US2452953A - Circuit interrupting apparatus - Google Patents

Description

Nov. 2,1948. w. E. PAUL Erm.

CIRCUIT INTERRUPTING APPARATUS 2 Sheets-Sheet 1 Filed April 6, 1945 n, 7 J, f4@ abn a v. //////WL./V wl u e H O a m O D El, .wf @E mE m v @www t n ,mmTaA f mwRMw A. S e .m .n T y b Nov. 2, 1948.

w. E. PAUL ETAL CIRCUIT INTERRUPTING APPARATUS 2 Sheets-Sheet 2 Filed April 6, 1945 .m ,y ,n a e n sua Mr r. a m B O .tEeEt n mhfA mwmw nu .a m T. W R W ws T .m y .m b J 3 2 Patented Nov. 2, 1948 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTING APPARATUS William E. Paul, Schenectady, N. Y., and Julius W. Timmerman, Jr., Sprlngileld, and Ralph E. Bold, Drexel Hill, Pa., assignors Ato General Electric Company, a corporation of New York Application April 6, 1945, Serial No. 586,892

(Cl. 20G-148) 'z claims. 1

Our invention relates to improvements in circuit interrupting apparatus and more particularly it relates to circuit interrupting means which em'- ploy a blast of iluld such as air or other gas to extinguish the arc formed when the circuit is broken between relatively movable contacts. Speciiically our invention is an improvement on United States Letters Patent 2,284,842, Prince et al., granted June 2, 1942, and assigned to the same assignees as the present application.

Circuit breakers of the type disclosed in the above mentioned Prince et al. patent in which a blast of gas is directed at high velocity transversely across the arc gap formed between the separating circuit interrupting contacts to extinguish the arc have been used both extensively and successfully for some years. Such circuit breakers have come to be known as cross blast circuit breakers to distinguish them from another type of air blast circuit breaker generally referred to as an axial blast circuit'breaker. It would be desirable to provide a fluid or gas blast circuit breaker of the type disclosed in the above mentioned Prince et al patentin which a much smaller interrupting unit is required and yet where the interrupting capacity is not decreased.

It is known that in iiuid or air blast circuit breakers it is advantageous to constrain the are within the region where the extinguishing iluid blast is concentrated so that a high cooling effect is obtained, minimum arc energy is liberated, and the arc gases and products are thereby reduced in so far as is possible.' Circuit breakers have been designed in which the contacts are separated to a predetermined short gap until after the arc is extinguished after which subsequent opening movement of the contacts is resumed for isolating PuI'pOses. It is obvious that a complicated operating mechanism must be provided if the contacts are to be separated to a predetermined distance with relative separation thereafter either halted or slowed down'until the arc is extinguished, after which 'further separation thereof takes place. The advantages of a short or preferred arc gap can also be obtained by employing a fixed gap construction by means of a stationary intermediate arcing electrode which is rendered effective after a predetermined initial separation of the contacts and remains so until the arc has been extinguished.

It is an object of our invention to provide a new and improved gas blast circuit breaker employing an interrupting structure which is considerably smaller and less expensive than prior art constructions while having equal or greater interrupting capacity.

It is another object of our invention to provide a uid blast cross blast type of circuit breaker employing a fixed gap construction capable of interrupting larger amounts oi power than was heretofore possible with a structure considerably larger in size and more expensive.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of our invention reference may be had to the accompanying drawings in which Fig. 1 isa side elevational view of an interrupting device embodying our invention; Fig. 2 is an enlarged perspective view. partly in section, of the circuit interrupting device shown in Fig. 1; Fig. 3 is a sectional view taken on line 3--3 of Fig. l; Fig, 4 is a partial sectional view of an interrupting device embodying a modification oi our invention; Fig. 5 is a View like Fig. 3 taken on line 5-5 of Fig. 4 assuming that no parts of Fig. 4 are cut away, and Fig. 6 is a view taken on line 6-6 of Fig. 4, also assuming that no parts of Fig. 4 are cut away.

Referring now to Figs. 1, 2, and 3 of the drawings, there is illustrated an electric circuit interrupting device l comprising an arc extinguishing structure 2 which includes a movable contact 3 and a stationary contact 4, stationary contact i being best shown in Figs. 2 and 3. In Figs. 1, 2 and 3 the movable contact 3 is illustrated as being separated from the stationary contact and in fact being clear of the arc extinguishing structure 2. The movable contact 3 is provided with a tip 5 formed of arc resisting material which tip will be generally referred to as the arcing tip 5. Movable contact 3 is connected by suitable means, such as a sliding contact or the like, to an external electrical circuit generally indicated at 6.

The xed or stationary contact 4 comprises a plurality of current carrying contact ngels 1 and a plurality of longer arcng lingers 8, preferably formed of arc resistant material and adapted to cooperate with arcing tip 5 of movable contact 3. The 'contact lingers I and 8 are arranged in a contact assembly and held in this relationship by a suitable member 9 clearly shown in Figs. 2 and 3. vThis fixed or stationary contact assembly is bolted to an H-sectioned conducting member II which will be described in greater detail and which is electrically connected to terminal strips l2 which in turn are connected to an external electric circuit I3. It will be understood that contact fingers l and 8 are provided with suitable aeaaoaa spring means or the like to provide the desired contact pressure when in engagement with mov-s able contact 3. In the closed position of the circuit breaker movable contact i3 is seated between conta-ct fingers 'i and 8 of fixed or stationary contact 4. Upon relative separation of contacts 2i and 4 the final separation occurs between arcing tip 5 and long arcing ngers il.

Although we have illustrated a circuit interrupting device i as controlling a single phase current iiowing in external circuits t and mit will be understood that our invention is adapted ior single phase or polyphase application and is particularly adaptable for use with operating mechanisms such as are disclosed and claimed in Patent 2,436,190, Boisseau et al., and Patent 2,436,191, Timmerman, both led November 17, 1944, both granted February l`7, 1948, and assigned to the same assignee as the present application. These eopending appli-cations clearly show how'the interrupting device of our invention can be used in a polyphase circuit breaker.

The arc extinguishing structure 2 is a boxlike structure having side walls id and iii, end walls it and il, top wall it and bottom wall lil. These walls are preferably formed of some suitable gas evolving material, many such materials being available in the art, and an example of which is hard ber. The Walls M, iii, it, il, iii and it] are suitably tongued and grooved so as to form a gas-tight or relatively gas-tight box or arc extinguishing structure when tted together and held as a unitary structure by suitable iastening means, such as bolts 2li, each passing through the sidewalls il and iii, with some passing through various ones of the walls, it, iii, and i9. Preferably the arc extinguishing structure 2 is completely supported by i-i-sectioned conducting member il. The upper ilange 2i of il-sectioned conducting and supporting member ii which supports iixed Contact Il extends into arc extinguishing structure 2 so that fixed contact l is positioned in one corner of the box-lilre structure. Suitable bolts 22 passing through the arm 2i of i-i-shaped or sectioned conducting and supporting member ii and side walls ifi and i5 of the arc extinguishing structure 2 firmly hold the arc extinguishing structure 2 to i-i-shaped member il. rIhe ends of bolts 2E terminate in blister-like clamps 23 to spread the clamping force over a larger area of the insulating side walls ifi and i5. These clamps are provided with rounded surfaces as is clearly shown in. Figs. l and 3 to afford electrostatic shielding for the bolt heads and ends which are recessed in the clamps.

As in the above-mentioned Prince et al. patent, it is desired to direct a blast of air or other gas 01 uid under pressure across the arc gap formed between separating contacts 3 and fi. To this end, end Wall il is provided with an opening 2d and a blast supply conduit 25, preferably formed of insulating material, is suitably fastened to end wall I l by clamping means including bolts 26 so as to be in sealing engagement therewith with the opening in the conduit 25 registering with the opening 2d. Conduit 25 is preferably connected to a suitable source of gas or iiuid under pressure in a manner such as is clearly disclosed in the above-mentioned Boisseau et al. and Timmerman copending applications.

it will be obvious to those sirilled in the art that during a circuit interrupting operation the air or gas blast contacting with the arc will produce highly heated arc gases which must eventually be exhausted from arc extinguishing structure 2, and to this end there is provided an exhaust conduit 2i which is in registry with an opening formed in top wall it. ing means including bolts 28 hold exhaust conduit 2i] in sealing engagement with the arc extinguishing structure 2.

The are extinguishing structure 2 is preferably supported on a suitable insulator 29 to the base of the circuit breaker housing, as is disclosed in the above mentioned Boisseau et al. and Timmerman copending applications. insulator iid, which may be suitably shimmed to provide the proper level on the floor, supports a contact base :iii permanently fastened to insulator 29 by suitable means, such as cap screws 3i inserted in counterbores 32. Contact base d@ is provided with an elongated transverse aperture 33 which is connected to a rectangular recess it extending from aperture to the end of contact base titi, Preierably contact base Sii is a casting with the edges thereof rounded, Ias is clearly indicated in Figs. l and 2, for electrostatic shielding. The contact or terminal strips |12 are permanently connected .by fastening means to the inclined face 3i of contact base 3i). IThe ends of the contact strips i2 project above the recess 3d to form a wedging contact surface Sii. The lower ange t9 of l-ishaped conducting and supporting member ii is of rectangular coniiguration with beveled front and rear edges, one of which is indicated at to. This flange is adapted to fit within the recess 3G and forms a dove-tailed pedestal for the arc extinguishing structure 2. Accommodated within the transverse slot is a V-shaped clamping bloclr lli. A single clamping bolt i2 in contact base 3@ engages clamping block di, which in turn forces the dove-tailed pedestal comprising iiange into intimate mechanical and electrical contact with the contact base 3@ and the current carrying contact strips i2. Preferably, clamping bolt 32 thrusts against resilient means, such as spring washers (not shown) so that a limited resiliency exists unaffected by slight contraction or expansion of the several parts due to temperature changes.

With the supporting means `for the arc extinguishing structure i2 described above, the arc ex tinguishing structure 2 may readily be removed merely by backing ori clamping screw d2 and disconnecting supply conduit 25 and exhaust conduit 2i. 'Ehe arc extinguishing structure 2 can then be slid toward clamping screw Il?? thereby loosening clamping block di, after which the chute unit Z including its dove-tailed pedestal il may be lifted out of recess 3i. In this removal operation the permanently fastened xed contact base 30 and contact strips i2 have remained undisturbed so that when arc extinguishing structure i2 is replaced or a similar structure substi tuted, no realignment is necessary.

The movable contact 3 is movable through an opening 43 in top wall i3 of arc extinguishing structure 2. In order to prevent arc gases from leaking through the portion of opening 43 not filled by moving contact we have provided an air seal which comprises a pair of recesses L36, one on either side of the space occupied by movable contact which recesses are formed in insulating members d5 which ill the excess space in arc extinguishing structure 2 above xed contact Suitable air ducts d@ and il? lead air from conduit t5 directly to pockets or recesses it thereby providlng a high pressure air seal and insuring that no hot arc gases will exhaust from arc extinguishing structure E through opening This arrangement is somewhat similar to that disclosed Suitable clampof a sliding contact assembly generally indicated at i including a plurality of spring pressed contact fingers 52 which are adapted to be in sliding engagement with movable contact 3. This sliding contact assembly 5| is preferably supported between suitable insulating members in arc extinguishing structure 2 so as to define the fixed gap 48 which has a predetermined dimension of the order of one-half inch or less, this dimension depending to a considerable extent upon the circuit constants involved. In any event, fixed gap 48 may be defined as a preferred gap in that its dimension is the preferred dimension for most satisfactory arc extinction. It is obvious from the above description of the fixed gap 48 that upon relative separation of contacts 3 and 4 the arc drawn between arcing fingers 8 and arclng tip 5 will be transferred to the fixed gap even without the provision of any fluid blast as soon as the separation between contacts 3 and 4 exceeds the dimension of gap 45. The fluid blast issuing from conduit will facilitate the transfer of the arc to the fixed gap 48. Movable contact 3 will c remain electrically contacted to electrode 49 until it moves out of engagement with sliding contact 5i, before which time the arc across gap 48 will have been extinguished.

The portion of arc extinguishing structure 2 beyond fixed gap 48 comprises the arc chute. In view of the fact that with the fixed gap construction described the arc is maintained at a relatively short length andthe quantity of hot arc gases produced is much smaller than in prior art constructions, the arc chute may have very small dimensions. Mounted Within the arc chute por'- tion of arc extinguishing structure 2 is a single partition or barrier 53 which is preferably formed of a gas evolving insulating material, such as liber or the like. This single barrier or partition 53 divides the arc chute into two passages generally indicated as 54 and 55 and partition 53 has its transverse insulating edge portion closely adjacent to the fixed gap 48 whereby the arc across gap 48 is stretched around the edge portion of partition 53, part of the arc extending into passageway 54 and the other portion of the arc extending into passageway 55. In order that the arc drawn may be in more intimate contact with gas evolving insulating material, there is provided an insert of insulating material 56 in arc passageway 54 and a corresponding insulating insert 51 in are passageway 55. Both of these inserts of insulating material insure that the arc formed across fixed gap 48 will be cooled by coming in contact with the gas evolving insulating material. Furthermore, the wedge- like inserts 56 and 51 fill up the corner pockets of the spaces adjacent the contact structure and cooperate with the partition 53 to provide a pair of widely divergent expansion chambers in which the heated blast and arc gases are permitted free expansion without causing disadvantageous eddies, back currents or dead gaseous regions within these spaces.

To cool the hot expanded arc gases we provide arc cooling means 58 and 55 mounted in passageways 54 and 55, respectively. As shown, the cooling means 58 and 59 comprise a series of metal plates, such as copper, spaced from each other in any suitable way so as to permit the arc gases or vapors readily to pass therebetween. These plates are shown as secured in place on pins or bolts 5D which may extend through the chute side walls or may extend into recesses formed in the side walls.

The above-described arc extinguishing structure of our invention therefore differs in several respects from that of the above-mentioned Prince et al. patent and the prior art. We believe these differences constitute the improvements which are conjointly accountable for the improved interrupting performance of our new and smaller arc chute and which differences now will be summarized, Firstly, the use of the preferred are gap releases lesser quantities of are products than formerly by limiting the liberated arc energy. Secondly, the use of widely divergent internal chambers, constituted by the slant sides of members 55 and 51 and the surfaces of barrier 53 provide for the immediate streamlined expansion of the heated blast fluid and arc gases beyond the gap. Thirdly, the use of but a single transverse barrier effectively limits the unrestricted looping of the blasted arc into the expansion space. In this last connection, we have ascertained that in comparable divergent chutes which are sectionally divided by several divergent transverse barriers, the arc invariably is extinguished before it has been drawn by the moving contact beyond the edge of the second barrier; consequently, a large portion of the blast fluid would be directed wastefully into the subsequent Dassageways defined by the remaining transverse divergent barriers. Accordingly, in providing but two passageways by the intervention of the single barrier 53, all of the released blast is usefully directed into the twin passages into which the arc or its products are injected. By omitting the superfluous barriers, more space is afforded closely adjacent the arc for the free expansion of the gases and for the earlier interposition of a greater mass of cooling structure in the exhaust passages. The hot gases, encountering the broad front of the cooling structures 58 and 59 are cooled with resultant 'decrease in pressure so that the arc chute passages need not continue diverging downstream of the entrance to the cooling area. For these several reasons, the combination of the above features makes it no longer necessary to provide a large divergent chute of unwieldy mass and complicated configuration which hitherto was thought to be necessary. Hence, a smaller simplified rectangular are extinguishing structure, such as is exemplified in the drawings, is rendered practicable; moreover. such structure is economical to manufacture, easy to manipulate and of greater interrupting emclency withal.

In order to prevent the arc gases flowing in passageways 54 and 55 from coming together too soon. we provide an insulating partition 6i fastened to the end of partition 53 and arranged at right angles therewith, as is clearly shown in Fir. 2, to guide the arc gases into exhaust conduit 2'?. To reduce the back pressure near the exhaust end of the arc chute, we have found it desirable to enlarge vthe volume of the arc chute exhaust -by providing pockets 62 and 53 associated with the passageways 54 and 55, respectively.

As in the above mentioned Prince et al. patent the movable contact blade 3 is comparatively thin in cross section whereby the arc extinguishing structure 2 may be so designed that a high velocity air blast may be concentrated in a small space at the exact placewhere it should be, namely, between -the arcing tip 5 and arcing fingers 8 and across fixed gap 48.

It has been found desirable in order to aid inthe circuit interrupting operation, to insert a resistance in series with the arc. To this end there is provided a resistance 64 having terminals -65 and 58, respectively, which resistance is molded in a slab of insulating material (il. Prefer-ably this slab of insulating material 5l containing the resistor G4 is bolted to one of the side walls of the arc extinguishing structure 2, such as the side wall I4. The c-onstruction and arrangement of resistor B4 is not our invention but is disclosed and claimed in the copending application of Ralph E. Bold, Serial No. 586,893, filed concurrently with the present application.

In accordance with our invention the terminal 66 of resistance 64 is connected by a suitable screw 68 with the electrode 49 of fixed gap 138. On the other hand, the terminal 65 of resistance 64 is connected by means of a lbolt 55 with a conductor 'ill embedded within partition 53. Conductor 'l0 has an enlarged probe electrode portion ll of arc resisting material extending out of the edge of barrier or partition 53 adjacent fixed gap et while a reduced cross sect-ion conducting portion thereof extends through an elongated opening in par- Itition 53 so as to be electrically connected with terminal 55 of resistance 5d.

In the above-mentioned Prince et al. patent, a comparable recovery voltage limiting resistance is inserted through the agency oi an exposed metallic probe which extends between 1two of the transverse divergent insulating barriers wi thin the arc chute. One of the factors contributing to the improved performance of the circuit breaker of our invention is believed to be due to the shielding of the heretofore exposed probe whereby only the tip of the electrode projects into the chute in` terior. By this arrangement, the undesirable re lease of metallic particles during interruption -is minimized, for the embedded electrode is influenced by the cooling effect of ythe gas which is generated from the adjacent surface of the fiber barrier. Moreover, lby. shielding the entire probe within the central division barrier excepting at its point of emergence into the chute interior, this point can be so selected and positioned that the resistor becomes inserted (by the'breakdown of the electrode gap) only under those conditions during the interrupting process when it is known that such insertion will be most effective. Tho single transverse division barrier therefore con stitutes a predominantly important member of our interrupting structure, for its leading edge d-ivides the arc or its products',vits nat surfaces prevent the reuniting of the divided products until rendered impotent by the cooling structure, while its body forms insulating .protection and mechanical su-pport for theinternal connection to the external resistance.

We have found that with the resistor connected to the gap electrode i9 of the sliding contact 5i and to probe electrode l i, a very superior perform.

ance is obtained. Although we do not wish 'to be bound Iby the following theory, we believe .that this superior performance can be explained by the fact that as the arc is drawn the arcing tip E5 of movable contact 3 causes the initiai Iblast to s `lengthen the arc in passageway 55 to 'a greater exten-t than the arc in passageway 54. This is because arcing tip 5 blocks a considerable amount of the gas flow into arc passageway 54, just as the contacts begin to separate. Consequently, the arc drawn is interrupted in arc Ipassageway 55 at the first current zero due to the greaterelongation of the arc in passageway 55. The recovery voltage which immediately follows the interruption will impress full voltage across the gap Ibetween probe electrode 'H and fixed gap electrode 50 because the resistor 64 causes probe electrode 'H to have the same potential as gap electrode 49. Since the sap between probe electrode 'll and the xed gap electrode 50 is full of ionized particles by virtue of o the much longer arc which existed at the entrance to passageway 55, the gap between Iprobe electrode ll and fixed gap electrode 50 is more likely to break. downthan the gap between probe electrode 1i and fixed gap electrode 49 which latter gap is comparatively free of -ionized arc products. Consequently, if the gap between probe electrode 'li and fixed gap electrode 5l! breaks down due to the magnitude of the recovery voltage, the resistor 54 connected in accordance with the above description is inserted in the circuit in series with the arc thereby insuring positive clearing of `the arc and interruption at the next current zero without danger -of severe voltage surges. We have found that the .performance of the circuit interrupting device of our invention is superior with the resistance 64 .connected as described than if it were connected across probe electrode 'li and fixed gap electrode 5U. It is believed .that the theory underlying this superior performance set forth above is correct, although it is possible that the superior performance might be explained in som-e other manner of which we are not now aware. In any event the theory set `forth above is given by way of explanation only.

The operation of the circuit interrupting device described above will be obvious to those skilled in the art in view of the detailed description includ- (lli) ed above. A blast of air is preferably lprovided both during the circuit opening and the circuit closing operations, as yis disclosed in the labove mentioned Prince et al. patent. As already stated, we have found that an arc chute constructed in accordance with our invention will interrupt circuits having as high a current and voltage rating as arc chutes occupying several times the amount of space of the present arc chutes.

Where higher continuous currents must be carried the circuit ybreaker described above may be modified somewhat in accordance with the a1- rangement disclosed in Figs. 4, 5 and 6, where the corresponding parts thereof are designated by the same reference numerals as in Figs. l, 2 and 3. The arc extinguishing structure generally indicated at l2 in Figs. 4, 5 and 6, differs in that the arc extinguish-ing structure is a few inches thicker to accommodate an auxiliary blade i3 which auxillary blade i3 is arranged in parallel with movable contact 3 having arcing tip 5. A suitable cross head 'i4 electrically and mechanically interconnects movable blade contact 3 and movable auxiliary contact i3. The top wall i8' which yis correspondingly wider than the wall i8 of the arc extinguishing structure 2 -described above, is provided in addition to the opening Q3 with an opening l5 for auxiliary blade 113. The inserts i6. lll, and iii of insulating material mounted around the paths of movable contacts 3 and 'i3 are provided with recesses @d and 'lil to provide the air 9 seals described above in connection with arc extinguishing structure 2.

As in Fig. 2 an H-sectioned conducting member I I' is provided having a flange 2 I which supports the stationary contact assembly I' including the fingers 1 and arcing fingers 3 and a second set of contact fingers I displaced from the contact fingers 1 and] so as to be engageable by auxiliary blade contact 13 when the circuit breaker is closed. When the circuit breaker is in the closed position both blade contact 3 and auxiliary contact 13 form closely adjacent parallel paths to carry the circuit current. However, the auxiliary contact 13 is not provided with any arcing tip so that the cooperating contact ngers 80 are used solely as current carrying fingers. Furthermore, auxiliary circuit yinterrupter illustrated in Figs. l, 2 and 3 contact 13 separates from contact fingers 80 a predetermined time before arcing ltip 5 separates from arcing fingers 8. With this arrangement no are designated by the same reference numerals marked with a prime.

The operation of the circuit interrupter disclosed in Figs. 4, 5 and 6 is substantially identical with that disclosed in Figs. 1, 2 and 3 except for the initial transfer of the current carried by auxiliary contact 13 to main contact 3 upon relative separation of the contacts.

While we have shown and described particular embodiments of our invention, it will be obvious to -those skilled in the art that various changes `and modifications may be made without departing from our invention in its broader aspects and we, therefore, aim in the appended claims to cover all such changes and modifications asfall within the true spirit and scope of our invention.

What we claim 'as new and desire to secure by arc is drawn between auxiliary contact 13 and 20 Letters Patent of the United States is: contact fingers 80 lbecause all the current.trans---lf An electric circuit breaker of the fluid blast which leads air supplied from conduit 25 across i contact fingers 8B. A suitable passageway is lprovided for permitting this auxiliary air blast supplied across contact fingers 80 -to enter the arc chute portion and pass out of exhaust conduit 21.

As -is known in the art, a plurality of spaced blades is capable of carrying more continuous current than a single blade having a cross-sectional area equal to the combined areas of the plural blades. By arranging an auxiliary current carrying blade closely adjacent-the main blade 3 so that it cooperates within the extinguishing structure 2 in accordance with our invention, in preference to arranging it external `to the chute, the main advantages are threefold'. Firstly, the overall width of the circuit breaker is reduced to a practical minimum, especially with respect to the live .parts and which, in `the present embodiment, would be the overall dimension including the blister-like clamps 23 as shown in Figs. 5 and 6. Secondly, the close spacing of -the blades minimizes any cantilever unbalance that might occur in the crosshead 1I, for the eective leverages involved' are relatively small. This aspect is important for it will be understood that any blade within the chute is subject to a transient piston action impressed on its end, due to the internal chute pres sure during the application of the blast. For lthis reason it is preferable that the main and auxiliary blades be made of similar cross-section and mass so that they may be disposed symmetrically about their common operating rod. Thirdly, the 'auxiliary blade 13, which may be arranged to separa-te momentarily ahead of the main contact portion of the blade 3, is caused to separate only after the initiation of the blast so that at lthe moment of transfer of current from the auxiliary blade to the interrupting shunt path through the arcing Atip 5 of blade 3, the blade 13 separates in a zone of high dielectric pressure iluid, thereby minimizing any sparking at the end of blade 13 .incident to this current transfer process.

It will be observed -that the portions of the cir. cuit interrupter disclosed in Figs. 4, 5 and 6 which type comprising a pair of relatively movable contacts, a source of fluid under pressure, means for supplying a blast of fluid from said source substantially at right angles to the -path of contact movement whereby the blast is directed transversely to the arc gap formed between the contacts upon separation thereof, an arc chute into which an arc drawn between `said contacts is directed by the blast, a pair of electrodes defining a fixed gap associated with said contacts for maintaining the arc gap length constant following a predetermined separation of said contacts, a divergent expansion space within said chute immediately adjacent to and downstream from said gap, a partition of insulating material in said arc chute dividing said arc chute ,including said expansion space into two passages, said partition having `.its transverse insulating edge portion closely adjacent to said fixed gap, an electrode within said chute and spaced from said contacts to -providea break-down spark gap, a resistance associated with said chute connected to one of said contacts and to said electrode. said electrode and the internal chute electrical connection thereto being embedded substantially along their entire length within said insulating partition.

2. An electric circuit breaker of the fluid blast type comprising a pair of relatively movable contacts, a source of fluid under pressure, means for supplying a blast of fiuid from said source substantially' at right angles to the path' of Contact movement whereby the blast is directed transversely to the arc gap formed between the contacts upon separation thereof, anarc chute into which an arc drawn between said contacts is directed by the blast, a divergent expansion space immediately adjacent to and downstream of said contacts, a partition of insulating material in said arc chute dividing said arc chute lincluding said expansion space into two passages, said partition having its transverse insulating edge portion closely adjacent to said relatively movable contacts, an electrode within said chute and spaced from said contacts to provide a breakdown spark gap, a resistance associated with said chute connected to one of said contacts and to said electrode. said electrode and the internal chute electrical connection thereto being embedded substantially along their entire length within said insulating partition.

3. An electric circuit interrupter of the fluid blast type comprising an arc chute, a stationary contact fixedly mounted to said arc chute within il said chute, a cooperating movable contact arranged to be separated from 'said stationary contact to draw an arc adjacent the entrance to said arc chute, a source of fluid under pressure, means for supplying a blast of fluid from said source substantially at right angles to the path of contact movement whereby the blast is directed transversely of the arc gap formed between the contacts upon separation thereof, a conducting member connected to said stationary contact and extending out of said arc chute, a flange on said conducting member extending out of said arc chute, an insulating support for said arc chute having a conducting plate containing a recess mounted thereon, said recess being adapted to receive said flange, an external electrical circuit permanently connected to said conducting plate, and means comprising a single screw for forcing said flange of said conducting member supporting said arc chute into electrical engagement with' said external electrical circuit, whereby said are chute may readily be removed from. said insulating support by manipulating said single screw and without disturbing the connections of said external electrical circuit.

4. An electric circuit interrupter, an arc chute, a stationary contact iixedly mounted to said arc chute within said chute, a cooperating movable contact arranged to be separated from said stationary contact to draw an arc adjacent the entrance to said are chute, a conducting member connected to said stationary contact and extending out of said arc chute, a flange on said conducting member extending out of said arc chute, an insulating support for said arc chute having a conducting plate containing a recess mounted thereon, said recess being adapted to receive said flange in slidable relation therein, an external electrical circuit permanently connected to said conducting plate, and means coinprising a single screw for forcing said flange of said conducting member supporting said arc chute into electrical engagement with said external electrical circuit, whereby said arc chute may readily be removed from said insulating support by manipulating said single screw and without disturbing the connections oi said external electrical circuit.

5. An electric circuit interrupter comprising an arc extinguishing structure, a stationary contact flxedly mounted within said structure, a cooperating movable contact arranged to be separated from said stationary contact to draw an arc in said arc extinguishing structure, a conducting member connected to said stationary contact and extending out of said arc extinguishing structure, a ange on said conducting member having at least one bevelled edge, an insulating support for said are chute having a conducting plate containing a recess mounted thereon, said recess being adapted to receive said flange in slidable relation therein with the bevelled edge toward one end of said recess, an external electrical circuit comprising a terminal permanently connected to said conducting plate at said one end of said recess, and means comprising a single screw for forcing the bevellecl edge of said flange ci said conducting member supporting said arc extinguishing structure into electrical engagement with said terminal of said external electrical circuit, whereby said arc chute may readily be removed by manipulating said single screw and without disturbing the connections for said external electrical circuit.

t?. in electric circuit interrupter comprising aesaens l2 arc extinguishing structure, a stationary contact xedly mounted within said structure, a cooperating movable contact arranged to be separated from said stationary contact to draw an arc in said arc extinguishing structure, a conductingmember connected to said stationary contact and extending out of said arc extinguishing structure, a iiange on the portion of said conducting member extending out of said arc extinguishing structure, an insulating support for said arc chute having a conducting plate .containing a recess mounted thereon, said recess being adapted to receive said flange so as to provide a dove-tailed pedestal for said arc extinguishing structure, an external electrical circuit comprising a terminal permanently connected to said conducting plate, a clamping block engaging said flange, and means comprising a single screw for forcing said clamp ing block and consequently said flange of said conducting member supporting said arc extinguishing structure into electrical engagement with said terminal of said external electrical circuit, whereby said are chute may readily be removed by manipulating said single screw and without disturbing the connections for said external electrical circuit.

7 An electric circuit breaker of the uid blast type comprising, a housing structure including oppositely disposed plates of insulating material arranged to form a box-like structure, a pair of spaced insulating members secured to opposed internal surfaces of said structure for dividing said structure into an arcing chamber and an arc chute and for aiording a communicating passage between said arcing chamber and said arc chute through the space between opposed ends of said members, the surface of said mem bers on the side thereof adjacent to said arc chute being tapered, a pair of relatively movable contacts in said arcing chamber, means for supplying a cross blast of pressure fluid through said arcing chamber and the space between said members and into said arc chute, a transverse exhaust passageway leading from said arc chute to atmosphere, and an are divider in said arc chute having its leading edge disposed between the tapered surfaces of said members and having its trailing edge angularly disposed with respect to the main body portion thereof for forming two fluid passageways leading through said are chute and into said exhaust passageway.

WlLLiAM E. PAUL. JULTLUS W. TIMMERMAN, Ja.. RALPH E, BLD.

REFERENCES @FEED The following references are of record in the ille o this patent:

UNITED STATES PATENTS ./ltfma Baker et al. Apr. li, i944

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