GB308080A - Improvements in and relating to optical instruments and devices for determining the average diameter of fibres in fibrous materials - Google Patents

Abstract

308,080. Ewles, J. March 15, 1928. Gauges-apparatus.-Comprises an instrument for measuring the mean diameter of fibre in a wisp of fibres by making use of the diffraction of light rays. A tube A of metal or other suitable material is fitted near one end with a diaphragm B. Telescoping into the tube A is a longer tube C fitted at the outer end with a readily removable eyepiece C1 formed as a cap C2 fitting over the tube C. A diaphragm C3 is also provided at the end of the tube C and is provided with a central viewing aperture in line with the aperture in the eyepiece. The diaphragm B is provided with a narrow slit B1 along a diameter, and parallel therewith, symmetrically arranged on either side, are pairs of small holes B2, B3. A tuft of fibres such as wool, cotton, &c. is laid across the eyepiece in the diametrically opposite slots C4 and the cap moved over the end of the tube with the fibres against the diaphragm C3, the cap being turned to bring the fibres into the plane of the slit B1. If the eye is applied to the eyepiece, and the device directed towards a source of light such as daylight or an opal glass electric bulb, a series of dark and light or of coloured bands is seen. The tube C is now adjusted longitudinally until the centre of the first dark band, or say red band, nearest the slit lies on one pair of holes B2 or B3. The position of the edge of the outer tube on the scales will then give the average diameter of fibre in the sample. The scales are calibrated by using fibre of known diameter. In a modification, the diaphragm B has a central circular aperture and the small holes are positioned on a concentric circle, the bands being seen as concentric circles.