US3629765A

US3629765A - Circuit breaker

Info

Publication number: US3629765A
Application number: US38336A
Authority: US
Inventors: Richard J Hanson
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1970-05-18
Filing date: 1970-05-18
Publication date: 1971-12-21
Anticipated expiration: 1988-12-21
Also published as: CA923529A

Abstract

A circuit breaker having a bimetallic member normally in a circuit closed position in which it engages a stationary terminal to provide a conductive path therebetween, but which is movable toward a circuit open position when heated in response to an electric current in excess of a predetermined magnitude being passed therethrough. The circuit breaker also includes a resistance heater in the form of a printed circuit bonded to the bimetallic member and which is in a parallel circuit with the bimetallic member. When the bimetallic member is moved toward its circuit open position the current flows through the resistance heater to maintain the bimetallic member in a heated condition and in its circuit open position.

Description

United States Patent [72] inventor Richard J. Hanson FOREIGN PATENTS m A l N g g? 1,151,859 5/1969 Great Britain 337/107 0. E 53 18 1970 Primary Examiner-Bernard A. Gilheany [45] Patented Dem 21 1971 Assistant Examiner-Dewitt M. Morgan [73 1 Assignee Gum. Motors corponfion Attorneys-W. E. Finken and W. A. Schuetz Detroit, Mich.

ABSTRACT: A circuit breaker having a bimetallic member [54] CIRCUIT BREAKER normally in a circuit closed position in which it engages a sta- 4 Chin, 5 Drawing Figs. gormrzl termmal to tplroitnde adconductue path therebetwe'fn, u w 1c is mova e owar a c1rcu1 open pos1t1on w en [52] US. Cl 337/103, heated in response to an electric current in excess of a 337/107 337/1 13 predetermined magnitude being passed therethrough. The cir- [51] II. C ..ll0lh37/54, cuit breaker also includes a resistance heater in the form of a 61/013 61/04 printed circuit bonded to the bimetallic member and which is FIG oiSearch in a parallel circuit with the bimetallic member. w the 1 381 bimetallic member is moved toward its circuit open position [56] Rehnnm Cited the current flows through the resistance heater to maintain the UNnED STATES PATENTS bimetallic member in a heated condition and in its circuit open osition. 2,403,803 7/1946 Kearsley 337/ I03 UX p /d I0 .49 a

CIRCUIT BREAKER The present invention relates to a circuit breaker, and in particular to a circuit breaker having a bimetallic member which ismovable toward a circuit open position when heated in response to a current in excess of a predetermined magnitude passing therethrough.

l-leretofore, bimetallic circuit breakers have been provided for breaking an electric circuit when current in excess of a predetermined magnitude was passed therethrough. These circuit breakers comprised a bimetallic member operatively connected to a load device and a stationary contact operatively connected with a power source, or vice versa. The bimetallic member was normally disposed in a circuit closed position in which it engaged the stationary contact to provide a conductive path therethrough. However, when the current passing through the bimetallic member exceeded a predetermined magnitude, the bimetallic member was heated which caused the same to be moved away from the stationary contact to break the electric circuit. When the bimetallic member cooled, it returned toward its circuit closed position.

It is also known in the art to provide auxiliary heating means to keep the bimetallic member heated and in its circuit open position. These auxiliary heaters were connected in parallel with the bimetallic member, but were separate therefrom. When the bimetallic member moved to its circuit open position the current passed through the resistance heater to maintain the bimetallic member in a heated condition. An advantage of this latter type of circuit breaker is that it remains in its circuit open position until the current from the power source is shut off. Bimetallic circuit breakers having such auxiliary heating means are shown in US. Pat. Nos. 1,830,578, l,70l ,757, 2,884,50] and 3,265,839.

The present invention provides a new and improved bimetallic circuit breaker which is more compact than known circuit breakers and which has an auxiliary resistance heater in the form of a printed circuit bonded directly onto an insulated portion of the bimetallic element. The current is normally shunted through the bimetallic element when it is in its normal circuit closed position, but passes through the printed circuit resistance heater when the bimetallic element moves to a circuit open position to maintain the bimetallic element in the latter position.

Accordingly, it is a broad object of the presentinvention to provide a new and improved bimetallic type circuit breaker which is of a compact construction and which includes an auxiliary resistance heater in the form of a printed circuit secured or bonded directly onto the bimetallic element to heat the latter and maintain it in its circuit open position upon being moved thereto.

Another object of the present invention is to provide a new and improved circuit breaker having a stationary terminal, a bimetallic member which is normally disposed in a circuit closed position in which a contact surface thereon engages the terminal, but which is movable toward a circuit open position when heated in response to a current in excess of a predetermined magnitude being passed therethrough, and a resistance heater in the form of a printed circuit bonded on an electrically insulated portion of the bimetallic member and having a first contact surface in electrical engagement with the bimetallic member and a second contact surface biased by said bimetallic member into constant electrical engagement with a curved contact surface on the stationary terminal, and wherein the second contact surface of the resistance heater rolls on the curved contact surface of the stationary terminal when the bimetallic element is moved to its circuit open position, the current passing through the resistance heater to maintain the bimetallic element heated when the latter is in its circuit open position.

The present invention further resides in various novel constructions and arrangement of parts, and further objects, novel characteristics and advantages of the present invention will be apparent to those skilled in the art to which it relates and from the following detailed description of the illustrated embodiment hereof made with reference to the accompanying drawings forming a part of this specification and in which similar reference numerals or characters are employed to designate corresponding parts throughout the several views, and in which:

FIG. 1 is an elevational view, with portions shown in section, of the novel circuit breaker of the present invention;

FIG. 2 is a plan view of part of the circuit breaker shown in FIG. 1;

FIG. 3 is an end elevational view of the circuit breaker shown in FIG. 1;

FIG. 4 is an enlarged fragmentary view of part of the circuit breaker shown in FIG. 1; and

FIG. 5 is an enlarged fragmentary view of part of the circuit breaker shown in FIG. 1 and looking in the direction of the arrows 5-5.

As representing an illustrated embodiment of the present invention, the drawing show a circuit breaker 10. The circuit breaker 10 could be used in various applications wherein it is desired to interrupt an electric circuit in response to a current in excess of a predetermined magnitude passing therethrough. It is particularly useful, however, in automotive applications, such as for use as an overload protector for an electric motor for operating vehicle components, such as a window regulator mechanism.

The circuit breaker 10 comprises, in general, a housing or support member 12, a stationary terminal 14 which is adapted to be electrically connected to a load device, such as an electric motor, a stationary terminal 16 which is adapted to be electrically connected to a suitable power source, such as a battery of a vehicle, a bimetallic member 18 which is supported in cantilever fashion by a stationary terminal 16, and a resistance heater 20 bonded to the bimetallic member 18 and which is electrically connected in parallel with the bimetallic member 18.

The housing or support 12 could be of any suitable shape or construction, but is here shown as comprising a hollow member made from a suitable electrically insulating material. The housing 12 comprises a pair of

end portions

12a and 12!) having transverse or radially extending

slots

21 and 22 therein, respectively, and an annular intermediate portion which defines a chamber 23. The housing 12 has an opening 24 along a side portion thereof which is in communication with the chamber 23.

The stationary terminal 14 comprises an elongated flat metal blade, preferably steel, which is supported by the housing 12 intermediate its ends. The stationary terminal 14 has a pair of spaced elongated detents 14 a which are snap fittingly received within recesses 21a in the end portion 12a of the housing 12 and in communication with the slot 21 to securely retain the stationary terminal 14 in place upon the latter being inserted sidewise through the slot 21. The stationary terminal 14 has a forward portion 14b which extends within the chamber 23 and is supported by the housing 12 in cantilever fashion. The stationary terminal 16 comprises a flat blade which is secured to the other end portion 12b of the housing 12, and in the same manner as the stationary terminal 14.

The stationary terminal 16 supports the bimetallic member 18 in cantilever fashion. To this end, one end of the bimetallic member is welded or otherwise secured to the stationary terminal 16. The bimetallic member 18 is an elongated, flat, thin member and can be made from any suitable metallic materials, such as two different steel alloys. The bimetallic member 18 at its free end 18a has a contact surface in the form of a silver alloy contact 1812 which is engageable with a contact surface in the form of silver alloy contact 14c located intermediate the ends of the stationary tenninal 14.

The bimetallic member 18 is movable between circuit closed and circuit open positions. The bimetallic member 18 is normally disposed in a circuit closed position, as shown by the solid lines in F 16.1, in which the contact 18b engages the contact 14c on the stationary terminal 14 to provide a conductive path between the

stationary terminals

14 and 16 via the bimetallic element 18. When bimetallic member 18 is in its circuit open position, as shown by the phantom lines in FIG. 1, the contact 18b is out of engagement with the contact 14c on the stationary terminal 14 and thus, the conductive path between the

stationary terminals

14 and 16 is broken. The bimetallic member 18 is movable from its circuit closed position towards its circuit open position when the current passing therethrough exceeds a predetermined magnitude. When the current exceeds a predetermined magnitude it heats the bimetallic member 18 to.a temperature to cause the same to be moved toward its circuit open position.

In accordance with the provisions of the present invention, a resistance heater in the form of a printed circuit is provided to maintain the bimetallic member 18 in its circuit open position when the latter has moved thereto. As shown in FIG. 5, the printed circuit 20 is in the form of a resistance grid bonded or secured to a layer or film of insulating material 30, the latter in turn being bonded or secured to the underside of the bimetallic member 18. The printed circuit 20 is preferably made from stainless steel and the insulating material could be any suitable material, such as a ceramic layer, or plastic film, such as that sold under the trademark Kapton.

The printed circuit 20 includes a contact surface or portions 20a which is in constant electrical engagement with the terminal 16. It also includes a contact surface or portion 20b which is in constant engagement with the upper curved or convex surface 14d of the free end of the stationary terminal 14, The printed circuit 20 is formed by an etching process. lnitially a stainless steel sheet is bonded or secured to the insulated backing layer and then the stainless steel is etched to provide the grid circuit shown in H0. 5. This type of process is well known in the art and hence, will not be described in detail. 7

An important feature of the present invention is that the contact surface 20b of the printed circuit 20 remains in constant engagement with the convex surface 14d of the stationary terminal 14 as the bimetallic member 18 moves between its circuit closed and circuit open positions. This is accomplished by biasing the bimetallic member 18 into engagement with the surface 14d and by providing a rolling action between the contact surfaces 14d and 20 b when the bimetallic member 18 moves between its positions. As can be seen in FIG. 1 and 4, the bimetallic member 18 is caused to be slightly bowed and in opposition to the self-biasing forces tending to maintain the member 18 planar, when in its circuit closed position, as a result of the engagement between the free end of the terminal 14 and the bimetallic member 18 adjacent its end connected to the terminal 16. The self-biasing forces of the bimetallic member 18 maintains the contact surface portion 20b of the printed circuit in engagement with the contact surface 14b.

When the bimetallic member 18 moves toward its circuit open position, as shown by the phantom lines in H6. 1, the contact surface 20b of the printed circuit rolls on the convex surface 14d of the stationary terminal 14 so as to remain in engagement therewith. In the circuit open position the current, which is normally shunted through the bimetallic member 18 to the stationary terminal 16, passes from the stationary terminal 16 through the resistance grid 20 to the stationary terminal 14. This maintains the bimetallic member 18 in a heated condition and in its circuit open position. The resistance value of the grid is correlated to the desired value of the current or amperage passing through the circuit so that the value of the current after passing through the resistance grid 20 is very low.

When the power source is disconnected from terminal 16, such as by opening a switch between the power source and terminal 16, the bimetallic member 18 will cool and move to its circuit closed position.

Although the illustrated embodiment thereof has been described in great detail, it should be apparent that certain modifications, changes, and adaptations may be made in the illustrated embodiment, and that it is intended to cover all such modifications, changes and adaptations which come within the spirit of the present invention.

What is claimed is: V

1. A current responsive circuit breaker comprising; a terminal member; a bimetallic member; one of said members being adapted to be operatively connected to an electrical power source; the other of said members being adapted to be operatively connected to a load; said bimetallic member being supported in cantilever fashion and having a contact surface adjacent its free end which is engageable with said terminal member, said bimetallic member being normally disposed in a circuit closed position in which said contact surface adjacent its free end engages the terminal member to provide a conductive path therebetween, said bimetallic member being movable away from said terminal member toward a circuit open position to break the conductive path therebetween in response to being heated by passage of a current in excess of a predetermined magnitude therethrough; a layer of electrically insulating material on a portion of said bimetallic member, a resistance heater in the form of a printed circuit on said layer, said printed circuit having first and second contact surfaces in constant engagement with a surface on said bimetallic member and said terminal member, respectively, whereby when said bimetallic member is in its circuit open position the current is passed through said printed circuit to maintain the bimetallic member in a heated condition and in its circuit open position, said bimetallic member being self-biased into engagement with the terminal member and said second contact surface rolls on said terminal member while maintaining engagement therewith when the bimetallic member moves to its circuit open position.

2. A current responsive circuit breaker comprising: a terminal member; a bimetallic member; one of said members being adapted to be operatively connected to an electrical power source; the other of said members being adapted to be operatively connected to a load; said bimetallic member being supported at one end in cantilever fashion and having a contact surface adjacent its free end which is engageable with said terminal member, said bimetallic member being normally disposed in a circuit closed position in which said contact surface adjacent its free end engages said terminal member to provide a conductive path through the bimetallic member, said bimetallic member being movable from said circuit closed position toward a circuit open position in which said contact surface adjacent its free end disengages the terminal member to break the conductive path therethrough in response to being heated by passage of a current therethrough in excess of a predetermined magnitude, a layer of electrically insulating material on a portion of said bimetallic member, a resistance heater in the form of a printed circuit on said layer, said terminal member having a curved contact surface, said printed circuit having first and second contact portions in constant engagement with said bimetallic member and said curved contact surface on said terminal, respectively, whereby when said bimetallic member is moved toward its circuit open position the current will be passed through the resistance heater to maintain the bimetallic member in a heated condition so that it remains in its circuit open position, said bimetallic member being self-biased into engagement with said curved contact surface on said terminal and said second contact surface rolling on said curved contact surface of said terminal member when the bimetallic member is moved between its positions.

3. A current responsive circuit breaker comprising a support member,; a flat blade terminal supported by said support in cantilever fashion and having a curved contact surface at its free end; a second stationary terminal supported by said support and spaced from said first terminal; a bimetallic member which is secured to said second terminal and is supported thereby in cantilever fashion, said bimetallic member having a contact surface adjacent its free end which is engageable with said first terminal intermediate the ends of the later, said bimetallic member being normally disposed in a circuit closed position in which said contact surface adjacent its free end engages said terminal to provide a conductive path between the terminals, said bimetallic member being movable away from its circuit closed position toward a circuit open position to break the conductive path therethrough in response to being tion and in a circuit open position, said bimetallic member being self-biased into engagement with said curved contact surface of said first terminal, said second contact portion of said printed circuit rolling on said curved free end of said first terminal when the bimetallic member is moved toward its circuit open position.

4. A current responsive circuit breaker as defined in claim 3 and wherein said printed circuit is in the form of a grid.

1? i i i i

Claims

3. A current responsive circuit breaker comprising a support member,; a flat blade terminal supported by said support in cantilever fashion and having a curved contact surface at its free end; a second stationary terminal supported by said support and spaced from said first terminal; a bimetallic member which is secured to said second terminal and is supported thereby in cantilever fashion, said bimetallic member having a contact surface adjacent its free end which is engageable with said first terminal intermediate the ends of the later, said bimetallic member being normally disposed in a circuit closed position in which said contact surface adjacent its free end engages said terminal to provide a conductive path between the terminals, said bimetallic member being movable away from its circuit closed position toward a circuit open position to break the conductive path therethrough in response to being heated by passage of a current in excess of a predetermined magnitude therethrough, a layer of electrically insulating material on a portion of said bimetallic member, a resistance heater in the form of a printed circuit on said layer, said printed circuit having first and second contact surface portions in constant engagement with said second terminal and the curved free end of said first terminal, respectively, so that when said bimetallic member is moved towards its circuit open position the current will pass through the resistance heater to maintain the bimetallic member in a heated condition and in a circuit open position, said bimetallic member being self-biased into engagement with said curved contact surface of said first terminal, said second contact portion of said printed circuit rolling on said curved free end of said first terminal when the bimetallic member is moved toward its circuit open position.