US1700896A - Triode tube - Google Patents

Description

Feb. 5, 1929. 1,700,896

s. M. KINTNER TRIODE TUBE Filed July 3. 1926 WITNESSES: lNVENTOR ATTORNEY Patented Feb. 1929.

UNITED STATES PATENT OFFICE.

sexual. in. Human, or PITTSBURGH, rnNNsYnvANIA, AssIeNon T0 wnsrmenousn ELECTRIC & MANUFACTURING GOMPANY, .A CORPORATION on PENNSYLVANIA.

TRIODE TUBE.

} Application filed July 3,

My invention relates totriodcs and. it has particular relation to devices in which it is desired to make the space between the electrodes as small as is consistent with manu-" facturing' requirements. In making triode tubes of certain types, in.

particular, such as are used for radio re-j ceiving' purposes, it is often important that the tubes shall operate with extremely low power consumption in order to permit operationof such devices from commercially availsize which are spaced by distances which would ordinarily be considered as out of question in devices adapted forcommercial a to a radio receiving tube, such as 1s shown production.

, A tube of the type which has been found best adapted for the conditions outlined above comprises a straight-line filament surrounded by a helical it has been possible to manufacture such tubeswith clearances of the order of mils between the individual electrode elements. Since the grid helix is made of very thin, wire, it is necessary to provideya stiffening member for the samein the shape of a grid post disposed lengthwise the helix and welded to the wires thereof. While the grid post does not perform any essential function in the way of controlling the electron discharge. from the cathode,it must, nevertheless, be disposedin the very narrow space between the cathode and the anode cylinder and, in view of the practical clearance limitation of about 20 inils between the conducting parts of the electrodes, it was necessary'to increase the radius of the plate cylinder by an amount equivalent to the tbickn'essof the grid post, or about 20 mils, in order to makepossible the manufacture and operation of such tubes without excessive waste resulting electrodes. It -is clear that the'increase' of from accidental short circuits between the plate diameter which appeared thus, to be necessary'for the accommodation of the post materiallydetracted' from qualities of the tube.

'According to my invention, thebenefits I 1 derived from the extremely small clearance limit between the major portions of the aci. 't as been necessary to degrid and a cylindrical plate and 1926. Serial No. 120,437.

reducing the clearance in the portions of the interelectrode space in which the grid post is located, by slightly deforming the cylindrical shape'of the plate, and, in some cases, of the grid, so that the major portions of the electrode surfaces are spaced from each other by a distance corresponding to the smallest permissible clearance limit.

In the accompanying drawings Figure 1 is an enlarged elevational' view of a radioreceiving tube embodying my invention, portions of the envelope and the electrodes being broken away,

Fig. 2 is a horizontal sectional view of the electrode assembly in Fig. 1, taken along the line II-II, and

"Figs. 3' to 6 are views, similar to Fig. 2,

showing modifications of my invention.

My invention will be explained as applied in Figs. land 2 of the drawing, in which a tipless envelope .1 has a reentrant stem 2 which is provided with a fiat p'ress 3 inwhich are fused four lead-in wires 5 to 8 serving to'support, and to provide electrical connections .to, concentrically arranged cathode,

grid and anode members 9, 10 and 11, respectively.

As explained hereinbefore, the tubes of the i type under consideration are designed to operatefrom small-power sources, such as com -mercially available dry cells, and, accordingcathode filament, grid and anode cylinder as 'close' to each other as possible in order to obtain a maximum amplification factor at a minimum plate impedance. l a v The electrode assembly illustrated in the drawing presents the utmost limit of development in this direction that hasbeen' reached, the controlling limitation in the re duction of the 'interelectrode spaces being, of course, that the. tube)- shall be suitable for commercial production in large quantities without danger of waste'because of short circuits due to small clearances.

The cathode member 9' is made in the shape of a thin, straight-line filament pro vided' with tips 13, the lower tip being welded,

the lead-in wire 5, and the upper tip being Welded to a spring 14 held by a carrier rod 15 which is secured to an extension of the lead-in wire 6."

The grid member 10 has the "shape of a rod 21 held, at its lower end, on the plate leadin wire 8 and, at its upper end, on a bracing rod 22 which is fused into the glass head 19 similar to the grid-bracing rod 18.

As shown in Fig. ,2, the plate is made by bending a substantially rectangular. sheetmetalpiece into tubular form and folding side ends of the sheet to. form a pair of contacting extensions 25 provided with a longitudinal groove 26 fitting over the plate carrier rod 21.

The entiresupporting structure is so ar-- ranged as to positivelyso locate the cathode,

grid-and plate with respect to each other as to prevent microphonic noises that may result from even small vibrations caused b shocks or other forces transmitted to the tube.

The filament 9 is maintained, at all times, in taut condition by the spring 14 at the upper end thereof. V

In order to reduce the clearance between the electrodes to a minimum and, at the same time, to providespace for the grid post, the tubular anode or plate 11 is notmade of circular shape, as was usual heretofore, but of oval or pear shape, and the grid post is positioned on the side of the tubular plate which bulges-outwardly at 27. This shape of the plate and location of the grid makes it possible to keep down the spacing between the outer cylindrical surface of the grid and the cooperating cylindrical portion of the major part of the plate down to the lowest'limit required for manufacturing, and other, reasons and, at the same time, to provide the same minimum clearance in the portion of the interelectrode space where the grid post is located. I11 other words, the major part of the plate llis made to conform to the shape of a cylinder having a radius which exceeds the radius of the grid cylinder by the amount of clearancejrequired: However, on the side where the grid post 17 is located, outside the grid helix 10, the plate 11 deviates from the cylindrical shape and is provided with the outward bend27 increasing at this portion, the width of-v the late by an amount correspending to the width of the grid post 17.

The improvement resulting from the foreconsideration.

going electrode structure is obvious when it is considered that, for the past several years, it wasthought necessary to make the plate in the shape of a cylinder having a radius corresponding to the distance between the filament'9'and the outwardly bent portion 27 of. the plate 11; that is, 'to the sum of the radius of the plate which would be required were there no grid posts to be inserted in the space between the electrodes plus the width of the grid post. Small as the change may appear, it is nevertheless of very great practical consequence since it enables a decrease in the plate impedance, and a proportionate increase of the'mutual conductance of the tube by 15 to 20%, as against the prior-art tubes. The beneficial effect is large because of the small magnitude of the clearances, as com- I pared to the width of the Thus, in actual tubes made according to my invention, the outer diameter of the grid helix is about mils and the width of the post is about 22 mils. Adding the required clearance of 20 mils to the grid radius of 45 mils we obtain 65 mils as 'a radius for the major cylindrical part of the grid 11. The distance between the outwardly bent portion 27 and the center of the tubes is then approximately 87 mils, corresponding to an increase of about 37% over the spacing of the other portions of the anode from the cathode. Since the plate impedance increases approximately directly with the radius of the plate cylinder, it is clearthat a tube with an 87 mil plate radius has a materially larger plate impedance than that of the tube made according'to my inven-' tion.

It is, of course, understood that the precise figures for the electrode dimensions given above are deviated from, to a. more or less extent, in the practical construction of the tubes, and are chiefly intended to give a better understanding of the principles underlying the invention and not to limit the scope thereof.

The principles underlying the tubecongrid post under fication shown in Fig. 3, the plate 3l'of a shape similar to that shown in Fig. 2, is made so that plate 31' deviates from its cylindrical shape at the place where the two lateral extensions 32 meet to form the plate supporting pin 26, the grid post 17 being located in the widened interelectrode space adjacent there- The modification of my invention shown in. Fig. 4 distinguishes from those of the previous figures in that the' grid is of the oval type, being made in an automatic machine with the grid helix 34 wound around the grid post 17 so that the g1'id post is dis I 1. In an electfon-rlischarge tube, a cathposed in the spacebetween the cathode 9 ode having an electron-emitting outer surand the grid helix 34. The shape of the face, a tubular electrode surrounding said by a distance corresponding to the width of .grid and the plate.

grid llellX' conforms thus to .the principles cathode, a conducting supporting post exoutlined in connection with the shaping of tending .into the space betwen said cathode the plate 11 in Figs. 1 and 2.

g The major and said electrode and filling a substantial portion of the grid helix conforms to :1- cyl part or said space, 1 the adjacent opposite inder having a radius corresponding to the surface portions of said electrodes being so minimum clearance distance from the filaspaced that the free insulating clearances ment, withthe side of the grid helix adja: are substantially uniform. throughout the cent to the grid post being bent outwardly entire inter-electrode space.

2. In an electron-discharge tube, a centhe post to provide the same minimum clear v ance between the" inner side of the grid post electrode-enclosing said cathode member and and the filament f The plate 31 may then a'conducting post extendingparallel to said have the-"same shape as that shown in Fig.

cathode member in the space therebetween, the manor portions of the opposing adjacent 3, giving equidistant spacing between the surfaces of said cathode and said electrode Fig. illustrates "the applicationof the having the same uniform clearance except same principles to a grid that is supthepor'tionsbetween which said post is disported on'two posts 17 and 37 The tubuposed, the clearance at said last-mentioned lar plate-38 has, in this case, two outwardly portions being equal to the clearance bebent portions39 to rovide'the additional tween the major portions of the electrodes clearances necessary or accommodating the plus the width ofsaid post.-

two posts. 3. In an electron-discharge tube, alinearly In the constructions hereinbefore deextending cathode member, a tubular grid scribed, the cathode was always assumed to surrounding said cathode member; a tubut-ral straight-line cathode member, a tubular be a straight-line filamentary member, of lar anode surrounding said'grid, apost supsmall width and, in determininq the clear-' portin said grid and disposedparallel to ances between the grid and the filament, the the axis thereof, said rid'and anode-being width or the shape of the latter appeared to of such shape and width be of little influence. However, the prinlating clearances between the electrodes are that the radial ihsu ciples underlying my invention are not in substantially uniform throughout the interany way limited to filamentary cathodes, only electrode space.

but may be. applied to cathodes of any type. 4. In a hot cathode electron discharge Thus, in the modification shown in Fig. 6, tube, a central linearly extending cathode, the cathode 41 is made in the shape of a rod a tubular grid helix surrounding said cathmember, the outer'surface of which. con-. ode, a tubular plate surroundingsaid grid stitutes on oval-shape, electron-emitting helix, a conducting rod extending parallel cathode element 42 which is heated by a pair to said cathode and supporting the turns of of internally disposed filamentary heater the helix in the space between said cathode wires 43, as described in Canadian Patent No. and said plate; the insulating clearance in a 265,517.. To secure the benefits derived from radial direction between the cathode and the close spacing of the electrodes, the grid 44 plate at the portion where said rod is 10- is madein the shape of an oval helix which cated being substantially equal to the radial is equi-distantfrom the oval surface of the insulating clearance between theother porface thereof is spaced from the geometrical minimum insulating clearances body conforming to the outward boundary ma or portions of the electrodes without arrangement shown in Fig. 6, a practically cathode member 41. The tubular plate 45is tions of said electrodes, increased. by the then madeof such shape that the inner surwidth of the grid-supporting post to secure between of the grid helix with the associated grid transgressing the limiting insulating clearposts by a distance equal to the minimum ance required fromreasons of manufacture inter-electrode clearances. In case of the or operation.

cylindrical plate 45 is thus obtained, the ing. a linearly extending filament, a tubular wide spaces between the fiat sides of the grid grid helix surrounding said cathode and a 44 and the adjacent portions of the plate tubular anode surrounding said grid, said cylinder 45 being used to locate therein two electrodes being so shaped and spaced from grid-supporting posts 46. each otherthatthe distances between adja- Many other modifications of my invention cent portions of the major parts of the sevwill suggest themselves to those skilled in'the eral electrodes shall be as small as is permisart and it is desired that the scope of the insible from practical considerations, a gridvention shall not be limited except as defined supporting post extending into the" space beby the appended claims and by the prior art. tween said cathode and said anode and ex- I claim as my invention: U tending parallel thereto, said plate being 5. In an electron-discharge tube comprisbent outwardly to provide additional clear ance throughout the portion of the tube accommodating said grid post.

6. In a hot cathode electron discharge tube, a straight-line filamentary cathode, a cylindrical grid concentrically disposed around said cathode, a gridpost disposed lengthwise ot-said grid and supporting the same, a tubular plate surrounding said grid and grid post, the inajor portion of said plate constituting a cylindrical surface substantially concentric with said cathode and so spaced therefrom as to give substantially the minimum permissible insulating clearance, said plate having an outward lengthwise bend at the portion adjacent to said grid post to accommodate the same while retaining substantially the same insulating clearances as between adjacent portions of the several electrodes at the portions of the electrodes removed from said grid post.

7. In an electron-discharge tube, a substantially straight-line filamentary cathode,

a helix of'fine wire constituting a substantially cylindrical grid coaxial with said'cath ode, a tubular anode surrounding said grid, said anode having the shape of a cylindrical member substantially coaxial with said cathode and having a lengthwise outward bulge at one portion of the periphery thereof to increase, at that portion, the distance between the plate and the cathode, and a conducting post disposed lengthwise of the wires of the helix to support the same, said post being located in the portion of inter-electrode space adjacent to said outer anode bulge to secure substantially the same insulating clearances throughout the entire inter-electrode space of the tube.

i In testimony whereof. I have hereunto subscribed my name this 24th day of June, 1926.

- SAMUEL M. KIN TNER

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