Abstract:
A valve for substantially reducing emissions from a level gauge. A lower end of the valve fits in a first interior cavity of the level gauge, which is in gaseous communication with an emission limiting bore in the level gauge. A second internal cavity is defined in said valve body and a seat is disposed near the bottom of the second internal cavity. A bore of substantially reduced cross-sectional area is disposed in the lower end of the valve body and is in gaseous communication with the second internal cavity A thumbscrew opens and closes the valve at the seat. An orifice vents gas or liquid from the second internal cavity when the thumbscrew is off of the seat. A low emissions level gauge and related methods are also disclosed

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to level gauges, such as are used on vessels for containing pressurized gases or liquids 
         [0002]    More particularly, the present invention relates to an improved fixed liquid level gauge which substantially reduces emissions while refilling the vessel, and to an adapter for retrofitting existing level gauges to also substantially reduce emissions. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many vessels are suited for refilling when the gas or liquid within the tank is depleted. One such example is a propane tank. Fixed maximum liquid level gauges are currently used on propane tanks to assist in refilling of the tank, such as when the tank is refilled with a filling hose. Such gauges are employed to avoid overfilling of the tank. Typically, these liquid level gauges have a tube which extends downwardly into the tank to a predetermined, or to a fixed depth from the top of the tank. 
         [0004]    As the propane tank is being refilled, the liquid level within the tank rises until it comes into contact with the bottom end of the tube. When the liquid propane comes into contact with the bottom end of the tube, liquid propane is pushed up into the tube, through an emission limiting bore in the level gauge, and begins to discharge through a bleeder valve in the fixed liquid level gauge. As the liquid propane discharges through the bleeder valve portion of the gauge, a mist or cloud is formed, much like a cloud created by the melting of solid carbon dioxide. This indicates to the person filling the tank, that the tank is now full and that the filling process should be terminated. Thus, the fixed liquid level gauge is also a safety device that assists in preventing the overfilling of the tank. 
         [0005]    When the filling of the tank is completed, the bleeder valve portion of the fixed liquid level gauge should be closed or shut off to prevent further discharge and loss of the propane fuel However, this discharge of propane fuel during the filling process also emits propane into the air, thereby tending to increase the amount of pollution in the air Certain jurisdictions are particularly desirous of reducing any pollutants and have laws which limit the amount of pollutants which may be emitted into the atmosphere. 
         [0006]    There has therefore been a need for an improved fixed liquid level gauge that substantially reduces the amount of gas, such as propane, that is discharged while refilling the tank. 
         [0007]    A general object of the present invention is therefore to provide an improved fixed maximum liquid level gauge which substantially reduces the amount of gas discharged into the atmosphere while refilling of a tank. 
         [0008]    Another object of the present invention is to provide an adapter for a fixed maximum liquid level gauge that retrofits existing level gauges to also substantially reduce the amount of gas discharged into the atmosphere 
         [0009]    A further object of the present invention is to provide an improved low emission fixed maximum liquid level gauge which is economical to utilize on tanks 
         [0010]    Yet another object of the present invention is to provide an adapter or valve for a fixed maximum liquid level gauge which retrofits existing level gauges in an effective and economical manner to substantially reduce emissions. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to a valve for substantially reducing emissions from a level gauge. The valve fits into a level gauge which has a first interior cavity which is open when a thumbscrew is open from the level gauge. The first interior cavity of the level gauge is in gaseous communication with an emission limiting bore in the level gauge. The valve includes a valve body with a threaded lower end, the lower end adapted to fit into the interior cavity of the level gauge when the thumbscrew is removed from the valve body. A second internal cavity is defined in the valve body and a seating area disposed near the bottom of the second internal cavity. A bore is disposed in the lower end of the valve body; the bore in the valve body being of substantially reduced cross-sectional area compared to the emission limiting bore in the level gauge. This bore in the valve body provides gaseous communication between the lower end of the valve body and the second internal cavity. Means is provided for opening and closing the valve by permitting, or by not permitting, gaseous communication between the bore and the second internal cavity. An orifice extends between the second internal cavity and an exterior surface of the valve body to vent gas or liquid from the second internal cavity when the means for opening or closing the valve permits gaseous communication between the bore and the second internal cavity. 
         [0012]    The bore disposed in the lower end of the valve body preferably has a diameter of 0.025 inches, or less. The means for opening and closing the valve may comprise a thumbscrew. A seat may be disposed at the bottom of the second internal cavity and resilient means may be disposed on the bottom end of the thumbscrew to contact the seat when the thumbscrew is in a closed condition, thereby preventing gaseous communication between the second internal cavity and the bore. 
         [0013]    The present invention is also directed to methods for retrofitting a level gauge with a low emission valve to substantially reduce emissions from the level gauge. The method includes the steps of removing the thumbscrew from the level gauge, fitting a lower end of the valve into the interior cavity of the level gauge, defining a second internal cavity in the valve, disposing a seating area near the bottom of the second internal cavity, disposing a bore in the lower end of the valve with the bore being of substantially reduced cross-sectional area compared to an emission limiting bore in the level gauge, the bore in the valve body providing gaseous communication between the lower end of the valve body and the second internal cavity, providing means for opening and closing the valve by permitting, or by not permitting, gaseous communication between the bore and the second internal cavity, and extending an orifice between the second internal cavity and an exterior surface of the valve to vent gas or liquid from the second internal cavity when the means for opening or closing the valve permits gaseous communication between the bore and the second internal cavity. 
         [0014]    Further steps of the methods may include limiting the bore to a diameter of 0.025 inches, or less, providing a thumbscrew as the means for opening and closing the valve, disposing a seat at the bottom of the second internal cavity, and disposing resilient means on a bottom end of the thumbscrew to contact the seat when the thumbscrew is in a closed condition, thereby preventing gaseous communication between the second internal cavity and the bore. 
         [0015]    The present invention is further concerned with a level gauge for reducing emissions from a vessel, the level gauge includes a valve body with a threaded lower end, the lower end adapted to attach the level gauge to the vessel, a tube extending from the lower end of the level gauge into the vessel, the tube having a passageway extending therethrough, an internal cavity defined in the valve body, a seating area disposed near the bottom of the internal cavity, a bore disposed in the lower end of the valve body, the bore in the valve body being of substantially reduced cross-sectional area compared to the cross-sectional area of an emission limiting bore in the level gauge, the bore in the valve body providing gaseous communication between the emission limiting bore of the level gauge and the internal cavity, means for opening and closing the valve by permitting, or by not permitting, gaseous communication between the bore and the second internal cavity, and an orifice extending between the internal cavity and an exterior surface of the valve body to vent gas or liquid from the internal cavity when the means for opening or closing the valve permits gaseous communication between the bore and the second internal cavity 
         [0016]    Preferably, the diameter of the bore in the valve body is about 0.025 inches, or less The means for opening and closing the valve may be a thumbscrew A seat may be disposed at the bottom of the second internal cavity, and resilient means may be disposed on a bottom end of the thumbscrew to contact the seat when the thumbscrew is in a closed condition, thereby preventing gaseous communication between the second internal cavity and the bore. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention, together with its objects and the advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures, and in which: 
           [0018]      FIG. 1  is a perspective view illustrating a prior art fixed maximum liquid level gauge; 
           [0019]      FIG. 2  is an exploded perspective view of the prior art fixed maximum level gauge of FIG,  1 ; 
           [0020]      FIG. 3  is a cross-sectional view of the fixed maximum level gauge shown in  FIGS. 1 and 2 , with the cross-section taken along section lines  3 - 3  in  FIG. 1 ; 
           [0021]      FIG. 4  is a perspective view of a valve for the fixed maximum level gauge illustrated in  FIGS. 1-3  in accordance with the present invention; 
           [0022]      FIG. 5  is an exploded perspective view of the valve shown in  FIG. 4  in accordance with the present invention; 
           [0023]      FIG. 6  is a cross-sectional view of the valve shown in  FIGS. 4 and 5  in accordance with the present invention, with the cross-section taken along section lines  6 - 6  in  FIG. 4 ; 
           [0024]      FIG. 7  is a perspective view of the valve shown in  FIGS. 4-6  mounted in the fixed maximum level gauge of  FIGS. 1-3  to provide an improved low emission level gauge in accordance with the present invention; and 
           [0025]      FIG. 8  is a cross-sectional view of the low emission level gauge shown in  FIG. 7  in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    It will be understood that the invention may be embodied in other specific forms without departing from the spirit thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. 
         [0027]    With reference to the drawing Figures,  FIGS. 1-3  illustrate a prior art fixed maximum liquid level gauge, generally designated  100 . Level gauge  100  includes a valve body  102 , which may have a lower treaded portion  104  and an intermediate or upper hexagonal portion  106  for use with a tool to tighten the threaded portion when the level gauge  100  is to be installed on a gaseous or liquid vessel. 
         [0028]    Extending downwardly from the valve body  102  is a tube  108 . A distal end  110  of the tube  108  may be flared to a larger diameter, which provides for quicker filling of the tube  108  when the liquid in the associated vessel reaches the bottom of tube  109 . Tube  108  has a central passageway  112  extending generally axially through the tube, from the distal end  110  to the valve body  102 . The length of tube  108  may vary depending upon the application and the size of the vessel used with the level gauge  100 . For example, the length of tube  108  is generally sized such that the distal end will engage the fluid in the vessel when the vessel is about 80 percent full. For a typical 20 pound propane tank, tube  108  would be about 4 inches (about 10 cm) long. This provides expansion room in the unfilled portion of the tank for the liquid contained in the tank as the ambient temperature varies. 
         [0029]    In a manner known to the art, the level gauge  100  is installed on a gaseous or liquid vessel by inserting the tube  108  into the vessel until the threaded portion  104  of the valve body  102  contacts a corresponding female connector which is affixed to the vessel. Tube  108  then extends, usually downwardly, into the vessel That portion of valve body  102  above the treaded portion  104  is then outside of the vessel and may be utilized and monitored as further described below. 
         [0030]    As seen in  FIG. 3 , the lower end of valve body  102  has an axial bore  115  extending upwardly into the valve body. Bore  115  may be sized to receive the upper end of tube  108  therein, such as in an interference fit for retaining tube  108  in valve body  102 . Valve body  102  has an emission limiting bore  150 , which extends between the end of tube  108  and an interior cavity  154  in valve body  102 . Bore  150  is typically a number  54  drill size, which is equivalent to about 0.055 inches or about 1.8 mm. Bore  150  thus provides for gaseous and/or liquid communication between tube  108  and interior cavity  154 , but limits the amount of gas or liquid which may pass through the level gauge when the thumb screw  120  is in an open position. In the example of  FIG. 3 , a raised area about the upper end of bore  150  provides a seat  152  about the bore  150 . 
         [0031]    As best seen in  FIGS. 2 and 3 , the upper end of valve body  102  has threads  156  in the interior cavity for receiving complementary threads  124  about a shank portion  122  of a thumb screw  120 . For ease of use, thumb screw  120  may have a knurled outer surface  126 . A cylinder  130  of resilient or semi-resilient material is inserted into the bottom of thumb screw  120  such that cylinder  130  is disposed above the seat  152  when the thumb screw  120  is screwed into the interior cavity  154  of valve body  102 . 
         [0032]    Normally, thumb screw  102  is turned tight in valve body  102  such that the resilient material  130  at the bottom of the thumb screw is in contact with the seat  152  of valve body  102 , thereby preventing gaseous or liquid communication between tube  108  and the interior cavity  154 . However, during refilling of the vessel associated with level gauge  100 , the thumb screw  120  is backed off of the seat  152 , as shown in  FIG. 3 . Some gas or liquid, such as propane, is then discharged through tube  108 , through the emission limiting bore  150 , into interior cavity  154  and out of orifice  140  into the surrounding atmosphere. 
         [0033]    As the vessel is being filled, the propane is compressed at a pressure in which it assumes a liquid state. When the liquid propane reaches the distal end  110  of tube  108 , liquid propane is forced up tube  108 , up emission limiting bore  150 , and into interior cavity  154 , and out of orifice  140 , into the surrounding atmosphere. Many gases, including propane, are invisible. However, the immediate evaporation of the liquid propane into the atmosphere at the orifice  140  causes cooling of moisture in the atmosphere which forms a cloud near orifice  140 . This provides a visual indication to the person filling the vessel that the vessel is now filled to its recommended capacity. 
         [0034]    While the foregoing prior art level gauge  100  works well for its intended purpose, there are ever increasing concerns about the amount of pollution created by many sources, including the filling of propane tanks and the like, 
         [0035]    In accordance with one aspect of the present invention, a valve  400 , for retrofitting the prior art fixed maximum level gauge  100  of  FIGS. 1-3  to substantially reduce undesired emissions, is illustrated in  FIGS. 4-6 . Valve  400  includes a valve body  402 , which may have a treaded portion  404  at a lower end  411  and an intermediate or upper hexagonal portion  406 . 
         [0036]    As seen in  FIG. 6 , the lower end  411  of valve body  402  has an axial bore  462  extending upwardly into the valve body. Bore  462  may be suited to receive a plug  460  of resilient material therein. Preferably, plug  460  has a bore  464  extending axially through the plug. Bore  464  is preferably larger than bore  450  extending between plug  460  and the interior cavity  454  of valve body  402 . Bores  450  and  464  thus provide for gaseous and/or liquid communication between the bottom end  411  of valve  400  and its interior cavity  454 . A raised area about the upper end of bore  450  provides a seat  452  about the bore  450 . 
         [0037]    As mentioned above, valve body  402  has an intermediate bore  450 , which extends between the upper end of plug  460  and an interior cavity  454  in valve body  402 . Bore  450  is typically a number  72  drill size, or smaller, which is equivalent to about 0.025 inches or about 0.8 mm. It will be appreciated that the cross-sectional area of bore  450  is related to the square of the diameter. Thus, the area of bore  450  in valve  400  is about one-fifth of the cross-sectional area of the bore  150  of the prior art level gauge  100  in  FIG. 3 . This means that the amount of gas or liquid that will be released through valve  400  during refilling procedures will be five times less than the amount of gas that will be released through the prior art level gauge  100 . Bore  450  is therefore more restrictive to the passage of gas or liquid therethrough than bore  150 . Of course if the size of bore  450  in valve  400  is made even smaller than 0.8 mm, correspondingly less gas or liquid will be emitted by the valve  400  as compared to the level gauge  100 . In the example shown in  FIG. 6 , bore  464  in the resilient material of plug  460  is considerably larger than the bore  450 . However, the sizes of bores  450  and  464  could be reversed if desired. 
         [0038]    As best seen in  FIGS. 5 and 6 , the upper end  403  of valve body  402  has threads  456  in the interior cavity  454  for receiving complementary threads  424  about a shank portion  422  of a thumb screw  420 . For ease of use, thumb screw  420  may have a knurled outer surface  426  A cylinder  430  of resilient or semi-resilient material is inserted into the bottom of thumb screw  420  such that cylinder  430  is disposed above the seat  452  when the thumb screw  420  is screwed into the interior cavity  454  of valve body  402 . A lock nut  442  may be disposed on the threads  404  at the lower end  411  of valve  400 . 
         [0039]    Thus, when thumb screw  402  is turned tight in valve body  402 , as shown in  FIG. 6 , the resilient material  430  at the bottom of the thumb screw is in contact with the seat  452  of valve body  402 , thereby preventing gaseous or liquid communication between the bottom end  411  of valve  400  and the interior cavity  454 . However, during refilling of the vessel associated with valve  400 , the thumb screw  420  is backed off of the seat  452 . Some gas or liquid, such as propane, is then discharged through bore  464 , bore  450 , interior cavity  454  and orifice  440  into the surrounding atmosphere. 
         [0040]      FIGS. 7 and 8  illustrate the retrofitting of a prior art level gauge  100  shown in  FIGS. 1-3  with the valve  400  shown in  FIGS. 4-6 , to provide an improved low emission level gauge  700  in accordance with the present invention. When thumb screw  120  ( FIGS. 1-3 ) of level gauge  100  is removed, the lower end  411  of valve body  402  of valve  400  ( FIGS. 4-6 ) may be threaded into the inner cavity  154  of level gauge  100 . Valve body  402  is then effectively piggybacked onto valve body  102 . Locknut  442  may then be tightened against valve body  102  to firmly retain valve body  402  in valve body  102 . 
         [0041]    When valve body  402  is fully inserted into valve body  102 , resilient plug  460  comes to rest against the seat  152 , thereby preventing any gas or liquid in passageway  112  from escaping through orifice  140 . Instead, any gas or liquid in the level gauge  100  is now redirected through the significantly smaller bore  450  in valve body  402 . If thumbscrew  420  is away from seat  452 , as shown in  FIG. 8 , the gas or liquid will continue through bores  464  and  450 , into internal cavity  454  and then be released through orifice  440 . Thus, the smaller cross-sectional area of bore  450  in valve body  402 , than that of the emission limiting bore  150  in level gauge  100 , will substantially reduce the amount of gas or liquid released into the atmosphere at orifice  440 . 
         [0042]    It will be appreciated that, due to the fineness of bore  450 , that it may occasionally become blocked by dust or dirt carried by the gas or liquid. In such instances, the valve  400  may be removed from the level gauge  700 . Valve  400  may then be replaced by another valve. Replacement or reworking of valve  400  may, thus, be more economical than replacing the entire level gauge  700 . Of course, it may also be impractical and dangerous to remove the level gauge from the tank when the tank still has pressurized gas and/or liquid remaining in it. 
         [0043]    While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects,