US2908782A - Circuit breaker - Google Patents

Description

Oct. 13, 1959 Filed April 4, 1957 G. W. KIESEL ETAL CIRCUIT 'BREAKER 5 Sheets-Sheet l INVENTORS -4 GEORGE W Klssu.

EMERY M. WEGH ATTOPNE Y s. w. KIESEL ETAL 2,908,782

CIRCUIT BREAKER Filed April 4, 1957 5 Sheets-Sheet 2 INVENTORS GEORGE W. KIESEL, EMERY M. \A/EGH WM? C ATTORNEY Oct. 13, 1959 w. K!ESEL ETAL 2,908,782 szacuzw BREAKER Filed April 4,, 195'? 5 Sheets-Sheet 5 Gzoaes W. KasszL, EMERY M. Wren WM/9? G ATTORNEY Oct. 255 G. w. KIESEL ETAL 2,908,782

CIRCUI'IY BREAKER Filed {it 5 Sheets-Sheet INSULATION INSULATION INVENTORS' GEORGE W. KlzscL, EMERY M.\/\/EGH ATTORNEY INSULATION United States Patent CIRCUIT BREAKER George W. Kiesel, Bristol, and Emery M. Wegh, Terryville, Conn., assignors to General Electric Company, a corporation of New York Application April 4, 1957, Serial No. 650,599

12 Claims. (Cl. 200-88) Our invention relates to electric circuit breakers and particularly to multipole electric circuit breakers of the type including a molded insulating casing and adapted for use, either singly or in panelboards, for the control of electric light and power circuits in residential, commercial and industrial buildings.

In recent years, relatively small, compact, plug-in type single-pole circuit breakers have become popular for use in residential, commercial, and industrial buildings. A circuit breaker of the type referred to is shown, for instance, in Patent No. 2,627,563, issued February 3, 1953, to W. A. Thomas and assigned to the same assignee as the present invention. Panelboards of the type containing contacts adapted to receive such plug-in circuit breakers, also in wide use, are shown in Patents No. 2,738,445, and 2,738,446, issued March 13, 1956, to H. J. Hammerly et al. and to W. J. Fleming, respectively, and also assigned to the same assignee as the present invention.

Such compact plug-in circuit breakers have heretofore been available only in single-pole and two-pole forms, rated to 50 amperes at 125 volts. There has for some time been a need, however, for three-pole circuit breakers of this type and size, which can also be plug-in mounted in such panelboards. Such three-pole circuit breakers have heretofore not been available because of the difficulty of providing one which will meet the electrical requirements in the small space available. Such a breaker must, for instance, be rated at substantially double the voltage of the single and two-pole devices, i.e., 240 volts, and at currents of the same or greater value, i.e., 10-70 amperes, while occupying substantially the same space per pole as the single pole version.

The problem is further illustrated by comparing the size of the required three-pole plug-in breaker with that of the smallest three-pole breaker of similar rating in general use heretofore. Such a prior three-pole circuit breaker, generally as shown in Patent No. 2,640,127 issued May 26, 1953, to R. N. Rowe and assigned to the same assignee as the present invention, has the following dimensions: 4 /8" x 6" x 3%" or a volume of 83.5 cubic inches. The three-pole breaker required by the plug-in panelboards referred to above, and which is provided by applicants present invention, has the following dimensions: 3 x 3%" x 2 /8 or a volume of 27 cubic inches. It will be seen that the prior breaker is approximately three times the size of the breaker of the present invention.

It is, therefore, a general object of our invention to provide an extremely compact and efiicient multipole circuit breaker and especially a compact and efficient plug-in type multiple circuit breaker, suitable for use in existing plug-in type panelboards.

In providing such a compact multipole circuit breaker, it is necessary to provide (1) an operating mechanism capable of supplying a sufiicient amount of contact pressure to each of three sets of contacts, (2) are extinguish- 2,908,782 Patented Oct. 13, 1959 ICC? ing means or are chutes large enough to contain and extinguish relatively high voltage arcs, and (3) thermal and magnetic tripping mechanism for each pole, capable of operating quickly and of withstanding momentary high short circuit currents. These primary circuit breaker components must be adequate to perform their particular functions and must also be of a size able to be contained in the small space available. In addition, an insulating housing must be provided, and these components must be so arranged and spaced with respect to each other within the housing that flash-over does not occur from one part to another on high voltage surges, even after severe arcing, and provision must also be made whereby the critical operating parts are shielded so as not to be burned, distorted or destroyed by the heat of such high power are interruptions.

Such flash-over may occur during or following an opening operation of the circuit breaker, between the stationary contact, which is at one potential after opening and some other metallic part such as the movable contact, the operating mechanism, or the trip device, all of which are at a potential opposite to that of the stationary contact after opening. Breakdown or flash-over may also occur from pole to pole within the breaker when the breaker is in closed condition.

It is an object of our invention to provide a compact multiple circuit breaker having its operating mechanism isolated from its arc interruption chamber.

It is another object of our invention to provide a compact multiple circuit breaker having the tripping mechanism for each pole isolated from other tripping mechanisms and from the arc interruption chamber and also effectively shielded from the efiects of arc chamber exhaust gases.

It is a further object of our invention to provide a circuit breaker having a pro-assembled operating mechanism which can be easily, quickly, and accurately mounted within a recess in an insulating casing.

It is a further object of our invention to provide a circuit breaker including a multi-part insulating casing adapted to receive and support the circuit breaker parts, in which different, selected, materials are used in such a way as to provide dimensional stability where critically needed to support and space the mechanism parts, and to provide arc resistance where needed to guard against arcing or flash-over respectively.

Other specific objects will in part be pointed out and in part become apparent as the following detailed description proceeds.

In accordance with our invention, we provide a compact multipole circuit breaker having an insulating casing with a number of side-by-side pole chambers, each containing a stationary contact within an arc extinguishing chamber or chute. An operating mechanism of the overcenter spring type is located in one of the pole chambers above the arc chutes and simultaneously operates a plurality of contact arms each pivoted above the respective one of the arc chutes and adapted to move through the chute to engage the stationary contact thereon. A bimetal trip device has a portion extending alongside each arc chamber for independently or conjointly tripping the mechanism; and means are provided for effectively shielding the casing, the operating mechanism, and the trip devices from carbonizing, burning, welding, heat distortion or other adverse effects often caused by are interruption products, especially during interruption of short circuit currents. Such shielding is, in accordance with our invention, provided by a novel arrangement and configuration of the circuit breaker parts themselves as well as by the provision of protective insulating material at strategic locations. By this means, although no particfiular venting provision is made in the insulating casing, the explosive products of arc interruption under short circuit current conditions are either contained within the arc interruption chamber, or, even though extending into other parts of the circuit breaker housing, are prevented from coming directly in contact with critical portions of the circuit breaker and tripping mechanism.

In accordance with one aspect of our invention, we provide a compact multipole circuit breaker having a generally rectangular insulating casing which is made up of two housing members, one member containing a preassembled operating mechanism and supporting the trip devices with respect thereto, and the other member mounting only the stationary contacts and are chutes and providing room for a portion of the trip devices.

In accordance with another aspect of our invention,

the two housing members comprise different materials respectively, one member being molded of a material of high dimensional stability to assure accurate spacing of the operating mechanism relative to the trip devices, and the other member being molded of a material of high are resistance material to minimize adverse effects of arc interruption.

, In accordance with a further aspect of our invention, the operating mechanism is pre-assembled in its own supporting frame and is merely inserted into the corresponding recess in the top portion of the housing. It is accurately positioned by projections carried by the outer sides of the frame and received in tapering grooves in the casing walls. The assembled mechanism is retained in the recess, when the top and bottom are assembled, by retaining means carried by the bottom part acting on compressible portions of the side frames.

Whilethe specification concludes with claims particularly pointing out and distinctly claiming the subject matter whichwe regard as our invention, it is believed the invention will be better understood from the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a side elevation view of a three-pole circuit breaker constructed in accordance with our invention, the side of the enclosing housing being removed to show the parts, and the circuit breaker being shown in the normal open-circuit condition;

Figure 2 is a side elevation view similar to Figure 1 but with the circuit breaker shown in the closed-circuit condition;

Figure 3 is a sideelevation view similar to Figure 1 but with the circuit breaker shown in the automatically opned or tripped condition;

Figure 4 is an exploded view of the insulating housing of the circuit breaker of Figure 1, shown as in Figures 1-3;

Figure 5 is a perspective view of the operating mechanism and movable contact assemblage of the circuit breaker of Figure 1, parts thereof being broken away;

Figure 6 is an exploded view of the parts of the circuit breaker of Figure 1, including the operating mechanism, movable contact assemblage, and one line terminal, arc chute, trip device and load terminal;

Figure 7 is an end elevation view of the circuit breaker of Figure l as viewed from the line terminal end;

Figure 8 is an end elevation view of the circuit breaker of Figure l as viewed from the load terminal end, a portion of one of the load terminal clamping members being broken away;

Figure 9 is an exploded view of the circuit breaker of Figure l as viewed from the side thereof;

Figure 10 is a view of the top housing member, taken on the line 1l10 of Figure 9, the operating mechanism and trip devices being omitted;

Figure 11 is a view of the bottom housing member taken on the line 1111 of Figure 9, one of the arc extinguishing structures being omitted and two are extinguishing chamber covers being omitted; and

Figure 12 is a detail view showing a modified form of common trip bar for use in the circuit breaker of Figure 1; and

Figure 13 is a sectional view of a modified form of the invention, shown as incorporated in a two-pole circuit breaker.

In the drawings, we have shown our invention as embodied in a three-pole electric circuit breaker having a generally rectangular insulating housing comprising a top housing member 10 and a bottom housing member 11 adapted to be connected together by suitable means such as by tubular rivets 12, Figure 9, passing through holes 14, Figures 10 and 11, in the top and bottom housing members respectively. Referring to Figures 10 and 11, the top housing member 10 has three elongated recesses 15, 16 and 17 extending substantially from end to end thereof and separated by barriers 18 and 19 integral with the top housing member. The bottom housing member 11 is also provided with three elongated generally parallel recesses 26, 21 and 22 therein separated by barriers 23 and 24 also integral with the bottom housing member.

The barriers 18 and 19 are cut away at 18' and 19' to provide an unobstructed transverse passageway at the front of the top housing member 19 for a purpose to be described. The barriers 23 and 24 are cut away at 23 and 24' to provide an unobstructed transverse passageway at the back portion of the bottom housing member 11 for a purpose to be described. The recesses 15, 16, 17 are adapted to register with the recesses 20, 21, 22 when the top and bottom housing members 10' and 11 are assembled together to provide three elongated closed recesses or pole chambers.

Each of the recesses 20, 21 and 22 has supported within it at one end thereof a plug-in type line contact socket 25. The socket 25 comprises a generally U-shaped member, Figure 6, having the legs thereof brought closer together at their extremities than at the bight of said U, and a generally U-shaped resilient reinforcing clip member- 26 embracing the sides of said U-shaped line contact member adjacent their extremities. The bottom housing member 11 is provided with three L.-shaped corner slots 27 providing access to said line contact socket 25 by suitable means such as by a blade-type contact (not shown).

The line socket 25 further includes a contact supporting portion 28 integral therewith and extending from the bight of said U and having a stationary contact 29 fixedly attached thereto by suitable means such as by welding.

For the purpose of cooling and extinguishing arcs adjacent said stationary contact 29, we provide arc extinguishing means adjacent each of the stationary contacts 29 and including a generally U-shaped insulating support 30, Figures 6 and. 11. The U-shaped insulating member 30' is preferably formed of a strong sheet insulating material such as vulcanizing cellulosic fiber, and supports between the sides thereof a plurality of notched metallic arc extinguishing plates 31. The U-shaped insulating piece 30 is supported in place by the corresponding outer walls of the bottom insulating housing member 11, by portions of the barriers 23 and 24, and also by short transversely extending barriers 32 integral with the outer walls and the barriers of the bottom housing member 11. The transversely extending barriers 32 are cut away or notched to provide an entrance portion 33 to each of the arc extinguishing chambers.

Barriers 131 serve. to provide isolation of the upper portions of the trip devices in the two outer poles from the arc chambers and also serve as stops to limit whipping or resilient overtravel of the, contact arms in these poles.

The stationary contact supporting portion of the line contact 25 extends over the top edge of the bight wall of the U-shaped' member 30, thereby supporting the line contact member 25 in place in the recess 20. The line contacts-25 are further supported in their respective chambers by shoulders 34 integral with the bottom insulating housing member 11 which are adapted to engage corresponding shoulders 35 on the line contact member. The contact support 28 is shielded from the effects of arcing by a generally U-shaped fiber insulating piece 30'.

Three movable contacts 36 are provided, each being rigidly attached to the outer end of resilient contact arms 37 which in turn are rigidly attached to an insulating contact cross arm 38. The contact supporting arms 37 are preferably shielded by insulation strips 39 as shown, especially in high amperage rating devices.

The insulating contact cross arm is supported for movement by a generally U-shaped contact operating member 40. The contact operating member 40 is provided with two aligned slots 41 adjacent the bight thereof, and the contact cross arm 38 extends through the aligned slots 41 and is rigidly attached to the bight of the contact operator 40 by suitable means such as by rivets 42. It will be observed however that the contact cross arm 38 is supported on the operating member 40 at three points, i.e., against the bight portion of the contact operator 40 and against the edges of the slots 41 formed in the side portions of the contact operator 40. This supporting arrangement not only distributes the stress exerted on the contact cross arm 38 by the contact operator 40, but also restrains any tendency of the contact cross arm 38 toward warping or twisting. The contact operating member 40 is supported in the top housing member for rotation about a fixed pivot 43 and is adapted to be operated between open and closed circuit positions in a manner and by means'to be described.

The circuit breaker of our invention also includes three load connecting terminals each comprising a load terminal strap 44 which is generally L-shaped and has its outer extremity bent downwardly to retain thereon a generally tubular wire clamping member 45 which may be of steel, and which carries a wire clamping screw 46. The load terminal strap 44 has its inner portion extending within each of the recesses 15, 16 and 17 of the top housing member 10 respectively and is anchored to the top housing member by a clamping screw 47 extending through a slot 48 in the end wall of the top housing member 10 (see particularly Figures 8 and 10) and into threaded engagement with the vertical portion of the load terminal strap 44. The extreme inner end 49 is returnbent, and has fixedly attached thereto an elongated bimetallic strip 50. For the purpose of adjusting the normal position of the bimetallic strip 50 with respect to the insulating housing member 10, we provide a calibrating screw 51 threadedly engaging the vertical portion of the terminal strap 44 and adapted to exert a pressure against the upper portion of the bimetallic strip 50.

For the purpose of preventing current flow between screw 51 and the bimetallic'strip 50, an insulating member 52 is provided which is generally T-shaped and adapted to extend through an opening 49 in the bight portion of the return-bent portion 49 of the terminal strap 44. The lower end of the bimetallic strip 50 is connected by a flexible electrical conductor 53 to the movable contact 36. In order to protect the flexible conductor 53 from the effects of arcing, we provide an in sulating sheath of woven glass fiber material 54.

The flexible braid 53 is attached to the contact supporting arm 37 directly behind the movable contact 36. It will be observed, especially by reference to Figure 1, compared to Figure 2, that the flexible braid undergoes a severe sharp bending immediately adjacent the movable contact 36. This bending is so sharp that, with ordinary methods of attachment, breakage would occur in the flexible conductor at this point after a number of operations of the breaker. Such breakage is prevented in the present design however by means of a supplementary supporting clip 55. The clip 55 includes a generally U-shaped portion, the outer ends of the U being bent over the edges of the contact supporting arm 37, and the intermediate portion of the U encircling the flexible connector immediately adjacent the point at which it is welded to the movable contact. The clip 55 further includes an arcuate tang portion extending from the bight of the U and adapted to engage the flexible connector and to prevent the connector from bending too sharply at this point of connection (see particularly Figure 1 and Figure 3).

The current path may now be traced through the circuit breaker in the following sequence: Current enters at the line contact 25 and goes to the stationary contact 29, to the movable contact 36, through the end portion of the contact supporting arm 37 to the flexible conductor 53, to the bimetallic strip 50, to the load terminal strap 44.

For the purpose of moving the contact operator 40 about its pivot 43 to move the movable contacts between open and closed circuit positions, and to releasably retain such contacts in the closed circuit position, we provide a circuit breaker operating mechanism 56 shown in perspective in Figure 5 and shown in exploded relation in Figure 6. The operating mechanism shown is disclosed and claimed in application Serial Number 650,600, filed April 4, 1957, by Emery M. Wegh and assigned to the same assignee as the present application.

The operating mechanism includes two opposite side frame members 57 and 58, supported in spaced-apart relation by spacer pins 59 and 60. The spacer pins 59 and 60 include shouldered portions for supporting and spacing apart the side frame members and also integral extensions 61 and 62 adapted to project through the side frame members and to extend outwardly from the outer side of such frame members for a purpose to be described.

A releasable carrier member or trip member 63 is supported for pivotal movement between the side frames 57 and 58 on a carrier pivot pin 64. The carrier pivot pin 64 is also shouldered and aids in spacing the side frames 57 and 58. Upper and lower pairs of toggle links 65 and 66 respectively are also provided. The upper pair of toggle links 65 extend one on each side of the carrier 63 and are pivotally supported thereon at one end by a pivot pin 67. The lower pair of toggle links 66 are more widely spaced apart and are individually pivoted on the U-shaped contact operator 40 by short pivot pins 68. The upper and lower pairs of toggle links 65 and 66 have their mutually adjacent ends connected and supported by a toggle knee pin 69. The upper toggle links 65 are pivotally supported on a central enlarged portion of the pivot pin 69, and the more widely spaced lower toggle links 66 are pivotally supported on reduced outer portions of the pivot pin 69. The pivot pin 69 is terminated at the outer surface of the lower toggle links 66 and is headed over to retain the links 66 thereon.

A pair of tension-type operating springs 70 are supported at one end in grooves in a relatively stationary spring anchor pin 71 which extends from side to side of the mechanism and has reduced end portions 72 resting in notches 73 cut in the corners of a projecting portion of the manually operating member 74. The lower ends of the operating springs 79 are attached to the toggle knee pivot pin 69, on the portion of the pin between each of the adjacent ends of the upper and lower toggle links. The manual operating member 74 is pivotally supported on knife-edge type pivots by means of notches 75 therein adapted to rest on outwardly bent lug portions 76 integral with the side frame members 57 and 58 respectively. The manual operating member 74 is provided with a manually engageable insulating handle portion 77 having a portion adapted to project through an aperture 78 in the top wall of the top housing member 10 and having an arcuate enlarged portion within the casing housing adapted to close the remaining portron of the aperture 78 in all positions of the handle.

The insulating handle member 77 is adapted to be carried by the operating member 74 and to operate the member 74 by means of interfitting portions'including shoulders 79 on the insulating handle 77 and edge portions 80 of the operating member 74. For the purpose of facilitating assembly of the operating mechanism and the insulating handle 77 into the top housing member in a manner to be described, a temporary holding clip 81, Figure 6, is provided, comprising a generally U-shaped length of resilient wire having portions bent over so that its side portions are L-shaped, and hooked in under the top bight portion of the handle member 74. The handle member 74 has a portion of the bight thereof lanced out and offset from the general plane thereof thereby providing an opening to receive the clip 81 and also a support to prevent the clip 81 from falling within the operating member 74.

Assuming the carrier member 63 to be stationary in the position shown in Figures 1 and 2, the switching action of the operating mechanism may be described as follows. In Figure l the parts are shown with ,the movable contact in the open circuit position and the toggle links 65 and 66 in the collapsed condition. As the handle member 77 is moved forward to rotate the operating member 74- in a clockwise direction, the upper ends of the operating springs 70, carried by the spring anchor pin 71 are carried in a clockwise direction until the line of action of the springs 70' passes across the pivot pin 67 of the upper toggle links 65. When this occurs, the springs 70 exert a force on the toggle knee pin .69 urging it to the right as viewed in Figures 1 and 2, toward a toggle straightened position. The parts then quickly move to the position shown in Figure 2, with a snap action. In this position, the resilient contact arms 37 are slightly deformed, exerting a predetermined contact pressure between the movable contact 36 and the. stationary contact 29. Conversely, when the handle member 77 is moved to the left as viewed in Figures 1 and 2, the upper ends of the operating springs 70 are carried in a counterclockwise direction and when the line of action of the spring 78 passes across the pivot pin 67, the toggle links move to a collapsed position with a snap action and the parts return to the normal off position shown in Figure 1.

For the purpose of releasably restraining the carrier member 63 in the normal or latched position shown in Figures 1 and 2, we provide a retaining latch 83, pivoted between the side frame members 57 and 58 at 84, and having an aperture 85 adapted to receive a latching portion 86 of the carrier 63.

For permitting operation of the latch member 83 by any one of two or more trip devices in a manner to be described, we provide an insulating common-trip bar 87 which extends transversely across all three pole compartments 20, '21 and 22 of the bottom housing member 11. The common-tripbar 87 is preferably formed of a highly arc-resistant and heat-resistant material so as to withstand the efifects of arcing from the arc chambers and to shield the current responsive trip assembly (to be described). Suitable materials for the trip bar 87 include glass-bonded mica or Mycalex, polyester and epoxy molding compounds reinforced by glass fiber, plastic resin bonded asbestos, and ceramic materials such as porcelain and bonded alumina. The commontrip bar 87 is rigidly attached to the retaining latch 83 by suitable means such as by rivets 88, and has a central portion 89 provided with a hole 90 adapted to receive one end of a trip bar biasing spring 91, the other end of which is anchored on the frame spacer pin 59. The action of the trip bar biasing spring 91 is such as to constantly bias the common-trip bar and the latch member 83 in a clockwise direction into latching engagement with the latch portion 86 of the releasable carrier 63.

It will be observed that in the normal oil? and on conditions shownin'Figures 1 and 2 respectively, the operating springs are under tension, placing the upper toggle links 65 in compression and exerting a force on the releasable carrier 63 through the pin '67, which tends to move the releasable carrier 63 in a clockwise direction as viewed in Figures 1 and 2. Such movement of the carrier 63 is normally restrained by the latching engage ment of the projection 86 with the retaining latch 83.

For the purpose of providing both thermal and mag= netic current responsive tripping action, we provide each pole of the circuit breaker with a bimetallic strip 50 described above, adapted to carry current therethrough, and, in addition, a magnetic armature member 110. The armature 110, shown more clearly in exploded view Figure 6 includes a bifurcated main portion terminating in upper bearing surfaces 111 each adapted to pivot in knifeedge fashion in molded bearings 112 (see Figure 4) in the top housing member 10. The armature is retained in mounted engagement in the V-shaped pivot bearings 112' by means of an armature biasing spring 113, which has one end hooked into a lanced-out portion 114 of the load terminal strap 44, and has the other end connected by an insulating link 115 to a projecting tongue 110' integral with the lower portion of the armature 110. The magnetic armature 110 is further provided with an integral flag-shaped portion or extension 116 having its outermost portion bent downwardly so as to present an edge 117 which is adapted to extend in front of the lower extremity of the bimetallic strip 50. The armature biasing spring 113 biases the armature 110: in a clockwise direction and normally maintains the edge 117 against the forward surface of the bimetallic strip 50.

A magnetic core member 118 is also provided, being attached to the lower portion of the bimetallic strip 50 by suitable means such as by welding, and is generally U-shaped to present pole portions 118 at either side of the bimetallic strip 50*.

The operation of the thermal and magnetic trip device is as follows. Assuming the breaker to be in the closed circuit condition of Figure 2, during a continued overload condition which is below a short circuit value, the bimetallic member 50 is heated by the action of current passing therethrough, and deflects or warps in a way to cause the lower end thereof to move to the right as viewed in Figures 1 and 2. As the lower end of the bimetallic strip 50 moves to the right, it exerts force against theedge 117 of the armature 110 and carries the armature 110 with it, until the toe portion of the armature extension 116 engages the common trip bar 87. Continued movement of the bimetal 50 and the armature 110 to the right moves the lower end of the trip bar 87 to the right, rotating the latch member 83 in a counterclockwise direction and withdrawing the retaining edge of the aperture 85 from the latch portion 86 of the carrier 63. Upon release of the latch portion 86, the operating springs 70 move the carrier member 63 in a clockwise direction until the extension 119 on the carrier 63 strikes the spacer pin 60.

As this rotation of the carrier member 63 occurs, the pivot pin 67 of the upper toggle links is carried across the line of action of the operating springs 70, thereby reversing the rotational bias of the operating springs 70 i on the upper toggle links, collapsing the toggle links and moving the movable contacts to the open circuit position as shown in Figure 3. The movement of the movable contact operator and contact arms toward the open circuit position is limited by the contact operator 40 striking the pivot pin 64 of the carrier member 63. This tripping action occurs regardless of whether the movable operating handle 77 is forcibly restrained in the on position such as by an operators hand. When the operating handle 77 is released, however, the handle member 77 is automatically returned to a central position as indicated in Figure 3 by further action of the operating spring 70. This handle-return action takes place because the lower endsof the operating springs 70 have been moved to the left by the collapsing action of the toggle links, and therefore the line of action of the operating springs 70 now passes to the left hand side of the handle pivot point 75 as viewed. This return movement of the manual operating member 77 counterclockwise as described, is

limited by the engagement of a resetting pin 120 carried by and extending from side-to-side of the manual operating member 74, which pin engages a resetting cam portion of the edge of releasable member 63.

In order to reset the circuit breaker, assuming that the bimetallic member 50 has cooled sufficiently to permit the latch biasing spring 91 to return the latch member 83 to proper position, the manually engageable handle portion 77 is moved manually from the central position or trip position of Figures 3 to the normal oif or resetting position of Figure 1. During this movement, the resetting pin 120 rides'along the resetting cam portion 121 of the carrier 63 and rotates the carrier 63 counterclockwise about its pivot 64 until the latching projection 86 once again enters the aperture 85 in the latch 83. At this point, the latch biasing spring 91 returns the latch 83 to its extreme clockwise position, such clockwise movement being limited by the engagement of the portion of the latch 83 immediately below the aperture 85 with the edge portion of the carrier member 63 immediately below the latching projection 86, assuring a fixed, predetermined maximum latch engagement.

Instantaneous or magnetic tripping action occurs when currents of a short circuit magnitude pass through the circuit breaker and through the bimetallic strip 50. When this occurs, the magnetic field associated with such current forms magnetic poles at 118' of the core member 118, thereby creating an attraction between the armature 110 and the magnet 118. Since the bimetallic strip 50 is relatively stiff compared to the resilience of the magnetic armature biasing spring 113, the armature 110 moves to- Ward the bimetallic strip 50 and toward the magnet 118 as shown in Figure 3. When this occurs, the toe portion of the armature extension 116 engages the common trip bar 87 and rotates the latch member 83 in counterclockwise direction, causing tripping in the same manner as described above. Resetting following such magnetic tripping is accomplished in the same manner as previously described in connection with thermal tripping.

As mentioned above, the exact calibration of the circuit breaker may be altered by adjusting the calibrating screw 51 which exerts a force between the main portion of the terminal strap 44 and return bent portion 49 which carries the bimetallic strip, either opening it out wider or allowing it to return to a more nearly closed position by reason of its resilience. This adjusts the angular position of the bimetallic strip 50 with respect to the remaining parts of the circuit breaker and particularly with respect to the common trip bar 87.

In Figure 13 we have shown our invention as embodied in a two-pole circuit breaker. The construction in this form is substantially identical to that of Figure 1 excepting that the casing includes only two pole chambers, and the contact cross-arm 38 and the common trip bar 87 have been shortened correspondingly.

In Figure 12 we have shown a modified form of common trip bar. In this modification, the common trip bar 122 instead of being formed entirely of insulating material, is formed of a metallic material such for instance as aluminum, which is coated with a suitable coating 122 of insulating material, such for instance as an epoxy resin plastic. We have found that an aluminum common trip bar treated so as to have an aluminum oxide coating thereon and subsequently given a coating of insulating plastic particularly nylon performs satisfactorily.

In order to support the operating mechanism of our improved circuit breaker in such a manner as to pro- 10 tect it from the effects of arc interruption in the closely adjacent arc-interrupting chamber, We have devised an arrangement and supporting means whereby the completely assembled mechanism is inserted and supported in the upper half of the insulating housing, that is, in housing member 10, and We have likewise devised means whereby the trip devices for each of the three poles of the circuit breaker is also supported in the upper half of the insulating casing, that is in housing member 10, and particularly is supported in such housing member with respect to the operating mechanism and its associated latch and trip bar. Accordingly the operating mechanism is provided with relatively short projections 61 and 62 described above extending outwardly from the outer surfaces of the side frame portions 57 and 58.

In addition, the central chamber 16 of the upper housing member 10 is provided with two pairs of recesses or slots 123 and 124 adapted to receive the projections 61 and 62, respectively. The slots 123 and 124 are also provided with an intermediate portion which is slightly constricted so as to aiford a defeatable resistance to the entry of the projections. In addition, each of the side frame members 57 and 58 is provided with an integral vertically deformable portions 125 for a purpose to be described.

The distance between the side frames 57 and 58 is preferably made less than the corresponding distance between the barriers 23 and 24 of the lower housing member 11, so that in the two pole form the width of the circuit breaker may be reduced to eifectively two thirds that of the three pole form without interfering with the mounting and support of the operating mechanism thus permitting the same mechanism to be used for both the two and three pole forms. For the purpose of supporting the mechanism in the upper housing member 10 and in the downwardly opening slots 123 and 124, as well as for the purpose of further isolating the operating mechanism from the arcing products produced in the lower chambers, we provide arc extinguishing chamber covers 126. Each of the arc extinguishing chamber covers 126 is supported on ledges 127 in each of the recesses 20, 21 and 22, and has a slot cut therein to permit the entry of the contact operating arms 37 in the outer pole chambers 20 and 22, the arc extinguishing covers 126 serve primarily to isolate the effects of arcing in each of the associated chambers. In the central chamber 21, the arc extinguishing cover 126 performs this same function and in addition provides a supporting base which is adapted to engage the deformable portions 126 of the side frame members 57 and 58 and to thereby hold the operating mechanism in its proper location in the upper housing member 10.

The two deformable portions 125 are initially formed so as to extend below their finally assembled position. So that as the housing members are placed together and suflicient force is exerted the portions 125 are deformed slightly, thereby providing a resilient retaining force to retain the mechanism in position.

The assembly of the complete three pole circuit breaker therefore preferably follows the following sequence. First the operating mechanism is assembled between the side frames 57 and 58 with the movable contact arms and movable contacts, and also with the flexible conductors 53 and each of the bimetallic strips 50 and load terminal straps 44 and connectors 45 attached thereto. The handle member 77 is inserted in place on the manual operating member 74 being resiliently retained thereon by the retaining clip 81. The top housing member 10 may then be inverted and the assembled mechanism inserted therein so that the projections 61 and 62 rest in the entrance portion of the slots 123 and 124. Additional manual pressure upon the side frames 57 and 58 causes the projections 61 and 62 to snap into their final location in the extreme portion of the slots 123 and 124. This subassembly may therefore be conveniently handled before the addition of the lower housing member 11 without the mechanism falling out. The trip devices including the bimetallic strips and load terminal straps are then inserted into corresponding recesses in the top housing member the load terminal strap mounting screw 47 being already inserted in its threaded hole therein, such assembly being permitted by the entrance slot 48. The load terminal strap mounting screw 47 is then tightened mounting the load terminal member and bimetal in fixed position in the upper housing member. Following this, the armature members 110 are assembled by hooking the extension portions 116 around the extreme end of the bimetallic strip 50 and placing the bearing edges 111 in the corresponding molded bearings 112 in the casing, and by hooking the armature biasing spring in position between the terminal strap and the armature. It will be observed that the armature biasing spring 113 serves not only to bias the armature member 110 into mounted condition in its inverted V-shaped bearings in the upper housing member, but also to bias it clockwise so that the edge 117 is normally maintained in proper engagement with the surface of the bimetallic strip St). Following assembly of the parts in the upper housing member 10, the arc extinguishing assemblies comprising the support member 30 the arc plates 31 and the line contact member 25 carrying the stationary contact 29 are assembled as one unit into the corresponding recesses in the lower housing member 11. The are extinguishing cover members 126 are then placed over the arc extinguishing assemblies. The circuit breaker is then ready for the final assembly operation and is in the condition shown in Figure 9. The top and bottom housing members are then brought together and suflicient force exerted to deform the deformable portions 125 of the side frames 57 and 58 and rivets 12 are passed through the aligned holes 14 in the top and bottom housing members and spun over to retain the parts together. It will be observed that following such final assembly, the clamping member 45 encircling the load terminal strap 44 and the tubular clamping member 45 are supported by an insulating piece 130 which in turn is sup ported by projecting bosses 128 projecting from extensions of the side wall portions and of the barrier portions 23, 24 of the bottom housing member 11. In the form shown in Figure 8, the strap 44 and the member 45 are supported directly by the bosses 128 and the piece 130 is omitted.

The completed circuit breaker is adapted to be held in mounted condition by suitable retaining means (not shown) adapted to engage projecting ledges 129 below the load terminal members 45. The design of the ledges members 129 and the bosses 128 is such as to remove the necessity for undercutting in the molding of the bottom housing member 11. Accordingly the design is such that no part of the lower housing member 11 projects directly above the ledge surface 12?, the bosses 128 being offset to one side of such vertical location. It will be observed that the design of the housing is such that top and bottom mating housing members 10 and 11 are provided each including three registering longitudinal recesses 15, 16, 17 and 2t), 21, 22 separated by registering barriers 18, 19 and 23, 24, and that these recesses each of which serves as a separate pole chamber, are crossed by a transverse passageway, the transverse passageway being offset longitudinally and located at op posite ends of the circuit breaker proper. In this manner maximum isolation and maximum compactness is achieved.

We furthermore provide a circuit breaker which meets all the required tests referred to above at a reduced cost, by choosing for the casing parts a particular combination of materials. Accordingly, we construct the top housing member of a material having a high degree of dimensional stability, without regard for its arc resistance characteristics; and we construct the bottom housing member of 12 a material having a high degree of arc resistance characteristics, without regard for its dimensional stability characteristics.

We define a material having a high degree of dimensional stability as being one which is such thatstructure of the type described herein molded therefrom do not display any change in dimensions in ordinary storage or use such as might prevent proper fitting of parts mounted therein or thereon or cause malfunctioning of the apparatu-s. Such dimensional changes for instance maybe caused by shrinkage, swelling, warping, or cold-flowing. The term cold-flowing is used to mean permanent distortion or yielding of a material under sustained pressure at ordinary temperatures, i.e., (0-100 C.).

We define a material having a high degree of are resistance as being one which has an arc resistance rating as testedby the American Society'for Testing Materials test method No. D495, of at least seconds. I

We prefer to construct the top housing member of a general-purpose type, wood-flour filled phenohformaldehyde molding compound. We prefer to construct the bottom housing member of an alpha-cellulose filled urea-formaldehyde molding compound.

General-purpose wood-flour filled phenolic molding compound, as is well known, has a high degree of dimensional stability. Its arc resistance, however, is relatively poor, since it tracks or forms a conductive path when exposed to arcing.

Urea-formaldehyde molding compound, with alphacellulose filler, does not have a high degree dimensional stability in configurations such as represented by housing member 11. its arc resistance, however, is of a high degree, being in the neighborhood of to seconds by the A.S.T.M. test method referred to.

By using each of these materials in an application where its superior characteristic is important and its other characteristics relatively unimportant,, we are able to provide a circuit breaker of substantially reduced cost.

Instead of general-purpose phenolic molding com pound, we may of course use for the top housing member any one of a number of other plastic molding materials having a high degree of dimensional stability; Specifically, we may use melamine-formaldehyde molding compounds, or polyester type molding compounds. Various other materials having a high degree of dimensional stability will occur to those skilled in the art.

In addition, while we prefer to use a urea-formaldehyde molding compound for the bottom housing member for cost reasons, we may utilize any of the well known suitable molding materials having a high degree of arc resistance, i.e., a material having an arc resistance of 80 seconds or more. Such materials include the melamine and polyester materials as well as glass-bonded mica or Mycalex materials and phenolics, epoxy resins and other materials incorporating special fillers to increase their are resistance.

The tapering construction of the slots 123 and 124 provides for easy and rapid insertion of the assembled mechanism is place in the top housing member 10 and also provides accurate final positioning. By means of the assembly shown the operating mechanism including its supporting frame members is mounted in the insulating casing without being positively fastened thereto. This construction not only saves time and expense in assembly, but provides a safer construction than those utilizing screws going through the housing which need to be insulated from outside the housing.

The manual operating member 74 is generally U-shaped and thesides thereof extend alongside of the mounting side frames 57 and 58 of the operating mechanism. Space or clearance must therefore be provided between the inner Walls of the mounting chamber 16 and the sides of the frame members 57 and 58 to allow free movement of the manual operating member 74. This spacing is also provided by the extended projections 61 and 62.

The common trip bar 87 is preferably made in the form of a relatively wide, thin, flat member so that it is adapted to act as a shield interposed between the entrance portions 33 of the arc extinguishing chambers and the trip device including the bimetallic strip 50, the magnetic core 118 etc.

The design of the circuit breaker housing and especially the lower housing member 11 is such as to provide substantially no venting from the arc extinguishing chamber outside of the casing. This total enclosure affords maximum safety to surrounding apparatus. While much of the hot gases generated by arc interruption are forced out of the entrance 33 against the flexible conductor 53 and toward the trip device, serious damage is prevented to these parts. Damage to the flexible conductor 53 is prevented although it is directly in the stream of are extinguishing gases by reason of the flexible woven glass sheath 54. It has been found that although the temperature of the flame and gases is suflicient to melt such glass and produce a sizable hole in such a sheath, that even thereafter the effect of such flame and gases on the conductor 53 is not further destructive. This is assumed to be because the melted glass coats the individual strands of the flexible conductor affording it protection.

While we have shown only two embodiments of our invention, it will be readily appreciated that many modifications thereof may easily be made, and We intend therefore, by the appended claims, to cover all such modifications as fall within the true spirit and scope of our invention.

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

1. A multipole electric circuit breaker comprising a generally rectangular insulating casing having a plurality of pole chambers, a plurality of arc extinguishing chambers in side-by-side relation in one corner thereof, a stationary contact supported within said housing in each of said are extinguishing chambers, a movable contact arm pivotally supported within said housing above each of said are extinguishing chambers and carrying a movable contact thereon adapted to move between open and closed circuit positions out of and into contact with the stationary contact therein, operating mechanism above said are exinguishing chambers and adapted to move all of said movable contacts between said open and closed circuit positions, a current responsive trip device within each of said pole chambers and including at least a portion extending adjacent each of said are extinguishing chambers, a common trip bar having a portion extending transversely across all of said pole chambers between said current responsive trip means and said are extinguishing chamber comprising a relatively wide thin flat member serving to shield said current responsive trip means from are interruption products generated by interruption of short circuit currents within said are extinguishing chamber.

2. A multipole electric circuit breaker comprising a generally rectangular insulating housing including a plurality of side-by-side pole chambers, each having an arc extinguishing chamber at one end thereof, a relatively stationary contact in each of said chambers, a movable contact arm of relatively Wide thin flat material supported for pivotal movement about an axis above each said are extinguishing chamber and carrying a relatively movable contact movable thereby within said arc extinguishing chamber into and out of engagement with said relatively stationary contact, current responsive trip means in said insulating casing adjacent each of said are extinguishing chambers, a common trip bar having a portion extending transversely across all of said pole chambers between said current responsive trip means and said are extinguishing chambers comprising a relatively wide thin flat member serving to shield said current responsive means from are interruption products generated in said are extinguishing chamber, and a transversely extending contact cross arm of relatively wide thin flat material oper atively connected to said operating mechanism and extending across said pole chambers above said are extinguishing chambers, said contact arms and said contact cross arm cooperating to shield said operating mechanism from the effects of arcs generated in said are extinguishing chamber.

3. A multipole electric circuit breaker comprising a top insulating housing member having three longitudinally extending recesses therein and a first transversely extending recess contiguous with said longitudinally extending recesses, a contact cross arm supported in said transversely extending recess, a movable contact arm in each of said longitudinally extending recesses carried by said contact cross arm, a single operating mechanism supported in one of said longitudinally extending recesses and including a trip member biased for movement to cause automatic opening movement of all of said movable contact arms, and a latch member normally restraining said trip member, a bottom insulating housing member having three longitudinally extending recesses therein, a stationary contact in each of said longitudinally extending recesses, a second transversely extending recess in said bottom housing member contiguous with each of said longitudinally extending bottom recesses, a common trip bar carried by said latch member in said one longitudinally extending top recess and extending in said transversely extending bottom recess across all said pole chambers.

4. An electric circuit breaker comprising a top insulating housing member having a recess therein, a bottom insulating housing member, a stationary contact mounted in said bottom housing member, a movable contact carried by said top housing member and operable to engage and disengage said stationary contact when said top and bottom housing members are fastened together, a preassembled operating mechanism in said recess adapted to operate said movable contact and including a plurality of movable parts pivotally supported between two opposed mechanism side frames, means positioning said operating mechanism in said recess without said mechanism being positively fastened to said top housing member, means carried by said bottom housing member for engaging said mechanism side frames when said top and bottom housing members are fastened together to retain said mechanism in said top housing member, and fastening means connecting said top and bottom housing members together.

5. An electric circuit breaker comprising an insulating casing, a pair of relatively movable contacts within said casing, operating mechanism for operating said relatively movable contacts between open and closed circuit conditions, said operating mechanism comprising a pair of opposed side frame portions and an operating member having portions extending along the outer side of said opposed side frame portions, a recess in said insulating casing, means for supporting said operating mechanism within said recess Without said mechanism being positively fastened to said casing includng a plurality of projections carried by said opposed side frame portions and directed outwardly thereof and adapted to engage the side walls of said insulating casing recess whereby to support said mechanism in said recess with said side frame portions spaced from said side Walls to provide clearance for movement of said operating member between said side walls and said side frames.

6. An electric circuit breaker comprising a two-part insulating housing including a top part and a bottom part, a recess in said top part adapted to receive and contain an operating mechanism, a recess in said bottom part, a relatively stationary contact in said bottom recess, arc extinguishing means in said bottom recess, operating mechanism including a pair of opposed side frame portions, a plurality of spacer pins supporting and spacing said side frame portions fiom each other, a manually 15 operable member having side portions overlying the outer portions of said side frame portions, said operating mechanism being adapted to be received within said recess in said top part of said insulating enclosure, said spacer pins having integral extensions extending through said side frame portions and projecting therebeyond and adapted to engage the side walls of said recess to support said operating mechanism in said recess with said side frame portions spaced from the side wall portions of said recess to provide clearance for said operating handle.

7. An electric circuit breaker comprising an insulating casing, a pair of relatively movable contacts within said casing, operating mechanism for operating said contacts between open and closed circuit positions, said operating mechanism being adapted to be preassembled before insertion in said casing, said casing having a recess adapted to receive and contain said preassembled operating mechanism, said operating mechanism including a plurality of relatively short projections projecting outwardly from the outer sides thereof, said recess includ ing a plurality of slots in the side walls thereof corresponding to said projections and adapted to receive said projections when said mechanism is inserted in said recess to accurately position said mechanism within said casing without said mechanism being positively fastened thereto.

8. An electric circuit breaker as set forth in claim 7 wherein said slots in said recess include an intermediate portion of narrower width than the extreme inner portion whereby to provide a snap-in retaining means for holding said mechanism in said casing.

9. An electric circuit breaker comprising a bottom insulating housing member having an arc extinguishing chamber therein, a top insulating housing member having a recess therein, a stationary contact mounted in said are extinguishing chamber, a movable contact, an operating mechanism adapted to move said movable contact into and out of engagement with said stationary contact in said are extinguishing chamber, said operating mechanism being received within said recess in said top member without being positively fastened thereto, said are extinguishing chamber having a ledge portion along at least opposite sides thereof, an arc extinguishing cham ber cover of insulating material supported on said ledge portions, fastening means connecting said top and bottom members together in superposed relation, said mechanism including a portion adapted to be engaged by said cover to retain said mechanism in said recess in said top member.

10. An electric circuit breaker comprising an insulating housing member having a recess therein, a relatively stationary terminal member mounted in said recess, a bimetallic strip in said recess extending generally parallel to said terminal member and having one end connected thereto, a movable contact member, means connecting the other end of said bimetallic strip to said movable contact member, operating mechanism for operating said movable contact including a normally latched member releasable to effect automatic opening movement of said movable contact, a magnetic armature plate between said bimetallic strip and said terminal member, molded bearing surfaces in said recess adapted to pivotally support said armature, said armature including an extension extending around said bimetallic strip, and biasing means biasing said armature into engagement with said bimetallic strip and also into engagement with said molded pivot bearings, said armature also including a portion adapted to engage said releasable trip member to cause automatic opening of said circuit breaker.

11. An electric circuit breaker comprising at least two relatively movable contacts movable between open and closed circuit positions, operating mechanism for operating said contacts between said open and closed circuit positions, said operating mechanism including a member movable to cause automatic opening of said contacts, a trip device including a relatively stationary terminal memher, an elongated bimetallic strip having one end con nected to said terminal member and having its intermediate portion extending parallel to butspaced apart from the intermediate portion of said terminal member, means connecting the other end of said bimetallic strip toone of said relatively movable contacts whereby said bimetallic strip is adapted to carry current therethrough, a magnetic armature member pivotally supported in the insulating material of said casing at one end and having a lost motion connection with said bimetallic strip at the other end, a magnetic core member carried by said bimetallic strip on the opposite side thereof from said armature member, said armature member being attracted toward said bimetallic strip by said' magnetic core member upon the occurrence of relatively high overload currents, and biasing means biasing said armature-away from said bimetallic member, said movement being limited by said lost-motion connection, said biasing member also biasing said armature member into said molded bearings.

12. An electric circuit breaker comprising a two part insulating casing including a top part and a bottom part, said bottom part including a relatively stationary contact and are extinguishing means adjacent thereto, said top part including operating mechanism for operating said contact between open and closed circuit position, said operating member including a member releasable to cause automatic opening of said contacts, said top part also including a trip device for causing releasing movement of said releasable trip member upon the occurrence of predetermined electrical conditions, said trip device including a terminal member mounted against one wall of said casing and an elongated bimetallic strip having one end attached to said terminal member and having its intermediate portion extending parallel to but spaced apart from the intermediate portion of said terminal member, and a magnetic armature extending generally parallel to said bimetallic strip and pivotally supported at its upper end in generally V-shaped molded bearings in saidinsulating casing said armature having a limited lost motion connection with the outer end of said bimetallic. strip,.

a magnetic core member carried by said bimetallicv strip:

on the side thereof opposite said armature member, said armature member being attracted toward said bimetallic.

strip by said magnetic core member upon the occurrence bimetallic member and also in retained engagement in:

said molded bearings.

References Cited in the file ofthis patent UNITED STATES PATENTS 2,020,332 Sachs Nov. 12, 1935 2,073,965 Jackson Mar. 16, 1 937 2,094,966 Sachs Oct. 5, 1937 2,214,695 Jennings Sept. 10, 1940 2,348,228 Scott 1 May 9, 1944: 2,390,039 Slayter et a1. Nov. 7, 1945 2,416,163 Dyer et all Feb. 18, 1947. 2,419,125 Dorfman et a1. Apr. 15, 1947' 2,446,027 Scott July 27, 1948 2,558,908 Paige July 3', 1951 2,645,693 Cole et all July 14, 1953 2,678,359 Brumfield' May 11, 1954' 2,797,277 Dorfman et a1 -1 June 25, 1957 2,797,278 Gelzheiser et al June 25, 1957 2,806,109 Sterling Sept, 10, 1957 2,811,607 Dorfman et al Oct. 29, 1957

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