US3145281A - Multipole circuit breaker with trip devices located in the housing of a single pole - Google Patents

Description

MULTIPOLE CIRCUIT BkEIAKER WITH TRIP DEVICES LOCATED IN 8, 19.64 R c. INGWERSEN 3,145,281

THE HOUSING OF A SINGLE POLE Filed Jan. 23, 1961 4 Sheets-Sheet 1 INVENTOR. Fzbiar/ 6? I71; averse g- 13, 1964 R. c. INGWERSEN 3,145,231

MULTIPOLE CIRCUIT BREAKER WITH TRIP DEVICES LOCATED IN THE HOUSING OF A SINGLE POLE Filed Jan. 23, 1961 4 Sheets-Sheet 2 Filed Jan. 23, 1961 Aug. 18, 1964 R C. INGWE RSEN 3,145,281

MULTIPOLE CIRCUIT BREAKER WITH TRIP DEVICES LOCATED IN THE HOUSING OF A SINGLE POLE 4 Sheets-Sheet 3 III 7 awn/5045f g- 13, 1954 R. c. INGWERSEN 3,145,231

MULTIPOLE CIRCUIT BREAKER WITH TRIP DEVICES LOCATED IN THE HOUSING OF A SINGLE POLE 4 Sheets-Sheet 4 Filed Jan. 23, 1961 4 M A w 1 n 1 w} w 4: H i a my I I //I I. w 4 1 a k j d 4/0 n 7 1 7 M J M FIX! 4 y W w M] L w M W 1 ITIVFM. .TTH HTIOHI IH; I" a HUN P"- U J M II. \lflfi JL q a 4 4 w M, 7 M 1 z, m 7

J 0 i a W I J M i M United States Patent Office 3,145,281 Patented Aug. 18, 1964 3,145,281 MULTIPOLE CIRCUH BREAKER WITH TRIP DE- VICES LOCATED IN THE HOUSMG GB A SIN- GLE POLE Richard C. Ingwersen, Jackson, Micln, assignor, by mesne assignments, to Mechanical Products, Inc., Jackson, Mich., a corporation of Delaware Filed Jan. 23, 1961, Ser. No. 84,244 1 Claim. (Cl. 200-116) This invention relates generally to electric circuit breakers and more particularly to an improved multipole, trip free common trip circuit breaker.

Multipole automatic electric circuit breakers are often used to protect branch electrical circuits having connected therein, for example, a multi-phase electric motor. Such circuit breakers generally comprise a plurality of electrically isolated pairs of separable contacts, a releasable operating mechanism for effecting simultaneous separation of the respective pairs of contacts, and a trip device responsive to predetermined conditions in any one phase of the electrical circuit to release the operating mechanism and open each phase of the electric circuit.

Generally, the trip device of such circuit breakers comprises a latch mechanism and a current responsive member operable to effect movement of the latch. The latch must be relatively strong mechanically in order to retain the operating mechanism in the closed condition with sufficient contact pressure to insure the electrical integrity of the circuit breaker, yet must be releasable upon relatively' slight movement of the current responsive member in any one phase. The current responsive member must be sensitive to a relatively small increment of current above a preselected maximum and have a physical response characteristic capable of releasing the latch. These requirements are aggravated in multipole circuit breakers wherein contact pressure is directly related to the number of poles of the breaker.

Multipole circuit breakers heretofore known and used are generally impracticable for use in low current applications where relatively rapid and sensitive overload response is required in that characteristically relatively large currents are required to effect response of the trip device. The thermal inertia of the relatively large bimetallic members usually employed as current responsive members limits the sensitivity thereof sufliciently to preclude their use for the protection of low current circuits. Conversely, bimetallic members having a sensitivity sufiiciently high enough to be usable in circuits normally rated at, for example, one ampere or less, generally do not have sufficient mechanical strength to eifect release of a latch.

Because many modern multi-phase electrical circuits are normally rated at one ampere or less, there is a present need for a multipole circuit breaker that will act quickly and positively in such low current circuits upon the occurrence of relatively small overloads. Such a multipole circuit breaker should be capable of easy calibration and should retain its initial calibration despite subjection to adverse operating conditions. These latter specifications are particularly important in, for example, aircraft applications wherein the circuit breakers are subjected to relatively wide ambient temperature variations and severe vibration.

Such a circuit breaker should also be capable of withstanding relatively high fault currents over and above normally encountered overload currents.

A multipole circuit breaker in accordance with the present invention insures positive overload protection for relatively low current three-phase circuits by utilizing a trip device for each pole comprising a pair of elongated, electrically conductive wires having a positive temperature co-efficient of expansion, the elongation thereof being additive so as to increase the sensitivity of the trip device to relatively small overload currents. The trip devices are located within the housing for a single pole of the circuit breaker to maximize the elliciency thereof in releasing the contact operating mechanism upon the occurrence of a predetermined overload condition.

It is therefore one object of this invention to provide an improved automatic multipole circuit breaker for the protection for relatively low current, multi-phase circuits.

Another object of this invention is to provide a multipole circuit breaker that operates substantially instantaneously upon occurrence of a relatively small current overload.

It is a further object of this invention to provide multipole circuit breakers having trip devices for each pole thereof including extensible current carrying wires which substantially instantaneously heat and elongate upon the occurrence of predetermined current conditions to elfect release of an actuating mechanism and disengagement of a plurality of movable contacts from their associated fixed contacts.

It is a still further object of this invention to provide an improved multipole circuit breaker that is relatively easily calibrated and such calibration is maintained despite adverse operating conditions.

These and other objects of the invention will be apparent in the following detailed description, claim and drawings wherein:

FIGURE 1 is a side elevational view of a multipole circuit breaker in accordance with the present invention;

FIG. 2 is a cross-sectional view taken substantially along the line 22 of FIGURE 1;

FIG. 3 is a cross-sectional view taken substantially along the line 33 of FIG. 2;

FIG. 4 is a cross-sectional view taken substantially along the line 4-4 of FIG. 3; and

FIG. 5 is a cross-sectional view along the line 5-5 of FIG. 3.

Referring now to the drawings, a multipole trip-free, common trip electric circuit breaker 10, in accordance with an examplary embodiment of the present invention comprises an insulating housing 12 made of, for example, Bakelite. The housing 12 comprises a plurality of complementary sections 1446, 18-20, and 22-24 that are retained together as by a plurality of machine screws 26 to form three poles, 28, 3t) and 32 of the circuit breaker 11), respectively. Three pairs of electrically isolated terminals 34-36, 38-40 and 42-44 project from the poles 23, 3t) and 32, respectively, for connection to opposite sides of an external three-phase electrical circuit so that current normally flows from one terminal through the circuit breaker to its associated terminal, movement of the separable contacts of any one pole to the tripped or open position due to current overload or manual actuation effecting interruption of the current flow through each pole of the circuit breaker 10, as will be described.

A plurality of fixed contacts Stl, 52 and 54 are supported internally of the poles 28, 3t? and 32 on inner end portions 56, 58 and 6th of the terminals 34, 38 and 42, respectively. The terminals 36, 4t) and 44 extend inwardly of the poles 28, 3t and 32 for electrical connection to complementary movable contacts through suitable pigtails and current responsive trip devices, as will be described.

As best seen in FIG. 3, a manual operator 76 extends externally of and is slidably supported by the housing 12 for in and out movement. The operator 70 comprises an inner plunger shaft 72 having an upper end portion 73 which extends into a guideway 74 formed in the upper end of the sections 18 and 20 of the housing 12.

taken substantially A transversely extending pin is fixedly supported by the sections 13 and 20 and extends through a slot 76 in the inner plunger portion 72 for guiding the travel thereof. A pin 73 is supported on a lower end portion 82 of the inner plunger shaft 72 and extends through a slot 32 in an outer plunger shaft 84 of the manual operator 711 so as to function as a lost motion connection between the shafts '72 and $4. The upper and lower end portions 73 and 8b of the inner plunger shaft 72 extend into a molded central hub portion 85' and are rigidly affixed thereto as by potting.

The outer plunger shaft 84* extends through a front wall 96 of the housing 12 and has a knob 92 secured thereto as by a pin 94. The knob 92 is preferably formed from an insulating material, for example, Bakelite, and is shaped to facilitate manual operation of the circuit breaker 1d. The outer plunger shaft 84 is normally urged outwardly of the housing 12 by a helical compression spring 1% that extends between a base in a suitable spring retainer recess 1112 in the knob 92 and a fixed abutment plate 1114 that is supported within a suitable recess in the sections 18 and 2d of the housing 12.

The inner plunger shaft 72 is normally resiliently urged outwardly of the housing 12 by a tensioned coil spring having one end portion 112 connected to a bracket 116 that is secured to a cross bar 118 as by rivets 1219. The other end 122 of the spring 110 is connected to a pin 123 on a toggle lever 124, which is pivoted. on a pin 125 journaled in an upstanding portion 126 of the abutment plate 104. A second coil spring 127 extends between a bracket 128, which is secured to the cross bar 118 as by riveting, and a pin 124 that is fixedly mounted in the housing 12. The spring 128 functions as an auxiliary to the spring 114), as will be described.

The toggle lever 124 carries a roller 1% that is normally biased by the spring 116 clockwise into engagement in complementary notches 130 and 132 in the inner and outer plunger shafts 72 and 34, respectively. The spring 110 is sufiiciently strong so that when it is tensioned to the position illustrated in FIG. 3, it holds the roller 126 in the notches 13d and 132 and thereby restrains the outer plunger shaft 84 of the manual operator '70 from movement outwardly of the housing 12 under the bias of the spring 100. However, the notch 132 in the outer plunger shaft 84 has an upper edge portion 134 so sloped that when tension in the spring 111) is relieved upon automatic opening of the circuit breaker 10, the roller 126 is cammed counterclockwise out of the notch 132 permitting movement of the outer plunger shaft 84 under the bias of its operating spring 1%.

Movement of the roller 126 outwardly of the notches 132 is also effected upon downward movement of this outer plunger shaft 34 upon manual operation of the circuit breaker 1t), downward movement of the inner plunger shaft 72 being effected due to engagement between the pin 7'8 on the inner shaft 72 and the upper end of the slot 82 in the outer plunger shaft 84. Thus, a lost motion connection between the two shafts 72 and 84 is provided which permits both manual and automatic operation of the circuit breaker.

The contact carrying cross bar 118 is connected to a generally U-shaped latch lever 15% as by a plurality of rivets 152, the lever being pivotally supported as by a pin 154 extending through the hub 85. The latch lever 150 has a transverse latching surface 158 thereon for engagement with the trip device, as will be described.

A plurality of movable contact carriers 1611, 162 and 164 are supported Within the poles 28, 3t and 32, respectively, by the cross bar 11%, being secured thereto by a plurality of rivets 166. The contact carriers 161 162 and 164 carry movable contacts 1711, 1'72 and 174 that are engageable with the fixed contacts 51 52 and 54 to complete a circuit through the poles 28, 3t) and 32, respectively.

The latch lever 15%) is normally restrained against rotation responsively to the urging of the springs 110 and 127 by a trip lever 175 having a latching surface 176. The trip lever 175 is supported for rotation with respect to the housing 12 as by pivots 177 on a common trip bar 189. The trip lever 17 5 is fixedly secured to the common trip bar 1811 as by screws 181. The pivots 177 are journaled in suitably aligned apertures 182 and 184 in the downwardly depending legs of a pair of trip device frames 186 and 187. The lever 175 and common trip bar form what essentially is a bellcrank. The arrangement is such, as will be described in greater detail, that when the current responsive member in any one phase of the circuit expands responsively to a current overload, the common trip bar 181) is rotated clockwise as viewed in the drawings, against the bias of a spring 1911, thus releasing the latch lever 150 and tripping the circuit breaker 10.

Trip devices 2%, 262 and 204 are provided for each of the poles 28, 3t) and 32, respectively, but are mounted as a subassembly within the center pole 30. The trip devices 2%, 262 and 204 comprise a pair of wires 210- 212, 214-216 and 2184320. However, because the trip devices are similar in construction, only the trip device 2112 seen in FIG. 3 will be described in detail.

The wires 214 and 216 are enclosed within separate glass tubes 221 and 222 supported adjacent to each other in a support block 224. The hot wire 216 is fixed at one end to a conductive end plate 226 which is fitted within and. rests against the lower end of the tube 222, and to which the pigtail 228 is attached to connect the trip device 202 to the terminal 41). At the upper end of the trip device 202, both of the wires 214 and 216 are fixed to a lever 23d which is pivoted on a fixed pivot 232.

The lower end of the hot wire 214 is fixed to a conductive member 240 which is slidably fitted within the lower end of the glass tube 221 and is normally urged downwardly by a spring 242 fitted around the tube 221 and seated between a radial shoulder on the member 240 and the lower face of the mounting block 224, through which the tubes 221 and 222 extend. The spring 242 is fitted around the outside of the tube 221 and is thereby protected to a large extent against the heat dissipated by the wire 214 within the tube 221, thus avoiding excessive heating of the spring 242, which might otherwise affect the temper thereof. The reliable service life of the circuit breaker 10 is thus improved since the spring 242 retains its initial resilience and operating force indefinitely. It should be noted that the wires 214 and 216 are normally heated to relatively high temperatures when they are subjected to circuit overloads, and in the absence of heat insulating means such as the glass tubes 221 and 222, the heat emitted by the wires may have a pronounced affect on the calibration of the trip device. The trip device frames 186 and 187, trip devices 200, 202 and 204, including a pair of insulating spacers 250 and 252 therebetween, common trip bar 180 and trip lever 175 constitute a separate sub-assembly, which may be separately adjusted and tested before it is fitted into the housing 12, thus materially reducing manufacturing costs. This construction also permits ready and simple replacement in the event it is desired to change the current rating of the circuit breaker 10. As best seen in FIG. 5, the sub-assembly is firmly fixed within the center pole 30 by means of suitable machine screws 254.

The common trip bar 180, which constitutes the short arm of the bellcrank, carries three calibration screws 260, 262, and 264 that are aligned with the Wires 210, 212 and 214, respectively. Suitable apertures 256, 268 and 270 are provided in the wall 90 of the housing 12 to permit manual adjustment of the screws 261), 262 and 264, respeetively, to adjust the response of the trip devices 200, 202 and 204 to a preselected current overload value.

The lower ends of the Wires 210, 214 and 218 are connected to the movable contacts 170, 172 and 174 by suitable pigtails 230, 282 and 284 thereby to complete a circuit through the respective poles 28, 3t and 32 of the circuit breaker when the contacts 170, 172 and 174 are in the closed condition with respect to their associated contacts 50, 52 and 54, respectively.

Operation of the circuit breaker 10 upon the occurrence of an overload or a short condition in any one of the phases of an electrical circuit contained in the circuit breaker is effected by elongation of the current carrying wires thereof. For the purpose of describing automatic operation of the circuit breaker 10, reference is made to the trip device illustrated in FIG. 3 for the pole 30 of the circuit breaker, it being understood that the trip device for the poles 28 and 32 function in a similar manner.

Upon the occurrence of a predetermined electrical condition, the Wire 2 16 elongates, allowing the yoke or lever 230 to pivot counterclockwise about its pivot 232. Similarly, the wire 214 elongates, thereby permitting the conductive member 240 to move downwardly with respect to the tube 221 under the bias of the spring 242. Downward movement of the member 240 is transmitted to the common trip cross bar 180 through the adjustment screw 262, clockwise rotation thereof being transmitted to the trip lever 175, retracting the latching surface 176 thereof from engagement with the complementary latching surface 158 on the latch lever 150. The latch lever 150 thereupon rotates counterclockwise under the bias of the springs 110 and 127, separating the movable contacts 52 and 172 and, obviously, concurrently separating the other pairs of separable contacts. Because the bias of the springs 110 and 127 is released upon rotation of the latch lever 150, the toggle lever 124 is moved outwardly of the recesses 130 and 132 in the inner and outer plug shafts 72 and 84, permitting the shafts 72 and 34 to move outwardly of the circuit breaker under the bias of the spring 100.

It is to be understood that the specific construction of the improved electrical circuit breaker herein disclosed and described is presented for the purpose of explanation 5 and illustration and is not intended to indicate limits of the invention, the scope of which is defined by the following claim.

What is claimed is:

A multipole electric circuit breaker comprising a plurality of discrete electrically isolated laterally aligned poles in separate housings, a plurality of stationary contacts within said poles, respectively, a plurality of movable contacts engageable with the stationary contacts, a single releasable operating mechanism for effecting movement of the movable contacts out of engagement with the stationary contacts, respectively, a single trip device including a plurality of current responsive elements housed in only one of said poles and electrically connected in series with the movable contacts, respectively, and a common trip bar disposed within and extending transversely of said one of the poles, said common trip bar being engaged so as to be actuatable by any one of said elements in response to a predetermined electrical condition to release the operating mechanism thereby to effect movement of the movable contacts out of engagement with the stationary contacts.

References Cited in the file of this patent UNITED STATES PATENTS 1,635,674 Hynes July 12, 1927 2,038,105 Hammerly Apr. 21, 1936 2,134,593 Wulsten Oct. 25, 1938 2,421,830 Cole et al. June 10, 1947 2,548,617 Purpura Apr. 10, 1951 2,797,277 Dorfman et al June 25, 1957 2,822,446 Stanback et al Feb. 4, 1958 2,824,191 Christensen et al Feb. 18, 1958 FOREIGN PATENTS 220,846 Australia Mar. 23, 1959

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