GB2095476A

GB2095476A - Vacuum switching devices

Info

Publication number: GB2095476A
Application number: GB8208182A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1981-03-20
Filing date: 1982-03-19
Publication date: 1982-09-29
Also published as: JPS57168435A; DE3111789A1

Abstract

A vacuum switching tube (10) is fastened to a conducting support (12) so that a fixed current-conducting bolt (11) of the tube passes through an aperture (25) in the support and the tube (10) can undergo limited pivotal adjustment relative to the support. The adjustment is facilitated by a bearing ring (30) positioned around the bolt (11) between the support (12) and the evacuated envelope of the tube (10). The bearing ring (30) is formed with a spherically curved annular concave bearing surface facing towards the said envelope and cooperates with an opposing convex annular bearing surface (29) provided around the bolt (10), where it projects from the said envelope, so as to permit such adjustment in any direction. <IMAGE>

Description

SPECIFICATION Vacuum switching devices Th invention relates to vacuum switching devices.

/A vacuum switching device with an evacuated switching tubehaving a fixed current-conducting bolt projecting from the evacuated envelope of the tube and secured through an aperture in a support having a bearing surface curved concavely towards the envelope of the switching tube so as to permit limited pivotal movement of the tube is described in German Patent Specification 2331 503. The support at its side towards the switching tube envelope has a concave surface against which bears a corresponding convex surface of the switching tube. In addition, pressure is maintained between these complementary surfaces by means of a spring arranged to be effective between the end of the fixed currentconducting bolt and the side of the support that is remote from the switching tube envelope.The fixed bolt can be inserted through the opening of the support with such a retaining spring already positioned on the bolt, and fastening is achieved by means of a bayonet fitting.

Such a pivotable fastening of the switching tube can be particularly useful when the switching tube is comparatively long, as is ordinarily the case with a tube for use at high operating voltages, for example 30 kV or more. Without such a fastening, which provides for tolerance compensation, there would be a danger that the opposite end of the switching tube, where a movable current-conducting bolt is located, would be subjected to rather large forces of deflection away rom an intended normal position, there being an actuating mechanism adjusted for connection to the movable bolt at its intended normal position. Tolerance compensation at the point pf connection of the actuating mechanism with the switching tube may be unacceptably expensive.

An object of the present invention is to provide a pivotable fastening arrangement, in a vacuum switching device, which is simpler and therefore potentially cheaper to produce than the prior arrangement.

According to the present invention there is provided a vacuum switching device including an evacuated switching tube of the type having a fixed current-conducting bolt, one end portion of which projects from the evacuated envelope of the tube, wherein the said one end portion of the bolt passes freely through an aperture in a support member and retaining means are arranged to inhibit withdrawal of the bolt from the aperture, thereby to secure the switching tube to the support member, whilst permitting limited pivotal adjustment of the disposition of the tube relative to the support member, there being between the support member and the said envelope a bearing member formed with an aperture, through which the said one end portion of the bolt passes freely, and formed around that aperture with a spherically curved annular bearing surface which is concave towards the said envelope and bears against an opposing convex annular bearing surface, provided around the said one end portion of the bolt, so as to facilitate such pivotal adjustment.

In one embodiment of the invention, the said bearing member is a ring having at one side thereof a surface region formed as a spherical segment and consituting the concave bearing surface of the member. The said aperture in the support member is circular, and the internal diameter of the ring is greater than the diameter of the aperture in the support member. It is generally significantly easier to produce such a ring, being a separate component part, than it is to work an equivalent spherical segmental surface into a fixed support member of the switching device.This arrangement also affords the possibility of mounting the switching tube so that the longitudinal axis of the fixed currentconducting bolt is displaced with respect to the central axis of the aperture of the support member, thereby facilitating precise positioning of the switching tube whilst connecting a switch actuating mechanism to its movable current-conducting bolt.

Reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 diagrammatically shows a diagrammatic part-sectional side elevation of a vacuum switching device in which the present invention can be embodied, and Figure 2 shows an enlarged view, partly in axial section, of parts of the device of Figure 1, illustrating how the present invention can be embodied therein.

The vacuum switching device of Figure 1 is a power circuit-breaker, indicated generally by the reference numeral 1, having an actuating mechanism contained in a housing 2. The housing 2 is constructed in the form of a box having a wall 5 which bears on its exterior two rails 3 and 4, to which there are secured upper and lower rod insulators 6.

The insulators 6 are angled with respect to the wall 5 as shown. Connected to upper rod insulator 6 is a head piece 7 to which one end of a vacuum switching tube 10 is attached so that a fixed current-conducting bolt 11 at that end of the tube 10 is placed in connection with a connecting rail 12.

The lower rod insulator 6 carries an actuating base 13, on which a bell-crank lever 14 is mounted which connects an insulating switch rod 15 to a movable current-conducting bolt 16 of the switching tube 10.

A flexible current lead 17 connects the currentconducting bolt 16 to a lower connecting rail 20. The insulating switch rod 15 is coupled to the actuating mechanism in the housing 2 by a contact-pressure spring 21. The actuating mechanism contained in the housing 2 can be in the form of, for example, a spring-loaded drive as disclosed in German Offenlegunsschrift 2717958.

Figure 2 shows the upper end of the switching tube 10, and a portion of the connecting rail 12, which could be replaced by some other form of conductive support member, that is formed with a bored aperture 25 through which the currentconducting bolt 11 passes freely. The aperture 25 is larger in diameter than the current-conducting bolt 11. At the top of the evacuated envelope of the switching tube 10 there is provided a convex spherically-curved annular bearing surface 29, formed substantially as a spherical segment, which sur rounds the bolt 11. This bearing surface 29 could be formed on the top of an end cap 26 of the tube 10, as illustrated in the left-hand half of Figure 2.In the following description, however, it is assumed that the curved bearing surface is formed on a separately produced ring 27 which is centred on the bolt 11 and rests on a plane bearing or contact surface 28 as illustrated in the right-hand half of Figure 2.

The convex upper surface of the ring 27 is complementary in form to a concave sphericallycurved annular bearing surface provided on a separately produced ring 30 which is interposed between the support member 12 and the ring 27 and surrounds the bolt 11. The spherically-curved surfaces of the rings 27 and 30 are of like radii of curvature and cooperate, in close contact with one another, to supportthe switching tube 10 in a manner permitting limited pivotal adjustment of the disposition of the switching tube in any direction, in the manner of a ball and socket joint.Within certain limits the switching tube 10 can be mounted, if desired, with a lateral displacement relative to the central bore axis of the aperture 25, since the diameter of the aperture 25 is greater than the diameter ofthecurrent- conducting bolt 11; in addition, the internal diameter (31) of the ring 30 is greater than the diameter of the aperture 25.

With the above-described components alone, it would be possible to fasten the switching tube 10 in the position represented, inclined with respect to the central bore axis of the aperture 25, by screwing a nut onto the connecting bolt 11 above the support member 12 with a pressure spring inserted between the said nut and the member 12. Such a fastening, however, results in a moment tending to align the switching tube 10 with the central axis of the aperture 25. Such an effect can be avoided by means of other components shown in Figure 2, namely a second pair of bearing rings, on the upper surface of the member 12, remote from the rings 27 and 30.A lower ring 34 of this second pair, which is located in a cylindrical bored recess 33 in the member 12, is formed with an upwardly facing concave spherically curved annular bearing surface which surrounds the bolt 11 An upper ring 35, fitted around the current conducting bolt 11, has a complementary convex spherically-curved bearing surface which cooperates with the bearing surface of the lower ring 34. A nut 36 allows the switching tube 10 to be fixed in any desired position that is permitted by the dimension ing of the various components, since the fastening provided by the rings 33 and 34 and the nut 36 is completely neutral when the tensioning nut 26 is tightened, that is without any tendency to depart from a selected disposition under the influence of the tension.

It is advisable to produce the rings 27 and 30 out of materiais which are good conductors, so as to enable current transfer from the switching tube 10 to the connecting rail 12 to be achieved with low losses, without using an additional current lead. The use of the separate ring 30 is advantageous, as compared with working a concave spherically-curved bearing surface directly into the support member constituted by the connecting rail 12, because the ring 30 can be silver-plated, in a known way, more cheaply than could a corresponding concave bearing surface worked into the conductor 12. To achieve a good low-loss current transfer, it is generally sufficient to silver plate just the respective areas of the ring 30 that contact the ring 27 and connecting rail 12.As can be seen from Figure 2, there is an extended areal contact, rather than mere point contact, between the switching tube 10, the rings 27 and 30, and the connecting rail 12.

The effective centre of rotation, or of pivoting, of the fastening arrangement can be preselected by appropriate choice of the respective radii of curvature of the spherically curved bearing surfaces of the two pairs of cooperating rings 27/30 and 34/35, which radii can be chosen substantially independently of one another. In the illustrated embodiment, the radius of curvature of the interacting rings 27 and 30 is different from that of the rings 34 and 35. By making the radius of curvature of the rings 34 and 35 smaller than that of the rings 27 and 30, the centre of pivoting of the switching tube 10 is made to lie near the top end of the current-conducting bolt 11.

A pivotable fastening such as that described above is particularly advantageous for switching tubes of comparatively great length, because with such tubes the problem of tolerance compensation is particularly significant. However, such a fastening can also be used for other vacuum switching tubes, for example to provide for tolerance compensation in relation to an actuating mechanism. Furthermore, the invention can be used either for a single-pole or a multipolar vacuum switching device. The vacuum switching device shown in Figure 1 could, for example, be a three-poie switch, wherein three switching tubes 10 are attached one behind the other to the rails 3 and 4 by means of rod insulators 6 as shown.

Claims

1. A vacuum switching device including an evacuated switching tube of the type having a fixed current-conducting bolt, one end portion of which projects from the evacuated envelope of the tube, wherein the said one end portion of the bolt passes freely through an aperture in a support member and retaining means are arranged to inhibit withdrawal of the boltfrom the aperture, thereby to secure the switching tube to the support member, whilst permitting limited pivotal adjustment of the disposition of the tube relative to the support member, there being between the support member and the said envelope a bearing member formed with an aperture, through which the said one end portion of the bolt passes freely, and formed around that aperture with a spherically curved annular bearing surface which is concave towards the said envelope and bears against an opposing convex annular bearing surface, provided around the said one end portion of the bolt, so as to facilitate such pivotal adjustment.

2. A device as claimed in claim 1, wherein the aperture formed in the bearing member is greater in diameter than the aperture in the support member.

3. A device as claimed in claim 1 or 2, wherein the said convex annular bearing surface is formed on an auxiliary bearing member which encircles the said bolt and is located between the bearing member of claims 1 and the said envelope.

4. A device as claimed in claim 1,2 or 3, wherein the said retaining means include a supplementary bearing member which encircles the bolt, at a side of the said support member that is remote from the said envelope, and is formed therearound with a spherically curved annular bearing surface that is concave and faces away from the said support member, and further include an additional bearing member which encircles the bolt and is formed therearound with a convex annular bearing surface that engages in complementary manner with the bearing surface of the said supplementary bearing member so that the latter is held in position between the said support member and the said additional bearing member.

5. A device as claimed in claim 4, wherein each of the annular bearing surfaces of claim 1 has the form of a segment of a sphere of a first radius, and each of the respective annular bearing surfaces of the said supplementary bearing member and the said additional bearing member has the form of segment of a sphere of a second radius, different from the said first radius.

6. A vacuum switching device substantially as hereinbefore described with reference to either the right-hand or the left-hand half of Figure 2 of the accompanying drawing.

7. A vacuum switching device substantially as hereinbefore described with reference to Figure 1 and Figure 2 (either the right-hand or the left-hand half thereof) of the accompanying drawing.