Focal plane shutter device

Claim 1

IN A FOCAL PLANE SHUTTER DEVICE FOR CAMERAS, THE COMBINATION COMPRISING: A PAIR OF CURTAIN DRUMS SPACED IN PARALLEL RELATION TO EACH OTHER; A CURTAIN WOUND ENDWISE THEREBETWEEN AND HAVING AN APERTURE THEREIN; A SHEAVE COAXIAL WITH END OF SAID DRUMS AND SUPPORTING AN ENDLESS BAND THEREBETWEEN; A MASK FIXED TO SAID BAND ADJACENT TO THE APERTURE OF SAID CURTAIN DEFINING THEREBY THE WIDTH OF THE EXPOSURE SLIT DURING EXPOSURE; SPEED TRANSFORMING MEANS HAVING AN OUTPUT DRIVINGLY CONNECTED TO ONE OF SAID SHEAVES FOR TRANSPORTING THE MASK ACROSS A PICTURE FORMAT; EPICYCLIC GEAR MEANS AND LOST-MOTION MEANS CONNECTED IN SERIES BETWEEN THE OUTPUT OF SAID TRANSFORMING MEANS AND ONE OF SAID DRUMS FOR TRANSPORTING SAID CURTAIN IN UNISON WITH SAID MASK, SAID EPICYCLIC GEAR MEANS INCLUDING CARRIER ADJUSTING MEANS FOR VARYING THE POSITION OF SAID CURTAIN RELATIVE TO SAID MASK, AND SAID LOST-MOTION MEANS PROVIDING LIMITED RELATIVE MOTION BETWEEN SAID MASK AND SAID CURTAIN FOR OCCLUDING THE APERTURE DURING REWIND; A SPRING MOTOR DRIVINGLY CONNECTED TO THE INPUT OF SAID TRANSFORMING MEANS FOR TRANSPORTING SAID MASK AND CURTAIN IN ONE DIRECTION DURING EXPOSURE; AND REWIND MEANS OPERATIVELY CONNECTED TO ONE OF SAID SHEAVES FOR TRANSPORTING SAID CURTAIN AND MASK IN THE OPPOSITE DIRECTION DURING REWIND; SAID TRANSFORMING MEANS INCLUDING GEARS HAVING PITCH LOCI DETERMINED FOR TRANSLATING THE VELOCITY OUTPUT OF SAID SPRING MOTOR TO A CONSTANT VELOCITY AT SAID MASK; WHEREBY A UNIFORM EXPOSURE IS ATTAINED THROUGHOUT THE PICTURE FORMAT FOR ALL FILM SENSITIVITIES.