FIELD OF THE INVENTION

The present invention relates to the field of valves. Especially, the invention relates to a rupture disc valve assembly, preferably for high-pressure washers.

BACKGROUND OF THE INVENTION

Rupture discs, also known as burst discs, are safety devices used in various industries to protect equipment, processes, and personnel from overpressure conditions. They function by bursting or rupturing at a predetermined pressure threshold, allowing the release of pressure to prevent catastrophic failures or explosions. Rupture discs provide quick and reliable pressure relief when compared to traditional relief valves. They are typically thin, flat, circular, or domed metal components made from materials, such as stainless steel, aluminium, or nickel alloys.

When integrated into valves, the assembly is called a rupture disc valve assembly. This assembly combines the functions of a valve and a rupture disc to provide pressure relief and control within a single unit. The valve controls the flow of fluid while the rupture disc ruptures at a predetermined pressure threshold. Hence, under normal operating conditions, the integrated valve functions as a regular control valve, regulating the flow of the process fluid. If the pressure inside the system exceeds a predetermined limit, the rupture disc within the valve bursts, creating an opening for the excess pressure to escape.

A specific problem arises for high-pressure washers. Here, the water pressure in the pipeline fluctuates frequently when the machine goes from standby mode to work mode, and vice versa. This results in the rupture disc undergoing metal fatigue, and thus very poor service time of the high-pressure washer.

One solution is to raise the rupture pressure of the rupture disc, for example by using thicker disc. But in practice (for example to comply with EN 1829-1, 4.2.2 Safety devices to prevent excessive pressure), that usually requires the maximum allowable working pressure also to be raised, leading to use of higher rated and more expensive components.

SUMMARY OF THE INVENTION

Hence, an improved high-pressure washer would be advantageous, and in particular a rupture disc valve assembly with a durable rupture disc would be advantageous.

An object of the present invention is to provide a high-pressure washer with improved service time. This may be solved by providing an improved rupture disc valve assembly that solves the above-mentioned problems of the prior art.

A first aspect relates to a rupture disc valve assembly, configured to be connected to a pump, wherein the rupture disc valve assembly comprising:

- a rupture disc, sitting in a drainage passage, in situation that fluid pressure between the pump and the rupture disc not exceeding a threshold, the rupture disc being complete to block the drainage passage, while in situation that pressure between the pump and the rupture disc exceeding the threshold, the rupture disc being able to rupture to open the drainage passage;

- a non-return valve, connected between the rupture disc and the pump, being configured to let fluid generated by the pump to go only one way from the pump to the rupture disc.

A second aspect relates to a system for pumping fluid, the system comprising:

- a pump unit adapted for pumping fluid; and

- a rupture disc valve assembly in fluid communication with the pump unit via a pipeline; wherein the rupture disc valve assembly comprises:

- a drainage/fluid passage comprising a first section in fluid communication with the pipeline, and a second section;

- a rupture disc embedded in the fluid passage to block fluid from passing from the first section to the second section; wherein when the fluid pressure between the pump unit and the rupture disc is above a pre-set threshold, the rupture disc is configured to burst to open the drainage/fluid passage between the first and second sections; and - a non-return valve connected to, or forming part of, the first section of the drainage/fluid passage and positioned between the rupture disc and the pipeline, wherein the non-return valve is configured to allow fluid to pass from the pump unit, via the pipeline and first section of the drainage/fluid passage, to the rupture disc.

In some embodiments, the rupture disc valve assembly comprises a housing, the rupture disc and the non-return valve both being set inside the housing.

The non-return valve being integrated inside the housing, makes the rupture disc valve assembly compact and of simple structure.

In one or more embodiments, the non-return valve is a backflow ball valve. These valves enable one-direction flow while preventing backflow. Ball valves employ a spherical ball inside the flow path to prevent reverse flow. As they rotate during operation, self-cleaning occurs as the ball rotates.

In some embodiments, the rupture disc valve assembly comprises a block part, wherein the fluid being able to go through the block part, while any part of the non-return valve would be blocked by the block part from reaching to the rupture disc.

The block part works as a safety part. In situation that the rupture disc breaks due to high pressure, the non-return valve will not be shoot out.

Specially, the non-return valve comprises a support and a ball, the housing comprising an inlet at one end near the pump, wherein the ball being set inside the housing, and the ball being able to move between the inlet and the support to open and close the inlet, the support separating the ball and the rupture disc, the support comprising at least one hole, the fluid being able to go through the hole, while the ball being not able to go through the hole.

Specially, the support comprises at least two holes.

In case the rupture disc bursts, and the ball moves to block one hole, at least one other hole is open to release pressure. Specially, the non-return valve further comprises an elastic part, the elastic part being set between the ball and the support.

The elastic part is used in practice to ensure the ball being guided to close the inlet, so as to minimize any backflow before ball making sealing.

Specially, the support comprises a first support part of a cylindrical shape, the elastic part being a coil spring, and the elastic part being set around the first support part.

Specially, one end of the first support part facing the ball comprises a concave part.

The concave part creates a stable contact area for the first support part when contacting with the ball. Especially in burst scenario where water is drained, the ball can be kept by the concave part from tipping away from center when flow rush through.

In some embodiments, the support comprises a second support part, the second support part being in touch with the rupture disc to seal space between the rupture disc and the housing.

Specially, the second support part has a bowl shape to form a disc chamber, the rupture disc being at least partly set in the disc chamber, at least part of the disc chamber is in the same shape as the rupture disc.

The bowl shape fits with the rupture disc, to make a seal with the rupture disc once a head of the rupture disc valve assembly is tightened.

In some embodiments, the non-return valve also comprises a sleeve, the ball being at least partly inside the sleeve.

The sleeve gives a guide for the ball during its movement, to keep the ball in the center.

Specially, the sleeve comprises a main chamber and at least one groove, the ball being set in the main chamber but not being able to go into the groove, fluid being able to flow through the groove. The groove creates space for water to go through, especially making drainage passage around the ball in case of exceeding maximum pressure of the rupture disc.

Specially, the inside hole of the sleeve comprises a first chamber and a second chamber at each end of the sleeve, and a third chamber between the first chamber and the second chamber, the inner diameter of the first chamber is larger than the inner diameter of the second chamber, the inner diameter of the third chamber is larger than the inner diameter of the second chamber.

This inner structure makes water easily flowing into the housing and further flowing to the rupture disc.

In some embodiments, the rupture disc valve assembly comprises a drainage cup, the drainage cup comprising a side wall which covering at least part of the exit of the drainage passage.

The drainage cup can work as a baffle when the rupture disc breaks and water sprays out.

In a second aspect, the invention provides a high-pressure washer, comprises a pump and a pipeline, the pump being connected to the pipeline to be able to provide high pressure water, wherein the high-pressure washer also comprises a rupture disc valve assembly according to the first aspect of this invention, the rupture disc valve assembly is connected to the pipeline.

After thousands of trigger activations, the water pressure in the pipeline fluctuates, but the water pressure at the rupture disc keeps stable. So, the rupture disc has a long lifetime.

In one or more embodiments, the drainage/fluid passage is formed in a housing comprising the first section, and a head part comprising the second section, and wherein the housing and the head part are releasably fastened to one another.

In one or more embodiments, the non-return valve is positioned within the housing and configured as forming part of the first section. In one or more embodiments, a part of the non-return valve is configured as a support for the rupture disc.

In one or more embodiments, the rupture disc is releasably fastened between the head part and the non-return valve.

In one or more embodiments, the system further comprises a safety shield mounted, preferably releasably mounted, to the head part, the safety shield comprising a wall part adapted for covering at least part of an outlet of the drainage/fluid passage, wherein the outlet(s) is/are positioned in the second section.

In one or more embodiments, the drainage/fluid passage is formed in a housing comprising the first section; wherein the non-return valve is positioned within the housing and configured as forming part of the first section; wherein the nonreturn valve comprises a support, and a ball; wherein the housing comprises an inlet to the first section; wherein the ball is adapted for moving between the inlet and the support to open and close the inlet; wherein the support is adapted for separating the ball from the rupture disc.

In one or more embodiments, the support comprises at least one channel/hole, thereby allowing fluid/water to flow to the rupture disc, said at least one channel/hole forming part of the first section of the drainage/fluid passage.

In one or more embodiments, the non-return valve comprises an elastic part, the elastic part being positioned between the ball and the support.

In one or more embodiments, the support comprises a first support part of a cylindrical shape, and wherein the elastic part is a coil spring positioned around the first support part. In one or more embodiments, a first end of the first support part is facing the ball, and wherein the first end comprises a concave part adapted for receiving the ball.

In one or more embodiments, the support comprises a second support part adapted for abutting the rupture disc, thereby functioning as a seal between the rupture disc and the housing.

In one or more embodiments, the second support part is shaped to form a chamber adapted for receiving at least a part of the rupture disc.

In one or more embodiments, the non-return valve further comprises a sleeve configured as a guide for the ball in its movement between the inlet and the support.

In one or more embodiments, the sleeve comprises a main chamber, and at least one groove, wherein the main chamber is configured for receiving the ball, and wherein the groove(s) is/are of a size and/or shape preventing the ball from moving therein, while at the same time allowing a part of the fluid/water entering the inlet to bypass the ball during its movement towards the support.

In one or more embodiments, the sleeve further comprises a first chamber facing the inlet and configured as an antechamber to the main chamber and the at least one groove.

In one or more embodiments, the sleeve further comprises a second chamber facing the support and configured as a collection chamber to the main chamber and the at least one groove. In one or more embodiments, at least a part of the main chamber and the at least one groove is pre-filled with an anti-freeze fluid, preferably during transport and storage of the system.

A third aspect relates to a high-pressure washer comprising the system according to the present invention.

BRIEF DESCRIPTION OF THE FIGURES

The apparatus according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

FIG. 1 is a schematic drawing illustrating a rupture disc valve V' of prior art.

FIG. 2 is a section side view of a rupture disc valve V' of prior art.

FIG. 3 is a schematic drawing illustrating a first embodiment of a rupture disc valve assembly V according to the invention.

FIG. 4 is a section side view of a first embodiment of a rupture disc valve assembly V according to the invention.

FIG. 5 is part of a section side view of the first embodiment of a rupture disc valve assembly V according to the invention.

FIG. 6-7 are schematic drawings illustrating an embodiment of a support of a rupture disc valve assembly V according to the invention.

FIG. 8 is a schematic drawing illustrating a second embodiment of a rupture disc valve assembly V according to the invention. FIG. 9 is a schematic drawing illustrating an embodiment of a rupture disc valve assembly V according to the invention, which is connected to a pump.

FIG. 10 is a schematic drawing illustrating an embodiment of a sleeve of a rupture disc valve assembly V according to the invention.

FIG. 11 is a section side view of the sleeve in FIG. 10.

DESCRIPTION OF REFERENCE SIGNS

V' Rupture disc valve

V Rupture disc valve assembly

P Pump unit

10, 10' Housing

11 Inlet

20, 20' Head

21, 21' Central hole

22, 22' Drainage hole

23 Protrusion part

30, 30' Rupture disc

40 Non-return valve

41 Support

411 First support part

4110 Concave part

412 Second support part

4120 Chamber

4121 Bottom wall

413 Channel/Hole

42 Sleeve

420 Protrusion

42m Main chamber

42g Groove

421 First chamber

422 Second chamber

423 Middle chamber 43 Ball

44 Elastic part

50 Drainage cup

51 Side wall

60 Fastener

61 Bolt

62 Spring washer

DETAILED DESCRIPTION OF AN EMBODIMENT

Figures 1-2 show an example of a rupture disc valve assembly V' (referred to as valve assembly V' hereinafter). The valve assembly V' comprises a housing 10', a head 20', and a rupture disc 30'. The rupture disc 30' is placed between the housing 10' and the head 20'. The housing 10' is hollow inside, while the head 20' comprises a central hole 21' and several connecting drainage holes 22'.

The housing 10' is adapted for being connected to a pipeline with a pump. In a situation where the pressure inside the pipeline is below a maximum allowable working pressure, the rupture disc 30' will seal the central hole 21' at one of its ends, thereby preventing water flowing to the drainage holes 22'. In a situation where the pressure inside the pipeline exceeds the maximum allowable working pressure, the rupture disc 30' will break to reduce the water pressure.

Figures 3-7 show an exemplary embodiment of a rupture disc valve assembly V (also referred to as valve V hereinafter) according to the invention. Although the valve assembly V may be used in other fluid pumping systems, the following will describe its integration in a high-pressure washer.

A high-pressure washer normally comprises a pump unit, which will deliver high- pressure water through a pipeline to a water gun. A trigger is integrated in the water gun to control the spraying operation, i.e., to allow or prevent water from being forced out of the water gun's barrel. To prevent the water pressure inside the pipeline from becoming too high, the rupture disc valve assembly V is operably connected to the pipeline. Referring to Figures 3-4, the valve assembly V according to the invention is here shown comprising a housing 10, a head 20, a rupture disc 30, a non-return valve 40 (also referred to as NRV 40 hereinafter), a drainage cup 50, and a fastener 60.

The housing 10 is hollow inside and comprises a drainage/fluid passage. At a first end (hereinafter called the upstream end, relative to the fluid/water flow) of the drainage/fluid passage, an inlet 11 is formed. The inlet 11 is configured to be connected to the pipeline in the high-pressure washer, or in another type of system for pumping fluid. An opposite second end (hereinafter called the downstream end, relative to the fluid/water flow) of the drainage/fluid passage is in fluid communication with the head 20. The rupture disc 30 it positioned within the drainage/fluid passage, thereby blocking it.

In a situation where the pressure inside the pipeline is below a maximum allowable working pressure, the rupture disc 30 will block the drainage/fluid passage; while in situation where the pressure inside the pipeline exceeds the maximum allowable working pressure, the rupture disc 30 will break/rupture to allow water/fluid from the pipeline to escape through the drainage/fluid passage.

The NRV 40 is positioned upstream to the rupture disc 30. Water is only able to bypass the NRV 40 in one direction from the inlet 11 to the rupture disc 30. Thus, once the pump starts, water will flow into the housing 10 through the inlet 11. Then, within the maximum allowable working pressure, a certain amount of water will stay inside the housing 10 in the area between the NRV 40 and the rupture disc 30 even though the trigger changes its activation mode (from active to inactive), or the pump changes its working mode (from active to inactive), thereby keeping the pressure stable at the upstream side of the rupture disc 30. At the downstream side of the rupture disc 30, which is open to the surrounding air, the pressure is also basically stable.

As a result, when the high-pressure washer changes mode from standby mode to work mode, and vice versa, the pressure at both sides of the rupture disc 30 is kept stable. The rupture disc 30 will thereby not easily be subject to metal fatigue, resulting in a relatively longer service time of the rupture disc 30 and the entire high-pressure washer. In the shown embodiment, the NRV 40 is positioned inside the housing 10. The NRV 40 is here shown comprising a support 41, a sleeve 42, a ball 43, and an elastic part 44.

The support 41 is configured to support both the rupture disc 30, and the elastic part 44. Furthermore, the support 41 is also configured as a blocking part to prevent the ball 43 from ejecting out of the housing 10 in a situation when the rupture disc 30 breaks.

Referring to Figures 5-7, the support 41 is shown comprising a first support part 411 and a second support part 412. The first support part 411 has a smaller outer diameter than the second support part 412.

The second support part 412 is shown having a bowl shape, which forms a disc chamber 4120 (see e.g., Figure 7). The rupture disc 30 is partly mounted inside the disc chamber 4120, with the upstream side of the rupture disc 30 being in contact with the second support part 412. At least part of the disc chamber 4120 is of a corresponding shape as the rupture disc 30. When the head 20 is mounted on top of the rupture disc 30, the head 20 presses from the top side (once the head 20 is tightened), thereby keeping the rupture disc 30 in place. At the same time, the outer circumference of the second support part 412 seal with the inner surface of the housing 10, the upstream side of the rupture disc 30 seal with the second support part 412, the downstream side of the rupture disc 30 seal with the head 20, and the head 20 seal with the housing 10. This structure ensures a watertight/fluid-tight sealing across the rupture disc 30 within the drainage/fluid passage.

The bottom wall 4121 of the bowl-shaped second support part 412 forms one or more channels/holes 413 (here, four are shown). Preferably, the diameter of the channel/hole 413 is smaller than diameter of the ball 43. The bottom wall 4121 functions as a separating wall for the ball 43, which allows water to flow to the rupture disc 30, but at the same time keeping the ball 43 away from the rupture disc 30. This structure makes the second support part 412 to work as a blocking part, which is useful especially in the situation when the rupture disc 30 ruptures, to avoid the ball 43 from shooting out of the housing 10, like a bullet under pressure.

Preferably, the number of holes 413 is at least two to avoid that the ball 43 can block all holes 413, thereby preventing the release of pressure.

The first support part 411 is connected to the second support part 412. The first support part 411 has a cylindrical/tubular shape and stretches towards the ball

43. The first support part 411 mainly functions as a support for the elastic part

44.

In this embodiment, the elastic part 44 is a coil spring. The elastic part 44 is positioned/mounted around the first support part 411. One end of the elastic part 44 faces the ball 43 and the elastic part 44 is thereby adapted to push the ball 43 against the inlet 11 in order to close the inlet 11 when the water/fluid pressure is relatively low in the pipeline, e.g., when the pump unit is inactive. When the pump unit is active, the water/fluid pressure is relatively high in the pipeline. This pressure acts on the ball 43 and elastic part 44, and the elastic part is forced away from the inlet 11 while being compressed (or stretched depending on the specific configuration), making the ball 43 move towards the first support part 411, resulting in fluid/water flowing through the inlet 11. As soon as the water/fluid pressure drops, the coil spring 44 forces the ball back into contact with the inlet 11, thereby preventing a complete emptying of the drainage/fluid passage upstream to the rupture disc 30.

It should be noted that, the elastic part 44 is not necessary in all embodiments, e.g., in an embodiment where the housing 10 is configured to be positioned with the inlet 11 facing downwards. Here, gravity will act on the ball 43, and once the water/fluid pressure at the upstream side of the ball decreases, the ball 43 will fall down to seal the inlet 11.

Preferably, the end of the first support part 411 facing the ball 43 forms a concave part 4110 adapted for receiving the ball 43, as e.g., seen in Figure 6. When the rupture disc 30 ruptures, the ball 43 may thereby be caught by the concave part 4110. In this way, the concave part 4110 prevents the ball 43 from tipping away from the centre when the water/fluid flow rush through. Preferably, the inner surface of the concave part 4110 is cone shaped. This embodiment provides a stable support for the ball 43 as the contact area will then be circular.

The sleeve 42 is shown positioned around the elastic part 44. The outer peripheral surface of the sleeve 42 is configured to obtain an interference fit (also called friction fit) with the housing 10, to fix the sleeve 42 in the radical direction R (see e.g., Figures 4 and 5). One end of the sleeve 42 touches the bottom wall of the housing 10, while the other end of the sleeve 42 touches the second support part 412, thereby keeping the sleeve 42 fixed in the axial direction A.

The upstream part (again relative to the fluid flow) of the sleeve 42 abuts the inlet 11, and the downstream part of the sleeve 42 abuts the hole(s) 413 formed in the second support part 412. The sleeve 42 keeps the ball 43 in the centre, and at the same time makes drainage passage around the ball in case the fluid pressure exceeds the maximum allowable working pressure.

Referring to Figures 10 and 11, the sleeve 42 is shown comprising a main chamber 42m and four grooves 42g surrounding the main chamber 42m. The ball 43 is positioned in the main chamber 42m, while the grooves 42g each are adapted for directing fluid/water through the sleeve 42 and into each hole 413 in the second support part 412. Hence, in general, the number of grooves 42g corresponds to the number of holes 413 in the second support part 412.

Between two adjacent grooves 42g a protrusion 420 is formed, which is used to guide the ball 43 during its movement. The inner diameter of the main chamber 42m is preferably slightly larger than the diameter of the ball 43. For example, the protrusion 420 and the ball 43 has a clearance fit. In this configuration, the sleeve 42 functions as a guide for the ball 43.

Preferably, the inner hole of the sleeve 42 comprises a first chamber 421, a second chamber 422, and a middle chamber 423 (see e.g., Figures 5 and 10. The first chamber 421 is positioned at the upstream side, the second chamber 422 is positioned at the downstream side, and the middle chamber 423 is positioned between the first chamber 421 and the second chamber 422. The inner diameter of the first chamber 421 is here shown to be larger than that of the middle chamber 423, which makes the water/fluid free to flow into the grooves 42g.

The inner diameter of the second chamber 422 is also shown larger than that of the middle chamber 423. The second chamber 422 is directly linked to the hole 413, which both contribute to an easier water/fluid flow towards the rupture disc 30.

Preferably, structure of both ends of the sleeve 42 are symmetrical, or in other words, the first chamber 421 and the second chamber 422 are the same, which makes the assembling of the sleeve 42 easier.

Referring to Figures 3 and 4, a head 20 is shown fixed to the end of the housing 10 opposite to the end with the inlet 11. The head 20 is hollow and comprises a central hole/channel 21 along the axial direction A. This central hole/channel 21 is in fluid communication with the housing's drainage/fluid passage. The end of the head 20 furthest away from the rupture disc 30 forms at least one drainage hole 22 (six drainage holes 22 are shown in this embodiment), here opening along the radical direction R, perpendicular to the central channel 21. The drainage hole 22 connects the central channel/hole 21 and the air outside, forming an outlet to the central channel 21. When the water pressure inside the pipeline exceeds the maximum allowable working pressure, the rupture disc 30 will break, and fluid/water will flow through the central channel 21 and out of the drainage hole 22. In this way, the rupture disc valve assembly (V) comprises a drainage/fluid passage comprising a first section (here the housing's drainage/fluid passage), and a second section (here the central channel 21 in the head 20). The first section is in fluid communication with the pipeline, although this communication may be blocked by the ball 43 when the fluid pressure within the pipeline is relatively low. At the time when the rupture disc 30 brakes, the second section will also be in fluid communication with the pipeline, via the first section.

Preferably, the head 20 is provided with an external thread, and the housing 10 with an internal thread. In this way, the head 20 may be mounted to the housing by being partly inserted into the housing 10 and thereby the head 20 is mounted on top of the rupture disc 30, as explained above. Preferably, the head 20 comprises a protrusion part 23 at the end furthest away from the drainage hole(s) 22. The protrusion part 23 is inserted into the disc chamber 4120 of the support 41, as also explained above. The protrusion part 23 abuts the rupture disc 30 to fix the rupture disc 30 in the axial direction A.

By using a threaded connection, the housing 10 and the head 20 can easily be assembled and disassembled, which also makes it easy to perform maintenance of the rupture disc 30.

It should be noted that the water/fluid filled space inside the housing 10, between the ball 43 and the rupture disc 30, may be configured to be relatively small. In this way, when disassembling the head 20 from the housing 10, the impact force from the water/fluid within the space is to be considered safe.

A drainage cup 50 may be fixed to the head 20 via a fastener 60 (see e.g., Figures 3 and 4). The drainage cup 50 is here shown comprising a side wall 51. The side wall 51 is adapted for covering the drainage hole 22 in the axial direction A. A gap is formed between the side wall 51 and the head 20. Thus, when high- pressure water/fluid sprays from the drainage hole 22, the side wall 51 will work as a safety shield, preventing the flow of fluid/water from damaging people or objects in the vicinity.

Preferably, the fastener 60 comprises a bolt 61 and a spring washer 62. In this embodiment, the head 20 comprises a threaded hole at the end where the drainage hole(s) 22 is/are located. The bolt 61 matches with the threaded hole.

Figure 8 shows a second embodiment of the rupture disc valve assembly V according to this invention. In the following description of the second embodiment, only the differences to the first embodiment are explained in more detail. The explanations with respect to the first embodiment are also valid in the same way or in analogously the same way for the second embodiment. Same reference numerals designate the same features that have been explained with reference to the first embodiment or functionally equivalent features. Compared to the first embodiment, the rupture disc valve assembly V does not comprise a drainage cup, also the fastener is not needed. Without a drainage cup, water/fluid will freely spray out when rupture disc ruptures.

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. For example:

(i) As a part of the rupture disc valve assembly, the NRV is not limited to be integrated within the housing 10.

For example, referring to Figure 9, the NRV 40 could be positioned outside of a housing (not shown in the figure), while the rupture disc 30 could be positioned inside a housing, while the NRV could be connected to the housing at a position upstream to the housing.

(ii) The NRV is not limited to have the same structure in the first embodiment. Any kind of non-return valve could be applied to keep a certain amount of water inside the housing 10 to create stable water pressure for the rupture disc 30.

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.