US 3271614 A
Description (OCR text may contain errors)
Sept. 6, 1966 J. M. SCOTT 3,271,614 ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PROVIDING A RADIAL FORCE UPON SUPPORT RODS Filed Aug. 18, 1961 5 Sheets-Sheet l WITNESSES INVENTOR John M. Scorr fl/a yfi v m ATTORNEY Sept. 6, 1966 J. M. SCOTT 3,271,614
ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PROVIDING A RADIAL FORCE UPON SUPPORT RODS Filed Aug. 18, 1961 5 Sheets-Sheet 2 Fig.4.
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Sept. 6, 1966 J. M. SCOTT 3,271,514
ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PROVIDING A RADIAL FORCE UPON SUPPORT RODS 5 Sheets-Sheet 5 Filed Aug. 18, 1961 United States Patent 3,271,614 ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PRQVHDING A RADIAL FORCE UPON SUPPORT RODS John M. Scott, Linthicum Heights, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Aug. 18, 1961, Ser. No. 132,371 6 Claims. (Cl. 315-3.5)
This invention relates to electron discharge devices and more particularly to microwave tubes of the traveling wave type.
Discharge devices of the class described herein generally comprise an elongated evacuated envelope with an electron beam producing means disposed at one end thereof for the production and projection of an electron beam along a predetermined path within the envelope and a slow wave propagating means, usually comprising an electrical conductor in the form of a helix, for propagating electromagnetic waves along the length of the envelope in an interacting relationship with the electron beam. In relatively high powered tubes of this type, considerable heat is generated within the helix by beam interception and radio-frequency losses. As the temperature of the helix rises, so too does its resistance with a resulting diminishment in the radio-frequency power output of the tube. Further, in some tubes, this heating effect may be so great as to completely destroy the helix or other slow wave structure. It is essential, therefore, that adequate means be provided for removing the generated heat from the helix.
Accordingly, it is the general object of this invention to provide a new and improved traveling wave tube.
Another object of this invention is to provide an improved envelope structure for a traveling wave tube.
A further object of this invention is to provide a novel multiple segment envelope for supporting the slow wave structure of a traveling wave tube in an eflicient heat transfer relationship with the envelope.
Briefly, the present invention accomplishes the above cited objects by providing a multiple segment envelope in a traveling wave tube for supporting the slow wave propagating means. This structure permits the adjustment of the slow wave structure within the envelope and ensures better contacts between the helix, support rods, and envelope to provide a more efficient heat transfer path from the helix to the envelope.
Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.
For a better understanding of the invention, reference may be had to the accompanying drawings, in which:
FIGURE 1 is a schematic representation showing a traveling wave tube embodying the present invention;
FIG. 2 is an exploded perspective view of the envelope of FIGURE 1 showing one embodiment of the invention;
FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 1;
FIG. 4 is an exploded perspective view showing a step in the manufacture of the envelope shown in FIG. 3;
FIG. 5 is a cross-sectional end view showing a second step in the manufacture of the envelope shown in FIG. 3;
FIG. 6 is a fragmentary exploded view showing an assembly feature of the present invention;
FIG. 7 is a cross-sectional view of a modification of an envelope in accordance with the present invention;
3,271,614 Patented Sept. 6, 1966 FIG. 8 is a perspective view of the preferred embodi-- ment of this invention; and
FIG. 9 is an end view of a modification of the embodiment of FIG. 8.
With specific reference to FIG. 1, there is shown, by way of example, an electron discharge device of the traveling wave tube type which comprises an elongated, evacuated envelope 11 which is of constant cross-sec tional area and is made of suitable material such as copper or molybdenum. At one end of the envelope 11, and disposed within an enlarged portion 13 which may be made of glass and which is hermetically sealed to the envelope 11, is an electron beam source, indicated generally by the reference character 2. This source comprises an electron emissive cathode 17, a focusing electrode 19, and an accelerating electrode 21. These elements are connected to suitable sources of voltage, which have not been shown, and collectively act to direct a beam of electrons centrally along the axial length of the envelope 11 to the opposite end of the envelope at which point is located an electron collector 23. The collector 23 is positioned transversely to the electron beam within a second enlarged glass portion 15 located at the opposite end of the envelope 11 from that of the electron gun assembly and is hermetically sealed thereto. The collector is also connected to a suitable source of voltage which is not shown. A slow wave propagating means 25, for the propagation of radio frequency energy is disposed centrally within the envelope 11 for the major portion of its axial length and is coaxial with and in an interacting relationship with a major portion of the electron beam. The propagating means comprises an electrical conductor usually in the form of a helix, which helix may be single-wound, cross-wound or bifilar-wound and may be of wire, tape, or of other configuration in accordance with good engineering principles. Electromagnetic energy may be applied to the helix or lsow wave propagat ing structure by means of a coaxial cable 29 which extends and is sealed through the side of the envelope 11, or by any other suitable electrical network. A second coaxial cable 31 is provided at the opposite end of the helix for the removal of radio frequency energy from the helix.
The helix 25 is supported within the envelope 11 by a plurality of supporting members 27 which are disposed along the axial length of the envelope for substantially the entire length of the helix. As is shown in FIGS. 3 and 7, these supporting members 27 are substantially keystone shaped in cross-sectional area (although they may be of circular or other configuration) and are made of a suitable heat conducting, electrical insulating ceramic such as alumina or beryllia. While four equally spaced keystone support members are shown in the drawings, this number is not critical and the number of supporting members and their relative spacing about the helix may be varied as the individual case may require.
In order to prevent the electron beam from spreading to such an extent that it would pass out of the interacting region and possibly intercept the slow wave propagating means, it is necessary to provide some form of focusing means. Focusing in the present instance is provided by producing a magnetic field axially along the envelope structure. This field is achieved by providing a long annular solenoid 33 which surrounds the envelope for the entire length of the helix 25. To simplify the present drawing and description, the magnetic field producing solenoid 33 is only schematically illustrated and the source of energization is not shown.
With reference to FIGS. 2 and 3, there is shown one embodiment of the instant invention. The envelope 11 of FIG. 1, as shown in this embodiment, comprises two trough or channel shaped members or segments 11a and 1112 having mating longitudinal edges 43 and 45, respectively. Segment 11a is provided with a pair of upstanding flange portions 35 which extend longitudinally along its inner radius. Segment 11b is likewise provided with a pair of upstanding flange portions 37 which extend longitudinally along its outer radius. These two pair of flange portions abut one another along their length and co-act to assure the proper alignment of the segments 11a and 11b as is best illustrated by FIG. 3. Keyways or depressed portions 39 may be provided in the interior surface and along the axial length of the envelope 11 to more accurately and securely locate the support rods 27, the number of keyways being equal to the number of support rods.
The preferred method of constructing the two segment envelope structure is shown in FIGS. 4 and 5. A first block of envelope material 11b is machined to form a central recessed portion 57 as is illustrated in FIG. 4. A second block of envelope material 11a is machined to form a central upstanding portion 59 which is of such dimensions so as to closely fit within the recessed portion 57 of block 1112. Small longitudinal slots, 51 and 53, are machined into each of the blocks 11b and 11a, respectively, to provide a center hole for drilling purposes, as will be explained later. The blocks 11b and 11a are easily machined, for example by milling, to great accuracies to ensure a close mating structure. After the blocks have been machined as above, they are fitted together and held in place by suitable clamps 49 (FIG. 5), and the center bore 55, which forms the cavity into which the helix is placed, is now formed longitudinally through the blocks 11a and 11b. The preferred method of forming this bore is by gun drilling, i.e., rotating the drill in one direction and the work piece in the opposite direction, with the slots 51, 53 acting as a centering hole. After the center bore 55 has been formed, the outside of the envelope may be shaped to the desired form in accordance with the method of focusing and/or cooling system to be used. In the present embodiment (FIG. 2), the outside of the envelope is circular in shape. The envelope segments may now be separated and the keyways 39 machined, for example by milling, into the inner surface of the envelope.
FIG. 6 illustrates one method by which the two piece structure of the present embodiment may be used to increase the contact pressure between the helix 25, support rods 27 and envelope 11. As the lack of sufficient contact pressure is the greatest source of resistance to heat flow from the helix to the envelope it is important that this pressure be increased to an extent suflicient to offer a low resistance heat path. By the use of the two piece structure of the instant invention, the assembly within the envelope 11 may be adjusted to increase the contact pressure before the final assembly is made. This adjustment may be in the exchange of components such as substituting one supporting rod 27 for another which may be of slightly different size. A further adjustment may be the substitution of one helix for another. Small quantities of metal may be removed from the keyways or shims 47 of desired length and thickness and made of a suitable heat conducting material, such as copper, may be added. These adjustments may be made singularly or in any combination to ensure good contact pressures and hence eflicient heat transfer paths.
Thus, it may be readily seen, that the multiple piece structure of the instant invention allows for the ready adjustment of the internal structure within the envelope to assure sufiicient contact pressure at all points to provide an efiicient heat conducting path from the helix 25 through the support rods 27 to the envelope 11.
After the final adjustment of the internal structure has been made, the envelope with its internal structure may be placed in a suitable jig, which has not been shown, and
4. the braze 41 made along the mating edges 43, 45 to mechanically join and hermetically seal the envelope 11.
FIG. 7 shows a modification of the invention which differs from that shown in FIGS. 2 through 6 only in that the self-aligning feature occasioned by the upstanding flanges 35 and 37 is not present. While this embodiment does not provide for the self-alignment, it does permit the adjustment of the internal structure within the envelope 11 prior to the brazing operation. From this, it is evident that the nature of the division of the envelope members is not critical but in fact can be made in a number of ways. It is also evident, although it has not been shown, that the envelope 11 may be made in more than two pieces.
The preferred embodiment of the present invention is shown in FIG. 8. This embodiment comprises a two piece envelope 11 in which the exterior envelope wall is non-circular. Each segment of the envelope 11 is provided with a flange portion 71 which extends longitudinally along the length of the envelope and which co-acts to form mating surfaces of the envelope segments. Two or more holes 65 are formed, for example by drilling, vertically through each of the flange members and pins 69, which may be of the'same material as that of the envelope and which serve to align the envelope segments are then fitted into each of the holes 65.
Brazing material 41 is positioned in suitable grooves 73 formed longitudinally along the mating surfaces 75. After the envelope assembly and necessary adjustments for good thermal contact have been made, the envelope is heated to a temperature sufficient to melt the brazing material 41 and allow it to flow to effect mechanical bonding and hermetic sealing.
The particular exterior configuration of the envelope 11 is not critical and as illustrated in FIG. 8 is one which is adapted for water cooling of the outside of the envelope 11. FIG. 9 illustrates the use of alignment pins in an envelope of circular design. In this instance, the holes 65 are formed in the envelope walls perpendicular to each of the mating surfaces 75 of each envelope segment and alignment pins 69 are fitted into each of the holes of one segment. The pins 69 are of sufficient length to extend into and substantially fill the holes of the second segment when the envelope is assembled.
From the above it is apparent that there has been disclosed a multiple piece envelope which will provide for an improved heat conducting path from the helix 25 to the envelope 11. While there have been shown and described what are at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangements shown and described and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
I claim as my invention:
1. An electron discharge device comprising an envelope, means disposed at one end of said envelope for the production of an electron beam along the length of said envelope, electron collecting means disposed at the opposite end of said envelope, slow wave propagating means disposed within said envelope for the propagation of electromagnetic energy along the length of said envelope, and means inserted between and abutting said envelope and said slow wave propagating means for conducting heat from said slow wave propagating means, said envelope comprising first and second channel members mechanically joined together to exert a radial force upon said means for conducting heat from said slow wave propagating means, and to ensure an etlicient heat transfer between said slow wave propagating means and said envelope.
2. An electron discharge device comprising electron beam forming and collecting means, means for the propagating of electromagnetic energy along a path coaxial with and in an interacting relationship with said electron beam, means comprising at least two segment channels defining a cavity for the disposition of said propagating means, means supporting said propagating means disposed in an abutting and in a thermal transfer relationship with said envelope, each of said envelope segments being joined to form said envelope and to establish a force upon said supporting means to enhance said thermal transfer relationship,
3. An electron discharge device comprising an envelope, means defining an electron beam source disposed at one end of said envelope, means for collecting said electron beam disposed at the opposite end of said envelope, means disposed within said envelope for the propagation of electromagnetic energy along a path coaxial and in an interacting relation with said electron beam, said envelope comprising multiple segments co-acting to form a cavity for the disposition of said propagation means, and support members disposed between and abutting said envelope and said propagation means and made of a heat conducting material, said segments being joined together to exert pressure upon said support members and said propagation means to insure an efficient heat transfer relationship therebetween.
4. An electron discharge device comprising means for forming and collecting an electron beam, means for the propagation of electromagnetic energy along a path coaxial and in an interacting relationship with said electron beam, envelope means comprising a plurality of channel segments co-acting to define a cavity for the disposition of said propagation means, and a plurality of support mernbers disposed between and abutting said envelope means and said propagation means and made of a material having the property of conducting heat, said segments joined together to apply a radial force upon said support members and said propagation means whereby an efiicient thermal contact is established between said support members and said envelope means, and between said support members and said propagation means.
5. An electron discharge device comprising means for forming an electron beam, means for collecting said electron beam, means for the propagation of electromagnetic energy along a path coaxial with and in an interacting relationship with said electron beam, an envelope comprising a plurality of mating channel members so as to 45 form a cavity for the disposition of said wave propagation means, and support members disposed between and abutting said envelope and said propagation means and made of a material having the properties of electrical insulation and of heat conduction, said mating members having depressions to receive said support members, said mating members being joined together to establish a force upon said support members and said propagation means to ensure an eflicient heat transfer relationship between said support members and said propagation means.
6. An electron discharge device comprising means for forming and collecting an electron beam, means for the propagation of electromagnetic energy along a path coaxial with and in an interacting relationship with said electron beam, a plurality of channel segments defining an envelope in which said propagation means is disposed, a plurality of support members disposed between and abutting said propagation means and said envelope and made of a material having the properties of conducting heat and of being electrically insulating, said segments having depressed portions for receiving said support members, said segments being joined together to exert a force upon said support members and said propagation means to ensure an efficient heat transfer relation between said segments and said wave propagation means, and heat conductive shims inserted in said depressed portions to abut against said support members and to exert a force upon said support members.
References Cited by the Examiner HERMAN KARL SAALBACH, Primary Examiner.
GEORGE N. WESTBY, C. O. GARDNER, S, CHAT- MON, IR., Assistant Examiners.