-
The present invention relates to pipework components and systems, and more particularly relates to systems for flushing pipes, taps, and related components, and for components that make up such systems. It has particular utility with water pipes, but can be used with pipework arranged to carry other fluids too.
-
There is, in many countries, a regulatory requirement making it mandatory to take action to prevent the growth of Legionella bacteria in water systems. A part of this is the prevention of water from stagnating in pipework, tanks, and taps etc. Thus, those with responsibility for water systems in public buildings, factories, commercial premises, hospitals, care-homes etc. are generally required by the relevant safety authorities to flush through their water systems on a regular basis, e.g. daily, weekly or monthly to prevent any such stagnation. For example, in the UK, the Health and Safety Executive guidance on the control of Legionella bacteria in hot and cold water systems states that 'Dutyholders are required to prevent or control the risk from exposure to legionella. Precautions include physical methods such as regular movement of hot and cold water in distribution pipework, regular flushing of outlets to ensure water cannot stagnate in the hot and cold water systems'. Typically, employers in the UK are encouraged to flush through water taps and showers on their premises for at least two minutes on a weekly basis. This is especially important for water outlets that are otherwise infrequently used.
-
Often such flushing is done manually - by an employee physically turning on water taps, timing a two-minute flush and possibly, for a hot-water tap, recording the water temperature attained at the end of the flush. There is now a move to automate these flushes as doing so by a manual method is very labour intensive. Sometimes an automated flush will be done through the tap/shower itself. However, this requires automatic flush outlets to be fitted, at significant expense, and comes with a potential risk of scalding or flooding as the water flows, unsupervised, into the basin/shower tray, etc. An electrical power source to the tap fitting is also required, which adds to the expense where this is not available.
-
To avoid retrofitting premises with expensive flushing outlets, a less expensive and potentially safer solution is to fit an auto-flushing valve into the pipework such that the water flushes directly down a drain. This solution can be easily retrofitted into existing water systems. Typically, the water supply pipe to the tap would be cut and a three-way Tee-piece fitted to reconnect the pipe to the outlet but also to provide an extra pipe run to the auto-flushing valve and then on to a drain.
-
However, there is a problem with this approach. In a retrofit to an existing water outlet, the take-off point tapped into the water supply pipe that diverts the fresh water to the drain is often necessarily fitted some distance upstream of the tap or other outlet, due simply to the physical layout of the plumbing arrangement and the surrounding fixtures and fittings causing an inability to get very close to the body of the tap or shower head. In such a situation the pipework downstream of the valve - all the way to the outlet - will not be flushed out when the valve opens to the drain. The water trapped within this section of pipework can potentially become stagnant. This section of pipework that remains unflushed is known in the water industry as a 'dead-leg'.
-
European patent application No. 22177368.2 discloses a means for flushing the water in the dead leg section of pipework, that involves inserting a fitting in the vicinity of the flushing valve, located upstream at or near an end of a dead leg section, the fitting having a narrow pipe that can feed down into the dead leg section, and can flush water through. This provides a significant improvement, and can in some circumstances be used to flush the whole of the dead leg section. However, in some installations it can be inconvenient mounting a valve and pipework in a location that allows a narrow pipe to be fed through a sufficient distance to the tap or other outlet.
-
Embodiments of the invention have the object of addressing one or more of the above shortcomings of the background art, or which provide an alternative flushing system.
-
According to a first aspect of the present invention there is provided a flushing system for a dead-leg section of pipework, comprising a flush valve for fitting, in use, into an upstream part of the pipework, and an expansion vessel for fitting, in use, in a section of the pipework downstream from that of the valve, where at least some of the downstream section of pipework constitutes a dead-leg, wherein the expansion vessel comprises a chamber and an inner pipe arranged to sit within the pipework, in fluid communication with the fluid in the pipe to which it is attached, when installed and wherein the expansion vessel is arranged, when in use, to connect to fluid in the pipework via the inner pipe, that is arranged to extend either downstream or upstream from the point where the expansion vessel is attached to the pipework.
-
Embodiments will typically be used in water systems, where measures need to be taken to reduce the risks presented by stagnant water in dead leg regions of pipework from becoming a health hazard. Embodiments encourage movement of fluid present in a dead leg pipe section when a flush valve, upstream of the dead leg, is activated. It takes advantage of the pressure differential that occurs in the pipework when a valve, such as the flush valve, is activated, to use this pressure change to move potentially stagnant water in the dead leg.
-
It should be noted that the pipework into which the system is installed does not form part of the invention.
-
Embodiments of the invention allow movement of fluids, such as water, within dead leg pipework to help alleviate issues with stagnant water remaining in the pipe as it sits there.
-
In some embodiments the chamber in the expansion vessel that is in fluid communication with the fluid in the pipework is arranged to have a volume that expands or contracts according to increases or decreases in the pressure of the fluid respectively. Here, "fluid communication" means that fluid is able to flow from the pipework into the expansion vessel, and more particularly, into the volume that expands with increasing pressure, or contracts with decreasing pressure.
-
The flush valve may be an automatically operated valve that is arranged, when activated, to direct water in the pipework to a drain. Flush valves are used in current flushing systems, and so their use will be clear to the normally skilled person. A normally skilled person will also appreciate that if a water pipe under a high static water pressure has a flush valve fitted that is then opened and feeds the water into an open drain, then the water pressure within that pipe will fall close to zero. Thus, in this scenario, there is a significant pressure differential exhibited in the water pipe, depending on whether the flush valve is open or closed. Typically, the flush valve may be operated for a period of between one minute and five minutes periodically, such as daily or weekly. In some embodiments the flush valve may be arranged to operate, for each periodic flushing cycle, in a plurality of activations. For example, it may be switched on once, and left to drain water for the desired time, but it may also be switched on a plurality of times, e.g. two, five, or ten times for a total duration similar to that previously done in a single burst. This provides the advantage of a plurality of pressure changes in the dead leg which, as will be explained below, aids the invention in flushing a dead leg more effectively.
-
In embodiments the expansion vessel connects to fluid in the pipework via an inner pipe, that is arranged to sit within the pipework, and to extend either downstream or upstream from the point where the expansion vessel is attached to the pipework. By having an inner pipe that sits within the pipework of the dead leg and to extend in a direction ether upstream or downstream, it encourages fluid to flow along the pipe as it gets ejected from the expansion vessel when the pressure changes (i.e. when the pressure drops within the pipework). Where the expansion vessel is at or close to the tap end of a dead leg, then it may be more beneficial to have an inner pipe that directs water downstream towards the tap, so as to flush it. Elsewhere, it may be more beneficial to have an inner pipe arranged to push water back towards the flush valve.
-
In some embodiments having an inner pipe, the inner pipe incorporates one or more valves and apertures that promote movement of fluid primarily in one direction along the inner pipe. Thus, in such embodiments, there may be a separate inlet, having a one-way valve, in one part of the inner pipe or expansion vessel, and a separate outlet in the pipe, again having a one-way valve. Thus the expansion vessel may take fluid in through the inlet, and expel it through the outlet.
-
In some embodiments the expansion vessel may form part of a tap installable on the pipework, the tap being to provide user access to the fluid within the pipework. This has the advantage that the expansion vessel is right at the downstream end of the dead leg, and so it is able to move water that sits at this otherwise often hard to get to part of the pipework. The expansion vessel may be built into the tap as a fully integrated element thereof, or it may be arranged to attach to a part of the tap, such as at or near the part of the tap that connects to the pipework.
-
Preferably, in some embodiments where the expansion vessel is in, or alongside, the tap, the system further incorporates an inner pipe that runs from the expansion vessel and runs upstream within at least a part of the dead-leg pipework, and further wherein there is a valve on the inner pipe that allows fluid only to flow away from the expansion vessel when flowing through the inner pipe. This valve therefore prevents fluid from flowing towards the tap, via a route through the inner pipe. This means that water drawn in to the expansion vessel as the pressure increases won't be water that it has previously just expelled and is within the inner pipe. Thus, a better movement of water along the dead leg, that cycles water further back upstream towards the flushing valve is achieved.
-
More preferably, in such systems, there may also be a valve in the dead-leg pipe that prevents flow of fluid back from the tap region through the pipe, except via the inner pipe.
-
In some embodiments the system may comprise a plurality of expansion vessels that are attached to the dead-leg section of the pipework at different places thereon. By having multiple expansion vessels, a greater quantity of water may be moved inside the dead leg portion of the pipe with each cycling of the pressure caused by activation of the flush valve.
-
It will be appreciated that the, or each, expansion vessel has a differential volume, this being the difference between the volume of the first region (i.e. the region that is filled by the fluids from the dead leg pipe) when the water in the pipe is at a high pressure, and the volume of the first region when the water in the pipe is at a low pressure. The high and low pressures are those when the flush valve is closed, and open, respectively.
-
In a preferred embodiment, the differential volume of the expansion vessel(s) present on the dead leg is of the same order as that of the volume of water in the dead leg. It may not be practical to achieve this in some environments, due to an excessive dead leg length, or cost or practicality of installing a suitable number and size of expansion vessels. In that case a smaller differential volume may be used. It will be appreciated that as the ratio of the differential volume in the expansion vessel(s) to that of the volume in the dead leg decreases, then the effectiveness - per flushing cycle - is reduced, but it will still have some beneficial effect on flushing the dead leg. Preferably therefore, the said ratio is greater than 0.5, such as 1, but other, increasingly less preferred embodiments may have smaller ratios, such as 0.3, 0.2, 0.1 or 0.05. Although less preferred, they are still useful. More flushing cycles may be required to get good clearance of the dead leg as the ratio reduces.
-
In some embodiments, the expansion vessel or vessels do not have any inner pipes directing the fluid upstream or downstream. In some embodiments incorporating multiple expansion vessels on a dead leg section, the vessel nearest the tap end may have an inner pipe directed downstream towards the tap itself, and preferably with the inner pipe having a port to the dead leg pipe close to or at the tap itself.
-
In some embodiments the chamber in the expansion vessel has a moveable, or resilient flexible region that is responsive to pressure changes within the chamber. In some embodiments the chamber in the expansion vessel comprises a cylinder having a piston that is biased in position with a resilient means, and wherein an increase in pressure within the cylinder acts to move the piston within the cylinder, increasing the volume thereof.
-
An advantage of having a piston arrangement is that the flexible resilient means, such as a spring, or rubber material, can be largely or entirely separated from the fluid. If the fluid is water, then having rubber material in contact with the water can be disadvantageous, in that it can break down over time, leading to potential leaks, but also any organic material contained therein can act to feed bacteria as it ages. Also, over time, and due to the large number of times the rubber sheet will flex back and forth in use, microscopically small cracks can appear in the rubber sheet, and these small cracks can harbour dangerous biofilm. A piston-type expansion vessel may advantageously comprise a piston made of a metal or inorganic polymer, or similar material. Preferably, no, or very little, organic material will be in contact with the fluid in the pipework. Where a rubber material is used, for example as a seal, then preferably the amount of rubber in contact with the fluid in the pipe work is kept small, through use of other materials where possible.
-
In some embodiments that use a piston, the piston is arranged to have a resting position, when at zero fluid pressure, that excludes substantially all of the fluid from the chamber. Thus, when a flushing tap is activated and the pressure in the pipework drops right down, then substantially all of the fluid in the chamber is expelled into the pipework, resulting in a more efficient flush.
-
In some embodiments the resilient means comprises a spring. The spring may be a metal spring, or may be made from rubber, or some other resilient, stretchable material. The rubber may be a synthetic butyl elastomer. Alternatively, the resilient means may be provided by air pressure, or through a weight acting compressively on a closed region, etc.
-
It will be appreciated that, in use, the expansion vessel should be connected between the flush valve and a tap.
-
According to a second aspect of the present invention there is provided a tap, valve, or other water outlet comprising of a handle for allowing release of a fluid, and an expansion vessel comprising a chamber having a volume for storage of the fluid, the volume being variable dependent upon the pressure of the fluid in the tap, the tap being arranged to be used as an expansion vessel in a system as described herein.
-
Thus the tap, valve or other water outlet is able to provide the function of the expansion vessel as described above, whilst also providing the functionality of the tap.
-
Embodiments of the invention are further described hereinafter, by way of example only, with reference to the accompanying drawings, in which:
- Figure 1 diagrammatically illustrates an embodiment of the invention, showing a pipe system with a dead leg, and with a flush valve and an expansion vessel;
- Figure 2 diagrammatically illustrates another embodiment of the present invention, wherein an expansion vessel is positioned within a tap at a downstream end of a dead leg;
- Figure 3 diagrammatically illustrates a further embodiment, wherein an expansion vessel is incorporated into a tap, and wherein an (optional) internal pipe and valve arrangement aids the flow of water back through the pipe as the expansion vessel is filled and emptied due to pressure changes in a connected pipe;
- Figure 4 diagrammatically illustrates a further example, wherein a plurality of expansion vessels are positioned along a section of dead leg pipework; and
- Figure 5 diagrammatically illustrates an alternative design for an expansion chamber as may be used in embodiments of the invention.
-
Figure 1 shows a first embodiment of the present invention, installed on a pipe network. A water pipe 10 supplies water to different parts of a building, such as an office, a factory, a hospital etc. This is of course a much simplified view of what would be a much more complex system. Typically there are many water pipes in such buildings, depending for example on the size of building. Spurring off from these pipes are other, often smaller diameter pipes that might feed individual taps. One such pipe 12 is shown, and which has a tap 14 at its end. This pipe passes water along it when the tap 14 is turned on. There will typically be many such spurs 12 coming off a main pipe 10. Thus, there is normally a throughput of water along pipe 10 caused by the various taps, showers, etc., to which it ultimately connects, drawing water off. The water in pipe 10 therefore is changed regularly, and hence there is little chance of any water remaining stagnant in there for any length of time likely to lead to any biological issues such as buildup of biofilm etc. Water that is in pipework such as pipe 12 is dependent upon the tap 14 that sits at the end of the pipe being activated, to flush water through, to be replaced by fresh water from pipe 10. If the tap 14 isn't used for longer periods of time, then the cleanliness of the water sitting in the pipe can become an issue, with the danger of biofilm buildup, or other problems such as Legionella virus becoming prevalent. Thus, as discussed above, it is preventable by regular activation of the tap 14. This doesn't always occur for various reasons, and so, according to an embodiment of the invention, an expansion vessel 16 has been fitted to the pipe 12 at a point as close to the tap 14 as possible, given the arrangement of the pipework.
-
The expansion vessel in this embodiment comprises of a metal container that is divided into first and second regions, separated by a flexible, resilient membrane 18, made from a synthetic butyl elastomer. Only one of the regions is open to the water from the pipe 12. Water from pipe 12 is hence able to freely enter the vessel 16, but only within the first region. The volume of the first region is dependent upon the pressure of the water within the pipe 12. If the pressure is relatively high, then the water will press harder against the membrane 18, increasing the volume in the first region, with a commensurate decrease in the volume of the second region. The second region is an enclosed region within the expansion vessel that is pressurized with compressed air. The pressure therein is adjustable by means of a valve (not shown) through which air can be added with a pump, or vented to atmosphere, and is adjusted in use dependent on the pressure of the fluid in the pipe to which the vessel is connected, so as to get a good range of differential volume. If the water pressure lowers in the pipe 12, then the volume of the first region will reduce, as the flexible membrane 18 returns towards its resting tension due to the stretchiness of the membrane 18. As the volume in the first region reduces, the water contained therein will pass back into the pipe 12.
-
Automatic flush valves are often installed in pipework to allow for water to be flushed away. It is not always possible to install them in the optimal places, which generally would be immediately adjacent to the tap end of a dead leg branch of pipework. An automatic flush valve 20 is shown in Figure 1, that has a power connection 22, and a drain pipe 24. It is installed in the dead-leg section of pipework 12, and in practice will be installed as close to the tap end 14 of the pipe as possible, but has been shown nearer the connection to the main pipe 10 here for clarity. When activated by a suitable power source, the valve 20 opens and directs water to flow down the drain pipe 24 to a drainage network. It will be understood by those of ordinary skill in the art that when a flush valve is activated, so as to flush water in the pipework into an unpressurised drain pipe, then the water pressure within the pipe will drop. This pressure drop propagates along the pipework. Hence, activation of the valve 20 will cause the water pressure at the feed pipe of the expansion vessel 16 to similarly drop. As explained above, this will cause water within the expansion vessel to be at least partially expelled back into the pipe 12, through its connection to pipe 26. The direction of the exit pipe promotes a movement of water along the pipe 12, which helps to promote movement of water in the dead leg pipe 12, and hence to aid movement and replacement of water in the whole pipe.
-
It can be seen then that activation of the flush valve 20 causes movement of the water within dead leg pipe 12, helping to recirculate and change the water therein due to the presence of the expansion vessel placed in the dead leg section of the pipe. It will be appreciated that any pressure changes, such as those caused by other taps operating on the pipe network will also have a similar effect, although perhaps reduced in effectiveness if the pressure drop isn't so big.
-
Figure 2 shows another embodiment of the invention, this time incorporating an expansion vessel that forms part of a tap. A tap 40 is connected to a pipe 42, which comprises a dead leg section of pipework in a greater network of water pipes. The tap 40 comprises a rotatable handle 44 which, when rotated in a certain direction will raise up a plug 46 from an aperture 48, often a valve seat, thus providing a path for water to flow down to the tap exit point, or spout, 50. In as far as has been described so far, it is a conventional tap. The tap however further comprises an expansion chamber 52 that has a flexible, resilient and impermeable membrane 58, that divides the chamber into a first 54 and a second 56 regions. In this sense the chamber is similar to chamber 16 described in relation to Figure 1. The chamber is on a side of the tap that is in direct fluid communication with the pipe 42, when the tap is closed. Thus, the chamber is subject to the various pressure changes that might occur in the pipe, as flush valves or other taps are activated. The expansion chamber 52 behaves similarly to that described in Figure 1, in that an increase in pressure in pipework 42 will push more water into the chamber, increasing the volume of the first region 54, and reducing it in region 56. The elastic nature of membrane 58 means that when pressure in pipe 42 reduces, such as when a flushing valve is activated, water within region 54 will be forced back upstream into the pipework 42. This helps move the water within the pipe as previously described, and so helps to flush it from the dead leg. Normal operation of the tap is unaffected. When the tap is activated by turning the handle 44 then water will flow from both the chamber, and from the pipe 42.
-
It will be appreciated that other taps will also be suitable for this purpose, i.e. incorporating a built-in expansion vessel. Such taps may have, for example, a ceramic disc cartridge style of valve, such as the popular quarter turn taps. As the expansion vessel is arranged to sit on the pressurised side of the valve within a tap, the type of valve mechanism is not relevant to the invention.
-
Figure 3 shows a further embodiment of the invention, again with an expansion vessel incorporated into a tap. The tap and its operation is the same as that described in relation to Figure 2. Reference numerals of Figure 2 are therefore replicated in Figure 3. Instead of being fitted directly to a pipe however, it is fitted to another fitting that sits between pipe 42 and tap 40, and which incorporates an inner pipe and a pair of one-way valves. In more detail, the fitting 60 comprises of a pair of couplings, 62, 64 for attaching the fitting between a pipe 42 and a tap 40. It further comprises of an inner pipe 66 having two ends, that is arranged when fitted to sit within the pipe 42, with a first end 68 of the inner pipe positioned ideally within the tap body near to the expansion vessel 52, and with a second end 70 of the inner pipe sitting upstream of the fitting. Preferably the second end 70 is located some distance, such as 20cm, 30cm, 40cm, 50cm upstream of the fitting, although clearly other distances may be used depending on the details of the particular installation. The inner pipe is held in place with a plate 72 that sits transversally in the pipe, and which blocks flow of water through the fitting except either through the inner pipe 66, or through a port 74 in the plate. A one-way valve 76 allows water to freely flow out of the inner pipe back upstream, away from the tap. A one-way valve 78 is arranged in the port 74, that allows water to flow only in the direction of the tap 40.
-
When there is an increase in pressure in the pipe 42, then water will tend to flow along the pipe, through port 74 and into the expansion vessel 52, similar to as explained in relation to Figure 2. The valve 76 prevents water flowing through the inner pipe under this condition. When the pressure reduces, when for example a flush valve (e.g. 20 of Figure 1) is opened, then the operation of the membrane 58 pushes water back along the pipe 42, with the only way it can move being through the pipe 66, due to the operation of valve 78 cutting off that flow route. In this way the water expelled from the expansion chamber 52 gets pushed much further back upstream than would otherwise be the case.
-
A preferred aim of this arrangement is to move water expelled from the expansion chamber within the tap as far as practically possible upstream into the pipe 42, to encourage it to leave the dead leg. Clearly, in many arrangements it won't be practically possible to do this, so a further preferred aim is to move water up to, and preferably beyond, any further expansion vessels that may be fitted to the dead leg pipework 42. Water that is moved up to there can then be further propelled by the action of this other expansion vessel, and any others that might be located on the dead leg, up to the flush valve and hence to a drain.
-
Figure 4 shows an embodiment of the invention having a plurality of expansion vessels positioned on different parts of a dead leg section of pipework. As explained above, it is beneficial for the differential volume of all expansion vessels on a length of dead leg pipework, to be ideally similar to that of the volume of fluid in the pipe. One convenient way of accomplishing this is to distribute this differential volume over more than one expansion vessel. This is shown in the figure. Various parts of a dead leg section of pipework 80 are shown, having expansion vessels thereon. A tap 82 is located at a far end of the pipe 80. Set back from the tap along the pipework is an expansion vessel 84. It has an open connection allowing fluid flow thereinto via an inner pipe 86. This inner pipe 86 is fed, during installation of the vessel 84, along the pipe 80, and is arranged with its open end to sit at, or very close to, the tap 82.
-
Further back along the pipe 80 from the vessel 84 is another expansion vessel 88, again open to fluid from the pipe 80. This vessel 88 does not have an inner pipe, and so is arranged to draw and eject water (according to pressure changes in the pipe 80 as previously explained) into the pipe 80 with no directionality.
-
Yet further back along the pipe is another expansion vessel 90, again open to fluid present in pipe 80. This expansion vessel 90 has its fluid feed to and from pipe 80 via an inner pipe 92 that is directed back upstream. Hence, when in normal operation, and the fluid pressure in pipe 80 drops due e.g. a flush valve 94 being switched on, fluid will be ejected back upstream to be eventually ejected by the flush valve.
-
It has been found that, although directional pipes such as pipe 86 and pipe 92 are useful in pushing fluid in particular directions, it is not essential for the operation of embodiments of the invention. As all of the expansion vessels present on a dead leg will respond to a lowering of pressure at the same time, then the additional fluid introduced to the pipe from the expansion vessels tends to push the fluid back upstream, and hence nearer to a flush valve, and so increases the chances that it will be expelled in due course.
-
The embodiments shown above have all had a particular type of expansion vessel, namely one comprising a pipe to draw water from a main fluid pipe (either with an inner pipe inserted into the main fluid pipe, or not), and a chamber divided into two regions, separated by an impermeable, resilient membrane. For all of these embodiments, other types of expansion vessel may be used. One such alternative type of expansion vessel is shown in Figure 5. An expansion vessel 100 is shown attached to a pipe 102, such as a dead leg section of pipe. It is attached by a fitting 104, which has a screw mount for the vessel 100. The vessel comprises a cylinder 106 with a piston 108 that is able to slide up and down the cylinder 106. The piston has a guide rod 110 attached thereto, which feeds through a hole in a support cap 112. A compression spring 114 sits between the piston and the support cap, which biases the piston 108 into a lower part of the cylinder when no, or a relatively low, external fluid pressure (i.e. a pressure in the pipe 102) is present. The piston is sealed against the cylinder to prevent fluid leaking out from the pipe 102. When the fluid pressure in the pipe 102 increases, such as up to a standard working pressure, the pressure pushes the piston up towards the top of the cylinder, so increasing the volume of the cylinder below the piston, and providing a temporary store of fluid. When the pressure drops, due e.g. to activation of a flush valve on the pipe 102, then the spring 114 forces the piston down, ejecting at least some of the water in the cylinder back into the pipe. Thus, it acts as an expansion vessel able to provide a similar function to those described above.
-
Note that the embodiments have been shown and described in a simplified manner, and there may be other details of pipework, and components, such as seals, materials etc. that would be understood by the normally skilled person.
-
The invention has largely been described in terms of being used with a fluid. Typically, the fluid will be a liquid, and typically the liquid will be water. However, the invention has utility with other fluids also, where there is a desire not to allow a fluid to remain stagnant in a dead leg branch of pipework.
-
The functions described herein as provided by individual components could, where appropriate, be provided by a combination of components instead. Similarly, functions described as provided by a combination of components could, where appropriate, be provided by a single component. The figures are not drawn to scale.
-
Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
-
Features, integers, or characteristics described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.