Radioactive source housing with remotely operated shutter

Claim 1

A RADIOACTIVE SOURCE HOUSING COMPRISING, A FRAME MEMBER; FIRST AND SECOND PULLEY ELEMENTS ATTACHED TO SAID FRAME MEMBER, EACH OF SAID PULLEY ELEMENTS BEING ADAPTED FOR FREE ROTATION ABOUT ITS OWN AXIS; A SHUTTER MEMBER PIVOTALLY ATTACHED NEAR ONE END THEREOF TO SAID FRAME MEMBER; A THIRD PULLEY ELEMENT ADAPTED FOR FREE ROTATION ABOUT ITS OWN AXIS AND DISPOSED INTERMEDIATE SAID FIRST AND SECOND PULLEY ELEMENTS, SAID THIRD PULLEY ELEMENT BEING ADAPTED FOR TRANSLATIONAL MOTION WITH RESPECT TO SAID FRAME MEMBER; GUIDE MEANS ADAPTED TO LIMIT THE TRANSLATIONAL MOTION OF SAID THIRD PULLEY TO A PREDETERMINED PATH; MEANS CONNECTING SAID SHUTTER MEMBER TO SAID THIRD PULLEY SUCH THAT WHEN SAID THIRD PULLEY IS IN A FIRST POSITION ALONG SAID PREDETERMINED PATH, SAID SHUTTER MEMBER IS IN ONE POSITION AND WHEN SAID THIRD PULLEY IS IN A SECOND POSITION ALONG SAID PREDETERMINED PATH, SAID SHUTTER MEMBER IS IN A SECOND POSITION; A CABLE MEMBER THREADED AROUND SAID FIRST, SECOND, AND THIRD PULLEYS SUCH THAT WHEN SAID CABLE IS TAUT, SAID THIRD PULLEY IS PLACED IN SAID FIRST POSITION ALONG SAID PREDETERMINED PATH; MEANS CONSTRAINING SAID THIRD PULLEY TO REMAIN IN SAID SECOND POSITION ALONG SAID PREDETERMINED PATH WHEN SAID CABLE IS NOT TAUT; ACTUATING MEANS SEPARATE FROM SAID FRAME MEMBER AND ADAPTED TO TAUTEN AND LOOSEN SAID CABLE; A RADIOACTIVE SOURCE EMITTING A BEAM OF PENETRATING RADIATION, SAID SOURCE BEING DISPOSED RELATIVE TO SAID SHUTTER MEMBER SUCH THAT SAID SHUTTER MEMBER ABSORBS SUBSTANTIALLY ALL OF SAID BEAM OF PENETRATING RADIATION ONLY WHEN SAID SHUTTER IS IN SAID ONE POSITION CORRESPONDING TO SAID FIRST POSITION OF SAID THIRD PULLEY.