DD257182A3

DD257182A3 - rotational viscometer

Info

Publication number: DD257182A3
Authority: DD
Publication date: 1988-06-08

Abstract

Die Erfindung betrifft ein Rotationsviskosimeter mit koaxialen Messzylindern vorzugsweise bei angetriebenem Aussenzylinder nach dem Couette-Typ. Ziel der Erfindung ist es, durch eine reibungsfreie Drehfuehrung des Innenzylinders im Bereich kleinster Drehwinkel die Empfindlichkeit der Kraftmomentmesseinrichtung gegenueber parasitaeren Kraeften wesentlich zu verringern sowie eine einfache Anpassung an unterschiedliche Messbereiche zu erreichen. Das wird erfindungsgemaess erreicht, indem der Innenzylinder mit Hilfe konzentrisch angeordneter Federstaebe mit dem Gehaeuse fest verbunden ist. Die Federstaebe haben zugleich die Aufgabe von Lagerungs-, Zentrierungs- und Federelementen. Bei angetriebenem Aussenzylinder wird am Innenzylinder ein der Viskositaet der Messfluessigkeit proportionales Kraftmoment wirksam, welches auf geeignete Weise zur Anzeige gebracht wird. Durch Veraenderung der Anzahl und der Steifigkeit der Federstaebe kann der Messbereich in weiten Grenzen ohne Veraenderung der Zuordnung von Innen- zu Aussenzylinder auf einfache Weise geaendert werden. Anwendungsgebiet sind alle Rotationsviskosimeter mit koaxialen Messzylindern und vorzugsweise angetriebenem Aussenzylinder, die mit stark veraenderbarem Messbereich eingesetzt werden. Fig. 1The invention relates to a rotational viscometer with coaxial measuring cylinders, preferably with a driven outer cylinder of the Couette type. The aim of the invention is to substantially reduce the sensitivity of the force torque measuring device to parasitic forces by means of a friction-free rotational guidance of the inner cylinder in the region of the smallest rotational angle and to achieve a simple adaptation to different measuring ranges. This is achieved according to the invention by the inner cylinder with the help of concentrically arranged Federstaebe is firmly connected to the housing. The Federstaebe also have the task of storage, centering and spring elements. When the outer cylinder is driven, a moment of force proportional to the viscosity of the measuring fluid acts on the inner cylinder and is displayed in a suitable manner. By changing the number and the stiffness of the Federstaebe the measuring range can be changed within wide limits without changing the assignment of inner to outer cylinder in a simple manner. Field of application are all rotational viscometers with coaxial measuring cylinders and preferably driven outer cylinders, which are used with strongly variable measuring range. Fig. 1

Description

embodiment

Die Erfindung wird nachfolgend durch ein Ausführungsbeispiel erläutert (Figur 1 und 2). Der Spalt zwischen Außenzylinder 1 und Innenzylinder 3 ist mit der zu untersuchenden Meßflüssigkeit 2 gefüllt. Der Innenzylinder ist über die starre Achse 11 mit der unteren Befestigungsplatte 6 und die obere Befestigungsplatte 10 starr mit dem Gerätegehäuse 7 verbunden. An den planparallelen Befestigungsplatten 6 und 10 sind die Federstäbe 4 in den Bohrungen 9 mit Hilfe der Befestigungsschrauben 12 fest eingespannt. Vorzugsweise sind die Federstäbe 4 konzentrisch in der Weise angeordnet, daß mindestens 3 Federstäbe zur Zentrierung des Innenzylinders 3 nicht demontierbar sind, während die Anzahl der übrigen Federstäbe beliebig erhöht werden kann, um eine Meßbereichserweiterung zu erreichen. Bei angetriebenem Außenzylinder 1 wird über die zu untersuchende Meßflüssigkeit 2 auf den Innenzylinder 3 ein Kraftmoment übertragen, das eine Verdrehung des Innenzylinders entsprechend dem Rückstellkraftmoment der Federstäbe 4 bewirkt. Die Verdrehung im Bereich kleiner Winkel der mit dem Innenzylinder starr verbundenen unteren Befestigungsplatte 6 gegenüber dem Gerätegehäuse 7 wirkt über die Metallzunge 13 auf einen berührungslosen elektromechanischen Wegsensor 8 und wird in ein elektrisches Signal umgewandelt und in bekannter Weise zur Anzeige gebracht. Durch die Veränderung der Anzahl oder der Steifigkeit der Federstäbe 4 kann auf einfache Weise eine Meßbereichsveränderung erfolgen.The invention is explained below by means of an embodiment (FIGS. 1 and 2). The gap between outer cylinder 1 and inner cylinder 3 is filled with the test liquid 2 to be examined. The inner cylinder is rigidly connected to the device housing 7 via the rigid axle 11 with the lower mounting plate 6 and the upper mounting plate 10. At the plane-parallel mounting plates 6 and 10, the spring rods 4 are firmly clamped in the holes 9 by means of the fastening screws 12. Preferably, the spring rods 4 are arranged concentrically in such a way that at least 3 spring rods for centering the inner cylinder 3 are not removable, while the number of remaining spring rods can be arbitrarily increased in order to achieve a Meßbereichserweiterung. When the outer cylinder 1 is driven, a force moment is transmitted to the inner cylinder 3 via the test liquid 2 to be examined, which causes a rotation of the inner cylinder in accordance with the restoring force moment of the spring rods 4. The rotation in the range of small angles of the rigidly connected to the inner cylinder lower mounting plate 6 relative to the device housing 7 acts on the metal tongue 13 on a non-contact electromechanical displacement sensor 8 and is converted into an electrical signal and brought in a known manner for display. By changing the number or stiffness of the spring rods 4 can be done easily a Meßbereichsveränderung.

Die Federstäbe 4 sind im Ausführungsbeispiel als Federgelenkstäbe mit zwei möglichst weit auseinanderliegenden Blattfedergelenken 5 ausgebildet. Dadurch werden Störungen durch parasitäre seitliche Kräfte weitgehend vermieden und hauptsächlich die in tangentialer Richtung wirkenden Kräfte angezeigt. Die Meßstabilität wird insbesondere bei der Untersuchung hochviskoser und inhomogener Flüssigkeiten verbessert. Die Federgelenkstäbe 4 sind konzentrisch auf einem Kreisumfang so angeordnet, daß die Blattfederebenen zum Drehpunkt des Innenzylinders zeigen.The spring rods 4 are formed in the embodiment as a spring joint rods with two leaf spring joints 5 as far apart as possible. As a result, disturbances due to parasitic lateral forces are largely avoided and mainly the forces acting in the tangential direction are displayed. The measurement stability is improved, in particular in the investigation of highly viscous and inhomogeneous liquids. The spring joint rods 4 are arranged concentrically on a circumference so that the leaf spring planes point to the center of rotation of the inner cylinder.

Claims

11. rotational viscometer with coaxial measuring cylinders with driven outer cylinder and preferably electromechanical sensor for measuring the moment of force analog rotation of the spring-mounted inner cylinder, characterized in that the inner cylinder (3) on the device housing (7) by means of interchangeable spring rods (4) concentric with the axis of rotation of the inner cylinder (3) is fixed, wherein the Encien of the spring rods on the inner cylinder (3) and the device housing (7) are rigidly clamped.

2; Rotary viscometer according to item 1, characterized in that the number of spring rods (4) arranged concentrically to the axis of rotation can be varied for the purpose of measuring range change.

3. · rotational viscometer according to item 1 and 2, characterized in that the spring bars (4) are designed as spring joint rods, each with two as far apart friction-free spring joints (8).

For this 2 pages drawings

Field of application of the invention

The invention relates to a rotational viscometer with low-inertia torque measuring device using coaxial measuring cylinder with preferably driven outer cylinder after the Couette type.

Characteristic of the known technical solutions

To measure the flow behavior of Newtonian and non-Newtonian fluids, rotary viscometers with coaxial measuring cylinders of the Couette type are predominantly used. Between the measuring cylinders is the test liquid to be examined. If preferably the outer cylinder is rotated at a known angular velocity, the momentum of the viscosity of the measuring liquid acts on the Irinenzylindein proportional to the force. This is preferably measured by means of electrical sensors, although flow limits and time-dependent flow properties are to be determined with sufficient accuracy. The moment of force acting on the inner cylinder is to be compensated by spring or mass forces. In the case of low-torque torque measuring devices, centrally arranged torsion springs or spring elements tangentially acting on a lever arm are known. As a rule, the inner cylinder with ball bearings or air pressure bearings is mounted centrally with low friction. Another disadvantage here is that the function of the storage can be endangered by contamination and corrosion, or expensive and thus costly design solutions are required. Also known are low-drive torque measuring with a torsion bar as spring, storage and centering element, which is firmly connected to the minnows. In such a storage parasitic loads, especially lateral forces that irisbesondere in the measurement of highly viscous and inhomogeneous media act on the inner cylinder can lead to significant measurement errors. The assembly of the cylinder system and the preparation of the medium must therefore always be done with the utmost care. The replacement of the torsion bar for Meßbereichveränderung requires complex conversion measures and is always connected to a subsequent centering and calibration of the cylinder system.

Object of the invention

The aim of the invention is to substantially reduce the sensitivity of the Kraftmomentmeßeinrichtung to parasitic loads and to provide a simple mechanical adaptation to different measuring ranges by a frictionless rotation of the irons cylinder of a rotational viscometer in the smallest turning angle.

Explanation of the essence of the invention

The invention is the technical task zug round to create a low-drive force measuring device for rotational viscometer, are excluded in the interference by friction of the inner cylinder bearing, which allows a cost range extension within wide limits without costly conversion and without subsequent centering and calibration of the Meßzylindersystems and low sensitivity to parasitic Has loads. According to the invention, this object is achieved in that the inner cylinder of the rotational viscometer is fixedly connected by concentrically arranged spring rods with the device housing. The spring bars have the function of storage, centering and spring elements. When the outer cylinder is driven, a force moment proportional to the viscosity of the measuring fluid becomes effective on the inner cylinder, which rotates the inner cylinder to the point of equilibrium with the restoring force moment of the spring bars. This twist can be thoughtfully measured as a translational displacement with a displacement sensor or directly as a change in the direction of an angle sensor. Another feature of the invention is that the measuring range of the rotational viscometer can be changed by changing the number of spring bars within wide limits without changing the assignment of the inner and outer cylinders. To increase the sensitivity in the direction of action of the inner cylinder tangentially engaging frictional forces the spring rods are provided with two spring joints as far apart as possible, the spring joint axes are directed concentrically to the axis of rotation of the inner cylinder.