US2068568A - Metal tank vapor electric device - Google Patents

Description

Jan. 19, 1937. E. H. REID ET AL METAL TANK VAPOR ELECTRIC DEiICE Filed oci. 17, 1934 2 Sheets-Sheet 1 Inventohs: Eugene H. Reid, Fnedewick I-iAndePson Their Abt ovnne 2 Sheets-Sheet 2 r a m r w\% ww I \\\\\\\\\\\\\\\\\\\\\\\\\&W

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Jan. 19, 1937. E. H. REID ET AL METAL TANK VAPOR ELECTRIC DEVICE Filed Oct. 17, 1934 Patented Jan. 19, 1937 UNITED STATES PATENT OFFICE METAL TANK VAPOR ELECTRIC DEVICE Application October 17, 1934, Serial No. 748,617

5 Claims.

Our invention relates to vapor electric devices having a cathode of vaporizable material, particularly to mercury arc rectifiers or inverters of the metal tank type, and its general object is the provision of an improved vapor electric device of this type wherein highly efficient operation is attained and manufacture and repair of the device are facilitated.

The vapor electric device in accordance with the present invention is preferably of the type in which the evacuated tank is provided with a detachable cover.

Various arrangements of cooling domes, internal cooling chambers, coils, etc. have been proposed in connection with mercury are devices, for condensing the vapor rising directly from the cathode. These arrangements have tended in general to present difiiculties in the assembly of the apparatus. To avoid these difficulties we provide a vapor condensing element constituted by a unitary, cylindrical, doublewalled member which is welded as a unit to the detachable cover and extends downwardly therefrom into the tank space and to a point adjacent the cathode. This unitary member not only ensures a large condensing surface but it further shields the anodes from mercury spray and at the same time operates as a baflle element to constrict the are passing between anodes and cathode.

In previous anode seal mounting arrangements for mercury are devices the seal support has been welded directly to the tank Wall or cover. These arrangements have had the disadvantage that the seal was not removable from the wall or cover without damage thereto. We have overcome this difficulty by providing, in accordance with the present invention, a seal structure such that the seal is easily removable and thereafter easily welded again in operating position, without afiecting the tank wall or cover.

A further feature of the present invention is a simple and effective shield and bafile means for the anodes of mercury are devices, comprising a metal shield in which is mounted a graphite member of special form constituting a baflie unit which presents a very large deionizing surface to the arc and which is easily adjustable within the shield to determine the spacing between anode and bafile.

Our invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope will be set forth in the appended claims.

Referring to the drawings, Fig. 1 is a side elevational view partly in section of a vapor electric device in which our invention has been embodied, Fig. 2 is a detail View on an enlarged scale of an easily removable and replaceable seal structure in accordance with our invention, and Fig. 3 is a fragmentary view partially in section showing an insulating mounting means for an anode shield.

Fig. 1 illustrates a vapor electric apparatus In which may comprise a mercury arc rectifier, inverter, or similar device having a mercury cathode H, a plurality of main anodes I2, only one of which is shown, and a starting anode l3 mounted within a metal tank M which is preferably closed at the top by a detachable metal cover l5.

In order to condense the vapor rising from the cathode II, a cooling dome I6 is provided, which has a portion ll extending above the tank cover I 5 and a portion I8 extending into the space within the tank to such a point that mercury spray from the cathode II is prevented from being projected into contact with the anodes, the gap between the lower end of dome portion I8 and the bottom of the tank being sufiiciently narrow to cause the portion l8 to function also to a considerable extent as a baiile member constricting the are passing between anodes and cathode.

The dome I6 is a unitary construction constituted by two concentric cylinders 20 and 2| both closed at the top, the inner cylinder 20 being open at the bottom for the passage of vapor from cathode I I. The cylinders 20 .and 2| are spaced apart to provide a chamber for the circulation of a cooling medium, the entire inner surface of inner cylinder 20 and all of the outside surface of cylinder 2|, which is below the cover [5, thus together providing a large cooling surface for the removal of heat losses.

This unitary structure formed by the cylinders 20 and 2| and their top plates is easily assembled into the apparatus It] by slipping the cover l5 over the unit and welding together the outside cylinder 2! and the inner edges of the cover, the cover with the condensing dome unit welded thereto being thereafter fastened to the tank ID as by bolts 22.

As better shown in Fig. 2 an anode seal for an anode such as l2, comprises an insulating sealing member 23 which preferably is formed of a mixture of mica and lead borate molded to a tube surrounding the anode stem 24 and to a metal tube 25 which may in turn be welded to the seal supporting metal sleeve 26. In previous anode seal constructions of this type the sealsupporting sleeve 26 was welded directly to the tank top plate, or cover member I5. Removal of the seal structure involved damaging of the tank member I5 and also difficulty in replacing the seal in position on the tank.

In order to provide for easy removal and replacement of the seal structure, in accordance with our invention the seal-supporting member or sleeve 26 is not welded directly to the surface or edge of tank member I5 but to an extension 21 of member I5. This extension preferably projects on the opposite side of member I5 from that on which the seal is located. The extension 21 is preferably thinned at its outer portion 28. Seal-supporting member 26 is likewise provided with an extension 29, which may have a thinned end portion 30, the extension portions 28 and 30 being welded together all around at their outer ends to form a vacuum tight joint.

Obviously the extension 21 of tank member or cover I5 may be formed integrally with member I5, but it is preferable to form extension 21 as a ring or sleeve separately from member I5 and to connect this sleeve permanently, and vacuum tight, to tank member, or cover, I5 as by welding to form the joint 3|.

To remove the seal structure from the tank cover I5, assuming the anode I2 and its shield, as hereinafter to be described, have been detached, it is only necessary to remove a small portion of the welded ends of the extensions 2! and 29. Thereafter the seal structure may be replaced in position and the ends of the extensions 21 and 29 rewelded. This process may be repeated several times without change in or damage to the tank member or cover I5.

The provision of an easily removable and replaceable anode seal structure, as above described, is accomplished not only without material increase in complication and cost but with increased accessibility to the welded joint, which is cut to remove the structure, and with an appreciable decrease in overall height of the anode structure over that required in previous arrangements wherein the seal supporting sleeve 26 was welded directly to the tank top member or cover I5.

As shown in Fig. 1, essentially the same mounting arrangement as hereinbefore described in connection with the seal structure for the main anodes I2 is preferably provided, in accordance with our invention, for the mounting of the operating structure 32 of the starting anode I3. Instead of welding a seal supporting sleeve 33, corresponding to the main anode seal supporting sleeve 26 of Fig. 2, directly to the condensing dome top plate 34, the supporting sleeve 33 is welded to an extension of the plate 34 to form the vacuum tight joint 36. Extension 35 may be formed integrally with plate 34 but is preferably a ring or sleeve welded to plate 34 and surrounding sleeve 33.

In connection with the mounting means for the starting anode structure (I3, 32) the operations of cutting off a portion of sleeves 33 and 35 at the welded joint 36 to remove the starting anode and of thereafter replacing this structure and rewelding, are substantially the same as the operations, hereinabove described, involved in the removal and replacement of the main anode seal structure described in connection with Fig. 2.

Referring to the anode shield and baflle arrangement shown in Fig. l, and partially, on an enlarged scale, in Fig. 2, an anode shield 31 of extension sleeve 21 of tank cover l5 and to shield 31, the shield being held from turning by a key 4 I. The shield is thus easily removable for access to the welded joint 30 as required in the removal and replacement, hereinbefore described, of the main anode seal structure.

In order to provide a suitably large deionizing surface to the are passing between anodes I2 and cathode II a cylindrical graphite baffle unit 42 is mounted in the shield, as shown in Fig. 1.

In assembling the shield and baffle, the baffle 1..

unit 42 is slid into the shield to a point where the proper spacing is provided between the anode I2 and the baiile, the ba-file being then looked in this desired position by any suitable means.

The baffle 42 while highly effective is at the same time of simple construction, being preferably a relatively thick disk of graphite drilled full of holes. In the present embodiment of the invention the graphite plate is four inches in thickness and the holes are two and one-eighth inches in diameter, the walls between adjacent holes being of thin cross section, which in the form illustrated in the drawings is of the order of three-sixteenths inch. The illustrated construction permits making the walls even thinner, as low as one-sixteenth inch, the baffle still remaining a strong mechanical structure. Such a very thin-walled graphite structure is of advantage when used as a baflle element in a mercury arc device since the collection of foreign gases by the graphite structure is thereby lessened.

It will be understood that while the bafile unit 42 has been described as of a definite thickness and as having openings of a definite diameter,

these dimensions may be changed to meet varying conditions. In any mercury arc device the baffling effects in the device and consequently the operating characteristics of the device depend on the size of the openings for the passage of the arc and on the deionizing area. illustrated and described herein lends itself quite easily to different operating conditions. Thus for a high voltage mercury arc device smaller holes in the baffle may be employed to increase the baffling effect, and if necessary the depth of the holes may also be increased. For a low voltage mercury arc device the hole diameter may be increased and the depth of the holes decreased.

The shield and baffle means constituted by shield 31 and graphite unit 42 have been described herein as at the potential of tank I4, the members 25 and 21 to which shield 31 is shown as electrically connected, being at tank potential. The shield 31, in which is mounted the bafile unit 42, may, however, be insulated from tank I4,

preferably by the means shown in Fig. 3 wherein the shield 31 is provided with a number of lateral extension members, such as lugs or ears 43 spaced about and welded to the outside wall of the shield.

Between the upper edge of the shield and the under surface of tank wall member or cover I5 is placed an insulating member 44, which is, preferably, constituted by a U-shaped or channelshaped metal member or ring 45 coated on its The baffle design .i.

upper and lower surfaces with enamel layers 46, 7

this insulating member being held firmly in place between the member [5 and the shield 31 when the latter is in operating position.

In order to draw the shield 31 upwardly into operating position and at the same time to insulate the lugs or cars 43 from the member H3, insulating and supporting members 48 are interposed between the ears and member l5, the ears being connected to the members 48 by means such as cap screws 41, the members 48 being connected to tank wall or cover I5. The insulating and supporting members 48 may be connected directly to wall l5, but it is preferable to connect these members, as by means such as studs 49, to extensions of the wall l5 projecting downwardly therefrom, the extensions being constituted preferably by nuts 55 welded to the wall l5 and the studs 49 being screwed into these nuts.

It will be noted in connection with the shield supporting arrangement illustrated in Fig. 3 that this arrangement may be modified very easily, if desired, in such a manner that the shield, instead of being insulated from the tank, is at tank potential as in the arrangement shown in Fig. 2. This change in the arrangement illustrated in Fig. 3 may be effected merely by omitting insulating ring 44 and insulating and supporting members 48, and by providing, in place of the short screws 41, bolts or cap screws which are long enough to extend upwardly into nuts 58. The shield will then be in electrical contact with wall or cover !5 which is at tank potential.

It will be understood that control elements such as grids may be associated with the main anodes l2, and that means may also be provided to impress predetermined potentials on the control elements.

Our invention has been described herein in a particular embodiment for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims we intend to cover any such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent in the United States is:

1. In a vapor electric device of the metal tank type having an anode and a metal shield surrounding the anode, means to mount said shield insulatingly on a wall of said tank including a metal member connected to said shield and extending laterally thereof, an insulating member mounted between an edge of said shield and said wall, a second insulating member, means to connect said second insulating member to said laterally extending member, and means to connect said second insulating member to said wall.

2. In a vapor electric device of the metal tank type having an anode and a metal shield surrounding the anode, means to mount said shield insulatingly on a wall of said tank including an insulating ring interposed between a circular edge of said shield and said wall and means to maintain said ring in contact with said edge and said wall, said second-named means comprising a plurality of metal lugs connected to and spaced circumferentially of said shield, a plurality of insulating members interposed between said lugs and said wall, means to connect said lugs to said insu lating members, and means to connect said insulating members to said wall.

3. In a vapor electric device of the metal tank type having an anode and a metal shield surrounding the anode, means to mount said shield insulatingly on a wall of said tank including an insulation-coated metal member interposed between an edge of said shield and said wall, a plurality of metal members connected to said shield and spaced circumferentially thereof, a corresponding plurality of metal members connected to said wall, and a plurality of insulators connected between said first-named metal members and said second-named metal members.

4. A seal structure for a vapor electric device of the metal tank type having a metal tank wall, including a metal support for the seal having an extension welded vacuum-tight at its outer edge to the corresponding outer edge of an extension member in connection with said wall, said extensions being of such length that after the cutting off thereof at said edges to remove the weld and thereby to permit removal of the seal from said wall the portions of said extensions remaining are of sufficient length for the rewelding together of said extensions at their outer edges without causing undue flow of welding heat away from said weld.

5. A seal structure for a vapor electric device of the metal tank type, including a metal sleeve fastened vacuum-tight to a wall of the tank and having an extension, and a seal supporting sleeve having an extension normally welded vacuumtight at its outer edge to the outer edge of said first-named extension, said extensions being of such length that after the cutting ofi thereof at said edges to remove the weld the portions of said extensions remaining are of substantial length sufficient for rewelding together and subsequently cutting apart said extensions at their outer edges several times without causing undue flow of welding heat to those portions of said sleeves from which said extensions project, thereby to permit several successive replacements of said seal on said wall and removals of said seal therefrom.

EUGENE H. REID. FREDERICK H. ANDERSON.

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