WO2000036381A1 - A level sensor with a float - Google Patents

Abstract

A level sensor for a liquid container (18), comprising a float (11) housed in the container (18) and connected to a support (10) by connection means adapted to allow the float (11) to move in accordance with a variation in the liquid level, and means for actuating (20) at least one sensitive element (14) when the liquid reaches a respective predetermined level, is characterized in that the connection means comprise a flexible element (12) projecting from the support (10).

Description

A level sensor with a float'

DESCRIPTION

The present invention relates to a level sensor with a float for liquid containers and to a container comprising the level sensor.

The present invention also relates to apparatus for producing hot water and/or steam for domestic use, comprising a water container with which a level sensor of the above-mentioned type is associated.

Various level sensors are known, in which a float housed in a liquid container is connected to a support so as to be movable in accordance with a change in the liquid level.

The float generally has a permanent magnet which can actuate a sensitive element of an external circuit when the liquid reaches a predetermined level of filling of the container. This circuit can be enabled to operate and control one or more functions associated with the container such as, for example, in apparatus for producing hot water and/or steam, the supply of the water, the supply of fuel to the burner, etc. In float level sensors of the prior art, according to one type of construction, the float is connected to the support by a rigid arm of which one end is hinged to the support of the level sensor and the opposite end is connected to the float. When the liquid level changes, the float can thus rise or fall, describing an arc of a circle having its centre at the connecting point between the support and the arm.

According to another construction of the prior art, the float may be connected to the end of a rod the top of which can slide vertically between two opposite positions inside a guide of a collar which is connected to the support and can house the rod.

The upward movement of the rod in response to a corresponding rise in the liquid level can move a permanent magnet which is disposed on top of the rod and which in turn can actuate a sensitive element of an operating and control circuit.

The float level sensors of the prior art mentioned above have the serious disadvantage that their operation is often compromised by deposits and scaling of lime and/or impurities contained in the liquid, which frequently form on the sensors during the useful life of these instruments. In particular, the formation of scaling on the above-mentioned sensors in the region of the hinge coupling or of the rod has the effect of partially or completely preventing the movements of the float when the liquid level changes, thus compromising the correct operation and the life of the sensor.

This occurs particularly in float sensors fitted in apparatus for producing hot water and/or steam, owing to lime deposits and scaling which form very frequently and quickly. In this situation, the above-mentioned disadvantage is further aggravated by the fact that the float level sensor has to be removed from the apparatus periodically in order to be cleaned or replaced, with considerable additional costs . The technical problem upon which the present invention is based is that of providing a float level sensor for liquid containers which has a long useful life without having the disadvantages mentioned above with reference to the prior art. This problem is solved by a level sensor for a liquid container comprising a float housed in the container and connected to a support by connection means which allow the float to move in accordance with a variation in the liquid level, and means for actuating at least one sensitive element when the liquid reaches a respective predetermined level, characterized in that the connection means comprise a flexible element projecting from the support .

The use of a flexible element in the level sensor according to the invention overcomes the above-mentioned technical problem in an excellent manner since it is possible to achieve, between the support and the element, a pivotable connection which is not affected substantially by deposits or scaling of lime or other impurities .

In the level sensor according to the invention, the flexible element may be made of any material having flexibility characteristics suitable for satisfying specific requirements of the movement of the float and hence of operation of the sensor, at the same time also taking account of the temperature of use and of the chemical and physical characteristics of the liquid.

For example, the flexible element may be constituted by a strip of a fabric, preferably a glass-fibre fabric impregnated with silicone, or even a strip of a flexible moulded material, preferably Teflon, but is not limited to these materials .

Further characteristics and advantages of the float level sensor according to the present invention will become clearer from the following description of a preferred embodiment thereof, given by way of non- limiting example, with reference to the appended drawings, in which:

Figure 1 shows a float level sensor according to the invention, in section,

Figures 2 and 3 show, schematically and in section, the sensor of Figure 1 mounted in a liquid container, and show the operation of the sensor.

With reference to the drawings, the float level sensor according to the invention comprises a float 11 connected to a bracket-like support 10, both of which are intended to be housed in a container.

The support 10 has an end portion 15 which is made to project from the container when the support 10 is anchored thereto, in conventional manner.

The support 10 also has a blind hole 21 extending longitudinally from the end portion 15 and housing a conventional reed relay 14 which can be connected to an external circuit by means of suitable wires 13. In the embodiment described, the float 11 is constituted by a hollow body of substantially rectangular cross-section, the upper end 11a of which is connected to a corresponding end of a flexible element which is constituted by a strip 12 of a glass-fibre fabric impregnated with silicone. The connection to the float may be achieved by conventional methods such as, for example, gluing, fusion with a portion of the material of the float, or releasable connection by means of screws . The opposite end of the strip 12, however, is connected in conventional manner to the end of the support 10 which is intended to be housed in the container, so that the strip 12 projects from the support 10. The float 11 also comprises a permanent magnet 20 which can interact with the reed relay 14 in response to the reaching of a predetermined liquid level, as will be shown in the following description.

In the embodiment described, the magnet 20 has an end portion 20a which projects from the upper end 11a of the float 11 and from the strip 12 to actuate the reed relay 14.

Naturally, an expert in the art will be able to arrange the magnet 20 in any position inside or outside the float body, according to contingent and specific requirements .

Figures 2 and 3 show the operation of the float level sensor described above, installed in a container which can be associated, for example, with apparatus for producing hot water and/or steam. The container is constituted by a body 18 of rectangular cross-section and has two lower openings 27 and 28 connected, respectively, to a liquid inlet duct 24 in fluid communication with a pump 19 and a liquid-outlet duct 25, in which a flow-regulation valve 26 is interposed.

For apparatus for producing hot water and/or steam, the duct 24 may be used for the admission of "cold" water and the duct 25 for the delivery of the corresponding "hot" water produced by heating of the water by means of an electrical resistor or other conventional heating means associated with the container.

The level sensor of the invention is housed in the body 18 and the support 10 is anchored to a side wall thereof in conventional manner, with its end 15 projecting from the container body 18.

The reed relay 14 is connected to an operating and control unit 23 which in turn can operate the pump 19.

Naturally, according to specific requirements, an expert in the art will be able to connect the reed relay

14 to other functions associated with the container such as, for example, in apparatus for producing hot water and/or steam, to the fuel supply to the burner.

In the view of Figure 2, the liquid admitted from the duct 24 has filled the container until a predetermined maximum level 16 has been reached.

In this situation, the permanent magnet 20 of the float 11 is situated in the vicinity of the reed relay 14 and is actuating this element so as to keep the blades of the contacts separated, thus breaking the circuit.

The pump 19 is consequently in the stopped condition and the liquid in the container can be delivered by the duct 25, upon demand, by the operation of suitable means controlling the valve 26. When the liquid level falls, the float 11 tends to move downwards due it its own weight, at the same time remaining constantly in contact with the free surface of the water.

This movement causes the strip 12 of flexible material to bend in the vicinity of the region of contact with the support 10 so that the float describes a substantially circular arc during its movement.

At the same time, the movement of the magnet 20 away from the reed relay 14 allows the blades of the contacts to close the circuit, as shown in Figure 3.

The operating and control unit 12 consequently receives a signal from the reed relay 14 and operates the pump 19, allowing liquid to enter the container from the duct 24. Naturally, an expert in the art will be able to associate with the sensor according to the invention, a system of time filters or equivalent means which enable sudden changes in the liquid level, and hence in the angular position of the float, for example, due to turbulence in the liquid or to other transitory disturbances, to be ignored.

The main advantage of the float level sensor lies in the fact that it has a long useful life since any lime deposits or scaling on the flexible element, particularly in the region of the pivotable connection to the support of the sensor, do not create any significant obstruction to the movements of the float with variations of the liquid level .

A further advantage lies in the fact that the lime deposits and scaling do not substantially alter the flexibility of the flexible element, so that the sensor of the invention also determines the level very accurately.

A further advantage of the level sensor according to the invention also lies in its simple and economical construction and in the fact that it is widely applicable to containers using liquids of any type, over wide temperature ranges.

Naturally, in order to satisfy specific and contingent requirements, an expert in the art may apply to the above-described float level sensor, many modifications and variations all of which, however, are included within the scope of protection of the invention as defined by the following claims. For example, he may vary the shape and size of the support, of the float, or of the flexible element in dependence on specific requirements.

He may also replace the reed relay 14 with other equivalent sensitive elements such as, for example, a magnetic switch of another type, or an electric, electronic or mechanical switch or, for specific requirements, may even provide a plurality of sensitive elements and respective means for actuation when respective predetermined liquid levels are reached. Finally, as a variant of the above-described level sensor which is particularly advantageous for removable containers, the flexible element provided with the float may be connected directly to the container, possibly releasably, for example, on an internal wall thereof. In this case, the sensitive element may be housed in a space formed in the container or may even be disposed outside the container.

Claims

1. A level sensor for a liquid container (18), comprising a float (11) housed in the container (18) and connected to a support (10) by connection means adapted to allow the float (11) to move in accordance with a variation in the liquid level, and means (20) for actuating at least one sensitive element (14) when the liquid reaches a respective predetermined level, characterized in that the connection means comprise a flexible element (12) projecting from the support (10) .

2. A level sensor according to Claim 1, in which the flexible element (12) comprises a strip of a fabric.

3. A level sensor according to Claim 2 , in which the fabric is a glass-fibre fabric impregnated with silicone.

4. A level sensor according to claim 1, in which the flexible element (12) comprises a moulded material.

5. A level sensor according to Claim 4 , in which the moulded material is Teflon.

6. A level sensor according to any one of the preceding claims, in which the support (10) is a bracket- like support having an end portion (15) which is intended to project from the container (18) .

7. A level sensor according to Claim 6 , in which the support (10) comprises a blind hole (21) which extends longitudinally from the end portion (15) in order to house the at least one sensitive element (14) .

8. A level sensor according to any one of the preceding claims, in which the float (11) is constituted by a hollow body and comprises the actuation means (20) for actuating the at least one sensitive element (14) .

9. A level sensor according to any one of the preceding claims, in which the at least one sensitive element is a reed relay (14) and the actuation means comprise at least one permanent magnet (20) .

10. A level sensor according to any one of Claims 1 to 8, in which the at least one sensitive element (14) is selected from the group comprising magnetic, electric, electronic and mechanical switches.

11. A container (18) for a liquid, comprising a first opening (27) and a second opening (28) for the inlet and for the outlet of the liquid, respectively, characterized in that it further comprises a level sensor according to any one of the preceding claims.

12. Apparatus for producing hot water and/or steam for domestic use, comprising a container (18) according to Claim 11, water-supply means (19) in fluid communication with the at least one first opening (27) , heating means associated with the container (18) for heating the water, and a unit (23) for operating and controlling the supply means (19) , the operation and control unit (23) being in communication with the level sensor in order to interrupt the supply of water when a predetermined maximum level (16) is reached in the container (18) .

13. Use of a level sensor according to any one of Claims 1 to 10 for controlling the level of a liquid in a container.

14. Use according to Claim 13, in which the liquid is water and the container forms part of apparatus for producing hot water and/or steam.