The Mechanical Handling and Storing of Material

THE HANDLING OF MATERIAL BY PNEUMATLC MEANS 209 the same elevation; two to each carry 15 tons of grain per hour to the same height; and one to convey the grain 40 ft. in a horizontal line, and then to the hopper described as being 40 ft. above the ground. The pipes acted as conduits, the grain being carried to its destination by the force of the air current, which, owing to the construction of the nozzle at the end of the pipe, sucked up the grain by reason of the blast entering the conduit pipe through the nozzle. Fig. 281 shows the system adopted in practice by the Atmospheric Grain Co. for discharging grain from a vessel to a mill, warehouse, or to another vessel. After a series of experiments, the nozzle shown in Fig. 282 was adopted. It consists of an annular jet nozzle fitting at the entering end into the contracted throat j of the discharge trumpet j', secured at its wide end to the first length of pipe of the grain conduits c. The inner nozzle 1 is screwed into a deep socket b and fitted with a lock nut b for regulating the open- ing of the annular jet of air issuing at j. The compressed air enters at D. The inlet end of the nozzle 1 is formed into a short trumpet h for leading in the grain. Of course the shape of the trumpet is altered if the nozzle is used horizontally or in an oblique position. THE SUCTION SYSTEM This is the most frequently used of the three systems, although it is believed that it will not convey for distances Fig. 281. Application of Blast System of Elevating. much over 500 ft. In this appliance—which is more particularly applicable where material from different points is to be collected to one central point—the exhauster is placed at the delivery end of the installation. This system in its earliest form undoubtedly owes its existence to F. E. Duckham, M.Inst.C.E. The principle of his elevator will be readily understood from the following introductory description, bearing in mind what has already been said in regard to elevators working by compressed air. The plant of the Duckham system consists essentially of an air-tight vacuum tank or receiver, 8 to 14 ft. in diameter, and about 10 to 20 ft. high. This tank is hopper bottomed, and is erected, if floating, on a machinery barge, or if stationary in a building, at such a height that grain falling from the bottom of it, after discharging through an air-lock, could be delivered by gravity down 14