Method for making waveguide components

Abstract

Metallic sheet stock is stamped in accordance with certain predetermined patterns to derive members, some of which are bent to predetermined shapes, to define waveguide components which are utilized as components of microwave devices such as TR tubes. The stamped metal members are, in the case of cold rolled steel, copper plated and brazed together in a suitable jig structure to form the final composite microwave component, such as a TR tube. Waveguide flanges, iris structures, and waveguides are constructed in this manner.

Description

BACKGROUND OF THE INVENTION

The present invention relates in general to an improved method for making microwave waveguide components, such as TR tubes, from parts stamped from metallic sheet stock material, whereby the manufacturing costs are substantially reduced.

DESCRIPTION OF THE PRIOR ART

Heretofore, microwave TR tubes, utilized as receiver protectors in radars, have been constructed by the use of extruded waveguide either of steel, copper or aluminum. The extruded waveguide sections have been slotted and drilled to receive certain waveguide obstacles, such as cones and inductive irises of the conventional TR tubes. The waveguide obstacles were mounted within the slotted or drilled portions of the extruded waveguide sections and assembled with waveguide flanges which were often made by stamping of rectangular blanks from sheet stock followed by milling and drilling operations. In some cases, the waveguide flange blank was drawn to provide an axially directed lip at the inner rectangular opening in the flange which was to receive the waveguide or other components to which the flange was to be affixed.

After the TR tube components were assembled they were brazed together to form an integral assembly which was then evacuated and filled with a suitable ionizable gas.

Examples of prior art TR tubes are found in the following U.S. Pat. Nos.: 2,710,932 issued June 14, 1955 and 2,734,171 issued Feb. 7, 1956.

The problem with the prior art method of fabricating TR tubes was that a substantial amount of machining was required on the various components. In addition, the extruded waveguide was relatively expensive, especially in small quantity.

Accordingly, it is desirable to provide an improved method for making TR tubes and the microwave components thereof which eliminates much of the machining heretofore performed on the various components.

SUMMARY OF THE PRESENT INVENTION

The principal object of the present invention is the provision of an improved method for making TR tubes and components thereof.

In one feature of the present invention, a section of rectangular waveguide is formed by stamping a rectangular blank of metal from sheet stock and then bending the metal stamping into a channel having an open side. A second stamping from metallic sheet stock is employed as a cover for covering the open side of the channel to define the rectangular waveguide. The cover is sealed to the channel member by brazing, welding or the like.

In another feature of the present invention, waveguide iris is formed by stamping a member from metallic sheet stock. The stamped member is perforated with a certain pattern such that when the stamping is bent, a waveguide iris obstacle is obtained which is dimensioned to be received within a section of rectangular waveguide.

In another feature of the present invention, an internally flared waveguide flange assembly is formed by stacking a plurality of rectangular rings at the lip of a rectangular opening in a stamped plate. The stacked rings are brazed together and to the plate to form a composite flange assembly having an internally flared lip.

In another feature of the present invention, the waveguide body of a TR tube is formed by stamping from sheet stock a first member having a pattern of perforations therein to receive waveguide obstacles to be disposed within the body of the TR tube. The stamped member is then bent into an open sided channel, the waveguide obstacles are inserted into the perforations and a stamped cover member is positioned over the open sided channel containing the waveguide obstacles. The assembly is then sealed together to form the body of a TR tube.

In another feature of the present invention, a dual waveguide flange having internal shoulders around two rectangular openings in the flange is formed by brazing together a plurality of metallic stampings from sheet stock one of the stampings having dual rectangular apertures in side-by-side relation of smaller inside dimensions than the rectangular opening in the adjacent metallic stamping, whereby upon brazing the two members together the internal shoulder is formed in the composite dual waveguide flange assembly.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a pair of stampings to be utilized in the fabrication of a section of rectangular waveguide,

FIG. 2 is a view similar to that of FIG. 1 showing the bottom metallic stamping being bent to form a channel structure,

FIG. 3 is a perspective view of the rectangular waveguide fabricated according to the method of FIGS. 1 and 2,

FIG. 4 is a view similar to that of FIG. 1 depicting the pattern of apertures stamped into the members when the members are to form the body of a TR tube,

FIG. 5 is a perspective view of a metallic stamping forming the first step in the fabrication of a dual tandem TR tube according to the method of the present invention,

FIG. 6 is a perspective view of the shape into which the plate of FIG. 5 is bent to form the tandem iris obstacles,

FIG. 7 is a perspective view of the assembly of the waveguide obstacle of FIG. 6 in the channel shaped portion of the body formed by bending the bottom stamping of FIG. 4,

FIG. 8 is a view similar to that of FIG. 7 depicting the step of closing the open side of the channel body member and insertion of the cone obstacles within the irises of the body,

FIG. 9 is a perspective view similar to that of FIG. 8 showing the structure of FIG. 8 with waveguide flanges affixed to opposite ends thereof,

FIG. 10 is a view similar to that of FIG. 5 depicting an alternative iris type stamping,

FIG. 11 is a view similar to that of FIG. 6 depicting the method of bending the plates of FIG. 10 and showing the relation of the resultant iris obstacles relative to the apertured cover plate,

FIG. 12 is an exploded perspective view depicting the method for fabrication of an internally flared rectangular waveguide flange,

FIG. 13 is an axially foreshortened longitudinal sectional view of a section of waveguide employing the flanges of FIG. 12 and being closed at one end by means of a gas tight window,

FIG. 14 is a perspective view similar to that of FIG. 4 depicting an alternative stamping for the channel portion of the body of a TR tube,

FIG. 15 is a perspective view of the stamping of FIG. 14 after bending to form the channel shape,

FIG. 16 is a perspective view of a stamping employed as the cover plate for closing the open side of the channel of FIG. 15,

FIG. 17 is a plan view of a stamped iris obstacle,

FIG. 18 is a perspective view of the main body portion of a TR tube employing the components of FIGS. 14-17,

FIG. 19 is a view similar to that of FIG. 14 depicting an alternative method for making the body of a TR tube,

FIG. 20 is a view similar to that of FIG. 16 depicting an alternative cover,

FIG. 21 is a view similar to that of FIG. 17 depicting an alternative stamped waveguide iris obstacle,

FIG. 22 is a perspectie view similar to that of FIG. 18 depicting an alternative TR tube,

FIG. 23 is an exploded view of a dual waveguide flange made according to a method of the present invention,

FIG. 24 is a sectional view of the structure of FIG. 23 taken along line 24--24 in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-3 there is shown a method for fabricating a section of rectangular waveguide according to the present invention. More particularly, a first rectangular metallic sheet 11 is stamped out of metallic sheet stock. Sheet 11 has a width w corresponding to the sum of twice the height of the waveguide plus the width of the waveguide. The member has a length 1 corresponding to the desired length of waveguide to be fabricated. Similarly, a rectangular cover member 12 is stamped from sheet stock and has a width b corresponding to the width of the waveguide and a length l corresponding to the length of the waveguide to be fabricated.

In a typical example of an X-band waveguide, members 11 and 12 are stamped from 1010-1020 No. 18 gauge cold rolled steel sheet stock. The stamped cold roll steel members 11 and 12 are then copper plated.

In the next step as shown in FIG. 2, member 11 is folded or bent into a generally U-shaped channel having an open side or top portion. The fold lines 13 and 14 run longitudinally of the member 11 and serve to fold up narrow side wall portions 15 and 16 which have heights, a, approximately equal to one-half the width b of the channel. Plate 12 is then positioned over the open side of the channel and joined along the side edges of the cover 12 to the upstanding marginal side edges of the channel 11, as by brazing, to obtain a composite rectangular waveguide 17 as shown in FIG. 3.

The advantage to this method of making a rectangular waveguide, as contrasted with procuring extruded rectangular waveguide, is that, in small lot quantities the waveguide section may be made of any desired length merely by determining the length of the stampings without having to procure large runs of extruded waveguide which would then be cut to the proper length. During the brazing step, a suitable brazing jig, not shown, holds the cover plate 12 in position relative to the adjoining upper lips of the side walls 15 and 16.

Referring now to FIGS. 4-9 there is depicted a method of the present invention for fabrication of an X-band TR tube. As shown in FIG. 4, the waveguide body portion of the TR tube is fabricated in the same manner as shown in FIG. 1, namely, rectangular members 11' and 12' are stamped from metallic sheet stock. However in the case of members 11' and 12' the members are also, at the time they are stamped, pierced with a certain predetermined pattern of holes or apertures 18 and 19 to receive certain waveguide obstacles such as cones. In the case of the bottom U-shaped channel member 11', one hole 18' is provided in that portion of the member 11' which will be foldled up to form a side wall of the main body. This hole 18' is provided for evacuation and gas fill of the TR tube.

A pair of inductive iris obstacles are formed by stamping from cold roll steel sheet stock material a rectangular member 21 with a pattern of apertures 22 therein which will form the inductive irises when the member 21 is folded. Next, the member 21 is folded along fold lilnes 23-26 such that the resultant obstacle has a height, a, and a spacing c between a pair of inductive iris portions 22 of the obstacle. The semicircular end portions of the apertures 22, when folded, are in registration with holes 18 and 19 in the top and bottom walls of the resultant waveguide.

The obstacle 21 is assembled within the waveguide channel portion 11', as shown in FIG. 7. The obstacle 21 is precisely positioned therein by means of a suitable assembly jig, not shown, and then secured in place, as by spot welding at 28 or welding the foot portions 29 of the obstacle 21 to the bottom wall of the channel member 11'. The cover plate 12' is then affixed over the open side of the channel member 11' and cone shaped obstacles 31 are inserted through the aligned apertures 18 and 19 into the iris openings in the obstacle 21.

After these elements have been assembled, the assembly is provided with waveguide flanges 32 at opposite ends. The assembly is then brazed together by means of brazing wire strategically located adjacent seams to be formed in the brazed assembly. The resultant X-band TR tube is shown in FIG. 9. After the brazing step, waveguide window assemblies, not shown, are sealed across the openings in opposite flanges 32 and the TR tube is evacuated and filled with a suitable ionizable medium, in the conventional manner. An X-band TR tube fabricated according to the method of FIG. 4-9 results in a substantial cost savings in parts and materials and avoids substantially all relatively expensive machining operations.

Referring now to FIGS. 10 and 11 there is shown an alternative method for fabricating a TR tube particularly suited for S-band. More particularly, the method of fabrication is similar to that previously described with regard to FIGS. 4-9 with the exception that the waveguide iris obstacles are formed in a different manner. As in the case of obstacle 21 of the previous example, an iris obstacle 34 is stamped from sheet stock as shown in FIG. 10. The obstacle 34 includes a central aperture 35 which is to form the iris opening. The iris opening is generally rectangular with a semicircular cutout at one end and with a spike structure 36 stamped out of the metal stock projecting axially of the aperture 35. The obstacle 34 has a width b corresponding to the inside width of the waveguide in which it is to be disposed. A second semicircular cutout 37 is provided in one end of the member 34.

The member is then folded along fold lines 38 and 39 to form a generally channel-shaped member which is positioned on its side transversely within the guide in the manner as indicated in FIG. 11. In a typical example, three such obstacles 34 will be positioned in side-by-side relation to define three inductive irises 35 in tandem along the length of the waveguide section. The semicircular cutouts in the folded members mate with and are located in registration with three apertures 41 in the cover plate 12 to permit upper cone members to be positioned within the waveguide in transverse registration with the lower spike members 36 to establish discharge gaps therebetween.

The obstacles 34 are spot welded to the lower channel member 11 in the manner as previously described with regard to FIG. 7. The assembly is brazed together to form a gas tight TR tube body. Waveguide flanges are affixed to opposite ends of the waveguide body in the manner as will be described in FIGS. 12 and 13.

Referring now to FIGS. 12 and 13 there is shown a waveguide flange assembly 42 which is fabricated according to the method of the present invention. More particularly, the flange 42 includes a first generally rectangular plate 43, as of 10 gauge 1010-1020 cold rolled steel which is stamped out of sheet stock with a central rectangular aperture 44 and bolt holes 45. A rectangular axially directed flange portion 46 is provided at the lip of the central aperture 44. This flange is formed, according to the present invention, by stamping three annular ring members 47 from cold rolled steel sheet stock. The rings 47, in a typical S-band flange assembly, each have a thickness as of 0.062 inch and a radial width of 0.10 inch. The inside aperture of each of the rings 47 is dimensioned to be equal to the inside dimensions of the aperture 44 in flange plate 43. The flange plate 43 and the rings 47 are copper plated and then overplated with silver. The plated members are then stacked together in a brazing fixture and brazed in a hydrogen furnace at 925.degree.C for 5 minutes. The silver serves as a brazing material. The completed flanges 42 are then brazed to the opposite ends of the TR tube body in the manner shown in FIG. 13. A gas tight microwave window assembly 49 is brazed to the inner lip 46 of one of the flange members 43.

The advantage of fabricating the flange 42 according to the present invention, wherein the stamped parts are brazed together to form the composite flange structure 42, is that the flange need not be ground flat as is the case when the internal flange portion 46 is made by drawing of a stamping.

Referring now to FIGS. 14-18 there is shown an alternative method for fabricating a TR tube according to the present invention. The method is similar to that previously described with regard to FIGS. 4-9 with the exception that the iris plates 51, as shown in FIG. 17, are stamped from sheet stock and provided, at the time of stamping, with tabs 52 at the outer periphery of the iris plate 51. The bottom wall stamping, as shown in FIG. 14, which is to form the bottom and sides of the main waveguide body 11, is also stamped with a pattern of apertures 50 to receive the bottom tab 52 and the two side tabs 52 on the iris plates 51. The bottom wall stamping 11 is folded along fold lines 13 and 14 to form the bottom and side walls of the waveguide structure. The cover plate 12, as shown in FIG. 16, is similarly stamped with a pattern of apertures 55 to receive the two upper tabs 52 of the iris plates 51. In addition, circular apertures 56 are punched in transverse registration with the tab apertures 55 and along the longitudinal center line of the cover plate 12 to receive the upper cone assemblies 57. The iris plates 51 are transversely inserted into the channel shaped member 11 and then the cover plate 12 is assembled to capture the respective iris plates 51 in their proper position. The cover plate 12 is then held in position by a suitable jig and the assembly is brazed to provide the composite TR tube body as shown in FIG. 18.

Referring now to FIGS. 19-22 there is shown an alternative method for fabricating a TR tube according to the present invention. The method is similar to that previously described with regard to FIGS. 14-18 with the exception that the stamping for the cover plate 12", as shown in FIG. 20, has the same width w as the stamping which is to form, when folded, the bottom half of the waveguide. The bottom half is shown in FIG. 19 as stamping 11".

The bottom and top half stamping 11" and 12" are punched at the time of stamping with a certain pattern of apertures 50 and 55 to receive waveguide obstacles, such as the tabs 52 of iris plates 61 of FIG. 21. The stampings 11" and 12" are folded along fold lines 13 and 14 and 62 and 63, respectively, such that the upturned side walls 15 and 16 of the bottom channel 11" extend a distance only one-half of the height, a, of the waveguide. Similarly, the top half as folded along fold lines 62 and 63 has downturned side walls 64 and 65 which are downturned by only one-half the height, a, of the waveguide. Three iris plates 61 are located within the lower channel 11" and then the cover member or channel 12" is positioned over the lower channel to close the open side thereof as shown in FIG. 22.

The assembled waveguide and irises 61 are then held in a suitable jig and a heliarc weld is made along the two opposed side seams at the mating lips of the side walls of the lower and upper channel members 11" and 12" of the assembly. Cone obstacles are then assembled within the apertures 56 in alignment with the lower spike portions 36 of the iris plates 61. Windows and flanges are affixed. Brazing material is positioned along the internal and external seams and the unit is then brazed in a furnace to produce a gas tight TR tube body. The method of constructing a TR tube as described with regard to FIGS. 19-22 is particularly suitable for fabrication of an L-band TR tube.

Referring now to FIGS. 23 and 24 there is shown a method, according to the present invention, for fabrication of a dual waveguide flange assembly 68. The dual waveguide flange 68 is affixed as by brazing over the end of a pair of side-by-side rectangular waveguides, not shown. The composite flange 68 is fabricated by brazing together three stampings 69, 71 and 72 which have been stamped from cold rolled steel sheet stock. The first stamping 69 comprises a centrally apertured rectangular plate having dimensions of the rectangular opening 73 corresponding to that required to be affixed to a pair of side-by-side waveguides. In a typical example, flange member 69 is stamped from 1010-1020 cold rolled steel of 14 gauge thickness. The flange plate 69 is also stamped or punched at the time it is stamped from sheet stock with a pattern of bolt holes 74.

The second stamping 71 is similar to stamping 69 in that the bolt pattern is the same and the outside dimensions of the rectangular plate are the same as those of plate 69. However, plate 71 is apertured with a pair of side-by-side rectangular apertures 75 with a septum 76 separating the apertures 75. The apertures 75 correspond to the inside dimensions of the rectangular waveguides to which the flange is to be affixed.

The third stamping 72 is substantially the same as that of the second stamping 71 with the exception that the septum 76' is narrower and the side-by-side rectangular apertures 77 have inside dimensions corresponding to the outside dimensions of the rectangular waveguide to which they are to be affixed. The apertures 77 and 75 in respective plates 71 and 72 are coaxially aligned. The stampings 61-72 are copper plated then overplated with silver and held together for brazing in the manner previously described with regard to fabrication of flange 42 of FIG. 12. The composite flange assembly 68 is then ready to be affixed to dual waveguide assemblies.

The advantage to the method of fabricating the flange 68 according to the method of the present invention is that expensive machining steps are avoided. The cost of a relatively large flange is greatly reduced utilizing the method of the present invention. Generally speaking, utilizing the methods of the present invention for fabricating TR tubes and waveguide components, the direct manufacturing costs of labor and materials are cut in approximately half as contrasted with the prior method which utililzed machining of stampings and extrusions.

Claims

What is claimed is:

1. A method for making a microwave waveguide apparatus comprising the following steps:

bending a first metallic sheet into an open-sided rectangular channel member,

forming a second metallic sheet to provide a waveguide obstacle having outline dimensions fitting the inner transverse dimensions of said channel, said obstacle including an opening to define a waveguide iris, said forming of said second sheet including the step of bending at least one side of said sheet to form an angular foot projecting from said side,

positioning said obstacle within and transverse to said channel with said foot abutting a surface of said channel,

covering the open side of said channel with a third metallic sheet, and

sealing said channel, said obstacle and said third sheet together to form a tubular waveguide with said obstacle closing said waveguide except for said iris in said obstacle.

2. The method of claim 1 wherein the step of forming said second sheet includes bending two parallel angular feet on opposite sides of said second sheet and the step of covering said open side of said channel includes abutting said third sheet to one of said angular feet.

3. The method of claim 1 wherein said opening in said second sheet is shaped to include a reentrant projection.

4. The method of claim 1 wherein the line of said bending crosses said opening, whereby a cut-out is formed in said foot.

5. The method of claim 4 further including the step of forming an aperture in one of said first and said third sheets and wherein the step of positioning said obstacle includes aligning said cut-out with said aperture.

6. The method of claim 5 further including the step of positioning a metallic cone-shaped waveguide obstacle within said aperture with the tip of said cone-shaped obstacle projecting into said iris.

7. In a method for making a microwave waveguide apparatus, the steps of:

bending a first metallic sheet into a first open-sided channel member,

forming in a second metallic sheet at least one opening to define two waveguide irises,

bending said second sheet into a second channel having aligned openings in both sidewalls, said second channel being dimensioned to fit within said first channel,

positioning said second channel within and transverse to said first channel,

covering the open side of said first channel with a third metallic sheet, and

sealing said first and second channels and said third sheet together to form a tubular waveguide with two axially spaced transverse obstacles, each containing an iris.

8. The method of claim 7 wherein the step of bending said second sheet includes bending the ends of the sidewalls of said second channel to form angular feet positioned in a surface parallel to the bottom wall of said second channel and wherein the step of positioning said second channel includes abutting one of the parallel surfaces of said feet to said bottom wall of said first channel.