Patent Number: 043141579
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the figures and particularly to FIG. 1, a radiography exposure device 20 is depicted. The device 20 includes a pistol grip cable drive 22, the safety lock 24 of the invention, a shield 26 and a source of radiation 28 which is shown extended from the shield 26. The pistol grip cable drive 22 includes a pistol grip 30 and a crank 32 rotatably mounted thereto. Crank 32 can extend radiation source 28 from shield 26 when it is turned in the indicated clockwise direction and can retract source 28 into shield when the crank is turned into the indicator counterclockwise direction. Cable drive 22 further includes cable guide tubes 34 and 36. Guide tube 34 is connected to lock 24 and guide tube 36 is positioned dependently below guide tube 34. When the radiation sources is being extended from the shield 26, the cable 38 upon which the radiation source 28 is mounted moves from cable guide tube 36 around crank 32 and through cable guide tube 34. When the source 28 is being retracted into shield 26, the cable 38 moves through cable guide tube 34 around crank 32 and is stored in cable guide tube 36. It is to be understood that the radiographer or operator of the radiography exposure device for purposes of safety stands many feet away from the shield 26 when the source 28 is extended therefrom in order to make the above reference inspections. Thus, the cable guide tubes 34 and 36 are many feet long so that the pistol grip 30 is quite removed from the shield 26. Further as the source 28 must in some instances be moved many feet outside of the shield in order to be correctly positioned for making the necessary inspections, the cable guide tube 36 must be sufficiently long to store the excessive cable length as the source of radiation 28 is retracted into the shield 26. Examining the shield 26 and the safety lock 24 of the invention, it can be seen in FIG. 2 that the shield 26 includes a housing 40 and a carrying handle 42. An S-shaped tube 44 is provided in the housing 40 for receiving the source of radiation 28. S-shaped tube 44 is comprised of titanium in a preferred embodiment. It is to be appreciated that the radiation source 28 is held in the middle of the S-shaped tube in the locked or stored position to further isolate the radiation source from the openings at the end of said S-shaped tube which are then not in line with said radiation source. Surrounding the S-shaped tube 44 is radiation shield material 46 which isolates the radiation source 28 from the environment. Radiation shield material 46 is supported and cushioned by foam material 47. As presented in FIG. 2, the shield 26 contains the radiation source 28 in a locked and secure position so that the shield and the source can be transported to the work site. For the purpose of transportation, the cable 38 includes a disconnectable pig tail 48 onto which the radiation source 28 is mounted. A cable connector 50 is located on the opposite end of pig tail 48 from the radiation source 28. As can be seen in FIG. 4, connector 50 includes a housing 51 which contains a spring biased pin 53 which is actuated by peg 55. With pin 53 moved rightwardly in FIG. 4 a mating end of the cable 38 can be inserted in slot 57 defined by housing 51. When peg 55 and thus pin 53 are released, cable 38 is positively locked in connector 50. Spaced from the radiation source 28 is a stop 52 which is selectively trapped by the safety lock 24 of the invention, as will be discussed hereinbelow. For purpose of transportation, a cap 54 is placed over the connector 50 to prevent dust and other contaminants from entering the safety lock 24. Additionally, for purposes of safety and transportation, a safety plug 56 is inserted into the end of the S-shaped tube 44 from which the radiation source 28 extends. Safety cap 56 includes a short pig tail cable 58 with a blunted end 60. End 60 is positionable immediately adjacent the radiation source 28, in the middle portion of the S-shaped tube 44, for purposes of isolating and positively positioning the radiation source 28 during transportation of the shield 26. FIG. 3 depicts an end elevational view of the shield 26 with the cap 54 placed over the end of the connector 50. Turning to FIG. 4, an exploded perspective view of the safety lock 24 of the invention is depicted. Safety lock 24 includes a lock housing 62 which is welded along line 64 to the housing 40 of the shield 26 with a heli-arc welding technique so the lock housing cannot be easily removable from the shield 26. Safety lock 24 further includes a locking means on cylindrical key lock 66 having key 68, which locking means 66 is received in a first bore 70 defined by the lock housing 62. Bore 70 is counter sunked to receive the flange portions of the key 68. Key 68 is of the type having a cylindrical barrel 72 which is received in annular channel 74. Cylinder barrel 72 includes teeth (not shown) on the internal surface thereof, which teeth mate with the cylinder key lock housing 69 to allow an internal portion 76 of the cylinder key lock 66 and pin 77, eccentrically mounted to internal portion 76, to turn as key 68 is turned. Upstanding from cylinder barrel 72 is a tab 78 which is slidable into a key way 80. When the key 68 is inserted in the cylinder key lock housing 69 and turned to effect turning of the eccentric pin 77, tab 78 lockingly secures key 68 in housing 69. The non-rotating outer portion of housing 69 is positionably secured with respect to the housing 62 of the safety lock 24 by a set screw 82 received in threaded bore 84. Located immediately below cylindrical key lock 66 is the means 86 for receiving the stop 52 of the pig tail cable 58. Said receiving means 86 includes a retaining cylinder 88 defining a central threaded bore 90 for receiving a mating end of cable guide tube 34. Further, receiving means 86 includes a spring 92 and a annular receiver 94 having a central bore 96. Receiving means 86 is received in a second bore 98 defined by lock housing 62. Further, housing 62 defines additional bores 100, 102 and 107 which communicate with bore 98. Bore 96 of receiver 94 is aligned with bore 100 and engaging means or pins 104 and 105, extending from receiver 94, are received through bores 102 and 107. As will become apparent hereinbelow, pin 104 extends farther from receiver 94 than does pin 105. The spring 92 is held between retaining cylinder 88 and receiver 94 in bore 98 and said retaining cylinder 88 is held in position relative to bore 98 by a plurality of said set screws 106. Safety lock 24 includes a trapping means 108 which includes a slide 110 received in a rectangular passage 112 defined by lock housing 62. As can be seen in FIG. 4, bores 70 and 98 are substantially parallel to each other and perpendicular to slide 110 and passage 112. The upper end of slide 110 includes an indicator tab 111. Slide 110 includes a first aperture 114 which has a first substantially vertical and elongate aperture portion 116 and a second sloping and elongate aperture portion 118 directed downwardly from the upper most portion of the vertical portion 116. Slide 110 further includes an additional elongate bore 120 which is positioned to selectively receive the end of pin 104 which extends from annular receiver 94. Located adjacent the bottom portion of slide 110 is an indentation 122 which can selectively receive the end of pin 105. Adjacent indentation 122 and communicating with the lower edge of slide 110 is an additional aperture 124. Additional aperture 124 includes an upper portion 126 which is sized to receive pig tail cable 48 but not stop 52 and a middle portion 128 which is sized to receive stop 52 which communicates with upper portion 126. Further, aperture 124 includes a lower portion 130 which communicates with middle portion 128 and with the lower edge of slide 110. Lower portion 130 is sized to receive the pig tail cable 48 but not the stop 52. Slide 110 is biased upwardly in rectangular passage 112 by a spring arrangement 134. Spring arrangement 134 includes a spring 136 and a guiding and supporting elongate pin 138. Spring 136 and pin 138 are received in passage 112 with the head of pin 138 being received in an indentation 140 which communicates with said passage 112. Further, an end of spring 134 contacts a shoulder 141 of slide 110. OPERATION OF THE INVENTION The fully locked position for the safety lock 24 is shown in FIGS. 9 and 10. As can be seen in FIG. 9, in the fully locked position, the key 68 can be removed from the key housing 69, so that said key can be stored separately from the exposure device 20 so that no unauthorized use can be made of the device. Further as the key is a cylinder type strong box key the likelihood of the cylinder lock 66 being opened by available substitutes for the key are remote. With the source 28 in the locked position, eccentric pin 77 is positioned in the lower end of the sloping portion 118 of aperture 114 to lock slide 110 in its lower most position. Simultaneously stop 52 is received in bore 100 and against receiver 94 and is retained therein as the upper portion 126 of aperture 124 is aligned with the bore 100 restricting the movement of stop 52. Pin 104 is urged through elongate bore 120 by the spring 92. To unlock the safety lock, the key 68 is inserted into the cylinder housing 69 and given a quarter turn to the right so that pin 77 is positioned at the upper end of the vertical portion 116 of aperture 114. Crank 32 is then cranked so that cable 38 is retracted, causing the stop 52 to urge annular receiver 94 rearwardly compressing spring 92 against receiving cylinder 88. As this occurs pin 104 is removed from elongated bore 120 and spring 136 urges slide 110 upwardly until slide 110 is stopped by eccentric pin 77 contacting the lower end of vertical portion 116 of aperture 114. With the slide 110 in this position (FIGS. 5, 6), tab 111 extends furthest from housing 62 and gives a visual indication to the operator that he is operating safety lock 24. Stop 52 is still trappingly retained in bore 100 by the lowermost portion 130 of additional aperture 124. At this point pin 104 is first received in aperture 124 between upper portion 126 and middle portion 128. In order to untrap the stop, the operator must urge the slide 110 downwardly into position as shown in FIGS. 7 and 8 so that pin 105 is received in indentation 122 so as to determine the position of slide 110. With slide 110 in said position, the middle portion 128 of aperture 124 is aligned with bore 100 so that crank 32 can urge stop 52 through said middle portion into the S-shape tube 44 of the shield 26 and simultaneously urge the source 28 out of the shield 26. It is to be understood, that in the positions shown in FIGS. 5, 6, 7, and 8, key 68 cannot be removed from the key housing 69 and thus no authorized copies of said key can be made. After the radiography procedures are performed, the source 28 is retracted back into the shield 26 and the stop 52 is drawn through the middle portion 128 of the aperture 124 until it rests in bore 100. Retraction of stop 52 urges annular receiver 94 against spring 92 and receiving cylinder 88, so as to remove pin 104 from indentation 122 allowing spring 138 to urge slide 110 upwardly until tab 111 is in its upwardly most position as shown in FIGS. 5 and 6. Again, there is visual indication given by tab 111 that the stop 52 and thus the radiation source 28 are in the trapped position. At this point either the slide 110 can be reset into the positions of FIGS. 7 and 8, to allow the source 28 to be again extended from the shield 26 to do additional radiography, or lock 24 can be operated to place the slide in the positions of FIGS. 9 and 10 preparatory to removing key 68. It is to be understood that with the lock in the position as shown in FIGS. 7 and 8, the stop 52 can always be received in the bore 100 so as to trap the stop 52 and thus the radiation source 28 in the shield 26 each time the source 28 is retracted into the shield 26. Thus, the safety lock does not prevent the return of this source to the shielded position. Assuming that the radiography procedures are completed, and that the source is to be locked in the trapped position, tab 111 of slide 110 is urged downwardly after the cable has been retracted so as to remove pins 104 and 105 from the path of slide 110. Thus, slide 110 can be urged downwardly against spring 136 until eccentrically mounted pin 77 contacts the upper most portion of vertical aperture portion 116. In this position, upon the release of cable 38, the pin 104 is urged by spring 92 into elongated bore 120 as can be seen in FIGS. 9 and 10. The shorter pin 105 contacts the side of slide 110 at a point spaced from indentation 122. With the slide in this position the key can be turned in a counterclockwise manner to lock the slide in position. With the eccentrically mounted pin 77 in the position shown in FIG. 10, the key 68 can be removed from the lock. It is to be understood that bore 96 of annular receiver 94 has a diameter which is smaller than stop 52. Thus the source 28 can not be removed through the back of the safety lock through bore 96 even when the safety lock is in the unlocked and untrapped position. As it can be seen that the above safety lock meets all the guidelines set forth by the Nuclear Regulatory Commission and is simpler and more efficient than the existing prior art. In particular, the present lock includes a housing 62 which is not easily removable from the shield with readily available tools as the housing is heli-arc welded to the shield, and thus, when the safety lock 24 is locked, it is difficult to remove the source of radiation from the shield except with the correct key. Also, the safety lock 24 does not prevent the return of the source into the shielded position as the safety lock only traps the stop 52 when it is in the position as indicated in FIGS. 5 and 6 so that the source of radiation is in the middle portion of the S-shaped tube 44. Additionally, it is not possible to unlock the safety lock 24 with an easily available substitute for the key as the key 68 is a cylinder type strong box key. Further, it is to be understood that it is not possible to operate the cylindrical key lock 66, due to the arrangement of slide 110, to remove said key 68 from key housing 69 until the stop 52 is trapped by slide 110 and thus until the source is in the fully shielded position in shield 26. Finally the tab 111 provides an indication of the position of source 28 and also the state of safety lock 24, thus reducing the chance of inadvertent exposure of the radiographer to the source of radiation. Other aspects, objects and advantages of the invention can be obtained from the study of the drawings, the disclosure and the appended claims.