US2666866A

US2666866A - Ruggedized electron tube

Info

Publication number: US2666866A
Application number: US167789A
Authority: US
Inventors: Hans J Prager
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-06-13
Filing date: 1950-06-13
Publication date: 1954-01-19
Anticipated expiration: 1971-01-19

Description

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Jan. 19, 1954 H. J. PRAGER RUGGEDIZED ELECTRON TUBE Filed June 13. 195o z'sheets-shet 1 NVENTOR HHN: J PPHGE RNEY Jan 19, 1954 H. J. PRAGER 2,666,866

RUGGEDIZED ELECTRON TUBE Filed June 13, 1950 'g INVENTOR Patented Jan. l9, 195.4

UNITED RUGGEDIZED ELECTRON TUBE Hans J. Prager, Maplewood, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application June 13, 1950, Serial No. 167,789

My invention relates to electron tubes and more particularly to a ruggedized electron tube having high vibration and impact shock resistance for reduced microphonic disturbances, and to a method of fabrication of such tube.

Microphonic disturbances in electron tubes are usually caused by movement of one or more parts of a tube in relation to other parts of the tube. When such one or more parts lacks sufficient rigidity of support they respond in movement to vibrations of the tube and to impact shocks to which the tube may be subjected. Such movement may involve the entire electrode assembly in relation to the enclosing envelope of the tube, and additionally or alternatively may be interelectrode. When movement of the entire electrode assembly occurs in relation to the tube envelope, impacts take place between electrode assembly supports, such as mica spacers and the wall of the envelope. For example, when the electrode assembly including a mica spacer is movable within an envelope, impacts of the edge of the mica spacer against the inner wall of the envelope give rise to clicks that result in audible disturbances during operation of the tube. When the movement is interelectrode and involves for example the control grid, in relation to the anode and cathode, the control function of the grid becomes erratic and introduces undesirable components in the output of the system in which the tube is used.

Various means have heretofore been proposed for eleminating microphonic disturbances in electron tubes. In an attempt to avoid bodily movement of the electrode assembly in relation to the tube enevolpe, the assembly has been provided with a mica spacer having fingers for resiliently engaging the inner wall of the envelope. However, this has not been entirely successful because of the inherent weakness of the fingers. Continued flexure of the fingers results in deflocculation or delamination of the mica material of which the spacer is made, which eventually deprives the ngers of their support function. In addition, where impact shocks are of major force magnitude, the fingers are unable to restrain movement of the electrode assembly with respect to the tube envelope. Other means such as metallic springs or snubbers have shown no marked superiority over fingered micas in this respect. Neither has it been found feasible to rely on a tight fit between the edges of the mica spacer and the inner wall of the envelope because of the variations in diameter of commercially available envelope parts. This variation may be as much as 0.07.

4 Claims. (C1. 313-258) Prior means for eliminating movement of individual electrodes with respect to other tube parts have included eyelets in mica spacers to which electrodes have been fixed, and metallic clips xed to the spacer and to electrodes. These means however are relatively expensive and while they restrain movement of individual electrodes, they have no effect on the movements of the electrode assembly as a whole with respect to the tube envelope.

The structures heretofore devised have introduced an additional problem. This problem is encountered during manufacture of the tube and concerns the step of extending the tube mount into its associated envelope. Prior mount structures have been provided with a transverse dimension to assure a snug fit between the mount and the inner walls of the envelope. Some electron tubes employ tube envelopes having a transverse dimension at the open end thereof through which the mount is extended, that is substantially the same as that of the interior portion of the envelope adapted to receive the mount. The snug t referred to therefore characterizes the mount and envelope during the step of assembling these parts and impedes this assembly step. This problem is further aggravated by variations in diameter of commercially available envelopes.

It is therefore an object of the invention to provide a ruggedized tube for reducing microphonics.

Another object of the invention is to provide an improved electron tube in which both the relectrode assembly as a unit and the individual electrodes therein are effectively restrained against movement with respect to other parts of the tube. p

A further object is to provide a support in an electron tube that simultaneously supports the individual electrodes in the tube against relative movement and also restrains movement of the electrode assembly as a whole with respect to the tube envelope.

Another object is to provide a support for an electrode assembly that is universally suitable for supporting said assembly in envelopes of indifferent diameter Within predetermined tolerance limits.

A further object is to provide an electron tube designed for ease in extending the mount into the envelope, thereby facilitating manufacture of the tube.

The foregoing objects are accomplished by a tube incorporating the invention and including an envelope having a domed end and a mount having an insulating spacer plate adjacent one end of the mount, the plate having transverse dimensions for easy entrance into the envelope but for lexure when engaging the dome of the envelope. However, a problem is encountered in providing a spacer plate that will flex when its edges are subjected to a force component by the dome portion of the envelope. If the spacer plate were round and all edge portions thereof were engaged by the domed portion of the envelope, a iiexure of the plate would tend to produce folds in the plate adjacent its edge. However, spacer plates are usually made of a material such as mica which is not susceptible to folding without breakage.

Accordingly it is a further object of the invention to provide a spacer plate that is flexible without producing folds therein or otherwise damaging the plate.

One embodiment of the invention accomplishing the foregoing objects comprise an electron tube including an envelope having a closed domed end and a mount including a stem at one end thereof and an insulating spacer plate at the other end having a transverse dimension smaller than the diameter of the envelope at regions thereof spaced from the dome but larger than that of the domed region. As a consequence of the larger transverse dimensions of the spacer plate as compared with the domed portion of the envelope, a flexure of the spacerwill resultwhen the envelope is pushed down on the mount and causes the spacer to engage the dome portion of the envelope. This fiexure will cause the edges of the spacer to rmly engage the inner wall of the envelope at the domed portion thereof. The engagement between the envelope wall and the spacer will involve substantial edge portions of the spacer so that the danger of defiocculation of the spacer is reduced. The relatively large area J which disposes the axes of apertures or passage- Ways therein in angular relation to electrode supports extending through the apertures, to thereby tighten the engagement between the spacer and the electrode supports referred to.

To accomplish a iiexure of the spacer plate without producing folds therein, the plate is provided with several relatively flat or obtuse corners resulting in a divisionv of the plate into segments, each being subjected to an individual flexure without involving a sharp definition between the segments. The plate may be provided with two or' more of the fiat corners referred to, the flexures of the corners assuring a required area of contact between the tube envelope and the edge of the spacer for desired resistance to movement of the spacer in relation to the envelope wall.

While the invention will be pointed out with particularity in the appended claims, it may best be understood from the following detailed description of an embodiment thereof presented for purposes of illustration only and not by way of limitation, taken in connection with the accompanying drawing, in which:

Figure 1 is an elevation of an electron tube according to the invention, the tube being provided with two spaced upper spacers;

Figure 2 is a plan view of one shape of spacer plate that may be employed in practicing the invention;

Figure 3 is an exploded view partly in section of a tube mount and envelope and indicates the novel manner in which the parts are assembled in accordance with the method of the invention;

Figure 4 is an elevation partly in section with the tube mount and envelope in desired position for sealing the envelope to the stem of the mount and with the envelope pushed down so that the top spacer of the mount is exed by the domed portion of the envelope;

Figure 5 is an elevation partly in section of an electron tube having only one upper spacer incorporating the invention;

Figure 6 shows the locations on the spacer to which flexing forces are applied; and

Figure 7 is a greatly enlarged view of a portion of a exed spacer and a grid side rod and shows the improved engagement between the side rod and spacer that is provided according to the invention.

Referring now in more detail to the drawing, there is illustrated in Figure 1 an electron tube including a glass envelope I0, a base II and two electrode assemblies I2, I3. The electrode assemblies are supported between a lower insulating spacer I4 Aand an upper insulating spacer I5. Each of the assemblies is provided with an electrode which may be the anode having upper portions IS, I'I which project above the upper face of spacer I5. Each of the spacers Hi, I5 have smaller transverse dimensions than the inner diameter of the envelope l0 at portions thereof spaced from the dome I8. An additional plate i9 of insulating material is disposed above the upper plate I5 in spaced relation thereto and rests on the ends of the electrode portions i6, I1. A stem 20 shown in Figures 3 and 4 supports the lower ends of the electrode assemblies I2, I3. Said electrode assemblies with their plates I4, I5 and I9, and said stem, form an electron tube mount.

According to the invention, the plate I9 is provided with transverse dimension for ready extension of the end cf the mount remote from the stem into the open end 2| ofthe envelope I!) as shown in Figure 3. During such extension the edges of all the plates referred to are spaced from the inner walls of the envelope to facilitate the assembly of the mount and envelope. However, when the mount is extended into the envelope so that the plate I 9 engages the curved Walls of the dome I8, a force will be exerted on the edges of the plate IQ in a downward direction. This force is opposed by an upward force applied to the plate I9 by the electrode portions I6, I'I on which the plate originally rested. The effect of these two opposed forces is to cause a flexure of the plate I9 as shown in Figures l and 4. This exure provides a firm engagement between the plate I9 and the inner wall of the envelope, which engagement is adapted to withstand substantial impacts applied to the tube, without permitting relative movement of the electrode assemblies andthe envelope.

To permit iieiiure of plate I9 to take pl'ace without forming folds in the material of the plate, the plate is preferably provided with two or more soft corners. In Figure 2 is shown a plate I9 having relatively

soft corners

22, 23, 24, 25. Engagement between the corners referred to and the inner wall of the dome portion I8 of the envelope will result in individual flexures in each of the four quadrants shown in dotted lines, adjacent quadrants merging in gradual curves and not in folds.

The tube structure shown in Figures l, 3 and 4 is primarily designed to prevent relative movement between the upper part of the mount and the envelope I8. In Figures 5, 6 and '1 is depicted a tube construction wherein a flexed spacer plate simultaneously restrains movement between individual electrodes as well as between the upper part of the mount and the envelope wall. s

The tube shown in Figure by way of example is a triode having a cathode 26, a grid 21 supported on grid side rods 28, 29 and a tubular anode 38 having shoulders 3I, 32 for bearing against an upper spacer plate 33 and shoulders 34, 35 for bearing against a lower spacer plate 38.

The anode includes ears 31, 38 projecting from the upper spacer plate, and ears 39, 48 extending below the lower spacer plate. r

According to the invention, the spacer plate 33 which may be similar in shape to the plate I8 shown in Figure 2, is of smaller transverse dimension than the inner diameter of the tubular portion of envelope 4I but of larger transverse dimension than the inner diameter of the domed portion 42 of the envelope. Thus the mount including the electrode assembly referred to and the stem 43 is readily extendable into the tubular portion of the envelope 4I, and the plate 33 is flexed when brought into engagement with the dome 42. This results in a rm support of the electrode assembly with respect to the envelope 4I that prevents relative movement thereof even when severe impacts are applied to the envelope.

The flexure of plate 33 results from the forces applied thereto when the edges of the plate engage the dome 42 of the envelope as shown in Figure 6. The arrows 44, 45 indicate the locations on the spacer to which the downwardly applied force is transmitted by the dome. The arrows 46, 41 indicate the locations on the plate at which a force counteracting the force indicated by the arrows 44, 45 is applied. This counteracting force is applied by the shoulders 3|, 32 on the anode 29.

In addition to supporting the electrode assembly against movement in relation to the envelope of the tube, flexed plate 33 also more rmly engages electrodes projecting through apertures therein. For example, as shown in Figure 7, the aperture 48 in the spacer 33 is large enough to permit free entrance of grid side rod 29 therethrough when the spacer is unflexed. However, when the spacer plate is subjected to flexure, opposite edges 49, 58 of the aperture arev compressed to firmly engage the side rod. The upper portion of both side rods 29, 28 as well as the anode ears 31, 38 are similarly engaged by the spacer plate 33, whereby the electrodes are restrained effectively against relative motion.

The features of the invention residing in the exed spacer plate therefore effectively accomplishes the two purposes of simultaneously restraining relative movement between the upper portion of an electron tube mount and the envelope enclosing it, as well as relative movement between individual electrodes included in the mount. The restraint of movement in both of these respects is a substantial contribution to the elimination of microphonics in the tube.

One way in which a device including a flexed spaced plate according to the invention may be fabricated is shown in Figures 3 and 4. The tube mount including the electrode assemblies I2, I3 and stem 28 having an exhaust tubulation 5I is supported on fixture 52. The support is accomplished by extending the exhaust tubulation into an opening y53 in the fixture 52. A ring member 52a. extends upwardly from support fixture 52 for engaging the stern 28. The opening 53 has a bottom shelf 54 against which the free end of the tubulation 5I rests. The envelope I8 is supported by fixture 55 above and in line with the tube mount referred to with a predetermined engaging force. A push-down member 58- having an insert 51 of heat and shock insulating material is afxed to the push-down member 56 forengaging the upper domed portion I8 of the bulb I8. The push-down member 56 is mounted above the bulb I8 for Vertical movement for pushing the bulb downwardly over the mount and .against the engaging force of the fixture 55.

The downward thrust of the push-down member I58 is of predetermined magnitude, the downward limit of the thrust being shown in Figure 4. When this limit is reached the plate I9 is flexed by engaging the dome I8 and the lower end of the envelope is in position for sealing to the stem 28. A burner 58 is then caused to play flames in well known manner at the location of the desired seal, while the envelope I8 is held in its downward position by the push-down member 56. After the envelope I8 is sealed to the stem 28, the push-down member 58 is raised to permit removal of the sealed tube assembly.

The electron tube may then be completed by exhausting in well known manner and the base I I be affixed to the evacuated tube.

It is apparent from the foregoing that I have provided a novel electron tube construction that is rugged and contributes to a substantial reduction if not compelte elimination of microphonics in the tube output. A novel and advantageous method of manufacture is also provided in that the assembly of a tube mount and envelope is facilitated by employing a mount of less transverse extent than the space within the envelope without sacrificing ultimate rm engagement between the upper part of the mount and the envelope.

It is obvious that various modifications may be made in the example described without departing from the spirit of the invention, and it is therefore desired to include such modifications within the scope of the appended claims.

I claim:

1. An electron tube including an envelope having converging walls at one end thereof, and a mount having a flexible insulating spacer plate at one end thereof, said plate having a larger transverse dimension than the space between said converged walls, said plate being transversely positioned between said converging walls and bodily flexed thereby at substantially all portions of the plate including a central portion thereof, whereby said one end of said mount is ruggedly supported against movement with respect to said walls, said mount including electrodes extending through said plate, said electrodes being locked in said plate by said bodily flexure thereof.

2. An electron tube including an envelope, and a mount enclosed by said envelope, said mount including electrodes and having a iiexible insulating spacer plate, said plate having passageways extending therethrough and receiving end portions of said electrodes, said plate being bodily flexed throughout a transverse dimension thereof by engagement with inner walls of said envelope, whereby said mount is rmly supported against movement with respect to said envelope and the axes of said passageways are angularly disposed with respect to the axes of said end portions of said electrodes extending therethrough for firm engagement of said electrodes by said plate.

3. An electron tube including a mount, said mount having an insulating spacer plate coaxially disposed at one end thereof, said plate having passageways extending therethrough normal to the flat surfaces of said plate when attened and receiving end portions of electrodes in said mount, said plate being flexed adjacent said passageways, whereby said passageways are angularly disposed with respect to said mount for firmly engaging said end portions for preventing relative movement of said electrodes.

4. A ruggedized electron tube including an envelope having a domed end and a mount having one end extending into said domed end, said mount having at said one end thereof a spacer plate, having relatively obtuse corners and curvatures between said corners engaging said dome. said plate being bodily exed throughout its extent by a forceful engagement of said domed end by said obtuse corners and curvatures of the plate, said plate having passageways extending therethrough, said mount including electrodes extending axially of said envelope and into said passageways, whereby said mount is ruggedly supported in said envelope and said passageways are angularly disposed axially with respect to said electrodes for locking said electrodes in said plate.

HANS J. PRAGER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,930,090 Gaidies Oct. 10, 1933 2,078,371 Deane Apr. 27, 1937 2,366,220 Spencer Jan. 2, 1945