US1892538A - Vacuum switch - Google Patents

Description

Dec. 27, 1932. D. c. PRINCE VACUUM SWITCH 'Filed March 25, 1928 Fig.1.

Inventor David C. Prince,

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His Attorngy Patented Dec. 27, 1932 UNITED STATES PATENT OFFICE DAVID C. PRINCE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK VACUUM SWITCH Application filed March 23, 1928. Serial No. 264,115.

My invention relates to switches and more particularly to a switch of the vacuum type. In switches of this character, it is sometimes desirable to employ an evacuated vitreous receptacle the switch contacts being mounted 1 between the glass receptacle and the contact supporting conductors whereby the contacts, as Well as the supporting lead1ngin conductors may be adjusted and centered within the receptacle, and whereby the latter may be flexibly balanced between the conductors so as to be substantially unaffected by slight jarring actions of the contacts or leading-in conductors.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, will best be understood from reference to the following specification when considered in connection with the accompanying drawing in which Fig. 1 shows partly in elevation and partly in section a vacuum switch embodying the features of my invention; Fig. 2 is a plan view of a modified form of switch element; while Fig. 3 is a cross sectional view taken on the line 33 of Fig. 2.

Referring to the drawing, I have indicated at 1 an evacuated vessel having a central enlarged bulb portion and oppositely disposed extensions or neck portions 2, 3. Leading-in conductors shown as rods 4 and 5 provided at their end portions with switch contacts 6 and 7 extend through the neck portions 2 and 3 respectively and are flexibly connected thereto. These rods 4 and 5 also serve respectively as supporting and operating members for the switch contacts 6 and 7 as will presently be described.

Each rod is provided with suitable means for making circuit connections thereto. As illustrated the rods are screw-threaded as indicated at 8, for securing them to the supply conductors 9 and 10. The outer end portion of neck 2 is secured to a suitable metal collar 11 which mu st maintain a vacuum tight seal therewith. Where a suitable glass vessel is used the collar may be made of thin copper which can be stretched by glass or 'suitable alloys may be used such as chromium-iron or nickel-iron with a copper brazed surface examples of which are known to those skilled in the art. As illustrated the upper portion of the collar is crimped to form an expansible tubular member or sylphon bellows 12. The outer end of the bellows 12 is provided with a closure member 13 having a screw-threaded opening 14 to accommodate the conductor 4. Member 14 is silver soldered or otherwise suitably secured and sealed to the conductor 4. A metal shield 15 is mounted on the collar 11 and extends withinthe neck portion 2 and beyond the junction of the neck portion of the vessel with the collar 11. A thin metal plate 16 is mounted on the conductor 4 adjacent the inner end of the shield 15. Shield 15 and plate 16 protect the seal between the vessel and collar 11 and also the bellows 12 from injury from bombardment during evacuation and operation of the switch in breaking a circuit. Although I have shown collar 11 as integral with the bellows 13 it will be apparentthat these parts may be separate and that the collar 11 and shield 15 could be silver soldered, if desired, to bellows 12.

A metal collar 17, bellows member 18, shield 19 and plate 20 are similarly mounted at the end of the neck portion 3. The bellows 18 is made appreciably more flexible than the bellows 12 in case the contact 7 is arranged to be moved into and out of engagement with contact member 6, as'is intended in the arrangement illustrated, by suitable operating mechanism such as the toggle mechanism T for actuating the rod 5, which is slidably mounted in a suitable support S. The contact member 6 is held substantially stationary within the receptacle 1, the rod 4 being secured to a suitable support S1. The greater flexibility of the member 18 may be obtained in various ways, for example, by

dependently of the evacuated vessel but with a flexible vacuum-tight connection thereto and thereby effectively insures that the jars or shocks to which the contacts or leading-in conductors may be subjected are not transmitted to the evacuated receptacle 1.

The switch contacts may be solid members of relatively large mass, as indicated at 6 and 7 in Fig. 1. However, spring pressed contacts may be employed if desired, as indicated in Figs. 2 and 3. If spring pressed contacts are employed I have found it desir able to employ molybdenum spring members since molybdenum when freed from occluded gas retains its flexibility or spring action even when subjected to very high temperatures, such as would be encountered in the evacuation of the switch container.

WVhile in the present case I have illustrated the molybdenum spring feature as applied to a yieldably pressed contact finger, it is to be understood that my invention in this respect is of broader application and that I may utilize such springs in vacuum switches to bias the contacts to the closed or open posi tion where desired or in any relation of utility where the spring must maintain its resiliency even though subjected to a high temperature.

In Fig. 3, I have shown four spring contacts 21 mounted on molybdenum springs 22 which are secured in any suitable manner to a metal block 23, screw-threaded to a leadingin conductor 24. The opposite switch contact 25 corresponds to the contact 7 in Fig. 1 and is movable into and out of contact with the switch members 21.

The vessel should preferably be exhausted and subjected to heating during exhaust to free all parts inside the vessel as well as the walls of the vessel from occluded gases so that the highest practicable vacuum. shall continue to be maintained during the life of the switch. It is desirable to degas the larger metal parts before they are assembled in the switch. Aspointed out in Letters Patent to Langmuir No. 1,558,436, dated October 20, 1925, after metal has been freed from occluded gas reabsorption of gas will not readily take place even though it is exposed to air or other gases. After the switch has been as sembled the vessel should be baked out during exhaust and the exhaust should be continued while metal parts in the vessel and particularly the contacts are subjected to heating by high frequency and bombardment. A vacuum which is more perfect than a tenth of a micron is necessary for proper operation of the switch on any commercial voltage and the excellence of the switch improves as the vacuum is made better and better. I have obtained good results with a vacuum of the order of .01 of :1 micron but still lower pressures are desirable.

As pointed out in my copending application Serial No. 264,114, filed concurrently herewith assigned to the same assignee as this application, a low meltin point metal such as copper should be used or the contacts for operation on alternating current circuits, while for operation on direct current circuits the cathode or negative contact should be ofa high melting point metal such as tungsten. A separation of copper contacts by a distance of the order of one inch is sufficient to interrupt an alternating current circuit of more than 50,000 volts and the relatively low temperature cathode spot emission of the co per contacts will ensure the interruption 0 the circuit only substantially at the zero oint of the current wave so that only a relatively small amount of energy will be dissipated in the switch and voltage surges will not be produced.

What I claim as new and desire to secure by Letters Patent of the United States, is 2- 1. In combination, an evacuated receptacle, a switch mounted therein, said switch comprising a pair of contact members and means for operating the contacts and flexibly supporting the receptacle to reduce jars and shocks comprising a conducting rod secured to each of said contact members and a sylphon bellows sealed to each rod and to the evacuated receptacle.

2. In combination, a rece tacle, a switch mounted therein, said switc comprising a pair of contacts and a pair of leading-in conductors connected to support said contacts, mounting structure for said receptacle comprising flexible members sealed to each of said receptacles and to said leading-in conductors, one of said members having an appreciably greater flexibility than the other of said members to permit operation of the contacts into and out of engagement.

3. In combination, an evacuated vitreous receptacle, a switch mounted therein, said switch comprising a pair of contact members, leading-in conductors connected to said contact members, a pair of metal collars sealed to said receptacle, a flexible connection between each of said collars and each of said leading-in conductors, and shieldin means mounted on said collars and exten in inwardly beyond the junction of said co lars with said vitreous receptacle.

4. In a vacuum switch, the combination of a pair of switch contacts, an evacuated receptacle therefor, and supporting means for said receptacle comprising a flexible vacuum tight seal connected to each contact and said receptacle for preventing transmission of jars and shocks from the contacts to the receptacle.

5. In a vacuum switch, the combination of an evacuated receptacle, a pair of switch contacts, separate supporting means extend ing through said receptacle for supportin each contact therein, and a vacuum tight se between each supporting means and the receptacle including a flexible sylphon bellows for preventing transmission of jars and shocks from the contacts to the receptacle.

6. A power current interrupter comprising a vacuum-tight housing, a supportin means for said housing, vacuum-tight flexi 1e connections between said housing and said supporting means providing a resilient mounting for the housing, relativel movable electrodes within the housing an a vacuum ambient for said electrodes.

In witness whereof, I have hereunto set my hand this 14th day of March, 1928.

DAVID C. PRINCE.

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