Measuring and testing – Volume or rate of flow – By measuring electrical or magnetic properties
Reexamination Certificate
1998-08-27
2001-07-17
McCall, Eric S. (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring electrical or magnetic properties
Reexamination Certificate
active
06260420
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to inductive flow meters.
Practitioners skilled in this art are familiar with the type of inductive flow meter having a flow channel section that is defined by an electrically insulating inside wall, with the flow channel section containing two electrodes that are diametrically opposed across a cross-section of the flow channel section and exposed to the flow medium that is under investigation. Insulated measurement signal lines are connected to the electrodes, and a magnetic field generating system that is situated outside the flow channel section is used to generate a magnetic field that passes through the flow channel section in the vicinity of the cross-section referred to above, which contains the electrodes. This magnetic field is essentially perpendicular to a connecting line between the electrodes and is perpendicular to the longitudinal axis of the flow channel section, being established between the pole shoes of the magnetic field generating system that are arranged on opposing sides of the flow channel section. The field windings of the magnetic field generating system can be energized either with direct current or with alternating current, and a measurement signal that is a function of the flow of an electrically conductive medium within the flow channel section (a DC voltage signal or an AC signal, depending on the manner in which the exciter winding of the magnetic field generating system has been energized) can be tapped off. Inductive flow meters of this general design and their method of operation are familiar to the practitioner skilled in the art.
For example, DE-OS 1 773 484 shows a measurement channel body containing the flow channel section manufactured from plastic, with the electrodes and the measurement signal lines that lead to them insert-molded. This results in a defined position of the electrodes and the measurement signal lines relative to the flow channel and reduces the costs associated with calibrating and adjusting operations for the production of large numbers of such a device.
U.S. Pat. No. 4,428,241 shows measurement signal lines that lead to the electrodes of a flow meter of the general type in question, arranged on a circuit board like a printed circuit. The circuit board is held by special retaining devices in a defined position relative to the magnetic field generating system of the flow meter, with the circuit board situated adjacent to a measurement channel body that contains the flow channel section, and a pole of the magnetic field generating system passing through an opening in the circuit board.
Publication DE-OS 3 401 377 shows and describes an inductive flow meter of the general type described above, in which the electrodes that are exposed to the flow medium are embedded in the wall of a flow channel body that contains the flow channel section. Measurement signal lines are routed from the flow channel body through peripheral and axial grooves in the pole shoe arrangement of the magnetic field generating system. However, these measurement signal lines are not held in a fixed position within narrow limits, either by the measurement channel body or by the magnetic field generating system.
SUMMARY OF THE INVENTION
It is the task of the present invention to create an inductive flow meter of the type described in the introduction hereto, which lends itself to large-scale production, is of comparatively simple construction that ensures a high level of mechanical strength, and permits precise mounting of its parts, the construction of which reduces the expenditures that are associated with equalizing and adjusting operations performed during serial production.
According to one aspect of the invention, an inductive flow meter has a measurement channel body that incorporates a flow channel section with an electrically insulating inner wall, and two electrodes that are diametrically opposed to each other across a cross-section of the flow channel and exposed to the medium that is under investigation. The electrodes are enclosed in the measurement channel body in the same way as insulated measurement signal lines that lead to the electrodes and the connecting points to the electrodes. A magnetic field generating system establishes a magnetic field that passes through the flow channel section in the area of said cross-section, which is essentially perpendicular to the connecting line between the electrodes and perpendicular to the longitudinal axis of the flow channel section. The magnetic field is established between pole shoes of the magnetic field generating system, said pole shoes being arranged on opposing sides of the measurement channel body. The measurement signal lines are stamped out blanks of conductive foil or conductive sheet metal.
In some embodiments, the measurement signal lines are formed from electrode material, and the electrodes are connected in one piece to the measurement signal lines and form part of the stamped out conductive foil blanks or the conductive sheet metal blanks.
In some cases, the measurement signal lines are formed as conductor strips that are embedded in the measurement channel body, with their wide dimension oriented so as to be essentially parallel to the magnetic field generated by the magnetic field generating system.
In some embodiments, the measurement channel body is divided in its cross-section plane that contains the electrodes and is formed from two shaped bodies that can be combined. The electrodes, the measurement signal lines, and their connection points to the electrodes are sealed into matching recesses on the parting line.
In some embodiments, the measurement channel body is an injection-molded part in which the electrodes, the measurement signal lines, and their collection points to the electrodes are cast, at least in part.
In some embodiments, the electrodes and/or the measurement signal lines are provided with extensions that project beyond the outer surface of the measurement channel body, these extensions being intended for insertion into the core print of the injection mould during production of the measurement channel body.
In some embodiments, the measurement signal line that leads to the electrode on one side of the measurement channel body passes through the measurement channel body wall directly in a radial direction, whereas the measurement signal lines that lead to the other electrode incorporate measurement signal lines sections that are symmetrical to the magnetic field of the magnetic field generating system and to the cross section plane that contains the electrodes.
In some embodiments, the measurement signal lines sections within the measurement channel body incorporate axially routed line sections that run upstream and downstream between cross section planes from the cross section area of the measurement channel body that is occupied by the magnetic field generating system and/or from such cross section areas to the cross-section area of the measurement channel body that contains the electrodes.
In some instances, at least one of the axially routed long pieces of the measurement signal lines sections runs in an axial rail-like rib of the wall of the measurement channel body.
In some cases, the measurement channel body and/or on pole shoe elements of the pole shoes of the magnetic field generating system that lie against this from the outside there are recesses and/or projections that are of a matching shape for securing the relative positions of the magnetic field generating system and of the measurement channel body.
In some embodiments, the measurement channel body incorporates recesses on its side walls that are adjacent the pole shoes and opposite each other. The recesses match the shape of the particular pole shoe and accommodate the pole shoe elements that are near the flow channel cross-section in such a way that at least in some areas the pole shoe surfaces that face each other are separated from the flow channel section wall by measurement channel body material that is of reduced thickness.
In some
Ketelsen Andres
Ketelsen Jörn-Ove
Fish & Richardson P.C.
Ketelsen Broder
McCall Eric S.
Patel Jagdish
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