Abstract:
An overflow protection device includes a valve body having an inlet conduit passing vertically therethrough. The inlet conduit includes an outlet end below a valve chamber. A valve within the valve chamber is movable between and open and closed position. A float is pivotally mounted below the valve and the float cams, an actuator upwardly when the float experiences a less than full tank and cams the actuation downwardly to permit the valve to move downwardly when the float rises to a predetermined level as it floats on the liquid within the tank.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an overflow protection device. Specifically relates to an overflow protection device for a pressurized gas tank. 
     Pressurized gas tanks are often used for containing liquid propane, but the present invention relates to tanks which may contain other gases that are under pressure to the point where they are in a liquid form. 
     Many of these gases expand substantially by volume for every 10° F. to which the tank is exposed. For example, liquid propane expands at approximately 1.5% by volume per 10° F. Propane tanks are designed so that when they contain the specified weight of propane at 60° F., approximately 20% by tank volume remains available for expansion of the liquid. The present invention is intended to ensure the tanks are not filled beyond this expansion space. 
     Overflow protection valves currently available and in widespread use do not necessarily ensure this protection. They often contain excessive numbers of operating and sealing components. Also they are often gas pressure operated and therefore performance depends upon pressures created by the fill equipment. Performance is also subject to false triggers where with rapid and fast start up of incoming gas the overflow protection valves accidentally shut down. Many overflow protection valves are of large diameters that interfere with the outage tube extending from the bottom of the main supply valve. 
     Therefore, a primary object of the present invention is the provision of an improved overflow protection valve and method for operating same. 
     A further object of the present invention is the provision of an overflow protection device that utilizes a simple ball/seat design, thereby eliminating gas driven pistons. 
     A further object of the present invention is the provision of a valve that eliminates the use of elastomeric components which often become damaged or corroded as a result of exposure to certain gases. 
     A further object of the present invention is the elimination of springs used in prior overflow protection devices. 
     A further object of the present invention is the provision of an improved overflow protection device which eliminates the elastomeric seals that often can be contaminated with oils, rust and water found within the propane that quickly degrade the seal integrity and thereby cause a loss of pressure or high co-efficient of friction between the seal and the cylinder. 
     A further object of the present invention is the provision of an improved overflow protection device that eliminates gas driven pistons that impede the flow of incoming liquid, but to do so require a central gas port to direct energy under the piston for its moving power. 
     A further object of the present invention is the elimination of gas pressure ports used to port vacuum or pressure to the usable side of a piston. Usually these ports are in the 0.050 to the 0.060 diameter range and are subject to plugging by rust and other particulate matter naturally present in propane. 
     A further object of the present invention is the provision of a reduction in the diameter of the valve, thereby eliminating interference normally encountered with the main supply valves outage tube. 
     A further object of the present invention is the provision of a ball retainer that serves three distinct functions: 1) It prevents the ball from elevating during gas discharge and blocking or impeding the flow of gas through the inlet and vapor port. 2) The legs of the ball retainer provide a cage to control the ball axially above the seat and in approximate vertical alignment with the ball lift pin thereby reducing side loading on the lift pin. 3) A convex top directs incoming liquid around the ball reducing the frictional loading on the ball and subsequently on the operating mechanism. There are four ribs that provide space for incoming liquid to pass around the retainer and which prevent the expansion of the incoming liquid to vapor until after the liquid is below the center line of the ball. This results in lowered pressure below the ball, and when the ball is free to move downwardly it will do so in response to this pressure differential. 
     A further object of the present invention is the positioning of the exhaust ports as high as possible in the tank so as to prevent liquid propane from entering the ports during appliance use of the propane within the tank, particularly when the tank is exposed to high temperature. 
     A further object of the present invention is the provision of a lower body design that incorporates exhaust ports that are oriented at 90° to the float arm&#39;s operating plane, thereby directing the incoming propane away from the float. 
     A further object of the present invention is the provision of a ball/seat arrangement that in concert provide a valve that operates at all pressures, especially those in very low pressure ranges. 
     A further object of the present invention is the provision of a valve that upon failure permits the valve ball to naturally fall into the seat, thereby preventing fill and requiring service. 
     A further object of the present invention is the provision of a valve that provides extremely high flow rates of both vapor and gas in both directions. 
     A further object of the present invention is the provision of an improved valve that is economical to manufacture, durable in use, and efficient in operation. 
     SUMMARY OF THE INVENTION 
     The foregoing objects may be achieved with an overflow protection device that includes a valve body having a gas conduit extending through the valve body. The gas conduit comprises a conduit inlet opening for introducing pressurized gas, a conduit outlet opening for permitting the pressurized gas to exit, and a valve chamber between the conduit inlet opening and the conduit outlet opening. A valve is within the valve opening and is mounted for movement from a closed position preventing pressurized gas from passing from the conduit inlet opening to the conduit outlet opening to an open position permitting pressurized gas to pass from conduit inlet opening to the conduit outlet opening. The valve is biased to the closed position by the pressure of the pressurized gas from the conduit inlet opening. A float is movably mounted to the valve body. A cam is associated with the float and is movable in response to the movement of the float between a full position and a less than full position. An actuator is mounted for movement within the valve body and is in engagement with the cam. The actuator is movable in response to the movement of the float to the less than full position to engage the valve and hold the valve in the open position. The actuator is movable in response to movement of the float to the full position to withdrawn from the valve and permit the valve to move to the closed position. 
     According to another feature of the present invention, a valve retainer is positioned between the valve and the conduit inlet opening of the valve body. 
     According to a further feature of the present invention, the valve retainer includes a valve cavity partially surrounding the valve. 
     According to another feature of the present invention, the valve includes four sides surround the valve cavity. A first two of the four sides are adjacent one another and have a first length. A second two of the four sides are adjacent one another and have a second length less than the first length, so as to imbalance the pressure on the ball and bias it to its closed position when the actuator is withdrawn. 
     According to another feature of the present invention, at least one of the first two of the four sides includes a lower edge having a notch formed therein. 
     According to another feature of the present invention, the valve cavity is partially spherical in shape and the valve is a ball. 
     According to another feature of the present invention, the actuator comprises a pin and the valve body includes a pin bore loosely housing the pin. A pin includes an upper end within at least a portion of the conduit between the valve and the conduit outlet opening. 
     According to another feature of the present invention, the float and the cam are rigid with respect to one another so that the cam moves in unison with the float. 
     According to another feature of the present invention, the cam includes a first cam surface engaging the actuator during the time that the actuator holds the valve in an open position and includes a second cam surface engaging the actuator during the time that the actuator permits the valve to move to its closed position. 
     While the above invention may be utilized in combination with a pressurized gas tank for any of a plurality of gases, the preferred form of the invention is for use with a propane gas tank. 
     The foregoing objects may be achieved by the method of the present invention by connecting a valve body within the gas chamber to the gas inlet opening. The valve body includes a conduit comprising a conduit inlet end in communication with the gas inlet opening, a conduit outlet opening for introducing pressurized gas into the gas chamber, and a valve chamber between the inlet opening and the outlet opening. 
     The method further comprises positioning a valve in the valve chamber, the valve being movable from an open position permitting the pressurized gas to flow from the conduit inlet opening through the conduit outlet opening to a closed position preventing the pressurized gas from flowing from the conduit inlet opening to the conduit outlet opening. A float is mounted to the valve body for movement from a less than full position to a full position, the float having a cam surface thereon. An actuator is engaged with the cam surface. The actuator has a first end engaging the cam surface and a second end positioned adjacent the valve. The method includes moving the actuator to engage the valve and hold the valve in the open position in response to movement of the float and the cam to the less than full position. 
     The method further comprises moving the actuator to withdraw from engagement with the valve so as to permit the valve to move to the closed position in response to movement of the float and cam to the full position. The valve is biased to its closed position. However, the valve is always free to move to its open position by being pushed upwardly out of the way of discharging gas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a pressurized gas tank showing the overflow protection valve mounted therein. 
     FIG. 2 is an exploded perspective view of the overflow protection device of the present invention. 
     FIG. 3 is a sectional view showing the overflow protection device in its less than full position. 
     FIG. 4 is a sectional view similar to FIG. 3, but showing the overflow protection device in its full position. 
     FIG. 5 is a perspective view of the unique retainer utilized with the present invention. 
     FIG. 6 is a perspective view of the retainer showing the bottom of the retainer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the numeral  10  generally designates a pressurized fluid tank having a gas chamber  12  therein. A main supply valve  14  of conventional construction is mounted within a tank gas inlet opening  16  to provide communication from the exterior to the gas chamber  12 . The main supply valve  14  includes an inlet  13  adapted to be mounted to a source of pressurized gas, an outlet  15  adapted to be mounted to an overflow protection device  18 , and a hand valve  19  which may be moved to an open or closed position as desired. The overflow protection device  18  includes a valve body  20 , a float  22  having a float arm  24  thereon and a cam  26  at the opposite end of the float arm from the float. The float, float arm, and cam are pivotally mounted to the valve body  20  for pivotal movement about axis  28 . 
     Referring to FIGS. 2-4, the valve body  20  includes a first lower flange  30  and a second lower flange  32  which are spaced apart from one another to form a cam slot  34 . The cam  26  is adapted to be fitted within the slot  34  and mounted therein for pivotal movement about the axis  28  provided by the pin shown in FIG.  2 . The cam  26  includes a cam surface  36  which comprises a concentric portion  38  that is concentric to the pivotal axis  28 , and a notch portion  40 . At opposite ends of the cam surface  36  are two cam tabs  42 ,  44 . 
     As shown in FIGS. 3 and 4, the valve body  20  includes a central vertical pin bore  46  therein. A valve body cap  48  is operatively secured over the valve body  20  by press fitting, welding, or the like. 
     A conduit  50  extends centrally downwardly through the valve cap  48  and the valve body  20  and includes a conduit inlet  52 , a conduit outlet  54 , and a valve chamber  56  between the conduit inlet  52  and the conduit outlet  54 . As can be seen in FIGS. 3 and 4, the conduit outlets  54  comprise radial bores that communicate with the central bore provided by conduit  50 . For purposes of illustration conduit outlets  54  are shown perpendicular to the axis  28  of float arm  24 . However, it is preferred that conduit outlets  54  extend parallel to axis  28  to avoid engagement of the gas and/or liquid exiting therefrom with the float arm  24 . 
     A cone shaped valve seat  58  is provided within the valve chamber  56  and a valve ball  60  is adapted to move from an unseated position shown in FIG. 3 to a seated position shown in FIG. 4 which engages the cone shaped valve seat  58  and prevents fluid from passing to the conduit outlets  54 . 
     A retainer  62  is shown in partial surrounding relationship over the valve ball  60 . Retainer  62  includes four corner posts  64  (FIGS. 5 and 6) which are in communication with angled ridges  66  at the upper end of the retainer  62 . The angled ridges terminate in pointed upper ends  68  which are positioned slightly above a retainer top  70 . The retainer  62  includes two adjacent long side walls  72  and two adjacent short side walls  74 . A notch  76  is provided in one of the long side walls  74 . The retainer also includes a partial spherical cavity  78 . The reason for the two short side walls is to expose the ball to unequal pressure from the propane being entered into the valve chamber  56 , thereby preventing the ball  60  from becoming stuck or lodged within the cavity  78 . 
     The retainer  62  is fixed within the upper cone shaped portion of valve cavity  56 . Ribs  64 ,  66  create a space between the walls of valve cavity  56  and the retainer  62 . The sum of this space approximates the cross section of conduit inlet  52  so as to prevent the expansion of the liquid into gas until after the liquid is below the center of the ball. Changing of the liquid to a gas below the center of the ball creates a bias of the ball in a downward direction as a result of the unequal pressure between the liquid above the ball and the gas below the ball. This bias urges the ball downwardly without need of springs and permits its downward movement when an actuator  80  moves downwardly. 
     An actuator pin  80  is mounted for vertical sliding movement within the pin bore  46 . The actuator pin includes an upper end  82  which is slidably mounted within the conduit  50  and which engages the ball  60  when in its upper position shown in FIG.  3 . The lower end  84  of pin  80  is in frictional contact with the cam surface  36  of cam  26 . 
     In operation, the float  22  is in its lowermost position when the propane tank  10  is empty. In this position which is shown in FIG. 3, the concentric cam surface  38  engages the lower end  84  of pin  80  and forces the pin  80  upwardly so that the upper end of the pin  80  engages the ball  60 . This lifts the ball upwardly out of engagement with the seat provided by the cone shaped valve seat  58 . This permits the propane fluid under pressure to pass around the retainer  62  and the ball  60  and downwardly and outwardly through the conduit outlets  54  at the bottom of conduit  50 . As the tank fills the float engages the upper surface of the liquid therein and begins floating upwardly. When the liquid reaches a predetermined height, the float  22  has pivoted from the position shown in FIG. 3 to the position shown in FIG.  4 . In this position, the notch portion  40  of the cam surface  36  has moved adjacent the pin  80 , and the pin  80  is permitted to drop downwardly so as to permit the valve  60  to drop downwardly in response to gravity and also in response to the pressure from the propane being submitted into the valve chamber  56 . Valve  60  is biased downwardly by the imbalance of the liquid pressure above ball  60  and the expanded gas pressure below ball valve  60 . When the ball  60  seats against the cone shaped seat  58 , fluid can no longer pass from the inlet portion  52  of conduit  50  to the outlet conduits  54  of the conduit  50 . This prevents pressurized fluid from over filling the tank  10 . Preferably, the float  22  is set in such a manner that when the fluid within the tank  10  reaches approximately 80% of full, the ball  60  is permitted to seat against the cone shaped valve seat  58  as shown in FIG.  4 . 
     The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.