US2981813A - Vacuum switch - Google Patents

Description

A ril 25, 1961 Filed July 21, 1958 J. E. JENNINGS VACUUM SWITCH 2 Sheets-Sheet l INVENTOR. JO EMME 7'7 JENNINGS WJW H/S ATTORNEY April 25, 1961 J. E. JENNINGS VACUUM SWITCH 2 Sheets-Sheet 2 Filed July 21, 1958 INVENTOR. JO EMMETT JENNINGS VACUUM SWITCH Jo Emmett Jennings, San Jose, Calif., assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif a corporation of California Filed July 21, 1958, Ser. No. 749,751

6 Claims. (Cl. 200-144) My invention relates to vacuum switches, and particularly to a high frequency double-break vacuum switch.

One of the objects of my invention is the provision of a double-break vacuum switch having low residual electrostatic capacity between the contacts.

Another object is the provision of a double-break vacuum switch in which the contacts are designed for low thermal resistance, low contact resistance and high current carrying capacity.

Still another object of the invention is the provision in a double-break vacuum switch of means for automatically grounding the disconnected movable contact assembly.

A still further object of the invention is the provision of resilient compensating means for accommodating overtravel of the movable contact actuator stem.

Another object of the invention is the provision of a vacuum switch having a movable contact mechanism within the envelope operable from outside the envelope and having insulating means interposed therebetween.

Still another object of the invention is the provision of a double "break vacuum switch whichis operable independent of atmospheric pressure.

A still further object of the invention is the provision of a vacuum switch having a contact mechanism normally held closed by a resilient means.

Another object of the invention is the provision of a vacuum switch which may be locked in either a closed or open position of the contacts.

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 half sectional view, partly in elevation, showing the movable-contact means in its normally closed position.

Fig. 2 is a plan view.

Fig. 3 is a fragmentary vertical sectional view taken in the plane indicated by the line 3-3 of Fig. 1. Parts of the structure are shown in elevation.

Pig. 4 is a fragmentary vertical sectional view taken in the same plane as Fig. 1, but showing the contact mechanism held in open position.

Figs. 1, 2 and 3 are drawn one and one-half times actual size, and Fig. 4 is drawn twice actual size.

Broadly considered, the high frequency double-break vacuum switch of my invention comprises a vacuurnized envelope including a dielectric shell closed at oneend by a metallic end cap. A plurality of pairs of contact rods extend into the envelope'and constitute spaced contact points within the envelope and terminal leads outside the envelope, where they may be readily connected into a circuit. Extending into the envelope and movably mounted 'onthemetallic end 'cap'is an actuator stem. The stem States Patent may be manipulated from outside the envelope, and movable spring-pressed contact means within the envelope and supported on the actuator stem are provided to engage and disengage selected pairs of contact points to make and break a circuit therebetween.

More specifically, my double-break vacuum switch comprises a vacuumized envelope including an elongated dielectric shell or bulb 2 symmetrical about a longitudinal axis and closed hermetically at one end by a metallic end cap 3. At its other end the bulb is provided with an integral dielectric end wall 4. The bulb shown and described is formed from transparent glass, but it will of course be understood that any other suitable dielectric material may be used.

Adjacent the end wall 4, the bulb is provided with two oppoistely disposed apertures 6, each of which accommodates an inwardly extending contact rod 7. The outer end portion 8 of each contact rod is brazed within the outer cylindrical portion 9 of a metallic terminal sleeve provided with an integral flared inner end portion 12, hermetically bonded to the glass bulb about each aperture in the conventional Housekeeper seal. Terminal sleeve and contact rod thus cooperate to hermetically close each aperture. To facilitate brazing of sleeve and contact rod portions, a peripheral groove 13 is formed in the contact rod portion 8 to accommodate a. ring of brazing material for hermetically uniting the parts after assembly.

The inner end portion 14 of each cylindrical contact rod 7 constitutes a contact point and is cut away on its under side to provide a flat rectangular contact surface 16. The opposite upper side of the contact rod is cut away in a plane diverging away from the plane of contact surface 16, thus providing an inclined surface 17 intercepted at its lower end by a flat rectangular surface '18 parallel to and spaced from the contact surface 16. The contact surface 16 thus provides the large surface area necessary for the efficient transfer of heat and electrical energy, while the cut-away upper surfaces 17 and 18 substantially reduce residual electrostatic capacity between the opposed pair of main contact points 14 While permitting heavy electrical conduction.

Vertically and circumferentially spaced from the main contact rods 7 and extending into the envelopeat right angles to the longitudinal axis thereof is a second or auxiliary pair of opposed contact rods 19. Each of the rods is supported directly on and hermetically sealed to the glass bulb. The portion of each rod extending outside the bulb constitutes a terminal lead while the end of the rod extending into the envelope constitutes a contact point and is shaped to provide a fiat upwardly facing contact surface 21. The inner ends of the auxiliary contact rods, like the inner ends of the main contact rods, are spaced apart and are adapted to be selectively engaged or disengaged to make or break a circuit therebetween.

Means are provided mounted on the end cap 3 and movable to engage and disengage a selected pair of said contact points. Extending into the envelope is an actuator stem formed by a metallic rod 22 slidably journaled in a bearing tube 23 integrally and hermetically brazed on the end cap 3. The bearing tube and end cap are concentrically related with respect to the central longitudinal axis of the switch. The outer end portion of the rod is threaded as at 24 for connection to an operating means (not shown), and limit or lock means for the rod are provided by the cooperation of a transverse groove 26 in the rod and set screw 27 in the head 28 of bearing tube 23. The screw normally slidably engages the fiat bottom of the groove and provides an abutment against which the sides of the groove impinge when the rod is axially moved in or out in the bearing tube. The flat end of the screw impinging against the rod also prevents inspring 52 will be compressed as shown advertent rotation of the rod. When desirable, the screw may be jammed tight against the rod to lock it immovable in a selected position.

The inner end of the rod 22 is connected to the closed inner end 29 of an expansible metallic bellows 31 which surrounds major portions of both bearing tube and rod, and has its open outer end 32 hermetically united to the bearing tube and end cap 3. A metal ring 33 surrounding the open end of the bellows and interposed between bellows and end cap and brazed to both reinforces both bellows and end cap and insures a hermetic union. A coil compression spring 34 within the bellows is interposed between the inner end thereof and thebearing tube and normally urges the stem and bellows assembly into the envelope in a switch-closing direction. "It will thus be seen that inward expansion of th'e'bellowswith a consequent inward movement of the rod 22, is effected even in the absence of atmospheric pressure outside the envelope. T

Seated concentrically on the inner end of the bellows within the envelope and integrally united therewith and with the inner end portion of rod 22, is a hollow cylindrical metallic ferrule 36 providing an annular flanged seat 37 within which the lower end portion of an axially extending dielectric post 38 is brazed. The dielectric post forms an integral part of the actuator stern and is contained wholly within the vacuumized envelope. From adjacent the inner end of the bellows the post extends the levelof the main contact points, and adjacent its upper end is reduced in diameter to provide a bearing portion 42 upon which is slidably and rotatably journaled a movable contact means 43. A shoulder 44 in the stud shaft limits relative movement of shaft and contact means in one direction, while a nut 46 threaded and brazed to the upper end of the stud shaft retains the contact means on the bearing portion of the stud shaft. The contact means 43 is preferably a copper disk formed with a flat upper face 47 adapted to engage the downwardly facing contact surfaces 16 of the contact points 14 in flat surface engagement to provide a minimum of contact resistance.

A bearing sleeve 48 rigidly fixed to the contact means and interposed between the contact means and the stud shaft insuresa minimum amount of wear for long troublefree operation. I

Adjacent its lower end the stud shaft is provided with a peripheral flange 49 on which is brazed a transversely extending resilient strip 51. The strip constitutes contact means proportioned to span the space between the contact points 21 and adapted to be selectively engaged or disengaged therewith as shown best in Fig. 3. Interposed between the stud shaft and the conical underside of the contact disk is a coil spring 52, normally urging the contact disk upwardly into resilient engagement with the contact points 14. Working in opposition to the spring 52 is a second coil spring 53 which is interposed between the contact disk and the nut 46. Together, the

. springs 52 and 5-3 cooperate to resiliently retain the floating contact disk 43 at a predetermined position on the stud shaft when the main switch contacts 14 are open. When the switch contacts 14 are closed by permitting the actuator stem and contact disk to be propelled inwardly by spring 34 and/or atmospheric pressure, the lower and provide a measure of overtravel protection by permitting relative movement between the contact disk and the shaft after engagement has been made by the contact disk. The

. 4 1 spring 52 also insures that slight variations in the surface contacts will be accommodated by resilient compensation by the spring loaded contact disk. This resilient mounting of the movable contact eliminates the impact shock and bounce of the rapidly closing switch contact and thus contributes to the long life and efficient operation of the switch. The spring 53 absorbs the impact shock caused by the suddent application of force on the actuator stem in a switch-openingdirection. As soon as the inertia of the contact disk has been overcome the energy stored in the spring 53 will be released and disengagement of the contact disk accelerated.

Such downward movement of the actuator stem to disengage the contact disk 43 from the contact points 14 effects engagement of the outer ends of resilient contact strip 51 with the contact points 21. In use, the leads 19 are preferably connected to a ground circuit so that in the disengaged position of the contact disk 43, the entire movable contact assembly is at ground potential. This effectively eliminates the feedthrough of energy between the open main contact points during high frequency operation of theswitch. The switch disclosed is designed to operate at 60mc. and 35 amperes R.M.S., at potentials ranging between 5 to 7.5 kv. peak.

To mount the switch in a panel 54, shown in dash lines in Fig. 1, an annular ring 56 having threads on its outer periphery is brazed to the end cap 3. A complementary clamp nut 57 is adapted to be threaded onto the ring 56 and against the panel to secure the switch in position. The clamp nut may be knurled or provided with spanner wrench apertures 58 as shown.

I claim:

1. A vacuum switch comprising a vacuumized envelope including a dielectric shell and a metallic end cap closing one end of the shell, a plurality of pairs of contact rods constituting spaced contact points within the envelopeand terminal leads outside the envelope, an actuator stem movably mounted on the end cap and hermetically extending into the envelope, and movable contact means within the envelope including a main contact disk slidably journaled, on said actuator stem and a resilient auxiliary contact bar fixedly supported on the actuator stem and'm'ovable thereby to engage and disengage selected pairs of said contact points to make and break a circuit therebetween.

'on said stem and spring means are provided interposed between the contact disk and the stem to resiliently impede said sliding movement.

3. The combination according to claim 1, in which movement of the actuatorstern in one direction effects resilient engagement of the main contact disk with one pair of contact points and movement of the actuator stem in the other direction effects engagement of the auxiliary contact bar with another pair of said contact points.

4. The combination according to claim 1, in which said actuator stem within the envelope includes a nonconductive dielectric portion and a conductive metallic portion insulated from said end cap by the dielectric portion, and said main contact disk and contact bar are mounted on the metallic portion of the stem.

5. The combination according to claim 1 in which a bearing tube is mounted on the end cap, said actuator stem includes a portion slidably journaled in the bearing tube, and means are provided interposed between the bearing tube and the associated portion of the stem to control movement of the stem.

6. In a vacuum switch having a vacuumized envelope, the combination comprising a pair of contact rods constituting terminal leads outside the envelope and extending into the envelope, the inner end portions of the contact rods within the envelope constituting a first pair of contact points and'being ,cut away on the same sides thereof to provide flat contacting surfaces facing in the same direction and cut away on the opposite sides thereof to provide flat divergent surfaces inclined away from said flat contacting surfaces, a contact disk mounted within the envelope and movable into or out of engagement with the fiat contacting surfaces of said first pair of contact points to make or break a circuit therebetween, a second pair of contact points Within the envelope spaced from the first pair, and an auxiliary contact her Within the envelope movable to engage and disengage said second pair of contact points.

References Cited in the file of this patent UNITED STATES PATENTS White Nov. 14, 1911 6 Farmer et al. Apr. 15, Burnharn Dec. 2, Prince July 14, Parsons Apr. 4, Baruch Nov. 21, Smith June 7,

Williams Dec. 4, Jennings May 28, Steward et a1 July 15, Schwager Feb. 3, Reece July 28, Walters Oct. 13,

FOREIGN PATENTS Great Britain Mar. 6, Great Britain Dec. 18,

Images