US2336036A - Circuit breaker - Google Patents

Description

Dec. 7, 1943.

A. B. RYPINSKI 2,336,036

CIRCUIT BREAKER Filed Feb. 2'7, 1940 5 Sheets-Sheet l INVENTOR ALBERT B. RYPINSKI ATTORNEY Dec. 7,1943. A B RYPTNSKI 2,336,036

CIRCUIT BREAKER Filed Feb. 27, 1940 v 5 Sheets-Sheet 2 gummy 4 I INVENTOR no. a. ALBERT a. RYPINSKI Dec. 7, 1943. A, B RYPINSR. 2,336,036

C IRCUIT BREAKER v I Filed Feb. 27, 1940 v 5 Sheets-Sheet 3 mnmazm INVENTOR ALBERT B. RYPINSKI ATTORNEY 5 Sheets-Sheet 4 A. B. RYPINSKI CIRCUIT BREAKER Filed Feb. 27, 1940 INVENTOR ALBERT B. RYPINSKI ATTORNEY FIG. 9.

Dec. 7, 1943.

w m r.

FIG. ll.

FIG. l2.

Dec. 7, 1943. I A. B. RYPINSKI CIRCUIT BREAKER Filed Feb. 2'7, 1940 5 Sheets-Sheet 5 FIG. 13.

FIG. l4.

INVENTOR ALBERT B. RYPINSKI ATTORNEY Patented Dec. 7, 1943 2,335,036 CIRCUIT BREAKER Albert B. Rvpinskl, Laurclton, N. Y., aosignor to Metropolitan Device Corpontlon, Brooklyn, N. Y.. a corporation of New York Application February 27, 1940, Serial No. 321,022

- 3 Claims.

herein disclosed relates to a v circuit breaker of the protecoperotcs automatically to open tive type which.

I the circuit; upon overloads and short circuits independently of the seasonal operation and in particulor to e breaker or the hind described v in the co pez application Serial $09,521 filed Dccem id, 1939.

new objects of the invention is to provide s .icuit breaker construction n which the several s are arranged and co 'ructed r are readily and easily as misled number of operations. Another operating 1 use of tools. tion is to clone-l object of is construction in. v

J Chillll is reodil; in the case; to pro provide to unit of;

stiuotio' opera ing mean case; to prom circuit broi case through a.

provide a cow H for the ci r is in sembled o sashes.

The foregoing objects and certain edventsgcs which will ".fter appear are recall d in the circuit bree or, co tituting one specific example of an embodini t the invention, illmtroted in the accompenyhig drawings and described in detail below. The drawings include:

Fig. 1 whi h is an exploded isometric view of one form of circuit breaker embodying the invention; 45

Fig. 2 which is an. i ometric view of the some illustrating the relation of the case, assembled unit of opecatlng ports, and the cover;

Fig. 3 which is aplsn of the assembled circuit breaker; '0

Fig. 4 which is a sectional. side elevation of the same taken along the line i -4 of Fig. 2?;

Fig. 5 which is a sectional side elevation taken along the line 55 of Fig. 3;

Fig. 6 which is a sectional side elevation similar to Fig. 4 showing the parts in an intermedi ate position;

.Fig. 7 which is a side elevation of a part of the circuit breaker, the switch element;

Fig. 8 which is a transverse section 01 the circult breaker taken along the line 88 of Fig. 3;

Fig. 9 which is a, fragmentary sectional elevetion 01' a detail of the switch element;

Fig. 10 which is a. plan of a duplex unit;

Fig. 11 which is a. sectional side elevation i1 lustrating the circuit breaker of Fig. 10 assen q bled in a switch box;

Fig. 121s a plan of a. multiple unit;

Fig. 13 which is a. plan of a duplex case with an integral cover; and

Fig. 14 which is a. sectional side elevation oi the same.

The circuit breaker illustrated in Figs. 1 to l primarily includes the operating mechanism that consists of the ports Al to A5; a case B in which, in the assembled breaker, the operating parts are housed; stationary contacts Cl and C2; and a bottom or base D upon which the stationary contacts are mounted and which closes the lower or open end of the case. The operating parts Al to A5 assemble as a unit (Fig. 2) and are rc= ceived in the case by insertion in the open, lower end. An opening is provided in the top of the case through which the finger piece of the part- A3 extends. The base D with the contacts CE and C2 mounted thereon closes the lower endc the case, the contacts extending up into the cess.

The five operating parts Al to'A5 assemble to gather as an operative unit (Fig. 2) and in the assembled relation are held together as a unit by the interengagement of the parts. A slide been 111g plate I constitutes the part AI. This slide has a bearing opening 2 therethrough apprcxi mately at the center thereof. A stub shaft or pivot 3 is formed integral with the plate adjacent the upper end thereof. At the upper end the slide Al is provided with a. thinner extension or tongue 4. A similar tongue 5 is'provided at the lower end of the bearing slide.

The shaft 3 of the slide AI forms a. pivot upon which the lever that constitutes the part'AZ is' cess 1 in rear surface thereof. The other end 8 of the lever is shaped as illustrated for the purpose of engaging in a cam action relation with This switch element is in the form of a rotor.

after be decribed.

The operating handle of the circuit breaker, A3,

includes in one piece a shaft 9, a disk-like radially supporting wall ll] adjacent one end of the shaft, a substantially axially extending flange II and a finger piece l2 extending radially outwardly from the flange and having a sealing opening therethrough. Between the shaft and the outer end of the supporting wall Hi, there is formed in the wall a circular spring cavity indicated by the numeral l3. The shaft 9 is enlarged at this point and has a keyway 4 formed therein, the side walls of which converge toward the inner or supporting wall end of the shaft. Through the supporting wall, adjacent the flange N, there is formed an arcuate opening I5 shaped as illustrated. The radially inner surface of the flange H is undercut at Hi from the outer face and through the supporting wall, forming a shoulder I! which constitutes a latch-engaging surface. On the other face of the handle there is formed in the flange II a recess |8 having the configuration illustrated in Fig. 1.

Extending axially through the flange and adjacent the shoulder l1, there is a threaded hole I9. The end of this hole at the wall I0, is irregularly shaped. A set screw 20 having its end 2| shaped as shown and commonly known as a dogpoint hardened set screw is mounted in the threaded hole. The shaped end 2| of the screw serves as a detent, part of the current releasable means of the circuit breaker, and it may be adjusted for a purpose that will hereinafter appear. When the screw is adjusted to the proper-position, cement 22 is forced into the irregular opening in the flange i and into the sunken socket in the set screw. When this cement hardens it renders the screw inaccessible.

The part A4 is a spring element which serves to efiect the automatic operation of the circuit breaker. The spring element consists of a single spring that includes a central loop 23 and a torsional spring section on each side of the loop that is wound from the central loop outwardly.

Both torsional sections 24 and 25 of the spring are wound in the same direction. The end of the spring section 23 is bent at a sharp angle to form a radial inwardly extending key 26, and the end of the section 25 is bent to form an outwardly extending key 21. It will be obvious that with the central loop 23 fixed or restrained, the twosections of the spring may be wound in the same direction against the loop to provide bias. In this way, therefore, bias, as will hereinafter appear, in the same direction, on the operative parts of the circuit breaker, is attained with a single spring. Winding the spring up a partial revolution will provide a sufficient bias for effecting dependable operation of the circuit breaker.

A switch element is represented bythe part A5. It is bored axially to receive and be rotatably mountted upon the shaft 9 of the handle. In the assembled condition it is in effect housed or partially encased, in the handle, The rotor has a circular spring cavity 28 (Fig. 7) formed at one side wall thereof. In the outer wall of the spring cavity of the rotor, there is provided a keyway 29. Radially outwardly of the spring cavity there are formed contact receiving recesses 30. These contact recesses have end walls 3| and 32 extending substantially radially. 'One side 33 of the end wall 3| forms a cam surface that co-operates with the curved end 8 of the lever A2.

The switch element contacts are mounted on the rotor to be within the recesses 30. One contact 34, which is rectangular, is mounted adjacent the end wall 3|. One of the flat surfaces thereof bears against the end wall and an ad- J'acent flat surface bears against a short tangential wall 35 which engagement prevents rotation of the contact. The other contact 36 which is likewise rectangular is angularly spaced from the contact 34. The contact 36 is prevented from rotating by engagement of one of the flat surfaces thereof with the wall 32 and an adjacent flat surface with a surface 31 formed substantially tangential to the inner circumferential wall of the recess 30.

The contact 34 (Fig. 9) has a reduced rounded and shouldered extension 38 which passes through the rotor wall 39'. The end portion of this rounded extension is further reduced in diameter and forms a rivetportion 40 by which one end of a bimetal strip 4| of substantially the shape of an inverted V is secured to the face of the rotor.' Theother contact 36 is similarly constructed and the end portion thereof forms a rivet 42 by means of which the other end of the bimetal 4| is secured to the face of the rotor.

On the face of the rotor to which the bimetal 4| is secured, there are three raised sections, one 43 at each end of the bimetal where the bimetal is secured to the rotor and the other 44 of materially smaller area at the apex of the bimetal. In this way the bimetal is, for the greater portion, spaced from the, rotor and the transfer of heat from the bimetal is minimized. As constructed, each contact on the rotor has the function of acting as (1) a contact, (2) a rivet which secures one'end of the bimetal strip to the face of the rotor and (3) an electrical conductor between the contact and the bimetal strip. The contacts may be soldered or brazed to the bimetal to prevent loosening. The reduced cross section of the rivet ends of the contacts minimize the transfer ofheat from the bimetal strip to the contact surface.

These several elements Al to A5 constitute the operating mechanism of the circuit breaker and may be assembled together as a unit. The assembly is accomplished as follows: The bearing plate Al is laid down and the latching lever A2 is placed on the shaft 3. The handle A2 is laid over the bearing plate so that the lever A2 enters the arcuate opening IS in the handle and the end of the shaft 9 enters the bearing opening 2.

Next the spring element A3 is dropped in the handle spring cavity with its key 26 in the key- 53 way I4. The loop 23 of the spring is now pulled ba:k to a point at which it snaps in place in the recess I in the latching tooth end of the lever. The end of the spring loop 23 is shaped to more or less conform to the curvature of the surface of the lever A2 which it engages. The rotor, which has previously had the contacts 34 and 36 and the bimetal 4| assembled on it, is dropped in place over the spring, the shaft 9 extending through the hole in the rotor. The rotor is then turned about the shaft until the key 21. of the spring enters the keyway 23. This end of the spring is now located in the rotor and turning movement of the rotor winds up the spring. After the rotor has been turned suiiiciently, it may Cal to fully enclose the spring and to insure alinement of the movable parts. The spring now holds the bimetal 4| with its edge engaging against the detent 2| and by its tension on the parts serves to retain the several parts together in their be pressed into place, sliding along the shaft 9,

aesacec pick up the assembled circuit breaker unit and electrical-insulating, non-corrosive material. It

is molded in one piece in the form shown and is open at thebottom. The end walls 45 and 45 extend below the bottom. Through the end wall 45, there is a pair of similar, parallel vents or having the shape illustrated and terminating in recesses 48 at the top of the case. Like vents as extend through the end wall 46 and terminate in recesses 50. The top is shaped as illustrated and includes two barriers i and 52 extendin therefrom, one on each side of an opening 53 through which the finger piece 52 of the operating unit extends.

In the inner surface of the side wall 54, there is provided a slot 55 for the bearing slide A2 of the operating unit. At the upper end of the slot E55, there is an undercut recess 53 (Fig. 8) in which the tongue 4 is received. The inner surface of the opposite side wallb'l is provided with a slot 58 in which the extended end of the shaft 5) of the operating unit is received. This latter slot is rounded at its inner end and in the assembled circuit breaker forms a bearing on three sides for the extended end of the shaft 9.

The stationary contacts Cl and C2 (Figs. 1, 2 and 5) are assembled on and secured to the base D. Contact Cl includes a heavy metal contact piece 59 and a resilient, spring contact strip 88 that is considerably wider than the contact piece 59. One end of the contact piece 59 is bent as illustrated and has secured thereon a heavy rectangular contact block 5! that engages a shoulder formed on the contact piece. This block is preferably provided with a reduced extension 82 that extends through an opening in the contact piece and is headed over. The block may in addition be soldered or brazed to the contact piece. At the other end, the contact piece includes a portion 83 of the same Width as the contact strip 36 to one end of which it is secured by rivets extending through alined Openings in the two pieces. Contact C2 is similar to contact CI including a contact piece 64, a contact block 65 and a contact strip 66. The contact block- 55 is secured to the contact piece 64 which in turn is secured to the contact strip 56. These pieces are shaped as shown, the contact piece in this instance being flat and the contact strip 66 being longer than the contact strip 60. The contact blocks may be of a. silver alloy such as tungsten silver and welded on the contact pieces.

At the end of the contact strip 58 opposite to that end to which the contact piece 59 issecurcd, there is formed in the strip an opening. The metal at the edge of this opening is shaped to form an off-set boss 61. A similar off-set boss 68 is provided in the contact strip 55. These off-set bosses are provided for securing the contact strips to the underside or bottom of the base D.

Like the case, and all parts of the circuit breaker except the electrical conducting parts and the detent, the base D is made of Bakelite or some equally efficacious and strong, electrical-insulating, non-corrosive material and molded in one piece. The base includes a central inwardly extending projection 59 concaved at its inner surface and having a recess therein to accommodate the contact piece 59. At each end of the base, there is provided a contact strip recess, recesses H and I2, in which the contact strips 60 and 66 are received. Extending from the bottom of the base and transversely thereof, there is 2.

central barrier 13 which electrically separates the ends of the contact strips 60 and 86. On one side of the barrier, there is molded in the base, a hol- 10w, internally threaded, cup-shaped bushing lid having a reduced end extension 5. A similar bushing 76 having a reduced extension TI is embedded in the base on the other side of the barrier. -The extension 75 or" the bushing 14 extends through the boss 8? of the contact strip 89 and it is spun over to secure the contact strip 6b to the bottom of the base. In like manner, the extension Tl. on the bushing 76 extends through the boss 58 on the contact strip 53 and is spun over to secure the contact strip 38 to the base.

When thus secured on the base, th contact strip extends through the contact strip recess "ii. The bent section of the contact piece 59 is received in the recess i0 and th contact Si is positioned above the projection 69 with its contacting surface facing upwardly. Similarly, the Contact strip 35 extends through the recess Th contact :35 is positioned above the projection with the contact surface towards the projection. Terminal screws l8 and T9 are received in the bosses l4 and it respectively and are thus accessible fo making electrical connectionsto the stationary contacts from the outside of the case.

As previously stated the assembled operative unit, consisting of the parts Al to may be slipped into the case. To plac the assembled unit in the case, the bearing plate I is entered in the slot and the extended end of the shaft 9 of the case. With the operative unit in the case and in open-circuit position (Fig. 6), the base D with the contacts Cl and C2 assembled thereon is placed in position on th bottom of the case. The whole circuit breaker is then secured together by rivets or screws 30 extending through alined openings St at diagonally opposite corners of the base and case. These openings are formed through lugs 82 on the base and case.

It is, of course, desirable that the electrical testing of the breaker, to determine its correct calibration be done before the breaker is permanently fastened in place; This may be done by assembling the breaker without fastening the case to the base, passing current through the breaker and observing its tripping time on a definite current. If not correct, it is only necessary to slip the operating unit out of the case sufficiently to expose the adjusting screw 28, turn the screw "the desired amount, fill th opening with cement 22, slip the breaker unit back in place and rivet the entire assembly as described. Either the sealing or riveting operations render the adjustment on the breaker inaccessible which is a requirement of the Fire Underwriters.

In the assembled circuit breaker the spring loop 23 acts upon the lever A2, and serves to hold the lever in latching relation with respect to the shoulder I! on the handle. The spring engaging surface on the end of the lever is designed so as to resolve the force exerted by the spring to effect the necessary latching movement of the lever and at the same time to permit ready disengagement of the latch and the latching surface upon exertion of a force on the-finger piece l2 in a direction to move the finger piece to the off position. The opposite end of the lever is shaped as illustrated for the purpose of engagement with the cam surface 33 on the rotor (Figs. 6 and 7) which is positioned and arranged such that as it moves to open-circuit position the cam engages the lever and moves the lever to the un+ latched position. This arrangement provides a positive means for effecting unlatching movement of the lever when the rotor moves to opencircuit position.

When the rotor A is released by virtue of the warping of the bimetal and moves to open-circuit position, the force exerted on the lever A2 ,by the loop 23 of the spring is lessened. The

force exerted by the loop is dependent upon how tightly the coil 24 and 25 are wound. When the tension on one of the coils is lessened by unwinding, as by movement of the switch element to open-circuit position, the force exerted by the loop is correspondingly decreased. Thus, the handle is more easily unlatched when the rotor moves to open-circuit position and the cam 33 engages the end 8 of the lever.

The recess l8 in the flange ll of the handle provides clearance for the end of the bimetal 4| as it travels with the rotor and independently of the handle to open-circuit position. In the assembled unit, the bimetal strip extends radially to a point beyond the end 2| of the screw 20. The edge of the bimetal is cut away as shown to conform with the shape of the detent screw, and the engaging edge thereof may be rounded to provide a point contact with the screw and so minimize the friction tending to retard warping of the bimetal. The rear edge of the bimetalat the apex end bends away from the detent to form a lead-in 33 and so efiect ready relatching after the bimetal has escaped and cooled. Under bias of the spring, the bimetal engages, in latching relation, the detent end 2| of the screw 20 to cause the rotor to follow the handle under spring propulsion, from on to off position when the handle is manually operated. By turning the screw 29 the extent of engagement between the bimetal and the detent 2| may be adjusted. In this way the amount the engaging end of the bimetal must move to be released from the detent may be changed and the value at which the breaker opens predetermined. This in turn establishes the capacity or rating of the breaker.

The operation of the assembled circuit breaker will now be described. If the handle is moved to the closed-circuit or on position, a circuit is established (Fig. 5) from terminal 18 through contact 6| contact 34 bimetal 4| contact 36 to terminal i9. In this position, the stationary contact strips are under tension by reason of the engagement of the switch element contacts 34 and 36 with the stationary contacts and the contact strips exert a force on the rotor inadirection to move the rotor to off posit on. This force adds to the speed with which the rotor operates when the breaker trips.

The circuit breaker may be manually operated to open or close the circuit. As previously described, the relation of the engaging surfac I! of the handle and the lever A2 is such that while providing a secure latch, it releases upon exerting a force upon the finger piece |2 in a direction to move the handle to open-circuit position. Thus, since the rotor, under normal conditions, is latched to and follows the handle by spring action as explained above, the circuit breaker may be actuated manually in the manner of an ordinary switch,

When the circuit breaker is in the on position and an excessive current passes through it, the bimetal becomes heated, warps in a manner well known and usual with a bimetal, and becomes disengaged from the detent 2|. The warping or 5 bending of the bimetal may be rapid in the case of a heavy flow of current due to a short circuit or it may be slow or delayed where there is but a slight overload. In either event when the bimetal becomes released from the detent, the rol0 tor is moved by the spring to the open-circuit position as illustrated in Fig. 6. As the rotor nears th open-circuit position, the cam surface 33 on the rotor engages the end 8 of the-latching lever A2 and positively moves the lever to unlatched position. When this occurs, the handle is released and under the action of its end of the spring moves to open-circuit position and in doing so the detent 2| passes the bimetal. When the bimetal cools and returns to its normal position, it again alines with the detent. If it be cooled before the handle arrives at the "ofi position, the lead-in 83 on the bimetal permits the detent to pass the bimetal. The rotor is thus again latched with the handle for movement to on position. It will be apparent that while there is an overload or a short circuit, the breaker cannot be held in closed-circuit position because the contact carrying rotor is only latched to the handle by means of the bimetal, and holding the handle will not prevent the bimetal escaping and the rotor moving to ofi" position. It is well established in circuit breaker and electrical contactor design that a heavy current will effect opening of separable contacts more quickly by magnetic repulsion between the parts carrying currents in the same direction, than in the case with lighter currents. In the circuit breaker described above both breaks in the circuit, at the contacts, are so related that the rotor is impelled toward open-circuit position by the magnetic forces at the time of operation. on short circuits; these forces are of considerable magnitude and assist in driving the rotor rapidly toward open-circuit position.

In addition the expanding gases produced by the arc serve the same purpose. The net result is that on a short circuit, where it is important that the circuit be interrupted as rapidly as possible, the rotor is urged toward open-circuit position by (1) both sections 24 and 25 of the spring A4, (2) spring pressure of the contact strips 30 and 66, (3) the magnetic action of the arc stream and current-carrying parts, and (4) the pressure exerted between the stationary and movable contacts by the expanding hot gases.

In Figs. 10 and 11, a duplex circuit breaker is illustrated in which the terminals ar brought out to the ends of the circuit breaker. The circuit breaker there illustrated includes a case 84 having two cavities open from the bottom and arranged side by side to accommodate two operative units 85 and 86. A duplex base 81 is also provided which closes the bottom of the case. This base has end extensions 88 and 89 that extend beyond the ends of the case. A recess 90 is provided in the extension 88, at the transverse center thereof and an opening 9| is provided through the extension at the recess A similar recess 92 and opening 93 is provided-in the extension 89. The base is secured to the case by screws 94 and 95 extending through alined openings in the case and base and nuts 96 and 97 threaded on the lower ends of the screws 94 and 95 respectively.

The stationary contact 98 for the circuit breakaseaceeer unit 86 is connected to ccnn 93 by a terminal screw we. The connector strip 35 extends beyond the end of the base and on to the extension 88. On the of strip 99, there is provided a solderless connector The other stationary contact I02 cooperating with the unit 86 is connected to a contact strip H13 by a terminal screw I04. This strip extends beyond the other end of the case and on to the extension 89 of the base. On the end or the strip I03, there is mounted a solderless connector I05. Similar connector strips I06 and I! with solderless connectors I08 and I09 are provided for connection with the stationary contacts of the circuit breaker unit 85. It will be obvious that the handles of the circuit breaker units 85 and 86 may be independently or conjointly operable, the latter arrangement being efiected merely by connecting the finger pieces together.

In Fig. 11, the circuit breaker of Fig. 10 is illustrated as mounted in a cabinet or box III) that is provided with a cover I I I. The cover I I I has an opening IIIa therethrough in which a projecting section IIZ of the case 84 is received. The circuit breaker is secured to the bottom of the box by screws H3 and I I4 extending through the openings 9| and 93 through the base and engaging in alined threaded openings in the bottom of the box. With this arrangement, the solderless connectors for making connection to the circuit breaker are accessible upon removing the cover of the box.

Fig. 12 illustrates an arrangement of a multiple circuit breaker case. In the arrangement illustrated there is provision for eight circuit breaker units II5, four on each side of the cen ter line II6. A-solderless connector ill is provided for individual connection with one of the stationary contacts of each circuit breaker unit. The other stationary contacts of the several circuit breaker units on one side of the center line II6 are connected in common through the terminal screws II8 to a contact strip H9 extending transversely of the several breaker units. This contact extends beyond the last circuit breaker and on to an extension I28 of the .base. On the end of the strip, there is provided a solderless connector I2I.

The case of the circuit breaker units may be formed integral with a box cover. This arrangement is illustrated in Figs. 13 and 14 for a duplex circuit breaker. In this constructiomthe duplex case I22 is formed with an integral box cover I23. The cover is provided with a series of reenforcing ribs I24 on each side of the breaker case and a depending circumambient flange I25 that serves as a reenforcing rib and as a box engaging flange. In Fig. 14 the unit is illustrated as arranged on a box I26.

In each of the constructions illustrated in the drawings and described above, the parts in the assembled unit have a total width such as to provide only a working clearance, with the side walls of the case. When the assembled unit is slipped in place in the case and the entire 'cirreferred to that is readily and easily as embled bearings all of which are of noncorr rial. The working parts of the breaker may be cuit breaker assembled and secured together, the

bearing plate hold one side of the assembled unit in its correct position and in conjunction with the close fit of the moving parts with the sides of the case holds all the other parts in their correct position.

From the foregoing description of the embodiments of the circuit breaker illustrated in the drawings, it will be seen that by this invention there is provided a. circuit breaker of the kind assembled as a unit, tested and adjusted. The entire circuit breaker is held together by a minimum number of fastening devices, and the operating parts are held in an assembled unit through the interrelation and interengagement of the parts.

It will be also apparent that the circuit breakers illustrated in the drawings and described above are built up of a series or" unit parts, each unit part having its constituent elements assembled and secured to it, but the units as a Whole are assembled together in such a way that one unit may be replaced by another with a minimum of effort. In addition, certain units may be put together to form sub-assemblies and the design is such that one sub-assembly may be replaced by another with a minimum of effort. More specifically, there is provided (1) a rotating contact and bimetal element, (2) a handle and detent element, (3) a latch element and its supporting slide, (4) a spring element, (5) a case element, and (6) a base element carrying the stationary contacts and line connectors. Of these sub-assemblies or elements, (1), (2), (3), and (4) may be assembled as separate units and used with various combinations of elements (5) and (6).

The result is a system of assembly elements that may be made up into a great many combinations of ampere capacity and number of circuit breakers in a group with a minimum number of parts and with a minimum amount of effort required to make the changes. For example by'selection of only element (1), the breaker may be made to be either of fifteen to twenty or of twenty-five ampere capacity. By selection of elements (1) and (6), a breaker of lower ampere capacity may be changed to one of thirty-five or fifty ampere capacity. Changes in element (6) may be made to make units of two, four, six, eight or more circuit breakers.

It will be obvious that various changes may be made by those skilled in the art in the details of the several embodiments of the invention illustrated in the drawings and described in detail above within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A circuit breaker of the 'kind described comprising in combination a case open along one edge and having a groove along each side wall, an assembled unit of operating parts, the case providing only working clearance for the assembled unit at one side thereof, a side bearing plate on the assembled unit and a shaft extending from the other side of the assembled unit, the shaft and bearing plate being receivable in the grooves in the side walls of the case.

2. A circuit breaker of the kind described comprising in combination a case of electrical insulating material open along one edge, and having grooves in the side walls extending in from the open edge, a pair of resilient contact strips secured to the case and extending into the case, a terminal associated with each contact strip accessible on the outside of the case, an assembled unit of circuit breaker operating parts including a bearing plate at one side thereof and a shaft extending from the other side of the assembled unit, the shaft and bearing plate being receivable in said grooves in the side walls and the case providing only working clearance for the assembled unit, and a closure element for the open edge of the case.

3. A circuit breaker of the kind described comprising in combination a case open along one edge, a groove in each of two opposite walls extending inwardly from the open edge, an assembled circuit breaker unit proportioned to slip in the case with a close operating lit, a shaft end on said unit receivable in one of said grooves, and a bearing element carried by the unit and receivable in the other 01' said grooves, a closure element for the case arranged to secure the unit in :Jlace in the case and in operative relation there- ALBERT B. RYPINBKI.

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