PISTON BLOWERS. The Chinese bellows is one of the earliest and simplest forms of piston blowers. It consists of a square chamber of wood, with a close-fitting piston, which, when drawn back, sucks air in through a flap valve like the ordinary bellows-valve, and when pushed forward compresses this air and forces it out through a nozzle. The modern form of piston blower is virtually an air-pump or compressor for producing low pressures. (See Ata-ComenEs sons.) Its rust extensive use is for supplying the air-hlast to blast-furnaces, Bessemer con verter:, etc. Stearn is the power most com monl• used hut gas-engines have recently been introduced, and any other power, such as a fall of water. may be employed. A blowing-engine of modern construction usually consists of a steam ylinder and an air-eylimb r set, tandem, either vertically, one above the other, or horizontally, one ahead of the other, with a common piston rou and a heavy fly-wheel to regulate the t:MI. The air-cylinder is 'usually placed upper most in :1 vertical engine and foremost in a hori zontal engine, and the air is usually compressed on both the forward and the return stroke of the piston. Often the steam-cylinders are compound ed. The air from the air-•ylinder passes some times into a receiver, but more often directly into the blast-pipes, AN hich are made large enough to act as a receiver or reservoir for maintaining a steady supply of air to the furnaces.
The following are brief descriptions of a num ber of representative modern blowing-engines: A blowing-engine built for the Hernadthaler Iron-Works at Krompach, Hungary, in 1898, is a horizontal cross-compound engine, with a high pressure steam-cylinder 35 inches in diameter, a low-pressure cylinder 54 inches in diameter, and an air-cylinder 76 inches in diameter, all with a stroke of 55 inches. The contract with the build
ers required that this engine should have a ca pacity of 2S,250 cubic feet of air at 10 pounds pressure, with a steam-pressure of 112 pounds, and making revolutions per minute. Among the more important vertical blowing-engines are those for the Dominion Iron and Steel Company of Sydney, Cape Breton, Canada, to supply the blast for the five blast-furnaces built in 1900. These engines have high-pressure. steam-cylinders 50 inches in diameter, low-pressure steam-cylin ders 96 inches in diameter, air-cylinders 96 inches in diameter, and a piston-stroke of 60 inches.
The largest gas-engine blower ever built is that constructed by the John Cockerill Company, of Seraing• Belgium, and exhibited at the Paris Exposition of 1900. This engine is of 600 horse power: the gas-cylinder is 51.2 inches in diame ter, with a piston-stroke of 55.1 inches: the air-cylinder is 66.9 inches in diameter, with a piston-stroke of 55.] inches, and the engine is horizontal, with the air-cylinder ahead of the power-••l index.