Rotary rheometer

Details Rotary rheometer Rotary rheometer

2002-03-29

2003-07-08

Lefkowitz, Edward (Department: 2856)

Measuring and testing

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

Viscosity

C073S054380

Reexamination Certificate

active

06588254

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates generally to rheometers, which are used to characterize materials by measuring the materials viscosity, elasticity, shear thinning, yield stress, compliance and/or other material properties.
2. Background of the Invention
Rotary rheometers, viscometers or viscosimeters are used to measure fluid or other properties of materials such as their viscosity by rotating, deflecting or oscillating a measuring object in a material, and measuring, for example, the torque required to rotate or deflect or oscillate the object within the material. As used herein, the term “rheometer” shall mean rheometers, viscometers, viscosimeters and similar instruments that are used to measure the properties of fluid or similar (see list below) materials. The term “measuring object” shall mean an object having any one of several geometries, including, for example, cones, discs, vanes, parallel plates, concentric cylinders and double concentric cylinders. The materials may be liquids, oils, dispersions, suspensions, emulsions, adhesives, biological fluids such as blood, polymers, gels, pastes, slurries, melts, resins, powders or mixtures thereof. Such materials shall all be referred to generically as “fluids” herein. More specific examples of materials include asphalt, chocolate, drilling mud, lubricants, oils, greases, photoresists, liquid cements, elastomers, thermoplastics, thermosets and coatings. As is known to one of ordinary skill in the art, many different geometries may be used for the measuring object in addition to the cylinders, cones, vanes and plates listed above. The measuring objects may be made of, for example, stainless steel, anodized aluminum or titanium. U.S. Pat. Nos. 5,777,212 to Sekiguchi et al., 4,878,377 to Abel and 4,630,468 to Sweet describe various configurations, constructions and applications of rheometers.
The fluid properties of materials are generally dependent on their temperature. For that reason, it is generally important that the temperature of the material being tested is known and is homogeneous. If the temperature of the material being tested were not homogeneous, the accuracy and validity of the measurement would be seriously compromised. Thus the temperature of the fluid is generally accurately controlled, and is preferably made as homogeneous as possible, for example by using a fluid bath or a Peltier plate. Compared to a fluid bath, a Peltier plate temperature control system provides a more rapid heating and cooling of the sample, and is more economical, because it does not require an expensive controlled-temperature fluid circulator.
FIG. 1A
is a schematic perspective view of a rotary rheometer
100
, showing lead screw
101
, draw rod
102
, optical encoder
103
, air bearing
104
, drive shaft
105
, drag cup motor
106
, measuring object
107
(shown in
FIG. 1A
as a parallel plate), heating/cooling assembly (eg., a Peltier plate)
108
, temperature sensor
110
(eg., a Pt temperature sensor), surface
111
, normal force transducer
112
, and auto gap set motor and encoder
113
.
FIG. 1B
is a schematic drawing of a concentric cylinder configuration in position on the rheometer of
FIG. 1A
, showing the control jacket
120
of the concentric cylinder configuration on top of normal force transducer
112
of rheometer
100
.
FIG. 1B
shows a cylindrical measuring object
121
(used in this configuration instead of the parallel plate measuring object
107
shown in FIG.
1
A).
In operation, control jacket
120
contains sample cup
201
.
FIGS. 2A and 2B
are schematic drawings of a top view and a cross-sectional view of a prior art sample cup.
FIG. 2A
shows sample cup
201
, which has top flange
203
with top flange lip
202
, and fixing holes
205
. Sample cup
201
also includes sample bore
207
and cover location lip
209
. Cover location lip
209
is used to locate a cover that may be used, if necessary, to minimize evaporation from the sample.
FIG. 2A
also shows the upper end
204
of the sample cup
201
and lower end
206
of sample cup
201
.
FIG. 2B
shows the upper end
204
and the lower end
206
of sample cup
201
, as well as fixing holes
205
, sample bore
207
, sample cup base
208
and location lip
209
. The fixing holes are used to prevent rotation of the sample cup during a test run. As shown in
FIGS. 2A and 2B
, the upper end
204
of the sample cup has a larger outer diameter than its lower end
206
.
FIGS. 3A and 3B
are a top view and a cross-sectional view of a prior art control jacket
301
. Control jacket
301
has fixing holes
303
,
304
,
312
, and
314
, top lip
302
, cabling hole
305
and sensor hole
306
. Fixing holes
314
are used in conjunction with holes
205
(shown in
FIGS. 2A and 2B
) to prevent rotation of the measuring cup. Fixing holes
312
are used to fix the heating/cooling assembly, fixing holes
304
are used to fix the lower mounting plate and fixing holes
303
are used to fix the outer sleeve/cover. Sensor holes
306
and
313
are used for temperature sensors.
FIGS. 3A and 3B
also show cover locations
307
and
308
, sample cup location chamfer
311
, the outer surfaces
309
and
3
10
of the control jacket and the main bore of the control jacket
315
(which is where sample cup
201
fits into control jacket
301
) and air hole
321
. Cover locations
307
and
308
are used to locate the cover/sleeve that fits over the outer jacket.
FIG. 3B
also shows the heating/cooling assembly
322
, which is used to heat or cool the control jacket and the sample cup. For example, heating/cooling assembly
322
may be a Peltier plate.
As shown in
FIG. 3C
, in operation sample cup
201
fits inside control jacket
301
, such that an isolation gap is formed between sample cup
201
and control jacket
301
.
U.S. Pat. No. 6,240,770 to Raffer discloses a rotary viscosimeter having an isolation gap between a measuring cup and a temperature control cup. Because of the isolation gap, the measuring cup and the temperature control cup are in good heat conducting contact only in the vicinity of their upper circumferences, such that the heat conduction between the measuring cup and the temperature control cup is restricted to the upper ends of the measuring and control cups only. A heat pump, such as a Peltier block, is used to control the temperature of the temperature control cup so that heat is supplied to the measuring cup in a controlled manner via the mutual contact area at the upper ends of the measuring and control cups.
SUMMARY OF THE INVENTION
The present invention is a rotary rheometer having a concentric cylinder configuration. The concentric cylinder configuration includes a control jacket and a sample cup. The sample cup fits snugly inside the control jacket, such that the sample cup is in substantial thermal contact with the control jacket along at least twothirds of the length of the sample cup, and preferably along the greater part of the length of the sample cup (e.g., more than 80% of the length). The sample cup and the control jacket are fabricated from a good heat conducting material, such as, for example, HE30 aluminum. Copper or silver alloys or stainless steel could also be used. A heating/cooling assembly, positioned, for example, beneath the control jacket, is used to heat and/or cool the control jacket, thus heating and cooling the sample cup. In a preferred embodiment of the invention, the heating/cooling assembly is a Peltier plate. The sample cup includes a generally annular chamber, which ensures that the sample experiences a uniform temperature.
Preferably, the bottom of the sample cup is not in contact with the bottom of the control jacket, i.e., there is a gap between the bottom of the sample cup and the bottom of the control jacket such that there is a disk-shaped lower chamber that is in fluid communication with the annular chamber in the sample cup.


REFERENCES:
patent: 1658950 (1928-02-01), Stein
patent: 2096222 (1937-10-01), Bock
patent: 2382979 (1945-08-01), Demb
patent: 2437194 (1948-03-01), Harrin

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