| 1. | Device to indicate the level of a liquid (2) contained in a tank (1), comprising an element (3) floating on the liquid (2), the device being characterised in that a permanent magnet (4) is associated with the floating element (3) to move vertically together therewith, and in that a corresponding ferromagnetic element (8) is arranged on the opposite side of the wall of the tank (1) with respect to the permanent magnet (4) to move vertically together with the permanent magnet (4) and the floating element (3), the magnetic force of attraction of the permanent magnet (4) being greater than the weight of the ferromagnetic element (8). |
| 2. | Device as in Claim 1, characterised in that the permanent magnet (4) is mounted on the floating element (3) and the ferromagnetic element (8) is able to slide vertically outside the tank (1) to indicate the corresponding vertical position of the floating element (3) and hence of the level of liquid (2). |
| 3. | Device as in Claim 1 or 2, characterised in that a magnetic or ferromagnetic band or strip (9) is arranged vertically in contact with the wall of the tank (1) to act as a vertical magnetic guide for the permanent magnet (4). |
| 4. | Device as in Claim 3, characterised in that the band or strip (9) extends downwards as far as the lower end of the tank (1), including the bottom. |
| 5. | Device as in Claim 2, characterised in that the ferromagnetic element (8) consists of a body rotating on the outer surface of the tank (1). |
| 6. | Device as in Claim 5, characterised in that the rotary body consists of a sphere. |
| 7. | Device as in Claim 1, characterised in that the floating element (3) comprises a hermetically sealed float chamber, in correspondence with one edge of which a permanent magnet (4) is mounted, in such a manner that the permanent magnet (4) and the relative magnetic flux are as near as possible to the inner wall of the tank (1). |
| 8. | Device as in Claim 7, characterised in that a vertical guide (7) made of non. magnetic material is provided inside the tank (1) in order to guide the float chamber vertically. |
| 9. | Device as in Claim 8, characterised in that an elastic element (6) collaborates with the float chamber to hold the permanent magnet (4) adherent to the inner wall of the tank (1). |
| 10. | Device as in Claim 7, characterised in that the permanent magnet (4) is in the shape of a wheel and is mounted to rotate on a horizontal pin mounted on the float chamber. |
| 11. | Device as in Claim 1, wherein the tank (1) comprises a vertically movable floating cover (3), characterised in that the cover performs the function of the floating element (3) and in that the permanent magnet (4) is constrained to the cover. |
| 12. | Tank to contain a liquid (2), characterised in that a band or strip (9) made of magnetic or ferromagnetic material is arranged vertically in contact with the outer wall of the tank (1) and is suitable to vertically guide a permanent magnet (4) associated with an element (3) floating on the liquid (2). |
| 13. | Tank as in Claim 12, characterised in that the band (9) is applied to the outer wall. |
| 14. | Tank as in Claim 12, characterised in that the band (9) is inserted in the outer wall when the tank itself is manufactured. |
Another system, and certainly more commonly used, is to make a hole in the bottom of the container and attach a union elbow, which may also have a tap; a transparent pipe made of glass or plastic is connected to the union, and the pipe is raised vertically outside the tank, up to the top thereof.
When liquid is poured into the tank, it will enter the transparent pipe too, due to the principle of communicating vessels, and since this pipe is visible from outside, it is possible to know the level of liquid inside the tank, at any moment.
Although this system may be considered to be a good one, it does have some disadvantages which may be overcome by using the invention we shall later describe.
First of all, the liquid which rises in the outer pipe always leaves deposits on the wall of the pipe and as time goes by it gets dirtier until it becomes opaque and then it is no longer possible to know the level of liquid.
In the case of wine or milk, when the liquid is in an intermediate situation and remains still for some time, flowers will form in the wine and cream will form in the milk and when the liquid is finally removed, there will be circles on the pipe which, as the operation is repeated over the course of time, increase in number and form a mass of mold and dirt; at a certain point, it will therefore be
necessary to remove the pipe from the unions, clean it and replace it.
This is a rather annoying operation and often, when it is repeated, there are leakages of liquid from the base; very often, you end up by removing the pipe, stopping up the holes at the bottom and checking the level of liquid through the upper cover just like in the old days.
To overcome these shortcomings, we have invented the system which we shall describe hereafter.
Once upon a time liquids were contained in wooden barrels, or in tanks made of concrete or iron.
Recently, tanks with thin walls made of fibreglass or stainless steel have come into use.
The advantage of using these materials is that they are light and therefore easy to move, but above all because they are extremely easy to clean, particularly stainless steel, so much so that the use of this material is rapidly spreading.
The system using the pipe is used, as we have just described, in these tanks too, even though they are relatively new, in order to know the level of liquid inside, unless they are plastic containers which are in any case transparent and therefore the level of liquid is immediately visible.
These materials have thin walls, and both fibre glass and stainless steel have the characteristic feature that they are not sensitive to the flux which a permanent magnet emits, and therefore the flux of the magnet passes through these materials and makes its presence felt if there is a body on the opposite side of the wall which is sensitive to this flux.
SUMMARY OF THE INVENTION It is therefore easy to understand how, if we put inside
the tank a permanent magnet and we make it float on the liquid as much as possible, and if we put a body of ferrous material, sensitive to the magnet, near the wall and outside the tank, in correspondence with the permanent magnet, this body will be attracted by the magnet and, if it is light enough, such as a latten ball, it will remain suspended on the outer wall and therefore visible, and will indicate the position of the magnet inside, which will correspond to the level of the liquid in the tank.
To make the magnet float on the level of the liquid, it will be enough to put it in a float chamber whose volume has been calculated and which will be able to float, carrying the magnet and possibly some ballast to balance the weight of the magnet which will be located in the float chamber.
The float chamber will have to have thin walls at the point where the magnet rests and will have to be made of a material which is not sensitive to the magnetic flux.
Variations in the level of the liquid in the tank will also entail movements of the float chamber floating inside, and therefore of the magnet; and outside the container the spherical body made of light latten will also be displaced on the wall.
We shall call this outer body, made of light latten and preferably round, the"FLY".
When it has been attracted by the magnet, the fly will follow the movements thereof from the outside, and will also hold the magnet as close as possible and therefore also as close as possible to the inner wall of the tank (unless the liquid undergoes strong turbulence or mixing).
If the float chamber with the magnet, inside the tank, does not have a guide, its movements on the level of the liquid can be not only vertical but also horizontal and it can then happen that the fly, even though it may still be on
the wall, will come into a position where it will no longer be visible.
That is why it is appropriate to include a vertical guide, so that the float chamber is obliged to stay on that line and so that it can follow the level of liquid only on that line.
In this way we shall always be certain to have the magnet on the perpendicular, in contact as much as possible with the inner wall even when the liquid is turbulent or agitated.
BRIEF DESCRIPTION OF THE DRAWINGS The embodiment and working of the device according to the invention will become more easily comprehensible with the help of the attached drawings, given as a non-restrictive example,wherein: Fig. 1 shows a tank for liquids provided with the device according to the invention; Fig. 2 shows an enlarged, sectioned detail of the device according to the invention; Fig. 3 shows a first variant of the device according to the invention; Fig. 4 shows an enlarged, sectioned detail of the device shown in Fig. 3; Fig. 5 shows a second variant of the device according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows a tank 1 with a liquid 2 inside which arrives about half-way up the tank; a float chamber 3 floats on the liquid 2 and carries a permanent magnet 4 inside; at the bottom of the float chamber there is some ballast 5.
The float chamber 3 can move up and down, and vice versa, with the level of the liquid 2, guided by a rod 7 attached vertically inside the tank 1.
On the outer wall of the tank 1 and in correspondence with the permanent magnet 4 there is a spherical element 8 of ferromagnetic material, which will indicate the position of the permanent magnet 4 and, since it is floating on the liquid 2, it will also indicate the level of the liquid 2 itself.
It is easy to understand how the displacement of the liquid 2, both up and down, entails the displacement, inside the tank, of the permanent magnet 4 contained in the float chamber 3 and, consequently, the displacement outside of the spherical element 8, or fly.
In Fig. 2 it is also possible to see that the device according to the invention can comprise a guide rod 7 for the float chamber 3 and an elastic element 6 or feather, suitable to hold the float chamber 3 adherent to the inner wall of the tank.
In this form of embodiment the vertical guide 7 is arranged inside the tank 1.
The guide 7, which is a rod which can have different sections according to how the float chamber 3 has to be constrained, vertically breaks the smooth inner surface of the tank 1 and for this reason may sometimes cause a problem.
For example, it may impede a perfect cleaning.
There are so-called"ever full"tanks; these are cylindrical tanks which are not closed at the top, and the cover is made to float on the liquid 2; when the tank has to be hermetically sealed, the air chamber which is already housed on the outer edge of the cover is inflated. The air chamber, thus inflated, will fill the space between the wall of the tank and the cover, and the liquid 2 contained inside will no longer be in contact with the outside air.
It is easy to understand how, in such a case, a vertical
rod cannot exist inside the tank.
There are other cases where it is not acceptable to have the rod inside, and we have found how to put the guide outside so that the inner wall remains smooth, homogenous and without protrusions.
In this case (Figs. 3 and 4), the guide will be welded vertically outside the tank and will consist of a band or strip 9 of ferrous material sensitive to magnetic flux.
In this case, inside the tank, the float chamber 3 containing the permanent magnet 4 rests on the liquid 2, and is directed into the zone where, on the outside, the vertical band or strip 9 made of ferrous material is positioned. The strip 9 can be applied on the tank after it has been made, or it can be incorporated in the outer wall thereof when the tank is actually manufactured.
The permanent magnet 4 perceives the presence of the ferrous material and is attracted in correspondence with the strip 9.
Variations in the level of the liquid will make the position of the permanent magnet 4 vary, either up or down, but it will remain in any case on the vertical.
It is true that the outer ferrous guide 9 will absorb part of the magnetic flux, but there will always be a residual part to attract the element 8 onto the wall and keep it there; since this element 8 is free to move, it will follow the displacement, up or down, of the permanent magnet 4 and will therefore indicate the level of the liquid 2 inside the tank 1.
It should be noted that if the flux emitted by the permanent magnet 4 is strong enough, and if the wall of the tank is thin enough, the flux may manifest itself even outside a tank made of ferromagnetic material, even though it may only be for a limited zone, but which will still be
sufficient to hold the element 8.
In this situation, in order to be able to slide along the wall of the tank 1, the magnet will have to have a wheel shape 10 (Fig. 5), because it would not be able to slide if it were of another shape, since it is strongly attracted by the ferrous material.
The magnet 10 and the float chamber 3 will thus take on the approximate shape of a wheelbarrow.
This shape of the magnet 10, like a wheel, can also be used on any tank 1.
The difference between the inner guide 7 and the outer guide 9 is that the first must be made of non-magnetic material, while the second, in order to fulfil its function as a guide, must be made of ferromagnetic material so as to be able to attract the permanent magnet 4 located inside the tank and to keep it attracted.
To be able to float, the permanent magnet 4 need not necessarily be located inside the float chamber 3; it may also be located on the level of the liquid 2 in another manner, such as for example, in the case of"ever full" tanks, it can be anchored to the floating cover and will thus follow the level of the liquid 2.
The flux emitted by the permanent magnet 4, apart from attracting the element 8, may be used to act on a micro- switch, for a light or bell, of a known type and which is not shown in the drawings.