US1955214A - Electric switch or circuit breaker - Google Patents

Description

April 17, 1934. w w rr Y ET AL 1,955,214

ELECTRIC SWITCH OR CIRCUIT BREAKER Filed March 15, 1932 ZSheets-Sheet 1 2 20 I 6 I in 3%4" 14 P I -l4 15 16 ll 4 I 4 18 'L 19 Fzg. I. E

A 7' TORNE Xi April 1934- w. B. WHITNEY ET AL 1,955,214

ELECTRIC SWITCH OR CIRCUIT BREAKER Filed March 15. 1932 3 Fig.5.

2 Sheets-Sheet 2 IN VENTORS HTTORNEYS Patented Apr. 17, 1934 ELECTRIC SWITCH OR CIRCUIT BREAKER Willis Bevan Whitney, Edmund Basil Wcdmore, and Alexander Morris Cassie, London, England, assignors to The British Electrical and Allied Industries Research Association, London, England, a British company Application March 15, 1932, Serial No. 599,006 In Great Britain May 9, 1931 14 Claims.

This invention relates to electric switches and like interrupters for electric circuits in which the contacts or electrodes separate when the circuit is broken and a blast of fluid such as gas or oil, or a mixture of gas and liquid, or a spray of liquid particles, is forced towards the arc set up between the electrodes.

It has already been proposed to construct an electric switch with a piston on which one of the electrodes is mounted and arranged so that a spring is compressed when the switch is closed so that when the circuit breaker or switch opens again the spring acts on the piston to force fluid into the arc. The object of the present invention, however, is to provide a simple and efficient means for setting the piston and a spring or its equivalent ready for operation and for enabling the piston to be insulated from the moving electrode when the latter has fully opened.

In all high tension circuit breakers the problem is to extinguish the are set up when the electrodes separate, effectively and quickly. In the ordinary explosion pot when the electrodes separate pressure for extinguishing the arc is generated in a more or less closed pot, and although some products of arcing will escape around the retracting electrode, movement of fluid in the neighbourhood of the arc is necessarily sluggish until the moving electrode leaves the pot when the arc stream at the aperture is surrounded by a fluid blast. In these conditions it is improbable that oil will be driven radially into the arc gap and in any event a considerable interval of time in the circumstances must elapse between the start of arcing and the application of any blast to any part of the arcing region with the result that during this period much of the oil is blown out of the pot without any useful action on the arc. Furthermore, in the ordinary explosion pot when interrupting small currents there is often insufiicient energy available to set up any appreciable blast. The present invention provides means for producing a blast which can act effectively when interrupting currents at the low part, or at any other part of the current range. The invention provides structures ensuring that the blast comes into immediate effective action at the start of arcing and ensuring that oil is driven radially into the arc gap by a pressure which is greater than the arc pressure and is therefore able to overcome the latter. A piston is therefore provided to force oil through and across the are into contact with the switch electrodes and through a hollow electrode in order to produce rapid and effective cooling and extinguishing of the are. This movement of the fluid is produced by the piston and the pressure set up by the products of arcing is, according to the present invention, employed to assist the action of a spring 7 in actuating the piston.

The invention may be applied to the form of switch set forth in our copending patent application Serial No. 607,470 filed April 25th, 1932, in which a piston is provided and is arranged so that pressure set up by the products of arcing acts on opposite surfaces, in which case, the energy stored in the spring is used to better advantage or is reinforced in moving the piston by the resultant pressure of the arcing products acting on one of the faces of the piston.

In order that the invention may be clearly understood and readily carried into effect, some examples of constructions of circuit breakers in accordance with the invention will be described with reference to the accompanying drawings, in

Which:-

Figure l is a central vertical section, and

Figure 2 is a cross-section on the line II-II in Figure 1 of one form of the improved switch, in which the pressure of the are products acts more or less differentially on both faces of a piston as set forth in the said copending application Serial No. 607,470 filed April 25th, 1932.

Figure 3 is a central vertical section of a further form of switch in accordance with the invention, the action of the spring being only supplemented by the pressure of the are products if an outlet at the top is made sufficiently small; and

Figure 4 is a horizontal cross-section on the line VV in Figure 3.

Referring first of all to Figures 1 and 2, a switch structure consists of a metal container 1 substantially of cylindrical shape with a metal top plate 2 screwed into the cylindrical wall and secured to the lower end of the lead-in insulator 3. The fixed contacts 4 of the switch are carried on a downwardly extending tube 5 which is screwed into a recessed plate 6 secured to the top plate 2.

An annular piston 7 fits around the tubular extension and slides with the outer surface of its top disc 8 in contact with the cylindrical wall of the container 1 and with the outer surface of its lower disc 9 in contact with a tubular member 10 which is screwed into the container 1 immediately above the clamping ring 10a which holds the base of the switch in position. The moving contact of the switch is a solid contact 11 and is shown in the closed position within the fixed contacts 4. The piston 7 is also shown in its uppermost position in which it has been pushed 11 separate act differentially on the lower sur'-' face of the disc 9 of the piston and on the uppersurface of the disc 8, and as'the upper surface is larger than the lower surface, there is an unbal,

anced pressure tending to push the piston '7 downwards. However, in accordance with the present invention, a spring 14 is provided intended to-give the starting downward movement to the piston '7 so that fluid such as oil or gas may be'forced toe wards the contacts at or before the time thatfarc ing commences, which, owing to the inertia of the moving parts could not occur in the absence of the spring 14. It will be noticed that theupper part of the tube 5 is divided to leave spaces between four webs 15, and a spider ring 16 is placed on th e top of the ring 8 of the piston with radial arms 17 passing between the webs 15. Then a thrust ring 18 is placed within the tube 5' on top of the radial arms 1'? of the spider'lfi and the spring 14 bears on the thrust ring 18. The spring 14 therefore, presses on the piston'7 and the latter isheld in the uppermost position shown by reason of the fact thatthe moving switch contact 11 acts through a rod19, which, in this example, is of insulating material extending'down from thespider 16 so a s to press up the spider and com press the spring 14 allowing the spring 12 to raise the piston to the position shown. Seep holes are shown at 20 in the top plate Zand at 21 in 'the fixed contacts 4. I 1 I a When the switch is opened the parts act as follows:The moving contact 11 is moved downwards, for example, by the usual cross-bar and therefore relieves the pressure on the rod 19 and on the spring 14. The latter immediately begins to expand to push down thepistonfi, but at the same time an arc is struck between the fixed con-' tacts 4 and the moving contacts 11. The products of arcing set up a pressure acting on the upper and lower faces of the piston, because the pressure passes through the central passageway in Lth'e fixed contacts 4, through the windows between the webs 15 of the tube 5 and therefore has access to the top of the piston '7. If therefore the spring 14 is pressed downwardly on to the piston, this difierential pressureitakes control and-moves.- the J piston fully down until the pressure escapes through an exhaust port 22.by which time the arc will have been extinguishedby the oil or other insulating fluid which has been driven across the arc, through the centralipass'ageway inthe contacts 4, and ultimately out of the exhaust port 22 by the motion of the piston'iQ At this stage the switch has reached the fully open' position and by reason of the release of pres sure above the pistonthe spring 12 will be able to lift the latter andas soon as the switch. is closed, 'the piston willbe completely reset into its fullyiraised position because the moving contact 11 is lifted to take oil the pressure of the spring 1 4. Of course, the male and female contacts and 11 may be replaced by butt contacts, in which case, the rod or elongated. I

In the form of construction illustrated in Figures 3 and 4, corresponding parts are numbered in the same way as in Figures 1 and 2. InEigure plunger 19 would be suitably 3, the lower part of the switch contain-er is not shown but it is identical with that shown in Figure 1 except for the tubular member 10 which is not needed in the embodiment of Figure 3. In this case, however,-the piston '17 has surfaces of the same area 'on top andbottom so-that there is no diiferential pressure exerted, and the whole of the downward movement of the piston 7 is in this case produced by the spring 14 which is of larger diameter-than'in Figure 1 and presses directly upon'the piston 7. When the switch is opened the downward movement of the piston forces oil up through the passageway in the centre of the contacts 4 and through the spaces between the fixed switch contact 4 and the moving contact 11, and in this case, the oil so forced up and other productscan be so swept out that an ex- :haust outlet 22, which is at the top of the container, is therefore constantly open as there is no need to retain pressure until the piston has reached practically'the bottom of its stroke. In this case also, the pistonv has at the top castellations 13 for increasing the guiding surface. The size'of the exhaust outlet 22 may be varied from a mere seep hole up to' thepoint at which the whole. of the top of the container 1 is practically open. The smaller theoutlet 22, the more nearly equal is the pressure of the fluid onbothsides of the piston 7 and the less interference is there with the free: action of the. spring 14. The rod 7a of insulating material screwedinto the piston 7 and guided in thecover plate 2 is connected to a switch in an auxiliary trip circuit so as to close that switch only {when the main circuit breaker'is fully closed. By this means tripping of the circuit breaker is prevented until the piston 7 has reached its uppermost position. .1 from the above examples, it. will be understood that in cases in which a piston is used to drive liquid towards thearc, one or more fine seep holes as shown at 23in Figure 3 may also be provided through thepiston toregulate the level of any fluid which may be used below the piston and to prevent the formation of a gastrap or the seep hole' 2 3 in Figure3 mayibe formed at anydesired 12 level in the lower part-of the sidewall of the piston 7 to determine the boundaries of a gas trap. These holes, however, must not belarge enough to allow any serious escape of liquid through them during the opening operation 7 Since, generally speaking, the spring or springs employedin accordance with the present invention, act in thesame direction as the springs usually provided for opening circuit breakers, these usual springs may beldispensed with in some cases, and the spring, for example, the spring 14 in Figure 3, acting through the piston 7' and stem 19 would open the circuit breaker. This action may be facilitated by enlarging theupp-er end of the' moving oontactll and including a resilient or yielding joint in its operating mechanism so that, in the closed position, the contact 11 butts against the lower end of the stationary contact 4 instead of entering into it. 7 i r We claim:@ 140 1. Anelectric circuit interrupter, comprising in combination, a casing formed with slide surfaces,"a'pis'ton' mounted within said casing to slide on saidsurfaces and formed with a passageway, a'fixed electrode mounted in said casing, a'mov- 145 able electrode mounted so that products liber-. ated by the arc'set up upon separation of said electrodes are placed in communication with both faces of said'piston'through the passageway thereof, airesilient;energy storing device in oper 5 (ill ative connection with said piston so as to drive piston chamber, a piston mounted to slide in chamber and formed with opposite faces of different effective areas, a pair of "relatively movable electrodes mounted in said casing so that products liberated by the are set up on separation of said electrodes are placed in communication with both faces of said piston, a resilient energystoring device mounted to impart energy to said piston so as to assist the differential pressure of the arc products in effecting the operative stroke of said piston, and current connections to said electrodes, one of said electrodes being movably mounted in operative connection with said resilient device so as to stress the latter and store energy therein upon closure of the circuit interrupter.

3. An electric circuit interrupter comprising in combination, a casing shaped toform an internal piston chamber, a pair of relatively'movable electrodes mounted in said casing, a piston arranged to slide in said piston chamber, a resilient energystoring device in operative connection with said piston so as to drive the latter to cause fluid to move towards the are set up between said electrodes upon separation thereof, and current connections to said electrodes, said piston and one of said electrodes being formed with a passageway connecting the spaces in the said casing on the two sides of said piston andone of said electrodes being operatively connected to said piston to cause storage of energy in said resilient device during closure of the circuit interrupter.

4. An electric circuit interrupter comprising in combination, a casing formed with an internal piston chamber, a piston mounted within said casing to slide in said chamber and formed with two faces of different effective area, a fixed electrode mounted in said casing, a movable electrode mounted to co-operate with said fixed electrode, a resilient energy-storing device in operative connection with said piston so as to drive said piston when released to cause fluid to move towards the arc and current connections to said electrodes, said piston and said movable electrode being formed with a passageway connecting the spaces in said casing on the two sides of said piston and allowing the arcing products to have access to both faces of said piston.

5. An electric circuit interrupter comprising in combination, a casing formed with an internal piston chamber, a fixed electrode mounted in said casing, a movable electrode mounted to co-operate with said fixed electrode, a piston insulated from said electrodes and mounted within said casing to slide within said piston chamber and formed with a passageway to provide communication between the arc set up upon separation of said electrodes and the spaces within said casing on both sides of said piston, a resilient energy-storing device in operative connection with said piston so as to drive said piston when released to cause fluid to move towards the arc, and current connections to said electrodes, said movable electrode being in operative connection with said resilient device so as to stress the latter and store energy therein upon closure of the circuit interrupter.

'6. An electric circuit interrupter comprising in combination, a casing serving as anarcing chamber and shaped to form an internal piston chamber, a-fixed electrode mounted in said casing, a movable electrode mounted to co-operate with said fixed electrode, a piston exposed to the pressure set up by the products of arcing within said casing, said piston being mounted to slide within said piston-chamber and being formed with 'a passageway permitting the pressureset up by the products of arcing to have access to both faces of said piston, means for moving said movable electrode in the same direction as said piston both during opening and closure of the circuit interrupter, a resilient energy-storing device in operative connection with said piston soas to drive said piston when released to cause fluid to move towards the arc set up between said electrodes upon separation thereof, and current connections to said electrodes, said movable electrode being in operative connection with said resilient device so as to stress the latter and store energy therein upon closure of the circuit interrupter.

7. ,An electric circuit interrupter comprising in combination, a casing shaped to form an internal piston chamber, a piston mounted to slide within said chamber and formed with a passageway, a resilient energy-storing device mounted to act upon said piston so as to drive said piston when released to cause fluid to move towards the are formed between said electrodes upon separation thereof, a fixed electrode mounted in said casing, a movable electrode mounted so that the products liberated by the arc set up upon separation of said electrodes are afforded access to the spaces within said casing on both sides of said piston through the passageway thereof, a thrust member interposed between said movable electrode and said energy-storing device, and current connections to said electrodes, said movable electrode being operative through said thrust member and said piston to stress said energy-storing device and store energy therein upon closure of the circuit interrupter.

8. An electric circuit interrupter comprising in combination, a casing shaped to form an internal piston chamber, a pair of relatively movable electrodes mounted in said casing, a piston mounted to slide within said piston chamber so as to force fluid towards the are set up between said electrodes upon separation thereof, and having its opposite faces located in closed pressureretaining spaces within said casing, a resilient energy-storing member in operative connection with said piston to effect the operative stroke thereof and current connections to said electrodes, one of said electrodes being mounted to move and being operatively connected to store energy in the said resilient member during the closing movement of the circuit interrupter and the other of said electrodes being formed with a hollow passageway to enable pressure set up by the products of arcing to have access to both faces of said piston and to act on one of the faces of said piston to assist the action of said resilient member.

9. An electric circuit interrupter comprising in combination, a casing shaped to form an internal piston chamber, a pair of relatively movable electrodes mounted in said casing, a piston formed with its opposite surfaces of unequal areas mounted to slide within said piston chamber so as to force fluid towards the are set up between said electrodes upon separation thereof, and having its opposite surfaces located in closed pressuree'retaining spaces within said casing, a resilient energy-storing" member in operative connection with said piston to effect the operative stroke ithereof iandfcurrent connections to said electrodes, one of said electrodes beingmounted tormove and being operatively' connected to store ener'gy'within said resilient member and said other electrode being formed' with a passageway enabling products .of arcing 'to have "access-to both-faces offs'aid piston to"exert'a diiferential pressure :assisting *t-he action' of said-re'silient member "during-"the "opening movement of the circuit interrupter; i 1 t w 10..An electric circuit interrupter comprising in combination, a casing shaped to "form aninternal piston chamber, a pair of relatively movableelectrodes mounted in said casing, 'a piston shaped withopposite faces of different efiective areas and mounted to slide within said piston chamber was to forcefiui'd 'towards'the are setup between said electrodes upon separation thereof, said piston beingformed with a passageway to allow access of are products to both faces thereofga resilient energy-storing device in operative: connection with said piston'toeffect the operative stroke thereof and current connections to said electrodes, one'of said electrodes being mounted to move' and being operatively connected to store energy in .said resilient device but independently of said piston;- so that any are formed 'upon' opening or closing the circuit interrupter sets up pressure which may "be expendedzpupon" said piston to move samewithout acting to retard oraccelerate the motionxofxsaid movingelectrode. 1' 1-1 An electric circuit interrupter comprising in combination, a casing shaped to form" an internal'piston'chamber, a pair of relatively movable'electrodes mountedin said casingga piston mounted to slide within said-piston: chamber so as to forcefiuidtowards the arc 'set up between said electrodes upon separation'thereof; a spring-in operative connection'with said vpiston'to effect the operative stroke thereof, a second-spring weaker than said first mentioned spring and connected to urge said piston into its fully.:set position during closing of the, circuit-interrupter and current connections between said electrodes; one of said electrodes being mounted'to' move and being operatively connected to'store energy in said first-mentioned spring during the closing movement of the circuit interrupter.

12. An electric circuit interrupter comprising in combination, a casing shaped to form an'internal piston chamber, a pair of relatively movable electrodes mounted in. said *casingya piston mounted to 'slidevwithin said: piston chamber so as to force fluid towards the are set up between said electrodes uponseparation-thereof, a spring in meritioned spring independently of movement of said 'p'iston during the closing movement of the circ'uit interrupter and said piston being shaped so as toafiord the arc products-access to one face thereof so as to" exert pressure thereon to assist the action of said first-mentioned spring.

'='-13'.'An electric circuit interrupter" comprising in-co'mbination, a casing shaped to form-an internal piston chamber,-a piston formed with faces of unequal effective'areas andmounted within said piston chamber to divide same into" primary and secondary-"chambers connected togetherbya passageway-passing through said piston, a pair' o'frelatively movable electrodes mounted in'sa id casing and separable to form an'arc in said primary chamber so'as'to set up pressure operative upon both faces of said piston, as'pring in operativeconnectionwith said piston as to urge same in the same direction as'thepressureac'ting'on the larger face thereiof,: a second spring Weaker thansaidfirst-mentio'ned spring-and connected to urge said piston into its fully set position during closing of 1 the circuit interrupter and current connections between said iele'ctrodes, one of said electrodesbeing mounted to move and being operatively connected to store energy in said first-mentioned spring but independently ofsaid piston, during the closing movement of the circuit interrupter.

'14 electric circuit interrupter comprising in combination, a casing shaped to form an arcing enclosure, a pair ofrelatively movable electrodes mounted'in said casing to separate to form a'n arcin'said 'enclcsure, a pumping device having two operating surfaces of'unequal eifective areasand bothin communication with said areing enclosure and operative to force fluidtowards said ar c'Qa" resilient energy-storing member in operative connection with said pumping device to effect the'operative stroke'thereof and current connections tosaid electrodes,-one'ofsaid *elec: trodes being mounted to move and being opera= tively connected-tostore energy in said resilient member and the products of arcinghaving ac- 'cess to the two operating surfacesof said pumping device to exert a differential pressure assisting the action of said resilient member during the opening movement of the circuit interrupter. WILLIS BEVAN WHITNEY. V EDMUND BASIL WEDMORE. a

" r ALEXANDER MORRIS CASSIE..;

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