WO2005026698A1 - An arrangement in a rheometer and a container for use in a rheometer - Google Patents

An arrangement in a rheometer and a container for use in a rheometer Download PDF

Info

Publication number
WO2005026698A1
WO2005026698A1 PCT/SE2004/001342 SE2004001342W WO2005026698A1 WO 2005026698 A1 WO2005026698 A1 WO 2005026698A1 SE 2004001342 W SE2004001342 W SE 2004001342W WO 2005026698 A1 WO2005026698 A1 WO 2005026698A1
Authority
WO
WIPO (PCT)
Prior art keywords
container
bob
fluid
oscillating
movements
Prior art date
Application number
PCT/SE2004/001342
Other languages
French (fr)
Inventor
Jan-Eric Litton
Lars JÄGARE
Håkan Bergström
Sven Erik Larsson
Original Assignee
Viscocheck Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Viscocheck Ab filed Critical Viscocheck Ab
Publication of WO2005026698A1 publication Critical patent/WO2005026698A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
    • G01N11/16—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by measuring damping effect upon oscillatory body
    • G01N11/162—Oscillations being torsional, e.g. produced by rotating bodies

Definitions

  • the invention relates generally to rheometers and more specifically to a container for use in rheometers.
  • d namic measurements of viscoelasticity of fluids are made in that the fluids are exposed to stress or strain that varies harmonically with time.
  • a harmonic force or a harmonic displacement is applied to a boundary surface.
  • the fluid is in a container in which a bob is located.
  • a harmonic movement of e.g. the container By forcing a harmonic movement of e.g. the container, a shearing of the fluid is introduced which results in a moment on the bob.
  • the bob is not fixed in the container. Thus, the only contact between the bob and the container is via the fluid.
  • a disadvantage with known rheometers is the friction introduced by the journaling of the container and the bob that can affect the measurement of the resulting moment as well as the control of the applied force or displacement.
  • a disposable closed container is desirable.
  • a closed container is known from US 2003/0084708 Al according to which the bob is carried by a needle bearing in the container.
  • the object of the invention is to bring about a rheometer and a disposable closed container that enable accurate measurements of viscoelasticity by avoiding problems with friction.
  • a rheometer for measuring characteristics of a fluid, comprising a container for the fluid, a bob that is located in the container to be in contact with the fluid, oscillating means for causing oscillating relative movements between the container and the bob to expose the fluid to shearing, measuring means for determining the movements of the container and the bob, and calculating means for calculating rheological properties of the fluid in response to the movements of the container and the bob, in that the bob is suspended in the container in tension loaded wires extending between the ends of the bob and the bottom and the top, respectively, of the container.
  • a container for receiving a fluid for measuring characteristics of the fluid the container being adapted to be connected to oscillating means for oscillating the container around its longitudinal axis, a bob being located in the container to be in contact with the fluid such that the container and the bob perform oscillating relative movements to expose the fluid to shearing upon oscillation of the container, and the container being adapted to enable measurement of at least the oscillating movements of the bob upon oscillation of the container, in that the bob is suspended in the container in tension loaded wires extending between the ends of the bob and the bottom and the top, respectively, of the container.
  • FIG. 1 is a schematic cross-sectional view of an embodiment of a rheometer according to the invention with a sample container according to the invention. DESCRIPTION OF THE INVENTION
  • Fig. 1 is a schematic cross-sectional view of an embodiment of a rheometer 1 according to the invention.
  • the rheometer in Fig. 1 comprises axial and radial air-bearings 2 for positioning a driving unit for receiving a container 3 for a sample of a fluid whose characteristics, e.g. viscoelasticity, are to be determined, in a housing (not shown).
  • the driving unit comprises a motor having a stator 4 with windings and a rotor 5.
  • the rotor 5 that is e.g. of drag cup type is adapted to receive the container 3.
  • the stator 4 is supplied with current to impart an oscillating movement to the rotor 5 under control of a control device 15 to achieve a controlled oscillation of the rotor 5.
  • the rotor 5 is provided with a cavity that is adapted to the shape of the container 3 to keep the container 3 firmly locked in the cavity of the rotor 5.
  • an optical rotational encoder is used.
  • the optical rotational encoder comprises a disc 6 having a centre hole in which the rotor 5 in Fig. 1 is fixed.
  • the edge of the disc 6 is provided with markings (not shown) such that the movements of the disc 6 can be measured by means of e.g. a laser device 8.
  • a bob 9 is suspended to be in contact with the fluid such that upon oscillation of the rotor 5, the container 3 and the bob 9 will perform oscillating relative movements to expose the fluid in the container 3 to shear forces.
  • the fluid sample container 3 can be made of e.g. plastics.
  • the inside of the container 3 that is exposed to the fluid can be coated with e.g. gold in order to reduce slip and surface chemistry for a specific fluid such as whole blood.
  • the bob 9 can comprise e.g. a hollow heavy metal cylinder of e.g. brass with plastic end caps.
  • the cylinder can also be filled with some suitable material. It is also possible to injection mold e.g. polycarbonate directly > into the cylinder, thereby also forming the end caps.
  • the container 3 can be of a disposable type.
  • the bob 9 is axially suspended in the container 3 by means of tension loaded wires 10 fixed between the ends of the bob 9 and the top and bottom, respectively, of the container 3.
  • the wires 10 can be fixed to the ends of the bob 9 in connection with the injection molding process mentioned above.
  • the wires 10 are tension loaded in order to centre the bob 9 in the container 3.
  • tension springs 11 are provided in the top and the bottom ends of the container 3. It would be possible to mount such tension springs in only one of the ends of the container but that would result in a substantial decrease in shock tolerance.
  • the wires 10 are preferably multi-filament fibres made up of a number, e.g. 80, of unbraided and untwisted filaments of liquid crystal polymer, each filament having a circular diameter of roughly 23 micrometers, e.g. of the type manufacture under the trademark VECTRAN® by Celanese Acetate LLC, Charlotte, NC, USA.
  • the advantage of using such wires is that they offer high tensile strength at the same time as they offer very low torsion rigidity. Since the wires 10 are neither braided nor twisted, the friction between the individual fibres due to relative movement between the fibres, causing cross sectional deformation and stretching under torsional movement, will be very low. Thus, the torsional damping, i.e.
  • Such fibres are not brittle. This means that they are easy to mount.
  • the position of the bob 9 in the container 3, i.e. its angle of deflection, upon oscillation of the container 3 via the rotor 5, is measured by means of a device 12 e.g. by irradiating a small rough section of the cylindrical surface of the bob 9 above the fluid surface with a narrow bandwidth light source, e.g. a single mode diode laser, and registering the obtained speckle pattern by means of a CCD camera.
  • Optical access to the bob is gained through a window 13 on the container 3, through which said rough cylindrical surface of the bob 9 can be observed as well as illuminated.
  • a calculating device 14 is provided.
  • the calculating device 14 in Fig. 1 has two input terminals connected to output terminals of the position detectors, i.e. laser devices 8 and 12, respectively, in Fig. 1.
  • the calculating device 14 is connected with an output terminal to the control device 15 to supply the latter with information on the oscillation of the rotor 5 as well as the bob 9.
  • information on the oscillation of the rotor 5 as well as the bob 9 is necessary.
  • viscoelasticity of the fluid sample in the container 3 can be determined in a manner known per se.

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
  • Examining Or Testing Airtightness (AREA)

Abstract

In a rheometer (1) for measuring characteristics of a fluid, comprising a container (3) for the fluid, a bob (9) that is suspended in the container (3) to be in contact with the fluid, oscillating means (4, 5) for causing oscillating relative movements between the container and the bob to expose the fluid to shearing, measuring means (8, 12) for determining the movements of the container and the bob, and calculating means (14) for calculating the rheological properties of the fluid in response to the movements of the container and the bob, the bob is suspended in tension loaded wires (10) extending between the ends of the bob and the bottom and the top, respectively, of the container (3).

Description

AN ARRANGEMENT IN A RHEOMETER AND A CONTAINER FOR USE IN A RHEOMETER
TECHNICAL FIELD The invention relates generally to rheometers and more specifically to a container for use in rheometers.
BACKGROUND OF THE INVENTION
By means of rheometers, d namic measurements of viscoelasticity of fluids are made in that the fluids are exposed to stress or strain that varies harmonically with time. A harmonic force or a harmonic displacement is applied to a boundary surface. Typically, the fluid is in a container in which a bob is located. By forcing a harmonic movement of e.g. the container, a shearing of the fluid is introduced which results in a moment on the bob. Normally, the bob is not fixed in the container. Thus, the only contact between the bob and the container is via the fluid.
A disadvantage with known rheometers is the friction introduced by the journaling of the container and the bob that can affect the measurement of the resulting moment as well as the control of the applied force or displacement.
For certain fluids, e.g. blood, a disposable closed container is desirable.
A closed container is known from US 2003/0084708 Al according to which the bob is carried by a needle bearing in the container.
The use of a needle bearing causes problems with friction in the needle bearing as well as with the calibration of the container. It will not be possible to perform calibrations on an empty container since the friction will depend on the lifting force resulting from the displacement of the liquid by the bob. Further, the friction will depend on lubricating effects from the fluid under examination that may be drastically differing from the effects even when using calibration liquids. Also, when handling the container, it will be sensitive to impacts. Moreover, accurate measurement of the movement of the bob will be difficult.
SUMMARY OF THE INVENTION The object of the invention is to bring about a rheometer and a disposable closed container that enable accurate measurements of viscoelasticity by avoiding problems with friction.
This is attained according to the invention in a rheometer for measuring characteristics of a fluid, comprising a container for the fluid, a bob that is located in the container to be in contact with the fluid, oscillating means for causing oscillating relative movements between the container and the bob to expose the fluid to shearing, measuring means for determining the movements of the container and the bob, and calculating means for calculating rheological properties of the fluid in response to the movements of the container and the bob, in that the bob is suspended in the container in tension loaded wires extending between the ends of the bob and the bottom and the top, respectively, of the container.
This is also attained according to the invention by a container for receiving a fluid for measuring characteristics of the fluid, the container being adapted to be connected to oscillating means for oscillating the container around its longitudinal axis, a bob being located in the container to be in contact with the fluid such that the container and the bob perform oscillating relative movements to expose the fluid to shearing upon oscillation of the container, and the container being adapted to enable measurement of at least the oscillating movements of the bob upon oscillation of the container, in that the bob is suspended in the container in tension loaded wires extending between the ends of the bob and the bottom and the top, respectively, of the container.
BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic cross-sectional view of an embodiment of a rheometer according to the invention with a sample container according to the invention. DESCRIPTION OF THE INVENTION
Fig. 1 is a schematic cross-sectional view of an embodiment of a rheometer 1 according to the invention.
The rheometer in Fig. 1 comprises axial and radial air-bearings 2 for positioning a driving unit for receiving a container 3 for a sample of a fluid whose characteristics, e.g. viscoelasticity, are to be determined, in a housing (not shown).
The driving unit comprises a motor having a stator 4 with windings and a rotor 5. The rotor 5 that is e.g. of drag cup type is adapted to receive the container 3. The stator 4 is supplied with current to impart an oscillating movement to the rotor 5 under control of a control device 15 to achieve a controlled oscillation of the rotor 5.
In the embodiment in Fig. 1 , the rotor 5 is provided with a cavity that is adapted to the shape of the container 3 to keep the container 3 firmly locked in the cavity of the rotor 5.
It should however be understood that the container equally well can be provided with separate means for locking it to corresponding means in the rotor.
To enable measurement of the oscillating movements, i.e. the angle of deflection, of the rotor 5 with the container 3, an optical rotational encoder is used. The optical rotational encoder comprises a disc 6 having a centre hole in which the rotor 5 in Fig. 1 is fixed. The edge of the disc 6 is provided with markings (not shown) such that the movements of the disc 6 can be measured by means of e.g. a laser device 8.
In the container 3 for holding a sample of a fluid whose characteristics are to be determined, a bob 9 is suspended to be in contact with the fluid such that upon oscillation of the rotor 5, the container 3 and the bob 9 will perform oscillating relative movements to expose the fluid in the container 3 to shear forces. The fluid sample container 3 can be made of e.g. plastics. The inside of the container 3 that is exposed to the fluid can be coated with e.g. gold in order to reduce slip and surface chemistry for a specific fluid such as whole blood.
To obtain a sufficient moment of inertia, the bob 9 can comprise e.g. a hollow heavy metal cylinder of e.g. brass with plastic end caps. The cylinder can also be filled with some suitable material. It is also possible to injection mold e.g. polycarbonate directly > into the cylinder, thereby also forming the end caps.
Depending on the type of fluid that is to be measured, the container 3 can be of a disposable type.
In accordance with the invention, the bob 9 is axially suspended in the container 3 by means of tension loaded wires 10 fixed between the ends of the bob 9 and the top and bottom, respectively, of the container 3. The wires 10 can be fixed to the ends of the bob 9 in connection with the injection molding process mentioned above.
The wires 10 are tension loaded in order to centre the bob 9 in the container 3.
In Fig. 1, to tension load the wires 10, tension springs 11 are provided in the top and the bottom ends of the container 3. It would be possible to mount such tension springs in only one of the ends of the container but that would result in a substantial decrease in shock tolerance.
In accordance with the invention, the wires 10 are preferably multi-filament fibres made up of a number, e.g. 80, of unbraided and untwisted filaments of liquid crystal polymer, each filament having a circular diameter of roughly 23 micrometers, e.g. of the type manufacture under the trademark VECTRAN® by Celanese Acetate LLC, Charlotte, NC, USA. The advantage of using such wires is that they offer high tensile strength at the same time as they offer very low torsion rigidity. Since the wires 10 are neither braided nor twisted, the friction between the individual fibres due to relative movement between the fibres, causing cross sectional deformation and stretching under torsional movement, will be very low. Thus, the torsional damping, i.e. the energy loss, in such wires will be very low. Further, since these fibres are characterized by high dimensional stability in a range of loading, thermal, and chemical environments, the need for calibration of single containers can be avoided, a prerequisite for low cost mass-production of disposable containers.
Moreover, such fibres are not brittle. This means that they are easy to mount.
It is also possible to mix different types of liquid crystal polymers in order to optimize the handling properties of the wires 10, e.g. to enable melting of the ends of the wires in the mounting process.
The position of the bob 9 in the container 3, i.e. its angle of deflection, upon oscillation of the container 3 via the rotor 5, is measured by means of a device 12 e.g. by irradiating a small rough section of the cylindrical surface of the bob 9 above the fluid surface with a narrow bandwidth light source, e.g. a single mode diode laser, and registering the obtained speckle pattern by means of a CCD camera. Optical access to the bob is gained through a window 13 on the container 3, through which said rough cylindrical surface of the bob 9 can be observed as well as illuminated.
To determine the characteristics, e.g. viscoelasticity, of the fluid sample in the container 3, a calculating device 14 is provided.
The calculating device 14 in Fig. 1 has two input terminals connected to output terminals of the position detectors, i.e. laser devices 8 and 12, respectively, in Fig. 1. The calculating device 14 is connected with an output terminal to the control device 15 to supply the latter with information on the oscillation of the rotor 5 as well as the bob 9. To control the shearing that the fluid is exposed to, information on the oscillation of the rotor 5 as well as the bob 9 is necessary.
By calculating movements, i.e. the angle of deflection, of the rotor 5 and the bob 9, viscoelasticity of the fluid sample in the container 3 can be determined in a manner known per se.

Claims

1. An arrangement in a rheometer (1) for measuring characteristics of a fluid, comprising
- a container (3) for the fluid, - a bob (9) that is located in the container (3) to be in contact with the fluid,
- oscillating means (4, 5) for causing oscillating relative movements between the container (3) and the bob (9) to expose the fluid to shearing,
- measuring means (8, 12) for determining the movements of the container (3) and the bob (9), and - calculating means (14) for calculating rheological properties of the fluid in response to the movements of the container (3) and the bob (9), characterized in that the bob (9) is suspended in the container (3) in tension loaded wires (10) extending between the ends of the bob (9) and the bottom and the top, respectively, of the container (3).
2. The arrangement according to claim 1, characterized in that the wires (10) are multi- filament fibres.
3. The arrangement according to claim 2, characterized in that the multi-filament fibres are unbraided and untwisted.
4. The arrangement according to any of claims 1 - 3, characterized in that the multi- filament fibres are of liquid crystal polymer.
5. The arrangement according to any of claims 1 - 4, characterized in that the bob (9) is provided with a rough surface section to enable non-contact determination of its movement.
6. A container (3) for receiving a fluid for measuring characteristics of the fluid, the container (3) being adapted to be connected to oscillating means (4, 5) for oscillating the container (3) around its longitudinal axis, a bob (9) being located in the container (3) to be in contact with the fluid such that the container (3) and the bob (9) perform oscillating relative movements to expose the fluid to shearing upon oscillation of the container (3), and the container being adapted to enable measurement of at least the oscillating movements of the bob (9) upon oscillation of the container (3), characterized in that the bob (9) is suspended in the container (3) in tension loaded wires (10) extending between the ends of the bob and the bottom and the top, respectively, of the container (3).
7. The container according to claim 6, characterized in that the wires (10) are multi- filament fibres.
8. The container according to claim 7, characterized in that the multi-filament fibres are unbraided and untwisted.
9. The container according to any of claims 6 - 8, characterized in that the fibres are of liquid crystal polymer.
10. The container according to any of claims 6 - 9, characterized in that the bob (9) is provided with a rough surface section to enable non-contact determination of its movement.
PCT/SE2004/001342 2003-09-18 2004-09-17 An arrangement in a rheometer and a container for use in a rheometer WO2005026698A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0302483A SE525764C2 (en) 2003-09-18 2003-09-18 Device in a rheometer and container for use in a rheometer
SE0302483-3 2003-09-18

Publications (1)

Publication Number Publication Date
WO2005026698A1 true WO2005026698A1 (en) 2005-03-24

Family

ID=29212485

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE2004/001342 WO2005026698A1 (en) 2003-09-18 2004-09-17 An arrangement in a rheometer and a container for use in a rheometer

Country Status (2)

Country Link
SE (1) SE525764C2 (en)
WO (1) WO2005026698A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102830132A (en) * 2012-08-28 2012-12-19 郑州大学 Stress monitoring-based fiber/polymer interfacial shear crystallization on-line detector
CN106596334A (en) * 2016-12-08 2017-04-26 哈尔滨工业大学 Tensile shear rheometer and method for testing rheological properties of alloy solid-liquid two-phase region by using tensile shear rheometer

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030084708A1 (en) * 2001-11-02 2003-05-08 Abnett Albert C Free rotor viscometer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030084708A1 (en) * 2001-11-02 2003-05-08 Abnett Albert C Free rotor viscometer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102830132A (en) * 2012-08-28 2012-12-19 郑州大学 Stress monitoring-based fiber/polymer interfacial shear crystallization on-line detector
CN106596334A (en) * 2016-12-08 2017-04-26 哈尔滨工业大学 Tensile shear rheometer and method for testing rheological properties of alloy solid-liquid two-phase region by using tensile shear rheometer
CN106596334B (en) * 2016-12-08 2019-08-02 哈尔滨工业大学 A method of utilizing high-temerature creep instrument beta alloy solid-liquid two-phase region rheological properties

Also Published As

Publication number Publication date
SE525764C2 (en) 2005-04-19
SE0302483D0 (en) 2003-09-18
SE0302483L (en) 2005-03-19

Similar Documents

Publication Publication Date Title
US9261446B2 (en) Rotational viscometer
US4941346A (en) Vibration-type rheometer apparatus
US11340151B2 (en) Rotational viscometer for measuring the viscosity of substances
JP5093599B2 (en) Viscosity / elasticity measuring apparatus and method
US10613010B2 (en) Intertial torque device for viscometer calibration and rheology measurements
US20040173009A1 (en) System and method for automatic identification of a detachable component of an instrument
JPH0660870B2 (en) Viscoelasticity measuring device and measuring method
JPS6139620B2 (en)
US4045999A (en) Rotational viscometers
EP2943770A1 (en) An optical fiber-based force transducer for microscale samples
US7207210B2 (en) Multi-decade viscometric or rheologic measurements of a material undergoing state change
WO2005026698A1 (en) An arrangement in a rheometer and a container for use in a rheometer
US10976230B2 (en) Rotation viscosimeter and method for determining the viscosity of materials using a rotation viscosimeter
CN115144575A (en) Detection probe for thromboelastogram
LU84185A1 (en) MEASURING DEVICE
US6571609B1 (en) Digital viscometer with arm and force sensor to measure torque
US5315886A (en) Apparatus for drawing off and dispensing a predetermined quantity of a liquid
RU2038578C1 (en) Micro-viscosimeter
RU2109266C1 (en) Rotational viscosimeter
JP2882855B2 (en) Rotational viscometer
EP0900369A1 (en) Measuring device comprising an excitable frequency gauge
JP6650955B2 (en) Spinnability measuring device
SU1132200A1 (en) Device for determination of plastic plasticity and solidification rate
Herschel The Improved MacMichael Viscosimeter
JPS6311820A (en) Wire torsion balance

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BW BY BZ CA CH CN CO CR CU CZ DK DM DZ EC EE EG ES FI GB GD GE GM HR HU ID IL IN IS JP KE KG KP KZ LC LK LR LS LT LU LV MA MD MK MN MW MX MZ NA NI NO NZ PG PH PL PT RO RU SC SD SE SG SK SY TJ TM TN TR TT TZ UA UG US UZ VN YU ZA ZM

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GM KE LS MW MZ NA SD SZ TZ UG ZM ZW AM AZ BY KG MD RU TJ TM AT BE BG CH CY DE DK EE ES FI FR GB GR HU IE IT MC NL PL PT RO SE SI SK TR BF CF CG CI CM GA GN GQ GW ML MR SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase