US1875765A - Vacuum switch - Google Patents

Description

Sept. 6, 193?. A. SCHERBIUS YAQUUH SWITCH Filed May 28. 1928 .1 12 min lor:

Patented Sept. 6, 1932 UNITED STATES ARTHUR SCEEBBIUS, 01' BERLIN-WANNSEE, smut! VACUUM QWITCH Application filed Kay 28, 1938, Serial No. 281,281, andla Germany July 1, 1987. 7

It is known to allow contacts of metals of high melting points to work in vacuum vessels or in vessels filled with neutral ases. It has been found that with such switc es there is a tendency at heavy loads for arcs to form in the interior of the vessel, whereb a limit is set to their employment. It is ound by experience that the arcin starts for the most part not directly after t e hi h load is put on but very frequently only a er the switch has reviously worked almost without any spar ing. The arcthen extends to the const'ructional material consisting of metals of lower melting point and makes the switch, 16 which has for a long time been working without sparking, useless in a fraction of a second.

The present invention obviates this disadvantage.

.The invention is illustrated in the accompanying drawing, which shows in Figs. 1 to 7 inclusive various constructional forms partly elevational and partly sectional.

In Figure 1, 1 denotes a vacuum-tight vessel. The switch consists of two metal strips 2 and 3, which by the aid of screws 4 are secured to an insulating piece 5. The metal strips 2 and 3 each carry a contact in, 6 and 7 respectively, of material difiicu to fuse such as tungsten either alone or welded on pins of another material such as nickel, iron and copper. The invention consists in surrounding these pins by a small tube 8 consisting of insulating material which surrounds at least at their'ends the contacts with a small space. This tube may be supported by the contacts themselves and loosely arranged thereon. As an insulating material it is preferable to employ a material that is rather diflicult to fuse, magnesia, steatite, porcelain, quartz for example.

In Figure 2 is illustrated another constructional example, in which the contacts 9 and 10 consist of tungsten cups, which are welded on to pins 11 and 12.

In Figure 3 the little tube 8 consisting of insulating-material is enclosed by a conducting metal sleeve 14, for the purpose of so iding the electric fields that the maximum so eld strength occurs in the solid insulating material. The sleeve is formed from copper, iron, or aluminum.

In Figure 4, besides the little tube 8 consisting of insulatin material, there are also applied at the feet 0 the contact pins protecting plates 16 and 17, which consist of metal of high melting point, for instance tungsten, molybdenum or tantalum.

In Figure 5 also such protecting plates 18v and 19 are provided, which in this example are bent up in a cup-shaped manner and are surrounded by the little tube 20.

In Figures 6 and 7, again, constructional examples are illustrated for larger switches, actuated by magnetic force.

In figure 6, 21 denotes the vacuum-tlght vessel. 22 and 23 are contact pins. The contact 22 passes to the exterior through a fusing piece 24. The contact 2?, on the contrary, is secured in an iron cylinder 25, and the current is supplied to this contact through a fusing piece 26. A spring 13 is 1nse rted between the leading-in wire and the 11011 cylinder 25. If a magnet 27 ls-excited the. iron cylinder is attracted and the contacts 22 and 23 are separated from one another. 28 is a protective tube accordmg to the 1nvention.

The switch shown in Figure 7 is constructed similarly to that of Figure 6, with the difference that the protective tube 29 In this switch has an expansion in the middle, and

moreover protective plates 30 and 31 are also provided at the clamping points of the contact-s, and partly embrace the protect1ve vessel 29. The switches according to Figures 6 and 7 are intended for particularly large power outputs. It is immaterial for the 1nvent-ion whether the switch is actuated by heat, as for example by the bending of double metal strips, or by magnetic forces as in Figures 6 and 7, or even by electrical forces, as. for example by means of two condenser lates facing one another in a vacuum, or by resilient displacement at any part of the wall of the vessel with vacuum-tight closure. The protective vessel 29 is prov1ded w1th a sleeve or layer 32, of the same material as the sleeve 14 shown in Fig. 3. It is ObVlOllS loo that when the contacts 22 and 23 (Fig. 7)

are closed, i. e. in metallic contact with each other, there are no electro-static lines of force at the contact point. However, when the I contacts are moved a small distance apart for opening the contact connection, the current passes over through the medium surrounding the contacts, i. e. the electric current passes out of a conductor of slight resistance over into a medium of comparatively great resistance. A difference in voltage or pressure thereby arises between the contacts, and this voltage or pressure difierence produces electro-static lines of force.

The invention consists quite generally in surrounding the contact points of switches which work in vessels with vacuum-tight closure with a protecting tube or protecting vessel with as effective a closure as possible, in order to obviate the passage of electrical discharges or arcs to the carriers and parts other than the contact point. It is not necessary that the protective tube or protective vessel should be closed in an absolutely fluid-tight manner at its end, but it is desirable to make the free space between the contact pin or contact carrier and the protective tube or protecting vessel as small as possible.

What I claim is:

1. Electric switch comprising in combination, a vacuum-tight vessel, separable contacts therein movable away from each other during the switching, carriers for the contacts, an enveloping body of insulating ma- 85 terial difiicult to fuse and substantially spaced in its middle portion from the contacts and surrounding both contacts, said enveloping body closely surrounding the contacts at its outer ends, thereby protecting the carriers of the contacts against an are which is formed on the contacts and tends to travel to the carriers.

2. Electric switch comprising in combination a vacuum-tight vessel, separable contacts therein movable away from each other during the switching operation, carriers for the contacts, an enveloping body of insulating material diflicult to fuse and substantially spaced in its middle portion from the contacts, said enveloping body closely surrounding the contacts at its outer ends, cupshaped protecting plates of materialdiflicult to fuse provided at the bases of the contacts and together with the enveloping body thereby protecting the carriers of the contacts against an are which is formed on the contacts and tends to travel to the carriers.

3. Electric switch comprising in combination a vacuum-tight vessel, separable contacts therein movable away from each other during the switching operation, carriers for the contact, an enveloping body of insulating material difiicult to fuse and substantially spaced in its middle portion from the contacts, said enveloping body closely surrounding the contacts at its outer ends, a conducting metal layer closely surrounding the enveloping body and together with the latter protectin the carriers of the contacts against an arc w ich is formed on the contacts and tends to travel to the carriers.

4. Electric switch comprising in combination a vacuum-tight vessel, separable contacts therein movable away from each other during the switching operation, carriers for the contacts, an enveloping body of insulating material diflicult to fuse and substantially spaced in its middle portion from the contacts, said enveloping ody closely surrounding the contacts at its outer ends, a conducting metal la er closely surrounding the enveloping b0 y, cup-shaped protecting plates of refractory material provided at the bases of the contacts and together with the enveloping body protecting the carriers of the contacts against an are which is formed on the contacts and tends to travel to the carriers. In testimony whereof I have signed my name to this specification.

ARTHUR SCHERBIUS.

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