US3002068A - Circuit breakers - Google Patents

Description

FIG. I

INVENTOR ALFRED E. MAIER AT TORNEY 3,002,068 g i V V CIRCUIT BREAKERS Alfred E. Maier, Colonia, N ..I., assignor to Federal Pacific Electric Company, a corporation of Delaware 7 Filed Aug. 4, 1960, Ser. No. 47,435 8 Claims. (Cl. 200-88) The present invention relates to electric switching apparatus, more particularly to manually operated circuit breakers having an over-centering toggle for operating the moving contact assembly and an over-current release arrangement for controlling the toggle.

Circuit breakers of this type have been known and used for several decades. To increase the current-carrying capacity it is understood that the sizeand strength ther, a single operating mechanism is commonly employed to operate multipole circuit breakers. The moving contacts are on a common shaft and (due to minor misalignment) one moving contact may engage its companion stationary contact slightly ahead of the movable contacts in the other poles. 'The overtravel spring in each pole takes up any such disparity and insures contact pressure in each pole. Arcing at the contacts may also cause dimensional changes by erosion of the contacts. The overtravel spring accommodates such contact dimensional variations.

The contacts initially come into engagement. before the toggle over-centers, and the over-centering operation builds up stress in the overtravel spring. If higher operating currents dictate a substantial increase in contact pressure, a correspondingly stronger contact-overtravel spring is required and correspondingly increased strength of the over-centering spring is needed.

In a toggle mechanism, the use of heavier or stronger springs tend to impose heavier bearing stresses and to create greater amounts of friction at the joints of the toggle, which increases still further the required strength of over-centering toggle-operating spring. Increased bearing friction also reduces the sensitivity of the toggle as it approaches and reaches dead-center in the contact-closing direction.

' 'In a common type of mechanism the over-centering springs are connected between the knee of the toggle and the operating handle. Over-centering of the toggle is insured despite bearing friction and heavy overtravel springs by driving the handle ends of the over-centering springs beyond dead-center relative to the toggle United StatesPateht O links. For overcoming both a stronger over-travel spring and an increase in friction at the toggle bearings, the handle would ordinarily have to be operated considerably beyond that corresponding to dead-center position of the toggle. the handle, and greater elongation of the springs.

This involves a longer operating stroke for The fact that the springs must be elongated farther than would be the case with only a nominal amount of bearing friction and only a minimum strength of contact over-travel springs tends to limit the maximum stiflness of the springsthat can be used with the usual mechice more powerful mechanism that acts with a clean-cut snap when the toggle is over-centered.

It is accordingly an object of the present invention to improve over-center spring mechanisms in order to enable springs of increased stifiness to be used.

Mere increase in the strength of springs used might be achieved with larger springs. Space limitations may prevent this. In the novel embodiment of this invention detailed below, increased spring strength is realized 7 without resort to over-size springs by reducing the ex tent of elongation required, thereby making possible the ueof relatively small springs of such stiffness that their elastic limit might well be exceeded if the usual clongation were needed.

A feature of this invention resides in provision of a novel mechanism that minimizes the required elongation of the over-centering springs when the mechanism ,is'operated in the contact-closing direction.

More particularly it is an object of this invention to improve over-centering spring-and-toggle circuit breaker mechanisms by reducing the required spring elongation in its contact-closing operation, without however reducing the desired extent of collapse of the toggle in contact-opening operations and without interfering with the resulting operation of the circuit breaker by the 0pf crating handle, and without disturbing the trip-free" contact-opening operation of the toggle is increased by an increase in the required handle travel beyond deadccnter" in the on direction. Accordingly another object of the invention is to improve circuit breakers having overtravel spring mechanisms by minimizing the required over-center travel of the operating handle.

Excessive elongation of the over-center spring has the further effect of unduly increasing the required manual operating efiort. It also increases the length of slot provided in the circuit breaker cover for the operating handle, a change thatvis undesirable for many reasons.

Accordingly, it is a broad object of the present invention to improve circuit breakers having over-center spring mechanisms with a view to minimizing the foregoing limitations resulting from the use of springs of increased stiffness. This and other objects of the invention are accomplished in the illustrative circuit breaker described below as an embodiment of the invention in its various aspects. The illustrative circuit breaker includes a positive drive coupling between the operating lever and the knee of the toggle, arranged for mechanically driving the collapsed toggle in the contact-closing direction part-way toward its dead-center condition. More particularly, a bail is pivoted to the manual operating lever and is guided to engage and drive the knee of the toggle in the operating on" stroke of the manual operating lever for picking up and driving the toggle part-way to the dead-centered configuration. During this positive drive, the burden on the operating springs is held to a minimum. Moreover, since the knee of the toggle is shifted toward the deadcenter configuration, the degree of over-centering and elongation of the springs required to induce over-centering of the toggle and snap-action closing of the contacts is minimized, and stifler springs can be used Without increase in space requirements. Still further, by minimizing the extent of over-centering of the springs in relation to the Patented Sept. 26, 1961 K 3 toggle during a contact closing operation, the reverse operation of the circuit breaker is improved for both manual opening and for automatic overload release of the circuit breaker. High contact pressure and powerful contact opening bias become available through the use of stiffer springs without, however, the attendant disadvantages heretofore described.

The nature of the invention in its various aspects and further objects and features of novelty will be better appreciated from the more detailed description of the illustrative embodiment below, in which reference is made to the accompanying drawings. In those drawings:

FIG. 1 is a side view of a circuit breaker embodying the invention shown in the open configuration of its operating mechanism with portions being broken away and others shown in section for purposes of clarity;

FIG. 2 is a fragmentary view similar to FIG. l showing the operating mechanism in the configuration it assumes just prior to snap-closing of the contacts, the relative position of the contact arm also being shown in broken lines in the open configuration of FIG. 1;

FIG. 3 is a detail view of the closed contacts and the moving contact support viewed as in FIGS. 1 and 2; and

FIG. 4 is a fragmentary cross-section of the operating mechanism viewed from the line 4-4 in FIG. 1.

-Referring to the drawings, the circuit breaker mech anism is enclosed in a molded case including a cover and a base 12. A circuit through the circuit breaker '(when it is closed) extends from one terminal 14 to the stationary contact 16, thence to movable contact 18, along conductive flexible braid and metal bar 22 to the opposite terminal 24. Movable contact arm 26 which carries contact 18 is carried by pivot 44 in contact arm carrier 28, and biased by compression springs 29 in the direction to build up contact pressure when the contacts are closed (FIG. 3). Where the contacts are open, the swing of contact arm 26 is enforced by spring 29 and is limited by engagement of portion 26a of the contact arm with the bottom edge 28a of the channel-shaped contact arm carrier 28. Contact arm carrier 28 is afiixed to the insulated shaft 30 the ends of which are pivoted in corresponding bearing portions of the molded base 12. Plural contact arm carriers 28, with respective contact arms 26, are mounted on the aforesaid shaft for coordinated operation of the contacts of a multi-pole circuit breaker.

An over-centering spring mechanism is provided for operating the contacts between the closed and open positions and for effecting automatic release and opening of the contacts in response to an overload. The operating mechanism includes a manual operating lever 32 and handle 33. Lever 32 is pivoted at its lower extremity in a fitted frame 34. An overload release member or cradle 36 has a pivot 33 fixed in the frame 34. A pair of toggle links 40 and 41 are pivotally connected to each other at knee 42. These toggle links have a top pivot 43 and a bottom 44 pivot in members 36 and 28. Where there are plural contact carriers 28, for a corresponding number of poles, there is here (as is usual) only a single operating mechanism for all of the contacts operated by square shaft 30. Two pairs of springs 45 extend between manual lever 32 and the knee 42of the toggle although only one pair is visible in FIGS. 1 and 2.

The right hand extremity of cradle 36 is normally restrained by a latch roller 46 carried by a common trip bar 48 that extends across all of the poles (where there are plural poles). A spring lever 49 biased upwardly by spring 50 and counterclockwise about its pivot is normally restrained by a combined ambient temperature compensating bimetal and latch 52 which has a stationary pivot near its lower end. A current responsive bimetal 54, adapted to be heated by flow of current through bar 22, is arranged to flex upward when heated. The upward deflection of bimetal 54 pivots latch 52 clockwise in a direction to release spring lever 49, thus operating trip bar 48 and latch roller 46 so as to release cradle as when over-current conditions heat bimetal 54 sufficiently. A magnetic tripping arrangement, including pole structure 56 and armature 58, is also arranged to drive latch 52 clockwise in the releasing direction, this magnetic arrangement operating in response to instantaneous severe overload currents. The right-hand extremity of armature 58 underlies a portion of latch 52, as shown, and spring 59 biases the armature counterclockwise about its pivot.

The circuit breaker is illustrated in FIG. 1 in its open condition, with cradle 36 latched so that the mechanism is in condition for driving the contacts closed when operated. This is accomplished by moving manual lever 32 to the left in the drawings. The upper ends of tension springs 45 are correspondingly shifted to the left, and when the resulting spring tension through knee 42 is shifted so as to act along the line to the left of the upper pivot 43 of the toggle in cradle 36, the knee is biased to the left and tends to straighten the toggle. This occurs with a snap-action, and suddenly drives the contact carrier .28 in the closingdirection driving movable contact 18 against the stationary contact to and increasing the stress in overtravel spring or springs 29 (in the case of multiple poles). 4

When the contacts have been closed in this manner, the line of upward thrust through knee 2 passes to the left of the upper toggle pivot 43 in cradle 36. In the event of an over-current, cradle 36 is released for counterclockwise swing about pivot 38, and the upper toggle pivot 43 shifts to the left and across the resultant line of action of the springs 45. When this takes place, the tensioned overcenter springs 45 are free to cause sudden collapse of the toggle and correspondingly, to lift the various contact oarriers 28 as a unit from their closed position. I

The action of' the toggle mechanism, including the toggle links and the over-centering spring arrangement, which should be firm and quick-acting, is dependent upon the various masses involved and is also dependent upon the strength of the springs. For circuit breakers rated for large currents, firm contact pressure and relatively large contacts are needed, and strong over-center springs are desirable. This produces a tendency toward significant and potentially troublesome friction at knee 42 as well as at the upper pivot 43 of the toggle. In order to overcome this friction, it might be possible to provide increased room for handle 33 and manual lever 32 to move further to the left in the on position in order to increase the extent of over-centering of the springs beyond the line between knee 42 and upper pivot 43 of the toggle. Where the space for such additional movement is limited the gain is marginal and there is danger that the mechanism will not become over-centered and that therefore the contacts 16, 18' will remain open. However, even if such provision is made, there is still considerable danger of permanently deforming the springs 45 due to the increased elongation caused by the longer stroke of the handle 33 while the knee 42 of the toggle remains close to its original position as illustrated in FIG. 1. The additional stretch of the springs 45 could of course be accommodated without damage to the springs by employing springs that are relatively soft and therefore readily capable of considerable elongation without permanent deformation. However, this would defeat efforts to increase the circuit breaker rating and accordingly it is important that the strongest springs practicable be used.

The foregoing mechanism is greatly improved through the provision of a bail 60 pivoted at its extremities to manual lever 32. The bail shown is generally U-shaped member having a bight portion formed to engage the knee 42 of the toggle during part of the toggle erecting motion of lever 32. A pair of guide projections 62 extend, integrally, from fixed frame 34, and limit the clockwise motion of the bail. While gravity normal-1y maintains ball 60 in engagement with guide projections 62, the bail is also effective even if the breaker were mounted unnaturally in inverted position, since, when the manual lever spogoas 3b. is operated the bail is still constrained against the toggle close to the knee by close spacing between the cradle. and the bight of bail 60. v

. When handle 33 of the circuit breaker is moved toward the left in the contact-closing direction, bail 60 is operated by lever 32 in the direction to drive the toggle knee 42 in the toggle erecting or straightening direction. At the same time, the line of action of the overcenter springs 45 shifts down with a snap, forcing the movable contacts 18 against the fixed contacts 16. Over'centering movements of links 40and 41 carry the toggle away from bad 60. The extent ofover-centering of the mechanism is limited by engagement of the toggle knee 42 with the portion of treleasable member 36 adjacent to its pivot 38. It is relatively easier toovercome the friction of the toggle pivots in erecting the toggle from the configuration in FIG. 3 than from that shown in FIG. 1. For this reason the snap operation ofthe toggle, for closing of the contacts, occurs when the line of action of the springs 45 has traveled only a short distance beyond dead-center. ;,,Were bail 60 omitted, it wouldbe necessary ,for the handle to move considerably farther to the left in order to reach and then insure over-centering of the toggle links fromtheir position illustrated in FIG. 1. This in turn would require substantially greater elongation of the springs and thereby impose a limitation on the stiffness of the springs which could be used. Softer springs, it will be appreciated, tend to reduce the available contact pressure that can be built up at the contacts, when closed, and to reduce the speed of opening of the contacts. Soft springs limit the mass of the moving contact structure that can be. operated with the quick motion that is especially desirable in the opening direction for effective current interruption.

Where the end position of handle 33 is achieved with only a minimum of over-travel beyond dead-center, it becomes possible to utilize only a minimum of counterclockwise swing of cradle 36 for shifting the upper pivot 43 of the toggle to the left (in the toggle collapsing direction) Consequently, a greater speed of response of the overload-release mechanism may be expected than in the case where bail 60 is omitted and a longer overcentering travel of the handle is involved.

Cradle 36 is shifted counter-clockwise about its pivot when released by operation of the trip mechanism, due to the action of tension springs 45 in urging the entire toggle upward. With the improvement afforded by bail 60, it is feasible to minimize the swing of cradle 36 in an overload-release operation. This means that most of the stored energy in the springs 45 is conserved for lifting the contact carrier 28 quickly and thus driving the contacts 16 and 18 apart. It is important to conserve the spring effort available for opening the contacts in View of appreciable increases in mass of contacts 18, contact arms 26, and braid 20 that may be occasioned by higher current ratings. g

The circuit breaker is trip-free, in that the mechanism is entirely free to open the circuit even if the handle 33 should be operated and then held in the closed position while over-current-release takes place. Notably, the addition of bail 60 does not in any way interfere with the opening operation of the breaker, either naturally or under overload release conditions. When the breaker is opened unnaturally, it is evident that lever 32 shifts bail 60 out of position in which it might obstruct collapsing motions of the toggle. When handle 33 is naturally held on during an automatic overload release operation, bail 6 60 does not interfere with the contact-opening operation of the contacts. This is because the principal motion of the toggle links is bodily upward and there is only a limited movement of the toggle links toward bail 60 while cradle 36 remains in its released condition and the handle is in its on position. When the handle is returned to off and therebeyond to reset position, the toggle merely approaches bail 60 as it resumes the configuration of FIG. 1. g

In FIG. 2 the position of contact arm 26 in solid lines represents the condition of the contact arm just prior of I open position of the contact arm (as in FIG. 1).

the over-centering of the springs in relation to the upper toggle link 40, and the dotted lines represent the fully In practice this is of no concern, and satisfactory operation of the apparatus is not impaired, since the gap between contacts 16 and 18 is ample until the actual snap-closing operation occurs.

Description of certain portions of the illustrative mechanism have been omitted, deliberately excluding details which might conceiveably be of interest, in as much as those details are apparently unnecessary to an understanding of the present invention. For example, the overcurrent release mechanism illustrated is more fully described in copending application S.N. 852,013, filed November 10, 1959, assigned to the assignee hereof. I

The nature of the invention and various adaptations and modifications will be readily appreciated by those skilled in that art in view of the foregoing description of the illustrative embodiment; and it is therefore appropriate that the invention should be broadly construed in accordance with its full spirit and scope. What is claimed is:

1. Switching apparatus including companion contacts, a movable contact member carrying one of said contacts, a pair of toggle links pivoted to each other at a knee and including one link pivoted to said movable contact member for effecting operation thereof, amanual operating member movable between open and closed" positions, a spring connected to the knee of the toggle and arranged to be overcentered relative to the other spring mechanism connected to said mova'ble contact member, said mechanism including an operating member 'movable between open and closed positions, a spring operable overcenter by said operating member for biasing the contacts open and closed correspondingly, and a part operable by said manual operating member in positive driving relation to the remainder of said overcentering mechanism during only an initial portion of the movement of the operating member from open toward closed position thereof.

3. A circuit breaker including companion contacts, a movable contact member carrying one of said contacts, a pair of toggle links for operating said movable contact member, a releasable member and over-current releasing means normally effective to latch said releasable member, an operating member movable between open and closed positions, a spring connected to the knee of the toggle and to said operating member, respectively, the extremities of said toggle being pivoted to said releasable member and to said movable contact member respectively, and a bail pivoted to the operating member and having a bigh't portion formed to engage the knee of the toggle in the toggle erecting direction during only a portion of the closing operation of the operating member.

4. A circuit breaker including companion contacts, a

movable. contact member carrying one of said contacts, a pair of toggle links for operating said movable contact member, a releasable member and over-current releasing means normally effective to latch said releasable member, an operating member movable between open and closed positions, a spring connected to the knee of the toggle and to said operating member, respectively, the extremities of said toggle being pivoted to said releasable member and to said movable contact member respectively, and a bail pivoted to the operating member and a bight portion formed to engage the knee of the toggle in the toggle erecting direction during only a portion of the closing operation of the operating member, said releasable member in its latched condition being disposed adjacent said bail so as to guide the latter toward the toggle knee.

5. A circuit breaker including companion contacts, a movable contact member carrying one of said contacts, a pair of toggle links for operating said movable contact member, a releasable member and over-current releasing means normally effective to latch said releasable member, an operating member movable between open and closed positions, a spring connected to the knee of the toggle and to said operating member, respectively, the extremities of said toggle being pivoted to said releasable member and to said movable contact member respectively, and positive drive means mounted on said operating member and engageable with the toggle in driving relation thereto during only part of the movement of the operating member from open toward closed position thereof for operating the toggle links from their collapsed position toward an erected position.

6. A circuit breaker including companion contacts one of which is afiixed to a movable contact member, a pair of toggle links for operating said movable contact member, a fixed frame, a releasable member pivotally mounted on said fixed frame and over-current releasing means normally effective to latch said releasable member, an op erating member pivotally mounted on said fixed frame for movement between open and closed positions, a spring connected to the knee of the toggle and to said operating member, respectively, the extremities of said toggle being pivoted to said releasable member and to said movable contact member respectively, a bail pivoted to said operating member and engageable with the toggle in driving a relation thereto during movement of the operating 111cmher from open to closed position thereof for operat ing the toggle links from their collapsed condition toward an erected position, and means mounted on said fixed frame for guiding said bail into engagement with said toggle.

7. A circuit breaker including a releasable member, over-current control means normally effective to latch said releasable member, a pivoted contact arm, a pair of toggle links pivoted to each other at a knee and pivoted respectively to said releasable member and to said movable contact member, a manual operating member movable between an open and a closed position, a tension spring between said toggle knee and said manual operating member said spring being arranged to act substantially along the line passing through the knee of the toggle and the pivot point of the toggle and releasable member, nd positive drive means mounted on said operating lever for contacting said toggle mechanism adjacent said knee and assisting said toggle in the erecting direction only to a partially erected position upon operation of said manual operating member from said open to said closed position, said positive drive means functioning only prior to said spring passing over the aforesaid line.

8. In a circuit breaker having over-current control means the combination comprising, a fixed contact, a movable contact, a pivoted contact carrier supporting the movable contact for cooperation with said fixed contact, a releasable member normally latched in position by said over-current control means, a pair of toggle links pivoted to each other at a knee and pivoted respectively to said releasable member and said contact carrier, a manual operating member movable from an open to a closed" position, a tension spring between said toggle knee and said manual operating member, said spring adapted to move said knee over-center of the line between the other pivot points of the toggle from a position closely adjacent thereto, positive drive means mounted on said manual operating member for delivering aid knee to said position adjacent said line only when said operating member is moved from said open position toward said closed" position to erect said toggle.

No references cited.

Disclaimer 3,002,068.--rilf1ed E. Maz'ew, Colonial, N .J CIRCUIT BREAKERS. Patent dated Sept. 26, 1961. Disclaimer filed Dec. 12, 1962, by the assignee, Federal :Pacz'fia Electm'c Company. Hereby enters this disclaimer to claims 1 and '2 of said patent.

[Ofiicial Gazette J anuamy 22, 1963.]

Disclaimer 3,002,068.rilfred E. Maz'ev', OOIOIliZL, N .J CIRCUIT BREAKERS. Patent dated flSept. 26, 1961. Disclaimer filed Dec. 12, 19612, by the assignee, Fecleml Pacific Electric Company. Hereby enters this disclaimer to claims 1 and 2 of said patent.

[Ofiicz'al Gazette J (mm/my 252, 1.963.]

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