CONTINUOUSLY OPERATING DRUM-TYPE PRESS DRIER

SECHEUSE A TAMBOUR DE FONCTIONNEMENT CONTINU

English Abstract

The object of the invention is to provide a
continuously operating drum-type press
drier, especially for bark desiccation. The
drier comprises an inclined rotating drum
(1) provided with perforations (2) and a
cylinder (3) which is fitted therein and
forms with the drum, in the lower part
thereof, a clamp cheek. The bark mass fed
into the drum, at the front end thereof, is
subjected several times to compression while
the drum is rotating, before being
discharged through the rear end of the drum.
To enhance the dewatering, the cylinder (3),
according to the invention, is also provided
with perforations (4) at the front end
thereof, while the rear end of the cylinder
is unperforated. The perforation can
comprise approximately a third of the length
of the cylinder (3). Water guiding members
(9, 10) are arranged at the rear end of the
cylinder in order to guide the discharged
water past the pressed bark mass which is
discharging.

Claims

CLAIMS
1. A constantly operating drum-type press drier, especially for bark
dewatering, comprising a rotating drum provided with perforations and
mounted in a slightly declined position, thus having an upper and a lower end,
a hollow cylinder mounted rotatably within the drum and at least partly
perforated, so as to effect dewatering also through the interior of the
cylinder,
said cylinder having a front end and a rear end disposed at said upper and
lower end, respectively,
inlet means for introducing material to be dewatered between said drum and
said cylinder at said upper end of the drum,
outlet means for discharging dried material at the lower end of the drum,
water guiding means for guiding separated water past the dried material at the
lower end of the cylinder,
the cylinder being adapted to settle according to the thickness of the
material
to be pressed, and the material being subjected to compression several times
while travelling through the drum,
characterized in that the cylinder is perforated only at its upper end and is
nonperforated at its lower end.
2. A drum-type press drier according to claim 1, characterized in that
the cylinder is perforated along a shorter part than half of its length, e.g.
approximately a third of its length.
3. A drum-type press drier according to claim 1 or 2, characterized
in that the perforations of the cylinder are conical and expand inwards.
4. A drum-type press drier according to any of the preceding claims,
characterized in that the water guiding means comprises a flanging attached
to the rear end of the cylinder which forms an extension of the drum and
extends past the discharging point of the pressed material at the rear end of
the drier.
5. A drum-type press drier according to claim 4, characterized in that
the water guiding means additionally includes a flanging and a groove or a
similar member which interlocks with the said flanging underneath thereof.

Description

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Continuously operating drum-type press drier
The object of the present invention is a continuously
operating drum-type press drier, especially for the drying
of bark, in which the material to be dried is desiccated
between a rotating drum, provided with perforations, and
cylinder which rotates therein and settles according to the
thickness of the material to be pressed. The drum is mounted
in a slightly inclined position and the feeding of the
material is effected at the upper front end. Matter is
subjected to compression several times while travelling from
the front end of the drum to the rear end thereof.
At least two kinds of continuously operating drum-type press
driers are already known. The first type, such as the presser
according to Finnish patent application 812 805, published
April 15, 1982, is one in which the presser drum does operate
continuously, but the material to be pressed is fed into the
whole length of the drum and is subjected to compression only
once before each discharge from the drum. Another known type
differs from the one mentioned in such a way that the material
to be compressed is fed to the front end of the drum and is
subjected to compression several times before arriving at the
end of the presser drum, as disclosed in Finnish patent FI
62330 issued December 1, 1979.
Different ways of enhancing the operation of such presser
driers are known. It is known to provide the cylinders with
edges or grooves which are intended to provide either more
effective conveying of the material or improved dewatering.
In drum-type driers in which the material is subjected to
compression only once and where the drum is completely
horizontal, it is also known to provide the cylinder with
perforations throughout its length so that a part of the
dewatering is effected through the cylinder. In such a press

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where the material to be pressed is discharged from the drum
immediately after the pressing, for instance by a screw
conveyor above the cylinder, the dewatering can be effected
through both ends of the cylinder without it being subjected
to contact with the dried bark through the holes of the
cylinder.
The above construction can not, however be used in the
solution according to said Finnish patent FI 62330 because
while the roller is inclined, the water can get in contact
with bark which has already been pressed once, while draining
from the front end of the cylinder towards the rear end of the
cylinder. Therefore it has not been possible to use
perforated cylinders with this type of pressers.
The purpose of the present invention is to provide an
improvement to the invention according to said Finnish patent
FI 62330 or its amendment granted as Finnish patent 72340
issued May 27, 1987. Namely, it has been observed that
especially in such drum-type press driers where the drum is in
an inclined position and the material is consequently
subjected to compression several times while travelling
through the drum, an improved dewatering effect can be
implemented by providing the cylinder with perforations in a
certain way. More specifically, the drum-type press drier is
characterized in that the cylinder is hollow and is perforated
along part of its length, seen from the front end, to effect
the dewatering also through the interior of the cylinder, as
the cylinder is unperforated at the end portion thereof and is
provided with water guiding members at the rear end thereof
for discharging the water and for guiding it past the pressed
material.
According to a preferred embodiment, the cylinder is
perforated through a shorter part than a half of its length,
for instance approximately through one third of its length.
However, the length of the perforated part depends on

3
several factors, such as the angle of tilt of the drum. The
holes are preferably conical in shape expanding inwards.
In the following the invention is explained in more detail
b wa of exam le and b reference to the a a d
Y Y p y pp n ed drawing
which illustrates an application of 'the drum-type press
drier according to the invention, as seen from the side and
in cross-section.
The drier is comprised of drum 1 of solid metal which is
provided with perforations 2 expanding outwards. Drum 1 is
mounted in a slightly inclined position in such a way that
the front end, on the right in the figure, is slightly
higher.
Cylinder 3 is fitted inside the drum and it settles
according to the thickness of the material to be pressed
inside drum 1, generally in a sharply inclined position in
such a way that the front end on the right is higher. Thus
the compression gap is tapered towards the rear end.
Cylinder 3 is supported by shaft 5 with the aid of radial
abutment rings 6 provided with through-openings 7.
The feed of the material, in this case wet bark, is effected
at the front end of the drum, from above, with the aid of
feed pipe 8. The cylinder is rotated by machinery not
illustrated and the drum rotates with the cylinder because
of the bark material located therebetween. The incoming bark
is subjected to compression for the first time immediately
at the feed end, between the drum and the cylinder. ~lhile
rotating, the cylinder lifts the bark to the top from where
the bark again falls between the drum and the cylinder,
proceeding in an axial direction towards the lower end of
the drum. This pressing pradecure is repeated, until the
bark finally falls out of the drum through the lower end

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thereof. In respect to the operation of such a drum-type
press drier, reference can be made here to said Finnish patent
FI 62330.
The cylinder deviates from the said previous solution in
that it is not closed, but has a hollow construction built
according to the above method and dewatering holes 4 are
arranged at the front end thereof, according to the
invention. With the aid of these holes the water can not
only be discharged through outer drum 1, but can also be
discharged through the interior of the cylinder, as
illustrated in the figure.
It is also essential, according to the invention, that the
perforation of the cylinder is arranged on only part of the
length of the cylinder, for instance a third of this length.
Thus the water can be discharged during the first
compression both through the cylinder and the drum and then
drain down the cylinder without mixing with the bark which
has already been pressed once. The shape of holes 4 is
preferably conical expanding inwards. This prevents the
blocking of the holes.
The discharge of the water from the interior of cylinder 3
is so arranged that the water is allowed to pass the pressed
mass of bark which is being discharged. Flanging 9 can be
connected, for instance, to the rear end of the cylinder, in
the way illustrated in the figure, the rear end of the
flanging opens up in such a way that it is directed
inclinedly downwards in the lower part of the cylinder.
Groove 10 is interlocked with this and its front end, as
viewed in another direction, is curved following flanging 9.
It is, of course, also possible to arrange the dewatering
via shaft 5.

Representative Drawing