Optics: motion pictures – Camera and/or projector drive mechanisms – With speed regulation or selection
Patent
1990-09-25
1993-02-16
Hayes, Monroe H.
Optics: motion pictures
Camera and/or projector drive mechanisms
With speed regulation or selection
352182, 352187, G03B 2148
Patent
active
051875080
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a film transport device DE-PS 27 22 378 teaches a film transport device with a film transport sprocket intermittently driven by a drive motor, the teeth of said sprocket engaging the holes in the film with play and transporting said film stepwise. A control device controls the drive motor of the film transport sprocket in such fashion that the sprocket advances the film by one frame width at a time. The transport process is divided by a current pattern supplied to the drive motor of the film transport sprocket at each frame step, into an acceleration phase, a braking phase, and a final-positioning phase.
A mark detector is provided for final positioning, said detector, with a fixed spatial relationship to the individual frames, scanning marks on the film and generating from them control signals for the drive motor, so that the film, depending on the position of the deviation of the film-integral marks from a predetermined set position, is transported further forward or backward. Then the deviation from the set position is again detected and final positioning of the film repeated if required until the set position is reached. Either the holes in the film serve as film-integral marks, or marks exposed onto the film are used.
In the known film transport device, although the step control of the drive motor for the film transport sprocket is accomplished with a high degree of precision, because of the unavoidable play upon engagement of the teeth in the film holes, however, positioning errors occur which result in the frames not being located exactly in front of the film gate.
DE-OS 32 17 014 teaches a film transport device with a claw mechanism driven by a drive motor, the transport and locking claws of said mechanism engaging the film holes with play and advancing the film stepwise by one frame width at a time and final-positioning it at the film gate. Final positioning of the frames to be projected is accomplished either by using the frame to be reproduced itself or by using a reference mark associated with the frame.
In the event of a deviation of the individual film frame in the film gate from a preset position, a signal is generated by a sensor which is used to correct the deviation, with one of two wedge-shaped adjusting elements being moved in the direction of the film, thus shifting the film in the film transport direction or against the film transport direction.
DE-GM 18 91 272 teaches a device for pressing films in the film channel of a film projector with a claw mechanism, in which two guide wedges are rigidly disposed on the bottom of the film channel, symmetrically in the direction of film travel, and on the inside of the film path door for each guide wedge, at least two pressure wedges arranged in sequence in the film travel direction are individually spring mounted. When the film path door is closed, the pressure wedges press the film passing through against the guide wedges and clamp the film against the film gate.
The goal of the present invention is to improve the film transport device according to the species with respect to more precise final positioning of the film frames to be projected.
The solution according to the invention provides a film transport device with improved final positioning of the frames to be projected.
The solution according to the invention takes its departure from the fact that with a fixed spatial relationship between the film transport device and the film moved through the film transport device, even taking into account unavoidable play between the film holes and the teeth of a film transport sprocket engaging the film holes, exact positioning of each frame in front of the film gate is ensured. Such a fixed spatial relationshipo is provided when one tooth of the film transport sprocket engages, with zero play, the front or rear edge of a hole in the film at the moment a frame is projected.
If it is determined in this fashion which tooth of the film transport sprocket abuts the front or rear edge of a hole in the film, the movement of the fil
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patent: 3819258 (1974-06-01), Butler et al.
patent: 4022525 (1977-05-01), Boudouris et al.
patent: 4150886 (1979-04-01), Merkel et al.
patent: 4215921 (1980-08-01), Miller
patent: 4697896 (1987-10-01), Fox
Arnold & Richter Cine Technik & Co. Betriebs KG
Hayes Monroe H.
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