Note: Descriptions are shown in the official language in which they were submitted.
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CONTINUOUSLY OPERATING PRESS
The invention relates to a continuously operating press
for the production of chipboard, fibreboard, and plywood
sheets, of the type disclosed in German Patent no. 40 l0 308.
For continuously operating presses of this kind, heating
plate systems are known, from German Patent no. 37 43 933, in
which heating zones are formed, transversely to the direction
of feed of the press material, by longitudinal passages,
whereby a varying temperature profile can be controlled.
Thus, for example, by increased temperature in the middle of
the heating plate, a better vapour removal from a press
material by increased vapour pressure from the interior to the
exterior, and a specifically central heat supply into the
press material during the production of narrow chipboard, can
be achieved. On changing over from wide chipboard to narrow
chipboard, the energy consumption is thereby smaller and the
dishing effect of the steel belt (varying thermal heat
extension) can also be balanced out.
However, the heating plates are also the rolling supports
for the roller rods. For that reason, the transitions are
made correspondingly toothed. The transitions of the three
heating plates are also arranged with a gap, adapted for
thermal expansion. Partly increased surface pressings in the
transition region from one heating plate to the next heating
plate are thereby produced for the roller rods, the acceptable
specific surface pressure for the compression of the chip cake
being further minimized, particularly in the high pressure
region of the press, so that, partly in this region, only
transition pressures in the range of about 30 atmospheres are
acceptable. However, pressures up to 50 atmospheres are
required technologically. By the fan-shaped, zigzag
transitions in the transition region, furthermore, very high
production costs arise in the manufacture of the installation
connections of the longitudinally bored heating plates.
The purpose and reason of the longitudinally bored
heating plates according to Patent no. 37 43 933 are to be
able to produce narrower chipboard because of the specifically
central heat supply. In addition, the advantage of utilizing
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higher compression pressures can also be used, for boards with
high (sawdust) density, because of the narrower width.
However, because of the limited allowable specific pressures,
this is not utilizable. In practical operation in continuous
presses, the use of such heating plates has the effect that a
strong abrasion of the supporting surfaces is produced, even
after short service periods of about 3,000 - 6,000 hours.
This abrasion results not so much in a general removal of the
support surfaces, but it forms, in the through-direction, at
approximately the spacing of the roller rods, corresponding
transverse grooves (with wave crests and wave valleys). In
association therewith, increased running noises occur which,
as the abrasion increases, lead to critical oscillations in
the entire press system.
According to the main Patent no. 40 10 308, the last-
mentioned disadvantages are avoided by the provision, at the
roller surfaces of the heating plates, of roller plates
having a thickness of 7 - 23 mm and a Brinell hardness of 250
or greater, the roller plates being heat treated on both sides
for two-sided use, and/or through-hardened and having a
precision finish, and a plurality of roller plates being
arranged in succession, separated from one another by
expansion gaps, with saw-tooth connections. It is to be noted
as an advantage of the main patent that, by the increased
surface hardness of the roller plates, an ideal rolling
support for the roller rods is produced. Since no wear occurs
at the surface, as in the case of a support directly against
the heating plates, an increased life expectancy for the
roller rods themselves is also to be expected. The faultless
rolling of the roller rods on the roller plates also
encourages an exact control of the path of the steel belt.
Under the effect of hydraulic pressure forces, a partially
topographically increased surface peak pressure in the
vicinity of 250 atmospheres can be produced, i. e. with the
hardened roller plates according to the main patent, the press
system is fully functional with respect to an economically
advantageous useful life.
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The invention is based on the problem of so further
developing the press according to the main patent that, with
increased temperature in the longitudinal middle of the
press surface, a varying temperature profile can be
controlled, that no increased production costs arise in the
manufacture of the longitudinally bored heating plates and
that the advantages wh~.ch hold true for the main patent
remain completely maintained.
According to one aspect of the invention, there is
provided, a continuously operating press for the production
of chipboard, fibreboard, plastic material boards, plywood
boards of the like, with flexible, endless steel belts,
which transfer the press pressure and also draw the material
to be pressed through the press, guided over drive drums and
guide drums around the press table and press ram and which
are supported, with an adjustable press gap, on heater
plates of the press table and the press ram on roller rods
which are guided with their axes transverse to the direction
of advance of the belts, the roller rods rolling on heating
plates provided on the press table and the press ram,
according to Patent 4,010,308, characterized by heater
plates (11) the ends (20) of which have a straight interface
connection and the passages (16) of which extend parallel to
the longitudinal direction of the press, the passages (16)
being connected to a plurality of differently heatable
heating areas (I to VI) .
According to another aspect of the invention there is
provided a continuously operating press comprising: a press
table; a press ram facing said press table and defining an
adjustable pressing gap therebetween; first and second
flexible endless steel bands which transfer a pressing
pressure to and draw a material to be pressed through said
adjustable gap; driving drums and deflecting drums which
drive said first and second endless steel bands around said
press table and said press ram, respectively; rolling bars
which support said endless steel bands and which move with
said endless steel bands, said rolling bars being disposed
°
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with their axes being transverse to the running direction of
said steel bands and extending over the entire working area
of said press; heated platens attached to said press table
and press ram, respectively, said rolling bars rolling on
said heated platens, said heated platens having end surfaces
which are connected to one another via straight butt joints,
said heated platens having bore holes formed therein which
extend parallel to the longitudinal direction of said press
and which are independently heatable to provide a plurality
of heating surfaces in each of said heated platens; roll
platens at least partially covering said heated platens and
extending over the entire working area of said press, said
roll platens having a thickness in a range of 7 mm to 23 mm
and a Brinell hardness of 250, said roll platens being heat
treated on opposite surfaces, said roll platen surfaces
having a precision ground finish; and expansion joints
joining said roll platens and extending obliquely relative
to the running direction of said steel bands.
In a combination of the solutions according to German
Patent 37 43 933 and German Patent 40 10 308, the above-
mentioned disadvantages are avoided and compensated
according to the invention, in an advantageous manner.
Further useful features of the subject matter of the
invention are described below.
With reference to the drawing, an exemplary embodiment
of the press according to the invention is described in
greater detail. In the drawings:
Figure 1 shows a schematic illustration of a
continuously operating press in side view;
Figure 2 shows a portion "G" of the press according to
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Figure 1:
Figure 3 shows a plan view "X" of two rolling plates
according to Figure 2;
Figure 4 shows a temperature-time-path diagram with a
temperature profile; and
Figure 5 shows the heating areas of the press table and
the press ram without the rolling plates.
According to Figure 1, the continuously operating press
comprises the press table 2, the movable press ram 3 and
cables (not shown) connecting these. For adjusting the gap 4,
the press ram 3 is moved upwardly and downwardly by hydraulic
piston-cylinder arrangements (not shown) and is held in the
selected position. The steel belts 5 and 6 are guided by
respective drive drums 7 and 8 and guide drums 9 and 10 around
the press table 2 and the press ram 3. For the reduction of
friction between the heating plates 11 provided on the press
table 2 and press ram 3 and the moving steel belts 5 and 6,
respective roller rod mats, which are likewise moving, are
formed of roller rods 1. The roller rods 1, the axes of which
extend transverse to the direction of movement of the belts,
are connected together at both longitudinal sides of the press
in guide chains 12 at predetermined spacings and are guided
through the press on the heating plates 11 of the press ram 3
and the press table 2, on one side, and also on the steel
belts 5 and 6, rolling from the steel belts.
Figures 2 and 3 show in a section D-D a portion G from
Figure 1, by which the,provision of the roller plates 13 on
the heating plates 11 of the press table 2 is illustrated. The
roller plates 12 are also bolted by means of connecting bolts
14 and 18 to the heating plates 13. In the direction of
throughput, at the beginning the roller plates 13 are fixed by
means of securing bolts 15 as a fixed point to the heating
plates 11. The transition from one roller plate 13 to another
are formed as saw-tooth connections 19 and can be made as
trapezoidal or round arches., an expansion gap 17 also being
notable as a compensation for heat expansion.
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Figures 4 and 5 show the press areas comprising the
heating plate 11 at the inlet, the heating plate 11' at the
middle and the heating plate 11 " at the press outlet. As
shown in the temperature-time-path diagram of Figure 4, the
temperature profile is formed from the heat energy jump in the
heating zone a at the inlet, the decreasing temperature in the
heating zone b and the heating zone c at the outlet with a
lower temperature. In order to be able to control a
temperature profile transverse to the longitudinal direction
of the heating plates 11, 11' and 11 " , or the longitudinal
direction of a continuously operating press, the heat transfer
passages 16 are arranged in the longitudinal direction, the
heat transfer passages 16 arranged in the longitudinal
direction being distributed in different heat areas I to VI,
i. e. each individual heating area I to VI can be differently
adjusted, e. g. to a temperature level F. The width of the
press material passing through is indicated by e.
By a hydraulic and/or electrical control device, through
temperature sensors on the heating plates 11, 11' and 11" and
a size dependent on the width a of the press material, the
temperature level F can be controlled by switching or
connection of individual heating areas I to VI or by the
introduction of temperature media at different temperatures
into the heat transfer passages 16 of the heating plate 11, i.
e. a temperature profile F with a temperature increasing from
the longitudinal sides B-B to the longitudinal centre A-A can
be developed. The temperature supply to the heat transfer
passages 16 arranged in the longitudinal direction of the
press is effected in the heating plates 11, 11' and 11 "
through the ducts 21 on the side facing the steel belts 5 and
6 perpendicular to the heating plate surface of this rear
side. In this way, the necessary heat energy can be
deliberately supplied only in the region of the press material
width e, whereby, as already described above, belt undulations
are avoided and at the same time heat energy is saved since
little radiant heat is lost.
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According to the invention, the heater pate 11 located
under or above the roller plate 13 can be made without saw-
tooth connections in the interface 20 between the individual
heating zones a, b and c. By the straight interface 20, as
already illustrated in figures 2 and 3, the heating plates 11
can be made relatively simply in the return 22 of the heating
medium. The supply and discharge ducts 21 are arranged from
the exterior, perpendicular to the heating plate 11 at the
plate interface edge 20 in a simple manner. In combination
with the roller plate 13, the heating plates do not require to
be connected by welding - as previously usual - in the
transitions, i. e. between a and b or b and c in the region of
the interface edges if no fan-shaped transitions have to be
utilized. The temperature sensing, through the flat interface
20, in particular in the transition zones, is to be effected
substantially more exactly since the transition region is
considerably smaller, i. e. in summary a temperature sensing
transverse to and along the heating plated is more exactly
obtained.
