Device for warning when a person is submerged beneath water

A device for warning when a person is submerged beneath water, comprising a timing circuit having first and second terminals and being responsive to a voltage applied to the first terminal for connecting the second terminal to the first terminal after a predetermined time interval and an alarm unit connected to the second terminal of the timing circuit. A normally open water-sensitive switch is provided for attaching to a part of the person's body which is normally above water and is coupled to the first terminal of the timing circuit. An electrical supply is coupled to the water-sensitive switch for applying the required voltage to the first terminal of the timing circuit when the water-sensitive switch is submerged beneath water. A normally deflated float may be worn by the person so as to be automatically inflated in response to the alarm signal.

FIELD OF THE INVENTION 
This invention relates to a device for warning when a person is submerged 
beneath water. 
BACKGROUND OF THE INVENTION 
When a person sinks to the bottom of a pool of water, or even floats 
unconscious on the surface of the water, his lungs stop functioning and 
his brain is therefore deprived of oxygen. If this situation is allowed to 
continue for more than a few minutes, irreparable damage will be done to 
the brain even if the person is resuscitated. However, if the drowning 
person is detected quickly and removed from the water, there is still a 
very short time period during which resuscitation may be effected before 
permanent damage ensues. Thus, rapid detection and identification of a 
drowning body is essential if resuscitation is to be at all possible and 
if permanent damage is to be avoided. 
Clearly, detection of a drowning body which remains floating on the surface 
of the water may easily be effected manually by means of a life-guard, 
when present. Consequently, effort has generally been expended into 
detecting a drowning body which is submerged beneath the surface of the 
water. Most prior art devices are based on detecting disturbances in the 
water and actuating a suitable alarm when such disturbances are detected. 
Such an approach may also be used in order to monitor unauthorized entry 
into a swimming pool and to provide an alarm in the event of such 
unauthorized entry. 
Thus, for example, U.S. Pat. No. 4,747,085 (Dunegan) discloses a swimming 
pool alarm system for actuating an alarm in response to the movement of a 
person in a swimming pool. The system includes a transmitter mounted below 
the surface of the swimming pool for continuously transmitting ultrasonic 
sound waves through the body of water, and a similarly positioned receiver 
detects sound waves in the water and generates an electrical signal in 
response thereto. The electrical signal is continuously monitored, and the 
movement of a person in the pool alters the received ultrasonic sound 
waves and the corresponding electrical signal so as to produce a 
corresponding alarm signal. 
The device disclosed by Dunegan et at., and which is typical of its genre, 
is based on the assumption that a drowning person struggles violently 
prior to sinking and therefore gives rise to disturbances in the water 
which can be monitored. 
In contrast to such an approach, U.S. Pat. No. 5,043,705 (Rooz et al.) 
discloses a system for detecting a motionless body in a pool consequent to 
a swimmer sinking to the bottom of the pool, usually after losing 
consciousness. In such circumstances, the swimmer no longer moves and 
therefore detection based on monitoring disturbances in the water is no 
longer possible. The system disclosed by Rooz et al. is based on scanning 
the lower surface of the pool so as to extract successive frames of image 
data which are analyzed in order to detect a contour of a body which 
remains substantially motionless for longer than a predetermined time 
interval. 
There are drawbacks associated with both of the above-mentioned approaches. 
Thus, devices of the type described by Dunegan et al. are intended to 
provide a warning in the event of unauthorized disturbances within the 
swimming pool. Such systems are effective only when the pool is empty. 
People swimming in the pool inevitably cause disturbances which require 
that the alarm systems of the type described by Dunegan et al. be disabled 
in order to prevent them from operating. In other words, alarm systems of 
this type are primarily intended to protect domestic swimming pools or 
even public swimming pools when not in use and the life-guard is not 
present. 
The purpose of such alarm systems is generally to protect against 
unforeseen slipping in the water and to provide a warning that someone has 
entered the pool when it is, as yet, unauthorized for use. Such an 
approach is obviously important to guard against small children slipping 
into the water or against somebody who falls in when it is dark and cannot 
climb out unaided. 
The fact that such devices must be disabled when use of the pool is 
authorized, severely militates against their use for detecting a swimmer 
in distress. Such a drawback is overcome by the system disclosed by Rooz 
et al., but their system is sophisticated and therefore expensive. 
Yet another drawback associated with all systems of the type described is 
that they must somehow be mounted in conjunction with the swimming pool 
itself. Thus, specifically, there are provided ultrasonic transmitters and 
detectors which must be affixed to the pool. This might possibly be 
acceptable for domestic pools, but provides insufficient protection for a 
member of the public who may swim regularly at different pools. Unless 
each pool is protected by a suitable monitoring device which is enabled 
when the pool is open to the public, the resulting protection is 
inadequate. 
Such a drawback would, of course, be overcome if the detection means 
typically associated with prior art systems were somehow associated not 
with the pool but rather with the swimmer himself. No such approach has 
been contemplated in hitherto proposed systems. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a device for warning when a 
person is submerged beneath water, in which the drawbacks associated with 
hitherto proposed systems are significantly reduced or overcome. 
According to a broad aspect of the invention there is provided a device for 
producing a warning signal when a person is submerged beneath water, the 
device comprising: 
a timing means having first and second terminals and being responsive to a 
voltage applied to the first terminal for connecting the second terminal 
to the first terminal after a predetermined time interval, 
a signalling unit connected to the second terminal of the timing means and 
responsive to the voltage thereon for producing said warning signal, 
a normally open water-sensitive switch for attaching to a part of the 
person's body which is normally above water and being coupled to the first 
terminal of the timing means, and 
an electrical supply coupled to the water-sensitive switch for applying 
said voltage to the first terminal of the timing means when the 
water-sensitive switch is submerged beneath water. 
In accordance with a preferred embodiment of the invention, the signalling 
unit is part of an alarm unit comprising a transmitter worn by the person 
for transmitting a warning signal after he is submerged for a 
predetermined time interval and a receiver remote from the person for 
receiving the warning signal and producing an alarm signal. An alarm 
indication means is coupled to the receiver and is responsive to the alarm 
signal for producing an audible or visual warning.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows a device depicted generally as 10 comprising a water-sensitive 
switch 11 for attaching to a part of a person's body which is normally 
above water such as, for example, his forehead. A timing means 12 has a 
first terminal 13 connected to one contact of the water-sensitive switch 
11 and a second terminal 14 connected to an alarm unit 15. A battery 16 is 
connected to a second contact of the water-sensitive switch and to a 
battery check circuit 17. A normally-open manual switch 18 is connected 
across the first and second terminals 13 and 14, respectively, of the 
timing means 12, for short-circuiting the timing means 12, if required. 
The device operates as follows. The battery 16 provides a predetermined 
voltage which is insulated from the first terminal 13 of the timing means 
12 so long as the water-sensitive switch 11 remains open (i.e. its normal 
state). However, when the water-sensitive switch 11 is submerged beneath 
water, the normally-open contacts thereof close, thereby applying the 
battery voltage to the first terminal 13 of the timing means 12. The 
timing means 12 is constructed to connect the first and second terminals 
13 and 14, respectively, after a predetermined time interval which may be 
pre-set within the range 40 to 60 sec. Thus, upon submerging the 
water-sensitive switch 11 beneath water and maintaining it beneath water 
for the pre-set time interval, the battery voltage 16 is applied, via the 
water-sensitive switch 11 and the timing means 12, to the second terminal 
14 of the timing means 12 and hence to the alarm unit 15. Typically, the 
alarm unit 15 provides an audible sound which alerts a life-guard, or a 
neighboring swimmer, that the person wearing the device is in distress. 
The battery check 17 is typically provided with an indicator lamp for 
providing an indication that the battery voltage is sufficiently high to 
permit effective operation of the device. 
The manual switch 18 short-circuits the timing means 12, thereby activating 
the alarm unit 15 whenever the water-sensitive switch 11 is submerged 
beneath the water, regardless of the elapsed time during which the 
water-sensitive switch 11 has been submerged. Thus, the manual switch 18 
is useful for divers, for example, and other similar underwater swimmers 
who, by means of the manual switch 18, are able to send distress signals 
when their oxygen supply is short, or for any other reason, regardless of 
the status of the timing means 12. 
FIG. 2 shows a detail of the alarm unit 15 in accordance with a first 
preferred embodiment of the invention. There is provided a transmitter 20 
which is worn by the swimmer and transmits a warning signal when the first 
and second terminals 13 and 14, respectively, of the timing means 12 are 
connected to each other. A receiver 21, remote from the transmitter 20 and 
typically fixed to a swimming pool (see FIG. 3), receives the warning 
signal and produces a corresponding alarm signal which, in turn, is fed to 
an alarm indication means 22 for producing the desired warning. 
Alternatively, the alarm unit 15 may be constituted by a simple alarm 
circuit, including a buzzer, which is connected directly to the timing 
means 12. 
FIGS. 3 and 4 show alternative scenarios of the device 10 in actual use. 
Thus, as shown in FIG. 3, the receiver 21 is fixed to a wall 23 of a 
swimming pool 24 beneath the level 25 of water therein. The alarm 
indication means 22 is fixed above the water level 25. A swimmer 26 wears 
the device 10 around his forehead, the device 10 being fixed thereto by 
means of a flexible headband 27. When the swimmer 26 is submerged beneath 
the water level 25 for longer than the pre-set time interval, the 
transmitter 20 emits a warning signal, this being detected by the receiver 
21, so as to produce an audible or visual alarm signal via the alarm 
indication means 22. 
The transmitter 20 is typically directional, thereby permitting the warning 
signal transmitted thereby to be detected only by a receiver 21 which is 
located within a reception zone of the transmitter 20. Therefore, for 
large pools, a plurality of receivers 21 may be provided around a 
periphery of the pool, each of the receivers being connected either to a 
common alarm indication unit or, alternatively, to separate alarm 
indication units, as required. The provision of a separate alarm 
indication unit for each receiver, provides immediate feedback to a 
lifeguard or other security personnel of the approximate direction from 
which the warning signal was transmitter and hence in which the swimmer 26 
is located. 
The warning signal may be acoustic such as ultrasonic, optical such as 
infra-red or a radio-frequency (r.f.) signal. In the event that r.f. 
signals are employed, an antenna may be connected to the transmitter 20, 
the antenna preferably being constituted by a flexible electrically 
conductive belt which may also serve as the headband 27 and 27a. 
Alternatively, several transmitters 20a-20d may be disposed 
circumferentially round the headband 27, each for transmitting a 
respective acoustic, optical or r.f. signal, as required to a 
corresponding receiver. 
FIG. 4 shows a second embodiment wherein the alarm unit is integral with 
the device itself and, again, is worn by the swimmer 26 around his 
forehead by means of the headband 27. In this case, the alarm unit 15 
provides an audible signal which may be heard from outside of the pool 24 
in order to alert a life-guard; or, indeed, may be heard from within the 
pool by a neighboring swimmer. 
In order to render the device attractive, particularly to young children, 
the headband 27 may be covered with a decorative material. 
FIGS. 5 and 6 show pictorially a third embodiment of the invention wherein 
the swimmer 26 wears a normally deflated float 28 which is responsive to 
the warning signal for inflating. Such floats are well known and may be 
provided with a manually operated pull cord for manually inflating the 
float. Life jackets operating on this principle are usually provided in 
aircraft, for example. Typically, inflation occurs as a result of a 
chemical reaction which produces gases which inflate the float. Electrical 
operation may be achieved via a suitable transducer so that the float 28 
inflates in response to the warning signal. In such case, manual operation 
may still be achieved by operating the manual switch 18 connected across 
the timing means 12. 
In such an embodiment it is not desirable that the float be electrically 
coupled to the device 10 by means of an electrical wire. Therefore, a 
receiver may be mounted on the float for receiving the warning signal 
transmitted by a transmitter coupled to the device 10. If desired, the 
warning signal can be transmitted remotely by a life guard if a swimmer 
disappears from view and the life guard, or other auxiliary, suspects that 
he may be in danger. By such means, the life guard can induce the swimmer 
to float to the surface of the pool. 
It will be appreciated that, during use, the device 10 will frequently be 
submerged beneath the water level 25 for short time periods. However, this 
is of no consequence during normal swimming, since, between strokes, the 
swimmer 26 will raise his head above the water surface 25, thereby causing 
the water-sensitive switch 11 to open and reset the timing means 12. Thus, 
any natural tendency of the head to become submerged beneath the water 
level consequent to normal swimming is not an impediment to the use of the 
device. 
It will also be appreciated that, particularly for very young children, the 
device 10 may equally be secured to the child's ankle so as to provide a 
warning even if he steps into a shallow paddling pool. By such means, the 
device will alert the child's parents that the child has entered the pool. 
It will further be appreciated that, whilst the device has been described 
with particular reference to its use as a swimming pool alarm, it may also 
be worn by children, or elderly people, when bathing so as to provide an 
immediate warning if they become submerged beneath the water level for 
longer than a predetermined period of time.