US2896307A - Grid manufacturing process - Google Patents

Description

c. A. WHITELEY 2,896,307

GRID MANUFACTURING PROCESS July as, 1 59' 2 Sheet s-Sh et 1 Filed May 14, 1954 L1 U L Ll l I I H 29v T 28 INVENTOR I Cf/AALEZSA. H/TELEY BY I Z 1:96:

ATTORNEY a MANUFAcrG PROCESS Charles A. Whiteley, East Meadow, N.Y., assignorto The Sperry Rand Corporation, a corporation of Dela- Ware Application May '14, 1954, Serial No. 429,807 4 Claims. (Cl. 29-25. 14)

The present invention relates to a process of manufacturing grids for use in electron beam tubes such as klystrons, travelling wave tubes and high frequency triodes.

One of the most reliable and efficient kinds of grids prominently used in electron beam tubes is comprised of spaced, cantilever-type vanes mounted upon an annular supporting member and projecting inwardly thereof. The individual vanes of some grids of this type are free from each other at their inner ends within the supporting member. In other grids of this type the vanes of certain pairs of vanes are joined together at their inner ends so that the aforesaid pairs are each comprised of an integral element bent into a desired configuration similar to a V, for example.

Yet another type of grid which has been used in klystron tubes, for example, is comprised of a plurality of spaced vanes extending across the interior of an annular grid supporting member. The vanes are alfixed to the inner surface of the aforesaid member at opposite regions thereon with the front and back edges of the vanes being coplanar, respectively.

The vane elements of most grids of the aforedescribed types are formed from thin strip sections of metal. Each section must be of predetermined length and sharply bent at one or more places to form one or more vane elements and integral supporting portions therefor. The supporting portions are made to conform to the inner surface of the annular grid supporting member and are soldered or brazed, for example, to the aforesaid surface.

Heretofore it has been difficult to form grids of the aforedescribed types. Accurate bends are required to be made in the metallic strip sections so that a rugged assembly having a predetermined distribution of grid elements can be produced. Generally such bends have been made while the metallic strip sections are at room temperature, a cold-bending process, and it has been time-consuming and expensive to make the bends with the required precision to provide an accurate and rugged grid assembly. Furthermore, since sharp bends are generally required, the cold-bending process may result in a grid having elements which are unduly weak and fragile at the bends.

It is an object of the present invention to provide an improved process of manufacturing grids for use in electron beam tubes.

It is a further object to provide a process of manufacturing vane type grids which is less time-consuming and less expensive than processes heretofore known in the art.

It is still another object of the present invention to provide a process as aforedescribed for accurately manufacturing vane-type grids of more rugged construction than similar grids of the same type and size heretofore known in the art.

The foregoing objects are attained by a process which includes the steps of: interwinding an elongated metallic element back and forth across parts of the face of a jig from one to another of a plurality of predeterminedly shaped and distributed protuberances extending fromsaid jig face; heating the assembly comprising said jig and said element to a predetermined temperature and tightening said element about said protuberances so that por tions of said element are heat-bent and closely conformed to parts of said protuberances; and cooling said assembly to thereby permanently fix the shapes of the bends in said element and provide a rigid and accurate configuration suitable for a grid in an electron beam tube device. 7 g

If the jig has an appreciably higher temperature coefiicient of expansion than that of the grid element the tightening part of the process can be efliected by heat expansion during the heating step, provided the ends of the grid element are anchored.

Furthermore, if at least some of the jig protuberances are in a ring around the axis of the jig and have outer-5 most parts conformal to an annulus, an annular grid supporting member can be readily bonded to portions of the grid element which are interwound therearound. If the supporting member has: a slightly lower temperature coeificient of expansion than that of the jig, the heating step will cause the jig to expand and the aforementioned grid element portions to be compressed against and more closely conformed to the inner surface of the annular supporting member. The bonding is achieved by providing suitable brazing means having a melting point lower than that to which the assembly is heated between the inner surface of said supporting member and the aforesaid grid element portions.

The foregoing process and all of the objects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description of the invention taken in connection with the accompanying drawings in which:

Figs. 1, 2 and 3 are perspective views of three different types of grids which can be manufactured in accordance with the process of the present invention;

Fig. 4 is a plan view of a jigfror forming the grid shown in Fig. 1;

Fig. 5 is a side view of the jig shown in Fig. 4;

Fig. 6 is an exploded view in perspective illustrating the aforementioned jig, a grid element interwound thereon and ring members utilized in the grid forming process;

Fig. 7 is an enlarged sectional view of the jig and interwound grid element of Fig. 6, and shows the position of the ring members shown in Fig. 6 at an intermediate stage in the grid forming process;

Fig. 8 is a sectional view of'the jig and interwound element similar to that shown in Fig. 7, and shows the position of the ring members shown in Figs. 6 and 7 at a further stage in the grid forming process;

Fig. 9 is a plan View of a further jig for forming the grid shown in Fig. 3; and r Fig. 10 is a side view, shown in Fig. 9.

A first grid assembly manufactured in accordance with the process of the present invention is shown in Fig. 1. This assembly is comprised of a thin metallic element 11 which is bent to form a plurality of V-shaped sections 12, supporting portions 13 and V-shaped sections 14 symmetrically disposed about an axis of an annular metallic supporting member 16. The supporting portions 13 are rigidly fixed to or mounted upon the inner surface of member 16. The vertexes of V-shaped sections 12 are located inward of member 16 by equal distances along alternate ones of equally spaced radii of member 16. The vertexes of V-shaped sections 14 are located further inward of member 16 by equal distances along other alternate ones of the aforementioned equally spaced radii of member 16.

partly in section, of the jig The grid assembly shown in Fig. 1 is of the cantilever type since there is no support-of the arms or vanes of the V-shaped sectionsrlz and 14at their inner ends within the grid Supporting member 16. Since certain pairs of arms are joined together at their inner ends to form the V- shaped sections 12 and 14, the grid shown in Fig. 1 is usually designated as a pyramid-type grid. d V

A' modification of the pyramid-type grid illustrated in Fig. l is shown in Fig. 2. In the latter figure the grid is comprised of a plurality of J-shaped metallic sections 17 rigidly mounted and symmetrically disposed upon the inner surface of an annular, metallic supporting member 18. Bent portions 19 of sections 17 are utilized to rigidly support each section upon member 18. The adjacent sections 17 of the cantilever type grid assembly shown in Fig. 2 are mirror images of each other. Therefore, this assembly could be readily formed from the structure shown in Fig. 1 merely by cutting or shearing the V- shaped sections thereof at their apexes. Yet another type of grid assembly which can be manufactured in accordance with the process of the present invention is illustrated in Fig. 3. This assembly is comprised of a thin metallic element 21 formed into a plurality of curved vane sections 22 and supporting portions 23. The supporting portions 23 are rigidly mounted upon the inner surface of an annular, metallic supporting member 24. A uniform spacing is-provided between the vane sections 22 with the narrow front and back vane edges being coplanar, respectively. The grid assembly shown in Fig. 3 is known in the art as an arched-vane grid. The vane sections 22 are curved so that changes in temperature to which the grid may be subjected will not cause the front and back edges thereof to deviate from their original planes.

Referring to Figs. 4 and 5, a cylindrical mandrel or jig 26 is provided for forming the grid assembly shown in Fig. 1. The jig 26 is comprised of a bottom cylindrical section 27, an upper coaxial cylindrical section 28 having a smaller diameter than section 27, a flat, annular jig seat 29 outward of section 28 at the top of section 27, and a plurality of spaced protuberances 31, 32 and 33 extending from a flat upper face 30 of jig section 28.

The sides of protuberances 31, 32 and 33 are perpendicular to the face 30 of section 28. Each protuberance has the same thickness along the axis II through the center of jig 26. This thickness should generally be as large as the width of the metallic element 11 shown in Fig. 1.

The protuberances 31 are all of the same size and shape. Six of these protuberances 31 are symmetrically disposed in a ring concentric with the aforementioned axis II of jig 26 as shown in Fig. 4. The innermost ends of protuberances 31 nearest the axis II of jig 26 are spaced from the axis of jig 26 by equal distances determined by how far inward it is desired for the V-shaped elements 14 of Fig. 1 to project. These innermost ends stantially aligned with a side of an adjacent protuberance 31, the other side of each protuberance 33 being aligned with a side of an adjacent protuberance 32. The outermost parts or ends of protuberances 33 farthest from axis II of jig 26 are conformal with the cylindrical side of the section 23 of jig. 26.

One of the protuberances 33 is divided in half to provide a slot 34 through the middle thereof. The width of the slot 34 is made slightly larger than twice the thickness of the metallic element 11. This is done so that end portions 36 and 37 of element 11 can be anchored in slot 34 during the grid forming process.

The dot-dash lines back and forth across parts of the face 30 of jig 26 in Fig. 4 illustrate generally the positions that V-shaped elements 12 and 14 and portions 13 of the grid shown in Fig. 1 would assume if this finished grid were seated upon the face 30 of jig section 28 to envelop the jig protuberances. It can readily be seen, therefore, that the particular sizes, shapes and locations of protuberances 31, 32 and 33 are specifically determined in accordance with particular configuration of the grid to be formed.

The jig 26 shown in Fig. 4 is composed of metal having a relatively high temperature coefiicient of expansion compared with the temperature coefiicient of expansion of the metal of grid element 11. The jig 26 including its protuberances 31, 32 and 33 is formed by machining, casting or any other conventional jig forming process known in the art.

Referring to Fig. 6, the element 11 shown interwound upon jig 26 is originally in the form of a flat strip of metal having a greater width than thickness. A first end portion 36 of the metallic strip is inserted edgewise into the slot 34 of one of the protuberances 33 of the jig 26 to begin the grid forming process. The strip is then bent in a clockwise direction around one half of the outermost part of this protuberance 33, drawn toward the axis II of jig 26 across part of its face along the aligned sides of the aforesaid element 33 and the most adjacent element 32, bent around the innermost curved end of this protuberance 32, and drawn back along the aligned sides of the aforesaid element 32 and the next protuberance 33 displaced in a clockwise direction from the protuberance 33 containing the slot 34. This procedure is continued until the metallic element 11 is interwound back and forth around the outermost end part of each protuberance 33 and the innermost end part of each protuberance 32 and the innermost end part of each protuberance 31. One narrow edge of element 11 is maintained in abutment with the face 30 of section 23of the jig 26, the opposite narrow edge thereof being coplanar with the tops of pro- I ttuberances 31, 32 and 33.

are located at positions corresponding to the apexes of the aforementioned V-shaped sections 14.

.The protuberances 32 are also of the same size and shape, though having a different size and shape than the protuberances 31. Six protuberances 32 are symmetrically interposed between the six protuberances 31, respectively. The innermost ends of protuberances 32 nearest the axis II of jig 26 are spaced from the aforesaid axis by equal distances determined by how far inward it is desired for the V-shaped elements 12 in Fig. 1 to project, these ends being located at positions corresponding to the apexes of the aforementioned V-shaped sections 1 2.

:The protuberances 33 are also of the same size and shape, and are symmetrically disposed in a ring concentnc with protuberances 31 and 32. Twelve protuberances 33 are provided in the particular jig construction illustrated. Each of protuberances 33 is arranged to be opposite a space between a protuberance 31 and a protuberance 32. One side of each protuberance; 33 is sub After the interwinding of element 11 about all of the jig protuberances, a second end portion 37 is bent around the other half of the outermost part of the protuberance 33 containing the slot 34, and inserted into the slot 34 adjacentthe first end portion 36. The two end portions- 36 and 37 of element 11 should fit tightly within the slot 34 to thereby anchor the ends of element 11 with respect to the jig 26.

A ring element 38 preferably composed of the same metal as jig 26 is shown in Fig. 6 in concentric relationship with the jig. The thickness of element 38 along its axis is equal to the thickness of jig section 23 along the axis II. An upper inner section 39 of ring element 33 has an inner diameter which is larger than the diameter of jig section 23 by an amount which is slightly greater than the thickness of element 11. A lower inner section 41 of element 38 is chamfered. This is shown more clearly in Figs. 7 and 8.

The annular grid supporting member 16 is also shown in Fig. 6 in concentric relationship with jig 26 above element 38. Member 16 is composed of a metal having a temperature coefiicient of expansion slightly lower than the temperature coefficient of expansion of jig 26.

senses?- The inner surface of member 16 is plated with suitable brazing material for bonding member 16 to the outer portions 13 of the grid element 11. The inner diameter of member 16 is of the same order of magnitude as the inner diameter of section 39 of ring element 38.

The ring element 38 is first located in relation to the jig 26 at the position shown in Fig. 7, the cham fered section 41 thereof facilitating the placing of element 38 down over the end of the jig 26 so that part of section 39 of element 38 forces the outer portions of grid element 11 inward toward the outermost end parts of the jig protuberances 33. The annular member 16 is then placed on top of element 38 as shown in Fig. 7 so that part of this member also engages the outer portions of element 11. The member 16 and element 38 are then pushed downward until the bottom of element 38 abuts the annular jig seat 29 and the bottom of member 42 rests upon the top of element 38 at the locations shown in Fig. 8. The outermost portions of grid element 11 outward of jig protuberances 33 are, therefore, maintained in compression toward the end parts of the protuberances 33 by the annular grid supporting member 16.

The parts shown in Fig. 6, after being assembled as shown in Fig. 8, are then placed in an oven and heated in a hydrogen atmosphere to a temperature above the melting point of the brazing material on the inner surface of member 16. During the heating the jig 26 expands rapidly outward of its axis. The outward expansion of jig 26 from its axis causes element 11 to be tightened about the jig protuberances 31, 32 and 33 because of the fact that element 11 has a much lower temperature coefi'icient of expansion and its ends are anchored in the slot 34 of a jig protuberance 33. Thus, the outer portions 13 of element 11 are heat bent and conformed to the outermost end parts of the jig protuberances 33 and the apexes of the V-shaped sections of element 11 are heat-bent and conformed to the innermost ends of protuberances 31 and 32.

If the inner diameter of member 16 is properly chosen relative to the diameter of jig section 28, the thickness of element 11, and the difference in expansion of jig 26 and member 16 because of their dilferent temperature coefiicients, the portions 13 of element 11 become firmly compressed against the inner plated surface of member 16 during the heating. This occurs because the member 16 has a slightly lower temperature coefiicien-t of expansion than jig 26. Therefore, since the assembly is heated to a temperature above the melting point of the brazing material plated to the inner surface of member 16, the outer surfaces of the portions 13 of element 11 can become rigidly bonded to the inner surface of member 16.

After heating the assembly for a sufiicient time at the proper temperature, the jig 26, ring element 38 and annular member 16 are removed from the oven and allowed to cool. The jig 26 contracts and element 11 becomes firmly afiixed to member 16 upon hardening of the brazing material. After cooling, the grid assembly can be readily removed from the jig 26.

In one particular type of grid which has been made by the aforedescribed process to have a configuration as shown in Fig. 1, the grid element 11 is composed of tungsten. The supporting'member 16 for such a grid is composed of a nickel-copper alloy containing 63 to 70 percent nickel. Copper brazing material is employed for bonding or fixing the inner surface of member 16 to portions 13 of grid element 11. The copper has been plated to the inner surface of member 16 before the grid assembling and brazing steps, for example.

The assembly comprising jig 26 and element 38 utilized to form grids of the particular materials described above. is composed. of a high chromium stainless steel type No. 302 as described on pages 3-l9 of Kents Mechanical Engineers Handbook, 11th ed., Design Shop Practice. This type steel is desirable because it has a much higher temperature coefficient of expansion than that of tungsten. Furthermore, the surfaces of an assembly of such material become oxidized during the heating process so that the grid element 11 and annular grid supporting member 16 will not become bonded to the steel by the copper brazing material. Suflicient oxidation occurs, even in a hydrogen gaseous atmosphere, because of an inherent content of moisture therein. If desired, moisture can be added to the gaseous atmosphere to increase this oxidation during the heating of the jig.

To form a grid utilizing the particular materials described above the assembly such as is shown in Fig. 8 should be heated in the oven containing the hydrogen atmosphere for six to eight minutes at a temperature between 1120-1140 degrees centigrade. It has been found desirable to place a 'weight or weights of some sort on top of the jig 26 and interwound element 11 to insure that element 11 does not buckle upward during the heating. After heating, the aforedescribed assembly is removed from the oven for cooling. After cooling the aforementioned weight or weights are removed and the grid is ready to be taken from the jig.

A grid having .l-shaped sections 17 as shown in Fig. 2 can be manufactured by first forming a grid as shown in Fig. 1 by the aforedescribed process. Then, the V- shaped sections 12 and 14 are suitably out or sheared by any suita ble tool to provide the J-shaped sections 17 wherein the longer radial arms of adjacent sections are next to each other and the shorter radial arms of adjacent sections are next to each other.

Obviously other cantilever-type grids could also be formed by the aforedescribed process. For example, a pyramid-type grid wherein all of the V-shaped sections such as 12 and 14 of Fig. 1 extended inwardly of the grid supporting ring by equal distances could be made. This would merely require a jig wherein the innermost ends of all of the inner jig protuberances such as 31 and 32 in Fig. 6 were contiguous with the same circle. The apexes of the V-shaped sections of the grid formed therefrom could be cut to form yet another type grid having radial arms extending inwardly of the grid supporting ring by equal amounts with their inner ends free of each other. Furthermore, the apexes of the V-shaped sections could also be cut to form a grid having J-shaped sections wherein a long arm of each J-shaped section is adjacent the short arm of an adjacent section.

Referring to Figs. 9 and 10, a jig 46 is shown for manufacturing an arched-vane grid as shown in Fig. 3. The jig 46 is comprised of a bottom cylindrical section 4'), an upper coaxial cylindrical section 48 having a smaller diameter than section 4 7, a first set of protuberances 49 -60, and a set of rod-like protuberances 62 on a flat face 61 of jig section 48. The jig i6 is composed of a metal having a substantially higher temperature coeflicient of expansion than that of the thin metallic element 21 of Fig. 3.

The protuberances 49-60 and 6-2 all have the same dimensions along the axis Iii-11 of jig 46. These protu'berances are shaped and located as shown in the plan view of Fig. 9 so that the dot-dash lines illustrated therearound and between the protuberances conform generally to the outline of the configuration formed by the narrow edge of grid element 21 of the finished grid shown in Fig. 3.

The parts of protuberances 49-60 farthest from the axis II-II of jig 4-6 are conformal with the cylindrical side of the section 48 of jig 46. The sides of the protuberances 4960 are perpendicular to the jig face 61.

The rod-like protuberances 62 are also perpendicular to the jig face 61. Protuberances 62 are equally spaced along a diameter of the jig face 61 and located at the sositions shown in Fig. 9 so that the sections 22 of the grid shown in Fig. 3 will attain the proper curvature when forming the grid.

To provide the grid of Fig. 3, an elongated strip of metal 21 having a greater width than thickness is interwound back and forth across parts of the face 61 of jig 46 from protuberance 49 to protuberance 55, following the general path of the dot-dash lines in Fig. 9. The end portions 23 and 23 of the element 21 shown in Fig. 3 are bent around ends of protuberances 49 and 55, respectively, to provide suitable anchorage.

Once the element 21 is interwound upon the jig 46 as described, the process of making permanent heat bends in the grid element and mounting the element in an annular grid supporting element 24 is undertaken. This process is identical with that described with reference to Figs. 6-8 so need not be repeated.

Since changes in the aforedescribed process and grid assemblies of different configurations and/or different materials than specifically described herein could be made without departing from the scope of the present invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process of forming a grid for an electron beam tube device, comprising anchoring one end of an elongated strip-like metallic element upon a jig having an appreciably larger temperature coefiicient of expansion than said metallic element, interwinding said element in edgewise relationship with respect to a face of said jig back and forth in the same plane across parts of said jig face from one to another of a plurality of predeterminedly shaped and distributed protuberances extending from said jig face to thereby provide a substantially planar vane-type grid configuration, anchoring the other end of said element upon said jig, placing a grid supporting member around said element upon said jig in close relationship with portions of said element for bonding between said element and said member upon application of heat, heating the assembly comprising said jig, said element and supporting member to thereby expand said jig relative to said element and tighten said element about said protuberances so that portions of said element are heat-bent to closely conform to parts of the peripheries of said protuberances, and cooling said assembly to thereby rigidly bond said element to .said member and permanently fix the shapesof the bends in said element and provide for ready removal of said element from said jig after contraction thereof.

2. A process of forming a grid for an electron beam tube device, comprising interwinding an elongated metallic strip-like element back and forth in the same plane across parts of the face of a jig from one to another of a plurality of predeterminedly shaped and distributed protuberances extending from said jig face and anchoring the ends of said element upon said jig, said jig having an appreciably larger temperature coefiicient of expansion than said metallic element, enveloping said protuberances and interwound element with an annular supporting member having a slightly lower temperature coefficient of expansion than said jig and an inner periphery in close proximity with wide portions of said element around parts of a first group among said protuberances, said inner periphery of said supporting member being substantially conformal with said parts of said first group of protuberances and separated from said portions of said element by a material for uniting said member and element in response to heating thereof, heating the assemblycomprising said jig, said element and said supporting member to thereby expand said jig relative to said element and supporting member and tighten said element about said protuberances, said wide portions of said element being thereby heat-bent and closely conformed to said parts of said first group of protuberances and said inner periphery of said supporting member, and cooling said assembly to thereby permanently fix the shapes of the bends in said element and unites said element to said supporting member to provide for ready removalof said element and supporting member from said jig after contraction thereof.

3. A process of forming a grid for an electron beam tube device, comprising interwinding an elongated metallic strip-like element having a first temperature coeificient of expansion back and forth in the same plane across parts of the face of a jig in edgewise relationship with respect to said face fr m one to another of a plurality of predeterminedly shaped and distributed protuberances extending from said jig face, seating a grid supporting ring member upon said jig around the interwound element, said ring member having a lower temperature eoefficient of expansion than said jig with the inner surface of said ring member being plated with a brazing material and in close proximity to wide portions of said element about outermost protuberances furthest from the center of said ring member, heating the assembly comprising said jig, the interwound element and the supporting member above a melting point of said brazing material to expand said jig so that said outermost peripheral parts of said outermost protuberances are in closer proximity to said ring element and said interwound element is heat-bent about said protuberances, and cooling the foregoing heated assembly in order to permanently bond said grid element to said ring member and to enable said grid element and supporting ring member to be removed from said jig so as to provide a rugged vane-type grid suitable for electron beam tubes.

4. A process of forming a grid, comprising the steps of: anchoring one end of a thin, elongated metallic strip-like element upon a metallic jig having a plurality of predeterminedly distributed protuberances from a face of said jig, a group of said protuberances being disposed in a ring, said jig having a substantially larger temperature c0- efficient of expansion than said element; drawing said element back and forth in the same plane in edgewise relationship across parts of the face of said jig and bending said element about parts of said protuberances to form a substantially planar vane-type grid configuration generally like a predetermined configuration suitable for a grid in an electron beam tube device; anchoring the other end of said element upon said jig; placing an annular grid supporting member in surrounding closely spaced relationship with said group of said jig protuberances so that portions of said element are between said group of protuberances and the inner surface of said supporting member, means being provided for brazing said portions to said member; heating the assembly comprising said jig, said element, said supporting member and said brazing means to a temperature above the melting point of said brazing means, the heat causing said jig to expand for forcing said portions of said element in closer relationship with said grid supporting member and said element to become tightened about said protuberances to thereby cause the configuration of said element to more closely conform to said predetermined configuration; and cooling said assembly to rigidify said element and cause said portions to become rigidly bonded to said supporting member by said brazing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,609 Werner Apr. 16, 1946 3,654,940 Law Oct. 13, 1953 2,678,486 Chick et a1. May 18, 1954 2,738,438 Shepherd Mar. 13, 1956 2,825,839 Beck et a1. Mar. 4, 1958

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