US2686889A - Cathode sleeve - Google Patents

Description

Aug. 17, 1954 F. J. PILAS 2, 39 CATHODE SLEEVE Filed Dec. 8, 1950 mvzqrron 2 2E 11]: Elaw agM ATTORNEY to avoid damage to the sleeve.

Patented Aug. 17, 195 4 FFICE CATHODE SLEEVE Frank John Pilas, Kearny,

Radio of Delaware N. J., assignor to Corporation of America, a corporation Application December 8, 1950, Serial No. 199,752

3 Claims. 01. s12-27m My present invention relates to electron tube electrode assemblies, and more particularly to a sleeve type cathode having a structure for facilitating the mounting of parts forming said assemblies and to a method of mounting a cathode sleeve in an electrode assembly and inserting a heater in said sleeve.

Some types of electron tubes include two spaced parallel insulating plates between whichan electrode complement is mounted to form an electrode assembly. A relatively large proportion of such tubes use a cathode of the indirectly heated type comprising a metal sleeve having an electron emissive coating on its outer surface and a resistance heater within the sleeve for energizing the emissive coating.

Several problems are encountered during the fabrication of a tube of the type referred to. One of these problems concerns the operation of inserting the heater into the sleeve. Some heaters are of the folded type and include a plurality of series connected strands. It is impractical to bind the strands to prevent separation thereof during handling. Therefore, no matter how carefulthe operator is to keep the strandstogether, some spread, though slight, of the strands is likely to occur. Since the operator usually holds a heater with atweezer intermediate its ends during the operation of threading it into a cathode sleeve, the spread of the strands is most pronounced at the ends thereof. Since the threading operation involves first the extension of anend of the heater assembly into an end portion of the sleeve, it will be appreciated that the spread referred to is a serious obstacle to the heater insertion operation. This problem becomes particularly acute where relatively small sized cathode sleeves are involved.

Another problem presented during manufacture of a tube of the type under discussion, is that of mounting the cathode between the two spacer plates referred to. The spacer plates are providedwith registering apertures which should have a diameter for assuring a snug fit between the cathode sleeve and the plates to restrain movement of the sleeve with respect to the plates". The operation of extending the sleeve through the apertures in the plates referred to is therefore critical and requires the utmost care Such damage would result if forced entry of the sleeve in the apertures should be attempted without full registry between the apertures and the sleeve. The amount of care required to avoid such damageappreciably slows down the electrode may be in the form of a continuous 2 assembly operation. Furthermore, the relatively high order of care required, precludes, or at least renders more difficult, a machine method of mounting;

Another problem concerns the provision of a suitable tab for the cathode sleeve for connection to a lead-in. In some instances the tab is a separate member fixed to the sleeve as by welding. To eliminate this welding operation, tabs integral with the sleeve have been used. However, such integral tabs require a complicated sleeve making process, and in addition are relatively occur.

It is accordingly the object of the invention to provide an improved electrode assembly.

Another object of my invention is tofacilitate the assembly of electrodes in the manufacture of electron tubes.

A further object of my invention is to reduce tolerance. requirements in an electrode mounting operation.

Another object is to provide a cathode sleeve particularly adapted for mechanized mounting in an electrode assembly.

A further object is to provide a cathode sleeve having means for facilitating insertion of a heater provide a cathode sleeve of increased resistance to The foregoing objects are attained as the result of a novel structure of the cathode sleeve. This structure comprises a sleeve having a taper in one or both end portions thereof. The taper may be provided either in a plane that is inclined with respect to the axis of the sleeve, or peripheral recession of an end of the sleeve, preferably in the form of a helix. In each case, the walls of the sleeve at an end portion thereof are partly removed, to effectively enlarge the opening in said end portion of the sleeve. The portion of the sleeve wall in registry with the removed portion, in addition, serves as a guide for extending a heater therein, for initially entering an aperture in aspacer plate when mounting the sleeve on such plate, and also serves as a rugged integral tab of the sleeve. The taper or peripheral recession referred to results in the formation of a relatively sharp leading edge of the sleeve that is extendable with reduced critical control into weak so that tab deformations frequently sleeve causes it to slide on its tapered or recessed end until a portion of the sleeve proper is completely extended into the aperture in the plate. The taper or recession may be provided at a suitable angle with respect to the sleeve axis to assure a complete mounting of the sleeve on the plate without requiring a damaging magnitude of force for its accomplishment.

Further objects and advantages of the invention will become evident from the following more detailed description thereof taken in connection with the appended drawing wherein:

Figure l is an elevation of one form of cathode sleeve according to the invention;

Figure 2 is a view along the line 2-2 of Figure 1, and shows the relatively large opening in an end of the sleeve;

Figure 3 is a cross-section along the line il--3 of Figure 1 and shows the normal size of the sleeve;

Figure 4 shows. a. blank of sheet metal stock from which the sleeve of Figure 1 may be formed;

Figure 5 is a side elevation of a modified form of cathode sleeve wherein the ends taper continuously from a starting point to a point spaced therefrom longitudinally of the sleeve;

Figure 6 is a, cross-section along the line t-i3 of Figure 5; and

Figure '7 is a blank of sheet metal from which the sleeve of Figure 5 may be formed.

Referring now to the drawing in more detail, there is shown in Figure 1 one form of cathode sleeve according. to the invention- In this form, the sleeve m is provided with tapered ends ll, i2. Each of the tapers ll, I2 is formed in such a manner that the ends of the sleeve are disposed in planes inclined with respect to the longitudinal axis of the sleeve- As a result of the tapers in the ends of the sleeve, .an enlarged opening l3 (Fig. 2) is provided for ease in threading a heater into the sleeve, and pointed leading ends I l, 85 are formed for facilitating the operation of. mounting. the sleeve on a spacer plate it.

As is shown best in Figure 2,v the tapered end construction of the cathode sleeve of the invention provides a wall portion ll, the inner surface of which is exposed, that is of advantage in threading a heater into the sleeve Hi. This exposed inner surface is adapted to serve as a backing against which a stranded heater may be placed in orienting its leading end with the interior of the sleeve. In addition, the taper results in an enlarged area defined by the-periphery of the end portion, as shown in Figure 2. This area is appreciably larger than the area defined by a normal periphery of the sleeve, as shown in Figure 3. The resultant. enlarged opening in the sleeve further contributes to ease in extending the heater therein. Less critical control of the heater insertion operation is therefore required according to the invention and this permits faster schedules to be adopted. Moreover, mechanized methods of heater insertions are rendered feasible in view of the reduction in tolerance requirements that the sleeve structure permits.

In addition to facilitating the heater insertion operation, the sleeve of the invention is of appreciable aid in mounting the sleeve on an insulating spacer plate. Thus, as shown in Figure 1, the relatively sharp points l4, l5 resulting from the tapered construction of the sleeve, provide ends of relatively small area in respect of the aperture it in the spacer plate It. The step of registering the point IS with the aperture is therefore accomplished with reduced requirements for critically registering the sleeve with the aperture. A satisfactory registration of the pointed sleeve end it with the aperture it results when the sleeve is in any one of a number of different positions with reference to the plate it. For example, the position of the sleeve shown in phantom in Figure 1 is. tolerable initially during sleeve mounting operation. Although as shown in phantom, the point it of the sleeve is displaced from the portion of the wall defining aperture is which it is intended to engage, it will assume the desired position as the sleeve is extended further into the aperture. Thus, if the sleeve is initially extended as shown in phantom, the taper it will engage an upper edge of the wall defining the aperture in spacer it, and will slide thereon in response to a force applied longitudinally of the sleeve. The sliding movement will continue until the wall of sleeve it} forming point 55, reaches the desired portion of the wall defining. aperture it, as shown in solid lines in Figure 1.

The angle between the planes of tapers I l and i2 and the longitudinal axis of the sleeve is shown to be approximately 45. This angle is satisfactory for most types of sleeves, in that it effectively translates a force applied longitudinally of the sleeve into a movement of the sleeve in a path parallel to the planes of the tapers, without causing buckling. or other deforming dam-.

age to the sleeve. However, if the sleeve is made of relatively thin metal and therefore incapable of receiving thrusts. of even relatively small magnitude during a mounting operation without buckling, the angle between the plane of the tapers and the longitudinal axis of the sleeve may be reduced. In such instance the tapered end 52 will respond in a sliding movement across an edge defining aperture 18, to a longitudinally applied force of sumciently low magnitude for preserving the sleeve from deformation;

The sleeve It is extended into aperture is until the embossment. E9 on the sleeve abuts against the spacer plate it. In view of therelatively close tolerances. permitted by the tapered con-,.

struction of the sleevebetween the sleeve; and aperture diameter, the; sleeve is engaged snugly around a periphery thereof by the walls defining aperture It. ,This snug engagement, in addition to the embossment iii, serves effectively to restrain movement of the sleeve in relation to the spacer plate. The restraint of such movement contributes to an improved electron tube: in that it removes one source of objectionable. micro.- phonics.

While the end 65 of the sleeve it is preferably extended through aperture it under conditions wherein the spacer plate it is held fixed in a suitable jig, not shown, and movement, is ime parted to the sleeve, the end it of the sleeve-is extended into another spacer plate, not shown, preferably while the sleeve is held on' the jig. referred to and the otherspacer plate is moved.

into suitable position forengagement between.

an aperture therein and the end It of the sleeve; After such initial engagement is effected a force in a downward direction and lonigtudinally of the sleeve I9 is applied to the other plate referred to, to cause the taper H to slidingly engage an.

edge of the plate for desired extension of a continuous peripheral portion of the sleeve,v spaced from the taper referred to, through the aper-- ture in the plate. While no embossment is provided at this end of the sleeve, the position of;

the plate. longitudinally of the sleeve may be determined by a surface of the jig referred. to.

An alternative procedure for. mounting the sleeve on twospaced insulating flats, may involve first mounting other electrodes between the plates, as a consequence of which the plates are fixed relative to each other in desiredspace relation. The sleeve l 0 may then be extended through registering. apertures in the plates by a unidirectional movement from one end of the plate array. Inthis case, end I 4 would serve as the leading end of the sleeve, and extension of thesleeve through the plates would proceed until the embcssment through which the sleeve was first extended. In view of the unidirectional travel of the sleeve through the plates during this mounting procedure, it is necessary that be tapered.

As shown in Figures 2, 3 and 4 the sleeve I0 is formed from fiat sheet metal stock 20 having converging tapers 2|, 22, 23, 24. The converging the leading end 14 only,

points 25, 26 of the tapers result in the formation of the points l4, l5 when the flat stock is rolled to sleeve form as shown in Figure -l. Furthermore, when formed into a sleeve, the side edges of the stock are shaped to providethe lock seam 21 shown in Figures 2 and 3.

It is preferable according to the invention to dispose the lock seam 2'! at a position remote from the pointed portions I 4, l5 of the sleeve. This is for the reason that the larger mass of material at the lock seam precludes desired sharp- IS on the sleeve engages the plate and -;further lends :the cathode structure to mechanized assembly methods.

A modified sleeve structure 28 is shown in Figures 5 and 6. This structure is formed from a fiat sheet metal stock 29 shown in Figure 7, having tapers Bil, 3| at. the ends thereof extending rectilinearly from one side of the stock to the other. Thetapersreferred to preferably converge to provide a side 32 of the stock that is spaced longitudinally from the ends 33, 34 formed by the other side 35 of the stock. Therefore, when thestcck 29 is rolled to provide the sleeve shown in Figure 5, the lock seam 36 shown in Figure 6, is spaced from the ends 33, 34. The endsreferred to form relatively sharp leading ends of the sleeve 28 as well as integral tabs on the sleeve. The end portions of the sleeve taper from said ends 33, 3.4 to the location of the lock seam 36 and forman edge inclined with respect to the longitudinal axis of the sleeve. The edge can be thus formed to lie along a helix. When an end of this sleeve is inserted into an aperture in a spacer plate, such as plate 16 shown in Fig-.

ure 1', the relatively sharp ends 33, 34 thereof are easily registered with the aperture and full registry of the sleeve 28 with the aperture is effected on application of a force to either the sleeve or plate, longitudinally of the sleeve. Such full ness of the points I4, l5 required for the most advantageous practice of the invention. Consequently, as shown in Figure 2, the lock seam is disposed diametrically opposite the location of the points l4, IE on the While the tapers 2| to 23 shown in Figure 4 are presented as rectilinear, this is merely for illustrative purposes. It will be obvious that a slight departure from such rectilinearity is nec-j essary in order to provide an end portion ll, of

Figure 1, terminating in a plane.

The tapered end portions of the sleeve It] in addition to facilitating the threading of a heater into the sleeve and contributing advantages tothe mounting of the sleeve in an electrode assembly also provides a desired integral cathode tab of increased ruggedness. Any one of the end portions l4, l5 may serve as the tab, depending on its orientation in an electron tube. The ruggedness of both these portions renders any one of them suitable for service as a tab for connection to a lead-in. Several advantages accrue from the use of one of the end portions 14, I5 as a cathode tab. One of these advantages is manifested in freedom from deformation of the tab during normal handling prior to mounting the cathode in an electrode assembly. Another advantage is the ability of the tab to receive directly the pressure of welding electrodes without damage. A further advantage resides in the fact that the tab is always ina desired position, as

the result of an easily effected rotational orientation of the sleeve during the mounting step. This is distinct from the bent or other undesired form assumed by conventional cathode tabs during a mounting operation. The rigid and fixed character of the cathode tab provided according to the invention further aids the welding operation referred to, in that no preliminary straightening of the tab is necessary for accomplishing the weld. This speeds up production,

periphery of the sleeve;

registry results from the sliding action of the tapered end of the sleeve along an edge defining theaperturein the plate. The tapers in the ends of thesleeve referred to may be made as steep or flat as required by a sleeve of particular wall thickness and. strength. The sleeve of Figure 5 may also be provided with an embossment 31 which serves a function similar to that of em- ,bossment 19 previously described in connection with Figure l.

While the sleeve shown in Figure 5 is characterized by the same ease in mounting it on spacer plates as the sleeve of Figure 1, the latter form of sleeve is preferable. This preference is dictated by the relative weakness of the pointed portions 33, 34 of sleeve 28. These portions, it will be noted lack the support provided by the continuous periphery of end portions H of sleeve I 0.

Each of the cathode sleeves I0 and 28 has a coating 38, 39 of an electron emitting material. This coating is preferably applied after the sleeves are formed from the sheet metal stock 20, 29.

It will be appreciated from the foregoing that I have provided a cathode sleeve of novel structure having several important advantages. One

-of these advantages resides in facilitating mounting the sleeve on spacer plates. Another advantage is the relatively snug fit between the sleeve and the walls defining apertures in the plates permitted by the cathode sleeve of the invention. This snug fit would not be feasible with conventional cathode sleeves, since the apertures receiving such sleeves must be enlarged to permit extension of a sleeve thereuntc. A further advantage is the ease with which a heater may be inserted into the sleeve. This ease results from the funnel-like efiect provided by the tapered end portions, which appreciably enlarge the entrance area into the sleeve. A still further advantage is the provision of a rugged integral tab on the cathode sleeve.

I claim:

1. A cathode sleeve having a taper extending across one end thereof, said taper providing a leading end of said sleeve of less cross-sectional area than a cross-section ofsaid sleeve, whereby epsasae 7, registry between said snugly receiving said creasedfacility.

2. A 'cathode sleeve of predetermined wall thickness, one end of said sleeve having a taper extending angularly thereacross, the angle of said taper with respect to the axis. of saidsleeve.

sleeve, is effected with inbeing predetermined for force fitting said sleeve.

4. An electrode assembly for an electron tube.

comprising an insulating spacer plate having an. aperture therein, a sleeve type cathode havingv a lock seam extending through saidaperture; one end of said cathode being tapered to provide an opening therein of larger area than. a. transverse. section of said sleeve, whereby one portion of said tapered end is less remote from the other end of. said sleeve than otherportions of said tapered end, said lock seam being disposed in said one portion, whereby the more remote portion of said tapered end forms a relatively sharppoint for facilitating mounting said sleeve in said aperture.

5. An electron tube electrode assembly including an insulating spacer plate having an opening extending therethrough, and a cathode sleeve exend and a passageway for:

tendingxth-rough: said opening, an end of said.

S188V8$1D6llldif1 a portionmore remotefrom said plate'than: another portion thereof, and a taper fromv said. portion to said: another portion, whereby said; remoteportion comprises an integral lead for. said cathode having improved resistance to deformation.

6;. A. cathode sleeve having an edge defined by a helix, for facilitating integration of said sleeve in an. electron tube mount.

7. A cathode sleeve terminating at one end thereof in; an; edge, said edge being co-extensive with a. periphery of said sleeve, and extending in ahclicalzpath axially ofsaid sleeve for facilitating mountingrsaid sleeve in an aperture in an insulating-plate; and for providing. a rugged integral tab onsaid sleeve for connection to a lead-in.

8a A cylindrical sleeve for an, indirectly heated cathode having a seam extending along one side thereof, one end of said sleeve being tapered to provide a. relatively. sharp leading end on said sleeve onset-axially away fromsaid seam, and an embossment adjacent said one end extending transversely of the sleeve for ruggedizing said relatively sharp leading end.

References. Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,612,635 Hart Dec. 28; 1926 2,001,355 White May 14, 1935 2,029,482 Haslauer Feb. 1, 1936 2 ,324,177 Smith July 13, 1943 2,536,677 Brunner et a1. Jan. 2, 1951

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