US1992109A

US1992109A - Electric switch

Info

Publication number: US1992109A
Application number: US632073A
Authority: US
Inventors: Whitehead George Ethelbert
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-11-18
Filing date: 1932-09-07
Publication date: 1935-02-19
Anticipated expiration: 1952-02-19
Also published as: BE391064A; BE401277A; FR743261A; GB412673A; GB392930A; DE621297C; DE658260C; GB392926A; FR768027A

Description

ELECTRIC SWITCH Filed Sept. 7, 1932 2 Sheets-Sheet 2 a t NO /V//./// m /w F 3. 2 Z l7 4 4 w fiu 2 J m m 9. w E 0MP 542 9 fay 8M. v w V m l 9 A N Z n K 0 7 0 4 2 4 71/4 8 3 n w 9.

ATTORNEY Patented Feb. 19, 1935 ELECTRIC SWITCH George Ethelbert Whitehead, Bhiwbina, near Cardiff, Wales Application September 1, 1932, Serial No. 632,013

In Great Britain November 18, 1931 20 Claims. (01. 290-150) This invention relates to,electrical switches or circuit breakers constructed for breaking relatively heavy currents such that means are essentially provided tor'reducing the damage to the switch and contacts due'to the arcing. The commonest means to this end is to immerse the contacts in oil or to provide so-called explosion pots or to provide. an oil or air blast in an endeavour to limit or extinguish the damaging arc. Such means are only partly eflective and a great many proposals have been made for increasing the effectiveness, including the pumping of the oil at considerable pressure over or between the separating contacts or through one of them in the form of a socket. Nevertheless it is universally considered that the weight and the complication of and -the volume occupied by circuit breakers in general are still inconveniently large or the cost of ,any effective arrangement of circuit breaker is undesirable.

The object of'the present invention is to pro vide circuit breakers of improved rupturing capacity without increasing the cost and complication at the "same time to reduce the size of same. I i

To enable the invention to be clearly understood it will now be described with reference to the accompanying drawings in which:-

Fig. 1 is a sectional elevation of one convenient form of circuit breaker in accordance with the invention, I

Fig. 2 is a sectional elevation on a larger scale of one of the fixed contacts shown in Fig. 1,

Fig. 3 is a sectional plan on the line IHIII of Fig. 2.

Fig.4 is a sectional plan on the line IVIV of Fig. 2.

Fig. 5 is a sectional elevation of another form of fixer? contact and explosion pot.

Fig. 6 is a sectional elevation of a still further form of "flxed contact and explosion pot.

Fig. '7 is a sectional elevation, somewhat dia-.

grammatic, similar to Fig. 1, showing a screwthreaded rotatable pump piston for efiecting isolation.

Referring to the drawings and more particularly to Fig. 1 thereof, the latter shows somewhat diagrammatically a circuit breaker having the preferred form of contacts in accordance with the invention these being separately illustrated in Figs. 2, 3' and i to which reference should also .made Fig. 1 showing also the preferred arrangement' of the pump and piston.

Inlfig. 1 the. circuit breaker tank is indicated at 1 andthe main cover at 2 whilst the fixed contacts of the circuit breaker comprise the arcing contacts 3 and the main contacts 4 with which co-operate respectively the moving contacts comprising the arcing contacts 5 and the main contacts 6, the moving contacts being carried in the well known manner upon the transverse bridge '1 which is carried upon the cross bar 8 which at its ends (not shown) isattached to thellsual pull rods surrounded by springs (also not shown) The fixed contacts 3, 4 are disposed in the shroud ing tubes 9 which are fixed in the cross partition or barrier 10 in the centre of which is secured the pump cylinder 11 in which operates the pump piston 12. The latter is formed with one or more perforations such as 13 which are adapted to be closed by the face of a valve 14 which is normally urged downwards by a spring 15 which abuts at its other end against the cover 2 where it surrounds a projection 16. The valve 14 has secured centrally to it a stem 17 which passes freely through a central hole in the piston 12 and is formed at its lower end with a shoulder 18 so that-the valve has limited axial move ment with respectto the piston. The bridge member '7 carries an upstanding projection 19 which is adapted to engage the lower end of the valve stem 17. The arrangement is such that 20 of the housings 21 and out through the openings 22 in the latter, through the shrouding tubes 9 to the upper side of the barrier 10. It will be appreciated that the oillevel in the main tank 1 must be maintained slightly above the upper ends of the shrouding tubes 9. In Fig. l the parts of the circuit breaker are shown when the contacts are just about to close.

Referring now especially to Figs, 2, 3 and 4, thehousing in the particular arrangement illustrated comprises a comparatively thick walled metal cylinder, preferably of'brass, which may be in the form of a casting, which cylinder is adapted to be secured, such as by the means shown to a.

main supporting stem23. The face 4 of the main contact is provided by the flange 24 at the lower end of the cylinder 21 and with said face 4cooperates the main moving contact 6 in the form of a laminated brush comprising a plurality of radial portions circularly distributed aroundthe arcing contact 5 which is in the form of a plug secured in any convenient readily detachable manner to the moving bridge '7. The plug 5, when within the housing cylinder 21, engages three circularly distributed arcing tips 3, of which only one is shown for simplicity in Fig. 4. The arcing tips 3 are fixed to the lower ends of respective rigid fingers or bars 25 which at their upper ends have secured to them substantially hemispherical members 26 which make circular line contact through three holes 27 formed in the upper ends of the explosion pot cylinder 21, good electrical contact being thereby obtained between the arcing tips 3 and the cylinder 21. The fingers 25 furthermore are urged towards the axis of the housing cylinder 21 by means of compression springs 27' located by heated studs 28screwed into the cylinder 21, as will be readily followed from an inspection of Fig. 2. Each finger 25 is disposed in a longitudinal recess 29 formed in the outer surface of the cylinder 21. It will be appreciated that the fingers 25 can be readily re-- moved from the housing cylinder 21 whilst the arcing tips 3 can be readily removed from the fingers 25, being conveniently held thereon by means of headed screws and nuts 30. The openings 31, through which the arcing tips 3 extend, are sufliciently large to permit oil to escape through the holes all around the arcing tips whereby the latter may be efilciently cooled.

In order to provide an effective oil seal between the housing cylinder 21 and the shrouding tube 9 in which it is located, suitable packing such as leather or fibre may be provided, as indicated at 32, which latter is retained in position by means of a ring such as 33 and set screws. The mouth of the explosion pot cylinder 21 is preferably made conical or flaring as shown, care being taken to remove high spots to which the arc might tend to pass.

Referring next to Fig. 5 of the accompanying drawings: the housing therein illustrated comprises a carrier member 34 adapted to be connected to the terminal stem 23, such as by means of a screw thread and by means of a nut (not shown). The member 34 conveniently has a hexagonal cross-section, to three alternative faces of which are secured rigid fingers which are similar and are secured to the member 34 similarly to the manner in which the fingers 25 shown in Figs. 2, 3 and 4 are secured to the cylinder 21, with the exception that the members 25 engage in recesses 35 instead of in holes 27. The arcing tips 3 in the arrangement shown in Fig. 5 are longer than are the arcing tips 3 in the ar rangement shown in Figs. 2, 3 and 4, whereby the total continuous current carrying capacity is greater, particularly if the plug contact (for use with the arrangement shown in Fig. 5) is of hexagonal section. Also secured to the member 34 on the three remaining faces thereof are fingers or strips 36 which at their lower ends are rigidly secured to the mouth ring 24. It will be appreciated that in Fig. 5 only one finger 25 and one finger 35 is shown, but that since there are three of each, an effective electrical cage or enclosure is provided which is similar in effect to the arrangement shown in Figs. 2, 3 and 4. the oil escape from the housing of Fig. 5 through the spaces between the

fingers

25 and 36.

The arrangement shown in Fig. 6 is generally similar to that shown in Fig. 5 with the exception The are gases and that the entry mouth ring 24 is split radially into three portions and is carried by fingers 36 which are pivotally mounted in a manner which is exactly similar to that provided for the tingers 25.

The co-operating plug 5 is adapted to engage the arcing contact tips 3 as previously herein described and is provided with a portion 37 of larger diameter which is adapted to engage within the split mouth ring 24 and to expand the latter. The arrangement is such that, when the larger portion 37 of the plug contact is withdrawn irom the ring 24, the latter contracts and forms an electrically complete ring, and this occurs before the sparking plug 5 leaves the contact tips 3, that is to say the ring is complete before the are actually commences.

Withregard to the actual contacts shown in the preceding figures, it is to be understood that one of the contacts. conveniently that which is the moving contact, is of any elongated form such as the illustrated plug form or it may be a blade for example. The other contact will normally be the fixed contact, and it will be appreciated that its actual contacting surface is located between the open end or mouth ring of the housing 21 and the other end of said housing.

It will be appreciated that the housing 21 has openings such as 22 in Figs. 1-4 or the spaces between the fingers or

bars

25 and 36 in Figs. 5 and 6 which permit the gases to escape essentially in the direction opposite to that of the opening movement of the plug contact 5. It is further essential that the fixed contact members, such as the arcing tips 3, moderately protrude from the inner surface of the wall of the housing 21 into the space therein in such manner, such as by making the contacts 3 of bulbous form, that there is at all times a free, though possibly tor tuous, channel through the housing extending from the mouth ring, about the contacts and the surfaces thereof which are in engagement and out through the aforesaid gas escape openings, whereby the cooperating surfaces which are tually in contact with each other are closely bounded or surrounded by an immediately adjacent annulus of the body of insulating fluid (pr erably oil) contained within the housing 21, which fluid annulus will contract upon the arc as it starts while the arc will tend to remain extended between the plug contact 5 and said protruding arcing tips 3. It will be appreciated that the housed contacts are made prominent with respect to the inner surface of the latter with the further object of preventing one end of the are from going to said surface which thus cannot of itself con stitute the contacting surface of a socketccn tact. Where the circuit breaker contacts are of the plug and socket form, one of the contacts must be split, and in practice the arcing tends to weld up the split, and one of the objects of the present invention is to avoid any such tendency.

Furthermore, the internal cross sectional dimensions, and to some extent also the internal longitudinal dimensions of the housing 21and its mouth ring 24, are preferably small enough in relation to the cross sectional dimensions of the plug contact 5 or equivalent to exert influences close proximity to the are as to be engaged thereby (and thus short circuit the are) in case the are should persist and I; W and. thus lengthen to extinction, namely, by rapidly removing the are more, at the commencement of arcing and for a short time afterwards, the mouth ring is largely closed by the plug contact. The gas escape openings can be made relatively small but for a liquid immersion fluid they must be sufficiently large to prevent any marked action of the well known explosion pot type. High explosion pressure is, in fact, definitely undesirable, so that the gas escape openings must be larger for a dense insulating fluid, such as oil, than for a gas, such as air.

The present invention includes within its scope circuit breakers in which (a) oil is pumped as above described, (b) wherein the oil is present but is not pumped, wherein there is no oil, and (d) wherein a gas, such as air, is pumped.

In the circuit breaker of the present invention the pressure in the. housing is believed to maintain the are slim and thus to provide in itself a distinct arc quenching effect, while the fluid flow, when provided, is also highly beneficial in arc gases apart from its cooling and insulating effects. The are is prevented from following the fluid flow because the gas escape openings are moderately restricted. The housing, however, is essentially effective as anelectrical case, which prevents the are from leaving it.

An important feature of the present invention is that the oil is already flowing under pressure before the instant of contact separation and this is permitted by reason of the distance through which the plug contact moves when the switch is tripped, before it parts company with the housed contacts 3. It is also important that the housed contacts 3 should have relatively small actual surfaces of contact by'which "they engage the moving contact. Further improvement is obtained for dividing the housed contact into a plurality of contacts, namely three, in the several arrangements illustrated by Figures 1-6.

Referring next to Fig. '7 which, for the sake of clearness is m ade,,somewhat diagrammatic, the arrangement is generally similar to that shown in Fig. 1 with the exception that the cylinder 11 is rotatable without being longitudinally movable and is externally screw-threaded for about half its length, as partly illustrated at 38, and the cylinder 11 is adapted to be rotated by a worm 39 and worm wheel 40 attached to an axial end shaft 41 of the cylinder.

The normally fixed contact stems 23 in the 1 usual insulating sleeves or bushings are rigidly carried in a tray 42 and are also slidable through guide holes 43 in the cover 2 of the circuit breaker.

"Secured'to the tray 42 is an internally threaded" ring 43a which co-operates. with the thread 38 of the cylinder 11. As hereinbefore set forth, by rotation of the worm 39 from any convenient external handle or handwheel the pump cylinder 11 can be rotated so as to move the fixed contact stems 23 and the fixed contacts 3 and explosion pots 21 up 'or down for effecting isolation or coupling up of the circuit breaker with respect to the remainder'of the switchgear, of which the circuitbreaker may form a part. No claim is herein made per se to the known general method of effecting isolation by moving the contact stem 23 with respect to the circuit breaker tank 1 and cover 2.

As will already be appreciated, the invention is not limited to the fixed arcing contacts being of the "arcing tip" type shown in Figs. 2-4, 5 and 6,

since other prominent'forms of arcing tip can be employed, that is to say contact members which project inwards from the walls of, into the space within, the housing 21. In this connection see Figs. 8 and 9 which illustrate two alternative forms of co-operating contacts by way of example. I

In Fig. '1 the mouth ring 24 is shown comparatively large but it will be appreciated that the actual annular space between the mouth and the contact member 45 or 5 will vary in size according to other conditions which are obtaining, such as the viscosity of the fluid medium which is pumped and the sectional area of the outlet openings such as. 22 from the explosion pots 21, the aim in all cases being to create around the arc a comparatively high fluid pressure and also to obtain an appreciable flow of oil for cooling purposes.

It will be understood that the contacts shown by Figs. 1-4, Fig. 5, and Fig. 6 in combination with the housings 21 shown respectively in these figures or groups of figures are novel independently of any complete circuit breaker structure and per se form separate features of the present invention. 7

Whilst the several forms of housings herein specifically described are inherently of metal and are set forth and claimed as being of metal, it is to be understood that the housings of the invention may alternatively be mainly of metal and partlyof insulating material. For example the gas outlet openings can be reduced in size by adding pieces of insulating material and such may constitute a method of controllingthe fluid pressure.

It will be understood that many modifications, further than those hereinbefore indicated, may be made within the scope of the invention:

I claim:-- v

1. A circuit breaker comprising a-tubular metallic, arc-confining housing having an entrance opening provided by a metal ring, contact means in conducting relation with said housing extending radially inwardly from the inner longitudinal wall surface thereof and providing a contact surface spaced radially inwardly of said wall surface and just within said ring, a cooperating contact member having a portion of less cross-sectional area than the area of said opening insertable through said ring opening without contact with the ringand engageable with said contact means at said contact surface, said housing having at least one further opening for the free exhaust therethrough of gas in a diiection opposite to the path of opening movement of said cooperating contact member, the inner surface of the housing closely adjacent to the zone of engagement of the contact means and cooperating contact affording a relatively large and cool metallic surface engaged by an are upon undue persistence, and said ring functioning to thwart the drawing of an arc therethrough upon detachment of the contact member.

2."-'A circuit breaker comprising a tubular metallic, arc-confining housing having an entrance opening provided by a metal ring, contact means in conducting relation with said housing extending radially inwardly from the inner longitudinal wall surface thereof and providing a contact surface spaced radially inwardly of said wall surface and just within said ring, a cooperating contact member having a portion of less cross-sectional area than the area of said opening insertable through said ring opening without contact with the ring and engageable with said contact means at said contact surface, said housing having at least one further opening for the free exhaust therethrough of gas in a direction opposite to the path of opening movement of said cooperating contact member, a liquid insulating medium in the space between the cooperating contact member and housing, the inner surface of the housing closely adjacent to the zone of engagement of the contact means and cooperating contact affording a relatively large and cool metallic surface engaged by an are upon undue persistence, and said ring functioning to thwart the drawing of an arc therethrough upon detachment of the contact member.

3. A circuit breaker comprising a pair of relatively longitudinally movable cooperating contacts between which the arcs occur on breaking circuit, one of said contacts being of elongated form, and a tubular metal housing for the other contact located in electrical connection with and between the ends of said housing which is provided with at least one moderately restricted opening not bounded by the surface of the housed contact for the free escape of arc gases and which housing is provided elsewhere with a ring entry mouth also of metal through which said elongated contact can enter with slight annular clearance to engage only the housed contact, said latter contact protruding radially from the inner surface of the housing towards the path of the elongated contact in the form of at least one narrow member which terminates near saidentry mouth and provides at all times at least one free and unobstructed channel through the housing from the entry mouth, past the contacts, to the gas escape opening, the inner wall of said housing surrounding and being slightly spaced from the zone of engagement of the contacts.

4. A circuit breaker as claimed in claim 3, including a tank, a horizontal barrier therein having an opening in which said tubular metal contact housing is located, and a charge of insulating fluid filling said tank at least to the height of the barrier.

5. A circuit breaker as claimed in claim 3, wherein the mouth ring of the housing constitutes one non-arcing main current-carrying contact while the other non-arcing main current-carrying contact annularly surrounds the elongated contact at such distance from its arcing end that the main contacts separate before the other pair of contacts.

6. A circuit breaker as claimed in claim 3, wherein the housed contact is divided into a small number of contact elements symmetrically distributed around the housing and leaving at all times free spaces between them.

7. A circuit breaker as claimed in claim 3, wherein the housed contact is mounted on the exterior of the housing and is resiliently urged through an opening in the wall of the latter.

8. A liquid blast circuit breaker comprising 00-- operating contacts engaged over a comparatively small area, a metallic housing for and in conducting relation with one of said contacts and in which said contacts engage each other and initiate separation, insulating liquid within said housing providing an annulus around said area of engagement prior to and at the instant of separation, and means for placing said liquid including said annulus in compression before and during contact separation, said housing affording a relatively large and cool metallic surface disposed so adjacent the contacts as to be engaged by an are upon undue persistence thereof, substantially as set forth.

9. A circuit breaker comprising a liquid-containing tank, a fixed barrier extending transversely of said tank and having a pair of open ings, a tubular metallic housing mounted in one of the said openings, a contact in said housing between its ends and in electrical connection therewith, said housing having an entry mouth and also an opening spaced from and not bounded by the contact surface of said housed contact, a contact movable into said housing through the entry mouth to engage only the housing contact in spaced relation to the housing, and a mechanical pump movable. in the other opening of said pair, independently of the movable contact, for forcing the liquid contained in said tank into said entry mouth and substantially unrestrictedly through said housing from one side to the other of said barrier.

10. A circuit breaker comprising a liquidccntaining tank, a fixed barrier extending transversely of said tank and having a pair of openings, a metal contact housing mounted in one of said openings, a contact in and in electrical con nection with said housing, said housing having an entry mouth and a gas-escape opening both in spaced relation with the contact surface of said housed contact, a contact movable through the entry mouth into said housing to engage only the first-named contact, a spring-loaded piston working in the other opening of said pair for forcing the fluid through said housing substantially unrestrictedly from one side to the other of said barrier, said spring-loaded piston being unconnected with said first-mentioned contact so as to be capable of pumping movement independently of the opening movement of the contacts, and said second-mentioned contact having a member to engage said piston and load its spring when said latter contact is moved to closing position.

11. A circuit breaker of the character described, comprising a finger-like fixed contact, a cooperating movable contact of elongated form, a metal housing in conducting relation with said fixed contact, said housing having a metal ring entry mouth for said movable contact, and said fixed contact being disposed between the ends of said housing and protruding radially inwardly from the inner surface of said housing, said housing comparatively closely surrounding and slightly spaced from the moving contact when the latter engages the housed contact, said housing having an opening for the free escape of arc gases in a directicn opposite to the direction of opening of the movable contact and the fixed and movable contacts being shaped to afford at all times a free channel through'said housing for the flow of fluid from said ring entry mouth, around the engaging surfaces of said contacts and out through said gas escape opening without appreciable restriction by the contacts, fluid-constraining means associated with said entry mouth and fluid pumping means for forcing fluid into said ring entry mouth and through said housing just before, during and after the instant of contact separation.

12. A circuit breaker as claimed in claim 11, wherein the housing is of tubular form and has the first-mentioned contact extending inwardly through its wall, a fastening member positioning the first-mentioned contact against the outside of said housing, and resilient means urging said member inwardly oi the housing.

'13. A circuit breaker as claimed in claim 11, wherein the housing comprises a small number of longitudinally disposed and circularly distributed, contact carrying bars, means pivotally mounting said bars, means resiliently urging said bars inwards, andbars alternating with the firstnamed bars carrying the ring entry mouth.

14. A circuit breaker as claimed in claim 11, wherein the housing comprises a small number of longitudinally disposed and circularly distributed pivoted bars, means pivoting said bars and resiliently urging them inwards, one set of alternate bars carrying bulbous contacts, and the ring mouth consists of segments carried by the other bars, said elongated contact having a portion of enlarged dimension to engage and spread said segments, and means urging said ring segments into electrical contact with one another upon the opening of the circuit breaker and before the arc commences.

15. An electrical switch having a main contact provided with a chamber therein open at one end, said main contact having a constantly open escape opening through its wall leading from said chamber, an auxiliary contact carried by and in conducting relation with the main contact extending through said wall and inwardly into said chamber between said opening and said open end of the chamber, a second main contact, said second mainco'ntact having an opening movement relative to the first main contact in a direction away from said opening toward said open end of 40 the chamber and being disposed in said chamber in relatively close, spaced relation to the side wall of the chamber with its main zone of engagement with the first main contact adjacent the open end of the latter, and said second mentioned main contact being engaged with ,the auxiliary contact between said zone of engagement and said p nin 16. An electrical switch having a main contact provided with a chamber therein open at one end, said main contact having'a constantly open escape opening through its wall leading from said chamber, an auxiliary contact carried by and inconducting relation with the main contact ex'-' tending through said wall and inwardly into said chamber between said opening and said open end 01' the chamber, a second main contact, said second main contact having an opening movement relative to the first main contact in a. direction away from said opening toward said open an end of the chamber and being disposed in'said chamber in relatively close, spaced relation to the side wall of the chamber with its main zone of engagement with the first main contact adjacent the open end of the latter, said second mene5 tioned main contact being engaged with the auxiliary contact between said zone of engagement and said opening, and means operable'to pump a.

liquid through said chamber and opening in adirection opposite to the direction oi opening movement of the second mentioned main conri. An electrical switch according to this 15 wherein the free end of the second mentioned main'contact and the wall or said chamber at its is entrance are tapered at substantially the same inclination, and the said zone of engagement of the main contacts surrounds said entrance.

18. An electrical switch having a main contact of bell shape provided with constantly open 'escape openings through its wall in spaced relation to the open end and leading from said chamber,

auxiliary contacts in alternating relation with said openings carried by and in conducting rela-- tion with the main contact extending through said wall and inwardly into said chamber between said opening and said open end of said chamber, a second main contact, said second main contact having an opening movement relative to the first main contact in a direction away from said opening toward said open end of the chamber, said main contacts having their main zone of engagement adjacent the open end of the first mentioned contact, and said second mentioned contacts extending into said chamber and engaged with the auxiliary contacts and positioned thereby out of contact with the side wall of the chamber.

19. An electrical switch having a main contact provided with a chamber therein open at one end, said main contact having a constantly open escape opening through its wall leading from said chamber, an auxiliary contact carried by and in conducting relation with the main 'contact extending through said wall and inwardly into said chamber between said opening and said open end of the chamber, a second main contact, said second main contact having an opening movement relative to the first main contact in a direction away from said opening toward said open end of the chamber and being disposed in said chamber in relatively close, spaced relation to the side wall of the chamber with its main zone of engagementwith the first main contact adjacent the open end of the latter, said second mentioned main contact being engaged with the auxiliary contact between said zone of engagement and said opening, and means cushioning and urging said auxiliary contact toward said chamber.

20. An electrical switch having a main contact 0! bell shape provided with constantly open escape openings through its wall in spaced relation to the open end and leading from said chamber, auxiliary contacts in alternating relation with-said openings carried by and in conducting relation with the main contact extending through extending into said chamber and engaged with the auxiliary contacts and positioned thereby out or contact with the side wall of the chamber, means attaching the auxiliary contacts to the first main contact having springs cushioning and urging said auxiliary contacts toward said chamber, the free end of the second mentioned main contact and the walls of said chamber at its entrance being tapered, the said zone of engage-' ment of the main contacts being around said entrance, and means operable to pump a liquid through said chamber and opening in a direction opposite to the direction of opening movement oi the second mentioned main contact.

momentum-BERT