US 3823287 A
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[ VACUUM SWlTGllll  Inventor: Hans Bettge, Berlin, Germany  Assignee: Siemens Alttiengesellschait, Berlin and Munich, Germany 221 Filed: .lan.l1tl,1972 21 App1.No.:2l16,523
 Foreign Application Priority Data [in 3,823,287 [451 Jul 9,1974
3,622,724 11/1971 Sofianek ..200/144B Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson Circumferential current flow which serves to draw contact members together in a vacuum is produced by a vacuum switch having cup-shaped switch contacts having ring-shaped side portions which are subdivided by slots 'into segments. The circumferential direction of the current is produced by circumferential slots in the side portions which slots consist of a gap which extends parallel through the contact surface and connects with a vertical, chordially aligned cut in the contact surface.
5 Claims, 4 Drawing Figures Apr. 1, 1971 Germany 2015528  US. G1 2011/1144 B  llnt. 1C1. Hillllli 33/66  Field oi Search 200/ 144B, 166 B  References Cited UNlTED STATES PATENTS 3,225,167 12/1965 Greenwood... ZOO/144B FATENTEDJUL W V weaves? QQ R WNI L 1 VACUUM swrrcn BACKGROUND OF THE INVENTION This invention generally relates to an electric switch and more particularly concerns a vacuum switch wherein two contacts relatively movable toward and away from each other have opposed planar contact surfaces facing each other wherein at least one of the contact surfaces takes the form of a ring-shaped bridge which is subdivided into segments by slot means to force the current which flows between the opposed contacts into a path which path has a component extending in the circumferential direction of the ringshaped bridge means.
It is known in the prior art as shown, for example, in the German Letters Patent 1,196,751 to have ringshape bridges of the contact pieces divided into segments, however, the slots which define the segments are inclined with respect to the axis of the bridge. As a result, the prior art contact arrangements have a noticeable component of the current extending in the direction of the axis of the opposed contacts.
It is also known from the German Letters Patent 1,236,053 to provide the particular segments with a slot extending between points of the end surfaces of the segment which slots are staggered with respect to each other about the ring-shaped bridges in order to force the current to flow in a path with a component in the circumferential direction of the ring-shaped bridges. In this prior art embodiment, however, a relatively large axially directed current component is sought to be avoided by providing a projection on the contacting surface of the contacting pieces so that the arcing across the contacts is caused to occur at a specified place. Thus, according to this prior art construction even though the current flowing through the contacts will have a circumferentially directed portion, the concentration of the arcing across the projections will have the effect of deteriorating the electrical properties of the vacuum switch.
SUMMARY'OF THE INVENTION The disadvantages of the prior art are overcome by the vacuum switch means according to the invention herein'comprising a pair of generally axially aligned opposedcontacts, 'at least one of which contacts has a ring-shaped bridge means that is subdivided into segments by generally circumferentially extending slot means whereby the current flowing through the switching contacts follows a path as close as possible to the contacting surfaces and is directed practically exclusively in a direction tangential to the'axis of the switching contacts. This current path produces a magnetic field under the influence of which a light are occurring between the opposed contact surfaces is moved around the ring-shaped contact surface. By this means and by means of chordally aligned slots in the contact surface a reignition of the lighting ark and damage to the contact surfaces is avoided.
The slot means has a first and second portion with the first portion of the slot means lying in a plane generally parallel to the contact surfaces and the second portion of the slot means extending between the first portion and the contact surfaces. The second portion of the slot may be generally perpendicularly inclined to the contact surface and may be positioned to lie on a chord 2. of the ring-shaped bridge means. When both of the opposed contacts have the ring-shaped bridge means thereon the first portions of the slot means on each of the contacts may be arranged to extend in opposite directions from their respective second portions whereby the magnetic fields produced by each will be attractive to each other. By means of the structural features hereabove set forth the current flowing through the contacts is almost entirely free of axial components near the contact surface and flows in a distinctly circumferential direction about the ring-shaped bridge means to produce a magnetic field which forces a light are occurring between the contact surfaces to move around the contact surfaces. The chordally arranged vertical cuts forming the second portion of the slot means facilitate the passage of the light arcs over the vertical cuts in the contact surface so that the light arc may move freely around the ring-shape bridges.
In order to obtain the desired current loop with the distinct tangential direction of the current in each contact, the contact pieces are advantageously designed symmetrically and arranged in' the vacuum switch staggered in relationship to each other circumferentially by about one-half the length of the segments. I
In order to increase the mechanical rigidity of the switching contacts the first portions of the slot adjacent the second portions may be supported by bridging members consisting of a material which has a lower electric conductivity than the material of the contacts. Advantageously we have found that where the bridging member comprises a screw means it is easily adjustable to maintain the slot means at a predetermined width.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken inconjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure and in which:
FlG. 1 is a schematic longitudinal section of a vacuum switch showing the contacts in an enclosure;
FIG. 2 is an enlarged schematic perspective view of a pair of opposed, axially aligned contacts each having a ring-shaped bridge means thereon;
FIG. 3 is a plan view of the lower contact of FIG. 2 further illustrating the chordal alignment of the second portion of the slot means and the positioning of the bridging members; and
FIG. 4 is an enlarged cross sectional elevational view taken through the area indicated by the circled portion IV in FIG. 3.
DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 11 there may be seen in cross section a vacuum tight enclosure made of a cylindricallyshaped insulator member 1 having upper and lower metallic end plates 2 and 3 respectively, which enclosure may be subjected to a very high vacuum. The insulator 11 may be made of a glass or ceremic material. In the housing two switching contacts 4 and 5 generally axially aligned and of generally similar size and shape are arranged in pairs opposite and facing toward each other. As shown, the upper contact 4 is attached to a generally fixed conductor 6 and the lower contact 5 is attached to a movable conductor 7. Each of the condu'ctors 6 and 7 are attached to a'suitable electrical potential outside the enclosure. A metal connector member 8 which may be a metal bellows, seals the vacuum switch where the conductor 7 is guided movably through the vacuum tight housing of the vacuum switch.
The contacts 4 and 5 are shown in greater detail in FIGS. 2 through 4. Thus, FIG. 2 is an enlarged perspective view of the contacts and conductors 4, 6 and 5, 7, greatly spaced from each other to allow the construction to be clearly seen. As shown, the contacts are nearly full size. From FIG. 2 it may be seen that the contacts 4 and 5 may be referred to as being cupshaped with a ring-shaped bridge means 11 upstanding from a generally planar base 9. Since the contacts 4 and 5 are the same, the same reference numerals have been used with reference to each. One side of the base has the ring-shaped bridge means extending therefrom, the other side of the base 9 has the conductors 6 and 7, respectively connected thereto. The ringshaped bridge 10 has an upper planar surface 10a which faces and is generally parallel to the upper planar surface 10a on the opposing contact. As shown, the contacts 4 and 5 are each circular and of similar size. Also, the contact surfaces 10a are of similar width.
The ring-shaped bridge 10 of each of the switching contacts 4 and 5 is subdivided into three segments by slot means having a first portion 11 and a second portion 12. The second portion 12 of the slot means is a generally vertical cut into the ring-shaped bridge 10 extending from the upper contact surface 10a to a point generally even with the ,upper surface of the base 9. The first portion 11 of the slot means extends in one direction from the second portion 12 of the slot means and lies in a plane parallel to the plane of the contact surface 10a. As shown, these two planes will be generally perpendicular to the central axis of the contacts and their respective conductors. As may be best seen from F IG. 2 the arrangement of the slot means in the contacts 4 and 5 may be identical so that when the contacts 4 and 5 are positioned in opposite, facing relationship the first portions 11 of the slots will extend in opposite directions from the vertical second portions 12. The contact pieces are advantageously designed symmetrically and arranged in the vacuum switch staggered circumferentially in relationship to each other by about one-half the length of the segments whereby the current is caused to flow circumferentially. Thus, the current is forced into a path from its respective conductor through the base 9 into the bridge 10 through the portion which connects the bridge 10 with the base and then practically exclusively in the circumferential direction of the ring-shaped bridges 10 in the segments of the bridges which are above the first portion 11 of the slot means. By this means the current is looped about in the rotary path of the segments and in a path parallel to the contact surfaces 10a. These current loops can produce a strong magnetic field which field is practically exclusively directed vertical to the current direction of a light arc coming about between the switching contacts 4 and 5 when the contacts are separated. Due to this magnetic field the light are is moved with extremely high speed over the contact surface 10a of the ring-shaped bridges 10 in a circular path. In order, to assure that the light arc may move freely 4 around the ring-shaped bridges the second portions 12 of the slot means are arranged to lie on a chord with respect to the circumference of the ring-shaped bridges 10.
The contact arrangement which has been illustrated and described is advantageously effected in such a way that some of the cross sectional surface areas of the current supply with respect to the segments of the ringshaped bridge 10, i.e., the'cross sectional surfaces of the bridge 10 between a slot 11 and a cut 12 of an ad jacent slot, is equal to the cross section of the rod-shaped conductors 6 or 7, respectively. The individual segments 10 are advantageously spaced in the axial direction of the switching pieces 4 and 5 by means of supports 13 in order to mechanically support the individual segments 10 at the end remote from their end of attachment to the base 9. These supports are made of a material such as a metal alloy of lower electrical conductivity than the material of which the contacts 4 and 5 are formed.
As may be best seen in the cross sectional view of FIG. 4 the supports 13 may comprise screws which are inserted through the base 9 of a switching contact in the area of the free end of the segment of the bridge 10. If the switching contacts 4 and 5 consist mainly of copper, the screw bridging member may consist of an ironnickel-cobalt alloy without interfering with the current path in the switching contacts.
The invention herein is not limited to the sample embodiment as illustrated. For example, the number of segments does not need to be three but may be more or less. With respect to the bridging member 13 it will be understood that this may comprise a ceramic disc rather than the adjustable screw as shown. A vacuum switch according to this invention is characterized in that high currents such as currents above 4kA can be switched off safely and reliably by means of this easily and economically constructed apparatus. Also, as has been explained in detail, the light arc is necessarily moved extremely fast by the magnetic field over the contact surface 10a whereby the surface 10a will wear very well and as a result the vacuum switch according to the invention will enjoy a long useful life with little maintenance.
Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as might reasonably and properly come within the scope of my contribution to the art.
1. A vacuum switch means comprising a pair of generally axially aligned opposed disc-shaped contact members with raised portions on the outer periphery thereof which form a ringshaped bridge means, said bridge means having a single generally planar contact surface subdivided into segments by generally circumferentially extending slot means, said slot means having first and second portions, said first portion of said slot means lying in a-plane generally parallel to the contact surfaces of the contacts, whereby current flowing through the bridge means is forced into a path with a component extending in the circumferential direction of said ring-shaped bridge means so that a magnetic field is created in a generally axial direction, wherein said second portion of said slot means extends between said contact surfaces and said first portion of said slot means, and wherein both of saidv contacts have said ringshaped bridge means thereon, said first portions of said slot means on each of said contacts extending in opposite directions from their respective second portions, and wherein said slot means on one of said contacts is circumferentially staggered with respect to the slot means on the other of said contacts, and wherein said slot means are staggered by about onehalf the length of said segments.
2. A vacuum switch means according to claim 1 wherein said second portion of said slot means lies on a chord of the ring-shaped bridge means.
3. A vacuum switch means according to claim 1 t 6 wherein said ring-shaped bridge means are each divided into three segments.
4. A vacuum switch means according to claim 1 wherein said first portions of said slots adjacent said second portions are supported by bridging members consisting of a material which has a lower electric conductivity than the material of the contacts.
5. A vacuum switch means according to claim 4 wherein said bridging members comprise a screw means adjustable to maintain said slot means at a predetermined width.