Patent Publication Number: US-6901944-B2

Title: Fluid control apparatus

Description:
FIELD OF THE INVENTION 
   This invention relates to fluid control devices. More particularly although not exclusively it discloses an improved pressure cutoff valve for vehicle tyres. 
   BACKGROUND TO THE INVENTION 
   Correct pressure in vehicle tyres is of considerable importance. Excessive pressure can cause premature tread wear and loss of traction in the wet. Low pressure on the other hand can cause loss of stability when cornering and tyre failure from excessive wall flexing. While most service stations provide facilities for drivers to check their tyres the gauges are often defective or at best inaccurate. In order to alleviate such problems valves have been proposed for tyres which during filling automatically cut off the air supply once a preset pressure is reached. The user therefore does not need to be concerned about monitoring tyre pressure during filling. Rather it is only necessary to maintain the air hose fitting on the tyre valve until it automatically cuts off. These valves typically use a piston which is biased to an open position by a compression spring during filling but is moved against said bias to a closed position when an applied force from the internal tyre pressure reaches a preset amount of say 200 kpa. Existing valves have the disadvantage however that the compression spring and piston are located in the base of the valve assembly which is therefore enlarged and protrudes a substantial distance through into the interior of the tyre rim. This obstructs the fitting of the tyre and can result in the base of the valve housing being damaged during initial inflation as the tyre bead expands onto the rim. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of this invention to ameliorate the aforementioned disadvantage and accordingly a apparatus for regulating air flow into a rim mounted pneumatic vehicle tyre is disclosed, said apparatus having an elongated valve housing with an inlet end, an outlet end and a central portion, the outlet end including a rim insertion portion configured to fit into an aperture in the tyre rim, a piston disposed within said housing and including a valve member, a coil spring acting between said housing and piston whereby in use of said apparatus the piston is biased to an open position for passage of air into said tyre and is movable against said bias under force of air pressure build-up in said tyre to a closed position at which the valve member seals against a valve seat to close off said passage of air wherein the spring acts in tension and said piston is located within said central portion of the housing clear of the rim insertion portion so that said rim insertion portion is of a reduced size not to obstruct the mounting of said tyre. 
   Preferably said piston is fitted with a visual indicator to show position. 
   It is further preferred that the valve housing be fitted with a schrader type one way valve at the inlet end. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The currently preferred embodiment of this invention will now be described with reference to the attached drawings in which: 
       FIG. 1  is a perspective side view of an automobile tyre valve according to the invention, 
       FIG. 2  is a vertical cross-sectional of the valve of  FIG. 1  when in the open position, and 
       FIG. 3  is a cross-sectional view along the lines A—A of  FIG. 1 , 
       FIG. 4  is a cross-sectional view similar to  FIG. 2  but with the valve in the closed position, and 
       FIG. 5  is a cross-sectional view of a spring tension adjustment plug which can be fitted to the valve of FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIGS. 1 and 2  the valve housing  1  may comprise an elongated cylindrical casing with an inlet  1 A at the top as shown and an outlet  2  at the bottom. The outlet end of the housing preferably comprise an insertion sleeve  3  with a groove  4  and shoulder  5  which adapt said sleeve for fitting through an aperture in a pneumatic tyre rim  5 A. Preferably the outlet end is moulded from rubber or other suitable material to obtain the necessary pressure tight seat to the rim. At the inlet end  1 A there is a short pipe section  6  of reduced diameter to connect with an air supply hose nozzle such as that provided at service stations. Immediately below this is a transparent cap  7  through which the position of an internal indicator band can be viewed as described later. 
   Referring more specifically to  FIGS. 2 and 3  there is a piston  8  which is longitudinally slidable between the housing cylinder wall  9  and a central tube  10 . The tube  10  is part of a sub-assembly which includes the pipe  6  with a schrader type inlet valve  11  of known construction. This sub-assembly is threaded into or otherwise rigidly connected to the housing at  12 . The transparent cap  7  also fits onto the housing at this location and provides a view window between the top of said housing  12 A and the pipe  6 . As the pipe  6  and housing are fixed relative to one another this cap  7  takes no load and can therefore be of nonstructural material such as a low cost plastic. There are O-rings  13 ,  14  fitted to provide a sliding pressure tight fit between both the outside of piston  8  and cylinder  9  as well as the internal piston bore  15  and tube  10 . Preferably a directional low friction cup seal  16  may also be fitted into a nich  17  in the piston immediately below O-ring  13  to further ensure against air leakage between the piston and cylinder. The piston  8  at its upper end mounts the indicator band  18  and towards the lower end the bore  15  is fitted with a valve member having a bevelled head  19  and upwardly directed needle  20 . The needle extends up through a seat  21  formed at the base of tube  10 . The seat is shaped to form a pressure tight seal when engaged by the bevelled head  19  of the valve member. There is also a tension spring  22  which acts between a transverse pin  23  located across the housing just above the insertion sleeve and the centre  24  of the piston. Preferably the spring at one end hooks over pin  23  and at the other end seats in spiral grooves around the centre of the piston. In  FIG. 2  the piston is held to its lowermost position where the band  18  abuts the top of the housing. In accordance with this invention it will be noted that the tension spring  22  and piston  8  move within the centre portion of the housing above the insertion sleeve  3 . This allows the rim insertion sleeve at the outlet end to be greatly reduced in diameter and length. It therefore provides virtually no obstruction to the tyre bead during initial mounting and inflation of said tyre on the rim. The moulded rubber construction of the insertion sleeve with the current embodiment also allows the housing  1  to flex relative to the tyre rim to reduce the chances of breakage. 
   In the open position of  FIG. 2  a supply of pressurised air is able to flow through the inlet schrader valve  11 , down through tube  10 , around open valve member  19 , through ports  26 , along clearance space  27  between the spring  22  and housing to enter the tyre (not shown) through outlet  2 . As the pressure inside the tyre builds up however a force (arrow B) acts against the underside of the piston moving it upward. At a preset cutoff pressure of say 200 kpa determined by the underside area of the piston  8 , the deflection constant of the spring  22  and the position of valve seat  21  the upward displacement of the piston  8  causes the valve head  19  to close into said seat as shown in FIG.  4 . This cuts off further air flow into the tyre. It will also be noted from  FIG. 4  that the band  18  simultaneously moves upward within transparent cap  7  to indicate that the preset pressure has been reached in the tyre and the cutoff valve  19  is closed. If tyre pressure subsequently falls below this preset pressure the piston and indicator band  18  move downwardly under the tension force of spring  22  to show low pressure and the valve  19  opens in preparation for filling. Leakage of air out of the tyre however is prevented by the one way operation of the schrader valve  11  which only allows discharge through deliberate depression of insert stem  28 . 
   As an alternative to the fixed transverse pin  23  for holding the lower end of the spring  22  a threaded anchor plug  29  as shown in cross-section by  FIG. 5  may be turned into the housing at the same location. This plug has an upstanding pin  30  with a circumferential groove  31 . The lower end of the spring is then shaped to seat in this groove so that rotation of the plug using an allen key or the Like on socket  32  adjusts the spring tension and thus the cutoff pressure of the valve. A series of apertures  33  around the periphery of the plug allows air to pass through to the outlet  2 . 
   It will thus be appreciated that this invention at least in the form of the embodiment disclosed provides a novel and useful improvement to vehicle tyre valves. Clearly however the example described is only the currently preferred form of the invention and a wide variety of modifications may be made which would be apparent to a person skilled in the art. For example the shape and configuration of the transparent cap and the preset cutoff pressure may be changed according to application. Also while it is currently preferred to construct the valve and housing from a corrosion resistant metal such as brass the invention extends to the use of any other suitable material. 
   For the purposes of this specification expressions such as “top”, “bottom”, “below”, “upper” and “lower” etc refer to the valve housing in one position of use as illustrated are are not to be taken as necessarily limiting.