GB2360619A

GB2360619A - Water leak alarm

Info

Publication number: GB2360619A
Application number: GB0029417A
Authority: GB
Inventors: Peter Terrance May
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-12-10
Filing date: 2000-12-04
Publication date: 2001-09-26
Also published as: GB9929304D0; GB0029417D0

Abstract

A water leak detection device for a domestic appliance such as a washing machine 35 comprises a moisture sensor 15 and an alarm 25, in which the moisture sensor has a moisture absorbent element 20 locatable in the vicinity of the appliance to absorb moisture leaking therefrom, a physical property of the moisture absorbent element varying with the quantity of moisture absorbed. The element 20 may be in the form of a strip or pad. A circuit (Fig. 2, not shown) includes components responsive to changes in conductivity of the element 20 to actuate the alarm 25, and a low battery voltage detector which can energise an LED indicator 30. A guard excludes water from any source other than the appliance.

Description

2360619 LEAK ALARM The present invention relates generally to a device for

detecting leaks and 5 specifically to such a device for use in domestic situations.

The present invention finds utility in situations where a domestic appliance, for example, washing machines, hot water boilers, refrigerators and freezers may be subject to water leaks. In many cases where these appliances are in need of repair, a water leak may provide an early indication that the article is in need of attention. This may allow the user to detect a fault earlier than is otherwise possible and attend to preventative repairs before the problem becomes more serious.

Moreover, if a water leak goes undetected the area surrounding the appliance could also be damaged. For example water may leak into a floor containing wooden floorboards or structural supports; if water comes into contact with them they will rot over a period of time.

In many cases a water leak may be small at first and then grow to something more serious. The amount of water required to be leaking from an appliance before it is drawn to the user's attention may be in some cases significant, for example in the case of a hot water tank or boiler that is shut away in a cupboard, a small leak may go undetected for some time, but of course the continual collection of water in a confined space may cause considerable structural damage which is not visible from 2 the outside. In such cases a small leak, for example from a washing machine which if noticed early may be repaired very simply, might if not noticed worsen and ultimately lead to substantial repair bills.

Although hygrometer apparatus for detecting the presence of water in structures is known, such devices are expensive and suitable only for conducting specific tests for the presence of water when such presence is suspected. There is thus a need for a device which is inexpensive, simple to use, and adapted for domestic use and for monitoring over time.

Accordingly there is provided a water leak detection device for a domestic appliance susceptible to water leaks, comprising a moisture sensor and an alarm, in which the said moisture sensor has a moisture absorbent element locatable in the vicinity of the appliance to absorb moisture leaking therefrom, a physical property of the said moisture absorbent element varying with the quantity of moisture absorbed.

Depending on the likely source and destination of any leaks the moisture absorbent element may be elongate to allow it to be positioned so as to extend around at least part of the area occupied by the appliance. In other embodiments the moisture absorbent element may be formed as a pad upon which an appliance is placed.

3 In a preferred embodiment the moisture sensor is formed as an elongate strip element. Such a strip may be used to encircle the base of the appliance to detect water around the base.

The moisture absorbent element may be formed from material that exhibits differential electrical conductivity properties which are dependent on the amount of water that has been absorbed. Preferably the conductivity of the moisture absorbent element increases as the amount of water absorbed increases, although in other embodiments the reverse may be true.

Where the moisture absorbent element is formed from material that exhibits differential electrical conductivity properties dependent on the amount of water absorbed, when a predetermined level of conductivity is achieved the moisture sensor may trigger the alarm to sound. The predetermined level of conductivity may be variable, which may be achieved in a number of ways, for example varying the electrical power required to activate the alarm or by judicious choice of the properties of the material used to form the moisture absorbent element.

The power source for the detection device may be a battery, however other power sources such as mains power are not beyond the scope of the invention.

Where the power source is a battery there may further be provided means for indicating the battery charge status. The indicator may alert the attention of the 4 user at a predetermined time before the power source will fail to allow sufficient time for the battery to be replaced.

There may also be provided means for avoiding inappropriate activation of the alarm. For example where the moisture sensor is positioned around the base of a washing machine, the washing machine may be in the vicinity of the sink of a kitchen or utility room, in which case it is possible that water from other sources from the washing machine may inadvertently splash onto the moisture absorbent element. A water resistant guard may be positioned to prevent water other than that from the appliance coming into contact with the moisture absorbent element.

One embodiment of the invention will now be more particularly described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic perspective view of a water leak detection device according to the present invention; Figure 2 is a circuit diagram illustrating the components of the water leak detection device of Figure 1.

Referring first to Figure 1 there is shown a water leak detection device generally indicated 10, comprising a moisture sensor 15, a moisture absorbent element 20, an alarm 25 and a visual indicator 30.

The moisture absorbent element 20 is an elongate strip which in this embodiment is positioned on the floor so as to surround the base of a domestic appliance 35 which is shown in broken outline. The element 20 is normally dry and in this state will either be non-conductive or will conduct only a small electrical current. Each end of the element 20 is connected to the moisture sensor 15.

If the element 20 becomes wet at any point along its length its electrical conductivity as a whole will increase. The moisture sensor 15 detects the resulting increase in current and triggers the alarm 25 to sound when this increase reaches a predetermined value.

In this embodiment the power supply for the water leak detection device 10 is a battery (not shown) which can be housed within the casing of the moisture sensor 15. When the charge remaining in the battery falls to a predetermined level the indicator 30 is illuminated to remind a user to replace the battery. The alarm may also be energised with a characteristic signal, such as a series of short pulses, to draw the user's attention to the need for a fresh battery. Although shown as a separate light source in Figure 1, the visual indicator may be a light emitting diode mounted in the casing of the device 15.

Referring now to Figure 2, the circuit shown comprises a transistor pair 36, comprising two NPN transistors 37, 38 in a Darlington pair configuration. The base of the transistor 37 is connected to the terminal 40 of a pair of terminals 39, 40 to which the absorbent conductive strip 20 is connected in use of the apparatus.

6 The terminals 39, 40 are respectively connected between positive and negative supply lines 41, 42 via respective resistors 43, 44 in series with the absorbent conductive strip 20 connected to the terminals 39, 40 to form a potential divider.

The supply rails 41, 42 are connected to a battery (not shown) via battery terminals 50, 5 1. The potential of the terminal 40 is thus determined by the conductivity of the strip 20. If moisture is absorbed by the strip 20 to make it more conductive (that is less resistant) The potential of terminal 40 rises until the transistor 37 is triggered to conduct, thereby triggering transistor 38. The collectors of the two transistors 37, 38 are connected to an integrated circuit 1C2 which is supplied from the power lines 41, 42 and has an output pin 45 connected to an audible indicator (acoustic transducer) 46. When transistor 38 becomes conductive 1C2 emits an output on pin 45 to energise the alarm.

The circuit also includes a battery condition monitor comprising an integrated circuit IC 1 connected across the power supply lines 41, 42. A light emitting diode 30, the anode of which is connected to the positive supply line 41 via a resistor 47, is connected to pin 8 of ICI. The biasing of the integrated circuit via resistors 48, 49, 51, 52, 53, 54 and 55 is such that this holds the power lines 41, 42 at the nominal battery voltage, for example 9v, as the battery potential falls over time, until it reaches a critical threshold value, upon which it triggers to indicate low battery level by illuminating the light emitting diode 30.

A polarity protection diode 56 ensures that the two integrated circuits ICI and IC2 do not interfere with one another. Integrated circuit 1C2 has an external RC circuit 0 1 4 7 comprising resistor 57 and two capacitors 58, 59 which ensures that once the circuit is triggered to sound the alarm 46 it remains triggered so that even if a leak is intermittent and the sensor strip 20 dries or partially dries before the alarm is noticed, it will nevertheless sound continuously to draw the occupant's attention to 5 the potential leakage problem.

8

Claims

1 A water leak detection device for a domestic appliance susceptible to water leaks, comprising a moisture sensor and an alarm, in which the said moisture sensor has a moisture absorbent element locatable in the vicinity of the appliance to absorb moisture leaking therefrom, a physical property of the said moisture absorbent element varying with the quantity of moisture absorbed.

2. A water leak detection device as claimed in Claim 1, in which said moisture absorbent element is elongate and flexible to allow it to be positioned so as extend around at least part of the area occupied by said appliance.

3. A water leak detection device as claimed Claim 1 or Claim 2, in which the moisture absorbent element is formed from material that exhibits different electrical conductivity properties dependent on the amount of water absorbed.

4. A water leak detection device as claimed in Claim 3, in which the electrical conductivity of the moisture sensor increases as the amount of water absorbed increases.

5. A water leak detection device as claimed in any of Claims 5 to 7, in which when a predetermined value of said physical property is achieved the moisture sensor triggers the alarm to sound.

9 6. A water leak detection device as claimed in any preceding claim, in which the power source is a battery.

7. A water leak detection device as claimed in Claim 6, in which there are 5 further provided means for indicating the battery charge status.

8. A water leak detection device as claimed in Claim 11, in which there are means for avoiding inappropriate activation of the alarm comprising a waterresistant guard positioned so as to prevent water other than that leaking from the 10 said appliance coming into contact with the moisture absorbent element.

9. A water leak water leak detection device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.