Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Title of the Invention
MULTIPLE SENSIWG DEVICE AND
SENSING DEVICE THEREFOR
Back~round of the Inventi_n
.
This invention relates to sensing devices for physical
~ characteristics, and is more particularly directed to a low
- cost sensing device for sensing such parameters as magnetic
field, electric field, gas flow, linear acceleration and
angular acceleration. The invention is particularly directed
to simplified devices or combination of devices of this
type, which are particularly adaptable for use in aircraft.
It will, of course~ be apparent that the invention may be
advantageously employed in other fields.
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While devices are known for the detection of each of
these parameters, in general the devices are relatively
expensive, so that their use is restricted, and they are not
adaptable to application having limited life. The present
invention is therefore directed to the provision of a novel
multiple sensing device of low cost, which is capable of
accurately sensing all of these above parameters. The
invention is also concerned with the provision of separate
sensing devices for sensing each of these parameters.
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Summar~ of the Invention
Briefly sta~ed, in accordance with the invention, one
or more sensing devices is mounted ~or rotation on a shaft,
and commuta~or means are connected to encable coupLin~ of the
sensed vol~age from the sensing device. The sensing devlces
are adapted to produce alternating voltage si~naLs, the
instantaneous maximum amplitudes of the signals correspond-
ing generally to the vector of the measured physical
characteristic in a given plane, such as a plane normal to
the axis of rotation. As a consequence, substantially
complete data regarding the physical characteristics may be
provided by employing two of the multiple sensing devices.
In accordance with the invention, a magnetic ~ield
sensing device for determining a magnetic field vector
normal to the shaft, comprises a pair of magnetic coils
symmetrically affixed to rotate with the shaft. A sensing
device for ascertalning the vector of an external electric
field may comprise a pair of electrodes mounted for rotation
with ~he shaft, with the external ends of the electrodes
being uninsulated. Gas flow, such as air flow, in a
direction normal to the axis of the shaft may be detected by
a crystal plate mounted, perferably on the end of the shaft,
this crystal being bendable about an axis parallel to the
plate and normal to the shaft. Angular acceleration about
axes normal to ti~e shaft may be detected by a pair of
crystals extending radially from the shaft, and having
bendin~ axes normal to the shaft. The radially outer
extremities of the latter crystals may be joined by a
symmetrical, i.e., annular, reaction mass. In addition,
linear acceleration normal to the shaft may be obtained by a
pair of similar crystals compressable in a direction normal
to the axis of the shaft. Masses may also be provided at the
radial outer extremities of these crystals.
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Brief Description of the Drawin~s
In order that the invention will be more clearly under-
stood, it will now be disclosed ln greater detAll with
reference to the accompanying drawings~ in which:
Figs. 1-5 are simplified illus~rations of magnetic
field, electric field, gas flow, linear acceleration and
angular rate sensing devices employed in accordance with the
invention;
Fig. 6A-6D are views illustrating, in simplified form,
four consecutive positions of the sensing rotor of Fig. 5;
Figs. 7A-7D are figures illustrating, consecutively,
the side views corresponding to the views of Figs. 6A-6D,
respectively;
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Fig. 8 illustrates the output of the two crystals of
~o Figs. 6A-6D and 7A-7D,
:
Fig. 9 illustrates the sum of the voltages generated as
illustra~ed in Fig. 8;
Fig. 10 is an exploded cross-sectional view of a
portion of a multi-probe assembly in accordance with a
preferred embodiment of the invention;
Fig. 11 is a cross-sectional view of an electric motor
rotor that may be employed in combination with the system of
Fig. 10;
Fig. 12 is a cross-sectional view of a multi-probe
assembly, incorporating the elements of fig. 10;
Fig. 13 is a cross-sectional view of a further embodi-
ment of a multi-probe assembly, in accordance with the
invention; and
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Fig. 14 is a simplified illustration of one application
of a pair of multi-probe assemblies in accordance with the
invention, on an aircraft.
Description o~ the Preferred ~mbodirnents
The present invention is directed to the provlsion of a
mul-iple sensing device, particularly ldaptable for use on
aircraft, but which ~ay oE course have other applications.
The concept of a multiple sensing device for physical
parameters necessitates the combination of indiviclual sens-
ing devices adaptable to combination, for sensing purposes,
in an accessable manner, in order to achieve the desired end
result, and hence the present invention of necessity incorp-
orates a number of individual sensing elements responsive to
different physical characteristics. The individual sensing
devices may, of course, have separate utility, even though
-~ -they are particularly adaptable to being combined for ~he
desired purpose.
Referring now to the drawings, Figs. 1-5 illustrate in
simplified form the principles of operation of the five
sensing devices with which the present invention is primari-
ly concerned. It will, of course, be apparent that a
multiple sensing device in accordance with the invention may
additionally incorporate other sensing means, or that, when
desired, one or more of the illustrated sensing means may be
omitted.
~ s those treated in Fig. 1, a magnetic field sensing
device is comprised of a pair of identical coils 10 mounted
in a column plane on opposite sides of a shaft 11, for
rotation with the shaft. Assuming the shaft extends into the
coordinate direction Z and that the coils are connected
e~ternally by way of a suitable commutator, the device of
Fig. 1 will produce an alternating voltage of a freq~ency
corresponding to the rotary speed of ~his shaft, and having
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an instantanteous peak when the plane of the coils is
aligned with an external rnagnetic field, such as the earth's
magnetic field. The magnitude of the o~ltput voltage is
dependent upon the component of the e~ternal magnetic fieLd
in the X/Y plane. In the arrangement of Fig. 1, it is
apparent that the greatest po~tion of the output volta~e is
developed by the radia]ly outermost portions of the coils.
The output voLtage is a sine wave when the Eield is
linear. When the inciden~ magnetic field is not linear,
i.e., contails gradients, harmonics of the fundamental are
generated. In the simple case, the second harmonic is the
most dominant. In effect, the main field and the gradient
fields give uniquely different signal frequencies.
` In the electric ield sensor illustrated in Fig. 2, a
pair of electrodes 12 extend radially in opposite directions
from the shaft :Ll, with the radiantly outermost portions of
the electrodes being uninsulated. The radiantly intermediate
portions of the electrodes are preferably insulated. It is
apparent that, with the inner ends of the electrodes
connected externally of the device by way of a suitable
commutator, the device will produce a sine wave voltage
output of a frequency corresponding to the rate of rotation
of the shaft ll. The voltage arises from the fact that the
non-insulated radially outer ends of the electrodes 12
rotate in a static electric field 9 such as the static
electric field of the earth, whereby the instantaneous
maximum of the sine wave voltage output occurs when the
electrodes are aligned with this electric field. The ampli-
tude of the ~oltage corresponds to the gradient of the
static electric field in the X/Y plane.
.,
In the sensing device of Fig. 3, a plate piezo electric
crystal 13 is mounted on one end of the shaft ll for
rotation therewith. The plane of the crystal 13 is parallel
to the axis of the shaft 11, and the crystal is arranged so
that it may be bent about axes normal to the axis of the
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shaft 11. Suitable electrodes of conventional nature (not
shown) are affixed to the crystal, so that stress upon the
crystal normal to the sha~t ll results in the generation o~
a pie~o elect-ric voltage, which may be directed externaLly
of the device by a suitable commutator asse~bly. If a
component of a gas flow is in the X/Y pLane o ~he de~ice~
it is apparent that the gas flow, lmpinging upon the
crystal, will stress the crystal so that an alternating
voltage will be produced. The alternating voltage ~-ill have
a frequency corresponding to the rate of rotation of the
sha~t 11 with the instantaneous peaks occuring when the
bending axis oE the crystal is normal to the component of
the gas direction in the X/Y plane. The crystal may be
referred to as a "bender" crystal. The amplitude of the
voltage corresponds to the component of the gas flow in the
X/Y plane, assuming, as above, that the shaft extends in the
Z direction. In -the arrangement of Fig. 3, the crystal thus
serves as a restoring spring and a signal generator, and may
be advantageously employed as an air mass data probe.
In Fi~. 4, a pair of crystals 14 are mounted on
opposite sides of the shaft 11, for rotation therewithO The
crystals 14 are oriented to be compressible in a direction
normal to the shaft 11. If desired, suitable masses 15 may
be provided at the radially outer extremities of the
crystals 14. If suitable leads are connected conventinally
to the crystals 14, and directed externally of the device by
way of a suitable commutator assembly, it is apparent that
an alternating output voltage will be produced having a
frequency corresponding to the rate of rotation of the
shaft. The instantaneous maximum of the voltage occurs when
the crystals are aligned with a component of linear acceler-
ation in the X/Y plane, and the amplitude of the output
voltage thus corresponds to the linear acceleration of the
shaft in the X/Y direction. The sensitive axes of the
crystals are thus oriented to react to acceleration paraLlel
to the spin plane of the device. The two crystals are
electrically interconnected in order to provide an additive
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output for ~hese two elements.
In Fig. 5, LWO crystals 16 are also mounted on opposite
sides of the shaft 1l. In the arrangement of Fig. 5,
however, the crystals are mounted to be bendable, and have
bending axes normal to the axis of the shaft. IE desired, a
reaction mass such as annular mass 17 may be provided
symmetrically at the radially outer ends of ~he crystals.
The arrangement of Fig. 5 constitutes an anguLar velocity
probe, based upon the gyroscopic operation of an elastically
restrained body rotating at high velocity. The initial
member and the restoring springs thus constitute the sarne
eLement, as in the case of the air mass data probe of Fig. 3
and the linear acceleration probe of Fig. 4. The two bender
crystals are arranged in a dipole fashion for common mode
rejection and inertial balance. In the arrangement of Fig.
5, angular momentum of the masses reacting as a result of an
applied angular velocities at right angles to the spin axis
of shaft ll, results in the generation of a voltage by the
crystals which is sinusoidal in distribution and exhibits a
frequency identical to the rate of rotation of the shaft.
The two crystals of the arrangement of Fig. 5, are prefer-
ably interconnected to their respective commutators in the
opposite sense from that of the device of Fig. 4.
The operation of the rate of gyro of Fig. 5 may be more
readily understood with reference to Figs. 6-9. Thus, Figs.
6A-6D represent four consecutive positions of the crystals,
with coun~erclockwise revolution, as may be seen from the
end of the shaft 1l. In these figures, the two crystals are
identified as crystals -16' and l6". The shaft is assumed to
be continuously rotating. Referring to Fig. 7~ which depicts
a side view of the device of Fig. 6, it is assumed that the
axis of the shaft ll has been displaced through an angle
alpha. The shaft ll and the hub 18 on the shaft in which the
crystals 16' and l6" are mounted, are adequately rigid so
tha~ they both may substantially instantaneously exhibit
their new positions without deformation. The radially outer
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ends of the crystals, however, due to gyroscopic action,
remain for some time oriented as though the angular dis-
placement of the shaft ll had not occurred. This is, of
course, particularly true if a reaction mass i5 linked to
the radially outer ends of the crystals. As a consequence o
the gyroscopic action, the crystals bend about their mechan~
ical axes, as ilLustratecl in Figs. 7A-7~ respectively, to
result in output voltages as illustrated in Fig. 8. It is
thus seen that the instantaneous peaks of the resultant
alternating voltage occur when the crystals extend normal to
the axis of rotation about the angle alpha. Since the output
of the crystals are of different polarity, the crystals are
interconnected in reverse sense, to produce the resultant
output voltage as illustrated in Fig. 9.
In the arrangement of Figs. 5-9, it is apparent that
the crystals are employed as gyroscopic elements, with or
without the provision of a reaction mass, and tha~ the
strain on the crystals is proportional to input angular
2U rate. The amplitude of the output is proportional to the
input angular rate, and the phase of the output is related
to the direction of the input angular rate of angular
displacement of the rotating shaft in a direction normal to
the axis of the shaft. In other words, if the shaft 11 is
angularly dlsplaced about an a~is in the X/Y plane, the
output of the rate gyro or angular velocity sensor of Fig. 5
is proportional to the rate of rotation about the axis in
the X/Y plane, then the phase of the output voltage is
related to the orientation of the axis of rotation in the
X/Y plane, assuming again that the shaft 11 extends in the Z
direction.
Fig. 10 is an exploded partially cross-sectional view
of a portion of a multi-probe assembly in accordance with a
preferred embodiment of the invention. This view illustrates
pirmarily the rotor components, to show that they can be of
modular construction, whereby a multi-probe assembly may be
~abricated of any of the desired sensing probes. It will of
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course be apparent that the cover construction for such a
multi-probe assembly will be dependent upon the components
chosen for use in the assembly.
As illustrated i.n Fig. 10~ the multi-probe assetnbly is
compriced of an air data probe 30, an electric field probe
31, a magnetic field probe 32, an angular velocity and
linear acceLeration probe 33, and a slip ring 34 and brush
block assembly 40. In addition, the assembly includes a gas
drive ring 35 for the pneumatic drive of the rotor. All of
the elements of Fig. 10, except the brush block assembly 40,
constitutes a part of the rotor.
The gas drive assembly 35 may be comprised of a
metallic rin~ 41 having gas drive slots 42 on its radially
outer periphery, whereby the ring may be rotated by direct-
ing a jet of air tangentially against this outer periphery.
The ring 41 has a recess 43 in one face thereof, Eor
receiving the magnetic field probe 32. In addition, a
- 20 circular coaxial recess 44 is provided in the outer face for
receiving the angular velocity and linear acceleration probe
33.
The magnetic field probe is comprised of a circular
disc 50 of insulating material, within which the two
magnetic sensing coils 51 and 52 are embedded. The coils 51
and 52 have radially outer extremities 53 which extend
axially of the disc for substantially its full axial
dimension. The coils 51 and 52, which are identical 9 have
radial returns squashed down axially, as illustrated in Fig.
10, with the axial extension of the radial innermost
portions of the coil being at a minimum. As a consequence,
the radial returns are so positioned with respect to the
spin axis of the device tha-t the axial return is near the
center of rotation. This in effect gives the section line at
the major radius most of the charge generating capacity for
the probe. The disc 50 is fitted, by suitable conventional
means, for rotation on a shaft 54. The shaft 54 is
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preferably holLow, and serves as a bearing for the assembly,
to Pxtend through a housing (not shown in Fig. lO)o Suitable
interconnectin~ wires for the coils 51 and 52, as well as
Eor interconnecting the coils ~o the s:lip ring assembly~ are
illustrated at 55.
The shaf~ 54 may be affixed only to the magnetic
sensing assembly, with the ring 50 being Eitted tightly for
rotation in the recess 43. Alternatively, the shaft 54 mcly
extend through the ring 50 and be Eltted to the gas drive
ring 41.
The electric field probe 31 and the air data probe 30
are adapted to sense data which requires their physical
location outside of the housing of the device. Consequently,
` the electric field probe may be comprised of an insulating
: disc 58 having a central bore adapted to fit over the shaft
54. The disc 58 may be connected to the shaft 54 for
rotation by any conventional means. The disc 58 has a pair
of radially extending holes 59 through which the electrodes
60 ex~end. Suitable enlarged ends, such as conductive balls
61, may be provided at the ends of the electrodes 60 for
sensing the earth's static electric field. The inner ends of
the electrodes 60 extend into a recess 62 in the face of the
disc 58, for interconnection with conductors 63 extending
through the shaft 54, the conductors 63 advantageously
extending completely through the device for interconnection
with the slip rings 64 of the slip ring assembly 65.
As will be apparent from the following disclosure, a
portion of the housing of the device may extend be~ween the
magnetic field probe and the electric field probeO
The air data probe is aLso comprised of an electrically
insulating rotating body member 70 having a disc shaped base
adapted to fit for rotation either into the recess 62 of the
- electric field probe or, if desired, directly on the end of
the shaft 54. The body 70 may be an axial extension 71 for
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enclosing a crystal 72. A further crystaL 73 extends axially
beyond the insulating body 70, to serve as the air flow
sensor as above described. The crystal 72 w;thin extension
71 serves as a reference, and is thereby interconnected
diEferentially with the crystal 73. The conducto~ connected
to those crystals may be led to a connector 74 afflxed in
the base 70, for interconnection with the slip ring conduc-
tors 63.
10The angular velocity and linear acceleration probe may
form a combined unit 33, as illustrated in Fig. 10. For this
purpose, the assembly may be comprised of a cylindrical
; housing 76 adapted to be fitted for rotation in the recess
44 of the gas drive ring. The housing 76 may contain a pair
of radially extending crystals 77 at the central portion
extending to a hub 78, to serve as the linear acceleration
probe as discussed in accordance with the above principles.
The linear acceleration probe is disposed axially centrally
of the device 33. In addition, a plurality of pairs of
bender crystals 79 may be positioned axially on each side of
the linear acceleration probe, for the sensing of angular
velocity as discussed above. Suitable conventional conduc-
tors are provided (but this is not shown) connected to the
crystals, for interconnection with the slip ring assembly
65.
The slip ring assembly 65 may be fitted directly to the
above lower end of the assembly 33, for example, on studs 80
on the lower end of the assembly 33, in order to complete
the rotary structure of the device. The slip ring assembly
has a plurality of slip rings 64, adapted to be connected to
each of the sensing probes as above discussed. While the
drawing of Fig. 10 does not show these conductors, it is
apparent that suitable apertures may be provided in the
housings of the structure9 for enabling the necessary
interconnections. For this purpose~ it is of course not
necessary that a single shaft extend throughout the rotor
assembly, since the individual components of the structure
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may be provided with internally embedded conductors for this
purpose. As a consequence, it is apparent that a modular
construction nlay be achieved, whereby the elements may be
interconnected as desired.
While the brush block 40 for cooperatlon with the slLp
ring assembly 34 is not a rotary member, ;t has been
illustrated in simplified form in Fig. 10, to illustrate in
general a preferred manner by which the signals generated ln
- 10 the various probes may be led externally of the device. The
slip rings 64 may be at the axial end of the slip ring
assembly, axially beyond a bearing portion 81 of the rotor
assembly, in order to simplify construction of the device.
In the use of the device in accordance with the
invention, it is of course necessary to establish the phases
of the different alternating voltages generated by the
sensing devices, in order to be able to ascertain the
directions of the varlous sensed physical quantities. For
this purpose, in accordance with one embodiment of the
; invention, reference markings 82 may be provided on one face
of the gas drive ring 41, for cooperation wi-th a suitable
sensing device, such as a photoelectric sensing device 123
of conventional nature as illustrated in Fig. 13. It will of
course be apparent that any other forms of reference
generated of conventional nature may aLternatively be
employed in combination with the multi-probe device of Fig.
10 .
While the device of Fig. 10 is particularly adaptable
for gas drive, it will be apparent that it may also be
employed with an electric motor drive. For this purpose, the
gas drive ring 41 is provided with an annular recess 85
radially outwardly of the recess 44. A motor rotor 86 for
example as illustrated in Fig. 11, may bc mounted in the
recess 85, for rotation with the rotor. The recess 85 has a
sufficient radial dimension th~t a stator assembly affixed
to the housing (not shown) in Fig. lO) may also be fitted
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into recess 85. For example, the stator may extend axially
from the end housing of the assembly. It is therefore
apparent that the device of Fig. lO may be modified for
electric drive with a minimum of modification.
Fig. i2 shows the assembly o~ Fig. L0 in cross sectlon,
with ~he elements of the rotor interconnected together in
their preferred form. In addition, it shows the brush bLock
assembly 40 mounted in a recess in insuLatLng housing, 907
for cooperation with a slip rln~ assembly. Ihe housing
member 90 serves as one cover of the device, and is bolted
to a metal base block 91, for example, to enable the rigid
mounting of the device as desired. In addition, the central
portion of the housing 92 is affixed to the base 9L. The
cover 90 in the housing is provided with suitable bearings
93, to engage the portion 81 of the shaft of the rotor. The
upper portion 94 of the housing, which serves as a cover,
extends betwen the magnetic and electric field sensor, and
is provided with bearings 95 for the shaft portion 54. The
portions 92 and 94 of the housing may also be of insulating
material.
The arrangement of Fig. 12 is adapted for gas drive,
and for this purpose the housing 92 is provided with a gas
; drive inlet 96, positioned to direct air or other gas
against the turbine blades of the gas drive ring 41. An
outlet for the gas may extend by way of an aperture 97 in
the lower cover 90, which communicates with an aperture 98
in the mounting base 91.
As discussed above, -the multi-probe sensor in accord-
ance with the invention may be formed of a lesser number of
- components. Thus, as illustrated in Fig. 13~ the multi-probe
sensor is comprised of a rotary unit incorporating only a
pair of bender crystals 100 mounted Eor rotation with a
shaft lOl. The crystals lO0, as is apparent in Fig. 13, do
not extend inwardly -to the shaft, their bases being fixed in
a suitable block or hub L02 radially outwardly spaced from
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~he shaft 101 proper. In the arrangement of Fig. 13, the hub
or blocks 102 are affixed to one side of a web of the gas
drive ring 103, and a further hub or set-up blocks 104 is
provided on the other side of the web. From these blocks or
hub a pair of addit:ional bender crystals 104 are provided
extending radiaLly inwardly. The inner ends of these latter
crystals are not rigidly affixed to any compvnent to the
structure. The crystals lOS are mounted so that they are
bendable about axes parallel to the shaft 101. As a
consequence, the output of the crystals 100 correspond to
acceleration and the output of crystals 105 corresponds to
rate.
A gas inlet llO is provided in the housing 111 for
driving the shaft 101. In addition, the reference generator
120~ discussed above, is mounted in the housing lll for
coooperation with ~h~ suitable reference scale 121 on a ace
of the gas drive ring 103. The reference generator may
comprise a reference source of light 122, such as an LED,
cooperating with a suitable photosensitive devlce 123 of
conventional nature, for producing a reference signal output
related to the position of the rotor of the device. The
device of Fig. 13 is provided with a suitable slip ring and
brush assembly 125.
It will of course be apparent that other combinations
of units may be employed, in accordance with the invention.
Since the multi-probe sensor in accordance with the
invention provides two axis data, a pair of such multi-probe
assemblies may be employed to provide all the necessary
three-dimensional data with respect to the measured physical
quantity. This is particularly useful, for example, in
aircraft. Thus, as illustrated in Fig. 14, a pair of
multi-probe devices 130 of the type illustrated in Figs. 10
and L2 may be mounted with orthogonal axes on an aircraft
131. This arrangement enables the inputting of sufficient
data to the aircraft to enable the calculation of the
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earth's magnetic and electric field, as well as external air
flow and linear acceleration and angular veLocity of the
aircraft. The probe assembly is inexpensive, and readily
fabricated.
It i5 of course apparent that the electrlc circuits for
comparison oE the phase oE the reEerence generator with the
measured quan~ity may be of conventional nature, and hence
need not be discussed in detaiL in this speclEication.
Typical performance characteristics of a multi-probe
assembly, in accordance with the invention, are provided in
Table 1 of this disclosure.
It is further apparent that this multi-probe assembly,
in accordance with the invention, by employing a single
rotary shaft, reduces cost and power consumption in this
provision of need for sensing the necessary data, as well as
a decrease in volume and mechanical complexity by an order 20 of magnitude. Further, it is apparent that the majority of
components of the structure may be formed of molded plastic.
While the invention has been disclosed and described
with reference to a limited number of embodiments, it will
be apparent that variations and modificatlons may be made
therein, and it is intended in the following claims to cover
each such variation and modification as falls within the
true spirit and scope of the invention.
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