Focal plane shutter

Claim 1

THE IMPROVEMENT OF A FOCAL PLANE SHUTTER ASSEMBLY COMPRISING A FOCAL PLANE SHUTTER SUPPORTING FRAME, FIRST AND SECOND SHUTTER CURTAINS MOUNTED FOR MOVEMENT IN SAID FRAME TO PROVIDE AN EXPOSURE FUNCTION, FIRST ROTATABLE CAM MEANS COUPLED TO SAID FIRST SHUTTER CURTAIN BY A CAM FOLLOWER AND GEAR TRAIN, SECOND ROTATABLE CAM MEANS COUPLED TO SAID SECOND SHUTTER CURTAIN BY A CAM FOLLOWER AND GEAR TRAIN, DRIVE MOTOR MEANS ADAPTED TO BE COUPLED TO SAID GEAR TRAINS FOR DRIVING SAID FIRST AND SECOND ROTATABLE CAMS AT THE SAME ROTARY VELOCITY, SELECTIVELY ACTUATABLE DIFFERENTIAL MEANS COUPLED TO THE GEAR TRAIN FOR SAID SECOND ROTATABLE CAM MEANS TO VARY THE PHASE RELATIONSHIP BETWEEN SAID FIRST AND SECOND ROTATABLE CAM MEANS TO THEREBY VARY THE SPACING BETWEEN THE EDGES OF SAID SHUTTER CURTAINS DAMPING MEANS POSITIONED BETWEEN SAID FIRST ROTATABLE CAM MEANS AND THE CAM GEAR FOR SAID SECOND ROTATABLE CAM MEANS AND IN FRICTIONAL CONTACT THEREWITH TO IMPROVE THE ACCURACY OF THE EXPOSURE FUNCTION, AND ROLLER MEANS FOR SAID CURTAINS COUPLED TO SAID GEAR TRAINS FOR EFFECTING THE DESIRED MOVEMENT OF SAID SHUTTER CURTAINS.