GB2210454A - Fluid level sensor - Google Patents

Abstract

A sensor for sensing fluid levels within a container. The sensor is in the form of a tubular member 2 of resilient material having an optical system which passes a light beam through an interior cavity of the tubular member. Deformation of the tubular member by pressure from float 12 results in a variation of the light beam detected and measurement of this variation gives an indication of the level of fluid in the container. The tube may be stainless steel with a non-reflective lining and may be straight or slightly bowed in its undeformed state. Lenses 9 concentrate the light beam between lamp 4 and detector 7. <IMAGE>

Description

"Sensor" This invention relates to a sensor especially but not exclusively for use in sensing fluid levels.

There are existing mechanical and optical sensors for use in sensing and maintaining a selected fluid level in a container.

The mechanical systems conventionally comprise a ball cock having a float on one end of a shaft, the float resting on the water and the rising fluid level causing the float to rise, pivoting the shaft such that a valve controlling the flow of the fluid is either opened or closed.

Conventional optical systems comprise a lens positioned at or just below the selected maximum fluid level and arranged such that a beam of light falling onto the lens is refracted back to an optical sensor. When the fluid floods the surface of the lens, the refraction is distorted and the absence of light on the optical sensor causes a feed-back system to cut off a valve controlling the flow of fluid.

In both instances, the sensors and/or the valves are in contact with the fluid and exposed such that dirt accumulates preventing efficient operation.

According to the present invention there is provided a sensor for sensing fluid levels comprising a tubular member of resilient material and an associated optical system said system having an emitter and being adapted so as to pass light along an interior cavity of the tubular member to a receiver, such that when the tubular member is resiliently deformed the light passage in relation to the sides of the tubular member is altered, such alteration being registered by the receiver of the optical system.

Preferably, the optical system is sealed within the tubular member.

Preferably, said tubular member is of a cross-section best suited to respond to the force applied and to result in deformation.

The tubular member may have a non-reflective lining and, in un-deformed state, be straight or slightly curved or bowed.

Preferably, the optical system comprises an emitter at a one end of the tubular member and a receiver at the other end.

preferably, the emitter is provided with a lens to concentrate the light beam; most preferably, the receiver is also provided with a lens.

The receiver may register the particular area of light reception on the receiver's lens and/or just the light's presence or absence on any part of the lens. Preferably, the receiver is interconnected with an electrical feed-back system which helpswcontrol the force which is resulting in deformation.

Preferably, the tubular member is of stainless steel.

Preferably, in the form of a fluid level indicator, the tubular member spans a fluid container, the deformation being caused by a float resting on the fluid that, on abutting and a subsequent upward force by continued rising fluid level, resiliently deforms the tubular member. The resilient deformation causes bowing of the member and a consequent variation in the light beam's passage in relation to the sides of the tubular member and therefore a variation in light reception. The receiver and feed-back system can be adapted so as to cause closure of a fluid ingress valve on the registering of such a variation.

The invention may be used to measure deformation as caused by a force exerted upwardly, downwardly or to either side, depending on the horizontal or vertical orientation of the tubular member, and thus the sensor may be used for example, as a flow sensor or pressure sensor.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view from the side of a sensor according to the present invention in use as a fluid level sensor; Fig. 2 is a schematic part-sectional view of the sensor of Fig. 1 in undeformed state; Fig. 3 is a schematic part-sectional view corresponding to Fig. 2 of the sensor in a deformed state; and Fig. 4 is a sectional view illustrating a further embodiment of the present invention.

Referring to the drawings, there is shown a sensor 1 in use to sense fluid levels, said sensor 1 comprising a tubular member 2 of resilient material and an optical system, shown generally at 3. The tubular member 2 is placed so as to span a fluid container 13.

The optical system 3 is sealed in the tubular member 2 and thus not exposed to the external environment. The system 3 comprises an emitter 4 at one end of the member 2, which emitter 4 is adapted to send a light beam 5 along the interior 6 of the tubular member 2 to a light receiver 7 at the opposite end of the tubular member 2, the receiver 7 being connected to a feed-back system, shown generally at 8, which controls the rate of fluid entry to the container 13.

Both emitter 4 and receiver 7 are provided with a lens, 9, 9' respectively, to clarify the beam of light 5.

On the application of a certain degree of force, schematically shown at 10, the member 2 is resiliently deformed such that the passage of the beam of light 5 is now received on a different area of the light receiver 7 or not received at all (see Fig. 3 in particular) the beam of light 5 alters its path in relation to the walls 11 of the member 2. The light receiver 7 registers this alteration and the feed-back system 8 reduces or maintains the force and thus the deformation experienced, not allowing a subsequent increase.

The force is applied to the sensor 1 by a float 12 resting on the surface of the fluid. As the fluid level rises the float 12 rises too, until it abuts and eventually deforms the tubular member 2 spanning the fluid container 13. This deformation alters the path of the beam of light 5 in respect to the walls 11 of the tubular member 2. This change is registered by the receiver 7 and, via the feedback system 8, the fluid ingress valve 14 to the container 13 is closed, only re-opening when fluid egress relaxes the strain on the sensor 1 and the light 5 once more is registered by the receiver 7 this, in turn, resulting in fluid ingress valve 14 re-opening.

The sensor 1 of this embodiment is a stainless steel tubular member 2 of circular cross-section and of a very slight diameter so as to be readily deformable.

Referring now to Fig. 4, there is shown a modified embodiment of the present invention. This embodiment comprises a boss 21 which is fitted to an aperture in the said wall 22 of a tank containing fluid 23, the level of which is to be monitored. The boss 21 carries a substantially U-shaped hollow tubular conduit 24. A light source 25 feeds a light beam down a fibre optic conductor 26 through the boss 21 to a transmit lens or termination 27 located at one end of the conduit 24. The light beam passes along the top portion of the conduit 24 into a receiving lens 28 where it is collected and passed through a further fibre optic cable 29 through the boss 21 to a decoder circuit 30. The decoder circuit may include feedback means to shut off the supply of fluid to the tank. A fluid 31 is mounted on the top portion of the conduit 24 between the transmit lens 27 and the receiving lens 28.

It will be noted that this embodiment does not span the whole width of the tank but it may be preferable that support means be provided in the form of a clamp 38 in order to ensure that deformation of the top portion of the conduit 24 results in the fluid level reaching the float 30.

Alternatively, the lower portion of the conduit 24, that is the portion carrying the fibre optic 29, may be made more rigid to offer sufficient support to the top portion 24 in which the light beam is located.

It will be clear that a sensor of the same principle as that used as a fluid level sensor may be used in registering a different force, exerted from above or from below, or from either side as the sensor may be placed vertically, for example, when in use as a flow meter. The sensor 1 may be analogous or register only the absence or presence of deformation depending on the requirements.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims (9)

1. A sensor for sensing fluid levels comprising a tubular member of resilient material and an associated optical system said system having an emitter and being adapted to pass light along an interior cavity of the tubular member to a receiver, such that when the tubular member is resiliently deformed the light passage in relation to the sides of the tubular member is altered, such alteration being registered by the receiver of the optical system.

2. A sensor as claimed in Claim 1, wherein the optical system is sealed within the tubular member.

3. A sensor as claimed in Claim 1 or 2, wherein said tubular member is of a cross-section best suited to respond to the force applied and to result in deformation.

4. A sensor as claimed in any preceding claim, wherein the tubular member has a non-reflective lining.

5. A sensor as claimed in any preceding claim, wherein the emitter and the receiver are provided with respective lenses to concentrate the light beam.

6. A sensor as claimed in any preceding claim, wherein the receiver is interconnected with an electrical feed-back system which controls the force which is effecting deformation.

7. A fluid level indicator comprising a tubular member located within a fluid container, float means to effect deformation of the tubular member to effect variation of a light path along the tubular member, means for transmitting a light beam along said tubular member, means for receiving said light beam, and means for detecting variation in the light beam to produce a control signal representative of the level of fluid in the container.

8. A sensor for sensing fluid levels substantially as hereinbefore described with reference to the accompanying drawings.

9. A fluid level indicator substantially as hereinbefore described with reference to the accompanying drawings.