The Mechanical Handling and Storing of Material

2 I O THE MECHANICAL HANDLING OF MATERIAL a shoot to the grain-receiving vessel or other destination. This vacuum tank is placed in communication with the exhauster by means of a pipe. Two or more ranges of pipes may be attached to the vacuum tank. These pipes are flexible and are all of sufficient length to reach to the furthest corner of the vessel to be discharged. The end of the pipe where the grain enters is of special design, to be •described later on. It is generally called a nozzle, but necessarily it bears but little resemblance to the blast nozzle, of the previous type. When the exhausters are started a partial vacuum is formed within the tank or canister through a connecting pipe, and upon the nozzle end of the pipe being immersed in the grain to a depth of a few inches, the air is drawn in at the orifice of the nozzle, which carries it up the pipe to the vacuum tank. The air, by sudden Fig. 282. Blast Nozzle of Pneumatic Elevator. expansion from a 5 or 6 in. pipe into a large vacuum tank, allows the grain to fall to the bottom of the tank and pass away by means of an air-lock valve, whilst the air is drawn down through a connecting pipe into the air-pumps, and is led away from them by pipes. COMBINED SUCTION AND BLAST SYSTEM This combination is sometimes used when the distance to which the grain is to be conveyed exceeds 1,000 ft., or in the event of grain having to be collected from a variety of points to a central station and distributed again to a number of points some distance away. For such installa- tions the best position for the compressor and exhauster is somewhere between the two terminals, whichever may be most suitable to the locality. This system of transmitting grain by pneumatic means consists of a combination of the blast and suction systems. The grain is sucked into a vacuum chamber as already mentioned, and from this tank is conveyed by means of a blast of compressed air through flexible pipes to any point ‘desired. The tank may be divided into two sections, and fitted with a system of valves in such a manner that the two sections of the tank are alternately under the influence of blast or suction, or the grain may be discharged through from the vacuum tank into a second air-tight chamber which This chamber is fitted with a an automatic or other valve is in communication with the compressed air chamber. grain-discharging pipe, and the grain is forced through it by means of the compressed air as already described. There have been several practical applications of this latter system which appear to have given satisfaction. Messrs Haviland & Farmer experimented with the blast system for some years, but after much experimenting with the patents taken out by Walker and others between the years 1886 and 1890, it was found that such difficulties were inherent in the blast system of elevating as seriously to interfere with any chance of ultimate success, and it was therefore abandoned by them. The velocity at which the grain travelled in the pipes was so great as to break the grain on reaching the bends in the pipes, and even where the berries were not actually broken, the husk was abrased, the action in the pipes being like that of a decorticator. A yet greater objection was the dust nuisance, as the grain and the accompanying air current escaped together from the delivery end of the