Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Cleaning or foaming ability
Patent
1987-06-03
1989-11-07
Levy, Stewart J.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Cleaning or foaming ability
73843, 374 46, G01N 324
Patent
active
048783790
DESCRIPTION:
BRIEF SUMMARY
This invention relates to rheometers. The term "rheometers" includes not only viscometers but also instruments for determining elastic or plastic deformation of samples of material. By means of suitable rheometers measurements can be made of the elastic or plastic deformation of solid and semi-solid materials under predetermined forces and of the elastic or plastic deformation of flowable materials under forces insufficient to bring about continuous flow as measurable by a viscometer. Some rheometers are capable of measuring the deformation of samples of flowable material through the viscoelastic range and into the continuous flow region to enable elastic or plastic deformation as well as viscosity readings to be obtained from the one instrument.
The invention is particularly concerned with rheometers comprising relatively displaceable elements (hereafter called "shearing elements") for subjecting an intervening sample of material to shear forces, and more particularly to so-called rotation rheometers in which the relative displacement of the elements is rotational, whether unidirectional or oscillatory or a combination of both.
For a rheometer reading to be fully reliable the sample must be at a known temperature at the time the measurement is made. It is therefore important for the temperature of the sample to be controllable. Many rheological measurements have to be made while the sample is kept heated to a predetermined temperature above the environmental temperature.
Most prior art rheometers for testing samples at elevated temperature are provided with heating means for heating the environment around the shearing elements. In some rheometers the shearing elements are cylindrical elements arranged one inside the other and heat is supplied by heated water which is circulated through a heating jacket surrounding the outer element [cf e.g. the article entitled "A concentric cylinder air turbine viscometer" by S. S. Davis, J. J. Deer and B. Warburton in Journal of Scientific Instruments (Journal of Physics E) 1968 Series 2 Volume 1, pp 933-935]. In other known rheometers, the shearing elements are operated within a convection oven.
It is also known to employ an electrical resistance heating system using a heating resistor incorporated into a fixed shearing element.
The prior art rheometers are satisfactory for certain measurement purposes but their range of practical usefulness is restricted by heating and temperature control factors. There is an increasing requirement for rheological tests to be performed at temperatures well above those for which existing rheometers are suited. For example there is need for various synthetic polymers to be tested at temperatures much higher than 150.degree. C. Heating of materials to such high temperatures by means of rheometer heating systems of the known kinds would take much more time than can be afforded in many testing laboratories. Moreover testing would have to be restricted to materials which are not impaired by retention at the high temperatures for the time which would be necessary.
One object of the present invention is to provide a rheometer having a heating system by which samples of material can be economically heated even to temperatures well above 150.degree. C. in a very short time.
According to the present invention there is provided a rheometer comprising two elements ("shearing elements") between which a sample of material to be tested can be located, means for relatively displacing said elements so as to subject a said sample to (a) controlled shear force(s), means for heating the sample to a controlled extent, and means for automatically indicating a deformation or flow parameter of the material under the applied force(s), characterised in that there is at least one said shearing element which is made of or includes electrically conductive material and the heating means comprises an induction heater having at least one induction heating coil or loop located to permit induction heating of that electrically conductive material.
The invention utilises
REFERENCES:
patent: 2574715 (1951-11-01), Sontag
patent: 3479858 (1969-11-01), Umeno et al.
patent: 3535914 (1970-10-01), Veith et al.
Carri-Med Ltd.
Levy Stewart J.
Roskos Joseph W.
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