Abstract:
The present invention is a wheel assembly having a rim with a valve aperture extending therethrough that is designed to receive a valve having a simplified a construction that can be seated directly within a tire wheel assembly to minimize the number and type of components necessary for the valve. The valve includes a main body that is positionable in a sealed and recessed or embedded configuration within the aperture in the wheel rim in communication with the interior of the tire and with a pressurized air source that is used to inflate or deflate the tire. The main body encloses a valve mechanism that includes a components situated within the main body in a manner that enables the parts to be easily removed, cleaned and/or replaced if necessary without having to remove the entire valve assembly from the wheel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority as a divisional application from U.S. patent application Ser. No. 11/680,303, filed on Feb. 28, 2007, which claims priority from U.S. Provisional Patent Application Ser. No. 60/778,040, filed on Mar. 1, 2006, which are each incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to tire inflation valves, and more specifically to a tire inflation valve that is releasably imbedded within a tire rim that forms part of a central tire inflation system of a vehicle. 
       BACKGROUND OF THE INVENTION 
       [0003]    In order to inflate and deflate the tires forming part of the wheels on a vehicle, valves are located on the rims or hubs of the wheels to be used for selectively inflating and deflating the tires disposed around the wheel rims. Air can be directed through the valves either into or out of the tires to increase or decrease the air pressure in the tires, correspondingly altering the ride characteristics of the individual wheel, and the overall vehicle. 
         [0004]    On most occasions the valves are only accessible from the exterior of the wheel, such that it is necessary to exit the vehicle to use the valve to inflate or deflate the tire. However, various central tire inflation systems have been developed that provide valves on the wheel rims that can be remotely activated from the cab or other driver compartment for the vehicle. These systems enable an individual to control the flow of air into and out of the vehicle tires using the valves to vary the ride characteristics of the tires as necessary. Examples of systems of this type are illustrated in each of Howald et al. U.S. Pat. No. 6,474,383, and Wang et al. U.S. Pat. No. 7,168,468, both of which are incorporated by reference herein. In each of theses patents, the rim of the wheel is formed with internal passages that enable air to be selectively passed from a compressed air supply through the passages to a valve. The valve is selectively operable from within the passenger compartment or cab of the vehicle to enable air to flow through the valve and into the tire through the passages formed in the rim. The passages are formed in either the outer rim (as in the &#39;383 patent) or in the inner rim (as in the &#39;468 patent) and form a flow path from an inlet for the compressed air through the rim and the associated valve to an opening on the exterior surface of the rim component that is located between the opposed sides of the wheel formed by the inner and outer rim sections. This outlet is also located between the beads of a tire mounted to the wheel, such that air exiting the outlet is retained within the tire to increase the air pressure, i.e., inflate the tire as desired. 
         [0005]    Nevertheless, these prior art central tire inflation systems utilize passage designs that require the valves utilized therewith to have designs which require a number of additional components for the incorporation of the valves into tires for use with existing central tire inflation systems. These additional components greatly increase the cost and complexity of the valves, causing the valves to fail on a regular basis, necessitating that the valves be repaired and/or replaced on a consistent basis. 
         [0006]    Additionally, the configuration of the passages in the rim in the prior art systems requires that the valve be positioned in an abutting relationship with the passages on the exterior surface of the rim component, i.e., surface-mounted on the rim. This positioning for the valve on the exterior of the rim in an exposed location where the valve can easily be damaged by debris or other objects striking the valve when the vehicle is in operation. In most instances, a wheel cover is required to protect the valve and other ancillary components for the central tire inflation system, such as hoses and fittings. The wheel cover is formed of steel or a composite material, and can trap rocks within the cover when in use, turning the cover into a rock tumbler that enables the rocks to damage the valve and other components of the CTIS system on the wheel that the cover is meant to protect. 
         [0007]    As a result, it is desirable to develop a valve for use in a central tire inflation system that includes a minimum of parts and that can be incorporated into a number of different types of wheels. Also, it is desirable to develop a valve that can be positioned within a rim of a wheel incorporating a central tire inflation system that in a recessed or imbedded manner to effectively reduce the profile of the valve on the exterior of the wheel, thereby reducing the likelihood of the valve being struck and damaged during operation of the vehicle. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the present invention, a tire valve is provided that includes a simplified construction that can be seated directly within a tire wheel. The valve includes a main body that is positionable in a sealed configuration within an opening in the wheel rim in communication with the interior of the tire via passages formed within the rim. The body is also positioned within the opening in communication with a pressurized air source that is used to inflate or deflate the tire by passing air through the valve and along the passages to the tire. The main body encloses a valve mechanism that can be selectively operated in response to variations in the air pressure supplied to the valve, such that control of the operation of the valve can be remotely controlled via a controller connected to the pressurized air source. The positioning of the valve within the opening formed in the rim operates to reduce the profile of the valve that is positioned on the exterior of the wheel, to greatly reduce the chance of the valve being struck and damaged when the vehicle is in operation. 
         [0009]    According to another aspect of the present invention, the valve is releasably mounted in the opening, such that the valve can be removed from the opening and replaced without having to remove the wheel, or a component of the wheel from the vehicle. An anchor ring is secured around the valve on the exterior side of the rim, and serves to both protect the valve within the opening and to maintain the valve in position with regard to each of the passages within the wheel and the pressurized air inlet. The valve is releasably secured to the anchor ring, such that the valve can be removed from the rim and the anchor ring without disengaging the anchor ring from the rim, or having to remove the rim from the vehicle. 
         [0010]    According to another aspect of the present invention, the valve mechanism housed in the main body of the valve includes a minimum of moving parts to simplify the construction of the valve and to increase the longevity of the valve. These components are situated in a single, self-contained unit within the main body beneath a removable cap in a manner that also enables the valve mechanism to be easily removed, cleaned and/or replaced if necessary without having to remove the entire valve assembly from the wheel. 
         [0011]    Numerous other aspects, features and advantages of the present invention will be made apparent from the following detailed description taken together with the drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The drawings illustrate the best mode currently contemplated of practicing the present invention. 
           [0013]    In the drawings: 
           [0014]      FIG. 1  is an isometric view of a wheel assembly constructed according to the present invention; 
           [0015]      FIG. 2  is a front plan view of the wheel assembly of  FIG. 1 ; 
           [0016]      FIG. 3  is a cross-sectional view of the wheel assembly along line  3 - 3  of  FIG. 2 ; 
           [0017]      FIG. 3A  is a circular sectional view along line  3 A- 3 A of  FIG. 3  showing a first embodiment of a valve cartridge used in the wheel assembly of the present invention in the open position; 
           [0018]      FIG. 3B  is a circular sectional view along line  3 B- 3 B of  FIG. 3  showing the valve cartridge in a closed position: 
           [0019]      FIG. 4  is a cross-sectional view of a second embodiment of the valve cartridge utilized in the wheel assembly of  FIG. 1  in the closed position; 
           [0020]      FIG. 5  is a cross-sectional view of the valve cartridge of  FIG. 4  in the open position; 
           [0021]      FIG. 6  is an isometric view of the main body of the valve cartridge of  FIG. 4 ; 
           [0022]      FIG. 7  is a side plan view of the main body of  FIG. 6 ; 
           [0023]      FIG. 8  is a top plan view of the main body of  FIG. 6 ; 
           [0024]      FIG. 9  is an isometric view of an anchor ring utilized with the valve cartridge of  FIG. 4 ; 
           [0025]      FIG. 9A  is a cross-sectional view of a securing cup utilized with the valve cartridge of  FIG. 4 ; 
           [0026]      FIG. 9B  is an exploded, cross-sectional view of the securing cup and valve cartridge of  FIG. 9A ; 
           [0027]      FIG. 10  is a bottom isometric view of a valve seat used in the valve cartridge of  FIG. 4 ; 
           [0028]      FIG. 11  is a top isometric view of the valve seat of  FIG. 10 ; 
           [0029]      FIG. 12  is an isometric view of a disk screen used in the valve cartridge of  FIG. 4 ; 
           [0030]      FIG. 13  is an isometric view of a valve bushing of the valve cartridge of  FIG. 4 ; 
           [0031]      FIG. 14  is an isometric view of a cap used in the valve cartridge of  FIG. 4 ; 
           [0032]      FIG. 15  is a top isometric view of a piston used in the valve cartridge of  FIG. 4 ; 
           [0033]      FIG. 16  is a bottom isometric view of the piston of  FIG. 15 ; 
           [0034]      FIG. 17  is an isometric view of a ring screen used in the valve cartridge of  FIG. 4 ; 
           [0035]      FIG. 18  is an isometric view of a first embodiment of a valve stem utilized with the valve cartridge of  FIG. 4 ; 
           [0036]      FIG. 19  is an isometric view of a second embodiment of a valve stem utilized with the valve cartridge of  FIG. 4 ; 
           [0037]      FIG. 20  is an isometric view of a third embodiment of the valve stem utilized with the valve cartridge of  FIG. 4 ; and 
           [0038]      FIG. 21  is a cross-sectional view of the first embodiment of the valve cartridge in the closed position as shown in  FIG. 3B . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a wheel assembly  1000  including an inner rim member  10  and an outer rim member  24  is illustrated in  FIGS. 1-3B . The inner rim  10  includes a peripheral wall  12  adapted to support an inflatable tire  200  and an outer flange  14  at one end of the wall  12 . Opposite the outer flange  14 , the inner rim  10  includes a mounting wall  16  extending inwardly from the peripheral wall  12 . The mounting wall  16  defines a central opening  17  that receives a hub (not shown) and includes a number of first openings  18  spaced around the circumference of the mounting wall  16  adjacent the peripheral wall  12 , a number of second openings  19  spaced inwardly from the first openings  18  opposite the peripheral wall  12 , and a valve mounting opening  20  disposed between adjacent second openings  19 . 
         [0040]    Each of the first openings  18  receives a wheel stud  22  therein that extends through the mounting wall  16  for connecting the outer rim  24  to the inner rim  10 . The outer rim  24  and the outer flange  14  on the inner rim  12  define the outer edges of the wheel assembly  1000  within which opposed beads (not shown) of a tire (not shown) are mounted and retained. The second openings  19  are used to mount the wheel assembly  1000  on a number of hub bolts (not shown) that can secure the wheel assembly  1000  and tire to the hub (not shown) of a vehicle (not shown). 
         [0041]    The inner rim  12  also includes an air passage or channel  26  formed in the inner rim  10  that extends from the valve opening  20  through the peripheral wall  12 . The air channel  26  is formed in the inner rim  10  in any suitable manner, such as by drilling, and terminates in a groove  28  formed in the peripheral wall  12 , and that preferably extends radially inwardly from the channel  26  towards the center of the wall  12 . When the outer rim  24  is affixed to the inner rim  10 , the outer rim  24  is positioned over the air channel  26  and a portion of the groove  28  to define an air flow path between the valve opening  20  and the exterior of the peripheral wall  12 , over which the tire is positioned, thereby creating a path for introducing and removing air from the interior of the tire. 
         [0042]    Alternatively, the shape and direction of the groove  28  can be varied as desired, so long as the end of the groove  28  opposite the channel  26  is not completely obscured by the outer rim  24 . Additionally, the groove  28  can be omitted entirely, and the channel  26  can be formed to extend from the opening  20  to a point on the peripheral wall  12  below the outer rim  24  when the outer rim  24  is secured to the inner rim  10 . Also, the outer rim  24  can be formed in a manner that allows communication between the channel  26  and the tire when the wheel assembly  10  is completed, such as by forming the groove  28  in the outer rim  24 . Further, the inner rim  10  and the outer rim  24  can be formed as a single piece rim (not shown), eliminating the need for securing the sections to one another. 
         [0043]    Within the valve opening  20  is mounted a control valve cartridge  30  that is used to control the flow of air into and out of the tire  200 . By mounting the valve cartridge  30  within the opening  20  extending through the inner rim  10 , and located radially inwardly of the outer rim  24 , the valve  30  is protected from being damaged by objects stuck by and striking the inner rim  10  or outer rim  24 . This is because when the valve  30  is disposed within the opening  20 , a much smaller portion of the valve  30  is disposed on the exterior surface of the wheel assembly  1000 . Also, the positioning of the valve opening  20  adjacent to the first openings  18  and second openings  19  positions the wheel studs  22  and the hub mounting bolts close to the portion of the valve  30  outside of the opening  20 . The studs  22  and bolts are longer than the valve  30 , such that they prevent objects and debris from being able to move far enough into the wheel assembly  1000  to contact the valve  30 . 
         [0044]    Referring now to  FIGS. 4-20 , in one embodiment, the valve cartridge  30  includes a main body  32  that is positioned within and frictionally or sealingly engaged with the valve opening  20 . The main body  32 , as best shown in  FIGS. 4-8 , includes a lower end  34  and an upper end  36  connected to one another. The lower end  34  is preferably cylindrical in shape, and includes a number of air inlet shafts  38  extend through the lower end  34  that are aligned with one or more mating holes (not shown) in the wheel hub (not shown) to provide a connection to the pressurized air supply (not shown) used to inflate or deflate the tire  200 . The lower ends of the inlet shafts  38  are covered by disk screen  40  ( FIG. 12 ) engaged within the lower end of the main body  32 . Between the shafts  38  is disposed a central chamber  42 . The central chamber  42  has a wide upper portion  43   a , and a narrow lower portion  43   a  from which extend a number of air outlet shafts  44  which are positioned between and oriented perpendicular to the inlet shafts  38 . The outlet shafts  44  are surrounded on their outer ends on the exterior of the main body  32  by a cylindrical ring screen  46  ( FIG. 17 ) formed similarly to the disk screen  40 . Above and below the screen  46  on the exterior of the main body  32  are disposed channels  48  in which are located sealing members  50  to enable the main body  32  to frictionally and sealingly engage the circumference of the valve opening  20 , securely holding the valve  30  therein. 
         [0045]    The upper end  36  defines a central recess  52  that extends the entire length of the upper end  36 . Opposite the recess  52 , the exterior of the upper end  36  includes a screw thread  54 . To assist the sealing members  48  and  50  in securely holding the valve  30  within the valve opening  20 , an anchor plate or ring  56 , best shown in  FIGS. 4 ,  5 , and  9 , is threadedly engaged with the thread  54  on the upper end  36 . The anchor plate  56  includes a circular central part  58  that defines a central opening  60  having a threaded interior surface  62  matable with the thread  54 . Extending from the central-part  58 , and preferably from approximately opposite side of the central part  58 , are a pair of securing flanges  64  each having an aperture  66  defined therein. The apertures  66  can receive bolts (not shown) therein that secure the flanges  64  to the inner rim  10 , and the valve  30  within the opening  20 . 
         [0046]    As an alternative to the anchor ring  56 , especially for use in situations where the rim  10  is not sufficiently thick to enclose the valve cartridge  30 , a valve cup  300  is illustrated in  FIGS. 9A and 9B . The cup  300  is formed with an open upper end  302  and a closed lower end  304  between which extends a circular wall  306 . The circular wall  306  includes a lower section  310  and an upper section  308  separated by an annular shoulder  312 . The lower section  310  includes a number of apertures  314  formed therein that extend through the lower section  310  generally perpendicular to the wall  306 . The upper section  308  includes a threaded interior surface  316  that extends the length of the upper section  308 . A bottom wall  318  forming the closed lower end  304  includes an air inlet  320  that is in fluid communication with the interior  322  of the cup  300 . The air inlet  320  is positioned within a sleeve  324  that extends outwardly from the bottom wall  318  and includes a threaded exterior surface  326  extending the length of the sleeve  324 . 
         [0047]    The main body  32  of the valve cartridge  30  can be positioned within the cup  300  by inserting the lower end  34  into the lower section  310 , and threadedly engaging the upper section  36  with the interior surface  316  of the upper section  308 . The interior surface  316  allows the upper end  36  to be inserted into the cup  300  until the upper end  36  contacts the annular shoulder  312 . In this position, the upper end  36  of the main body  32  extends outwardly from the upper end  302  of the cup  300 , while the lower end  34  is spaced a short distance above the lower end  304 . Additionally, when the main body  32  is fully inserted within the cup  300 , the air outlet shafts  44  in the lower end  34  are generally aligned with the apertures  314  in the lower section  310 , and are sealed off from the upper end  302  and lower end  304  of the cup  300  by the sealing members  50  located within the channels  48  extending around the lower end  34 . Also, because the upper end  36  is positioned above the upper end  302  of the cup  300 , the cap  70  can be engaged with the main body  32  as discussed previously, to retain the various components of the valve cartridge  30  within the main body  32 . 
         [0048]    Either prior to or after insertion of the main body  32  within the cup  300 , the cup  300  can be secured to a wheel rim  10  such that the apertures  314  are positioned in alignment with the passage  26  to enable air passing through the valve cartridge  30  and out the outlet shafts  44  to enter the passage  26 . Also, the sleeve  324  within which the air inlet  320  is disposed is engageable with a threaded hub air outlet (not shown) to both securely engage the air inlet  320  for the cup  300  with the air outlet on the hub, and to provide added support to the cup and valve cartridge  30 . 
         [0049]    To hold the valve components of an interior valve mechanism  81  within the central recess  52 , a cap  70  is engageable with the thread  54  above the anchor plate  56 . As best shown in  FIGS. 4 ,  5  and  14 , the valve cap  70  is generally cylindrical in shape, having a top wall  72  from which downwardly extends a circular side wall  74 . The side wall  74  includes a threaded interior surface  76  that is engageable with the thread  54  on the upper end  36 . Immediately adjacent the top wall  72 , the side wall  74  includes a peripheral notch  78  that is co-linear with the threaded interior surface  76  and that encloses a sealing member  80  therein. Thus, when the cap  70  is engaged with the upper end  36  of the main body  32 , the sealing member  80  sealingly engages the upper end  36  above the thread  54  to provide and airtight sea between the upper end  36  and the cap  70 . Being threadedly engaged with the upper end  36 , the cap  70  is also removable from the main body  32  in order to clean or replace the interior components of the valve  30  without also removing the main body  32  from the valve opening  20 . This is due to the ability of the main body  32  to be secured within the valve opening  20  by either or both of the sealing members  48  and  50  and the anchor plate  56 , which are each located below the cap  70 . 
         [0050]    Turning now to  FIGS. 4 ,  5 ,  10  and  11 , the interior valve mechanism  81  includes a valve seat  82  is disposed within the central recess  52  of the upper end  36  of the main body  32 . The valve seat  82  includes a wide upper end  84  and a narrow lower end  86 . The narrow lower end  86  includes a number of air flow tubes  88  formed therein that extend from the exterior of the lower end  86  into fluid communication with a central opening  90  located in the center of the lower end  86 . The lower end  86  also includes an axially extending ring  92  at the lowermost end. The ring  92  provides an alignment and engagement point for the lower end  86  of the valve seat  82  to rest on and sealingly engage a sealing ring  94  located within the wide upper end  43   a  of the chamber  42  in the main body  32 . This engagement provides an airtight seal between the lower end  86  of the valve seat  82  and the main body  32 . 
         [0051]    The wide upper end  84  of the valve seat  82  defines an inner chamber  96  that is disposed concentrically with the central opening  90  in the lower end  86 . As best shown in  FIGS. 10 and 11 , on the exterior of the upper end  84  opposite the chamber  96  are formed a number of spaced air flow passages  98  that extend the entire length of the upper end  84  to allow air entering through the shafts  38  in the main body  32  to flow upwardly around the valve seat  82 . Immediately below the upper end  84  of the valve seat  82 , the passages  98  extend inwardly into fluid communication with the inner chamber  96  of the valve seat  82 . 
         [0052]    Inside the upper end  84  of the valve seat  82  adjacent the opening  90 , the chamber  96  defines a circular retaining wall  100  having an annular shoulder  102  defined therein. The retaining wall  100  and shoulder  102  are used to receive and engage a valve bushing  104 . As best shown in  FIGS. 4 ,  5  and  13 , the valve bushing  104  is generally cylindrical in shape and defines a central aperture  106  that, when bushing  104  is disposed on the shoulder  102  within the retaining wall  100 , is positioned concentrically with the chamber  96  and the opening  90  in the valve seat  82  as well as with the central chamber  42  in the lower end  34  of the main body  32 . A sealing member  108  is positioned between the bushing  104  and a peripheral flange  110  separating the opening  90  from the chamber  96  to provide an airtight seal between the bushing  104  and the upper end  86  of the valve seat  82 . 
         [0053]    Referring now to  FIGS. 4 ,  5 ,  15  and  16 , a valve piston  112  is disposed within the chamber  96  above the bushing  104 . The piston  112  is generally cylindrical in shape with a diameter slightly less than that of the interior of the chamber  96 , and including a peripheral recess  114  within which is disposed a sealing member  116 . The piston  112  is slidably movable within the chamber  96  and the sealing member  116  engages the chamber  96  in manner that provides an airtight seal between the piston  112  and the chamber  96  as the piston  112  moves within the chamber  96 . 
         [0054]    The piston  112  also includes a threaded bore  118  extending through the center of the piston  112  in a direction perpendicular to the recess  114 . The bore  118  is threadedly engaged with a threaded end  120  of a valve stem  122 , best shown in  FIGS. 4 ,  5  and  18 - 20 . The valve stem  122  extends from the threaded end  120  downwardly through the aperture  106  in the bushing  104 . Downwardly from the threaded end  120 , the stem  122  has a diameter slightly less than that of the aperture  106  in the bushing  104 , such that the busing  104  provides a guide for the movement of the valve stem  122  when moved as a result of the movement of the piston  112 . Below the bushing  104 , the stem  122  extends through the opening  90  and into the chamber  42 , where the stem  122  terminates with a radial stem flange  124  positioned below and in sealing engagement with the sealing flange  94  opposite the valve seat  82 . The stem flange  124  includes a number of tines  126  that extend outwardly from the flange  124  and are crimped or bent inwardly to grip one end of a spring  128 . The spring  128  is positioned between the stem flange  124  and the lowermost end of the central chamber  42 , such that the spring  128  urges the valve stem  122  and the piston  112  upwardly, to sealingly engage the flange  124  with the sealing flange  94 , and to position the piston  112  adjacent the upper end  84  of the valve seat  82 . The stem flange  124  can also include various spring-engaging features in different embodiments ( FIGS. 18-20 ) that enhance the ability of the flange  124  to stay in engagement with the spring  128 , such as outwardly extending or angled tabs  129 , a securing ring  130  extending downwardly from the flange  124  and having a diameter larger or smaller than that of the spring  128  for the spring  128  to seat therein or therearound, respectively, or a  130  ring including a slot (not shown) that receives and engages a part of the spring  128  to positively hold the flange  124  on the spring  128 . 
         [0055]    Looking now at  FIG. 4 , when the valve  30  is not in operation no air flow is passing through the valve  30 , such that the bias of the spring  128  urges the flange  124  against the sealing flange  94  to prevent any air flow from the inlet shafts  38  in the lower end  34  of the main body  32 , through the air tubes  88  in the lower end  86  of the valve seat  82  and past the sealing flange  94  into the air outlet shafts  44  in the lower end  43  of the main body  32  to the tire  200 . However, upon activation of the central tire inflation system to which the valve  30  is connected, a pressurized air flow is directed from the hub through the air inlet shafts  38  and along the air flow passages  98  in the valve seat  82  into the upper end  36  of the main body  32  above the piston  112 . The pressure of the air flow builds in the upper end  36  until the pressure overcomes the bias of the spring  128  and the air pressure in the tire  200  acting through the valve  30 . Normally, this pressure is selected to be approximately one-third of the pressure in the tire  200 , but the valve  30  can be set to operate at alternative pressures depending upon the particular use to which the valve  30  is put. Once the pressure in the upper end  36  reaches this point, the pressure presses downwardly on the piston  112 , causing the piston  112  and valve stem  122  to move downwardly with respect to the bushing  104 , valve seat  82  and main body  32 . Sufficient movement of the piston  112  due to the air pressure in the upper end  36  above the piston  112  disengages the stem flange  124  from the sealing flange  94 , allowing air to flow around the stem flange  124  and into the tire  200  through the air outlet shafts  44 , as shown in  FIG. 5 . Once the desired air pressure for the tire  200  has been reached and sensed by the central tire inflation system, the air flow to the valve  30  through the air inlet shafts  38  is stopped, allowing the spring  128  to re-engage the stem flange  124  with the sealing flange  94  and maintain the desired pressure in the tire  200 . The valve  30  may also include a suitable venting member (not shown) to enable the valve  30  to eliminate any backpressure in the valve  30  that occurs during the operation of the valve  30 . 
         [0056]    Referring now to  FIGS. 3A ,  3 B and  21 , another embodiment of the valve  230  is illustrated. The valve  230  is formed similarly to the valve  30  illustrated and discussed previously, with the same general configuration as the previous embodiment, including the main body  32 ′, the valve seat  82 ′ and the cap  70 ′. 
         [0057]    However, the valve seat  82 ′ is modified to eliminate the air flow passages  98  and to include a pair of sealing members  232  and  234  disposed on the exterior of the valve seat  82 ′ within grooves  236 . The sealing members  232  and  234  are preferably low friction seals and extend around the valve seat  82 ′ in the grooves  236  generally perpendicular to the longitudinal axis of the valve seat  82 ′ and function to provide an air-tight seal between the valve seat  82 ′ and the upper end  36 ′ of the main body  32 ′. Thus, no air flow occurs between the main body  32 ′ and the valve seat  82 ′ as in the previous embodiment. 
         [0058]    To provide the air flow to the top of the valve body  82 ′ that acts on the piston  112 ′, the valve stem  122 ′ is formed with an internal passage  238  that extends from the end of the stem  122 ′ located within the piston  112 ′ along the center of the stem  122 ′ to a point spaced from the stem flange  124 ′ an generally in at least partial alignment with the air flow tubes  88 ′ in the lower end of the valve seat  82 ′. At this point, the passage  238  communicates with a bore  240  extending into the stem  122 ′ generally perpendicular to the passage  238 , which allows air flow from the tubes  88 ′ to pass through the bore  240  and into the passage  238 . The air then flows up through the passage  238  to the upper end of the stem  122 ′ into the space between the piston  112 ′ and the cap  70 ′ to provide the motive force on the piston  112 ′. 
         [0059]    This air flow through the stem  122 ′ operates to move the piston  112 ′ against the bias of a spring  128 ′, as in the previous embodiment. However, the spring  128  has been moved from the central chamber  42 ′ in the lower end  34 ′ of the main body  32 ′. In this embodiment, the spring  128 ′ is disposed within the chamber  96 ′ of the valve seat  82 ′ between the lower end of the piston  112 ′ and the lower end  86 ′ of the valve seat  82 ′. The spring  128 ′ is positioned around the bushing  104 ′ and urges the piston  112 ′ towards the cap  70 ′. In this location, the spring  128 ′ is positioned within the valve  230  such that the spring  128 ′ can be removed with the other moving parts of the valve  230  disposed within the main body  32 ′ when the components are to be replaced. The removal of the spring  128 ′ from the lower end  34 ′ of the main body  32 ′ also allows for a greater amount of air flow through the lower end  34 ′, because the spring  128 ′ is no longer present to obstruct this air flow. 
         [0060]    In this embodiment, the stem flange  124 ′ on the valve stem  122 ′ is also modified to include an upwardly extending peripheral tab  242 , as opposed to the simple circular flange  124 ′ in the previous embodiment. This tab  242  is pulled into positive sealing engagement with the lower side of the seal  94 ′ by the spring  128 ′, and provides a secure air-tight seal until actuation of the valve  230 . 
         [0061]    Additionally, to address the problem of backpressure within the valve  30 ′, the upper end  36 ′ of the main body  32 ′ includes a bore  244  that is extends through the screw thread  54 ′ on the upper end  36 ′, but that is covered by the cap  70 ′ when the cap  70 ′ is engaged with the thread  54 ′. This bore  244  communicates with an aperture  246  formed in the upper end  86 ′ of the valve seat  82 ′ that communicates with the central chamber  96 ′ in the valve seat  82 ′ and functions as a vent to reduce any back pressure present within the valve  230  during operation, by allowing the pressurized air to escape the valve  230  through the clearance between the threads  54 ′ on the main body  32 ′ and  76 ′ on the cap  70 ′. 
         [0062]    In addition to the description of the previous embodiments, the wheel assembly  1000  and valve  30  of the present invention can also be modified in various manners to provide added functionality to the assembly  1000  and valve  30 . For example, the upper end  36  of the main body  32  and the upper end  86  of the valve seat  82  can be chamfered to enable the components of the valve  30  to be assembled and disassembled more easily. Also, the various structural components of the valve  30  can be formed from any suitable fluid-impervious material, such as a metal or hard plastic, to reduce the overall weight of the valve  30 . 
         [0063]    Various alternatives are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter regarded as the invention. 
         [0064]    We hereby claim: