US4504881A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Protective circuit for an electric motor
Assignee: Victor Company of Japan Ltd
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Filing: 1982-12-10
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Granted: 1985-03-12
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Expires: 2002-12-10
Abstract
Abstract A protective circuit for an electric motor comprises a frequency signal generating circuit for generating a frequency signal in accordance with the rotational speed of the motor, a switching circuit switched over to either permit or cut off supply of current to the motor, and a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of the motor, and cutting off the supply of current to the motor by the switching circuit.
Inventors
- 👤 Kinzo Wada
- 👤 Ken Enami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 00:14
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/093
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
151 words
A protective circuit for an electric motor comprising: frequency signal generating means for generating a frequency signal in accordance with the rotational speed of the motor; a switching circuit switched over to either permit or cut off supply of current to said motor; a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of said motor, and cutting off the supply of current to said motor by said switching circuit; and a rotational speed control circuit responsive to the generated frequency signal from said frequency signal generating means, for controlling the rotational speed of the motor; said detecting circuit comprising an oscillator for producing a reference frequency signal, and a frequency counter reset by the frequency signal from said frequency signal generating means, for counting the output reference frequency signal of said oscillator.
Claim 2
Dependent Claim
151 words
A protective circuit for an electric motor comprising: frequency signal generating means for generating a frequency signal in accordance with the rotational speed of the motor; a switching circuit switched over to either permit or cut off supply of current to said motor; a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of said motor, and cutting off the supply of current to said motor by said switching circuit; and a rotational speed control circuit responsive to the generated frequency signal from said frequency signal generating means, for controlling the rotational speed of the motor; said detecting circuit comprising an oscillator for producing a reference frequency signal, and a frequency counter reset by the frequency signal from said frequency signal generating means, for counting the output reference frequency signal of said oscillator.
Claim 3
Dependent Claim
48 words
A protective circuit as claimed in claim 1 in which said counter produces an output when a period with which the counter is reset by said frequency signal becomes larger than a predetermined period, to cut off the supply of current to said motor by said switching circuit.
Claim 4
Dependent Claim
52 words
A protective circuit as claimed in claim 2 in which a frequency dividing ratio of said counter is n, and said counter produces an output when the period of said frequency signal becomes larger than a predetermined period and n reference frequency signals are counted before being reset by said frequency signal.
Claim 5
Dependent Claim
97 words
A protective circuit as claimed in claim 1 in which said switching circuit comprises a switching element connected within a current circuit of said motor, said switching element being switched over between ON and OFF states, and a flip-flop controlled responsive to the output of said counter, said flip-flop having a first terminal for receiving an input which causes the switching element to switch over from an ON state to an OFF state and a second terminal for receiving an input which causes the switching element to switch over from an OFF state to an ON state.
Claim 6
Dependent Claim
36 words
A protective circuit as claimed in claim 4 which further comprises a circuit for supplying a reset signal to said counter and said flip-flop when a power source is turned OFF and thereafter turned ON again.
Claim 7
Dependent Claim
29 words
A protective circuit as claimed in claim 1 in which said rotational speed control circuit carries out a control so that the rotational speed of said motor becomes constant.
Claim 8
Dependent Claim
71 words
A protective circuit as claimed in claim 1 in which said frequency signal generating means comprises a frequency generator for generating a signal having a frequency in accordance with the rotational speed of said motor, and a wave shaping circuit for subjecting an output signal of said frequency generator to wave-shaping, to produce a pulse having a period in accordance with the frequency of the output signal of said frequency generator.
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) | 1988-03-11 | 1988-09-10 | 1989-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-03-11 | 1992-09-10 | 1993-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-03-11 | 1996-09-10 | 1997-03-12 | $7700.00 | Window Closed / Lapsed |