US3053954A - Electric circuit breaker - Google Patents

Description

P 11, 1952 c. JENCKS ETAL 3,053,954 Q ELECTRIC CIRCUIT BREAKER Filed April 5, 1961 2 Sheets-Sheet 1 3a UNI.

33 22 20 o at 2 Q \Jl pum 49 25 35 l 28 IN VEN TORS CHARLES L. \JENCKS, FRANK H.MURPHY A TTORNEY p 11, 1962 c. L. JENCKS ETAL 3,053,954

ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed April 5, 1961 INVENTORS CHARLES L. dENcKs FRANK H.MuRPHY BY (EM/4. @4417 A TTOR/VEY lattes 3,053,954 ELECTRIC CHRCUE'I ltREAKER Charles L. lencks, Avon, and Frank H. Murphy, West Hartford, Conn, assignors to General Electric Company, a corporation of New York Filed Apr. 5, 1961, Ser. No. 100,960 6 Claims. (Cl. 2tltllti6) Our invention relates to electric circuit breakers and particularly to electric circuit breakers of the type including a molded insulating casing and current responsive tripping means provided with means accessible externally of the main insulating casing for permitting adjustment thereof by the user within predetermined limits.

Electric circuit breakers of the molded case type commonly include current responsive tripping means which is adjustable within predetermined limits by the users. Such circuit breakers are ordinarily of the multipole type, such as three-pole circuit breakers, and an adjusting knob is provided for each pole, which is accessible through the top wall of the insulating casing for adjustment within predetermined limits. More recently such circuit breakers have also been provided, with means which may be adjusted by the manufacturer before complete assembly of the circuit breaker, whereby the range of adjustment permitted the user may itself be varied, so that the needs of the particular user may be more accurately supplied and whereby the adjustment or calibration of the circuit breaker may be more readily and efficiently performed. Thus, for example, in one form, a circuit breaker is provided including magnetic tripping means having a magnet and a pivotally supported armature. The armature is adjusted by means of a cam carried by a shaft having a knob accessible externally of the insulating casing. A first adjusting means is provided which adjusts the tension or spring force against which the armature must operate and a second adjustment is provided by which the cam member is bodily shifted with respect to the pivot point of the armature so that the effective action or mechanical advantage of the cam on the armature is varied. Such a construction is shown for example in application Serial No. 62,184, filed October 12, 1960, by K. W. Klein and D. B. Powell, and assigned to the same assignee as the present invention.

While the construction disclosed in the abovementioned application is quite satisfactory for certain types and sizes of electric circuit breakers, it is not readily adaptable to the more rigid space requirements of certain other circuit breakers, and it is not readily usable in circuit breakers where it is not feasible to provide adjusting means for adjusting the tension of the armature bias spring.

It is an object of the present invention to provide an electric circuit breaker of the type including adjustable tripping means which is more compact than types previously available.

It is another object of the present invention to provide an electric circuit breaker including adjustable tripping means wherein adjustment is permitted over a predetermined range and wherein the maximum and minimum of such range may be independently set, and which adjustment is nevertheless simple and inexpensive.

In accordance with the invention in one form, an electric circiut breaker is provided including a molded insulating casing having at least one pair of separable 'contacts and operating mechanism for operating the contacts, the operating mechanism including a member releasable to cause automatic opening of the contacts. The circuit breaker also includes automatic tripping means comprising a relatively stationary magnetic field piece adapted to be energized by current passing through 3,653,954 Patented Sept. '11, 1962 said breaker, and a movable armature adapted to be attracted to the field piece. Means is further provided for adjusting the position of the armature, the adjusting means including an elongated supporting shaft having a knob accessible for rotation from outside the insulating casing. The supporting shaft carries a cam member which is movable along the shaft, and which is lockable at a predetermined location on the shaft. A cam plate or cam follower is provided between the cam mem ber and the armature and includes an elongated cam follower surface on which the cam member is adapted to operate, and a projecting screw adapted to engage the armature.

By means of the apparatus provided, a selected end point of the adjustment range may be determined by adjusting the projecting screw which engages the armature. The extent of the range, and therefore the other of the end points of the range, may be adjusted by adjusting the position of the cam member bodily along the supporting shaft.

The invention will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view, partially in section, of an electric breaker embodying the subject in- Vention;

FIGURE 2 is an end elevation view of a portion of the current-responsive tripping mechanism of the circuit breaker of FIGURE 1, taken generally on the line 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary sectional view of a portion of the circuit breaker of FIGURE 1, the section being taken through the tripping mechanism and showing a portion of the latching mechanism;

FIGURE 4 is a view of the current-responsive tripping mechanism of one pole of the circuit breaker of FIGURE 1, as shown in FIGURE 2, but with the adjusting cam shown in a different adjusted position;

FIGURE 5 is a fragmentary View of the adjusting mechanism similar to FIGURE 4, but with the adjusting cam in a different bodily adjusted position;

FIGURE 6 is an exploded perspective view of the magnetic tripping mechanism of one pole of the circuit breaker of FIGURE 1, and

FIGURE 7 is a fragmentary perspective view of a portion of the tripping mechanism showing particularly the ambient temperature compensating means.

In the drawings, the invention is shown as embodied in an electric circuit breaker having a molded insulating casing including a base 10 and a cover 11. The base 10 and the cover 11 are each provided with integral barrier portions forming three elongated pole chambers extending from end to end of the casing.

For convenience, FIGURE 1 is taken generally on a line through the central pole chamber, excepting that the trip unit, to be described is shown in full.

A plurality of line terminals 12, one for each pole chamber are supported on line terminal straps 13 at one end of the base 10. Each of the line terminal straps 13 is attached to the base by suitable means such as by a screw 14. Each of the line terminal straps 13 carries a line contact 15 at the inner end thereof. A movable contact is provided mounted on a contact carrier member 16 which in turn is pivotally supported on a contact arm 17 by a pivot pin 18. The movable contact carrier 16 is connected, by means of a flexible electrical conductor 19 to the current responsive tripping assembly 20 to be described. The current is carried through the tripping assembly 20 by means of a conductor 20A, having terminal portions- 203 and 20C. (See FIGURE 3.) The current path is then completed from the trip unit 20 to a load terminal strap 21 which supports a load terminal connector 22. The load terminal strap 21 is fixedly attached to the base by means of screw 23.

As previously described, the current carrying parts just described are repeated in each of the three pole chambers of the circuit breaker.

For the purpose of providing simultaneous operation of the contact member of each of the pole chambers, the contact arms 17 are each fixedly attached to a contact cross arm 24.

The contact arm 17 of the center pole is pivotally supported on a pivot pin 17A carried by the mechanism side frames 25. The contact arms for the two outer poles are supported on the extending portions of the contact cross arm 24.

The movable contact member 16 for each of the poles is pivotally supported on th contact arm 17 by means of a pivot pin 18 as previously described. For the purpose of providing contact pressure, a compression spring 26 is provided between th movable contacts 16 and the forward projecting portion of the contact arm 17. The spring 26 is retained in place by a projecting stud 27 carried by the contact member 16 and also by a generally cup-shaped retainer 28 carried by the forward end of the contact arm 17.

An operating mechanism is provided for the purpose of operating the movable contacts 16' between open and closed circuit position and for releasably restraining the contacts in the closed circuit position, whereby to permit automatic opening upon the occurrence of predetermined current conditions, in a manner to be described. The operating mechanism, which is positioned Within the central pole chamber, includes a pair of opposed side plates 25, which serve to support the mechanism, including the pins 17A and 18 previously described. The operating mechanism also includes a releasable support member 2? which is pivotally supported on a pivot pin 34} extending between the opposed side plates 25. The member 29 has a projecting latch portion 31 releasably held by a latch member 32 which is movable to cause release of the member 29 in a manner to be described. The releasable member 29 serves to support the normally stationary pivot pin 33 which pivotally supports a pair of upper toggle links 34 (only one shown) which are connected by a knee pivot pin 35 to a pair of lower toggle links 36. The lower toggle links 36 extend through slots 37 in the contact arm 17 and are connected by pivot pin 18 to the contact arm 17. A manually engageable handle member 38 is supported on a metallic handle support member 39, which in turn is pivotally supported in the insulating casing on a pivot pin 40.

A tension spring 4-1 is connected between the central portion of the handle 38 and the toggle knee pivot pin 35. When the handle is in the on position as shown in FIGURE 1, the tension spring ll acts on the pivot pin 35 in such a way as to maintain the toggle links 34, 36 in a straightened condition, holding the movable contact member 16 against the stationary contact member 15. When the handle 38 is moved to the left to the off position, the tension spring 41 passes across the line of centers of the pivot pins 35 and 33 and causes the pivot pin 35 to move to the left, collapsing the toggle links 34-36, and moving the movable contact arm 17 to open circuit position.

When the handle 38 is in the on position as shown in FIGURE 1, and the latch member 32 is moved, in a manner to be described, so as to release the latch projection 31 of the releasable member 29, the releasable member 29 moves under the action of the spring 41 in a clockwise direction. As the member 29 moves in a clockwise direction, the pivot pin 33 moves upwardly and at the same time across the line of action of the spring 41, thereby reversing its direction of pull on the knee pivot pin 35, and permitting the toggle links 34-456 to move to collapsed position and the movable contact members 17 to move to open circuit position, even though the handle 38 is retained in the on position.

Following such a tripping operation, the parts may e returned to their original condition by moving the handle 38 to the left, during which movement a depending portion 39a of the handle support 39 engages the releasable member 29 and rotates it counterclockwise until the latch projection 31 becomes reengaged with the latch member 32.

The construction and operation of the trip unit 20 will be described with particular reference to FIGURES 3 through 6. The current responsive tripping mechanism is contained within a separate insulating enclosure which is removable as such from the main circuit breaker enclosure, this removable assembly being referred to for convenience as a trip unit 20. The enclosure of the trip unit as includes a first portion 45 and a second portion 46. A latch mechanism supporting frame 47 is rigidly attached to the outer face of the first portion by suitable means such as by rivets 48. A pivot pin 49 is rigidly supported between the opposed side portions of the frame 47. The primary latch member 32 is pivotally and slidably supported on the pivot pin -19 and is biased in a counterclockwise direction by means of spring 50. A secondary latch member 51 is also pivotally supported on the frame 47 by pivot pins 52.. The secondary latch member 51 carries a roller 53, and the primary latch member 32 has an engagement with the roller 53 such that the primary latch 32 when loaded by the releasable member 29, biases the secondary latch 51 for rotation in a clockwise direction as viewed.

The secondary latch 51 is restrained from rotating in a clockwise direction by reason of its engagement with a secondary latch retaining member 54 which is rigidly carried by a trip bar 55, see FIGURE 3.

In operation therefore, rotation of the trip bar 55 in a clockwise direction as viewed in FIGURE 3, moves the secondary latch retaining member 54 out of the path of movement of the secondary latch 51 and permits the secondary latch 51 to move in a clockwise direction, which in turn permits the primary latch 32 to rotate in a clockwise direction, releasing the releasable member 29.

For the purpose of causing rotation of the trip bar 55 in response to overload current conditions, a bimetallic strip is provided, which is mounted on a return-bent portion 26D of the main current conductor 20A extending through the trip unit at that particular pole. This returnbent portion 20D acts as a heater to produce heat which causes deflection of the bimetallic strip 56. The bimetallic strip 56 is mounted on the heater portion 20D by suitable means such as by rivets 58.

The bimetallic strip 56 acts on, the trip bar 55 through engagement with a calibrating screw 59, carried by a second strip of bimetallic material 60, which is rigidly supported at its opposite end on the trip bar 55, so that the end thereof carrying the calibrating sscrew 59 is free to move as the strip 60 deflects. The strip 60 functions to provide ambient compensation, since when the ambient temperature increases, the bimetallic strip 60 deflects in the same direction that the main bimetallic strip 56 deflects, thereby producing no relative movement between them, and therefore no change in calibration of the circuit breaker.

For the purpose of limiting the effect of the ambient compensating bimetallic strip 6%, there is provided an adjustable carrier stud 61 which is threadedly engaged in the trip bar 55 and is locked with respect thereto by a lock nut 62. The stud 61 carries a pair of flanges 63 and 64 which act as tops to limit the deflection of the ambient compensating bimetallic strip 60 in each direction.

In addition to the means just described for providing time-delayed tripping action, there is provided, in accordance with the present invention instantaneous acting adjustable tripping means, together with means whereby the user may adjust the current level required to actuate such tripping means, within a predetermined selected range.

In accordance with the invention, there is provided at each pole of the circuit breaker of FIGURE 1, a relatively stationary magnetic field piece 66 (see FIGURE 2) which is rigidly attached to the base of the trip unit by suitable means such as by rivets 67. Each of the field pieces 66 is generally U-shaped and is arranged so that the conductor 20A passing through the trip unit at each pole, passes through the U of the corresponding magnetic field piece 66. For the purpose of actuating the trip bar, a movable armature 68 is provided which is fixedly attached to a supporting shaft 69 by suitable means such as by setscrew 70. The shaft 69 is supported for vertical sliding movement by engagement in a hole 66A in the bight portion of the magnetic field piece 66 and in a hole in a support and guide bracket 71 which is supported on the heater portion by the same rivets 5% which mount the bimetallic strip. A compression spring 72 is provided which acts between the support 71 and a projecting flange '73 on the shaft 69, so as always to urge the shaft 69 in an upward direction.

An adjustable stop is also provided for the armature 68, together with means for adjusting said stop through a predetermined range, and for determining the starting point and extent of such range. For this purpose a cam plate 74 is provided which is pivotally supported on a pivot pin 75, carried by an upstanding portion of the field piece 66. The cam plate 74 includes a projecting cam follower portion 77 for a purpose to be described. The cam plate 74 also carries an adjusting screw 78 which is threadedly engaged therein and which is locked with respect thereto by the lock nut 79. The cam plate 74 is biased at all times in a counterclockwise direction by means of a spring St).

For the purpose of adjusting the position of the cam plate 74', there is provided an adjusting cam 81, which is threadedly carried by a shaft 82. The shaft 82 has its lower end journalled in an opening in the inturned portion of the extension 76 of the field piece 66, and has its upper end journalled in an opening in the top wall of the insulating casing of the trip unit. The cam member 81 is normally locked against movement with respect to the shaft 82 by suitable means such as by a lock nut 83.

The upper end of the shaft 82 is provided with an enlarged portion 84 which provides a shoulder portion overlying a portion of a washer 85 which in turn overlies the outer surface 45A of the casing portion 45. The portion 84 also carries a control knob 86, with an indicating arrow 87 thereon, for a purpose to be described.

In order to provide a frictional retaining force to maintain the knob 86 and shaft 82 in any predetermined preset position, there is provided a retaining washer 8S, having depending downwardly pointing teeth or projections thereon whereby it may be moved upwardly on the shaft 82 but cannot move downwardly thereon. A compression spring member in the form of a spring washer 39 is provided on the shaft 82 between the washer 88 and the inner surface 45B of the insulating casing portion 45. When the parts are assembled, the spring member 39 is trapped with a predetermined force between the retaining washer 88 and the inner surface 45B of the insulating casing, whereby the spring member 89 exerts a downward force on the washer 88 and on the shaft 82, maintaining the shaft 82 in frictionally retained engagement against unintentional rotation at all times.

Referring particularly to FIGURE 2, it will be observed that when the cam 81 is turned to a position in which the lowest point thereof is in engagement with the cam follower portion 77, the cam follower portion 77 extends substantially parallel to the shaft 82. This position represents the extreme counterclockwise portion of the cam "plate 74 and therefore the highest position of the screw 78 and of the armature 68.

When the cam member 81 is rotated to its maximum position, as shown in FIGURE 4, the cam plate 74 is rotated clockwise so that the projecting screw 78 depresses the armature 68 to reduce the air gap and to thereby lower the setting at which the magnetic trip will operate.

The position of the parts as indicated in the FIGURE 2 represents the maximum air gap setting. As previously mentioned, in this setting the cam follower surface of the portion '77 extends parallel to the shaft '82. It will now be observed that the position of the armature 68 may be adjusted without rotating the cam plate 74, by loosening the lock nuts 79 and adjusting the projecting screw 78.

When the cam 81 is turned to the position in which the armature is depressed the maximum amount, as shown in FIGURE 4, the position of the cam plate 74, and therefore of the armature 68, may be further adjusted by adjusting the vertical position of the cam member 81 on the shaft 82. This may be accomplished by loosening the lock nut $3 and by rotating the shaft 82. When the desired setting has been achieved, the insulating knob 86 is pushed onto the enlarged portion 84 of the shaft 82 in a proper position so that the arrow 87 points to a predetermined high marking on the circuit breaker casing.

While the various adjusting means may be utilized in a number of ways, the following procedure has been found to be desirable in calibrating a circuit breaker to meet certain predetermined requirements: (1) the shaft 82 is rotated to the position in which the cam follower surface of the portion 77 extends parallel to the shaft 82 (the maximum gap position as shown in FIGURE 2); (2) the device is tested by passing current through it to determine the amount of current required to cause the armature to pull in; if this amount of current is found to be too high, the adjusting screw 7 8 is turned inwardly to reduce the air gap; if the amount of current required to produce pull-in is found to be too low the adjusting screw 78 is backed off to increase the air gap; thus any desired pull-in point may be achieved with the cam 81 at its high or maximum setting; (3) the shaft 82 is rotated so that the cam 81 is in the position in which the cam 81 has rotated the cam plate 74 the maximum amount (as shown for example in FIGURE 4); the device is tested at this setting and if it is found that the current required to cause the armature to pull in at this seting is higher than the amount which is desired, then the lock nut 83 is loosened and the cam member 81 is held from rotating while the shaft 82 is turned. This causes the cam 81 to move downwardly on the shaft 82, thereby producing a greater deflection of the cam plate 74, as shown for example in FIGURE 5. If on the other hand it is found that at the low setting the current required to cause the armature to pull-in is too low, then the lock nut 83 is loosened and the shaft 82 is rotated in a direction to cause the cam 81 to move upwardly on the shaft 82, thereby producing lesser deflection of cam plate 74 at this setting.

It is to be noted that all adjustment is performed before the customers adjusting knob 86 is mounted. When the adjusting knob 86 is mounted, it is inserted on the enlarged portion 84 of the shaft 82 with the arrow 87 exactly in alignment with the high or low marking on the upper surface of the circuit breaker cover '11.

The shaft 69 has a headed portion 69a which is adapted to engage a washer 69b over-lying an extending portion of the trip bar 55. When the armature 68 is drawn toward the magnet 66, therefore, the shaft 69 moves downwardly and the head 69a engages the washer 69b and rotates the trip bar 55 to cause tripping.

While there has been shown and described only one embodiment of the invention, it will be readily apparent that many modifications thereof may be made, and we therefore intend, by the appended claims, to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising at least one pair of relatively movable contacts, operating mechanisms for operating said movable contacts between open and closed circuit positions, said operating mechanism including a member releasable to cause automatic opening of said contacts, current responsive means for causing the release of said releasable member upon the occurrence of predetermined current conditions, said current-responsive means comprising a relatively stationary magnet, an armature movable with respect to said stationary magnet, an electrical conductor including at least a portion passing between said magnet and said armature, biasing means biasing said armature away from said magnet, adjustable stop means for limiting the movement of said armature away from said magnet said adjustable stop means comprising a cam plate including an elongated cam follower portion and a projection adapted to engage said armature, an elongated shaft, a cam member carried by said shaft and disposed and arranged to engage said cam follower surface whereby rotation of said cam member moves said cam plate and causes said cam plate to engage said armature to move said armature with respect to said magnet, said cam member being axially adjustable along said shaft, to vary the mechanical advantage of said cam on said cam follower surface. I

2. An electric circuit breaker comprising at least one pair of relatively movable contacts, operating mechanism for operating said contacts between open and closed circuit positions, said operating mechanism including a member releasable to cause automatic opening of said contacts, current-responsive means for causing release of said releasable member upon the occurrence of predetermined current conditions, said current-responsive means including a relatively stationary magnet, an armature movably supported with relation to said magnet, means biasing said armature away from said magnet, adjustable stop means for limiting the movement of said armature away from said magnet comprising a pivotaliy supported cam plate, said cam plate including a cam follower portion, an elongated operating shaft extending parallel to said cam follower surface in at least one adjusted positon of said cam plate, a cam member carried by said elongated shaft and disposed and arranged to engage said cam follower surface whereby rotation of said cam member causes pivotal movement of said cam plate to Vary the adjusted position of said armature, and means for adjustably positioning said cam member at selected positions axially along said supporting shaftv 3. An electric circuit breaker as set forth in claim 2, wherein said cam plate also includes an adjusting screw engaging said armature, and means for locking said adjusting screw with respect to said cam plate.

4. An electric circuit breaker comprising at least one pair of relatively movable contacts, operating mechanism for moving said contacts between open and closed circuit positions, said operating mechanism including a member releasable to cause automatic opening of said contacts, current-responsive means for causing release of said releasable member upon the occurrence of predetermined current conditions, said current-responsive means comprising a relatively stationary magnet, an armature supported for movement relative to said stationary magnet, an electrical conductor disposed to energize said magnet upon the passage of curent therethrough, biasing means biasing said armature away from said magnet, adjustable stop means for adjustably positoning said armature, said adjustable stop means including a pivotally supported cam plate, a projection carried by said cam plate and disposed and arranged to engage said armature, said cam plate including an elongated cam follower surface, an elongated shaft extending generally parallel to said cam follower surface in at least one possible adjusted position of said cam plate, said shaft having a threaded portion, a cam member threadedly supported on said threaded portion of said shaft, whereby rotation of said supporting shaft while said cam member is restrained from rotation causes movement of said cam member axially along said shaft, and means for locking said cam member against rotation on said supporting shaft.

5. An electric circuit breaker as set forth in claim 3, said circuit breaker also including insulating means enclosing said current-responsive means, an aperture in said insulating enclosing means, said supporting shaft including an end portion projecting through said aperture, and an insulating control knob mounted on said projecting end portion of said shaft to permit operation of said shaft from outside said insulating enclosure.

6. An electric circuit breaker as set forth in claim 3, said circuit breaker including insulating means enclosing said current-responsive means, an aperture in said insulating enclosure means, said supporting shaft including an end portion projecting through said aperture, a washer on said shaft overlying the outer surface of said enclosure means, an enlargement on said shaft overlying said washer, a compression spring member on said shaft adjacent the inner surface of said enclosure, abutment means carried by said shaft within said enclosure, said compression spring member being compressed between said inner surface of said enclosure and said abutment to frictionally retain said shaft against rotation.

References Cited in the file of this patent UNITED STATES PATENTS 2,508,178 Lindstrom et al May 16, 1950 2,586,326 Grissinger et al .d Feb. 19, 1952 2,673,264 Cole Mar. 23, 1954

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