The Mechanical Handling and Storing of Material

214 THE MECHANICAL HANDLING OE MATERIAL Fig. 290. Machinery Barge Built on Haviland & Farmer’s System. introduced a new air trap under the vacuum chambers which works on a different principle altogether to Duckham’s. They also use a device for packing the pistons of the exhausters by means of water, with the object of entirely doing away with the loss of power occasioned by the slackness of the pistons, and of lubricating and cooling the walls of the cylinders, thus reducing heat and friction and the resulting wear and tear. The water is admitted through a hollow piston rod to the body of the piston under pressure, and from thence is allowed to escape through small openings and to press against the walls of the cylinders, thus preventing any air pass- ing the pistons. The makers attach great import- ance to this invention, which they confidently anticipate will effect a great improvement in the working of pneumatic grain elevators. Fig. 290 represents a machinery barge, as built by Messrs Haviland & Farmer. It shows the filter dust collector, which has been introduced into tfae exhaust chamber, as well as the water dust collector on the deck of the machinery barge. Undoubtedly these dust collectors are of great advantage, as they will retain the most harmful dust, but it is questionable whether the water dust collector will entirely collect the finest dust. They claim that the use of their dust collectors will permit of the pistons being fitted with ordinary metallic packing rings, and that metallic valves may be used on the exhausters. The illustration shows a tank which has a patent gauze chamber which is for the purpose of keeping back coarse dust and chaff, whilst the water dust collector is for the purpose of elimi- nating the finer particles of dust which are not retained by the filter dust collector. Upon the elevated grain and air entering the vacuum tank e, through pipe j, the greater portion of the dust, husks, etc., is prevented by the fine gauze filter v from entering the suction pipe G leading to the fine dust collector x. Some of the coarse impurities are deposited along with the grain and with it discharged through the air-lock revolving wheel valve k, and thence taken by spouts and deposited in the warehouse or the lighter. To prevent the air scattering the grain as the former rushes out of the pockets of the wheel valve k, and blows up through the grain as each pocket