US2247684A - Photoelectric sorting apparatus - Google Patents

Description

July 1, 1941. w. H. HICKOK E HOTOELECTRIC SORTING APPARATUS Fly. 3

Filed 001;. 51, 1940 AMPLIFIER INVENTOR WILLARD H. HICKOK ATTORNEY Patented July 1, 3941 PHOTOELECTRIC SORTIING APPARATUS Willard H. Hickok, Bloomfield, N. 3., assignor to Radio Corporation of America, a corporation or Delaware Application October 31, 1910, Serial No. 363,668 6 claims. (01. zoo-iii) Another object is to provide low cost apparatus for selecting materials or objects in accordance with color variations of the objects; and it is a still further object to provide sorting apparatus with which the elemental areas of the materials or objects to be inspected may be sequentially analyzed for quality or color defects.

In accordance with my invention I move one or more objects to be examined or sorted under a narrow strip of light which is reflected upon a photoelectric tube having av number of charge storage electrodes and on which elemental area, images of the objects to be examined are ex-.

pended in the direction of motion of the objects to produce electrostatic chargesrepresentative of the quality or color of the object images. The electrostatic charges are sequentially neutralized to produce a current fiowwhlch is simultaneously applied to one or more selecting mechanisms which are synchronized with the neutralization of the electrostatic charges. These and other objects, features, and advantages of my "invention will be apparent when considered in view of the following description and the accompanying drawing in-which:

Figure 1 is a perspective view of sorting apparatus made in accordance with my invention and incorporating a single photoelectric tube; Figure 1 2 is a perspective cross-sectional view of a portion of the electrode and, Figure 3 is a crosssection of a portion ofthe apparatus shown in Figure 1.

In accordance with my invention a number of objects to be examined and from which imperfect or off color objects are to be sorted are carried by an' endless belt under a relatively narrow strip or beam of light extending transversely of the belt in its direction of motion. Elemental strip images of the objects to be sorted are projected upon a charge storage electrode comprising a number of segments preferably equal to the number of side-by-side objects on the endless belt. These images generate charges which are sequentially dissipated by an electron beam scanned across the electrode segments to generate ing.

sequentialcurrent impulses which are applied in order of their occurrence to a plurality of discharge mechanisms arranged in the same order as the order in which the objects appear on the endless belt.

Referring to Figure l, I will first describe the photoelectric tube used in combination with my sorting apparatus. The tube i comprises a high- 1y evacuated glass envelope enclosing a conventional type electron gun and a fiat target or mosaic electrode 2 symmetrically positionedin the envelope so that its front surface may be scanned by a beam of electrons from the electron gun and also may have projected upon it elemental optical images of the objects tobe inspected. since the images are produced by light irom objects situated outside the tube, aportion of the tube such as the transparent window 3 is made optically uniform so the images may be projected upon the mosaic electrode Zwith a minimum of distortion.

The electron gun assembly 4 comprises an electron emitting cathode 5 from which an-electron stream may be drawn, a control electrode e to control the average electron intensity connected to the usual biasing battery, and a first anode l maintained positive with respect to the cathode 5. 'I'he electron stream leaving the first anode l is accelerated, and concentrated into an electron scanning beam focused on the trout surface of the mosaic electrodet by a second anode 8 which is preferably a conducting coating on the surface of the bulb i nearand in the neck of the bulb but removed from that portion through which is projected the optical image. The first anode l and the second anode 8 are maintained at the desired positive potentials, such as 300 and 1000 volts respectively with respect to the cathode 5 by a battery 9. Conventional electromagnetic deflection coils l0 are used to sweep the beamin one direction only across the target or mosaic electrode 2. In the modification shown the deflectipn coils are so arranged as to sweep the beam in a singleplane which is perpendicular to the plane'of the draw- It is obvious that conventional electrostatic deflection plates may be substituted for the single set of deflection coils if desired.

The mosaic electrode as best shown in Figure 2 comprises a sheet of insulating material such as -'a sheet of mica H having on one side, that is the front surface, a discontinuous photosensitive structure of line formation and on the opposite side or rear surface a continuous coating of electrically conducting material. The discontinuous photosensitive structure comprises a number of closely spaced but mutually insulated and electrically isolated photosensitized metallic conductors l2, each of which extends across the mica to the opposite edge. The number of photosensitized metallic conductors depends upon the particular application of my sorting apparatus. Thus, if it is desired to sort a great number of objects simultaneously, such as might be made to flow along parallel grooves on an endless belt, the number of conductors I2 would be made equivalent to the number of grooves or objects extending crosswise of the belt. However, the number of conductors l2 may exceed the number of crosswise objects to be inspected, but in operation only a number equivalent to or a multiple of the number of crosswise objects to be inspected need be utilized. The mosaic electrode is positioned in the tube in such a manner that it may have optical images of the objects to be inspected projected on its front surfaces, and also so positioned that it may be scanned by the electron beam from the electron gun which scans or sweeps across the photosensitized metallic lens such as along a path represented by the dashed line l3.

In making the mosaic electrode 2, I select a 2 mica as narrow continuous rectilinear strips or conductors |2 which extend from one edge of the sheet of mica to the other edge and are of low electrical resistance throughout their length. For the inspection of a large number such as 100 of side-by-side objects, 100 of these conductors are provided, the conductors being of equal width and very closely separated one from the other. The rectilinear conductors may be applied most conveniently by printing the sheet of mica with a line cut having lines of the desired length and width, and inked with a silver containing printing vehicle, preferably-finely divided silver powder, mixed to form apaste with a volatile binder, such as oil of Wintergreen or oil of rosemary. As an alternative method, the multiple line type of mosaic may be formed on the sheet of mica H by a process somewhat similar to that disclosed by Tedham et al., in their U. S. Patent No. 2,077,442, by vaporizing the metal to be deposited and condensing the metal on the sheet of mica through a grid-like mask composed of a screen of parallel wires which cover the mica leaving parallel sections of the mica exposed so that the metal can condense thereon. During the evacuation process of the tube such volatile binders as may be present are removed and the metal lines or conductors I2 are oxidized and photosensitized such as by depositing thereon caesium or other alkali metal. A process for satisfactorily oxidizing a somewhat similar mosaic electrode is disclosed by S. F. Essig in his U. S. Patent No. 2,062,122 and a process for sensitizing a mosaic electrode in his U. S. Patent No. 2,065,570. I

The next step in preparing the mosaic electrode is to deposit on the rear side of the sheet of mica opposite the side which supports the the light reflected by the objects 2|.

individually separated metallic conductors l2, the uniform coating of metal such as platinum or other conducting material which serves as a signal plate M for the mosaic electrode 2.

To strengthen the thin mica sheet H which carries the individual metallic conductors and the electrically conductive coating such as platinum on the opposite side and which is inherently weak because of its thinness, I prefer to use a relatively thick backing sheet I5 also preferably of mica and of the same shape and area as the sheet II. On the side of the backing sheet facing the signal plate M of conducting material, I provide a conductive coating "5 also preferably of metal such as platinum in good electrical contact with the platinum coating [4 to assure minimum electrical resistance between various points on the coating l4 and the external.

circuit which is connected through the lead I! to a frame or clip-member I8 which grips the two edges of the mica and which is in electrical contact with the signal plate through the coating [6.

Referring again to Figure 1, I provide a moving belt 20 on which the objects 2| to be in spected are arranged along parallel grooves 23,

dashed lines 24- is projected from a light source 25 through suitable lenses and a slotted or apertured mask 26 upon the objects 2| to be inspected. The objects 2| may for example be almonds which are to be selected in accordance with abrasions occurring on the skin covering. Thus assume cleaned almonds are to be selected from those'from which the skin has not been entirely removed. As the objects are moved by the belt.

20 under the beam of light represented at 24, images of the objects are projected upon the conductors l2 of the mosaic electrode 2 by an objective lens 21 and a pair of cylindrical lenses 28 which expand the images of the objects 2| in a direction parallel with the motion of the belt 20. It will be obvious that an image of each of the objects to be inspected will be focused upon a corresponding conductor l2 of the mosaic electrode 2 which, being photoelectrlcally sensitive, will lose electrons and acquire a positive charge varying in quantity in accordance with Thus, in the example considered, almonds having abrasions will produce greater electrostatic charges than those having no abrasions. Electric currents representative of the electrostatic charge on ,each of the conductors l2 generate signals across an output impedance 29 connected between the lead I1 and ground in a time sequence determined by the rate of scanning the conduztors l2 by the electron beam. The signals are applied to an amplifier 30 of, the conventional type and thence to a distributing circuit to actuate the selecting apparatus.

More particularly, and as shown in Figure 3;

the output of the amplifier 30 is connected sequentially to a plurality of differential current solenoids shown schematically at 3|--34 through a single segment commutator 35 mounted on a shaft 35 which is driven by a motor 37. The number of solenoids 3|34 correspond to the number of parallel tracks. 23 of the bel -'20 so sliding on the commutator 38 is connected .to

one end of the serially-connected deflection coils in, the opposite end of which is grounded. To complete the circuit I provide a source of potential such as the battery 39 connected to the slip rings and thence to the resistance commutator 8, the mid-point of the battery 39 being grounded. The resistance characteristic of the commutator 38 and the potential supplied by the battery 39 are so chosen that for one complete revolution of the commutator 38 the electron beam from the electron gun is magnetically deflected across the conductors l2 of the mosaic electrode 2 and is returned to its starting pointwhereupon the deflection is repeated by further rotation of the commutator 38. The motor 31 also preferably drives the endless belt 26 through a suitable gear reduction mechanism. This gear reduction may be varied for the inspection of difierent objects or of materials depending on the size of the objects or materials and the degree of inspection required. Thus the gear reducing mechanism should be constructed so that the movement of the belt 20 is relatively slow where it is wished to inspect the objects very closely, that is, for defects occurring within small distances on the objects to be inspected. If, however, objects or materials wherein the defects are relatively large are to be inspected, the belt 20 may be moved at a correspondingly increased speed.

In operation, an image of each of the objects 2| is focused upon one of the conductors E2 of the mosaic electrode 2. Thus, as indicated above, if there are four side-by-side objects 2| to be inspected, four images will appear on the four or even multiple of four conductors l2 thereby developing an electrostatic charge on each of the conductors representative of the light reflecting property of the individual objects. If, however, the amount of light reflected by one of the objects 2|, such as due to a difierence in color or surface condition of the one object, is different from .the amount of light reflected by the other objects, the electrostatic charge on the corresponding conductor will vary with respect to the charges on the other conductors. ,As the electron beam sweeps across the four conductors, such as along the scanning line [3, the signal impressed across the output impedance 29 and consequently on the amplifier 30 will be the same when the beam impinges upon three of the conductors, but the signal will be difierent when the electron beam impinges upon the remaining conductor I2. Since the electron beam is synchronized with the particular solenoid in circuit at any one time, a difi'erence in signaldue to scanning any one conductor l2 will produce a corresponding difference in energy applied to the particular difierential current solenoid and, consequently, the solenoids receiving a difference in signal will cause a rejection of the particular object or objects '25 which do not correspond to a predetermined standard.

While I have described .the apparatus made in accordance with my invention-with reference to a purelyschematic drawing it will be apparent that my invention is by no means limited to the exact form described or to its use in the specific application referred to but .that many variations may be made in the particular structure used, such as by the use of different rejectors for the solenoids and scanning and switching means of different mechanical types or of the electronic type, without departing from the scope of the invention as set forth in the appended claims.

What I claim as new is:

1. A photoelectric sorting apparatus comprising a photoelectrically sensitive tube including means to generate an electron beam, 2. target electrode having a plurality of elongated photosensitive charge storage elements, capacitive means associated with said charge storage elements, and means to scan said beam over said elements, a conveyor adapted to support a plurality of objects to be sorted corresponding in to conform to a predetermined standard of light reflection from said objects.

2. A photoelectric sorting apparatus comprising an electron beam, tube including means to generate an electron beam, a target electrode in the path of said beam having a plurality of elongated photosensitive charge storage elements, and a signalelectrode in'capacitive relation with said plurality of elements, a conveyor adapted to suport a plurality of objects lying side-by-side across said conveyor and to move the objects in a direction substantially normal to the sideby-side relationship of said objects, means to focus an elongated optical image of each of said objects on a corresponding section including at least one storage element of said target, to produce electrostatic charges representative of the surface condition of said objects, a plurality of discharge means associated. with said conveyor to discharge from said conveyor the objects not conforming to a predetermined standard of light reflection from said objects, means to sweep said beam in regular sequence over said charge storage elements to neutralize said electrostatic charges, and means to connect said signal electrode to each of said plurality of discharge means in a sequence determined by the sequence of sweeping said. beam over 'said elements.

3. Apparatus as claimed in claim 2 wherein said last-mentioned means comprises a commutator to connect said signal electrode to each arranged in parallel .rows longitudinally thereof,

and to move said objects in a direction parallel with said rows, means to focus an optical image of one of said objects in each row upon a corresponding charge storage element, a plurality of 'means associated with said conveyor to discharge objects from each row of said objects, means to scan said electron beam over said charge storage elements, an electrical circuit including an amprising a plurality of elongated photoelectrically sensitive charge storage members extending in the direction of movement of said conveyor and corresponding in number to at least the number of parallel rows of objects on said conveyor, a signal electrode in said tube capacitively associated with said plurality of charge storage members, means in said tube to generate and direct an electron beam toward said charge storage members, means to scan said beam over said storage members in a direction normal to their length, optical means between said conveyor and said tube to focus an optical image of one of the aaaaeaa objects in each row of objects upon a, corresponding charge storage member of said tube, discharge means associated'with each row' of objects on said conveyor to discharge objects therefrom, an amplifier connected to be energized from said signal electrode and means to sequentially connect said amplifier to each of said discharge means in a time sequence determined by the rate of scanning said electron beam over said charge storage members.

6. A photoelectric sorting apparatus comprising a conveyor, a plurality of side-by-side channels on said conveyor to direct objects to be sortedalong a corresponding number of rows on said conveyor, a photoelectric tube associated with said conveyor, an electrode in said tube comprising a plurality of charge storage members the number of saidmembers being at least as great as the number of said channels of said conveyor, a signal electrode capacitively coupled.

with said charge storage members, means to generate and sweep an electron beam across said charge storage members, means to project an optical image of an object in each channel of said conveyor upon a corresponding charge storage member in said tube, a magnetically operated discharge mechanism associated with each of the channels of said conveyor, and means to connect each of said discharge mechanisms with said signal electrode during the time the said electron beam is being swept across a corresponding charge storage member in said tube.

WILLARD H. HICKOK.

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