Patent GB-646608-A (GB)
Title: An instrument for indicating the length and distribution of fibers
IPC: G01B11/02
Filed: 1948-05-05
Abstract: 646,608. Inspecting fibres. ROBERT - SHAW-FULTON CONTROLS CO. May 5, 1948, No. 12388. Convention date, July 2, 1947. [Class 120(iii)] [Also in Group XL(b)] In an instrument for examining the distribution of cotton fibres along the length of a sample, the response of a photo-cell to a beam of light passed through the sample is balanced by or brought to a predetermined difference from the output of a further photo-cell by varying the distance of a second light source from a second photo cell, the distance the source is moved to obtain balance being an indication of the fibre distribution. As shown in Fig. 1, a fluorescent tube sends a horizontal band of light through a collimator 78 comprising a number of rectangular blocks of translucent material cemented together with an opaque cement at their largest faces. In this Figure the tube and collimator are shown in an inoperative position but the whole may be pivoted about 71 so that the light passes inwardly through cotton samples, held in each of combs 83. Behind each of the samples 82 is the end of a light guide which may be of Lucite and which serves to concentrate the light passing through the sample on to a photo-cell 90 or 91, situated at the rear of the panel shown in the Figure. Balancing photo-cell 66, Figs. 1 and 4, is mounted on a plate 57 itself slidable in guides at the rear of a main plate 41<1> adjustable horizontally by a wheel 46 and screw 44 and carrying a light source 53. Plate 57 is sprung towards its extreme left hand position so that movement of plate 41<1> to the right tends to increase the distance of source 53 from cell 66. Since the response of photo-cells 90, 91 varies exponentially with fibre distribution and the response of cell 66 as the inverse square of its distance from the source, a cam 48 is carried by a plate 41' to modify the relative movement of the photo-cell and light source through a bell crank lever 60 one end of which rides on the cam surface and the other an adjustable pin 65. A card is mounted on plate 41<1>. In use, rotation of a handwheel 22 acts through gearing 27, 28 and helical rod 30 to move combs 83 upwardly passing the fibres between the light source and the end of the light guides. At the same time an arm 32 raises a pen 40 at the same speed as the comb marking the card. The position of the plate 41<1> is meanwhile continuously adjusted by a handwheel 46 so that a meter indicating the difference in output of a pair of photo-cells 90, 91 and photo-cell 66 is maintained at balance or at a predetermined reading. Humidity detecting and measuring.- Samples of linen embossed cellophane are found to transmit more light under conditions of high humidity than low. Such standard samples may be used to measure changes of humidity or to operate controls to maintain the humidity constant. Circuits.-(Fig. 6). A voltage regulating transformer 96 feeds parallel photo-cells 90, 91 forming with cell 66 two arms of a bridge circuit, the other two arms of which are constituted by resistors 105, 106. The out of balance voltage resulting from unequal illumination of the two arms is applied between the grid and cathode of one side of a double triode valve 112. The bias of the other side is adjustable by a potentiometer 127 so that with switch 94 open mirror galvanometer 140 may be adjusted to zero.