Patent Publication Number: US-3875445-A

Title: Meshed cathode for electron tubes of the grid-controlled type

Description:
United States Patent Bachmann et al.  
 [54] $55553 gg g iggg fkggggg FOREIGN PATENTS 0R APPLICATIONS 987,46I 3/1965 United Kingdom................. 3l3/34l [75] Inventors: Robert Bachmann, Dottingen; Hans Noll Dletlkon both of Switzerland Primary ExaminerAlfred E. Smith [73] Assignee: BBC Brown Boveri &amp; Company Assistant Examiner-Saxfleld Chatmon, Jr.  
  Limited, Baden, Switzerland Attorney, Agent, or Firm-Pierce, Scheffler &amp; Parker [22] Filed: Sept. 5, 1973 [21] Appl. No.: 394,489 [57] ABSTRACT A meshed cathode structure particularly for use in Foreign Application U&#39; Data high power grid-controlled transmitting tubes com- Sept 6. 1972 Switzerland l303l/72 prises an electrically conductive tubular current leadin member provided with a frusto-conical support [52] US. Cl 313/348, 3 [3/34], 3l3/348, which is also electrically conductive. The periphery of the frusto-conical support is provided with circular ar- [51] rays of uniformly spaced apertures and recesses, the J J arrays being offset circumferentially relative to one [58] Field of Search 3l3/34l, 346, 348 another. and the adjoining ends of two cylindrical meshed cathode components are welded respectively [56] References Cited at mesh junction points at the apertures and recesses.  
  UNITED STATES PATENTS 3.449.616 6/1969 Sarrois 313/348 x 6 Clams 2 Drawmg F 9| z y a 1 1 \N i p I PATEMEQ AFR I M5 MESHED CATHODE FOR ELECTRON TUBES OF THE GRID-CONTROLLED TYPE The present invention relates to an improved construction for a meshed cathode structure for electron tubes, particularly for maximum power, grid-controlled transmitting tubes, wherein adjacent ends of component cathodes are rigidly connected to a coaxial supply conduit, which is connected to a lead in the tube base.  
  It is already known to provide meshed cathodes with holding members, which are mounted in an insulated manner on a central supporting rod, in order to prevent deformation of the meshed cathode in its axial direction, if a thermal expansion of the cathode wires occurs. The holding members are intended to establish an improvement in the mechanical stability of the meshed cathode in the axial direction. (DBGM l 823 41]). It  
 is further known, in a meshed cathode provided with a central supporting rod, to mount a ring in an insulated manner on this supporting rod, the external diameter of the ring being equal to the internal diameter of the meshed cathode. (British Pat. No. 987,46l). According to the German Laid-open Specification No. L901 .208. a meshed cathode is likewise known which comprises, opposite a supporting rod, an insulated annular disc which has an external diameter coinciding substantially with the internal diameter of the meshed cathode in such a manner that the cathode wires of the meshed cathode bear loosely against the annular disc.  
  The known devices have various disadvantages, how ever, which consist. in particular, in that in large meshed cathodes, particularly in those which have a long length of the cathode in comparison with the diameter, there is the risk of deformation during operation. Even in so called two-tier meshed cathodes, there is a serious disadvantage in the fact that the incandescent length of the whole cathode is interrupted in the middle, the length ofthis interruption depending essentially on the construction of the connection of the abutting ends of the two component cathodes to the current supply at the center of the cathode.  
  It is the object of the invention to provide a multitier. preferably two-tier. meshed cathode for maximum power electron tubes, the cathode center of which can be taken individually out of the electron tube through tubular supports, so that the interruption in the incandescent length, which is caused by the support of the cathode center, is only minimum.  
  According to the invention, the above-mentioned problem is solved by the fact that a current-conducting support is provided to connect the grid portions forming the meshed cathode.  
  It is a particular advantage if the support is an annular member which comprises apertures and recesses at the outer periphery.  
  The advantage of the construction according to the invention consists in particular in that the current supply to the meshed cathode can be effected through a single conduit while the annular member is mounted on the tubular duct for the cathode center (CF conduit). This leads to the possibility of the interruption in the incandescent length of the two cathode parts being considerably reduced.  
  According to a further embodiment, it is provided that the outer periphery is constructed in the form of a serpentine bend. This construction enables the two parts of the meshed cathode to be offset circumferentially by half a horizontal mesh diagonal in relation to one another.  
  As a result of this arrangement, it is possible to weld the ends of the two component cathodes, substantially at the same height, to the support, by means of arc welding, so that the ring thus formed and the connecting piece to the tubular duct for the cathode center (CF conduit) again form a frusto-conical unit.  
  With the supporting ring thus formed, it is further possible to achieve that the upper cathode component is welded to the support for the cathode center being offset circumferentially by half a mesh diagonal in relation to the other and likewise offset in height by half a mesh diagonal in relation to the other so that the two cathode components are aligned one above the other with the minimum possible interruption. Mutual alignment of the two cathode components is of particular importance when the wire arrangement forming the control grid in the electron tube has to have a specific orientation with regard to the cathode wires and specifically with regard to their points of intersection.  
  The foregoing, as well as other objects and advantages inherent in the invention will become more apparent from the following detailed description of preferred embodiments of the improved cathode structure and the accompanying drawings illustrating them, the two views, FIGS. 1 and 2 presented being in perspective.  
  With reference now to FIG. 1 of the drawing, the supply conduit is designated by l which is disposed concentrically with a tubular duct 2 for feeding current to the cathode center. Secured to duct 2 is an annular support 3 having a frusto-conical configuration and to which the two-part cathode structure is secured at its center. Formed at the outer periphery 4 of the support 3 is a serpentine web 5 established by a circumferential array of uniformly spaced apertures 6 and a circumferential array of uniformly spaced recesses 7 having the same spacing as the apertures 6. The apertures 6 and recesses 7 are circumferentially i.e. laterally offset in such manner that each aperture 6 is located centrally between adjacent recesses 7.  
  The meshes 8 of the two cylindrical meshed cathode components 9, 9 are welded onto the web 5 in such manner that the welding points 10 for the meshes 8 are disposed so that, for example, the upper meshed cathode component 9&#39; is welded to the upper edges of the recesses 7 in the periphery of support 3 circumferentially offset from the lower meshed component 9 welded to the lower edges of the aperture 6 by half a horizontal mesh diagonal 11, and wherein the ends of the two components, i.e., the welding points thereof are disposed at the same height on the support web 5. In FIG. 2, which is similar to FIG. 1, in addition to having the welding points 10 for the meshes 8 of the two cylindrical cathode components laterally offset by half a horizontal mesh diagonal the upper and lower meshed grid components 9&#39;, 9 are likewise offset from one another in the vertical direction by half a vertical mesh diagonal 12. As a result, it is possible to secure the two meshed cathode components 9, 9&#39; to the support structure 3 with the minimum possible interruption.  
 We claim:  
  1. A meshed cathode structure for electron tubes and which is particularly useful for high power gridcontrolled transmitting tubes which comprises a supply conduit connectible to a lead-in in the base of the tube,  
 a current-conducting support for the cathode structure secured to said supply conduit, said support being constituted by an annular member which includes a first circumferential array of uniformly spaced recesses pro vided in the peripheral edge of said annular support member and a second circumferential array of uniformly spaced apertures provided in the peripheral portion of said annular support member and circumferentially offset from said circumferential array of recesses so as to lie intermediate the latter, a first cylindrical meshed cathode component, the meshes at one ,end of which are secured at said circumferentially spaced recesses, and a second co-axial cylindrical meshed cathode component adjacent said first cathode component and wherein the meshes at one end thereof are secured at said circumferentially spaced apertures.  
  2. A meshed cathode structure as defined in claim 1 wherein said annular cathode support member has a frusto-conical configuration.  
  3. A meshed cathode structure as defined in claim 1 wherein the circumferentially spaced arrays of recesses and apertures at the peripheral portion of said annular cathode support establish a serpentine web for securing the ends of said first and second meshed cathode components thereto.  
  4. A meshed cathode structure as defined in claim 1 wherein said cylindrical meshed cathode components are offset circumferentially relative to one another by half a horizontal mesh diagonal and wherein the ends thereof are disposed at the same height on said support.  
  5. A meshed cathode structure as defined in claim 1 wherein said cylindrical meshed cathode components are offset circumferentially relative to one another by half a horizontal mesh diagonal and wherein the ends thereof are offset vertically relative to one another by half a vertical mesh diagonal.  
  6. A meshed cathode structure as defined in claim 1 wherein welds uniting the ends of said cylindrical meshed cathode components with said support at the apertures and recesses provided thereon are effected at junction points of the mesh.