Rotary viscometer with an air bearing

Details Rotary viscometer with an air bearing Rotary viscometer with an air bearing

1999-08-31

2001-01-02

Noori, Max (Department: 2855)

Measuring and testing

Liquid analysis or analysis of the suspension of solids in a...

Viscosity

C073S843000

Utility Patent

active

06167752

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a rotating viscometer with a measuring motor which drives a measuring shaft which carries a disc mounted in an air bearing of a stator, and with a normal force measuring device having at least one position sensor to determine axial movements of the measuring shaft on the basis of viscoelastic properties of the substance to be investigated, more particularly fluid. The substance to be investigated may be of any kind and should exhibit plastic-elastic behavior, like, for example, rubber, honey, solutions, emulsions, oils, plastics etc.
A rotating viscometer of the type specified in the introduction is known from German patent publication DE 27 33 099 B1, for example. This publication describes a rotating viscometer on the plate-cone or plate-plate principle with two contra-rotating measuring surfaces, with a device for measuring the tempering chamber surrounding the lower measuring surface, wherein the device for measuring the normal force is located in its own housing separate from the measuring surfaces, which, in relation to the machine frame or the tempering chamber, may be located underneath the same by means of a releasable connection. In this arrangement, the normal force on the lower measuring plate is ascertained via the deflection of a bar. This rotating viscometer is complex in construction and the measured values obtained relating to the applied normal force are influenced by a plurality of equipment parameters.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a rotating viscometer, with which the temperature influences for determining the normal force may be determined with a sufficiently high degree of accuracy required by rheologists. Moreover, the rotating viscometer should be capable of being produced simply and so as to be operationally reliable and should allow the highest degree of measurement accuracy. When investigations of solids are performed, they are advantageously preloaded axially with a normal force.
These objects are achieved according to the invention with a rotating viscometer of the type specified in the introduction in that, in order to measure the normal force in the vicinity of the air bearing, the position sensor(s) is (are) arranged in the vicinity of the air bearing on the stator, more particularly embedded in the stator, and absorb the movements of the disc relative to the stator occurring in the axial direction of the measuring shaft. With the rotating viscometer according to the invention, the normal force may be measured without force and without contact, more particularly without friction, without the structure becoming complicated or the measurement accuracy or the operational reliability being adversely affected.
In a constructionally simple embodiment of a rotating viscometer if the features of possible position sensors are, in particular, capacitive, inductive and/or optical (interferometric) position sensors which do not cause any forces in the axial direction of the measuring shaft and cause no friction between the stator and the bearing disc, i.e. force-free and non-contact position sensors.
Very accurate measured values relating to the spacing or the changes of this spacing are obtained which may be evaluated extremely satisfactorily to determine the normal force.
Advantageous embodiments of rotating viscometers of the invention have position sensors acting without force and without contact formed at advantageous locations.


REFERENCES:
patent: 3886789 (1975-06-01), Brookfield
patent: 4176002 (1979-11-01), Quenisset et al.
patent: 5905606 (1999-05-01), Johnson et al.

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