WO2003048695A1

WO2003048695A1 - Centering device for a rod-type or wire-type probe

Info

Publication number: WO2003048695A1
Application number: PCT/EP2002/013851
Authority: WO
Inventors: Armin Wendler
Original assignee: Endress + Hauser Gmbh + Co. Kg
Priority date: 2001-12-07
Filing date: 2002-12-06
Publication date: 2003-06-12
Also published as: AU2002352224A1; DE10160239A1

Abstract

Level measuring devices comprising rod-type or wire-type probes, which are disposed on the neck of a container having rod-type or wire-type probes, incur the following dangers; rod-type or wire-type probes can be pressed out of their desired perpendicular position whereupon the free hanging probe in the opening or neck of the container can be moved into a slanted position and engages with the opening in the wall of the container or the neck. The measurements can thus be impaired or even impossible to carry out, especially if the opening or the neck are made from metal. According to the invention, the probe (6) in the level measuring device (1) is provided with a centering device (10) in the region of the neck (7) of the container (4). Said centering device has at least one centering element (11) which centres the probe (6) in the neck (7) and prevents the probe (6) from touching the inner wall (12) or an edge (13) of the neck (7).

Description

Centering device for a rod or rope-shaped probe

The invention relates to a centering device for a rod-shaped or rope-shaped probe, in particular for a probe of a fill level measuring device of industrial process measurement technology, which is used to determine the fill level of a medium in a container.

Various types of level measuring devices with rod-shaped or rope-shaped probes are known. Fill level measuring devices are known, among others, in which the rod-shaped or rope-shaped probe represents an electrode of a capacitive measuring system or a waveguide for a TDR measuring system. What they have in common is that the probe is inserted into the container, e.g. a large industrial tank with the medium inside. A housing of the fill level measuring device, in which a measuring or evaluation electronics of the respective measuring system is usually accommodated, is usually attached to or on the container, in the upper area thereof. Many containers, in which the fill level measuring devices described are used, are provided with a nozzle in their upper or lid area. Other containers have a relatively thick concrete wall and a bushing where the level measuring device is installed. In both cases, the rod-shaped or rope-shaped probe, which is attached to the housing of the level measuring device, hangs in the bushing or in the socket.

A disadvantage of all of these arrangements is that the medium in the lower region of the container can push the rod-shaped or rope-shaped probe out of its desired, preferably vertical position, as a result of which the probe freely suspended in the passage or in the neck of the container is inclined Position can be brought to the neck so that it touches the bushing in the wall of the container or the nozzle. This worsens the measurement or may even make it impossible, in particular if the bushing or socket is made of metal.

In addition, in cases where the medium in the container is strongly moved and thus causes the probe to oscillate, the probe hanging and moving obliquely in the container may rub against an edge of the nozzle or the feedthrough, so that continuous Movement is damaged.

BESTATIGUNGSKOPIE The invention is therefore based on the object of improving the arrangement of a rod-shaped or rope-shaped probe of a fill-level measuring device in a bushing or a nozzle so that even with moving medium in the container it is prevented that the probe with the bushing or nozzle comes into contact.

This object is achieved according to the invention by a centering device used with the rod-shaped or rope-shaped probe, which has at least one centering element which centers the probe in the socket and prevents the probe from touching the inner wall of the socket.

In a particularly preferred embodiment of the invention, the centering element is essentially disk-shaped.

A special embodiment of this embodiment relates to a disk-shaped centering element which is fastened on a guide sleeve which surrounds the probe.

In a further preferred embodiment of the invention, several centering elements are used which are essentially rod-shaped.

In yet another preferred embodiment of the invention, a plurality of essentially spring-elastic and strip-shaped centering elements are used.

Embodiments of the described preferred embodiments of the invention relate to centering elements that can be spread apart by the probe.

In yet another preferred embodiment of the invention, the centering element is essentially ring-shaped.

Yet further refinements of a preferred embodiment of the invention relate to one or more centering elements which are fastened on or in a guide device.

In another embodiment of the invention, the guide device is fastened on a guide sleeve which surrounds the probe. In still other configurations of the centering device according to the invention, the centering element or elements are composed of several parts which are detachably connected to one another.

Furthermore, further refinements of the invention provide that the guide device and / or the guide sleeve are composed of several parts which are detachably connected to one another.

The invention is based on the idea of simply centering the rod-shaped or rope-shaped probe of the fill level measuring device with the aid of a device to be mounted thereon or in a container socket or in a bushing in the container and to prevent contact of the probe on the container, without a device having to be provided or permanently installed on the container side. The centering device according to the invention is assembled together with the rod-shaped or rope-shaped probe or with the level measuring device and can also be removed again. The invention is described and explained below with reference to various exemplary embodiments shown in the drawing:

Figure 1 is a basic sketch of a level meter mounted on a container with a centering device according to the invention.

Figure 2 is a sketchy side view of an embodiment of the centering device according to the invention on an enlarged scale compared to Figure 1;

3 is a sketchy side view of another embodiment of the centering device according to the invention on an enlarged scale compared to FIG. 1;

FIG. 4 shows a sketchy top view of a special embodiment of the centering devices according to FIG. 3; 5 shows a sketchy side view of a further exemplary embodiment of the centering device according to the invention on an enlarged scale compared to FIG. 1;

FIG. 6 shows a sketchy plan view of a special embodiment of the centering devices according to FIG. 5 on an enlarged scale;

FIG. 7 shows a sketchy plan view of another special embodiment of the centering devices according to FIG. 5 on an enlarged scale in comparison;

FIG. 8 is a sketchy plan view of a special embodiment of the centering devices according to FIG. 5;

FIG. 9 shows a plan view of the centering device according to FIG. 6 on an enlarged scale; and

FIG. 10 shows a sectional illustration of the centering device according to FIG. 9 for a sectional plane illustrated in FIG. 9 by a line marked with X-X.

In the exemplary embodiments of the invention shown in the drawing, components or component groups which correspond in their structure and / or in their function are provided with the same reference numerals for a better overview and for simplification.

1 shows a sketch of a field measuring device 1 for determining the fill level 2 of a medium 3 in a container 4. The field measuring device 1 comprises a housing 5 and a rod-shaped or rope-shaped probe 6 and is mounted on a nozzle 7 of the container 4 in the example shown here. As such, the field measuring device 1 can also be attached in any way to or on the connection piece 7, the probe 6 running through the connection piece 7 into the interior of the container 4 and immersing it there - at least partially - into the medium 3. In the area of the nozzle 7, the probe 6 is provided with a centering device 10 which has at least one centering element 11 which centers the probe 6 in the nozzle 7 and prevents the probe 6 from touching an inner wall 12 or an edge 13 of the nozzle 7. The field measuring device 1 is, for example, a capacitive or TDR fill level measuring device used in industrial process measuring technology, the rod-shaped or rope-shaped probe 6 of which is an electrode or a waveguide for electromagnetic measuring signals. Such devices are known and are therefore not explained in detail here. A measuring electronics of the field measuring device 1, likewise not explained or shown here, which is accommodated in the housing 5 as usual, is supplied via a connecting line 14, not described here, via which the measured values or control data obtained or generated by the field measuring device 1 are also passed.

2 shows a special embodiment of the centering device 10 mounted in the nozzle 7 according to the invention. In this embodiment, the centering device 10 comprises several, preferably at least three, centering elements, of which only two centering elements are here for simplification

11.2.1 and 11.2.2 are illustrated. Each of the centering elements 11.2.1 and

11.2.2 comprises two individual strips or rods 15.1a, 15.1b and 15.2a, 15.2.b. The strips or rods 15.1a, 15.1b or 15.2a, 15.2.b of the individual centering elements 11.2.1 and 11.2.2 are in turn connected to one another by means of rotary joints 16.1.1, 16.2.1. The strips or rods 15.1a, 15.1b or 15.2a, 15.2.b are fastened at their respective other ends by means of further rotary joints 16.1.2, 16.1.3, 16.2.2 and 16.2.3 guide rings 17.1 and 17.2. These guide rings 7.1 and 17.2 are arranged on a guide sleeve 18 enclosing the probe 6 and fastened there, preferably in the exemplary embodiment of the invention shown in FIG. 2 the upper guide ring 17.1 being fixed on the guide sleeve 18 in the axial direction and the lower guide ring 17.2 on the Guide sleeve 18 are axially displaceable.

From the hinged strips or rods 15.1a, 15.1b or 15.2a, 15.2. b, the guide rings 17.1 and 17.2 and the guide sleeve 18, a kind of scissors grid is formed, so that when the lower guide ring 17.2 is axially displaced, as illustrated by the unspecified double arrow, which consists of the strips or rods 15.1a, 15.1b and 15.2 a, 15.2. b formed centering elements 11.2.1 and 11.2.2 can be spread apart from the probe or placed on it. The axial extension of the guide sleeve 18 is preferably chosen to be greater than the maximum distance between the guide rings 17.1 and 17.2 when the centering elements 11.2.1 and 11.2.2 are folded together. For the assembly of the field measuring device 1 and the probe 6 on the nozzle 7, the centering device 10, which is usually supplied in the folded state and fastened on the probe 6, is unfolded by moving the guide ring 17.2 to such an outer diameter that it can be carried out with little effort without great difficulty Fit can be introduced into the nozzle. The movable guide ring 17.2 can be fixed in the desired end position on the guide sleeve 18 by simple means, for example by at least one set screw, preferably a grub screw, in said guide ring or by gluing. Of course, it is also possible without limitation of the invention to implement the upper guide ring 17.1 movably and the lower guide ring 17.2 axially fixed on the guide sleeve 18. It is not necessary for the function of the centering device 10 that it is firmly clamped inside the connecting piece.

3 shows another embodiment of the centering device according to the invention. On the guide sleeve 18 enclosing the probe 6, a single guide ring 17.3 is fastened, to which in turn a plurality of resilient, strip-shaped centering elements are fastened, of which only the two spring-elastic, strip-shaped centering elements 11.3.1 and 11.3.2 are illustrated due to the selected representation. These spring-elastic, strip-shaped centering elements 11.3.1 and 11.3.2 are curved outwards, shaped and matched to the inside diameter of the connecting piece in such a way that, when installed, they allow the probe 6 to be centered well. At their free ends 19.1 and 19.2, the spring-elastic, strip-shaped centering elements 11.3.1 and 11.3.2 are not connected to the guide sleeve 18 and can be moved on the latter. It is thereby achieved in a simple manner that, as shown in FIG. 3, in the idle or installed state, the spring-elastic, strip-shaped centering elements 11.3.1 and 11.3.2, which are bulged outwards, can be compressed for installation. Since the outer diameter of the centering device 10 is variable in this way, it is sufficient to keep one or a few standard sizes of a centering device 10 in stock for connecting pieces with different inner diameters.

For a better illustration, FIG. 4 shows a top view of the centering device 10 according to FIG. 3 installed in a connecting piece 7. This centering device 10 has three spring-elastic, strip-shaped centering elements 11.3.1, 11.3.2 and 11.3.3, which bear against the socket 7 on the inside and so center the probe 6 enclosed by the guide sleeve 18. As shown in Fig. 4, it is possible to assemble the guide sleeve 18 and the guide ring 17.3 from prefabricated parts which are connected to one another, for example by screws. This has the advantage that the probe 6 does not have to be inserted through the guide sleeve 18 before it is attached to or in the field measuring device 1 (see also FIG. 1). The centering device 10 according to FIG. 4, which can be assembled from individual parts, can also be placed on probes which are already attached to the field measuring device 1. Such centering device 10 are therefore also suitable for retrofitting already assembled field devices with probes. In principle, all the embodiments of the invention described hitherto and below can be designed to be divisible in a similar manner in order to use the advantage described above for the different forms of centering elements 11.

5 and 6 show yet another embodiment of the centering device 10 according to the invention, in which the centering element is essentially disk-shaped. This disk-shaped centering element 11.5 is attached directly to the guide sleeve 18 surrounding the probe 6. It preferably comprises a relatively thin disc which is reinforced in its edge region where it can touch the inner wall of the connecting piece, for example in accordance with a cross section shown in dashed lines in FIG. 5.

If the outer diameter of the centering element 11.5 is desired to be relatively large, holes 20 or other forms of openings can be provided, as shown in FIG. 6, in order to save weight.

Another embodiment of the centering device 10 according to the invention mounted in a nozzle 7 is shown in FIG. 7. Here, the centering element 11.6 is formed from an outer ring 11.6.1, which is fastened to the guide sleeve 18 by means of webs 11.6.2, 11.6.3 and 11.6.4. With this construction, a further weight reduction can be realized. Of course, the invention is not limited to the three webs 11.6.2, 11.6.3 and 11.6.4 shown here, but it can also be implemented with a different number of webs as required. Fig. 8 shows yet another embodiment of the centering device 10 according to the invention, which is suitable for connecting pieces of great length, where it is important to center the probe 6 over a greater length and to hold it in position. In order to satisfy this, the centering device 10 according to FIG. 8 has two Centering elements 11.8.1 and 11.8.2, which are spaced in the desired manner and fastened on the guide sleeve 18. The centering elements 11.8.1 and 11.8.2 illustrated in FIG. 8 can be those which correspond to the disk or ring-shaped centering elements shown in FIGS. 5, 6 and 7. Without restricting the invention, however, two or more of the rod-shaped or strip-shaped centering elements shown in FIGS. 2 to 4 can also be arranged one above the other.

Another embodiment of the centering device 10 is shown in FIG. 9. This in turn is an embodiment with a centering element 11.9, which is folded up for transport to the place of use and which can be folded there to a desired outside diameter, corresponding to the inside diameter of the connector 7), and fixed in this position. For this purpose, the centering element 11.9 comprises a plurality of kinked rods or strips which are firmly connected to a guide ring 21, which in turn is fastened on the guide sleeve 18 which surrounds the probe 6. Because of the illustration chosen for FIG. 9, only two kinked rods 11.9.1 and 11.9.2 can be seen. In the transport or rest position, an upper part of the bent rods 11.9.1 and 11.9.2 facing the guide ring 21 bears against or almost against the guide sleeve 18. By means of an expanding cone 22 which is displaceable on the guide sleeve 18 and can be fixed in its desired end position and which is pushed towards the guide ring 21, the bent bars 11.9.1 and 11.9.2, as illustrated in FIG. 9, can be adjusted to the desired and in relation to them Spread to the inside diameter of the socket selected outside diameter. In this position, the expansion cone 22 is locked on the guide sleeve 18. 10 and 11 show a particularly preferred embodiment of the invention. Here, a centering element 11. 10 designed as a wheel is provided with a central bore 23, the diameter of which corresponds to the outer diameter of the guide sleeve 18. The guide sleeve 18, which in turn receives the probe 6 (not shown here) in its central bore, has at its lower end a support disk 22 on which the centering element 11.10 inserted over the guide sleeve 18 comes to rest. The centering element 11.10 is fixed in this position by a clamping ring 23. This situation is shown in Fig. 10. 10 and 10 also illustrate how the guide sleeve 18 and thus the entire centering device 10 can be easily attached to a probe 6 by means of grub screws 24.1 or 24.2. The embodiment of the invention shown in FIGS. 10 and 11 enables the centering element to be replaced or replaced by another with other dimensions in a simple manner. As a result, the centering device can be easily adapted to different nozzle diameters.

The individual parts of all the centering devices shown in the drawing can in principle consist of any material, of metal or plastic, provided that the strengths required for centering the respective probe are achieved. However, the centering elements should preferably not be able to form an electrically conductive connection with the connecting piece. Either they are made of non-conductive material or they are coated on the outside. The guide sleeve can also be made of a metallic material; However, it has been shown that the function of the probe of the fig meter is less impaired by a guide sleeve made of non-conductive material.

Claims

claims

1. Centering device (10) for a rod-shaped or rope-shaped probe (6) of a field measuring device (1) for determining the fill level (2) of a medium (3) in a container (4), the field measuring device (10) in, on or mounted on a nozzle (7) of the container (4) so that the probe (6) runs through the nozzle (7) into the interior of the container (4), which centering device (10) has at least one centering element (11), the centers the probe (6) in the socket (7) and prevents the probe (6) from touching the inner wall of the socket (7).

2. Centering device according to claim 1, wherein the centering element (11.5) is substantially disc-shaped.

3. Centering device according to claim 2, wherein the disc-shaped centering element (11.5) is fixed on a guide sleeve (18) which surrounds the probe (6).

4. Centering device according to claim 1, in which a plurality of centering elements (11.2.1, 11.2.2) are used which are essentially rod-shaped.

5. centering device according to claim 1, wherein a plurality of centering elements

(11.3.1, 11.3.2, 11.3.3) can be used, which are essentially spring-elastic and strip-shaped.

6. Centering device according to one of claims 4 or 5, in which the centering elements (11.9.1, 11.9.2) can be spread apart by the probe.

7. Centering device according to claim 1, wherein the centering element (11.5) is substantially annular.

8. centering device according to one of claims 5 to 7, in which the or the centering elements (11) on or in a guide ring (17) are attached.

9. centering device according to claim 8, wherein the guide ring (17) is fixed on a guide sleeve (18) which surrounds the probe (6).

10. Centering device according to one of claims 1 to 9, in which the or centering elements (11.2.1, 11.2.2) are composed of several parts (15.1a, 15.1b, 15.2a, 15.2b) which are detachably connected to one another ,

11. Centering device according to one of claims 8 to 10, in which the guide ring (17) are composed of several parts which are detachably connected together.

12. Centering device according to one of claims 9 to 11, wherein the guide sleeve (18) are composed of several parts which are detachably connected together.