US2928019A - Traveling wave electron discharge device - Google Patents

Description

March 8, 1960 H. LEVIN 2,928,019

TRAVELING WAVE ELECTRON DISCHARGE DEVICE Filed March 11, 1957 6 Sheets-Sheet 1 Inventor HERBERT L LEI/W Agent March 8, 1960 H. 1.. LEVIN TRAVELING WAVE ELECTRON DISCHARGE DEVICE Filed March 11; 1957 wh mmm March 8, 1960 H. L. LEVIN 2,928,019

TRAVELING WAVE ELECTRON DISCHARGE DEVICE Filed March 11, 1957 e Sheets-Sheet 3 March 8, 1960 H. L. L EVlN TRAVELING WAVE ELECTRON DISCHARGE DEVICE 6 Sheets-Sheet 4 Filed March 11, 1957 Inventor HERBERT L, LEV/IV y 62W Agent H. L. LEVIN TRAVELING WAVE ELECTRON DISCHARGE DEVICE March 8, 1960 6 Sheets-Sheet 5 Filed March 11, 1957 By WA 0M Agent March 8, 1960 H. L. LEVIN 2,923,019

TRAVELING WAVE ELECTRON DISCHARGE DEVICE Filed March 11, 1957 6 Sheets-Sheet 6 III 96 ,Z flo 86 9 0 87 I Inventor 88 8 Hmamr 4. 15w f0? 5 Agent United States Patent 4,928,019 TRAVELING WAVE ELECTRoN DISCHARGE DEVICE Herbert L. Levin, Paterson, NJ, assign'or to international Telephone and Telegraph Corporation, Nutley, -N.J., a

corporation of Maryland Application March 11, 1957, Serial No. 645,198- 40 Claims. (Cl. 315-.-3.'5)

This invention relates to taveling wave electron discharge devices and more particularly to the traveling wave amplifier type.

Traveling wave amplifier tubes have various structural configurations; One general form has an electron gun in a bulb-like glass enclosure with the radio frequency interaction section and the electron collector electrode disposed in a long slender glass enclosure. The radio frequency interaction section includes an input connection for the radio frequency energy at or immediately adiacent the output of the gun and an output connection at the other end of the section adjacent the electron collector electrode. These radio frequency energy connections are usually disposed at right angles to the axis of..the propagating structure. This type of tube structure is fragile and the disposition of the radio frequency energy connections interrupt the magnetic field and usually necessitate a special type structure for the means to produce the magnetic field for electron beam collimation, whether it be a solenoid or a permanent magnet.

Another general type of tube employs an all-metal vacuum housing of substantially the same diameter throughout its length which provides a relatively rugged tube construction. In certain of these all-metal tubes, the construction is such that the terminals for the electrodes of the gun unit are disposed at one end of.the tube and the terminals for the radio frequency input and output connections are disposed at the other end of the tube, substantially parallel to the longitudinal axis of the vacuum housing. The connection between the input terminal and the input end of the propagating structure isaccomplished by a transmission line disposed within the vacuum housing extending the entire length thereof substantially parallel to the propagating structure. This structure .is such that the radio frequency energy terminals and connections will not interfere with the magnetic field and thereby enables the employment of a solenoid or permanent magnet of usual symmetrical configuration. The inclusion of the radio frequency energy input connecting line within the vacuum housing necessit ates employing a housing, particularly in the inter- ;action region, having an increased diameter with respect to the glass envelope type tube mentioned 'hereinabove. This adds weight to the tube itself. Further, in view of this increased diameter, the magnetic field producing means must have an increased size and hence increased weight to provide sufiic'ient magnetic field density to insure that 'the magnetic field is of sufficient strength and is axial of the propagating structure to properly collimate the electron beamtraveling therethrough. The increased weight of the solenoid necessitated by this type of tube structure increases the weight of the entire solenoidnube package. This increased weight is a distinct disadvantage in certain applications, such as in airborne equipment. In addition the inclusion of the radio frequency input connection transmission line within the vacuum housing creates an isolation problem between 2,928,019 Patented Mar, 8, 1960 ice the input and output ends of the propagating structure.

The proximity of the input radio frequency connection to the output of the propagating structure provides a feedback path between the connecting transmission line and the vacuum housing which will cause undesired oscillation within the amplifying tube. This structural arrangement necessitates adding components to attenuate energy in this undesirable feedback path and thereby isolate the output end of the propagating structure from the input end thereof.

Because of the unique requirements of traveling Wave tubes, these tubes have been difiicult to manufacture and the problems of assembly have been such as to require precision handwork in assembling these tubes. This has resulted in these tubes being very expensive. Moreover, due to the type of structureemployed in the traveling wave tubes of the prior art, any defects in any part of the tube have usually resulted in the loss of the entire tube.

An object of. this invention is to provide a compact, easily assembled traveling wave tube, so arranged that the tube may be easily cut open to permit salvage, repair or substitution of tube elements and then just as easily re-welded and evacuated.

Another object of this invention is to provide a travelingwave tube formed from a number of'subassemblies. In accordance with this object, an embodiment is provided in which the vacuum housing is fabricated from three subassemblies made of inexpensively machined blanks, cups and tubings which are brazed together and accurately machined and in which these subassemblies and the internal subassemblies may then be assembled by relatively unskilled labor, joined together, such as by heliarc welding, to form-vacuum type joints and which then are finally bent to achieve the critical alignment of the electron gun with the propagating structure.

Another object of this invention is to provide a traveling wave tube structure with the terminals for the electrodes of the gun unit at one end of the tube and the radio frequency input and output terminal connections at the other end .of the tube which is relatively light in weight, which has decreased internal volume, and which employs .a lighter weight solenoid to provide a tube vsolenoid of vastly decreased weight.

Another object of this invention is to provide a traveling wave tube structure which provides complete isolation between the input and output of the propagating structure.

Still another object .of this invention is to provide a traveling wave tube structure which enables complete interchangeability of parts and subassemblies.

A further object of this invention is to provide a traveling wave tube structure reducing to a minimum the internal volume of the tube and the number of internal parts which perm-its a' more rapid outgassing and an improvement in the vacuum. 7

Still a further object of this invention is to provide a novel support arrangement for an electron gun unit and a support arrangement for the propagating structure to'facili-tate the achievement of the above-identified obj'ects and further to provide a traveling wave tube which relatively free from the effects of differential expansi-ons, vibrations and accumulations machining tolerances. 'An important feature of this invention is the provision of an easily assembled traveling wave tube structure comprising a vacuum housing having a central portion containing the propagating structure and two end portions, one of said end portions containing the electron .gun .unit and the other of said end portions containing the collector electrode. An inwardly turned cup=lil e e sssu ed dia entea an o .th c n ra por- U tion for engagement with an inwardly extending tubular formation included on each of the end portions. The inner ends of each of the cup-like members are then hermetically sealed to the inner ends of the respective tubular formations of the end portions to provide the vacuum housing.

Another important feature of this invention is the provision of an electron gun unit mounted on the stem header as an integral subassembly. The integral subassembly engages the inner surface of an outwardly extending tubular formation of the end portion of the vacuum housing containing the electron gun for coaxial positioning therein. The outer end of the stem header, in the form of an outwardly extending cup, is hermetically sealed to the outer end of the outwardly extending tubular formation.

Still another important feature of this invention is the provision of an electron gun unit mounted on the stern header as an integral subassembly by means including pressure exerting members, such as springs, to substantially eliminate efiects of differential expansions, vibrations and accumulations of machining tolerances.

Still a further important feature of this invention is the provision of a magnetic barrier disc in the collector electrode end portion enabling radio frequency terminal connection to be made to the propagating structure within the inside diameter of the tubular magnetic field producing means for electron beam collimation. This disc in conjunction with a disc in the electron gun unit end portion appropriately aligns the magnetic field producing means with the beam path. The first mentioned disc includes a central aperture for electron beam passage therethrough and carries thereon the inwardly extending tubular formation for engagement with the inwardly turned cup-like member of the central portion. The engaged members are eccentrically related to the electron beam path to permit the radio frequency input terminal connection to pass through an aperture in the magnetic barrier disc outside the eccentric vacuum housing configuration and inside the tubular magnetic field producing means for entrance into the vacuum housing adjacent the input end of the propagating structure. The first mentioned disc also includes an aperture therethrough into the eccentric vacuum housing configuration to permit connection of an output radio frequency terminal to the output end of the propagating structure.

A further important feature of this invention is to provide a magnetic carrier member in each end portion having a central aperture for the passage of the electron beam therethrough and carrying thereon a support and alignment member for the propagating structure, one of said support and alignment members retaining therein a pressure exerting member to exert a force on the end of the propagating structure to substantially eliminate the effect of differential expansions, vibrations and accumulation of machining tolerances.

A feature of this invention is the provision of a tubular collector electrode that is also employed as the exhaust tubulation for the traveling wave tube structure of this invention.

Another feature of this invention is the provision of a re-entrant seal to support and insulate the collector electrode-exhaust tubulation from the magnetic barrier of this end portion.

Still another feature of this invention is the provision of a heat radiator in heat conducting relation with the collector electrode-exhaust tubulation comprising a massive member to form a heat sink and a plurality of washerlike fins fastened thereto. The fins include lips on their inner diameter and dimples spaced circumferentially near the peripheral edge thereof, said lips and said dimples space adjacent fins and provide rigidity to the structure.

A further feature of this invention is the provision of a lip on the peripheral surface of the magnetic barrier of the collector electrode end portion to seat the traveling wave tube in proper relationship with the solenoid.

Still a further feature of this invention is the provision of a traveling wave structure assembled from a plurality of component subassemblies to form a complete but not necessarily aligned traveling wave tube where the final and critical alignment of given ones of the subassemblies, such as the electron gun and propagating structure, is achieved by bending the hermetically sealed housing.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with th accompanying drawings, in which:

Fig. l is a view in elevation of a preferred embodiment of a traveling wave tube-solenoid package in accordance with the principles of this invention;

Fig. 2 is a view in elevation of the three vacuum housing subassemblies of the traveling Wave tube of Fig. 1;

Figs. 3A and 3B is an enlarged cross-sectional view of the tube of Fig. 1;

Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 3A;

Fig. 5 is a cross-sectional view taken along line 5-5 of Fig. 3B;

Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 3B;

Fig. 7 is an enlarged cross-sectional view of the propagating structure spring-loaded support arrangement;

Fig. 8 is a cross-sectional view taken along line 8-8 of Fig. 7;

Fig. 9 is a cross-sectional view taken along line 9-9 of Fig. 3A;

Fig. 10 is a cross-sectional view taken along line 10-10 of Fig. 9;

Fig. 11 is a cross-sectional view taken along line 11-11 of Fig. 9;

Fig. 12 is a cross-sectional view taken along line 12-12 of Fig. 9;

Fig. 13 is a cross-sectional view taken along line 13-13 of Fig. 9;

Fig. 14 is an elevational view of a modification of the radio frequency energy terminal connections of Fig. 1; and

Fig. 15 is an enlarged cross-sectional view taken along line 15-15 of Fig. 14. I

Referring to Figs. 1 to 6, the traveling wave tube this invention is shown to comprise a vacuum housing 1 having an end portion 2, a central portion 3 and an end portion 4. An electron gun unit is disposed within end portion 2 to project an electron beam along a given rectilinear path in housing 1. A propagating structure 6 is disposed in central portion 3 with its principal longitudinal axis parallel to and adjacent the beam path for transmission of radio frequency energy in interacting relation with the electrons projected from gun unit 5. One form of propagating structure 6 is illustrated in Figs. 3 to 6 to include a helical conductor 7, such as tungsten or molybdenum, supported between a plurality of dielectric support rods 8 and positioned to be coaxial with the beam path. A collector electrode 9 is included as a component of end portion 4 and is disposed to intercept the electrons of the electron beam. A radio frequency coupling means for the input and output of propagating structure 6 is mounted in end portion 4. Central portion 3 has secured thereto adjacent the ends thereof inwardly turned cup- like members 11 and 12 for respective engagement with tubular formations 13 and 14 disposed on the inner ends of end portions 2 and 4, respectively. The inner ends of member 11 and formation 13 and the inner ends of member 12 and formation 14 are hermetically sealed by weld beads and 16, respectively.

Radio'frequency coupling means-10 includes terminal connection 17 of rigid coaxial structure fabricated as an integral part of end portion 4. Terminal connection 17 includes a cylinder 17a fabricated as an integral part of end portion 4 which is a continuation of aperture .18 through disc 19 at an angle to the beam path. Outer conductor 20 is sealed to cylinder 17aat 17b and inner conductor 21 protrudes through aperture 18 in connecting 20 and inner conductor '21 are inserted into cylinder 17a as an integral uni-t prior to sealing at 1'71 b. Conductor 21 is hermetically sealed to the. wall of outer conductor 20 by glass-to-metal seal 22. Connected to connection 17 is coaxial transmission line connection 23 having coaxial connector 24 connected thereto. This provides an arrangement to couple amplified wave energy from the output of structure 6. The wave energy input portion of means 10 includes coaxial connector 25 fastened at the end of coaxial transmission line connection 26 which passes through aperture 27, of disc 19 and extends parallel to central portion '3 to rigid coaxial terminal connection Terminal connection 28 includes cylinder 28a which is fabricated as an integral part of central portion 3 by fastening it at an angle in aperture '29 through the bottom 30 of'cup-likc member 11. Outer-conductor 31 is sealed to cylinder 23a at 28b and inner conductor 32 protrudes through aperture 29 in conneoting relation to the input end of structure 6. Outer conductor 2% and inner conduotor 21 are inserted into cylinder 28a as an integral unit prior to sealing at 2812. Glass-tometal seal 33 provides the necessary hermetic sealing of terminal connection 28. Transmission line connections '23 and 26 are preferably flexible coaxial lines, but it would be possible to employ rigid type of coaxial lines;

The diameters of end portion 2 and end portion 4 are such that central portion 3 and transmission line connection 26 are contained within the diameters thereof. This enables tubular magnetic field producing means'or solenoid 34 to be supported and aligned by the diame ers of components of end portions 2 and 4. It is to be understood that while tubular means 34 will be referred to as a solenoid, a permanent magnet may be substitutedtherefor also with a resulting saving in weight. By reducing the diameter of central portion 3, there is realized a reduction in the internal volume of the traveling wave tube,

and hence it is much easier to outgas the tube thereby stepping up the production of these tubes. Further, by employing the above constructiom solenoid 34 is brought closer to structure 6. As a consequence, the diameter of the solenoid and the weight thereof can be reduced. This results in a great saving in weight of thesolenoid-tube package.

Fig. 2 illustrates the three main housing subassemblies which enhance the easy assembly of the tube. The subassemblies or portions 2, 3 and 4 are fabricated of inexpensively machined blanks, cups and tubings, which are brazed together and then finally machined to obtain important dimensions. The internal subassemblies, such as electron gun unit and propagating structure 6, are inserted in their proper location within the main housing subassemblies. The assembly of these subassemblies may be accomplished by relatively unskilled workers in a fixture with certain joints between these subassemblies being heliarc welded or otherwise secured to form a. vacuum type joint, such as by weld beads 15, 1'6 and 35. Since certain surfaces of these subassemblies need not be accurately machined, particularly the engaging surfaces, there may be an accumulation of machining tolerances which will result in misalignment between the axes of gun unit 5 and structure -6. The critical alignment of the electron gun unit 5 with propagating structure 6, after completion of 'the assembly of all subassemblies, is achieved by bending'the entire tube assembly at central portion 3. This bending operation is made possible by the relatively small diameter of central portion 3 and the fact that there areno interfering members around central portion 3.

The tube structure of this invention employs exposed weld joints such as at 15, 1-6 and 35. These joints are so arranged that they can be easily cut open to permit easy salvage, repair or change of tube subassemblies. Besides .tlte ease "of assembling the tube, which may be accomplished on a production line basis where the different subassemblies are fed to the line, the structure of tube has certain other advantages such as the location of the input transmission line connection 26 with respect to structure '6. With this input connection disposed outside the vacuum housing, there is obtained complete isolation between input and output of propagating structure 6.

Certain other features and advantages of this invention [will be discussed as the tube is described in greater detail in connection with Figs. 3A and 3B.

The housing portions 2, 3 and 4, as mentioned above, are each made of standard blanks,.cups and tubings. These parts do not have critical dimensions or closetolerances and the effect of the accumulation of blank tolerances in the pie-machined, brazed subassembly is not important. In the single brazing operation of .a sub assembly, there is an important secondary effect in that all the parts are fully annealed and the subsequent ma;- chining to close tolerances will not beadversely aifected by warping or other distortion due to stress relief. The parts are designed so that they are self-jigging and are easily loaded into a brazing fixture where they are retained by weights only. The omission of screws in the brazing fixtures eliminates the problem of screws seizing the fixture. Where an upside down braze is necessary, the blanks are machined such that they retain the brazing material. The efiect of the accumulation of tolerances and clearances is eliminated since each subassembly is machined as a unit after brazing. This insures concentricity and perpendicularity of important electrical surfaces and seating or engaging surfaces.

Referring with greater particularity to Figs. 3A and 3B, the elements of the different subassemblies will be discussed. In Fig. 33 end portion 4 includes disc 19 ofmagnetic material, such as iron, at propagating structure retaining ring 36 of non-magnetic material, such as Monel, to position structure 6 coaxial of the beam path and prevent the shifting thereof, an output coaxial seal 22, a glassto-metal type seal, to hermetically seal aperture 1.8, and tubular formation 14 which acts as a seating and welding member for member 12.

Disc 19 has therethrough a flared aperture '37 for passage of the electron beam to the collector electrode 9. vIn addition, the disc'19 includes an aperture 13 for entrance of the output coaxial terminal connection 17 therethrough to remove radio frequency energy from the output of propagating structure 6. Aperture 18 and hence connection 17 are disposed at an angle to the-axis of electron beam path to facilitate the attachment of transmission line connection 23 to terminal connection .17. -In addition disc 19 includes an aperture 27 through which input trans mission line connection 26 is passed for eventual entrance into assembly 2 for connection to the input end of propagating structure 6. Disc 19 acts as the magnetic barrier for the magnetic flux of solenoid 34 and .is a continuation ofthe magnetic path and .hence restricts the magnetic field for useful application along the axis of propagating structure 6, the path along which the electron beam travels. Disc 19 further includes lip 38 which acts to position the traveling wave tube in proper relationship with solenoid v34. The peripheral surface 39 machined .to be concentric with the axis of structure 6 acts as a seating and alignment surface for solenoid 3 4 to assure the .best possible alignment between the axis of solenoid 34 and the axis of structure 6, the beam path.

Tubular formation 14 is made .ofanon-magnetic material, such as stainless steel or .Monel, and has machined therein a seating surface 40 which properly locates and aligns portions 3 and 4 when member 12 .is engaged .in formation 14. Tubular formation 14 is hermetically fastened to disc 19 in an eccentric relationship to the beam path. This eccentric relationship permits transmission line connection 26 to pass-through .disc 19 outside housing 1 and inside solenoid 34 and hence cooperates in providing complete isolation between the input and output of structure :6. 1

Collector electrode 9 composed of a heat conducting material, such as copper, is in the form of an elongated tube. This configuration reduces hot spots since the electron beam can impinge on a larger surface of the collector as it spreads. Collector electrode 9 further provides the tubulation through which the tube is exhausted. After exhaust electrode 9 is pinched closed and hermetically sealed at 41 such as by a cold weld technique. Electrode 9 is sealed to and supported from disc 19 by means of the re-entrant seal 42. Seal 42 is brazed to a stepped metallic cylinder 43 which has one end brazed to the surface of disc 19. Seal 42 further includes a stepped metallic cylinder 44 having one end brazed to collector 9 and a glass member 45 to provide a hermetic seal for insulating gap 46 between cylinders 43 and 44. The employment of the re-entrant seal 42 reduces the internal volume which must be exhausted through collector 9 and reduces the overall length of the tube.

Turning now to Fig. 3A, end portion 2 is illustrated as comprising an outwardly extending tubular formation 47 composed of magnetic material, such as iron, which acts as a magnetic shield for the electron gun unit and a support therefor. Disposed in transverse relationship with formation 47 at the inner end thereof is a disc 48 composed of a magnetic material, such as iron, to provide a continuation for the magnetic flux and hence concentrates the magnetic flux along the beam path. Disc 48 includes therethrough an aperture 49 for passage of the electron beam along the electron beam path. Connected thereto, such as by a brazing operation, is the aperture cone 50, composed of a non-magnetic material such as Monel, which functions as the anode of electron gun unit 5 and has an aperture 51 which is disposed to be a continuation of aperture 49.

At the outer end of formation 47 there is an inner diameter 52 for stem header 53. Stem header 53 is in the form of an outwardly extending cup having a metal portion 54 and a glass or ceramic bottom 55. Bottom 55 provides a hermetic seal for stem header 53 and includes therethrough rigid rods or beads 56 of a material such as Kovar. Stem header 53 is fabricated as an integral partof gun unit 5 and engages diameter 52 to form a hermetic seal when weld bead 35 is disposed at the ends of formation 47 and stem header 53.

Further along the longitudinal dimension of formation 47 is another seating surface 57 which is juidiciously disposed to provide abearing surface for washer-like aligning member 58 of the electron gun unit 5 to position the electron gun unit along the longitudinal axis of the traveling wave tube and coaxially of the beam path.

Brazed coaxially of aperture 49 on disc 48 is a retaining ring 59 to properly cooperate with retaining ring 36 to position propagating structure 6 coaxially of the beam path. When the tube is assembled, there is placed in ring 59 a washer 60 of spring material which is bent to provide a spring-like force against rods 8 of propagating structure 6. In transverse relation to and in contact with washer 60 and the ends of rods 8 is a washer 61. By this arrangement propagating structure 6 is springloaded to insure proper seating and alignment under shock or vibration conditions and to further eliminate effects of accumulation of tolerances in the construction of the traveling wave tube. A second function of this spring arrangement is that of acting as a shield to prevent the electron beam from hitting the ends of the ceramic rods 8 which would result in a build-up of electrical charge and hence a distortion of the electron beam as it passesthrough propagating structure 6. The ring 59 may becomposed of a non-magnetic material, such as Monel, while the washers 60 and 61 are composed of a material, such as tungsten or molybdenum, to provide the required compressional force. Figs. 7 and 8 illustrate an enlarged view of the spring loading arrangement of propagating structure 6.

Peripheral surface 62 of disc 48 like peripheral surface 39 of disc 19 is properly machined to provide a reference surface for the concentricity of the inside and outside surfaces of end portion 2 and further to cooperate with surface 39 to provide a seating surface for the inner diameter of the solenoid 34 which thereby properlyaligns solenoid 34 with the electron beam path. Securedto disc '48 is inwardly extending tubular formation 13- of nonmagnetic material, such as stainless steel or Monel, to provide a seating and welding member for cup-like member 11 of central portion 3. I

Central portion 3 comprises cup-like members 11 an 12 brazed to the opposite ends of tubing 64. To the extremity of tube 64 adjacent member 11 is attached a short sleeve 65 which extends into the cavity between disc 48 and the bottom of member 11. Sleeve 65 has an aperture or slot 66 therethrough which permits the entrance of the matching strip between the input end of helix 7 and inner conductor 32 of terminal connection 28 The purpose of sleeve 65 is to break up or interrupt the cavity formed between disc 48 and member 11 to prevent the possibility of this cavity'oscillating at a frequency in the band of frequencies launched on helical conductor 7. All members comprising the central portion 3 are composed of a non-magnetic material, such as stainless steel or Monel, to prevent any interruption or distortion of the magnetic field produced by solenoid 34. Cup- like members 11 and 12 are machined to obtain the correct distance between the discs 48 and 19 and have the diameters machined to be perpendicular thereto such that they properly engage formations 13 and 14. Tubing 64 which surrounds structure 6 has a diameter such that it is below the waveguide cut-off frequency for the operating frequency of the traveling wave tube. Cup-like member 12 is eccentric with respect to the axis of the propagating structure and therefore will properly mate with tubular formation 14 which was described previous as also being eccentric. The machining of the outside diameter of members 11 and 12 serve at least four purposes. This machining assures a proper fit with formations 13 and 14, respectively; it serves to thin the walls thereof to facilitate the welding at the ends thereof to provide a vacuum joint, to provide relief so that weld beads 15 and 16 will not exceed the diameter of discs 19 and 48 and further to obtain a reasonably sharp corner which permits the employment of a compact seating surface such as at 40 and 67.

After all the subassemblies are formed and machined to the proper diameters, the electron tube is assembled as follows. Propagating structure 6 is inserted into ring 36 of end portion 4 and impedance transition 83 is welded to inner conductor 21 and structure 6. Central portion 3 is then slipped over structure 6 to engage member 12 with tubular formation 14. Sleeve 65 is put into position and fastened and the connection is made between impedance transition 84, inner conductor 32 and structure 6. Tubular formation 13 is then slipped into engagement with member 11 with ring 59 and springs and 61 in engagement with the ends of rods 8 of structure 6. Finally, the gun unit 5 and the integral stem header 53 are inserted into end portion 2. The end of stem header 53 is then welded by a heliarc or similar method to the end of tubular formation 47, such as depicted by weld head 35; the inner ends of member 11 and tubular formation 13 are welded together such as depicted by weld bead 15 and the inner ends of member 12 and formation 14 are welded together, such as depicted by weld bead 16. The weld beads 35, 15 and 16 are vacuum tight. These three welded joints and the members that are joined are so arranged that the weld beads can be machined off and complete subassemblies may be replaced, repaired or salvaged and then the joint may be re-welded to place the traveling wave tube back in condition to be processed for operation.

The concentricity of the critical inside and outside dimensions of end portion 2 is attained by a sequence of 9 machining operations. and permits the checking of the internal alignment from the outside of; the tube. The tube structure is soarranged that after exhaust and seal-in at 41 of collector electrode 9, the tube is bent in approximately the center of central poition3 to achieve the best possible alignment of propagating structure 6 and electrongun unitS. v Heat radiator structure 63 comprises massive cylinder 69 of heat conducting material, such'as copper, and a plurality of Washer-like fins 70 of heat conducting material, such as copper, soldered to cylinder 69. Massive cylinder 69 is fastened to electrode 9 and forms a part thereof prior to the exhaust operation and then fins 70 are fastened to cylinder 69 after the pinch off of electrode 9. Washers 70 each have a lip 71 on the insidediameter thereof and'dimples 72 spaced circumferentially near the outer periphery of washers 70; The lips 71 are in contact with adjacent ones ofwashers 70' to space them thus eliminating the need for spacers and a separatelymachined core to which. fins would ordinarily be secured. Dimples 72 serve to space adjacent washers at the outer edge thereof, to strengthen the softened fins and to produce turbulence in the air stream for increased heat transfer. Radiator 68 is brazed as a complete unit. Lipsv 71 and dimples 72 are brazed to the adjacent fins by painting them with eutectic silver solder powder or asimilar soldering material. The massive cylinder 69 acts as a heat sink which will increase the conduction of, heat from the collector electrode 9 and hence to fins 70. This arrangement increases the heat transfer due to the more homogeneous brazed fin arrangement.

Transmission line connections 23 and 26 are preferably fiexible coaxial cables. Transmission line connections 23 and 26 are separated and insulated by separator 73,moun ted as an integral part of the completed tube. Connections 23 and 26 are insulatedand held in position by grommets 74: and75. disposed in apertures 7'6 and 77 of separator 73. Centrally disposed of separator 73 is aperture 78 which has spun over edge thereof an end of tubing 79. This tubing 79 and hence separator 73. is mounted as an integral part of the tube by fastening tubing 79 tomassivecylinder 69. by means of machine screws 80. Solder lug 80a is fastened by screw 80; and provides 7 a means to supply collector potentialto electrode, 9. By placing a disc 81 over aperture 78 f separator 73, the seal 41 of collector electrode-exhaust tubulation Sis. protected. Disc 81 may be used to attach alabelor' may be the: label to identify the tube make and may contain'other pertinent information. Separator 73' also serves as a handle for use when the tube is insertedginto; or removed from the solenoid 34. When placed in the-solenoid. 34, the tube is positioned relative thereto by: lip 38 on disc 19 and held in. position by a latch arrangement onsolenoid 34 (not shown) 3 Propagating structure 6 is supported directly from surfaces on discs 19 and 48, rings 36 and 59, which: are easily machined concentricallyiwith solenoid seating surfaces 39 and 62 on-the periphery of these discs. Thus the best possible alignment of the axes of propagating.

structure 6 and the axes of the solenoidz magnetic field is.

attained. Bending of. the tubefor: alignment-purposes has no effect. on the position. of propagating structure 6.. It will'be noted that there are notintermediate parts for ca'ting propagating structure. 6', onthe barrier or walls of discs. 19 and 48;

Cup-like-member 1-1 is-provided with a frusto -conic'al member 82 having a slot therethrough for input terminal connection 28. The function ofmember 82 is to stiffen member 11 and tubing 64 sothat when the tube is bent to achieve tlie alignment betweent'ne electron gum and the propagating structure, the weldwhetween. member 11' andtubing 64-: will not. break. or; otherwise impair thevacuum joint. Member 82ruggedizes-the.assembly: to assure that the portion 2-is notbent with respectto-portion S affer alignment by bending.

. of structure 6. There is no brazing operation at engage-e" Y The impedance transition sections at each end of pro pagating structure 6 is shown in this illustration toinclude a microstrip type of transmission line transition section 83 and 84 (see Figs. 4 and 6) following the teachings described in the copending application of R. E. White, Serial No. 312,083, Pat. No. 2,794,144, filed September 29, 1952, for ,Traveling Wave Electron Discharge Devices. It is to be understood however that any suitable transition section between the high impedance of helical conductor 7 and the relatively low impedance of the coaxial terminalconections may be employed provided that an excessive radial dimension is not necessary for such a transition.

Various glass-to-metal seals have been described as a part of the overall tube structure. It is to be understood that ceramic-to-metal seals may be substituted therefor without altering the structural organization described andillustrated.

Referring to Figs. 3A and 9-13, electron gun unit 5 will be described in more detail. The focusing electrode 85 is secured" to dielectric tubes 86 by means of strap 87. The metallic strap 87 is brazed to tubes 86 by first coating the outer surface of the dielectric material with a metallic substance and then brazing strap 87 thereto. Fastened to strap 87 between each of dielectric tubes 86' is a tab 88 (Fig. 11) which is extended to the surface of focussing; electrode 85 to make a positive connection thereto and. thus properly position this electrode coaxially of tubes: 86. The cathode surface 89 is crosswise cathode cylinder 90 disposed coaxially of tubes 86 and focussing electrode? 85 by cooperation of cylindrical sleeve 91 of metallic foil composition and flanged cylinder 92. On the flange of. cylinder 92 are disposed apertures to encircle tubes 86'- which through a brazing operation, similar to" the one:

. mentioned above with respect toelectrode 85, secures atidi supports the cathode surface 89 for projection of anelee tronbeam along the axis of the traveling wave tube.

Tubes 86 are held in position by apertures through alignement member 58 such that when member 58 is in en? gagement with surface 57, cathode surface 89" and focus sing electrode 85- are in proper alignment withthe axis;

ment point 57.

Heater filament 93- isinserted within cathode cylinder 90 and the proper potentialis appliedth'ereto' by centrally disposed lead 94, strap 95 secured to one of tubes 86 and a flexible lead 96 fastened between strap 95 and one" of the rigid leads of stem; header. 53, lead 56a. The return path for filament. 93. isv through cathode cylinder 90; sleeve 91, cylinder 92 and flexible lead 97 connected-to lead 56b of stem header 53. This filament return is also brazed to aligning member 58 and extends through a d i'- electric tube 103 positioned in an aperture of member-58 and an aperture of flanged cylinder 92 and hence" to lead 56d of. stem: header 53 where it is brazed. Onee'nd of getter '100is connected to lead 56d and the other end is connectedtolead 102 between tubes 101 and 103. Lead- 56d supplies potential to the getter for activation thereof.

The rest of the circuit is lead 102' to member 58 which is at ground potential.

Transverse of flanged cylinder 92 is disposed adisc- 104 of material. such as molybdenum supported by'r'o'ds 105 to substantially close the end of cylinder 92. Ape? ture 106 is provided for'passa'geof lead 94 threugn 104; Disc 104act's to reflect the hearof the filameiit baclcto back-of. cathode surface 89. This aet-imrreunees 11 the amount of filamentary power that would be required if disc 104 were omitted.

It will be noted that cathode surface 89 has centrally located thereof an aperture 107. Aperture 107 is disposed at a location previously noted to be turned out by back bombardment caused by positive ions. It was discovered that if a small aperture was placed in this location, the life of the cathode was increased, hence the purpose for disposing of aperture 107 in cathode surface 89.

Stem header 53 as has previously been mentioned is an integral part of electron gun unit 5. Rods 56 and hence stem header 53 are connected to dielectric tubes 86 by means of L-shaped rods 108 where the shorter portions 109 are fastened to rods 56 and the longer portions 110 are inserted in the end of tubes 86. Coaxially of the long portion 110 of rods Hi8 are disposed springs 111. One end of each of springs 111 is connected to rods 56 to prevent unravelling thereof. The other end of each of springs 111 engages the end of tubes 86 and exerts a pressure thereon when the electron gun unit is seated against seating surface 57 and stem header 53 is welded in position. The action of springs 111 is to eliminate the effects of differential expansions in electron gun unit 5, vibrations experienced by the entire tube and an accumulation of tolerances in unit 5 and end portion 2. These springs further eliminate screw fastening which may be vibrated loose. As will be observed, the electron gun unit 5 includes all electrical connections including those to the stem header 53 and is thus a complete subassembly and is easily assembled, and further is easily removed and replaced as a unit which facilitates the achievement of another of the objects of this invention, that of easy repair and salvage of individual subassemblies.

The outwardly extending cup-like configuration of stem header 53 permits the attachment of flexible leads 112 (Fig. 1) to the rigid stem header leads 56 and further permits potting with plastic or silicon rubber to eliminate high voltage breakdown at high altitudes or under other adverse environmental conditions. This open type structure facilitates the potting operation and eliminates entrapped air spaces.

The arrangement of the major subassemblies is such that they may be easily leak detected and repaired by replacement of defective vacuum seals without any remachining operation.

" A comparison of a prior art traveling wave tube and the traveling wave tube of this invention, both with similar electrical characteristics, accents the saving in the tubesolenoid package weight that was gained by the structural arrangement described herein.

6 is inches x 7 inches x 11% inches.

Package size 4 inches x 4 inches x 11% inches.

Tube weight 1 pound 4 ounces 1. 1 pound.

Solenoid weight 41 pounds 5 pounds 4 ounces.

Tube-solenoid package 42 pounds 4 ounces (5 pounds 4 ounces.

weight.

'This table demonstrates that the new package weight was reduced to less than that of the old package weight even though the tube weight was not drastically reduced. This great decrease in weight is possible because one turn of solenoid winding has the same magnetic effect regardless of its position within the solenoid. When the tube is made smaller and the solenoid is made smaller (the number of layers of windings remaining constant) we have, in effect, removed the long, heavy outer layers of windings and have replaced them with much shorter inner layers of windings.

.Referring to Fig. 14, a modification of the radio frequency coupling means of Figs. 1, 2 and 3 is shown. Structures that are the, same here as in Figs. 1, 2 and 3 12 have the same reference characters herein. The electrically insulated supporter and separator 73,- to hold in position transmission line connections 23 and 26, has been eliminated. The length of flexible'connections 23 and 26 have been shortened and coaxial connectors 113 and 114 are provided immediately adjacent end portion 4, connectors 113 and 114 transducing from small diameter connections 23 and 26 to larger diameter coaxial lines of exterior circuitry. The flexibility of connections 23 and 26 permits making connections to the desired angle required or necessary in the installation in which the tube is being employed. Protection for seal 44 of collectortubulation 9 in this modification is provided by cup 115 which is fastened by screw 116 to the massive cylinder 69 of radiator 68.

Fig. 15 illustrates an enlarged cross section of coaxial connector 113 which is identical to connector 114. Connector 113 includes therein a tapered outer shell 117 and a tapered inner conductor 118 which provides a smooth impedance transition and conductor size transition between the flexible transmission line connection 23 and 26 and the coaxial lines coupled to exterior circuitry.

The structural arrangement of the tube herein described results in the following advantages. 1) The tubes employing the described structure exhibit excellent alignment of gun unit 5 with helix 7 more consistently than those tubes of similar electrical characteristic but of the old mechanical arrangement. (2) The tube has readily lent itself to salvage, repair, rebuilding and has been found to be easily assembled and aligned. (3) The breakdown of the tube into subassemblies which are easily leak detected has proven economical because repairs on defective parts in a subassembly stage are simple and the subassemblies, are saved. (4) The use of heliarc welding of the final assembly has been found to be quick and reliable and has no adverse eifect on adjacent members. (5) The tube of this invention is more quickly assembled than prior art tubes with similar electrical characteristics. The principle of putting the skill into the machined parts instead of into skilled handwork in the assembly of the tube has been completely adhered to throughout with the result that subassemblies are accurately machined, inspected, stocked, sent to the assembly room and then easily assembled by unskilled labor. (6) There are no blind vacuum joints in this tube structure. (7) The structure of the various subassemblies and seals have reduced the internal volume of the electron tube and the number of internal parts and thus permits a more rapid outgassing and an improvement in the vacuum achieved.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A traveling wave electron discharge device comprising a vacuum housing including a central portion and two end portions, a wave propagating structure disposed in said central portion, an electron gun unit disposed in one of said end portions to project an electron beam in a path along the longitudinal axis of said central portion and in interacting relation with the wave propagated on said propagating structure, a collector electrode disposed in the other of said end portions, two inwardly turned cuplike members, one secured adjacent each end of said central portion, each of said end portions having at their inner ends a tubular formation for engagement with the respective cup-like members of said central portion, the inner end of each of said cup-like members being hermetically sealed to the inner ends of the respective tubular formations of said end portions and radio frequency coupling means for said propagating structure.

'2. A device according to claim 1, wherein said one of said end portions includes a first disc disposed transversely 13.. thereof having an aperture therethrough coaxial of said beam path and a first support means closelyadjacent said aperture and said other of said endportions includes a second disc disposed transversely thereof having an aperture therethrough coaxial of said beam path and a second support means closely adjacent the aperture of said second disc, said first and second support means cooperating to support said propagating struc ure coaxially of said beam path, said first support means further including a pressure-exerting member bearing on the end of said propagating structure to effect a spring loading thereof.

3. A device according to claim 1, wherein said collector electrode is in the form of an elongated exhaust tube extending lengthwise in the path of said electron-beam and hermetically sealed at a given point therealong.

4 A device according to claim 3, further including means to enclose the seal of said exhaust tube.

5. A device according to claim 3, further including a heat radiator assembly having a relatively massive member surrounding said exhaust tube at a point therealong and a plurality of washer-like fins secured to said massive member, each of said fins having lipsdisposed on their inner diameter and dimples disposed in circumferential spaced relation adjacent the outer periphery thereof, said lips and said dimples being in contact with adjacent ones for said collector electrode includes a re -entrant hermetic seal.

9. A device according to claim '8, wherein said reentrant hermetic seal includes a first metallic cylinder of step-like configuration having one end thereof hermetically sealed to said other side of said disc, 2. second metallic cylinder of step-like configuration having one end.

thereof hermetically sealed to said exhaust tube at a given 5.

of said first and second cylinders to hermetically seal the passage therebetween.

10. A device according to claim 7, wherein said inner tubular formation and its engaging cup-like member are disposed eccentrically with respect to the central ape r ture of said disc, said disc including a first aperture therethrough for entrance into said inner tubular formation and a second aperture therethrough disposed externally of said inner tubular formation and said radio frequency coupling means includes an output radio frequency connection having a first terminal connection extending through said first aperture, means to hermetically seal said connection to the wall thereof and means to couple said terminal connection to the output end of said propagating structure and an input radio frequency connection having a second terminal connection associated with said one of said end portions for connection to the input end of said propagating structure and a transmission line connection extending through. said second aperture and parallel to said central portion for connection to said second terminal connection.

11.. A device according to claim 10, wherein said radio frequency coupling means further includes a second transmission line connection coupled to said first terminal connection and a means to support and separate the transmission line connections including means connected to said other of said end portions and disposed with respect thereto to protect the hermetic seal of said exhaust tube 12. A device, according toclaim 1, wherein said one of said'end portions includes at its outer end a tubular.

formation and said electron gun unit is mounted on an outwardlyextending cup and movable therewith for engagement with the outer tubular formation of said one of said end portions, the'outer end of said outwardly extending cup being hermetically sealed to the outer end of said 7 outer tubular formation.

inner tubular formation hermetically sealed to the other side of said disc. r I

14'. A device according to claim 13, wherein said outer tubular formation and said inner tubular formation are sealed to said disc in coaxial relation to said beam path.

15. A device according to claim 14, further including an apertured cone fastened to said one side of said disc extending outwardly therefrom in'cooperating relationship with said electron gun unit, the aperture of said cone being disposed to form a continuation of the aperture of said disc.

v 16. A device according to claim 14, further including support means secured to said disc coaxially of said beam path for receipt of the input end of said propagating structure for coaxial support and alignment thereof with said beam path, said support means including a pressure-exerting member disposed in confined relationship therewith in and bearing against the end of said propagating structure for spring loading thereof.

17. A device according to claim 14, wherein the cup of said central portion for engagement with said tubular formation includes an aperture through the bottom thereof spaced from said central portion and at an angleto said beam path and a frusto-conical member disposed within said cup between the bottom thereof and said central portion, said frusto-conical member having an aperture therethrough in alignment with the aperture in the botbottom of said cup and said one side of said disc, said sleeve having a slot therethrough for passage of said means to couple.

20. A device according to claim 13, wherein said outer tubular formation includes a circumferential, shoulder on the interior surface thereof at a given point therealong.

and said electron gun includes a plurality of support elements, a plurality of electrodes mounted on said support elements and a washer mounted on said support elements.

for engagement with said shoulder to align said electrodes alongthe axis of said disc when said outwardly extending cup is in engagement with said outer tubular formation.

21. A device according to claim 20, further including means to compressively connect said support elements to said outwardly extending cup for spring loading of, said support elements when said washer is in engagement with:

said shoulder.

i 22. A device according to claim 20, wherein said elec-.

tron gun unit further includes an anode member secured to said disc having an aperture therethrough in coaxial.

23. A device according to claim 22, wherein said out- Wardly extending cup includes a plurality of rigid electrically conductive, hermetically sealed rods extending therethrough and means to compressively connect said support elements to said rods. 7 u

24. A device according to claim 23, wherein said suppoit elements are dielectric tubes and said means to compressively connect include an L-shaped rod associated with each of said support elements having its shorter portion connected to said conductive rod and its longer portion inserted in said dielectric tubes and a spring encirclingv the longer portion of each of said L-shaped rods with one end thereof connected to said conductive rods and the other end thereof compressively bearing against the end of said dielectric tube.

25. A device according to claim 24, wherein said electron gun unit further includes a plurality of electrical leads connected between said conductive rods and certain of said electrodes.

26. A device according to claim 1, wherein said other of said end portions includes a disc disposed transversely thereof having a centrally disposed aperture therethrough coaxial of said beam path with said inner tubular formation hermetically sealed to one side thereof and said collector electrode supported from the other side thereof.

27. A device according to claim 26, wherein said inner tubular formation and its engaging cup-like member are disposed eccentrically with respect to the central aperture of said disc, said disc including a first aperture therethrough for entrance into said inner tubular formation and a second aperture therethrough disposed externally of said inner tubular formation and said radio frequency coupling means includes an output radio frequency connection having a first terminal connection extending through said first aperture, means to hermetically seal said connection to the wall of said first aperture and means to couple said terminal connection to the output end of said propagating structure and an input radio frequency connection having a second terminal connection associated with said one of said end portions for connection to the input end of said propagating structure and a transmission line connection extending through said second aperture and parallel to said central portion for connection to said second terminal connection.

28. A device according to claim 27, wherein said radio frequency coupling means further includes a second transmission line connection coupled to said first terminal connection and a means to support and separate the transmission line connections.

29. A traveling wave electron discharge device comprising a vacuum housing including a central portion and two end portions, said central portion having a smaller diameter than said end portions, a wave propagating structure disposed in said central portion, an electron gun unit disposed in one of said end portions to project an electron beam in a path along the longitudinal axis of said central portion and in interacting relation with the wave propagated along said propagating structure, a collector electrode disposed in the other of said end portions, means adjacent each end of said central portion to hermetically seal said central portion to each of said end portions in coaxial relation to said beam path, a tubular means to produce a magnetic field axially of said central portion, and a radio frequency coupling unit associated with said other of said end portions, said coupling unit having separated input and output terminal connections for said propagating structure, said output terminal connection entering said vacuum housing at said other of said end portions and said input terminal connection extending parallel to and spaced from said central portion within said tubular means and entering said vacuum housing at said one of said end portions.

30. A device according to claim 29, wherein each of said end portions include a magnetic barrier disposed transversely thereof having a centrally disposed aperture coaxial of said beam path to engage the inner surface of 1'6" said tubular means adjacent the end thereof to align the longitudinal axis thereof with said beam path and said magnetic barrier of said other of said end'portions includes a second aperture therethrough adjacent the periphery thereof for'passage of said input terminal con-v nection between the outer surface of said central portion and the inner surface of said tubular means.

31. A device according to claim 30, wherein said magnetic barrier of said other of said end portions includes a lip on the peripheral surface thereof for abutment against the end of said solenoid.

32. A device according to claim 30, wherein said means hermetically sealing said central portion to said one of said end portions includes an inwardly turned cup-like member having an aperture in the bottom thereof spaced from said beam path secured adjacent the end of said central portion and a tubular formation extending inwardly from said one of said end portions for engagement with said cup-like member, said cup-like member and said tubular formation being in coaxial relation to said beam path.

and said input terminal connection is hermetically sealed in the aperture in the bottom of said cup-like member to be in connecting relation with the input of said propagating structure.

33. A device according to claim 30, wherein said means hermetically sealing said central portion to said other of said end portions includes an inwardly turned cup-like member secured adjacent the end of said central portion and a tubular formation extending inwardly from said other of said end portions for engagement with said cuplike member, said cup-like member and said tubular formation being in eccentric relation to said beam path and said second aperture is disposed externally of the eccentric members.

34. A device according to claim 33, wherein the magnetic barrier of said other of said end portions includes a third aperture therethrough at an angle with respect to said beam path and disposed within said eccentric members and said output terminal connection is hermetically sealed in said third aperture to be in connecting relation with the output of said propagating structure.

35. In a traveling wave electron discharge device having an elongated wave propagating structure disposed to provide interaction between the waves propagated therealong and an electron beam projected along a given rectilinear path, a support and alignment arrangement for said propagating structure including a disc in transverse relation to said beam path having an aperture therethrough for passage of said beam axially thereof disposed adjacent each end of said propagating structure, a seating member fastened to each of said discs coaxially of said central aperture in supporting relation to the ends of said propagating structure and a pressure-exerting member disposed in confined relation in one of said seating members in contact with the end of said propagating structure for spring loading thereof.

36. An electron gun unit comprising a tubular housing having a circumferential shoulder on the inner surface thereof at a given point along its length, an outwardly extending cup, a plurality of rods extending through and hermetically sealed in the bottom of said cup, a plurality of dielectric tubes disposed parallel to the axis of said tubular housing, a plurality of electrodes supported by given ones of said plurality of tubes coaxially therewith, means connecting said tubes to said rods to form an integral unit and means fastened to said tubes coaxially therewith in abutting relation with said shoulder to align said electrodes coaxially of the housing axis, the outer end of said outwardly extending cup being hermetically sealed to the outer end of said tubular housing.

37. A device according to claim 36, further including electrical leads connected between said rods and said electrodes, certain ones of said leads extending through others of said tubes.

said means fastened to said tubes is in abutting relation with said shoulder.

39. A device according to claim 36, wherein said means 2 connecting said tubes to said rods include an L'-shaped member having its shorter iportion connected to each.

one of said rods and its longer portion inserted into each of said certain of said tubes and a spring encircling the longer portion of each of said members with one end thereof connected to the associated one of said rods and the other end thereof bearing against the end of the associated one of said rods and the other end thereof bearing against the end of the associated one of said tubes to apply a compressive force thereto when positioned in said housing.

40. A device according to claim 36, wherein one of said electrodes includes a cathode surface crosswise a tubular formation disposed coaxially of the housing axis, said tubular formation having a flange for connection to said tubes, a filamentary element disposed within said tubular formation adjacent the cathode end thereof and a vdisc disposed adjacent the flange end of said tubular formation to reflect the heat of said filamentary element to said cathode surface.

References Cited in the file of 'this'patent UNITED STATES PATENTS 2,510,448 Wideroe June 6, 1950 2,708,727 Quate May 17, 1955 2,727,179 Lally et al Dec. 13, 1955 2,745,983 Dohler et a1. May 15, 1956 2,776,389 Peter Jan. 1, 1957 2,779,891 Morton Jan. 29', 1957 2,788,465 Bryant et a1. Apr. 9, 1957 1 2,789,246 Wang Apr. 16, 1957 2,790,105 Hines et a1. Apr. 23, 1957 2,792,515 Borderick et a1 May 14, 1957 2,800,605 Marchese July 23, 1957 2,812,467 Kompfner Nov. 5, 1957 2,834,909 Beaver May 13, 1958 FOREIGN PATENTS 1,075,211 France Apr. 14, 1954

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