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(11) | EP 0 865 833 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A reflective background for a sorting machine |
| (57) A background for an electro-optical sorting machine viewing station where fungible
products pass during sorting and are distinguished by being acceptable or nonacceptable
in at least two spectral ranges comprising a first layer responsive to light reflectivity
in a shorter spectral range and nonresponsive in a longer spectral range and a second
layer behind the first layer and responsive to a longer spectral range that is received
following penetration of the first layer. The first layer can be paint, transparent
tape or a thin film. The second layer is preferably painted metal, plastic, wood or
a wood and glue combination. |
Background of the Invention
Field of the Invention
[0001] This invention pertains to optical sorting machine backgrounds that match in at least two wavelength ranges the products sorted by the sorting machine, one range of which is normally represented by a color in the visible spectrum and the other range of which is normally in the infrared spectrum.
Description of the Prior Art
[0002] A typical sorting machine of the type with which the present invention is used is a high speed sorting machine typically used for sorting fungible products in the food industry or otherwise. For example, individual edible beans are caused to flow by gravity feed down a steep channel or chute to be sorted by such a machine to separate "substandard" beans from standard ones. The term "substandard" applies to beans that are outside of a predetermined acceptable range of "color" hue in one or more bands of radiation, which bands are in some cases outside of the visible color spectrum. In the simplest case, the items are sorted for variation from a hue or shade of color, including a shade of black or white and thus a shade of gray, in a single spectrum. Such a sorting procedure is referred to as monochromatic sorting since only a single radiation spectrum is being observed. In a more complex optical color sorting operation, the flow of items is sorted to determine when an item is reflecting an unacceptable radiation amount in either of two radiation bands. Such a sorting procedure is referred to as bichromatic sorting. It will be apparent that more than two radiation bands can be employed, if desired.
[0003] Optical sorting machines of the type generally described above employ sensors that include one or more photodetectors, such as photodiodes. The photodetectors are positioned to observe the illuminated product stream through a light admitting window. The stream passes between an optical sensor and a background having a color or shade that matches the product stream in standard color or shade so that only a variation in a product color or shade causes a detection event. The illumination is from one or more lamps directed at the product stream to cause standard reflectivity from standard products in the one or more radiation bands being observed and to cause substandard reflectivity from substandard products in those bands.
[0004] The machines also include an ejector mechanism located downstream from the sensor or sensors and actuated by an electrical signal originating from sensor detection. when a substandard item or product is detected, an electrical signal is produced and the ejector is actuated just as the substandard product and the mechanism are in alignment. Therefore, there is a very slight delay from the time of sensing to the time of ejecting. The typical ejector mechanism is usually an air ejector.
[0005] As mentioned, the product stream flows in front of a background having a color or shade that is critical to the overall operation in that it has to match the standard product under detection in the wavelength or bands being observed by the sensors. This is usually accomplished by carefully painting the background, letting the background dry and then operating the machine or otherwise analyzing whether the color or shade of the background is acceptable. For bichromatic sorting, the background has to be acceptable in reflectivity characteristics in two bands, which is virtually impossible to tell by a casual observation, especially when one of these bands is in the infrared spectrum rather than the visible spectrum. Much time is consumed by such a procedure, and such trial-and-error technique still can result in not matching exactly the acceptable radiation ranges as desirably as could be otherwise accomplished by the invention hereafter described. That is, the reflectivities of paint in both the visible spectrum and the infrared spectrum rarely ever exactly match a product in such spectrums because of the differences in the product's material and the background underlying material, which is usually a metal.
[0006] The texture of a typical product beneath its surface is important to how the infrared spectrum range reacts or reflects, whereas the surface condition of such product is important to how the visible spectrum range reflects. The attempts to treat the surface only of the background with a mixture of paint shades, for example, does not address how the subsurface or substrate material of the background reflects the infrared spectrum range. The use of different projected colors onto the background, such as described in U.S. patent 5,265,732 issued November 30, 1993 in the name of William C. Long, still does not address the condition of the material beneath the reflecting surface.
[0007] Therefore, it is a feature of the present invention to provide an improved background for sorting machines that is layered to have a first layer that is responsive to reflected light in a short wavelength range and a second layer that is responsive to reflected light in a longer wavelength spectrum range that penetrates the first layer and is reflected from the second layer.
[0008] It is another feature of the present invention to provide an improved background for sorting machines that is layered to have a first layer that is responsive to reflected light in the visible spectrum range and a second layer that is responsive to reflected light in the nonvisible infrared spectrum range that penetrates the first layer and is reflected from the second layer.
[0009] It is yet another feature of the present invention to provide an improved layered background for sorting machines of the type described above wherein the first layer is a plastic laminate, thin film or transparent tape and the second layer is a different material such as a wood/glue substrate.
Summary of the Invention
[0010] The background improvement in accordance with the present invention operates in conjunction with an electro-optical viewing station of a machine for sorting small fungible items in a flow of such products. Normally, such a machine used with the background improvement hereof is a bichromatic sorting machine having at least one viewing station aligned with respect to a product channel for illuminating the product stream therein with light in a preselected visible spectrum range and with radiation in a preselected nonvisible infrared spectrum range. The lamp sources are usually associated with a filter to produce the desired bichromatic radiations associated with known reflected responses of the product being sorted. That is, normal or acceptable products are known to reflect in each of the preselected spectrum ranges above respective trip levels. However, an unacceptable product will not reflect above at least one of these trip levels, which will produce an ejection signal for the product that is nonacceptable. Such sorting machine operation is well-known in the art.
[0011] The background is important since it is selected to match the acceptable products in each of the bichromatic spectrum ranges. Thus, when there is no product flowing or when there is a gap between products, there is no production of an ejection signal.
[0012] The background is produced by selecting a substrate material and color that reflects the longer wavelength of the bichromatic waves employed. The substrate can be wood or plastic and can have a glue surface for being attached to the surface layer that is selected to reflect the shorter wavelength of the bichromatic waves employed. Preferably, the shorter wavelength is in the visible spectrum range and the longer wavelength is in the nonvisible infrared spectrum range. The surface layer can be paint selected at the predetermined correct color or hue or can be a thin film or thin transparent tape. It has been discovered that a background of this nature more naturally matches the color in the two operating ranges of the bichromatic sorter than the prior art. This may be because the longer wavelength radiation penetrates the surface layer to reflect off the underneath or substrate layer that has a texture akin to the subsurface texture of the sorted products for reflective purposes, although there may be some other technical explanation.
[0013] It is obvious that each optical viewing station can be equipped with more than one background of substantially the same makeup when multiple viewers are employed to view the product stream at different angles. Also, more than two spectrum ranges can be employed, if desired.
Brief Description of the Drawings
[0014] So that the manner in which the above-recited features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in detail, more particular description of the invention briefly summarized above may be had by reference to the exemplary preferred embodiment thereof which is illustrated in the drawings, which form a part of this specification. It is to be noted, however, that the appended drawings illustrate only a typical preferred embodiment of the invention and are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
In the drawings:
Fig. 1 is a side view of an electro-optical sorting machine incorporating at least one background in accordance with the present invention.
Fig. 2 is a top view of an optical viewing station of an electro-optical sorting machine, such as shown in Fig. 1.
Fig. 3 is a simplified schematic illustrating the use of a background in accordance with the present invention.
Fig. 4 is a cross-sectional view of a background in accordance with the present invention and illustrating its laminar or layered structure.
Description of the Preferred Embodiments
[0015] Now referring to the drawings, and first to Fig. 1, a high speed sorter for separating nonstandard fungible products or items from a passing stream or flow of such products is shown. Generally, machine 10 includes one or more channels or chutes or slides 12 at a steep angle, usually over 45° and preferably nearly vertical on the order of 80°. The channels are held in position by a framework 14 and are gravity fed the products to be sorted at the top by a hopper 16 attached to the same framework. The products feed from hopper 16 through dividing vibratory feeder 18 to channels 12. Although a commercial machine usually has two or more channels 12 operating simultaneously with respect to the products that flow respectively through them, for simplicity of discussion, machine 10 is discussed hereinafter as including only a single channel 12.
[0016] The products to be separated or sorted by machine 10 are small fungible items, such as edible beans. Edible beans, it will be appreciated, are individually identifiable by color in one or more spectral bands. The feed from the hopper via the vibratory feeder and down the channel is all by gravity action. The flow of the products is only slowed from free fall by the friction caused by the bends and the surfaces of the path. The products do move, however, at a fast rate and in large quantity, as is well known in the art.
[0017] An optical viewer or sensor 20, described more fully below, is located toward the bottom part of the channel. As the flow of products passes past the sensor, any nonstandard or substandard products are sensed or detected. It will be appreciated that such sensing or detection requires the substandard products to be distinguished both from the standard products and the background. Typically, a substandard item, such as an edible bean, is detectable on the basis of its being darker or lighter or of a different color or hue from an acceptable range of darkness, lightness or color predetermined for standard or acceptable items. This sensing can be in a single spectral range for monochromatic detection, in two separated spectral ranges for bichromatic detection, or in a plurality of spectral ranges for multichromatic detection. It is understood that a "spectral range" can be wholly or partially in the visible spectrum or can be wholly or partially in the nonvisible spectrum. For example, sensing in the infrared range is commonly done. When a substandard product or item is sensed, an electrical signal is produced that results in an ejection of the substandard item by the actuation of an ejector mechanism.
[0018] An ejector 36 or product separator located underneath and adjacent optical sensor means 20 is actuated by the actuation electrical signal just mentioned to produce an air blast to remove the unwanted substandard product from the flow of products in the product stream. The ejector can be a mechanical ejector, if desired. When the actuation signal occurs, typically, a solenoid valve is operated to release or emit an air blast at the product stream to timely remove the substandard item. The delay in actuation is very short following the time of sensing, the timing being such to produce the desired expelling of the detected substandard item and is accomplished in a manner well known in the art. The items thus removed in the process fall down into reject accumulator 28 for subsequent disposal. The items not removed continue down channel extension 30 to be gathered or packaged as quality products passing the preset standards and avoiding removal. The control of the flow and the sensitivity of the sensors are controlled by preset controls that are well-known in the art.
[0019] Now referring to Fig. 2, the viewing or optical sensor and related components of the machine are illustrated as seen from above. Sensor means 20 generally is a ring-like structure with a center opening 32, the flow of the products to be separated or sorted as discussed above passing through the opening at a "window" location or plane. This is the electro-optical viewing station for the machine. The optical or viewing mechanism is well-known and generally includes three evenly, peripherally spaced individual sensors 37, each of which could include a photocell or photodiode. At least three lamps 38 are included in a plane, one for each individual sensor. Each lamp 38 projects a beam against a separate background 40, the reflection therefrom and from any products flowing between the background and the photocell sensor being detected by the sensor. The reason that three sensors are employed is to ensure sensing a substandard item that is detectable from only one direction and not necessarily from another direction. Only one lamp 38 is shown for each viewing combination of photocell sensor 37 and background 40. In actual practice, there are usually multiple lamps 38 for illuminating the product stream uniformly and the same or additional multiple lamps for illuminating the background uniformly.
[0020] Now referring to Fig. 3, a schematic side view illustration of a product stream of products 42 is shown passing by a source or lamp 38, as described above. The reflection of light from source 38 is from background 40 when no product interrupts the light from source 38, as shown by paths 44 and 46. Because the background matches the reflectivity characteristics of an acceptable product in each of the bichromatic bands or spectrum ranges, detector 48 and electronics 50 connected thereto react as if acceptable products are in view, which means that no ejection signal is produced. It should be noted that a detector 48 typically includes a photodiode or similar sensor, a beamsplitter and/or filtering system for separating the received light into the desirable spectral ranges. The electronics includes suitable amplifiers and level detectors for producing the desired ejector actuation at the appropriate delay time to eject detected non-acceptable products. All of the above is well-known in the art and need not be described further in detail.
[0021] Background 40 is comprised of two layers, namely, a first or forward layer 52 that receives the light from lamp source 38 first and is matched to be responsive to the shorter of the spectrum ranges employed in sorting the product. Normally, this will be in the visible spectrum range centered on a frequency that is known to cause an appreciable reflective response from an acceptable product. For example, for edible beans, a known operable sorting range in the visible spectrum is 400 nm to 500 nm. For another example, for sunflower seeds, a known operable sorting range in the visible spectrum is 600 nm to 700 nm. Layer 52 may be merely a matching paint applied to substrate layer 54, or it may be the thin film that is glued to the substrate of countertop laminate such as "Formica".
[0022] The longer wavelengths of the light from the source are normally in the infrared spectrum range and will penetrate first layer 52 without causing a response. However, the substrate or second layer 54 underneath layer 52 is selected to be reflective responsive to the second frequency or spectrum band of operation for the product being sorted. For example, for edible beans, a known infrared spectrum range that causes a suitable response is 1500 nm to 1600 nm. This response has been found to be produced by the wood and glue combination employed for the substrate of countertop material such as "Formica. For sunflower seeds, a known infrared spectrum range that causes a suitable response is 1500 nm to 1600 nm. This response has been found to be produced by the painted metal and glue employed for attaching the first layer to the second layer. The technical explanation may be overly simplistic; however, a large number of experiments verify the results, as described above.
[0023] It may be noted that because the substrate layer is protected by the top or first layer and, thus, does not degrade greatly in use except for age. That is, dust build-up is not usually a problem. In many cases since the first spectrum range is usually broader than the second, and dust build-up can be tolerated, not only is the match of the background with respect to the spectrum ranges better, as hereinabove described, the maintenance and control problems for the overall sorting machine are reduced with respect to using heretofore conventional backgrounds.
1. In a bichromatic sorting machine for color sorting a stream of fungible products,
selected from a group of products, each group differing from the other in wavelength
sorting requirements, passing an electro-optical viewing station into acceptable products
of predetermined acceptable color and reflectivity range and nonacceptable products
of a color or reflectivity outside of the predetermined acceptable color and reflectivity
range which comprises
a background for the electro-optical viewing station of the same acceptable color and reflectivity as within the range of acceptable color and reflectivity in a short wavelength range and within a long wavelength range for the acceptable products,
lamp means for reflecting light from the product stream in the short wavelength range and in the long wavelength range,
first and second optical sensors for respectively sensing the quantity of reflected light present in the short wavelength range band and the quantity of reflected light present in the long wavelength range band as the stream of products pass by the viewing station,
a comparator connected to each of the optical sensors and to a respective predetermined minimum standard level for determining if the quantity of light present in the respective short wavelength range band and long wavelength range band is above the respective predetermined minimum standard level, and
a product separator for separating products, from the stream of products, that reflect
light in the respective short wavelength range band and long wavelength range band
below either of the respective predetermined minimum standard levels,
the improvement in said background, which comprises
a first layer responsive to reflected light in the short wavelength range band and non-responsive and penetrable in the long wavelength range band to permit light in the long wavelength range band to pass therethrough, and
a second layer behind said first layer responsive to reflected light in the long wavelength range band.
2. A background in accordance with claim 1, wherein the short wavelength range band is
in the visible spectrum and the long wavelength range band is in the infrared spectrum.
3. A background in accordance with claim 2, wherein said first layer is a thin film and
said second layer is a different material from said first layer.
4. A background in accordance with claim 2, wherein said first layer is a plastic laminate
and said second layer is a wood/glue substrate.
5. A background in accordance with claim 2, wherein said second layer is a painted substrate
and said first layer is a thin transparent tape affixed to the surface of said second
layer.
6. A background for an optical sorting machine for matching the products to be sorted
therein in at least a short wavelength range band and a long wavelength range band,
which comprises
a first layer response to reflected light in the short wavelength range band and non-responsive and penetrable in the long wavelength range band to permit light in the long wavelength range band to pass therethrough, and
a second layer behind said first layer responsive to reflected light in the long wavelength range band.
7. A background in accordance with claim 6, where the short wavelength range band is
in the visible spectrum and the long wavelength range band is in the infrared spectrum.
8. A background in accordance with claim 7, wherein said first layer is a thin film and
said second layer is a different material from said first layer.
9. A background in accordance with claim 7, wherein said first layer is a plastic laminate
and said second layer is a wood/glue substrate.
10. A background in accordance with claim 7, wherein said second layer is a painted substrate
and said first layer is a thin transparent tape affixed to the surface of said second
layer.