Patent Number: 052723496
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus A of the present invention is shown in FIGS. 1, 2, and 3. The apparatus includes a housing 10 which is covered with a shield 12 preferably lead or another suitable material that can prevent the escape of harmful radiation. The housing 10 is manipulated by lifting on a bail 14 which is shown partially in FIG. 1. In essence, bale 14 is a rod that extends over the top of the housing 10 and is connected to the opposite side of housing 10. Guide tubes 13 engage rods (not shown) to align housing 10 with well 18 for attachment. This allows a hook or similar grasping device to be used to lift the entire housing 10, along with cover 16 shown in FIG. 3 into position above a well 18 (see FIG. 9). Typically, well 18 extends into a vessel or other storage container (not shown) and has an inner space 20 to accommodate belt 22 and the source holder 24 (see FIG. 4). When shipping the source holders 24 to a particular site for use in a well 18, the housing 10 has cover 16 mounted to brackets 26. A pair of pins 28 extend through openings 30 (see FIG. 1) to secure the rear of cover 16 while bolts 32, coupled with nuts 34 and washers 36 are used to secure the cover 16 to lugs 26. A door 38 is connected by hinges 40 to base 42. Thus, the apparatus A is completely enclosed during shipment due to the securing of cover 16 to base 42, and door 38 being in the closed position and secured to cover 16. A lock 44 can be inserted through opening 46 to secure door 38 in the closed position against cover 16. Housing 10 has a bottom flange, which is not shown in FIG. 1, but is similar in construction to flange 48 shown in FIG. 9. Thus, the outlet flange 48 connected to housing 10 on its underside is adapted to be directly or indirectly mounted to well 18, which is shown in FIG. 9. The apparatus of the present invention is moved into position by lifting on bail 14 and placing the outlet flange 48 into alignment with the well 18, and securing the two together with a suitable clamp or connector. At that point, the cover 16 can be removed after opening door 38. When the housing 10 is in the position for shipment, a frame 50, comprising a rear locking bar 52 and a source holder locking bar 54 and locking rods 56 is used to secure the source holders 24 in the position shown in FIG. 1. The frame 50 also includes shields 58, which are typically stainless steel encased lead. The shields 58 are shown cutaway in FIG. 1 to provide further clarity in the drawing, but are in fact continuous members that shift with respect to rods 56 when a lock (not shown) is removed from hasp 60. Removing the lock from the hasp 60 allows source holder locking bar 54 to come forward pulling forward the shields 58 so that slot 62 is exposed. It should be noted that slot 62 extends in opposite directions from well opening 64. Accordingly, with the locking rods 56 in the position shown in FIG. 1, the source holders 24 are locked in the position shown and cannot be moved into slot 62 for mounting to belt 22 lowering into well opening 64. This is because rods 59 extend through the holders of sources 24. In the open position, rods 56 no longer extend through the frames of sources 24, and shields 58 no longer block path 62. The housing 10 also features a frame 66 which holds a drum 68. Drum 68 is rotated by moving crank 70. Crank 70 can be locked into place by inserting a lock through the drum locking lever or hasp 72. Wound around drum 68 is belt 22. As shown in FIGS. 8 and 5, belt 22 has openings on repeating center lines. The openings consist of a large circle 74 (see FIG. 5) intersected by a smaller circle 76 to form one cohesive cutout which repeats itself on belt 22. Other opening shapes or methods of attachment may be used without departing from the spirit of the invention. It is desirable to get the source holders 24 from the position shown in FIG. 1 to the position shown in FIG. 4 so that they can be lowered into well 18 for use. The first step in accomplishing this is to pull back source holder locking door 54 which exposes slot 62 to opening 64. Thereafter, the sources 24 can be taken and raised up by a frame 25 (see FIG. 6) until segment 78 (see FIG. 6) of frame 25 is brought to the elevation of slot 62 for sliding therethrough into well 64. At this time, while segment 78 is translated through slot 62 toward opening 64, radioactive source 80, which is preferably held in a stainless tube with a tungsten shield, is still within the housing 10 which is fully shielded. As shown in FIG. 1, the source holders of the preferred embodiment must be rotated 90 degrees to get them to go onto belt 22. The attachment of source holder 24 to belt 22 is illustrated in FIG. 4. Each source holder has a pair of headed studs 82 which are positioned so that when placed in alignment with the openings 74 and 76 of belt 22, each headed stud 82 will project initially through the larger circular opening 74. Thereafter, the source holder is slid down so that each headed stud 82 engages the smaller circular opening 76 for support. While the insertion of the headed stud through large opening 74 and smaller opening 76 is ongoing, handle 84 is pulled back into the position shown in dashed lines in FIG. 4. Pulling back the handle 84 retracts pin 86. After the headed studs 82 have landed in the smaller opening 76, handle 84 is released. Spring 88 pushes pin 86 outwardly as shown in FIG. 4 until it occupies the larger circular opening 74 and abuts the headed stud 82. At that point in time, the source holder 24 is securely fastened to belt 22 and handle 84 is in the position shown in solid lines in FIG. 4. More of belt 22 can be played out by turning drum crank 70. As a result of turning drum crank 70, a weight 90 (see FIG. 7), which is attached to the end of belt 22, helps to pull the belt downwardly into the well 18 (see FIG. 9). Rotation of crank 70 allows the weight 90 to go through opening 64. Thereafter, at selective hole locations on belt 22, the appropriate source holder 24 can be moved through slot 62 into position for mounting according to the procedure previously described and shown in FIG. 4. A belt support bracket 92 backs up belt 22 so that when the headed studs 82 are pushed through large opening 74 to be secured into smaller opening 76 adjacent thereto, the belt is supported to facilitate the attachment process. The apparatus A of the present invention also has a feature to prevent dropping the source holders 24 into space 20 of well 18 (see FIG. 9). Referring to FIGS. 1 and 2, there is a safety door 94 which is shown in the closed position in FIG. 1. With door 94 in the position shown in FIG. 1, the upper end of the source holders 24 cannot fit down opening 64. When it is desired to lower a source holder 24 beneath opening 64, lever 96 is actuated which on the one hand releases pawl 98. Pawl 98 is normally engaged to ratchet wheel 100 so as to prevent downward progress of tape 22 into well 18 unless the pawl 98 is released from contact from ratchet wheel 100 due to the operation of lever 96. As seen in FIGS. 1 and 2, pulling upwardly or in a clockwise direction on lever 96 pulls up link 102 which is in turn pivotally mounted to rod 104 which is connected to door 94. Door 94 is biased to a closed position by spring 106. Accordingly, the procedure is to strongly secure a source holder 24 to belt 22 by the method previously described and illustrated in FIG. 4. Thereafter, lever 96 is actuated and while it is held up, crank 70 is rotated to lower the belt further into well 18 to facilitate placement of additional sources. Having reached the point of accurately placing each source on the belt with the proper spacing, it is desirable to suspend belt 22 in space 20 of well 18 (see FIG. 8). First, an upper stop block 109 is attached to belt 22 to support it from rollers 114 and 116. The housing 10 is lifted and a lower stop block 108 is attached to belt 22. Lower stop block 108 has a pair of pins 110 and 112 which are spaced the same distance as a pair of adjacent circular openings 74. Using pins 110 and 112, the lower stop block 108 is attached to belt 22 and ultimately comes to rest inside the opening 20 of well 18. If the suspension point of the sources 24 needs to be changed by moving the entire belt 22, this can be readily accomplished as shown in FIG. 8. Belt 22 is raised until lower stop block 108 is readily accessible. At that time, if the block needs to be lowered, thereby raising belt 22, pin 110 is pulled out and the block is rotated about pin 112 until pin 110 engages the next lower opening as illustrated in FIG. 8. The rotation can be reversed to effectively raise the lower stop block 106 with respect to belt 22 by leaving pin 110 secure while undoing pin 112 and rotating the lower stop block 108 upwardly until pin 112 can be reinserted into the next highest circular opening 74. While the lower stop block 108 is being secured, belt 22 is independently supported separately from upper stop block 109. This is best shown in FIGS. 1, 4, and 5. As seen in FIG. 1, belt 22 travels between a pair of rollers 114 and 116. Rollers 114 and 116 are supported in a guide roller assembly 118 and are capable of translating in the two positions in FIG. 5. The rollers 114 and 116 are mounted to pins 120 and 122, respectively. Springs 124 and 126 bias the rollers 114 and 116 into the position shown in FIG. 1 where upper stop block 109 rests against rollers 114 and 116 to effectively support belt 22 on the guide roller assembly 118. Thereafter, the remaining portions of belt 22 are played out of drum 68, and belt 22 is detached from the drum 68 by moving rollers 114 and 116 to the side while leaving upper stop block 109 on belt 22. Belt 22 is marked so that placement of lower stop block 108 is guided by the location of upper stop block 109 on belt 22. Housing 10 can be removed from well 18 with upper stop block 109 still attached. This also facilitates accurate sources 24 placement on reinsertion of the sources 24 after maintenance procedures. While this procedure is going on, it is preferred to have lower stop block 108 firmly in position supporting belt 22 within space 20 of well 18 as shown in FIG. 9. Having ensured that belt 22 is firmly supported by stop lock 108, the housing 10 can be removed after belt 22 is detached from drum 68. At this point, the rollers 114 and 116 are moved to the dashed position shown in FIG. 5 where they no longer support belt 22. Accordingly, the guide roller assembly 118 is a temporary support for belt 122 used during the removal process for housing 10. Having removed the housing 10 at flange 48, the remaining segment of belt 22 is straightened as shown in FIG. 10 and a housing 128 is placed over the extended section of belt 22 above lower stop block 108. For clarity, lower stop block 108 is not illustrated in FIG. 10. Those skilled in the art can appreciate that various means of attachment to belt 22 can be employed. It is the separate mounting of the sources 24 and the means of attachment to belt 22 as the belt is being lowered into well 18 that allows the use of a compact drum 68 and as a result a more compact housing 10. While a safety door 94 is illustrated, various other means of preventing the sources 24 from falling through opening 64 can be employed without departing from the spirit of the invention. Various different materials can be used for the components; however, the preferred embodiment for the belt is inconel and the preferred materials for the source holder are stainless steel in combination with a shield about source 130 (see FIG. 6) made of tungsten. The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.