Patent GB-190625266-A (GB)
Title: Automatic Apparatus for Detecting Smoke and the like.
Inventor: DARWIN HORACE
Filed: 1906-11-09
Granted: 1907-09-12
Abstract: 25,266. Darwin, H. Nov. 9. Turbidometers.- Warning is given automatically when the smoke in a flue or chimney becomes denser than is permissible. Radiation from a luminous or thermal source traverses a column of the smoke and falls on sensitive devices connected with a relay to actuate a signal &c. when the percentage of radiation absorbed exceeds a certain value. The smoke-chamber forms part of separate apparatus, or smoke within the chimney may be used and the apparatus suitably disposed with regard to the chimney walls. Two beams from one source are preferably employed one beam only passing through the smoke, and the effects of the two beams on the sensitive devices being opposed to each other. In one form of the apparatus, Figs. 1 and 1<a>, lenses C1, C2 render the rays radiated from a Nernst-lamp filament approximately parallel, and two separate images are formed by the lenses D1, D, upon the sensitive device at E1, E2. One set of rays passing through clear air and the other through the smoke chamber. The smoke is kept in circulation by a fan &c. Cleaning-poles are provided or steam &c. used to keep the passages clear, or filtered air is preferably allowed to enter the smoke chamber slowly to prevent deposition of soot on the lenses. One thermopile, or two in series, separately adjustable, may be used as sensitive devices. The terminals E3, E4 of the thermo-electric system, which is adjustably mounted on the insulating-block E5, are joined to the coil of a moving-coil galvanometer which is arranged to give a clock-wise deflexion when the junctions E2 are hotter than the junctions E1. An adjustable diaphragm may be so placed between the lens D2 and the junctions E2 that the two sets of junctions just neutralize when the denseness of the smoke in the chamber B1 corresponds to the greatest permissible density in the chimney. Should the smoke become denser, the metal pointer H1 of the galvanometer, which is insulated from the coil H and is pivoted thereto at right-angles to the axis of freedom of the coil, leaves the fixed stop K and approaches the slowly revolving toothed wheel L, between which and the spring-controlled brushes L1, L2 it becomes engaged, thus completing an independent circuit and causing a bell to ring or other signal to be given. When engaged with the wheel L, the pointer H1 is carried round for the greater part of a revolution. Apparatus for recording on paper, kept in regular motion by clock-work, how often and at what times alarm signals have been given may be included in the independent circuit. This may comprise a tracing style or pen attached to the bell clapper. A quantitative record of the smoke density may be obtained by using recording- apparatus of which the galvanometer forms part. That described in Specification No. 10,844, A.D. 1905, may be used, the boom of the galvanometer being depressed at regular time intervals so that an inked thread is nipped between the recording-paper and a knife-edge formed on the boom, thus inking the paper. When apparatus of this type is employed, the relay shown in Fig. 2 may be dispensed with, a contact determining the closing of a relay circuit being made on the galvanometer boom being depressed when the deflexion exceeds a certain predetermined limit.