Note: Descriptions are shown in the official language in which they were submitted.
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(Translation)
Into Kerttula, Director
Malaga, Spain
1979
Continuously Operating Board Press
The pXesent ~nvention relates to a continuously
operating board press, in which the board material to be pressed
is led between two endless, continuously rotating press belts
in such a way that at least the upper press belt runs via a
pressure chamber, whereby a pressure medium exerts a pressure
load on the belt and board material.
A board press is here understood to be such a press
which may be employed for the pressing of boards, such as
plywood, chip, fiber or similar boards, further for laminating
various kinds of boards, for providing all kinds of boards with
a surfacing layer etc. In all these instances, the boards must
be subjected to pressure. The boards may be in the form of a
long web or in the form of shorter pieces,~which are fed con-
secuti~ely into the press.
In order that the handllng of the boards to be
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manufactured or processed might readily take place, one has
for a long time already endeavoured to change from operating
presses by charging to continuously operating presses. Such
a continuously operating press is described in U.S. Patent
No. 3,688,688. The previously known press operates satis-
factorily if boards which do not have a high compression level
are pressed, that is, ~y wh~ch the feeding thickness does not
greatly exceed the th~ckness of the f;nished board. For
example, plywood boards are such boards. If, on the other hand,
e.g. chip boards or fiber ~oards are pressed, the degree of
thickness of the ch;p mat fed ;nto the machine is considerably
greater than the thickness of the finished board emerging from
the machine. In this case, the compressing of the chip mat
caused difficulties. The difficulties w;th compressing actually
nullified the use of a continuously operating press.
The present invention ;ntends to produce a con-
tinuously operating board press which can also be used for the
pressing of such materials which must initially be compressed
at nominal thickness. The invention is characterized in that
the walls laterally bordering the pressure chamber are elastic,
that a weight plate, flexible at least in the longitudinal
direction of the press, is fastened to their lower edges, said
weight plate - due to its dead weight - always being located
on the upper press belt, that the weight plate is provided
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with one or more channels for the admission of a pressure
medium into the opening between the weight plate and the
press belt and that this opening is sealed off by means of
at least longitudinal closures.
The weight plate adapts itself according to the
quality of the board material. If the board material to be
processed is of such a type t~at it is more or less compressed
in the inltial phase of the pressing process, the weight plate
always automatically takes the form and position corresponding
to the compression. On the other hand, boards of various
thicknesses can be pressed in the press without any adjustment
measures, since the weight plate automatically adjusts itself
to all thickness degrees. Thus, one is freed from all
adjustments.
One and the same pressure acts on both sides of
the weight plate. As a result, the friction between the
closure and the press belt is only produced by the dead weight
of the weight plate. Consequently, the frlction is not high.
On the other hand, the friction is independent from the
pressure prevailing in the pressure chamber and from the
pressing program as well as from the thickness of the material
to be pressed.
According to the invention, the press does not have
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to be built consisting of two parts (one compressing part and
one part with constant thickness), lnstead it has a type of
structure which is unaltered along its entire length. Depending
on the condition of the board material to be pressed, the
compression distance can be shorter or longer. According to
the invention, the press adjusts to all pressing functions
independent from the length of the compressing distance.
According to the invention, the weight plate in
the board press can also be flexible in the transverse
direction. This is necessary in such instances, althouyh rare,
when the thickness of the board material to be pressed varies
in the transverse direction. With the weight plate being
flexible, one also achieves that the friction between the
closures and the pressing belt is unchanged in all situations
and that one can manage with quite simple closures.
According to the invention, the walls laterally
bordering the pressure chamber in the press are elastic. It
is understood herewith that they allow the movement of the
weight plate in a vertical direction.
An advantageous performance of the invention is
characterized in that the weight plate consists of rubber,
e.g. hard rubber, or of a synthetic material. Such a weight
plate adjusts itself in both a longitudinal and also in a
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ransversal direction to the shapes of the boards located in
the press process. A wire gauze or else chain-like elements,
which allow the flexibility of the weight plate, can be
mounted in the weight plate as reinforcement. The weight
plate must have such a proportion of weight that it adequately
presses the seals against the press belt. Naturally, the
weight plate can also be constructed simply from chain lamina
or from wire gauze.
A second favourable performance of the invention
is characterized in that the seals are fastened to the lower
surface of the weight plate. On the other hand, one can also
imagine such a problem solution in which the longitudinally
running closures are situated at the press belt in such an
instance where no transverse seals exist.
Usually, the boards are pressed according to a
pressure curve which, at the outset, gradually rises from
zero to a maximum and returns to zero. According to the
invention, such a pressure flow curve is easily attained. The
pressure chamber can be divided into consecutive component
chambers in which different pressures prevall. In order that
the pressure change at the partitions between the component
chambers i5 not too abrupt, closures transversely situated
underneath the weight plate can be provided at those points
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where the partitions are between the component chambers,with
an extension in the-longitudinal direction of the press
considerably exceeding the thickness of the partitions. Such
closures equalize the pressure change.
Heat is often required for the hardening of the
binding agent with pressing boards. According to the invention,
heat can be led to the board material located in the press
process by heating the pressure medium or by installing e.g.
electrical resistances in the weight plate.
In the press according to the invention, the
friction strives to move the weight plate in the direction of
the end of the press. In order to prevent this, the weight
plate is connected with the initial end of the press structure
by means of one or more horizontal joint arms. The joint
arms allow the movement of the weight plate in a vertical
direction.
In the ~ollowing, the invention will be described
with the help of an example and with reference to the enclosed
drawings, wherein
Fig. 1 shows a continuousroperating board press according to
one performance method of the invention,in a vertical,
longitudinal section.
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Fig. 2 shows the section along the line II - II in Figure 1.
Fig. 3 shows one detail in the longitudinally running vertical
section of the press~
In the draw~ng, reference number 1 refers to the
support on ~hich the press rests~ The lower part 2 and the
upper part 3 of the frame are attached to one another by
means of tension posts 6. Transparent protective plates 4,
consist~ng e.g. of bulletproof glass, are located on both
sides of the press along the entire length of the press
between the lower part 2 and the upper part 3. The primary
function of these is to prevent the spurting about of pressure
medium in case of possible leakage. The pressure medium can
be a liquid, for example, oil or a gas, for example, air.
In the event that a liquid is used for a pressure medium and
leakages occur, then the liquid collects in chamber 5, from
where it is again absorbed into the pressure system. No
loss occurs as a result of leakage.
The press comprises two endless press belts 7 and
8 ~hich limit the press opening between them. The bel~s can,
for example, consist of steel~ Belt 7 runs over the end rolls
9 and 10, whereas belt 8 runs over the end rolls 11 and 12.
The rolls 10 and 12, located on the right in Fig. 1, are
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drawing rolls. For the sake of clarity, the driving machinery
was omitted in the fIgure. In the example shown in the diagram,
the board material to be pressed consists of a chip mat 13,
which is fed into the press opening between the press belts 7
and 8 from where the chip board then emerges finished and pressed.
The lower press belt 8 and therewith also the chip
mat 13 is, with the a~d of a pressure chamber, loaded in an
upward direction, whereby this pressure chamber is subdivided
into five consecuti~e sections 15 - 19. The pressure is lowest
in the sections 15 and 19, and highest in section 17. To the
upper surfaces of the partitions 20 between the sections,
transversely running closures 21 are fastened which can consist
e.g. of a Teflon belt.
The upper press belt 7 and therewith also the chip
mat is pressed downward by means of a pressure chamber, whereby
the pressure chamber, corresponding to the pressure chamber
below, consists of five sections 22 - 26. Sections 22 - 26
are in the same positions as sections 15 - 19 below, and the
same pressure prevails in them as in the sections underneath.
The walls can consist, for example, of synthetic foil, e.g.
Teflon, or of a rubber-like material. The walls 27 are attached
tightly with their upper edge against the upper part 3 of the
~rame. On the other hand, the weight plate 28 is fastened
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tightly against the lower edges of the walls 27. The weight
plate consists of flexible material, for example, hard rubber
or the like. From each section 22 - 26, a channel 29 leads
in under the weight plate so that the pressure on both sides
of the weight plate 28 is equally great. A laterally situated
closure 30 is found under the weight plate 28 at each wall 27.
Furthermore, longitudinally running closures are found on the
edges of the weight plate 28. Similarly, the lower part 2
of the frame has correspondingly longitudinal closures 32.
By operation of the press according to the invention,
press belts 7 and 8 draw the material to be pressed 13 through
the press. Since the pressures in the sections 15 - 19 and
correspondingly in the sections 22 - 26 are equally high, the
friction between the closures 30 and the press belt 7, as well
as between the closures 21 and the press belt 8, is very slight.
Only the weight of the weight plate 28 influences the former
friction. The weight of the press belts and of the material
to be pressed in-between has, additionally, an effect on the
latter friction.
As can be seen in Fig. 3, closure 30 is developed
relatively ~ide. Accordingly, the pressure difference, which
in this case exists between sections 23 and 24, does not
abruptly effect the material to be pressed and is, in actuality,
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considerably more uniform.
Press belt 7 strives to shift the weight plate 28in the direction of the end of the press by frictional action.
In order to prevent this, weight plate 28 can be connected
with the in~tial end of the upper part 3 of the frame by means
of joint arms. The weight plate 28 can thereby move freely
in a vertical direction.
According to the drawing, freely rotatable rolls
34 are situated in the lower part of the structure. These
have the function to carry the package, which the press belts
7 and 8 and the material to be pressed in-between 13 yield,
in such a way that it does not sag in the middle.
It is clear to the expert that different methods
of perform~ng the invention can vary. By operating with
pressure liquid, two pair of lateral seals can, for example,
be provided, between which a leakage reservoir channel is
located. With flow pressure, one can operate without cross
closures, whereby then the highest pressure passes from the
middle section 24 through the weight plate 28, as well as
flowing under the weight plate toward both ends. The compart-
ments 22, 23, 25 and 26 are hereby sealed downward. At the
same time, one must ensure that the space for the opening
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between the weight plate and the press belt extends up to the
ends in accordance with the compartment pressures, whereby one
attains the same end result without cross closures. In the
opening or flow chamber, a pressure controlled fine regulation
of the flow space can be provided.
The lower pressure chamber 15 - 19 is, fxom the
standpoint of the invention, not essential as the lower half
of the press merely serves as a support;ng surface for the
pressure coming from above~ Therefore, the pressure chamber
15 - 19 can also be replaced by another type o~ construction.
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