Abstract:
A tire pressure monitor continuously indicating to a vehicle operator whether or not each tire on the vehicle, including a spare if present, is adequately inflated for safe “over-the-road” operation. The monitor includes an indicator associated with each tire to indicate when the air pressure in any individual tire on the vehicle is not inflated to a pressure adequate for safe operation. The monitor also includes a battery operated pressure sensitive radio frequency transmitter mounted on the outer end of a conventional tire valve stem and includes an antenna extending into each tire for transmitting a signal to an indicator assigned to each tire without interference from metal wheel components. The indicators are mounted on the instrument panel or dashboard of the vehicle. The signal transmitted from the transmitter on each tire valve actuates only the indicator associated with and receiving a signal from only the transmitter assigned to each tire.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. application Ser. No. 09/924,455 filed Aug. 9, 2001, entitled Vehicle Tire Air Monitoring System now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to tire air pressure monitors and more specifically to a monitor for continuously indicating to a vehicle operator that each tire on the vehicle, including a spare, if present, is adequately inflated for safe “over-the-road” operation. The invention also includes an indicator associated with each tire when the air pressure in any individual tire on the vehicle is not inflated to a pressure adequate for safe operation. The monitor includes a housing enclosing a pressure sensitive sensor, battery and radio frequency transmitter threadedly mounted on an outer threaded end of a conventional tire valve stem from which the Schrader valve element has been removed. The transmitter includes an antenna which extends into the interior of the tire for transmitting a signal to an indicator on the instrument panel or dashboard of the vehicle. The outer end of the housing has a conventional Schrader valve therein and the structure of the monitor enables air flow therethrough which permits inflation or deflation of the tire without removing the monitor. The signal transmitted from each transmitter to the receiver actuates only the indicator on the instrument panel associated with and receiving a signal from the transmitter monitoring the air pressure in the specific tire to which the indicator is assigned. The radio frequency transmitter and receiver enable a vehicle operator to observe an indicator for each tire so that the operator can determine whether each tire is adequately or inadequately inflated for safe operation of the vehicle. 
     2. Description of the Prior Art 
     The following U.S. patents, known to Applicant, disclose devices which relate to the invention disclosed in this application. 
     
       
         
               
               
               
             
           
               
                   
               
             
             
               
                 1,804,209 
                 4,048,614 
                 5,040,561 
               
               
                 2,149,555 
                 4,286,253 
                 5,289,160 
               
               
                 2,574,791 
                 4,363,020 
                 5,774,048 
               
               
                 2,727,221 
                 4,414,843 
                 5,987,980 
               
               
                 3,430,196 
                 4,468,650 
                 6,005,480 
               
               
                 3,938,078 
                 4,726,223 
               
               
                 3,982,225 
                 4,734,674 
               
               
                   
               
             
          
         
       
     
     The prior art in this field of endeavor discloses various devices associated with the tire valves or tires of vehicles to provide an indication of air pressure in each vehicle tire. The prior art devices include pressure sensitive switch mechanisms in each tire valve or valve stem wired individually to indicators on the instrument panel of a vehicle. The prior art also discloses pressure sensitive switches associated with vehicle tires to actuate a transmitter which transmits a wireless signal to an antenna on the vehicle associated with an indicator on the instrument panel or dashboard of the vehicle to indicate to the vehicle operator that a particular tire has an inadequate air pressure for safe operation of the vehicle. 
     The prior art does not disclose a monitor including a housing for a sensor, a transmitter and battery positioned therein with the housing being threadedly mounted on a tire inflation valve or valve stem from which the Schrader valve has been removed. The prior art also does not disclose a tire air pressure monitor in which the housing attached to the tire valve includes a Schrader valve in the outer end thereof with the components within the housing being constructed so that air can flow therethrough to enable inflation or deflation of the tire without removing the monitor. Additionally, the prior art does not disclose a transmitter having an antenna within the tire for wireless transmission of a radio frequency signal assigned to a particular tire to a receiver located within the cab of the vehicle and connected to an indicator actuated only by the transmitter in the tire to which a particular indicator is assigned to indicate whether the tire is either adequately inflated or inadequately inflated for safe operation of the vehicle. 
     SUMMARY OF THE INVENTION 
     The vehicle tire air pressure monitor of the present invention provides the operator of the vehicle with a separate continuous signal related to each tire on the vehicle, including a spare if present. Specifically, the monitor signals the operator whether each tire is adequately inflated for safe operation or each tire has an inflation pressure inadequate for safe operation of the vehicle. The monitor for each tire includes a pressure sensitive sensor, battery and transmitter utilizing radio frequency technology for wireless transmission of a signal to an indicator located within the cab of a vehicle for observation by the vehicle operator to indicate the inflation condition of each tire. The number of transmitters and indicators is the same as the number of tires on the vehicle. The indicators observable by the vehicle operator are associated with the monitor transmitters on the wheels on the vehicle thereby enabling the vehicle operator to receive an immediate warning when an indicator changes from indicating a safe operating air pressure in the tire to an unsafe air pressure in the tire with which the indicator is associated. 
     Accordingly, an object of the present invention is to provide a vehicle tire air pressure monitor for independently monitoring the air pressure in each tire on the vehicle and transmitting this information to receivers in the vehicle cab to actuate visual indicators thereby enabling an operator of the vehicle to immediately determine whether air pressure in each tire is adequate or inadequate for safe operation of the vehicle. 
     Another object of the present invention is to provide a monitor in accordance with the preceding object in which each transmitter is associated with a sensor and battery within the interior of a housing threadedly mounted on the outer end of an inflation valve for the vehicle tire. The transmitter includes a flexible antenna which extends into the interior of the tire to enable transmission of a radio frequency signal without interference from the tire rim or wheel. 
     A further object of the present invention is to provide a monitor for vehicular tire air pressure in accordance with the preceding objects in which the indicators observable by a vehicle operator are mounted in the instrument panel or dashboard of the vehicle with each indicator being assigned to and receiving transmitted radio frequency signals from one particular tire with the indicators including a green light indicating safe operating pressure of the tire and a red light indicating low and unsafe air pressure in the tire. 
     Still another object of the present invention is to provide a monitor for vehicle tire air pressure in accordance with the preceding objects in which the radio frequency transmitter and receiver utilize frequencies having characteristics in which the wireless transmitted signals are insufficient to cause interference with other radio frequency signals oriented externally of the vehicle on which the monitor is mounted. 
     Yet another object of this invention to be specifically enumerated herein is to provide a vehicle tire air pressure monitor in accordance with the preceding objects and which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation. 
     These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a vehicle instrument panel with multiple indicators mounted thereon in accordance with the present invention. 
     FIG. 2 is a schematic elevational view of an air valve stem having a monitor in accordance with the present invention screw threadedly mounted on the outer end of a valve stem in a tire and rim assembly. 
     FIG. 3 is a vertical sectional view of the monitor shown in FIG.  2  and illustrating the internal structure thereof. 
     FIG. 4 is a transverse sectional view, on an enlarged scale, taken along section line  4 — 4  in FIG. 3, illustrating external grooves on an internal component of the invention. 
     FIG. 5 is an exploded perspective view of the monitor illustrating structural detail thereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although only one preferred embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiment, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     As illustrated in FIG. 1, indicators  10  forming part of a tire air pressure monitoring system of the present invention are positioned in the instrument panel or dashboard  12  of a vehicle cab generally designated by reference numeral  14 . Preferably, the indicators  10  are positioned so that a vehicle operator occupying the operator&#39;s seat  16  rearwardly of the steering wheel  18  can observe the indicators  10  which are located in any position generally forwardly of the vehicle operator to enable quick and easy visual observation of the indicators  10  without any substantial distraction of the vehicle operator from observing road and traffic conditions to enable the vehicle operator to safely operate the vehicle and observe the indicators  10 . 
     FIGS. 2-5 illustrate a monitor generally designated by reference numeral  16  for tire air pressure constructed in accordance with the present invention. The monitor  16  is mounted on a conventional air valve stem  19  extending through and sealingly engaged with a metal rim  21  on which a tire  20  is mounted. The monitor  16  includes a housing generally designated by reference numeral  22  having an internally screw threaded lower member  23  screw threaded onto a shortened upper screw threaded end  24  of the valve stem  19  from which the Schrader valve core has been removed. As illustrated in FIG. 3, the lower member  23  is internally threaded at  26  and includes external opposed flat areas  28  for engagement by a wrench or other suitable tool when attaching or removing the monitor  16  from the valve stem  19 . The lower member  23  also includes an externally threaded area  30  immediately above the flat areas  28  and a smooth external peripheral area  32  above the threaded area  30 . 
     As illustrated in FIGS. 3 and 5, the upper end surface of the lower member  23  includes a plurality of radial grooves  34 . The radial grooves  34  extend from the upper outer peripheral edge of the extended peripheral area  32  to an upper peripheral edge  35  of an internal, generally cylindrical passageway  36 . The passageway  36  extends throughout the length of the lower member  23  thereby communicating the interior of the tire  20  with the exterior of the upper end of the lower member  23 . 
     The housing  22  also includes a generally cylindrical, tubular upper member  38  which has an internally threaded lower end area  40  for screw threaded engagement with threaded area  30  on the lower member  23 . The upper member  38  includes a smooth internal cylindrical area  42  above the threaded area  40 . A peripheral internal groove  44  is provided in the area  42  at the upper end of threaded area  40  for receiving an O-ring seal  46  which sealingly engages the external surface of the upper end of the smooth peripheral area  32  of lower member  23  when the lower member  23  and upper member  38  are screw threadedly assembled. The upper end of upper member  38  inclines or tapers inwardly at  48  to a cylindrical upper end  50  on the upper member  38 . The cylindrical upper end  50  has a diameter substantially less than the diameter of the upper member  38  and has flat areas  52  to receive a wrench or other tool to enable assembly and disassembly of the lower member  23  and upper member  38  by use of the threaded areas  30  and  40 . 
     Projecting upwardly from the upper end  50  of upper member  38  is a smaller diameter tubular externally and internally threaded extension  54  adapted to receive a conventional valve stem cap (not shown). The threaded interior surface  56  of extension  54  is in communication with an internal bore  58  in cylindrical upper end  50 . The bore  58  and threaded interior surface  56  are configured to threadably receive a Schrader valve core  57  to retain air pressure within the tire  20  and housing  22 . The Schrader valve core  57  that was removed from the valve stem  19  may be inserted into the extension  54  with the threads  56  engaging the externally threaded surface of the Schrader valve core  57  in a manner well known. Preferably, a new Schrader valve core is used to assure positive valve closure and long lasting operation. 
     Fitted in the interior of the upper member  38  is a rigid cylindrical tubular casing  60  positioned in the smooth interior area  42  of upper member  38 . The lower flat end  62  of casing  60  rests on the upper end of lower member  23  without blocking the radial grooves  34  in the upper end of the lower member  23 . The external surface  64  of the casing  60  includes a plurality of longitudinal grooves  66  extending throughout the length of the casing  60  to provide air and pressure flow communication between the tire  20  and the passageway  58  through the passageway  36 , the radial grooves  34 , and the longitudinal grooves  66 . This communication permits inflation or deflation of the tire  20  while the monitor  16  is mounted on the valve stem  19 . The upper end portion of casing  60  is internally threaded at  68  for threaded engagement with a cap  70  which forms a closure for the upper end of casing  60 . The cap  70  preferably includes a transverse groove  72  in its upper surface to enable a screwdriver or other similar tool to assemble or remove the cap in relation to the casing  60 . The lower flat end  62  of casing  60  includes a short depending projection  74  having a passageway  76  therethrough which communicates the hollow interior  78  of casing  60  with passageway  36  in lower member  23  and thus with the tire  20 . 
     Positioned within the interior  78  of casing  60  is a radio frequency transmitter  80 , battery  82  and air pressure sensor  84 , preferably in the form of circular wafers oriented in stacked relation as schematically shown in FIGS. 3 and 5. The battery  82  provides a power source to actuate the transmitter  80  when the sensor  84  senses an unsafe air pressure in the tire  20 . Attached to the transmitter  80  is a flexible antenna wire  86  which extends downwardly through the passageway  76  into the tire  20  a distance to enable an antenna  88  to transmit a signal to actuate the indicator  10  corresponding to the tire  20  on which the monitor  16  is mounted to warn the vehicle operator of unsafe tire pressure in a specific tire  20 . 
     The separable components of the housing  22  enable replacement of the battery  82  and inspection and replacement of the sensor  84  and transmitter  80 , if necessary. The housing components are preferably constructed of lightweight plastic material to enable effective balancing of the vehicle wheels. Also, the interior of the casing  60  may be sealed with epoxy or the like with the entire casing and components to be replaced as a single unit. 
     Each transmitter  80  and antenna  88  are located in the tire  20  in a position that the metal wheel components will not interfere with radio transmission of a wireless radio frequency signal having a frequency associated with the particular tire  20  with which the valve stem  19  is associated. The signal from the transmitter is received by the indicator  10  that includes a receiver tuned to receive the radio frequency signal transmitted from the transmitter  80 . Each indicator  10  receives a signal from only the transmitter  80  to which the indicator  10  is assigned inasmuch as the transmitter  80  and receiver in the indicator  10  are tuned to the same radio frequency. This enables each indicator  10  to be assigned or relate to an individual tire  20  on the vehicle so that the vehicle operator can immediately determine the inflation condition in each tire on the vehicle. 
     Each indicator  10  in accordance with the present invention includes a visual signal, such as a green light to indicate safe tire pressure and a red light to indicate an unsafe air pressure. The visual signal can be constant or flashing with preferably the green light being constant and the red light flashing. It is within the scope of the present invention to include other types of signals such as audible signals which are clearly recognizable and of sufficient volume to enable a vehicle operator to hear the audible signals above the usual noises associated with vehicle operation. 
     In operation, as long as all of the vehicle tires  20  are properly inflated for safe operation of the vehicle, all indicators  10  will indicate that safe operating conditions exist in all tires. However, if one or more tires lose air pressure to a level that is unsafe for continuous operation of the vehicle, then the signal changes to indicate unsafe air pressure in readily identifiable tires thereby enabling the vehicle operator to take immediate action to remedy the unsafe operating condition. 
     Typically, the transmitter will continue to indicate safe operating conditions if the air pressure in the tire remains within about 5% to 10% of the recommended air pressure. For example, if heavy truck tire pressure is recommended to be 100 psi, the transmitter would not transmit a signal until the air pressure in the tire reduces to approximately 90 psi. In a passenger car where the recommend pressure may be 35 psi, the transmitter will transmit a signal when the tire pressure reduces to approximately 31 or 32 psi. The percent reduction in pressure from the recommended pressure to the signal transmitting pressure can be varied depending upon the vehicle and the criticality of the air pressure with regard to possible overheating of the tire, extra tire wear, tread separation and the like, which can result in the vehicle operator losing control of the vehicle and causing accidents resulting from serious deterioration of the handling characteristics of the vehicle due to tire failure. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.