US2806920A - Circuit breaker - Google Patents

Description

Sept. 17, 1957 C. W. JONES CIRCUIT BREAKER Filed March 29, 1954 INVENTOR. W /fes,

United States Patent CIRCUIT BREAKER Clifford W. Jones, Mount Clemens, Mich, assignor to Square D Company, Detroit, Mich., a corporation of Michigan Application March 29, 1954, Serial No. 419,281

7 14 Claims. (Cl. 200-116) This invention relates to apparatus for making and breaking electric circuits, and more particularly to an electric circuit breaker manually operable for switching operation and automatically operable to break the circuit in response to current overload.

An object of the present invention is to provide an improved automatic electric circuit breaker, which is of an extreme simplicity of construction and assembly, which employs a minimum of parts, and which may be produced at low cost.

Another object of the present invention is the provision of an automatic circuit breaker having a novel improved latch construction.

.A;further object of the present invention is an automatic circuit breaker having an improved latch construction providing for ease and simplicity of calibration adjustment.

Another object of the present invention is the provision of a circuit breaker having a bimetallic member which has a fixed and a free end, a movable contact carrying arm being fixedly mounted to the free end of the bimetallic member, a resilient latch being provided for engaging the contact carrying arm and retarding its movement from a first to a second operating position, the latch being releasable upon the application of suflicient force to the contact arm by either the bimetallic member or a manually operable handle and being adjustable in height to determine the calibration point of the circuit breaker.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended claims illustrating certain preferred embodiments in which:

Figure 1 is a side elevational view of the circuit breaker of the present invention with the side cover broken away to show the internal parts in the normal On position.

Figure 2 is a sectional view of the latch of the present invention along the plane of line II-II of Figure l.

Figure 3 is a partial sectional view of a modified form of the latch of the present invention generally along the plane of line 11-11 of Figure 1.

Figure 4 is a sectional view along the plane of line lVIV of Figure 3.

The circuit breaker of the present invention is of the general type illustrated and claimed in the patent for Circuit Breaker No. 2,666,114 and in the copending application for Circuit Breaker filed September 16, 1952, Serial No. 309,862, and issued December 14, 1954, as Patent No. 2,697,151.

Figure 1 illustrates the device of the present invention with the parts in the normal On position. As shown therein, the device comprises a box-like base 1 of insulating material, having an open side which is normally closed by a Hat cover piece 2 of insulating material, with cover piece 2 being attached to'the base 1 by suitable means such as spun-over rivets.

{integrally molded into the base 1 are a plurality of "recesses of three sides, one of these sides being the back wall of the base 1. Into one of these recesses at the left 2,806,920 Patented Sept. 17, 1957 of Figure 1, there is pressed a terminal member 3 having an end 4 which projects beyond one end wall of the base 1, and receives there a terminal screw 5. To the other end of the terminal member 3 there is welded a main bimetal 6, the high expansion side of which forms the upper surface as viewed in Figure 1. To the free end of the bimetal 6 there is welded a movable contact arm 7, having a return bent loop portion 8 near the bimetal 6, and carrying a movable contact 9 at its free end. The arm 7 is formed of a resilient spring strip and is strengthened by a stiffening rib over that portion between loop 8 and contact 9 to rigidity the same, while the loop portion 8 is not so stiffened so that it is readily deformed against its inherent resilience.

, Disposed so as to cooperate with the movable contact 9 is a fixed contact 11 which is welded to a contact terminal 12, fitted into suitable recesses molded in the base 1. Terminal 12 has a projection 13 which protrudes through a recess in the bottom in base 1, the projection 13 and a jaw spring 14, which also is positioned within a base 1 recess, serving to provide for resiliently clamping the breaker to a bus bar. Spaced from the cooperat ing members 13 and 14 an amount equal to the spacing between adjacent bus bars employed with the circuit breaker is a non-current carrying bus jaw 15, which is fitted into a base 1 recess, and which has dependent resilient arms, which in the mounted position of the current breaker, help hold it into position upon the bus bar structure, this bus jaw 15 being in no way connected to any of the current carrying parts of the circuit breaker.

To the free end of the main bimetal 6 there is welded a magnetic armature plate 16 having an upturned flange 17 at its free end. Mounted on the plate 16 is a spring 18 having a pair of upstanding portions 19 and 21. Rotatably mounted upon a pivot pin 22 integral with the side of base 1 is a manually operable handle 23, the handle 23 being biased to the Oif position, not specifically illustrated herein, by a handle spring 20. In the under surface of handle 23 there is provided a slot 24 having a pair of camming sides 25 and 26. The under surface of handle 23 is also provided with an additional camming surface 27 and an integral shoulder 28, the purpose of which will be subsequently explained.

Referring to Figure 1, there is mounted on the base 1, with its legs embracing contact arm 7, a resilient latch 29, shown in cross section in Figure 2. Latch member 29 is provided with a pair of legs 31 and 32, leg 31 being substantially straight but curved slightly transversely to present a smooth line surface to arm 7. Leg 32 is provided at its upper extremity with an oifset portion 33 which is bent from the main portion of the leg 32, and centrally located along the line of bend is a short, coined nub 34 having a sharp corner which projects slightly from the line of bend. The bight 35 of latch member 29 is, as may be seen in Figure 2, made as horizontal as possible, with whatever variance from horizontal being an extremely slight concave bow toward the legs 31 and 32.

Mounted within a suitable recess in the base 1 is a yoke 36 of magnetic material which is of cross-sectional U shape, the yoke 36 having an end extension 37 of reduced width which projects between the legs of latch 29 and rests upon the fiat bottom surface 35 thereof. Threaded into a suitable aperture in the bottom surface of the yoke 36 is an adjusting screw 38 which is fitted into a recess in base 1 and is accessible when jaw spring 14 is removed. Below the latch 29 and between the latch 29 and the recess in the base 1 into which the latch 29 is fitted, there is positioned a resilient shim 40 having a concave contour lengthwise of the base 1 with its legs engaging the base 1 and its central upraised portion engaging the latch 29. The resilient shim 40 biases the latch against the end extension 37 of the yoke 36 and, as will be more fully explained hereinafter, provides a means for calibration adjustment of the latch 29 toward or away from the circuit closed position of contact arm 7 as illus trated in Figure 1.

In Figures 3 and 4 there is illustrated a modified form of the latch member of the present invention. As will be seen from a consideration of Figure 3, a different shape contact arm 43 is provided which cooperates with a modified latch 44 having a pair of similar legs 45, near the extremity of each of which there is provided an 01?- set portion 46 bent from the main portion thereof and each provided with a nub 47 similar to nub 34 of arm 7. The opposite edges of contact arm 43 are offset at the latch, as shown in Figure 3, to cooperate with the offset portions 46 on the latch.

It will readily be seen that the assembly of the parts into the base is an extremely simple operation which comprises merely fitting the parts into their allotted positions in base 1, and fixing the cover 2 to the base to close the open side of the base. Portions 50 are provided which are molded integrally with the base 1 and the terminal members when forced into their respective openings shear off the tops of portions 50 so that the terminal members are held tightly in position. After assembly, the bimetal 6 and the contact arm are given an initial set so that they will move the contact 9 to the closed circuit position. In other words, the initial bias of bimetal 6 and the contact arm causes the contacts 9 and 11 to engage. The operating contact pressure between the contacts is supplied through the bias of the latches 29 or 44 operating through the upper ofiset portions thereof on the under edges of the contact arm, as shown in Figures 2 and 3. This pressure is increased as the energy is stored in the resilient looped portions prior to both manual and automatic tripping as hereinafter described.

For any given design of the breaker as to size and material, there will be a definite force available at the free end of bimetal 6 to effect opening movement of the contact arm at the desired current rating. In calibrating the breaker, screw 38 is adjusted to vary the position of the projection 37 and, hence, the vertical position of the latch itself, until the proper enggaement is provided between contact arm and latch offset to permit release of the contact arm at the predetermined pressure and, hence, at the desired current rating.

The operation of the improved latch mechanism will now be described:

Adjustment of the latch mechanism of the circuit breaker of the present invention is affected by rotation of the screw 38 to position the projection 37 within the latch member. The latch member 29 is continuously biased into engagement with the projection 37 by the resilient shim 40. As the adjusting screw 38 is rotated, the latch 29 is moved vertically up and down within the circuit breaker base 1 to position the offset portion 33 or 46 with respect to the contacts closed position of the contact arm 7. As the latch member (29 or 44) is moved upwardly toward the contact arm (7 or 43), the surface engagement between the offset portions 33 or 46, respectively, is increased or decreased slightly. The latch 29 or 44 is, by this degree of engagement, bowed by its inherent resilience into a more open U shape as the latch is moved upwardly, or into a tighter U shape as the latch is moved downwardly through its cooperation with the offset side portions of the contact arms 7 or 43 respectively. The position of the latch with respect to the contact arm determines the amount of force which will be required to snap the contact arm through the latch. That is, with the contact arm engaging a smaller portion of the offset portions 33 or 46 of the latch, and with the latch bowed into an open U shape the contact arm need exert a lesser force on latch legs 3132 or 45 to push the contact arm through the latch. With the latch in a tight U shape, a larger surface of engagement is provided between the contact arm and the offset portions of the latch and the contact arm is required to push the latch into a more open U shape before the contact arm may pass through the latch, thereby increasing the current carrying calibration of the circuit breaker.

The operation of the circuit breaker will now be described:

The parts are shown in Figure l in closed circuit or On position. In this position, cam 25 of handle 23 is biased by handle spring 20 into engagement with portion 19 of spring 13. The offset portion 33 of the latch 29 engages the underside of the contact arm 6, biasing it upwardly. To open the circuit, handle 23 is rotated in a counterclockwise direction. The initial force exerted on handle 3 in this direction is translated through camming surface 25 to portion 19, causing deformation of the spring 18. Portion 19 assumes a slanted position and engages flange 17 of plate 16 to force it downwardly upon continued movement of handle 23. The movement of plate 16 is transmitted to the free end of bimetal 6 which, in turn, moves the end of the contact arm attached thereto downwardly. Inasmuch as the looped portion of the movable contact arm is relatively resilient and the remainder of the contact arm relatively rigid, there is a stressing of the looped portion and a partial rotating of the movable contact arm about the offset portions (33 or 46) of the latch (29 or 44) as a fulcrum. Movable contact 9 is urged more strongly against the fixed contact 11 as this partial rotation occurs. The pressure applied to the movable contact arm will be increased until such time as the oifset portions are no longer able to hold the movable contact arm and it will be seen that the contacts are, therefore, inherently opened at the moment of maximum pressure, this minimizing burning of the contacts. When this condition is reached, the legs of the latch (29 and 44) are forced apart and the contact arm will be moved with a snap action, resulting from the rapid release of the energy stored in the loop portion 8 to the open circuit condition. As the contact arm passes below the coined nubs (34 or 47) spring 18 moves below the end of the cam side 25, whereupon handle 23 is free to rotate under the bias of handle spring 21 to the position of open circuit. It will be apparent that in that position, cam surface 27 of handle 23 is engaged by the upper surface of spring 18 and serves to hold the movable contact arm in the open circuit position.

To move the parts from the Off position, not herein shown, to the On position of Figure I, handle 23 is rotated in a clockwise direction. In this movement, cam 27 rides along the upper surface of spring 18, and shortly before cam 27 leaves spring 18, cam side 26 engages portion 21 of spring 18, moving it inwardly. This movement of portion 21 is necessary as the distance between the upwardly facing surfaces of portion 19 and 21 is greater than the width of slot 24. Further movement of the handle 23 in this clockwise direction then permits the device to assume the position of Figure l; the bias of the bimetal 6 and the contact arm 7 and the force exerted by offset portion 33 of latch 29 effecting this closing operation with a snap action.

With the parts in the position of Figure 1, if handle 23 is rotated clockwise, it is apparent that cam side 25 will be disengaged from portion 19 of spring 18. When this occurs, that component of force transmitted by handle spring 20 which tends to force bimetal 6 toward the Off position will be removed. Cam side 26, however, will, by that movement, be forced against portion 21 of spring 18 and will thereby tend to restore an opening force to bimetal 6 whereby the calibration of the breaker will remain substantially unchanged.

With the parts in the On position, should a sustained overload occur, which is of a magnitude to cause the main bimetal 6 to be sufiiciently deflected, the end of the bimetal 6 connected to the end of the movable contact arm will cause, initially, a partial rotation of the contact arm as previously described until the resilient looped portion of thecontact arm is sufficiently stressed to effect a snap opening movement of the movable contact. Handle 23 will then be moved in a counterclockwise direction under the bias of handle spring 20 to the Off position.

With the circuit breaker in the On position, should a heavy overload current through the circuit breaker occur, the flux emanating from such overload current will cause the magnetic armature plate 16 to be attracted to the core 36, the resulting force upon the contact arm tending to effect the snap opening of the movable contact 9 away from the fixed contact 11 in a manner similar to the opening on manual operation and on bimetal flexure from heating alone.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit position, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit position to oppose such changes, and adjustable means operable upon said latch to move said latch in a direction normal to the plane of said arm, said movement being effective to adjust the height of said latch within said circuit breaker and with respect to said arm and thereby the amount of opposition to changes in circuit position to vary the calibration of said circuit breaker.

2. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit position, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit position to oppose such changes, adjustable means operable upon said latch to vary the height of said latch to move said latch in a direction normal to the plane of said arm, said movement being effective with respect to said arm and thereby the amount of opposition to changes in circuit position to vary the calibration of the circuit breaker.

3. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current condition, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm, the ends of said legs of said U-shaped latch being inclined generally outwardly and presenting a sharp edge at the point of incline into the path said arm traverses during changes in circuit conditions to oppose such changes, said arm having the sides thereof inclined upwardly, complementary with said inclined surfaces of said latch and in engagement therewith in closed circuit position, and adjustable means to vary the height of said latch relative to said arm to determine the calibration of said circuit breaker.

4. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current condition, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm, one leg of the U-shaped latch being inclined generally outwardly and presenting a sharp edge at the point of incline, the opposite leg presenting a substantially continuous smooth surface, said arm having one side thereof inclined upwardly, complementary with said inclined surface of said latch and in engagement therewith in closed circuit position, and adjustable means to vary the height of said latch relative to said arm to determine the calibration of said circuit breaker.

5. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path the arm traverses during changes in circuit positions to oppose such changes, resilient means biasing said latch toward said arm, and adjustable means operable upon said latch to adjust the height thereof within said circuit breaker against the bias of said resilient means to thereby vary the amount of opposition to movement of the arm to open circuit position to determine the calibration of said circuit breaker.

6. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit positions to oppose such changes, resilient means biasing said latch toward said arm, means holding said latch against said resilient means, and adjustable means operative upon said holding means to adjust the height of said latch against the bias of said resilient means to vary the amount of opposition to change in circuit position to determine the calibration of the circuit breaker.

7. In a circuit breaker, a fixed contact, a movable con tact, a supporting arm for said movable contact movable to open and closed circuit positions, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and 1n the path said arm traverses during changes in circuit positions to oppose such changes, resilient means biasing said latch toward said arm, and adjustable means operative upon the bight of said latch to position said latch against the bias of said resilient means with respect to said arm to vary the amount of opposition to change in circuit position to determine the calibration of the circuit breaker.

8. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, means normally biasmg said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm, the ends of the legs of said U being inclined generally outwardly and presenting a sharp edge at the point of incline in the path said arm traverses during changes in circuit positions to oppose such changes, said arm having the sides thereof inclined upwardly complementary with said inclined surfaces of said latch, resilient means biasing said latch toward said arm, and adjustable means for adjusting the height of said latch within said circuit breaker against the bias of said resilient means to vary the degree of engagement between said inclined portions and thereby the calibration of said circuit breaker.

9. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit positions to oppose such changes, a resilient, bowed shim disposed beneath the bight of said latch, and adjustable means operating upon the bight of the latch to compress said shim to vary the height of the latch relative to the arm to determine the calibration of the circuit breaker.

10. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current condition, a resilient restraining member having a leg disposed adjacent said arm and substantially parallel to the plane of movement of said arm, the end of said leg being inclined generally outwardly and presenting a sharp edge at the point of incline in the path said arm traverses in moving to open circuit position, and adjustable means operable to move said restraining member in a direction normal to the plane of said arm whereby said sharp edge is moved substantially parallel to the direction of movement of said arm to determine the calibration of said circuit breaker.

11. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal curstraining member in a direction normal to the plane of said arm whereby said sharp edge is moved substantially parallel to the direction of movement of said arm to determine the calibration of said circuit breaker.

12. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current condition, a resilient restraining member having legs disposed at opposite sides of said arm, one leg of said restraining member being inclined generally outwardly and presenting a sharp edge at the point of incline, the

opposite leg presenting a substantially continuous smooth surface, said arm having one side thereof inclined upwardly, complementary with the inclined surface of the end of said one leg and in engagement therewith in closed circuit position, and adjustable means operable to move said restraining member in a direction normal to the plane of said arm whereby said legs of said restraining member are moved substantially parallel to the direction of movement of said arm to determine the calibration of said circuit breaker.

13. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact movable to open and closed circuit positions, bimetallic means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal current conditions, a resilient, generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit positions to oppose such changes, resilient means biasing said latch toward said arm, and adjustable means operable upon said latch to move said legs in a direction normal to the plane of said arm, said movement being effective to adjust said legs substantially parallel to the direction of movement of said arm against the bias of said resilient means to thereby vary the opposition to movement of the arm to open circuit position to determine the calibration of said circuit breaker.

14. In a circuit breaker, a fixed contact, a movable contact, a supporting arm for said movable contact, movable to open and closed circuit positions, means normally biasing said arm toward closed circuit position but reversing said bias upon occurrence of abnormal conditions, a resilient generally U-shaped latch having the legs thereof disposed at opposite sides of said arm and in the path said arm traverses during changes in circuit positions to oppose such changes, resilient means biasing said latch toward said arm, means holding said latch against said resilient means, and adjustable means operative upon said holding means to move said latch in a direction normal to the plane of said arm, said movement being effective to adjust said latch substantially parallel to the direction of movement of said arm against the bias of said resilient means to vary the opposition to change in circuit position to determine the calibration of said circuit breaker.

References Cited in the file of this patent UNITED STATES PATENTS 2,102,545 Rowe Dec. 14, 1937 2,191,588 Sattler Feb. 27, 1940 2,300,530 Swingle Nov. 3, 1942 2,666,114 Jackson Jan. 12, 1954 FOREIGN PATENTS 131,673 Australia Mar. 8, 1949 1,034,820 France Apr. 15, 1953 Mia

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