US3538475A - Circuit breaker with current limiting fuse means - Google Patents

Description

1970 A. R. CELLERINYIS CIRCUIT BREAKER WITH CURRENT LIMITING FUSE MEANS Filed-Dec. 20. 1966 I 4 Sheets-Sheet 1 INVENTOR Albert R. Cellerini WITNESSES f fw BY W WW4 W ATTORNEY Nov. 1970': I A. R. CELLIEVRINI I 3,538,475

CIRCUIT BREAKER WITH CURRENT LIMITING FUSE MEANS Filed Dec. 20. 1966 4 Sheets-Sheet 2 FIG.2.

3,538,475 CIRCUIT BREAKER WITH CURRENT LIMITING FUSE MEANS Albert R. Cellerini, Beaver, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 20, 1966, Ser. No. 603,251 Int. Cl. H01h 85/50 US. Cl. 337-7 Claims ABSTRACT OF THE DISCLOSURE An improved circuit breaker of the type comprising an enclosed trip device and a fuse unit supported on a pair of generally L-shaped conductors in proximity to the trip device. The fuse unit comprises fuse plunger means extending into the trip device enclosure to operate the trip bar of the trip device when the fuse blows.

In the patent application of Albert R. Cellerini et al., Ser. No. 305,792, filed Aug. 30, 1963, now. Pat. No. 3,287,534, there is disclosed a molded-case or insulatinghousing type circuit breaker having a removable trip device that operates automatically in response to. certain overload current conditions to trip the breaker. The insulating housing is provided with a back opening at one end thereof, and a main conductor that extends through the trip device is positioned over the back opening and connected to an external terminal connector at the back opening. The space above the main conductor at the end of the insulating housing is empty.

An object of this invention is to increase the interrupting capacity of the above-mentioned type of circuit breaker without enlarging the overall dimensions of the insulating housing by providing improved current-limiting fuse means in the end space adjacent the trip device.

Another object of this invention is to provide an improved compactly constructed molded-case type circuit breaker with trip means for automatically opening the circuit breaker contacts upon the occurrence of certain overload current conditions and with current-limiting fuse means that will interrupt severe fault currents and that will operate automatically to operate the trip device to open the circuit breaker contacts when the severe fault currents are interrupted.

Another object of this invention is to provide an improved current-limiting molded-case type circuit breaker that can eificiently carry current through the circuit breaker without undue heating.

A general object of this invention is to provide an improved relatively inexpensive current-limiting molded-case type circuit breaker.

The invention, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIG. 1 is a side sectional view illustrating the center compartment of a three-pole circuit breaker with part of the trip device being shown in broken lines for clarity, and with certain parts being broken away;

FIG. 2 is a side sectional view of part of the circuit breaker illustrated in FIG. 1;

FIG. 3 is view of the three-pole trip device seen in FIG. 2 with the cover of the insulating trip device enclosure removed and with three main conductors of the three-pole units being shown in section;

United States Patent 0 3,538,475 Patented Nov. 3, 1970 FIGS. 4, 5 and 6 are side, front and top views respectively of one of the main conductors seen in FIG. 2;

FIGS. 7, 8 and 9 are side, front and top views respectively of another of the main conductors seen in FIG. 2;

FIG. 10 is a top view of the fuse seen in FIG. 2;

FIG. 11 is an end view of the fuse seen in FIG. 10;

FIG. 12 is an end view of one of the external terminal connectors seen in FIG. 1;

FIG. 13 is a bottom view of the external terminal connector seen in FIG. 12; and

FIG. 14 is a top view, on a reduced scale relative to FIG. 1, of the circuit breaker seen in FIG. 1.

Referring to the drawings, there is shown in FIG. 1 a circuit breaker 3 comprising an insulating housing 5. The insulating housing 5 comprises a molded insulating base 7, that is molded as an integral unit, and a molded insulating cover 9, that is molded as an integral unit, secured to the base 7. An operating mechanism 11, a trip device 13, fuse means 15 and an arc-extinguishing unit 17 are all supported in the housing 5 on the base 7. The circuit breaker 3 is a three-pole circuit breaker comprising three compartments disposed in a side-by-side relationship. The center compartment or pole unit (shown in FIG. 1) is separated from the two outer pole units by cooperating insulating barriers 18 and 19 that are molded integrally with the housing cover 9 and base 7 respectively. The operating mechanism 11 is disposed in the center pole unit.

Each pole unit comprises a stationary contact 21 that is fixedly secured to a rigid conductor 23 that is secured to the base 7 by means of bolts 25. In each pole unit, a movable contact 27 is secured to a contact arm 29 that is pivotally mounted on a switch arm 31 by means of a pivot pin 33. Each of the switch arms 31 is pivotally supported at one end thereof on a support bracket 34 by means of a separate pivot pin 35. The switch arms 31 for all three of the pole units are connected to move in unison by means of an insulating common tie bar 37 that is fixedly connected to all three of the switch arms. Each of the contact arms 29' is biased about the associated pivot 33 by means of a spring 39 to provide contact pressure in the closed position.

The switch arms 31 are operated to the opened and closed positions by means of the operating mechanism 11. The operating mechanism 11 comprises a toggle link 41 that is pivotally connected to an extension 43 of the center-pole switch arm 31 by means ofa pivot pin 45. The toggle link 41 is pivotally connected to another toggle link 47 by means of a pivot pin 53. The upper end of the toggle link 47 is pivotally connected to a trip member or releasable member 51 bymeans of a pivot pin 53. The trip member 51 is pivotally supported at one end thereof on the supporting bracket 34 by means of a pivot pin 57. The other end 59 of the trip member 51 is held in a latched position by means of a latch structure 61. The latch structure 61 is of the type more specifically described in the patent to G. G. Grissingeret al., Pat. No. 2,586,- 326, issued Feb. 19, 1952 and assigned to the assignee of the instant case. The operating mechanism 11 also comprises an inverted U-shaped operating lever 63 that is pivotally supported on the bracket 34 by means of pins 65 that engage the inner ends of the legs of the U-shaped operating lever 63. An insulating shield 67, for substantially closing an opening 69 in the front of the cover 9, is secured to the upper end of the operating lever 63. An insulating handle portion 71, formed integral with the insulating shield 67, extends out through the opening 69 in the front of the cover 9 to permit manual operation of the breaker. Two overcenter springs (only one being shown in FIG. 1) are connected under tension between the knee pivot pin 53 of the toggle 41, 47 and the upper end of the operating lever 63. A pin 77 is secured to the upper end of the lever 63 in order to suport the upper ends of the springs 75.

In each pole unit, an arc-extinguishing unit 81 is provided to extinguish the arc drawn between the associated contacts 21, 27. Each arc-extinguishing unit 81 comprises an insulating housing 83 and a plurality of stacked magnetic steel plates 85 supported within the housing 83. The moving contact 27 moves within a generally V-shaped opening in the stacked plates 85, and the are drawn between the contacts is magnetically moved to the right (FIG. 1) into the plates 85 to be extinguished during circuit interruption. Each of the arc-extinguishing units 81 is secured to the associated rigid conductor 23 by means of four bolts 89 (only two of which are seen in FIG. 1) that are threaded into tapped openings in the associated conductor 23.

For each pole unit, the circuit breaker 3 is provided with two external rear-type terminal connectors 231 that are positioned at opposite ends of the circuit breaker. The terminal connectors 231 will be hereinafter more specifically described.

The circuit breaker contacts are manually operated between the closed and opened positions by movement of the handle 71. Movement of the handle 71 in a counterclockwise direction from the on to the oif position moves the line of action of the spring means 75 to the left to an overcenter position to effect a collapse of the toggle 41, 47 to pivot the switch arm 31 for the center-pole unit in a counterclockwise direction about the associated pivot 35 to an open position in a Well known manner. This movement, because of the connection of all of the switch arms 31 by means of the common tie bar 37, simultaneously moves all of the three switch arms 31 to the open position.

The contacts are manually closed by reverse movement of the handle 71 to the on position. This movement moves the operating lever 63 to move the line of action of the overcenter spring means 75 to the right to thereby reset the toggle 41, -47 to move all three of the switch arms 31 simultaneously to the closed position in a wellknown manner.

Referring to FIGS. 2 and 3, the trip device 15 comprises a trip-device insulating enclosure comprising a molded insulating base 113 and a molded insulating cover 115 that is secured to the base 113 by suitable securing means. The three thermal-and-rnagnetic tripping means 116 are supported in three compartments in the trip device enclosure 113, 115, which compartments are separated by means of insulating barriers 117. The trip device 15 comprises a molded insulating trip bar 119 that passes through suitable openings in the barriers 117 and is common to all three of the pole units. The trip bar 119 is pivotally supported on a bracket 121 that extends out of the base 113 and that is supported on a suitable supporting bracket 123 that is secured to a rigid main conductor 125. A separate laminated U-shaped magnetic member 126, for each pole unit, is suitably mounted in the associated compartment of the trip device by means of bolts 127 that secure the magnetic member to the trip-unit base 113. Each of the main conductors 125 passes through the opening in the associated U-shaped magnetic member 126 and is held in place by means of a bolt 129 that extends into a suitable opening in the conductor 125. A separate movable armature 131 is pivotally supported on one leg of each of the magnetic members 126 and is biased to an open position by means of a spring 133. A separate rod 135 is pivotally connected to each armature 131, and each of the rods 135 has a head portion 137 for engaging and operating the trip bar 119 upon sufficient energization of the electromagnet 126, 131. The tripping electromagnet is energized by current flowing through the associated main conductor 125.

The circuit breaker contacts are tripped open upon the occurrence of an overload current above a first predetermined value and below a second predetermined value by operation of any one of the tripping electromagnets. When one of the tripping electromagnets is energized sufiiciently by an overload current through the associated main conductor 125, the magnetic armature 131 is attracted toward the magnetic yoke 126, and the armature pivots on the one leg of the yoke 126 and moves into engagement with the other leg of the yoke 126. During this movement, the associated rod is pulled down, whereupon the head 137 thereof engages the trip bar 119 causing the trip bar 119 to rotate in a counterclockwise (FIG. 2) direction. This movement elfects a releasing movement of the latch structure 61 to disengage the latch structure 61 from the trip member 51 (FIG. 1) in a well known) manner. Upon release of the trip member 51,. the springs 75 act to rotate the trip member 51 in a clockwise (FIG. 1) direction about the pivot 57 and to collapse the toggle 41, 47 to thereby pivotally move the three switch arms 31 in a counterclockwise direction to the open position. During the automatic tripping operation the line of force of the spring means 75 operates to move the operating lever 63 and handle 71 to an intermediate position between the on and off positions in a well known manner to provide a visual indication that the circuit breaker has been automatically tripped.

Following an automatic tripping operation, it is necessary to reset and relatch the circuit-breaker mechanism before the contacts can be closed. This is effected by moving the handle 71 to the full off position. During this movement, a pin 138, that is supported on the operating lever 63, engages a shoulder 139 on the trip member 51 to move the trip member 51 in a counterclockwise direction about the pivot 57. Near the end of this movement, the free or latching end 59 of the trip member 51 cams the latch structure 61 to the left against the bias of spring means (not shown) and moves below the latching end of the latch structure 61 whereupon the latch structure 61 is biased back to the latching position seen in FIG. 1 to relatch the trip member 51 in a well known manner. The breaker contacts can then be operated in the previously described manner by movement of the handle 71.

An adjusting mechanism is provided for adjusting the position of each armature 31 to thereby permit selection of the overload current that will be required to magnetically trip the circuit breaker. The adjusting mechanism is specifically described in the patent to G. F. Thomas et al., Pat. No. 3,073,925, issued Jan. 15, 1963. Thus, only a brief description of the adjusting mechanism is given herein. The adjusting mechanism comprises a cam member 141 (FIG. 3) having an upper cam surface that is engaged by one end of a lever 143 that is pivotally supported intermediate its ends on a supporting bracket 145 that is attached to the yoke 126. A rod 147 extends upward from the cam 141 to an adjusting knob 149 that protrudes through a suitable opening in the trip device enclosure and through a suitable opening in the front of the circuit breaker housing. Rotation of the adjusting knob 149 rotates the cam 141 to pivot the lever 143 whereupon an adjusting screw 151 on one end of the lever 143 moves against the upper side of the associated armature 131 to pivot the armature 131 to thereby vary the magnetic air gap and therefore the minimum overload current which is required to magnetically trip the circuit breaker.

Thermal tripping means is provided to effect automatic tripping of the circuit breaker with a time delay upon the occurrence of certain overload currents below said first predetermined value. The thermal tripping means in each pole unit comprises another U-shaped laminated magnetic yoke 155 (FIG. 2) through which the main conductor 125 passes. A separate unlaminated magnetic bar 157 connects the upper legs of each of the magnetic yokes 155. A separate bimetal 159 is supported on a separate short circuit conducting coil 161 that is disposed over each of the bars 157. Upon the occurrence of certain overload currents below said predetermined value the hysteresis losses in the bar 157 in the form of heat will be conducted to the bimetal 159, and heat generated by eddy currents in the coil 161 will be conducted to the bimetal 159 to heat the bimetal whereupon the bimetal will bend to the left (FIG. 2) to engage an adjusting screw 165 that is supported on the trip bar 119 to thereby rotate the trip bar 119 counterclockwise after a time delay to effect a tripping operation of the circuit breaker in the same manner as was hereinbefore described with regard to the electromagnetic tripping operation.

The main conductor 125 (FIGS. .2 and 7-9) is a rigid generally L-shaped (FIG. 7) conducting member that is cast as an integral unit. The main conductor 125 comprises a horizontal leg 171 and a vertical leg 173 that extends generally normal to the direction of extension of the horizontal leg 171. An opening 175 is provided at the back of the horizontal leg 171 for receiving the bolt 129 (FIG. 3). The horizontal leg 171 is provided with two openings 177 therein for receiving mounting bolts that will be hereinafter described. The vertical leg 173 is provided with three tapped openings 179 at the front thereof. As can be seen in FIGS. 1 and 2, the horizontal leg 171 of the main conductor 125 rests at one end thereof on a ledge 181 of the circuit breaker base 7 and at the other end thereof on a conducting member 183. A bolt member 1785 connects the conducting member 183 to the base 7. Two bolts 187 pass through suitable openings in part of the support 123, through the openings 177 (FIGS. 79) in the horizontal leg 171 of the conductor 125, through suitable openings in the conductor 183 (FIG. 1), and they are threaded into two tapped inserts 189 (only one of which is seen in FIG. 1) in the base 7 to secure the bracket 123, conductor 125 and conductor 183 in position on the base 7. As can be seen in FIG. 1, a laminated flexible conductor 193 is connected at one end thereof to the conductor 183 and at the other end thereof to the associated contact arm 29.

Referring to FIGS. 1, .2, 10 and 11, a separate fuse 195 is mounted in each compartment or pole unit of the circuit breaker. Each fuse 195 comprises a fuse body 197 and two fuse terminals 199, 201 at the opposite ends of the fuse body 197. Each of the fuse terminals is a flat rigid conductor. Two openings 203 (FIG. 10) are provided in the terminal 199, and two openings 205 are provided in the terminal 201. A plunger support 207 extends from one end of the terminal 199, and a plunger 209 protrudes from the support 207. The fuse 195 is constructed such that upon the occurrence of severe fault currents over the second predetermined value, the fuse will blow instantaneously to interrupt the fault circuit in the associated pole unit, and the plunger 209, which is spring biased toward the outer position and maintained in the position seen in FIG. 10 under normal current conditions, Will be released whereupon the plunger 209 will be forced outward to engage the trip bar 119 (FIG. 2) to rotate the trip bar 119 in a counterclockwise direction to whereby trip the circuit breaker opening the circuit breaker contacts in the manner that was hereinbefore described. The plunger, and the spring means for operating the plunger, may be of the type illustrated in the Rawlins et al., Pat. No. 2,435,844, issued Feb. 10, 1948, or other means may be used. As can be seen in FIG. 2, the fuse 195 is mounted at one end thereof on the main conductor 125 and at the other end thereof on a main conductor 211.

The main conductor 211 (FIGS. 1, 2 and 4-6) is a generally L-shaped (FIG. 4) rigid conducting member that is cast as an integral unit. The main conductor 211 comprises a horizontal leg 213 and a vertical leg 215 that extends upward normal to the direction of extension of the horizontal leg 213. The main conductor 211 is provided with two openings 217 therein that receive two bolts 219 (FIG. 2). The bolts 219 are threaded into tapped inserts 221 in the base 7 to fixedly secure the main conductor 211 on the base 7. Two tapped openings 223 are provided in the front of the vertical leg 215 for receiving mounting bolts. As can be understood with reference to FIG. 2, two mounting bolts 225 pass through the two openings 203 (FIG. 10) and they are threaded into two of the tapped openings 179 (FIG. 9) to secure the fuse terminal 199 to the front face of the vertical leg of the main conductor 125. Two bolts 227 pass through the two openings 205 in the fuse terminal 201, and they are threaded into the .two openings 223 (FIG. 5) in the vertical leg of the main conductor 211 to fixedly secure the fuse terminal 201 to the main conductor 211. The main conductors and 211 are rigid members to provide supporting strength for supporting the fuse 195. It can be understood that there is another pair of main conductors 125, 211 and another fuse in each of the other two pole units of the three pole circuit breaker. In each pole unit, the insulating cover 115 of the trip device 15 is provided with an opening 228 (FIG. 2) therein for receiving the fuse plunger support 207 and the fuse plunger 209 that extend into the opening adjacent the trip bar 119 so that the plunger 209 is positioned to actuate the trip bar 119 when the fuse blows.

As can be seen in FIG. 9, there are three tapped openings 179 in the conductor 125. The two fuses 195 that are mounted in the center pole and in the pole on the right (FIG. 3) will be mounted by means of two bolts that extend through the two upper (FIG. 9) openings and the plungers 209 of these two fuses will engage the trip bar 119 at 229 and 230. The fuse 195 that is mounted in the pole on the left (FIG. 3) will be turned over from the position seen in FIG. 10 and mounted by means of two bolts that extend through the two lower (FIG. 9) Openings. The plunger 209 of this fuse will engage the trip bar 119 at 234 (FIG. 3).

Referring to FIGS. 12 and 13, there is shown therein a conducting T-shaped external terminal connecting member 231 comprising a top part 233 having four openings 235 therein and a bottom part 237 having a plurality of openings 239 therein. The top surface 241 of the terminal connector 231 is a generally fiat surface. The bottom surface 243 of the internal main conductor 211 (FIG. 4) is a fiat bottom surface, and there are four tapped openings 245 therein disposed at the four corners of an imaginary square. The openings 235 (FIG. 13) of the terminal 231 are also disposed at the four corners of an imaginary square to align with the openings 245 of the internal main conductor 211 (FIGS. 4 and 6). In each pole unit, the base 7 of the circuit breaker 3 is provided with an opening 249 (FIG. 1) in proximity to one back end thereof and an opening 251 in proximity to the other back end thereof. In each pole unit, an external terminal connector 231 is connected to the associated internal main conductor 211 by means of four bolts 253 that pass through the openings 235 (FIG. 13) in the terminal connector 231 and that are threaded into the tapped openings 245 (FIG. 6) in the main conductor 211. The upper front fiat face 241 (FIG. 12) of the external terminal connector 231 engages the back flat face 243 (FIG. 4) of the internal main conductor 211. The other external terminal connector 231 in each pole unit is connected'to the associated internal conductor 23 by means of four bolts 257 that pass through the four openings 235 (FIG. 13) in the terminal connector 231 and that are threaded into four suitable tapped openings in the back of the internal conductor 23. The terminal connectors 231 are accessible for connection to bus bars at a circuit breaker installation. As is more specifically set forth in the above-mentioned patent application of Albert R. Cellerini et al., Ser. No. 305,792, now Pat. No. 3,287,534, the external terminal connectors 231 can be rotated 90 and connected by means of the same bolts extending through the openings in the terminal connectors and being threaded into the associated tapped openings of the internal conductors.

The circuit through the center pole unit of the circuit breaker 3 (FIG. 1) extends from the external terminal connector 231 (on the left) through the main conductor 211, the fuse terminal 201, the fuse body 197, the fuse terminal 199, the main conductor 125, the conductor 183, the flexible conductor 193, the contact arm 29, the contacts 27, 21, the conductor 23 to the other external terminal connector 231. Upon the occurrence of certain overload current conditions below a first predetermined value in any of the three pole units of the circuit breaker the previously described thermal tripping operation will occur releasing the trip member 51 to simultaneously open the contacts of all three pole units. Upon the occurrence of overload current conditions above the first predetermined value and below a second predetermined value in any of the pole units of the circuit breaker the previously described electromagnetic tripping operation will occur to release the trip member 51 and open the contacts of all three pole units. Upon the occurrence of a severe overload above the second predetermined value in any of the pole units, the fuse 195 in that pole unit will blow instantaneously to limit the amount of current that will pass through the circuit breaker and to interrupt the circuit, and when the fuse blows the plunger 209 of the blown fuse will be released to extend outward and rotate the trip bar 119 to thereby effect release of the trip member 51 and simultaneous opening of the contacts of all three of the pole units. The plunger 209 will remain extended to hold the trip bar in a tripped position to thereby prevent a resetting operation on the circuit breaker mechanism so that until the blown fuse is replaced the circuit breaker contacts will remain in the open position. As can be understood with reference to FIG. 14, the cover 9 of the circuit breaker 5 is secured to the base 7 by four bolts 255 that are positioned in openings in the barriers of the cover 9 and base 7, which barriers separate the adjacent pole units, and that are threaded into suitable tapped openings in the base 7 to secure the cover 9 in position. In order to remove the cover 9, the bolts 55 are removed and the cover is lifted off of the base. All of the working and movable parts of the circuit breaker are mounted on the base 7 so that the cover 9 is easily lifted off while the internal parts of the circuit breaker remain in position on the base 7. With the cover removed, the bolts 225, 227 (FIG. 1) of the blown fuse are removed and the blown fuse 195 is replaced by a good fuse. When the blown fuse is removed, the trip bar 119 returns back v to the operating position so that after a good fuse is placed in position and after the cover is again mounted on the base with the four bolts 255 (FIG. 14) the circuit breaker mechanism 11 can be reset in the manner previously described and the circuit breaker can then be operated in the previously described manner.

As can be understood with reference to FIGS. 1 and 14, the circuit breaker housing 5 comprises a front having an opening 69 therein for the operating handle 71 and a back having the openings 249, 251 (FIG. 1) therein for permitting connection of the terminal connectors 231 to the conductors 211, 23. The circuit breaker housing 5 comprises side wall means 257 (FIG. 14) between the front and back which side wall means 257 comprises two side walls 259 and two end walls 261. Each fuse 195 (FIG. 1) is positioned lengthwise in the circuit breaker in the space at one end of the circuit breaker adjacent the trip device 15. Each fuse 195 is supported at one end terminal thereof on the front of a vertical leg of a generally L-shaped rigid conductor 125 that comprises a horizontal leg that extends through the trip device to energize the thermal and electromagnetic trip of the associated pole unit. The other end terminal of each fuse 195 is supported on the front of a vertical leg of another generally L-shaped main conductor 21.1 that comprises a generally horizontal leg 213 that extends under the main body portion of the fuse. A generally fiat back face of each leg 213 is positioned over an opening in the back of the insulating housing to receive connection with a generally fiat face of an external terminal connector 231.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential features of the invention. It is desired, therefore, that the language of the appended claims be given as reasonably broad an interpretation as is permitted by the prior art.

I claim as my invention:

1. A circuit breaker comprising an insulating housing, said insulating housing comprising a front, a back and side wall means, said insulating housing having a length and width determined by said side wall means and a height determined by said front and back, said insulating housing having a first opening therein in the front thereof, an operating mechanism in said insulating housing and comprising an operating handle extending from said first opening, said operating mechanism comprising a pair of contacts and a latched trip member releasable to effect automatic opening of said contacts, a trip device in said insulating housing positioned between said latched trip member and a first end of said insulating housing in the lengthwise direction of said insulating housing, said trip device comprising a trip bar operatively movable to effect release of said trip member, a first unitary main conductor comprising a first generally horizontal leg and a first generally vertical leg, said first unitary main conductor being supported in said insulating housing with said first generally horizontal leg extending lengthwise through said trip device toward the second end of said insulating housing opposite said first end and with said first generally vertical leg extending toward said front of said insulating housing, said insulating housing having a second opening therein in the back thereof in proximity to said first end of said insulating housing, a second unitary main conductor comprising a second generally horizontal leg-and a second generally vertical leg, said sec- 0nd unitary main conductor being supported in said insulatin g housing with said second generally horizontal leg extending lengthwise in said insulating housing toward said second end of said insulating housing and with said second generally horizontal leg being positioned over said second opening and with said second generally vertical leg extending toward said front of said insulating housing, a fuse unit comprising a fuse body and a pair of fuse terminals at opposite ends of said fuse body, means mounting said fuse unit on said first and second main conductors with one of said fuse terminals being mounted directly on said first generally vertical leg and the other of said fuse terminals being mounted directly on said second generally vertical leg and with said fuse body being positioned over said second generally horizontal leg, said fuse unit being constructed to blow upon the occurrence of overload current conditions over a predetermined value to interrupt the overload, said fuse unit comprising fuse plunger means operating automatically when said fuse blows to operatively move said trip bar to effect release of said trip member to thereby effect opening of said contacts, an insulating trip-device enclosure supported in said insulating housing and enclosing said trip device, said trip bar being supported in said insulating trip-device enclosure, said insulating trip-device enclosure having opening means therein, and said fuseplunger means extending through said opening means in said trip-device enclosure and being positioned opposite said trip bar in said trip-device enclosure.

2. A circuit breaker according to claim 1, and removable bolt means mounting said fuse terminals on said first and second generally vertical legs.

3. A circuit breaker according to claim 1, said second generally horizontal leg of said second main conductor having a fiat-face connecting surface at the back thereof over said second opening, an external terminal conductor having a flat-face connecting surface at the front thereof, and means connecting said flat-face connecting surface of said external terminal conductor to said flat-face connecting surface of said second generally horizontal leg at said second opening.

4. A circuit breaker according to claim 1, said insulating housing comprising a two-part housing comprising a base molded as an integral unit and a cover molded as an integral unit, and removable securing means removably securing said cover to said base and removable to permit removal of said cover from said base to thereby permit removal of said fuse unit.

5. A circuit breaker according to claim 4, said operating mechanism, said trip device and said first and second unitary main conductors with said fuse unit mounted thereon all being mounted on said base.

References Cited UNITED STATES PATENTS BERNARD A. GILHEANY, Prmary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R.

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