US3989361A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Film speed control for sound motion picture projector
Assignee: Polaroid Corp
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Filing: 1974-12-19
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Granted: 1976-11-02
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Expires: 1994-12-19
Abstract
Abstract A sound motion picture system in which sound is recorded on movie film. A constant speed capstan drives the film past a sound transducer, and a claw drives the film incrementally past a film gate. A projection lamp, a DC power supply, and an induction motor for driving the claw are energized from a common source. A film loop between the transducer and the film gate controls a switching circuit for unbalancing the current to the induction motor to control the speed of the motor without materially affecting the rms value of the current supplied to the lamp or the peak - to - peak value of the voltage supplied to the DC power supply.
Inventors
- 👤 Thomas A. O. Gross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 02:00
CPC Classifications
G; G03; G03B; G03B31/00; H; H02; H02P; H02P23/00; H02P23/10; H02P5/00; H02P5/46; H02P5/48; H02P5/485
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
332 words
A sound motion picture system, comprising means forming a projection station at a first location, a projection lamp located at said projection station, a film drive claw located at said projection station, means forming a sound station at a second location, a film drive capstan located at said sound station, means for guiding a strip of film over a path from said capstan to said claw, said path including a region in which the film is free to form a loop of variable length, an induction motor, means operated by said motor for driving said claw, capstan drive means for driving said capstan at constant speed, said motor comprising a set of windings linked by a common core, means connecting one of said windings in series with said lamp, first and second input terminals adapted to be excited by an alternating voltage, first and second output terminals connected to at least one of said windings, means connecting said first input terminal to said first output terminal, a rectifier connecting said second input terminal to said second output terminal to allow current of a first polarity to flow therebetween, an electronic switch connecting said second input terminal to said second output terminal when said switch is closed by an applied signal, a variable potential divider connected between said input terminals for producing an output voltage that is a controllable portion of the voltage applied to said input terminals, means responsive to the length of a loop of film in said region for controlling said potential divider, and voltage responsive means effective when an alternating voltage is applied to said input terminals and responsive to the voltage produced by said potential divider for applying a signal to close said switch for the balance of the duration of each half cycle of voltage on said input terminal that will cause current of a polarity opposite said first polarity to flow through said switch when the voltage produced by said potential divider reaches a predetermined value.
Claim 2
Dependent Claim
332 words
A sound motion picture system, comprising means forming a projection station at a first location, a projection lamp located at said projection station, a film drive claw located at said projection station, means forming a sound station at a second location, a film drive capstan located at said sound station, means for guiding a strip of film over a path from said capstan to said claw, said path including a region in which the film is free to form a loop of variable length, an induction motor, means operated by said motor for driving said claw, capstan drive means for driving said capstan at constant speed, said motor comprising a set of windings linked by a common core, means connecting one of said windings in series with said lamp, first and second input terminals adapted to be excited by an alternating voltage, first and second output terminals connected to at least one of said windings, means connecting said first input terminal to said first output terminal, a rectifier connecting said second input terminal to said second output terminal to allow current of a first polarity to flow therebetween, an electronic switch connecting said second input terminal to said second output terminal when said switch is closed by an applied signal, a variable potential divider connected between said input terminals for producing an output voltage that is a controllable portion of the voltage applied to said input terminals, means responsive to the length of a loop of film in said region for controlling said potential divider, and voltage responsive means effective when an alternating voltage is applied to said input terminals and responsive to the voltage produced by said potential divider for applying a signal to close said switch for the balance of the duration of each half cycle of voltage on said input terminal that will cause current of a polarity opposite said first polarity to flow through said switch when the voltage produced by said potential divider reaches a predetermined value.
Claim 3
Dependent Claim
282 words
In a sound motion picture system, the combination comprising a combined induction motor and transformer having an output shaft, a secondary winding, a primary winding adapted to drive said shaft and energize said secondary winding, a projection lamp, means connecting at least a portion of one of said windings in series with said lamp, first film transport means connected to said shaft and adapted to engage a strip of film at a first location to drive the film at a speed determined by the speed of said shaft, second film transport means adapted to engage the same strip of film at a second location and operable to drive the film at constant speed, whereby the length of film between said film transport means is increased when the speed at which said first film transport means drives the film differs from said constant speed in a predetermined sense, sensing means located adjacent the path of a strip of film driven by said film transport means for producing an output signal governed by the length of the film strip between said locations, and switching means adapted to be connected to a source of alternating voltage and responsive to said output signal when so connected to supply alternating current to said primary winding having a direct current bias, said switching means responsive to said output signal to interrupt the flow of current to said primary winding from the beginning of each half cycle of a predetermined polarity until the voltage rises to a level determined by said output signal to adjust the speed of said first film transport means toward said constant speed and thereby maintain a constant average length of film between said locations.
Claim 4
Dependent Claim
282 words
In a sound motion picture system, the combination comprising a combined induction motor and transformer having an output shaft, a secondary winding, a primary winding adapted to drive said shaft and energize said secondary winding, a projection lamp, means connecting at least a portion of one of said windings in series with said lamp, first film transport means connected to said shaft and adapted to engage a strip of film at a first location to drive the film at a speed determined by the speed of said shaft, second film transport means adapted to engage the same strip of film at a second location and operable to drive the film at constant speed, whereby the length of film between said film transport means is increased when the speed at which said first film transport means drives the film differs from said constant speed in a predetermined sense, sensing means located adjacent the path of a strip of film driven by said film transport means for producing an output signal governed by the length of the film strip between said locations, and switching means adapted to be connected to a source of alternating voltage and responsive to said output signal when so connected to supply alternating current to said primary winding having a direct current bias, said switching means responsive to said output signal to interrupt the flow of current to said primary winding from the beginning of each half cycle of a predetermined polarity until the voltage rises to a level determined by said output signal to adjust the speed of said first film transport means toward said constant speed and thereby maintain a constant average length of film between said locations.
Claim 5
Dependent Claim
96 words
The apparatus of claim 2, in which said switching means comprises a pair of input terminals adapted to be connected to a source of alternating voltage, and in which said sensing means comprises a photosensitive impedance, a fixed impedance, means connecting said impedances in series with said terminals, means for illuminating said photosensitive impedance over a path interrupted by a strip of film between said locations when the length of the film exceeds a predetermined length, and voltage responsive switching means controlled by a predetermined voltage across one of said impedances for producing an output signal.
Claim 6
Dependent Claim
13 words
The apparatus of claim 3, in which said fixed impedance is a capacitor.
Claim 7
Dependent Claim
13 words
The apparatus of claim 3, in which said fixed impedance is a resistor.
Claim 8
Dependent Claim
42 words
The apparatus of claim 2, in which said switching means comprises a rectifier and a controlled rectifier connected together in anode-to-cathode relationship, and in which said controlled rectifier has a gate terminal connected to said sensing means to receive said output signal.
Claim 9
Dependent Claim
51 words
The apparatus of claim 2, in which said motor comprises a stator on which said energizing winding is wound, a secondary winding on said stator, a projection lamp at said projection station, and means for connecting at least a portion of one of said windings in series with said projection lamp.
Claim 10
Dependent Claim
31 words
The apparatus of claim 7, in which said constant speed drive means comprises an electric motor, and further comprising means connected to said secondary winding for supplying current to said motor.
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) | 1979-11-02 | 1980-05-03 | 1980-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-11-02 | 1984-05-03 | 1984-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-11-02 | 1988-05-03 | 1988-11-02 | $7700.00 | Window Closed / Lapsed |