Abstract:
An apparatus and method for providing uniform X-Ray irradiation to material carried in a plurality of containers. The apparatus includes an X-Ray tube providing a linear source of irradiation and also a 4pi (360 degrees) irradiation. The material to be irradiated is placed in containers suspended on a vertical carousel wheel type structure. The individual containers are mounted receive irradiation throughout the rotation of the wheel. The tube is mounted approximately at the axis or center of the wheel. In operation, the containers of material are rotated around the tube, and due to their orientation and the 4 pi irradiation from the source, each and all the containers receive a uniform irradiation for the material contained therein.

Description:
[0001]    The present application is related to U.S. Pat. Nos. 6,212,255 and 6,614,876 issued to Randol E. Kirk, the inventor hereof, which patents are incorporated herein by reference. The present application is also related to U.S. Pat. No. 6,389,099 issued to Gueorgui Guerorguiv titled “Irradiation System and Method Using X-Ray and Gamma-Ray Reflector” and to US Patent Publication 2007/0025515 titled “X-ray Tube With Cylindrical Anode” issued to of Randol E. Kirk and Daniel F. Gorzen. In fact, the present application discloses one specific system wherein the X-ray tube with a cylindrical anode has an extremely beneficial use. US Patent Publication 2007/0025515 is also incorporated herein by reference. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    The present invention generally relates to a more efficient apparatus and method for irradiation of material utilizing X-rays. While the invention will be described for use for the sterilization of food products, the invention is also applicable to various fields in which efficient irradiation of material is in demand including industrial and medical sterilization. 
         [0003]    The FDA has approved the use of ionization radiation from three different sources of irradiation that produce essentially equivalent pathogen reduction. The three approved sources are gamma rays from radioactive cobalt-60 or cesium-137, linear accelerators producing electron energies less than ten million volts, and X-Rays generated from equipment energies of less than five million volts. 
         [0004]    Each of said types of sources are in present use throughout the USA for the sterilization of food products. The present invention utilizes an X-Ray source of irradiation that is believed to have a number of advantages over the other two types of sources that need not be discussed in detail herein. Such other sources are generally much larger in size and scale are much higher in initial cost, and pose higher safety hazards normally requiring more sophisticated irradiation protection. 
       SUMMARY OF INVENTION 
       [0005]    An apparatus and method for providing uniform X-Ray irradiation to material carried in a plurality of containers. The apparatus includes an X-Ray tube providing a linear source of irradiation and also a 4pi (360 degrees) irradiation. The material to be irradiated is placed in containers suspended on a vertical carousel wheel type structure. The individual containers are mounted receive irradiation throughout the rotation of the wheel. The tube is mounted approximately at the axis or center of the wheel. In operation, the containers of material are rotated around the tube, and due to their orientation and the 4 pi irradiation from the source, each and all of the containers receive a uniform irradiation for the material contained therein. 
         [0006]    The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompanying drawings, listed herein below, are useful in explaining the invention. 
     
    
     
       DRAWINGS 
         [0007]      FIG. 1  is a view of the X-Ray tube to show its elongated body; 
           [0008]      FIG. 2  is an isometric view of the X-Ray tube and the material holding containers positioned in the vertical carousel structure; 
           [0009]      FIG. 3  is a front view of the vertical carousel wheel structure; 
           [0010]      FIG. 4  is a side view of the wheel structure and the unique mounting or positioning of the X-Ray tube; and 
           [0011]      FIG. 5  is a graph showing the uniform source of irradiation provided to the containers in accordance with the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0012]    Refer first to  FIG. 1  that shows a side view of the linear source of irradiation comprising X-Ray tube  11 . This linear source of irradiation is the subject matter of the above cited publication number 2007/0025515 which publication is adopted herein by reference. X-ray tube  11  has a cylindrical housing  12  and includes an elongated filament  20  mounted within a perforated cylindrical and tubular anode  23 . In the embodiment of the X-ray tube  11  in  FIG. 1 , the length of the tube is 17.2 inches in length and 4.5 inches in diameter. Power to the tube is provided through a high voltage connector  22 . Tube  11  provides a linear, rather than a point source, of irradiation and a 4pi/360 degree emission. The tube is cooled by means of a water jacket  14  encircling the housing  12 . 
         [0013]    Tube  11  provides a 4 pi/360 degree emission utilizing basic concepts disclosed in the above cited references. In addition to the concepts of a linear anode disclosed in US publication 2007/0025515, reference is also made to U.S. Pat. No. 6,389,099 which discloses the concept of a radiation reflector. Reference is also made to U.S. Pat. No. 6,614,876 which discloses the concept of combining the radiation energy from multiple sources to irradiate a product as well as the concept of utilizing reflected photon energy from various surfaces to add to or combine with the direct radiation energy to provide enhanced irradiation. The linear tube  11  is a basic component of the method and apparatus of the invention, as will become clear. 
         [0014]    The graph of  FIG. 5  depicting rads output on its vertical axis of abscissa and length in centimeters on it horizontal axis of ordinates. The two plots in  FIG. 5 , line A and line B, depict the output of the X-ray tube  11  of  FIG. 1  for two modifications of the X-ray tube to measure the dose peak and uniformity of output of the tube. Referring still to  FIG. 1 , it has been found empirically that the dose peak and uniformity are dependent on at least three factors; the size and shape of the face of support  17  holding the filament  20 , the diameter of the perforated anode  23 , and the size and shape of the cap piece  19  on the distal end of the filament. It appears that the diameter and size of all three of the cited components contribute to shape the electron output of the tube and determine the field effect. 
         [0015]      FIGS. 2 ,  3  and  4  show the configuration of the inventive apparatus that comprises a rotatable mechanism for carrying product which is to be irradiated by the X-Ray tube  11 . Basically, the mechanism consists of a Ferris wheel type structure or system  16  having two spaced wheels  18  and  19  affixed to one another by braces or rods, generally labeled  21 . The product to be irradiated is set or placed in containers  24 . The embodiment of system  16  shown herein has six cylindrical containers. Each container is mounted on a respective cradle assembly  27 . The cradle assemblies  27  are mounted in a spaced pattern between the wheels  18  and  19  and along the periphery of the wheels, as clearly shown in the  FIGS. 2 ,  3  and  4 . 
         [0016]    The mounting of the cradle assemblies  27  is similar to that of a well known Ferris wheel; that is, each cradle  27  is swingably (the cradle can move back and forth as a swing about a mounting pivot pin) mounted on a horizontally extending axle (hung similarly to a Ferris wheel seat) so that the cradle center of gravity causes the cradle to maintain the similar orientation throughout its circular path around the periphery of the system. The cradle assemblies  27  are shaped to receive containers  24 , which may be cylindrical in shape. The containers  24  carry (contain) the product or goods to be irradiated. 
         [0017]    Refer now to  FIG. 1 , as well as to  FIGS. 2 and 3 . The X-ray tube  11  (tube housing  12 ) is mounted in a stationary position at the approximate center of the wheel structure  16  by a mechanical wheel and axle drive  23  to enable the wheel structure  16  to rotate about the tube housing  12  mount. The passive mounting or distal end of the axle  31  mounts wheel  19  to a suitable support, see  FIG. 2 . As can be appreciated, the axle  23  drives the wheel  18  which in turn is connected through rods  21  to move wheel  19  which is mounted on passive axle  31 . High voltage power to the high voltage connector  22  of tube  11  is connected through through known types of cables and insulating connectors generally indicated at  25 . 
         [0018]    Note now a unique feature of the structure of mechanism  16 . As best seen in  FIGS. 2 and 3 , the cylindrically shaped X-Ray tube  11  is mounted slightly off center of the wheel axis, indicated by dashed line  33  in  FIG. 2 . The orientation of  FIGS. 2 and 3  shows the tube  11  which is axially mounted in its housing  12  to be off centered below the axis  33 . The purpose for this construction will be explained herein below. 
         [0019]    In operation, product is placed inside the containers  24 . The product in containers  24  receives the radiation energy from tube  11  and is set or placed in the container and should not tumble or revolve within the container  24  when the cradle  27  and wheels  18  and  19  rotate the container. Recall the similarity to a Ferris wheel wherein a person sits in the seat in an upright position, and even though the person is rotated on and by the wheel the seat assembly enables the person to remain in an upright position. Similarly in the present structure, the container  24  is rotated by the wheels and is structured to retain its initial orientation to also retain the product in its initial orientation and position. 
         [0020]    However, because the container  24  is mounted to retain it&#39;s initial orientation the container seat does not move in an exact circle. The seat wobbles in its rotation, and is closer to the axis  33  of the wheel when it is above the axis and further from the axis when it is below the axis. In  FIGS. 2 and 3 , note see the axis of the labeled  33  and the imaginary dotted circle labeled  39  about the axis  33 . By reference to circle  39  it can be seen that the cradles  27  carrying the containers  24  rotate in a wobbling manner about circle  39 . 
         [0021]    A well known principle in X-ray technology is that radiation energy is related to the distance between the X-ray source and the product receiving the energy. (Assume for purposes of the following explanation that  FIG. 3  represents a clock face). In the inventive structure  16 , the side (say bottom side) of each of the containers  24  is closest to the tube  11  when the container is at its highest position (12 o&#39;clock position) and receives the most radiation energy from the tube. In contrast, the other side (say top side) of each container receives the least radiation when the container is at its lowest position (6 o&#39;clock position). This action would continue throughout each cycle for each of the containers. 
         [0022]    As alluded to above and as will be described further, the present invention provides an apparatus to assure that a more uniform irradiation is provided to all of the product in each container. Refer now mainly to  FIG. 3 . In operation, as the carousel  16  is rotated, the containers  24  are moved about the axis of rotation  33 . As the cylinders  24  are moved around axis  33  the side of each of the containers  24  facing the tube  11  changes. Note in  FIG. 3 , an imaginary dot “A” painted on the container  24  (for present explanation purposes) at the one o&#39;clock position points upwardly to the right. As the container  24  is rotated clockwise by the wheels, to the three o&#39;clock position, the dot “A” points to the right; at the five o&#39;clock position, the dot “A” points downwardly to the right. As the container continues to rotate, to the 11 o&#39;clock position the imaginary dot “A” is rotated almost back to its initial position. Note, of course that there are six containers  24 , all of which are moving concurrently and that the above explanation is applicable to each container as it moves about its circle. 
         [0023]    In  FIG. 3 , the axis of the wheels is labeled as  33 ; the stationary position of the X-ray tube  11  is indicated by imaginary dotted line circle  39 , and the wheels  18  and  19  move around the tube. If the tube were to be mounted on the axis  33  of the wheels, the distance between the tube  11  and each of the containers  24  would vary as the containers move around the tube. This is clearly indicated by the overlapping of the circular line  39  by containers at the one o&#39;clock position and eleven o&#39;clock position. If the tube  11  were mounted along the axis of the wheel, a higher amount of radiation energy would impinge on one side of the container  24 , mounted at the relative axis of the wheels simply because it is closer to the tube at that position. 
         [0024]    The inventor has found that a more uniform irradiation from the X-Ray tube  11  to the product in each of the containers  24  is obtained by mounting the tube  11  in a position that is offset from the axis of the wheels  18  and  19 , as clearly shown in  FIG. 2 . This feature is also indicated in  FIG. 3  by the dotted circle labeled  11 , that depicts the relative position of the tube. The distance that the containers  24  moved downwardly relative to the circle  39  can be calculated, or the axis  33  can be empirically determined. The tube is mounted in position, and offset downwardly from the axis  33  to compensate for the amount of variation in the relative position of a container in the twelve o&#39;clock position and a container in the six o&#39;clock position. The purpose, of course, is an attempt to maintain the distance of the containers from the X-Ray tube  11  relatively constant as each container is moved on by its cradle affixed to wheels  18  and  19 . 
         [0025]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.