US2590523A - Circuit interrupter contact pressure increasing device - Google Patents

Description

March 25, 1952 A w EDWARDS 2,590,523

CIRCUI INTERRUPTER CONTACT PRESSURE INCREASING DEVICE Filed 001. l1, 1947 IE6 g "E /04 /oa wlTNEssES: INVENTOR ndrewh/adwrds.

5% 7%/ Q .7. w @672W ATTORNEY Patented Mar. 25, 1952 CIRCUIT INTERRUPTER CONTACT PRES- SURE INCREASING DEVICE Andrew W. Edwards, Pittsburgh, Pa., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 11, 1947, Serial No. 779,277l

(Cl. D-87) 14 Claims.

This invention relates generally to electric circuit interrupters and more particularly to such low as possible in order to limit the size of the l electrical contact opening device. One example of such a device is an automatic reclosing circuit breaker having a series coil to separate the breaker contacts against a closing bias. Inasmuch as the energy required to open the contacts of such a circuit breaker is directly proportional to the contact pressure, the high contact pressures required to prevent opening of the contacts due to the magnetic forces encountered on short circuit conditions, require an undesirably large size of operating coil.

One object of this invention, therefore, is to provide in a circuit interrupter, means for automatically increasing the contact pressure in response to increases in current carried by the contacts, while at the same time not imposing any appreciable increase in the amount of force required to Separate the contacts.

Another object of this invention is to provide in a circuit interrupter, novel means providing sucient pressure on the contacts to prevent them from opening due to the magnetic forces present under short circuit conditions while at the same time permitting separation of said contacts by a much lesser force.

Another object of this invention is to provide in a circuit interrupter having current responsive magnetic means for separating the interrupter contacts, novel means causing the magnetic means to increase contact pressure on overloads and to remove such increased pressure at least when said magnetic means eiects actual contact separation.

These and other objects of this invention will become more apparent upon consideration of the following detailed description of the preferred embodiments thereof, when taken in connection with the attached drawing, in which:

Figure l is a substantially central vertical section View of a circuit breaker embodying this invention; and

Fig. 2 is also a substantially central vertical section view of a part of a circuit breaker like that shown in Fig. 1, but illustrating another embodiment of the invention.

This invention is illustrated on the drawing as being embodied in one formvof automatic reclosing circuit breaker, with the particular breaker herein illustrated being more particularly described and claimed in the copending applications of J. M. Wallace et al., Serial No. 719,524, led December 31, 1946, on Circuit Interrupters; J. M. Wallace et al., Serial No. 719,572, filed December 2l, 1946, on Circuit Interrupters; and J. M. Wallace et al., Serial No. 718,942, led December 28, 1946, on Circuit Interrupters, and issued November 20, 1951 as Patent No. 2,575,738; all of which are assigned to the same assignee as this invention. This circuit breaker is mounted in a metal tank 2 having a closed bottom wall and an open top and adapted to be lled with a liquid up to the level L, preferably an arc extinguishing liquid such as oil or the like. Preferably, the tank is lined at least over the bottom wall and up to a point adjacent the open top of the container with a liner 3 of insulating material such as ber, or the like. The upper end of tank 2 is provided with an outwardly extending flange 4 on which the flange 8 of a cover casting 6 is adapted to be seated, preferably, with a gasket l0 interposed therebetween. Flange 8 of cover casting 6 may be provided with an integral lip l2, and the cover may be secured to the tank in any desired manner, such for example as by bolts (not shown) extending through openings in cover iiange 8 and secured to suitably formed brackets on the tank.

The breaker contacts, arc extinguishing structure and the contact actuating mechanism are all adapted to be supported in tank 2 from cover casting 6 by means of a pair of integral supporting lugs l5 (only one of which is shown) depending from the top wall of the cover casting and adapted to engage spacer sleeves I8 of insulating material suitably secured to supporting lugs i6 and to a supporting casting 20. A supporting plate 22 may be supported from casting 2i), so that a solenoid coil 24 may be mounted between casting 2D and supporting plate 22, with the central opening in the coil aligned with openings provided in casting 2D and plate 22. Supporting casting 29 and supporting plate 22, together with the bolts (not shown) securing them together are of a magnetic material, such as iron or the like, to complete a magnetic circuit of low reluctance outside of solenoid coil 24, which terminates at opposite ends o-f the central opening through the coil in which the Working air gap of the coil is located.

Spaced stationary contacts 26 oi the breaker are each supported from plate 22 by a support 28 of insulating material, such as ber, formed of inverted U-shape, with the stationary contacts being mounted in openings provided in the base portions 30 of each support 28, and with the upper ends of each support 28 having laterally extending langes 32 by means of which each support is secured to supporting plate 22. As illustrated, each contact 26 is formed as the head of a bolt ESS to which a conductor may be secured, as by the nuts 34.

Stationary contacts 26 are adapted to be closed by engagement therewith o a bridging contact 36 having contact tips 38 at opposite ends thereof for engagement with the stationary contacts, respectively. Bridging contact 35 is supported substantially centrally thereof on a slidable contact actuating rod 44 by a pivot pin 40 for limited pivotal movement about a transverse axis. Contact rod 44 being mounted for longitudinal sliding movement through coil 24 and aligned openings in plate 22 and casting 2li, it will be observed that bridging contact 35 is ree to adjust itself to the stationary contacts by restricted pivotal movement about its pivotal mounting 4,0. Contact rod 44 should be of an insulating material such asfiber or a molded insulating material.

The supports 28 for stationary contacts 25v form arc extinguishing means for the arcs drawn between the ends of the bridging contacts 35 and stationary contact 25, respectively, when the bridging contact is moved upwardly to open the circuit.

' The upper end of contact actuating rod 44 has connecting links 45 pivoted thereon as by a pivot pin 48, with the upper ends of these connecting links mounted on a common pivot pin 50 for a pairl of toggle levers 52 and 54. Toggle levers 52 and 5,4 are both formed of sheet material,l with lever 54 being bent to substantially channel form with outwardly extending flanges 5,5 adapted to be received at the free ends thereof in recesses 58 provided in the spaced downwardly depending fingers of an angled supporting bracket i) which, in turn, is secured as by a screw 64 to a lug 62 integral with'the cover casting. YA coil tension spring 63 has one end hooked into` an opening provided in toggle lever 52, and has the opposite end thereof hooked over an integral spring support on the cover casting. Toggle lever 52 has an integral hook portion 55 passing through an opening in lever 54 to limit separation of the levers.

It will be observed that in the closed circuit position of the breaker illustrated on the drawing, the line of action of toggle spring 63 is below the pivot supporting recesses 58 for toggle lever 54, and accordingly, the toggle spring acts to bias bridging contact 36 into engagement with stationary contacts 25 of the breaker, under a predetermined pressure. However, as soon as contact operating rod 44 moves upwardly to separateA the bridging contact from the xed contacts of theA breaker, toggle lever 54 will pivot about recesses 58 and the line of action of toggle spring 58 Will thus be caused to approach that pivot point so that in response to a very small contact separation the line of action of toggle spring 58 will pass through pivot recesses 58 which is the on-center position of the resilient toggle arrangement comprising toggle levers 52 and 54 and toggle spring 68. As a practical matter, the opening movement of the contacts necessary to move toggle levers 52 and 54 to the on-center position mentioned above may be made very small, in one actual device being on the order of one-quarter of an inch. When toggle levers spring 68.

52 and 54 reach their on-center position referred to above, further relative movement of the two toggle levers in the same direction is prevented because the upper edge of toggle lever 52 engages the base of the central channel formation oi toggle lever' 54. Moreover, since the point at which toggle spring 68 is hooked into lever 52 then substantially coincides with recesses 58 in which toggle lever 54 pivots during contact opening movement, it will be apparent that the remainder and major part of contact opening movement will occur substantially uninfluenced by toggle spring 68.

Substantially the reverse o1 the above operation occurs when contact operating rod 44 moves downwardly to close the circuit from the full open contact position, because during the nrst and major part of contact closing movement, levers 52 and 54 will be in engagement so that such movement will be uniniiuenced by toggle However, as soon as pivot 5U passes below a line drawn from the remote end of toggle spring 68 through pivot recesses 58 for link 54, toggle spring 63 will then be effective to move the toggle levers .toward the full line position shown in Fig. l, and the force exerted by toggle spring 6B thus tending to close the contacts will continue to increase as toggle levers 52 and 54 move further away from their on-center positions.

Solenoid coil 24 previously mentioned is adapted to be energized under certain conditions for automatically opening the circuit breaker` contacts. The central opening through coil 24 preferably is provided with a cylindrical sleeve 'i4 in which a solenoid core 'l5 is adapted to be slidably mounted in a piston-like manner. Core i6 is in the form of a cylindrical sleeve having opposed slots 18 in the upper portions thereof adapted in the normal closed circuit position of the device illustrated in Fig. l to extend partly abovev and partly below supporting plate 22, by engagement of an exterior shoulder 83 adjacent the upper end of the core with a sleeve 8B which has an external rib 85 held between the sleeve 'I4 for the coil and supporting plate 22. rlhe lower end of core 'i6 is provided with opposed openings 8|, for a purpose to be hereinafter clescribed,

A contact actuating sleeve 82 is telescoped over contact actuating rod 44 and its lower end is received in core 'i6 preferably being threadably mounted therein. A coil compression spring 86 is provided within actuating sleeve 82 on contact actuating rod 44 and it is adapted to react between core 'i6 and a pin 88 extending transversely through actuating rod 44.

The circuit through the circuit breaker thus far described may nowbe traced from the points where it enters tank '2 through one of a pair of terminal bushings 90 (only one being shown), with each bushing being secured to cover casting 5 as by bolts 94, and each being provided with a conductor element which extends through the bushing and emerges from a reduced extension illv of the bushing seated in an openingv provided in the top Wall of cover casting 6. The circuit proceeds by conductor 98 directly to one fixed contact 26 of the breaker. When the contacts are in engagement, the circuit then proceeds through bridging contact 38 to the other fixed contact 26, and then by Way of a conductor |00 to one terminal of solenoid coil y24. The other terminal of coil 24 is adapted to be connected by a conductor |02 to the conducting means in the other terminal bushing 90. It will be apparent that solenoid coil 24 is connected in series in the circuit through the circuit breaker so as to be energized at all times an amount dependent upon the value of the load current flowing in the circuit..

For any given rating of circuit breaker, solenoid coil 24 is designed to become suiciently energized when the load current in the circuit eX- -ceeds its rating as to attract core 16 and move it upwardly within sleeve '|4. Assuming the upper end of sleeve 14 to be closed so fluid cannot escape, core I6 will move upwardly relatively rapidly until the bottom of slots 18' reaches sleeve 80, whereupon there is no longer any vent for fluid contained in cylindrical sleeve 14, and it then becomes necessary upon further upward movement of core 16 to displace the liquid in sleeve '|4 above the core through the relatively small clearance between the core and sleeves '|4 and 82. Accordingly, opening movement of the core will be slowed up by the aforesaid dashpot action an amount determined by the current value of the overload, and, therefore, an inverse time-current characteristic on opening is 0btained. Finally, when openings 8| clear the upper edge of sleeve 80, the space within sleeve 'I4 is freely vented through openings 8| to the bottom of core 16, so that core 16 will no longer be restrained by the dashpot action, and the nal opening movement thereof may be relatively rapid. As soon as core 'I6 commences its upward travel, bridging contact 36 being held engaged by toggle spring 68 does not move, so that spring 86 is compressed until the energy stored in spring 86 is sufiicient to overcome the wardly. As soon as actuating rod 44 moves upwardly, the force exerted by toggle spring 68 begins to decrease and in a very short distance has substantially no value at all, so that the remaining major part of the circuit opening movement of bridging contact 36 occurs extremely rapidly due to expansion of spring 86. Flange 89 is provided on rod 44 to obtain a positive contact separation in the event there is any sticking or welding of the bridging contact to stationary contacts 26, by engagement therewith of a shouldered sleeve 83 mounted in the upper end of actuating sleeve 82. In either case, it is apparent that toggle levers 52 and 54 will be moved to their on-center position in the manner previously described, and bridging contact 36 will be moved by spring 86 to its full open circuit position.

When the breaker contacts have attained their full open circuit position, the parts associated therewith are biased to return by gravity. This closing bias is relatively light and will be opposed by the dashpot action of core 16. Accordingly, the return movement will be relatively slow until pivot point 50 moves below the line of action of toggle spring 68 when toggle levers 52 and 54 are in engagement, whereupon bridging contact 36 will be rapidly moved to effect a snap-action closing of the breaker contacts by toggle spring 68. Moreover, at about this same time the lower ends of slots 16 in core 16 will clear the lower edge of sleeve 80 so as to vent the dashpot comprising sleeve 14 and core 16.

In order to provide for maintaining the breaker contacts separated and to also provide for manual operation, spring means are provided for holding the breakerv contacts open in response to the occurrence of a predetermined number of closely succeedingv circuit interrupting operations, which means Vcan be manually actuated. This means comprises a toggle lever |04 having a slot |06 at-one end thereof for receiving a pin |08 mounted between spaced supporting arms I0 integral with cover casting 6. The other end of toggle lever |04 is pivoted, as by a pivot pin ||2, to the adjacent end of a second toggle lever ||4, and this, in turn, is mounted on a pivot pin ||6 intermediate its ends on cover casting 6. A slot |20 is provided through the cover casting 6 for receiving the other end of toggle lever ||4 which acts as a manual operating handle at the exterior of the circuit breaker casing, being provided with a hook eye 22 in its outer end. A coil compression spring |24 is mounted on toggle lever |04 and reacts between washers mounted on the toggle lever, one of which engages supporting pin |08, and the other of which engages a shoulder located adjacent pivot ||2. Normally, toggle levers |04 and ||4 are held with pivot |2 below the center-line connecting pins |08 and ||6, with the outer end of lever 4 positioned in and beneath an integral hood |26 on cover casting 6, in engagement with an adjustable stop screw |28 mounted in the hood.

In the position of toggle levers |04 and ||4 illustrated, they have no effect on operation of the circuit breaker as previously described, being normally inactive in this respect. However, the common pivot pin ||2 of toggle levers |04 and ||4 is extended at one side toward toggle levers 52 and 54 and in the normal position of the parts extends beneath the adjacent flange 56 of toggle lever 54. Accordingly, if it is desired to manually open the circuit breaker contacts, a hook stick or similar operating member may be inserted in hook eye |22 of toggle lever ||4 and pulled downwardly to rotate the toggle lever in a counterclockwise direction about its supporting pivot ||6 to move toggle levers |04 and I4 overcenter in an upward direction, and in doing this, the common pivot pin |I2 engages the adjacent iiange 56 of toggle lever 54 and moves it upwardly in a counterclockwise direction, thus carrying contact actuating rod 44 with it to separate bridging contact 35 from stationary contacts 26. The contacts will be held open by spring |24 which maintains toggle levers |04 and 4 in their upper overcenter position. With the breaker contacts maintained at their open circuit position following the manual circuit opening operation described above, it will be apparent that the outer end of toggle lever |4 projects below hood |26 of cover casting 6 so as to provide a readily visible indication that the breaker contacts are maintained at an open circuit position. It will further be apparent that the breaker contacts may then be closed only by manual operation of toggle lever ||4 in the opposite direction, that is, by exerting an upward force on the outer end of the toggle lever to rotate it in a clockwise direction to move it and toggle lever |04 back overcenter to the full line position illustrated on the drawing. This manual operation of toggle lever |4 does not directly close the breaker contacts but merely permits closure of the contacts in the manner previously described, that is, initial closing movement of the contacts being due to the bias of gravity, until bridging contact 36 is closely adjacent stationary contacts 26 when toggle spring 68 is moved below its on-center position and suddenly becomes effective to finally move the contacts into engagement rapidly.

An integrating mechanism for automatically moving toggle levers |04 and ||4 upwardly over center and thus preventing reclosure of the circuit breaker only in response to a predetermined number of closely successive circuit interrupting operations, and at the same time for auto-` matically controlling the circuit opening and closing times in a predetermined manner in any sequence of' a plurality of closely successive circuit opening operations, is provided comprising a cylindrical tube secured in casting 20, and this tube has a plug |32 threaded into the lower end thereof with the plug having a small central opening controlled by a ball-check valve |355, which permits flow of uid into the lower end of tube |30 but prevents outow. An integrating piston |36 is mounted in cylindrical tube |3S and normally rests on the upper end of plug |32, being provided with a reduced extension |38 at the upper end thereof, having a plurality of spaced circular flanges hit forming rack teeth thereon, and having an elongated extension It? on the extreme outer end thereof which is positioned below an extension N3 on toggle lever |04. A pawl lever is pivotally mounted at one end as at |46, this end of pawl lever hit being split with legs located at each side of tube |33 and with pivot |45 supported on spaced supporting flanges MI integral with casting 20. Pawl lever |44 has a connecting web intermediate its ends, and at the other end thereof the sides or" the lever are extended outwardly and laterally as at |43, to normally be in engagement with a washer terior shoulder on this sleeve.

| by a coil tension spring |52 hooked over the remote edge of the web of the pawl lever at one end and anchored to an ear integral with casting 20 at its other end. Pawl lever i4 is provided with a pawl member |56 pivoted thereon as at |56, and biased by a spring |53 in a counterclockwise direction to a position wherein a portion of pawl member |54 engages the connecting web of pawl lever |554.

In order to control the opening and closing times of the circuit breaker contacts to provide for different opening and closing times on predetermined circuit opening and closing operations in any sequence of closely successive operations, as on continuing overloads, the dashpot formed by sleeve 'M and solenoid core i5 has a vent |113 at the upper end thereof which is annular in form being provided in casting 20 about actuating sleeve 82. Annular vent |74 communicates with a laterally extending passage |16 also formed in casting 20, so that fluid may escape from the upper end of sleeve 'it through annular vent llil and passage ITB, and then through a pair of opposed openings |18 in tube |30, from whence it may escape through a discharge opening |30, also formed in casting 2e. The openings H8 in integrator tube |30 are aligned with passage |16 and discharge opening 2&0.

With the parts oi the circuit breaker at their normal positions illustrated in Fig. 1, it will be apparent that when the circuit breaker operates to open the circuit, the upper end of dashpot sleeve 'Hi being open through annular vent VM, passage |76, openings il' and discharge opening ISE?, solenoid core 7B will be moved very rapidly upwardly since the liquid in dashpot sleeve 7L!- above the core may be freely vented through the vent passages mentioned above, and consequently the initial circuit opening operation of the breaker will occur substantially instantaneously. Assolenoid core 'I6 moves upwardly, washer |50 will; be carried upwardly with actuating sleeve 8 2-`v and thus carry the free end of paWl lever MilA upwardly with it to move pawl member |54 into engagnment with the upper one of flanges |40 on inte,- grating piston |36, to thus carry the piston upwardly a predetermined distance throughout opening movement of sleeve 82. Integrating piston |36 is not, however, carried upwardly a distance sufficient to entirelyremove reducedvportion |38 thereof from between openings. |184 in cylinder |30, so that the vent passageway from the upper end of dashpot cylinder '|4- willnot be blocked oii` by piston |35. When the breaker recloses following such a first circuit interrupting operation, suchreclosure will also occur extremely rapidly because core 'i6 does not have any dothpot action in its dashpot sleeve ,14 due to the upper vent for the sleeve still being open. Accordingly, the first opening and reclosing of the circuit breaker contacts will both occur substantially instantaneously with no time delay interposed; due to the dashpot action of core 'I6 in dashpot sleeve 7G. During reclosing of the breaker the first time, integrating piston |35 is left at the positionl to which it was advanced, since pawl member |54; is free to disengage the circular flanges |40, and if the breaker remains closed, integrator pistonV |36 will slowly reset to the position shown in Eig-s", l and 2, this resetting movement being relatively slow due to the necessity of displacing liquid drawnv into the lower end of cylinder- 30 byv advancement of piston |36 during the opening Voperation, past the relatively small clearance between cylinder |30 and piston |36. This meanS, of course, that if an overload appears on the circuit at a later time, the breaker contacts willthen be substantially instantaneously openedl and closed in the manner described above.y

However, if the breaker immediately reopens after a rst opening and reclosing operationl pawl member lethis time will engage thenextlower circular flange |50 on the integrator pistonI |36 and raise the pistona further amountsufcient tc bring the piston between side openings |18 of integrator cylinder |30, so that the integrator piston acts as a valve to close off the vent passage |14 from the upper end of dashpot cylinder-14. Inasmuch as the integrator piston y|36 does not close the vent passage until bridging contact 36 ,is substantially at the end of its` circuit opening movement, this second closelyl successive-circuit opening operation will, like the first, occur-substantially instantaneously with substantially-no delay due to dashpot cylinder 14 and core. 116. However, on the succeeding reclosing operation, integrator piston |36 having closedthe'vent; at the top of dashpot cylinder 14, this reclosing` operation will be delayed in the-mannerpreviously described by the dashpot actionV ofcore L6 in cylinder 1li. This second` reclosing operation will result in leaving piston |36 at the furtheradvanced position described above, from whichit 'eventually will reset in the manner-previously described if the breaker remains closed, so that an overload appearing on the circuit at. a later time will result in the breaker operating inthe manner described above for the rst and second closely succeeding circuit opening and. closing operation. However, in the eventl the overload continues after the second closely succeedingV circuit opening and closing operations, the breaker will again open, and thistimeithe openingloperation will be delayed by the dashpot action of'core 16 in dashpot sleeve '|4, since integrator piston |36 has not had time to recede from the position to which it was advanced on the second opening operation of this series of closely succeeding circuit opening operations, where it blocks the vent passage from the upper end of dashpot sleeve 14.

The circuit closing operation of the breaker following the third opening will be delayed in the manner previously described, inasmuch as such third opening operation results in further advance of integrator piston |36 Where it still blocks the vent passageway from the upper end of dashpot sleeve 14. rIlhe breaker may then continue to open and reclose if the overload continues, with each opening and closing being delayed by the dashpot action of core 16 in dashpot sleeve 14 until iinally pawl member |54 advances integrator piston |36 an amount suicient to cause the upper extension |42 thereof to engage the extension |43 of toggle lever |04, and move this lever upwardly over center so that toggle spring |24 will maintain the contacts separated in the manner previously described. It is thus apparent that toggle levers |04 and ||4 will be automatically moved upwardly over center to maintain the breaker contacts separated only in response to a predetermined number of closely successive circuit opening and closing operations, usually four such operations; however, in the event a lesser` number of closely successive opening and closing operations occurs, the integrating mechanism will reset and the breaker contacts will be automatically held open only when the predetermined number of opening and closing operations occurs in close succession. Obviously, after the breaker contacts have been automatically actuated to a position where they are held open by toggle spring |24', they can be reclosed only by manual operation of toggle lever I4 in the manner pre viously described.

In the preferred sequence of operations leading to the breaker contacts being maintained in open circuit position mentioned above, that is a sequence of four operations, it will be apparent that with the apparatus described above, the rst two opening operations will occur substantially instantaneously and the second two opening operations will be delayed with an inverse time-current characteristic due to the dashpot action of core 16 invdashpot sleeve 14. Moreover, the reclosing times in any such sequence of four closely successive opening and closing operations will con prise a first substantially instantaneous closing operation, with the remaining circuit closing operations being delayed by the dashpot action of core I6 in dashpot sleeve 14.

If desired, a protective gap device IE6 of the expulsion type may be provided to prevent operation of the breaker on Voltage surges, with the outer tube of the protective device mounted intermediate its ends on an extension |60 of supporting plate 22 at the underside of solenoid coil 24, being secured thereto as by nuts |10 threaded on the tube of the protector device. One terminal |12 of the protective device may be connected with conductor and one side of solenoid coil 24, with the other terminal of the protective device (not shown) connected with the other terminal of coil 24 and conductor |52. This,

arrester and its particular manner of mounting and connection with this type of apparatus is more particularly disclosed and claimed in the copending application of H. L. Rawlins and J. M. Wallace, Serial No. 694,074 on Overvoltage Protective Devices, led August 30, 1946now issued tective device |66 connected in the manner described herein and in the aforesaid copending application is to provide a by-pass for solenoid coil 24 on voltage surges such, for example, as those due to lightning strokes, which are not overloads on the circuit and, consequently, it is not desired that the breaker open on such surges.

With most contact constructions, and the contact structures shown in Fig. 1 are no exception, the magnetic and mechanical forces are such that on high values of current these forces may cause separation of the contacts and hence cause arcing at unauthorized times with the attendant dangers and bad effects thereof. Thus, with the contact structure shown in Fig. l, on high overload currents, such as short-circuit currents, the flux crowded in the corners defined by the bridging contact 35 and bolts |86 produces a relatively high force tending to move bridging contact 36 upwardly away from iixed contacts 26. Moreover on extremely high currents the temperature of the contacts may get so high as to inelt and cause a boiling of the material of the contact faces which creates a mechanical force tending to separate the contacts. In order to prevent this it is necessary that an extremely strong Contact pressure spring 68 be provided, and, of course, the stronger spring 68 is made to be, the larger coil 24 must be to overcome that spring.

In accordance with this invention, spring 68 need only be strong enough to exert sufficient contact pressure to prevent opening of bridging Contact 36 on currents not substantially higher than normal load currents. Upon the occurrence of overload currents, particularly those of high value, such as short-circuit currents, the pin 88 which also forms the upper reaction point for coil spring 86, is made to be of a magnetic material, such as iron, so that when such high currents pass through coil 24, pin being at the opposite end of the working gap of the coil from core 18, the attraction of pin 88 to the core causes Contact rod 44 to be pulled downwardly with a relatively large force augmenting that of contact pressure spring 63. This action causes the contact pressure to be quite large and prevents premature contact opening due to the magnetic forces induced by such high currents at the contacts. This, of course, is of particular importance in an automatic reclosing circuit breaker of the type disclosed herein where certain operations are delayed by the dashpot action of core 16 in dashpot sleeve I4 for purposes of coordinating with other interrupting apparatus in the circuit, such as fuses. Obviously, if the contacts open prematurely, the purpose of providing time delay is destroyed. However, even on the instantaneous opening operations of the breaker, it is highly desirable that the contacts do not separate before they are made to separate by core 15, in order to keep the arcing time at a minimum. As core 16 moves upwardly, it compresses spring 8B, as previously described, and works against the magnetic and spring forces holding the contacts closed. As core 'I6 approaches the lower end of the flange |15 extending from casting 20 into solenoid coil 24, the flux path to pin 88 is shortened so as to effectively magnetically shunt pin 488 out of the magnetic circuit with the result that it ceases to exert any substantial contact pressure. The parts are arranged so that this decrease in contact pressure due to the magnetic effect of pin S8 occurs at substantially the same instant that the contacts are parted by core 15, leither by force stored in spring 86, or by engagement of the upper end of sleeve 83 with collar 88 on the contact rod.

Because it has been found desirable to keep the area of such magnetic material relatively small in order that the flux acting thereon to augment contact pressure may be most effectively shunted out at the time the contacts are actually separated by the solenoid, but a small amount of magnetic material need be provided on contact rod i4 as exemplified by pin 88. Of course it is not necessary that the flux to pin 8B be shunted out at the upper end of movement of core '16, because if the mass of magnetic material on contact rod dei is kept small, the force due to its flux will be small relative to the force due to the iiux to the stationary frame 2E) of magnetic material. Pin S8 thus might be positioned on rod is below the lower end of the flange on casting 20, although the particular arrangement illustrated is preferred. It is apparent that other forms of magnetic material could be employed however, such, for example, as the collar 182 of magnetic material illustrated in Fig. 2. Collar |82 may be secured to contact rod 44 in any desired manner, such, for example, as by riveting or the like, and acts to augment contact pressure, especially when high currents are present in the circuit, in the same manner as the pin 8S of Fig. l. inasmuch as all the remaining parts shown in Fig. 2 are identical with corresponding parts shown in Fig. l and the same reference numerals are applied thereto, it is believed that the operation thereof is readily apparent from the above description of operation of the device shown in Fig. l, and accordingly a complete description thereof for the parts shown in Fig. 2 will not be given in order to avoid repetition.

It is believed apparent that in accordance with this invention there is provided means for auginenting contact pressure when it is needed on heavy overload currents, such as short-circuit currents, with provision that such augmented force is relieved at least by the time the circuit breaker contacts are actually separated. More specifically, the augmented contact pressure is obtained by providing magnetic material associated with the contacts in a magnetically operated switch, which material also acts as a support for one end of the spring which takes up lost motion between the contacts and the magnet core.

Having described preferred embodiments of the 'invention in accordance with the patent statutes, it is desired that this invention be not limited to these particular constructions inasmuch as it will be apparent, particularly to persons skilled in this art, that many modications and changes may be made in these particular structures without Vdeparting from the broad spirit and scope of this invention. It will thus be readily appreciated that the invention may be employed with other types of circuit breakers, or even with circuit controlling devices other than circuit breakers.

I claim as my invention:

l. A circuit interrupter, comprising, separable contacts which are biased into engagement, contact separating means having a part movable a predetermined amount before causing separation of said contacts, means acting on said contacts and responsive to overload currents in the circuit to exert additional pressure on said Contact, and means cooperating with said additional pressure means and positioned Vto be operated by said part at a point adjacent but spaced from the end of its aforesaid movement to render said additional pressure means substantially less eiTectiVe just before said part causes separation of said contacts.

2. A circuit interrupter, comprising, separable contacts which are biased into engagement, contact separating means having a part movable a predetermined amount before causing separation of said contacts, means acting on said contacts for exerting additional pressure on said contacts to Vprevent opening of said contacts by the magnetic forces due to current overloads, and means cooperating with said additional pressure means and positioned to be operated by said part at a point adjacent but spaced from the end of its aforesaid movement to render said additional pressure means substantially less effective just before said part causes separation of said contacts.

3. A circuit interrupter, comprising, separable contacts which are biased into engagement to automatically close the circuit following a circuit interrupting operation, a solenoid coil connected in series circuit relation with said contacts, a solenoid core biased to a normal position at one end of the working gap of said coil and from which it is moved by attraction of said coil on overload currents a predetermined distance before causing movement of one of said contacts away from the other to open the circuit, and

means of magnetic material secured to said one contact and being positioned in said working gap at a point spaced from said core and adjacent the other end of said gap so that the contact pressure is increased in response to excess currents in the circuit.

4. A circuit interrupter, comprising, separable contacts which are biased into engagement to automatically close the circuit following a circuit interrupting operation, a solenoid coil connected in series circuit relation with said contacts, means forming a low reluctance path for the flux of said coil outside of said coil and terminating adjacent the ends of said coil to form a working gap within said coil, a solenoid core biased to a normal position at one end of the Working gap of said coil and from which it is moved by attraction of said coil on overload currents a predetermined distance before causing movement of one of said contacts away from the other to open the circuit, means of magnetic material secured to said one contact and being positioned adjacent the other end of said Working gap and within the adjacent end of said low reluctance path means, so that the contact pressure is increased in response to excess currents in the circuit and is decreased when said core has traversed said predetermined distance.

5. A circuit interrupter, comprising, separable contacts which are biased into engagement, overload-responsive means including an operating part having lost motion with respect to one of said contacts and being biased to a normal position from which said part must be moved a predetermined amount before causing separation of said contacts, magnetic means responsive to overloads to exert additional pressure on said contacts, and magnetic shunting means movable with said operating part so that when the latter moves an amount less than said predetermined amount from its normal position said additional pressure magnetic means is shunted and thus rendered substantially less effective.

6. A circuit interrupter, comprising, separable contacts which are biased into engagement, overload-responsive means including an operating part having lost motion with respect to one of said contacts and being biased to a normal position from which said part must be moved a predetermined amount before causing separation of said contacts, magnetic means responsive to overloads to exert additional pressure on said contacts, and magnetic shunting means movable with said operating part so that when the latter moves an amount less than said predetermined amount from its normal position said additional pressure magnetic means is shunted and thus rendered substantially less effective.

7. An automatic reclosing circuit breaker cornprising, separable contacts which are biased into engagement, an operating rod directly connected with one of said contacts and movable in one direction to separate said contacts, a solenoid coil connected in series circuit relation with said contacts and positioned about said rod, a solenoid core slidably mounted on said rod, a coil compression spring mounted on said rod and reacting between said core and an abutment on said rod to bias the core to its normal position adjacent one end of said coil, and said abutment being of a magnetic material and located in the field of said coil at a point adjacent the other end of said coil so as to be acted upon by said coil in response to heavy overload currents to increase the pressure on said contacts.

3. An automatic reclosing circuit breaker, comprising, separable contacts which are biased into engagement, an operating rod directly connected with one of said contacts and movable in one direction to separate said contacts, a solenoid coil connected in series circuit relation with said contacts and positioned about said rod, a solenoid core slidably mounted on said rod, a coil compression spring mounted on said rod and reacting between said core and an abutment on said rod to bias the core to its normal position adjacent one end of said coil, means forming a low reluctance path outside of said coil terminating adjacent opposite ends of the coil, and said abutment being of a magnetic material and located adjacent the other end of said coil and in the adjacent end of said low reluctance path so as to be acted upon by said coil in response to overload currents to increase the pressure on said contacts, and to substantially decrease such additional pressure as said core is moved by the coil to actuate said rod to separate the contacts.

9. An automatic reclosing circuit breaker, comprising, separable contacts which are biased into engagement, an operating rod directly connected with one of said contacts and movable in one direction to separate said contacts, a solenoid coil connected in series circuit relation with said contacts and positioned about said rod, a solenoid core slidably mounted on said rod, a coil compression spring mounted on said rod and reacting between said core and a pin extending transversely through said rod to bias the core to its normal position adjacent one end of said coil, and said pin being of a magnetic material and located in the field of said coil at a point adjacent the other end of said coil so as to be acted upon by said coil in response to heavy overload currents to increase the pressure on said contacts.

10. An automatic reclosing circuit breaker, comprising separable contacts which are biased into engagement, an operating rod directly connected with one of said contacts and movable in' one direction to separate said contacts, a solenoid coil connected in series circuit relation with said contacts and positioned about said rod, a solenoid core slidably mounted on said rod, a coil compression spring mounted on said rod and reacting between said core and a collar on said rod to bias the core to its normal position adjacent one end of said coil, and said collar being of a magnetic material and located in the field of said coil at a point adjacent the other end of said coil so as to be acted upon by said coil in response to heavy overload currents to increase the pressure on said contacts.

l1, A circuit interruptor, comprising, separable contacts, a solenoid coil connected in series circuit relation With said contacts, means forming a low reluctance path for the ilux o1 said coil outside of said coil and terminating adjacent the ends of said coil to form a Working gap Within said con, a solenoid core biased to a normal position at one end of the working gap of said coil and from which it is moved by attraction of said coil on overload currents a predetermined distance before causing movement of one of said contacts away from the other to open the circuit, means of magnetic material secured to said one contact and being positioned adjacent the other end of said Working gap and the adjacent end of said low reluctance path means, so that the contact pressure is increased in response to excess currents in the circuit and is decreased when said core has traversed said predetermined distance.

12. A circuit interrupter, comprising, separable contacts, a solenoid coil connected in series circuit relation with said contacts, means forming a low reluctance path for the flux of said coil outside of said coil and terminating adjacent the ends of said coil to form a working gap Within said coil, a solenoid core biased to a normal position at one end of the working gap of said coil and from which it is moved by attraction of said coil on overload currents a predetermined distance causing movement of one of said contacts away from the other to open the circuit, means of magnetic material secured to said one contact and being positioned adjacent the other end of said working gap and the adjacent end of said low reluctance path means, said means of magnetic material having a mass which is materially less than that of the means forming said low reluctance path, so that the contact pressure is increased in response to excess currents in the circuit and is decreased when said core has traversed said predetermined distance.

i3. A circuit interrupter, comprising, separable contacts, a solenoid coil connected in series circuit relation with said contacts, means forming a low reluctance path for the flux of said coil outside of said coil andterminating adjacent the ends of said coil to form a working gap within said coil, a solenoid core biased to a normal position at one end of the Working gap of said coil and from which it is moved by attraction of said coil on overload currents a predetermined distance before causing movement of one of said contacts away from the other to open the circuit, means of magnetic material secured to said one contact and being positioned adjacent the other end of said working gap but spaced from the adjacent end of said low reluctance path means, said means of magnetic material having a mass which is materially less than that of the 15 means forming said low reluctance path, so that the contact pressure vis increased in response to excess currents in the circuit and is decreased when said core has traversed said predetermined distance.

14. A circuit interrupter, comprising, separable contacts., a solenoid coil connected in series circuit relation with said contacts, means forming a low reluctance path for the ux of said coil outside of said coil and terminating adjacent the ends of said coil to form a Working gap Within said coil, a solenoid core biased to a normal position at one end of the working gap of said kcoil and vfrom which it is moved by attraction of said coil on overload currents a predetermined distance before causing movement of one 0I" said contacts away from the other to open the circuit, means of magnetic material secured to said one contact and being positioned adjacent the other end of said working gap but spaced from the adjacent end of said low reluctance path means in a direction toward said one end of the gap, said means of magnetic material having a mass which is materially less than that of the means forming said low reluctance path so that the contact pressure is increased in response to excess cur- 16 rents in the circuit and is decreased when said core has traversed said predetermined distance.

ANDREW W'. EDWARDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 532,537 Davis Jan. 15, 1895 727,713 Thomson May 12, 1903 816,112 Mershon Mar. 27, 1906 949,997 Cubitt Feb. 22, 1910 1,395,327 Aalbers; Nov. 1, 1921 1,395,348 lvacNeill Nov. 1, 1921 1,564,104 Caricho Mar. 27, 1928 1,709,947 Prantl Apr. 23, 1929 2,069,082 Walle Jan. 26, 1937 2,311,714 Thompson Feb. 23, 1943 2,402,722 Bean et al June 25, 1946 FOREGN PATENTS Number Country Date 133,805 Austria June 26, 1933

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