US3017479A - Vacuum switch - Google Patents

Description

Jan. 16', 1962 .1.- E. JENNINGS 3,017,479

VACUUM SWITCH Filed Jan. 29, 1959 INI/ENTOR JO EMMETT his A TTORNQ.

United rates Patent 3,017,479 VACUUM SWITCH Jo Emmett Jennings, San Jose, Calif, assignor, by mesne assignments, to Jennings Radio Manufacturing Corporation, San Jose, Calif, a corporation of Delaware Filed Jan. 29, N59, Ser. No. 789,925 3 Claims. (Cl. 200-144) My invention relates to vacuum switches, and particularly to a miniature single pole, double throw vacuum switch or relay.

One of the objects of my invention is the provision of a vacuum switch or relay of small size, light weight, and possessing a rigidity of construction not found in conventional switches and relays.

Another object of my invention is the provision of a vacuum switch having a high current carrying capacity with a minimum of contact resistance, and requiring very low power to operate.

Still another object of the invention is the provision of a vacuum switch capable of meeting impact and vibration limitations imposed in missiles, aircraft and grounded equipment environments.

Another object is the provision of a vacuum switch capable of withstanding high operating temperatures at elevated current ratings of the order of ll50 amperes.

The invention possesses other objects some of which with the foregoing will be brought out in the following description of the invention. 1 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 half sectional view of the switch of my invention.

FIG. 2 is a horizontal sectional view taken in the plane indicated by the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary view in vertical section of a modified terminal ring and shield assembly.

FIG. 4 is a fragmentary view in vertical section of another modified terminal ring and shield assembly.

FIG. 5 is a plan view of the contact plate assembly shown removed from the envelope.

FIG. 6 is a plan view of a modified contact plate having a reinforced peripheral contacting portion.

Switch gear requirements for modern day uses in missilery, super-sonic aircraft and other specialized applications have far outstripped the availability of conventional switch gear possessing the required qualities. The necessity for reliability in a switch has become absolute, the penalty for failure often being catastrophic. The ability to withstand extreme fluctuations in temperature without causing adverse operating characteristics is another quality essential to reliable operation. Minimum weight of the entire switch is an important factor in determining applicability of the device in an environment where weight is critical; and minimum weight of moving elements within the switch is an important consideration in maintaining the inertial characteristics at low values.

Reliability is measured also in terms of permanence of electrical characteristics over an extended life span which today means millions of cycles in a short length of time, or years of intermittent operation with a complete absence of maintenance or mere inspection at long intervals. Thus, low inductance, low contact resistance, high current carrying capacity, and minimum bounce of fast acting contacts due to low inertia and low mass are important qualities to be included in modern switch gear.

To provide all these desirable qualities in one device is the broad object of the present invention, which broadly comprises an evacuated envelope formed from a series of aligned dielectric rings or washers arranged and in- Patented Jan. 16, 1962 tegrally united into a unitary rigid and light weight hollow cylindriform structure. Rigidity in the structure is enhanced by annular metalic terminal rings interposed hermetically between adjacent dielectric rings and integrally united thereto. The terminal rings and dielectric rings are proportioned and arranged so that an inner peripheral portion of each terminal ring provides a contact portion within the envelope while an outer peripheral portion provides an external terminal outside the envelope. The dielectric and metallic ring complex is hermetically sealed at each opposite end by an end plate structure integrally united to the end dielectric ring in the complex. Within the envelope is provided a mobile contact plate assembly adapted to reciprocate therein to make or break a circuit through selected terminal rings. The contact plate assembly is supported by and insulated from the end cap structures. Reciprocation of the contact plate assernbly is effected by a spring within the envelope which normally urges the assembly in one direction, and electromagnetic means outside the envelope, cooperating with an armature inside the envelope to selectively move the assembly in the opposite direction. Means are provided within the envelope to shield the interior surfaces of the dielectric rings against the condensation of contact metal vaporized by rapid opening and closing of the switch contacts.

In greater detail, the miniature vacuum switch of my invention comprises a unitary hollow housing or envelope formed from a multiplicity of axially arranged dielectric washers or rings 2 having each opposite side metallized to provide a surface capable of being brazed. The rings are preferably formed of ceramic approximately A thick and having an outside diameter of approximately for the switch illustrated. interposed between adjacent ceramic rings and integrally united thereto are a multiplicity of annular metallic terminal rings or platelike members 3, each ring having an inner peripheral portion 4 and an outer peripheral portion 6 arranged concentrically with the ceramic rings. The terminal rings are preferably stamped from molybdenum sheet stock ranging in thickness from .005 to .010", and that portion of each ring which extends outside the hollow envelope is nickel plated to prevent oxidation under adverse atmospheric conditions.

The inner peripheral portion 5 of each terminal ring, best shown in FIG. 2, is provided with an integral axially otfset fixed contact formed by a multiplicity of annularly arranged and circumferentially spaced resilient contact portions 7 formed by cutting radially extending slits 8 in the inner peripheral portion of each terminal ring. The width of the slits 3 have been exaggerated in the drawing for clarity, it being understood that the slits need not be any wider than will permit independent action of each resilient portion. If desired, each resilient contact portion 7 may be provided with a tungsten contact button or pad 9 brazed thereon and forming a reinforcement for each resilient portion. The tungsten buttons or pads increase the current carrying capabilities of the switch and increase the life thereof. In FIG. 1 the contact portion within the envelope is illustrated as axially offset a small amount to lend stability to this poriton of the structure. However, if desired, the offset may be omitted and the contact portion exended inwardly in the same plane as the remainder of the terminal ring. This construction is shown in FIG. 4. In some instances it may be desirable to increase the amount of the offset, as shown in FIG. 3, so that a cylindrical flange 12 is provided concentric with and lying closely adjacent the inner periphery of the adjacent cerarnic ring. In addition to providing stability, the concentric flange 12 constitutes a shield interposed between the contact button 9 and the interior of the envelope to prevent the condensation thereon of vaporized contact metal.

To further insure that vaporized metal does not con dense on the interior surfaces of the ceramic rings addi tional shields are provided integrally interposed between each terminal ring and each adjacent ceramic ring. These shields comprise a transverse annular portion 13 arranged concentrically with the ceramic and metal ring complex and hermetically brazed therebetween. A cylindrical flange -14, integral with the annular portion 13 at its inner periphery, extends axially closely adjacent and concentric with the inner periphery of each ceramic ring. As shown in FIG. 1, the flanges 14 supported on opposite sides of the same ceramic ring are proportioned to overlap in radially spaced concentric relation to prevent vaporized contact metal from reaching the inner periphery of the ceramic rings.

The ceramic-metal ring complex is sealed at each oppo site end by metallic end plate structures integrally united hermetically to the end ceramic ring. The end plate structure at one end comprises an annular plate 16 axially aligned and brazed to the annular portion 13 of the uppermost shield. An integral cylindrical flange 17 extends outwardly therefrom and with the plate 16, forms an annular seat within which a domed end cap 18 is seated. The end cap is provided with a peripheral cylindrical flange 19 concentrically contiguous within the flange 17. The outer free edges 2110f the flanges 17 and 19 are flush and heliarc brazed to integrally unite the domed end cap and annular plate 16-17 to hermetically seal this end of the envelope. A tubulation or tip-off 22 fixed in the domed cap provides means for evacuating the envelope.

The other end of the envelope is hermetically sealed by an annular plate 23 integrally united adjacent its outer periphery to the end ceramic ring, which is also provided with a shield 13-14. A hollow cylindrical metallic housing 24 hermetically sealed at one end by a transverse wall 26 integrally united thereto, and having a metallic core 27 fixed thereon and extending therethrough, is hermetically united to the plate 23 within its inner periphery. Within the housing 24, an energizab'le coil 28 surrounds the outer end of the core, and is detachably secured therein by a cover plate 29 closing the outer end of the coil housing and detachably secured to the outer end of the core by a screw 31. Terminals 32 on the cover plate provide means for connecting electric power leads 33 into the coil.

Mounted within the evacuated and hermetically sealed envelope is an armature 34, responsive to the magnetic field generated by the coil when energized. A lower dielectric bearing block 36-, preferably ceramic, is brazed to the armature and functions to slidably mount the armature for axial movement on a central stud shaft 37 fixed in the inner end of the core. A coil spring 38, interposed between the housing wall 26 and the armature, normally urges the armature away from the inner end of the core.

Fixed across the upper end of the ceramic bearing 36 is a thin metal base plate 39, forming a support on which an axially aligned movable contact plate assembly is mounted. The contact plate assembly comprises a cen tral metallic rod ill having an integral cap 42 at its lower end which in turn is brazed to the supporting base plate 39. At its upper end, the rod 41 is slidably journaled in the central bore 43 of a dielectric bearing block 44 brazed to the underside of the domed cap 18. The bearing forms a guide to retain the contact plate assembly centrally located, and with the lower bearing block 36, cooperates to electrically insulate the mobile contact plate assembly from the two end plate structures.

Brazed about the rod 41 intermediate its ends is a copper sleeve 46. integrally mounted on the sleeve at each end thereof is a transverse contact plate 47, having a multiplicity of resilient contact portions 48 formed about its outer periphery by slits 49 cut radially into each plate.

Each plate is proportioned so that its resilient contact portions &8 lie opposed to the resilient contact portions 7 and contact buttons 9 on the fixed terminal rings. To lend rigidity to each contact plate, a dielectric back plate 51 is brazed to the sleeve and to each contact plate within the peripheral zone formed by the resilient contact portions. The dielectric back plate also serves to bring the fulcrum for each resilient contact portion closer to the point of contact, thus insuring a minimum amount of contact bounce.

As shown in FIG. 1, two additional contact plates 47 are provided spaced along the sleeve, each contact plate being operatively associated with an adjacent terminal ring. Each contact plate is provided with resilient contact portions 48, and strengthened by a conical back plate 51. It will be noted that in the arrangement illustrated, the two upper contact plates are arranged to be normally closed against the opposed fixed contacts, while the two lower plates are arranged to be held normally open by the coil spring 38.

Double throw operation of the switch is conveniently accomplished by electrically connecting the terminal portions of the two intermediate outer terminal leads 6 by means of a clip 52 brazed therebetween. Connecting the clip 52 into a circuit will thus cause current to flow through the normally closed circuit in the direction of the arrows. If the coil is now energized, the contact assembly will be moved downwardly by the armature, breaking the upper normally closed circuit, and the lower normally open circuit will be closed, and maintained closed until such time as the coil is deenergized. The coil spring 38 will then move the movable contact plate assembly upward away from the core.

From the foregoing it will be noted that contact resistance is reduced to a minimum by providing fiat con-- tacting surfaces which provide substantially 360 of sur face contact over an appreciable annular zone. This construction renders the switch capable of handling ex-- tremely heavy currents despite the small size of the switch.

An additional advantage flowing from the use of resilient contact portions is the increase in switch life due to the overtravel protection afforded. The ability of the structure to resiliently absorb impact shocks, caused either by operation of the switch itself, or by extraneous forces inherent in the environment in which the switch is used, insures that the contacts will remain closed under adverse shock and vibration conditions, with a minimum of bounce or chatter of the contacts, thus increasing the reliability of the switch.

I claim:

1. A vacuumized switch comprising a plurality of metallized rings, a metallic annular plate-like terminal member interposed between adjacent ceramic rings and integrally united thereto to unite all the rings in a hermetically tight ring assembly, each terminal member having radially inwardly and outwardly extending annular portions providing respectively a contact within the envelope and a terminal lead outside the envelope, said radially inwardly extending annular portion comprising a plurality of spaced apart integrally connected contact portions, an end plate structure hermetically closing each opposite end of the ring assembly to form a hermetically sealed envelope, a contact plate assembly movably supported Within the envelope on one of said end plate structures and movable into and out of engagement with a terminal member, said contact assembly being centrally arranged within the envelope and having an elongated stem forming the movable support on one of said end plate structures, a plurality of contact plates fixed on the stem at spaced intervals corresponding to the spacing between terminal members, said contact plates being circular and having an outer peripheral portion coextensive with said contact portions on each terminal member with radially extending slots in said outer peripheral portion to form resilient contact fingers for matching cooperation with respective contact portions on the terminal member and an annular back up member for each contact plate positioned on the opposite side thereof from the respective terminal member and of a size that its peripheral edge provides a fulcrum for each adjacent resilient contact finger whereby to insure a minimum amount of contact bounce and the ability of the switch to absorb impact shocks and remain closed under adverse conditions, and switch actuating means supported on said envelope and operatively connected with the contact plate assembly to move the resilient fingers of the contact plate into and out of engagement with the cooperating terminal contact portions.

2. A vacuumized switch according to claim 1 wherein each of the contact portions of each terminal member is provided with a contact pad attached thereto to provide reinforcement and increased current carrying capacity.

3. A vacuumized switch according to claim 1 wherein each of said annular plate-like terminal members has the inner peripheral portion axially offset a small amount to lend stability to this portion of the terminal members.

References Cited in the file of this patent UNITED STATES PATENTS 1,783,279 Burnham Dec. 2, 1930 2,180,661 Baruch Nov. 21, 1939 2,421,267 Huber May 27, 1947 2,843,701 Steward et a1. July 15, 1948 2,868,922 Leonard Jan. 13, 1959 2,886,668 Steward et a1. May 12, 1959 2,886,671 Steward et a1. May 12, 1959 2,908,780 Walters Oct. 13, 1959 FOREIGN PATENTS 389,463 Great Britain Mar. 6, 1933 594,282 Germany Mar. 14, 1934

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