Statement of Corresponding Applications

The present invention claims priority to New Zealand Patent Application No. 777813, and New Zealand Patent Application No. 789714, the entire contents of each are herein incorporated in their entirety by reference.

Field of Invention

This invention relates to a monitoring and alert system.

It should be noted that the present invention has particular application to monitoring systems for use with monitoring systems concerned with the "three waters" - namely drinking water, wastewater (which includes sewage) and stormwater. However, the principles behind the present invention can be applied to other systems particularly those where it could be desirable to detect the presence or absence of a substance such as a fluid.

For example, the present invention may be used in various fluid systems having pipework and/or reservoirs including but not restricted to milking systems, internal guttering on roofs, oil pipelines, factories, farm effluent pits, sewage pits, flood protection on rivers, water reservoirs, bilge areas in boats, cellars, early flood prevention, farm troughs and dams.

Background to the Invention

The smooth running of a city's three waters infrastructure is paramount to the operation of a city.

Recognition of the importance of this has been heightened with the New Zealand Government currently reviewing how to improve the regulation and supply arrangements of the three waters to better support New Zealand's prosperity, health, safety, and environment. Similar work is being done elsewhere around the world.

With an aging municipal infrastructure network that is expensive to replace, the emphasis has fallen to actively managing and mitigating existing sewer and stormwater assets. Water systems are large, overly complex, and difficult to monitor in a reliable cost-effective way. They have many nodes and intersections with pipes, pits, and reservoirs. It can be difficult to know when and where a blockage, leakage or an event associated with over-capacity has occurred. Often there is considerable pollution through the likes of sewage overflow occurring before a blockage or another adverse condition is identified and remedied.

Further, with increasing expansion of residential areas, there is increased pressure on pumping stations to perform as more houses are added to existing networks with adverse weather events. Storm water systems are also more likely to over-flow. Therefore, it would be desirable to have a simple inexpensive system that could give ready warning of pumping station failures or failures within a linked water system.

Of the three water systems, drinking water is the easiest to monitor as it is usually a single-phase system. Often complex sensor systems are used to monitor consumption so that the consumer can be charged accordingly.

However, multiple phase systems which have foaming and solids (such as stormwater and wastewater (sewage)) are more difficult to monitor. Usually, the main monitoring requirement is to determine blockages, leakages, or over-flows due to over-capacity.

Access in municipal water systems to fix blockages is often by maintenance (maintenance hole) covers. However, knowing which access point is the right one to use is often not clear and considerable time and money can be wasted by trying to find the source of a problem. Municipal bodies simply do not have the budget to physically have a person inspect a maintenance hole for overflowing issues on a regular basis, resulting in spills into the streets and adjacent environments such as lakes, rivers, oceans, or stormwater infrastructure.

As an example of the above, the Wellington Region in New Zealand had a target for 2020 of less than one hundred wastewater spills. Yet it has experienced 2096 spills (including raw sewage spills onto Lambton Quay a major Wellington CBD Street, covering the footpath). This results in potential health issues, fines, reputational damage, additional clean-ups, and public scrutiny. Ideally, there could be provided a system that is cost-effective for a party to implement and can cover most if not all areas of concern in a fluid system.

There have been several attempts to address issues with water monitoring as can be seen below.

NZ 624958 describes an intelligent network of underground sensors in a water system that detect changes in fluid pressure, flow, and noise. This data is used to not only provide alarms as necessary, but also to calculate conditions of interest which include indicators of water theft and tampering. However, this system is complex, requires advanced sensors and is correspondingly expensive. Further, the conditions of interest are often not required in many water monitoring systems and this system is over engineered for simpler requirements, such as determining when a blockage occurs and where. Many of the sensors in this system would not work in a multiple phase system.

US 8279080 describes a network which has several sensors primarily concerned with metering water flow rate and consumption. It uses water flow to power the system and transmit data as required. Again, the sensors are not suitable for use in a multi-phase system such as sewers. And flow meters in general are expensive and unsuitable for large systems. Further, the degree of complexity and corresponding expense in this system does not make it feasible to use in large networks.

US 6414605 describes a communications unit in a pit lid which receives information from wired sensors in a water system. It should be appreciated that wired sensors are difficult to install in a water system and difficult to maintain. This is especially so in a "dirty water system" such as stormwater or sewage. Conversely, wireless sensors that rely on RF transmission are often not reliable in transmitting accurate data when underground.

CA 2754418 describes a complex system detection of blockages or breakages in pipes. This uses audio signals from multiple sensors within the fluid in the pipes and transmits signals along the pipes carrying the fluid using them as a wave guide. The aim of the system is to determine types of blockages - say fat build-up, tree roots and hairballs. The pipe system is a difficult environment in which to transmit and receive data of sufficient quality to perform the calculations on blockage type, thus requiring a complicated and expensive monitoring system. In general, it should be appreciated many sensor methods such as ultrasonic, mercury switches, float switches and similar devices have proven unreliable in the underground environment coping with additional debris and clogging and are prone to faulty readings and or fouling over time.

As can be seen, there is a need to have a simple reliable and inexpensive system for monitoring fluid systems, - particularly one that enables blockages, leakages, or over-capacity in a fluid system to be easily detected.

It is an object of the present invention to provide a monitoring system that solves one or more of the above-mentioned disadvantages, or to at least provides the public with a useful choice.

Summary of the Invention

According to a first aspect of the invention, there is provided a monitoring system for a fluid system the monitoring system including: at least one transmitting device positioned within the fluid system, and at least one receiving device having a signal path to the transmitting device, and at least one communications device for transmitting a signal that could be indicative of an alert condition wherein the transmitting device is capable of transmitting a signal with the property of being attenuated or blocked by fluid along the signal path the monitoring system characterised in that the transmitting device is positioned such that a change in the signal along the signal path from the transmitting device to the receiving device whether transmission, attenuation or blockage is indicative of an alert condition in the fluid system.

In preferred embodiments, it is the blockage or attenuation of the signal in the signal path that is indicative of an alert level. The fluid system can be in several forms, being any system where the presence or absence of fluid is required to be detected. Fluid systems that the present invention can be used with include (but is not limited to) milking systems, oil pipelines, factories, farm effluent pits, sewage pits, drainage ditches, flood protection on rivers, water reservoirs, bilge areas in boats, cellars, commercial guttering, early flood prevention, farm troughs and dams.

The present invention has particular application to networked fluid carrying systems such as those having interconnected pipes, conduits, reservoirs, and the like. While reference will now be made to application of the present invention to a sewage system, the present invention can be applied to other fluid systems and other networked fluid carrying systems.

The transmitting device will in preferred embodiments be transmitting a radio frequency signal. Radio transmitters are relatively inexpensive, and the RF signal readily blocked by immersion in water and other fluids found in a sewage system or other fluid systems.

It should be appreciated that having a signal that is only blocked by full immersion can be a significant advantage - particularly when the present invention is used in "dirty" systems where contaminants such as less degradable tissues and solid waste could accumulate on the transmitter.

In one embodiment the signal will one commonly used in networking systems such as a Bluetooth Low Energy (BLE) signal which operates at a frequency of 2.4GFIz. As a general principle, it should be appreciated that the higher the frequency of a signal, the more readily the signal can be blocked by water and other fluids.

It should be appreciated that other types of signals could be transmitted by the transmitting device, but with present technology RF transmission appears to be well suited, particularly as there are relatively inexpensive RF transmitters currently available.

For ease of reference, the transmitting device will now be called a beacon In some embodiments of the present invention, there may be two or more beacons associated with a single receiver. For example, the beacons may be positioned at different heights in a shaft. Depending on which beacons are transmitting or not, the level of fluid within that shaft can be approximated.

If the beacons have unique identifiers (say BLE UUID) then the position of a blockage or leakage and the subsequent rise or fall of fluid can be easily determined.

If the present invention is to be used for something like flood protection in a river scenario, numerous beacons can be used.

For example, the beacons could be installed at known lengths apart say at one metre. The positioning and rate of flooding and/or water receding can be determined from detecting a signal or not from the beacons and their position.

Multiple beacons can be used in reservoirs with the present invention - for example, a sewage pit. If for example, multiple beacons installed at one metre intervals from the top of a sewage pit can give one metre indications as to how far the pit is from overflowing.

In another embodiment, the fluid system may be a boat with multiple beacons on the interior boat surfaces (such as floors and the bilges) and other beacons in the infrastructure of the boat (such as the skin) which can determine where a leak has occurred,

Preferably the beacons are wireless. If so, the beacon will in most cases require an independent power supply. The beacon's energy can be conserved by using a weak signal (like BLE) to preserve battery life.

It should be noted, that in preferred embodiments, the beacon will transmit either at an optimised pulse frequency or continuously. This gives a constancy in the system and allows for operational variables of the system to be made at other less numerous parts of the system - such as the receivers, communications unit, or a server with which the communications unit talks.

Some embodiments of the present invention may be deployed above ground. These may use alternative power supplies to those underground - such as solar power.

It should be noted that a weak signal is also more readily blocked by fluid. With present technology, continuous and optimised pulse frequency signal transmission can be achieved with minimal power drain. Also, the beacons likely to be used for this purpose will be relatively inexpensive, being just "dumb" (as opposed to smart) emitters.

However, a low powered pulsed signal may also be transmitted from the beacon. Or, in other embodiments, the receiving device (or another device - say the communications unit) may send a signal to the beacon to wake the beacon up - causing it to send a signal back.

While in some embodiments the beacon signal may be continuously read by the receiver and/or communications unit, these devices can be power hungry and data intensive.

The inventors have found that a sampling frequency of around 60 minutes works satisfactorily for municipal sewage systems. However, other time intervals may be used depending on the time sensitive nature of the installation and or data and power capacity. Note that in preferred embodiments, the communications unit can be remotely re-programmed to increase or decrease the time sampling intervals.

It should be appreciated that sewage systems have extraneous matter to water including various solids, human wastes, and fats. This matter can interfere with the operation of conventional sensors and other devices. Therefore, in an exemplary embodiment, the beacon has a smooth non-stick surface to discourage extraneous matter sticking thereto.

Preferably the housing of the beacon is robust enough to be readily cleaned - such as with high pressure water.

Preferably also the beacon, receiving device and communications unit are configured and housed to prevent sparks, and be waterproof and flame retardant. This is particularly important in sewage systems which can contain flammable gases. These devices may also be resin coated to help with waterproofing, spark retarding and general robustness. The beacons may be attached to the system by a variety of means depending on the system conditions. Preferably however the beacons are removable allowing for replacement when necessary.

In sewage systems, the conditions include potentially fast flowing fluid, high pressure fluid, turbulence, rats, and projections such as climbing rungs and reinforcing bars. A suitable attachment method for a beacon in this type of location could be by a rat resistant tie (say made from stainless steel or carbon fibre) on the underside of a climbing rung. High powered magnets could also be used.

The receiving device may come in several forms and in one embodiment may be a BLE receiver.

The communications device (now referred to as a comms unit) can come in many forms.

One function of the comms unit is to communicate an alert signal provided by the absence or not of a signal from a beacon. This can be communicated in a variety of ways for example, an audible siren, flashing light and so forth. It is envisaged that in many cases, that communication will be to a server which is able to work out from the IDs of the beacons where the fault is likely to be. It should be noted that with a networked system a server may receive multiple alert conditions from many sites allowing the server to triangulate sites of concern.

Some communications systems that the present invention may use include Cellular - (CAT Ml, LTE, NBIoT) LAN -(Wifi, BLE) LPWAN - (Sigfox LoRaWAN) Mesh - (Zigbee).

For ease of operation, it is envisaged that the receiving device and the comms unit will be associated with each other and may even share the same housing.

For ease of reference the receiving device and comms unit shall be referenced as part of a single unit, now called a head unit.

The head unit may also send regular signals to a server (analogous to a device heartbeat), so that the server knows that the head unit is functioning, has enough battery power or if the head unit is underwater indicating another potential alert condition. Remote communication by the head unit to a server can also flag and transmit firmware updates over the air to a microcomputer embedded in the head unit.

In an exemplary embodiment, the head unit is associated with an access port to the system being monitored - such as a sewage system. The enables maintenance workers to access blockages/leakages and the like near to where they are detected. As well as providing access to the monitoring system.

The term "associated with" can mean attached to or nearby the access port or the vicinity thereof. As an example, the head unit may be attached to the underside of an access port cover such as a man-hole cover.

In some embodiments the head unit may be integrated with an access port cover.

In a preferred embodiment, the head unit may be attached to a maintenance hole cover above a vertical shaft leading to a sewage system. And the beacons(s) transmitting to the head unit may be positioned within that shaft.

As man-hole covers can block RF signals, in some embodiments, an aperture or hole may be drilled into an existing manhole cover. The hole is preferably of a size into which part of the head unit can be located. This hole can allow signal from the head unit to be transmitted through to a server or the like. Most likely the hole would be comparatively small in diameter - say 20mm.

In some embodiments the hole may be covered with a RF transmissive cap (say made from a plastics material). If the cap is brightly coloured, then that provides a visual indication to a maintenance worker that this cover has a monitoring system.

To prevent water flowing through the man-hole cover and blocking the signal, the head unit can be designed such that water can drain away from the head unit into the sewage system.

Preferably, the head unit is made to be sufficiently flexible that it can resist the forces placed on maintenance holes (and surrounding areas) through traffic and the like. It should be appreciated that some embodiments will require two head units per set of beacons to provide security through redundancy.

According to a second aspect of the invention, there is provided a kitset for use in a monitoring system for a fluid system, the kitset including: at least one transmitting device and at least one receiving device, and at least one communications device for transmitting an alert condition wherein the transmitting device is capable of transmitting a signal with the property of being attenuated or blocked by fluid along a signal path the kitset further including instructions on how to position the transmitting device such that any one or more of the transmission, attenuation or blockage of a signal along the signal path from the transmitting device to the receiving device is indicative of an alert condition in the fluid system.

According to a third aspect of the invention, there is provided a method of operating a monitoring system for a fluid system, the monitoring system including: at least one transmitting device positioned within the fluid system, and at least one receiving device, and at least one communications device for transmitting an alert condition wherein the transmitting device can transmit a signal with the property of being attenuated or blocked by fluid along a signal path and the monitoring system has the transmitting device positioned such that any one or more of the transmission, attenuation or blockage of a signal along a signal path from the transmitting device to the receiving device is indicative of an alert condition in the fluid system the method of operating the monitoring system including the steps of: a) transmitting a signal from the transmitting device on a continuous or non-continuous basis along the signal path to the receiving device, and b) checking whether the signal has been broadcast and/or received, attenuated or blocked by the receiving device, and c) communicating to a server information from step b) which could be indicative of an alert condition in the fluid system.

In a preferred (but not necessarily exclusive) mode of operation, there are multiple sites in the sewage system having beacons and head units in accordance with the present invention.

Typical sewage systems have vertical shafts extending from maintenance holes at ground level into a pipe system underground. Often the vertical shafts have one or more pipes (or conduits) entering the shaft or exiting therefrom. Often the pipe(s) carrying sewage into the shaft are positioned above the pipe(s) that convey the sewage from the shaft.

It is envisaged that there may be one or more beacons (preferably wireless) situated in or on the wall of the shaft. The beacons will preferably be sited and/or shaped such that contaminating matter will not adhere to the beacon.

In many cases the positioning of the beacons will be above the normal expected levels of sewage in the shaft. Therefore, if the head unit does not receive a signal from a beacon, then that can be indicative of a possible blockage or over-capacity causing sewage levels to back up.

In some embodiments the head unit will only transmit information indicative of an alert condition to a server. As in, not transmitting if the signals received (or not) are indicative of a normally operating system.

The head unit may also transmit a regular pulsed signal (heartbeat) that indicates to a receiver (such as a server) that the head unit is functioning normally.

In other embodiments, the head unit could transmit raw information to a server which is receiving information from other beacons in the shaft and other sites in the sewage system. The server can then calculate if there is an alert condition. This calculation may be simple - a simple alarm if a signal is not received.

Or, the calculation may be more sophisticated, considering such factors as: a) timing of the signals received, attenuated, and not received, and b) the positioning of the relevant beacons in a shaft (can give levels), and/or c) the positioning of beacons in a pipe d) the sites of the beacons e) The cross-section of the pipes

The above can provide a picture of factors around an alert condition such as: a) possible blockages, over capacity and or leakages, b) urgency of the condition, c) location of the condition d) how widespread the condition is e) and the best place to access the system to fix the problem f) water flow rate

While it is envisaged that there will be a central server used as above, an embodiment could include the use of mobile servers. For example, a monitoring/maintenance cart may be driven along a fluid system and receive notifications from head units.

It can be seen that the present invention has several advantages over the prior art.

Inexpensive simple beacons can be used which indicate merely the presence or not of fluid within a system as a result of the signal path being blocked or transmissive. No other readings such as noise, pressure, or flow (as found in many other systems) are needed to determine leakages or blockages. The binary nature of data used in the present invention leads to a simple low-cost system.

The present invention suffers none of the former issues as only a full immersion of the beacon in liquid will stop the signal being broadcast. This makes the present invention much more resilient to false readings, foulings and simple to install and operate. Further, this low-cost nature of the present invention means that many beacons and monitoring sites can be used within the budgets of potential users such as city councils.

Further, the transmission (or not) of simple data from the beacon to head unit overcomes the inherent problems of trying to transmit complex data within a noisy environment as required by most monitoring systems of pipe networks. All is needed is to detect whether the path is blocked or not.

In embodiments that choose to place beacons in the vertical shafts, data transmission (or not) is even easier to attain with few if any false positives or negatives. Further, as these shafts are usually connected to an access port, placement and maintenance of the beacons is much easier to achieve than placing them in the other pipes making up the networked system.

In preferred embodiments, associating the head unit with a maintenance hole cover makes for a robust, easy, and cost-effective system to maintain.

Embodiments of the present invention that incorporate the head unit into a man-hole cover enables the monitoring system to be installed quickly (under 10 minutes per maintenance hole) and readily installed, maintained and be very resilient.

By having in preferred embodiments, the server receiving data indicative of alert conditions, minimal intelligence is required at the individual sites, again making for simplicity and cost-effectiveness. A single server can provide calculations around alert conditions instead.

The invention can also provide a 7 day / 24-hour live monitoring alert system. Instant alerts by text message and or email to an emergency response team can pinpoint potential spills before they happen and enable spill maintenance teams to do remedial maintenance before the fact.

The data over the entire system can be available to the customers via an Application Programming Interface (API) which can be used in network wide modelling to pinpoint choke points and particular areas of additional risks. Installation into every sewer maintenance hole will prevent environmental disasters and protect the pristine environment New Zealand is known for, enable councils to reduce their maintenance costs and preserve their public reputation.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention.

Some embodiments of the invention will be described below by way of example only, and without intending to be limiting, with reference to the attached drawings.

Brief Description of the Drawings

Figure 1: Illustrates diagrammatically a possible site configuration for a sewage system in accordance with the present invention, and Figure 2: illustrates another site configuration for a sewage system, and

Figure 3: illustrates in a flow chart a potential method of operation of the present invention, and

Figure 4: illustrates some alternative uses of the present invention, and

Figures 5 to 7: illustrate various views of a preferred head unit in accordance with present invention.

Brief Description of Preferred Embodiments of the Invention

With reference to various aspects of the present invention, a possible site configuration (1) for the present invention is shown in Figure 1,

A maintenance hole cover (2) is positioned flush to a road surface (3) over a vertical shaft (4).

Two pipes (5) and (6) enter the shaft (4) and in normal operation will introduce wastewater (7) into the shaft (4).

Attached to the underside of the man-hole cover (2) is a receiver and a communications unit combined into a head unit (8).

The head unit (8) includes a GPy device which is a multi-band modem that can transmit cellular data on various networks. The device also has inbuilt connectivity via Bluetooth to the beacons (10, 11). The GPy is a Micropython-programmable triple bearer which offers Wi-Fi, BLE and cellular CAT-M1/NB1. The heart of the head unit (8) (GPy) is an ultra-low power usage microcontroller capable of communicating via Wi-Fi, BLE and cellular CAT-M1/NB1 to connect to our server / cloud. It is powered by long shelf-life batteries which are exchangeable. Battery readings will be reported back to the server at regular intervals to allow for timely maintenance.

A beacon (10) with a unique identifier is situated on the wall of the shaft (4) across from and slightly above the entry port of the pipe (5) into the shaft (4)

Likewise, a beacon (11) with another unique identifier is situated on the wall of the shaft (4) across from and slightly above the entry port of the pipe (6) into the shaft (4).

The beacons are Bluetooth Low Energy beacons. They are waterproof with a long battery life with ultra- low power chipset series and BLE 5.0 technology. The Beacon broadcasts 2.4GHz radio signals at regular and adjustable intervals. The firmware can be updated wirelessly.

Beacons can be renamed with unique identifiers to be identified by the head unit.

Not shown in Fig. 1, the beacons ((5) and (6)) are shaped to resist clumping of contaminating matter that could adversely affect the receipt of signals from the beacons ((5) and (6)) by the head unit (8).

Another pipe (13) exits the shaft (4) and in normal operation will carry wastewater (7) from out of the shaft (4).

An alternative site configuration (20) is shown in Figure 2.

This shows a vertical shaft (21) topped by a maintenance hole cover (22).

The maintenance hole cover (22) has hole (23) sized to receive a cap (24). An antenna (not shown) is placed at the top of the configuration (20) below the maintenance hole cover (22). The hole (23) enables the head unit (25) to transmit data to the network.

The head unit (25) contains a receiver and communications unit in one housing. On top of the head unit (25) is a locating pin (26) which fits into the hole (23) from the underside of the maintenance hole cover (22).

In some embodiments there will be a strong magnet (27) on top of the head unit (25) is used to affix the head unit (25) to the underside of the maintenance hole cover (22).

An alternative and preferred configuration of attaching a head unit is illustrated in Figures 5 to 7. The head unit (25) connects to a specifically designed bracket (42) which is attached to the head unit. The bracket has a 36mm dome which fits into the drilled hole in the m maintenance hole and allows the aerial to protrude to the outside. The aerial is embedded inside the bracket (figure 5-7). The entire head unit and bracket are attached to the manhole by two 6mm screws.

Down the inside of the shaft (21) are several metallic climbing rungs (28). Beacons (29) and (30) are attached to rungs (28) at by stainless steel cable (31).

In this depiction, beacon (30) is positioned below the fluid level of the shaft (21). Therefore, the signal emitted by the beacon (30) is blocked by the fluid (32) from reaching the head unit (25).

Conversely the beacon (29) is positioned above the fluid level and its signal can be received by the head unit (25).

It should be appreciated that depending on various maintenance hole configurations, there may be alternative ways by which the beacons can be introduced into in the sewer system. For example, some councils are using a grate on top of the maintenance holes to prevent accidental falling in. In this situation, a looped wire can pass through the grate holes and secure the beacons (29. 30).

In configurations without a grate, another attachment configuration can require the drilling of a 6mm hole in the underpart of the maintenance hole cover (2) called a pizza slice and loop the stainless steel cable directly into this hole (2).

Installation of a head unit (25) will take approximately 10 minutes making use of the existing maintenance holes (22) and infrastructure. A cordless drill will create a 36 mm hole (23) in the existing maintenance hole (22) on-site. A cap (24) will cover the outside hole (23) to keep out dirt, with the head unit (25) attached below the maintenance hole by magnets (27). This allows easy swapping of head units (25) for maintenance purposes.

An alternative method illustrated in Figures 5 to 7 utilises a bracket (42) which is attached to the head unit sits through the 36mm hole and allows the enclosed aerial to just protrude above the maintenance hole to allow comms

Figure 3 illustrates one way that a site could operate in accordance with the present invention.

Beacons from multiple sites send out continuous signals. The head unit is programmed to listen to these signals at variable set time intervals depending on circumstances of the environment. Faster intervals in critical fast changing environments say 5 minutes (critical sewers near fresh water) or much longer intervals say 6 hours in rain filled water tanks.

If a signal is received at the expected time with the expected strength (no or little attenuation), then fluid is below the beacon (not blocking the signal). The head unit preferably advises the server that operation is normal. Flowever, in some embodiments, the head unit may only signal an alert condition as below.

If a signal is not received at the expected time, then it is likely that fluid is above the beacon (blocking the signal). The head unit then advises the server that there is an alert condition.

The server then takes this information and combines it with information received from other sites to calculate likely extent and location of the alert condition.

Figure 4 illustrates use of the present invention in some other sites, namely a Flood Basin (A), Ship Bilge (B) and Fuel Tank (C).

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to". The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.