Patent ID: 12209893

DETAILED DESCRIPTION

FIG.1shows a side view of a partially sectioned embodiment of a magnetic-inductive flow meter according to the invention. The structure and measuring principle of a magnetic-induction flowmeter are known in principle. A medium having an electrical conductivity is conducted through a measuring tube1. A device for generating a magnetic field is attached in the measurement segment16in such a way that the magnetic field lines are oriented substantially perpendicular to a longitudinal direction defined by the measuring tube axis. The device comprises at least two components. A saddle coil or a coil is preferably suitable as the first component. The second component has a magnetically conductive, in particular soft magnetic material, and comprises a coil core arrangement made of at least one coil core around which a coil wire of the coil is wound, at least one pole shoe arrangement with at least one pole shoe, and/or a field return arrangement consisting of at least two field returns. The pole shoe is inserted into an opening17in the carrier body2. Given an applied magnetic field, a flow-dependent potential distribution arises in the measuring tube1, which distribution is tapped with two measuring electrodes attached oppositely to the inner wall of the measuring tube1. As a rule, these are arranged diametrically and form an electrode axis, or are intersected by a transverse axis which runs perpendicular to the magnetic field lines and the longitudinal axis of the measuring tube1. Using the measured measurement voltage U, the flow rate v and, with additional consideration of the tube cross-sectional area, the volumetric flow rate V of the medium can be determined. In order to prevent the measuring voltage applied to the first and second measuring electrodes3from being conducted away via the tube, the inner wall is lined with an insulating material, for example a plastic liner (not depicted inFIG.1but depicted inFIG.4). To fasten the liner, a support body6is arranged between carrier body2and liner. According to the depicted embodiment, the support body6has a material which comprises sintering pellets. The support body6is produced by means of a sintering method. For this purpose, a sintering core is inserted into the interior of the carrier body2, and the cavity formed from the sintering core and the inner lateral surface of the carrier body2is filled with sintering pellets. The forming of the support body6takes place under increased pressure and/or temperature. After the formation of the support body6, a flowable liner is applied to the support body6. The flowable liner runs into the pores of the support body6, whereby the fastening of the liner to the support body6and thus also to the carrier body2is realized.

The magnetic field built up by the device for generating a magnetic field is generated by a direct current of alternating polarity clocked by means of an operating circuit. This ensures a stable zero point, and makes the measurement insensitive to influences due to electrochemical disturbances. A measuring circuit is configured to read out the induced measurement voltage applied to the first and second measuring electrodes, and an evaluation circuit is designed to determine the flow rate v and/or the volumetric flow {dot over (V)} of the medium depending on the measured measuring voltage.

Commercially available magnetic-inductive flowmeters have two further electrodes in addition to the measurement electrodes. On one hand, a fill level monitoring electrode, which is optimally attached at the highest point in the measuring tube1, serves to detect partial filling of the measuring tube1and is configured to forward this information to the user and/or to take into account the fill level in determining the volumetric flow {dot over (V)}. Furthermore, a reference electrode, which is usually attached diametrically with respect to the fill-level monitoring electrode, or at the lowest point of the measuring tube cross-section, serves to ensure sufficient grounding of the medium. Magnetic-inductive flow meters are known which have an additional temperature sensor which extends into the interior of the measuring tube1.

A first recess4is incorporated on the inner side5in the inlet region3of the carrier body2. The first recess4is helical. Furthermore, the outlet region11of the carrier body2has a second recess12, which is helical. In the inlet region3, a subregion13is present in which the wall thickness of the carrier body2decreases continuously opposite to the flow direction. The first recess4extends into the subregion13. For reasons of symmetry, the outlet region also has a subregion in which the wall thickness of the carrier body2decreases continuously in the flow direction and into which the second recess12extends.

According to the depicted embodiment, the material thickness of the support body6varies in the flow direction. In the measuring segment of the measuring tube1, the inner lateral surface of the support body6has a cylindrical basic shape. The cross-sectional area of the support body increases steadily in the direction of the inlet and the outlet. The inner lateral surface is designed as a cone in the segment.

FIG.2shows an enlargement of the outlet region11of the embodiment depicted inFIG.1. For reasons of symmetry, the configuration of the outlet region11corresponds to the configuration of the inlet region. The outlet region11or the second recess region15has a subregion13in which the wall thickness of the carrier tube2decreases in the flow direction. This serves to facilitate the filling of the sintering pellets into the cavity formed by the sintering core and carrier body. The inner lateral surface of the support body has a cylindrical basic shape in the subregion13. As can moreover be seen, the second recess12has a radial depth that varies in the direction of flow.

FIG.3shows a further enlargement of the outlet region11of the embodiment fromFIG.1. The first recess and the second recess12respectively have a pitch angle α.

FIG.4shows a longitudinal section of another embodiment of the magnetic-inductive flow meter according to the invention. According to the depicted embodiment, the support body6has an inner lateral surface whose basic shape is cylindrical. The electrically insulating liner7extends on the inner lateral surface. According to the inventive embodiment, the liner7is formed from a plastic which is applied in liquid form to the support body and is subsequently cured. By applying the liner7in a liquid state, the liner can extend into the pores of the support body produced by the sintering method and thus also catch.

Two diametrically arranged measuring electrodes9,10are configured to tap a measuring voltage induced in a flowing medium. For this purpose, the measuring electrodes9,10are connected to a measuring circuit (not depicted). The measuring electrodes9,10are arranged in the measuring portion of the measuring tube1, just like the device for generating a magnetic field8. This is arranged in an interlocking manner in a receptacle18which is formed in the support body6and extends through an opening17provided in the carrier body2. The receptacle18and opening17respectively have a longitudinal axis21,22. In the depicted embodiment, the two longitudinal axes21,22are situated atop one another. The receptacle18has an edge23which adjoins flush with the inner lateral surface of the opening17.

The carrier body2has a total length20. The carrier body has a first recess region14and a second recess region15. The first recess region14has a first length, and the second recess region15has a second length24. Taken together, the first length and the second length24form a characteristic length. The characteristic length corresponds to at least 12% of the total length20.

Unlike in the previously depicted embodiment, the inner lateral surface of the carrier body2in the first recess region14and in the second recess region15is formed cylindrically.

LIST OF REFERENCE SIGNS

1Measurement tube2Carrier body3Inlet region4First recess5Inner side6Support body7Liner8Device for generating a magnetic field9Measurement electrode10Measurement electrode11Outlet region12Second recess13Subregion14First recess region15Second recess region16Measuring segment17Opening18Receptacle20Total length21Longitudinal axis of the receptacle22Longitudinal axis of the opening23Edge24Second lengthα Pitch angle