US1952184A - Vacuum switch - Google Patents

Description

March 27, 1934. w K RANKlN 1,952,184L

VACUUM SWITCH Filed Dec. 18, 1929 2 Sheets-Sheet l Inventor.' William KjFarl/dr,

by MMM H i s Atto Prwey.

" March 27, 1934. W, K, RAMON 1,952,184

VACUUM SWITCH Filed Dec.V 18, 1929 2 Sheets-Sheet 2 Irwvemtcv: William KFankiT,

His Attorney UNITED STATES PATENT OFFICE VACUUM SWITCH William K. Rankin, Lansdowne, Pa., assigner to General Electric Company, a corporation of New York Application December 18, 1929, Serial No. 415,030

2 Claims. (C1. ZOO-144) My invention relates to vacuum switches, and metal, such as copper or steel, to which is secured, more particularly to that type wherein relatively as by welding, an extension casing 4 for contain- .;j movable contacts within an evacuated chamber ing the movable element of the Switch- The are directly and positively separated by means vacuum switch is suitably supported by the in- 5 exteriorly of said chamber, sulating bushings 5 which are mounted on fixed 60 In vacuum switches of the type wherein an supports. operating lever for the switch contacts extends In order that the vacuum chamber shall be exteriorly of the vacuum chamber through a sealvacuum-tight When heated due t0 Current ing diaphragm, the life of the sealing means has traversing the switch, the walls of the switch l0 generally been limited to a comparatively small casing are composed of a substantially de- 65 number of switching operations due to excessive oxidized metal which pIeCllldeS any leakage 0f stresses set up in the sealing diaphragm by movegas through the metal et e temperature 10We1 ment of the switch rod. When the switch rod, as than approximately 750 C. If the metal has not is generally the case, extends through and is been sufficiently deoXidZed, the OXideS in the sealed to the sealing diaphragm the stresses set metallic structure permit a certain amount of 70 up near the union often cause small cracks in gas leakage therethrough when it is heated therethe seal, thereby impairing the vacuum to such by impairing the vacuum. an extent that the switch fails to interrupt its A conduit 6, communicating with an extension rated capacity. It may also happen that the 7, is provided for evacuating the switch chamber sealing diaphragm, which is generally composed from air and other gases, the eXtehSOh 7 being 75 of metal, may become slightly porous so as to Connected to asuitable pump (not shown) during leak gas when it is heated during operation of the the evacuating DIOCBSS- switch, thereby impairing the vacuum. Referring more DaT'ClllaIlY t0 Fig. 2, the lead- An object of my invention is to provide an imin conductor stud 3 extends Vthrough the bushing proved vacuum switch Structure wherein the 2 and terminates in a fixed contact 8 for coact- 80 switch contact operating member may be ing with a movable contact 9. The sealing bushactuated an indefinite number of times without ing 2, Which COmDI-Ses 110 Dart 0f the present causing failure.of the sealing diaphragm, and invention and is described and claimed in a cowherein the evacuated switch chamber shall be pending application, comprises an outer insulatr maintained vacuum-tight. ing shell 2 disposed between end caps 10 and 85 f Another object of my invention is the provision 11. The conductor stud 3 is secured to a collar 12 of a sealing diaphragm which shall have an un to which are fixed a plurality of spaced rods 13,

l broken surface with respect to the switch contact each of said rods being biased upwardly by a operating member, and which shall permit direct spring 14 seating on the upper side of the cap 10 and positive actuation of said member by means and bearing against a washer or stop member 13 90 exterior of the evacuated switch chamber. on the rod. It will be noted, therefore,- that the My invention will be more fully set forth in springs 14 tend to bias the conductor stud upthe following description referring to the accomwardly with respect to cap 10 through which the panying drawings, and the features of novelty conductor stud may move freely. The lower end 4o which characterize my invention will be pointed of the conductor stud is provided with ra nut 15 95 out'with particularity in the claims annexed to which when tightened bears against a shield 16, and forming a part of this specification. a plate 17, and an insulating spacer 18 to draw Referring to the drawings, Fig. 1 is a perspecthe conductor stud downwardly and to place the tive view of a vacuum switch embodying my springs 14 under tension. The function of the invention; Fig. 2 is an elevational view, partly in shield 16 is to prevent short circuiting of the 100 section, of the vacuum switch illustrated in Fig. insulating spacer 18 by the formation of a con- 1; Fig. 3 is a fragmentary top view of the ducting metallic coating thereon.' When the casdiaphragm operating structure illustrated in Figs. ing 1 is highly evacuated free molecules are re- 1 and 2, and Fig. 4 is a sectional view taken along leased from the surface of the metal walls and the line 4-4 of Fig. 2. travel across the intervening space towards the 105 In Fig. 1 there is illustrated a vacuum switch insulating spacer. If no means are provided for comprising a main vacuum chamber 1 having intercepting these free molecules from the metal mounted at its upper end an insulating bushing 2 walls, a molecular deposition of the metal is for a lead-in conductor stud 3. The vacuum formed on the insulating member so that it is chamber 1 comprises a cylindrical casing of soon short-circuited and the conductor stud 110 CAD.

placed in contact with the casing. The shield 16, however, being cup-shaped, substantially encloses for the most part the outer surface of the member 18 so that it serves to intercept the free moiecules and any other metallic particles tending to short-circuit the insulating spacer. The spacing member 18 abuts an intermediate sealing platev 2() which is maintained in position by a clamping plate 19 and an annular row of bolts 2l coacting with a flange 21 forming a substantially integral part of the switch chamber. In a simple construction the members 19, 21 and 21 are sometimes omitted and the top 20 silver soldered directly on the casing 1.

The sealing means for the conductor stud comprises an insulating sleeve or collar 22 of material such as glass having its upper edge sealed to a flexible member, as a copper spinning 23, and its lower edge to a similar member 24, The sealing member 23 is fused or otherwise sealed to a ilange 25, in turn suitably sealed to the conductor stud. The lower edge of the sealing member 24 is sealed to the sealing plate 2O which is in turn sealed, as by welding or by a low melting point alloy, to the main chamber 1, thereby completing the seal for the conductor stud.

The movable contact 9 oi the switch which is adapted to engage the stationary contact 8, is mounted at the end of a switch operating member, as a rod or lever 26, extending through the switch extension casing 4. The contact 9 is electrically connected to the exterior of the switch through a ilexible conductor 27 which is electrically connected to the metallic casing 4 and terminal member 28. The sealing means for the switch operating rod comprises in the present instance a flexible diaphragm 29 of suitable resilient material secured and sealed at its outer periphery, as at 30, to the casing 4. The diaphragm 29, which is substantially defined by a single plane, has concentric corrugations and is provided centrally thereof with an extension or hub-like portion 31 which is closed at the outer end and extends exteriorly with respect to the casing 4. Within the recess formed by the portion 3l is disposed the end 32 of the switch lever. The diaphragm 29 accordingly presents an unbroken surface with respect to the switch oper- .ating member and obviates the necessity of a sealed union between the diaphragm and said member. The extension 3l is considerably thicker than the portions of the diaphragm near its outer periphery, and is reinforced at 33, tapering .in thickness, where the extension joins the plane of the diaphragm, it being at this point where high stresses may be set up by movement of the switch member.

The material of the diaphragm 29 is preferably of metal which will not permit leakage of any gas therethrough at any temperature below '750 C. An example of such a metal is completely deoxidized copper. The term completely deoxidized, however` shall be understood to include that condition wherein the metal may be annealed in hydrogen gas just below its melting point without becoming porous. Although the diaphragm and switch parts may become heated to anv appreciable extent during operation of the switch, the operating temperature will be considerably less than 750 C. so that no leakage of gas will take place through the diaphragm to impair the vacuum.

It should be noted at this point that the switch operating member is sealed entirely within the evacuated chamber, and that no portion thereof extends exteriorly of the exible sealing dia.- phragm. This arrangement is a decided advantage over that type of vacuum switch wherein the switch operating member, in order to be directly and positively actuated, extends bodily through the sealing diaphragm and is joined thereto by a sealed union. In the latter instance, the stresses set up at the sealed union may not only impair the vacuum within the container, but necessitate a very slight movement of the switch member in order that the diaphragm shall not be actually cracked or broken.

In accordance with my invention, the switch operating member 25, though totally sealed within the vacuum chamber, is directly and positively actuated by a pivoted structure disposed exteriorly of the vacuum chamber, which is controlled in any suitable manner. To this end, the hub, or extension 31 of the diaphragm is engaged by a clamp 34 which serves not only to grip the extension 32 of the switch member tightly through the resilient diaphragm material, but to transmit pivotal movement thereto in a manner presently described. The clamp 34 is provided with extensions 35 having pivot studs mounted within the fixed bearing members 36, as best illustrated in Fig. 3. The clamping structure, therefore, comprises a pivoted yoke which may be connected to a pair of operating levers 37 extending along opposite sides of the switch casing and connected to the main operating rod 38 which may be actuated in any suitable manner. As illustrated in Fig. 3, the center line of the pivotal mountings for the operating yoke extends through the plane of the diaphragm 29 so that pivotal movement is imparted to the switch operating member 26 with a minimum movement at the sealing diaphragm, and particularly with absence of transverse movement. Furthermore, the stress is reduced to a minimum in the diaphragm for a. given opening movement of the switch.

In the event that an appreciable angular movement of the switch lever 26 is required, the sealing diaphragm may take the form of a metallic bellows, or of a multiple diaphragm arrangement, wherein the pivot point of the lever is substantially in the plane of the union between the diaphragm and the casing, as illustrated in the present instance.

For the purpose of determining the degree oi' vacuum within the switch casing, there is provided apparatus, designated generally at 39, comprising a Parini Hale hot wire gauge and an ionization gauge. rIhis apparatus is known in the art and a detailed disclosure thereof is not believed necessary. The apparatus is in communication with the interior cf the switch chamber through a tube 40.

In order that a very high degree of vacuum may be maintained at all times within the switch casing, an auxiliary chamber (not shown), in communication with the switch chamber may be provided containing a suitable gas absorbing material, as zirconium, for example. If the parts of the switch have not been thoroughly degassied by well known methods for removing occluded gases from the switch parts, the gas absorbing material is effective to remove these gases if, and when, they are formed so as to maintain the original high vacuum.

A means for sealing off the switch Casing after it has been evacuated to a desirable extent may comprise any suitable arrangement, and in the present instance the lower end of the switch casing, which communicates with. the exhaust conduits 6 and 7 is adapted to be sealed by the cap 41 whose outer edge seats within an annular recess 42 in the lower wall of the switch chamber within which a low melting point alloy 43 is placed. The cap 41 is seated within the recess 42 while the alloy is molten so that upon cooling a perfect seal is made.- For the purpose of properly seating the cap 41 after the switch casing has been evacuated, an operating rod 44 secured to the cap extends through the exhaust conduit 6 and terminates in a pointed portion 44' bearing within a recess formed in a second lever 46 extending through a. lateral extension 47 of the conduit. The rod 44 is normally biased into engagement with the rod 46 of a weight 45 secured centrally on the rod 44 by Cotter pins or the like. A sealing diaphragm structure 48, more clearly illustrated in Fig. 4, and similar in structure to that previously described, is adapted to transmit movement between the operating crank 49 having a screw connection, as at 50, with the operating arms 51 of the diaphragm, for raising or lowering the cap 41. A strip 52 of resilient material, mounted at one end with respect to the switch casing and connected to the cap 41, is provided for guiding the movement of the cap with respect to its seat. The operation of the sealing arrangement is believed to be obvious, it being necessary to state merely that the alloy 43 is melted by suitable application of heat when the switch is to be sealed and the crank 49 rotated so as to move the rod 44 and seat the cap 4l within the alloy, which is then permitted to harden.

Other apparatus and means for sealing the cap have been devised, and by way of further example, the cap may be raised instead of lowered into a position exteriorly of the casing so that the seal may be readily inspected.

When the switch is to be installed for actual operation, the evacuating and sealing structure comprising the parts 6, 7, 48 etc. are removed. The loose connection between the rods 44 and 46 permits the conduit 6, and the apparatus associated therewith, to be lowered after it has been unclamped at its upper part from the rest of the structure.

What I claim as new and desire .to secure by Letters Patent of the United States, is:

1. In a vacuum switch comprising an evacuated chamber and relatively movable contacts disposed therein, a continuous flexible diaphragm independent of and sealing a contact operating member within said chamber, said diaphragm having an extension within which one end of said operating member is disposed, and pivotally mounted contact actuating means exterior of said chamber engaging said extension for transmitting pivotal movement through the diaphragm to said operating member for causing engagement and disengagement of said contacts.

2. In a vacuum s'witch comprising an evacuated chamber, relatively movable contacts disposed therein and a pivoted operating member for caus- 100 ing engagement and disengagement of the contacts, the combination of a flexible diaphragm forming a part of said chamber for sealing said operating member entirely therein, said diaphragm having an unbroken surface and com- 105 prising a hub-like recess centrally thereof within which one end of said operating member is disposed, and switch actuating means exteriorly o'f said chamber in engagement with said hublike portion for imparting pivotal movement to 110 the operating member.

WILLIAM K. RANKIN.

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