Note: Descriptions are shown in the official language in which they were submitted.
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K 2640 - R/Wo
APPARATUS FOR THE FRACTIONATION AND SCATTERING OF
PARTICLES, ESPECIALLY FIBROUS PARTICLES
The present invention relates to an apparatus for the fractionation of
particles, especially fibrous particles, of different sizes, in particular of
fibers chips or the like of lignocellulose and/or containing cellulose,
comprising a metering hopper containing the non-fractionated particles, a
substantially areal screening apparatus inserted after the metering hopper
and a supply unit of the metering hopper by which the particles from the
metering hopper can be brought onto the surface of the screening
apparatus. Furthermore, the invention is directed to an apparatus for the
scattering of preferably fibrous particles, especially fibrous particles with
an admixed binder, in particular wood fibers, wood chips or similar
particles having such an apparatus for the fractionation.
Apparatuses of this kind are known from the German patent specification
17 28 502. In this document a scattering device is described for the
manufacture of multilayer chip mats in which roller rakes are provided at
the base of the metering hopper containing the non-fractionated particles
via which the particles are supplied to a thrower type sifting roller
arranged after the metering hopper. The particles which impinge on the
thrower type sifting roller are fractionated and thrown onto an oscillating
screen arranged beneath the thrower type sifting roller. The fractionation
thereby takes place in accordance with the principle of throw sifting, so
that larger and thus heavier particles fall on one region of the screen
which is further removed from the thrower type sifting roller and smaller
particles come to lie on the screen closer to the thrower type sifting roller.
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2
Through the movement of the oscillating screen the impinging particles
are loosened up further, whereupon they are shed through the oscillating
screen onto a conveyor belt arranged beneath the oscillating screen for the
production of a mat.
Apparatuses of this kind have several disadvantages. On the one hand it
is unavoidable that the screening apparatus used becomes clogged up in
the course of time, in particular since the particles falling onto the
screening apparatus are normally mixed with binder. A cleaning of the
screening apparatus is relatively time consuming and thus cost-intensive,
since the operation of the apparatus must be interrupted during the
cleaning. On the other hand both the throughput and also the quality of
the fractionation is not satisfactory in apparatuses of the initially named
kind.
20
The object of the inventio» is to so design an apparatus of the initially
named kind that on the one hand no clogging of the screening apparatus
arises and on the other hand the throughput can be improved with a
simultaneous improvement of the sifting quality.
Starting from an apparatus of the initially named kind this object is
satisfied, in accordance with the invention, in that a transport device is
provided in the region of the surface of the screening apparatus having a
plurality of portioning segments movable along the surface of the
screening apparatus, within each of which a respective portion of the
particles brought by the supply unit onto the surface of the screening
apparatus is transportable and in particular movable over the surface of
the screening apparatus. F~Zrthermore the object is satisfied by an
apparatus for the scattering of preferably fibrous particles, especially
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fibrous particles with an admixed binder, in particular of wood fibers,
wood chips or like particles, in particular for the manufacture of shaped
articles, principally in the form of boards, comprising an apparatus for the
fractionation in accordance with the invention and a conveyor belt
arranged beneath the screening apparatus for receiving a mat formed by
the particles which pass through the screening apparatus.
In accordance with the invention a metering of the particles applied onto
the screening apparatus thus takes place in mutually independent part
quantities which are transported by the transport device of the invention
over the surface of the screening apparatus. Through the movement of the
particles along the surface of the screening apparatus a clogging up of the
screening apparatus is prevented, on the one hand, and, on the other
hand, a force acting on the particles is produced which has a component
directed perpendicular to the screening apparatus. Through this force the
particles are pressed through the screening apparatus so that the
through-put of the apparatus is correspondingly increased. Through the
metering of the particles a better fractionation is achieved, because a more
complete through-mixing of the particles is possible within the relatively
small quantities of particles which are respectively located within a
portioning segment, whereby a situation is prevented in which small
particles located at the top side of the bulk material have no possibility of
passing downwards, past the larger particles lying beneath them, to the
screening apparatus.
In the bulk material arranged within the portioning segments a rotational
and/or turn-over movement of the particles arises through the movement
across the screen surface and promotes a mixing of the particles, whereby
the sifting quality is increased.
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In accordance with an advantageous embodiment of the invention at least
some of the portioning segments each include a scraping element which
contacts the surface of the screening apparatus and is scrapingly guided
over the surface of the screening apparatus during the movement of the
portioning segments. Through a scraper element which lies under a light
pressure on the surface of the screening apparatus, for each or at least
some of the portioning segments, the cleaning effect which arises during
movement of the portioning segments over the surface of the screening
apparatus is further enhanced. At the same time the force component
acting on the particles in the direction perpendicular to the screen surface
is increased by the scraper elements so that an increase of the throughput
is achieved.
The transport apparatus is preferably designed as a scraper belt, in
particular an endless scraper belt. In this manner a particular simple and
cost-favourable design of the transport apparatus is possible. In this
connection the scraper belt is advantageously made permeable for the
particles in the direction perpendicular to the surface of the screening
apparatus, at least aver a part region, so that the particles from the
metering bunker can be shed by a supply unit through the scraper band
onto the screening apparatus. A complicated design of the supply unit can
spared in this manner.
In accordance with a further advantageous embodiment of the invention
the scraper belt includes in particular plate-like drivers which are
preferably provided at regular intervals on an endless chain- or belt-like
Garner element. The carrier element can in this respect in each case be
centrally arranged at the drivers. However, the several carrier elements, in
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particular two chain-like or belt-like carrier elements can be provided
which are respectively secured in the region of the lateral outer edges of
the drivers. In this manner the stability of a scraper belt formed in
accordance with the invention is increased.
5
The drivers are preferably releasably secured to the carrier element or to
the carrier elements and/or of air impermeable design. In this manner it is
ensured that, on the one hand, the drivers used are ideally matched to the
screening apparatuses that are used and, on the other hand, that worn
drivers can be exchanged for new ones.
In accordance with a further advantageous embodiments of the invention
the scraper elements are each formed by a section of the drivers. In this
manner a particularly cost-favourable design of the apparatus of the
invention is possible since no separate components are required for the
scraper elements. The drivers are in particular made flexible, at least in
their sections which form the scraper elements, and are for example made
of hard rubber. In this way an adaptation of the scraper elements to the
surface of the screening apparatus is possible so that it is ensured, even
with a certainly regularity in the screen surface, that the scraper elements
contact the surface of the screening apparatus for the certain pressure
over their full width and also over their full range of movement.
In accordance with a further preferred embodiment of the invention the
drivers are made abrasion-resistant, at least in their sections which form
the scraper elements and have in particular an abrasion-resistant coating,
for example a Teflon coating. The sections of the drivers which form the
scraper elements can in this arrangement be made both in one piece with
the drivers and also made as separate components. If the scraper
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elements are formed as separate components and they are preferably
releasably mounted on the drivers so that they can be exchanged in the
case of wear.
In accordance with a further advantageous embodiment of the invention
the drivers are made, at least in their sections forming the scraper
elements, of water-repellent non-adherent material. In this way a situation
is avoided in which the particles with the admixed binder remain stuck to
the drivers, whereby the receiving capability of the portioning segments
could be restricted.
In accordance with a further preferred embodiment of the invention the
screening apparatus include in particular two screening zones with
different screen openings. In this way a situation is achieved in which
particles of different size are fractionated by the screen zones with the
differently sized screen openings. In particular the screen zones are
arranged behind one another along the direction of movement of the
portioning segments, which can move over the surface of the screening
apparatus, with the screen openings of the screen zone or screen zones
lying in the direction of movement of the portioning segments preferably
being larger than the screen openings of the screen zone or screen zones
lying opposite to the direction of movement. In this way a situation is
achieved in which, on sweeping over the screen surface, first of all the
particles with a smaller diameter pass through the screening apparatus
while the next largest particles then pass through the screen following this
in the next screen zone. Depending on the number of screen zones and the
size of the screen openings the desired fractionation of the particles is
thus achieved. The fractionated particles can in this arrangement either
be shed into different capture devices for the different particle sizes, or,
for
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example, onto a moving conveyor belt arranged beneath the screening
apparatus on which a mat can be produced in this manner having
different particle sizes distributed over the thickness.
In accordance with a further advantageous embodiment of the invention
the endless scraper belt is guided over two deflection rollers so that a
lower belt section extends directly at the surface of the screening
apparatus and an upper belt section extends at a certain spacing from the
surface of the screening apparatus, in particular in each case
substantially parallel to the surface of the screening apparatus. In this
manner a particularly compact design of the apparatus of the invention is
possible. A receiving apparatus for the reception of separated out particles
is preferably provided, at least at one end of the scraper belt, in particular
in the region of the deflection rollers. These particles can be foreign bodies
which are present in the bulk material, such as for example screws or
nails. However, lumps or particles which exceed a maximum permissible
size, and which thus cannot pass through even largest screen openings of
the screening apparatus, can also be separated out and can be lead away.
In accordance with a further preferred embodiment of the invention an
intermediate floor is provided at least regionally between the upper and
the lower belt sections, with the ends of the drivers opposite to the
sections which form the scraper elements contacting the intermediate floor
so that these ends are guided scrapingly over the intermediate floor during
the movement of the portioning segments. With this embodiment belt
material which is initially brought out of the metering bunker via its
supply unit onto the intermediate floor can be brought in a defined
manner to a specific position between the deflection rollers.
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In this arrangement, in accordance with a preferred embodiment, the
intermediate floor can extend from the one deflection roller in the direction
of movement of the upper belt section to the oppositely disposed other
deflection roller, with a region, which is permeable for the particles in the
direction perpendicular to the surface of the screening apparatus, being
formed between this other deflection roller and the end of the intermediate
floor adjacent this other deflection roller. An initial separation of foreign
bodies or particles with a size which lies above the size of these screen
openings can take place here, especially when this region is formed by
further screening apparatuses which can have relatively large screen
openings. Only the particles passing through the further screening
apparatus fall onto the lower lying screening apparatus over which they
are moved away by the means of the transport device.
In accordance with a further preferred embodiment of the invention two
scraper belts arranged behind one another in the longitudinal direction
are provided, with the scraper belts in particular being arranged with
mirror symmetry relative to one another. A distribution device, in
particular in the form of a pendulum distributor, is advantageously
provided in this embodiment after the supply unit of the metering hopper,
by means of which the particles which are lead by the supply unit from
the metering hopper can be supplied, in particular alternately supplied, to
the two scraper belts. Through this design it is possible, starting from one
metering hopper, to distribute particles onto two different scraper belts. It
is possible, especially when the two scraper belts can be driven in opposite
directions, so that the two upper belt sections move away from one
another, and when an intermediate floor is provided in the already
described manner between the upper and the lower belt sections, for the
particles brought by the distribution apparatus onto the respective
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intermediate floors to be transported to the outwardly disposed ends of the
scraper belts in opposite directions and to be respectively brought there
onto the screening apparatuses arranged beneath the scraper belts. It is
possible, with corresponding dimensioning of the screen openings of the
screening apparatuses, in particular when the size of the screen openings
increases in the direction of movement of the lower belt sections, for a
symmetrical mat with a lower fine cover layer and an upper fine cover
layer which include a coarse middle layer between them to be formed on a
moving conveyor belt arranged beneath the screening apparatuses.
Instead of a distribution apparatus two metering hoppers can for example
also be provided by which the two scraper belts are fed with particles.
The screening apparatus and/ or the further screening apparatus is
preferably formed in all embodiments as an oscillating screen or as a
vibrating shaking screen. In this connection the bulk material dispensed
onto the screening apparatus is further loosened up whereby fine particles
and subsequently medium-sized particles disposed remote from the screen
more rapidly reach the screen openings and pass through them.
In accordance with a further preferred embodiment of the invention the
oscillating screen is movable to and fro via a crank drive. In this
connection the maximum stroke of the oscillating screen advantageously
amounts to between ca. 10 cm and 1 m, preferably to between ca. 30 cm
and 70 cm and in particular to ca. 50 cm.
Through the movement of the oscillating screen, which can be adjustable
in its frequency, the chips lying on the screens are made more uniform
and are sifted out fraction-wise in accordance with the screen openings.
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The drivers can scrape over the surface of the screens during this or can
be moved relative to it at a small spacing.
Since both the drivers and also the oscillating screen are simultaneously
5 in motion and, as a result of the changing direction of movement of the
oscillating screen, a co-movement and then an opposite movement is
produced, particles arranged in the portioning segments are repeatedly
stacked up and turned at the front and rear sides of the drivers.
10 Especially when, in accordance with a preferred embodiment, the
maximum speed of movement of the oscillating screen in the transport
direction is greater than the transport speed of the portioning segments,
the particles collect at the sides of the drivers disposed opposite the
transport device when the drivers and the oscillating screen are moved in
the same direction. In this manner the particles are thrust against the
rear sides of the drivers and turned.
If the oscillating screen moves opposite to the transport direction of the
portioning segments, and thus opposite to the direction of movement of
the drivers, then the particles are turned over at the front-sides of the
drivers.
Through this repeated turning over a uniform distribution of the particles
is achieved within the portioning segments which enables the smaller
particles to migrate rapidly through the total quantity of the particles
arranged within a portioning segment in the direction of the screen
surfaces and to fall through the screen openings.
In addition the self cleaning effect of the screens is increased by the
simultaneous but different speeds of movement and directions of the
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oscillating screen and the drivers. Since the lower edges of the drivers
scrape on the surface of the oscillating screen, or are arranged at a small
spacing from the latter, particles which are stuck in the screen openings
are broken as they are swept over by the drivers or they are pressed
through the screen openings. A clogging of the screen is thereby
precluded.
In accordance with a further advantageous embodiment of the invention
the portioning segments are made so that they are at least regionally
closed at the sides. In this way a situation is achieved in which an
emergence of particles and particle dust sideways out of the portioning
segments is avoided, so that the environment of the apparatus is kept
practically dust-free.
Sealing elements, especially lobe-like sealing elements are advantageously
provided in the lateral regions of the portioning segments and are in
particular secured to the lateral end faces of the drivers. Through the lobe-
like sealing elements a simple sealing of the portioning segments is
possible, and it is also made possible to retrospectively equip existing
apparatuses with the sealing elements in a simple manner.
In accordance with a further preferred embodiment two respective sealing
elements following one another in the transport direction overlap at least
regionally, whereby in each case a seal extending through the whole width
of a portioning segment is produced. Through this overlapping design
account is taken of the fact that in designing the transport apparatus as
an endless scraper belt the drivers have a greater spacing relative to one
another at their radially outwardly disposed edges than between the
radially inwardly disposed edges when moving around the deflection
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rollers. Since a fixed seal of the lateral regions of the portioning segments
is not possible in this case the seal can be advantageously achieved by
overlapping sealing elements. Fundamentally it is also possible to make
the sealing elements for example flexible, with it being possible to achieve
the flexibility on the one hand by specific material characteristics and on
the other hand for example by a type of accordion fold.
In accordance with a further preferred embodiment a middle sealing
element, especially a middle sealing element formed as a side-wall, is
arranged between the upper and the lower belt sections laterally outside of
the portioning segments. In this arrangement the central sealing element
preferably seals off laterally substantially the whole region between the
upper and the lower belt sections. Through the middle sealing element the
region between the upper and the lower belt sections is sealed off relative
to the environment so that the freedom of the environment from dust is
further improved by the middle sealing element.
A respective middle sealing element is preferably provided at both sides
outside of the portioning segments, so that dust emergence in the
environment is prevented on both sides of the apparatus.
The middle sealing element is preferably sealingly connected to the sealing
elements which terminate the portioning segments of the side and stands
in scraping and sealing contact with the latter, in particular with moved
sealing elements. In this manner the total lateral region is sealed off by a
substantially continuous unitary sealing unit consisting of the middle
sealing elements and the sealing elements which terminate the portioning
segments at the side, so that the side environment of the apparatus of the
invention is practically dust-free.
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In order to prevent emergence of dust upwardly out of the apparatus an
upper sealing element formed especially as a wall section is provided, in
accordance with a further advantageous embodiment, above the upper
belt section.
In accordance with a further advantageous embodiment of the invention a
transport device is provided above the portioning segments with which the
particles which emerge from the metering hopper can be transported to a
predetermined region above the screening apparatus. The transport device
can in particular be formed in this arrangement as a preferably endless
transport belt.
The transport apparatus can in this arrangement be additionally provided,
or provided in place of the already described intermediate floor since the
function of transporting the particles emerging from the metering hopper
to a predetermined region above the screening apparatus can be satisfied
both by the transport device and also by the intermediate floor in
conjunction with the upper belt section moved over the intermediate floor.
Thus, all the advantages and combinations of features described with
respect to the embodiment with an intermediate floor can also be possible
and hereby claimed in an apparatus with a transport device, especially a
transport device formed as an endless transport belt. By the way of
example it is possible, via the transport device, to bring the particles
dispensed from the metering hopper onto the transport device in the
region of the one deflection roller to the oppositely disposed other
deflection roller and their to dispense them through the scraper belt onto
the surface of the screening apparatus.
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In accordance with a further advantageous embodiment of the invention
th.e fractionating apparatus is made displaceable relative to the conveyor
belt in the longitudinal direction in an apparatus in accordance with the
invention for the scattering of particles. In this way, in particular when a
cyclically operating press is disposed after it for the pressing of the mat,
the next mat can already be scattered by movement of the fractionating
apparatus relative to the conveyor belt so that, after pressing has been
completed, the next mat is already fully scattered and can be supplied
directly to the cyclically operating press.
Furthermore, it is possible in accordance with the invention for middle
layer roller scattering heads to be provided for the scattering of a middle
layer of a mat in addition to one or more fractionating apparatuses in
accordance with the invention, which are used for the scattering of one or
more cover layers.
Further embodiments of the invention are set forth in the subordinate
claims.
The invention will be explained in more detail in the following with
reference to the embodiments and to the drawings in which are shown:
Fig. 1 a schematic side-view of an apparatus formed in
accordance with the invention for the fractionation of
fibrous particles, such as for example wood fibers, wood
chips or like particles with at least one admixed binder,
Fig. 2 a detailed view of the apparatus shown in Fig. 1,
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Fig. 3 an apparatus formed in accordance with the invention for
the formation of a symmetrical mat,
5
Fig. 4 a further embodiment of the invention,
Fig. 5 a partly sectioned perspective illustration of a further
embodiment of the invention and
15
Fig. 6 a further embodiment of the invention.
Fig. 1 shows a metering hopper 1 in which three back scraping rakes 2 are
arranged. The bulk material consisting of differently sized particles 3, for
example of fibrous chips and binder is supplied to the metering hopper 1
from above, as is indicated by the arrow 4.
A floor belt 6 running over two deflection rollers 5 is arranged at the lower
side of the metering hopper 1 and forms a supply unit 8 together with a
carry out roller 7.
The particles 3 fed into the metering hopper 1 fall onto the floor belt 6 and
are evened out there by the back scraping rakes 2 in the arrow directions
shown and are conveyed along an arrow 9 in the direction of the carry out
roller 7.
An endless scraper belt 10 guided over two deflection rollers 9, 9' is
arranged beneath the caxry out roller 7 and can be moved by rotation of
the deflection rollers 9, 9' in accordance with the arrows 11. The scraper
belt 11 includes an upper belt section 12 and a lower belt section 13, with
the lower belt section 13 being movable on a rotation of the deflection
rollers 9, 9' in the direction of an arrow 14.
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The scraper belt 10 consists of a belt-like carrier element 15 on which
plate-like drivers 16 standing substantially perpendicular to the belt-like
carrier element 15 are secured at regular intervals. Portioning segments
17 are formed between the drivers 16 and are made permeable in the
direction perpendicular to the belt-like carrier element 15.
A screening apparatus 19 formed as an oscillating screen 18 is so
arranged beneath the scraper belt 10 that the lower edges of the drivers
16 of the lower belt section 13 contact the oscillating screen 18 and, with
a movement of the lower belt section 13 along the arrow 14, scrape with a
specific pressure over the surface of the oscillating screen 18. The
oscillating screen can be moved to and fro via non-illustrated means in
accordance with a double arrow 20 and include two screen zones 21, 22
with different screen openings 23, 24, with the screen openings 24 formed
in the screen zone 22 being larger than the screen openings 23 formed in
the screen zone 21. The screen zones 21, 22 can in this arrangement be
formed for example as mesh screens, round-hole screens, elongate hole
screens or as any other known screen types as desired.
A receiving apparatus 25 formed as a conveyor belt is arranged beneath
the end of the oscillating screen 18 adjacent the deflection roller 9', with
the transport direction of the receiving apparatus extending perpendicular
to the plane of the drawing.
A conveyor belt 26 is provided beneath the screening apparatus 19 and
extends along its conveying direction indicated by an arrow 30 parallel to
the direction of movement of the lower belt section 13 illustrated by the
arrow 14.
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The particles 3 led away by the carry out roller 7 from the metering hopper
1 fall through the portioning segments 17 of the upper belt section 12 of
the scraper belt 10 until they land on the surface of the oscillating screen
18. Through the movement of the scraper belt 10 a metering of the
continuous particle inflow is achieved on the surface of the oscillating
screen 18 into individual particle portions which are arranged within the
portioning segments 17, with the individual portions being moved by the
drivers 16 over the surface of the oscillating screen 18 in the direction of
the arrow 14.
On sweeping over the first screen zone 21, those particles 3' having
dimensions smaller than the size of the screen openings 23 pass through
the screen openings 23 formed in the oscillating screen 18 and fall onto
the lower lying conveyor belt 26. In contrast those particles 3" having
dimensions larger than the size of the screen openings 23 are shifted by
the drivers 16 over the surface of the oscillating screen 18 until they reach
the second screen zone 22. On being swept over the screen zone 22 those
particles 3" having dimensions smaller than the size of the screen
openings 24 pass through the oscillating screen 18 and fall onto the lower
lying conveyor belt 26. Particles 3"' which are larger than the screen
openings 24, such as for an example excessively large fiber particles,
lumps or foreign bodies fall onto the receiving apparatus 25 and are
transported away by the latter after leaving the screen zone 22.
The particles 3', 3" which pass through the oscillating screen 18 form a
mat 27 on the conveyor belt 26, with the small particles 3' passing
through the oscillating screen 18 in the region of the first screen zone 21
impinging first of all onto the conveyor belt 26 and thus forming a lower
layer 28 of the mat 27. The large particles 3" which pass through the
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oscillating screen in the region of the second screen zone 22 fall onto the
lower layer 28 formed by the small particles 3' and form an upper layer
29.
The mat 27 formed in this manner can be transported on the conveyor
belt 26 in the direction of the arrow 30 to a non-illustrated pressing device
and pressed in this device in known manner to form a board. In the
context of the invention it is also possible and advantageous to arrange a
further apparatus of this kind after the apparatus of Fig. 1 in mirror-
image like manner such that additional large particles 3" pass onto the
mat 27 and onto them smaller particles, whereby one obtains a
symmetrically build-up mat which can be pressed to a shaped article. An
apparatus of this kind is described further below with reference to Fig. 3.
In accordance with the detailed view shown in Fig. 2 formations 31 are
formed on the drivers 16 by which the drivers 16 are releasably secured to
the belt-like carrier element 15.
The drivers 16 are flexibly designed so that the lower section 32 of the
drivers 16, which scrape over the surface of the oscillating screen 18
during a movement of the lower belt section 13 along the arrow 14, adopt
the curved shape shown in Fig. 2. As a result of the curved shape of the
lower sections 32 of the drivers 16 a force directed in the direction of an
arrow 33 act on the particles 3 arranged within the portioning segment 17
formed between the drivers 16 and has a component perpendicular to the
surface of the oscillating screen 18. As a result of this force the particles
3
arranged within the portioning segments 17 are pressed in the direction of
the oscillating screen 18, whereby the through-put through the oscillating
screen 18 is increased. Furthermore, through the pushing movement of
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the drivers 16, a turn-over movement indicated by arrows 34 arises in the
portions of the particles 3 arranged within the portioning segments 17, so
that small particles disposed remote from the screen are conveyed as a
result of this turn-over movement in the direction towards the surface of
the oscillating screen 18 and can pass through the oscillating screen 18
through the screen openings 23.
Furthermore it is evident from Fig. 2 that clogging of the oscillating screen
18 is prevented by the drivers 16 which scrapingly sweep over the surface
of the oscillating screen 18 so that a complicated cleaning of the oscillated
screen 18 is not required.
In the embodiment shown in Fig. 3 in which elements identical to the
apparatus of Fig. 1 are provided with the reference numerals used in Fig.
1, two scraper belts 34, 36 arranged in series in the longitudinal direction
and each followed by a screening apparatus 39, 40 formed as an
oscillating screen 37, 38 are provided instead of one scraper belt with a
screening apparatus provided after it.
The scraper belts 35, 36 are designed substantially identically to the
scraper belt 10 described in connection with Fig. 1 and are driven in
opposite directions via the deflection rollers 9, 9' as is indicated by arrows
41 to 44.
The scraper belt 35 includes an upper belt section 45 and a lower belt
section 46, with an intermediate floor 47 extending over the full width of
the scraper belt 35 being arranged at the lower side of the upper belt
section 45. The intermediate floor 47 is so positioned in this arrangement
that the inwardly disposed edges of the drivers 16 contact the upper side
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of the intermediate floor 47 and are scrapingly guided over the
intermediate floor 47 on a rotation of the scraper belt 35.
The intermediate floor 47 extends from the inwardly disposed deflection
5 roller 9 up to shortly before the outwardly disposed deflection roller 9',
with a region 49, which is permeable for the particles 3 in the direction
perpendicular to the oscillating screen 37 being formed between the end
48 of the intermediate floor 47 and the outwardly disposed deflection roller
9,.
In the same manner the scraper belt 36 has upper and lower belt sections
50, 51 with an intermediate floor 52 which is contacted by the inwardly
disposed edges of the drivers 16 being provided at the lower side of the
upper belt section 50 and with these edges being scrapingly guided over
the intermediate floor 52 during a rotation of the scraper belt 36.
A pendulum distributor 53 is arranged in the region between the carry out
roller 7 and the scraper belts 35, 36 and has two pendulum flaps 56
which can be swung along an arrow 54 about axes 55 as well as a wedge-
like separating element 57 with two oblique surfaces 59, 60 the tip 53 of
which is directed into the center between the axes 55.
Scattered material conveyed out of the metering hopper 1 by the carry out
roller 7 is alternately directed by the same sense pivoting of the pendulum
flaps 56 onto the respective oblique surfaces 59 and 60 of the wedge-like
separating element 57, from which the particles 3 of the scattered material
are respectively guided to the scraper belts 35 and 36 respectively.
The particles 3 fall onto the intermediate floors 47 and 52 respectively,
with portions of the scattered material containing a certain quantity of
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particles 3 being formed inside the portioning segments 17 each formed
between two adjacent drivers 16. These portions are conveyed by the
drivers 16 moving over the intermediate floors 47, 52 in the direction of
the outwardly disposed deflection rollers 9' where they fall, after passing
the ends 48, 61 of the intermediate floors 47, 52, downwardly through the
open regions 49, 62 in the direction of the oscillating screens 37, 38.
The particles 3 falling onto the surface of the oscillating screens 37, 38 are
fractionated in accordance with their size, as was already described in
connection with Fig. 1, with a symmetrical mat 27 with two outer layers
63, 64 containing small particles 3' and an inner layer 65 containing large
particles 3" being formed on the conveyor belt 26 in the embodiment of
Fig. 3 as a result of the symmetrical layout with two mirror-image scraper
belts 35, 36.
Particles 3"' which are toa large are respectively deposited at the inwardly
disposed deflection rollers 9 onto a receiving apparatus 25 and are
transported away by the latter.
In the embodiment shown in Fig. 4, in which elements formed identically
to Figs. 1 and 3 are again designated with the same reference numerals as
in Figs. 1 and 3, an intermediate floor 66 is arranged beneath the upper
belt section 50 with a further screening apparatus 68 adjoining its end 67
and with the inwardly disposed edges of the drivers 16 being scrapingly
guided on a rotation of the scraper belt 36 both over the surface of the
intermediate floor 66 and also over the surface of the further screening
apparatus 68.
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22
A screening apparatus 69 is arranged beneath the lower belt section 51
with the outwardly disposed edges of the drivers 16 being scrapingly
guided on rotation of the scraper belt 36 over its surface.
The fuxther screening apparatus 68 has screen openings 70 and the
screening apparatus 69 has screen openings 71, with the screen openings
70 being made larger than the screen openings 71.
Three receiving apparatuses 72, 73 and 74 are provided beneath the
scraper belt 36, with the receiving apparatus 72 being located over the
length and width of the screening apparatus 69, the receiving apparatus
73 being located in the region beneath the deflection roller 9' and the
receiving apparatus 74 being located in the region beneath the deflection
roller 9.
If particles 3 are dispensed in accordance with the arrow 4 onto the
surface of the intermediate floor 66 and then the particles 3 are guided
portion-wise through the drivers 16 of the scraper belt 36 over the surface
of the intermediate floor 66 up to its end 67 and thus subsequently over
the surface of the screening apparatus 68. Since the screen openings 70 of
the screening apparatus 68 are relatively large essentially all particles 3
fall through the screen openings 70 onto the surface of the screening
apparatus 69. Only particles 3"' which exceed a permissible maximum size
defined by the size of the screen opening 70 are led up to the deflection
roller 9' via the surface of the screening apparatus 68, where they
subsequently fall into the receiving apparatus 73 and are further
processed or separated out.
The particles 3 which impinge on the surface of the screening apparatus
69 are guided by the drivers 16 in individual portions over the surface of
CA 02286623 1999-10-15
23
the screening apparatus 69 with particles 3' having dimensions smaller
than the size of the screen openings 71 passing through these and being
caught by the receiving apparatus 72.
Particles 3" of which the dimensions lie beneath the size of the screen
openings 70 but above the size of the screen openings 71 are conveyed
beyond the end of the screening apparatus 69 and drop into the receiving
apparatus 74.
A separation of particles of different size is thus possible through the
described apparatus. In this connection, instead of one screening
apparatus 69, two or more screening apparatuses connected in series with
differently sized screen openings can also be provided and in this case a
separate receiving apparatus for catching the particles corresponding to
the respective screen opening is present beneath each of these screening
apparatuses.
In the embodiment shown in Fig. 5 elements already described with
reference to Fig. 1 to 4 are provided with the same reference numerals.
As can be seen from Fig. 5 plate-like elements 80 are provided at the end
faces of the drivers 16 and are connected via the formations 31 to the belt-
like carrier element 15 formed as a link chain. The sealing elements have
a substantially rectangular shape and a size such that in each case the
ends of two adjacently disposed sealing elements 80 overlap when the
associated drivers 16 are guided over the screening apparatus 19.
In the region of the deflection rollers 9, 9' the radially outwardly disposed
edges of two adjacent sealing elements 80 move away from one another so
that a V-shaped gap 81 arises between two adjacent sealing elements.
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24
In order to enable a problem-free overlap of the sealing elements 80 the
respective oppositely disposed overlapping zones 82, 83 of the sealing
element 80 are arranged laterally offset relative to one another so that the
overlapping zone 82 is offset to the outside and the overlapping zone 83 is
offset to the inside, whereby the best possible friction-less overlapping of
these end regions 82, 83 with the corresponding end regions 82, 83 of the
adjacent sealing elements 80 is made possible.
The portioning segments 17 are substantially fully sealed off by the sealing
elements 80 in both the upper and lower belt sections 12, 13 so that an
emergence of particles or dust arranged in the portioning segments 1? is
reliably prevented.
In the region between the upper and the lower belt section 12, 13 a middle
sealing element 84 formed as a side-wall is provided, of which only the
respective end regions 84' and 84" are shown in Fig. 5, as a result of the
illustrated part-section. The middle sealing element 84 is in scraping
contact at its upper and lower edges 85, 86 with the radially inwardly
disposed edges of the sealing elements 80, so that a seal against emerging
particles or dust takes place over the entire side surface of the scraper belt
10.
Thus it is ensured that the belt-like carrier element 15, for example
formed as a link chain, and also the deflection rollers provided with teeth,
as well as the further outwardly disposed elements of the apparatus,
remain substantially dust-free.
CA 02286623 1999-10-15
An upper sealing plate 87 which is only partly shown in Fig. 5 is arranged
above the upper belt section 12 and also prevents an escape of dust
upwardly.
5 The screening apparatus 19 consists in the embodiment shown in Fig. 5 of
five screen zones 75 to 79, each with differently sized screen openings,
with the size of the screen openings increasing from the screen zone 75 to
the screen zone 79. Depending on the application a different number of
different screen zones can be provided in order to thereby control the
10 structure and the quality of the mat produced with the apparatus.
The movement of the screening apparatus 19 formed as an oscillating
screen 18 in accordance with the double arrow 20 is produced, in the
illustrated embodiment, by a crank drive 88 the speed of rotation of which
15 is preferably adjustable. The crank drive 88 comprises a crank rod 89 the
end 90 of which is connected via a joint 91 to a roller guide 92.
The roller guide 92 includes a spatially fixedly arranged rail 93 provided
with running rollers on which a roller block 94 is displaceably mounted.
20 The roller block 94 is connected to the screening apparatus 19 so that
with a displacement of the roller block 94 along the rail 93 via the crank
drive 88 the oscillating screen 19 is likewise shifted.
By means of the crank drive 88 a very easily moving and controlled to and
25 fro movement of the screening apparatus is produced.
The link chain 15 can for example also be formed as a roller chain or as
another suitable belt-like carrier element. In just the same way the sealing
elements 80 can have a different form, so long as it is ensured that the
portioning segments 17 are substantially sealed off sidewise by the sealing
CA 02286623 1999-10-15
26
elements 88, in particular when the drivers 16 sweep over the screening
apparatus 19.
Fig. 6 shows an apparatus formed in accordance with the invention which
corresponds substantially to the apparatus shown in Fig. 3. Instead of the
intermediate floors 47, 52 shown in Fig. 3 two endless transport belts 95,
96 are provided onto which the particles 3 conveyed out of the metering
hopper 1 are brought via the pendulum distributor 53. The transport belts
95, 96 are driven in the direction of the arrows 97, 98 so that the particles
3 lying on the transport belts 95, 96 are transported in the direction of the
open regions 49, 62 and fall through the latter in the direction of the
oscillating screen 37, 38.
Thus the same functionality can be achieved through the transport belts
95, 96 as through the intermediate floors 47, 52 shown in Fig. 3.
Advantageous in this respect is the fact that the friction present when
using the intermediate floors 47, 52, between the lower edges of the
drivers 16 and the intermediate floors 47, 52, and the wear associated
therewith is avoided. The transport belts 95, 96 can be used in all
embodiments instead of the intermediate floors so that an apparatus in
accordance with Fig. 4 can also for example be built-up in a corresponding
manner with transport belts.
In all described apparatuses a sifting of known kind, such as for example
a wind sifting, can be fundamentally effected in addition to the described
screen sifting in order to further increase the quality of sifting. This can
be
achieved in that one wind sifting apparatus is arranged in each case
between the described screening apparatuses and the conveyor belt lying
beneath them.
