|Publication number||US3497838 A|
|Publication date||Feb 24, 1970|
|Filing date||Apr 22, 1968|
|Priority date||Apr 22, 1968|
|Also published as||DE1920175A1|
|Publication number||US 3497838 A, US 3497838A, US-A-3497838, US3497838 A, US3497838A|
|Inventors||Harper George S, Merriken Lyal N|
|Original Assignee||Airpax Electronics|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (11), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Feb. 24, 1970 L. N. MERRIKEN ET AL 3,497,838
CIRCUIT BREAKER HAVING INER'IIAL DELAY Filed April 22, 1968 5 Sheets-Sheet 1 FIG. 5.
INVENTORS Lya/ N. Merr/ken George S. Harper ATTORNEYS Feb. 24, 1970 MERR|KEN ETAL 3,497,838
CIRCUIT BREAKER HAVING INERTIAL DELAY Filed April 22, 1968 5 Sheets-Sheet a FIG. 2.
INVEN'ZORS Lya/ /V. Men/ken George 8. Harper ATTORNEYS Feb. 24, 1970 MERR|KEN ET AL 3,497,838
CIRCUIT BREAKER HAVING INERTIAL DELAY 5 Sheets-Sheet 3 Filed April 22. 1968 FIG. 3.
INVENTORS Lya/ /V. Merrl'ken George 8 Harper ATTORNEYS FebQ24, 1970 MERRlKEN ET AL 3,497,838
CIRCUIT BREAKER HAVING INERTIAL DELAY 5 Sheets-Sheet 4 Filed April 22, 1968 FIG. 4.
A r V ($1 um mllllllll llllllmmn Lya/ N. Merri/ren George .5. Harper ATTORNEYS Feb. 24, 1970 1.. N. MERRIKEN ET AL 3,497,838
CIRCUIT BREAKER HAVING INERTIAL DELAY 5 Sheets-Sheet 5 Filed April 22. 1968 INVENTORS y Mo, r a 8H 3 N6 mm Nb ATTORNEYS United States Patent 3,497,838 CIRCUIT BREAKER HAVING INERTIAL DELAY Lyal N. Merriken and George S. Harper, Cambridge, Md.,
assignors to Airpax Electronics Incorporated, Cambridge, Md., a corporation of Maryland Continuation-impart of application Ser. No. 545,434, Apr. 26, 1966. This application Apr. 22, 1968, Ser. No. 729,486
Int. Cl. Htilh 7/08, 43/02 US. Cl. 335-64 10 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of copending application Ser. No. 545,434, filed Apr. 26, 1966 which is in turn a continuation-in-part of the then copending application Ser. No. 377,993, filed June 25, 1964, now US. Patent 3,251,232.
The present invention is directed to an improved electromagnetic circuit breaker which will not trip out when subjected to high amplitude current for a short time. The circuit breaker incorporates a balanced inertia wheel for effectively increasing the inertia of the circuit breaker armature to introduce a time delay before the breaker trips out when subjected to very high overload currents.
As is well known, circuit breakers are used in numerous devices where it is desired to protect electrical equipment against overload. Important advantages include the fact that the conventional electromagnetic circuit breaker is resettable and may be tripped repeatedly without any necessity for replacement or repair. However, one of the disadvantages of the electromagnetic circuit breakers is that they have a tendency to trip out when subjected to high amplitude current for a short time. This is often referred to as nuisance tripping and occurs in some cases in conjunction with the starting of certain types of electrical motors and inductive and capacitive loads.
The present invention provides a device for overcoming this nuisance tripping so that the circuit breaker is substantially insensitive to very high amplitude currents which last for only a short time. At the same time, the device of the present invention preserves the other advantageous features of the more conventional circuit breaker including its response to small overloads and to large overloads of long duration. This is accomplished by introducing into the circuit breaker in a simple and inexpensive manner, an increased mechanical delay which only has a significant effect for overloads in excess of about 400% of rated current for the breaker. As the result, the breaker has the capacity to take electrical pulses of higher amplitude and/or longer electrical pulse duration before tripping.
The increase in capacity is achieved through the provision of an inertial wheel in the breaker to introduce an additional time delay. That is, a certain predetermined amount of force is required to move the armature, operate the mechanism, and open the contacts in a conventional circuit breaker. The provision of a balanced inertia wheel in the circuit breaker increases the dynamic mass of the breaker mechanism but does not change the amount 3,497,838 Patented Feb. 24, 1970 ice of force required to operate the breaker. Thus, since the force required to operate the mechanism is essentially the same with or without the inertia wheel, but the dynamic mass of the mechanism is increased by the mass of the inertia wheel, the acceleration is decreased. The result is that a mechanical time delay is introduced into the circuit breaker which, in many cases of high amplitude current, is sufficiently long to prevent the breaker from tripping and allow the short duration high surge of current to pass. If, however, the surge of current continues for some reason, the circuit breaker of the present invention will trip.
When subjected to overload currents at or below about 400% of the rated current, the circuit breaker of the present invention maintains the specified calibration of a circuit breaker not having an inertia wheel. This is because the inertia wheel is balanced and does not exert any appreciable force on the armature. It is only at currents above 400% of rated current that the inertia wheel begins to have a significant affect on the trip time of the breaker.
It is therefore one object of the present invention to provide a circuit breaker having improved operating characteristics.
Another object of the present invention is to provide a circuit breaker having increased capacity to take electrical pulses of higher amplitude and/or longer electrical duration, as compared with similar conventional circuit breakers.
Another object of the present invention is to provide a circuit breaker having an increased time delay for overload currents in excess of about 400% of rated current.
Another object of the present invention is to provide a simplified and inexpensive arrangement for incorporating, in a circuit breaker, an additional mechanical time delay without at the same time significantly modifying the amount of force required to trip the breaker.
Another object of the present invention is to provide a circuit breaker with a balanced inertia wheel coupled to the breaker armature, thereby effectively increasing the dynamic mass of the armature.
These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims and appended drawings wherein:
FIGURE 1 is a perspective view of a circuit breaker in its housing constructed in accordance with the present invention;
FIGURE 2 is a side view of the breaker of FIGURE 1 with the housing removed, showing the breaker mechanism in relatched open position with the contacts open;
FIGURE 3 is a partial sectional view similar to that of FIGURE 2, showing the mechanism in a position where the contacts are closed;
FIGURE 4 is a partial sectional view similar to FIG- URES 2 and 3, showing the mechanism in an intermediate or tripped open position;
FIGURE 5 is a vertical cross section taken along line 55 of FIGURE 2;
FIGURE 6 is an enlarged section taken along lines 6-6 of FIGURE 2, but showing the threaded ferrule in place;
FIGURE 7 is an enlarged perspective view showing the detail of the sear pin and striker bar assembly;
FIGURE 8 is a detailed view showing engagement of the sear pin and striker bar assembly with the forked lever of the breaker of FIGURE 1;
FIGURE 9 is an enlarged perspective view of the electro magnet armature bell crank assembly;
FIGURE 10 is an enlarged view of the inertia wheel mounted on its support; and
FIGURE 11 is an exploded view showing the details of the inertia wheel and axle rivet on which it rotates.
Referring to the drawings, the novel circuit breaker of the present invention, illustrated in FIGURE 1, comprises a housing 10, which is formed of a molded plastic having good electrical insulating properties. Supported in the housing is a frame 11 upon which is mounted the operating elements of the circuit breaker to move a movable contact 12 into and out of engagement with a fired contact 13.
Movable contact 12 is secured to a lever 14 pivotally and slidably mounted on the frame by a pin 15 passing through an elongated opening 16 in the lever. Pin 15 is mounted on the frame 11, intermediate its ends while the ends extend beyond the frame and fit snugly into cooperating recesses 17, molded in the housing halves 10 and 10 as seen in FIGURE 5. A spring 18 is wound around pin 15 and is provided with a biasing arm 19 hearing against the lever 14 and with a reaction arm 20 bearing against the frame 11. Portions of the frame 11 are omitted in FIGURES 3 and 4 for the sake of clarity. The entire frame 11 is illustrated in FIGURE 2.
An actuating lever 21 is pivotally mounted on the frame 11 by a pin 22. The pin 22 is mounted in the frame intermediate its ends while the ends extend beyond the frame and fit snugly into cooperating recesses 22' molded in the housing 10 as best seen in FIGURE 5. A spring 23 is wound around the pin 22 and has a biasing arm 24 bearing against a pin 25 and also a reaction arm 26 bearing against the frame 11. Pivotally mounted on pin 25 is an L-shaped link 27 and this link is pivotally connected to a spaced pair of links 28 by pin 29. The links 28 are pivotally connected by a pin 30 to straddle the lever 14.
Rotatably supported in link 27 at the bend of the L is the shaft of a sear pin 31 which sear pin is provided with a reduced section 32 between the links which is provided by grinding a fiat sufrace 32 on the shaft 31 (FIGURE 7) which acts as a sear for edge 42 of a forked cam lever 40. An arm or striker bar 33 is mounted rigidly and non-rotatably on shaft 31 and carries a tab 34 bent up from the end of the arm. One end of shaft 31 is square to accommodate the square hole in arm 33. After assembly, the end of shaft 31 is peened tight against arm 33, permanently keying the shaft and arm together. A spring 35 is wound around shaft 31 and is provided with arms 36 and 37 bearing respectively against a stop 38 integral with one arm of link 27 and against an extension 39 of arm 33. The spring is wound to urge extension 39 against the stop.
Forked lever 40 is pivotally mounted on pin 25 between the parallel arms of link 27. One leg 41 of the fork is provided with an edge portion 42 for engagement with the sear portion 32 of shaft 31, and the other leg 43 of the fork is provided with a curved cam section 44 for engagement with a pin 45 carried by links 28. Between the legs at the end of cam section 44 is a locking recess 46.
Frame 11 is provided with a shelf 47 on which is mounted an electromagnet 48 having a winding, one end of which is connected in series with a terminal 49 and the other end in series with a braided flexible copper wire 50 secured to lever 14, for completing a circuit through movable contact 12, fixed contact 13, and contact support 51 to terminal 52. An armature 53 is pivotally mounted on the frame by a pin 54 and is secured to an armature lever 55 to form therewith a bell crank '56 shown in detail in FIGURE 9. A spring 57 is mounted on pin 54 to bias the bell crank 56 toward the position shown in FIGURE 2. The free end of the armature lever forms an arcuate trigger cam surface 58. In the closed contact position, the linkage is in the position shown in FIGURE 3 with the tab portion 34 adjacent the arcuate trigger cam surface 58 at the end of armature lever 55.
Referring to FIGURES l0 and 11, the armature bell crank 56 pivots about pin 54 secured to frame 11. Slot 84 in the bell crank receives a projection or pin 83 mounted on a brass inertia wheel 82. Wheel 82 is mounted for rotation on an axle rivet 81 which pases through a central aperture 86 in the wheel and through a suitable aperture in a flat support plate soldered or otherwise rigidly attached to frame 11. Wheel 82 is preferably balanced about its rotational axis 87 and is cut away as at 88 and 89 so that the bell crank 56 acts through the center of the wheel. In this way, the wheel is completely balanced so that it can be rotated by the bell crank without exerting any substantial retarding force on the crank, other than that due to rotary inertia of the wheel.
The housing is formed of two mirror image sections 10 and 10' (FIGURES 1 and 5) which are secured together by rivets 62 passing through openings in the housing. One of the sections, such as section 10, is provided with an elongated groove 70 and the other section is provided with an elongated tongue which is snugly received in the groove. This tongue-in-groove arrangement is for the purpose of accurately aligning the housing sections in assembly.
Each housing section is provided with recesses 63 molded in the meeting faces. The recesses 63 are provided with an enlarged portion 64. When the sections are secured together as shown in FIGURE 5, the recesses 63 combine to provide openings which receive threaded metal ferrules 65 (FIGURE 6) with hexagonal heads by which the assembly is secured to a support. The recesses 66 combined to provide openings for the reception of the threaded terminals 49 and 52.
In operation, on overload, the electromagnet 48 is energized to a point where it attracts armature 53 and causes the bell crank 56 to rotate counterclockwise about pin 54. Slot 84 in the leg of the bell crank shown in FIGURE 9, engages with crank pin 83 of the inertia wheel 82. The inertia wheel 82 is attached to the support plate 80 by axle rivet 1 but freely rotates about the rivet.
Before the armature 53 can rotate to a point where it will trip the breaker mechanism, it has to rotate the balanced inertia wheel 82 in a clockwise direction in FIG- URE 10. Under conditions of high current overload through the electromagnet 48, the inertia wheel 82 increases the length of time it takes to rotate the armature 53 as compared to a circuit breaker not having an inertia wheel. However, under conditions of low cuirent overload, the inertia wheel 82 does not restrict the travel of armature 53 via the bell crank and the time required for the armature 53 to rotate is substantially the same as a similar breaker not having an inertia wheel.
When armature 53 rotates counterclockwise, the armature lever 55 (FIGURE 9) brings the trigger cam surface 58 into contact with tab 34 to rotate striker bar 33 and shaft 31. Rotation of shaft 31 presents the reduced section 32 to the edge 42 of the fork 40, allowing the fork 40 to rotate counterclockwise about pin 25 to release pin 45 from recess 46 as illustrated in FIGURE 4. The release of pin 45 allows the linkage to collapse and the lever 14 to pivot about pin 15 to separate the contacts 12 and 13. The are drawn by the separating contacts is extinguished by its reaction to the arc chutes 59 and 60 in the usual manner. Vent opening 67 is provided in the casing 10 closely adjacent the arc chutes and serves as a pressure release for the gases produced by arcing. The force of spring 23 reacts against pin 25 to rotate the lever 21 to the position shown in FIGURE 2. The movement of pin 25 about pin 22, under the urging of spring 23, realigns links 27 and 28 and fork 40 to replace pin 45 in recess 46 as shown in FIGURE 2. In order to close the contacts, the handle is rotated clockwise about pin 22 to force the linkage down to rotate lever 14. When the contacts close, they become a pivot about which lever 14 is rotated against the force of spring 18 to load the spring and linkage for future toggle action.
It is apparent from the above that the present invention provides an improved circuit breaker, particularly insensitive to short duration high overloads. A balanced inertia wheel effectively increases the dynamic inertia of the bell crank 56 and its armature 53 and is particularly etfective at overloads exceeding 400% of the rated current to increase the trip time of the circuit breaker. That is, according to the basic formula F=MA, the increase in mass afiorded by the inertia wheel 82 under the influence of the same tripping force, reduces the acceleration of the armature so that it takes longer to move to a position where the breaker is tripped. The inertia device of this invention is of relatively simple and inexpensive construction and requires no modification of the basic circuit breaker mechanism. At the same time, it substantially increases the capacity of the breaker to resist overload currents and substantially reduces the so-called nuisance tripping previously encountered in conventional circuit breakers.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not rectrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
What is claimed and desired to be secured by United States Letters Patent is: t
1. In a circuit breaker having an electromagnet and a contact trip mechanism, a bell crank pivoted adjacent said electromagnet including a first portion forming an armature for said electromagnet, said bell crank including a second portion for actuating said trip mechanism after a predetermined amount of movement of said crank, and pivotally mounted balanced inertia means coupled to said bell crank for efiectively increasing its dynamic mass to overload currents in excess of about 400% of the rated current through said electromagnet.
2. Apparatus according to claim 1 wherein said inertia means comprises a balanced inertia wheel mounted for is rotatably mounted in the pivotal plane of said bell crank.
6. A circuit breaker for protecting against electrical overloads comprising an electromagnet, a pair of contacts, a toggle mechanism coupled to one of said contacts for moving said one contact away from the other of said contacts, an armature pivoted adjacent said electromagnet and including means for tripping said toggle mechanism, and pivotally mounted balanced inertia means coupled to said armature for increasing the trip time of said breaker for currents through said electromagnet in excess of approximately 400% of its rate current.
7. A breaker according to claim 6 wherein said inertia means comprises a balanced inertia wheel mounted for rotation about a fixed axis adjacent said armature.
8. A circuit breaker comprising an electrically insulating housing, an electromagnet mounted in said housing,
a pair of contacts in said housing, a toggle mechanism in said housing for moving one of said contacts away from the other, said toggle mechanism including a sear, a bell crank pivoted adjacent said electromagnet for tripping said sear, a portion of said bell crank forming an armature for said electromagnet, a balanced inertia wheel mounted for rotation about a fixed axis in said housing, and means coupling said bell crank to said inertia wheel whereby pivotal movement of said bell crank causes said inertia wheel to rotate.
9. A circuit breaker according to claim 8 wherein said wheel carries a projection, said bell crank having a slot slidably received in said projection.
10. A circuit breaker according to claim 8 wherein said wheel is rotatably mounted in the pivotal plane of said bell crank.
References Cited UNITED STATES PATENTS 1,554,652 9/1925 Pons 200-33 1,774,966 9/1930 Eaton 335-64 2,064,657 12/1936 Goff 335-64 898,649 9/ 1908 Higughi 58-28 FOREIGN PATENTS 259,580 6/ 1949 Switzerland.
BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US898649 *||Mar 17, 1908||Sep 15, 1908||Monnosuke Higuchi||Electric clock.|
|US1554652 *||Nov 22, 1920||Sep 22, 1925||Gen Electric||Time-element device|
|US1774966 *||May 15, 1926||Sep 2, 1930||Gen Electric||Time-element device|
|US2064657 *||Feb 28, 1935||Dec 15, 1936||Gen Electric||Control device|
|CH259580A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3749873 *||Aug 18, 1971||Jul 31, 1973||Airpax Electronics||Circuit breaker housing|
|US3959755 *||Dec 13, 1974||May 25, 1976||Airpax Electronics Incorporated||Circuit breaker with improved delay|
|US4117285 *||Aug 19, 1977||Sep 26, 1978||Airpax Electronics Incorporated||Snap action circuit breaker|
|US4237436 *||Jan 15, 1979||Dec 2, 1980||Heinemann Electric Company||Circuit breaker having a modified armature for time delays at high transient currents|
|US4882557 *||Nov 13, 1987||Nov 21, 1989||Airpax Corporation||Multipole circuit breaker system with differential pole operation|
|US4885558 *||May 22, 1986||Dec 5, 1989||Airpax Corporation||Circuit breaker|
|US4926157 *||May 3, 1988||May 15, 1990||Airpax||Circuit breaker|
|US6034586 *||Oct 21, 1998||Mar 7, 2000||Airpax Corporation, Llc||Parallel contact circuit breaker|
|US6420948 *||Oct 20, 1999||Jul 16, 2002||Airpax Corporation, Inc.||Parallel contact circuit breaker|
|US6853274||Jun 19, 2002||Feb 8, 2005||Airpax Corporation, Llc||Circuit breaker|
|USRE31690 *||Sep 17, 1980||Oct 2, 1984||No. American Philips Corp.||Snap action circuit breaker|
|International Classification||H01H73/38, H01H71/12, H01H71/44, H01H3/00, H01H73/42, H01H3/60, H01H73/00|
|Cooperative Classification||H01H73/38, H01H71/446|
|European Classification||H01H71/44C, H01H73/38|