Reflection Classifier

Abstract

Apparatus for classifying articles according to their surface reflectivities including a conveyor for transporting articles, a light source for illuminating an article supported on the conveyor and plural light-dependent resistors positioned to receive light from the source reflected by an illuminated article. Electrical circuits connected to the resistors interpret the amount of light received thereby, and produce an output signal which is related to the reflectivity of the article's surface.

Description

This invention relates to apparatus for classifying articles according to their surface reflectivities. For purposes of illustration, a preferred embodiment of the invention is described herein in connection with the classification of prefinished wood panels.

In the manufacture of articles, such as prefinished wood panels, an important step is the classifying and separating of finished panels into groups according to their surface shadings. In the past, such classification has typically been carried out by a person observing panels traveling on a conveyor, and deciding which classification is appropriate for each panel.

This practice has a number of drawbacks, however. To begin with, after even a relatively short period of time, a person performing in this manner often becomes fatigued and unable to maintain uniformity among the panels selected for the various respective classes. More specifically, with such fatigue a person may select for one class a panel which he might, at an earlier time, have designated for another class. Thus, panels within a given class in the past have often varied widely in their surface shades. This is obviously undesirable where, as is usually the case, a customer expects to receive a group of panels having similar shades.

A related problem results from the inability of a person to discriminate consistently between panels having only slightly different shades. More specifically, this inability to discriminate makes it difficult for a manufacturer to offer a wide range of panels divided into many different groups, with only subtle shade differences distinguishing the various groups.

A further difficulty with the practice outlined is that it is relatively slow and uneconomical.

Therefore, a general object of the present invention is to provide novel apparatus for classifying articles, such as prefinished wood panels, to obtain groups of articles having similar and relatively uniform shades, which takes care of the above-mentioned drawbacks in a practical and satisfactory manner.

More specifically, an object of the invention is to provide such apparatus which performs automatically and speedily, and with a relatively high degree of consistency.

Thus, the invention contemplates novel electrical means for classifying an article according to its surface reflectivity, such reflectivity being related to the article's surface shade. According to a preferred embodiment of the invention, articles are transported on a conveyor through a housing wherein they are illuminated, and the amount of light that they reflect from such illumination measured by light-dependent resistors (having varying resistance depending upon the light received). Such resistors are connected to novel switching circuits (one for each class of articles to be selected) which are sensitive to the resistance values of the resistors. For a given article which is observed, the appropriate circuit produces an output signal related to the surface reflectivity of the article. Output signals from the various circuits may be employed to control further processing, for example sorting, of the articles.

The organization contemplated performs with a relatively high degree of objectivity, and as a consequence produces good uniformity among panels chosen for each class. In addition, with electric circuits employed, the organization performs quite rapidly.

These and other objects and advantages attained by the invention will become more fully apparent as the description which follows is read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified fragmentary side elevation illustrating classifying apparatus constructed according to the invention;

FIG. 2 is a view taken along line 2-2 in FIG. 1; and

FIG. 3 is a schematic diagram, partly in block form, illustrating electrical circuits employed in the apparatus of FIGS. 1 and 2.

Turning now to the drawings, and referring first to FIGS. 1 and 2, indicated generally at 10 is apparatus as contemplated herein for classifying prefinished wood panels according to the surface reflectivities of such panels. The apparatus comprises a housing 12 including upright front and rear walls 14, 16, respectively, joined at their opposite sets of ends by upright sidewalls 18. The housing further includes top and bottom pieces 20, 22, respectively, suitably joined to the front, rear and sidewalls. The spacing between the front and rear walls is less than the length of the panels which are to be classified. The inside surfaces of the parts making up the housing are suitably coated, as by painting, with a coating which has a minimum reflectivity (such as a dull black coating).

Extending through elongated, transversely extending openings 24, 26 provided in walls 14, 16, respectively, are plural, laterally spaced-apart, power-driven conveyor belts, such as belt 28 (which is the only one shown in the drawings). Belts 28 serve to transport a prefinished wood panel, such as panel 30, through the housing in the direction of arrow 32 (FIG. 1). The belts constitute support means herein, and define a path of travel for a panel through the housing.

Suitably mounted on the inside face of top piece 20 is a pair of laterally spaced, elongated fluorescent lamps 34, 36 which extend along the front and rear margins, respectively, of the top piece. These lamps, also referred to herein as a light source, function to illuminate the top surface of a panel supported on belts 28 inside the housing. Fluorescent lamps are preferred because of their ability to produce diffuse light, and because they can be preaged, whereby for the remainder of their lives they produce a substantially constant level of illumination.

Also mounted on top piece 20 inside the housing are two rows or light-dependent variable resistors, such as resistors 38, 40, with five resistors provided in each row in the particular embodiment described. The resistors are conventional units whose resistance values vary inversely with the amount of light shining upon the resistors. Broadly speaking, therefore they constitute sensing means producing a different response within a range of responses with the particular response produced at any given time being related to the amount of reflected light received. The vertical spacing provided in housing 12 between these resistors and conveyor belts 28 is such that each resistor can, in effect, view the entire top surface area of a panel supported inside the housing. The resistors are prevented from receiving light directly from lamps 34, 36 by means of a pair of elongated shields 42, 44. Shields 42, 44 are mounted on top piece 20 in the spaces between the rows of resistors, and lamps 34, 36, respectively.

Considering FIG. 1, mounted on bottom piece 22 is a pair of light-dependent resistors, or delay-producing sensing devices, 46, 48 which are similar to resistors 38, 40. Resistor 46 is positioned closely adjacent wall 14, and resistor 48 is adjacent wall 16. Resistors 46, 48 comprise part of a delay means herein (which will be more fully described later) and are positioned whereby, with no workpiece disposed over the belts inside the housing, they receive light directly from lamps 34, 36. Light is blocked from these resistors, however, as a workpiece travels through the housing. More specifically, after panel 30 has traveled a short distance into the housing, for example to its solid outline position in FIG. 1, resistor 46 is prevented from receiving light from the lamps. At a somewhat later time, when the panel has moved to its dash-dot outline position 30A in FIG. 1, both resistors 46, 48 are prevented from receiving such light.

Turning now to FIG. 3, indicated generally at 50, 52 is a pair of what is called herein light-responsive switching circuits. Circuits 50, 52 are connected to previously mentioned resistors 38, 40, respectively, shown in block form. At 54 is a circuit connected to previously mentioned resistors 46, 48, (also shown in block form).

Considering circuit 50, it comprises a pair of transistors 56, 58. The base of transistor 56 is biased through a voltage divider containing, in series, a fixed resistor 60, light-dependent resistor 38, and a variable resistor 62. Resistor 60 is connected to a source of negative voltage through a conductor 64, and resistor 62 is connected to a source of positive voltage through a conductor 66. The collector of transistor 56 is connected to conductor 64 through a resistor 68, and the emitter of the transistor is connected through a variable resistor 70 to conductor 66.

Transistor 58 has its base connected directly to the collector of transistor 56, and its emitter connected through a diode 72 to the emitter of transistor 56. The collector of transistor 58 is connected through a diode 74 to a conductor 75, and is connected directly to one end of the solenoid 76a in a relay 76. Solenoid 76a constitutes an output signal producer herein, and has its other end connected to conductor 75. Relay 76 when in a deenergized state, includes normally closed switch 76c. On energizing of solenoid 76a, switch 76b opens before switch 76c closes, so that the switch is known as a break-before-make switch.

Circuit 52 is similar to circuit 50. Thus, circuit 52 includes a pair of transistors 80, 82 corresponding to transistors 56, 58, respectively, resistors 84, 86, 88, 90 corresponding to resistors 60, 62, 68, 70, respectively, and a pair of diodes 91, 92, corresponding to diodes 72, 74, respectively. The junction between resistors 84, 88 is connected to a source of negative voltage through a conductor 96 which corresponds to conductor 64. The junction between resistors 86, 90 is connected to a source of positive voltage through a conductor 98 which corresponds to conductor 66.

Further describing circuit 52, at 100 is a relay corresponding to relay 76. Relay 100 includes a solenoid 100a, a normally closed switch 100b, and a normally open switch 100c. One end of solenoid 100a is connected directly to the collector of transistor 82, and the other end of the coil is connected to a conductor 102 which corresponds to conductor 75. One end of conductor 102 is connected to switch 76b and the other end is connected to switch 100b.

Circuits (not illustrated) similar to those shown at 50, 52 are provided for the other eight light-dependent resistors included in the rows of resistors mounted on top piece 20 in the housing. Connected to and extending away from switch 100b to one of such other circuits is a conductor 104 which corresponds to conductor 102. Conductors 102, 104, switches 76b, 100b, and the corresponding conductors and switches associated with the other circuits mentioned constitute interlock means herein.

As can be seen clearly in FIG. 3, circuit 54 is similar in many respects to circuits 50, 52. Thus, circuit 54 includes a pair of transistor 106, 108 which correspond to transistors 56, 58, respectively, in circuit 50. The interconnections provided between transistors 106, 108, are very much like those provided between transistors 56, 58, except that instead of there being a single light-dependent resistor included in the base bias circuit for transistors 56, 58, except that instead of there being a single light-dependent resistor included in the base bias circuit for transistor 106, resistors 46, 48 are connected in parallel therein. Light-dependent resistors 46, 48, together with a fixed resistor 47 and a variable resistor 49, comprise a voltage divider connected to the base of transfer transistor 106. The collector of transistor 108 is connected directly to one side of the solenoid 110a of relay 110. The other end of solenoid 110a is connected through a conductor 112 to a source of negative voltage. Relay 110 further includes a normally open switch 110b having one side connected to conductor 112 and the other side connected to previously mentioned conductor 75.

Explaining now how the described apparatus performs, and considering first the internal operation of circuit 50, variation in the value of the resistance of resistor 38, as differing amounts of light shine on it, causes the voltage applied to the base of transistor 56 also to vary. More specifically, an increase in the amount of light shining on the resistor causes its resistance to drop, and this results in the voltage applied to the base of the transistor 56 conducts. A similar but reverse action takes place when the amount of light required to make transistor 56 conduct shining on resistor 38 decreases. The amount of light required to make transistor 56 conduct is determined by the setting of resistor 62.

Assuming for the moment that switch 110b is closed, with too little light shining on the resistor 38 to cause transistor 56 to conduct, transistor 58 is in a conducting state. Transistor 58 conducts because, with switch 110b closed, appropriate negative voltages are applied to its base and collector. And it will be noted that with transistor 58 conducting, current flows through solenoid 76a causing switch 76b to open, and switch 76c to close.

Upon sufficient light shining on resistor 38 causing transistor 56 to conduct, transistor 56 short circuits the emitter and base of transistor 58. This causes transistor 58 to become nonconductive.

It should be noted that when switch 110b is open, no negative voltage is provided the collector in transistor 58, although negative voltage is provided the base therein through conductor 64 and resistor 68. Therefore, in such a case, regardless of the state of transistor 56, transistor 58 cannot conduct.

Circuit 52 and the similar circuits provided for the other resistors mounted on top piece 20 each perform in a similar manner. In the embodiment shown, the various circuits are adjusted whereby the transistors therein corresponding to transistors 56, 80 are switched to a conducting state with different degrees of illumination of the respective light-dependent resistors connected to the circuits. For example, circuit 50 is adjusted to make transistor 56 conduct with a relatively small amount of illumination of resistor 38. Circuit 52 is adjusted so that transistor 80 conducts when the illumination or resistor 40 is somewhat greater. The other circuits may be adjusted whereby their transistors corresponding to transistors 56, 80 conduct at progressively higher levels of illumination.

Referring briefly to the internal operation of circuit 54, it will be recalled that resistors 46, 48 are positioned in housing 12 to receive light directly from lamps 34, 36. Because these resistors are connected in parallel, so long as such light shines directly upon one of them, their combined resistance value will be relatively low. With such the case, resistor 49 is adjusted whereby transistor 106 ordinarily is in a conducting state. With transistor 106 conducting, the case and emitter of transistor 108 are short circuited, and transistor 108 cannot conduct. Therefore, with transistor 106 conducting, relay 110 is nonenergized, and switch 110b is open.

However, upon the parallel resistance value of resistors 46, 48 increasing, which will occur whenever a panel traveling through the housing prevents light from shining simultaneously upon both of the resistors, transistor 106 switches to a nonconducting state. When this occurs, transistor 108 conducts and energizes relay 110, with switch 110b then closing.

Considering now how panels transported through housing 12 are classified, a panel which reflects too little light to cause conduction of any of the transistors corresponding to transistors 56, 80, will result in relay 76 becoming energized. More specifically, when the panel reaches a position in the housing covering both resistors 46, 48, relay 110 energizes causing switch 110b to close. Closing of switch 110b applies a negative voltage from conductor 112 through conductors, such as conductors 75, 102, and switches, such as switches 76b, 100b, to one set of ends of the various relay solenoids corresponding to solenoids 76a, 100a.

With such voltage present, momentarily all of the transistors corresponding to transistors 58, 82 conduct and cause the relays connected to their collectors to energize. Accordingly, the switches in such relays corresponding switches 76b, 100b, tend to open. However, since switch 76b is the closest one electrically to conductor 112 which furnishes the negative voltage just mentioned, it has a controlling effect upon the solenoids in the other relays. More specifically, opening of switch 76b breaks the supply of negative voltage to all of the other relay solenoids, whereupon they become deenergized. Since these relays are break-before-make relays closing of their switches corresponding to switch 100c never occurs.

Relay 76 remains energized so long as switch 110b remains closed, and thus switch 76c closes. Closure of switch 76c, therefore, is effective to produce an output signal, and may be employed to indicate the presence of a very dark panel; and the switch may be used to operate other equipment (not shown), for example a sorter, which controls further processing of the panel.

Upon the panel traveling to a position where its trailing edge has moved beyond resistor 46, switch 110b opens. Thereupon, relay 76 becomes deenergized, switch 76b closes, and switch 76c opens.

Let us assume now that a somewhat lighter panel than the one just mentioned travels into the housing. When the panel moves to a position preventing light from shining on resistors 46, 48, switch 110b closes as described previously.

The panel being lighter than the previous panel, it produces conduction of transistor 56. It will be assumed, however, that the panel is not light enough to cause conduction of transistor 80 in circuit 52. With transistor 56 in circuit 50 conducting, transistor 58 is prevented from conducting, and therefore relay 76 remains nonenergized. Switch 76b remains closed, and switch 76c remains open.

However, the solenoids in the other relays corresponding to relay 76 momentarily become energized with closing of switch 110b. But relay 100 immediately opens switch 100b. When this occurs, the supply of negative voltage to all relay solenoids supplied through conductor 104 is broken, and they become deenergized. Solenoid 100a remains energized, nevertheless, because switches 76b, 100b are closed. Therefore, switch 100c closes. Accordingly, closure of switch 100c may be employed to indicate the presence of a somewhat lighter panel than the one first mentioned.

Upon the panel moving to a position exposing resistor 46 to light from the lamps, relay 110 becomes deenergized, and this in turn causes relay 100 to become deenergized.

In a similar fashion, the other relay switches corresponding to switches 76c, 100c may be employed to indicate progressively lighter panels.

Thus, the invention provides novel automatically operating electrical apparatus for classifying articles according to the amount of light reflected from their surfaces. The number of classes of articles which can be designated, and the range of surface shadings which are accepted within a given class, can easily be adjusted. This can be done by providing an appropriate number of circuits, such as circuits 50, 52 in FIG. 3, and by adjusting such circuits to respond to different preselected levels and ranges of illumination. For example, in circuit 50, the resistance value of resistor 62 determines generally the level of illumination that the circuit responds to, and the resistance value of resistor 70 determines the illumination range throughout which the circuit responds.

Accordingly, the apparatus is capable of producing a classification of articles where the color shadings of the articles in a given class are quite uniform. In addition, the organization proposed is capable of handling a fairly rapid flow of articles through the housing. For example, apparatus has been constructed according to the invention which is capable of handling successive panels transported on belts at a speed of several hundred feet per minute.

An important feature in the invention contributing to its accuracy is the novel interlocking circuit which interconnects the normally closed switches in the relays corresponding to relays 76, 100. Because of this interlocking circuit, it will be noted that at a given time only one type of output signal can be produced.

Still another important feature of the invention is the time delay introduced between the time that the panel first enters the housing and the time that it has traveled far enough to cause energizing of relay 110 whereupon an output signal can be produced. Such a feature insures that a relatively large surface area of a panel will be reflecting light to the overhead resistors, whereby the apparatus will accurately classify the panel. Were only a small area of the panel reflecting light at the time an output signal is produced, it is obvious that the panel could be wrongly classified if this area were considerably lighter or darker than the remaining portion of the panel.

While a preferred embodiment of the invention has been described herein, it is appreciated that variations and modifications are possible without departing from the spirit of the invention.

Claims

I claim:

1. Apparatus for classifying articles according to their surface reflectivities comprising:

a light source;

support means for supporting an article in a position where the article is illuminated by said source;

plural light-sensing devices positioned to receive light from said source reflected by an article supported on said support means, each of said devices producing a response within a range of responses with the particular response produced being related to the amount of reflected light received;

plural electrical circuit means each operatively connected to and associated with a different one of said light-sensing devices, and each circuit means being sensitive to a different subrange in said range of responses producible by its associated light-sensing device and producing an output signal on sensing a response in its respective subrange of said range; and

interlock means operatively connected to said plural circuit means permitting only one of said circuit means to produce an output signal at a given time.

2. The apparatus of claim 1, wherein each circuit means comprises an output signal producer and electronic switching means operatively interconnecting said signal producer and the sensing device associated with the circuit means, said switching means being operable to effect energizing of said signal producer with the sensing device for the circuit means receiving less than a certain amount of light.

3. The apparatus of claim 2, wherein each sensing device comprises a light-dependent resistor whose resistance value depends upon the amount of light shining on the resistor.

4. The apparatus of claim 3, wherein the switching means in each circuit means comprises a transistor whose base voltage depends upon the resistance value of the light-dependent resistor for the circuit means.

5. The apparatus of claim 2, wherein said interlock means comprises plural switches through which power is supplied to energize said output signal producers, each of said switches being operatively connected to and actuated by a different output signal producer.

6. Apparatus for classifying articles according to their surface reflectivities comprising:

a housing;

a conveyor for transporting an article through said housing;

a light source in said housing adapted to illuminate an article transported therethrough on said conveyor;

plural light-sensing devices positioned in said housing to receive light from said source reflected by an article on said conveyor, each of said sensing devices producing a response within a range of responses with the particular response produced being related to the amount of reflected light received;

plural electrical circuit means each operatively connected to and associated with a different one of said light-sensing devices, and each circuit means being sensitive to a different subrange in said range of responses producible by its associated light-sensing device and producing an output signal on sensing a response in its respective subrange of said range; and

interlock means operatively connected to said plural circuit means permitting only one of said circuit means to produce an output signal at a given time.

7. The apparatus of claim 5, which further comprises delay means operatively connected to said plural circuit means operable to prevent the production of an output signal from any one of said circuit means until an article on said conveyor has traveled a given distance into said housing.

8. The apparatus of claim 7, wherein said light source and sensing devices are disposed on one side of the path of travel for articles on said conveyor and said delay means comprises a pair of delay-producing sensing devices, spaced along the length of said path and disposed on the other side thereof, said delay-producing sensing devices each facing said light source, and being positioned whereby an article traveling through said housing prevents light from said source from shining on the devices.

9. The apparatus of claim 8, wherein said delay means further comprises a switch through which power is supplied to said plural circuit means, said switch being closed upon light from said source being prevented from illuminating both of said delay-producing sensing devices simultaneously.

10. Apparatus for classifying articles according to their surface reflectivities comprising:

a slight source;

plural light-sensing devices for sensing light reflected from the source by an article;

a circuit for each sensing device including a relay having a signal and a nonsignal producing state, and an electronic switching means which is made conductive or nonconductive dependent upon the quantum of light sensed by the light-sensing device associated with the circuit;

each circuit on its switching means being conductive, being constructed to place its relay in one of its said states with such state being common to all the circuits; and

the quantum of light needed to be sensed by a light-sensing device to produce conduction in the electronic switching means of the circuit associated with the device being different for the various circuits.