GB1599697A - Electrode probes for indication of a liquid level - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO ELECTRODE PROBES FOR INDICATION OF A LIQUID LEVEL (71) We, ELOF GUNNAR JOHANSSON, of Langbrodalsvägen 111, S-i 25 31 Älvsjö, Sweden, and BENGT ANDERS LANEBO of Yrkesvägen 37, 141 43 Huddinge, Sweden, both of Swedish nationality, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a device for detecting a change in the level of a liquid in a container, such as water in a boiler.

It is known to use for this purpose one or more electrodes which depend into the liquid so as to provide a signal when the liquid level falls below the lower end of an electrode. It is also known to surround the electrode electrodes in a tubular housing, open at its top and bottom ends so that the liquid level inside the housing remains the same as the liquid level in the remainder of the container, the housing serving to prevent waves or turbulence in the container from causing false or erratic signal emission by the electrode or electrodes.

However, the provision of a tubular housing can have drawbacks, especially if the liquid in the container is to be heated by a heat source close to the housing, in which case liquid within the housing may be raised to a higher temperature than ambient liquid.

Froth and foam are also liable to become trapped in the housing and cause a difference between the liquid levels inside and outside the housing.

A principal object of the present invention is to provide means whereby the aforementioned drawbacks are overcome or avoided.

In accordance with the present invention there is provided a device for detecting a change in the level of a liquid in a container, the device comprising a tubular housing adapted to be located generally vertically in the container so that, in use, an open, lower end of the housing will be below the normal level of liquid in the container, the housing having one or more openings near its upper end so that, in use, the level of liquid in the housing will correspond with the liquid level in the container outside the housing, and one or a plurality of electrodes located within the housing so that, in use, the lower end of the or each electrode is above the lower end of the housing, wherein there is further provided a deflector so positioned in spaced relation to said lower end of the housing that liquid entering said lower end from the container must follow a path with respect to the housing having both radial and axial components.

The deflector may be connected to the housing by a plurality of connecting members spaced from one another circumferentially of the housing.

The deflector preferably presents a convex face toward the housing, and may be formed by connecting together at their peripheries two similar, dished elements with their concave faces presented toward one another, the lower of the two elements being apertured to prevent the development, in use, of a pressure difference between the interior of the deflector and ambient liquid.

The cross-sectional area of the deflector is preferably slightly greater than the crosssectional area of the open, lower end of the housing.

In a modification of the invention a tubular extension of generally frusto-conical configuration is provided integral at its larger-diameter end with the lower end of the housing and open at its lower, smallerdiameter end and the deflector is positioned in spaced relation to said smaller-diameter end and is of greater cross-sectional area than said smaller-diameter end.

The or each electrode is preferably maintained in spaced relation to the internal wall of the housing by resilient support means spanning the interior of the housing intermediate its ends and adapted to permit the passage therethrough of liquid rising or falling in the housing. The support means preferably comprises a sleeve of plastics material surrounding the or each electrode and fitting in a respective aperture in a plate spanning the interior of the housing, the plate having additional apertures not occupied by sleeved electrodes for the passage through the plate of liquid. The or each sleeve may be of P.T.F.E. and may be made to have a bore of greater diameter than the external diameter of an electrode to be inserted therein.The said additional apertures in the plate may comprise a central aperture in which a bush is fitted adapted to prevent the insertion therethrough of an electrode and a plurality of slots elongated radially of the plate.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view, partly in section, of a device in accordance with the invention, Figure 2 is a perspective view and Figure 3 is a sectional elevation of resilient support means for the electrodes in the device of Figure 1, Figure 4 is a side view on an enlarged scale of the deflector forming part of the device of Figures 1 to 3, Figure 5 is a side view of a modified deflector and tapered extension used in the embodiment of Figure 6, and Figure 6 is a perspective view of a second embodiment of the invention.

The device illustrated in Figure 1 comprises a tubular housing 3 having, below an end cover I thereof, a mounting flange 2 whereby the housing can be located in a liquid container, such as a water boiler, so as to depend vertically from the top or cover of the container into liquid contained therein. A number of electrodes 4,4' are mounted in the housing 3, being electrically insulated from the mounting flange 2 in known manner. The electrodes 4,4' are of different lengths but the longest of them is shorter than the housing 3.

Thus the electrodes will provide respective signals indicative of a rise or fall of the liquid level within the housing 3 and since the latter is open at its lower end and has vent holes 5 near its upper end this will normally correspond to the liquid level in the container outside the housing 3.

In accordance with the invention a deflector 6 is arranged in spaced relation to the open, lower end of the housing 3 so that liquid entering or leaving the housing 3 must follow a path which has both radial and axial components with respect to the housing 3. In the embodiment illustrated the deflector 6 is of slightly greater cross-sectional area than the open, lower end of the housing 3 and is in the form of a hollow structure comprising two mutually inverted dished elements joined at their peripheries so that the deflector 6 is convex both downwardly and toward the open end of the housing 3. To prevent the development of a pressure difference between the interior of the deflector 6 and ambience the lower of the two dished members is provided with openings 7.

The electrodes 4,4' are supported intermediate their ends by a circular plate 8 spanning the interior of the housing 3 and provided with radial slots 10 and a central aperture so that the plate 8 will not affect the level of liquid within the housing 3. In addition to its central apertures the plate 8 has circumferentially spaced holes in which respective sleeves 9 of P.T.F.E. or another heat-resistant resilient plastics material are located to receive respective electrodes 4,4'. Preferably a bush 11 is located in the central aperture in the plate 8 to prevent the accidental insertion therethrough of one of the electrodes when the device is being assembled.

The device shown in Figures 1 to 4 is used in the following manner: The housing 3 is inserted through a hole provided for it in the top or cover of a liquid container (not shown) so that it depends below the intended level of liquid in the container. The mounting flange 2 is bolted in place using the holes therein shown. The electrodes 4,4' are then inserted, their lower ends preferably being pointed to facilitate the insertion of each electrode through a respective one of the sleeves 9.

When the sleeves 9 are of P.T.F.E. the bore of each sleeve preferably has a diameter 0.2 to 0.4 mm greater than the external diameter of the associated electrode to allow for shrinkage of the plastics material when subjected to heat. This will also prevent the sleeves 9 gripping the electrodes 4,4' so tightly that they could not be removed after a period of use, e.g. to replace an electrode.

The convex upper surface of the deflector 6 assists in avoiding the deposit of solid particles on top of the deflector and provides, in conjunction with the open, lower end of the housing 3, a preferred flow path for liquid entering or leaving the housing 3. The effects of turbulence or bubbles caused, for example, by the location of a burner unsuitably close to the lower end of the housing 3, are minimised by this flow path.

In the modification shown in Figures 5 and 6 a generally frusto-conical extension 12 is provided at the lower end of the housing 3 and a deflector 6 is fixed in spaced relation to the open, lower end of the extension 12. The deflector 6 in the embodiment is of similar construction to that of the embodiment of Figures 1 to 4 except that it is smaller, being of slightly greater diameter than the smallerdiameter end of the extension 12.

In both embodiments of the invention the deflector is spaced from the open, lower end of the housing 3, or its extension 12, by a gap of between 5 and 20 mm, preferably of between 10 and 15 mm. The length of the housing 3 will always exceed that of the longest electrode 4,4' therein, measured from the flange 2, so that if the longest electrode indicates the lowest level to which liquid in the container will be allowed to fall the open lower end of the housing 3, or its extension 12, will always remain below the level of liquid in the tank.

It will be appreciated that the deflector 6 may have forms other than as illustrated, for example it might be a simple, flat disc or it might have a flat underside or comprise two mutually inverted cones.

WHAT WE CLAIM IS: 1. A device for detecting a change in the level of a liquid in a container, the device comprising a tubular housing adapted to be located generally vertically in the container so that, in use, an open, lower end of the housing will be below the normal level of liquid in the container, the housing having one or more openings near its upper end so that, in use, the level of liquid in the housing will correspond with the liquid level in the container outside the housing, and one or a plurality of electrodes located within the housing so that, in use, the lower end of the or each electrode is above the lower end of the housing, wherein there is further provided a deflector so positioned in spaced relation to said lower end of the housing that liquid entering said lower end from the container must follow a path with respect to the housing having both radial and axial components.

2. A device as claimed in claim 1, wherein the deflector is connected to the housing by a plurality of connecting members spaced from one another circumferentially of the housing.

3. A device as claimed in either preceding claim, wherein the deflector presents a convex face toward the housing.

4. A device as claimed in claim 3, wherein the deflector is hollow and is formed by connecting together at their peripheries two similar, dished elements with their concave faces presented toward one another and the lower of the two elements being apertured to prevent the development, in use, of a pressure difference between the interior of the deflector and ambient liquid.

5. A device as claimed in any one of the preceding claims, wherein the cross-sectional area of the deflector is slightly greater than the cross-sectional area of the open, lower end of the housing.

6. A device as claimed in any one of claims 1 to 4, wherein a tubular extension of generally frustoconical configuration is provided integral at its larger-diameter end with the lower end of the housing and open at its lower, smaller-diameter end and wherein the deflector is positioned in spaced relation to said smaller-diameter end and is of greater cross-sectional area than said smaller-diameter end.

7. A device as claimed in any one of the preceding claims, wherein the or each electrode is maintained in spaced relation to the internal wall of the housing by resilient support means spanning the interior of the housing intermediate its ends and adapted to permit the passage therethrough of liquid rising or falling in the housing.

8. A device as claimed in claim 7, wherein the support means comprises a sleeve of plastics material surrounding the or each electrode and fitting in a respective aperture in a plate spanning the interior of the housing, the plate having additional apertures not occupied by sleeved electrodes for the passage through the plate of liquid.

9. A device as claimed in claim 8, wherein the or each sleeve is of P.T.F.E. and is made to have a bore of greater diameter than the external diameter of an electrode to be inserted therein.

10. A device as claimed in claim 8 or claim 9, wherein the said additional apertures in the plate comprise a central aperture in which a bush is fitted adapted to prevent the insertion therethrough of an electrode and a plurality of slots elongated radially of the plate.

11. A device for detecting a change in the level of a liquid in a container substantially as herein described with reference to and as shown in Figures 1 to 4 or Figures 5 and 6 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. lower end of the housing 3, or its extension 12, will always remain below the level of liquid in the tank. It will be appreciated that the deflector 6 may have forms other than as illustrated, for example it might be a simple, flat disc or it might have a flat underside or comprise two mutually inverted cones. WHAT WE CLAIM IS:

1. A device for detecting a change in the level of a liquid in a container, the device comprising a tubular housing adapted to be located generally vertically in the container so that, in use, an open, lower end of the housing will be below the normal level of liquid in the container, the housing having one or more openings near its upper end so that, in use, the level of liquid in the housing will correspond with the liquid level in the container outside the housing, and one or a plurality of electrodes located within the housing so that, in use, the lower end of the or each electrode is above the lower end of the housing, wherein there is further provided a deflector so positioned in spaced relation to said lower end of the housing that liquid entering said lower end from the container must follow a path with respect to the housing having both radial and axial components.

2. A device as claimed in claim 1, wherein the deflector is connected to the housing by a plurality of connecting members spaced from one another circumferentially of the housing.

3. A device as claimed in either preceding claim, wherein the deflector presents a convex face toward the housing.

4. A device as claimed in claim 3, wherein the deflector is hollow and is formed by connecting together at their peripheries two similar, dished elements with their concave faces presented toward one another and the lower of the two elements being apertured to prevent the development, in use, of a pressure difference between the interior of the deflector and ambient liquid.

5. A device as claimed in any one of the preceding claims, wherein the cross-sectional area of the deflector is slightly greater than the cross-sectional area of the open, lower end of the housing.

6. A device as claimed in any one of claims 1 to 4, wherein a tubular extension of generally frustoconical configuration is provided integral at its larger-diameter end with the lower end of the housing and open at its lower, smaller-diameter end and wherein the deflector is positioned in spaced relation to said smaller-diameter end and is of greater cross-sectional area than said smaller-diameter end.

7. A device as claimed in any one of the preceding claims, wherein the or each electrode is maintained in spaced relation to the internal wall of the housing by resilient support means spanning the interior of the housing intermediate its ends and adapted to permit the passage therethrough of liquid rising or falling in the housing.

8. A device as claimed in claim 7, wherein the support means comprises a sleeve of plastics material surrounding the or each electrode and fitting in a respective aperture in a plate spanning the interior of the housing, the plate having additional apertures not occupied by sleeved electrodes for the passage through the plate of liquid.

9. A device as claimed in claim 8, wherein the or each sleeve is of P.T.F.E. and is made to have a bore of greater diameter than the external diameter of an electrode to be inserted therein.

10. A device as claimed in claim 8 or claim 9, wherein the said additional apertures in the plate comprise a central aperture in which a bush is fitted adapted to prevent the insertion therethrough of an electrode and a plurality of slots elongated radially of the plate.

11. A device for detecting a change in the level of a liquid in a container substantially as herein described with reference to and as shown in Figures 1 to 4 or Figures 5 and 6 of the accompanying drawings.