US2581997A - Electron tube structure and the manufacture thereof - Google Patents

Description

'J. E. BEGGS Jan. 8, 1952 ELECTRON TUBE SIRUCTUIQE AND THE MANUFACTURE THEREOF Original Filed Aug. 10, 1944 -45. Inventor:

James E. Beggs,

O CAPACITALCE u e M n w J A .6 H U b device which is not affected Patented Jan. 8, 1 952 ELECTRON TUBE STRUCTURE AND THE MANUFACTURE THEREOF James E. Beggs, Scotia, N. Y., assignor to General Electric York.

Company, a corporation of NEW1.-.

Original application August 10, 1944, Serial No. 548,859, now Patent No. 2,402,119, dated June 18, 1946. Divided and this application July 12, 1945, Serial No. 604,676 I 6 Claims. (01. 29-2513) I The present application is a division of my copending application S. N. 548,859, filed :August 10, 1944, now Patent No. 2,402,119, granted June 18, 1946, and assigned to the assignee of the present application and relates to electronic. tube structures and to methods and apparatus used in the manufacture thereof.

It is known that. in the use of electronic tubes for radio and high frequency circuits, the interelectrode capacitance of the tube and the total tube capacity have a considerable effect on the opvide a new and improved apparatus for accurately spacing the electrodes in an electron tube.

It is a still further object of my invention to provide a new and improved arrangement for positioning the grid structure in an electronic tube.

A further object of m invention is to provide a new and improved method of spacing electrodes in an electron tube.

Still another object of my invention is to provide a new and improved capacitance measuring by changes in atmospheric conditions.

Briefly stated, in accordance with one aspect of my invention, I provide a new and improved planar grid structure for an electron tube and a method and an apparatus for assembling the grid structure into a tube by means of which,

while the tube is being assembled, the capacitance between a pair-of electrodes is adjusted between narrow limits to a desired value. Alternatively, in accordance with another aspect of my invention, the total capacitance of the tube including that of the seals and metallic parts thereof is adjusted to a predetermined value by controlling the spacing between a pair of electrodes to provide a tube particularly useful in radio frequency circuits. .A capacitance measuring device which uses air as its-sole dielectric and which is not afiected by changes in temperature and humidity conditions is employed to insure the precise valu of capacitancefor the tube. a

For a better understanding of m invention, referencemay be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. Fig. l of the drawing is a vertical sectional view of a portion of an electron tube embodying the invention; Fig. 2 illustrates the grid structure and a tool used in its assembly into. a tube; Figs. 3 and 4 are perspective views of grid structures which may be employed in the tube of Fig. lpFig. 5is aperspective view of apparatus used in assembling the portionof the electron tube shown in Fig. l; and Fig. 6 is a sectional view of a portion of the apparatus of 1 Referring particularly to Fig. l, th ere is shown a portion or an electronic tube having an anode shell I and a grid ,shell 2 maintainedin spaced relation by a.vitreous cylinder 3 sealed between opposing flanged portions of the shells. The shellsl and 2 are formed preferably of a suitable, metallic material, such as copper or silverplated steel, and the seal 3 is formed of a suitable insulating material which wets with the plating of the members I and 2, suchas for examples. boro silicate glass. The anode shell I is hollow and has a neck portion 4 which terminates in an active anode orelectron receiving portion 5. Positioned within the grid shell 2, in a manner to be explained more in detail hereinafter, is a grid assembly comprising a tubular conductive mem her 6 flared inwardly at its upper end to form a flange 1 across which is sealed a grid 8. The cylinder 6 around its outer periphery is provided with a plurality of ridges or corrugations 9 which maintain the cylinder 6, in a desired "position within the grid shell 2 during assembly operation.

In Fig. 2 the gridcylinder 6 is shown in position on a stud I0 used in adjusting the position of the grid assembly within the grid shell 2. Fig. 3 is a perspective view of the grid assembly shown in Figs. 1 and 2 and illustrates more. clearly the corrugations 9 on the tube 6 and .the flange 1 across which is stretched a mesh grid 8. The grid 8, preferably while under tension, is soldered to the upper vface of the-flange 1 durin the construction of the grid assembly. Y

Fig. 4 shows an alternative grid assembly for use in a tube having planar electrodes and which comprises a grid cylinder I I having a plurality of serrations or louvers l2 and a flange l3 at its upper end. A circular washer I l having a central opening I5 has soldered thereto a plurality of closely spaced parallel grid wires 16. Preferably the grid wires I6 are united tothe-washeril jabutted against the stop 28. rod 29 has an intermediate portion 3l of reduced as by soldering and thereafter the composite grid washer structure is placed upon the flange l3 and attached thereto as by welding.

In Fig." 5-:th'ere is shown apparatus particularly use'iulsin assembling the portionof the tube structure shown in Fig. 1 to obtain predetermined spacing between the anode surface 5 and the grid 8 to provide a desired capacitance between these electrodes. The apparatus of id includes a base portion I! which contains a source of unidirectional potential-and. a capacitance bridge (not shown). A press? supponteclupnh the base I! includes a base portion l9 upon which is mounted a block 20 of insulation material which carries the stud i and reciprocating plunger 21 secured to the lower port H 1 member 22. The rack member 22 engages a driving pinion (not shown) in the head 2 3 of the press and is actuated by means of a lever 24. The vertical movement 'of the plunger 2! may be measured by means of a suitable micrometer 25. The plunger 21 is adapted to fit into the anode shell I to place the grid shell 2 over the grid cylinder 6, the latter being supportedon thestud f6.- Electric connection to the plunger 21 for :pnrposes to be pointed out later is made :by means ofa lead 25 which is grounded to the press l3.

Located in thebase portion 19 of the :press is a sleeve 21 for receiving a capacitance rod and a stop 2 8 for limiting the nio'tion of that rod. This portion of the apparatus is shown in enlarged sectional view in Fig. 6, the capacitance rod 29 being shown in position within the left-hand sleeve '21 1 andthe right-hand sleeve 30 and The capacitance diameter connecting twopdrtions of larger diameter which are machined to makea goodiit with the inner surface of the sleeves 2 and 30. Cooperating with the intermediate portion 3l--to form therewith an air core capacitance is an annular metallic member 32 attached to a stud '33 which is in screw-threaded engagement with the stud l0 and supported from the block 20 of insulating material. The'f xed annular electrode 32'has a central aperture which likewise is of the inner diameter of the sleeves 21 and 30 so that in positioning the capacitance rod 2-9 in the sleeves 21 and 30, the right-hand end of the :rod passes through the opening of the electrode 32 a to check its concentricity withthe movable electrode '3l of the capacitance. The fixed electrode 32 which is maintained at a positive potential is connected by means of a lead 34 to a capacitance bridge "35 supplied with operating potential from any suitable source represented conventionally by the battery 36. The capacitance bridge is of conventional' form and the details thereof are not shown in the drawings. The bridge includes a meter 3'l'connected across opposite pointscf the arms thereof inthe usual manner. capacitance formed by the electrodes 3!,132 is connected in one of the arms of the capacitance bridge 35 in a well known manner and is innarallel with the fixed capacitance .of. the press 1-8 In the operation of the apparatus shown in Figs. and 6 to obtain a. desired interelectrode capacitance .of an electron tube, according to on method, first, a ca acitance rod having :aninterr mediate section 31 of a diameter sufilcient to form with the electmde 32 the exact yalue -.of apa ity which is desiredior an electrcn htybe s placed i positionin thesleeyesfl ;and.. 3; the reading of the met r Blis hated h eai t r the rodv 29 is removed, a' rid y inder i3 is p aced 9 a seek 2L8 by the vitreous cylinder 3 of the electron tube structure. A capacitance therefore is formed between-theanode' shell and the grid shell and cylinder, which capacitance is substituted for thekngwn capacity pf the electrodes 3|, 32 in .the same of the capacitance bridge. As the plunger 2| is lowered, the reading of the meter ,3! is noted until a deflection is obtained which is the same as that obtained with the standard capacity pf theelebtrodes 3|, 32 present in the bridge arm. Since the interelectrode capacitance of the tube assembly is substituted for the previous standard capacity, when the same reading is obtained, the interelectrode capacity is fixed at the desired value. It is apparent that with this particular method .of adjusting the capacitance, the :presence'of any capacitance of the press and wiring is balanced out for the two readings. During the positioning of the grid cylinder in the grid shell 2, the corrugations 0r ridges 9 or the spring fingers 1.2, as the case y be, by engaging the inner walls .of shell .2 511D- port the cylinder 6 or I! therein. When a de; sired interelectrode spacing is obtained the tube structure is removed from the press I8 and the grid cylinder is spot-welded in place.

The above described method for obtaining a desired interelectrode capacitance is particularly useful in constructing an electronic tube for low frequency purposes, where the interel t d capacitance includes the effect of seals, th n.- velope, and other portions'of the tube. For tubes constructed for high frequency work, wher th seal 3 may be displaced from the active electrode parts by a distance that is an appreciable portion of a wave length and its presence has little or no effe t upon the des red value of t rele trade capa i ance. the followin met d of l ng a tube. wh ch balances cut the capa i: tance due .to t e presence f e s al a envelop f a tube, is 9i i mpc tanc this method. with a capacitan e ro 9 n erted to give a desired interelectrode capacitance across th capa ance bri e arm he a d cylinder 6 is la in Di at n n ste l am an amide grid assembly is placed thereover and located y me ns i ihapii ge :2! e active mi su face 15 and t e arid Q ar sm at 'by 5511b? tal iia istan e. this manner the capa ity of the fixed tube elements is connected in para-1'- lelrwith t e st nda d .t ier a e capacityf cacti-amen t es is he; adii si v a s ed d flecihn a t e m ter p 7; b y a min-sca e re d es- :a bi i i reading thu'ls cha n d messe 99 th fi sq'cana e he in e ement and the ter 5 a d capacity tween t e cleanse it. .32- Th e s n remov d t r move he-stan a d capa f m h b d a m an n in re r d .QaP Q tan e o the same t lus is in t tute th rein? .bvi o er n plunger to brine the id i3 loser to the anc g surfac .5 until the s me efle ion im t rfil is .o ta ned- T is ives a tween; sur men o th capacit nce existing sol l be.- tween the id ;8 and the anode su face 5, iiivalue of whi h it is desired to set equal t the known standard .or reference capacity- 7.

In the use of the apparatu to; p sitioning the electrodes in tubes, standard capacity elements or rods 29 having intermediate portions 3| of different diameters of course may be employed to ob tain different interelectrode capacities of the tubes. One of the important features of the capacity balancing device is the fact that the sole dielectric which exists between the active electrodes 3|, 32 is the same as that which exists between the anode surface 5 and the grid 8 so that the capacity setting is independent of temperature and humidity conditions. This dielectric, being air, is a relatively stable one. .The effect of the dielectric block 20 formed of a material which ordinarily is effected by temperature and humidity is balanced out for all measurements. Another advantage of the use of the apparatus shown is that each electronic tube during its construction is adjusted to give the exact value of interelectrode capacitance desired. This value may take into account either the presence of the seals and envelope of the tube or may balance out the effect of these elements of the tube.

In some cases it may be desirable to assemble tubes according to the physical spacing between the anode and grid, rather than to obtain a desired interelectrode capacitance. For such cases also the apparatus of Fig. 5 may be employed, the micrometer 25 being used to measure the spacin between electrodes. The grid-to-anode spacing may be alternatively established by means of high frequency resonant circuits or any other desired means. It has been found that in the use of this particular apparatus and method for assembling electronic tubes, tubes have been manufactured which approach more closely to a desired uniform characteristic than those manufactured by any other apparatus or method heretofore employed.

While I have shown a particular embodiment of my invention it will of course be understood that I do not wish to be limited thereto since various modifications may be made and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Apparatus for manufacturing an electronic tube of the type havin a first planar electrode, an annular member axially aligned with said electrode, and a second planar electrode adjustably supported within said annular member, comprising means for supporting said second electrode, means for adjusting the position of said second electrode within said annular member, and means for measuring the capacitance between said pair of electrodes as said position is adjusted.

2. Apparatus for manufacturing an electron tube of the type having a pair of planar electrodes comprising means for supporting a pair of electrodes in opposed relation within an envelope, means extending into the envelope for adjusting the position of one of said electrodes, and means connected with said means for supporting a pair of electrodes for measuring the capacitance between said electrodes as said position' is adjusted.

3. The method of manufacturin an electronic tube having a pair of planar electrodes which comprises adjusting the spacing between said electrodes, and measuring the capacitance between said electrodes as said spacing is adjusted.

4. Apparatus for manufacturing an electronic tube comprising means for adjusting the physical spacing of a pair of electrodes of said tube, a

capacitance bridge including a reference capacitor connected in one arm thereof, said electrodes being connected in parallel with the reference capacitor in one arm of said bridge, and means removably mounting a part of said capacitor whereby said reference capacitor may be removed from said arm during periods when said spacing is adjusted to obtain a, desired value of capacitance between said electrodes.

5. The method of manufacturing an electronic tube which comprises establishing abridge circuit which includes a reference capacitance and the capacitance between a pair of electrodes of said tube in a parallel circuit in one arm of said bridge circuit, obtaining a reading dependent upon the resultant capacitance of said parallel circuit with said electrodes widely spaced apart,

removing said reference capacitance from said circuit, and adjusting the position of said electrodes until said reading is again obtained.

6. The method of manufacturing an electronic tube which includes the steps of using a reference capacitance to obtain a reading indicative of a desired interelectrode capacitance, removing said reference capacitance and substituting therefor the capacitance between said electrodes, and adjusting the position of said electrodes until said reading is obtained again.

JAMES E. BEGGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,873,704 Graham Aug. 23, 1932 2,291,445 Beyer July 28, 1942 2,337,056 Mathias et al Dec. 21, 1943

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