U.S. patent number RE29,031 [Application Number 05/570,321] was granted by the patent office on 1976-11-09 for circuitry for sorting fruit according to color.
This patent grant is currently assigned to FMC Corporation. Invention is credited to Charles S. Greenwood, Donald W. Irving.
United States Patent |
RE29,031 |
Irving , et al. |
November 9, 1976 |
Circuitry for sorting fruit according to color
Abstract
A circuit for detecting the color of a fruit on a conveyor by
measuring the light reflected from the surface of the fruit at a
viewing station and for providing an appropriate discharge signal
so that the fruit will be discharged to a particular discharge
location at a position spaced downstream from the viewing station.
The circuit includes .[.means .]. .Iadd.a light collecting device
and filters .Iaddend.for separately measuring the amount of light
reflected within two distinct bands of wavelengths of light,
continuously computing the ratio of the same to derive an analog
ratio signal, and comparing the ratio signal with a plurality of
predetermined ratio signals in order to obtain said appropriate
discharge signal. A memory circuit is included so that discharge
signals for a plurality of fruit can be stored for an indeterminate
period of time before any one of such fruit is directed to its
discharge location.
Inventors: |
Irving; Donald W. (San Jose,
CA), Greenwood; Charles S. (Santa Clara, CA) |
Assignee: |
FMC Corporation (San Jose,
CA)
|
Family
ID: |
26940500 |
Appl.
No.: |
05/570,321 |
Filed: |
April 21, 1975 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
249974 |
May 3, 1972 |
03750883 |
Aug 7, 1973 |
|
|
Current U.S.
Class: |
209/564; 209/587;
209/582; 356/407 |
Current CPC
Class: |
B07C
5/342 (20130101) |
Current International
Class: |
B07C
5/342 (20060101); B07C 005/342 () |
Field of
Search: |
;209/74R,74M,111.6
;250/226 ;356/178 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Rolla; Joseph J.
Attorney, Agent or Firm: Kelly; R. S. Guernsey; L. B. Tripp;
C. E.
Claims
What is claimed is:
1. In an apparatus for sorting fruit according to the color
thereof, circuitry comprising detection means for producing a pair
of continuous light reflection signals indicative of the amount of
light reflected by a fruit within two different bands of
wavelengths of light, means for continuously electrically dividing
said signals to provide an analog ratio signal which is
proportional to the ratio of said light reflection signals, a
plurality of comparators each of which is arranged to
simultaneously compare said ratio signal with a predetermined fixed
ratio signal, and means operatively connected to each of said
comparators for providing a discharge signal representative of a
decision to direct said fruit to a particular discharge
location.
2. In an apparatus for sorting fruit as set forth in claim 1, means
for storing said discharge signal until such time as said fruit is
in position to be directed to said particular discharge location,
and means responsive to said last named means for providing a
signal to operate a discharge mechanism when said fruit is in a
position to be directed to said discharge location.
3. In an apparatus for sorting fruit as set forth in claim 2
wherein said means for storing said discharge signal comprises a
primary memory means and a reserve memory means, means operative to
normally transfer said discharge signal to said primary memory
means but being operative to transfer a discharge signal to said
reserve memory means if a signal is already present in said primary
memory means, and means operative to transfer any discharge signal
in said reserve memory means to said primary memory means each time
that a fruit is moved to its discharge location whereby two fruit
may be analyzed by said detection means before the discharge of
either fruit to its discharge location.
4. In an apparatus for sorting fruit as set forth in claim 1
wherein said bands of wavelengths of light are distinct with no
overlapping thereof.
5. In an apparatus for sorting fruit as set forth in claim 4
wherein one of said bands is comprised of wavelengths of light of
greater than about 750 nanometers and wherein the other of said
bands is comprised of wavelengths of light of between about 560
nanometers and about 630 nanometers.
6. In an apparatus for sorting fruit as set forth in claim 1
wherein each of said comparators is arranged to provide an output
signal if said analog ratio signal is greater than the fixed ratio
signal associated with said comparator, and a logic circuit for
simultaneously analyzing the output signals of each of said
comparators in order to provide said discharge signal.
7. In an apparatus for sorting fruit as set forth in claim 6
including gating means connected between each of said comparators
and said logic circuit, and means for sensing the presence of said
fruit at a location wherein said detection means will receive the
reflected light from said fruit, said sensing means being operative
to open and close said gating means to permit signals to be passed
to said logic circuit only when a fruit is in position to reflect
light to said detection means.
8. In an apparatus for sorting fruit according to the color
thereof, circuitry comprising detection means for producing a pair
of continuous light reflection signals indicative of the amount of
light reflected by a fruit within two different bands of
wavelengths of light, means for continuously electrically dividing
said signals to provide an analog ratio signal which is
proportional to the ratio of said light reflection signals, means
for comparing said ratio signal with a plurality of signals each of
which are equal to a different predetermined fixed ratio signal,
means operatively connected to said comparing means for providing a
discharge signal representative of a decision to direct said fruit
to a particular discharge location, and means for rendering said
means for providing a discharge signal operative during the period
of time which is required for said fruit to be conveyed past said
detection means, said means for providing a discharge signal being
arranged to provide said discharge signal in accordance with the
peak value of said analog ratio signal during the time that said
fruit is conveyed past said detection means.
9. In an apparatus for sorting fruit as set forth in claim 8
wherein said comparing means comprises a plurality of comparators
each of which provide an output only if the analog ratio signal
which is applied to the input thereof is greater than the
predetermined fixed ratio signal applied to the input of the
comparator.
10. In an apparatus for sorting fruit according to claim 9 wherein
said means for providing a discharge signal includes a plurality of
bistable elements each of which are connected to the output of one
of said comparators, each of said bistable elements being arranged
to change state upon the reception of an output signal from its
associated comparator.
11. In an apparatus for sorting fruit according to claim 10 wherein
each of said bistable elements comprises a flip-flop circuit, and a
logic circuit connected to the outputs of said flip-flop circuits
for simultaneously analyzing said outputs of said flip-flop
circuits in order to provide said discharge signal. .[.12. In an
apparatus for sorting fruit according to the color thereof,
circuitry comprising first fruit sensing means for detecting the
presence of a fruit at a viewing station, means for receiving the
light reflected from said fruit and for providing a discharge
signal in accordanc with the color of said fruit and representative
of a decision to direct said fruit to a particular discharge
location, said means for providing said discharge signal being
activated by said first sensing means, second sensing means for
detecting the presence of said fruit at a discharge station which
is spaced downstream in the direction of movement of said fruit
from said viewing station, discharge circuit means operatively
connected to receive said discharge signal when activated by said
second sensing means so as to cause said fruit to be directed to
the correct discharge location in accordance with the color
thereof, and means for storing said discharge signal for an
indeterminate period of time prior to activation of said discharge
circuit means, said signal storing means having a capacity to store
a plurality of discharge signals at any given time whereby a
plurality of fruit may be viewed before discharge of any one of
such fruit to its discharge location..]. .[.13. In an apparatus for
sorting fruit as set forth in claim 12 wherein said means for
storing said discharge signal comprises a primary memory means and
a reserve memory means, means operative to normally tranfer said
discharge signal to said primary memory means but being operative
to transfer a discharge signal to said reserve memory means if a
signal is already present in said primary memory means, and means
operative to transfer any discharge signal in said reserve memory
means to said primary memory means each time a fruit is moved to
its discharge location..]. .[.14. In an apparatus for sorting fruit
as set forth in claim 12 including means operatively connected to
said first sensing means for causing the transfer of a dischrge
signal into said signed storing means when the period of detection
of a fruit by said first fruit sensing means ceases..].
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to circuitry for sorting objects
according to the color thereof, and more particularly, it pertains
to circuitry for sorting fruit according to color by separately
measuring the light reflected from the surface of a fruit within
two different bands of wavelengths of light and comparing the
same.
2. Description of the Prior Art
Colorimetry, i.e., the analysis of objects upon the basis of their
color, has many industrial applications, particularly in the paint
and dye industries, and complex and sophisticated circuits have
been devised for accurately determining various shades of color.
Generally speaking, attempts to apply the methods and sorting
circuitry of these industries to the sorting of fruits and
vegetables have been unsuccessful for a number of reasons. In
matching paints and dyes, one set of measurements often suffices to
establish the color of an entire batch. Even in continuous process
control, changes in the color of the paints and dyes are usually
gradual, and circuitry which can adjust itself rapidly to large
changes in color is not required. In fruit and vegetable sorting,
on the other hand, the color of each article must be separately
determined, usually in a small fraction of a second, and successive
determinations may lie at the extremes of the range of
measurement.
The matching of paints or dyes of different composition requires a
knowledge of their reflectance properties throughout the visible
spectrum. A system of trichromatic coefficients is used to describe
their variance in reflectance in the simplest possible terms.
Logically then, the color of paints and dyes is usually measured in
terms of these coefficients. Whereas this system is desirable for
the comparison of different combinations of pigments, it is
needlessly cumbersome for the color classification of any one fruit
or vegetable. For example, it is not usually necessary to
distinguish a yellow lemon from a green apple. It may, rather, be
safely assumed that any one peculiarity in the reflectance
properties of an apple of a given color will be characteristic of
all apples of the same color. Hence, color measurements of fruit
and vegetables can usually be confined to only one or two regions
of the spectrum wherein such anomalies are known to occur.
Great precision is required in the matching of paints for the eye
is able to distinguish small variations in color. Precise
determination of the color of fruits and vegetables is seldom
justified. Even if apples could readily be sorted into twenty-five
color classes, it would scarcely be practical to market this number
of grades. Furthermore, the variation in color over the surface of
a piece of fruit is usually so great as to make a precise color
measurement meaningless, and, in accordance with usual fruit color
sorting practices, grading is performed upon the basis of the
percentage of the "characteristic" color on the surface of the
fruit.
Color sorting circuitry which has been specifically designed for
the sorting of fruits and vegetables generally provides some means
for measuring the reflectance properties of the fruit or vegetable
being tested. The reflectance of a surface is a measurement of the
percentage of incident light reflected by it, and colored objects
have different reflectances for light of different wavelengths. The
relationship between reflectance and the illuminating wavelength
for a fruit being tested will produce a characteristic curve which
can then be used in the design of apparatus and circuitry for color
rating that fruit. That is to say, a fruit may be classified as to
color by suitably measuring, describing, and classifying its
reflectance curve, and fruit may be sorted into different grades by
denoting the differences between the reflectance curves for the
various grades and testing for these differences. The efficacy of
such a system depends to a great extent upon the nature of the
particular criterion used to describe and characterize the
reflectance curves.
Several criteria of color similarity have been investigated in the
past, and circuitry has been developed for their measurement. None
of these circuits have proven to be wholly successful, however, in
the high speed sorting of fruit and vegetables. The simplest prior
art method of classifying a fruit as to color was circuitry which
characterized the reflectance curve for the fruit by a single
measurement of reflectance. Obviously, this measurement was made in
the region of the spectrum where the change in reflectance between
consecutive color grades was greatest. In color grading Washington
delicious apples, for example, measurements of the reflectance
would be made at a wavelength of approximately 560 nanometers
wherein the variation in reflectance between the color grades is
greatest. To measure this reflectance, the fruit was illuminated
with a light restricted to a narrow band of wavelengths in the
vicinity of 560 nanometers, or the fruit was illuminated with light
of a wide band of wavelengths with an optical filter being used to
receive the reflected light so as to restrict the transmitted light
to a narrow band of wavelengths in the vicinity of 560 nanometers.
The reflected light was directed to a photodetector, and the
resulting photoelectric current was proportional to the reflectance
of the fruit. The problem with such methods of making color
determinations is that the measured reflectance not only varies
with the color of the fruit but also varies with the intensity of
illumination, the photodetector sensitivity, the fruit size, and
the location and orientation of the fruit with respect to the light
source and the photodetector. These latter factors usually made the
reflectance measurements unreliable and led to errors in color
grading.
An improvement over the aforedescribed circuits is provided by
circuitry which measures the reflectance in two bands of
wavelengths of light rather than in just one band. One of the
selected bands will include a wavelength wherein the variation of
reflectance between distinct color grades is at a maximum, and the
other band will comprise wavelengths wherein there is little or no
variation in reflectance between the different color grades of
fruit. The determination of the color of a fruit can then be
measured by observing the difference in the value of the
reflectance at the two different bands of wavelengths. While such a
system is more sensitive to color variations than the
aforedescribed circuitry, this circuitry was still primarily
dependent upon the total amount of light reflected from the surface
of the fruit which total light varied due to a variety of factors
and none of which were directly related to the color of the
fruit.
A still further method of determining fruit color, wherein the
measured value is largely independent of the total amount of light
received from a fruit being inspected, has been used in certain
color sorting apparatus. This method utilizes the aforedescribed
method of measuring the reflectance properties of a fruit at two
distinct wavelengths; however, rather than merely computing the
difference between the two measurements, the ratio of these two
measurements is computed so as to eliminate the errors due to
variations in the total amount of light reflected because of
factors other than color. While such a method is generally used in
the trichromatic color measuring devices of the paint and dye
industries and has been adapted in a few instances in fruit and
vegetable color sorters, the circuitry which has been designed to
carry out such a method has proven to be exceedingly complex and
expensive and, therefore, not readily adaptable to the fruit and
vegetable packing industry wherein competition with the human fruit
sorter is keen. Examples of fruit sorting circuitry which utilized
such a method of sorting, or variations thereof, include the
circuitry shown in the prior U.S. Pat. Nos. to Powers 2,933,613,
Cox 3,012,666, and Cox 2,244,826.
Another prior art color sorting apparatus is disclosed in the
patent to Roberts et al 3,206,022. The circuitry disclosed in this
patent utilized a ratio monitoring system wherein reflectance
values at two selected wavelengths of light were measured. A
predetermined percentage of one measurement was then compared with
the other measurement on a "zero monitoring" system, or
differential basis, whereby a series of such comparisons based upon
predetermined fixed ratios established the limits of the tested
reflectance ratio. This system eliminated the errors due to varying
intensity in the light received from the fruit because of factors
other than color (typically, the size of the fruit), although the
system did not obtain a true reflectance ratio reading. While the
circuitry was not as complex as the true ratio detection systems
and represented a compromise between the ratio detection systems
and the simpler circuitry of the prior art, it still was complex
enough that it required frequent servicing and high initial cost.
Furthermore, adjustments were difficult to make, and the circuitry
was not readily adaptable to sorting different types or varieties
of fruit. The performance of the apparatus utilizing the circuitry
shown in the Roberts et al patent did not represent a sufficient
increase in sorting capacity to overcome the inertia of the
conservative and skeptical fruit packing industry. .Iadd.
Another prior art sorting apparatus is disclosed in the patent to
Mustert 3,679,314. The apparatus disclosed in this patent uses
alternating light beams of different spectral intensity
distribution to provide output signals which are compared by means
of a divider that forms a ratio of signals. An evaluating circuit
makes an acceptance decision if the ratio is within given tolerance
limits. The patent does not show or suggest the circuitry necessary
to form the ratio of signals or to make the acceptance decision.
The apparatus shown in Mustert is used to test the genuineness of
bank notes which are in a fixed position near a source of light.
.Iaddend.
SUMMARY OF THE INVENTION
With the circuitry of the present invention a simple and effective
means is provided for obtaining a true ratio signal representing
the continuous ratio of the reflectances of the surface of a fruit
at two distinct bands of wavelengths of light. As with the
circuitry of the prior art, photodetector means are utilized for
converting the reflected light into a pair of electrical signals
which are indicative of the amount of light reflected by a fruit
within the two different wavelength bands. These light reflection
signals are then continuously electrically divided to provide an
analog ratio signal which is proportional to the ratio of the light
reflection signals which, in turn, corresponds to the relative
amount of the "characteristic color" in the fruit. Means are
provided for comparing this ratio signal with a plurality of fixed
ratio signals representative of the cut points between adjacent
color grades, and logic circuitry is connected with such comparing
means to interrogate the various comparisons so as to obtain a
discharge signal in order to direct the fruit being viewed to a
particular discharge location in accordance with its determined
color grade.
One of the special features of the present invention resides in the
circuitry for storing the discharge signal after it has been
determined and prior to the discharge of the fruit to its
appropriate discharge location. This signal storing circuitry
includes a memory capable of storing a plurality of discharge
signals at any given time whereby a plurality of fruit may be
viewed before discharge of any one of such fruit to its discharge
location. Furthermore, the presence of a fruit at both the viewing
station and the discharge station is detected by sensing means
which operate the color determining and the discharge circuitry of
the present invention so that the effective viewing and discharge
of randomly spaced, irregularly sized, and irregularly conveyed
fruit may be obtained.
Another special feature of the present invention is the fact that
the color detecting circuitry is arranged to operate continuously
during the period of time in which the fruit is conveyed past the
photodetector means which latter means can be arranged to view only
a small portion of the fruit at any given time. The circuitry then
operates to provide a discharge signal in accordance with the peak
value of the analog ratio signal whereby spot defects in the fruit
can be detected and the fruit graded accordingly.
The circuitry of the present invention has a distinct advantage
over the aforedescribed circuits of the prior art in that it is
simple and includes relatively few expensive components thereby
making it adaptable for use in the fruit packing industries wherein
cost is a most important factor. Furthermore, the circuitry
provides a true continuous ratio reading of the reflectance values
at the two selected bands of wavelengths of light. Thus, the
apparatus can be readily adjusted for handling different types and
grades of fruit, and the test procedures utilized in setting up the
apparatus are simplified since the true relationship of any
particular fruit to the color standards can be accurately and
readily determined.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram representation of the circuitry of the
present invention.
FIG. 2 is a schematic diagram of the circuitry and the main
functional apparatus components of the present invention showing in
greater detail than FIG. 1 the various circuit elements.
FIG. 3 is a graph showing as ordinate, the ratio signal in volts,
and as abscissa, time. A curve is shown which illustrates a typical
ratio signal received from a test apple being viewed, and the
various predetermined fixed ratio signals are indicated so that the
color grade of the test apple can be readily ascertained.
FIG. 4 is a graph showing as ordinate, absorbance, and as abscissa,
wavelength in nanometers. Three reflectance curves are shown
indicative of the representative reflectance, or absorbance, values
for three typical color grades of apples.
FIGS. 5 through 9 are diagrammatic operational views of an
apparatus adapted to utilize the circuitry of the present
invention, such Figures sequentially illustrating the color grading
operation upon a pair of apples which are successively graded and
discharged from their transport conveyor.
FIG. 10 is a chart which diagrammatically illustrates the logic
level conditions of the circuitry of the present invention during
grading and discharging operations as disclosed in FIGS. 5-9.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As pointed out hereinbefore, the circuitry of the present invention
is adapted to be utilized in connection with color sorting
apparatus wherein individual fruit are conveyed past a viewing
head. At the viewing head the fruit is illuminated and the light
reflected from the surface of the fruit is received and split into
two equal portions which are each passed through an optical
filtering means to restrict the wavelengths of light transmitted.
The light from the filters is directed to a pair of photodetector
means where it is converted into a pair of electrical signals. The
signal from each photodetector, the amplitude of which is
proportional to the intensity of the light reflected in that band
of wavelengths of light passing through the associated filter, is
then processed with the circuitry of the present invention to
accurately determine the color grade to which the fruit belongs and
also provide a discharge signal which is stored until the fruit
reaches a discharge location where a reject signal activates the
proper mechanism to discharge the fruit from its supporting
conveyor.
The aforedescribed apparatus, as broadly specified, has been
utilized previously in the color sorting of fruit, and such prior
art devices may be utilized with the circuitry of the present
invention. However, a preferred form of fruit color sorting
apparatus, which is particularly adapted to be utilized with the
circuitry of the present invention, is disclosed in the U.S. Pat.
application .[.of Charles S. Greenwood et al, Attorney's docket SJ
6025, filed on even date herewith..]. .Iadd.Ser. No. 249,925, now
U.S. Pat. No. 3,770,111. .Iaddend.Reference to this patent
.[.application.]. may be had for a further and more complete
description of the optical and mechanical details of the fruit
color sorting apparatus.
While the circuitry of the present invention may be utilized in
sorting fruit or vegetables of any type, such circuitry is
particularly adaptable to the sorting of apples which pose some
special problems for automatic sorting apparatus. Consequently, the
following description will be directed specifically toward
circuitry for sorting Washington Delicious apples although it will
be understood that the identical circuitry might be used to sort
other types of fruit and vegetables with but minor adjustments to
the optical filter means and to the ratio measuring circuitry in
order to vary the sorting grades in accordance with the
characteristic color of the particular fruit or vegetable being
viewed.
A particular fruit variety will have a characteristic pattern of
wavelengths associated with its surface color, and the selection of
the optical filter means is made so that an increase in the ratio
of the electrical input signals corresponds directly to an increase
in the amount of characteristic color in the fruit being viewed. In
the present case, with Washington Delicious apples, downgrading
(and hence sorting) occurs when an increase in green relative to
the desired red color is detected on the apple surface. The
circuitry of the present invention is thereby adjusted so as to
measure the increase in the green-red ratio, and, since the
circuitry is set to detect the peak value of the ratio between the
light reflection input signals, the circuitry comprises a "peak
green" detection system.
FIG. 4 shows the characteristic absorbance curves for three
commercial color grades of Washington Delicious apples with such
curves being shown within a portion of the visible spectrum of
approximately 500 to 750 nanometers. Reflectance, which is measured
as a percentage of the incident light reflected from the surface of
an object, is computed by measuring the intensity of the output of
the photodetectors which receive the reflected light. The
absorbance is the logarithm of the inverse of the reflectance. For
example, an absorbance of unity indicates a reflectance of 10 per
cent while an absorbance of zero indicates a reflectance of 100 per
cent. From FIG. 4 it will be apparent that the maximum spread
between the three absorbance, or reflectance, curves exists between
500 nanometers and 630 nanometers with the greatest degree of
divergence occurring in the green light range at about 550
nanometers. Also, it will be noted that the curves converge in the
infra red range at the upper end of the visible spectrum above 750
nanometers.
As pointed out previously, the present invention utilizes the prior
art method of measuring the reflected light from the surface of the
fruit within two distinct bands of wavelengths. However, rather
than attempting to measure reflected light within narrow wave
bands, the present invention utilizes as wide a wave band as
possible for each input signal so as to increase the amount of
reflected light received by the photodetector means in order to
make the circuitry as insensitive as possible to noise and other
variations in signal strength not due to changes in color of the
fruit being viewed. Accordingly, the lower band (Band X) is
selected with a lower limit of 560 nanometers and an upper limit of
630 nanometers in order to eliminate the false readings which would
occur due to the crossover of the curves in the red area. The upper
band (Band Y) is selected in the infra red spectrum with a lower
limit of about 780 nanometers and with the upper limit limited only
by the ability of the photodetectors to convert the higher
wavelengths to electrical energy. It will be appreciated,
therefore, that the highest grade, or "extra-fancy", apples will
show the lowest ratio between the light reflectance signals, the
next highest grade, or "fancy", apples will show the next lowest
ratio, and the lowest grade, or "cull", apples will show the
highest ratio.
The circuitry of the present invention is shown schematically in
the block diagram illustration of FIG. 1. A pair of electrical
signals X and Y are received from the sensor photocells, or
photodetector means, which measure the intensity of the reflected
light from the surface of the fruit within the aforedescribed two
distinct bands X and Y. These signals are then directed to a ratio
circuit 10 which performs a continuous electrical division in order
to obtain the analog ratio signal. This signal, by means to be
described in more particularity hereinafter, is compared with a
plurality of predetermined fixed ratio signals, and the information
from these comparisons is directed through a gate 14 to a grading
circuit 16. The grading circuit includes logic circuitry to
establish the color grade of the apple with the information
received from the ratio circuit and to provide an appropriate
discharge signal. The discharge signal is then passed through a
gate 18 and a gate 20 to a primary memory circuit 22. However, if
it is established that the primary memory circuit already contains
a discharge signal from a previously graded (but not discharged)
apple, then the discharge signal is transferred through a secondary
gate 24 to a reserve memory circuit 26. A memory select circuit 30
is utilized to interrogate the primary memory circuit each time
that a new signal is presented to the gate 20. This memory select
circuit operates to direct the signal either through the gate 20 to
the primary memory circuit (if the primary memory circuit is
unoccupied) or to direct it through the gate 24 to the reserve
memory circuit. Each time that a discharge signal is transferred
out of the primary memory circuit a gate 28 is activated to
transfer any signal in the reserve memory circuit into the primary
memory circuit. Transfer of the signal out of the primary memory
circuit is through a gate 34 to a reject circuit 36 for fancy
apples or to a reject circuit 38 for cull apples. A reject circuit
for the extra-fancy apples could also be provided, but with the
apparatus of the present invention it is desired that these apples
remain on their transport conveyor, and therefore, no special
rejector, or discharging, means is provided for this highest grade
of apples.
A view timing circuit 12 also forms a portion of the circuitry of
the present invention and operates in conjunction with a fruit
position sensing means at the viewing station. This circuit 12
produces a "view" signal to activate the gate 14 and transfer
information from the ratio circuit to the grading circuit and also
produces a "read" signal to activate the memory select circuit 30
and the gate 18 to transfer the fruit discharging signal either to
the primary memory circuit 22 or to the reserve memory circuit 26.
A further function of the view timing circuit 12 is to reset the
grading circuit and to clear the reserve memory and the primary
memory circuits during periods when no fruit are being sorted.
A reject timing circuit 32 also forms a portion of the circuitry of
the present invention and operates in conjunction with a fruit
position sensing means at the discharge station. This circuit
activates the gate 34 to cause the reject circuits 36 and 38 to
become active and also activates gate 28 so that signals will be
transferred from the reserve memory circuit 26 to the primary
memory circuit 22 after each fruit discharge. The reject timing
circuit also functions to clear the reserve memory circuit and the
primary memory circuit after each fruit discharging operation.
A more complete depiction of the circuitry of the present invention
and the associated sorting apparatus is presented diagrammatically
in FIG. 2. A fruit F is adapted to be carried in a horizontal
direction by a conveyor 40. At a viewing station, shown in the
upper left hand corner of FIG. 2, the fruit is detected by the
first position sensing means as the leading edge of the fruit
breaks the light beam between a light source 42 and a photocell 44.
This activates the view timing circuit 12. As the apple moves
downstream of the position sensing means, light from a plurality of
light sources 45 is reflected from the surface of the fruit and is
directed through a narrow channel 48 to light collecting means 46
which splits the reflected light into two equal portions and
directs it through a pair of optical filters 50 and 51 to
photodetector means 52 and 53 the outputs of which provide the
electrical signals X and Y respectively. The optical filters 50 and
51 are provided to restrict the light which the associated
photodetector receives to those wavelengths previously described.
Obviously, if the apparatus is designed to color grade fruit other
than Washington Delicious apples, the filters 50 and 51 may be
changed in order to vary the nature of the characteristic color
detected by the circuitry of the present invention.
Once a color determination has been made by the circuitry of the
present invention, the appropriate discharge signal is held in the
primary memory circuit 22 until the apple reaches the discharge
station, shown in the upper right hand corner of FIG. 2. At the
discharge station the leading edge of the apple will be sensed by
the beam between a light source 56 and a photocell 58 to activate
the reject timing circuit 32. When this circuit is activated one of
three fruit discharging operations will occur. Either (1) a
solenoid SOL-1 will be activated to discharge the apple off of one
side of the conveyor (in the case where the apple is graded
"fancy"), (2) a solenoid SOL-2 will be actuated to discharge the
apple off of the opposite side of the conveyor (in the case where
the apple is graded as a "cull"), or (3) neither solenoid will be
actuated thereby allowing the fruit to pass downstream on the
conveyor 40 (in the case where the apple is graded "extra-fancy").
Obviously, other forms of fruit discharging apparatus could be
utilized with the circuitry of the present invention if
desired.
In considering the operation of the circuitry shown in FIG. 2, it
will be understood that those elements designated with the numerals
"FF" are set-reset flip-flop circuits wherein a low or "0" signal
applied to the upper, or S, input will cause the lower output to go
to 0 and the upper output to go high, or "+". This state will
remain until a reset signal is applied to the lower, or R, input
which will cause the upper output to go to 0 and the lower output
to go to a + condition. Conventional AND gates have been identified
with the letter "A", conventional NAND gates have been designated
with the letters "NA", and conventional inverters have been
identified with the letter "I".
The ratio circuit 10 comprises one of the main functional
components of the circuitry of the present invention and will be
seen to include a matched pair of amplifiers 60 for amplifying the
light reflection signals X and Y. The amplified signals are then
transferred to a divide network 62 which performs a continuous
electrical division upon the two input signals so that the output
thereof is proportional to a dimensionless quantity representing
the ratio of the input signals. In the present case the reflectance
in the visible band X is divided by the reflectance in the infra
red band Y so that the lowest obtained ratio signals will be those
of the "extra-fancy" apples while the highest obtained ratio
signals will be those of the "cull" apples (see FIG. 4). A
preferred circuit for producing a continuous electrical division
process upon the low level input signals (0-10 volts) is a
differential input divider network, Model No. 4094/15C,
manufactured by Burr-Brown Research Corporation of Tuscon, Arizona.
The voltage output of this divide circuit 62 is then separately
applied to a pair of differential comparators 63 and 64. Comparator
63 is provided with an additional voltage input V1, and comparator
64 is provided with an additional voltage input V2. The comparators
comprise differential amplifiers wherein an output will be present
if and only if the input from the divide network 62 exceeds the
other input V1 or V2. Referring to FIG. 3, it will be noted that
the ratio signal from the divide network 62 will rise to some
continuously varying level as the fruit is viewed and will remain
there throughout the time that the fruit is inspected. The lower
voltage V1, which is applied to the comparator 63, defines the cut
point between the "extra-fancy" grade and the "fancy" grade. If the
ratio signal during any time which the fruit is being inspected
exceeds this voltage, a signal will be transmitted from comparator
63. Likewise, if the ratio signal at any time during the viewing of
the fruit exceeds the higher voltage V2, a signal will be
transmitted from comparator 64 indicating that the apple is a
"cull." The apple, whose ratio signal is indicated in FIG. 3, will
be seen to be graded "fancy" since its peak ratio signal exceeds
the first cut point voltage V1 but does not exceed the second cut
point voltage V2.
Prior to the activation of the ratio circuit 10, the view timing
circuit 12 will be activated as the fruit F breaks the beam to the
photocell 44. This will cause a pulse to be created by a Schmidt
triggering circuit 70 which pulse is applied to the gate of an
inverter 71, to one of the inputs of a NAND gate 74, and to the
input of a monostable multivibrator, or one-shot circuit, 77 which
provides a negative output pulse of 40 milliseconds. At the end of
the 40 millisecond delay period, both inputs to gate 74 will be +
so that the output thereof will go to 0 which will cause the output
of AND gate 75 to go to 0. With a negative pulse out of AND gate
75, a sharp reset pulse is provided by the resistor-capacitor
circuitry R1-C1 and applied to reset a pair of flip-flops in the
grading circuit 16 so that they will be ready to receive new
grading information. Also, inverter 76 inverts the negative pulse
from gate 75 to obtain the "view" signal which is applied to the
gating circuit 14 so as to permit the transfer of signals from the
comparators 63 and 64 into the grading circuit.
After the fruit has passed the position sensing beam to the
photocell 44 at the viewing station, the output from the trigger
circuit 70 will cease to activate the one-shot circuit 72 which
provides a 3 millisecond positive pulse to a one-shot circuit 73
and a 3 millisecond negative pulse to the AND gate 75. The negative
pulse to AND gate 75 maintains the "view" signal on for three
milliseconds after the apple has passed the position sensing beam
in order to permit the trailing portion of the apple to be viewed.
Also, the negative pulse from one-shot 72 will activate the "view"
signal (for a 3 msec. period) if a small apple passes through the
detection beam in less than 40 msec. Since the fruit may translate
on the conveyor 40 and therefore not be moved at a uniform speed,
the viewing operation is strictly controlled by the position
photocell 44 in the manner indicated. The one-shot 73 has a short
1.5 microsecond pulse output which provides the "read" signal to
trigger the gate 18 which passes the discharge signal information
from the grading circuit to the memory circuits 22 or 26. The view
timing circuit also includes a delay circuit 78 which, when
activated by a positive pulse from the deactivation of the one-shot
77, will provide a clearing signal after a 300 millisecond delay
time (provided no new apple has been sensed by photocell 44 in the
meantime) to clear the registers in both memory circuits and to
keep them clear until an apple again breaks the beam to photocell
44. This delay time is long enough to allow any apple to clear the
discharge station after it has been viewed, and the clearing signal
is provided for the purpose of preventing misinformation from
remaining in the memory circuits to create possible errors in the
discharging of all subsequent apples.
As shown in FIG. 2, the grading circuit 16 comprises a pair of
set-reset flip-flops, a pair of inverters and an AND gate which
components are arranged so that only one of the three output lines
will have a signal thereon. The output signal will depend upon the
input information from the comparators 63 and 64. If an
"extra-fancy" apple is being graded, both inputs to the grading
circuit will be at a high logic level, or +, and the uppermost
output line will be + with the other two outputs being at a 0 logic
level. If a "fancy" apple is being graded, the input from
comparator 64 will be + while the input from comparator 63 will be
0 which will result in the middle output line being + with the
other two outputs being 0. Finally, if a "cull" is being graded,
the two inputs to the grading circuit will be 0 and the lowermost
output will be +.
Upon the application of the "read" signal from the one-shot circuit
73, the gate 18 is activated to transfer the determined discharge
signal to a second gate 20. The memory select circuit 30 determines
whether the signal will then be transferred through the gate 20 the
primary memory 22 or through the gate 24 to the reserve memory 28.
This memory select circuit includes a NAND gate 90 having three
inputs connected to the flip-flops in the primary memory all of
which inputs will be + so long as none of the flip-flops have been
set by the transmission of grading information thereto. If all
three inputs to NAND gate 90 are + the output will be 0 which
condition will maintain the output of NAND gate 91 high so as to
cause the discharge signal to be transferred through the gate 20
into the primary memory. However, if the output of NAND gate 90 is
+, due to information being present in the primary memory, the
output of NAND gate 91 will go to 0 upon the application of the
"read" signal and a pulse is passed through an inverter 92 and
applied to the gate 24 so that information is transferred to the
reserve memory rather than the primary memory. Thus, if a discharge
signal is read for a second fruit before the preceding fruit has
been discharged, the second signal will be transferred to the
reserve memory 28 where it will remain until the discharge of the
first fruit.
The reject timing circuit, which is shown at the right hand side of
FIG. 2, includes a Schmidt triggering circuit 79 which is activated
when the beam to the position sensing photocell 58 is broken. This
activates a 15 millisecond one-shot circuit 80 which applies a
positive pulse into NAND gate 81 to make the output thereof go to 0
which is inverted by inverter 82 and applied to a one-shot circuit
83. After a 1.5 microsecond delay, the one-shot 83 will apply a
positive pulse to one-shot 84 which, after another 1.5 microsecond
delay, will apply a positive pulse to the one-shot 85 which, after
a further 1.5 microsecond delay, will apply a positive pulse to the
one-shot 86. The latter one-shot circuit applies a 1.5 microsecond
pulse to reset the reserve memory 26. One-shot 85 applies a 1.5
microsecond positive pulse to activate gate 28 to transfer
information from the reserve memory to the primary memory. One-shot
84 provides a pulse to reset or clear the primary memory while
one-shot 83 provides a 1.5 microsecond positive pulse to activate
gate 34 and transfer information out of the primary memory to the
selected solenoid SOL-1 or SOL-2 to eject the fruit F to the
appropriate discharge location. The reject timing circuit thereby
provides a sequenced operation which begins when a fruit interrupts
the beam to photocell 58. Immediately thereafter a pulse is
transferred to gate 34 to initiate the appropriate discharge of the
fruit. After 1.5 microseconds, the primary memory is reset, i.e.,
cleared of any information. After another 1.5 microseconds the
information in the reserve memory, if any, is transferred to the
primary memory. Finally, after another 1.5 microseconds, the
reserve memory is reset.
The reject timing circuit also includes a NAND gate 88, a capacitor
C2, and a one-shot circuit 87 which are connected between the
output of NAND gate 81 and the input thereof. This circuit provides
a means to lock out the reject circuit after the apple interrupts
the beam at the discharge station so that any belt deflections
caused by the reject pulse and the discharge of the apple will not
be able to retrigger the circuit. The capacitor C2 causes a delay
in the transfer of the pulse from the NAND gate 88 to the one-shot
81 so that the successive one-shots 83, 84, 85 and 86 will be
activated before the circuit is locked out. The one-shot circuit 87
provides a pulse for a sufficient length of time, about 40
milliseconds, so that no further signal from photocell 58 will be
able to retrigger the circuit until after the fruit at the station
has been discharged.
Considering the aforedescribed circuitry, the diagrams of FIGS.
5-9, and the chart of FIG. 10, a brief resume of the operation of
the circuitry will now be given. As shown in FIG. 5, two apples are
moving along the conveyor 40 -- a leading apple F1 of large size
and a trailing apple F2 of small size. Both the primary memory and
the reserve memory will be clear at this time. When the leading
apple F1 breaks the beam to the photocell 44 nothing happens for 40
milliseconds. After that time, the "view" signal will be activated
so that information will begin to be transferred from the ratio
circuit 10 through gate 14 to the grading circuit 16. The 40
millisecond delay is to permit travel of the fruit from the
photocell 44 to the viewing light 46 and to allow for possible
translating movement of the fruit rearwardly upon the conveyor. As
the fruit F1 passes the light collecting means 46, the grading
circuit will continue to operate until the trailing edge of the
fruit passes the photocell 44 (FIG. 6). At that time the "read"
signal pulse of 1.5 microseconds is actuated to transfer
information from the grading circuit into the primary memory. After
3 milliseconds, the view signal stops. Also, a reset pulse is
provided to reset the grading circuit for the next apple.
As shown in FIG. 7, a small apple F2 may pass through the viewing
station before the preceding large apple F1 has been discharged.
This small apple may pass the photocell 44 in a period of time of
less than the 40 milliseconds. When this happens, the "view" signal
will be turned on when the trailing edge of the apple clears the
photocell 44 which at the same time also activates the "read" and
"reset" signals. The discharge signal for small apple F2 will be
stored in the reserve memory since the discharge signal for apple
F1 is already stored in the primary memory.
As shown in FIG. 8, the leading apple F1 arrives at the discharge
station and breaks the beam to the photocell 58. This apple is
ejected from the conveyor in accordance with its grade as stored in
the primary memory and the primary memory is cleared. The discharge
signal for apple F2 is then shifted from the reserve memory to the
primary memory and the reserve memory is cleared. As shown in FIG.
9, the small apple F2 arrives at the discharge station breaking the
beam to photocell 58 and is rejected according to its grade which
information is now stored in the primary memory. The primary memory
is then cleared. After 340 milliseconds from the time that the
leading edge of the apple F2 was detected by photocell 44, the
clear signal from delay circuit 78 is provided to clear both of the
memory circuits and eliminate any accumulated errors util a new
fruit moves across the beam to photocell 44 to reinitiate the
foregoing procedure.
From the foregoing description it can be seen that the circuitry of
the present invention provides a simplified scheme for readily
obtaining a continuous signal measuring the dimensionless ratio
between the light reflected from the surface of a fruit within two
distinct bands of wavelengths of light. The circuitry can be
adapted to be used with almost any type of conventional conveying
and discharge mechanisms, and special sensing circuitry has been
integrated with the color determining circuitry so that an
indeterminate period of time may be allowed between the time that a
fruit is sensed at the viewing station and the time that it is in
position to be discharged at the discharge station whereby the
sorting apparatus can be simplified in its construction to permit
fruit to be randomly conveyed at non-uniform speeds.
Although the best mode contemplated for carrying out the present
invention has been herein shown and described, it will be apparent
that modification and variation may be made without departing from
what is regarded to be the subject matter of the invention.
* * * * *