United States Patent
`Williams
`
`[19]
`
`[54] TIRE PRESSURE MONITOR
`
`[76]
`
`Inventor:
`
`John J. Williams, 5890 Boeta CL,
`Paradise, Calif. 95969
`
`[21] App]. No.: 726,358
`[22] Filed:
`Jul. 5, 1991
`
`Int. Cl.’ .............................................. B60C 23/00
`[51]
`[52] US. Cl. ................................... 340/447; 73/1465;
`200/6122; 340/442
`[58] Field of Search ............... 340/539, 447, 442, 445;
`73/1464, 146.5; 116/34 R; ZOO/61.22, 61.25
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`2.860.321 11/1958 Strickland et al.
`.
`340/447
`4,237,728 12/1980 Belts et al.
`ZOO/61.25
`4,286,253
`8/1981 Nagy ......
`
`..
`.. 340/539
`4,311,985
`1/1982 Gee et al.
`6/1982 Frazier et al.
`.....
`4,334,215
`340/447
`
`1/1988 Morrison. Jr. et al.
`73/146 5
`4,717,905
`
`4,978,941 12/1990 Brown
`340/447
`
`5,001,457
`3/1991 Wang .
`340/447
`
`
`.............. 340/447
`5,025,244
`6/1991 Huang
`
`Primary Examiner—fin F. Ng
`Assistant ExaminereBrent A. Swarthout
`
`ABSTRACT
`[57]
`A tire pressure range monitoring apparatus or system
`for sensing high and low tire air pressures outside as-
`signed limits and communicating information regarding
`
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`usoos 10921 3A
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`Patent Number:
`
`Date of Patent:
`
`5,109,213
`
`Apr. 28, 1992
`
`tire pressure to an operator of a vehicle. The tire pres-
`sure monitor is comprised of a battery powered wheel
`attachable unit having high and low tire pressure sen-
`sors with electrical switches; a digital encoder activated
`by the pressure sensors; a pressure change restrictor for
`preventing transitory air pressure changes from activat-
`ing the pressure sensor switches; and an RF transmitter
`and antenna for transmitting digital information. A ve~
`hicle attachable unit for receiving and processing the
`digital information is attachable to the vehicle remote of
`the wheel, and is comprised of an RF receiving antenna;
`an RF receiver; a digital decoder; and a display controla
`ler. One vehicle attachable unit may function with a
`plurality of wheel attachable units on a given vehicle. A .
`visual display in communication with the vehicle at—
`tachable unit is located convenient to the vehicle oper-
`ator, and will display for the operator an anomaly
`sensed in tire pressure, and precisely identify the tire
`and pressure condition of the tire involved. False alarms
`are essentially eliminate through the use of digital infor-
`mation pertaining to a particular tire, and through a
`required match in digital source identification infonna-
`tion between wheel attachable units of a given vehicle
`with a vehicle attachable unit of the same vehicle prior
`to the vehicle attachable unit fully responding and send-
`ing information to the visual display.
`
`6 Claims, 10 Drawing Sheets
`
`lOW
`VOLTAGE
`DETECTOR
`
`TRANSMITT ER
`
`ON/OFF
`"ME" sw1rc11
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`HIGH 8: LOW
`PRESSURE
`SENSORS
`81
`MANIFOLD
`
`Pet’r Exhibit 1005
`Continental v. Wasica
`IPR2014-00295
`
`Page 000001
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`

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`US. Patent
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`Apr. 28, 1992
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`Sheet 1 of 10
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`US. Patent
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`US. Patent
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`Apr. 28, 1992
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`US. Patent
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`Apr. 28, 1992
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`Sheet 6 0:10
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`Page 000007
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`US. Patent
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`Apr. 28, 1992
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`Sheet 7 of 10
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`5,109,213
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`US. Patent
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`Apr. 28, 1992
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`Sheet 8 of 10
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`US. Patent
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`Apr. 28, 1992
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`US. Patent
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`Apr. 28, 1992
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`Sheet 10 of 10
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`

`

`1
`
`TIRE PRESSURE MONITOR
`
`5,109,213
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`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to safety, operatin g cost,
`planned maintenance and/or repair of vehicles using
`pneumatic tires. The present
`invention more particu-
`larly relates to systems and devices for sensing air pres-
`sure in pneumatic tires of a vehicle, and to tire pressure.
`monitors of the type which are capable of sensing incor-
`rect pressure and alerting the operator of a vehicle of
`incorrect tire pressure while the vehicle is being oper—
`ated.
`
`10
`
`15
`
`2. Description of Prior Art
`A past art search was conducted at the U.S. Patent
`and Trademark Office to examine known tire pressure
`monitors. The following U.S. Patents disclose tire pres-
`sure monitors considered pertinent to my invention:
`A patent issued to T. A. Gee et al in Jan. 1982, U.S. 20
`Pat. No. 4,311,985, discloses a tire pressure monitor and
`de-energization circuit therefore. The Gee et al patent
`discloses a device which is activated by a centrifugal
`switch when the vehicle moves and then continuously
`monitors the tire air pressure. The Gee et al device 25
`further utilizes a receiver in the passenger compartment
`which receives pulsed signals from a transmitter, and by
`counting the pulsed signal determines the tire pressure
`condition. The Gee et al device samples the tire pres-
`sure only when the pressure exceeds a preset value and 30
`notes the condition to the operator. False alarms and
`radio interference do not appear to be adequately ad-
`dressed, and consequently false signals are seen to be a
`likely problem in the Gee et al device.
`A patent issued to D. M. Brown in Dec. 1990, U.S. 35
`Pat. No. 4,978,941, discloses a low tire pressure detec-
`tor. This device is hub mounted and uses a transmitter/-
`receiver to send a low pressure alert signal to the opera-
`tor. The device senses a low pressure signal from a low
`pressure switch and transmits this signal to the operator. 40
`The operator may then stop the vehicle and by inspect-
`ing each individual wheel, determine which tire has the
`under pressure condition. An indicator is located on
`each wheel to assist the operator in determining the low
`pressure tire. Isolation from other vehicles to reduce the 45
`number of false signals is obtained only partially
`through delay logic, and consequently,
`false alarms
`with this device are seen to be a likely relatively fre-
`quent problem.
`A patent issued to A. N. Strickland et al in Nov. 1958, ‘50
`U.S. Pat. No. 2,860,32l, discloses a tire alarm system,
`which senses both high and low tire pressure. The
`Strickland et al system uses pressure sensors and radio
`transmitters and receivers to notify the operator of a
`high or low pressure condition. The method of signal- 55
`ing is by transmitting a given frequency for each tire.
`Interference between vehicles equipped with this de-
`vice does not appear to be adequately addressed, and
`consequently, false alarms are also seen to be a likely
`problem with this system.
`A patent issued to C. F. Morrison Jr. et al in Jan.
`1988, U.S. Pat. No. 4,717,905 discloses a warning sys-
`tem for tire air pressure including means for remotely
`energizing a sensing device. Several means are dis-
`cussed including using RF transmission, through a re- 65
`ceiving antenna and capacitors which will store the
`received power and supply this power to the pressure
`sensors and transmitter which transmits to the receiver
`
`60
`
`2
`the status of the tire. The system appears to use a pres-
`sure transducer to transmit the actual tire pressure when
`activated The data is transmitted at a different fre-
`quency for each tire or set of tires. Also described is the
`use of tuned antennas which are affected by tire pres-
`sure which results in changed antenna impedance
`which in turn indicates a tire pressure. Calibration of the
`antennas would give information on pressure changes.
`The devices described in this patent use radio frequency
`devices and antenna responses primarily to detect tire
`anomalies.
`A patent issued to E. J. Nagy in Aug. 1981, U.S. Pat.
`No. 4,286,253, discloses a tire pressure sensing and
`alarm system. The Nagy device uses a radio transmitter
`and radio receiver activated by a low pressure switch
`which causes a transmitter to transmit to a receiver
`which then presents an audio or visual display to the
`operator. The operator may then stop the vehicle and
`inspect each wheel to determine the particular wheel on
`which the low pressure tire is located. Nagy does not
`appear to address false signals or radio interference.
`The tire pressure monitors of the prior art are similar,
`and to the present invention for that matter, typically
`including pressure sensors or pressure transducers,
`radio or infrared transmitters and receivers, and dis-
`plays or alarms to alert the vehicle operator of a prob-
`lem in tire pressure. Each of the prior art tire pressure
`monitors seem to have one or more undesirable attri-
`butes which may explain the apparent general absence
`of the use of such devices, and indicate there exists a
`need for an improved tire pressure monitor or monitor-
`ing system. Some of the problems found in the prior art
`devices include the monitoring of low tire pressure
`only;
`the lack of adequate structuring to safe guard
`against internally generated false signals and false sig-
`nals caused by other vehicles having similar tire pres-
`sure monitors; the problem of requiring visual inspec-
`tion of each wheel to determine which tire has an incor-
`rect air pressure; and excessive use of battery power.
`SUMMARY OF THE INVENTION
`
`The present invention is an improved tire air pressure
`monitor or monitoring system that will sense tire air
`pressures above and below an acceptable value and
`inform the vehicle operator of the particular tire or tires
`involved including the high or low pressure condition
`of the involved tire(s) without the vehicle operator
`having to inspect each wheel. Additionally, my tire
`pressure monitor is structured to be easily maintained; is
`modular in construction; and operates in a manner
`which minimizes battery power use. My invention is
`additionally structured to notify the operator if a low
`battery condition exists, and may be tested by the user
`for operational status. My invention further eliminates
`the false signal problem resulting from radio frequency
`interference and/or from other tire monitoring sources
`as well as transient air pressure changes resulting from
`operating conditions.
`'
`The preferred structure of the present invention does
`not require removal of the tire from the rim or wheel for
`installation or maintenance, and the pressure settings or
`values at which the pressure sensors initiate information
`transmitting may be adjusted by the user to a particular
`desired tire pressure operating range.
`Additionally, the primary electronics and electrical
`circuits which may be advantageously utilized in the
`present invention are known and readily available. This
`
`Page 000012
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`5,109,213
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`3
`being particularly evident in the electric-powered ga—
`rage door and wireless security monitor
`industries
`where digital electrical circuitry to essentially eliminate
`false signals has been developed and put into wide use
`with excellent results.
`My invention includes a battery powered wheel at-
`tachable unit. One wheel attachable unit is utilized for
`each tire to be monitored. The wheel attachable unit is
`comprised of a protective housing containing high and
`low tire pressure sensors each with electrical switches
`or contacts; an air flow or pressure change restricting
`arrangement
`for preventing transitory air pressure
`changes within a tire from activating the pressure sen-
`sor electrical contacts; a digital encoder activated or
`initiated by electric current passed through the contacts
`of the pressure sensors; and an RF (radio frequency)
`transmitter and antenna for transmitting digitally en-
`coded binary information in the 360 to 470 KHZ band.
`The digitally encoded binary information preferably
`contains three distinct primary pieces of information
`which are:
`transmission source identification; wheel
`identification; and high or low air pressure status of the
`identified wheel. Additionally a forth piece of informa-
`tion is contained within and at the start of the RF trans-
`mission which is an alert signal which will be under-
`stood with further reading.
`The present invention additionally utilizes a vehicle
`attachable unit for receiving and processing the digi-
`tally encoded information generated and transmitted by
`the wheel attachable unit(s). The vehicle attachable unit
`is powered by the vehicle electrical system, although
`any suitable electrical powering source might be used.
`The vehicle attachable unit is attachable to the vehicle
`remote of the wheels, and is comprised of an RF receiv-
`ing antenna; an RF receiver; a digital decoder; a power
`supply; and a display controller for driving a visual
`display placed convenient to the vehicle operator. A
`single vehicle attachable unit may function with a plu—
`rality of wheel attachable units on a given vehicle. The
`visual display is in communication with the vehicle
`attachable unit most directly by way of electrical con-
`ductors, and will display for the operator an anomaly
`sensed in tire pressure. An audible alert tone may also
`be used to draw the attention of the vehicle operator to
`the visual display when information pertaining to a tire
`is being displayed.
`With the present invention, false alarms are essen-
`tially eliminated through the use of digital encoding and
`decoding of information; bit assignments pertaining to
`each particular tire, and further through a required
`match in digital transmission source indicating informa-
`tion between wheel attachable units on a given vehicle
`with a vehicle attachable unit on the same vehicle prior
`to the vehicle attachable unit fully electronically rec
`sponding to a signal and sending information to the
`visual display in the vehicle.
`The invention may be shipped in ready-to-install kit
`form, wherein the individual components have been
`previously factory set and labeled for simple installation
`on a vehicle having a designated number of wheels
`(tires) to be monitored. Alternately, the invention may
`be shipped from the factory in a condition allowing
`field setting of DIP switches by the user during installa-
`tion to meet the user‘s unique requirements. With the
`process of field setting of DIP switches, each tire of a
`given vehicle is initially assigned a wheel number by the
`user. and a digital wheel identification code is set in the
`wheel attachable unit of the wheel that is assigned that
`
`4
`wheel number. The digital wheel identification code is
`assigned by the user initially setting wheel identification
`DIP switches located on each wheel attachable unit of
`the vehicle. Each wheel attachable unit on a single
`vehicle will have the wheel identification DIP switches
`set differently from the other wheel attachable units on
`that particular vehicle so digital information identifying
`the particular wheel of that vehicle having incorrect
`pressure may be transmitted by the wheel attachable
`unit affixed to the wheel (tire) having incorrect air pres—
`sure. For example, a vehicle having four tires being
`monitored will have a wheel attachable unit on each
`wheel, with each wheel having been initially assigned a
`different wheel number 1 through 4 by the user, and
`each wheel attachable unit having the wheel identifica-
`tion DIP switches set to provide for digital information
`representative of the wheel number to be transmitted in
`the event of incorrect tire air pressure. This transmitted
`digital information containing information identifying
`the particular tire with incorrect pressure, ultimately
`will be displayed for the vehicle operator in a manner
`indicating a wheel number, I, 2, 3, or 4. Also, through
`preset bit assignments in the wheel attachable units and
`vehicle attachable units, the vehicle operator will addi-
`tionally receive information pertaining to the wheel
`number identified on the visual display which will indi-
`cate whether the identified wheel (tire) has unaccept-
`able high or low air pressure so the vehicle operator
`may take corrective action before a complete tire failure
`or in the event of a tire failure may take action as re-
`quired.
`transmission source
`The required match in digital
`indicating information between wheel attachable units
`on a given vehicle with a vehicle attachable unit on the
`same vehicle is also initially user set through a plurality
`of source identification DIP switches located on each
`wheel attachable unit, and also located on the vehicle
`attachable unit. Each tire in which the tire pressure of a
`given vehicle is to be monitored receives a wheel at-
`tachable unit, with each wheel attachable unit having
`the source identification DIP switches all set identically
`on that vehicle, and the same vehicle receives a single
`vehicle attachable unit with the source identification
`DIP switches of the vehicle attachable unit set identi-
`cally to all of the wheel attachable units on that vehicle.
`The settings of the source identification DIP switches
`of the wheel attachable units determine part of the digi-
`tal
`information transmitted by the wheel attachable
`units to the vehicle attachable unit on the vehicle when
`a tire pressure problem is sensed. If the source identifi-
`cation DIP switches of the vehicle attachable unit are
`not set the same as a transmitting wheel attachable unit,
`the vehicle attachable unit will not electronically recog-
`nize the signal as being proper, and thereby unrecog—
`nized signals will not cause the vehicle operator to
`receive a false display. A vehicle attachable unit may
`receive incompatible or undesirable signals
`from
`sources such as a wheel attachable unit having a differ
`ent setting on the source identification DIP switches,
`which may be on an adjacent vehicle also utilizing my
`invention. The source identification DIP switch settings
`will allow the vehicle attachable unit on a given vehicle
`to determine by comparison whether a signal is from a
`wheel attachable unit on that vehicle or some other
`vehicle.
`
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`This wheel identification and separate source identifi-
`cation system is easily accomplished utilizing digital
`infonnation transmitted and received, and bit assign-
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`Page 000013
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`5
`ments to essentially eliminate false information from
`being displayed to the vehicle operator. Additionally,
`since the wheel and the source identification DIP
`switches may beset in the factory or user set in the field,
`all of the wheel attachable units may be advantageously
`manufactured identically to one another, and all of the
`vehicle attachable units may be manufactured identi-
`cally to one another which contributes in minimizing
`the purchase cost to the end user.
`It should be noted that a tractor and trailer are treated
`as two separate vehicles, although only one visual dis-
`play will be positioned convenient to the vehicle opera-
`tor. If the tractor is towing two trailers, then the ar-
`rangement is treated as three vehicles, By treating the
`tractor and the trailer(s) as separate vehicles, trucking
`companies utilizing the present invention on all of their
`tractors and trailers will have the freedom to attach any
`of their trailers to any of their tractors without confu-
`sion between the wheel attachable units and vehicle
`attachable units, and may implement this interchanga-
`bility without resetting any of the DIP switches, due to
`the source identification DIP switches being set differ,-
`ently on each vehicle. Spare tires may be monitored if
`desired.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrative of the primary
`electrical and some mechanical components of the bat-
`tery powered wheel attachable unit in accordance with
`the immediate invention.
`FIG. 2 is a cross sectional view of a suitable high
`pressure sensor with an electrical switch which may be
`utilized as part of the immediate invention to effect
`electrical current flow When exposed to overly high tire
`air pressure.
`FIG. 3 is a cross sectional view of a suitable low
`pressure sensor with electrical switch which may be
`utilized as pan of the immediate invention to effect
`electrical current flow when exposed to excessively low
`tire air pressure.
`FIG. 4 shows the. high pressure sensor and the low
`pressure sensor. with both pressure sensors connected
`to a cross sectioned air pressure manifold in accordance
`to the immediate invention. Further shown are small air
`flow restrictive orifices from the manifold to the pres-
`sure sensors.
`
`FIG. 5 is a side view of one possible mounting base
`and protective housing for protectively containing most
`of the components of the wheel attachable unit.
`FIG. 6 is a perspective view of the protective housing
`of FIG. 2 showing removable panels which allow ac-
`cess to the DIP switches and replaceable battery
`therein.
`FIG. 7 is a panial view of a wheel with a pneumatic
`tire as part of a set of dual wheels common to large
`vehicles. Additionally shown are two wheel attachable
`units in accordance to the immediate invention mounted
`to the wheel and oppositely disposed from one another
`to help maintain wheel balance. One wheel attachable
`unit is for the outer shown tire, and the other is for the
`inner tire of the dual set as may be ascertained from
`HO. 8.
`FIG. 8 is an illustrative drawing showing the relative
`location of the major individual components of the
`immediate invention on a typical tractor/trailer installa-
`tion.
`FIG. 9 is a block diagram illustrative of the primary
`electrical components of the vehicle attachable unit
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`attachable to a vehicle remote of the wheels in accor-
`dance with the immediate invention.
`FIG. 10 is illustrative of a 19 bit information code
`DIP switch buss,
`the bit assignments, and the DIP
`switches in accordance with the immediate invention.
`FIG. 11 is illustrative of a suitable visual display for
`use with the present invention.
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`The drawing figures, in general, illustrate the opti-
`mum mode for implementing the invention. FIG. 1
`shows a schematic functional block diagram of a wheel
`attachable unit 01. Wheel attachable unit 01 includes a
`manifold 20, high pressure sensor 30 and low pressure
`sensor 40. a battery 12, and operational circuits and
`electronics all contained within a protective housing 50.
`Components for communicating tire air pressure to
`pressure sensors 30 and 40, namely valve extension tube
`55, valve stem tee adapter 56 and any components asso-
`ciated therewith may be considered part of wheel at-
`tachable unit 01. High pressure sensor 30 by sensing
`high tire pressure, or low pressure sensor 40 by sensing
`low tire pressure will cause either shunt elements 31 or
`41 to move and close switch contacts 39 or 49 which in
`
`turn will apply electrical power from a 9 volt alkaline
`battery 12 to the timer 15 and encoder 18. A five second
`timer 15 is located in series with ON/OFF switch 13
`and after the contacts 39 or 49 of the pressure sensors 30
`or 40 have been closed and the circuit completed, will
`immediately send to encoder 18 electrical power from
`battery 12. Upon receipt of electrical power, encoder 18
`will then generate proper digitally encoded information
`and communicate the information to transmitter 14 to
`be transmitted by RF transmission via antenna 19. An-
`tenna 19 is a short fixed wire antenna contained in hous-
`ing 50. Antenna 19 allows RF radiation from transmit-
`ter 14 to be transmitted. Transmitter 14 will transmit RF
`signals in the 360 to 470 KHZ frequency band using
`frequency shift keying (FSK), although other modula-
`tion modes could be used. The nominal transmitter 14
`range is 20 feet, however the range could vary based on
`design choice. After the first transmission from trans-
`mitter 14, timer 15 will “clock down” and allow the
`digitally encoded information to be transmitted at five
`second intervals, and will continue in this mode until
`battery 12 power is exhausted or the tire pressure has
`been brought to normal and contacts 39 or 49 again
`opened by the normal pressure. Timer 15 extends oper-
`ating life of battery 12 and improves operation of the
`system, as will be understood with continued reading.
`OFF/0N switch 13 is used to turn the power consum-
`ing electronic of wheel attachable unit 01 on or off for
`' maintenance, changing encoder 18 settings, changing
`tires 102 or for any reason required.
`Encoder 18 includes a DIP switch buss 70 with a
`plurality of two-position DIP switches 75 shown in
`FIG. 10 and indicated in FIG. 1. Encoder 18 with DIP
`switch buss 70 has factory or user preset electronic
`functions, bit assignments and a bit string generation for
`alert 71; transmission source identification 72; high or
`low pressure status 73; and wheel identifications 74
`which will be further discussed later. These functions
`are either permanently set in the factory or set with DIP
`switches 75 in the factory or in the field. Interface elec»
`tronics between encoder 18 and transmitter 14 are also
`included. High or low pressure status 73 functions to
`generate either a high pressure code or low pressure
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`5,109,213
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`7
`code. and also functions in an alternate mode in con-
`junction with low voltage detector 10 to indicate low
`voltage in battery 12.
`Low voltage detector 10, upon sensing low voltage in
`battery 12, switches power from battery 12 to encoder
`18. Encoder 18 then generates information identifying
`the wheel 100 to which the wheel attachable unit 01 is
`attached by its designated wheel number, the transmis-
`sion source, and information representing both a high
`and a low pressure condition of the identified wheel
`(tire). Encoder 18 then communicates this information
`to transmitter 14 for RF transmission to vehicle attach-
`able unit 60. Vehicle attachable unit 60 will be explained
`later in detail, as will display 80. Vehicle attachable unit
`60 does however contain electronic components and
`circuits which will receive, compare, process and com-
`municate the information from wheel attachable unit 01
`to display 80. This transmit mode ofunit 01 will con-
`tinue uninterrupted with high and low pressure status
`73 segment of DIP switch buss 70 functioning in con-
`junction with low voltage detector 10 unit until the
`power of battery 12 is exhausted. The information com-
`municated via vehicle attachable unit 60 to display 80
`will cause the lighting of both a red LED 87 and green
`LED 88 both placed adjacent a wheel 100 on display 80.
`The lighting of one or both of the LEDs identifies a
`given wheel on display 80. The vehicle wheels 100 are
`individually shown on display 80 by a graphic wheel
`display containing an assigned wheel number therein,
`and is illustrated in FIG. 11 and designated with 82. The
`red LED 87 indicates low tire air pressure, and green
`LED 88 indicates high tire air pressure. Since a tire
`cannot simultaneously have both high and low air pres-
`sure, when both LEDs 87 and 88 associated with a
`wheel identified on display 80 are activated, the opera
`tor will be alerted that battery 12 in the wheel attach-
`able unit 01 on the identified wheel 100 has low power
`and should be replaced or recharged. If wheel attach-
`able unit 01 happens to be in the transmitting mode, that
`is, a low or high tire pressure condition has actually
`been identified by high or low pressure sensors 30 or 40,
`and a low battery condition occurs, the transmit mode
`will occur, however the high or low pressure status 73
`segment of encoder 18 and DIP switch buss 70 function-
`ing in conjunction with low voltage detector 10 will
`include upon recognition of low battery power,
`the
`signal to be transmitted to the vehicle attachable unit 60
`that will cause the lighting of both a red LED 87 and
`green LED 88 adjacent an identified wheel on display
`80. The vehicle operator should check the battery 12
`and at the same time check the pressure of the identified
`wheel (tire) to be safe when both LEDs 87 and 88 asso-
`ciated with a wheel 100 identified on display 80 are
`activated.
`The components of wheel attachable unit 01 are
`readily available. Conventionally, transmitter 14, en-
`coder 18 with DIP switch buss 70 and antenna 19 are
`manufactured and procured as one integral unit from
`existing suppliers. Low voltage detector 10 may be
`procured from many sources. Battery 12 is readily avail-
`able as is the ON/OFF switch 13. Encoder 18 with DIP
`switch buss 70 is in wide use in such applications as
`garage door opener controllers, wireless security moni-
`tors, toys and others, as is transmitter 14.
`There are many existing variations of high and low
`pressure sensors with switches, contacts, or solid state
`components which could conceivably be utilized to
`sense pressure and effect electrical current in circuits.
`
`IO
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
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`55
`
`65
`
`8
`FIG. 2 shows a suitable high pressure sensor 30. High
`pressure sensor 30 is comprised of electrical power
`leads 32-1 and 32-2 connected one each to two electrical
`switch contacts 39 which upon excessively high pres—
`sure, shunt element 31 affixed to moveable piston 36
`moves toward and closes contacts 39 to allow electrical
`power from battery 12 to energize timer 15, encoder 18
`and transmitter 14 of wheel attachable unit 01. Other
`parts of high pressure sensors 30 are the rotatable pres-
`sure adjustment cap 37 supporting contacts 39 which by
`tightening will compress a pressure spring 35 requiring
`higher air pressure to move shunt element 31 to the
`point of closing switch contacts 39. Additional parts are
`housing 34, pressure diaphragm 33, piston 36 and ple-
`num 38. If the air pressure were to increase in plenum
`38, piston 36 would, through force of the air pressure
`acting on diaphragm 33, compress spring 35 and move
`shunt element 31 in closer proximity to contacts 39.
`When contacts 39 are connected by shunt element 31,
`electrical energy is caused to flow through wires 32-1
`and 32-2. Only if the pressure exceeds the high pressure
`setting of sensor 30 will timer 15, encoder 18 and trans-
`mitter 14 of wheel attachable unit 01 be activated by
`high pressure sensor 30.
`‘
`Significant forces. other than air pressure, acting on
`piston 36 and diaphragm 33, are perpendicular to the
`axis of the wheel 100. High pressure sensor 30 is
`mounted in wheel attachable unit 01, and wheel attach-
`able unit 01 is mounted to a wheel 100 in a manner such
`that the axis of piston 36 is parallel to the axis of the
`wheel, thereby minimizing inertia and centrifugal forces
`acting on piston 36 and diaphragm 33 that might lead to
`a false closure of contacts 39.
`FIG. 3 shows a suitable low pressure sensor 40. Low
`pressure sensor 40 is comprised of electrical leads 42—1
`and 42-2 connected one each to two electrical switch
`contacts 49. Upon sensor 40 being exposed to exces-
`sively low pressure, contacts 49 are connected by shunt
`element 41 allows electrical power from battery 12 to
`energize timer 15, encoder 18, and transmitter 14 of -
`wheel attachable unit 01. Other parts of low pressure
`sensor 40 are the pressure adjustment cap 47 supporting
`contacts 49 which by tightening will compress the pres-
`sure spring 45 requiring lower pressure to move shunt
`element 41 to the point of contacting switch contacts
`49. Pressure above a given level pressing against dia-
`phragm 43 will hold shunt element 41 away from
`contacts 49. Additional parts are the pressure spring 45
`which is used in conjunction with the pressure adjust-
`ment cap 47 to set response pressure, the housing 44, the
`pressure diaphragm 43, the piston 46, and the plenum
`48. If the pressure were to decrease in plenum 48, piston
`46 would, through the force of spring 45 acting on
`diaphragm 43, move toward plenum 48 and move shunt
`element 41 in closer proximity to contacts 49. When
`contacts 49 contact shunt element 41, electrical energy
`is caused to flow through wires 42-1 and 42—2. Only if
`the low pressure drops below the low pressure setting
`of sensor 40 will the timer 15. encoder 18 and transmit-
`ter 14 of wheel attachable unit 01 be activated by low
`pressure sensor 40. Low pressure sensor 40 is mounted
`with the piston 46 axis parallel to the wheel axis for the
`same reasons high pressure sensor 30 is mounted with
`the same orientation.
`FIG. 4 shows manifold 20 and high and low pressure
`sensors 30 and 40 attached to the housing 22 w