GB2416898A

GB2416898A - Subsurface wave sensing pool alarm

Info

Publication number: GB2416898A
Application number: GB0417511A
Authority: GB
Inventors: Vincent Robert Brewer
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-08-05
Filing date: 2004-08-05
Publication date: 2006-02-08
Also published as: GB0417511D0; GB0516305D0; GB2416899A; EP1624427A1

Abstract

A swimming pool alarm comprises at least two sensors 100 each providing a subsurface wave 104 signal, a processor extracting physical wave parameters from these signals, a detector to determine if the parameters correspond to the accidental immersion of a body, and an alarm signalling device. The processor may filter the wave signals. The system may comprise a monitor to deactivate the system on detection of normal pool use and reactivate it on detection of non-use of the pool. Storage means may be included for storing parameters corresponding to accidental immersion of a body. The system may be programmable by the user so that the user indicates normal use of the pool and non-use of the pool.

Description

POOL ALARM

The present invention relates to a pool alarm.

Pool alarms, also known as "fall alarms" or "immersion alarms" are well known. Many of these alarms sense sub- surface waves to detect a person or animal accidentally falling into a pool. As these alarms detect waves below the surface of the water, they are less sensitive to disturbances caused by wind and rain on the pool surface than alarms which detect surface waves. However, sub- surface waves caused by sanitizing and cleaning equipment, reflections of surface waves on the pool walls, the effects of wind and rain, and the settling down of water after the intended use of the pool, all create sub- surface waves which can result in nuisance "false alarms" due to the erroneous detection of sub-surface waves not cuased by an immersion.

To prevent this, the sensitivity of the alarm is reduced which renders these alarms less prone to false alarms due to disturbances on the water surface. Consequently, these alarms are less responsive to accidental immersions in the pool. This inevitably reduces the efficacy of the alarm and reduces its reliability. If the sensitivity is increased, the unit is more prone to false alarms, the user has therefore a reduced confidence in the alarm. This results in the alarm being ignored or deactivated so that the pool poses a danger to both humans and animals in the vicinity of the pool.

It is an object of the present invention to obviate or at least mitigate the above described problems and/or to provide improvements generally.

According to the invention there is provided a method and an apparatus of detecting an accidental immersion of a body as defined in any of the accompanying claims.

The processor provides wave parameters which correspond to the physical parameters of the sub-surface waves.

Consequently, the alarm is only triggered in response to the physical pool conditions which correspond to the accidental immersion of a body in water. This greatly improves the accuracy and reliability of the alarm and significantly reduces the occurrence of false alarms without compromising the sensitivity of the alarm. Within the context of this application, the sensed wave parameters correspond to immersion wave parameters if the parameters or derivatives of the parameters are of the same order of magnitude to the immersion wave parameters. The sensed wave parameters and immersion wave parameters are thus substantially similar but not necessarily substantially identical.

The alarm of the present invention differs from conventional alarms in that multiple wave sensors are used in an arrangement to enable sensing of the physical parameters of the waves. This greatly improves the reliability of the alarm over conventional sub-surface alarms as the alarm is less susceptible to sub-surface waves caused by non-immersion disturbances.

According to an aspect of the invention, there is provided a method of detecting an accidental immersion of a body comprising providing: a) an arrangement of at least two sensors, the sensor arrangement sensing subsurface waves, each sensor providing a sub-surface wave signal; b) a processor for processing the signals to calculate sub-surface wave parameters; c) a detector for detecting sub-surface wave parameters which correspond to immersion wave parameters of an accidental immersion of a body; d) an alarm signalling device, and e) an activator for activating the alarm signalling device in response to the detector, the method further comprising sensing sub-surface waves, the detector activating the alarm signalling device in response to the detected immersion wave parameters.

The wave characteristics of sub-surface waves in the pool following normal usage, or due to the effects of wind on the surface of the water are distinguishable from the sub surface wave characteristics due to a body immersing, or "falling" into the body of water. We have discovered that the wave characteristics for a body that passes gently into the body of water during normal use of a pool, or even the waves that occur as a result of normal use entry into the pool, differ from the wave characteristics due to the accidental immersion of a body such as a person or pet into the pool. The pool alarm of the invention can therefore remain activated even during normal use of the pool.

The sensor arrangement comprises sensors arranged in a fixed relationship relative to one another such as in an array. This arrangement enables the calculation of wave parameters from the combined wave signals for each sensor and from the individual wave signals. The wave parameters may comprise the wave velocity, frequency, wave length, direction relative to the sensors, depth or height relative to the water surface, amplitude and/or a combination of the aforesaid parameters. The processor preferably comprises one or more filters to filter the wave signals to facilitate processing of the wave signals and to provide the aforesaid wave parameters.

The wave parameters are then fed to a detector which is adapted to detect the particular wave parameters corresponding to an accidental immersion of a body into the water. Upon detection of the immersion wave parameters, the activator activates the alarm to notify the user.

The wave parameters corresponding to an immersion wave may be stored in the detector. The immersion wave parameters may be pre-defined. Alternatively, the immersion wave parameters may be recorded when a body is immersed in the pool by the detector when the alarm is initially set up or activated. In the latter case, the alarm set-up is adaptive to the conditions in which the alarm is used. The detector may also be adapted to record wave parameters during conditions corresponding to non-use of the pool and use of the pool. In this way the detector can detect use and nonuse conditions of the pool which allows the alarm to be de activated and activated accordingly. When the alarm is de- activated, the alarm is in a "sleep" mode whereby sensing of waves, processing and detection still continues.

However, the alarm signalling device is not activated in response to a detected immersion wave.

In another embodiment, the processor comprises a suitable electronic circuit that filters out the signals of interest from the wave signals provided by the sensor arrangement, and feeds the signals to the detector. The detector may comprise a microprocessor which has been programmed with codes specifically written to contain algorithms capable of extracting information from the sensed wave signals in order to detect the immersion wave parameters or wave characteristics.

As the alarm detects physical wave characteristics which are specific to an immersion wave or a wave caused by a body falling into water, the pool alarm and method are thus capable of detecting the immersion of a body falling into a body of water from the effects of the pool settling after use and/or wind or rain interfering with the surface of the water in the pool. Also, the pool alarm and method may be capable of detecting the immersion of a body falling into the water during normal usage of the pool.

In a preferred embodiment, the processor may comprise a model for extracting wave characteristics from the sensed wave signals. The model may define algorithms for extracting the wave characteristics from the sensed wave signals.

According to another aspect of the invention, there is provided a pool alarm for sensing sub-surface waves, comprising an arrangement of at least two sensors, each sensor providing a sub-surface wave signal, a processor for processing the wave signals to calculate sub-surface wave parameters, a detector for detecting wave parameters corresponding to the accidental immersion of a body, and an alarm signalling device, the detector activating the alarm in response to the detected immersion wave parameters.

The processor may be adapted to cross-correlate the wave signals of the sensors. In this way, it is possible to calculate the wave velocity from the cross-correlation of the sensor signals.

In an advantageous embodiment of the invention, the pool alarm comprises a processor which is adaptive to the specific pool characteristics to thereby distinguish sub surface waves due to accidental immersion of a body in water from conventional, non-accidental wave characteristics such as those caused by wind interaction on the surface of the pool.

In another embodiment of the invention, the sensor arrangement comprises an optical sensor, an acoustic sensor, a pressure sensor or another suitable sensor and/or a combination of the aforesaid sensors. The sensors may be active such as a doppler sensor or passive such as a pressure sensor.

In a preferred embodiment, the sensor arrangement comprises at least three sensors. The sensors are preferably arranged in an array. The sensors may all be arranged in one plane.

In use, the plane may be located approximately horizontally or vertically relative to the water surface. The sensor may also be arranged in multiple planes which are each spaced relative to one another. Each plane may comprise the same number of sensors. In a preferred embodiment, the sensor arrangement comprises a pair of three or four sensors with the pair being arranged in two spaced planes such that each plane comprises three or four sensors.

In another embodiment of the invention, the processor comprises a model for extracting wave characteristics or wave parameters from the sensed wave signals. The model may define algorithms for extracting or otherwise calculating the wave parameters from the sensed signals. The processor may further comprise suitable filters for filtering non relevant wave parameters from the wave signal. The filters may be adjustable to control the sensitivity of the alarm.

The pool alarm may comprise means for controlling the detector to control the sensitivity of the alarm. We have discovered that the waves corresponding to the accidental immersion of a body in water are of a relatively low frequency of typically less than 20 Hz and particularly less than 10 Hz. Therefore, the filters are adapted to remove signals of frequencies higher than this frequency from the sensed signal.

In another advantageous embodiment of the invention, the pool alarm comprises a pool condition monitor for monitoring the condition of the pool, the condition monitor automatically activating the detector following non-use of the pool for a pre-determined time. The processor may comprise the condition monitor.

The condition monitor is adapted to detect whether the pool is being used or whether the pool is unused on the basis of the wave parameters or sensed wave signals. If the pool is unused for a period of time, the condition monitor activates the detector automatically to activate the pool alarm. This allows the pool alarm to operated continuously and automatically, whereby no user intervention is necessary.

In another embodiment of the invention, the detector is adapted to record the immersion wave parameters. Upon initial activation of the pool alarm, a body is immersed in water corresponding to an accidental immersion in water of a body. The wave signals corresponding to this immersion are processed and the corresponding immersion wave parameters are recorded by the detector. In subsequent use, if the sensed wave signals have wave parameters which are similar or correspond to the recorded immersion wave parameters, then the alarm is activated. This particular embodiment of the invention has the advantage that the pool alarm can be installed in any pool and can be operated effectively in any conditions.

The invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 presents a diagrammatic view of a pool alarm, Figure 2 presents a diagrammatic view of another sensor arrangement, and Figure 3 presents a diagrammatic view of a pool alarm sensor.

The pool alarm 10 comprises a sensor arrangement A, comprising sensors 12. Each sensor 12 provides wave signals to the processor 14. The processor 14 is adapted to detect an immersion wave from the sensed wave signals and to activate an alarm signalling device (not shown).

Two sensor arrangements Al and A2 are shown in Figure 1.

Sensor arrangement Al comprises three sensors 12 arranged in a single plane. Sensor arrangement A2 comprises four sensors 12 arranged in a single plane.

The alternative arrangement B in Figure 2 comprises six sensors 12 arranged in two spaced planes (B1) or eight sensors 12 arranged in two spaced planes (B2).

The processor 14 calculates the wave parameters of the sensed waves. The wave parameters comprise the wave frequency, amplitude, velocity and direction of the sub surface waves in relation to the sensor arrangement A, B. The processor further comprises a comparator for comparing the calculated wave parameters with the immersion wave parameters which correspond to the accidental immersion of a body in the pool. - 9 -

In use, the sensor arrangement A, B is submerged in the pool and activated to detect sub-surface waves corresponding to the accidental immersion of a body in the pool.

The signals from the sensor arrangement A, B are processed to calculate wave parameters. The calculated parameters are compared to the immersion wave parameters. If the calculated parameters correspond to or are similar to the immersion wave parameters, the processor 14 activates the alarm signalling device.

In an alternative embodiment, the alarm 10 is self- activating if, for a predetermined period of time, wave parameters are detected which correspond to an unused state of the pool. This provides a fully automatic pool alarm which does not require user intervention to activate the alarm.

Figure 3 presents a sensor arrangement 100 submerged in a pool below the surface 102 of the pool to detect sub- surface waves 104. The sensor arrangement is located at a suitable distance below the surface 102 of the water.

There is thus provided a pool alarm comprising a sensor arrangement which is adapted to sense wave characteristics relating to wave velocity, wave length, wave frequency, amplitude and/or other wave characteristics which correspond to the accidental immersion of a body in water.

As the sensor arrangement measures the physical parameters of the subsurface wave, it is possible to distinguish waves corresponding to the accidental immersion of a body in water from sub-surface waves due to normal disturbances of the pool caused by wind, rain or other interactions with the pool.

Claims

1. A method of detecting an accidental immersion of a body in a pool comprising providing: a) an arrangement of at least two sensors, each sensor providing a sub-surface wave signal, b) a processor for processing the wave signals to provide sub-surface wave parameters, c) a detector for detecting sub-surface wave parameters corresponding to the accidental immersion of a body, d) an alarm signalling device, e) an activator for activating the alarm signalling device in response to the detector, the method further comprising: f) sensing sub-surface waves and activating the alarm signalling device in response to the detected accidental immersion.

2. A method according to claim 1, characterized in that the processor comprises a model for extracting wave parameters from the sensed wave signals.

3. A method according to claim 1 or 2, characterized in that the processor comprises a filter for filtering the sensed wave signals.

4. A method according to any of the preceding claims, characterized in that the method comprises providing a condition monitor for monitoring the condition of the pool, the monitor de-activating the activator upon detecting normal pool use.

5. A method according to any of the preceding claims, characterized in that the method comprises providing means for storing wave parameters.

6. A method according to claim 5, characterized in that the detector comprises a comparator for comparing the wave parameters with stored immersion wave parameters, the comparator activating the activator upon the wave parameters corresponding to the stored immersion wave parameters.

7. A method according to claim 5, characterized in that during normal pool use, wave parameters are stored such that the comparator activates the activator upon the sensed wave parameters being substantially different from the stored wave parameters to indicate non-use of the pool.

8. A method according to any of claims 5 to 7, characterized in that the detector automatically activates the activator upon the sensed wave parameters being substantially similar to stored wave parameters corresponding to non-use of the pool.

9. A method according to any of claims 5 to 8, characterized in that the detector automatically de- activates the activator upon the sensed wave parameters being substantially similar to stored wave parameters corresponding to normal use of the pool.

10. A method according to any of claims 8 or 9, characterized in that the detector is programmable such that the user indicates normal use of the pool and non-use of the pool.

11. A pool alarm comprising: a) an arrangement of at least two sensors, each sensor providing a sub-surface wave signal, b) a processor for processing the wave signals to provide sub-surface wave parameters, c) a detector for detecting wave parameters corresponding to the accidental immersion of a body, d) an alarm signalling device, e) an activator for activating the alarm in response to the detected immersion wave parameters.

12. A pool alarm according to claim 11, characterized in that the wave parameters comprise physical wave parameters such as amplitude, velocity, frequency, wave length, wave direction in relation to the sensor, wave depth and/or any of the aforesaid parameters.

13. A pool alarm according to claim 11 or 12, characterized in that the processor comprises a model for extracting wave parameters from the sensed wave signals.

14. A pool alarm according to any of claims 11 to 13, characterized in that the processor comprises a filter for filtering the sensed wave signals.

15. A pool alarm according to any of claims 11 to 14, characterized in that the processor is adapted to cross correlate the wave signals of the sensors.

16. A pool alarm according to any of claims 11 to 15, characterized in that the sensor arrangement comprises at least two pairs of sensors each pair being arranged in a single plane, the planes being spaced relative to one another.

17. A pool alarm according to any of claims 11 to 16, characterized in that the processor comprises a model for extracting wave characteristics from the sensed wave signals.

18. A pool alarm according to any of claims 11 to 17, characterised in that the detector and processor are integrated.

19. A pool alarm according to any of claims 11 to 18, characterised in that the detector de-activates the activator upon detecting normal pool use.

20. A pool alarm according to any of claims 11 to 19, characterised in that the alarm comprises means for storing the wave parameters.

21. A pool alarm according to claim 20, characterised in that the detector comprises a comparator for comparing the wave parameters with stored immersion wave parameters, the comparator activating the activator upon the wave parameters corresponding to the stored immersion wave parameters.

22. A pool alarm according to claim 21, characterised in that during normal pool use, wave parameters are stored such that the comparator activates the activator upon the processed wave parameters differing from the stored wave parameters.

23. A pool alarm according to claim 21 or 22, characterised in that the detector automatically activates the activator upon the sensed wave parameters being substantially similar to stored wave parameters corresponding to non-use of the pool.

24. A pool alarm according to any of claims 20 to 23, characterised in that the detector automatically de activates the activator upon the sensed wave parameters being substantially similar to stored wave parameters corresponding to use of the pool.

25. A pool alarm according to any of claims 23 or 24, characterized in that the detector is programmable such that the user indicates normal use of the pool and non-use of the pool.

26. A pool alarm substantially as herein before described and as shown in any of the accompanying drawings.