WO2006053723A1

WO2006053723A1 - Device for measuring a filling level according to the plumb line principle

Info

Publication number: WO2006053723A1
Application number: PCT/EP2005/012257
Authority: WO
Inventors: Jörg Mohr
Original assignee: Horn Gmbh & Co. Kg
Priority date: 2004-11-19
Filing date: 2005-11-15
Publication date: 2006-05-26
Also published as: DE202004018047U1

Abstract

The invention relates to a device for measuring the filling level of a filling medium (1) in a medium (2) according to the plumb line principle, comprising a rope roller (3), a guide rope (4) and a test body (5) arranged on the guide rope (4). The test body (5) can be brought into contact with the surface of the filling medium (1). The guide rope (4) runs over the rope roller (3) in such a way that the roller can be rotated by moving the guide rope in an upward and downward movement. A means (6) for measuring the rotation of the rope roller (3) and an electronic evaluation system (7) are also provided. The latter is adapted for use with a liquid as a medium that is to be measured, whereby the filling level thereof is to be measured in a continuous manner. The test body (5) is thus embodied as a float and floats on the surface of the liquid (1), and the rope roller (3) is associated with a tensing means (8) enabling the guide rope (4) to be continuously tensed between the test body (5) and rope roller (3), whereby the test body (5) cannot be raised without liquid (1). .

Description

Device for level measurement according to the plumb line principle

The present invention relates to a device for filling level measurement of a filling medium in a container according to the plumb bob principle with the features of the preamble of claim 1.

From the prior art forming the starting point of the present invention, a device for filling level measurement of a filling medium in a container (DE 197 30 196 C2) is known, which works according to the plumb line principle. This measurement method is currently only applied to bulk solids, e.g. in grain silos and other often very tall containers. Here, a test weight is arranged on a running over a pulley guide cable. For level measurement, the guide cable is uncoiled by the pulley by electric motor until the test weight hits the surface of the filling medium. As a result, the rolling process of the guide cable is stopped. In order to determine the filling level of the filling medium in the container, the pulley is assigned a means for measuring the rotation of the rope pulley. This means detects the An¬ number of revolutions and the direction of rotation of the pulley during the rolling process of the guide cable and forwards this information to a transmitter. The information is further processed in the evaluation electronics. Based on a reference value, the transmitter indicates the level of the filling medium in the container.

The previously explained, known device is not suitable for Füll¬ measurement of liquids. With the known device, a continuous measurement of the filling level is not possible. On the contrary, whenever information about the filling level is desired, the test body must be brought into contact with the surface of the filling medium in order to determine the filling level from the rotation of the rope pulley taking place. Such a device is also complicated in construction and expensive because the test body is moved by an electric motor. However, the great advantage of this device, as already explained, lies in the fact that even very slender, high containers with a filling height of 50 m and more with, as a result, nevertheless can be checked as a filling medium at the same time little effort in terms of the level of the bulk material.

In a device for level measurement, which is also suitable for liquids (DE 198 49 706 Al), a plurality of sensors are arranged in the container containing the liquid at different heights. The individual sensors report to an evaluation electronics whether they are covered by liquid or not. In such a device, the accuracy in terms of level measurement is determined by the distance between two superimposed sensors. Incidentally, this device is hardly suitable for retrofitting in a container already in use. Moreover, this device is hardly suitable for very tall, slim container, since a sufficient measurement accuracy, ie a small distance of the sensors, a very large number of sensors must be used.

For the level measurement of liquids, in which the filling level is continuously measurable, the current standard technique is based on the measurement of the position of a float floating on the surface of the liquid (DE 198 23 190 A1). The float is guided in a parallel tube separated from the actual container but connected to it by the system of communicating tubes, in which a measuring electrode and a counter electrode extend over the full height. The float is constantly in the range of a measuring electrode and a counter electrode, by means of which the float position is measured capacitively. It is obvious that this system is relatively expensive, especially if you have to cope with a very tall, slim container, so a considerable height measurement.

The invention is based on the problem, the initially explained, known, device for measuring the filling level of a filling medium in a container according to the plumb bob principle in such a way and further develop that it is suitable for measuring the level of liquids.

The above-mentioned problem is solved in a device for level measurement with the features of the preamble of claim 1 by the features of male of the characterizing part of claim 1. Advantageous developments are the subject of the subclaims.

The basic idea of the present invention is to make the test body as a float so that it floats on the surface of the liquid. The pulley is associated with a clamping means, so that the Führungs¬ rope between the test specimen and pulley is always stretched. However, the tension of the guide rope is not sufficient to be able to lift the test body without liquid. As the level in the container changes, the position of the test body changes and the pulley is rotated by the guide cable. This rotation is measured and evaluated with respect to the fill level. The level is thereby continuously measurable. An electric motor drive is not required.

While in a device for level measurement of a filling medium in a container which operates on the plumb line principle, the test body is a massive metal body which would immediately sink to the bottom in a liquid, but does not do so in a bulk material such as grain, but instead There simply bumps on the surface of the test body floats in the inventive device on the surface of the liquid and can follow the surface of the liquid as the liquid level rises and falls. While the test body in the known Vor¬ direction, which operates according to the plumb bob principle, is refilled with bulk material, such as grain, from the bulk material and its storage does not change, so then the actual level of the filling medium in the container not more correctly reproduced, follows in the erfindungsgemä¬ Shen embodiment of the device operating according to the plumb bob principle of the test body always the liquid level and thus always returns the level in the container properly. The transmission of this always correct position of the test body to the evaluation electronics takes place by means of the always tensioned guide rope and the measurement of the rotation of the rope pulley for the guide rope.

In connection with the explanation of the test body and the statement that it floats on the surface of the liquid, it should be noted that immersion of the test body into the liquid should also be partially or even below the surface of the liquid of this term with detected , Functionally necessary is that the liquid and the test body are in an equilibrium, which ensures a defined position of the test body relative to the liquid level of the liquid. Then the position of the test body in the container allows a safe conclusion on the position of the surface of the liquid, ie the liquid level in the container. The exact position of the test body relative to the liquid, however, is dependent on the specific weight of the test body in relation to the specific weight of the liquid.

Particularly preferred is an embodiment of the device for Füllstands¬ measurement, in which the tensioning means of the pulley is arranged so that the auf¬ passing clamping force over the clamping path of the clamping means is substantially li¬ near. This ensures that distortions due to a non-linearity of the clamping force does not occur. A non-linearity of the clamping force can also be taken into account by the transmitter, but this is relatively expensive.

Furthermore, an embodiment of the device is preferred in which the means for measuring the rotation of the pulley has a non-contact detection means.

In addition, an embodiment of the device is advantageous in which the evaluation electronics are designed with a learning mode. In the learning mode, the actual filling level can be set as a reference for a given position of the test body. The device can thus be adjusted individually for each container.

In the following the invention will be explained in more detail with reference to a drawing with reference to a preferred embodiment. In the course of this explanation, further refinements and developments and further features, properties, aspects and advantages of the invention will be explained. The single FIGURE shows a schematic representation of a erfmdungs gemä¬ Shen device for level measurement.

The single FIGURE shows a device for level measurement of a liquid 1 in a container 2 which operates on the plumb line principle. The device for level measurement has a cable pulley 3, a guide rope 4 and a test body 5 arranged on the guide cable 4. The test body 5 is by means of the guide cable 4 with the surface of the liquid

2 can be brought into contact. The cable pulley 3 is rotatably mounted and the guide cable 4 extends over the pulley 3 so that it rotates during an up and down movement of the guide cable 4. Here and preferably, the Führungs¬ rope 4 can be wound on the pulley 3 and unwound from this. It can also be provided that the guide cable 4 runs only on the pulley 3 and is wound on a further roll. The guide cable 4 may be designed as a normal rope, as a wire rope, as a string, as a chain o. The like.

Furthermore, a means 6 for measuring the rotation of the pulley 3, ie how often or by how many degrees the pulley 3 rotates, and a transmitter 7 are provided.

The test body 5 is designed as a float and floats on the surface of the liquid 1. It is understood by "swimming on the surface" also immersing the test body 5 in the liquid 1 to below the surface of the liquid 1. Function is necessary, that the liquid 1 and the test body 5 are in an equilibrium position. The exact position of the test body 5 in the container 2 is dependent on the specific weight or the density of the liquid 1 on the one hand and the specific weight or density of the test body 5 on the other hand.

The pulley 3 is associated with a clamping means 8. The tensioning means 8 is arranged such that the guide cable 4 between the test body 5 and the pulley

3 is always curious. However, the clamping force provided by the tensioning means 8 is not sufficient to be able to lift the test body 5 without the buoyancy force of the fluid 1.

The measurement of the level of the liquid 1 in the container 2 assumes that the test body 5 floats on the liquid 1. If the filling level in the container 2 changes, the test body 5 undergoes this change. If the test body 5 sinks with the liquid level in the container 2, a tensile force is exerted on the guide cable 4 and the cable pulley 3 is rotated in the downward direction following the tensile force. Does the test body 5 with the Liquid level in the container 2, the guide cable 4 is relieved and the tensioning means 8 rotates the pulley 3 in the upward direction to keep the guide rope 4 permanently stretched.

The means 6 for measuring the rotation of the pulley 3 detects the rotation of the pulley 3 and passes this information to the transmitter 7 on. In the transmitter 7, the signal is converted into an indication of the now current level of the container 2. The level is thus continuously measurable.

The tensioning means 8 for the guide cable 4 is here and preferably as a spring, in this case designed as a spiral spring. Further, the clamping means 8 is arranged here so that the clamping force occurring over the clamping path of Spann¬ means 8 is substantially linear. This has the consequence that the rotation of the pulley 3 runs uniformly and is not disturbed by a non-linearity of the clamping force. However, if such an arrangement is not encountered, it is advantageous to carry out the evaluation electronics 7 in such a way that this takes account of any non-linearity of the clamping force that occurs and indicates the level in the container 2, taking into account this nonlinearity. As a result, the slight change in the position of the test body 5 on the surface of the liquid 1, which is caused by the different clamping force of the clamping device 8, can also be taken into account.

In the embodiment of the apparatus for level measurement shown, a transmission 9 is arranged between the tensioning means 8 and the pulley 3. The clamping means 8 is directly associated with an element of the transmission 9 and the pulley 3 via the transmission 9 indirectly. If the transmission 9 is now designed as a reduction gear, it can be ensured in a particularly simple way that the occurring clamping force is substantially linear over the clamping path of the clamping device 8.

The means 6 for measuring the rotation of the pulley 3 is here and preferably designed so that it also detects the direction of rotation of the pulley 3 er¬. Thus, not only an indication of a change in the level of the liquid 1 in the container 2 is possible, but also whether the container 2 ge filled or emptied. The means 6 for measuring the rotation of the pulley 3 has here and vor¬ preferably a transmission gear 10 with an impeller 11. The transmission gear 10 is connected to the pulley 3 in a gear, so that a rotation of the pulley 3 is transmitted to the transmission gear 10 and thus to the impeller 11. By means of a detection means 12 as part of the means 6 for measuring the rotation of the rope pulley 3, the rotation of the running wheel 11 is then detected, from which it is possible to deduce the rotation of the rope pulley 3. The transmission gear 11 serves to increase the accuracy of detecting the rotation of the pulley 3.

As has already been explained above, the means 6 for measuring the rotation of the cable pulley 3 has a detection means 12. This is embodied here and preferably as non-contact detection means 12. Particularly suitable for such an application is an optical, magnetic, inductive or capacitive detection means 12. In this regard, DE 197 30 196 C2, which has been used as a starting point for the plumb bob principle, contains some interesting suggestions.

Depending on the embodiment, the pulley 3 or, as here, the impeller 11 at least one of the detection means 12 associated Beinflussungselement 13. In the present case, a plurality of magnets are arranged as influencing elements 13 of the detection means 12 on the impeller 11 and preferably distributed uniformly over the circumference thereof. The detection means 12 is designed as a reed switch and the pulley 3 and the impeller 1 1 arranged opposite fixed. If the pulley 3 rotates, the reed switch receives a signal each time a magnet passes it and sends it to the evaluation electronics 7. The number of magnets on the pulley 3 and the impeller 11 determines the accuracy of the measurement of the rotation of the pulley 3. Instead of a reed switch as Detektions¬ means 12, for example, the use of a Hall sensor is possible. It is also possible to use two detection means 12 or a larger number of detection means in conjunction with one or more influencing elements 13 in order to optimize the measuring accuracy with regard to angle and direction of rotation as required. _ _

An alternative to the measurement is also a fork light barrier or a combination of two or more fork light barriers, which cooperate with one or more perforated discs.

In the present case, the pulley 3 is designed as a pulley. As such, it has a guide groove 14 in which the guide cable 4 is guided. An Abrut¬ rule of the guide cable 4 of the pulley 3 is thus prevented.

The transmitter 7 is here carried out with a learning mode in which the actual level of the liquid 1 in the container 2 at vorgebe¬ ner position of the test body 5 is set as a reference size. This adjustability of the evaluation electronics 7 serves to adapt the device for level measurement to any desired container 2.

When winding the guide cable 4 on the pulley 3, the Wik- keldurchmesser changes depending on the already wound length of the guide cable 4. Since the rotation of the pulley 3 depends on the winding diameter of the guide cable 4, a change in the winding diameter to inaccuracies in the statement of the filling level. In order to prevent this, the evaluation electronics 7 is designed accordingly and takes into account the changing winding diameter when calculating the fill level.

The transmitter 7 here and preferably further comprises a level indicator 15, from which the current level of the liquid 1 in the container 2 can be read, and a transmitter 16 for remote data transmission. By means of the transmitter 16 is thus the level of the liquid 1 in the container 2 beispiels¬ example, to a central control unit transferable.

The evaluation electronics 7 has a low power consumption, in particular when a detection means 12, which functions according to the pulse encoder principle, is used, for example with the reed sensor described above. Here and preferably, therefore, the detection means 12 and the evaluation electronics 7 can be operated battery-powered and thus independent of the mains. This allows a particularly simple retrofitting of the device. Overall, a great advantage of the device according to the invention for level measurement lies in the fact that this level measurement according to the plumb bob can now be carried out for liquids and can thus also be easily retrofitted to an existing container. In this case, despite the use of the discontinuously operating plumb bob principle, such a configuration is made here that the fill level of the liquid to be measured can be continuously measured.

Claims

claims:

1. A device for level measurement of a filling medium (1) in a Be¬ container (2) according to the plumb bob principle, with a pulley (3), a guide cable (4) and one on the guide cable

(4) arranged test body (5), wherein the test body (5) with the surface of the filling medium (1) is brought into contact, wherein the guide cable (4) over the pulley (3) runs, that this by an up and Abbewegung of the guide cable (4) is rotatable, wherein a means (6) for measuring the rotation of the pulley (3) and a

Evaluation electronics (7) are provided, characterized in that the filling medium to be measured (1) is a liquid that the filling level is continuously measurable, that the test body (5) is designed as a float and on the surface of the liquid (1) floats and that the pulley (3) is associated with a tensioning means (8), so that the Führungs¬ rope (4) between the test body (5) and pulley (3) is always tense, but without the test body (5) without liquid (1) lift to be able to.

2. Device according to claim 1, characterized in that the tensioning means (8) is designed as a spring, preferably as a spiral spring.

3. Apparatus according to claim 1 or 2, characterized in that the clamping means (8) is arranged so that the occurring clamping force over the clamping path of the clamping means (8) substantially linear over the Spann¬ path of the clamping means (8) runs.

4. Device according to one of the preceding claims, characterized gekenn¬ characterized in that between the clamping means (8) and the pulley (3) a gear (9) is ange¬ arranged and that the tensioning means (8) an element of the transmission (9) directly and indirectly associated with the pulley (3) via the gearbox (9), wherein, preferably, the transmission (9) is designed as a reduction gear.

5. Device according to one of the preceding claims, characterized in that the means (6) for measuring the rotation of the pulley (3) is designed so that it also detects the direction of rotation of the pulley (3), and / or in that the means (6) for measuring the rotation of the cable pulley (3) has a transmission gear (10) with an impeller (11).

6. Device according to one of the preceding claims, characterized gekenn¬ characterized in that the means (6) for measuring the rotation of the pulley a non-contact detection means (12), in particular an optical, magnetic, inductive or capacitive detection means (12), wherein , Preferably, the pulley (3) or the impeller (11) at least one of the detection means (12) associated influencing element (13), wherein, further preferably, the detection means (12) as Reedschalter or Hall sensor and the influencing element (13) as a magnet or a plurality of magnets is embodied, or the detection means (12) is designed as a light barrier, in particular as a fork light barrier, and the influencing element (13) as a perforated disc.

7. Device according to one of the preceding claims, characterized in that the pulley (3) is designed as a pulley.

8. Device according to one of the preceding claims, characterized gekenn¬ characterized in that the transmitter (7) is designed with a learning mode in which the actual filling height at a predetermined position of the test body (5) is adjustable as a reference size.

9. Device according to one of the preceding claims, characterized marked, in that the evaluation electronics (7) are designed so that a change in the winding diameter of the guide cable (4) during winding is taken into account.

10. Device according to one of the preceding claims, characterized in that the evaluation electronics (7) comprises a level indicator (15) and / or a transmitter (16) for remote data transmission and / or that the detection means (12) and the evaluation (7 ) battery operated benie.