METHOD FOR DETECTING THE LIQUID LEVEL IN AN INNER CONTAINER

The present invention relates to method for measuring the contents of a liquid in special containers such as wine boxes and similar containers for liquids. The invention further relates to containers suitable for carrying out such a method.

Today there exists a wide variety of cardboard containers having an inner bag of plastic or similar material containing some form of liquid. One instance of this is wine in BIBs (Bag in Box) of various sizes. A BIB consists of a paperboard or like carton with a bag of plastic or the like arranged therein which contains the actual wine. A typical size for a BIB is 3 litres.

BIBs have become very popular, partly because the wine keeps well even after it has started to be dispensed. This is because the bag inside the carton which contains the wine collapses as the wine is dispensed without allowing any air to enter, which is what happens when wine is poured from a bottle. If the wine comes into contact with air for a longish period of time, the air spoils the wine as the wine becomes oxidised.

One disadvantage of "box wine" is however that it is not so easy to see how much is left in the carton and therefore it is less easy to keep a check on what has been consumed. In addition, it is not possible to measure the temperature of the wine in a conventional manner, which is extremely desirable in order to be able to serve the wine at the correct temperature.

FR-Al 2653877 describes a device consisting of an opaque container having a second, inner container. The purpose of the device is to be able to determine how much liquid the inner container contains. The inner container rests against an elastic pocket containing a measuring fluid which is in communication with a tube on the outside of the outer container. When the mass of the container containing the liquid that is to be measured changes with a change in volume, this will exert a greater or lesser pressure on the elastic pocket and this is read as a level change in the tube that is visible on the outside of the outer container. Embodiments are also described where spring systems in the bottom of the outer container are actuated by the weight of the contents of the inner container, and this is indicated by means of various connections that provide a reading which can be read off through a window in the outer container. The systems described in this document are relatively complex and are not suitable for use in, for example, a

wine box where the solution used should be extremely simple and inexpensive to produce.

JP A 59042418 describes a volume measuring device that is based on the use of a strain gauge. The use of an electronic circuit allows the volume of liquid to be known by means of audible signals. The device requires re-setting for each volume measurement and therefore is not suitable for the purpose of the present invention.

The object of the present inventions is to teach a method for measuring the level and the temperature in containers containing liquid or liquid-like substances where known methods for level measurement and temperature measurement cannot be used directly, or where such methods would be too costly for the purpose.

In what follows, the methods will be described for a standard 3-litre BIB, but the methods can be applied to many other liquid containers and are thus not limited to only being applicable to cartons for wine.

The basis for the methods is the detection of the change in permittivity in a capacitor that is arranged in the carton, the change in permittivity being due to a change in the amount of wine in the bag inside the carton. The change in permittivity will thus be proportional to the remaining wine in the bag.

Accordingly, the present invention provides a method for detecting the liquid level in an inner container, preferably a bag, disposed within an outer container, characterised in that the contents in the inner container are detected by changes in permittivity in a capacitor located on the wall of the outer container, the changes in permittivity being caused by the change in the liquid contents in the inner container.

The present invention further provides an outer container intended as packaging that is to contain an inner container, preferably a bag, which is characterised in that metallised areas are formed on the interior surface of the container, and that the container, in a window formed in one of its side faces, comprises a display for displaying measured values.

A capacitor is obtained by providing metallised faces on parts of the interior surface of the outer container. The capacitor faces can be arranged in any way in the outer

container provided that no short circuit occurs. The metallised faces can be obtained by the application of metal foil or by brush application.

The required electrical energy for establishing a field between the capacitor plates may be provided either by means of solar cells or by means of a battery. It is preferable to use a battery that is activated by the user when he starts using the wine box.

This activation may easily be carried out in that a tab or the like is arranged on the carton which the user pulls off when the carton is to be taken into use, or by other techniques as described in more detail below.

Between capacitor plates there may in general be air, a vacuum or an insulating material, and in special cases also liquids or gases. The medium between the capacitor plates is, in the illustrated case involving a wine box, varying amounts of liquid.

Permittivity as a value describes how an electric field affects and is affected by a dielectric medium, and is determined by the ability of the material to polarise in response to the field, and thereby reduce the electric field inside the material. Thus, permittivity relates to a material's ability to transmit an electric field. In general, permittivity is not a constant; it varies as the conditions between the capacitor plates change, and can thus be used as a measurable value in connection with the present invention.

The temperature sensor used in connection with the present invention is a standard temperature sensor that is known in the art.

The problem associated with measuring the liquid contents in a BEB is that there is limited space in the container. Furthermore, the bag of liquid must not be damaged and moreover the carton must be mass-producible using existing packaging machines without the automatic machines having to undergo extensive alterations. As the bottling plants receive the cartons flat, the sensor must be a part of the carton and be equally flat.

The present invention will be described in more detail below with reference to the attached drawings, wherein:

Figure 1 shows the inside of a carton for use as an outer container, in an unfolded state, as it is when delivered to the bottling plants.

Figure 2 shows the outside of the outer container in an unfolded state, with a display inserted.

Figure 3 shows a section through the side of the outer container which contains said display.

Figure 4 shows a part of the inner surface of the outer container where the individual parts can be seen.

Figure 5 shows the inside of the unfolded outer container with the individual parts mounted.

Figure 6 is a drawing indicating the course of the field lines between the capacitor faces.

Referring to Fig. 1, it shows the inside of a carton that is unfolded as it is when delivered to the bottling plants. A) indicates the actual carton as punched out so that it can be folded to form a box. B) indicates an area of the carton which is metallised either with an electrically conductive paint and/or with a metal or graphite coating, and which constitutes one of the capacitor faces. C) indicates the back of the electronic circuit which is inserted into a hole punched out in the carton. In this way, an electronic temperature sensor is provided that detects the temperature in the carton. D) indicates an extension of the sensor which together with C) is metallised on the surface and thus constitutes the other of the capacitor plates. An insulating material H), shown in Fig. 3, is disposed between C) and D) and the surface B) to prevent short-circuiting of the plates B) and C) and D). When the electronic circuit is inserted into its hole, one or more spring contact points to the metallised surface B) are arranged thereon, whereby soldered connections are thus avoided.

Fig. 2 shows the outside of the carton unfolded with surface F) on which all printing is arranged. G) indicates the front of the electronic instrument where temperature and the level are shown on an LSD display. A battery, which is activated by dispensing wine, is arranged on the front of the instrument. Activation can take place either by pulling the drawing tap that is inside the box out through the hole E) in Fig. 1, or it can be activated by removing a plastic strip that rests against the battery poles.

Perforations are arranged around the punched-out hole for the electronic instrument so that after use, it is easy to pull the instrument out and dispose of it as electronic waste.

The electronic instrument contains the electronics that convert the change in permittivity into a readable figure on the display which can show remaining contents in the box in either remaining glasses, litres or any other volume or weight figure. This figure can alternate between showing the amount of liquid in the box and the temperature therein, or there may be two rows of figures showing the same simultaneously.

Fig. 3 shows a section through the carton and the instrument, the individual references being the same as mentioned above.

Fig. 4 is a drawing of the box when folded where the individual components can be seen inside.

Fig. 5 shows the carton from the inside as in Fig. 1, but where the metallised face B) has been replaced by a metallised film or paint I).