US3376462A - Electron discharge device grid having parallel cross straps connected at the center thereof - Google Patents

Description

April 2, was

G. MIALE ETAL ELECTRON DISCHARGE DEVICE GRID HAVING PARALLEL CROSS STRAPS CONNECTED AT THE CENTER THEREOF Filed June 24, 1965 FIG.3.

6O so FIGS WITNESSES f/M 4M4 INVENTORS Goliurdo Miole 81 Edward R. Compognu ATTbRNEY III Patented Apr. 2, 58

fiice 3,376,462 ELECTRON DISCHARGE DEVICE GRID HAVING PARALLEL CROSS STRAPS CONNECTED AT THE CENTER THEREOF Goliardo Miale and Edward R. Campagna, Bath, N.Y.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 24, 1965, Ser. No. 478,002 7 Claims. (Cl. 313350) ABSTRACT OF THE DISCLOSURE This invention relates to a frame grid type of electrode for an electron discharge device including a pair of side rods disposed in a substantially parallel relation, a plurality of grid wires disposed between and supported by the pair of side support rods, and at least one pair of frame straps disposed between and secured on both sides of the side support rods. More particularly, the frame straps are so shaped that a portion of one frame strap may be connected to a portion of the other frame strap and that the frame strap is withdrawn from the surface of an adjacently disposed electrode.

This invention relates to electron discharge devices and more specifically to improvements in electrode structures therefor.

In those applications of electron discharge devices where the device is being operated at high frequencies and/or at low noise levels, the spacing between a cathode element and a lateral grid wire of a control or first grid electrode of this device must be made smaller and with greater precision than in other electron discharge devices. If the spacing between the cathode element and the grid electrode is not accurately controlled, a great difference in the performance of similarly designed electron discharge devices will be obtained when produced by mass production methods. The transconductance of such devices in general varies as a function of the spacing between the lateral grid wires of the control grid element and the surface of the cathode element; therefore, this spacing should be made as small as possible and must be accurately set if a product having improved, uniform characteristics is to be manufactured.

Another difiiculty in the production of high performance electron discharge devices results from the necessity of providing a grid element having a greater number of turns per inch of the lateral grid wire and of using a very thin lateral grid wire. In the ordinary type of grid element structures, there are no means to establish an accurate and rigid spacing between the side support rods upon which the lateral grid wire is suspended. Also as a greater number of turns per inch of lateral grid wire is used, it is necessary to reduce the wire diameter to a magnitude as low as .3-.5 mils. Thus as the wire diarneter becomes smaller and the turns per inch greater, the tension exerted upon the two separated, non-rigid side rods becomes great enough to physically bend the side rods. This in turn distorts the shape of the finished grid, which will make it difficult if not impossible to provide the desired uniform cathode to grid distance.

A possible solution of this problem has been the utilization of a frame type support structure upon which the fine lateral grid wire may be suspended. Typically, such frame structures consists of two support rods which are interconnected rigidly with a plurality of members or straps. It is noted that such structures may be formed as by stamping out a unitary member or by welding the individual straps to the side support rods. In either case, a

rigid structure is provided about which the fine lateral grid wire may be disposed.

Such a grid electrode structure has been more thoroughly described in a copending application, entitled Assembly of Electrodes with Aligned Grid Wires for Electron Discharge Devices, by Goliardo Miale and Anton van der Jagt, Ser. No. 438,272, and assigned to the assignee of this invention. More specifically, this copending application describes a grid structure commonly known as half frame grids comprising a pair of side support rods, a strap disposed on one side of said support rods, and a plurality of lateral grid wires disposed and suspended upon the other side of the side support rods. One of the many advantages of this structure is that the lateral grid wires of this structure may be positioned within .001 to .0015 inch of an adjacent electrode without interference from the strap which rigidly supports and spaces the side support rods from each other. Though the desirability of maintaining an accurate and small spacing between the cathode element and a control grid electrode has been noted above, the copending application fully discusses the advantages of maintaining an accurate spacing between a first or control grid electrode and a second or screen grid electrode or" half-frame variety. Specifically, it has been verified that by maintaining a minimum distance between the first grid electrode and a second grid electrode that the number of electrons absorbed by the second grid electrode and as a result the noise figure of the electron discharge may be significantly reduced. As further shown in the above-mentioned copending application, half-frame grids are incorporated into a tetrode electron discharge device as the second grid electrodes. A principal advantage of the half-frame grid structure is that it may be positioned very close to an adjacent element. In ordinary full frame grid structures, sup port straps are placed on either side of the side support rods and as a consequence may contact an adjacent element thereby limiting the spacing between this element and the grid structure. However, by placing the straps on only that side of the side support rods remote from the lateral grid wires, the lateral grid wires may be spaced at extremely close distances from the adjacent element.

However, when attempts were made to wind half-frame grid structures with a turns per inch of lateral grid wire in the order of 300' to 400, it was discovered that a portion of the laterial grid wires were only loosely suspended between the side support rods. Upon further investigation, it was found that the side support rods had a tendency to rotate under the influence of the winding of the lateral grid wires due to the lack of a supporting strap on both sides of the grid electrode structure. As more fully explained in the above-mentioned copending application, the frame grid electrodes are formed by rotating the side support rods as by a grid lathe and by continuously moving the electrode grid structure as the lateral grid wire is being fed onto and wound about the side support rods. The result of the revolving action was to provide loose lateral grid wires in the initial stages of the winding due to the increasing tension placed upon the side support rods by the lateral grid wire as the process of the winding is continued. Thus, those lateral grid Wires that are wound upon the grid electrode at the end of the winding process are placed under great tension, while those lateral grid wires initially wound are loosely supported upon the side support rods.

Typically at the end of the manufacturing process, each of the electron discharge devices are subjected to a microphonic test which detects the high frequency vibration of the lateral grid wires while the tube is being mechanically shocked. The results of this test may be observed on a monitoring or scope device as a fluctuation in the plate current; the looser the lateral grid wires, the greater the signal recorded and the longer it takes for this signal to subside. Further, it may be well understood that loosely suspended lateral grid wires may be easily deformed so as to effect differences in the spacing between the lateral grid wire and an adjacent electrode and thereby produce different parameters between each of the electron discharge devices.

Accordingly, it is the general object of this invention to provide a new and improved electron discharge device.

It is another object of this invention to provide an improved electron discharge device wherein the lateral grid wires of a grid electrode are securely supported and spaced with respect to adjacent elements of the device.

It is a further object of this invention to provide a new and improved electrode grid structure wherein the side support rods are securely positioned with respect to each other.

It is another object of this invention to provide an improved electrode grid structure which can be wound with high turns per inch of lateral grid wires under high tension without a deformation of either the side support rods or the lateral grid wires.

A still further object of this invention is to provide an improved electrode grid structure for an electron discharge device wherein the side support rods are rigidly spaced and supported from each other without mechanical or electrical interference with adjacent elements of the electron discharge device.

Briefly, the present invention accomplishes the abovecited objects by providing an improved electron discharge device, wherein there is incorporated an electrode structure having support members or straps fixedly disposed on either side of the side support rods. Further, a portion of the straps disposed on either side of the side support rods is securely attached to the strap disposed upon the other side of the side support rods to thereby provide a structurally rigid structure. In addition, it is desired to form that strap in proximity to an adjacent element of the electron discharge device so that the strap is substantially removed from the surface of the adjacent element. In one particular embodiment of this invention, the support members or straps disposed on either side of the side support rods are each shaped and attached to form a structure having an X configuration. In an alternative embodiment, that strap in proximity to the adjacent element is so bent or formed that a portion thereof may be attached to that strap upon the opposite side of the side support rods which retains its linear shape.

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 shows a partially sectioned view of an electron discharge device in which this invention has been incorporated;

FIG. 2 shows an isometric view of an electrode as sembly which has been incorporated in the electron discharge device of FIG. 1;

FIG. 3 shows a plan view of the grid electrode structure of this invention and an adjacent element which may be incorporated into the electron discharge device of FIG.

FIG. 4 shows a side view of the grid electrode structure shown in FIG. 3; and

FIG. 5 shows a plan view of an alternative embodiment of the grid electrode structure and an adjacent element which may be incorporated in the electron discharge device of FIG. 1.

Referring now to the drawings and in particular to FIG. 1, there is shown an electron discharge device employing the present invention in its preferred form. The electron discharge device 10 is comprised of an envelope 12 made of a suitable material such as glass with an electrode assembly indicated generally by the character 24 enclosed therein. The envelope 12 shown is of conventional design includes a tipped off exhaust 13 on top of the envelope 12 and a button stem header 14 closing off the bottom portion of the envelop 12. A plurality of electrically conductive terminals or lead elements 18 are sealed through the header 14 and are connected to the elements of the electrode assembly 24 by the interconnecting leads 16. The terminals 18 not only supply the necessary voltage to the elements of the electrode assembly 24, but also act in conjunction with a pair of insulating elements 20 and 22 to support the electrode assembly 24 within the envelope 12.

Referring now to FIGS. 1 and 2, the electrode assembly 24 includes an electron emissive element or cathode 26 of the indirectly heated type which extends through and is supported in apertures 27 and 29 respectively of the insulating elements 22 and 20. A folded heater element 38 is disposed within the cathode 26 to energize a layer 56 of a suitable electron emissive material such as one of the barium strontium carbonate. A pair of grid electrodes 32 and 30 are disposed on either side of and in planes parallel to the cathode 26. The grid electrodes 30 and 32 are of the half-frame variety and are comprised of (see also FIGS. 3 and 4) side support rods or side members 40 which are spaced and supported in a parallel relationship from each other by support members or cross straps 46 and 48. Upon that side of the grid electrodes 30 and 32 adjacent the cathode 26, there is fixed to the side sup port rods or side members 40 a plurality of lateral grid wires 44 disposed in a substantially parallel relationship to each other. It is noted that no lateral grid wires 44 are disposed upon the other side of the grid electrodes 30 and 32. Further, the side rods 40 of the grid electrodes 30 and 32 are mounted within apertures 41 within the spacer elements 20 and 22.

Two substantially planar anode elements 34 and 36 (see FIG. 1) are disposed in planes parallel to and on either side of the grid electrodes 30 and 32 respectively. The anode elements 34 and 36 are supported by the spacer elements 20 and 22; more specifically, each of the anode elements 34 and 36 have tab portions which extend through slots 52 of the spacer elements 20 and 22. As, shown in FIG. 2, the side rods 40 may be secured to the spacer element 22 as by stops 54 which are attached to the side rods 40 as by welding. It may be understood that the straps 46 and 48 directly abut against one side of the spacer element 22 and that the stops 54 abut against the other side of element 20 to thereby securely mount the grid electrodes 30 and 32 upon the spacer element 22.

In one exemplary embodiment of this invention, the anode elements are made of an aluminum clad steel. Further, the grid element comprises a pair of side rods made of molybdenum and having a diameter of .0305 inch, and frame straps made of molybdenum for maintaining the side rods spaced at a distance of .200 inch. A plurality of lateral grid wires made of tungsten and having a diameter of .0004 inch is wound with a turn per inch of 413 about a section of the side rods .320 inch long. The frame straps are disposed .364 inch from each other and are securely attached to the side rods as by welding.

As disclosed in the above-mentioned copending application, the grid elements may be manufactured by first forming a ribbon including a pair of side rods rigidly spaced from each. other by the frame straps, and then winding the lateral grid wires thereabout as upon a grid lathe. In order to eliminate the waste of removing the lateral grid wires from one side of the ribbon to form the half-frame grid, it is suggested that two ribbons may be wound simultaneously thereby disposing a single set of grid wires upon only one side of each ribbon. After the winding process, the ribbons may be separated as by cutting the lateral grid wires joining the ribbons together. Further, lateral grid wire may be further conserved if the the ribbons are offset from each other so that the frame straps do not directly abut against each other but instead lie upon the side rods of the opposite ribbon.

As shown in FIGS. 3 and 4, the grid electrodes of this invention have been designed to be placed at a minimum distance from an adjacent element such as the cathode 26, while supporting the side rods 40 rigidly with respect to each other. In particular, a portion of the support members or straps 46 and 48 intermediate the side rods 40 are securely attached to each other. In a preferred embodiment of this invention, the portions of each of the straps 46 and 48 are secured to each other as by spot welding. In the alternative, the portions of the straps 46 and 43 could be attached as by a clip 50. Further as shown in FIG. 3, the strap 48 has been so shaped so as to prevent any mechanical or electrical interference with the adjacent element (i.e. cathode 26). Specifically, the strap 48 has been bent inward and away from the surface of the adjacent element so as to provide a greater spacing A between the grid electrode and the adjacent element. The straps of a regular or full frame grid must be spaced at a greater distance from the adjacent cathode because of the thickness of these straps. It has been found that the maximum grid electrode strength is obtained when the shape of the straps approaches that of an X (see FIG. 3). In addition, the bent or curved straps 46 and 48 may make it possible for such a grid electrode to be spaced from an adjacent element by distances as small as .001 inch to .0015 inch.

Although the above explanation and drawings have been directed to that case where a grid electrode is spaced from a cathode, it is pointed out that the grid electrode of this invention could likewise be spaced at a minimum distance from another grid electrode. As disclosed in the above-mentioned copending application, a half-frame grid electrode could be spaced at a close distance from a first or control grid thereby assuring that the current absorbed by the second half-frame grid and the noise factor are minimized. It is noted that the half-frame grid of this invention could be easily incorporated into the electrode assembly of the copending application as a second or screen grid electrode. Further, the specific method as disclosed in the above-mentioned copending application of winding the lateral grid wire about the side support rods to insure the accurate alignment of the active portions of the grid laterals of adjacent grid electrodes could likewise be adapted to wind the grid wire upon the side support rods of the electrode structure of this invention.

Referring now to FIG. 5, an alternative embodiment of this invention will be described. This electrode structure comprises a pair of side support rods 6t) which are disposed and supported in a parallel relationship by straps 66 and 68 which are in turn secured upon opposite sides of the support rod 60 as by welding. Further, a portion of the straps 66 and 68 intermediate the side rods is secured as by welding or in the alternative by a clip 79. A plurality of lateral grid wires 67 are disposed in a plane and suspended from the side rods 60. As shown in FIG. 5, the curvature of the strap 68 may be varied to provide greater clearance or spacing between the straps 68 and the surface of an adjacent element (i.e. cathode 26).

While there has been shown and described what is at present considered to be the preferred embodiment of this 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 arrangemens 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.

We claim as our invention:

1. An electrode for an electron discharge device comprising a pair of side rods disposed in a spaced apart relationship to each other, a plurality of uniformly spaced grid wires extending between and supported upon said side rods, and a pair of straps extending between and attached to said side rods, each of said straps having a portron secured to a portion of the other strap to provide a rigid structure.

2. An electrode for an electron discharge device comprrslng a pair of side rods held in a spaced apart relat onship by a pair of frame straps extending between said side rods, each of said side rods disposed between and attached to said frame straps, and a plurality of lateral grid wires extending between and supported upon said side rods, a portion of each of said frame straps secured to a portion of the other frame strap.

3. A frame type grid electrode for an electron discharge device comprising a pair of side rods held in a substantially parallel and spaced apart relationship to each other by two pairs of frame straps extending between and positioned at either end of said side rods, each of said side rods disposed between and attached to each of said frame straps, and a plurality of lateral grid wires disposed in a uniformly spaced relation between said two pairs of frame straps, said plurality of lateral grid wires extending between and attached to said side rods, each of said pairs of frame straps having a frame strap with a portion thereof secured to a portion of the other frame strap.

ft. An electrode for an electron discharge device comprising a pair of side rods held in a spaced apart relationship from each other by a pair of straps extending between and supporting said side rods, each of said side rods disposed between and secured to said frame straps, and a plurality of grid wires extending between and supported in a plane by said side rods, said straps being so formed as to be withdrawn from said plane and to allow a portion of each of said straps to be attached together.

5. An electron discharge device comprising a first and second electrode, said first electrode including a pair of side rods held in a spaced relationship from each other by a pair of straps extending between and attached to said side rods, and a plurality of lateral grid wires disposed between and suspended from said side rods, said second electrode having a surface disposed adjacent said first electrode, said straps being so formed as to be withdrawn from said surface and to allow a portion of each of said straps to be attached together.

6. An electron discharge device comprising a first and second electrode, said first electrode including a pair of side rods held in spaced relationship by a first and second strap each extending between and attached to said side rods, and a plurality of uniformly spaced lateral grid wires disposed between and suspended from said side rods, said second electrode having a surface disposed adjacent said first Strap of said first electrode, said str-aps being shaped that a portion of said first strap is secured to said second strap and that said first strap is recessed from said surface to thereby allow said first and second electrodes to be closely spaced from each other.

7. An electrode for an electron discharge device c0mprising a pair of side rods held in a substantially parallel, spaced apart relationship with each other by a pair of frame straps extending between and supporting said side rods, said side rods disposed between and attached to said frame straps, and a plurality of lateral grid wires extending between and suspended upon said side rods, said frame straps being shaped in an X configuration and having portions thereof securely attached to each other.

References Cited UNITED STATES PATENTS 3,258,637 6/1966 Schiekel 3l3350 JOHN W. HUCKERT, Primary Examiner. A. J. JAMES, Assistant Examiner.

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