ELECTRIC SWITCH PROVIDED WITH AN ARC-BLASTING UNIT

Abstract

This electric switch comprises an arc-blasting unit with a compression cylinder (25) enclosing a compression chamber (27) mobile together with the mobile contacts (2), and a stationary piston (13) at an end of the compression chamber, provided with a support rod made up as a blowpipe (9) which channels the gas compressed in the chamber when the contacts separate to a nozzle (10) that directs the flow to a separation place (12) of the contacts so as to efficiently blast electric arcs. The arrangement is lightweight and occupies little space.

Claims

1-8. (canceled)

9. An electric switch comprising: at least one fixed contact; at least one mobile contact sliding in front of the fixed contact in a movement direction between a closed position at which it is joined with the fixed contact and an open position at which it is separated from the fixed contact; at least one fixed blowpipe parallel to the movement direction, the at least one fixed blowpipe comprising a nozzle at a front end, the nozzle being directed towards a place at which the mobile contact separates from the fixed contact, and a piston at a rear end; a mobile enclosure connected to the mobile contact and sliding around the at least one fixed blowpipe and around the piston, a compression chamber, which communicates with the nozzle, being defined by the mobile enclosure, the piston and the at least one fixed blowpipe.

10. The electric switch according to claim 9, wherein the compression chamber is provided with a valve that opens at a negative pressure of less than 1 bar inside the compression chamber.

11. The electric switch according to claim 10, wherein the valve is provided on the piston.

12. The electric switch according to claim 9, wherein the piston has an elongated shape, and the enclosure has a corresponding elongated cross-section.

13. The electric switch according to claim 12, further comprising a plurality of the fixed contacts and the mobile contacts, the mobile contacts being mobile together, and a plurality of blowpipes, each of the plurality of blowpipes being associated to a respective one of the fixed contacts and of the mobile contacts, wherein the piston is single and common to all the plurality of blowpipes, and wherein the enclosure is also single.

14. The electric switch according to claim 13, wherein the plurality of blowpipes are arranged in a row along the piston, and the fixed contacts and the mobile contacts are arranged in rows parallel to the row of the plurality of blowpipes.

15. The electric switch according to claim 9, wherein the enclosure is fastened to a carriage that also displaces the mobile contact.

16. The electric switch according to claim 9, wherein the enclosure and the blowpipe are both arranged with overlaps with the mobile contact along the movement direction.

17. The electric switch according to claim 9, wherein the mobile enclosure comprises at least one opening at a front face, through which the at least one fixed blowpipe extends.

18. The electric switch according to claim 9, wherein the piston and the mobile enclosure are located aside the at least one mobile contact with respect to a longitudinal direction of the at least one mobile contact, without being in extension of the at least one mobile contact in the longitudinal direction.

19. The electric switch according to claim 9, wherein the at least one fixed blowpipe has a wall provided with openings just before the piston.

20. The electric switch according to claim 15, wherein the carriage comprises at least one axis connected to a near part of the at least one mobile contact.

21. The electric switch according to claim 20, wherein the at least one axis extends through a longitudinal slot made through a contact unit surrounding the at least one mobile contact, and the carriage is supported by the contact unit.

Description

[0012] These and other aspects, characteristics and advantages of the invention will now be exposed in greater detail with the comment of the following figures, which disclose a particular embodiment of the invention in a purely illustrative way:

[0013] FIG. 1 shows a cutaway view through one pair of contacts with corresponding blowpipe, the switch being at the closed position;

[0014] FIG. 2 shows the same view for the open position of the switch;

[0015] FIG. 3 particularly shows the inside of the compression system during a closing operation with open valves; and

[0016] FIG. 4 shows the compression system again, but in an opening operation with closed valves.

[0017] FIGS. 1 and 2 partly illustrate an earthing switch comprising at least one pair of contacts comprising a fixed contact 1 and a mobile contact 2, a front end of which can penetrate into the fixed contact 1.

[0018] The mobile contact 2 is reversibly moved in a movement direction X-X (FIG. 1). The invention can be implemented independently on the number, kind and layout of contact pairs. For instance, the switch can be three-phase and the fixed and mobile contacts are aligned in straight rows perpendicular to the movement direction X-X.

[0019] The arrangement also comprises blowpipes 9 located aside the pairs of fixed contacts 1 and mobile contacts 2. Front ends of the blowpipes 9 are equipped with nozzles 10.

[0020] The figures show that the blowpipes 9 are straight, continuously hollow tubes, and the nozzles 10 are provided with a curved or elbowed drilling 11 that is directed towards places 12 at which the mobile contacts 2 separate from the fixed contact 1 and electric arcs will thus be present. The blowpipes 9 are in the same number as the pairs of fixed and mobile contacts, are also arranged in a straight row and extend at a short distance above respective ones of the mobile contacts. Rear ends of the blowpipes 9 are connected to a piston 13 which is common to all the blowpipes 9, as illustrated by FIGS. 3 and 4. The walls of the blowpipes 9 have openings 14 just before the piston 13.

[0021] The mobile contacts 2 slide in mobile contact tulips 15. The mobile contact tulips 15 are supported by tubular contact units 16 in the extension of the mobile contacts 2. A carriage 17 is supported by the contact units 16 and slides on them. It comprises axes 18 which are articulated to rear parts of the mobile contacts 2 and extend through the contact units 16 through longitudinal slots 19 machined at the upper and lower surfaces of the contact units 16. The switch operation consists in movements of the carriage 17, displacing the axes 18 between opposite ends of the slots 19 and the mobile contacts 2 between the closed position of the contacts of FIG. 1, in which the mobile contacts 2 extend in the front cavity 6, and the open position of FIG. 2, in which the mobile contacts 2 are completely retracted into the mobile contact tulips 15 and central bores 20 of the contact units 16. The carriage 17 is displaced by a driving mechanism-(not shown).

[0022] An enclosure in the shape of a compression cylinder 25 is fastened to the carriage 17 and displaced with it. It comprises openings 26 at the front face, through which the blowpipes 9 extend. The piston 13 is contained in the compression cylinder 25. The piston 13 has an elongated rectangular shape, and the compression cylinder 25 a similarly elongated rectangular cross-section, so that they extend over the entire width of the row of mobile contacts but with a reduced height and can thus be accommodated easily in usual housings. Seals are provided at the openings 26 and around the piston 13 so that a compression chamber 27 defined by the compression cylinder 25 and the piston 13 generally communicates with the outside only through the nozzles 10. However, valves 28 are present on the piston 13. They are generally closed by sets of compression springs 29, but are able to open slots 32, and establish a supplementary communication of the compression chamber 27 with the outside, when a threshold of negative pressure is reached in the compression chamber 27.

[0023] When the switch must open, the carriage 17 is slid rearwards, the mobile contacts 2 separate from the fixed contact tulips 1, and an electric arc appears between them at the separation places 12. The compression cylinder 25 is slid on the blowpipes 9, and the compression chamber 27 shrinks. The gas contained therein is compressed and flows outside at the nozzles 10, which deflect it towards the separation places 12. The flows remain concentrated in thin beams directed precisely by the nozzles 10. Most of the blast energy therefore contributes to the arc extinction, in contrast with known devices in which the gas flow would be spread in the front cavity 6 comprising the contacts so that the overall efficiency would be lower. The valves 28 remain closed.

[0024] And when the switch returns to the closed state, a reverse movement is made, and the compression chamber 27 expands. A negative pressure buildup appears inside so that the valves 28 open by uncovering slots 32 punched through the piston 13 for facilitating a gas ingress into the compression chamber 27 until the pressure has increased at a degree allowing the springs sets 29 to bring the valves 28 back on the piston 13.

[0025] An originality of the invention is that the piston 13 is stationary but the enclosure surrounding itthe compression cylinder 25is mobile, in contrast to known devices in which a piston depends on the mobile contacts and the enclosure in which the piston slides is a part of the housing or another stationary structure. The inventive arrangement enables a compact layout in which the piston 13 and compression cylinder 25 are not a longitudinal extension of the mobile contacts but are located aside them. The driving mechanism is simple and lightweight, the compression cylinder 25 and the mobile contacts being moved together by the same mechanism (the carriage 17). The piston rodsthe blowpipes 9can be made up with bores for channeling the gas flow and directing it accurately towards the even placesthe separation places 12where it is needed. Also, the pressure variations in the compression chamber 27 during the swift connecting and disconnecting movements develop opposing forces that dampen these movements at the end of their respective stroke.

[0026] The separation place 12 to which the gas flow is directed is not necessarily adjacent to the fixed contacts as in these drawings, but can be present at any location between the fixed contacts and the mobile contacts at the open position, in which the arc could be present.

[0027] While the detailed description concerned an earthing switch, the invention could be implemented in other kinds of electric switches.

[0028] There is no condition on the gas filling the housing, which may be an insulating gas like SF6 or not.