminate panel with two veneer central
seams.
The applicable formula then reads:
VT,n - ( (2.S) + (1.R) J - 23z S.
If it is assumed that in plywood and LVL veneering
operations veneer panels of 4 feet can be milled or
manufactured, then by laying the edges over one another for
a seam, 2x4 or even 3x4 foot wide veneer panel strands can
be manufactured in an endless strand. That means that a
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continuously operating press for veneer laminates for
widths of 8 or 12 feet can come into operation, in
comparison with the current state of the art of LVL presses
with 4-foot bed width. This produces for the same press
factor (pass-through speed and throughput rate) a twofold
to threefold increase in output whereby a greater width in
terms of the entire plant entails lower production costs
than the operation of two or three single unit press lines
alongside each other. As well, the product is more
economical to produce owing to the reduced wastage while
the installation costs for a doubled or tripled production
output can be considerably reduced in comparison to two or
three 4-foot wide installations.
The cited advantages of the process according to the
invention also come to fruition if a single- or multi-stage
press is used in the plant instead of the continuously
operating press.
Further advantageous measures and embodiments of the
object of the invention become apparent from the following
description and drawings.
Shown are:
Figure 1 a side view of the plant according to the
invention for the performance of the procedure
according to the invention;
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Figure 2 shows the veneer assembly composition with
veneer panel length (H), veneer panel
projection (L) and veneer panel overlap (y);
Figure 3 an overwidth veneer panel strand with a
stiched seam;
Figure 4 a section G-G as per Figure 3; and
Figure 5 an overwidth veneer panel strand with two
stiched seams.
Figure 1 shows a complete overview and perspective
representation of the plant according to the invention for
carrying out the process according to the invention.
As seen from the longitudinal arrangement of the plant
according to Figure 1, the sections of the plant indicate
the following:
A Veneer panel glue application device,
B Veneer panel sticking device,
C Veneer panel location and interlinking device,
D Prepress with pre-heating device,
E Continuously operating press, and
F Veneer laminate (finished product).
Plant Section A:
Veneer panels (1) formed from veneer sheets with
veneer thicknesses typically of 1 mm to about 4.6 mm and
surface dimensions of typically 4'x 8' or 3'x 6' feet
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(about 1.2 x 2.4 m) are run at high speed from the veneer
panel stacks (not shown) through the glue application
machine (2) and fed to transfer belt (3). Only the upper
side of the veneer panels (1) is glued, permitting good
transportability on the belts and roller paths through the
entire plant section (B) to and including plant section
(E). According to Figure 2, only the topmost veneer panel
(m) of a veneer assembly (9, 10 or 11) is not glued.
Adhesion is formed in each case by the glueing of the
veneer panel (n) lying underneath. The layer structure of
a strand is numerically registered in its passage through
line sections (A, B and C,) the veneer panels (1) are
correspondingly counted in the feed-in to the glue
application device.
Plant Section B:
From Figures 3 and 4 it can be seen that before the
assembly of a veneer panel strand (29) in the veneer panel
laying device (33) and introduction into the continuously-
operating press (18), veneer panels (1 and 1'), each four
feet wide (A and B) are stitched together with a stitching
machine with a stitched seam (30) into an over-width veneer
panel (34) and fed over a feed belt (6) into the veneer
panel laying device (33). Figure 5 shows by way of
illustration the stitching of three veneer panels (1, 1'
and 1") into an over-width veneer panel (34). Figure 4
shows further the advantageous central separation cut strip
(R) in relation to the wider edging cut strip (S) after
pressing in the continuously operating press (19), with the
longitudinal edges of the veneer laminate panel (31)
equalized and the stitching seam (30) removed.
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Plant Section C:
The loading, layering and joining of the veneer panels
(1) in the veneer panel laying device (33) is carried out
as described in German Patent No. DE-OS 196 27 024.
Figure 2 shows the interlinked and interleaved building
up of the veneer panels (1) into several veneer assemblies
(9, 10 and 11) to a veneer panel strand (28), whereby the
individual veneer panels (1) after being mechanically
interleaved by veneer overlap (y) are glued to the
corresponding veneer panels (m, n, o, p) of a veneer
assembly (9, 10 or 11). In the process, the constant
operating speed and the same geometrical positions of
veneer panel length (H), veneer panel projection (L) and
veneer panel overlap (y), constantly produce the same
veneer assembly situation, that is the consolidation of
veneer panels (1) with each other into an assembled strand.
Plant Section D:
This section with pre-press and pre-heating device is
optional. The continuously formed veneer panel strand (28)
is taken up by roller path (7) and fed to the intake roller
table and the pre-press with pre-heating (15). This pre-
press (15) consists of intake roller table (14) with an
integrated pre-heating, which can typically be generated by
UHF or a microwave field or by convective or radiant heat.
Plant Section E:
This section relates to any type of continuously
operating press (18) for gluing and for pressing the veneer
panel strand (28). The upper and lower steel belts (27) are
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supported against the heated compression/heating plates,
possibly by means of roller rods.
Plant Section F:
After leaving the continuously operating press (18), the
continuously and endlessly emerging veneer laminate (31) is
fed to a finishing station, that is, the endless laminate
(31) is cut into construction elements, beams and support
elements for prefabricated houses.
