Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
1998-09-29
2001-01-16
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C475S012000
Reexamination Certificate
active
06173623
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of photographic film scanners and, in particular, to two-speed gear drive apparatus that selectively operates film transport drive mechanisms at in forward and reverse directions at selectable, widely disparate speeds.
BACKGROUND OF THE INVENTION
Film transport mechanisms used in photographic film scanners can be configured with DC or AC motors, stepper motors or servo motors used to operate the transport mechanism at different film transport speeds. Film scanners require precise positioning of the film strip, particularly during the image scanning operation for quality results. Drives for this purpose typically include DC motors with position feedback using encoder wheels or disks. Transport speed can be changed by varying the voltage supplied to the DC motor thus making the selection of appropriate operating speed a relatively simple matter. However, the requirement for precise positioning makes the feedback control with encoder wheels a complex and relatively costly approach to transport design. Stepper motor drive systems have the advantage that precise positioning can be readily achieved. However, a film scanner having a high/low speed ratio of, for example, on the order of 40 to 1, requires that a relatively costly stepper motor be used to realize such a high range of speed variation since inexpensive stepper motors are generally limited to a low range of speed variation. For film scanners intended to be mass produced for consumer applications, it is necessary to minimize the product cost which mitigates against use of the more costly stepper motor transport designs.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided dual speed film transport gear drive apparatus that comprises a film transport drive motor unit having a stepper motor and an input drive gear and a film transport mechanism having an output driven gear. The apparatus includes a movable gear module having an intermediate low speed gear drive and an intermediate high speed gear drive, said gear module being movable between first and second positions for selectively interconnecting one or the other of said intermediate gear drives between said input drive gear and said output driven gear. The apparatus also includes a gear shifting unit including a reversible cam drive motor and a gear shifting cam coupled to said movable gear module for positioning said gear module into one of said first and second positions to thereby drive said film transport mechanism at a selectable low or high speed. The direct gear drive provides precise positioning of the film transport which is critical in film image scanning. Additionally, the use of the cam driven gear shifting mechanism allows the use of a low cost stepper motor having a relatively narrow range of speed variation thereby providing a low cost solution to the high speed/low speed requirements of a film transport drive.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
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Castor David A.
Kolb Theodore R.
Boos, Jr. Francis H.
Eastman Kodak Company
Marmor Charles A
Pang Roger
Schindler, Jr. Roland R.
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