Flow measuring device

Abstract

A flow measuring device comprising a measurement signal-generating sensor element and a metal connection element, especially one manufactured in a generative manufacturing method, for connecting the measurement signal-generating sensor element with an opening or sensor nozzle of a tube, where the connection element is connected with a pressure-bearing component comprising a sleeve and a wall, which extends over the entire cross section in parallel projection in the direction of a longitudinal axis of the sleeve, wherein the pressure bearing component has at least one electrical cable guide and a potting compound, wherein the potting compound fills the sleeve partially or completely, and wherein the pressure bearing component is arranged in the opening or in the sensor nozzle of the tube radially behind the connection element with reference to the longitudinal axis of the tube.

Claims

1. A thermal flow measuring device, comprising: two measurement signal-generating sensor elements; a metal sensor housing having a hollow body and two pin sleeves protruding outward from the hollow body, wherein each sensor element is disposed at an end of a respective pin sleeve, and wherein the sensor housing is adapted to connect the sensor elements to an opening or a sensor nozzle of a tube or pipe having a tube longitudinal axis; and a pressure-bearing component including: a sleeve having a cross-section and a longitudinal axis; a wall extending over the entire cross-section of the sleeve in a parallel projection in a direction of the sleeve longitudinal axis; at least one electrical cable guide extending through the wall; and a potting compound filling the sleeve at least partially, wherein the pressure-bearing component is attached to a rear side of the sensor housing behind the two pin sleeves, wherein when the flow-measuring device is installed in the opening or in the sensor nozzle of the tube or pipe, the pressure bearing component is disposed in the opening or in the sensor nozzle of the tube or pipe adjacent the rear side of the sensor housing that is perpendicular to the tube longitudinal axis and such that the pressure-bearing component seals the opening or tube nozzle behind the sensor housing; wherein an outer diameter of the sensor housing increases from a medium-contacting end face of the pin sleeves to the hollow body.

2. The flow measuring device of claim 1, wherein the pressure-bearing component includes at least one electronic component that is embedded in the potting compound.

3. The flow measuring device of claim 1, wherein the sensor housing is manufactured by a generative manufacturing method, including by an selective laser melting method from a granular metal material or by a metal injection molding method.

4. The flow measuring device of claim 1, wherein the sensor housing is monolithically embodied.

5. The flow measuring device of claim 1, wherein the pressure-bearing component includes one or more ledges on an inner surface of the sleeve opposite the wall, the one or more ledges structured to anchor the potting compound.

6. The flow measuring device of claim 1, wherein a wall thickness of the wall relative to a diameter of the cross-section of the sleeve has a ratio of at least 1 to 30.

7. The flow measuring device of claim 1, wherein a wall thickness of the wall relative to a diameter of the cross-section of the sleeve has a ratio of at least 1 to 10.

8. The flow measuring device of claim 1, wherein the at least one electrical cable guide is embodied as a hole in the wall, the hole having. an average hole diameter of 0.2 to 1.5 mm.

9. The flow measuring device of claim 1, wherein the pressure-bearing component is embodied to be welded and/or screwed into the opening or the sensor nozzle of the tube or pipe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in greater detail based on an example of an embodiment for a thermal flow measuring device and with the help of the appended drawing. These descriptions and the figures are by way of example and are not intended to limit the scope of protection of the present invention. The sole FIGURE of the drawing shows as follows:

(2) FIG. 1 shows a sectional view of a sensor housing of a thermal, flow sensor of the invention.

DETAILED DESCRIPTION

(3) Conventional, thermal flow measuring devices usually use two, as equally as possible embodied, heatable, resistance thermometers, which are arranged in, most often, pin-shaped metal sleeves, so-called stingers, or in cylindrical metal sleeves and which are in thermal contact with the medium flowing through a measuring tube or through the pipeline. For industrial application, the two resistance thermometers are usually installed in a measuring tube. The resistance thermometers can, however, also be directly mounted in the pipeline. One of the two resistance thermometers is a so-called active sensor element, which is heated by means of a heating unit.

(4) The heating unit is either an additional resistance heater, or in the case of the resistance thermometer is a resistance element, e.g. an RTD (Resistance Temperature Device) sensor, which is heated by conversion of an electrical power, e.g. by a corresponding variation of the measuring electrical current. In the field of thermal flow measurement, the active sensor element is also often called the heater. The second resistance thermometer is a so-called passive sensor element: It measures the temperature of the medium.

(5) Usually, in a thermal flow measuring device, a heatable resistance thermometer is so heated that a fixed temperature difference is established between the two resistance thermometers. Alternatively, it is also known to supply a constant heating power via a control unit.

(6) If there is no flow in the measuring tube, then an amount of heat required for maintaining the specified temperature difference is constant with time. If, in contrast, the medium to be measured is moving, the cooling of the heated resistance thermometer depends essentially on the mass flow of the medium flowing past it. Since the medium is colder than the heated resistance thermometer, heat is transported away from the heated resistance thermometer by the flowing medium. In order, thus, in the case of a flowing medium, to maintain the fixed temperature difference between the two resistance thermometers, an increased heating power is required for the heated resistance thermometer. The increased heating power is a measure for the mass flow of the medium through the pipeline. The heating power can be described by a so-called power coefficient (PC).

(7) If, in contrast, a constant heating power is supplied, then, as a result of the flow of the medium, the temperature difference between the two resistance thermometers lessens. The particular temperature difference is then a measure for the mass flow of the medium through the pipeline, or through the measuring tube, as the case may be.

(8) There is, thus, a functional relationship between the heating energy needed for heating the resistance thermometer and the mass flow through a pipeline, or through a measuring tube, as the case may be. The dependence of the heat transfer coefficient on the mass flow of the medium through the measuring tube, or through the pipeline, is utilized in thermal flow measuring devices for determining the mass flow. Devices, which operate on this principle, are produced and sold by the applicant under the marks, ‘t-switch’, ‘t-trend’ or ‘t-mass’.

(9) FIG. 1 shows a variant of a thermal flow measuring device 1 of the invention in greater detail. In such case, one sees especially a housing of a measuring transducer of the thermal flow measuring device 1, which is referred to hereinafter as sensor housing 4. Sensor housing 4 is manufactured of metal and can be embodied as a plug-in sensor and be arranged, for example, in a sensor nozzle 2 of a tube 3 or in an opening of the tube 3. Tube 3 can be a measuring tube or can be part of an existing pipeline.

(10) In addition to the measuring transducer, the thermal flow measuring device 1 also includes an evaluation unit 10, which can be built into the measuring transducer.

(11) The sensor housing 4 to be described here for a measuring transducer represents only an especially preferred embodiment of the invention.

(12) Sensor housing 4 includes a hollow body 13, which can be arranged directly in the sensor nozzle 2.

(13) Hollow body 13 has a rounded base area, from which the at least two, a first and a second, pin sleeves 6 protrude into the lumen, thus into the interior, of the tube 3.

(14) Hollow body 13 in the embodiment of FIG. 1 is dome shaped. It can, however, also have another shape and be embodied, for example, cylindrically, frustum or frusto pyramid shaped.

(15) FIG. 1 shows two pin sleeves 6. However, also other pin sleeves, e.g. three or four pin sleeves, can be provided, in the case of which the flow measuring device can preferably combine other functionalities, e.g. drift detection and direction detection, in a thermal flow measuring device.

(16) The present invention can in a simplified embodiment also have only the two pin sleeves 6. The pin sleeves 6 are connected with the hollow body 13 as one piece and connecting seam freely, especially in the connection region. The terminology, connecting seam, in the sense of the present invention means a weld seam, adhesive seam, solder seam, brazed seam or the like.

(17) Especially preferably, the housing, thus the totality of pin sleeves and hollow body, is monolithically embodied.

(18) The first and second pin sleeves 6 have, in each case, a medium-contacting end face 14. Such is shown rounded in FIG. 1; it can, however, also be embodied flat.

(19) Each of the two pin sleeves has, especially in the region of the medium-contacting end face 14, a sensor element 5, which is arranged in the interior of its pin sleeve 6. A first sensor element 5 is, in such case, embodied as a heating element and a second sensor element 5 is embodied as a temperature sensor, for ascertaining the temperature of the medium. Both sensor elements can be in the form of a heatable temperature sensor, e.g. a Pt-100 or Pt-1000 resistance temperature sensor.

(20) The pin sleeves 6 can, in each case, be embodied in a stepped manner, whereby a better introduction and positioning of the sensor elements 5 in the pin sleeves 6 through the terminal opening on the end of the pin sleeves 6 facing away from the medium can occur.

(21) The pin sleeve 6 is associated with the sensor housing 4, which in the context of the present invention serves as a connection element 22, which connects the sensor elements 5 with the sensor nozzle 2.

(22) The geometric embodiment of a pin sleeve 6 is such that, starting from the end face 14, firstly, a first section 20 with a cylindrical pin sleeve wall and a first continuous cylinder outer diameter d1 follows. At a step 15 there follows a second section 19 with a cylindrical pin sleeve wall and a second continuous cylinder outer diameter d2. The second section can also have, for example, a conical shape. In such case, the diameter d2 is an average value.

(23) Following on the second section 19 is then a third section 16 with a conical shape. The transition between the first and second sections 19 and 20 is not abrupt, but, instead, has a continual increasing of the diameter from the first diameter d1 to a second diameter d2. The step 15 is, consequently, not abrupt, but, instead, exhibits a gradual changing of the diameter. Then, there arrives the third section 16 of the pin sleeve, which is frustoconically shaped and in the case of which the diameter d gradually grows in the course of the frustum up to a transition to the hollow body 13. The pin sleeves 6 have a length l1 of at least 10 mm.

(24) The stepped construction of the pin sleeves advantageously provides a greater stiffness of the pin sleeves.

(25) Associated with the section 20 according to the definition of the present invention is the end face 14. In this section 20 of a first of the two pin sleeves 6, a sensor element 5 is arranged. The sensor element, especially the heating element, does not absolutely have to contact the end face 14 or a cylindrical lateral surface of the pin sleeve, but can, instead, preferably be thermally coupled with the wall of the pin sleeve via a copper bridge. The same holds also for the additional, optional pin sleeves. A corresponding arrangement and its advantages are described in detail in DE 10 2008 015 359 A1.

(26) Arranged in the section 20 of the second of the two pin sleeves 6 is a temperature sensor for ascertaining the temperature of the medium. This can likewise be embodied as a heatable resistance thermometer, wherein during operation of the thermal flow measuring device 1 preferably one of the resistance thermometers can be actively heated and one of the resistance thermometers can be unheated.

(27) The wall thickness of the pin sleeves 6 amounts, at least in the section 20, to less than 0.5 mm, preferably less than or equal to 0.4 mm, especially 0.1 to 0.4 mm. Due to the thin wall thickness, an especially more favorable heat transfer can be achieved.

(28) The length l2 of section 20 can be at least 2 mm, preferably, however, 3-10 mm.

(29) The ratio of the length l2 to the diameter d1 for the first section 20 is preferably greater than 5, especially preferably equal to or greater than 7.

(30) In a preferred embodiment of the invention, the average ratio d.sub.average value/l1 for the total pin sleeve, amounts preferably to greater than 4, wherein the diameter applied is always that of the particular length of the section of the pin sleeve, in which the diameter is actually present. In the case of a frustum, such as in section 16, an average value of the diameter can be formed.

(31) Sensor housing 4 is manufactured of metal. An especially preferred metal can be steel, especially stainless steel, or Hastelloy. Alternatively, e.g. for strongly-corrosive media, also titanium can be utilized as wall material.

(32) Preferably, the sensor housing 4 is manufactured monolithically. In this way, a defined heat transfer is achieved.

(33) Additionally, the sensor housing 4 can be provided with a metal outer coating, in order, in given cases, to increase the resistance to certain media. This outer coating according to the present invention is not, however, part of the housing 2, but, instead, is a material ply applied supplementally on the housing 4.

(34) Sensor housing 4 is especially preferably manufacturable in a generative manufacturing method. Especially preferable, in such case, are radiation melt methods, such as e.g. selective laser melting, which is also known as the SLM method, in order to manufacture such an item with correspondingly thin wall thickness and corresponding length of the pin sleeves.

(35) In the case of the SLM method, a metal powder can be applied in a thin layer on a surface. The metal powder is then locally completely melted by laser radiation and solidified to a solid material layer with a coating thickness of typically 15-150 μm. Then, the surface is lowered by the magnitude of the coating thickness and a new material layer deposited. In this way, the housing 4 of the measuring transducer is gradually formed. Stresses in the material and corrosion susceptible seam locations are not present in such case.

(36) The thermal flow measuring device 1 of the invention additionally includes a pressure bearing component 7, which adjoins at an interface 21 at the hollow body 13. The pressure bearing component 7 is preferably deformation stable at least up to a maximum pressure of 40 bar.

(37) The pressure bearing component 7 includes a sleeve 12 with a longitudinal axis A and a wall 18, which extends over the entire cross section of the sleeve 12. The sleeve can preferably have a circularly shaped or rectangular cross section. It can especially preferably have a cylindrical shape.

(38) The surface normal of the wall 18 can preferably extend in parallel with the longitudinal axis A of the sleeve 12. The wall 18 can, however, also be arranged inclined in the sleeve 12.

(39) The end face and the wall 18 do not absolutely have to be arranged terminally on the sleeve 12, but, instead, can also be arranged, for example, in the middle of the sleeve form of the annular wall region and extend there over the entire cross section.

(40) Arranged in the sleeve 12 are preferably electronic components, thus e.g. boards and the like. These electronics components are embedded in a potting compound 8. The potting compound 8 fills especially the sleeve 12 partially or completely. Arranged in the wall 18 is at least one hole or a number of holes acting as electrical cable guides 9. These serve for the feedthrough of one or more signal lines and/or energy supply lines 17 between the sensor elements 5 and the evaluation unit 10. The holes can preferably have an average hole cross-section between 0.2 and 1.5 mm.

(41) For position securement of the potting compound 8, the sleeve 12 includes on the inner side a ledge 11. Alternatively or supplementally to ledges, the sleeve 12 can have grooves and/or a screw thread for anchoring the potting compound 8. At the same time, a better sealing of the potting compound is achieved.

(42) The wall thickness of the wall 18 has with reference to a diameter of the sleeve cross section of the sleeve 12 a ratio of preferably at least 1 to 30. Especially in the case of a dome shape of the wall 18, a lower wall thickness can be selected than in the case of a planar shape of the wall 18.

(43) The wall thickness of the wall 18 has in the case of a planar shape with reference to a diameter of the sleeve cross section of the sleeve 12 a ratio of preferably at least 1 to 20, especially preferably at least 1 to 10.

(44) Thus, the wall 18 can have a wall thickness of preferably at least 0.5 mm and especially preferably 1 to 2 mm.

(45) The one or more openings, or holes, of the electrical cable guide 9 can preferably likewise be filled with potting compound 8.

(46) The potting compound can be embodied, for example, based on an epoxide.

(47) The sleeve 12 and the wall 18 are preferably formed of a metal and especially preferably of stainless steel or Hastelloy. The unit is preferably monolithically constructed.

(48) In FIG. 1, the two measurement signal-generating sensor elements 5, thus the heating element and the temperature sensor, are arranged via a monolithic, connecting seam free, connection element 22 in the form of a sensor housing 4 on the tube 3, or in the sensor nozzle 2 of the tube 3, as the case may be.

(49) Corresponding connection elements 22 are also known from the field of ultrasonic flow measuring devices and from the field of vortex flow measuring devices.

(50) In ultrasonic flow measuring devices, it can be an element for reducing the body sound, i.e. an element which bears the ultrasound generating element, e.g. the ultrasonic transducer, and by means of which such is affixed to a tube wall. Also here, following this element for reducing the body sound, a pressure bearing component can be arranged, analogously to the component 7 of FIG. 1. This body-sound lessening element is monolithic and especially manufacturable by one of the above-described, generative manufacturing methods.

(51) In vortex measuring devices, capacitive sensors, so-called DSC sensors, are often applied. In order to prevent mechanical deformation of a sensor paddle in the case of pressure spikes, a stop is provided. This stop can be arranged, for example, in cage or arch shape in the region of the sensor paddle and supplementally limit its movement. Also this element can be manufactured by means of a generative manufacturing method. This stop is monolithic and is especially manufacturable by one of the above-described generative manufacturing methods.