METHOD FOR MANUFACTURING A MAGNETO-INDUCTIVE FLOW MEASURING DEVICE WITH PARTIALLY REDUCED CROSS SECTION

Abstract

A method for manufacturing an apparatus for measuring flow of a fluid flowing through a measuring tube of metal using the magneto-inductive principle, comprising the method steps as follows: securing first and second collars of metal externally on the measuring tube with an orientation perpendicular to the tube axis of the measuring tube lining the measuring tube internally with an electrically non-conductive, elastic liner and altering a measuring section of the measuring tube located at least partially between the first collar and the second collar by means of cold deformation in such a manner that the cross sectional area of the measuring section is reduced compared with the cross sectional area of an inflow section of the measuring tube located upstream from the measuring section and an outflow section of the measuring tube located downstream from the measuring section.

Claims

1-16. (canceled)

17. The method for manufacturing an apparatus for measuring flow of a fluid flowing through a measuring tube of metal using the magneto-inductive principle, comprising the steps as follows: securing first and second collars of metal externally on the measuring tube with an orientation perpendicular to the tube axis of the measuring tube; lining the measuring tube internally with an electrically non-conductive, elastic liner; and altering a measuring section of the measuring tube located at least partially between the first collar and the second collar by means of cold deformation in such a manner that the cross sectional area of the measuring section is reduced compared with the cross sectional area of an inflow section of the measuring tube located upstream from the measuring section and an outflow section of the measuring tube located downstream from the measuring section.

18. The method as claimed in claim 17, wherein: the first collar is located in the region of a transition between the inflow section and the measuring section; and the second collar is located in the region of a transition between the measuring section and the outflow section.

19. The method as claimed in claim 17, wherein: the first collar is located in the region of the inflow section; and the second collar is located in the region of the outflow section.

20. The method as claimed in claim 17, wherein: the first collar and the second collar are located in the region of the measuring section.

21. The method as claimed in claim 17, wherein: a housing is secured on the first collar and on the second collar.

22. The method as claimed in claim 17, wherein: a measuring tube with circular or rectangular cross section is used.

23. The method as claimed in claim 17, wherein: the measuring section has after the cold deformation an altered cross-sectional area geometry, especially a rectangular profile.

24. The method as claimed in claim 17, wherein: said cold deformation is performed by means of at least two rams, which are pressed externally of the measuring tube between the first collar and the second collar from two oppositely lying sides of the measuring tube.

25. The method as claimed in claim 17, wherein: on at least two oppositely lying sides of the measuring tube, in each case, at least one welded stud is externally secured, and the welded studs are positioned centrally along a connecting line extending through the first collar and the second collar and parallel to the tube axis.

26. The method as claimed in claim 25, wherein: the magnet system is secured on the welded studs.

27. The method as claimed in claim 25, wherein: the welded studs are secured to the measuring tube before said cold deformation; and for said cold deformation at least two rams are used, which have cavities for the welded studs.

28. The method as claimed in claim 17, wherein: after said cold deformation, at least two measuring electrodes are secured in the or to the measuring tube.

29. The method as claimed in claim 17, wherein: a liner with a hardness of less than Shore 90 A is used.

30. The method as claimed in claim 29, wherein: a liner of polyurethane, soft rubber, hard rubber or PTFE is used.

31. The method as claimed in claim 17, wherein: the first collar and the second collar are welded and the welded studs are secured to the measuring tube by spot welding.

32. The method as claimed in claim 17, wherein: cross sectional area of the measuring section is reduced compared with the cross sectional area of the inflow section and the outflow section by factor of 1.1 to 1.5.

Description

[0030] The invention as well as advantageous embodiments thereof will now be described based on the figures of the drawing. The figures of the drawing show as follows:

[0031] FIG. 1 a magneto-inductive flow measuring device according to the state of the art,

[0032] FIG. 2 a measuring tube lined with a liner and having first and second collars secured thereon,

[0033] FIG. 3 an illustration of cold deformation by means of two rams acting on a measuring tube of FIG. 2.

[0034] FIG. 4 a cold formed measuring tube with mounted magnet system.

[0035] FIG. 1 shows a magneto-inductive flow measuring device 1 for measuring flow of a fluid 2 flowing through a measuring tube 3. Measuring tube 3 is provide in the region facing the fluid, i.e. on the inside over the entire length, with an electrically insulating liner 4. Measuring tube 3 is conveniently subdivided into an inlet section 3a, a measuring section 3b, on which the sensor unit is placed, and an outflow section 3c. Shown for the sensor unit are a measuring electrode pair 8 for sensing the induced voltage and the magnet system 9,9′, which is represented in FIG. 1 by two boxes. Magnet system 9,9′ comprises at least two coils 9,9′ for producing the magnetic field 10 and, in given cases, also pole shoes and/or field-guiding sheet metal pieces for implementing an advantageous spatial distribution of the magnetic field. The connecting axes of the measuring electrode pair 8 and the field coils 9,9 extend mutually perpendicularly to one another, wherein the two field coils and the two measuring electrodes 8 are positioned respectively on oppositely lying sides of the measuring tube 3.

[0036] The sensor unit with its respective components such as e.g. the measuring electrode pair 8 and the magnet system 9,9′ is usually surrounded at least partially by a housing 5. Provided in the housing 5 or in the present case outside of the housing 5 is furthermore an electronics unit 6, which is connected electrically via a connecting cable 7 with the field device 1. The electronics unit serves for signal registration and/or—evaluation or for power supply of the coils, as well as interface to the outside, e.g. for measured value output or adjustment of the device.

[0037] First steps of the method of the invention for reducing the cross section of the measuring tube in the measuring section are shown in FIG. 2. First, a first collar 11 and a second collar 11′ are secured externally on the measuring tube 3. Then, the measuring tube 3 is lined internally with an electrically non-conductive liner 4. In this example, the measuring tube 3 has a circularly round cross sectional area.

[0038] The performing of a cold deformation of the invention is illustrated in FIG. 3. The cold deformation is performed by means of two rams 12, 12′, which are pressed against the measuring tube in the region between the first 11 and the second collar 11′ from two oppositely lying sides of the measuring tube 3. The first and second collars 11,11′ effect a stabilizing of the measuring tube 3 during this procedure. In this example, no welded studs are provided. It is understood, however, that the rams 12,12′ in another example of an embodiment can also have cavities for previously mounted, welded studs.

[0039] After the forming, the respectively required components of the sensor unit of the flow measuring device can be mounted. First, for example, the at least two measuring electrodes 8,8′ can be secured and then the magnet system 9,9′.

[0040] FIG. 4 shows, finally, a cold formed measuring tube 3′ with mounted magnet system 9,9′ placed on two welded studs 13,13′. Also shown is a housing 5 welded on the first and second collars 11,11′. The arrangement of a housing 5 directly on the first and second collars 11,11′ is especially easy to accomplish and requires no additional structural means. As a result, the first and second collars serve a double function: stabilizing the measuring tube 3 during the cold deformation and supporting the housing 5.

REFERENCE CHARACTERS

[0041] 1magneto inductive flow measuring device according to the prior art [0042] 2 flowing fluid [0043] 3 measuring tube [0044] 4 electrically insulating lining, liner [0045] 5 housing unit or housing [0046] 6 electronics unit [0047] 7 connecting cable [0048] 8,8′ measuring electrodes [0049] 9,9′ magnet system with at least two coils [0050] 10 magnetic field perpendicular to the flow direction of the fluid and to the connecting axis of the measuring electrodes [0051] 11,11′ first and second collars [0052] 12,12′ rams [0053] 13,13′ welded studs