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US3617846A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dc motor projector drive system
Assignee: Bell and Howell Co
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Filing: 1969-12-30
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Granted: 1971-11-02
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Expires: 1989-12-30
Abstract
Abstract Drive system for operating a motion picture projector in synchronism with a sound reproducing unit in which a DC motor is connected to an unregulated DC voltage-supply source through a voltage-dropping device which is controlled through a first regulator circuit from a speed control signal and which is controlled through a second regulator circuit to regulate the maximum adjusted DC motor voltage. During silent operation, the first regulator circuit is inactive and the second regulator circuit is adjustable to adjust DC motor speed. During sound reproduction, the second regulator circuit is set at a relatively high voltage position (free run maximum speed). In both operations, the effect of changes in supply voltage and other variables is minimized to stabilize operation.
Inventors
- 👤 Sanford M Hanberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:53
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/29; H02P7/2913; H02P7/288; H02P7/2885; Y; Y10; Y10S; Y10S388/00; Y10S388/907; Y10S388/909
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
310 words
In a system including an operating shaft to be rotated in accordance with an intermittently operable pulsed reference signal at a speed within a certain range, sensing means arranged to develop an output speed signal corresponding to the speed of rotation of said operating shaft, comparison means responsive to said reference signal during operable periods and to said output speed signal and arranged to develop a control signal corresponding to the difference between said reference signal and output speed signal, a power input circuit arranged for connection to an electrical power source subject to voltage variations, a load circuit including an electric motor for driving said shaft, a load voltage dropping device in series between said power input circuit and said load circuit, first regulating means responsive to said control signal and arranged to control said load voltage dropping device to control voltage to said motor and to oppose changes in said output speed signal relative to said reference signal, and second regulating means responsive to the load circuit voltage applied to said load circuit during inoperative periods, and arranged to oppose changes in said load circuit voltage away from a regulated value, and to control the speed of said operating shaft in the absence of said reference signal, said reference signal being in the fOrm of periodic pulses at a rate corresponding to the desired speed of rotation of said operating shaft, said output speed signal being in the form of periodic pulses at of rate corresponding to the actual speed of rotation of said operating shaft, said comparison means comprising a flip-flop triggered to a reset condition by said output speed signal pulses and to a set condition in response to said reference signal pulses and said first regulating means comprising means for cutting off conduction of said voltage dropping device in said reset conditions of said flip-flop.
Claim 2
Dependent Claim
310 words
In a system including an operating shaft to be rotated in accordance with an intermittently operable pulsed reference signal at a speed within a certain range, sensing means arranged to develop an output speed signal corresponding to the speed of rotation of said operating shaft, comparison means responsive to said reference signal during operable periods and to said output speed signal and arranged to develop a control signal corresponding to the difference between said reference signal and output speed signal, a power input circuit arranged for connection to an electrical power source subject to voltage variations, a load circuit including an electric motor for driving said shaft, a load voltage dropping device in series between said power input circuit and said load circuit, first regulating means responsive to said control signal and arranged to control said load voltage dropping device to control voltage to said motor and to oppose changes in said output speed signal relative to said reference signal, and second regulating means responsive to the load circuit voltage applied to said load circuit during inoperative periods, and arranged to oppose changes in said load circuit voltage away from a regulated value, and to control the speed of said operating shaft in the absence of said reference signal, said reference signal being in the fOrm of periodic pulses at a rate corresponding to the desired speed of rotation of said operating shaft, said output speed signal being in the form of periodic pulses at of rate corresponding to the actual speed of rotation of said operating shaft, said comparison means comprising a flip-flop triggered to a reset condition by said output speed signal pulses and to a set condition in response to said reference signal pulses and said first regulating means comprising means for cutting off conduction of said voltage dropping device in said reset conditions of said flip-flop.
Claim 3
Dependent Claim
46 words
In a system as defined in claim 1, said electric motor being a DC motor, and said load voltage-dropping device including a power transistor, unidirectional conduction means in series with said motor to prevent application of the back EMF of said motor to said power transistor.
Claim 4
Dependent Claim
108 words
In a system defined in claim 1, a motion picture projector film drive mechanism driven by said operating shaft, a tape unit for developing sound to accompany film driven by said drive unit and arranged to supply said reference signal, said first regulating means comprising means for periodically rendering said voltage-dropping device nonconductive with the percentage of time of conduction of said control device being controlled in accordance with said control signal, and photocell means for sensing control marks on film driven by said film guide mechanism for rendering said first regulating means operable during reproduction of sound by said tape unit and inoperable during silent film projection.
Claim 5
Dependent Claim
59 words
In system as defined in claim 3, manual adjustment means for manually adjusting said second regulating means to adjust said regulated value of load silent voltage and to obtain a selected film speed during silent film projection, said manual adjustment means being set at a maximum voltage position when said first regulating means is rendered operable during sound projection.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |