US3211869A

US3211869A - Gas-blast electric circuit-breaker having contact fingers biased against auxiliary contact after disengagement from throat contact

Info

Publication number: US3211869A
Application number: US91459A
Authority: US
Inventors: Gonek Stanislaw Mieczyslaw; Rowlinson Henry
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1961-02-24
Filing date: 1961-02-24
Publication date: 1965-10-12
Anticipated expiration: 1982-10-12

Description

Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 24. 1961 7 Sheets-Sheet l FIG.1

Oct.12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 4, 19"" 0.1. 7 Sheets-Sheet 2 j SE Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT 7 Sheets-Sheet 3 Filed Feb. 24. 1961 FIG. 3

GONEK 'ETAL GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS Oct. 12, 1965 s. M.

BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT 7 Sheets-Sheet 4 Filed Feb. 24, 1961 ol llwl ll.

FIG. 4

FIG. 6

Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 24, 1961 7 Sheets-Sheet 5 FIG. 5

Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT 7SheetS-Sheet 6 Filed Feb. .24, 1961 S. M. GONEK ETAL Oct. 12, 1965 GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS 7 Sheets-Sheet 7 Filed Feb. .24. 1961 age 1 31 i IL 9 m 0 F 8 2 w 4 mm d 9 V' M C N 8 84 a a? 8 Q 2, f 9 1 J l J 0 Q wu A/ United States Patent 3,211,869 GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAV- ING CONTACT FINGERS BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGE- MENT FROM THROAT CONTACT Stanislaw Mieczyslaw Gonek and Henry Rowlinson, Stafford, England, assignors to The English Electric Company Limited, London, England, a British company Filed Feb. 24, 1961, Ser. No. 91,459 14 Claims. (Cl. 200-448) This invention relates to gas-blast electric circuitbreakers, that is to say to circuit-breakers of the kind in which means are provided for causing a blast of gas, usually air, to pass between the co-operating surfaces of the interrupter contacts, as they are separated to effect an opening operation of the circuit-breaker, so as to maintain the dielectric strength of the medium between the contacts at a high value and thereby to assist in extinguishing any are formed between the contacts when interrupting a current.

According to the invention, a gas-blast circuit-breaker includes cooperating first and second main contact members relatively movable between engaged and disengaged positions, one said main contact member having a plurality of contacts individually biased when the main contact members are in their engaged position int-o engagement with a contact face of the other main contact memher; and an auxiliary contact member capable of limited movement relative to the first main contact member and arranged so that during an opening operation the cooperating contact surfaces of the main contact members separate before those of the second main contact member and the auxiliary contact member, to which the load current is transferred from the first main contact member and which is at least temporarily biased towards the second main contact member, a blast of gas which is passed between the co-operating contact surfaces of the second main contact member and the auxiliary contact member as they subsequently separate being passed in its passage through the contact region first between the cooperating contact surfaces of the main contact members and subsequently between those of the second main contact member and the auxiliary con-tact member. Both the maincontact members preferably have a generally tubular formation, the auxiliary contact member sliding within the bore of the first main contact member and the gas blast being exhausted through the second main contact member.

In a circuit-breaker according to the invention, two or more pairs of interrupting contacts may be provided, each pair of contacts, together with the enclosure, valves and other components peculiar thereto, constituting a circuit interrupter. Components of the circuit-breaker such as support insulators and a compressed gas receiver may be common to all the interrupters of the circuitbreaker.

The foregoing and other features of the invention will be evident from the following description, with reference to the accompanying drawings of various air-blast circuit interrupter constructions embodying the features of the invention in their preferred forms.

In the drawings, FIGS. 1, 2 and 3 are longitudinallysec-tioned views of an interrupter construction, showing the contacts in their closed, arcing and isolated positions respectively,

FIG. 4 is an enlarged view of the contacts of the same interrupter in their arcing position,

FIG. 5 is a detail of an alternative base arrangement,

FIGS. 6 and 7 show an alternative contact arrangement with the contacts respectively in their closed and arcing positions, and

3,211,869 Patented Oct. 12, 196? FIGS. 8 and 9 are longitudinally-sectioned views, with the contacts respectively in their closed and arcing positions, of an alternative interrupter construction.

The supporting structure of the interrupter shown in FIG. 1 comprises a hollow cylindrical insulator 10 mounted on a base cast-ing 11 and forming an enclosure 10a. Vertical mounting is assumed for convenience, but the interrupter is suitable for mouting in any position. A top cap assembly 12 provides one electrical connection to the interrupter, as indicated at 13, the other being made at 14 to the base casting. A flange 15 in the base casting is provided for connection to a source of compressed air, not shown in the drawing.

The interrupter contacts comprise a main fixed throat contact 16, forming part of and depending from the top cap assembly 12, and a composite moving contact assembly 17. The latter includes a tubular main contact member 18 which is divided at its upper end by a series of longitudinal cuts to form a series of contact fingers 19, biased inwardly by means of circular garter springs 20. In the closed position of the interrupter, as shown in FIG. 1, the upper ends of the inwardly-directed cont-act surfaces 19a of the contact fingers 19 engage a corresponding contact surface 16a on the outer circumference of the throat contact 16. Further contact fingers 21,.forming part of the base casting 11 and outwardly biased by a spring 22, provide the electrical connection between the moving cont-act assembly 17 and the base casting. f

The moving contact assembly 17 is mounted for limited sliding movement in the base casting 11, its movement being controlled by the selective admission of compressed air to either the upper or the lower side of a piston 23 attached to the lower end of the tubular contact merr ber 18;. An annular blast valve 24 forming part of the moving contact member 17 co-operates with an annular seating 25 to control the admission of compressed air to the annular passage 26 defined by the interior sulfface of the insulator 10 and the outside of the movingc-ontact assembly 17.

The moving cont-act assembly 17 also includes an auxiliary arcing contact 27, mounted within the tubularspace defined by the contact fingers 19. of the movingcontact member and capable of limited sliding movement relative to that member. A spring 28 biases the contact surf-ace 27a of the arcing contact member 27 into contact, when the interrupter is closed,-with a corresponding inner con; tact surface 16b of the throat contact 16. Themove ment of the arcing contact 27 relative to the moving contact member 18 can be controlled by the admission of compressed air to a cylinder 29 formed in the moving contact member, in which .a piston 30 attached to the arcing contact 27 can slide.

In the absence of a supply of compressed air to the cylinders controlling the movement of the moving parts, the contacts are biased together by springs 31 situated within the hollow main contact member 18. In these conditions the blast valve 24 is closed on to its seating 25.

The interrupter top cap assembly 12 carries, in addition to the fixed throat contact 16 and its associated varcing probe 32, an exhaust valve 33. This valve is normally biased by a spring 34 to the open position shown in FIG. 1 but is capable of being moved so as to cooperate with an annular seating 35 in closing an annular exhaust passage 36 leading from within the bore of the throat contact 16 to the outside atmosphere. A delay valve 37 controls the movement of the exhaust valve 33, as will hereinafter be explained, in accordance with the variation in air pressure within the annular space 26 surrounding the interrupter contacts.

The operation of the interrupter will best be understood by considering the break-and-make operating sequence. FIG. 1 shows the interrupter in its closed state;

the current path through the interrupter is completed by the engagement of the contact surface 19a of the contact fingers -19 with the outer contact surface 16a of the throat contact 16, the blast valve 24 being closed and the exhaust valve 33 open. Compressed air from the supply connected to the flanged union 15 fills the space 38 below the blast valve 24. The action of this air pressure on the blast valve 24 is to supplement the upward biasing effect of the springs 31 on the movable cont-act member 18; in order to balance to some extent the effect of this pressure, compressed air is also supplied through the passage 39 to the upper side of the piston 23, which has an area slightly less than that of the blast valve 24. The interior of the moving contact member 18, and the cylinder of the arcing contact piston 30, are at this stage connected to the atmosphere through

passages

40 and 41 respectively, and a further passage 42 connects the lower end of the cylinder 43 in which the piston 23 slides with the atmospher'e. It will be understood that .althought the

passages

39, 40, 41, 42 are shown emerging from the outer surface of the base casting 11, there to be connected to suitable valve gear for the admission of compressed air or for its evacuation to the atmosphere, this is done for convenience in explanation only, and in practice the valve gear may be housed within the base casting'll.

An opening operation ofthe interrupter is initiated by tripping an air valve tosupply compressed air through the passage 41 to the lower-side of the arcing contact piston 30. Thissupplenients the effect of the spring 28 in providing contact pressure between the contact surface 27a of the arcing contact 27 and the inner contact surface 16b of the throat contact, and by its reaction on the moving contact .member 18 overcomes the pressure of the springs 31 and the effect of the unbalanced pressure on the blast valve 24 soa-s to cause the moving contact member 18 to move downwards. A sliding union 44 in the passage41 permits the continuance of the supply of air to thecylinder 29v during this movement. As soon as the movement of the moving contact member 17 lifts the blastva'lve 24 from its seating 25, the pressure unbalance .acrossthe blast valve is removed and as a result the movement of the moving contact member is accelerated. During this initial movement of the moving cont-act member 18 the contact fingers 19 are withdrawn from the throat contact 16 and move inwardly under the biasing action of the garter springs 20 to embrace and make confact with the cylindrical contact surface 27b of the auxiliary contact 27, to which the current through the interrupter is now transferred. The pressure difference across the arcing contact 27, in addition to the air pressure in the cylinder 29 and the action of the spring 28, ensures that the arcing contact 27 remains pressed firmly in contact with the throat contact 16 during this part of the operation.

As the movement of the moving contact member 18 continues, the arcing contact 27 reaches the limit of its travel relative to it. Further movement of the moving contact member 18 carries with it the arcing contact 27 and hence separates the contact surfaces 27a, 16b of the arcing contact and of the throat-contact, permitting the flow of the full air blast through the interrupter; when the movement of the moving contact assembly is complete the contacts are in the relative position shown in FIG. 2. The movement of the contacts may be buffered by the action of the piston 23 within its cylinder 43 and of the arcing contact piston 30 within its cylinder 29. During this part of the operation an arc is drawn between the arcing {contact 27 and the throat contact 16, being transferred to the arcing probe 32 within the throat contact by the blast of gas which flows through the open blast valve and to the atmosphere through the bore 160 of the throat contact and the open exhaust valve 33. On the opening of the blast valve 24 and the subsequent filling of the interior enclosure a of the insulator 10 with air under pressure, air is fed through a passage 45 to the delay 4 valve 37, which after an interval long enough to ensure the extinction of the are drawn between the contacts applies compressed air to the upper sides of the piston 46 formed in the exhaust valve 33 and causes the exhaust valve to move to its closed position. Finally, the passage 41 is exhausted to the atmosphere and the arcing contact 27 moves under the action of the air pressure in passage 26 acting on the upper side of piston 30, to the retracted position shown in FIG. 3, thus providing a contact gap of adequate electrical strength, even at atmos= pheric air pressure, to obviate the provision of a separate series or isolating switch. The interior enclosure 10a of the insulator 10 remains full of air under pressure.

In order to return the interrupter to its closed position compressed air is simultaneously applied to the cylinder 29 through the passage 41, to the lower end of the cylinder 43 through the passage 42, and to the lower side of the exhaust valve piston 46 through a passage not shown in the drawing. Thus the. arcing contact 27 is'returned to the position shown in FIG. 2, projecting beyond the end of the tube defined by the contact fingers 19; the exhaust valve 33 is opened to allow a blast of air to pass through the circuit-breaker, and the moving contact assembly 17 commences to move as a whole towards its closed position. As soon as the contact surface 27a of the arcing con-tact 27 engages the inner arcing surface 16b of the throat contact 16, it acts as a valve to interrupt the air blast. The air pressure which as a result builds up in the annular space 26 surrounding the contacts causes the arcing contact 27 to be pressed firmly against the contact surface 16b of the throat contact. As the movement of the moving contact member 18 continues, the surfaces 19a of the contact fingers 19 engage the outer surface 16a of the throat contact and disengage from the arcing contact 27, thus transferring the current to the

main contact surfaces

19a, 16a. Finally the blast valve 24 engages its seating 25and cuts off the supply of air to the interior enclosure 10a of the insulator. The air trapped therein is allowed to escape by means of a bleed passage 47 communicating with the interior of the throat contact 16 and thence with the atmosphere, the exhaust valve 33 remaining open.

As the contacts approach each other, under live circuit conditions an arc may be struck between the arcing contact 27 and the throat contact 16. The presence of the blast of air through the interrupter ensures that this are is immediately swept into the throat contact 16 and transferred to the arcing probe 32, in the same manner as during an opening operation. The transfer of the current from the arcing contact to the contact fingers 19 of the moving contact member 18, which bear on a different contact surface 16a of the throat contact, ensures that the main current-carrying

surfaces

19a, 16a are unaffected by arcing during either opening or closing operations.

FIG. 4 of the drawings shows an enlarged view of the interrupter contacts. It shows that the arcing contact 27 is built up from a body member 48, a central arcing insert 49 and an annular arcing face 50 surrounding it and providing the contact surface 27a. An annular arcing ring 51 is provided within the throat contact 16 and provides the inner contact surface 16b. On the formation of an arc between the contacts either during an opening or a closing operation, only the initial flashover is. carried by the outer arcing face 50 and the throat c-ontact arcing ring 51, the are being immediately transferred to the central arcing insert 49 and the arcing probe 32 of the throat contact and remaining there until subsequently extinguished at a current zero.

FIG. 4 also shows that in the relative positions of the contacts adopted during arcing conditions the profile of the composite moving contact assembly 17, being free from abrupt discontinuities, is such that the electrical field intensity between the contacts is not therebyunduly raised. Furthermore the flow of compressed air over the contact surfaces to the interior of the throat contact 16 can occur as indicated by the arrows substantially without turbulence.

FIG. 5 shows a detail of a circuit-breaker in which two interrupters 52 are mounted in opposed in-line formation on a common base casting 53. Each interrupter 52 is generally similar to the interrupter shown in FIGS. l-3, but the blast valves 24 shown in those figures are omitted, being replaced by a single sleeve-type blast valve 54 closing the compressed air inlet to the base casting 53. This enables the length of the interrupter to be reduced, compared with the interrupter of FIGS. l3, and hence effects a considerable reduction in the length of the double interrupter assembly. The control of the interrupter becomes more complex, since the blast valve 54 has to be opened and closed in synchronism with the movements of the contacts and since the pressure unbalance across the blast valve 24 of FIGS. 1-3 can no longer be employed to assist in controlling the movements of the contacts.

The blast valve 54 is controlled by the admission of compressed air to the cylinder 55 in which slides an an nular piston 56 formed in the end of the blast valve. The annular face of the valve co-operates with an annular seating 57 in the base casting, this seating being recessed as shown to protect it from the blast of air. A deflector 58 helps to ensure the free flow of air to the interrupters when the blast valve is open.

An alternative contact arrangement, suitable for substitution for the contact arrangements shown in FIG. 4 is illustrated in FIGS. 6 and 7 of the drawings. The contacts here shown comprise a throat contact 60 and a composite second contact assembly 61. In the interrupter construction shown in FIGURES l to 3, the throat contact 60 would be fixed and the second contact assembly 61 would move; but this arrangement could of course be varied in the application of the contact arrangement shown in FIGS. 6 and 7 to other interrupter constructions.

The throat contact 60 is provided with an annular arcing ring 62, fitted within its throat aperture, and with a series of at least three contact fingers 63 spaced around the throat contact outside the arcing ring 62. The contact fingers 63 are generally L-shaped in radial section,

tion 63a fits into a corresponding groove 60a in the throat 'contact 60, which may consist of a series of grooves of cylindrical section, either connected or separate. The

surfaces of the grooves 60a and of the end portion 63a of the contact finger can thus slide over each other and allow the contact finger 63 to move under the action of biasing springs 64. The large contact area thus provided reduces the risk of the sliding contact surfaces becoming welded together. A lip at the end of the lower arm of the contact finger 63 engages a rim of the arcing ring '62 to limit the movement of the contact finger.

The throat contact 60 is also provided with a central arcing probe 65 within its bore 600.

The second contact assembly 61 comprises a generally cylindrical main contact member 66 and an arcing contact member 67 arranged to slide within the end of the main contact member 66 between positions in which it is at least partly retracted within the main contact member, as shown in FIG. 6, and in which it projects beyond the contact member, as shown in FIG. 7, to provide a composite contact surface so shaped that it does not cause the electrical field intensity between the

main contact members

60 and 66 to be unduly high at any point and does not cause local turbulence of the air blast.

The main contact member 66 terminates in an annular contact surface 66a, arranged to make butt contact with the contact surface 63b of the contact finger 63 of the throat contact 60, contact pressure being supplied by the springs 64.

The arcing contact 67 is provided with an arcing ring 68, which has a contact surface 68a which, in the closed position of the contacts, makes contact with the contact surface 62a of the arcing ring 62 of the throat contact and is also provided with a central arcing insert 69. A good electrical connection between the main contact member 66 and the arcing contact 67 is ensured by the provision of contact strips and biasing springs 70 between the two contact members. Movement of the arcing contact 67 in relation to the main contact 66 is effected by supplying compressed air through a passage 71 to the lower side of the arcing contact 67 and by exhausting this passage to the atmosphere. In addition biasing springs, not shown in the drawing, may be employed.

Any are formed in operation is struck between the arcing rings 62 and 68, but is swept by the air blast into the throat contact to be established between the probe 65 and the arcing insert 69 of the arcing contact.

The interrupter construction shown in FIGS. 8 and 9 of the drawings is generally similar to that shown in FIGS. 1 to 3 but embodies certain further features and operates in a rather different manner.

The interrupter structure comprises a hollow insulator mounted vertically (although suitable for mounting at any other angle) by means of a base casting 81 and having a top cap assembly 82; the base casting and the top cap assembly from the electrical connections to the interrupter as indicated diagrammatically at 83 and 84 respectively. The base casting 81 is provided with a flanged joint 85 for connection to a supply of compressed air, which is in a permanent connection with the interior enclosure 80a of the insulator 80.

The interrupter contacts comprise a movable throat contact 88 and a composite contact assembly 89 consisting essentially of a tubular member 90 supported from the base casting 81 (of which it may form part) so as to project into the insulator 80., At its upper end the contact member 90 is divided by a series of longitudinal cuts to form a series of three or more contact fingers 91, which are biased by circular garter springs 92, and possibly also by their own resilience, towards the interior of the tube they define. An arcing contact member 93 'is mounted within the contact fingers 91 so as to be capable of limited sliding movement between the position in which its tip is approximately in line with the tops of the contact fingers 91, as shown in FIG. 8 and that in which it projects beyond the contact fingers 91 as shown in FIG. 9. A guide member 94 terminating in a piston 95 is mounted on the contact member 90 by means of a boss 96; the piston 95, sliding within the cylinder 97 formed in the arcing contact 93, serves both to guide and control the arcing contact in its movement. A passage 98 which opens on to the upper surface of the piston 95 is normally supplied with air under pressure but can be exhausted to the atmosphere. A spring 99 biases the arcing contact 93 outwardly from the contact member 90.

The throat contact 88 has a bore 88c and is arranged to slide longitudinally within a support tube 100 formed as an extension of the insulator top-cap base member 101. The lower end of the support tube 100 is divided in the same way as that of the contact member 90 to form a series of three or more contact fingers 102 inwardly biased by circular garter springs 103. Webs 104 connect the throat contact 88 with a piston rod 105, which at its upper end carries a piston 106 sliding within a cylinder 107 in the top-cap cylinder block 108. The lower end of the piston rod is extended downwards to form the arcing probe 109 of the throat contact.

The choice of the throat contact 88 as the movable main contact of the circuit-breaker simplifies the provision 110 will be in its upper position. tains air under pressure.

.later be described. An annular piston 111 formed at the top of the valve sleeve 110 controls the movements of the latter, which is upwardly biased by springs 112 at its lower end.

A contact pressure spring 113 biases the throat contact 88 downwardly towards engagement with the lower contact.

The interior of the throat contact 88 communicates with the atmosphere by means of an annular passage 114. An annular exhaust valve 115, sliding within an annular recess in the top-cap cylinder block 108, can co-operate with an'annular seating 116 in the top-cap base member 101 to close the passage 114, being biased towards this position by a spring 117. An annular piston 118 formed on the top of the exhaust valve member 115 slides in a cylinder 119 to which compressed air can be supplied to control the movement of the exhaust valve.

The valve gear by means of which the supply of air to the various cylinders is controlled is not shown in the drawing, but it may take any convenient form and may be situated either within the circuit-breaker structure or externally.

The operation of the interrupter will now be described by going through a break-an d-make cycle of operations.

In the closed position of the interrupter, shown in FIG. 8 of the drawings, the inwardly-directed contact surfaces 91a of the contact fingers 91 of the lower contact member 90 engage a corresponding outwardly-directed contact surface 88a of the throat contact 88. In this position the contact fingers 91 are forced apart so that they do not bear against the outer periphery of the arcing contact 93, the circuit through the circuit-breaker being completed solely by the contact fingers 91 and their co-operating contact surfaces on the throat contact 88. The arcing contact 93 is, however, biased upwardly by its spring 99 so that the contact surface 120a of an arcing ring 120 set into its surface makes contact with the contact surface 121a of a corresponding arcing ring 121 within the aperture of the throat contact 88.

Before the commencement of an opening operation, the exhaust valve 115 will be closed, and the sleeve valve The insulator 80 con- To initiate an opening operation of the interrupter, compressed air is supplied through a connection 129 to the lower side of the exhaust valve piston 118. The upper side of this piston being as indicated in permanent connection with the atmosphere, the force of the valve closing spring 117 is overcome and the exhaust valve 115 opens. The interior of the throat contact 88 is thus vented to the atmosphere, but the engaging contact surfaces of the throat contact and the arcing contact 93 act as a valve to prevent the flow of compressed air to the interior of the throat contact, the effect of the difference in air pressure across the contacts being to increase the contact pressure between the arcing contact and the throat contact. This increase of contact pressure is sufficient to overcome the force exerted by the throat contact pressure spring 113 and to cause the throat contact 88 to move upwards slightly. This allows a flow of compressed air to pass from the annular space 122 surrounding the contacts to the lower face of the throat contact piston 106 through the passage 123 to the top-cap cylinder block 108 and through the open sleeve-valve port 124, thereby accelerating the throat contact 88 in an upward direction. The air trapped above the piston 106 in the cylinder 107 is exhausted partly through a bleed aperture 126 and partly through a further port 127 in the sleeve valve As the throat contact 88 moves upward, it is disengaged from the contact fingers 91 of the lower contact member 90, which move inwardly to transfer the current to the arcing contact 93, which is still being pressed against the throat contact 88 by the combined action of the spring 99 and of the air pressure difference across the contacts. When the arcing contact 93 reaches the end of its travel relative to the contact member 90, defined by the travel of the piston 95 within its cylinder 97, the contact surfaces of the arcing contact 93 and of the throat contact 88 are separated, and (if the circuit-breaker is carrying a current) an arc is drawn between them. The separation of the contact surfaces has, however, allowed a blast of gas to fiow between them into the interior of thethroat contact 88 and through the open exhaust valve to the atmosphere. The are is therefore swept into the throat contact 88, being transferred to the arcing probe 109 of the throat contact and the central arcing insert 128 of the arcing contact 93. Only the initial flash is thus carried by the arcing rings and 121 of the two contacts, and all the arcing products are swept into the throat contact and away to the atmosphere.

As the piston 106 approaches the end of its travel, its periphery closes the port 127 in the sleeve valve 110; the subsequent reduced rate of escape of air from the cylinder 107 buffers'the movement of the throat contact.

The condition of the interrupter when the moving contact asembly reaches the limit of its stroke is shown in FIG. 9. It will be seen from this figure that the profile presented by the combined surfaces of the arcing contact 93 and of the contact fingers 91 does not present discontinuities which would raise the electrical stress in the space between the contacts to an undesirable extent and which might result in local turbulent flow of the air blast between the contacts.

At a moment after the initiation of an opening operation by which any are formed between the contacts will have been extinguished, a delay valve, not shown in the drawings, vents the lower side of the exhaust valve piston 118 to the atmosphere through the connection 129, and the exhaust valve closes under the action of its spring 117. The blast of gas through the interrupter therefore ceases. At the same time the passage 98 leading to the upper face of the arcing contact control piston 95 is exhausted to the atmosphere, and the air pressure on the arcing contact causes it to retract within the contact fingers 91, thus increasing the gap between the opposed contact surfaces of the circuit-breaker sufliciently to provide adequate electrical isolation without the use of a separate series isolating switch. The entire interior of the insulator 80 remains full of air under pressure, and the dielectric strength of the medium between the opposed contact surfaces is therefore maintained at a high value.

With reference to this condition of the interrupter, it will be noted that with the exhaust valve 115 in its closed position as shown in FIG. 8, the pressure of the air within the insulator 80 exerts a differential effect on the valve member 115 and biases it towards its closed position. This eifect is produced by the difference of the diameters of the annular exhaust valve seating 116 and the toroidal sealing member preventing air leakage past the upper part of the exhaust valve. Thus when the interrupter is open and the insulator 80 contains air under pressure, the exhaust valve 115 will be maintained in its closed position, preventing loss of air from within the insulator, even though its biasing spring 117 should fail.

The seating 116 of the exhaust valve is housed within a recess in the lower wall of the annular exhaust passage 114; its surface is therefore protected from the hot gases and are products flowing past it during operation of the circuit-breaker.

These features of the exhaust valve and its seating could equally well be applied to the exhaust valve of the interrupters shown in FIGS. 1 to 3 and in FIG. 5.

In order to initiate a closing operation of the interrupter, air under pressure is admitted through the passage 98 to the upper face of the piston 95, restoring the arcing contact 93 to its projected position in relation to the contact fingers 91. At the same time the exhaust valve 115 is opened under the action of air pressure applied to the lower face of the piston 118. A blast of air commences to flow through the interrupter, which is then in the condition shown in FIG. 9. Also at the same moment air is supplied through the connection 131 to the upper face of the piston 111 formed at the top of the sleeve valve 110, forcing the sleeve valve to its lower position. This allows air under pressure to flow through the port 132 of the sleeve valve to the upper side of the throat contact piston 106. The throat contact 88 therefore commences to move downwardly, the air trapped below its piston being exhausted to the atmosphere through a further port 133 at the lower end of the sleeve valve 110 and through the open exhaust passage 114.

As the contacts approach each other, a point will be reached at which the electrical strength of the gap between them is less than the potential difference between them. Owing to the blast of gas flowing between the contact surfaces, the dielectric strength of the intervening medium will be high and the contacts will be very close to each other before flashover in fact occurs between the arcing rings 120 and 121 of the two contacts. The are formed will be at once swept by the air blast into the throat contact 88 and transferred to the central arcing surfaces 128 of the arcing contact and the arcing probe 109 of the throat contact. Further movement of the throat contact causes the arcing rings 120 and 121 to make contact,

short-circuiting and extinguishing the arc. Since the arcing contact 93 is small and light, and is biased towards engagement with the throat contact 88 both by means of the spring 99 and by means of the air supplied under pressure to the upper face of its piston 95, rebound is most unlikely to occur. Furthermore, on engagement of the contact surfaces, these act as a valve to interrupt the flow of air through the circuit-breaker, and the pressure dilference across the arcing contact 93 ensures that the latter is pressed even more firmly against the throat contact 88.

Continued movement of the throat contact causes the contact fingers 91 of the lower member 90 to engage the contact surface 88a of the throat contact, and the load current is transferred to these contact surfaces.

The closing operation now being completed, the exhaust valve 115 is allowed to close by venting the connection 129. The interrupter remains full of air at atmospheric pressure.

Finally the passage 131 is exhausted to the atmosphere to allow the sleeve valve 110 to return to its upper position in readiness for a further opening operation.

The alternative contact arrangements described with reference to FIGS. 6 and 7 for the interrupter of FIGS. 1 to 4 are equally applicable to the interrupter of FIGS. 8 and 9.

What we claim as our invention and desire to secure by Letters Patent is:

1. A gas-blast electric circuit-breaker comprising first and second contact members, said contact members being relatively movable between engaged and disengaged positions, said second contact member having an external cylindrical contact surface, and said first contact member having a plurality of contact fingers disposed in a ring, said fingers being individually biased in an inward direction transverse to the direction of relative movement of said first and second contact members so as to engage, when the first and second contact members are in their engaged position, with said external cylindrical contact surface, an auxiliary contact member mounted on said first contact member within said ring for limited movement relative to said first contact member and laterally disposed with respect to and adjacent to said plurality of contact fingers, means at least temporarily to bias the auxiliary contact member towards said second contact member whereby the auxiliary contact member remains pressed firmly in contact with said second contact member during separation of said first and second contact members during opening operation of the circuitbreaker, and whereby on separation of said plurality of contact fingers from said external cylindrical contact surface during said opening operation said fingers move to make contact with the auxiliary contact member.

2. A gas-blast electric circuit-breaker as claimed in claim 1 wherein said auxiliary contact member has an external cylindrical contact surface with which said fingers make contact on separation from said second contact member.

3. A gas-blast electric circuit-breaker comprising a first contact member, a second contact member having a bore, an external cylindrical contact surface surrounding the mouth of said bore, and an internal annular contact surface within said mouth, said contact members being relatively movable between engaged and disengaged positions, means defining an exhaust passage leading from said bore at least temporarily to atmosphere, said first contact member having a plurality of contact fingers individually biased in an inward direction transverse to the direction of relative movement of said first and second contact members so as to engage, when the first and second contact members are in their engaged position, with said external cylindrical contact surface, an auxiliary contact member mounted on said first contact member for limited movement relative thereto, laterally disposed with respect to and adjacent to said plurality of contact fingers, and having an annular contact surface, means at least temporarily to bias the auxiliary contact member towards said second contact member whereby the annular contact surface of the auxiliary contact member remains pressed firmly in contact with said internal annular contact surface of the second contact member during separation of said first and second contact members during opening operation of the circuit-breaker, and whereby on separation of said plurality of contact fingers from said external cylindrical contact surface of said second contact member during said opening operation said plurality of contact fingers moves to make contact with the auxiliary contact member, wall means defining an enclosure within which said first and second contact members are situated, and means to supply gas under pressure to said enclosure during opening operation of the circuit-breaker whereby when said auxiliary contact member separates from said second contact member a blast of gas passes first between the co-operating contact surfaces of said first and second contact members and subsequently between those of the second main contact member and the auxiliary contact member.

4. A gas-blast electric circuit-breaker comprising a first contact member, a second contact member having a bore, said contact members being relatively movable between engaged and disengaged positions, means defining an exhaust passage leading from said bore to atmosphere, an auxiliary contact member mounted within said first contact member for limited movement relative thereto projecting from said first contact member, and adapted to make sealing contact with said second contact member, wall means defining an enclosure within which said first and second contact members are situated, means to supply gas under pressure to said enclosure during at least part of a closing operation of the circuit-breaker, and means to cause relative movement of said first and second contact members towards one another until said auxiliary contact member makes sealing contact with said second contact member, whereby prior to making of said sealing contact said gas escapes through said bore in said second contact member and after making of said sealing contact further escape of gas is prevented, and further including a blast valve controlling admission of gas to said enclosure, and forming part of said first contact member,whereby said blast valve opens as Sald'fiISt contact member moves from an engaged position to a disengaged position.

5. A gas-blast electric circuit-breaker including a circuit interrupter having three co-operating interrupter contacts, namely a first main contact, a second main contact, and an auxiliary contact, said first main contact having a fixed tubular base and having its end divided to form a series of contact fingers integral with said fixed tubular base, said contact fingers being biased inwardly and being formed with inwardly-directed contact surfaces, said second main contact being moveable, having a hollow bore, an aperture of which opens towards sa1d first main contact, and being formed with an outwardly- .directed cylindrical contact surface and with an arcing contact surface surrounding said aperture, said auxiliary contact being slidably mounted on said first main contact, concentrically with said contact fingers, for movement between a first position in which it projects beyond said contact fingers and a second position in which it is substantially within said contact fingers, said auxiliary contact being formed with an arcing contact surface to cooperate with the arcing contact surface of said second main contact and with an outwardly-directed cylindrical contact surface of smaller diameter than the cylindrical contact surface of said second main contact, said circuitbreaker also comprising means urging said auxiliary con- .tact to said first position, whereby in the closed position of the interrupter the inwardly-directed contact surfaces of said contact fingers engage the outwardly-directed cylindrical contact surface of the second main contact and .are'radially spaced from the outwardly-directed cylindrical contact surface of said auxiliary contact, and the arcfirst main contact before it separates from the auxiliary contact, said contact fingers moving inward after disengagement from said outwardly-directed cylindrical contact surface of said second main contact to make contact with the outwardly-directed cylindrical contact surface of' said auxiliary contact, thereby transferring the current to the latter..

6. A gas-blast electric circuit-breaker as claimed in claim 5, comprising also means enclosing said interrupter contacts to define an'enclosure surrounding said interrupter contacts, compressed gas supply means in permanent connection with said enclosure, and means connecting said hollow bore of the second main contact at least temporarily to atmosphere during opening of said circuit interrupter, whereby during opening of said circuit interrupter a blast of gas passes from said compressed gas supply means, through Said enclosure, between said contact fingers and said second main contact, and then between the arcing contact surface of the second main contact and the arcing contact surface of the auxiliary contact into said hollow bore and thence to atmosphere. 7. A gas-blast electric circuit-breaker as claimed in claim 6, comprising also an arcing probe within said hollow bore of the second main contact, whereby, when "swept into said hollow bore by said blast and thus to atmosphere.

8. A gas-blast electric circuit-breaker including a circuit interrupter having three co-operating interrupter contacts, namely a first main contact, a second main contact, and an auxiliary contact, said first main contact having a fixed tubular base and having its end divided to form a series of contact fingers integral with said fixed tubular base, said contact fingers being biased inwardly and being formed with inwardly-directed contact surfaces, said second main contact being moveable, having a hollow bore, an aperture of which opens towards said first main contact, and being formed with an outwardlydirected cylindrical contact surface and with an arcing contact surface surrounding said aperture, said auxiliary contact being slidably mounted on said first main contact, concentrically with said contact fingers, for movement between a first position in which it projects beyond said contact fingers and a second position in which it is substantially within said contact fingers, said auxiliary contact being formed with an arcing contact surface to co-operate with the arcing contact surface of said second main contact and with an outwardly-directed cylindrical contact surface of smaller diameter than the cylindrical contact surface of said second main contact, said circuitbreaker also comprising means urging said auxiliary contact to said first position relative to said first main contact, including resilient means abutting both said auxiliary contact and said first main contact, whereby during closing of said circuit interrupter firstly the arcing contact surface of said auxiliary cont-act engages the arcing contact surface of said second main contact and later the inwardly-directed contact surfaces of the contact fingers engage the outwardly-directed cylindrical contact surface of the second main contact and disengage from the smaller-diameter outwardly-directed cylindrical contact surface of the auxiliary contact, any are which is drawn being struck between said arcing contact surfaces.

9. A gas-blast circuit-breaker comprising a circuit interrupter having three co-operating interrupter contacts, namely a first main contact, a second main contact, and an auxiliary contact, said first main contact having a fixed tubular base and having its end divided to form a series of contact fingers intergral with said fixed tubular base, said contact fingers being biased inwardly and being formed with inwardly-directed contact surfaces, said second main contact being moveable, having a hollow bore, an aperture of which opens towards said first main contact, and being formed with an outwardly-directed cylindrical contact surface and with an arcing contact surface surrounding said aperture, said auxiliary contact being slidably mounted on said first main contact, concentrically with said contact fingers, for movement be tween a first position in which it projects beyond said contact fingers and a second position in which it is substantially within said contact fingers, said auxiliary contact being formed with an arcing contact surface to cooperate with the arcing contact surface of said second main contact and with outwardly-directed cylindrical contact surface of smaller diameter than the cylindrical contact surface of said second main contact, said circuitbreaker also comprising means urging said auxiliary contact to said first position, said circuit-breaker comprising also means enclosing said interrupter contacts to define an enclosure surrounding said interrupter contacts, compressed gas supply means in permanentconnection with said enclosure, an exhaust valve connected to said hollow bore to control the outlet of gas therefrom, bias means to bias said exhaust valve to the closed position, means to cause relative movement of said second main contact away from said first main contact and from said aux- 1liary contact to an open position of the interrupter, and means to open said exhaust valve during said relative movement to allow a blast of gas to flow between the contacts into said hollow bore and through the open exhaust valve to atmosphere, said bias means causing the exhaust valve to reclose so that said enclosure remains full of air under pressure whereby to provide adequate electrical isolation without the use of a separate series isolating switch.

10. A gas-blast electric circuit-breaker including a circuit interrupter having three co-operating interrupter contacts, namely a first main contact, a second main contact, and an auxiliary contact, said first main contact having a fixed tubular base and having its end divided to form a series of contact fingers integral with said fixed tubular base, said contact fingers being biased inwardly and being formed with inwardly-directed contact surfaces, said second main contact being moveable, having a hollow bore, an aperture of which opens towards said first main contact, and being formed with an outwardlydirected cylindrical contact surface and with an arcing contact surface surrounding said aperture, said auxiliary contact being slidably mounted on said first main contact, concentrically with said contact fingers, for movement between a first position in which it projects beyond said contact fingers and a second position in which it is substantially within said contact fingers, said auxiliary contact being formed with an arcing contact surface to cooperate with the arcing contact surface of said second main contact and with an outwardly-directed cylindrical contact surface of smaller diameter than the cylindrical contact surface of said second main contact, said circuitbreaker also comprising means urging said auxiliary con tact to said first position relative to said first main contact including resilient means abutting said auxiliary contact and said first main contact, piston-and-cylinder means comprising a piston element and a co-operating cylinder element, one said element being structurally united with said auxiliary contact and the other said element being structurally united with said first main contact, for slidably mounting said auxiliary contact on said first main contact, means enclosing said interrupter contacts to define an enclosure surrounding said interrupter contacts, compressed gas supply means in permanent connection with said enclosure, said circuit-breaker further comprising fixed structure including a support tube and cylinder means, said second main contact being mounted in said support tube to slide longitudinally therein, a .piston rod within the hollow bore of said second main contact, webs connecting said second main contact with said piston rod, piston means connected to said piston rod and slidably mounted in said cylinder means, means to supply gas under pressure to said cylinder means to actuate said piston means to move said second main contact between open and closed positions of said circuit interrupter, said fixed structure defining passage means communicating at least temporarily between the interior of said support tube and atmosphere, whereby a blast of gas flowing between the contacts and through said hollow bore may pass between said webs, through said support tube and through said passage means to atmosphere irrespective of the position of said second main contact.

1 1. A gas-blast electric circuit-breaker as claimed in claim comprising also an annular exhaust valve mounted in said fixed structure and moveable between a first position in which the interior of said support tube communicates freely with atmosphere and a second position in which said passage means is closed, bias means to bias said exhaust valve to said second position, said fixed structure also including a cylinder, a piston mounted to slide in said cylinder and structurally united with said exhaust valve, and further comprising means to supply gas under pressure to said cylinder to overcome said bias means and move said annular exhaust valve to said first position.

12. A gas-blast electric circuit-breaker as claimed in claim 11 comprising also a communication between said cylinder means and said passage means upstream of said annular exhaust valve, whereby on opening of said annular exhaust valve said cylinder means is vented to atmosphere and the force loading said piston means in the sense of closing said circuit interrupter is reduced.

13. A gas-blast electric circuit-breaker including a circuit interrupter having three only co-operating interrupter contacts, namely a first main contact, an auxiliary contact slidably mounted on said first main contact, and a sec-ond main contact movable relative to said first main contact and to said auxiliary contact between engaged and disengaged positions, said first main contact having a tubular base and having its end divided to form a series of contact fingers integral with said tubular base, said contact fingers being biased inwardly and being formed with inwardly-directed contact surfaces, said second main contact being formed with a first outwardlydirected cylindrical contact surface and with a first arcing contact surface, said auxiliary contact being formed with a second arcing contact surface to co-operate with said first arcing contact surface and being formed with a second outwardly-directed cylindrical contact surface which is of smaller diameter than said first outwardly-directed cylindrical contact surface and which is substantially within and surrounded by said contact fingers, and means urging said auxiliary contact towards said second main contact, whereby during opening of said interrupter said inwardly-directed contact surfaces separate from said first outwardly-directed cylindrical contact surface before said first arcing contact surface separates from said second arcing contact surface, and said contact fingers move inward so that the inwardly-directed contact surfaces engage said second outwardly-directed cylindrical contact surface.

14. A gas-blast electric circuit-breaker comprising a first contact member, a second contact member having a bore, said contact members being relatively movable between engaged and disengaged positions, means defining an exhaust passage leading from said bore to atmosphere, an auxiliary contact member mounted within said first contact member for limited movement relative thereto projecting from said first contact member, and adapted to make sealing contact with said second contact member, wall means defining an enclosure within which said first and second contact members are situated, means to supply gas under pressure to said enclosure during at least part of a closing operation of the circuit-breaker, and means to cause relative movement of said first and second contact members towards one another until said auxiliary contact member makes sealing contact with said second contact member, whereby prior to making of said sealing contact said gas escapes through said bore in said second contact member and after making of said sealing contact further escape of gas is prevented, and exhaust valve means disposed in said exhaust passage, whereby opening of said exhaust valve permits gas under pressure in said enclosure to escape therefrom through said bore.

References Cited by the Examiner UNITED STATES PATENTS BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, E. JAMES SAX, ROBERT K. SCHAE- FER, Examiners.

Claims

1. A GAS-BLAST ELECTRIC CIRCUIT-BREAKER COMPRISING FIRST AND SECOND CONTACT MEMBERS, SAID CONTACT MEMBERS BEING RELATIVELY MOVABLE BETWEEN ENGAGED AND DISENGAGED POSITIONS, SAID SECOND CONTACT MEMBER HAVING AN EXTERNAL CYLINDRICAL CONTACT SURFACE, AND SAID FIRST CONTACT MEMBER HAVING A PLURALITY OF CONTACT FINGERS DISPOSED IN A RING, SAID FINGERS BEING INDIVIDUALLY BIASED IN AN INWARD DIRECTION TRANSVERSE TO THE DIRECTION OF RELATIVE MOVEMENT OF SAID FIRST AND SECOND CONTACT MEMBERS SO AS TO ENGAGE, WHEN THE FIRST AND SECOND CONTACT MEMBERS ARE IN THEIR ENGAGED POSITION, WITH SAID EXTERNAL CYLINDRICAL CONTACT SURFACE, AN AUXILIARY CONTACT MEMBER MOUNTED ON SAID FIRST CONTACT MEMBER WITHIN SAID RING FOR LIMITED MOVEMENT RELTIVE TO SAID FIRST CONTACT MEMBER AND LATERALLY DISPOSED WITH RESPECT TO AND ADJACENT TO SAID PLURALITY OF CONTACT FINGERS, MEANS AT LEAST TEMPORARILY TO BIAS THE AUXILIARY CONTACT MEMBER TOWARDS SAID SECOND CONTACT MEMBER WHEREBY THE AUXILIARY CONTACT MEMBER REMAINS PRESSED FIRMLY IN CONTACT WITH SAID SECOND CONTACT MEMBER DURING SEPARATION OF SAID FIRST AND SECOND CONTACT MEMBERS DURING OPENING OPERATION OF THE CIRCUITBREAKER, AND WHEREBY ON SEPARATION OF SAID PLURALITY OF CONTACT FINGERS FROM SAID EXTERNAL CYLINDRICAL CONTACT SURFACE DURING SAID OPENING OPERATION SAID FINGERS MOVE TO MAKE CONTACT WITH THE AUXILIARY CONTACT MEMBER.