US3158723A - Arc-extinguishing means for power switches having stationary and movable contact pieces - Google Patents

Description

Nov. 24, 1964 a. BUECHNER ARC-EXTINGUISHING MEANS FOR POWER SWITCHES HAVING STATIONARY AND MOVABLE CONTACT PIECES 5 Sheets-Sheet 1 Filed March 5, 1961 INVf/QTOR GERHARD BUECHNER Nov. 24, 1964 G. BUECH'NER ARC-EXTINGUISHING MEANS FOR POWER SWITCHES HAVI STATIONARY AND MOVABLE CONTACT PIECES 5 Sheets-Sheet 2 Filed March 3, 1961 m y W NM w ///\\\M//\\\\\\\\\\\\\\\\\\\ mm A M /l/ll/l/l l z W Aw 8 H W W xm .1 9 8 I r///////////// Nov. 24, 1964 5. BUECHNER 3,158,723

ARC-EXTINGUISHING MEANS FOR POWER swrrcnas HAVING STATIONARY AND MOVABLE CONTACT PIECES Filed March 3, 1961 5 Sheets-Sheet 3 Fig.3 I/VVENTOR:

GKRHARD BUEOINER ATTORIYIF) 3,158,723 ES HAVING 1964 G. BUECHNER ARC-EXTINGUISHING MEANS POWER SWITCH STATIONARY AND MOV E commcw PIE. Filed March 3, 1961 I //v VEN TOR- GERHA RD 5 UECHNER BY Nov. 24, 1964 G. BUECHNER 3,153,723

ARC-EXTINGUISHING MEAN OR P R S CHE-S HAVING STATIONAR Y AND M BLE TAC IECES Filed March 3, 1961 5 Sheets-Sheet 5 INVEN TOR: GHPHARD BUECHNER- 5y W i I ATTORNEY United States Patent rev any AND This invention relates to electric power switches having stationary and movable contact pieces, and ass particular reference to an improved arc quenching means.

it is known to improve certain characteristics and properties of a switch, such as its freedom from arcingback, with the aid of forced fluid flow. For example, a pump piston moving with the contact pin can produce a fluid flow which washes the tip of said pin. Another known possibility is the injection of the arc quenching fluid into the extinction chamber, by a displacement brought about by the moving pin itself. Pump pistons provided with a special drive mechanism are also used for this purpose. A further method consists in producing an auxiliary are for building up the pressure, wnereby a fluid flow aimed the principal arc may be a nod. The last-mentioned method has the disadvantage that it depends on the intensity of the arc-current. However, the requirements or modern switch-gear, such as freedom from arcing-back when switching capacitive currents on and oil, call for a current more or less independent of the size of the switclroli current. The means opera c with pistons are of relatively si e construction a rugged in operation. They, howeve have disadvanage that only one of the contact pieces is washed by the iluid current. it is, however, of great advantage for are extinction that both are bases be washed by the fluid. This has been unequivocally corroborated by the l and experimental investigations. The process or circurnilow may e realized in cases where the is held ready under pressure at all times, such as in an blast circuit-breakers. Washing of both contact pieces then is only a question of the proper arrangement of the quenching elements. To sucllend, however, additional storage means is required which always has to malcc available the requisite quantity of pressurized fluid, even when not actuating the switch. in such case, however, the guarantee that the quencl'iing capacity of the switch is maintained at all times, is substantially smaller than in the case of follow-up pistons and the lil;

The deficiencies of the known mean of this type may be avoided by providing, in accordance with the teachings of the present invention, two concentric insulating tubes extending in direction of the switch-rod path. The

gap between these two tubes leads to an annular nozzle in the vicinity of a pair of stati nary contact pieces, and said gap has a further communication to the interior of the extinguishing means the vicinity of a pair of movable contact pieces which cause at least two fluid currents.

The advantage of the invention resides in the fact that the two pairs of stationary and movable contact pieces are washed by fluid without need for any additional storage means, and that tile s ace between the stationary ice and the movable contact pieces is subjected to a fluid current which is adjusted to the quenching conditions.

Forms of the invention are shown, by way of example, in the drawing, in which:

FIG. 1 shows a first form in vertical section; FIG. 2 illustrates schematically and on a much larger scale the position of the movable contact or burning pin shortly after separation of the metallic current path, i.e. shortly after creation of an arc; FIG. 3 sin r to FIG. 2 showthe lower position of the contact pin and contact head; 4- depicts a second form of the invention in a manner similar to 1; MG. 5 shows a third form with a different nozzle contact piece; am. EEG. 6 illustrates a fourth form with a pair of movable contact p eces affording an improved guiding of fluid along the burning contact Like carts are designated by the same numerals throughout the drawings. All the arrangements shown are sections of a complete switchgear unit. T .16 invcntion may be used with gaseous and liquid quenching agents, and for low and high-tension switches.

in FIG. 1 a iiange provided with a ter iinal or point of current supply is screwed to the upper lio'. To said flange is secured a metallic sleeve which holds the exterior insulating tube in the latter is disposed an intermediate tube also made of insulating material. The tube 5, together with an interior insulating tube 5, forms a plurality of channels and betwce these tubes. This communication terminates at its upper end in an inwar y directed annular nozzle-like gap 9/. At its lower end, openings 7 lead to the interior of the tube 4. Tube t at its lower end is closed by the metallic sleeve 19 and a flange screwed thereto which comprises a terminal or point of current supply ll.

serve as stc onary current conductors or Contact pieces as well as for guiding gas now. On body E3 is seated the laminated conact piece which the on-state of a metallic connection with the on the movable switch rod 126. The movable contact piece includes also a central part i? which is positioned in body 15 in the switch-on s. without, however, carrying any substantial current on. account of the great contact resistance. At the rear end of the movable contact piece is a piston defining formation 21. s e a cylinder within which the piston 21 moves. This der is filled with quenchi g fluid. From rod 1- electric current is cond'cc contact piece is and the inter, iezliate piece to the current terminal it. in a housing is disposed the mechanism for moving rod 16, which may co suitable means. Upper housing 1 is suitably for a butter chamber or may contain npers tors of known type.

in FIG. 2, contact head 15 with its pistonlilre lug has been moved sli 'htly out of the switch-on position. An arc has been formed between head If and a lamination of contact piece is. Further, the descending niston Zli has displaced quenching fluid. At the beginning of the .iovernent of the piston in switch-opening direction there is the possibility that quenching fluid will flow over the piston laterally and escape along 1'7 through the nozzle opening in the position shown, the piston has 3 just closed the annular flow-in space 23. On the other hand, gap 9 has just been uncovered by the upper edge of head 15. Piston 21 thus moves the fluid behind it through the openings '7 (FIG. 1) into the channels 8, whence it flows in a directed beam from gap 9. The short are 24 thereby is forced to form a loop which finally contacts body 13 so that a new are base is established there, while the arc base on one of the laminations 1.4 is extinguished. Also, the arc base of the movable contact piece changes, under the action of this fluid current, from the upper rim of head 15 to the burning tip 17. In this manner, the two contact functions, namely constant current contact and are contact, may be carried out separately and by means of different materials. During the further descent of head 15, piston 21 continues to move the fluid through the channels and gap 9, and the fluid escapes through body 13. The re base is thus shifted into the interior of nozzle 13, the extent of such travel depending on the flow intensity. In order to avoid, in the case of very pronounced fluid currents such as shortcircuit disconnections resulting from a heavy current produced by the arc itself, any unnecessarily great extension of the arc in its travel, a limiting pin 112 (Fl 1) may be provided. The nozzle 13 has the particul rly important function of screening the hot spot at the are base (which still emits electrons long after the arc been cxtin guished), with the aid of the advanced cold nozzle rim.

After having moved a certain distance, contact head 15 reaches the position shown in FIG. 3. It will be noted that the interior of the cylinder is provided with annular recesses exemplified by the region designated 23. These recesses are more closely spaced in the region occupied by the piston 21 during the initial portion of its stroke than in the region occupied by the piston during the later portion of its travel. As a result, the contact between the piston and the cylinder is greater during the initial portion of its stroke than later, whereby less fluid travels past the piston during the earlier part of the piston travel.

In FIG. 3, piston 21 has just left the portion of the interior insulating tube 6 which has the more closely spaced recesses, mid now laterally uncovers a much longer annular space. The fluid from the space below the piston thus can more freely flow around the piston in the axial direction of the cylinder, and thus flow directly along pin 17. The cross-sections of the openings in t. e piston and those of the channels 8 and of the gap 9 are so graded that the fluid current which previously flowed through the channels 8 now follows both paths and is divided in a predetermined ratio. The result is that the interior space about the are which previously had been washed only to a limited extent, now is intensively washed in the vicinity of the quenching position, and the arc column is thus cooled. The fluid flow about pin 17 which still continues after the arc has been extinguished, electrically screens the emitting hot spot left there from the switching path. For similar reasons, provision also has been made that the flow from gap 9 ceases only when the switching path has again been sufficiently consolidated electrically. Such flow of fresh fluid well insulates or screens the upper fixed contact pieces.

In the example shown in FIG. 4, tubular stationary contacts 25, 26 are provided in place of the laminated contact pieces 14, 18 of FIGS. 1 t0 3, and the movable contact head as well as the switch rod is formed as a tubular contact piece 27. Pin 17 corresponds to the former design, While in the former example, however, the piston producing the quenching fluid flow was an integral part of the reciprocable switch rod, 21 fixed piston 2% is used here. It is, however, also possible to use a piston which is driven in the opposite direction by the contact tube, for example by means of any suitable reversing gear. The other structural components correspond to those of FIG. 1, and the mode of operation of the example shown in FIG. 4 is as follows:

As soon as contact tube 27 through any suitable driving mechanism (not sh wn) is mo ed downwardly from the switch-on position, it displaces fluid from its interior due to the action of fixed piston 23, and the fluid flows along pin 17. The fluid present in the space between tube 6 and tube 27 is forced by a collar 29 on the outside of tube 27, which collar slides snugly in tube 6, through the openings 7, channels 8 and gap past nozzle contact 13 and through the opening in latter into the buffer chamber Further, when contact tube 27 moves into the drive housing as, the fluid present in the latter is displaced and flows through compensating bores 31, the openings 7, channels 8 and gap 9 to the fixed contact pieces 13 and 25.

In the example shown in HG. 5, I: again is the metallic flange which holds tne exterior insulating tube 4-. The intermediate insulating tube 5, the interior insulating tube 6 and gap 9 formed by the two tubes correspond to the parts of FIG. 1. The nozzle body 13 is practically unchanged in its outside dimensions. Additionally, however, bores 32 have been provided in upper portion, while the lower portion is formed as a sliding contact piece. The latter may be of any suitable nozzlelike construction. In the drawing, contact piece 33 is a slotted piece of tube with an annular ring in the switch-on position, the exterior tubular contact piece 25 as well as the interior nozzle contact-piece 33 are in metallic contact with the movable contact counterpieces 1'7 and 15 or 27. It is of advantage to so form the contact pieces that the inner pair of contact pieces 33, 17 is separated last during the switch-off procedure. The holes erve to enhance the fluid flow. Since the cross-sccticn of the openings in the nozzle contact piece 33 possibly may not sufflce for the quick discharge of fluid, additional venting means may be provided by increasing the number of bores 32.

In the form of invention shown in FIG. 6, a cap 35 having a central bore as is movable in contact tube 27. The lower edge of the cap is provided with a plurality of openings 37. The position shown corresponds to the position of contact tube 27 at the end of the switch-off movement. A bottom lug 30 of contact pin 1'7 has entered a damping bore of fixed piston 28. Bores 4d disposed laterally of pin 17 serve for letting quenching fluid flow from the space above piston During the switch-off movement, the displaced fluid flows through the bores 4% along pin 27 and through bore as of cap 3 into the quenching space. The openings 37 are closed by a bulge ti on contact tube 2". These openings serve for providing, during the switching-on movement, a possibility or reverse flow for the fluid present in front of cap 35, as then bore 36 in depressed cap 35 is fully occupied and closed by pin 17. The collar 29 provided on contact tube again produces, during the switch-off movement, the second fluid current through the openings 7, channels 3 and gap 9 to the fixed contact pieces. The compensating bores 31 in the lower metallic body Til allow the fluid to balance its pressure in the channels 8 and the drive housing What I claim as new and desire to secure by Letters Patent, is:

An electric switch including stationary and movable contact pieces and arc-quenching means, each of said contact pieces comprising a central arc-carrying contact and an annular current-carrying contact surrounding and spaced from said central contact; said current-carrying contacts being adapted to engage to close the switch and to disengage to open the switch, disengagement of said currentcarrying contacts engendering an are between them; said arc-quenching means includin an annular nozzle surrounding said current-carrying contacts, means for directing a fluid blast through said nozzle toward the interior of said annular contacts in order to shift the are from said current-carrying contacts to said arccarryiug contacts, and means for directing a fluid blast along the of said current-carrying contacts after said nozzle-directed blast has been effective long enough to shift the arc, said fluid-directing means including a piston movable with said movable contact piece and a cylinder within which said piston moves, the interior surface of the cylinder having annular recesses so spaced that during the initial portion of the piston stroke in the direction of switch opening the contact between the piston and cylinder is greater than during the later portion of the piston stroke, said cylinder being filled with quenching fluid and being provided with a communication between the region behind the piston and said annular nozzle, whereby the blast created during said initial portion of piston travel is directed mainly through said communication while the blast created during the later portion of piston travel is mainly past said piston in the axial direction of the cylinder.

References Qited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Sweden Nov. 10, 1936 Switzerland July 1, 1950 Austria Feb. 10, 1955 Great Britain Dec. 18, 1941

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