US3178542A - Vacuum switch and internal shielding therefor - Google Patents

Description

A ril 13, 1965 Filed March 26,

IEIIEI l J. E. JENNINGS 3,178,542

VACUUM SWITCH AND INTERNAL SHIELDING THEREFOR 1962 2 Sheets-Sheet 1 INVENTOR. (/0 Elma-7r dam was A il 13, 19 5 J. E. JENNINGS VACUUM SWITCH AND INTERNAL SHIELDING THEREFOR 2 Sheets-Sheet 2 Filed March 26, 1962 vr WW T N M MM mm M U M M M M n R United States Patent 3,178,542 VACUUM SWITCH AND INTERNAL SHIELDING THEREFOR Jo Emmett Jennings, San Jose, Calif., assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed Mar. 26, 1%2, Ser. No. 132,340 8 Claims. (Cl. 200-144) My invention relates to vacuumized electrical components such as vacuum switches and vacuum capacitors, and particularly to such implements having bellows to permit operation by an axially movable shaft. In the following description my invention is described as embodied in a vacuum switch, and is related in subject matter to my copending application Serial No. 106,394, filed May 1, 1961, and assigned to the assignee of the present in vention.

Vacuum switches with metallic bellows have usually utilized the bellows or the operating shaft passing through the bellows, to conduct electricity from one contact to a terminal. When the bellows must conduct electricity, other desirable qualities must be modified so that the operating life of the bellows is severely limited. When the operating shaft conducts electricity, it cannot be grounded; and insulation must be provided between the shaft and adjacent parts of the switch which are not in the circuit. Accordingly, it is a purpose of this invention to provide means whereby the operating shaft and bellows of a vacuum switch may be grounded when desired without their having to conduct electricity.

A further object of my invention is to provide means whereby the operating shaft and bellows of a vacuum switch are electrically isolated from the contacts and terminals thereof.

Another object of my invention is to provide aterminal in the side wall of the vacuumized envelope of a vacuum switch, and means connecting the terminal to a contact within the envelope so that both contacts and terminals are electrically insulated from the operating shaft and bellows of the switch.

Another object of my invention is to provide a replaceable bearing for use on vacuum switches, vacuum capacitors and like electrical implements having an axially movable operating shaft.

Another object of my invention is to provide a sealing ring for the hermetic sealing together of the two glass shells comprised in my vacuumized envelope, the ring being integral and without seams, and also providing a secure mounting for an external terminal remote from the mounting base of the switch structure.

Still another object of my invention is the provision of a vacuumized envelope in which a movable electrode is mounted on an operating shaft extending into the envelope through a bellows seal, and continuous conductive means connect the movable electrode to an external terminal remote from operator shaft and bellows.

The invention possesses other objects 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 drawings, since I may adopt variant forms of the invention within the scope of the appended claims.

Referring to the drawings:

FIG. 1 is a vertical, axial sectional view of a preferred embodiment of a vacuum switch incorporating my invention;

FIG. 2 is a cross sectional view of the switch taken in a plane indicated by lines 22 of FIG. 1;

FIG. 3 is a longitudinal. sectional view of the partially completed central sealing ring of the switch;

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FIG. 4 is a view similar to FIG. 3 but showing the completed sealing ring;

FIG. 5 is a sectional view of the completed seamless sealing ring showing the glass beaded flanges and the terminal ring brazed in the central portion thereof.

In general terms, my invention comprises a vacuumized envelope comprising two aligned dielectric shells, closed hermetically at each end, and hermetically joined together by a seamless sealing ring on which an outside terminal is brazed which is remote from both ends of the envelope. In the upper end of the envelope as shown in FIG. 1, a pair of electrodes, in this case the contactsof a switch, are arranged. One, a fixed contact, is firmly mounted in the metal end wall of the envelope and comprises the other outside terminal of my switch.

The other or movable contact is arranged on the inner end of a composite stem or operating shaft, extending downwardly (in FIG. 1) through the lower portion of the envelope and a bellows seal; and through a vertical replaceable bearing structure to the outside of the envelope, where it may be connected to a suitable operator. The inner end of the composite stem is a copper head block conductively connected to the remote terminal by a plurality of conductive flexible straps. The next section of the composite stem is a dielectric rod, mechanically connecting the copper head block to a steel shaft sealed by the bellows in an external and removable bearing structure mounted on the lower end wall of the envelope.

The significance of this arrangement of parts lies in the location of the conductive elements of the switch wholly in the upper (in FIG. 1) portion of the vacuumized envelope; and the bearing and bellows in the lower part, with a nearly impenetrable but flexible sputter shielding means between them. Thus no current is carried by either the bellows or the bearing or adjacent parts, which permits their grounding and better functioning.

Removal and replacement of the bearing sleeve without dismounting or disturbing other parts is an important feature of my switch, as is also the shielding structure protecting the interior of the glass surrounding the contacts from the high velocity particles thrown from them.

In more detailed terms, my invented structure, herein explained as a switch, comprises a vacuumized envelope 6, hermetically closed at one end by a copper plate 7, forming one of two external terminals of the switch, and at its opposite end by a steel plate 8, conveniently serving as a mounting base for the envelope. The side walls of the envelope are two axially aligned cylindrical glass shells 9 and 10 which may be the same in section or of ditlerent section as shown. The shells are hermetically sealed to the end plates by the conventional circular sealing flanges 12 and 13. The two shells are hermetically united by a continuous copper band com-prised of twin sealing flanges 14 and 16, oppositely extending and integrally united by a. centrally grooved circular copper band 17 between them. A two-piece ring 18 brazed in the groove provides a terminal ring midway between the two end plates.

The integral twin sealing flanges are important in providing a seamless and therefore hermetically tight connection between the shells, and a particularly good and strong mounting for the two-piece terminal ring.

Tungsten contacts and an operating stem are arranged on the long axis of the switch. Brazed centrally into the end plate 7 is a hollow mounting block 21, into the end of which the tubulation 22 is brazed. The side of the block is extended outwardly in a wide flange 23 to protect the tubulation, and a cross passage 24 through the block opens a passage through which air may be exhausted from the envelope. Secured in the lower end of the mounting block is a tungsten contact 26, aligned with the movable contact 27, secured in the hollow, round, mounting, head block 28, vented as shown by passages 29.

The offset center of a corona shield 31 is brazed into a recess in the lower face of head block 28, and the metallized end of the ceramic or sapphire rod 32 is brazed into the recess opposite the offset. This interfitting is, of course, to facilitate fast and accurate alignment of parts. At the lower end of the sapphire rod, a similar rigid connection is made through the corona shield 33 to the ead 34 of the steel stem 36, comprising the external member of the operating shaft, which also includes the internal dielectric rod 32 and the head block 28.

The rigid axially positioned operating shaft holds the movable contact 27 in alignment with the fixed contact; and moves it axially to make or break the circuit through the contacts. Means are provided for resiliently connecting the head block 28 to the circular band 17 on which the terminal ring 18 is fixed, so that additional lateral stability is given the head block 28, while at the same time permitting it, together with the component parts of the operating shaft, to move axially to close and open the contacts.

Brazed into the upper and lower inside corners provided by the offset portion of the terminal band 17, and extending circumferentialy therearound are fiat annular flanges 38 and 39, horizontally opposite flanges 41 and 42 respectively, formed integrally with head block 38. Spaced about each of the flanges 41 and 4-2 as closely as possible without overlapping; and brazed thereto and to the oppositely disposed flanges 38 and 39 respectively, are two sets or assemblies of copper bonding straps 43 and 44, each strap being corrugated as shown.

Of course but a single assembly of straps may be used, but where high currents are to be passed through the switch, two or more assemblies are indicated; and in such a case, the two assemblies are arranged as in FIG. 2 with the upper and lower straps in staggered relation. Thus arranged the strap assemblies provide a highly effective shielding to prevent high velocity particles from the contacts reaching the lower half of the envelope and vulnerable parts therein. Satisfactory bonding straps may be made of copper ribbon of the desired Width and a few thousandths of an inch thick.

A thin shield plate 46 is preferably brazed to the head block 28 in position to overlie protectively the upper assembly 43 of bonding strips; and another shield plate 47 brazed to the mounting block 21 near the end plate is found useful in collecting deposits which would otherwise tend to form a conductive coating on dielectric surfaces.

Means are also provided to prevent the deposit of a conductive film on the interior surface of the upper glass shell 9. Discrete and overlapping units are disposed around the entire inner surface of the shell 9. Each unit comprises a large and a small cylindrical metal band 51 and 52 connected on adjacent edges by an annular flange 53, common to both bands. The large band is somewhat smaller in diameter than the inside diameter of the shell and the unit is held in concentric relation to the shell by glass or ceramic or other dielectric spacers 54 which rest on the annular flange of each unit between the smaller band and the shell wall. Each unit is supported on the spacer of the next lower unit, the lowest resting on a spacer lying on the annular flange 38. A wider spacer 56 is interposed between the upper end plate and the adjacent unit.

As dictated by requirements of position, assembly or expansion the spacer may be a single annular ring, con-' tinuous or split, or it may be constituted of two or more sections, the function and purpose being the same.

Replaceable bearing means are provided on. the end plate 8 for insuring alignment of the operating shaft; and a bellows seal is interposed between the shaft and the end plate to preserve the vacuum within the envelope.

Axially arranged on the end plate or mounting base 8 is a cylindrical extension 58 partially closed by a reentrant hollow bracket or hearing support 59. The outer perimeter of the bracket is shouldered to receive the lower flange 61 of the bellows 62, and also the free edge of the base extension 53. The three parts are united by brazing to produce an hermetically tight connection.

The upper edge 63 of the bellows is also brazed to the shouldered head 34 of the stem 36, thus hermetically closing the envelope to the outer atmosphere by means of the flexible bellows. This disposal of parts leaves the stem 36, bracket 59 and the inside of the bellows open to the atmosphere, a condition which permits me to em ploy a bearing for the operating shaft which is readily removed and replaced without disturbing the switch otherwise or even demounting it from its supports.

The bore in the hollow bracket 59 is threaded to receive the threaded body of the bearing sleeve 64, which for rigidity extends well up into the bellows to provide a slide bearing for the stem 36 and a stable alignment axially for the entire operating shaft carrying the contact 27. Spanner wrench sockets 66 formed in the head flange of the bearing sleeve permit easy rem-oval of the bearing and its Withdrawal from the assembly over the free end of the stern, which of course has been previously disconnected from the operator. During operation and temperature changes, atmospheric air will pass into and out of the bellows through the bearing slide and threaded surfaces.

From the above it will be clear that long-life high temperature bellows best adapted to withstand the stresses imposed on a vacuum seal, may be used without regard to the difficult problems of current carrying capacity. Removal of the bellows and bearing structure from the function of current conduction, and the grounding of those parts if desired, makes possible a substantial reduction in manufacturing costs besides eliminating serious safety hazards in the final product.

Advantages of the replaceable bearing are very great, both in reducing costs of manufacture and in producing an article of great adaptability, longer life, and easier maintenance. A Teflon or other plastic bearing which may be required in the operation of a high current switch can, during manufacture, be replaced temporarily by a metal bearing capable of withstanding the temperature and other rigors of the exhaust process.

I claim:

1. A vacuumized switch comprising (I) a pair of adjacent and aligned dielectric shells,

(II) a conductive sealing band interposed between the aligned shells and having each edge hermetically united to the adjacent shell,

(III) rigid conductive plates hermetically closing the opposite ends of the joined shells, one of said plates constituting a terminal for the implement,

(IV) a fixed electrode mounted inside a shell and on the terminal plate,

(V) an axially disposed non-conductive operating shaft having a conductive head within the shells,

(VI) radially flexible conductive means integrally connecting the head to the sealing band,

(VII) an electrode mounted on the head,

(VIII) a slide bearing in the other end plate in which the shaft is disposed,

(IX) and hermetically tight flexible means surrounding the shaft and connecting the shaft to the last named end plate.

2. A combination according to claim 1 in which the radially flexible conductive means connecting the head to the sealing band comprises a plurality of thin corrugated metallic bands arranged circumferentially about the head to provide an effective spatter shield.

3. A combination according to claim 1 in which the radially flexible conductive means connecting the head to the sealing band comprises a plurality of thin corrugated metallic bands arranged circumferentially about the head in two axially spaced groups with the bands of each group overlying the spaces between the bands of the other group.

4. A combination according to claim 1 in which a two-part external radially extending conductive terminal ring is integrally united to the sealing band.

5. In an electric switch comprising a vacuumized envelope having a dielectric cylindrical side wall closed by end Walls,

(I) a fixed contact within the envelope and mounted in an end wall,

(II) a mobile contact within the envelope and mounted in the other end wall,

(III) means for moving the mobile contact to engage and separate the contacts,

(IV) a plurality of shielding units lining the dielectric side wall opposite the contacts,

(V) each unit comprising a large and small metal band connected on adjacent edges by an annular flange common to both bands, and

(VI) annular dielectric spacers disposed circumferentially about the small band of each unit, between adjacent units and between each unit and the dielectrio side wall.

6. In an electric switch comprising a vacuumized envelope having a dielectric cylindrical sidewall closed by endwalls,

(I) a fixed contact within the envelope and mounted in an endwall,

(II) a mobile contact within the envelope and mounted in the other endwall,

(III) means for moving the mobile contact to engage and separate the contacts,

(IV) a plurality of shielding units lining the dielectric sidewall opposite the contact,

(V) each unit comprising a large and small metal band connected on adjacent edges by an annular flange common to both bands, and

(VI) dielectric spacers disposed between the units and between the units and the dielectric sidewall,

(VII) each said spacer lying on the common flange and against the small band to hold the units free of contact with the sidewall.

7. In an electric switch enclosed by a dielectric cylindrical Wall,

larly arranged dielectric spacers are interposed between said common flange of selected spatter shield units and the edge of the large band of the unit next above.

References Cited by the Examiner UNITED STATES PATENTS 2,228,157 1/41 Steenbeck 313-413 2,358,553 9/44 Beldi 313239 2,863,026 12/58 Jennings 200144 2,892,911 6/59 Crouch 200144 2,897,322 7/59 Reece 200144 2,965,734 12/60 Timmerman 200144 2,966,569 12/60 Jennings 200144 2,976,382 3/61 Lee 200144 5 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

Claims (1)

1. A VACUUMIZED SWITCH COMPRISING (I) A PAIR OF ADJACENT AND ALIGNED DIELECTRIC SHELLS, (II) A CONDUCTIVE SEALING BAND INTERPOSED BETWEEN THE ALIGNED SHELLS AND HAVING EACH EDGE HERMETICALLY UNITED TO THE ADJACENT SHELL, (III) RIGID CONDUCTIVE PLATE HERMETICALLY CLOSING THE OPPOSITE ENDS OF THE JOINED SHELLS, ONE OF SAID PLATES CONSTITUTING A TERMINAL FOR THE IMPLEMENT, (IV) A FIXED ELECTRODE MOUNTED INSIDE A SHELL AND ON THE TERMINAL PLATE, (V) AN AXIALLY DISPOSED NON-CONDUCTIVE OPERATING SHAFT HAVING A CONDUCTIVE HEAD WITHIN THE SHELLS,

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