Film exposure counter
US4814805A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 4, 1988 |
| Grant date | Mar 21, 1989 |
| Priority date | — |
| Expiry date | Feb 4, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B1/66
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Automatic film advance in a camera to wind a film leader onto a take-up spool requires that an override switch be temporarily closed to nullify a film metering switch. Otherwise, the metering switch will de-energize a motorized film drive after the film leader is advanced only a single frame width, rather than the required several frame widths. To ensure that a mechanical exposure counter is rotated sufficiently from an initialized setting to close the override switch, when a drive member for the counter is rotated less than its normal distance because of lost motion in actuating the drive member following previous rewind of an exposed film off the take-up spool, the drive member and the counter include cooperating means adapted to rotate the counter the same angular distance from its initialized setting as the angular distance the counter is rotated from successive settings, with less rotation being required of the drive member during its first revolution.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.