US 3634723 A
A traveling wave tube construction includes a plurality of dielectric rods about the periphery of a spiral delay line, which rods and delay line are accommodated within a metal vacuum shell. The rods are disposed in rounded angles, in lateral cross section, of a regular polygon and at least one of the rods is provided with spring means for providing a firm, but elastic, lateral positioning of the spiral system.
Description (OCR text may contain errors)
United States Patent  inventors Franz Gross;
Paul Kahl, both of Munich; Wolf Wiehler, Neubiberg, all of Germany ] Appl. No. 46,135
 Filed June 15, 1970  Patented Jan. 11, 1972  Assignee Siemens Aktiengesellschaft Berlin and Munich, Germany  Priority July 24, 1969  Germany I54] TRAVELING WAVE TUBE WITH A SPIRAL DELAY NE 11 Claims, 6 Drawing Figs.
 11.8. CI 315/35, 315/36, 315/393  1nt.Cl l-l0lj 25/34  Field of Search.... 315/35, 3.6, 39.3
 References Cited UNITED STATES PATENTS 3,374,388 3/1968 Huber 3 I 5/3.5 3,209,198 9/1965 Long et al 315/35 3,107,312 10/1963 Kennedy 315/35 2,784,340 3/1957 Coulson 315/35 3,271,615 9/1966 Washburn,.lr. 3 l5/3.5 3,227,913 1/1966 Disman et al. 315/35 Primary Examiner- Herman Karl Saalbach Assistant Exnminer-Saxfield Chatmon, Jr. Attorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: A traveling wave tube construction includes a plurality of dielectric rods about the periphery of a spiral delay line, which rods and delay line are accommodated within a metal vacuum shell. The rods are disposed in rounded angles, in lateral cross section, of a regular polygon and at least one of the rods is provided with spring means for providing a firm, but elastic, lateral positioning ofthe spiral system.
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TRAVELING WAVE TUBE WITH A SPIRAL DELAY LINE BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to a traveling wave tube with a spiral delay line, and particularly to a traveling wave tube with a spiral 'delay line which is disposed within a metallic vacuum shell between a plurality of parallel dielectric rods which are secured laterally by means of a noncircular shaping of the inner cross section of the vacuum shell.
2. Description of the Prior Art A great number of systems for mounting spiral delay lines within the vacuum shell of a traveling wave tube are known in the prior art whereby, in the interest of good heat dissipation from the spiral to the outer vacuum shell of the tube, the peripheral dielectric rods enclosing the spiral are frequently made to bear directly against the vacuum shell of the tube. However, the difficulty then arises to provide an impact-proof mounting of the spiral, the rods and the vacuum shell.
One possibility'to even out tolerances in mounting consists of choosing the dimension of the inner recess of the vacuum shell slightly smaller than the diameter of an imaginary circumference about the rods so that the spiral is mounted slightly deformed, rigidly, and under pressure in the vacuum shell whereby the initial pressure is chosen necessarily high so that it will not be abolished even if there are possible expansion differences due to heating during the operation of the tube.
A further possibility to provide an impact-proof mounting consists of soldering the spiral with the rods, and then the rods with the vacuum shell. In addition to the drawback of complicating production techniques with such an arrangement, there results the difficulty that either the soldering spots may tear due to possible expansion differences, or that the ceramic rods may crack.
- It is already known for traveling wave tubes with a spiral delay line mounted with dielectric rods and a vacuum shell consisting of glass, to first make the vacuum shell including a widening of the shell by means of heating and then shrinking the shell onto the rods, whereby the inner cross section of the vacuum shell becomes noncircular so that the rods are mounted within the vacuum shell in longitudinal grooves after cooling. This results in a good fixation of the apparatus in the lateral direction. As an example of such a construction, attention is invited to U.S. Letters Pat. No. 2,869,217.
The last-mentioned arrangement also has several difficulties or drawbacks including that the arrangement can only be realized with tubes within a vacuum shell made of glass and that it is not possible without great difficulty to extend the application to arrangements with a metallic vacuum shell. There is an additional difficulty, therefore, to absorb possible thermic expansion differences, particularly in a way that prevents the ap plication of excessive pressure to the spiral.
SUMMARY OF THE INVENTION This invention has the primary object to provide a traveling wave tube with a spiral delay line which, in addition to provid ing good heat dissipation from the spiral to the vacuum shell, always guarantees a firm and elastic mounting of the spiral system.
In achieving the foregoing primary object in a traveling wave tube of the aforementioned kind in line with the teachings according to the present invention, a recess is provided in the vacuum shell extending in the axial direction adjacent at least one of the dielectric rods, into which recess a spring is inserted which bears against the surface of the rod facing away from the spiral. The rods may thereby be mounted in axial longitudinal grooves provided on the inner surface of a metal vacuum shell.
In a further development of the invention it is provided that, during the selection of n-rods, the inner cross section of the vacuum shell is provided in essentially the shape of a regular polygon of n sides, whereby the rods are then arranged longitudinally of the traveling wave tube adjacent the intersections of the sides of the correspondingly formed n-sided prism.
To increase the contact surfaces of the rods with the vacuum shell, which provides for a better heat dissipation and for a decrease of the outer diameter of the traveling wave tube, the edges of the polygon-shaped inner cross section may be rounded. According to a preferred embodiment of the invention, three rods are provided, so that the cross section of the vacuum shell has an inner surface which defines essentially an equilateral triangle.
As a further development of the invention, it is provided that the spring and the rod associated therewith have a metal plate arranged therebetween, which plate is essentially the width of the longitudinal groove. In addition to the metal plate and the rod, the centering means for the rod with respect to the groove is provided, in one embodiment the centering means being in the form of two circular centering rods which are inserted into the recess. The metal plate, preferably in the shape of a molybdenum strip, serves, among other things, to close off the line radially with respect to high frequencies so that the high'frequency chamber becomes smaller.
A sheet strip which has been bent in a meander-configuration in its longitudinal direction may serve as the aforementioned spring, or a straight elastic metal tube of round or oval cross section may be provided as the spring. However, it is preferable in a further embodiment of the invention that the spring is a sheet strip with a cross section which has been bent essentially U-shaped, such an embodiment of the spring does not only provide that the spring, independent of the length of the arrangement, can be inserted without difficulty, but it has also the additional advantage, that due to the independence of the free spring shanks which are laterally free to shift, subsequent shiftings at individual points along the arrangement can be evened out.
According to a further advantageous development of the invention, it may be provided that the spring is tensioned along the recess by means of deformation of the vacuum shell at a number of points. Due to this technique it is possible to produce the spring first without tension and thus, without any resistance, to insert the spring into the recess and to produce the entire spring tension only be means of deformation in the vacuum shell. Besides this construction and assembly technique, however, it is also possible to increase the tension of a spring which is inserted free of tension by providing deformations of the vacuum shell.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention, its organization, construction and operation will be best understood from the following description taken in conjunction with the accompanying drawings in which parts that correspond to one another have been provided with the same reference characters in the different figures, and in which:
FIG. 1 is an elevational view of a portion of a traveling wave tube shown in cross section taken substantially along the line H of FIG. 2;
FIG. 2 illustrates a lateral cross section of the apparatus in FIG. 1 taken along the lines II-II;
FIG. 3 is a lateral cross section of apparatus similar to FIG. 2 illustrating a tubular spring construction;
FIG. 5 is an elevational view of apparatus similar to that shown in FIG. 1 and illustrated in cross section taken substantially along the line VV of FIG. 6, particularly illustrating a tubular spring construction and a plurality of bores for accommodating a deforming punch to adjust spring tension; and
FIG. 6 is a lateral sectional view taken along the line VI- VI of FIG. 5, particularly illustrating the technique of deforming the metal vacuum shell for adjusting spring tension.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to FIGS. 1 and 2, it can be easily recognized that the traveling wave tube comprises a metallic vacuum shell I which has in cross section a triangular-shaped innersurface 2. A plurality of dielectric rods 3, 31 are provided about the periphery of a spiral l and are mounted along the edges of the triangular inner recess which have been rounded in this particular embodiment for better heat dissipation and smaller diameter of the apparatus.
A groove 4 is provided in the vacuum shell adjacent at least one of the dielectric rods, here the upper rod 31, which groove extends in the axial direction and serves for accommodating a spring 5 which bears against the adjacent rod 31. In the particular embodiment according to FIGS. 1 and 2, this bearing of the spring 5 on the rod 31 is effected by way of a metal plate 6 and a pair of rounded centering rods 7 which are positioned laterally with respect to the rod 31 so that the rod 31 is arranged between the centering rods 7. However, the spring might, bear directly on the rod 31.
FIG. 3 illustrates a cross-sectional view similar to that of FIG. 2 in which a metal tube 51 is provided as the spring in the place of the meander-shaped sheet strip 5. The metal tube 51 is slotted continuously along its length for flecture.
A preferred embodiment of the spring in the shape of a sheet strip 52 with a cross section that is substantially U- shaped, is illustrated in FIG. 4. A metal plate 6 is employed in this embodiment for high-frequency containment and includes a shaped portion 6 to serve for centering the upper rod 31.
The metal plate 6 could be dispensed with so that the spring 52 (with a decreased depth of the longitudinal recess or rather with a corresponding enlargement of the spring itself) would bear directly against the rod 31. In the case of a direct bearing of the U-shaped spring 52 against the rod 31, the spring is preferably turned over 180 when inserted into the groove 4 so that the two free shanks 53 of the spring 52 bear against the rear wall 41 of the longitudinal recess or groove 4.
With the aid of FIGS. 5 and 6, an arrangement is illustrated wherein the spring may be accommodated with or without pretensioning, the spring being inserted in the longitudinal groove 4. The tension of the spring is then produced, or increased, after mounting it by means of deformation of the vacuum shell. This technique, in addition to facilitating mounting, has the advantage that essentially larger spring pressures can be produced. To improve the deformation and mark the deformation points, bores 56 are prebored into the shell 1 for receiving an indenting tool 55, the force of which provides the desired deformation.
The invention is not limited to the illustrated sample embodiments. In addition to the possibility of the selection of more than three rods, it is for example possible to arrange longitudinal recesses for the accommodation of a spring behind several of or even all of the rods. It is also not necessary, as has been mentioned hereinbefore, that the inner cross section be triangular, but also a circular inner cross section could be selected which, according to the symmetric arrangement of the rods, has axial longitudinal grooves provided for the mounting ofthe rods.
Many changes and modifications may be made of the invention without departing from the spirit and scope thereof, and it is to be understood that we wish to include within the patent warranted hereon all such changes and modifications as may reasonably and properly be included within the scope of our contribution to the art.
What we claim as our invention is:
l. A traveling wave tube comprising an elongate metallic vacuum shell including a regular polygon cross section inner surface, a spiral delay line disposed within said vacuum shell, a plurality of parallel elongate dielectric rods of circular cross section spaced about and abutting and holding said delay line, said regular polygon cross section inner surface having arcuate-shaped angles conforming to the circular shape of said rods, some of said rods disposed in the angles and bearing against the arcuate shape thereof and the respective adjacent sides of the polygon to increase contact and promote heat dissipation, groove means in said inner surface adjacent at least one of said angles and adjacent at least one of said rods and bias means disposed in said groove means for urging sai one rod against said spiral delay line including an elongate spring disposed in and longitudinally of said groove means, and centering means disposed in said groove means between said spring and said one rod for centering said one rod in response to the force of said spring.
2. A traveling wave tube according to claim 1, wherein said inner surface in lateral cross section forms a triangle and said three rods are individually disposed in corresponding angles of said triangle.
3. A traveling wave tube according to claim I, wherein said centering means comprises a metal strip having a width substantially equal to the width of said groove means, said strip disposed between said spring and said rod.
4. A traveling wave tube according to claim 1, wherein said centering means comprises a metal strip disposed between said spring and said dielectric rod and having an arcuateshaped surface for receiving a portion of said rod.
5. A traveling wave tube according to claim 1, wherein said biasing means includes a metal strip disposed against said spring, and said centering means includes a pair of centering rods disposed between said strip and said dielectric rod for centering said rod therebetween.
6. A traveling wave tube according to claim 1, wherein said biasing means includes an elongate meander shaped spring.
7. A traveling wave tube according to claim 1, wherein said biasing means includes an elongate metal strip having a U- shaped cross section.
8. A traveling wave tube according to claim 1, wherein said biasing means includes an elongate elastic metal tube.
9. A traveling wave tube according to claim 1, wherein said biasing means includes an elongate elastic metal tube having a longitudinal slot therein and a oval cross section.
10. A traveling wave tube according to claim 1, wherein said biasing means includes an elongate elastic metal tube having a circular cross section.
11. A traveling wave tube according to claim I, wherein said metallic shell includes spaced-apart bores therein for receiving a tool to provide deformations along said groove means for tensioning said spring.