Camera shutter mechanisms

Claim 1

A FOCAL PLANE SHUTTER MECHANISM FOR AN AERIAL CAMERA AND THE LIKE, INCLUDING A PAIR OF ENDLESS OPAQUE FLEXIBLE BANDS DESIGNED TO MOVE ALONG A CLOSED PATH INTERSECTING THE FOCAL AXIS OF THE CAMERA TWICE, EACH BAND HAVING IN IT A NARROW APERTURE EXTENDING PERPENDICULARLY TO THE DIRECTION OF MOVEMENT OF THE BAND, AND A WIDE APERTURE HAVING ITS TRANSVERSE EDGES SPACAED FROM THE NARROW APERTURE BY UNEQUAL AMOUNTS, THE PAIR OF BANDS BEING DISPOSED SO THAT THE NARROW APERTURES IN THE BANDS ARE IN ALIGNMENT AND OVERLAP TO PROVIDE AN EXPOSURE SLIT DURING MOVEMENT OF THE NARROW APERTURES ALONG A FIRST PORTION OF THE PATH INTERSECTING THE FOCAL AXIS, AND SO THAT THE WIDE APERTURES ARE ALIGNED WITH EACH OTHER AND EXTEND OVER A SECOND PORTION OF THE PATH INTERSECTING THE FOCAL AXIS DURING MOVEMENT OF SAID EXPOSURE SLIT ALONG SAID FIRST PATH PORTION, WHEREBY WHEN THE MECHANISM IS DRIVABLY MOUNTED IN A CAMERA HAVING A TRAVELLING FILM AND A LENS SYSTEM, WITH SAID FIRST PATH PORTION ADJACENT TO THE FILM AND SAID SECOND PATH PORTION ADJACENT TO THE LENS SYSTEM, LIGHT IS PERMITTED TO FALL THROUGH BOTH PAIRS OF ALIGNED APERTURES ONTO THE FILM, THE PATH OF THE INNER BAND HAVING A CONVOLUTED PORTION AT EACH SIDE OF THE FOCAL AXIS, THE LENGTHS OF THE CONVOLUTED PORTIONS BEING UNEQUAL WHEREBY THE NARROW APERTURES ARE DISPLACED OUT OF ALIGNMENT WITH EACH OTHER DURING MOVEMENT OF THE NARROW APERTURES ALONG SAID SECOND PATH PORTION WHEREBY THE FILM IS MASKED AT ALL OTHER POSITIONS OF THE MECHANISM, THE MECHANISM INCLUDING MEANS TO DISPLACE THE PAIR OF BANDS AXIALLY RELATIVELY TO EACH OTHER TO VARY THE EFFECTIVE WIDTH OF THE EXPOSURE SLIT.