US2750476A - Method and device for extinguishing electrical arcs in circuit breakers - Google Patents

Description

June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICAL ARCS IN CIRCUIT BREAKERS 4 Sheets-Sheet 1 Filed June 8, 1953 INVENTOR.

Andr LATOUR Attorney June 12, 1956 A. L.ATOUR 2,750,476

METHOD AND DEVICE FOR EXTINGUISHING ELECTRICAL ARCS IN CIRCUIT BREAKERS Filed June 8, 1953 4 Sheets-Sheet 2 I rw- Fug. 2 Fig, 6 N.

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BY Andr LATOUR W M M Attorney Fig. 5

June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICAL ARCS IN CIRCUIT BREAKERS 4 Sheets-Sheet. 3

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June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICAL ARCS IN CIRCUIT BREAKERS 4 SheetsSheet 4 Filed June 8, 1953 INVENTOR.

LATOUR Andr BY Kama/1A MIAM RU Attorney Unite States Andre Latonr, Grenoble, France, assignor to Etablissemerits Merlin & Gerin, Grenoble, France Application June 8, 1953, Serial No. 360,299

Claims priority, application France October 13, 1949 Claims. ((31. 208-147} This in a continuation in part of my earlier patent application, Serial Number 188,148, filed on October 3, 1950, now Patent No. 2,668,890, issued February 9, 1954.

The invention refers to circuit breakers of the type in which the arc is drawn between separable contact members contained in an arc formation chamber provided with means for expanding the are into and within an arc extinguishing chamber contiguous with the arc formation chamber.

More particularly, the invention relates to an are extinguishing chamber which includes at least two parallel plates of insulating material, spaced apart from each other to leave a narrow space therebetween and disposed transversely of the direction of separation of the contacts or the initial direction of the arc, and wherein conductive elements or paths are provided in pairs diverging in V-form from each other and which draw the are or the arc in sections into the space or the spaces between the plates and turn the are or the are sections round into a position substantially perpendicular to the initial path of the arc.

In the method of the invention, the arc is caused to turn transversely of its initial direction into, and to expand within, the space between two plates, or as divisional arcs within the spaces between more than two'plates of insulating material provided with conductive paths and arranged transversely of the direction of separation of the contact members between which the arc is initially drawn. However, while the roots of the arc or of the arc sections travel along the conductive paths and approach the terminals of the conductive paths, the transversal development and expansion of the are or its sections is limited to a fraction of the transversal extension of the space or spaces between the plates. Thereon, while the roots of the are or of its sections are held upon the terminals of the conductive paths, part-ways along the plates, the arc is allowed, or its sections are allowed, to develop and expand transversely and longitudinally of the plates to a multiple of the transversal extension of the space or spaces between the plates, the are or each one of its sections in the form of a nearly annular loop within the space or spaces between the plates until extinction.

In accordance with a further development of this method, the arc, under the action of the electrodynamic forces, is allowed to develop and to expand further within the space, or the divisional arcs within the spaces between adjacent plates, until the arc has, or the divisional arcs have developed to a curve of an arcus of at least 1r, or, still further, have reached a nearly closed annular form, preferably of an arcus of 3/21r or more and thereon extinguish within the spaces or space.

In my U. S. patent application Serial Number 188,148, filed on October 3, 1950, now U. S. Patent No. 2,668,890, I have described and claimed a device for extinguishing an electric arc to be drawn between separable contact members, a device which includes a set of at least two spaced parallel plates of insulating material disposed transversely of the direction of separation of the contact members. These plates have on their faces conductive means atent O 2,750,476 Patented June 12, 1956 disposed and adapted to draw the arc into the space or spaces between the plates, turn it round into a position substantially parallel to the plates. The conductive means disposed on opposite faces of each plate diverge relatively to each other and terminate within the space at intermediate points of the space. The are is thus drawn as a whole or in sections into the space or spaces between the plates, turned round into a position substantially parallel to the plates and caused to form a peripherally expanding loop within the space or peripherally expanding loops within the spaces.

The present invention has for its object arrangements of the insulating plates and of the conductive elements carried by them which will allow the arc loops to expand within the space or spaces between juxtaposed, consecutive plates from their roots peripherally to a loop of a length which is a multiple of the greatest distance between the conductive elements, or to a nearly closed annular form of a multiple of the length of the opening angle between the electrodes from which the loops start to develop and to expand.

This expansion of the loops from their roots to curves of nearly closed annular form and of great length or arcs, and of generally circular or oblong form, within the loop developing spaces or chambers will result in highly favor able de-ionizing conditions of the chambers and to rapid extinction of the loop or loops within the chamber or chambers.

An arc loop developing between given electrodes, starting from a short flat are somewhat longer than the distance the roots, on their travel on paths diverging from each other in V-form, reach in their farthest position on the electrodes, will under the effect of the electrodynamic forces expand to a generally circular loop of a certain size. In order to allow full expansion within the loop chamber of the loop or are section, the conductive elements, in accordance with the invention, are so shaped and disposed that they end in the lower part of the spaces or loop chambers. The part of these spaces or chambers above the conductive elements is so dimensioned that when the geometric center of that part i. e. the useful part, or the part of the plate against which the arc develops, is joined by imaginary radii to the nearest points or lateral upmost tips of the diverging edges of the conductive elements or electrodes, these radii form an angle of an arcus less than 11' so that when the roots of the loops have travelled to said points or tips, the loops may develop within the spaces to a curve of an arcus of at least 11' or still further, to a nearly closed annular, generally circular curve of an arcus greater than 3/ 211'. Preferably, the angle of the radii is equal to or even less than 1r/4, in such a manner that the loop may develop to an arcus equal to or greater than 7/ 411-, allowing the shape of the loop to be almost circular.

With loops of such large size, the invention has for its object to hold the transverse dimensions of the loop chambers in certain limits.

An arc loop freely developing between given electrodes, starting from a short, flat arc, will, under the action of the electrodynamic forces, expand to a circular shape which for a given cutting power may actually be determined by the traces which the arc leaves on the faces of the insulating plates.

For the purpose of reducing the lateral extension of the arcs, the invention provides the plates laterally with marginal spacing members which may be integral with the plates or mounted as keys in grooves of the plates, or be secured thereto by any other convenient or conventional means. The lateral spacing members will thus space apart from one another the consecutive plates and, seen in the direction in which the arc is originally drawn will provide between each pair of juxtaposed, consecutive plates of the stack or set a flat spaceand at the same time will constitute the lateral closure walls of these spaces or chambers Within which the arc loop develops and expands.

In' order to reduce the width of the lateral extension of the-arc, in accordance with this feature of the invention, the distance between the walls, which laterally confine the are or loop developing and expanding space, is made narrower than the trace of a loop of average power indicates, so that a loop of average energy is compelled to take during its expansion an elongated or oblong form along the lateral walls. The plates will thus have their useful part in form of a rectangle, of a width less than the mean diameter of the loops formed by the arc for the cutting power considered.

The conductive elements are shaped with two symmetric wings integrally connected by a bridge which is to straddle thelower edge of the plate, the wings on opposite faces ofthe plates and opposite wings of each loop chamber thus being'substantially symmetrically arranged withrespect to the vertical median axes of the plates and of the loop chambers, respectively. The edges of each pairof wings'on opposite faces of the plates and, consequently, also of the pair on opposite faces of each chamber, diverge in V -form relatively to each other.

In accordance with a further development of the invention, these lateral spacing members or walls which determine by their spacing the transversal width of the loop developing and expanding chambers, may also hold the conductive elements firmly in position when they are of a thickness equal to or slightly higher than that of the conductive elements, so that when the plates are stacked together, adjacent plates hold or clamp between themselves the conductive elements of the enclosed space against displacement.

When it is desirable to extend further the length to which the loops may be drawn within the chambers, in accordance with another feature of the invention, the plates may be provided with obstacles which compel the are to take a sinuate or meandrous path. This may be achieved by providing additional, intermediate spacing members extended parallel to the longitudinal axis of the plate and projecting into the loop chamber; or by providing the lateral walls of the chamber with points which project into the interior of the chamber and thus extend slightly the length of the are.

In order to enhance the cooling effect of the plates through intimate contact between arc loop and plate, in accordance with a further feature of the invention, the loop-may be laminated or spread out thinly by reducing between adjacent plates the width of the clearance within which the loop may develop and expand. This may be achieved by lessening through increased thickness of certain parts of the plates the clearance which separates the plates, in such a manner that the loop while penetrating into this narrow clearance is flattened or laminated. Thus the center portion of the space for developing and expanding the arc, the portion of the space above opposite conductive elements, may be raised above the'remaining surface so as to compel the arc loop to flatten out in this center portion.

To the same end, there may be inserted above the part left free for the development for the arc and between adjacent plates, a flame-arrester which on the one hand diminishes the cross-sectional area of the passage and thus compels a close contact between loop and plate and, on the other hand, presents with its lower edge a surface on which the arc loop may abut while expanding in laminated form into the gaps between arrester-plate and. insulating plates. This edge may also be provided with points of insulating material projecting into the loop chamber, with the advantage that the length of the loop is slightly augmented.

The invention is further concerned with a modification of the device by means of which an apparatus with sub-. stantially the same cutting power, the same space requirement, and the same type of insulating plates furnished with conductive elements diverging in V-form, may be employed as a circuit breaker for high voltage and lower amperage and as a circuit breaker for high amperage and correspondingly lower voltage.-

To this end, there are intercalated between the insulating plates furnished with conductive paths unfurnished insulating plates. These unfurnished insulating plates are provided each with a notch extended from the lower edge upwards, towards the upper part of the plate. These notches are generally of wedge shape having their greatest width at their lower part so as to given open space or passage to the loop as it develops between oposite and diverging conductive paths on furnished insulating plates which face each other and between which the notched unfurnished insulating plates are intercalated or inserted.

In this way, the loop, while it develops and expands between two conductive elements which face each other and diverge relatively to each other, is divided into two half-loops, each of which is enclosed between a pair of consecutive insulating plates, one furnished, the other unfurnished. The cross-sectional area through which the hot gases, developed by the loop, escape, thus has been doubled without any increase of the distance or clearance between adjacent plates.

The amperage of the current to be interrupted may thus be increased to nearly the double compared with the arrangement where all the insulating plates, spaced at this same distance, are furnished with conductive paths while with the same requirement of space the number of convolution's of the helix which the are forms is reduced to one half and accordingly the admissible voltage. The cutting power thus remains unchanged.

These and other features of the invention will become apparent as the specific description of the invention proceeds in which the invention will be described with reference to the accompanying drawings which form part of this specification and which by way of example illustrate an embodiment of the invention. These drawings are to be understood explicative of the invention but not limitative of its scope. Other embodiments incorporating the principle underlying my invention are feasible without departing from the spirit and ambit of my appended claims.

In'the drawings:

Fig. l is, on a reduced scale and rather diagrammatically, a longitudinal section, partly along the middle plane, partly in front thereof, of an embodiment of a circuit breaker'provided with arc subdividing conductive elements with their insulating plates in accordance with the invention;

Fig. 2 is a front view of an insulating plate of' the invention furnished with a conductive element;

Figs. 3 to 6 are cross-sections along the lines 3-3; 44; 5-5; and an elevational section along line 6-6' of Fig. 2, respectively;

Fig. 7 is an exploded, partly fractional view of two consecutive insulating plates furnished with conductive elements;

Fig. 8 is a longitudinal section, similar to that of Fig. l,

of a set of insulating plates furnished with conductive elements alternating with unfurnished insulating plates as a modification of the embodiment of Figs. 1 to 7;

Fig. 9 is a front view, and

Fig. 10 an elevational section along line Ill-10 of Fig. 9 of an unfurnished insulating plate of this modification.

In Figs. 1 and 8 the fixed and movable contacts are respectively represented by 11 and 12'. The two contacts are located inside an arc formation chamber 13,- not shown here in detail.

In order to develop the ignited are more rapidly than the movement of the movable contact would allow, an arcing contact 15 may be placed Within the arc formation chamber of insulating material. The arcing contact 15 may be connected to the movable contact 12. A blow out coil 16 may also be employed which may be connected to one of the terminals 17 of the circuit breaker. The coil 16 acts upon the magnetic core 18 the legs 19 of which enclose the arc formation chamber.

In the upper part of the circuit breaker, above the arc formation chamber, there is arranged a set of plates 21, transversely of the contacts 11, 12 and 15, and in a space which constitutes the arc extinguishing chamber. The plates are of insulating material and are provided at their lower edge with a cutout 22 over which the conductive element with its wings 23, 24 is bent and which it straddles with its bridge 25, one wing 23 thus being in front, the other 24 in the rear of the appertaining insulating plate 21, as Figs. 2 to 7 illustrate.

The wings, at their inmost edges, where the arc loops start to develop, may be rectilinear as between 26 and 27 and their edges may then be curved, as at 28 so that conductive elements or wings on opposite faces of each plate and thus opposite elements in each space, between juxtaposed, consecutive plates of the set, diverge in V- form relatively to each other. In this way, the arc is drawn into the spaces between the plates, is turned round into a position parallel to the plates. Travelling along the curved edges 28 of the wings, the arc is caused to form peripherally expanding loops, or convolutions of a helix, in the spaces between successive furnished plates, successive positions of the loops being indicated in Fig. 2 by the broken lines a, b, c, d, e, f, and g.

The outer or lateral edges of the wings beyond their upmost lateral tips A, B are extended freely downwards inside the spaces between consecutive furnished plates as shown between the points 29, 30, Fig. 2, at a distance from the lateral spacing members or ribs 31, 32 by means of which the plates 21 may be stacked together to a set, Fig. 1. These lateral ribs or spacing members thus provide for a proper spacing of the plates to accommodate in the spaces therebetween the conductive elements and allow the arc loops to develop and expand.

As Fig. 2 illustrates, the conductive elements, wings 23, 24 are extended from their lower edge, or the straddling bridge 25, into the space or chamber between the plates and terminate in the lower part thereof. The part of the space above the conductive elements or the part of this space left free for the development of the loop, is so dimensioned that the imaginary radii from the geometric center C of this part, that is of the part 33, 34, 35 and 36, to the lateral tips A, B of the diverging elements or wings 23, 24 form an angle less than 1r/2, in the instance illustrated about 1r/4, or even a still smaller angle. Accordingly, when the roots of the loop have travelled to the tips A, B, the loops may develop within the space to a nearly closed annular form of an arcus greater than 3/21r, as the curves and g indicate.

In order to hold the transverse dimensions of the loop chamber in certain limits, the distance between the lateral spacing members or walls 31, 32 will be made narrower than the width a freely expanding loop would occupy so that the loop is compelled to take an oblong form along the lateral walls of the chamber, as likewise indicated by curves 7 and g.

v The heights of the spacing members, as a rule, will be substantially equal to the thickness of the conductive element, which they hold on the foot ledges 37, 38, as Figs. 1, and 6 illustrate. The plates, when stacked together, thus leave a small clearance between themselves.

In order to produce an intimate contact between loop and plate, the clearance between adjacent plates may be reduced. In order thus to attenuate the loop and enhance the cooling effect of the insulating plates, a portion 39 of the space for developing and expanding the arc, Figs. 2, 4, 6, may be raised above the remaining surface of the plate 21, thus leaving a narrow clearance 40 between boss 39 and the consecutive insulating plate 21.

To a. similar purpose, the plates may be provided at.

their top part with a flame-arrester 41 of insulating ma= terial. This flame-arrester is extended between the lateral spacing members 31, 32 and may be held in'position by supplemental, intermediate spacing members 42, 43. The flame-arrester is of a thickness so as to leave narrow clearances 44, 45', respectively, between arrester plate 41 and the appertaining plate 21 and between arrester plate and the juxtaposed, consecutive insulating plate. The arc, if not priorly extinguished, will be attenuated and effectively cooled and will thus be finally extinguished and prevented from issuing as a flame from the top of the set of the plates.

In order to make possible a further extension of the length of the loop within the loop chamber, the plates may be provided with obstacles, such as lateral, internally projecting points 48 at one or both of the lateral walls 31 or 32, points 49 at the internal ends of the spacing members 42, 43, which points compel the arc loops to take a meandrous path, as illustrated by curve g.

Figs. 8 to 10 illustrate an arrangement for heavy currents, relatively heavier than those for which the arrangement of Figs. 1 to 7 is to be employed and for correspondingly lower voltages.

Insulating plates 21 furnished with conductive elements 23, 24, such as described with reference to Figs. 2 to 7, are employed alternatingly with unfurnished insulating plates 51. These unfurnished plates are generally of the same configuration as the furnished plates 21, they may be provided with lateral spacing members or walls 31, 32, intermediate, longitudinally extended spacing members 42, 43, and with a flame-arrester 41 as described in detail with reference to Figs. 2 to 6.

The unfurnished plates 51, however, are distinguished through a notch 52, 53, generally of wedge shape and extended from the lower edge of the insulating plate upwards towards the upper part thereof, ending in a fine point near the flame-arrester 41. The notch is Wide at its lower part 52 so as to give open space or access to the loop at the origin of its formation. The loop thus is developed between a wing 23 to the rear of plate 51 and in front of the preceding furnished plate 21 and a Wing 24 in front of plate 51 and to the rear of the succeeding plate 21, the two wings being indicated in broken lines. The wings are respectively seated on a foot ledge or spacing member 37 of the preceding plate and a foot ledge or spacing member 55 of the unfurnished plate 41.

By means of this arrangement, the are drawn between the plates 21 by means of the conductive elements and turned round in loops, or convolutions of a helix, substantially parallel to the plates, will find for each loophalf a separate space for development and expansion, each loop-half enclosed between a furnished and an unfurnished plate with the cross-sectional area for the escape of the hot gases thus doubled without any increase of the narrow clearances through which the loops are to expand and thus without any adverse effect on the cooling and extinguishing capacity of the apparatus.

1 claim:

1. In a device for extinguishing an electric arc to be drawn between separable contact members, a set of at least two plates of insulating material disposed transversely of the direction of separation of said contact members, said plates having upon their faces conductive elements straddling the lower edges thereof, conductive elements on opposite faces of each plate and opposite elements in each space between juxtaposed consecutive plates of the set diverging in V-form relatively to each other, thereby to draw the are into the spaces between said plates, turn it round into a position substantially parallel to said plates and cause the arc to form peripherally expanding loops in said spaces; said conductive elements being extended from said lower edge into said spaces terminating in the lower part thereof, the part of the spaces above said elements being so dimensioned that the imaginary radii from the geometric center of said part to '7 the lateral tips of the diverging conductive elements form an angle less .than ,r so that when the roots of the "loops have travelled to said tips, the loops may develop within said spaces to a curve of an arcus greater than 1r.

2. A device as set forth in claim 1 wherein said angle is approximately 1r/4. so that the loops may develop within said space .to a nearly closed curve of an arcus of approximately 7/ 41r.

3. In a device for extinguishing an electric arc to be drawn between separable contact members. a set of at least two plates of insulating material disposed transversely of the direction of separation of the contact members, said plates having upon their faces conductive elements straddling the lower edges thereof, conductive elements on opposite faces of each plate and opposite elements in each space between juxtaposed consecutive plates of the set divering in V-form relatively to each other; thereby to draw the are into the spaces between the plates, turn it round into a position substantially parallel to said plates and cause the arc to form peripherally expanding loops in said spaces; said plates being provided with marginal spacing members forming lateral walls on the plates confining, when the plates are stacked together, laterally between juxtaposed, consecutive plates the loop developing and expanding space, the distance between said lateral walls being narrow so as to compel a loop of average energy to take during its expansion an oblong form along said lateral walls.

4. In a device for extinguishing an electric arc to be drawn between separable contact members, a set of at least two plates of insulating material disposed transversely of the direction of separation of the contact members, said plates having upon their faces conductive elements straddling the lower edges thereof, conductive elements on opposite faces of each plate and opposite elements in each space between juxtaposed consecutive plates of the set diverging in Vform relatively to each other; thereby to draw the are into the spaces between the plates, turn it round into a position substantially parallel to said plates and cause the arc to form peripherally expanding loops in said spaces; said plates being provided with marginal spacing members forming lateral walls on the plates confining, when the plates are stacked together, laterally between juxtaposed consecutive plates the loop developing and expanding space; said plates being further provided with means for reducing the clearance between juxtaposed plates.

5. A device as set forth in claim 4 wherein the center portion of the plate within the space for developing and expanding the loop is raised above the remaining surface of the plate thereby to produce an intimate contact be tween loop and raised plate surface and enhance the cooling effect of the plate.

6. A device as set forth in claim 4 wherein said plates comprise at their top parts a flame-arrester plate of insulating material disposed and extended between said lateral spacing members, said arrester plates being of a thickness so as to leave a narrow clearance between each arrester plate and its appertaining insulating plate and between said arrester plate and the juxtaposed consecutive plate, thereby to attenuate the loop, enhance the cooling effect of the plates, extinguish the are thus preventing the same from issuing as a flame from the top of said set of plates.

7. In a device for extinguishing an electric arc to be drawn between separable contact members, a set of at least two plates of insulating material disposed transversely of the direction of separation of the contact members, said plates having upon their faces conductive elements straddling the lower edges thereof, conductive elements on opposite faces of each plate and opposite elements in each space between juxtaposed consecutive plates of the set diverging in V-form relatively to each other; thereby to draw the are into the spaces between the plates, turn it round into a position substantially parallel to said plates and cause the arc to form peripherally expanding loops in said spaces; said plates being provided with marginal spacing members forming lateral walls on the plates confining, when the plates are stacked together, laterally between juxtaposed consecutive plates the loop developing and expanding spaces, said plates being further provided with projecting obstacles thereby to compel the arc loops to take meandrous paths.

8. A device as set forth in claim 7 wherein said plates comprise intermediate supplementary spacing members extended parailel to the longitudinal axis of each plate.

9. In a device for extinguishing an electric arc to be drawn between separable contact members, a set of at least two plates of insulating material disposed transversely of the direction of separation of said contact memers, said plates having upon their faces conductive elements straddling the lower edges thereof, conductive elements on opposite faces of each plate and opposite elements in each space between juxtaposed consecutive plates of the set diverging in V-form relatively to each other, thereby to draw the arc into the spaces between the plates, turn it round into a position substantially parallel to said plates and cause the arc to form peripherally expanding loops in said spaces; said plates being provided laterally with marginal spacing members, thereby to stack together the plates of said set and confine as lateral walls between adjacent plates said spaces for developing and expanding the loops therein; said lateral walls being of a height substantially equal to the thickness of said conductive elements so as for the plates, when stacked together, to leave a small clearance between themselves.

10. In a device for extinguishing an electric arc to be drawn between separable contact members, a set of plates of insulating material disposed transversely of the direction of separation of said contact members, alternate ones of said plates being furnished on their faces with conductive elements straddling the lower edges thereof, conductive elements of opposite faces of said alternate plates diverging in V-form relatively to each other; the other unfurnished plates of said set having each a notch extended from the lower edge of said unfurnished plates towards the upper part thereof, said notch being generally of wedge shape, wide at its lower part so as to give open space to the loop at the origin of its formation between each other facing opposite elements; said conductive elements being extended from said lower edge upwards and ending in the lower parts of the spaces between adjacent ones of said plates; thereby to draw the are between the plates, turn it round into a position substantially parallel to said plates, cause the arc to form peripherally expanding loops between said plates, each loop-half in a separate space and each enclosed between a furnished and an unfurnished plate.

11. The method of extinguishing an electrical are between separable contact members and at least two spaced parallel plates of insulating material arranged transversely of the direction of separation of said contact members and provided at their inside surfaces with conductive open-ended paths having their terminals partways along said plates; said method including the steps of drawing the are, causing its roots to travel along said conductive paths and causing thereby the arc to turn round as a whole, transversely of its initial direction, causing the roots of the arc to travel along said conductive paths and, during this travel and while the roots approach the terminals of said conductive paths, limiting the transversal development and expansion of the arc to a fraction of the transversal extension of the space between said plates, and, thereon, while the roots of the are are held upon said terminals, part-ways along said plates, allowing further development and expansion of the arc transversely and longitudinally of said plates and to a multiple of said transversal extension of the space between the plates and in the form of a nearly annular loop within the space between said plates and parallel thereto until extinction.

12. The method of extinguishing an electrical are between separable contact members and parallel plates of insulating material disposed in spaced relationship to one another and transversely of the direction of separation of said contact members and provided at their inside surfaces with conductive open-ended paths having their terminals part-ways along said plates; said method including the steps of drawing the arc, causing it to reach said conductive paths, thereby dividing said arc into several sections, causing the roots of each section to travel along said conductive paths and causing thereby each section as a whole to turn round, transversely of its initial direction, causing the roots of each arc section to travel along said conductive paths and, during this travel and while the roots approach the terminals of said conductive paths, limiting the transversal development and expansion of each arc section to a fraction of the transversal extension of the spaces between said plates, and thereon, while the roots of the arc sections are held upon said terminals, part-ways along said plates, allowing further development and expansion of each section transversely and longitudinally of said plates and to a multiple of said transversal extension of the space between said plates and to a nearly annular convolution of a helix into and within the space between adjacent ones of said plates and parallel thereto until extinction.

13. The method of extinguishing an electrical arc between separable contact members and at least two spaced parallel plates of insulating material arranged transversely of the direction of separation of said contact members and provided at their inside surfaces with conductive openended paths having their terminals part-ways along said plates and near to the entrance into the space between said plates; said method including the steps of drawing the arc, causing its roots to travel along said conductive paths and causing thereby the arc to turn round as a whole, transversely of its initial direction, causing the roots of the arc to travel along said conductive paths and, during this travel and while the roots approach the terminals of said conductive paths, limiting the transversal development and expansion of the arc to a fraction of the transversal extension of the space between said plates, and, thereon, while the roots of the are are held upon said terminals, part-ways along said plates and near to the entrance into said space, allowing further development and expansion of the arc, under the action of the electrodynamic forces within said space, transversely and longitudinally of the plates and to a multiple of said transversal extension of the space between the plates until the arc has reached a nearly closed annular form and thereon extinguishes.

14. The method of extinguishing an electrical are between separable contact members and parallel plates of insulating material disposed in spaced relationship to one another and transversely of the direction of separation of said contact members and provided at their inside surfaces with conductive open-ended paths having their terminals part-ways along said plates and near to the entrance into the spaces between said plates; said method including the steps of drawing the are, causing it to reach said conductive paths, thereby dividing it into several sections, causing the roots of each section to travel along said conductive paths and causing thereby each section to turn round as a whole, transversely of its initial direction, causing the roots of each arc section to travel along said conductive paths and, during this travel and While the roots approach the terminals of said conductive paths, limiting the traversal development and expansion of each arc section to a fraction of the transversal extension of the spaces between the plates, and, thereon, while the roots of the arc sections are held upon said terminals, part-ways along said plates and near to the entrance of each one of said spaces, allowing further development and expansion of each arc section, under the action of the electrodynamic forces, transversely and longitudinally of said plates and to a multiple of said transversal extension of the spaces between the plates and within said space, parallel to said plates, until each arc section has reached a nearly closed annular form of an arena of at least 3/21r and thereon extinguishes.

15. The method of extinguishing an electrical are between separable contact members and a set of spaced parallel plates of insulated material arranged transversely of the direction of separation of said contact members and furnished at their surfaces with conductive open-ended paths having their terminals part-ways along said plates, unfurnished plates being intercalated between said furnished plates, furnished and unfurnished plates thus alternating with one another and providing separate spaces, each of said spaces being constituted by a furnished and unfurnished plate in juxtaposition, said unfurnished plates having a notch extended from the lower edge to the upper part thereof, said notch being generally of wedge shape, wide at its lower part; said method including the steps of, after having drawn the arc, causing it to reach said conductive paths, thereby dividing the arc into several sections, causing the roots of each section to travel along said conductive paths and causing thereby each section as a whole to turn round, transversely of its initial direction, causing the roots of each arc section to travel along said conductive paths and, during this travel and while the roots approach the terminals of the conductive paths, limiting the transversal development and expansion of each arc section to a fraction of the transversal extension of the spaces between the plates, and, thereon, while the roots are held upon said terminals, part-ways along said plates, allowing further development and expansion of the arc sections, transversely and longitudinally of said plates and to a multiple of said transversal extension of the spaces between the plates, each section in the form of a nearly annular loop with each loop-half in one of said separate spaces, the loops at the origin of their formation passing through said notches.

References Cited in the file of this patent UNITED STATES PATENTS 2,436,189 Boehne Feb. 17, 1948 2,564,178 Strobel Aug. 14, 1951 FOREIGN PATENTS 253,098 Switzerland Nov. 1, 1948

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