US 3454918 A
Description (OCR text may contain errors)
y 1969 1.. w BRACKETT, JR 3,454,918
ELECTRICAL CIRCUIT BREAKER Filed June 29, 1967 Sheet of s gym, W;
y 1969 L. w. BRACKETT. JR 3,454,918
ELECTRICAL CIRQUIT BREAKER Filed June 29, 1967 Sheet fl of s \v 4 I 66 60 6 i 3/ a7 J4 l 70 9 0 x 7/ 60 M I V '?0 v y 1969 L. w. BRACKETT. JR 3,
ELECTRICAL CIRCUIT BREAKER Filed June 29, 1967 Sheet 3 of 5 if H'- U EH w P l 22 4 M4 H l H 9 i :2; 9 I ,20 Q 2Q2 44/ United States Patent Int. Cl. H01h 71/16 US. Cl. 337--75 2 Claims ABSTRACT OF THE DISCLOSURE An automatic circuit breaker of the trip free type has a push and pull operator which is pivoted to two links one on each side. The other ends of the links are pivoted to a contact slide and to a release lever, respectively. The release lever has a catch normally held by a bimetal latch. With the operator pivot past dead center, the contacts are held closed by the links extending between contacts and the catch of the release lever resting on the latch. The contacts open when the latch releases the catch upon abnormal loading, or when the operator pivot is pulled out of dead center.
BACKGROUND OF THE INVENTION Field 0]" the invention The invention relates to circuit makers and breakers responding to abnormal currents by way of a latch trip. Such circuit breakers it intended for use in critical circuitry and environment must be absolutely reliable. In many instances high current loads have to be handled by circuit breakers confined within severely restricted space which requires miniaturization. Simplicity of components and manner of assembly, assuring reliability and compactness, is indicated for circuit breakers of this general type.
Description of the prior art Wedging cam mechanisms according to Patent No. 2,960,587 of Nov. 15, 1960, to Morris B. Wood, were found to be especially Well suited for purposes of the above field of ar't However, while these breakers are uncomplicated, compact and reliable for many purposes, the interrelation of the components of their motions by way of rollers moving on cam surfaces, is not absolutely positive and therefore not perfect under certain severe conditions. It has been proposed to omit the rolling motion on contact cams with bar linkages, such as in Patents Nos. 2,955,177, 3,036,178, 3,142,737 and 3,265,835. In copending application Ser. No. 611,887 of Lawrence W. Brackett, Sr., filed on Jan. 26, 1967, a linkage acts between operator and tripping mechanism. It was apparently believed that, as an obvious expedient of conventional engineering, the self-adjusting and peculiarly flexible roller wedging cam, and should be retained for at least one circuit breaker component. The present inventor recognized that even a single rolling motion may become detrimental. Among several reasons, twin rollers which are preferable for purposes of symmetry, will wear unequally and lead to misalignment causing erratic operation. Circuit breakers according to the present invention avoid, as a departure from the previous motions, all rolling and wedging components, making it possible to use instead only rigid and positively acting linkages.
SUMMARY OF THE INVENTION Circuit breakers according to the invention have an operator arranged for reciprocation crosswise to the paths of movable contact means biased away from the fixed contacts, and of the moving end of a release lever. To the operator (preferably to the end of a rod swinging at the end of the operator) are pivoted on opposite sides two linkages, one pivoted at its other end to the movable contact means and the other to the release lever. The release lever has a catch biased away from a latch. carried by a load responsive means (in the preferred embodiment a bimetal structure). The biasing force on the contacts is stronger than that on the release lever. With the contacts in normally open position the operator is pulled out. In this position the location of the pivot common to both linkages causes the biasing forces to keep the contact securely open. Upon depressing the operator the common pivot moves through dead center, and the contacts are secured in closed position, against the biasing forces, by being held firmly against the latched release lever. When an abnormal load condition changes the position of the load responsive means, its latch releases the catch and the contact means open.
In a preferred aspect, the movable contacts are mounted on a linearly guide slide to which the linkage fro-m the operator is pivoted.
Circuit breaker according to the present invention include as an often preferable component a bimetal ele ment which is fabricated from two straight bimetal strips each fastened at one end with the other ends free to swing with changing temperature. The free ends are connected by a conductive cross bar which need not be heat responsive, whereas the conducting cross connection has the purpose of forming the above-mentioned latch which in normal condition holds the catch of the release lever, and hence the contacts in closed position.
In this manner, the object of permanent alignment and firm connection of all members of the mechanism is attained and wholly secure operation without any loose movement provided. Pairs of rollers with linear pressure regions subject to wear at critical points are avoided. The structure as a whole is simple, rugged, inexpensive in manufacture and assembly, and reliable under severe conditions including shocks and vibrations, even if built to very small size.
These and other objects and aspects of the invention appear from the following description of its principle, mode of operation, and practical embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a circuit breaker according to the invention;
FIG. 2 is an elevation with one-half of the housing removed, of the circuit breaker with the movable contacts in normally open position, the operator being pulled from the housing;
FIG. 3 is an isometric schematic of the electrical and spatial organization of the circuit breaker;
FIG. 4 is a fragmentary elevation, similar to FIG. 2, of the circuit breaker in closed position;
FIG. 5 is a fragmentary elevation similar to FIG. 2, of the circuit breaker in trip free open position;
FIG. 6 is a section on lines 6-6 of FIG. 2;
FIG. 7 is a section on lines 77 of FIG. 4;
FIGS. 8 and 9 are top and side elevations, respectively, of the bimetal element incorporated in FIGS. 2 to 7; and
FIGS. 10 and 11 are top and side elevations respectively of a U-shaped bimetal element that can be substituted for that of FIGS. 8 and 9.
DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1, 6 and 7, the circuit breaker has a split housing 10 which provides supporting and guiding structure for the breaker mechanism and consists of two shells 11, 12 which secure between them a barrier plate 15 by means of appropriate housing recesses. This supporting structure is held together by rivets such as indicated at 16 in FIG. 2. A cover plate 18 is fastened to the housing by means of bushing 19 which is threaded for securing the circuit breaker to a panel, if desired. The bushing 19 guides the operator plunger 20 carrying a push and pull button 21. The plunger 20 has two prongs 20.1, 20.2 (FIGS. 2 and 6) to which is fixed the operator rod pivot pin 22. The prongs 20.1 and 20.2 have ears 25, 26, respectively, (FIG. 6) which are guided in appropriate grooves 27, 28 of the respective housing shells.
Two fixed contacts 31 and 32 (FIGS. 2, 3, and 7) are secured and electrically connected as follows. Contact bars 33, 34 are confined in appropriate recesses of the housing, as well known in this art. The bar 33 carries at one end the fixed contact 32 and is curved forwardly within the housing to end in terminal 33.1. The bar 34 forms at its outer end the terminal 34.1 opposite the terminal 33.1 as indicated in FIGS. 3 and 6. The bar 34 is curved backward as indicated at 34.2 in FIGS. 2 and 3 and ends in a stump 34.3 where it carries electrically conducting thereto, the free end of a strip 42 of the bimetal element 40 to be described herein below. The fixed contact 31 is mounted on a contact bar 35 which is somewhat thinner than the bars 33 and 34 and is joined at its horizontal arm 35.1 to the other strip 41 of the bimetal element.
The movable contacts 51, 52 are conductively fixed to a metal slide 53 (FIGS. 2, 6 and 7) which has a slot 53.1 securing the biasing spring 58. Pressurably inserted therein are two guide pins 53.5 and 53.6 which slide in grooves 53.7 and 53.8 of the respective housing shells, as clearly indicated in FIGS. 6 and 7. For positive guidance the slide has an additional pin 54 with protruding ends 54.1 and 54.2, extending into the guide grooves 53.7 and 53.8, similar to pins 53.5 and 53.6. Opposite the movable contacts, the slide 53 has a projection 55 carrying pressed into a perforation, the pin 56, the ends of which protrude at 56.1 and 56.2 for the purpose to be described below. The slide 53 is biased away from the fixed contacts by a comparatively strong spring 58 that is coiled about a pin 59 carried in appropriate recesses of the respective housing shells (FIG. 2). One end of the spring 58 rests against a face of the interior wall of the housing whereas the other end bears on the slide 53 as indicated in FIGS. 2, 6 and 7.
The above-mentioned bimetal element 40 (shown separately in FIGS. 8 and 9) consists of two straight bimetallic strips 41 and 42 which are bent at one end as shown at 41.1 in FIG. 2. They are fixed, such as by welding, to the above-described contact bar 35 at 35.1 and terminal bar 34 at 34.3, respectively, as indicated in FIG. 3 and also shown in FIG. 2. The other ends of the straight bimetallic strips 41 and 42 are rigidly connected to a cross bar 44 (FIGS. 2 and 9) which is of conductive metal but preferably not temperature-responsive, such as formed from a solid piece of metal. The cross bar 44 is welded to the bimetal bars such as indicated at 44.1 and 44.2 in FIG. 8. A latch head 45 is fastened, such as riveted, to the latch bar, as indicated at 46. It will be appreciated that the bimetal element as a whole is conductive from 35.1 to 34.3 and thus completes the electric circuit from bar terminal 33.1 through fixed contact 32, movable contact 52, slide 53, movable contact 51, fixed contact 31, bar 35, bimetal strip 41, cross bar 44, bimetal strip 42, bar 34 to terminal 34.1. The bimetal element is adjustable in conventional manner, such as by way of a screw 40.1 which is threaded in bar 35.1 and loose in the housing.
The release lever 60 is pivoted on a pin 61 which is supported in housing recesses, indicated at 61.1. A lever plate 60.1 has two parallel linkages ears 62, 63 with elongated holes 62.1 and 63.1, and two pivot ears as indicated at 64.1, all stamped and bent as a single piece.
A spring 66, preferably of beryllium copper is welded to the lever plate at 67 where the ears 64.1 are bent over, and presses with the other end on the release lever pin 68 (FIG. 7). A biasing spring 69 is coiled around the pin 61 and rests with one end 69.2 against a boss of the housing, whereas the other end is at 69.3 bent to engage the lever plate 60.1, as shown in FIGS. 2 and 7. It will. be evident that the release lever is biased towards the contacts of the mechanism whereas the contact slide 53- is by spring 58 biased away from the fixed contacts. Spring 58 is stronger than spring 69. The swinging end of the release lever 60 forms at 60.1 a catch capable of engaging the latch head 45 of the bimetal element 40 as shown in FIG. 4. It will be evident that upon the latch of the bimetal element moving downwardly the release lever will be moved by the stronger spring 58 from the position shown in FIG. 4 to that shown in FIG. 5.
Hinged on the above-described pin 22 of the operator is an operator rod 70, the other end of which engages a link pivot pin 71 on which are pivoted the release links 73 and 74 and on the outside thereof the contact links 75 and 76. The release links are on the other side pivoted on pin 68 of the release lever. The other ends of the contact links 75 and 76 are pivoted on the pin 56 of the contact slide 53. The pins 56, 68 and 71 have shoulders and riveted ends as indicated in FIG. 7 for the purpose of securely holding the various links.
The operation of the above-described circuit breaker is as follows.
In normally closed position as shown in FIG. 4 the operator button 21 is pushed in and pin 71 is below dead center so that the release lever 60 is pressed, against the bias of its spring 68, towards the latch 45 whereas on the other side the contact slide 53 with movable contacts 51, 52 is pressed, against the bias of spring 58, towards the fixed contacts 31, 32. Due to the positive guidance of the contact slide by pins 53.5, 53.6 and 54.1, 54.2 and the confinement of pin 68 within the oblong holes 62.1, 63.1 against spring 66, the position of the contacts is securely maintained. It will be noted that all springs cooperate to maintain the linkages braced against each other to provide good contact pressure. It will further be noted from FIGS. 4 and 3 that the current path traced above, including the bimetal element 40, is established.
For opening the circuit breaker, the button 21 is pulled out to the position shown in FIG. 2. The common pivot pin 71 goes above dead center permitting the strong spring 58 to separate the slide contacts 51, 52 from the corresponding fixed contacts 31, 32. Spring '69 retains the rod 70 and the plunger 20 in the once established position. The release lever springs are ineffective.
Upon an overload occurring in the circuit of which the closed breaker in position FIG. 4 is a part, the bimetal element is heated, the strips 41 and 42 bent downwardly and the catch 60.1 is released by the latch head 45. As shown in FIG. 5, the contact slide is moved away from the fixed contacts by spring 58 against the weaker spring 69. The plunger remains in depressed position and pulling it up will not be able to close the contacts against the bias of spring 58 so long as overload exists with the bimetal element deflected and the catch released.
It will be noted that the spring 66 is capable of keeping the pin 68 towards one side of the oval hole in open (FIG. 2) and trip-free (FIG. 5) positions whereas the pin is pressed against the spring 66 when the breaker is closed as shown in FIG. 4. The spring 66 is the strongest spring in the system, stronger than both springs 58 and 69. In this manner, the spring 66 provides predeterminably favorable contact pressure not interfered with by any other component of the mechanism. Furthermore, due to the play provided by the elongate pivot perforation means 62.1, 63.1, the spring 66 compensates for contact wear without changing the contact pressure. Resilient and yet certain and secure operation in spite of disturbances such as shock and vibration is with certainty maintained.
While the above-described embodiment uses a bimetal element as load responsive means, it will be understood that other, such as magnetic, tripping expedients can be used within the above-described combination. For example, the latch head 45 can be arranged at the end of a magnet armature.
FIGS. and 11 show a modification of the bimetal element wherein it is formed of a continuous bimetallic strip 140, with a latch element 145 directly fastened thereto. It will be understood that the element according to 'FIGS. 8 and 9 is less expensive and more certain as to operation, since it is not affected by a transverse bimetal effect at the bend between the two straight portions.
1. A circuit breaker having two contact means fixed side by side to a support and two contact means movable on a slide biased away from the fixed contact means and electrically connected for bridging the fixed contact means, load responsive means in series with the fixed contact means and having latch means, a release lever having catch means biased away from the latch means, an operator mounted for reciprocation obliquely to the paths of the movable contact means and the catch means of the lever, a rod hinged to the operator to swing between contacts and release lever, and a pivot pin at the swinging end of and operator rod;
wherein an improvement comprises:
first rigid linkage means pivoted on the one side to the operator and on the other side to the release lever, for positively coupling the operator-and the catch means; and
second rigid linkage means pivoted on the one side to the operator and on the other side to the movable contact means, for positively coupling the operator and the movable contact means;
each of the two rigid linkage means having a pair of parallel links each with one end pivoted on the pivot pin of the operator rod, the release lever being pivoted on one side to the support and on the other side to the other ends of the first pair of parallel links, the movable contact slide being pivoted to the other ends of the second pair of parallel links, said other ends of said first pair of links having pivot perforation means, and the release lever including elongated pivot perforation means near said other side of the lever,
a pivot pin through said other ends of the first pair of said links and said perforation means completing a pivot, and
spring means fixed with one end to the release lever near its support pivot end and pressing with the other end on said pivot pin to bias it away from the lever in its elongate perforation means, providing constant contact pressure and compensation of contact wear;
whereby movement of the pivot of operator rod and links beyond its dead center rigidly secures the fixed and movable contact means in closed position, bearing against the bias of contact means and catch means on the latch means in normal position, and whereby the contacts open when the catch means is released by the latch means in response to changing load conditions, or the operator rod and links pivot is moved to the other side of dead center.
2. Circuit breaker according to claim 1 wherein said load responsive means includes:
two effectively parallel bimetal strips fastened at adjacent respective ends in electrical relation with the contact means;
a conductive bridge of inconsequential thermal response conductively fixed across the strips adjacent their other ends, respectively, opposite the catch means of the release lever, and
an angle shape fastened with one leg to the bridge and with the other leg projecting beyond the bridge towards the catch means to form said latch means for engaging said catch means.
References Cited UNITED STATES PATENTS 3,217,125 11/1965 Brackett 337- 3,265,835 8/1966 Wood 337-6'7 2,516,670 7/1950 Bourne 337-59 FOREIGN PATENTS 206,036 11/ 9 Austria.
BERNARD A. GILHEANY, Primary Examiner. DEWITT M. MORGAN, Assistant Examiner.
US. Cl. X.R. 33759