US3818168A

US3818168A - Latch mechanism for toggle actuated circuit breaker

Info

Publication number: US3818168A
Application number: US00311283A
Authority: US
Inventors: A Norden
Original assignee: GEN SWITCH CO
Current assignee: GEN SWITCH CO; GENERAL SWITCH CO US
Priority date: 1972-12-01
Filing date: 1972-12-01
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18
Also published as: IT997837B; CA982201A; JPS4986879A; FR2209202B3; GB1424929A; FR2209202A1

Abstract

A new and improved circuit breaker is provided and comprises a breaker housing of a readily available and relatively inexpensive material which is particularly resistant to tracking to prolong the operational life of the breaker, and latch arm locating means within said housing which greatly reduce the effects of housing dimensional instability upon the calibration and operation of the breaker and provide for extremely precise breaker operation.

Description

Umted States Patent 1191 1111 3,818,168 Norden June 18, 1974v [54] LATCH MECHANISM FOR TOGGLE 2,426,880 9/1947 Jackson et al. 200/67 PK ux ACTUATED CIRCUIT BREAKER 2,627,564 2/1953 En'cson 337/70 2,917,607 12/1959 Sterling 200/144 C Inventor: Alexander R- Nor e e o k, 3,287,522 11/1966 Casey 337/70 N.Y.- 3,288,965 11/1966 Klein 337/70 73 A :GeralSthC ,G t Sslgnee 2; 1 c ompany rea Primary ExaminerR0bert K. Schaefer Assistant Examiner-William J. Smith Filed: 1972 Attorney, Agent, or Firm-Harry Cohen 211 App]. No.: 311,283 1 71 1 ABSTRACT [52 us. (:1... 200/153 G, 200/144 c. 200/010. 42, n and improved eireuit breaker is provided d 335/43 comprises a breaker housing of a readily available and 51 Int. Cl. 110111 3/46 relatively inexpensive material which is Particularly [58] Fi ld f s h 200/153 H 67 PK DIG 42 resistantto tracking to prolong the operational life of 200/ 144 (j 153 (3; 37/75; 359,71) 72; the breaker, and latch arm locating means within said 1 335 1 1'43 21 1 housing which greatlyreduce the effects of. housing v dimensional instability upon the calibration and opera- 56] R f re (111 5 tion of the breaker and provide for extremely precise UNITED STATES PATENTS 2,361,848 10/1944 Johnson 337/75 x 6 Claims, 5 Drawing Figures LATCH'MECHANISM FOR TOGGLE ACTUATED CIRCUIT BREAKER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a new and improved circuit breaker.

2. Description of the Prior Art Although a very wide variety of circuit breakers are known in the prior art and do function in generally satisfactory manner, it may be understood that many of the same do display not insignificant operational difficulties and/or are inordinately expensive to manufacture. More specifically, the housings of many of the circuit breakers of the prior art are subject to tracking in the face of internal arcing with resultant substantial reduction in the operational life thereof. Efforts to alleviate this tracking problem in the breakers of the prior art include the coating or the layering of the housing interior with a material which will not track with resultant significant increase in the cost of the breaker. In many of the other circuit breakers of the prior art, the changes in dimensions of the breaker housing which may result, for example, from post-moulding shrinkage and warpage of the plastic material of the breaker housing, affect the operating components of the breaker with resultant negative and disadvantageous effect upon the calibration and operating characteristics of the breaker. In like manner, the calibration of many of the circuit breakers of the prior art is seriously affected by their utilization in a high vibrational stress operational environment.

Other significant shortcomings of the prior art circuit breakers include undue complexity in design and method of assembly, with resultant increase in cost.

OBJECTS OF TI IE INVENTION It is, accordingly, an object of this invention to provide a new and'improved circuit breaker which displays particularly precise and reliable operational characteristics.

Another object of the invention is the provision of a circuit breaker as above which may be precisely calibrated.

Another object of this invention is the provision of a circuit breaker as above which is substantially resistant to tracking.

A further object of this invention is the provision of a circuit breaker as above which is of relatively simple and straight-forward design and method of assembly, and which requires only the use of readily available components of proven dependability in the manufacture thereof, to thus provide for relatively low breaker cost and insure long periods of satisfactory maintenance-free operation thereof.

SUMMARY OF THE INVENTION New and improved circuit breaker means are provided and comprise a housing of substantially nontracking material having a cavity formed therein. A latch arm is pivotally mounted at one extremity thereof in said housing and extends for latching at the other extremity thereof into a latching notch provided therefor in a latch member. Locating means are provided on said housing and locate said latch arm relative to said latch member at a location on the former relatively closely spaced from said other extremity to thereby reduce the effects of housing instability on the latching function. A contact arm is pivotally mounted on a pivot provided therefor on said latch arm, and a manually operable member is pivotally mounted on said housing and includes a handle which projects from the latter for the manual operation thereof. An over-toggle spring is pivotally mounted from said manually operable member and said contact arm and is operable, upon unlatching of said latch arm in response to an overload or short circuit condition in the breaker-protected line, to pivotally move said contact arm to open the circuit breaker contacts. Manual movement of said manually operable member, with said latch arm in the latch position thereof, is also effective in conjunction with the ef fect of said spring to move said contact arm to open the circuit breaker for servicing of the line or the like. A calibration screw is provided and is readily adjustable from without said housing to calibrate the unlatching of the latch arm, and the mounting means for said calibration screw include vibration-resistant means to inhibit the unwanted loosening of said screw under the effects of a high vibrational stress operational environment of the circuit breaker. Assembly of the circuit breaker is facilitated and rendered relatively inexpensive by the fact that all of the operating components thereof lie substantially flat in the housing cavity whereby no special fixtures of the like are required for such assembly.

DESCRIPTION OF THE DRAWINGS The above and other objects andsignificant advantages of the invention are believed made clear by the following detailed description thereof taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of the circuit breaker with the housing cover plate removed and the circuit breaker in the closed position thereof;

FIG. 2 is a side elevational view in the nature of FIG. 1 showing the circuit breaker in the automatically tripped position thereof;

FIG. 3 is a side elevational view in the nature of FIGS. 1 and 2 showing the circuit breaker in the manually tripped or open position thereof;

FIG. 4 is a cross-sectional view taken along line 44 in FIG. 1; and

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a circuit breaker constructed and operative in accordance with the teachings of this invention is indicated generally at 10 and comprises a housing 12 which is in turn constituted by an appropriately formed housing body 14 and a mating, appropriately formed cover plate 16 which fits tightly thereover and is secured to said housing body by rivets 18 extending therebetween. When assembled, the housing body 14 and cover plate 16 define an interior chamber 17 therebetween in conventional manner. The housing body 14 and cover plate 16 are preferably made of a suitably electrically insulative and relatively inexpensive material in the nature of urea formaldehyde which, although not exceptionally stable dimensionally, decomposes ablatively and thus offers very substantial, if not total, resistance to tracking (the formation of an electrically conductive path by carbonization in the presence of an arc with resultant unacceptable provision of a current flow path within the circuit breaker housing) to very significant advantage as should be obvious to those skilled in this art.

The housing body 14 comprises a pivot pin 20 moulded therein which extends intothe chamber 17. A manually operable member 22 is pivotally mounted on the pin 20 and includes a generally arcuate, breaker op erating portion 24 which is disposed as shown within said chamber, and an integral, manually operable handle 26 which extends therefrom to without the housing 12. The manually operable member 22 is preferably made from the same electrically insulative material as the housing 12,. and is manually pivotally movable through manual actuation of the handle 12 from the FIG. 1 portion thereof wherein the circuit breaker 10 is closed to the H6. 3 portion thereof wherein the breaker is in the manually open position thereof. In addition, and as discussed in greater detail hereinbelow, the member 22 is automatically pivotally movable upon overload tripping of the circuit breaker 10 from the FIG. 1 position thereof to the FIG. 2 position thereof wherein the breaker is in the automatically tripped, open position thereof.

A generally cylindrical, stepped boss 30 is moulded into the housing body 14 and extends as shown into chamber 17. A latch arm 32, which is preferably made of steel and which is formed from a single appropriately configured strip which is bent over to provide the spaced, double-wall construction as most-clearly depicted in FIG. 5, is disposed as shown in the cavity 17 with one extremity thereof being pivotally connected to the boss 30 by th extension of the latter through a slightly oversized aperture 34 formed in said latch am. The other extremity of the latch arm 32 terminates as shown in a generally triangular latch portion 36, and an adjacent notch 38 which, through cooperative association with a housing body-moulded. stop 40, functions to determine the point at which the latch arm 32 is latched, again as discussed in greater detail hereinbelow. Clearance for pivotal movement of the latch arm 32 about boss 30 is provided in part by a housing bodymoulded spacer rib 42 which spaces the former from the housing body. A stop for counter clockwise pivotal movement of latch arm 32 about boss 30 is provided by a housing body-molded boss 29. A pivot pin is formed as best seen in H0. on the latch arm 32 by a bent-over portion thereof.

A contact arm is indicated at 46 and is preferably made of copper or other suitable, highly electrically.

conductive material. The contact arm 46 extends as shown between thespaced walls of the latch arm 32 and is fulcrumed or pivotally carried from the latter on pivot 44. A generally T-shaped end portion 48 is formed as shown on the contact arm 46 and, upon pivotal movement of the contact arm 46 about the movable latch arm pivot 44, this end portion ismovable through an arc as generally defined by an arcuate cutout 50 in the member 22 and as limited by a housing body-moulded stop 52. A contact 54 is carried as shown from the other end portion of the contact arm 46 and cooperates with a fixed contact 56 which is in turn carried by a housing-mounted conductor 58. The conductor 58 terminates in a bayonet-type connector 60 which extends as shown from the housing 12 to enable the convenient connection of the circuit breaker on a circuit board.

v is cut from the latch member 64 extends as shown into 4 An over-center or over-toggle spring is indicated at 62 and is connected as shown to the member 22 and contact 46 by the extension of the respective, bent-over spring extremities into

mounting apertures

61 and 63 provided therefor in said member and arm.

A latch member is indicated at 64 and is preferably made of a single piece of relatively thin strip steel which is formed as shown by appropriate bending thereof. The latch member 64 is disposed as shown in the cavity 17 with freedom for pivotal movement in a V notch 69 in housing'12, and a strip spring 66 which cooperative association with a housing back-moulded boss 68 to spring bias the member 64 for clockwise rotation relative to its pivot in notch 69.

The bimetal strip 70 which is formed of two metals having dissimilar coefficients of thermal expansion and secured together in back-to-back relationship, is mechanically and electrically connected at one extremity thereof, as bywelding, to a copper conducting plate 72 which is in turn fixedly disposed in the housing 12 by tight friction fit between housing back-

moulded bosses

74 and 76, and moulded-in pocket 77, to thus fixedly position strip 70.

A box-like connector is indicated at 78 and isfixedly disposed in the housing 12 by a fit between moulded housing bosses 80 and 82. The plate 72 extends into and terminates in the connector 78. A connection screw 84 extends into connector 78 and an aperture 86 is formed in the housing back 14 to enable the extension of a suitable conductor into the connector 78 for finn connection therewithin to plate 72 by tightening of connection screw 84 through housingback aperture 88.

A latch notch 90 having a small lip portion 92 is formed as shown in the latch member 70 and the extremity of the latch ann latch portion 36 may be seen to extend thereinto for latching when the breaker 10 is in the closed position thereof of FIG. 1.

A calibration screw mounting is provided by doubly bent over

portions

91 and 93 of the latch member 64 and slightly misaligned threaded apertures formed therein. A calibration screw 94 of any suitably nonconductive material is threaded as shown through said apertures and extends into surface contact with the bimetallic element whereby may be understood that clockwise rotation of said screw, as through housing back aperture 96, will function to move the latch member 64 closer to the bimetallic member 70, and vice versa. The slight misalignment of the calibration screw mounting apertures in the springy material of latch member 64 will advantageously render the calibration screw particularly resistant to accidental loosening in OPERATION Withthe circuit breaker 10 on line and in the closed position thereof of FIG. 1, it may be understood that a current path is provided therethrough from .contact member 58, closed

contacts

56 and 54, contact arm 46, conductor 98, bimetallic element 76, conducting plate 72 and connector 73. In this closed position of the circuit breaker the latch arm 32 is maintained in the depicted position thereof relative to the fixed pivot at boss 30 by the latching of the remote latch arm extremity (latching portion 36) in latch notch of the latch member 64. In the closed breaker position, the contact arm 46 is maintained in the depicted position thereof relative to its pivot 44 on the now fixedly positioned latch arm 32, by the biasing action of spring 62 which biases contact arm contact 54 into abutment with the fixed contact 56 on contact member 58. This same bi asing action of spring 62 is, of course, effective to bias manually operable member 24 about pivot into the depicted position thereof wherein handle 26 abuts housing body wall portion 102. In this closed position of the circuit breaker 10, it may be seen that pivot pin 44 lies to right of an imaginary'line drawn between the respective ends of the over-toggle spring 62 at

spring mounting apertures

61 and 63, and that there is a small gap between stop 52 and the adjacent leading contact arm edge I64.

Upon the occurrence of an excess current condition in the circuit breaker circuit, it may be understood that bimetallic member 76 will respond by bowing to the right as seen in FIG. 1 with resultant generally pivotal movement of the latch member 64 in this same direction under the action of calibration screw 94. As this occurs, the latch arm 32 is released from the latch notch 90 due to the movement of the latch member 64 away from the latch arm with the result that the support for the latch portion end of the latch arm disappears to thus free the latch for counter-clockwise pivotal movement about boss 30 under the spring-biased action of contact arm 46 against latch arm pivot 44. Very shortly after commencement of such movement, the leading edge 104 of contact arm 46 will abut boss 52 to thus establish an artificial sliding pivot for the contactarm at said boss and initiate generally counter-clockwise pivotal movement of the contact arm about said sliding pivot.

This pivotal movement of the contact arm 46 and latch arm 32 will continue as described until the movement of pivot pin 44 in conjunction with the slide rotation of contact arm 46 about the boss'52 brings spring aperture 63 to the right of the imaginary line through pivot pin 44 and spring aperture 61, at which point conventional over-toggle action of spring 62 will occur with resultant counter-clockwise movement of contact arm 46 to the position shown in Fig. 2 with the underside of contact arm portion 48 resting against boss 52, and the contact 54 separated as shown from contact 56 to open the breaker. During the counter-clockwise rotation of latch arm 32, but before it comes into contact with the moulded boss 29, a finger portion 33 of latch arm 32 strikes moulded projection 23 of the manually operable member 22, causing clockwise rotation of member 22 about moulded pivot pin 20, until such rotation brings portion 25 of the member 22 against the upper surface of latch arm 32, as illustrated in FIG. 2. Thus may be understood that the automatically tripped position of handle 26 will be detennined by the configuration of latch arm 32, alone, and will readily indicate that the breaker has been tripped.

Automatic tripping of the circuit breaker it) in the face of a short circuit in the line protected thereby would occur in substantially the same manner de* scribed directly hereinabove for a normal overload trip with the exception that, under short circuit conditions, the articularly large load applied to bimetallic element 76 would electro-rnagnetize the same to immediately and rapidly magnetically attract the latch member 64 thereto to rapidly release latch arm 32.

Manual opening of the circuit breaker 10 as, for example, to enable servicing of the line protected thereby, is effected by movement of the manually operable member 22, through manual operation of handle 26, from the FIG. 1 position of said member to the FIG. 3 position thereof. Thus, and understanding that latch arm 32 remains latched in latch member 64 and accordingly in substantially fixed position during such manual breaker opening, it may be seen that the substantially fixedly positional latch arm pivot pin 44 will initially (FIG. 1) lie to the right of the imaginary line drawn between spring and mounting

apertures

61 and 63. However, as clockwise pivotal movement of the manually operable member 22 about pivot 20 progresses, said imaginary line will be moved generally to the right to and through the point at which the substantially fixed pivot pin 44 lies thereon. As this occurs, the over-toggle spring 62 will be effective to rapidly pivotally move, in snap-action fashion, the contact arm 46 about pivot pin 44 from the position of the former in FIG. I to the FIG. 3 position thereof, as determined by the abutment of projection 51 of contact arm and portion 48 with boss 52, to separate the

contacts

56 and 54 to the extent depicted in FIG. 3 and thus open the circuit breaker 10.

It is well known that with high momentary inrush currents (such as experienced in closing a circuit containing large numbers of incandescent lamps) there is a tendency to form light stickwelds between contacts. In the event that a light stick weld has developed at the contacting silver tungsten surfaces of

contacts

56 and 54, it is possible that the overtoggle force of spring 62 may prove insufficient to break such a stick weld when handle 26 is moved from FIG. l to FIG. 3 position. Should contact arm 46 fail to start to rotate in the contact opening direction at the point at which the manual operation of member 22 moves the line of action of spring 62 to bias contact arm 46 to open contacts, further rotation of member 22 produces mechanical interference between the molded projection 23 of member 22 and projection 49 of the contact arm portion 48, creating a camming prying and levering force on contact arm 46, rotating it counterclockwise, thus breaking the stick weld.

Comparison of FIGS. 2 and 3 will make clear that the

contacts

56 and 54 are separated to the substantially greater extent when the circuit breaker 10 is automatically tripped than when the latter is manually tripped. This is so because in the first instance, the position of contact arm 46 is determined by the abutment between the underside of end portion 48 and boss 52 and, in the second instance, is determined by the abutment between end portion projection 51 and the boss 52. More specifically, it may be understood that in actual practice, said contact separation may, for example, be approximately 5/ 16 inch upon manual tripping of the breaker l0 and approximately 15/16 inch upon automatic tripping thereof.

Return of the circuit breaker to the closed position of FIG. 1 from the manually opened position of FIG. 3 isreadily effected by manual pivotal movement of the member 22 to return the latter to its FIG. 1 position. In this instance, as the imaginary line connecting the over-toggle spring ends moves generally from right to left to and through the latch arm pivot pin 44, it may be understood that spring 62 will be effective to rapidly pivotally move, again in snap-action manner, the contact arm 46 about pivot pin 44 from the contact arm position of FIG. 3 to the position thereof of FIG. 1 to re-close

contacts

56 and 54.

Return of the circuit breaker 10 from the automatically tripped position thereof of FIG. 2 to the closed position thereof of FIG. I is initiated by clockwise pivotal movement of the manually operable member 22 from the FIG. 2 to the FIG. 3 position thereof to abut and pivotally move the latch arm 32 to the latched position thereof wherein latch portion 36 is re-engaged in latch member latch notch 90 beneath lip'9 2 and locating notch 38 again overlies stop 40. As this pivotal v movement of the latch arm 32 occurs,wit h attendent generally arcuate movement of the latch arm pivot pin 44, it may be seen that generally pivotal movement of the contact am 46 under the action of spring 62 about moving pivot pin 44 will result, and will initially comprise a general cammi'ng action of the boss 52 upon contact arm end portion 48. As latch arm 32 becomes re-latched, the pivot pin 44 again becomes a substantially fixed pivot. Counterclockwise pivotal movement of the member 22, through action of spring 62 about said fixed pivot will then be effective to return contact the circuit breaker 10 are substantially minimized.

More specifically, it may be understood that since the distance between stop 40 and the latch member notch 90 is very substantially less than the distance between pivot 30 and said latch member notch, the effect of housing instability upon the essentially closely controlled relative disposition of latch member'latch portion 36 and the latching notch 90 is very substantially minimized in like manner. Thus, for example, if in actual practice the circuit breaker 10 is configured to have a stop 40 latching notch 90 distance of about one-tenth the distance between pivot pin'30 and said latching notch, it should be clear that the effects of dimensional instability of housing 12 upon breaker latching operation should be reduced by a factor of l0 to very significant advantage as should be obvious. A further significant advantage of the minimization of the effects of housing dimensional instability on the latching operation of the circuit breaker l0 resides in the fact that the same enables unlatching of the latch arm 32- to occur accurately in response to very limited travel, for example 0.030 inch, of the latch member 64 to thereby provide for extremely precise breaker operation as should be obvious.

Assembly of the circuit breaker 10 is greatly simplified, to significant economic advantage, by the fact that all of "the operating breaker components lie substantially flat within the housing body 14 and may thus be readily and quickly inserted thereinwithout the use of specialized assembly fixtures or the like.

While I have shown and described the preferred embodiment of my invention it will be understood that the invention may be embodied otherwise than as herein expressly shown or described and that in said embodiment certain changes in the details or construction and in the arrangement of parts may be made without departing from the invention within the scope of the appended claims.

What is claimed is: y

l. A circuit breaker comprising, a, housing, a latch arm, a latch member, cooperating latching means on said latch arm and said latch member for latching the former to the latter, means on" said housing for pivotally mounting-said latch arm relative to said latch member, locating means on said housing for locating said latch arm relative to said latch member at a location on the former between said pivotal mounting means and said latch arm to thereby reduce the effects of the dimensional instability of said housing upon the latching of said latch arm on said latch member.

2. A circuit breaker as in claim 1 wherein, said latch arm location is substantially closer to said cooperating means than to said pivotal mounting means.

3. A circuit breaker as in claim 1 wherein, the distance along said latch arm from said location to said cooperating means is approximatelyone tenth that of the distance along said latch arm from said location of said pivotal mounting means.

4. A circuit breaker as in claim 1 wherein, said housing is constituted by a substantially non-tracking mateing means are fixed relative to said latch arm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,818, 168 Dated n 1 97A Inventor(s) Alexander R. Norden It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, column 8, line 36, "am" should read Signed and Scaled this eighteenth D3) of November 1975 [SEAL] Arlest:

R=UTH C. MASON C. MARSHALL DANN UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,818,168 Dated June 97 Inventor(s) Alexander R. Norden It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, column 8, line 36, "arm" should read arm En'gncd and Scaled this eighteenth Day Of November 1975 [SEAL] Arrest.

RUTH C. MASON C. MARSHALL DANN =I H K ffll't ('mnmisslum'r 0] Parents and Trademarks UNITED, STATES :PATENT OFFICE CERTIFICATE O CORRECTION Patent No. 5, 18,168 I Dated 97 v Inventor(s) Alexander R. N orden It is certified that error appears in the above-identified patent and that saidvLetters Patent are hereby corrected as shown below:

Claim 1 column 8, line 36, "arm" should read member Signed and Scaled this ninth Day of March 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents and Trademarks

Claims

1. A circuit breaker comprising, a housing, a latch arm, a latch member, cooperating latching means on said latch arm and said latch member for latching the former to the latter, means on said housing for pivotally mounting said latch arm relative to said latch member, locating means on said housing for locating said latch arm relative to said latch member at a location on the former between said pivotal mounting means and said latch arm to thereby reduce the effects of the dimensional instability of said housing upon the latching of said latch arm on said latch member.

3. A circuit breaker as in claim 1 wherein, the distance along said latch arm from said location to said cooperating means is approximately one tenth that of the distance along said latch arm from said location of said pivotal mounting means.

4. A circuit breaker as in claim 1 wherein, said housing is constituted by a substantially non-tracking material.

5. A circuit breaker as in claim 3 wherein, said housing is constituted by a substantially non-tracking material.

6. A circuit breaker as in claim 1 wherein, said locating means are fixed relative to said latch arm.