Patent Number: 039393550
Section: claims

1. In a lock assembly for securing an isotope source in a radioisotope camera shield, a pigtail extending from said source and adapted to extend and withdraw the isotope source relative to the camera shield,  a hollow lock casing adapted to be secured to the radioisotope camera shield and having a longitudinal lock chamber opening to the camera shield, and a lock barrel chamber extending at right angles with respect to said lock casing,  a stop on the source pigtail,  a lock barrel in said barrel chamber, and biased in an extended position relative to said lock barrel chamber,  a key cylinder in said lock barrel,  means operable by turning movement of said key cylinder to hold said lock barrel in a retracted position relative to said chamber or release said lock barrel to be extended from said chamber, and  three cooperating movable elements for locking and releasing said stop, two being operated by turning of the key cylinder and retracted or extended movement of the lock barrel and the third being operated by withdrawal tension on the pigtail and requiring an overt act on the pigtail in addition to turning of the key cylinder and release of the lock barrel to release the pigtail for extension outside of the camera shield for use. 2. The lock assembly of claim 1, wherein the first of said three cooperating movable elements includes a stop lever pivoted within said lock chamber and biased to engage said stop and retain the source pigtail within the camera, the second includes hook means pivoted to said lock barrel to depend therefrom into said longitudinal lock chamber and biased to engage and lift said stop lever out of the path of said stop on the source pigtail upon extended movement of the lock barrel with respect to the lock chamber, and the third includes a lock spool slidable along said lock chamber and biased toward the camera in locking position in the lock chamber and moved to release said stop lever by tension on the source pigtail and stop. 3. The lock assembly of claim 2, wherein the stop lever has a trip member thereon disposed intermediate the ends thereof and adapted to be engaged by said lock hook upon extensible movement of said lock barrel from said lock chamber and lift said stop lever out of the path of said stop on the source pigtail upon reverse movement of said lock spool away from the camera shield. 4. The lock assembly of claim 3, wherein spring means bias said lock hook to engage said trip member, second spring means bias said stop lever to engage said stop on said source pigtail, and wherein said trip member has an upper surface camming said lock hook to engage and lift said trip member and stop lever upon extension of said lock barrel relative to said lock barrel chamber. 5. The lock assembly of claim 4, wherein spring means stronger than the spring means biasing said lock lever to engage said truncated ball on the source pigtail, lift said lock barrel relative to said lock barrel chamber upon release of the lock barrel by the key and move said hook to engage said lock lever and move said lock lever upward to its upper limit of travel. 6. The lock assembly of claim 5, wherein said first and second springs are oppositely acting torsion springs and said third spring is at least one compression spring. 7. The lock assembly of claim 5, wherein the trip member is held from upward movement by said lock spool and released by reverse movement of said lock spool out of the path of said trip member. 8. The lock assembly of claim 7, wherein said trip member has a downwardly facing abutment surface adapted to be engaged by said lock hook and has an oppositely facing abutment surface adapted to be engaged by said lock spool to hold said stop lever in a locking position until reverse pull on said source pigtail removing said spool out of registry with said stop surface. 9. The lock assembly of claim 4, wherein said trip member has a downwardly facing abutment surface adapted to be engaged by said lock hook to lift said stop member upon extensible movement of said lock barrel, and has an oppositely facing abutment surface adapted to be engaged by said lock spool, and engaged by said lock spool by the bias of said lock spool toward said camera, to hold said stop lever in a locking position until reverse pull on the pigtail moving said lock spool out of registry with said oppositely facing surface of said trip member to release said trip member and lock lever and condition said lock lever to release said stop on said source pigtail upon a predetermined reverse pull on the source pigtail. 10. The lock assembly of claim 9, wherein the first and second spring means are oppositely acting torsion springs and at least one compression spring stronger than said torsion springs serves to extend said lock barrel upon release by the key cylinder. 11. The lock assembly of claim 10, wherein the barrel chamber has a shell therein forming a liner for said chamber and bearing for said lock barrel, wherein a guide connection is provided between said shell and lock barrel to guide said lock barrel for rectilinear movement relative to said shell, and wherein a pin and aperture lock is provided between said lock barrel and shell and retractable by turning movement of the key cylinder to a release position. 12. The lock assembly of claim 11, wherein stop means are provided engageable by said stop spool to prevent complete withdrawal of the source pigtail from the camera shield. 13. The lock assembly of claim 11, wherein the truncated ball is automatically trapped at the full retracted position of the pigtail and ball. 14. The lock assembly of claim 11, wherein means are provided to prevent depression of the barrel while the source pigtail is in exposed position.