US3688874A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Elevator motor control system employing power amplifier with output current limiting arrangement
Assignee: Otis Elevator Co
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Filing: 1971-08-09
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Granted: 1972-09-05
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Expires: 1991-08-09
Abstract
Abstract An arrangement for an elevator control system employing a power amplifier for supplying excitation current to a dynamo winding for controlling the speed of the elevator car wherein the magnitude of the current of both polarities which the amplifier is capable of supplying is limited in response to the approach of the car to a predetermined distance of a landing at which it is stopping and wherein only the limitation for one polarity is removed in response to the generation of a signal to start in a direction corresponding to that one polarity.
Inventors
- 👤 John Lusti
- 👤 William Paul Reid
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 07:01
CPC Classifications
B; B66; B66B; B66B1/00; B66B1/24; B66B1/28; B66B1/30
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
258 words
In a control system for an elevator car operable to transport loads between a plurality of landings in response to signals to start from and to stop at said landings, a hoisting motor for said car, a generator applying voltage to said motor to control the speed thereof, a field winding for said generator controlling the magnitude of the voltage applied to said motor, a power amplifier operable to supply variable excitation current of either polarity to said filed winding to enable said generator to apply sufficient voltage to said motor to operate said car at any speed from zero to a predetermined rated speed in either the up or the down direction of travel, a resistance circuit connected in series with said power amplifier and said field winding limiting the magnitude of both polarities of current said power amplifier is capable of supplying to said field winding thereby limiting the speed of said car in both directions of travel to a speed less than said predetermined rated speed and conductance means responsive to a signal to start to travel in a particular direction providing a circuit in parallel with said resistance circuit to enable sufficient current of only the polarity associated with said particular direction to flow from said power amplifier to said field winding to enable said car to operate at said predetermined rated speed in said particular direction only, said parallel circuit being interrupted in response to the approach of said car to within a predetermined distance of a landing at which it is stopping.
Claim 2
Dependent Claim
258 words
In a control system for an elevator car operable to transport loads between a plurality of landings in response to signals to start from and to stop at said landings, a hoisting motor for said car, a generator applying voltage to said motor to control the speed thereof, a field winding for said generator controlling the magnitude of the voltage applied to said motor, a power amplifier operable to supply variable excitation current of either polarity to said filed winding to enable said generator to apply sufficient voltage to said motor to operate said car at any speed from zero to a predetermined rated speed in either the up or the down direction of travel, a resistance circuit connected in series with said power amplifier and said field winding limiting the magnitude of both polarities of current said power amplifier is capable of supplying to said field winding thereby limiting the speed of said car in both directions of travel to a speed less than said predetermined rated speed and conductance means responsive to a signal to start to travel in a particular direction providing a circuit in parallel with said resistance circuit to enable sufficient current of only the polarity associated with said particular direction to flow from said power amplifier to said field winding to enable said car to operate at said predetermined rated speed in said particular direction only, said parallel circuit being interrupted in response to the approach of said car to within a predetermined distance of a landing at which it is stopping.
Claim 3
Dependent Claim
28 words
In a control system according to claim 1, wherein said resistance circuit includes separate up and down direction resistor elements, each limiting the current of its associated polarity.
Claim 4
Dependent Claim
40 words
In a control system according to claim 2, load responsive means operable to vary the magnitudes of the resistance of both the up and down direction resistor elements in response to the magnitude of the load in the elevator car.
Claim 5
Dependent Claim
38 words
In a control system according to claim 3, wherein said power amplifier includes an up polarity output circuit and a down polarity output circuit, said up and down direction resistance elements being connected to their respective output circuits.
Claim 6
Dependent Claim
49 words
In a control system according to claim 4, wherein said load responsive means includes a plurality of switches, each operable in response to a separate magnitude of load whereby the magnitudes of the resistance of said up and down direction resistor elements are variable in a plurality of steps.
References Cited (Backward Citations)
US3410367A
Cited
US3536969A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-09-05 | 1976-03-06 | 1976-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-05 | 1980-03-06 | 1980-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-05 | 1984-03-06 | 1984-09-05 | $7700.00 | Window Closed / Lapsed |