US3917070A - Method and system for grading articles according to color - Google Patents

Abstract

Tobacco leaf is graded by the steps of passing the leaf before a photo-detector, limiting the wave length sensed by the detector to between 660 and 680 m Mu , preferably 670 m Mu , measuring the remission value of the leaf and classifying the leaf in response thereto at selected predetermined levels of remission value.

Description

United States Patent Asfour [45] Nov. 4, 1975 [54] METHOD AND SYSTEM FOR GRADING 2,823,800 2/1958 Bliss 209/11 1.6 ARTICLES ACCORDING o COLOR 2,933,613 4/ 1960 Powers.... 209/111.6 X 3,064,136 11/1962 Mann 209/ll1.6 X Inventor: Emll Asfour, 21 wenglram 8704, 3,206,022 9/1965 Roberts... 209/1 1 1.6 x Herrliberg, Switzerland 3,380,460 4/1968 Fuis 209/111.6 X Filed: g 9 3,515,273 6/1970 Seaborn 209/11 1.7

[21] Appl' Primary ExaminerAllen N. Knowles Related US. Application D t Attorney, Agent, or Firm-Murray Schaffer [63] Continuation of Ser. No. 235,342, March 16, 1972,

abandoned. [57] ABS RACT LS. Tobacco leaf is graded the steps of passing the leaf IIBt. Cl. before a photo detector the ave length Fleld of Search 356/173, 178, sensed by the detector to between 660 and 680 m a, 356/186, 195 preferably 670 m [1,, measuring the remission value of the leaf and classifying the leaf in response thereto at Referemes Clted selected predetermined levels of remission value. UNITED STATES PATENTS 2,678,725 5/1954 Jacobson 209/111.6 14 Clams 4 Drawmg F'gures POWER SUPPLY INPUT J J TRIGGER J PD AMPL. GATE GEN. RELAY 22 PHOTOSENSOR l 22 l FILTER 24 I BACK- 2O GROUND CLASSIFYING I FIG. 2 MEANS US. Patent Nov. 4, 1975 Sheet 1 of 3 3,917,070

LIGHT \L|GH T GRE'LN GREEN -DARK BROWN 400 20 40 so so 5'00 20 10 so so 600 20 40 so so voo m FIG. I

POWER SUPPLY I A G T JJ INPUT J J TRIGGER J PD AMPL. GATE GEN. w RELAY 22 PHOTOSENSOR l |=Q\22 I FILTER 24 I I BACK- 2O I GROUND CLASSIFYING FIG.Z E E a l US. Patent Nov. 4, 1975 Shee t 2 of3 3,917,070

MUI

U.S. Patent Nov. 4, 1975 sheet 3 of3 3,917,070

Qm GI METHOD AND APPARATUS FOR GRADING ARTICLES ACCORDING TO COLOR This is a continuation of copending application Ser. No. 235,342 filed Mar. 16, 1972, now abandoned.

The present invention relates to a system for grading leaf tobacco and in particular to apparatus for automatically sorting tobacco leaf according to selected grades.

Although texture, size of leaf, moisture and chemical content are all factors influencing the taste and smokability of tobacco leaf, it has long been recognized that leaf may be most easily graded (if not with 100% accuracy) for these attributes by its apparent color. Apparent color is being defined as that color which the naked eye senses and recognizes. Within the last decade several attempts have been made to automatically sort leaf or tobacco product by photo-electrically determining their apparent color. Reference may be made to US. Pat. Nos. 3,373,870 and 3,380,460 for two such examples. Generally, the determination is made by comparison with a given standard such as a preselected leaf, a fixed color plate or a background color. A more recent system has involved the use of photo-electric means to determine two or more of the absolute color values, defined as the value of the true color components such as red, green, yellow, etc., which make up the apparent color of a given leaf, and by classifying a leaf as having more or less of any one or more of the given colors. All of these systems including the earlier systems are dependent on the determination of at least one given absolute color and employ photo-electric means to sense the desired color component.

In addition to those factors mentioned earlier which effect its appearance, tobacco leaf color is modified by such things as the degree of moisture and level of natural surface wax or germ found in the leaf. Moreover, tobacco leaf is highly perishable and fragile, being subject to physical and chemical change during storage and handling. These factors are readily observable by the hand picker. However, because they only imperceptibly change the actual color they are rarely observable under a photo-electric sensor which determines true or absolute color. The prior systems are also costly, complex, excessively large, difficult to produce and hard to maintain over long periods of use. Furthermore, these systems provide only a degree of statistical efficiency which is acceptable only in contrast with the cost of hand labor.

It is the object of the present invention to provide an improved system for photo-electrically grading tobacco leaf.

It is the object of thepresent invention to provide a system for grading tobacco which is not dependent upon the determination of the absolute leaf color.

It is another object of the present invention to provide automatic leaf grading apparatus which is simple, economical and easy to manufacture and use.

It is another object of the present invention to provide automatic leaf grading apparatus which is more efficient and reliable than heretofore known.

,These objects as well as others together with numerous advantages will be observed from the following disclosure of the preferred embodiments of the invention.

SUMMARY OF THE INVENTION According to the present invention. a method has been developed whereby tobacco leaf is graded by the steps of passing the leaf before a photo-detector, limit- 2 ing the wave length sensed by the detector to. between 660 and 680 m ,u., preferably 670 m u, measuring the remission value of the leaf and classifying the leaf in response thereto at selected predetermined levels of remission value.

Further in accordance with the present invention a novel system and apparatus including electronic circuitry is provided to enable a scanning device such as a photo sensor to provide an electrical signal indicative of the light transmission of the article to be converted into a pulse signal for operating an instantaneous classifying means, only at a given level of light transmission.

Full details of the present invention will be found in the following disclosure and the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a graph plotting the levels of remission values of various species of leaf against a wave length range between 400 and 700 m ,u, and

FIG. 2 is a schematic representation of a simple current for carrying out the present invention, and

FIGS. 3a and 3b are a schematic diagram showing greater detail of the current of FIG. 2; FIG. 3 is in two parts, being viewed by connecting sheet a to sheet b so that the arrows ABC coincide.

DESCRIPTION OF THE INVENTION For the purposes of this disclosure it is to be understood that the term transmission is the overall light energy output of an object. Light transmission is a conventional measure of such energy and is determined by conventional photometric instruments, quite conventional, and which need not be further described here. Transmission value or synonomously remission value is the proportion of light energy actually emitted as a ratio of the total energy which might be emitted. It is defined as a percent Transmittance is employed to define the transmission ratio corrected for variations in reflection.

The various species of tobacco leaf vary in light energy transmission, and as would be predicable the yellower varieties, such as the Virginia tobaccos have a high remission value while the Turkish and Burley tobaccos for example, have lower remission values. It has been determined, however, that all tobacco have an ascending remission value when correlated to an ascending wave length scale, irrespective of absolute color content of the leaf. Thus, as is seen in the graph of FIG. 1, where several leaf groups of different apparent colors are compared. The curves represent the average value of homogeneously chosen leaf, not necessarily from differing varieties or species, but each being classified by the eye test as within the same grade. As indicated, curve 10 represents yellow leaf, curve 12 the light brown, 14 light green, 16 green and 18 dark brown.

In conventional classification, bright or yellow leaf is most desirable and is, therefore, virtually never picked out of any grade. The very dark brown or black and dark green leaf on the other hand, are virtually always picked out, while the intermediate colors of light brown, brown and light green are selectively picked or chosen to be retained depending on the grade desired. It is to be understood that the five classes of leaf shown in FIG. 1 is only representative of the color of tobacco leaf since many shades lie between the very bright yel- 3 lows and the very dark browns or blacks.

The curves seen in FlG. 1 are plotted by determining the remission value at given wave lengths under a standard light intensity. The abscissa represents the wave length measured in standard angstrom units in p. of nonometers or r l n m the equivalent of 1m X l Conventionally, the symbol m ,u is used. Readings were taken between a low value of less than 400 m p. and a high valve of over 700 m ,u.. The ordinate represents the remission valve, as a percent (70) ranging from zero (0) indicating the absence of energy and one hundred (100) indicating a full energy level.

Each of the leaf variety sampled at or below the 400 m [.L wave length level produced virtually identically and negligible remission values and as the sampling proceeded to higher wave lengths the remission value for each leaf rose in a positive and almost linear curve. Except for the apparent bright yellow specie the slope of each curve was relatively shallow and sometimes overlapped with another. The apparent bright yellow is significantly greater in energy level than the other species.

In order to establish the validity of the curves, several similar examples were made under different degrees of light source intensity. It was found that when the light source intensity was increased, either by increasing the voltage or by increasing the number of lamps, the remission value of the leaf was displaced upward upward on the ordinate. Notwithstanding this displacement, the average values within each group remained relatively and proportionately the same and the curves of each group rose from a base remission value below 400 m u at the same slope, although there was, in fact, greater space between the remission of one group and that of another. For example, the space between the curves of light and dark green spread out along the ordinate, but, in fact each started from a higher base. This showed that light source intensity had no effect on the relative remission curves in either slope or value although the various groups exhibited individual upward displacement in absolute remission values.

A startling and unexpected observation was made with respect to each specie in the remission values taken in the wave length range between 660 to 680 m ,u. Within this narrow range the remission curve for each of the selected species, regradless of apparent or absolute color value, clips or falls to an inversion point. Thereafter, it continues its rise at a steeper slope than before. It would appear that the actual inversion point coincides at approximately the 670 m p. value. As it is to be observed, the inversion point for each specie lies at a given remission value distinct from that of any of the other species, although those for the light green and dark brown samples, lie close to each other. Since the transmission value or overall energy emission of the leaf is the result of all factors governing light transmission, including absolute color, texture, physical characteristic etc., the inversion point is a distinctive photoprint or clear indication of the apparent color of the leaf. The inversion point of each curve may be changed by varying the light intensity incident on the leaf, however, since the curves retain their proportional slope and relative separations from each other, under any constant light conditions, there is always an inversion point at approximately 670 m ,u. wave length. Thus, the selective determination of remission values within the range of 660 to 680 m ,u. has enabled tobacco leaf to be classified and graded for any apparent color.

4 Consequently, the objects of the present invention are met by the novel method of grading tobacco leaf as to apparent color comprising the steps of passing the leaf before a photoelectric sensor, limiting the response rangeof the sensor within a wave length of 660 to 680 m ,u., measuring the remission value of the leaf andclassifying the leaf in response to selected predetermined levels of remission value.

The advantages of the present invention lie in its simplicity. Various, mechanical, optical and even elec-. tronic devices and methods may be employed to limit the ranges of the photo-detector within the prescribed wave length, leaving remaining a single variable factor, namely, the proportional voltage indicative of the remission value, which must be measured. Broad spectrium photo-detectors may be used and their wave length band response limited by electronic circuitry. While such devices are no doubt, easily available, the present invention permits the use of less sophisticate equipment in that narrow band specialty photo-detectors may be employed without complicated auxiliary equipment. It is preferred to employ a photo-detector matched closely to the 660 m y. to 680 m uband. Such photo-detectors matched to a i 10 m p. band width are relatively inexpensive, and simple, and present very little problem in their use. The photo-detector, of course, is intended to convert the light energy level incidenton it into a proportional constant voltage signal. Since to bacco processing plants have notoriously unstable light conditions, it may be desired to use a light interference filter to more narrowly match the transmitted wave length to the optimum operating wave length of 670 m ,u.. Filters operable in half band widths or less are available. Suitable electronic circuitry can be assemblied to provide the comparison and trigger functions. The broad concept of the present method is not limited by the choice of apparatus which may be used and many;

variable embodiments are possible.

The present invention is, however, intended particularly for use in the automatic grading system described in the aforementioned companion application. Since such automatic systems are designed to operate at high speeds and effect continuous grading of rapidly moving streams of tobacco, a preferred mechanical and elec-, tronic arrangement has been developed which exemplifies the present invention. Reference to the aforementioned application, in the following disclosure of the preferred embodiment is made, as if more fully set forth therein.

As seen in FIG. 2, a schematic layout of a suitable. system for carrying out the present inventionis depicted. A photo-sensor and detector PD, such as that manufactured by the Hamamatsu T V Co., Ltd., Hamamatsu City, Japan, under model number R T V R 424, is located above a table 20 or other support, such as the end plate shown in the aforementioned application, over which the tobacco leaf T is carried. A light source 22, such as an ordinary incandescent bulb or series of bulbs is arranged to concentrate its light upon the passing leaf. The light source need only supply an intense light sufficient to reflect a degree of energy which is easily measurable, otherwise the light source is not critical. However, low voltage lamps such as those common in use in automobiles, provide a safe low heat pro-, ducing light source is extremely efficient and more than sufficient for operation in this invention, since the photo-sensor-detector is, in any event, only required to sense a portion of the emitted light energy of the leaf;

the remission value comprising a ratio.

Preferably, the lights are 12 volt 45 watt incandescent bulbs, of the type used in motor vehicles or such,

arranged in series of nine. Thus, they may be directly connected to a 110 power source. It has'been found that by arrangement two banks of nine bulbs to each side of the leaf picking table to be tested, there is provided adequate light for illuminating and providing reflection sufficient to measure remission. The light banks are generally placed 8-12 inches from the table or leaf to be scanned and out of the way of the photodetector. They may, if desired, be placed higher. Since only a portion of the light energy is to be measured, the strength of the light source need not be great, and interference from ambient or transient light is relatively negligible. Higher voltage lamps may be used to provide a higher displaced remission reading, if desired.

Inserted between the photo-cell PD and the table is a filter 24 matched with the photo-detector PD to be within the desired wave length range and preferably as close to the preferred wave length of 670 m p. as possible. Metal interference filters, in less than /z% band widths, consisting of two semi-transparent metallic coated mirrors separated by an absorption free intermediate film, (dielectric) the thickness of which determines the spectrum band are preferable. Such filters, for example, are manufactured by Balzers Aktiengesellschaft, Lichtenstein, under the trade name Filtraflex" and are available in the US. The filter acts to insure a one parameter photo-optic system in which the function of the photo-detector is solely to register the level of remission.

The photo-detector PD is easily connected to an amplifier circuit A which amplifies the voltage produced by it, and then passed to a comparison circuit CC which has an electronic gating subcircuit G preset by a biasing voltage level control L to a desired voltage indicative of the standard level of light remission sought. The gate may be designed to open or close on the reaching of this biasing level by the photo-detector, or in the alternative, on either falling below or above this level, as may be desired. It is preferred that it function to provide a pulse signal when the remission voltage drops below a level indicative of a given inversion point. Upon actuation of the gate a switching or trigger circuit T operates relay means R for classifying the leaf by ei- I ther removing the leaf from the table or letting it remain thereon, as is shown in the companion application.

The comparison circuit CC may be set at the desired operational voltage arbitrarily by merely providing it with a variable voltage source which would control the gate. It is only necessary to initially condition the gate and it need not be periodically recalibrated or continuously brought to such a standard condition. This is so, because the photo-detection apparatus is matched and fixed at a given wave length and reads remission value only as a proportional output at the selected inversion prints. 'The only variable in the system of detection is the remission value of the leaf scanned and therefore, the gate may be preset at the level of inversion desired and thereafter left alone. Presetting the gate with a fixed biasing voltage, arbitrarily attained, would be simple electronically but would complicate the grading process as a whole, since such a level, being arbitrary, would not be directly indicative to the actual leaf grade on the table. Accordingly. it is preferred that the biasing voltage be obtained by setting the gate level as a result of a fixed background plate over which the leaf passes. Thus, the background plate s own remission value can initially condition the system, so that only remission variations in leaf scanned will directly cause operation of the trigger mechanism. Spurious and extraneous signals are eliminated to a great extent, by this system. The conventional colored background plate may be used, although color per se, is no longer critical. The preferred biasing or preset condition is made through the photo-detector itself, which senses only remission value rather than color. Therefore all that is required is a background plate having a light energy transmission ratio comparable to the leaf grade to be selected. It may be of any color, in fact, in the companion application the background plate is made of a shuttered assembly of a white plate having a plurality of holes overlying a plate having black dots. A glass overlayer is used to space the leaf from the white plate. By adjusting the two plates, various degrees of white and black are obtained, varying the light transmission ratio. Other similar devices and constructions may be employed which can establish a desired remission value. It will also be obvious that once the biasing voltage is set to the initial background transmission level the plate is no longer of any significance in the detection process. It may if desired be removed.

It will thus be seen that by the use of the general apparatus described in FIG. 2, the method of sensing the leaf at a given limited wave length, determining the transmission ratio at that wave length, and actuating a classifying means in response thereto can be easily obtained, and that many suitable circuit arrangements can be made, all within the skill of the artisan in these fields. A preferred circuit arrangement is, however, shown in FIG. 3.

The electronic system of FIG. 3 comprises a power pack PP, connected via a main switch S and a fuse F1 to a common source of AC current. The power pack PP is adapted to have a rectified output of poled 15 volts DC. One of the advantages of the present apparatus is that it lends itself to ready adaption to printed and integrated circuit design. In this event a secondary rectifying circuit RC may be included to insure against unwanted interference in each of the printed circuit boards.

The cathode of the photo-detector PD, such as the Hamamatsu, described earlier, is connected to the negative power source terminal and its output lead connected to the operational amplifier circuit A adapted to produce an amplified voltage signal directly responsive to the remission values sensed by the photodetector PD. The amplifier circuit comprises a known integrated transistorized circuit IC (for example, such as that manufactured by Teledyne Philbrick Nexus, Allied Drive at Route 128, Dedham, Mass. catalogue No. 1020). The integrated circuit comprises an arrangement or transistors, resistors, capacitors etc., forming a chopperless differential amplifier. The operational amplifier IC has dual inputs a and b and an output 0. The internal contents of the device IC, is not shown as the device is produced as a commercial package and is well known. In general, the biasing voltage for the amplifier is provided through the a terminal and the offset voltage through b terminal. The current through the amplifier circuit is the difference between the two inputs and takes the polarity of the highest input. Such devices operate at extremely low voltage and current inputs and are extremely sensitive to change in current flow alnected to the offset terminal b of the amplifier 1C The operational amplifier /.C is set by a potentiometer P together with resistors R 1' and condenser providf ing a voltage divider circuit having noise reducing and feed back characteristics. The operational amplifier 1C is thus limited to a desired voltage range by adjustment of the potentiometer P bringing the voltage range closer to the operational range of the remission values actually measured; The biasing terminal a of the operational amplifier 1C, is connected to ground so that a constant low biasingvoltage is impressed which would not interfere with the transmission of the remission voltage current through the operational amplifier.

The output of the operational amplifier is passed directly to the gating circuit G, that is, to the offset terminal b of another integrated transistorized amplifier circuit 1C of the same type as the operational amplifier 1C The biasing input a of the gating amplifier 1C is connected to a potentiometer P and a stepping switch W in series with it. The output c of the gating amplifier 1C is connected with a condenser C, which normally blocks unipolar current flow from the gating amplifier 1C The level of biasing voltage input at terminal a of the gating amplifier 1C is preset by the combination adjustment of the potentiometer P and the stepping switch W, to a level just above that of the remission voltage of passable or good leaf to be scanned. Thus polarity reversal will occur only if the remission voltage is less than that of a good leaf, namely, occurring at or below the inversion point. This biasing voltage is obtained by initially setting a background plate of desired light transmission characteristics beneath the photodetector. Preferably, the light transmission is equal to the lowest good quality leaf to be passed by the detector. The photo-detector thus produces a unipolar volt.- age indicative of the grade of bad or unwanted leaf to be rejected. This voltage is passed, as explained, through the operational amplifier 1C to the offset input b of the gating amplifier 1C The potentiometer P and stepping switch W are then adjusted to raise the voltage level on the biasing input a to a point just above the offset level. As soon as a level of voltage greater than that of the offset voltage is received, the gating amplifier 1C will reverse in polarity tripping the condenser C If maintained in this state the detection system will pass good leaf and sense only bad leaf having a voltage less than that of the biasing voltage. The combined potentiometer P and stepping switch W voltage is set to provide a biasing voltage at a current of only a few .millivolts above that of the remission value at the inversion point or to a slightly better level than the inversion point of the leaf grade to be rejected. In this manner the gating amplifier 1C runs constantly at remission voltages substantially equal to the background plate and allows all good leaf passing the photo-detector, but reverses polarity and current flow on the production of a remission value which fall below the pre determined amount set on the biasing input, thus rejecting bad leaf.

The-tripping of the condenser C by reversal of the gating amplifier 1C produces a pulsing signal in line P.S. passing through a normally closed contact k ofa manual switch K into a trigger circuit T adapted to operate a solenoid relay U which operates switch contacts U and U adapted to actuate a pair of solenoid air valve rejectors. See FIG. 3a. 'As will be noted the gate G functions by maintaining ..a constant voltage level at a given polarity at the biasing input..As soonas this voltage level becomes greater than the offsettingvoltage, the polarity of the gate amplifier 1C changes, producing the pulse signal through the condenser. To insurethat the gate amplifier again reverses its polarity to permit the sensing of succeeding leaf, the solenoid U has a switch contact U arranged with the control potentiometer P and stepping switch W which instantly causes the gate G to reverse polarity. This resetting operation, it will be noted, is not a recalibration of the compression voltage since the calibration voltage never varies and remains the same, as the position of the potentiometer P and stepping switch W is not changed. The resetting operation merely permits the instantaneous reestablishment of dominance of the offset poled voltage on the gate G to permit the next voltage signal from the amplifier A to be passed to the gate 1C without delay. In fact, the resetting operation is so swift that the speed of the conveyor movement described in the aforementioned patent can be raised to well over 1000 ft./minute, without any mis-detection caused by electronic delay.

The potentiometer P is necessary only when one or more photo-cell units are used in conjunction with a single table. Since there are inherent variances in photo-detection cells, even under the most careful manufacturing standards, the individual cells must be matched against each other. Potentiometer P permits this matching by allowing each cell to be individually set at a predetermined selective level. The multiposi' tion stepping switch W is connected in series to the po tentiometer P each contact being connected to a resistor of different value than the other. A switch S- is inserted in the line so as to permit the multiposition stepping switch W to be cut-out when the potentiometer P is being initially adjusted. When several photodetecting units are employed as indicated above, the stepping switches of each may be mounted on a com mon shaft so that they may be provided with a common setting.

The purpose of the stepping switch is to allow the ad justment of the biasing voltage level on bias input a of the gate G to be set in dependence on the background plate corresponding to grade to be scanned, and to per mit this adjustment for all the photo-detectors employed in unison on a single table. Since the entire circuit operates in the low voltage ranges and in milli ampere currents the stepping switch need be graduated only in very small voltage increments. Once the stepping switch is calibrated for the particular grade it may be locked into place and operation of the table commenced and conducted indefinitely. Similarly, the background plate may be removed as soon as the step ping switch is properly fixed, since the biasing voltage on input a of the gating amplifier will not change. However, the background plate is kept in place in order to insure'that the same light and transmission conditions through the operation occur.

The trigger circuit T comprises a silicon power unidirectional transistor T in a two stage resistor-capacitor coupled circuit arrangement, the operation of which will be evident. An array of timing resistors and condenser bridge the transistors T and T to provide a time delay circuit to hold the signal for a predetermined time interval. The trigger circuit operatesthe s0- lenoid relay U which is bridged bya diode D limiting: i

current flow through the circuit. to insure against .transient or spurious excess current from the-pulse signal,

The solenoid relay controls contacts U and U which,

actuate the solenoid air valves v -and 2V controlling the air ejection means andthelplate air cleaning blasts respectively, described in I the companion application. I

The solenoid U also controlsa' switching 'contactUg,

which alternates between contact withthe potenti o'mek. ter P and the stepping s'witch'W t verse the polarity on the stepping switch andpot tiofri'eter; P5

voltage signal. The sol'e'r'i'oid r'elay Contact 'U i rnally closed in contact with 'steppiii'g switch; and moves'into contact with potentiometer Pgonactuation;

Leading from the output of thefoperational amplifier 1C and bypassing the gate amplifier is alead to the meter circuit. This circuit comprises an integrated transistorized amplifier circuit 1C similar to those noted above. It includes its own potentiometer P which is adjusted to set the level of voltage to the meter and a suitable feed back and compensating resistorcondenser components.

The manual switch K is adapted to open the contact k and inserting via a second contact k the meter M bypassing the gate G so that the actual value of the voltage indicative of the remission value may be read. The switch k has a third contact k which simultaneously closes a light circuit having a lamp L indicating the operation of the meter and the bypassing of the gate G.

Connected to the normally closed portion of contact U, of solenoid relay U is an indicating lamp L A green light may be used as it will be maintained lit when the detector senses good leaf. Connected to the normally closed portion of the contact U is another lamp L indicating the reversal of the solenoid U and consequently the presence of a signal pulse through the gate G. It may be red. The red signal indicates the drop of remission value lower the inversion point and conse quently the presence of a bad leaf.

It will thus be seen that the present invention provides a simple yet highly improved method of sensing and sorting leaf into various grades. The circuitry and electronic apparatus are highly adaptable to high speed operation, in line with the basic method of sense leaf based solely upon a singly variable factor. Various changes and modifications are obvious and it is to be understood that the present disclosure is illustrative only and not limiting of the invention.

What is claimed is:

l. A system for grading articles according to apparent color comprising means for supporting said articles, a photo-sensor having detector means for sensing the light remission value of each said article, means restricting the response of said photo-sensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photo sensor producing a signal variable in response to the level of said light remission in said range, means for converting said signal to a voltage proportional thereto, a gating circuit adapted to convert said voltage into a pulse at a given level of said voltage. trigger means responsive to said pulse. and classifying means responsive to said trigger means for removing said article from said support.

r 10 i 2The systemaccording to claim 1 including means for providing an initial source of light remission of a given value, and meansforficoordinating said gating cir-" cuit thereto to cause only articles of a remissivity differ ent from said given value-to besorted.

3. The system according to claim 2 wherein said means'for providing an initial source of light 'remission isiadjust-able to selected levels thereof.

4. Thefsystem accordin'g'ito claim 1' wherein? the means for restricting the response of said photo-sensor is limited-to the se nsing of lightfremission in a wave length band of substantially 660 to 'rnillimicr'ons.

5. The system according to claim including means for controlling the gating circuit topas'sa pulsevoltage on sensing the inversion in said 'e'u'rve;

6. The'system accbrdingto claim 5 including'an adj justable signal limiting i'riea'ns asbiarw with said gating means for establishinga selected level of electrical si'grialto provide saidjvol'tag epul se." F

7. Apparatus for continuously and automatically grading leaf tobacco comprising means for conveying an endless stream of spaced tobacco leaves, means for illuminating each said leaf with a broad-spectrum light, a photo-sensor for determining as an electrical signal "the light remission of each said leaf as it passes said sensor, said photo-sensor being limited to respond to wave lengths within a predefined range, a first amplifier for converting said signal to a voltage proportional to said light remission, a second amplifier responsive to said proportional voltage comprising a gating circuit including biasing means for passing a voltage of a predetermined level relative to the level of voltage obtained at the inversion point of the curve of light remission of a predefined leaf, a circuit adapted to convert the voltage of said predetermined level into a pulse signal, a trigger circuit including solenoid means responsive to said pulse signal for operating a leaf classifying means adapted to divert said leaf producing said pulse signal. 8. The apparatus according to claim 7 wherein said biasing means comprises at least one variable resistor. 9. The apparatus according to claim 7 wherein said circuit adapted to convert the voltage into a pulse signal includes a condenser and means operable by said Solenoid to restorethe state of said condenser simultaneous with the operation of said leaf classifying means. 10. In a system for continuously and automatically grading random leaf tobacco into acceptable and nonacceptable classes, comprising moving said leaves in a continuous stream at random orientation to a sensing station, illuminating said sensing station with a broad spectrum light source, locating a photo-sensor at said sensing station, limiting the normal response of said photo-sensor to a wave length range within predefined limits, said photo-sensor providing a signal indicative of the light remission of each leaf as it passes said station within said predefined limits, a gating circuit responsive to said signal, said gating circuit including means for limiting its response to a level corresponding to the point of inversion of said light remission at ascending wave lengths, means converting said voltage passed by said gating circuit into a pulse signal, pneumatic means arranged at said sensing station responsive to said pulse to remove said leaf from said station on determination of a voltage corresponding to said point of inversion. 11. The system according to claim 10 wherein a plurality of photo-sensors are arranged at said sensing station each scanning a separate portion thereof and each 1 1 connected to a separate amplifier, gating and pneumatic means.

12. A system for grading articles according to apparent color comprising a photo-sensor having detector means for sensing the light remission valve of each said article, means restricting the response of said photosensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photo-sensor producing a signal variable in response to the level of said light remission in said range means for converting said signal to a voltage proportional thereto, a gating circuit adapted to convert said voltage into a pulse at a given level of said voltage, and classifying means responsive to said pulse for sorting said articles.

13. A system for grading articles according to apparent color comprising a photo-sensor having detector means for sensing the light remission value of each said article, means restricting the response of said photosensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photo-sensor producing a signal.

variable in response to the level of said light remission in said range, a circuit responsive to said signal and adapted to produce a trigger signal at a given level of apparent color and wherein said circuit is responsive to both said first signal and said reference voltage level to produce said trigger signal.

Claims (14)

1. A system for grading articles according to apparent color comprising means for supporting said articles, a photo-sensor having detector means for sensing the light remission value of each said article, means restricting the response of said photosensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photosensor producing a signal variable in response to the level of said light remission in said range, means for converting said signal to a voltage proportional thereto, a gating circuit adapted to convert said voltage into a pulse at a given level of said voltage, trigger means responsive to said pulse, and classifying means responsive to said trigger means for removing said article from said support.

2. The system according to claim 1 including means for providing an initial source of light remission of a given value, and means for coordinating said gating circuit thereto to cause only articles of a remissivity different from said given value to be sorted.

3. The system according to claim 2 wherein said means for providing an initial source of light remission is adjustable to selected levels thereof.

4. The system according to claim 1 wherein the means for restricting the response of said photo-sensor is limited to the sensing of light remission in a wave length band of substantially 660 to 680 millimicrons.

5. The system according to claim 4 including means for controlling the gating circuit to pass a pulse voltage on sensing the inversion in said curve.

6. The system according to claim 5 including an adjustable signal limiting means associated with said gating means for establishing a selected level of electrical signal to provide said voltage pulse.

7. Apparatus for continuously and automatically grading leaf tobacco comprising means for conveying an endless stream of spaced tobacco leaves, means for illuminating each said leaf with a broad-spectrum light, a photo-sensor for determining as an electrical signal the light remission of each said leaf as it passes said sensor, said photo-sensor being limited to respond to wave lengths within a predefined range, a first amplifier for converting said signal to a voltage proportional to said light remission, a second amplifier responsive to said proportional voltage comprising a gating circuit including biasing means for passing a voltage of a predetermined level relative to the level of voltage obtained at the inversion point of the curve of light remission of a predefined leaf, a circuit adapted to convert the voltage of said predetermined level into a pulse signAl, a trigger circuit including solenoid means responsive to said pulse signal for operating a leaf classifying means adapted to divert said leaf producing said pulse signal.

8. The apparatus according to claim 7 wherein said biasing means comprises at least one variable resistor.

9. The apparatus according to claim 7 wherein said circuit adapted to convert the voltage into a pulse signal includes a condenser and means operable by said solenoid to restorethe state of said condenser simultaneous with the operation of said leaf classifying means.

10. In a system for continuously and automatically grading random leaf tobacco into acceptable and non-acceptable classes, comprising moving said leaves in a continuous stream at random orientation to a sensing station, illuminating said sensing station with a broad spectrum light source, locating a photo-sensor at said sensing station, limiting the normal response of said photo-sensor to a wave length range within predefined limits, said photo-sensor providing a signal indicative of the light remission of each leaf as it passes said station within said predefined limits, a gating circuit responsive to said signal, said gating circuit including means for limiting its response to a level corresponding to the point of inversion of said light remission at ascending wave lengths, means converting said voltage passed by said gating circuit into a pulse signal, pneumatic means arranged at said sensing station responsive to said pulse to remove said leaf from said station on determination of a voltage corresponding to said point of inversion.

11. The system according to claim 10 wherein a plurality of photo-sensors are arranged at said sensing station each scanning a separate portion thereof and each connected to a separate amplifier, gating and pneumatic means.

12. A system for grading articles according to apparent color comprising a photo-sensor having detector means for sensing the light remission valve of each said article, means restricting the response of said photo-sensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photo-sensor producing a signal variable in response to the level of said light remission in said range means for converting said signal to a voltage proportional thereto, a gating circuit adapted to convert said voltage into a pulse at a given level of said voltage, and classifying means responsive to said pulse for sorting said articles.

13. A system for grading articles according to apparent color comprising a photo-sensor having detector means for sensing the light remission value of each said article, means restricting the response of said photo-sensor to a defined wave length range approximately coextensive with the wave length range at which the remission curve of a specific article at ascending wave lengths inverts, said photo-sensor producing a signal variable in response to the level of said light remission in said range, a circuit responsive to said signal and adapted to produce a trigger signal at a given level of said first signal, and classifying means responsive to said trigger signal.

14. The system as in claim 13 further including means for selectively setting a reference voltage level at a value corresponding to the inversion level at said defined wavelength range of an article having a desired apparent color and wherein said circuit is responsive to both said first signal and said reference voltage level to produce said trigger signal.

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