GB2180060A - Agricultural product sorting - Google Patents

Abstract

Agricultural products such as coffee beans, peanuts and beans are sorted into acceptable and unacceptable categories based on colour characteristics of the products as they descend in a chute (14) from a loading hopper (10) and vibratory feeder (12) through a zone of illumination. Disposed equiangularly about the zone are three optical sensor stations each one having a framing station 22 in which received light from successive portions of the product is directed onto ends of a bundle (26) of optic fibres which conveys the light to an optical divider (32) which divides the light into two colour illumination level components. Photodiodes (48, 54) convert the two colour illumination level components into electrical component level signals. Processing circuits C compare the electrical component level signals, after removal of background illumination level, with reference levels to determine if the colour of the individual ones of the product is within acceptable limits. The background illumination level is periodically sampled by the processing circuitry and the background levels removed from the component level signals are updated if necessary. <IMAGE>

Description

SPECIFICATION Agricultural product sorting This invention relates to optical/electronic sorting of agricultural products.

U.S. Patent No.3,012,666 discloses a technique of electronic colour sorting of agricultural products.

Colour masks defining limits between acceptable and unacceptable colours for the product as a relative mixture of two component colours were electro nicallyformed. Agricultural products were optically scan ned to measure the relative presence of these component colours, and the measurements taken werecompared with the limits defined by the colour masks. Products with colours found unacceptable were then separated.

As pointed out in U.S. Patent No.3,899,415 in actual use, sorters using the foregoing coloursorting technique in service often encountered several factorswhich would causethe limit settings to fluctuate.

To compensateforthis, an adjustment, known as normalisation, of the electronic settingsfor accept- able colourwas periodically made with a normalising circuit. According to U.S. Patent No.3,899,415, a separate normalising circuitfor component colour and for each optical sensor was needed. This significantly increased the number of electronic components in the sorter. Since these types of sorters often were required to perform in remote areas of underdeveloped nations and under harsh service conditions, reliability ofthe sorters and maintenance and the availability of replacement parts were frequently encountered problems.

Further, it is necessary to insure that the colour component signals being processed at any particular time came in actuality from the same scanned portion ofthe product, requiring synchronisation ofthe receipt and processing for each ofthe component colour signals received from the optical scanning portion of the apparatus. Again, harsh service conditions often in remote locales made this a substantial problem.

U.S. Patents Nos. 3,066,797 and 3,993,899 used light conducting members as fibre optic bundles in sorters ofthistype. The bundles offibre optic mat erial were divided into groups of bundles, one for each component colour, and each group passed through a different colour filter to a photocell to sep agate for processing the colour components of the object being scanned. Physical division ofthefibre optics into bundles, however, accentuated the framing problems. Each optical fibre in effect faced one portion ofthe surface ofthe object being scanned.

When this fibre was separated into one of the colour groups, however, only that colour component of that surface area of the productwas available for pro- cessing and comparison. The use of small diameter optic fibres was mentioned, butthis increased the cost of the sorter. Another possibility discussed was random distribution of the fibresforthe different colours within the bundle.

According to the invention there is provided a sorting apparatus for sorting agricultural products into acceptable and unacceptable categories based on colour characteristics ofthe products as they decend in a chute or conduitthrough a zone of illumination, comprising (a) optic fibre means for sensing the light reflected from a framed image of successive portions of the product in the zone of illumination, (b) optical divider means optically coupledto said optic fibre means for dividing the sensed light from the product into plural colour illumination level components, (c) meansforconvertingthepluralcolourillum- ination level components ofthe sensed light into electricai component level signals, (d) processing circuit means for comparing the component level signalswith reference levels to determine if the colour ofthe individual ones ofthe pro duct is within acceptable limits, and (e) ejector means for separating unacceptable ones of the product from those which are acceptable.

In an embodiment of the invention the products arefedfroma hopperthroughachuteorconduitpast azone of illumination in a chamber. Opticfibres sense the light reflected and form a framed image of successive portions ofthe product in the zone of illumination. The sensed light in the opticfibres isthen optically divided or split into atleasttwo colour illumination level components, which are converted into electrical signals. The component level electrical signals are compared with reference levels in a processing circuit to determine if the colour of the product is within acceptable limits. Unacceptable ones ofthe product are then separated from those which are acceptable.By framing the image of the product before splitting it into component colours, the need for mechanical adjustment of the optics to synchronise presentation of the colour images to the processing circuit is removed.

Plural lightsensorsare used aboutthe zone of illustration to insure that the framed image extends about a complete band of the product. In the processing circuit, the illumination component level signal for each of the sensors is compared with a reference level. The reference level for each of the component level signals of each ofthe plural sensors is individually adjusted based on sampled light conditions inthezoneof illuminationto adjustforvariations in background light in the zone of illumination and variations in parameters of the electronics and optics of the apparatus. Adjustment of the reference levels ofthe component level signals is done in a cyclic scan sequence, simplifying and reducing the numberof electronic components required in the apparatus.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a sorting apparatus formed according to the invention; Figure2 is an elevation view, taken partly in cross section of optical components ofthe sorter of Figure 1; Figures 3 and 4 are isometric views of portions of the optical components of Figure 2; Figure 5 is schematic electrical circuit diagram of an electronic processing circuit of sorting apparatus formed according to the invention; Figures 6, 7,8 and 9 are schematic electrical circuit diagrams of portions of the circuit of Figure 5; and Figures 10 and ii are electrical signal waveforms present in the circuit of Figures 5,6,7,8 and 9 atvarioustimes ofthe operating cycle ofthe sorting appar atus of Figure 1.

In the drawings, the letter S designates generally a sorting apparatus. The sorter S sorts agricultural products into acceptable and unacceptable categories based on colour characteristics of the products. The agricultural products may be,forexample, coffee beans, othertypes of beans, peas, peanuts, as well as otherfruit and vegetable or other products.

The products to be sorted are received in a hopper 10 (Figure 1) at an upper portion ofthesorterS.The products move from the hopper 10 under the influence of a vibratory feeder 12 to a chute of conduit 14.

The feeder 12 further functions to form the productto be sorted into a single stream as the products enter the chuteorconduit 14. The productdescends through the conduit 14 past a zone of illumination within a viewing station V. In the sorter S,thefeeder 12 is periodically disabled to clear chute 14 and a blast of air blown through the viewing station Vto cleartheviewing station V of dust or other debris as best can be done.

Individual ones of the product are illuminated by a suitable numberof lightsources spaced aboutthe periphery of the viewing station Vso that all surface portions of the product are illuminated as the pro- duct passes through the viewing station. Light reflected from iiluminated portionsofthesurfaceofthe product is received in a suitable number of optical sensor stations 0. The number of optical stations 0 for the viewing station V is typically equal to the number of light sources in the viewing station V. For example, three optical stations O,functioning as separate channels, are spaced at one-hundred twenty degree intervals with respect two the centre of the viewing station V.It should be understood, however, that other numbers of stations may be used as well.

The optical stations O are optically coupled, in a manner to be set forth, to an electronic processing circuit P (Figures 5 to 9) contained in an electronics housing 16 (Figure 1). In the processing circuit P, component level signals are compared with es tablished reference levelsto determine ifthe colour ofthe individual ones ofthe product being viewed by the optical station 0 is within acceptable limits.

When the colourof individual ones of the product is not within acceptable limits, an ejector 18,typically pneumatic, is activated bythe processing circuit Pto separate the unacceptable ones ofthe product from those which are acceptable. Acceptable product passes from an opening 19atlowerend 14a ofthe chute into a suitable container, while unacceptable product is moved by ejector 18 and falls from an opening spaced from the opening 19 into a separate container.

Considering the optical system 0 more in detail, each ofthe optic stations 0 is of like construction and operation and thus the details of operation of only one are setforth in the drawings (Figures 2 - 4). In the optic station 0, a first lens 20 of a framing assembly 22 senses light conditions in the viewing station V as the product stream falls, underthe influence of gravity,through the chute 14. The lens 20 focuses the lightthrough a second lens 24 onto a plurality of optic sensors in the form of opticfibres 26 arranged in a planealong a rearwall 28 of the framing station 22. The focal length of lenses 20 and 24 are preferably selected to offer a reduction in size of the product.A set screw 30 is provided intheframing station 22so that minor adjustments in the position of the optic fibres 26 with respect to the lens 24 may be made for alignment and focusing purposes.

Lenses 20 and 24 receive lightwhich is composed of background light reflected from a reference or standard, located on an opposite side oftheviewing station from the framing station 22 and light reflected from any portion of one or more items of product present before the framing station 22. Lenses 20 and 24 transmit light from the viewing station V onto the fibres 26 in such a mannerthatfor large items of product successive portions of these items ofthe product are scanned or framed as the items descend past framing station 22. The surface area of an item or items of product samples by one framing station 22 would thus be composed of a sequence of several such frames formed in station 22.However, each frame in a sequence is separately processed in the processing circuit P so that items with unacceptable colour spots on small areas of their surface may be detected and sorted out from acceptable items. For smallertype items of product, the entire item may be framed atone time.

The optic fibres 26 entend from and transport light sensed from the framed portions of the product to an optical dividing lens 32. The optical dividing lens 32 is optically coupled to the optic fibres 26 and divides the sensed lightfrom the product present in the viewing station into plural colour illumination level components. The opticfibres 26 are arranged at the opti cal divider 32 so that at least one of such fibres is cen- trally located (Figure 4) in a rear mounting member or insert 34, with the remaining ones of the fibres 26 wrapped in a circular fashion aboutthe central fibre orfibres. The mounting member340fthe optical div ides 32 is mounted in a first body portion 36 ofthe optic divider 32.Light from the optic fibres 26 representing sensed lightfrom the framed portion of the product is received by a focusing lens 38 mounted in a second body portion 40 of divider 32 onto an optic splitter, such as half-silvered mirror member42. A portion ofthe light is reflected by the mirror 42 and passes in a direction indicated by an arrow 44 through a lens 45 and afilter46which is adapted to pass light of a first colour such as blue onto a photodiode 48 ofthe processing circuit P (Figures 2 and 6).

A portion ofthe light passes through the optic splitter mirror 42, as indicated by an arrow 50, through a lens 51 and a filter 52, which is adapted to pass light of a second and different colour such as red onto a photodiode 54 ofthe processing circuit P. It should be un derstood thatthe colours red and blue for filters 46 and 52 are given only bywayofexample and that other colours may be selected depending on the type of product being sorted and the type of optic splitter used.

In the processing circuit P, a comparator circuit C for each colour component of each ofthe plural optic stations 0 compares the component level signal with a reference level to determine if the colour of the portion ofthe product presented to the optical sensor 0 is within acceptable limits. Ifthe portion presented to the optical sensor O is not within acceptable limits, the ejector 18 is activated to separate the unacceptable product from the otherwise acceptable ones of the product.

In the processing circuit P, a comparator circuit C (Figure 7) compares the component level signal with a background adjusted reference level to determine if the colour of the portion of the product presented to the sensor is within acceptable limits. The background adjustment is done to compensate forvariations in optic conditions in the viewing station V caused by dust and the like and forvariations in electronic parameters and tolerances due to heat and other conditions. The component level sensed signal presented to the comparator circuit C has been reduced in a background reduction circuit B (Figure 6) prior to comparison with the reference level.Cyclically and periodically, under control by an operation control circuit K (Figure 5) the feeder 12 is disabled, and light conditions in the viewing station V are sampled by the optic system 0 in the absence of product to obtain a background reference illumination level.

In the event that the background level signal has departed from an established normal setting,the background reference level is re-calibrated in an adjusting circu it A. During such recalibration, the adjusting circuitA is electronically connected in a sequence to the background reduction circuit B for each colour component of each optical sensor station 0. A particular reduction circuit B remains connected to the adjusting circuit A for a period of time to ascertain that such a reduction circuit is within a normal setting, orifit is out of normal setting, until it has been adjusted to such a state. A new background reduction circuit B is then electronically connected to the adjusting circuitA by the control circuit K.The adjusting process continues in such a sequence until all background reduction circuits have been adjusted to a normal setting. By sequentially electronically connecting the various background circuits B to a single adjusting circuits, a substantial reduction in parts is afforded.

In the processing circuit P, the photodiode 48 is el ectrically connected through a preamplifier 60 (Figure 6) to a buffer amplifier 62. The electrical signal atthe output of the buffer-amplifier62 repre- sentsthe illumination component level or intensity of a particular colour component, in this instance blue, sensed by the photodiode 48 in the viewing station V. The output signal from the buffer amplifier 62 is furnished to a background component removal amplifier 64 ofthe background removal circuit B.The background removal amplifier 64 removes background reference illumination levels from the com ponent level signal presented thereto and furnishes a component level signal to a colour mixing matrix R of the comparator circuit C and to the adjusting circuitA (Figure 8) directly. An inverter 68 (Figure 6) is connected to the amplifier 64to furnish an inverted illumination level signal to the colour mixing matrix R ofthe com parator circu it C and directly to the adj usting cir- cuit A. The outputs of amplifiers 64 and 68 arefurni shed through the resistor mixing matrix circuit R (Figure 6) which forms an electronic colour mix mask in the mannerof United States Patent No. 3,012,666.

The mixing matrix R also receives signals from the other background circuit B forthe othercolourlight filterfora particular channel. The mixing matrix R, in themannerofUS. Patent No. 3,012,666, formsfour colour mixture levels for the comparator circuit C.

Thecomparatoramplifiers 66 and 70 in circuitCcom paretwoofthefourcolourmixturelevelsignals furnishedtheretofrom the matrix Rwith colour mixture reference reference levels set by potentiometers 72 and 74, respectively.

In the event the colour mixture level presented to comparator 66 is not within the colour mixture reference level furnished thereto, indicating that the colour of the product is unacceptable, such as being too lightincolour,comparator66furnishesan output signal energising an indicator light emitting diode 76 and activating a transistor 78. Transistor78 when activated sends a trip signal through an OR gate 80 (Figure 5) to an ejector control circuit E (Figures Sand 9) which causes the ejector 18toseparate the unacceptable product.In the event the illumination level presented to the comparator amplifier 70 is not within the set colour mixture reference level furnished thereto, again indicating that the colour of the product is unacceptable, such as being an undesirable reddish-yellow, an output pulse is formed by the comparator amplifier 70 energizing a light emitting diode 82 and activating the transistor 78, again causing a trip signal to be sentthrough the OR gate 80 the ejector control circuit E.

The photodiode 54 (Figures 2 and 6) is electrically connected through a preamplifier 84to a buffer amplifier 86. The electrical signal at the output of buf fer amplifier86 represents the illumination compo- nent level or intensity of a particular colour compo- nent, such as red, sensed by the photodiode 54 in viewing station V. The output signal from the buffer amplifier86 is furnished to a background removal amplifier 88 of background removal circuit B. Back- ground removal amplifier 88 removes background reference illumination levels from the component levels from the component level signal presented thereto and furnishes a red component level signal to the mixing matrix Rand to the comparator circuit C.

An inverter 92 is connected to the amplifier 88to furnish an inverted red illumination level signal to the mixing matrix R into the comparator circuit C.

Comparator amplifiers 90 and 94 in circuit C compare the remaining two colour mixture level signalsfurnished thereto from matrix R with colour mixture reference levels set by potentiometers 96 and 98, respectively.

In the event the colour mixture level presented to comparator 90 is not within the colour mixture reference level furnished thereto, indicating that the colour of the product in unacceptable, such as being too dark red, comparator90forms an output signal energizing an indicator light emitting diode 100 and activating the transistor 78, sending a trip signal to the ejector control circuit E in the manner setforth above.

Should the colour mixture level presented to the comparator 94 not be within the colour mixture reference level furnished thereto, indicating an unacceptable colour product, such as being too dark in overall colour, comparator 94forms an output signal energizing a light emitting diode 102 and activating the transistor78. desired, the operation of the entire first viewing channel may be inhibited by a control switch 104which inhibits the operation ofthe transis- tor78.

The output from the background removal amplifier 64 is also furnished to a level detector 106 of the adjusting circuit A (Figure 8). Similarly, the outputfrom inverter68 is furnished to a level detector 108 ofthe adjusting circuit A. Level detector 106 is connected to a NOR gate 110, while level detector 108 is connected to a NOR gate 112. Gates 110 and 112 function as sampling gates and electronically scan the status of level detectors 106 and 108, respectively, in response to an Enable 1 pulse (Figure 10) formed in a control circuit Kin a mannerto besetforth.

In the event level detector 106 or 108 detects a setting ofthe background signal forthe amplifier connected thereto which is out of a normal range,the NOR gate associated therewith changes output state, a condition which is detected by a NAND gate 114 and provided to a first inputof detector NAND gate 116. Since only one Enable pulse is formed at any particulartime, only one set of sampling gates, such as gates 110 and 112, is electronically connected through to the detector NAND gate 116 at anytime.

The output from the background removal amplifier 88 is also furnished to a level detector 124 ofthe adjusting circuitA. Similarly, the output from the inverter 92 is furnished to a level detector 126 of the adjusting circuit A. Level detector circuit 124 is connected to a NOR gate 130 while level detector circuit 126 is con nectedto a NOR gate 128. Gates 128 and 130function as sampling gates and scan the status of the level detectors 124 and 126, respectively, in response to an Enable2 pulse (Figure 10) formed in the control circuit K. In the event either level detector 124 or 126 detects a setting of backg round signal forthe amplifier connected thereto which is out of a normal range, the NOR gate associated therewith changes output state.A NAND gate 132 connected to a second input ofthe detector NAND gate 116 indicates such a change of state.

The level detector amplifiers of the adjusting cir cuitAchange status to a high output status if the background removal amplifier connected thereto is out of its normal range. Thus, when the status ofthe level detector amplifiers in the adjusting circuit A are checked by the Enable pulses, NAND gate 114 or 132, as the case may be,transits to a high status so that an input signal is provided to the NAND gate 116 indicating a high status to the gate 116 is the amplifier being re-calibrated is not in tolerance.

Thesampling NORgate 110foran above limitsin- dication from background removal amplifier 64 is connected to a first diode of a bank of parallel connected diodes 148. The sampling NOR gate 112 for the indication of a below limits condition from background removal amplifier 64 is connected to another diode inthe parallel diodebankl34.Similarly,sam- pling gates forthe remaining two channels indicating above and below limit conditions in the particular background removal amplifiers connected thereto are connected to the remaining of the parallel connected diodes.

In the event that any ofthe background removal amplifiers are indicated to be below normal limit background conditions, the diode in the bank 134 of parallel connected diodes associated therewith is rendered non-conductive, causing an inverting NAND gate 14Qto enable a down count control gate 142 of a down/up selector gate pair 144. Similarly, the above limit sensing NOR gates 128 and 130 ofthe adjusting circuitAfor each ofthe level intensity background removal amplifiers B are electrically connected in parallel through a group of parallel connected diodes 148to an inverter 150to enable an upcountcontrol gate 151 of the down/up selector 144.

Timing control ofthe adjusting circuit A includes a master oscillator or clock 152 which forms system clock pulses for the processing circuit Pat a suitable frequency, such asthree-hundred hertz, as indicated byawaveform 152 when enabled by a Low Reset pulse waveform 154 (Figure 10) formed in control cir cuit Kin a mannerto besetforth.Amonostablemult- ivibrator 156 forms a Count pulse waveform 158 at each trailing orfalling edge in the waveform 152. A monostable multivibrator 160 forms a gate check waveform 162 on each rising or leading edge ofthe waveform 152.The gate check waveform 162 is furnished to a bi-stable multivibrator 164which is also connected to the detector NAND gate 116so thatthe status of multivibrator 164 is indicative ofthe output of gate 116. Finally, a monostable multivibrator 166 is connected to the multivibrator 160 and forms a status set waveform 168 in the form of a series of pulses, each occurring at the end of a preceding pulse in the gate checkwaveform 162.

A diode 169 is connected to the output of monostable multivibrator 160 while a diode 170 is connected to the output of monostable multivibrator 166 to cause a status check waveform 172 to be presented to a NAND gate 174. The NAND gate 174 investigates the status of bi-stable multivibrator 164 in response to the positive-going trailing edge of each successive pulse of waveform 172. Gates 116 and 174together with multimotors 164 and 176 form a decision logic circuit to determine if the sampled background levels need adjustment. When a background removal amplifier is indicated not to be in tolerance, the output of gate 174 is driven high causing a bi-stable multivibrator 176 to remain in the state it was set in by waveform 168. The bi-stable multivibrator 176 thus permits a NAND gate 178to pass count pulses of waveform 1 to the down/u p selector 144 and a twostage recalibration counter 180 composed of counter stages 182 and 184. Counting, either up or down, as indicated continues until the amplifier being scanned is indicated in tolerance. NAND gate 186 is simultaneously disabled during counting so that clock pulses are inhibited from passing through it.

If an amplifier being scanned is indicated to be in tolerance, etherwithout adjustment or after adjust- ment, the NAND gate 186 is enabled since gate 174 has caused multivibrator 176 to change state. NAND gate 186 then permits a single count up pulse of waveform 158 to be passed to increment contents of achannel oraddresscounter 188 (Figure6).

Channel counter 188 forms a sequence of digital counts ofthree bits (Figure 11) from one to seven which are decoded by a decoder 190 to form a sequence of seven Enable pulses, Enable 1 through En able7, inclusive (Figure 10). The first six of such enable pulses sequentially electronically connect with and scan the background reduction amplifiers for each colour component of each viewing channel in the sorter S. The final enable pulse, Enable 7, is a resetting pulse used to reset operating conditions in the operating control circuit K after recalibration cycle so that sorting operations may again resume.

Recalibration counter 180 (Figure 8) forms a digital count representing a specific amplitude setting which is furnished over a pair of buses, bus 1 and bus 2 sequentiallyto a storage register 192 (Figure 6) for the adjustment circuit A for each colour component of each colour signal. If the background comparator amplifier B for such colour component is determined to be within tolerance, no change in the contents of the register 192 is made because no adjustment is needed.Should the background comparatorampli- fier Bfora particular colour component be determined not to be within tolerance, the contents of the storage register 192 are adjusted by the counter 180 by counting either upwardly or downwardly, as controlled up/down selector 144, until the amplitude set- ting of the particular amplifier is within tolerance.

The digital count stored in each of the count registers 192 is converted to an analog output signal in a con verter 194andfurnished as an inputto the signal background amplifier B associated therewith.

The operating control circuit K (Figure 9) controls the overall operating cycles of the sorter S, as has been set forth. A monostable multivibrator 200 es tablishesasuitabletime limit, such asseveral minutes, during which normal sorting operations occur.

The multivibrator 200 is triggered by a multivibrator 202 in response to the formation of the Enable7 pulse (Figure 10) from the decoder 190 (Figure 6) at the end of each recalibration operation. Multivibrator 200 may be disabled and inhibited from operating by an operator of the sorter S by depressing a manual normalization switch 204 or a feeder control switch 206.

The manual recalibration switch 204 is electrically connected to a monostable multivibrator in a logic circuit 208, which forms a pulse furnished through a gate in logic circuit 208 to disable the muitivibrator 200 as well as multivibrator 210 and 212 if the feeder control switch 206 is offorgrounded.

The feeder control switch 206 is electrically connected through a gate in the logic circuit 208 to a gate 214 connected between the multivibrator 200 and 210 and when open or on causes the gate 214to triggerthe monostable 210 and thereafter monostable 212.

During normal operations, at the expiration ofthe time limit set by the multivibrator 200, a pulse is formed and passes through the NAND gate 214 causing the multivibrator 210 to form an output pulse of a suitable duration, such as one or more seconds, for product to empty from chute 14.

The multivibrator 212 is activated for a shorttime, such as one or more seconds, at the end of the pulse formed bythe multivibrator210to permit a blast of air to clear the viewing station V of dust and debris to the extent possible. The pulse formed in the multivibrator212 is furnished to an electrical or electronic switch 216 which activates an air solenoid, permitting a blast of air to be blown through the viewing station V prior to recalibration operations.

Are-calibrate Enable gate 218 is electrically connected through an inverter 220 to the monostable 200 and directly to the monostables 210 and 212 so that at the end ofthe period of time set by the time constants ofthe three monostables, the low reset pulse waveform 154 (Figure 10) is formed by an in vertex 222 enabling re-calibration operations to begin. Afeeder inhibit gate 224 is electrically connected to the monostables 210 and 212 so that, via an inverter 226, a gate 228 and an inverter 230 inhibit operation of the feeder 12 during the time that the remaining product in the chute isfalling from the chute 14, and also during the time that the airsolenoid is activated to clearthe chute 14 and viewing station V.

Gate 228 is also electrically connected at an input terminal to the feeder inhibit gate 218 sothatthefee- derl2 is rendered inactive during re-calibration. The gate 228 is also connected at an inputterminal to a lamp failure detector curcuit 232 to inhibit operation of the feeder 12 in the event that any of the illuminating lamps in the viewing station V should fail. The lamp failure circuit 232 may beforexampie, a resistor electrically connected in series with the lamps and a voltage detector to detect interruption of cu rrentflow through the lamp associated therewith and drive the output ofthe lamp failure detector 232 furnished to the gate 228 to a low condition, inhibiting the feeder through a feeder activator circuit 234.

The feeder activator circuit 234 is conventional and permits the feeder to operate through a feeder control circuit 236. The amplitude ofvibrations ofthe feeder 12 may be adjusted, if desired, by a vibration control knob 238 associated with the feeder control 236.

In the ejector circuit E (Figure 9) an inhibit logiccir- cuit 240 receives an overall trip signal from the OR gate 80 in the event of detection of an unacceptable colour characteristic in an agricultural product in the viewing station V by any one ofthe particularviewing channels. The inhibit logic circuit 240 may be ofthe form of a pair of parallel connected electronic switches ortransistorswhich inhibit the passage of trip pulses through the logic 240 and inhibit operation ofthe ejector as the chute 14 is being cleared and also during recalibration operations.

During normal sorting operations, however, logic circuit 240 is inactive and any trip pulse from the OR gate 80 passes into a shift register 242 driven by a clock or oscillator 244. The trip pulse presented to the ejector control circuit E from the gate 240 passes thorugh the shift register 242 for a time controlled by the number of stages in shift register 242 and thefrequency of pulses from the oscillator 244. In this manner, the time interval forthe unacceptable pro- ductto pass from the viewing station Vto the ejector 18 may be set and established. The frequency of the oscillator 244 may be adjusted by a delay control knob 246.The overall trip pulse after passage through the shift register 242 activates a monostable multivibrator 248 which controls the time that the ejector 18 is activated in response to each trip pulse.

The duration of thins time may be adjusted by a control knob 250. The trip pulse passing from the shift register 242 also passes through a bypass inverter 252 enabling the ejector to remain activated in the eventthatthetrip pulse formed in the processing circuit P is longer in time duration than the time constantofthe monostable multivibrator 248. The output ofthe monostable 248 and the inverter 252 are passed through an OR gate 254 to activate a power switch 256 which causes the ejector 18 to separate the unacceptable product from the acceptable.

In the operation ofthe sorter S, products to be sorted are loaded into the hopper 10 and moved therefrom bythefeeder 12through the chute 14pastthe viewing station 16. Portions of individual ones of the product are optically framed in the optical system 0 and thereafter split into colour component levels.

These colour component levels are compared with background adjusted reference levels in the processing circuit Pto determine whether or not the colour characteristics ofthe ones ofthe product are within acceptable limits. For those ones ofthe prod ucts not within acceptable colour limits, the pro- cessing circuit P activates the ejector control circuit E to separate the unacceptable ones of the product from those having acceptable colour characteristics.

Sorting ofthe product continues for the time duration set in the monostable multivibrator 200 ofthe operating control circuit K. Afterthis time limit elapses and the viewing station V is cleared by a blast of air, re-calibration of the background referance amplifiers occurs.

The control circuit K enables the counter 188 via the inverter222, starting a re-calibration cycle. During the re-calibration cycle, the background level amplifiers B for each component colour of each channel are compared with actual ambient optical conditions in the viewing station 1 6to determine whether our notthe background reference levels for such amplifiers are within acceptable limits oftolerance. It is important to notethatthis comparison is done in a sequential mannerfor each set ofamplif- iersforeach component colour in each channel. In this manner, a single adjusting circuit A may be used, permitting a manifest reduction in the number of component electronic parts over the prior art and greatly simplifying field operations.

In the eventthatthe background settings for a particular colour componentfor a particularchannel are found to be normal, the counter 188 is incremented and the next component colour or next channel in the sequence is then investigated. In the eventthata setting for optical background intensity for a component colour is determined to be out of acceptable limits of tolerance for a particular channel, the contents ofthe counter 180 are increased or decreased as need be under control of up/down selector 144, until the background setting forthe particular amplifier is within acceptable limits. Oncethe background setting forthe amplifier B in question has been brought within acceptable limits, address counter 188 is then incremented and amplifiers for a new component colour of a channel arethen addressed by the decoder 192.

The foregoing disclosure and description ofthe invention with reference to the drawings are illustrative and explanatory thereof, and various changes in the size, shape, materials, components, circuit elements, wiring connections and contacts, as well as in the details of the illustrated circuitry and construction may be made without departing from the scope of the appended claims.

Claims (10)

1. An apparatus for sorting agricultural products into acceptable and unacceptable categories based on colour characteristics of the products as they descend inachuteorconduitthrough a zone of illumination, comprising (a) means for sensing the light reflected from successive portions of the product in the zone of illumination at plural sensors about the periphery of the zone of illumination, (b) means for dividing the sensed lightfrom the portions ofthe product into plural coiourillumination level components, (c) means for converting the plural colour illum- ination level components of the sensed light into electrical signals, (d) comparator circuit means for each of said plural sensors for comparing the component level signals with reference levels to determine ifthe colour ofthe portion ofthe product presented to the sensor is within acceptable limits, (e) said meansforsensing lightalsocomprising means for periodically sampling the background light condition in the zone of illumination in the absence of product, (f) means for storing an electrical signal representing the peridocally sampled background light condition, (g) means for each of the plural sensors for removing the sampled background level from the component level signal, and (h) means for sequentially electronically connecting said means for adjusting with each of said means for removing.

2. An apparatus as claim in Claim 1, wherein said means for adjusting the reference levels comprises (a) level setting means for selectively increasing or decreasing the sampled background level, and (b) control means for causing said level setting means to increase the sampled background level when required and to decrease the sampled background level when required.

3. An apparatus as claimed in Claim 1,further comprising decision circuit means for determining if the sampled background levels need adjustment by said meansforadjusting.

4. An apparatus as claimed in Claim 3,further comprising means responsive to said decision circuit means for activating said means for sequentially connecting.

5. An apparatus as claimed in Claim 1 wherein said comparator circu it means includes means for forming at least one reference level for a mixture of illumination component level signals.

6. An apparatus as claimed in Claim 1 ,wherein said comparator circuit means includes means for forming upper and lower reference levelsfora mixture of illumination component level signals.

7. An apparatus as claimed in Claim 1,further comprising ejector means responsive to said comparator circuit means for separating agricultural products with unacceptable colour characteristics.

8. An apparatus as claimed in Claim 1, wherein the agricultural product falls from the conduit past said ejector means, and further comprising pulse for ming means for activating said ejector means for a settime interval in response to said comparatorcircuit means.

9. An apparatus as claimed in Claim 8, further comprising means for bypassing said pluse forming means if conditions ofunacceptablecolourchar- acteristics exceed the set time interval of said pluse forming means.

10. An apparatus as claimed in any preceding claim, further comprising means for disabling said comparator circuit means for at least one of said plural sensors.

10. An apparatus ascaimed in Claim 1,further comprising means for disabling said comparator circuit means for at least one of said plural sensors.

11. A sorting apparatus for sorting agricultural products into acceptable and unacceptable categories based on colour characteristics ofthe products as they descend in a chute or conduitthrough a zone of illumination, substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 - 11 above have been deleted or textually amended.

(b) New or textually amended claims have been filed asfollows:

1. An apparatus for sorting agricultural products into acceptable and unacceptable categories based on colour characteristics of the products as they descend in a chute orconduitthrough azoneofillumina- tion, comprising (a) plural sensors located above the periphery of the zone of illumination for sensing the light reflected from successive portions of the product in the zone of illumination, and for periodically sensing the background light condition in the zone of illumination in the absense of product, (b) means for dividing the sensed lightfrom the said portions of the product into plural colour illumination level components, (c) means for converting the said plural colour illumination level components of the sensed light from the said portions of the product into component level electrical signals, (d) means for each of the plural sensors for reducing the respective component level electrical signal to compensate for a background reference level, (e) meansforstoring a background level electrical signal representing the periodically sensed background light condition, (f) adjusting meansforsequentially electronically connecting said storing meansto each of said reducing means and for adjusting the said background reference level to correct to the stored background level electrical signal, and (g) comparator circuit means for each of said plural sensors for comparing the reduced component level electrical signals with reference levels to determine if the colour of the portion of the product presented to the sensor is within acceptable limits.

2. An apparatus as claimed in claim 1, wherein said adjusting means comprises (a) level setting means for selectively increasing or decreasing the background reference level, and (b) control means for causing said level setting means to increase the background reference level when required and to decrease the background reference level when required.

3. An apparatus as claimed in claim 1 or 2,further comprising a decision circuit means for determining if the background reference levels need adjustment to correspond to the stored background level electrical signal.

4. An apparatus as claimed in claim 3,further comprising means responsive to said decision circuit means for activating said adjusting means.

5. An apparatus as claimed in any preceding claim, wherein said comparator circuit means includes means forforming at least one reference level for a mixture of illumination component level signals, the said comparator comparing the mixture of illumination component level signals with the reference level for the mixture.

6. An apparatus as claimed in claim 5, wherein said comparator circuit means includes means for forming upper and lower reference levels for the mix- ture of illumination component level signals.

7. An apparatus as claimed in any preceding claim, further comprising ejector means responsive to said comparator circuit means for separating agri cultural products with unacceptable colour characteristics.

8. An apparatus as claimed in claim 7, wherein the agricultural product falls from the conduit past said ejector means, and further comprising pulse forming means for activating said ejector means for a set time interval in response to said comparator circuit means.

9. An apparatus as claimed in claim 8,further comprising means for bypassing said pulse forming means if conditions of unacceptable colour characteristics exceed the set time interval of said pulse forming means.