US3038047A - Ambient temperature compensated circuit breaker - Google Patents

Description

AMBIENT TEMPERATURE COMPENSATED CIRCUIT BREAKER Filed March 17. 1958 Jm MZL@ United States Patent Otce 3,038,047 Patented June 5, 1962 3,033,047 AMBIENT TEMPERATURE CGMPENSATED CIRCUIT BREAKER John F. Marquis, St. Charles, Ill., assigner to Littelfuse, Incorporated, Des Plaines, Ill., a corporation of Illinois Filed Mar. 17, 1958, Ser. No. 721,771 9 Claims. (Cl. 20G-116) The principal object of this invention is to provide an improved circuit breaker for protecting an electric circuit, which operates in the fractional and low integral amperage ranges, which will carry rated amperage at above normal ambient temperature, which accomplishes these results without need for extra parts such as heater coils, extra bimetal leafs, etc., which is simple in construction and fool proof in operation, which provides for increasing contact pressure up to the point of opening the circuit, and which provides good contact wiping action.

Briefly, the ambient temperature compensated circuit breaker of this invention includes an insulating base `and an enclosing cover suitably secured thereto. It also includes a resilient bimetallic latch member having a first leg secured at one end to the base, a second leg carried at one end by the free end of the iirst leg, and a contact shoulder on the free end of the second leg. It further includes a resilient blade, preferably of bimetallic blade, carried at one end by the lbase and having a contact shoulder on its free end. Terminal connections are pro- K vided for lthe latch member and blade for connecting them into an electric circuit, these terminal connections also providing means for mounting the latch member and blade on the insulating base.

The contact shoulders on the latch member and blade normally overlap and resiliently latch and contact each other for completing the electric circuit through the latch member and the blade. The resilient blade resiliently operates against the resilient latching action of the contact shoulders to separate the contact shoulders when permitted thereby for opening the circuit. One of the legs, the first leg, of the latch member operates on an increase in temperature thereof `to increase the latching action of the contact shoulders, and the other of said legs, the second leg, o-f said latch member operates upon an increasing temperature thereof to decrease the l-atching action of the contact shoulders. The temperature of the second leg of the latch member is more responsive to the current flow in the electric circuit than the temperature of the tirst leg of the latch member. As a result, the second leg operates principally in response to current flow to open the circuit breaker upon an excess current flow, while the first leg operates primarily in response to ambient temperature conditions to cause opening of the circuit at a higher temperature as the ambient temperature increases. Thus, the circuit breaker of this invention is substantially fully compensated for ambient temperature conditions.

The resilient blade is also preferably formed of bimetal and operates upon an increase in temperature thereof to increase the separating force thereof, the temperature of the bimetallic blade being primarily responsive to the current flow in the electric circuit. After the circuit breaker is opened upon an excess current ow, it may be manually reset by a push button slidably carried by the cover.

Further objects of this invention have to do with the details of construction of the circuit breaker and with the cooperative relationships between the component parts thereof.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the yaccompanying speciiication, claims and drawing in which:

FIG. l is a perspective view of the ambient temperature compensated circuit breaker of this invention.

FIG. 2 is an enlarged vertical sectional view illustrating the circuit breaker of this invention in closed position.

FIG.- 3 is a view similar to FIG. 2` but illustrating the circuit breaker in open position.

FIG. 4 is a horizontal section-al view through the circuit breaker taken substantially along the line 4-4 of FIG. 3.

FIG. 5 is a further enlarged view of a portion of the latch member and blade showing in more detail the cooperation between the contact shoulders thereof.

FIG. 6 is an exploded perspective view of the latch member, `blade and terminal connection for the blade.

The ambient temperature compensated circuit breaker of this invention is generally designated at 10. It includes a base 11 formed of insulating material, such as Bakelite or the like. A latch member 12, formed of conventional bimetal, is provided at one end with a hole 13 through which a rivet 14 extends for securing the latch member 12 to the base 11 and to a terminal connection 15. The high expansion side of the bimetallic latch member faces upwardly while the low expansion side faces downwardly. A iirst leg 16 of the latch member 12 is bent upwardly from the base 11 so that upon an increase in temperature of the first leg 16, it may bend downwardly in response t-hereto. The free end of the first leg 16 is provided with an upwardly extending leg 17 which is preferably struck from the leg 16. The free end of the second leg 17 is provided with a contact shoulder 18. The high expansion side of the second leg 17 faces outwardly while the low expansion side faces inwardly so that upon a temperature increase in the leg 17, it bends or llexes inwardly, that is to the right as illustrated in FIGS. 2, 3 and 5. The cross-sectional area of the second leg 17 is smaller than the cross-sectional area of the first leg 16 and, accordingly, the second leg 17 offers more resistance to current tlow than the tirst leg 16. In this way, the second leg 17 is primarily responsive to current flow through the latch member 12 While the rst leg 16 is primarily responsive to ambient temperature conditions. The relative responses of the second leg 17 and the first leg 16 to current flow conditions and to ambient temperature conditions, respectively, may be selected by appropriately selecting desired crosssectional areas.

A resilient blade 20 which is also preferably formed of conventional bimetal is secured at one end 21, by spot welding or the like, to a bracket portion 2'2 of a terminal connection 23 having an extension 24 extending through the insulating base 11. The terminal connection 23 is provided with a hole 26 through which a rivet 25 extends yfor securing the terminal connection 23 to the insulating base y11. The resilient bimetallic element 20 is pre-bent so as to extend upwardly as illustrated in IF'IG. 3. The high expansion side of the bimetallic blade 2t) faces downwardly while the low expansion side faces upwardly. The free end of the bimetallic blade 20 has a downwardly extending portion 27 which car- -ries a contact shoulder 28, in the form of a rounded contact riveted thereto. When the bimetallic blade 20 is pushed downwardly to the position illustrated in FIGS. 2 and 5, the contact shoulder 28 on the blade 20 overlaps and resiliently latches and contacts the contact shoulder 18 on the latch member 12 and the contact shoulders are normally resiliently held in this latching contacting position. The cross-sectional area of the bimetallic blade is so selected as to oifer resistance to current flow therethrough. As a result, the temperature of the lbimetallic blade is primarily responsive to the current flow therethrough.

A cover 3i), `formed of sheet `metal or the like, encloses the blade 20 and latch member 12 and rests against the insulating base 11. The cover is held in place on the base 11 by ears 31 extending through slots in the base 11 and being bent over the bottom of the base 11. The cover 30 is provided with a sleeve portion 32 in which is slidably mounted a plunger 33 having a button 34. The plunger 33 and button 34 are preferably formed of insulating material, such as Bakelite or the like. The inner end of the plunger 33 is adapted to engage the blade 20l for latching together the contact shoulders 28 and 18. The inner end of the plunger 33 is preferably provided with a push-on clip to prevent removal of the plunger from the cover.

The electric circuit to be protected is connected to the terminal connections 15 and 24 so that the latch member 16 and the blade 20 are connected in series in the circuit. When the plunger 33 is depressed, the resilient blade 21B is positioned downwardly and the contact shoulders 28 and 18 resiliently latch and contact each other for completing the electric circuit through the latch member and blade. The current iiow through the blade 210 and the second leg 17 of the latch member 12 operates to heat the same :and as the temperature of the blade 20 increases, the force tending to move the blade 20 upwardly is increased. As the temperature in the second leg 17 increases, the contact shoulder 18 tends to move away from the contact shoulder 28. When the temperatures of the blade 20 and the second leg 17 increase, as the result of an excess current flow therethrough, the resilient latching and contacting action of the contact shoulders 18 and 28 are decreased to a point where the resilient force of the blade 20` overcomes the same to separate the contact shoulders 18 and 28, as illustrated in FIG. 3. Thus, the circuit is broken upon an excess current flow therethrough. As the ambient temperature of the circuit breaker increases, the iirst leg 16 of the latch member is iiexed downwardly in accordance with the ambient temperature condition, and this downward flexing of the first leg 16 causes the latch shoulder 18 to engage with more force, the latch shoulder 28. As a result, when the ambient temperature of the circuit breaker is high, the temperatures of the bimetallic blade 20 and the seco-nd leg 17 of the latch member must be higher to separate the contact shoulders 18 'and 28. ln this way, the first leg 16 of the latch member 12 operates substantially completely to compensate for changes in ambient temperature conditions so that the circuit breaker will open lat substantially predetermined current flows therethrough regardless of ambient temperature conditions. By reason of this construction, it is also seen that contact pressures between the Contact shoulders 18 and 28 increase up to the point of opening the circuit, which provides for full current carrying capacity until the circuit is quickly opened. Because of the [latching and contacting relation of the contact shoulders 18 and 28 a good contact wiping action therebetween is also provided. When the circuit breaker is opened, in the manner described above, it may be reclosed by manually positioning the reset button 34.

While for purposes of illustration, one form of this invention has been disclosed, other forms thereof may become apparent to those skilled in the `art upon reference to this disclosure and, therefore, this invention is to be limited only to the scope of the appended claims.

l claim as my invention:

1. An ambient temperature compensated circuit breaker comprising, :an insulating base, a resilient bimetallic latch member having a iirst leg secured at one end to the base, a second leg carried at one end by the free end of the rst leg and a contact shoulder on the free end of the second leg, a resilient blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member is affected by the current flow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby, one of said legs of said latch member operating upon an increase in temperature thereof in a direction to increase the latching force of the contact shoulders, land the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease the latching `force of the contact shoulders.

2. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member having a first leg secured at one end to the base, a second leg carried at one end by the free end of the first leg and a contact shoulder on the free end of the second leg, a resilient blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections `for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member is affected by the current iiow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally resiliently latching land contacting each other for completing the electric circuit through the latch member and the blade, said resilient l blade resiliently operating against the resilient latching force of the contact shoulders in a `direction to separate the contact shoulders when permitted thereby, one of said legs of said latch member operating upon an increase in temperature thereof in a direction to increase the latching` force of the contact shoulders, and the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease the latching `force of the contact shoulders, `and the temperature of sai-d other leg of said latch member being more responsive to the current flow in the electric circuit than the temperature of said one leg of said latch member.

3. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member having a iirst leg secured at one end to the base, a second leg carried at one end by the free end of the first leg and a contact shoulder on the free end of the second leg, a resilient bimetallic blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member and blade is affected by the current -flow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in 1a direction to increase the separating force thereof, one of said legs of said latch member operating upon an increase in temperature thereof in a `direction to increase the latching force of the contact shoulders, and the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease :the latching force of the contact shoulders.

4. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member having a first leg secured at one end to the base, a second leg carried at one end by the free end of the first leg and a contact shoulder on the free end of the second leg, a resilient bimetallic blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member and blade is affected by the current flow through the electric circuit and by ambient temperature conditions, said contact -shoulders on the latch member and -blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in a direction to increase the separating force thereof, one of said legs of said latch member operating upon an increase in temperature thereof in a direction to increase the latching force of the contact shoulders, and the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease the latching force of the contact shoulders, the temperature of the bimetallic blade being operatively responsive to the current flow in the electric circuit.

5. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member having a first leg secured at one end to the base, a second leg carried at one end by the free end of the first leg and a contact shoulder on the free end of the second leg, a resilient bimetallic blade carried at one i end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member and blade is affected by the current ow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in a direction to increase the separating lforce thereof, one of sai-d legs of said latch member operating upon an increase in temperature thereof in a direction to increase the latching force of the contact shoulders, and the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease the latching force of the contact shoulders, the temperature of the bimetallic blade being operatively responsive to the current ow in the electric circuit, and the temperature of said other leg of said latch member being more responsive to the current ow in the electric circuit than the temperature of said one leg of said latch member.

6. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member carried at one end by the base and having a contact shoulder on its `free end, a resilient bimetallic blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade -for connecting them into an electric circuit wherein the temperature of the latch member and blade is affected by the current flow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in a direction to increase the separating force thereof, said bimetallic latch member operating upon an increase in temperature thereof in a direction to increase the latching -force of the contact shoulders.

7. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member carried at one end by the base and having a contact shoulder on its free end, a resilient bimetallic blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member and blade is aieetcd by the current ow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in a direction to increase the separating force thereof, said bimetallic latch member operating upon an increase in temperature thereof in a direction to increase the latching force of the contact shoulders, the temperature of the bimetallic blade being more responsive to the current flow in the electric circuit than the temperature of said latch member.

8. An ambient temperature compensated circuit breaker comprising, an insulating base, a resilient bimetallic latch member having a rst leg secured at one end to the base, a lsecond leg carried at one end by the free end of the first leg and a contact shoulder on the free end of the second leg, a resilient blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the vlatch member is affected by the current ow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other for completing the electric circuit through the latch member and the blade, said resilient blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby, one of said legs of said latch member operating upon an increase in temperature thereof in a direction to increase the latching force of the contact shoulders, and the other of said legs of said latch member operating upon an increase in temperature thereof in a direction to decrease the latching force of the contact shoulders, a cover secured to the ybase and enclosing the latch member and blade, and a push button carried by the cover for engaging the blade to reset the contact shoulders after they have separated.

9. An ambient temperature compensated circuit breaker comprising, an insulating base, la resilient bimetallic latch member carried at one end by the base and having a contact shoulder on its free end, a resilient bimetallic blade carried at one end by the base and having a contact shoulder on its free end, and terminal connections for the latch member and blade for connecting them into an electric circuit wherein the temperature of the latch member and -blade is affected by the current flow through the electric circuit and by ambient temperature conditions, said contact shoulders on the latch member and blade normally overlapping and resiliently latching and contacting each other `for completing the electric circuit through the latch `member and the blade, said resilient bimetallic blade resiliently operating against the resilient latching force of the contact shoulders in a direction to separate the contact shoulders when permitted thereby and operating upon an increase in temperature thereof in a direction to increase the separating force thereof, said bimetallic latch member operating upon an increase in temperature thereof in a `direction to increase the latching force of the contact shoulders, a cover secured to the base and enclosing the latch member and blade, and a push button carried by the `cover for engaging the blade to reset the contact shoulders yafter they have separated.

References Cited in the file of this patent UNITED STATES PATENTS Donle Oct. l0, Lawton Feb. 27, Sundt Ian. 11, Elliott Dec. 29, Cole Aug, 20, Cole July 28,

FOREIGN PATENTS France Feb. 6, France Sept. 5,

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