EP0458869A1 - Appareil et procede pour determiner les caracteristiques d'une poudre - Google Patents

Appareil et procede pour determiner les caracteristiques d'une poudre

Info

Publication number
EP0458869A1
EP0458869A1 EP19900903617 EP90903617A EP0458869A1 EP 0458869 A1 EP0458869 A1 EP 0458869A1 EP 19900903617 EP19900903617 EP 19900903617 EP 90903617 A EP90903617 A EP 90903617A EP 0458869 A1 EP0458869 A1 EP 0458869A1
Authority
EP
European Patent Office
Prior art keywords
vibration member
powder
vibration
particle size
amplitude
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP19900903617
Other languages
German (de)
English (en)
Inventor
Haroun Mahgerefteh
Brian Briscoe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BTG International Ltd
Original Assignee
BTG International Ltd
British Technology Group Ltd
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 BTG International Ltd, British Technology Group Ltd filed Critical BTG International Ltd
Publication of EP0458869A1 publication Critical patent/EP0458869A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/002—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis

Definitions

  • This invention relates to an apparatus and a method for determining characteristics of a powder sample, in particular the mean particle size and/or the mass of the powder.
  • the present invention provides an apparatus for determining characteristics of a powder sample, comprising a vibration member, means to mount a container for powder on the vibration member, means to vibrate the vibration member, and means to measure the vibration characteristics of the vibration member.
  • the present invention also provides a method for determining characteristics of a powder sample comprising the steps of mounting a container partly filled with the powder on a vibration member, vibrating the vibration member in order to fluidise the powder, measuring the vibration characteristics of the vibration member, and determining from the measured vibration characteristics the characteristics of the powder sample.
  • the inventors have found that by detecting the amplitude of forced vibrations of a stiff member driven at resonance on which is mounted a container partly filled with a powder or by observing the rate of decay of amplitude of free vibrations of the same from resonance, it is possible to measure the mean or average size of the powder.
  • the inventors make use of the fact that when the maximum acceleration of the container becomes equal or greater than that due to gravity, the powder inside the container 1 levitates' or 'fluidises' . This , results in frictional interactions between the powder particles themselves; particle/particle interactions and also interactions between the particles and the walls of the container; particle/wall interactions.
  • the vibration and measuring means form part of a manually tuned circuit which can identify the resonant frequency and amplitude of the vibrating member. More advantageously, it is found that best results are obtained when measurements are carried out at--, the primary resonant frequency of the vibrating member.
  • Figure la shows a schematic representation of a measurement device according to the invention.
  • Figures lb and lc show in elevation and plan view a modification of the device of figure la.
  • Figure 2 is a schematic diagram of the manual tuning electronic circuit for detecting the resonant frequency, amplitude and decay profile of the vibration member of the measurement device of Figure 1.
  • Figure 3 is a graph of amplitude of vibrations at resonance v particle size for particle size measurement device of Figure 1 using 500 mg of Ballotini solid glass spheres of various size ranges (0-900 _m) and a drive voltage of 1000 mV.
  • Figure 4 is a graph showing the variation of the resonant period (inverse of the primary resonance frequency) v particle size for the same conditions as in Figure 3.
  • Figure 5 is a graph showing the variation of resonant period with powder mass for 310-420 ⁇ m. size range using a drive voltage of 1000 mV and manual tuning.
  • Figure 6 is a graph of the decay of amplitude of free vibrations from resonance with time for the measurement device of Figure 1 using 500 mg of 45-70 ⁇ m size range of powder and 1000 mV drive voltage.
  • Figure 7 is a graph of the decay profile of amplitude of vibrations for the measurement device of Figure 1 from resonance using 500 mg of powder of various size ranges and a cut-off drive voltage of 1000 mV.
  • Figure 8 is a graph of the variation of the decay constant with mean particle size using the data presented in Figure 7.
  • Figure 9 is a schematic representation of the vibrating rod device for operation in aggressive environments.
  • a beam 1 in the form of 3mm diameter, 70 mm long silver steel rod is securely clamped at one end between two mild steel jaws 3,4 using screws 5, 5 1 .
  • a mild steel measuring pan 2 is screwed on to the free end of the beam which is previously suitably threaded.
  • the clamping distance of jaws 3, 4 on the beam 1 should be small. This is a matter of experiment but with the present device, the maximum clamping distance was 2mm.
  • the powder to be analysed is placed in the measuring pan 2 which is in the form of a cylindrical tube closed at its lower end and threaded on its outer surface to take on a suitably threaded cap 6.
  • the pan is normally filled up to about 1/5 of its volume by the powder prior to measurements ⁇ -for the particular drive input used in these experiments.
  • the rod 1 is mechanically excited by a magnetic flux generated by an electromagnet 7 which is placed at about 2 mm below the measuring pan 2.
  • the electromagnet comprises of a laHiinated soft iron core wound with approximately 1500 turns of '0.3 mm dia copper wire.
  • the frequency and amplitude of vibrations are monitored in a conventional manner by an optical device comprising an infra-red emitter 8 and infra-red receiver 8 1 placed on either side of rod 1.
  • the ,emitter 8 and the receiver 8 - are mounted onto a clamp 4 by a bracket 9.
  • a plate 10 acts as a support plate for the whole assembly. This is welded to the jaw 4.
  • Figure lb is a schematic representation of an alternative design of the vibrating rod assembly.
  • the rod 11 is made of a 0.5 mm thick tapered mild steel plate as represented in more detail in Figure lc. This is sandwiched in between a mild steel cylindrical container 12 and cover 13 and is securely clamped at either end using four mild steel bolts 14.
  • the rod is vibrated at its centre using an electromagnet 15.
  • the container 16 containing the test powder is attached to the centre of the rod at right angle to its plane.
  • the vibrations are monitored using an optical detector 17 placed at either side of one of the rod's arms..
  • FIG 2 shows schematically an electronic circuit for the detection of resonant frequency, resonant amplitude and decay profile of the vibration component 19 (comprised by beam 1, measuring pan 2, cap 6 and powder sample in Figure 1).
  • the vibration component 19 is vibrated by the electromagnet 7 which is in turn driven by a sinusoidal voltage generated by an oscillator 20 through a 30 W variable gain power amplifier 21.
  • a typical peak to peak "drive voltage" (drive input) applied is 1 volt as measured across the electromagnet.
  • drive voltage drive input
  • the vibration component 19 is vibrated and tuned to its resonant frequency by manually varying the drive frequency to the electromagnet 7 using the oscillator 20.
  • Resonant frequency is defined as the frequency corresponding to the maximum amplitude of vibration detected as a voltage signal by the optical detector 22 (comprised of the infra-red emitter 8 and receiver 8 1 in Figure 1) .
  • the voltage signal is first amplified using a pre-amplifier 23 before being monitored by a digital multimeter 24, for amplitude measurements and a frequency meter 25 for frequency measurements.
  • Both the optical detector and the pre- amplifier are powered by a power supply unit 26.
  • a typical amplitude and frequency of vibration at resonance are ca 0.5 mm and 100 Hz. Operation in this range results in a maximum acceleration which is significantly greater than that due to gravity thus ensuring particle fluidisation during forced vibrations.
  • the vibration member 19 is first driven into resonance using the above procedure.
  • the oscillator voltage signal is then turned off ("cut off") and the decay in the amplitude of free vibrations with time is immediately monitored using a conventional transient chart recorder 27. It will be seen that both techniques allow the measurement of the mean particle size.
  • Figure 3 shows a graph of amplitude of vibration of the vibrating member at resonance plotted against various particle size ranges as indicated by vertical lines, in the diagram.
  • the data refer to 500 ⁇ 0.1. mg of Ba ⁇ lotini glass sphere samples and a constant drive voltage of 1000 mV with manual tuning. The glass spheres were previously classified by size using a sieving technique.
  • Data points refer to the resonant amplitude (mV) corresponding to the mean size of each particle size range.
  • mV resonant amplitude
  • Such data may provide a calibration curve for subsequent measurements. It should, however, be appreciated that such calibration curve may only be used in conjunction with the same mass of powder with which the device has been calibrated against and using the same drive voltage supplied to the electromagnet. Fortunately, however, the- mass of powder may be easily determined from a measurement of the resonant frequency as it is independent of the particle size.
  • the data in Figure 4 confirms this.
  • the figure ' shows the variation of the period of vibration at resonance (inverse of the resonant frequency) plotted against the mean particle size for 500 mg of various size range Ballotini glass spheres using the same conditions as in Figure 4.
  • the period corresponds to the time taken for the vibrating member to complete 1 cycle which can be measured to ⁇ lxl0 ⁇ 6 s using the frequency meter.
  • the resonant period is independent of the particle size.
  • the maximum deviation is ⁇ 2xl0 ⁇ 6 s which is reflected in a mass resolution of ⁇ lxl0 ⁇ 3 g; Figure 5.
  • This data indicates that the variation of the resonant -period with powder mass is linear. This is consistent with established theory of vibrating members with a concentrated mass attached at the free end (see for example, Prescott, J. , "Applied Elasticity" (London: Longman) Ch. IX, 1924) .
  • Figure 5 relates to a 310-420 ⁇ size range chosen as an example.
  • the drive voltage is 1000 mV.
  • the figure may, therefore, serve as a calibration curve for determining the mass of powder of various size ranges as the resonant period is independent of particle size.
  • the mass of powder under test is first measured. This measurement is either conducted directly or is done by determining the resonant frequency and using the resonant frequency v mass calibration curve (e.g. Figure 5) . The resonant amplitude is then measured and this is directly related to the average particle size using the appropriate calibration curve (e.g. Figure 3) for the same mass of powder and drive voltage.
  • only the mass measurement may be desired in which case only the resonant frequency need be determined.
  • FIG. 6 shows data obtained for 500 mg of the Ballotini spheres of 45-70 ⁇ m size range using this technique.
  • the voltage applied to the electromagnet was 1000 mV prior to 'cut-off.
  • the response is found to be a function of mass of powder.
  • this mass may be easily determined from the same data as the frequency of vibrations during the decay period (free vibrations) remains substantially the same as the resonant frequency during for.ced vibrations and is independent of particle size. This is especially useful in the case of mechanical pulsing.
  • Figure 7 shows the same data for particles of various size ranges. For simplicity, only the decay profiles are given for each powder size. It is evident that the rate of decay of amplitude with time is specific to the particle size. To analyse such data, it is known from theory (see*for example French, A.P., "Vibrations and Waves” (Massachusetts; MIT Introductory Series) pp 62-68, 1970) that for damped free oscillations the amplitude of vibrations A(t) at time t is given by:
  • a 0 is the amplitude of vibrations at zero time (in this case the resonant amplitude) , and is defined as a decay constant which is a measure of the degree of damping. 7 is determined from Equation (2) by plotting In [A(t)] vs t and measuring the slope.
  • FIG 9 shows a schematic representation of the apparatus.
  • the vibrating rod 31 is- securely clamped or welded at an intermediate point along its length.
  • One end is attached to the test cell 32 exposed to the high temperature environment, here designated as the "remote end", whilst the other side is driven and detected using the electromagnet 33 and the optical detector 34 respectively.
  • This side is designated as the “drive end” which is normally maintained at ambient conditions.
  • Heating is supplied by a 5KW power heater 36 and temperature is monitored using a thermocouple 37.
  • the test cell 32 is partly filled with the powder under analysis and its cap incorporates a wire gauze to allow the test sample to be directly accessible to the outside environment.
  • the vibrational characteristics may be sensed using conventional displacement detectors such as optical capacitance, eddy current, inductive or strain gauge transducers; the said vibration member may be set into oscillatory motion by manually varying the frequency of an alternating sinusoidal or square wave , ⁇ urrent supplied by an oscillator via a suitable amplifier to a solenoid placed in close proximity of the vibrating system;
  • the phase lag together with the pulse duration of a pulsating driving signal relative to the detected signal may be adjusted at will at various point during the oscillatory motion of the vibration member; 0 - the vibrating system may automatically tune to its resonant frequency using a closed loop circuit whereby the sensed signal is fed back to the solenoid via a suitable power amplifier thus doing away with the need for the oscillator; 5 - the mean particle size may be related to the power required in order to maintain a constant amplitude of vibrations during resonance; the container to be partly filled with the powder under test may be mounted directly on top of a 0 mechanical agitator; the vibration member's quality factor, "Q", may be related to the standard deviation from the mean size of a powder sample under test; the vibrational characteristics such as Q, resonant 5 frequency, phase lag between drive and detected signal and amplitude of vibrations all monitored during forced and/or free vibrations from resonance may provide data on particle size distribution; improvements in size resolution in terms of mean,

Landscapes

  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Sampling And Sample Adjustment (AREA)

Abstract

L'invention décrit un analyseur granulométrique comprenant un dispositif cantilever à l'extrémité libre duquel est monté un récipient partiellement rempli de la poudre soumise à essai. Pour déterminer la granulométrie moyenne, on met le système en mouvement oscillatoire et on mesure la masse de l'échantillon de poudre à partir de la fréquence de résonance et de là en mettant en corrélation l'amplitude de résonance des vibrations avec la granulométrie moyenne au moyen d'une courbe d'étalonnage préalablement obtenue pour la même masse de poudre. Dans une variante, la granulométrie moyenne peut être déterminée par la mesure des caractéristiques vibratoires du système de vibration pendant les vibrations libres dues à la résonance consécutive à l'interruption de l'excitation.
EP19900903617 1989-02-14 1990-02-13 Appareil et procede pour determiner les caracteristiques d'une poudre Withdrawn EP0458869A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB898903320A GB8903320D0 (en) 1989-02-14 1989-02-14 Particle sizer
GB8903320 1989-02-14

Publications (1)

Publication Number Publication Date
EP0458869A1 true EP0458869A1 (fr) 1991-12-04

Family

ID=10651667

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900903617 Withdrawn EP0458869A1 (fr) 1989-02-14 1990-02-13 Appareil et procede pour determiner les caracteristiques d'une poudre

Country Status (3)

Country Link
EP (1) EP0458869A1 (fr)
GB (2) GB8903320D0 (fr)
WO (1) WO1990009573A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9218659D0 (en) * 1992-09-01 1992-10-21 Atomic Energy Authority Uk Aerosol sampler
FR2762094B1 (fr) * 1997-04-10 1999-05-21 Automation Et Dev Ind Du Sud Capteur de surveillance de la maturation de fruits sur l'arbre
GB2356711B (en) 1999-11-25 2003-01-22 Technometrics Ltd Particle size distribution analyser
CN115200819B (zh) * 2022-07-13 2026-04-21 中国科学院合肥物质科学研究院 一种悬臂梁共振频率和品质因子的测量方法和装置

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2243432A1 (en) * 1973-07-31 1975-04-04 Schlumberger Compteurs Dust content meter - for measuring dust in circulating gases
IT1059840B (it) * 1975-11-25 1982-06-21 Fiat Spa Procedimento e dispositivo per il controllo della qualita di pezzi fusi..particolarmente pezzi di ghisa sferoidale
GB1585708A (en) * 1977-12-20 1981-03-11 Shell Int Research Method and means of detecting solid particles in a fluid flowing through a conduit
JPS6238345A (ja) * 1985-08-14 1987-02-19 Hitachi Ltd 固形粒子の分析方法及び装置
GB8609687D0 (en) * 1986-04-21 1986-05-29 Atomic Energy Authority Uk Particle detection
JPS6345520A (ja) * 1986-05-20 1988-02-26 Shinko Denshi Kk 振動式荷重測定装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9009573A1 *

Also Published As

Publication number Publication date
WO1990009573A1 (fr) 1990-08-23
GB2231154B (en) 1993-04-28
GB9003228D0 (en) 1990-04-11
GB8903320D0 (en) 1989-04-05
GB2231154A (en) 1990-11-07

Similar Documents

Publication Publication Date Title
US3926271A (en) Microbalance
EP0144437B1 (fr) Consistometre
US3796088A (en) Method and device for measuring the viscosity of a liquid or the concentration of solid matter suspended in a liquid
JP2730673B2 (ja) 超音波を導入するカンチレバーを用いた物性の計測方法および装置
US4679427A (en) Apparatus for measuring viscosity
JPH0145569B2 (fr)
PL177239B1 (pl) Lepkościomierz oscylacyjny
US3449940A (en) Apparatus for measuring physical properties of materials
US3492858A (en) Microbalance
US4050530A (en) Method and apparatus for determining weight and mass
Kovalik et al. Mechanical loss in fibers for low noise pendulums
US3385104A (en) Mass presence sensing apparatus
EP0458869A1 (fr) Appareil et procede pour determiner les caracteristiques d'une poudre
JPH04346087A (ja) 磁気特性測定装置
JPH09504867A (ja) 慣性質量測定器の力補償器
JPS5915837A (ja) 高温流体の粘度測定装置
US3375707A (en) Transducer driver
JP2582137B2 (ja) 液体の物理的性質測定方法及びその装置
US6829955B1 (en) Particle size distribution analyser
Woodward A laboratory test of Mach's principle and strong-field relativistic gravity
FR2462701A1 (fr) Perfectionnements aux viscosimetres a vibrations du type epingle
US6756548B2 (en) Apparatus and method for measuring mass in a microgravity environment
SU682796A1 (ru) Устройство дл измерени сдвиговой в зкости и упругости сред
CN110441401A (zh) 增材制造材料结构阻尼系数测试方法及装置
JPH04503569A (ja) 粉体の特性を測定するための装置及び方法

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19910809

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE FR GB LI

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: BRITISH TECHNOLOGY GROUP PLC

RAP3 Party data changed (applicant data changed or rights of an application transferred)

Owner name: BRITISH TECHNOLOGY GROUP LTD

17Q First examination report despatched

Effective date: 19930326

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19950509