Plastic sorter

Details Plastic sorter Plastic sorter

2002-03-13

2004-04-13

Walsh, Donald P. (Department: 3653)

Classifying, separating, and assorting solids

Electrostatic

Attracting and repelling

C209S127100, C209S127200, C209S127300, C209S129000, C209S130000

Reexamination Certificate

active

06720514

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a plastic sorter for sorting and separating plastic pieces collected and crushed for recycling, according to their types.
BACKGROUND ART
One of the well-known techniques of sorting plastic pieces is a static separating plastic sorter
101
such as the one shown in FIG.
19
. The plastic sorter
101
is composed of a tribo electrifying apparatus
104
for electrifying a plurality of types of plastic pieces
102
so that the plastic pieces have different polarities and amounts of electrification depending on their types, the tribo electrifying apparatus being arranged below a hopper
103
through which the plastic pieces
102
are introduced, and a static separator
105
arranged below the tribo electrifying apparatus
104
for separating the electrified plastic pieces
102
according to their polarities and amounts of electrification.
The static separator
105
comprises a drum electrode
106
arranged below a chute of the tribo electrifying apparatus
104
, an opposite electrode
107
arranged obliquely above the drum electrode
106
, and a brush
108
for scraping off the plastic pieces
102
attached to an outer peripheral surface of the drum electrode
106
. The drum electrode
106
is constructed so as to be freely rotated around a horizontal shaft in a direction shown by an arrow in the drawing and is grounded. The opposite electrode
107
has, for example, a negative electrode of a high-voltage power source apparatus
109
connected thereto, with a positive electrode of the high-voltage power source apparatus
109
grounded. This connection allows a high voltage to be applied between the opposite electrode
107
and the drum electrode
106
to form a sorting static field
110
. To collect the plastic pieces
102
passed through the sorting static field
110
, according to their types, a first separating container
112
and a second separating container
113
which are separated from each other by a separator
111
are arranged under the drum electrode
106
.
In this plastic sorter
101
, the plastic pieces
102
are introduced into the hopper
103
and then fed therefrom to the tribo electrifying apparatus
104
, where they are agitated. Then, the plastic pieces
102
are frictionally contacted with one another and thus tribo-electrified so as to have predetermined polarities and amounts of electrification depending on their types and according to their electrification ranks. Then, the plastic pieces
102
, fed from the tribo electrifying apparatus
104
onto the drum electrode
106
, pass through the sorting static field
110
between the drum electrode
106
and the opposite electrode
107
and have their falling tracks varying according to their polarities and amounts of electrification before being housed in the separate separating containers
112
and
113
.
The principle of this static separation will be described with reference to FIG.
20
.
When the tribo-electrified plastic pieces
102
are dropped onto the drum electrode
106
, rotated in the direction shown by the arrow in the drawing, image force Fm, centrifugal force Fc and gravity G act on these plastic pieces
102
. Then, when the drum electrode
106
is rotated to feed the plastic pieces
102
into the static field
110
, plastic pieces
114
negatively electrified contrary to the drum electrode
106
are subjected to static force Fs acting in a direction in which the plastic pieces
114
are attracted to the drum electrode
106
, whereas plastic pieces
115
positively electrified like the drum electrode
106
are subjected to static force Fs and centrifugal force Fc acting in a direction in which the plastic pieces
115
repel the drum electrode
106
. If the sum of the vectors of the image force Fm, centrifugal force Fc, gravity G, and static force Fs acts outward of the drum electrode
106
, then the plastic pieces
102
follow such falling tracks that they leave the drum electrode
106
before being collected in the second separating container
113
. In contrast, if the sum of the vectors lies on the drum electrode
106
, the plastic pieces
102
are attracted to the drum electrode
106
or fall below the drum electrode
106
before being collected in the first separating container
112
.
The plastic pieces
102
are separated from one another by setting conditions for the high-voltage power source apparatus
109
such as the voltage at the apparatus
109
and the location of the separator
111
so as to control the above-described forces acting on the plastic pieces
102
. Accordingly, one of the conditions for precise separation is the reliable action of the image force Fm and centrifugal force Fc on the plastic pieces
102
.
When, however, the plastic pieces
102
, which are in the form of a laminated mass by the tribo electrifying apparatus
104
, are fed from the chute, they are likely to be laminated on a surface of the drum electrode
106
. Consequently, the image force Fm and the centrifugal force Fc do not properly act on the plastic pieces
102
, which are thus not precisely separated from one another.
Further, it is contemplated that the static force Fs may be increased to allow the plastic pieces
102
to be more precisely separated from one another. When, however, the voltage applied to the drum electrode
106
and the opposite electrode
107
is increased, corona discharge occurs between the drum electrode
106
and the opposite electrode
108
to generate corona ions, which may affect the electrified state of the plastic pieces
102
to reduce the separation accuracy.
Furthermore, in this static separating plastic sorter
101
, if the atmospheric humidity is high at the time when the plastic pieces
102
are electrified or statically separated from one another, the plastic pieces
102
may not be electrified easily or the time for which an electrification potential is retained may decrease, thus making the polarities and amounts of electrification of the plastic pieces
102
unstable. Consequently, the plastic pieces
102
cannot be appropriately separated from one another in the sorting static field
110
, thereby making the falling tracks of the plastic pieces
102
unstable to hinder the plastic pieces
102
from being precisely separated from one another.
It is thus an object of the present invention to provide a plastic sorter that can more precisely separate plastic pieces from one another according to their types.
DISCLOSURE OF INVENTION
The present invention provides a plastic sorter comprising a tribo electrifying apparatus for tribo-electrifying a plurality of types of plastic pieces by agitation, a feeder for feeding the plastic pieces electrified by the tribo electrifying apparatus, a static separating section for statically separating and sorting the plastic pieces fed by the feeder, according to their polarities and amounts of electrification, and a collecting section for collecting therein the plastic pieces passed through the static separating section and separated from one another, the static separating section being provided with a drum electrode that can be freely rotated around a horizontal shaft and an opposite electrode arranged opposite the drum electrode via a space used as a sorting static field, wherein the feeder is provided with a feed tray for guiding the electrified plastic pieces onto the drum electrode and a vibrator for vibrating the feed tray.
With this construction, the feed tray for guiding the electrified plastic pieces to the drum electrode is provided with the vibrator, thereby making it possible to vibrate the plastic pieces being moved on the feed tray to disentangle the massive plastic pieces to form a thin uniform layer. Accordingly, a large number of plastic pieces form a thin uniform layer on the drum electrode so as not to be laminated, so that the plastic pieces can be reliably subjected to appropriate image force and centrifugal force. Thus, appropriate force can be applied to the plastic pieces in a sorting static field, thereby allowing the plastic pieces to be precisely separated from o

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