Note: Descriptions are shown in the official language in which they were submitted.
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1.
BAC~G~UND OF THE INVENTION
The instant invenkion resides in the ark of
monitoring devices and is more particularly related
to such devices for aircrat. It is extremely impor-
tant that aircraft tire pressure be known to the
pilot to reduce the possibility of blowouts. It is
well known that the likelihood of a blowout substan-
tially increases with tire pressure changes above or
below a particular desired level, and that such blow-
outs not only result in a loss of the tire itself,
but seriously increase the likelihood of further
property damage ~r human injury.
Hexetofore in the art, applicant has not
been made aware of any tire pressure monitoring sys-
tems which will allow a continual monitoring of the
tire pressure during both static and dynamic condi-
tions. Brushes have ~een used in the past to act as
commutatoxs for transferring an electrical signal
from a rotating to a stationary member. However,
"brush dancing" is experienced when used in the
environment of an aircraft wheel and noise or spuri-
ous signals are generated which substantially reduce
the integrity of the sensing system. Further, brush-
es are subject to contamination in the wheel environ-
ment and are generally characterized by an undesir-
a~ly high resistance path.
The prior art has also taught certain types
of interconnections between rotating and stationary
members for transmitting tire pressure signals util-
izing an induction technique. However, such systems
have generally required close tolerances between
the static and dynamic coils, which tolerances must
not chanqe with movement of the wheel. Accord~ngly,
concentricity problems have made such systems unsuit-
able for the aircraft industry.
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2,
Other approaches to sensing and tran~mit-
ting electrical signals indicative of tire pressure
have utilized magnets ~aintained within the wheel,
operating upon a magnetic field principle. However,
problems have been experienced with the carrying
of magnets within the wheel due to size and weight
requirements. Such systems have generally not been
accepted. Similarly rejected as being insufficient
have ~een the tire pressure indicators utilizing
r 10 apparatus producing an audi~le signal. However, such
systems have been of a nature that a signal is emit
ted only during the period that the tire is actually
goinq flat or losing pressure. If the operator is
not near the tire or vehicle during the period that
pressure is being lost, the signal will not be dis-
cerned by anyone and the usefulness of such system
will be totally lost.
It has there~ore ~ecome desirable to pro-
vide in the art, a tire pressure communication device
which provides substantially noise-free output sigW
nals while being of sufficiently simplistic nature
(~ that it is capable of operating in the severe envir-
onment of an aircraft wheel without reduction of
system integrity.
ASl~:CTS OF THE IN~IENTION
In light of the foregoing, in accordance
with one aspect of the invention, there ;s provided a
tire pressure communication device which, without the
presence of noise and spurious signals, communicate~
a signal indicative of tire pressure from a rotatable
tire to a stationary portion of the aircraft.
In accordance with another aæpect of the
invention, there is provided a tire pressure communi-
cation device wherein no brushes are necessary for
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3.
electrical communication from a rotating to a stationary
structure.
In accordance with still another aspect of the
invention, there is provided a tire pressure communication
device wherein tolerance and concentricity problems inci-
dent to the prior art are overcome and in which the prior
art problems of contamination from the ambient are sub-
stantially reduced.
In accordance with still another aspect of the
invention, there are provided tire pressure communication
devices which are reliable in operation, relatively
simplistic in design~ readily conducive to implementation
of presently existing aircraft, and easily implemented
using state-of-the-art apparatus.
An aspect of the invention is as follows:
Apparatus for sensing the pressure of an aircraft
tire and for communicating such pressure sensin~ from a
rotating tire to a stationary portion of the aircrat, com-
prising:
tire pressure sensing means comprising a first
set of races connected to and rotatable with the tire;
signal receiving means comprising a second set of
races fixedly secured to a stationary portion of the air-
craft; and
communication means comprising a plurality of ball
bearings preloaded between respective pairs or said first
and second sets of races, said ball bearings being main-
tained between said races in four-point contact for com-
municating a signal indicative of tire pressure from said
sensing means to said receiving means.
DESCRIPTION OF DRAWINGS
For a complete understanding of the aspects,
structure, and techniques of the invention
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4.
reference should be had to the following detailed
descripti.on and accompanying drawings wherein:
Fig. 1 is an illustrative view oP a first
embodiment of the invention utilizing a tire pressure-
controlled Bourdon tu~e for regulating a magne.tic
gap;
Fig. 2 is a sectional view of another embod-
iment of the invention wh~rein tire pressure is used
~or regulating a bellows which in turn controls the
core of an LVDT; and
Fig. 3 is a sectional view of a commutator
made in accordance with the invention utilizing pre-
loaded ball bearings for achieving necessary elec-
trical communication.
DE:TA:I-LED I)~SC:l~IPTI~N O.F PR}~FER~ED ~IMENTS
Referring now to the drawings and more
particularly Fig. 1, it can be seen that a first
embodiment of a tire pressure communication device is
designated generally by the numeral 10. That device
includes a Bourdon tube 12 adapted for interconnec-
tion with an aircraft wheel by means of connector
straps 14. The connector straps 14 are of a flexible
nature and are adaptable ~or centering and maintain-
ing the tu~e 12 appropriateIy within a portion of the
wheel housing. Flexibility is desired sincel as will
be discussed ~mmediately, the diameter o~ the tube 12
fluctuates with tire pressure and, accordingly, the
straps 14 must be flexible to maintain ~he tube 12
therewithin.
A standard pressure inlet 15 is provided in
communication between the tu~e 12 and the tire. The
inlet 15 may pass through the wheel frame and into
the envelope defined by the tire and the wheel for
making such communication~ Such interconnection is,
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5.
of course, well ~ithin the capahilities of one
skilled in the art. Accordingly, there is communi-
cated to the Bourdon tube 12 a pressure correspond-
ing to t~e internal pressure of the associated tireO
A magnetic core piece 16, of suitable
material for conducting magnetic fluxt is fi~edly
secured to a nonrotating portion of the aircraft in
ju~taposition to the portion of the wheel maintain-
ing the tu~e 12. While t~e actual structure to
which the core piece 16 wlll be a~fi2ed will vary
from aircraft to aircraft, suita~le places for
maintaining t~e same would ~e found on the brake
frame, axle, torque tubes, or the like. Suffice i~
to say t~at the core plece 16 is so positioned
that a magnetic gap is maintained between the faces
of tAe core piece and the Bourdon tube 12 as the
wheel carrying the tu~e is rotated.
Connected about the core piece 16 are
inductive coils 18,20. One of these coils, in this
case coil 18, is an input coil receiving an elec-
trical signal from an appropriate signal source on
the aircraft. This sïgnal is electromagnetically
induced into t~e output core 20, with the signal
strength`being controlled b~ the size o~ the magnetic
gap existing between the faces of the core 16 and
the tube 12~ It will, of sourse, be understood that
the tube 12 is metallic or of other ~agnetic flux-
conducting material.
In operation, an input signal of fixed
signal strength is provided over the input lines to
the coil 18. An output signal is induced into the
coil 20 and sensed over the output lines 24, with
the output sisnal strength being dependent upon the
size of t~e magnetic gap or the proximity of the
tube 12 to the faces of the core piece 16. Such
proximity, or size of the magnetic gap, is directly
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6.
':
`; dependent upon the t.ire pressure communicated via
the inlet 15 to t~e Bourdon tube 12. Accordingly,
the signal strengt~ of the output of the coil 20 may
be directl.y correlated with tire pressure.
The ~enefît of the ~mbodiment of Fig. 1 is
that the core piece 16 may ~e ~ounted inside, out-
side, or alongside of the expandible and contract-
ible tube 12. Additionally the input coil 18 may
be excited with a large current so that small vari-
ances in concentricity of the tu~e 12 or in the
input ~ignal strength will be relatively unimportant
when translated to the output signal of the coil 20.
Further, means ot~er than the Bourdon tu~e 12 might
~e utilized in the general theme of the invention to
effectuate a change in the magnetic gap. For exam-
ple, the Bourdo~ tu~e 12 could be replaced with a
bellows in communication with internal tire pressure,
; such pressure'affectua~ing ~h,e expansion or con~
traction of the bellows which is maintained in juxta- -
position with a core piece for regulating a magnetic
gap.
' With re~erence now to Fig. 2, it can be
seen that a second embodiment of a tire pressure
: communica~ion device is designated generally by the
numeral 30. Here a wheel frame 32 is pro~ided with
a characteristic passageway 34 adapted for co~muni-
cating tîre pressure'~rom the. inner cavity of a tire
to a bellows 36. The ~ellows, of rubber, flexible
plastic, or ot~er suitably expandi~le material, is
connected to the movable core 38 of an LVDT. The
core 38 is selectïvely positiona~le in the center of
coil 40. These cores are connected to a housing 41
which is fi~edly attached to a stationary and non-
rotatable mem~er of the aircraft such as an axle,
torque tube,' brake housing, or the like. A sleeve
or guide 43 is maintained by the housing 41 and is
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adapted for receiving th.e core 38. In one embodi-
ment of the inventi.on t the core 38 may rotate with
the wheel frame 32 in the gulde or slee~e 43. ~he
axial position of the core in the center of the
coil 40 is controlled by the bellows 36 via tire
pr~ssure communicat;ng through the passageway 34~
With continued reference to Fig~ 2, it can
be sPen that the sleeve 43 may be characterized by
an internal hexagonal ~ore 44. ln this embodiment,
the core 38 is characterized by a spherical hex-
t agonal head 46 adapted for making mating engagement
with the bore 44. A driven mem~er 48 or other
appropriate shaft is connected to the guide 43 at
one end t~ereof as shbwn. The other end of the
driven mem~er 48 may be connected to the rotor of a
wheel speed transducer such as those standardly used
in antiskid sy~tems in the aircraft industry. In
this embodiment, the core 38 rotates with the wheel
32 and, by mea`ns of the mating engagement at 44,46,
drives a shaft or other appropriate means 48 for
providing a mechanical input signal to a wheel speed
transducer.
As briefly mentioned a~o~e, the tire pres-
sure communicates to the hellows 36 via the passage-
way 34 to longitudinally position the core 38 in the
center of the coil 40 of the LVDT. The positionin~
of the core 38 result~ in a particular output signal
fxom the LVDT in standard fashion, which signal
can be applied to appropriate meter means in the
3Q cockpit. The core 38 may either be freely rotatable
within a guid~ or sleeve 43 or, alternatively, may
be used for driving a wheel speed transducer through
mating interconnection with the guide 43.
With reference now to Fig. 3j it will be
noted that yet another embodiment of a tire pressure
communication device is designa~ed generally by the
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8.
numeral 50. This apparatus includes a stationary
housing 52 adapted to ~e secure~ t~ a stationary
part of the aircrat such as an axle, brake hous-
ing, or the like. A ~ushing 54 is provided with
appropriate insulators to maintain races 56,57
within the hous;ng 52. A driving arm 58, connected
to and rotatable with a wheel (not shown), receiYes
an inner portion of each of the races 56,57, while
the outer portions thereof are received by the
housing 52. Leads 60-66 are interconnected with
the races 56,57 with the fixst two such leads being
connected to the inner races and rotatable there-
with as driven by the arm 58. These leads may be
connected to a standard pressure transducer or
appropriate pressure sensing means maintained
within the tire itself. Communication from the
leads 60,62 is made with the leads 64,66 via ball
bearings 68 maintained between the inner and outer
portions of the races 56,57.
The ball bearings 68 are maintained
between the race surfaces as f~ur-point contact
bearings which have been preloaded therebetween.
In other words, the inner and outer races are
each characterized by "V" grooves such that the
ball bearings contact on only two points on each of
the "V" surfaces on both the inner and outer race
portion. Preloading is accomplished in the stand-
ard fashion of thermally assembling the races
to achieve forced contacting engagement in a four
point pre-loaded manner. Further, the races 56,57
may be packed with a conductive grease serving to
both reduce friction and aid in conductivity.
In operation, the leads 60,62 rotate
with the inner race portions of the races 56,57
~5 while the wheel is rotating. The leads 60,62
communicate with the pressure transducer to trans-
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mit an electrical si.gnal ~ack. to the inner race
porti.ons which are, in turn t passed across the ball
bearings 68 to the outer race portion and thence, by
leads 64,66, to appropriate meters in the cockpit.
Of course, a large plurality of ball bear-
ings 68 are maintained ~y each of t~e races 56,57
and, with a large plurality of such ball bearings
being present, interc~mmunicating with each other on
each race by means of conductive grease and by being
thermally preloaded, chatter and ~unce are substan-
tially el;minated such that the output signal of
the pressure monitor is a pure signal as passed to
the ~eter.
Thus it can ~e seen that the o~jects of
the invention have been satisfied by the structure
presented hereina~ove. While in accordance with the
patent statutes, only the best modes and preferred
embodiments of the lnvention have been presented
and descri~ed in detail, it is to be understood that
the invention is not limited thereto or thereby.
Consequently, for an appreciation of the true scope
`. and breadth of the invention, reference. should be
had to the appended claims.
