GB2341007A

GB2341007A - Fluid level sensor

Info

Publication number: GB2341007A
Application number: GB9917821A
Authority: GB
Inventors: David John Dean; Malachi Christopher Mckenna
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-13
Filing date: 1999-07-29
Publication date: 2000-03-01
Anticipated expiration: 2019-07-29
Also published as: GB9817667D0; GB9917821D0; GB2341007B; GB9910906D0; GB9912708D0

Abstract

A fluid level sensor comprises a switch 16 and a switch operating element 18 that are moved towards and away from each other by a varying water level, the arrangement being such that the relative movement of the switch and the switch operating element causes the switch to adopt either a first or a second switching position. One of the switch or switch operating element is housed in a float 18, while the other element 16 is held fixed. Preferably, the switch 16 is an electrical reed switch and the switch operating element is a magnet 20. In an embodiment the liquid level sensor controls a water supply from a reservoir to a water consumer such as a plant container. In another embodiment, the level sensor is used to detect the level of a liquid, and to actuate an alarm.

Description

2341007 Plant Water_Lng__,$ym The present invention relates to level

sensors, and particularly concerns sensors for detecting water levels and for providing control signals dependent on water levels. The sensors may be used in water supply systems to detect a minimum level and initiate a water supply operation, or may be used to detect a maximum water level and initiate an alarm or a protective device such as a PUMP.

In a domestic or office situations it is often necessary to provide a water supply to a plant growing in a container during a period of time when the home or office is uninhabited. Hitherto, it has been proposed to simply stand plant containers in a bath of water to maintain a water level in the bottom of the plant container. A disadvantage of this arrangement is that plants must be moved to the bath, and if the building is uninhabited for a long time then the water in the bath may be completely used up and the plants may die.

The present invention seeks to provide a plant watering system which can provide a continuously available water supply to a plant over an extended period of time, 2 without the need either f or human intervention, or the need to be connected to any mains services.

A further objective of the present invention is to 5 provide a reliable water level sensor of simple construction.

Yet another objective of the present invention is to provide a water level detection and warning system, which can be used in domestic environments to over its householders to rising water levels either within or outside a dwelling.

According to a f irst aspect of the present invention, there is provided a liquid level sensor comprising a housing and a float block movable relative to the housing in response to a changing liquid level, a switch and a switch operating element being mounted respectively to the housing and to the float block, or vice versa, so that movement of the float block relative to the housing changes a spacing between the switch and the switch operating elements, the arrangement being such that the switch adopts a first switching position when adjacent to the switch operating element and a second switching position when spaced from the switch operating element.

3 A second aspect of the present invention provides a liquid level detecting system comprising a liquid level sensor, a power source, and alarm means energisable by the power source when the switch of the sensor is in a first switching position.

A third aspect of the present invention provides a water supply system comprising a reservoir, a supply duct leading from the reservoir, and a valve for controlling a flow of water through the supply duct, the valve being movable from an open to a closed position by an actuator, and the actuator being controllable by a level sensor.

A fourth aspect of the present invention provides a water supply system comprising a reservoir, a supply duct leading from the reservoir, and a pump for causing a flow of water through the supply duct, the number being controllable by a level sensor.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a partially cutaway perspective view of a plant holder including a level sensor embodying the 4 invention; Figure 2 is an exploded view of the water level sensor; Figure 3 is a sectional view taken in the plane III-III of figure 2; Figure 4 is a schematic view to illustrate the operation of the plant holder; Figure 5 is an enlarged view of the valve of figure 4; and Figures 6a and 6b are schematic views of an alternative level sensor embodying the invention.

Referring to the drawings, figure 1 shows a self -watering plant holder comprising a substantially frustoconical container 1 having a circular base 2 and a conical upstanding sidewall. An upper part of the sidewall 3a is offset radially outwardly from a lower part 3b, and a circumferentially extending shelf 4 joins the upper and lower parts of the side wall.

Resting on the shelf 4 is a partannular reservoir 5, which extends in the circumferential direction for a suf f icient distance so as to be securely supported by the shelf 4. Preferably, the reservoir 5 extends approximately half way round the shelf 4, and most preferably extends over more than half the circumference of the shelf. At one end of the reservoir 5 a battery compartment 5a houses a battery 6 to provide electrical power. The reservoir 5 may extend completely round the circumference of the shelf 4, and may have a battery compartment 5a separated from the reservoir by radially extending dividing walls.

Extending downwardly from the reservoir 5 is a feed tube 7, which leads via an electromagnetic valve to a combined supply container and level sensor 8 positioned on the base 2 of the container 1. From the battery compartment 5a, wires 9 lead from the battery 6 to the level sensor 8.

The combined supply container and level sensor 8 is shown in more detail in figure 2. The supply container comprises a base 10 with a cylindrical upstanding sidewall 11. A perforated lid 12 which has a circumferential rebate 13 at its lower edge fits over the upper edge of the sidewall 11. openings 14 are formed in 6 the upper part of the side wall 11, and the feed tube 7 extends through one of the perforations in the lid 12, so as to be able to discharge water into the supply container. In an alternative embodiment (not shown) the feed tube 7 may discharge through one of the openings 14 in the side wall 11.

The base 10 of the supply container is formed in its underside with a recess 15 to accommodate a reed switch 16, which is connected by wires to the battery 6 and to an electromagnetic valve, to be described later.

Two pairs of guide ribs 17 extend upwardly along the side walls 11 of the supply container, at diametrically opposite locations. A float block 18 positioned centrally in the supply container has a pair of positioning bars 19 extending from its respective ends, the free ends of the positioning bars 19 being each received between a respective pair of guide ribs 17. The cooperation between the positioning bars 19 and guide ribs 17 maintains the float block 18 vertically above the recess 15 containing the reed switch 16.

Attached to, or as in the illustrated embodiment embedded 25 within, the float block 18 is a magnet 20. When the 7 float block 18 is positioned adjacent the recess 15, the magnet 20 causes the reed switch 16 to adopt a first position, and when the float block 18 is moved away from the recess 15 the influence of the magnetic field of the magnet 20 on the reed switch decreases, allowing the reed switch to change state.

Figure 4 shows schematically the operational components of the plant container of figures 1 to 3. The electromagnetic valve is shown generally at 21 and is a two-position spool valve. The valve is shown in the closed position in f igure 4, and in figure 5 the valve is shown in the open position.

The electromagnetic valve 21 comprises a substantially cylindrical chamber 22 in which a spool 23 is axially movable between open and closed positions. Inlet and outlet ports open into the cylindrical chamber, respectively to allow the egress and egress of liquid therefrom. In the closed position, as shown in figure 4, the spool is positioned so that a larger diameter section 23a of the spool blocks both the inlet and outlet ports. The school is connected to a magnetic core 24 by an operating rod 25 extending axially out of the cylindrical chamber 22. A spring 26 urges the spool 23 towards the 8 closed position of the valve 21.

The magnetic core 24 is situated within a winding 27 which, when energised with electricity from the battery 6, attracts the magnetic core 24 so as to move the spool of the valve 21 to the position shown in figure 5, against the force of the spring 26.

The reservoir 5 as a duct 28 leading to the inlet port of the valve 21, and the outlet port of the valve 21 leads via the f eed tube 7 to the supply container. In the illustrated embodiment, the feed tube 7 is made of flexible plastics or rubber tubing, and is attached to the valve 21 and to the lid 12 of the supply container by means of respective spigots.

The battery 6 forms a circuit with the winding 27 and the reed switch 16 connected in series. The reed switch 16 has a fixed contact 30 and a movable contact 31, the switch being arranged so that the contacts 30 and 31 are separated by gravity when the magnet 20 is spaced from the reed switch 16. When the magnet 20 is placed adjacent the reed switch 16, the moving contact 31 is attracted to the magnet 20 and moves into contact with the fixed contact 13, completing the series circuit and 9 energising the winding 27. A manually operable "on-of f 11 switch (not shown) may be provided either in the battery compartment or on a cover of the battery compartment, connected in series with the winding 27 and reed switch 16 to provide a manual override capability.

In use, the combined supply container and level sensor is placed in the bottom of the container 1, and the f eed tube 7 is led upwardly from the supply container to the reservoir 5. The electrical wires 9 are led to the battery compartment 6, to connect the battery, winding 27, and reed switch 16 in series. Compost or other plant growing medium is then placed in the container to fill it, and one or more plants are then planted in the plant growing medium. The reservoir 5 is then filled with water.

Since the supply container will be empty, the float block 18 will rest on the recess 15, and the magnet 20 will attract the moving contact 31 of the reed switch 16 to close the electrical circuit. The winding 27 will then be energised, and will attract the core 24. This will move the spool 23 of the valve 21 to the open position, allowing water to flow through the duct 28, the valve 21, and the feed tube 7 into the supply container.

AS the supply container is filled with water, the float block 18 will rise and move the magnet 20 away from the reed switch 16. As the float block 18 and magnet 2 0 move away f rom the reed switch 16, at a predetermined distance 5 the magnet 20 can no longer support the movable contact 31 and the reed switch opens, breaking the electrical circuit. The winding 27 is de-energised and the spring 26 returns the spool 23 to the right as shown in the figures, closing the valve 21 and cutting off water flow to the supply container.

It will be understood that the positioning of the openings 14 in the side wall 11 of the supply container is preferably such that when the water level is at the lowermost part of the openings 14, the float block 18 is supported a sufficient distance away from reed switch 16 for contact between the fixed and moving contacts 30 and 31 to be broken. This arrangement will maintain the desired level of water only within the supply container.

If the openings 14 are placed below the desired level, then the lower part of the container 1 will be filled to the desired level of water, as water will flow out of the openings 14 and the water level within the supply container will only rise f urther once the plant container 1 has been filled to the level of the openings 14.

11 The presence of water in the supply container maintains the growing medium in the plant container damp, and provides water to the roots of the plant. As the plant draws water from the supply container, the level within the supply container falls and as the float block 18 moves closer to the reed switch 16, the contacts of the reed switch are again closed. This causes the valve 21 to be opened, to replenish the supply of water in the supply container to a point at which the float block 18 is raised sufficiently for the reed switch contacts to reopen and de- energise the winding 27 again.

Preferably the reservoir 5 is so dimensioned as to be able to contain sufficient water to provide an adequate supply of water to the plant or plants in the plant container for an extended period of time, preferably two or more weeks.

In an alternative arrangement, not illustrated, the 20 sensor 8 may be positioned in the bottom of a plant container, and fed with water by a supply tube 7 from a reservoir outside the plant container. The water from the reservoir may be fed by gravity, using the sensor 8 to control a valve 21 as has previously been described.

Alternatively, the sensor 8 may be connected in series 12 with a pump and a battery, so that when the magnet 20 of the sensor is adjacent the reed switch 16, the circuit is completed and the pump operates to supply water to the sensor 8. It will be appreciated that in such an arrangement the size of the reservoir is not limited by the dimensions of the plant container, and the water level in the reservoir may be below the level of the plant container. It is further foreseen that a reservoir of enlarged capacity may be provided with a number of pumps each supplying water to a respective sensor 8, with the pumps operating from the same power source. The power source may be a battery, or may be the mains electricity supply, with the voltage suitably adjusted by means of a transformer and/or rectifier.

The sensor 8 in the previous embodiments provides an electrical output signal when the water level within the sensor drops to a predetermined minimum. If the sensor 8 is mounted in an inverted position, with the reed switch 16 uppermost and the lid 12 lowermost, the sensor 8 may be used to detect when a rising water level reaches zi predetermined height. Mounting the sensor 8 at the required position and connecting its electrical output to a power source and an alarm may then, for example, provide a system for warning a householder of a rising 13 water level in either a bath or a basin so that an overflow can be avoided. The sensor 8 may alternatively be mounted outside a building, to detect a rising water level and give warning of a flood.

Figures 6a and 6b show an alternative arrangement of a sensor. In this embodiment, the sensor comprises a housing 60 containing a fixed magnet 61. A float block 62 contains a reed switch 63, the float block the mounted for movement towards and away from the magnet 61. Limit stops 64a and 64b are engageable with the housing 60 to limit the range of movement of the float block 62. The housing 60 is provided at its lower part with apertures to admit liquid into the housing, and allow liquid to drain out of the housing. A vent opening 66 is provided at the upper part of the housing.

The sensor shown in figures 6a and 6b provides an electrical output when a rising liquid level reaches a predetermined height. The reed switch 63 is connected in series with a power source and an alarm such as a bell, an indicator light, or the like.

The reed switch 63 is arranged so that when the float block is in its lowermost position, with limit stop 64a 14 in contact with the body 60 of the sensor, the magnetic field of the magnet 61 causes the reed switch to adopt a first switching position. This may be either an open or a closed position. As a liquid level outside the housing

60 rises, liquid flows into the housing through the openings 65 and air escapes from the housing through the vent opening 66. The float block 62 is lifted by the rising liquid level within the housing 60 part moving the reed switch 63 away from the magnet 61. Upward movement of the float block 62 is arrested when the limit stop 64b contacts the housing 60. At a predetermined position between the uppermost and lowermost positions of the float block 62, the influence of the magnet decreases to such an extent that the reed switch changes from its first switching position to a second switching position. If the first switching position is one wherein the reed switch contacts are open, then the second switching position will be one in which the reed switch contacts are closed, and vice versa.

If the sensor is intended to provide an alarm when a rising liquid level reaches a predetermined height, the switching positions of the reed switch are so arranged that current is applied to the alarm bell or indicator light when the float block 62 is moved away from the magnet 61. By reversing the switching positions of the reed switch, the sensor may be used to provide an alarm when a liquid level falls below a predetermined height.

In a particularly advantageous embodiment of the sensor, an alarm and power source may be integrated into the float block 62, as is shown schematically at 67. The alarm may be an audible or visible alarm, or may comprise a radio transmitter operating on a predetermined frequency and sending an alarm signal to a tuned radio receiver. The sensor may be positioned so that the switching position of the reed switch changes when the liquid level to be monitored reaches a predetermined height, and either a fall or a rise in level may be signalled.

The casing and float block of the sensor may be moulded from plastics material, the float block being advantageously moulded with its internal components, if any, in situ.

The openings allowing water to flow into or out of the sensor housing may be covered with a permeable membrane or a mesh, to prevent ingress of foreign bodies which might obstruct the free movement of the float block.

Claims

16 Claims

1. A liquid level sensor comprising a housing and a float block movable relative to the housing in response to a changing liquid level, a switch and a switch operating element being mounted respectively to the housing and to the float block, or vice versa, so that movement of the float block relative to the housing changes a spacing between the switch and the switch operating elements, the arrangement being such that the switch adopts a first switching position when adjacent to the switch operating element and a second switching position when spaced from the switch operating element.

2. A liquid level sensor according to claim 1, wherein the switch is a magnetic al lyoperated reed switch, and the switch operating element is a magnet.

3. A liquid level sensor according to claim 1 or claim 2, wherein the magnet is mounted in the float block and the reed switch is mounted in a recess in the housing.

17

4. A liquid level sensor according to claim 1 or claim 2, wherein the magnet is mounted in the housing, and the reed switch is mounted in the float block.

5. A liquid level sensor according to any preceding claim wherein the housing comprises a generally cylindrical container having openings adjacent its axial ends for the inflow and outflow of fluids.

6. A liquid level sensor according to claim 4, further comprising a power source and means for outputting an alarm signal connected in series with the reed switch, and mounted in the float block.

7. A liquid level detecting system comprising a liquid level sensor according to any of claims 1 to 5, a power source, and alarm means energisable by the power source when the switch of the sensor is in a f irst switching position.

8. A liquid level detecting system according to claim 7, wherein the alarm means is arranged to provide an 18 audible or visible alarm signal.

9. A liquid level detecting system according to claim 7, wherein the alarm means is arranged to provide a radio 5 alarm signal.

10. A liquid level detecting system according to any of claims 7 to 9, wherein the switch, the power source an alarm means are contained within the float block.

11. A water supply system comprising a reservoir, a supply duct leading from the reservoir, and a valve for controlling a flow of water through the supply duct, the valve being movable from an open to a closed position by an actuator, and the actuator being controllable by a level sensor according to any of claims 1 to 6.

12. A water supply system comprising a reservoir, a supply duct leading from the reservoir, and a pump for causing a f low of water through the supply duct, the number being controllable by a level sensor according to any of claims 1 to 6.

19

13. A water supply system according to claim 11 or claim 12, wherein a plurality of supply ducts lead from the reservoir, and each supply duct is associated with a respective level sensor.

14. A liquid level sensor substantially as described herein with reference to figures 1 to 4, or figures 6a and 6b of the accompanying drawings.

15. A water supply system substantially as described herein with reference to figures 1 to 5 of the accompanying drawings.