US3551867A - Circuit breaker - Google Patents

Description

Dec. 29, 1970 R. c. INGWE'RSEN CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed March l2. 1969 INVENTOR ATTORNEYS United States Patent Omce 3,551,867 Patented Dec. 29, 1970 3,551,867 CIRCUIT BREAKER Richard C. Ingwersen, Treasure Island, Fla., assignor to Allied Control Company, Inc., New York, N.Y. Filed Mar. 12, 1969, Ser. No. 806,664 Int. Cl. Htllh 71/16 U.S. Cl. 337-63 7 Claims ABSTRACT F THE DISCLOSURE A trip-free circuit breaker of the push-pull type having a rocker lever carried on the push-pull actuator, the rocker lever having a fulcrum point at one end and a contact at the other end, and a mechanical latch carried on the rocker lever and having unitary pivotal movement therewith for supporting the rocker lever in circuit closing position.

BACKGROUND OF THE INVENTION embodied a relatively large number of components parts including molded parts with metal inserts. In production such devices have 'been diicult to calibrate and have had a tendency to lose their calibrations under service conditions, especially under conditions involving vibration and repetitive manual actuation. Surface wear in such prior circuit breakers has been the cause of most of the problems experienced.

SUMMARY OF THE INVENTION According to the present invention, an all metallic actuator has been provided with the elimination of all molded parts with metallic inserts. By redesigning the functional structure of the circuit breaker, in the order of 35% fewer parts are employed over previously accepted commercial designs. The resulting simplicity makes the circuit breaker easier to assemble and materially reduces calibration problems. At the same time a substantial reduction in manufacturing cost is realized as the parts are fewer and simpler, there is less scrap of plastic parts and nish requirements have been minimized. Moreover, it has been possible to effect a substantial saving in initial tooling cost as Well as reducing the cost of tool maintenance.

Obviously, the aforementioned improvements in cost savings would be of no practical consequence without an accompanying high degree of reliability. To that end all critical wear surfaces of the circuit 'breaker are either work hardened, as in the case of the thermostatic bimetal, or heat treated as in the case of the beryllium copper components. Also, the stored forces for effecting circuit breaking upon overload are well balanced to avoid cocking and binding of the component parts.

DRAWINGS In the illustrated forms of the invention, FIG. 1 is a side elevational view of one form of the circuit breaker with the front half of the case shown removed and the circuit closed,

FIG. 2 is a cross-sectional view taken on line II-II of FIG. 1,

FIG. 3 is a view similar to FIG. 2 taken on line III- III of FIG. 1,

FIG. 4 is a fragmentary plan view of the contact rocker member,

FIG. 5 is a fragmentary sectional view through the shoulder screw of the actuator elements,

FIG. 6 is a View similar to FIG. 1 showing the circuit open,

FIG. 7 is a fragmentary view similar to FIG. 1 showing the circuit about to be closed by manual operation,

FIG. 8 is an exploded view of the component parts shown in FIG 1, and

FIG. 9 is a fragmentary side elevational View of a modified form of contact.

DETAILED DESCRIPTION In the form of the invention shown in FIGS. 1 through 8, the circuit breaker 10 comprises a molded case having a front part 12 and a back part 14 held together by four suitable fasteners 16. Terminals 18 and 20 are received in opposed slots provided in the parts 12 and 14 in a Well known manner. A suitable panel attachment bushing 22 is received in opposed semi-circular depressions in the parts 12 and 14 in an equally well known manner. Attached to the terminal 18 by welding, or otherwise, is the thermal element 24. A lixed contact 26 is carried on the terminal 20.

ACTUATOR MECHANISM The mechanism for manually opening and closing the circuit breaker 10 through the exposed actuator button 28 of suitable insulating material, comprises two separate, relatively movable linear members preferably stamped from a sheet of half hardened beryllium. One such element is in the form of an actuator slide 30 having a hole 32 in its lower end to receive a pin 34 of insulating material to attach the button 28 to the slide 30. The upper end of the slide 30 is bent to provide an anchor tab 36 for the extension spring 38. Between the ends of the slide 30, a laterally extending latch cam 40 is provided.

The other element of the actuator mechanism takes the form of an actuator bar 42 having a tapped hole 44 to receive the threaded end 46 of the shoulder screw 48. An elongated hole 50 is provided in the actuator slide 30 in. which the cylindrical shank 51 of the screw 48 is disposed, the head of the screw 48 holding the slide 30 and bar 42 assembled to each other, yet permitting limited lost motion along their longitudinal axes defined by the amount of clearance of the shank 51 of the screw 48 in the elongated hole 50. Above the hole 44 and centered on the bar 42 is a reamed hole 56 to receive a suitable shoulder rivet 57 for pivotally supporting the contact rocker lever assembly.

To guide the slide 30 and bar 42 of the actuator mechanism for longitudinal movement, the back part 14 of the case is provided with a generally rectangular depression 58 which, with the surface 60 of the front part 12 of the case, provides a four sided guide for the upper end of the bar 42. The lower end of the bar 42 is supported for longitudinal movement between the projections 62 defined on the horizontal leg of the L-shaped guide 64. The vertical leg 65 of the guide 64 is shown attached to an interior wall surface of the back part 14 of the case by drive pin 65', or other suitable means.

Actuator slide is supported for longitudinal movement in the rectangular slot 66 provided in the insulating bushing 68 disposed within the panel attachment bushing 22 with a press t. As the button 28 and the trip indicator 70 are both located within the bushing 68 with a free guiding tit, the relatively snug llt between the lower end of the slide 30 and the slots in the button 28 and trip indicator 70 results in the slide 30 having a relatively long support bearing in the bushing 68 and overcoming any tendency to cock or bind.

In practice, there is relatively little lateral clearance bctween the diameter of the shank 51 of the shoulder screw 48 and the parallel sides of the elongated hole 50 through which the screw 48 extends. As a result, the upper end of the slide 30 is guided for longitudinal movement relative to the actuator bar 42 upon the shank 51 of the screw 48, When the limits of relative movement are reached, as defined by the ends of the elongated hole 50, the slide 30 and bar 42 will have unitary movement and the upper end of the slide 30 will be guided by the bar 42, the `bar 42, in turn, being guided in its movement by the depression 58 and surface 60 and the projections 62 on the guide 64.

CONTACT ROCKER LEVER ASSEMBLY The movable contact 72, which is engaged and disengaged with the fixed Contact 26 to make and break the circuit, is carried upon a contact rocker lever assembly 75 pivotally supported on the actuator bar 42 by the shoulder rivet 57. Preferably, the rocker lever comprises front and rear parts 76 and 78, one of which is the mirror image of the other except for the size of the holes 74 to receive the stepped down diameter of the shoulder rivet 57. Outturned ears 80 and 82 are provided on the parts 76 and 78 to which is secured to the contact blade 84 by rivets or drive pins 85. The movable Contact 72 is carried on the `blade 84.

In practice, the parts 76 and 78 are stamped from quarter hard beryllium copper sheet while the contact blade 84 is formed from half hard beryllium copper sheet. It will be seen from FIG. 4 that the central portion 86 of the parts 76 and 78 are outwardly offset to provide clearance space 42 for the actuator bar 42, the clearance space being sufficient to enable the assembly of the parts 76, 78 and 84 to pivot through a substantial arc on the bar 42 about the axis of the shoulder rivet 57. The depth of the offset of each central portion 86 is approximately onehalf the thickness of the bar 42 whereby the rocker lever assembly, while freely pivotable on the bar 42, is lirmly supported and guided by opposite sides of the bar 42 directly adjacent the hole 56 in the bar 42 through which the shoulder rivet 57 extends. Each of the parts 76 and 78 have a spring tab portion 88 at one end and a ledge portion at the opposite end, which ledge portion of each of the parts 76 and 78 collectively form a two-ply ledge 90. The insulating bushing 68 is provided with spring anchor tabs 94 and 96, the spring 38 being attached to the tab 94 and the extension spring 98 being attached to the tab 96.

THERMAL ELEMENT The thermal element 24 is formed in part from a strip 24 of suitable thermostatic bimetal or trimetal material having a resistance to suit the desired ampere rating. In form, it is generally U-shaped with one vbimetallic leg 100 welded or riveted to a nonthermostatic L-shaped member having at its upper end a llange 104 which is welded, or otherwise rigidly attached, to the terminal 18. The other bimetal leg 106 of the strip 24 has, at its upper end, an offset inturned flange 108 having its active portion substantially disposed on the center line of the case delined by the parts 12 and 14. As the low expansion side 4 of the thermostatic strip 24' is disposed on the outside of the legs 100 and 106, on overload the leg 106 will be displaced to the left, as viewed in FIGS. 1 and 6. An adjustment screw 24, disposed in a threaded aperture on the part 14, bears against a surface of the nonthermal member 102 to shift the position of the flange 108 relative to the two-ply ledge 90 of the contact rocker lever assembly 75.

MECHANICAL LATCH When the actuator bar 42 is in its closed circuit position, which is its up position as seen in FIG. l, the bar 42 is held against the tension of the extension spring 98 by the mechanical latch 109 rigidly attached at one end to the rocker lever assembly adjacent the two-ply ledge 90. Preferably, the mechanical latch 109 s formed from a sheet of half-hard beryllium copper. As stamped from the sheet, the latch blank is perforated to receive the twoply ledge and is flanged to rest on top of the parts 76 and 78. The upper perforated end of the latch 109 is then welded in position on the ledge 90 and, thereafter, heat-treated along with the assembly 75. The vertical leg of the latch 109 depends from the rocker lever assembly 75 to terminate in an angularly disposed portion 116 adapted to rest on one of the projections 62 on the guide 64. The latch 109 is of sufficient width as to enable the nose portion 116 while resting on the projection 62 to also extend laterally therefrom a sufficient distance to be engaged by the latch cam 40 on the actuator slide 30. With the circuit closed, the latch cam 40 is disposed out of actuating contact with the nose portion 116. When the cam 40 is lowered by manual movement of the slide 30 engages that portion of the nose portion 116 laterally disposed with reference to the projection 62 and urges the nose portion 116 from its position of support on the projection 62 whereupon the component parts collapse into the position similar to that disclosed in FIG. 6 with the exception that the leg 106 of the thermal element will not be thermally displaced, as shown in FIG. 6, but will be disposed in the position shown in FIG. 7.

At the time the actuator slide 30V is lowered by manual force applied -to the button 28 to manually open the circuit breaker, as described in the preceding paragraph, the lost motion connection between the slide 30 and the bar 42 enables the latch cam 40 to move into engagement with the nose portion 116 of the latch portion 109 without movement being imparted to the bar 42 upon which the rocker lever assembly 75 is carried. As the assembly 75 is held against clockwise pivotal movement about the axis of the shoulder rivet 57 by engagement of the twoply ledge 90 with the fulcrum abutment flange 108, the nose 116 will tend to resist movement along the face of the projection 62 upon which it rests and some deflection of the latch 109 must take place before the nose portion 116 can be displaced by the latch cam 40. Through this arrangement the resiliency of the latch 109 resists manual movement of the slide 30 along. with the tension of the springs 38 and 98. Also, any tendency for the nose portion 116 of the latch 109 to be vibrated off its position of normal rest upon the projection 62 is avoided.

OPERATION In FIG. 6, the actuator bar 42 is shown in its down position following an overload. The thermal strip 24', having been overheated, is shown with the leg portion 10'6 moved to the left from the position shown in FIG. 1. The actuator slide 30 is, likewise, in its down position with the button 28 in its extreme projected position and the trip indicator 70 is disposed to visually indicate that the circuit breaker has been actuated and the circuit is open.

Upon cooling, the thermal strip 24' will return to the position in FIGS. 1 and 7 to relocate the flange 108 inthe path of movement of the two-ply ledge 9 0 of the contact rocker lever assembly 75. To restore the circuit breaker to its closed circuit position of FIG. l, an upward push is exerted on the button 28 to raise the actuator slide 30 into the position shown in FIG. 1. As the shoulder screw 48 on the bar 42 is resting on the lower end of the elongated hole 50 in the slide 30 with the circuit open, the bar 42 will move upwardly as a unit with the slide 30.

As the bar 42 moves upwardly, the two-ply latch 90 will engage beneath the flange 108 to swing the contact rocker lever assembly 75 into the position shown in FIG. 1 with the movable contact 72 in stressed engagement with the fixed contact 26 to close the circuit.

To support the bar -42 in the position shown in FIG. l closing the circuit, the latch 109 must be so located and shaped, as well as calibrated by adjustment of the screw 24", so as to dispose the latch nose portion 116 on the projection 62 of the fixed guide 64. The necessary movement of the latch 109 is assured by the engagement of the two-ply ledge 90 with the underside of Ithe fulcrum ange 108 which causes the contact lever assembly 75 to be rocked counterclockwise as it is being simultaneously lifted on the bar 42. With this movement taking place the latch cam 40 is disposed in its elevated position clearing the nose 116, as shown in FIG. 7. The continued forward movement of the bar 42 will cause the nose portion 116 of the latch 109 to be snapped over the edge of the projection `62 and upon the latch supporting surface thereof into its final position of rest, as shown in FIG. 1.

With the component parts in the position shown in FIG. 1 the springs 38 and 98 are fully tensioned. If the manual force holding the button 28 fully elevated is then removed, only the latch 109 with its nose 116 resting on the projection 62 is acting to prevent the tension of the springs 38 and 98 from collapsing the circuit breaker components into the open circuit position of FIG. 6.

It will be understood, with the component parts shown in FIG. 1, that the tension of the spring 38 on the slide 30 is being resisted by the cam 40 resting on the nose portion 116, the tension of the spring 38 being insufficient to cause the cam 40 to displace the nose 116` from its position of rest on the projection 62 with the circuit closed.

Upon the occurrence of the short or overload, the flange 108 will be moved from its latching position above the two-ply ledge `90 and the tension of the spring 98 will rock the contact lever assembly 75 about the axis of the shoulder rivet 57 to separate the contacts 26 and 72 with snap action. As the latch 109 will have unitary movement with the assembly 75, the rocking action on the part of the assembly 75 will remove the latch nose 116 from the projection 62 and the component parts will collapse into the state shown in FIG. 6.

Preferably, the combined length of the latch 109 and its nose portion 116 is such that some slight deflection of the thermal element 24 and the resilient contact blade 84 carrying the movable contact 72 is required to raise the bar 42 sufliciently to allow the latch nose 116 to swing counterclockwise into its position of rest above the projection 62. Thus, when the manual force on the button 28 is released, the latch 109 is supporting the stress of the deflection of the thermal element 24 and the contact blade 84 as well as the tension of the spring 98. It will be noted that all of these forces are acting in substantially the same vertical plane.

It should be further noted that only with respect to the thermal element 24 is there any provision for calibration. All the components which react against the thermal element 24, directly or indirectly, are substantially in balance and act only in the plane in which the bar 42 and the active part of the flange 108 are disposed. In this regard the contact lever assembly 75 comprises two similar parts disposed on opposite sides of the bar 42 and presenting a two-ply support defining the ledge portion 90 to the flange 108. Likewise, the latch 109 is in complete balance on the bar 42. By supporting the latch nose 116 on that portion of the projection 62 disposed in the plane of the bar -42 substantial balance is maintained with respect to the forces acting on the latch 109 through the shoulder rivet 57.

As to the forces which are brought to acton the latch nose 116 through the latch cam 40, it will be observed that the cam 40 is in juxtaposition to the plane of the bar 42.

For the sake of clarity, the usual flexible conductor 120, extending between the contact 72 and the thermal element 24, is shown broken away except for its points of attachment with the contact blade 84 and the tab 122 on the leg 106.

MODIFICATION In FIG. 9 is shown a modification of the movable contact structure in which the contact 124 is carried upon an L-shaped arm 126 pivotally supported on the contact lever assembly on the pivot pin 128. A stop 130 limits rocking of the arm 126 counterclockwise about the axis of the pin 128 under the stress of the spring 98. Clockwise movement of the arm 126 will increase the tension on the spring 98 with the reaction being taken by the contacts 26 and 124.

I claim:

1. In a trip-free circuit breaker of the type described, the combination with an actuator, of a rocker lever pivotally supported on said actuator intermediate the ends of said lever, one end of said lever constituting a fulcrum point and the other end carrying a movable contact, a fixed body portion in which said actuator is disposed for relative movement, a fixed contact carried on said body portion, a thermostatic conductor including a fulcrum displaceable upon overload with which said fulcrum point normally engages to rock said lever about its pivot point upon manual manipulation of said actuator in one direction to impart translatory motion to said lever, during said manipulation and following engagement of said fulcrum point with said fulcrum said lever is caused to rock about said fulcrum point to move said movable contact into engagement with said fixed contact to close the circuit in which said thermostatic conductor is disposed, energy-storing means energized by said manipulation and tending to rock said lever in a direction to separate said contacts to open the circuit said means being operatively connected between said body portion and said lever, a mechanical latch carried on said lever and having a unitary pivotal movement therewith for supporting said lever in circuit-closing position and resisting said energystoring means with said fulcrum point engaging said fulcrum and restraining pivotal movement of said lever about its pivot in a circuit-opening direction, and means supporting said thermostatic conductor relative to said fulcrum point whereby the heat of an overload will displace said fulcrum from engagement with said fulcrum point to enable said lever to be rocked by said energy-storing means in a direction to open the circuit.

2. In a trip-free circuit breaker of the type described in claim 1 having means on said actuator for operating said latch when said actuator is moved in the opposite direction to enable the pivot of said lever to move relative to said fulcrum to rock said lever in a direction to separate said contacts to open said circuit.

3. In a trip-free circuit breaker of the type described in claim 2 wherein said actuator is manually manipulated in both directions to open and close the circuit.

4. In a trip-free circuit breaker of the type described in claim 1 wherein said actuator is of the push-pull type having two linear parts with a lost motion connection between them, said lever being pivotally carried on one of said parts and means on the other of said parts for engaging said latch to render the same inoperative when said actuator is moved in a direction to open said circuit.

5. In a trip-free circuit breaker of the type described in claim 4 wherein a cam is provided on said other part and disposed adjacent said seat for displacing said latch from said seat upon movement of said other part in a. circuit-opening direction.

7 8 6. In a trip-free circuit breaker of the type described References Cited in claim 1 wherein a xed seat is provided for said latch, UNITED STATES PATENTS said latch having a portion for engaging said seat t0 resist rocking movement of said lever about its pivot with 2816192 12/1957 Ingwersen 337-63 said fulcrum point engaging said fulcrum. 5 BERNARD A. GILHEANY, Primary Examiner 7. In a trip-free circuit breaker of the type described D M MORGAN Assistant Examiner in claim 6 wherein said latch, when engaged on said seat, reacts against said lever at a point between one end of U.S. C1. X.R. said lever and its pivotal connection with said actuator. 337-66, 74

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