US2977493A - Vapotron boiler - Google Patents

Description

March 28, 1961 Filed July 9, 1959 P. E. CANE VAPOTRON BOILER 2 Sheets-Sheet 1 PHILIP ERNEST CANE March 28, 1961 P. E. CANE 2,977,493

VAPOTRON BOILER Filed July 9, 1959 2 Sheets-Sheet 2 INV'ENTOR PHILIP ERNEST CANE BY I C Q United States Patent VAPOTRON BOILER Philip Ernest Cane, Bush Hill Park, Eufield, England,

assignor to Siemens Edison Swan Limited, London,

This invention relates to electron tubes of the kind known by the registered trademark Vapotron and in particular to so-called boilers therefor in which anode cooling is effected by causing the heat generated thereat to produce vaporisation of a cooling liquid, usually water, contained in the boiler with at least the anode immersed therein.

Broadly speaking, a Vapotron boiler simply comprises a chamber containing a cooling liquid in which at least the main anode of the tube to be cooled is immersed, heat generated by the tube being dissipated in vaporising the cooling liquid. The vapour thus produced rises clear of the anode and is replaced by further cooling liquid by a thermo-siphon effect, a heat exchanger being associated with the boiler to continuously condense the vapour.

In one particular form the Vapotron boiler is constituted by a liquid-tight chamber in which the tube to be cooled is immersed in water or other liquid. In operation, the heat produced by the tube boils the liquid and the resultant vapour (steam) is condensed in a heat exchanger external to the boiler, the condensate being returned to the boiler for further use.

In another form in which the Vapotron boiler is again constituted by a liquid-tight chamber inwhich the tube to be cooled is immersed in Water or other liquid, the requirement for an external heat exchanger is dispensed with by providing inside the boiler, in position surrounding the Vapotron tube, a heat exchanger constituted by a tubular helix of copper or other good thermally conductive metal through which a constant stream of cooling liquid, also usually water, is passed. In this form the vaporised liquid (steam) and also the hot liquid in the vicinity of the anode rises within the space embraced by the cooling helix and in so-doing is cooled by the cooling liquid flowing through the helix; the cooled liquid in the boiler then passes down the outside of the helix and returns to the bottom of the boiler ready to be heated again.

Due to their bulk, Vapotron boilers have hitherto normally been made from a light aluminium alloy in order to keep their weight to a minimum, while the main anode of a Vapotron tube, being required to be a good thermal conductor, is usually made from copper. This has the disadvantage, however, that the aluminium alloy of the boiler and the copper of the anode (and also the copper tubular helix when an internal heat exchanger is used) are in contact with the liquid in the boiler at the same time, with the result that an electrolytic action may, and in the case of water does, take place between the dissimilar metals, resulting in electrolytic corrosion at the inside surface of the boiler.

It has previously been attempted to overcome this electrolytic corrosion by applying a protective non-metallic coating of varnish to the inside surface of the boiler but the best results so far achieved by this method give a boiler life of only about 2,000 hours. The method was found to be unsatisfactory mainly because of the difiiculty of economically producing a completely impervious coating of varnish. Whatever method was employed for applying the varnish coating, there was a tendency for pinholes to be left through which the liquid could reach the inside surface of the boiler alloy and where this happened' an electrolytic corrosive action was set up which caused the varnish coating to peel away from the surface and so expose more of it.

It is apparent that this electrolytic corrosion could be avoided by making the boiler of the same metal (copper or other) as the anode and, if provided, the cooling helix. However, in the case of copper the thicknessfof boiler wall then required to produce a non-porous boiler is likely to make theweight and cost prohibitive. Other metals such as Monel metal and stainless steel, which would not be subject to the electrolytic corrosion, are commercially unsuitable because of their weight and cost.

It is an object of the present invention to provide a Vapotron boiler which does not suffer from the disadvantage of electrolytic corrosion and which, moreover, has other distinct advantages over boilers made from an aluminium alloy or other metal.

With this object in view, an electron tube of the Vapotron kind is provided, in accordance with the invention, with a boiler constituted by an insulating container made from a resin-bonded fibre-glass material. Besides being free from electrolytic corrosive action, a boiler thus con,- stituted has the advantages that it is cheap to produce and is light in weight. Moreover, the good electrical insulation properties of the fibre-glass material eleminates the need to support the boiler on special insulated mountings such as are necessary with the hitherto used metallic,

boilers, which, when the tube is in operation, are at the operating potential of its anode. This last feature there,- fore represents a definite advantage over known Vapotrons with metallic boilers, particularly in view of the high operating voltages often used with Vapotron tubes.

In carrying out the invention, for which a suitable fibre-glass material is that known as Orglass, the dimensions of the Vapotron boiler may approximate closely to those of the aluminium-alloy boilers previously employed. The fibre-glass boiler may be made by using a mandrel which has the same size and shape as the re quired interior of the boiler and applying successive layers of fibre-glass treated with an epoxy or other suitable bonding resin until the desired thickness for the boiler wall has been reached. Appropriate curing of the resin is then effected either by simply leaving it for a suitable time if the resin is self-curing or by subjecting it to an appropriate heat treatment.

If required, as may be the case where the fibre-glass boiler is intended for use with, and has therefore to support, a large Vapotron tube of appreciable weight, one or more metallic strengthening members may be embedded in an appropriate portion of the boiler during the formation thereof.

Two examples of Vapotron tubes with fibre-glass boilers in accordance with the invention are shown'in the accompanying drawings in which:

Fig. l is a partially cut-away perspective view of a fibre-glass boiler containing a Vapotron tube for which anode cooling can be effected in conjunction with a heat exchanger (not shown) provided externally of the boiler, and

Fig. 2 is a partially cut-away perspective view of a fibre-glass boiler containing a Vapotron tube for which anode cooling can be effected in conjunction with a heat exchanger provided inside the boiler.

Referring to Fig. l, a generally cylindrica lly shaped Vapotron boiler 1, which is operable at atmospheric pressure and which in accordance with the invention is made from a resin-bonded fibre-glass material, comprises a chamber portion 1a for containing cooling liquid 2, and

an integral mounting base 1b permitting the boiler 1 to be mounted in an upright position. The upper end of the chamber portion 1a is formed with an outwardly extending rim 3 to which is secured a tube supporting member 4 forming a top cover for the Vapotron boiler 1. This member 4, which is also made of resin-bonded fibre-glass material and is strengthened by means of a metallic strengthening member 5 embedded within it, has a central recessed circular portion 4a defining an aperture bounded by an annular ledge 6 on which the Vapotron tube 7 is mounted in the manner shown, such tube 7 to this end being provided at a point between a vacuum envelope 7a and a copper anode structure 7b thereof with a flange 8, suitably of copper, which engages with the ledge 6. With the Vapotron tube 7 so mounted, its copper anode structure 7b extends into the chamber portion 1a of the boiler 1 and is immersed therein in the cooling liquid 2.

There is provided externally of the Vapotron boiler 1 a heat exchanger (not shown) which serves to condense vapour (steam) produced in the boiler 1 at the surface of the anode structure 7b during operation of the Vapotron tube 7: this vapour passes into the heat exchanger by way of a vapour outlet tube 9 located at the top of a laterally projecting portion 1c of the boiler chamber portion 1a, and condensate passes from the heat ex changer back into the bottom of the portion In by way of an inlet pipe 10. The projecting portion 10 of the chamber portion 1a is provided with a window 11 through which the level of the cooling liquid 2 can be observed.

Referring to Fig. 2, a fibre-glass Vapotron boiler 12, which in this instance is operable at an internal pressure above atmosperic pressure, comprises a genenally rectangular chamber portion 12a and a cylindrical mounting base 12b. The upper end of the chamber portion 12a is formed with an outwardly extending rim 13 to which is secured a cover 14 for the chamber portion 12a, a seal 15 of rubber or other suitable material being provided between the rim 13 and the cover 14. As in Fig. 1, the cover 14 in Fig. 2 has a central recessed circular portion 16 defining an aperture bounded by an annular ledge 17 on which the Vapotron tube 18 is mounted in the manner shown, the Vapotron tube 18 being to this end fitted, as in the ease of the Vapotron tube 7 in Fig. 1, with an annular copper flange 19 between its vacuum envelope 18a and its copper anode 18b. In this instance, however, because the internal operating pressure of the Vapotron boiler 12 is above atmospheric pressure, a rubher or other sealing ring 17' is disposed between the ledge 17 and the flange 19, while clamps 20 are provided to clamp the Vapotron tube 18 in position.

There is provided inside the chamber portion 12a, in position surrounding the anode 1812, a cylindrical copper shield 21 which in turn is surrounded by a tubular copper helix 22. The chamber portion 12a is intended to be filled with water or other cooling liquid (not shown) to approximately the top of the shield 21, while through the tubular helix 22, which constitutes an internal exchanger, is passed further cooling liquid, suitably also water. An inlet 23 and a similar outlet hidden behind the tube 18 in Fig. 2, afiord access to the helix 22 for passing the cooling liquid therethrough. In operation, as a result of the heating of the cooling liquid in contact with the anode 18b, vapour and hot liquid rise inside the shield 21 and a circulation is set up which brings the hot liquid down the outside of the shield 21, there to be cooled by contact with the tubular helix 22.

With the arrangement of Fig. 2, there may be provided in the cover 14 a pressure actuated switch (not shown) which is effective to disconnect the electrical supply from the Vapotron tube 18 if the internal pressure of the Vapotron boiler becomes too high due to excess vapour in the latter as a result, for instance of failure of the cooling liquid supply through the tubular helix 22.

There may also be provided with either of the two arrangements just described a valve safety switch of the type disclosed in UK. patent specification No. 809,170. This switch would disconnect the anode supply from the Vaptron tube if there is an insufiicient level of cooling liquid in the boiler.

What I claim is:

1. In combination with an electron tube having an anode structure cooled by vaporization at its surface of a cooling liquid in which said structure is immersed, a boiler for containing the cooling liquid comprising an insulating container made of resin-bonded fiber-glass material and into the interior of which the anode structure extends.

2. In combination with an electron tube having an anode structure cooled by vaporization at its surface of a cooling liquid in which said structure is immersed, a boiler for containing the cooling liquid comprising an insulating container made of resin-bonded fiber-glass material, and a top cover for said container also made of resin-bonded fiber-glass material and having embedded metallic strengthening, the electron tube being supported through said top cover with its anode structure extending into the interior of the container.

3. An electron tube with boiler as claimed in claim 2, wherein said top cover has a central recessed portion defining an aperture bounded by an annular ledge, the tube having a mounting flange by which it is supported by said ledge.

4. In combination with an electron tube having an anode structure cooled by vaporization at its surface of a cooling liquid in which said structure is immersed, a boiler for containing the cooling liquid comprising an insulating container made of resin-bonded fiber-glass material, said container having a chamber portion for containing the liquid and into the interior of which the anode structure extends and an integral insulating mounting base.

References Cited in the file of this patent UNITED STATES PATENTS 2,556,616 Ellis June 12, 1951 2,909,696 Cooper Oct. 20, 1959 FOREIGN PATENTS 948,343 Germany Aug. 30, 1956

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