Patent Number: 039393550
Section: description

DESCRIPTION OF PREFERRED EMBODIMENT OF INVENTION In FIG. 1 of the drawings, I have illustrated a radioisotope camera 10 forming an isotope shield and having an S-shaped shielded passageway 11 extending from the front to the back of the camera and shielding a radioisotope source 13 in the camera when not in use. The camera is of a form generally well-known to those skilled in the art, and has bracket plates 15,15 at opposite ends of the camera extending above the camera proper and forming a support for a handle 16. The handle has an externally threaded coupling 17 at one end and an internally threaded coupling 18 at its opposite end for respectively detachably holding a safety plug 19 and a safety cap 20. The safety plug 19 is adapted to be threaded on a coupling 21 in communication with the exit end of the shielded passageway 11. The safety cap 20 is adapted to be threaded within the enlarged diameter end of a passageway 22 (FIG. 2) leading into a lock casing 23 in axial alignment with the locked end of the shielded passageway 11, as indicated by broken lines in FIG. 1. The handle 16 thus provides a convenient means for carrying the safety plug 19 and safety cap 20 to be attached to the camera and the lock casing 23, respectively, when the radioisotope source is not in use, as well as a carrying means for the camera. The source 13 is suitably coupled to the end of a flexible pigtail 25, shown as being in the form of a tube and extending along the shielded passageway 11 and through and to the outside of the lock casing 23. The pigtail 25 has a truncated ball 27 (FIG. 2) connected thereto intermediate its ends, forming a stop for the pigtail and accommodating turning of the pigtail to position a coupling 29 on the end of the pigtail in a convenient position to be coupled to its drive cable 29a to extend and retract the isotope source from or within the shielded passageway 11. The isotope source and pigtail are extensibly and retractably moved by a conventional cranking mechanism which is no part of the present invention, so need not herein be shown or described. The source pigtail 25 and truncated ball 27 extend along a hollow interior lock chamber 30 of a lock spool 31 movably mounted in the hollow interior portion of the lock casing 23. The lock spool 31 has an interior shouldered portion 32 forming a stop for the truncated ball 27 and pigtail 25. A cooperating stop lever 33 is bifurcated at each end and is pivoted to a transverse pivot shaft 34 for movement about an axis transverse to axial movement of the pigtail and truncated ball 27. The stop lever 33 extends through a slotted portion 35 of the lock spool into the hollow interior portion thereof and has spaced abutment surfaces 36. The abutment surfaces 36 form locking surfaces for the truncated ball 27, to hold said ball 27 in its locked position in the lock casing 23. The pivot shaft 34 is spaced from the end plate 15 of the camera shield by spaced brackets 37 extending from the end plate 15 into the hollow interior of the lock casing. A torsion spring 39 encircles the pivot pin 34 and abuts an interior wall 28 of the lock casing 23 and an abutment wall 40 between the furcations of the stop lever 33 to bias the stop lever in a clockwise direction into the locked position shown in FIG. 2. As shown in the drawings, the lock spool 31 has a keyway 41 in its bottom surface for dirt passage during compressed air cleaning operations, the compressed air exiting through the passageway 22. The lock spool 31 also has a plurality of sockets 43 therein for springs 44 biasing said stop spool towards the end plate 15. The lock casing 23 has a right-angled hollow boss 38 in communication with the interior of the lock casing. The hollow interior portion of the boss 38 forms a chamber for a lock barrel 45. The lock barrel 45 is slidably carried in an outwardly opening shell 46 retained to the hollow interior portion of the boss 38 as by a set screw 47. The lock barrel 45 is slidably guided for rectilinear extensible movement relative to the shell 46 by a pin 48, which may be a machine screw extending from the lock barrel and slidably guided along a slot 49 in the shell, to not only accommodate extensible and retractable movement of the lock barrel 45 along the shell, but also to retain the lock barrel to the shell. The lock barrel 45 forms a barrel for a key cylinder 50 (partially shown) and turned by a key 51. The key cylinder contains the usual tumblers which are effective for withdrawing a pin 53 from an apertured portion 52 in the shell 46 to accommodate extension of said lock barrel relative to the shell 46 and to hold said lock barrel in an innermost retracted position relative to the shell. The key cylinder 50 is a conventional key cylinder carrying tumblers (not shown), effective to withdraw the pin 53 from the shell 46 by turning movement of the key 51. The lock barrel 45 is biased by a plurality of springs 54 to be extended from the shell 46 when the pin 53 is withdrawn from the shell 46. These springs are stronger than the torsion spring 39, to effect release of the lock upon withdrawal of the pin 53 from the apertured portion 52, as will hereinafter more clearly appear as this specification proceeds. The key 51 and key cylinder 50 form no part of the present invention, except to control the pin 53 to form a selective lock for locking the lock barrel in its retracted position, so need not be shown or described further. The lock barrel 45 has a bifurcated hanger 59 extending downwardly therefrom into the hollow interior portion of the casing 23, when the lock is in its locked position. The hanger 59 forms a mounting for a pivot pin 60 for a lock hook 61. Said lock hook has a hooklike lower end and extends between the furcations of the stop lever 33. A torsion spring 63 turned about the pin 60 biases said lock hook in a direction shown in the drawings as a counterclockwise direction to engage a downwardly facing abutment portion 65 of a trip member 64. The trip member 64 is carried by the stop lever 33, between the furcations thereof. Said trip member 64 also has an upwardly facing stop portion 66 on its side opposite from said abutment portion and adapted to engage under an abutment 67 in the locking spool 31. This holds the stop lever 33 from release, as the hook 61 engages beneath the abutment portion 65 of the stop lever 33, upon release of the barrel 45 by turning movement of the key 51, from the solid line position shown in FIG. 1 to the dotted line position shown in this figure and the solid line position shown in FIG. 5, until tension is placed on the coupling 29. Movement of the spool 31 in a direction which, in FIG. 2 is to the right, releases the stop portion 66 from the lock spool and accommodates the hook 61 to lift the stop lever 33 to its released position upon extensible movement of the lock barrel by the springs 54. It should be understood that the springs 54 are stronger than the torsion spring 39, to assure lifting of the lock lever out of registry with the lock spool upon extension of the lock barrel 45 relative to the shell 46. To release the lock, the pin 53 is released from the aperture 52, by turning of the key 51 to the dotted line position shown in FIG. 2. The springs 54 (FIG. 3), are stronger than the spring 39, and will then lift the lock barrel 45 from the shell 46 and position the lock hook 61 to engage under the abutment portion 65. As tension is applied to the coupling 29 to release the stop portion 66 from the abutment 67 of the lock spool 31, the lock hook 61 will raise the stop lever 33. The sequence of releasing the lock, therefore, is that as the key is turned to a release position, the lock barrel 45 will rise half of its total movement. The hook 61 will then engage the abutment portion 65, the stop portion 66 being restrained by the abutment 67 as the spring 54 pushes the lock barrel 45 upwards. Tension on the coupling 29 will then move the spool 31 to the right. This will allow the stop lever 33 to be raised by the hook 61 as springs 54 move the lock barrel 45 upward. It may be seen from FIGS. 3 and 4 that as the lock barrel is extended relative to its shell and lifts the stop lever 33 into the position shown in FIG. 3, the spring 44 biasing the lock spool 31 toward the end plate 15 of the camera, will move the lock spool 31 into the extreme position to the left, as shown in FIG. 4. Upon movement of the lock spool 31 from the position shown in FIG. 3 to the position shown in FIG. 4, the lock spool 31 will cam the lock hook 61 to release said lock hook from the trip member 64 and accommodate the trip member 64 to rest on the top surface of the lock spool 31, as biased into engagement with said top surface by the torsion spring 39. The isotope source 13 and pigtail 25 may then be extended from the camera by cranking to a position of use. The truncated stop ball 27, however, limits the amount of withdrawal of the isotope source and prevents complete withdrawal of the source pigtail 25 from being drawn to the right through the lock casing and camera. It should further be understood from FIG. 5 that the isotope source is withdrawn in the camera shield and the truncated stop ball 27 comes into engagement with the interior shouldered portion of the stop spool 31 and moves said spool 31 against the bias of the spring 44 from the position shown in FIG. 4 to the position shown in FIG. 5, that the stop lever 33 will be released from the spool and the torsion spring 39 will move the stop lever 33 into position to place the abutment surfaces 36 thereof to stop movement of the stop ball 27 toward the camera. The isotope source thereby is automatically locked in the camera, even though the lock barrel is extended. This acts as a safeguard to prevent unintentional release of the isotope source from the camera shield when once withdrawn. As, however, the lock spool 31 is moved to the right by reverse cranking of the source pigtail, the stop portion 66 of the trip member 64 will be released from the abutment 67. The torsion spring 63, biasing the lock hook 61 against the upper inclined surface of the trip member 64, will hold the stop member in its locking position as biased in such a position by the torsion spring 39 until depression of the lock barrel and then the extension of said lock barrel by the springs 54. It will further be understood from FIG. 4 that the barrel 45 cannot be depressed to a lock position while the ball 27 is in the position shown or extended from the camera. Depressing the barrel 45 moves the lock hook 61 through the stop lever 33 to rest on top of the spool 31. The hook cannot engage the abutment portion 65 at this position and the lock barrel 45 returns to its up position upon pressure release.