US1881510A

US1881510A - Method and apparatus for providing the casings of electrical apparatus with inert atmospheres

Info

Publication number: US1881510A
Application number: US152047A
Authority: US
Inventors: Talma T Greenwood
Original assignee: Condit Electrical Manufacturing Corp
Current assignee: Condit Electrical Manufacturing Corp
Priority date: 1926-12-01
Filing date: 1926-12-01
Publication date: 1932-10-11
Anticipated expiration: 1949-10-11

Description

Oct. 11, 1932. T; T. GREENWOOD METHOD AND APPARATUS FOR PROVIDING THE CASINGS OF ELECTRICAL APPARATUS WITH INERT ATMOSIHERES' Filed Dec 1 1926 2 Sheets-Sheet l Oct. 11-, 1932. T. T. GREENWOOD 1,881,510

METHOD AND APPARATUS FOR PROVIDING THE CASINGS OF ELECTRICAL APPARATUS WITH INERT ATMOSPHERES Filed Dec. 1, 1926 2 Sheets-Sheet 2 lza V 70 A nil ' mnon AND urann'rus casings.

Patented Oct. 1 1, 1932.

PATENT OFFICE TALMA T. GREENWOOD, OF EAST TEMPLETON, MASSACHUSETTS, ASSIGNOR TO CONDIT- ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS FOR PROVIDING THE CASINGS OI ELECTRICAL APPARATUS WITH INERT ATMOSPHERES v Application filed December 1, 1926. Serial No. 152,047.

. 5 oil and the gases and vapors of the oil, and

for preventing fires and explosions in such Electric switches and transformers, for in stance, are contained in casings and immersed in oil or other equivalent liquid for the pur- J so pose of providing a high quality of insulation between conductors at different potentialsand also for the purpose of rapidly extinguishing the circuit-interrupting arc of an electric switch, and an are which may sometimesoccur under the oil in a transformer.

When the contact members of an oil-immersed electric switchare separated under load,-large amounts of oil gases and vapors may be generated by the circuit-interrupting are.

-This also is the case when an arc occurs under oil in a transformer casing. It is common practice to provide switches and transformers with gas expansion spaces above the oil into which the oil gases and vapors can expand, when formed, whereby to keep down the internal pressure of the casing. Ordinarily air is present in the gas expansion space, either entering the casing through leaks in the casing joints or through especially provided vent passages that are employed to permit the casing to breathe under variations of the volumes of the elastic fluid and liquid contents thereof under temperature and barometric variations.

\Vhen oi-l "gases and vapors and air are present within the enclosing casing in suitable proportions, the mixture is combustible and will explod'e'when ignited due to heat of the arc, a static discharge or other means,

and may seriously damage the casing and apparatus. The insulatin oil or other liquid,

7 also, commonly is slow y auto oxidizable in usefulness of'the liquid.

the presence of the oxygen of the air and thickens or-sludges, thereby impairing the To remedy or avoid the aforesaid fiiculties it has been proposed to maintain an inert, or more particularly, a substantially oxygenfree atmosphere within the casing and above the oil by the use of a material which reacts chemically with the oxygen of the air to remove it from the gaseous atmosphere with-.

in, the casing. The materials commonly sug-' gested have been phosphorus, the alkali metals and the like wherein the oxygen and the material united'to form an oxide of the material. In all cases the oxide has been apermanent oxide and the material, after having been oxidized, has been unfit for further service and must be replaced by fresh material. The materials heretofore proposedhave been fairly expensive, and charges thereof must be frequently removed so that the yearly cost of maintenanceof an inert atmosphere by the use of such-materials is relatively great. Furthermore, if the charge is not removed when or before it is spent, the

which can be re-activated-when its oxygen.

absorbing or combining ability is temporarily exhausted, whereby greatly to reduce the expense of maintaining the inert atmosphere.

A further object of the inventionis the provision of an enclosed oil-immersed electrical apparatus and a temporary container for the oxygen content of the air within the apparatus enclosure, in which container the oxygen is temporarily retained and is isolated from the atmosphere of the casing and from which container the oxygen can be removed to condition the container for continued service.

- Ayet further object isthe provision of means automatically-operative to remove the oxygencontentof an enclosing casing and to discharge the oxygen externally of said case mg.

A further object is generally to improve .the construction and operation of electrical apparatus andthe production of inert atmospheres therefor. v

Fig. 1 is a side elevation of an electric switch embodying the invention, the switch being shown in section.

' Fig. 2 is an enlarged sectional elevation of the de-oxygenating apparatus embodying the.

invention.

Fig. 3 is an end-view of the apparatus of Fig. 1.

Fig. 4 is a diagrammatic view illustratingthe circuit connections for effecting the automatic operation of the-apparatus.

Fig. 5 is a modified form of the de-oxygen ating apparatus.

The electrical apparatus here shown as associated with the invention, comprises an electric switch having the enclosing casing 10 adapted to contain a' body of oil in which the fixed switch members 12 and movable switch member 14 are immersed. The casing is provided with a cover 16 through which the insulated switch terminals 18 are extend-;

ed. The casing is adapted to contain a gas expansion space 20above the body of the oil. In accordance with this invention, the gas expansion space is adapted to contain an inert atmosphere which is not combustible with the gases and oil or the equivalent liquid or with the gases and vapors thereof or with air. To

this end, I provide means to remove the oxygen from the gaseous atmosphere within the casing and also to remove the oxygentrom.

air entering the casing whereby to maintain the expansion space filled mainly with nitrogenfor with an atmosphere having such a low content of oxygen that it is non-combustible. In carrying out my invention, I pro-- suitably high temperature, as to a dark red heat. When heated to a higher temperature,

.or subjectedto a reduced pressure, or both.

the barium dioxide gives up its oxygen and is Ire-converted to barium oxide. I have herein utilized this principle of barium oxide to maintain an inert atmosphere within the casing of an electrical apparatus.

- Fig. 5 shows a simple form of the invention wherein a charge 22 of barium oxide is disposed within a suitable container 24, the open top of which is closed by the removable cover 26. Said container is provided with an upper laterally-extended neck 28 adapted to be se-' cured removably to the side wall of the casing 10 of the electrical apparatus and having a passage 30 therein aligned with an opening 32 in the side wall of said casing. The container 24 is also provided with alower laterally-extended neck 34 having a passage 36 therein which is aligned with a lower opening 38 in said casing 10. Said container 24 is also provided with a passa e 40 which is adapted to communicate with t e atmosphere. The charge of oxygen-removing material is supported upon a perforated wall or screen 42 located above said passages 36 and a wall '44 disposed immediately beneath said screen 42 serves to isolate said two passages.

An electric heating coil 46 is disposed in said body of oxygen-removing material and is adapted to heat said'material to a suitable temperature. As thus arranged, the heat of said coil 46'serves to set up by thermal action a circulation of the atmosphere within said casing 10 through the lower passage 36 and upwardly through the porous mass of oxygen-removing material 22 and thence through the upper passage 28 back into the casing. In itsv passage through the material 22, the oxygen of the gaseous atmosphere within the casing 10 is abstracted so that the remaining atmosphere consists largely of nitrogen."

The casing 10 is adapted to breathe through the opening 40 upon changes of temperature so that some of the inert gas may escape to the atmosphere upon a rise of temperature of the contents of the casing. When the pressure drops within the casing,

" however, air is drawnin through the pas-- sage 40 and as it passes upwardly throu h the material 22, the oxygen thereof is a stracted so that the gas that passes into the casing 10 is practically free from'its oxygen content," or will be shortly subsergiently rendered so by rapid circulation t oxygen-removing material. The preferred form of the invention is illustrated in Figs. 2, 3 and 4 wherein means are provided not only to absorb the oxygen but subsequently to discharge the abstracted oxygen into the atmos-- 'phere. As shown in these figures, the

oxygen-removing material is enclosed within a cylindrical container 50, the open top of which is provided with a removable cover 52 rough the e and the open bottom of which is provided with a removable cover 54.

Said container is secured removably to the side wall of the'casin'g 10 and is provided with anupper passage 56 which is in register with the-upper opening 32 in the "side wall of said casing. Said container is also provided with a. lower passage 58 which is in register with thelower opening 38 of said casing.

Said container is also provided with a second passage 60 in the upper end thereof which is adapted to communicate with the atmosphere. 'Said

passages

60 and 56 are adapted to be opened and closed alternately by means of

valve members

62 and 64 respectively.

Said valve members are carried upon a rod 66 which is connected with a-plunger or armature 68 at one end. Said plunger is.

- 60. A spring 72 serves to urge said plunger and the valve' in the opposite direction whereby normally to maintain said valve 64 open and said passage 60 closed.

The porous mass 74 of oxygen-removing material, as barium oxide, is contained within a cylindrical basket 7 6 which is freely movable in-a vertical direction in said container 50 and is adapted to be a practically gas tight fit therein so that said basket serves as a seal to prevent direct communication between said lower passage 58 and said upper passage 56. Said basket is provided with a plurality of peripherally-disposed perforations or openings 78 in its side wall and near the bottom thereof through which the gas in said passage 58 may pass into the interior of said basket and thence upwardly through the material therein. Said basket is provided with a foraminous bottom wall 80 which is 2 adapted to support the material. The bottom cover 54 is provided with a passage 82 therein which is adapted to communicate with the atmosphere and said passage constitutes a breather passage or opening.

Y An electric heating coil having the two electrically-connected

heating sections

84 and 86 is disposed within said basket and is adapted 'to heat thematerial therein. The

terminals

88 and 90 of said sections are flexible and are brought out through a suitable terminal block 92. A third flexible terminal 94 is also brought out from the junction between said

sections

84 and 86 to said terminal block 92. Said basket 76 is supported upon a sensitive compression spring 96 which is adapted to permit thebasket to move within said container in response to changes in weight of the oxygen-removing material therein contained. Said basket is provided with a stem 45 98 which is extended freely through said bottom cover 54 and into a switch casing 100 carried by said bottom. Said stem is operatively connected with a quiok-acting switch 102 of any usual or suitable construction, which switch is so arranged that it closes when the basket has been moved downwardly a prede termined distance; and said switch is adapted to open when said basket is moved upwardly a predetermined distance. The normal disposition of the parts is illustrated in Fig. 2 wherein the oxygen-removing material is in free communieation with the interior of the switch casing and also with the atmosphere through the opening 82. Both. sections 84 5 and 86 of the heater coil are adapted to be energized so that the body of material 74 is maintained at a suitable temperature to be active and to absorb or combine with the oxygen of tlfe gaseous contents of the casing 10 and also to absorb or combine with the oxygen of the air that may enter the container 50 through the opening 82 on its way to the interior of the casing. As the material, as barium oxide, absorbs oxygen and thereby becomes gradually converted into barium dioxide it increases in weight so that the basket 76 gradually descends within the con tainer 50. d

When the amount of absorbed or combined oxygen is sufficiently great, the basket is moved into such a position that it is caused to operate the switch 102 and close the switch circuit.

'70. The section 84 of the heating coil thereby receives moreenerg-y and so operates to heat the barium oxide to a higher temperature, thus driving off the absorbed or COID- bined oxygen and discharging it to the atmos phere through the passage 60. As the barium dioxide loses oxygen it decreases in weight so that the basket 76 rises within the container 50. When suiiicient oxygen has been liberated, as when a large proportion of the barium dioxide has been re-converted into barium oxide, the basket 76 is adapted to move upwardly a suiiicient distance to effect the opening of the switch 102. The solenoid is thus cut out of the circuit and the spring 7 2 effects the closing of the passage 60 and the opening of the passage 56 so that the normal or operative condition of the de-oxygenating apparatus is restored. Both sections of the heater coil are thus placed in service and the barium oxide cools down to that temperature at which it is active in absorbing or combining withthe oxygen of the gas in contact therewith.

As thus arranged, a single charge of gas removing material serves in definitely to maintain an inert gas within the casing 10 of the electricalapparatus. The material serves as a temporary container for the oxygen and is automatically caused to abstract the oxygen from the interior of the casing 10 and to liberate it externally of the casing.

For certain purposes the barium oxide may be replaced by some other material, as char coal, for instance, which has the power to absorb ox en in lar er uantities than other The connections of the switch cir- 'cuit are illustrated in Fig. 4 and are such that fied without departing from the spirit of the invention.

I claim: 1. The method of providing an inert atmosphere for the casing of-an electrical apparatus which consists in placing barium oxide in communication with the interior of the casing and activating "the barium oxide to cause it to combine with the oxygen in the casing and subsequently isolating the barium oxide from circulatory communication with the atmosphere of the casing, subjecting the bar ium oxide to such conditions as to cause of the casing when the weight of the barium oxide has increased materially due to its increased oxygen content and subjecting the barium oxide to such conditions as to cause it to liberate the'combined oxygen free from intermixture with the inert atmosphere of the casing, and subsequently replacing. the

I oxygen-free barium oxide in communication with the atmos here of the casing.

3QThe combination with the casing of an 3 electrical apparatus, of a temporary contain-1 er for the oxygen content'of the atmosphere 1 of said casing comprising a body of barium oxide and automatically operative means governed by the oxygen content of said barium oxide to place said barium oxide body alternately in and out of fluid circulatory communication with'the casing-atmosphere, and means to subject said barium oxide body to varying conditions when in and out-of communication with the casing atmosphere.

, 4. The combination of the casing of an electrical apparatus, and means to provide said casing with an inert atmosphere comprising atemporary container for the oxygen content of the casing-atmosphere, and means governed bythe amount of abstracted oxygen in said container to condition said container to abstract the oxygen content of the casing-atmosphere and also to liberate the abstracted oxygen free from the inert vatmosphere of said casing. j

5. The combination" of the casing of an electrical apparatus, and means to provide" 0 v and-also to liberate the abstracted oxygen said casing withan'ine'rtatmosphere com prising a temporary container for the oxygen content of the casing-atmosphere, and automatically operative: means governed by the amount of abstracted oxygen in said-com tainer to condition said container to abstract the oxygen content of the casing-atmosphere freefrom the inertatmosphere of'said casing, said temporary container including a body of barium oxide.

6. The combination of the casing of an terior of the casing, and means to heat said body toone temperature when in communication-with the interior of the casing to cause said body to absorb oxygen from the casing atmosphere and to another temperature when out of communication with the interior of the casing to cause it to give up the absorbed oxygen.

7. The combination of the casing of an electricalapparatus, and means to provide said casing with an inert atmosphere, said means including an oxygen-abstracting .body, means automatically operative in response to the amount ofoxygen in said body to place said body into and also out of fluid circulatory communication with the interior of the casing, and means to heat said body .to one temperature when in communication with the interior of the casing and to' another temperature when out of communication with the interior of the casing.

8. The combination of the casing of an electrical apparatus, and means to provide said casing with an inert atmosphere, said means comprising a body of barium oxide, means to place said body into and also out of fluid circulatory communication with the-interior of the casing, and means to heat said body to one temperature when in communication with the interior of the casing and to another temperature when out of communication with the interior of the casing, both the aforesaid means further characterized by being operable in response to variations in weight of said body.

9. The combination ofthe casing of electrical apparatus and means to provide said casing with an inert atmosphere comprising means to remove the oxygen content of said casing and automatically-operative means governed by the amount of removed oxygen arranged to govern the operation of'said I oxygen removin means. a

10, The combination of the casing of an electrical apparatus,-a-nd a de-oxygenating apparatus associated therewith having automatically-operative means governed by the amount of oxygen abstracted alternately to place said apparatus infiuid circulatory communication with the interior of said casing and with the atmosphere-outside of said case ing. a 11. De-oxygenat1ng apparatus comprising a container for a mass of oxygen absorbing material, said container having a. pair of gas passages and automaticallyoperative means governed by the amountof absorbed oxygen to open and close said passages alternately.-

1'2. De-oxygenating apparatus comprising a container having a pair of gas passages, a

basket for the absorbing material movably disposed within said container and adapted to assume a position therein proportionate to the oxygen content of the oxygen absorbing material, and means controlled by said basket to open-and close said passages alternately.

13. De-oxygenating apparatus comprising a container, a basket for absorbing material movably disposed therein and adapted to assume a position proportionate to the oxygen content of the absorbin material, an electric heater element dispose to heat the contents of said basket, and means governed by the position of said basket within said container to vary the heating efiect of said heating element.

'14. De-oxygenatingapparatus comprising a container having a passage for oxygen-free as and a passage for oxygen-laden gas,.a basket for oxygen absorbing material movably disposed Within said container and adapted to assume a position therein governed by the oxygen content of the oxygen absorbing material, a heating element disposed to heat the contents of the basket, and means governed by the position of said basket with in said container arranged to open and close said passages alternately and also to vary the heating effect of said heating element.

In testimony whereof, I have signed my name to this specification.

TALMA T. GREENWOOD.