US3155802A

US3155802A - U-shaped cradle for circuit breaker

Info

Publication number: US3155802A
Application number: US108812A
Authority: US
Inventors: Ernest R Wortmann
Original assignee: ITE Circuit Breaker Co
Current assignee: ITE Circuit Breaker Co
Priority date: 1961-05-09
Filing date: 1961-05-09
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03

Description

Nov. 3, 1964 E. R. WORTMANN 3,155,802

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9. 1961 6 Sheets-Sheet 1 IN VEN TOR. ae/v'sr f WO PT MW Nov. 3, 1964 I E. R. WORTMANN 3,155,302

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 2 CDCD' n l BY INVENTOR. h m 5v A. IK/OEr/ M/M Nov. 3, 1964 E. R. WORTMANN 3,155,302

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 5 I N V EN TOR. 501 552" 1?. zwer/v/i/v/v Nov. 3, 1964 E. R. WORTMANN U-SHAPED CRADLE FOR CIRCUIT BREAKER W I I M 6 Sheets-Sheet 4 l "1 n "E;

Filed May 9, 1961 Nov. 3, 1964 E. R. WORTMANN U-SHAPED CRADLE FOR CIRCUIT BREAKER 6 Sheets-Sheet 5 Filed May 9. 1961 Nov. 3, 1964 E. R. WORTMANN 3,155,802

U-SHAPED CRADLE FOR CIRCUIT BREAKER Filed May 9, 1961 6 Sheets-Sheet 6 INVENTOR. 4 ERA 5 7 WOffMflA W Affa/ewzw' United States Patent $355,362 FLT-SHAPED ClEADlLE BUR ClllQlJlli Ernest ll. Wortmann, Dreael il'ill, Pa, assignor to l-='ll=ll Circuit Breaker tlompan Philadelphia, Pin, a corp-w ration of Pennsylvania Filed May 9, 1961, Ser. No. 5,312 ll @lalms. (ill. fwd- 153) This invention relates to multi-phase molded case circuit breakers in general and more particularly to a novel construction for the contact operating mechanism thereof, including a U-shaped cradle the utilization of which achieves faster contact speed and enables greater contact separation for a given overall case size.

In multi-phase molded case circuit breakers it is customary to utilize a single contact operating mec ianism for all phases. Typically, a circuit breaker of this type is a three-phase unit in which the current carrying paths through the phases are identical and parallel to each other with the single operating mechanism positioned the center phase.

The contact operating mechanism usually comprises a latchable cradle mechanism for supporting a toggle linkage operatively connected to move the movable contacts into and out of engagement with the stationary contacts under the influence of the main operating springs. With the cradle unlatched the mechanisms cannot operate the toggle linkage so as to bring the contacts into engagement.

in previous designs the cradle was placed in the center plane of the mechanism between the toggle linkages and the operating springs. As larger contact travel was required in order to obtain greater contact separation, it became necessary to move the cradle pivot away from the area of contact motion or else shape the movable contact arm in such a manner as to clear the cradle bushing when the contacts were disengaged. Either prior art arrangement required increased overall mechanism height which is usually not available. It was thought that moving the cradle bushing would solve the problem. How ever, it was found that additional clearance for the operating springs was required when the cradle bushing was moved.

is a means of saving material and space circuit breaker designers have for years been striving to achieve more compact constructions. For the reasons outlined above, a limiting factor appea ed to be the cradle bushing.

The instant invention overcomes the dirficulty of the prior art by providing a latchable cradle constructed as a U-shaped member with the bushings therefor extending outwardly from the arms of the U. The toggle linkage and operating springs are placed between the arms of the U. Since the cradle bushing does not span the toggle linkage and spring area, the cradle bushing does not interfere with movement of the spring or contact linkage, so that greater contact travel and increased operating forces are possible within smaller space limits than was possible with prior art constructions.

Prior art constructions, in order to preserve symmetry,

required that an equal number of springs be positioned on each side of the cradle. Thus, at least two springs were required. With the utilization of a U-shapcd cradle, a single operating spring may be utilized, thereby reducing the number of parts and the number of handling operations required during assembly. Even when two springs are utilized they may be placed side by side in the center plane of the mechanism so that overall width may be maintained at a minimum. in prior art constructions the springs were on opposite sides of the center plane.

The circuit breaker construction to be hereinafter described includes means whereby contact travel is more rapid during an automatic tripping operation than in contact travel of prior art devices. In prior art devices, dur'ag the tripping operation the movable contact arm moved very little during the initial large movement of the cradle until such time as the knee of the toggle was moved over center. By this time the operating springs had eX pended most of their energy, so that movement of the contact arm thereafter for most of its travel was at a relatively slow speed.

In the device to be hereinafter described, the knee of the toggle rests against the cradle when the circuit breaker is closed. Upon automatic tripping the cradle and toggle move as a unit for a very short distance. Thereafter, a stationary surface is engaged by a rounded surface of one of the toggle links, driving the knee of the toggle over center very soon after movement of the cradle is initiated and while the operating springs are still heavily loaded. Thus, from this point on, movement of the contact arm is very rapid, resulting in improved interruption.

The construction to be hereinafter described is such that with the contacts fully separated after an automatic tripping operation, the rounded surface of the toggle, previously mentioned, is positioned extremely close to a stationary surface. If the movable contact tends to rebound, the rounded surface reengages the stationary surface, thereby limiting the rebound of the contact arm to a very short travel. Additional travel is strongly resisted by the operating spring. In addition, oscillations are very slight since the operating spring is very lightly loaded until the surfaces engage on rebound.

In prior art circuit breakers, as the contacts are brought into engagement the toggle linkage, as it is brought over center, has the movement thereof abruptly arrested by engagement with a surface positioned normal to its direction or" toggle travel. This places a great strain on the connecting pins of the toggle and cradle. in the device of this invention, upon circuit breaker closing, the knee of the toggle engages a surface of the cradle positioned at an incline with respect to the knee direction of travel. The sloping surface permits overtravel with the contact pressure spring absorbing excess energy.

Accordingly, a primary object of this invention is to provide a novel contact operating mechanism for a circuit breaker.

Another object is to provide a contact operating mechanism in which the cradle is a U-shaped member with the toggle linkage and operating springs placed between the arms of the U.

Still another object is to provide a novel circuit breaker mechanism for obtaining a large contact motion together with a high closing force.

A still further object of this invention is to provide a contact operating mechanism with novel means for reducing wear of the cradle and toggle linkage pins.

Another object is to provide an operating mechanism for a mult-i-phase circuit breaker which requires only a single operating spring.

These as well as other objects of this invention shall become readily apparent after reading the following escription of the accompanying drawings in which:

FIGURE 1 is a perspective of a circuit breaker constructed in accordance with the teachings of the instant invention. The cover of the circuit breaker is removed to reveal the internal mechanism thereof.

Fl -UB5 2 is a plan view of the circuit breaker in FIGURE 1 with the cover removed.

FEGURE 3 is a cross-section taken through the center phase of the circuit breaker through line 3-3 of FIG- URE 2 looking in the direction of arrows 3-3.

FXGURES 47 are side elevations of the contact operating mechanism with certain elements partially cut away. in PlGURE 4 the circuit breaker is in the closed position. in FIGURE 5 the circuit breaker, after having 'Operating member 45 straddles been in a closed position, is tripped and the upper toggle linkage has just engaged a stationary surface of the frame, which will rapidly force the knee of the toggle over center. open position. In FIGURE 7 the mechanism is in the manual open position.

FIGURE 8 is an exploded view of the contact operating mechanism.

Now referring to the figures; circuit breaker It? is provided with a molded insulating housing comprising base 11 and removable cover 12 joined along line I3. Circuit breaker It is a three-phase unit, so that base ill is divided into three parallel compartments by partitions Id, 15. Each of the parallel compartments houses the current carrying members for the respective phases.

Since each phase is comprised of identical-current carrying members, only the current carrying parts of the center phase will be described. These current carrying parts comprise load terminal connecter 16, load terminal 17, the looped extension 18 thereof extending through instantaneous trip magnet 19, through a portion 20 of terminal 17 having a reduced cross-section so as to serve as an indirect heater for bimetal time delay tripping element 21. The current path continues through conductor 22, flexible braid 23, movable contact arm 24, and movable contact 25 to stationary contact 26, which is mounted upon line terminal strap 27, having tulip line terminal connecter 28 mounted thereto by screw means 29.

The movable contacts 25 of all three phases are operated simultaneously into and out of engagement with their respective stationary contacts 26 by means of a single operating mechanism. 3% which is positioned in the center compartment. Each of the movable contact arms 24 is pivotally mounted at 31 to its individual U-shaped holder 32 between the arms thereof. Each holder 32 is provided with a portion 33 which defines a rectangular opening having insulating tie rod 3d disposed therein. Tie rod 34 extends through all three housing compartments so that the contact arm holders 32 of all three phases are mounted thereto. The outer phases are each provided with angle brackets 35 which provide support for bearing pins 3b to which holders 32 are pivotally mounted. It is clearly seen that movement of tie rod 34 brings about the simultaneous movement of all three contact arms 242-.

Leaf spring 37, fixedly mounted to holder 32 by rivet 3%, acts upon adjusting screw 39 to urge contact arm 24 in a counterclockwise direction with respect to FIG- URE 3 toward engagement withholder surface ill. As clearly shown in FIGURE 3, when

contacts

25, 26 are in engagement, contact arm 24 is spaced from holder surface 4b. In the outer two phases, screw means 41 secures load terminal member conductor 22 and bracket 35 to base lll, while in the center phase screw means 41 secures load terminal strap 17, conductor 22 and mechanism frame 42 to base llll.

Frame 42 is a somewhat U-shaped member having pins extending outwardly from the arms thereof. frame 42 with pins 44 being disposed within the open ended slots 43 at the lower end (with respect to FIGURE 1) of operating member 45. Manual operating handle 49 is mounted at the upper end of member 45 and includes a portion extending externally of housing as, I2 through aperture in cover 12. Spring 51, interposed between member 45 and handle 4.9 biases a portion ofhandle 49 against the inner surface of cover 12.

In FIGURE 6 the mechanism is in the tripped Intermediate latch member -56 is pivotally mounted Bar 55 is an insulating member extending across all three base compartments being pivotally mounted at the ends thereof to uprights 56. Tension spring 57 biases bar counterclockwise to latching position which is established through its engagement with adjusting screw threadably mounted to one of the uprights 56.

Operating mechanism also includes cradle dd, a toggle linkage comprising links 62, es, and operating spring means 64, 65. As best seen in FIGURE 2, cradle 6-3 is a generally U-shaped member whose web fill faces the load end of circuit breaker it when cradle 6t) is in latched position as in FIGURES 4 and 7. Cradle 69 is maintained in this position through the engagement of latch plate so, mounted to web er, with the web 67 of intermediate latch member 4-6, whose extension 53 is in engagement with latch plate 54, carried by tripper bar 55. Cradle titl is biased to its tripped position of FIGURE 6 by spring means 64, 65, as will become evident as this description proceeds.

Common tripper bar 55 is rotatable in a clockwise direction upon the occurrence of predetermined circuit conditions to release the cooperative engagement of

members

53, 54 and 66, e7. That is, upon the occurrence of a persisting fault the free end of bimetal 21 deflects to the right with adjusting screw 68 engaging tripper bar extension 69. Upon the occurrence of a severe overload, armature 70 will be attracted by magnet 19 with adjusting screw '71 moving to the left to engage tripper bar extension '72.

Pins 77 extending outwardly from the arms of cradle 6t pivotally mount cradle so to frame 42;

Toggle linkage

62, 63 as well as spring means 64, 65 are mounted between the arms of cradle 60. It is to be noted that each of the toggle links 62, 63 are split members.

Lower toggle link as is connected at one end to movable contact arm 24- at pin 31 while the other end is connected to pin 73 which forms the knee of

toggle linkage

62, 63. Upper toggle link 62 is connected at one end to pin 73 and at the other end is pivotally connected at '74 to cradle so. The upper ends of

springs

64, 65 are secured to operating member 45 while the lower ends of

springs

64, 65 are secured to plate '75 which is pivotally mounted to pin '73. Collars 76 position links 62, 63 axially on pin 73.

Springs

64, 65 are tension members so it is readily seen that they bias cradle 60 counterclockwise about pins 77, bias operating member 45 against pins 4-3, and

bias contacts

25, 26 both into and out of engagement depending upon the position of toggle knee 73.

Circuit breaker Ill is operated manually between the 0n (FIGURE 4) and Off (FIGURE 7) positions by means of handle 49. With circuit breaker lltl closed movement of handle 49 to the right with respect to FIG- URE 4 moves the upper end of springs 64, as to the right. .At such time as the force of

springs

64, 65 acts along the line positioned to the right of the line joining knee '73 and pivot 74, knee 73 will be drawn over center to the

rightand contacts

25, 26 will be operated to the disengaged position of FIGURE 7. It is to be noted that contact arm 24 has passed through a line extending between the cradle bushings formed by spaced pins 77 so that a large contact separation is obtained The open position of contact arm 24 is established by the engagement of holder projections 78 with cradle on near its pivot '77. e

In

operating contacts

25,26 into engagement toggle knee 73 moves rapidly to the left with respect to FIG- URE 7. ts movement must be arrested in a very short time interval. This is accomplished by having the ends of knee pin 73 engage cradle surface 85. It is to be noted that surface is positioned at a substantial incline, approximately 45, with respect to the direction of travel of pin 73 just prior to its stoppage. i Inclined surface 85 causes a downward component of force to be exerted on contact arm holder 32; with this component of force being absorbed by contact arm biasing spring 37; J

areasoa As circuit breaker 1d operates from the On position of FIGURE 4 to the tripped position of FIGURE 6,

cradle 66 and

toggle links

62, 63 move substantially as a unit clockwise about bushing '77 for a short distance during which the contacts remain engaged. Thereafter, as seen in FIGURE 5, the rounded cam surface 8t? engages the frame inward extension 81.

Cradle 6% continues counterclockwise carrying the pivot 74 for toggle link 62 to the left forcing toggle knee 73 rapidly to the right. Thus, for a relatively short cradle movement toggle knee 73 moves over center and an almost fully loaded spring means 64, 65 is then free to bring about rapid contact separation.

Not only does the engagement of surfaces 80, 81 serve to kick toggle knee 73 over center but it also serves as an anti-rebound means. That is, when circuit breaker 16 trips open, contact arm 24 tends to rebound closed from the tripped position of FIGURE 6. In doing so toggle 62, 63 must be extended soon bringing earn surface Eli) into engagement with frame 42 at 31. Continued movement of contact arm 24 toward closed position is strongly resisted by springs 64. 65 which in this position require strong forces for loading thereof.

Cradle 69 is returned to latched position through the engagement of operating member projection 83 which engages cradle 64! at 34.

Although there has been described preferred embodiments of this invention, many variations and modifications will now be evident to those skilled in the art and, therefore, the scope of this invention is to be limited not by the specific disclosure herein detailed, but only by the appended claims.

I claim:

1. In a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member; a pivotal mounting for said cradle, said mounting comprising individual pin means for each arm of the cradle, said pin means being axially aligned and spaced from each other, each of said pin means extending outboard of its respective arm; said contact arm movable in the region intermediate said arms and through the axis of said pin means when operating into and out of engagement.

2. In a circuit breaker, a pair of cooperating contacts and a mechanism for operatin said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member; a pivotal mounting for said cradle, said mounting comprising individual pin means for each arm of the cradle, said pin means being axially aligned and spaced from each other, each of said pin means extending outboard of its respective arm; said contact arm and said first means being positioned between the arms of the cradle; said contact arm movable in the region intermediate said arms, and through the axis of said pin means, when operating into and out of engagement.

3. In a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into-engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member pivotally mounted on pins extending outwardly of the U-arms; said contact arm and said first means being positioned between the U-arms; said first means comprising a toggle linkage with one end connected to said cradle and the other end connected to said contact arm; said contact arm movable in the region intermediate said arms and through the axis of said pin means when operating into and out of engagement.

4. In a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member pivotally mounted on pins extending outwardly of the U-arms; said contact arm and said first means being positioned between the U-arms; said first means comprising a toggle linkage with one end connected to said cradle and the other end connected to said contact arm; said spring means comprising a tensioning member secured at one end to the toggle knee and positioned between the U-arms.

5. In a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member pivotally mounted on pins extending outwardly of the U-arms; said contact arm being mounted to a stationary pivot and having a portion movable through a line extending between said pins as said contacts are operated into and out of engagement.

6. in a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member pivotally mounted on pins extending outwardly of the U-arms; said contact arm and said first means being positioned between the U-arms; said first means comprising a toggle linkage with one end connected to said cradle and the other end connected to said contact arm; said spring means comprising a tensioning member secured at one end to the toggle knee and positioned between the U-arms; said spring means comprising a first and a second coiled member positioned in a plane extending parallel to the plane of movement of said cradle and acting generally in the same direction.

7. In a circuit breaker, a pair of cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first rneans connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position, an operating spring means urging said cradle to a tripped position; said cradle comprising a U-shaped member pivotally mounted on pins extending outwardly of the U-urms; said contact arm and said first means comprising a toggle linkage with one end connected to said cradle and the other end connected to said "i 9 contact arm; said spring means comprising a tensioning member secured at one end to the toggle knee and positioned between the U-arms; said spring means comprising a first and a second coiled member positioned in a plane extending parallel to the plane of movement of said cradle and acting generally in the same direction; said coiled members each being centered between said U-arms.

8. In a circuit breaker, a pair or" cooperating contacts and a mechanism for operating said contacts into and out of engagement; said mechanism comprising a latchable cradle, a movable contact arm carrying one of said cooperating contacts, first means connecting said cradle and said contact arm in a manner such that said contacts cannot be operated into engagement unless said cradle is in a latched position; an operating spring means urging said cradle to a tripped position; said cradle being pivotally mounted at stationary bushing means and including a saeoa first and a second arm; said contact arm and said first means being positioned between said arms.

9. The circuit breaker as set forth in claim 8 in which the spring means comprises a tensioning member positioned between said arms.

10. "i" he circuit breaker as set forth in claim 9 in which the bushing means is comprised of pins extending outboard of said first and said second arms.

11. The circuit breaker as set forth in claim 10 in which the contact arm is mounted to a stationary pivot and includes a portion movable through a line extending between said pins as said contacts are operated into and out of engagement.

References Cited in the file of this patent Urnrnn STATES PATIENTS 2,829,219 Christensen Apr. 1, 1958

Claims

1. IN A CIRCUIT BREAKER, A PAIR OF COOPERATING CONTACTS AND A MECHANISM FOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISM COMPRISING A LATCHABLE CRADLE, A MOVABLE CONTACT ARM CARRYING ONE OF SAID COOPERATING CONTACTS, FIRST MEANS CONNECTING SAID CRADLE AND SAID CONTACT ARM IN A MANNER SUCH THAT SAID CONTACTS CANNOT BE OPERATED INTO ENGAGEMENT UNLESS SAID CRADLE IS IN A LATCHED POSITION, AN OPERATING SPRING MEANS URGING SAID CRADLE TO A TRIPPED POSITION; SAID CRADLE COMPRISING A U-SHAPED MEMBER; A PIVOTAL MOUNTING FOR SAID CRADLE, SAID MOUNTING COMPRISING INDIVIDUAL PIN MEANS FOR EACH ARM OF THE CRADLE, SAID PIN MEANS BEING AXIALLY ALIGNED AND SPACED FROM EACH OTHER, EACH OF SAID PIN MEANS EXTENDING OUTBOARD OF ITS RESPECTIVE ARM; SAID CONTACT ARM