FIELD OF THE INVENTION  
       [0001]     This invention relates to a system for monitoring certain conditions of inflated tires of vehicles, and more particularly to such a system having an improved sensor means.  
       BACKGROUND OF THE INVENTION  
       [0002]     In U.S. Pat. No. 6,034,596, incorporated herein by reference, there is disclosed a system for monitoring the pressure and temperature of the tires of a vehicle which generally consists of a set of sensors mountable on the valve stems of the vehicle tires, and a control unit mounted on the vehicle, provided with means for transmitting signals between the control unit and the sensors. Each of such sensors generally includes a housing having a threaded opening, adapted to be threaded onto a tire valve stem to thereby intercommunicate the interior of the tire with the interior of the housing, and pressure and temperature sensors, a microcontroller, a transmitter/receiver and a power supply mounted within such housing. Such system operates in a manner whereby the control unit may selectively activate such sensors, query such sensors for pressure and temperature data which are transmitted to the control unit, process such transmitted data signals and display such processed data for the user.  
         [0003]     Although such sensors have been highly effective in sensing pressure and temperature conditions when mounted on the valve stems of tires, and transmitting data signals corresponding to such conditions to the control unit, they present an obstacle when seeking to connect a compressed air line to the valve stems of the tires for adjusting the pressures of the having to remove and replace each sensor. Such requirement of removal and replacement of such sensors each time the inflation pressure of the tire is adjusted has been found to be an inconvenience to the user which renders the use of such sensors less attractive.  
         [0004]     It thus is the principal object of the present invention to provide a sensor of the type described which does not require its removal and displacement each time the pressure of the tire on which it is mounted is adjusted.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention overcomes the disadvantage of such prior art system in having to remove and replace a sensor each time the pressure of a tire is to be adjusted by providing a sensor including a housing defining a closed chamber, having a first threaded opening permitting the housing to be threaded onto the valve stem of a tire, and a second opening, an abutment disposed in the housing engageable with the pin of the valve stem for depressing such pin and thereby opening the valve stem when the housing is threaded onto the valve stem, thereby intercommunicating the interior of the tire and the housing chamber, a valve disposed in the second opening in the housing having a pin adapted to be depressed by a component of a compressed air line for supplying compressed air to and through the housing chamber, means disposed on the housing for sensing the pressure within the chamber, means connected to the sensing means for receiving and processing signals therefrom corresponding to sensed pressures; and means coupled to the receiving and processing means for transmitting processed signals corresponding to the sensed pressures to the control unit of the system. Preferably, such device includes additional means for sensing ambient pressure and the temperature of the interior of the tire and transmitting such data to the control unit, and a battery for powering the sensors, processor and transmitter of the device. It further is preferred that such device be provided with a transmitter/receiver so that it may be activated, deactivated and queried by the control unit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention will be described below in detail with reference to several drawings, in which:  
         [0007]      FIG. 1  is a vertical cross section of a sensor device embodying the present invention;  
         [0008]      FIG. 2  is a schematic of the electronic components of the sensor device shown in  FIG. 1 ;  
         [0009]      FIG. 3  is a schematic of the electronic components of the control unit for the sensor device shown in  FIGS. 1 and 2 ;  
         [0010]      FIG. 4  is a vertical cross section of a sensor device according to another embodiment; and  
         [0011]      FIG. 5  is a vertical cross section of a sensor device having a dust cap mounted thereon. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     Referring to the drawings, there is illustrated a system for monitoring certain conditions of an inflatable tire of a vehicle which generally consists of at least one sensor device  10  mountable on a valve stem  11  of a tire  12  and a control unit  79  which may be either mountable on the vehicle or detached for use as a portable unit. The sensor device includes a housing  13  defining a chamber  14 , a valve  15  and electronics module  16 . Valve stem  11  is of a conventional construction consisting of an elongated body member  17  having a longitudinal bore  18  therethrough and a valve core  19  disposed in an enlarged section  20  of bore  18 . Valve core  19  includes a substantially cylindrical body member  21  seated in enlarged section  20  and a valve  22  disposed in a longitudinal bore  23  therein. The free end of cylindrical body member  21  is provided with a set of exterior threads  24  and a set of interior threads  25 .  
         [0013]     Valve core  19  is of a conventional construction found in most valve stems and includes a base section  26  provided with a set of external threads to permit the valve to be threaded into cylindrical body member  21 , a cylindrical section  27  depending from base section  26 , a pin  28  extending through base section  26  and depending cylindrical section  27 , a valve element  29  mounted on a lower free end of pin  28  and engageable with an edge of cylinder section  27  comprising a valve seat and a spring  30  disposed between base section  26  and valve element  29  which functions to bias pin  28  in an upward direction as shown in  FIG. 1  to cause valve element  29  to engage and thus be seated on the lower edge of cylindrical section  27  to close the valve. Base section  26  further is provided with an internal passageway intercommunicating the space above base section  26  and the interior of cylindrical section  27 . Under normal conditions, spring  30  assisted by pressure within the tire will cause valve element  29  to be seated on the lower edge of cylindrical section  27  to maintain the valve in the closed condition. The valve may be opened simply by depressing the upper end of pin  28  to unseat valve element  29  against the biasing action of spring  30 . When the valve is thus opened, the space above base section  26  communicates with the lower end of bore  23  through the internal passageway in base section  26  and cylindrical section  27 .  
         [0014]     Housing  13  generally consists of a cup-shaped base member  31  and a cooperating cap member  32 . The base member has a substantially frusto-conical side wall  33  provided with a set of circumferentially spaced projections  34  at the open end thereof and an end wall  35 . The end wall is formed with a recess  36  which is disposed axially relative to side wall  33  and is defined by a section  37  having a frusto-conical configuration inverted relative to side wall  33 . The outer end of recess  36  is enlarged as at  38  to accommodate an O-ring seal  39 , and the inner end thereof is provided with an axially disposed opening  40 . Recess  36  has essentially the same configuration as the upper end of valve stem  11  which is adapted to be received therein as shown in  FIG. 1 . It further is provided with a set of internal threads  41  to permit the device  10  to be threaded onto the upper end of the valve stem, on threads  24 , as shown in  FIG. 1 . Disposed at the inner end of recess  36  is an annular sealing gasket  42  which is adapted to be interposed between the upper end of the valve stem and the end portion of section  37  when the sensor device  10  is mounted on the valve stem as shown in  FIG. 1 . O-ring  39  and gasket  42  function to provide seals between the sensor device and the valve stem except for opening  40 .  
         [0015]     Cap member  32  includes a cylindrical section  43  having a circular edge adapted to be seated on an annular edge of wall section  33  and a plurality of circumferentially spaced, projections  44  equal in number to and registrable with projections  34  to permit the cap member to be secured to the base member by means of a set of screws  45 , an end wall section  46  and a cylindrical neck section  47 .  
         [0016]     The free end of neck section  47  has a reduced outer diameter and is provided with a set of external threads  49  to accommodate a threaded closure cap, and an internal set of threads  50 . Threaded within opening  48  on threads  50  is valve core  15 . Valve core  15  is disposed in axial alignment with valve core  19  and the combination of neck section  47  and valve core  15  have essentially the same configuration as that portion of valve stem  11  received within recess  36  including valve core  19 . Valve core  15  includes a base section  51  adapted to be threaded onto internal threads  50  of opening  48 , a cylindrical section  52  depending from the base section and having a circular edge defining a valve seat, a pin  53  extending through base section  51  and cylindrical section  52 , a valve element  54  mounted on an inner end of pin  53  and adapted to engage the valve seat provided on the end of cylindrical section  52  and a spring  55  which functions to retain valve element  54  seated on the valve seat provided by cylindrical portion  52 . Base section  26  further includes a passageway therethrough intercommunicating the exterior of the device and the interior of cylindrical section  52 .  
         [0017]     The free, inner end of wall section  33  is enlarged to provide an annular shoulder  60  onto which there is adapted to be seated a holder  61 . The holder consists of an open, cup-shaped member seated on annular shoulder  60  which is adapted to be received partially within base member  31  and cap member  32  when the cap member is mounted on the base member as shown in  FIG. 1 , and a depending section  62 . Mounted on depending section  62  is an actuating pin  63  which is disposed in axial alignment with pin  28  of valve core  22 , extends through opening  40  and gasket  42  and depresses pin  28  to open valve core  22  when holder  61  is mounted on annular surface  60  and cap member  32  is mounted on base member  31  as shown in  FIG. 1 . Holder  61  supports a printed circuit board  64  on which there is mounted an ambient air temperature sensor  65 , a tire air temperature sensor  66 , a pressure sensor  67 , a radio transceiver  68  including a transmitter  69  and a receiver  70  and a microcontroller  71 , shown schematically in  FIG. 2 , and a battery  72  for powering the sensors, microcontroller and transceiver.  
         [0018]     When sensor device  10  is screwed onto valve stem  11  as shown in  FIG. 1 , actuating pin  63  of holder  61  will cause pin  28  of valve  22  to be depressed and thus unseat valve element  29 . Under such conditions, an air passageway will be formed through opening  40 , the inner opening of gasket  42 , the internal passageway in base section  26 , cylindrical section  27  and opening  18  to intercommunicate the interior of tire  12  and chamber  14  of housing  13 . Under such circumstances, the temperature and pressure of the air in chamber  14  will be at the same temperature and pressure as the air in the tire and may be sensed by sensors  65 ,  66  and  67 . As described in greater detail in U.S. Pat. No. 6,034,596, whenever the electronics unit in sensor device  10  as illustrated schematically in  FIG. 2  is activated, sensors  65 ,  66  and  67  function to sense ambient air temperature, interior tire temperature and interior tire pressure, microcontroller  71  functions to process data signals from the sensors and transmitter  69  functions to transmit processed data signals from the microcontroller to control unit  79 .  
         [0019]     Control unit  79  may be powered by batteries or connected to the electrical system of a vehicle. It consists of a bi-directional radio transceiver  80  including a transmitter  81  and a receiver  82  which transmit and receive signals to and from transceiver  68  of the sensor device, an ultra-low powered CMOS microcontroller  83  which queries the sensor device, receives sensing signals from transmitter  69 , processes such signals and supplies measured readings to an alpha-numeric display module  84  and tire status to a display  85 , and a keypad  86 . The keypad includes mode and select buttons of  87  and  88 , an alarm silence button  89  and up and down control buttons  90  and  91  for parameter entry.  
         [0020]     In the operation of the system as described, the sensor device is mounted on the valve stem of a tire to be monitored as shown in  FIG. 1  and power is supplied to the control unit. A self diagnostic check is made initially involving the displays, communication with the sensing device and the system electronics. The control unit then transmits a wake up call to the sensor device. Such signal activates the electronics of the sensor unit from its normal lower power mode. The sensors in device  10  then measure pressure and temperature and transmit signals corresponding to such data and location data to receiver  82  of the control unit. Such data is then displayed on displays  84  and  85 . In applications where a plurality of sensor devices are employed such as on a set of tires of a vehicle, the control unit is operable to query each of such devices and displays the sensed data on the display of the control unit. A more detailed description of the monitoring of one or more sensor devices by the control unit is provided in U.S. Pat. No. 6,034,596.  
         [0021]     Although sensor device  10  may be removed from the valve stem of a tire simply by unscrewing it from the valve stem, it is intended to be permanently mounted thereon. Such permanent mounting will not interfere with either checking or adjusting the pressure of the tire in that either a pressure gauge or compressed air hose may be connected to the outer end of the device. Whenever a pressure gauge or a compressed air line is applied to the outer end of the sensor device, a protruding portion of the gauge or connecting fixture of a compressed air line will cause pin  53  of valve core  15  to displace axially and thus unseat valve element  54 . Under such circumstances, the gauge or line-connecting fixture will communicate with the interior of the tire through the sensor device. The pressure in the tire may thus be gauged, increased or decreased without removal and replacement of the sensor device.  
         [0022]     Housing  13  may be formed of any suitable dielectric material and by any method. Preferably, the housing is molded of a plastic material such as ABS. Although the housing has been described as having a particular configuration consisting of two components and secured together by a set of screws, it will be appreciated that it may be formed in any suitable configuration providing a set of valve cores as described to permit the gaging or adjusting of the tire pressure without removing the sensor device. It may consist of any number of components and may have any components thereof secured together by any suitable means.  
         [0023]     In the preferred embodiment of the invention, the control unit functions to query each sensor device mounted on one or more vehicles with unique electronic identification or serial numbers that activate each sensor device to transmit data. The control unit may be permanently or removably mounted on a vehicle or be used as a portable unit. Furthermore, the system may be used to determine vehicle weight or its load. By using pressure and temperature measurements and incorporating information regarding tire volume, flexing properties and appropriate calculation factors, weight can be determined. By comparing the different weights on the tires, a load-balance parameter may be calculated to properly load the vehicle  
         [0024]     In an alternative embodiment of the invention, shown in  FIG. 4 , the sensor device  10  is provided with a dust prevention mechanism, comprising a ball member  94  and a spring  95 . The dust prevention mechanism is a closure device that prevents dust from contacting the valve core  15  of the sensor device  10 .  
         [0025]     In this embodiment, neck section  47  of cap member  32  is extended out from its length of the previous embodiment. The outer threads  49  are also extended. The upper segment of neck section  47  has a chamber  92  that intercommunicates the valve core  15  of the cap member  32  with the exterior of the cap member. The chamber  92  contains ball member  94 , which is prevented from moving outside the chamber  92  via chamfers  93 ,  96  on an upper and lower side of the chamber  92 . As ball member  94  moves against chamfer  93 , the chamber  92  is sealed from the environment and debris outside the cap member  32  and prevents dust from contacting valve core  15 . A spring  95  biases ball member  94  into contact with chamfer  93 . In its operation, when a line connecting fixture is attached to cap member  32  to inflate the tire, the air pressure against the ball member  94  causes the spring  95  to collapse moving the ball member away from the chamfer  93 , which is shown in  FIG. 4 . Air may then pass through the chamber  92 . The ball member  94  may also be manipulated manually. The tire may then be filled in a normal manner.  
         [0026]     In an alternative to incorporating the dust prevention mechanism into the neck portion of device  100 , the dust prevention mechanism may be in the form of a dust cap  97 , which is shown in  FIG. 5 . The general operation of the dust cap  97  is analogous to the operation of the dust prevention mechanism shown in  FIG. 4 , the difference being the components are separated. Dust cap  97  has inner threads  100  that screw onto outer threads  49  of neck section  47 . Dust cap  97  is provided with a cap chamber  101  having chamfers  98  and  99  on an upper and lower side thereof. A similar ball member  94  and spring  95  are also shown.  
         [0027]     From the foregoing detailed description, it will be evident that there are a number of changes, adaptations and modifications of the present invention which come within the province of those persons having ordinary skill in the art to which the aforementioned invention pertains. However, it is intended that all such variations not departing from the spirit of the invention be considered as within the scope thereof as limited solely by the appended claims.
A sensor device mountable on a threaded valve stem of an inflatable tire of a vehicle having an actuating pin adapted to be depressed by a component of an air gauge or a connecting fixture of a compressed air line, generally consisting of a housing defining a closed chamber, having a first threaded opening permitting such housing to be threaded onto the valve stem, and a second opening; an abutment pin disposed in the housing engageable with the actuating pin of the valve stem for depressing the actuating pin of the valve stem and thereby opening the valve stem when the housing is threaded onto the valve stem, providing an intercommunication of the interiors of the tire and the housing; a valve disposed in the second opening of the housing having an actuating pin adapted to be depressed by the component of an air gauge or connecting fixture of a compressed air line; a sensor mounted in the housing for sensing the pressure in the housing chamber; a microcontroller connected to the pressure sensor for receiving and processing signals therefrom corresponding to sensed pressures; and a transmitter mounted on the housing and coupled to the processor for transmitting processed signals corresponding to sensed pressures.