US3118034A

US3118034A - Automatic circuit breaker

Info

Publication number: US3118034A
Application number: US59561A
Authority: US
Inventors: Lawrence W Brackett
Original assignee: WOOD ELECTRIC CORP
Current assignee: WOOD ELECTRIC CORP
Priority date: 1960-09-30
Filing date: 1960-09-30
Publication date: 1964-01-14
Anticipated expiration: 1981-01-14

Description

Jan. 14, 1964 w BRACKET-r 3,118,034

AUTOMATIC CIRCUIT BREAKER United States Patent Otice 3,118,034 Patented Jan. 14, 1964 3,118,034 AUTMATIC CHRCUH BREAKER Lawrence W. llraclrett, Georgetown, Mass., assigner to Wood Electric Corporation, Lynn, Mass., a corporation of Massachusetts Filed Sept. 30, 1960, Ser. No. 59,561 2 Claims. (Cl. 26d- 116) The eld of this invention is that of circuit breakers, and the invention relates more particularly to circuit breakers of the non-trip free type.

Circuit breakers of the trip-free and non-trip free type have previously been well known in the circuit breaker art. However, whereas trip-free circuit breakers have been adapted to open circuits rapidly and automatically in response to high, instantaneous current overloads, circuit breakers of the non-trip free type have generally been confined to relatively low current application wherein manual holding of the breaker in closed circuit, or nontrip free, position would not cause injury to the breaker and have accordingly not been adapted to open circuits rapidly. Nevertheless certain circuit breaker applications, such as breakers used in aircraft control circuits, require that a breaker be adapted not only to open rapidly and automatically for protecting a circuit against high instantaneous current overloads without injury to the breaker but also to be held in non-trip free position for short periods with corresponding durability.

Objects of this invention are to provide a non-trip free circuit breaker which is adapted to open rapidly and automatically; to provide a non-trip free circuit breaker which is adapted to open automatically in response to relatively high instantaneous current overload without injury to the circuit breaker, which can be manually held in closed circuit or non-trip tree position when conditioned by current overload, and which is adapted to open a circuit rapidly upon release from non-trip free position while conditioned by current overload.

The substance of the invention can be briey summarized as to characteristic aspects thereof as follows.

Circuit breakers according to the invention comprise in a principal aspect, fixed contact means, movable contact means cooperable therewith for closing a breaker circuit, a pair of pivotally mounted cam members, one of which is adapted to move the movable contact means between open and closed circuit positions, and means biasing the cam means together. Latch means engage the other of the cam members and are adapted to release engagement of said member in response to overload current in the breaker circuit. An operating member movable between open and closed circuit positions carries wedging means which are adapted to be moved between the cam members for moving said one cam member between open and closed circuit positions in response to movement of the operating member when the other cam member is engaged by the latch means, and which are adapted to be automatically released from between the cam members for permitting the cam biasing means to move said one cam member to open circuit position when said other cam member is released from latch engagement in response to overload current in the breaker circuit. According to this invention, means are carried by the operating member which are engageable with said one cam member, whereby manual holding of the operating member in closed circuit position will hold the one cam member in closed circuit position independently of latch engagement of said other cam member.

In a preferred embodiment of this invention, a pair of cams and a movable Contact member are pivotally mounted on a common pivot, and means are provided for biasing the contact member away from one of said cam members and for limiting the extent of separation of the Contact member and said cam. In this construction the operating member has Wedging rolls pivotally suspended therefrom which are adapted to be moved between the cams for manually opening and closing the breaker circuit in response to movement of the operating member when the other of the cams is latched and which are adapted to be released automatically from between the cams when said other cam is released from latch engagement in response to overload current in the breaker circuit. A slide carried by the operating member is guided by sliding engagement with the cam pivot and has a portion engageable with said one cam by means of which, when the operating member is manually held in closed circuit position, said one cam member is held in closed circuit position independently of latch engagement with said other cam.

rl`hese and other objects and aspects of the invention will appear from the following description of a preferred embodiment thereof illustrating its novel characteristics.

The description refers to drawings in which:

FIG. 1 is a section View taken on vertical axis of the circuit breaker showing the breaker in closed circuit position;

HG. 2 is a section view similar to FIG. l showing the circuit breaker in open circuit position;

FIG. 3 is a section view similar to FIG. l showing the circuit breaker in non-trip free position;

FIG. 4 is a section view taken along lines 4 4 of FIG.

FiG. 5 is a perspective View of a cam incorporated in this circuit breaker; and

PEG. 6 is a perspective View of a second cam incorporated in this circuit breaker.

Referring to the drawing, l@ indicates a circuit breaker casing which encloses the breaker operating mechanism i12. The casing comprises a substantially rectangular open-ended box lle, of insulating material such as glasslled asbestos, and is provided with a metallic cover 16 which is secured thereto by means of rivet 16.1 and which is preferably insulated from the breaker operating mechanism by an insulating piece 16.2. internally-threaded bushings 13 are pres-tted within casing cover apertures in conventional manner and serve for mounting the circuit breaker on an instrument panel. The casing cover also has a neck 2@ in which an operating member 22, preferably of insulating material, is slidably mounted.

The circuit breaker terminals 26 and 2S preferably have terminal screws 26.1 and 28.1 for facilitating electrical connection thereto. The terminal 2o, which is of short length, is secured within the casing by means of rivet 2.6.2 and carries a fixed contact 27, whereas the terminal 2S extends within the casing along one casing side and has a bifurcated end 23.2 tted within a recess 143.1 formed in the casing side wall. Preferably an insulating tube 28.3 disposed between the bifurcated ends of the terminal 28 provides electrical clearance between the terminal and the adjacent mounting bushing llti. Terminal mounting screws Zi extend through the casing side wall and threadedly engage the terminal 28 for a purpose to be described below.

Within the casing there is a pivot pin 30 which its within casing apertures 36.1, 30.2 and preferably is secured therein and electrically insulated with a potting material such as an epoxy resin as indicated at 39.3. A movable contact member 32 is pivotally mounted on the pin 3b by means of a rolled end 321 and carries the Contact 33 which is cooperable with the fined contact 27 for closing the breaker circuit. A cam member 34 having a rolled end 34M is similarly mounted on the pin 30 and is biased away from the movable contact member 32 by means of a helical coil spring 35. Cam member 34 has an extension arm 34.2 which is adapted to be engaged with the lip 32.2 of the movable Contact member for limiting separation of the cam member and the contact member 32. The cam member is provided with the cam surface .34.3 and has horizontally extending portions which also serve as cam surfaces. A cam member 36, which is also mounted for rotation on the pin 3d as shown in FIG. 6, is provided with ears 36.1 slotted as at 36.2 to receive the pivot pin 36 and has a cam surface 36.3 recessed at 36.4. This cam member also has a shoulder 36.5 for a purpose to be described below. The

cam members

34 and 36 are biased together by

springs

39 and 49 respectively, each spring being secured between a respective cam member as at 34.5 and 36.6 respectively and pins 4l mounted in slots 41.1 in the casing walls.

A link 42 is secured at each side of the operating member 22 by means of the pivot pin 42.1, and between the links there are three wedging rolls, including two outer rolls 44.1 and an inner roll 44.2, coaxially mounted on pivot pin 44.3. The rolls 44d and 44.2 are adapted to engage the cam surfaces 34.3 and 36.3 respectively.

A bimetallic latch member 46 of substantially U- shape is secured to the terminal 28 by conventional means such as soldering or brazing and carries the latch plate 46.1, secured thereto by means of rivets 46.2, which is adapted to engage the shoulder 36.5 of the cam member 36. Preferably but not necessmily the terminal mounting screw 23.4 may support a magnet core 4S which is insulated from the terminal 28 and the mounting screw 28.4 by an insulating piece 453.1 and an insulating bushing 43.2 respectively. The magnet core, if provided, is cooperable with the magnet armature 43.3 attached t the bimetallic member 46. As thus constructed the degree of latch plate engagement with the shoulder 36.5 can be conveniently adjusted by means of the screws 28.4 after breaker assembly and the screws can then be electrically insulated with a potting material as at 28.5.

A flexible braid 49 soldered to the bimetallic member 46 and the movable contact members 32 completes the breaker circuit. The breaker circuit then extends from the terminal 2S through the bimetallic latch member 46, flexible braid 49, the movable contact member 32, the

contacts

33 and 27 to the terminal 26.

The pivot pin 42.1 carried by the operating member 42 also supports the slide member Sil for movement with the operating member. The slide member includes the slotted end portion Sill which slidably engages the cam and contact member pivot 30 for guiding movement of the slide in response to movement of the operating member and is provided with a cam surface 56.2 adapted to be slidingly engaged with the cam surface extensions 34.4 ot the cam member 34.

FIG. 2 illustrates the open circuit position of the circuit breaker provided by this invention showing the operating member in fully extended position and the contact arm 32 separated from the cam member 34 to its fullest extent. In this construction, downward movement of the operating member advances the wedging rolls 44.1 and 44.2 between the

cam members

34 and 36. Since the shoulder 36.5 of the cam member 36 is normally engaged by the latch plate 46.1 and cannot be rotated, the cam member 34 will be rotated in a counterclockwise direction whereby the contact member 32 is similarly rotated in a counterclockwise direction for closing the breaker circuit. Further downward movement in the operating member 22 snaps the wedging roll 44.2 within the cam recess 36.4 further rotating the cam member 34 for resiliently loading the breaker contacts through the spring and for locking the wedging rolls between the cam members. This position of the circuit breaker is illustrated in FIG. 1.

The circuit breaker can be moved from the closed p0- sition shown in FIG. 1 to the open circuit position shown in FIG. 2 by manually withdrawing the operating mem- 75 ber 22, and therefore the wedging rolls 44.1 and 44.2, from between the cam members. When this occurs, the springs 39 and 4d biasing the

cam members

34 and 36 together return the cam member 34 to the original position shown in FlG. 2 whereby the cam extension arm 34.2 rapidly snaps the movable contact member 32 to open circuit position.

Alternatively when the circuit breaker is in the closed circuit position shown in FlG. 1 the circuit breaker iS automatically operable to be moved to open circuit position in response to current overload in the breaker circuit. Overload current in the breaker circuit, by heating the bimetallic member 46, causes ilexing of said member and releases engagement of the cam shoulder 36.5 by the latch plate 461. When this occurs, the cam member 36 is permitted to rotate in a clockwise direction releasing the wedging rolls 44.1. and 44.2 from between the cam members whereupon the springs 3S and 49 cooperate to return the cam members to original position and also litt the operating member to its fully extended, open circuit, position. lf the overload current in the breaker circuit is relatively high, even if for very short duration, a magnetic field will be established within the magnet core 48 whereby the magnet armature 48.3 will be attracted thereto, similarly flexing the bimetallic member and releasing latch engagement of the cam shoulder 36.5. lt can be seen that the circuit breaker provided by this invention is adapted to open the breaker circuit automatically in response to current overload in the circuit, and that, whether current overload occurring with* in the circuit comprises a relatively low overload of long duration or a relatively high overload of short duration, the breaker contacts will be separated with such rapidity that the breaker will escape substantial injury.

However even though bimetallic latch member 46 is conditioned by a current overload, either of relatively low or relatively high degree, the operating member 22 can be manually held in depressed, closed-circuit position whereby the slide S6 slidably engages the cam member 34 for moving said cam member to closed circuit position, as shown in FIG. 3. Similarly upon release of the operating member 22 from its non-trip free position, the Springs 38 and 4d will return the

cam members

34 and 36 to the original position as shown in FlG. 2 for snapping the contact member 32 to open circuit position.

While the preferred embodiment of this invention has been illustrated, it should be understood that this invention includes all modiiications and equivalents which fall within the scope of the appended claims.

I claim:

l. A circuit breaker comprising an insulating casing, a Contact fixed within the casing, a pivot pin mounted within the casing, a pair of cams pivotally mounted on said pin, a movable contact member cooperable with the fixed contact for closing a circuit, said member being connected with one of said cams for movement with said cam between open and closed mount positions, means biasing the cams together, latch means normally engaging the other of said cams and adapted to release engagement of said cam in response to overload current in the breaker circuit, an operating member slidably mounted in the casing for movement between open and closed circuit positions, and wedging means pivotally connected to the operating member and adapted to be wedged between the cams in response to movement of the operating member for moving said one cam between open and closed circuit positions when said other cam is engaged by the latch means, said wedging means being automatically released from between the cams for permitting said biasing means to move said one cam and said operating member to open circuit position when said other cam is released from latch engagement, in combination with an additional member carried by the operating member and slidingly engaged with said pivot pin, said additional member having a projection engageable with said one cam,

whereby the operating member can be manually held in closed circuit position for holding said one cam member in closed circuit position independent of latch engagement with said other cam member.

2. A circuit breaker comprising an insulating casing, a contact xed within the casing, a pivot pin mounted within the casing, a pair of cams pivotally mounted on said pin, a movable contact member cooperable with the fixed Contact for closing a circuit, means biasing the contact member away from one of said cams, means limiting separation of said one cam and contact member, a bimetallic latch normally engaging the other of said cams, said latch being interposed in the breaker circuit and being adapted to ilex in response to relatively low overload current in the circuit thereby to release engagement of said cam, a magnet armature carried by the bimetallic latch, electromagnet means adapted to be actuated by relatively high overload current in the breaker circuit for attracting said armature to flex said bimetallic member, an operating member slidably mounted in the casing for movement between open and closed circuit positions, wedging rolls suspended from the operating member for movement therewith, said rolls being adapted to be wedged between the cams for moving said one cam to load said contact member resiliently in closed circuit position and to be drawn from between the cams for permitting said Contact member and cam biasing means to snap the contact member to open circuit position when said other cam is latched, said rolls being automatically released from between said cams for permitting said biasing means to snap said one cam and operating member to open circuit position when said other cam is released from latch engagement, and a slide member carried by said operating member and guided by sliding engagement with said pivot pin, said slide having a surface engageable with said one cam whereby when said operating member is manually held in closed circuit position said one cam will be held in closed circuit position independently of latch engagement of said other cam.

References Cited in the iile of this patent UNITED STATES PATENTS 2,287,875 Grober June 20, 1942 2,409,917 Von Hoorn Oct. 22, 1946 2,613,296 Wood Oct. 7, 1952 2,813,168 Mascioli et al Nov. 12, 1957

Claims

1. A CIRCUIT BREAKER COMPRISING AN INSULATING CASING, A CONTACT FIXED WITHIN THE CASING, A PIVOT PIN MOUNTED WITHIN THE CASING, A PAIR OF CAMS PIVOTALLY MOUNTED ON SAID PIN, A MOVABLE CONTACT MEMBER COOPERABLE WITH THE FIXED CONTACT FOR CLOSING A CIRCUIT, SAID MEMBER BEING CONNECTED WITH ONE OF SAID CAMS FOR MOVEMENT WITH SAID CAM BETWEEN OPEN AND CLOSED MOUNT POSITIONS, MEANS BIASING THE CAMS TOGETHER, LATCH MEANS NORMALLY ENGAGING THE OTHER OF SAID CAMS AND ADAPTED TO RELEASE ENGAGEMENT OF SAID CAM IN RESPONSE TO OVERLOAD CURRENT IN THE BREAKER CIRCUIT, AN OPERATING MEMBER SLIDABLY MOUNTED IN THE CASING FOR MOVEMENT BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS, AND WEDGING MEANS PIVOTALLY CONNECTED TO THE OPERATING MEMBER AND ADAPTED TO BE WEDGED BETWEEN THE CAMS IN RESPONSE TO MOVEMENT OF THE OPERATING MEMBER FOR MOVING SAID ONE CAM BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS WHEN SAID OTHER CAM IS ENGAGED BY THE LATCH MEANS, SAID WEDGING MEANS BEING AUTOMATICALLY RELEASED FROM BETWEEN THE CAMS FOR PERMITTING SAID BIASING MEANS TO MOVE SAID ONE CAM AND SAID OPERATING MEMBER TO OPEN CIRCUIT POSITION WHEN SAID OTHER CAM IS RELEASED FROM LATCH ENGAGEMENT, IN COMBINATION WITH AN ADDITIONAL MEMBER CARRIED BY THE OPERATING MEMBER AND SLIDINGLY ENGAGED WITH SAID PIVOT PIN, SAID ADDITIONAL MEMBER HAVING A PROJECTION ENGAGEABLE WITH SAID ONE CAM, WHEREBY THE OPERATING MEMBER CAN BE MANUALLY HELD IN CLOSED CIRCUIT POSITION FOR HOLDING SAID ONE CAM MEMBER IN CLOSED CIRCUIT POSITION INDEPENDENT OF LATCH ENGAGEMENT WITH SAID OTHER CAM MEMBER.