US2648797A - Grid construction - Google Patents

Description

Aug. 11, 1953 L. c. WERNER 2,648,797

GRID CONSTRUCTION Filed June 4, 1951 2 Sheets-Sheet 1 INVENTOR z. c. h/E/F/VEE.

Aug. 11, 1953 L. c. WERNER 2,643,797

GRID CONSTRUCTION Filed June 4, 1951 2 Sheets-Sheet 2 INVENTOR l. C. WEK/VEK.

ATTORNEY This invention relates to electron discharge devices, a nd in particular relates to structure for the control electrode therein.

Asis well known, the control electrode for electrical discharge tubes usually consists of a cage or grid formed by winding a wire or filament ofsuitable material helically about two or more upright rods parallel to the central axis of the tube. In most types of tubes, the cathode is positioned within this helical winding, and it is usually necessary to maintain throughout the operative life of the tube a uniform and accurate spacing of the turns of the helix, both between the turns themselves and between the turns and the cathode surface which the helix surrounds. These considerations require some way of fastening the helical winding, turn by turn, to its supporting rods; and such a fastening poses a problem of very considerable difiiculty, particularly in the case of high power or high voltage tubes.

In many such high voltage tubes, the electron emissivecathode consists of a plurality of heated tungsten wires, extending parallel to the central axis of the tube and at uniform radial distance therefrom. The cathode filaments may then be considered as elements of a cylindrical surface. In such cases, the control electrode is usually supported on rods lying on the same radial planes of this cylinder as the respective cathode filaments and at a slightly greater radial distance than the latter. Thusin Fig. 2 of the drawings, the control electrode is a wire, wound helically about four support rods which, respectively lie on the same radial plane through the central axis of the tube as do the four vertical filaments which constitute the cathode.

In high power tubes the control electrode usually comprises a molybdenum wire and it might seem simple to spot weld the turns of this wire to the support rods; but. it hasbeen found in actual practice that this .procedure was unsatisfactory and caused frequent breakage of the molybdenum wire. The above-mentioned. practice was accordingly superseded by an expedient shown in Fig; 1 of the drawings in which the turns I of the grid wire were held properly spaced apart along the support rod 2 by a helical wrapping 3 somewhat larger in diameter than the post 2 However, to insure that slight displacements of the grid wire I didnot permit it to slip past the turns of the helix 3, it wasnecessary that thelatter should extendradially inward toward the cathode filament vfor some d istance beyond the inner edgeof the grid wire I [as is shown a in Fig.1. This inward projectionnaturally limits Westinghouse ElectricCorpo'ration, East Pitts-P z:";iburgh,rPa;;-a corporation of Pennsylvania ltp plication luner'i, masters... 122937;;

9 Claims. (Cl.3 1'3-' -35 0) the minimum spacing which wasposs'ible'betwee the grid wire "I" and; the" adjacent leg' i of the cathode: filament and was otherwise 'fouri'd' 'unsatisfactory. i i

fIn its general aspect the present invention has for its object an improvement in the'supporting structure for the grids of electrical discharge tubes. More particularly, the present invention has for its object thesecuring of th'e'grid wire to its supporting posts "with greater reliability andless intrusion 'oii thelimited spacing between the grid wire and the'cathode' filament than was possible with 'control" electrode structures of the prior art. Stillanother object-bf this invention is to farm vide a :supportings'tructure for electrical discharge tube grids which can be made economical- 1y andis susceptible of being carried out readily in factory production.

Other objects of the invention will become apparent to those skilledin the art to which "it appertainsboth direct reference thereto and by implication from the" context.

Referrin'g'to the accompanying drawings in which like numerals of 'reference indicate similar parts'throughoutf the severalviws: T i Fig. 1 is'a sectional'vi'e'w indicating a support structure for control electrodes upon which'the present inv'entio'n improves; "i

Fig. 2 is a view partly in elevation andflpartly in section of a high power electrical discharge tube having "a control electrode structure embodying one form or this invention;

Fig. 3" isa detail view to a" large scale fsh'o'wing one modification of this invention; r

Fig. 'e'and Fig."5 are" respectively a view in elevation and in plan of'onem'ember of the struc-'- rare in Fig. 3;'

Fig.6 is a'plan view of a control electrode embodying the arrangement of Fig. 3;

Fig. 7 'i's'a View in perspective of another modificatiori of my invention; f

Fig. 8 is a view in elevation of still a third modification of my invention; r 1. 9 is a perspective' view illustrating still another modificationof my invention;

lFigflO is a View in elevation of the support'post used in Fig.9;

ll is a plan view of the control electrode usingthe str 'icture of Fig 9 and w I Fig. 12 is aiplan view of a controlelectrode employing a" modification of the arrangement of I urning in stem to the; aawmgs." Fig. has alre'a'ds been described in s' -ufiici'ent detail above".

Referring to Fig. 2, an electrical discharge tube referred to generally by the reference numeral I I is of the general type shown in U. S. Patent No. 2,398,608, issued April 16, 1946, to the present applicant and H. J. Bailey and assigned to applicants present assignee. Since this tube is fully described in the aforesaid patent, it is only necessary to state here that it comprises an anode I2, a pair of tungsten cathode filaments, each of hairpin form, supported with their legs 4 parallel to an equi-distant from the central axis of the anode I2, and a control electrode comprising a molybdenum wire I of helical form supported on four molybdenum posts 2 which are in the same radial planes of the anode I2 as are the four legs of the cathode filaments 4. The cathode filaments 4 are held at their lower ends in vertical posts which are supported in turn from brackets I5 afiixed to terminal posts 1 which are sealed vacuum tightthrough a glass bowl 8 to which the anode I2 is likewise sealed. There are two terminals I which are respectively connected through their brackets 6 to one end of each of the pair of cathode filaments 4, so that when the brackets I are respectively connected to the two sides of a heating circuit current flows up one side of each cathode filament 4 and down the other side to the other bracket 6 and terminal post I.

The support posts 2 for the control electrode wire I are rigidly based on an annular member I3 which may be supported from a post I4 at the center of the bowl 8 by a suitable bracket I5 which, for the sake of simplicity, in the drawing, is shown broken away in Fig. 2, since it forms no part of the present invention.

The upper end of the four posts 2 may be fastened to a top plate I6 to brace them rigidly. The upper ends of the hairpin filaments I; are held spaced rigidly apart by a member I? which is so thin and light as to require no outside support.

The modification of the invention which is shown in more detail in Fig. 3 is used in the posts 2 of Fig. 2. In this arrangement, the upper parts of the posts 2 are cut one-half away along a central plane in each which is perpendicular to the radial plane passing through the axis of the tube II and containing an adjacent limb of the cathode filament 4. The post 2 after this cutting operation is thus properly illustrated by the member 2, as shown in Fig. 3. At intervals corresponding to the spacing desired for the turns of the grid wire I, the cut face of each post 2 is provided with suitable grooves 2| of proper size to accommodate the grid wire I. Once the turns of the grid wire have been placed in this position in a manner to be described more fully below, they are locked and held in that position by a cap 22 of such form as to replace the portion of the support post 2 which had been cut away. The cap 22 is likewise provided with proper grooves to fit over the portions of the grid wire I already installed in position.

The cap 22 is held in the'above-described position by a helical binder wire 23, the convolutions of which have an internal diameter just sufficient to slip over the post 2 and cap 22 and an axial spacing equal to that between the turns of the helical wire I.

Fig. 4 is a proper illustration of both the cap 22 and the portion of the support post 22 which it engages; and Fig. 5 is a top view of Fig. 4.

The grid wire I may be put in place on the support rods 2 after the latter are fixed in position on the support member I3 by inserting through a circular central opening in member I3 a cylindrical mandrel having four longitudinal grooves into which the upper portions of the posts 2 can fit, and having a diameter equal to the internal radius desired for the helical control electrode. The grid wire I may then be wound about this mandrel with the turns positioned in the grooves 2|, and the four cap members 22 may then be put in place to hold'it. The cap members 22 may be fastened in position temporarily, or, if desired, by such a procedure as spot welding them at their ends to support post 2. The mandrel may then be withdrawn and the helical wrapping 23 be slipped, with a screw-like motion, over the posts 2. The top-plate I6 may then be put in position and the grid structure is ready for positioning in the tube II on the support post I4.

Fig. 6 is a section along the line VI-VI in Fig. 2 and showing the form of the complete control electrode.

In accordance with another modification of the invention, the support post 2, as above described, may be made of semi-tubular material of the form illustrated in Figs. '7 and 8 and designated by numeral 25. At intervals equal to the desired spacing for the grid turns, the support posts 25 may be punched to strike out projecting tongues 25 which are bent into an L-shape, as shown in Fig. '7. After the posts 25 are mount ed on support members I3 in a manner similar to that described for the posts 2 in Fig. 2, a mandrel provided with suitable longitudinal grooves for the posts 25, and having a diameter equal to that desired for the internal diameter of the helical control electrode may be placed in position and the grid wire I wound in helical configuration with the respective turns nesting in the L-shaped tongues 26. The four support rods 25 will, of course, have to be cut to length properly so that the tongues 26 are each positioned at the correct distance from the support members to sequentially engage the turns of the helical wire I properly. After the grid wire I is thus placed in position, the L-shaped tongues 25 may be bent back over the wire I to hold it firmly in position. The mandrel may then be removed from the structure and the grid completed and installed in the discharge tube in the same way as in Fig. 2.

Fig. 8 shows a support rod 3! of the same shape in cross section as that described in connection with Fig. 7 but in which the tongues 25 are required to be so closely spaced lengthwise of the support rod to accommodate the axial spacing of the grid wire I, that tongues 26 would interfere with each other if they extended parallel to the longitudinal dimension of the support rod. Hence in Fig. 8, the tongues are punched at an angle to the longitudinal axis of the support rod.

Figs. 9 and 10 show still another embodiment of the invention. The control electrode support post @I, which rep-laces the posts 2 in Fig. 2, is provided with a series of substantially chordal grooves 32 spaced at proper intervals along its length to correspond with the spacing desired between the turns of the control electrode. The four support rods ii thus grooved, and cut to length so that the distances of the grooves from the support member I3 are sequentially pro-per to position the helical ribbon I relative to member I3, have the winding I installed in proper position in the manner which will be described more fully below. The wire I is then locked in position in the grooves by a helical binder 43 quite similar to the binder 23 described in connection with Fig. 3 which may be performed and slipped into position on the rod 4| with a rotary movement like a screw being threaded into position.

The invention contemplates the alternatives of grid-supporting posts 4% either at the outside of the grid-wire convolutions, as in Fig. 11, or at the inside thereof as in Fig. 12. In the first instance, to install the wire I in position, it is first wound into a helix with desired spacing and internal diameter on a suitable mandrel. The rods 4| are then respectively positioned at points spaced 90 apart on this mandrel with their offset lower portions positioned in radial planes passing through the axis of the helix. The support member I3 may then be attached to the lower ends of the support rods 4!. The mandrel may then be withdrawn and the binders 43 rotatively slid downward into position on the four posts 4|. The top plate l6 may then be attached to the upper ends of the posts 4| In the embodiment of the posts located internally of the grid-wire convolutions as in Fig. 2, the grooves in the support posts 4! which contain the helical wire I are located in the radially outward faces of the latter. In this case, the support rods 4| may be assembled, as in the previous instance, with the support member I3 before the helical winding I is put in place. A 4

mandrel having an outside diameter equal to that desired for the internal radius of the helical grid and provided with four suitable grooves to receive the posts 4! may then be slipped into position through the central opening in the support member 13. The wire 1 may be wound as a helix fitting in the grooves 42 in the posts, after which the mandrel is withdrawn. A helical binder wire 43 may then be rotatively slid downward into place on each of the support posts 4! in the same manner as has been described above.

I claim:

1. A control electrode for electrical discharge devices comprising a wire helically wound on a plurality of substantially parallel posts, each post comprising two cooperating clamping members having transverse grooves on their adjacent faces which coact to grip the respective turns of said wire, and a helical binder closely surrounding each said post.

2. A control electrode for electrical discharge devices comprising a wire helically wound on a plurality of substantially parallel posts, each post comprising two cooperating clamping members having transverse grooves on their adjacent faces which coact to grip the respective turns of said wire.

3. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each post comprising two cooperating clamping members having transverse grooves on their adjacent faces, the grooves on one member being superposed on the grooves in the other member to form a channel for the respective turns of said helix.

4. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each post comprising two cooperating clamping members having transverse grooves on their adjacent faces, the grooves on one member being superposed on the grooves in the other member to form a channel for the respective turns of said helix, and a helical binder closely surrounding each said post.

5. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each post having the form of a cylinder split down the middle, the faces adjacent said split coacting to grip the respective turns of said wire.

6. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each post having the form of a cylinder split down the middle, the faces adjacent said split coacting to grip the respective turns of said Wire, and a helical binder closely surrounding each of said posts.

7. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each said post having the form of a cylinder split down the middle, the faces adjacent said split being provided with tranverse grooves coacting to grip the respective turns of said Wire.

8. A control electrode for electrical discharge devices comprising a wire wound helically on a plurality of substantially parallel posts, each said post having the form of a cylinder split down the middle, the faces adjacent said split being provided with transverse grooves coacting to grip the respective turns of said wire, and a helical binder closely surrounding each said post.

9. A support-post for an electrical discharge tube control electrode comprising two cooperating clamping members having transverse grooves on their adjacent faces, the two halves of each post gripping the turns of said helical wire passing between them in a transverse direction, and a liaelical binder closely surrounding each said Dos LEO C. WERNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,570,265 Lebbink Jan. 19, 1926 1,934,097 Simon Nov. 7, 1933 1,957,223 Murphy May 1, 1934 2,1 5 Barker Dec. 19, 1939 2,4 3,41 Walker et a1. Dec. 30, 1947 2,444,740 Jonker July 6, 1948

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