US3703694A

US3703694A - Contact operating mechanism for contact breaker

Info

Publication number: US3703694A
Application number: US193915A
Authority: US
Inventors: John W Bullock
Original assignee: Arrow Hart Inc
Current assignee: Arrow Hart Inc
Priority date: 1971-07-15
Filing date: 1971-10-29
Publication date: 1972-11-21
Anticipated expiration: 1989-11-21
Also published as: DE2135969A1; AU3124571A; DE2135969C3; GB1349973A; FR2146916B1; CH552890A; NL7109993A; BE770472A; FR2146916A1; DE2135969B2; AT315284B; AU445838B2

Abstract

A contact closure mechanism for a circuit breaker has a pair of contact arms bearing contacts which are pivotally mounted at their mid-sections on the ends of outwardly extending projections formed on a member slidable along an axis. A coiled contact pressure spring urges the contact arms into closure relationship with respective stationary contacts to establish electrical contact. A coiled contact opening spring coaxially disposed with respect to the pressure spring, selectively urges the slide member in one direction along the axis when the latching load pressure is relieved, causing the contact arms to pivot and their contacts to separate from the fixed contacts a distance which is exponential with respect to movement of said slide member. As the slide member moves, rocker cams forming an integral part of the opposing inside housing walls, are engaged by the contact arms which causes a rolling, pivotal separating movement to occur between the respective contact pairs of the circuit breaker.

Description

United StatesPatent Bullock 154] CONTACT OPERATING MECHANISM FOR CONTACT BREAKER [72] Inventor: John W. Bullock, Northridge, Calif. [73] Assignee: Arrow-Hart, lnc., Hartford, Conn.

[22] Filed: Oct. 29, 1971 [21] App1.No.: 193,915

Related US. Application Data [63] Continuation of Ser. No. 11,259, Feb. 13,

1970, abandoned.

[52] US. Cl. ..337/62, 200/170 A [51] Int. Cl....H01h 71/16, HOlh 73/06, HOlh 73/30 [58] Field of Search...200/l6 A, 165, 170 A; 337/62,

2,335,082 ll/1943 Platz ..337/66 [4s] Nov. 21, 1972 Primary Examiner-Bemard A. Gilheany Assistant Examiner'Dewitt M. Morgan Attorney-William F. Sonnekalb, Jr. et al.

[57] ABSTRACT A contact closure mechanism for a circuit breaker has a pair of contact arms bearing contacts which are pivotally mounted at their mid-sections on the ends of outwardly extending projections formed on a member slidable along an axis. A coiled contact pressure spring urges the contact arms into closure relationship with respective stationary contacts to establish electrical contact. A coiled contact opening spring coaxially disposed with respect to the pressure spring, selectively urges the slide member in one direction along the axis when the latching load pressure is relieved, causing the contact arms to pivot and their contacts to separate from the fixed contacts a distance which is exponential with respect to movement of said slide member. As the slide member moves, rocker cams forming an integral part of the opposing inside housing walls, are engaged by the contact arms which causes a rolling, pivotal separating movement to occur between the respective contact pairs of the circuit breaker.

17 Claims, 7 Drawing Figures PATENTEDnnm m2 sum 1 OF 2 v K 2 @wg Q .wm! my wm mvw WW 1 m 5 w 7/ 7 Z ,M a W 2 H m a MW z w. 4 a 5 4. 4 4 a 7 5 4, d 2 v 3 o a, o 7 w {0 0 Z 4 Z Q I w 5 .2 Q 0 lfl|lll m mm um I! 0 4,1 0 W W. Z Ov JIM 47 IL 0 4. M47 i Q Q a CONTACT OPERATING MECHANISM FOR CONTACT BREAKER BACKGROUND OF THE'INVENTION 1. Field of the Invention This invention relates to electrical circuit breakers and more particularly to a novel circuit breaker incorporating a contact closure mechanism providing the same contact pressure from unit-to-unit and providing maximum contact opening clearance.

2. Brief Description of the Prior Art Heretofore circuit breakers have been made that are manually operable between open and closed positions and which open automatically by the action of a thermal element on occurrence of an overload current. Also, such devices have been made so that they cannot be manually held closed if the overload persists, i.e., they are trip-free. In-certain cases the prior devices consisted of three principal assemblies, namely, a switch assembly, a latching assembly capable of moving the switch into closed position and holding it there, and a releasing assembly for automatically releasing the latch assembly to allow the switch assembly to move into open position.

In at least one prior construction of the type above mentioned, all three assemblies of the circuit breaker are compressed together in the switch-closed position with the contacts of the switch assembly being held firmly engaged against a strong spring force urging them apart, providing resistance against operation upon shock or vibration.

One of the major problems encountered with prior switch assemblies is that of attaining sufficient contact clearance or separation between the movable and stationary terminal contacts so as to avoid the possibility of electrical arcing, sparking or establishment of an electrical circuit even though the contacts are not engaged. Also, since the movable contacts rely upon the thermal element for transfer of motion, it is found that contact pressure differs in similar circuit breaker con.- structions in a given production run. Also, since there are many variables in the latch assembly, contact pressure is adversely affected so that sufficient contact opening clearance cannot be assured repeatedly from one production unit to the next.

SUMMARY OF THE INVENTION The difficulties and problems encountered with conventional switch assemblies for circuit breakers are obviated by the present invention which provides a dual, coaxial spring actuation for the switch assembly in which a main contact spring operates against movable contact members to forcibly urge the movable contacts into engaging relationship with stationary terminalcontacts. The second or opening spring effectively operates against the movable contact support to rotatably separate the movable contacts from the stationary terminal contacts upon release of the latch assembly in response to an overload condition of the thermal element. Means are provided on the opposing inside wall surfaces of the circuit breaker housing for engaging the movable contacts after initial separation with the stationaryterminal contacts, whereby a rolling motion ensues which increases the distance between the previously mated contacts at an exponential rate. Therefore, it is among the primary objects of the present invention to provide a novel switch assembly for a circuit breaker of the type herein described having contact closures adapted to provide opening clearances substantially greater than can be attained in conventional breakers. I

Another object of the present invention is to provide a novel switch assembly for circuit breakersv of the type herein described whereby the contact pressure will be the' same in all circuit breakers of similar design of a given production run.

Still another object of the present invention is to provide a novel circuit breaker with means to enable the contact load pressure to by-pass the thermal element and also to enable the movable contact assemblies to separate from stationary contacts at an exponential rate, so as to provide a contact opening clearance approximately three times a normal clearance obtainable by employing conventional contact closure mechanisms.

. Yet another object of the present invention is to provide a circuit breaker of the character described having a pair of fixed contacts and, a pair of movable contacts wherein the movable contacts pivot in a rocking action during the closing and opening thereof so as to produce a self-wiping action to keep the contacts clean.

Still another object of the present invention is to provide a novel contact closure mechanism for a circuit BRIEF DESCRIPTION OF THE DRAWING I The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is an elevation view with one half of the housing removed of the novel circuit breaker incorporating the contact closure mechanism of the present invention in closed position.

FIG. 2 is a view similar to FIG. 1 illustrating the contact closures in their fully open position.

FIG. 3 is an exploded perspective view of major component parts comprising the latch assembly and contact closure mounting assembly.

FIG. 4 is an enlarged view of a portion of the latch assembly illustrating the trip cams of latch mechanism in their latched position in solid lines.

FIG. 5 is a cross-sectional view of the trip cams as taken in the direction of arrows 55 of FIG. 4.

FIG. 6 is an enlarged fragmentary elevational view, partly in section, of the contact closure mechanism employed in the circuit breaker of FIGS. 1 and 2.

FIG. 7 is a side elevational view of inside side of one portion or side of the circuit breaker housing with the operating mechanismremoved.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a circuit breaker 10 employing the present invention is illustrated. In general, the circuit breaker includes a latch assembly designated, generally, by numeral 11, and a thermal element release assembly for releasing the latching assembly is designated, generally, by numeral 12. Immediately beneath the thermal element release assembly, there is a switch assembly designated generally by numeral 13. The latch assembly, thermal element release assembly and the switch asse'mbly are enclosed within a housing 14. The housingcomprises a pair of identical sections which are held together by suitable fasteners to define an interior cavity in which the components of the circuit breaker are located. Only one half of the housing is illustrated. The latch assembly 11 may take the form of any preferred assembly which is capable of moving the switch assembly to a make or closed position and for holding the switch assembly in this position until released. Conventional latch assemblies include a guide 15 for movably supporting a manual operating button 16 which includes an extended portion or sleeve 17 disposed within the interior cavity of the housing. The present invention is not limited to a particular latch assembly. Although any suitable latch assembly may be used such as that disclosed in US. Pat. No. 2,986,620, for example, a particularly suitable and advantageous form is shown in the drawing, and claimed in my copending application Ser. No. 147,449, filed May 27, I971, entitled Circuit Breaker.

As illustrated, the latch assembly 11 includes a central mounting shaft 18 for supporting an upper trip cam 20 of two

engageable cams

20,22. Shaft 18 is coaxially and coextensively disposed with respect to a lower shaft 21 which carries lower trip cam 22. It should be understood that the

members

20 and 22 which function as, and constitute, latch members are frequently referred to herein as cams, for the sake of simplicity. The

trip cams

20,22 are provided with slots defined by body portions so that when a mating occurs between alternate slots and body portions of the respective trip cams, the trip cams will interleave so that loading tension is released from the latch assembly to permit release of the switch assembly. The

trip cams

20 and 22 are rotated relative to one another by the thermal element release assembly 12 which includes a spirally coiled bimetal strip 23 having braided

wires

24 and 25 welded to the opposite ends thereof and, in turn, having their opposite ends welded to a pair of

movable contact arms

26 and 27. The

movable contact arms

26 and 27 form a part of the switch assembly and are pivotally mounted at their respective mid-sections to the ends of the opposite

lateral projections

28 and 29 carried on a vertical slide member 30. The slide member 30 carries shaft 21 and includes a guided body portion which extends downwardly through an insulating washer 31 which is held in a recess in the housing 14.

Fixedly secured on opposite sides of the housing 14, there is provided a pair of stationary terminals 32 and 33 which include fixed

contacts

34 and 35 residing in the housing cavity. The fixed contacts are adapted to be selectively engaged by

contact buttons

36 and 37 mounted on the

movable contact arms

26 and 27. As illustrated in FIG. 1, contact pressure is maintained by means of a main contact spring 40'which is coaxially disposed about the body portion of slide member 30 and is expandably disposed between the bottom of the housing 14 and a flange 41 carried on insulating washer 31. The contact pressure is established by means of the forcible urging of spring 40 against flange 41 which bears against the extreme ends of the

contact arms

26 and 27 so as to pivot the arms in a direction causing the

contacts

36 and 37 to press against the fixed

contacts

34 and 35, respectively.

As shown in FIG. 1, the latch assembly is depressed with the button 16substantially enclosed by member 15 and the opposing ends of trip latches or

cams

20 and 22 are bearing against one another. This arrangement loads the latch assembly and the switch assembly but does not load the thermal element release assembly. The pressure loading extends through the abutting ends of the trip latches or

cams

20,22 and extends down to the lower shaft 21 and into a lower guide 42 and operating spring 43 compressed between. The spring 43 is'compressed between a flange on lower guide 42 and the upper end of an inner bore in slide member 30. The spring 43 is held substantially compressed due to the fact that the opposing ends of the trip cams are en gaged which places a load through the lower shaft 21 opposing the force of spring 43.

However, when the cams are rotated with respect to each other in response to rotation of the bimetal thermal element 23, the body portions of the cams will meet with the corresponding slots so that the expansion of spring 43 will urge the cams together and permit the slide member 30 to move upwardly. I

As the slide member 30 moves upwardly, the flange 41 of the insulating washer 31 bears against the oppos ing ends of the

contact arms

26 and 27 in response to the expansion of spring 40. This upward moving action causes the contact arms to pivot about their pivot connection with

projections

28 and 29 on the slide member 30. As the distance increases between the pivot connections and the upper surface of the flange 41 against which the opposing ends of the contact arms are bearing, the clearance or opening distance between the fixed contacts and the movable contacts become .greater at an exponential rate. The opposing ends of the contact arms bear against the upper surface of flange 41. A pair of semi-circular cams or aligned rounded members 44 carried on the inside surface walls of the housing halves are engageable by the upper surface of the contact arms in response to upward movement of the slide member so as to effect fixed and movable contact separation at an exponential rate. The inside surface wall is indicated by numeral 45 and semicircular flange 44 is shown in dotted lines in FIG. 1 since it lies behind the mass of slide portion 30. Furthermore, the opposing ends of the contact arms are bifurcated so that the opposite legs embrace the opposite sides of the slide member 30 so as to accommodate its mass therebetween.

FIG. 3 is an exploded view of the central components of the circuit breaker to showthe relative position and location, thereof, for assembly. Of particular note are the

trip cams

20 and 22 which have cylindrical body portions that are slotted lengthwise from one end, forming

parallel legs

45,46, respectively. The extremities of the

legs

45 and 46 include opposing end surfaces Referring now to FIG. 7, one of the pair of housing halves is illustrated in which the'inside wall surface is indicated by numeral 45 for the internal cavity in which rocker or semi-circular surface 44 is disposed. The semi-circular surface 44 is bordered by parallel spaced

sections

60 and 61 between which slide member 30 47 and 48 which normally abut one another- However,

as previously described, upon rotation'of trip cam 22 with respect to trip cam 20 in response to movement of the bimetal element 23, the parallel legs 46 of lower cam 22 will be brought in register with the slots of upper cam 20. This permits the slide member 30 to move upwardly by the forcible urging of spring 43. To minimize friction the lower shaft member 21 seats on a ball or sphere 50 which is supported in a recess 51 in slide member 30.

As shown in the enlarged views of FIGS. 4 and 5, the thermal element release assembly includes the bimetal 23 having its inner end, indicated by numeral .52, physically secured to an insulating mounting piece 53 via a J shaped member 54 having its outer end anchored to the housing. Member 54 also has the braided wire 24 electrically connected to it by welding. Mounting piece 53 is fixedly secured to the lower trip cam or latch 22 so that the rotary movement of the bimetal coil istranslated into rotational movement of the'lower trip latchas the bimetal coils and uncoils when it becomes heated on occurrence of an overload current and cools after the breaker trips open. It is to be understood that any together but permitting rotation of the shaft relative to I the slide. As shown in solid lines, the contact arms are in their closed or engaged positions with respect to the fixed

contacts

34 and 35. While the contact arms are in the solid line position, it can be seen that spring 40 urges the upper surface of flange 41 of the insulating washer 31 against the yoke end of the contact arm so as to forcibly urge the movable contact into engagement with the fixed contacts. Also, it can be seen that an annular bore or opening 56 is provided in the body portion of the slide member 30 to accommodate the spring 43. The spring 43 operates at its lowerend against the base flange of member 42 while its upper end presses against a portion of the slide'member terminating the annular bore 56 on the slide member. The slide member 30 is further provided with an elongated axial shank 57 which is slidably inserted into the lower guide 41 to guide the movement of the slide.

As shown in broken lines in FIG. 6, the slide member 30 is in its fully raised or upward position, being forcibly urged there by spring 43 when the cam latches 20,22 are interleaved. In the elevated positions, a substantial clearance is provided between the movable and fixed contacts.

vertically moves. The upward limit of the slide member is restricted by means of engagement with the lower surface of a block 62 disposed between the walls and 61. The bimetal coil is substantially disposed between rounded

beads

63 and 64. Housing walls further provide

surfaces

65 and 66 on which fixed

contacts

34 and 35 may be supported via .the terminals 32 and 33. It is to be fully understood that although one half portion of housing 14 'is illustrated in FIG. 7, another identical half portion is employed which cooperates with the internally projecting surfaces and walls such as semi-circular portion 44,

sections

60 and 61, block 62, and

beads

63 and 64, so that the internal cavity may readily house the components previously described and illustrated.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a circuit breaker, a housing, a latch assembly enclosed in said housing, a thermal release assembly connected with said latch assembly for releasing it upon occurrence of an overload current, a switch assembly held in closed position by said latch assembly, said switch assembly comprising a member slidable along an axis, a guidemember supported from said housing and slidably supporting said slidable member formovement along said axis, a pair of arms pivotally mounted on said slidable member, a moving contact at one end of each arm, fixed contacts supported by said housing each engageable by one of said moving contacts, first resilient means between said'contact arms and said housing urging the opposite ends of said arms in a direction to press said moving contacts against said fixed contacts when said latch assembly is in latching condition, and second resilient means between said housing and said slidable member acting on said slidable member in a direction to cause contact separation, when said latch assembly becomes unlatched.

2. The invention as defined in claim 1 wherein said first resilient means comprises a coiled compression spring engaging the housing, and a supporting member slidable relative to said slide member and engaged by said spring and engaging said opposite ends of said contact arms. 4

3. The invention as defined in claim 2 wherein said opposite ends of said contact arms slidably bear against said supporting member.

4. The invention as defined in claim 1 wherein said first resilient means comprises a coiled compression spring and second resilient means comprises a compressed helical spring coaxial with said first spring.

5. A circuit breaker as claimed in claim 1 having means fixedly supported relative to said housing, en-

gageable by said contact arms in response to movement of said slidable member to effect contact separation at an exponential rate.

6. The invention as defined in claim 1 wherein the opposing inside wall surfaces of said housing includes aligned rounded members engageable by said contact arms in response to said movement ofsaid slidable member to effect contact separation at an exponential rate.

7. The invention as defined in claim 1 including stop means on said housing engageable with said slidable member to limit movement thereof.

8. The invention as defined in claim 1 wherein said slide member includes a pair of outwardly extending projections and pivot connections coupling each of said contact arms at its mid-section to one of said projections.

9. The invention as claimed in claim 1 having supporting means on said slidable member, and pivot means on said supporting means pivotally supporting said contact arms between their ends.

10. In a circuit breaker having a housing comprising a pair of identical half sections enclosing a latch assembly, a thermal release assembly operably secured tosaid latch assembly for releasing. said latch assembly and a switch assembly held in its closed position by said latch assembly wherein said switch assembly comprises: v x

a slide member coaxially disposed with respect to said latch assembly and said thermalrelease assembly;

a guide member fixed to said housing for'slidably mounting said slide member for vertical movement thereon;

a pair of contact arms pivotally connected to said slide member, each arm having a contact carried on one of its ends for selective engageable contact with a fixed contact secured to said housing;

first resilient means disposed between said contact arms and said housing forcibly urging against the ends of said arms opposite to their ends carrying said contacts for applying contact pressure between said fixed and movable contacts; and

second resilient means coaxially disposed with.

the upper surface of said washer bears against said opposite ends of said contact arms.

12 The invention as defined in-claim 11 wherein said opposite ends of said contact arms slideably bear against the top of said washer and the opposite end thereof being disposed for carrying said contact.

13. The invention as defined in claim 10 wherein said second resilient means comprises a compressed helical spring.

14. The invention as defined in claim 10 wherein the opposing inside wall surfaces of said housing pairs include aligned rounded members engageable b said contactarms in response to said movement of sai slide contact arms at its mid-section to one of said projections.

17. In a circuit breaker having a housing enclosing a latch assembly, a thermal release assembly operably secured to said latch for releasing said latch assembly upon occurrence of an overload, and a switch assembly held in it's closed position by said latch assembly wherein said switch assembly comprises:

a slide member coaxially disposed with respect to said latch assembly and said thermal release assembly;

a guide member supported by said housing and slidably mounting said slide member for axial movement;

a pair of contact arms pivotally mounted on said slide member, each arm having a contact carried on one of its ends, fixed contacts supported by said housing and selectively engageable by said movable contacts;

first resilient means disposed between said contact arms and said housing forcibly urging the ends of said arms opposite to their ends carrying said contacts in a direction to apply pressure of said movable contacts against said fixed contacts; and

second resilient means coaxially disposed with respect to said first resilient means and operably coupled between said housing and said slide member urging said slide member in a direction to relieve the contact pressure causing pivoting of said arms and contact separation in response to release of said latch assembly.

Claims

1. In a circuit breaker, a housing, a latch assembly enclosed in said housing, a thermal release assembly connected with said latch assembly for releasing it upon occurrence of an overload current, a switch assembly held in closed position by said latch assembly, said switch assembly comprising a member slidable along an axis, a guide member supported from said housing and slidably supporting said slidable member for movement along said axis, a pair of aRms pivotally mounted on said slidable member, a moving contact at one end of each arm, fixed contacts supported by said housing each engageable by one of said moving contacts, first resilient means between said contact arms and said housing urging the opposite ends of said arms in a direction to press said moving contacts against said fixed contacts when said latch assembly is in latching condition, and second resilient means between said housing and said slidable member acting on said slidable member in a direction to cause contact separation, when said latch assembly becomes unlatched.

2. The invention as defined in claim 1 wherein said first resilient means comprises a coiled compression spring engaging the housing, and a supporting member slidable relative to said slide member and engaged by said spring and engaging said opposite ends of said contact arms.

5. A circuit breaker as claimed in claim 1 having means fixedly supported relative to said housing, engageable by said contact arms in response to movement of said slidable member to effect contact separation at an exponential rate.

6. The invention as defined in claim 1 wherein the opposing inside wall surfaces of said housing includes aligned rounded members engageable by said contact arms in response to said movement of said slidable member to effect contact separation at an exponential rate.

10. In a circuit breaker having a housing comprising a pair of identical half sections enclosing a latch assembly, a thermal release assembly operably secured to said latch assembly for releasing said latch assembly and a switch assembly held in its closed position by said latch assembly wherein said switch assembly comprises: a slide member coaxially disposed with respect to said latch assembly and said thermal release assembly; a guide member fixed to said housing for slidably mounting said slide member for vertical movement thereon; a pair of contact arms pivotally connected to said slide member, each arm having a contact carried on one of its ends for selective engageable contact with a fixed contact secured to said housing; first resilient means disposed between said contact arms and said housing forcibly urging against the ends of said arms opposite to their ends carrying said contacts for applying contact pressure between said fixed and movable contacts; and second resilient means coaxially disposed with respect to said first resilient means and operably coupled between said housing and said slide member urging said slide member upwardly to relieve the contact pressure in response to release of said latch assembly.

11. The invention as defined in claim 10 wherein said first resilient means comprises a coiled, compressed spring operating between the housing and an insulating washer slidably carried on said slide member wherein the upper surface of said washer bears against said opposite ends of said contact arms.

12. The invention as defined in claim 11 wherein said opposite ends of said contact arms slideably bear against the top of said washer and the opposite end thereof being dispOsed for carrying said contact.

14. The invention as defined in claim 10 wherein the opposing inside wall surfaces of said housing pairs include aligned rounded members engageable by said contact arms in response to said movement of said slide member to effect contact separation at an exponential rate.

15. The invention as defined in claim 10 including a block carried on each of said housing opposing wall surfaces engageable with said slide member to limit movement thereof.

16. The invention as defined in claim 10 wherein said slide member includes a pair of outwardly extending projections and pivot connections coupling each of said contact arms at its mid-section to one of said projections.