US1046083A

US1046083A - Vapor electric apparatus.

Info

Publication number: US1046083A
Application number: US56969310A
Authority: US
Inventors: Charles A Kraus; Roy D Mailey
Original assignee: Individual
Current assignee: Individual
Priority date: 1910-06-30
Filing date: 1910-06-30
Publication date: 1912-12-03
Anticipated expiration: 1929-12-03

Description

G. A. KRAUS & R. D. MAILBY. VAPOR ELECTRIC APPARATUS. I

APBLIUATION FILED JUNE so, 1910.

Patented Dec. 3, 1912.

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uNrrED .sri-atrasA @TENT OFFICE CHARLES A. KRAUS, OF 'NEWTON HIGHLANDS, AND ROY D. MAILEY, 0F LYNN,

MASSACHUSETTS.

VAPOR ELECTRIC APPARATUS.

Specification of Letters Patent.

Patented Dec. 3, 1912.

Application led June 30, l1910. `Serial No. 569,693;

' and ROY D. MAILEY, both citizens of the United States, and reside-nts, respectively,

of Newton Highlands and Lynn, in the counties of Middlesex and Essex and State of Massachusetts, have invented new and useful Improvements in Vapor Electric Apparatus, of which the following is a specification.

Our invent-ion relates to the construction of vapor electric apparatus and has for its object the provision of an electrode structure which will be durable, as little as possible susceptible to breakage and which in its electrical operation shall po-ssess large capacity, eiiiciency and ability to preserve continuity of operative conditions.

As a typical example of vapor electric apparatus we take for purposes of description a vapor rectifier of which the characteristic members are a hermetically sealed container to include highly rarefied' mercury vapor, at least two anodes and one cathode and leads from these electrodes which pass through the walls of the container.

Vapor rectiiers such as heretofore generally used have employed glass as the material of which the container is composed. Owing to the diiiiculty of sealing leads of generous dimensions through the walls of a glass container, and owing also to the diiiculty of withdrawing heat from differ-V ent parts in the interior of the container, it has not, so far as we are informed, been found feasible to construct( durable rectifie-rs capable of converting currentsl substantially in excess of'50 amperes. Glass rectiiers even of this capacity are disadvantageously large considering the nature of the material of which they are composed and thus present difficulties in manufacture, while breakage in handling, and transportation of such glass rectifiers has proved a serious source of loss. Moreover, a glass container and rectier whatever its size, is by its i nature and under the conditions of operation a delicate apparatus since its interior `is exhausted to very low pressure and contains a body of liquid mercury which under the vacuum conditions is liable to break the container unless it is handled very carefully.

It has been suggested to employ metal as the material for containers of such apparatus, but so far as our experience and observation go, the design and structural featuresof such apparatus have not been so far perfected as to afford a vapor electric apparatus which meets the conditions 'of commercial requirements. A difficulty has been in the lack of known means for introducing the electrode leads through the walls of the container in such amanner as to provide forelectrical insulation, impervious as to gases and resistance to'thermal change and mechanical shock. 7e have invented a new -mode of unit-ing electrode leads to a metal container which will be herein shown and described but which forms the subject matter of an application for patent of the United States Serial No. 514,908, tiled by us on or about the 27 th day of August, 1909.

In a rectifier capable of converting 1000 amperes', presumably 15,000 oules of` energy are expended per second within the container, of which about one-third is developed at the anode surfaces. To be eective, an apparatus to accomplish such a conversion must be provided not alone with means for withdrawing heat through the walls of the container itself, but also with means for disposing of the heat generated at the electrodes. For a given resistance the amount of heat evolved in the electrode leads themselves is proportionate to the square of the current. At 1000 amperes the heat developed would be thus 400 times asfgreat as in a rectifier carrying only 50 amperes. Therefore, in a rectifylng apparatus which is to carry large currents it is necessary to makethe electrodes and their leads of very substantial dimensions and this necessity further increases the ditliculty of providing' insulating joints between the leads and the container which are capable of withstanding the mechanical and thermal strain placed uponl them. These difficulties, however, while very largely met and compensated for by the improved joint referred to in our said application Serial No. 514,908, may still further be obviated by the employmentof means for regulating and dispersing the heat incident to the operation of such an apparatus.

The accompanying drawing illustrates an example of vapor electric apparatus embodying the within described inventions. This drawing represents in vertical section, a mercury arc rectifier of which A is a metal container preferably cylindrical in form and lconstructed of cold rolled steel. The sides, top and bottom of this container should be as thin as is consistent with the requisite. strength so that the weight of the rectifier' may be reduced to a mimimum and its heat radiating capacity be as large as possible.

B and C are the anodes; B', C ,their respective leads; D is a mercury cathode insulated from the container by an enamel lining E; and D is the cathode lead which, like the anode leads, is introduced through the top T of the container.

The leads are attached to and insulated from the container by the joints consisting essentially of two steel tubular members G and H to which an annular member of vitreous or fritted insulating material F fused by means of a suitably low-mclting vitreous flux.' The tubular members G are Welded to the top T of the container and therefore constitute extensions of the container wall. The outer ends of the tubular members H are welded respectively to the electrode leads B, C', D. The tubular hoods Acomposed ofthe metal members G and I-I and the insulating annulus F thus surround the leads which, in4 passing through the extensions, are spaced from the innelkwalls thereof so that the joint itself is not heated by direct contact with the lead of which the temperature may be considerably elevated.. Since a vacuum intervenes between the lead and the internal Walls of the hood which comprises the joint, it is only by radiation that heat may be transferred across. The junction between the lead and the outerI tubular member H is made at some distance above the fused joints, so that the heat conducted through the metal hood member H is reduced as far as necessary; electrode connections and joints such as above described constitute the subject matter of our said application No. 514,908.

The rectifier herein illust-rated is shown as, provided with one main anode E and a smaller auxiliary anode C. A complete single phase rectifying system would consist of tWo rectifying units of the type herein illustrated which may be connected according t-o the system described in application for United States patent Serial No. 514,907, filed on or about AugustQ?, 1909. In such system the anode C is merely an auxiliary anode of -which the purpose is to maintain the arc during the half cycle when thefarc is inoperative at the main anode. While our improvements herein described are not restricted to use with rectifiers of this special type,` they are so shown since We find this type particularly useful in the rectification of `large currents. Another' advantage inheres in the fact that the current flowing in the rectifier is small at the time the potential between the cathode and the anode is at a maximum. In a 500 anipere rectifier working at l1000 volts (virtual) the auxiliary current may be made as low as three amperes. If the customary type of rectifier is employed wherein both anodes do equal duty, the current atthe active anode would be 700 amperes at the time the potent-ial'at t-he other anode is at its maximum value, say 1400 volts. The presence of a high current on vone electrode i u a rectifier while the potential at the other electrode is high, We have found to be conducive to the breaking down of the surface resistance to the passage of the current through the inactive electrode; in other words, under these conditions the electrode is liable to lose its effectiveness as an electrical check valve so that an arc is formed between the anodes of the rectifier, interrupt-ing the normal operation of the apparatus and exposing it to danger of injury. Therefore, We recommend that only a single main anode be included in a container. Under these conditions it is possible to place the anode directly above the mercury and in close proximity thereto, an arrangement which insures greater flexibility and certainty of operative conditions and also reduces to a minimum t-h`e potential drop between the anode and the cathode since this potential is a function of the distance between t-he anode and the cathode.

As we have already pointed out, in current rectifiers of large capacity a large amount of heat is necessarily generated at t-he surface of an anode. The temperature of an anode should not be allowed to reachv too high a value because this is liable to produce an evolution of gases' which are 105 undesirable in a rectifier and is also liable to impair the check valve efficiency of the electrode. The temperature of the anode depends upon the quantity of energy dissipated at .its electrically operative surface and on t-he area of its radiating surface.

If the anode is placed fairly near the mercury surface of the cathode the greater portion of the current passes through the portion of the anode lying nearest the cathode and as a result such portions of the anode are raised to a much higher temperature than others. In general, it will be found necessary to make the radiat-ing surface of the anode much larger than the active electrode surface. It is highly advantageous also to provide for ready conduction of heat away from the active electrode surface toV other portions of the apparatus which may act as radiating surfaces. As metals of .high radiating capacity, such as copperl or silver, would be attacked and eventually dissolved by mercury, it is not practical to employ them in situations where they come in Contact with metallic mercury or mercury vapor. We have, therefore, constructed an anode with a core of copper enveloped in upper portion at the sides and top of this electrode marked WV, acts merely as a radiating surface and heat is conducted to thls surface by the copper core J. If desired,

the surface W may be treated so as to improve its radiating capacity; it may be oxidized superficially or given ablack coating for this purpose. (The above described electrode structure, involving a highly conductive core, protected by a shell of material unaffected by mercury, forms the subject mat-ter of an application for patent, Serial No. 569,695, filed by us on or about June 30, 1910.)

The characteristic check valve action. of a rectifier-,anode depends upon its physlcal condition as a non-volatile solid material. lf, therefore, liquid mercury strikes the anode the valve action is liable to be interrupted by the presence of a volatile material y upon it and this volatile material, if present on the anode, usually causes the formation of a cathode are. When a rectifier is in operation the mercury of which the cathode is composed is in more or less violent agitation and particles of it are constantly being spattered and thrown off and therefore when, as we prefer for reasons stated above, the main anode is placed near to the cathode surface, it is advisable and, in many cases, necessary to screen the anode against the approach and contact of liquid mercury. For this purpose we surround the sides of the anode and the anode lead by av shield or jacket M of insulating material such as glass, porcelain or fused quartz and secure thereto at the lower end a screen N which may be composed of iron-wire gauze, or a perforated plate or plates; the essential characteristic of such screen being that it shall be pervious to gases and afford a path for the current through the gas, while serving as a protection herein against the passageof liquid mercury particles.

Not only does the screen N protect the anode B from being spattered with liquid mercury, but also with an arrangement such as just described, the vapor in vigorous circulation from the cathode does not pass immediately by and over the anode surface. ve find this to be advantageous since when large currents are being rectified, the mercury vapor circulates withsuch speed and violence as to carry particles' of liquid mercury along with it and cause them to impinge upon the anode surface. If, as is sometimes the case, it is desirable t allow a gentler stream of mercury vapor to pass overthe anode surface in order to remove foreigny gases therefrom, this controlled and beneicial circulation may be secured by providing small openings as m in the upper part of the hood M which surrounds but does not hug closely to the sides of the anode B. Vith this arrangement, even though the mercury vapor currents in the main body of the container are violent, the screen N and Ventilating openings m regulate and modify the gaseous currents so that the benefit of washing vthe anode with mercury vapor may be secured without incurring danger from spattering of liquid mercury.

In order to provide an electrode of which the electrically active surface shall be of small extent in contrast with the heat radiating surface, we make the electrode preferably in the form shown in the drawings, namely, an inverted cup or bowl on which the electrically active portion will be located for the most part, if not entirely, upon the rim K, the remainder of the surface of this electrode affording a comparatively large heat radiating area. While some heat radiation will proceed from the interior of the cup or bowl, the chief advantage in making the electrode thus bowl-shaped lies in the reduction of its total weight, excess weight being disadvantageous for the reason that the welded and fused joints by which the electrode lead is secured to the container are necessarily of small area and relatively distant from the active electrodeitself; hence an excessively heavy electrode at the end of the long electrode lead will endanger the integrity and permanency of the sealing joints. The function of the electrode core J is thermal only, as it is assumed that the steel or iron of which the lead B is composed possesses ample current-carrying capacity. Thus, the core J need not extend l into the lead B', as its function is to conduct heat away from the active anode surfaces which are presented to the cathode and are relatively small, to electrically inactive parts of the structure, whence heat will be radiated. So long as the outer metal shell of the electrode and its lead suiiice to carry current, the core might be. electrically nonconductive, if there were such a thing as a rood thermal conductor which is also elec- 2tjrically non-conductive.

s That we claim and desire to secure by Letters Patent is:

1. In a vapor electric apparatus, a container including a mercury cathode, an electrode suspended within the container and a shield of insulating'material surrounding trode suspended 4Within the container, a

shield of insulating material surrounding said electrode provided with a'screen pervious to mercury vapor -between said electrode and the mercury cathode.

3. ln a vapor electrlc apparatus, a container including a mercury cathode, an elec- -trode suspended within the container, a

shield of insulating material surrounding sald electrode provided W1th a screen ervious to mercury vapor between sald e ectrode and the mercury cathode, and with Ventilating apertures to permit circulation of Vapor within the shield over the electrode surface.

4. In a vapor electric apparatus, a container containing a mercury cathode, am electrode suspended within the container and a shield comprising insulatingvmaterial surrounding the electrode, and a screen between said electrode and mercury cathode.

Signed by us at Boston, Massachusetts, this twentieth day of June, 1910.

CHARLESA. KRAUS. ROY D. MAILEY.