BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to the manufacture of elbows for rectangular microwave
guides.
[0002] Elbows for rectangular microwave guides are used to make directional changes of approximately
90° or less, both in the plane E containing the electrical field and in the plane
H containing the magnetic field.
2. Description of the Prior Art
[0003] Several designs of elbows exist at present. A first type of elbow consists of a tube
with a folded rectangular section to whose ends connection flanges are attached by
soldering. A monolithic version of this type of elbow is manufactured by molding according
to the method known as the lost-wax method. In both cases, the cost of manufacture
is relatively high.
[0004] Another type of elbow is obtained from two complementary parts in each of which a
half-tunnel equal to the entire length of the elbow is hollowed out from a plane connection
face. The two half-tunnels are then placed so as to face each other and the two parts
are joined by means of a plurality of screws. In this way, elbows are made with their
tunnel, on the side external to the change in direction, having a transition face
with a sequence of steps or levels. This design enables the use of simple and efficient
machining technologies such as milling. However, the assembling of the two parts by
screws may give rise to defects of coincidence between the two half-tunnels. These
defects, however minute they might be, could have harmful effects. Furthermore the
assembling screws, which must be sufficient in number to provide for a satisfactory
link, take up a considerable volume of the material of the two parts and therefore
hinder the miniaturization desired for most applications.
[0005] The invention is the result of research conducted on elbows for rectangular microwave
guides with a view to achieving the following goals: simplicity of manufacture giving
rise to an economical cost price, efficient reproducibility to enable mass production
within tight tolerance values, high aptitude for miniaturization through the utmost
elimination of the constraints of space requirement other than those inherent in the
functional dimensions.
SUMMARY OF THE INVENTION
[0006] To this end, the invention consists of a method for the manufacture of an elbow for
rectangular microwave waveguides, said elbow comprising an internal tunnel formed
by two rectilinear sections that meet to define a dihedron on the internal side of
the change in direction and, facing the peak of said dihedron, on the external side
of the change in direction, a stepped transition face, wherein the method consists
of the making, by machining in one block, from two faces of said block forming the
connection ends of the elbow, of two rectangular boreholes that meet so that, at their
meeting place, they define said dihedron on the internal side of the change in direction
and said stepped transition face on the external side of the change in direction.
[0007] Provided that the steps of said transition face are straight steps, said boreholes
can advantageously be made by the milling technique which provides a totally satisfactory
degree of precision for the applications aimed at (working at frequencies of 10 to
20 GHz) and would remain sufficient well beyond these frequencies (at least up to
60 GHz).
[0008] Furthermore, in the monolithic elbow thus made, the totality of the volume of remaining
material becomes available to receive fastening screws for the elements to which it
will be connected thus enabling a maximum reduction of this volume of material and
therefore of the total space requirement of the elbow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The characteristics and advantages of the invention mentioned here above, as well
as others shall appear more clearly from the following description made with reference
to the appended drawings, of which:
- Figure 1 is a schematic view in perspective of an elbow made according to the present
invention;
- Figure 2 is a sectional view along the line II-II of Figure 1;
- Figure 3 is a view similar to that of Figure 2 showing a second exemplary embodiment
of an elbow made according to the present invention; and
- Figure 4 is a schematic view in perspective of a block comprising two elbows made
according to the present invention.
MORE DETAILED DESCRIPTION
[0010] If we consider first of all Figures 1 and 2, they illustrate the invention by representing
an elbow C for a rectangular microwave waveguide. This is a right-angled elbow with
a change in direction in the plane E (containing the electrical field) corresponding
to the height b of the guide. It is made of a standard material such as an aluminum
alloy.
[0011] The elbow C consists of a parallelepiped block 1 with two orthogonal connection faces,
respectively F1 and F2, between which the internal guiding tunnel T has been machined.
In practice, this tunnel consists of two orthogonal boreholes A1, A2 with a rectangular
section (a, b) respectively formed out of the faces F1 and F2. These two orthogonal
boreholes A1, A2 meet in defining, on the internal side of the change in direction
(Figure 2), a straight dihedron with a peak S and, on the external side of the change
in direction, a cut-corner transition face P substantially at 45°, facing the peak
S and formed by a succession of steps G. The steps G are straight steps. Each of them
therefore has a wall parallel to the walls with a width a of the borehole A1 and a
wall parallel to the walls with a width a of the borehole A2.
[0012] The elbow C is advantageously made by milling, for example by a machining process
in which, first of all, the borehole A1 is made with a back that is stepped on one
of its sides to form the set of steps G. After this, the borehole A2 is made. As a
variant, it is possible to stop the machining of the borehole A1 at the first step,
namely the highest step in this borehole, or to stop the machining at an intermediate
step, and then make the remaining steps during the machining of the borehole A2.
[0013] Figure 3 shows an elbow of the same design as the elbow C described here above which
shows all its characteristics and consequently has the same references along with
the prime sign. The elbow C' can also be made by milling as explained in the previous
paragraph and it actually differs from the elbow C only in the fact that its steps
G' have their number considerably increased as compared with the number of the steps
G, their dimensions of course being reduced to a corresponding degree can be seen
in the succession of parallel lines of fine dots and dashes giving a schematic view
of the machining increments in one dimension. As a result, the transition face P'
becomes a plane wall or more precisely it can be likened in practice to a plane wall
in which henceforth the step levels G' no longer have any effect other than that of
giving it a certain roughness.
[0014] Figure 4 illustrates another advantage of the invention enabling several elbows to
be associated in the form of several guidance tunnels T1, T2 machined side by side
in a single block 10.
[0015] It goes without saying that the above description pertaining to elbows designed for
changes in direction in the plane H is also valid for elbows designed for changes
of direction in the plane E which can be made exactly in the same way.
1. A method for the manufacture of an elbow for rectangular microwave waveguides, said
elbow comprising an internal tunnel formed by two rectilinear sections that meet to
define a dihedron on the internal side of the change in direction and, facing the
peak of said dihedron, on the external side of the change in direction, a stepped
transition face, wherein the method consists of the making, by machining in one block,
from two faces of said block forming the connection ends of the elbow, of two rectangular
boreholes that meet so that, at their meeting place, they define said dihedron on
the internal side of the change in direction and said stepped transition face on the
external side of the change in direction.
2. A method according to claim 1 for the manufacture of an orthogonal elbow, wherein
the tunnel is machined by milling, the steps being straight steps made during the
milling of one of the boreholes.
3. A method according to claim 1 for the manufacture of an orthogonal elbow, wherein
the tunnel is machined by milling, the steps being straight steps, a part of the steps
being made during the milling of one of the boreholes and the remaining part being
made during the milling of the other borehole.
4. A method according to one of the claims 1 to 3, wherein the transition face is made
with a large number of small-sized steps so that it is an almost plane wall.
5. An elbow for rectangular microwave waveguides, obtained by the implementation of the
method according to one of the claims 1 to 3.
6. A set of several elbows for rectangular microwave waveguides combined in a single
unit, wherein this set comprises, in a monolithic block, guidance tunnels obtained
by the implementation of the method according to one of the claims 1 to 3.