Rotary viscosimeter

Details Rotary viscosimeter Rotary viscosimeter

2000-02-29

2001-06-05

Williams, Hezron (Department: 2856)

Measuring and testing

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

Viscosity

C073S054430, C073S054230

Reexamination Certificate

active

06240770

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to rotary viscosimeters in which a test sample is placed into a cylindrical measuring cup. A rotary measuring cylinder extends into the cup so that the sample is disposed in a gap between the cylinder and the cylindrical wall of the cup. Forces required to rotate or angularly deflect the cylinder are measured and used to determine the viscosity of the sample.
FIG. 1
schematically illustrates a known rotary viscosimeter which employs a rotary cylinder and which forms the basis for the present invention. Such a rotary viscosimeter uses a measuring motor
1
which rotates a measuring cylinder
7
via a shaft
4
. The relationship between the torque on the motor shaft and its electrical supply, particularly its current consumption, frequency or phase shift, are known. The torque generated by a test sample
6
can therefore be determined from a parameter of the electric supply for the motor. In addition, an angle sensor
2
is provided for determining the angular rotational position of shaft
4
or the number of its rotations. Also important is a bearing for journalling shaft
4
. Depending on the constructional details and the required torques, roller bearings or, as in the illustrated case, air bearings
3
can be used.
Generally speaking, three different measuring systems with standardized geometry are in use, and they include cone/plate measuring systems, plate/plate measuring systems and, as shown in
FIG. 1
, cylinder measuring systems.
Such a rotary viscosimeter further has a relatively rigid support
8
for measuring motor
1
and bearings
3
. The support holds a measuring cup
5
which receives sample
6
, measuring cylinder
7
and, if applicable, a temperature control system for maintaining a constant sample temperature.
For determining the parameters of the sample, the torque can be measured by rotating shaft
4
at a constant rpm (CSR test). It is also possible to apply a constant torque to shaft
4
and to measure the rpm or rotational deflection of the shaft (CSS test). Finally, shaft
4
can be subjected to a sinusoidally or otherwise oscillating rotational movement (oscillation test). This last testing method permits one to determine the elastic component of sample
6
in addition to its viscosity.
Samples
6
can be liquids, gels, pastes, melts, as well as granulates or powder made from solid bodies. The viscosity of such samples is highly dependent on the temperature, which frequently can change as much as 10% per 1° C. An accurate determination of the viscosity therefor requires a homogeneous temperature distribution within the sample, particularly the portion thereof in measuring gap
10
. Since the viscosity of many samples, such as heat curing cements and resins, also changes with time, it is desirable to heat or cool the sample and attain a uniform sample temperature in as short a time as possible.
FIG. 2
schematically illustrates a coaxial cylinder measuring system. Sample
6
that is to be measured is in a gap
10
between the inner surface of a stationary measuring cup
6
having a radius “R” and measuring cylinder
7
which has a radius “r”, a height “h”, and is driven by motor
1
. The sample completely surrounds the measuring cylinder. Upon rotation of measuring cylinder
7
, the sample in gap
10
is sheared and its viscosity can be determined from the rpm, the torque, and the geometry of the gap. An accurate determination of the viscosity requires a uniform temperature distribution in the sample, particularly in the area of gap
10
, which has a thickness “s”. In addition, the temperature of the sample must be accurately measured. Since a temperature sensor placed inside gap
10
would affect the shearing of the sample, it is necessary to measure the temperature outside the gap but as closely as possible to the sample. A convenient location for placing temperature sensor
3
is the wall of measuring cup
5
.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a rotary viscosimeter of the type described above which assures that the sample temperature is as uniform as possible, and which attains such a uniform temperature distribution as quickly as possible and can retain it for a relatively long period of time.
In accordance with the invention, this is attained by providing the rotary viscosimeter with a measuring cup that is surrounded by a heat control cup. An isolation gap is formed between the two cups to provide good heat isolation for the measuring cup. The measuring cup and the temperature control cup are in heat conducting contact in the vicinity of their upper circumferences to restrict heat conduction between them to that area. In addition, the temperature control cup is constructed of a material which is a good heat conductor, such as Al, a Cu alloy and the like. A fast distribution of the heat conducted to the upper portion of the measuring cup is assured by constructing it also of a material which is a good heat conductor, such as Al, a Cu alloy and the like. In this context, it is noted that undesirable heat losses or temperature increases in the measuring cup do not occur because the temperature control cup substantially prevents unwanted heat energy supply to or withdrawal from the measuring cup. A heat pump, preferably a Peltier block, controls the temperature of the temperature control cup so that heat energy is supplied to the sample in the measuring cup in a controlled manner via the upper circumferences of the cups where they are in mutual contact.


REFERENCES:
patent: 1924969 (1933-08-01), Wheeler
patent: 4185493 (1980-01-01), Feinstein
patent: 5308953 (1994-05-01), Grudzien, Jr. et al.

Affiliated with

Also associated with

Rating

Rotary viscosimeter does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rotary viscosimeter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary viscosimeter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2460857