THE SUCTION PNEUMATIC GRAIN-LIFTER
is the invention of Mr. Fred E. Duckham, engineer of the Millwall Docks, London. The ships in which grain is brought to England often contain a "mixed" cargo as well; and that the unloading of this may proceed simultaneously with the moving of the wheat it is necessary to keep the hatches clear. As long as the grain is directly under a hatchway, a bucket elevator can reach it; but all that is not so conveniently situated must be brought within range of the buckets. This means a large bill for labour, even if machinery is employed to help the "trimming." Mr. Duckham therefore designed an elevator which could easily reach any corner of a ship's interior. The principal parts are a large cylindrical air-tight tank, an engine to exhaust air from the same, and long hoses, armoured inside with a steel lining, connected at one end to the tank, and furnished at the other with a nozzle. These hoses extend from the receiving tank to the grain, which, when the air has been exhausted to five or six pounds to the square inch, flies up the tubes into the tank. At the bottom of the tank are ingenious air-locks, to allow the grain to pass into a bin below without admitting air to spoil the vacuum. The locks are automatic, and as soon as a certain quantity of grain has collected, tip sideways, closing the port through which it flowed, and allowing it to drop through a hinged door. Two locks are attached together, the one discharging while the other is filling. An elevator of this kind will shift 150 tons or more an hour. Mr. Duckham claims for his invention that it has no limit in capacity. It is practically independent of everything but its own steam power; and the labour of one man suffices to keep its flexible suckers buried in grain. No corner is inaccessible to the nozzle. The pipes occupy only a very small part of the hatchway. They can be set to work immediately a vessel comes alongside. As many as a quarter of a million bushels are handled daily by one of these machines.
The pneumatic elevator is often installed on a floating base, so that it may be moved about in a dock.