Abstrict This invention presents a method of clearing a sensor field of
debris, including liquids, through the use of an air curtain. An
embodiment of this invention addresses the problem of impurity buildup
in the sensing field of an optical sorter. An air curtain is created
which prevents film buildup between the light sensor and the light
source by blowing material and impurities, which form the film as
they fall off articles being sorted, out of the sensing field.
Claims What is claimed is:
1. A device to form an air curtain to prevent a film buildup in
a sensing field, said device comprising:
an airflow plane aligned with a path of articles and offset a distance
from said path;
a slide over which articles slide, said slide disposed between
the article path and said airflow plane, wherein said slide is offset
from said airflow plane such that said slide and said airflow plane
define an air passage; and
a fluid conduit adapted to conduct air from an air supply to said
air passage such that film is prevented from building up in the
sensing field, said fluid conduit in fluid conductivity with said
air passage.
2. A device to compensate for false optical signal readings due
to dirt, film, and other impurities building up between a light
sensor and a light source, where the light sensor is capable of
sensing light and generating signals having amplitudes corresponding
to magnitudes of a light sensed by the light sensor, and the light
source is capable of emitting light, and where the light sensor
and the light source are positioned such that a cullet path passes
through the emitted light and attenuates the light sensed by the
light sensor, thus allowing for sorting of cullet based upon an
amount the sensed light is attenuated compared to a baseline amplitude
value, said device comprising:
an airflow plane parallel to the cullet path and offset a distance
from the cullet path, where said airflow plane is adapted to receive
the light sensor;
a wearcover over which cullet slide disposed between the cullet
path and said airflow plane, the wearcover offset a spaced distance
from said airflow plane so that said wearcover and said airflow
plane form an airflow passage in said spaced distance there between,
where said airflow passage is adapted to receive air and direct
air between the light sensor and the cullet path; and
a fluid conduit adapted to conduct air from an air supply to said
air passage, said fluid conduit adapted to be in fluid conductivity
with said airflow passage such that air may be conducted from the
air supply to said airflow passage.
3. The device of claim 2, wherein the wearcover includes a terminating
end, said terminating end terminating prior to a plane in which
the light sensor and the light source lie.
4. The device of claim 3, wherein said airflow plane includes a
terminus, said terminus located downstream of the plane in which
the light sensor and the light source lie, wherein downstream is
defined by a cullet path direction.
5. The device of claim 4, wherein said airflow plane terminus is
curved away from the cullet path, and said curve is sufficiently
gradual so as to maintain a pneumatic wall attachment phenomena.
6. The device of claim 2, wherein said airflow plane is further
adapted to receive a transparent cover adapted to be received in
said airflow plane to cover the light sensor.
7. The device of claim 6, wherein said transparent cover is further
adapted to be in optical connection with the light sensor.
8. The device of claim 7, wherein said optical connection includes
silicone grease.
9. The device of claim 7 wherein the wearcover includes a terminating
end, said terminating end terminating prior to a plane in which
the light sensor and the light source lie.
10. The device of claim 9, wherein said airflow plane includes
a terminus, said terminus being located downstream of the plane
in which the light sensor and the light source lie, wherein downstream
is defined by the cullet path direction.
11. The device of claim 10, wherein said airflow plane terminus
is curved away from the cullet path, and said curve is sufficiently
gradual so as to maintain a pneumatic wall attachment phenomena.
12. An air curtain former to compensate for false optical signal
readings due to film building up between a light sensor and a light
source in an optical sorting machine, wherein the light source emits
light, the light sensor senses the emitted light and generates signals
corresponding to the magnitude of sensed light sensed by the sensor,
and the light sensor and the light source are positioned such that
a cullet path passes through the sensed light, thereby attenuating
the sensed light, thus allowing for optical sorting of cullet based
upon an amount the sensed light is attenuated compared to a baseline
amplitude value, said air curtain former comprising:
an airflow plane parallel to the cullet path and offset a distance
from the path of cullet, said airflow plane adapted to receive the
light sensor;
a wearcover over which cullet slide disposed between the cullet
path and said airflow plane and offset a spaced distance from said
airflow plane, where said wearcover and said airflow plane define
an airflow passage there between, and where said airflow passage
is adapted to direct air between the light sensor and the cullet
path so that film does not buildup between the light sensor and
the light source; and
a fluid conduit in fluid connectivity with said airflow passage
such that air may be conducted from an air supply to said airflow
passage.
13. The air curtain former of claim 12, wherein said airflow plane
is further adapted to receive a transparent cover adapted to be
received in said airflow plane to cover the light sensor such that
air may be directed between said transparent cover and the cullet
path, and where said transparent cover is further adapted to be
in optical connection with the light sensor.
14. The air curtain former of claim 13, wherein said airflow plane
includes a terminus, said terminus located downstream of the sensed
light, wherein downstream is defined by the cullet path direction.
15. The air curtain former of claim 14, wherein said terminus of
said airflow plane is curved away from the cullet path, where said
curve is sufficiently gradual so as to maintain a pneumatic wall
attachment phenomena.
16. A method to limit false optical signal readings due to film
buildup between a light sensor and a light source in an optical
sorting machine, wherein the light source emits light and the light
sensor senses the emitted light, generates signals corresponding
to the magnitude of sensed light sensed by the sensor, and where
the light sensor and the light source are positioned such that cullet
pass through the sensed light, thereby attenuating the sensed light,
thus allowing for optical sorting of cullet based upon an amount
the sensed light is attenuated compared to a baseline amplitude
value, said method comprising the step of propagating air between
the light sensor and a cullet path; and placing an airflow plane
an offset distance from a wearcover such that the wearcover is between
the cullet path and the airflow plane and the wearcover and the
airflow plane form the air passage. Description Be it known that I, Arthur G. Doak, a citizen of United States,
residing at Nashville, Tenn.; have invented "An Air Curtain
Former for Creating an Air Curtain to Compensate for Impurity Buildup."
BACKGROUND OF THE INVENTION
This invention relates to clearing sensors of debris to provide
more accurate sensing data. A particular embodiment specifically
relates to reducing film buildup over optical sensors in an optical
sorting machine due to impurities carried along with the articles
to be sorted.
Optical sorting machines, of the type to which an embodiment of
this invention relates, work on the principle of light attenuation.
Generally, sorters of this type are used to sort articles, such
as glass cullet or other material, for post consumer recycling and
processing. The glass cutlet are intermixed with dirt, sand, and
other impurities; it is not economically viable to preclean the
cullet. Although optical sorting of glass is offered as an example,
the problems of impurity build-up applies to any sorting machine.
For example, metallic build-up on an eddy current sensor can affect
its operation. Liquid or particulate build-up on a plastic sorting
machine can affect its operation.
Optical sorters of this type generally work as follows. The cullet
pass through a sensing field where light of different wavelengths
is emitted by light sources and sensed by sensors. The sensors generate
signals corresponding to the magnitude of light sensed. Cullet of
different color attenuate different wavelengths of light different
amounts. This attenuated light signal is compared against a baseline
value for the signal to determine the color of the cullet.
Impurities carried along with the cullet buildup over the sensors.
This shifts the attenuation value and leads to missorts. These missorts
may lead to less pure sorted lots. Lower quality lots are, thus,
passed on for subsequent processing. Alternatively, cullet having
potential value are erroneously discarded due to shifted attenuation
readings.
Prior art has attempted to compensate for impurity, or film, buildup
by increasing, or lowering, the baseline value over time. This has
proved less than satisfactory. One reason for the short fall is
that the impurity layer is not uniform. As the film layer builds,
cutlet tend to create furrows in the film layer. This results in
nonuniformities in the film layer, and tends to lead to missorts.
The prior art has also attempted to solve the problem by cleaning
the screen. However, the cleanser can affect the sort.
The prior art has also attempted to solve the problem by repeatedly
replacing the wearcover; this increases expense and down time.
What is needed is a device to reduce light attenuation shifts due
to film build up in an optical sorting device. This needed system
must be efficient and economical. This needed system must decrease
down time. This needed system must efficiently clean the sensor
area to reduce the effects of particulate and fluid build-up. This
needed system is lacking in the prior art.
SUMMARY OF THE INVENTION
This invention presents apparatus and methods to clear sensors
of debris through use of an air curtain. Reliability of the sensor
data is, thus, improved. Generally, most sensors susceptible to
distortion by debris, or impurities, including liquids, in the sensing
field, may benefit from this invention. One embodiment of this invention,
in particular, addresses the problem of impurity buildup in the
sensing field of any sorter including an optical sorter. Buildup
of film and other impurities affect the attenuation values because
light is attenuated by the film as well as the article to be sorted.
These articles are generally glass cullet. Glass cullet, generally,
are broken pieces of glass bottles and the like. The shifted attenuation
readings lead to article missorts. This invention overcomes attenuation
problems due to nonuniformities associated with cullet furrowing.
The nonuniformities in the film layer are overcome by providing
a layer of air between the sensors (or sensor) and the cullet. Impurities
often fall off often the cutlet as the cullet pass through the sensing
field. An air curtain is created which protects the sensors from
film buildup by blowing impurities out of the sensing field.
The device which creates the air curtain has an airflow plane below
a slide on which cutlet slide. The slide in a cullet sorting machine
is frequently called a `wearcover`. The slide portion of the device
ends at the sensing field. In the sensing field emitted light is
sensed by sensors and attenuated by cullet.
Between the slide and airflow plane is an air passage. Air is forced
through the passage with sufficient force to provide an air curtain.
The air curtain blows impurities which fall toward the sensors out
of the sensing field, typically downstream, thus, providing an air
curtain over the sensors.
Beyond the sensing field, the airflow plane is curved away from
the wearcover. The air layer will follow the curved plane. This
phenomena of the air layer adhering to the airflow plane is generally
referred to as "pneumatic wall attachment." This phenomena
is employed to divert the air stream below the path of the cullet.
Diverting the air stream below the cutlet path limits the chance
that the air curtain may interfere with the ejector. The ejector
used with the sorter is generally an air jet, or air valve. After
through the sensor field, cullet are then ejected from the cullet
stream by an ejector, or allowed to pass.
In one embodiment, the sensors are covered with a transparent cover
which is in plane with the airflow plane and below the layer of
air. To reduce optical distortion, the transparent cover is adapted
to be bonded to the sensors with transparent silicone grease, or
similar substance. The silicone grease provides an optical connection
medium with properties similar to the transparent cover.
An object of the invention is to provide a device to reduce light
attenuation shifts due to film build up in an optical sorting device.
Another object of the present invention is to provide a system
for cleaning the sensor area of any sensing system.
Another object of the present invention is to provide a system
which is economical to manufacture and use; and may be adapted to
use with existing sensing systems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cutaway side view of an air curtain former.
FIG. 2 is a cutaway side view of an air curtain former in connection
with an air supply and a sensor.
FIG. 3 is a cutaway side view of an air curtain former in operation
with an ejector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Applicant's invention will be best understood when considered in
light of the following description of the preferred embodiment of
the invention as illustrated in the attached drawings wherein like
referenced numerals and characters refer to like parts.
FIG. 1 shows an air curtain former 5. It includes an airflow plane
10 and a transparent cover 20. The transparent cover 20 sits in
plane with the airflow plane 10 and below the path an air layer
will flow. Beyond the sensing field 82, the airflow plane 10 includes
a curve 12 and a terminus 15.
The curve 12 curves away from the path of the cullet to limit possible
interference with the ejector jets by the air curtain. The curve
12 and the terminus 15 may be separated by a fall away (14), as
in FIG. 1, or merged into a single curve, as in FIG. 3. The curve
12, if used, should be sufficiently gradual so as to maintain a
pneumatic wall attachment phenomena.
FIG. 1 also includes a slide (or wearcover) 30 parallel to the
airflow plane 10. Together the wearcover 30 and the airflow plane
10 form an air passage 40. The slide 30 includes a terminating end
35 which terminates at the onset of the sensing field 82. FIG. 2
show the slide terminating end 35 ending prior to a plane in which
the light source 90 and the light sensor lie 92.
In one embodiment, the airflow plane curve 12 is downstream of
the plane in which the light 90 and the sensor 92 lie. Downstream
is defined in the direction of the cullet path. A fluid conduit
50 for conducting air supplied to the air passage is also shown
in FIG. 1.
FIG. 2 shows an air curtain former 5 substantially similar to the
air curtain former shown in FIG. 1, however, it is shown with the
light source 90 the light sensor 92, and the cullet 84. The forced
air layer 80 which flows through the air passage 40 is also shown
in FIG. 2. The air layer 80, as shown, adheres to the airflow plane
10 around the curve 12 of the airflow plane 10. An upstream slide
96 delivers cullet 84 to the air curtain former 5; the cullet then
pass through the sensing field 82.
FIG. 3 shows an air curtain former 5 substantially similar to the
air curtain former shown in FIGS. 1 and 2. FIG. 3 further shows
an ejector system 70 including a splitter 72, an ejector nozzle
74 and a solenoid valve 76. The solenoid valve 76 allows air from
an air supply 94 to eject ejected material 83 and allow non-ejected
material 85 to pass downstream.
The preferred embodiment is an air curtain former 5 for forming
an air curtain to compensate for false signal readings which are
due to dirt, film, and other impurities building up between the
light sensor 92 and the light source 90. The light sensor 92 senses
the emitted light and generates signals. The signals have amplitudes
corresponding to the magnitude of the light sensed.
It will be apparent to those skilled in the art of sensors, that
the invention may be used to clear foreign material, including debris,
film, liquid, and the like, from a multitude of sensor types. Some
sensor types that may benefit from an air curtain to clear the sensing
field include those that use magnetic fields, electromagnetic fields
(including thermal and nuclear radiation), acoustic fields, and
optical sensing. Generally, any sensor field which may be distorted
by impurities, and not effected by air flow, may benefit from the
invention. In those systems which may be interfered with by air
flow, the air curtain may be adapted to limit, or avoid, interference
by the air flow. The curve 12 shown in FIGS. 1 through 3 is an example
of one such adaptation; it diverts air away from the cullet stream
using pneumatic wall phenomena.
Referring to an optical sorting machine of the type in which a
preferred
embodiment of this invention is used, when cullet 84 pass through
the sensing field 82, the cullet 84 attenuate the light sensed.
Different color cullet 84 attenuate different wavelengths of light
different amounts. For instance a red cullet would attenuate a green
light wavelength more than a red light wavelength. The attenuated
signal is compared to a baseline amplitude value for the given wavelength
of light; color of the cullet can be determined from an attenuation
analysis.
Cullet are, however, intermixed with film, dirt, sand and the like.
Cullet carry this film with them through the sensing field 82. The
film rubs off and is deposited on the sensor 92. The film layer
further attenuates the light source 90; this leads to false optical
signal readings. Missorted cullet 84 result from this attenuation
shift.
An airflow plane 10 is oriented parallel to the path of the cullet
84. The airflow plane 10 is adapted to receive the light sensor
92. A transparent cover 20 fits in plane with the airflow plane
10 and beneath the path an air layer 80 will take. The transparent
cover 20 covers and protects the sensor 92. The transparent cover
20 is adapted to be bonded to the sensor 92 with transparent silicone
grease. The silicone grease should be packed in and around the sensor
92 and up against the transparent cover 20. This reduces bending
and light defraction as the emitted light passes through different
mediums. The silicone grease has properties more similar to the
transparent cover than air, so the light rays are bent less than
if they were to pass through an air medium after passing through
the transparent cover 20 before being sensed by the sensors 92.
One of the preferred embodiments also includes a slide (or wearcover)
30 which is oriented parallel to the airflow plane 20. The wearcover
30 is offset from the airflow plane 10 to form an airflow passage
40. The wearcover 30 has a terminating end 35 which abuts the sensing
field 82. The other end of the wearcover 30 mates with an upstream
slide 96. The upstream slide 96 provides a means for the cullet
84 to ultimately reach the sensing field 82.
A fluid conduit 50 conducts air supplied from an air supply 94
to the airflow passage 40 such that an air layer 80 flows along
the airflow plane 10. Film and impurities are thereby blown off
of, and away from, the sensor 92 as the cullet pass through the
sensing field 82.
The airflow plane 10 has a terminus 15 and a curve 12. The curve
12 is curved away from the cutlet path. It is sufficiently curved
to divert the air layer 80 away from the cullet path. If the curve
12 is curved or bent too sharply, the air layer 80 will not adhere
to the wall. If the air layer 80 is not diverted, it may interfere
with passage of material through the ejector.
Cullet are then ejected from the cullet stream by the ejector system
70, or allowed to pass. One such ejector system 70 employs a splitter
72 and air forced through an ejector nozzle 74. The ejector nozzle
74 is attached to an air supply. A solenoid valve 76 operates to
allow air through the ejector nozzle 74 and blow ejected material
83 out of the path of non-ejected material 85. The non-ejected material,
or accepted cullet, continue downstream.
Because there is no film buildup to attenuate the light, the light
is only attenuated by the passing cullet, and the attenuated light
more accurately represents the colors of the cullet. The more accurate
color distinction results in fewer missorts which improves purity
of the sorted lot and increases the material to be processed on
down the line. Because the sensor was cleared of attenuating debris
in an economical manner, greater profit is derived from the purer
sorted lot.
Thus, although there have been described particular embodiments
of the present invention of "Air Curtain Former for Creating
an Air Current to Compensate for Impurities," it is not intended
that such references be construed as limitations upon the scope
of this invention except as set forth in the following claims. |