Classifying – separating – and assorting solids – Electrostatic – With vibrating trough charging of particles
Reexamination Certificate
2000-07-31
2002-04-02
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Electrostatic
With vibrating trough charging of particles
C209S127100, C209S129000
Reexamination Certificate
active
06365857
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plastics sorting apparatus for sorting plastic chips obtained by fragmenting disposed plastic articles.
BACKGROUND ART
In recent years, the commitment to recycling garbage has been growing fast. The most common types of plastic that are consumed as raw material for plastic articles are vinyl chloride resin, polyethylene resin, polypropylene resin and polystyrene resin, and it seems that they account for major part of disposed plastics that are collected. To recycle such plastics, it is necessary to separate them by type.
Conventionally, a plastics sorting apparatus
50
as shown in
FIG. 5
is used to sort plastic chips containing a plurality of different types of plastics as mentioned above. This plastics sorting apparatus
50
includes a charging device
52
and an electrostatic sorting apparatus
55
. The charging device
52
charges batches of a predetermined amount of fragmented chips of different types of plastic while stirring them. The charged plastic chips
51
are then sorted by passing between a metal drum electrode
53
and an electrode plate
54
.
The main section
56
of the charging device
52
is provided with an insertion portion
57
and an ejection portion
58
. Inside the main section
56
, a stirring member
59
is provided for stirring the plastic chips
51
that have been inserted into the main section
56
through the insertion portion
57
. Above the insertion portion
57
, a belt conveyer
60
is arranged so as to supply chips of fragmented plastic
51
. The charging device
52
performs batch processing, which means that after the predetermined amount of plastic chips
51
has been stirred for a certain time, a batch of charged plastic chips
51
is ejected from the ejection portion
58
onto the metal drum electrode
53
.
The metal drum electrode
53
is freely rotatable. Moreover, the electrode plate
54
is fastened in opposition to the metal drum electrode
53
. An anode of a high-voltage power source
61
is connected to the metal drum electrode
53
, and a cathode of the high-voltage power source
61
is connected to the electrode plate
54
. This builds up an electrostatic field for sorting between the metal drum electrode
53
and the electrode plate
54
. A first collecting container
62
and a second collecting container
63
are arranged below the metal drum electrode
53
.
The following is an explanation of how this configuration operates.
A batch of a predetermined amount of fragmented plastic chips
51
is dropped from the belt conveyor
60
into the main section
56
of the charging device
52
. Inside the main section
56
, the different types of plastic chips
51
are stirred for a certain period of time and are charged by being rubbed against one another. The charged plastic chips
51
are then ejected in batches from the ejection portion
58
of the charging device
52
onto the peripheral surface of the rotating metal drum electrode
53
. Those plastic chips
51
that have been charged positively are repelled by the metal drum electrode
53
and attracted by the electrode plate
54
, and fall into the first collecting container
62
. Those plastic chips
51
that have been charged negatively are attracted by the surface of the metal drum electrode
53
, and fall into the second collecting container
63
, due to the rotation of the metal drum electrode
53
.
While the plastic chips
51
are being stirred in the main section
56
of the charging device
52
, no new plastic chips
51
are fed by the belt conveyor
60
. After the plastic chips
51
have been stirred for a certain time and all plastic chips
51
have been ejected from the ejection portion
58
of the charging device
52
, the next plastic chips
51
are fed from the belt conveyor
60
to the charging device
52
.
However, in this conventional apparatus, the charging device
52
performs batch processing, which means that after a predetermined amount of plastic chips
51
has been stirred for a certain time, a batch of charged plastic chips
51
is ejected. Therefore, a large amount of plastic chips
51
is ejected from the charging device
52
onto the peripheral surface of the metal drum electrode
53
each time, and there is a danger that the plastic chips
51
accumulate on the peripheral surface of the metal drum electrode
53
to form a layer that is thicker than is appropriate for electro static sorting. This poses a problem that the plastic chips
51
between the metal drum electrode
53
and the electrode plate
54
cannot be accurately sorted anymore.
It is therefore an object of the present invention to provide a plastics sorting apparatus capable of adjusting the feeding amount of plastic chips during the feeding of charged plastic chips onto a movable electrode so as to optimize the electrostatic sorting.
DISCLOSURE OF THE INVENTION
A plastics sorting apparatus in accordance with the present invention includes:
a charging device for charging a batch of a certain amount of different types of fragmented plastic chips while stirring the plastic chips, and
an electrostatic sorting device for sorting plastic chips that have been charged with the charging device by passing them between a pair of sorting electrodes, characterized in that:
the charging device ejects a batch of plastic chips after stirring the plastic chips for a certain period of time T that is necessary to charge the plastic chips;
one of the pair of sorting electrodes is a stationary electrode, and the other of the pair of sorting electrodes is a movable electrode that is arranged to oppose the stationary electrode and adapted to rotate at a peripheral speed v;
the apparatus further comprises
a first feeding device for feeding batches of a feeding amount W
1
of the plastic chips to the charging device; and
a second feeding device for continuously feeding onto the movable electrode of the electrostatic sorting device a feeding amount per unit time W
2
of plastic chips that have been ejected in batches from the charging device; and
the feeding amount per unit time W
2
can be adjusted so as to satisfy
W
1
/T≦W
2
≦v×B×H×D
where B is a width of the movable electrode, H is an average thickness of the plastic chips that have been fed onto the movable electrode, and D is a bulk density of the plastic chips.
With this configuration, the first feeding device feeds batches of different types of fragmented plastic chips in feeding amounts W
1
to the charging device, and the charging device stirs and charges the plastic chips for a certain period of time T. Then, the plastic chips are ejected in batches from the charging device, fed at a feeding amount per unit time W
2
by a second feeding device onto the movable electrode of the electrostatic sorting device, and pass between the rotating movable electrode and the stationary electrode. By this, the plastic chips are separated into positively charged plastic chips and negatively charged plastic chips.
In this process for sorting the plastic chips, by satisfying W
1
/T≦W
2
, after all the batch of plastic chips that have been ejected from the charging device are fed by the second feeding device to the movable electrode, the next (successive) batch of plastic chips is ejected from the charging device and fed by the second feeding device to the movable electrode. Thus, it can be avoided that, while first plastic chips that have been ejected from the charging device are being fed to the movable electrode with the second feeding device, successive plastic chips that are ejected later are added to the first plastic chips that are still in the second feeding device. Consequently, such a problem can be avoided that plastic chips pile up between the charging device and the second feeding device.
Moreover, by satisfying W
2
≦v×B×H×D, the feeding amount of plastic chips can be set optimally for electrostatic sorting, and the plastic chips that have been fed to the movable electrode form a layer on the movable electrode that has a suitable thickness for electrostatic s
Daiku Hiroyuki
Inoue Tetsuya
Maehata Hidehiko
Tamakoshi Daisuke
Hitachi Zosen Corporation
Kusner Mark
Rodriguez Joseph C
Walsh Donald P.
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