Fiber length analyzer

A system for analyzing the size distribution of a wood pulp fiber sample comprising:

• (a) source means for providing a fluid consisting essentially of the wood pulp fiber sample dispersed in a liquid;
• (b) a measurement station including a measurement cell having an inlet and an outlet for said fluid and means for measuring the size of each fiber that passes through the cell from the inlet to the outlet;
• (c) first conduit means for delivering only said fluid from the source means to the inlet of the measuring cells;
• (d) means for maintaining a substantially constant volumetric flow rate of fluid through the first conduit and measuring cell;
• (e) wherein the measurement cell includes
• (1) a single flow tube fluidly connected at a first end only to the first conduit means and at a second end to the cell outlet, said flow tube having an axis, a substantially transparent measurement portion intermediate the ends and a transition portion that gradually narrows at an angle of convergence of less than about 30.degree. to the axis in the direction of flow between the first end and the measurement portion, such that the fibers pass through the measurement portion aligned with the tube axis in spaced-apart, serial order,
• (2) a single light source for projecting a single beam of light at a preselected intensity through the measurement portion transversely to the tube axis, as the fluid passes therethrough,
• (3) single sensor means for detecting variations in the intensity of the light that passes through the measurement portion in response to the passage of each dispersed fiber through the beam as the fluid passes through the measurement portion;
• and
• (f) wherein the measurement station includes processing means responsive to the sensor means for recording fiber size distribution values commensurate with the variation in detected light intensity.

A system for analyzing the size distribution of a fiber sample comprising:

• (a) source means for providing a fluid consisting essentially of the fiber sample dispersed in a liquid;
• (b) a measurement station including a measurement cell having an inlet and an outlet for said fluid and means for measuring the size of each fiber that passes through the cell from the inlet to the outlet;
• (c) first conduit means for continuously maintaining a flow of said fluid from the source means to the inlet of the measuring cell;
• (d) second conduit means for continuously maintaining a discharge flow of said fluid out from the outlet of the measuring cell;
• (e) means for maintaining a substantially constant volumetric flow rate of fluid through the first conduit, measuring cell, and second conduit;
• (f) wherein the measurement cell includes
• (1) a hollow, elongated housing defining a flow axis,
• (2) a flow tube coaxially and removably supported within the housing and fluidly connected at a first end to the first conduit and at a second end to the second conduit, said flow tube having a substantially transparent, measurement portion intermediate the ends, such that the fibers pass through the measurement portion on the tube axis in spaced-apart, serial order,
• (3) a light source secured to the housing for projecting a single beam of light through the measurement portion transversely to the tube axis, as the fluid passes therethrough,
• (4) sensor means secured to the housing for detecting variations in the intensity of the light that passes through the measurement portion in response to the passage of each dispersed fiber through the beam as the fluid passes through the measurement portion;
• and
• (g) wherein the measurement station includes processing means responsive to the sensor means for recording fiber size distribution values commensurate with the variation in detected light intensity.

A system for analyzing the particulate content of a fluid sample comprising:

• (a) source means for providing a fluid consisting essentially of said particulates dispersed in an otherwise substantially pure liquid at a concentration of less than about 0.001 per cent,
• (b) a measurement station including a measurement cell having an inlet and an outlet for said fluid and means for sensing each particle that passes through the cell from the inlet to the outlet;
• (c) first conduit means for continuously maintaining a flow of said fluid from the source means to the inlet of the measuring cell;
• (d) second conduit means for continuously maintaining a discharge flow of said fluid out from the outlet of the measuring cell;
• (e) means for maintaining a substantially constant volumetric flow rate of fluid through the first conduit, measuring cell, and second conduit;
• (f) wherein the measurement cell includes
• (1) a flow tube fluidly connected at a first end only to the first conduit means and at a second end to the second conduit means, said flow tube having an axis and a tapered angle of convergence of less than about 30.degree. preceding a substantially transparent measurement portion with a round flow diameter in the range of about 1.0-3.0 mm such that the particles pass through the measurement portion in spaced-apart, serial order;
• (2) a slotted optical switch light source for projecting a single beam of light through the measurement portion transversely to the tube axis, as the fluid passes therethrough;
• (3) sensor means for detecting, without polarization or beam splitting, variations in the intensity of the light that passes through the measurement portion in response to the passage of each dispersed particle through the beam as the fluid passes through the measurement portion and for generating a sensor signal commensurate with said intensity;
• and
• (g) wherein the measurement station includes processing means including a cascaded series of high gain operational amplifiers, responsive to the sensor signal, for counting particles commensurate with the variation in detected light intensity.