Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
a) Field of the invention
The present invention relates to a new electrical device,
hereinafter called "quadrant driver", for use to rotate and
thus acuate a microwave switch.
b) Brief description of the prior art
Microwave switches have been in use for some decades in the
telecommunication industry. Their purpose is to direct
microwave signals from one initial input/output
configuration into a final input/output configuration.
Switching from one configuration to the other and vice versa
is achieved by driving a rotor forming part of the switch
from one position to another position at 90 from the first
one and vice versa.
In an electrically driven microwave switch, the movement of
the switching rotor is traditionally obtained by the use of
an external DC or stepper motor. Standard bearing and
groove Geneva linkage is often used to couple the motor to
the switching rotor. The advantage of the Geneva linkage is
that it eliminates unwanted bounces of the switching rotor
at the end of each rotation.
The external DC or stepper motors and associated mechanisms
that are presently being, used to drive the rotors of
microwave switches are quite efficient. However, they are
big in size and require maintenance.
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SUMMARY OF THE INVENTION
An object of the present invention is to provide a new
electrical device, or "quadrant driver", for driving the
switching rotor of a microwave switch, which device
advantageously replaces the DC or stepper motors that have
been used so far.
The quadrant driver according to the invention is intended
to be used for driving the rotor of a microwave switch at
90 from one given input-output configuration to another
given input-output configuration and vice versa. This
quadrant driver basically comprises:
- a housing:
- a magnet and bearing holder rotatably mounted inside said
housing, said holder supporting, on one side, a thin, high
magnetic density magnet and, on the other side, a bearing
operatively connected to the rotor of the microwave swith to
rotate the same when said holder is itself rotated, said
holder and magnet being rotated between two rest positions,
each of said rest positions corresponding to one of the two
configurations of the microwave switch;
- a pair of coils concentric to mild steel cores, said cores
being mounted within the housing so that one of the cores
faces with a given offset the magnet when this magnet is in
one of its rest positions and the other core faces with a
given offset the magnet when said magnet is in the other of
its rest positions, said cores permanently spaced apart from
the magnet; and
- means to selectively energize each of the coils to cause
rotation of the magnet and associated holder from one of its
rest position to the other, and vice versa, whenever
desired.
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An other object of the present invention is to provide a new
electrical driven, microwave switch incorporating the
quadrant driver as defined hereinabove as electrical means
to drive it.
The quadrant driver according to the invention has the
following advantages as compared to the existing DC or
stepper motors:
- it is smaller in size (size reduction)
- it is lighter (weight reduction)
- it is less expensive to produce (production cost
reduction)
- it is less expensive to maintian (maintenance cost
reduction) and
- it is easy to adjust to any driving voltage.
A detailed description of the invention will now be given
with reference to the accompanying drawings.
BRIEF DESCRIPTION OP THE DRAWINGS
Figs. la and lb are top plan views of a microwave switch
body without any motor or quadrant driver, showing the
switching rotor in its two opposite positions;
Fig. 2 is a perspective view of an existing microwave
switch, provided with a conventional driving box and
external motor;
Fig. 3 is a perspective view of a microwave switch provided
with a quadrant driver according ot the invention;
Fig. 4a and 4b are cross-sectional, side elevational and
bottom plan views of the quadrant driver shown in Fig. 3, in
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one of its two positions;
Fig. 5 is a schematic representation of the quadrant driver
electrical circuit; and
Fig. 6 is an exploded view of a single coil and mild steel
core used in the quadrant driver according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
Figs. 1 to 3 shows a microwave switch 1 of conventional
structure, comprising a cubic body 3 having ports 5,7,9,11
in its lateral faces. A switching rotor 13 is rotatably
mounted in the body 3. As better shown in Figs la and lb,
the rotor 13 has a pair of opposite, 90 oriented passages
15,17 which, depending on the position of the rotor, connect
part 5 to part 7 and part 9 to part 11 ~first position shown
in Fig. la) or part 5 to part 11 and part 7 to part 9
(second position shown in Fig. lb), respectively.
Up to now, rotation of the rotor 13 from its first to second
position and vice-versa has been achieved with a driving
mechanism as shown in Fig. 2, comprising a driving box 21
including a power connector 23 and a Geneva linkage (not
shown) operatively connected at one end to a groove 19
provided on top of the rotor (see Figs. la and lb) and, at
the other end, to a DC or stepper motor 25.
In accordance with the invention, the same rotation in
achieved with a quadrant driver 27 as shown in Fig. 3, which
is much compact in size, very simple in structure and very
efficient in use, the driver 27 including on its top surface
a power connector 29 and a knob 31 for manual override.
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Referring now to Figs. 4 to 6, the quadrant driver 27
according to the invention, basically comprises quadrant
driver housing 33. This driver housing which is preferably
made of metal such as aluminum, provides support to the
driving mechanism disclosed hereinafter. It is mounted on
the switch body 3 by means of mounting screws (not shown).
The housing 33 include~ a mild steel plate 35 acting as
magnetic shield on its outside top part (see Fig. 4a) in
order to curve downwards the magnetic lines generated by the
coils located inside the housing as will be described
hereinafter.
The housing 33 also includes a Geneva arm assembly 37
comprising a rotatable stainless steel shaft 39 and a magnet
and bearing holder 41 attached to the shaft 39. A high
density magnet 43 is secured to one side of the holder 41
and a ball bearing 45 is secured to the other side. The
ball bearing that is preferably very small, provides the
link to the rotor 13 of the microwave switch 1. The knob 31
for manual override is attached to the shaft 39 on the
outside of the quadrant driver housing 33.
The magnet and bearing holder 41 can rotate about the axis
of the shaft 39 between two positions at 90 from each
other, as shown with the arrow in Fig. 4a. The housing 33
includes two adjustable mechanical stops 47, 49 fixed to the
housing walls at 90 to each other, in order to stop the
magnet and bearing holder 41 in the proper position at the
end of each travel.
The housing also includes the power connector 29 to bring
power to a pair of coils 51,53.
The coils 51,53 are made of a wire of the proper size.
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Typically the coils are formed out of a few thousands loops
of wire. The size of the wire and the number of loops
depend on the driving voltage requirements and on the size
of the quadrant driver itself. Each coil is mounted
5 concentric to a mild steel core 55 (see Fig. 6). Each mild
steel core 55 is secured to the quadrant driver housing 33
usually by screws 57 inserted into a threaded hole 59
provided for this purpose on top of the core 55 so that the
broad side of the core 61 faces with a given offset the high
10 density magnet 43 (see Fig. 4) which can be made of samarium
cobalt or equivalent, in the form of a thin disk or slab.
At least two miniature lever switches 63, 65 (see Fig. 4b)
at 90 to each other, are secured to the quadrant driver
15 housing, close to the coils 51,53, respectively. The
function of these two switches is to cut the power from the
energizing coils 51,53 at the end of the travel of the
magnet and bearing holder 41. They are mechanically
activated by the magnet and bearing holder assembly when
20 this assembly is near the end of each of its back and fro
90 rotations. More than one miniature lever switch can be
activated at the same time at the end of each travel, to
indicate, by way of example, the final position of the
rotor.
Connecting wires are provided, as well as spark suppression
diodes 67 and AC to DC transformers as is shown in Fig. 5,
to interconnect the above mentioned elements. The spark
suppression diodes 67 across the coils are recommended when
30 DC power is used to energize the coils. AC to DC
transformers are necessary when only AC power is available.
The quadrant driver 27 disclosed hereinabove operates as
follows to drive the rotor of the microwave switch 1.
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When both coils are de-energized, the attraction between the
magnet 43 and the mild stell core 61 of the corresponding
coil keeps the magnet 43 and bearing holder 41 in a first
initial position. In this position, the device is
magnetically latched. If the ball bearing 45 is engaged in
the groove 19 of the microwave switch rotor 13 (Fig. 1), the
rotor will be Xept in that position. If, say, coil 53 is
now energized with a DC current of such direction to create
a magnetic field of the same polarity of the magnet 43
facing the coil 53, there will be a repulsion between the
magnet 43 and the coil 53. As the coil and the magnet are
slightly offset tsee Fig. 4), the magnet 43 and magnet
holder 41 will move in a radial motion away from coil 53
towards coil 51, the center of this rotation being the axis
of rotation of the shaft 39. If a high magnetic density
magnet 43 (samarium cobalt or equivalent) is used together
with an appropriate current in the coil, the repulsion is
sufficient to quickly drive the rotor 13 of the microwave
switch 1 linked to the magent 43 and bearing holder 41 by
the ball bearing 45 groove 19 combination. As the magnet 43
approaches the other coil 51, the repulsion from coil 53
decreases but the magnetic attraction from the mild steel
core 51 increases. It must be noticed that the magnet and
magnetic cores are never in contact as a small air gap 69 is
left between the two (Fig. 4a). Near the end of the
rotation, the miniature switch 65 will open, interrupting
the current to the coil 53. The magnetic attraction between
the coil 51 and the magnet 43 will pull the magnet and
bearing holder 41 in its f,inal position, 90 away from its
initial position. At this point, the microwave switch rotor
13 will be rotated 90 degrees from its initial position.
Also at this point, the quadrant driver is ready for a new
operation that starts by energizing coil 51.
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The Geneva linkage is important in this arrangement to
prevent the rotor 13 from bouncing back as it would
otherwise suffer due to its suddent stop in its final
position. This bounce back is an undesirable feature in
5 - microwave switches.
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