4,067,376
`[11]
`119]
`United States Patent
`
`Barabino
`[45]
`Jan. 10, 1978
`
`[54] TIRE PRESSURE WARNING SYSTEM
`
`Inventor:
`[75]
`[73] Assignee:
`
`3251;” A' Barabino, North Reading,
`’
`Safety Research & Engineering
`Corporation, North Reading, Mass.
`[21] App]. No.: 649,846
`.
`.
`.
`[22] Fded'
`
`Jun..16, 1976
`
`[62]
`
`[56]
`.
`
`,
`Related US. Application Data
`Division of Ser. No. 421,538, Dec. 4, 1973, Pat. No.
`3,934,223“
`Int. (21.2 .‘...................... B60C 23/04; B600 23/12
`[51]
`[52] U.S. Cl.
`................................. 152/418; 116/34 R;
`116/114 PV
`[58] Field of Search .................. 152/415, 418; 340/58;
`, 137/223, 226; 116/34 R, 114 PV, DIG. 16
`.
`References Cited
`U-S- PATENT DOCUMENTS
`6/1960 Bedford .........
`. 152/418
`
`.
`.. 152/418
`5/1970
`Bepristis et
`
`Barabino ........
`116/34 R
`6/1973
`116/34 R
`2/1975
`Bluem ........
`
`.. 152/418 X
`9/1975 Marocco
`Lorenz et al.
`..... 116/34 R
`8/1976
`
`2,939,504
`3,511,294
`3,738,308
`3,866,563
`3,905,412
`3,977,355
`
`Primary Examiner—Drayton E. Hoffman
`Assistant Examiner—Fred A, Silverberg
`Attorney, Agent, or Firm—Morse, Altman, Oates &
`Belle
`
`[57]
`ABSTRACT
`Excessively high or low tire pressure is detected auto-
`matically with a warning signal generated for the opera-
`tor. A device is attached to each wheel and includes a
`spring-loaded piston mounted for reciprocation in a
`cylinder formed in the device. The cylinder is provided
`with a porting arrangement which opens only at certain
`pressure limits. When the ports are opened a sonic or
`ultrasonic signal is generated and detected by sensors
`located in proximity to each wheel. The signals de-
`tested by the sensors are processed and utilized to actu-
`ate a warning signal that provides a visual and/or audio
`output for the operator. Means are provided for dis-
`criminating between background noise and the gener-
`ated signal as well as to discriminate as to the location of
`the affected tire. In a modification of the invention, a
`reserve chamber is integrated into the body of the
`wheel and is adapted to replenish automatically air lost
`from the tire.
`
`1 Claim, 7 Drawing figured
`
`
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`
`Pet’r Exhibit 1008
`Continental v. Wasica
`IPR2014-00295
`
`Page 000001
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`

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`US. Patent
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`Jan.10,1978
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`Sheet] of4
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`4,067,376
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`US. Patent
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`US. Patent
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`Jan. 10, 1978
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`US. Patent
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`Jan. 10, 1978
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`Sheet 4 of 4
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`4,067,376
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`

`1
`
`TIRE PRESSURE WARNING SYSTEM
`
`CROSS-REFERENCE TO RELATED
`APPLICATION.
`
`This application is a division of U.S. application Ser.
`No. 421,538 filed Dec. 4, 1973 now U.S. Pat. No.
`3,934,223.
`
`BACKGROUND OF THE INVENTION
`1. Field ofthe Invention
`This invention relates generally to tire pressure warn~
`ing systems and more particularly is directed towards a
`new and improved system for providing warning sig-
`nals to the operator in the event of either high or low air
`pressure in a tire. This invention also relates to a system
`for automatic replenishment of air lost from a tire while
`the vehicle is in motion as a means for minimizing the
`effects of a blowout.
`2. Description of the Prior Art
`In U.S. Pat. Nos. 3,489,998, 3,659,264 and 3,738,308
`there are disclosed tire pressure alarm systems for
`motor vehicles wherein a serious change in air pressure
`is detected by the operator. This is done in the first
`patent by the means of a device fitted to the wheel
`adapted to generate a sonic signal in the event of an
`abnormally low pressure. A microphone is located in
`proximity to the wheel and, in the event of a signal from
`the device, the operator is alerted by an alarm on the
`dashboard, for example. In the second patent, both high
`and low pressures are detected by means of a reed that
`is vibrated by an excessive change in pressure. Again,
`the sensing device is located in proximity to the wheels
`and is actiVated by sympathetic vibration with the reed
`on the tire. Finally, the last patent discloses a wheel-
`mounted device incorporating an air-operated whistle
`responsiveto both high and low pressure with sensors
`located in proximity to the wheels and with sensors
`operatively connected to an operator signaling system.
`The present invention has for one of its objects the
`improvement in systems of the foregoing type.
`A more specific object is to provide a tire pressure
`warning system that is quickly and easily installed. An-
`other object of this invention is to provided atire pres-
`sure warning system capable of discriminating between
`tires and also a system that is substantially insensitive to
`spurious noises. A further object of this invention is to
`provide a tire pressure warning system with a memory
`capability in the event of a substantial change of tire
`pressure occurring while the operator is not in the vehi-
`cle. Still another object of this invention is to provide a
`tire pressure warning system incorporatedwith an auto-
`matic pressure replenishing system functional while the
`vehicle is in motion or at rest.
`
`SUMMARY OF THE INVENTION
`This invention features a tire pressure warning system
`comprising a pressure responsive device mountable on
`the stem or to the wheel of a pneumatic tire and adapted
`.to emit a sonic or'ultrasonic signal whenever the pres-
`sure within the tire exceeds a maximum or minimum
`range. Each device involves a spring-loaded piston
`mounted for reciprocation in a cylinder formed with
`p ports at axially spaced locations. The movement of the
`piston in response to the change in tire pressure opens
`and closes the ports to deliver air to the signal produc-
`ing portion of the device, typically a discharge aperture
`configured to produce a sharply tuned whistle. A sonic
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`or ultrasonic detecting device is located in proximity to
`each wheel, typically mounted in fixed position within
`the wheel well of the chassis. Each pickup is connected
`through amplifying circuitry to an alarm unit in the
`vehicle and typically on the dashboard whereby the
`operator will be alerted whenever the device is actuated
`by reason of high or low air pressure in any tire.
`In a modification of the invention, an automatic air
`pressure replenishing system is provided. In the modifi-
`cation, each wheel is formed with an integral annular
`chamber adapted to store a quantity, of compressed air
`under high pressure. A pressure relief valve connects
`between the chamber and the pneumatic tire and is
`adapted to release air from the chamber into the tire
`whenever pressure within the tire drops below a prede-
`termined limit. The modification includes a signal gen-
`erating device which warns the driver of the change in
`tire pressure.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a sectional view in side elevation of a tire
`valve made according to the invention,
`FIG. 2 is a schematic diagram of a tire pressure warn-
`ing system made according to the invention,
`, FIG. 3 is a detailed sectional view showing a modifi-
`cation of the invention,
`FIG. 4 is a sectional view in side elevation of the
`modification,
`FIG. 5 is a detailed sectional view of a portion of the
`valving in the modification,
`FIG. 6 is a sectional side view’ of another modifica-
`tion of the invention, and,
`*
`FIG. 7 is a sectional side View of yet another modifi-
`cation of the invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Referring now to the drawings and to FIG. 1 in par-
`ticular, the reference character 10 generally indicates a
`pressure responsive signalling device adapted to be
`screwed onto a standard valve stem 12 normally fitted
`to a wheel 14 on which a pneumatic tire 16 is mounted.
`The device 10 is comprised of a housing 18, typically of
`cylindrical construction, closed at its upper end by a cap
`20 and at its lower and formed with a tapped socket 22
`adapted to threadably engage the stem 12. The cap 20 is
`held to the top of the body 18 by means of an annulus 24
`engaging cooperating shoulders 26 and 28 formed re-
`spectively on the cap 20 and on the upper end of the
`body 18.
`The cap is formed with a central opening 30 through
`which extends a post 32 carried by a piston 34 mounted
`for reciprocation within a cylindrical chamber 36 in the
`body 18. The post 32 is formed with a central passage 38
`terminating at its upper portion with diverging ports 40
`which open to the atmosphere and at its lower portion
`terminating in a radial passage 42 communicating with
`the interior of the cylinder above the piston 34. The
`post passes through the opening 30 which is slidably
`sealed by an O-ring 44 mounted in an annular recess in
`the cap 20.
`The piston 34 is normally urged downwardly by
`means of a compressed coil spring 46 trapped between
`the cap 20 and the top of the piston 34. The spring is
`selected to have sufficient force to maintain the piston
`34 in a balanced position between a pair of axially
`spaced ports 48 and 50 normally located, respectively,
`above and below the piston 34. The piston 34, as shown
`
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`is of a generally cylindrical configuration
`in FIG. 1,
`formed with an annular groove 52 in which is seated an
`O-ring 54 slidably and sealingly engaging the walls of
`the cylinder.
`Accross the lower portion of the cylinder is formed a
`wall 56 having internal axial passages 58. The wall 56
`forms into a downwardly extending neck 60 projecting
`into the tapped socket 22 and adapted to bear against
`the movable valve element in the stem 12 in order to
`open that valve when the device 10 is screwed into
`position. The upper portion of the socket 22 is provided
`with an O-ring 62 for sealing the valve stem to the
`device 10. With the device mounted in position, the
`same air pressure in the tire 16 will develop in the lower
`portion cylinder below the piston 34, forcing the piston
`into the balanced position. In the event that the pressure
`in the tire drops by reason of a leak or otherwise, the
`spring 46 will force the piston downwardly against the
`lowered air pressure, thereby moving the piston past the
`lower port 50, allowing a small amount of air to leak
`around the piston to the upper side of the cylinder from
`which it will flow through the port 42, up through the
`passage 38 and out of the ports 40.
`The passageway 38 and ports 40 are configured to
`produce either a sonic or ultrasonic signal which will be
`detected by a sensor 64‘ mounted in close proximity to
`the wheel. Typieally, the sensor is mounted in fixed
`position within a wheel well so that whenever a signal
`is generated by the device it will be picked up by the
`sensor. Likewise, if the pressure within the tire builds up
`excessively to exceed a predetermined limit, the piston
`34 will be forced upwardly against the force of the ‘
`spring 46 until it moves past the upper ports 48. In its
`upper position, a small amount of air again will leak
`around the piston and flow out through the passage 42,
`the passageway 38 and the ports 40, again generating a
`sonic or ultrasonic signal to be picked upby the sensor
`64.
`I
`'
`The O-rings 44 and 54 preferably are fabricated from
`a material having low friction characteristics. While
`material such as Teflon or the like is acceptable,‘ other
`low friction, elastomeric O-rings are available which
`provide a good sliding seal having very low friction
`characteristics. For example, anti-friction treated 0-
`rings having excellent characteristics are available from
`Parker Seal Company of Culver City, California. Other
`parts of the device Such as the housing, piston and stem
`may be fabricated from other materials including stain-
`less steel, or various plastics. For example, glass re-
`inforced nylon resins such as produced by Du Pont
`under the trademark “Zytel” is suitable since it is a high
`strength resin adaptedfor injection molding techniques.
`“Minlon” also available from Du Pont may be em-
`ployed to advantagein the device.
`To provide a visual verification of a tire pressure
`problem, the stem 32 may be color-coded at its outer
`extremity. Preferably, two color bands may be applied
`near the end of the stem so that any movement of the
`stem as a result of a change of tire pressure will be
`readily observable by direct inspection. For example, if
`the tire pressure is too high, thelower band will appear
`whereas if the pressure is too low, the upper band will
`disappear.
`While the device 1015 designed for mounting on an
`existing standard valve stem 12, obviously it may be
`easily modified to replace the entire stem and be
`mounted directly to the wheel as suggested in the em-
`bodiment of FIG. 6. In FIG. 6 a generally cylindrical
`
`’4
`housing 70 is provided with an enlarged base 72 which
`may be of rubber or the like formed with an annular
`outer shoulder 74. The base portion of the housing
`provides a snap-in mounting similar to a conventional
`tire stem and adapted to engage a wheel rim 76 in the
`manner shown. The housing 70 is formed with a central
`cylindrical chamber 78 in which a piston 80 is mounted
`for reciprocation The piston carries a tubular stem 82
`and1s formed with a central passage 84 terminating in
`its lower end with radial inlet passages 86 and at its
`upper end in diverging outlet ports 88 A spring 90 is
`employed to provide a counter-balancing force to the
`pressure of air in the tire. The inner walls of the cham-
`ber 78 are ported at 92 and 94 and function in a manner
`similar to that of the FIG. 1 embodiment whereby ex-
`cess motion of the piston through either an increase or
`decrease in air pressure will result in the escape of a
`small amount of air from the tire to actuate a sonic or
`ultrasonic signal at the ports 88. The chamber 78 com-
`municates with the interiorof the tire through a passage
`96 extending through the base at 72.
`In order to permit the tire to be filled with air through
`the device, a standard filler valve 98 is mounted to the
`outer end of the stem 82 and air pressure will open the
`valve 98. Pressure applied to the end of the stem 82 will
`force the piston to its lowermost position alloWing air to
`pass dewn through the passage 84 out through the ports
`, 86 and around the piston through grooves 100 formed in
`the lower end of the cylinder in the chamber 78. The
`30
`grooves 100 also communicate with radial slots 102 at
`the base of the chamber communicating with the pas-
`sage 96. It will be understood that when the stem 821s
`in its lowered position, the ports 88 will be closed by the
`upper portion of the housing 70. Again, the upper end
`of the stem may be color coded to provide visual verifi-
`cation of tire pressure.
`.
`Referring now to FIG. 7 of the drawings there is
`illustrated a further modification of the invention, and
`in this embodiment a temperature compensating ‘ar—
`rangement
`is provided to minimize the effects of
`changes1n temperature due either to ambient weather
`conditions or‘to heat generated by rotation of the tire.
`As shown in FIG. 7 a housing 104 may be formed with
`atapped socket for threading the same to an existing tire
`stem 106 or may be formed with an enlarged base as in
`the FIG. 6 embodiment to replace the standard stem,
`The housing 10415 formed with an internal cylindrical
`cavity 108 closed at its upper end bya cap 110 through
`which extends a stem 112 carried by a piston 1141n a
`manner similar to the previous embodiments. However,
`in the present instance a sleeve 116'is mounted coaxially
`Within the cavity 108 and formed withan internal cylin- .
`drical chamber having spaced ports 118 and‘ 120 at the
`upper and lower portions of the sleeve providing escape
`passages for air from the tire1n the event of high or low
`tire pressure as in the principal embodiment. As before,
`a spring 1221s provided to counter-balance normal tire
`pressure. The stem 112 is, of course, formed with an
`> internal passage 124 for generating sonic or ultrasonic
`signals whenever air. is released. The sleeVe 116 is fitted
`within the chamber 108 as by an O-ring 124, and at its
`lower portion mates with an annular or cup-shaped
`expansion member 126 which, depending upon the tem-
`perature, will cause the sleeve 116 to be axially dis—-
`placed upward or downward effectively Changing the
`position of the ports 118 and 120 to compensate for
`temperature changes. The member 126 can be selected
`from a variety of materials having appropriate coeffici-
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`5
`ent of expansion characteristics selected to expand and
`contract at a rate different from that of a device as a
`whole so that a relative movement of the sleeve will be
`produced. In this fashion, compensation is made for
`changes in tire pressure due to changes in temperature.
`The temperaturecompensating member can be at the
`base of the chamber as shown, or may be at the top of
`the chamber and positioned against the cap 110 with the
`lower end of the sleeve being free to move up or down.
`Alternatively, a temperature compensating member
`may be introduced at either end of the spring 122 in
`order to provide the correcting compensation. Other
`variations will appear to those skilled in the art.
`In order to protect the discharge ports on the stem
`from becoming plugged by an accumulation of dust,
`dirt, ice, snow, etc., protective covers may be provided
`as suggested in FIG. 7, for example. In the FIG. 7 em-
`bodiment, semi-cylindrical covers 130 and 132 are pro-
`vided on the end of the stem 112, the covers being
`hinged by pins 134 and adapted to cover discharge
`orifices 136. Light frictional pressure provided between
`the hinge pins and the covers will be sufficient to keep
`the covers in a closed position against the stem, closing
`the ports 136. However, should air be released by actua-
`tion of the device as by high or low tire pressure, the air
`passing out through the orifices 136 will'blow the cov-
`ers into the open position shown on the right-hand side
`of FIG. 7 allowing the signal generator to produce the
`sonic ultrasonic signal. The covers obviously may be
`provided on the other embodiments.
`The pickup sensors 64, which are provided to detect
`actuation of any or all the valve devices, are located in
`proximity to each wheel. Preferably a sensor is mounted
`in each wheel well of the vehicle and one also may be
`provided in the trunk of the vehicle to monitor the air
`pressure of the spare tire. All of the sensors are con-
`nected to a common signal processor 140 which,
`in
`turn, provides an output to a display 143 which conve-
`niently is panel mounted on the dashboard of the vehi-
`cle. The sensor 64 may be any one of a variety of de-
`vices. However,
`in practice, it has been found that a
`miniature piezoceramic resonator provides particularly
`satisfactory performance. Other suitable devices may
`include electret based transducers for detecting sonic or
`ultrasonic signals generated by actuation of the devices.
`The processing circuitry 140 provides amplification
`of signals received from the sensors, compares that
`signal‘with a reference signal and then, once detected,
`‘actuates a memory circuit which, in turn, will actuate
`the display. For the sake of simplicity in describing the
`operation of the circuit, it will be assumed that a single
`sensor is employed to monitor the various wheels. The
`output of the sensor 64 is fed through an amplifier 143
`prior to being fed into the processing circuitry 140. The
`processor 140 is powered in the preferred embodiment
`by the automobile’s electrical system through a lead
`144. The amplified signal is fed into the processor and
`through an operational amplifier detector U-l. This is a
`broad band detector and the bias network for the detec-
`tOr U-1 includes diodes CR1 and CR2, resitors R1
`through R5, and capacitor C1. Resistors R15 and R16
`form an attenuator where the signals come out of the
`amplifier. The signal from the operational amplifier
`detector U-l is then processed through an RC network
`comprised of a resistor R6 and capacitor C2 providing
`integrating functions to build up smoothly each half
`cycle of the amplified signal and eliminate noise spikes.
`This integrated signal
`is compared with a reference
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`voltage across a variable potentiometer 145 which sets
`the threshold for a comparator U2. It will be under-
`stood that the post detection integrator formed by the
`RC circuit R6 and C2 must exceed the reference from
`the potentiometer 145 before the comparator U2 will
`switch. Typically, the comparator U2 will switch from
`high to low in non-linear fashion and upon which event
`it will couple with a flip-flop circuit including transis-
`tors Q1 and Q2. Once the flip-flop circuit is set, a warn—
`ing light DSZ will be illuminated and a buzzer Bl will
`be actuated through the driver circuit which includes a
`transistor Q3.
`It will be noted that the display panel is connected to
`a switch 147 controlled by the car’s ignition switch 149.
`When the ignition switch is off, the switch 147 will be
`opened and the display functions will not operate. How-
`ever, insofar as the flip-flop provides memory functions
`the warning light, as well as the buzzer, will be actuated
`when the ignition key is turned on and the switch 147 is
`closed if a tire pressure event has occurred during the
`time when the switch 147 was open. This feature thus
`will give a warning to the driver if a low pressure or
`high pressure condition occurs while the car is idle.
`The display includes an operating light DSl, which
`preferably is a light-emitting diode similar to the warn—
`ing light D82. The warning light D82 preferably is red
`while the operating light D81 is green. The function of
`the operating light is to inform the operator that the
`system is functioning properly. A reset switch $1 is
`provided to reset the circuit after actuation. By utilizing
`both a buzzer and a warning light, the operator will
`have both an audio as well as a visual warning when an
`unusual tire pressure condition occurs.
`Additional display elements may be added for more
`complex installations. For example, separate warning
`lights may be provided for response to tire-pressure
`warning device actuation on different sides of the vehi-
`cle. In such a system, the valves on the tire on the left-
`hand side, for example, may be tuned to generate a
`signal of a different frequency. Such an arrangement not
`only provides more useful information for the operator,
`but also minimizes the possibility of a false signal being
`generated between passing vehicles. Thus, if a car mov-
`ing in one direction should experience a tire pressure
`condition and its system generates a signal, it will not
`actuate the sensing system in a passing vehicle moving
`in the opposite direction.
`The different frequencies from the valve may be
`obtained by mechanical configuration of the sonic gen-
`erator. As an alternative measure, the sensors 64 on one
`side of the vehicle may be tuned to detect only the
`resonant frequency generated by the tire valve while
`the sensors on the other side of the vehicle are tuned‘to
`pick up only fundamental frequencies from the valve. In
`such a case, all of the valves on both sides would be
`matching and generating at least resonant and funda-
`mental frequencies when actuated. This same type of
`discrimination may be employed on a truck to distin-
`guish between inboard and outboard tires for trucks
`equipped with tires mounted in pairs.
`In the illustrated embodiment of the processor cir-
`cuitry and display, the display is powered only when
`the vehicle ignition key is on. The processing circuitry,
`on the other hand, remains active on a standby basis at
`all times to acquire and record the sonic warning signal
`should the pressure condition be reached when the
`vehicle is at rest and the ignition is in an off position.
`
`— P
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`Referring now to FIGS. 3, 4 and 5 of the drawings,
`there is illustrated a modification of the invention and,
`in this embodiment, an automatic air replenishment
`system is provided in combination with a pressure signal
`generating device whereby air lost from a tire, whether
`by a slow leak or a blowout, will be automatically re-
`placed even when the car is in motion. Simultaneously,
`a signal will be generated to warn the driver of the
`condition. The system includes a wheel 150 formed
`with the usual rim 152 in which a pneumatic tire 154 is 10
`mounted. The wheel 150 normally fabricated from steel
`in the usual manner, however, the wheel also includes a
`chamber 156 which preferably extends concentrically
`about the inner portion of the wheel and is of annular
`shape as best shown in FIG. 4. The chamber 156 is 15
`formed by inner and outer walls 158 and 160 extending
`in spaced concentric relation and sealed to the wheel to
`form an airtight pressure chamber adapted to store
`compressed air of perhaps 400 psi for extended periods
`of time. The compressed air is introduced to the cham- 20
`her 156 by a standard filling valve 162 mounted through
`the side wall of the wheel.
`Air delivery from the chamber 156 to the tire 154 is
`controlled by means of a release valve 164 which, in
`turn, is controlled by means of a pressure-sensing and 25
`signal generating valve 166 mounted to the wheel. The
`valve 166 includes a piston 168 mounted for reciproca-
`tion within a cylinder 170 and normally urged to the
`right as viewed in FIG. 3 by means of a compressed
`spring 171. The piston carries a stem 172 projecting out 30
`through the wheel within a concentric fixed sleeve 174.
`The stem 172 includes a central passage 176 and at its
`outer end carries a standard filling valve 178 whereby
`the tire may be filled initially to normal pressure. Air is
`fed through the valve 178, through the passage 176 and 35
`into the cylinder 170 at the right hand side of the piston
`168. The air then passes through an opening 180 into the
`tire. The piston moves back and forth within the cylin-
`der 170 according to changes in tire pressure.
`Extending from the right side of the piston 168 is a 40
`rod 182 projecting into the release valve 164 and
`mounted for reciprocating movement within a cylindri-
`cal chamber 184. The chamber 184 communicates with
`the pressure chamber 156 through a pair of passages 186
`and 188, one being larger than the other. The smaller 45
`passage 188 serves to replenish air to the tire during a
`slow leak condition whereas in the event of a blowout,
`both passages 186 and 188 are employed to feed air to
`the tire. The rod 182 carries three axially spaced O—rings
`190, 192 and 194. Under normal pressure conditions the 50
`piston 168 and rod 182 will be in a position as shown in
`FIG. 3. However, in the event of a slow leak, tire pres-
`sure will drop and the piston and rod will move to the
`right as viewed in FIG. 3, opening the passage 188 and
`allowing air to flow from the chamber 156 through the 55
`passage 188, thence through the chamber 184 and out
`through a port 196 and into the tire 154. At the same
`time, air will pass through a passage 198 formed in the
`rod 182 and out through the left hand side of the piston
`168, flowing between the stem 172 and the sleeve 174 60
`out through an orifice 200 which will generate a sonic
`or ultrasonic signal to be picked up by the sensors to
`warn the driver of the low pressure condition. In the
`event of a sudden drop in pressure, as occasioned by a
`blowout, the rod 182 will move to a maximum right 65
`hand position, opening both ports 186 and 188 threrby
`allowing a much greater flow of air from the chamber
`156 to the tire to compensate for the loss of pressure in
`
`8
`the tire. Again, a signal will be produced by air flowing
`through the passage 198 to actuate a sonic or ultrasonic
`signal generator. The system is designed to supply air
`pressure to the tire in proportion to the rate of loss and
`sustain a predetermined pressure such as 23 psi.
`Referring now to the FIG. 5 of the drawings, there is
`illustrated a further modification of the invention and in
`this embodiment a simple piston valve 202 is mounted in
`a wall 160’ corresponding to the wall 160 of the FIGS.
`3 and 4 embodiment wherein an auxiliary supply of
`compressed air is maintained in a pressure chamber
`formed within a wheel. However, in place of the valve
`device 164 utilized in the FIG. 3 arrangement, the sim-
`ple valve 202 is employed in the FIG. 5 embodiment. In
`FIG. 5, the wall 160’ is formed with a stepped opening
`204 in which the piston valve 202 is mounted. The open-
`ing 204 on the tire pressure side, which is the right hand
`side of FIG. 5,
`is substantially larger in diameter than
`the opening on the auxialiary tank or the left hand side
`of the wall as shown in FIG. 5. Similarly, the piston 202
`is formed with a relatively large diameter head 206 on
`the right hand side and a relatively narrow diameter
`stem 208 on the high pressure auxiliary tank side. Both
`the head 206 and the stem 208 are provided with 0-
`rings 210 and 212, respectively, to provide a seal be-
`tween the valve and the opening. The walls of the open—
`ing 204 are provided with ports 214 and 216 through
`which compressed air may flow from left to right when
`the piston 202 moves to the right whenever the forces
`on opposite sides of the piston become unbalanced.
`It will be understood that the large diameter of the
`head and the small diameter of the stem results in the
`forces on the piston being effectively balanced even
`though pressure on the left hand side of the wall 160’ is
`substantially higher than the pressure on the tire side.
`However, if there is a drop in pressure on the tire side,
`the forces on the floating piston will become unbal-
`anced causing the piston to move to the right as viewed
`in FIG. 5. This motion of the piston will open the ports
`214 and 215 allowing high pressure compressed air to
`flow into the tire until the forces are again equalized. In
`the event of a blowout, all of the air in the auxiliary tank
`will be quickly transferred into the tire. When using the
`valve device in FIG. 5, a tire pressure warning device
`of the sort shown in FIG. 1, for example, may be em-
`ployed in order to keep the driver advised of the condi-
`tion.
`’
`
`Obviously, various means may be provided to pre-
`vent the valve from coming completely out of the open.
`ing 204. For example, a screen or annular shoulder can
`be provided on the tire side of the wall 160’ to limit the
`movement of the valve.
`Having thus described the invention, what I claim
`and desire to obtain by Letters Patent of the United
`States is:
`
`1. An automatic air replenishment and low pressure
`warning system for a pneumatic tire, comprising
`a. a wheel adapted to support a tire mounted thereto,
`b. said whee] being formed with spaced tire support-
`ing front and rear walls joined at their inner portions
`and an annular wall between said front and rear walls
`defining an integral annular concentric chamber
`adapted to store a quantity of compressed air at a pres-
`sure higher than the normal pressure in said tire,
`c. normally closed pressure responsive valve means
`connecting said chamber to the interior of said tire
`and adapted to open when the pressure in said tire
`
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`4,067,376
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`9
`drops to a predetermined level whereby replenish-
`ing pressurized air is delivered into said tire,
`d. said valve means including a release valve fixed to
`said annular wall and formed with a cylindrical
`chamber therein, a spring loaded rod movably
`mounted in said chamber and adapted to open and
`close said chamber according to the pressure in
`said tire,
`. said valve means formed with a passageway and
`including an acoustical signal generating device
`
`10
`operatively connected to said rod through said
`passageway and adapted to produce an acoustical
`warning signal in the event of a low pressure condi-
`tion in said tire, and,
`f. acoustic sensing means disposed remotely from said
`tire and responsive to an acoustic signal generated
`thereby, said sensing means including warning
`means actuated by said sensing means upon sensing
`of an acoustic signal.
`‘
`fi
`i
`t
`k
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`5
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`10
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`15
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`20
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`25
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`30
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`35
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`45
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`50
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`55
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`65
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