Non-destructive inspection of material in container

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10/629,868, which was filed on Jul. 30, 2003 now U.S. Pat. No. 6,895,072, and is accordingly entitled to the benefit of and priority to U.S. Provisional Application 60/457,319. Both of the aforementioned applications are incorporated by reference herein.

[0002] This invention concerns the non-destructive inspection of materials housed in containers, and more specifically the inspection of such materials using X-ray beams.

[0003] Inspection of various production products has become increasingly important in recent years. Traditionally, product inspection has been limited to physical inspection of the product by a worker on the production line. Obviously, this form of inspection is less than optimal. As such, two more useful devices were developed and became the standard inspection apparatus: a check weigher and a metal detector. Each of these devices has its own inherent limitations, and even the system in combination lacked the ability to provide much information. Therefore, a need exists for an inspection system that can provide more detailed and variable data. The types and breadth of inspection data needed vary from product to product.

[0004] It is well-known to carry out non-destructive inspections of materials, including materials in containers, with X-ray beams. In general, a typical basic x-ray device is a linear array comprising a high voltage power supply to power a x-ray tube wherein a beam of x-rays is directed at the product. The x-ray beam passes through the product to ultimately impinge upon a sensor or sensors, such as a row of detector diodes. Such x-rays devices typically then display an image of the material based on the x-rays. This image can provide valuable information which a normal optical image cannot. The formation of images due to light or X-ray differs. The major difference is that optical images are created by light reflection on the object surface and X-ray images are formed due to X-rays absorption by passing through a material. Thus, an optical image gives information about the object's surface and an X-ray image supplies information about the inner structure of the object.

[0005] An X-ray image is a silhouette, where the degree of transparency is dependent on the density, thickness and the atomic number of the material. Using the current technology this information can be separated and coded into a false color. The atomic number information is coded into the hue value of a color image in HIS (Hue, Intensity, Saturation) format. The mixed information about the thickness and the density is coded into intensity of a color. A certain percentage of X-ray energy is absorbed by the material due to a process known as electron ionization. The amount of energy absorbed depends on the density and atomic number of the material. As a result, the detected X-ray attenuation provides a picture of the absorbed energy on the irradiated objects. Due to the absorbed energy being relative to the atomic number, it can be used in the material discrimination process.

[0006] In general, the lower the atomic number, the more transparent the material is to the X-rays. Materials composed of elements with a high atomic numbers absorb radiation more effectively causing darker shadows in an X-ray image. Substances with low atomic numbers absorb less X-ray radiation, hence their shadowgraph appears a lighter color. The absorption of the X-ray radiation by a material is proportional to the degree of X-ray attenuation and is dependent on the energy of the X-ray radiation and the following material parameters: thickness, density, and atomic number

[0007] A problem encountered when using such apparatus and systems, especially when inspecting food in containers, is that the geometry of the containers often causes undue lines in detector images thereof, which detract from the quality of such images and, therefore, negatively affect interpretations of the images. None of the apparatus and methods described in the above-mentioned patents adequately overcomes this problem. X-ray inspection of food products in glass jars to eliminate broken glass contaminants presents a unique challenge due to the crown typically found in the jar bottom. Single view systems are offered but the coverage on the jar bottom is limited as this crown will “hide” the contaminant resulting in the fact that the contaminant must be of a size large enough to extend above the crown as viewed by the x-ray system. These systems are designed with a geometry of shooting the x-ray beam parallel to the jar bottom. If the jar bottom were perfectly flat then 100% coverage of the jar bottom can be achieved. The amount of the crown ajar exhibits determines how much of the jar bottom a single view system can effectively inspect. The larger the crown, the less coverage of the jar bottom is achieved. Typical crowns range between about 4.0 mm and about 12.0 mm in height. A single view system well effectively cover, for example, about 40% of the jar bottom for a 4.0 mm crown height. This coverage is reduced as the crown becomes larger, for example, to about 20% for a crown of 12.0 mm.

[0008] Dual view x-ray systems are known where the x-ray beams are at a 90° angle from one and other, both beams being parallel to the jar bottom. This increases the coverage of the jar bottom to between 40% and 80% depending on the crown height. A number of the systems described in these patents employ two or more X-ray beams at substantial angles to one another for producing two or more images that can be interpreted from the two different perspectives. This increases an amount of information available for interpreting the images.

[0009] Thus, it is an object to provide an X-ray inspection apparatus (as well as a method) that produces an intuitive, easy-to-read detector image of material in conveyed containers.

[0010] According to an embodiment, an apparatus and method for non-destructive inspection of materials housed in containers are provided. The method includes orienting an X-ray beam emitter and detector to direct and detect a first X-ray apparatus on a first side of a conveyor along which the materials are conveyed. A second X-ray apparatus is located on the opposite side of the conveyor. Each X-ray apparatus is adapted to provide at least two X-ray beams, such as through the use of a dual beam generator, with each X-ray beam having a corresponding X-ray detector. For example, the X-ray apparatus may be adapted to have four X-ray detectors. In a preferred embodiment, by using two x-ray apparatus located on opposite sides of a conveying line, each having two detector apparatus in association therewith, the present invention is able to provide an improved image of the bottom crown of a container. Preferably, the two X-ray beams on each side of the conveyor are angled 45° with respect to each other (22.5° with respect to the conveyor).

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

[0021] The present invention provides a system and method which eliminate the “hidden” areas of the prior art systems by orienting the x-ray beams to be parallel to the slope of a crown 10 in the container 16. In one embodiment illustrated in FIG. 2, system has a structure of two x-ray apparatus 42a and 42b oriented on opposite sides of the conveyor 20 traveling through the system. Each apparatus emits a dual beam at 45° from one and other. Four x-ray sensor devices 14a, 14b, 14c, 14d are placed on the opposite side of the conveyor from their respective tube. This inspection structure with two dual beam tubes and four sensors allows substantially 100% inspection of the glass jar bottom.

[0022] FIG. 1 depicts the area of a crown 40 detected by an apparatus of the prior art. The prior art apparatus does not provide adequate detection as it is capable of detecting only a small portion of the area below the crown 40, and the angle of crown creates difficulty in obtaining a clean image of even that area.

[0023] FIG. 3 depicts a first view of a four view (i.e. four beams and detectors) system. This view provides a full coverage of 40% of the jar bottom that is on the detector side of the conveyor. The second view shown in FIG. 4 also covers 40% of the jar bottom but is at a 45° angle from the first view and thus shifts the full coverage by 45°. The combination of these two views results in full coverage of 60% of the jar bottom with an overlap between the two views.

[0024] The third view shown in FIG. 5 represents the results of a detector on the opposite side of the conveying line in regard to the detectors shown in FIGS. 3 and 4. This view provides full coverage of 40% of the jar bottom, opposite the first view by changing the tube/detector relationship such that the x-ray beam is shot from the opposite side of the jar. The result is picking up an additional 20% of the jar bottom for full coverage and adding to the overlap. The fourth view shown in FIG. 6 adds the final 20% of the jar bottom for full coverage.

[0025] Combining the four views, as shown in FIG. 7, allows for each individual view to be optimized for the 40% of the jar bottom that the view is inspecting and ignoring the 60% of the jar bottom because the addition views will cover that area. Thus an improved image of substantially 100% of the jar bottom is obtained with no shadows or hidden areas.

[0026] While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

[0027] In addition, an apparatus and method in accordance with the principles of the present invention may further comprise various additional inspection features such as but not limited to check-weighing capability, missing item detector, void detection, and reject stations. The reject station may utilize, but is not limited to, a signal only, an indicator light, a single lane air blast, a single piston side push arm, a vertical side impulse push arm, or a horizontal side impulse push arm.

[0028] Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.