The present invention relates to a caisson for housing a pump in a fuel tank, the caisson comprising an elongate tubular element made from a fluid impermeable material and having an opening at a proximal end and an orifice at a distal end, a valve plate having a valve seat and being displaceable arranged on the caisson between a closing position in which the valve seat of the valve plate abuts the distal end of the caisson and closes the orifice, and an opening position in which the valve plate is arranged at a distance from the orifice to provide a flow through the orifice. The caisson comprising one or more resilient members biasing the valve plate towards its opening position, and a closing mechanism for positioning the valve plate in its closing position. BACKGROUND OF THE INVENTION

Ships, in particular, using LNG, Butane, Ethane or Propane-gas as fuel need to have the gas stored in a tank. The gas is typically pumped from the tank to the motor consuming the gas. The pump is typically arranged in a caisson extending from an upper part of the tank and into the interior of the tank. It is often a requirement that the pump used for pumping the gas can be serviced and in order to avoid emptying the tank and in order to do so, attempts have been made to provide a shut-off mechanism, a foot valve, at the bottom of the caisson. By applying such a foot valve, the interior of the caisson can be closed off from interior of the tank, whereby the pump arranged in the caisson, ideally, can be retracted from the caisson while still keeping the gas in tank under pressure.

Previous solutions of foot valves functions in the same manner as check valves by a disc (or in some cases a ball) is seated against an orifice thus preventing any flow trough said orifice. The disc is held against the seat by its own weight and in some cases also a closing spring. When the pressure difference of the two disc sides is relatively high the disc is lifted from the seat and a flow through the orifice is now possible.

While this is a workable solution, the inventors have realized that in case of shutting-off a caisson used in an tank storing gas, this solution may suffer from the drawback that it cannot be assured that the valve mechanism is prevented from up opening up un-intentionally as the pressure in the tank may exceed the opening pressure of the check valves. US2015217987 Al discloses a foot valve assembly for a submergible pump, including a substantially open-ended submergible pump housing having an interior volume. The foot valve assembly also includes an actuator configured to be operated by pressurized fluid. The foot valve assembly also includes a sealing mechanism positioned at the open end of the submergible pump housing and configured to alter fluid flow into the pump housing. The sealing mechanism is attached to the actuator. The actuator is configured to move the sealing mechanism between a first position and a second position, the first position being a closed position and the second position being an open position. However, this device in US2015217987 Al is a "fail-close" valve, being

constructed so that a force is needed to open the valve, in some embodiments disclosed as comprising a manual mechanical override system.

OBJECT OF THE INVENTION

An object of the invention is to apply a closing mechanism in a caission for housing a pump in a container, such as a fuel tank.

SUMMARY OF THE INVENTION

The invention relates, in a fist aspect, to a caisson for housing a pump in a container, such as a fuel tank.

In the following, the terms proximal end and distal end is preferably used to detonate the upper part and lower part of an embodiment, respectively.

The caisson comprises:

- an elongate tubular element made from a fluid impermeable material and having an opening at a proximal end and an orifice and a valve seat at a distal end; - a valve plate being displaceable arranged on the caisson between a closing position in which the valve plate abuts the distal end of the caisson at the valve seat and closes the orifice; - an opening position in which the valve plate is arranged at a distance from the orifice to provide a flow through the orifice.

The caisson may also comprise:

one or more resilient members biasing the valve plate towards its opening position;

a closing mechanism for positioning the valve plate in its closing position.

By "biasing" is typically meant that a force is to be applied to close the valve. Thus, a caisson according to preferred embodiments is typically constructed so that a force is to be applied to close the valve.

A caisson according preferred embodiments may comprise a closing mechanism comprising a tie rod, a wire or chain, and a pulling mechanism for providing a pull in the wire. The tie rod may be connected to the wire at a proximal end and to the valve plate at a distal end. The wire or chain may extend from the proximal end of the tie rod to the pulling mechanism, so as to move the plate into its closing position when deploying the pulling mechanism. The pulling mechanism preferably comprises a winch, a hydraulic operated piston, a pneumatic operated piston and/or a solenoid to which the wire or chain is connected.

Another embodiments of the closing mechanism may comprise a hydraulic or pneumatic actuator. The pneumatic actuator may further comprise a piston arranged in a cylinder arranged on the caisson, preferably at a lower end thereof. Preferably, the piston being hydraulically activated by supplying fluid to the cylinder to reciprocate between two longitudinal distanced positions in the cylinder. The actuator may further comprise a tie rod connected to the piston at a proximal end and connected to the valve plate at a distal end. The reciprocating motion of the piston results in the movement of the plate between its opening and closing position.

In some embodiments, where the closing mechanism may comprise a solenoid, the solenoid may comprise a tie rod made from metal and an electrical coil encircling at least a part of a tie rod. The tie rod may preferably be connected to the valve plate at a distal end. When an electrical current is applied to the electrical coil the tie rod is pulled into and maintained in the coil, and thereby moving the plate into its closing position.

In addition or alternately embodiments according to the present invention may also comprise one or more resilient members, such as a mechanical spring, which biases the valve plate towards its opening position. The force of the resilient members should preferably be sufficient enough to overcome the pressure difference from the tank in order to bias the valve plate towards its opening position.

Preferably, one or more sealing elements may be provided in or at the distal end of the tubular element to provide a seal between the valve plate and the distal end of the tubular element and encircling the orifice.

Preferably, a seal element may be provided in the valve plate to provide a seal between the valve seat and the distal end of the tubular element. Preferably, the seal element encircles the orifice, when the valve plate is in its closing position.

Preferably, a caisson according to the present invention may comprise at the distal end of the tubular element a flange, in which the orifice may be provided. The flange may preferably be releasable connected to the tubular element of the caisson.

Preferably, the seal element may be arranged on or in the flange.

Preferably, the length of the tubular element as measured between the distal and proximal end may preferably be between 1 and 30 meters, such as between 1 and 25 meters, such as between 1 and 8 meters, preferably between 1 and 5 meters, such as between 1 and 3 meters;

Preferably, the diameter or equivalent diameter (4*Area/peri meter) of the tubular element may be constant throughout its length and is preferably between 0.25 and 1 meters;

In another aspect of the invention, the invention relates to a container for storing fuel, such as LNG, Butane, Ethane or Propane-gas, and the container may comprise a caisson according to first aspect of the invention.

Thus, compared to the prior art valve where the opening and closing is controlled by the difference in pressure between the top and bottom side of a disc or, the opening and closing can be controlled independently by the closing mechanism according to the present invention. As presented herein, the closing mechanism may comprising a wire pull or a pneumatic, electrical or hydraulic pistons. The resilient member assures an opening of the valve when for example the wire pull is relaxed.

In the present context a number of terms are used in a manner being ordinary to a skilled person; however, some of these terms are elucidated below:

Foot valve is preferably used to reference the combination of the orifice/opening into the caisson at the lower end of the caisson and the member closing the orifice/opening in sealed manner. The foot valve may also comprise a flange on the caisson and the closing mechanism.

Caisson is preferably used to detonate a submerged watertight box in a container, such as a fuel tank. The caisson houses a pump for pumping fluid, such as liquid, such gas from the tank to the motor consuming the gas.

BRIEF DESCRIPTION OF THE FIGURES

The present invention and in particular preferred embodiments will now be described in more detail with reference to the accompanying figures. The figures show ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 is a schematically illustration of a cross sectional view of a fuel tank comprising a caisson according to a preferred embodiment of the invention;

Figure 2 is a schematically illustration of a cross sectional of a caisson according to a preferred embodiment of the invention; the caisson is illustrated with the foot valve open in the left figure and with the foot valve closed in the right figure;

Figures 3, 4 and 5 illustrates schematically in cross sectional views different embodiments of closing mechanisms for closing the foot valve in a caisson;

Figure 6 illustrates schematically yet a further embodiment of a caisson according the present invention; fig. 6a shows the foot valve open, fig. 6b shows the foot valve closed and fig. 6c is perspective cross sectional view of fig. 6a, and

Figure 7 illustrates schematically a further embodiment in which tie rods extends to a position above the proximal end of the elongate tubular member.

DETAILED DESCRIPTION OF AN EMBODIMENT

Reference is made to figure 1 and figure 2 illustrating a caisson for housing a pump in a container. The container is typically a fuel tank 17 e.g. storing LNG, Butane, Ethane or Propane-gas on e.g. ship where the gas is used a fuel for the motor of the ship and/or motors for auxiliary equipment of the ship. However, the container may be used for storing other items than fuel and may even be used for storing powdery substances.

As illustrated in fig. 1 and fig.2, the caisson comprising - or is made from - an elongate tubular element 1. The tubular element 1 is made from a fluid impermeable material and having an opening at a proximal end and an orifice 2 and a valve seat 4 at a distal end. The tubular element 1 may be a single piece, such welded in one piece and arranged in the container e.g. by welding. With reference to fig. 1 and fig.2, the distal end of the tubular element 1 is the end being farthest away from the upper part of the container and the proximal end being closest to the upper part of the container. The elongate tubular element has a valve plate 3 being displaceable arranged on the caisson 23 (in the embodiment shown being displaceable arranged on the elongate tubular member 1) between a closing position in which the valve plate 3 abuts the distal end of the caisson 23 (in the embodiment shown at the distal end of the elongate tubular element ) at the valve seat 4 and closes the orifice 2, and an opening position in which the valve plate 3 is arranged at a distance from the orifice to provide a flow through the orifice. Thus, when valve plate 3 is in its opening position as shown in fig. 1 and fig.2, fluid can flow from the interior of the container, through gap in-between the valve seat 4 and the valve plate 3 and through the orifice 2 thereby entering into the interior of the elongate tubular element 1.

As also illustrated in fig. 1 and fig.2, an impeller may be arranged inside the elongate tubular element 1 ; the impeller may advantageously be arranged close to the orifice 2 on a rotational shaft 14 whereby upon rotation of the shaft 14, the impeller may suck - or pump - fluid from the interior of the container through the orifice 2 and deliver the fluid to the outside of the container through the upper opening of the elongate tubular element 1 (it is noted that although the upper opening of the elongate tubular element 1 is shown as opening into the exterior, the opening will in most case be connected to a distribution pipe).

The caission 23 also comprises one or more resilient members 5, such as a mechanical spring, which biases the valve plate 3 towards its opening position (please note that in fig. 2, an arrow is used to symbolize the resilient members 5). By biasing the valve plate 3 towards its opening positioning, the valve can be seen as being "normally" open unless a force is applied to the valve plate to move it towards its closing position. The movement of the valve plate 3 towards it closing position is provided in the embodiment shown in fig. 2 by closing mechanism 18 for positioning the valve plate 3 in its closing position. In a particular preferred embodiments, the resilient members 5 are four mechanical springs, preferably geometrically equally disposed, which in case of a being disposed along a circular perimeter means disposed with 90 degrees in between each mechanical spring. This means that an external force is to be applied to close the valve.

In fig. 5 one embodiment of a closing mechanism for closing the foot valve is disclosed. The closing mechanism comprises a sufficient number of tie rods 7, in order to engage the valve seat 3 and move it vertically towards its closing position to the valve seat 4. From the proximal end of the tie rod 7 a wire or chain 8 is connected to a pulling mechanism 9, such as a winch. The winch being a cylindrical element comprising a groove, when rotating around its axis the wire or the chain may be pulled. The winch could be made from stainless steel and may be driven by an electric motor or a hydraulic pump. The number of pulling mechanisms should correspond to the number of tie rods 7. The tie rod 7 extends through a hole in the flange 16 to the valve plate 3 and is connected at the distal end to the valve plate 3. Preferably the embodiment should have 2, 3, 4 or 5 tie rods equally distributed along the periphery of the flange 16. The pulling mechanism 9 may provide a pull in the wire, and thereby applying a force to the valve plate 3 to move it vertically towards its closing position.

When the valve plate 3 is in fully closed position, one or more sealing elements 22, such as an O-ring, is provided in the distal end of the tubular element 1, to provide a seal between the valve plate and the distal end of the tubular element 1. The grip from the tie rods will loosen op, as the fluid from the interior of the container will provide a pressure and thereby a force on the valve plate 3, keeping the valve plate in its closed position.

The embodiment also comprises one or more resilient members 5, such as a mechanical spring, which biases the valve plate 3 towards its opening position. The force of the resilient members should be sufficient enough to overcome the pressure difference from the tank in order to bias the valve plate towards its opening position.

In fig. 3 a different embodiment of a closing mechanisms for closing the foot valve is disclosed. The closing mechanism comprises a hydraulic or pneumatic actuator 10, which could be made from stainless steel. The closing mechanism further comprises a piston 19 arranged in a cylinder 20 arranged on the caisson. By supplying fluid to the cylinder 20 the piston hydraulically activates and

reciprocates between two longitudinal distanced positions in the cylinder 20. The fluid may be supplied from a hydraulic pump, comprising a sufficient number of valves, in order to move the piston in upwards and downwards direction.

The closing mechanism comprises a sufficient number of tie rods 7, in order to engage the valve seat 3 and move it vertically towards its closing position to the valve seat 4. The number of pulling mechanisms should correspond to the number of tie rods 7.

The reciprocating motion of the piston 19 provides a pull in the tie rod 7 connected to the piston at a proximal end. The tie rod 7 is connected at the distal end to the valve plate 3, through a hole in the flange 16. Preferably the embodiment should have 2, 3, 4 or 5 tie rods equally distributed along the periphery of the flange 16.

The tie rod 7 provides a movement of the valve plate 3 between its opening and closing position, when the piston 19 is hydraulically activated. The grip from the tie rods will loosen op, as the fluid from the interior of the container will provide a pressure and thereby a force on the valve plate 3, keeping the valve plate in its closed position. The embodiment also comprises one or more resilient members 5, such as a mechanical spring, which biases the valve plate 3 towards its opening position. The force of the resilient members should be sufficient enough to overcome the pressure difference from the tank in order to bias the valve plate towards its opening position.

In fig. 4 another embodiment of closing mechanism for closing the foot valve is disclosed. The closing mechanism comprises a solenoid 21 and an electrical coil 11 encircling at least a part of the tie rod 7, made from metal. The tie rod 7 is connected at the distal end to the valve plate 3, through a hole in the flange 16. Preferably the embodiment should have 2, 3, 4 or 5 tie rods equally distributed along the periphery of the flange 16.

The tie rod 7 is pulled into and maintained in the coil 11 when an electrical current is applied to the electrical coil 11, and thereby moving the valve plate 3 towards its closing position. The electrical current may be supplied by a power supply. The grip from the tie rods will loosen op, as the fluid from the interior of the container will provide a pressure and thereby a force on the valve plate 3, keeping the valve plate in its closed position.

The embodiment also comprises one or more resilient members 5, such as a mechanical spring, which biases the valve plate 3 towards its opening position. The force of the resilient members should be sufficient enough to overcome the pressure difference from the tank in order to bias the valve plate towards its opening position.

Preferably, one or more sealing elements is provided in or at the distal end of the tubular element, to provide a seal between the valve plate and the distal end of the tubular element, which seal elements encircles the orifice, when the valve plate is in its closing position.

In addition or alternatively, a seal element 22 is provided in the valve plate 3. The seal element provides a seal between the valve seat 4 and the distal end of the tubular element 1 and encircling the orifice 2, when the valve plate 3 is in its closing position. The seal element 22 is arranged on or in the flange 16, which preferably is releasable connected to the tubular element 1 of the caisson. The seal element 22 may be in form of an O-ring as disclosed in e.g. fig. 6.

In fig. l the tubular element 1 may have a length between 1 and 8 meters

(measured between the distal and proximal end). The diameter or equivalent diameter (4*Area/peri meter) of the tubular element 1 is constant throughout its length and is between 0.25 and 1 meters.

As disclosed in fig. 6, the closing mechanism may be in the form of a rod with a eyebolt , which are mounted firmly into the topside of the flange. The rods of the eyebolts passes through bore holes in the flange 16, and wires or chains 8 are connected to the eye of the eyebolts. When a closing of the foot valve is wanted the wire is pulled and the valve plate 3 is pulled up against the valve seat 4. A sealing may be added in the valve plate 3 or flange which would further reduce any flow through the valve when the valve seat is against the valve plate thus completing the flange sealing connection. The upper part of the flange 16 is preferably welded to the elongate tubular element 1. The lower part of the flange 16 is connected to the upper part of the flange with bolts equally distributed along the periphery of the flange 16. In the embodiment shown in fig. 6, the lower part of the flange 16 defines the size of the orifice 2.

Figure 6 further illustrates the foot valve in two different positions: the upper left hand side figure where the foot valve is in its open positon and the upper right hand side figure where the foot valve is in its closing position.

In a further embodiment, see fig. 7, the tie rods 7 extends to a position above the proximal end of the elongate tubular member 1 and is connected to a pulling mechanism for providing a pull in the tie rods 7. The pulling mechanism may comprise a nut 24 cooperating with a thread (not illustrated in fig. 7) provided on the tie rod 7 so that upon rotation of the nut 24, a pull is provided in the tie rod 7. It is noted that the nut 24 has a fixed vertical position e.g. by abutting a surface or otherwise maintained in fixed vertical position while allow rotation of the nut. Alternatively, the pulling mechanism may comprise a hydraulic operated piston, a pneumatic operated piston and/or a solenoid to which the tie rods 7 are connected; the pulling mechanism is preferable arrange in position above the tank. In a particular preferred embodiment two such tie rods 7 are used which tie rods 7 are disposed with an angle of 180 degrees in between. Still further, this tie rods are in a particular preferred embodiments, the tie rods are cylindrical typically with a diameter of 6-12 mm, such 6-10 mm, preferably 6 mm.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

LIST OF REFERENCE SYMBOLS USED

1 elongate tubular element (of caisson)

2 orifice

3 valve plate

5 4 valve seat

5 spring

6 impeller

7 tie rod

8 wire or chain

10 9 winch

10 hydraulic or pneumatic actuator

11 electrical coil

12 magnetic actuator

14 rotational shaft

15 15 bolt

16 flange

17 fuel tank

18 closing mechanism

19 piston

20 20 cylinder

21 solenoid

22 seal element

23 caisson

24 nut