US2535669A - Electric discharge tube and means for cooling the anode thereof - Google Patents

Description

Dec. 26, 1950 R CLAY 2,535,669

ELECTRIC DISCHARGE TUBE AND MEANS FOR COOLING THE ANODE THEREOF Filed Oct. 21, 1946 ,2 Sheets-Sheet 1 FIG. /0.

INVENTOR I P/E rm HAJO pun; Deceased I 6y JOR/S DANIEL HElJL(GR$,Adm/'nisfraf0r ATTORNEY.

Dec. 26, 1950 CLAY 2,535,669

ELECTRIC DISCHARGE I'UBE AND MEANS FOR COOLING THE ANODE THEREOF Filed Oct. 21, 1946 2 Sheets-Sheet 2 IILUHIIIIIIII 1, E 2 g 2 2q J Z 2 E1 1 E 1 IX ks 1 a E /75 5 .2 m/vs/vrw? P/EZ'ER 114.10 CLAY Deceased 40578 DAN/EL HE/JL/GERS, nammi'srrmr ATTORNEY Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE ELEcrRIcn sciiAnGE TUBE AND, MEANS FOR COOLING THE ANODE' THEREOF Application October 21, 1946, Serial No. 704,691 In the Netherlands August 7, 1-945 Section 1, Public Law 690,, August 8, 1946 Patent expires August 7, 1965 2 Claims.

having a cylindrical cooled wall or wall portion are known. As a rule, these are electric discharge tubes of high power in which the anode is cooled. It has been proposed to provide such anodes with cooling fins. It has been found in practice that, in order to obtain the cooling desired, it is nec essary to give these coo-ling fins comparatively large surface areas. This involves that the fins or ribs have a considerable length in a radial direction. Apart from the large space occupied by the Whole construction and its considerable weight, another drawback is that a material temperature drop occurs in the fins and further, due to the large size, a high electrical capacity ensues which is highly undesirable.

In order to economize in weight, attempts have been made to make the fins of aluminium in-' stead of copper Which is to be considered as the most suitable material because of its high thermal conductivity. In this case, a saving in weight is obtained, but since aluminium has a lower heat conductivity than copper, the temperature drop in the fins increases, due to which the cooling becomes less effective.

In the form of construction according to the present invention all of the said drawbacks are obviated. Shorter fins suffice, with the result that the drop of temperature is smaller andthe whole construction becomes so much less voluminous that even with the use of copper a re;ative-:y small weight is attained. Owing to the small drop intemperature the load of the part to be cooled, for example an anode, may be high. Moreover, the electrical capacity of the anode provided with a cooler according to the present invention becomes materially lower as compared to the wellknown constructions owing to the smailer size of the former.

Finally the constructionaccording to the invention may be used for anodes having a con siderable length. This is not the case with the conventional constructions.

When using cooling fins extending in an axial direction, the construction according to the present invention has some further advantages over the conventional constructions. Owing to the smaller size the total thermal conductivity in an=axial direction of the Whole system of the anode/coder is lower than in the constructions hitherto used. The great advantage is that at the anode end, where the dissipation is low, the temperature is materially lower than at the area where the dissipation is a maximum. In discharge tubes having a glass envelope" and metal anode the metal-to-glass seal has, in general a minimum dissipation, with the result that this area,- in the form of construction according to the invention, has alower temperature than the other parts of the anode, owing to which on the one hand the risk of cracking, leaks or the like is highly reduced and on the other hand operation at a higher anode temperature is possible with-' out incurring the risk of the metal-to-glass seal becoming too hot.

The electric discharge tube according to the invention exhibits the feature that in the immediate vicinity of the wall to be cooled there are means to bring a cooling medium through acer tain number of parallel-connected paths, each having a length of A; at most of one of the dimen sions of this wall, in intimate contact with this wall or with heat exchanging means on this wall, the'surface part of this wall, where the medium is in intimate contact with this wall or with heat exchanging means on'this' wall, amounting to at least half the total surface area of the saidwall.

As a rule, the said paths will have a maximum length of of the smallest dimension of the wall portion to be cooled. Sometimes however, for example when the two dimensions (diameter and height) of the wall to be cooled are much the same, the length of these paths for the medium may bechosen to exceed one third of the smaller dimension of the wall-but smaller than one third of the larger dimension of the wall, without any deleterious effect with respect to the resistance of flow of the medium. The length of the paths for the medium may, as an a'ternative, be given the last-mentioned value if the viscosity of, the medium has a very low value. If the medium; during the cooling of the wall or the wall portion intima'tely'contacts only or substantially with the heat exchanging means on the wall and consequently not with the wall itself, the surface of the wall portion which is provided withithe s e means amounts at least to half the total surface of the wall. In the case under consideration the expression cylinder has to be understood to mean a surface which is formed by moving a line paralel with itself along a closed cont'nucus or broken line or a surface at least approximately havingthis form. l A

To reduce the resistance experienced by the medium, the exchanger according to t em s tion comprises a large number of short parallelconnected gas ducts. As a result thereof, the speeds of the gas are small which is contributive to the exchange of heat. To prevent the current of heat from attaining an undue value per surface unit, we proceed in such a manner, in designing the heat-exchanger so that over at least half the surface area of the cylindrical wall the medium is in intimate contact with the wall or heat-exchanging means on this wall. The wall, with which the medium is in heat-exchanging contact, may either be smooth or, as has already been stated, comprise heat-exchanging means which may, for instance, consist of projecting parts such as ridges. Ridges for increasing the transfer of heat are known per se. Owing to the excellent properties of the heat exchanger according to the invention, however, the projecting parts may be shorter than with the conventional constructions. Apart from the advantage of saving material, thus obtained in general, the additional advantage is secured that the capacity of the metal parts of the discharge tube is much smaller than in the case of using the hitherto known constructions.

In definite cases, when proceeding according to the present invention, the usual liquid cooling, which usually involves numerous complications, may be replaced by cooling by means of gas e. g.

air

According to one form of construction of the discharge tube according to the invention the wall portion to be cooled is provided on the outside with a large number of projections, the paths for the cooling medium extending in between these projecting parts partly joining a channel system, in which a pressure is maintained which is different from that of the surroundings of the tube. Consequently, in this form of construction the cooling medium is caused to circulate artificially. It is, for example, possible to arrange a fan in the said channel system. Such a form of construction has the special advantage that the cooling of the wall portion concerned is particularly effective. Such an artificial circulation will practically always be used in high-power tubes. The discharge tube may be provided with an inlet and outlet channel system, or only with one channel system for the cooling medium, which in this case serves solely for supply or fo the outlet. In this case the outlet or the inlet for the cooling medium opens out into the surroundings of the tube According to one form of construction of the discharge tube according to the invention the wall of the channel system is formed by partitions located around or between the projecting parts on the wall portion of the tube to be cooled.

It has already been pointed out that when making use of the recognitions on which the invention is based, a cooling system is obtainable which has a much smaller size than that which is used for discharge tubes that are cooled according to the hitherto usual methods. In the case of a discharge tube having a comparatively small power it will generally be possible, according to the invention, to make the tube and the associated cooling system form a constructional Lmit. With discharge tubes for higher powers the constructional association of discharge tube and corresponding cooling system, consequently consisting of the means forming the paths for the medium and of one or more channel systems, will not always be feasible. In this case the tube and the said parts may consist of some few structural parts. Thus for instance, it may be imagined that the part to be cooled of such a discharge tube, usually the anode, is designed in the conventional way and is housed in a suitably proportioned cavity of the cooling system. In the last-mentioned case the component parts of the cooling system are preferably made from electri cally insulating material to prevent the electrical properties of the tube from being adversely affected. If, in contradistinction thereto, the tube and the cooling system form a constructional unit, the small size of the cooling system often permits also the parts of the cooling system to be made from metal, for instance copper.

As an alternative, the projecting parts e. g. ribs or fins may be fastened to the anode, the channels for the inlet and outlet of the cooling medium being made of separate structural parts. In this case, the ribs or fins will frequently be made of metal, for instance copper, whilst the walls of the channels may consist of insulating material.

If, for instance, a very large quantity of cooling medium has to be passed per time unit over a very great length of the part of the discharge tube to be cooled along the portion of the tube to be cooled, so that there would be a likelihood of the system of channels having a very large radial size, it is advisable, according to another form of construction of the discharge tube according to the invention, to provide the tube with more than one system of channels, which systems are interconnected in parallel.

From the foregoingit appears that the invention permits the cooling system of a discharge tube to be given a much smaller size than it has hitherto been possible. Furthermore cooling by means of gas, will now be possible in many cases where a liquid cooler ha hitherto been used for a discharge tube. Owing to the small size of the coolingsystem its heat capacity is, of course, also low. It is possible, for instance, that due to stoppage of current from the mains for one reason or another, the fan forcing the cooling medium through the cooling system stops. Upon cut-off of the voltage, the discharge tube will also be put out of action, it is true, but therein such a quantity of heat may be accumulated that this heat, upon finding its way to the coolingsystem, damages the latter, for instance due to the melting of soldered joints or the like. Threfore, in an installation comprising one or more cooled discharge tubes according to the inventicn, it is advisable to provide means for making the current of cooling medium circulate for some time after the discharge tubes have been put out of action and irrespective of the fact that there is a voltage available or not. This may, for instance, be realised by fitting on the shaft of a fan a fly wheel having such a mass as to realise the purpose aimed at.

According to the invention the parallel-connected paths for the cooling medium along the Wall portion of the tube to be cooled or along the heat exchangingmeans on this portion of the tube may extend substantially at right angles to the axis of the tube. structurally this may, for instance, be effected by providing on the portion of the tube to be cooled, a number of annular plates which are spaced apart from one another. As an alternative one or more metal strips may be wound edge-on around this portion of the tube and fastened thereto. In order to form the channel systems in these constructions a number of preferably tri-angular partitions extending substantially parallel with the axis of the tube may, according to the invention, be fitted against .5 the outer walls of the members forming on the tube the parallel-connected paths for the medium, the said partiticns cooperating with other partitions in such a manner as to form a number of channels for the supply of the cooling medium and a number of channels for the outlet thereof. The tube with the partitions be connected to a supply and an outlet duct for the cooling medium. In such a case, a fan causes the ccoling medium to flow along th portion of the tube to be cooled. As a rule it is more efficient to place the fan in a delivery pipe (and consequently not in a suction pipe), because the volume of the cold cooling medium, Which has consequently not yet been heated by the heat given cit by the tube, is much smaller than the volume of the cooling medium heated by the tube.

The partitions which consequently, according to the last-mentioned embodiment of the invention, may extend substantially parallel with the axis of the cooled portion of the tube may then be shaped as an isosceles triangle and are positioned in such a manner with respect to the axis of the tube, that the bisector of the vertical angle of this triangle intersects the axis of the tube perpendicularly. This shape of the partitions generally permits a very small surface area of the partitions, as result of which the tube com prising such a cooling system has a low electrical capacity. For this reason this construction is particularly suitable to make the partitions and the portion of the tube to be cooled form a constructional unit. In this case the partitions are usually made from metal.

If a discharge tube, in which the wall portion to. be cooled is very large, has to be equipped with two systems of channels for the supply or outlet of the cooling medium,as has been set out above, it is advisable, according to a further embodiment. of the invention, to connect two of such channel-systems to a common supply or outlet pipe. this pipe surrounding the tube as a cylindrical casing.

According to the invention it is also possible to make the parallel-connected paths for the medium extend substantially parallel with the axis of the portion of the tube to be cooled.

The means forming these paths m y consist of one or more staggered metal strips, which are secured, for instance by soldering, to the portion of the tube to be cooled. About these members, which consequently form the parallel-connected paths for the medium to be cooled, a certain number of chambers may be formed, according to th invention, which alternately contact with the supplyand the outlet for the cooling medium. In this case thewalls of the chambers extending normally to the axis of the tube may consist of rectangular, preferably square, plate-shaped members. According to the invention the partitions constituting the outer walls of. the chambers may consist of bent parts of the plate.- shaped members. Against the outer walls of the chambers may be placed two supply and/or two outlet ducts for the cooling medium.

It has still to be pointed out that the cooling system, according, to the present invention, is-not only suitable for cooling transmitting tubes-but also for X-ray tubes, rectifying tubes and seen, in short whenever a, discharge tube has to be cooled intensively In order that the invention may be clearly understood and readily carried into effect, it will now be de cribed more fully with reference to the accompanying drawing and Figure 1 is a cross-sectional view of a segment of one nd portion of an anode cooler arrangement in accordance with the invention, the section being taken on a plane normal to the axis of the anode.

Fig. 2 is a view in side elevation of a system comprising the inventive concept illustrated in Fig. 1;

Fig. 3 is a cross-section taken on lines X'-X of Fig- 2;

Fig. 4 is a vertical cross-section of a modification of the invention applied to an anode, the section being taken on a line IV-IV indicated in Fig.

Fig. 5 is a cross-sectional view on. lines IflI-XII of Fig. 4;

Fig. 6 is a vertical cross-section of a still further modification of the device shown in Fig. 2;

Fig. 7 is a cross-sectional View of a portion of another form of cooling system applied to an anode in accordance with the invention, the section being taken in a radially disposed plane;

Fig. 8 is a cross-sectional view of a system incorporating the invention of Fig. 7;

Fig. 9 is a cross-section on lines IX-IX of Fig. 8;

Figure 10 is a perspective viewof a section: of the device cut from Figure 8 at X-X with part of the casing 11 broken away to better illustrate the cooling medium flow.

In Fig. 1 reference numeral 4D indicates, a section of a wall of an anodeto which is attached by soldering or other means an annular plate section 4|. To the outer edge of the plate are secured partitions 42. Between the partitions t2 are formed ducts 43 which serve for the supply and outlet of a cooling medium the. paths of which are indicated by arrows. The length. of the path of the cooling medium in which. heat transfer takes place is very short in comparison with the dimensions of the surface to be cooled which may be seen by reference to the embodiment of the invention shown" in Fig-i 2'. In Fig 2 the anode 44 is provided with a large number of annular plates 45 which have interstices having a height 1). Each of these interstices is a portion of the path for the cooling medium, and thus: a very large number of short parallel: paths are provided for this cooling medium. E-a'chot these paths is connected to radial ducts 45 0f sheet metal which ducts are positioned in aligned recesses in plates 45 along four lines which extend parallel to the axis of the anode. These ducts lead coolingmedium away from the interstices through elongated slits 4! provided in the side walls of the ducts and extending substantially thelength thereof. The ducts 4t each gradually increase in radiusdown the length of. the anode 44 and finally terminate in a commonpipin-gr H8, in which a low pressure is maintained to 'faciliftate the movement of the medium past the anode plates-44 through theslits 41 inthe ducts 45' and down them towards the larger ends thereof to the outlet duct 48. In Fig, 3*the ducts 45* are shown to contact the anode 44 as-they are positioned in the aforesaid aligned recesses. The course of flow of the mediumacross-the plat 45 and through the" slits 4T inthe ductile is indicated by arrows'in Fig. 3;

Inthe construction-shown in- Figs. 4 andfiathe paths; through which the cooling" medium contacts with the partsof thetube:tobemoolemare still shorten. Similarly to the construction shown in Figs. 2 and3 the anode 5UIt0'b'e cooled is furnished witha large number of 511 that are spaced apart from one another. To the outer edge of these rings are secured the triangular partitions 52 which are shown in side view in Fig. 4. These partitions form a certain number of radial ducts about the anode. These ducts are alternately closed at their sloping sides 53 by plates I53 shown in Fig. or at the bottom I54 by plates 54 shown in cross-section in Fig. 4. In Fig. 5 the ducts closed at the top ar shaded. The ducts which are open at their sloping sides serve for the supply of air. The cooling air, upon entering the space between two rings 5!, moves in a radial direction as shown in Fig. 5, and enters the space between two partitions 52, which is closed at the side by a plate I53 but communicates at the bottom with the outlet duct 55, in which is maintained a sub-atmospheric pressure by means of a fan.

The construction shown in Fig. 6, in which the anode 60 to be cooled is very long in proportion to its width, comprises two parallel-connected systems of ducts for the outlet of the cooling air. One system is defined by cooperation between the partitions 6! while the other is defined by several between the partitions 62. Similarly to Fig. 4, the spaces between the partitions 6| and the spaces between the partitions 62 are alternately closed by other partitions at the sloping top and bottom sides thereof. The spaces between the partitions 6! which are open at the sloping bottoms thereof and the spaces between the partitions 62 which are open at the sloping tops thereof communicate with a common outlet duct 63 via a cylindrical casing 64 which surrounds the anode 66. Owing to the fact that the partitions BI and 62 are shaped as isosceles triangles of which the bisectors of the vertical angles thereof out the axis of the anode perpendicularly, the partitions 6i and 62 may be given a small radial dimension. This is advantageous in conjunction with reducing the electrical capacity of the tube.

In the construction of the cooling system for a discharge tube as shown in Figs. 7, 8, 9 and 10, the direction of the currents of the cooling medium, in performing the cooling action is substantially parallel with the axis of the anode, in contradistinction to what takes place in the construction shown in Figures 1 to 6. The principle of this cooling method is illustrated in Fig. '7, in P which the axis of the anode it is represented by H--II. This anode is furnished with a large number of radial ribs H which extend substantially parallel with the axis HH. These ribs may, for instance, be obtained by soldering a series of metal strips to the anode as at it. The outer edge of these ribs is adjoined by a certain number of plates 73, the spaces between these plates alternately acting for the supply and outlet of the cooling medium. This is illustrated in Fi '7.

The supply and outlet for the cooling medium can be realised in simple manner as shown in Figs. 8, 9 and 10. Around the ribs H are provided a certain number of square plates is which are spaced apart from one another by a distance q. The spaces between two plates are alternately closed at the sides 1 and s or t and u as clearly shown in Figs. 9 and 10. The sides t and u are joined by the ducts 14 which are formed by housing 11 as best shown in Figures 8 and 10. The ducts M consequently communicate with these spaces between the plates 13, of which the sides It and u are open. If a sub-atmospheric pressure is maintained in the duct '15 to which are connected the ducts 14, this results in that, as shown in Figs. 9 and 10, air is aspirated from the surroundings of the tube into the chambers of which the sides r and s are open, finds its way between the ribs H, performs its cooling action between them and moves axially relatively to the anode, thus entering the spaces between plates 13, which are open at the sides t and u, and is subsequently sucked oif through the ducts M into the outlet duct 15. In the case under view, similarly to the previous forms of construction, the plates 73 may consist of metal or insulating material and may or may not be rigidly secured to the anode.

What is claimed is:

1. An electric discharge tube having a cylindrical cooled anode wall and means for cooling the anode by heat exchange with an external cooling medium, said means including a plurality of parallel cooling elements secured in heat exchange relationship to the wall and extending in the direction of the main axis of the cylindrical wall to form longitudinal passageways between adjacent elements, means forming a plurality of chambers along the lengths of said parallel elements, said means comprising a plurality of rectangular plate-shaped members which extend normally to said axis, each of said chambers being open to said passageways between said plates, alternate chambers each having a pair of cooling medium inlets at opposite ends thereof, the remaining chambers each having a pair of cooling medium outlets at opposite ends thereof, the cooling medium inlets being aligned along a plane parallel to said axis, the cooling medium outlets being aligned along another plane parallel to said axis, said first plane being at right angles to said second plane, and a pair of ducts, each of said ducts being located at one of said opposite ends of said remaining chambers, and being connected to said outlets.

2. An electric discharge tube having a cylindrical cooled anode wall and means for cooling the anode by heat exchange with an external cooling medium, said means including a plurality of parallel cooling elements secured in heat exchange relationship to the wall and extending in the direction of the main axis of the cylindrical wall to form longitudinal passageways between adjacent elements, means forming a plurality of chambers along the lengths of said parallel elements, said means comprising a plurality of rectangular plate-shaped members which extend normally to said axis, each of said chambers being open to said passageways between said plates, alternate chambers each having a pair of cooling medium inlets at opposite ends thereof, the remaining chambers each having a pair of cooling medium outlets at opposite ends thereof, the cooling medium inlets being aligned along a plane parallel to said axis, the cooling medium outlets being aligned along another plane parallel to said axis, said first plane being at right angles to said second plane, and a pair of ducts, each of said ducts being located at one of said opposite ends of said remaining chambers, and being connected to said outlets, and a common exhaust duct connected to both said pair of ducts.

JO'RIS DANIEL HEIJLIGERS, Administrator of the Estate of Pieter Haao Clay,

Deceased.

(References on following page) I REFERENCES CITED Number The following references are of record in the 23610 file of this patent: UNITED STATES PATENTS 214311157 Number Name Date 2,434,676 1,565,969 Spiro Dec. 15, 1925 2,455,957 1,978,424 Gebhard Oct. 30, 1934 2,166,685 Henderson et a1. July 18, 1939 2,289,984 Mouromtsefi et a1. July 14, 1942 1 Number 2,324,034 Skene July 13, 1943 514,651

Name Date Blanche Nov. 7, 1944 Young Aug. 20, 1946 Spender Apr; 22, 1947 Zelinka Nov. 18, 1947 Spender Jan. 20, 1948 Spencer Dec.. 14, 1948 FOREIGN PATENTS Country Date Great Britain Nov. 14, 1939

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