Note: Descriptions are shown in the official language in which they were submitted.
CA 02625914 2008-03-17
Title: Apparatus and method for separating plastic film from waste
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to an apparatus and a method for separating
plastic film material from waste. Waste, other than specific types of
industrial or agricultural waste generally contains substantial amounts of
flexible plastics, such as film material of garbage bags and packaging
material. For an effective recycling of plastic material, it is desirable to
have
such plastic film waste separated from the other waste. For the processing
of categories of waste, it is desirable that the waste contains no or very
little
plastic film material.
In U.S. patent 4 067 506, Japanese patent application publ.
No. 54 022 4777, European patent application 0 050 259 and U.S. patent
6 241 097, apparatuses are disclosed in which plastic film material is
separated from waste by bringing waste in contact with circulating hooks
that engage plastic film material more than other material brought in
contact with the hooks. The circulating hooks displace engaged film
material away from the other waste and the engaged film material is
subsequently disengaged from the hooks and transported away for further
processing and storage.In these apparatuses, a stream of waste from which
plastic film
material is to be separated is caused to come in contact with the hooks by
causing the waste to drop or slide to the hooks under the influence of
gravity.
SUMMARY OF THE INVENTION
It is an object of the invention to achieve an effective separation of
film material efficiently, by effectively engaging and disengaging film
materials.
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According to the invention, this object is achieved by providing an
apparatus for separating plastic film material from waste, having:
a supply track for supplying waste, the supply track extending in a
supply direction to its downstream end; and
a plurality of hooks mounted on a drum for circulating the hooks
along a trajectory through an engagement area near the supply track and
through a disengagement area downstream of the engagement area;
wherein the engagement area is located higher than the supply
track and/or in the supply direction beyond the downstream end of the
supply track, such that, in operation, a remainder of the waste passes by the
trajectory of the hooks without contacting the hooks; and
wherein the hooks project from the drum via openings in the
circumferential surface of the drum and are retractable into a
circumferential surface of the drum.
The invention may also be embodied in a method for separating
plastic film material from waste, in which waste is supplied along a supply
track in a supply direction and a plurality of hooks are circulated along a
trajectory through an engagement area near the supply track and through a
disengagement area, wherein, in each rotation of the drum, the hooks are
extended from the drum into positions projecting via openings in the
circumferential surface of the drum and are retracted into the
circumferential surface of the drum.
Since the hooks that are rotated along with the drum are retracted,
no separate members for stripping caught film material are required and
the construction can be relatively light and simple and is suitable for
rotation at relatively high rotational speeds. Moreover, the openings in the
drum via which the hooks project and are retracted only need to be small so
that the inside of the drum can be well shielded from the waste material.
Particular embodiments of the invention are set forth in the dependent
claims.
CA 02625914 2012-07-12
2a
In one aspect, there is provided an apparatus for separating plastic film
material from
waste, comprising: a supply track for supplying waste, the supply track
extending in a supply
direction to its downstream end; and a plurality of hooks mounted on a drum
for circulating
the hooks along a trajectory through an engagement area near the supply track
and through a
disengagement area downstream of the engagement area; wherein the engagement
area is
located higher than the supply track and/or in said supply direction beyond
the downstream
end of the supply track, such that, in operation, a remainder of the waste
passes by the
trajectory of the hooks without contacting the hooks; and wherein the hooks
project from the
drum via openings in a circumferential surface of the drum and are retractable
into the
circumferential surface of the drum, wherein the hooks are coupled to the drum
so as to be
extended while moving through the engagement area; and wherein the hooks are
mounted to
the drum via double lever members that are pivotable relative to the drum and
carry cam
followers positioned for engagement by cam profiles that are arranged axially
outside of the
drum.
In another aspect, there is provided a method for separating plastic film
material from
waste, comprising: supplying waste along a supply track in a supply direction;
and circulating
a plurality of hooks along a trajectory through an engagement area near the
supply track and
through a disengagement area, wherein, in each rotation of the drum, the hooks
are extended
from the drum into positions projecting via openings in the circumferential
surface of the
drum and are retracted into the circumferential surface of the drum, wherein
the hooks are
extended while moving through the engagement area, and further comprising
generating an
upward airflow through the supply track and/or in the vicinity of the
downstream end of the
supply track causing a fraction of the waste, containing the plastic film
material, to be
diverged to the hooks in the engagement area from a remainder of the waste,
while the
remainder of the waste passes by the hooks without contacting the hooks.
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Further features, effects and details of the invention are described
with reference to an example shown in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic side view of an example of an apparatus
according to the invention;
Fig. 2 is a schematic side view in cross-section of the apparatus
shown in Fig. 1; and
Fig. 3 is a schematic side view of an alternative example of an
apparatus according to the invention.
DETAILED DESCRIPTION
The invention is first described with reference to the example
shown in the drawings and the various alternative options within the
framework of the invention are discussed.
The apparatus shown in the drawings is equipped with a supply
track 1 for supplying waste. The supply track 1 extends in a supply direction
(arrow 3) to a downstream end 4 thereof.
Hooks 5 are mounted on a hook carrier in the form of a drum 6 for
circulating the hooks 5 in a sense of circulation (arrow 7) along a trajectory
through an engagement area 8 near the supply track 1 and through a
disengagement area 9 downstream of the engagement area 8.
A blower 10 is arranged for generating an upward airflow 11 in the
vicinity of the downstream end 4 of the supply track 1 for blowing a fraction
12 of the waste 2 to the hooks 5 in the engagement area 8 (in the drawings
only one hook 5 of a plurality of hooks in a row in axial direction of the
drum
6 is visible).
The engagement area 8 is located higher than the supply track and
in the supply direction 3 beyond the downstream end 4 of the supply track 1,
such that, in operation, a remainder 13 of the waste 2 is passed by the
trajectory of the hooks 5 without contacting the hooks 5.
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Underneath the downstream end 4 of the supply track 1, the
engagement area 8 and the disengagement area 9, a discharge conveyor 14
is arranged for transporting away the remainder 13 of the waste 2.
In operation, waste 2 is supplied along the supply track 1 in the
supply direction 3 while the hooks 5 are circulated along a trajectory
through the engagement area 8 and the disengagement area 9. The upward
airflow 11, which does not need to be vertically upward, but may just have
an upward directional component as in the present example, in the vicinity
of the downstream end 4 of the supply track 1 causes the fraction 12 of the
waste 2, which is easily entrained by an airflow and contains the plastic film
material, to be diverged to the hooks 5 in the engagement area 8. The
remainder 13 of the waste 2 passes by the hooks 5 without contacting the
hooks 5.
By the upward airflow 11, a fraction 12 of the waste 2 that is easily
entrained by an airflow, such as sheet material, is separated from the waste
2 and blown against the hooks 5 in the engagement area 8. Thus, in a
simple manner a fraction 12 of the waste 2 containing the plastic sheet
material is separated from the remainder 13 of the waste 2 and brought in
contact with the hooks 5, where the relatively flexible plastic sheet material
is engaged by the hooks 5 and other material, such as paper, is not engaged
by the hooks 5 and allowed to drop back once it is outside the upward
airflow 11. The remainder 13 of the waste does not contact the hooks 5 and
is thus prevented from interfering with the procedure of sorting out plastic
film material on the basis of its propensity to be engaged by the hooks 5 and
drops onto the discharge conveyor 14.
According to the present example, the engagement area 8 is located
closely beyond the downstream end 4 of the supply track 1. Furthermore,
the blower 10 is arranged for generating the upward airflow 11 in the
vicinity of the downstream end 4 of the supply track 1 and the engagement
area 8 is located higher than the supply track 1 and in the supply direction
3 beyond the downstream end 4 of the supply track 1, such that, in
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operation, the remainder 13 of the waste drops from the downstream end 4
of the supply track 1 without contacting the hooks 5.
In the vicinity of the downstream end 4 of the supply track 1, and
in particular downstream of the supply track 1, the upward airflow 11 is
disturbed very little by the structure of the supply track and the easily
entrained fraction 12 of the waste 2 separates out relatively easily from the
remainder of the waste, because, in the stream of waste falling freely from
the downstream end of the supply track 1, the waste to be entrained by the
airflow is not clamped underneath other waste.
The easily entrained fraction 12 of the waste 2 will generally not
only contain plastic film material, but also other thin walled materials, such
as paper and cardboard. To counteract that such materials are also engaged
by the hooks 5, the apparatus according to the present example is further
equipped with a blower 15 for generating a counter airflow 16 along the
hooks 5 in and downstream of the engagement area 8. The counter airflow
16 is directed in a direction with a component opposite to the direction of
movement of the hooks through that airflow in and downstream of the
engagement area 8 and blows material that is not effectively hooked-on by
the hooks 5 off the hooks 5, so that at least a substantial portion of the
paper and other non-plastic film material that initially clings to the hooks 5
is removed from the hooks 5 before it is entrained by the hooks 5 for
processing with the plastic film material. As in the present example, the
counter airflow 16 is preferably directed with a downward component.
The fraction 12 of the waste that is easily entrained by an airflow
and that is hooked by one or more of the hooks 5 may be composed of not
only plastic film material but also of other materials clinging to or held in
the plastic film materials. For instance a garbage bag containing some
garbage may be effectively hooked by the hooks 5. However, such impurities
in the stream of sorted plastic film material may disturb the further
processing of the sorted plastic film material.
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To reduce the amounts of impurities in the sorted plastic film
material, it is provided according to the present example, that the apparatus
is equipped with a discharge channel 17 having an inlet 18 above the
disengagement area 9 and with a ventilator 19 for generating an airflow
through the disengagement area 9 towards the inlet 18 and through the
discharge channel 17. Because the plastic film material is removed from the
hooks 5 by generating an airflow through the disengagement area 9 and
towards and through the discharge channel 17, items of plastic film
material that hold or are connected to substantial amounts of impurities,
such as garbage bags that contain at least some waste, will generally be too
heavy to be entrained by the suction applied via the discharge channel 17.
Such heavy items therefore drop down onto the discharge conveyor 14 and
are not discharged with the sorted plastic film material.
As is shown in Fig. 2, the hooks 5 project from the drum 6 via
openings in the circumferential surface of the drum 6 and are retractable
into a circumferential surface of the drum. By retracting the hooks in the
disengagement area 9, disengagement of the material hooked onto the hooks
is facilitated by stripping of the caught film material from the hooks.
Furthermore, winding of waste material around the circulating hooks is
prevented. Since the hooks 5 that are rotated along with the drum 6 are
retracted, no separate members for stripping caught film material are
required and the construction can be relatively light and simple and is
suitable for rotation at relatively high rotational speeds. Moreover, the
openings in the drum 6 via which the hooks 5 are retracted only need to be
small so that the inside of the drum 6 is well shielded from the waste
material.
To achieve and operate the retractability of the hooks, the hooks 5
are mounted to the drum 6 via double lever members 20, of which only one
is designated by a reference numeral. Each time a row of hooks 5 extending
in axial direction of the drum is carried by a pair of the double lever
members that are mounted on opposite end faces of the drum 6 and are
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pivotable relative to the drum 6 about axes 21. Cam followers 22 are
positioned for engagement by cam profiles 23 that are arranged axially
outside of the drum 6. When a row of hooks 5 enters the disengagement area
9, the associated cam followers 22 contact the cam profile 23 and pushes the
cam follower radially inwardly towards the axis of the drum as the cam
follower moves along the cam profile 23. This causes the associated double
levers 20 to pivot relative to the drum 6, so that the associated hooks 5 are
retracted into the drum 6. When a row of hooks 5 approaches the
engagement area 8, the associated cam followers 22 reach a section of the
cam profile 23 of which the radial distance to the axis of the drum 6
increases in the rotational sense 7, so that the cam follower 22 is again
allowed to move away from the axis of the drum 6 and does so under
influence of springs (not shown) that bias the double lever members 20 into
positions in which the hooks 5 project maximally from the drum 6. Because
the hooks 5 are extended while moving through the engagement area 8
where the material 12 that is to be engaged selectively reaches the
circulation path of the hooks 5, effective and selective engagement of film
material by the hooks 5 is enhanced, because the hooks are to some extent
"stabbed" into the film material to be engaged. Since the hooks 5 project
from the drum 6 in the sense of circulation, extending the hooks 5 also
causes the velocity of the hooks 5 in circumferential sense of the drum 6 to
be increased temporarily, which is advantageous for more effectively
engaging film material. A further advantage of extending the hooks 5
relatively late is that the likelihood that heavier material 13 that drops
along the drum 6 is hit or caught by the hooks is reduced and/or the stream
of heavier material passing 13 along the drum 6 can pass more closely along
the drum 6.
The hooks 5 are curved about the pivot axes 21, so that narrowly
fitting openings (gap width preferably smaller than 0,5 cm) in the
circumference of the drum 6 are sufficient to allow the hooks to be extended
and retracted. Because moreover the pivot axes are positioned forwardly in
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the sense of rotation 7 of the drum 6, the hooks 5 are curved in the sense of
rotation 5, which is advantageous for reliably engaging plastic film material.
While the invention is described above with reference to an
example, it will be readily apparent to the skilled person that within the
framework of the inventions, many variants are conceivable. For instance,
the hooks may be only partially retractable or not retractable at all.
Also, the discharge channel 17 for removing plastic film material
from the hooks 5 by suction may be dispensed with, for instance if the
purpose of removing plastic film material is mainly to clear the remainder of
the waste from plastic film material. If the discharge channel 17 for
removing plastic film material from the hooks 5 by suction is dispensed
with, it is preferred that a separate discharge conveyor or chute is arranged
for separately collecting and discharging all materials that have passed over
the drum, for instance under a portion of the circumference of the drum
facing away from the supply track.
The supply track 1 is in the form of a conveyor belt, but may also
be provided in another form, such as in the form of a chute or a screw
conveyor.
The engagement area where plastic film material is brought in
contact with the hooks and engaged by the hooks may be positioned above
the supply track instead of downstream of the downstream end 4 of the
supply track 1 as shown in the present example. In such an embodiment,
the blower for generating an upward airflow for blowing a fraction of the
waste that is easily entrained by an airflow against the hooks will be located
more upstream than in the example shown to blow through supply track.
Separation of the easily entrained fraction of the waste may be facilitated by
including agitators for agitating waste lying on the supply track in the area
of the upward airflow.
The trajectory along which the hooks can be circulated does not
need to be circular, but may for instance have an elongate shape, for
instance by providing that the hooks are carried by a conveyor chain.
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Fig. 3 shows an alternative example an apparatus according to the
invention, wherein an engagement area 108 is located in a supply direction
103 beyond and below a downstream end 104 of a supply track 101. A
blower 110 is arranged for blowing an easily entrained fraction 112 of waste
102 with a horizontal airflow 111 out of a stream of waste that drops from
the downstream end 104 of the supply track 101. The easily entrained
fraction 112 of the waste is blown against hooks in the engagement area
108. The remainder 113 of the waste drops further without contacting the
hooks.
