GB497491A - Improvements in apparatus for indicating and/or recording the density of solid particles, such as smoke, in a gaseous medium - Google Patents

Abstract

497,491. Photo-electric apparatus. ELLIOTT BROS. (LONDON), Ltd., and PIZZEY, C. F. June 24, 1937, Nos. 17600 and 33259. [Class 40 (iii)] Relates to apparatus for indicating or recording the density of solid particles, such as smoke, in a gaseous medium of the kind comprising a light source for projecting a light beam through the medium and a selenium or other cell for receiving the beam and giving the desired indications. According to the invention the cell is mounted in a heat insulated chamber provided internally with cooling means, and the indicating instrument is heavily damped to give indications averaging over an appreciable time period say ten seconds. As shown in Fig. 1 for the indication of smoke density in a boiler chimney or flue 8, the light source is placed on one side in a casing 3, the cell on the other side in a casing 16, and the flue has openings 6, 7 for the passage of the light beam 5. If there is a possibility of a positive pressure forming in the flue, the openings are provided with flap valves adapted to close on the occurrence of such pressure. The light casing 3, Fig. 2, comprises a thin walled box attached to a front plate 3<1> mounted on a bracket 4. The lamp 1 is mounted on a slide 9<1> adjustable between a screw 10 and a spring 11. The light beam 5 is formed by a lens 2 enclosed by a glass plate 12 and protected by a tubular shield 13. The cell casing 16, Fig. 3, similarly comprises a thin-walled box attached to a front plate 16<1> mounted on a bracket 17 and fitted with a lens 15, a glass covering plate 18 and a tubular shield 19. The cell 14 is detachably secured by a cross-bar 14<1> in the inner end of a tube 20 attached to the front plate 16<1> by a heat-insulating ring 21 of synthetic resin composition. A copper tube 25 is coiled around tube 20 and cooling water circulates therethrough. An insulating lining of synthetic resin composition encloses the space around the tube 20, and heat-insulating materials, such as glass-wool, glass-silk, or granulated cork, is placed between the lining 22 and the outer box 16. In addition, a thermostat 27 in close contact with the coiled tube 25 is provided and is adapted if the pressure becomes excessive to give an alarm or to cause an additional or alternative cooling means to come into operation. Terminal boxes 34, 35 are provided at the sides of the cell box 16 for the connections of the cell and thermostat respectively. A terminal box 33 is provided at one side of the lamp box 3 for the lamp connections ; and on the other side a terminal box 36 is provided and connected to the terminal box 34, so that an indicating device can be connected to the box 36 to be read close thereto for use in making adjustments. The indicating device in regular use would normally be at a distance.