Fluid transport containers and control means therefor

Abstract

 A fluid transport container 1 has a foot valve (2) and an outlet valve (3) connected through a conduit (4). In order to prevent a shock being generated in the conduit (4) when the outlet valve (3) is closed during discharge of fluid, control means are provided to ensure that the foot valve (2) is closed with the outlet valve (3). The control means allows the foot valve (2) to re-open shortly thereafter to permit an accurate dipstick reading to be taken.

Description

[0001] This invention relates to fluid transport containers, such as containers forming part of or carried by road and rail tankers, and to control means therefor.

[0002] Fluid containers of e.g. road tankers are often provided with a so-called foot valve located in a lower region of the container through which fluid may be discharged from the container during unloading and by means of which a container may be filled with fluid by bottom loading under pressure. After bottom loading has been carried out, it is usual to join the foot valve to a further, outlet valve of the container via a conduit extending to an accessible position usually to one side of the container, the outlet valve being adapted to be coupled to a delivery hose leading e.g. to a garage storage tank.

[0003] In such containers it is normal to measure the quantity of fluid to be discharged from the container by means of a dipstick inserted through an aperture in the roof of the container, the dipstick being calibrated so that the volume of liquid in the container can be directly read from the wetting level on the dipstick. However, it is traditional that the dipstick be calibrated to indicate the total volume of fluid inclusive of the fluid contained in the conduit between the foot valve and outlet valve of the container, and therefore a dipstick reading is taken at such time when the foot valve is open.

[0004] However, if it is desired to take a dipstick reading after only a part of the contents of the container has been discharged, e.g. if a customer does not require the entire contents of a container, this arrangement suffers from the disadvantage that when the outlet valve is closed against the flow of discharging fluid, which may be as much as 1000 litres per minute, a substantial shock is generated in the conduit. When the outlet valve is closed there is a transient pressure of the order of 300psi in the condult. Not only does this generate a lot of noise but in the long run is likely to damage the conduit which is designed to operate at normal pressures of up to about 70 psi.

[0005] Viewed from a first aspect the invention provides a fluid transport container comprising a foot valve arranged in a lower part of the container and connected or connectable to an outlet valve via a conduit, and control means for opening and closing said valves, said control means being adapted to close the foot valve at substantially the same time as the outlet valve is closed and to open the foot valve shortly thereafter.

[0006] By means of this arrangement, at least in its preferred forms, the generation of a substantial shock upon closure of the outlet valve is prevented since by closure of the foot valve the fluid in the conduit is no longer under pressure. Since the foot valve is reopened shortly afterwards, a dipstick reading of the amount of fluid remaining in the container can readily be taken.

[0007] In a particularly preferred embodiment the control means is responsive to back pressure generated at the outlet valve when closure of the outlet valve is initiated. Preferably the foot valve is opened in response to a pneumatic, hydraulic or electrical signal and the back pressure generated at the outlet valve is used to switch off this opening signal. In particularly preferred embodiments the foot valve is opened by a hydraulic or pneumatic signal and the back pressure is used to switch a valve to shut off this hydraulic or pneumatic signal.

[0008] Preferably the reset period, that is the time after which the foot valve is reopened, can be adjusted to any desired length.

[0009] An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:-

Fig. 1 is a schematic transverse cross-section through one compartment of a fluid container of a road tanker,

Fig. 2 is a schematic side elevation (partly in section) illustrating an outlet valve coupled to a delivery hose, and

Fig. 3 shows a detail of the outlet valve shown in Fig. 2.

[0010] Referring first to Figure l, a fluid container 1 includes a foot valve 2 connected to an outlet valve 3 via a conduit 4, the outlet valve 3 being adapted to be coupled to a delivery hose 5 e.g. on a garage forecourt. The container also includes a vent valve 6 and a dip tube 7 adapted to receive a dipstick (not shown).

[0011] The valves 2, 3 and 6 are all pneumatically operable, and are opened in response to a pneumatic signal applied via a control unit 8. The control unit includes pneumatic switches numbered one to seven for each of the compartments of the tanker, the other compartments being fitted with the same components as the illustrated one. Pneumatically operable valves are known in the art and typically comprise actuating means in the form of a piston and cylinder coupled to the valve closure means.

[0012] The illustrated container also includes a dipstick locking means 9 which is described in detail in British patent application no. 8624531. The dipstick locking means is also controlled by the control unit 8 in such a way that the dipstick is not released unless the foot valve 2 is open.

[0013] The pneumatic circuitry connecting the valves 2, 3 and 6 and the locking means 9 to the control unit 8 is illustrated schematically in Figure 1. Thus, the vent valve, foot valve and dipstick locking means are connected in series to a pneumatic switch of the control unit which in turn is connected to a pneumatic gas pressure source (not shown). The outlet valve, which may comprise a known so-­called API valve is also connectable in series with the vent valve and foot valve. In the "dip" configuration the operator actuates the switch so as to connect the vent valve, foot valve and dipstick locking means in series to the pressure source, so that the two valves open sequentially and only then is the dipstick locking means released. As discussed in British patent application 8624531, this ensures that a dip reading cannot be taken without both the vent valve and foot valve being open and thus the conduit 4 connecting the valves 2 and 3 being full of product. In the "dip" configuration the outlet valve remains closed. The operator may then take a dip reading so that the customer can be advised of the total amount of fluid carried by the container. In the "drop" configuration the outlet valve 3 is also opened by a pneumatic signal from the control unit 8.

[0014] When it is desired to release only part of the contents of the container, the operator depresses a manually operable pneumatic switch 20 provided externally on the container adjacent the dip tube, which causes a pneumatic signal to be applied to the outlet valve 3 so that fluid is discharged from the container. In this configuration, the outlet valve 3 is only open whilst the switch 20 is depressed, and the operator may close the valve once the desired amount of product has been delivered, as may be measured by the dipstick.

[0015] The outlet valve 3 is shown in more detail in Figs. 2 and 3. Preferably, though not essentially, the outlet valve is of the type described in European patent application 86307902.6 which can only be opened when it is connected to a fluid delivery conduit. Referring to Fig. 2, an outlet valve 3 for a transport container in the form of an API valve of a sort generally well known in the art includes a closure member 10 movable between an open condition wherein fluid may be released from the container into a delivery hose 5 and a closed condition (shown in broken lines in Fig. 2) wherein a discharge of fluid is prevented. The closure member is pneumatically operable by means of a piston 11 coupled to the closure member and displaceable in a chamber 12 in response to pneumatic pressure introduced into one side of the chamber via a duct 13. Thus, application of pneumatic pressure through duct 13 into the left-hand side of the chamber 12 causes movement of the closure member 10 rightwardly into its open condition. A biasing spring (not shown) is provided to return the closure member 10 to its closed condition when no pneumatic pressure is applied via the duct 13.

[0016] As shown in Fig. 2, coupling means 14 are provided for releasably connecting the valve 3 to the delivery hose 5, the coupling means 14 including a male part 15, which in the illustrated embodiment forms part of the valve housing, and a complementary female part 16 connected to the hose 5. Locking members 17 are adapted releasably to interconnect the male and female parts, as is known in the art.

[0017] In the illustrated valve, means are provided to prevent the valve from opening when not connected to a conduit via the coupling means 14. Such means comprises a pneumatic switch 18 arranged in the supply line 19 connecting the duct 13 to a pressure gas source via a remote control unit (not shown). The switch 18 comprises a housing 22 mounted to the valve housing and defining an axial bore 23 having radially arranged inlet and outlet ducts 24. Disposed in the bore 23 is a plunger 25 carrying an O-ring seal 26. A biasing spring 27 is adapted to urge the plunger 25 leftwardly as shown in the drawings, whilst an operating member 28 carried by the plunger is arranged to co-operate with a forward peripheral edge 29 of the female part 16 of the coupling means 14 when the parts of the coupling means are interconnected. Thus, as shown in Fig. 2 when the parts 15, 16 are interconnected, the operating member 28 is urged rightwardly against the biasing force of the spring 27 so that the plunger is moved into an open condition wherein the inlet and outlet ducts 24 communicate with one another. In this condition, pneumatic gas pressure can be applied to the chamber 12 via the duct 13 and the valve can be opened as desired consequent upon the line 19 being connected to the pressure gas source via the appropriate pneumatic switch of the remote control unit (not shown). However, when the female part 16 and thus the delivery hose 5 are detached from the valve 3, the biasing spring 27 urges the plunger leftwardly into the condition shown in Fig. 3, wherein the O-ring seal 26 is located axially between the inlet and outlet ducts 24 so that the duct 13 and chamber 12 are isolated from the line 19. In this condition, it will be appreciated that the valve cannot be opened by inadvertent application of pneumatic pressure to the line 19 e.g. consequent upon the operator selecting the wrong pneumatic switch in the remote control unit.

[0018] As shown in Fig. 2, the pneumatic switch 18 is connected to the duct 13 via a T-junction 30, the other arm of the T being connected to an indicating means at the remote control unit adapted to provide a visual indication consequent upon application of pneumatic pressure. This provides the operator with confirmation that the valve has been duly opened, and the absence of a visual indication will alert the operator to the fact that no gas pressure has been applied to the duct 13 and therefore to the possibility of the wrong switch having been selected on the remote control unit.

[0019] If it is desired to empty a part of the contents of the container 1 the outlet valve 3 is opened either by manual operation of pneumatic switch 20 on the top of the container, with the switch on the control unit 8 being in the "dip" condition, or by setting the switch on the control unit to the "drop" state. In either case the control unit 8 sends a pneumatic signal via a shuttle valve arrangement 31 to duct 13 to open valve 3, and another signal to open the vent valve 6, and foot valve 2 and release the dipstick locking means 9.

[0020] As is shown in Fig. l, the shuttle valve arrangement 31 includes a pilot line 32 which controls the switching state of the shuttle valve. When a valve opening signal is sent from the control unit 8 to the outlet valve 3, the shuttle valve is switched to the position shown in Fig. 1 in which the control unit is connected to duct 13. However, when the outlet valve is to be closed, and the valve opening signal from the control unit is removed, the pressure in the pilot line 32 is greater than that in the line leading from the control unit to the shuttle valve and the shuttle valve is switched to its alternative position in which the duct 13 is connected through a pilot line 33 to a foot valve control switch 34.

[0021] The foot valve control switch 34 is positioned in the line from the vent valve 6 to the foot valve 2 and is normally biassed by a spring 35 to connect the vent valve to the foot valve to allow the foot valve to be opened. However when closure of the outlet valve is initiated, the shuttle valve 31 is switched to connect duct 13 with the control switch 34. The back pressure that is then present in the chamber 12 is transmitted through line 33 and switches the foot valve control switch against the bias of the spring 35 to disconnect the foot valve from the vent valve and thus close the foot valve.

[0022] With the foot valve closed, the back pressure developed in chamber 5 is then released through an adjustable bleed valve 36. Once the back pressure has fallen below a certain level the spring 35 switches the foot valve switch 34 into its normal position in which the vent valve and foot valve are connected so as to re-open the foot valve. Naturally this reset period can be varied as desired by adjusting the opening of the bleed valve, but a typical reset period would be about 2 seconds.

[0023] It will thus be seen that, as soon as the outlet valve begins to close, the foot valve is automatically shut, almost instantaneously, to prevent the generation of a shock in the conduit 4. Closure of the foot valve generates no similar shock owing to the large reservoir capacity of the container. After a short period of time the foot valve is automatically re-opened to permit an accurate dipstick reading to be taken.

Claims

1. A fluid transport container comprising a foot valve arranged in a lower part of the container and connected or connectable to an outlet valve via a conduit, and control means for opening and closing said valves, said control means being adapted to close the foot valve at substantially the same time as the outlet valve is closed and to open the foot valve shortly thereafter.

2. A fluid transport container according to claim 1 wherein the control means is responsive to back pressure generated at the outlet valve when closure of the outlet valve is initiated.

3. A fluid transport container according to claim 2 wherein the foot valve is opened in response to a pneumatic, hydraulic or electrical signal and the back pressure generated at the outlet valve is used to switch off this opening signal.

4. A fluid transport container according to claim 3 wherein the foot valve is opened by a hydraulic or pneumatic signal and the back pressure is used to switch a valve to shut off this hydraulic or pneumatic signal.

5. A fluid transport container according to claim 4 comprising a control line from said control means to said outlet valve whereby said outlet valve may be opened in response to a hydraulic or pneumatic signal, a shuttle valve being disposed in said control line switchable between a first position in which said outlet valve is connected to said control line and a second position in which said outlet valve is connected to a pilot line, said pilot line leading to a foot valve control switch for interrupting a foot valve opening signal, the arrangement being such that said shuttle valve is switched to said second position upon commencement of closure of said outlet valve whereby the back pressure may be transmitted along said pilot line to actuate said foot valve control switch to close said foot valve.

6. A fluid transport container according to claim 5 wherein said foot valve control switch is spring-biassed into a normally open position to permit opening of said foot valve, and wherein a bleed valve is provided whereby upon closing of said control switch the pressure in said pilot line is removed and the control switch is opened by said spring-biassing.

7. A fluid transport container according to any preceding claim wherein the reset period after which the foot valve is reopened may be adjusted to any desired length.

Drawing