US2173023A - Mercury-cathode rectifier - Google Patents

Description

P 3 J. G. w. MULDER 2,173,023

MERCURYCATHODE RECTIFIER I Filed March 17, 1937 JG wmuzazez" Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE MEROURY- CATHODE RECTIFIER Application March 17, 1937, Serial No. 131,491 In Germany March 20, 1936 7 Claims.

My invention relates to single-phase mercurycathode rectifiers particularly those of the type described in my copending U. S. patent application Ser. No. 67,155, filed March 4, 1936, now

5 Patent #2,170,482.

Such rectifiers comprise an envelope having a cup-shaped metal portion and a glass portion hermetically fused together, a mercury cathode in the bottom of the metal portion, which portion 10 may be artificially cooled, and a main anode arranged parallel with the axis of the envelope and above the surface of the mercury cathode. To obtain a compact construction the main anode is disposed at a comparatively short distance from 15 the mercury cathode, and as there is a direct discharge path between the anode and the cathode, there is considerable danger of arcing back at high A. C. voltages. More particularly, in such tubes the liquid mercury is vigorously 2() splashed from the mercury surface by the motion of the cathode spot thereon and by the highlycompressed mercury vapor formed in the vicinity thereof, and may readily strike the anode and .cause arcing back particularly at high anode 5 voltages,

In accordance with the present invention I overcome the above difiiculties by providing in the discharge space between the main anode and the surface of the mercury cathode, partitioning 30 means which intercept straight lines between any point on the active cathode area and any point on the main anode while allowing for the passage of the discharge.

Such partitioning means prevent the liquid mercury particles, or the high-pressure mercury vapor issuing from the cathode, from directly reaching the anode by insuring that these particles deposit on other colder portions of the tube and that locally-limited rises of the 40 mercury vapor pressure are smoothed out before reaching the anode surface.

By the term the active cathode area as used herein and in the claims is meant that part of the mercury cathode surface which can be cov- =45 ered by the cathode spot of the discharge. Thus parts of the surface outside the area defined by limiting bodies placed in the cathode mercury would not form part of the active cathode area.

In one embodiment of my invention I provide ,5 in the discharge space of the rectifier, a labyrinth-like structure comprising a plurality of partitioning or barrier members alternately projecting from opposite directions into the dis- :charge path, whereby the discharge space-as 55 viewed in the direction cathode-anodeappears to be covered in an overlapping manner over its entire cross section and a curved path is left free for the discharge between the anode and the cathode. By increasing the number of partitioning members-depending upon the value of the anode vo1tagethe labyrinth effect of the structure can be increased accordingly. The number of partitioning members used is limited only by the resulting increase in the voltage drop of the discharge, and by the ignition difiiculties. 10

As such a multi-labyrinth structure may introduce ignition difliculties, I overcome this difilculty by making one or more of the members of conductive material, electrically insulate same from the other parts of the tube, and apply thereto a desired potentiaL. Thus the individual partition.- ing members can be given suitable potentials in a manner known per se, whereby the ignition of the discharge occurs in steps from the cathode to succeeding partitioning members.

To improve the functioning of the partitioning members, I increase the condensation effect thereof by securing at least one of the members in good heat-transferring relationship to an artificially-cooled member projecting into the discharge space. Such a cooling member may axially transverse the anode or the mercury cathode in a manner known per se and project into the discharge space from above or below.

Further features and advantages of my invention will appear as the description progresses.

In order that my invention may be clearly understood and readily carried into effect, I shall describe same more fully with reference to the accompanying drawing, in which: 5

Figure 1 is a sectionized sideview of a rectifier embodying the invention; and

Fig. 2 is sectionized side-view of a rectifier according to another embodiment of the invention.

The rectifier shown in Fig. 1 has an envelope comprising a cup-shaped metal portion I, for instance of chrome iron, to which is hermetically fused at IS a vitreous portion 2. I-Iermetically sealed in portion 2 is a metal disc in carrying a terminal 5, and a conductive rod II to the lower end of which is secured a cylindrically-shaped" main cathode 1. Rod 1| serves as a supply conductor for anode I and is surrounded by a tube 5! of insulating material, for instance steatite.

Supported from tube 5| is a cylindrical shield I4, for instance of molybdenum plate, closed at its top and serving to protect seal l5 from the detrimental effect of the discharge in the manner described in my above-mentioned patent. Supported from shield 14 by suitable clamps and eX- tending through a groove in the periphery of anode l is a guide tube 9 of insulating material, for instance steatite. A conductive rod 8 is slidably disposed within the bore of tube 9 and carries on its lower end an ignition anode 4, and on its upper end an iron plunger l0.

Plunger I3 is electrically connected through a compression spring H to an iron core I2 supported by a conductive rod 6 from a disc hermetically sealed in the upper end of a protruding part of portion i. A coil 13 having one lead connected to rod 6 surrounds glass portion 1 in the vicinity of core l2 and serves to move the assembly consisting of plunger l0, rod 8 and anode in a vertical direction to thereby lift anode 4 from a mercury cathode disposed at the bottom of portion I.

To restrict the free movement of mercury 2, concentrical rings H and 18, for instance of molybdenum, are secured, for instance welded, to the bottom of portion I and extend slightly from the surface of the mercury.

Disposed at the center of mercury 3 and extending slightly above the surface thereof, is a cylindrical metal member I5, whichserves to anchor the cathode spot in known manner. Member i6 is preferably formed of a metal which has a higher dissolving speed in mercury than does copper and which amalgamates better than does iron or molybdenum, for instance nickel. Anchoring members of this type have been described in detail in the copending U. S. patent application Ser No. 125,943 to Jurriaanse, now Patent #1118387.

Metal portion 1 is artificially cooled, and for this purpose is surrounded by a cooling jacket 20 provided with an inlet opening 2| and an outlet opening 22 for the circulation of a suitable cooling medium such as water or oil. Jacket 20 is secured to the bottom of portion 1 by a suitable bolt i9 also serving as a supply conductor for cathode 3, whereas a ring-shaped member closes the top thereof.

In accordance with the invention, partitioning means are provided in the discharge path between anode l and cathode 3 to prevent back discharge. For this purpose a ring 23, for instance of molybdenum, and having an aperture 54 is supported from and in direct metallic contact with portion l-for instance by having its periphery welded thereto-whereas a disc 23 of conductive material, for instance of molybdenum and of larger diameter than aperture 54 is fixedly supported from insulating tube 9 so as to extend normally to the axis of main anode T and substantially coaxially therewith. Due to these partitioning means the discharge must pass, as indicated by the arrows 52 through aperture 54, and is deflected by disc 23 to pass over the artificially cooled wall of portion I before reaching the lower surface of anode 1. As ring 23 is in direct metallic contact with the artificially-cooled wall of portion i, it is maintained at a relatively low temperature whereby the condensation of the mercury vapor therein is increased.

It should be noted that the disc 24 and ring 23, or a plurality of such discs and rings, form a labyrinth-like structure, and that a straight line between any point on the anode and any point of the active surface area of the cathode 3 is intercepted by either ring 23 or by disc 24.

To facilitate ignition of the tube, a given potential may be applied to the disc 24, and for this purpose a supply lead 53 is provided which is connected to a terminal 66 led through the vessel wall by means of the metal disc 61. Thus disc 24 may also have the functions of a control grid. For ignition purposes disc 23 may be given a positive voltage of the order of volts.

If it is desired to make the arrangement more eificient, a larger number of alternately-arranged members, similar to disc 23 and ring 23, may be used, and by making the outer diameter of the discs greater than the diameter of the apertures in the rings the discharge path between the cathode and anode will have several curves. In such a construction several of the partitioning members can be given suitable potentials so that the ignition of the discharge takes place in steps from the cathode to succeeding partitioning members. In such cases it is advisable to pre-connect series-resistances of suitable values to limit the current.

The rectifier shown in Fig. 2 has an envelope comprising a cup-shaped metal member 39 and a ring-shaped metal member 2'? secured together by a vitreous ring 38 sealed to members 39 and 21 at 55 and 56, respectively, and a vitreous portion 29 fused to the upper edge of member 27 at 5T.

Secured to a threaded projecting portion of member 2T is a main anode 25 provided with a central bore 58 and an eccentric bore 59. A suitable 1ug'28 secured to member 21 serves as a supply terminal for anode 26.

Sealed in the upper portion of member 29 is a disc 63 provided with a terminal 33. Secured to the lower surface of disc 65 and extending through aperture 59 is a conductive rod 6| carrying on its lower end an ignition member 3i, or igniter, consisting of a semi-conductive material such as silicon carbide. An insulating tube 32 surrounds rod tl and is supported by member 3 I.

Sealed to member29 at 62 isa tubular member 33 having an outlet opening 3", and an inlet opening 35 in the form of a tube extending almost to the bottom of member 33. Member 33 is provided with a terminal 34 and extends through aperture 58 into the discharge space with a clearance so as to be insulated from anode'2ii. A suitable circulating liquidfSi, for instance water or oil, is circulated in the direction of the arrows to cool member 33.

Disposed in the bottom of metal portion 39 is a mercury cathode lflfand concentric rings 43 and 50 which, similar to rings l8 and IQ of Fig. I, prevent free movement of the mercury.

A cooling jacket 42 having an outlet opening 43 surrounds member 39 and is secured thereto by a hollow bolt 3| having an inlet opening 44 and two outletopenings G5. Jacket 42 is closed at its upper end by a metal member 5 3 welded to member 39 andscrewed to the top edge of cooling jacket 42.

An annular cathode spot anchoring member 38, for instance of nickel, is secured to the upper portion of bolt 4| and to member 39, for instance by being welded thereto. Bolt M is provided on its lower end with an external thread cooperating with suitable nuts to form'a liquid-tight seal at the point of support of jacket 32. A terminal 33 secured to bolt 4|, serves as a supply terminal for cathode 40.

As indicated by arrows, a suitable circulating cooling fluid such as water or oil passes through opening 34, through the hollow of bolt 4|, through openings 45, and, after passing through cooling jacket 42, leaves through the outlet opening 43.

According to the invention the discharge path between anode 26 and cathode 40 is intercepted at several points. For this purpose a .ring 41 having an aperture 65 is peripherally secured to member 39, for instance by welding, and members 31 and 46 of conductive material and having a larger diameter than aperture .65 are secured, for instance welded, to members 33 and 4| respectively. Thus members 31 and 46 are maintained at a desired low temperature by means of the circulating cooling fluid flowing through in members 33 and 4| respectively, whereas member 41 is also maintained at a low temperature by being directly connected to the cooled wall of member 39. Furthermore the fiow of cooling liquid through member 4| insures an even cooling in the immediate vicinity of the foot point of the discharge.

The terminal 34 may be used in conjunction with disc 3! as a control member for influencing the passage of the discharge through the tube, and for this purpose it is important to thoroughly insulate member 33 from anode 26.

Thus a construction such as shown in Fig. 2 has the advantage that the anode, the mercury cathode, and the discharge space between these two electrodes are subjected to a supplementary cooling whereby still larger quantities of energy can be taken up inside the very compact discharge space or, conversely, the voltage drop in the arc and the corresponding losses can be reduced. In either case the security against arcing back of the tube is materially increased. With such a construction it is possible even at high anode voltages, for instance 500 volts A. C. and more, to accurately rectify currents of considerable intensity for instance of several hundred amperes.

Furthermore the problem of providing an insulated current supply lead for a partitioning member acting as a control grid is solved in a simple manner by using the cooling member 33 for this purpose.

While I have described my invention in connection with specific examples and applications, I do not wish to be limited thereto but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:

1. A single-phase mercury-cathode rectifier comprising an envelope having a cylindrical cupshaped metal portion and a glass portion hermetically sealed to the edge of said metal portion, a mercury cathode in said metal portion, an anode axially disposed in the envelope and spaced from said cathode, partitioning means forming a circuitous discharge path between said anode and cathode and intercepting a straight line between any point on said anode and any point on the active cathode area, said means comprising an annular partitioning member snugly fitting into said metal portion and secured thereto, and a partitioning member of conductive material supported from said glass portion and insulated from the other portions of the rectifier, and means for applying a potential to said member.

2. A single-phase mercurycathode rectifier comprising an envelope having a cup-shaped metal portion and a glass portion hermetically fused together, a mercury cathode in said metal portion, a main anode of slightly smaller cross section than the metal portion and provided with a bore, said anode being supported from said glass portion and lying partly within said metal portion, a member supported from said glass portion and extending through said bore, and means to form a circuitous discharge path between said anode and cathode and intercepting a straight line between any point on said anode and any point on said cathode, said means comprising an annular plate snugly fitting into said metal portion and secured at its edge to the surface thereof, and a disc carried by said member.

3. A single-phase mercury-cathode rectifier comprising an envelope having a cup-shaped metallic bottom portion and a vitreous upper portion hermetically sealed together at the periphcry of the tube, a mercury cathode in the bottom of said cup-shaped portion and in direct metallic contact therewith, a main anode axially disposed in said envelope and extending into the space enclosed by said vitreous portion, said anode being spaced from said cathode to form a discharge path, partitioning means between said anode and cathode and intercepting a straight line between any point on the anode and any point on the active cathode area while allowing for the passage of a discharge between said anode and cathode, said means comprising a metal barrier secured with a metallic connection at its periphery to said metallic bottom portion to ensure good transfer of heat, and means to artificially cool said metallic bottom portion and said metal barrier.

4. A single-phase mercury-cathode rectifier comprising an envelope having a cup-shaped metallic bottom portion and a vitreous upper portion hermetically sealed together at the periphery of the tube, a mercury cathode in the bottom of said cup-shaped portion and in direct metallic contact therewith, a main anode axially disposed in said envelope and extending into the space within said vitreous portion, said anode being spaced from said cathode to form a discharge path, partitioning means between said anode and cathode intercepting a straight line between any point on the anode and any point on the active cathode area while allowing for the passage of a discharge between said anode and cathode, said means comprising a metal ring secured with a metallic connection at its periphery to said metallic bottom portion to ensure good transfer of heat, and a metal disc, a member supported from said vitreous portion and carrying said disc, and means to artificially cool said metallic bottom portion and said ring.

5. A single-phase mercury-cathode rectifier comprising an envelope having a cup-shaped metallic bottom portion and a vitreous upper portion hermetically sealed together at the periphery of the tube, a mercury cathode in the bottom of said cup-shaped portion and in direct metallic contact therewith, a main anode axially disposed in said envelope and extending into the space within said vitreous portion, said anode being spaced from said cathode to form a discharge path, partitioning means between said anode and cathode and intercepting a straight line between any point on the anode and any point on the active cathode area while allowing for the passage of a discharge between said anode and cathode, said means comprising a metal barrier secured with a metallic connection at its periphery to said metallic bottom portion to ensure good transfer of heat, and a metal member, means to artificially cool said metallic bottom portion and said barrier, and means for cooling said metal member including a memher extending through the discharge space of'the tube.

6. A single-phase mercury-cathode rectifier comprising an envelope having a cup-shaped metallic bottom portion and a vitreous upper portion hermetically sealed together at the periphery of the tube, a mercury cathode in the bottom of said cup-shaped portion and in direct metallic contact therewith, a main anode axially disposed in said envelope 2nd extending into the space within said vitreous portion, said anode having a bore and being spaced from said cathode to form a discharge path, partitioning means between said anode and cathode and intercepting a straight line between any point on the anode and any point on the active cathode area while allowing for the passage of a discharge between said anode and cathode, said means comprising a metal barrier secured with a metallic connection at its periphery to said metallic bottom portion to ensure good transfer of heat, and a second metal barrier, means to cool said second metal barrier including a member passing through the bore in said anode, and means to artificially cool said metallic bottom portion and said first metal barrier.

7. A singlephase mercury-cathode rectifier comprising an envelope having a cup-shaped metallic bottom portion and a vitreous upper portion hermetically sealed together at the periphery of the tube, a mercury cathode in the bottom of said cup-shaped portion and in direct metallic contact therewith, a main anode axially disposed in said envelope and extending into the space within said vitreous portion, said anode being spaced from said cathode to form a discharge path, partitioning means between said anode and cathode and intercepting a straight line between any point on the anode and any point on the active cathode area while allowing for the passage of a discharge between said anode and cathode, said means comprising a metal barrier secured with a metallic connection at its periphery to said metallic bottom portion to ensure good transfer of heat, and a second metal barrier, means to cool said second barrier including a member extending through the mercury cathode, and means to artificially cool said metallic bottom portion and said first barrier.

JOHANNES GIJSBERTUS 'VVILHELM MULDER.

Images