It is known in the art relating to film transparency viewers to provide a viewer for viewing transparencies contained on a filmstrip. It is further known, relative to filmstrip viewers, to use a filmstrip that is stored in a conventional film cartridge in which a leader portion of the film extends externally for use in attaching the cartridge held film to a take-up spool in the viewer.
Recently, a new type of film cartridge, called a "thrust cartridge", has been developed for cameras wherein the film is capable of being thrust out of the cartridge by rotating the cartridge spool in the appropriate direction. This feature allows the film within a cartridge to be completely enclosed within the cartridge, rather than having the end of the film extending therefrom. Specifics regarding the structure and operation of one type of thrust cartridge can be found in commonly-assigned U.S. Pat. No. 5,231,438, issued Jul. 27, 1993.
When loading a thrust cartridge in a camera, the cartridge is loaded through the loading opening and the loading door is closed to prevent light from entering the camera and exposing the film. The cartridge spool is then rotated in the appropriate direction to thrust the film from the cartridge and through the film track. Once the film reaches the end of the film track, it is engaged by the take-up roll. Thereafter, a transfer of drive power occurs between the cartridge spool and the take-up spool. That is, the thrusting of the film by the cartridge spool is deactivated, and further movement of the film is provided by a pulling action of the take-up spool. When rewinding of the film into the cartridge is desired, drive power is provided by the cartridge spool by rotating the cartridge spool in the appropriate direction to rewind the film.
U.S. Pat. No. 5,287,136, issued Feb. 15, 1994, discloses a camera with a film drive that automatically advances and rewinds a thrust film cartridge. To thrust film from the cartridge, a controller directs a motor to drive the cartridge spool in the advance direction to thrust film from the cartridge. Once the film is advanced into engagement with the take-up spool, the controller actively directs the motor to stop driving the cartridge spool and to commence driving the take-up spool. When rewind of the film is desired, the controller directs the motor to stop driving the take-up spool and to commence driving the cartridge spool in the rewind direction. To perform the various drive functions, the described camera utilizes a combination of a reversible motor, two on/off clutches, and a controller for selectively activating and deactivating the motor and the clutches.
There has now also been developed a manual film transport apparatus for cameras using film in thrust cartridges. The apparatus generally includes a camera body adapted to receive a thrust film cartridge. Also included are a thrust spindle for engagedly receiving a thrust cartridge spools a take-up spool, and a drive mechanism (e.g., a thumb wheel or ratchet lever) for simultaneously driving both the thrust spindle and the take-up spool in a thrust direction such that a surface speed of the take-up spool is faster than a surface speed of film being thrust from the thrust cartridge.
In one embodiment, the drive mechanism may include a drive wheel operatively interconnected with both the thrust spindle and the take-up spool. A first one-way clutch is operatively connected to the drive wheel and the thrust spindle to allow the drive wheel to drive the thrust spindle in the thrust direction while substantially preventing the drive wheel from driving the thrust spindle in a rewind direction. For example, the first clutch may include a driver element operatively associated with the drive wheel and a follower element operatively associated with the thrust spindle. In addition, the drive mechanism may further include a second one-way clutch operatively connected to the drive wheel and the take-up spool to allow the drive wheel to drive the take-up spool in the thrust direction while substantially preventing the drive wheel from driving the take-up spool in the rewind direction. The second clutch may include a driver element operatively associated with the drive wheel and a follower element operatively associated with the take-up spool.
In order to provide synchronous motion of the first and second clutches, the drive mechanism preferably includes a direct mechanical interconnection between the first clutch and the second clutch. For example, such direct mechanism interconnection may be through a belt, a chain or a gear train. The apparatus may further include a rewind mechanism (e.g., a rewind knob) for driving the thrust spindle in a rewind direction. A third clutch may be operatively positioned between the rewind mechanism and the rewind spindle to allow the rewind mechanism to drive the rewind spindle in the rewind direction while substantially preventing the rewind mechanism from driving the rewind spindle in the thrust direction.