US 5,327,778 AGranted

Apparatus and method for viscosity measurements using a controlled needle viscometer

OwnerNoh A. Parkinventor

Life of this patent

Estimating the term…

Loading patent…

Abstract

An apparatus and method are disclosed for accurately determining viscosity of Newtonian and non-Newtonian fluids using a controlled needle viscometer. The controlled needle viscometer includes a vertical sample insert tube filled with the liquid of which the viscosity is to be determined. Using a needle guide at the top of the sample insert tube, a body having a known density is made to fall through the liquid in the sample insert tube. Using the time that the controlled needle takes to fall between two known distance marks or transducers, the velocity of the needle falling through the liquid is determined. Thus, the viscosity can be calculated by using the velocity of a controlled needle. In the method, viscosity, shear rate and shear stress can be calculated according to a modified power law model.

Claims10

Dependent claims

An apparatus for determining the viscosity of fluids, comprising:

a vertically oriented sample insert tube for holding fluid whose viscosity is to be determined, said sample insert tube having a cylindrical wall having an internal diameter and a vertical axis;
means operatively associated with said sample insert tube for maintaining said sample insert tube at a constant temperature;
a controlled needle received in said sample insert tube for axial movement therein, said controlled needle comprising an elongated cylindrical body having an external diameter and rounded ends and having an upwardly extending guide rod coupled to one of said ends in axial alignment with said body, a weight support associated with said rod, whereby weight may selectively be applied to said controlled needle, said body having a length of at least twice the internal diameter of said sample insert tube and the diameter of said body being equal to or less than 0.95 times the internal diameter of said sample insert tube;
a guide surface operatively associated with said sample insert tube at an upper end thereof and adapted to receive and engage said guide rod, whereby said guide surface and said guide rod maintain said controlled needle coaxial with the vertical axis of said sample insert tube;
markings on said cylindrical wall of said sample insert tube, said markings being spaced by a predetermined distance indicative of distance of fall of said controlled needle within said sample insert tube;
and means operatively associated with said markings for measuring the time of fall of the controlled needle through the predetermined distance.

3 more elements

A method for determining the viscosity of a Newtonian fluid, comprising the steps of:

a. providing a sample insert tube having a diameter D;
b. filling the sample insert tube with a fluid for which the viscosity is to be determined;
c. providing a controlled needle having a diameter d.sub.2 and a length N, and having attached thereto a rod extending out of said sample insert tube and having a diameter d.sub.1, such that the ratio k.sub.2 =d.sub.2 /D is at most 0.95 and N/D is at least 2.0, said step of providing a controlled needle including the further step of adjusting the density of the controlled needle by applying to the needle weights external of the needle to control the velocity of the needle through the fluid;
d. inserting the controlled needle into the fluid filled sample insert tube;
e. maintaining a constant temperature in the fluid filled sample insert tube;
f. allowing the temperature of the controlled needle to reach the temperature of the fluid;
g. allowing the controlled needle to fall through the fluid filled sample insert tube;
h. measuring the time, t seconds, taken for the controlled needle to fall a predetermined distance F relative to the wall of the sample insert tube;
and
i. calculating the viscosity.

7 more elements

A method for determining the viscosity of a non-Newtonian fluid, comprising the steps of:

a. providing a sample insert tube having a diameter D;
b. filling the sample insert tube with a fluid for which the viscosity is to be determined;
c. providing a controlled needle having a diameter d.sub.2 and a length N, and having attached thereto a bar having a diameter d.sub.1, such that k.sub.2 =d.sub.2 /D is at most 0.95 and N/D is at least 2.0, said step of providing a controlled needle including the further step of adjusting the density of the controlled needle by applying to the needle weights external to the needle to produce a velocity of the needle through the fluid of almost 0 to 50 cm per second.
d. inserting the controlled needle into the fluid filled sample insert tube;
e. maintaining a constant temperature in the fluid filled sample insert tube;
f. allowing the temperature of the controlled needle to reach the temperature of the fluid;
g. allowing the controlled needle to fall through the fluid filled sample insert tube;
h. measuring the time, t seconds, taken for the controlled needle to fall between predetermined distance F relative to the wall of the sample insert tube;
and
i. calculating the viscosity.

7 more elements

Dependencies are inferred from the claim text.