US3337764A - Cool discharge tubes of hollow ring-like construction - Google Patents

Description

Aug. 22, 1967 H. MENOWN ETAL COOL DISCHARGE TUBES OF HOLLOW RING-LIKE CONSTRUCTION Filed April 15, 1964 J m F 644 fllmm m M w M BY ATTQRNEY United States Patent 3,337,764 COOL DISCHARGE TUBES OF HOLLOW RING-LIKE CONSTRUCTION Hugh Menown and Ronald Ernest Lake, Essex, England, assignors to English Electric Valve Company, Limited, London, England, a British company Filed Apr. 15, 1964, Ser. No. 359,946 Claims priority, application Great Britain, Apr. 29, 1963, 16,697/ 63 10 Claims. (Cl. 313-30) This invention relates to discharge tubes and has for its object to provide improved, economical and mechanically strong discharge tube structures suitable for high power operation and which will lend themselves to eflicient forced cooling by fluid coolants which may be gas or liquid. The principal, though not the exclusive application of the invention, is to high power thyratrons, e.g. high power hydrogen filled thyratrons.

In various types of discharge tube and in particular in high power thyratrons, very substantial amounts of heat are produced on one or more of the electrodes. For example, in the case of a high power thyratron, very considerable amounts of heat are produced on the grids, especially on the so-called second grid and power limitation is often set by the ability to cool this grid. In many tubes also, including high power thyratrons, there are other electrodes the anode in particular--which require cooling if high powers are to be produced from a tube which is relatively small physically..A tube structure which will lend itself to efiicient forced cooling by fluid coolant therefore offers very substantial advantages and the present invention seeks to provide improved tube structures which, from the point of view of cooling, are a good deal better than the normal structures at present generally employed and wherein the electrodes are housed in the customary more or less cylindrical envelope and forced cooling, it any, is effected by forcing the coolant past the outside of the envelope with improved cooling obtained by such expedients as providing that portion of the anode which is outside the envelope with external fins or the like in the coolant stream.

According to this invention in its broadest aspect the hermetically sealed envelope of a hermetically sealed discharge tube comprises an inner substantially cylindrical composite wall having at least one part of its length made of metal and the remainder of its length made of insulating material, said wall constituting the wall of a coolant conduit passing axially through the tube, the remaining walls of the envelope being outwardly of and extending around said inner wall to provide a hermetically sealed envelope space encircling said conduit, the electrodes of the tube including at least one electrode of high heat loading and which is in good heat conducting relationship with said metal length.

Preferably said one electrode includes a portion which is of hollow ring-like construction having its innermost wall constituted by said metal length.

In a preferred construction in accordance with the invention said one electrode includes an inner portion which is of hollow-ring-like construction having its innermost wall constituted by said metal length and an outer portion also of hollow ring-like construction encircling and spaced from said inner portion, said outer portion being supported by an outer substantially cylindrical supporting wall structure co-axial with the coolant conduit.

Preferably the insulating material is ceramic material though other suitable insulating materials may be used.

Where necessary any of the electrodes may be made of or supported by double walled structures arranged for the passage of coolant therethrough. In a construction in which said one electrode has inner and outer portions of 3,337,764 Patented Aug. 22, 1967 hollow ring-like construction, the outer portion encirclmg and being spaced from the inner and the inner portion having its innermost wall constituted by the aforesaid metal length of the coolant conduit, said metal length may be provided with apertures giving access for coolant to the interior of said inner portion. In this case one or more coolant pipes hermetically sealed to and bridging the space between the inner and outer portions may be provided to pass coolant from the interior of the inner portion to the interior of the outer portion, coolant which has passed through said portions and said pipe or pipes being taken oif from the interior of the outer portion.

As stated the principal, though not the exclusive application of the invention is to thyratrons.

According to a feature of this invention a thyratron has a hermetically sealed envelope comprising an inner substantially cylindrical composite wall having an intermediate part of its length made of metal, said inner composite wall constituting a coolant conduit extending axially through the thyratron; an outer insulating sleeve coaxially surrounding an insulating length forming one end of the conduit wall; a ring-like anode between said sleeve and said insulating length of conduit wall and sealed to both; a second grid structure comprising a hollow inner ring-like portion having its innermost wall constituted by the metal length of the conduit wall and an encircling outer ring-like portion spaced from said inner portion, the inner portion being sealed to said insulating length of conduit wall and the outer portion being sealed to said sleeve, said inner and outer portions having end walls facing and spaced in the axial direction from a wall of the anode; a second co-axial insulating sleeve of substantially the same diameter as the first and interposed between a radial wall of the outer portion of the second grid structure and sealed at one end thereto, said second sleeve being sealed at its other end to one side of a substantially annular priming electrode at right angles to the tube axis and having its inner circular end approximately opposite the space between the inner and outer portions of the second grid structure; a third co-axial insulating sleeve of substantially the same diameter as the other two and sealed at one end to the other side of the priming electrode; a cathode shield having a substantially coaxial cylindrical portion and sealed at one end to the remaining end of the third sleeve; cathode means in the annular space between the cylindrical portion of the cathode shield and another insulating length of the coolant conduit; and means completing the hermetically sealed envelope in which the cathode means and the operating parts of the cathode shield and the priming, second grid and anode structures are situated. In the case of a hydrogen thyratron with indirectly heated cathode means, the hermetically sealed envelope may also include a space housing one or more hydrogen capsules adapted to replenish the hydrogen filling, electrical heaters on said capsule or capsules and connections between the cathode heating means and said electrical heater or heaters.

If desired there may be provided apertures in the innermost wall of the inner portion of said second grid, said apertures providing communication between the interior of the conduit and the interior of said inner portion; pipes providing communication between the interiors of the inner and outer portions of the second grid across the space between said portions; and means providing egress for coolant from the interior of said outer portion.

The coolant may be any suitable gas or liquid, e.g. air or transformer oil.

The invention is illustrated in the accompanying simplified drawings which show one embodiment of the invention as applied to a high power hydrogen filled thyratron. In the drawings, FIGURE 1 is a simplified elevation view in centre line section of a high power hydrogen filled thyratron; FIGURE 2 is a plan view looking down on the tube of FIGURE 1; FIGURE 3 is a plan view taken in the same direction as FIGURE 1 but with the anode removed and FIGURE 4 is a fragmentary section view of a portion of a thyratron of alternate construction.

Referring to the drawings, it will be seen that the general envelope arrangement is quite different from that of an ordinary known discharge tube inasmuch as it is constructed to provide an axial conduit 1 running up the middle of the tube and with the various electrodes disposed around it. This, conduit is composed, in effect, of lengths of insulatingpreferably ceramic-material and metal. The part of the conduit which is uppermost in FIGURE 1 is composed of a cylinder 2 of ceramic material which is co-axially within and spaced from an external sleeve 3 also of ceramic material. In the space between the parts 2 and 3 and round the upper end of the conduit is a ringlike channel-sectioned anode 4 with the openside of the channel uppermost and the parallel cylindrical walls thereof sealed to the parts 2 and 3. Next below the anode 4 is a so-called second grid which consists of two separate structures 5 and 6. The structure 5 is of hollow ringlike form with a small step in the ring between a cylindrical wall 5a and a second cylindrical wall 5b of rather smaller diameter, the second cylindrical wall 5b being of the same diameter as the part 2 and constituting a metallic length of the conduit wall. The outer wall of the structure 5 is similarly stepped and includes two cylindrical portions 50 and 5d.

The second structure 6 includes outer and inner cylindrical walls 6a and 6b of which the former is sealed to the sleeve 3 and the latter extends below the former and continues into an annular wall 60 which leaves a gap 6d providing access to the interior of the structure 6. The uppermost walls 5e and 6e of the structures 5 and 6 are co-planar. They face and are spaced from the annular wall of the anode 4. The walls 50 and 6b are spaced from one another and define a cylindrical gap for electron flow in directions parallel to the axis.

The first or priming grid 7 of the thyratron is of annular form and is hollow being made of suitable metal bent back on itself in re-entrant fashion with the re-entrant bend projecting into the tube as shown. One of the two parallel walls of the grid 7 is sealed to one end of a short ceramic sleeve 8, the other end of which is sealed to the wall 6c. The other of the parallel walls of the grid 7 is sealed to one end of a further short ceramic sleeve 9. The ceramic parts 3, 7 and 9 are all of the same diameter.

The upper end of the wall 5b is sealed to the lower end of the part 2 and the lower end of the said wall 512 is sealed to the upper end of a ceramic cylinder 10 which also forms part of the wall of the conduit 1. Co-axially surrounding the part 10 is a hollow cathode shield 11 formed of metal bent as shown to provide an annular portion 11a and a cylindrical portion 11b. The annular portion 11a is sealed to the lower end of the sleeve 9.

In the space between the cylindrical portion 11b and the ceramic member 10 is a cathode arrangement which may be a single cathode of ring form or, as shown, may consist of a number of similar cathode units disposed in a ring round the conduit. These cathode units are of the indirectly heated type and of known construction being only schematically represented. The only parts of these cathode structures which are referenced are the cathode heaters 12.

Below the ceramic member 19 is a ceramic cylinder 13 which again forms part of the central conduit wall and which is surrounded by a ceramic sleeve 14 which is of the same diameter as the cylindrical portion 11b of the cathode shield and is sealed to the lower end thereof. In the space between the parts 13 and 14 are mounted hydrogen reservoirs of known form, e.g. hydrogen filled palladium tubes with heaters 15 wound on them. The heaters of the hydrogen reservoirs are shown in the example illustrated as being in parallel with the cathode heaters, though this arrangement is not necessary and separate connections may be provided if required. The heater connections shown are referenced 16 and suitable connections (not shown) are provided for the cathode or cathodes. At the bottom the parts 13 and 14 are sealed to a metal closure ring 17.

With this construction, and assuming that the wall 512 is a solid unperforated wall (as it could be) the hermetically sealed envelope of the tube will consist of the portion of the conduit wall between the ring 17 and the annular face of the anode 4, the said annular face, the part of the member 3 between the annular face of the anode and the wall 6e, the said wall 6e, the walls 6b and 6c, the sleeve 8, the grid 7, the sleeve 9, the cathode shield 11, the sleeve 14 and the closure wall 17. Very good cooling can be obtained by pumping air, transformer oil or other suitable coolant up the central conduit, for the second grid has its wall 50, where much heat may be generated, in excellent heat conducting relationship with the wall 5b which itself forms part of the conduit. Also the cooling of the anode 4 is inherently very good. Furthermore, the hollow construction of the priming grid and the cathode shield considerably facilitates cooling of these electrodes also, though, of course, it is not necessary to make them of hollow construction.

If desired, any or all of the electrodes which are of hollow construction-and in the illustrated embodiment this includes the priming grid and the cathode shield may be force cooled by pumping coolant through the electrode or electrodes in question using their hollow construction to provide coolant paths through them. Also the wall 5b may be provided with apertures 19 so that coolant from the conduit can enter the structure 5. If this is done this wall will no longer constitute part of the hermetically sealed envelope but its place as part of the envelope will be taken by the remaining walls of'the structure 5. If coolant access apertures are provided in the wall 5b it is preferred to provide coolant paths from the interior of the structure 5 to the interior of the structure 6 so that coolant paths will exist between the conduit 1 and the gap 6d as illustrated in FIGURE 4. Such coolant paths may be provided by short pipes between the interiors of the structures 5 and 6 bridging the gap between the walls 50 and 6b. Three such pipes, referenced 18, appear in the View of FIGURES 3 and 4. By suitably angularly spacing the pipes around the axis, a sufiicient coolant flow can be obtained without appreciable interference with the electron flow up between the walls 5c and 6b.

The invention is not limited to the particular construction shown, though this is considered to be a good one. For example, the hydrogen reservoirs in the illustrated embodiment are shown in the annular space below the cathode, but obviously the hydrogen reservoirs need not be located in this position.

We claim:

1. A discharge tube having a hermetically sealed envelope which comprises an inner substantially cylindrical composite wall having at least one part of its length made of metal and a remaining part of its length made of insulat-ing material, said wall constituting the wall of a substantially cylindrical coolant conduit passing axially through the tube, the remaining walls of the envelope being outwardly of and extending around said inner wall to provide a hermetically sealed envelope space encircling said conduit, the electrodes of the tube including at least one electrode of high heat loading and which is in good heat conducting relationship with said metal length, said one electrode including an inner portion which is of hollow ring-like construction substantially enclosing an an ular cavity therein and having its innermost wall constituted by said metal length.

2. A tube as claimed in claim 1 wherein said one elecm) trode includes an outer portion also of hollow ring-like construction encircling and spaced from said inner portion, said outer portion being supported by an outer substantially cylindrical supporting wall structure coaxial with the coolant conduit.

3. A tube as claimed in claim 1 wherein the insulating material is ceramic material.

4. A tube as claimed in claim 1 wherein said one electrode includes an outer portion of hollow ring-like construction, the outer portion encircling and being spaced from the inner and said metal length being provided with apertures giving access for coolant to the interior of said inner portion.

5. A tube as claimed in claim 5 wherein one or more coolant pipes hermetically sealed to and bridging the space between the inner and outer portions are provided to pass coolant from the interior of the inner portion to the interior of the outer portion, coolant which has passed through said portions and said pipe or pipes being taken off from the interior of the outer portion.

6. A thyration having a hermetically sealed envelope com-prising an inner substantially cylindrical composite wall having an intermediate part of its length made of metal, said inner composite wall constituting a coolant conduit extending axially through the thyration; an outer insulating sleeve co-axially surrounding an insulating length forming one end of the conduit wall; a ring-like anode between said sleeve and said insulating length of conduit wall and sealed to both; a second grid structure comprising a hollow inner ring-like portion having its innermost wall constituted by the metal length of the conduit wall and an encircling outer ring-like portion spaced from said inner portion, the inner portion being sealed to said insulating length of conduit wall and the outer portion being sealed to said sleeve, said inner and outer portions having end walls facing and spaced in the axial direction from a wall of the anode; a second coaxial insulating sleeve of substantially the same diameter as the first and interposed between a radial wall of the outer portion of the second grid structure and sealed at one end thereto; a substantially annular priming electrode at right angles to the tube axis and having its inner circular end approximately opposite the space between the inner and outer portions of the second grid structure; said second sleeve being sealed at its other end to one side of the priming electrode; a third co-axial insulating sleeve of substantially the same diameter as the other two and sealed at one end to the other side of the priming electrode; a cathode shield having a substantially co-axial cylindrical portion and sealed at one end to the remaining end of the third sleeve; cathode means in the annular space between the cylindrical portion of the cathode shield another insulating length of the coolant conduit; and means completing the hermetically sealed envelope in which the cathode means and the operating parts of the cathode shield and the priming, second grid and anode structures are situated.

7. A thyratron as claimed in claim 6 wherein the hermetically sealed envelope also includes a space housing at least one hydrogen capsule adapted to replenish the hydrogen filling, electrical heaters on said at least one capsule and connections between the cathode heating means and said electrical heater or heaters.

8. A thyratron as claimed in claim 7 wherein there are provided apertures in the innermost wall of the inner portion of said second grid, said apertures providing communication between the interior of the conduit and the interior of said inner portion; pipes providing communications between the interiors of the inner and outer portions of the second grid across the space between said portions; and means providing egress for coolant from the interior of said outer portion.

9. A tube as claimed in claim 1 having a coolant gas within said conduit.

10. A tube as claimed in claim 1 having a coolant liquid within said conduit.

References Cited UNITED STATES PATENTS 2,609,517 9/1952 McCullough 3l3 .23O 2,654,844 10/1953 Eitel et al 313-249 FOREIGN PATENTS 844,155 8/1960 Great Britain.

DAVID J. GALVIN, Primary Examiner.

Claims (1)

1. A DISCHARGE TUBE HAVING A HERMETICALLY SEALED ENVELOPE WHICH COMPRISES AN INNER SUBSTANTIALLY CYLINDRICAL COMPOSITE WALL HAVING AT LEAST ONE PART OF ITS LENGTH MADE OF METAL AND A REMAINING PART OF ITS LENGTH MADE OF INSULATING MATERIAL, SAID WALL CONSTITUTING THE WALL OF A SUBSTANTIALLY CYLINDRICAL COOLANT CONDUIT PASSING AXIALLY THROUGH THE TUBE, THE REMAINING WALLS OF THE ENVELOPE BEING OUTWARDLY OF AND EXTENDING AROUND SAID INNER WALL TO PROVIDE A HERMETICALLY SEALED ENVELOPE SPACED ENCIRCLING SAID CONDUIT, THE ELECTRODES OF THE TUBE INCLUDING AT LEAST ONE ELECTRODE OF HIGH HEAT LOADING AND WHICH IS IN GOOD HEAT CONDUCTING RELATIONSHIP WITH SAID METAL LENGTH, SAID ONE ELECTRODE INCLUDING AN INNER PORTION WHICH IS HOLLOW RING-LIKE CONSTRUCTION SUBSTANTIALLY ENCLOSING AN ANULAR CAVITY THEREIN AND HAVING ITS INNERMOST WALL CONSTITUTED BY SAID METAL LENGTH.

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