US3708771A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overload protection for electric motors
Assignee: CJ FUCHS Ltd A BODY CORPORATE OF REPUBLIC OF SOUTH AFRICA
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Filing: 1970-12-09
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Granted: 1973-01-02
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Expires: 1990-12-09
Abstract
Abstract Electric overload protection apparatus comprising current sensitive means, connectable in an electric circuit and operative to perform an actuating function, such as to cause interruption of the electric circuit or to set off an alarm, when current flow through the current sensitive means exceeds a predetermined rated magnitude. The current sensitive means has a delayed response dependent on the magnitude of the excess current. Setting means is provided for changing the rating of the current sensitive means in a single step from a predetermined normal value to a predetermined higher value. The current sensitive means preferably includes at least one thermal sensitive bimetallic current conductor element which is arranged to flex and release a normally inoperative trigger when current flow through the bimetallic element exceeds the rated magnitude. The trigger is biased towards an operative position in which it can perform an actuating function.
Inventors
- 👤 L Read
- 👤 K Schreckenberg
- 👤 L Klein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:31
CPC Classifications
H; H01; H01H; H01H71/00; H01H71/10; H01H71/12; H01H71/14; H01H71/16
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
199 words
Electric overload protection apparatus comprising delayed response thermal sensitive; current conductor means connectable in an electric circuit and displaceable in accordance with the magnitude of current flowing therethrough; trigger means biased towards an operative position in which it can perform an actuating function; control means normally holding the trigger in inoperative position and arranged to be actuated by displacement of the thermal sensitive current conductor means to release the trigger; and sensitivity setting means operable upon the control means and resiliently biased towards a normal position at which the sensitivity of operation of the control means is maintained at a normal operating value so that the trigger is released when current flow through the thermal sensitive current conductor exceeds a predetermined normal magnitude, the sensitivity setting means being displaceable against the action of the bias to an overcurrent position at which the sensitivity of operation of the control means is decreased temporarily to a value such that the trigger is released only when an overcurrent of predetermined magnitude in excess of the normal magnitude flows through the thermal sensitive conductor means, the sensitivity setting means being automatically returnable to its normal position by the bias when not being displaced.
Claim 2
Dependent Claim
199 words
Electric overload protection apparatus comprising delayed response thermal sensitive; current conductor means connectable in an electric circuit and displaceable in accordance with the magnitude of current flowing therethrough; trigger means biased towards an operative position in which it can perform an actuating function; control means normally holding the trigger in inoperative position and arranged to be actuated by displacement of the thermal sensitive current conductor means to release the trigger; and sensitivity setting means operable upon the control means and resiliently biased towards a normal position at which the sensitivity of operation of the control means is maintained at a normal operating value so that the trigger is released when current flow through the thermal sensitive current conductor exceeds a predetermined normal magnitude, the sensitivity setting means being displaceable against the action of the bias to an overcurrent position at which the sensitivity of operation of the control means is decreased temporarily to a value such that the trigger is released only when an overcurrent of predetermined magnitude in excess of the normal magnitude flows through the thermal sensitive conductor means, the sensitivity setting means being automatically returnable to its normal position by the bias when not being displaced.
Claim 3
Dependent Claim
250 words
Electric overload protection apparatus including trigger means biased towards an operative position in which it can perform an actuating function; stop means normally holding the trigger in inoperative position, the trigger and stop means being relatively displaceable to release the trigger, the relative positioning of the stop means and the trigger when the latter is held inoperative being variable to vary the relative displacement required to release the trigger; at least one thermal sensitive, bimetallic current conductor element connectable in an electric circuit and arranged to flex to an extent dependent on the magnitude of current flowing therethrough, flexure of the bimetallic element acting to relatively displace the stop means and the trigger; and sensitivity setting means operative to change the relative displacement between the trigger and the stop means required to release the trigger, the sensitivity setting means being resiliently biased towards a normal position at which the relative positioning of the trigger and the stop means is held in a normal condition so that the trigger is released after a predetermined normal relative displacement caused by current flow through the bimetallic element in excess of a predetermined normal magnitude, the sensitivity setting means being displaceable against the action of its bias to an overcurrent position at which the relative positioning of the trigger and the stop means is temporarily changed to a condition such that the trigger is only released after an increased relative displacement caused by an overcurrent of predetermined magnitude in excess of the normal magnitude.
Claim 4
Dependent Claim
250 words
Electric overload protection apparatus including trigger means biased towards an operative position in which it can perform an actuating function; stop means normally holding the trigger in inoperative position, the trigger and stop means being relatively displaceable to release the trigger, the relative positioning of the stop means and the trigger when the latter is held inoperative being variable to vary the relative displacement required to release the trigger; at least one thermal sensitive, bimetallic current conductor element connectable in an electric circuit and arranged to flex to an extent dependent on the magnitude of current flowing therethrough, flexure of the bimetallic element acting to relatively displace the stop means and the trigger; and sensitivity setting means operative to change the relative displacement between the trigger and the stop means required to release the trigger, the sensitivity setting means being resiliently biased towards a normal position at which the relative positioning of the trigger and the stop means is held in a normal condition so that the trigger is released after a predetermined normal relative displacement caused by current flow through the bimetallic element in excess of a predetermined normal magnitude, the sensitivity setting means being displaceable against the action of its bias to an overcurrent position at which the relative positioning of the trigger and the stop means is temporarily changed to a condition such that the trigger is only released after an increased relative displacement caused by an overcurrent of predetermined magnitude in excess of the normal magnitude.
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) | 1976-01-02 | 1976-07-03 | 1977-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-02 | 1980-07-03 | 1981-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-02 | 1984-07-03 | 1985-01-02 | $7700.00 | Window Closed / Lapsed |