US2299772A

US2299772A - Seal arrangement

Info

Publication number: US2299772A
Application number: US415484A
Authority: US
Inventors: Chauncey G Suits
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1941-10-17
Filing date: 1941-10-17
Publication date: 1942-10-27
Anticipated expiration: 1959-10-27

Description

Oct. 27, 1942- C. G. sul-rs 2,299,772

SEAL ARRANGEMENT Filed Oct. 17, 1941 Inventor'. Chauncey G. Suits,

by HM( ttorney.

Patented Oct. 27, 1942 SEAL ARRANGEMENT Chauncey G. Suits, Schenectady, N. Y., assg'nor to General Electric Company, a corporation of New York Application October 17, 1941, Serial No. 415,484

8 Claims.

application relates to a seal adapted for use in electrical devices such as transformers, capacitors and switches which contain a dielectric medium at a pressure in excess of several atmospheres.

One of the objects is to provide an improved apparatus for supporting terminal structures and lead-in members.

Another object is to provide an improved means for reducing strain on the terminal structures of apparatus employing diiierential pressures.

A further object is to provide a structure embodying cooperation between insulated terminal members and the casing containing electrical apparatus in order to eliminate strain on the seal between the insulation of the terminal members' and the casing.

While seals between insulating members and the casings of electrical apparatus are well known in the art, when high pressures are used in such apparatus, diiiiculty has been encountered in satisfactorily protecting these seals. 'I'he diiierence between the pressure inthe casing and the outside atmosphere creates strains tending to break the bond with the seal either at the insulator or the casing. While the bond with a casing may be protected by the use of welds and similar methods of uniting metals, that with a vitreous or ceramic insulator is not so easily protected.

My invention proposes to protect such a junction by providing additional support at this point.

It is an important feature of the present invention to insulatingly seal an electrical conductor through a wall part having differential pressures on opposite sides of the wall part by hermetically sealing the conductor to a surrounding insulator and providing a supporting member, joined to the wall part to abut a shoulder on the insulator and resist the tendency of the insulator to move under the influence of the large differential pressures acting on it.

While not limited thereto, the invention has been found especially applicable in connection with high pressure switches of the liquid contact type and in the following description will be exempliiied by reference to such a switch..

For convenience in illustrating one embodiment of the invention it will be described as applied to a switch of the type disclosed in my copending application, S. N. 331,797, iiled April 26, i940, and assigned to the assignee of the present application.

The novel features of my invention will be described with greater particularity in connection with the accompanying drawing and set forth in the accompanying claims.

In the drawing, Fig. l is a longitudinal section of a circuit breaker utilizing the insulator supporting and sealing means of this invention; Fig.

2 is an enlarged sectional View of my improved insulator supporting and sealing means; and Fig. 3 is a perspective view of a part of the circuit breaker illustrated in Fig. 1.

Referring now to Fig. 1, I have illustrated my invention as applied to a circuit breaker I0 employing a liquid contact material, such as mercury, which circuit breaker comprises a pressureconfining casing Il, illustrated as a metallic cylinder so constructed as to withstand'relatively high pressures therein. One end of casing II is closed by a metallic closure member I2 preferably welded thereto and associated with a suitable threaded terminal I3 through which connections to an external circuit may readily be made. A suitable passage I4 is provided in closure member I2 and is sealed ofi at I5 as by welding when the circuit breaker has been completely constructed and nlled with an appropriate gas (e. g., hydrogen) under pressure. The other end of the pressure confining casing II is provided with a terminal I6 which is supported relative to casing II by means oi the supporting structure of this invention hereinafter to be described.

The terminal I supports at its inner extremity, that is, within the casing l I, a complex electrode 2| having two

Contact portions

22 and 22 and an intermediate portion 22 which connects the two contact portions (see Fig. 3). During the normal use of the switch the

contacts

22 and 22 engage a quantity of mercury within the casing and in contact with the casing walls. For satisfactory operation the casing should be lled with mercury to the level indicated by the dotted line 20. With this arrangement a complete circuit is provided through the switch between the terminals I3 and I6.

In order to facilitate the circuit-interrupting function of the switch, there is further provided within the switch casing I I a cup-shaped member Il of insulating material which is held in abutment with the surface of the electrode contact part 22 kby means of a compression spring I8. The 'cup Il, which is preferably of ceramic material, is provided with a shallow end, remote from the supporting means I8 and closed by a barrier or dam I9. In operation, the switch circuit is broken by tilting the surface so that the dam I9 cuts the surface of the mercury in the manner explained in my above-mentioned copending application. In order additionally to assist the circuit-interrupting operation, there is associated with the electrode structure 2i an arc chute 23 which is provided with ends 2li and 25 and a top cover member 2S adapted to prevent arc gases from escaping the` confining space formed by the chute. Also associated with this arc chute is a deionizing means 21 comprising alternate layers of iiat and corrugated screen. Furthermore, pressure-contining casing I l is provided with an insulating liner 28 to prevent any arcing to the walls of the casing Il.

In order to permit the arc which is formed across barrier I9 during the circuit-interrupting operation to be forced into the arc chute 23,.

magnetic means in the form of a horse-shoe shaped electromagnet 2Q (Fig. 3) is provided. This electromagnet is mounted outside the Walls of the ceramic cup il with its poles adjacent to the ybarrier i9. A number of turns of the part 22 are wound around the central portion of the electromagnet 2Q so that the current owing to the contact r22" through this part just prior to complete circuit interruption is enabled to develop a magnetic field between the poles of the electromagnet. A suitable insulating means 3l is provided between the structure of the electromagnet 29 and the' part 22.

United to the inner extremity of the terminal i6 is a. stud 32 having a threaded portion for connection with the electrode 2l. A lock nut 33 is used to insure a tight connection between 32 and 2l.

As has been previously noted herein, my present invention is primarily concerned With the problem of providing an insulating seal arrangement for the terminal l and its associated parts the name of A. W. Hull and Roy W. Moore, and` is in direct sealing contact with a metal sleeve 313 which surrounds the terminal I6. It is the function of this sleeve to permit a slight contraction of the glass of the insulator 35 to occur after the casting procedure without producing an excessive strain such as might be developed if the glass were welded directly to the rigid structure of the terminal I6 itself. In order to make the joint lbetizveen the terminal l and the glass insulator oi' gas-tight character, `there is provided a thimble-like member 3l which' is placed over the head of stud 32 and fused into the glass insulator 35, preferably as a part of the original casting operation. The member 3l may be welded to the stud 32 to provide a hermetic joint.

Embedded in and sealed to the mass of the glass insulator 35 at its outer circumference is the inner edge of an annular ring 38 which extends between the insulator and the wall of the metal casing l I to which it is sealed, for example, by Welding as indicated at All. In order to permit slight expansive movement of the casing to occur without thereby rupturing the seal between the part 38 and the' glass insulator 35, the 'former is due to thermal strains. The relationship of the.`

parts is such that the weight of the insulator 85 f* bent transversely into a concave form. Between one of the transversely bent portions of the ring and the adjacent surface of the insulator there is provided an idler ring 39 which is in direct sealing engagement with the glass and which prevents the glass from sealing to the ring 33 in the region subtended by the idler ring.

In order to relieve the strain on the joint between the annular ring 38 and the insulator 35 caused by the diiierence in pressure which emsts between the outside and inside of the casing li the glass insulator is provided in accordance with my present invention with a shoulder iii which cooperates with a correspondingly formed surface on the cap part Bil of the casing. A lead gasket lli interposed between the shoulder 39 and the aforesaid surface of the cap 36 serves to distribute the stress equally over the conical surface of the insulating member 35. The internal surface of the cap 3@ also serves as a supporting abutment for the contour i2 of the member 353. The hermetical closure of the structure is coin= pleted by means of the Weld i3 between the thin outer edge of the ring li? and the attenuated edge of the cylindrical container l. This weld may. because of its location relative to insulator 35, be made without danger of cracking the insulator and yof the elements mounted on it are eectively supported by the cap 3B independently of the seal between the part 38 and the insulator thereby relieving the seal of any strain due to vthis cause.

As a result of the construction described in the foregoing, the sealing arrangement realized is of a character well adapted to withstand differential pressures amounting to many atmospheres while providing at the same time a completely lier= metical seal which does not depend upon gasketing to be gas tight. For example, a mercury switch arrangement such as that illustrated may employ an internal filling of a gas such as hydrogen at a pressure of as high as pounds per square inch or more without danger of iracturingA the seal or developing gas leakage.

In the construction of seals of the character described it is desired that the sleeve 3Q, the thimble-like member 3l, the annular ring and the idler ring 3Q be made of a metal having a co= efficient of thermal expansion substantially the same as that of the insulator material. Numerous sealing combinations which meet reduirea ment are now available inasmuch as glasses have been developed which are adapted to seal satisu factorily with iron or with alloys of iron with nickel or nickel-cobalt. A

While I have described a particular embodi ment of my invention, it will. be obvious to these skilled in the art that various changes and mcdl= nca-tions may be made without actually departing from the invention. I, therefore, desire by the appended claims to cover all such changes and modications as fall within the true spirit and scope of the foregoing disclosure.

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

l: A terminal structure for encased electrical apparatus of the type emplodrig pressures difiering substantially from atmospheric comprisn ing an insulator having a shoulder portion, a metal ring having one edge embedded in said insulator and connected to a part of the apparatus casing to provide a seal for said terminal structure, and another part of the casing engag apparatus subjected to relatively high pressures comprising an insulator, a shoulder portion on said insulator, a metal ring having its inner edge embedded in said insulator adjacent said shoulder and connected to a portion of the apparatus casing to form a seal, and a further portion of said casing engaging both said shoulder and said metal ring to form a support therefor.

3. A terminal structure for encased electrical apparatus subjected to relatively large pressures, comprising a lead-in conductor for said apparatus, an insulator surrounding said conductor and sealed thereto, a shoulder on said insulator, a metal expansion ring embedded in said insulator adjacent said shoulder and sealed to a part of the casing for said apparatus, a portion of said metal ring conforming to one contour of saidshoulder, an idler `ring disposed between the shoulder and the metal ring, and another part of said casing abutting another contour of said shoulder and a second portion of the metal ring to provide a support for both said metal ring and said shoulder.

4. A terminal structure for encased electrical apparatus of the type employing pressures diftering substantially from atmospheric comprising an insulator having a shoulder portion, a metal ring having one edge embedded in said insulator and connected to a part of the casing to provide a seal for said terminal structure, and another part of the casing engaging said shoulder portion and adapted to absorb mechanical stresses attributable to said pressure differential, and a deformable gasket interposed between said shoulder and said member to equalize the stresses on said shoulder.

5. An arrangement vfor insulatingly sealing an electrical conductor through a wall part having differential pressures on opposite sides of the Wall part, said arrangement comprising an insulator surrounding and hermetically joined to the said conductor, a metal ring having its inner edge sealed into the outer portion of .the in-l sulator and disposed on the side of said wall part exposed to the greater of said differential pressures, a shoulder provided on said insulator adjacent to the region of its union with said metal ring, and a surface on said wall part abutting said shoulder and an unembedded portion of said ring for resisting the tendency of said insulator and ring to move or become deformed under the influence of said diierential pressures.

6. A glass-to-metal seal for joining an insulator to a casing comprising, a shoulder on said insulator, a metal expansion ring partially embedded in said insulator adjacent said shoulder and sealed to said casing, a portion of 'said metal ring conforming to one contour of said shoulder, an idler ring'disposed between the shoulder and the metal ring, and a member abutting another contour of said shoulder and a second portion of the metal ring and joined to said casing to provide a support 'for both said metal ring and said shoulder.

'7. A glass-to-metal seal for joining an insulator to a wall comprising, a shoulder on said insulator, a metal expansion ring having its inner edge embedded in said insulator adjacent said shoulder and its outer edge sealed to said Wall, a portion of said metal ring conforming to one contour of said shoulder, and a member abutting another contour of said shoulder and a second portion of the metal ring and joined to said wall to provide a support for both said metal ring and said shoulder.

8. A glass-to-metal seal for joining an insu lator to a casing` comprising, a shoulder on said insulator, ametal expansion ring partially embedded in said insulator adjacent said shoulder and joined to said casing to form a sealing connection between the casing and the insulator, a portion of said metal ring conforming to one contour of said shoulder, an idler ring disposed between the shoulder and the metal ring, a member abutting another contour of said shoulder and a second portion of the metal ring and joined to said casing toprovied a support for d both said metal ring and said shoulder, and a gasket located between said shoulder and said member to equalize the stress on said shoulder. CHAUNCEY G. SUITS.