Abstract:
An overfill prevention valve for mounting on the filling inlet of a liquid storage tank has an elongated, tubular valve body provided with an inlet at one end and one or more outlets in the sidewall thereof. A pressure-actuated piston is moveable between an open position spaced below an annular valve seat between the inlet and outlets and a closed position engaging the valve seat to close the outlet. An orifice in the top of the piston communicates with an actuating chamber on the opposite side of the piston so that a measure of piloting liquid flows into the chamber and out a pilot hole at the bottom of the valve body during normal filling operations. A buoyant float is slidable along a hollow guide tube attached to the bottom of valve body and communicates with the pilot port for closing a discharge hole in the guide tube when the float rises to an upwardly buoyed position due to the liquid in the tank reaching a predetermined maximum level. Such closure of the discharge hole causes the pressure within the chamber to rise, shifting the piston to its upper, closed position against the valve seat, thereby closing the outlets and terminating further flow into the tank.

Description:
TECHNICAL FIELD 
   This invention relates to liquid control devices and, more particularly, to a valve that can be installed at the filling inlet of a liquid storage tank, such as a shallow tank used to hold home heating oil or diesel fuel for backup generators, to prevent overfilling of the tank. 
   BACKGROUND 
   Fuel storage tanks of the foregoing type are typically filled from a tank truck by means of a hose that is coupled with an inlet pipe or fitting on the tank. Fuel from the truck is typically pumped into the tank at relatively substantial pressures. Although the pumps are typically operable to shift into a by-pass mode when the pump senses by back-pressure that the tank is full, it is often desirable to stop the fill cycle before the pump goes into by-pass. For example, in some instances the fuel may start spilling out a vent on the tank if the operator waits for the pump to stop the flow. At the same time, however, it is desirable to fill the tank as full as possible, for a number of reasons. 
   Various types of overfill preventing valves are known in the art. However, not all are readily installable through narrow fittings or inlet pipes on pre-existing tanks. Moreover, not all are simple, effective and reliable. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary vertical cross-sectional view through a liquid storage tank showing an overfill prevention valve in accordance with the present invention installed in an inlet opening in the top wall of the tank, the piston of the valve being shown in its open position; 
       FIG. 2  is a fragmentary cross-sectional view similar to  FIG. 1  but showing the piston in its closed position; 
       FIG. 3  is a fragmentary vertical cross-sectional view of the overfill prevention valve of  FIGS. 1 and 2  installed within a larger diameter inlet fitting of a liquid storage tank. 
   

   DETAILED DESCRIPTION 
   The present invention is susceptible of embodiment in many different forms. While the drawings illustrate and the specification describes certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments. 
     FIGS. 1 and 2  show a tank  10  having a top wall  12  in which is disposed an inlet opening  14  that provides access to the interior of tank  10 . Valve mounting structure broadly denoted by the numeral  16  comprises an annular flange  18  having an internally threaded bore  20  that is axially aligned with opening  14 . Flange  18  overlies wall  12  and is fixed thereto such as by welding. 
   An overfill prevention valve broadly denoted by the numeral  22  is supported by flange  18  and projects downwardly into the interior of tank  10  through opening  14 . Valve  22  includes an elongated, hollow valve body  24  having an inlet  26  at the upper end  28  thereof, at least one, and preferably four, outlets  30  in the sidewall of body  24  downstream from inlet  26 , an annular valve seat  32  between inlet  26  and outlets  30 , and a pair of diametrically opposed, transversely extending pilot ports  34  adjacent the lower end  36  of body  24 . An upper bore  35  extends axially from inlet  26  to seat  32  and tapers toward a reduced diameter as seat  32  is approached. A lower bore  37  of constant diameter extends axially from seat  32  to lower end  36  and is somewhat larger in diameter than upper bore  35  at seat  32 . 
   Lower end  36  of valve body  24  is closed by virtue of a plug  38  that is externally threaded so as to be threadably received by internal threads on the lower end of lower bore  37 . Plug  38  has a centrally disposed, cylindrical riser  40  spaced radially inwardly from adjacent wall portions of valve body  24  and having the pilot ports  34  located therein. 
   Riser  40  has an axially extending bore  42  that intersects transverse pilot ports  34  and extends downwardly therefrom through the bottom of plug  38 . The lower portion of bore  42  is internally threaded and securely receives the upper externally threaded end of a guide tube  44  projecting downwardly from plug  38 . Guide tube  44  defines an internal passage  46  communicating with bore  42  of riser  40 . A pair of diametrically opposed, transversely extending discharge holes  48  are provided in the sidewall of guide tube  44  at a location between the bottom of valve body  24  and the lower end of guide tube  44  in communication with passage  46 . 
   The lower end of guide tube  44  is closed by a threaded cap  50  which also serves as a lower limit stop for a cylindrical float  52  shiftably mounted on guide tube  44  for vertical movement along the latter between a lower position as illustrated in  FIG. 1  and a raised position as illustrated in  FIG. 2 . An upper limit stop  51  in the form of a press nut or tinnerman, for example, may be provided on guide tube  44  above holes  48  to engage the top of float  52  and limit its upward movement after holes  48  have been covered. Guide tube  44  and float  52  comprise further components of valve  22 . 
   Float  52  has an axially extending bore  54  extending the full length thereof through which guide tube  44  extends. Bore  54  is of sufficiently large diameter to permit float  52  to easily slip along the length of guide tube  44  between its two extreme positions. It will be noted that in the lower position of  FIG. 1 , float  52  uncovers and clears discharge holes  48 , while in the upwardly buoyed position of  FIG. 2 , float  52  covers discharge holes  48 . 
   Valve  22  further includes a hollow piston  56  that is shiftably received within lower bore  37  in sliding, sealing engagement with the internal sidewall surfaces thereof. Piston  56  has a conical nose  58  facing in the upstream direction and an annular skirt  60  integral with and extending downwardly from the lower extremity of nose cone  58 . The interior of piston  56  thus cooperates with the lower end  36  of valve body  24 , particularly plug  38  with its riser  40 , in defining an expandable actuating chamber  62  whose dimensions depend upon the vertical position of piston  56  within lower bore  37 . In this respect, it will be noted that piston  56  is shiftable vertically within lower bore  37  between an open position as illustrated in  FIG. 1  wherein the piston is spaced away from seat  32  and a closed position as illustrated in  FIG. 2  wherein the external surface of nose cone  58  makes sealing engagement with seat  32 . When piston  56  is in its open position of  FIG. 1 , outlets  30  are uncovered and in communication with inlet  26 , while when piston  56  is in its closed position of  FIG. 2 , outlets  30  are covered by skirt  60  of piston  56 , blocking communication between inlet  26  and outlets  30 . 
   Nose cone  58  is slightly truncated, presenting a flat, uppermost tip  64 . An orifice  66  located at tip  64  communicates upper bore  35  with chamber  62 . A buoyant ball  68 , preferably but not necessarily hollow, is located within actuating chamber  62  and normally rests upon a shallow dished recess  70  in the upper end of riser  40 . The diameter of ball  60  is such that it cannot escape from chamber  62  through the annular area defined between skirt  60  and riser  40 . However, ball  68  is free to move buoyantly between recess  70  as shown in  FIG. 1  and the bottom edge of orifice  66  as shown in  FIG. 2  to close orifice  66 . 
   The upper end  28  of valve body  24  projects upwardly through and beyond flange  18 . This provides a means by which an internally threaded coupling neck  72  may be threaded onto valve body  24 . Coupling neck  72  is adapted to receive a mating coupler on the end of a supply hose (not shown) from the tank truck and has an internal, axially extending bore  74  that communicates with inlet  26  of valve body  24 . 
   Pilot ports  34  are substantially smaller than orifice  66 , guide tube passage  46 , and discharge holes  48 . In one preferred embodiment, the combined cross-sectional area of pilot ports  34  is approximately ½ the cross-sectional area of orifice  66 , approximately ¼ the cross-sectional area of passage  46 , and approximately ¼ the combined cross-sectional area of discharge holes  48 . 
   Operation 
   Valve  22  is in the condition illustrated in  FIG. 1  just prior to the refilling of tank  10 . In this condition, piston  56  is in its open position spaced downwardly from valve seat  32 , ball  68  is resting upon the floor of recess  70 , and float  52  is in its lowered position uncovering discharge holes  48 . Thus, when a delivery hose is connected to coupling neck  72  and liquid is pumped under pressure through the hose and into neck  72 , the liquid is free to flow through valve body  24  and out outlets  30  into the interior of tank  10 . The sloping conical surface of nose cone  58  of piston  56  is helpful in directing the incoming liquid toward outlets  30  at this time. 
   As liquid is flowing through outlets  30  into the tank  10 , a piloting stream of liquid also passes through orifice  66  and into chamber  62 . However, such piloting liquid immediately leaves chamber  62  via pilot ports  34 , bore  42 , passage  46  in tubular member  44 , and discharge holes  48 . Thus, the pressure within chamber  62  is no higher than that of the main incoming flow through outlets  30 . Consequently, piston  56  remains in its open position of  FIG. 1 . 
   As the liquid level within tank  10  approaches a predetermined maximum, float  52  is progressively buoyed up along guide tube  44  until the maximum liquid level is reached, at which time float  52  will completely cover discharge holes  48  as illustrated in  FIG. 2 . Such covering of discharge holes  48  by float  52  causes the pressure to rise within chamber  62  until it becomes sufficient to overcome the opposing pressure of the inflowing liquid through outlets  30 . At that point, the increased pressure within chamber  62  causes piston  56  to rise up into sealing engagement with seat  32 , thereby effectively closing outlets  30  and preventing further inflow into tank  10 . If the pump on the tank truck is provided with a by-pass valve, the back pressure created within the hose when piston  56  closes outlets  30  triggers the pump to shift into its by-pass mode. When the operator detects that the pump is in its by-pass mode, he can then turn off the pump. 
   The buoyancy of ball  68  keeps it seated up against the bottom of orifice  66  when chamber  62  is filled with piloting liquid and piston  56  is in its closed position. This prevents the pressurized pilot liquid within chamber  62  from squirting upwardly through orifice  66  and relieving pressure within chamber  62  sufficiently to allow piston  56  to drop down to its opened position of  FIG. 1 . If piston  56  were to drop, chamber  62  would once again become filled with pressurized liquid from upper bore  35 , causing the piston  56  to then rise back into engagement with seat  32 , and then fall and rise again and again in repeated, undesirable cycling actions. 
   Once the operator turns off the pump at the tank truck, the pressure within upper bore  35  falls, although there is still a head of liquid within the supply hose, coupling neck and upper bore  35 . The piloting liquid within chamber  62  slowly bleeds out of that area via the discharge holes  48  and the clearance space between float  52  and the exterior of guide tube  44 . As this happens, piston  56  descends within valve body  24 , reopening outlets  30  and allowing the trapped head of liquid within the delivery line to drain therefrom into tank  10  until the line and all areas above valve  56  have been emptied. 
   Depending upon a number of factors, it may be desirable to have valve  22  shut off when the liquid level in tank  10  is lower than that illustrated in  FIG. 2 . For example, governing bodies in different parts of the country may have different standards as to the maximum percentage of the tank volume that can be filled with liquid. The shapes of tanks can vary significantly such that the same maximum fill percentage could result in a liquid level that is spaced further below the top wall  12  in one tank than in another differently shaped tank. In order to achieve lower shut off, the upper threaded end  28  of valve body  24  above outlets  30  could be lengthened so as to increase the overall length of valve body  24  without adversely affecting the relationship between piston  56  and outlets  30 . Another approach would be to lengthen guide tube  44  in the area above holes  48  so as to dispose float  52  deeper into the tank without adversely affecting the relationship between float  52  and outlets  48 . If the maximum liquid level in the tank can be higher than that illustrated in  FIG. 2 , the portion of tube  44  above holes  48  could be shortened and the stop  51  eliminated. The bottom of valve body  24  may or may not serve as the upper limit of travel of float  52  in that instance. 
   ALTERNATIVE EMBODIMENT 
   In the alternative embodiment of  FIG. 3 , overfill prevention valve  22  is installed within a tank  200  having an inlet opening  202  in top wall  204  that is substantially larger in diameter than inlet opening  14  of the first embodiment. Thus, while valve  22  in  FIG. 3  is identical to that previously described, the mounting structure  206  for supporting valve  22  on tank  200  is different. 
   In this regard, instead of a flange  18 , mounting structure  206  includes an upstanding tubular fitting  208  that overlies opening  202  and has a passage  210  in axial alignment therewith. Fitting  208  has an externally threaded upper end  212 . 
   Mounting structure  206  further includes a coupling neck  214  having an upright tubular portion  216  and an enlarged, annular skirt portion  218  fixed to the lower end of tubular portion  216  and projecting downwardly therefrom. Skirt portion  218  is internally threaded so as to threadably receive the externally threaded upper end  212  of fitting  208 . 
   Tubular portion  216  includes a smooth-walled, upper bore  220 , as well as a slightly enlarged, internally threaded lower bore  222 . The externally threaded upper end  28  of valve  22  is threadably received by bore  222  so as to support valve  22  in depending relationship from coupling neck  214 . 
   The valve body  24  is smaller in diameter than passage  210  within fitting  208 . Thus, coupling neck  214  supports valve  22  in such a way that body  24  thereof projects downwardly into passage  210  in radially spaced relation to the interior surface of fitting  208 . Consequently, an annular space  224  is defined within passage  210  between valve body  24  and fitting  208 . Guide tube  44  and float  52  project down through opening  202  and into the interior of tank  200 . 
   Valve  22  in  FIG. 3  in conjunction with the larger diameter hole  202  operates in the same manner as in the first embodiment with respect to the smaller opening  14 . However, it will be appreciated that with the arrangement of  FIG. 3 , liquid exiting through the outlets  30  enters the annular space  224  and passage  210  above the top wall  204  of tank  200  before gravitating through opening  202  and into the interior of the tank. This arrangement also enables the tank to be filled to a higher level than in the first embodiment inasmuch as valve  22  is supported in a higher position on tank  200 . Guide tube  44  and float  52  are still disposed within the interior of tank  200 , but the entirety of valve body  24  is located above opening  202 . 
   It is contemplated that in one commercial form of the invention, coupling neck  214  and valve  22  will be supplied as a preassembled unit. Such unit can then be simply threaded onto the fitting  208  of a preexisting tank  200 . 
   The inventor(s) hereby state(s) his/their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his/their invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.