CA1062345A - Module for cavity resonance devices - Google Patents

Abstract

A B S T R A C T

A module for forming the side walls of a cavity resonance device comprises a metal extrusion shaped in cross-section to be of a rectangular U-shape. The walls forming the free ends of the U are provided adjacent each of their free edges with first shaped portions forming part of the extrusion and extending longitudinally there-along. At least one of the walls forming the U-shape module is provided adjacent each edge of the outer surface of said wall with second shaped portions forming part of said extrusion and extending longitudinally therealong. The first shaped portions and the second shaped portions are res-pectively designed so that the two first shaped portions of one module may respectively be slid longitudinally into, to interfit with, the two second shaped portions of another module to connect such modules mechanically and electrically at each interfitting of a first and a second shaped portion.

Description

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Tl~i.5 illv~?ntion relates to a module for the formatinn o C~!i.y resonance devic~s wherc two or m~re of such devicos are to be arranged side by side.

By cavity resonance devices are devices for use at between 25 Megacycles and 1200 Megacycles (from high frequency by microwave frequencies) comprising an outer conductor which is a hollow metallic shell with or without a central conductor. The outer shell may be of many cross-sectional shapes but this invention is concerned wi~h a device where the cross-section is rectangular and most commonly square. Cavity resonance devices fitting the above description and with which the invention might be used include : band-pass filters, band stop fil~ers, wave guides, ` cavity resonators and transmission line transformers.
, Since the invention is designed to provide a modular construction for such devices located side by side it will `` apply most frequently tos~lch devices as filters, cavity resonators and transformers which are commonly placed side by side and infrequently to wave guides which are usually used -r $~J - . -. 20 singly.

!,,, It is an ob~ect of the invention to provide a mo~ule ;~1 for use in the assembly of a plurality of side by side cavity resonance devices which module is a metallic extrusion in the shape of rectangular U-shape. (By "longitudinally" in the specification and claims herein, I mean in the direction of extrusion). The free edges of the walls forming the ~, ~ "uprights" of the U are provided with first shaped portions .-~'. ~
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3 ~ 5 ~le~igne~ to ~t!~s;:rit witll ~y sliding longitLIdinally a]ong second s~ s~ons provided adjacent each end of the ~utside of on~ of the walls of the rectangular U-shaped extrusion. T~lus with the two first shaped portions of one module interfi~ting with pair of second shaped portions of another module results in the provision of a square or rect-angular cavity resonance device having three sides f ~OM the first mentioned module and a fourth side provided by on~ wall ¦ of the last mentioned module. ~hree sides of another cavity 3 lo resonance device, side by side with the first are provided.
! A number of modules may be assembled in this way if desired If, with the number of modules assembled, corresponding to the desired number of side-by-side cavity resonance devices, one of the modules has only three sides, the fourth wall may be provided by a separate wall with a pair of second shaped portions.

Since the module is formed from an extrusion, it may be cut to any length desired.

Although the extruded modules may be formed fro~ any ¦ 20 extrudable metal with suitable conductivity, the requirements of economy and ease of fabrication will dictate that the metal used is aluminium, brass, bronze or copper- and the preferred one of these is aluminium.
' Prior methods of providing multi-section cavity resonance devices (most commonly filters) are as follows :
1. Use separate devices joined with sections of . . .
transmission line or ~oined by welded or brazed waveguide apértures.

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2. U~e ~ J~ c section devices having common w~lls containi~ r~-~re~ or loops. The whole ilter section may be cast l:.on aluminium, bronze or the like.

3~ Use multiple section devices with common walls ,~ fabricated by making a multiple section extrusion.
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4. Use multiple sections formed by providing multiple four sided square or rec~angular extrusions placed with side walls of respective sections juxtaposed as clo~ely as possible and connected by aligned apertures in the juxtaposed walls with or without common connecting probes or loops.

Separate devices ((1) above) joined by coaxial ,cable or wave guides are expensive and inefficient relative , ,, to the other devices described. Multiple section devices ((2) and (3) above) having co~mon walls formed by casting ' -or extrusion ~are relatively efficient and may be economical if the particular shapes chosen are sufficiently in demand , to be manufactured in sufficiently large quantities. However these last mentioned multiple section devices have two principal disadvantages. (a) Such devices are only economical when manufactured in large quantities to a common pattern.- ~'-`
Thus such devices are not versatile enough to be used for a large number of different filter (or other resonance device) configurations each having but a limited yearly sales potential. (b) The provision of holes or other coupling mean~ through the common wall between sections of such multiple section devices is difficult and expensive due to difficulty of access. The use of multiple sections fonmed by four s~ded . '~ ' - 3'~
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~ 6 ~3'~5 `~ sections juxt~p~ ed wal] to wall with each other (4) above suffers rom t~ fact that leakage occurs between adjacent juxtapos~d ~sa~l~ r.o ~atter how precisely they are made or aligned. Moreovex such precise manuf~cture or ali~nment is expensive. A further disadvantage of the last mentioned method arises from the fact the juxtaposed walls between connected sections require aligned apertures. Such aligned apertures require precision forming which is both difficult 1 and expensive due to the difficulty of access once the sections i 10 are connected and the imprecision of alignment when the ~ apertures a~e separately formed in disconnected sections.
: . ,. ~. .. 1 - The inventive construction using extrusions having three of the required four walls and forming a rectangular U~shape in cross-section overcomes the disadvantages of the prior methods. The production of multiple sections using the number of such modules corresponding to the number o~
sections, and with the open sides of the U closed (in at least some cases) by the walls of similar modules, provides multiple sections which are relatively inexpensive and electrically efficient. Moreover the three sided modules arë
constructed so that they may be easily assembled into a variable number of multiple sections or relatively large vsriety of multiple sections. The production of special multiple sections in small volume can thus be performed economi-cally. Because three æided modules are used, the connected 8ections in a multiple 8ection device may always (if desired) be connected by a single wall. In such case there is no problem of leakage between or of alignment of apertures in double walls.

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Irl ~irawin~s which illus~rate preferred embodimellts of the invention :

~igure l shows the cross-section of an extrusion in accord with the invention;
, Figure 2 shows the cross-section of a number of connected modules each formed of the cross-section of Fi~ure l;
Figure 3 shows a member for use with modules formed from the extrusion of Figure l;
Figure 4 shows a multi sectional c~vity resonance device formed from the extrusions of Figure l;
Figure 5 shows the coupling of members of the type shown in Figure 4;
Figure 6 shows a cross-section of another extrusion in accord with the invention; and `1 Figure 7 shows the connection of four extrusions of ;'i the type shown in Figure 6 in the formation of a four section cavity resonance device.
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In the drawings, Figure 1 shows an extrusion 10 of -~3 generally rectangular U cross-section. At each corner w~e~ --the wall 12 forming the cross-bar of the U joins a wall 14 forming the upright of the U, the extrusion is shaped to form an outwardly open circular groove 16 with the defining ex-;~ trusion material 18 and 19 extending approximately 3/4 of the ~ -way about of the circle of the groove and with the opening directed outwardly at about 25 to the side walls of the 'extrusion. It will be noted that the shaped portions are pre-ferably arranged so that the side walls 14 of the extrusion are of smooth contour and the shaped portions only interrupt-~ the end wall 12 or cross-bar of the U-shaped extrusion. The ;t ' - 5 -i.. " . - . .
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The free cd~es ~f the w~lls 14 are provided with shi~rted po~tion3i 2G, ~ rJed to complemen~ the circular grooves 16, at the e~ r-utirt~ corncrs as hereinafter described. The shaped portions 20 on one module are arranged to abut against the outer lip l~ deining the circular groove 16 of another module. The shaped portion 20 is shaped to conform to the I curvature of the circular groove adjacent it's lip 19. The I extensions 20 or "male members" of one module are slid ` longitudinally into the circular grooves ~ or "female members"
~- 10 o the other member to form the arrangement described and - best shown in Figure 2. It wIll be obvious that with the embodiment shown the modular fvrm allows the assembly, in a ; line, of as many sections as desired. The end section will have only three walls and the fourth wall is provided by a plate 26 (shown in Figure 3) shaped to define at each edge the two circular grooves 18, similar to those on a module so that the plate may be slid longitudinally over and relative to ~he portions 20 of the open-~nded module. The circular shape of the grooves 18, (and the conforming shape of the .,.~;
~ 20 male member 20 are not essential to the invention). For most J applications however it is important that the groove defining surfaces define opposed faces on one of which the male member will lie and further def~ne inwardly curved surfaces on each . .~1, , .
side of the opposed surfaces. This is so that a screw (pre~erably "thread forming" as distLnct from "thread cutting"
~ msy be inserted into the passage remainLng between the male ¦ member and the defining surface of the female member spaced therefrom. The pressure exerted by the screw moves the male member ol-twardly clamping it firmly against the adjacent surface .

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: ' . ' . . . ', ' ' 3 ~ 5 of the ~r~v~Je defining member thus clamplng the two ~ module~ flrm!,~ t~gethex. A similar screw attachment is m used to fi~ily fa~ten the end plate in place. The action af a screw 24, as above described is shown in Figure 5. The clamping not only gives good mechanical connectiDn but good electrical connection to properly ensure the electrical qualities of the device. The screw of course is used, not only for clamping but fox attachment of the end cap of the device, which will be provided with whatevex electrical elements (~e.g. probe, loop, central conductor or s~mple closure) are required for the sections of the multisection , ~ ,-, ~ -;
device.
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~ Although the modules may be constructed where the .
male members 20 at the free edges of one module are spaced to -~ confonm to the spacing of the female members (grooves 16 ~-~ deined by extents 18 and 19) so that they may be simply slid ' . ..
longitudinally there into. However it is preferred to shape the extrusion so that the side walls 14 are slightly toed in and hence male members 20 are more narrowly spaced relative to the female members of the module to which the former are to be attached. The 'toe in' of walls 14 is shown in Figure l.
To connect the male members 20 of one module into the female members o~ another the male members are spread to obtain the proper spacing before being slid longitudinally therealong.
The extrusion must therefore be designed to be sufficiently -~e~ilient for bending of the side walls 16 about lines running longitudinally therealong ~ufficient to allow the necessary sp~reaa~ng of the male members. The result of "spreading" the male member~ to enter the female members is that the fonmer -. .' ~ '.

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bea~ inw.~r(li.y nn the la~ter creating a better electrical conrlectlon. The mDdular shape of Figure l is a single extrusion as is th~ d ~lember of Figure 3. Such extrusions may obviolsly be simply out to any length desired.

The embodiment of Figure 1 to 5 is designed to provide any plurality of sections arranged in a line.

A multi-section device comprising four modular sections is shown in perspective in Figure 4. The end module which would otherwise define only three side walls of a cavity resonance device is closed by an end member 26 of the type shown in Figure 3. The four section multi^section device?is closed at each end by end caps 28 held in place by screws 30.
The screws 30 clamp the extensions 20 against the groove de-fining members 19 as best indicated in Figure 5. Since there ~ are no male members 20 in the grooves 16 in the section at - the left of Figure 4 compressible fillers 32 will be used if - the screws 30 are to be the same size as the others. It may also be necessary to slightly off set the end holes for screws ; 30 since these will be concentric with their grooves 16 while the others will not. Ang necessary apertures or connections through the common walls between the sections (i.e. walls 12) are made and any connecting equipment is installed before the individual modules are assembled to each other. The end cap may be provided with whatever equipment e.g. probes, loops, central conductors etc are required for the particular sections.
These are not shown as they are conventional and well known 4 to those skille~ in the art as are the criteria for their design and performance.

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The en-l~o~ilr~nt of Figure 6 sl-ows a module 38 de~igned not only to pro~?ide e:lt~ t:U end multisections as shown iLI Figure 6, but also al~ows t~e assembly of multi-section cavity resonance devices with its U-shaped members arranged in differing orienta-tions .

- In Figure 6 a rectangular U-shaped extrusion is shown. In this embodiment circular grooves 40 whose inner defining surface encompasses about 270 of a complete circle axe located, nol: only at each end of the cross bar or end ~- 10 wall 44 of the U but also at the free edges of the "uprights"
of the U o~ side walls 42. The gap in the shaped poxtions de~ining the circular grooves is at substantially 45 to the side walls 42 and end wall 44 of the module (when the side walls 42 are biased to be perpendicular to the end walls). As in the embod~ment of Figure 1 to 5 the shaped portions defining the circular grooves are arranged so that they do not interrupt ;i the outer contour of the side walls 42.

At the free edges of the side walls 42 the inner lip 46 of the shaped portion defining inner exeent is provi~ `
20 with a lip 48 extending to curve (oppositely from the lip curvature) over the ends of the lips defining portions of circular grooves 40 and to provide an extent which will rest against the - -corresponding surface defining the circular groove of another similar module. It will be noted that the two lips 48 or male members may be inserted into pairs of grooves 40 or ~emale members with the modules in the same orientation in the same manner as in the embodiment of Figures 1-5 with (and using an fitting end r~ember not shown but analogous to that of FLgure 3~. However it . _ 9 - :

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wili also i:)e ~ d th~t the male meMbers 48 on one m~ldule may be inser.ed in th~ female members at each edge of a side wall 42 oL ane~!ler module so that the side wall 42 of the second module forms the fourth wall of the first module, and the modules are relatively oriented at 90 to each o~her. Thus an I. shaped arrangement of three or more modules may be provided with an end plate on the open end of one of the modules, or four modules may be arranged in a square as shown in Figure 7. Modules are again connected bg longitudinal sliding 10 of the male members of one module into the female members of another.

With the embodiment of Figures 6 and ~ it is still considered advantages to have the side walls 22 resllient and slightly toed in (as shown in Figure 6~ to be biassed outwardly to fit in to the female members for good electrical connection.
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Again the module 38 is a single extrusion.

Also as with the embodiment of Figures 1-5 the second embodiment does not have to define circul~ contours . , .
~t~ 20 and circular male members to conform thereto. It is necessary ~ that the inner surface of the female groove enconrass a ^~ sufficient part of a completed ring that when the male member ,,, is inserted therein the outward pressure of a screw will bear in one direction on the male member clamping it on a portion of the defining surface of a female member, while bearing on an opposed female member defining surface to exert the clamping pressure. Also if it i9 desired to have connected modules oriented at 90 to one another than the female member must have symmetry about a plane at 45 to the end and side walls 42 and .

'~ 44 of a mo~lc~ wh2r l)e end and side walls are mutually per-pendI.cula~: .

~ re a mod~lle is sufficiently large in dimensions perpendicu~ tO ~L~e iongitudinal direction, it mag be desirable to have screws to hold down the end cap other than at the corners. Provision for extra screws may be provided by the `
small grovves ~8 defined in the extrusion of Figure 6, such grooves may also be provided in the embodiment of Figur~ l-S.

End caps may be applied to the embodiment of Figures 6 and 7 in a similar manner to the way they are applied to the embodiment of Figures 1-5, The end caps will be pr~vided with equipment conforming to the character of the sections to which they are attached. Before assembly the side walls of the modules may be provided with any needed connecting apertures, probes or the like.

The male and female members described are the best ., .
~' way known to me of connecting the modules. However in its - broadest aspect of the invention relates to a module for a '~ cavity resonance device which is generally a rectangular or square U-shaped metal extrusion of conducting metal with first r~ shaped portions adjacent the free edges and at least one pair second shaped portions respectively adjacent the opposite end of the outside of a side or end wall shaped to receive the first shaped portions when longitudinally slid thereinto. Thus ~3 the module allows the formation of multiple sections when the two ~3 first shaped portions of one module are slid longitudinally into the second shaped portions of another module.
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Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows :

1. Module for forming the side walls of a cavity resonance device for use at between 25 Megacycles and 1200 Megacycles comprising a metal extrusion :
shaped in cross-section to be of rectangular U-shape, the walls forming the free ends of the U being provided adjacent each of their free edges with first shaped portions forming part of said extrusion and extending longi-tudinally therealong, at least one of the walls forming the U-shaped module being provided adjacent each edge of the outer surface of said wall with second shaped portions forming part of said extrusion and extending longitudinally therealong, said first shaped portions and said second shaped portions being respectively designed so that the two first shaped portions of one module may respectively be slid longitudinally into to inter-fit with the two second shaped portions of another module to connect said modules mechanically and electrically at each interfitting of a first and a second shaped portion, whereby there is formed, by the said one module and said at least one wall of said another module, an electrical conductor which is a hollow metallic conductor.

2. A module as claimed in claim 1 wherein said extrusion is made of aluminium, bronze, brass or copper.

3. Module for forming the side walls of a cavity resonance device as claimed in claim 1 wherein said walls are slightly resiliently bendable about lines parallel to the extrusion direction, and said first shaped portions are spaced closer together than the spacing required to interfit with the corresponding second spaced portions, with the wall resiliency being such as to allow the first shaped portions to be spread to allow said first shaped portions be longitudinally slid along the corresponding second spaced portions, whereby the first shaped portions said walls adjacent said free edges which interfit with second shaped portions press inwardly under such resiliency on surfaces of said second shaped portions.

4. Module for forming the side walls of a cavity resonance device as claimed in claim 1 wherein one of each of a first shaped portion and a second shaped portion which are designed to interfit, is a male member and the other is a female member and the design is such that, with the male member in said female member, an aperture is defined extending in the direction of the extrusion for receipt of a screw, said maile and female members being so designed that upon insertion of said screw, said male member is clamped firmly against said female member.

5. A module as claimed in claim 3 wherein said extrusion is made of aluminium, bronze, brass or copper.

6. A module as claimed in claim 4 wherein said extrusion is made of aluminium, bronze, brass or copper.

7. A module as claimed in claim 1 wherein a pair of said second shaped portions are located respectively adjacent each corner where a wall forming the upright of a U-shaped extrusion meets the wall forming the cross-bar of such U-shaped extrusion, whereby assembly of two such modules with the first shaped portions, of one module slid longitudinally along the last mentioned second shaped portions of the other module results in the closure of the opening in one U-shaped module by the wall forming the cross-bar in the other U-shaped module.

8. A module as claimed in claim 3 wherein a pair of said second shaped portions are located respectively adjacent each corner where a wall forming the upright of a U-shaped extrusion meets the wall forming the cross-bar of such U-shaped extrusion, whereby assembly of two such modules with the first shaped portions, of one module slid longitudinally along the last mentioned second shaped portions of another module results in the closure of the opening in one U-shaped module by the wall forming the cross-bar in the other U-shaped module.

9. A module as claimed in claim 4 wherein a pair of said second shaped portions are located adjacent each corner where a wall forming the upright of a U-shaped extrusion meets the wall forming the cross-bar of such U-shaped extrusion, where assembly of two such modules with the first shaped portions of one module slid longitudinally along the last mentioned second shaped portions of the other module results in the closure of the opening in one U-shaped module by the wall forming the cross-bar in the other U-shaped module.

10. A module as claimed in claim 1 wherein a pair of second shaped portions are located adjacent opposite ends of at least one wall forming one of the uprights of the U-shaped extrusion, whereby assembly of two such modules with the first shaped portions of one module slid longitudinally along the last mentioned second shaped portions of the other module results in the closure of the opening in one U-shaped module by the last mentioned wall forming the upright in the other U-shaped module.

11. A module as claimed in claim 3 wherein a pair of second shaped portions are located adjacent opposite ends of a wall forming one of the uprights of the U-shaped extrusion, whereby assembly of two such modules with the first shaped portions of one module slid along the last mentioned second shaped portions of the other module results in the closure of the opening in one U-shaped module by the last mentioned wall forming the upright in the other U-shaped module.

12. A module as claimed in claim 4 wherein a pair of second shaped portions are located adjacent opposite ends of a wall forming one of the uprights of the U-shaped extrusion, whereby assembly of two such modules with the first shaped portions of one module slid along the last mentioned second shaped portions results in the closure of the opening in one U-shaped module by the last mentioned wall forming the upright in the other U-shaped module.