Patent GB-918525-A (GB)
Title: Improvements in and relating to smokemeters
Inventor: HARTRIDGE LESLIE
IPC: G01N21/53
Filed: 1958-04-29
Abstract: 918,525. Photo - electric smoke - meters. HARTRIDGE Ltd., LESLIE. April 24, 1959 [April 29, 1958], No. 13598/58. Class 40 (3). Relates to a smoke-meter for determining the density of the exhaust gases of an internalcombustion engine in which light from a lamp 21, Fig. 1, is directed through a tubular chamber 8 containing the smoke on to a photo-cell 23 connected to a meter 35. In such apparatus the light reaches the photo-cell (1) directly from the lamp 21 and (2) after reflection at the interior surface of the chamber 8 and the intensity of the latter component depends upon the amount of moisture condensed upon and soot deposited on said surface. According to the present invention sharp-edged annular ribs 43 are provided inside the chamber 8 to prevent the reflected light from reaching the photo-cell. The invention is described as applied to a smoke-meter as described in Specification 704,052 comprising a smoke chamber 8 and a similar reference chamber 10 containing clean air. The lamp 21 and photo-cell 23 are mounted at the ends of two arms, one of which, 26, is shown in the end elevation, Fig. 5, and the arms are rigidly attached to a shaft 24 located below and parallel to the chambers 8 and 10, the shaft 24 being rotatable by a hand lever, Fig. 2 (not shown), to align the lamp and photo-cell with either chamber. In operation the lamp and photo-cell are first aligned with the reference chamber 10 and a resistance 36 in series with the meter 35 is adjusted to give a predetermined reading on the meter. The lamp and photo-cell are then aligned with the smoke chamber 8 and the resultant meter reading indicates the smoke density. The chambers 8 and 10 are mounted in a container 1 with end walls 2 and 3 having holes 11 opposite the smoke chamber 8 and additional holes 12 to receive the ends of the reference chamber 10. The lamp 21 and photocell 23 are enclosed in housings 4 and 5 attached to the end walls 2 and 3. The smoke and air are introduced at the middle of the chambers 8 and 10 via intakes 13 and 18, respectively, and escape through the common outlets 20 so that the lamp 21 and photo-cell 23 are protected from the smoke by the exhaust stream of air passing round them. A liquid trap 70, Fig. 5, and a pressure relief valve 79, Fig. 5, are provided at the smoke inlet 13. As shown in Fig. 6 the smoke chamber 8 comprises two tubes 7a interconnected by a hollow cylindrical muff 44 having a flanged neck forming the smoke inlet 13, each tube 7a comprising two semi-cylindrical troughs 7b arranged edgeto-edge and having a plurality of knife-edged ribs. The troughs may be of any suitable heat and acid resistant, moisture absorbent, material, e.g. biscuit ware. The ends of the units 7a are chamfered and are received by seats 53 on the muff 44 and seats 54 on end-rings 55 which are urged towards the muff 44 by compressionsprings 61 surrounding pegs 62 projecting from the rings and entering holes 63 in the end-plates 2, 3. The reference chamber 10 comprises two tubes 9a and a muff 64 similar to the corresponding units of the smoke chamber 8 but the outer chamfered ends of the tubes 9a bear against seats 66 at the ends of sleeves 67 which pass through the holes 12 in the end-plates 2, 3. In a modification, Fig. 7 and Figs. 8 and 9 (not shown), each tube 7a and 9a comprises a plurality of flanged tube units 86 partially nested one in another so that the flanges 87 form the internal ribs. The units 86 may be formed of plastic material or anodized aluminium.