Film transport device

Details Film transport device Film transport device

1990-10-26

1992-12-29

Hayes, Monroe H.

Optics: motion pictures

Camera and/or projector drive mechanisms

With speed regulation or selection

352182, 352187, G03B 2148

Patent

active

051755734

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a film transport device.
DE-C2-27 22 378 teaches a film transport device having an intermittently driven film transport sprocket whose teeth engage the film perforations and transport the film stepwise. A control device controls the motor driving the film transport sprocket so that the latter advances the film one frame at a time. Film transport is controlled by a pattern for the current supplied to the drive motor of the film transport sprocket as each frame is advanced, that divides the process into an acceleration phase, a deceleration phase, and a position-adjustment or final positioning phase.
A marking detector is provided for final positioning, said detector, in a fixed spatial relationship to the individual frames, scanning markings on the film and using them to generate drive motor control signals so that, depending on the amount the film-integral marking deviates from a predetermined specified position, the film is either advanced or transported backward. Then the deviation from the specified position is detected once more and final positioning of the film is repeated as necessary until the specified position is reached. The film-integral marking can be in the form either of perforations in the film or of markings made on the film during exposure.
DE-A1-32 17 014 teaches a film transport device with a claw mechanism driven by a drive motor, the transport and locking claw of said device engaging the film perforations with play, advancing the film stepwise one frame at a time, and final-positioning it in the image window. Final positioning of the frames to be projected is accomplished either by using the actual frame to be projected or by using a reference marking associated with said frame.
Since the film pitch in known film transport devices uses a time interval of only 10 milliseconds, at a film speed of 24 frames per second or approximately 41 milliseconds, 31 milliseconds remain for exposure or projection of one frame, ensuring high image brightness and quality.
One disadvantage of known frame transport devices is that abrupt transitions in acceleration and deceleration of the film transport generate considerable noise, and damage to the film perforations cannot be ruled out. This is especially true when film resistance is increased by a splice, for example, so that in order to accelerate the film within the fixed acceleration phase, the film perforation is engaged with greater force and then the film is braked more sharply, further increasing the noise level and the risk of damaging the film.
DE-C2-27 60 024 teaches a control device for film transport in a film projector with a rotary shutter and a main motor on whose shaft a perforated disk is mounted, associated with a control circuit for generating control signals as a function of the angular position of the motor shaft. The control signals from the control circuit power the main motor through a power amplifier and are divided into three phases of movement, with constant acceleration being given to the main motor within a first shaft rotation angle, the main motor being kept at a constant speed at a second shaft rotation angle, and then braked at constant deceleration in a third shaft rotation angle.
In this known control device for intermittent transport of individual frames, constant acceleration and constant deceleration are used, with the film being transported through a predetermined angle of rotation at constant speed between the two intervals. In this manner, film tension is kept constant, avoiding peak loads in film tension and providing protective frame transport even at higher film transport speeds.
However, because of the abrupt transitions from the acceleration phase to the synchronous phase at a constant speed and from the synchronous phase to the deceleration phase, increased loads on the film and loud noise cannot be avoided. In this known control device, too, increased film resistance imposes a much greater load on the film, since a predetermined distance must be covered during the fixed transport i

REFERENCES:
patent: 3248029 (1966-04-01), Money
patent: 3565521 (1971-02-01), Butler et al.
patent: 3642357 (1972-02-01), Meyer
patent: 3819258 (1974-06-01), Butler et al.
patent: 4022525 (1977-05-01), Boudouris
patent: 4150886 (1979-04-01), Merkel et al.
patent: 4697896 (1987-10-01), Fox

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