WO2002037438A1

WO2002037438A1 - A water activated child safety alarm

Info

Publication number: WO2002037438A1
Application number: PCT/GB2001/004825
Authority: WO
Inventors: Stephen Wintersgill; John Robinson
Original assignee: Dynamic Products Ltd
Current assignee: Dynamic Products Ltd
Priority date: 2000-11-04
Filing date: 2001-10-31
Publication date: 2002-05-10
Anticipated expiration: 2003-05-04
Also published as: GB0027017D0; AU2002212455A1

Abstract

A water activated child safety alarm comprises a base unit and a beacon unit, upon immersion in water the beacon unit detaches itself from the base unit, floats to the water's surface and emits an audible alarm signal. The two sections may separate as a resultof the release or generation of a volume of gas in a cavity formed between the two sections. The gas is preferably generated by the decomposition of a highly energetic polymer, such as nitrocellulose, set in a polymeric binder, such as a crosslinked polyurethane elastomer, the binder acting as a sacrificial adhesive, bonding the two sections together.

Description

A Water Activated Child Safety Alarm

The present invention relates to a water safety device for children or other weak swimmers, the device activating upon submersion in water and alerting nearby people in the event that the wearer inadvertently enters a swimming pool or other body of water.

Various alarm devices for alerting an adult to the fact that their child has fallen into a swimming pool are detailed in the prior art, however, all have shortcomings which are addressed by the current invention.

US 5,144,285 (GORE) and US 5,138,300 (CHANCE) both work on the same principle. In each case, a transmitter is attached to the child and a receiver is mounted at the edge of or in the swimming pool. When the child becomes submersed in water, the transmitter is activated and sends a signal to the receiver, the receiver then acts on the signal by either sounding an audible alarm or transmitting a further signal to an intermediate receiving station.

In the case of US 5,486,814 (QUTNONES) a transmitter is constantly active until the , device is submersed in water at which point transmission ceases. A receiver activates upon interruption of the signal and either sounds an audible alarm or signals a pager or telephone interchange instructing them to call a predetermined number to notify the child's parent/guardian.

In all three cases, there is no contingency to inform the supervising adult as to where the child is and all three devices are only effective around a swimming pool equipped with the appropriate receiver system. There also appears to be no contingency for the device becoming accidentally wetted, as might happen, for instance, in a water pistol fight. QUINONBS has a further shortcoming, in as much as the alarm will also sound if the child moves out of the transmitter range, hence interrupting the signal to the receiver. The present invention seeks to overcome or obviate the problems associated with the prior art devices and provide a clearly audible alarm, suitable for a child to wear, which activates upon submersion in water allowing a supervising adult to quickly locate' and rescue the child.

The present invention is a self-contained alarm system designed to be worn either on a wrist/ankle band, on a belt buckle, as a badge or brooch or otherwise attached to a child's clothing. The device comprises two main sections, a base section comprising a wrist/ankle band, a belt buckle, badge or brooch or a section attached to clothing and a buoyant beacon section containing water sensing equipment, an audio alarm and means for releasing itself from the base section. Thus when a child becomes submersed in water, the beacon section senses the submersion, releases itself from the base section, floats to the water's surface and sounds an audible alarm in close proximity to the child.

. Since the device is intended for use by children, it is important that the device is not in danger of becoming detached from the child, through tampering or other causes. Thus the device may be equipped with a child proof clasp or locking mechanism on its strap, thereby preventing a child from detaching the device itself, whilst still allowing an adult to remove it for them.

The tamperproof clasp may take any suitable form, but preferably comprises either a co- operating pair of male/female connectors, so arranged as to require two hands or a cheap tool in order to undo. Alternatively the tamperproof clasp could take the form of a strap passing through a clasp member, the clasp member having one or more projections which pass through openings or perforations in the strap, the projections being enclosed within the clasp, and therefore only accessible to someone with two hands available to open the clasp. Alternatively the tamperproof clasp may take the form of a standard clasp and hole arrangement, with a further one or more locking elements, forced through one or more further holes in the strap, said further holes being smaller than the standard holes, thus making it impossible for a small child to remove the strap from its wrist.

The audible alarm is preferably produced by a piezoelectric transducer linked to a pulsing circuit to generate a siren type sound. However, any speaker or amplifier system small enough to fit into a wristwatch sized cavity yet produce a signal of sufficient amplitude to attract attention could be used.

The device preferably has an ability to differentiate between being splashed and being fully immersed in water.

The system used to differentiate between splashing and immersion may simply relate to. the duration which the water detection circuit is completed i.e. if the device is underwater for 0-3 seconds it does not activate, if submersion lasts longer than 3 seconds it is assumed to be an emergency situation and the device activates.

In this system, the 3 seconds delay, whilst the device is ascertaining whether an emergency exists or not, maybe used to charge a capacitor, if such a capacitor is needed to provide a sufficient charge for a subsequent detonation. ^{' ' '}

The system used to differentiate between splashing and immersion may alternatively comprise some form of splash guard covering one or both of the contacts, the splash guard may be in^' the form of an absorbent material such that a splash will not provide a complete bridge between the two contacts, but prolonged submersion will, since it will take a predetermined amount of time for the splash guard to become saturated.

The separation of the two sections is preferably achieved via the controlled release of a compressed gas, alternatively an expandible polymer may be disposed between the two sections.

The term explosive, as used herein, is in no way intended to limit the materials used to those which are legally classed as high or low explosives, particularly the term is not intended to exclude substances classed as gas generants, pyrotechnics or propellants.- The term explosive is used to refer to any chemical substance which, when activated, undergoes a rapid, gas formation reaction. The device may hold a small explosive charge, detonation of said charge producing a . volume of gas under pressure. The explosive charge is preferably selected from one or more of the following: glycidyl nitrate polymers, glycidyl azide polymer, polytetrazoles, polytriazoles, nitrocellulose and its derivatives, dinitropolystyrene, nitrated polybutadienes, nitrated polyethers, butanetriol trinitrate, pentaerythritol tetranitrate, metriol trinitrate, nitroglycerine and its derivatives, hexanitrostilbene, dipicramid, sodium azide, lead azide, potassium nitrate, silicon dioxide, triazole compounds, tetrazole compounds, salts of 5-nitrobarbituric acid, salts of 5- nitroorotic acid, salts of dicyanamide, nitrate salts of amines and nitrate salts of substituted amines, trinitrotoluene, cyclotetramethylenetrinitramine and cyclotrimethylenetrinitramine.

The two sections, base and beacon, may be attached to one another using a highly energetic, adhesive mixture preferably made up of an explosive set in a resin, the resin being such that it vaporises on activation of the explosive, however, any adhesive mixture which will break down, to form a volume of gas, under a self sustaining chain reaction after initiation, will suffice. Alternatively the explosive may be in the form of an energetic gas generating polymer with properties such that a separate resin system is not required, the polymer acting both as the gas generator and as the resin glue.

The resin may comprise a polymer binder. The polymer binder is preferably selected from the group consisting of fluoroelastomers, crosslinked polybύtadiene rubber, crosslinked polyacrylic rubber, crosslinked polyurethane elastomers and polyvinyl alcohol/acetate. This list is provided as a series of examples only as it is recognised, and would be readily appreciated by one skilled in the art, that any number of different resins/binders would equally serve the purpose required herein. Any binder or resin which will allow the glueing together of two plastic components, yet will rapidly vaporise, thereby effecting release of said two components, upon exposure to rapid heating would be suitable for use herein.

The gas generation reaction, or polymer expansion, is preferably initiated by either a charge differential across two electrodes or by application of heat such as by an electric fusehead, a squib, a "patent detonator" or a blasting cap. The term "patent detonator" is not intended to infer the ownership of a patent, rather it is a common military term for a detonator comprsing an electric fusehead and a small, initiating explosive charge.

The beacon section is preferably shaped to leave a cavity, preferably a symmetrical cavity, more preferably an annular cavity around its base when inserted into the base section, this cavity rapidly fills and pressurises when the compressed gas is released or generated. This ensures the pressure generated to release the beacon section is applied evenly across the entire underside of the beacon, thus reducing the chances of the beacon becoming jammed in the base - section.

The beacon section may have an apertured or fenestered portion on its upper surface to aid the transmission of sound from the device, the apertures being sealingly covered, either inside or outside the beacon casing, with a gas permeable, water impermeable membrane.

The device preferably has a switch to deactivate the alarm after a child has been rescued, this switch may take the form of a cord or plug which, when removed, irreversibly deactivates the device.

The device preferably includes a battery sensor, which detects the battery charge and gives a persistent warning signal when there is no longer sufficient charge in the battery to fully operate the device. The warning signal may take the form of an intermittent loud beeping, in a similar manner to a smoke alarm.

The device may further comprise a second unit emitting a constant electromagnetic signal, preferably a radio signal, the first unit further comprising a receiver. The second unit is then worn by a supervising adult, and the first unit arranged such that it sets of the audible alarm, but does not initiate separation, when the signal is interrupted. Thus when the child strays beyond a predetermined distance from the supervising adult, the alarm sounds and the adult is quickly able to relocate the child. The second unit may be designed such that the amplitude, and therefore range, of the transmitter is adjustable, thus allowing the supervising adult to decide how far the child should be allowed to stray before the alarm is activated.

Figure 1 : Shows a 3D view of the two sections of the device.

Figure 2: Shows a 3D stacked view of the various components of the beacon section of the device.^'

In a first embodiment, the device comprises two main sections, a base section 1 and a beacon section 2. The base section is in the form of a detachable wristband (not shown) with a flattened cup 12 located thereon. The bottom 13 of the cup 12 is substantially thicker than the remainder of the base, section 1, and may have a metal/metallised lining.

The beacon section 2 contains all of the working parts of the device. The outer casing of the beacon section 2 comes in two parts, the lower portion 21 has a thickened base 22, which may be metallised on its interior surface. Protruding through the base 22 of the beacon 2 are the contacts 23 of a "squib" or an electric fusehead (Not Shown), immediately above the base 22 the lower casing 21 is shaped to hold a battery 24 above which is mounted a printed circuit board (PCB) 25 which controls the device. Above the PCB 25 is mounted a piezoelectric transducer 26 with an output of approximately 100 dB. The upper section 27 of the beacon 2 carries two contacts 28, 29 both attached to the PCB 25. Section 27 is irreversibly attached to section 21/ forming an airtight enclosure, with enough air being trapped inside the upper section 27 to provide the beacon with a positive buoyancy with respect to water.

The PCB 25 carries several discrete circuits:

There is a water detection circuit which activates the device when an aqueous bridge is made between contacts 28 and 29.

There is a timing/counting circuit which is activated when the water detection circuit detects submersion. The is a pulsing circuit to control piezoelectric transducer, thus producing a loud, siren type sound. There is a squib circuit which is activated when a current is passed across contacts 23.

The beacon section 2 is secured to the base section 1 in two ways, firstly there is an O- ring 30 around the circumference of the beacon section 2 providing an airtight seal against the lip 14 of cup 12, secondly the bottom 22 of the beacon section is secured to the bottom 13 of the cup 12 by a thin layer of highly energetic adhesive (Not Shown), preferably a mixture comprising an explosive set in a castable resin, the resin being such that when the explosive is discharged, the resin is vaporised thereby breaking the bond between the two sections of the device..

The device works in the following manner, if contacts 28, 29 are bridged by an aqueous medium, such as sea water, the water detection circuit becomes active and the timing circuit begins to count. If, after 0-3 seconds the aqueous bridge is broken, then the device decides that it has merely been splashed, and returns to its dormant state, if however, after this time the device is still active then the squib and the siren are activated. When the squib is activated, a very rapid reaction commences in the adhesive. This reaction generates a volume of gas (mainly a combination of carbon dioxide and nitrogen) which is retained under pressure by the O-ring 30. When the pressure reaches a predetermined level, preferably 2-4 atmospheres (202 - 405 KPa) the beacon 2 ejects itself from the base section 1 and, due to its positive buoyancy, floats to the surface, where the piezoelectric transducer can clearly be heard by passers by or by a supervising adult.

Whilst the single embodiment is pesented as a wrist worn device, it will be readily apparent to a person skilled in the art that there are a number of other possibilities within the scope of the present invention, for instance it could be worn on an ankle strap, a belt buckle or the like. It should be noted that the preceding embodiment is given as an example only, and is in no way intended to limit the scope of the invention, which is defined by the claims.

Claims

1. A water safety device comprising a base unit and a beacon unit, the beacon unit detaching itself from the base unit upon immersion in water, floating to the surface and emitting an alarm signal.

2. The device according to claim 1 , wherein the base unit is in the form of a .wrist/ankle strap, a belt, a belt buckle or a badge or brooch.

3. The device according to either of claims 1 or 2, wherein the attachment mechanism for the device is a childproof mechanism.

4. The device according to any preceding claim, wherein separation of the two sections is achieved via the release of a compressed gas.

5. The device according to any preceding claim, wherein separation of the two sections is initiated by an expanding polymer.

6. The device according to any preceding claim , wherein separation of the two sections is initiated by a rapid, gas forming chemical reaction.

7. The device according to claim 6, wherein the reactant(s) involved in said rapid, gas forming reaction' re set in a resin, the resin being such that it vaporises on activation of the reactants, such that the resin acts as a sacrificial adhesive to bond the two sections together, said adhesive decomposing during the reaction, not only to produce a volume of gas, but also to remove the bond between the two sections.

8. The device according to either of claims 6 or 7, wherein the device's casing immediately adjacent the area of adhesion is thickened to withstand the generated heat and pressure.

9. The device according to any preceding claim, wherein the alarm signal is an audible alarm.

10. The device according to claim 9, wherein the audible alarm signal is generated using a piezoelectric transducer contained within the beacon section.

11. The device according to claim 9 or 10, wherein the casing adjacent the audible signal generator is fenestered or apertured to better allow transmission of sound from the device, said fenestrations/apertures being sealingly covered with a gas permeable, water impermeable membrane.

12. The device according to any previous claim, wherein the water detection circuit is activated by two contacts disposed on the beacon's casing.

13. The device according to claim 12, wherein the water detection circuit has a built in safeguard to prevent the device from activating when it is merely splashed.

14. The device according to claim 13, wherein the safeguard is in the form of a timer, and the device is not activated unless water contact is detected continuously for a predetermined period of time.

15. The device according to claim 14, wherein water contact must be continuous for 0 - 10 seconds before the device is activated.

16. The device according to any of claims 15, wherein the time delay whilst the device is ascertaining whether an emergency exists or not, is used to charge a capacitor, if such a

^" capacitor is needed to provide a sufficient charge for the subsequent initiation of the gas producing reaction.

17. The device according to claim 16 wherein the safeguard is in the form of a splash barrier on or near one or both of the contacts.

18. The device according to any preceding claim, wherein the base and beacon sections are shaped in a manner that leaves an annular space around the bottom of the beacon section, said space rapidly filling with gas and pressurising when the release mechanism is activated, to ensure a clean separation of the two sections.

19. The device according to any preceding claim, further comprising a deactivation switch, allowing the alarm to be turned off after use.

20. The device according to any preceding claim, further comprising a battery alarm circuit, said circuit checking the battery levels and sounding an audible alarm when the battery is no longer sufficiently charged for the device to function properly.

21. A device substantially as hereinbefore described with reference to the accompanying figures.