GB2518214A

GB2518214A - An integrated bilge pump system

Info

Publication number: GB2518214A
Application number: GB1316357.1A
Authority: GB
Inventors: Paul Holland
Original assignee: ENERGY SOLUTIONS UK Ltd
Current assignee: ENERGY SOLUTIONS UK Ltd
Priority date: 2013-09-13
Filing date: 2013-09-13
Publication date: 2015-03-18
Also published as: GB201316357D0

Abstract

A switch unit 200 for a bilge pump system 100 comprises a low-level sensor 204 positioned to correspond to a lower tolerance level; a mid level sensor 206 positioned to correspond to an upper tolerance level; and a switch 802, all positioned within a watertight housing (fig 6, 202). The sensors detect a liquid level around the housing 202 and actuate switch 802 to make or break an electrical connection between a pump 300 and a power supply 400, to maintain the liquid level between the lower and the upper tolerance levels, and can start the pump when liquid rises above the upper level and stop it when the liquid falls below the lower level. There may be a high level sensor 208 corresponding to a danger level to transmit a warning signal and actuate the pump, and a manual override switch 210. Sensors can be solid state or capacitive, detecting the presence of water, but switching off the pump if oil or fuel is detected. The switch unit can connect to a monitor (fig 3, 700) displaying the status of the pump, the power supply and the liquid level and a remote controller (fig 3, 500). Over-current sensor 900 can break the connection depending on detected current and self-check timer 804 can actuate the switch for a short period at regular intervals.

Description

An Integrated Bilge Pump System The present invention relates to a bilge pump system. In particular, the present invention relates to a switch unit for a bilge pump system and a bilge pump system incorporating such a switch unit for removing liquid from the below-deck area, such as the bilge area, of a marine vessel.

In embodiments, the present invention relates to a switch unit for use in an integrated bilge pump system that removes much of the complication encountered during installation and incorporates additional safety features.

In marine vessels such as boats and yachts, seawater is often collected in the below-deck area along with waste matter including oil and other liquid waste. For example, seawater that is washed aboard and oil/fuel from the engine area are often collected in the bilge area of a yacht. It is known to use water pump systems to remove the built-up liquid, often referred to as "bilge water', from the below-deck area of a marine vessel to prevent potentially dangerous flooding of the area. Bilge pump systems are disclosed in, for example, WO-A-98/00643 and WO-A-03/042536.

An example of known water pump systems, such as the system 10 shown in Figure 1, includes a central switchboard 12 connected to a pump 14, float switches 16, and a power supply 18. The float switches 16 provide signals to the central switchboard 12 that are indicative of the water level in the below-deck area and the central switchboard 12 directs these signals to the deck area, such the bridge of a marine vessel. Audio-visual indicators 20 such as lights and buzzers may be provided to receive signals from the central switchboard 12 to allow an operator, such as the captain of the vessel, to monitor the conditions in the below-deck area. Manual switches 22 are provided to control the central switchboard 12 to direct power from the power supply 18 to activate and/or deactivate the pump 14 when necessary. A circuit breaker 24 may be provided additionally to disengage the power supply 18 in case of an electrical fault.

High-power electrical cables 26 are often used to connect the power supply 18, which is located away from the bilge area, to other components of the system 10. In particular, the high-power cables typically extend between the central switchboard 12 and the manual switches 22.

In these known water pump systems, the float switches 16 that are typically used are incapable of distinguishing between water and oil, and are vulnerable to debris getting caught under the switch, which renders them ineffective and may lead to the pump 14 running dry. It is also of importance that the float switches 16 are correctly positioned to ensure proper operation of the system 10. As such, installation is often a complex procedure due to the precision required to position the float switches 16. In addition, care must be taken in order to ensure that all connections are waterproof and to meet industry electrical safety standards. Although best efforts can be made, these known water pump systems are still prone to water ingression on terminations and high voltage-drop in the electrical wiring due to the length of high-power wiring required, rendering them incompatible with standards. Furthermore, since float switches are unable to distinguish between water and oil/fuel, known water pumps that use float switches often discharge water and oil/fuel indiscriminately, which is environmentally unfriendly and is illegal in many jurisdictions.

There is therefore a need for an improved pump system.

According to the first aspect of the present invention, there is provided a switch unit for a bilge pump system having a pump and a power supply connectable to the switch unit, the switch unit comprising: a housing arranged to be watertight; a low-level sensor disposed within the housing and positioned to correspond to a lower tolerance level; a mid-level sensor disposed within the housing and positioned to correspond to an upper tolerance level; a connector switch disposed within the housing and actuatable to make or break an electrical connection between the pump and the power supply; wherein the sensors are arranged to detect the liquid level in an area surrounding the housing; wherein in use, the sensors are operable to actuate the connector switch to make or break the electrical connection to activate and deactivated the pump so as to maintain the liquid level between the lower tolerance level and the upper tolerance level.

The present invention therefore provides a unitary device for detecting the level of bilge water in the bilge area of a marine vessel. With the sensors provided within a single watertight housing, the number of components that require accurate positioning is reduced, making the installation process easier and less demanding. Incorporating the sensors in a single unit also reduces the number of vulnerable electrical connections.

Considering for example, the system 10 of Figure 1, it can be seen that each of the float switches 16 has an electrical connection to the central switchboard 12. By incorporating the sensors into the switch unit these external connections can be dispensed with. By providing the switching connections between the pump and the power supply within the watertight housing, the switch unit of the present invention integrates the sensing components with the high-power switching components within a single watertight housing, thus reduces the length of high-power cables required, making it simpler to meet voltage diop lequirements of international standards.

Preferably, the position of the low-level sensor relative to the position of the mid-level sensor is fixed. Alternatively or additionally, the housing is shaped to receive the sensors.

In embodiments, the low-level sensor is configured to transmit a deactivation signal to break the electrical connection in response to the liquid level falling below the lower tolerance level. Additionally or alternatively, the mid-level sensoi is configured to transmit an activation signal to make the electrical connection in response to the liquid level exceeding the upper tolerance level, In some embodiments, the switch unit further comprises a high-level sensor positioned to correspond to a danger level; wherein the high-level sensor is operable to make the electrical connection in response to the liquid level exceeding a danger level; wherein the danger level is gleater than the upper tolerance level. Preferably, the high-level sensor is configuied to transmit a waining signal to make the electrical connection in response to the liquid level exceeding the danger level.

In some othei embodiments, at least one of the sensois is a solid state sensor; wherein the solid state sensor is arranged to detect the presence of at least one of water, oil, or fuel in the area surrounding the housing, and is operable to transmit a signal to break the electrical connection in response to the detection of the presence of oil or fuel.

The switch unit of the present invention is thus able to distinguish between water and oil/fuel and avoids environmentally unfriendly discharge of oil/fuel.

Alternatively or additionally, the switch unit further complises a manual operator switch disposed in the housing and aiianged to be opeiable to make or break the electiical connection.

The switch unit may also comprise a connector for connecting the switch unit with a monitoring device arranged to display at least one of: the liquid level, the status of the power supply, the status of the pump, or a warning sign when the liquid level exceeds the danger level.

In some further embodiments, the switch unit further comprises an over-current sensor disposed within the housing and arranged to detect the current in the electrical connection; wherein the over-current sensor is operable to break the electrical connection in response to the detected current.

In yet further embodiments, the switch unit also comprises a controller disposed within the housing, operatively coupled to the sensors and the connector switch, wherein the controller is configured to receive the transmitted signals and to actuate the connector switch in response to the received signals. :15

Preferably, the controller is further configured to actuate the connector switch in response to a remote signal.

Additionally or alternatively, the switch unit further comprises self-check circuitry arranged to make the electrical connection for a short period of time at regular time intervals.

The switch unit of the present invention therefore automatically ensures that the pump does not go through prolonged periods of inactivity so that reliability issues attributed to inactivity can be mitigated.

According to another aspect of the present invention, there is provided a bilge pump system for a marine vessel, the system comprising a switch unit according to the first aspect of the present invention, a pump arranged to be activated to remove liquid from an area surrounding the switch unit, and a power supply arranged to supply power to the pump.

Preferably, the bilge pump system further comprises a monitoring device connected to the switch unit, the monitoring device being arranged to display at least one of: the liquid level, the status of the power supply, the status of the pump, ora warning sign when the liquid level exceeds the danger level.

Alternatively or additionally, the bilge pump system further comprises a remote control unit operatively coupled to the switch unit and arranged to be operable to make the electrical connection.

According to a further aspect of the present invention, there is provided a switch unit for a bilge pump system having a pump and a power supply connectable to the switch unit, the switch unit comprising: a housing arranged to be watertight; a low-level sensor disposed within the housing and positioned to correspond to a lower tolerance level; and a mid-level sensor disposed within the housing and positioned to correspond to an upper tolerance level; wherein the sensors are arranged to detect the liquid level in an area surrounding the housing; wherein in use, the sensors are operable to make or break an electrical connection between the pump and the power supply to maintain the liquid level between the lower tolerance level and the upper tolerance level.

Embodiments of the present invention will hereinafter be described by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a known water pump system; Figure 2 is a schematic illustration of a bilge pump system; Figure 3 is a schematic illustration of a variation of the bilge pump system of Figure 2; Figure 4 is an illustration of a monitoring device of the bilge pump system of Figure 3; Figure 5 is a detailed illustration of a switch unit of the bilge pump system of Figure 2 and Figure 3; Figure 6 is a side view and front view of an example of the housing of the switch unit; Figure 7 is a schematic diagram of a bilge pump system; and Figure 8 is a schematic diagram of an alternative bilge pump system.

Referring to Figure 2, a schematic illustration of a bilge pump system 100 according to an embodiment of the present invention is shown. In this embodiment, the bilge pump system 100 includes a switch unit 200. The switch unit 200 has connections to connect to a bilge pump 300 and to a power supply 400. For example, the connections may be of a simple "plug-and-play" type with features that meet the American Boat and Yacht Council (ABYC) and ISO requirements.

In general, the switch unit 200 is positioned in the below-deck area of a marine vessel.

For example, the switch unit 200 may be installed in the bilge area of a yacht. In particular, and as will be explained in more detail, the switch unit 200 is positioned appropriately to measure and detect the level of bilge water in the bilge area surrounding the switch unit 200 so that when the detected level of bilge water exceeds a certain upper tolerance level, the bilge pump 300 is activated to remove any excess bilge water. It will be appreciated that any suitable known bilge pump may be used in the bilge pump system 100 and that the bilge pump 300 may be installed in any suitable location so that it is able to remove excess bilge water effectively. It will also be appreciated that any suitable known power supply may be used in the bilge pump system 100 and may be located away from the bilge area to avoid water damage. For example, atypical commercially available bilge pump may operate with a 12V or24V power supply.

Referring still to Figure 2, the switch unit 200 may optionally have connections to connect to a remote control unit 500 and/or a monitoring device 700 (shown in Figure 3). In general, the connections between the switch unit 200 and the remote control unit 500 and/or the monitoring device 700 are of a type similar to those used in data communication, such as Ethernet communication connections, to reduce the amount of high-power cables required in the bilge pump system 100. Indeed, the signals sent between the remote control unit 500 and the switch unit 200 are control signals to control the switch unit 200 rather than power signals to operate the pump. In other words the switch unit 200 can operate as a relay to ensure that power is provided to the pump when required, without requiring a high power connection to the remote control unit 500.

The remote control unit 500 generally performs several functions. For example, the remote control unit 500 may be configured to receive from the switch unit 200 signals that are indicative of, but not limited to, the level of bilge water in the area surrounding the switch unit 200, the operating status of the bilge pump 300, and the operating status of the power supply 400. The remote control unit 500 may also have an indicator that warns a user of the bilge pump system 100 when the level of bilge water in the area surrounding the switch unit 200 exceeds a danger level, above which operation of the bilge pump 300 alone would not be adequate to remove the excess bilge water. The remote control unit 500 may be further provided with a manual activation/deactivation switch to allow a user to activate or deactivate the bilge pump 300 whenever it is required.

As will be explained in more detail below, the switch unit 200 may also include circuitry that allows power to be supplied from the power supply 400 to the bilge pump 300 via the switch unit 200. This eliminates the need for additional high-power cables between the switch unit 200 and other external switch, such as the remote control unit 500, to reduce the amount of high-power cables required.

In some embodiments of the bilge pump system 100, the power supply 400 is connected to the rest of the bilge pump system 100 via a circuit breaker 600. The circuit breaker 600 is configured to provide current protection to the bilge pump system by disengaging the power supply 400 from the bilge pump system 100 in case of an electrical fault such as a power overload.

Referring to Figure 3, a variant of the bilge pump system 100 of Figure 2 is shown. In this variant, the connections of the switch unit 200 are arranged to connect to a monitoring device 700 in addition to the remote control unit 500. Signals from the switch unit 200 are received by the monitoring device 700, which has a number of indicators. For example, in some embodiments, the below-deck area of a marine vessel may have a number of switch units 200 installed. In these embodiments, the monitoring device 700 is equipped with sets of indicators 702, 704... etc, each responsible for indicating the level of bilge water in the area surrounding an individual switch unit 200. In particular, a set of indicators 702, 704... etc, may have lights or other suitable means of alerting the user that the level of bilge water is below a lower tolerance level and the bilge pump 300 is deactivated, or is between an upper tolerance level and the lower tolerance level and the bilge pump 300 is activated to remove excess bilge water, or is above a danger level and is increasing at an unacceptably high rate and emergency action should be taken.

Figure 4 shows an example of a monitoring device 700 in more detail. In this example, the monitoring device 700 is a panel and has six sets of indicators 702, 704... etc, each responsible for indicating the level of bilge water in a particular part of the below-deck area of a marine vessel. For example, one set of indicators 702 may be configured to indicate the level of bilge water in the area surrounding a switch unit 200 that is installed in the engine room of a yacht, and another set of indicators 704 may be configured to indicate the level of bilge water in the area surround a switch unit 200 that is installed in the pod of the yacht. It will be appreciated by a skilled person that the monitoring device 700 may be customised to have any suitable number of sets of indicators to correspond to the number of switch units 200 that have been installed.

Referring still to Figure 4, each set of indicators may, for example, have a PUMP SUPPLY OK" indicator showing that the bilge pump 300 is functioning normally and can be activated or deactivated if required, a "PUMP RUNNING" indicator showing that the level of bilge water is between an upper tolerance level and the lower tolerance level and the bilge pump 300 is activated to remove excess bilge water, and a HIGH LEVEL ALARM" indicator showing that the level of bilge water is above the danger level and is increasing at an unacceptably high rate and emergency action should be taken. Optionally, the monitoring device 700 further includes an audio indicator such as a speaker or a buzzer (not shown) that emits a noise when the level of bilge water in any of the areas monitored exceeds the danger level. The indicators may be lights such as light emitting diodes and it will be appreciated by a skilled person that other suitable means of providing a visual indication may be used. It will also be appreciated that there may be more than three lights in each set of indicators.

Referring now to Figure 5, an example of a switch unit 200 of the bilge pump system is shown in detail. In the embodiment shown in this figure, the switch unit 200 has a housing 202 that is generally arranged and configured to be watertight so as to ensure that the components inside the housing 202 are protected from being damaged when the switch unit 200 is submerged in bilge water. The housing 202 is formed of a watertight material and has within it the other components of the switch unit 200 thus making the switch unit 200 watertight. Clearly various sockets and the like are provided through which water may be able to ingress if left open. However, the housing 202 as a whole with the sensors on the inside is formed of a watertight material.

An assembly of sensing components, either a unitary sensor or a group of sensors, is provided within the housing 202 to detect the level of bilge water in the area surrounding the housing 202 of the switch unit 200. The housing 202 may be shaped in any suitable way to receive the sensing components whilst remaining watertight. In particular, in the example shown, the sensing components may be enclosed within the housing 202 so as to be protected, whilst being able to detect the level of bilge water in the area surrounding the exterior of the housing 202.

In the embodiment shown in Figure 5, the switch unit 200 is provided with a low-level sensor 204 and a mid-level sensor 206. The low-level sensor 204 and the mid-level sensor 206 are each provided within the housing 202 and respectively positioned to correspond to a lower tolerance level and an upper tolerance level. As it will be appreciated by a skilled person, the tolerance levels reflect the amount of bilge water that a marine vessel can acceptably hold, and the position of the low-level sensor 204 relative to the position of the mid-level sensor 206 may be fixed within the housing 202 or vary according to the location at which the switch unit 200 is installed. Optionally, a high-level sensor 208 is also provided within the housing 202 of the switch unit 200. A controller and electrical connections (not shown in Figure 5) are provided within the housing 202 to connect the power supply 400 with the bilge pump 300, and a manually operated override switch 210 is optionally provided in the housing 202 of the switch unit to allow the electrical connection between the bilge pump 300 and the power supply 400 to be manually made or broken.

It will be appreciated that the designation of "low-level sensor" refers to any suitable means for determining when the bilge water level falls below the lower tolerance level as described above, and is not limited to a dedicated individual senor. Similarly, mid-level sensor 206 and the high-level sensor 208 may be any similarly suitable means and are not limited to dedicated individual sensors.

The mid-level sensor 206 functions as a trigger point so that the bilge pump 300 is activated when its operation is required. To this end, the mid-level sensor 206 is arranged to be operable to detect and determine the level of bilge water in the area surrounding the housing 202 of the switch unit 200. If the detected level is above the upper tolerance level, which is determined by the position of the mid-level sensor 206 relative to the housing 202 and by the position at which the switch unit 200 is installed, -10 -the electrical connection between the power supply 400 and the bilge pump 300 is made to activate the bilge pump 300 to remove bilge water.

The low-level sensor 204 functions as a stop point so that the bilge pump 300 is deactivated when its operation is not required. To this end, the low-level sensor 204 is arranged to be operable to detect and determine the level of bilge water in the area surrounding the housing 202 of the switch unit 200. If the detected level is below the lower tolerance level, which is determined by the position of the low-level sensor 204 relative to the housing 202 and by the position at which the switch unit 200 is installed, the electrical connection between the power supply 400 and the bilge pump 300 is broken to deactivate the bilge pump 300 to stop the removal of bilge water. In particular, the low-level sensor can be arranged to be at a position that corresponds to a minimum operating level for the bilge pump 300 to ensure that the bilge pump 300 does not continue to operate when the level of bilge water falls below the minimum operating level.

By this arrangement of the mid-level sensor 206 and the low-level sensor 204, provided that the rate at which the level of bilge water is increasing is less than the rate at which the bilge pump 300 can remove bilge water, the level of bilge water may be automatically maintained at between the upper tolerance level and the lower tolerance level. Pre-arranging the low-level sensor 204 and the mid-level sensor 206 within the housing 202 also eliminates the need to accurately position and align many switches to ensure that the bilge pump system 100 functions effectively. This is particularly advantageous since an incorrect positioning or relative positioning of the sensors may lead to pump failure or unsafe levels of bilge water accumulating. By fixing the relative positions, a degree of safety guarantee is provided and the previously complex process of installing water pump systems is made more robust and reliable.

In embodiments that include a high-level sensor 208, the high-level sensor 208 functions as a warning mechanism in case when the rate at which bilge water builds up is greater than the rate at which the bilge pump 300 removes bilge water, and the bilge water level exceeds a danger level that is greater than the upper tolerance level. To this end, the high-level sensor 208 is arranged to be operable to detect and determine the level of bilge water in the area surrounding the housing 202 of the switch unit 200.

If the detected level exceeds the danger level, an alert may be sent to a monitoring

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device or a warning indicator, such as a warning light or a siren, whilst the bilge pump 300 remains activated to continue the removal of bilge water.

It will be appreciated by a skilled person that the components of the switch unit 200, including the sensors 204, 206, 208 and the override switch 210, may be arranged in the housing 202 in any suitable way so that the switch unit 200 as a whole remains watertight and that any component sensitive to water are protected from water damage. It will also be appreciated by a skilled person that the relative positions of the sensors 204, 206, 208 within the housing 202 may be dependent on the particular marine vessel and the layout of the bilge area into which the bilge pump system 100 is to be installed. In the examples shown three sensors are shown although it will be appreciated that in some embodiments only two may be provided. Indeed, if a greater number of control levels for bilge water is desired then a number greater than three, such as say, four, five or more could be provided.

The housing 202 also includes sockets or connectors through which data and power may be communicated. In the example shown, waterproof power connectors 211, 213 may be provided such as the I P67 Delphi Socket MP480 (for connection 211 to the power supply) and an 1P67 Delphi Socket MP280 (for quick and reliable connection 213 to the bilge pump). In addition an RJ12 socket 215 is provided for a control connection to the remote control unit 500. In one embodiment the remote control connection between the switch unit 200 and the remote control unit 500 is wireless and achieved using any appropriate wireless protocol, e.g. RE, Bluetooth, etc. Figure 6 is a view of an example of the housing 202 of the switch unit 200. The watertight nature of the switch unit 200 may be achieved for example by forming the housing 202 of the switch unit 200 from a unitary moulded piece of plastic 201. One example of a suitable material is ABS PA-763 acrylonitrile butadiene styrene. In the example shown, some dimensions are included although it will be appreciated that these are merely exemplary. The dimensions can be changed or selected for a particular application. It is preferred that the body of the housing 202 is generally elongate (in the example shown, approximately 15cm long compared to a width of approximately 6.5cm) and relatively flat (about 2cm thick). By dimensioning the switch unit 202 in this way, a large vertically orientated face is provided which enables the desired relative positioning of the sensors to be achieved. A backing (not shown) may be fixed on to the back of the housing to enclose it and make it substantially watertight.

-12 -In the example shown, connecting flanges 207 are provided with through holes 209 to receive fastenings such as screws or rivets.

Alternatively (not shown in Figure 6), the housing 202 may be of an open-shell shape, such as a tub, tray, shoebox or bucket, into which the components of the switch unit aie disposed. To achieve a wateitight switch unit 200, wateipioofing material may be dispensed into the housing 202 to provide water protection. For example, liquid resin may be dispensed into the housing 202, which then hardens around the components within the housing 202 to protect the components from water damage.

The haidened resin also provides structural support tor the switch unit 200 and the components within the housing 202.

Referring now to Figure 7, a schematic illustration of the circuitry of the switch unit 200 connected to the bilge pump system 100 is shown. In this figure, the contiollei is provided in the form of a central processing unit 800 (CPU), and the electrical connection between the bilge pump 300 and the power supply 400 is provided in the form of a connector switch 802 disposed within the housing 202 of the switch unit 200.

The CPU 800 is operatively coupled to the low-level sensor 204, the mid-level sensor 206, and to the high-level sensor 208. The CPU 800 may also be operatively coupled to the remote control unit 500, and optionally to the monitoring device 700 and the override switch 210. The CPU 800 is configured to leceive signals fiom the sensors 204, 206, 208. Based on the ieceived signals, the CPU 800 actuates the connector switch 802 to make or break the electrical connection between the power supply 400 and the bilge pump 300 to activate or deactivate the bilge pump 300 to maintain the bilge watel level between the lower toleiance level and the upper toleiance level.

When the connection is made, power flows through the connector switch 802 to the bilge pump 300. In addition, the CPU 800 may also be controlled to activate the bilge pump 300 on a regular basis irrespective of detected water levels to ensure that the pump remains in working oidei.

It will be appreciated that any other suitable forms of controllers, including digital or analogue controllers, may be provided in place of the CPU 800.

In paiticular, the mid-level sensor 206 is configured to detect the level of bilge water in the area surrounding the housing 202 of the switch unit 200 and to transmit an activation signal that is indicative of the level of bilge water to the CPU 800 if the -13 -detected level exceeds the upper tolerance level as described above. In response to receiving the activation signal from the mid-level sensor 206, the CPU 800 actuates the connector switch 802 so as to make the electrical connection between the power supply 400 and the bilge pump 300 to activate the bilge pump 300 to remove bilge water. The low-level sensor 204 is configured to detect the level of bilge water in the area surrounding the housing 202 of the switch unit 200 and to transmit a deactivating signal that is indicative of the level of bilge water to the CPU 800 if the detected level falls below the lower tolerance level as described above. In response to receiving the deactivation signal from the low-level sensor 204, the CPU 800 actuates the connector switch 802 to break the electrical connection between the power supply 400 and the bilge pump 300, thus deactivating the bilge pump 300 to stop the removal of bilge water.

By activating and deactivating the bilge pump 300 in this manner, the level of bilge water may be automatically maintained at a level between the upper tolerance level and the lower tolerance level. Additionally, by providing the connector switch 802 within the housing 202 of the switch unit 200, the amount of high-power cable required in the bilge pump system 100 may be reduced.

Similar to the mid-level sensor 206 and the low-level sensor 204, the high-level sensor 208 is configured to detect the level of bilge water in the area surrounding the housing 202 of the switch unit 200 and to transmit a warning signal that is indicative of the level of bilge water to the CPU 800 if the detected level exceeds the danger level. As described above, the rate at which bilge water is increasing is likely to be greater than the rate at which the bilge pump is removing bilge water when the level of bilge water exceeds the danger level. Accordingly, the CPU 800 is configured to perform a number of different functions in response to receiving the warning signal from the high-level sensor 208.

For example, the bilge pump system 100 may be connected to the above-described remote control device 500 and/or the above-described monitoring device 700 when is use. A warning indicator may be provided on the remote control unit 500 shown in Figure 2 or on the monitoring device 700 such as the "HIGH LEVEL ALARM" indicator shown in Figure 4. In response to receiving the warning signal, the CPU 800 may transmit a signal to the remote control unit 500 and/or the monitoring device 700 to activate the warning indicator. Additionally, the CPU 800 is also configured to maintain -14 -the electrical connection between the bilge pump 300 and the power supply 400 to ensure that the bilge pump 300 continues to remove bilge water.

Optionally, as shown in Figure 7, the switch unit 200 may further include an over- current sensor 900 provided within the housing 202 of the switch unit 200. The over-current sensor 900 is arranged to detect the current passing through the electrical connection between the bilge pump 300 and the power supply 400. For example, the over-current sensor may be configured to detect the current passing through the connector switch 802. If the detected current exceeds a safe value, the over-current sensor 900 transmits a signal to the CPU 800, which then actuates the connector switch 802 to break the electrical connection between the bilge pump 300 and the power supply 400 to prevent electrical damage.

In some embodiments, the switch unit 200 may have self-check circuitry 804, either provided within the CPU 800 or as a separate component, that is configured to actuate the connector switch 802 for a shod period of time at regular time intervals automatically with no signals received from the sensors to activate the bilge pump 300 for a short period of time at regular intervals. For example, the self-check circuitry 804 may be configured to actuate the connector switch 802 to activate the bilge pump 300 automatically for a period of 0.5 seconds to 15 seconds every 24 hours to a week.

Such an arrangement ensures that the bilge pump 300 is operated regularly to avoid prolonged periods of inactivity, which is a common cause of breakdown in bilge pump systems.

Referring back to Figure 5, in some embodiments of the switch unit 200, the sensors may each be provided in pairs in case of a failure with any one of the sensors 204, 206, or 208. For example, as shown in Figure 5, sensors 204a, 206a, and 208a are provided and correspond respectively to sensors 204, 206, and 208. In these embodiments, the CPU 800 is configured to receive signals from sensors 204, 206, and 208 when these are in normal operation, and is configured to receive the signal from the corresponding sensor 204a, 206a, or 208a automatically if any of sensors 204, 206, or 208 fail. Additionally, the remote control unit 500 and/or the monitoring device 700 may include indicators and the CPU 800 may be configured to transmit signals to the remote control unit 500 and/or the monitoring device 700 to actuate these indicators when a sensor 202, 204, 206 fails. By having such redundancies in the sensors, a level of fail-safe operation may be provided.

-15 -In an alternative embodiment shown in Figure 8, instead of providing redundancies in the sensors only, the complete backup of the components of the switch unit 200 shown in Figure 6 is provided. As shown in Figure 8, the backup components are generally indicated by the same reference numerals as those in Figure 7, with the additional designation of "a". Specifically, the backup includes a redundant low-level sensoi 204a, and redundant mid-level sensor 206a, a redundant high-level sensor 208a, a redundant manually operated override switch 210a, a redundant over-current sensor 900a, a redundant connector switch 802a, redundant self-check circuitry 804a, and a redundant CPU 800a. In addition, a redundant synchionisation channel 810 is piovided, communicatively coupling CPU 800 and CPU 800a. In this airangement, redundancy is provided for the CPU 800 in addition to the sensors. In use, when CPU 800 fails, the redundant synchronisation channel 810 is operable to ensure that the functions of the switch unit 200 is transferied to CPU 800a so that opelation of the bilge pump system 100 may continue.

In some embodiments, at least one of the sensors 204, 206, 208 may be of a type suitable for detecting the presence of oil or fuel in bilge water in addition to detecting the level of bilge water in the area surrounding the housing 202 of the switch unit 200.

For example, at least one of the sensors 204, 206, 208 may be a solid state sensor such as a capacitive fluid sensor. In these embodiments, the sensors 204, 206, 208 are configured to tiansmit a signal to the CPU 800 to actuate the connector switch 802 to break the electrical connection to deactivate the bilge pump 300. By this arrangement, the removal and discharge of bilge water that has oil/fuel can be avoided.

Capacitive fluid sensors aie paiticulaily desirable as they can sense the presence of bilge water through the wall of the housing 202 and thus the switch unit 200 can be watertight whilst still enabling the presence of bilge water to be detected.

Embodiments of the present invention have been desciibed with paiticular reterence to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the appending claims.

Claims

-16 -Claims: 1. A switch unit for a bilge pump system having a pump and a power supply connectable to the switch unit, the switch unit comprising: a housing arranged to be watertight; a low-level sensor disposed within the housing and positioned to correspond to a lower tolerance level; a mid-level sensor disposed within the housing and positioned to correspond to an upper tolerance level; a connector switch disposed within the housing and actuatable to make or break an electrical connection between the pump and the power supply; wherein the sensors are arranged to detect the liquid level in an area surrounding the housing; wherein in use, the sensors are operable to actuate the connector switch to make or break the electrical connection to activate and deactivated the pump so as to maintain the liquid level between the lower tolerance level and the upper tolerance level.
2. A switch unit as claimed in claim 1, wherein the position of the low-level sensor relative to the position of the mid-level sensor is fixed.
3. A switch unit as claimed in claim 1 or 2, wherein the housing is shaped to receive the sensors.
4. A switch unit as claimed in any of the preceding claims, wherein the low-level sensor is configured to transmit a deactivation signal to break the electrical connection in response to the liquid level falling below the lower tolerance level.
5. A switch unit as claimed in any of the preceding claims, wherein the mid-level sensor is configured to transmit an activation signal to make the electrical connection in response to the liquid level exceeding the upper tolerance level.
6. A switch unit as claimed in any of the preceding claims, further comprising a high-level sensor positioned to correspond to a danger level; wherein the high-level sensor is operable to make the electrical connection in response to the liquid level -17 -exceeding a danger level; wherein the danger level is greater than the upper tolerance level.
7. A switch unit as claimed in claim 6, wherein the high-level sensor is configured to transmit a warning signal to make the electrical connection in response to the liquid level exceeding the danger level.
8. A switch unit as claimed in any of the preceding claims, wherein at least one of the sensors is a solid state sensor; wherein the solid state sensor is arranged to detect the presence of at least one of water, oil, or fuel in the area surrounding the housing, and is operable to transmit a signal to break the electrical connection in response to the detection of the presence of oil or fuel.
9. A switch unit as claimed in any of the preceding claims, further comprising a manual operator switch disposed in the housing and arranged to be operable to make or break the electrical connection.
10. A switch unit as claimed in any of the preceding claims, further comprising a connector for connecting the switch unit with a monitoring device arranged to display at least one of: the liquid level, the status of the power supply, the status of the pump, or a warning sign when the liquid level exceeds the danger level.
11. A switch unit as claimed in any of the preceding claims, further comprising an over-current sensor disposed within the housing and arranged to detect the current in the electrical connection; wherein the over-current sensor is operable to break the electrical connection in dependence of the detected current.
12. A switch unit as claimed in any of the preceding claims, further comprising a controller disposed within the housing, operatively coupled to the sensors and the connector switch, wherein the controller is configured to receive the transmitted signals and to actuate the connector switch in response to the received signals.
13. A switch unit as claimed in claim 12, wherein the connector is further configured to actuate the connector switch in response to a remote signal.

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14. A switch unit as claimed in any of the preceding claims, further comprising self-check circuitry arranged to make the electrical connection for a short period of time at regular time intervals.
15. A bilge pump system for a marine vessel, the system comprising a switch unit according to any of the preceding claims, a pump arranged to be activated to remove liquid from an area surrounding the switch unit, and a power supply arranged to supply power to the pump.
16. A bilge pump system as claimed in claim 15, further comprising a monitoring device connected to the switch unit, the monitoring device being arranged to display at least one of: the liquid level, the status of the power supply, the status of the pump, or a warning sign when the liquid level exceeds the danger level.
17. A bilge pump system as claimed in claim 15 or 16, further comprising a remote control unit operatively coupled to the switch unit and arranged to be operable to make the electrical connection.
18. A switch unit substantially as described hereinabove with reference to the accompanying drawings.
19. A bilge pump system substantially as described hereinabove with reference to the accompanying drawings.