US3166658A - Vacuum switch and envelope construction therefor - Google Patents

Description

Jan. 19, 1965 J. E. JENNINGS 3,166,653

VACUUM swrrcu AND ENVELOPE CONSTRUCTION THEREFOR Filed July 5. 1962 dofuufirrt/awm/as INV EN TOR.

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6/5 Alf/DEWEY United States Patent 3,166,658 VAtTUUM SWITCH AND EI IVELQlPE QU NS'ERUCTIQN THEREFQR Jo Emmett Jennings, San Jose, Calif., assignor to .Eennings Radio Manufacturing Corporation, San Jose, Calif, a

corporation of Delaware Filed July 5, 1962, Ser. No. 207,668 6 Claims. (Cl. 2tlll144) My invention relates to vacuum switches; and particularly to a vacuum switch incorporating an envelope structure capable of contraction and expansion to effect relative opening and closing movement of the switch contacts.

Another object of the invention is the provision of a vacuum switch in which a portion of the envelope comprises alternate hermetically connected dielectric rings and metallic expansion portions so that a wide range of expansion and contraction of the envelope portion is secured with almost negligible fiexure of the expansion portions with consequent long life of the envelope.

Still another object of my invention is the provision of a hermetically tight envelope having oppositely disposed rigid metallic endwalls on which fixed and movable switch contacts are rigidly mounted and a cylindrical sidewall including expansion portions enabling relative movemerit of the switch contacts by controlled relative movement of the endwalls.

A still further object of the invention is the provision of a vacuum switch in which the tendency of the contacts to bounce upon closing is greatly diminished by increasing the effective area on which atmospheric pressure exerts a contact-closing force.

Still another object of the invention is the provision of a vacuum switch'in which the contact-opening force resulting from sudden heavy current surges is countered by a greatly increased contact-closing force.

A still further object of the invention is the provision ofa vacuum switch envelope which provides alternate dielectric and metallicenvelope portions constituting series capacitors dividing theivoltage differential between switch contacts when the contacts are in open position.

Still another object of the invention is the provision of i a vacuum switch in which current does not flow through the expansible portion of the envelope as in conventional vacuum switches utilizing a bellows construction closely surrounding the operating shaft of the switch.

A still further object of the invention is the provision of a vacuum switch assembly including an expansible and contractible envelope detachably secured within a protective dielectric housing.

Another object is the provision of a vacuum switch assembly including an expansible envelope and an actuator shaft cooperating with a detachable housing assembly to retain one end of the envelope immobile while providing a slide bearing for mobility of the other end of the envelope.

Still another object of the invention is the provision of a vacuum switch assembly encapsulated within a detachable dielectric housing which leaves only the switch terminals exposed outside the housing.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be brought out in the following description of the invention. I do not limit myself to the showing made by the said description and the drawing, since I may adopt variant embodiments of the invention within the scope of the appended claims.

Referring to the drawing, the figure is a half sectional hermetically closed at opposite ends by rigid metallic endwalls or plates on the inner faces of which mutually extending axially aligned switch contacts are rigidly secured or integrally formed. The parts are proportioned so that V contraction of the sidewall brings the contacts into tight abutment, whereupon further contraction of the sidewall is prevented by such abutment of the contacts. Opening movement of the switch contacts is effected by application of a'controlled opening force to one of the endwalls in opposition to the closing force exerted by atmospheric pressure; Closing of the contacts is cfiected by removal of the controlled opening force. The entire envelope is preferably encapsulated in a detachable protective dielectric housing, one end of which provides a slide bearing for the operating shaft which controls movement of the mobile endwall. A particular advantage of the contractible and expansible envelope sidewall construction lies in the almost negligible amount of flexure of the expansible sections even upon a full excursion of the mobile endwall. Ruptureof the envelope due to workhardening and breakdown of the expansible sidewall portions is therefore unlikely.

In more specific detail, and referring to the drawing, the vacuum switch of my invention comprises a plurality of axially spaced and aligned ceramic rings 2, preferably formed from aluminum oxide (A1 0 or beryllium oxide (BeO), metalliz'ed on their end edges with a molybdenum-manganese metalizing compound and assembled into a composite tubular wall structure by hermetically brazing a short expansible metallic portion 3, for instance a tubular metallic bellows, between each two adjacent ceramic rings.

In the expansible wall structure shown, four pairs of ceramic rings are utilized, the ceramic rings of each pair having a tubular expansible metallic portion hermetically interposed therebetween. Each of the ceramic rings electrically insulates two adjacent metallic envelope portions, thus. providing capacitance between the insulated metallic portions dividing the voltage diiferential across opposite ends of the wall section among the several elements thereof.

t Toenable facility in fabrication, each of the expansible metallic portions is provided at each end with a radially extending annular plate section 4 having a cylindrical flange 6 on its outer periphery proportioned to closely surround the outer cylindrical periphery of the associated ceramic ring. The ceramic rings and expansible metallic portions are thus self-jigging and may be alternately stacked with an appropriate brazing ring (not shown) interposed between each annular plate section and the metalizedend surface of the associated ceramic ring. This enables the entire expansible sidewall to be brazed in one pass through the brazing furnace.

' To further facilitate fabrication of the vacuum switch, and to preclude the necessity of having to subject the brazed sidewall to repeated heat cycling, the ceramic ring at each end of the'sidewall has brazed thereon a modifiedv annular metallic sealing ring 7 having radially outwardly extending parallel flanges 8 and 9, the flange 8 abutting and brazed to the metalized end of the associated end ceramic ring. The expansible metallic portions 3 may conveniently be fabricated from thin copper, but other materials less susceptible to workhardening and possessing a thermal expansion and contraction characteristic compatible with the ceramic used is p referred. The sealingring'7 may be fabricated from a view of a vacuum switch embodying my invention. The

figure is drawn approximately full size.

,7 Broadly considered, my vacuum switch comprises a contractible and expansible composite tubular sidewall he portions.

I wall 12,- preferably formed from copper and having a heavy central body portion 13, provided with a radially V tungsten or some other suitable material.

areas-es outwardly extending peripheral flange l4, heliarc welded as at 16 to the associated flange 9 of the sealing ring 7. The heavy central body portion of the endwall tapers inwardly toward the longitudinal axis of the sidewall, and terminates in an integral central cylindrical stud 17 having a reduced diameter extension 18, bored to receive a cylindrical contact member 19, conveniently of The contact member may of course be formed of copper as an integral extension on the stud 17. From the foregoing it will be apparent that providing a heliarc union as at in eliminates subjection of the sidewall to a repeated brazing temperature and eliminates the necessity of heating the massive endwall 12 to brazing temperature with consequent delay because of the necessity to cool the structure before additional operations are performed. The heliarc flange 14 may of course be omitted and the parts brazed together when desired.

The other end of the expansible sidewall is closed by an inwardly extending conical metallic shell 21 constituting a mobile endwall, the shell having at its apex end a cylindrical extension 22 closed at one end by a wall 23 and at its other end opening into the interior 24 of the hollow conical shell-like endwall. The large base of the conical shell is provided with a radially outwardly extending flange 26 hermetically heliarc welded as at 2'7 to the flange 9 of the associated sealing ring '7 as previously discussed. A tubulation 28 is arranged on the conical endwall within the interior thereof as shown for use in evacuating the envelope.

Brazed by one of its ends to the conical shell within the cylindrical extension 22 is a coaxially arranged outwardly extending slide shaft 29, arranged at one end to receive the threaded end 31 of the conductive operating shaft extension 32, which also functions as an external terminal for suitable connection of the mobile contact member 33 in an appropriate circuit by a lead 34. The mobile contact extends from adjacent the innermost end of the conical shell 21, where the contact member is suitably brazed within a bore formed in shaft 29 and to the Wall 23. When desired, the mobile contact may form an integral extension of the shaft, and the shell 21-may likewise be formed integrally with the shaft as by casting. The mobile contact is thus movably supported by the endwall and, upon expansion and contraction of the envelope, moves in correspondence with the endwall. To connect the mobile contact into a circuit, the extension 32 of the conductive operating shaft 31 is reduced in diameter as at 36 and threaded to receive a nut 37. A terminal lead connector 38 is tightened against the nut by a second lock nut 39, and the dielectric end 41 of the conventional or other operator is threaded on the shaft end as shown. 7

It is preferred that the expansible ceramic-bellows envelope by protected by mounting it within a detachable encapsulating case or housing 42, conveniently molded of nylon, silicon, fibreglass or other dielectric material in a cylindrical cup-shape having a bottom wall 43 and closed at its other end by a removable end or cover plate 44, secured by suitable screws 46, and provided with a centrally disposed slide bearing 47 forming a hub for the plate 44 and slidably receiving the slide shaft 29 therein.

In this construction, the upper electrically conductive endwall 12 of the vacuumized envelope is seated against the dielectricbottom wall of the cup. To connect the fixed endwall 12 into a circuit, a copper or other metal grommet 49 extends through an aperture in the bottom wall of the dielectric cup to conductively abut the metal endwall 12 of the envelope. The grommet is provided with a flange 51 abutting the bottom wall of the housing so'that the bottom wall lies captured between the flange and envelope endwall l2. Grommet and endwall are thus held securely against the cup bottom by the threaded stud 52, brazed into the endwall and carrying a nut 53 over the intervening terminal lead connector 54. The stud 52 thus serves as a terminal for the connection of the switch into a circuit in addition to detachably securing the envelope within the housing. The envelope is of course vacuumized, but the protective housing remains at atmospheric pressure, and if desired may be provided with apertures for the free flow of air around the envelope in addition to the vent opening 56 in cover plate 44.

From the above it will be clear that the switch contacts may be engaged or disengaged by selective axial movement of the operating shaft, and that during such movement the vacuumized envelope is compressed or expanded with but small flexure of any single bellows fold, and with complete preservation of the vacuum in the envelope. The multiplicity of operative movements with negligible fatigue of the bellows folds which is thus provided assures a long and almost indefinite operative life for the vacuum switch, while the enclosing housing gives security against injury from outside sources.

It will also be apparent from the foregoing description and the drawing that placing the expansible metallic por- 'tions in the sidewall results in a greatly increased effective area against which atmospheric pressure may act in order to close the switch contacts and keep them closed. Additionally, removing the expansible metallic member or bellows away from the operating shaft as is the custom in conventional vacuum switches, has the beneficial result of removing the bellows from the electrical circuit through the switch. This facilitates cooling of the evacuated envelope and the associated contacts, thus increasing the power levels at which the switch may be operated.

I claim:

1. A vacuum switch comprising an evacuated envelope including a composite tubular sidewall comprising alternate metal and ceramic portions and axially spaced metallic endwalls closing opposite ends of the tubular sidewall, a switch contact supported on each opposite metallic endwall with in the evacuated envelope, said sidewall includingan expansible portion enabling relative movement of the metallic endwalls to elfect corresponding relative movement of the switch contacts to make or break a circuit through the switch, and a dielectric housing enclosing the evacuated envelope and supporting at least one of the endwalls of the evacuated envelope for movement relative to the dielectric housing. I

2. The combination according to claim 1, in which one of the metallic endwalls closing the evacuated envelope comprises an inwardly extending conical portion, and a conductive slide shaft is secured to the apex end thereof and extends out of the dielectric housing.

3. The combination according to claim 2, in which a dielectric slide bearing is provided on the dielectric housing extending into said conical endwall to slidably support the conductive slide shaft adjacent its inner end.

4. The combination according to claim 2, in which said dielectric housing is cup-shaped and includes a bottom wall to which one of said axially spaced endwalls is detachably secured and a detachable end plate closing the open end of the cup-shaped housing and providing a centrally disposed tubular slide bearing extending into the associated conical endwall and slidably surrounding the slide shaft.

5. An hermetically tight hollow envelope comprising a composite sidewall including a plurality of axially spaced tubular ceramic sections and an expansible tubular metallic member interposed between each two adjacent tubular ceramic sections, means on each expansible tubular metallic member to coaxially align the tubular metallic member with the associated tubular ceramic sections, a metallic bond hermetically interposed between the coaxially aligned ceramic sections and each associated expansible metallic member, and rigid endwalls an expansible sidewall having a plurality of coaxially aligned hermetically united tubular ceramic and metallic portions and rigid endwalls disposed across opposite ends of the sidewall, means forming an hermetic union between each endwall and the associated end'of the sidewall comprising a peripheral metallic flange on the endwall, and a sealing ring hermetically bonded to the associated end of the sidewall and having a flange thereon hermetically welded to the pheripher-al metallic flange on the endwall.

Refierences Ci ed in the file of this patent UNITED STATES PATENTS Porter July 13, Jennings Apr. 11, Beers et a1. Apr. 23,

-FOREIGN PATENTS France Feb. 21, Australia Feb. 20,

Claims (1)

1. A VACUUM SWITCH COMPRISING AN EVACUATED ENVELOPE INCLUDING A COMPOSITE TUBULAR SIDEWALL COMPRISING ALTERNATE METAL AND CERAMIC PORTIONS AND AXIALLY SPACED METALLIC ENDWALLS CLOSING OPPOSITE ENDS OF THE TUBULAR SIDEWALL, A SWITCH CONTACT SUPPORTED ON EACH OPPOSITE METALLIC ENDWALL WITH IN THE EVACUATED ENVELOPE, SAID SIDEWALL INCLUDING AN EXPANSIBLE PORTION ENABLING RELATIVE MOVEMENT OF THE METALLIC ENDWALLS TO EFFECT CORRESPONDING RELATIVE MOVEMENT OF THE SWITCH CONTACTS TO MAKE OR BREAK

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