Abstract:
An air pressure gauge assembly is mounted to the valve stem of a tire or integrated into a wheel rim for continuous monitoring of the tire inflation pressure. The gauge assembly includes a check valve functionally coupled to the valve stem so that the check valve provides the common function of the valve stem, including allowing for inflation and deflation. The assembly also includes a pressure sensor coupled to a visually perceptible pressure indicator on a dial face.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to air pressure gauges for pneumatic tires and, more specifically, to an air pressure gauge assembly mounted to the valve stem of a tire for continuous monitoring of the tire inflation without interfering with the common function of a valve stem; and an air pressure gauge assembly permanently mounted to the rim of a wheel for continuous monitoring of the tire inflation. 
     2. Description of the Prior Art 
     Proper tire inflation is important for fuel economy of a vehicle and prolongs the life of a tire. By maintaining proper tire inflation, optimum performance of a vehicle can be reached while keeping the operating costs relatively low and the safety relatively high. Under inflation of a tire can cause excessive wear of the tire, tire failure, loss of fuel economy, excessive engine drag, increased emissions, and depletion of fossil fuels. 
     In general, the air pressure of a tire is checked by removing a cap from a valve stem, applying a pressure gauge to the valve stem to get a pressure reading, and replacing the cap onto the valve stem. In order to simplify this process several replacement valve caps have been developed, which indicate when the tire pressure falls below normal, for example U.S. Pat. No. 5,365,967 issued to Moore, U.S. Pat. No. 4,606,391 issued to Achterholt, and U.S. Pat. No. 5,040,562 issued to Achterholt. A lower then normal tire pressure is indicated by color codes or other indicator means. These devices only indicate a low tire pressure without displaying the real pressure of the tire. To inflate the tire, the valve cap still needs to be removed and the correct tire pressure needs to be determined after inflation with a traditional pencil gauge or other type of external gauge before the valve cap can be replaced. 
     Prior art also includes air pressure gauges mounted directly to a tire valve stem, for example U.S. Pat. No. 4,924,697 issued to Hunt et al., U.S. Pat. No. 5,377,539 issued to LaSalle, and U.S. Pat. No. 5,503,012 issued to Rabizadeh. Other air pressure gauges are directly substitutable for a conventional valve stem, for example U.S. Pat. No. 3,969,936 issued to Lindsay, but require the tire to be deflated for installation thereof. The prior art further includes air pressure gauges mounted to a gauge-securing threaded aperture typically provided in the wheel of a pneumatic tire for an aircraft, for example U.S. Pat. No. 4,248,080 issued to Chuck. All of these devices monitor and indicate the tire inflation pressure continuously. While some devices need to be removed for inflating the tires, others do not interfere with the tire inflation through the valve stem and also monitor the air pressure while inflating the tire. Still most of these air pressure gauges are connected to the tire valve stem and are driven by the air coming through the valve stem. This can cause a problem when replacing the tire and/or the valve stem. Also, if a prior art pressure gauge is accidentally broken off or fractured, air may leak causing hazardous deflation of the tire. Depending on the tire positions, prior art air pressure gauges may be hard to read. Devices that extend the valve stem may influence the balance of the wheel. 
     Therefore a need existed to provide an air pressure gauge assembly mounted to a valve stem that has the capability of inflating and deflating the tire through the gauge itself, that not only continuously displays the tire pressure but is easy to read, that also may be able to indicate a warning for lower than normal air pressure, and therefore eliminates the use of an external handheld air pressure gauge. 
     A further need existed to provide an air pressure gauge assembly mounted to a valve stem that is relatively compact, light weight, and extends the valve stem relatively little to avoid curb contact and interference with the wheel balance. 
     A still further need existed to provide an air pressure gauge assembly mounted permanently to the wheel rim of a vehicle that does not interfere with the tire valve stem, that continuously displays the tire pressure in an easy to read way, and that may also be capable of indicating a warning for lower than normal air pressure. 
     A still further need existed to provide an air pressure gauge assembly that is able to withstand substantial impact and to seal the tire if the housing thereof is accidentally broken off or fractured. 
     A still further need existed to provide an air pressure gauge assembly that does not cause a problem when exchanging tires and/or the valve stem. 
     A still further need existed to provide an air pressure gauge that is sturdy enough to withstand the centrifugal forces of the rotating tire. 
     A still further need existed to provide an air pressure gauge that is relatively inexpensive, reliable, and of little or no maintenance. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an air pressure gauge assembly for continuous monitoring of the inflation pressure of a tire that can be mounted to a valve stem and has the capability of inflating and deflating the tire through the gauge itself, that continuously displays the tire pressure in an easy to read way, and may be able to indicate a warning for lower than normal air pressure. 
     It is a further object of the present invention to provide an air pressure gauge assembly mounted to a valve stem that is relatively compact and extends the valve stem relatively little to avoid curb contact and interference with the wheel balance. 
     It is a further object of the present invention to provide an air pressure gauge assembly for continuous monitoring of the inflation pressure of a tire that can be permanently mounted to the rim of a wheel and does not interfere with the valve stem of the tire, that continuously displays the tire pressure in an easy to read way, may be able to indicate a warning for lower than normal air pressure, and is relatively compact and light weight. 
     It is a still further object of the present invention to provide an air pressure gauge assembly that is able to seal the tire if the gauge body is accidentally broken off or fractured. 
     It is a still further object of the present invention to provide an air pressure gauge assembly that is sturdy enough to withstand the centrifugal forces of the rotating tire. 
     It is a still further object of the present invention to provide an air pressure gauge assembly that is relatively inexpensive, reliable, and of little or no maintenance. 
     BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with one embodiment of the present invention, a valve stem mountable, flow-through air pressure gauge assembly for continuous monitoring of tire inflation pressure is disclosed comprising, in combination: a gauge body of compact design, a sensing element, means for mounting the gauge body to an existing valve stem, a pressure indicator, a dial face including a display light, a power source, a lens cover, and an air exhaust check valve. 
     In accordance with another embodiment of the present invention, an air pressure gauge assembly mountable through the wheel rim of an inflatable tire for continuous monitoring of tire inflation pressure is disclosed, comprising, in combination: a gauge body of compact design, a sensing element, means for mounting the gauge body in an airtight connection through a aperture in the wheel rim of an inflatable tire, means for allowing air to flow from the tire into the sensing element and sealing the wheel rim airtight in case the gauge body is accidentally broken off above the wheel rim or fractured, a pressure indicator, a dial face including a display light, a power source, and a lens cover. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the sensing element is a Bourdon tube, a c-tube, a helix-coil, or a diaphragm. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the pressure indicator is in a geared or non-geared connection with the sensing element. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the dial face is analog or digital and includes a warning light that is a steady light or a flashing light. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the display light is a LCD/LED or an INDIGLO nightlight. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the power source is an internal or an external power source. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the lens cover is a viewing non-magnifying lens or a magnifying lens. 
     In accordance with still another embodiment of the present invention, an air pressure gauge assembly is disclosed, wherein the gauge is liquid filled or non-liquid filled. 
     The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a valve stem mountable, flow-through air pressure gauge assembly according to the present invention. 
         FIG. 2  is a cross sectional view of a first preferred embodiment of the valve stem mountable, flow-through air pressure gauge assembly. 
         FIG. 3  is a cross sectional view of a second preferred embodiment of the valve stem mountable, flow-through air pressure gauge assembly. 
         FIG. 4   a  is a top view of an analog dial face of the air pressure gauge assembly of  FIGS. 2 and 3 . 
         FIG. 4   b  is a top view of a digital dial face of the air pressure gauge assembly of  FIGS. 2 and 3 . 
         FIG. 4   c  is a side view of the analog dial face covered with a magnifying lens of the air pressure gauge assembly of  FIGS. 2 and 3 . 
         FIG. 5   a  is a cross sectional view of a third preferred embodiment of the valve stem mountable, flow-through air pressure gauge assembly. 
         FIG. 5   b  is a top view of an analog dial face of the air pressure gauge assembly of  FIG. 5   a.    
         FIG. 6   a  is a cross sectional view of a fourth preferred embodiment of the valve stem mountable, flow-through air pressure gauge assembly. 
         FIG. 6   b  is a cross sectional view of a fifth preferred embodiment of the valve stem mountable, flow-through air pressure gauge assembly. 
         FIG. 7  is a side view of an air pressure gauge assembly mountable through the wheel rim of an inflatable tire according to the present invention. 
         FIG. 8  is a cross sectional view of a first preferred embodiment of the air pressure gauge assembly mountable through the wheel rim of an inflatable tire. 
         FIG. 9  is a cross sectional view of a second preferred embodiment of the air pressure gauge assembly mountable through the wheel rim of an inflatable tire. 
         FIG. 10  is a top view of a digital dial face of the air pressure gauge assembly of FIG.  8  and FIG.  9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  a side view of a valve stem mountable, flow-through air pressure gauge assembly  10  according to the present invention is shown. The air pressure gauge assembly  10  generally comprises a gauge body  11 , a sensing element  12 , a pointer  13  that is a pressure indicator, a dial face  40 , a lens cover  15 , and an air exhaust check valve  16 . The air pressure gauge assembly  10  can be mounted, preferably screwed and locked, onto a typical valve stem  20  of an inflatable tire. The connection is sealed with a washer, preferably an o-ring  21 . A warning light  17  can be installed under the lens cover  15 , powered by an external power source  18  mounted to the outside of the gauge body  11 . 
     Turning now to  FIG. 2 , a cross sectional view of a first preferred embodiment  30  of the valve stem mountable, flow-through air pressure gauge assembly  10  is shown. In the first preferred embodiment  30  of the air pressure gauge assembly  10  the sensing element  12  (shown in  FIG. 1 ) comprises a Bourdon tube  32 . The Bourdon tube  32  is configured as a spiral coil disposed concentrically around a sensing coil manifold  33  that is mounted to a part of a sensing element housing  31 . The Bourdon tube  32  is disposed in an airtight chamber  34  that can be non-liquid or liquid filled. The inner end of the Bourdon tube  32  is fixed in a sealed connection around an orifice, hidden from view, in the wall of the sensing element housing  31 . By mounting the gauge body  11  to the valve stem  20 , the lower end of the sensing element housing  31  depresses the valve core, hidden from view, inside the valve stem  20  and therefore, allows air to flow from inside the tire into an inner chamber  47  of the sensing element housing  31  and into the hollow interior core of the Bourdon tube  32 . The washer  21 , preferably an o-ring, provides an airtight connection of the gauge body  11  and the valve stem  20 . Should the gauge body  11  accidentally be broken off or fractured, the depressed valve core, hidden from view, inside the valve stem  20  will be released to seal the valve stem  20  and to maintain the air pressure inside the tire. The Bourdon tube  32  will coil more tightly or uncoil more loosely in response to the air pressure condition within the core of the tube. The Bourdon tube  32  can coil either clockwise or counter-clockwise. In one preferred embodiment, the distal end portion of the Bourdon tube  32  is sealed tight with an end extremity being fashioned into the configuration of a pointer  13  (non-geared). In another preferred embodiment, the distal end portion of the Bourdon tube  32  is sealed tight and connected to a gear that moves the pointer  13 . The sensing element  12  can also be a helix coil (as shown in FIG.  3 ), a diaphragm (as shown in  FIG. 5   a ), a c-tube, similar to “Power Flex™ Movement” manufactured by ASHCROFT®, or an electronic simm chip. 
     Still referring to  FIG. 2 , the air exhaust check valve  16  comprises a plunger  35 , an air exhaust compressing spring  36 , a check valve o-ring  37 , and an air intake manifold cover  38 . The air intake cover  38  is threaded on the outside to accept a standard valve stem cap. The air exhaust check valve  16  allows tire inflation or deflation through the gauge assembly  30  itself. 
     Referring now to  FIG. 3 , a cross sectional view of a second preferred embodiment  300  of the valve stem mountable, flow-through air pressure gauge assembly  10  is shown. In the second preferred embodiment  300  of the air pressure gauge assembly  10  the sensing element  12  (shown in  FIG. 1 ) comprises a helix-coil  320 . The helix-coil  320  is a spiral/helical wound Bourdon tube. The helix-coil  320  is able to resist shock and vibration to a higher extent then other variations of a Bourdon tube. Using the helix coil  320  expensive liquid filled gauges can be avoided. 
     In all other aspects is the air pressure gauge assembly  300 , shown in  FIG. 3 , identical to the air pressure gauge assembly  30 , shown in FIG.  2 . 
     Referring now to  FIGS. 4   a  to  4   c , possible variations of the dial face  40  of the air pressure gauge assembly  30  and  300 , of  FIGS. 2 and 3 , will be discussed. 
     In one preferred embodiment, a warning light  17  is installed beneath the dial face  40 . The warning light  17  is powered by an external power source  18  (shown in  FIGS. 1 and 3 ) or an internal power source  39  (shown in FIG.  2 ), preferably a cadmium battery. The warning light  17  indicates a lower than normal air pressure and can be adjusted to be turned on if tire air pressure decreases by a certain amount, for instance 2 psi or 4 psi. The warning light  17  can get a signal from a sensor or a pressure switch  43 , where an electrical circuit is opened or closed in response to a predetermined hydraulic pressure entering the switch from a connected source, preferably the Bourdon tube  32 . The warning light  17 , preferably a LCD/LED, can be steady or flashing. In another preferred embodiment, a display light  41 , also powered by the external power source  18  or the internal power source  39 , is integrated into the display to enhance the readability of the dial face  40 . The display light  41  is also connected to an on/off switch  42 , in order to be turned on only if needed. There can be one or more display lights installed as necessary. In one preferred embodiment, the display light  41  is an INDIGLO nightlight installed beneath the dial face  40 , as shown in FIG.  3 . In another preferred embodiment, the display light  41  is a LCD/LED. In still another preferred embodiment, the dial face  40  is luminescent. 
     In one preferred embodiment, the dial face  40  is an analog display  44  having indicia and a dial scale thereon for indicating the air pressure detected by the sensing element  12 , as shown in  FIG. 4   a . In another preferred embodiment, the dial face  40  is a digital display  45 , preferably a LCD/LED display, as shown in  FIG. 4   b . The dial face  40  is covered with a lens cover  15 . In one preferred embodiment, the lens cover  15  is a non-magnifying lens glued on top of the gauge body  11 , as shown in  FIGS. 1 and 2 . In another preferred embodiment, the lens cover  15  comprises a magnifying lens  46 , as shown in  FIG. 4   c . The gauge body  11  and the magnifying lens  46  are preferably manufactured through injection mould. The pointer  13  is bent upwards to allow viewing from the side as well as from top. 
     Turning now to  FIG. 5   a , a cross sectional view of a third preferred embodiment  50  of the valve stem mountable, flow-through air pressure gauge assembly  10  is shown. In the second air pressure gauge assembly  50  the sensing element  12  (shown in  FIG. 1 ) comprises a diaphragm  51 , preferably having a doughnut-shape. The diaphragm  51  has a sealed connection, through seals  52 , to the inner chamber  47  of the sensing element housing  31 . By mounting the gauge body  11  to the valve stem  20 , the lower end of the sensing element housing  31  depresses the valve core, hidden from view, inside the valve stem  20  and therefore, allows air to flow from inside the tire into an inner chamber  47  of the sensing element housing  31  and into the hollow interior of the diaphragm  51 . The diaphragm  51  will expand or contract in longitudinal direction in response to the air pressure condition within. In one preferred embodiment, the distal end portion of diaphragm  51  is connected with a pointer  13  (non-geared).  FIG. 5   b  shows an analog dial face  46  for the air pressure gauge assembly  50 . Furthermore, the air pressure gauge assembly  50  exhibits all other characteristics and variations shown for the air pressure gauge assembly  30 , as shown in FIG.  2 . 
     Referring now to  FIG. 6   a , a cross sectional view of a fourth preferred embodiment  60  of the valve stem mountable, flow-through air pressure gauge assembly  10  is shown. The gauge body  11  of the valve stem mountable, flow-through air pressure gauge assembly  60  has a right angle (90°) from air intake base  16  to valve stem  20 . 
     The gauge body  11  of the valve stem mountable, flow-through air pressure gauge assembly  600  (as shown in  FIG. 6   b ) has an extended right angle (90°) from air intake base  16  to valve stem  20 . The right-angled gauge body  11  of the valve stem mountable, flow-through air pressure gauge assembly  60  and  600  can be used in connection with all other preferred embodiments of the valve stem mountable, flow-through air pressure gauge assembly  10  as shown in  FIGS. 1  to  5 . 
     Referring now to  FIG. 7 , a side view of an air pressure gauge assembly  70  mountable through the wheel rim  72  of an inflatable tire according to the present invention is shown. The air pressure gauge assembly  70  mountable through the wheel rim  72  of an inflatable tire comprises a gauge body  71 , a dial face  40 , and a pointer  13 . The gauge body  71  is mounted in an airtight connection through a aperture in the wheel rim  72 , similar as a typical valve stem, using an outer rim air seal  73 , an inner rim air seal  74 , and a rim-fastening nut  75 . The gauge body  71  can also be mounted using a threaded fitting through the wheel rim  72  into a gauge-securing threaded aperture. The outer rim air seal  73  and the inner rim air seal  74  are washers, preferably o-rings. In one preferred embodiment, a warning light  17  and/or a display light  41  is installed with the dial face  40 , powered by an external power source  18  and connected with an on/off switch  42 . The dial face  40  is shown as an analog dial face bent in a right angle for improved readability of the dial face  40 . 
     Turning now to  FIG. 8 , a cross sectional view of a first preferred embodiment  80  of the air pressure gauge assembly  70 , mountable through the wheel rim  72  of an inflatable tire, is shown. The first preferred embodiment  80  of the air pressure gauge assembly  70  comprises a Bourdon tube  32  as sensing element  12  as described in conjunction with FIG.  2 . 
     Inside the sensing element housing  31 , a ball check valve  81  is mounted so that air from the tire can flow into an inner chamber  47  of the sensing element housing  31  and into the hollow interior core of the Bourdon tube  32 . Should the gauge body  71  accidentally be broken off above the wheel rim  72  or fractured, the ball check valve  81  will seal the tire and maintain the air pressure inside. 
     Referring now to  FIG. 9 , a cross sectional view of a second preferred embodiment  90  of the air pressure gauge assembly  70 , mountable through the wheel rim  72  of an inflatable tire, is shown. The second preferred embodiment  90  of the air pressure gauge assembly  70  comprises a diaphragm  51  as sensing element as described in conjunction with FIG.  5 . In a third preferred embodiment, the sensing element  12  used in the air pressure gauge assembly  70  is a helix-coil  320 , as shown in FIG.  3 .  FIGS. 8 and 9  show the dial face  40  not angled as one preferred embodiment of the present invention. In another preferred embodiment, the dial face  40  comprises a digital display  41  as shown in FIG.  10 . 
     The air pressure gauge assembly  70 , mountable through the wheel rim  72  of an inflatable tire, also comprises all variations and preferred embodiments of the valve stem mountable, flow-through air pressure gauge assembly  10 , as shown in  FIGS. 1-6 . 
     The gauge bodies  11  and  71  have a compact design, but are not limited to any particular shape, material, or color. 
     By introducing the air pressure gauge assembly  70 , mountable through the wheel rim  72  of an inflatable tire, the continuous monitoring of the air pressure of inflated tires is made possible without interfering with the operation of the tire valve stem and replacement of the tire. The valve stem mountable, flow-through air pressure gauge assembly  10 , offers the convenience of being mounted to an existing tire valve stem and still allowing inflating or deflating of the tire there through while continuously displaying the air pressure. 
     Both types of air pressure gauge assemblies  10  and  70  provide the tire to be sealed in case the gauge body  11  or  71  is accidentally broken off or fractured. Furthermore, both types of air pressure gauge assemblies  10  and  70  provide several variations of easy to read dial faces  40  and  73 , including a warning light for lower than normal air pressure and a display light. Also, both types of air pressure gauge assemblies  10  and  70  are of compact design and relatively inexpensive, reliable, and of little or no maintenance. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.