US3684144A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Film tensioning device for motion picture projectors
Assignee: EPRAD Inc
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Filing: 1970-11-02
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Granted: 1972-08-15
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Expires: 1990-11-02
Abstract
Abstract A device for tensioning motion picture film against a rotating drum to reduce audio distortion caused by fluctuations in film speed. A curved bar is pivotally mounted at its center with ends positioned on opposite sides of the drum. Guide rolls are attached to the ends of the bar with each guide roll rotating about an axis parallel to the axis about which the drum rotates. A substantially constant length of film extends from a driven sprocket, around one guide roll, the drum and the other guide roll, and over a second driven sprocket. The pivot to which the bar is mounted is biased to tension the film against the drum. Small fluctuations in the length of film between the two sprockets are dampened by fluctuations in the position of the bar and the guide rolls and by the inertia of the drum.
Inventors
- 👤 Angelo Boudouris
- 👤 Geofrey T Gray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:31
CPC Classifications
G; G03; G03B; G03B1/00; G03B1/56; G03B31/00; G03B31/02
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
121 words
A device for tensioning motion picture film against a rotatable drum to reduce fluctuations in the speed of the film comprising, in combination, a pair of guide rolls, means rotatably mounting said guide rolls on opposite sides of the drum including a bar extending between opposite sides of the drum, a pair of pins on which said pair of guide rolls rotate and means attaching said pins to said bar on opposite sides of the drum with said pins parallel to the axis on which the drum rotates, the film passing over one guide roll, the drum and the other guide roll, and means for urging said guide roll mounting means in a direction to tension the film against the drum.
Claim 2
Independent Claim
121 words
A device for tensioning motion picture film against a rotatable drum to reduce fluctuations in the speed of the film comprising, in combination, a pair of guide rolls, means rotatably mounting said guide rolls on opposite sides of the drum including a bar extending between opposite sides of the drum, a pair of pins on which said pair of guide rolls rotate and means attaching said pins to said bar on opposite sides of the drum with said pins parallel to the axis on which the drum rotates, the film passing over one guide roll, the drum and the other guide roll, and means for urging said guide roll mounting means in a direction to tension the film against the drum.
Claim 3
Dependent Claim
72 words
A device for tensioning motion picture film against a rotatable drum, as defined in claim 1, wherein said means for urging said guide roll mounting means comprises a lever arm having one end attached to a pivot, means pivotally attaching said bar to said lever arm, and bias means mounted to pivot said lever arm to urge said bar in a direction where said guide rolls tension the film against the drum.
Claim 4
Dependent Claim
92 words
A device for tensioning motion picture film against a rotatable drum, as defined in claim 1, wherein said means for urging said guide roll mounting means comprises a guide, a shaft having two ends, said shaft being mounted to slide in said guide, means pivotally attaching said bar to one end of said shaft, a spring, and means compressing said spring between said guide and the other end of said shaft whereby said shaft and said bar are urged in a direction wherein said guide rolls tension the film against the drum.
Claim 5
Dependent Claim
49 words
A device for tensioning motion picture film against a rotatable drum, as defined in claim 3, wherein said compressing means includes an adjustable nut threadably engaging said other end of said shaft whereby adjustment of said nut changes the tensioning force exerted on the film by said guide rolls.
Claim 6
Dependent Claim
30 words
A device for tensioning motion picture film against a rotatable drum, as defined in a claim 3, and including means for limiting rotational movement of said shaft in said guide.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-15 | 1976-02-14 | 1976-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-15 | 1980-02-14 | 1980-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-15 | 1984-02-14 | 1984-08-15 | $7700.00 | Window Closed / Lapsed |