US 3095037 A
Description (OCR text may contain errors)
June 25, 1963 H. BOHM 3,095,037
AIR COOLER FOR POWER TUBES Filed June 15, 1959 9 )AMM' j .r/Mev United States Patent 3,095,037 AIR COOLER FOR POWER TUBES Helmut Biihm, Freiburg, Germany, assignor to Miwag Mikrowellen A.G., Basel, Switzerland Filed June 15, 1959, Ser. No. 820,337 Claims priority, application Germany June 14, 1958 2 Claims. (Cl. 165-47) The present invention relates to arrangements of cooling fins for electron tubes with metallic body (exterior anode), especially of the magnetron type and its object is to provide an efficient cooling at minimum expense by a special arrangement and structure of the cooling fins used.
It is well known to cool an electron tube by suitably arranging cooling fins on said electron tube and direct an airflow on said cooling fins. The rate of flow necessary depends upon the total cooling fin area and the separation of neighbouring cooling fins. Arrangements using circular cooling fins with their planes perpendicular to the axis of the electron tube with their inner edges in direct contact with the electron tube body (or exterior anode) in such a way as to form a number of rings around the electron tube body are known. In this way individual cooling fins with spacers between them form a package which is then slid over the electron tube proper or soldered to it. Other arrangements already known make use of radial cooling fins parallel to the axis of the electron tube with the cooling fins forming straight, curved, or angled planes. Typical examples of the both arrangements are shown in U.S. Patent 2,289,984.
With both arrangements mentioned above cooling fins must have a certain minimum separation and as electron tube bodies (or exterior anodes) have rather small dimensions only a limited number of cooling fins can be provided in this way. Thus the total area is small, too, calling for a high rate of airflow. This high rate of airflow applied to closely arranged cooling fins causes noise in addition to the noise of the blowers used.
An object of the invention is to provide an arrangement of cooling fins for electron tubes with metallic body (or exterior anode), especially of the magnetron type, in which cooling fins plus spacers between them form a package in such a way that their planes are perpendicular to the electron tube axis with said package in direct contact with the electron tube body.
Typical of this invention are fan-shaped cooling fins with their outer edges lying on a cylinder (FIG. 1). By this fan-shaped arrangement of cooling fins the total cooling area is appreciably enlarged with constant values for the length of thermal conduction paths and accompanying reduction of resistance ofiered to the airflow and nearly equal dimensions as compared with already known arrangements. By optimizing the utilization of the available surface of the electron tube body (or exterior anode) for producing a thermal contact between electron tube and cooler an optimum thermal conduction path is provided. In this way the great advantage of the invention disclosed is seen, as now the airflow produced by a normal coolingfan is suflicient. Cooling has become more economical and nearly noiseless.
In a preferred form of this invention the package is divided into two groups with both of them fastened to the electron tube body under mechanical stress. In this way the cooler can be arranged using building-blocks with the latter put together with easily removed means and the whole package formed in this way fastened to the electron tube body. In this way damaged parts can be easily replaced The arrangement disclosed in this invention is given in the following figures. FIG. 1 shows the arrangement fastened to the electron tube body looking perpendicular on the electron tube axis; FIG. 2 shows the same arrangement looking parallel to the electron tube axis. FIG. 3 shows a cross-sectional view in a plane normal to the axis of the cylindrical body. In the example shown the cooling-package is divided into two groups because of other RF-or evacuating means fastened to the tube envelope and leading to the inside.
The package-groups 1 and 2 are fastened to the electron tube body by means using mechanical stress in the following manner: A thin plate of metal (or spacer) 5 with thickness equal to the airgap 3 between the two packagegroups is inserted into said .airgap 3 as far removed from the electron tube body (or exterior anode) 4 as possible. This metal plate 5 thus forms a sort of pivotal point for the mechanical fastening means. Into both packagegroups 1 and 2 an axle 6 close to the electron tube body 4 is inserted. By means of two stretching-screws 7 between the axles 6 both package-groups are tightened. The latter turn around the inserted metal plate and enclose the electron tube body like a bracket. To get a very tight contact each package-group has to embrace more than half the electron tube body. The inner edges 8 of cooling fins 9 and the metal spacers 10 are tightly pressed against the electron tube body. In FIG. 1 the permanent magnets are represented by 11 and 12 is a magnetic short-circuit. In FIG. 2 the permanent magnets and the magnetic shortcircuit are omitted to provide a better View. 13 is the RF-output, 14 are the heater supporting connections, and 15 is the connection used for evacuating. The airflow is in a direction equal to the viewing direction in FIG. 1.
It may be sufficient to use the above mentioned method for fastening the cooler to the electron tube or the packages can also be soldered directly to the electron tube body. As shown in FIG. 3, the fins 9 are soldered directly to the body as at :16. In practice greater mechanical strength and rigidity as well as better thermal contact provided by direct soldering will be preferred against the easy replacement offered by the alternative assembly method mentioned above. The cooling fins used are all or groupwise cut to equal size. They can be pre-assembled together with the appropriate number of spacers with the help of a calibre and finally riveted. The cooling-fin groups thus formed may then be fastened to the electron tube body as described above.
What I claim is:
1. Apparatus for cooling a magnetron of the type having a generally cylindrical body and having connecting means extending outwardly from a relatively small portion of said cylindrical body comprising:
two packages of cooling fins mounted on and extending away from said cylindrical body, each of said fins in each of said packages having an inner edge, an outer edge and lateral edges; an inner portion of each of said fins extending perpendicularly to the main axis of the cylindrical body;
the inner edge of each of said fins conforming to the surface of a portion of said cylindrical body;
the arcuate length of the inner edge of each of the fins in one of the packages being less than the arcuate length of the inner edge of each of the fins in the other pack-age;
the remaining portions of each of said fins as bounded by said outer edge, said lateral edges and the outer end of said inner edge thereof being spread apart from each other in a fanlike manner so as to define wedge-shaped spaces therebetween for the straight passage of a coolant air stream in a direction perpendicular to the axis of said cylindrical body;
said two packages being arranged whereby the inner edges of said fins substantially encompass said cylin- 3 drical body with the exception of said outwardly exwherein the sum of the 'arcuate lengths of said conformtending connecting means; ing inner edges of said fins in said two packages is greater means defining a pivot member lying in a plane parallel than one-half the circumferential length of said cylindrito the axis of-said cylindrical body and spaced outcal bodyoutef Surface Cross-Sectionwardly of the outer surface of said cylindrical body, 5 said packages being in contact with said pivot mem- References Cted m the file of this Patent h UNITED STATES PATENTS and means for drawing said packages together about 37 3 3 H i Dec 3 1901 said pivot to draw said conforming inner edges of 317,976 Kinraide Apr, 7,- 90 each of said fins into intimate contact with said cylin- 10 1,271,246 Recklinghausen et al. July 2, 1918 drical body. 1,869,637 Walworth Aug. 2, 1932 2. Apparatus for cooling a magnetron as in claim 1 2,422,819 Becker June 24, 1947