Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Reexamination Certificate
1998-09-17
2001-11-06
Kwok, Helen (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
C356S338000, C356S394000
Reexamination Certificate
active
06311550
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for measuring particles in suspension, the suspension comprising at least wood fibers and/or equivalent fibers, in which method each fiber-like particle in a flowing suspension is one by one optically imaged and measured in a substantially equilateral capillary tube.
The invention also relates to a measuring instrument for measuring particles in suspension, the suspension comprising at least wood fibers and/or equivalent fibers, and the measuring instrument comprising a substantially equilateral capillary tube and being arranged to optically measure one by one each fiber-like particle in a flowing suspension in the capillary tube.
BACKGROUND OF THE INVENTION
To ensure paper quality it is important to know the properties of the wood fibers used in paper making. Important properties include fibre length, fibre thickness and fiber wall thickness. Fiber fibrillation is another important feature. According to prior art these properties can usually be measured by a microscope. In addition, the fiber length can also be measured in an automated manner, in which case this method is suitable for rapidly changing industrial circumstances. The length of a fiber or a fiber-like particle is measured by using a line camera and a thin circular capillary tube. The fibers move one by one in a thin tube from which the line camera forms an image on its detector surface. The fiber length can be formed using the number of pixels covering the fiber image. This method is an efficient way of measuring fiber length, but other fiber properties thus remain unmeasured.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is thus to provide a method and a measuring instrument implementing the method so as to solve said problems and to measure all important properties of fiber-like particles at the same time if needed.
This is achieved with a method of the type described in the preamble, characterized in that for measuring the length of the fiber-like particle a position of the fiber-like particle is determined and a real image is formed of the fiber-like particles from at least one direction in the equilateral capillary tube one or more times at least for measuring the length and the transverse measure of the fiber-like particles, and the imaging of the transverse measure of the fiber-like particle is controlled by means of the length measurement of the fiber-like particle in order to determine an imaging point.
The measuring instrument of the invention is, in turn, characterized In that the measuring instrument comprises at least two cameras, one of which being arranged to form a real image of the fiber-like particle, to determine the position; and length of the fiber-like particle, and a second camera being arranged to form a real image of the fiber-like particles in the capillary tube one or more times at least for measuring the transverse measure of the fiber-like particles, and the measuring instrument is arranged to control the imaging of the transverse measure of the fiber-like particle by means of the position of the fiber-like particle in order to determine an imaging point.
Several advantages are achieved with the method and instrument of the invention. The solution of the invention can be used to measure length, thickness, wall thickness and fibrillation at the same time. Furthermore, the measures and properties of the fiber can be measured from two different directions. This information allows to accurately define the quality of different wood pulps, for example separately for each wood quality. The lignin content in fibers can also be measured.
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Lehmikangas Keijo
Löytynoja Lauri
Kwok Helen
Ladas & Parry
Metso Field Systems Oy
Politzer Jay L.
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