Advancing material of indeterminate length – Means to engage longitudinally spaced modifications in material – Rotating sprocket
Patent
1990-11-19
1993-09-14
Stodola, Daniel P.
Advancing material of indeterminate length
Means to engage longitudinally spaced modifications in material
Rotating sprocket
226 82, 226 87, G03B 124
Patent
active
052441377
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a file transport device. DE-U-70 00 099 teaches a film transport device with a driven film transport sprocket, each of whose transport teeth has a base with a trapezoidal cross section at its foot end which widens that tooth foot on all sides. The top of the base runs at a distance from and parallel to the surface of the film transport sprocket and serves as a film support so that the film is not supported by the surface of the film transport sprocket, but by the top of the corresponding base. The known film transport device serves to transport both Super-8 film and Standard-8 film using the same film transport sprocket.
A film transport device is known from DE-A1-28 18 910 which has a sprocket connected with the drive shaft of a stepping motor, the teeth of said sprocket engaging the holes in a film for stepwise advancement of the film in a motion-picture camera or in a film projector. The sprocket replaces a claw system used to advance the film, thus reducing the moved masses, increasing the reliability of film transport, and reducing transport noise. In addition, projection at nearly any speed is possible.
A prerequisite for using a sprocket is an intermittently moved drive motor so that the film is correspondingly moved intermittently through the film gate. Stepping motors or DC motors with a corresponding control circuit can be used as drive motors, with the DC motor permanently coupled to an angle indicator disk on which optical, magnetic, or mechanical codes are provided, said codes being scanned by a scanner, said scanner delivering corresponding motor positioning signals to the control device to control the DC motor.
In the known device, the film is guided along a flat contact plate provided with a projection window, located between a light source and projection optics. In addition, an element can be provided which presses the film against the contact plate into the position in which it engages the sprocket. In addition, the known device has the ability to guide the film around the sprocket.
One disadvantage of the known film transport device is that although step control of the drive motor for the sprocket is accomplished with a high degree of precision, a distance must be maintained between the arc of the sprocket and the element pressing the film against the sprocket, so that splices, which are approximately twice the film thickness, can pass through the film transport device without the film being damaged at these points or torn by jamming. Because of the unavoidable play upon engagement of the teeth of the sprocket in the film holes, positioning errors occur both in the direction of movement of the film and also in the plane perpendicular thereto, so that the frames are not located precisely in front of the film gate, resulting unavoidably in blurred projection and changing image position.
The goal of the present invention is to improve a film transport device according to the species in such manner that it reliably transports even thicker film areas with splices or film ends glued on top of one another.
The invention is based on the fact that with a special contour of the film transport sprocket in the area between the root of the tooth and the tooth circle, the film pressure skid that presses the film against the film transport sprocket can be positioned at a minimum distance from the film transport sprocket while maintaining a necessary play between the film transport sprocket and the film pressure skid, so that firstly an exact engagement of the teeth of the film transport sprocket in the film holes is ensured and secondly assurance is provided that even splices can be transported through the gap between the film pressure skid and the film transport sprocket without any risk of jamming or resultant damage to the film holes and/or tearing of the film.
This ensures exact positioning of each frame in front of the film gate in the transport direction and in the film plane, ensuring constantly sharp image projection and accurate frame spacing. In addition, the film has
REFERENCES:
patent: 4394949 (1983-07-01), Gomi
Blaschek Otto
Popp Thomas
Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Bowen Paul
Stodola Daniel P.
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