|Publication number||US2594851 A|
|Publication date||Apr 29, 1952|
|Filing date||Apr 12, 1948|
|Priority date||Apr 17, 1947|
|Publication number||US 2594851 A, US 2594851A, US-A-2594851, US2594851 A, US2594851A|
|Inventors||Bertele Hans Carl|
|Original Assignee||Bertele Hans Carl|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (7), Classifications (13)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Apnl 29; 1952 H. c. BERTELE METAL VAPOR ELECTRIC DISCHARGE APPARATUS Filed April 12, 1948 3 Sheets-Sheet 1 FIG. 2.
Hana Q. BRTELE April 29, 1952 H. c. BERTELE 2,594,851
METAL VAPOR ELECTRIC DISCHARGE APPARATUS Filed April 12, 1948 3 Sheet,s5heet 2 IO F/G.5.
24- 2s 6 sq F/ j) HANS: C. BERTELE April 29, 1952 H. c. BERTELE METAL VAPOR ELECTRIC DISCHARGE APPARATUS Filed April 12, 1948 3 Sheets-Sheet 5 I I J i HANs C. BERTELE Affor Patented Apr. 29, 1952 UNITED METAL VAPOR ELECTRIC niscmmeu APPARATUS Hans Carl Bertele, Purley, England Application April 12, 1948, Serial No. 20,424 In Great Britain April 17, 1947 Clain1s. (01. 313-29) This invention relates to metal vapour electric discharge apparatus, and more particularly to mercury vapour rectifier valves of the arc type including a cathode formed by a pool of liquid mercury.
In such apparatus it has been found necessary to provide considerably greater space Within the envelope than Was required to accommodate the electrodes and the arc path, and this factor has increased both the bulk and weight and consequently the cost of the apparatus. The need for such additional space within the valve envelope is due to intense evaporation of mercury caused by heating at the arc spot.
Various proposals have been made for distributing the are spot in vapour discharge apparatus by means of spot anchoring elements and proposals have also been made for enhancing the cooling of the cathode pool by bathing the pool container externally with a liquid coolant or by cooling the anchoring elements by means of heat dissipating arrangements. Applicant has now discovered that, with an are spot distributed around the periphery of a pool container the metal wall whereof has a thickness of the order of 0.5-2 mm. according to the thermal conductivity of the metal used, extended heat dissipating surfaces can be provided for such container in contact with a cooling medium and will effectively prevent undue rise of temperature in the cathode and enable satisfactory operation to be accomplished. In effect applicant achieves adequate reduction of mercury evaporation by arranging for extremely paths resulting in a low heat flow resistance be tween the cathode spot and the coolant, which resistance is lower than hitherto.
The present invention thus provides improved valve arrangements including effective cooling means for the mercury at the arc spot whereby the evaporation therefrom, and consequently the necessary size of envelope is reduced.
In a vapour electric discharge apparatus according to the invention including a cathode formed by a pool of vaporisable liquid metal for emitting an arc discharge, the are spot is extended around and anchored to the upper peripheral edge of the cathode pool by formingthe inner surface of the pool container at such peripheral edge of an arc resisting metal which is wetted by the cathode liquid to produce a concave meniscus while not being sputtered by ion bombardment therefrom under the operating conditions, and a short heat transfer path of g the order of 0.5-2 mm., resulting in a low heat short heat transfer flow resistance, is provided between the containing surface at such peripheral edge and a heat dissipating surface or member external to the pool container in contact with a cooling medium.
In the'practice of the invention as applied to mercury pool cathodes, a suitable arc resisting metal such as molybdenum or tungsten which is wetted by the mercury is used for the manufacture of the pool container or provided as a linin strip to its inner peripheral surface around the meniscus of the mercury pool, and it will be understood that the arc will become anchored to. such peripheral area by its natural tendency to seek the edge of the mercury meniscus and remain anchored to the wetted surface.
The container is externally shaped to form fins or extended heat dissipating surfaces, or it has directly joined to it a member or members of high thermal conductivity material such as copper not itself suitable as a pool container material providing such extended heat dissipating surfaces. In either case, only an extremely short heat transfer path of about 0.5-2 mm, corresponding approximately to the thickness of the container wall, separates the heat dissipating members from the are spot and with the wide distribution of the are spot the rise in temperature thereat is minimised and the evaporation of the mercury reduced or even eliminated. In one embodiment of the invention the mercury pool is contained in a steel cup having its inner surface lined with molybdenum where it is in contact with the edge of the mercury meniscus, and having bonded to its corresponding outer surface a ring of high conductivity material such as copper formed with radiating fins suitable for air cooling for instance by a fan placed underneath the apparatus.
The area of the are spot may further be enlarged by providing the appropriate portion of the mercury container with a spongy lining of say molybdenum or tungsten and/or a thin layer of oxide of either metal in place of or in addition to the peripheral lining described, such a sponge or oxide being adapted to retain or distribute the mercury at the wetting edge and spread the are over its surface.
Accordingly in a further embodiment the mercury container is provided with a wide substantially horizontal annular flange having its inner edge. corresponding with the periphery of the meniscus of the mercury pool in a central well, while its upper surface is coated with molybdenum sponge or oxide which retains mercury in its pores or interstices. The underside of the horizontal flange is provided with an annular finned cooling member of copper so that, as in the previous embodiment, the heat transfer path to the cooling member is no longer than the thickness of the mercury container wall.
The invention will be further described with reference to the accompanying drawings where several embodiments are illustrated diagrammatically by way of example and in which:
Fig. 1 shows a known arrangement of glassenvelope rectifier employing an arc-fixing device in the middle of the cathode pool, while Figs. 2 to 5 show the improved cathode arrangements according to the invention employing a metal cup sealed to the glass envelope or body of a rectifier.
Figs. 6 and 7 illustrate the application of the invention to valves having steel bodies respectively with and without metallic contact between said body and the cathode.
Fig. 8 shows a pool container provided with an annular flange for spreading the arc.
Fig. 9 showing a cathode pool container formed with an annular trough for the mercury and having a supplementary arc-fixing surface, and
Fig. 10 showing a combination of a central pool with an annular trough and a supplementary arcfixing surface.
Referring now to the drawings and first more particularly to Fig. 1, a mercury vapour rectifier valve of a known type, selected as an example of the class of apparatus with which the invention is concerned, is shown having a glass envelope l formed with a plurality of lateral arms 2 each carrying an anode such as 3. The lower portion of the envelope 1 is formed as a container 4 for a mercury cathode pool 5. In such known type of valves an arc-fixing device is sometimes employed inside the pool, and in the example shown a helical strip 6 of molybdenum or tungsten is immersed in the centre of the pool for this purpose and is supported on a metal rod 1 which passes through the bottom of the container 4 to act also as the cathode lead for connection to the electric circuit. The valve is mounted on a carrier 28 under the pool container 4 and a fan or blower 9 is provided for eifecting cooling of the lower part of the valve. The degree of effective cooling however is limited in view of the poor heat conductivity of the glass container 4 and the relatively lon heat path between the arc fixing device 6, where the arc-spot is anchored during operation, and the air-cooled outer surface of the container 4.
In the succeeding Figs. 2 to 10 which illustrate the present invention, the lower portions of the envelope 1 are shown, and the: cathode lead and fan or other optional circulating device are omitted for simplicity, and in Figs. 2 to 5 and 7 to 10 the upper part of the envelope and the anode or anodes are also omitted.
In Fig. 2 there is shown a simple application of the invention wherein a molybdenum or tungsten cup or pool container 4 is sealed to the lower open end of a glass envelope I and is provided with integral radial radiating fins 8 for air cooling with or without the aid of a fan. The are spot will settle at, and be extended around, the edge of the mercury meniscus, which is illustrated at 5a, and there is an extremely short heat transfer path from the location of the are merely through the thickness of the wall of the cup 4 to the heat disseminating outer surfaces of the cup and the fins 8.
In the modification shown in Fig. 3 the radial fins 8 are formed on a separate ring to of a good heat conductor such as copper which is bonded to the molybdenum or tungsten cup 1 with a maximum area of contact. The cup '4 in this example is preferably drawn or pressed from sintered molybdenum or tungsten sheet.
In the embodiment of Fig. 4 a molybdenum or tungsten pool container 4 is lined with a ring 12 of the same material in a spon y form and/or coated with oxide for distribution of the mercury at the pool edge and consequent better spreading of the are spot. No fins are shown in this example, and a finned ring Ii] similar to that shown in Fig. 3 may be provided and/or cooling by forced circulation of air or water may suitably be applied.
Fig. 5 shows a combination of the finned copper ring iii of Fig. 3 with the molybdenum or tungsten sponge or oxide liner of Fig. 4, the metal pool container 4 being sealed, as in Figs. 2 to 4, to a glass envelope I.
In the arrangement shown in Fig. 6 a steel envelope I is formed at its lower end as a cup or container 4for the mercury pool 5 and is pro vided at the wetting edge of the pool 5 with a molybdenum or tungsten liner 1? and with an external copper ring 50 finned at 8 as in the embodiment shown in Fig. 5. Since in this case the cathode system is not insulated from the metal envelope I, an internal insulating lining or ring i3 is provided above the liner 12 to prevent the cathode spot riding up the walls of said envelope.
In the construction shown in Fig. 7 a total steel clad valve body I is formed at its lower end as a cooling jacket [4 for a molybdenum or tungsten pool container 4 which in this case is mounted within, and insulated from, the body I by a pressure tight insulating ring l5 formed by glass moulded in situ. The jacket I4 is provided with an inlet i! and outlet l8 for the circulating fluid cooling medium which may be air or liquid accordin to the electric currents involved and is passed under pressure through the space between the container 3 and the jacket wall. To prevent accidental metallic contact between the cathode and the body i due to mercury deposits on the glass of the ring IS, a cylindrical shield I5 is formed on the latter and is provided with an inwardly projecting annular flange 19.
In a further embodiment shown applied to a glass envelope valve in Fig. 8, in place of the liner 12 the mercury container 4 is provided with a wide substantially horizontal annular flange 23 having its inner edge corresponding with the periphery of the meniscus of the mercury pool in a central well 2|, while its upper surface is coated with spongy molybdenum or oxide 22 which retains mercury in its pores or interstices and thus distributes the are over such annular member. The underside of the horizontal flange 2B is provided with an annular finned cooling member H) so that, as in the previous embodiments, the heat transfer path to the cooling surface is as short as the mere thickness of the wall of the mercury container.
In the construction shown in Fig. 9 the bottom of a molybdenum or tungsten pool container 25 is formed with a frusto-conical central upward projection 25 the flat top of which is coated with molybdenum or tungsten sponge or oxide 26 and is arranged to be approximately at the same height as the surface of the mercury pool 5. A. thin film of mercury is held in the interstices of the sponge or oxide 26 which acts as an auxiliary arc-fixing surface additional to the peripheral wetted edge 5a of the surface of the container 24 when the electric current exceeds a given intensity. A copper ring or cup 30 is bonded to the outside of the container 24 and the projection 25 and is provided with cooling fins B.
A similar arrangement is shown in Fig. 10, the additional arc-fixing sponge or oxide surface indicated at 36 being in this case of annular form and being located at the top of an annular boss 35 formed on the bottom of the molybdenum or tungsten pool container 34. As in the previous embodiment, a copper ring or cup 40 fits over, and is bonded to, the outer surfaces of the container 34 and its annular boss 35 and has integral cooling fins 8.
It will be understood that in the constructions shown in Figs. 9 and a lining of sponge or oxide may be provided at the outer periphery of the mercury meniscus 5a as shown at l2 in Figs. 4 to 6 and described in connection therewith.
While the constructions having cooling fins are primarily suited for air cooling with the aid of a fan placed preferably beneath the valve, it will be appreciated that, particularly where very heavy currents are involved, the fins may be surrounded by a jacket for either forced or thermosiphonic circulation of a liquid cooling medium.
By this invention, owing to the extension of the are spot and the shortening of the heat transfer path to the external cooling means, smaller, simpler and more economical electric discharge apparatus for a given power output are obtained wherein internal cooling means may be dispensed with as well as the bafiies normally employed to deflect from the anodes the jets of vapour produced by evaporation at the are spot.
Furthermore, the present invention is applicable to liquid cathode electric discharge apparatus for any of the purposes for which they are suitable and having a lass, metal or composite envelope containing any number of anodes with or without grids or other additional electrodes, it being understood that the term liquid cathode refers to the conditions obtained during operation of the apparatus and therefore includes substances other than mercury which are normally solid but are liquified at the operating temperatures of the discharge apparatus.
Finally, by reducing or eliminating the evaporation of the cathode liquid during operation, the arc path to the anode or anodes may also be reduced with corresponding improvement in the efficiency of the valve.
What I claim is:
1. In vapour electric discharge apparatus the combination with an envelope containing an anode, of a cathode formed by a pool of vaporisable liquid, a container for such pool constituting a lower part of said envelope and formed at the upper peripheral-edge of said pool with an arc-fixing surface of a metal of the group of arc-resisting metals constituted by molybdenum and tungsten, which liquid bathes the metal arc-resisting surface to form a concave meniscus edge thereat, and are heat dissipating means external to the pool container in direct high thermal conductivity metallic connection with the arc-fixing surface.
2. Vapour electric discharge apparatus according to claim 1 including a pool container of ferrous metal having the arc-fixing surface provided by an internal coating of the arc-resisting metal.
3. Vapour electric discharge apparatus accord"- ing to claim 1 having the surface at which the arc is fixed provided by an internal coating of sponge of the arc-resisting metal on the cathode pool container.
4. Vapour electric discharge apparatus according to claim 1 having the surface at which the arc is fixed provided by an internal coating of oxide of the arc-resisting metal on the cathode pool container.
5. Vapour electric discharge apparatus according to claim 1 having the heat dissipating means provided as external cooling fins on the pool container.
6. Vapour electric discharge apparatus according to claim 1 having the heat dissipating means.
provided as external cooling fins formed on a ring of good heat conducting material bonded to the external surface of the pool container.
7. In vapour electric discharge apparatus according to claim 1, including a metal envelope, a downward extension of the lower portion of such envelope formed as a spaced jacket around the pool container for the circulation of cooling medium, and a gas-tight ring of insulating material between the container and such jacket.
8. In vapour electric discharge apparatus according to claim 1, a central well in. the pool container within an annular flange having its inner edge corresponding with the upper peripheral edge of the liquid of the pool, and a lining of sponge of the arc-resisting metal on the upper surface of said flange operative to retain a film of the liquid and distribute the arc-spot thereon.
9. In vapour electric discharge apparatus according to claim 1, a central well in the pool container within an annular flange having its inner edge corresponding with the upper peripheral edge of the liquid of the pool, and a lining of oxide of the arc-resisting metal on the upper surface of said flange operative to retain a film of the liquid and distribute the arc-spot thereon.
10. In vapour electric discharge apparatus according to claim 1, an additional cooled arc-fixing surface of the arc-resisting metal located within the pool at the level of the upper surface of the latter.
11. In vapour electric discharge apparatus according to claim 10, a central upward projection from the bottom of the pool container the top surface of which constitutes the additional arcfixing surface and is coated with sponge of the arc-resisting metal to retain a thin film of the cathode liquid.
12. In vapour electric discharge apparatus the combination with an envelope containing an anode, of a molybdenum container for a cathode pool, a portion of which container also acts as an arc-fixing structure, and metallic means having heat dissipating surfaces on the outside of said portion of the container in contact with a gaseous cooling medium.
13. In vapour electric discharge apparatus the combination with an envelope containing an anode, of a tungsten container for a cathode pool, a portion of which container also acts as an arcfixing structure, and metallic means having heat dissipating surfaces on the outside of said portion of the container in contact with a gaseous cooling medium.
14. In vapour electric discharge apparatus the combination with an envelope containing an anode, of a cathode formed by a pool of vaporisable liquid in a lower part of said envelope, a container for such pool formed at the upper periphand pool edge with an arc-fixing surface of a metal of the group of arc-resisting metals constituted by molybdenum and tungsten bathed by the liquid, and are heat dissipating means external to the pool container in direct high thermal conductivity metallic connection with the arc-fixing surface through a heat transfer path less than two millimetres in length.
15. A vapour-electric device comprising, a metal container, an anode in spaced insulated relation in said container, a pool of vaporisable reconstructing cathode material in said container and a layer of sponge refractory metal in said container.
HANS CARL BERTELE.
REFERENCES CITED The following references are of record in the file of this patent:
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|U.S. Classification||313/18, 313/328, 313/29, 313/44, 313/45, 313/173|
|International Classification||H01J13/06, H01J13/32|
|Cooperative Classification||H01J13/32, H01J2893/0075, H01J13/06|
|European Classification||H01J13/06, H01J13/32|