Section 7.—BLOWING AND EXHAUSTING.
Some of the mechanical blowers are too well known to need illustration here; such are the ordinary Beam Blowing Engine, as in use for blast furnaces, Vertical Blowing Engine, and Horizontal Blowing Engine. In all these a cylinder and piston form the blowing device. Nearly every form of rotary engine (see [Section 75]) may, by reversal, be converted into a blowing machine. See Root’s patent, [No. 1307]; Baker’s, [1325], and others in common use. Fans, centrifugal, (see [No. 1337]) are still the commonest blowing machines, and are especially suited for light pressures and large volumes of air; but for pressures of from 1⁄2 lb. per square inch and upwards, the rotary or cylinder types are best. The following are devices not so well known, but sometimes useful:—
[101]. The “Trompe,” or water-jet blower. Water under pressure is discharged through a rose into a funnel-shaped inlet, carrying with it a quantity of air (see [Section 45]); the water runs off at an overflow, and the air is led away by a pipe.
[102]. Steam-jet blower. (See [Section 45].)
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[103]. Organ bellows. The lower “feeders” pump alternately into the double-tier upper “reservoir,” which has the upper set of ribs inverted, as shown, to equalise the pressure throughout its rise. The reservoir is loaded with weights to the required pressure.
[104]. Smiths’ bellows, either circular or hinged at one side.
The valves used for bellows are plain flap valves faced with leather similar to [No. 1619].
[105]. Bell, or gasometer blower, for light pressures and large volumes.
[106]. Regulator, or reservoir, for blowing engines to steady the blast. The weighted piston serves the same purpose as an air vessel to the ordinary pump.
[107]. Disc blower, with elastic diaphragm piston.
[108]. One-crank three-throw blower, for organs, &c., to give a continuous blast. The three feeders deliver into the central triangular box.