Optics: measuring and testing – For light transmission or absorption – Of fluent material
Patent
1987-05-27
1988-12-20
Rosenberger, R. A.
Optics: measuring and testing
For light transmission or absorption
Of fluent material
356246, G01N 2105, G01N 1502, G01N 1510
Patent
active
047922338
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an improved measurement cell for the measurement of the diameter of fibrous material by light scattering methods and in particular to the measurement of the diameter of fibre snippets, dispersed in a liquid, by light absorption in an apparatus known as the Fibre Diameter Analyser (FFDA or FDA). This apparatus is intended for measuring the diameter distribution of wool fibres or similar material and employs a measurement cell through which fibres are carried as a disperse suspension in a liquid flow.
Measurement cells used in apparatus for fibre diameter have used parallel sided, square cross-section conduits in the sensing zone.
In a publication by L. J. Lynch and N. A. Michie in the Textile Research Journal page 653, Vol. 46 No. 9, September 1976 the cell described was of square cross-section 2 mm by 2 mm.
In a previous publication by Lynch and Michie in Wool Technology and Sheep Breeding pages 22-27 Vol. XX No. 11, December 1973 a cell of 2 mm square is described with a means to electrostatically align fibres perpendicular to the flow of liquid through the cell.
In the prior art schemes the need for the fibre snippets to pass through the sensing zone at an angle to the direction of flow is recognized. In the case where no alignment mechanism is used this is not achieved since hydrodynamic forces tend to align fibres parallel to the flow direction.
When electrostatic fibre alignment is used a specially selected dispersing liquid must be employed to achieve a difference in dielectric constant between the fibres and the liquid. A high voltage must also be employed. These requirements are not practical for commercial applications.
In general the object of this invention is to produce an improved apparatus for the measurement of fibre diameter of snippets of textile fibres.
It is a further object of this invention to provide a means to obtain more favourable fibre orientation for measurement in the apparatus known as the FFDA or FDA.
It is also an object of this invention that as a result of this more favourable orientation that the measurement of a sample of fibre snippets should more closely correspond with measurement made on a similar sample of the same material by microscopic techniques.
It is also an object of this invention to increase the proportion of the fibre snippets which can be measured and to eliminate any difference in proportion between small and large diameter wool fibres.
Basically the above, as well as other objects, are obtained in accordance with this invention by causing the fibres, in suspension in a suitable dispersing liquid, to pass through a measurement cell with walls diverging in the dimension perpendicular to both that of the measurement beam and of the direction of flow. This divergence causes fibre snippets to take angles substantially different from that produced by hydrodynamic alignment in a parallel-sided cell.
Thus in this manner fibres will have an orientation such that measurement is favoured as they pass through the sensing beam.
The present invention consists in a flow cell having a body defining a passage through which a fiber-containing fluid can be caused to flow in a first direction. The body has two opposite walls defining sides of the passage, the walls being parallel to each other and transparent to radiation whereby fibers in the fluid can be illuminated and viewed by radiation travelling in a second direction through the walls and the fluid. Each of the walls lies in a first plane, the passage being further defined by a pair of opposite diverging flat surfaces each lying in a second plane, with the first planes being at right angles to the second planes. The second planes are parallel to the second direction of the radiation and are at an angle to the first direction of the fluid flow thereby forming a tapered passage having a first smaller end and second larger end, the passage having a width which increases uniformly and progressively from the first end to the second end. The passage has an inlet at the first end and an outlet at th
REFERENCES:
patent: 3728032 (1973-04-01), Noll
patent: 4056324 (1977-11-01), Gohde
Commonwealth Scientific and Industrial Research Organisation
Rosenberger R. A.
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